 J. Paul Getty, Standard Oil of California, Richfield Oil Corporation, Shell and Mobil all once had holdings on the Edison field.Smaller independents absorbed these holdings, and in 2009 there were 40 separate operators on the field.Some of the largest of these at the end of 2008 were Vaquero Energy, with 352 wells; Naftex Operating Company, with 163, and Sequoia Exploration, Inc. with 93.