f c s production gas (unpublished) from (oklahom mclennan ......leavenworth county, ks (from bostic...

-38 -37 -36 -35 -34 -33 -32 -31 -30 -29 -28 -27 0 5 4 6 7 8 9 10 1 2 3 -70 -60 -50 -40 -70 -60 -50 -40 ? ? ? MICROBIAL GAS MIXED GAS ? -260 -240 -220 -200 THERMOGENIC GAS -180 -160 -140 0.01 0.1 1 10 100 mixing MICROBIAL GAS THERMOGENIC GAS 0.5 1.0 1.5 2.0 2.5 SOURCE ROCK MATURITY (Ro %) ? ? (Tebo & upper Neutral) (Croweburg ) (Mineral) (Riverton) (Riverton) (Tebo & upper Neutral) (Croweburg) (Weir-Pitt ) (Weir-Pitt ) (Mulky) (S. Mound Sh.) (Lexington) (S. Mound Sh.) (Lexington) (Hushpuckney Sh.) (Hushpuckney Sh.) (multi-zone) (multi-zone) (Weir-Pitt) (Mineral) (Rowe) (Riverton) (Lexington) (Excello Sh.) (Mulky) (Aw) (Riverton) (Mulberry) (Bevier) (Mineral) (Tebo) (Dry Wood) (Mulberry) (Tebo) (Dry Wood) (Mineral) (Bevier) (Mulky) (Mineral) (Weir-Pitt ) (Rowe) (Riverton) (Lexington) (Excello Sh.) (Mulky) (Aw) (Riverton) COAL RANK (color-coded to BTU value) Cherokee & Marmaton Gps. data from Barker and others (1992); Newell (1997) VITRINITE REFLECTANCE (color-coded to coal rank) shales in Cherokee & Marmaton Gps. A B A B A C C 1.11 0.61 0.47 0.41 0.36 0.73 0.69 0.49 8,300 9,500 10,500 11,500 13,000 14,000 14,250 15,000 high-volatile bituminous subbituminous medium-volatile bituminous lignite APPROXIMATE RANK increasing rank VITRINITE. REFLECT. (R o %) HEATING VALUE (BTU/lb) (dry, ash-free) 420 425 425 430 435 440 450 460 approximate correlation of coal Rock- Eval Tmax to vitrinite reflectance is from Bostick and Daws (1994) ROCK-EVAL Tmax (deg. C)) coal rank classification chart from McLennan and others (1995) thermogenic methane lignite sub-bitum. bituminous anthracite graphite from Boyer (1989) ethane+ hi-vol med-vol low-vol semi meta biogenic methane nitrogen carbon dioxide GAS GENERATION IN COAL 1 conventional gas (from Jenden and others, 1988) Mill Creek Schrader Silver City, Thayer Brewster, Elk City, Mapleton NE, Neosho Falls, Olathe Clinesmith, Easton, McLouth NW, Pomona, Sallyards, Welch-Mohr Kingston Brewster, Irish Valley, Neosho Falls, Paola- Rantoul, Tucker Logsden U. PENN M. PENN MSSP L. ORD field name and symbol (see map) colored coded according to origin of gas, as indicated by δ 13 C and δD isotope crossplot (see right) (green = microbial gas; blue = mixed gas; brown = thermogenic gas) Elk City FIELD AGE of PAY LOCATION MAP CONVENTIONAL GAS SAMPLES oil oil & gas gas 25 mi N Thayer Silver City Kingston Mill Creek Irish Valley N.E. Mapleton Olathe Logsdon N.W. McLouth Pomona Tucker Welch-Mohr Sallyards Brewster Clinesmith Elk City Neosho Falls Easton Schrader Paola-Rantoul coalbed gas (with coal identified) LOCATION MAP COALBED GAS SAMPLES 25 mi N Montgomery Co. samples symbol colored-coded according to location (see map) Montgomery County, KS Cass County, MO Leavenworth County, KS (from Bostic and others, 1993) "northern samples" -- Bourbon arch and eastern flank of Forest City basin (exact locations still proprietary) (Weir-Pitt) North 5S 10S 15S 20S 25S 30S 35S 0 0.5 1.0 1.5 2.0 TOWNSHIP % Helium 200 400 600 800 1000 1200 1400 Douglas, Shawnee Gps. (Virgilian) Lansing, Kansas City, Pleasanton Gps. (Missourian) Cherokee, Marmaton Gps. (Desmoinesian) Leavenworth Co. coal desorption gases (after Bostic and others, 1993) 1060 BTU/scf 2245 100% methane 950 BTU/scf 2245 90% methane BTU and He Content for Eastern KS Pennsylvanian Gases (projected onto a north-south crossplot) BTU/scf methane ethane 90.52% propane butane+ nitrogen carbon dioxide helium hydrogen 0.09% 0.01% (trace) 0.12% 0.92% 8.34% (trace) Assay of Osborn Energy coalbed production gas (unpublished) from northern Miami Co. (913 BTU) Leavenworth Co. coal desorption gases (Bostic and others, 1993) Miami Co. coalbed production gas Miami Co. coalbed production gas 25 mi. (Nebraska) (Oklahoma) Cass Co. coal desorption gas