The objective of this paper is to evaluate experimentally, the effect of temperature on the three-phase brine-oil-gas relative permeabilities of an unconsolidated sand system. Two and three-phase relative permeabilities have been measured at 75 °C and 125 °C. The experiments were performed under steady-slate conditions. These measurements were conducted in Ottawa sand using a clean mineral oil, 1% brine and nitrogen gas.
The measured relative permeabilities showed no significant temperature effect. The three-phase brine relative permeability was found to be a function of brine saturation alone. The three-phase gas relative permeability was always lower than the two-phase values. This is consistent with some of the previously published results. The oil relative permeability was found to vary with the saturations of the other fluids. Oil isoperms were concave towards the oil apex. Filially, oil relative permeabilities were compared with predictions obtained using modifications of Stone's method I and II. The prediction of Stone I was good for both temperatures. But Stone II predictions were consistently lower than the experimental values.
Three-phase relative permeability plays an important role in the numerical simulation of oil recovery processes. Thermal methods for heavy oil recovery, such as steam drive and in-situ combustion involve the simultaneous flow of three immiscible fluids through the porous rock formation at elevated temperatures.
Over the past 25 years, a number of studies have reported temperature effects on two-phase relative permeabilities in porous media. Several of these1–6 report a significant effect of temperature on oil/water relative permeability. Although it is probable that three-phase relative permeabilities would also be temperature sensitive, no experimental study of the effect of temperature on three phase relative permeability has been reported. Whether or not three-phase relative permeabilities are temperature sensitive for a given system can only be determined by experimental evaluations.
The objective of this work was to evaluate experimentally whether the three-phase relative permeabilities are temperature sensitive for a given system or not.
The experiments were performed under steady-state conditions, thus minimizing instability phenomena. and allowing for control of saturation history. The relative permeability for each fluid was calculated by applying the following form of Darcy's law to each fluid: Equation (1) (Available in full paper)
All the variables in Equation 1 (other than q, and ΔP1 can be measured separately. Because the usual objective of such measurements is to determine the relationship between relative permeability and saturation, it was also necessary to measure the saturation of each fluid under steady-state conditions for each set of flow rates. Oil saturation was measured by the material balance method. Brine saturation was measured by the electrical resistivity method. A calibration curve, relating the electrical resistivity index of the core to its brine saturation, was established by carrying out two phase oil/brine and gas/brine tests. The resistivity index was measured directly by measuring the ratio of the electrical resistance of the core and the resistance of the fully brine saturated secondary cell.