Two- and Three-Phase Relative Permeabilities of Micellar Fluids

Abstract

Summary. Two- and three-phase relative permeabilities have been measured for a low-interfacial-tension (IFT) brine/oil/surfactant/alcohol mixture in Berea sandstone cores. The measurements were done at steady-state conditions with a constant nominal capillary number of 10–2. These are the first three-phase micellar relative permeabilities reported to date. Continuous and slug displacements of both partitioning and nonpartitioning radioactive tracers were run for each steady-state experiment. The effluent tracer data from these experiments were analyzed by a capacitance model. Both excess phases flowing with the microemulsion showed significant capacitance effects, but the microemulsion did not. The absence of capacitance indicates that the microemulsion was probably the wetting phase in these low-IFT flows, even more wetting than the excess brine phase in these low-IFT flows, even more wetting than the excess brine phase. The relative permeability of each phase is a function of only its phase. The relative permeability of each phase is a function of only its own saturation during three-phase flow. Polymer dissolved in brine had little effect on the relative permeabilities of brine and microemulsion in two-phase flow. Introduction The transport of three liquid phases is a significant element of several EOR processes, mainly because of the microscopic trapping of phases by capillary forces. Such trapping is significant in two-phase flow, but its importance in three-phase flow (except for the gas/water/oil case) is unknown. The main goal of this research is to investigate transport properties-phase trapping, relative permeabilities, dispersivities, and capacitance permeabilities, dispersivities, and capacitance parameters-experimentally in three-phase flow. This paper deals parameters-experimentally in three-phase flow. This paper deals with relative permeabilities; phase trapping, dispersivitics, and capacitance parameters (except as they relate to our relative permeability experiments) are given elsewhere. Two-phase relative permeability measurements with low-IFT fluids have been reported by several investigators. The following differences set our work apart.We measured relative permeabilities in three-phase flow at low IFT and constant capillary number.We estimated phase saturations with both material balance and tracer breakthrough data. Salter and Mohanty used nonpartitioning tracers for both weting and nonwetting (bone and oil) phases during two-phase flow. Here, we report the results of tracer displacements for two- and three-phase flows with partitioning tracers, which were used primarily between Phases 1 and 3 or between Phases 2 and 3. No other three-phase-flow tracer data have been reported.We used tracer slugs in some cases. Although the study of miscible slug displacements goes back to 1965, this is the first time that slugs have been used for two-and three-phase flow or for low-IFT surfactant flow.We used micellar fluids with and without polymer. Deans and Coats and Smith were the first to develop a model of single-phase flow that divided the pore space into flowing and dead-end fractions. Stalkup and Baker extended the model to two-phase, steady-state miscible displacements. Salter and Mohanty modified this model for tracer displacements under steady-state, two-phase flow. Salter and Mohanty assumed that each phase has flowing, dendritic, and isolated fractions. Only the flowing and dendritic fractions can be produced. Their model did not include mass transfer between phases. The resulting capacitance/dispersion equation was solved by Laplace transform. In this paper, we take an approach similar to that of Salter and Mohanty to model the tracer-breakthrough curves for low-IFT fluids. The major differences from the Salter and Mohanty approach arethe model divides each phase into two parts, flowing and dendritic, rather than three because the experiments are performed at a very low IFT and the possibility of having an isolated portion is small;the model allows mass transfer between phases;the model can be used for both two-and three-phase flows; andthe capacitance/dispersion equations are solved by finite differences. Analysis Capacitance/Dispersion Model. The capacitance/ dispersion model is useful for evaluating capacitance/dispersion effects in micellar displacements and for improving saturation estimates. In this model, mixing in the flowing fraction is described by a dispersion coefficient. Mass transfer between the flowing and dendritic fractions is modeled by mass transfer coefficients. SPEFE p. 327