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 CO2-enhanced oil recovery (CO2-EOR) operations for a site in the Northern Michigan Basin, U.S. At the site, CO2 was cycled through a series of 10 carbonate reef structures 1500-2000 m deep in the subsurface. The CO2 mobilized oil in the reefs, and the operator produced 294 321 metric tons (2 290 000 barrels) of oil with CO2-EOR at the site from 1996 to 2017. In the process, a total of 2 089 000 metric tons of CO2 were stored in the deep rock formations, which is a very large volume for CO2-EOR applications of this scale. The life cycle analysis accounted for greenhouse gas emissions related to CO2 capture, compression, pipeline transport, CO2 injection, oil processing, CO2 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 CO2 capture, "gate-to-gate" CO2-EOR operations, and downstream fuel product refining/combustion had total emissions of 1 929 443 metric tons of CO2 equivalent. Thus, the life cycle analysis showed -159 907 metric tons of CO2 equivalent net balance for the CO2-EOR system for 1996-2017. The CO2-EOR system obtains CO2 from a gas processing facility that separates CO2 from natural gas produced in the area, and the CO2 would be otherwise vented to the atmosphere. A ready source of CO2 that allowed a large volume of associated CO2 storage, compressors that run on natural gas, a small pipeline distribution network, highly contained reservoirs, and government incentives to encourage CO2 storage also contributed to the lower CO2 emission balance when compared to other CO2-EOR life cycle studies. While this site had many favorable factors to result in net negative emissions, it provides an example of managing CO2-EOR operations and optimizing associated CO2 storage to reduce net greenhouse gas emissions.