Maria MastalerzMaria MastalerzIndiana Geological SurveyIndiana Geological Survey , IU, IUDariusz StrapocDariusz StrapocArndt SchimmelmannArndt SchimmelmannDepartment of Geological Department of Geological Sciences,Sciences,IU, Bloomington IU, Bloomington

Origin of Coalbed Gas in Indiana: Origin of Coalbed Gas in Indiana: Insights from Isotopic RatiosInsights from Isotopic Ratios

INTRODUCTIONINTRODUCTIONWhat is coalbed gas?What is coalbed gas?

Natural gas formed and stored in coalsNatural gas formed and stored in coals (mainly adsorbed on micropores <2nm)(mainly adsorbed on micropores <2nm) Consists mainly of Consists mainly of CHCH44 + some C + some C22, C, C33, C, C44, CO, CO22, N, N22 Generated by:Generated by:

1) thermal cracking of OM1) thermal cracking of OM from coal, if Ro > 55% - from coal, if Ro > 55% - the treshold value the treshold value (thermogenic gases – C(thermogenic gases – C11-C-C4 4 hydrocarbons)hydrocarbons)

2)2) microbial activity (biogenic methane)microbial activity (biogenic methane)

INTRODUCTIONINTRODUCTIONMicrobially generated methaneMicrobially generated methane

Microbial consortiaMicrobial consortia (consuming the organic (consuming the organic matter from coal, mainly long chain aliphatics): matter from coal, mainly long chain aliphatics): acetogens, acetotrophs, with acetogens, acetotrophs, with COCO22 reducing reducing methanogensmethanogens as a terminal step as a terminal step CO2 + 4H2 = CH4 + 2H2O

Content ofContent of biogenic CH biogenic CH44 can be up to 100% can be up to 100% in shallow coals’ gas and with Ro<55% in shallow coals’ gas and with Ro<55% (<200m)(<200m)

In deeper and/or In deeper and/or more mature coalsmore mature coals it is it is mixed with thermogenic gasmixed with thermogenic gas and their ratio and their ratio can be assessed using can be assessed using molecular and molecular and isotopic analysesisotopic analyses of the gases of the gases

OBJECTIVES OF THIS OBJECTIVES OF THIS STUDYSTUDY

CBM OriginCBM Origin Establish method of Establish method of representative representative

coalbed gas samplingcoalbed gas sampling from desorption from desorption canisterscanisters

Generate Generate compositional and isotopiccompositional and isotopic

data of coalbed gases (data of coalbed gases (C1-C4C1-C4 hydrocarbons, hydrocarbons, COCO22) in Indiana) in Indiana

Evaluate Evaluate thermogenicthermogenic and and biogenicbiogenic contribution to the total gascontribution to the total gas

Determine controls on gas distributionDetermine controls on gas distribution

>2.8m3/t

>3.4m3/t

Gas content of Indiana coals

Recently desorbed

Gas content(raw basis)

Variations in measured gas content

Degree of saturationDegree of saturation

Spr 373 Seel 448.7 Seel 897 Seel 452 Seel 5560

20

40

60

80

100

120

%

Modified from Meissner, 1984

Coal maturity (Ro) and maximum

thermogenic gas potential of coal

vscoalbed gas content in Illinois Basin coals

IllinoisBasin

Indianacoals

KY

In addition to thermogenic gas, Indiana coals have another source of gas

(biogenic methane ??) 3 9 15

[m3/t]

RESULTSRESULTS

1.0

0.8

0.6

0.4

Maximum Thermogenic gas potential

Coal Rank

subbituminous

high volatilebituminous C

high volatilebituminous B

high volatilebituminous A

medium volatile bituminous

Study Study areaarea

SE Illinois BasinSE Illinois Basin Core samples of Core samples of

Pennsylvanian coals: Pennsylvanian coals:

Herrin Herrin

Springfield (V)Springfield (V)

Houchin Creek (IVa)Houchin Creek (IVa)

Survant (IV)Survant (IV)

Seelyville (III)Seelyville (III) Range of vitrinite Range of vitrinite

reflectance 0.55-0.62% reflectance 0.55-0.62% (high volatile bituminous C (high volatile bituminous C coals)coals)

ILIN

KY

fault zone

100km

SamplingSampling

N2DI w ater w /BenzalkoniumChloride

Vo

lum

e m

easu

ring

dev

ice

Sam pling bottle (rubberseptum , crim ped)

