A New Method for the Measurement of Gas Relative Permeability and Water Saturation Simultaneously in Low-Permeability Cores

Abstract

ABSTRACT Since water is pumped into low permeability formations during stimulation treatments, two-phase rock property measurements are important if one wishes to model the effects of water upon gas recovery. Relative permeabilities are necessary to describe the flow of more than one phase in a porous medium. Conventional steady-state measurements of relative permeabilities have extremely long stabilization times. Several days may be necessary to generate one relative permeability point. The determination of water saturations by gravimetrics may result in significant error due to handling of the core. The purpose of this study is to present a new method for measuring gas relative permeability and water saturation simultaneously in low permeability cores. This two-phase transient technique incorporates the analytical solution developed in the early portion of this research project. Under conditions where the water is considered immobile and incompressible, the analytical solution can be used to match effective gas permeability and gas porosity simultaneously from the same transient data. The new method has been verified with numerical simulation and actual measurements on cores. An extensive series of measurements were performed on two Travis Peak cores to measure the gas relative permeability curve, to check reproducibility of the measured values, and to establish the proper testing techniques.