Minimizing Greenhouse Gas Footprint of Enhanced Oil Recovery Operations Through Optimizing Injected Fluid Composition

Abstract Most oil and gas fields face the dual challenge of optimizing recovery and minimizing CO2 and greenhouse gas footprint from depleting fields. Although tertiary recovery strategies including CO2 and produced gas injection are adopted, the cost and miscibility uncertainty associated with pure CO2 and produced gas streams remains a challenge. Therefore, this paper assesses the impact of pure and blended compositions of produced gas and CO2 in simultaneously improving the oil recovery efficiency and minimizing the GHG footprint of petroleum development projects. We performed an experimental coreflood of a single-stage water alternating gas flood using CO2. Carbonate cores and crude oil with properties typical to a Permian field were studied. X-ray computed tomography (CT) before and after gas injection enabled investigations of fluid retention at the core scale. A sample field model was applied to investigate the impact of injected fluid composition on field-scale GHG reduction and oil recovery. We observed increased CO2 storage in the optimal produced gas and CO2 blend compared to pure CO2 injection. We benchmarked the GHG emissions and oil recovery across differing injected gas compositions at the end of the WAG flood against a base case of waterflooding only. Our results revealed lower emissions and high recovery by switching to an optimal injection composition. The results suggest optimal compositions of produced gases and CO2 exist with a capacity to further improve the oil recovery and storage efficiency of CO2 while minimizing the overall GHG footprint of oil and gas operations. We demonstrate experimentally how alteration of injected fluid composition can simultaneously increase oil recovery, reduce GHG emissions, and increase CO2 storage capacity. Adoption of this work has the potential to mitigate the flaring of produced gases and costs associated with pure CO2 injection while ensuring low carbon footprint operations in the oil and gas sector.