CO2-EOR中多相流冲蚀下的油管点蚀行为研究

According to serious pitting corrosion of steels in the process of promoting integration technology of geological storage of CO2 and CO2—Enhanced oil recovery, the assembly high temperature and high pressure corrosion tester will be used to build supercritical CO2 saturated oil/brine/suspended solid multiphase flow, and the experimental conditions are set refer to the oil reservoir pressure , temperature and formation water quality. Because J55 steel was commonly used in oil field, it is selected as the corrosion sample. The automatic 3 d microscopic imaging system will be used to scan multi-viewshed of new corrosion sample to select the appropriate sample, and the MATLAB software are used to extract and gather image information of the tested sample. Then, the pitting recognition and quantitative measurement technology will be established. The oil and gas water three phase experiment system is used to build the contact between the change of supercritical CO2 saturated oil/brine/suspended solid multiphase flow and the change of physical and chemical properties of the multiphase flow, and then the contacts is used to explain the pitting behavior changes with the multiphase flow environment changing. Meanwhile, the comparisons between scanning electron microscope, energy spectrometer and X-ray diffraction analysis results of the typical pitting areas are used to eaxplain the effect of physical and chemical properties changes on pitting corrosion. As a result, J55 steel pitting behavior in the SC-CO2 saturated oil/brine/suspended solid multiphase flow are clarified at molecular level .

本研究以油田储层压力、温度和地层水水质变化范围为参照系，拟通过自行构建的高温高压腐蚀测定系统形成超临界CO2饱和的油/盐水/悬浮固体多相流冲蚀工况，以油田常用的管材J55作为腐蚀对象，借助三维显微成像系统对试样表面特征进行甄选，对动态失重实验后的挂片进行大面积扫描并依靠MATLAB软件对图像信息进行提取和统计建立点蚀识别和定量测定技术；构建多相流体系因素变化与其引起的物理或化学性质变化之间的联系，进而解释点蚀行为的变化。同时，对比典型点蚀区域扫描电镜、能谱仪 和X-衍射仪的理化性质分析结果，进一步从微观领域解释上述多相流各体系因素变化与点蚀参数之间的对应关系，从分子水平揭示超临界CO2饱和的油/盐水/悬浮固体多相流冲蚀下的点蚀形成机理。

CO2-EOR过程中存在严重的采出井油管腐蚀，腐蚀尤其是点蚀问题阻碍了CCS与CO2-EOR集成技术的推广进程，但点蚀定量分析是其行为研究的瓶颈，也制约了SC-CO2饱和油/盐水/悬浮固体多相介质（SSMM）中钢材的腐蚀、点蚀的深层次研究。本研究以油田储层压力、温度和地层水水质变化范围为参照系，首先通过自行构建的高温高压腐蚀测定系统形成SSMM冲蚀工况，然后以油田常用管材J55为对象，借助三维显微成像系统对动态失重实验后的挂片进行大面积扫描并依靠MATLAB软件对图像信息进行提取和统计建立了点蚀识别和定量测定技术，用拟合方程中的2个特征参数描述分别定量描述腐蚀与点蚀及其二者之间的联系，再利用新技术构建了多相流体系因素变化（含水率、温度、压力、分压、矿化度、流速、时间、悬浮颗粒种类、乳化程度）与腐蚀、点蚀特征数据之间的联系，阐明了各条件下腐蚀与点蚀的发展趋势，发现当含水率在70%左右点蚀发生趋势最大，提出了CO2分压和矿化度对平均腐蚀和点蚀影响的新规律，并建立CO2分压影响腐蚀与点蚀的模型，同时以陕北某CO2驱实验井参数为依据，通过计算油管内温度-压力分布，研究了不同井深和同一井深不同分压的SSMM中J55碳钢的腐蚀与点蚀规律，揭示了沿井深腐蚀与点蚀分布的变化和CO2驱替剩余压力对采出井的腐蚀与点蚀分布情况的影响，建立了油管点蚀失效预测模型，最后通过研究腐蚀产物膜对电化学腐蚀行为的影响，提出不同条件下产生的腐蚀产物膜使体系中电化学反应主要受阴极反应控制，且主要受电极表面Fe的溶解和腐蚀产物膜的钝化和修复影响，而当腐蚀产物膜致密时，腐蚀主要受离子在腐蚀产物膜中扩散控制；腐蚀产物膜疏松时，保护作用弱，离子很容易到达金属表面并直接与金属基体接触，腐蚀主要受活化控制，从分子水平揭示了SSMM中钢材的腐蚀、点蚀与腐蚀进程之间的联系，进一步验证了腐蚀产物膜及其形态对平均腐蚀速率和点蚀起决定性影响的结论，为后续SSMM中钢材的腐蚀研究提供了理论依据和研究新思路与领域。