North Dollarhide (Devonian) Unit: Reservoir Characterization and CO₂ Feasibility Study

In order to implement a CO₂ flood in the North Dollarhide (Devonian) Unit (NDU), detailed reservoir characterization and engineering studies were prepared using 3-D seismic, classical geology and reservoir engineering, and a fieldwide reservoir simulation. Routine and special core analyses, PVT analyses, and well tests taken during recent development aided in the reservoir and fluid characterizations. A black oil reservoir model matched available production and pressure history of the reservoir, and forecasted future production under water injection and CO₂ injection using mixing rules developed with the aid of a 1/4 5-spot compositional model. History matching presented a special challenge since Devonian and uphole Clearfork production was commingled between late 1970 and 1990, and therefore actual Devonian production and pressures were not implicitly known.