Hydrocarbon gas liquids (HGL) are produced when raw natural gas is processed at natural gas processing plants and when crude oil is refined into petroleum products. Most HGLs produced in the United States are separated from natural gas at natural gas processing plants.
Hydrocarbon gas liquids production from natural gas processing
HGLs are present as gases in geologic formations that contain natural gas. Raw, or untreated, natural gas produced from natural gas wells and oil wells is called wet gas because it sometimes contains HGLs, along with water vapor and other nonhydrocarbon gases. HGLs should not be confused with lease condensate separated out of associated and nonassociated natural gas at lease facilities. The liquid condensate is usually added to crude oil in pipelines that transport oil to refineries.
Natural gas is usually treated at natural gas processing plants before it enters natural gas transmission pipelines. HGLs extracted at these plants are called natural gas plant liquids. Natural gas that has been processed to remove most of the HGLs and nonhydrocarbon compounds is called dry gas, which is mostly methane. Natural gas pipeline operators have strict specifications for the characteristics (such as the heat content) of the dry natural gas they accept, which in turn, limits the amount of HGLs contained in natural gas that is transported through these pipelines.
Mixed HGL streams (also known as Y-grade) are separated from each other by fractionation. Fractionation facilities may be co-located at natural gas processing plants, or they may stand alone and receive mixed HGL streams from several processing plants. Fractionation facilities separate some or all of the individual HGLs that are sold as purity products—ethane, propane, normal butane, and isobutane. These HGL products are at least 90% one type of HGL molecule.
Most natural gas processing and fractionation plants in the United States are in areas where natural gas and crude oil production is concentrated. In 2022, HGL production from natural gas processing accounted for about 90% of total U.S. HGL production.
Hydrocarbon gas liquids production from crude oil refining
HGL production at petroleum refineries can occur during the distillation process, which separates HGLs in crude oil from other crude oil fractions. HGL production can also occur at refinery cracking units, which break longer-chained (heavier) hydrocarbons into lighter molecules and yield HGLs alongside distillate or gasoline-blending components. All refinery olefins are produced at refinery cracking units.
Propane and propylene are the primary HGLs produced and sold as separate purity products by petroleum refiners. Most other HGLs produced at refineries are burned as fuels or used to make gasoline and petrochemical feedstock.
Last updated: December 26, 2023.