Design of Novel Solution of Flexible Pipe for Offshore Oil Offloading Transfer

Spread moored FPSO (Floating Production and Storage Offloading) vessels are generally used for the large West African oil fields. The oil is transferred from the FPSO to shuttle tankers via an Oil Loading Terminal (OLT). 2 to 3 large diameter flexible lines are connecting the FPSO to the OLT. The final connection between the OLT and the shuttle tanker is made by floating hoses.The single length of each flexible pipe can be typically 2,300 meters or higher, and the internal diameter is generally very large in the order of 15_23″ to minimize the pressure drop and the offloading time.Conventional flexible pipe is the most suitable solution for this application. However, its long length and large diameter require a large number of buoyancy modules which are necessary to support the substantial weight generated by the steel armor wires.An alternative to steel is Carbon Fiber Composite (CFC). This material is not only twice as strong and five times lighter than a high strength steel but it is also characterized by its exceptional performance in fatigue. As the weight of the composite armor flexible pipe is significantly reduced, the use of buoyancy is no longer necessary. The pipe can also be manufactured in a single length without intermediate connection.A qualification program based on a 19″ internal diameter prototype has been launched. This is the first time that a large internal prototype with Carbon Fiber Composite Armor (CFA) and end-fittings have been designed and manufactured. The main goals are to confirm the suitability of the CFA flexible pipe for oil offloading application in accordance with the design tools. The mechanical behavior responses of the CFA are monitored by strain gages when the flexible pipe is in straight and curved positions under internal pressure and bending cycles.The paper will present the main mechanical properties and the overall performance of the flexible pipe designed and tested.The economic viability will be demonstrated by showing how the CFC material cost is positively offset by the removal of the buoyancy modules and a faster offshore installation.Copyright © 2014 by ASME