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. PETE 311 RESERVOIR PETROPHYSICS 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 effect 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, 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 permeabilities.
Demonstrate the techniques of averaging porosity, permeability, and reservoir pressure data.
Demonstrate capability to perform calculations relating to all concepts above.
(These are minimum skills to be achieved/demonstrated)

7. PETROPHYSICS
Why do we study petrophysics?

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

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

10. DEFINITIONS - SEDIMENTARY ROCK
Clastic Sedimentary Rocks
(Such as
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
Rock Formed from the Weathered
Products of Pre-Existing Rocks and
Transported by Water, Wind, and
Glaciers

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

12. SEDIMENTARY ROCK TYPES
Relative Abundances
Mudstone
(Siltstone
and shale;
clastic)
~75%
Sandstone
and conglomerate
(clastic)
~11%
Limestone and
Dolomite
(carbonate)
~14%
This slide shows the relative abundance of the major sedimentary rock types. These rocks comprise approximately 99% of all sedimentary rocks, including hydrocarbon source rocks and traps. Sedimentary rock can be divided into two major classes.
CLASTICS
- Sandstone, conglomerate, siltstone, and shale
- Comprised mainly of silicate minerals
- Classified on the basis of grain size and mineral composition
CARBONATES
- limestone and dolomite
- consist mainly of the carbonate minerals calcite
(limestone) or dolomite (dolostone)

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

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

15. GENERATION, MIGRATION, AND TRAPPING OF HYDROCARBONS
Seal
Seal
Fault
(impermeable)
Oil/water
contact (OWC)
Hydrocarbon
accumulation
in the
reservoir rock
Migration route
Seal
Several conditions must be satisfied for an economic hydrocarbon accumulation to exist. First, there must be sedimentary rocks that have good source rock characteristics and have reached thermal maturity. Second, the hydrocarbons must have migrated from the source rock to a potential reservoir, which must have adequate porosity and permeability. Finally, there must be a trap to arrest the hydrocarbon migration and hold sufficient quantities to make the prospect economic. Hydrocarbon traps usually consist of an impervious layer (seal), such as shale, above the reservoir and barrier such as a fault or facies pinch that terminates the reservoir.
Reservoir
rock
Top of maturity
Source rock

16. DESCRIBING A RESERVOIR
Structural Characterization
Since petroleum reservoirs are generally located many thousands of feet below the surface, it is necessary to use sophisticated tools, such as wireline logs, to gather important information about the reservoirs. This information is then interpreted by highly trained industry professionals, using various mathematical and empirical models, to determine fundamental reservoir properties, such as porosity and permeability.

17. STRUCTURAL HYDROCARBON TRAP
This structural trap is formed by an anticline and a normal fault.
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. FLUID DENSITY ˚ API = 141.5 - 131.5 ٧ ˚ API = API gravity 
= specific gravity
˚ API = API gravity
What are the standard reporting conditions? 

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 a rock that is occupied by voids (pores).
Origins and descriptions
Factors that effect porosity
Methods of determination