“The top 100 oil fields in the United States accounted for 20.6 billion barrels of crude oil and lease condensate proved reserves, or 56% of the U.S. total in 2013. The top 100 natural gas fields accounted for 239.7 trillion cubic feet of natural gas proved reserves, 68% of the U.S. total. Proved reserves are defined as estimated quantities of oil and natural gas that analysis of geologic and engineering data demonstrates with reasonable certainty are recoverable under existing economic and operating conditions.”