Montgomery Co. coal desorption gas Cass & Montgomery Co. coal desorption gas Cass & Montgomery Co. coal desorption gas 0 5S 10S 15S 20S 25S 30S 35S 3000 2000 1000 0 470 460 450 440 430 420 410 (oil window) North TOWNSHIP 25 mi. (Nebraska) (Oklahoma) Douglas, Shawnee Gps. (Virgilian) Lansing, Kansas City, Pleasanton Gps. (Missourian) Cherokee, Marmaton Gps. (Desmoinesian) T max maturity for eastern KS shales (projected onto a north-south crossplot) Rock-Eval T max maturation scale data from Barker and others (1992); Newell (1997) Eastern Kansas conventional gas (from Jenden and others, 1988) Coalbed gas Ethane δ 13 C vs. % Ethane in Total Hydrocarbons Eastern Kansas coalbed and conventional gases Ethane δ 13 C (PDB) Ethane % (increasing biogenesis) REGIONAL TRENDS IN THERMAL MATURATION Thermal maturation, as displayed by the vitrinite reflectance and coal rank maps above, increases southward in the Kansas part of the Western Interior Coal Basin. The most prolific gas generation in coals occurs at medium-volatile bituminous rank. Kansas coals are less thermally mature (generally high-volatile bituminous ranks) and hence contain less gas. A north-south projection of the Rock-Eval Tmax maturation parameter for shales from well cuttings and cores in the Forest City basin, Bourbon arch, and Cherokee basin (see diagram at right) also indicates a southward increase in thermal maturation. At a given depth, there is less maturation in the Forest City basin than further south in the Cherokee basin. This may be caused by higher heat flow in southeastern Kansas, or northward movement of higher-temperature waters out of the Arkoma basin onto the cratonic platform during the late Paleozoic Ouachita orogeny. These trends in maturation indicate that operators attempting to produce coalbed gas in the marginally mature strata in the Bourbon arch and Forest City basin should concentrate on the deepest coals, which should have better gas content. 100 200 300 400 500 0 1000 2000 0 3000 medium-vol bituminous high-vol Abituminous high-vol B bituminous high-vol C bituminous subbituminous C ESTIMATED MAXIMUM PRODUCIBLE METHANE CONTENT BY DEPTH AND RANK (after Saulsberry and others, 1996) gas content (scf/ton) 250 0 500 750 15 10 gas content (cc/g) 5 0 Eastern Kansas Coals anthracite low-vol bituminous subsurface depth (feet) subsurface depth (meters) volatiles driven off POSSIBLE THERMOGENIC AND BIOGENIC ORIGINS OF KANSAS COALBED GAS The desorption diagrams above are from two wells in adjacent counties in the Cherokee basin. The deepest coals in Montgomery County (to the west) register gas contents from 250 to 300 scf/ton. The same coals in Labette County (to the east) are buried less deeply, and they have gas contents considerably less than the Montgomery County coals. However, the Iron Post coal at 382 ft (116 m) depth in the Labette County well has an unexpectedly large gas content (>100 scf/ton), exceeding that of the deeper coals. A microbial or mixed thermogenic-microbial origin for this gas is suggested. Pennsylvanian coal-bearing units crop out at the surface in Cherokee County (the county immediately east of Labette County). Downdip movement of fresh water from the outcrop may augment biogenic production of coalbed gas in shallow coals along the eastern flank of the Cherokee and Forest City basins. A possible consequence to this model is that separate thermogenic and biogenic production fairways in the same coal may be present. The thermogenic fairway would be deeper in the basin where there is sufficent burial and confining pressure. The biogenic fairway would be updip and closer (and likely parallel) to the outcrop where basinal brines would be diluted by meteoric waters carried downdip from the outcrop. Montgomery County Labette County Cherokee County (from Lange and others, 2003) GAS ISOTOPIC DATA A crossplot of