Extending throughout much of the Appalachian Basin, the Marcellus shale is stratigraphically the lowest member of the Devonian age Hamilton Group, and is divided into sub-units. The formation is mainly composed of black shale and contains lighter shales and interbedded limestone layers as result of sea level variations during deposition almost 400 million years ago. It is overlain by the Mahantango shales and Tully limestone and uderlain by the Onondaga limestone, Huntersville chert, and Oriskany sandstone. Having a potentially prospective area of over 44,000 square miles, the Marcellus shale is one of the largest shale plays in North America and covers portions of New York, northern and western Pennsylvania, eastern Ohio, western Maryland, and most of West Virginia. In its 2011 Annual Energy Outlook report, the EIA reported technically recoverable reserves of approximately 400 TCF of natural gas in the Marcellus shale. Recovering 400 TCF of natural gas from a shale resource requires tremendous amounts of water that is used primarily for hydraulic fracturing. Care must be taken to ensure minimal environmental impact; e.g., use of fresh water, when developing this resource while continually increasing operational efficiency.
Gas Technology Institute (GTI)
Research Partnership to Secure Energy for America (RPSEA)
Gas Technology Institute (GTI), with funding from the Research Partnership of Secure Energy for America (RPSEA), initiated an industry cooperative research project, that, aside from other tasks, aims to examine the contribution of gas production from natural fractures in addition to predicting the spatial distribution and population characteristics of these natural fractures systems. The natural fracture systems in conjunction with hydraulic fracturing are the key drivers for gas production. Hence, in addition to understating the natural fracture attributes, it is necessary to optimize hydraulic fracturing treatments so that a synergistic effect is achieved whereby the natural fractures are exploited for enhanced gas production. As such, much of the research was focused on hydraulic fracture design and optimization with support field data acquisition.
A team of experts including five universities, one national laboratory, and one industry consortium, worked together with service companies and a major producer in the heart of the Marcellus Shale. The goal was to evaluate reservoir characteristics and determine optimal completion and stimulation techniques and develop technologies that increase gas production while minimizing environmental impact. Dedicated research was focused on the areas of: geology, reservoir engineering, high-resolution rock imaging, dynamic flow behavior of shale gas, hydraulic fracture modeling and diagnostics, and microseismic imaging. The cooperative efforts resulted in better understanding of the Marcellus Shale reservoir and enhanced understanding of fracturing dynamics thus leading to more efficient fracturing techniques that reduce environmental impact while producing more gas.