Thermal Maturity Data Used by the U.S. Geological Survey 

for the U.S. Gulf Coast Region Oil and Gas Assessment

By Kristin O. Dennen, Peter D. Warwick, and Elizabeth Chinn McDade

Open-File Report 2010–1072

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

KEN SALAZAR, Secretary

U.S. Geological Survey

Marcia K. McNutt, Director

U.S. Geological Survey, Reston, Virginia: 2010

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Suggested citation:

Dennen, K.O., Warwick, P.D., and McDade, E.C., 2010, Thermal maturity data used by the U.S. Geological Survey for 

the U.S. gulf coast region oil and gas assessment: U.S. Geological Survey Open-File Report 2010–1072, 7 p. plus 

one appendix. (Available at http://pubs.usgs.gov/ofr/2010/1072/.)

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Although this report is in the public domain, permission must be secured from the individual 

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iii

Contents

Introduction.................................................................................................................................................................... 1

Description of Data ........................................................................................................................................................ 1

Suggestions for Using and Interpreting the Data ........................................................................................................... 3

Geochemical Analyses............................................................................................................................................... 3

Latitudes, Longitudes, and Identification Information ................................................................................................. 4

Elevation Estimates ................................................................................................................................................... 4

Acknowledgments ......................................................................................................................................................... 4

References Cited........................................................................................................................................................... 5

Appendix A.—Thermal Maturity Data ............................................................................................................................ 7

Tables

1. Thermal maturity data for core and cuttings samples from oil and gas wells—Descriptions............................. 2

2. Thermal maturity data for coal core, surface, and mine samples—Descriptions .............................................. 3

A–1. Thermal maturity data for core and cuttings samples from oil and gas wells.................................... [Tables.xls] 

A–2. Thermal maturity data for coal core, surface, and mine samples...................................................... [Tables.xls] 

Conversion Factors

Multiply By To obtain

Length

foot (ft) 0.3048 meter (m)

Temperature in degrees Celsius (°C) may be converted to degrees Fahrenheit (°F) as follows:

°F=(1.8×°C)+32
1

Thermal Maturity Data Used by the U.S. Geological Survey 

for the U.S. Gulf Coast Region Oil and Gas Assessment

By Kristin O. Dennen,1 Peter D. Warwick,

1 and Elizabeth Chinn McDade2

Introduction

The U.S. Geological Survey (USGS) is currently assessing the oil and natural gas resources of 

the U.S. Gulf of Mexico region using a total petroleum system (TPS) approach (Klett and others, 2000). 

An essential part of this geologically based method is evaluating the effectiveness of potential source 

rocks in the petroleum system. The purpose of this report is to make available to the public RockEval 

and vitrinite reflectance data from more than 1,900 samples of Mesozoic and Tertiary rock core and coal 

samples in the Gulf of Mexico area in a format that facilitates inclusion into a geographic information 

system (GIS). These data provide parameters by which the thermal maturity, type, and richness of 

potential sources of oil and gas in this region can be evaluated. 

Description of Data

The data are divided into spreadsheets—data from oil and gas well cores and cuttings samples 

(table A–1) with American Petroleum Institute (API) numbers (American Petroleum Institute, 1979) and 

data from gulf coast coal core, surface, and mine samples (table A–2). Sample analyses are 

accompanied by geospatial data (latitude, longitude, and sample elevation estimates) and geographical 

information (county and State). API numbers are supplied with oil and gas well data to facilitate use of 

gulf coast region online State oil and gas databases to access more information. 

Variable headings for the oil and gas well and coal sample tables differ slightly because coal 

samples do not have API numbers. Tables containing variable headings and explanations appear in 

tables 1 and 2. 

 

1

U.S. Geological Survey, Reston, Va. 2

McMoRan Oil and Gas LLC, New Orleans, La.
2

Table 1. Thermal maturity data for core and cuttings samples from oil and gas wells—Descriptions. [Abbreviations used: API, American Petroleum Institute; CO2, carbon dioxide; ft, foot]

Variable heading Description or explanation

API no. A unique number that identifies a well site and cores taken from that well in public well 

records. It specifies the State, the county or parish, and in some States, a permit number for the 

well issued by the State in which the well is drilled.

