Storing Natural Gas

The storing of natural gas can be done for an indefinite period of time. The process of exploration, production, and transportation of natural gas is a long process and it is not necessary that natural gas that reaches its application areas will be used immediately. Hence it is injected into storage facilities which can be either storage tanks or underground facilities, usually located near market centers that do not have an immediate supply of natural gas.

The underground storages are of three types: depleted gas reservoirs, salt domes and aquifers. The gas is injected during the phase of low demand and extracted during the phase of higher demand. Though it may not be always practical, the storage near the ultimate end-users helps in meeting best the volatile demands.

Depleted Gas Reservoirs: They make use of a depleted underground natural gas reservoir that contained oil and/or gas originally. Gas is injected back into the reservoir so as to re-fill the reservoir. Depleted gas reservoirs are those formations on the earth that have already been tapped of all their recoverable natural gas. This leaves an underground storage, geologically capable of holding natural gas. Of the three types of underground storage facilities, depleted reservoirs are the cheapest and easiest to develop, operate, and maintain. The graphic given below depicts a typical depleted reservoir gas storage facility using vertical wells.


Salt Domes: Also known as salt cavern storage, salt domes are open caverns located at depths several thousands feet below the earth's surface. They are accessed by one or more wells per cavern. Underground salt formations thus provide an option for natural gas storage. These formations are suitable to natural gas storage because salt domes allow little injected natural gas to escape from the formation. The walls of a salt dome are very thick and heavy which makes it very resilient against reservoir degradation over the the storage facility's life. The graphic shows a typical salt cavern facility.


Aquifers: Aquifers are the most expensive and the least desirable type of natural gas storage facility. They are underground porous, permeable rock formations that act as natural gas storage facilities.

Delivering and Transporting of Natural Gas

The natural gas remains in the storage facilities till it is added into the pipeline and distributed as and when the demand arises. Natural gas is moved by pipelines from gas plants to consumers. When chilled to very cold temperatures, natural gas is transformed into a liquid and can be stored in this form. This is liquefied natural gas (LNG) which can be loaded onto tankers and moved across the ocean to deliver gas to other countries. Once in this form, LNG takes up only 1/600th of the space that it would in its gaseous state. Once the ship reaches the destination areas, it can be shipped by truck or trailers in large chilled tanks close to users or it can be turned back into gas to add to pipelines. Tank trucks can carry LNG or compressed natural gas (CNG) over shorter distances.

The delivery and distribution of natural gas to its point of end use is done by a distribution company . Distribution involves moving small volumes of gas at lower pressures over shorter distances and it is distributed to a large number of individual users. While in some large commercial, industrial and electric generation applications, natural gas is received directly from high capacity interstate and intrastate pipelines. Most others receive natural gas from a local distribution company (LDC).