brian e. lock university of louisiana, lafayette prepared for lgs meeting, september 21, 2011
DESCRIPTION
The Eagle Ford Shale Outcrop Studies Related to the Oil and Gas Potential of a Major Unconventional Reservoir. Brian E. Lock University of Louisiana, Lafayette Prepared for LGS meeting, September 21, 2011 Lauren Peschier and Nick Whitcomb (UL graduate students) contributed to the study. - PowerPoint PPT PresentationTRANSCRIPT
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The Eagle Ford Shale Outcrop Studies Related to the Oil and
Gas Potential of a Major Unconventional Reservoir.
Brian E. LockUniversity of Louisiana, LafayettePrepared for LGS meeting, September 21, 2011
Lauren Peschier and Nick Whitcomb (UL graduate students) contributed to the study
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Outline
• Resource Plays and the Eagle Ford
• Stratigraphy and Sedimentology of the Outcrops
• Application of the Outcrops to Understanding the Eagle Ford Resource Play
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Keys to a Successful Resource Play
• Original organic richness and generation potential– Kerogen type (from Rock-Eval analysis)– TOC values (determine TOCo?)
• Maturation (includes primary and secondary cracking)– Ro
– Tmax (from Rock-Eval analysis)– TTI
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S1: existing hydrocarbons
S2: kerogen
S3: CO2 from spent kerogen
S3
Tmax
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S1: existing hydrocarbons
S2: kerogen
S3: CO2 from spent kerogen
S3Values as mg/gm of sample: if S1 >1 mg/g = oil show if S2 > 5 mg/g = good source rock
HI (Hydrogen Index) = (S2/TOC).100OI (Oxygen Index) = (S3/TOC).100PI (Production Index = S1/(S1+S2)
Tmax: 400-430o immature435-450o oil zone>450o overmature
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Keys to a Successful Resource Play(continued)
• Retention of oil/gas in the resource reservoir– Gas adsorption and free oil and gas, vs. primary migration
• Porosity– Increases with maturation and hydrocarbon generation
• Brittleness – Mineral composition (from X-Ray Diffraction analysis)
• Quartz• Carbonates• Clays
– Open natural fractures (not cemented) or hydraulically fractured during stimulation
• (note – reservoir quality lower in areas of greater open fractures)
Jarvie et al., AAPG Bulletin, 2007
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resource shales
REGIONALSTRATIGRAPHYEagle Ford and Austin considered
a single reservoir unit
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MaverickBasinDelaware/Rio Grande
Aulacogen
Lower Cretaceous reef tr
end
Edwards reef
Sligo reef
Delaware Basin
Notes:Maverick Basin Eagle Ford has different tectonic, thermal and diagenetic history from the Reef Trend Eagle Ford, and is thick and over-pressured. Thermally mature rocks have been uplifted.
Maverick BasinEagle Ford
Lower CretaceousReef Trend Eagle Ford
Delaware Basin
Delaware/Rio GrandeAulacogen
Rio Grande Embayment
field areaEF outcrops
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Lozier Canyon
The field study area – Eagle Ford outcrops
Outcrop Q
Outcrop G
Outcrop D
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Not present in the subsurface
Lower member(“facies A” of BP workers).
unstable slope deposits;slump foldsdebris flows
turbiditetraction deposits - ? contourites
Lowstand Systems Tract
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debris flow
debris flow
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Ash/turbidite marker bed extends from Comstock to Lozier Canyon (about 40 miles)
Buda Formation
ash/turbidite
debris flowclast
New LGSVice-President
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Sources of authigenic kaolinite (and silica)?
• numerous ash beds throughout the Eagle Ford are composed almost entirely of kaolinite (possible source of diagenetic silica)
ash bed inlower member
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Authigenic dolomite and kaolinite filling vug in lower member. Note: dolomite (and de-dolomite) rhombs are almost universally present in Cretaceous carbonates in southwest Texas.
kaolinite
dolomite
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The productive interval (lower Eagle Fordin the subsurface)
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limestone“shale” (marlstone)
limestone
upper beds of middle member (more calcareous)
Road cut G-1
Middle member (productive interval) in outcrop
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upper membermiddle member
lowest chalky limestone
Road cut G-2
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Lozier Canyon – bluffs expose full Eagle Ford section
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Lozier Canyon section
Austin Chalk
middle member
upper member
Lower member (obscured)
Buda Limestone
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Lozier Canyon middle member:rock is fresh because of stream undercutting the bluff.
