GEOHERITAGE OF OIL EXTRACTION: URBAN OIL FIELDS OF LOS ANGELES, CALIFORNIA, USA

The Los Angeles Basin represents the optimum conditions for the generation and entrapment of hydrocarbons: the world’s richest oil deposit. The unique abundance of oil derives from a thick section of organic-rich shale source rocks, rearranged by the area’s geologic and tectonics to provide the thermal history to bring the organic-rich material into the “oil window.” Finally oil migrating upward from the shales is trapped in sandstone reservoir rocks by abundant folding and faulting. These traps are not ubiquitous, the most famous surface seep is the La Brea Tar Pits in Los Angeles’s Miracle Mile, which contains one of the best-studied assemblages of Tertiary-era vertebrates. Seeps were a commodity for the area’s indigenous population to craft seaworthy boats and store fresh water in the desert environment.

Oil was first discovered in the L.A. Basin in 1865, and 1880 brought in the Brea Oil Field, followed by the Los Angeles City, Beverly Hills, Salt Lake, Long Beach and Signal Hill oil fields. Of the region’s 70 distinct oil fields, approximately 40 are currently active. Due to a growing land demand in the 1960’s from aerospace, filmmaking, and housing, Los Angeles and oil companies took advantage of directional drilling technology to create the concept of urban oil fields. The original dispersed oil fields were abandoned and replaced with 15 urban oil islands approximately 1-2 acres in size. The urban oil islands were developed when offshore oil extraction was expanding, and the space race was producing a strong “can do” attitude in Los Angeles. Modelled on offshore platforms, the urban oil fields were surrounded by a sea of expanding urban development.

The urban oil fields employ a variety of camouflage methods to reduce their environmental footprint and increase community compatibility. Oil fields disguised as synagogues, modern art exhibits, and office buildings, or wrapped by golf courses or invisibly tucked away in the most unlikely of corners lead to a unique setting where production from the richest oil field in the world is hiding in plain sight.