Método da redução de dimensão univariada aplicado na análise de fadiga de estruturas de cabeças de poços de petróleo considerando o efeito simultâneo de ondas de mar local e de swell

Abstract

Due to the observation of dynamic motions in wellhead structures during drilling operations, wellhead fatigue became a major concern for the oil industry. One of the most important causes is the wave action on the floating unit to which the riser is connected. Waves can be classified from their origin. The local sea waves are those generated by the local wind. Swell waves are those generated in a distant location that reach the region of interest. It is not common to deal with these two types of waves independently and simultaneously in a traditional fatigue analysis, mainly due to the high computational cost associated with the adequate modeling of both wave sources. Thus, this work proposes the use of the Univariate Dimension Reduction Method (UDRM) to calculate the fatigue damage in wellhead structures considering the effects of wind-sea and swell waves. The main advantage of this procedure is that it drastically reduces the number of numerical simulations of the structural system required in the assessment of fatigue. The methodology is applied to two case studies considering the environmental conditions of the Brazilian coast. The results and efficiency of the UDRM are compared to those obtained through an approach based on the Monte Carlo Simulation. The comparison’s results indicate UDRM is a feasible alternative for calculating the fatigue lives of offshore wellhead structures subjected to sea and swell waves, reducing substantially the computational costs of the required analyses.