Experimental study of gas slippage in two-phase flow

Gas slippage in single-phase gas flow (the Klinkenberg effect) has been investigated extensively. Few papers, however, have been published on the gas slippage in gas/liquid two-phase flow. The gas relative permeabilities at water saturations close to the residual value have been found to be significantly greater than I in both nitrogen/water and steam/water flow through rocks. These values became less than 1 after the calculation was calibrated by taking the two-phase gas slip effect into consideration. The gas relative permeabilities have been measured at different mean pore pressures, and the values of two-phase gas slip factors have been computed at different water saturations. The effects of temperature on both nitrogen and steam slip factors also have been studied and compared. These data have then been used to conduct a calibration to obtain intrinsic gas relative permeabilities that do not vary with the test pressures. It has been found from the present work that neglecting the two-phase gas slip effect may overestimate gas relative permeabilities. It is the intrinsic gas relative permeabilities instead of those measured at low test pressures that should be used in numerical simulation or other reservoir-engineering calculations.