Factors Affecting Liquid-Liquid Relative Permeabilities of a Consolidated Porous Medium

Abstract

Abstract Many laboratory displacement tests have been performed to study factors affecting relative performed to study factors affecting relative permeability curves, residual saturations, and shape permeability curves, residual saturations, and shape of recovery curves. Three sintered artificial porous materials and pure fluid mixtures have been used for this systematic study. The factors were interfacial tension, the viscosity and the velocity of the fluids (in the dimensionless group / v), the wettability, and the viscosity ratio. The results can be used as guidelines for research on recovery processes. Introduction Waterflooding is by far the most common secondary recovery technique. Several processes (polymer injection, surfactant injection, hot water injection, etc.) attempt to improve sweep efficiency by affecting some of the factors involved in the displacement process. For orienting research on these processes, process. For orienting research on these processes, a good knowledge of how these parameters affect local displacement efficiency and over-all sweep efficiency in the reservoir is required. We present here an attempt to understand the effects of such parameters:at the microscopic level on the shape of relative permeability curves and the values of final saturations obtained by flooding, andat the macroscopic level, on the behavior of one-dimensional displacement. Effects of the morphology of the porous medium were not included in this study. We mainly examined the effects of fluid properties on fluid displacement in only three specific porous media. These three artificial sintered media were made of Teflon, stainless steel and alumina. For the following reasons they were very well suited to the systematic investigation undertaken:they are homogeneous and so the results are not subject to macroscopic heterogeneity effects;they are identical in the same series, thus permitting the results to be compared from one experiment to anothertheir constant and well-defined chemical composition makes it possible to perform wettability measurements outside the porous medium;they are consolidated like most of reservoir rocks;they have good mechanical properties and so can be washed successively without being altered andthe three media used correspond to three possible cases of wettability, i.e., Teflon is strongly oil-wet, alumina is strongly water wet, and stainless steel may have intermediate wettability depending on the fluids considered. Some of our results reported here (concerning experiments with Teflon at a viscosity ratio of one) were presented earlier. THEORY The elementary laws governing the distribution and flow of two phases in a porous material are quite well known:(1)viscous-flow laws in each phase (Navier and continuity equations),(2)phase (Navier and continuity equations),(3)solid-liquid boundary condition (zero velocity),(3)dynamic equilibrium laws of liquid-liquid interfaces (capillary law and continuity of velocities and viscosity stresses), and(4)solid-liquid-liquid contact line equilibrium laws with hysteresis and velocity dependency. Nevertheless the complexity of porous media, coupled with the difficulty of introducing the wettability law in a mathematical form, makes it impossible to go from flow properties on a microscopic pore scale to flow laws formulated on a macroscopic scale, i.e., relative permeability curves and capillary pressure curves. Use of dimensional analysis and reasoning with simple pore schemes are two ways of approaching this pore schemes are two ways of approaching this problem. problem. The parameters involved in the phenomenon under study are the following:fluid viscosities 1 and2,specific gravities P1 and P2,interfacial tension,pore dimension and morphology M,the wettability,system evolution prior to the moment of study K, andexternal conditions, i.e., a mean velocity v or a pressure gradient in the zone investigated. Three of these parameters, namely, M, and K, have complex meanings and cannot be specified by a single number. JPT P. 39