Going underground

Around the world, energy companies are racing to develop new technologies. For companies with sizeable reserves of hydrocarbons - oil and gas - the challenge is to find a way to harness the energy in them without releasing into the atmosphere carbon dioxide (CO2), a greenhouse gas that contributes to global warming.

At Tjeldbergodden in mid-Norway, the two energy giants Statoil and Royal Dutch Shell are hoping to build the world’s biggest carbon-capture storage facility. They want to construct alongside it a gas-fired power plant to power the electricity grid in a region which, in the absence of innovation, will suffer from an energy crisis in a few years’ time.

Capturing and storing CO2 is a highly effective way of reducing carbon emissions, but is very costly because of the huge amount of energy needed. On the other hand, there are environmental benefits and the two companies are looking for ways to use the CO2 productively. After removing CO2 in the capture plant, the companies aim to use the same CO2 for industrial purposes by injecting it into existing oil reservoirs to push the remaining oil to a production well, in a process that is termed enhanced oil recovery. The CO2 will then be piped off and permanently stored underneath the sea bed.

Statoil, Norway’s national oil company, started pumping CO2 into aquifers at the Sleipner field in the Utsira formation under the North Sea a decade ago, but there is still debate about how to store the CO2 safely.

Together with the Norwegian University of Science and Technology and other research institutions, Statoil is monitoring the CO2 behaviour at Sleipner, and ten years of experience indicates that the CO2 will remain in place.

It is possible to store CO2 onshore as well, but most people would be uneasy about finding massive carbon vaults underneath their homes or gardens.

So the most convenient solution, albeit costly, will be to transport CO2 through pipelines to the North Sea, where, according to some experts, it is possible to store all of Europe’s CO2 emissions from the next century.

The two companies are certain that the project is technically feasible, but it still faces commercial challenges. The use of CO2 for oil recovery has never before been done offshore and there are also uncertainties about how much extra oil can actually be recovered. It will require expensive modifications to the offshore installations for them to handle large quantities of CO2.

Statoil and Shell estimate that they will be able to capture 85% of CO2 from the power plant, the equivalent of 1 million cars, or 6% of Norway’s total green-house gas emissions. And, if all goes well, the project will be up and running in 2011-12 - earlier, they say, than similar projects elsewhere in Europe.

Increased oil recovery is not the only goal for the two companies, says Anders Ystad of Statoil.

The companies are also looking to convert the North Sea oil platforms Heidrun and Draugen, which are currently powered by gas turbines, to run off electricity from the power plant. The conversion would reduce emissions of CO2 and nitrogen oxides emissions offshore.

"Of course, we want to increase the recovery of oil, but we are also aiming to reduce our emissions and develop technology that can be retro-fitted to existing coal or gas-fired power plants," says Ystad.

"We are building on existing technological knowledge, but there are significant challenges related to up-scaling this know-how to this project’s ambitions.

"Our capture plant at Tjeldbergodden will be about ten times larger than any existing plant."

While not shy about hiding the potential benefits in transferable technology, the companies are looking for government support. They believe that a project on such a scale would give not just Shell and Statoil the possibility to take the lead on CO2 capture, but Europe as a whole.

"We are unable to do this on our own," says Ystad, "this is a pioneer project and we are dependent on support from the Norwegian authorities as well as the EU."

Key elements of the project

• A 860 MW power plant that will produce 7.1 TWh annually (approximately 5% of Norway’s power consumption), of which 6.1 TWh will be available for the market

• A CO2 capture plant that will remove some 85% of the CO2 from the exhaust gas by using a chemical solvent. This is the equivalent of 2.5 million tonnes of CO2 a year

• A pipeline that will transport the CO2 to Draugen field (and later the Heidrun field) for enhanced oil recovery. After that, the CO2 will be permanently stored in aquifers underneath the seabed

Around the world, energy companies are racing to develop new technologies. For companies with sizeable reserves of hydrocarbons - oil and gas - the challenge is to find a way to harness the energy in them without releasing into the atmosphere carbon dioxide (CO2), a greenhouse gas that contributes to global warming.