Natural gas is a naturally occurring hydrocarbon that consists mostly of methane. It is usually found in underground formations of porous rock, and can be found either alone or in association with oil. During the production process, wells are drilled into the porous rock and pipes are used to bring the natural gas to the surface. In most wells, the pressure of the natural gas is enough to force it to the surface and into the gathering lines.
Gathering lines link production areas to central collection points. Some natural gas gathering systems include a processing facility, which removes natural gas liquids, and impurities such as natural gas liquids, water, carbon dioxide or sulfur that might corrode a pipeline, and inert gases such as helium that could reduce the energy value of the gas.
The pipeline transmission system, the “interstate highway” for natural gas, consists of 220,000 miles of high-strength steel pipe 20 inches to 42 inches in diameter. It moves huge amounts of natural gas thousands of miles from producing regions to local natural gas utilities and sometimes directly to large users of natural gas. Compressor stations every 75 to 100 miles boost the pressure that is lost through the friction of gas moving through steel pipe.
Local distribution companies are the “city streets” for natural gas. This is where meters measure the gas and where a sour-smelling odorant is added to help customers smell even small quantities of natural gas. The local gas company then uses distribution pipes, or “mains,” to bring natural gas service to most U.S. homes and nearly 5 million businesses.
To help ensure reliable service, local natural gas companies can store natural gas underground for use during peak demand, such as cold days. Underground storage accounts, on average, for about 20 percent of the natural gas consumed each winter.