Keys to Increasing Production Via Air Injection in Gulf Coast Light Oil Reservoirs

Abstract

Abstract Following the long-term commercial success of air injection as a secondary light oil recovery process in the Williston Basin (documented in SPE 27792, 28733, & 35393), Amoco, with the support of the U.S. Department of Energy, is piloting the use of air injection for tertiary light oil recovery at West Hackberry Field in Southwestern Louisiana. Air injection is ongoing at West Hackberry under the following two operating conditions:In a watered out oil reservoir, air is injected to generate incremental oil recovery through the Double Displacement Process (DDP, SPE 28603). DDP is the gas displacement of a water invaded oil column to recover additional oil through gravity drainage. West Hackberry possesses steeply dipping high permeability light oil reservoirs that exhibit water drive recoveries of 50%-60% of the OOIP versus gravity drainage recoveries of 90% of the OOIP. Although insufficient air has been injected to see production response, reservoir pressure has increased by 500 psi and air injection is continuing.In a low pressure reservoir with a gas cap and a thin oil rim, air is injected into the gas cap to push the oil rim to downstructure wells, to repressure the reservoir, and to gain the improved recovery benefit derived from DDP. As of May of 1997, the first two low pressure reservoirs to undergo air injection have increased production by a combined total of 150 BOPD (or 60%) above the normal decline. To build upon these results, air injection will be extended to similar reservoirs in the field. Key project aspects discussed in detail include:valuable field experience gained from injection and production operations,the use of laboratory tests in the selection process for target reservoirs,the interpretation of laboratory results obtained from the combustion tube and the accelerating rate calorimeter, andthe numerical reservoir simulation employed to forecast tertiary oil bank development and movement, recovery profiles, and tie-in experimental and field data. P. 65