The South Belridge Oil Field is a large oil field in northwestern Kern County, San Joaquin Valley, California, about forty miles west of Bakersfield. Discovered in 1911, and having a cumulative production of over 1.5 billion barrels of oil at the end of 2008, it is the fourth-largest oil field in California, after the Midway-Sunset Oil Field, Kern River Oil Field, and Wilmington Oil Field, and is the sixth-most productive field in the United States. Its estimated remaining reserves, as of the end of 2008, were around 494 million barrels, the second-largest in the state, and it had 6,253 active wells. The principal operator on the field was Aera Energy LLC, a joint venture between Royal Dutch Shell and ExxonMobil.