Risks to Drinking Water from Oil and 

Gas Wellbore Construction and 

Integrity

Case Studies and Lessons Learned

Briana Mordick

Oil & Gas Science Fellow

Natural Resources Defense Council

1
BAINBRIDGE TOWNSHIP, OHIO

Case Study 1

2
Incident Summary

• December 15, 2007: Explosion at a home in Bainbridge Township, 

Geauga County, OH

• Investigators determine natural gas is entering homes via water 

wells

• Ohio Department of Natural Resources, Division of Mineral 

Resources Management (DMRM) evaluates local oil and gas wells to 

determine source of natural gas

• Ohio Valley Energy Systems Corp (OVESC) identifies problems with 

their English No. 1 well, assumes responsibility for incident, and 

initiates corrective action

• DMRM initiates monitoring program, measures response of water 

wells to corrective action at the English No. 1, performs remedial 

water well work, provides methane monitoring equipment to 49 

homes, and provides replacement drinking water to 48 homes.

3
Glacial Till

Aquifers

Ohio Shale

“Big Lime”

Oriskany

Newburg

Clinton

Packer Shell

Simplified Stratigraphy at English No. 1

TARGET FORMATION 3600-3900’

4
Glacial Till

Aquifers

Ohio Shale

“Big Lime”

Oriskany

Newburg

Clinton

Packer Shell

Conductor Casing

5
Glacial Till

Aquifers

Ohio Shale

“Big Lime”

Oriskany

Newburg

Clinton

Packer Shell

Conductor Casing

Surface Casing Fully Cemented

6
Glacial Till

Aquifers

Ohio Shale

“Big Lime”

Oriskany

Newburg

Clinton

Packer Shell

Conductor Casing

Surface Casing Fully Cemented

TD = 3926’ 7
Glacial Till

Aquifers

Ohio Shale

“Big Lime”

Oriskany

Newburg

Clinton

Packer Shell

Conductor Casing

Surface Casing Fully Cemented

Production Casing

TD = 3926’ 8
Glacial Till

Aquifers

Ohio Shale

“Big Lime”

Oriskany

Newburg

Clinton

Packer Shell

Conductor Casing

Surface Casing Fully Cemented

Production Casing

TD = 3926’ 9
Glacial Till

Aquifers

Ohio Shale

“Big Lime”

Oriskany

Newburg

Clinton

Packer Shell

Conductor Casing

Surface Casing Fully Cemented

Production Casing Open Annulus

TOC = 3640’

TD = 3926’ 10
Glacial Till

Aquifers

Ohio Shale

“Big Lime”

Oriskany

Newburg

Clinton

Packer Shell

Conductor Casing

Surface Casing Fully Cemented

Production Casing Open Annulus

TOC = 3640’

TD = 3926’

Perfs = 

3720-3740’

11
Glacial Till

Aquifers

Ohio Shale

“Big Lime”

Oriskany

Newburg

Clinton

Packer Shell

Conductor Casing

Surface Casing Fully Cemented

Production Casing Open Annulus

TD = 3926’ 12
Glacial Till

Aquifers

Ohio Shale

“Big Lime”

Oriskany

Newburg

Clinton

Packer Shell

Conductor Casing

Surface Casing Fully Cemented

Production Casing Open Annulus

TD = 3926’ 13
Glacial Till

Aquifers

Ohio Shale

“Big Lime”

Oriskany

Newburg

Clinton

Packer Shell

Conductor Casing

Surface Casing Fully Cemented

Production Casing Open Annulus

TD = 3926’ 14
Glacial Till

Aquifers

Ohio Shale

“Big Lime”

Oriskany

Newburg

Clinton

Packer Shell

Conductor Casing

Surface Casing Fully Cemented

Production Casing Open Annulus

TD = 3926’ 15
Glacial Till

Aquifers

Ohio Shale

“Big Lime”

Oriskany

Newburg

Clinton

Packer Shell

Conductor Casing

Surface Casing

Production Casing

Fully Cemented

Open Annulus

TD = 3926’ 16
Glacial Till

Aquifers

Ohio Shale

“Big Lime”

