"gas storage" . "underground storage facility" . "underground storage facilities" . "cavern" . "underground gas storage facilities" . . "underground gas storage" . "line-packing" . "stored" . "store natural gas" . "natural gas storage" . "storage sites" . "natural gas" . "storage of natural gas" . "Natural gas storage" . . . "Natural gas storage" . "Natural_gas_storage#Salt_formation" . "Natural gas storage#Salt formation" . . . "storage" . "gas storage system" . "Natural Gas Transmission" . "gas storage sites" . "gas storage facility" . "salt caverns" . "natural gas storage tank" .