Self-sealing CO2 could close CCS cracks

A new process could automatically seal cracks in underground carbon dioxide stores, according to researchers in Edinburgh.

The team from Heriot-Watt University said the technology would react to the leaks before they are detected at the surface injection site and produce a substance that blocks the tiny fissures in the rock.

The process involves adding a substance to the CO2 before it is injected into the ground that precipitates into a sealant at any points where leaks cause a change of density in the gas.

The Heriot-Watt team have completed a two-year proof-of-concept project funded by Scottish Enterprise that helped establish that the idea was economically feasible.

Four energy companies ­– Scottish and Southern Energy, France’s GDF Suez, Sweden’s Vattenfall and Brazil’s Petrobras – are now funding a three-year Joint Industry Project to apply the technology to the field.

Gordon Winton, business development executive at Heriot-Watt’s Institute of Petroleum and Engineering said the process was more to do with fluid dynamics than chemical reaction.

‘It’s based on a non-harmful process and wouldn’t cause any environmental damage,’ he told The Engineer.

Guaranteeing a secure way to store CO2 after it is captured from fossil fuel power plants remains a stumbling block for carbon capture storage (CCS) projects designed to reduce greenhouse gas emissions.

The typical concept is to inject it deep underground into porous rock deposits and empty oil or gas reservoirs that sit underneath an impermeable layer of caprock.

But there are concerns that seismic activity could free the CO2 and that even holes of less than 1mm in diameter could allow it to leak out.

A storage facility in Weyburn, Canada, was last month forced to deny it had sprung a leak after local landowners reported animal deaths they blamed on high CO2 concentrations detected on their property.

seal
An additive to the CO2 will automatically precipitate as a sealant when the gas density drops

Project director Professor Mehran Sohrabi said the Heriot-Watt process was particularly useful because CO2 detected at the surface could be miles away from the underground puncture, making it hard to find the original leaking point.

‘You don’t need to have any equipment or anything to do apart from have that mechanism in there when you store the CO2 and that will give you an additional layer of safety,’ he said.

‘Even if you think your reservoir is 100 per cent leak-proof, given the timescale involved in CO2 injection and with all the geologic activity, tectonic activity, earthquakes, a leak-proof reservoir today might not be leak-proof 100 years later.’