An Investigation into the Relative Effectiveness of CO2 and Hydrocarbon Gas as an EOR Injectant for a Marginal Onshore USA Sandstone Reservoir

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CO2 injection is a widely employed and highly successful method for Enhanced Oil Recovery (EOR) onshore USA. Despite the benefits, there are significant challenges to CO2 injection, including corrosion and adverse rock–mineral interactions. Furthermore, CO2 supply is not always easily available, and gas transportation costs may be prohibitive especially for marginal assets. The shale boom has flooded the market with natural gas, with an accompanying drop in gas prices. The relative abundance of hydrocarbon gas warrants investigation into the viability of using this gas as a CO2 substitute. Coreflooding and slimtube experiments were carried out to compare the effectiveness of supercritical hydrocarbon gas and CO2 injection for enhanced oil recovery. These experiments were used to calibrate a numerical simulation model. Different blends of hydrocarbon gasses were assessed as EOR injectants resulting in the proposal of a gas mixture with displacement efficiencies comparable to CO2.