1

PRELIMINARY RESULTS FROM COAL-BED METHANE DRILLING IN

PANOLA COUNTY, TEXASP.D. WARWICK, U.S. Geological Survey, Reston, VAC.E. BARKER, U.S. Geological Survey, Denver, CO

J.R. SANFILIPO, U.S. Geological Survey, Reston, VAL.E. MORRIS, Texas A&M University, College Station, TX

Available on the Internet at http://energy.er.usgs.gov

U.S. Department of InteriorU.S. Geological Survey Open-File Report 00-048

This report is preliminary and has not been reviewed for conformity with U.S. Geological Survey editorial standards and stratigraphic

nomenclature. Any use of trade names is for descriptive purposes only and does not imply endorsement by the U.S.G.S.

Figure 1. Title page.

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INTRODUCTION - OUTLINE

* This is work in progress! Only preliminary data are presented

* Overview of NE TX/LA coal geology & drill site location

* Results: coal and gas physical characteristics & geochemistry

* Conclusions and where do we go from here?

•Acknowledgements: Phillips Coal, TXU Mining Company, and co-workers at TX A&M and USGS

Figure 2. Introduction and outline. In June, 1999, the U.S. Geological Survey (USGS) and Texas A&M University drilled two coal bed methane test holes in Panola County, Texas. The following diagrams provide some preliminary results from drilling and samples collected. The first hole (USGS-PA-1) contained no measurable gas. The second hole (USGS-PA-2), contained some coal gas, and is the focus of this presentation.

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Coal Fields of the United States

~ 6,000 ft depth

Coal Rank

Lignite

Sub-bituminous

Medium and High-volatile BituminousLow-volatile Bituminous

Anthracite

*

*

*

*

** of unknown extent

Coal Fields of the United States

~ 6,000 ft depth

Figure 3. Coal field map of the United States. Note the relative size of the Gulf Coast coal region compared to other coal-bearing regions of the country. Also note that the Gulf coal-bearing strata dip southward into the Gulf of Mexico basin. An estimated 6,000 ft (1828 m) depth to top of the coal-bearing formations is shown.

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TX LA

AROK

County/Parish Boundary

State Boundary

JACKSON GROUP

EXPLANATION

20 0 20 40 60 Miles

20 0 20 40 60 Kilometers

CLAIBORNE GROUP

WILCOX GROUP

Surface Geology

(Eocene)

(Eocene)

(Paleocene - Eocene)

Figure 4. Generalized outcrop of coal-bearing units and major structural features in the Sabine Uplift area of Northeast Texas and Northwestern Louisiana.

5

Eoc

ene

Pal

eoce

ne

Upp

er

Cre

t.

Claiborne Group

Navarro Group

Jackson Group

Wilcox Group

Midway Group

Stratigraphy of coal-bearingintervals in the U.S. Gulf Coastal Plain

Coal zone

Figure 5. Stratigraphy of coal-bearing units in the Gulf Coastal area. Arrows indicate position of major coal zones. Most coal mine production is from the Wilcox Group.

6

Historical Coal Mining Sites

County/Parish Boundary

State Boundary

JACKSON GROUP

EXPLANATION

20 0 20 40 60 Miles

20 0 20 40 60 Kilometers

CLAIBORNE GROUP

WILCOX GROUPCoal Mining Permit Areaand Mine Name

Surface Geology

TX LA

AROK

(Eocene)

(Eocene)

(Paleocene - Eocene)

Figure 6. Generalized outcrop of coal-bearing units and location of current and historic coal mines in the Sabine Uplift area of Northeast Texas and Northwestern Louisiana. Coal beds cored from shallow drill holes (<150 ft or 46 m deep), near the Calvert and Jewett mines, showed no gas content when tested.

7

x

x

County/Parish Boundary

State Boundary

JACKSON GROUP

EXPLANATION

20 0 20 Miles

20 0 20 Kilometers

CLAIBORNE GROUP

WILCOX GROUPCoal Mining Permit Areaand Mine Name

Surface Geology

(Eocene)

(Eocene)

(Paleocene - Eocene)

TX LA

AROK

Figure 7. Close-up map of the Sabine Uplift area. Green “X” indicates location of stratigraphic control from drill holes. Green line is approximate line of section for cross section from Luppens (1987). Black “X” indicates location of 1999 USGS coal-bed methane test holes. Areas colored red are surface coal mine permits.

