ABSTRACT
Natural gas, coal, and oil supply about 85% of the nation’s energy, with natural gas supplying about 22% of the total (USEIA, 2008a) (Figure 2.1). Natural gas plays a key role in meeting U.S. energy demands, and its percent contribution to the U.S. energy supply is expected to remain fairly constant for the next 20 years. The United States has abundant natural gas resourcesmore than 1744 trillion cubic feet (Tcf) of technically recoverable natural gas, including over 300 Tcf of proved reserves (the discovered, economically recoverable fraction of the original gas in place) (USEIA, 2008b, 2010). Technically recoverable unconventional gas (shale gas, tight sands, and coa bed natural gas) accounts for 60% of the onshore recoverable resource. At the 2010 U.S. production rate, approximately 26.86 Tcf, it is estimated that the
current recoverable resource could provide enough natural gas to supply the United States for the next 110 years (USEIA, 2012) (Figure 2.2). Note that, historically, estimates of the size of the total recoverable resource have grown over time as knowledge of the resource has improved and recovery technology has advanced. Unconventional gas resources are a prime example of this trend; for example, U.S. proved reserves of wet natural gas increased by 11% in 2009 to 284 Tcf (USEIA, 2010).
