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 that are profitable, provided enough HCPV (hydrocarbon pore volume) of CO₂ is injected in the reservoir and sweep and that 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:

1. reducing CO₂ injection pressure thereby reducing the volume of purchased CO₂ while at the same time maintaining miscibility (optimum displacement efficiency) and
2. exploring the possibility of mobilizing reserves in the water-oil transition zone below the original oil-water contact.