Old UK oilwells could be turned into CO2 burial test sites

08/12/2021 13:12
Dec - Old UK oilwells could be turned into CO2 burial test site.jpg

Exhausted oil and gas wells would be turned into the UK’s first deep test sites for burying carbon dioxide next year, under plans from a consortium of universities and energy companies.

There are hundreds of active onshore oil and gas wells in the UK. But as they come to the end of their lives, some need to be redeployed for trials of pumping CO2 underground and monitoring it to ensure it does not escape, the group says. The test wells could also be used to assess how hydrogen can be stored underground.

CO2 capture and storage (CCS) will be a significant part of tackling the climate crisis, according to the Intergovernmental Panel on Climate Change and the UK’s official advisers, the Climate Change Committee (CCC). The reservoirs under the North Sea provide the biggest potential storage for CO2 from fossil fuel burning, but the consortium said reusing existing onshore wells was the fastest and cheapest way to research and develop safe and effective systems.

The Net Zero Rise (Research Infrastructure for Subsurface Energy) project involves the universities of Newcastle, Oxford and Durham, and the fossil fuel companies IGas and Third Energy.

It has identified 20 candidate wells, mainly in Yorkshire and the Midlands. A CCS test site would bury a relatively small amount of CO2, about 1,000 tonnes, at 1-3km depth. The cost of repurposing a well, plus two monitoring wells and the monitoring equipment would be about £5m, the group said.

“CO2 storage in the North Sea is probably going to be very important, but we need an onshore capability, a national asset, so we can do testing and look at what monitoring is adequate to understand where the CO2 has gone,” said Prof Richard Davies, at the University of Newcastle, who is leading the project.

“If we don’t do this soon, we will lose an opportunity to use this infrastructure,” he said, because exhausted wells are usually filled with cement. “These assets are already there, while drilling [new] boreholes is very expensive and adds a certain amount of risk. The range of boreholes we have will also give opportunities to test different rock types.”

Test sites already exist in the US, Canada and Australia, but Davies said UK facilities would be better as they could have very similar geology to that under the North Sea. The British Geological Survey is also examining the case for an underground CO2 storage research laboratory.

Hydrogen is seen as part of the move to a low-carbon economy and being able to store it underground would help ensure a secure energy supply. It is a tiny molecule and large rock salt formations are likely to be best at trapping the gas, but the UK has few such deposits.

“We want to look at hydrogen as well,” Davies said. “Could it go into sandstone which is sealed by a shale, a fine-grained, low-permeability rock? Can we monitor hydrogen underground if it was to be stored there?”

A CCS project in the Sleipner gas field in the North Sea has pumped millions of tonnes of CO2 under the sea floor since 1996. “It’s a pioneering project, in that they proved it can be done at scale and over a long period of time, and they could monitor it effectively,” said Davies. “But it’s not a test facility that’s open to other organisations – it’s an Equinor project – and it’s in one type of rock formation only.”

The government’s net zero strategy anticipates 50m tonnes of CO2 being captured and stored by the mid-2030s, and ministers are backing the development of CCS hubs on the north-west and east coasts of England.

Read the full story here.

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