Environmental Impacts of Petroleum Production:

Initial Results from the Osage-Skiatook 

Petroleum Environmental Research Sites, 

Osage County, Oklahoma 

Water-Resources Investigations Report 03-4260

U.S. Department of the Interior 

U.S. Geological Survey 
ENVIRONMENTAL IMPACTS OF 

PETROLEUM PRODUCTION: INITIAL

RESULTS FROM THE OSAGE-SKIATOOK 

PETROLEUM ENVIRONMENTAL

RESEARCH SITES, OSAGE COUNTY,

OKLAHOMA 

U.S. GEOLOGICAL SURVEY 

WATER-RESOURCES INVESTIGATIONS REPORT 03-4260 

Prepared in cooperation with the 

U.S. Environmental Protection Agency 

Department of Energy National Petroleum Technology Office 

Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by

the U.S. Government
ENVIRONMENTAL IMPACTS OF 

PETROLEUM PRODUCTION: INITIAL

RESULTS FROM THE OSAGE-SKIATOOK 

PETROLEUM ENVIRONMENTAL

RESEARCH SITES, OSAGE COUNTY,

OKLAHOMA 

Yousif K. Kharaka and James K. Otton, editors 

U.S. GEOLOGICAL SURVEY 

WATER-RESOURCES INVESTIGATIONS REPORT 03-4260

Prepared in cooperation with the 

U.S. Environmental Protection Agency 

Department of Energy National Petroleum Technology Office 

Menlo Park, California 

2003 

ii
U.S. DEPARTMENT OF THE INTERIOR 

GALE A. NORTON, Secretary 

U.S. GEOLOGICAL SURVEY 

CHARLES G. GROAT, Director 

For Additional Information 

Write to: 

Copies of this report may be 

obtained from the authors or

Yousif K. Kharaka 

U. S. Geological Survey, MS 427 

345 Middlefield Road 

Menlo Park, California 94025, USA 

Mail: ykharaka@usgs.gov

More current information about the 

OSPER "A" and "B" sites is available at: 

http://ok.water.usgs.gov/skiatook/

U.S. Geological Survey

Information Center

Box 25286, MS 517

Denver Federal Center

Denver, CO 80225

iii
Contents

Page 

Introduction and Summary 

By Yousif K. Kharaka and James K. Otton............................................................................... 1 

Abstract................................................................................................................................. 1 

Introduction........................................................................................................................... 2 

OSPER “A” and “B” Sites.................................................................................................... 4 

Scientific Approach .............................................................................................................. 6 

Initial Summary Results........................................................................................................ 8 

Future Plans .......................................................................................................................... 9 

Acknowledgements............................................................................................................. 11 

References........................................................................................................................... 11 

Produced Water and Hydrocarbon Releases at the Osage-Skiatook Petroleum Environmental 

Research Sites, Osage County, Oklahoma: Introduction and Geologic Setting

By James K. Otton and Robert A. Zielinski ............................................................................ 14 

Abstract............................................................................................................................... 14 

Introduction......................................................................................................................... 15 

“A” Research Site ............................................................................................................... 16 

Lease History .................................................................................................................. 23 

Geology of the “A” Site.................................................................................................. 23 

Hydrology ....................................................................................................................... 30 

“B” Research Site ............................................................................................................... 31 

Lease History .................................................................................................................. 34 

Geology of the “B” Site .................................................................................................. 35 

Conclusions......................................................................................................................... 40 

References........................................................................................................................... 41 

Preliminary Geophysical Characterization of Two Oil Production Sites, Osage County, 

Oklahoma – Osage-Skiatook Petroleum Environmental Research Project

By Bruce D. Smith, Robert J. Bisdorf, Robert J. Horton, James K. Otton, 

and Ray S. Hutton ................................................................................................................... 42 

Abstract............................................................................................................................... 42 

Introduction......................................................................................................................... 42 

Methods............................................................................................................................... 43 

Geophysical Surveys at Site A............................................................................................ 43 

DC Resistivity Soundings............................................................................................... 43 

EM31 Survey .................................................................................................................. 46 

Geophysical Surveys at Site B............................................................................................ 46 

DC Resistivity Survey..................................................................................................... 46 

EM31 Survey .................................................................................................................. 49 

Conclusions......................................................................................................................... 54 

References........................................................................................................................... 54 

iv
Contents--continued 

Page 

The Fate of Inorganic and Organic Chemicals in Produced Water from the Osage-Skiatook 

Petroleum Environmental Research Sites, Osage County, Oklahoma

By Yousif K. Kharaka, James J. Thordsen, Evangelos Kakouros, and Marvin M. Abbott..... 56 

Abstract............................................................................................................................... 56 

Introduction......................................................................................................................... 57 

OSPER Sites....................................................................................................................... 58 

Methods and Procedures..................................................................................................... 62 

Laboratory Measurements .............................................................................................. 62 

Results and Discussion ....................................................................................................... 62 

OSPER “A” Site ............................................................................................................. 73 

OSPER “B” Site.............................................................................................................. 77 

Summary and Conclusions ................................................................................................. 81 

Acknowledgements............................................................................................................. 81 

References........................................................................................................................... 82 

The Fate of Petroleum and Other Organics Associated with Produced Water from the OsageSkiatook Petroleum Environmental Research Sites, Osage County, Oklahoma

By E. Michael Godsy, Frances D. Hostettler, Ean Warren, V. Vincenzo Paganelli, 

and Yousif K. Kharaka............................................................................................................ 84 

Abstract............................................................................................................................... 84 

Introduction......................................................................................................................... 84 

Materials and Methods........................................................................................................ 87 

Microbial Number Determinations................................................................................. 87 

Core Sample Collection .................................................................................................. 87 

Water Sample Collection and Analysis.......................................................................... 88 

Production Oil Sample Collection .................................................................................. 88 

Results and Discussion ....................................................................................................... 91 

Microbial Populations..................................................................................................... 91 

Aerobes........................................................................................................................... 92 

Facultative Aerobes ........................................................................................................ 93 

Obligate Anaerobes (Respiratory) .................................................................................. 93 

Obligate Anaerobes (Fermentative)................................................................................ 93 

Site A Microbially Important Geochemistry .................................................................. 93 

Site A Microbial Populations.......................................................................................... 94 

Study Area Production Oils............................................................................................ 94 

Characterization of Site A Oils....................................................................................... 96 

Site B Microbially Important Geochemistry................................................................... 97 

Site B Microbial Populations.......................................................................................... 98 

Characterization of Site B Oils....................................................................................... 98 

Conclusions......................................................................................................................... 99 

References......................................................................................................................... 101 

v
Contents--continued 

Page 

Impact of Oil Production Releases on Some Soil Chemical Properties at the OSPER Sites

By Don H. Kampbell, Youn-Joo An, Matthew W. Smith, and Marvin M. Abbott................. 103 

Abstract............................................................................................................................. 103 

Introduction....................................................................................................................... 103 

Experimental Methods...................................................................................................... 104 

Results and Discussion ..................................................................................................... 107 

References......................................................................................................................... 110 

Hydrologic Controls on the Subsurface Transport of Oil-field Brine at the Osage-Skiatook 

Petroleum Environmental Research “B” Site, Oklahoma

By William N. Herkelrath and Yousif K. Kharaka................................................................ 111 

Abstract............................................................................................................................. 111 

Introduction....................................................................................................................... 111 

Field Site Description ....................................................................................................... 112 

Hydrology and Solute Transport in the Waste Pit Area ................................................... 114 

The Brine Source in the Waste Pit................................................................................ 114 

Ground-Water Flow from the Waste Pit to the Lake.................................................... 114 

Water Flow in the Unsaturated Zone............................................................................ 115 

Solute Transport............................................................................................................ 115 

Preliminary Modeling Results.......................................................................................... 116 

Discussion......................................................................................................................... 120 

Summary and Conclusions ............................................................................................... 121 

References......................................................................................................................... 122 

Use of Soil Extracts to Define the Extent of Brine-impacted Soils and Bedrock at the OsageSkiatook Petroleum Environmental Research “B” Site, Northeastern Oklahoma

By Robert A. Zielinski, Cynthia A. Rice, and James K. Otton .............................................. 124 

Abstract............................................................................................................................. 124 

Introduction....................................................................................................................... 124 

Site Description................................................................................................................. 126 

Methods............................................................................................................................. 126 

Results and Discussion ..................................................................................................... 127 

Additional Considerations ................................................................................................ 130 

Conclusions....................................................................................................................... 130 

References......................................................................................................................... 132 

Characterization of Soils at an Active Oil Production Site: Effects of Brine and Hydrocarbon 

Contamination

By Cynthia A. Rice, James D. Cathcart, Robert A. Zielinski, and James K. Otton .............. 133 

Abstract............................................................................................................................. 133 

Introduction....................................................................................................................... 133 

Methods............................................................................................................................. 134 

Results and Discussion ..................................................................................................... 136 

Summary........................................................................................................................... 146 

References......................................................................................................................... 146 

vi
Contents--continued 

Page 

Real-time Kinematic (RTK) Surveying at the Osage-Skiatook Petroleum Environmental 

Research Sites, Osage County, Oklahoma

By Marvin M. Abbott............................................................................................................. 147 

Abstract............................................................................................................................. 147 

Introduction....................................................................................................................... 147 

Global Positioning System................................................................................................ 149 

Equipment Requirements and Methods............................................................................ 149 

Accuracy of the RTK GPS Technology............................................................................ 152 

Summary........................................................................................................................... 154 

References......................................................................................................................... 155 

vii
Conversion Factors

Multiply By To obtain

millimeter (mm) 0.03937 inch (in.)

centimeter (cm) 0.3937 inch (in.)

meter (m) 3.281 foot (ft)

kilometer (km) 0.6214 mile (mi)

hectare (ha) 2.471 acre

cubic meter (m3) 6.290 barrel (petroleum, 1 barrel = 42 gal)

liter (L) 0.2642 gallon (gal)

cubic meter per second (m3/s) 70.07 acre-foot per day (acre-ft/d)

cubic meter per second (m3/s) 35.31 cubic foot per second (ft3/s)

liter per second (L/s) 15.85 gallon per minute (gal/min)

cubic meter per day (m3/d) 264.2 gallon per day (gal/d)

gram (g) 0.03527 ounce (oz)

kilogram (kg) 2.205 pound (lb)

kilopascal (kPa) 0.009869 atmosphere, standard (atm)

kilopascal (kPa) 0.01 bar

meter per day (m/d) 3.281 foot per day (ft/d)

meter per kilometer (m/km) 5.27983 foot per mile (ft/mi)

meter squared per day (m2/d) 10.76 foot squared per day (ft2/d)

Temperature can be converted to degrees Celsius (°C) or degrees Fahrenheit (°F) by using the 

following equations

°F = (1.8 × °C) + 32

°C = (°F - 32) / 1.8

Specific conductance is given in microsiemens per centimeter at 25 degrees Celsius (μS/cm at

25°C).

Concentrations of chemical constituents in water are given either in milligrams per liter (mg/L) or micrograms 

per liter (μg/L)

viii
Introduction and Summary 

By Yousif K. Kharaka and James K. Otton 

Abstract 

Exploration for and production of petroleum have caused major detrimental impacts 

to soils, surface and ground waters, and the local ecosystems in the United States. These 

impacts arise primarily from the improper disposal of large volumes of saline water produced 

with oil and gas, from accidental hydrocarbon and produced water releases, and from

abandoned oil wells that were not correctly sealed. It is important to understand the longterm and short-term effects of produced water and hydrocarbon releases from these sites in 

order to develop risk-based remediation plans. Remediation is particularly needed in aging 

and depleted fields where land use is changing from petroleum production to residential, 

agricultural or recreational uses. 

About 20 scientists from the USGS and other governmental agencies and academia 

are involved in a multidisciplinary investigation to study the transport, fate, and natural 

attenuation of inorganic salts, trace metals, organic compounds and radionuclides present in 

produced water, and their impacts at the Osage-Skiatook Petroleum Environmental Research 

(OSPER) “A” and “B” sites, located on the Osage Reservation in Osage County, Oklahoma. 

Stakeholders in the project include the Osage Nation, which holds the mineral rights, the 

Bureau of Indian Affairs with trust responsibility, and the Army Corps of Engineers, which 

owns the surface rights at these sites and manages adjacent Skiatook Lake. The 4250-hectare 

Skiatook Lake provides drinking water to local Tulsa suburban communities and a rural 

water district, and offers recreational fishing and boating opportunities to tens of thousands 

of visitors each year. 

Approximately 1.5 and 1.0 hectare of land at the OSPER “A” (depleted Lester lease) 

and “B” (active Branstetter lease) sites, respectively, are affected by salt scarring, tree kills, 

soil salinization and brine and petroleum contamination due to the leakage of produced water 

and associated hydrocarbons from brine pits and accidental releases from active and inactive 

pipes and tank batteries. The leases are typical of many depleted and aging petroleum fields 

in Osage County, which ranks among the top oil and gas producing counties in Oklahoma 

with about 39,000 wells. Oil and gas production has occurred in Osage county for over one 

hundred years, but current production is mainly from stripper wells (averaging ~2.8 bbl/d oil 

and >30 bbl/d brine) that are shallow, mostly 300-700 m in depth, and produce from several 

sandstones of Pennsylvanian age. 

Results to date show that the produced water source is a Na-Ca-Cl brine (~150,000 

mg/L total dissolved solids), with relatively high concentrations of Mg, Sr, and NH4, but low 

SO4 and H2S. With the exception of Fe and Mn, the concentrations of trace metals are low. 

Results also show that some and, eventually, the bulk, of inorganic salts and some dissolved 

organic species in the released brine from both sites will reach Skiatook Lake. 

Results at the “A” site show that the salts have essentially been removed from the 

sandy soil which formed in a surficial layer of eolian sand, but degraded and weathered oil 

persists on the surface of old oil and brine pits, close to sites of old tanks, on old channels 

1
that carried oil from tanks to the oil pits and other impacted areas. Results also show a plume 

of high salinity water (5,000-30,600 mg/L TDS) is present at intermediate depths that extend 

from below the old oil and brine pits to Skiatook Lake. No liquid petroleum was found in the 

contaminated groundwater, but soluble petroleum byproducts, including organic acid anions 

and other volatile organic compounds (VOCs) are present. Results to date clearly show that 

significant amounts of salts from produced-water releases and petroleum hydrocarbons still 

remain in the soils and rocks of the impacted area after more than 60 years of natural 

attenuation. At the “B” site significant amounts of produced water from the two active brine 

pits percolate into the surficial rocks and flow towards the Skiatook Reservoir; but only 

minor amounts of liquid petroleum leave the brine pits and reach the Skiatook Reservoir. At 

both sites, results show that the chemical composition of released brines is modified further 

by sorption, mineral precipitation/dissolution, transpiration, volatilization and bacterially 

mediated oxidation/reduction reactions. 

Introduction 

Oil and natural gas currently are the main sources of primary energy in the USA, 

supplying about 63% of the energy consumption. Forecasts indicate that by 2025 natural gas 

and oil consumption will increase by 50% and 48%, respectively (EIA, 2003). Oil and gas 

production started in the USA in 1859, when the Drake’s well was drilled near Titusville in 

Venango County, PA (Dickey, 1959). To date, a total of about 3.5 million oil and gas wells 

have been drilled in 36 states, but currently only about 880,000 are in production (Kharaka 

and Wanty, 1995; Breit and others, 2001). Petroleum production, drilling operations, and 

improperly sealed abandoned wells have caused major contamination of surface and ground 

waters and soils in energy producing states (USEPA, 1987; Richter and Kreitler, 1993; 

Kharaka and others, 1995; Kharaka and Hanor, 2003). Contamination results mainly from the 

improper disposal of some of the large volumes (currently 20-30 billion barrels per year) of

saline water produced with oil and gas, and from hydrocarbon and produced water releases 

caused by equipment failures, vandalism, flooding, and accidents. 

Prior to the institution of Federal regulations in the 1970’s, produced waters, which 

are highly saline (TDS may exceed 350,000 mg/L dissolved solids), may contain toxic 

metals, organic and inorganic components, and radium-226/228 and other naturally occurring 

radioactive materials (NORM), were often discharged into streams, creeks, and unlined 

evaporation ponds causing salt scars and surface and ground water pollution (Collins, 1975; 

Kharaka and Thordsen, 1992; Otton and others, 1997a,b,c, 2001; Zielinski and others, 1998; 

Otton and Zielinski, 1999). These releases and the improper disposal of produced water are 

national issues that concern managers of Native American, Federal, and State lands, as well 

as oil and gas producers and lessees, mineral rights and lease owners, State and Federal 

regulators, and surface landowners (ASTM, 1999; Billingsley, 1999; Carty and others, 1997; 

Federal Leadership Forum, 2000; USEPA, 1987; Wilson and Frederick, 1999). 

Beginning in early 2001, about 20 scientists from the USGS and other governmental 

agencies and academia have been conducting a multidisciplinary investigation to study the 

transport, fate, and natural attenuation of inorganic salts, trace metals, organic compounds, 

and radionuclides present in produced water, and their impacts on soil, surface and ground 

waters and the local ecosystem at the Osage-Skiatook Petroleum Environmental Research 

(OSPER) “A” and “B” sites, located in Osage County, OK (fig. 1). The authors of this 

2
“A” SITE

“B” SITE

SKIATOOK

LAKE

0

6

10

0 12 MILES

20 KILOMETERS

80 160 KILOMETERS

50 100 MILES

0

0

EXPLANATION

Gray = 1 - 8 oil wells per square mile

Black = 9 - 32 oil wells per square mile

Red = 33 – 128 oil wells per square mile

Yellow = 129 - > 256 oil wells per square mile

Oil wells on 43,300 square miles on map

Total oil wells in Oklahoma – 450,000

(1995 National Assessment of United States Oil and Gas

Resources)

A

C

B

Figure 1. Distribution of petroleum wells in Oklahoma, Osage County, and the study 

areas. A – Location of 450,000 wells in Oklahoma; B – Location of 38,500 wells 

(radius of each well=1/4 mile, after Abbott, 2000) in Osage County. C – Location of 

many shut-in and operating wells in and near the OSPER “A” and “B” sites on 

Skiatook Lake. 

3
chapter organized a special session on OSPER at the Ninth International Petroleum

Environmental Conference (IPEC-9) in Albuquerque, NM, 22-25, October 2002. The 

session, titled “Fate and Transport of Brine and Hydrocarbon Releases in Soils and Water, 

Northeast Oklahoma”, attracted 10 presentations (http://ipec.utulsa.edu/). Even though 

reports from many of the presentations were posted at the IPEC web site, all the presenters 

agreed to modify their IPEC reports and or write new reports for this volume. All the reports 

received additional reviews and were further modified to conform to the USGS format. 

Detailed studies are continuing at these two sites to evaluate the long-term and shortterm effects of hydrocarbons and the dissolved and suspended constituents of produced water 

on soil and ground and surface waters and the natural processes that may be mitigating those 

effects. Results from these studies may serve to guide estimates of human and ecosystem risk 

at these and similar sites and the development of risk-based corrective actions by USEPA and 

Tribal environmental officials (Billingsley, 1999). Corrective actions are particularly needed 

in aging and depleted fields, where land use is changing from petroleum production to 

residential, recreational, agricultural or other uses (Carty and others, 1997). 

OSPER “A” and “B” Sites 

The two research sites, OSPER “A” and “B,” are located within the Lester and 

Branstetter leases, respectively, adjacent to Skiatook Lake, a 4,250-hectare reservoir 

completed in 1987 that provides drinking water to the local communities and is a major 

recreational fishery (fig. 1). The sites are located in the Central Oklahoma platform in the 

southeastern part of the Osage Reservation in northeastern Oklahoma (fig. 1). Both sites are 

in a dissected area of modest relief, with oak forests covering the slopes and tall grass present 

on most ridge crests. Geological mapping by Otton and Zielinski (this volume) show the area 

to be underlain by interbedded shale, siltstone, and sandstone. Thicker resistant sandstone 

units typically form the hill crests. Hill slopes are underlain by shale, siltstone, and thin 

sandstone beds. 

Because they met our selection criteria, the OSPER sites were selected for detailed 

multidisciplinary investigations in June 2000, following a two-year national search effort. 

The geologic and climatic settings of these sites resemble those of much of the major 

southern mid-continent oil- and gas-producing areas of the USA. Oil and gas production has 

occurred in these leases for about one hundred years, resulting in impacts that include soil 

salinization with resultant destruction of soil textures and deep erosion, death of proximal 

vegetation, stress on peripheral vegetation, salinization of surface and ground waters, 

saturation of soils with crude oil of varying age, and weathering and dispersal of crude oil 

components and trace elements. An important selection criterion that was met is the fact that 

the sites are located on Federal lands; the Osage Nation holds the mineral rights, the Bureau 

of Indian Affairs (BIA) and the EPA have trust responsibility, and the Army Corps of 

Engineers owns the surface rights at these sites (Kharaka and others, this volume). 

The OSPER “A” site, located in section 13, T22N, R10E, has an area of about 1.5 

hectare that is impacted by produced water and hydrocarbon releases that occurred primarily 

60-85 years ago (fig. 2). The site is underlain by 1) a surface layer of eolian sand of varying 

thickness (up to about 80 cm); 2) colluvium that ranges from large boulders of sandstone to 

thin, granule-pebble conglomerate; 3) weathered shale, siltstone, and sandstone; and 

4
0

N

B

B

B B

B B B B B

B

B

B

B

B B B B

B

B

B

B

B

B

B

B

B B

Legend

Oil-impacted soils

Sandstone outcrop

Slightly to deeply eroded areas

Wann Formation

Old redwood

Drainage trace tanks

Terrace edge in 

deeply eroded areas

Artifical fill, asphaltic 

oil and weathered oil

Clem Creek sand member Lower shale member, minor sandstone

Pennsylvanian

Late Pleistocene/Holocene

Colluvial 

gravel

Layer

Area Cobbles B and boulders

Aeolian sand, silt, and clay, 

B

P

P

P

P

?

Natural soil pedestal P within deeply eroded area

Trees

Trees

Trees

Trees

Trees

Trees

Trees

Grass,

forbs Road

Grass,

forbs

Grass,forbs 

isolated trees

Grass,forbs,

isolated trees

x

x

x

x

x

x

xx

x

x

x

x x

x x x

x

x

x x

x

x

x

x

AE13

AE14

AE15

AE16

AE18

AE17

AA01

AE01

AE02

AE19 AA03

AA02

AA04

AE04

AE09 AE10

AE11

AE12

AE06

AE07

AE05

AE08

AE03

AP-01

Skiatook

Lake 50 100 ft

0 10 20 30 m

0

TRANSECT

(Fig. 9)

Asphaltic pits 

• highly weathered oil 

• one pit contains relatively 

fresh tank sludge(?) 

Lower area (north)

• steeper slope 

• prominent salt scar 

(~2 m deep) 

• salt (& gypsum) at 

surface 

Upper area (south) 

• gentle slope 

• tree kills from early(?) 

salt releases 

• revegetated with 

grasses 

Figure 2. Geologic map of the OSPER “A” site showing the locations of the oil pits, 

other production features, drilled water wells and outline of the impacted areas. Note 

the location of the Cedar Creek arm of Skiatook Lake to the north of the site. The 

main arm of Skiatook Lake is just to the southwest. 

4) underlying unweathered bedrock. Much of the site appears to have been impacted by early 

salt-water releases that killed the pre-existing oak forest. The salt-impacted soils 

subsequently prevented younger oak trees from colonizing much of the site except where 

single trees or clumps of trees found favorable conditions. The gently sloping upper part of 

the site is slightly eroded in places and has been mostly revegetated with grasses, forbs, 

sumac, and a few trees. This area drains into the main arm of Skiatook Lake just off the map 

to the southwest. The lower, steeper, more heavily salt-impacted portion has been eroded to 

depths of as much as 2 m. Seepage of salt water from a shallow sandstone aquifer continues 

and active salt scarring persists. This area drains into the Cedar Creek arm of Skiatook Lake 

to the north (fig. 2). 

5
Drilling at the Lester Lease started in 1912, and most of the over 100,000 bbl of oil 

produced by 1981, was obtained prior to about 1937. Oil production, which was entirely 

from Bartlesville sand at depths of 450-524 m, ended about 10 years ago (BIA, unpublished 

lease records, 2000). Oil and produced water collected in two redwood tanks at the top of the 

site was transported via ditch to two roadside pits at mid-site. Remnants of decades-old 

produced water and hydrocarbon spills (now highly degraded and weathered oil) are 

scattered around the site. One pit at this site contains relatively fresh asphaltic oil and high 

salinity brine (Godsy and others, this volume). 

The “B” site, located within the Branstetter lease in sections 29 and 32, T22N, R10E, 

is actively producing and has ongoing hydrocarbon releases and salt scars that have impacted 

an area of about one hectare. The site includes an active production tank battery and adjacent 

large brine pit (fig. 3), two injection well sites, one with an adjacent small pit, and an old tank 

battery. The large pit is about 15 m from the shoreline of the Skiatook Lake; all the other 

sites are within 45 m of the lake. Three salt scars that were partly “remediated” in 2000 by 

saline soil removal, tilling and soil amendments, extend down slope from the active tank 

battery, the injection well/pit, and the old tank battery site to the lakes’ edge. Two small 

creeks cross the northern and southern parts of the site. The upper part of the site is 

characterized by a thin surface layer of eolian sand mixed with sandstone-clast colluvium

underlain by weathered and unweathered shale, whereas the lower part of the site is underlain 

by 1) a surface layer of eolian sand (20-70 cm thick); 2) colluvial apron and alluvial deposits 

of varying thickness comprised of sandstone pebbles, cobbles, and boulders with a fine sandy 

to clayey matrix; 3) weathered shale; and 4) unweathered bedrock (Otton and Zielinski, this 

volume). 

The Branstetter lease was initially drilled in 1938 and increased activity occurred in 

1947-51, when A.H. Ungerman purchased the lease. Approximately 110,000 barrels of oil 

were produced from the lease before water flooding for enhanced recovery began in 1953. 

Currently there are about 10 wells that produce 1-3 bbl/d oil, and 50-100 bbl/d brine; all the 

produced fluids are collected and separated in the tank battery adjacent to the large brine pit 

(S. Hall, oral communication, 2002). The two brine pits at this site are not lined and receive 

brine and hydrocarbon releases from broken pipes and tank leaks; they also receive large 

volumes of surface-water flow from precipitation. The brine in these pits is generally pumped 

into collection tanks by submersible pumps, but these occasionally fail causing filling and 

overflow of brine pits, as happened in November and December, 2001 for the large brine pit. 

Scientific Approach 

The complexity of the multiple processes operating at these sites requires a multidisciplinary team to examine the geology, geophysics, hydrology, geochemistry, 

microbiology, and ecosystem dynamics to generate a credible interpretive analysis useful to 

the stakeholders and the scientific community. The research team for this investigation is 

comprised of scientists from the Geologic, Water Resources, and Biologic Resources 

Disciplines of the USGS and from the USEPA, BIA and local universities. This team is 

unique in its ability to address the relevant issues, including the fate of the contaminants and 

site remediation and land use. 

6
Figure 3. View of the large brine pit , the active tank battery, and the partly 

remediated salt scar adjacent to Skiatook Lake at the OSPER “B” site (photo 

courtesy of Ken Jewell, USEPA). 

Intensive investigations aimed at mapping the geology and impacted areas and other 

cultural features at the OSPER sites started in February 2001 (Otton and Zielinski, this 

volume). Water, oil and gas samples were taken from eight oil wells located in the 

Branstetter lease and in areas adjoining the Lester lease to characterize the crude oil and 

produced water contaminant sources. Water samples were also obtained from Skiatook Lake 

and shallow groundwater wells in the region and from brine pits, seeps and creeks in both 

sites (Kharaka and others, this volume). Initial surface soil sampling (0-15 cm) was 

conducted at site “B” in March, 2001 to determine the chemical signature of added salts and 

the spatial distribution of soil salinity in relation to areas of visible salt scarring (Zielinski 

and others, this volume). Ground electromagnetic (EM) and DC resistivity geophysical 

surveys were carried out in September 2001, and the data were used to interpret the 

subsurface distribution of saline soil, water, and bedrock at both sites (Smith and others, this 

volume). 

A total of ~60 Geoprobe , auger and rotary wells (1-71 m deep) were drilled, cored, 

completed and sampled at both sites in February and March 2002. Three deep rotary wells 

were drilled as stratigraphic holes in nearby “unimpacted” areas. The location of the other 

wells were based on: (1) The presence of salt scars, excessive soil and rock erosion, brine and 

asphalt pits, degraded oil, dead trees and shrubs and other visible surface features; (2) results 

of electrical conductance, Cl, Br and SO4 measurements on aqueous leachates from samples 

of shallow soil (0-15 cm) and selected soil profiles (0.5-1.7 m); and (3) results of shallow 

7
penetrating (<10 m) electromagnetic (EM) and deeper (30-60 m) DC resistivity surveys. 

Additional Geoprobe and auger wells were drilled at both sites in November 2002 and in 

March and April 2003, but results from these are not discussed in this volume. 

Core samples from impacted and “pristine” areas were studied (Rice and others, this 

volume) using visual and microscopic description, X-ray powder diffraction of the bulk soil 

and clay-sized fraction, particle size analysis, cation exchange capacity, and selective 

extraction of iron species to establish the differences in the mineralogy, sorption of Na and 

other chemicals and geochemical behavior of soils impacted by saline water compared to 

those from unimpacted areas. A number of grab and core samples from impacted and 

“pristine” areas were also used by Kampbell and others (this volume) to determine a number 

of key parameters, including nitrates, organic matter, total petroleum hydrocarbons (TPH), 

conductivity, chlorides, and dehydrogenase activity (DHA - a measure of viable biomass) 

that are essential for the development of guidelines for stabilizing or restoring impacted 

areas. A series of oil, water, brine, and soil samples were characterized and analyzed for 

geochemical parameters that are indicative of microbial activity. Characterization of the 

resident microbial populations and the varying stages of weathering and biodegradation of 

oils were completed for a number of these samples and are reported by Godsy and others 

(this volume). 

Based on repeated water table measurements in wells, chemical analyses of water 

samples, and field observations, Herkelrath and Kharaka (this volume) developed conceptual 

models of the hydrology and solute transport mechanisms near the major brine pit at OSPER 

“B” site. They propose two main mechanisms for solute transport from the waste pit to the 

lake. One mechanism is the relatively slow and steady flow of saline ground water from the 

waste pit to the lake in a near-surface aquifer. The other mechanism is relatively fast 

overland flow of salt-laden runoff during rainfall. Using the USGS model SUTRA, they 

simulated steady-state ground-water flow and solute transport from the pit to the lake. 

Preliminary modeling results indicated that the solute travel time from the pit to the lake in 

saline ground water is 2-4 years. 

All the wells, other sampling sites and features were surveyed with high accuracy 

real-time kinematic (RTK) GPS equipment in June and July 2002. This differential 

correction method of surveying requires a GPS base station, a GPS rover unit and radio link 

between the units. The accuracy achieved is better than ±10 cm horizontally and vertically 

(Abbott, this volume). 

Initial Summary Results 

As detailed in the individual reports in this volume, a great deal has been 

accomplished in the last two years at the OSPER “A” and “B” sites, especially with regard to 

the geologic, geophysical, hydrologic and geochemical characterizations. Results to date 

show that impacts of produced water and associated hydrocarbons on soil and ground and 

surface waters at both sites and surrounding areas are widespread and pervasive. All wells 

show some degree of contamination from produced water and/or associated petroleum or its 

degradation products. Thus, it has been very difficult to obtain soil and water samples from

“pristine” areas. In fact, one of the two stratigraphic wells outside the OSPER “B” site, but 

close to a production well, showed both oil and brine contamination and the other showed 

8
impacts from produced water. A “background” well, drilled 0.6 km to the NW of the OSPER 

“A” site initially (March, 2001) had freshwater (450 mg/L TDS), low DOC values and other 

characteristics of the pristine local groundwater; repeated sampling did not change the 

inorganic composition of water from this well but DOC concentrations continued to increase. 

Our latest (June 2003) sample from this well showed no significant change in the inorganic 

composition of water, but small oil globules and relatively high concentrations of DOC and 

BTEX were obtained. 

Results of water samples from nearby oil wells, the tank battery at the “B” site, and 

brine pits and seeps indicate that the produced water source for both sites is/was a Na-Ca-Cl 

brine (~150,000 mg/L total dissolved solids), with relatively high concentrations of Mg, Sr, 

Fe, Mn and NH4, but low concentrations of SO4, H2S and dissolved organics (Kharaka and 

others, this volume). Results show that the area source oils are paraffinic-naphthenic light oil 

(~35o API gravity), containing n-alkanes as the dominant components unimpacted by 

biodegradation. The oils at the inactive “A” site are similar although vary in stages of 

biodegradation. Microbial populations at both sites are degrading the water-soluble crude oil 

compounds. The geochemical evidence and make-up of the microbial populations at both 

sites indicate that the systems are slightly different but based on free energy yields, are 

poised at the level of iron reduction (Godsy and others, this volume). An important result 

from this investigation is the fact that the distribution of the high salinity groundwater plumes 

mapped on the basis of chemical analysis of water are in general agreement with the 

distribution observed from aqueous leachate data from soil and bedrock core samples as well 

as from the geophysical surveys. 

Results at the OSPER “A” site show that the salts have essentially been removed 

from the sandy soil and underlying surficial sediments, but degraded and weathered oil 

persists on the surface of old oil and brine pits, close to sites of old tanks, on old channels 

that carried oil from tanks to the oil pits, and other impacted areas. Results also show a plume 

of high salinity water (5,000-30,000 mg/L TDS) is present at intermediate depths that extend 

from below the old oil and brine pits (see fig. 9, Kharaka and others, this volume) to Skiatook 

Lake. No liquid petroleum was found in the contaminated groundwater, but soluble 

petroleum byproducts, including organic acid anions and other VOCs are present. Results to 

date clearly show that significant amounts of salts from produced-water releases and 

petroleum hydrocarbons still remain in the soils and rocks of the impacted area after more 

than 60 years of natural attenuation. 

At the “B” site significant amounts of produced water from the two active brine pits 

percolate into the surficial rocks and flow towards Skiatook Lake.Only minor amounts of 

liquid petroleum leave the brine pits and reach Skiatook Lake. Preliminary hydrologic 

modeling indicates that the solute travel time from the brine pit to the lake in saline ground 

water is slow, requiring 2-4 years. The above results and conclusions are tentative and may 

be modified after additional sampling from existing and new wells, tracer tests, hydrologic 

parameter determinations and hydrologic and geochemical modeling are completed. 

Future Plans 

We expect that detailed geological, geophysical, hydrologic, geochemical and 

ecological studies at these two sites will continue for 3-5 more years, with the emphasis 

9
shifting from site characterization to investigating the relevant hydrogeochemical processes 

and determining the rates of transport and degradation of solutes. Additional deep drilling, 

however, is needed at the OSPER”A” site to map the depth and the horizontal boundaries of 

the 3-D plume of high salinity water (5,000-30,000 mg/L TDS) with chemical and isotopic 

characteristics similar to those of the source produced water. The depth of this plume is not 

currently well defined; the one well that penetrates into a deeper aquifer has lower salinity 

(~2,000 mg/L TDS), but high Fe, Mn and dissolved organics. The horizontal plume 

boundaries are also not well delineated, since all wells deeper than 2 m at the site encounter 

the plume. Drilling at the OSPER “B” site would be mainly to investigate brine penetration 

below a thick (>5 m thick) shale formation. 

The existing and future wells at the “A” site will be sampled to investigate the natural 

processes that modify the chemical composition of the groundwater plume. Processes of 

interest include mixing and dilution of saline groundwater with pristine groundwater and 

percolating water from precipitation; sorption; mineral precipitation/dissolution; 

evapotranspiration; and volatilization and bacterially mediated oxidation/reduction reactions. 

Ultimately, we plan to model the transport of reactive and conservative solutes in the shallow 

aquifer(s) and exchange with the Skiatook Lake water column. 

The rate of salt removal from the “A” site by surface runoff is being determined by 

measuring the volume and chemical composition of water flowing over a weir installed close 

to the Skiatook Lake in a location that captures most of the surface and ‘base’ flow from this 

site following precipitation. Results to date show that the present-day natural salt-removal 

processes at this site are slow, thus providing a valid explanation for the fact that large 

amounts of salts from produced-water releases still remain in the groundwater plume after 

more than 65 years of natural attenuation. 

It is likely that the rate of ground-water movement from the main produced-water pit 

at the “B” site to Skiatook Lake may be independently checked by looking at age-dependent 

changes in the radium-isotope composition of the produced water. A study is underway to 

examine changes in the Ra-228 to Ra-226 ratio between source water the pit and water in a 

shallow well near the lake’s edge. This technique relies on the half-life differences between 

Ra-228 (5.75 years) and Ra-226 (about 1600 years). Most produced waters contain modest 

(but measurable) activities of radium. 

Additional future studies would include the fate and transport of hydrocarbon 

degradation products, hydrocarbon-related trace elements, produced-water salts, and 

produced-water trace elements, especially the toxic components, including uptake and 

residence in soils, reservoir sediments, oak trees, and other macrobiota. Our goal is to 

quantify the sub-lethal effects of produced water salt and hydrocarbon releases on oak 

species – tree ring growth and foliar response to major and minor elements and soluble 

hydrocarbons. There is a proposal, not yet funded, to investigate the impacts of produced 

water and associated hydrocarbons on clam species and other biota in the Skiatook Lake. 

Finally, four plots have been planted with Bermuda grass and a selection of trees to study site 

restoration. We anticipate major findings from each of these investigations and tasks, and 

results that would be important not only to petroleum sites in the Osage County, but 

throughout the USA and beyond. 

10
Acknowledgements 

We are grateful to the Osage Indian Nation, to the Army Corps of Engineers and 

Bureau of Indian Affairs, as well as the field operators for permission to conduct research at 

these sites. We are grateful also for the financial support for this research provided by DOE 

National Petroleum Technology Office, E&P Environmental (Nancy Comstock and Dan 

Gurney, project coordinators). Most of the drilling at these sites has been carried out with 

equipment and operators from USEPA, Ada Research Laboratory (Donald Kampbell, 

Supervisor). James Thordsen spent considerable time and effort setting up figures and tables 

for all the chapters and formatting the text, including the references to meet the USGS format 

for WRI reports. 

References 

Abbott, M.M., 2000, Water quality of the Quaternary and Ada-Vamoosa aquifers on the 

Osage reservation, Osage county, Oklahoma, 1997: Water-Resources Investigations 

Report 99-4231, 76 p. 

Abbott, M.M., [this volume] 2003, Real-Time kinematic (RTK) surveying at the OsageSkiatook Petroleum Environmental Research sites, Osage County, Oklahoma: U.S. 

Geological Survey Water-Resources Investigations 03-4260, p. 147-155. 

American Society for Testing and Materials, 1999, ASTM standards on assessment and 

remediation of petroleum release sites: ASTM, Committee E-50 on Environmental 

Assessment, 126 p. 

Billingsley, Patricia, 1999, Oklahoma’s oilfield pollution risk-based assessment and 

cleanup program, in Sublette, Kerry, ed., Proceedings of the 6th International 

Petroleum Environmental Conference: Environmental Issues and Solutions in 

Petroleum Exploration, Production and Refining: Houston, TX, University of Tulsa, 

CD-ROM, p. 1011-1020. 

