Improving Veslefrikk recovery

November 12, 1998, 08:00 CET

More oil is to be squeezed out of the reservoirs in Statoil's Veslefrikk field in the North Sea.

The long-term aim is to improve the recovery factor from 48 to 57 per cent with the aid of modern drilling and well technology, reports Gro Aksnes, petroleum technology manager for Veslefrikk operations.

Some 65 million barrels of oil have been identified in addition to the basic estimate of roughly 343 million barrels in recoverable reserves for Veslefrikk.

These "additional" barrels will be tapped with sidetracks - new wells drilled out to the side from existing producers in order to reach an oil pocket.

"We're hoping to achieve multilaterals - in other words, producing simultaneously from parent well and sidetrack," says Ms Aksnes.

Injecting water and gas simultaneously represents another approach being considered for driving more oil out of the reservoirs. But this relatively new method requires further study.

Low-pressure production is also being assessed. This involves the use of multiphase pumps to boost wellstream pressure. Statoil resolved this autumn to install such devices for the first time on its Gullfaks A and B platforms in the North Sea.

The average recovery factor for Statoil-operated fields off Norway currently stands at 48.4 per cent, but the group aims to raise this to 54.3 per cent by 2005.

Statfjord can currently claim the best performance, with a recovery factory of 62 per cent. But it can be difficult to make comparative use of this factor because reservoir properties differ sharply from field to field.