Refers to the bank of natural resources, such as natural gas, natural gas liquids, petroleum, coal, lignite, energy available from water power, and solar and geothermal energy. Estimated Potential Natural Gas Resources. Refers to an estimate of the remaining natural gas in a specified area which are judged to be recoverable. Estimated Proved Natural Gas Reserves. An estimated quantity of natural gas which analysis of geologic and engineering data demonstrates with reasonable certainty to be recoverable in the future from known oil and gas reservoirs under anticipated economic and current operating conditions. Reservoirs that have demonstrated the ability to produce by either actual production or conclusive formation test are considered proved.