Carty, D.J., Crawley, W.W. and Priebe, W.E., 1997, Remediation of salt-affected soils at 

oil and gas production facilities: American Petroleum Institute, Health and 

Environmental Services Department, API Publication Number 4663, paginated in 

sections. 

Collins, A.J., 1975, Geochemistry of oil field waters: Elsevier Scientific Pub. Co., New 

York, 496 pp. 

Dickey, P.A., 1959, The first oil well: Journal of Petroleum Technology, v. 9, p. 14-26. 

Energy Information Administration (EIA), 2003, Annual Energy Outlook 2003 With 

Projections to 2025: Overview. Washington DC. 

Federal Leadership Forum, 2000, Interagency coordination of environmental 

management of oil and gas resources, Greater Rocky Mountain Region, Fact Sheet: 

U.S. Government Printing Office 2000-845-114. 

Godsy, E.M., Hostettler, F.D., Warren, Ean, Paganelli, V.V., and Kharaka, Y.K., [this 

volume] 2003, The fate of petroleum and other organics associated with produced 

water from the Osage-Skiatook petroleum environmental research site, Osage 

County, Oklahoma: U.S. Geological Survey Water-Resources Investigations 03-

4260, p. 84-102. 

11
Herkelrath, W.N. and Kharaka, Y.K., [this volume] 2003, Hydrologic controls on the 

subsurface transport of oil-field brine at the Osage-Skiatook petroleum

environmental research “B” site, Oklahoma: U.S. Geological Survey WaterResources Investigations 03-4260, p. 111-123. 

Kampbell, D.H., An Y-J., Smith, M.W., and Abbott, M.A., [this volume] 2003, Impact 

of oil production releases on some soil chemical properties at the OSPER sites: U.S. 

Geological Survey Water-Resources Investigations 03-4260, p. 103-110. 

Kharaka, Y.K., and Thordsen, J.J., 1992, Stable isotope geochemistry and origin of 

waters in sedimentary basins, in Clauer, N. and Chaudouri, S., eds., Isotope 

Signatures and Sedimentary Records: Germany, Springer-Verlag, p. 441-466. 

Kharaka, Y.K., Thordsen, J.J., and Ambats, G., 1995, Environmental degradation 

associated with exploration for and production of energy sources in USA, in

Kharaka, Y.K., and Chudaev, O.V., eds., Water-Rock Interaction (WRI-8), 

Rotterdam, A.A. Balkema, p. 25-30. 

Kharaka, Y.K., Lundegard, P.D., and Giordano, T.H., 2000, Distribution and origin of 

organic ligands in subsurface waters from sedimentary basins, in Giordano, T.H., 

Kettler, R.M. and Wood, S.A., eds., Ore Genesis and Exploration: The Role of 

Organic Matter: Reviews in Economic Geology, v. 9, p. 119-131. 

Kharaka Y.K., Thordsen, J.J., Kakouros, Evangelos, and Abbott, M.M. [this volume] 

2003, Fate of inorganic and organic chemicals in produced water from the OsageSkiatook Petroleum Environmental Research sites, Osage County, Oklahoma: U.S. 

Geological Survey Water-Resources Investigations 03-4260, p. 56-83. 

Kharaka, Y.K. and Hanor, J.S., 2003, Deep fluids in the continents: I. Sedimentary 

basins. In Drever, J.I., ed., Treatise On Geochemistry, v.16, p. 294-336. 

Otton, J.K., Asher-Bolinder, Sigrid, Owen, D.E., and Hall, Laurel, 1997a, Effects of 

produced waters at oilfield production sites on the Osage Indian Reservation, 

northeastern Oklahoma: U.S. Geological Survey Open-File Report 97-28, 48p. 

_____1997b, Effects of produced water at some oilfield production sites in southern 

Illinois: U.S. Geological Survey Open-File Report 97-448, 99p. 

Otton, J.K., Zielinski, R.A., Owen, D.E., Asher-Bolinder, Sigrid, and Hall, Laurel, 

1997c, Environmental effects of produced waters at oilfield production sites in the 

Big Sinking Creek and Schumaker Ridge areas, Lee County, Kentucky: U.S. 

Geological Survey Open-File Report 97-511, 41p. 

Otton, J.K. and Zielinski, R.A., 1999, Chemical criteria for determining the origin and 

dispersion of highly soluble salts in soils and waters near an oilfield operation, 

Logan County, Colorado, in Sublette, Kerry, ed., Proceedings of the Fifth 

International Petroleum Environmental Conference- Environmental issues and 

solutions in petroleum exploration, production and refining, October 20-23, 1998, 

Albuquerque, New Mexico: South-central Environmental Resource Alliance and 

the University of Tulsa, , CD-ROM publication, p. 953-973. 

Otton, J.K., Breit, G.N., Kharaka, Y.K. and Rice C.A., 2001, A national produced-water 

geochemistry database: http://energy.cr.usgs.gov/prov/prodwat/intro.htm.

Otton, J.K. and Zielinski, R.A., [this volume] 2003, Produced water and hydrocarbon 

releases at the Osage-Skiatook petroleum environmental research studies, Osage 

county Oklahoma: Introduction and geologic setting: U.S. Geological Survey 

Water-Resources Investigations 03-4260, p. 14-41. 

12
Rice, C.A., Cathcart, J.D., Zielinski, R. A., and Otton, J.K., [this volume] 2003, 

Characterization of soils and rock at an active oil production site: Effects of brine 

and hydrocarbon contamination: U.S. Geological Survey Water-Resources 

Investigations 03-4260, p. 133-146. 

Richter, B.C. and Kreitler C.W., 1993, Geochemical techniques for identifying sources 

of ground-water salinization: Boca Raton, C. K. Smoley, CRC Press, 258 p. 

Smith, B.D., Bisdorf, R.J., Horton, R.J., Otton, J.K., and Hutton, R.S., [this volume] 

2003, Preliminary geophysical characterization of two oil production sites, Osage 

county, Oklahoma-Osage Skiatook petroleum environmental research project, U.S. 

Geological Survey Water-Resources Investigations 03-4260, p. 42-55. 

USEPA, 1987, Management of wastes from the exploration, development and 

production of crude oil, natural gas and geothermal energy: EPA/530-SW-88-003. 

Wilson, M.J., and Frederick, J.D., eds., 1999, Environmental engineering for exploration 

and production activities: Society Petroleum Engineers Monograph Series, 1999, v. 

18, 114 p. 

Zielinski, R.A., Otton, J.K., and Budahn, J.R., 1998, Use of radium isotope data to assess 

NORM contamination at an E&P site, in Sublette, Kerry, ed., Proceedings of the 

Fourth International Petroleum Environmental Conference, Environmental issues 

and solutions in petroleum exploration, production and refining, September 9-12, 

1997, San Antonio, Texas: South-central Environmental Resource Alliance and the 

University of Tulsa, 15 pages, unpaginated text. 

Zielinski, R.A., Rice, C.A., and Otton, J.K., [this volume] 2003, Use of soil extracts to 

define the extent of brine-impacted soils at the Osage-Skiatook Environmental 

Research “B” site, northeastern Oklahoma: U.S. Geological Survey WaterResources Investigations 03-4260, p. 124-132.

13
Produced Water and Hydrocarbon 

Releases at the Osage-Skiatook Petroleum 

Environmental Research Sites, Osage 

County, Oklahoma: Introduction and 

Geologic Setting 

By James K. Otton and Robert A. Zielinski 

Abstract 

The U. S. Geological Survey (USGS) is investigating the impacts of produced water 

and hydrocarbon releases at two research sites adjacent to Skiatook Lake in southeastern 

Osage County near Tulsa, Oklahoma. Site “A” is an area where produced water and 

hydrocarbon releases occurred primarily 65-90 years ago in an area of oak forest. The site is 

located in section 13, T22N, R10E near the neck of a small peninsula that extends into Lake 

Skiatook. The entire site is underlain by a surface layer of eolian sand and colluvium, and 

weathered and unweathered shale, mudstone, siltstone, clayey sandstone, and sandstone. 

Much of the site appears to have been impacted by early salt-water releases that killed the 

oak forest. The gently sloping upper part of the site is slightly eroded in places whereas the 

lower, steeper, more heavily salt-impacted portion has been eroded to depths of as much as 2 

m. The site has been mostly to partly revegetated with forbs and grasses. However, only a 

few oak trees have established themselves. Oil from two redwood tanks at the south part of 

the site was transported via ditch to two roadside pits at mid-site. Oil spills from pipeline 

breaks and other tanks (no longer present) are scattered around the site. The oil in the west 

pit is highly weathered, but the east pit contains what appears to be relatively fresh asphaltic 

material.

Site “B” is located in section 29, T22N, R10E at the west end of a small bay of Lake 

Skiatook. The site includes an active production tank battery and adjacent large pit, two 

injection well sites, one with an adjacent small pit, and an old tank battery platform, all 

within 45 m of the lake. Hillslopes on the upper part of the site are characterized by a thin 

surface layer of eolian sand and sandstone clasts, underlain by weathered and unweathered 

shale. The lower terraced part of the site is underlain by a surface layer of eolian sand and 

sandy to clayey colluvium and alluvium about 1.5 m thick and weathered and unweathered 

shale. Three salt scars extend downslope from the active tank battery, the injection well/pit, 

and the old tank battery platform to the lake edge. The area underlain by shallow saline 

ground water is substantially larger than the salt-scarred areas. Hydrocarbons can be 

detected in the shallow ground water adjacent to the active pit and at the lake edge below the 

pit. 

14
Introduction 

In February 2001, the U. S. Geological Survey (USGS) initiated investigations of the 

impacts of produced water and hydrocarbon releases at two research sites adjacent to 

Skiatook Lake in southeastern Osage County near Tulsa, Oklahoma (figs. 1 and 2). These 

studies are designed to provide an in-depth understanding of the impacts of highly saline 

produced water and hydrocarbons on soils, vegetation, surface water and shallow ground 

water, and lacustrine fauna. These sites were chosen because of the similarity of the geologic 

and climatic setting of the sites to broad areas of the south-central U.S. oil-producing region, 

the presence of Federally owned lands and mineral rights under the jurisdiction of the 

Department of the Interior, and an adjacent public water supply and recreational fishery. 

Both sites are on land owned by the U.S. Army Corps of Engineers. The Osage Nation holds 

the mineral rights. Project results can be used to plan and evaluate cost-effective site 

remediation strategies, determine the rate of site restoration by natural processes, develop 

simple assessment techniques for other oil and gas production sites, and establish historic 

natural resource damage. 

Both sites are in a dissected area of modest relief underlain by interbedded shale, 

mudstone, siltstone, and sandstone of the Pennsylvanian Wann Formation. Thick, resistant 

sandstone units typically form the hillcrests. Shale, mudstone, siltstone, and thin sandstone 

beds underlie hillslopes. Core drilling by the USGS indicates that the depth of weathering of 

the bedrock is about 10-25 m on the ridges and 5-6 m in small stream valleys. 

These sites are located in the Cross Timbers ecosystem area of northeastern 

Oklahoma (Kuchler, 1964). Oak forests cover the hillslopes. The principal oak species are 

black jack oak (Quercus marilandica) and post oak (Quercus stellata). Grassslands and 

stands of oak occur on most ridge crests. Historically, this area has been used for grazing 

and hunting. Under natural conditions, fires control oak encroachment on grasslands. 

In February and March of 2001, the sites were surveyed and mapped to characterize 

the local geology and cultural features. In February and March of 2002, both sites were 

drilled with a rotary rig, a hollow-stem auger rig, and a direct-push tool (Geoprobe). 

This paper provides the geographic and geologic framework for understanding and 

interpreting the results of the accompanying papers that follow. 

Figure 1. Location map for the Skiatook Lake area in southeastern Osage County. 

15
Figure 2. 1999 Landsat image of the Lake Skiatook area showing the location of 

research sites “A” and “B”. State Highway 20 traverses east-west across the middle 

of the image. 

“A” Research Site 

The “A” site occurs in section 13, T22N, R10E at the neck of a small peninsula that 

extends into Skiatook Lake between the Cedar Creek arm of the lake to the east and the main 

stem (Hominy Creek) (figs. 2 and 3) to the southwest. The site is characterized a mostly 

open area within oak forest. Vegetation mapping (fig. 4) shows that the site can be divided 

into two sections, one, north of the road, and the other, south of the road. The open area 

south of the road is vegetated by grasses, forbs, sumac, isolated oak, willow, and locust trees, 

and blackberry. A large sandstone outcrop area, devoid of vegetation except for lichen and 

mosses, lies in the southwest corner of the site. Remnants of redwood oil tanks sit on 

sparsely vegetated sandstone outcrop in the southeast corner. Patchy weathered asphaltic oil 

covers an area surrounding the tanks. Several small oak trees grow within the area of 

weathered asphalt. A patch of immature oak trees occurs just north of the redwood tanks. 

16
Figure 3. 1995 aerial photo of part of section 13 showing the location of the “A” 

research site (outlined in white, about 140 x 230 m) adjacent to Skiatook Lake. The 

pencil lines are quarter-section delineations. Note the Highway 20 bridge at lower 

right. 

A narrow corridor of weathered asphalt extends from the area around the two tanks 

north to two unlined pits (A and B, fig. 4). This feature follows an unlined trench (fig. 5) that 

appears to have been designed to carry produced fluids from the two redwood tanks to the 

pits. This trench cuts across the natural topographic slope, which is northwest on this part of 

the site. The channel splits just upslope from the two pits with one branch leading to each 

pit. A badly corroded pipe exits pit A through its northern berm, and this pipe likely served 

to allow oil to be pumped from the pit into a tanker truck. The main channel changes 

direction about halfway between the tank area and the pit area and it appears that oil 

overtopped the channel at this point and spilled onto adjacent soils (fig. 4). Pit A contains 

tarry or asphaltic hydrocarbon (fig. 6) on most of which which no vegetation grows. Oak 

trees lie to the east of the pit and a large, isolated oak tree grows just to the north of the pit 

berm (fig. 6). Pit B is located to the west and shares a common berm with Pit A (figs. 4 and 

7). This pit contains weathered asphalt. Sparse grasses grow on much of the surface. Water 

ponds at the low (north) end of the pit after rainfall. Two small, low areas occur west and 

southwest of the two pits (fig. 4). During wet weather, the ground in these low areas is water 

saturated. 

17
A B 

Figure 4. Vegetation map of the ”A” site. 

18
Hydrocarbons occur in soil northeast and southeast of the redwood tank area (fig. 4). 

Both of these oil occurrences lie adjacent to repaired breaks in a pipeline passing the site and 

appear to be more recent than oil associated with the tanks, based on the degree of 

weathering. Weathered hydrocarbons also occur in a patch of soil about 6 x 6 meters just 

west of pit B. 

In the southern part of the site near the two redwood tanks, the soil tends to be sandy 

because of the sandstone outcrop and subcrop. Weathered asphaltic oil fragments, mixed 

with sand, have washed downslope from the redwood tank area and the area of the eastern 

pipeline break forming areas of sandy outwash barren of vegetation contiguous with the 

initial spills. 

This area south of the road drains in two divergent directions (fig. 8). A drainage 

divide crosses this area from southeast to northwest such that most of the area south of the 

road drains northwestward then westward off the site, eventually into a tributary arm of the 

main (Hominy Creek) stem of the lake. An area adjacent to the road that includes the two 

pits lies north of the drainage divide. Thus the surface area around the pits appears to drain 

mostly northward towards the Cedar Creek arm of the lake (figs. 4 and 8). 

North of the road is an area of deeply eroded and disturbed soils (figs. 4 and 9). 

Sparse grasses grow except where the soil salt content is high. The deeply eroded section is 

largely delineated by a terrace edge (fig. 4). Much of the section of disturbed soils (fig. 4) is 

oriented approximately east-west across the south-central part of the area north of the road. 

Features on the 1937 aerial photo for the site suggest that this is the trace of an older road. 

The road was apparently moved southward as headward erosion of two gullies impinged on 

the roadbed. Three soil pedestals, in which the pre-erosion soil profile is preserved, occur 

within the deeply eroded section (see small, irregular hachured areas in fig. 4; two pedestals 

are shown in fig. 10). They are capped with grasses and forbs. A small oak tree grows on 

one pedestal. A small promontory on which two oak trees are growing extends into the 

deeply eroded section from the southwest. The area is drained by several washes that 

coalesce to the north before leaving the site. Flow occurs in these drainages only after 

rainfall, although it may persist for several days in the drainage at the north edge of the site 

(figs. 4 and 10). Bedrock, including three outcrops of resistant sandstone ledges, is exposed 

in the deeply eroded section. A small wet soil area occupies the west corner of the deeply 

eroded section (fig. 4). 

Effluorescent salt crusts are observed at various times of the year. They commonly 

occur on the lower part of the central sandstone outcrop (fig. 4, north central part of deeply 

eroded area) and on the surface of the alluvium along the channel below the central outcrop. 

Salts also are common around the soil pedestal in the south-central part of the deeply eroded 

area (fig. 11). 

19
Figure 5. Trench with weathered 

asphalt between redwood tanks 

and pits (looking south upslope 

towards the location of the tanks). 

Note the sumac with one or two 

small oaks to the right and the 

mature oak forest in the 

background above the site. 

Figure 6. Pit “A” with asphaltic 

hydrocarbons. The central part of 

the pit is devoid of vegetation. 

Sparse grasses grow in the upper 

part (close to the viewer). 

Figure 7. Pit “B” with highly 

weathered hydrocarbons and 

sparse grasses. The 

photographer is standing on the 

berm between the two pits. The 

north edge of the pit berm is to 

the upper right. A willow tree 

grows just beyond this berm (see 

fig. 4). Sumac is growing beyond 

the pit to the left. 

20
Figure 8. Topographic map of the “A” site showing the drainage divide.

21
Figure 9. The deeply eroded 

area, August 2000, from near the 

road looking north. 

Figure 10. Surface flow 

disappearing below the surface of 

the stream alluvium within the 

deeply eroded area, March 10, 

2001. Two soil pedestals are 

delineated by arrows (right and 

left). Sandstone bedrock outcrop 

is delineated by a rectangle. 

Figure 11. Salt effluoresence 

adjacent to soil pedestal. 

22
Lease History 

The following lease history is summarized from files of the Bureau of Indian Affairs in 

Pawhuska, OK. Initial drilling on the lease was in late 1912 and 1913. Production is entirely 

from the Pennsylvanian Bartlesville Sand (local, informal name) at depths of 450-425 m. Initial 

oil production for some of the 1913 wells was as much as 100 barrels/day (bbls/day). However, 

as of July 1, 1915, aggregate oil production for 8 wells was 46 bbls/day. The most recent drilling 

dates from 1976 and 1977 and was designed to retrieve oil from part of the lease that was due to 

be flooded when the Skiatook Lake was completed (as it was in 1984). 

Most wells have been plugged and abandoned, some as early as 1913. Several well sites 

are presently under the waters of Skiatook Lake. All of these have been plugged and abandoned. 

However, many of these wells were plugged prior to the 1950s with “sand pumpings”, wood, 

lead, rock, “heavy mud”, and “blue shale.” These had to be replugged prior to flooding of the 

reservoir because these materials tend to fail. The usual reason for plugging and abandoning was 

low production. One well, plugged in 1931, was producing 2 gallons of oil and 25 bbls of 

water/day. Another, plugged the same year, was producing 1.5 bbls of oil and 20 bbls water/day. 

Production through 1981 was about 100,000 bbls of oil. Anecdotal reports indicate that 

the lease produced substantial quantities of gas that was used locally to power pumping units 

(Marvin Abbott, USGS, 2001, oral communication). As of 2002, one well on the lease still had a 

gas-fired pump. Records do not indicate that the lease was ever considered for waterflooding. 

At least one production well was converted to a salt-water disposal well. One initial production 

report notes that the oil was 35o

 API gravity. 

Geology of the “A” Site 

The site is typically underlain by: 1) a surface layer of modern eolian sand or mixed 

eolian and slopewash sand of varying thickness (0 cm to 1 m); 2) sandy or clayey colluvium that 

ranges from a thin layer of granule-pebble weathered sandstone-clast conglomerate to large 

boulders of sandstone; 3) weathered shale, mudstone, siltstone, clayey sandstone, and sandstone; 

and 4) similar underlying unweathered bedrock. The eolian sand, colluvium, and the uppermost 

part of the weathered bedrock are exposed in the deeply eroded area and were also observed in 

several Geoprobe holes at the site. A more complete section of weathered bedrock down to and 

penetrating into unweathered bedrock was observed in auger holes. 

Bedrock Geology 

Lithology 

The bedrock units (figs. 12 and 13) mapped at the surface at the “A” site are part of the 

Pennsylvanian Wann Formation (Gardner, 1957). The sandstone in the uppermost part of the 

site near the redwood tanks (figs. 12 and 13) is herein mapped as the lower part of the Clem

Creek Sandstone Tongue of the Wann Formation whereas the underlying rocks which are locally 

exposed in the lower part of the site belong to the lower shale member which here is comprised 

of beds of shale, siltstone, clayey sandstone, sandstone, and mudstone. 

The lowermost part of the Clem Creek sand forms the sandstone outcrop in the southwest 

corner of the open area (fig. 12). Patches of sandstone interspersed with thin sandy soil occur 

around the two redwood tanks showing that the Clem Creek sand also underlies the tanks. 

23
Figure 12. Geology of the “A” site showing locations of drillholes and cross sections. 

24
Figure 13. Generalized bedrock section at “A” research site. Thicknesses are 

estimated from contour map. Section is part of the Pennsylvanian Wann Formation 

(Gardner, 1957). 

The contact between the Clem Creek tongue and the underlying sequence is not exposed on the 

site, but can be recognized by a gentle break in slope at the low, north edge of laterally 

discontinuous exposures of nearby sandstone. 

Bedrock is not exposed between outcrop of the Clem Creek Sandstone Tongue near and 

southwest of the redwood tanks and the road that traverses the site. Shallow auger holes south of 

the road (AE05, 06, 07, fig. 12) show that the bedrock in this area is comprised mostly of clayey 

sandstone, with lesser sandy shale and siltstone. A single large sandstone boulder occurs in the 

gently eroded area west of the pits (“B”, fig. 12). It is unclear whether this is a colluvial boulder 

derived from sandstone outcrops upslope or outcrop of an underlying resistant sandstone layer 

within the bedrock. 

North of the road, in the deeply eroded area, clayey sandstone, mudstone, shale, siltstone, 

and sandstone crop out. All units are weathered and most units form poor exposures except in 

some of the deeper gullies. Resistant sandstone ledges crop out in three areas: the west edge, the 

center, and the north part of the deeply eroded area (fig. 12). The outcrop at the west edge 

consists of cross-bedded sandstone. The weathered surface is mottled grayish orange, yellow 

gray, and olive gray1

. Small surface pits weather moderate yellow brown. 

 

1

 Colors used here and elsewhere are derived from the “Rock Color Chart” published by the Geological Society of 

America. 

25
The resistant sandstone outcrop in the center is exposed in a deep gully where it is 

underlain by less resistant clayey sandstone and sandy mudstone. It consists of thickly bedded 

sandstone. Small pits pockmark most exposed sandstone surfaces. Pits up to about 10 cm across 

have formed locally in the weathered surface. Broken surfaces are very light gray to light gray in 

color whereas the weathered surfaces are typically mottled very light gray and dark yellow 

orange to moderate yellow brown, occasionally moderate red to gray red. The small pits 

coincide with vertical burrows whose cross-sections can be seen on some weathered surfaces or 

on freshly broken rock. 

The sandstone outcrop to the north consists of thickly bedded sandstone, which is very 

light gray to light gray on freshly broken surfaces. It weathers dark yellow orange to moderate 

yellow brown, occasionally moderate red to gray red. This outcrop is weakly pitted in exposures 

near the lake and at the south end of the outcrop. Except for the intervening patch of overlying 

colluvium and eolian sand, this outcrop would be continuous with the sandstone in the center. 

To the southeast of the deeply eroded area is an arcuate zone of large flat slabs of 

sandstone up to 3.6 m across mapped as part of the colluvium (ENE-trending, light reddish 

brown area marked by a string of “B”s in fig. 12). These sandstone slabs dip gently downslope 

along the length of the exposure. Many are contiguous, but in some places gaps occur between 

slabs. These sandstone slabs are interpreted as large pieces of a well-indurated bed that have 

weathered from the outcrop, have been undercut by erosion of the less-resistant underlying 

sediment, and have moved downslope. If so, the sandstone bed from which these slabs are 

derived may lie beneath the overlying surficial cover a few meters upslope. It appears that this 

sandstone bed does not extend westward across the width of the research site as no sandstone 

ledge is exposed along strike in the deeply eroded area where gullies extend southward towards 

the edge of the road (fig. 12). 

The bedrock units exposed at the surface in the deeply eroded area persist in the 

subsurface and were observed in Geoprobe and auger holes as portrayed in figures 14 and 15. 

Figure 14 is an east-west cross section along the road through augerholes AA04, AA02, and 

AA03. These three augerholes intercepted sandstone, clayey sandstone, mudstone, and shale. 

Some thin coaly beds were intercepted in AA04. The sections are dissimilar enough between the 

three holes that no correlation from one hole to the next seems reasonable. Unweathered 

bedrock was intercepted in AA02 and AA04 at depths of 14.4 m and 4.6 m, respectively. AA03 

did not penetrate unweathered bedrock. 

Figure 15 is a north-south cross section that extends from the sandstone outcrop area 

north to a point close to the lake. All holes south of the road are shallow. Thus, bedrock 

information is limited in that part of the cross section. 

Structure 

The sedimentary section on the peninsula is everywhere very gently dipping, and the 

regional dip is on the order of 1-2o

 to the west (Gardner, 1957). Locally in the Skiatook Lake 

area, however, the section is faulted and gently folded. Small domal structures occur in the 

section that are often the locus of oil accumulation in the subsurface. 

26
Figure 14. East-west cross section along the road showing thin surficial sediments and underlying be

in depth of weathering between hole AA04 and AA02. See figure 12 for location of cross section. 
Figure 15. North-south cross section extending from the sandstone outcrop area north to a point clos

showing surficial sediments and underlying bedrock. See figure 12 for location of cross section. 
The sandstone bedrock ledge in the northern part of the deeply eroded area extends 

southwest to the outcrop in the center of the deeply eroded area, interrupted only in one area 

by overlying uneroded colluvium and eolian sand. Along its extent, the upper contact 

appears to rise in altitude from about –35 feet with respect to datum to about –29 feet with 

respect to datum (figs. 8 and 12). If so, this information suggests a local southeasterly dip for 

this sandstone bed, although the strike and dip are not measurable without at least one 

additional reference point because the outcrop is so linear. In the central sandstone outcrop, 

one bedding surface in the lower part of the exposure shows a series of filled fractures, the 

most prominent of which are oriented 040o

, approximately parallel to the trend of the 

sandstone outcrop. These fractures may be related to a local structural feature, such as a 

small fault or the crest of a small anticline or both. The transition from weathered bedrock to 

unweathered bedrock in both AA04 and AA02 takes place where the section is changing 

from dominantly sandstone to dominantly shale (fig. 14). This transition is offset about 10 m

vertically between the two holes. A fault may be inferred between AA04 and AA02. The 

apparent dip on the sandstone beds at the surface in the deeply eroded area may represent 

drag on a normal fault 

Specific structural interpretations cannot yet be drawn from the exposures in the 

deeply eroded area or from the drillhole data and mapping of the rest of section 13 may have 

to be completed to determine whether faults or small folds are present. 

Surficial Geology 

The surficial deposits consist of colluvium, eolian sand, and mixed eolian sand and 

sandy slopewash. These units are exposed in the deeply eroded area north of the road and in 

the more gently eroded areas west and southwest of the two pits south of the road (fig. 12). 

The colluvium ranges from a thin layer of weathered granule-pebble sandstone-clast 

conglomerate to large boulders of sandstone within a sandy matrix. The weathered granulepebble sandstone-clast conglomerate is the most widespread facies, occurring in the gently 

eroded areas west of the pits and around most of the margin of the deeply eroded area. These 

granule to pebble beds blanket parts of the deeply eroded area forming small terraces (figs. 8 

and 12) adjacent to some of the stream channels. The granule to pebble colluvium and 

overlying eolian sand are well exposed in the soil pedestal in the north-central part of the 

deeply eroded area (fig. 16). Locally, a clayey colluvial facies is present. This facies 

consists of isolated sandstone clasts in a clayey matrix comprised of weathered shale. It 

appears to consistently underlie the sandy granule-pebble colluvium, but additional 

exposures need to be documented to confirm that relationship. 

The boulder beds in the colluvium occur downslope from outcrop or subcrop of 

resistant sandstone beds on the northwest and northeast sides of the deeply eroded area 

(marked by “B” in the northern part of fig. 12). The boulders that occur about 10-15 m

north-northeast of the sandstone outcrop at the west edge of the deeply eroded area (fig. 12) 

are identical in appearance (presence of crossbeds, color and weathering characteristics) to 

the sandstone in the outcrop and thus are inferred to have been derived from it. A train of 

sandstone cobbles and boulders is also exposed in the small scarp along the northeast edge of 

the deeply eroded area. These boulders resemble the sandstone slabs found to the southeast 

(discussed above) and may be derived from that outcrop/subcrop area. 

29
Throughout the central and northern parts of the site, eolian sand forms a discrete 

layer that mantles the underlying colluvium and is widely exposed at the surface in areas 

around and within the deeply eroded area (figs. 12, 14, 15, and 16). It is composed of very 

well sorted, fine to very fine sand grains. Thin pebbly layers and isolated sandstone pebbles 

occur within the lower part of the eolian sand suggesting that the eolian sand has been locally 

reworked by slopewash, since the sandstone pebbles are derived from upslope exposures of 

weathered bedrock. An A soil horizon, characterized by stained fine sand, is developed in the 

upper part of the eolian sand layer (fig. 16). In the south part of the site, the eolian sand 

appears to be mixed with sand derived from weathering of the sandstone bedrock exposed 

there. 

Figure 16. Stratigraphic section exposed in a soil pedestal within the deeply eroded 

area. The pick is 0.65m long. Sandstone clasts below the pick are eroded from the 

colluvial layer. 

Hydrology 

During wet periods such as early March 2001, water flows across the surface in small 

drainage ways and water-saturated ground occurs at the surface at several localities within 

the research site Most of the drainage ways and saturated localities are marked in blue or 

with a marsh symbol on figures 4 and 12. Present, but not mapped in figure 12, is modern 

alluvium that occupies the valley floor under the main channel for a few tens of meters 

upvalley from the lake. Based on the observed textures of the units exposed in the deeply 

eroded area and the location of wet places, it seems likely that the colluvium and the eolian 

sand are the most permeable units on the site. Among the bedrock units, it seems likely that 

the sandstone beds are the most permeable. Following rainfall, water seeps from the 

sandstone outcrop in the center of the deeply eroded area days after the rest of the site has 

dried up (fig. 10). Ephemeral salt crusts form on the lower parts of the sandstone outcrop 

and on the surface of the alluvium as drying occurs. 

30
“B” Research Site

The “B” site occurs in the southeast corner of 28, T22N, R11E in southeastern Osage 

County about 5.3 km southeast of the “A” site. It consists of a mostly open area on a 

hillslope and terrace at the west end of a small bay off the main part of Skiatook Lake. Two 

small streams feed into the bay to the north and south of the research site. The open area is 

surrounded by mature oak forest that covers the adjacent hillslopes. Access roads cross the 

site and traces of an older roadbed marked by limestone gravel occur in the central part of the 

site. The open area is occupied mainly by grasses and forbs, cut and fill, pits, salt scars and a 

few isolated oak trees and a few small groves of oaks (figs. 18 and 19). 

At least three tank batteries have been constructed at this site. An active tank battery 

and adjacent pit about 26 m across occur in the south part of the site. A salt scar extends 

from the east edge of the pit berm down to the lake (figs. 18 and 19). An old tank battery 

site, presently (2002) marked by a flat graded area with some piles of rubble, occurs in the 

central part of the site (fig. 19). A second salt scar extends down to the lake from the east 

edge of this graded area. Two tanks were removed in 1999. A tank, injection well, and pit 

about 10 m across occur in the north part of the site and a third salt scar extends downslope 

towards the lake from the east edge of the pit berm (fig. 19). This salt scar terminates in a 

shallow pit separated from the lake by a low berm. An additional injection well occurs on 

the northeast part of the site across the north creek (fig. 19). 

Oil-saturated soils occur on the hillslope to the west of the southern tank battery. 

They are associated with breaks in two pipelines (unmapped) that traverse the upper part of 

the site. Another area of oil-saturated soil occurs just east of the pit adjacent to the southern 

tank battery. The 1960 aerial photo suggests that a tank that predates the present pit was 

located at this site. Three small areas of oil-saturated soils are located near the stream in the 

northern part of the site. They are also near old pipeline breaks. 

The salt scars below the 3 tank batteries were remediated in the fall of 1999 by 

removing 15 cm of salty surface soil, replacing it with clean soil, covering the areas with 

straw, and seeding with winter wheat (G. Berschue, U.S. Army Corps of Engineers, 2001, 

oral commun.). Salt crusts are common on the remediated areas and have also been observed 

in a barren patch of saline ground near the lake’s edge (fig. 19). Growth of planted grasses 

was reasonably successful the first growing season (2000), but most of the grasses have since 

died, especially below the active pit. 

31
Figure 17. Aerial photo (1995) of the “B” research site at west end of small bay 

(outlined in white). 

Figure 18. Aerial view of grassy area with active tank battery, pit, salt scar, and 

Skiatook Lake, south part of site “B.” The lake level is above the normal pool 

elevation. Photo by Ken Jewell, U.S. Environmental Protection Agency, Ada, 

Oklahoma. 

32
Figure 19. Features and vegetation map, “B” research site. 

33
Figure 20. Topographic map of the “B” research site 

The entire site slopes generally eastward towards the lake or the small creek (fig. 20). 

The lower parts of the site adjacent to the lake and north stream form a gently sloped terraced 

area. During lowstands of the reservoir, it is apparent that the north and south stream

channels are incised below the level of this terrace. 

Lease History 

As with the “A” site, the following lease history is summarized from files of the 

Bureau of Indian Affairs in Pawhuska, OK. This lease was initially drilled in 1938. 

34
Production began in 1939. The initial target was the Bartlesville Sand (local name). The 

productive unit proved to be the Cleveland Sand (local name). The Cleveland Sand occurs at 

depths of 260-305 m below the surface. Oil is localized by a small, northeast-trending dome 

with about 10 m of structural relief. The initial production was solution-gas driven. 

Waterflooding was initially investigated in 1948 and began in late 1951 when a single saltwater disposal well was drilled into the productive unit and used to test the potential for 

waterflooding. A full-fledged waterflood was proposed in March 1953 and began shortly 

thereafter. In January 1953, there were 10 producing wells on the lease averaging 21 

bbls/day total oil production. Through January 1953 the lease had produced a little less than 

110,000 bbls of oil. Production continues today at approximately 10 bbls/day for the lease 

(S. Hall, lease operator, oral commun., 2002). 

Geology of the “B” Site 

The entire site is underlain by bedrock composed of 1) near-surface weathered shale, 

and minor siltstone and sandstone and 2) similar underlying unweathered bedrock. Eolian 

sand and sandstone-clast colluvium of varying thickness cover bedrock on the hillslopes and 

thicker eolian sand, colluvium, and alluvium cover bedrock in the terraced area adjacent to 

the lake (fig. 21). 

Bedrock Geology 

Lithology 

The bedrock units mapped at the surface at the “B” research site are part of the 

Pennsylvanian Wann Formation (Gardner, 1957). The lower shale member of the Wann 

underlies the entire area of figure 21. Thick sandstone beds of the Clem Creek Sandstone 

Tongue crop out upslope west of the map area and are the likely source of many of the 

sandstone clasts that occur in the colluvium and alluvium at the site. 

The shale is well exposed in the road cut on the hillslope west of the northern tank 

and injection well. The upper 0.5 meters of the shale weathers moderate red orange to 

moderate red brown and grades downward to weathered shale that is light olive gray, yellow 

gray, and, locally, very dark yellow orange in color. 

Two to three thin sandstone beds, in aggregate probably less than 1 meter thick, occur 

in the site area. They crop out in the bottom of the north streambed just upstream from the 

lake (fig. 21). From there to the east, their trace is covered by alluvium and fill, but beyond 

the fill area the sandstones can be observed as large blocks of sandstone float along the steep 

hillslope at the edge of the lake. Similar sandstone crops out on the west side of the active 

pit. This sandstone can be traced southward into trees south of the site area. It is uncertain 

whether the sandstone beds in the stream bottom are the same as the sandstone beds exposed 

in the pit. 

In all outcrop and float areas, the sandstone is very fine-grained, light olive gray on 

fresh surfaces, and weathers moderate yellow brown, dark yellow brown, dark yellow 

orange, and moderate red orange. It is well cemented and has very well-developed joints 

spaced 10-50 cm apart that cause the sandstone to break up into slabs 12-20 cm thick and as 

much as 1.8 m long. 

35
Figure 21. Geologic map of the “B” research site showing geology of the exposed 

lake bottom and locations of drillholes and cross sections. 

36
Figure 22. East-west cross section through the active tank battery down to the lake. See figure 21 fo

section. 
Figure 23. North-south cross section through surficial sediments underlying the terrace. See figure 2

cross section. 
The shale and thin sandstone beds were encountered in three augerholes (BA01, 02, and 

03, fig. 21) and in the lowermost part of several Geoprobe holes (fig. 21). The bedrock geology 

observed in these holes is portrayed in figures 22 and 23. The thin sandstones observed in the 

west wall of the active pit can be correlated with sandstones at depth in augerhole BA02 (fig. 

22). In all three augerholes, several very thin sandstones 2-5 cm thick were observed, some of 

them water bearing. The thickness of weathered bedrock ranges from 3-5.5 m. The sandstones 

and shales in unweathered bedrock are varying shades of gray. Thin concretionary beds 

typically less than 1 cm thick are common in the shale. 

Exposed sandstone beds on the bluffs around the site dip gently westward, although 

exposures within the site are insufficient to establish the local dip. 

Surficial Geology 

The surficial deposits overlying the shale and sandstone consist of colluvium, eolian 

sand, and alluvium (along the creek to the north). On the steep hillslopes west of the three tank 

battery sites (fig. 21), the colluvium is relatively thin and does not form a discrete layer, but 

rather colluvial material occurs as scattered granules, pebbles, cobbles, and boulders of sandstone 

within a matrix of clayey eolian sand. These sandstone clasts sometimes rest directly on the 

underlying weathered bedrock and sometimes lie within or on the surface of the sandy layer. 

Colluvium is much thicker (1 m, or more) on the steep southeast-facing hillslope 

northeast of the north creek adjacent to the injection well pad. Angular granules, pebbles, 

cobbles and boulders of sandstone in a sandy matrix are exposed in the road cut at the edge of 

the cut and fill area surrounding the injection well north of the creek (fig. 21). 

Low on the hillslopes below the tank batteries is a break-in-slope (fig. 20) below which is 

a terrace underlain by a thicker section of colluvium and overlying eolian sand. This section 

averages 1.5-1.8 m thick (fig. 23). The colluvium varies from pebbles, cobbles and boulders of 

sandstone in a matrix of clayey to silty sand to clayey, shale-clast colluvium with only scattered 

sandstone clasts. The sandstone clasts in the sandy facies are usually friable and often have a 

thick oxidation rind. 

