Effect of Los Lobos Thrust Fault on Tertiary Recovery in West San Ardo Oil Field, Salinas Basin, California
J. E. Laing
Field observations and correlation of wireline logs from wells in the west San Ardo oil field reveal the geometry and character of the Los Lobos thrust fault. The Los Lobos thrust is a northwest-trending, southwest-dipping fault of Pliocene to Pleistocene age, located in the southwest Salinas basin. The surface trace separates the Salinas River on the east from the Aurignac Hills on the west. The Aurignac Hills form the hanging wall and are comprised of fine-grained rocks of the Monterey Formation, which have been thrust northeast over oil-productive Aurignac sand, a shallow marine shelf sand of Miocene age. Analyses of electric and dip logs indicate that the fault plane is steepest near the surface, and flattens with depth. Deformation on the hanging wall involves tight olding with limb distances ranging from 50 to 100 ft, slickensides, and abundant imbricate thrusts that change in orientation from horizontal to vertical over distances of several hundred feet. Deformation on the footwall is much less intense, consisting of drag folding and additional thrust faulting, decreasing in intensity eastward away from the Los Lobos fault plane. These associated thrust-faults displace the oil-productive Aurignac sand and affect Tertiary recovery of low-gravity oil.
AAPG Search and Discovery Article #91035©1988 AAPG-SEPM-SEG Pacific Sections and SPWLA Annual Convention, Santa Barbara, California, 17-19 April 1988.