Evaluation Geological Engineering Basics GEOL 4233 Class April 27, 2008 Dan Boyd Oklahoma Geological Survey Norman, Okla

1. Evaluation Geological Engineering Basics GEOL 4233 Class April 27, 2008 Dan Boyd Oklahoma Geological Survey Norman, Oklahoma

2. Geological Engineering Overview • Reservoir Issues • Porosity • Permeability • Fluid Saturation • Fluid / Pressure Terminology & Concepts • Fluid (Water, Oil Gas) • Pressure (Saturation, Mobility, Compressibility) • Drive Mechanisms • Oil • Gas • Multiphase Flow Issues (Coning) • Reservoir Management • General Principles • Production Curves • Improved Recovery

3. General Reservoir Issues • Porosity • Permeability • Fluid Saturations

4. Porosity • Storage Capacity • Nominal Pay Cutoffs • Oil: 10% • Gas: 8% • Porosity Types • Intergranular (clastics) • Intercrystaline (carbonates) • Fracture • Dissolution (moldic, vuggy, cavernous) • Logs • Density • Neutron • Sonic

6. Booch Core Porosity vs. Depth

7. Schematic Porosity vs. Depth Plot (Hard Rock Country) 15,000’ 20,000’ 5,000’ 10,000’

8. Permeability • Producibility • Kv – Kh (vertical vs. horizontal) • Conventional Reservoirs • Fractured Reservoirs • Unconventional Reservoirs • Relative Permeability • Enhanced Permeability • Acid Treatment • Fracture Stimulation • Logs • Spontaneous Potential (SP) • Resistivity Suite

12. Booch Core Porosity vs. Permeability (Maximum Values)

13. Core Porosity vs. Permeability Plot

14. Fluid Saturation • Water • Wetting (dewatering) • Connate • Irreducible (Swirr) • Oil • Water displacement (Soi) • Fractured Reservoirs • Unconventional Reservoirs • Gas • Molecular Size (mobility) • Water/Oil displacement (Sgi)

15. Schematic Reservoir Grain Size vs. Water Saturation Grain Size (permeability) Shale (Magnified) Water Saturation Initial (complete pore volume) – Irreducible (rims only)

16. Reservoir Sandstone Good Porosity = Lots of Space for Petroleum Pores (blue)

17. Conventional vs. Non-Conventional Gas Accumulations

19. Unconventional (Low-Perm) Shale (Organic-Rich) 1 Inch

21. Pressures / Fluids

22. Fluid Terminology Water: Connate Movable vs. Irreducible

23. Schematic Reservoir Grain Size vs. Water Saturation Grain Size (permeability) Shale (Magnified) Water Saturation Initial (complete pore volume) – Irreducible (rims only)

24. Fluid Terminology Water: Connate Movable vs. Irreducible Salinity (ppm): Chlorides vs. T.D.S. Fresh – Brackish – Normal Marine - Hypersaline Secondary Recovery (Waterflood) Compressibility (10x rule)

25. Water Support Likely

26. Water Support Unlikely

27. Fluid Terminology Oil: Gravity (API) Viscosity (cp) GOR (gas to oil ratio) Saturated vs. Undersaturated (gas cap – secondary gas cap)

28. Fluid Terminology Oil: Gravity (API) Viscosity (cp) GOR (gas to oil ratio) Saturated vs. Undersaturated (gas cap – secondary gas cap) Contrast with Condensate Live vs. Dead Sweet vs. Sour

29. Fluid Terminology Gas: Heating Value Condensate Yield Condensate vs. Oil Wet vs. Dry Sweet vs. Sour Other Components (CO2, N2)

30. Pressure Terminology ‘Normal’ Pressure (hydrostatic) Under-pressure (fluid leak-off) Over-pressure (incomplete de-watering) Measurements: Reservoir Pressure (BHP, calculated vs. measured) Flowing Tubing Pressure (FTP, at surface) Casing Pressure (between casing and tubing)

35. Saturation Pressures Oil : Bubble Point Gas : Dew Point (retrograde – occurs in reservoir)

36. Fluid Mobility / Compressibility • Molecular Size Mobility Compressibility • Gas - Small High Very High • Oil - Large Medium Moderate (~GOR) • Water - Medium Low Low (10x Rule)

37. Drive Mechanisms

38. Oil Reservoir • Drive Mechanisms • Solution Gas Drive (dissolved gas) (also called depletion) • Gas Expansion Drive (gas cap) • Water Drive • Combination Drive • Gravity Drainage

42. Unconformity Trap

44. Schematic Gravity Drainage Shallow (Low Pressure)

45. Gas Reservoirs

46. Gas Reservoir Drive Mechanism Dominantly Depletion Gas Gas / Water Contact

48. Coalbed Methane Production