Characterization of the Dynamic Loads Between Spar Top-Tensioned Riser Buoyancy Cans and Hull: Horn Mountain Field Data Measurements and Predictions

Abstract

The Buoyancy Can Riser Tensioner (BCRT) systems are designed to provide tension to Top-Tensioned Risers (TTRs). BCRT systems do not transfer the riser weight to the floater and they minimize the interaction between the floating platform and the riser system. For deepwater field developments, this attractive feature allows efficient design of the floaters as well as the riser systems. Although, the vertical riser load is not transferred to the hull, the BCRT system makes lateral contact with the hull at several locations. During the past 3 years, analytical models have been developed to characterize mechanics of the contact between two large floating bodies (buoyancy can and hull) and compliant guide hardware has been developed. Placement of a compliant guide between the hull and the BCRT has become the current practice for design of Spar floaters. The initial development of the analytical models and the compliant guide hardware coincided with the Horn Mountain project. The project team placed extensive instrumentation on the hull and compliant guides with a vision to confirm robustness of the guides and to calibrate analytical models used during the design phase. This paper presents a summary of the data collected on the performance of the Spar hull, compliant guides, and the riser systems for storms up to 25 ft of significant wave height. Analytical methods and predictions are presented to characterize the dynamic interaction between the BCRT system and Spar hull.