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The AAPG/Datapages Combined Publications Database

Pacific Section of AAPG


Selected Papers of the Pacific Section Annual Meeting, Sacramento, California, 1983
Pages 97-130

The Resurrection of the Half Moon Bay Oil Field San Mateo County, California

A. J. Horn


The history and development of the Half Moon Bay Oil Field, one of the oldest in California, is reviewed. The importance of understanding the micro-geology of the area (structural, stratigraphic, and lithological) is emphasized to provide optimum well location and well completion procedures.

The author suggests that right lateral fault movement is critical to a determination of structural entrapment of commercial quantities of oil and gas in the Pliocene (Purisima), Miocene and Eocene rocks underlying the Oil Field. It is suggested that two important faults in the Field are branches of the San Gregorio Fault and related to the tectonics of the San Andreas and Pilarcitos Fault.

Previous well completions did not consider adequately the clays in the potentially productive zones and have, therefore, failed to prove the commercial viability of the known oil accumulations.

The return of oid wells (originally drilled ca. 1910) to commercial production from very thin Pliocene intervals indicates that considerable potential remains that requires re-evaluation.

The hindrance of current San Mateo County regulations to proceed with proper evaluation is reviewed.

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