Correlation and volumetrics of upper Repetto and Pico Formation gas sands, Long Beach Unit, Wilmington oil field, California

Gas producing sands are widespread in the Long Beach Unit of the Wilmington oil field. They are of potential economic value, and present serious safety hazards for oil drilling. Yet they have been little studied. Existing well data are used herein to identify and map the gas sands in the Long Beach Unit and to calculate the volumes of gas within each sand unit.;Several gas-producing intervals are located between the KF and S stratigraphic subzones in the Pliocene Pico and Repetto Formations. The gas sands in descending order are the A10, A14, A15, A16 (PG) and the A20. Subsurface structure contour maps, produced from the well data, show that the gas-sand intervals decrease in thickness from west to east across the Long Beach Unit, primarily in the area of the Junipero and Temple Avenue faults where shale interbeds are prevalent. The structure contour maps were also used to calculate the volume of gas within the sands. Gas is concentrated on the west side of the Long Beach Unit in an area around Grissom Island. Faults within the gas-sand interval serve as barriers that inhibit gas migration. The greatest gas volume is in the A16 gas sand, potentially the most prolific gas-producing reservoir, which contains approximately 932 MMCF of gas. The second most potentially productive interval is the A15 gas sand which contains approximately 414 MMCF.