The Barnett Shale as a Model for Unconventional Shale Gas ...docshare01.docshare.tips/files/23135/231357125.pdf · Generation Migration Accumulation Preservation Processes For high
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• Microfractures present, but limited visible fractures evident at surface
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Has expulsion of Barnett generated hydrocarbons into younger or older
formations occurred?
• Low maturity oils in the western basin are all Barnett (8 horizons fingerprinted including the deeper Ellenburger) and are very high quality for low maturity (ca. 40oAPI).
• Higher maturity oils in Wise County are also Barnett sourced oils with similar properties although color is slightly different.
Thus, expulsion is episodic (different times and maturities)
n.b. This also explains natural ground water contamination in the basin.
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In the Western Ft. WorthBasin, oils from the:•Barnett•Caddo•Canyon•Chester•Chappel•Conglomerate•Ellenburger•Flippen•Gardner•Harry Key Ls•Hodge Eagle•Hope•MoranAre all Barnett-sourcedoils (43) based on oilfingerprinting results(Ref: Jarvie et al, 2001)Stratigraphic Column: Courtesy of Rich Pollastro, USGS
Stratigraphic Column
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Barnett Shale:Petroleum Potential and Maturity Trend
0200400600800
100012001400
380 430 480 530 580
THERMAL MATURITY (Tmax in oC)
BO
/ A
F (b
ased
on
S2)
Kerogen transformationtrend line
Lampasasoutcrops !
Gas Window
If high TOCthese are also gas windowdespite low (unreliable)
Tmax values
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General Observations
• High TOC marine shales are more efficient expellers of hydrocarbons– 1% poor 3% fair 10% excellent
• High TOC and clay content aid retention of hydrocarbons by adsorption
• Episodic expellers, a.k.a. pressure cookers: Generate HCs, form vapor lock – critical pressure exceeded, vent, and reseal; repeated depending on burial history
Shale Gas Evaluation Criteria:Geochemical Risk Factors
TOC [10]
Ro [2.2]
GAS [1000000]Tmax [600]
TR [1]
TOC < 1.00%
%Ro < 1.1
< 100,000 ppmheadspace gas
Tmax < 450
TR < 0.70
Minimum valuesfor gas prospects
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Shale Gas Evaluation Criteria:Wise County Example
TOC [10]
Ro [2.2]
GAS [1000000]Tmax [600]
TR [1]
High maturity shale:All risk factors favorablefor high BTU gas
Min. valuesfor gas prospects
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Shale Gas Evaluation Criteria:Barnett Analog – Gas but Oil Window Maturity
TOC [10]
Ro [2.2]
GAS [1000000]Tmax [600]
TR [1]
Min. valuesfor gas prospects
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Antrim Shale:Biogenic Petroleum System
TOC [10]
Ro [2.2]
GAS [1000000]Tmax [600]
TR [1]
Measured Antrim data
Min. valuesfor gas prospects
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Know Petroleum System Character
1. Biogenic gas shale petroleum systems2. Mixed biogenic/thermogenic gas shale systems3. Thermogenic gas shale petroleum systems
A. source and reservoir not the samei. timing of expulsion, migration, trap, and seal formationii. dependent upon source rock OM type, maturityiii. could be primary or secondary gas expelled from source
B. source and reservoir the same i. secondary gas generation (maturity/temperature)ii. timing of oil decomposition, episode of expulsion
4. Tight gas sands5. Coal bed methane (primary gas generation)
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What does it take for a commercial gas discovery in the Barnett Shale?
• Thermal maturity at some point in the past to reach 150oC+ for conversion of kerogen to oil/gas and oil to gas
– %Ro > 1.1% but less than 2.1% to avoid reservoir destruction and high CO2 yields
– TR > 0.80– Tmax > 450oC– TOC values > 4%
• Uplift prior to expulsion / venting
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Evaluation of Gas Potentialwhile drilling – sweet spot identification
• Gas samples from gas flow line – new technique –an indication of “lost” gas (gas desorbed from the reservoir into the mud)
• Canned cuttings samples (desorbed gas) – the amount of gas (SCF/ton) that will be liberated from cuttings
• Cuttings gas analysis (gas liberated upon crushing cuttings – an indication of “frac” yields)
• TOC, Rock-Eval, TEGC, and vitrinite reflectance analyses (is it rich enough, converted enough (TR and Ro) to have generated commercial amounts of hydrocarbons)
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Using Gas Composition and Isotopesfor sweet spot and maturity assessments
-70.00
-65.00
-60.00
-55.00
-50.00
-45.00
-40.00
-35.00
-30.00
-25.00
-20.00-45.00 -40.00 -35.00 -30.00 -25.00 -20.00
δ 13C Ethane (ppt)
δ13C
Met
hane
, Pro
pane
(ppt
)
Methane vs. EthanePropane vs. Ethane
70%
50%
30%
20%
60%
40%
10%
Bact
eria
l Met
hane
3.00%
Ro=0.50%
1.20%
1.00%
0.70%
1.50%
2.00%
700
750
800
850
900
950
1000
1050
1100020406080100
GWR and LHR OVERLAY
GWRLHR
WellSweetSpots
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CONCLUSIONS
• Barnett Shale has world-class petroleum potential; limiting factors are – thermal maturity– episodic expulsion– seals (leaky through time due to venting)
• Other unconventional resources have similar characteristics, but also some unique twists
• Risks can be reduced by careful evaluation of thermal maturity (kerogen conversion) and timing of events (generation, expulsion)
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ReferencesArmentrout, John The Quest for Energy: Rewarding Careers in Petroleum Exploration, AAPG website slide set, February 2000 (http://www.aapg.org/slide_bank/armentrout_john/index.shtml).
