The San Miguelito Oil Field is a large and currently productive

oil field A petroleum reservoir or oil and gas reservoir is a subsurface accumulation of hydrocarbons contained in porous or fractured rock formations. Such reservoirs form when kerogen (ancient plant matter) is created in surrounding rock by the presence ...

in the hills northwest of the city of Ventura in southern

California California is a U.S. state, state in the Western United States, located along the West Coast of the United States, Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the List of states and territori ...

in the United States. The field is close to the coastline, with U.S. Highway 101 running past at the base of the hills, and is sandwiched between the larger

Ventura Oil Field The Ventura Oil Field is a large and currently productive oil field A petroleum reservoir or oil and gas reservoir is a subsurface accumulation of hydrocarbons contained in porous or fractured rock formations. Such reservoirs form when kerog ...

to the east and the

Rincon Oil Field The Rincon Oil Field is a large oil field on the coast of southern California, about northwest of the city of Ventura, and about east-southeast of the city of Santa Barbara. It is the westernmost onshore field in a series of three fields whi ...

, which is partially offshore, to the north and northwest. Discovered in 1931, and with about 7 million barrels of oil remaining out of its original 125 million, it ranks 44th in the state by size, and at the beginning of 2009 had 61 producing oil wells, all operated by Vintage Production California LLC, a subsidiary of

Occidental Petroleum Occidental Petroleum Corporation (often abbreviated Oxy in reference to its ticker symbol and logo) is an American company engaged in hydrocarbon exploration in the United States, and the Middle East as well as petrochemical manufacturing in the ...

. p. 63, 165

Geographic setting

The oil field is one of several following the east-west trend of the Transverse Ranges: to the west is the

and the offshore Dos Cuadras field, and to the east the much larger

. Total productive area of the field, projected to the surface, encompasses about , about one and a half square miles.California Department of Conservation, Division of Oil, Gas, and Geothermal Resources (DOGGR). ''California Oil and Gas Fields, Volumes I, II and III''. Vol. I (1998), Vol. II (1992), Vol. III (1982). PDF file available on CD from www.consrv.ca.gov. p. 574 On the coast between Ventura and

Carpinteria Carpinteria (; es, Carpintería, meaning "Carpentry") is a small seaside city in southeastern Santa Barbara County, California. Located on the Central Coast of California, it had a population of 13,264 at the 2020 census. Carpinteria is a po ...

, the stretch known locally as "the Rincon", the hills rise steeply from the shore, with the coastal U.S. Highway 101 occupying much of the narrow strip between the beach and the sharply rising hills. A cluster of seaside homes is on the ocean side of Highway 101 at Solimar Beach (marked as "Dulah" on the USGS topographic map of the area). One of the field's pumpjacks is visible on the mountain side of the highway, at sea level, just north of the Solimar Beach exit; almost all the other oil wells are out of the line of sight from any public road, as are the other oilfield structures (tank farms, processing units, and others). The predominant vegetation in the hills is

chaparral Chaparral ( ) is a shrubland plant community and geographical feature found primarily in the U.S. state of California, in southern Oregon, and in the northern portion of the Baja California Peninsula in Mexico. It is shaped by a Mediterranean c ...

and

coastal sage scrub Coastal sage scrub, also known as coastal scrub, CSS, or soft chaparral, is a low scrubland plant community of the California coastal sage and chaparral subecoregion, found in coastal California and northwestern coastal Baja California. It is w ...

. Terrain on the hills is steep, and the unpaved access roads make numerous switchbacks. Some of the hillsides are bare where landslides have stripped them, and the terrain in this area is unusually prone to landslides. Climate in the area is

Mediterranean The Mediterranean Sea is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean Basin and almost completely enclosed by land: on the north by Western and Southern Europe and Anatolia, on the south by North Africa, and on the e ...

, with cool, rainy winters and mild, dry summers, cooled by morning coastal clouds. Elevations on the field range from sea level to over on the highest ridgetops. Runoff from the oil field is west and southwest down ephemeral, seasonal drainages into the Pacific Ocean.

