Offshore riser damage-resistant design by state-of-the-art multidimensional reliability concept and generalized 4-parameter Weibull estimator

Abstract

Energy transportation systems are becoming economically viable as marine and offshore technologies, including both renewable and hydrocarbon energy-generating sources, advance, thereby diversifying the energy mix. Marine risers, umbilicals, and other flexible pipelines are employed by deep-sea mining, offshore wind farms, Floating Production, Storage & Offloading units (FPSOs), offshore platforms, and marine green renewable energy installations. Marine risers are commonly used to connect fixed/floating platforms to subsea equipment during offshore drilling and production operations. Future applications of riser technology will include deep-sea mining. Consequently, understanding the dynamic behavior of offshore marine risers is critical to ensuring the overall operating stability and safety of various offshore systems. Marine offshore risers, widely used in the offshore industrial sector, are often subject to excessive dynamic environmental stresses. Accurate evaluation of the dynamic response of deep-sea flexibles to subsurface currents is required for various offshore, ocean, naval, and marine facilities, particularly for Vortex-Induced Vibrations (VIV), which are crucial for design and operational safety. The investigation analyzed the effects of hydrodynamic sea-current stresses on marine risers, accounting for realistic in situ environmental variables, using a representative experimental dataset. This case study demonstrated that, under adverse sea- or ocean-current loads, it is feasible to accurately evaluate environmental damage or failure risks associated with riser dynamics, modelled as a multivariate system. A novelty and engineering advantage of the recently developed multidimensional structural damage risk assessment concept is its ability to handle multivariate systems with intricate cross-correlations among essential components or dimensions. This study also introduces and cross-validates a novel semi-analytical estimator for extrapolated failure probability.