大牛地奥陶系马五段硫化氢腐蚀机理与影响因素

为了解决大牛地气田硫化氢腐蚀严重问题,分析了硫化氢腐蚀机理以及影响腐蚀程度的因素。结合大牛地奥陶系马家沟组马五段地质条件以及硫化氢赋存条件确定该区域硫化氢形成的机理,为硫酸盐热化学还原反应;且该区域存在的大量石膏层为含硫化氢气体提供了良好的圈闭条件。硫化氢腐蚀模拟试验模拟了马五段地层水环境对N80钢和P110钢的腐蚀程度,P110钢的腐蚀程度较N80钢轻微,两者均属于极严重腐蚀。结合腐蚀表面微观形貌观测与腐蚀产物能谱分析得出:大牛地奥陶系马家沟组马五段硫化氢腐蚀机理为高温高压下CO2/H2S电化学腐蚀为主;并伴随有高Cl-破坏腐蚀产物膜加速腐蚀。硫化氢腐蚀影响因素分析得出温度和CO2含量增加会加速硫化氢腐蚀。

Corrosion mechanism for hydrogen sulfide in the fifth section of Dovician Majiagou formation in Daniudi gas field

Based on formation characteristics of Dovician Majiagou formation and the conditions for hydrogen sulfide(H2S) reservation, the generation mechanism for H2S is ascertained as sulfate thermo-chemical reaction (TSR), and massive gypsum providing trapping condition for H2S. Corrosion simulation test of H2S to steel products indicates that corrosion of P110 was lighter than N80, and both of them are excessively corrosion. Results of micro morphology analysis and corrosion products analysis demonstrates that corrosion mechanism is mainly electrochemical corrosion of CO2/H2S under high temperature and pressure, combined with chloride ions accelerating corrosion velocity. Analysis for influence factors of H2S illustrate that temperature and CO2 content accelerate corrosion.