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Bacteria yield more oil

February 8, 2001, 08:00 CET

A new Statoil-patented method which improves oil recovery with the aid of bacteria is to be adopted on the group's Norne development in the Norwegian Sea.

Results from an earlier pilot project suggest that about 30 million additional barrels could be recovered from this field over 15 years, says Kjell Arne Jakobsen, staff engineer for petroleum technology on Norne.

When a reservoir is drained with traditional technology, 15-45 per cent of the original oil remains behind.

The viscosity and density of the crude are crucial for the recovery factor. But bacteria which exist naturally in the sea have properties which thin the oil.

Such micro-organisms multiply when provided with oxygen, and "wash" oil away from the pore walls in the reservoir - allowing these reserves to be recovered.

"The bacteria are the same as those used to clean beaches after oil spills, for instance," says Egil Sunde, the staff engineer in well technology who helped to develop the bacterial technology.

He pursued this work in partnership with the University of Bergen in Norway and Austrian oil and gas group OMV.

Norne has been selected for a full-scale pilot off Norway because oxygen is not removed from water injected into its reservoir, thanks to the use of stainless steel in the subsea installations.

Bacteria cultivation is being launched as soon as construction of a fertiliser plant on the Norne ship has been completed.