CCUS井水泥环腐蚀预测模型及影响因素

Prediction model and influencing factors of cement sheath corrosion in CCUS wells

关键词:  CCUS井  CO₂腐蚀  水泥环  沉淀  腐蚀深度 

Key words:  CCUS well  CO₂ corrosion  cement sheath  sediment  corrosion depth

摘要:

目的CCUS井的水泥环长期处于CO₂腐蚀环境中,水泥环将被腐蚀导致CO₂泄漏,需对腐蚀速率进行预测。然而目前的腐蚀预测模型以井眼和半经验公式为主,导致水泥环腐蚀预测不准确,制约了CCUS井水泥环腐蚀防治技术的研究。 方法针对这一问题,基于CO₂和钙质量守恒定律,建立了CO₂腐蚀深度预测模型,并利用该模型分析了腐蚀时间、温度、CO₂分压、水灰比和耐腐蚀材料加量对腐蚀深度的影响规律,并建立了评价模型,对影响因素的影响程度进行排序。 结果CO₂腐蚀深度随腐蚀时间、温度、Cl—浓度、CO₂分压、水灰比及含水饱和度增加而增大,随着水泥环密度、耐腐蚀材料加量增加而减少；水泥环中CO₂含量随腐蚀深度呈非线性降低。影响因素由强到弱为:含水饱和度>耐腐蚀材料>水灰比>CO₂分压>腐蚀时间>水泥环密度>Cl—浓度>温度。 结论研究成果对于CCUS井控制CO₂对水泥环的碳化腐蚀保障井筒完整性具有指导意义。 

Abstract:

ObjectiveThe cement sheath of CCUS well is exposed to CO₂ corrosion environment for a long time, and the cement sheath will be corroded, leading to CO₂ leakage. Therefore, it is necessary to predict the corrosion rate. However, the current corrosion prediction models mainly rely on wellbore and semi empirical formulas, which leads to inaccurate prediction of cement sheath corrosion and restricts the research on the prevention and control of cement sheath corrosion in CCUS wells. Methods In response to this issue, a CO₂ corrosion depth prediction model was established based on the conservation laws of CO₂ and calcium mass. This model analysed the impact of corrosion time, temperature, CO₂ partial pressure, water-cement ratio, and corrosion-resistant material dosage on corrosion depth. An evaluation model was also established to rank the degree of influence of these factors. ResultsThe research results indicated that the CO₂ corrosion depth increased with the corrosion time, temperature, chloride ion content, CO₂ partial pressure, water-cement ratio, and water saturation, and decreased with the cement sheath density and corrosion-resistant material dosage. Additionally, the CO₂ concentration within the cement sheath showed a non-linear decrease with the increase in corrosion depth. The strength of the influencing factors was:water saturation > corrosion resistant material > water-cement ratio > cement ring density > CO₂ partial pressure > corrosion time > chloride content > temperature. ConclusionThe research results have guiding significance for controlling CO₂ carbonization corrosion of cement sheath in CCUS well to ensure well integrity.