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An accumulation, pool, or group of pools of hydrocarbons or other mineral resources in the subsurface. A hydrocarbon field consists of a reservoir with trapped hydrocarbons covered by an impermeable sealing rock or trapped by hydrostatic pressure. (Source: Schlumberger 2019)


A tall stack equipped with burners used as a safety device at wellheads, refining facilities, gas processing plants, and chemical plants. Flares are used for the combustion and disposal of combustible gases. The gases are piped to a remote, usually elevated, location and burned in an open flame in the open air using a specially designed burner tip, auxiliary fuel, and steam or air. Combustible gases are flared most often due to emergency relief, overpressure, process upsets, startups, shutdowns, and other operational safety reasons. Natural gas that is uneconomical for sale is also flared. Often natural gas is flared as a result of the unavailability of a method for transporting such gas to markets. (Source: U.S. Energy Information Administration 2019)

flowback water

The fracturing fluid that returns to the surface through the wellbore during and after a hydraulic treatment. (Source: The Geological Society of America 2019)


A body of rock strata, of intermediate rank in the hierarchy of lithostratigraphic units, which is unified with respect to adjacent strata by consisting dominantly of a certain lithologic type, or by possessing other unifying lithologic features. (Adapted from: Schlumberger 2019)

fracturing fluid

The water and chemical additives used to hydraulically fracture the reservoir rock, and proppant (typically sand or ceramic beads) pumped into the fractures to keep them from closing once the pumping pressure is released. (Source: The Geological Society of America 2019)


The amount or number of occurrences of an attribute or health outcome among a population. (Adapted from: Centers for Disease Control and Prevention 2014)

fugitive emission

Intentional or unintentional release of volatile chemicals during extraction, processing, and delivery of fossil fuels to the point of final use. (Source: Carras et al. 2006)