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

Abstract

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.

A Gate-to-Gate Life Cycle Assessment for the CO2-EOR Operations at Farnsworth Unit (FWU)

“…The natural gas upstream represents the emissions from the recovery of natural gas delivered to the plant; this in many situations is a small quantity since the plant utilizes part of the gases separated in the combustion processes. These are estimates generalized for the processes of these techniques with actual production and injection data from FWU, and the results are similar to published studies [9,15,24]. 6 highlights the emission factors and mass emissions of key unit processes as defined in the boundary of the LCA.…”

“…Thus, improving the energy efficiency of compression would significantly reduce the life-cycle GHG emissions. Unfortunately, increasing the efficiency of compressors is technically challenging [9]. Differences in the life cycle emissions of compressors, however, may differ depending on the energy source since each source has its emission factor (660 kgCO 2 /MWh for coal powered plant, 423 kgCO 2 /MWh for natural gas powered, etc.).…”

“…Injection of pressurized CO 2 into oil reservoirs causes crude oil to swell, decreases viscosity thus increasing crude mobility, and develops miscibility as interfacial tension is reduced [8]. CO 2 -EOR is common in the US in the Permian Basin, Rocky Mountains, Northern Plains, and Louisiana-Mississippi, all regions that have access to natural CO 2 and/or large natural gas processing plants that may produce high volumes of CO 2 as a by-product [9]. International CO 2 -EOR projects include the Weyburn-Midale CO 2 project in Saskaatchewan, Canada and the Lula field in the Santos Basin, Brazil (offshore) [10].…”

“…Figure 7. Reproduced gate-to-gate emission factors of other CO 2 -EOR fields[9], in comparison to FWU CO 2 -EOR.…”

Salt Precipitation and Cement Degradation During Co2storage: A Brief Review

“…Most of these processes are very expensive, nevertheless CO2 captured by these processes can be used to recycle CO2 and produce new products that aggregate values and can be sold transforming such technologies economically feasible [7]. Whilst the aforementioned processes do not become practicable, many companies, mainly oil companies have used their own technologies to store CO2 in aquifer or depleted oil reservoirs, to recover additional oil using CO2 as a tertiary recovery method [8], or in case of unconventional scenarios, as shales gas in USA, CO2 has been used as a working fluid to efficiently fracture the reservoir [9], or in Brazil's pre-salt fields, where the content of CO2 can reach up to 44%, the produced CO2 is directed reinjected into the same reservoir to solve simultaneously two problems, CO2 releasing to atmosphere and enhanced oil recovery (EOR) [10]. Despite the oil industries have been using CO2 injection for more than 20 years, they are still facing different challenges [11].…”