Experimental study of two-phase flow in three sandstones. I. Measuring relative permeabilities during two-phase steady-state experiments

Hysteretic relative permeability curves for three different sandstones were determined during two-phase steady-state experiments. On the one hand, the experimental device designed and developed is inspired, according to the manner in which the end effects are reduced, by the Penn-State method. On the other hand, semi-permeable membranes were used upstream of the flow to separate the two fluids (gas and liquid) injected. Having corrected the gas relative permeability curves for the Klinkenberg effect, our present results were compared to that obtained previously using a modified version of the transient pulse-decay method with two different saturating liquids. Gas relative permeability curves obtained by this method or by steady-state experiments, where both fluids are mobile, have shown good agreement. Thus, one can conclude that gas effective permeability does not depend, neither, on the percolating liquid or on its mobility and that viscous coupling effects are negligible for such type of flows. Saturation history has proved to have more influence on the gas relative permeability than on that of the wetting phase. We finally show that result analysis, along with pore structure information accessible from mercury intrusion tests, would enable the specification of a pore entry radii range, controlling the steep part of the relative permeability curves. For sandstone samples tested here, these pores are of comparable sizes. (C) 2002 Elsevier Science Ltd. All rights reserved.