Fatigue Analysis of Wenchuan Scientific Drilling BHA under Complex Conditions

Longmenshan earthquake fault zone has experienced several earthquakes in history, the formation is extremely broken and contains some very loose and strong water-sensitive shale formation. Due to the complexity of engineering of geological conditions, drilling accident-prone. In this paper, for example WFSD-4 well, and use of ANSYS Workbench to establish a simplified of fracture accident of WFSD-4 well drill collars, analysis stress and fatigue damage of BHA model. The results showed that the maximum stress occurs at the bottom of the drill string, the first position of fatigue failure is in the drill string at the bottom of the drill bit, the entire drill string fatigue life is 1.66 × 10e9 cycles, and through the analysis to guide the design, manufacture and use of BHA.