Experimental investigation of the live oil-water relative permeability and displacement efficiency on Kingfisher waxy oil reservoir

Abstract

Oil-water relative permeability is not only the basis for studying the oil-water two-phase flow characteristics, but also one of the indispensable parameters for the reservoir numerical simulation and production dynamic analysis. Waxy oil has obvious viscosity-temperature characteristics and wax precipitation phenomenon, resulting in complex and diverse factors affecting the relative permeability. Presently, no systematic investigation on the oil-water relative permeability and displacement efficiency of wax oil reservoir exists, especially using live oil as experimental oil. In this paper, the accurate wax appearance temperature (WAT) and necessary aging time of experimental oil and cores were determined using ultrasonic detection and spontaneous imbibition methods, respectively. Subsequently, the viscosity, wettability, relative permeability and displacement efficiency of live oil and crude oil were compared and analyzed at different temperatures. Finally, the influencing factors of live oil-water relative permeability and displacement efficiency, namely, solution gas, temperature, permeability, wettability, water injection parameters and wax precipitation were comprehensively analyzed and studied. Experimental results showed that the WAT, wettability and viscosity of live oil are different from those of crude oil, thereby causing the difference in relative permeability and displacement efficiency of live oil and crude oil. When the temperature is above the WAT, the dominate influencing factor is oil viscosity, while the effect of core permeability is not obvious. When the temperature drops below the WAT, the precipitated wax not only causes a sharp increase in the oil viscosity, but also forms a wax film on the surface of flow channel to transform the rock wettability from hydrophilicity to lipophilicity. Furthermore, the wax film narrows the flow channel and the wax particles block the small pore throats. All these changes caused by wax make the relative permeability and displacement efficiency before and after the wax precipitation very different. The effect of permeability becomes significantly because of the physical deposition and pore throat plugging. Similarly, the displacement efficiency of different water injection parameters is the result of the interaction of multiple mechanisms. This investigation not only provides a systematic and reliable measuring method for the oil-water relative permeability and displacement efficiency of waxy live oil reservoirs, but also improves our understanding of the multiphase flow mechanisms in waxy oil reservoir.