Evaluation of Enhanced Oil Recovery Potential using Interfracture Water Flooding in a Tight Oil Reservoir

The recovery factor of horizontal wells in tight reservoirs after stage fracturing is low. The effect of water huff-puff on enhancing oil recovery is not obvious. Water channeling is serious during interwell water displacement. Conventional EOR (enhance oil recovery) methods are not effective. Scholars have proposed the method of interfracture water flooding after horizontal well fracturing to improve recovery efficiency in tight reservoirs. In order to study the EOR effects of interfracture water flooding and huff-puff in tight reservoirs, three different EOR schemes were designed: interfracture synchronous water flooding (IFSWF), interfracture asynchronous water flooding (IFAWF), and water huff-puff. The experiment results show the following: (1) in the physical simulation experiment of homogeneous cores, after injection of 0.8 PV formation water, the recovery rates of huff-puff, IFAWF, and IFSWF were 25.7%, 33.7%, and 38.6%, respectively. (2) In the simulation of fractured cores, the oil concentration of IFAWF is 2.7 times higher than that of IFSWF. (3) In the simulation of formation energy replenishment by fractured core, the formation pressure increased by IFAWF is 1.9 times higher than the pressure increased by IFSWF. The results of this study show that interfracture asynchronous flooding can increase the utilization efficiency of injected water, overcome heterogeneity, effectively supplement the energy of tight reservoir, increase the swept area, and improve the recovery factor. IFAWF is a more suitable EOR method for tight reservoirs. The findings of this study contribute to a better understanding of how to select methods to enhance tight oil recovery. At the same time, it provides a method and idea for improving oil recovery of shale oil with lower reservoir physical properties.