苏里格气田上古生界主要含气层系粘土矿物分布及其主控因素

鄂尔多斯盆地苏里格气田上古生界主要含气层下石盒子组盒8段及山西组山1段储层中广泛分布粘土矿物,研究不同类型粘土矿物的含量变化及其主控因素对于低渗透储层的改造与保护具有重要作用。利用粘土矿物X-射线衍射、砂岩薄片、铸体薄片等资料综合研究,认为山1段、盒8^下亚段、盒8^上亚段的粘土矿物类型主要有绿泥石、伊利石、高岭石及伊蒙混层,并利用单因素分析法研究了主要粘土矿物的纵向及平面分布特征,同时对粘土矿物分布差异的主控因素进行了综合分析。研究表明,3个不同物源区的母岩类型决定了粘土矿物的原始成分,温暖潮湿到干旱气候条件的转化影响粘土矿物的风化或蚀变程度,河流沉积环境的强水动力条件、pH值及弱还原环境等为粘土矿物的沉积、转换及保存提供了条件;经历晚成岩阶段B期后长石蚀变导致伊利石增加,储层物性变得更差。

Clay mineral distribution and its controlling factors in the Upper Paleozoic gas reservoirs of Sulige gas field

Clay minerals distribute widely in the gas reservoirs of the 8^th member of the Shihezi Formation and the 1st member of the Shanxi Formation in the Upper Paleozoic of the Sulige gas field in Ordos Basin.The study of clay mineral content changes and main controlling factors plays a very important role in the low-permeability reservoir stimulation and protection.Based on a comprehensive study of data such as X-ray diffraction,thin sections and cast thin sections of clay minerals,and so on,we proved that the clay minerals in the 1^st member of Shanxi Formation and the upper and lower 8^th member of the Shihezi Formation are mostly chlorite,illite,kaolinite and illite-smectite mixed-layer.The horizontal and vertical distributions of these minerals are studied with the single factor analysis method and the main controlling factors for their distribution difference are also analyzed.The results show that the mother rocks in different provenance regions determined their original composition,climate condition changes from relatively warm and wet to dry controlled their weathering and alteration degrees,and strong hydrodynamics,proper pH value and weak reductive environment of fluvial sedimentary environment provided favorable conditions for their deposition,transformation as well as preservation.However,the increase of illite content from alteration of feldspar during the late diagenetic stage B caused the lowering of reservoir quality.