The short answer to your question is at least a few decades, probably 30 years. As the second largest natural gas field in the world, at approximately 95,000 square miles and estimated to contain upwards of 410 trillion cubic feet of gas, this is an industry that will be around for quite some time. In 2011, the entire United States consumed 24 Tcf of natural gas, meaning that the Marcellus alone could supply just under 20 years of supply.