MEDWEDEFF, DONALD A., ARCO Exploration and Production Technologies, Plano TX, JOSEPH T. C. LIN, TIMOTHY R. CARR, and JOHN M. STAFFORD, ARCO Oil and Gas Company, Bakersfield, CA

ABSTRACT: Superposition of Basement Involved Structures and a Detached Thrust System: A Model for Existing and Potential Production in the San Emigdio Mountains, San Joaquin Valley, California

Seven balanced cross sections document the structural fabric of the San Emigdio Mountains and the adjacent San Joaquin Valley. Major tectonic elements are (1) the Los Lobos normal fault (LLF), (2) the White Wolf reverse fault (WWF), and (3) the Pleito fold-and-thrust belt (PTFB). The Oligo-Miocene LLF system created the distinction between the San Joaquin basin to the north and the Tejon platform to the south. Superposed on the LLF is the younger WWF which has further uplifted the Tejon platform. Along strike, the WWF alternately rotates, truncates, and overrides the LU. The even younger low-angle, PTFB is primarily developed on the Tejon platform, but locally interferes both the LLF and WWF. Superposition of these structures control the hydrocarbon traps.

Wheeler Ridge field (73+ MMBOE) is created by the superposition of the PFTB atop of pre-existing basement structures. The field produces from ten Eocene to L. Miocene sands. Some sands are structurally controlled. Due to the complex structural setting, this 1922 field has been extended by discovery of additional reservoirs including a 1989 gas and condensate find in the Oligocene section. This success triggered our comprehensive structural reevaluation. Other fields along and south of the WWF trend are North Tejon (basement involved anticline; 56 MMBOE), Tejon (stratigraphic trap; 36 MMBOE) and Pleito (fault trap; 12 MMBOE) fields.

The new structural model suggests two play types for exploration potential: (1) additional fault traps along the WWF trend; and (2) subthrust plays beneath the Pleito thrust The prolific production history of the WWF trend and large structures mapped beneath the Pleito thrust bode well for future exploration in the San Emigdio Mountains area.

AAPG Search and Discovery Article #90988©1993 AAPG/SVG International Congress and Exhibition, Caracas, Venezuela, March 14-17, 1993.