Simulation study of CO2 and water alternating gas (WAG) injection for enhanced oil recovery in a green field reservoir

CO₂-enhanced oil recovery (EOR) offers a dual benefit of boosting hydrocarbon production while reducing greenhouse gas emissions. While widely applied in mature reservoirs, its potential in green field settings, reservoirs with no prior production, remains underexplored. In this study, CO₂ injection was selected based on favorable reservoir conditions: light oil (density 800.91 kg/m³), high initial pressure (300.94 bar), and moderate-to-high permeability (228.15 md), which together support miscible displacement and efficient sweep. This study investigates the performance of three EOR strategies: continuous CO₂ injection, water injection, and water alternating gas (WAG), using a synthetic green field reservoir. The objective is to evaluate recovery efficiency and sensitivity to key parameters. A three-phase, fully implicit black oil simulation was conducted using ECLIPSE 100, selected for its compatibility with available fluid data and built-in miscible flood option. The model featured a vertical injector–producer pair and a 20-year simulation period. Sensitivity analysis was performed on injection rate, reservoir pressure, porosity, permeability, and WAG cycle duration. CO₂ injection yielded the highest recovery (71.6% OOIP), followed by WAG (69.6%) and water injection (38.6%). Key reservoir parameters included porosity of 0.2285, permeability of 228.15 md, and initial pressure of 300.94 bar. Limited variation in WAG performance was observed due to the narrow cycle range tested.