Page 307 - Principles of Applied Reservoir Simulation 2E

Chapter 28

Rock and Fluid Models

The interaction between reservoir rock and in situ fluids is modeled with
relative permeability and capillary pressure data. This chapter defines the three-
phase oil relative permeability model used in WINB4D and its use in
transmissibility calculations. It then presents additional details of the fluid
property model after reviewing a few commonly used thermodynamic terms.

28.1 Three-Phase Relative Permeability

Relative permeability curves are some of the most critical data in the
simulator because relative permeability curves can have a significant impact on
simulator performance. Relative permeability curves are an important part of
the algorithm that is used to model the interaction between reservoir rock and
fluids. Unfortunately, relative permeability curves are often among the missing
or poorer quality data.
Relative permeability data are affected significantly by alterations in
wettability conditions in the core. Ideally, the relative permeability data should
be measured in the laboratory under the same conditions of wettability that exist
in the reservoir. One method of approaching this ideal is to use preserved,
"native state" core samples.
"Native state" core samples are cores that are drilled using crude oil or
a special coring fluid designed to minimize wettability alterations. The cores
are sealed at the well site to minimize exposure to oxygen or drying and then
preserved until ready to undergo flow testing in the laboratory. However, this

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