SCOTTISH scientists have uncovered vital clues on how to develop safe carbon capture technology by studying an ancient underground reservoir of CO2.

The researchers – from Edinburgh, Glasgow and Strathclyde universities – have analysed a natural well of the greenhouse gas in the United States to see just how much leaks out over millennia.

Scotland hopes to be at the forefront of carbon capture – with proposals to use emptied oil wells to store CO2 generated by power stations.

However, research is still needed on ways of keeping such stores of the gas safe.

The Scottish researchers studied leakage from a natural underground reservoir of CO2 cut by two geological faults near Utah's Green River.

Crucially, they found man-made leakages, such as from abandoned oil wells, transmit higher CO2 levels than natural faults in rock.

Neil Burnside, of Edinburgh University, said: "Studying an ancient natural CO2 reservoir has given us enormous insight into how man-made storage sites could behave in the long term.

"This work further highlights wellbore leakage is the largest risk to geological storage projects."

Professor Zoe Shipton of Strathclyde University said: "This study gives us a record of how and where CO2 and water have moved up a geological fault zone over the last 400,000 years."