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Eoc

ene

Pal

eoce

ne

Upp

er

Cre

t.

Claiborne Group

Navarro Group

Jackson Group

Wilcox Group

Midway Group

Stratigraphy of the LA Sabine Area

100 ft

Black Lake B

Top coal

Naborton 2 or

Cow Bayou 1 or

Naborton 3 or

Naborton 4 or

Naborton 5

B lack Lake A Cow Bayou and Younger Forma tions

Dolet Hills Form ation

Naborton Formation

Sandstone and siltstone

Mudstone and claystone

Coal and carbonaceous shale

Limestone

Chemard Lake

Yellow seam

Red seam

Green seam

Coalbed names

Figure 8. Detailed stratigraphy of the coal-bearing part of the Louisiana Sabine Uplift. Italicized coalbed names are from Williamson (1986).

9

Regional Stratigraphy For TX Sabine

M in e d c o a l b e d

1 1 3 4 4 -O HR K - 4 C R E K L A WC A R R IZ OO A K H IL L M IN E

M A R T IN L A K E M IN E

U . W I L C O X

'S IM S B O R O ' (? )

B l a c k L a k e B e d(? ) o f L o u i s i a n a

D O L E T H IL L S M IN E

L . W I L C O X

M ID W A Y

S Y - 1 C

1 0 0 f t

1 2 5 0 -

0 -

R e s G a mD e n

Wilc

ox

Figure 9. Composite boreholes showing regional correlation of the undivided Wilcox Group in the Texas part of the Sabine Uplift. Data modified from Oak Hill mine permits (1134-OH) and Kaiser (1990). Red arrows indicate stratigraphic position of coal beds mined at surface mines shown on figure 6.

10

300

200

100

0

-100

-200

-300

-400

-500

300

200

100

0

-100

-200

-300

-400

-500

300

200

100

0

-100

-200

-300

-400

-500

300

200

100

0

-100

-200

-300

-400

-500

Elevation (ft)

Resistivity

Natural Gamma

Gamma - Gamma density

Mining area East West

TX|LA

After Luppens (1987)Naborton No. 2 ~20ft thick

WestEast

Figure 10. Regional cross section from Luppens (1987). Note that this is one cross section joined as indicated by the join line. Heavy black lines indicate stratigraphic position of the Naborton No. 2 or Chemard Lake coal zone. The arrow indicates an area where the Naborton No. 2 bed is about 20 ft (6 m) thick. Drill hole USGS-PA-2 was located in this area. Note the area where the coal is mined (upper section). Location of the line of section and mining area is shown on figure 7.

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Figure 11. Photograph of Texas A&M drill rig on site at USGS-PA-2.

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250

200

150

100

50

0

-50

-100

250

200

150

100

50

0

-50

-100

USGS-PA-1USGS-PA-2

Calipe

rGam

ma

Density

Resistiv

ity

Ele

vatio

n (f

t)

SandstoneMudstoneCalcareous SandstoneCoal

?

Figure 12. Generalized stratgraphic column and geophysical logs from USGS core holes in Panola County, Texas. Locations are shown on figure 7. Only USGS-PA-2 contained coal bed gas.

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Figure 13. Coal core being measured and described prior to insertion into the desorption canisters at USGS-PA-1. Note clay parting in coal core on the left end of the core. The clay parting occurs at depth 331.2 – 331.35 ft (USGS-PA-1) or about 0.2 ft from the top of the coal bed in both USGS-PA-1 and PA-2.

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Figure 14. Close-up of clay parting in USGS-PA-1. This is probably a volcanic ash or tonstein. The clay parting occurs at depth 331.2 – 331.35 ft (USGS-PA-1) or about 0.2 ft from the top of the coal bed in both USGS-PA-1 and PA-2. A similar ash parting occurs in the same position of the coal being mined at the Dolet Hills and Oxbow mines in Louisiana (fig. 6; also see Ruppert and Warwick, 1994). The occurrence of this ash layer supports Luppens (1987) regional correlation shown on figure 10.

