Research on wave-loading fatigue of drilling riser in ultra-deep water drilling

Drilling riser is the key equipment for oil and gas development in deep water.The motion of floater in drilling system and wave load may lead to fatigue failure.Under the condition of the ultra-deep water,the interactions between the floater and slender strings are particularly pronounced.The wave-loading fatigue of riser calculated by the traditional de-coupled approach may be inaccurate.So a finite element model of a complete moored drilling system in the ultra-deep water was built.The study on the wave-loading fatigue characteristics of the riser based on the coupled system analysis indicated that the low-frequency fatigue induced by the low-frequency motions of floater is an important contributor to fatique failure of the riser and influenced significantly by the coupling effects between the floater and slender strings.The accurate prediction of floater motion is important to analyze the wave-loading fatigue of riser.The coupled system analysis is recommended for analysis on wave-loading fatigue of riser.