The Water Flooding Seepage Mechanism in the Inter-Fractures of Horizontal Wells in Tight Oil Reservoirs

Tight oil reservoirs face significant challenges, including rapid production decline, low recovery rates, and a lack of effective energy replenishment methods. In this study, a novel development model is proposed, based on inter-fracture injection following volumetric fracturing and relying on a high-temperature and high-pressure large-scale physical simulation system. Additionally, the CMG (Computer Modelling Group Ltd., Calgary City, Canada) software is also used to elucidate the impact of various single factors on the production of horizontal wells while filtering out the interference of others. The effects of fracture spacing, fracture half-length, and the injection-production ratio are studied. Results indicate that under rejection pressures of 6.89, 3.45, and 1.88 MPa, the times to establish stable flow are 50, 193, and 395 min, respectively. Higher injection pressures lead to an increased oil recovery efficiency, with the highest observed efficiency at 16.93%. This indicates that, compared with conventional medium and high permeability reservoirs, tight oil reservoirs exhibit similar pore throats and larger capillary forces when oil and water flow in both phases. Higher pressures reduce capillary forces, displacing more oil droplets, thus enhancing oil recovery efficiency. Moreover, under inter-fracture displacement conditions, the pressure gradient at both the injection and production ends remain consistent, with minimal pressure loss near the wellbore. This feature ensures that the crude oil in the middle of the reservoir also possesses displacement energy, thereby enhancing overall crude oil displacement efficiency.