Lease/well name Most wells are named for the person leasing or owning the land where the well is drilled. If 

multiple holes are drilled on a property, then the name is usually followed by a number.

Field name Name of the oil or gas field in which the well is situated. This is usually specified in public 

well records. If the well is not associated with a particular field, then the well is usually called 

a “wildcat.”

Remarks, longitude and 

latitude

Arkansas township and range coordinates were converted to latitude and longitude using the 

University of Montana’s conversion program available at http://www.esg.montana.edu/gl/trsdata.html. 

Longitude Decimal degrees of longitude.

Latitude Decimal degrees of latitude.

Remarks, sample elevation 

estimates (ft)

If a sample is from an offshore well, this elevation includes the depth of the water above the 

well location and is indicated by the remark “subsea.”

Sample elevation estimates 

(ft)

Subsurface core sample elevations were estimated by subtracting the core depth reported for 

the sample from the land surface elevation at the latitude and longitude of the core hole. 

Group or formation Geologic name of group or formation from which sample was taken.

Group or formation age Geologic name for the age of the group or formation from which sample was taken.

State State where well is located and where there are related public records.

County/parish County or (in the case of Louisiana) parish in which the well is located. If the sample is from 

an offshore well in Federal waters, then there is no county or parish name associated with it.

Tmax Temperature from RockEval analysis corresponding to maximum S2 production in °C.

S1 Milligrams of free organic compounds per gram of sample.

S2 Milligrams of hydrocarbons derived from kerogen, resins, and asphaltenes per gram of sample.

S3 Milligrams of CO2 per gram of sample released between 300° and 390°C.

PI Production index = S1 /S1 + S2-

TOC Total organic carbon content of sample in weight percent.

HI Hydrogen index = milligrams S2 per gram TOC × 100.

OI Oxygen index = milligrams S3 per gram TOC × 100.

Remarks TAI Range of visual reference scale used for TAI determination.

TAI Thermal alteration index; determined using a visual reference scale.

Remarks %Ro If the Ro values are calculated, then this is noted. The formula for calculating the value, if 

known, is provided.

%Ro Mean value of percent reflectance measurements of vitrinite in oil (American Society for 

Testing and Materials, 2007), unless otherwise noted.

Remarks, source of analyses In a single published report, different analytical laboratories providing analyses are indicated if 

given. If data are unpublished, then that and permission to publish the data are indicated.

Source of analyses Published reference from which the analyses were taken or laboratory that provided the 

analyses. 

Location source (if different 

from analytical source)

If the locations for the well core samples were not provided in the publication or by the 

analytical laboratory, then the locations were retrieved from a publically available online 

database of well locations.
3

Table 2. Thermal maturity data for coal core, surface, and mine samples—Descriptions. [Abbreviations used: CO2, carbon dioxide; ft, foot]

Variable heading Description or explanation

Sample name Name of sample provided in report from which the analyses were taken.

Sample type Description of sample type given in publication or by collector of a sample; whether it is from a 

surface sample (taken from an outcrop) or a well core or cuttings or taken from within a coal mine. 

The analysis source should be consulted for a complete description.

Location name Name of mine or geographical name of area of outcrop from which coal sample was taken.

Longitude Decimal degrees of longitude.

Latitude Decimal degrees of latitude.

Sample elevation 

estimates (ft)

Subsurface core sample elevations were estimated by subtracting the core depth or coal seam depth 

reported for the sample from the land surface elevation at the latitude and longitude at the sample 

site. If a sample was taken at the surface, then this is the height of the outcrop given by the collector 

or publication.

Group or formation Geologic name of group or formation from which sample was taken.

Group or formation age Geologic name for the age of the group or formation from which sample was taken.

State State where mine or surface sample was obtained.

County/parish County or (in the case of Louisiana) parish where the mine or surface sample was obtained.

Tmax Temperature from RockEval analysis corresponding to maximum S2 production in °C.

S1 Milligrams of free organic compounds per gram of sample.

S2 Milligrams of hydrocarbons derived from kerogen, resins, and asphaltenes per gram of sample.

S3 Milligrams of CO2 per gram of sample released between 300° and 390°C.

PI Production index = S1 /S1 + S2-

TOC Total organic carbon content of sample in weight percent.

