鄂尔多斯盆地伊金霍洛旗附近二叠系石千峰组岩石学、地球化学特征及其固碳能力分析

鄂尔多斯盆地是我国CO2地下埋藏的潜在目标区,位于伊金霍洛旗附近的中神监X井与CO2地下注入井中神注1井相邻,两者钻遇地层系统和岩石组合一致。为对示范区储层的固碳潜力和泥岩改造状况做出预测,为CO2地质储存的数值模拟研究提供基础地质信息和相关数据,通过偏光显微镜、扫描电镜、X射线衍射、X射线荧光等多种技术手段,开展了中神监X井石千峰组的岩石学和地球化学特征研究。结果表明石千峰组的砂岩岩石类型主要为长石岩屑砂岩和岩屑长石砂岩;泥岩主要由石英、粘土矿物和长石组成,其中,粘土矿物主要为伊利石,其次为蒙皂石、高岭石和绿泥石。预测在CO2注入后的流体-砂岩长期相互作用过程中,石千峰组砂岩可以通过形成片钠铝石、方解石、铁白云石和菱铁矿等固碳矿物,形成对CO2泄露而言的矿物圈闭,进而实现CO2的长期和安全封存;红色泥岩夹层将发生金属离子活化,导致泥岩褪色。

Petrologic and geochemical characteristics and carbon sequestration capability of the Permian Shiqianfeng Formation around Ejin Horo Banner of Ordos Basin

Ordos basin is the potential target zone of CO₂ underground storage in China. Well Zhongshenjian X is located near the Ejin Horo Banner, neighboring the underground CO₂ injection well "Zhongshenzhu One", and the two wells have the same formation system and rock composition. To predict the potential of carbon sequestration in the reservoir and the mudstone transformation conditions in the demonstration area and provide basic geological information and relevant data for numerical simulation of the CO₂ geological storage, the authors investigated petrologic and geochemical characteristics of Shiqianfeng Formation in well Zhongshenjian by means of polarizing microscope, SEM, X-ray diffraction and X ray fluorescence, and the results suggest that the sandstone of Shiqianfeng Formation is mainly feldspathic lithic sandstone and lithic feldspar sandstone, and the mudstone is mainly composed of quartz, clay minerals and feldspar, in which the clay minerals are mainly smectite and illite, followed by kaolinite and chlorite. It is inferred that sandstone in Shiqianfeng Formation could form the mineral trap relative to the CO₂ leaks by forming carbon sequestration minerals such as dawsonite, calcite, ankerite and siderite, and then the long-term and safe storage of CO₂ could be realized. In addition, metals were mobilized, resulting in the bleach of the red mudstone interlayer.