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

Hamling, J. A. - Presenter, University of North Dakota
Wildgust, N., University of North Dakota
Sorensen, J. A., University of North Dakota
Peck, W., UND Energy & Environmental Research Center
Gorecki, C. D., University of North Dakota

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.