The International Energy Agency is forecasting that the United States will surpass Russia and Saudi Arabia to become the world’s largest oil producer in 2015 and could be energy self-sufficient within 20 years.  United States energy production is currently led by Texas and North Dakota, as oil companies use the techniques of hydraulic fracturing and horizontal drilling to produce oil and natural gas from shale formations.   A more recent oil  discovery, California’s Monterey Shale, could yield about 15.4 billion barrels of oil accounting for roughly two-thirds of the U.S. total estimated shale oil reserves.  The oil extracted from that region could turn California into the nation’s top oil-producing state.