Midway-Sunset_Oil_Field

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Midway-Sunset Oil Field

The Midway-Sunset Oil Field is a large oil field in Kern County, San Joaquin Valley, California in the United States. Discovered in 1894, and having a cumulative production of close to of oil at the end of 2006, it is the largest oil field in California and the third largest in the United States. As of the end of 2006, its estimated remaining reserves amounted to approximately of oil.

Setting

The oil field runs southeast to northwest, with a length of approximately twenty miles and a width of three to four, from east of Maricopa to south of McKittrick, paralleling the Temblor Range to the southwest. Most of the oil field is in the Midway Valley and the northeastern foothills of the Temblor Range. To the northeast is the Buena Vista Hills, paralleling the Midway Valley and the Temblors; the mostly exhausted, and partially abandoned Buena Vista Oil Field lies beneath this adjacent low range of hills.

State Route 33 runs along the axis of the Midway-Sunset for much of its length, and the towns of Taft and Fellows are built directly on the oil field. Other oil fields along Route 33 going northwest within Kern County include the Cymric Oil Field, McKittrick Oil Field, and the large South Belridge Oil Field. Route 33 is not the only road through the field: roughly paralleling 33, but closer to the Temblor Range, is Midoil Road, which winds through the field and along its southwestern boundary. The road commences from Taft Heights, passes through Fellows, and rejoins Route 33 just south of Derby Acres. Crocker Springs Road, which goes over the Temblor Range to the Carrizo Plain, intersects Midoil Road about two miles south of its intersection with Route 33. Another road that passes through part of the Midway-Sunset Field is Petroleum Club Road, which runs southeast from Taft, and passes the site of the Lakeview Gusher.

Geology

While the Midway-Sunset field is a large contiguous area covering more than , it consists of 22 identifiable and separately-named pools in six geologic formations, ranging in age from the Pleistocene Tulare Formation (the most recent geologically, the closest the surface, and the first to be discovered), to the Temblor Formation, of Miocene age (the oldest, and one of the last to be discovered). Throughout the field, the Tulare is often the capping impermeable formation, underneath which oil collects, but in some areas it is a productive unit in its own right. Its average depth is 200 to .

One of the next pools to be discovered was the Gusher Pool, which, when found in 1909, took its name from the event itself: a large oil gusher. This occurrence was eclipsed spectacularly the next year, when drillers found the Lakeview Pool, unexpectedly drilling into a reservoir of oil under intense pressure, later estimated at approximately 1,300 psi from the heights attained by the spewing oil. The resulting Lakeview Gusher was the largest-lasting and most productive oil gusher in U.S. history.

Drillers continued to find new oil pools throughout the 20th century, with new discoveries still occurring in the 1980s. The most pools occur in the Miocene-age Monterey Formation, with depths usually to , although one discovery, the "PULV" Pool of 1979, was below ground surface. The only well developed at this depth, and the only well in the PULV pool, was abandoned a year after it was drilled.

Operations and estimated reserves

The principal operators of Midway-Sunset, as of 2008, were Aera Energy LLC, and Chevron Corp. As of the end of 2006, the most recent date for which data was available, the field contained 11,145 producing wells, more than any other oil field in California (the Kern River Field was second at 9,183). A traveler along State Route 33 between Maricopa and McKittrick will see hundreds of nodding donkeys, the relatively small proportion of the oil wells that are visible from the highway.

Several enhanced oil recovery technologies are have been employed at Midway-Sunset. Since the oil is heavy, and does not flow freely, it can be assisted by thermal methods, which include steamflooding, cyclic steam, and fireflooding. Waterflooding is also used.

While most of the oil has been removed from the field, it still contains an estimated of oil in-situ, which amounts to 18% of California's total estimated reserve of .

References

California Oil and Gas Fields, Volumes I, II and III. Vol. I (1998), Vol. II (1992), Vol. III (1982). California Department of Conservation, Division of Oil, Gas, and Geothermal Resources (DOGGR). 1,472 pp. Midway-Sunset information pp. 280-290. PDF file available on CD from www.consrv.ca.gov.
California Department of Conservation, Oil and Gas Statistics, Annual Report, December 31, 2006.