Wellman Unit CO2 Flood: Reservoir Pressure Reduction and Flooding the Water/Oil

Abstract

Abstract CO2 injection is a proven technology. Results from two decades of reservoir and economic performance prove that CO2 can 1) be transported over large distances via pipeline 2) handled and injected easily at well-site facilities and 3) recover oil that water injection could not mobilize. This has been accomplished at cost levels which are profitable provided enough HCPV (hydrocarbon pore volume) of CO2 is injected in the reservoir and sweep and displacement efficiency are sufficient. The most recent challenge involves optimizing efficiency of CO2 flooding, i.e. maximizing oil recovery while at the same time reducing operating expenses. A useful method to attain the goal of CO2 flood optimization is careful performance review of better performing CO2 floods. The Wellman Unit CO2 flood has a long history. This CO2 flood is one of the most successful CO2 floods documented in terms of CO2 utilization, i.e. MCF of CO2 required to recover one barrel of oil. This paper explores the role of laboratory experimentation for improvement of performance of a mature CO2 flood. In this paper, we will review the history of the Wellman Unit CO2 flood and examine two possibilities to optimize reservoir performance:Reducing CO2 injection pressure thereby reducing the volume of purchased CO2 while at the same time maintaining miscibility (optimum displacement efficiency) andExploring the possibility of mobilizing reserves in the water-oil transition zone below the original oil-water contact. P. 39