Among natural gas shale plays, the Barnett Shale in North Texas is getting a bit long in the tooth, but it can hold its own with the nation's other shale plays when it comes to proved reserves.

According to the latest statistics from the Energy Information Administration (EIA), the Barnett accounted for 9% of the country's 284 Tcf of proved reserves at the end of last year. It was followed by the Haynesville/Bossier at 4%; the Fayetteville, 3%; the Woodford, 2%; the Marcellus, 2%; the Antrim, 1%; and other shales accounting for less than 1%.

Combined, the shale plays accounted for 21% of the country's proved reserves of 284 Tcf, according to EIA. But the shale story is more dramatic when one looks at reserves growth.

Proved reserves of Alaska gas climbed 17.9% from the end of 2008 to the end of 2009. The Lower 48 onshore saw an increase of 2.5%, while Lower 48 offshore reserves declined 7.2% and coalbed methane reserves declined 10.6%, according to EIA statistics, which reflect discoveries plus/minus revisions and minus production.

But shale gas reserves climbed 76% from 2008 to 2009, which carried the United States to an 11.3% increase in proved reserves from year to year (see Shale Daily, Dec. 1).

Thanks mainly to the Barnett, Texas leads the shale states in the amount of shale gas reserves, followed by Louisiana, Arkansas, Oklahoma, Pennsylvania, Michigan and then the rest, according to EIA.