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Abstract This study suggests a new concept of the subsea production system based on a large-scale seabed storage tank that stores the well fluid temporarily and later transfers it to the shuttle tanker through the riser. This concept was assessed to have advantages of reduction in the floater size, freedom from transportation distance, insensitivity to sea depth, and environmentally friendliness over the conventional deepsea solutions. Several flow assurance hazards for this system were expected, and appropriate design measures and operational methods against the hazards were suggested. A feasibility study was performed for an oil field which was located at 2190 m deep producing the well fluid of black oil type. The capacity of the seabed storage tank was considered to be 300,000 m3. Simulation results showed that riser diameter should be 19 inch and the insulation layer should be thicker than 100 mm. Introduction Subsea production systems have been devolving rapidly over last decades. At first, a fixed type platform was developed for shallow water field. At the early stages, the jacket structure platform was used for production. Later follwed the gravity based structure which withstood external force with self-weight and the jack-up rig platform which could regulate own height with hoist. As the sea depth increased, the compliant type platform was developed. At first, the guyed tower was used for production. Continuously, the tension leg platform which was moored by tendons was followed and the spar platform which was a large-diameter, single vertical cylinder bouy developed as an alternative to conventional platforms. Recently, floating type platforms, like semisubmersible platforms and FPSOs were developed for deep water field. |
