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Abstract: Case Study of a Successful Low-Cost, Low-Pressure, Low-Volume Gas Injection Project in the Shallow Oil Zone, Naval Petroleum Reserve #1 (Elk Hills), Kern County, CA


A low-pressure, low-volume gas injection project was initiated in a small fault block in the Shallow Oil Zone (SOZ) in 1992 as a pilot project. Based on the data derived from the pilot a larger portion of the reservoir was selected for an expansion of the project. This area includes parts of five sections covering roughly two square miles. The geology and completion history of the wells in this area were ideal for the project. The expansion area (Phase 1) was isolated from the rest of the reservoir by a fault which was sealing at current reservoir pressure. Nearly all wells were single zone completions and of good mechanical condition. Reservoir pressure was raised from 6 psi to 45 psi by injecting approximately a total of 2.5 MMCFPD in eight gas cap injectors updip of the oilband.

Production in the gas injection project area was brought on line along with the rest of the field when the Naval Petroleum Reserve was put on full production in 1976. Production for the project area peaked at 5300 BOPD in 1979. It declined to a low of 2100 BOPD in 1992. In October 1993, eighteen months after gas injection started, production in the project area peaked at 5500 BOPD. Production is currently 5100 BOPD.

The SOZ sand being repressurized is the Sub Scalez One (SS-1). It is a Pliocene fluvial deltaic deposit of sands and clays. The SS-1 has been divided into twelve sublayers. Not all sublayers are present in all wells throughout the project area. Sublayer management has been critical in attempts to improve the oil production while limiting the gas production. The effectiveness of the gas injection project was enhanced by the drilling of new vertical and horizontal wells and the remediation of existing wells in the same area.

Search and Discovery Article #90945©1997 AAPG Pacific Section Meeting, Bakersfield, California