The Fatigue Life Calculation Of Workover Pipe Strings Serving In The Bending Section

In the process of conventional workover,downhole drilling tools fracture accidents,often takes extremely expensive,salvage at least loss of time,sometimes the salvage of failure and make the well scrap.According to the fracture accident of downhole drilling tools for many years accumulation and experimental research,the drilling workers recognized the vast majority of drill pipe is caused by fatigue fracture accident.This paper research on the topic of " The Fatigue Life Calculation of Workover Pipe Strings Serving in the Bending section ",the subject comes from shengli oilfield downhole operation company,according to the actual situation of workover operations research topic,topic has important theoretical value and practical significance.Project's goal is for oil field engineering and technical personnel to provide a set of software to calculate the operability,aims to use of workover drill pipe with a small size of fatigue life prediction.The workover drill string fatigue life prediction calculation software,is that bad downhole environment as the object,prediction and analysis of fatigue life of drill string in the curved interval,in order to guide the production and workover operations.This article tells the story of the string in the introduction part fracture failure as well as the background,the significance of and the string's fatigue life,stress analysis at home and abroad are analyzed.The second chapter mainly discusses the drill pipe rupture of general rules and main influencing factors and the drill string fatigue failure mechanism,fatigue fracture analysis of drill collar,thus can get tensile strength of tool materials,pipe material,the surface quality of the drill pipe,the combination effect of corrosion environment,the tensile and bending and cumulative fatigue problems constitute the main factors of the drill pipe fatigue fracture;String fatigue damage mechanism of the main stress damage,the drill string failure,fatigue damage and the vortex motion and vibration of the drill string four aspects;The corrosion mechanism of drill string at present is more,difficult to reach consensus;Structure,material and the load three factors to form the failure of drill collar.The third chapter through the analysis of the stress state and stress of drill pipe,drill string fatigue life calculation method.Fourth chapter through the programming calculation software,through six case study,including drill pipe,accumulated corrosion fatigue life,the calculation of slope section of maximum allowable bending curvature,at the same time for the drill pipe joint of drill pipe,thread fatigue failure by means of finite element analysis are verified and analyzed.The fifth chapter to prevent drill pipe fatigue fracture,corrosion failure and drill collar fatigue failure prevention suggested measures are putting forward.