South Mountain Oil Field
[1] As of the beginning of 2009, it retains 316 active wells, and has an estimated 1.4 million barrels (220,000 m3) of oil remaining recoverable with current technology.
The climate in the region is Mediterranean, with cool, rainy winters and warm, rainless summers, in which the heat is moderated by frequent morning coastal low clouds and fog.
Tectonic forces caused by the collision and lateral movement of the North American and Pacific Plates have compressed the area of the Oxnard and Ventura Basins from north to south, resulting in structural folds; oil has collected in those folds which form an anticlinal trapping mechanism.
[4][5] Oil in the South Mountain field is found in two producing horizons, one on each side of the Oak Ridge Fault.
The larger pool, and the one first to be discovered, is in the Oligocene-age Sespe Formation, trapped in the huge anticline of which South Mountain is the surface expression.
[3] Oil in the field is relatively young, with an estimated age of about 2 million years, and likely originated in the underlying Monterey Formation.
Additionally, biomarkers and hydrocarbon source modeling suggest a recent origin for the oil: the Monterey Formation is a fertile source rock for hydrocarbons and continues to produce oil, which migrates upwards, filling available reservoirs over time-spans measured in hundreds of thousands to millions of years.
Many of the canyons on the north side of the mountain were dammed with earthen berms to form improvised sumps or catchment basins for wells which blew out in the 1920s.
[5] In December 1955, the Bridge producing horizon was discovered, at about 7,500 feet (2,300 m) below ground surface in the Pliocene-age Pico Formation, and the discovery well flowed over 200 barrels (32 m3) in the first day.
This event mirrored a trend throughout coastal and offshore California, as the firms with large financial resources and international holdings decided to focus on easier-to-exploit oil fields elsewhere in the world.
