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Natural Gas Transportation 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.
Shell floats hull for world�s largest floating liquefied natural gas facility. The 488-meter-long-hull of Shell�s Prelude floating liquefied natural gas (FLNG) facility has been floated out of the dry dock at the Samsung Heavy Industries yard in Geoje, South Korea, where the facility is currently under construction. Once complete, Prelude FLNG will be the largest floating facility ever built. It will unlock new energy resources offshore and produce approximately 3.6 million tons of liquefied natural gas per annum to meet growing demand. FLNG will allow Shell to produce natural gas at sea, turn it into liquefied natural gas and then transfer it directly to the ships that will transport it to customers. It will enable the development of gas resources ranging from clusters of smaller more remote fields to potentially larger fields via multiple facilities where, for a range of reasons, an onshore development is not viable. This can mean faster, cheaper, more flexible development and deployment strategies for resources that were previously uneconomic, or constrained by technical or other risks. (Source: "Shell floats hull for world�s largest floating liquefied natural gas facility," PennEnergy, December 3, 2013.) US House approves bill aimed at increasing LNG exports - Oil & Gas Journal - 1/28/15
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.
References
Copyright 2000
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