methane δ 13 C and the δ D can be used to infer gas origin. Thermogenic methane carbon is typically isotopically heavy (i.e., less negative) whereas microbial methane carbon typically is isotopically light (i.e., more negative). Microbially-derived gas is also dry and largely void of heavier hydrocarbons (i.e., ethane, propane, etc.). A data set on isotopes of conventional gases from eastern Kansas (from Jenden and others (1988) can be compared to coalbed gas samples. The conventional gases (squares in the above diagram) range from biogenic to thermogenic in origin. A map of the data (see above, left) shows most biogenic and mixed biogenic-thermogenic gases are on the shallow eastern flank of the Forest City and Cherokee basins, whereas thermogenic gases are farther west in the deeper portions of the basins. There is no strong stratigraphic differentiation of these gases in which younger, less thermally mature formations display a stronger biogenic signature (see key for location map for conventional samples). This suggests that some conventional and coalbed gases in eastern Kansas could be what Scott (1999) termed "secondary biogenic gases" in which methanogenic bacteria modify existing hydrocarbons. Coalbed-gas methanes (circles in the above diagram) show no strong thermogenic signature. Gases from the Bourbon arch and eastern flank of the Forest City basin tend to be isotopically lighter than Cherokee basin gases, which is consistent with lesser thermal maturation northward. Bacterial modification of eastern Kansas coalbed and conventional gases is also suggested by the crossplotting of ethane δ 13 C with % ethane. Methanogenic bacteria more easily consume isotopically lighter carbon. In such circumstances, the residual ethane will become isotopically heavier (i.e., less negative) as it is consumed. Similar effects of microbial oxidation of heavier hydrocarbons in gas have been observed with Devonian shales in the Michigan basin (Schoell and others, 2001; Walter and others, 2001; Martini and others, 2003) and with Fruitland coal in the San Juan basin (Schoell and others, 2001). (diagram after Jenden and others, 1988) (diagram after Jenden and others, 1988) increasing maturation REGIONAL TRENDS IN GAS QUALITY Conventional gases have higher BTUs in southeastern Kansas, indicating a greater proportion of heavier hydrocarbons -- a trait that is consistent with the inferred greater maturation in this region. Shallower Pennsylvanian gases from the Missourian and Virgilian part of the section have greater percentages of noncombustable gases, which significantly lowers their heating value. Heating values for coalbed gases mimics the trend established by the conventional gases. Inasmuch as helium is not easily retained by adsorption, coalbed gases generally have low helium content, but the presence of helium in some coalbed gases suggests leakage from conventional reservoirs with well completion. CONCLUSIONS 1. A marked increase in drilling for coalbed gas has occurred in southeastern Kansas in the last three years, with a commensurate increase in coalbed gas production. 2. Most of the activity for coalbed gas has been in southeastern Kansas in the Cherokee basin, but isolated projects farther north in the Bourbon arch and Forest City basin are in progress. 3. Most Kansas coals are thin (<2 ft [0.6 m] thick), but several can be encountered in a given well. Water pumped from the coals is easily disposed, usually into the Arbuckle Dolomite, which lies a few hundred feet below the deepest coals. 4. The Forest City basin has several coal seams that are likely older than the Riverton coal, which is generally the oldest coal in the Cherokee basin and Bourbon arch. 5. Thickness trends in many coals follow a NNE-SSW depositional strike. 