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Silverthread Oil Field, Ventura County, California: A Hydrodynamic Trap

Robert N. Hacker, Richard L. Hester

Silverthread oil field is located in west-central Ventura County, California. An unusual combination of Miocene turbidite sand deposition, tight folding, faulting, and hydrodynamics have created an accumulation of over 6 million bbl of oil from 33 wells.

This field is also unique in that it lies beneath the convergence of several opposing major thrust faults which effectively hide any surface indication of structure at depth. Though previously and often explored by majors and other operators, the remarkable deduction and perseverance by Harry Browne and Argo Petroleum Corporation geologists led to the main area discovery in 1971.

Of exceptional interest is the interaction of classic hydrodynamic flow on the distribution of fluids within the reservoir.

Thirteen contour maps and numerous structure and stratigraphic sections were required to unravel the sand sequence, faulting, structure, and hydrodynamics. Because of high surface relief, most wells were directionally drilled from islands, and subsequent electric logs had to be "unstretched" using the Dental Dam technique to facilitate their correlation.

A large, lighted, three-dimensional model consisting of thirty-six 2 × 5-ft transparent plexiglass plates was constructed to show a simple resolution of the complexities of this area and will be part of the poster session. This display, we believe, will generate considerable interest in our presentation.

AAPG Search and Discovery Article #91038©1987 AAPG Annual Convention, Los Angeles, California, June 7-10, 1987.