How the Natural Gas Distribution System Works
The fundamental science behind what drives natural gas from underground reservoirs into homes, businesses, and power-generating plants across the country, is all about pressure. Gas flows from high pressure to low pressure – with a few stops along the way.
Gathering lines
Shaped in a network not unlike the branches of a tree, gathering lines connect production wells to a central collection line, widening as they approach the center of the system. From here, gas follows gathering lines to the processing plant.
Large compressors or turbines are used to pressurize the gathering lines.
At the processing plant
To clean and refine natural gas for commercial use, it must be processed. How much processing a particular store of natural gas will need depends on the type of gas (wet or dry) and on the depth and pressure of the reservoir.
During processing:
- Impurities are removed, including water, carbon dioxide, and sulfur, as these impurities can corrode the pipeline
- Helium and other inert gases are separated in order to retain the gas’s full energy value
- Small quantities of propane and butane are extracted to be used for chemical feedstocks and other applications
The long road
The transmission phase of the process moves gas long distances along 270,000+ miles of steel pipe. Every 50 to 70 miles, a compressor station re-pressurizes the gas to push it further along in its journey, with pressures ranging from 200 to 1,500 PSI. The last stop is at local distribution companies (LDCs).
After its arrival at the LDC, natural gas passes through a gate station to alleviate pressure in the line in preparation for distribution, measure how much gas has been received by the station, and have mercaptan (or a similar compound) added to the gas. Mercaptan is what gives natural gas its rotten-egg aroma so that consumers can easily detect any leak in their system.
Pressure regulation and delivery
Once it has left the LDC, it is ready to be delivered. Within the distribution system, regulators control line pressure to manage flow rates at different points. As the gas gets closer to the end consumer, the pressure typically drops, as does the diameter of the lines. System pressure is automated by sophisticated computer systems to ensure the correct line pressure at the point of consumption.
The 3 stages of natural gas delivery
- Production enterprises explore, drill, and extract natural gas from the ground, including building and maintaining the wells at extraction sites
- Transmission companies operate and maintain the pipelines that connect gas fields to regions with high demand for consumption
- Local utility companies distribute and deliver natural gas to the customer, including residential homes, commercial buildings, and industrial facilities
Figure 1. Natural Gas Delivery System. Adapted from “Delivering Gas to You,” by the American Gas Association. Retrieved August 14, 2021, from https://www.aga.org/natural-gas/delivery/.
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