Processing Natural Gas: Fundamental Steps

From oil and gas wells to consumers, natural gas is transported via infrastructure assets and processing steps, and several physical custody transfers occur.

Implementing quality standards for natural gas delivered through the mainline natural gas transportation system (pipeline) is essential to deliver consistent quality natural gas. Before wellhead natural gas can be safely supplied to the high-pressure, long-distance pipelines that transport natural gas to consumers, pollutants and hydrocarbon gas liquids (HGLs) may need to be eliminated. Natural gas is often transported to natural gas processing plants for treatment from natural gas and oil wells via a collection system of pipes.

Processing natural gas to remove oil, water, HGLs, and other pollutants like sulfur, helium, nitrogen, hydrogen sulfide, and carbon dioxide can be complicated and typically involves numerous procedures or stages. The number of steps and techniques necessary to produce dry natural gas of pipeline quality depends on the nature of the wellhead natural gas. These steps and procedures could be combined into a single unit or operation, carried out in a different sequence, at a different facility, or not at all.

Fundamental steps in the processing of natural gas

Gas-oil-water separators: The natural separation of the liquids from the gases in the natural gas occurs due to pressure relief in a single-stage separator. It may be necessary for some circumstances to separate the various fluid streams using a multi-stage separation procedure.

Condensate separator: At the wellhead, separators similar to gas-oil-water separators are typically used to separate condensates from the natural gas stream. Direct natural gas flow from the wellhead enters the separator, and the extracted condensate is put in storage tanks.

Dehydration: During dehydration, water that could form unwelcome hydrates or induce water condensation in pipelines is removed.

Removal of contaminants: The natural gas stream must also be cleared of nonhydrocarbon gases such as hydrogen sulfide, carbon dioxide, water vapor, helium, nitrogen, and oxygen. The most typical removal method involves passing natural gas through a vessel containing an amine solution. Amines can be recycled and regenerated for continued use and absorb carbon dioxide and hydrogen sulfide from natural gas.

Natural gas is often transported to natural gas processing plants for treatment from natural gas and oil wells via a collection system of pipes.

 

Nitrogen extraction: The natural gas stream is directed to a nitrogen rejection unit (NRU), which is further dehydrated using molecular sieve beds once the hydrogen sulfide and carbon dioxide have been brought down to acceptable levels.

Methane separation: At a natural gas processing facility, demethanizing the natural gas stream can be done separately or as part of the NRU operation. Some techniques used to separate methane from HGLs include cryogenic processing and absorption techniques.

Fractionation divides HGLs into constituent liquids based on their boiling temperatures. The petrochemical industry, oil refineries, and other HGL users may receive HGLs from the processing facility.

Pipelines transport natural gas from production areas to markets.

Natural gas transmission pipes are large-diameter pipelines that connect gathering systems in producing areas, natural gas processing plants, various receipt locations, and the primary consumer service areas over vast distances.

Various types of transmission pipeline

Interstate natural gas pipelines are in use and move gas between states.

Gas pipes that run entirely within a state's boundaries are known as intrastate pipelines.

Natural gas is delivered to consumers for consumption inside a state boundary by Hinshaw natural gas pipelines, which take delivery of the gas from interstate pipelines.

When natural gas reaches its intended use locations, it enters smaller-diameter pipelines before entering smaller service lines to residences or buildings.

Gas is kept in reserve for periods of high demand.

Natural gas demand varies daily and seasonal, although output and pipeline imports are generally stable in the near term. Natural gas is stored during times of low demand to ensure enough supplies are available during times of high demand. Large amounts of natural gas are kept in underground facilities, while smaller amounts are kept in above- or below-ground tanks.