The eolian sand layer overlying this colluvium is comprised of very fine-grained sand to 

clayey and silty very fine grained sand as much as 55 cm thick. The sand is very well sorted. A 

dark yellow brown soil horizon has formed in the upper part of it. The lower part of the eolian 

sand layer is dark yellow orange in color and includes granules and small pebbles of weathered 

sandstone suggesting some reworking of the sand, probably by slope wash. This layer erodes 

readily and has been stripped from much of the site (fig. 21), probably by erosion that followed 

road building and erosion after salt-water saturation of the soil below the tank batteries. 

The alluvium along the creek is composed of sand and gravel with abundant large 

cobbles and boulders of sandstone. At least one terrace occurs within the mapped alluvium. 

Near the lake, the creek has cut down to sandstone bedrock (fig. 21) and a stream-cut terrace 

edge about 0.75 m high composed of 0.45 m of weathered shale and 0.3 m of overlying 

colluvium is exposed. 

During lowstands of the reservoir (see below), lake bottom sediments are exposed 

(fig. 21). Areas of gravel and boulders, sand, and lake bottom silt and clay occur. The gravel, 

boulders, and sand represent sediment reworked from the alluvium and colluvium by wave 

action. Abundant leaf litter is mixed with the lake bottom silt and clay. 

39
Hydrology 

The stream at the northern edge of the site drains a small basin to the northwest and feeds 

into the waters of the cove. A second stream occurs south of the site (see fig. 17) and drains 

another small basin. Surface hydrology within the site has been altered substantially by the 

roads, cut and fill areas, pits, and erosion channels that originate in disturbed areas upslope from

the site. Water tends to follow these artificial drainageways. Water ponds in a small ditch along 

the dirt road northeast of the north tank battery during wet periods. 

The relatively thick section of colluvium and alluvium beneath the terrace represents a 

major pathway for subsurface movement of produced water releases from the pit towards the 

lake. 

The elevation of the lake surface varies in response to water input, evaporation and other 

losses, and releases by the U.S. Army Corps of Engineers. The normal pool elevation is 218 m

above sea level. During the course of this study the pool elevation has varied from a little over 

normal pool (fig. 19) to as low as 215.5 m. The lake surface elevation has an impact on the local 

hydrology in that it affects the local base level for ground water and surface water flow. Areas 

of ground water seeps are exposed under lowstand conditions. 

Conclusions 

Research sites “A” and “B” on Lake Skiatook provide excellent opportunities to study the 

impacts of produced water and hydrocarbon releases on soils, surface water, ground water, and 

the ecosystems they support. Site “A” is the older site where production activities ceased 

perhaps 65-70 years ago and the site has been partly reclaimed by natural processes. A salt scar 

persists on the lower part of the site north of the road and erosion continues. The upper part of 

the site has limited initial and continuing erosion although weathered asphalt mixed with sand is 

eroding from oil spill areas near the two tanks and moving downslope. These areas are devoid of

vegetation. Pit “A”, with relatively fresh-appearing asphalt, is devoid of vegetation in the main 

part of the pit, but some grasses are starting to colonize the upper margin. Pit “B” has a greater 

level of colonization by grasses although the north end of the pit, which frequently has ponded 

water, remains devoid of vegetation. Tree-ring chronology and geochemical studies of oak trees 

within and adjacent to the open area may lead to a better understanding of the site history and 

impacts. 

Movement of fluids in the subsurface of site “A” is likely to occur primarily in the 

relatively thin colluvium and overlying eolian sand. The persistence of vegetated pedestals 

within the deeply eroded area, even one pedestal that weeps salts, suggests that the salts can 

bypass the root zone of plants where the eolian sand and colluvium are thick enough. The upper 

part of the weathered bedrock may be storing and slowly releasing salt accumulated while an 

active source was present. The sandstone outcrop in the middle of the deeply eroded area 

continues to weep substantial amounts of salt suggesting that this sandstone may be a significant 

pathway for saline fluids in the weathered bedrock. 

The two pits are an apparent source of salt for the deeply eroded area. Two gullies are 

eroding headward towards the position of these two pits (fig. 21). Headward erosion in other 

directions suggests that other sources of salt may have originally been present at site “A”, but the 

direct evidence is now missing. The variable pitting and mottled very light gray to red, orange, 

40
and brown colors observed in the sandstone outcrops at this site are typical of salt-damaged 

sandstone observed by the authors at oil production sites throughout eastern Osage County. 

Site “B” has recent releases of produced water and hydrocarbon. This site provides an 

opportunity to evaluate the transport of produced water salts and hydrocarbons to Lake Skiatook. 

Aside from the physical impacts of road construction and site preparation through cut and fill, 

the salt scars below the three tank battery sites are the most visible impacts, although substantial 

erosion of the surface soil layer from much of the terrace area has occurred between the three salt 

scars. Isolated low soil pedestals are found within this terrace area suggesting that parts of the 

terrace were isolated from the causes of erosion (roads or shallow saline groundwater). 

The colluvium and alluvium beneath the terrace area is a likely pathway for transport of 

produced water. The amount of clay in the colluvium varies across the site suggesting that sandy 

colluvial facies are likely to have higher permeability and be a preferred pathway. The upper 

part of the weathered shale bedrock may store salts to some degree, but the shale would seem to 

be a barrier to downward movement of contaminants except where fracture permeability is 

significant. The thin sands and the concretionary beds may offer some pathways for fluid 

movement especially where they are fractured. 

A grove of small oak trees grows adjacent to the edge of the active pit berm. These trees 

are apparently hydrologically isolated from salt and hydrocarbon releases from the pit. Study 

and monitoring of these trees may lead to further insights regarding history and ecosystem

impacts at this site. 

References 

Gardner, William E., 1957, Geology of the Barnsdall area, Osage County, Oklahoma: 

Master’s thesis, The University of Oklahoma, Norman, Oklahoma. 

Kuchler, A.W., 1964, Potential natural vegetation of the conterminous United States (map 

and manual): American Geographical Society Special. Publication 36. 

41
Preliminary Geophysical Characterization of 

Two Oil Production Sites, Osage County,

Oklahoma – Osage-Skiatook Petroleum 

Environmental Research Project 

By Bruce D. Smith, Robert J. Bisdorf, Robert J. Horton, James K. Otton, and Ray S. Hutton 

Abstract 

Ground electromagnetic (EM) and dc resistivity geophysical surveys were used to 

interpret the subsurface distribution of salinized soil, water, and bedrock at two oil production 

sites (A and B) on Skiatook Lake in southeastern Osage County, Oklahoma and to characterize 

the larger scale geologic and hydrologic setting. EM measurements were made on grids of about 

1000 m2

 using a very shallow penetrating (less than 10 m) electromagnetic geophysical system

(EM31). At site A, high subsurface conductivities (more than 100 millisiemens/meter, mS/m) 

found immediately down slope from disposal ponds extended down the local drainage to below 

the normal pool elevation 231 m of nearby Lake Skiatook. At site B, three areas of high 

subsurface electrical conductivity were clearly associated with three salt scars and extended in 

the subsurface below the normal level of Skiatook Lake. DC resistivity soundings were made in 

and around the two sites in order to characterize deeper (30-60 m) electrical properties of the 

subsurface lithology and ground water. These soundings and borehole electrical logs show that 

the shale that dominates the local lithology is moderately resistive (20 to 100 ohm meters). The 

shale is clearly distinguishable from sandstone interbeds of higher resistivity and saline water 

bearing horizons of much lower resistivity. 

Introduction 

Ground geophysical surveys were done at the Osage Skiatook Petroleum Environmental 

Research project (OSPER) sites “A” and “B” in late September of 2001. Otton and Zielinski (this 

volume) describe the location, geologic setting, and oil production history of the study area. The 

near-surface lithology at site A is sandstone, mudstone, clayey sandstone, and shale, at site B it is 

mostly shale with minor siltstone and sandstone. Surface salt scars caused by release of salt 

water as part of past oil production activities are present at both areas. Oil production at the “A” 

site began in 1913 whereas it began in 1937 at the “B” site. Currently only site B is still 

producing. Geophysical work for the OSPER project has focused on the characterization and 

mapping of the subsurface geology and hydrology at each site and the surrounding area. 

Electrical geophysical logging has been done in two core drill holes at site B. 

42
Methods 

Both electromagnetic (EM) induction and galvanic dc resistivity survey methods were 

used at each site. Though each of these methods is very effective in subsurface mapping, both 

were affected to varying degrees by conductive metal, primarily tanks and flow lines from

production operations. Electrical properties of rocks can be measured in resistivity (ohm meter) 

or conductivity (siemens). The latter quantity should not be confused with conductance 

measurements of water, which are commonly expressed in microsiemens/cm (μs/cm), and are 

not a measure of the volume electrical conductivity but the point-to-point conductivity. Normal 

borehole geophysical resistivity logs are commonly expressed in ohm meters. Geophysical 

terrain conductivity systems commonly measure millisiemens, which can be related to ohm

meters as: 

1/(1000* ohm meter) = 1 millisiemens. 

In sedimentary rock, the bulk electrical conductivity is controlled by the porosity and 

conductance of the pore fluid. A porous rock containing water with a high conductance will also 

have a high electrical conductivity or a low resistivity. Thus electrical geophysical methods are 

popular in mapping plumes of saline water (Sharma, 1997). Other earth materials such as clays, 

siltstones, and shales can have high electrical conductivities. Therefore, high electrical 

conductivity is not uniquely correlated with poor water quality (high total dissolved solids, 

TDS). 

DC resistivity sounding methods are commonly used in ground water exploration and 

characterization (Sharma, 1997). An electrical current is applied directly into the ground through 

electrodes and the resulting voltage is measured with a second set of collinear electrodes. We

used a Schlumberger array where current electrodes were expanded from less than 1 meter to a 

maximum spacing of about 100m. Shorter current spacing was used when pipes and other metal 

objects interfered with larger spacings. Borehole logging contracted to Century Geophysics at 

site B used a “normal resistivity” method, which also induces a direct current into the earth. 

The electromagnetic (EM) induction method uses a wire loop as a transmitter and another 

loop as a receiver. The electromagnetic field in the transmitter induces a current to flow in the 

earth (in proportion to the electrical conductivity) that creates a secondary electromagnetic field 

that is detected by the receiver. We used an EM31 system that has loops separated by 3.1 m.

McNeill (1980) discusses the principles of this geophysical system. In the normal surveying 

geometry the transmitter and receiver loops are horizontal coplanar (vertical magnetic dipole, 

VMD) According to McNeill (1990), measurements with this coil configuration have a depth of 

exploration to about 4.5m. The measurement system can be rotated so the coil system is vertical 

coplanar (horizontal magnetic dipole, HMD), in which case the depth of exploration is about 

2.3m. 

Geophysical Surveys at Site A 

DC Resistivity Soundings 

The location of four dc resistivity soundings made at the site is shown in figure 1. 

Sounding number seven is located at the south end of the prominent salt scar discussed by Otton 

and Zielinski (2003). The digitized field measured apparent resistivities, interpreted subsurface 

43
Figure 1. Location map of Schlumberger dc soundings at the “A” site. Figure 1 of Otton 

and Zielinski (this volume) gives the general location of study areas. 

layer resistivities, and computed apparent resistivities for sounding 7 are shown in figure 2. Note 

that the x-axis of figure 2 represents both the distance between current electrodes for the 

measurement of apparent resistivity and depth of the layered earth in meters. The y-axis 

represents both the observed apparent resistivity and the interpreted layer resistivity. Sounding 

number 7 shows layers of very low resistivity, less than 10 ohm meters (100 mS/m). This 

interpreted low resistivity (high conductivity) zone from 1.5 to 8 m is due to saline waters that 

have caused the salt scaring rather than the presence of conductive clays. This interpreted 

subsurface zone correlates with high conductivities mapped in the EM311

 survey. The 

interpreted low resistivities do not extend to depth suggesting that the saline waters have not 

come from a source at depth directly beneath the sounding. This interpretation agrees well with 

nearby auger drill holes AA04 and AA02, which identified saline water in sandstone at depths of 

1.5 to 8 m.

The interpreted subsurface conductivities from the dc resistivity soundings are shown as a 

cross section in figure 3. The edge of the saline water layer is interpolated between soundings 7 

and 8 to the east. There is a pronounced decrease in interpreted subsurface conductivity for 

sounding 9 in comparison to sounding 6. On possible interpretation is that westward extension 

of high subsurface conductivity in the sandstone is terminated at a fault contact with relatively 

less permeable shale. 

44
Figure 2. Plot of apparent resistivity as a function of electrode separation (m) and 

interpreted subsurface resistivity as a function of depth (m) for dc sounding 7. Circles 

indicate digitized field observations. The solid line that resembles a stair step is the 

layered earth resistivity model as a function of depth that produces the best-fit 

theoretical solution (smooth solid line). 

Figure 3. Electrical cross section from interpreted Schlumberger dc soundings at site A 

shown as conductivity in millisiemens per meter. 

45
EM31 Survey 

The survey grid was constructed using measuring tape and compass. Points on the grid 

were tied to survey points used for geologic mapping (Otton and Zielinski, this volume). A 

surveying GPS system with better than .1 m accuracy (Abbott, this volume) was used to 

geographically position the geophysical survey grid. Survey lines were measured North-South 

every 10 m along an East-West baseline. A few fill-in lines were surveyed at 5 m. Stations along 

the lines were measured every 1 m. Apparent conductivity measurements were made with both 

the vertical and horizontal magnetic dipole (VMD and HMD) configuration. Figure 4 shows the 

conductivities for the VMD configuration (4.5 m). Results from the shallower (2.5 m) HMD 

configuration are not shown because survey results are much the same. This result is consistent 

with the 1.5 to 8 m depth of saline water observed in auger drill holes. 

High measured conductivities from 100 mS to nearly 200 mS are located entirely north of 

the East-West road through the middle of site A. The conductivity highs are undoubtedly the 

result of shallow saline waters, which probably contributed salts to the area of the salt scar. 

Probably sources of the saline water are the impoundment ponds located immediately south of 

the road (fig. 4). High conductivities are located further to the northwest than might be expected 

if these ponds were the only source of saline waters. Older temporary impoundment areas may 

also have been located further to the north during past oil production. 

The high subsurface conductivities shown in figure 4 end before the drainage enters 

Skiatook Lake. One shallow (1.6m) well near the lakeshore contains saline water of 12,000 TDS 

(Kharaka and others, this volume). This well is located at the terminus of the salt-scarred area 

and probably receives salts originated from the high conductivity, presumably contaminated area 

indicated in figure 4. 

Geophysical Surveys at Site B 

DC Resistivity Survey 

DC soundings were made along a 3-km-long E-W line that included site B (fig. 5). 

Sounding #1 is located near a 76-m rotary-drill hole (BR01) that was designed to define the 

lithology above site B and to evaluate the dc sounding that was done before the drilling. The first 

10 m of the hole is weathered sandstone that measured about 500 ohm meters (2 mS) on the 

normal resistivity geophysical borehole logs. From 10 m to about 30 m, the lithology is 

predominantly sandstone of resistivity that varies from 50 to 100 ohm meters (20 to 10 mS). The 

natural gamma logs show some clay rich zones less than 2 m thick within the sandstone that have 

low neutron porosity and resistivities of about 50 ohm meters (20 mS). Shale occurs below the 

sandstone to the bottom of the hole where there is a small “marker sandstone” less than 2 m

thick. Neutron porosity of the shale is much lower that the sandstone indicating that the shale is 

very tight and not a good aquifer. The actual formation resistivities cannot be accurately 

interpreted from these logs since a caliper log was not done. The sandstone portion of the drill 

holes are more likely to wash out which can have unpredictable effects on the normal resistivity 

log measurements. 

46
Figure 4. EM31 conductivity map for the vertical magnetic dipole (4.5 m depth of 

penetration) of site A at the OSPER study area. The solid lines show the 10m survey 

grid. Linework on the map shows features from the site geologic map (Otton and 

Zielinski, this volume). High conductivities are shown in the warmer colors (red and 

pink) and low conductivities are shown in cooler colors (green and blue). 

47
Figure 5. Location map of Schlumberger dc soundings at OSPER study site B. Figure 1 

of Otton and Zielinski (this volume) gives the general location of study areas. Sounding 

number 11 is at study site B. 

Interpreted subsurface resistivities for DC sounding #1 (fig. 6) are similar to the 

resistivity values (100 ohm meter) of the normal borehole log. Plotting conventions for figure 6 

are the same as discussed for figure 2. The high resistivity weathered zone (1 – 10 m) has 

interpreted resistivities of 1000 ohm meters with a thickness of a few meters. The apparent 

sandstone unit thickness of 30 m agrees well with the observed lithology in the nearby drill hole 

but the last 20 m a lower resistivity than the upper part of the underlying shale. The lower 

resistivity may be due to brackish ground water within the sandstone unit. BR01 is screened at 

15 –18 m where no water has been observed. The well is also screened at 26-31 m where the 

waters had a TDS of around 2,000 mg/l but increased in June of 2002 to 9,000 TDS (Kharaka 

and others, this volume). 

48
Figure 6. Plots of apparent resistivity as a function of electrode separation and 

interpreted subsurface resistivity as a function of depth in meters for dc sounding 1. 

Circles indicate digitized field observations. The solid line that resembles a stair step is 

the layered earth resistivity model as a function of depth that produces the best-fit 

theoretical solution (smooth solid line). 

DC soundings 13, 10, and 5 were made at the lake edge in October 2001, when the lake 

was about 1.8 m below the normal pool elevation. Both the sounding near study site B (numbers 

5 and 10) and away from the site (number 13) show that at the lake edge there is a subsurface 

shallow high conductive zone (fig. 7). This could be caused by shallow brackish water in the 

formation at lake level. At this time the interaction between lake water and ground water has not 

been studied, but additional electrical studies could shed light on this relationship. 

DC sounding number 11 was made near geoprobe hole BE04 (a direct push probe) 

located on one of the salt scars at site B (Otton and Zielinski, this volume). The interpreted 

sounding (fig. 8) shows that there is a near-surface zone of extremely low resistivity (less than 3 

ohm meters 330 mS/m) at 0.6 – 2.0 m depth. The low resistivity (high conductivity) is caused by 

saline water that is observed in this and other shallow boreholes. The saline waters are only 1-2 

m thick, suggesting that the shale bedrock acts as an effective confining layer, and that the saline 

waters have not penetrated the shale. 

EM31 Survey 

Ground conductivity measurements were made at 1 m intervals along grid lines trending 

northwest-southeast and spaced 10 m apart. Measurements were made with both vertical 

magnetic dipole (VMD, 5.5 m depth of exploration) and horizontal magnetic dipole (HMD, 2.25 

m depth of exploration) orientations. Figure 9 shows the conductivity map for the horizontal 

magnetic dipole. The northwestern-most salt scar (fig. 9) does not have an associated area of 

49
Figure 7. Electrical cross section from interpreted Schlumberger dc soundings (see fig. 

5) shown as conductivity in millisiemens per meter. Sounding number 11 is at site B. 

high subsurface conductivity. Metal pipes cause the conductive anomaly in this area. This area of 

the oil production facility also is the location of a salt-water injection well (Otton and Zielinski, 

this volume) for the complex. 

The middle salt scar (fig. 9) has a subsurface conductivity high that is slightly offset from

the center of the scar. The area of very saline shallow water is near geoprobe hole BE04, 

discussed previously. The zone of saline water trends northeast toward the creek and lakeshore. 

At the time the ground survey was done, the lake level was below normal. It does not appear 

that the very high salinity plume would extend under the lake. However, it should be noted that 

high conductivities occur along the stream channel, which is normally below lake level. 

The southeastern salt scar (fig. 9) is down slope from an active pit (shown in gray) that 

temporarily stores both brine and hydrocarbons from the adjacent tank battery. The salt scar is 

likely due to brines in this pit. Very high concentrations of salt are found in the colluvium just 

southeast of the berm around the pit, and at times, very high TDS (several thousand mg/l) have 

been observed at the base of the berm. The highest subsurface conductivity associated with the 

southeastern salt scar was measured in an area that is normally submerged when the lake is at 

normal level. 

Figure 10 shows the VMD conductivity data (5.5 m depth of penetration) and geologic 

features superimposed on a 1960 aerial photograph that was geographically registered (Abbott, 

2003) to the survey area. There are two areas (indicated by “1” and “2” in fig. 10) at the 

southeast part of site B that were associated with oil production in 1960 was taken, but are now 

below the normal lake level. In February of 2002 the lake level was still low and exposed parts 

of the two areas. A relic portion of a berm was noted at the circular feature labeled “1” (fig. 10). 

One possible interpretation of the circular features on the photograph is that the darker area (“2” 

in fig. 10) was a holding pond for hydrocarbons. The lighter feature (“1” in fig. 10) may have 

been a holding pond for brine. If this is the case then the much higher conductivities in this area 

might be a remnant plume from this storage area. The berm may have also served to retard the 

flow of more recent brine release from the existing storage pit. 

50
1000 100 10

CONDUCTIVITY (ms) 

Saline water

Fresh water

Figure 8. DC resistivity sounding number 11 and geoprobe borehole lithologic log. See 

Otton and Zielinski (this volume) for a description of lithologies. Yellow is colluvium, 

green is weathered bedrock, and gray is fresh shale bedrock. 

51
Figure 9. EM31 conductivity map for the horizontal magnetic dipole (2.25 m depth of 

penetration) of site B at the OSPER study area. The dotted lines show the 10m survey 

grid. Linework superposed on the map shows selected features from the site geologic 

map (Otton and Zielinski, this volume). High conductivities are shown in the warmer 

colors (red and pink) and low conductivities are shown in cooler colors (green and blue). 

52
1 

1 

2 

Figure 10. EM31 conductivity map for the vertical magnetic dipole (5.5 m depth of 

penetration) of site B at the OSPER study area superimposed on 1960 aerial 

photograph . The dotted lines show the 10m-survey grid. Features on the map are from 

the site geologic map (Otton and Zielinski, this volume). High conductivities are shown 

in the warmer colors (red and pink) and low conductivities are shown in cooler colors 

(green and blue). Areas marked 1 and 2 are likely man-made features associated with 

past oil production. The darker area (above the 2) is likely a hydrocarbon storage pond 

and the lighter area (above the 1) is likely a brine storage pond.

53
Conclusions 

Schlumberger dc resistivity soundings show that shales and sandstones at the two study 

sites have moderately high electrical conductivity ranging from 20-100 mS/m (10-50 ohm

meters). Generally shales have a lower electrical conductivity than sandstones due to higher clay 

content (McNiel, 1980). Shale in this geologic setting has low primary permeability, suggesting 

that ground-water flow in this unit probably is fracture controlled. Borehole resistivity and 

natural gamma logs support this interpretation. DC soundings on the hill above site B suggest 

that local sandstone aquifers carry brackish water but do not indicate highly saline waters. The 

lack of highly conductive clays in the geologic section reduces the likely hood that they are the 

source of high measured conductivity. Areas of very high conductivity, more than 100 mS/m are 

likely to be caused by saline waters. 

DC soundings completed near the lakeshore indicate very shallow (less than a meter) 

highly conductive (perhaps as high as 150 mS/m) layers near site B and several km away from

the contamination. Since the shallow high conductivity is at lake level, there is a strong 

possibility that the lake water, ground water, and sediments are interacting to cause the high 

conductivity zone. Additional studies are needed to map shallow ground water near the 

lakeshore. 

EM31 ground conductivity surveys at both sites suggest that saline waters associated with 

salt scars have a more complex subsurface distribution than the scar exposures. At the “B” site, 

the saline waters are confined to the upper few meters of colluvium and do not appear to 

significantly penetrate the shale bedrock. At site A, saline waters are also confined to within a 

few meters of the surface, however the shallow bedrock is porous sandstone. At site B, saline 

ground water is present at shallow depth including areas that are normally submerged by the 

lake. All of these observations suggest that saline solutions have a high residency time in the 

near-surface lithology even under high recharge conditions. 

Subsurface contamination from oil production practices is not always obvious. At site A, 

surficial hydrocarbons occur as tars from past spills and storage. Yet the geophysical data do not 

show that large volumes of saline water immediately below these areas. Release of saline waters 

down the hydraulic gradient from the surface tar has caused the local salt scar. There are several 

salt scars at site B, but only the middle scar appears to have a large enough volume of saline 

water to cause high ground conductivity. 

Geophysical ground conductivity measurements have defined specific locations of 

subsurface saline water at both sites. These conductivity maps could be used in designing 

remediation methods and prioritizing areas for additional work. 

References

Abbott, M.M., [this volume] 2003, Real-Time kinematic (RTK) surveying at the OsageSkiatook Petroleum Environmental Research sites, Osage County, Oklahoma: U.S. 

Geological Survey Water-Resources Investigations 03-4260, p. 147-155. 

Kharaka, Y.K., Thordsen, J.J., Kakourous, Evangelos, and Abbott, M.M., [this volume] 

2003, The fate of inorganic and organic chemicals in produced water from the OsageSkiatook Petroleum Environmental Research sites, Osage County, Oklahoma: U.S. 

Geological Survey Water-Resources Investigations 03-4260, p. 56-83. 

54
McNeill, J.D., 1980, Technical Note TN-6, Electromagnetic terrain conductivity 

measurement at low induction numbers, Mississauga, Ontario, Canada, Geonics 

Limited, (1980). 

McNeill, J.D., 1991, Use of electromagnetic methods for groundwater studies, in Ward, 

S.H., ed., Geotechnical and Environmental Geophysics, Volume I: Tulsa, OK, Society 

of Exploration Geophysicists, v. 5, p. 191-218. 

Otton, J.K. and Zielinski, R.A., [this volume] 2003, Produced water and hydrocarbon 

releases at the Osage-Skiatook petroleum environmental research studies, Osage County 

Oklahoma: Introduction and geologic setting: U.S. Geological Survey Water-Resources 

Investigations 03-4260, p. 14-41. 

Sharma, Prem V., 1997, Environmental and engineering geophysics, Cambridge, Cambridge 

University Press, 467 pp. 

55
The Fate of Inorganic and Organic 

Chemicals in Produced Water from the 

Osage-Skiatook Petroleum Environmental 

Research Sites, Osage County, Oklahoma 

By Yousif K. Kharaka, James J. Thordsen, Evangelos Kakouros, and Marvin M. Abbott 

Abstract 

We are involved in a multidisciplinary investigation to study the transport, fate, and 

natural attenuation of inorganic salts, trace metals, radionuclides and organic compounds present 

in produced water, and their impacts on soil, surface and ground waters and the local ecosystem

at the Osage-Skiatook Petroleum Environmental Research (OSPER) “A” and “B” sites. The two 

sites, located in Osage County, OK, are within the depleted Lester and active Branstetter leases, 

respectively. These leases are typical of many depleted and aging petroleum fields in southern 

mid-continent of USA. About 1.5 and 1.0 hectare of land at the “A” and “B” sites, respectively 

are affected by salt scarring, soil salinization and brine and petroleum contamination due to the 

leakage of produced water and associated hydrocarbons from brine pits and accidental releases 

from active and inactive tank batteries. Results to date show that the produced water source is a 

Na-Ca-Cl brine (~150,000 mg/L dissolved solids), with high concentrations of Mg, Sr, and NH4, 

but low SO4 and H2S. With the exception of Fe and Mn, the concentrations of trace metals are 

low. Eventually, the bulk of inorganic salts and some dissolved organic species in the released 

brine reach the adjacent Skiatook Lake, a 4,250-hectare reservoir that provides drinking water to 

the local communities and is a recreational fishery. 

For the OSPER “A” site, 35 water samples were obtained from an asphaltic pit and an 

adjacent weathered-oil pit, from a local stream channel and from 12 of 24 boreholes (1-35 m

deep), recently drilled and completed with slotted PVC tubing. Results show that the salinity of 

water from the asphaltic pit is comparable to that of the produced water source. Also, we have 

mapped a plume of high salinity water (3,500-25,600 mg/L TDS) that intersects Skiatook Lake. 

Chemical and isotope analyses of the collected samples, water level monitoring and additional 

sampling are continuing. Results to date clearly show that significant amounts of salts from

produced-water releases still remain in the soils and rocks of the impacted area after more than 

60 years of natural attenuation. 

About 60 water samples were obtained from the “B” site: from two brine pits, several 

brine pools and seeps in the impacted area, local streams, Skiatook Lake, and from 24 boreholes 

(1-71 m deep). Results show diluted brine and minor amounts of oil flow from the brine pits 

through the shallow eolian sand, colluvial and alluvial deposits to the Skiatook Lake. Its 

chemical composition is modified further by sorption, mineral precipitation/dissolution, 

transpiration, volatilization and bacterially mediated oxidation/reduction reactions. 

56
Introduction 

Oil and natural gas currently are the main sources of primary energy supplying about 

63% of the energy consumption in USA, and forecasts indicate that by 2020 natural gas and oil 

consumption will increase by 40% and 29%, respectively (EIA, 2000). Exploration for and 

production of petroleum typically involves activities such as road building, site clearing and 

leveling, seismic surveys, and drilling. Road building and site clearing impacts the soil and biota, 

and in arid environments can impact air quality by added dust to the atmosphere, and vehicle 

traffic can introduce invasive species to undeveloped areas. Drilling can introduce mud of 

various compositions into the subsurface and onto the surface, and may cause oil spills or 

drainage of produced waters. The volume of wastes generated from about 26,000 wells drilled in 

USA for oil and gas in 1993, including drilling mud, circulated cement, rock cuttings, 

completion fluids and produced water, is estimated at 0.13-1.0 billion bbl (Kharaka and Wanty, 

1995). The total number of wells drilled in the United States for the purpose of oil and gas 

production since 1859 is estimated to be 3.5 million in 36 states; only about 880,000 are 

currently in production (Breit and others, 2001). Improperly sealed, abandoned wells may act as 

conduits allowing the flow of high salinity water to the surface and shallow aquifers. 

Environmental impacts of petroleum production arise primarily from the improper 

disposal of large volumes of saline water produced with oil and gas, and from hydrocarbon and 

produced water releases caused by equipment failures, vandalism, flooding, and accidents. In 

1993, about 25 billion and 0.3 billion bbl of produced water were obtained with 2.5 billion bbl of 

domestic crude oil and 18 trillion ft

3

 of natural gas, respectively (Kharaka and Wanty, 1995). The 

volume of produced water in 1970 was about one-third as great, even though petroleum

production was higher (Kharaka and Wanty, 1995, Collins, 1975). This increase resulted because 

the volume of produced water relative to petroleum increases with time, typically reaching 98% 

of total fluids during the later stages of field production. 

The chemical composition of produced water is variable, but commonly it is highly saline 

with total dissolved solids (TDS) of about 5,000-350,000 mg/L (Kharaka and Thordsen, 1992). 

This water generally contains toxic metals, other inorganic chemicals, and BTEX (benzene, 

toluene, ethylbenzene and xylene) and other organic compounds, and may contain radium226/228 and other NORMs (naturally occurring radioactive materials) (Collins, 1975; Otton and 

others, 1997; Kharaka and others, 2000). 

Currently about 65% of the produced water from onshore fields is reinjected into 

producing zones for pressure maintenance and enhanced oil recovery (Kharaka and Wanty, 

1995). Deep well injection into formations with water salinities greater than 10,000 mg/l (>3,000 

mg/l, with exemption from regulations) accounts for about 30% of total produced water. The 

remaining water is discharged into surface waters, including coastal waterways, bayous, 

estuaries, streams, lakes and even evaporation and percolation sumps. Prior to the Federal 

regulations instituted in the 1970s, disposal of produced water was by the most economic method 

available. Historical methods included discharge into surface streams, storage in unlined 

impoundments, disposal in poorly maintained injection wells, and simply running the water over 

the ground. Impacts of these past practices are apparent in salt scars, dead trees and other 

vegetation, contamination of soil and surface water, and plumes of saline water that affect 

groundwater supplies. 

57
Accidental releases of produced water and petroleum and the improper disposal of 

produced water are national issues that concern managers of Federal, and State lands, as well as 

oil and gas producers and lessees, mineral rights and lease owners, State and Federal regulators, 

and surface landowners (USEPA, 1987; ASTM, 1999; Wilson and Frederick, 1999). In 1986, the 

U.S. Environmental Protection Agency (USEPA, 1987) conducted a survey of states to 

determine the sources of groundwater pollution. Oil and gas brine pits were identified by 22 

states as a significant source of groundwater pollution; two of the states identified these pits as 

the primary cause of pollution. 

About 20 scientists from government agencies and academia are involved in a 

multidisciplinary investigation to study the transport, fate, and natural attenuation of inorganic 

salts, trace metals, organic compounds and radionuclides present in produced water, and their 

impacts on soil, surface and ground water and the local ecosystem at the Osage-Skiatook 

Petroleum Environmental Research (OSPER) “A” and “B” sites, located in Osage County, OK. 

In this report we present data on the chemical and isotopic compositions of surface and ground 

waters at the two sites and of oil-field brine and ground water in the region. Results from all the 

studies will be used to evaluate the long-term and short-term effects of produced water and 

hydrocarbon releases from these sites. Results are expected to guide estimates of human and 

ecosystem risk at such sites and the development of risk-based corrective actions (Billingsley, 

1999). Corrective actions are particularly needed in aging and depleted fields, where land use is 

changing from petroleum production to residential, recreational, agricultural or other uses (Carty, 

and others, 1997). 

OSPER Sites 

The two research sites, OSPER “A” and “B” are located, respectively, within the Lester 

and Branstetter leases, and both are adjacent to Skiatook Lake, a 4,250-hectare reservoir 

completed in 1987 that provides drinking water to the local communities and is a major 

recreational fishery (figs. 1 and 2). The sites are located in the Central Oklahoma platform in the 

southeastern part of the Osage Reservation in northeastern Oklahoma. Both sites are in a 

dissected area of modest relief, with oak forests covering the slopes and tall grass present on 

most ridge crests. Geological mapping by Otton and Zielinski (Otton and Zielinski, this volume) 

show the area to be underlain by interbedded shale, siltstone, and sandstone. Thicker resistant 

sandstone units typically form the hill crests. Hill slopes are underlain by shale, siltstone, and 

thin sandstone beds. 

The geologic and climatic settings of the Lester and Branstetter leases resemble that of 

much of the major southern mid-continent oil- and gas-producing area of the U.S. The leases are 

also typical of many depleted and aging petroleum fields in Osage County, which ranks among 

the top oil and gas producing counties in Oklahoma with close to 40,000 wells (Abbott, 1999). 

Oil and gas production has occurred in Osage county for over 100 years, but current production 

is mainly from stripper (<10 bbl/d) wells (averaging ~2.8 bbl/d oil and >30 bbl/d brine) that are 

shallow, mostly 300-700 m in depth, and produce from several sandstones of Pennsylvanian age. 

The six oil wells sampled for this study and located in the Branstetter lease and from fields 

adjacent to the Lester lease, produced 1.5-4 bbl/d oil from Mississippi lime and Bartelsville, 

Cleveland and Tucker sands at depths of 333-538 m; brine production from these wells 

58
Figure 1. Geologic map of the OSPER “A” site showing the locations of the oil pits, 

other production features, drilled water wells and outline of the impacted area. 

59
Figure 2. Geologic map of the OSPER “B” site showing the locations of the large oil pit 

adjacent to the tank battery, the smaller pit at reinjection well, outlines of the three 

scarred and remediated areas, other production features, drilled water wells and several 

shorelines for the Skiatook Lake. 

60
comprised 94-99% of produced fluid. The Osage Nation holds the mineral rights, the BIA has 

trust responsibility, and the Army Corps of Engineers owns the surface at “A” and “B” sites. 

Site “A”, located within the Lester lease in section 13, T22N, R10E, has an area of about 

1.5 hectare that is impacted by produced water and hydrocarbon releases that occurred primarily 

60-85 years ago (fig. 1). The site is underlain by 1) a surface layer of eolian sand of varying 

thickness (up to about 80 cm); 2) colluvium that ranges from large boulders of sandstone to thin, 

granule-pebble conglomerate; 3) weathered shale, siltstone, and sandstone; and 4) underlying 

unweathered bedrock. Much of the site appears to have been impacted by early salt-water 

releases that killed the oak forest, however a few oak trees grow as single trees or clumps of trees 

within the original kill area. The gently sloping upper part of the site is slightly eroded in places 

and has been mostly revegetated with grasses, forbs, sumac, and a few trees. The lower, steeper, 

more heavily salt-impacted portion has been eroded to depths of as much as 2 m. Seepage of salt 

water from a shallow sandstone aquifer continues and active salt scarring persists. This area 

drains into the Cedar Creek arm of Skiatook Lake. 

Drilling at the Lester Lease started in 1912, and most of the over 100,000 bbl of oil 

produced by 1981, was obtained prior to about 1937. Production, which was entirely from

Bartlesville sand at depths of 450-524 m, ended about 10 years ago (BIA, unpublished lease 

records, 2000). Oil and produced water collected in two redwood tanks at the top of the site was 

transported via ditch to two roadside pits at mid-site. Produced water and hydrocarbon (now 

highly degraded and weathered oil) releases from pipeline breaks and tank batteries, that are no 

longer present, are scattered around the site. However, one pit at this site contains relatively fresh 

asphaltic oil and high salinity brine. 

Site “B”, located within the Branstetter lease in sections 29 and 32, T22N, R10E, is 

actively producing and has ongoing hydrocarbon releases and salt scars that have impacted an 

area of about one hectare (fig. 2). The site includes an active production tank battery and 

adjacent large pit, two injection well sites, one with an adjacent small pit, and an old tank 

battery. The large pit is about 15 m from the shoreline of the Skiatook Lake; all the other sites 

are within 45 m of the lake. Three salt scars that were partly remediated in 2000 by soil removal, 

tilling, and soil amendments, extend downslope from the active tank battery, the injection 

well/pit, and the old tank battery to the lake edge. Two small creeks cross the northern and 

southern parts of the site. The upper part of the site is characterized by a thin surface layer of 

eolian sand mixed with sandstone-clast colluvium underlain by weathered and unweathered shale 

whereas the lower part is underlain by 1) a surface layer of eolian sand (20-70 cm thick); 2) 

colluvial apron and alluvial deposits of varying thickness comprised of sandstone pebbles, 

cobbles, and boulders with a fine sand matrix; 3) weathered shale; and 4) unweathered bedrock. 

The Branstetter lease was initially drilled in 1938 and increased activity occurred in 

1947-51, when A.H. Ungerman purchased the lease. About 110,000 bbl oil was produced from

the lease before water flooding started in 1953. Currently there are about 10 wells that produce 

1-3 bbl/d oil, and 50-100 bbl/d brine; all the produced fluids are collected and separated in the 

tank battery adjacent to the large brine pit (S. Hall, oral communication, 2002). The two brine 

pits at this site are not lined and receive brine and hydrocarbons releases from broken pipes and 

tank leaks; they also receive large volumes of surface-water flow from precipitation. The brine in 

these pits is generally pumped into collection tanks by submersible pumps, but these 

occasionally fail causing filling and overflow of brine pits, as happened in November and 

December, 2001 for the large brine pit. 

61
Methods and Procedures 

We have carried out three major sampling trips (March, 2001; February and June, 2002) 

and several short trips, where only a few samples were collected, or only few field parameters 

(e.g. water level, conductance, temperature and dissolved oxygen (DO)) were measured. During 

March 2001, 15 water, four oil and three gas samples were obtained from wells adjoining the two 

sites to characterize the source fluids from oil wells, groundwater, and Skiatook Lake (table 1). 