Bowker, K.A., 2002, Recent development of the Barnett Shale play, Fort Worth Basin, RMAG Innovative Gas Exploration Concepts, Denver, CO October 1, 2002.
Burnham, A. K. and Robert L. Braun, 1990, Development of a detailed model of petroleum formation, destruction, and expulsion from lacustrine and marine source rocks, Advances in Organic Geochemistry 1989, Org. Geochem., Vol. 16, Nos. 1-3, pp. 27-39.
Claypool, G. E., and E. A. Mancini, 1989, Geochemical Relationships of Petroleum in Mesozoic Reservoirs to Carbonate Source Rocks of Jurassic Smackover Formation, Southwestern Alabama : AAPG Bulletin, v. 73, p. 904-924.
Demaison, G. and B. J. Huizina, 1994, Genetic Classification of Petroleum Systems Using Three Factors: Charge, Migration, and Entrapment, in: The Petroleum System – From Source to Trap, AAPG Memoir 60, L.B. Magoon and W.G. Dow, eds., AAPG, Tulsa, OK, 655 p.
Dembicki, Harry, 1986, Oil Show Detection by C5+ Hydrocarbon Mud Logging, SPE Formation Evaluation, pp. 331-334. Jarvie, Daniel M.,
Jarvie, Daniel M., Jack D. Burgess, Alex Morelos, Robert K. Olson, Phil A. Mariotti, and Robert Lindsey, 2001, Permian Basin Petroleum Systems Investigations: Inferences from Oil Geochemistry and Source Rocks, AAPG Mid-Continent Section Meeting, Amarillo, Texas, September 30-October 2, 2001, AAPG Bull. Vol. 85, No.9, pp. 1693-1694, oral presentation.
Jarvie, Daniel M., Brenda L. Claxton, Floyd "Bo" Henk,and John T. Breyer, 2001, Oil and Shale Gas from the Barnett Shale, Ft. Worth Basin, Texas, AAPG National Convention, June 3-6, 2001, Denver, CO, poster presentation.
Jarvie, Daniel M., 2001, Williston Basin Petroleum Systems: Inferences from Oil Geochemistry and Geology, The Mountain Geologist, Vol. 38, No. 1, pp. 19-41
Jarvie, Daniel M., Ron Hill, and Frank Mango, 2001, Effect of inorganic constituents on light hydrocarbon composition and compound distributions of crude oils, 20th International Meeting on Organic Geochemistry, Nancy, France, Sept. 10-14, 2001, abstract.
Jarvie, D.M., 1991, Total Organic Carbon (TOC) Analysis, in Treatise of Petroleum Geology, Handbook of Petroleum Geology, Source and Migration Processes and Evaluation Techniques, Ed. R.K. Merrill, AAPG Press, Tulsa, Ok.
Okui, A. and D. Waples, 1993, Relative permeabilities and hydrocarbon expulsion from source rocks, in: Basin Modelling: Advances and Applications, A.G. Dore et al, eds., NPF Special Publication No. 3, Elsevier, London, 675 p.
Schmoker, James., W., 1994, Volumetric Calculation of Hydrocarbons Generated, AAPG Memoir 60 The Petroleum System –From Source to Trap, L.B. Magoon and W.G. Dow, eds., pp. 323-326.
