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Shale Gas Production / Hydraulic Fracturing Overview
Shale gas refers to natural gas resources located in impermeable shale rock formations several thousand feet below the Earth’s surface. Shale gas extraction involves drilling into shale ‘plays’, or areas in the formation with a high concentration of gas reserves, and it also uses different techniques than conventional natural gas production, including horizontal drilling and hydraulic fracturing . Through horizontal drilling, wells are initially drilled vertically and then horizontally to run throughout shale formations. Following the drilling, hydraulic fracturing (sometimes referred to as “fracking”) involves injecting a mixture of sand, water, and chemicals to create small cracks in shale formations that enable easier natural gas extraction. Most of the 2 to 5 million gallons of fluid injected into a well are water, but the fluid used in hydraulic fracturing may also contain a variety of chemicals . These chemicals usually make up 0.5 to 2 percent of the overall volume of fluid used in hydraulic fracturing.
Due to the growth of shale gas production in recent years, there has been momentum at the state level to further evaluate the long-term risks of shale gas production on human health and the environment. This map provides an overview of existing and potential shale gas production in the United States using EIA’s most recent data (2011) , as well as certain state-level actions that address concerns over hydraulic fracturing safety. These actions include requirements for shale gas producers to disclose the chemicals used in hydraulic fracturing, assessments of shale gas practices, and in some instances, moratoriums on hydraulic fracturing.
Shale Gas Production
Many U.S. states are expanding existing shale gas operations or gaining access to shale gas resources, including several states that are not traditionally considered energy producers. Operators are currently drilling new wells in several states, dramatically increasing shale gas production volumes. Note that shale gas production volumes are measured in Billion Cubic Feet (Bcf). In 2011 , the United States consumed approximately 24,370 Bcf of natural gas. For comparison, a large natural gas fired power plant consumes about 7.3 Bcf of gas per year , which produces 730,000 megawatt-hours of electricity.
Fracking Fluid Chemical Disclosure Requirements
To improve transparency and to better assess the potential effects of hydraulic fracturing on drinking water resources and human health, several state governments have enacted requirements for shale gas producers to disclose the chemicals used in hydraulic fracturing fluids. Chemicals used in the process may be identified and reported using their unique Chemical Abstract Service (CAS) numbers. Depending on the state, disclosures must be made to a state agency or to an independent party, such as the Chemical Disclosure Registry (FracFocus.org), but rules may also include provisions for protecting trade secrets. The Chemical Disclosure Registry is managed by the Ground Water Protection Council (GWC) and Interstate Oil and Gas Compact Commission (IOGCC), two organizations that convene officials from multiple states to work on policies of common interest, such as hydraulic fracturing. The Chemical Disclosure Registry provides information on the location, dates, and chemicals involved with hydraulic fracturing activity.
State-Sponsored Studies of Shale Gas Production Practices
Several states have sponsored studies of shale gas production practices within their states to better understand shale gas production potential and identify possible safety concerns. Several states have commissioned the State Review of Oil and Natural Gas Environmental Regulations (STRONGER ) to conduct studies of state hydraulic fracturing policies and practices. STRONGER is a nonprofit organization that convenes stakeholders from state government, industry, and the environmental community to prepare its reports.
State Restrictions on Hydraulic Fracturing
Several states have imposed restrictions on hydraulic fracturing. Most of these restrictions have been imposed temporarily, usually to give time for a state to study shale gas production practices. To date, only Vermont has indefinitely prohibited hydraulic fracturing.