The Foinaven and Schiehallion Developments

Abstract The UK Quad 204 sector between the Shetland Islands and the Fames presents many challenges to offshore oilfield developments. The waters are deep and the weather and currents are harsh. The reservoirs are relatively modest on a world scale and being shallow require multiple drill sites and extensive use of horizontal wells. This paper describes the phased, fast track, parallel approach adopted by BP to substantially reduce historical discovery to production times. The first project Foinaven uses an FPSO based on a substantially rebuilt Russian submarine carrier, with two subsea well clusters giving an annual production of 85mbd. The second Schiehallion project is larger at 142mbd and will use a much larger FPSO with multiple subsea well clusters. Both developments will use shuttle tankers for oil export. This paper summarises the technology employed on the two projects and the tendering strategy used to achieve the timetables set. Introduction The Faeroes/Shetland Trough area or the Atlantic frontier as it has become known, has some of the deepest waters in the British offshore territory. Environmental conditions in the area are challenging. While wind and wave conditions are similar to those experienced in the Northern North Sea the currents are significantly more severe and complex, almost down to the seabed, due to interaction between the warm Gulf Stream and cold Arctic Stream. Foinaven, the first development in the Atlantic Frontier area, is located in two blocks, 204/19 and 204124a, which are operated by BP Exploration with Shell UK Exploration and Production as co-venturer. These blocks lie some 180 kilometres west of the Shetland Islands, in a water depth of between 400 and 600 metres - See Fig. 1. This presents a formidable technical challenge, as it is too deep for divers, and any development has to rely heavily on subsea technology for unmanned intervention. Foinaven is based on the recovery of 200 million barrels. [t is designed to produce early oil efficiently, safely and at low cost. A fast track schedule has been adopted for the project execution plan. The development centres on subsea wells completed on the seabed, producing oil via a manifold, through rigid flowlines and then flexible risers into a floating production, storage and offloading system (FPSO) which will be permanently stationed in the field. Shuttle tankers will export the crude oil - See Fig. 2. The project was sanctioned late October 1994 with first oil targetted for summer 96. More information on the reservoir and environmental are given in ref 1-3. The second development in the area is Schiehallion located some 12km to the East of Foinaven. As with Foinaven, Schiehallion shares similar environmental challenges with respect to water depths, currents, wave heights and winds. Clearly, therefore the learning from Foinaven has been fundamental in the development of Schiehallion.