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Appendix
• Terms• Other graphics and maturity/TR/temp correlation
table• Barnett Shale: TOC and Rock-Eval values• Solution to Schmoker’s oil and gas volume
calculation• SPI calculations• Identifying sweet spots• Oil and water saturation curves for SS and Sh• Using geochemistry in unconventional gas plays
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Terms• TOC = total organic carbon (organic richness)• %Ro = vitrinite reflectance (thermal maturity indicator)• TR = transformation ratio (extent of conversion of kerogen where e.g.,
(HIo-Hip) / HIo• Rock-Eval S1 = free oil content in rock• Rock-Eval S2 = remaining kerogen content in rock• Rock-Eval Tmax = temperature at maximum S2 yield; an indication of
thermal maturity• Primary cracking kinetics = rate at which kerogen decomposes into
hydrocarbons (oil and gas)• Secondary cracking kinetics = rate at which oil decomposes into gas
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Back-calculations of TOC
• At high maturity (85%+ Transformation Ratio (TR))
• A measure of the potential of a source rock to generate hydrocarbons over a given areal extent
• SPI = h (S1+S2) p / 1000– where h = thickness of source rock– S1+S2 data from Rock-Eval (mg HC/g rock)– p = density, assume 2.5 t/m3
• Must also account for migration and entrapment styles
Ref: Demaison and Huizinga, 1994
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SPI – Barnett Shale, Wise County• Assumptions:
– h = 250 ft. or 76.2 m– S1+S2 = 20.00 t/kg rock– p = 2.50 t/m3
• SPI = 76.2 x 20 x 2.5 / 1000= 3.81 t / m2
• Add U. Barnett (150 ft.)= 6.10 t / m2
• Increase S1+S2 (27.79 ave. per unit TOC) based on Lampasas outcrop yields
= 8.34 t / m2
• Maximum S1+S2 at Lampasas = 47.75= 14.38 t / m2
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EXAMPLES OF AVERAGE SOURCE POTENTIAL INDICES
(tons HC/m2)
1. Junggar (China): 652. L. Congo (Cabinda): 463. Santa Barbara Channel (U.S.A.): 394. San Joaquin (U.S.A.): 385. Central Sumatra (Indonesia): 346. E. Venezuela fold and thrust belt: 277. Offshore Santa Maria (U.S.A): 21
Ref: Demaison and Huizinga, 1994
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EXAMPLES OF SPI (cont.)(tons HC/m2)
8. Middle Magdalena (Colombia): 169. North Sea (U.K.): 1510. Central Arabia (S. Arabia): 1411. Niger Delta (Nigeria): 1412. Gulf of Suez (Egypt): 1413. San Joaquin - Eoc./Oligo. (U.S.A.): 1414. Ft. Worth - Barnett (U.S.A.): 13
Reserves estimated at 10 TCF or ~ 1.67B BOE
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Finding High BTU Gas
0%
20%
40%
60%
80%
100%
0 500 1000 1500 2000 2500 3000
GAS CALORIFIC VALUE (BTU)
DR
Y-t
o-W
ET
GA
S R
AT
IO
V. HighMaturity
HighMaturity Mod.
Maturity
BTU contentis controlled bywet gas content
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Identification of oil, wet or
dry gasby
fingerprinting directly from
cuttings or core chips:
TEGCAlso useful
for GORprediction
Oil Prone
Gas Prone
min0 2 4 6 8 10 12 14 16
pA
0
100
200
300
400
500
FID1 A, (C:\PROJECTS\MEC\H00-11~1\TEGC\31220000.D)
C9
C10 C
11
C12
C13
C14
C15
C16
C17
C18
C19
C20
C21
C22
C23
C24
C25
C30
C35
min2 4 6 8 10 12 14 16 18
pA
0
50
100
150
200
250
300
350
400
450
FID1 A, (C:\PROJECTS\MEC\H00-11~2\H00-11~1\31560000.D)
C9
C10
C11
C12
C13 C
14
C15
C16
C17
C18
C19
C20
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C7-determined Generation Temperatures for Barnett Oils
1.00
1.20
1.40
1.60
1.80
2.00
2.20
80 90 100 110 120 130 140 150
A V ER A GE GEN ER A T ION TEM PER A T U R E ( o C )
SPEARFISH
TYLER
CHARLES - M. CANYON
LODGEPOLE
BAKKEN
NISKU
DUPEROW
DAWSON BAY
WINNIPEGOSIS
INTERLAKE
RED RIVER
WINNIPEG
DEADWOOD
Barnett Oilson trend linewith Bakken oils
IncreasingGOR
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GORs can be predicted with some degree of accuracy from both vitrinite reflectance and
oil/condensate light hydrocarbons
Oil
Wet Gas
DryGasR2 = 0.9233
010002000300040005000600070008000
0 0.5 1 1.5 2CAL. VITRINITE REFLECTANCE (%Ro)
CA
L. G
OR
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TYPICAL SANDSTONE RESERVOIR ROCK
WATER SATURATION (%)
REL
ATI
VE
PER
MEA
BIL
ITY
Kro
Krw
Kromax
Krwmax
Krx
Swirr Swx Swc
1.0
0.90.80.70.6
0.5
0.4
0.30.20.1
0.00 10 20 30 40 50 60 70 80 90 100
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TYPICAL SHALE RESERVOIR ROCKis quite different from a conventional reservoir