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354356358360362364366368370372374

0 10 20 30 40 50 60Percent

Ash and moisture vs depthUSGS-PA-2 (ar)

Moisture(x = 28.49%)

Ash(x = 13.82%)

USGS-PA-1 average ash = 11.6% and moisture = 34.67% (ar)

dept

h (f

t)

Figure 15. Plot of ash yield and moisture (as received basis, ar) for gas-bearing coal samples from USGA-PA-2. Note the high ash yield in the middle of the bed. Average ash and moisture values for the coal samples from USGA-PA-1 are given at the bottom of the illustration.

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USGS-PA-2 Percent Sulfur (ar)

354356358360362364366368370372374

0.2 0.4 0.6 0.8 1

Sulfur (x = 0.52%)

dept

h (f

t)

Figure 16. Plot of sulfur content (as received basis, ar) for gas-bearing coal samples from USGS-PA-2.

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354356358360362364366368370372374

4000 4500 5000 5500 6000 6500 7000 7500 8000 8500 9000 9500

Btu MMmFx = 8422

USGS-PA-2 Btu (MMmF)de

pth

(ft)

_

ligA subC

Figure 17. Plot of calorific values (Btu/lb on a moist, mineral matter free basis, MMmf) for gas-bearing coal samples from USGS-PA-2. Note most samples plot above 8300 Btu/lb, the boundary between lignite and sub-bituminous.

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0

200

400

600

800

1000

1200

1400

1600

18000.2 0.25 0.3 0.35 0.4 0.45

Ro mean

Depth vs Rofor Naborton No. 2 Coal

Dep

th (f

t)

PRB data from Mavor and others (1999)

% Ro mean

USGS-PA-2

Texas data from Mukhopadhyay (1989)

PRB

Figure 18. Plot of vitrinite reflectance data for the Naborton No. 2 (Chemard Lake) coal in Texas. Blue points from Mukhopadhy (1989). Red point is from USGS-PA-2. White stars are from Powder River basin (PRB) data (Mavor and others, 1999). The deep samples (>1400 ft) with high (>0.4%) Ro values indicate coal rank increase with depth.

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Figure 19. Photograph showing constant temperature water baths used with the coal desorption canisters.

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Cumulative Desorbed Volume (cc) (USGS-PA-2-CN5)

-50

0

50

100

150

200

250

300

0 2 4 6 8

Square root of time (hr)

Cum

ulat

ive

deso

rbed

volu

me

(cc)

Cumulative Desorbedvolume (cc)

Lost gas estimate 40.0 ccraw total gas 0.26 g/cc (8.46 SCF/ton)daf total gas 0.43 g/cc (13.62 SCF/ton)

Figure 20. Example of one of the desorption plots from USGS-PA-2 (canister no. 5, which is about 5 ft (1.5 m) from the top of the coal bed; daf= dry, ash free basis).

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USGS-PA-2Desorbed Gas SCF/ton

355

360

365

370

3750 10 20 30 40

SCF/Ton

Dep

th (f

t)

SCF/Ton daf

SCF/T rawx = (11 SCF/t)

x = (7 SCF/t)_

_

Figure 21. Results of all desorption tests on coal from USGS-PA-2. Note the higher gas content in the upper part of the coal bed. daf = dry, ash free basis.

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(Modified from Whiticar, 1990; Clayton, 1998)

Figure 22. Isotopic composition of carbon (y axis) and hydrogen (x axis) for methane from a gas sample collected from one USGS-PA-2 coal sample. The values obtained from the sample are shown along the axes in red. Note that the gas sample plots in the mixed or transition zone between gases of biogenic and thermogenic origin and is different from Powder River basin (PRB) gases. Diagram after Clayton (1998).

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Diagram modified from Bernard and others (1978); Faber and Stahl (1984); and Whiticar (1994).

Figure 23. Bernard diagram for a gas sample collected from one USGS-PA-2 coal sample. The plot shows the molecular ratio of C1, C2 and C3(methane, ethane, and propane) and carbon isotopic composition in methane. The values obtained from the USGS-PA-2 sample are plotted along the axes in red. Note that the gas plots in the transition region of the diagram. The dryness of the gas indicates it is out of the thermal region. Diagram modified from Bernard and others (1978); Faber and Stahl (1984); and Whiticar (1994).

