Although present water depths locally exceed 6,000 ft, the tectonic and stratigraphic history of the southern California continental margin is related more closely to that of the mainland than to the oceanic basin. The exploratory approach presently used in the Ventura basin can be expected to be a model for exploration of the rest of the offshore borderland. Such an approach was used to prepare for the 1968 Federal offshore lease sale. A totally integrated exploration program was required, and included stratigraphic tests, modern geophysical surveys for purposes other than, but including structural mapping, paleontologic studies, onshore surface-geologic mapping, and ocean-floor geologic mapping and sampling by divers and diving submersibles.

The Ventura basin, two thirds of which is offshore, is an east-west-trending synclinal trough containing 40,000-50,000 ft of principally Tertiary marine clastic rocks. Structurally, it is characterized by major east-west thrust faults and tightly folded anticlinal trends. Although anticlinal accumulations provide the largest part of the Ventura basin petroleum, significant reserves occur in a wide variety of traps, including stratigraphic, fault, unconformity, and combination traps. Pliocene turbidite sandstone is the principal reservoir in the eastern part of the basin, and has yielded approximately 1 billion bbl of oil from onshore fields. Miocene, Oligocene, and Eocene marine to nonmarine clastic rocks are objectives on the west.

On February 6, 1968, industry bid a record $1.3 billion and spent $603 million for 383,341 acres; 50% of the acreage is in water deeper than 600 ft. Deep-water drilling technology is advancing rapidly as evaluation is underway.

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