Petrophysical Concepts

1
Petrophysical Concepts

• Porosity
• Permeability
• "Pore volume" compressibility

2
Porosity

• Example Dry rock cube (1 ft x 1 ft x 1 ft) has
  porosity 0.3.
• It is saturated with air at standard conditions
  and isolated from its environment.
• (Assumptions T constant and total
  connectivity.)
• What will be the pressure after injecting 3 SCF
  air into it?
• What difference does it make if connate water
  saturation is 50 ?

3
Porosity Classification

• Carbonate and Clastic Reservoir System
• Fabric Selective vs. Not
• Sandstone
• Depositional Environments and Reservoir
  Characteristics
• Sedimentary structures
• Diagentic changes in sandstones
• Questions?
• Pore space distribution, connectivity and other
  structural features

4
Flow
Shear Rate 1/s Shear stress Pa Viscosity
Pa.s
1/s
Pa.s
5
Flow in Porous Media Permeability
A
Darcy velocity
x
Permeability
6
Permeability vs Porosity

• Are they related?
• Log(k) vs. f

7
The concept of hierarchy (scale)

• Reservoir Scaling
• Micro/Macro/Mega/Giga scale reservoir features
• Schematics of Fracture Mechanics
• Fractures align perpendicular to the direction of
  least principle stress.
• Dual porosity

8
Fluid properties

• Gas
• Oil
• Water

9
Who drives the show?
10
Properties of Natural Gases

• Pseudoreduced temperature and pressures (for gas
  mixtures)
• Dranchuk and Abou-Kassem equation of state
  (DAK-EOS)
• Calculation of z-factor and gas compressibility.
• Gas viscosity (various approaches)

11
Properties of Reservoir Oil

• Oil formation volume factor (Standing
  correlation).
• Solution gas-oil ratio (Standing correlation).
• Discussion of alternative approaches
• Oil compressibility
• Oil viscosity

12
Properties of Reservoir Waters

• Water formation volume factor.
• Solution water-oil ratio.
• Water compressibility
• Water viscosity