Pacific Section AAPG, SPE and SEPM Joint Technical Conference

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Introduction To The San Ardo Field


The San Ardo field is one of Chevrons principle operated California assets, however it is the only one not found in the Central Valley. Discovery in 1947 by Hans Ashauer Jim Dorrance and Tom Baldwin led to competitive leasing resulting in a division of leases. Today they are held by two operators, Chevron and Aera. The San Ardo field is the largest oil field discovered in the Salinas valley to date. While San Ardo is a heavy oil field similar to other fields in the Salinas and San Joaquin Valley there are many differences that make it unique and challenging to develop. It consists of two sandstones called the Aurignac and the Lombardi Formations, with the latter lying on top. The trap for this reservoir is both structural and stratigraphic. A doubly plunging anticline that strikes NW — SE is the predominant structure, while stratigraphically the sands transition to shales on the flanks. Dips tend to be shallow, reaching 3∞-5∞ along the plunge axis and 7∞-9∞ along the flanks. It is capped by the Monterey Shale The production history is long and complicated, involving the use of many technologies throughout the years. Initially production could be sustained with zero to little stimulation; this is referred to as primary production. The advent of cyclic steam injection around the 1960's boosted production significantly throughout the field; this is referred to as secondary recovery. Currently both Aera and Chevron are using tertiary recovery methods; this involves continuous steam injection throughout the field with the use of dedicated injectors. Chevron's current development is focused in the Lombardi in two locations, the flat low lying terrain between the railroad and the Salinas River and in Section 13, located in the hills east of the Salinas River. Aera's current development also is primarily focused in the Lombardi. With over 65 years of drilling in the San Ardo field, data is abundant. Incorporating new technologies Chevron is focused on continued development of these reservoirs. The utilization of powerful 3D modeling has enhanced our understanding of the reservoir's properties and architecture. This has allowed more efficient development of the field and the implementation of new drilling technologies. Regular surveillance of the reservoir through observation wells aids in our understanding of the changes in the reservoir during production and steam injection. Chevron plans on many more years of successful production from the San Ardo field.