A new report has warned that millions of tonnes of dangerous gas could spew from the North Sea if carbon capture technology goes wrong.
A UK Government study seen by the Press and Journal says pioneering plans to inject CO2 emissions into spent oil and gas wells could lead to cracks opening up in the seabed.
It concludes that in a worst-case scenario, carbon dioxide could leak for “up to five years”.
Conditions off the north-east coast of Scotland are believed to be perfect for carbon capture and storage (CCS), which could create thousands of jobs in Peterhead.
But the report reveals that a crack – known as a fault-line – stretching up from a disused well to the seabed could potentially release up to 2.7million tonnes of carbon dioxide.
That would be equivalent to the annual exhaust fumes of 1.1million cars.
Last night, a leading environmental group said the papers revealed “some potentially major problems” – but that it was “reassured” that all but the worst-case scenarios could be dealt with.
A CCS project at Peterhead aims to capture carbon dioxide at the town’s power station then pump it into a depleted gas field.
However, last year academics at Bristol University wrote to MPs to outline the “risk” that using offshore oil and gas reservoirs could “have the potential to trigger earthquakes” and “reactivate faults and fractures”.
Their fears appear to be backed up by the government report, which investigated the risks and “financial consequences” of the technology failing.
It examined the impact of leaks from operating and abandoned wells, how they would be controlled and how much CO2 could escape.
The report says there can be “no absolute guarantee” that the CO2 will remain in the wells it is injected into.
It says the main source of problems could be abandoned wells, which could leak when the area is filled with carbon.
The report estimates that 1,000 tonnes a day could escape before a relief well – which would cost upwards of £25million – could be drilled.
While concluding that the chances of carbon injection fracturing the seabed are extremely low, it acknowledges that “there are few proven technical options for remediating leakage from a fault”.
CO2 could escape at a rate of 1,500 tonnes a day for up to five years in such a scenario, allowing 2.7million tonnes to escape into the atmosphere.
Friends of the Earth Scotland director, Richard Dixon, said the report highlighted some worrying cases, but he was reassured by the fact there were solutions for most problems.
He said: “There are some potentially major problems, but it is quite reassuring that there is a solution for all but the worst-case scenario.”
Energy giant Shell is driving forward a plan to develop CCS at Peterhead’s gas-fired power station.
The firm declined to comment. But a source within the major said the need for reservoir pressure management was “well understood both by regulators and the industry”.
A spokeswoman for the UK Government’s Department of Energy and Climate Change said the report showed all but the most extreme leaks could be dealt with quickly and economically.
“This technical report shows that a leak of carbon dioxide from a licensed storage site is very unlikely,” she said.
“The overwhelming body of evidence gives us confidence that a storage site licensed in accordance with European law will not leak.
“The report also concludes that if something unforeseen were to take place, then the situation could be remedied fairly quickly at a finite cost in all but the most extreme circumstances.”
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