Natural Gas and its Storage

The main reasons why to store gas in underground gas storages comprise:

• seasonal balancing – compensating the increased gas consumption during winter time by its withdrawal from the storage where the gas was stored during the summer period when the consumption is lower
• efficiency – gas purchase for lower prices, its storage, and subsequent withdrawal from the storage during the period of higher prices
• coverage of consumption peaks – unexpected increase of gas consumption can be quickly satisfied by gas withdrawal from the storage
• support of transmission flexibility – gas storages can be used to compensate any fluctuations in international gas transmission
• safety reserves – maintenance of reserve stock for the event of limitation or interruption of supplies from abroad

 

 
Figure: basic utilization of underground gas storages during individual seasons

Underground Gas Storages

An underground gas storage means all subsurface and surface equipment required for gas storage. Natural gas is stored in natural or artificial spaces in underground geologic formations. Several subsurface storage horizons or caverns can be technologically interconnected into a single common storage facility, which is designated as underground gas storage site.

 

 

Types of Underground Gas Storages

There are two basic types of underground gas storages:

1. Porous storages:

These usually are exploited deposit of crude oil or natural gas. Gas is stored in small pores and cracks in solid but porous and permeable rocks. The place in the deposit, which was opened by exploitation of crude oil or natural gas can be thus re-used for gas storage.

Another, less frequent type of porous storages are aquifers. These are rocks that perform the function of natural water reservoirs suitable for gas storage. The storage space is created by artificial forcing the water away into lower levels of the water bearing horizon.

 

2. Cavern storages:

Cavern storages consist of artificially created cavities. These can be salt caverns or abandoned coal or other mines, as well as spaces established specifically for the purpose of gas storage (e.g. Háje underground gas storage). The main advantage of these storages consists in easy management of gas flow and their high injection and withdrawal capacity.