3.5: Key Learnings

In this lesson, we discussed the following topics:

1. The properties of interest to petroleum engineers are divided into three categories:
   1. Rock properties
   2. Fluid properties
   3. Rock-Fluid interaction properties

2. These properties are most commonly used to improve our understanding of:
   1. Storage of oil, water, and gas in a petroleum reservoir
   2. Transport (movement) of oil, water, and gas in the reservoir

3. The rock properties that we discussed included:
   1. Porosity (ability of a rock to store fluids)
   2. Compressibility (property of the rock that governs how volumes behave with changes in pressure)
   3. Permeability (ability of a rock to transmit fluids)

4. Common methods used to determine porosity are:
   1. Laboratory measurements
      1. Grain determination by immersion
      2. Grain determination by Boyle’s Law
      3. Washburn-Bunting (mercury injection)
      4. Summation of fluids
   2. Well logs (field measurements):
      1. Sonic log
      2. Density log
      3. Neutron log

5. Common methods used to determine permeability are:
   1. Laboratory measurements: Core Floods
   2. Field measurements:
      1. Well tests (or pressure transient analysis)
      2. Permeability-porosity cross-plots

6. Fluid Properties:
   1. Formation volume factor: oil, gas, and water property that describes the reservoir volume occupied by one STB of liquid or one SCF of gas
   2. Compressibility: oil, gas, and water property that describes the change in volume with a change in pressure
   3. Viscosity: oil, gas, and water property that describes the ease with which a fluid can flow through a porous medium
   4. Density: oil, gas, and water property that quantifies the weight of a unit volume of fluid
   5. Specific gravity: oil, gas, and water property that normalizes the density to the density of a standard fluid – water for liquids and air for gases
   6. Bubble-point pressure: oil property describing the pressure that the first bubble of gas evolves from the oil with reducing pressures
   7. Solution Gas-Oil Ratio: oil property describing the amount of gas (in SCF) dissolved in one STB of oil
   8. Gas super-compressibility or real gas deviation factor: gas property that describes the deviation of a real gas from the ideal gas law
   9. API Gravity: oil property related to specific gravity
   10. Molecular weight: oil, gas, and water property that quantifies the weight of one mole of fluid molecules
   11. These properties (excluding molecular weight and specific gravity) are, in general, pressure dependent properties

7. Rock-fluid interaction properties
   1. Phase saturation: oil, gas, and water property describing the fraction of the pore-volume occupied by the phase
   2. Capillary pressure: oil-water and gas-oil property that describes the difference in the pressures between the paired pressures
   3. Effective permeability: oil, gas, and water property that describes the permeability to one phase in the presence of one or more other phases in the porous medium
   4. Relative permeability: oil, gas, and water property that is the ratio of the effective permeability to a phase divided by the absolute permeability of the porous medium
   5. These properties are, in general, saturation dependent properties