Like many of its peers, Gastar Exploration has hitched its star to exploring for natural gas (and some oil) in the US. The company's primary area of exploration and production is the Appalachian Basin ad its gas-bearing shale formations. Once active in Australia, Gastar Exploration is now focusing exclusively on lucrative US properties, primarily the Marcellus Shale play in northern West Virginia and southwestern Pennsylvania. It also owns oil and gas assets in Oklahoma. In 2012 the company had proved reserves of 248.9 billion cu. ft. of natural gas equivalent. Chesapeake Energy owns 10% of the company.