Center for Environmental Policy

This fact sheet is intended to give an overview
of the major elements of the issue of drilling in the Marcellus Shale.

The Marcellus Shale is a large, underground formation of sedimentary rock located at depths of a mile or more below most of Pennsylvania.  Large amounts of natural gas are embedded in the Marcellus Shale.

Natural gas is methane formed from the decomposition of prehistoric life forms.  It is used extensively as a fuel source and is judged to have fewer harmful emissions and produces less greenhouse gases than coal.

The gas is stored primarily in the tiny pore spaces of the shale.  Because of this, and because of the depth of the shale, it was not economically viable in the past to access the gas.

Recent estimates suggest that there are over 300 trillion cubic feet of recoverable natural gas held in the Marcellus Shale, enough to meet the needs of the U.S. for fourteen years.  Given these large potential returns from the Marcellus Shale, and with new drilling technologies now available, it has become economically practical to drill for the gas.

The new drilling technologies involve horizontal drilling into the shale formation, followed by the use of high pressure water to fracture the shale and release the gas. This process is known as “fracking” and involves the use of large volumes of water with other chemicals and salts to facilitate the fracturing.

There are several key social and economic advantages identified with accessing the gas in the Marcellus Shale.  These include:

• Potential jobs and other economic benefits in the drilling process;
• Decreasing dependence on foreign sources of energy;
• Lower greenhouse gases produced by use of natural gas;
• Potential for lowering energy costs in Pennsylvania.

However, a number of questions have been raised as to the environmental and social impact of this drilling.  These include:

• Effects of drilling operations on habitat and natural systems, including state and private forests;
• Source of fracturing (“frack”) water;
• Disposal of frack water and chemicals;
• Effect on drinking water, groundwater and surface water bodies;
• Socio-economic impact on rural communities.