Document 2503508

GAS GENERATION IN COAL
C
B
A
C
B
high-volatile
bituminous
8,300
0.36
0.41
0.47
0.49
9,500
10,500
11,500
0.61
0.69
0.73
13,000
14,000
14,250
A
15,000
1.11
Easton
420
425
thermogenic
methane
biogenic methane
nitrogen
carbon dioxide
430
Sallyards
low-vol
semi
meta
bituminous
anthracite
conventional gas (from Jenden and others, 1988)
field name and symbol (see map) colored coded according to origin of
gas, as indicated by δ13C and δD isotope crossplot (see right)
(green = microbial gas; blue = mixed gas; brown = thermogenic gas)
Douglas, Shawnee Gps. (Virgilian)
200
us
diu
l
vo
m-
250
bit
b
vol A
high-
um
ino
us
n
itumi
ous
500
Eastern
Kansas
Coals
750
0
5
10
15
gas content (cc/g)
uplift
(Nebraska)
surface
3
Croweburg
Lexington
2
"Labette"
50
1
Mineral
5
10
20
30
40 50 60 70 80 90 100
150
200
250
10
20
30
40
50
60
70
80
TIME (square root of hours since bottom hole time of core)
300
0
90
200
6
5
150
Iron Post
100
Dry Wood
Rowe
Neutral
Riverton
50
4
3
2
Fleming
1
Montgomery
County
Labette
County
Cherokee
County
(Penn.
eroded)
0 Days
0
approx. 15 mi. (25 km)
200'
5
10
20
30
40 50 60 70 80 90 100
150
200
250
10
20
30
40
50
60
70
80
TIME (square root of hours since bottom hole time of core)
300
90
GAS CONTENT (cc/gram)
(not including residual gas)
Scammon
Mulky
Rowe
4
Fleming
100'
100'
7
GAS CONTENT (scf/ton)
(not including residual gas)
5
Riverton
100
6
25 km
GAS CONTENT (cc/gram)
(not including residual gas)
GAS CONTENT (scf/ton)
(not including residual gas)
Weir-Pitt
150
25 mi
7
200
0 Days
0
surface
TYPICAL DESORPTIONS of LABETTE COUNTY COALS
0
50 m
200'
300'
500'
400'
500'
600'
"Labette"
Mulky
Fleming
Scammon
Weir-Pittsburg
100 m
300'
Iron Post
Fleming
600'
Lexington
700'
700'
800'
Croweburg
Mineral
900'
900'
Dry Wood
Rowe
Neutral
Riverton
1000'
(Tebo & upper Neutral)
Cass Co.
150 m
L. ORD
FIELD
Mill Creek
Schrader
?
0.5
1.0 1.5
2.0 2.5
SOURCE ROCK MATURITY (Ro %)
-60
-50
-40
(from Hamak and Driskill, 1996)
(diagram after Jenden and others, 1988)
-140
1.5Cass & Montgomery Co.
?
-180
MICROBIAL
GAS
-200
-220
-240
-260
?
Montgomery Co.
samples
(Croweburg)
(Weir-Pitt )
(Rowe)
(Lexington)
(S. Mound Sh.) (Mulky)
(Weir-Pitt )
(Tebo)
(Mineral)
(Mulky)
(Aw)
(Lexington)
(Hushpuckney Sh.) (Riverton)
(Riverton)
(Bevier)
(Mulberry)
(multi-zone)
(Mineral)
(Tebo & upper Neutral)
?
(Dry Wood)
-60
coalbed gas (with coal identified)
symbol colored-coded according to location (see map)
Kingston
Brewster, Irish Valley, Neosho Falls, PaolaRantoul,
Tucker
Logsden
methane
ethane
propane
butane+
90.52%
0.09%
0.01%
(trace)
8.34%
0.12%
0.92%
(trace)
TOWNSHIP
25 mi.
North
faulti
ng on
A crossplot of methane δ13C and the δD 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.).
Ethane δ13C vs. % Ethane in Total Hydrocarbons
Eastern Kansas coalbed and conventional gases
Eastern Kansas conventional gas
(from Jenden and others, 1988)
Coalbed gas
250 m
300 m
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 δ13C 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).
1200'
LABETTE
COUNTY
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-890266, 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, GTI01/0165, 1 sheet.
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, GroundWater 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.
J;]NS(F)
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.
Assay of Osborn
Energy coalbed
production gas
(unpublished) from
northern Miami Co.
(913 BTU)
Cass & Montgomery Co.
coal desorption gas
-40
(from Lange and others, 2003)
POSSIBLE THERMOGENIC AND BIOGENIC ORIGINS OF KANSAS COALBED GAS
Cherokee, Marmaton Gps.
(Desmoinesian)
5S 10S 15S 20S 25S 30S 35S
"northern samples" -- Bourbon arch and eastern flank of Forest City
basin (exact locations still proprietary)
350 m
MONTGOMERY
COUNTY
0
GAS ISOTOPIC DATA
200 m
1200'
Leavenworth Co.
coal desorption
gases (Bostic and
others, 1993)
Lansing, Kansas City, Pleasanton
Gps. (Missourian)
nitrogen
carbon dioxide
helium
hydrogen
0.5
Montgomery County, KS
Cass County, MO
Leavenworth County, KS (from Bostic and others, 1993)
THERMOGENIC
GAS
-50
(Weir-Pitt)
Douglas, Shawnee Gps. (Virgilian)
δ)37 O;]H AN; ä (P:6 )
1000'
Rowe
Riverton
Miami Co. coalbed production gas
1.0
MIXED GAS
(Excello Sh.)