Oriskany

Newburg

Clinton

Packer Shell

Conductor Casing

Surface Casing

Production Casing

Fully Cemented

Open Annulus

TD = 3926’ 17
Glacial Till

Aquifers

Ohio Shale

“Big Lime”

Oriskany

Newburg

Clinton

Packer Shell

Conductor Casing

Surface Casing

Production Casing

Fully Cemented

Open Annulus

TD = 3926’ 18
Glacial Till

Aquifers

Ohio Shale

“Big Lime”

Oriskany

Newburg

Clinton

Packer Shell

Conductor Casing

Surface Casing

Production Casing

Fully Cemented

Open Annulus

TD = 3926’ 19
Glacial Till

Aquifers

Ohio Shale

“Big Lime”

Oriskany

Newburg

Clinton

Packer Shell

Conductor Casing

Surface Casing

Production Casing

Fully Cemented

Open Annulus

“Out-of-zone” hydraulic 

fracture growth allows 

gas to migrate from the 

Clinton formation into 

the open annulus behind 

the production casing.

During primary 

cement job, 

large volume of 

cement goes 

into the highly 

porous Packer 

Shell “thief 

zone” , resulting 

in poor primary 

cement job.

As a result of the poor cement 

job, the shallow Ohio and 

Newburg gas-bearing zones are 

left open behind casing and the 

gas migrates into the annulus. 1

2

3

TD = 3926’

Surface-production 

casing annulus is shut in 

for 31 days and 

becomes overpressured, allowing gas 

to migrate horizontally 

and vertically into 

drinking water aquifers.

4

20
Areas of Dispute

• Was the over-pressurization of the annulus 

sufficient to fracture the geologic units exposed 

in the wellbore?

• If so, could these fractures create a permanent 

migration path for gas to reach groundwater?

• Can methane gas concentrations in domestic 

water wells be used to delineate such fracture 

networks?

• What is the nature and origin of the presence of 

black particulate matter in some domestic water 

wells?

21
MAMM CREEK FIELD, GARFIELD 

COUNTY, COLORADO

Case Study 2

22
Study Area

Source: USGS 2011

USGS, 2011

23
Study Area

Source: USGS 2011

URS, 2006

Papadopulos, 2008

Thyne, 2008

24
Incident Summary

• West Divide Creep Seep: COGCC detects BTEX compounds, methane, and heavy 

hydrocarbons (C2-C6) in West Divide Creek resulting from a poor cement job in a 

nearby gas well

• Due to water contamination incidents and increased gas drilling, Garfield County, 

CO commissions a series of studies to assess the risks to surface and groundwater 

from gas well development and human activities

• The United States Geological Survey (USGS), in cooperation with the Colorado 

Department of Public Health, also undertakes a study to determine the sources 

and sinks of nitrate and methane in Garfield County domestic water wells

• Sampling of domestic water wells shows elevated concentrations of methane; 

groundwater quality health standards are exceeded for fluoride, selenium, nitrate, 

and arsenic; aesthetic standards are exceeded for chloride, iron, manganese, and 

total dissolved solids (TDS).

– Fluoride and selenium do not appear to be related to oil and gas activity

– Nitrate concentrations most likely related to agricultural activity, septic system effluent, and 

animal waste

– Domestic water well hydrogeochemistry shows evidence of mixing between shallow 

groundwater and deep formation water in some wells

25
Areas of Dispute

• Temporal correlation of methane and chloride 

contamination and natural gas activity

• Nature and origin of methane in water wells

– Thermogenic vs. Biogenic

– Related to natural gas extraction?