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USGS-PA-2-CN2 Methane Adsorption

020406080

100120140160180200

0 200 400 600 800 1000 1200

Sample Cell Equilibrium Pressure (PSI)

Met

hane

Ads

orbe

d (S

CF/

Ton)

AS RECEIVED BASIS

DRY ASH FREE BASIS

Figure 24. Example of a methane sorption isotherm for a sample from near the top of the gas-bearing interval sampled in USGS-PA-2. Note the difference between the as-received and dry, ash-free bases.

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USGS-PA-2 Methane Adsorption (As Received)

0102030405060708090

100

0 200 400 600 800 1000 1200

Pressure (PSI)

Met

hane

Ads

orbe

d (S

CF/

Ton)

CN2 32.9, 7.9

CN6 32.7, 4.4

CN12 26.5, 19.1

CN16 32.2, 4.3

Moi

stur

e%

Ash

%

Fusain rich

Vitrain rich

PRB Pratt and others (1999)

Depths expected for Normal hydrostatic gradient (Tissot & Welte, 1978)

1000 ft 2000 ft

Figure 25. Plot of methane adsorption potential (as-received basis) for four samples from USGS-PA-2. The difference in adsorption potential may be associated with sample organic composition. Examination of sample CN16 in hand sample indicates it is fusain rich, and sample CN6 is vitrain rich. Expected depths are plotted above the corresponding pressures as derived from a normal hydrostatic gradient (from Tissot and Welte, 1978). Published adsorption values for Powder River basin (PRB) coals are plotted for comparison (green dots, data from Pratt and others, 1999). Sample number approximately indicates the depth in feet from the top of the coal.

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USGS-PA-2 Methane Adsorption (dry, ash free)

0

20

40

60

80

100

120

140

160

0 200 400 600 800 1000 1200

Pressure (PSI)

Met

hane

Ads

orbe

d (S

CF/

Ton)

CN2

CN6

CN12

CN16

Fusain rich

Vitrain rich

Figure 26. Plot of methane adsorption potential (dry, ash free basis) for four samples from USGS-PA-2 (same samples as shown on figure 25). Note that on a dry basis CN16 (fusain rich) and CN6 (vitrain rich) still diverge. Also note the effect of removing ash and moisture on the range of gas adsorbed. The grouping of samples CN2, CN6, and CN12 probably indicates that have these samples have similar organic compositions.

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USGS-PA-2-CN2CH4 and CO2 adsorption isotherms

0

200

400

600

800

1000

1200

0 200 400 600 800 1000 1200

Pressure (PSI)

Sto

rage

Cap

acity

(SC

F/To

n)

CH4 (ar)

CO2 (ar)

CH4 (daf)

CO2 (daf)

Figure 27. Comparison of methane and CO2 adsorption isotherms on as-received (ar) and dry, ash-free (daf) basis for sample CN2. CO2adsorption characteristics are important for determining the CO2 storage capacity for the coal.

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Kac

Kac

Ksm

Kol

Kes

Kes

Tm

Tk

Twi

Tin

Tin

Tc

Tc

Tr

Tb

Tb

Tqc

Tep

Tl

Tw Ts

Tcm

Ty

Tj

Tep

Ku

Ku

Tk

Kol

MEXICO

U.S.

100101

28

27

Laredo

Ki

Ki

Ki

Ki

Balcones Igneous Province

Ki

Qb

Ti

Ti

99

29

Ksm

Kl

Kl

Kl

CFE Power Plant

MICARE Mine Blocks

DosRepublicas Permit

FARCOMINING CO.

Eagle Pass

Uvalde

Qb

Qb

0 50 km

30 mi

KuKi

INDEX MAP

TX

N

BITUM

INO

US

SUBBITU

MIN

OU

SLIG

NITE

Geology &Rank mapof South Texas

(SanFilipo, 1999)

Figure 28. Geologic map lower Tertiary and Upper Cretaceous rocks in South Texas showing generalized rank boundaries. For explanation of map units see SanFilipo (1999). This area is currently undergoing exploration for coal bed gas. Note the anomalous increase in rank toward the southwest.

