Take a look at the latest story from the New York Times on shale gas revisions by the DOE. http://www.nytimes.com/2011/08/25/us/25gas.html

According to production history filed by operators in various states, shale gas volumes have not turned out to be as homogeneous as once thought. In the earlier days of the plays, it was widely touted that you could drop a bit and hit gas anywhere in one of these plays. Aubrey McClendon admitted, however, to [...]

There appears to be a great deal of confusion regarding production vs. reserves. A leading argument states that shale gas “[has risen] from 2 percent of all natural gas production in 2000 to 23 percent 10 years later,” a statistic the M.I.T. group called a “paradigm shift.” But this is misleading unless put into context. [...]