HI Hydrogen index = milligrams S2 per gram TOC × 100.

OI Oxygen index = milligrams S3 per gram TOC × 100.

%Ro Mean value of percent reflectance measurements of vitrinite in oil (American Society for Testing 

and Materials, 2007), unless otherwise noted. 

Remarks, source of 

analyses

If data are unpublished that is indicated. If special permission to publish the data was granted, that 

is indicated.

Source of analyses Published reference from which the analyses were taken or laboratory that provided the analyses. 

Location source (if 

different from analytical 

source)

If the locations for the core samples were not provided in the publication or by the analytical 

laboratory, then the locations were retrieved from a publically available online database of well 

locations. The database source of the location data is indicated.

Suggestions for Using and Interpreting the Data

Geochemical Analyses

Each sample entry in the dataset contains a reference to the source of the data. Because the 

sample analyses come from a variety of sources, it is important to understand how the analytical values 

were derived and how they can be compared. The source for each group of data should be consulted to 

ascertain the analytical methods and reporting conventions used. 

Definitions of the geochemical parameters used in source rock evaluation and descriptions of 

how source rock geochemical analyses are applied to petroleum exploration can be found in Peters and 

Casa (1994). The American Society for Testing and Materials (ASTM) (2007) methods D2797 and 
4

D2798 respectively contain detailed descriptions of how samples are prepared and analyzed for vitrinite 

reflectance measurements and how the measurements are reported.

Some of the major source rocks in the Gulf of Mexico, such as the Jurassic Smackover 

Formation, are marine carbonates. This creates a set of problems for thermal maturity interpretation

from vitrinite reflectance data owing to the frequently very low concentrations of nonmarine, plantbased materials from which vitrinite reflectance measurements are made. Two references that address

the problems of source rock thermal maturity evaluation in the Gulf of Mexico are Sassen and Moore 

(1988) and Jarvie and others (2001). 

Latitudes, Longitudes, and Identification Information

Sometimes the sources of the data and of the geospatial information are different. The authors 

verified and updated the well identification and location information where possible, but there may be 

recent changes in the API numbers owing to the fact that the API well identification system is being 

updated to reflect constantly evolving drilling technology (IHS Energy Group, 2008). For the data from 

Arkansas, only township and range figures were available, so those data were converted using the online 

calculator at Montana State University’s Website (http://www.esg.montana.edu/gl). 

Wells drilled before the introduction of digital recordkeeping may not appear in online 

databases; therefore it may be necessary to contact the appropriate State recordkeeping agency directly 

for up-to-date information. 

Elevation Estimates

Subsurface core sample elevations were estimated by subtracting the reported core depth from 

the land surface elevation at the latitude and longitude of the core hole. The accuracy of the estimated 

elevation estimations depends not only on the reported latitude and longitude but also on the source of 

data for the digital elevation model (DEM) used for the estimates. Because the land surface elevations in 

this report have been determined by several DEMs, it is best to consult the sources for each set of data

if extremely accurate sample elevations are needed. The USGS National Elevation Dataset (NED) is the 

basis for many DEMs (U.S. Geological Survey, 2002, 2006).

Acknowledgments

Keith F.M. Thompson, Roger Sassen, and Norman Guissano, Jr., Director, Geochemical and 

Environmental Research Group, College of Geosciences, Texas A&M University, were instrumental in 

the release of data associated with the Gulf of Mexico Petroleum Correlation Study (Thompson and 

Kennicutt, 1992). Crishun Brown of the Texas Railroad Commission provided assistance and copies of 

her research on locations of Texas wells that could not be located in the Texas Railroad Commission’s 

online database. Paul Walker of Baseline Resolution Weatherford Laboratories and P.K. Mukhopadhyay 

gave permission to release the proprietary analyses in Dow and Mukhopadhyay (1988). Donald 

Goddard and John E. Johnston III at the Louisiana Geological Survey gave permission for publication 

of the analyses from Goddard (1995). Sigrid Clift of the Texas Bureau of Economic Geology gave 

permission for publication of the analyses in Mukhopadhyay (1989). Charles Barker (emeritus) of the 

USGS gave permission for some of his analyses to appear in this report. Mike Lewan of the USGS 

allowed the release of some of his recent analyses and made helpful suggestions for reference works on 

the use and interpretation of thermal maturity data. Jennie Ridgley (emeritus) of the USGS provided 

new unpublished analyses of her work on core and cuttings samples from Texas and Louisiana. Paul 
5

Hackley and Jamey McCord of the USGS provided analytical data and sample location information. 

