Liuhua 11-1 Development- Phase I Installation

Abstract

Abstract The Liuhua 11-1 Field is situated in 1,020 ft (310 m) of water in the South China Sea. The Liuhua 11-1 Development Project includes a floating production system and floating production, storage and offloading vessel with joining pipelines and risers. The installation occurred in two phases occurring over 12-months to take advantage of two favorable weather seasons. Phase I, which forms the basis for this paper, was executed during May-July 1995 and includes laying of the moorings for both vessels and the hook-up of the FPS to its moorings. The scope of work and interface management required for installation of 21 mooring legs in this water depth is of particular importance. The vertical lay and tension system designed specifically for this project represented a large financial and engineering investment, The system was designed to lay the eleven mooring legs for the FPS and, ten mooring legs for the FPSO, and to tension the FPSO anchors to 1,323 kips (600 tomes) at the anchor. The system had to handle three sizes of stud link anchor chain and two sizes of bare spiral strand wire rope. The Phase H installation of February-April 1996 includes connection of the FPSO to its moorings and installation of the three pipelines and their risers. Introduction An overview of the Liuhua 11-1 Development Project is presented in OTC 8172 (Ref. 1) and Fig. 1. The development includes a floating production system (FPS), Nanhai 7Tao Zhan, permanently moored over subsea wellheads in 1,020 ft (310 m) of water. Its conversion is detailed in OTC 8187 (Ref. 2). It is a modified semi-submersible drilling rig equipped to provide drilling services and operate the subsea systems. Crude-burning generators on the FPS supply power to an eleetric submersible pump (ESP) in each well. Details of the ESPS are presented in OTC 8176 (Ref. 3). An overview of the subsea system is presented in OTC 8175 (Ref. 4). Produced well fluids are commingled in a subsea manifold located below the FIN and exported via two 13.5-in. flexible production lines that are linked to the manifold through independent tie-in bases and rigid jumpers. The two production lines together with a 6-in. flexible test line pass along the seabed from the tie-in bases to the floating production, storage and offloading (FPSO) vessel, Nanhai Sheng Li, located approximately 1.8 miles (3000 m) northwest of the FPS (Fig 2). The pipelines are reviewed in OTC 8188 (Ref. 5). They are made of flexible pipe and are connected to dynamic risers supported by discrete buoyancy collars. The pipelines are attached to the FPSO turret in a lazy wave configuration.