Carbon Balance of CO2-EOR for Net Carbon Negative Oil Classification

The question of whether carbon dioxide enhanced oil recovery (CO2-EOR) constitutes a valid geologic carbon storage option has been frequently asked by the general public and environmental sectors. Through this technology, operational since 1972, oil production is enhanced by injecting CO2 into depleted oil reservoirs in order displace the residual oil toward production wells in a solvent/miscible process. For decades, the CO2 utilized for EOR has been most commonly sourced from natural CO2 accumulations. More recently, a few projects have emerged where anthropogenic CO2 is captured from industrial facilities and utilized for EOR. Even though CO2 is being captured and therefore prevented from entering the atmosphere, an argument exist as to whether EOR represents a valid option for greenhouse gas emission reduction. The common concern does not question whether CO2 geologic storage occurs or not during EOR, but whether the CO2 volumes stored in the oil reservoir are countered by the CO2 emissions associated with the processes throughout the entire value chain. We intend to answer some of these questions through a DOE-NETL funded study titled “Carbon Life Cycle Analysis of CO2-EOR for Net Carbon Negative Oil (NCNO) Classification”. NCNO is defined as oil whose carbon emissions to the atmosphere, when burned or otherwise used, is less than the amount of carbon permanently stored in the reservoir in order to produce the oil. In this study we develop and apply a universal methodology for estimating the carbon balance of CO2-EOR with the overarching objective of making the determination of whether the oil produced through the operation can be classified as NCNO. As the carbon balance of an EOR operation depends significantly on the volumes of CO2 ultimately stored in the formation, we consider multiple injection scenarios, such as direct CO2 injection (DI) and water alternating gas (WAG) at different ratios. In addition, we consider energy intensive components of the operation not typically included in carbon life cycle analyses and similar studies, such as surface fluid handling. A universal methodology for NCNO classification will certainly benefit CO2-EOR operations as there might be an economic impact if potential future regulations provide value to the emissions and/or storage of CO2.