Delivering natural gas to consumers
Delivering natural gas from natural gas and oil wells to consumers requires many infrastructure assets and processing steps and several physical transfers of custody.
Natural gas delivery infrastructure has three categories:
Processing natural gas for pipeline transport
Natural gas transported on the mainline natural gas transportation (pipeline) system in the United States must meet specific quality measures so that the pipeline network (or grid) provides uniform-quality natural gas. Wellhead natural gas may contain contaminants and hydrocarbon gas liquids (HGLs) that must be removed before the natural gas can be safely transported through high-pressure, long-distance pipelines to consumers. Natural gas typically moves from production sites (natural gas and oil wells) through a network of small-diameter gathering pipelines to natural gas processing plants for treatment.
Natural gas processing can be complex and usually involves several steps to remove oil, water, HGLS, and other impurities such as sulfur, helium, nitrogen, hydrogen sulfide, and carbon dioxide. The impurities in wellhead natural gas determine the number of stages and the processes required to produce pipeline-quality, dry natural gas. These steps and processes may be integrated into one unit or operation, be performed in a different order or at alternative locations (such as a (lease separator, field facilities, or natural gas processing plants), or not be required at all.
Basic stages of natural gas processing and treatment
- Gas-oil-water separators: Pressure relief in a single-stage separator causes a natural separation of the liquids from the gases in the natural gas. In some cases, a multi-stage separation process is required to separate the different fluid streams.
- Condensate separator: Condensates are most often removed from the natural gas stream at the wellhead with separators, much like gas-oil-water separators. The natural gas flows into the separator directly from the wellhead. The condensate extracted there is sent to storage tanks.
- Dehydration: This process removes water that may condense in pipelines and cause undesirable hydrates to form.
- Contaminant removal: Nonhydrocarbon gases—such as hydrogen sulfide, carbon dioxide, water vapor, helium, nitrogen, and oxygen—must also be removed from the natural gas stream. The most common removal technique is to direct the natural gas though a vessel containing an amine solution. Amines absorb hydrogen sulfide and carbon dioxide from natural gas and can be recycled and regenerated for repeated use.
- Nitrogen extraction: Once the hydrogen sulfide and carbon dioxide are reduced to acceptable levels, the natural gas stream is routed to a Nitrogen Rejection Unit (NRU), where it is further dehydrated using molecular sieve beds.
- Methane separation: This process can occur as a separate operation in a natural gas processing plant or as part of the NRU operation. Cryogenic processing and absorption methods are some of the ways used to separate methane from HGLs.
- Fractionation: HGLs are separated into component liquids using the varying boiling points of the individual HGLs. HGLs from the processing plant may be sent to petrochemical plants, oil refineries, and other HGLs consumers.
Moving natural gas from production fields to markets
Natural gas transmission pipelines are wide-diameter pipelines and are often the long-distance portion of natural gas pipeline systems that connect gathering systems in producing areas, natural gas processing plants, and other receipt points to the main consumer service areas.
Three types of transmission pipelines
- Interstate natural gas pipelines operate and transport natural gas across state borders.
- Intrastate natural gas pipelines operate and transport natural gas within a state border.
- Hinshaw natural gas pipelines receive natural gas from interstate pipelines and deliver it to consumers for consumption within a state border.
When natural gas arrives at the locations where it will be used (usually through large pipelines), it flows into smaller diameter pipelines called mains and then into smaller service lines that go directly to homes or buildings.
Storing natural gas for times of peak demand
Demand for natural gas fluctuates daily and seasonally, but production and pipeline imports are relatively constant in the short term. Natural gas storage during periods of low demand helps to ensure that enough natural gas is available during periods of high demand. Natural gas is stored in large volumes in underground facilities and in smaller volumes in tanks above or below ground.
The United States uses three main types of underground natural gas storage facilities:
- Depleted natural gas or oil fields—Most natural gas storage is in depleted natural gas or oil fields that are close to consuming areas.
- Salt caverns—Most of the salt cavern storage facilities are in salt dome formations in the states bordering the Gulf of Mexico. Salt caverns have also been leached from bedded salt formations in states in the Midwest, Northeast, and Southwest.
- Aquifers—Water aquifers that have water-bearing sedimentary rock formations overlaid with impermeable cap rock are used as natural gas storage reservoirs, especially in the Midwest.
Last reviewed: February 17, 2023