外加厚P110钢级油管的断裂原因

Fracture Causes of External Upset P110 Tubing

某致密砂岩气井中规格为?73.02 mm×5.51 mm的外加厚P110钢级油管发生断裂,通过宏/微观形貌观察、化学成分分析、显微组织观察以及力学性能测试等方法分析了油管断裂原因。结果表明:断裂外加厚油管位于油管柱上部,承受较高的轴向拉应力,且其材料对硫化物应力腐蚀开裂敏感性较高,而气井采出气中存在的H_(2)S为油管提供了硫化物腐蚀环境,使得外加厚油管发生硫化物应力腐蚀开裂;油管的硬度较高,且组织内存在较大的硫化物夹杂,促使油管的断裂。

A external upset P110 tubing with a size of ?73.02 mm×5.51 mm used in a tight sandstone gas well was fractured. The fracture causes of the tubing were analyzed by means of macro/micro-morphology observation, chemical composition analysis, microstructure obsevation and mechanical property testing. The results show that the fractured tubing was located on the upper part of the tubing string, and subjected to a high axial tensile stress, and its material had a high sensitivity to sulfide stress corrosion cracking, and the H_(2)S in produced gas of the gas well provided sulfide corrosion environment for the tubing, resulting in the sulfide stress corrosion cracking of the external upset tubing. The hardness of the tubing was high, and there was a large sulfide inclusion in the structure, which promoted the fracture of the tubing.