Fundamentals of Fluid Flow in Porous Media

Chapter 2

Multi-phase Saturated Rock Properties:

Laboratory Measurement of Capillary Pressure

Laboratory experiments have been developed to simulate the displacing forces in a reservoir in order to determine the magnitude of the capillary forces in a reservoir and, thereby, determine the fluid saturation distributions and connate water saturation. Essentially four methods of measuring capillary pressure on small core samples are used:

• The Porous Diaphragm (or restored capillary pressure) Method
• The Centrifugal Method
• The Mercury Injection Method
• Dynamic capillary pressure method

Differences in wetting characteristics should be taken into account when applying laboratory data to the field. Thus air-water and mercury-air data obtained on cleaned core will represent a fully water wet system for the drainage case. They may not adequately describe a mixed or oil wet system. The closest one can get to this situation, on a routine basis, is with an actual oil water (oil-brine) system when one would expect to find lower S_wi values than a water wet system.