The Gullfaks Field: Applying Tomorrow's Subsea Technology

Abstract

Abstract More than a decade have passed since the completion of Statoil's first subsea production wells on the Gullfaks field in the Norwegian North Sea. Further development is now under way in the Gullfaks area, with the Gullfaks South, Rimfaks and Gullveig fields due to be tied back to the A platform. The license group consists of Statoil (operator), Norsk Hydro and Saga Petroleum. This Gullfaks satellites (GFSAT) project will again be adopting innovative technology. Being developed faster and more cheaply than comparable previous project, it will make an important contribution to continued profitable operation of the main field. A total of eight seabed templates with 31 slots are to be installed. The project also involves substantial modification on Gullfaks A. Production is due to start in October 1998. As early as 1993, GFSAT established functional requirements for rig-installable seabed templates and manifold systems with foundations based on cementing. Another goal set by the project was to reduce costs for subsea installations by 40 per cent compared with the Statfjord satellites. Statoil will be adopting the novel hinge over subsea template system (Host), subsea multiphase meters, interfaces that allow intelligent completions and so forth. Two heated flowline bundles will be connected together to cany wellstreams between Gullfaks South and Gullfaks A. On Gullveig, Statoil will be using a "pipe-in-pipe" solution reeled onto a drum and spooled out on the field. GFSAT will mark the first use in the North Sea of 13% Cr stainless steel in flowlines. These developments will contribute to the execution of several subsea projects world-wide. A cost effective subsea production system has been developed for future deepwater completions. Gullfaks history Gullfaks (fig 1) lies in 135 metres of water in block 34/10 on the Norwegian continental shelf, 175 kilometres north-west of Bergen, and covers 51 square kilometres. This acreage was awarded in 1978 to a group comprising Statoil (85 per cent, including the government direct financial interest of 73 per cent), Norsk Hydro (nine per cent) and Saga Petroleum (six per cent). Extensively faulted, the field comprises three major sandstone reservoir formations: Statfjord, Cook and the Brent group. It has been developed with three platforms - Gullfaks A, B and C. Gullfaks was a ship in Norwegian folklore that could sail with equal ease on land and water, and was the first name from Norway's popular folk tales to be applied to one of the country's offshore fields. Statoil moved straight up among the subsea technology front-runners in 1986 by installing the most advanced seabed system of its day on Gullfaks. Based on diverless completion, six of these subsea wells were tied back to the A platform during 1986-87. Today, a decade later, three of the first six subsea wells are still producing, and Statoil has won valuable experience which is transferred to new projects. The Gullfaks wells have been followed in short order by the Tornmeliten, Statfjord satellites, Sleipner East, Loke, Norne and Yme developments.