Earth Techs Help Assess Underground Carbon

Earth science technologies are now being used to assess captured and stored carbon dioxide, it has emerged. ERT – or Electric Resistance Tomography – is being drawn on to follow the progress of a mass of CO2 that’s been pumped beneath Cranfield Oilfield in Mississippi.

The work being carried out there forms part of the localised SECARB (South East Regional Carbon Sequestration Partnership – a link-up between utility firms, scientific organisations and others) project, which ultimately aims to place 1m tons of CO2 into underground containment.

ERT: CO2 storage technologies

ERT/ Electrical Resistance Tomography is a technique that allows structures located beneath the surface to be viewed, and it is used for various purposes including assessing the movement of groundwater and for archaeological digs. Atmospheric CO2 is one of the main greenhouse gases linked to climate change, but various CO2 storage technologies and techniques exist to try and stop it entering the atmosphere.

Right now, scientists in the US are using ERT down to a depth of 10,000 feet to see how the CO2 stored beneath the Mississippi oilfield is behaving. ERT has never been used at this deep a level before: prior to now, it hadn’t gone below 2,400 feet.

ERT involves a formation of electrodes which measure fluctuations in the movement of electrical resistance at a subterranean level. All that sounds pretty complicated, but to put it into context, at this site, the scientists have been able to establish that the injected CO2 has moved, by assessing resistance at different underground locations.

“We can image the CO2 plume as the fluid is injected”, geophysicist Charles Carrigan – who spearheads this ERT project stated, adding: “What we've seen is a movement of the plume outward from the injection well into the geologic formation used for storage.”

Underground CO2 Storage Sites

The ERT technique was developed over two decades ago, and it is closely related to standard tomography, in that energy waves are used to obtain an image. In the case of the stored CO2, it provides the scientists with insight into the carbon dioxide’s onward journey once it’s out of visual sight and entering dedicated underground CO2 storage sites.

“This is a great start for applying ERT to the very challenging sequestration environment”, Carrigan added. “We hope we can use ERT in the future at commercial CO2 underground storage sites.”

See also:

Pressurised Oxy-Fuel Combustion to Capture CO2

Carbon Conversion Technology offers Alternative to CCS