Failure Mechanism And Improved Technology Research Of Trenchless Directional Drill Pipe

Nowadays in non-open-cut directional drilling,pipe diameter is getting bigger and bigger and crossing length is getting longer and longer.Conventional API S135 drill pipe for petroleum exploration drilling cannot meet the requirements of high torque,high tension and high resistance for compression.Drill pipe failure accidents have happened frequently,resulting in the failures of non-open-cut directional drilling projects including the Second West-to-East Gas Pipeline Project.Therefore,it is urgent to conduct detailed study in drill pipe failure mechanism in non-open-cut directional drilling and develop new drill pipe suitable for underground crossing project with higher torsional strength and tensile strength,so as to improve the reliability of drill pipe and guarantee the operation of crossing project.Based on the technical background and engineering application requirements,the research subject of this dissertation "Drill pipe failure mechanism and improvement technique in non-open-cut directional drilling" is proposed.Detailed research content and specific research object are formulated.This dissertation is based on drill pipe failure cases of non-open-cut directional drilling at home and abroad,as well as the related document literature and technical research.This research is related to the 20-year’s achievements of the author in drill pipe safety and failure,as well as research achievements of the 12th Five-Year Plan PetroChina Scientific Research and Technology Development Project "Technical Research on Oil and Gas Pipelines Non-open-cut Directional Drilling in Complex Geology".This dissertation carries out drill pipe failure mechanism and improvement technique in failure analysis,fatigue life,crack propagation,material property and structure optimization.Detailed research thought,specific research approach and main research content are proposed,and the subject is completed successfully.The main research contents and research achievements are as follows.(1)Statistical data analysis of drill pipe failure in non-open-cut directional drilling is carried out and drill pipe failure modes and failure causes are concluded.Failure causes of specific failure accidents in underground crossing project is analyzed,which provides field data for the necessity of drill pipe safety research in non-open-cut directional drilling projects.(2)According to the analysis on drill pipe load and stress in on-open-cut directional drilling projects,the static and dynamic models of drill string are established.Based on specific drill string and operation condition,stress and strain of drill string are analyzed.The simulation results are consistent with the analysis results of failure reason,which indicates that the established static and dynamic models have some guidance value to the simulation analysis of drill pipe failure mechanism and improvement technique.(3)Theoretical and experimental study on drill pipe fatigue life are carried out.Fatigue experiments of API S135 small samples are conducted at tension,torsion and tension-torsion combined load.Fatigue life formulae and microscopic appearance of fracture are obtained,which provides experimental data for drill pipe failure mechanism in non-open-cut directional drilling.(4)Based on V150 drill pipe material,manufacturing technological problems of high strength and toughness V150 drill pipe in pipe body heat treatment and weld heat treatment are solved successfully.6-5/8" 10.92mm V150 drill pipe is successfully developed,which provides solutions for drill pipe safety in non-open-cut directional drilling.(5)Fatigue experiments of V150 small samples are conducted at tension,torsion and tension-torsion combined load.Fatigue life formulae and microscopic appearance of fracture are obtained,which provides experimental data for drill pipe safety in non-open-cut directional drilling.(6)Based on the difference of drill rig for non-open-cut directional drilling and petroleum drill rig,as well as the imperfection of API drill pipe structure,the design concept of"Non-elevator shoulder drill pipe for non-open-cut directional drilling" is proposed.According to three-dimensional simulation and optimization by finite element method,trial-manufacture and of drill pipe sample is completed and detection of the third test institution is finished.The overall performance of drill pipe achieves the expected target,which provides new thought and plan for drill pipe safety in non-open-cut directional drilling.(7)The developed 6-5/8" 10.92mm V150 drill pipe is used in field non-open-cut directional drilling application of China petroleum pipeline bureau traverses branch office.The application has effectively solved drill pipe failure problems and replaced the import of foreign drill pipe,which has generated great economic and social benefits.