The Marcellus Shale is now the largest natural gas-producing play. Increased drilling activity over the past 6 years has played a part in this growth.
Penn State University released an animation that clearly shows not only the increased growth in drilling in Pennsylvania but also how a few test wells can result in increased interest in an area. As you will see, in 2012 a few test wells were spud in Mercer and Crawford county, one can only wonder if those areas will look similar to Washington county in a few short years.