• Primary mechanism for deep Wasatch and/or 

Mesaverde formation water to mix with 

groundwater

26
Nature and Origin of Methane in Groundwater

STUDY METHANE TYPE ORIGIN TRANSPORT

URS, 2006 Biogenic Biogenic origin Not discussed

URS, 2006 Thermogenic Thermogenic origin • Natural fractures

• Gas drilling and 

production activities/ 

improperly abandoned 

wells

URS, 2006 Mixed/Unknown Uncertain origin Possible mixed sources

Papadopulos, 2008 Biogenic Biogenic origin Indeterminate

Papadopulos, 2008 Thermogenic Conventional thermogenic,

coalbed thermogenic, 

oxidized biogenic, or mixing

Indeterminate

Thyne, 2008 Thermogenic Conventional thermogenic or 

Microbial reduction of 

thermogenic Mesaverde CO2

to CH4

Gas drilling and production 

activities

USGS, 2011 Biogenic Deep Wasatch •Natural fractures

•Uncemented gas well annuli

USGS, 2011 Thermogenic Mesaverde thermogenic and 

oxidized biogenic

•Natural fractures

•Uncemented gas well annuli

27
Nature and Origin of Water Types

STUDY WATER TYPE ORIGIN TRANSPORT

URS, 2006 Na/Ca/Mg-HCO3 Shallow groundwater Precipitation/recharge

URS, 2006 Na-SO4; Na-SO4-HCO3 Unknown Unknown

URS, 2006 Na-Cl Deep groundwater • Fracture zones/structural features

• Gas wells

Papadopulos, 

2008

Mixed cation-bicarbonate anion, 

low TDS

Shallow groundwater Precipitation/recharge, flow along shallow pathways

Papadopulos, 

2008

Na-HCO3; Na-SO4(high TDS) Shallow or deep groundwater • Precipitation/recharge, flow along shallow pathways

• Vertical upward flow along natural fractures, wellbores, 

or hydraulic fractures

Papadopulos, 

2008

Na-Cl Deep groundwater/brine • Natural deeper flow processes

Thyne, 2008 Low TDS, Ca-Na-Mg-HCO3 Streams and water wells near 

surface streams

Precipitation/recharge

Thyne, 2008 Higher TDS, Na-Ca-HCO3-SO4 Water wells, deeper/not near 

streams

Precipitation/recharge

Thyne, 2008 Higher TDS, Na-Cl Williams Fork Formation 

(Mesaverde) produced water

Gas drilling and production activities

USGS, 2011 High-oxygen, high-nitrate, lowmethane; mixed cation-SO4-

HCO3, mixed cation-HCO3-SO4; 

young or mixed age

Shallow groundwater

(Evidence in some wells of 

septic system effluent, animal 

waste, fertilizer)

Precipitation/recharge

USGS, 2011 High-oxygen, high-nitrate, lowmethane; mixed cation-SO4-

HCO3, mixed cation-HCO3-SO4; 

old

Deeper groundwater (not 

Mesaverde)

Precipitation/recharge

USGS, 2011 Low-oxygen, low-nitrate, highmethane; Na-HCO3 to Na-Cl; 

mixed age or old

Primarily Mesaverde

formation water mixed 

w/some shallow groundwater

•Natural fractures

•Uncemented gas well annuli

28
Key Observations

• The study area is naturally faulted and fractured. Fault and fracture density 

increases near structural features, such as the Divide Creek Anticline

• For new wells:

– Surface casing must be set below the lowest USDW and cemented to surface

– Production casing must be cemented to 500’ above the top of gas in the Mesaverde (Williams 

Fork)

– The deep Wasatch may be left open to the annulus

– Older wells may have been constructed using different standards

• Gas production wells with persistent or recurring elevated bradenhead pressures 

have been identified near structural features

• Domestic water wells with elevated methane and chloride concentrations are 

often coincident with structural features

• Natural fractures and faults may

– Provide natural migration pathways for gas and fluids, both to groundwater and to the 

uncemented annular space of wellbores

– Cause complications in well drilling, construction, and completion

29
Challenges

• “Most water supplies within the Bainbridge investigation area do not have water analyses predating 

local oil and gas activities.” (DMRM, 2008)

• “Due to the absence of historic water quality data prior to drilling of gas wells to serve as a baseline 

in the area, the water quality issues observed in the study area could predate gas well drilling 

activities. We cannot make a definitive statement other than the water quality issues could be 

caused by natural conditions and/or potentially the presence of gas wells in the area.” (URS 2006)

• “Domestic wells (are) not placed to determine sources of contamination in groundwater. They are 

not evenly spaced around gas wells or within close enough proximity to determine the presence of 

chemicals associated with methane that degrade rapidly.” (Thyne, 2008)

• Construction and abandonment practices for older wells may pose a higher risk for migration of 

methane to groundwater. (Papadopulos, 2008)

• “The cementing problems encountered at the Schwartz 2-15B gas well are evidence that the 

presence of fractured intervals in this area may also affect cement integrity in gas well 

completions” (URS, 2006)

• “The effect on groundwater due to the introduction of drilling or well completion/hydrofracturing

fluids into the shallow aquifer was not investigated for this study. A study evaluating possible local 

effects of drilling or hydrofracturing fluids on domestic groundwater should be considered.” 

