More oil from better sand control

More oil than planned will flow from the three platforms on Statoil’s Statfjord field in the North Sea this year, thanks to an improved system for monitoring sand intrusion in the wells.

This strategy involves producing the sand carried by the hydrocarbons from the formation, and then separating it out of the wellstream in the platform processing system.

Statoil has also developed a technology which monitors sand production in a way which avoids damage to pipelines, chokes and other equipment.

Sand intrusion into oil wells has traditionally caused erosion in flowlines and, in the worst cases, the appearance of holes in these pipes.

While a field continues to produce on plateau, the answer to this problem is to close down wells which are producing sand.

In a tail production phase of the kind which Statfjord has now entered, measures which increase oil output and extend the field’s producing life are important for improving value creation.

Software developed by one of Statoil’s petroleum technology groups makes it possible to identify the corrosion threat in vulnerable parts of the production system.

”This has been combined with an improved sand detection system using duplicated detectors in the flowlines,” says Jamie Andrews, lead production engineer in Statfjord’s reservoir department.

”The result is that we can operate safely in a controlled way, even though it has been estimated that each platform handles roughly 50-75 tonnes of sand every year.”

During a pilot test on Statfjord B in the autumn of 2003, Statoil produced 3,400 barrels of additional oil per day without demonstrable damage to flowlines or other equipment.

Statfjord B adopted the full-scale sand management strategy in April, with the C platform following in mid-July and installation of detectors on Statfjord A scheduled for completion in late August.

According to Mr Andrews, sand treatment tests show that production can be increased by three-four per cent without damage to the equipment.

The Statfjord operations organisation has been able to draw on experience gained in a successful earlier project carried out on Statoil’s nearby Gullfaks field in 2001.