East Vacuum Grayburg-San Andres Unit CO2 Injection Project: Development and Results to Date

Abstract

ABSTRACT The East Vacuum Grayburg-San Andres Unit, operated by Phillips Petroleum Company, is the site of the first full scale miscible carbon dioxide injection project in the State of New Mexico. Since unitization in December, 1978, the unit has undergone infill drilling, repressurization by water injection, and is now in its second WAG (water-alternating-gas) cycle of CO2 injection. Early engineering efforts, based on the high fluid conductivity of the reservoir, prescribed the use of larger than normal downhole equipment in conjunction with the choice of an injection pattern with a high producer to injector ratio. This effort made possible the very short transition time between late primary production and early tertiary development. Due to over thirty years of primary production, reservoir pressure in the unit had fallen well below minimum misciblility pressure. Reservoir repressurization, accomplished with water injection, was conducted prior to the initiation of CO2 injection in September, 1985. During this time, the injection scheme was also determined, contracts for the purchase and delivery of the CO2 were negotiated, and design and construction of the CO2 injection system and produced gas gathering system were completed. Handling of the CO2 contaminated hydrocarbon gas production was also considered, resulting in the design and construction of a dehydration and reinjection facility. Treatment of the produced gas for the recovery of hydrocarbons is still under investigation. Results have been encouraging with a large percentage of the wells exhibiting no CO2 breakthrough to date. However, isolated cases of CO2 breakthrough have been observed in a small number of wells in the more heterogeneous section of the tertiary project area. Future plans for the project include continued monitoring of reservoir performance, the evaluation of a proposed ten acre infill pilot project, and optimization of the CO2 reinjection facility.