Effect of Temperature on Heavy-Oil/Water Relative Permeabilities in Horizontally and Vertically Drilled Core Plugs

Abstract

Effect of Temperature on Heavy-Oil/Water Relative Permeabilities in Horizontally Permeabilities in Horizontally and Vertically Drilled Core Plugs Summary Oil/water displacement tests were conducted in preserved core material at reservoir pressure and at various temperatures ranging from room temperature to 522F [272C] to evaluate the effect of temperature on relative permeabilities. Both horizontally and vertically drilled permeabilities. Both horizontally and vertically drilled plugs were tested to determine the influence of flow plugs were tested to determine the influence of flow direction on relative permeabilities and on their temperature dependence. Results show that temperature influences both the endpoint saturations and the endpoint effective permeabilities. Irreducible water saturation increased with increasing temperature, whereas the dependence of residual oil saturation on temperature was less clear-cut. The residual oil saturation appeared to decrease up to an optimum temperature, beyond which the trend reversed. The endpoint effective permeability to oil decreased with increasing temperature, while the endpoint effective permeability to water appeared to be independent of permeability to water appeared to be independent of temperature. The endpoint effective permeability to oil was found to be from one to two orders of magnitude lower in vertically drilled plugs compared with horizontally drilled plugs. On the other hand, endpoint water permeability appeared to be similar in both directions. Introduction Numerical simulation of thermal recovery processes requires data on relative permeability and its dependence on temperature and flow direction. Reliable data of this nature have not been commonly available because of the experimental difficulties involved in measuring relative permeabilities at high temperatures. Often, relative permeabilities at high temperatures. Often, relative permeabilities routinely measured at room temperature permeabilities routinely measured at room temperature are used to predict performance at higher temperatures. In history-matching past reservoir performance, treating relative permeability as an adjustable parameter often becomes necessary. As shown by Dietrich, relative permeabilities measured in unconsolidated sands differ permeabilities measured in unconsolidated sands differ from those required to history-match cyclic steam stimulation results by more than an order of magnitude. Many heavy-oil fields contain discontinuous shale breaks and thin, tight zones that lead to significant differences between vertical and horizontal permeabilities. Since override in the steam injection process can be affected strongly by such barriers, it is desirable to know whether relative permeability curves also show anisotropic behavior and, if so, how this behavior is also affected by temperature. Many investigators have studied the effect of temperature on relative permeability. Edmondson found that residual oil saturation (Sor) decreased with temperature and that changes in water/oil permeability ratio were different with different oils. Poston et al. investigated the influence of temperature on oil/water displacements in unconsolidated sands and concluded that irreducible water saturation increased and Sor decreased with increasing temperature. They also found that relative permeabilities to both oil and water generally increased with increasing temperature. Weinbrandt et al. found that, in Boise sandstone cores, an increase in temperature from room temperature to 175F [79C] resulted in increased irreducible water saturations, decreased Sor, increased endpoint water permeabilities, and increased oil permeabilities. They suggested that thermally induced mechanical stresses may be responsible for some of the observed changes in absolute and relative permeabilities. Lo and Mungan measured water/oil relative permeabilities in Berea sandstone and porous Teflon cores using the steady-state technique at porous Teflon cores using the steady-state technique at temperatures up to about 302F [150C]. They found that the effect of temperature on relative permeabilities was similar in the oil-wet and water-wet systems. They also found that increases in temperature caused decreases in Sor and increases in irreducible water saturation, and suggested that a temperature-induced change in the viscosity ratio may be responsible for the observed changes in relative permeability. In a more recent investigation, Sufi et al. permeability. In a more recent investigation, Sufi et al. found that relative permeabilities determined with clean oil and water in clean Ottawa sand were independent of temperature between 70 and 186F [21 and 86C]. Most of the reported studies on temperature dependence of relative permeabilities have been conducted with clean or extracted core materials and refined oils. JPT P. 1500