6. Thermal maturation increases southward into the Cherokee basin. This increase in maturation is manifest in the greater heating values of conventional gas and coalbed gas in this region. 7. A mixed biogenic and thermogenic origin of the coalbed gas in eastern Kansas is indicated by gas chemistry and stable isotopes. Some of the biogenic gas may be due to biogenic oxidation of existing hydrocarbons. 8. Possible biogenic and thermogenic production fairways may be present in eastern Kansas. REFERENCES Ayres, W.B., Jr., 2002, Coalbed gas systems, resources, and production and a review of contrasting cases from the San Juan and Powder River basins: American Association of Petroleum Geologists, Bulletin, v. 86, p. 1853-1890. Bostic, J., Brady, L., Howes, M., Burchett, R., and Pierce, 1993, Investigation of the coal properties and the potential for coal-bed methane in the Forest City basin: United States Geological Survey, Open-File Report 93-576, 44 p. Bostick, N.H., and Daws, T.A., 1994, Relationships between data from Rock-Eval pyrolysis and proximate, ultimate, petrographic, and physical samples of 142 diverse U.S. coal samples: Organic Geochemistry, v. 21, p. 35-49 Barker, C.E., Goldstein, R.H., Hatch, J.R., and Walton, A.W., and Wojcik, K.M., 1992, Burial history and thermal maturation of Pennsylvanian rock, Cherokee basin, southeastern Kansas: Oklahoma Geological Survey, Circular 93, p. 299-310. Brady, L.L, 1997, Kansas coal resources and their potential for coalbed methane, in McMahan, G., ed., Transactions of the AAPG Mid-Continent Section Meeting, Sept. 14-16, 1997, Oklahoma City, p. 150-163. Boyer, C.M., II, 1989, The coalbed methane resource and the mechanisms of gas production: GRI Topical Report GRI-89- 0266, p. 46. Cardott, B.J., 2001, Coalbed methane activity in Oklahoma, 2001, Oklahoma Coalbed-Methane Workshop: Oklahoma Geological Survey, Open-File Report of 2-2001, p. 93-139. Curtis J.B., 2002, Fractured shale-gas systems: American Association of Petroleum Geologists, Bulletin, v. 86, p. 1921- 1838. EIA, 2003, U.S. crude oil, natural gas, and natural gas liquids reserves 2002 Annual Report: http://www.eia.doe.gov/oil_gas/natural_gas/data_publications/crude_oil_natural_gas_reserves/cr.html . GTI (Gas Technology Institute), 2001, North American coalbed methane resource map: Gas Technology Institute, GTI- 01/0165, 1 sheet. Leavenworth Co. (from Bostic and others, 1993) δ O O δ ) O ΣCn C1 1- * 100 ( ) conventional oil or gas field faulting on east flank of Nemaha uplift faulting on east flank of Nemaha uplift (Penn. eroded) Montgomery Co. coalbed production gas (from Hamak and Driskill, 1996) Montgomery Co. coalbed production gas (from Hamak and Driskill, 1996) Hamak, J.E., and Driskill, D.L., 1996, Analyses of natural gases, 1994-95: United States Department of Interior, Bureau of Land Management, Technical Note 399, 68 p. Jenden, P.D., Newell, K.D., Kaplan, I.R., and Watney, W.L., 1988, Composition and stable isotope geochemistry of natural gases from Kansas, Midcontinent, U.S.A.: Chemical Geology, v. 71, p. 117-147. Johnson, T.A., in progress, Stratigraphy, depositional environments, and coalbed gas potential of Middle Pennsylvanian (Desmoinesian Stage) coals Ð Bourbon arch region, eastern Kansas: M.S. Thesis, University of Kansas, Lawrence, KS. Lange, J.P., 2001, Stratigraphy, depositional environments, and coalbed gas resources of the Cherokee group (Middle Pennsylvanian) Ð southeastern Kansas: M.S. Thesis, University of Kansas, Lawrence, KS, 257 p. Lange, J.P.; Carr, T.R.; and Newell, K.D., 2003, Stratigraphy, depositional environments and coalbed methane resources of Cherokee Group coals (Middle Pennsylvanian) -- southeastern Kansas: Kansas Geological Survey, Open-file Report, no. 2003-28; http://www.kgs.ku.edu/PRS/publication/2003/ofr2003-28/index.html. Martini, A.M., Walter, L.M., Ku. T.C.W., Budai, J. M., McIntosh, J.C., and Schoell, M., 2003, Microbial