The Eagle Ford Shale is a Cretaceous-age, black calcareous shale with a high organic carbon content located directly below the Austin Chalk underlying much of South Texas. The Shale formation in South Texas runs from the US-Mexico border north of Laredo extending just north of Houston. The more active part of the region is mainly in McMullen, Maverick, Dimmit, La Salle, Karnes, Live Oak and Atascosa countries. The first well was drilled in 2008 by Petrohawk Energy in La Salle Country. This well demonstrated that horizontal drilling and hydraulic fracturing techniques could be used to produce gas from the Eagle Ford Shale. It wasn't until 2010 when drilling permits in the Eagle Ford Shale began to drastically increase. In 2010, there were more than 1,000 permits issued. By 2012, more than 4,000 permits were issued throughout the year. The Eagle Ford Shale has quickly become one of the most heavily drilled rock units in the United States. Currently, through joint development with its partners, Mitsui currently has close to 35,000 net leasehold acres, and has participated in approximately 1,750 wells in shale play.