Water samples were also collected from several seeps, pools and shallow (~20 cm) holes mainly 

at the “B” site. During February, 2002, about 60 direct-push, auger and rotary wells were drilled 

at and near the two sites, cored, completed with slotted PVC tubing and, where water was 

present, sampled. The water level, conductance, temperature and DO were measured in these 

wells in April-May, 2002, and water sampling was carried out in June, 2002. 

A total of about 100 water samples have been collected from the two sites and adjoining 

areas. For the “A” site, 35 water samples were obtained from the asphaltic pit and adjacent 

weathered-oil pit, from a local stream channel and the Skiatook Lake, and from 12 of 24 

boreholes (1-35 m deep) discussed above. About 60 water samples were obtained from the “B” 

site, from the two brine pits, several brine pools and seeps in the impacted area, local streams, 

Skiatook Lake, and from about 20 boreholes (1-71 m deep) recently drilled and completed. 

Laboratory Measurements 

All of the water samples were analyzed at the USGS Water Resources laboratories in 

Menlo Park, CA. Concentration of chloride (Cl), bromide (Br), nitrate (NO3), organic acid 

anions, and sulfate (SO4) were determined by ion chromatography (IC) (Kharaka and others, 

2000, 2002). Inductively coupled plasma mass spectrometry (ICP-MS) was used to determine the 

concentrations of calcium (Ca) and other cations, trace metals, boron (B), and silica (SiO2). The 

reported concentrations for major cations and anions carry an uncertainty of ±3%. Precision 

values for minor and trace chemicals are generally ±5%, but could reach ±10% for values close 

to detection limits (Kharaka and others, 2002). 

Water isotopes were determined in the USGS Stable Isotope Laboratory in Menlo Park. 

Water isotopes are reported in δ – values that are expressed in parts per thousand (per mil, ‰) 

relative to the Standard Mean Ocean Water (SMOW). The Standard Deviation of reported values 

are ±0.2 ‰ for δ18O and ±2 ‰ for δD (Kharaka and others, 2002). 

Results and Discussion 

Stable water isotopes and concentrations of selected inorganic and organic chemicals 

from surface and ground water samples from OSPER “A” and “B” sites and adjoining areas in 

Osage County, OK are listed in tables 2 and 3, respectively. The data listed for water from rotary 

(AR and BR) wells, drilled with fresh water that likely effected the composition of formation 

water, and from relatively deep auger (AA and BA) wells, that may have been subject to cross 

formational flow prior to well completions, are only for the last samples collected in June, 2002. 

Additional sampling from these and other wells will be carried out in order to distinguish 

chemical changes related to drilling operations and to investigate spatial and temporal changes 

related to physical, chemical and biological processes.

62
Table 1. Chemical (inorganic and organic) and isotopic composition of ground water and produced wa

Osage County, OK. 

Site Name Hurn well Bolin well Reynolds #4 ECC #10 ECC #3 Lebow #8 Millard #3 ECC #5 Ungerm

Sample # 01OS-101 01OS-102 01OS-103 01OS-104 01OS-105 01OS-106 01OS-107 01OS-108 01OS

Date 03/05/01 03/06/01 03/06/01 03/07/01 03/07/01 03/08/01 03/08/01 03/09/01 03/0

pH 6.0 7.2 6.2 6.7 6.1 6.3 6.4 6.4 6

T (°C) 18 18 15 22 23 34 21 22 2

Li 0.016 0.008 36 8.0 38 11.5 6.0 27 7Na 69 36 51700 42400 55000 48600 38100 47000 392K 0.96 0.97 690 100 650 270 110 480 15NH4+ <0.1 0.5 38 79 45 78 56 48 5

Mg 25 19 1980 2350 2070 1830 1530 1910 15

Ca 57 36 11200 5400 11900 9960 6250 9980 69Sr 0.24 0.33 500 905 514 504 521 505 50Ba 0.14 0.21 451 339 461 879 311 309 39Mn 0.002 0.35 6.0 2.8 10.0 0.93 1.28 7.5 0.Fe 0.01 0.12 50 27 31 67 28 24 3Cl 216 24 110000 82100 113000 99500 75400 101000 785Br 0.86 0.13 346 285 364 346 335 320 33SO4 45.1 18.3 0.32 0.23 0.37 0.69 0.16 0.37 0.

HCO3 72 269 109 244 105 185 146 118 18

NO3 5.2 <0.02 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0

H2S <0.4 <0.4 <0.4 <0.4 <0.4 <0.4 <0.4 <0.4 <0

SiO2 26 14 <16 <16 <16 <16 <16 <21 <2

B 0.018 0.070 8.8 2.9 8.7 3.6 1.8 6.9 1TDS 518 420 177000 134000 185000 162000 123000 162000 128DOC 0.4 5 3 3326 7 Phenols (total) 0.10 0.11 0.12 0.18 0.

Benzene 0.77 0.70 0.49 0.90 0.Acetate <0.02 <0.02 0.9 2.2 0.5 2.4 0.6 5.2 1Formate 0.03 0.05 0.3 0.1 0.4 0.4 0.4 0.3 0δ18O (‰) -5.72 -5.73 -2.03 -2.95 -1.77 -2.57 -3.51 -2.18 -3

δD (‰) -35.16 -34.89 -9.91 -13.00 -9.32 -10.60 -19.06 -10.05 -17

T, temperature; TDS, total dissolved solids; DOC, dissolved organic carbon; solute concentrations in mg/l; <, less than.

Ground water wells Produced water from oil wells 
Table 2. Chemical (inorganic and organic) and isotopic composition of water samples from OSPER "A

Site Name AA-01d AA-02d AA-02s AA-03d AA-03s AA-04d AA-04s AE-04 AE-05 AE

well well well well well well well well well w

Sample # 02OS-430 02OS-427 02OS-426 02OS-429 02OS-428 02OS-425 02OS-424 02OS-434 02OS-332 02O

Date 06/13/02 06/12/02 06/12/02 06/12/02 06/12/02 06/12/02 06/12/02 06/13/02 03/03/02 06/

pH 6.5 6.9 6.2 6.7 6.6 7.0 5.7

T (°C) 16 18 19 16 19 22 

Li 0.16 0.05 0.07 0.13 0.04 0.08 0.04 0.001 0.001 0.Na 2180 525 3400 3250 1110 1150 1670 60 11.8 K 27 6.8 16 25 3.2 28 5.3 1.0 0.03 0Mg 2520 102 272 166 41 234 63 0.4 0.03 

Ca 3460 176 564 419 98 567 202 2.1 0.18 5Sr 8.6 2.9 8.4 5.2 3.4 4.9 7.7 0.07 0.004 0Ba 0.3 0.1 0.6 1.2 1.9 1.3 6.3 0.026 0.003 0Mn 5.1 0.49 1.7 14.5 2.2 4.3 12.5 0.013 0.001 0Fe <10 3 <5 6 6.5 <2.5 <2.5 0.1 0.07 0Cl 16100 436 7020 5630 1860 3410 3240 76.7 3.3 2Br 56 1.5 23 19.3 6.4 11.6 11.7 0.27 0.08 0SO4 696 668 137 23.4 5.7 56.8 5.9 10.2 14.2 6

HCO3 445 824 255 894 301 279 54 ND ND NNO3 <1 <0.2 <1 <0.2 <0.2 <0.5 1.8 1.2 1.1 0

SiO2 <43 24 <21 <21 19 18 29 11 10 

B 0.4 0.1 0.04 0.023 0.TDS 25500 2760 11700 10500 3450 5760 5310 180 50 DOC 99 113 2 203 53 2 4Acetate 171 200 0.08 517 101 <0.04 <0.04Formate <0.08 <0.08 0.09 <0.08 <0.08 <0.08 <0.04Propionate <0.2 <0.2 <0.2 0.7 3.3 <0.1 <0.05

Butyrate <0.2 <0.2 <0.2 0.5 <0.2 <0.1 <0.05

δ18O (‰)

δD (‰)T, temperature; TDS, total dissolved solids; DOC, dissolved organic carbon; solute concentrations in mg/l; <, less than.
Table 2. Chemical (inorganic and organic) and isotopic composition of water samples from OSPER "A

Site Name AE-07 AE-08 AE-10 AE-12 AE-13 AE-13 AE-15 AE-19 AR-01 AP

well well well well well well well well well w

Sample # 02OS-334 02OS-326 02OS-331 02OS-328 02OS-329 02OS-431 02OS-437 02OS-433 02OS-438 02O

Date 03/03/02 03/01/02 03/03/02 03/03/02 03/03/02 06/13/02 06/13/02 06/13/02 06/13/02 02/

pH 5.3 6.4 5.7 7.3 5.6 5.6 6.5 5

T (°C) 8 20 17 16 22 25 22 17

Li 0.002 0.048 0.025 0.032 0.024 <0.025 0.09 0.01 0.011 3Na 23 341 24 179 1980 2250 4030 50 23 32K 0.13 1.6 0.74 1.7 2.8 3 4 0.5 1.6 Mg 0.21 4.8 0.57 1.8 629 808 484 1.4 23 1

Ca 0.81 19 2.9 8.3 738 1020 1000 5.7 58 5Sr 0.037 1.2 0.19 0.59 23.3 25.4 16.9 0.25 0.36 4Ba 0.066 0.19 0.081 0.023 0.41 0.41 1.2 0.040 0.56 1Mn 0.007 0.39 0.086 0.029 105 87.8 2.8 0.14 2.1 6Fe 0.15 <0.05 0.02 0.05 2.0 6 <10 0.1 0.2 5Cl 20.0 580 17.4 37.6 6300 7770 9120 58.8 76.8 68Br 0.17 1.3 0.07 0.39 22.0 26.6 30.9 0.41 0.57 2SO4 20.6 14.3 28.5 4.9 92.3 248 115 16.8 5.6 4HCO3 3 ND 13 457 14 57 ND 221 2

NO3 1.2 0.08 0.25 3.1 10 <1 11 0.38 <0.02 

SiO2 11 11 10 2.9 9.6 25 <43 12 23 <

B 0.012 0.14 0.021 0.34 <0.025 0.08 0.02 TDS 81 1000 97 700 9930 12300 14800 181 436 11DOC 11 69 5 5 4Acetate 0.3 0.2 0.5 0.3 0.04 0.07 0.07 2Formate 0.3 0.1 1.2 0.2 <0.04 <0.08 0.07 Propionate <0.25 <0.05 <0.2 <0.05 <0.05 <0.2 <0.1 

Succinate <0.1 0.04 0.3 0.1 <0.12 <0.12 <0.02 δ18O (‰) -5.18 -5.92 -3.06 -5.31 -2

δD (‰) -27.79 -38.29 -18.65 -29.04 -1

(*) AP-01 well - butyrate = 4.2 mg/l, malonate = 0.17 mg/l.
Table 3. Chemical (inorganic and organic) and isotopic composition of water samples from OSPER "B

Site Name BA-01d BA-01s BA-02d BA-02s BA-03d BA-03s BE-03 BE-04 BE-06 BE

well well well well well well well well well w

Sample # 02OS-405 02OS-403 02OS-401 02OS-318 02OS-402 02OS-320 02OS-411 02OS-408 02OS-409 02O

Date 06/10/02 06/10/02 06/10/02 02/26/02 06/10/02 02/26/02 06/11/02 06/11/02 06/11/02 02/

pH 7.1 5.4 6.8 7.5 6.7 7.3 5.0 6

T (°C) 19 22 18 17 19 16 27 28 24 

Li 0.11 0.010 0.19 0.22 0.13 0.19 <0.013 0.04 0.012 0Na 1550 2080 831 1220 863 1410 2430 5640 1280 6K 16 4.5 19 35 12 30 6 15 1.5 NH4+ 

Mg 315 174 793 723 538 463 172 388 296 5

Ca 410 509 433 416 477 399 564 1100 195 1Sr 16.2 17.7 7.0 7.4 12.2 9.9 22.3 51.2 4.0 7Ba 0.023 0.60 0.010 0.055 0.010 0.042 1.3 1.8 0.46 1Mn 1.8 21 0.057 0.38 0.20 0.79 25.2 36.0 25.7 8Fe <0.13 0.8 <0.13 <0.25 0.9 <0.25 <2.5 <0.25 <0.13 1Cl 2050 4660 1140 1540 999 1800 5090 12000 3150 14Br 8.1 20.3 4.4 6.3 3 7.1 23 49 11 SO4 2420 99.0 3700 3910 3080 2840 61 76 96 1

HCO3 424 33 1030 990 808 829 17 1

NO3 <0.4 <0.5 <0.2 0.3 <0.2 <0.1 <0.5 6 <0.5 

H2S 0

SiO2 16 16 15 16 16 19 11 12 13 8

B 4.6 0.11 1.9 1.7 5.1 3.9 0.27 0.06 0TDS 7245 7635 7990 8880 6840 7830 8430 19300 5080 24DOC 1 8 12 1 8 Acetate <0.04 0.9 0.03 <0.08 <0.04 <0.04 0Formate <0.04 <0.04 <0.04 <0.2 0.05 0.06 0Succinate <0.15 <0.08 <0.02 <0.1 <0.04 <0.15 0δ18O (‰) -5.54 -5.52 -5

δD (‰) -32.38 -32.08 -3

T, temperature; TDS, total dissolved solids; DOC, dissolved organic carbon; solute concentrations in mg/l; <, less than.
Table 3. Chemical (inorganic and organic) and isotopic composition of water samples from OSPER "B" site -- c

Site Name BE-09 BE-10 BE-11 BE-12 BE-13 BE-15 BE-16 BE-17 BE-18 BR

well well well well well well well well well w

Sample # 02OS-412 02OS-413 02OS-420 02OS-421 02OS-307 02OS-410 02OS-417 02OS-418 02OS-407 02O

Date 06/11/02 06/11/02 06/12/02 06/12/02 02/21/02 06/11/02 06/11/02 06/11/02 06/11/02 06/

pH 6.0 4.4 6.4 6.7 6.3 6.4 6.1 7.1 6.2 6

T (°C) 24 23 22 22 12 24 23 35 23 

Li <0.025 <0.025 <0.050 <0.050 0.01 <0.013 0.04 0.08 0.018 0Na 3300 3060 4860 4000 3520 1180 2140 2030 2780 2K 4556 5.9 2 5.9 12 7.6 7NH4+ 3

Mg 145 624 1140 1360 974 313 1360 1700 253 3

Ca 309 840 1140 1190 874 360 500 502 552 6Sr 16.0 29.8 36.7 25.4 29.8 4.8 8.7 8.5 22.1 1Ba 0.90 0.51 0.49 0.076 0.23 0.17 0.035 0.037 0.58 Mn 51.1 65.2 22.6 3.4 284 9.2 108 15.6 45.4 3Fe 5 <5 <10 <10 116 <2.5 11 <2.5 32 <0Cl 6300 8180 12500 10500 9900 3090 3130 2020 5800 5Br 29 38 56 49 48 12 15 8 24 SO4 125 470 277 2520 583 385 6910 8860 290 9HCO3 185 0 232 447 181 142 325 1260 275 2NO3 <0.5 <0.5 <1 1.2 <0.5 4 <0.5 <1 <0.5 <

H2S 1.8

SiO2 <21 19 <43 <43 4.9 11 <21 15 11 

B 0.04 0.16 0TDS 10500 13300 20300 20100 17400 5500 14400 16400 10100 9DOC 21 9 12 12 19 14918 Acetate <0.02 <0.04 <0.04 <0.04 0.6 <0.02 0.04 <0.1 <0.04 0Formate 0.03 <0.04 <0.04 <0.04 0.7 0.04 0.05 <0.1 0.09 0Succinate <0.03 <0.04 <0.04 <0.06 0.04 <0.15 <0.2 <0.2 <0.04 <δ18O (‰) -5.12

δD (‰) -33.16
Table 3. Chemical (inorganic and organic) and isotopic composition of water samples from OSPER "B

Site Name EPA-1 injection main pit small pool large pool stream, Skiatook Lake Skiatook L

well pit at BA-01 at BA-01 at BA-01 near ACE at BE-0

Sample # 01OS-201 02OS-316 02OS-317 01OS-113 01OS-114 02OS-311 01OS-111 02OS-30

Date 12/11/01 02/25/02 02/25/02 03/13/01 03/13/01 02/22/02 03/10/01 02/22/0

pH 4.3 8.5 6.6 7.1 7.3 6.7 6.7 8.1 

T (°C) 12.1 11 7 13 11 11 7 12 

Li 2.9 1.1 1.4 0.015 0.002 0.029 0.002 0.002 Na 22700 12500 10600 1930 641 1190 14 21 K 56 37 36 5.4 2.4 4.3 2.2 2.5 NH4+ 20 <0.1 0.1 

Mg 1250 444 442 56 57 129 5.0 6 

Ca 5270 2450 1980 288 173 333 20 23 Sr 343 172 141 13.2 4.66 10.0 0.19 0.27 Ba 113 88.4 100 4.4 0.56 0.27 0.050 0.072 Mn 16.1 0.43 2.9 2.9 3.1 13.8 0.003 0.085 Fe 130 <1 40 <0.13 <0.05 17 <0.006 <0.01 Cl 52000 26200 21600 3560 1470 2550 25 39.7 Br 227 124 100 13.0 6.3 12 0.11 0.20 SO4 12.3 5.1 11.2 9.2 22.5 271 10.0 11.6 

HCO3 0 57 146 143 134 273 74 80 

NO3 <2 <1.5 <1 <0.4 0.7 <0.15 0.8 0.7 

H2S 0.4 

SiO2 <16.0 <6 4.6 2.0 4.0 8.8 2.8 1.5 

B 0.57 0.5 0.6 0.109 0.024 0.05 0.023 0.03 TDS 82100 42100 35300 6020 2520 4810 153 186 DOC 43 14 9 4 4 4 Acetate 0.05 0.6 1.1 0.06 Formate <0.08 0.3 0.1 0.2 Succinate <0.1 0.06 <1 <0.4 δ18O (‰) -3.54 -2.44 -4.30 -5.23 -5.83 -5.79 -2.46 -1.75 

δD (‰) -21.25 -26.45 -26.66 -31.50 -32.41 -37.70 -15.27 -13.66 
Results show that the produced water obtained (table 1) from the seven oil wells, one 

coal-bed methane well (01OS-110) and the composite reinjection tank has a relatively similar 

chemical composition; it is a hypersaline (115,000-185,000 mg/L total dissolved solids) Na-CaCl brine, that is dominated by Na and Cl, and has relatively high concentrations of Ca, Mg (fig. 

3), Sr, Ba and NH4, but very low amounts of SO4, HCO3 (fig. 4) and H2S. With the exception of 

Fe, the concentrations of trace metals are low, and the values of organic acid anions and other 

dissolved organic species are relatively low. The chemical composition of Skiatook Lake water 

and ground water in the area not impacted by petroleum operations (samples 01OS-111, -101, -

102, 02OS-438, table 1) shows major contrast from that of produced water. The water is fresh 

(153-518 mg/L total dissolved solids) and has comparable values for the equivalent 

concentrations of Na, Mg and Ca as well as those of Cl, SO4 and HCO3; this water, then, has 

much higher Mg and Ca concentrations relative to Na and much higher HCO3 and SO4 relative to 

Cl, when compared to produced water (figs. 3 and 4). Uncontaminated ground and surface 

waters are generally oxic, resulting in low concentrations of metals, including Fe (reaction 3, 

table 4) and Mn, as well as low DOC and organic acid anions (fig. 5). In anoxic water 

environment, present in produced water and petroleum contaminated water, Fe (reactions 1, 2, 

table 4) and Mn are mobilized from sediments, and organic acid anions, and thus DOC are 

generated by bacterial action on petroleum (Kharaka and others, 2000). These and other 

chemical properties and water isotopes that are different for produced and ground waters (fig. 6) 

are used to investigate the impact of produced water on the surface and ground waters of the 

contaminated areas (Abbott, 1999; Richter and Kreitler, 1993; Kharaka and others, 1995).

Table 4. Important water-mineral interactions at OSPER sites that modify the chemical 

composition of water from various sources. 

2FeS2 + 7O2 + 2H2O ⇔ 2Fe++ + 4SO4

- - + 4H+ (1) 

FeS2 + 2NO3

- + 2H2O ⇔ Fe++ + 2SO4- - + 4H+ + N2 (2) 

4Fe++ + O2 + 10H2O ⇔ 4Fe(OH) 3 + 8H+ (3)

8Fe+++ + CH3COOH + 2H2O ⇔ 8Fe++ + CO2 + 8H+

 (4) 

Fe++ + HS - ⇔ FeS + H+ (5)

H+ + CaCO3 ⇔ Ca++ + HCO3

- (6)

2H+ + CaMg(CO3) 2 ⇔ Ca++ + Mg++ + 2HCO3

- (7)

CH3COOH ⇔ CO2 + CH4 (8)

4.8H+ + Ca.2Na.8Al1.2Si2.8O8 + 3.2H2O ⇔.2Ca++ + .8Na+

 + 1.2Al+++ + 2.8H4SiO4 (9) 

Ca++ + SO4

- - + 2H2O ⇔ CaSO4.2H2O (10)

CH3COO-

 + SO4

- - ⇔ 2HCO3- + HS - (11)

69
0.001

0.01

0.1

1

Mg

/Cl

B site

A site

oil wells

gw

Skiatook L.

sea w ater

A

0.01

0.1

1

10

10 100 1,000 10,000 100,000 1,000,000

TDS (mg/L)

Ca

/Cl

B site

A site

oil wells

gw

Skiatook L.

sea w ater B

Figure 3. The Ca/Cl and Mg/Cl ratios as a function of water salinity for the oil-field 

brines, regional ground water (gw), Skiatook Lake and surface and ground waters from 

the impacted areas in the OSPER “A” and “B” sites. Note the generally lower ratios for 

the oil-field brines and diluted produced water. 

70
0.000001

0.0001

0.01

1

SO

4/Cl 

B site

A site

oil wells

gw

Skiatook L.

sea w ater

A

0.0001

0.01

1

100

10 100 1,000 10,000 100,000 1,000,000

TDS (mg/L)

HCO

3/Cl 

B site

A site

oil wells

gw

Skiatook L.

sea w ater

B

Figure 4. The SO4/Cl and HCO3/Cl ratios as a function of water salinity for the oil-field 

brines, regional ground water (gw), Skiatook Lake and surface and ground waters from 

the impacted areas in the OSPER “A” and “B” sites. Note the much lower ratios for the 

oil-field brines and diluted produced water. 

71
0.1

10

1000 DOC (

m

g

/

L)

B site

A site

oil wells

gw

Skiatook L.

sea w ater

A

1.0E-08

1.0E-06

1.0E-04

1.0E-02

1.0E+00

10 100 1,000 10,000 100,000 1,000,000

TDS (mg/L)

M

n/Cl 

B site

A site

oil wells

gw

Skiatook L.

sea w ater

B

Figure 5. The concentrations of DOC and the Mn/Cl ratios as a function of water salinity 

for the oil-field brines, regional ground water (gw), Skiatook Lake and surface and 

ground waters from the impacted areas in the OSPER “A” and “B” sites. Note the much 

higher DOC and Mn/Cl values for ground water from the impacted wells, especially at 

the “A” site. 

72
-6 -5 -4 -3 -2 -1 0

-40

-30

-20

-10

0

10

Battery tank

SMOW

GMWL

δ

D (permil)

δ

18O (permil)

 Regional groundwater

 Skiatook Lake

 Oil wells

 A site

 B site

Figure 6. Isotopic composition of water for the oil-field brines, regional ground water 

(gw), Skiatook Lake and surface and ground waters from the impacted areas in the 

OSPER “A” and “B” sites. Note the major differences in the isotope values of the 

produced water relative to ground water. 

OSPER “A” Site 

At OSPER “A” site, the water obtained from the asphaltic pit (02OS-324) has a salinity 

(110,000 mg/L TDS) and chemical composition that are comparable to that of the produced 

water source (fig. 7). The salinity of water obtained from the boreholes in the adjacent pit, which 

has more weathered and degraded oil (Godsy and others, this volume), and from those boreholes 

located close to the two pits, all have fresh water (≤ 1,000 mg/L TDS), indicating that the brine 

in the asphaltic pit is of limited volume and extent. Also, all the direct-push Geoprobe wells (AE 

designation in table 2) located to the south and west of the two oil pits (fig. 1) have fresh water, 

with compositions that indicate no mixing with produced water. If produced water was ever 

present in these shallow wells, then it was flushed and replaced with meteoric water from

precipitation. (See also results from soil analysis (Zielinski and others, this volume) and 

geophysical surveys (Smith and others, this volume)). 

73
100 50 0 50 100

Na

Ca

Mg

HCO3

SO4

Cl

02OS-324 - AP-01 well

170000 μS/cm

02/28/02 pH = 5.79 TDS = 111851 mg/l

100 50 0 50 100

Na

Ca

Mg

HCO3

SO4

Cl

02OS-324 - AP-01 well

02/28/02 pH = 5.79 TDS = 111851 mg/l

100 50 0 50 100

Na

Ca

Mg

HCO3

SO4

Cl

02OS-432 - AE-08

06/13/02 pH = 6.04 TDS = 131 mg/l

100 50 0 50 100

Na

Ca

Mg

HCO3

SO4

Cl

02OS-437 - AE-15

06/13/02 pH = TDS = 14818 mg/l

100 50 0 50 100

Na

Ca

Mg

HCO3

SO4

Cl

02OS-436 - AE-12

06/13/02 pH = TDS = 619 mg/l

100 50 0 50 100

Na

Ca

Mg

HCO3

SO4

Cl

02OS-433 - AE-19

06/13/02 pH = TDS = 186 mg/l

100 50 0 50 100

Na

Ca

Mg

HCO3

SO4

Cl

02OS-431 - AE-13

06/13/02 pH = 5.63 TDS = 12302 mg/l

Figure 7. Modified Stiff diagrams showing the salinity of water and the relative 

concentrations (in equivalent units) of major cations and anions in a transect from the 

asphaltic pit to Skiatook Lake at the OSPER “A” site. 

The salinity and chemical composition of water obtained from all the auger wells (AA 

designation, table 2) as well as from those direct-push wells (AE, table 2) located to the north of 

the two oil pits in the salt scarred area at the “A” site, show major impact from produced water 

operations (figs. 8 and 9). A plume of high salinity water (3,500-25,600 mg/L TDS) dominated 

by Na and Cl, intersects Skiatook Lake near well AE-13 (fig. 1) that has water salinity of 10,100-

12,300 mg/L TDS (see also Smith and others, this volume). The upper and lower boundaries of 

this plume are tentatively marked on the cross section (fig. 9) that shows the plume apex to be 

74
100 50 0 50 100

Na

Ca

Mg

HCO3

SO4

Cl

02OS-438 - AR-01

06/13/02 pH = 6.46 TDS = 435 mg/l

100 50 0 50 100

Na

Ca

Mg

HCO3

SO4

Cl

02OS-430 - AA-01d

06/13/02 pH = 6.54 TDS = 25548 mg/l

100 50 0 50 100

Na

Ca

Mg

HCO3

SO4

Cl

02OS-426 - AA-02s

06/12/02 pH = 6.23 TDS = 11659 mg/l

100 50 0 50 100

Na

Ca

Mg

HCO3

SO4

Cl

02OS-427 - AA-02d

06/12/02 pH = 6.91 TDS = 2761 mg/l

100 50 0 50 100

Na

Ca

Mg

HCO3

SO4

Cl

02OS-428 - AA-03s

06/12/02 pH = 6.64 TDS = 3446 mg/l

100 50 0 50 100

Na

Ca

Mg

HCO3

SO4

Cl

02OS-429 - AA-03d

06/12/02 pH = 6.73 TDS = 10494 mg/l

100 50 0 50 100

Na

Ca

Mg

HCO3

SO4

Cl

02OS-424 - AA-04s

06/12/02 pH = 5.66 TDS = 5287 mg/l

100 50 0 50 100

Na

Ca

Mg

HCO3

SO4

Cl

02OS-425 - AA-04d

06/12/02 pH = 6.99 TDS = 5757 mg/l

Figure 8. Modified Stiff diagrams showing the salinity of water and the relative 

concentrations (in equivalent units) of major cations and anions from the relatively deep 

rotary (AR) and auger (AA) wells in and near the OSPER “A” site. s- shallow screened 

interval, d- deep screened interval, see figure 9. 

75
215

217

219

221

223

225

227

0 20 40 60 80 100 120 140

Horizontal distance from AE-05 well, in meters

Altitude above mean sea level, in meters

AE-13

AE-15

AA-01

AA-04 AA-02 AA-03

AE-05

Skiatook

Lake

LAND SURFACE

SCREEN/SAND

INTERVAL AA-02d screen at

208.3-209.8 m

SALT SCAR

ASPHALTIC

PIT

DRY

25,600 14,800

12,300

2,760

5290

5,760

10,500

10,500

3,450

59

Figure 9. Water levels and salinity of water in wells along a transect from well AE-5 to 

AE-13, located in the littoral zone of Skiatook Lake at the OSPER “A” site. A plume of 

relatively high salinity water is present at intermediate depths in wells located below the 

asphaltic pit. Red and blue lines represent highest and lowest water levels, respectively, 

observed during the period March, 2001 to June, 2002. 

within 1 m from ground surface in well AA-03, which is the closest to the oil pits that likely 

were also the brine pits. Chemical data for water from the deeper perforated section (13.8-15.2 m

below ground level) of well (AA-02), we believe, will ultimately delineate the bottom of the 

plume. The salinity and chemical composition of water for the last sample from this section 

(02OS-427, table 2 and fig. 8) indicate a non produced water source; the concentration of acetate, 

DOC and possibly other components (table 2) could indicate contamination from an oil source or 

cross formational mixing from the shallow and contaminated section when the well was drilled. 

Additional sampling from this and new deeper wells will be used to better delineate the 

plume boundaries from this site. Results to date, however clearly show that significant amounts 

of dissolved inorganic and organic chemicals and hydrocarbons from produced-water and oil 

releases still remain in the soils and rocks of the impacted area after more than 60 years of

natural attenuation. 

76
OSPER “B” Site 

Even though the number of boreholes drilled at the two sites is comparable, a larger 

number of water samples (60 vs. 35) have been obtained from the “B” site compared to the “A” 

site. This results primarily because the “B” site is currently active and brine and associated 

hydrocarbons are added intermittently via the brine pits and accidental releases from broken 

pipes. Many of the water wells at the “A” site, in contrast to those at the “B” site, were found dry 

at the time of sampling because the oil wells in the Lester lease have been depleted for some time 

and no brine additions occur at this site. 

The salinity (133,000 mg/L TDS) and chemical composition of water in the composite 

water tank (table 3) are similar to those described earlier for the produced water from the 

sampled oil wells (figs. 3 and 4). The salinity and chemical composition of water in the two brine 

pits (fig. 2) vary greatly with time, reflecting primarily the mixing of produced water brine with 

dilute water from precipitation and runoff into the pits. The salinity of water in the small pit 

adjacent to the injection well, for example, was 13,000 mg/L TDS on 12/11/01 and 42,000 mg/L 

TDS on 2/25/02. The proportions of major anions and cations in both samples were similar and 

comparable to those of produced water, but the actual concentration were reduced by a factor 

close to 10 for the December sample and about three for the February sample. The concentration 

of a number of minor and trace chemicals that are sensitive to the redox state of the water (e.g. 

Fe, Mn, NH4, organic acid anions) are likely to be lowered in oxic conditions (e.g. reactions 1-3 

for Fe, table 4) by factors that are greater than those listed above. The concentration of some

chemicals (e.g. NH4, BTEX, organic acid anions) may be reduced also by volatilization. On the 

other hand, evaporation generally increases the concentrations of dissolved species, and the 

relatively higher concentrations of HCO3 in both samples likely result from bacterial degradation 

of oil. 

All the water samples obtained from pools, seeps and boreholes at this site (fig. 2) show 

variable impacts from produced water. The most saline sample, outside the brine pits, was 

obtained in December 2001 from a well located about 15 m down gradient and to the east from

the large brine pit, which generally has from about 0.2 to 2 m (maximum depth at overflow) of 

produced water with a thin layer of oil. The well brine (01OS-201, table 3) had a salinity (82,000 

mg/L TDS) and chemical composition approaching that of produced water. Water obtained from

the same well in February 2002, had a salinity of only 17,400, but the proportions of major 

cations and anions are similar to those of produced water. Water samples obtained in February 

and June 2002 from Geoprobe well BE-07 (figs. 2 and 10) located in the littoral zone of Skiatook 

Lake, about 65 m down gradient and to the east from the large brine pit, show a more uniform

salinity (24,000 and 20,000 mg/L TDS, respectively). The chemical composition of water from

this well has characteristics that are similar to that of produced water (fig. 11), that together with 

the presence of oil globules in the water, strong oil odor and high values measured for 

hydrocarbon gases and other VOCs (see also Godsy and others, this volume), clearly show that 

brine and minor amounts of hydrocarbons from the large brine pit reach the lake. Minor 

contamination of Skiatook lake with brine is indicated (02OS-309 vs 01OS-111, fig. 11), but this 

topic will be covered in detail in future reports. 

Additional direct-push wells (BE designation, fig. 2 and table 3) and one dual completion 

auger well (BA-02) were drilled to investigate the flow paths of brine and associated 

hydrocarbons from the large brine pit. In addition to well BE-07 discussed, oil globules in the 

water, strong oil odor and high values measured for hydrocarbon gases and other VOCs were 

77
214

215

216

217

218

219

220

221

222

223

224

105 115 125 135 145 155 165 175 185 195

Horizontal distance from BR-02 well, in meters

Altitude above mean sea level, in meters

BRINE

BA02 TANK BATTERY

Feb '02

June '02

BERM

BE11

BE09

BE08

BE07

SKIATOOK LAKE

WATER LEVELS

LAND SURFACE

SCREEN/SAND

INTERVAL

Figure 10. The high (green line) and low (red line) water levels measured wells in the 

transect A-A`, from well BA-02 to well BE-07, located in the littoral zone of Skiatook 

Lake at the OSPER “B” site. 

observed in well BE-09 and a 30 cm hand-dug well located close and down gradient from BE11. No visible oil was observed in water from other wells, but oil odor and measured 

hydrocarbon gases were obtained from most of the other wells located on the salt scarred, but 

“remediated” area below the brine pit. All the wells located in the salt-scarred area below the 

brine pit, especially those shown in figure 10, also had saline water with chemical characteristics 

of produced water (table 3, fig. 11). 

Water samples obtained from the two perforated zones of well BA-02 as well as those 

from wells BE-16 and BE-17 have high salinity (8,000-16,500 mg/L TDS) and chemical 

characteristics that could indicate a mixture of diluted produced water, high in Na and Cl and 

ground water, high in Mg, SO4 and HCO3 (fig. 12). Geochemical modeling using the latest 

version of SOLMINEQ (Kharaka and others, 1988) indicates another possible, but less likely 

explanation for the chemical composition of water from these samples. It includes dilution of 

produced water source, followed by dissolution of gypsum and dolomite and precipitation of 

calcite (reactions 10, 7 and 6, table 4). Regardless of the correct explanation, these results 

indicate a slower flow path from the large brine pit towards wells BA-02, BE-16 and BE-17 than 

towards the wells depicted in the transect A-A’ (fig. 10). Additional sampling, tracer tests and 

hydrologic parameter determinations and modeling (see also Herkelrath and Kharaka, this 

volume) are planned to investigate the flow in this system. 

78
100 50 0 50 100

Na

Ca

Mg

HCO3

SO4

Cl

02OS-309 - Skiatook Lake nr.BE-07

02/22/02 pH = 8.08 TDS = 186 mg/l

100 50 0 50 100

Na

Ca

Mg

HCO3

SO4

Cl

01OS-111 - Skiatook Lake nr. ACE

03/10/01 pH = 6.71 TDS = 153 mg/l

100 50 0 50 100

Na

Ca

Mg

HCO3

SO4

Cl

02OS-415 - BE-07

06/11/02 pH = 6.2 TDS = 19726 mg/l

100 50 0 50 100

Na

Ca

Mg

HCO3

SO4

Cl

02OS-422 - BE-08

06/12/02 pH = 6.68 TDS = 16029 mg/l

100 50 0 50 100

Na

Ca

Mg

HCO3

SO4

Cl

02OS-420 - BE-11

06/12/02 pH = 6.36 TDS = 20259 mg/l

100 50 0 50 100

Na

Ca

Mg

HCO3

SO4

Cl

02OS-317 - main pit

02/25/02 pH = 6.62 TDS = 35241 mg/l

100 50 0 50 100

Na

Ca

Mg

HCO3

SO4

Cl

02OS-401 - BA-02d

06/10/02 pH = 6.75 TDS = 7963 mg/l

Figure 11. Modified Stiff diagrams showing the salinity of water and the relative 

ll to

le

concentrations of major cations and anions in a transect from the BA-02 deep we

well BE-07, located in the littoral zone of Skiatook Lake at the OSPER “B” site. Samp

010S-111 taken near Army Corps of Engineers (ACE) field office. 

79
100 50 0 50 100

Na

Ca

Mg

HCO3

SO4

Cl

02OS-318 - BA-02 well (sh)

02/26/02 pH = 7.48 TDS = 8870 mg/l

100 50 0 50 100

Na

Ca

Mg

HCO3

SO4

Cl

02OS-421 - BE-12

06/12/02 pH = 6.65 TDS = 20075 mg/l

100 50 0 50 100

Na

Ca

Mg

HCO3

SO4

Cl

02OS-417 - BE-16

06/11/02 pH = 6.14 TDS = 14428 mg/l

100 50 0 50 100

Na

Ca

Mg

HCO3

SO4

Cl

02OS-317 - main pit

02/25/02 pH = 6.62 TDS = 35241 mg/l

100 50 0 50 100

Na

Ca

Mg

HCO3

SO4

Cl

02OS-416 - BE-13

06/11/02 pH = 6.59 TDS = 16544 mg/l

100 50 0 50 100

Na

Ca

Mg

HCO3

SO4

Cl

02OS-418 - BE-17

06/11/02 pH = 7.06 TDS = 16388 mg/l

Figure 12. Modified Stiff diagrams showing the salinity of water and the relative 

concentrations (in equivalent units) of major cations and anions from the main brine pit 

and Geoprobe wells located to the southeast of this pit; the latter wells appear to have a 

mixture of produced water and local ground water. 

Significant amounts of produced water, but no oil, reach the wells, water pool and even 

the creek adjacent to the scarred, but “remediated” area down gradient from the reinjection pit 

(fig. 2). The salinity of water from BE-03 and other wells, small pools and a large pool close to 

the creek has varied widely, ranging from 2,500 to 13,100 mg/L TDS, but the chemical 

composition is that of a diluted produced water. Sample 02OS-311, which was collected from the 

creek to the east of BA-01 well has a salinity of 2,500 mg/L TDS and chemical properties of 

diluted produced water. A specific water conductance of about 20,000 μsiemens/cm (μS/cm) was 

obtained with a probe from a location where this sample was obtained. 

80
A high specific water conductance (8,000 μS/cm) was also measured in the creek near 

well BE-19. This part of the creek, as well as wells BE-04, BE-05, BE-18 and BE-19 are located 

in the middle salt scarred and “remediated” area of the “B” site. This salt scar had a tank battery, 

located at its western end that was removed and the site “remediated” in year 2000. The four 

direct-push wells on this site have generally been dry. However, some water was obtained from

BE-04 and BE-19, that gave salinities of 19,200 and 10,100 mg/L TDS, respectively; the water is 

dominantly Na-Cl and has the other chemical characteristics of produced water. 

