Retracted: “A New Mathematical Model for Evaluating the Safe Margin of Deep-water Landing Operation”

Abstract

Abstract For an accurate prediction of heave induced dynamic tensile load on landing strings and determining the safe margin of deepwater landing operation, a comprehensive mathematical model is proposed in this study. The novelty of this mathematical model lies in that it incorporates the effect of Bottom Hole Assembly (BHA) as well as Guide Base Plate (GBP) which were neglected by other researchers. The proposed mathematical model is solved with Galerkin’s method and verified by comparing the corresponding results calculated by the numerical method established in a previous research work. The results of this model are used to compare with those from existing models to emphasize the important role that BHA and GBP act on heave-induced dynamic response of the landing string assembly. Meanwhile, criterion for evaluating the safe margin of deepwater landing operation is presented. Sensitivity analysis is carried out to investigate the effect of GBP area and hydrodynamic damping coefficients. This study shows that the maximum allowable heave amplitude of drillship is relatively small if its heave frequency is in the vicinity of the resonant frequencies of landing string assembly’s longitudinal oscillation. By incorporating the effect of BHA, the resonant frequency and stress state of landing string assembly both have changed; while, the GBP only affects the stress state. Besides, the dynamic tensile load decreases with the increase of GBP area and hydrodynamic damping coefficients in near resonant conditions. This work provides a theoretical guidance to the design of deep-water landing string, which is essential for deep-water drilling operation.