What lies beneath01 February 2006

Presentations at a recent seminar revealed the enormity of the tasks to be addressed if carbon capture and sequestration is ever to become a reality.

Worldwide, around 10bn tonnes of carbon dioxide produced by power stations and other point sources would be injected every year into deep strata, mostly under the sea - with 200m tonnes from the UK alone to be buried beneath the North Sea.

Projects have been piloted off the coast of Norway, and CO2 is being injected to enhance residual oil recovery, particularly in North America. But the risks of the technology not working or not achieving the desired goals are substantial.

A seminar was held at the end of November last year by the Department of Trade & Industry and the Norwegian Ministry for Petroleum and Energy. And the event, CO2 Capture and Storage: Collaborative Options for CO2 Storage beneath the North Sea, was marked by an agreement between UK Energy Minister Malcolm Wicks and Norwegian Minister Odd Roger Enoksen, to establish a "North Sea Basin task force".

The problem, of course, is global climate change, which is exacerbated by the 24bn tonnes of CO2 being released into the world's atmosphere every year - 5bn tonnes of are produced by the US, 3 bn tonnes by China and 3 bn tonnes by Europe, according to figures provided by Niels Peter Christensen of the Geological Survey of Denmark and Greenland.

CO2 is considered by most climate scientists to be the main cause of the problem, although equally eminent persons believe there are other, more important causes such as additional releases of water vapour, particularly into the upper atmosphere by high flying jets, and methane, produced largely by rotting rubbish. There are also others who argue that the problem is caused by industrial release of fossil heat, which would include nuclear. Russell Marsh, head of policy at Green Alliance, speaking at the seminar, said: "There is much more potential in renewables and energy efficiency in the UK and we would hope that carbon capture would not take attention away from these." He raised issues such as how long would the CO2 stay in storage, and who would be responsible for storage over thousands of years.

Few of the business people present at the event were reassured by Jeff Chapman, trade promoter for energy and environment, UKTI (UK Trade and Investment). He started by showing a slide which stated: 'Governments will not invest in CCS (Carbon Capture and Sequestration) projects', and added that the private sector will only invest if there are sufficient financial incentives, which he viewed mainly in terms of the EU Emissions Trading Scheme (ETS). He talked of the need for long-term schemes and commitments, despite the fact that Phase II of the ETS finishes in 2012, by which time the grand engineering schemes discussed would have only have just got underway.

The overwhelming impression was that there had been no clear decision on how any of the CCS schemes would be financed and regulated; what did seem clear was that complex rules and regulations were likely to be involved and would involve much bureaucracy.

Oil recovery
The idea that seemed to win much favour from those present was to use CO2 to pressurise strata to drive out residual crude oil from the North Sea. While this would still be cutting edge engineering on a grand scale, all attendees could see the benefits and potential profits. The technology is referred to as EOR - Enhanced Oil Recovery.

Niels Christensen described EOR as: "The smaller but more interesting option." The idea is to inject CO2 down one well into the oil-bearing strata and use the gas pressure to drive residual oil up through another well. According to the Kinder Morgan CO2 company, this can result in recovery of an additional 8-16% of oil. Such operations are being undertaken in North America, mainly as a better method of recovering residual oil than injecting sea water, surplus natural gas, or air. (Sea water introduces oil-feeding bacteria, gas is better sold for profit and air is liable to lead to partial oxidation of the oil.)

Christensen said it is unclear whether the North American experiences can be transferred to the North Sea, but he produced a map to show where the pipelines could be located. He declared that any such scheme would be "a much larger project than Airbus". He estimated costs to be in the region of one to five euro cents per kilowatt hour of energy and said that the technology should be viable provided oil remained above a breakeven price of $35/barrel (against long-term US predictions that oil will not drop below $40.) Christensen urged that decisions be taken quickly, before the North Sea platforms associated with ageing fields are decommissioned and infrastructure removed.

The barriers, he said, are the scale of the project. There is no North Sea 'master plan' and this is compounded by the shortsightedness of European climate and energy plans, the fixation of EU governments on CO2 as opposed to EOR, a lack of national research and development, and uncertainties about the business environment. He urged that North Sea Rim governments take the lead and address the problems.

Relevant expertise
Only one company has developed significant expertise injecting CO2 into reservoirs subsea: attendees were very interested to hear the experiences recounted by Tor Fjaeran, vice president corporate for HSE Statoil. The company has been injecting CO2 since 1996 at Sliepner. The gas that comes up contains 9% CO2, which has to be removed prior to sale and supply. Instead of venting the CO2, the company separates it and injects it into a sandstone saline aquifer that is 35% porous. The CO2 is injected into the bottom of the aquifer, which lies above the gas-bearing strata, and gradually dissolves in the water, which then sinks. About 1m tonnes of CO2 have been injected annually since the project started. Computer modelling indicates that the dissolution and sinking process will take 5,000 years to complete.

Its next project is Snøhvit, which will begin in 2007. In this case, the CO2 is piped from an onshore LNG plant, and 700,000 tonnes will be injected annually below the gas reservoir. On land, in a joint project with Sonatrach and Statoil, the 10% CO2 content of gas produced at Salah in Algeria is injected into water in the same strata that contains the gas, but beneath it. This could presumably assist gas recovery, but no mention was made of this. There are four gas production wells and three CO2 injection wells.

When we spoke to Tor Fjaeren after the seminar, he said there was a need to develop the technologies required in careful steps, one at a time, in order to avoid possible technological failures.

One of the reasons is that CO2 under pressure does not behave like oil, gas or air. Niels Christensen said that to lock it away, it is necessary to deposit it in strata at depths of 700m, 800m or deeper, in order that it exists as a supercritical fluid and not a gas to reduce its bulk. Saline water initially dissolves only a few per cent, but this proportion increases over time.

SOE

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