Summary and Conclusions 

About 100 water samples and several oil and natural gas samples were obtained from oil 

wells, domestic ground water wells, active and inactive brine and oil pits, seeps, pools, local 

streams, Skiatook Lake and from 50 boreholes (1-71 m deep), recently drilled and completed 

with slotted PVC tubing. Most of the samples are from OSPER “A” and “B” sites, located, 

respectively, within the depleted Lester and active Branstetter leases, in Osage County, OK. 

Results show that large amounts of produced water and associated petroleum from active and 

inactive brine pits and from accidental releases from broken pipes have impacted about 1.5 and 

1.0 hectare of land at the OSPER “A” and “B” sites, respectively. The impacts include salt 

scarring, soil salinization and oil contamination, and brine and petroleum contamination of 

ground water and surface water, including Skiatook Lake, a 4,250-hectare reservoir that provides 

drinking water to the local communities and is a major recreational fishery. 

At the “A” site, results show that the salts have essentially been removed by flushing 

from the soil and surficial rocks; but degraded and weathered oil persists on the surface of old oil 

and brine pits, close to sites of old tanks, on old channels that carried oil from tanks to the oil pits 

and other impacted areas. Results show that a plume of high salinity water (3,500-25,600 mg/L 

TDS) is present at intermediate depths that extend from below the old oil and brine pits to 

Skiatook Lake. No liquid petroleum was found in the contaminated groundwater, but soluble 

petroleum byproducts, including organic acid anions and other VOCs are present. Results to date 

clearly show that significant amounts of salts from produced-water releases and petroleum

hydrocarbons still remain in the soils and rocks of the impacted area after more than 60 years of 

natural attenuation. 

At the “B” site, significant amounts of produced water from the two active brine pits 

percolate into the surficial rocks and flow towards the Skiatook Reservoir; but only minor 

amounts of liquid petroleum leave the brine pits and reach the Skiatook Reservoir. 

The above results and conclusions are tentative and may be modified after additional 

sampling from existing and new wells, tracer tests, hydrologic parameter determinations and 

hydrologic and geochemical modeling are completed. These results, however, show that diluted 

produced water and minor amounts of oil flow from the brine pits through the surficial beds to 

the Skiatook Lake. 

Acknowledgements 

We are grateful to the Osage Indian Nation, to the Army Corps of Engineers and Bureau 

of Indian Affairs, as well as the field operators for permission to conduct research at these sites. 

We are grateful also for the financial support for this research provided by DOE National 

81
Petroleum Technology Office, E&P Environmental. Gil Ambats and James Palandri participated 

in field sampling, and Gil Ambats and Kathy Akstin carried out the chemical analysis reported 

here. 

References 

Abbott, M.M., 1999, Water quality of the Quaternary and Ada-Vamoosa aquifers on the 

Osage reservation, Osage county, Oklahoma, 1997: Water-Resources Investigation 

Report 99-4231, 76 p. 

American Society for Testing and Materials, 1999, ASTM standards on assessment and 

remediation of petroleum release sites: ASTM, Committee E-50 on Environmental 

Assessment, 126 p. 

Billingsley, Patricia, 1999, Oklahoma’s oilfield pollution risk-based assessment and cleanup 

program, in Sublette, Kerry (ed.), Proceedings of the 6th International Petroleum

Environmental Conference: Environmental Issues and Solutions in Petroleum

Exploration, Production and Refining: Houston, TX, University of Tulsa, CD-ROM, p. 

1011-1020. 

Breit G. N., Kharaka Y. K., and Rice C. A., 2001, National database on the chemical 

composition of formation water from petroleum wells, in Sublette, Kerry, ed., 

Proceedings of the 7th International Petroleum Environmental Conference: 

Environmental Issues and Solutions in Petroleum Exploration, Production and Refining, 

Albuquerque, NM, University of Tulsa. 

Carty, D.J., Crawley, W.W. and Priebe, W.E., 1997, Remediation of salt-affected soils at oil 

and gas production facilities: American Petroleum Institute, Health and Environmental 

Services Department, API Publication Number 4663, paginated in sections. 

Collins, A.J., 1975, Geochemistry of oil field waters: New York, Elsevier, 496 p. 

Energy Information Administration (EIA), 2001, Annual energy review 2000, Washington 

DC. 

Godsy, E,M., Hostettler, F.D., Warren, Ean, Paganelli, V.V., and Kharaka, Y.K., [this 

volume] 2003, The fate of petroleum and other organics associated with produced water 

from the Osage-Skiatook petroleum environmental research site, Osage County, 

Oklahoma: U.S. Geological Survey Water-Resources Investigations 03-4260, p. 84-102. 

Herkelrath, W.N. and Kharaka, Y.K., [this volume] 2003, Hydrologic controls on the 

subsurface transport of oil-field brine at the Osage-Skiatook petroleum environmental 

research “B” site, Oklahoma, U.S. Geological Survey Water-Resources Investigations 

03-4260, p. 111-123. 

Kharaka, Y.K., Gunter, W.D., Aggarwal, P.K., Perkins, E.H., and DeBraal, J.D., 1988, 

SOLMINEQ.88: A computer program for geochemical modeling of water-rock 

interactions, U.S. Geological Survey Water-Resources Investigations Report 88-4227, 

420 p. 

Kharaka, Y.K., Lundegard, P.D., and Giordano, T.H., 2000, Distribution and origin of 

organic ligands in subsurface waters from sedimentary basins, in Giordano, T.H., 

Kettler, R.M. and Wood, S.A., eds., Ore Genesis and Exploration: The Role of Organic 

Matter: Reviews in Economic Geology, v. 9, p. 119-131. 

Kharaka, Y.K., and Thordsen, J.J., 1992, Stable isotope geochemistry and origin of waters in 

sedimentary basins, in Clauer, N. and Chaudouri, S., eds., Isotope Signatures and 

Sedimentary Records: Germany, Springer-Verlag, p. 441-466. 

82
Kharaka, Y.K., Thordsen, J.J., and Ambats, G., 1995, Environmental degradation associated 

with exploration for and production of energy sources in USA, in Kharaka, Y.K., and 

Chudaev, O.V., eds., Water-Rock Interaction (WRI-8), Rotterdam, A. A. Balkema, p. 

25-30. 

Kharaka, Y.K., Thordsen, J.J., and White, L.D., 2002, Isotope and Chemical Compositions 

of Meteoric and Thermal Waters and Snow from the Greater Yellowstone National Park 

Region” U.S. Geological Survey Open-File Report 02-194, 56 p. 

Kharaka, Y.K. and Wanty, R.B., 1995, Water quality degradation associated with natural 

energy sources: U.S. Geological Survey Circular, Report C-1108, p. 25-27. 

Otton, J.K., Asher-Bolinder, Sigrid, Owen, D.E., and Hall, Laurel, 1997, Effects of produced 

waters at oilfield production sites on the Osage Indian Reservation, northeastern 

Oklahoma: U.S. Geological Survey Open-File Report 97-28, 48 p. 

Otton, J.K. and Zielinski, R.A., [this volume] 2003, Produced water and hydrocarbon 

releases at the Osage-Skiatook petroleum environmental research studies, Osage county 

Oklahoma: Introduction and geologic setting: U.S. Geological Survey Water-Resources 

Investigations 03-4260, p. 14-41. 

Richter, B.C. and Kreitler C.W., 1993, Geochemical techniques for identifying sources of 

ground-water salinization: Boca Raton, C.K. Smoley, CRC Press, 258 p. 

Smith, B.D., Bisdorf, R.J., Horton, R.J., Otton, J.K., and Hutton, R.S., [this volume] 2003, 

Preliminary geophysical characterization of two oil production sites, Osage county, 

Oklahoma-Osage Skiatook petroleum environmental research project, U.S. Geological 

Survey Water-Resources Investigations 03-4260, p. 42-55. 

USEPA, 1987, Management of wastes from the exploration, development and production of 

crude oil, natural gas and geothermal energy: EPA/530-SW-88-003. 

Wilson, M.J. and Frederick, J.D., eds., 1999, Environmental engineering for exploration and 

production activities Society Petroleum Engineers Monograph Series, v. 18, 114 p. 

Zielinski, R.A., Rice, C.A., and Otton, J.K., [this volume] 2003, Use of soil extracts to 

define the extent of brine-impacted soils at the Osage-Skiatook Petroleum

Environmental Research “B” site, northeastern Oklahoma: U.S. Geological Survey 

Water-Resources Investigations 03-4260, p. 124-132.

83
The Fate of Petroleum and Other Organics 

Associated with Produced Water from the 

Osage-Skiatook Petroleum Environmental 

Research Sites, Osage County, Oklahoma 

By E. Michael Godsy, Frances D. Hostettler, Ean Warren, V. Vincenzo Paganelli, and 

Yousif K. Kharaka 

Abstract 

During a multidisciplinary study at two oil production sites of differing ages near Lake 

Skiatook, Osage County, Oklahoma, a series of oil, water, brine, and soil samples were 

characterized and analyzed for geochemical parameters that are indicative of microbial activity. 

Characterization of the resident microbial populations was completed for a number of these 

samples. The area source oils are paraffinic-naphthenic light oil, containing n-alkanes as the 

dominant components unimpacted by biodegradation. The oils at the inactive OSPER “A” site 

are similar although vary in stages of biodegradation. Some nearby oils at the active OSPER “B” 

site do not correlate, suggesting that there is not significant subsurface transport of the spilled 

oils. Microbial populations at both sites are degrading the water-soluble crude oil compounds. 

The geochemical evidence and make-up of the microbial populations at both sites indicate that 

the systems are slightly different but based on free energy yields, are poised at the level of iron 

reduction. 

Introduction 

The U.S. Geological Survey is involved in a multidisciplinary investigation to study the 

transport, fate, and natural attenuation of inorganic salts, trace metals, radionuclides and organic 

compounds present in produced water and their impacts on surface and ground water and soils 

on the local ecosystem at the Osage-Skiatook Petroleum Environmental Research (OSPER) site 

A (fig. 1) and site B (fig. 2). About one hectare of land at each of the sites is affected by salt 

scarring, soil salinization, and petroleum contamination. The main environmental concern results 

from the fact that the sites are adjacent to Skiatook Lake, a 4,250-hectare reservoir, that provides 

drinking water and recreational fishing to the local communities. Petroleum wells and production 

tank batteries at site A have been inactive for some time and the bulk of the hydrocarbon (now 

degraded and weathered oil) and produced water releases occurred more than 60 years ago. One 

pit at this site however, contains relatively fresh asphaltic oil and high salinity brine. In contrast 

to site A, site B (approximately 6 km SSE.) includes an active production tank battery and 

adjacent brine and oil pit, an inactive tank battery and an injection well with a small brine pit. 

For this portion of the study, samples of sediments, water, oil, and brine were obtained 

from several oil wells at the site B and areas adjoining the sites A and B, from the main pit at the 

Site B, from the asphaltic pit and adjacent weathered oil pit at the site A and from several of the 

40 boreholes (1-71 m deep), recently drilled and completed. Samples of sediments and/or water 

84
Trees

Grass

Trees

Trees

Grass

Old redwood

tanks

Road

Trees

Grass

Trees

Trees

Trees Skiatook

Lake

Grass

Legend

Artificial fill, asphaltic

and weathered oil

Oil-impacted soils

0 10 20 30 m

N

Outline of

salt scar

Outline of

salt scar

AHA04

x AHA03

AHA02

x 

x AHA01

AE12

AE11

AE03

x

105

103

AG020-22703

AP01

AG020-22801

AZ01

AG020-22701

AG020-22702

x

x

x

x

x

Sandstone

shelf

AA04 x

AE09 AE10

AE08

x

x

AA03

x

AE07

x

AE06

x

x

AE05

AE04

x

x

x

x

x

AG020-22802

x

x

Figure 1. Sample locations for this portion of the study and important features at the 

site A location. Large arrows point to sample locations that are off the map area. 

85
Outline of

salt scar

Outline of

salt scar

Outline of

salt scar

0 10 20 30 m 

N

Oil impoundment 

fill line

Shoreline March 2001 

Shoreline 

December 2001 

Road

Legend Storage tanks 

Artificial fill, 

oil-impacted soils 

x

BE12 

x

BE11

x

BE10 

 x BE09

x 

BE08 

BE07 

x 

x BA03 

BU317 

BU314 

312 

+ 

313 

109 

BU303 

106 

x

x

Figure 2. Sample locations for this portion of the study and important features at the 

site B location. Large arrows point to sample locations that are off the map area. 

86
from these selected boreholes and from the brine and oil pits were obtained for characterization 

of the microbial population. Water samples for dissolved organics were obtained from selected 

boreholes with high salinity water and measurable hydrocarbon gases in the unsaturated zone. 

Soil and rock core samples were obtained from these selected boreholes to determine the amount 

and composition of oil sorbed onto the sediments. 

Results completed to date show the crude oil source throughout the area is a typical 

paraffinic-naphthenic light oil (API gravity of ~35), containing n-alkanes as the dominant 

components. Even though petroleum production is from shallow sandstones (450-524 m site A 

and 260-305 m site B, elevation above sea level), the oils show no sign of biodegradation, 

indicating that microbes are not particularly active in the associated high salinity (~150,000 

mg/L total dissolved solids) brine and possible inhibition by the hydrocarbon oil phase (currently 

under investigation). Microbial action, volatilization and water washing are likely responsible for 

the transformation of source oil to the asphaltic and weathered oil observed on the surface at site 

A. The leakage of oil with brine from the main active pit at site B is indicated by the detection of

a thin, but discrete oil phase in at least one borehole, the presence of hydrocarbon gases in 

several boreholes and the smell of oil in many sediment cores from the impacted area located 

downslope from this pit. The measured concentrations of dissolved organic carbon (DOC), 

acetate and other organic acid anions, benzene, toluene, ethylbenzene, xylenes (BTEX), phenols 

and other organics in the source brine are relatively low, but their values in water samples from

the impacted areas are higher and indicative of microbial activity. 

Materials and Methods 

Microbial Number Determinations 

Microbial numbers in both water and sediment samples were determined using a fivetube most probable number (MPN) analysis. Samples were serially diluted by an order of 

magnitude into pre-reduced anaerobically sterilized mineral salts solution. Aliquots of the 

dilutions were inoculated into six different media, designed to promote growth and the 

enumeration of aerobic heterotrophic, facultative and strict anaerobic heterotrophic, denitrifying, 

facultative and strict iron-reducing, sulfate-reducing, and methanogenic microorganisms (Bekins 

and others, 1999). 

Core Sample Collection 

Sediment samples were collected in clear polycarbonate liners using a Geoprobe® or with 

a hand auger using similar polycarbonate liners. The liners were cut and, with O2-free N2 flowing 

over the sediment, about 10 g of sediment was scooped out with a sterile spatula and placed in 25 

x 142 mm anaerobic isolation roll streak tubes (Bellco Glass Inc., Vineland, N.J.) filled with 20 

mL of prereduced, anaerobically sterilized, mineral salts solution (Holdeman and others, 1977) 

and 10 mg/L Tween 80® (a nonionic surfactant added to help remove microorganisms from the 

sediment) (Bekins and others, 1999). The tubes were then sealed, and allowed to stand for 2 hr to 

permit penetration of the Tween 80 into the sample. The tubes were opened with oxygen (O2)-

free nitrogen (N2) flowing over the surface and sonicated (10W for 30 s) to dislodge 

microorganisms into the mineral salts using a Branson Sonifer, Model 200, equipped with a 

microtip (Branson Corp., Danbury, Conn.). The samples were stored no more than 4 hr on ice 

(4°C) before microbial enumeration. 

87
Water Sample Collection and Analysis 

Water samples were removed using a peristaltic pump equipped with Teflon-lined tubing 

that had been previously cleaned with a detergent solution, rinsed with tap water and then with 

deionized water. Water samples were generally collected after pumping long enough to achieve 

stable pH and temperature values. 

Water samples were collected and analyzed for low molecular weight organic acid and 

inorganic anions by ion chromatography (Kharaka and others, 2000). Inorganic cations were 

analyzed by inductively coupled plasma/mass spectrometry (Kharaka and others, this volume). 

Both cation and anion samples were chilled at 4°C until analyzed. 

Water samples for dissolved methane (CH4) analyses of were collected in 60-mL syringes 

and injected into evacuated 30 mL serum bottles until atmospheric pressure was reached. The 

serum bottles contained an O2-free N2 atmosphere before evacuation. Samples were preserved 

with 50 mg/L mercury using mercuric chloride. Dissolved CH4 in the headspace was analyzed by 

a gas chromatograph equipped with a thermal conductivity detector after equilibration at ambient 

temperature (Godsy and others, 1992). The dissolved CH4 present in the water sample was 

calculated using Henry’s Law (Godsy and others, 1992). Water samples (20 mL) for microbial 

enumeration were collected with a disposable 60-mL sterile syringe and injected into an 

evacuated sterile 30-mL glass serum bottle. The serum bottles contained an O2-free N2

atmosphere before evacuation and were sealed with a butyl rubber stopper and secured with an 

aluminum crimp seal. All water samples were stored on ice for no more than 4 hr before 

inoculating the various microbial growth media onsite. 

Production Oil Sample Collection 

Four oils in current production from local oil wells near the study area are included in the 

sample set. Samples from site A and B included mud, rocks, sandy soil or sediment collected 

from surface accumulations or in cores, asphaltic surface oils, oil floating on water, and 

congealed oil from brine tanks. Table 1 describes the samples. Site samples were collected in 

pre-cleaned glass jars, refrigerated after collection, and then frozen until analysis. When the 

samples were unfrozen for analysis, any water was decanted off. One wet sediment sample 

(BE07) was air-dried and ground to about 30 mesh. Thirty grams was extracted with 

dichloromethane (DCM), filtered through glass wool, and the filtrate used for analysis (below). 

All other site samples were extracted with DCM after thawing. If traces of water were present, 

the water was removed by addition of anhydrous sodium sulfate, followed by filtration. Copper 

powder, pre-activated with concentrated hydrochloric acid, was also added to the DCM solutions 

before filtration in order to remove possible traces of sulfur. The four production oils (25 mg

each) were dissolved in DCM and treated with copper. Aliquots of each of the site samples were 

measured so that approximately 25 mg of extractable material was analyzed. For each sample, its 

DCM solution was concentrated to near-dryness under a gentle stream of dry N2, and the residue 

dissolved in 5 mL of hexane. 

The hexane solution was then loaded onto a liquid chromatography column layered with 

alumina and silica gel for compound class separation. The column was eluted with hexane and 

then 30% DCM in hexane, rinsing the 5 mL container with the 30% solution when the eluting 

solvent was changed. Two separate fractions were collected-aliphatic (hexane) and aromatic 

(30% DCM). These fractions were analyzed for aliphatic and aromatic hydrocarbons by gas 

88
Table 1. Sample and site descriptions. 

Field designation Description Site location Deg'n* 

Locally produced oils

103 Oil in current production N of site A A 

105 Oil in current production E of site A A 

106 Oil in current production NE of site B A 

109 Oil in current production SW of site B A 

Site A (02OS-) 

AG020-22701 Oil in mud, surface Oil/fill, down slope, edge pit 

 B/A 

AG020--22702 Oil in mud, surface Oil/fill, down slope, old area C+ 

AG020-22703 Oil in mud/sed., surface Oil/fill down slope, new area A/B 

AG020-22801 Mature asphalt, solids Oil/fill, down slope, old area D+ 

AE12-436 Traces oil floating on water Oil/fill, down slope, well C+ 

AP01, Sludge Pit Oil, sticky mud, 60 cm BLS** Oil/fill, down slope, new area A 

AP01, Sludge Pit Oil, sticky mud, 30 cm BLS Oil/fill, down slope, new area A 

AZ01 Sandy sed./oil, 50 cm BLS Oil/fill, down slope, edge pits D&C+ 

AHA04-20 cm Oil in mud, water, 20 cm" BLS Oil-impacted soil, core, upslope C++ 

AHA04-46 cm Oil in sandy mud, 46 cm BLS Oil-impacted soil, core, upslope C+ 

AHA04-66 cm Oil/ sed., water, 66 cm BLS Oil-impacted soil, core, upslope C/D+ 

AG020a-22802 Sand/sediment, 10 cm Pit far down slope, near lake D&A 

AG020b-22802 Gray mud/clay, 40 cm Pit far down slope, near lake A 

AE03 Old surface asphaltic tar by well, W edge of site A D 

Site B (02OS-) 

BE07 Wet soil, 1.2-2.1 m /66.5 cm E of tanks and pit C 

BU-314 Residual oil Brine tank battery (by pit) A 

BU-314 Congealed oil with water Brine tank battery (by pit) A 

BA03 Rocks/ oil, 5.7-5.8 m BLS NW of brine tanks and pit C 

BU-303 Viscous surface tar NW corner of site B A 

BU-317 Congealed oil on water Large main pit A 

312 Flocculent - water, 34.5 m West of site B, deep well 2 C 

313 Flocculent - water, 35.9 m West of site B, deep well 2 C 

*Deg'n = Degradation State, defined in text 

**BLS = below land surface 

chromatography/mass spectrometry (GC/MS) as Total Ion Chromatograms (TIC) and in the 

Selected Ion Monitoring mode (SIM). Compound identifications were made either by 

comparison with known standards or with published spectra. Chromatograms of a typical local 

production oil, including a TIC, an Extracted Ion Chromatogram (EIC) of m/z 83 

(alkylcyclohexanes), and a SIM chromatogram of terpanes (m/z 191) and steranes (m/z 217), 

with peaks of interest noted, are shown in figure 3. The TICs were used to evaluate the level of 

weathering or degradation of the samples. The state of weathering (table 1) ranged from A to D, 

where A = no/low degradation, n-alkanes dominant; B = n-alkanes minor, isoprenoids becoming 

prominent; C = no n-alkanes, isoprenoids dominant; and D = highly degraded, almost no residual 

components except high-molecular-weight biomarkers. Some samples from the site A included 

some anomalous high-end alkanes, indicated in table 1 with a “+”. 

89
αααC29 

A. Total Ion 

 Chromatogram (TIC) 

B. m/z 83 Extracted 

 Ion Profile (EIC)

 o o o o o o o 

 (n-alkylcyclohexanes) 

C. m/z 191 Selected Ion 

Monitoring (SIM) 

 Hopanes 

D. m/z 217 SIM 

 Steranes

 Biomarkers 

11

17

18

Pr

Ph

n-alkanes and 

isoprenoids 

30 

Biomarkers 

23T

Triplet αβC29 

αβC30

βαD27

βαD29 

ββC29

S R

αααC28 

S R

Response 

Time

Pr

Ph

Figure 3. Chromatograms of Production Oil 103. Most compounds of interest are 

identified in the text. Others: βαD27 = 13β,17α(H)-diacholestane (S+R); βαD29 = 24-

ethyl-13β,17α(H)-diacholestane (S+R); ββC29 = 24-ethyl-14β,17β(H)-cholestane (S+R). 

90
Selected biomarker ratios, listed below, were calculated from the TIC and SIM 

chromatograms using peak heights. These biomarker parameters were used to correlate the 

samples, and included the following ratios (table 2): 

1. Pr/Ph, pristane/phytane. This ratio of two ubiquitous isoprenoid hydrocarbons is widely 

used as a source parameter (Peters and Modlwan, 1993). 

2. 23T/C30, C23tricyclic terpane/17α,21β(H)-hopane. This ratio is a source parameter adapted 

from Peters and Moldowan (Peters and Moldowan, 1993). 

3. Tm/Ts, 17α-22,29,30-trisnorhopane/18α-22,29,30-trisnorneohopane. This ratio is used as 

both a source and maturity parameter (Seifert and Moldowan, 1978). 

4. Triplet, [C26-tricyclic terpane (S?) + C26-tricyclic terpane (R?)/C24-tetracyclic terpane. This 

source parameter was used to distinguish coastal tar residues in Prince William Sound 

(Kvenvolden and others,1995). 

5. C30/C29, 17α,21β(H)-hopane/17α,21β(H)-30-norhopane. This ratio was used by Palacas 

and others (1984) as a source parameter. 

6. C29S/(S+R), 24-ethyl-5α,14α,17α(H)-cholestane (20S)/ 24-ethyl-5α,14α,17α(H)-

cholestane (20S+20R). This sterane epimer ratio is commonly used in petroleum

geochemistry as a maturity parameter; the equilibrium value at full maturity is ~0.5 

(Mackenzie and others, 1980). 

7. C28R/C29R, 24-methyl-5α,14α,17α(H)-cholestane (20R)/ 24-ethyl-5α,14α,17α(H)-

cholestane (20R). This source parameter has been modified from discussions in Grantham

and Wakefield (1988) and Waples and Machihara (1991). 

8. RI, Refractory Index. This PAH ratio is a source parameter, the ratio of the major peak in 

the highly refractory C26 to C28 triaromatic sterane suite and in the monomethyl chrysenes 

(Hostettler and others, 1999). 

Results and Discussion 

Microbial Populations 

The general process of biodegradation of the water-soluble fraction (WSF) of crude oil 

occurs under specialized conditions. In the saturated subsurface, WSF compounds are used by 

the microorganisms as an electron donor for energy, and dissolved O2 is utilized preferentially as 

the primary electron acceptor. Once O2 is depleted, anaerobic microorganisms typically use 

available electron acceptors in the following order: nitrate ( ), producing N - NO3 2, or ferric iron 

( ), producing ferrous iron ( ), sulfate ( ), producing sulfide (S 3+ Fe 2+ Fe 2- SO4

2-), and carbon dioxide 

(CO2), producing CH4. By looking at both the spatial distribution of the different microbial 

populations present on/or within the sediment and in the pore water; and the spatial distribution 

and concentration of oxidation/reduction reactants and products, the mechanism(s) and rates of 

biodegradation can be assessed. A reconnaissance for the different physiological groups of 

microorganisms, along with the ground-water geochemistry, can provide information on the 

major microbial processes that may be occurring in the subsurface environment. The microbial 

population can be categorized under the following physiological groups: 

91
Table 2. Summary of results of geochemical correlation parameters from tars and oils. 

Ratios are defined in the text. 

––––––––––—— m/z 191 ––––––––––––– –—– m/z 217 –—– 

Site Pr/Ph 23T

C30

Tm

Ts Triplet C30

C29

C29

S

S+ R

C28

C29

 RI 

———————————————————————————————————————————————

Locally produced oils

103 1.5 2.1 0.50 7.1 1.9 0.48 0.20 0.30 

105 1.5 1.9 0.56 6.4 1.9 0.48 0.20 0.27 

106 1.5 2.6 0.41 7.7 1.9 0.48 0.20 0.25 

109 1.5 1.8 0.55 6.4 1.9 0.48 0.20 0.27 

Site A (02OS-)

AG020-22701 1.2 1.4 0.63 5.4 2.0 0.47 0.21 0.33 

AG020-22702 1.2 1.3 0.63 5.6 1.9 0.46 0.20 0.40 

AG020-22703 1.3 1.3 0.55 5.9 1.9 0.47 0.21 0.39 

AG020-22801 nc 1.2 0.57 5.8 1.9 0.47 0.20 0.46 

AE12-436 1.3 1.4 0.62 5.7 1.9 0.47 0.20 0.62 

AP01-61 cm, 1.5 1.3 0.64 6.1 1.8 0.46 0.18 0.43 

Sludge Pit

AP01-30.5 cm, 1.5 1.3 0.60 6.0 1.9 0.45 0.20 0.40 

Sludge Pit

AZ01 1.1 1.2 0.59 4.9 1.9 0.49 0.19 0.52 

AHA04-20 cm 1.1 1.5 0.58 5.6 1.9 0.47 0.19 0.33 

AHA04-46 cm 1.3 1.5 0.56 5.8 1.9 0.47 0.20 0.46 

AHA04-66 cm 1.1 1.4 0.59 5.5 2.0 0.47 0.19 0.40 

AGO20a-22802 1.4 0.70 0.63 3.6 1.7 0.58 0.20(*) 0.24 

AGO20b-22802 1.6 0.23 1.2 3.1 1.8 0.43 0.33 0.74 

AE03 nc 0.56 0.52 1.2 1.8 0.61 0(no C28) 0.24 

Site B (02OS-)

BE07 1.4 1.1 0.66 5.0 1.8 0.47 0.20 0.47 

BU-314 1.6 1.5 0.59 5.9 1.9 0.48 0.21 0.36 

BU-314 1.5 1.4 0.56 5.5 1.9 0.47 0.21 0.39 

BA03 1.4 1.2 0.62 4.8 2.0 0.48 0.22 0.78 

BU-303 1.5 2.0 0.46 6.5 2.0 0.48 0.20 0.26 

BU-317 1.4 2.2 0.48 6.8 1.9 0.47 0.20 0.62 

312 1.3 1.0 0.76 3.1 1.8 0.46 0.28 0.78 

313 1.4 1.1 0.75 4.8 2.0 0.47 0.20 0.68 

nc = not calculatable due to lack of constituents 

* = uncertain identification of relevant peak(s) 

Aerobes 

Microorganisms that utilize O2 as the terminal electron acceptor are termed aerobes and 

those that can only use O2 as the electron acceptor are termed obligate aerobes. The use of O2 as 

the electron acceptor always provides the most energy from a given compound and 

microorganisms capable of using other electron acceptors will always use O2 first.

92
Facultative Aerobes 

Because diffusion of molecular oxygen in water is about 100,000 times slower than it is 

in the gas phase, an oxic system can quickly become anoxic in saturated environments. The next 

most thermodynamically efficient electron acceptor commonly found in the environment is . 

Nitrate, nitrite ( ), and nitrous oxide ( ) are used as electron acceptors by many common 

facultative aerobic soil bacteria. These microorganisms simply switch to using the next best 

electron acceptor ( ) when O

- NO3

- NO2 N2O

- NO3 2 is not available. When has been utilized or is not present, 

most, but not all, of these microorganisms can switch to , the next best electron acceptor 

based on free energy yields. 

- NO3

3+ Fe

Obligate Anaerobes (Respiratory) 

These microorganisms are the obligate iron reducers, sulfate reducers, and CO2 reducing 

methanogens, each of which may be thought of as having a very truncated respiratory system. 

These organisms obtain very little energy from these processes, but still prevail under these 

meager conditions. The obligate iron and sulfate reducers can use acetate and/or molecular 

hydrogen (H2) as their energy source. The methanogenic microorganisms in this group use 

molecular H2 or formate as their energy source. The H2 is generated by the other group of 

anaerobes described immediately below. 

Obligate Anaerobes (Fermentative) 

Fermentation, by definition, is the use of organic electron donor to give a stoichiometric 

balance of protons and electrons in lieu of an electron acceptor (i.e. oxidation and reduction of 

the same organic compound). Many of these microorganisms produce H2 during the production 

of protons and electrons from more complex native or WSF compounds. Acetate fermenting 

methanogens are also included in this group. 

Site A Microbially Important Geochemistry 

Concentrations of low molecular weight fatty acids (e.g., butyrate, propionate, acetate 

and formate), known intermediates in the anaerobic microbial degradation of crude oil and other 

complex organic compounds (Godsy and others, 1992), are very high (210 mg/L acetate, site 

AP01) in the sludge pond near the road. These concentrations generally decrease moving 

downslope (Kharaka and others, this volume) suggesting anaerobic microbial processes 

predominate (AE08, AE09, and AE10, generally 0.8-1.2 m below land surface [BLS]). The 

exception to this trend occurs in the deeper wells AA03s (1.2-2.7 m BLS), and AA03d (3.3-4.9 

m BLS) where acetate concentrations reach 101 and 517 mg/L, respectively). Wells AA04s (1.8-

3.4 m) and AA04d (5.8-7.3 m), located outside of the area affected by the sludge pits have nondetectable levels of fatty acids; however, they have high total dissolved solids (TDS) and been 

affected by produced water. The DOC concentrations generally correlate positively with the 

concentrations of fatty acids. In addition to the volatile fatty acids, low concentrations of benzene 

(0.29 mg/L) and toluene (0.34 mg/L) were found in a water sample from AP-01. 

Sediment Fe2+/Fe3+ ratios (Rice and others, this volume) outside the oil-impacted soils 

(from the old southern tank farm to north of the sludge pits, AE04 to 07) at the site are low (< 

0.5) in shallow sediment (0-1.2 m, BLS) samples. The low Fe2+/Fe3+ ratios result from low Fe2+

93
concentrations on the sediments suggesting a lack of crude oil components for microbial 

biodegradation and thus iron reduction; however, the Fe3+ concentrations at these sites range 

from 0.5 to 1.0 mg/g. The total iron concentration in the water sample from the sludge pit (AP01) 

is 595 mg/L, strongly suggesting that microbial iron-reduction is occurring at the expense of the 

water-soluble components of the oil present in the pits. 

In addition, very low levels of were found throughout the site (Kharaka and others., 

this volume), and no measurable amounts of S

− NO3

2- were found even with the probable anoxic 

conditions as evidenced by the sulfate reducing microorganisms near the oil impacted soils and 

high concentrations of . Perhaps, the S 2− SO4

2- is precipitated as an iron sulfide (FeS) because of 

the high concentrations of Fe3+ throughout the area. Only trace amounts of CH4 were detected in 

the water samples throughout the area and downslope near the sludge pits, again strongly 

suggesting that microbial iron reduction is the predominant microbial process in and around the 

sludge pit. 

Site A Microbial Populations 

Microbial populations capable of aerobic growth are equal to or slightly larger than 

populations capable of fermentation suggesting that the population is mixed aerobic and 

facultative anaerobes (microorganisms capable of aerobic growth in the presence of O2, and 

fermentation or either denitrification and/or iron-reduction in the absence of O2 (table 3). This 

observation for the shallow samples AHA01 to 04 is consistent with a flow system that is driven 

by rainfall events. The rainfall contains dissolved O2 and when the event has passed, pore spaces 

with higher dissolved O2 will remain. Of the samples throughout this site, only a small 

proportion of the microorganisms are capable of denitrification (AE10 and 12 did not have a 

denitrifying population); this would be due to very low levels of found at this site. − NO3

Presumably, in samples downslope from the sludge pit (AE08, 10, and 12), anaerobic 

microorganisms should predominate. The iron reducing population at this site appears to be a 

mixture of facultative aerobes and strict anaerobic microorganisms with the strict anaerobic 

microorganisms predominating. This can be seen from the differences in the populations of iron 

reducing microorganisms minus the populations of denitrifying microorganisms. Relatively large 

numbers of microorganisms capable of sulfate reduction are present in samples throughout the 

site; however, they may not be particularly active since concentrations of S2- are very low even 

with the abundance of or the S 2− SO4

2- at the site is removed as FeS. In addition, only very low 

numbers (< 100 MPN/g) of methanogenic microorganisms were found at three sites (AHA01, 

AHA03 and AE12) indicating they may not be particularly active except near the sludge pits. 

Study Area Production Oils 

The four oils from currently producing oil wells serve as representative baseline samples 

for oils produced throughout this local area. These four oils share similar characteristics. They 

are typical paraffinic-naphthenic light oils, with an API gravity of approximately 35, containing 

n-alkanes as their dominant components. They are fully mature oils with very similar chemical 

fingerprints, as shown by the correlation parameters given in table 2. Small numerical 

differences in these parameters allow some differentiation between the four oils, but their overall 

natures are quite similar. Even though petroleum production is from shallow sandstones, these 

94
Table 3. Sample locations and Most Probable Numbers (MPN) of microbial populations 

on sediment and in water samples. 

[BLS = below land surface; ND = < 20-40/mL or g; >> = > E+6/mL or g; ~~ = approximate value E+2-4/g] 

Site # Notes 

Aerobes 

MPN/mL

Aerobes 

MPN/g

Fermentors 

MPN/mL

Fermentors 

MPN/g

Denitrifyers 

MPN/mL

Denitrifyers 

MPN/g

AEO8A 0-1.2 m, bottom 3.5E+06 2.8E+05 8.8E+03

AE08B 0-1.2 m, 25 cm from top >> 2.0E+05 8.7E+02

AE10 0-1.2 m, 25 cm from bottom 2.2E+05 1.1E+06 ND

AE12 0-1.2 m, 41 cm from top 1.4E+03 1.6E+05 ND

AHA01 ~20-30 cm BLS 5.2E+05 1.7E+05 9.7E+01

AHA02 ~20-30 cm BLS 1.8E+05 7.4E+04 ND

AHA03 ~20-30 cm BLS 8.3E+05 2.5E+06 1.4E+02

AHA04 20 cm BLS 1.8E+05 2.8E+04 1.4E+02

AHA04 46 cm BLS >> 8.7E+03 8.0E+01

AHA04 66 cm BLS 2.1E+06 1.5E+04 2.7E+01

BEW07 1.2 m BLS 2.4E+03 7.9E+02 ND

BE07A 0-1.2 m, 66.5 cm top 9.9E+04 9.3E+02 ND

BE07B 1.2- 2.1 m, 35.5 cm top 4.6E+04 1.3E+04 3.8E+01

BE08 1.2-2.1 m, top 6.0E+03 4.4E+03 ND

BE09S 1.2-2.1 m, bottom Shale 2.6E+03 8.8E+02 ND

BE09 1.2-2.1, 26 cm top 2.4E+03 6.0E+03 ND

BE10 0-1.2 m, 70 cm top 8.4E+04 1.0E+03 ND

BE11 1.2-2.1 m, 40.5 cm top 5.7E+03 5.7E+03 ND

BE12 1.2-2.1 m, 15 cm top 7.2E+05 7.9E+05 ND

Site #

Iron 

Reducers 

MPN/mL

Iron 

Reducers 

MPN/g

Sulfate 

Reducers 

MPN/mL

Sulfate 

Reducers 

MPN/g

Total 

Methanogens 

MPN/mL

Total 

Methanogens 

MPN/g

AEO8A 2.0E+06 9.4E+05 1.0E+00

AE08B >> 5.0E+03 ND

AE10 3.3E+06 2.6E+05 ND

AE12 2.6E+05 2.6E+03 4.0E+00

AHA01 5.2E+05 1.8E+04 4.3E+00

AHA02 1.4E+05 7.4E+03 ND

AHA03 2.5E+06 1.4E+04 7.7E+01

AHA04 9.2E+04 2.0E+03 ND

AHA04 >> 1.5E+04 ND

AHA04 >> 3.2E+05 ND

BEW07 2.4E+05 3.1E+02 7.0E+00

BE07A 1.3E+02 9.9E+02 ND

BE07B 4.6E+04 6.3E+03 2.5E+01

BE08 ND 1.5E+02 ND

BE09S ND ND ND

BE09 ND 1.4E+03 ND

BE10 4.9E+04 ~~ ND

BE11 1.4E+03 3.9E+02 ND

BE12 3.1E+06 1.8E+04 1.1E+02

95
fresh oils show no sign of biodegradation, indicating that their reservoirs and the associated high 

salinity brines are not conducive to microbial action on the hydrocarbon phase. However, as the 

oil has been mined, brought to the surface, and spilled throughout the study areas, the resultant 

oils exhibit widely varying levels of degradation. Volatilization, water washing, and microbial 

action are likely responsible for the transformation of the source oil to the surficial weathered, 

biodegraded, and sometimes asphaltic oils observed at the study sites. 

Characterization of Site A Oils 

The majority of oil samples from OSPER “A” site correlate closely with each other, 

despite being at highly variable stages of degradation (tables 1 and 2). Three samples in a core at 

the top of the production area (AHA04, samples from 20 cm, 46 cm, and 66 cm BLS), most 

likely represent older oil spilled from earlier production. They are degraded to the point of 

complete loss of the n-alkanes (“C”-stage), with the sample lowest in the core showing the most 

degradation, containing a highly weathered component (“D”) and only low levels of the 

isoprenoids characteristic of the C-stage. Degradation to the C-stage in a fuel oil spill is 

estimated to take at least 20 years (Christensen and Larsen, 1993). 

