高压对气井套管接头螺纹接触应力的影响研究

The influence of high pressure on thread contact stress of casing joints in gas wells

高温高压气井对螺纹密封性的要求要比油井更为严格。对于高压气井中的整个管柱,每一段处于不同的力学环境中,发生泄漏的可能性也不同,因此研究压力对气井套管接头螺纹接触应力的影响,对高压气井套管的合理使用尤为重要。利用弹塑性有限元分析方法,建立了API偏梯型螺纹套管接头的有限元模型,分析了气井压力对套管接头接触应力的影响,提供了研究压力对套管接头螺纹接触应力影响的方法。对于井口压力或井底压力超过34MPa的高压气井,应选用气密性良好的特殊螺纹接头,建议采用金属对金属的螺纹接头套管,以加强螺纹部位的连接强度和密封性能。

Thread sealing property in high temperature and high pressure gas wells is more important than that in oil wells. In the high pressure gas wells, each section of the casing string is under different dynamic conditions, leakage is possibly induced in different situations. Thus the investigation of pressure effect on the thread contact stress of casing joints in gas wells is especially important for proper application of casings in high pressure gas wells. The method of elastic-plastic finite element is deployed to establish a finite element model for API buttress thread casing joints, the effect of gas well pressure on the contact stress of casing joints is analyzed, methods are provided for studying the effect of pressure on the thread contact stress of casing joints. For the high pressure gas wellswith wellhead pressure or bottom-hole pressure over 34 MPa, special thread joints with better sealing performance should be selected. Casings with metal to metal thread joints are recommended for strengthening the intensity and sealing property of thread connections.