Due to the concentration of high-quality natural gas resources in deep and ultra-deep formations in China,drilling of ultra-deep wells presents higher performance requirements for drill strings.Titanium alloy drill pipes have become a research focus for ultra-deep natu-ral gas drill strings due to their advantages such as high strength,low density,corrosion resistance,fatigue resistance,heat resistance,and non-magnetic properties.In this study,a three-dimensional finite element analysis method is used to compare and investigate the effects of titanium alloy and steel drill pipe materials on the load-bearing and sealing performance of high load-bearing drill pipe joints under different external loading conditions.The failure modes and mechanical characteristics of the high load-bearing drill pipe joints under working condi-tions are also analyzed.The results show that the use of titanium alloy materials can reduce the overall stress level of the drill pipe joints by 20%and improve the torsional resistance by approximately 60%.However,under the same make-up torque,the sealing pressure of the main shoulder of titanium alloy joint is 15%～20%lower than that of the steel drill pipe joint.When subjected to composite loads of inter-nal pressure,tension and bending moment,the maximum critical point of the thread transitions from the fillet groove of the external thread shoulder to the first tooth root of the external thread shoulder.The overall stress level of the thread increases,while the sealing performance decreases.Therefore,to meet the requirements of ultra-deep natural gas drilling,when using a composite drill string of titanium alloy and steel drill pipes,it is recommended to appropriately increase the make-up torque of the titanium alloy drill pipe to improve the sealing per-formance of the thread joint.
关键词
超深井天然气开发/钛合金钻杆/高承载接头/三维力学/有限元分析/复合载荷
Key words
ultra-deep gas exploration/titanium alloy drilling pipe/high load-bearing joint/three-dimensional mechanical/finite element analysis/composite loads
维普
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