Feasibility of CO2-water alternate flooding and CO2 storage in tight oil reservoirs with complex fracture networks based on embedded discrete fracture model

Carbon Capture, Utilization and Storage (CCUS) becomes an efficient means to reduce CO2 emissions, enhance oil recovery (EOR) and increase CO2 sequestration. However, how to achieve the optimal EOR-Storage performance is challenging due to strong matrix heterogeneity, multi-scale fractures and complicated phase behavior. Gas breakthrough is often observed, decreasing CO2 macroscopic sweep efficiency and swept volume. This work tries to improve the EOR-Storage performance by CO2-water alternate flooding (CO2-WAG) and CO2 storage in tight oil reservoirs with complex fracture networks (CFN). The non-intrusive embedded discrete fracture model (EDFM) is used due to its high accuracy and low computation costs. An integrated numerical model of CO2-WAG and CO2 storage is developed to simulate the mass transfer and phase behavior of crude oil, water and CO2. The production performance is evaluated by different exploitation methods, including primary depletion, water flooding, continuous gas injection (CGI) and CO2-WAG. The parameters of CO2-WAG and CO2 storage are optimized, and gas breakthrough and CO2 plume migration are analyzed. The optimal CO2 EOR-Storage scheme is proposed, and oil production performance, storage capacity, dynamic migrating behavior of CO2 plume and minerals changes are predicted. This work offers guidance for CO2 EOR-Storage optimization in hydrocarbon reservoirs with CFN.