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30/10/2007 A project which began by looking at methods for carbon storage could also yield a simple answer to recovering methane from the ice-like substances known as hydrates.
Text: Kristin Gjengedal, Photo: Eivind Senneset
“This is a win-win solution,” says Bjørn Kvamme about the technique he and his colleagues at the University of Bergen (UiB) have developed for liberating methane through carbon injection.
“Everyone wants to get rid of carbon dioxide, while preliminary estimates indicate that gas hydrates hold twice as much energy as all known oil, coal and free gas deposits.”
International interest in hydrates has exploded recently, although Japan has spent many years studying how it could benefit from its rich offshore deposits of these substances.
India is devoting big money to mapping its hydrate resources, and plans to begin commercial production as soon as possible. Several industrial research programmes are also under way.
And the USA is the latest to show strong interest in order to reduce its dependence on imports from the increasingly unpredictable Middle East.
Gas hydrates consist primarily of methane trapped in the pores of an ice-like substance formed by binding water with hydrogen under high pressure and low temperature.
Such conditions prevail on the seabed or in areas with permafrost, for instance. The gas represents a huge source of energy if it could only be recovered.
“Several production methods are available, based on the fact that the stability of gas hydrates is a function of pressure and temperature,” Prof Kvamme explains.
“Adding heat or reducing the pressure can make them unstable and thereby allow the gas to be captured. But these methods also present drawbacks.”
Melting liberates large volumes of water as well as gas, which would be expensive to pump up. The cost of heating a deposit would also be high.
When gas hydrates switch from stable to unstable condition, the reduction in volume could – in the worst case – cause a sub-surface collapse.
“Our solution involves injecting carbon dioxide,” Prof Kvamme explains. “Under constant pressure, the thermal stability of the ice-like crystals will then be greater than with methane.
“This means that the injected carbon dioxide will replace the methane, leaving the volume about the same. Methane is liberated, while providing stable storage for the other gas.
“The system runs automatically, a fact we’ve demonstrated experimentally and are planning to do the same with cores taken from the sub-surface.”
Prof Kvamme has patented the process in cooperation with colleague Arne Graue at the UiB and US oil company ConocoPhillips, which has invested in the project.
Support has also been provided by the Research Council of Norway through its Petromaks project.
The method has been received with great interest by both industry and government, and Prof Kvamme expects this to continue rising. Although it is difficult to predict what role gas hydrates might play in the world’s future energy picture, he believes they will be very important.
“Energy policies in the individual countries will play their part,” Prof Kvamme notes. “Not all hydrate deposits are commercial, but the proportion which can be produced could change as the technology improves.
“Both Japan and India will undoubtedly make a commitment to full commercial operation, but we can’t know whether they’ll choose our method or different ones. Our personal view is that we’ve come up with the best approach financially and technically.”
Norway, which has so far lived well from oil and gas exports, is also starting to get interested in hydrates. A research project funded by the Research Council and headed by the UiB is now mapping deposits in the North Sea, primarily by seismic surveys.
If nothing else, it is important for industry to know where these resources lie so that subsea landslides are not accidentally triggered by disturbing them. Prof Kvamme and his colleagues are also continuing their efforts to improve the carbon injection method.
“The fact that the UiB is researching both location and production gives us a lot of expertise on how mapping can be combined with an evaluation of hydrate commerciality,” he says.
“Sooner or later, reserves of free gas will diminish and this expertise will then be ready to hand.”