Chris Garrity and Alex Karslen of the USGS advised on the uses of DEMs and provided GIS assistance. 

Mark Pawlewicz and Elizabeth Rowan of the USGS reviewed this report. Their comments and 

suggestions improved it, and the authors greatly appreciate their assistance.

References Cited

American Petroleum Institute, 1979, The API well number and standard state and county numeric codes 

including offshore waters: Dallas, Tex., American Petroleum Institute Bulletin D12A, 136 p. 

American Society for Testing and Materials, 2007, Gaseous fuels; Coal and coke, sec. 5 of Annual book 

of ASTM standards—Petroleum products, lubricants, and fossil fuels: West Conshohocken, Penn., 

American Society for Testing and Materials International, v. 5.06, 700 p. 

Dow, W.G., and Mukhopadhyay, P.K., 1988, The Deep Wilcox from south-central Texas: The 

Woodlands, Tex., Baseline DGSI Analytical Laboratories Project 87/434, 39 p. 

Goddard, D.A., 1995, Deltaic reservoir characterization, in Geological, petrophysical, and engineering 

applications: Baton Rouge, La., Louisiana Geological Survey Basin Research Institute Technical 

Report 95–2, 125 p. 

Hackley, P.C., Hook, R.W., and Warwick, P.D., 2005, Huminite reflectance measurements of Paleocene 

and Upper Cretaceous coals from borehole cuttings, Zavala and Dimmit Counties, south Texas: U.S. 

Geological Survey Open-File Report 2005–1144, 13 p., accessed January 27, 2010, at 

http://pubs.usgs.gov/of/2005/1144/. 

Hackley, P.C., Ratchford, M.E., and Warwick, P.D., 2006, Reflectance measurements of well cuttings 

from Ashley and Bradley Counties, Arkansas: U.S. Geological Survey Open-File Report 2006–1155, 

29 p., accessed January 27, 2010, at http://pubs.usgs.gov/of/2006/1155/. 

Hackley, P.C., and Warwick, P.D., 2005, Organic petrography of coals from a coalbed methane test 

well, Ouachita Parish, Louisiana: U.S. Geological Survey Open-File Report 2005–1134, 22 p., 

accessed January 27, 2010, at http://pubs.usgs.gov/of/2005/1134/. 

Hackley, P.C., Warwick, P.D., Breland, F.C., Jr., Richard, T.E., and Ross, K., 2007, Results from 

coalbed methane drilling in Winn Parish, Louisiana: U.S. Geological Survey Open-File Report 2007–

1061, 45 p., accessed January 27, 2010, at http://pubs.usgs.gov/of/2007/1061/. 

IHS Energy Group, 2008, API new numbering guidelines: Englewood, Colo., IHS Energy Group, 

accessed January 27, 2010, at 

http://www.ihsenergy.com/support/reference_materials/apiguidelines/general_guides.jsp. 

Jarvie, D.M., Morelos, A., and Han, Z., 2001, Detection of pay zones and pay quality, Gulf of Mexico—

Application of geochemical techniques: Gulf Coast Association of Geological Societies Transactions, 

v. 51, p 151–160. 

Klett, T.R., Schmoker, J.W., Charpentier, R.R., Ahlbrandt, T.S., and Ulmishek, G.F., 2000, Glossary, 

chap. GL of U.S. Geological Survey world petroleum assessment 2000—Description and results: U.S. 

Geological Digital Data Series 60, accessed January 27, 2010, at http://pubs.usgs.gov/dds/dds-060/. 

Mancini, E.A., Aharon, P., Goddard, D.A., and Barnaby, R., 2006, Resource assessment of the in-place 

and potentially recoverable deep natural gas resource of the onshore interior salt basins, north central 

and northeastern Gulf of Mexico: U.S. Department of Energy Final Report DE–FC26–03NT41875, 

179 p. 

