Vestprosess line laid

September 10, 1999, 10:00 CEST

Laying of the submarine section of Statoil's Vestprosess pipeline has been completed, with the system due to start operating on 1 October.

This part of the line runs from the Statoil Mongstad refinery complex near Bergen to Norsk Hydro's crude oil terminal at Sture further south.

"We've succeeded in laying the submarine section over a difficult seabed terrain in water depths down to 580 metres," says project director Ove Sembsmoen. "That's the deepest pipelaying ever undertaken off Norway."

The very irregular seabed meant that the line had to be laid through narrow valleys and tight curves. A total of 60 concrete "counteracts" have been laid to contain the line in the biggest swings.

In addition, a good deal of gravel has been deposited to support the line across free spans.

The pipeline was pulled ashore earlier this week after the Lorelay laybarge had completed the laying operating on 31 August.

To get the line in to land, Statoil adopted a "deflect to connect" method which has not previously been used so close to land.

This involved pulling the line into a pre-excavated trench in the inshore zone with the aid of winches on a supply ship and a mobile crane at the water's edge.

Since favourable weather conditions were essential for completing this operation, the work was delayed by about a week in relation to the original schedule.

"We now have to weld the submarine and land lines together and fill with gravel along the route," Mr Sembsmoen.

The new pipeline will transport condensate from Sture and Statoil's Kollsnes gas treatment plant to Mongstad, where the project has constructed a receiving station.

Other Vestprosess facilities at Mongstad include plants for fractionation of natural gas liquids and processing of liquefied petroleum gases.

Two rock cavern stores, for propane and butane respectively, have been completed. The work also covers construction of a new jetty and expansion of another.