Geology

The San Miguelito field is an accumulation of oil along the westernmost portion of the Ventura

anticline In structural geology, an anticline is a type of fold that is an arch-like shape and has its oldest beds at its core, whereas a syncline is the inverse of an anticline. A typical anticline is convex up in which the hinge or crest is the ...

, bounded on the north by the Grubb Thrust Fault, where the fault has pushed another closed anticline above the end of the Ventura Anticline. Petroleum-bearing units are sands of

Pliocene The Pliocene ( ; also Pleiocene) is the epoch in the geologic time scale that extends from 5.333 million to 2.58Miocene The Miocene ( ) is the first geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and means "less recen ...

age, and are given numerical designations increasing with depth: 1st Grubb, 2nd Grubb, down to 5th Grubb (as well as an additional "Grubb D" zone for units lower than 5th Grubb). These units are present on either side of the fault, but are offset by about 4,000 vertical feet. It is a deep reservoir, with the uppermost producing unit at an average depth of below ground surface, and the lowest over deep.DOGGR, p. 455 The California Department of Conservation groups together the Grubb 1-3 zones, Grubb 4-5 zones, Grubb D (Deep) zones as three distinct producing horizons.DOGGR 2009, p. 101. The oil is medium-grade with an

API gravity The American Petroleum Institute gravity, or API gravity, is a measure of how heavy or light a petroleum liquid is compared to water: if its API gravity is greater than 10, it is lighter and floats on water; if less than 10, it is heavier and sinks ...

of 31 in the first four Grubb zones, 25 in the 5th.

History, production and operations

While the adjacent large Ventura Avenue oil field was discovered in 1919, it was not until 1931 that prospectors thought of searching for oil near the western end of the Ventura Anticline, where the borehole had to reach a considerable depth before finding oil. The discovery well for the field was the Continental Oil Co. "Grubb No. 1", which reached below ground surface, drilling from a ridgeline about a half mile from the ocean, about above sea level. It flowed over 600 barrels a day, and development of the field began. In 1944 the 2nd Grubb Zone was discovered, and in 1950, the 3rd Grubb. Peak production from the field was in 1951 at 4.5 million barrels of oil. Further zones were discovered, with the 4th Grubb coming online in 1970, and the 5th Grubb in 1979. By 1983, the deepest well was already producing from . In order to increase reservoir pressure, several waterflooding projects have been undertaken on the field, commencing in 1955. Most of the water injection has been done in the Grubb 1-3 zones; only one waterflood well was active as of 2009 in Grubb 4-5, with 31 in Grubb 1-3. In 1993, Vintage Petroleum acquired both the San Miguelito and adjacent Rincon fields from

Mobil Mobil is a petroleum brand owned and operated by American oil and gas corporation ExxonMobil. The brand was formerly owned and operated by an oil and gas corporation of the same name, which itself merged with Exxon to form ExxonMobil in 1999. ...

Conoco Conoco Inc. ( ) was an American oil and gas company that operated from 1875 until 2002, when it merged with Phillips Petroleum to form ConocoPhillips. Founded by Isaac Elder Blake in 1875 as the "Continental Oil and Transportation Company". Curr ...

, and

Santa Fe Energy Santa Claus, also known as Father Christmas, Saint Nicholas, Saint Nick, Kris Kringle, or simply Santa, is a legendary figure originating in Western Christian culture who is said to bring children gifts during the late evening and overnight ...

. To improve operational efficiency, Vintage combined the two adjacent oil fields into a single operating unit.Vintage Petroleum, Inc. Form 10-K405: annual report for 1996
/ref> Occidental Petroleum acquired Vintage in 2006, retaining their name and making them a wholly owned subsidiary, and still operates the Rincon and San Miguelito fields under the Vintage banner.

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. Ventura Oil Field information pp. 572–574. PDF file available on CD from www.consrv.ca.gov. * ''California Department of Conservation, Oil and Gas Statistics, Annual Report, December 31, 2008.'' * Keller, Margaret. ''Ventura Basin Province'', U.S. Geological Survey Digital Data Series DDS-30, Release 2, one CD-ROM, 19 p. + supporting maps, figures, and tables
Available here

Notes

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