The TEN development project offshore Ghana (operated by Tullow Ghana Ltd and partners) includes one 6" gas production and six 8" oil production infield flowlines. The flowlines lengths vary from 3.2 km to 7.2 km and are located in water depths of 1200–1800 m. In order to achieve a high level of thermal insulation, these flowlines are fabricated from swaged pipe-in-pipe systems, developed by ITP. The pipes are double jointed and assembled onshore to produce double joint units of swaged pipe-in-pipe which are welded together on the J-lay vessel. An Izoflex layer is wrapped onto the inner pipe within the annulus. This novel configuration ensures excellent thermal insulation characteristics. This paper highlights the engineering and computational challenges faced and the efficient solutions developed during detailed design of these flowlines. All design activities and numerical solutions were performed in house by Subsea 7.
The Tweneboa, Enyenra and Ntomme (TEN) reservoirs are situated in the Deep Water Tano block approximately 60 km off the coast of Ghana, West Africa. The reservoirs are found in water depths ranging between 1,000 m and 2,000 m. The field is split into east and west sides by a subsea canyon. Following completion of the exploration and appraisals Tullow Ghana Limited and partners Kosmos Energy LLC, Anadarko Petroleum Corporation, Ghana National Petroleum Company and PetroSA are developing the TEN fields. The discoveries are being developed utilising a series of discrete subsea production centres tied-back to a turret moored FPSO. In addition, the FPSO will provide both gas injection and water injection service to the reservoirs in order to provide sweep and pressure support to the production wells and gas export to supply Ghana gas infrastructure with volumes of sales gas.
The field layout and architecture is shown in Fig. 1. The subjects of this paper are the six oil production lines as follows:
