The carbon dioxide (CO₂) sequestration capacities of selected oil fields in the Williston Basin, Powder River Basin, and Denver-Julesberg Basin in the northern Great Plains region of North America were estimated as part of the Plains CO₂ Reduction (PCOR) Partnership regional characterization. The estimates were developed using readily available reservoir characterization data obtained from the petroleum regulatory agencies and/or geological surveys from the oil-producing states and provinces of the PCOR Partnership region. Reconnaissance-level sequestration capacities were calculated using two methods depending on the nature of the readily available reservoir characterization data for each field. Maximum storage capacities were estimated for reservoirs where detailed data on original oil in place, cumulative production, reservoir thickness, porosity, temperature, pressure, and water saturation were available. The initial reconnaissance-level estimates indicate that more than 1100 oil fields within the three basins have a capacity to sequester nearly 10 billion tons of CO₂, with the potential to produce more than 2 billion bbl of incremental oil through CO₂-flood enhanced oil recovery activities.