High-Temperature Relative Permeabilities for Athabasca Oil Sands

Abstract

An experimental study of Athabasca bitumen/water relative permeabilities revealed little or no temperature effect on the relative permeabilities to water and bitumen over a range of 100 to 250°C [212 to 482°F]. Comparable results were obtained with both steadyand unsteady-state relative permeability measuring techniques. It was determined that the oil-phase relative permeability curve was convex. Measured curves were also compared with those obtained by history matching. IntroductionRelative permeability is one of the most important input variables for numerical reservoir simulation models. Knowledge of relative permeability curves and residual fluid saturations is needed to determine the oil production rate and ultimate recovery, respectively.Relative permeability generally has been represented as a function of saturation. Experimental measurement techniques developed in the 1950's and early 1960's for light-oil reservoirs include the steady-state technique and the unsteady-state, or dynamic, method. The latter has received more attention because of its faster turnaround time. Neither method seems superior, however, because of limitations inherent in each.Because of the experimental difficulties encountered in determining relative penneabilities, a suitable laboratory procedure that eliminates inlet and outlet end effects and resulting saturation gradients must be used. The experimental conditions usually are idealized and simplified by the use of small core plugs or reconstituted sand cores and rermed oils rather than native reservoir materials.The objective of this study was to measure experimentally the relative permeability to water and bitumen in unconsolidated sand cores. The difficulties of this task were compounded by the system's high temperatures and pressures and the bitumen's high viscosity . No published experimental data on residual fluid saturations, relative permeability curves, and the effect of temperature on these parameters exist for the Athabasca oil-sand system.'The temperature and pressure conditions encountered in the recovery of oil-sand bitumens (1.02 to 0.97 g/cm3 [8 to 14° API]) from deeply buried formations were reproduced in this study. Because of conflicting results in the literature regarding the effect of temperature on relative permeability, a simple system focusing on the fundamental properties that might cause temperature effects was used. The selected system consisted of unconsolidated silica sand, deionized water, and solvent-extracted Athabasca bitumen. Measurements were performed in the 100 to 250°C [212 to 482°F] temperature range. These idealized conditions minimized clay migration and high-temperature corrosion. The use of crude oil more closely represented the field conditions. In this way, experimental diffiulties were alleviated and the interpretation of relative permeability determination was eased.

Effect of Temperature on Athabasca Type Heavy Oil – Water Relative Permeability Curves in Glass Bead Packs

“…Sufi et al (1982) and Miller and Ramey (1985) have concluded that the variations in relative permeability with temperature are probably not related to fundamental flow properties and they are rather related to experimental artifacts. Polikar et al (1990) also stated that it is not possible to predict theoretically what the effect of temperature on relative permeabilities could be, and the results are system specific. Maini and Okazawa (1987) have also concluded that due to several artifacts involved in the experiments no effect of temperature could be justified.…”

“…After initializing the core, the separator was connected and the imbibitions process was initiated by injecting water at a rate of 0.8 cc/min. This rate was even less than 1 PV/h as recommended by Polikar et al (1990). During the water injection phase, the oil production was recorded versus time, and the pressure differential across the core was monitored as well.…”

“…On the other hand, there are some results published in the literature confirming no effect of temperature neither on the relative permeability nor on the end point saturations (Wilson, 1956;Sufi et al, 1982;Miller & Ramey, 1985). The two latter have concluded that the previously reported temperature dependant behaviors of relative permeability and residual saturations might have been affected by viscous instabilities, capillary end effects and / or difficulties in maintaining material balance (Polikar et al, 1990).…”

“…Maini and Batycky (1985) have also conducted their experiments on heavy oil and indicated the variations with temperature except for the k rw . Polikar et al (1990) worked specifically with Athabasca type bitumen and proposed no dependency on temperature. Sedaee Sola et al (2007) have performed some experiments using heavy oil and reported dependencies on temperature.…”

Temperature effects on the heavy oil/water relative permeabilities of carbonate rocks

“…They concluded that the obtained relative permeability increased with temperature. Polikar et al (1990) studied the effect of temperature on Athabasca oil sands. They used both steady and unsteady-state methods in the temperature range of 212-482°F and concluded that the results cannot be generalized due to unstable condition and viscous fingering.…”