Down slope, approximately 60-90 m from these samples, are eight samples from different 

areas of a sludge disposal pit. One area is obviously old and weathered, and its oils (AG020-

22702, AG020-22801) and oil floating on water from a well in its midsection (AE12) are at the 

C- or D-stages. Another section, where the oil is fresher and probably more recently dumped, 

three oils (AP01 30 cm and AP01 60 cm, along with AG020-22703) are at A-stage or slightly 

beyond, at an A/B-stage. Two samples from the downslope edge of the same pit area, where 

there is some overlap, are fairly fresh (AG020-22701, B/A-stage) and quite old (AZ01, D- with 

some C-stage), respectively. It is not known whether the eight pit-area oils migrated downslope 

from the production area over time or were dumped during and after production, but these eleven 

oils are clearly related (table 2). 

However, the other three oils from this site are not so closely related. Samples a- AG020-

22802 and b- AG020-22802, from two different horizons in a pit about 110 m further downslope, 

adjacent to the lake, are not the same as the upslope samples, and in fact, are somewhat 

dissimilar to each other. The first, from 10 cm depth, is a mix of highly degraded oil and fresh oil 

(D- and A-stages), and the second, from 40 cm depth, is quite fresh (A-stage). The old surface oil 

at the west edge of the site (AE03) is the most different, and probably is a remnant of a very old 

disposal pocket, possibly older than 100 years. Despite individual differences in the four 

different disposal pockets at site A, all the oils reflect the characteristics of the local oil province 

in their biomarker distributions. In addition, however, there is perhaps some extraneous oil 

product at some sites. Samples from the core at the production site and from downslope in the 

old part of the sludge pit contain additional components, low levels of an anomalous group of 

high molecular weight n-alkanes. The two new sludge pit samples, AP01-30 cm and AP01-60 

cm, also contain some high molecular weight n-alkanes, giving their GC/MS TIC two 

distribution maxima, the typical primary maximum at n-C18 and another at n-C28. These sample 

sites, therefore, may also be contaminated with some extraneous oil product such as lubricating 

oil or the like. 

There is no generally applied method to determine from the chemical profile whether the 

oil has been degraded aerobically or anaerobically. However, some recent work on crude oil 

spillage in Bemidji, Minnesota, suggests that in the latter stages of degradation, the profile of the 

96
homologous n-alkylcyclohexanes (m/z 83 chromatograms) can shed some light on this 

differentiation (Hostettler and Kvenvolden, 2002). These compounds are more refractory than nalkanes, and thus retain their contribution to the chemical signature of the source oil for a longer 

period after exposure to the environment. Their original distribution in a fresh oil is usually bellshaped (figs. 3B and 4). Weathering (aerobic degradation) attacks and removes the low 

molecular weight end of the series (Wang and others, 1998), whereas anaerobic biodegradation, 

particularly in the subsurface, slowly degrades homologs from the high molecular weight end 

(Hostettler and Kvenvolden, 2002). At site A the samples show variable amounts of low-end 

loss, even in the relatively undegraded samples, indicating that all the samples have undergone 

some physical weathering or aerobic loss. However, the more degraded samples (at about the Cstage, but beyond this stage samples are too degraded to interpret) show some loss from the high 

molecular weight end as well, indicating some anaerobic losses also. This pattern occurs to some

extent in the old fill-area (samples AG020-22702 and AE12) and possibly in the upslope oilimpacted soil samples at AHA04. 

Site B Microbially Important Geochemistry 

In contrast to the “A” site, the tank battery above the main pit at the “B” site is actively 

pumping oil and reinjecting the produced brine. A sample from the oil separation tank at this site 

(BU314) contains indicators of microbial activity, in spite of the extremely high TDS (133,000 

mg/L). In addition to acetate and formate (0.5 and 0.3 mg/L, respectively), benzene (4.0 mg/L), 

toluene (0.87 mg/L), ethylbenzene (0.73 mg/L), m- and p-xylene (0.71 mg/L), and o-xylene (0.43 

mg/L) were detected in the water sample. The water sample also contained 70 mg/L ammonia, 

35 mg/L total iron, and a lower pH (6.5) than other water samples in the area. These observations 

suggest the WSF of the oil is, even in the presence of extremely high TDS brines, undergoing 

biodegradation. The higher molecular weight fractions of the oil apparently do not biodegrade in 

the formation or in the oil separation system or tanks. These observations require further 

investigation before they can be confirmed. 

Water samples from the main pit just in front of the tank battery (BU317) also showed 

signs of microbial degradation of the WSF of the oil. In addition to high total dissolved iron (40 

mg/L), higher total organic carbon (43 mg/L), and a lower pH (6.6), the sample contained acetate 

(0.6 mg/L) and formate (0.3 mg/L). Benzene (0.23 mg/L) was also detected. Down slope from

the main pit to the lake, only low concentrations of acetate and formate (≤ 0.6 mg/L) were found. 

Sediment Fe2+/Fe3+ ratios (Hostettler and others, 1999) at this site are high (~45 to ~11) 

in shallow (0-1.2 m) samples near the lake water line and below the main pit (BE07, BE09, 

BE11, and BE16) strongly suggesting microbial iron reduction. The Fe2+/Fe3+ ratios in deeper 

samples (1.2-2.1 m) in the same holes and all samples further from the shore and the main pit 

have ratios generally < 1, with the exception of BE09 (12.6). This well is just downslope from

the main pit and appears to be in the flow path from the main pit to the lake. The low values for 

wells closer to the lake and out of the flow path suggests that these sites are influenced by the 

O2-rich lake water and aerobic microbial processes may predominate. 

As at site A, very low levels of were found throughout site B (Kharaka and others, 

this volume), and no measurable amounts of S

− NO 3

2- were found, even with the probable anoxic 

conditions as evidenced by the sulfate-reducing microorganisms near the oil impacted soils and 

high concentrations of . Only trace amounts of CH 2− SO4 4 were detected in the water samples 

97
throughout the area and downslope near main pit, again strongly suggesting that microbial iron 

reduction is the predominant microbial process in and around the main pit to the lake. 

Site B Microbial Populations 

Microbial populations capable of aerobic growth are equal to or less than populations 

capable of fermentation suggesting that the population is predominantly facultative aerobes 

(table 3). Only one sample, BE07 at 1.2 to 2.1 m, at this site contained microorganisms (38 

MPN/g) capable of denitrification, again due to the very low levels of found at this site. 

The iron reducing population would be strictly anaerobic since there are not a significant 

numbers of denitrifyers at this site. 

− NO3

Relatively large numbers of microorganisms capable of sulfate reduction are present 

throughout; however, as at Site A, they may not be particularly active or the S2-

 may have been 

precipitated out of solution. Only very small numbers (< 100 MPN/g) of methanogenic 

microorganisms were found at two sites (BE07 and BE12) indicating they may not be 

particularly active, as is the case with the sulfate reducing microorganisms. The water sample 

from BE07 has a population that is essentially the same as the two sediment samples from this 

site. The fact that the total population is evenly distributed between both the water and the 

sediment strongly suggests that the population is quite active. In situations where little or no 

microbial activity is taking place, up to 90% of the population is attached to the sediment 

(Bekins and others, 1999). In contrast to this finding, the sample taken in the shale (BE09S) has a 

population composed of only aerobic and fermenting microorganisms. Denitrifying, iron 

reducing, sulfate reducing, and methanogenic microorganisms were not detected in this sample. 

This is may be due to the overall impermeability of the shale and will be investigated in detail. 

Characterization of Site B Oils 

Samples from site B show more variation in their correlation parameters, indicating that 

the oils are probably from several slightly different collection sources. Two samples of fresh oil 

(BU314, congealed oils from the brine tank battery, at degradation state A) correlate with each 

other, and perhaps are similar to those in the main body of oils from site A (table 2). Two other 

fresh oil samples from the main pit just in front of the tank battery (sample BU317 and 303), 

which might be expected to be the same as the oils from the brine tanks, actually have slightly 

different parameters although they are at the same A-state of degradation. A C-degraded oil, 

BE07, from a subsurface core of wet soil, about 50 m in front of the main pit (sometimes 

submerged under the lake water), is again similar but not identical to that from the brine tanks or 

the main pit. Another sample from the subsurface, BA03, present in low amounts on rocks at 

almost 5.8 m below land surface, is also at the C-stage and is similar to the oil in BE07 except 

for one parameter. The two oils associated with flocculent material from the deep well just offsite west (312 and 313) are C-degraded and correlate fairly well with one another, and, again, are 

slightly different from the other oils. 

With respect to the type of degradation that has impacted the samples, all four A-state 

oils (from the brine tanks and the main pit) show only low-end, aerobic or weathering loss on the 

n-alkylcyclohexane chromatograms. The other four samples, all at C-degradation, show both 

low-end and high-end losses, indicating both weathering and anaerobic biodegradation. 

Examples are shown in figure 4. 

98
B. Oil with substantial

biodegradation

High-end loss

No high-end loss Some

low

end 

loss

Low

end

loss Pr

Pr

Ph

Ph

Time

Resp

o

nse

A. Oil with little

biodegradation

B. Oil with substantial

biodegradation

High-end loss

No high-end loss Some

low

end 

loss

Low

end

loss Pr

Pr

Ph

Ph

Time

Resp

o

nse

A. Oil with little

biodegradation

Figure 4. m/z 83 (n-cyclohexane profile showing an A-degradation sample (BU-317) and 

mple (BE-07). Also, compare figure 3A with figure 3B at a similar 

exanes.

l

that population (with the exception of the fermenting 

the

a C-degradation sa

degradation level. 

Conclusions 

At both sites, the native microbial populations are degrading the low molecular weight 

WSF crude oil compounds. This fraction includes low molecular weight alkanes, one and two

ring aromatic compounds, phenolic compounds, BTEX compounds, and n-alkylcycloh

These fractions along with some anthropogenic carbon are being used by the resident microbia

populations as electron donors, extracting the energy available, and reducing the appropriate 

inorganic electron acceptors for

populations). Both the geochemical evidence and make-up of the microbial populations in

oil-impacted soils at sites A and B suggests that the systems are thermodynamically poised at the

level of iron reduction (fig. 5). 

99
Iron Reducers

107

105

103

101

Aerobes

Fermenters

Sulfate Reducers Denitrifyers

Methanogens

AHA03 BE10

Iron Reducers

107

105

103

101

Aerobes

Fermenters

Sulfate Reducers Denitrifyers

Methanogens

AHA03 BE10

Figure 5. Star radial diagrams showing MPNs of six physiological microbial types 

present on the sediment at representative samples from OSPER “A” and “B” sites (See 

table 3 for actual numbers). Refer to the lower diagram for key to the arms’ labels and

MPN v

eters 

es. In

additio

out

oils

ct of the fluctuating water levels and input of

anthrop

alues. All values are in numbers per g dry weight sediment. Values less than the

minimum detectable numbers are plotted at the lowest tick mark. 

Because the shallow system upslope from the sludge pit at site A is apparently rainfall

driven (intermittent rainfall dissolved O2 input), the microbial populations, in general, are 

comprised of aerobes, facultative aerobes, and strict anaerobes. However, the high 

concentrations of volatile fatty acids and high dissolved iron and other geochemical param

of the system near and just downslope of the sludge pit suggests that the microbial population

should be predominantly facultative aerobes and strict anaerobes, with iron reducing 

microorganisms predominating. This was confirmed by microbial population analys

n, the population of sulfate reducers is only an order of magnitude less the iron reducers 

and the potential for a more active sulfate reducing population cannot be ruled out. 

In contrast to site A, it appears that the microbial populations are exclusively comprised 

of facultative aerobes and strict anaerobes at site B, due to the water-saturated soils through

the site. The hydraulic pressure from the main pond and the lake would tend to keep these s

saturated. It is unclear at this time the effe

ogenic carbon from the lake has on the nature of the microbial populations and the 

overall degradation pathways at this site. 

Oil residues throughout the study areas are all similar in their general characteristics, 

indicating that they are all from the same regional oil province. There are, however, enough 

100
small differences in correlation parameters within the oil samples that several slightly differe

sub-groups of oils can be observed. Thus, it appears that at Site A all the oils in the roughly 100

m area from the oil-impacted soil where original production occurred, downslope to where th

oil either flowed or was dumped, is the same oil, although at significantly variable stages of 

biodegradation. Oil samples from the three other, more distant sites are somewhat different and

thus probably represent different oil spillages. Oils that give possible evidence of anaerobic 

degradation are the four oils at the C-degradation level. These occur generally beneath land 

surface (the core at the upsl

nt

e

ope production site and the well sample in the fill area), except for 

AG020

s

es

of the non-water soluble, or high molecular weight components of the 

spilled oils. As at site A, the samples which show tentative evidence of anaerobic degradation are 

in the C-degradation stage, that is, the two from the deep well, BE07, and 

Refer

Bek ologic

Chri s in

ter Monitoring and Remediation, v. 23, p. 142-149. 

ation of

d

Hold be Laboratory Manual:

Hos

as a

ochemistry, v. 30, p. 873-879. 

Kharaka, Y.K, Lundegard, P.D., and Giordano, T.H., 2000, Distribution and origin of 

organic ligands in subsurface waters from sedimentary basins: Reviews in Economic 

Geology, v. 9, p. 119-132. 

-22702, which is from a surface mud in the older part of the fill area. In samples in a Ddegradation, the oils are too degraded for the method outlined in this work to determine the 

nature of the degradation. 

At site B the samples sort out in small groupings. These groupings are the two sample

from the brine tanks, the two samples from the main pit, and two from a deep well, then BE07

downslope from the pit and BA03 NW of the pit, the last two from the subsurface. There do

not seem to be a correlation between the oils at closely adjacent sites, that is, oil in the brine 

tanks, the main pit, or the downslope sample, indicating that there probably is not significant 

subsurface transport

the subsurface oils

BA03 listed above. 

ences

ins, B.A., Godsy, E.M, and Warren, Ean, 1999, Distribution of microbial physi

types in an aquifer contaminated by crude oil: Microbial Ecology, v. 37, p. 263-275. 

stensen, L.B. and Larsen, T.H., 1993, Method for determining age of diesel oil spill

the soil: Groundwater Wa

Godsy, E.M., Goerlitz, D.F., and Grbic ́-Galic ́, Dunja, 1992, Methanogenic biodegrad

creosote contaminants in natural and simulated ground-water ecosystems: Groun

Water v. 30, p. 232-242. 

Grantham, P.J. and Wakefield, L.L., 1988, Variations in the sterane carbon number 

distribution of marine source derived crude oils through geologic time: Organic 

Geochemistry, v. 12, p. 61-73. 

eman, L.V., Cato, E.P., and Moore, W.E.C., 1977, Anaero

Virginia Polytechnic Institute and State University, Blacksburg, Virginia, p.152. 

tettler, F.D. and Kvenvolden, K.A., 2002, Alkylcyclohexanes in environmental 

geochemistry: Environmental Forensics, v. 3, p. 293-301. 

Hostettler, F.D., Rosenbauer, R.J., and Kvenvolden, K.A., 1999, PAH refractory index

source discriminant of hydrocarbon input from crude oil and coal in Prince William

Sound, Alaska: Organic Ge

101
Kharaka Y.K., Thordsen, J.J., Kakouros, Evangelos, and Abbott, M.M. [this volume] 2003, 

Fate of inorganic and organic chemicals in produced water from the Osage-Skiatook 

Petroleum Environmental Research sites, Osage County, Oklahoma: U.S. Geological 

Survey Water-Resources Investigations 03-4260, p. 56-83. 

Kvenvolden, K.A., Hostettler, F.D., Carlson, P.R., Rapp, J.B., Threlkeld, C.N., and Warden, 

Augusta, 1995, Ubiquitous tar balls with a California-source signature on the shorelines 

of Prince William Sound, Alaska: Environmental Science and Technology, v.29, p. 

2684-2694. 

Mackenzie, A.S., Patience, R.L., Maxwell, J.R., Vandenbroucke, M., and Durand, B., 1980, 

Molecular parameters of maturation in the Toarcian shales, Paris Basin, France-1. 

Changes in the configuration of acyclic isoprenoid alkanes, steranes, and triterpanes: 

Geochimica et Cosmochimica Acta, v.44, p.1709-1721. 

Palacas, J.G., Anders, D.E., and King, J.D., 1984, South Florida Basin-a prime example of 

carbonate source rocks of petroleum in Petroleum Geochemistry and Source Rock 

Potential of Carbonate Rocks, American Association of Petroleum Geologists, Studies 

in Geology No. 18, p. 71-96. 

Peters, K.E. and Moldowan, J.M., 1993, The Biomarker Guide: Englewood Cliffs, New 

Jersey, Prentice Hall, p. 363. 

Rice, C.A., Cathcart, J. D., Zielinski, R. A., and Otton, J.K., 2003, Characterization of soils 

and rock at an active oil production site: Effects of brine and hydrocarbon 

contamination: U.S. Geological Survey Water-Resources Investigations 03-4260, p. 

133-146. 

Seifert, W.K. and Moldowan, J.M., 1978, Application of steranes, terpanes, and 

monoaromatics to the maturation, migration and source of crude oils: Geochimica et 

Cosmochimica Acta, v. 42, p. 77-95. 

Wang, Zhendi, Fingas, Merv, Blenkinsopp, Sandra, Sergy, Gary, Landriault, Mike, Sigouin, 

Lise, Fought, Julia, Semple, Kathleen, and Westlake, D.W.S, 1998, Comparisons of oil 

composition changes due to biodegradation and physical weathering in different oils: 

Journal of Chromatography, v. 809, p. 89-107. 

Waples, D.W. and Machihara, Tsutomu, 1991, Biomarkers for geologists-a practical guide 

to the application of steranes and triterpanes in petroleum geology: American 

Association of Petroleum Geologists, Methods in Exploration, No. 9, Tulsa, Oklahoma, 

p. 91. 

102
Impact of Oil Production Releases on Some 

Soil Chemical Properties at the OSPER Sites 

By Don H. Kampbell 

U.S. Environmental Protection Agency, Ada OK, USA 

and 

Youn-Joo An 

Oak Ridge Institute for Science and Education, Ada OK, USA 

and 

Matthew W. Smith 

Environmental Research Apprentice Program, Ada OK, USA 

and 

Marvin M. Abbott 

U.S. Geological Survey, Oklahoma City, OK, USA 

Abstract 

As part of a site characterization to develop guidelines for stabilizing or restoring 

degraded areas, surface and soil core samples were collected from two sites, a depleted and a 

producing field in old oil production areas near Skiatook Lake in Osage County, Oklahoma. The 

soil samples were analyzed for nitrate, organic matter, total petroleum hydrocarbons (TPH), 

conductivity, chloride, and dehydrogenase activity (DHA - a measure of viable biomass). Low 

levels of nitrate were observed for most of the samples, except those where animal activity had 

occurred recently. There was a direct relationship between high conductivity and high chloride 

values. The higher TPH values were associated with the presence of asphaltic oil waste in the 

soil. Viable biomass was detected in 80% of the 20 soil and core samples collected. 

Introduction 

Hydrocarbon and produced-water releases occur in oilfield operations as a result of 

equipment failures and other accidents. These releases, the disposal by injection of water coproduced with oil and gas, and the restoration of affected areas are national issues that concern 

watershed managers as well as regulators, surface landowners, and local residents. Most of the 

releases were related to past acceptable oilfield practices. Studies are now needed to evaluate 

and restore the ecosystems using cost-effective techniques. 

The two field sites studied have a long history of petroleum production (Otton and 

Zielinski, this volume). Crude oil and brine water have impacted the landscape surface, 

subsurface, and plant ecosystem. Measurements of soil salt content, nutrients, organic matter, 

petroleum hydrocarbons, and bacterial activity provide indicators of the level of contamination, 

the health of the soil, and possible success of restoration efforts. The information obtained will 

be helpful for developing an effective restoration program at these two sites. 

103
Experimental Methods 

Surface soil samples to a depth of six inches and core samples to a depth of four feet were 

collected from the depleted OSPER “A” (fig. 1) and producing OSPER “B” (fig. 2) sites, with 

locations described in table 1. Sample locations were selected on and away from the salt-scarred 

and/or asphaltic oil contaminated soils. Sampling was completed during April 2002 when 

temperatures were moderately warm. Soil samples were moist and had a friable texture. 

Dehydrogenase activity (DHA) was determined on freshly collected soil material. The 

procedure is described in Stevenson (1959) and the values are reported herein as micrograms of 

triphenylformazan per gram (μg/g) of moist soil. The remaining soil was air-dried and passed 

through a 10-mesh sieve (0.079 in.). Soil nitrates were measured on a dilute acid extract of 95% 

distilled water, 2% sulfuric acid, and 3% hydrochloric acid of the soil using a cadmium reduction 

method (EPA Standard Method 353.3). Percent organic matter of the air-dried soil samples was 

determined using a Model ST-OR 5020 LaMotte Company kit. Total petroleum hydrocarbons 

(TPH) were determined by an EPA-approved protocol by PetroFLAG identified as EPA-SW 846 

Method 9074. 

To standardize the analyses of different soils the extraction was done as soon as possible 

on freshly collected samples. It is important to note that the results of TPH methods can widely 

vary, but the method selected for TPH analyses is an EPA-approved reference method. All 

soil/core analyses were done by standardized published protocols. It should be noted that salt 

scars adjacent to the lake at the OSPER “B” site were subjected to some remediation using a 

straw/hay mulch application and grass seeding. Localized spots were partially successful. The 

organic measurement (OM) is for total organic matter while TPH is for petroleum hydrocarbons, 

but soluble plant organic matter can result in higher TPH amounts. Conductivity was determined 

in a 1:1 soil-water slurry using a conductivity meter (Orion Model 105 with conductance cell 

011510) as specified in USDA Handbook 60, 1954. Soluble chlorides were determined on a 

filtrate derived from a mixture of 30 mL water and 10 grams dry soil using a Waters Capillary 

Ion Analyzer. This report does not endorse the instruments or products used. They are 

mentioned merely as what was available in our analytical laboratory. 

Agronomists made measurements of soluble salts in a soil-water extract as far back as 

1897 (Whitney and Means, 1897). The choice of our methodology, however was not to 

correlate soluble salt levels with plant growth, but to measure relative differences between soil 

and core samples in contaminated and uncontaminated sites. A dehydrogenation process usually 

occurs during the biological oxidation of organic compounds in soil. The process usually 

involves a soil organic compound as a hydrogen donor and another component that acts as a 

hydrogen acceptor. These dehydrogenase systems are an integral part of viable microbial 

populations. In this study, DHA was used as an index of viable biomass. Changes in soil 

biomass have been used as a sensitive indicator of toxicity of pollutants (Horwath and Paul, 

1994). 

104
Figure 1. Sample locations at the “A” site. DKA01-DKA06 are soil and auger sites for 

this study. For an explanation of the features portrayed, see Otton and Zielinski (this 

volume). The green and light orange dotted locations are other site wells. 

105
Figure 2. Sampling locations at the “B” site. DKB01-DKB08 are soil and auger sites for 

this study. For an explanation of the features portrayed, see Otton and Zielinski (this 

volume). The green dotted locations are other site wells. 

106
Table 1. Location notes for surface and core samples, OSPER “A” and “B” sites. 

Location Notes

“A” site 

DKA01 Within patch of highly weathered asphaltic oil at site of old tank

DKA02 Open area of grasses and forbs adjacent to three large oak trees 

DKA03 Open area of grasses and forbs near wet spot

DKA04 Open area at edge of asphaltic oil-saturated soil along trench 

DKA05 Open area at edge of asphaltic oil-saturated soil along trench 

DKA06 Low end of substantial salt-scarred, deeply eroded area 

“B” site 

DKB01 Zone between salt-scarred and treed area 

DKB02 Open salt-scarred area downslope from pit and injection well, remediated in November of 1999

DKB03 Depression in open area below old tank battery, highly saline water present after rain events

DKB04 Midpoint of salt scar below old tank battery, remediated in November of 1999 

DKB05 Open grassy disturbed area between salt scars. 

DKB06 Salt scar below active pit and tank battery, remediated in November of 1999 

DKB07 Salt scar below active pit and tank battery, remediated in November of 1999 

DKB08 Edge of salt scar below active pit and tank battery, remediated in November of 1999 

Results and Discussion 

The concentrations of selected key chemicals in soil samples from OSPER “A” and “B” 

sites are reported in table 2. Results show low nitrate concentrations with most below the ppm; 

such low values are typical for non-fertilized soils in Oklahoma. Two soil-sample locations show 

several fold higher nitrate values, which most likely resulted from animal activity in the area. 

Although the nitrate levels were low they are sufficient to support the growth of native grasses. 

The nitrates were nearly uniformly distributed down to the deepest sampling depth of four feet. 

Organic matter ranged from 1.2 to 5.6%, which is typical for forest soils in this area of 

Oklahoma, but values > 2.5% may reflect a contribution from asphaltic oil contamination. 

Total petroleum hydrocarbons in soil were as high as 6320 ppm. The solvent for TPH 

may not have dissolved all of the dry weathered crude oil. TPH values above 1000 ppm were 

indicative of the presence of asphaltic oil in the soil. Although the TPH method used may have 

inherent problems with accuracy such as solvent extractable plant organic matter, it is an EPA 

approved procedure for petroleum hydrocarbons in soils. At the three profile locations, the 

highest TPH was detected at the two-foot depth. The “A” site had a more sandy textured soil, 

which would enhance downward movement of liquid crude oil. The relationship between TPH 

and organic matter is presented in figure 3. Correlation Coefficient was r = 0.595. The data 

shown in figure 3 suggests that up to two percent organic matter was primarily from natural 

sources such as plant material. Organic matter in the 2.5 to 5.5 percent range reflected a 

contribution from asphaltic oil contamination. 

Conductivity and chloride concentrations were used to detect the presence of produced 

water salts. Conductivity and chloride concentrations ranged from 64 to over 25000 μS/cm and 

3.9 to 5170 ppm, respectively. The relationship between conductivity and chloride 

concentrations is shown in figure 4. Correlation coefficient was r = 0.981. 

107
Table 2. Soil and core analyses from OSPER “A” and “B” sites. 

Sample Depth Nitrate OM TPH Conductivity Chloride DHA

(ft) (ppm) (%) (ppm) (μS/cm) (mg/L) (μg/g soil)

“A” site 

DKA01 0.0 - 1.3 0.15 3.3 1580 90 3.9 2.7 

DKA01 1.3 - 2.6 0.12 3.3 6320 418 31 2.3 

DKA01 2.6 - 4.0 0.15 3.8 6080 571 52 <0.1 

DKA02 0 - 0.5 0.06 1.8 262 86 4.2 3.6 

DKA03 0 - 0.5 0.18 2.7 122 125 4.1 33.2 

DKA04 0 - 0.5 0.21 5.0 1695 122 4.8 2.3 

DKA05 0 - 0.5 0.12 4.2 2336 64 4.2 5.4 

DKA06 0 - 0.5 0.12 1.2 89 572 147 4.4 

“B” site 

DKB01 0 - 0.5 0.12 1.8 365 184 11 3.3 

DKB02 0 - 0.5 0.12 1.5 31 4500 1310 9.9 

DKB03 0 - 0.5 14.4 2.4 166 25200 5170 5.8 

DKB04 0 - 1.3 0.18 1.5 257 3600 643 <0.1 

DKB04 1.3 - 2.6 0.18 1.2 42 1766 619 <0.1 

DKB04 2.6 - 4.0 0.12 1.5 <10 743 771 23.4 

DKB05 0 - 0.5 0.15 1.8 374 1470 133 37.9 

DKB06 0 - 1.3 0.15 2.7 2054 3800 745 15.1 

DKB06 1.3 - 2.6 0.15 2.7 2900 1156 518 <0.1 

DKB06 .18 - 1.5 0.18 1.5 90 391 327 17.8 

DKB07 0 - 0.5 0.15 2.4 1985 6700 1270 11.5 

DKB08 0 - 0.5 1.2 5.6 2584 4300 1460 43.8 

0

1000

2000

3000

4000

5000

6000

7000

0.0 1.0 2.0 3.0 4.0 5.0 6.0

Organic matter (%)

Tot

al petrol

e

u

m

hydroc

arbons (ppm)

r = 0.595

Figure 3. Relationship between total petroleum hydrocarbon (TPH) and organic matter 

(OM). 

108
0

1000

2000

3000

4000

5000

6000

0 5000 10000 15000 20000 25000 30000

Conductivity (μS/cm)

C

hloride (ppm)

r = 0.981

Figure 4. Relationship between chloride and conductivity. Note the high correlation 

between these parameters. 

0

1000

2000

3000

4000

5000

6000

7000

0 10 20 30 40

Dehydrogenase activity (nmol/g soil)

Tot

al petrol

e

u

m hydroc

arbons

(ppm)

50

r = -0.207

Figure 5. Relationship between total petroleum hydrocarbon (TPH) and dehydrogenase 

activity (DHA) showing no correlation. 

The relationship between TPH and DHA is shown in figure 5. A calculated correlation 

coefficient of r = -0.207 indicates that the relationship is not direct. DHA values listed in table 2 

indicate that most of the soil/core samples exhibited a variable biomass. High salt concentrations 

in the soil generally did not have an adverse effect on DHA values as indicated by figure 6. Low 

DHA in the vertical profiles appeared related to high TPH and conductivity for most samples. 

Interactions between TPH and conductivity did not generally influence DHA. High TPH and 

water-extractable chlorides did not cause low DHA in many samples because the oily residue 

may have combined with the brine salts to reduce solubility of chlorides while the vigorous 

water extraction for chlorides permitted an increase in this component. Chloride levels up to 

109
0

1000

2000

3000

4000

5000

6000

0 10 20 30 40 5

Dehydrogenase activity (nmol/g soil)

Chlorid

e (

p

p

m)

0

r = 0.052

Figure 6. The chloride and dehydrogenase activity (DHA) plot shows lack of any 

correlation. 

1500 ppm did not seem to suppress bacteria activities measured by DHA. Best fit by linear 

regression calculations between any two parameters was for conductivity versus chlorides. 

Notice: The U.S. Environmental Protection Agency through its Office of Research and 

Development funded and managed the research described here through in-house efforts. This 

document has not been subjected to agency review and therefore does not necessarily reflect the 

views for the agency and an official endorsement should not be inferred. 

References 

EPA Method 353.3, 1979, Methods for Chemical Analysis for Water and Wastes; EPA 

600/4-74-020; Environmental Protection Agency, Washington, D.C., p. 353.3-1. 

EPA Method 9074, 1999, Test Methods for Evaluating Solid Waste: Physical/Chemical 

Methods; EPA-SW-846, (Method 9074), Draft Update IV-A, Mar 1999: Environmental 

Protection Agency, Washington, D.C., Office of Solid Waste. 

Horwath, W.R. and Paul, E.A., 1994, Microbial Biomass, Methods of Soil Analysis, Part 2 

Chapter 36: Soil Science Society of America, Book Series #5. 

Otton, J.K. and Zielinski, R.A., [this volume] 2003, Produced water and hydrocarbon 

releases at the Osage-Skiatook petroleum environmental research studies, Osage county 

Oklahoma: Introduction and geologic setting: U.S. Geological Survey Water-Resources 

Investigations 03-4260, p. 14-41. 

Stevenson, I.L., 1959, Dehydrogenase activity in soil: Canadian Journal of Microbiology, v. 

5, p. 229-235. 

USDA Handbook 60, 1954; Diagnosis and Improvement of Saline and Alkali Soils; United 

States Regional Salinity Laboratory, Riverside, C.A. US Department of Agriculture. 

Whitney, M. and Means, T.H., 1897, An electrical method of determining the soluble salt 

content of soils: U. S. Department. of Agriculture, Division of Soils, Bulletin 8. 

110
Hydrologic Controls on the Subsurface 

Transport of Oil-field Brine at the OsageSkiatook Petroleum Environmental 

Research “B” Site, Oklahoma 

By William N. Herkelrath and Yousif K. Kharaka 

Abstract 

As a part of a multidisciplinary study of the impact of oil wells and oil production on the 

environment, we are investigating the hydrology and the fate and transport of contaminants at the 

Osage-Skiatook Petroleum Environmental Research (OSPER) “B” site, which is located at 

Skiatook Lake in Osage County, Oklahoma. Salt and crude oil from oil-well waste pits and 

accidental releases from oil tank batteries have contaminated soil, ground water, and surface 

water at this site. Based on soil cores, water table measurements, chemical analyses of water 

samples, and field observations, we developed conceptual models of the hydrology and solute 

transport mechanisms near a waste pit at the south end of the site. We propose two main 

mechanisms for solute transport from the waste pit to the lake. One mechanism is the relatively 

slow and steady flow of saline ground water from the waste pit to the lake in a near-surface 

aquifer. The other mechanism is relatively fast overland flow of salt-laden runoff during rainfall. 

Using the USGS model SUTRA, we simulated steady-state ground-water flow and solute 

transport from the pit to the lake. Preliminary modeling results indicated that the solute travel 

time from the pit to the lake in saline ground water is 2-4 years. 

Introduction 

A large quantity of water containing high concentrations of dissolved salts is produced as 

a byproduct of oil production. In the early days of the oil business in the United States, brine was 

commonly “disposed of” by dumping into streams or infiltration into the soil (Yergin, 1991). 

Present law requires that most brine be injected into deep formations. However, even today oilfield brine and oil are often spilled on the soil surface and into shallow emergency or reserve 

holding pits. The brine often flows out the bottom of unlined holding pits and into the groundwater system. Movement of the brine and the oil into the subsurface poses a threat to ground 

water quality. Nearby streams and lakes may also be threatened. It is important to understand the 

processes that influence subsurface transport of oil-field brine and associated oil and to 

document the effects on the environment in order to help regulators and other responsible parties 

make informed decisions regarding oil well siting and site remediation. 

In 2001 the U.S. Geological Survey, in cooperation with the U.S. EPA, began a 

multidisciplinary study of the impact of oil production on the near-field environment. Two oilfield sites, designated “Osage-Skiatook Petroleum Environmental Research” (OSPER) sites “A” 

and “B”, located near Skiatook Lake in Northeastern Oklahoma, were selected for intensive 

study. Oil and brine from producing oil wells has entered the subsurface at these sites, resulting 

111
in extensive killing of vegetation and degradation of local ground water and surface water 

quality. A research team of geologists, geophysicists, geochemists, hydrologists, microbiologists, 

and biologists is evaluating data obtained in the first field season at the OSPER sites. 

In this paper only results from the OSPER “B” site are presented. The purpose of the 

paper is to describe conceptual models of the hydrology and solute transport processes at the “B” 

site, and to present preliminary computer modeling simulations of ground-water flow and 

associated transport of dissolved salt from a waste pit at the southern end of the site B to 

Skiatook Lake. The general concepts developed in this paper are applicable to nearby areas 

where oil-field brines have been spilled.

Field Site Description 

As shown in the site map (fig. 1), at site B there is an oil tank battery and a waste pit 

located about 20 meters from Skiatook Lake. There also is a brine injection well and an 

associated smaller pit at the north end of the site. The land surface slopes upward west of the 

lake at approximately a 5% grade. Three areas where salt has killed the vegetation are denoted 

“salt scars” in figure 1. There are salt scars east of the oil tank battery, east of the injection well, 

and east of a location in the center of the site where a tank battery and pit have been removed. As 

a part of a remediation effort, in 2000 about 6 inches of saline topsoil was replaced, grasses 

planted, and hay mulch applied in the salt-scarred areas. However, as of 2002, there were only 

limited patches of grasses growing on the salt-scarred areas. 

Soil and rock cores (Otton and Zielinski, this volume) obtained at the site show that 

beneath 0.5-2 meters of surficial deposits (eolian sand, colluvium, fill, and alluvium), a layer of 

shale at least 6 meters thick underlies the site. The near-surface material near the waste pit is 

mapped as “fill” or “colluvium.” The colluvium consists of variable amounts of weathered shale 

and sandstone clasts in a sandy to clayey matrix. The fill is similar to the colluvium but often 

contains wood or construction debris. There is generally weathered shale beneath the colluvium. 

The soil which has formed in the eolian layer has been removed from much of the area near the 

salt scars. Pits and roads were made by cutting and filling local materials with a bulldozer. Much 

of the near-surface material near the waste pit is “fill.” 

A Geoprobe (direct-push) rig was used to obtain shallow (<6 meters deep), 2-inch 

diameter cores at 19 locations at the site. Sampling wells were installed at each of these 

locations. The wells were made by placing 1-inch diameter PVC pipe with a 1 to 6 foot well 

screen at bottom into the Geoprobe boreholes. Clean sand was packed into the annulus between 

the PVC pipe and the borehole. These wells are labeled “BE#” in figure 1. 

Six-inch diameter boreholes that were up to 16 meters deep were also cored at three 

locations using an auger rig. Two 2-inch diameter PVC wells with 5 to 10 foot long well screens 

at the bottom were installed in each borehole. There was a “deep” and a “shallow” well in each 

borehole. Sand was packed around the PVC pipe in the screened intervals. Bentonite was used to 

isolate the screened intervals from one another. These wells are labeled “BA#” in figure 1. 

112
Legend

Alluvium

Sandstone

Oil-impacted soils

Shale

Drainage trace

Water

Survey station

Artificial fill

Graded cut area, next to road

Pit

Road

Tanks

Waste 

Pit

0

0

50 100 ft

10 20 30 m

N

Thick colluvial apron

Stripped of soil cover

Soil profile intact

Colluvium on 

hillslopes

Road cut exposures

Colluvium

Sandstone 

(based on float)

Sandstone 

(outcrop along creek)

?

?

Exposed lake bottom

G- gravel & boulders

S- Sand

L- lake silt, mud, 

 and organic matte

L

G

G S

S

G

G

G

L

G

G

Outline of

salt scar

Outline of

salt scar

Outline of

salt scar

x

x

x

x x

x

x

x x

x

x

x

xx

x

xx

x

x

x

x

BE01

BE02

BE03

BA01

BA03

BE04

BE05

BE18

BE19

BE06

BE15

BE10

BE14

BE09

BE08

BE07 BE11

BE13

BE16

BE17

BA02

Shoreline

December 2001

Shoreline March 2001

x

x

BE12

B

B’

Skiatook Lake Site “B”

Oil tank battery

Reinjection

well

Lake

Lake

Lake

Figure 1. Map of OSPER “B” research site. 

113
Hydrology and Solute Transport in the Waste Pit Area 

Based on analysis of the soil cores, water table measurements in the wells, chemical 

analysis of water samples obtained from the wells and the waste pit, and other field observations, 

we developed preliminary conceptual models of the hydrology and solute transport mechanisms

in the waste pit area.

The Brine Source in the Waste Pit 

Equipment failures at the active oil production facility at the site lead to a periodic 

spillage of brine and associated oil into the waste pit at the south end of the site (fig. 1). Brine 

from the oil wells has a concentration of about 150,000 mg/L total dissolved solids (Kharaka and 

others, this volume). The brine fills the waste pit to a variable extent depending on the volume of

the spill. Once in the pit, the brine is diluted by precipitation. The pit collects some of the runoff 

from an area of about 600 m2

. 

