RESERVOIR PETROPHYSICS PETE 311

1. RESERVOIR PETROPHYSICS PETE 311

2. PETROPHYSICS Petrophysics is the study of rock properties and rock interactions with fluids (gases, liquid hydrocarbons, and aqueous solutions). Modified from Tiab and Donaldson, 1996, p. 1

3. RESERVOIR PETROPHYSICS PETE 311 COURSE DESCRIPTION • Systematic theoretical and laboratory study of physical properties of petroleum reservoir rocks • Lithology • Porosity • Compressibility • Permeability • Fluid saturations • Capillary characteristics • Rock stress • Fluid-rock interaction

4. RESERVOIR PETROPHYSICS • Course Objectives • By the last day of class, the student should be able to: • Define porosity; discuss the factors which affect porosity and describe the methods of determining values of porosity; • Define the coefficient of isothermal compressibility of reservoir rock and describe methods for determining values of formation compressibility; • Reproduce the Darcy equation in differential form, explain its meaning, integrate the equation for typical reservoir systems, discuss and calculate the effect of fractures and channels, and describe methods for determining values of absolute permeability;

5. RESERVOIR PETROPHYSICS • Course Objectives • Explain boundary tension and wettability and their effect on capillary pressure, describe methods of determining values of capillary pressure, and convert laboratory capillary pressure values to reservoir conditions; • Describe methods of determining fluid saturations in reservoir rock and show relationship between fluid saturation and capillary pressure; • Define resistivity, electrical formation resistivity factor, resistivity index, saturation exponent, and cementation factor and show their relationship and uses; discuss laboratory measurement of electrical properties of reservoir rocks; and demonstrate the calculations necessary in analyzing laboratory measurements;

6. RESERVOIR PETROPHYSICS • Course Objectives • Define effective permeability, relative permeability, and permeability ratio; reproduce typical relative permeability curves and show effect of saturation history on relative permeability; illustrate the measurement of relative permeability; and demonstrate some uses of relative permeability data. • Describe three-phase flow in reservoir rock and explain methods of displaying three-phase effective permeability. • Demonstrate the techniques of averaging porosity, permeability, and reservoir pressure data. • Demonstrate capability to perform calculations relating to all concepts above. • 11. Design and conduct experiments to determine porosity, rock compressibility, absolute and relative permeability, fluid saturation, capillary pressure, and electrical properties of reservoir rocks; analyze and interpret experimental data; and prepare laboratory reports. • (These are minimum skills to be achieved/demonstrated)

7. PETROPHYSICS • Why do we study petrophysics?

8. Geographic Extent of Petroleum System Extent of Play Extent of Prospect/Field O O O Stratigraphic Extent of Petroleum Overburden Rock System Essential Seal Rock Elements of Reservoir Rock Basin Fill Sedimentary Petroleum Pod of Active System Source Rock Source Rock Underburden Rock Petroleum Reservoir (O) Basement Rock Fold-and-Thrust Belt Top Oil Window (arrows indicate relative fault motion) Top Gas Window (modified from Magoon and Dow, 1994) Cross Section Of A Petroleum System (Foreland Basin Example)

9. PETROLEUM SYSTEM From Schlumberger Oilfield Glossary Timing of formationof the major elements of a petroleum system, Maracaibo basin, Venezuela.

10. Sedimentary Rock Rock Formed from the Weathered Products of Pre-Existing Rocks and Transported by Water, Wind, and Glaciers (Such as Clastic Sedimentary Rocks Shale, Siltstone, and Sandstone) Consist of Broken Fragments of Pre-Existing Rock (cf. Detrital) Carbonate Sedimentary Rocks (and Evaporites) May Form by Chemical Precipitation or Organic Activity DEFINITIONS - SEDIMENTARY ROCK

