RESERVOIR PETROPHYSICS
PETE 311
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
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
RESERVOIR PETROPHYSICS
Course Objectives
By the last day of class, the student should be able to:
1.
Define porosity; discuss the factors which affect porosity and
describe the methods of determining values of porosity;
2.
Define the coefficient of isothermal compressibility of reservoir
rock and describe methods for determining values of formation
compressibility;
3.
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;
RESERVOIR PETROPHYSICS
Course Objectives
4.
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;
5.
Describe methods of determining fluid saturations in reservoir rock
and show relationship between fluid saturation and capillary pressure;
6.
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;
RESERVOIR PETROPHYSICS
Course Objectives
7.
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.
8. Describe three-phase flow in reservoir rock and explain methods of
displaying three-phase effective permeability.
9. Demonstrate the techniques of averaging porosity, permeability, and
reservoir pressure data.
10. 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)
PETROPHYSICS
• Why do we study petrophysics?
Cross Section Of A Petroleum System
(Foreland Basin Example)
Geographic Extent of Petroleum System
O
Stratigraphic
Extent of
Petroleum
System
Pod of Active
Source Rock
Essential
Elements
of
Petroleum
System
O
Overburden Rock
Seal Rock
Reservoir Rock
Source Rock
Underburden Rock
Petroleum Reservoir (O)
Fold-and-Thrust Belt
(arrows indicate relative fault motion)
(modified from Magoon and Dow, 1994)
Basement Rock
Top Oil Window
Top Gas Window
Sedimentary
Basin Fill
Extent of Play
Extent of Prospect/Field
O
PETROLEUM SYSTEM
From Schlumberger Oilfield Glossary
Timing of formation of the major elements of a petroleum system, Maracaibo basin, Venezuela.
DEFINITIONS - SEDIMENTARY ROCK
Sedimentary Rock
Rock Formed from the Weathered
Products of Pre-Existing Rocks and
Transported by Water, Wind, and
Glaciers
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
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
-2
(i.e. Minerals With a CO3 Anion Group)
- Predominately Calcite (Limestone)
- Predominately Dolomite (Dolomite
or Dolostone)
Classified by Grain Size and Texture
SEDIMENTARY ROCK TYPES
Relative Abundances
Sandstone
and conglomerate
(clastic)
~11%
Mudstone
(Siltstone
and shale;
clastic)
~75%
Limestone and
Dolomite
(carbonate)
~14%
Grain-Size Classification for Clastic Sediments
Name
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
Millimeters
Micrometers
4,096
256
64
4
2
1
0.5
0.25
0.125
0.062
0.031
0.016
0.008
0.004
Commonly, phi-sizes are used
for sediment analysis
500
250
125
62
31
16
8
4
(modified from Blatt, 1982)
DUNHAM’S CLASSIFICATION - CARBONATES
Carbonate rocks can be classified according to the texture and grain size.
From Schlumberger Oilfield Glossary
GENERATION, MIGRATION, AND
TRAPPING OF HYDROCARBONS
Seal
Fault
(impermeable)
Oil/water
contact (OWC)
Migration route
Seal
Hydrocarbon
accumulation
in the
reservoir rock
Top of maturity
Source rock
Seal
Reservoir
rock
DESCRIBING A RESERVOIR
Structural Characterization
STRUCTURAL HYDROCARBON TRAP
This structural trap is formed by an anticline and a normal fault.
From Schlumberger Oilfield Glossary
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
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
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
TYPES OF HYDROCARBONS
• Composition
• Molecular structure
• Physical properties
PHYSICAL PROPERTIES OF
HYDROCARBONS
• Color
• Refractive Index
• Odor
• Density (Specific Gravity)
• Boiling Point
• Freezing Point
• Flash Point
• Viscosity
FLUID DENSITY
˚ API =
141.5 - 131.5
g
• What are the standard reporting conditions?
˚ API = API gravity
g
= specific gravity
FLUID VISCOSITY
• Importance
• Units – centipoises (μ, cp)
• Strongly temperature dependent
• Standard reporting conditions
DRILLING RIGS
Drillship
Semisubmersible
Jackup
Submersible
Land Rig
From Schlumberger Oilfield Glossary
ROTARY DRILL BIT, WORN
From Schlumberger Oilfield Glossary
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