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Conclusions

•USGS-PA-1 and shallow (<150 ft) Wilcox coals had only traces of gas

•USGS-PA-2 had a show of gas (about 7 (ar) or 11 (daf) scf/ton) •Isotopic signatures indicate the gas was generated in the transition zone between biogenic and thermogenic realms consistent with the approximate subbituminous rank of the coal

•Detailed coring and desorption/adsorption studies are needed to characterize the CBM production and CO2 storage potential for the Gulf Coastal Plain Province

•Our data suggest that deeper Gulf Coastal Plain Wilcox and Upper Cretaceous coal beds warrant testing for commercial CBM accumulations http://energy.er.usgs.gov

Figure 29. Conclusions.

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References

Ruppert, L.F., and Warwick, P.D., 1994, Volcanic ash fall material in the Chemard Lake lignite, Naborton Formation, Desoto and Red River Parishes, Louisiana [abs.]: The Society for Organic Petrology, Eleventh Annual Meeting Abstracts and Program, Jackson, Wyoming, v. 11, p. 90.

SanFilipo, J.R., 1999, Some speculations on coal-rank anomalies of the South Texas Gulf Province and adjacent areas of Mexico and their impact on coal-bed methane and source rock potential, in Warwick, P.D., Aubourg, C.E. and Willett, J.C., eds., Tertiary Coals in South Texas: anomalous cannel-like Coals of Webb County (Claiborne Group, Eocene) and lignites of Atascosa County (Jackson Group, Eocene) - geologic setting, character, source-rock and coal-bed methane potential: U.S. Geological Survey Open-File 99-301, p. 37-47.

Tissot, B. P., and Welte, D. H., 1978, Petroleum formation and occurrence; a new approach to oil and gas exploration: Berlin, Springer-Verlag, p. 521.

Whiticar, M.J., 1990, A geochemical perspective of natural gas and atmospheric methane, in Durand, B., and Behar, F. eds., Advances in Organic Geochemistry 1989: Oxford,Pergamon Press, p. 531-547.

Whiticar, M.J., 1994, Correlation of natural gasses with their sources, in Magoon, L.B., Dow, W.G., eds., The petroleum system - from source to trap: American Association of Petroleum Geologist Memoir 60, p. 261-283.

Williamson, D.R., 1986, Lignites of northwest Louisiana and the Dolet Hills lignite mine, in Finkelman, R.B., Casagrande, D.J. (eds.), Geology of Gulf Coast Lignites: Environmental and Coal Associates, p. 13-28.

Bernard, B.B., Brooks, J.M., and Sackett, W.M., 1978, Light hydrocarbons in recent Texas continental shelf and slope sediments: Journal of Geophysical Research, v. 83, p. 289-291.

Clayton, J.L, 1998, Geochemistry of coalbed gas - A review: International Journal of Coal Geology, v. 35, p. 159-173.

Faber, E., and Stahl, W., 1984, Geochemical surface exploration for hydrocarbons in the North Sea: American Association of Petroleum Geologists Bulletin, v. 68. P. 363-386.

Kaiser, W.R., 1990, The Wilcox Group (Paleocene-Eocene) in the Sabine Uplift area, Texas: depositional systems in deep-basin lignite: Bureau of Economic Geology, University of Texas at Austin Special Publication, 20 p.

Luppens, J.A., 1987, Distribution of lignite in the Lower Wilcox Group in the Sabine Uplift region of Texas and Louisiana, in Finkelman, R.B., Casagrande, D.J., and Benson, S.A., eds., Gulf Coast Lignite Geology: Environmental and Coal Associates, p. 262-267.

Mavor, Matt, Pratt, Tim, DeBruyn, Roland, 1999, Study quantifies Powder River coal seam properties: Oil and Gas Journal, April 26, 1999, p. 35-40.

Mukhopadhyay, P.K., 1989, Organic petrography and organic geochemistry of Texas Tertiary coals in relation to depositional environment and hydrocarbon generation: University of Texas at Austin, Bureau of Economic Geology Report of Investigations no. 188, 118 p.

Pratt, T.J., Mavor, M.J., and DeBruyn, R.P., 1999, Coal gas resource and production potential of subbituminous coal in the Powder River Basin: 1999 International Coalbed Methane Symposium Proceedings, Tuscaloosa, p. 23-34

Figure 30. References.