某气井井口管线计量阀刺漏原因

Leakage Causes of Ground Pipeline Measurement Valve in a Gas Well

针对某高产气井单井管线的计量阀发生剌漏,进行了现场失效情况和相关生产参数的调研,并进行了金相组织、能谱和化学成分分析。结果表明,阀体铸铁的金相组织和化学成分符合标准要求,内表面镀层、密封环和压盖材质化学成分也符合标准要求。计量阀本体和上游存在严重的冲刷腐蚀;计量阀阀球压盖上的环形沟槽的腐蚀是冲刷腐蚀与缝隙腐蚀的结果,这与压盖留有一环形缝隙结构缺陷有关。压盖与球体间暴露出来的铸铁是形成腐蚀坑槽的起因,但腐蚀沟槽的最终形成则是由冲蚀、气蚀和电偶腐蚀共同作用的结果。阀室内表面的腐蚀沟槽起因在于阀室内表面粗糙不均匀而受到冲蚀和气蚀作用,而后由冲蚀、气蚀和电偶腐蚀共同作用。

The pitting leakage of ground pipeline measurement valve in a gas well and its producing condition were investigated, and the failure reasons were analyzed by field research, metallographic structure, spectroscopy and chemical composition analyses. The results show that the microstructure and chemical composition of the valve and the chemical compositions of the inner surface plating, sealing ring and top cover meet the demands of the standards. There was serious erosion corrosion in the substrate and upstream of the valve. The ring ditch on the top cover of the valve ball resulted from the simultaneous action of erosion corrosion and crevice corrosion, which related to the structure defect of the ring crevice in the top cover. The finally formed ditch between the top cover and the ball resulted from erosion corrosion, gas corrosion and galvanic corrosion. The reason of the corrosion ditch on the inner surface of the valve was also the results of erosion corrosion, gas corrosion and galvanic corrosion on the coarse and uneven surface.