Gate-to-gate life-cycle assessment of immiscible CO2-EOR operation in heavy oil using real operation data

The urgent need to reduce greenhouse gas emissions while meeting global energy demands requires innovative approaches in oil production methods. While CO2 Enhanced Oil Recovery (CO2-EOR) shows promise, comprehensive life-cycle assessment (LCA) of its environmental impact and its dynamics in heavy oil fields remain limited. This study uses operation data from the Mervin oil field in Saskatchewan, Canada, to evaluate the LCA of CO2-EOR in a heavy oil reservoir. The Oil Production Greenhouse Gas Emissions Estimator (OPGEE) enables analysis of gate-to-gate carbon intensity and CO2 sequestration effectiveness in immiscible CO2 huff-and-puff operations. This work demonstrates that the studied CO2 huff-and-puff method for heavy oil EOR can achieve an average negative gate-to-gate carbon intensity of -1.99 gCO2eq./MJ considering full CO2 sequestration credit. This method reduces carbon intensity by 156% compared to traditional thermal EOR techniques, even without carbon credits. Emission sources include venting, burner, and vaporizer operations, contributing 68% of total emissions. The CO2 sequestration ratio decreases from 60% in first three years to 17% later, reflecting operational changes and varying fresh liquid CO2 injection ratios. This work provides useful insights for implementing and optimizing CO2-EOR systems in shallow heavy oil fields worldwide, contributing to less carbon intensive oil production practices.