Multiphase milestone

December 14, 1999, 08:30 CET

A new tool for simulating multiphase pipeline flow is being launched after five years of research in which Statoil has played a key role.

Multiphase flow – sending mixtures of oil, gas and water through the same pipeline – forms part of most field developments in which the group is involved.

This form of transport is used both to tie satellite fields to new or existing installations and to carry oil and gas ashore for final processing.

"The new-generation PeTra calculation tool will help to reduce costs by putting us in a better position to choose optimal pipeline dimensions," explains staff engineer Pål Hedne at Statoil's research centre in Trondheim.

"It will also reduce production shut-downs caused by unexpected flow conditions," he adds.

PeTra can be combined with other models to solve various problems associated with multiphase transport, such as wax and hydrate (hydrocarbon ice) formation at temperatures up to 20°C under high pressure.

The tool is particularly suitable for following slugs of liquid and inspection/cleaning pigs through a pipeline. Slugging occurs when fluids liquefy to form plugs separated by gas.

These slugs can be many hundreds of metres long and cause serious instabilities at the offshore or onshore receiving facility.

Development of PeTra was initiated by Statoil and funded by the group for the first three years. Financing was taken over for the two final years by the Norwegian Deepwater Programme (NDP).

The tool has recently been made available to the companies involved in the NDP, which are Norsk Hydro, Shell, BP Amoco, Conoco. Mobil and Exxon in addition to Statoil.

Development work was pursued in close collaboration with the Institute for Energy Technology at Kjeller outside Oslo.

Statoil, Hydro and Shell are concluding a collaboration agreement on multiphase flow in general and further development of PeTra in particular. The three also plan to exchange development and operational expertise.