While the existence of the field was suspected in the 1950s , the field was not discovered until 1968 . Unocal and several other oil companies took out leases on the field in February 1968 , and put in the first well , and the first platform , that same year . Data regarding the four platforms are as follows : Unocal succeeded in installing the first four wells from its Platform A by January 1969 , but their attempt to install the fifth well was catastrophic , and resulted in one of the most notorious environmental disasters in United States history . Because the drillers were using an insufficient length of protective casing , when the well hit a high-pressure zone in the field , it blew out , spewing enormous quantities of oil and gas into the water from the sea floor . While crews were able to cap the wellhead and relieve the pressure there , the adjacent geologic formations were not strong enough to contain the pressure , and lacking a steel protective casing , the reservoir fluid and gas ripped through the sedimentary sand layers directly on the ocean floor ; the result was the 1969 Santa Barbara oil spill of 80,000 to 100,000 barrels , which eventually coated over 40 miles of southern California coastline with oil , an ecological disaster which killed upward of 10,000 birds and numerous sea mammals and other creatures
1969 Santa Barbara oil spill
1969 Santa Barbara oil spill
Dos Cuadras Offshore Oil Field