While natural gas is clearly essential to the U.S. and world economies, estimates vary widely as to how much unharvested gas remains, though nearly all experts believe that gas reserves remain plentiful. According to a 2009 report from the Potential Gas Committee, the United States contains an estimated 2,074 trillion cubic feet of natural gas. That's an improvement from a 2006 report that pegged reserves at 1,532 trillion cubic feet. Some experts chalk up the large increase to improved drilling techniques. To give you an idea of how much natural gas remains, consider that the top five natural gas consumers used 1.8 trillion cubic feet of natural gas, according to the CIA World Factbook.
When estimating natural gas reserves, experts consider offshore reserves as well as the various types of "unconventional" gas -- shale gas, tight gas and coalbed methane. Some areas classified in this latter group may contain immense gas deposits, but recovery is often very difficult or prohibitively expensive. For example, it's believed that large shale deposits in the Appalachian Basin are rich with natural gas, yet only about one-tenth of it may be recoverable. At the same time, better drilling methods -- such as hydraulic fracturing, where high-pressure water is pumped into deep wells in order to release gas -- have made gas shale beds one of the fastest growing areas in natural gas extraction.
With better methods on hand, natural gas seems bound to increase its role in the future of energy.