In geology, a naturally occurring storage area, characteristically a folded rock formation, that traps and holds natural gas.
The reservoir rock must be permeable and porous to contain the gas, and it has to be capped by impervious rock in order to form an effective seal and prevent the gas from escaping. Typical reservoir rocks are sedimentary and include sands , sandstones , arkoses , and fissured limestones and dolomites . In the U.S. and certain other countries, artificial gas reservoirs are being created from depleted oil and gas fields, particularly near salt domes and in sedimentary basins, to store gas during periods of low consumption for later use.