Why Preesall?

The Preesall site is a strategically important halite (rock) salt body in the UK due to its size and location. It is one of the few known suitable sites in the UK that can safely accommodate gas storage in salt caverns.

The UK has two main types of underground gas storage:

  • Depleted oil/gas field storage, pore storage – this is where gas is stored in natural gas/oil fields which have produced all their economically recoverable oil or gas
  • Salt cavity storage and man-made void storage – this is where naturally occurring salt deposits, such as those at Preesall, are used to store gas

Depleted field storage requires considerable pressure, and therefore energy, to fill. As a result, these types of facility tend to be used for what is referred to as ‘seasonal storage’, where gas is injected over a long period of time, typically the summer, and is then supplied to the market in the winter when demand, and therefore prices, are higher.

Due to geology, there are only a small number of depleted onshore gas/oil fields and they tend to be relatively small in size. Offshore, the UK has far more opportunities, however, costs of construction, as with anything built offshore, rise considerably.

The opportunity to build salt cavity storage is limited both on and offshore by geology as the UK has only limited salt deposits. Of these, the shallower ones, those in Cheshire and Lancashire, benefit over the deeper deposits in that the pressure of the gas they are capable of holding tends to mirror the main UK National Transmission System (NTS). This, combined with the fact that salt caverns are capable of moving large quantities of gas either in or out very quickly, means that they lend themselves to providing the day to day flexibility required for security of supply as well as longer term seasonal cover.

Preesall also benefits from its location at the heart of the NTS where access to fast cycle gas storage is particularly helpful for the operation and stability of the system. Gas from the Preesall facility would enter the NTS at Nateby, which is on the main western legs of the NTS in an area that currently has considerable spare capacity, thus reducing the need for significant investment by National Grid in the NTS to accommodate Preesall’s gas flows.

Read more about the project in our leaflet, Securing the UK’s Energy Future

The Preesall site is one of the last few known suitable locations in the UK that is capable of storing gas in salt caverns.