Relative Permeability Curves For Bitumen And Water In Oil Sand Systems

Abstract

Abstract Relative permeability relationships for two- and three-phase flow are a vital part of numerical simulations, but are difficult to measure in the laboratory with any degree of certainty. When temperature is involved as an additional variable, the goal becomes more elusive. This paper presents steady state relative permeability measurements for Athabasca bitumen and water in resaturated sand packs. Injections of various bitumen/water mixtures were performed to cover the entire saturation range from irreducible water to residual oil. A total of thirteen experiments were performed, twelve vertically and one horizontally. Most measurements were conducted at 125 ºC. Additional measurements made at 175 ºC did not show any significant temperature dependence. A single set of bitumen-water relative permeability curves were obtained from the experimental data. The resulting curves exhibited an unconventional behaviour; the bitumen curve was found to be convex. This shape may be a reflection of the displacement process taking place. Furthermore, a comparison of experimentally obtained normalized relative permeability curves for Alberta heavy oils has shown that a wide variation existed among the reported data. Introduction In the last decade, computer-assisted simulation has become a major tool in evaluating and predicting reservoir performance. Description of reservoirs and understanding of oil displacement mechanisms due to primary, secondary or tertiary recovery processes are among the most important features of a good reservoir simulator. However, reliable input parameters are needed to carry out a satisfactory reservoir simulation and provide a predictive capability. These parameters have to be carefully measured in the laboratory. Caution should also be exercised in their interpretation and scale-up to reservoir conditions for use in reservoir simulation studies. Relative permeability is one such key parameter. Laboratory determined relative permeability functions are useful in analyzing immiscible displacement problems. The experimental techniques to measure relative permeability have been developed for light oil reservoirs. The measurements are performed either by the steady state (mixture njection) technique or the unsteady state (dynamic displacement) method. The latter has received more attention due to its faster turn-around time. However, both methods have inherent limitations. In dealing with heavy oils, the steady statemethod, although time-consuming, can provide the desired data. The purpose of this study was to determine the two-phase (oil-water) relative permeability-saturation behaviour for bitumen-containing unconsolidated water-wet sands. Steadystate measurements were conducted for the bitumen-hot waterclean unconsolidated sand system at 125 ºC. Some experiments were also conducted at 175 ºC. The shape of the resulting relative permeability curves was examined in terms of the displacement process taking place. The measured relative permeability data were also compared to the data available in the literature. Literature Review Relative Permeability Measurement The concept of relative permeability is an empirical extension of Darcy's Law from single to multiphase flow through porous media. Because the validity of this extension is uncertain, great care must be exercised when attempting to extend its area ofapplicability. Measurements of relative permeability have been performed since the mid-3Ds. Wycoff and Botset(1) described the relative permeability concept for oil, gas and water flowing simultaneously through a porous medium.