套管偏梯形螺纹接头泄漏机理的有限元分析

Using finite element analysis on leakage mechanism for leaning thread in casing

用弹塑性有限元法 ,建立了API套管偏梯形螺纹接头接触问题的有限元力学模型。根据该力学模型 ,讨论了四种不同载荷 ,即 ,无过盈配合 ,套管轴向拉伸载荷 5 0MPa ;径向过盈配合 0 .0 5mm ,无轴向应力 ;径向过盈配合0 .0 5mm ,轴向拉伸载荷 5 0MPa ;径向过盈配合 0 .1mm ,轴向拉伸载荷 336MPa。文中详细分析了这 4种载荷下 ,API偏梯形螺纹的接触压力分布大小以及其螺纹之间的间隙 ,为其泄漏机理研究提供了研究思路和方法。研究结果表明 ,偏梯形螺纹之间大部分存在着间隙 ,其密封性存在着较大的隐患 ,因此 ,提出开发特殊螺纹接头套管 ,以适应我国西部高压深井。

Finite element dynamic mode is established for API casing leaning thread contact by using elasticand plastic infinite element. Based on the dynamic mode, this paper presents the discussion on four different loads, that is,non-interference fit-50 MPa tensile load; radial interference fit (0.05 mm)-no axile stress;radial interference fit (0.05 mm)-50 MPa axile tensile load; radial interference fit (0.1 mm)-336 MPa axile tensile load. The four loads are analyzed and touching pressure distribution and clearance between threads are found, that provide the method to research leakage mechanism. The research result shows that clearance exists in most part of leaning thread and the hiden trouble is in thread sealing. This paper put forward that it is tme to develop special thread for casing to meet the requirement of hi-pressure, extra deep and horizontal wells.