Deposition Trends of the Amnicola and Tulare Sands, and Relevance to the Development of Asphaltenes in a Portion of the Cymric Oil Field, Western San Joaquin Valley, California
BELL, PAT, Irvine Valley College, Irvine, CA
The Cymric oil field is located on the southwestern margin of the San Joaquin Valley. The upper productive units include the lower Amnicola, and upper Tulare I and II sandstones. The Amnicola unit ranges from lacustrine to braided stream in depositional environment, it averages about 60 ft thick. The Tulare I and II sands are primarily braided stream to fan delta, with a thickness averaging about 300 ft total in the two units. The oil produced is of low gravity and is currently being produced by steamflood. The area studied is part of Chevron Fee land.
Wells containing asphaltenes are strongly correlated to major channels within the producing units. A combination of flushing by meteoric water and possible biodegradation of the oil, which was migrating updip into these sands along higher porosity and permeability trends, resulted in the production of asphaltenes in the wells of a portion of the Cymric field.
The development of a detailed stratigraphic framework allowed a recognition of a pattern to the problem wells, and suggested a plan of remediation and further planning for the development of the field. Certain other problem fields could be investigated by detailed stratigraphic means that could lead to better understanding of the placement of future well sites, or development of effective stream drive strategies with concomitant savings of time and field costs.
AAPG Search and Discovery Article #91009©1991 AAPG-SEPM-SEG-SPWLA Pacific Section Annual Meeting, Bakersfield, California, March 6-8, 1991 (2009)