Lompoc Oil Field

The Lompoc field follows the line of the Purisima Hills, a northwest-to-southeast trending range dividing the Santa Ynez Valley on the south from the Los Alamos Valley to the north, and the field is about long by across. The hills are a part of the Burton Mesa region, much of which is an ecological reserve maintained by the California Department of Fish and Game. Populated places close to the field include Vandenberg Village and Lompoc to the south, Vandenberg Space Force Base to the west, and Los Alamos to the east. One public road, Harris Grade Road, traverses the field from north to south. Several access points to the field are along this road. Most of the field's productive area, and most of the oil wells, are on the southern slope of the hills. Elevations on the oil field range from around on the west to at the summit of the Purisima Hills. Climate in the region is Mediterranean, with cool, rainy winters and dry summers during which the heat is greatly diminished by fog and northwesterly winds from the cold waters of the Pacific Ocean, which is about west of the field. Prevailing winds year-round are from the west-northwest. The north slopes of the hills contain stands of bishop pine as well as coast live oak forest; the south-facing slopes have mostly chaparral vegetation types, including coastal sage scrub. of rain falls in a typical winter. Drainage on the south side of the hills is to the Santa Ynez River, and then out to the sea via Lompoc; to the north, runoff goes to San Antonio Creek, which exits to the ocean through Vandenberg Space Force Base. A small discontiguous part of the field, the Northwest Area, is situated about a mile and a half northwest of the main part of the field, close to the main gate of Vandenberg Space Force Base. As of 2009, that area had 9 actively producing wells, as well as three used for water disposal. ==Geology==

The hills are the surface expression of an anticlinal structure consisting of the adjacent Lompoc Anticline and the Purisima Anticline, which are offset from each other by faults. The surface Paso Robles and Careaga formations are Pleistocene sediments. Underneath them is the relatively impermeable Sisquoc Formation, of Pliocene and Miocene age. Beneath this unit, and separated by an unconformity, is the oil-bearing rock, the fractured shale of the Miocene-age Monterey Formation, at the top of which oil has pooled, halted in its upward migration by the impermeable cap of the Sisquoc. The minimum depth at which oil has been recovered in the Lompoc field is approximately , and the average net thickness of the oil-bearing rock is 450 to . Total productive area of the field is . In the main part of the Lompoc field oil is medium grade, with an API gravity of 15 to 26; in the Northwest Area it is heavier and more viscous, with a gravity of 17 to 19.5. Only one pool or producing horizon has been defined, the "Monterey", discovered in 1903 and still producing as of 2009. The discontiguous Northwest Area also produces from the Monterey, but at a depth of approximately , and with a net thickness of . ==History, operations, and production==

With the success of the drilling in the Los Angeles Basin around 1900, and similar discoveries of oil in Kern County around the same time, prospecting for oil began to occur in Santa Barbara County as well. In 1901 the Orcutt field was discovered, and in 1903 the discovery well for the Lompoc field was drilled, after several failed attempts to find oil in the obviously promising anticlinal structure. A 1902 well was wrecked in an earthquake before it found oil. The discovery well, by the Union Oil Company of California, hit oil in March 1903, and initially produced . By 1911, the field had 33 producing wells on the field, six in the process of being drilled, and 15 had already been abandoned, either as dry holes or insufficient producers. Union Oil Company of California's 1905 Well, Hill 4 was the first oil well in which a shutoff was attained by pumping cement through the tubing and back of the casing. Peak production on the field did not occur until 1951, during which the operators reported almost of oil. An enhanced recovery project – gas injection to increase reservoir pressure – which had commenced in 1929 was discontinued in 1960, and production from the field continued to decline. Unocal divested most of its California assets in February 1996, selling them to Nuevo Energy. Plains acquired the field in 2002 with its purchase of Nuevo Energy, and continues to operate it as of the beginning of 2010. The Lompoc field was one of the properties transferred, along with the Lompoc Oil and Gas Plant, which then became, and remains, the principal processing plant for Plains's operations in the region. A total of 34 oil wells continued to pump from the field at the beginning of 2009, including 8 in the Northwest Area. Freeport McMoRan Oil and Gas acquired the operations in the field with their 2013 purchase of Plains Exploration & Production ==References==