Simulation of Inter-Fracture Injection and Production in Tight Reservoirs Based on Compartmental Embedded Discrete Fracture Model

Abstract

Abstract Although hydraulic fracturing enables economic production from tight formations, production rates usually decline quickly and result in low hydrocarbon recovery. Moreover, it is difficult for conventional flooding methods to provide enough energy supplement in the tight formations. This paper develops an innovative approach to enhance oil recovery from tight oil reservoirs through inter-fracture injection and production, including synchronous inter-fracture injection-production (SiFIP) and asynchronous inter-fracture injection-production (AiFIP). This improves flooding performance by transforming fluid injection between different wells to between adjacent fracture stages from the same horizontal well. The multi-stage fractured horizontal well (MFHW) comprises of recovery fractures (RFs), injection fractures (IFs) and natural fractures. In all the cases demonstrated in this work, the odd fractures and even fractures are defined as RFs and IFs respectively. Fluid is injected into IFs from injection tubing, and hydrocarbon is recovered synchronously or asynchronously through oil tubing connecting to the RFs. To quantitatively evaluate the performance of SiFIP and AiFIP in tight oil reservoirs, reservoirs are simulated based on the compartmental embedded discrete fracture model (cEDFM). The production performance of different recovery methods is compared, including primary depletion, water flooding, CO2 flooding, water Huff-n-Puff, CO2 Huff-n-Puff, SiFIP (water), SiFIP (CO2), AiFIP (water), AiFIP (CO2). The AiFIP and SiFIP achieve higher cumulative oil production than other methods. AiFIP obtained the highest cumulative oil production, which is more than two times that of primary depletion. The AiFIP (CO2) obtained almost the same cumulative oil production with SiFIP (CO2) with only 50% of CO2 injection rates, and AiFIP (water) obtained 19.3% higher cumulative oil production than SiFIP (water) with only 50% of water injection rates. Therefore, AiFIP is also a better choice when CO2 or water resource is not abundant. Sensitivity analysis is carried out to discuss the impacts of fracture and injection parameters on cumulative oil production. The fracture spacing, fracture networks, and injection rates influence the production significantly, followed by injection-production schedule and fracture length. The recommended well completion schemes of AiFIP and SiFIP methods are also provided, which is significant for the potential application of the proposed methods. This work illustrates the feasibility of SiFIP and AiFIP to enhance hydrocarbon recovery in tight reservoirs.