- valves

coalbed gascoalbed gas sampling from sampling from desorption canisters with Ndesorption canisters with N22

purging of tubingpurging of tubing

Off-line H,C-isotopic Off-line H,C-isotopic analyses ofanalyses of CHCH44

(oxidation of CH(oxidation of CH44 in quartz in quartz tube with CuO at 800C; tube with CuO at 800C; cryogenic separation of COcryogenic separation of CO22 and Hand H220; reduction of H0; reduction of H22O to HO to H22 in Uranium oven at 850C; dual in Uranium oven at 850C; dual inlet on Finnigan MAT 252 or inlet on Finnigan MAT 252 or Delta Plus)Delta Plus)

Continuous flow molecular Continuous flow molecular and C-isotopic analyses of C1-and C-isotopic analyses of C1-C4, COC4, CO22 using on-line GCC/MS using on-line GCC/MS (syringe injection module with variable (syringe injection module with variable sample size 0.05ul to 50ul; GC; oxidative sample size 0.05ul to 50ul; GC; oxidative reactor Cu, Ni, Pl at 850C; MS Finnigan reactor Cu, Ni, Pl at 850C; MS Finnigan MAT 252 or Delta Plus)MAT 252 or Delta Plus)

Analytical proceduresAnalytical procedures

75%

80%

85%

90%

95%

100%

Herrin,IL Springfld,IN Springfld,IL Springfld,KY Houchin Cr. Survant Seelyville

CO2

Butane

Propane

Ethane

Methane

RESULTS:RESULTS: Molecular composition of Molecular composition of coalbed gases from the coalbed gases from the Illinois BasinIllinois Basin

* N2 not included

150m

300m

Depth

Ro [%] 0.57 0.56 0.55 0.75 0.54 0.54 0.62Coal maturity (vitrinite reflectance)

after Whiticar 1999

-80

-70

-60

-50

-40

-300 -250 -200 -150 -100dD Methane [o/oo]

d13 C

Meth

ane [

o /o

o ]

.

Springfield, IN

Houchin CreekSurvant

Seelyville

Springfield, ILSpringfield, KY

Herrin, IL

Thermogenic field

Biogenic field -CO2 ReductionBiogenic

field – acetatefermentation

Mixing zone

CBM origin – genetic classifications:C vs H isotopes in CH4

CO2 reduction reaction used by methanogenic bacteria: CO2 + 4H2 = CH4 + 2H2O

after Martini et al. 2003

1

10

100

1000

10000

-70 -60 -50 -40 -30d13C (CH4) [o/oo]

C1/[C

2+C

3]

.Springfield, IN

Houchin Creek

Survant

SeelyvilleSpringfield, IL

Springfield, KY

Herrin, IL

Thermogenic field

Microbial field

CBM origin: C1/[C2+C3] gas wetnessindicator vs C-isotopes in CH4

Transition zone

Mixed

after Smith & Pallasser, 1996

-50

-30

-10

10

30

-120 -100 -80 -60 -40 -20 0d13C CH4 [

o/oo]

d13

C (C

O 2 )

[ o /o

o ]

.

Springfield

Houchin Creek

Survant

Seelyville

Springfield, KY

Springfield, IL

Herrin, IL

Therm

ogen

ic ga

ses

Micr

obial

CO 2

-redu

ction

Laboratorypyrolysisgases

CBM origin: C-isotopes in CH4 and CO2

-70

-60

-50

-40

-30

-20

0 0.2 0.4 0.6 0.8 1

Reciprocal Carbon Number

d13 C

[ o/ oo

] .

Pr

Et

Bu

Me

0.25 0.33 0.5

Estimation of biogenic CH4 content: Compound-specific C-isotopic data

method developed by Chung et al. 1987

Extrapolatedpure T-genic

methane

Assumedpure biogenic

CH4 -70 ‰

57% biogenic CH4

R2 = 0.983

-70

-60

-50

-40

-30

-20

0 0.2 0.4 0.6 0.8 1Reciprocal Carbon Number

d13 C

[ o / o

o ]

.

R2 = 0.331

-70

-60

-50

-40

-30

-20

0 0.2 0.4 0.6 0.8 1Reciprocal Carbon Number

d13 C

[ o /oo

]

.

R2 = 1

-70

-60

-50

-40

-30

-20

0 0.2 0.4 0.6 0.8 1Reciprocal Carbon Number

d13 C

[ o / o

o ]

.

Estimation of biogenic CH4 content: Compound-specific C-isotopic data

Danville 96%

Seelyville 59%

Springfield, IN 57%

Springfield, KY -12% (~0)

Extrapolatedpure T-genic

methane

Assumedpure biogenic

-70 ‰

R2 = 0.997

-70

-60

-50

-40

-30

-20

0 0.2 0.4 0.6 0.8 1Reciprocal Carbon Number

d13C

[ o / o

o ]

.

