The Slaughter Estate Unit CO2 Flood A Comparison Between Pilot and Field Scale Performance

This paper describes the performance of both a pilot and a Unit-wide carbon dioxide (CO2) flood in the Slaughter Estate Unit, Slaughter Field, Hockley County, Texas. The performance and design of both projects are compared and contrasted. The comparison yields insight into the process, the impact of flood design variables, and the effects of project scale. Between 1976 and 1984, Amoco Production Company conducted a pilot flood consisting of a double five-spot pattern of twelve acres in the Slaughter Estate Unit. A stream of CO2 and hydrogen (H2S) sulfide gas was injected using an alternating gas water injection ratio of 1:1 followed by chase gas. A 65% hydrocarbon pore volume (HCPV) slug of gas was ultimately injected. The pilot project has been the topic of several SPE papers. This paper summarizes the performance to provide a basis for comparison with the performance of the Unit-wide project. The pilot performance was extremely encouraging and supported a recommendation to implement a field scale flood in the Unit. In 1982, Amoco approved a project to start up a Unit-wide CO flood and injection began in late 1984. The original design of the Unit-wide flood involved injecting a 30% HCPV slug of pure CO2 using a 2:1 gas alternating water injection ratio. In response to changing 011 prices, the gas-water injection ratio and slug size have been modified to maximize the profitability of the project. The resultant gas-water injection ratio scheme is also expected to improve vertical sweep and reduce gas handling requirements. The Unit-wide project has responded very favorably to the injection of C02.