11. Clastic Rocks Consist Primarily of Silicate Minerals Are Classified on the Basis of: - Grain Size - Mineral Composition Carbonate Rocks Consist Primarily of Carbonate Minerals -2 (i.e. Minerals With a CO Anion Group) 3 - Predominately Calcite (Limestone) - Predominately Dolomite (Dolomite or Dolostone) Classified by Grain Size and Texture CLASTIC AND CARBONATE ROCKS

12. Sandstone and conglomerate (clastic) ~11% Limestone and Dolomite (carbonate) ~14% Mudstone (Siltstone and shale; clastic) ~75% SEDIMENTARY ROCK TYPES Relative Abundances

13. Name Millimeters Micrometers 4,096 Boulder 256 Cobble Commonly, phi-sizes are used for sediment analysis 64 Pebble 4 Granule 2 Very Coarse Sand 1 Coarse Sand 0.5 500 Medium Sand 250 0.25 Fine Sand 125 0.125 Very Fine Sand 62 0.062 Coarse Silt 31 0.031 Medium Silt 0.016 16 Fine Silt 0.008 8 Very Fine Silt 4 0.004 Clay (modified from Blatt, 1982) Grain-Size Classification for Clastic Sediments

14. DUNHAM’S CLASSIFICATION - CARBONATES Carbonate rocks can be classified according to the texture and grain size. From Schlumberger Oilfield Glossary

15. Fault (impermeable) Oil/water contact (OWC) Migration route Seal Reservoir rock Hydrocarbon accumulation in the reservoir rock Source rock GENERATION, MIGRATION, AND TRAPPING OF HYDROCARBONS Seal Seal Top of maturity

16. DESCRIBING A RESERVOIR Structural Characterization

17. STRUCTURAL HYDROCARBON TRAP This structuraltrap is formed by an anticline and a normalfault. From Schlumberger Oilfield Glossary

18. DOMAL TRAP • Are hydrocarbons in this field oil or gas? • What is the volume of hydrocarbons • In this trap? • What are the reserves? Closure. In map view (top), closure is the area within the deepest structural contour that forms a trapping geometry, in this case 1300 ft [390 m]. In cross section A-A', closure is the vertical distance from the top of the structure to the lowest closing contour, in this case about 350 ft [105 m]. The point beyond which hydrocarbons could leak from or migrate beyond the trap is the spill point. From Schlumberger Oilfield Glossary

19. WATER DRIVE What is the Drive Mechanism? A reservoir-drive mechanism whereby the oil is driven through the reservoir by an active aquifer. As the reservoir depletes, the water moving in from the aquifer below displaces the oil until the aquifer energy is expended or the well eventually produces too much water to be viable. From Schlumberger Oilfield Glossary

20. GAS EXPANSION DRIVE What is the Drive Mechanism? A gas-drive system utilizes the energy of the reservoir gas, identifiable as either as free or solution gas, to produce reservoir liquids. Are there other drive mechanisms? From Schlumberger Oilfield Glossary

21. TYPES OF HYDROCARBONS • Composition • Molecular structure • Physical properties

22. PHYSICAL PROPERTIES OF HYDROCARBONS • Color • Refractive Index • Odor • Density (Specific Gravity) • Boiling Point • Freezing Point • Flash Point • Viscosity

23. ˚ API = 141.5 g - 131.5 • What are the standard reporting conditions? ˚ API = API gravity g = specific gravity FLUID DENSITY

24. FLUID VISCOSITY • Importance • Units – centipoises (μ, cp) • Strongly temperature dependent • Standard reporting conditions

25. DRILLING RIGS Drillship Semisubmersible Jackup Submersible Land Rig From Schlumberger Oilfield Glossary

26. ROTARY DRILL BIT, WORN From Schlumberger Oilfield Glossary

27. Next Class: • RESERVOIR POROSITY • Definition: Porosity is the fraction of the bulk volume of a material (rock) that is occupied by pores (voids). • Origins and descriptions • Factors that effect porosity • Methods of determination