-70
1060 BTU/scf ≅
100% methane
Montgomery Co. coalbed production gas
(from Hamak and Driskill, 1996)
950 BTU/scf ≅
90% methane
coal desorption gas
-160
?
Silver City, Thayer
Brewster, Elk City, Mapleton NE, Neosho
Falls, Olathe
Clinesmith, Easton, McLouth NW, Pomona,
Sallyards, Welch-Mohr
10
9
8
7
6
5
4
3
2
(increasing biogenesis)
1
0
-38 -37 -36 -35 -34 -33 -32 -31 -30 -29 -28 -27
Ethane δ13C ä (PDB)
?
increasgrnk
m aha
minous
of Ne
l B bitu
flank
s
2000
high-vo
1000
bituminou
east
MSSP
0
low anthracite
-vo
l bi
tu m
ino
3000
faulti
ng on
100 200 300 400 500
high-vol C
Rock-Eval
Tmax
maturation
scale
0
0
subbituminous C
(Oklahoma)
5S 10S 15S 20S 25S 30S 35S
(oil
window)
410
420
430
440
450
460
470
gas content (scf/ton)
me
800
M. PENN
subsurface depth (meters)
600
2000
U. PENN
(after Saulsberry and others, 1996)
subsurface depth (feet)
400
Cherokee, Marmaton Gps.
(Desmoinesian)
<<< maturation increasing
1000
AGE of PAY
ESTIMATED MAXIMUM
PRODUCIBLE METHANE
CONTENT
BY DEPTH AND RANK
Lansing, Kansas City, Pleasanton
Gps. (Missourian)
Depth (m)
Depth (ft)
0
"northern samples"
(exact locations
proprietary)
1400
Cass Co. coal desorption gas
Montgomery Co. coal desorption gas
1200
1000
800
Miami Co. coalbed production gas
600
Leavenworth Co. coal desorption gases
(after Bostic and others, 1993)
400
200
0
2.0
Montgomery Co. coalbed production gas
(Oklahoma)
Elk City
data from Barker and others (1992); Newell (1997)
TOWNSHIP
Brewster
Kingston
(projected onto a north-south crossplot)
25 mi.
North
Elk City
Logsdon
0
(Riverton)
(Lexington)
-70
Irish Valley
Schrader
250
Weir-Pitt
0.01
Thayer
approximate correlation of coal RockEval Tmax to vitrinite reflectance is
from Bostick and Daws (1994)
250
MICROBIAL
GAS
Clinesmith
graphite
Tmax maturity for eastern KS shales
TYPICAL DESORPTIONS of MONTGOMERY COUNTY COALS
Neosho Falls
Tucker
sub-bitum.
(Mineral)
(Weir-Pitt)
(multi-zone)
(Riverton)
(Mulky)
N.E. Mapleton
med-vol
mixing
(Excello Sh.)
ethane+
lignite
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.
4
0.1
Welch-Mohr
hi-vol
Leavenworth Co. (from
Bostic and others, 1993)
(S. Mound Sh.)
Paola-Rantoul
435
440
450
460
(Mulberry)
(Rowe)
(Lexington)
(Dry Wood)
25 mi
(Weir-Pitt )
(Mineral)
(Mulky)
(projected onto a north-south crossplot)
(Aw)
volatiles driven off
data from Barker and others (1992); Newell (1997)
3000
(Hushpuckney Sh.)
Pomona
(Riverton)
(Tebo)
(Bevier)
(Mineral)
1
Olathe
Silver City
coal rank classification chart from
McLennan and others (1995)
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.
(Riverton)
Mill Creek
from Boyer (1989)
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.
10
BTU and He Content for Eastern KS Pennsylvanian Gases
N
LOCATION MAP
COALBED GAS
SAMPLES
THERMOGENIC
GAS
(Croweburg )
N.W. McLouth
medium-volatile
bituminous
REGIONAL TRENDS IN THERMAL
MATURATION
25 km
100
25 km
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.
east
flank
of Ne
m ah a
uplift
(Nebraska)
25 km
25 mi
conventional oil or gas field
(diagram after Jenden and others, 1988)
inc
ma reas
tur ing
a ti
on
25 km
N
LOCATION MAP
CONVENTIONAL
GAS SAMPLES
A
subbituminous
gas
Ethane %
25 mi
oil & gas
g
sin n
ea tio
cr ra
in atu
m
25 mi
oil
HEATING ROCK-EVAL
VALUE
Tmax
(BTU/lb)
(deg. C))
(dry, ash-free)
δ: O;]H AN; ä (SOOJ )
lignite
VITRINITE.
REFLECT.
(Ro%)
ΣCn
APPROXIMATE RANK
1
COAL RANK
(color-coded to BTU value)
Cherokee & Marmaton Gps.
(1- C ) * 100
VITRINITE REFLECTANCE
(color-coded to coal rank)
shales in
Cherokee & Marmaton Gps.
3
STABLE ISOTOPE - COMPOSITIONAL CROSSPLOTS
%Helium
2
BTU/scf
1
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.