Forbes has an interesting interview with George Mitchell, who cracked the Barnett Shale back in the 1980's and 1990's, making the play commercial for operators to drill. Mitchell sold out to Devon Energy (DVN) for billions in 2002. This technology that Mitchell employed in the Barnett shale has been transferred, with slight variations to other plays in North America, including the Haynesville and Marcellus Shales.
Forbes Interview