BG-SG特殊螺纹接头结构参数对密封性能的影响

摘要

BG-SG is a specifically designed premium connection for domestic shale gas wells drilling.It is composed of three parts of conical/conical seal structure , right angle torque shoulder structure and double-section thread structure , and applies in complex well conditions under big dogleg for having high strength & high torsion-resistance features . Based on control-variant approaches , the finite element method is used to study the effects on sealing contact pressure distribution and sealing performance of the connection structure parameters , such as the seal surface interference (δ) , the seal surface length ( l ) and the seal surface taper (ΔD/L ) .The analysis results show that δhas a positive effect on the sealing performance , however being too large can ’ t continuously contribute to increase the effective contact length , so theδvalue need to controlled at a appropriate amount not to cause plastic deformation or galling .Increasing parameter l can increase the effective contact length to some extent , while the value beyond a certain amount will result in a zero contact pressure zone within the seal surface region .Seal surface taper (ΔD/L) has different influences on either end of the effective contact length .Based on the analysis results , structure parameters of the connection is optimized , and the manufactured connection specimens passed the physical performance test , verified the validity of the finite element analysis .%BG-SG特殊螺纹接头是一种针对国内页岩气井专门开发的特殊螺纹接头形式，主要由锥面／锥面主密封结构、直角扭矩台肩结构和双段式螺纹连接部分组成，具有高连接强度、高抗扭等优点，适用于大狗腿度下的复杂井况。基于控制变量法的思想，运用有限元数值仿真计算方法分别研究了密封面过盈量（δ）、密封面长度（l）和密封面锥度（ΔD／L）等三个结构参数对接头密封接触压力分布和密封性能的影响。分析结果表明，δ的增大对接头密封性能有正面影响，但过大的过盈量并不能持续增加有效接触长度，且需控制其值不致引起接头结构的塑性变形或黏结；增加l值，可一定程度上增加密封面的有效接触长度，但超过某个特定长度以后则会在密封面中部产生零接触应力区域；ΔD／L对密封面两侧接触点附近的影响有所不同。根据分析结果优化设计了各结构参数，所开发接头顺利通过实物性能试验，验证了有限元分析的有效性。