CCUS环境下水泥单矿C_(3)S的CO_(2)腐蚀动力学研究

CO_(2)Corrosion Kinetics of C_(3)S in Cement Single Ore under CCUS Environment

在碳捕集、利用和封存(CCUS)井下,油井水泥因长期受井下高温、高压和高酸性流体的作用会遭受碳化腐蚀导致水泥环失效。为了模拟CO_(2)地质封存井下碳化腐蚀环境,本文将油井水泥的主要单相矿物硅酸三钙(C_(3)S)置于不同温度(30℃、60℃、90℃),并密封在8.0 MPa的气相或液相的CO_(2)碳化环境下,采用XRD和TGA相结合的分析方法,分析水泥单矿C_(3)S受CO_(2)腐蚀环境的影响规律。根据非稳态Fick扩散的渗透理论模型,建立腐蚀产物定量分析结果与腐蚀龄期的数学模型,拟合得到C_(3)S受CO_(2)腐蚀后的产物生成系数,以此评价不同CO_(2)腐蚀因素对C_(3)S的影响程度。结果表明:在CO_(2)气相环境中,温度升高将显著加剧对C_(3)S的腐蚀且产生溶蚀现象;而在CO_(2)液相环境下,高温(90℃)使C_(3)S水化反应加剧并形成阻滞层,降低CO_(2)对C_(3)S的腐蚀速率。

Under the carbon capture,utilization and storage(CCUS)well,the oil well cement will be carbonized and corroded due to the long-term action of downhole high temperature,high pressure and highly acidic fluid,resulting in the failure of the cement sheath.In order to simulate the carbonation and corrosion environment of CO_(2)geological storage well,the main single ore mineral calcium silicate(C_(3)S)of oil well cement was placed under different temperatures(30℃,60℃,90℃)and sealed 8.0 MPa gas or liquid phase CO_(2)carbonization environment.XRD and TGA were used to analyze the influence of C_(3)S in cement single ore by CO_(2)corrosive environment.According to the infiltration theoretical model of unsteady Fick diffusion,a mathematical model of the quantitative analysis results of corrosion products and corrosion age was established,and the product formation coefficient of C_(3)S after being corroded by CO_(2)was obtained by fitting,so as to evaluate the influences of different CO_(2)corrosion factors on C_(3)S.The results show that the increase of temperature significantly aggravates the corrosion of C_(3)S and leads to the dissolution phenomenon in the gas phase environment of CO_(2).While in the liquid phase environment of CO_(2),the high temperature(90℃)makes the C_(3)S hydration reaction intensify,forming a retardation layer and slowing down the CO_(2)corrosion rate to C_(3)S.