Large CO₂ Storage Volumes Result in Net Negative Emissions for Greenhouse Gas Life Cycle Analysis Based on Records from 22 Years of CO₂-Enhanced Oil Recovery Operations

Emissions were documented in a greenhouse gas emission life cycle analysis of 22 years of CO 2 -enhanced oil recovery (CO 2 -EOR) operations for a site in the Northern Michigan Basin, U.S. At the site, CO 2 was cycled through a series of 10 carbonate reef structures 1500–2000 m deep in the subsurface. The CO 2 mobilized oil in the reefs, and the operator produced 294 321 metric tons (2 290 000 barrels) of oil with CO 2 -EOR at the site from 1996 to 2017. In the process, a total of 2 089 000 metric tons of CO 2 were stored in the deep rock formations, which is a very large volume for CO 2 -EOR applications of this scale. The life cycle analysis accounted for greenhouse gas emissions related to CO 2 capture, compression, pipeline transport, CO 2 injection, oil processing, CO 2 recycle, dehydration, fugitive emissions, construction, land use, well drilling, oil transport, oil refining, hydrocarbon product combustion, and other processes. The analysis was based on site-specific operational records such as natural gas usage, drilling records, and system flow metering. Altogether, the upstream CO 2 capture, “gate-to-gate” CO 2 -EOR operations, and downstream fuel product refining/combustion had total emissions of 1 929 443 metric tons of CO 2 equivalent. Thus, the life cycle analysis showed −159 907 metric tons of CO 2 equivalent net balance for the CO 2 -EOR system for 1996–2017. The CO 2 -EOR system obtains CO 2 from a gas processing facility that separates CO 2 from natural gas produced in the area, and the CO 2 would be otherwise vented to the atmosphere. A ready source of CO 2 that allowed a large volume of associated CO 2 storage, compressors that run on natural gas, a small pipeline distribution network, highly contained reservoirs, and government incentives to encourage CO 2 storage also contributed to the lower CO 2 emission balance when compared to other CO 2 -EOR life cycle studies. While this site had many favorable factors to result in net negative emissions, it provides an example of managing CO 2 -EOR operations and optimizing associated CO 2 storage to reduce net greenhouse gas emissions.