<P> The number of actively drilling gas rigs was once regarded as a reliable leading indicator of near - future gas production . However, the average number of active gas drill rigs has fallen each year for four straight years from 2010 (942 rigs) to 2014 (332 rigs), a drop of 65 percent, even while gas production rose each year for the same period, from 21.3 trillion cubic feet (TCF) in 2010 to 25.7 TCF in 2014, an increase of 21 percent . Remaining proved reserves increased overall, from 301 TCF in 2013 to 338 TCF in 2013 (the last year for which reserves are available), an increase of 11 percent . The rise in gas production despite fewer rigs drilling has been explained by the greater efficiency in drilling, and the greater productivity of shale gas wells . </P> <P> Top producing gas fields in the United States, 2013 </P> <Table> <Tr> <Th> Rank </Th> <Th> Field </Th> <Th> State </Th> <Th> Discovery Year </Th> <Th> Billion cubic ft. / Year </Th> </Tr> <Tr> <Td> </Td> <Td> Marcellus natural gas trend </Td> <Td> Pennsylvania and West Virginia </Td> <Td> 2008 </Td> <Td> 2,836 </Td> </Tr> <Tr> <Td> </Td> <Td> Newark East Barnett Shale </Td> <Td> Texas </Td> <Td> 1981 </Td> <Td> 1,952 </Td> </Tr> <Tr> <Td> </Td> <Td> Haynesville Shale </Td> <Td> Louisiana and Texas </Td> <Td> 2008 </Td> <Td> 1,426 </Td> </Tr> <Tr> <Td> </Td> <Td> Eagle Ford Formation </Td> <Td> Texas </Td> <Td> 1962 </Td> <Td> 1,112 </Td> </Tr> <Tr> <Td> 5 </Td> <Td> Fayetteville Shale </Td> <Td> Arkansas </Td> <Td> 2005 </Td> <Td> 1,025 </Td> </Tr> <Tr> <Td> 6 </Td> <Td> San Juan Basin </Td> <Td> New Mexico and Colorado </Td> <Td> 1927 </Td> <Td> 1,025 </Td> </Tr> <Tr> <Td> 7 </Td> <Td> Carthage </Td> <Td> Texas </Td> <Td> 1936 </Td> <Td> 653 </Td> </Tr> <Tr> <Td> 8 </Td> <Td> Pinedale Gas Field </Td> <Td> Wyoming </Td> <Td> 1955 </Td> <Td> 568 </Td> </Tr> <Tr> <Td> 9 </Td> <Td> Sprayberry </Td> <Td> Texas </Td> <Td> 1949 </Td> <Td> 307 </Td> </Tr> <Tr> <Td> 10 </Td> <Td> Wattenberg Gas Field </Td> <Td> Colorado </Td> <Td> 1970 </Td> <Td> 305 </Td> </Tr> <Tr> <Th_colspan="5"> Annual production 2013 . Source: </Th> </Tr> </Table> <Tr> <Th> Rank </Th> <Th> Field </Th> <Th> State </Th> <Th> Discovery Year </Th> <Th> Billion cubic ft. / Year </Th> </Tr>

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