Structural History of the Lost Hills Aera of California and its Influence on Late Cenozoic Stratigraphy – Evidence from 3D Seismic

Gary A. Myers and Sean M. O'Connor
Aera Energy LLC, 10000 Ming Avenue, Bakersfield, CA 93311

The Lost Hills field is located on the western margin of the San Joaquin Basin along a Northwest-Southeast trending series of structural highs spanning nearly 50 miles, which encompasses the Lost Hills, Coalinga and Kettleman Dome structures. The field was discovered in 1910 with initial primary production from shallow sands in the Tulare and Etchegoin Plio-Pleistocene formations. Over the past 25 years, and with advances in completion technology, light oil and gas production has increased from siliceous shale reservoirs equivalent to the Miocene Monterey formation. Cumulative production from all zones is over 360 MMBO and 620 BCFG making it one of the largest oil and gas fields in California. A number of authors have addressed the issue of Miocene (and younger) correlative units along this trend. In 2001, WesternGeco completed the acquisition of a large, deep exploration-focused 3-D seismic survey across Lost Hills. The interpretive and visualization benefits of these data have helped resolve and distinguish litho-stratigraphic from chrono-stratigraphic units in the Lost Hills area. Southerly prograding clinoforms sets and a north-to-south lithologic change within the Upper Miocene/Lower Pliocene section are consistent with an uplifted source terrain to the north and west ; time-correlative units grade from interbedded siltstones and sandstones in the north to siliceous shales in the southern, distal parts of the depositional system. Likewise, the progressive structural uplift of the Lost Hills anticline has influenced the stratigraphic architecture, lithology and thickness trends of these time-correlative units in the area.

Past structural studies of the Lost Hills anticline have focused primarily on the mechanism of fold development: fault-bend folding vs. fault-propagation folding. The high quality of the Lost Hills 3-D seismic data helps relate smaller-scale cross-faulting to the uplift of the Lost Hills anticline and aids in understanding the localized effects these secondary structures may have on depositional processes and reservoir quality. In addition to improved understanding of the relationship between tectonic uplift and depositional trends in the Lost Hills area, this case history clearly demonstrates the benefit of 3-D seismic data well beyond its original intent and primary target design.

AAPG Search and Discovery Article #90076©2008 AAPG Pacific Section, Bakersfield, California