McDade, E.C., 1992, Organic-rich lower Tertiary shales, south Louisiana—Implications for petroleum 

source rock deposition: Baton Rouge, La., Louisiana State University Ph.D. dissertation, 255 p. 
6

Mukhopadhyay, P.K., 1989, Organic petrography and organic geochemistry of Texas Tertiary coals in 

relation to depositional environment and hydrocarbon generation: Bureau of Economic Geology, The 

University of Texas at Austin Report of Investigations 188, 118 p. 

Penn Virginia Oil and Gas, 2005, Horizontal wells—A viable method for exploitation of coalbed 

methane from the Wilcox coals of the central gulf coast: Mississippi/Alabama Division of the U.S. Oil 

and Gas Association 2007 Oil and Gas Forum Annual Meeting, 63d, October 17–19, 2007, Point 

Clear, Ala., accessed January 27, 2010, at 

http://www.usoga.com/events/presentations/Wilcox_lewis.pdf.

Peters, K.E., and Cassa, M.R., 1994, Applied source rock geochemistry, in Magoon, L.B., and Dow, 

W.G., eds., The petroleum system—From source to trap: Tulsa, Okla., American Association of 

Petroleum Geologists Memoir 60, p. 93–120. 

Price, L.C., 1982, Organic geochemistry of core samples from an ultradeep hot well (300°C, 7 km): 

Chemical Geology, v. 37, no. 3–4, p. 215–228. 

Price, L.C., 1989, Louisiana oil-oil correlation by iso-cyclic, aromatic, and gasoline-range 

hydrocarbons, with an appendix of organic-geochemical rock data from selected wells in the gulf 

coast: U.S. Geological Survey Open-File Report 89–358, 90 p., accessed January 28, 2010, at 

http://pubs.er.usgs.gov/djvu/OFR/1989/ofr_89_358.djvu. 

Price, L.C., and Clayton, J.L., 1990, Reasons for and significance of deep high-rank hydrocarbon 

generation in the south Texas gulf coast, in Gulf Coast Section Society for Sedimentary Geology 

Annual Research Conference, 9th, Proceedings: Tulsa, Okla., Society for Sedimentary Geology, p. 

105–137. 

Sassen, Roger, and Moore, C.H., 1988, Framework of hydrocarbon generation and destruction in eastern 

Smackover trend: American Association of Petroleum Geologists Bulletin, v. 72, no. 6, p. 649–663. 

Thompson, K.F.M., and Kennicutt, M.C., II, 1992, Correlations of gulf coast petroleums on the basis of 

branched acyclic alkanes: Organic Geochemistry, v. 18, no. 1, p. 103–119. 

U.S. Geological Survey, 2002, The national map—Elevation: U.S. Geological Survey Fact Sheet 106–

02, accessed January 27, 2010, at http://egsc.usgs.gov/isb/pubs/factsheets/fs10602.html. 

U.S. Geological Survey, 2006, National elevation dataset: U.S. Geological Survey, accessed January 27, 

2010, at http://ned.usgs.gov/. 

Wagner, B.E., Sofer, Z., and Claxton, B.L., 1994, Source rock in the Lower Tertiary and Cretaceous 

deep-water Gulf of Mexico: Transactions of the Gulf Coast Association of Geological Societies, v. 44, 

p. 729–736. 

Warwick, P.D., Breland, F.C., Jr., Hackley, P.C., Dulong, F.T., Nichols, D.J., Karlsen, A.W., Bustin, 

R.M., Barker, C.E., Willett, J.C., and Trippi, M.H., 2006, Analytical results from samples collected 

during coal-bed methane exploration drilling in Caldwell Parish, Louisiana: U.S. Geological Survey 

Open-File Report 2006–1213, 520 p., accessed January 28, 2010, at 

http://pubs.usgs.gov/of/2006/1213/. 

Warwick, P.D., SanFilipo, J.R., Karlsen, A.W., and Barker, C.E., 2005, Results of coalbed methane 

drilling in Panola County, Texas: U.S. Geological Survey Open-File Report 2005–1046, 155 p., 

accessed January 28, 2010, at http://pubs.usgs.gov/of/2005/1046/.
7

Appendix A.—Thermal Maturity Data

Table A–1. Thermal maturity data for core and cuttings samples from oil and gas wells. 

Table A–2. Thermal maturity data for coal core, surface, and mine samples.