泥岩盖层的溶蚀作用机理实验——不同pH值盐水中溶蚀速率变化规律

发布时间：2018-05-29 18:58

本文选题：泥岩盖层 + 水岩实验　；参考：《石油学报》2017年08期

【摘要】：为了查明泥岩在不同性质流体环境中的溶蚀速率及随时间的变化关系,以松辽盆地南部青山口组黑色泥岩为研究对象,开展4组pH值分别为3、5、7、9的水岩相互作用实验研究,实验持续时间为153d,泥岩粉末样品中黏土矿物含量为50%、石英和长石类矿物含量为35%、方解石为2%,还有少量菱铁矿和黄铁矿。结果分析表明,方解石在酸性流体中快速发生溶蚀溶解,Ca离子析出速率高于Mg、Si和Al离子;长石和黏土矿物溶蚀作用缓慢;在中性—碱性流体环境中形成了三水铝石片状矿物沉淀;方解石的快速溶蚀溶解消耗了酸性流体实验中的氢离子,导致溶液pH值由最初的3升高至7.5;4组实验开始的15d内反应速率较快,反应至50d时,各离子浓度基本保持稳定,即反应体系达到平衡状态,平衡状态下各组溶液的pH值为7~9,呈中性—弱碱性;据4组实验平衡状态下Si离子浓度计算得到的泥岩整体溶蚀速率为-13.29~-13.79 mol/(m~2·s),较为接近同等条件下蒙皂石或高岭石单矿物的溶蚀速率,略高于泥岩中含量最高的伊利石单矿物溶蚀速率。实验研究表明,地层中CO_2或有机酸等酸性流体能够对泥岩盖层产生溶蚀溶解作用,而酸性流体对泥岩盖层封盖能力的破坏程度取决于长期水岩相互作用至系统平衡的过程;封闭的流体环境有利于保护泥岩盖层,泥岩中含有适量的碳酸盐矿物有利于缓冲酸性流体对泥岩盖层的溶蚀作用,起到保护盖层封闭性的作用,而碳酸盐等矿物的沉淀作用能够提高盖层的封盖能力。
[Abstract]:In order to find out the dissolution rate of mudstone in different fluid environment and its relationship with time, taking the black mudstone of Qingshankou formation in the south of Songliao Basin as the research object, an experimental study on the interaction of water and rock with pH value of 3 / 5 / 7 / 9 was carried out. The experiment lasted for 153 days, the clay content in the mudstone powder sample was 50, the mineral content of quartz and feldspar was 35, the calcite was 2, and a small amount of siderite and pyrite were found. The results show that the dissolution rate of calcite in acid fluid is higher than that of MgO Si and Al ions, and the dissolution rate of feldspar and clay minerals is slow. In the neutral alkaline fluid environment, tribobsite flake mineral precipitates are formed, and the rapid dissolution of calcite consumes hydrogen ions in acid fluid experiments. As a result, the pH value of the solution was increased from the initial 3 to 7.5%, and the reaction rate was relatively fast within 15 days. When the pH value of the solution reached 50 days, the concentration of the ions remained stable, that is, the reaction system reached the equilibrium state. The pH value of the solution in each group was 7 ~ 9, which was neutral to weak alkalinity. The dissolution rate of mudstone is -13.29 ~ 13.79 mol/(m~2 / s ~ (-1), which is close to that of montmorillonite or kaolinite in the same condition. The dissolution rate of Illite is slightly higher than that of Illite, which contains the highest content in mudstone. The experimental results show that acid fluid such as CO_2 or organic acid can dissolve and dissolve mudstone caprock, and the damage degree of acid fluid to the capping ability of mudstone caprock depends on the process of long-term water-rock interaction to system equilibrium. The closed fluid environment is conducive to the protection of mudstone caprock, and the proper amount of carbonate minerals in mudstone is beneficial to buffer the dissolution of acid fluid to the mudstone caprock and play a role in protecting the sealing of the caprock. The precipitation of carbonate and other minerals can improve the capping ability of the caprock.
【作者单位】：中国石油化工股份有限公司石油勘探开发研究院;页岩油气富集机理与有效开发国家重点实验室;吉林大学地球科学学院;
【基金】：国家重点研发计划项目(2016YFB0600804) 国家自然科学基金青年基金项目(No.41602160) 中国博士后科学基金面上资助项目(2016M601225)资助
【分类号】：P618.13

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