Brian E. Lock University of Louisiana, Lafayette Prepared for LGS meeting, September 21, 2011

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

12. debris flow debris flow

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

14. 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)

15. 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.

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

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

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

20. Lozier Canyon – bluffs expose full Eagle Ford section

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

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

23. 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).

24. 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)

25. Parasequences in highway outcrop, middle member

26. 10 ft Parasequences in a core gamma ray log, from a Petrohawk well.

27. Deep water sedimentation and parasequences What controls limestone/shale alternations? Eustasy? Climate? Tectonics? or periodic gravity flows from unstable platform margin? Includes possible hypopycnal flow terrigenous clay and silt, suspended carbonate mud sea level fluctuation flocculation, pelletization few feet carbonate factory water depth clay CaCO3 hyperpycnalflow hundreds of feet shoaling marine snow deep water traction currents (meteorological? geostrophic?) parasequence 2 parasequence 2 mfs mfs limestone – brittle marl (“shale”) - ductile parasequence 1 parasequence 1 Is the limestone the base or the top of the parasequence?

28. Smaller scale cycles – result of climate/sea level variations or individual hyperpycnal flows?

29. Core photos from Petrohawk core with permission Note evidence of current action Inoceramid fragments Graded bed – white dots are planktic forams

30. copepod fecal pellet

31. Evaluating the Eagle Ford outcrops • Original organic richness and generation potential • Kerogen type • Rock-Eval analyses Oil prone

32. 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

33. 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

34. Kerogen Transformation modified Van Krevelen Diagram Van Krevelen Diagram

35. Evaluating the Eagle Ford Outcrops Close to, but not yet in oil window • Maturation Tmax from Lozier Canyon samples (UL). No Ro or TTI data available

36. 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)

37. 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

38. 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

39. Core photos from Petrohawk core with permission

40. Evaluating the Eagle Ford outcrops • Porosity • Increases with maturation and hydrocarbon generation

41. EM images, following Argon milling: Barry Wawak, Core Labs Note quantities of organic material (om), but Ro data unsatisfactory

42. Evaluating the Eagle Ford outcrops • Brittleness • Mineral composition • Quartz • Carbonates • Clays UL samples from Hwy 90, analyzed by Core Lab (Barry Wawak)

43. Our data from Lozier Canyon

45. 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)