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Attention to Detail: How a Big Commitment to Reservoir Description Has Made a Major Impact on Development at Elk Hills Oil Field

M. L. Wilson
Chevron U.S.A, Bakersfield, CA

Occidental became the operator of the Elk Hills oil field in February 1998 after purchasing approximately 80% of the field from the U. S. Department of Energy. Chevron continues to own the remainder of the field. By any measure, Elk Hills is a mature oil field. Although it is often customary with mature oil fields to reduce staff and harvest reserves, Occidental’s approach has been to allow for a staff that is capable of doing an unprecedented amount of detailed reservoir description. Such data as wireline pressure measurements, microresistivity image logs, through-casing resistivity logs, special core analyses, seismic reprocessing, and vertical seismic profiles are also being acquired at a tremendous pace.

Occidental‘s commitment to acquiring data and having enough staff to interpret this data and integrate the resultant information into individual reservoir descriptions has had significant impact on the results of development work at Elk Hills. Several examples can be shown. Elk Hills is a very complex oil field with 21 producible horizons in the Dry Gas Zone, 4 major reservoir sandstones in the Upper Shallow Oil Zone (SOZ), and 7 reservoir sandstones in the Lower Shallow Oil Zone. In addition, one of the Upper SOZ sandstones is divided into as many as 13 layers for reservoir management purposes. In the Miocene Stevens Zone, there are shale reservoirs associated with two major structures and 7 major sandstone reservoirs. Many of the development projects at Elk Hills have experienced significant breakthroughs in development proficiency due to improved reservoir description.

AAPG Search and Discovery Article #90904©2001 AAPG Pacific Section Meeting, Universal City, California