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lower beds,middle member
upper beds, middle member
2,000 ft long outcrop in same stratigraphic interval shows lateral consistency.
Note: most of the outcrop is weathered (oxidized iron).
Road cut Q
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grey patina (result of last 30 yearssince road-cut was made)
black colorof fresh
rock
Note laminae that pinch out – evidence for bottom currents (hyperpycnal flow)
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Parasequences in highway outcrop, middle member
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Parasequences in a core gamma raylog, from a Petrohawk well.
10 ft
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carbonate factoryhyperpycnal flow
marine snow
flocculation, pelletizationsea level fluctuation
hundredsof feet
few feet
clayCaCO3
depth
terrigenous clay and silt, suspended carbonate mud
shoaling
parasequence 1 parasequence 1
parasequence 2 parasequence 2
mfsmfs
Is the limestone the base or the top of the parasequence?
water
Deep water sedimentation and parasequencesWhat controls limestone/shale alternations? Eustasy? Climate? Tectonics?
or periodic gravity flows from unstable platform margin?
deep water traction currents(meteorological? geostrophic?)
limestone – brittlemarl (“shale”) - ductile
Includes possible hypopycnal flow
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Smaller scale cycles – result of climate/sea level variations or individual hyperpycnal flows?
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Core photos from Petrohawk core with permission
Graded bed – white dots are planktic forams
Inoceramid fragments
Note evidence of current action
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copepod
fecal pellet
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Evaluating the Eagle Ford outcrops• Original organic richness and generation
potential– Kerogen type
• Rock-Eval analyses Oil prone
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Evaluating the Eagle Ford outcrops• Original organic richness and generation
potential– TOC values (determine TOCo?)
Blue: data from BP study (Donovan et al., 2011). Red: from UL study
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Maturity
• TTI – estimate of time/temperature burial history. Not currently available
• Ro – vitrinite reflectance - microscopy
• Evolution on Van Krevelen plot (Kerogen Transformation Ratio – KTR) – from Rock Eval
• Tmax – from Rock Eval
• Production Index – from Rock Eval
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Van Krevelen Diagram
modifiedVan Krevelen Diagram
Kerogen Transformation
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Evaluating the Eagle Ford Outcrops• Maturation Close to, but not yet in oil window
Tmax fromLozier Canyonsamples (UL).
No Ro or TTIdata
available
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Vitrinite Reflectance (Ro) data
• Performed by USGS (Mark Pawlewicz) via Russ Dubiel, on US Hwy 90 samples.
• Essentially no vitrinite, only solid bitumen (two generations? – Ro values around 0.6 and a second bitumen from external source with higher Ro)
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Evaluating the Eagle Ford outcrops
• Retention of oil/gas in the resource reservoir– Gas adsorption and free oil and gas
• Oil types in the First Shot Field (Austin Chalk)(Corbet 2010) and general sourcing of other Cretaceous reservoirs from Eagle Ford demonstrates migration from the Eagle Ford
–
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Natural fractures
• Indicate brittleness (good!)• May have already permitted hydrocarbon
primary migration out of the reservoir (not so good!). – Experience in the Barnett Shale indicates that
areas that are most highly fractured are less productive
• Distinguish open fractures from calcite filled fractures
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Core photos from Petrohawk core with permission
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Evaluating the Eagle Ford outcrops
• Porosity– Increases with maturation and hydrocarbon
generation
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EM images, following Argon milling: Barry Wawak, Core Labs
Note quantities of organic material (om), but Ro data unsatisfactory
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Evaluating the Eagle Ford outcrops
• Brittleness – Mineral composition
• Quartz• Carbonates• Clays
UL samples from Hwy 90, analyzed by Core Lab (Barry Wawak)
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Our data from Lozier Canyon
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THANKS!• The following ran samples for me or paid to have them run:
– Barry Wawak, Core Labs– Russ Dubiel, USGS– Bruce Hart, ConocoPhillips
• The following supported my graduate students (Lauren Peschier, Nick Whitcomb) with grants:– GCAGS, GCSSEPM, STGS
• The following helped in the field:– Dr. Vicky Hover, Ashley Fife, Natasha Jeansonne, Rob Glaser, Aaron
Summerfield
• Dr. Art Donovan (BP) provided access to the Lozier Canyon outcrops• Mr. Billy Foster allowed us to access his land (Old Hiway road cut)