ABSTRACT: Hydrocarbon Potential in the Coastal Basins, Offshore Central California

James M. Galloway, Michael R. Brickey

The Minerals Management Service (MMS) and the U. S. Geological Survey recently published their national assessment of undiscovered, conventionally recoverable oil and gas resources. The MMS was responsible for the evaluation of the Federal outer continental shelf.

One of the most promising frontier areas for petroleum exploration studied by MMS is the offshore Central California province. It consists of the Point Arena, Bodega, La Honda, and Ano Nuevo basins. In evaluating these basins, comparisons were made to nearby productive basins (onshore and offshore) such as the Santa Maria and Salinas basins. Our interpretation of the geology indicates that these basins all share common structural and stratigraphic characteristics.

In evaluating the Central California province, emphasis was placed on determining the distribution and geologic history of Miocene-aged rocks, coeval with the Sisquoc, Monterey, and Rincon formations. The existence of petroliferous Miocene rocks in offshore Central California (evidenced in boreholes and outcrops) and the probable development of trapping mechanisms (analogous to those found in nearby productive areas), suggests that the offshore basins also contain oil fields.

The high case (F₅ fractile value) estimates of undiscovered, conventionally recoverable oil and gas resources suggest that at least 2.45 billion bbl of oil and 3.63 tcf of gas are present in the province. These estimates compare favorably with the estimates and long production histories for the onshore analog areas in the Santa Maria and Central coastal provinces.

AAPG Search and Discovery Article #91003©1990 AAPG Annual Convention, San Francisco, California, June 3-6, 1990