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 CO 2 Enhanced Oil Recovery (CO 2 -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 CO 2 -EOR in a heavy oil reservoir. The Oil Production Greenhouse Gas Emissions Estimator (OPGEE) enables analysis of gate-to-gate carbon intensity and CO 2 sequestration effectiveness in immiscible CO 2 huff-and-puff operations. This work demonstrates that the studied CO 2 huff-and-puff method for heavy oil EOR can achieve an average negative gate-to-gate carbon intensity of -1.99 gCO 2 eq./MJ considering full CO 2 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 CO 2 sequestration ratio decreases from 60% in first three years to 17% later, reflecting operational changes and varying fresh liquid CO 2 injection ratios. This work provides useful insights for implementing and optimizing CO 2 -EOR systems in shallow heavy oil fields worldwide, contributing to less carbon intensive oil production practices. • Real time-series operation data for CI assessment of heavy oil field CO 2 -EOR. • Net negative gate-to-gate CI of CO 2 -EOR huff-and-puff given full carbon credit. • Significant carbon intensity reduction via CO 2 -EOR compared to thermal EOR method. • CO 2 vaporizer, storage tanks heater, and venting as primary CI contributors.