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The Eagle Ford Shale Outcrop Studies Related to the Oil and Gas Potential of a Major Unconventional Reservoir.

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.

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The Eagle Ford Shale Outcrop Studies Related to the Oil and Gas Potential of a Major Unconventional Reservoir.

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  1. 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

  2. Outline • Resource Plays and the Eagle Ford • Stratigraphy and Sedimentology of the Outcrops • Application of the Outcrops to Understanding the Eagle Ford Resource Play

  3. 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

  4. S2: kerogen Tmax S1: existing hydrocarbons S3 S3: CO2 from spent kerogen

  5. HI (Hydrogen Index) = (S2/TOC).100 OI(Oxygen Index) = (S3/TOC).100 PI (Production Index = S1/(S1+S2) Tmax: 400-430o immature 435-450o oil zone >450o overmature S2: kerogen S1: existing hydrocarbons S3 S3: CO2 from spent kerogen Values as mg/gm of sample: if S1 >1 mg/g = oil show if S2 > 5 mg/g = good source rock

  6. 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

  7. resource shales REGIONALSTRATIGRAPHY Eagle Ford and Austin considered a single reservoir unit

  8. 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. Delaware Basin Delaware Basin Lower Cretaceous reef trend Rio Grande Embayment Maverick Basin Edwards reef Delaware/Rio Grande Aulacogen Delaware/Rio Grande Aulacogen field area EF outcrops Sligo reef Maverick Basin Eagle Ford Lower Cretaceous Reef Trend Eagle Ford

  9. Outcrop D Outcrop G Lozier Canyon Outcrop Q The field study area – Eagle Ford outcrops

  10. Lower member (“facies A” of BP workers). unstable slope deposits; slump folds debris flows turbidite traction deposits - ? contourites Lowstand Systems Tract Not present in the subsurface

  11. debris flow debris flow

  12. Ash/turbidite marker bed extends from Comstock to Lozier Canyon (about 40 miles) clast debris flow ash/turbidite New LGS Vice-President Buda Formation

  13. Sources of authigenic kaolinite (and silica)? ash bed in lower member numerous ash beds throughout the Eagle Ford are composed almost entirely of kaolinite (possible source of diagenetic silica)

  14. kaolinite dolomite 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.

  15. The productive interval (lower Eagle Ford in the subsurface)

  16. Road cut G-1 upper beds of middle member (more calcareous) limestone “shale” (marlstone) limestone Middle member (productive interval) in outcrop

  17. Road cut G-2 lowest chalky limestone upper member middle member

  18. Lozier Canyon – bluffs expose full Eagle Ford section

  19. Lozier Canyon section Austin Chalk upper member middle member Lower member (obscured) Buda Limestone

  20. Lozier Canyon middle member: rock is fresh because of stream undercutting the bluff.

  21. 2,000 ft long outcrop in same stratigraphic interval shows lateral consistency. Road cut Q upper beds, middle member lower beds, middle member Note: most of the outcrop is weathered (oxidized iron).

  22. black color of fresh rock grey patina (result of last 30 years since road-cut was made) Note laminae that pinch out – evidence for bottom currents (hyperpycnal flow)

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