production and modification of gases in sedimentary basins; a geochemical case study from a Devonian shale gas play, Michigan basin: American Association of Petroleum Geologists, Bulletin, v. 87, p. 1355-1376. Macfarlane, P.A., and Hathaway, L.R., 1987, The hydrogeology and chemical quality of ground waters from the Lower Paleozoic aquifers in the Tri-state region of Kansas, Missouri, and Oklahoma: Kansas Geological Survey, Ground- Water Series, no. 9, 37 p. McLennan, J.D., Schafer, P.S., and Pratt, T.J., 1995, A guide to determining coalbed gas content: Gas Research Institute, GRI-94/0396, p. 10.19. Merriam, D.F., 1963, The geologic history of Kansas: Kansas Geological Survey, Bulletin 162, 317 p. Nelson, C. R., 1999, Changing perceptions regarding the size and production potential of coalbed methane resources: Gas Research Institute, Gas Tips, Summer 1999, v. 5, no. 2, p. 4-11. Newell, K.D., 1997, Comparison of maturation data and fluid-inclusion homogenization temperatures to simple thermal models; implications for thermal history and fluid flow in the Mid-continent: Kansas Geological Survey Current Research in Earth Sciences, Bulletin 240, p. 13-27; online: www.kgs.ukans.edu/Current/1997/Newell/newell1.html. Newell, K.D., Brady, L.L., Lange, J.P., and Carr, T.R., 2002, Coalbed gas play emerges in eastern Kansas basins: The Oil and Gas Journal, December 23, p. 36-41. Saulsberry, J.L., Schafer, P.S., and Schraufnagel, R.A., 1996, A guide to coalbed methane reservoir engineering: Gas Research Institute, p. 2.9. Schoell, M., Muehlenbachs, K, Coleman, S., Thibodeaux, S., Walters, L., and Martini, A., 2001, Natural sites of bioconversion of CO2 and hydrocarbons in the subsurface; San Juan basin and Michigan basin (abs.): American Association of Petroleum Geologists Annual meeting Program, v. 10, p. A180. Scott, A.R., 1999, Review of key hydrologic factors affecting coalbed methane producibility and resource assessment, in Cardott, B.J., comp., Oklahoma Coalbed-Methane Workshop: Oklahoma Geological Survey, Open-File Report of 6-99, p. 12-36. Trumbull, J.V.A., 1960, Coal Map of the United States: U.S. Geological Survey, 1 sheet. Walter, L.M., McIntosh, A.M., Martini, A.M., and Budai, J.M., 2001, Hydrogeochemistry of the New Albany Shale: Gas Research Institute, GRI-00, 0158, 58 p. 25 mi 25 km 25 mi 25 km 25 mi 25 km 25 km 25 km STABLE ISOTOPE - COMPOSITIONAL CROSSPLOTS GAS CONTENT (scf/ton) (not including residual gas) TIME (square root of hours since bottom hole time of core) 0 50 100 150 200 250 0 10 20 30 50 60 70 80 90 Days 5 40 10 20 30 40 50 60 70 80 90 100 150 200 250 300 Lexington "Labette" Mulky Croweburg Fleming Mineral Scammon Weir-Pitt Weir-Pitt Rowe Riverton Lexington Mulky Mineral Fleming Scammon Rowe surface 100' 200' 300' 900' 1000' "Labette" 600' 1200' Riverton Weir-Pittsburg 400' 500' 700' TYPICAL DESORPTIONS of MONTGOMERY COUNTY COALS GAS CONTENT (scf/ton) (not including residual gas) TIME (square root of hours since bottom hole time of core) 0 50 100 150 200 250 0 10 20 30 50 60 70 80 90 Days 5 40 10 20 30 40 50 60 70 80 90 100 150 200 250 300 Fleming Rowe Riverton TYPICAL DESORPTIONS of LABETTE COUNTY COALS Iron Post Neutral Dry Wood Fleming Rowe surface 100' 200' 300' 900' 1000' 600' 1200' Riverton 500' 700' Croweburg Iron Post 800' Dry Wood Neutral LABETTE COUNTY MONTGOMERY COUNTY approx. 15 mi. (25 km) 2 3 4 7 6 5 4 3 2 1 0 GAS CONTENT (cc/gram) (not including residual gas) 7 6 5 4 3 2 1 0 GAS CONTENT (cc/gram) (not including residual gas) 50 m 300 m 150 m 250 m 200 m 100 m 350 m Depth (ft) Depth (m) 0 200 400 600 800 increasing maturation "northern samples" (exact locations proprietary) Cass Co. <<< maturation increasing

f c s production gas (unpublished) from (oklahom mclennan ......leavenworth county, ks (from bostic...

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