Cognac platform: Correlation of analytical predictions with field measurements of dynamic response

Abstract

Utilizing simplified structural and hydrodynamic models, a parametric study is performed comparing response predictions for the Cognac deepwater platform as it is subjected to wave-and-current forces. Comparisons for the parametric study include: quasi-static versus dynamic response solutions, modal contributions to the response, impact of considering fluid-structure interaction, effects of using various empirically modified linear wave models or the Hybrid Wave Model, and correlation of the analytical response predictions with Cognac field measurements. The results of this study indicate that: (1) the dynamic response of Cognac is very moderate, (2) the dynamic response is dominated by the fundamental mode, (3) the inertia-dominated wave-and-current forces provide minimal response reductions from interaction effects, (4) of the considered wave stretching schemes, Wheeler stretching technique combined with linear wave theory produces platform response results which are closest to those obtained using the higher-order Hybrid Wave Model, and (5) the platform responses predicted using the Hybrid Wave Model are in better agreement with the measured responses for Cognac than the predictions based on the various stretched linear wave models.