Experimental and Numerical Modeling of Three-Phase Flow Under High-Pressure Air Injection (HPAI)

Abstract

In this paper, an improved characterization of three-phase flow under HPAI conditions was achieved based on experimental results and numerical reservoir simulation.A three-phase coreflood experiment was conducted at reservoir conditions, using 37˚API stock tank oil, 84% nitrogen -16% carbon dioxide flue gas mixture, and 3% KCl brine. The aim of the test was to evaluate the effects that the highly liquid-saturated front produced by the thermal reactions has on the mobility of each phase. Departing from connate water saturation and reservoir pressure and temperature, sequential injection of water, gas and oil was carried out, followed by a final gas flood to residual liquid saturation. Other twoand three-phase tests performed on this rock specimen were published elsewhere. Numerical history matching was employed to determine oil-water and liquid-gas relative permeability (k r ) curves for both imbibition and drainage cases. A Combustion Tube (CT) test was simulated using both conventional k r curves and a set including hysteresis. The degree of hysteresis observed during the coreflood test was maintained for the CT simulation.History matching of the coreflood showed that k r to the gas phase is much smaller during liquid re-imbibition than during drainage. The use of gas phase hysteresis for the CT test allows for a better matching of liquid volumes and pressure drop. Analysis of the simulated data suggests that the reduction in gas phase mobility encourages an early increase in the oil rate, which is more consistent with experimental data than that predicted by a model with conventional k r . It also reveals that water distilled below the saturated steam temperature plays an important role on the increase of liquid saturation and oil mobilization.The improved characterization on relative permeability considering gas phase hysteresis for simulating HPAI enhances the predictive capability of the available commercial simulators, providing a more certain method to evaluate the technical and economical feasibility of a project. The ability to predict an early increase in oil rate, consistent with experimental observations, results in improved economics for the project.