Unocal in the context of Afghan Civil War (1996–2001)

The Dos Cuadras Offshore Oil Field is a large oil and gas field underneath the Santa Barbara Channel about eight miles southeast of Santa Barbara, California. Discovered in 1968, and with a cumulative production of over 260 million barrels of oil, it is the 24th-largest oil field within California and the adjacent waters. As it is in the Pacific Ocean outside of the 3-mile tidelands limit, it is a federally leased field, regulated by the U.S. Department of the Interior rather than the California Department of Conservation. It is entirely produced from four drilling and production platforms in the channel, which as of 2009 were operated by Dos Cuadras Offshore Resources (DCOR), LLC, a private firm based in Ventura. A blowout near one of these platforms – Unocal's Platform A – was responsible for the 1969 Santa Barbara oil spill that was formative for the modern environmental movement, and spurred the passage of the National Environmental Policy Act.

A fixed platform is a type of offshore platform used for the extraction of petroleum or gas. These platforms are built on concrete and/or steel legs directly planted onto the seabed, supporting a deck with space for drilling rigs, production facilities and crew quarters. Such platforms are, by virtue of their immobility, designed for very long-term use. Various types of structure are used, steel jacket, concrete caisson, floating steel and even floating concrete. Steel jackets are vertical sections made of tubular steel members, and are usually piled into the seabed. Concrete caisson structures, pioneered by the Condeep concept, often have in-built oil storage in tanks below the sea surface and these tanks were often used as a flotation capability, allowing them to be built close to shore (Norwegian fjords and Scottish firths are popular because they are sheltered and deep enough) and then floated to their final position where they are sunk to the seabed. Fixed platforms are economically feasible for installation in water depths up to about 500 feet (150 m); for deeper depths a floating production system, or a subsea pipeline to land or to shallower water depths for processing, would usually be considered.