Working gas (working gas volume) is the gas volume which can be withdrawn from a storage facility during an autumn-winter period and injected back into the storage during the spring-summer period.

Remaining working gas volume is the gas volume which can be withdrawn from an underground gas storage (UGS) facility in the forthcoming autumn-winter period provided that there is a certain gas volume in the UGS facility. The working gas volume essentially determines all parameters of a UGS facility. Its potential volume is determined by geometric sizes of the trap, capacity properties of the formation, pressure range in the formation during gas withdrawal.

In the process flow diagram of a UGS facility construction the working gas volume is determined on the basis of technological calculations with mathematical modeling. Upon that, it is necessary to take into account gas-saturated volume variation during operation of the storage facility as well as presence of a pressure sink in the formation. Working gas volume can be regulated by changing the pressure range and the pore volume (for storage facilities with active water drive). To provide gas withdrawal during the autumn-winter period and gas injection during the spring-summer period, the storage facility must have the adequate equipment and number of operational wells with a certain rated capacity. Operating conditions of the storage facility (maximum allowable pressure, injection and withdrawal rates, their profiles) have a substantial impact on the working gas volume.