Water and brine leave the pit by several mechanisms. The oil-field operator periodically 

pumps water out of the pit via an automated sump-pump system into water tanks that are pumped 

into the injection well. Also, we observed that when the pit contains water, brine often flows out 

through seeps on the east side of the pit berm at the top of the salt scar. The water flows out of 

the seep, on top of the soil for a few feet, and then infiltrates into the soil down slope from the 

pit. At times in the past, the pit has overflowed the east side of the berm. We hypothesize that 

brine also flows out through the bottom of the unlined pit. When the weather is hot, water may 

evaporate from the pit, which increases the brine concentration. However, there is generally a 

thin layer of oil on top of the water in the pit, which may inhibit evaporation of water. 

It is likely that quantitative understanding of the fate and transport of contaminants from

the waste pit will be limited by how accurately the source is characterized. The measured salinity 

of the brine that enters the ground near the pit varies greatly as a function of time (Kharaka and 

others, this volume). The flow rate out of the pit also varies as a function of liquid depth in the 

pit. Accurate characterization of the source will require frequent monitoring of the solute 

concentration and the water level in the pit. 

Ground-Water Flow from the Waste Pit to the Lake 

Figure 2 shows a simplified cross section of the subsurface beneath the B-B’ transect (fig. 

1). We hypothesize that the primary subsurface pathway for water flow from the pit to the lake is 

in the surface “fill” or “colluvium” layer (F/C). We hypothesize that the underlying undisturbed 

“weathered shale” layer is much less permeable than the F/C layer. 

The water table elevations measured in wells in June 2002 line up well with the measured 

water levels in the pit and the lake (fig. 2). The water-level measurements suggest that whenever 

there is water in the pit, there is ground-water flow from the pit to the lake in response to a 

hydraulic head gradient of about 0.05 m/m.

We carried out slug tests in the wells in order to estimate the hydraulic conductivity of 

the F/C layer. A slug test was initiated by inserting a solid volume of stainless steel into a well in 

order to displace water and rapidly raise the water level in the well. The subsequent transient 

decline in water level in the well was monitored with a pressure transducer. The slug tests were 

analyzed using the Bouwer and Rice (1976) method, as described by Butler (1997). Hydraulic 

114
conductivity values estimated from the slug test data ranged from about 1 cm/day to about 10 

cm/day. 

One can use the Darcy flow equation to estimate the flow rate from the waste pit to the 

lake. For example, assuming the F/C layer in figure 2 is a uniform, homogeneous, onedimensional aquifer, the flow rate per unit cross section is q = k (dp/dx), where k is the hydraulic 

conductivity, and dp/dx is the hydraulic gradient. Assuming the hydraulic conductivity is 10 

cm/day, and the gradient is 0.05, q ~ 1.8 m/year. 

Water Flow in the Unsaturated Zone 

Inspection of soil cores and observation of rainfall events at the site suggest that there is 

relatively little infiltration and recharge of fresh rainwater into the saturated zone. In the bare, 

salt-scarred areas of the site, because the soil is clay-rich, the drainable porosity of the soil is 

low. Drying of bare soil by evaporation is limited to a thin layer at the soil surface. Even after a 

long dry period, the subsoil remains nearly saturated. When it rains, the available porosity is 

quickly filled, the water table rises rapidly to the surface, and runoff begins. Soil surface sealing 

by mobile clays and air entrapment in the soil also enhance runoff. Most of the water that falls on 

bare soil flows toward the lake as runoff. Infiltration and recharge of fresh rainwater into the 

saturated zone is limited. After the rain, the water table falls rapidly back to the level that is 

supported by outflow from the waste pit. 

In vegetated areas, soil drying is more extensive because of plant root uptake. As a result, 

there is more infiltration and less runoff from vegetated areas. However, evapotranspiration is 

generally so high at the site that the plants rapidly remove water that has infiltrated into the root 

zone, and there is little ground-water recharge. 

Solute Transport 

We propose two main mechanisms for transport of solutes from the waste pit to the lake. 

One mechanism is the flow of saline ground water in the F/C aquifer. Brine from the pit flows 

down through the bottom of the pit and travels laterally in the aquifer to the lake. The weathered 

shale beneath the F/C layer is relatively impermeable, and not much brine penetrates into this 

layer. The saline ground-water flow is relatively slow and steady, and not much influenced by 

the weather, except that the level of water in the pit changes in response to rainfall and 

evaporation. We hypothesize that there is relatively little dilution of the saline ground water by 

rainwater once the brine has entered the aquifer. 

The second mechanism for solute transport is the overland flow of salt-laden surface 

runoff. Rainfall at the site generally comes in short bursts followed by dry periods lasting many 

days. During dry periods, as the bare soil surface dries by evaporation, ground water containing 

dissolved salts is pulled upward from the aquifer toward the surface by capillary action. The salt 

concentration in the water near the surface is increased by evaporation of water. Salt crystals 

may precipitate near the soil surface. We hypothesize that during rainfall rainwater rapidly mixes 

with the highly saline water in the surface soil, dissolves salt crystals, and carries dissolved salt 

down slope in runoff. It is likely that solute transport via the runoff mechanism is much faster 

than via the saline ground water flow mechanism.

115
-2

-1

0

1

2

3

4

5

6

7

8

9

10

0 20 40 60 80 1

Horizontal distance from point B in meters

Elevation above lake level in meters

Water

Fill

line

BE-11

BE-09

BE-08

Berm

Bottom

of pit

00

B

B'

Waste

Pit

Land surface

Top of weathered shale

F/C

F/C

Screen/sand in well

Water table

Lake

F/C = Fill or Colluvium

Figure 2. Simplified cross section beneath the B-B’ transect at OSPER “B” site. 

The fact that the brine is denser than water may influence mixing and solute transport. 

Fingers of brine tend to move downward into a porous material that is initially saturated with 

fresh water. This effect tends to increase mixing when salt water lies above fresh water. 

However, fresh rainwater infiltrating on top of a brine-filled aquifer tends to remain stratified 

and not mix with the brine.

Preliminary Modeling Results 

We used the U.S. Geological Survey model SUTRA (Voss, 1984) to simulate steadystate flow of ground water and subsurface transport of solutes from the waste pit to the lake. 

SUTRA is a two-dimensional, finite element model that solves the Darcy flow equation and the 

convection dispersion equation. The model is convenient to use because a graphical-user 

interface (Voss and others, 1997) is available to set up a problem and display results. Another 

advantage of SUTRA is that the program enables simulation of subsurface transport when the 

density of the flowing water solution varies as a function of solute concentration. Although this 

feature will be important in future work, in the simulations reported in this paper water density 

was assumed to be that of pure water. 

116
As a first approximation, we assumed that the area near the waste pit is underlain by a 

homogeneous aquifer that is one meter thick. The idealized aquifer roughly corresponds to the 

F/C layer in figure 2. We assumed the following values for aquifer parameters: hydraulic 

conductivity = 10.0 cm/day; porosity = 0.3; longitudinal dispersivity = 10.0 m, transverse 

dispersivity = 1.0 m. Hydraulic conductivity was assumed to be isotropic. 

The layout of the homogeneous aquifer problem and the boundary conditions are 

illustrated in figure 3. We used SUTRA to solve the areal flow problem. For the purposes of this 

simulation the waste pit was assumed to be a rectangle 7.6 meters wide and 15.2 meters long. 

The hydraulic head at the pit boundary was assumed to be constant, three meters above the 

constant head boundary at the lake. The domain boundaries to the west and north were assumed 

to be no-flow boundaries. 

Waste

Pit

Skiatook Lake

X in meters

Y

i

n

m

e

t

e

r

s

No-flow boundaries

Constant

head = 0

Constant

head = 0

Constant

head = 3 meters

Homogeneous aquifer

k = 10.0 cm/day

Figure 3. Problem layout and boundary conditions for the homogeneous, steady-state 

areal ground-water flow and transport problem at OSPER “B” site. 

117
Flow and transport were simulated for two years. Water flow was assumed to be steady 

state. We assumed the initial salt concentration in the aquifer was zero. At t=0, brine with a 

solute concentration of 100,000 mg/L was assumed to enter the aquifer at the pit boundary. 

Solute concentration in the lake was assumed to be zero. 

Results of the homogeneous simulation are illustrated in figures 4 and 5. Figure 4 shows 

the simulated distributions of hydraulic head and flow velocity. In figure 4, the flow velocity at a 

point is proportional to the length of the flow vector. As shown in figure 4, in the homogeneous 

simulation there was flow outward from the pit in all directions. The maximum flow velocity 

was toward the southeast, where the distance from the pit to the lake is minimum. Simulated 

concentration profiles after 600 days are shown in figure 5. Concentrations are expressed as a 

percentage of the initial source concentration, which was 100,000 mg/L. As shown in figure 5, in 

this simulation the brine plume spread out in all directions from the pit, but the concentration 

profiles were slightly advanced toward the southeast. Travel time of the solute from the pit to the 

lake, indicated by the arrival time of the 50% concentration profile at the lake, was about two 

years. 

Pit

Skiatook Lake

Hydraulic

head in

meters

Y

i

n

m

e

t

e

r

s

Figure 4. Simulated hydraulic head distribution and ground-water flow velocities at 

OSPER “B” site. Flow velocity at a point is proportional to the length of the flow vector. 

In this simulation hydraulic properties were assumed to be uniform. 

118
X in meters

Y in

m

e

t

e

r

s

50

60

70

Skiatook Lake

Concentration

in

percent

Figure 5. Simulated solute concentration profiles at OSPER “B” site 600 days after oilfield brine was placed in the waste pit. Concentration values are in percent of the source 

concentration. In this simulation the aquifer beneath the pit was assumed to be 

homogeneous. 

In contrast to the results of the homogeneous simulation, field evidence suggests that 

most of the flow is to the east, and there is reduced flow of brine south and west of the pit 

(Kharaka and others, this volume). One explanation of the discrepancy between the 

homogeneous simulation and the field results is that the hydraulic conductivity of the nearsurface materials south and west of the pit is reduced. We simulated the effect of a permeability 

barrier using SUTRA. As shown in figure 6, for this simulation the hydraulic conductivity west 

and south of the pit was assumed to be 1.0 cm/day, or 1/10 the assumed hydraulic conductivity 

of the rest of the aquifer. Flow and transport were simulated for five years. All other model 

parameters were unchanged. 

Results of the simulation with the permeability barrier are illustrated in figures 7 and 8. 

As shown by the velocity vectors in figure 7, in this simulation most of the flow was directed to 

the northwest. The concentration profiles shown in figure 8 are also lengthened toward the 

northwest. In this simulation, travel time of the solute front from the pit to the lake, indicated by 

the arrival time of the 50% concentration profile at the lake, was about four years.

119
Waste

Pit

Skiatook Lake

X in meters

Y

i

n

m

e

t

e

r

s

No-flow boundaries

Constant

head = 0

Constant

head = 0

Constant

head = 3 meters

k = 1.0 cm/day

k = 10.0 cm/day

Figure 6. Problem layout and boundary conditions for the steady-state areal groundwater flow and transport problem with reduced hydraulic conductivity west and south of 

the waste pit at OSPER “B” site. 

Discussion 

The ground-water flow and transport problems we solved were highly simplified, 

designed only to provide first-order hypotheses as an aid in organizing future experiments and 

data collection at the site. The model has many shortcomings. For example, a major problem is 

lack of knowledge of the effective aquifer porosity. According to the convection-dispersion 

solute transport model, the velocity of a solute front, vs, is approximately q / φ, where q is the 

Darcy flow velocity and φ is porosity. Assuming q = 1.8 m/year, and φ = 0.3, vs ~ 6 m/year. 

However, the velocity of a solute front traveling through a porous medium containing clay may 

be greatly increased compared to this estimate. Because the clay-rich fill/colluvium material at 

this site is highly heterogeneous, preferential pathways for flow probably exist in the F/C layer. 

Most of the pore space in the clay may be bypassed. As a result, subsurface transport of solute 

from the pit to the lake may occur much more rapidly. In order to gain an improved 

understanding of large-scale solute transport at the site, we plan to carry out tracer tests in order 

to measure solute travel times from the pit to the wells. 

120
Y

n

i

m

e

t

e

r

s

Hydraulic

head in

meters

Skiatook Lake

Pit

Figure 7. Simulated hydraulic head distribution and ground-water flow velocities at 

OSPER “B” site. Flow velocity at a point is proportional to the length of the flow vector. 

In this simulation, hydraulic conductivity west and south of the waste pit was reduced by 

a factor of 10. 

Summary and Conclusions 

As part of a multidisciplinary investigation of the impact of oil production on the 

environment, we are investigating the hydrology and the fate and transport of contaminants at the 

OSPER “B” field site, which is located at Skiatook Lake, Oklahoma. Salt and crude oil from oilfield operations have contaminated soil, ground water, and surface water at this site. 

Based on analysis of soil cores, well data, and field observations, we developed 

conceptual models of the hydrology and solute transport mechanisms at the southern end of the 

site, where oil-field brine from a waste pit has killed vegetation near the lake. We propose two 

main mechanisms for solute transport from the waste pit to the lake. One mechanism is the 

relatively slow and steady flow of saline ground water in an aquifer formed by a near-surface 

layer formed of fill and colluvium (F/C). We hypothesize that brine from the pit flows down 

through the bottom of the pit and laterally in the F/C aquifer to the lake. The second mechanism

for solute transport is overland flow of saline surface runoff. Evaporation from bare soil leads to 

high salt concentration near the soil surface. We hypothesize that during rainfall rainwater 

rapidly mixes with highly saline water at the soil surface and carries dissolved salt down slope in 

runoff. It is likely that solute transport via salt-laden runoff is much faster than via saline groundwater flow. 

121
Concentration

in

percent

X in meters

Y in

m

e

t

e

r

s

Skiatook Lake

50

60

70

Figure 8. Simulated solute concentration profiles at Skiatook Lake site “B” 600 days 

after oil-field brine was placed in the waste pit. Concentration values are in percent of 

the source concentration. In this simulation the assumed aquifer permeability west and 

south of the waste pit was reduced by a factor of 10. 

Using the USGS model SUTRA, we carried out preliminary computer simulations of 

steady-state ground-water flow and solute transport from the waste pit to the lake. Results 

obtained assuming homogeneous aquifer characteristics implied that there is ground-water flow 

and solute transport outward from the pit in all directions. The most rapid transport was toward 

the southeast, where the distance from the pit to the lake is minimum. In the homogeneous 

simulation, travel time of solute from the pit to the lake was about two years. However, field 

evidence suggests that there is reduced flow of brine south and west of the pit. In order to explain 

this discrepancy, we hypothesize that the near-surface materials have a reduced hydraulic 

conductivity west and south of the pit. We ran a second SUTRA simulation with assumed 

reduced permeability west and south of the pit. With the permeability barrier in place, most of

the flow was directed to the northwest. Inserting a permeability barrier increased the simulated 

solute travel time from the pit to the lake to about four years. 

References

Bouwer, H., and Rice, R.C., 1976, A slug test for determining hydraulic conductivity of 

unconfined aquifers with completely or partially penetrating wells: Water Resources 

Research, v. 12, p. 423-428.

Butler, J.J., 1997, The design, performance, and analysis of slug tests, Boca Raton, Fla., 

Lewis Publishers, 252 p.

122
Kharaka Y.K., Thordsen, J.J., Kakouros, Evangelos, and Abbott, M.M. [this volume] 2003, 

Fate of inorganic and organic chemicals in produced water from the Osage-Skiatook 

Petroleum Environmental Research sites, Osage County, Oklahoma: U.S. Geological 

Survey Water-Resources Investigations 03-4260, p. 56-83. 

Otton, J.K. and Zielinski, R.A., [this volume] 2003, Produced water and hydrocarbon 

releases at the Osage-Skiatook petroleum environmental research studies, Osage county 

Oklahoma: Introduction and geologic setting: U.S. Geological Survey Water-Resources 

Investigations 03-4260, p. 14-41. 

Voss, C.I., 1984, SUTRA: Saturated-Unsaturated Transport, a finite-element simulation 

model for saturated-unsaturated, fluid-density-dependent ground-water flow with 

energy transport or chemically-reactive single-species solute transport: U.S. Geological 

Survey Water-Resources Investigations Report 84-4369, 409 p.

Voss, C.I., Boldt, D., and Shapiro, A.M., 1997, A graphical-user interface for the U.S. 

Geological Survey’s SUTRA code using Argus ONE,” U.S. Geological Survey OpenFile Report 97-421, 106 p. 

Yergin, D., 1991, The prize: the epic quest for oil, money, and power: New York, Simon 

and Schuster, 928 p. 

123
Use of Soil Extracts to Define the Extent of 

Brine-impacted Soils and Bedrock at the 

Osage-Skiatook Petroleum Environmental 

Research “B” Site, Northeastern Oklahoma 

By Robert A. Zielinski, Cynthia A. Rice, and James K. Otton 

Abstract 

Soil and underlying weathered bedrock at an active oil production site were investigated 

to determine the chemical signature of added salts and the spatial distribution of soil salinity in 

relation to areas of visible salt scarring. Aqueous extracts (1:1 by weight) of brine-impacted 

soil/bedrock have elevated (anomalous) Cl concentrations or relatively low ratios of

conductance/Cl compared to extracts from samples collected offsite. The latter have low 

dissolved chloride and conductance (sandstone-derived) or sulfate as the dominant dissolved 

anion (shale-derived). Sampling of the upper 0-15 centimeters of the soil profile indicated that 

areas of high soil salinity are largely confined to locations of obvious salt scarring. Ratios of 

Cl/Br in extracts of chloride-rich surface soil are 250±30 and fall within the range of 220 to 320 

reported in local produced waters. Within the area of salt scars, elevated salinity persists to 

depths of from 1.2 to >3.0 meters based on samples obtained by direct-push techniques. 

Introduction 

Three distinct areas of salt scarring are present at an active oil production site (site “B”) 

that is under study by the U.S. Geological Survey (USGS) (Otton and Zielinski, this volume). 

The spatial distribution of these three areas of barren ground is directly related to three distinct 

point sources that provided recent and/or historical releases of highly saline produced water as 

surface spills or subsurface seepage from brine storage pits (fig. 1). Whereas the surface 

expression of highly saline soil is commonly apparent through loss of vegetation and increased 

erosion, the areal extent of less saline soils and the depth of salt penetration are not obvious. 

Such information is critical for assessing the full extent of environmental damage, the cost of any 

planned remediation, and the ongoing dispersion of introduced salt. 

Study site “B” provides an opportunity to test geochemical and geophysical methods that 

estimate the extent and severity of salt contamination. This report describes a geochemical 

method based on aqueous extracts of readily soluble salts. Dissolved salts derived from

produced water are identified by their distinctive chloride-rich composition and Cl/Br ratio 

compared to the sulfate-dominant salts of local soils and bedrock. Similar chemical indicators 

are used to identify sources of salinity in ground water near oil and gas production sites 

(Whittemore, 1983, 1988; Richter and Kreitler, 1987; Knuth, and others, 1990; Abbott, 1998). 

This method expands the scope of salinity-source investigations to include aqueous extracts of 

soil and bedrock and builds on the success of previous studies using soil extracts (Otton and 

Zielinski,1998, 2000; Zielinski, and others, 2000, 2001). 

124
Figure 1. Map of oil production site “B” showing oil production facilities, three areas of 

salt scarring (shown in gray), and vegetation. 

125
Site Description 

Study site “B,” located northwest of Tulsa in northeastern Oklahoma, was selected by the 

USGS for detailed studies of environmental impacts related to oil and gas production, associated 

natural attenuation, and remediation strategies. Multidisciplinary studies were initiated in 2001 

and are being conducted in cooperation with the landowner, lease holder, the Osage Nation, 

Federal, State, and local government agencies, and local universities. The site is situated along 

the present shore of Skiatook Lake, which was first filled in 1984. Local surficial deposits 

include eolian sand and silt, slope-wash, colluvium, and alluvium. Local bedrock of

Pennsylvanian age is predominantly shale with lesser amounts of thin interbedded sandstone. A 

more detailed description of the geologic setting of the site and its production history (1937 to 

present) is presented in Otton and Zielinski, this volume. 

Methods 

Initial surface soil sampling (0-15 centimeter (cm)) was conducted at site “B” in March, 

2001. Thirty samples were collected with a 5-cm-diameter stainless steel soil auger from the 

three salt scars, intervening areas, and other locations. All soil auger samples were stored in 

sealable plastic bags. In February of 2002, the site was sampled with hydraulically driven directpush equipment that provided continuous 4-cm diameter cores to depths ranging from 2.13 to 

5.48 meter (m). The cores were collected in plastic liners, capped, taped, and then transported to 

the USGS core library in Denver. Cores were stored under refrigeration until sampling. One 

5.48 m long core from a locality at the margin of the site was sampled in detail to characterize 

the local background soils and shallow bedrock. Other direct-push cores were typically sampled 

at the following depths; 1.22 m, 2.13 m, and 3.05 m, or final depth if less than 3.05 m.

Samples weighing approximately 200 grams were air-dried at 40°C and passed through a 

ceramic-plate jaw crusher with 3-millimeter opening. For soil samples the primary purpose of 

the crusher was to disaggregate clay-cemented clumps formed during drying, but small (<1 cm

diameter) rock fragments were also coarsely crushed during the process. For bedrock samples 

the crusher produced a similar average size of rock fragments for extraction. Exactly 100 g of 

crushed sample was weighed into a plastic beaker and 100 milliliters (ml) of deionized water 

added. Each 1:1 (by weight) mixture was stirred vigorously, allowed to stand overnight at room

temperature, and again stirred vigorously prior to pouring into a 250-ml polycarbonate centrifuge 

bottle. The slurries were centrifuged at 8,000 revolutions per minute for 40 minutes to remove 

suspended particles larger than approximately 0.1-micrometer diameter. Clear solution (~60 ml) 

was decanted and passed through a filter membrane of 0.45 micrometer pore size under pressure 

from nitrogen gas. 

Specific conductance and pH of each clear extract were measured immediately. Extracts 

were analyzed for dissolved chloride, sulfate, and bromide by ion chromatography using a 

Dionex 500 chromatography system equipped with an AS-14 anion exchange column. The 

eluent was a mixture of 0.0010 molar sodium bicarbonate and 0.0035 molar sodium carbonate 

(pH=9.0). Background-corrected counts under the peaks of interest were converted to 

concentration values based on a calibration of peak area (or peak height for Br) to concentration, 

as determined by contemporaneous analysis of a series of prepared standards. Sample dilutions 

were optimized to fall well within the concentration ranges of the standards. Analytical 

precision and accuracy were estimated based on replicate analysis of prepared and commercially 

126
certified standards and are better than 5 percent relative standard deviation (RSD) for chloride 

and sulfate, and better than 12 percent RSD for bromide values in excess of 1 part per million 

(ppm). Similar analytical precision of 1-14 percent RSD was obtained from three samples 

processed in duplicate. 

The detection limit for bromide by this technique is approximately 0.1 ppm. In cases 

where the bromide peak lies on a sloping shoulder of a much larger chloride peak, best results 

are obtained by inspecting the chromatogram and performing software optimization that permits 

operator subtraction of a visually determined background contribution. For bromide the reported 

concentrations are based on a calibration using only the most closely bracketing standards. Use 

of the “method of additions” is also recommended to best determine Br in solutions of high and 

variable Cl content. 

Results and Discussion 

Graphs of specific conductance versus dissolved chloride help distinguish extracts of 

chloride-contaminated samples from extracts containing natural salts (figs. 2a, 2b). Extracts of 

uncontaminated sandy soils and sandstone have low dissolved solids and chloride contents and 

plot near the origin. Extracts of uncontaminated shale-derived soils and shale can have elevated 

dissolved solids, but are dominated by dissolved sulfate rather than chloride. These latter 

extracts plot along trend lines that are closer to the conductance axis. Extracts that plot well 

outside the areas on the graph defined by local soils and bedrock are those with unusually high 

chloride concentration for their conductance and are interpreted to be variably contaminated with 

chloride-rich salts. 

At site “B” the upper 0-15 cm of soil is typically composed of eolian sand and silt, sandy 

to clayey colluvium, and reworked sandy to clayey fill material. Most extracts of surface soil 

from site “B” contain more than 530 ppm dissolved chloride, which exceeds the highest 

concentration observed in eight extracts from a 0.9-m soil profile collected offsite (fig. 2a). In 

addition, the conductance/Cl ratio for chloride-rich sandy surface soils is 4 or less, compared to a 

value of about 12 for the extracts of offsite sandy/silty soils. Extracts of deeper, direct-push core 

samples also fall into two distinct populations (fig. 2b). All extracts with less than 600 ppm Cl 

are from the 5.48 m-long shale-dominated core from the site margin, or from deeper portions of 

some onsite cores. These Cl-poor extracts show conductance/Cl ratios of ten or more. In 

contrast, most extracts of >600 ppm Cl are highly enriched in chloride and have conductance/Cl 

ratios of 6 or less. 

Spatial-chemical data (fig. 3) indicate that the chloride content of surface soil extracts is 

consistently elevated within, and adjacent to, the salt scars. The highest chloride concentrations 

are immediately downslope from the active brine storage pit (sample L3A), or adjacent to a pool 

of saline water located near the toe of one salt scar (sample T1P). Surface soils located between 

salt scars have lesser, but still anomalous chloride contents in their aqueous extracts. Earthmoving operations at the site probably contributed to this broader distribution of near-surface 

salts. One surface soil (T2B) located uphill from the large tank battery, adjacent to an old oil 

spill and just below an old separator tank, also showed locally anomalous chloride content (460 

ppm) in its extract. 

127
Figure 2. Chloride versus specific conductance in 1:1 aqueous extracts of (a) surface 

soils and (b) direct-push core samples from site “B.” Lines corresponding to selected 

conductance/chloride ratios are included for reference. 

128
Figure 3. Geochemical map showing the distribution of chloride–rich surface soils at 

site “B.” The size of plotted circles is indexed to ranges of chloride concentration in soil 

extracts, as indicated in the inset. The outlines of mapped areas are the same as in 

figure 1. Soil sample locations are indicated as site traverse (T prefix) or along the long 

axis of salt scars (L prefix). 

129
The spatial distribution of soluble chloride in surface soils is consistent with the 

introduction of chloride-rich salt from oil production operations. Additional support for a 

produced-water source is provided by Cl/Br ratios. Cl/Br ratios in extracts of 20 contaminated 

surface soils (255±30) fall within the range of 220-320 found for eight local produced waters 

collected in March, 2001 (Kharaka and others, this volume). In contrast, the Cl/Br ratio in 

extracts of seven uncontaminated surface soils was <100. For reference, the Cl/Br mass ratio in 

seawater is between 288 and 292 (Davis and others, 1998). 

Preliminary hand-auger sampling within the salt scars in May, 2001 indicated salt 

contamination to depths of refusal of 0.6 m and 0.8 m in older scars and 1.7 m in the scar from

the active pit. Deeper sampling with direct-push equipment in February 2002 indicated that 

anomalous chloride contents (>600 ppm) and low conductance/Cl ratios (<6.0) persisted in 

extracts of sandy to clayey colluvium and fill, and underlying weathered shale to depths of at 

least 1.22 m (fig. 4). Deepest salt penetration of 2.13 m to > 3.05 m was found in the salt scar 

from the active pit. Periodic spills of produced water or continuous seepage from the pit or from

an older pit located at the same site may account for the greater penetration of salt within this 

scar. Some direct-push sites located outside the present salt scars (sites 06, 13; fig. 4) showed 

salt to depths of 1.2 m, indicating the presence of older salt deposits or the lateral dispersion of 

salt by shallow ground water. Low lake levels at the time of direct-push sampling permitted 

more extensive sampling along the projected axes of salt scars (sites 07, 18) and confirmed that 

periodic submersion of sites does not remove the record of salt contamination in deeper horizons. 

Comparisons of salt penetration depths with lithologic descriptions of core samples (J.K. Otton, 

USGS, written commun., 2002) indicated that in some places salt has penetrated the entire 

thickness of sandy colluvium and as much as 1 m of underlying weathered shale. 

Additional Considerations 

The laboratory method described herein can be modified and adapted to provide real-time 

data for field application. In this case, specific conductance is measured on a freshly prepared 

1:1 slurry of sample and distilled water. Dissolved chloride concentration is measured with a 

commercially available chloride test strip (Hach Company, 1999) on a small volume of slurry 

water passed through a syringe-mounted filter. Rapidly measured field values of chloride 

concentration and conductance/Cl ratio will differ from laboratory values, but still provide useful 

relative comparisons between similarly measured background samples and contaminated 

samples. Such field measurements can provide preliminary reconnaissance of sites contaminated 

by produced water or can guide removal of saline soils from such sites. 

Conclusions 

Anomalous concentrations of chloride are present in aqueous extracts of soils and 

underlying weathered bedrock at study site “B.” The spatial distribution of chloride-rich soils 

indicates at least three point sources of introduced salt, and the Cl/Br ratio of salt in 

contaminated surface soils falls within the range of values for local produced water. Salt 

contamination is not entirely confined to areas of obvious salt scars but persists to a lesser extent 

over a broader area at the site. Depth of salt penetration is generally between 1.22 to 2.13 m but 

at some locations immediately downslope from an active pit, the salt has penetrated to depths in 

excess of 3.05 m.

130
Figure 4. Depths of penetration of chloride-rich salt in direct-push cores from site “B.” 

The size of plotted circles increases with apparent depth of chloride-rich salt, based on 

aqueous extracts of core samples. Circles with downward arrows indicate that 

anomalous chloride persisted to the bottom of the core. The outlines of mapped areas 

are the same as in figure 1. Numbers assigned to circles identify direct-push sites. 

Sites 07, 13, 16, 17 and 18 were cored during a low stand of the lake. 

131
The use of aqueous extracts to define the nature and extent of salt contamination in soils 

has broad applicability at sites where chloride-rich salts from oil and gas operations contrast with 

the composition of natural salts. The technique can be modified to provide rapid, real-time 

assessments during field-based operations. 

References 

Abbott, M.M., 1998, Freshwater resources and saline water near the Sac and Fox Nation 

tribal lands, eastern Lincoln County, Oklahoma: U.S. Geological Survey Open-File 

Report 96-4173, 58 p. 

Davis, S.N., Whittemore, D.O., and Fabryka-Martin, J., 1998, Uses of chloride/bromide 

ratios in studies of potable water: Ground Water, v. 36, p. 338-350. 

Hach Company, 1999, Products for Analysis: Loveland, Colorado, Hach Company. 

Kharaka, Y.K., Thordsen, J.J., Kakourous, Evangelos, and Abbott, M.M., [this volume] 

2003, Fate of inorganic and organic chemicals in produced water from the OsageSkiatook Petroleum Environmental Research sites, Osage County, Oklahoma: U.S. 

Geological Survey Water-Resources Investigations 03-4260, p. 56-83. 

Knuth, M., Jackson, J.L., and Whittemore, D.O., 1990, An integrated approach to 

identifying the salinity source contaminating a ground-water supply: Ground Water, v. 

28, p. 207-214. 

Otton, J.K., and Zielinski, R.A., 1998, Chemical criteria for determining the origin and 

dispersion of highly soluble salts in soils and waters near an oilfield operation, Logan 

County, Colorado: U.S. Geological Survey Open-File Report 98-426, 21 p. 

______2000, Simple techniques for assessing impacts of oil and gas operations on Federal 

lands—A field evaluation at Big South Fork National River and Recreation Area, Scott 

County, Tennessee: U.S. Geological Survey Open-File Report 00-499, 51 p. 

______[this volume] 2003, Produced water and hydrocarbon releases at the Osage-Skiatook 

petroleum environmental research studies, Osage County Oklahoma: Introduction and 

geologic setting: U.S. Geological Survey Water-Resources Investigations 03-4260, p. 

14-41. 

Richter, R.C., and Kreitler, C.W., 1987, Sources of ground water salinization in parts of 

west Texas: Ground Water Monitoring Review, v. 7, p. 75-84. 

Whittemore, D.O., 1983, Geochemical identification of salinity sources: in French, R.H. ed., 

Salinity in Watercourses and Reservoirs, Proceedings of the 1983 International 

Symposium on State-of-the-Art Control of Salinity, July 13-15, 1983, Salt Lake City, 

Utah Butterworth Publishers, p. 505-513. 

______1988, Bromide as a tracer in ground-water studies: geochemistry and analytical 

determination: Proceedings of the Ground Water Geochemistry Conference, February 

16-18, 1988, Denver, Colorado, National Water Well Association Publishers, p. 339-360. 

Zielinski, R.A., Otton, J.K., and Rice, C.A., 2000, Assessment of sources of soil salinity 

near an oil field production site using the chemistry of surface water and soil leachates: 

Proceedings Volume (CD-ROM) of the 7th Annual International Petroleum

Environmental Conference, November 7-10, Albuquerque, New Mexico, p. 1046-1059. 

Zielinski, R.A., Otton, J.K., and Johnson, C.A. 2001, Identifying sources of salinity near a 

coal mine spoil pile, north-central Colorado: Journal of Environmental Quality, v. 30, 

p. 1237-1248. 

132
Characterization of Soils at an Active Oil 

Production Site: Effects of Brine and 

Hydrocarbon Contamination 

By Cynthia A. Rice, James D. Cathcart, Robert A. Zielinski, and James K. Otton 

Abstract 

An active oil field, the Osage-Skiatook Petroleum Environmental Research (OSPER) site 

“B” in Osage County, Oklahoma is under study to determine the impacts of produced brine and 

hydrocarbon spills on soils. Characterization of soils in areas known to be contaminated as well 

as those believed to be uncontaminated were studied using visual and microscopic description, 

X-ray powder diffraction of the bulk soil and clay-sized fraction, particle size analysis, cation 

exchange capacity, and selective extraction of iron species. Results indicate that most brine and 

hydrocarbon contamination at site “B” occurs at shallow depths (< 240 cm) where the soil color 

and type varies from a dark brown topsoil to a red-orange sand, to a greenish-gray clay. Quartz 

is the dominant soil mineral with substantial clay minerals composed of kaolinite, illite, smectite 

or mixed-layer illite/smectite, and minor amounts of feldspar. The cation exchange capacity of 

bulk soil samples in uncontaminated and contaminated areas is similar, but the percentage of 

sodium on exchange sites is substantially higher in soils from contaminated areas. Some soil 

samples from areas contaminated by produced water have high soluble salts, but low percentages 

of sodium on exchange sites. High amounts of reduced iron (up to 98 % of the total iron) in soils 

from contaminated areas may record the passage of hydrocarbon-rich ground water. 

Introduction 

Release of produced saline water and hydrocarbons at oil- and gas-production sites can 

have a range of impacts on the environment. The scale and level of impacts depend on the size 

and frequency of the release(s) and the types and times of remediation (API, 1997). Impacts 

range from unsightly effects, such as oil-stained soils or salt scars to changes in the physical and 

chemical properties of soils and water. Characterization of soils at sites where produced saline 

water or hydrocarbons are released is thus important. 

Characterization of pre-spill and post-spill soil pH, mineralogy, exchangeable ion ratios, 

and other specific soil characteristics is necessary following a produced water or hydrocarbon 

release. The soil characterization assists in determining: 1) whether remediation is necessary; 2) 

the most effective type of remediation; and 3) any long-term monitoring requirements. At oil 

and gas production sites where saline and hydrocarbon releases may have occurred in the past, 

with or without remediation, soils may provide evidence of the release, the extent of 

contamination, the effectiveness of remediation, and an understanding of long-term

consequences of releases. 

Soils were studied at an oil production site in Osage County, Oklahoma that had been 

subjected to both produced saline water and hydrocarbon releases and the preliminary results are 

133
presented in this report. The goals of the soil characterization are to: 1) document the extent of 

brine and hydrocarbon contamination; 2) understand controls on the movement and retention of 

brine and hydrocarbons; and 3) determine the role of solid phases, such as clay and iron-bearing 

minerals, in natural mitigation. The types and amounts of clay minerals and oxidizers 

(particularly iron) are important because of the capacity of clay minerals to exchange cations that 

are dissolved in brines and the capacity of reactive ferric iron species to oxidize hydrocarbons. 

Releases of production fluids at the site (OSPER site “B”, fig. 1) have occurred as recently as 

1999 and sporadically prior to that time (Otton and Zielinski, this volume). The site is still active 

and has a tank battery containing produced water brine and oil, an unlined overflow pond below 

the tank battery, and a water disposal injection well (fig. 1). Three areas at the site (labeled as 

remediated area in fig. 1) were remediated after saline water releases in 1999 by removing the 

top 6 inches of soil, placing uncontaminated topsoil on the areas, and planting the areas with 

grass. The three remediated areas are considered contaminated areas in this study and are 

referred to herein as “affected areas”, while areas surrounding and away from the remediated 

areas, tank battery, and pond are considered “background areas”, even though future study may 

find that it is difficult to find truly pristine areas in a contaminated site such as this. A complete 

description of the site including the topography, geology, hydrology, vegetation, and history is 

given in Otton and Zielinski, this volume. 

Methods 

Samples were taken at site “B” (fig. 1) to characterize soils geographically as well as 

vertically. Surface soils were collected in May, 2001 as 15-cm-deep “grab” samples (fig. 1). 

Hand-auger cores were also collected in May 2001 at locations contaminated by saline produced 

water and hydrocarbons; samples were also taken in areas not exposed to contaminants (fig. 1). 

Hand-auger core penetration was maximized at each location with total depths varying from 58 

to 166 cm. In February 2002, 2-inch-diameter cores were also taken using the Geoprobe system

(fig. 1); depths of the cores varied from 1 to about 5.5 meters. 

Several methods were utilized for soil and solid-phase characterizations, including grain 

size analysis (percent sand or larger-size, silt, and clay), X-ray powder diffraction (XRD) 

analysis of bulk soils and clay-size (<2 μm) fractions, whole soil cation exchange capacity 

(CEC) analysis, and selective chemical extractions for iron. 

Percent of sand and larger-sized fraction (> 63 μm) was measured by wet sieving through 

a 230 mesh sieve. Silt-size (2-63 μm) and clay-size (<2 μm) fractions were separated by 

centrifugation. XRD was performed on bulk soils ground with a mortar and pestle and packed in 

a randomly-oriented powder specimen. Clay minerals were identified after XRD of a preferred 

oriented specimen of the < 2 μm fraction after the following treatments: 1) air-drying; 2) 

ethylene glycol saturation; 3) heating to 400oC; and 4) heating to 550oC. XRD patterns were 

analyzed by matching them with standard patterns using digital software (Jade, 1998) and a 

standard pattern reference library (International Centre for Diffraction Data powder diffraction 

file (McClune, 1998)). Semi-quantitative (± 20 percent) mineralogies of bulk samples were 

determined using reference intensity ratios (Snyder, 1992). 

134
0

0

50 100 ft

10 20 30 m

N

Legend

Oak trees

Grasses and forbs

some on old fill

Oil-impacted soils

Road cut

Remediated area

Pipeline

Drainage trace

Water

Individual oak trees

Old road bed, partly

gravelled, sparsely vegetated

Artificial fill

little or no vegetation

Graded cut and

fill area, next to road

Small oak grove

Edge of fill

Artificial

fill

Small

 oak

 trees

Fill

line

Old separator

Pit, no vegetation

Trailer

Road

 Edge of

disturbed area

 near road

Pumping unit

Hand auger core

15-cm Surface grab

Geoprobe core

Injection well I

Old

Tank

site

Tanks

Stream

Notes: Only one pipeline is mapped among many.

All oil-stained soils caused by pipeline breaks except

area adjacent to large pit.

