Types of LPG Storage
Above Ground Tanks are cylindrical bullet shaped tanks where LPG is stored under pressure.
Underground Storage tanks are tanks where LPG is stored underground. They are found at service stations, connected to boilers/steam generators, or connected to emergency generators.
Semi-buried mounded Tanks
Semi Buried Tanks are LPG storage tanks that are partially buried underground. Till recent years, bulk storage of highly inflammable Liquefied Petroleum Gas (LPG) was being done in above ground storage tanks. However some major fire / explosions underlined the need to review the design, procedure, maintenance, fire fighting and safety aspects of LPG handling.
A safer option was introduced in the form of Semi-Mounded LPG Storage Tanks since it provides intrinsically passive and safe environment and eliminates the possibility of BLEVE (Boiling Liquid Expanding Vapor Explosion). Mounded LPG Bullets are large, buried, horizontal cylindrical steel tanks with dished ends of size ranging between 3.5 to 7.0 meter diameter and lengths of 35 to 70 meters or more.
Underground caverns are underground naturally occurring or man-made caves that are used for storing LPG. The types of different underground storage are:
Disused mines are existing deep mines that were used for coal storage.These can be used to store LPG.
Aquifers are underground, porous and permeable rock formations that act as natural water reservoirs. Aquifers are the least desirable and most expensive type of natural gas storage facility for a number of reasons.
Depleted Oil and Gas Reservoirs
Oil and gas reservoirs are porous rock formations (usually sandstones or carbonates) containing hydrocarbons such as crude oil and/or natural gas that have been physically trapped.
Salt caverns are typically much smaller than depleted gas reservoirs and aquifers. However, deliverability from salt caverns is typically much higher than for either aquifers or depleted reservoirs. Therefore natural gas stored in a salt cavern may be more readily (and quickly) withdrawn, and caverns may be replenished with natural gas more quickly than in either of the other types of storage facilities. Moreover, salt caverns can readily begin flowing gas on as little as one hour’s notice, which is useful in emergency situations or during unexpected short term demand surges. Salt caverns may also be replenished more quickly than other types of underground storage facilities. Underground salt formations are well suited to natural gas storage in that salt caverns, once formed, allow little injected natural gas to escape from the formation unless specifically extracted. The walls of a salt cavern are strong and impervious to gas over the lifespan of the storage facility.
Mined Rock Caverns are mined underground using conventional mining techniques and consist of a system of shafts or ramps and drifts, forming cavities in solid rock deep underground, for example, in granite. Conventionally mined rock caverns are underground cavities constructed by using conventional mining techniques (shaft sinking, excavation of cavities by blasting or cutting). Mined rock caverns can be constructed in a certain range of geological formations which need to allow for the construction and operation of large, long-term stable caverns. These formations were initially considered intrinsically impervious to water and hydrocarbons. Later designs in the fractured rock used the head of water as a water curtain (hydrodynamic containment) to contain the hydrocarbon.