Shale gas

Shale gas is natural gas trapped in fine-grained shale formations. It is commonly extracted by drilling horizontally through the rock and creating fractures that let gas flow to a well.

Hydraulic fracturing: A method that injects pressurized fluid into rock to create fractures and improve fluid flow. It creates pathways through shale so trapped gas can flow toward a well.
United States natural gas production: The extraction of natural gas from fields across the United States. Shale gas drove much of the rapid growth in U.S. gas output since the 2000s.
Methane emissions: The release of methane into the atmosphere from human activities and natural sources. Leaks during shale gas production and transport can offset some climate benefits of gas use.
Conventional natural gas: Natural gas produced from permeable reservoirs where gas can flow readily to a well. Unlike shale gas, conventional gas typically needs no extensive fracture network to flow.
George P. Mitchell: An American oil and gas entrepreneur whose company helped make commercial shale gas production viable. His long-running experiments helped combine horizontal drilling with hydraulic fracturing in the Barnett Shale.
Horizontal drilling: A drilling technique that turns a wellbore to run sideways through a subsurface formation. A long horizontal well exposes more shale to fractures than a vertical well.
Liquefied natural gas: Natural gas cooled into liquid form for storage and transport by specialized vessels. Surplus shale gas can enter export markets after liquefaction.
Induced seismicity: Earthquakes triggered or influenced by human activities that alter subsurface stress or pressure. Wastewater disposal associated with shale development has triggered damaging earthquakes in some regions.
Tight gas: Natural gas held in low-permeability sandstone or carbonate formations. It shares the need for stimulation but occurs in rock other than shale.
Barnett Shale: A geological formation in north-central Texas that became a major shale gas production region. It served as a proving ground for techniques later used across U.S. shale plays.

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