Clarifying the Relationship of Enhanced Oil Recovery with Associated Storage of CO2

Carbon dioxide (CO₂) enhanced oil recovery (CO₂ EOR) is a proven technology to increase production from, and extend the lifespan of, conventional oil fields. The financial benefit of incremental oil production provides the motivation for CO₂ EOR operations. Growing interest in capturing anthropogenic CO₂ across a range of industrial sectors, motivated by recent 45Q tax credits, could translate to significant opportunities to expand the scale of CO₂ EOR operations across the United States. When anthropogenic CO₂ sources are used, widespread misconceptions still exist concerning the relationship between the CO₂ EOR process and the associated CO₂ storage that occurs as a consequence.

Metrics used by reservoir engineers, including CO₂ utilization factors, CO₂ retention, and incremental oil recovery, allow determination of EOR efficiency and the associated storage. The ability of geologic reservoirs to retain buoyant hydrocarbon fluids over geological timescales, combined with a CO₂ recycling system, maximizes the use of purchased CO₂ and ensures virtually all purchased CO₂ is ultimately stored.

Over 6 Mt of associated CO₂ storage incidental to CO₂ EOR has occurred at the Bell Creek oil field, illustrating the relationship between associated storage and EOR. Injection and production data collected from Bell Creek illustrate temporal relationships between purchased, recycled, and injected CO₂ quantities, utilization rates, and associated storage. A research-monitoring program conducted at Bell Creek by the Plains CO₂ Reduction (PCOR) Partnership effectively tracked injected CO₂ in the reservoir and demonstrated an absence of discernible impacts to shallow groundwater, surface water, and other environmental receptors.

The Energy & Environmental Research Center (EERC) has used this detailed knowledge of the generic relationship between EOR and associated storage to determine the potential economic and carbon management benefits of CO₂ EOR deployment in conventional oil fields across North Dakota.