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Frontier Tertiary Basins with Promising Hydrocarbon Potential, Offshore California

GALLOWAY, JAMES M., PETER R. SIMON, and MICHAEL R. BRICKEY, Department of the Interior-Minerals Management Service, Los Angeles, CA

Dwindling domestic petroleum reserves have drawn attention to areas of promising potential within the United States. The federal outer continental shelf (OCS) off of California remains one of the most likely sources of future domestic oil and gas. The Federal Government, as mandated by the OCS Lands Act, must evaluate the OCS for hydrocarbon potential and to make promising areas available for exploration and production.

Areas with the highest initial potential, such as the Ventura-Santa Barbara and Santa Maria basins, have been successfully explored and developed. However, since the 1960s, other areas have been repeatedly deferred from leasing. Within these deferred areas additional high potential exists.

Offshore Eel River basin, for example, contains the extension of the gas-producing Table Bluff trend. Seismic sections display amplitude and velocity anomalies, suggesting the possible presence of gas in offshore structures. Faulting, folding, and a thick Neogene marine section indicate a high probability of traps and source rocks being present.

A moderately thick Neogene section and excellent structural development is observed in the southern Point Arena basin. The few wells previously drilled indicate mature source rocks are locally present and fractured reservoir potential is good to excellent.

The structural geology of northern Bodega basin resembles that of Point Arena basin. Stratigraphic analogies are also evident, and the Neogene section appears to be thicker. This area should be considered a favorable petroleum habitat.

Ano Nuevo basin displays many similarities to the Santa Maria and Salinas basins. The structural development provides trapping mechanisms, and the two offshore wells indicate mature source rocks. The reservoir potential is fair to excellent.

Capistrano basin may be the least known of all the frontier offshore basins. Structural similarities to the Los Angeles basin suggest the likely formation of trapping mechanisms. Should stratigraphic similarities exist, then its oil and gas potential would be considered quite favorable.


AAPG Search and Discovery Article #91009©1991 AAPG-SEPM-SEG-SPWLA Pacific Section Annual Meeting, Bakersfield, California, March 6-8, 1991 (2009)