Enriched-Gas Miscible Flooding: A Case History of the Levelland Unit Secondary Miscible Project

Abstract

Performance is reviewed of an enriched hydrocarbon-gas Performance is reviewed of an enriched hydrocarbon-gas miscible-displacement process in the Levelland Unit. Cyclic injection of enriched gas and water has been in progress for about 4 years. No significant operational problems have been encountered. The project is experiencing response, but peak response has not yet been reached. Performance indicates this project will be an economic success. Performance indicates this project will be an economic success. Introduction The Levelland Unit secondary miscible project consists of 28 injection wells and 40 producing wells in the west central portion of the Levelland Unit, Levelland field, Hockley County, Tex. (Fig. 1). Production is from the San Andres formation at an average depth of 4,900 ft. The discovery well for this reservoir was drilled in 1946. The field was developed originally on a well spacing of 42.5 acres/well. In 1954, the Levelland Unit was formed to conduct secondary recovery operations. A pressure maintenance program was initiated in 1955, consisting of dry gas program was initiated in 1955, consisting of dry gas injection into 18 wells scattered within the unit. Three of these former dry gas injectors are located in the secondary miscible project. All dry gas injection operations had ceased by Feb. 1971. Water injection was initiated in parts of the Levelland Unit in Oct. 1964; however, water parts of the Levelland Unit in Oct. 1964; however, water injection in the area that became the secondary miscible project did not begin until later. project did not begin until later. In April 1970, the west central portion of the Levelland Unit was evaluated for infill drilling and possible miscible flooding. Infill development would establish a well spacing of 21.25 acres/well and was justified for either the straight waterflood case or for a miscible-flood case. All the proposed infill drilling has been completed. Original plans included miscible flooding of the entire west central portion of the unit. This was to be done in two phases beginning with 28 injection wells in the Phase 1 phases beginning with 28 injection wells in the Phase 1 area, with the remaining wells to the south to be converted at a later date; however, because of supply limitations of enriched gas, the Phase 2 area has remained on waterflood. Enhanced recovery will not take place in the Phase 2 area as a secondary operation. If enhanced recovery takes place as a tertiary-type operation, it most likely will be a place as a tertiary-type operation, it most likely will be a CO2 miscible flood rather than hydrocarbon miscible because of an insufficient additional supply of enriched gas. P. 919