4. Gastar Exploration ( GST) is an independent U.S.-based company engaged in the exploration, development and production of natural gas and oil. The company is pursuing natural gas exploration in the deep Bossier gas well in the Hilltop area in East Texas and the Marcellus Shale in West Virginia and central and southwestern Pennsylvania. As on Dec. 31, 2010, the company's total proved reserves stood at 49.9 billion cubic feet (Bcf) of natural gas and 61,300 barrels of oil, or 50.3 (Bcfe), of which 83% were proved developed reserves. Compared to December 2009, total proved reserves amounted to 48.5 Bcf of natural gas and 66,700 barrels of oil, or 49 Bcfe. In December 2010, the company acquired 61,800 net acres of leasehold in the Marcellus Shale concentrated in Preston, Tucker and Pendleton Counties of West Virginia for $28.9 million. The region accounts for five conventional wells producing around 500 million cubic feet per day of natural gas and the company plans to drill one of the Marcellus wells on this acreage during 2011. As on Dec. 31, 2010, Gastar's proved reserves in the Marcellus Shale region is approximately 2.8 Bcfe, representing 6% of company's total proved reserves. Analysts expect the stock to deliver an upside of 26% with a buy rating of 80%. The stock is trading at 13 times its estimated 2012 earnings.