Underground natural gas storage is a strategic link in the gas supply chain. It enables large volumes to be stored at high pressure, meaning that a quantity of gas will always be available, regardless of consumption. The volumes and pressures used are not compatible with storage at the consumers’ premises. Underground storage is therefore essential in ensuring the continuity of the natural gas supply to the general public and industrial customers alike.
As a responsible industrial operator, Teréga has made safety an absolute priority and has set itself ambitious targets to ensure maximal security at all stages from the design to the operation of underground storage. Strict rules issued and rigorously enforced by the authorities mean that underground storage is one of the safest storage methods.
Teréga operates two underground storage sites – Lussagnet and Izaute – in naturally gas-tight rock strata. Gas is stored between 500 and 700 m down, in a porous rock containing water (aquifer) at a location where the rock strata form a “bell structure”. The reservoir rock is overlaid with a layer of impermeable rocks more than 500 metres thick. This sort of structure means that a large quantity of natural gas can be stored at sufficient pressure, in a leak-tight fashion.