KOS extends subsea technology to meet Girassol requirements

In the course of the next few months, Kongsberg Offshore is due to make the first deliveries of subsea production equipment for Elf's Girassol development off Angola. The water depth at Girassol, at 1,420 meters, is the deepest for which KOS has yet supplied subsea facilities.

Under the EPC contract, which is worth more than $200 million and was awarded in mid-1998, the company is supplying the subsea production system consisting of 28 wellheads, 30 christmas trees and controls, 13 production manifolds and controls and two complete workover systems. There are also options for additional wellheads, trees, and manifolds.

Wellheads and subsea tree blocks are being manufactured by the Dunfermline, Scotland plant of FMC, KOS's parent company. Fabrication of the manifolds was subcontracted to Grenland Offshore in Norway.

The Girassol subsea production equipment is based on the modular design or building block philosophy developed by KOS, and represents an extrapolation of the technology developed for more conventional North Sea water depths, the company says. One key difference is that it is designed for guidelineless installation.

The foundations of the company's subsea technology were developed under technical agreements with Statoil, Elf, Shell and Mobil during the mid-1990s. This involved it in extensive programs of equipment engineering and qualification.

Deliveries to projects such as Statoil's Åsgard, Gullfaks South and Lufeng 2-1 developments, and Mobil's Zafiro followed. As projects arose in deeper water depths, it proved possible to extend the technology, with relevant engineering validation and qualification, to allow its application, without major modifications, in water depths up to around 2,500 meters.

KOS has now started the development of subsea production systems applicable to operations down to 4,000 meters and with the additional objective that the technology should meet the $10/bbl requirement.

Production availability is one of the main challenges in view of the high well productivity in deepwater. Qualification of equipment and failure prediction assessments are the key elements for any deepwater subsea development where the life of field design criteria is 20 years, the company says.

Another deep-water challenge is posed by the possibility of wax and hydrate formation in the wellstream. For this reason, the subsea trees, manifolds, jumpers, and flowlines are all insulated or thermally protected.

All subsea equipment will be prepared for installation offshore at a new base opened by FMC Energy System in Luanda. The base will also be equipped for the performance of maintenance activities, though this contract has not yet been awarded.

KOS will also assist Stolt Comex Seaway, a member of the Alto Mare Girassol consortium responsible for offshore installation, with the installation of some of the subsea items such as manifolds and jumpers.