Experimental study on physical modeling of flow mechanism in volumetric fracturing of tight oil reservoir

Abstract

This paper investigates the characteristics of oil-water two-phase flow after volumetric fracturing of horizontal wells in tight reservoirs. Based on a large-scale high-pressure, high-temperature experimental system for modeling horizontal well injection and production, the characteristics of the pressure distribution, cumulative liquid production, recovery factor, and liquid production rate of a matrix model and fractured model during the waterflooding process are compared and analyzed. The results show that, for both types of reservoirs, the fluid forms a high-pressure zone and a low-pressure zone during water injection. As the development progresses, the high-pressure zone continuously moves forward. There is a pressure step between the high-pressure zone and the low-pressure zone, which gradually decreases in magnitude as the pressure wave reaches the well. By this time, the main resistance before water breakthrough is the pressure step at the waterflooding front. The ultimate recovery is found to be 26.71% for the matrix model and 28.48% for the fractured model. Without an effective displacement system, the resistance of the horizontal well during waterflooding mainly acts on the oil-water interface. After the establishment of an effective displacement scheme, the resistance gradually expands to both sides of the water-swept zone. At this point, the formation of a dominant channel greatly weakens the displacement performance. Thus, it is necessary to rely on imbibition or surfactants in the later stages to improve the recovery factor.