Johnstone, D., Potts, A.E,, Marcollo, H., and Kurts, P., (2017) Proceedings of the 36th International Conference to Ocean, Offshore and Artic Engineering ASME 2017 OMAE, June 25-30, 2017 Tondheim, Norway.

Deepwater drilling risers have a substantial portion (>70%) of buoyancy modules covering their entire length. The circular cross-section of these modules acts as a bluff body exhibiting significant Vortex-Induced Vibration (VIV) response, resulting in fatigue in the riser/wellhead and drag force amplification of the riser. 

Drilling operations can be suspended when the drag force on the riser adversely affects the top and bottom angles, a response which is exacerbated by drag force amplification due to VIV.

In 2015 and 2016, Longitudinally Grooved Suppression (LGS)1 technology was developed to field qualified Technology Readiness Level (TRL of 6) [1] offering a technical advantage to drilling operators over existing options.

In order to investigate the relative performance and quantify the benefits of LGS over conventional cylindrical Drilling Riser Buoyancy Modules (DRBMs) with and without fairings, a series of case studies encompassing typical operating conditions at drilling locations in several regions around the world (including the Gulf of Mexico, Brazil, the North Sea, and Australia) have been carried out to examine the performance in terms of drag (affecting operability due to top angle) and fatigue damage rate of the riser. The results indicate that LGS outperforms conventional buoyancy risers and fairings-equipped risers with regard to riser operability limits and fatigue.

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