www.springer.com/12205 Energy Geotechnology A Critical Evaluation of Unconventional Gas Recovery from the

The Marcellus tight gas shale represents a significant resource within the northeastern United States. It is both a large reserve, with an estimated 30 to 300 TCF of recoverable gas, and is close to some of the largest prospective markets in the country. However, production is fraught with technological obstacles, the most significant of which include prospecting, access by drilling, stimulation, and recovery. Prospecting is difficult because viability of the reservoir relies both on the original gas in place and in the ability to access that gas through pre-existing fractures that may be developed through stimulation. Drilling is a challenge since drilling costs typically comprise 50 % of the cost of the wells and access to the reservoir is improved with horizontal drilling which may access a longer productive zone within the reservoir than cheaper vertical wells. Finally, stimulation methods are necessary to improve gas yields and to reduce the environmental impacts of both consumptive water use and the subsequent problems of safe disposal of fracwater waste. We discuss the challenges involved in the economic recovery of gas from tight gas shales in general and the Marcellus in particular