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Avoiding disappointments in exploration of the Barents Sea
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Published January 10, 2006

A great deal of oil may have leaked out of Barents Sea reservoirs 30 to 40 million years ago and during the more recent Ice Ages. A new report from SINTEF tells us which parts of the basin may have been emptied of their petroleum resources.

The report provides important information for companies that intend to prospect for oil and gas in the Barents Sea.

“Seven oil companies have already bought into the study, but it is still possible for other companies to obtain access to the results,” says project manager Kjell Øygard, a senior scientist at SINTEF Petroleum Research’s office in Stavanger.

SINTEF carried out the study in collaboration with the Norwegian companies PEGIS, Geolab Nor and PGS.

Plenty left to be exploited
SINTEF still believes that more effort should be put into exploratory drilling in the Barents Sea, and that new technology ought to be adopted in seismics, geology and drilling.

“Although large quantities of oil and gas have been lost, a great deal is still stored in special structures, for example in Snøhvit and Goliat. We need to remember that the Barents Sea is huge, and so far only a small fraction of the total area has been explored”, says Øygard.

Erosion and seabed uplift
However, in many parts of the Barents Sea, mankind is millions of years too late to become rich from the black gold that used to lie beneath the Arctic seafloor.

Some thirty to forty million years ago, Greenland began to move westwards, and the North Atlantic started to widen. In the process, new areas became seabed, and the uppermost layers were “scrubbed away” by erosion, allowing the layers below to rise. In many places this led to fracturing of the cap rock, i.e. the geological layers that had kept the reservoirs under seal until then.

Sources dried up
At the same time, the supply of oil to the reservoirs was drying up. This is because the source-rock formations were left lying too shallow, so that the temperatures in these rocks were not high enough to convert organic material into oil and gas.
 
Process repeated in the Ice Ages
During the Ice Ages that have occurred during the past couple of million years, there were additional, repeated phases of erosion and seabed uplift, accompanied once again by fracturing of the cap rock.

Erosion quantified and timed
The amounts of rock that were eroded in different parts of the Barents Sea - and the times at which this happened - were determined in detail during the SINTEF study. Then the effects of these changes on the petroleum geology were simulated.

The study showed that the probability of finding oil and gas was highest in the areas that had suffered least erosion.

By Svein Tønseth

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