GEO ExPro

An Excellent Reservoir

The Aldous/Avaldsnes prospect has grown into one of the largest discoveries 3in the North Sea ever, largely due to excellent reservoir properties.
This article appeared in Vol. 8, No. 6 - 2012

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An oily core sample from the giant discovery. Source: Statoil The Aldous/Avaldsnes discovery (see GEO ExPro Vol. 8 No. 5) is set to become the largest oil field in the entire North Sea. While Statoil is operating License 265, including Aldous, Lundin Norway is in charge of License 501 where Avaldsnes is located.  

The huge structure used to be considered as two different prospects, but the Statoil discovery published in August, following the Lundin discovery well last year, made it clear that a common oil/water contact between the Aldous and Avaldsnes structures had been established. The uncertainty for a large part lay in the existence of a saddle between Aldous and Avaldsnes, as can be seen on the cross section.

  • Source: Lundin

  • Source: Statoil

The latest reserve figures were presented by Statoil in October. While the low estimate for the entire structure is 1.7 Bbo, the high estimate has now risen to 3.3 Bbo. The latter figure compares with reserves figures from Ekofisk and Statfjord that are 3.5 Bbo. Both Statoil and Lundin leave the impression, however, that the reserve figures could continue to grow as the appraisal program continues. Regardless, this is the largest discovery in the world this year.

“Aldous/Avaldsnes is a giant, and one of the largest finds ever on the Norwegian continental shelf. Volume estimates have now in creased further because the appraisal well confirms a continuous, very good and thick reservoir,” says Tim Dodson, Execu tive Vice President forExploration in Statoil.

Good indeed! As evi dent from the diagram, porosities in the Jurassic sandstones are typically above 30%, often approaching 40%, with a few samples with porosities even above that figure. Lundin has previously said that the net to gross ratio in the reservoir is close to 100%. Permeabilities are also excellent. It is not often we see values exceed 1 Darcy, let alone 10 Darcy.

Contrary to what has been claimed by pessimists, it will be a long time before the sun sets on the Norwegian oil industry.

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