Effect Of Temperature On Bitumen-Water End Point Relative Permeabilities And Saturations

Abstract

Abstract This paper presents the results of an investigation on the effects of temperature on end point relative permeabilities for bitumen-containing systems. End point bitumen-water relative permeabilities and saturations were measured for constant rate floods through synthetic oil sand packs subjected to overburden pressure. A procedure was developed to obtain reproducible, clean, unconsolidated sand packs having porosities and absolute permeabilities of the same order of magnitude as rich oil sands. Bitumen and water displacement experiments were performed at constant temperatures and pressures representative of steamflood conditions. End point bitumen-water relative permeabilities and saturations were found to be independent of temperature in the range of 125 °C to 250 °C. The significance of this result can be important for reservoir engineers in predicting reservoir performance relative permeabilities for specific reservoir materials could be measured at some convenient temperature and be applied to the whole temperature range to which the reservoir is subjected to. Introduction The numerical ~imulation of thermal processes requires data on relative permeabilities and their dependence on temperature. However, reliable experimental data are not readily available. Thus, relative permeability is generally treated as an adjustable parameter for the history matching of past reservoir performance. Over the last thirty years, a number of laboratory studies have published conflicting results of temperature effects on two-phase relative permeabilities in porous media. Most experiments were performed on consolidated rocks, and only a few studies used reservoir cores and crude oils. Nakornthap and Evans(1) have summarized the temperature dependence of oil-water relative permeabilities reported in the literature. The general trend indicated that the oil and water relative permeability curves shifted to higher Water saturations. Using the unsteady State method, researchers working with heterogeneous porous media and oils of low to intermediate viscosity in the temperature range of up to about 150 °C reported that residual saturations and relative permeabilities were influenced by temperature(2–4). Other researchers working in the same temperature range with homogeneous sand cores and oils of intermediate viscosity reported the contrary(5,6). The only steady State relative permeabilities measured at elevated temperature (155 °C) were reported by Lo and Mungan(7). They found that temperature affected relative permeability curves in both water-and oil-wet systems similarly to the generally reported trends(1). They also indicated that, if the viscosity ratio remained constant, relative permeability curves were independent of temperature. The objective of this study was to determine the effect of temperature on relative permeabilities and saturations under controlled conditions using well-characterized systems. Twenty-five experiments were conducted on sand packs saturated with homogenized Athabasca bitumen and deionized water. The absolute permeabilities of the packs were measured at room and experimental temperatures. End point relative permeabilities and saturations were determined in the temperature range of 125 °C to 250 °C once a steady state condition with respect to the pressure drop across the pad bad been achieved. Experimental Apparatus and Procedures Apparatus The experimental apparatus was designed to measure two-phaserelative permeabilities under isothermal conditions up to 300 °C. A schematic diagram is shown in Figure 1.