(Papadopulos, 2008)

30
Solutions & Lessons Learned

• Detailed site characterization and planning

– Geologic and hydrologic

– Baseline water chemistry

– Gas sampling and composition (vertical and aerial)

– Temporal and aerial updates

• Wellbore construction and maintenance

– Hydrocarbon and brine bearing zones must be isolated

– Wellbore integrity and workovers

• Water quality monitoring plan and dedicated 

monitoring wells

• Hydraulic fracture modeling and measurement

• Must consider cumulative impacts

31
References

• Bair, E.S., Freeman, D.C., and Senko, J.M., 2010, Expert Panel Technical Report, Subsurface Gas Invasion Bainbridge Township,

Geauga County, Ohio: Prepared for the Ohio Department of Natural Resources Division of Mineral Resources Management

• Donato, S.A., Sterrett, R.J., and Hanna, B., 2009, Review of the Thyne Report’s Analysis and Conclusions of Mamm Creek 

Phase II Hydrogeologic Study: PowerPoint presentation prepared for the Colorado Oil & Gas Conservation Commission, 10 

p., 

http://cogcc.state.co.us/Library/Presentations/Glenwood_Spgs_HearingJuly_2009/(1_F)_ReviewOfTheThyneReport'sAnalysi

s_Conclusionof%20MammCreekPh2.pdf

• Eckstein, Y., 2009. Wellhead LEL records in Bainbridge residential water wells, PowerPoint presentation to Bainbridge Gas 

Invasion Expert Panel, 43 p., www.ohiodnr.com/mineral

• Gorody, Anthony, 2009, Summary Comments on the Report by Dr. G. Thyne: PowerPoint presentation prepared for the 

Colorado Oil & Gas Conservation Commission, 26 p., 

http://cogcc.state.co.us/Library/Presentations/Glenwood_Spgs_HearingJuly_2009/(1_G)_Summary_Comments_Report.ppt

• McMahon, P.B., Thomas, J.C., and Hunt, A.G., 2011, Use of diverse geochemical data sets to determine sources and sinks of 

nitrate and methane in groundwater, Garfield County, Colorado, 2009: U.S. Geological Survey Scientific Investigations Report 

2010–5215, 40 p.

• Ohio Department of Natural Resources, Division of Mineral Resources Management, “Report on the Investigation of the 

Natural Gas Invasion of Aquifers in Bainbridge Township of Geauga County, Ohio” September 1, 2008

• Papadopulos & Associates, Inc., 2008, Phase II hydrogeologic characterization of the Mamm Creek Field area, Garfield 

County, Colorado: Prepared for the Board of County Commissioners, Garfield County, Colorado, 41 p.

• Papadopulous & Associates, Inc., 2009, Evaluation of Thyne, 2008 “Review of Phase II Hydrogeologic Study” Mamm Creek 

Field Area, Garfield County, Colorado: PowerPoint presentation prepared for the Colorado Oil & Gas Conservation 

Commission, 29 p., 

http://cogcc.state.co.us/Library/Presentations/Glenwood_Spgs_HearingJuly_2009/(1_D)_Evaluation_of_Thyne_Report_vers

2%20(dv).pdf

• Thyne, Geoffrey, 2008, Review of Phase II Hydrogeologic Study prepared for Garfield County: Prepared for Garfield County, 

26 p., http://cogcc.state.co.us/Library/Presentations/Glenwood_Spgs_HearingJuly_2009/(1_A)_ReviewofPhase-IIHydrogeologicStudy.pdf

• URS Corporation, 2006, Phase I hydrogeologic characterization of the Mamm Creek Field area in Garfield County: Prepared 

for the Board of County Commissioners, Garfield County, Colorado, 86 p.

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