Assessment of Ultra Deepwater Riser Concepts for High-Motion Vessels

ABSTRACT:

The paper presents the results of the second half of a study funded by Research Partnership to Secure Energy for America (RPSEA) under project 10121-4401-02 Ultra-Deepwater Riser Concepts for High Motion Vessels. In the first half of the study, candidate riser systems consisting of alternatives to the steel catenary riser in both geometry – for the purpose of isolating the fatigue-critical riser touchdown zone from the motions of the vessel – and material were identified then down-selected to meet the constraints of high motion vessels like the conventional semi-submersible or a ship-shape floating, production, storage, and offloading vessel (FPSO). In addition to water depths approaching 10,000 feet, the present-day challenges of high pressure, high temperature, and sour well product are incorporated into the problem being framed.

Results from dynamic analyses of riser concepts passing through the down-selection process are used to assess both utilization of strength capacity and fatigue performance. Comparisons of dynamic responses highlight the differences of each riser concept’s behavior and provide understanding of the limitations of riser concepts. Assessments to other criteria such as cost, failure modes, and installation considerations are also used to ascertain safe riser systems that meet the performance demand of high-motion vessels.

Royer, B., Power, T.L., Ayewah, D. O., Head, W., “Assessment of Ultra Deepwater Riser Concepts for High-Motion Vessels,” Proceedings of the Offshore Technology Conference, Houston, Texas,  May 5–8, 2014.