FLEXIBLE SPOOLS SOLUTION FOR HYBRID RISERS BASE FOR GREEN FIELDS DEVELOPMENTS

摘要

Rigid spools are commonly used at the riser base of hybrid riser systems such as STTRs (Single Top Tensioned Risers) or BHORs (Bundle Hybrid Offset Risers) for the deep water oil fields. Rigid spools design is critical and governed by numerous operating constraints such as dynamic loadings (due to motion of the vertical riser, Vortex Induced Vibration, slugging, etc.), soil properties and soil/spools/structures interaction. Recent surveys on existing brown fields have highlighted unexpected issues on existing rigid spools. To solve these issues, an innovative flexible spool solution has been developed, combining unbonded flexible pipe structures in a "steep wave " configuration to accommodate the riser motions and FLET (Flowline End Termination) excursions avoiding soil deterioration and preventing unexpected spool behavior which could ultimately jeopardize its integrity. A steep wave configuration solution can be introduced with distributed buoyancy over the flexible spools length. This design allows a direct connection between the riser base assembly and the flowline termination, solving the embedment issue and easing accommodation of the hybrid riser motions. This paper describes the recent issues with rigid spools design and describes the solutions developed with flexible spool configurations to provide a more reliable riser base spools system for green fields.