Synergistic mechanism of enhanced heavy oil recovery by compound flooding using 3D visualization model

Abstract

Most of oilfields have entered the development stage of high water-cut and low recovery factors, and stabilizing oil production and controlling water production are the key to enhancing subsequent oil recovery. Adopting the 1/4 five-point injection-production well pattern, the chemical flooding experiments were conducted using a three-dimensional (3D) visualization sand-pack model with liquid drain orifices. A real-time image acquisition and dynamic observation device for detecting droplet textures as fluid flowing was developed with experimental system. In heterogeneous reservoirs with a high permeability contrast, the effects of oil-displacement agents on production dynamics, sweep morphology, and emulsifying characteristics of remaining oil at different locations were investigated to reveal the synergistic mechanism of compound flooding for enhanced oil recovery. The results showed that, in the main streamline region, the mean droplet diameter decreased, the distribution density increased first and then decreased, and the maldistribution decreased first and then increased with an increase in injection volume of the compound system. In the vertical region with the main streamline, the mean diameter and maldistribution reduced, and the distribution density increased owing to the synergistic mechanism. The viscosity reducer can increase sweep efficiency by 8.34% and recovery factor by 5.95% due to the viscous crossflow in the high permeability channel. The compound system can increase sweep efficiency by 15.92% and recovery factor by 12.67% due to the synergistic effect of emulsifying-tapping, emulsion plugging conversion, and profile control. Therefore, chemical compound flooding has great potential of enhancing heavy oil recovery in heterogeneous reservoirs due to the synergistic effect of the compound system.