Fatigue Life Prediction of Buckling String with Cracks in Horizontal Wells of Mining Engineering

Abstract

Fatigue damage in the rotating drill pipe in the horizontal well of mining engineering is usually resulted from cyclic bending stresses caused by the rotation of the pipe especially when it is passing through curved sections or horizontal sections. This paper studies fatigue life prediction method of rotating drill pipe which is considering initial crack in horizontal well of mining engineering. Forman fatigue life prediction model which considering stress ratio is used to predict drill string fatigue life and the corresponding software has been written. The program can be used to calculate the stress of down hole assembly, can predict stress and alternating load in the process of rotating-on bottom. Therefore, establishing buckling string fatigue life prediction model with cracks can be a good reference to both operation and monitor of the drill pipe for mining engineering.

Experimental Investigation and Analysis of Dynamic Buckling of Drill String in Horizontal Well

“…The general buckling configurations of the entire drill string are deduced with the suspended and continuous contact sections, respectively, depicted by beam-column model and buckling differential equation in consideration of the gravity [11][12][13]. Wang et al established buckling string fatigue life prediction model with Forman fatigue life prediction model which considering stress ratio is used to predict drill string fatigue life [14]. He derived an improved formula for critical buckling forces, which takes the well curvature into account.…”