Recent and Potential Growth of Known Recoverable Oil in California, U.S.A

Tennyson, Marilyn E.¹ (1) U.S. Geological Survey, Denver, CO

Known recoverable oil (KRO) (cumulative production plus proved remaining reserves) in California increased by almost 7 billion barrels of oil (BBO; 109 barrels), from 23.8 BBO in 1980 to 30.7 BBO in 2004, as reported by the California Division of Oil, Gas, and Geothermal Resources and the Minerals Management Service. 5.4 BBO of reserve additions came from San Joaquin Basin, which grew from 11.3 BBO to 16.7 BBO. Most of this increase, over 4 BBO, was from thermal recovery of heavy oil in shallow sandstone reservoirs. About 790 million barrels of oil (MMBO; 106 barrels) came from intensive development of diatomite reservoirs using fracture programs, infill drilling, waterfloods, and thermal recovery. Minor discoveries in the San Joaquin Basin since 1980 have added only about 55 MMBO to known recovery. About 1.3 BBO were added in coastal basins (Ventura-Santa Barbara, Santa Maria, and Salinas Basins). Almost 1 BBO of the additions were from offshore fields, some discovered before 1980 in the Santa Barbara Channel, and two discovered during the 1980s in the offshore Santa Maria Basin. About 330 MMBO came from improvements in recovery in discovered fields, notably Ventura field in the Ventura-Santa Barbara Basin. Numerous offshore discoveries made in the 1980s have never been developed; they remain entangled in legal disputes between the lessees and the Federal government, and their reserves, estimated at to be at least 1 BBO by the Minerals Management Service, are unproven. 900 MMBO were added to reserves in the Los Angeles Basin from 1980 to 2004, about 100 MMBO of which were from a 1976 offshore discovery, and the rest of which were from improvements in recovery in discovered fields, principally Wilmington field. No significant new fields were discovered.