某水平井用P110钢级套管接箍的开裂失效分析

Cracking Failure Analysis of P110 Steel Grade Casing Coupling for a Horizontal Well

对某水平井用P110钢级套管接箍在酸化压裂过程中发生的横向开裂失效进行了系统分析,通过宏观几何尺寸测量、化学成分分析、力学性能测试、组织分析、扫描电镜观察和能谱分析等方法分析了裂纹产生的原因。结果表明,接箍台肩根部的应力集中和超尺寸夹杂物引起的缺口效应叠加作用引发裂纹及并使其扩展,最终导致失效。断面有韧窝,但韧窝非常浅;裂纹周围并无明显塑性变形征兆,是非常危险的断裂形式。

Systematic analysis of the lateral cracking failure of P110 steel grade casing coupling in a horizontal well during acid fracturing was carried out.The causes of cracks were analyzed by methods such as macroscopic geometric size measurement,chemical composition analysis,mechanical property testing,structure analysis,scanning electron microscope observation and energy spectrum analysis.The results indicate that the stress concentration at the root of the coupling shoulder and the notch effect caused by the oversize inclusions induce cracks and cause them to expand,which ultimately leads to failure.The fracture has dimple topography,but the dimple is very shallow;there is no obvious sign of plastic deformation around the crack,which is a very dangerous form of fracture.