Fatigue Strength Evaluation of Drill Pipe for Challenging Deep Drilling Project - Japan Trench Fast Drilling (JFAST)

摘要

Japan Trench Fast Drilling Project (JFAST) was undertaken todetermine the mechanism of the catastrophic Tohoku Earthquake,which triggered off a huge tsunami. The targeted drilling sites werelocated about 1,000 m below the seafloor at water depths of 7,000 m.For such deep drilling, it is mandatory to evaluate the strength of thedrill string in terms of both maximum stress and fatigue strength. Thus,the cumulative damage ratio and the possible operation duration wereobtained using an M-N curve and analysis results of the momentdistribution as well as its occurrence probability. Moreover, the drillingdata acquired during the drilling operation was analyzed and to evaluatethe cumulative fatigue in JFAST operation.