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How is natural gas transported to homes and businesses?Natural Gas Pipelines
[Click on image to view full-size] Natural gas pipelines are used to move gas from the field to consumers. Gas produced from onshore and offshore facilities is transported via gathering systems and inter- and intra-state pipelines to residential, commercial, industrial, and utility companies. A natural gas pipeline uses pressure from compressors to move the gas through the pipeline. There were 185,744 miles of interstate natural gas pipelines in the US in 1997. Most natural gas pipelines operate using a complex have become so automated that they are capable of operating under command of a computer system that coordinates the operation of valves, prime movers, and conditioning equipment.
An interesting aspect of natural gas pipelines is the introduction of odorants into the gas system. Natural gas is almost odorless as it comes from the well or processing facility. If the gas is destined for use as a fuel in homes or industry, a chemical called a mercaptan is added to give the gas a distinctive odor so that people can easily smell it when its concentration in air reaches 1%. Gas and air mixed in this concentration are not hazardous, but a mixture containing 5% gas is explosive. The odorant makes leaks or other unburned discharges of the gas quite evident long before a real hazard exists. Odorants injected into the gas burned in homes or industry do not create odors while burning, nor do they leave troublesome residue. Odorants are usually not introduced into gas sent to petrochemical plants where the gas is used as a feedstock for producing other commodities such as plastics, since the mercaptan will frequently interfere with the chemical process. Liquefied Natural Gas (LNG)In order to transport natural gas in areas not served by pipelines, the gas is liquefied to reduce its volume. When the gas is liquefied, it shrinks to l/600 of its gaseous volume.
Natural gas is kept in refrigerated and insulated tanks to maintain in its liquefied state during transport. Natural Gas StorageAn important aspect of the natural gas market is natural gas storage. Natural gas demand is seasonal. We use more gas in the winter to heat our homes, than we do in the summer. This is illustrated in the graph on the right. Unfortunately, we can't just change natural gas production to meet these changes, so we store gas during the summer (April-October) and withdraw gas from storage in the winter (November-March). Please click on the link Natural Gas Supply and Demand to see the seasonal variation of gas demand. Natural gas is stored in depleted fields, salt caverns, and aquifers. Depleted gas or oil reservoirs are used most often and comprise the majority of storage. Aquifers are water reservoirs that are conditioned to hold the gas. Natural gas must be brought in to "condition" the aquifer site and it takes four years before the site can be used. The structural integrity and impermeability of salt domes make this underground a good choice. The high withdrawal and injection rates are also important characteristics. Please click on the link Natural Gas Storage to see a history of natural gas storage levels. For current storage levels, please see the EIA's Weekly Natural gas Storage Report.
Go to the Topic Listing For more information about natural gas transportation and storage, check out the following references:
Updated 11/27/07 |
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