双台肩钻具螺纹应力与密封性能影响因素分析

Analysis on the Factors Influencing Thread Stress and Sealing Performance of Double-Shoulder Drilling Tool

钻具连接螺纹接头强度和密封性能会对钻具的正常工作产生直接影响。为了保证油气开采顺利进行,有必要对钻具螺纹接头进行强度和密封性能分析。为此,以双台肩超高抗扭钻具连接螺纹为研究对象,考虑螺纹不对称性、螺旋升角以及主副台肩接触和螺纹齿面接触等因素,建立了包含进刀槽和退刀槽的钻具螺纹接头三维有限元模型。采用有限元分析方法开展了不同公差配合尺寸、不同载荷形式和不同材料下螺纹接头强度和密封性能分析。研究结果表明:由于间隙的存在,极限配合公差尺寸下螺纹应力比名义尺寸下螺纹应力大25%左右,且其副台肩密封失效;弯矩使螺纹应力和接触压力分布均呈现一侧增大一侧减小的现象,轴向载荷使螺纹应力大幅增大,最大增大了75%,同时主台肩密封失效;不同材料螺纹应力分布规律相同,在弹性模量减小1/2的条件下,螺纹应力以及接触压力均减小8%左右。因此,极限配合公差尺寸以及过大的轴向载荷会破坏螺纹接头的密封性能,材料对螺纹接头的性能影响不大。研究结果可为钻具螺纹接头设计和应用提供参考。

The normal operation of drilling tool is directly affected by the strength and sealing performance of its threaded joint.Therefore,in order to ensure the smooth progress of oil and gas production,it is necessary to analyze the strength and sealing performance of the threaded joints of drilling tools.Taking the connection thread of double-shoulder ultra-high torsion-resistant drilling tool as the research object,the three-dimensional finite element model of the threaded joint of drilling tool including engage groove and retract groove is established by considering thread asymmetry,helix angle,primary-secondary shoulder contact and thread tooth surface contact.In addition,the strength and sealing performance of threaded joint under different tolerance fit sizes,load forms and materials are analyzed by means of the finite element analysis method.The results show that due to the existence of the gap,the thread stress under the limit fit tolerance dimension is about 25%larger than that under the nominal dimension,and the sealing of its secondary shoulder fails.Due to the existence of bending moment,the distribution of thread stress and contact pressure presents the phenomenon of increasing on one side and decreasing on the other side.The axial load leads to the great increase of thread stress,which is up to 75%,while the sealing of primary shoulder fails.The thread stress distribution law of different materials is the same.When the elastic modulus is reduced by half,both thread stress and contact pressure drop by about 8%.In conclusion,limit fit tolerance dimension and excessive axial load can damage the sealing performance of threaded joints,and the difference in material has little effect on the performance of threaded joints.The research results can provide the reference for the design and application of the threaded joints of drilling tools.