Natural gas is a global energy source for homes, businesses, and industries. Its journey from underground reservoirs to end-users involves multiple stages of extraction, treatment, and distribution.
From Extraction to Processing Plants
Natural gas begins its journey deep beneath the Earth’s surface, extracted from underground reservoirs through drilling operations. At wellheads, the raw gas is a mixture of components, not just methane, often containing crude oil, water, and impurities that must be removed.
Initial processing at the well site removes liquids like water and oil. The gas then goes to processing plants for further purification. Contaminants such as hydrogen sulfide, carbon dioxide, water vapor, and mercury are extracted to meet pipeline quality standards. This purification is important because impurities like hydrogen sulfide are toxic and corrosive, and water vapor can form flow-impeding hydrates. The process also separates valuable natural gas liquids (NGLs) like ethane, propane, and butane for commercial use.
High-Pressure Transmission Pipelines
After processing, natural gas is transported long distances through a vast network of high-pressure transmission pipelines. These pipelines, often made of high-strength carbon steel, span thousands of miles. Mainline diameters typically range from 24 to 36 inches, with some reaching 48 inches.
Natural gas is compressed to high pressures, commonly between 500 and 1,500 pounds per square inch (psi), to efficiently move large volumes. Compressor stations, placed every 50 to 100 miles, re-pressurize the gas to maintain flow and pressure. Metering stations along the route accurately measure the volume of gas being transported.
Local Distribution Networks
The transition from long-haul transmission to local delivery occurs at city gate stations. Here, the high pressure of the incoming gas is significantly reduced to suit local network requirements. This pressure reduction is a necessary step before the gas enters community distribution systems.
A distinct odorant, typically mercaptan, is added to the naturally odorless natural gas at these city gate stations. Mercaptan has a strong, unpleasant smell often described as rotten eggs or cabbage, making gas leaks easily detectable by the human nose, even at very low concentrations. From these stations, a network of smaller-diameter mains and service lines carries the gas to individual homes, businesses, and industrial facilities. These local networks operate at much lower pressures, generally under 200 psi for mains and below 10 psi for service lines, ensuring safe delivery to end-use appliances.
Ensuring Safety and Reliability
Maintaining the safety and reliability of natural gas distribution involves continuous monitoring and stringent regulations. Regular inspections and advanced leak detection technologies are routine practices.
Methods include acoustic monitoring, gas sampling, thermal imaging, and fiber optic sensing, which can detect subtle changes in sound, temperature, or vibration indicating a leak. Pipeline integrity management programs utilize specialized tools known as “smart pigs,” which are pipeline inspection gauges equipped with sensors and magnets. These intelligent devices travel through pipelines, detecting potential issues such as corrosion, metal loss, cracks, and dents in the pipe walls using technologies like magnetic flux leakage and ultrasonic waves.
The Pipeline and Hazardous Materials Safety Administration (PHMSA) sets and enforces comprehensive safety regulations for pipeline design, construction, operation, and maintenance. PHMSA also collaborates with state agencies to ensure consistent oversight and promotes public awareness about natural gas safety.