Fatigue Damage Analysis of Drill pipes Using FEM and Cox Regression Model

Abstract

Drill pipe fatigue damage occurs under cyclic loading conditions due to, for instance, rotation in a dogleg region. This paper presents two approaches to evaluate damage in drillpipes; First, Finite Element Method is used to evaluate cumulative effects of fatigue damage with respect to the actual drilling conditions and the fatigue damage curves for smooth and die-marked drill pipes are obtained. Second, as a case study, the Cox Regression Model, a broadly applicable method of survival analysis is used to analyze the failure data of the southern oilfields of Iran. The resultant cumulative survival and hazard functions can reliably predict the time of failure.