A couple of weeks ago Centrica Storage quietly made an announcement on its website:
As part of CSL’s assurance programme and as a responsible operator and given the age of the field and installation, CSL has decided to limit the maximum operating pressure of the Rough wells to 3000 psi. CSL has decided to take the prudent step to test and verify the operating parameters of the Rough wells. It is anticipated that this limitation will last up to 6 months.Rough is an undersea gas storage facility, connected by pipeline to the terminal at Easington in Yorkshire:
It's able to store about 4 billion cubic metres of gas - or at least it was before the above announcement. Some more detail from Platts indicates that the reduction in operating pressure will reduce Rough's capacity by about a quarter. Because Rough comprises about 72% of the UK's total gas storage, this is equivalent to losing just under 20% from total storage capacity.
Now, Centrica Storage has said this is for six months, while tests are carried out, but Platts notes that the tests are needed because of concerns about well integrity - so it's possible that the capacity will be permanently reduced. Even if it isn't, the coming six months are exactly when the storage is normally refilled, so if full capacity is restored at the end of the testing period, it may well be too late to completely fill the storage.
So, let's assume the UK goes into next winter with 1 billion cubic metres of gas less in storage than usual - what might the impact be? 2013/14 was a mild winter, and Rough still had over 1.5 billion cubic metres left in it in March 2014. It was a different matter in April 2013, when it had actually gone below 'zero', eating into the gas cushion that was supposed to be left untouched. This year, there's about 0.5 billion cubic meters left in it right now - the situation was similar every year from 2008-2011 inclusive. This means that if the coming winter is mild, we should have no problems; if it is average, then we will probably need to increase imports, which will bump up prices; if it is cold, then we could well have a problem.
The graph below shows the levels in Rough over the past few years in GWh (10 GWh is about the same as 1 million cubic metres), so you can see the situation for yourself. Any year where the level dropped below 10,000 GWh is a year when the announced capacity reduction might have been a problem:
Let's hope and pray for a mild winter!