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The AAPG/Datapages Combined Publications Database
Houston Geological Society Bulletin
Abstract
Abstract: Geology of the Ventura Basin, California
as an Approach to Offshore Exploration
By
Exploratory approaches used in the Ventura Basin can serve as a model for exploration
of other offshore areas. In preparation for the 1968 Ventura Basin Federal
offshore lease sale, a totally integrated exploration program was required, consisting
of 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 feet 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 and unconformity. Pliocene turbidite sandstone is the principal
reservoir in the eastern part of the basin, and has yielded approximately 1 billion bbls.
of oil from onshore fields. Miocene, Oligocene, and Eocene marine to nonmarine
clastic rocks are objectives to the west.
On February 6, 1969, industry bid what was at the time a record high $1.3 billion
and spent $603 million for 383,341 acres; 50 percent of the acreage was in water deeper
than 600 feet. Currently, deepwater drilling and producing technology is advancing
rapidly as evaluation is underway.
Two separate areas in which Humble bought acreage and subsequently drilled
wildcats are discussed in detail. One area resulted in a major oil discovery and the
other, where Humble paid $45 million for the lease, is considered a failure. Actual
maps and cross-sections that were used prior to the sale are compared with current maps
that reflect changes resulting from drilling; in essence, a before and after series of
geologic maps are presented along with the "methodology" what was used in the geologic
interpretations. End_of_Record - Last_Page 3---------------