The Process

The mining of salt and the extraction of brine from man-made caverns in the Preesall salt deposit began in the 1870s and lasted until the mid 1990s. The storage of gas in specially constructed salt caverns is well established and in these times of concern about reliable energy supplies, the construction of Canatxx's underground gas storage facility will help meet peak and seasonal demand and avoid potential supply emergencies. The process for storing gas underground is common throughout the world, particularly in the United States and Europe, including the UK. The process for creating a cavern is known as “solution mining”.

The procedure involves creating a series of specially constructed underground caverns in locations, such as Preesall, where there is a thick high quality layer of salt underground. Salt is impervious to gas and is thus uniquely suitable for creating a safe pressure vessel for storing gas. Water is pumped through a borehole to dissolve the underground salt which is then extracted via the borehole in the form of a concentrated brine solution.

The exact size of each cavern is carefully controlled and is determined by the engineering design of each cavern which must be approved by the HSE before construction begins. After the solution mining process is completed, an example of a gas storage cavern in the Preesall rock salt would be an approximately tear drop shaped cavern that lies within the 200 to 300 meter thick rock salt. The cavern would be about 300 to 400 meters (1000 to 1300 feet) below the surface of the ground.

The cavern is monitored continuously during construction. Prior to commissioning the cavern is tested and must be approved by the HSE before operations begin.

Canatxx intends to connect the caverns by pipeline to the National Transmission System (NTS) which, as part of the National Grid, will ensure that gas is distributed throughout the UK. Gas will be stored in the caverns until gas demand requires Canatxx to pass it on to the National Grid.