Gas storage

Natural gas is much more difficult to store in quantity than other fuels.

In the days of coal gas we stored gas in gasholders which rose or fell depending on the gas volume being stored. Some designs have a diaphragm inside a fixed outer casing. Very few of these remain now. However, after decades of gas storage in this way, HSE  concluded that they are more dangerous than we had ever realised and tried to prevent  redevelopment at the Oval cricket ground in consequence. Their was not accepted at the planning inquiry.

Later, it seemed like a good idea to store gas in high pressure ‘bullets’ , but the quantities that could reasonably be stored this way are limited.

When the UK first moved to natural gas from coal gas, it came in from N Africa in liquid form, and concerns over the safety set in train a special review of the safety of people at Canvey island, which led to the first UK legislation specifically for major hazard sites. There are now 3  LNG storage plants  , known as Dragon, S Hook and Isle of Grain. These were built to accommodate gas brought in from the middle east, and elsewhere but other storage modes are preferred for gas which has not been liquefied.

Simply using the high pressure gas mains themselves provides some element of a buffer store, and the typical line pressure of 75 bar holds around 24t per km of 750mm pipeline of which around one third is available as ‘storage’, The storage available in this way is increased by a trend towards uprating the maximum operating pressure of existing pipelines to 85 barg. There are few other examples of pressure equipment getting stronger as it ages.

Storage in depleted gas fields, notably offshore in the North Sea in the Rough field and onshore at Hatfield Moor, has attractions, but the rate of flow in and out of these porous rock formations is limited. The operators of the Rough field have now signalled its closure, after evaluation of the costs of renewing old infrastructure. Humbly grove is a depleted field in Hampshire now adapted for storage.

Most recently gas storage in salt caverns has become the favoured method of storage. There are 9 caverns at Hornsea. Three sites in Cheshire are either being developed or expanded for this purpose:10 caverns at Holehouse , originally mined for salt production and now adapted; at Stublach near Middlewich, there will eventually be 20 caverns, and Hill Top 10 caverns. There are 9 more caverns at Aldbrough in E Yorkshire.

A salt dome used for gas storage at Bayou Corne, Louisiana USA developed a large sinkhole with gas bubbles emerging during July 2012. This in turn has caused ground movements threatening nearby gas pipelines. To date no large scale gas release has resulted, and the story has remained largely local news. It seems the sinkhole is the consequence of collapse of a cavern excavated for salt extraction not gas storage. It now covers 15 acres. There are lots of stories in the press, Here is a recent update