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Sword Field, Offshore California: Challenges in Making This Giant Oil Field Commercial

James H. Ballard

The major obstacles and challenges involved in exploration and development of a giant deep-water low-gravity oil field are exemplified in the undeveloped Sword field of offshore southern California.

In 1979, Conoco Exploration identified a northeast-southwest-trending basement high in 800-2,000 ft deep federal waters 12 mi southwest of Pt. Conception at the western end of the Santa Barbara Channel. The intended reservoir was fractured Miocene Monterey chert, siliceous shales or siltstones, and dolomites that are draped over the axially faulted anticlinal structure. Drilling of the initial well in OCS P-0322 in 1982 resulted in discovering the giant Sword field. A confirmation well drilled in OCS P-0320 indicates in-place reserves of well over 1 billion bbl. Although the discovered potential is significant, the low gravity (8.5°-10.5° API) of the oils discovered to date, along with water depths in excess of 1,500 ft, currently pose economic challenges to successful field development.

Conoco and its partners are addressing the current economic barriers on several fronts. A three-dimensional seismic survey has been conducted to delineate reservoir geometry and to define probable variations in pay thickness and fracturing. A market feasibility study will be undertaken to assess the demand for low gravity crude from offshore California. Finally, Conoco has developed proprietary technology called OCHOS (Offshore California Heavy Oil System), which uses an innovative oil and/or water emulsion technique to allow for more economic recovery of high-viscosity or low-gravity crudes.

AAPG Search and Discovery Article #91035©1988 AAPG-SEPM-SEG Pacific Sections and SPWLA Annual Convention, Santa Barbara, California, 17-19 April 1988.