A New Method for the Measurement of Gas Relative Permeability and Water Saturation Simultaneously Permeability and Water Saturation Simultaneously in Low-Permeability Cores
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. 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 sane transient porosity simultaneously from the sane transient data.
The new method has been verified with numerical simulatio an actual measurements on cores. An extensive series of measurements were performed on two Travis Peak cores to measure the 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.
Relative permeabilities are necessary to describe the flow of more than one phase in a porous medium. To model the cleanup behavior of porous medium. To model the cleanup behavior of drilling mud filtrate or stimulation fluids in a well completed in a low permeability gas reservoir, the gas-water relative permeability relationship must be determined. Relative permeability data can be obtained from core measurement made in a laboratory; however, such measurements are often difficult to obtain and to reproduce.
In high permeability core samples, water and gas are injected simultaneously through the core. After the flow rates and pressures stabilize, the relative permeability of each phase can be determined. This approach is called the steady-state method of determining relative permeability. Additional data points for the permeability. Additional data points for the gas-water relative permeability functio can be obtained by changing the gas and/or the water injection rates into the core an allowing the rates and pressures to once again stabilize. For high permeability cores, stabilization times are reasonable and the steady state method is acceptable.
For low permeability cores, however, the use of steady-state methods are not feasible. To establish gas and water injection rates at reasonable pressure differentials across these tight cores, the injectio rates are extremely small. Difficulty arises when one attempts to measure accurately these lo rates. Also, stabilization times can be prohibitively long.
Chowdiah has performed some steady-state relative permeability measurements in low permeability cores. permeability cores. P. 551