Innovative Supports of Risers and Corresponding Installation Procedures

Usage of FPSO in shallow water always presents challenges to keep flexible risers’ stresses at the TDP (TouchDown Point) below acceptable values. Depending on the water depth, the catenary configuration can impose excessive high stresses at the TDP and for this reason, configurations like Lazy S, Steep S, Lazy Wave, Steep Wave, Pliant Wave and other complex configurations should be used. Choosing the type of configuration is always dependent on, among others, local environmental conditions, FPSO’s behavior and supports, the water depth, the number of risers, bottom arrangement of them, possibility of line clashes and mainly the cost of the solution. Depending on the number of risers to be supported, construction, installation and keeping good reliability of structural solutions generate considerable increases in the overall investment and maintenance costs. The paper presents two innovative fixed submerged supports of flexible risers, in lazy S configuration, and their installation procedures, that manage to lower construction and installation costs and also decrease inspection tolls due to increased reliability of the structure in comparison to floating buoy solutions.