Barren, salty soil

S1

S2

A2

A1

S3

S4

S5

S6

S7

S8

S9

S10

S11

S12

S13

S14

S15

S16

S17

S18

S19

S20

Figure 1. Site and sample location map of OSPER “B” site, Osage County, OK. 

Modified from Otton and Zielinski, this volume. Geoprobe core sites in “offshore” 

positions were sampled during a lake lowstand. 

135
Cation exchange capacity was determined on 10 g of bulk soil using a modification of the 

method by Breit (1990). About 10 g of soil was placed in 250 mL polyethylene bottles with 

about 150 mL of a 1 M solution of SrCl2·6H2O; with weight of the bottle, sample, and solution 

recorded. Samples were periodically shaken over a period of about 16 hours to disaggregate the 

sample and replace Na, Ca, Mg, and K with Sr2+. At the end of the saturation period, the 

samples were placed on a wrist shaker for one hour. Most of the Sr solution was then separated 

from the solid by centrifuging and decanting and saved for analysis. Weight of the remaining 

solution, solid, and bottle was again recorded to determine the amount of residual fluid. An 

additional 150 mL of Sr solution was added to the bottle containing the solid and residual Sr 

solution and the saturation exchange procedure was repeated. 

Amounts of Na, Ca, Mg, and K in solutions were determined by atomic absorption 

spectrophotometry (AAS). Amounts of Na, Ca, Mg, and K in the saturation solutions 

represented both exchangeable cations as well as cations from soluble salts. The amounts of Na, 

Ca, Mg, and K from soluble salts were measured by dissolving the soluble salts in a separate 1 g 

of bulk soil in 15 mL of deionized water for 16 hours, followed by analyzing the solution 

separated by centrifugation. The amounts of Na, Ca, Mg, and K from soluble salts were then 

subtracted from amounts measured in the saturation solutions. 

Percentage of reduced iron (Fe2+) versus oxidized iron (Fe3+) in readily soluble iron 

phases was determined on 2 to 5 g of Geoprobe core samples immediately after collection. 

Samples were taken from the core interior and sealed in amber septum vials previously prepared 

with 40 mL of 0.5 N hydrochloric acid (HCl) flushed with nitrogen gas. Vials were periodically 

shaken for 24 hours to leach available iron (ion-exchangeable and dissolved) as well as iron in 

readily dissolved phases (iron monosulfides, siderite, and poorly crystalline iron phases, such as 

iron oxyhydroxides). This method is a modification of Heron and others (1994) who also 

reported recoveries of various species of iron. Concentrations of Fe2+ and total Fe leached from

the samples after 24 hours were determined using the ferrozine spectrophotometric method. 

Results and Discussion 

Size fractions and XRD analyses were performed on two hand-auger cores (A1 and A2) 

at site “B” (fig. 1). The two cores represent an “affected” area (core A1) and a “background” 

area (core A2) and field descriptions of these cores are given table 1. 

Particle size analysis indicates that the silt plus sand-size or larger fraction dominates 

both cored soils with the background soil core (A2) containing more silt in the upper section of 

the core (fig. 2). Clay-sized material in the background core (A2) is high (25 weight percent) 

near the surface, but decreases with depth to about 6 weight percent. In the affected core A1, the 

amount of clay-sized material is fairly constant in the upper meter of the core, then increases to 

over 25 percent at the base of the core. The silt-sized fraction is greater than the clay-sized 

fraction and also increases in lower portions of the core. Size analysis indicates a distinct 

lithologic change in affected core A1 just below a meter in depth that represents a contact 

between shallow soils and the areally extensive weathered shale of the Wann Formation 

described by Otton and Zielinski, this volume. 

The XRD mineralogy of whole-rock (bulk) soils from both cores show primary and 

secondary soil minerals that include quartz, feldspar, goethite, kaolinite, and other clay minerals 

that were indistinguishable in whole-rock XRD. Goethite was found in core in two samples 

136
Table 1. Field descriptions of samples from Core A1 (affected) core and Core A2 

(background) core. 

Core Depth (cm) Description 

A1 0 - 18 Color: 10YR 5/6 yellowish brown overall. Sandy clayey silt to sandy silty clay. 

Soft, some faintly mottled. Some roots. Abundant grit and granules. Some yellow 

red weathered clasts. Faint hydrocarbon odor. 

18 - 30 Color: 2.5Y 4/4 olive brown. Sandy clayey silt to sandy silty clay. Soft. Minor roots. 

Flecks and mottles of 10YR 5/8 yellowish brown weathered and unweathered 

sandstone chunks. Very faint hydrocarbon odor. 

30 - 44 Color: 10YR 5/6 yellowish brown. Sandy clayey silt to sandy silty clay. Soft. Clasts 

of sandstone to 2 cm. Small orange to red-colored weathered sandstone flecks. 

Moderate hydrocarbon odor. 

44 - 55 Color: 2.5Y 4/4 olive brown. Sandy clayey silt. Relatively dry. A few sandstone 

clasts to 2.2 cm. Uniform color. Faint to moderate hydrocarbon odor. 

55 - 65 Color: 2.5Y 4/4 olive brown overall. Sandy clayey silt to sandy silty clay. Color is 

greenish gray on freshly broken clods. Sandstone and siltstone clasts to 2.4 cm 

(sandstone clasts are red to orange). Moderate hydrocarbon odor. 

65 - 76 Color: 2.5Y 4/4 olive brown. Sandy to silty clay. Sandstone fragments to 1 cm. 

Thin roots and other pieces of black organic matter. Moderate hydrocarbon odor. 

76 - 86 Color: 2.5Y 4/4 olive brown overall. Sandy silty clay with abundant granules to 

small fragments of shale, siltstone, and sandstone. Mottled. Green gray on 

broken clods. Moderate to strong hydrocarbon odor. 

86 - 96 Color: 2.5Y 5/4 light olive brown. Chunks of sandstone clasts 2.5YR 4/6. Red 

dark reddish brown, also 10YR 5/8 yellowish brown, siltstone clasts yellow gray. 

Sandy clayey silt to sandy silty clay. Minor roots. Pieces of black plastic rope? 

Black organic fragments. Moderate hydrocarbon odor. 

96 -105 Color: mottled 10YR 5/6 yellowish brown and about 1/3 5Y 5/2 olive gray. Sandy 

clayey silt to sandy silty clay with abundant grit and granules. Soft. Sandy clasts, 

clay, colluvium. Hydrocarbon odor weaker. Clay matrix, clasts of reddish brownlargest pebble, flat, about 2 cm across. 

 105-117 Color: mottled 2.5Y 6/2 light brownish gray and 2.5Y 5/6 light olive brown. 

Reddish brown color toward bottom; 2.5YR 5/4 reddish brown as before. Sandy 

clayey silt to sandy silty clay with grit and granules. Still soft, but not as soft as 

above. Mostly clay; fragments of silty to clayey sandstone. Faint hydrocarbon 

odor persists.

117-125 Color: 2.5Y 4/4 olive brown and mottled 10YR 5/6 yellowish brown with spots of clayey

shale 2.5YR 4/8 red to reddish brown. Silty clay, mottled light olive brown, green gray 

and “red” (2.5YR 4/8 to 10R 4/8). Clay is stiff. Faint hydrocarbon odor. Upper portion –

colluvium; lower portion – clayey shale near bottom, probably getting into shale alone. 

137
Table 1. Field descriptions of samples from Core A1 (affected) core and Core A2 

(background) core – continued. 

Core Depth (cm) Description 

A1 125-136 Color: 2.5Y 5/4-5/6 light olive brown overall. Silty clay. Mottled olive brown, green gray, 

and light brown(7.5YR 6/6). Stiff. Faint overall hydrocarbon odor, clay with root 

impressions, slightly mottled with roots; hydrocarbon odor strongest in root 

impressions probably following root casts. 

136-147 Color: 2.5Y 5/4 light olive brown. 5Y 5/2 olive gray. Mottled clay with roots, a few 

siltstone or shale rock fragments. Clay is stiff. Faint hydrocarbon odor, root casts, 

abundant mottling around root casts. Small quartz pebbles to 1 cm. Making a small 

amount of water. 

147-157 Color: mottled 5Y 5/4 olive and 10YR 6/6 brownish yellow mottled with gray. 

Mottled clay. Still making a small amount of water, stronger hydrocarbon odor. 

Fragments of rock, siltstone; out of shaley zone siltstone fragments to 3 cm. 

2 distinct colors; sparse black organic plant fragments still in colluvial material (fill?). 

A2 0 - 17 Color: mottled 10YR 6/6 Brownish yellow with darker surface soil 10YR 4/2 dark 

grayish brown. Sandy silty clay with minor grit and granules of siltstone. Roots. 

Abundant organic matter responsible for darker color at surface. 

17 - 30 Color: 10YR 5/8 yellowish brown; slight mottling. Silty clay with minor grit and 

granules. Siltstone clast to 1.3 cm. Some rootlets and thin roots. 

30 - 44 Color: mottled 10YR 6/8 brownish yellow with speckles of 2.5YR 4/8 red. Mottled 

silty clay with minor grit and granules to 1.2 cm. Some rootlets. Clay content; harder 

to get out of auger; some decaying plant fragments. 

44 - 58 Color: 10YR 5/6 yellowish brown with specks of 2.5YR 4/8 red. Mottled sandy silty 

clay with siltstone clasts to 1.5 cm. Several large root fragments at bottom. 

58 - 69 Color: mottled 10YR 6/6 brownish yellow with 5Y 6/3 pale olive and 5YR 5/8 yellowish 

red. Mottled sandy silty clay with siltstone and sandstone clasts to 2 cm. Sandstone 

clasts are oxidized. Root material. 

69 - 79 Color: 10YR 5/8 yellowish brown mottled with 10YR 7/1 light gray. Sandy silty clay 

with highly weathered sandstone. Clasts (friable, breakable in fingers). Relatively stiff. 

Weathered colluvium; siltstone clasts with hematite? Stains; some 2.5YR 4/8 red. 

79 - 88 Color: Mottled 10YR 5/8 yellowish brown. 7.5YR 5/8 strong brown; 2.5YR 4/8 red 

and light gray. Mottled sandy silty clay. Green gray shale clasts to 1 cm. Minor roots. 

Four different colors in this sample. Some plant fragments, sandy to clayey with 

some Mn oxide staining. 

89 - 93 Color: 10YR 5/8 yellowish brown mottled with 10YR 7/1 light gray. Mottled sandy 

silty clay. Sandstone and siltstone clasts to 2 cm. Light gray rock with hematitic rind. 

Numerous siltstone chips with Mn oxide staining. Hole terminated at 1:17 PM by 

large rock at bottom. 

138
Figure 2. Percentages of three major size fractions in samples from two hand auger 

cores at OSPER “B” site. 

139
below the contact between shallow soils and the regional weathered shale (between 105-136 cm). 

Figure 3 shows the relative abundance of major minerals in cores A1 and A2. Quartz is the 

dominant mineral in both cores and kaolinite is the second most abundant. Also shown on figure 

3 is the percent of sand and larger-sized plus silt-sized content of the two cores. Quartz content 

in both cores is considerably less than the amount of material larger than clay-sized indicating 

that significant portions of the other minerals, especially mica and feldspar, are larger than claysize and may represent detrital material. Detailed XRD examination of the clay-sized fraction (< 

2 μm) from the two cores showed a mixture of clay minerals including kaolinite, illite, and 

smectite or mixed-layer illite/smectite. 

The CEC and exchangeable cation analyses of whole-rock soil from surface samples and 

from cores A1 and A2 are given in table 2 and plotted in figures 4 and 5. The range of CEC in 

the whole-rock samples of this study (1.5-28 meq/100g) fall within the ranges measured in soils 

(API, 1997). Although the CEC in a soil can be contributed by a variety of phases such as clay 

minerals, organic matter, and amorphous material, a simple exercise was performed on the 

whole-rock CEC ranges that assumed the CEC was primarily from clay minerals. The wholerock CEC values were normalized to the amount of material that was not quartz or feldspar and 

the resulting range of CEC values varied from 11-69 meq/100g in the affected core A1, and from

24-66 meq/100g in the background core A2. The lower normalized values (11 meq/100g) may 

represent samples that contain predominantly kaolinite (2-15 meq/100g) while the higher 

normalized values (66 and 69 meq/100g) may represent a mixture of clays such as illite (10-40 

meq/100g) and smectite (80-150 meq/100g). This would be consistent with the XRD analysis of 

the soils that showed varying amounts of kaolinite and other clay minerals; however, additional 

analytical work is required to confirm this hypothesis. Results show little difference in total CEC 

on a whole-rock basis or a normalized basis between the affected and background cores (fig. 4) 

or between the 15-cm surface grab samples relative to affected areas at the site (fig. 5). 

Results however show large differences among most samples in affected areas and 

elsewhere when the percentage of Na in exchange sites (the exchangeable sodium percentage or 

ESP) is examined. Because the produced water released at the Skiatook site is predominantly a 

Na-Cl type brine having total dissolved solids (TDS) as high as 185,000 mg/L and Na 

concentrations as high as 55,000 mg/L (Kharaka and others, this volume), the amount of Na on 

exchange sites in soils exposed to these brines is expected be relatively high. The range in ESP 

of core samples and surface samples is shown in table 2 and figures 4 and 5. The ESP is higher 

in most samples in the affected core A1 as compared to the background core A2. Figure 5 shows 

a similar pattern for the surface samples in that most samples in affected areas contain higher 

ESP than samples in areas not affected by produced water, independent of the total CEC. 

Surprisingly, there are a few samples from affected areas that have a low (<1) percentage 

of exchangeable Na (table 3, fig. 5). Some of these samples, however, have relatively high 

concentrations of water-soluble Na (fig. 6). All of the surface samples in figure 6 that have high 

(> 500 μg/g) water-soluble Na and very low (<1) ESP are within or very near areas exposed to 

produced saline waters. Total CEC for these samples range from 5-10 meq/100g, but the 

exchange sites within the soil are not affected by the high water-soluble Na in the samples. This 

may be controlled by the exposure time of soils to solution and/or the presence of competing 

cations such as Ca and Mg. 

140
Figure 3. Semi-quantitative percentages of minerals identified by X-ray diffraction of 

bulk samples from two hand auger cores at the “B” site. Clay minerals is a generic term 

that includes undifferentiated (in bulk) mica, illite, smectite or mixed layer illite/smectite. 

The percentage of sand or greater and silt-sized material in each sample is also shown. 

141
Table 2. Cation exchange capacity and water-soluble cation determinations for soils 

from core and 15-cm surface grab samples at Skiatook site “B.” 

[CEC = cation exchange capacity; ESP = exchangeable sodium percent; Norm. = 

normalized] 

Depth 

Exchangeable Bases 

(meq/100g) CEC

Norm. 

CEC ESP

Water Soluble Cations 

(μg/g) 

(cm) Ca Mg K Na (meq/100g) % Ca Mg K Na

Affected Core (A1):

0-18 8.0 1.9 0.04 1.8 12 59 15 0.42 11 66 730

18-30 6.6 1.8 0.11 2.2 11 54 20 1.1 5.5 22 860

44-55 2.0 0.83 0.04 0 2.8 11 0 52 17 15 940

76-86 3.0 2.3 0.09 2.0 7.5 25 27 75 31 11 880

105-117 2.3 2.9 0.08 1.3 6.6 32 20 34 35 5.2 600

125-136 5.3 8.6 0.29 2.3 16 49 14 1.1 2.9 3.5 470

147-157 2.7 8.3 0.21 2.4 14 69 18 0.33 6.0 23 330

Background Core (A2):

0-17 11 3.5 0.18 0.19 14 54 1.3 10 14 14 52

17-30 2.4 3.3 0.14 0.09 6.0 24 1.5 0.56 7.1 16 51

30-44 1.5 4.7 0.15 0.37 6.7 25 5.6 1.5 7.3 4.3 58

44-58 1.1 6.0 0.22 0.41 7.7 27 5.3 14 100 8.9 190

58-69 0.68 6.1 0.19 0.75 7.7 31 10 20 180 6.6 330

69-79 0.52 4.6 0.21 0 5.3 24 0 41 300 16 580

79-88 0.77 7.5 0.23 0.30 8.8 66 3.4 31 230 8.2 580

89-93 0.10 4.7 0.24 0 5.0 30 0 150 460 20 730

15-cm Surface Grab Samples:

S1 1.9 1.6 0.12 0.02 3.7 0.6 11 15 15 6.0

S2 10 3.7 0.28 0.09 14 0.6 3.7 8.3 23 35

S3 7.7 6.6 0.47 0.07 15 0.4 1.5 4.7 10 11

S4 9.4 2.9 0.05 0.99 13 7.4 0.56 7.9 31 310

S5 9.5 2.7 0.14 0.49 13 3.8 11 5.6 2.2 140

S6 3.7 1.4 0.06 0 5.2 0 220 130 8.4 1,50

S7 4.9 1.4 0.05 0 6.3 0 8.1 13 14 400

S8 0.79 0.54 0.09 0.03 1.5 2.3 10 10 28 2.9 

S9 8.0 2.2 0.13 0 10 0 50 29 18 2,00

S10 4.6 0.82 0 0.72 6.2 12 0.44 17 120 590

S11 8.0 2.1 0.21 1.3 12 11 430 130 36 3,40

S12 14 2.0 0.19 0.16 16 1.0 110 20 19 190

S13 7.1 1.1 0.10 1.2 9.4 13 120 13 12 450

S14 2.3 1.6 0.07 1.3 5.3 25 0.92 4.5 13 460

S15 6.4 1.1 0.06 0.63 8.2 7.6 3.5 10 26 380

S16 5.6 1.7 0.01 1.4 8.8 16 0.70 14 49 560

S17 5.4 0.86 0.03 0 6.3 0 15 15 21 1,10

S18 11 2.4 0.10 3.5 17 20 0.41 12 78 750

S19 14 2.7 0.15 11 28 40 4.0 15 55 1,60

S20 5.7 2.4 0.06 1.8 9.9 18 0.44 4.4 16 190

142
Figure 4. Total cation exchange capacity (CEC) and the amount of CEC occupied by 

Na for samples from two hand auger cores from OSPER “B” site. 

Some samples from the background core A2 and one grab sample have low ESP and high 

soluble Na; they also contained abundant soluble Ca and/or Mg. Therefore, while the amount of 

Na in the samples was relatively high, it was not present in sufficient amounts to compete with 

the more strongly preferred Ca and Mg on exchange sites. Another surface sample with low ESP 

and high soluble Na was collected on a high gradient slope. Soluble Na in this sample probably 

represents salt residue from rapid flow of produced water brine through soils that did not allow 

Na to exchange on all soil sites. Two other samples contained low ESP and high soluble Na, but 

it is not clear why the exchange sites did not have high Na. Although some samples from

Skiatook site “B” do not present a clear relation between water-soluble Na and ESP, the majority 

of samples indicate a positive correlation (fig. 6). 

Results from the measurement of water-soluble Na and ESP in soils from site “B” can 

provide an understanding of effects of produced water releases and efficiencies of remediation 

efforts on plant populations at the site. Plant growth is dependent on many factors, but two of 

the most important are soil salinity and sodicity and vegetation health and distribution at site “B” 

most likely reflects the relative soil salinity and sodicity at the site. The ESP and water-soluble 

results also identify two distinct populations of samples (fig. 6) that represent two separate 

effects from saline water that have to be addressed when considering mitigation measures. 

143
0-5

6-10

11-15

>16

Exchangeable

 Sodium %

Site B

Site B

0-5

5-10

10-15

>15

 Total CEC

meq/100 g

Figure 5. Areal distribution of the total cation exchange capacity (CEC) and the 

percentage of exchange sites occupied by Na (ESP) for 15 cm surface grab samples at 

OSPER “B” site. Site outline and structures are described in figure 1. 

144
Figure 6. Amounts of water-soluble sodium versus the percent of exchange sites 

occupied by sodium in samples from two hand auger cores and 15-cm surface grab 

samples at OSPER “B” site. 

Rapid flushing of soluble salts from the soil zone may be sufficient to mitigate areas that have 

samples with high soluble Na, but low ESP. The solution used to flush the area would need to 

contain a sufficient amount of soluble Ca or be applied in a manner that prevents the soluble Na 

from exchanging onto the soils. On the other hand, samples from areas with high soluble Na and 

high ESP may be more difficult to remediate because Na has exchanged onto clay minerals, soil 

dispersion may have occurred, and soil permeability may have decreased so infiltration of

remediating fluids may be limited. Soil amendments and mechanical mixing of soil amendments 

and remediating solutions may be necessary to remediate areas where Na exchange onto clay 

minerals has already occurred. 

The release of hydrocarbons at oil production sites can also impact soils at a site through 

both physical and chemical reactions. In particular, natural remediation of hydrocarbons in soils 

may occur as bacteria biodegrade the hydrocarbons by oxidation-reduction reactions that oxidize 

the organic matter using minerals as sources of electron acceptors in the process (Delin and 

others, 1998). Iron oxyhydroxides and other iron-bearing minerals are commonly sources of 

easily-reduced iron in many soils. A product of the oxidation-reduction reactions using iron 

phases is reduced iron (Fe2+) instead of oxidized iron (Fe3+) in soils and pore water. High 

percentages of Fe2+ in the readily available iron species in a soil, therefore, may reflect the 

passage and bioremediation of hydrocarbons. Preliminary analysis of reduced iron in 0.5 N HCl 

extractions of 19 samples from fresh core indicated that 11 of 19 samples had greater than 25 

percent reduced iron, with as much as 98 percent in some samples. Four samples from a core 

145
down gradient of the overflow pit at the active tank battery at Site B had reduced iron ranging 

from 12 to 98 percent suggesting that hydrocarbons had been biodegraded in soils below the pit, 

but that the biodegradation was occurring within relatively narrow (<1 m) bands of soil probably 

as a result of preferred flow of fluids in the soil. In addition, the 0.5 N HCl extractions indicated 

the presence of abundant available iron (230-3,000 μg/g) in the soils to aid in natural remediation 

processes. 

Summary 

Soils from shallow core and surface grab samples at OSPER “B” site, an active oil 

production site, display characteristics indicating the passage of produced saline water and 

hydrocarbons. Many samples in areas known to have been exposed to produced fluid release 

contain significant ESP as well as residual soluble Na. However, some samples in these 

impacted areas have elevated soluble Na, but low ESP, indicating that the presence of high 

soluble Na alone may not indicate that produced saline water has affected soil characteristics. 

Topographical controls on the passage of produced fluids as well as the chemistry of the 

exchange reactions may explain the lack of relation between many of these samples. Samples 

from areas considered to represent background conditions have ESP values that are generally 

readily distinguishable from affected areas even though bulk mineralogy may be similar. 

References 

American Petroleum Institute, 1997, Remediation of salt-affected soils at oil and gas 

production facilities, American Petroleum Institute Publication No. 4663. 

Breit, G.N., Rice, C., Esposito, K., and Schlottman, J.L., 1990, Mineralogy and petrography 

of Permian rocks in the Central Oklahoma Aquifer, U.S. Geological Survey Open-File 

Report 90-678, 49 p. 

Delin, G.N., Essaid, H.I., Cozzarelli, I.M., Lahvis, M.H., and Bekins, B.A., 1998, Ground 

water contamination by crude oil near Bemidji, Minnesota, U.S. Geological Survey Fact 

Sheet 084-98, 4 p. 

Heron, G., Crouzet, C., Bourg, A.C.M., and Christensen, T.H., 1994, Speciation of Fe(II) 

and Fe(III) in contaminated aquifer sediments using chemical extraction techniques, 

Environ. Sci. Technol. Vol. 28, pp. 1698-1705. 

Jade+, 1998, Materials Data Incorporated, Livermore CA. 

Kharaka, Y.K., Thordsen, J.J., Kakourous, Evangelos, and Abbott, M.M., [this volume] 

2003, Fate of inorganic and organic chemicals in produced water from the OsageSkiatook Petroleum Environmental Research sites, Osage County, Oklahoma: U.S. 

Geological Survey Water-Resources Investigations 03-4260, p. 56-83. 

McClune, W.F., (ed.), 1998, Powder diffraction file, International Centre for Diffraction 

Data, Newtown, PA. 

Otton, J.K. and Zielinski, R.A., [this volume] 2003, Produced water and hydrocarbon 

releases at the Osage-Skiatook petroleum environmental research studies, Osage county 

Oklahoma: Introduction and geologic setting: U.S. Geological Survey Water-Resources 

Investigations 03-4260, p. 14-41. 

Snyder, R. L., 1992, The use of reference intensity ratios in X-ray quantitative analysis, 

Powder Diffraction Vol. 7, 186 p. 

146
Real-time Kinematic (RTK) Surveying at the 

Osage-Skiatook Petroleum Environmental 

Research Sites, Osage County, Oklahoma 

By Marvin M. Abbott 

Abstract 

RTK methods offer high accuracy in real time. The RTK surveys require a GPS-base 

station, a GPS-rover unit, and radio link between the units. Some preparation is required before 

the RTK survey so a differential correction can be applied during the data collection. This 

preparation may include establishing a base station location by a static GPS survey. 

RTK surveys can be interrupted by tree canopy, minimum number of satellites, solar 

storms, distance from the base station, other radios in the area on the same frequency, and battery 

failure. Nearly all the factors affecting GPS positioning are eliminated by differential GPS 

methods. RTK surveys are not limited by line of sight from base station, darkness, lakes, or the 

minimum number of people needed. A single person can conduct RTK surveys, and multiple 

rover units can utilize one base station. 

Wells at the sites were surveyed with the RTK GPS equipment in June and July, 2002. 

The Northing difference ranged from –4 to +6 cm and the Easting difference ranged from –9 to 

+5 cm. The elevation difference ranged from –9 to +6 cm. 

Introduction 

Osage County is located in northeastern Oklahoma (fig. 1). There are two sites included 

in the Osage-Skiatook Petroleum Environmental Research program. Both sites are immediately 

adjacent to Skiatook Lake (figs 1, 2).An initial drilling investigation of both sites was conducted

in February and March, 2002. These locations included auger and rotary-drilled wells, geoprobe 

holes, hand-driven holes, other surface and soil sampling sites, and lake and stream sites (Otton 

and Zielinski, this volume).Real-time kinematic (RTK) global positioning system (GPS) surveys 

were used, because it is stable, fast, and accurate. Survey-grade GPS technology was used at the 

sites to document the locations of field investigations by 15 research scientists and associates, 

many reporting in this volume. 

This report presents a general discussion of the global positioning system (GPS) and 

discusses the equipment, methods, and limitations of the RTK-GPS. The report presents data 

from two RTK surveys in June and July, 2002. The data were used to evaluate the accuracy of 

the RTK-GPS technology. 

Thirty-eight permanent wells completed in February and March, 2002 were surveyed. 

The survey location for a well was marked so it could be measured on different dates. The 

surveys are in two different areas and utilize two different base station survey markers. 

147
Figure 1. Map showing the location of Osage County, Skiatook Lake, and the location 

of the two OSPER sites on Skiatook Lake. 

Figure 2. Aerial photograph of a part of the “B” site (photo courtesy of Ken Jewell, 

USEPA). 

148
Global Positioning System 

GPS is a worldwide radio-navigation system of 24 satellites and associated ground 

stations established by the U.S. Department of Defense (Trimble, 2003). The satellite locations 

are monitored by the Department of Defense. Each satellite transmits location data along with a 

pseudo random code (PRC) for identification to the GPS receiver. Positioning is determined by 

measuring travel time of radio signals from at least 4 satellites. The difference of the PRC from

the satellite and the PRC at the receiver is the travel time of the signal. Travel time is converted 

to distance by multiplying by the speed of light. 

Factors that affect GPS positioning are discussed in Trimble (2003); they include: 

1. Atmospheric disturbances in the ionosphere and troposphere; 

2. satellite signal reflected into a longer travel time before reaching the receiver by tall 

objects; 

3. satellite signal is blocked from the receiver; 

4. dilution of precision by satellite geometry or position; 

5. satellite location or orbit errors referred to as ephemeris errors; 

6. satellite clock error; and 

7. geoid height model precision of the area. 

Differential GPS methods involve two or more receivers, which are used either in static 

or kinematic surveys. One receiver is stationary and positioned on a known accurately surveyed 

point. The stationary receiver is referred to as a base station receiver. The base station receiver 

computes corrections between the surveyed point location and the satellite reported location with 

errors related to the factors listed above. Nearly all the factors affecting GPS positioning are 

eliminated by differential GPS methods. 

Static surveys use observations from receivers that are stationary during measurements 

(Sickle, 2001). Kinematic surveys have a base station receiver and a moving receiver, referred to 

as a rover unit, during measurements. Static surveys require differential correction to be made 

after the survey is completed. Kinematic surveys can differentially correct the data after the 

survey is completed or during the survey. During RTK surveying the base station provides the 

correction information to the rover unit by a radio link. The rover unit then performs the 

differential correction of the data during the survey. 

Equipment Requirements and Methods 

The RTK surveys require a GPS base station and a radio link between the base station 

and the rover unit (fig. 3) and a GPS rover unit (fig. 4). 

New survey-monument pins were established at both the “A” and “B” sites (fig. 5). These 

were used as the base station location during the RTK surveys. 

149
Figure 3. Base station equipment for RTK survey. 

Figure 4. Rover unit GPS for a RTK survey. 

150
Figure 5. Monument pin used for the base station location during a RTK survey. 

Prior to the RTK surveys, the locations of the monuments were established by differential 

static GPS surveys. These surveys occupied each of the two monuments for four hours. Postprocessing the data was by the Online Positioning User Service (OPUS) maintained by the 

NOAA-National Geodetic Survey (NGS). The data files were uploaded to the OPUS internet 

page at http://www.ngs.noaa.gov/OPUS/index.html using the form in figure 6.OPUS processed

the data relative to three sites on the NGS Continuously Operating Reference Station network 

(CORS). CORS provides GPS carrier phase and code range measurements in support of threedimensional positioning activities throughout the United States. 

OPUS establishes both horizontal and vertical positioning accuracies of a few centimeters 

relative to the National Spatial Reference System. A report is electronically returned to the 

sender. The first item required on the form is an electronic address (fig. 6). The time between 

uploading the static survey data and receiving the electronic report from OPUS was 2-3 minutes. 

A differential static survey of a NGS monument near Hominy, Oklahoma, west of 

Skiatook Lake (fig. 1), produced the following results.The differentially corrected static survey

differed from the NGS Data Sheet for the monument by a millimeter for both the northing and 

easting coordinates or about 1/16 of an inch. The vertical data for the NGS monument was not 

determined by differential survey leveling and therefore was not a measured value. 

During a RTK survey the rover unit must maintain lock on at least four of the same

satellites that the base station is tracking. Setup time at each rover unit survey location is less 

than a minute, if the rover unit maintains lock on the satellites and the radio link to the base 

station. Each rover unit location was occupied for 3 minutes. 

It is important the range pole and antenna be vertical and stationary during the 3 minutes 

of data collection. The legs of the bipod are secured in the ground and the pole is positioned 

before data collection begins. 

151
Figure 6. Online Positioning User Service uploading form. 

Distance from the base station to the rover unit is limited to 10 kilometers (6 miles). 

Accuracy of the rover unit location in the horizontal component is 1 centimeter (cm) plus 2 parts 

per million (ppm) times the distance from the base station and in the vertical component is 2 cm

plus 2 ppm times the distance from the base station. Maximum distance from the base stations at 

the A- and B-sites was 430 meters. The accuracy for the surveys would be 1 cm in the horizontal 

and 2 cm in the vertical. The red and white antenna pole in the picture (fig. 4) is 2 meters in 

height and 3 cm in diameter. 

Tree cover, solar storms, and moisture affect the rover unit (Trimble, 2003). Surveying 

under tree cover is difficult because the leaves blocks the satellite signal from the rover receiver 

and lock on the same satellites as the base station is lost. Solar storms affect the radio link 

between the rover unit and base station. Precipitation creates multiple paths to the receiver 

because of particles in the air. Although the equipment is water resistant, it is not recommended 

to submerge the equipment in water. A single person can conduct RTK surveys and multiple 

rover units can utilize one base station. 

Accuracy of the RTK GPS Technology 

All wells were marked with a measure point on the pipes. The wells were surveyed at the 

measure points in June and again in July, 2002 to test the precision of the RTK survey data. 

Table 1 presents the data and summary statistics comparing the two surveys, of the 38 wells and 

geoprobe holes at the two sites. The three columns on the right in table 1 were the calculated 

difference between the June and July, 2002 surveys. The Northing difference ranged from –4 to 

+6 cm and the Easting difference ranged from –9 to +4 cm. These differences are plotted in 

figure 7. The elevation difference ranged from –9 to +6 cm. The expected values of the elevation 

difference were twice the Northing and Easting mean value (Sickle, 2001). 

152
Table 1. Real-time kinematic survey data for wells at the A-site and B-site of the OsageSkiatook Petroleum Environmental Research program, June and July, 2002. 

June, 2002 July, 2002 DIFFERENCE 

WELL 

ID NORTHING 

(m)

EASTING 

(m)

ELEVATION 

(m) 

NORTHING

(m) 

EASTING

(m) 

ELEVATION 

(m) 

NORTHING 

(m) 

EASTING 

(m) 

ELEVATION 

(m) 

AR01 4030607.05 752464.69 209.92 4030607.00 752464.75 209.96 0.05 -0.06 -0.06

AA01 4030423.77 752716.02 193.39 4030423.80 752716.03 193.39 -0.03 -0.01 0.00

AA02 4030396.94 752719.98 195.06 4030396.95 752719.96 195.06 -0.01 0.02 0.00

AA03 4030394.66 752739.50 195.32 4030394.67 752739.47 195.31 -0.01 0.03 0.01

AA04 4030386.12 752693.42 195.11 4030386.10 752693.42 195.12 0.02 0.00 -0.01

AE02 4030445.16 752660.91 194.06 4030445.18 752660.95 194.11 -0.02 -0.03 -0.05

AE03 4030385.59 752638.20 192.60 4030385.58 752638.20 192.60 0.01 0.00 0.00

AE04 4030385.85 752697.55 195.16 4030385.83 752697.61 195.15 0.02 -0.05 0.01

AE05 4030365.89 752706.92 195.18 4030365.89 752706.93 195.17 0.00 -0.01 0.01

AE06 4030333.87 752727.31 196.78 4030333.88 752727.33 196.74 -0.01 -0.02 0.04

AE07 4030304.58 752746.41 198.00 4030304.59 752746.37 197.99 -0.01 0.04 0.01

AE08 4030384.01 752742.21 195.79 4030384.04 752742.22 195.79 -0.03 -0.01 0.00

AE09 4030389.43 752715.20 195.04 4030389.46 752715.23 195.03 -0.03 -0.03 0.01

AE10 4030388.78 752726.88 194.85 4030388.77 752726.89 194.83 0.01 -0.01 0.02

AE13 4030488.62 752744.93 189.36 4030488.61 752744.92 189.35 0.01 0.01 0.01

AE14 4030466.66 752722.66 189.96 4030466.66 752722.65 189.97 0.00 0.01 -0.01

AE15 4030459.94 752727.09 189.87 4030459.91 752727.09 189.88 0.03 0.00 -0.01

AE16 4030437.12 752733.51 191.61 4030437.11 752733.49 191.62 0.01 0.02 -0.01

AE17 4030435.93 752724.42 191.71 4030435.92 752724.43 191.70 0.01 -0.01 0.01

AE18 4030441.64 752740.44 192.01 4030441.66 752740.47 192.01 -0.02 -0.03 0.00

AE19 4030396.01 752740.09 195.28 4030396.01 752740.10 195.26 0.00 -0.01 0.02

BR01 4026214.70 756269.58 241.11 4026214.64 756269.54 241.12 0.06 0.04 -0.01

BA01 4026349.57 756584.28 190.46 4026349.57 756584.24 190.46 0.00 0.04 0.00

BA02 4026258.26 756572.21 194.79 4026258.30 756572.20 194.74 -0.04 0.01 0.05

BA03 4026316.87 756539.08 194.87 4026316.91 756539.10 194.87 -0.04 -0.02 0.00

BE01 4026366.07 756567.57 191.32 4026366.09 756567.66 191.41 -0.02 -0.09 -0.09

BE03 4026345.30 756581.89 190.51 4026345.27 756581.91 190.48 0.03 -0.02 0.03

BE04 4026312.29 756609.96 189.62 4026312.28 756609.96 189.61 0.01 0.00 0.01

BE05 4026312.15 756609.76 189.63 4026312.17 756609.75 189.60 -0.02 0.01 0.03

BE06 4026289.01 756630.66 189.67 4026289.03 756630.63 189.65 -0.02 0.03 0.02

BE08 4026266.78 756630.83 189.28 4026266.79 756630.84 189.29 -0.01 -0.01 -0.01

BE09 4026265.91 756616.42 190.20 4026265.94 756616.38 190.21 -0.03 0.04 -0.01

BE10 4026271.90 756613.66 190.21 4026271.91 756613.65 190.23 -0.01 0.01 -0.02

BE11 4026262.41 756605.74 191.31 4026262.45 756605.73 191.28 -0.04 0.01 0.03

BE12 4026259.14 756606.73 191.37 4026259.17 756606.73 191.39 -0.03 0.00 -0.02

BE15 4026277.50 756627.90 189.72 4026277.52 756627.92 189.72 -0.02 -0.02 0.00

BE18 4026321.39 756627.71 189.06 4026321.40 756627.68 189.00 -0.02 0.03 0.06

BE19 4026321.22 756627.49 189.06 4026321.21 756627.49 189.05 0.01 0.00 0.01

Summary Statistics of Difference (meter

Minimum -0.04 -0.09 -0.09

1st Quartile -0.02 -0.02 -0.01

Median -0.01 0.00 0.00

3rd Quartile 0.01 0.01 0.01

Maximum 0.06 0.04 0.06

Thirty of the 38 locations in figure 7 are within the larger shaded area for the 5 to 95 

percentile. The interquartile area on the plot is 3 cm, which is about the diameter of the red and 

white antenna pole for the rover unit (fig. 4). 

153
Figure 7. Plot of the difference between the Northing and Easting values for the June 

and July, 2002 surveys. 

Summary

RTK methods offer high accuracy in real time. The RTK surveys require a GPS base 

station, a GPS rover unit, and radio link between the units. Some preparation is required before 

the RTK survey so a differential correction can be applied during the data collection. This 

preparation may include establishing a base station location by a static GPS survey. RTK surveys 

can be interrupted by tree canopy, minimum number of satellites, solar storms, distance from the 

base station, other radios in the area on the same frequency, and battery failure. A single person 

can conduct RTK surveys. Multiple rover units can utilize one base station. Nearly all the factors 

affecting GPS positioning are eliminated by differential GPS methods. RTK surveys are not 

limited by line of sight from base station, darkness, lakes, or the minimum number of people 

needed. Wells at the sites were surveyed with the RTK GPS equipment in June and July, 2002. 

The Northing difference ranges from –4 to +6 cm and the Easting difference ranges from –9 to 

+5 cm. The elevation difference ranged from –9 to +6 cm. 

154
References 

Otton, J.K. and Zielinski, R.A., [this volume] 2003, Produced water and hydrocarbon 

releases at the Osage-Skiatook petroleum environmental research studies, Osage county 

Oklahoma: Introduction and geologic setting: U.S. Geological Survey Water-Resources 

Investigations 03-4260, p. 14-41. 

Sickle, J.V., 2001, GPS for Land Surveyors: Chelsea, Mich., Ann Arbor Press, Inc., 284 p. 

Trimble, accessed July 2003 at http://www.trimble.com/gps/what.html

155