Herrin, IL 89%

PrEt

Bu

Me

Examples of gas variations Sullivan County, IndianaExamples of gas variations Sullivan County, Indiana

R2 = 0.93

0

1

2

3

0 1 2 3 4

Total coalbed gas content [m3/t]

Bio

gen

ic o

r th

erm

ogen

ic C

H4

[m

3/t]

.

Biogenic CH4

Thermogenic CH4

Total CH4

Biogenic vs thermogenic CHBiogenic vs thermogenic CH44 contentcontent

Biogenic gas content – varies within coalbed (controls unknown, pore size distribution ~permability?, nutrients availability?), important contribution to total CBM (62% on average)

~constant

SeelyvillecoalSullivanCounty

0 1 2 3 4

159.2

159.5

159.8

160.1

160.4

Dep

th [m

]

.

Coalbed gas content [m3/t]

Thermogenic CH4

Biogenic CH4

Thermogenic gas content - almost constant, low and corresponding to Ro

Gas play concepts in Indiana Gas play concepts in Indiana

Indiana – biogenic methane Indiana – biogenic methane prevailingprevailing

RRoo at tresholdat treshold of thermogenic gas of thermogenic gas generation (generation (0.55-0.620.55-0.62%) %)

<50% thermogenic<50% thermogenic gasgas content content coal coal rarely rarely reached reached T>80CT>80C (upper (upper

limit of bacterial activity), limit of bacterial activity), therefore…therefore…

bacteriabacteria can be can be synsedimantarysynsedimantary oror

……transported with transported with fresh waterfresh water afterafter erosional uplifterosional uplift and/or and/or

……transported with water from transported with water from melting ice sheetsmelting ice sheets after last after last ice ice ageage into the coal after relaxation into the coal after relaxation of the cleats and fractures, orof the cleats and fractures, or

……transported with modern transported with modern meteoric watersmeteoric waters

Illinois

Indiana

Kentucky

Max rangeof ice

Gas play concepts in Indiana Gas play concepts in Indiana

Indiana – thermogenic Indiana – thermogenic gas present in low gas present in low

quantitiesquantities

tectonic and volcanic activitytectonic and volcanic activity (higher geothermal gradient) in (higher geothermal gradient) in the Western Kentucky fault zone the Western Kentucky fault zone

Ro Ro up to up to 0.8%0.8% corresponding to corresponding to ~140C (thermogenic gas ~140C (thermogenic gas generation treshold ~0.55%) generation treshold ~0.55%)

no secondary biogenic no secondary biogenic methanemethane generation generation

thus after erosional uplift ice thus after erosional uplift ice melt or meteoritic water melt or meteoritic water hadn’t hadn’t transported methanogenstransported methanogens to to the coalbedthe coalbed environment (ice environment (ice didn’t cover this area – higher didn’t cover this area – higher elevation)elevation)

fault zone

Illinois

Indiana

Kentucky

Max rangeof ice

CONCLUSIONSCONCLUSIONS

C isotopic data of COC isotopic data of CO22 and C and C11-C-C44 hydrocarbons plus H isotopic hydrocarbons plus H isotopic data of Cdata of C11 provide powerful tools provide powerful tools for assessing the coalbed gas for assessing the coalbed gas origin, evolution and alteration;origin, evolution and alteration;

Biogenic gas is the dominant Biogenic gas is the dominant component in CBM in Indiana component in CBM in Indiana (62% on average), whereas (62% on average), whereas thermogenic gas occurs in lower thermogenic gas occurs in lower but variable quantities;but variable quantities;

The highest volumes of gas are The highest volumes of gas are expected in areas where there is a expected in areas where there is a substantial amount of substantial amount of thermogenic gas and also there thermogenic gas and also there were (were (are?)are?) favorable conditions favorable conditions for biogenic gas generationfor biogenic gas generation

-150

-130

-110

-90

-70

-50

-30

-10

10

30

-20 -15 -10 -5 0 5

d18O (o/oo)

dD

(o

/oo

)

.

GMWL (Craig, 1961b)GMWL (Rozanski, et al., 1992)CBM Dugger, SpringfieldCBM Dugger, Seelyville (T)CBM Dugger, Seelyville (Jer)Pleistocene meltw aterNew Albany ShalePresent day meteoricSilurian-Devonian, Illinois B.Iron creek source w ater

CBM in Indiana – renewable resource??

meteoric

prod water

Gas is beautiful!