According to the U.N. Intergovernmental Panel on Climate Change (IPCC), which issued a special report on CCS in 2005, a properly selected site should securely store at least 99 percent of the sequestered CO2 for more than 1,000 years. James Dooley, a senior research scientist at Pacific Northwest National Laboratory and an IPCC lead author, considers that to be a reachable goal. "If it took all that energy to shove [the CO2] into that sandstone, it's going to take a lot of energy to get it out," he notes. "Like an oil field, where we get out half or less of the original oil in place, a lot of the CO2 gets stuck in there. It's immobilized in the rock."
Encouraged by the success of the Sleipner project, Statoil recently began another CO2 injection program at the Snohvit natural gas field in the Barents Sea, despite the requirement that they build a 95-mile (150-kilometer) pipeline on the seabed to pump the CO2 to where it can be sequestered.
And since 2005, oil giant BP and its partners (including Statoil) in the In Salah gas field in Algeria have been stripping the nine billion cubic meters of natural gas produced there annually of the 10 percent carbon dioxide it contains and pumping a million metric tons of liquid CO2 back into the underlying saline aquifer through three additional wells at a cost of $100 million.
BP uses a variety of techniques, including satellite monitoring, to observe the impact of the CO2 storage (and natural gas removal). Whereas some areas sank by roughly 0.24 inch (six millimeters) as natural gas was extracted, near the CO2 injection wells the land rose by some 0.39 inch (10 millimeters), according to Gardiner Hill, manager of technology and engineering for CCS at BP's alternative energy arm.
"The gas has been down there about 20 million years so we know [the reservoir] has integrity," he says. The DoE's National Energy Technology Laboratory is also working on developing appropriate monitoring, verification and accounting technologies.
BP and Statoil are not doing these CCS projects for charity, of course. A Norwegian government tax on carbon of roughly $50 per metric ton inspired the CO2 sequestration at Sleipner and Snohvit. "It costs a fraction of the tax," Kaarstad says. "We are actually making money out of this."
Both Statoil and BP foresee more money-making CO2 storage opportunities. Hill notes that if CCS is deployed on a very large scale, society will need the expertise of the oil industry—its "100 years of understanding the subsurface," he says. "We would expect the experience we are building through this to position BP to take advantage of any future business."
"My one prediction is that this is going to be a very big industry, storing CO2 underground but transporting it, as well," Kaarstad adds. "It's not going to happen overnight, but it will probably be as big as natural gas after a few decades."