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Trapping the gas


Carbon capture and storage (CCS) could be an industry the size of present day North Sea oil, geologists tell the British Science Association. Ted Nield reports.

Geoscientist Online Wednesday 9 September 2009

CCS is, in many ways, simply the reverse of the oil and gas business, putting climate-changing CO2 gas back in the ground after fossil fuels have been burnt, Dr Mike Stephenson, Head of Energy at the British Geological Survey, told the British Science Association yesterday at the Annual Festival of Science at Surrey University, Guildford. CCS is one of the ways that Britain could achieve its stated emission reductions as well as help other big CO2 producers to reduce theirs.

“In Britain we're lucky in being close to one of the largest areas of potential storage for CO2 in Europe” said Stephenson. The rocks under the North Sea could absorb about 22 billion tonnes of CO2, which is 180 years of CO2 from the UK's 20 largest point sources. This is a hefty reduction in Britain's emissions."
bsa The CCS business could be huge: estimates suggest a value of c. £2-4 bn/yr to the UK by 2030, sustaining between 30,000 and 60,000 jobs, with a cumulative value of c. £25-45 billion between 2010 and 2030. The government sees the CCS business as taking off from regional clusters like the Humber, Teesside, Thames Gateway, the Firth of Forth and Merseyside - where existing hydrocarbon and other industrial infrastructure might be used and offshore engineering expertise can be harnessed.

Other circum North Sea countries are also seeing the value of their subsea pore space and thinking strategically about the future. Further afield, in the Gulf Coast of the United States where CCS is close to being commercially viable because of the value of CO2 to the enhanced oil recovery business, the USGS is describing Texan pore space as the 'CO2 sink for the USA'.

But what stands in the way of this great future? There are a number of problems said Stephenson, some technical, some social.

“The 22 billion tonne estimate of storage capacity is just that - an estimate. Most of it (about 14 billion tonnes) is made up by so-called saline aquifers - or sedimentary rocks (usually sandstones) that contain pore spaces between particles full of very salty water. The saline aquifers provide most of the storage space but their behaviour and capacity are not known very well. Gas and oil fields that are partially depleted can also be used to dispose of CO2, and their capacities are well known; but this capacity is quite small (only about 5 billion tonnes for depleted gas fields).
“We need to understand the effect of displacing water when we pump CO2 into saline aquifers, and we need to know precisely how much safe storage space there is. This understanding must span large areas of the North Sea since saline aquifers are extensive, running above and below oil and gas fields and across international borders. Saline aquifers are thus a regional and international issue.”

“Our research is showing that we can accurately monitor the movement of CO2 almost 1000m below the seabed using seismic techniques, as well as model and predict further movement with some confidence. We can also the measure the thickness of very thin CO2 layers in the subsurface using time-frequency spectral decomposition of seismic waves. This work has been done in a saline aquifer in the Sleipner Field in Norway where CO2 has been injected at a rate of a million tonnes per year for 10 years. The results are promising, but more research is needed to develop the investor confidence which will finance large-scale industrial CCS.”

Another problem – which Stephenson describes as “a possible show stopper” - is public acceptance. CCS has made an appearance in the quality Sunday papers, but has not yet reached the “red top” papers yet. “CCS is a big development, a big geo-engineering solution to the Earth's climate problem. There are similarities with the development of genetically-modified crops. But GM crops never got going in Britain - even now only 2% of Britons say they are 'happy to eat GM foods'. The perception is that the science of GM was poorly communicated and that the public saw GM crops as a stitch-up between big business, the government and the scientists. Stephenson fears that without better science communication, CCS might go the same way and a great opportunity could be lost.

Stephenson says that the next big step for geologists is to improve estimates of North Sea storage capacity, to improve imaging and monitoring of buried CO2 and to continue to develop a role for the Survey in realising North Sea CCS.