陆相碎屑岩中粘土矿物的形成机理及蚀变规律—以济阳坳陷始新统孔店组为例

Formation Mechanism and Alteration of Clay Minerals in Clastic Rocks—Take the Kongdian Fm. of Paleogene in Jiyang Depression for Example

摘要: 粘土矿物是碎屑岩中重要的填隙物，对油气储层有着重要的地质意义。本文利用X衍射、扫描电镜、铸体薄片和电子显微镜等方法，对济阳坳陷始新统孔店组粘土矿物的特征、形成机理、蚀变规律及影响因素进行了研究。结果表明：济阳坳陷始新统孔店组所含粘土矿物主要为伊利石、高岭石、绿泥石和伊/蒙混层，伊利石在扫描电镜下呈蜂窝状、丝缕状和丝带状，高岭石呈书页状、蠕虫状，绿泥石呈叶片状、细鳞片状，伊/蒙混层则呈不规则细粒状、鳞片状；粘土矿物的形成机理可分为陆源碎屑粘土矿物形成机理和自身粘土矿物形成机理两种，陆源碎屑粘土矿物形成机理与水动力强度有关，自生粘土矿物的形成机理受地温，成岩流体性质的影响，在一定的温度下，成岩流体在碱性范围内易形成蒙脱石、伊利石、绿泥石而在酸性范围内则有利于高岭石的形成；古地温和成岩流体共同控制了粘土矿物的形成机理和蚀变过程，当地温为70℃~140℃时，蒙脱石和高岭石蚀变形成伊利石；当地温升高到100℃~140℃时，伊/蒙混层蚀变成伊利石；当成岩流体由酸性变为碱性时，高岭石蚀变形成绿泥石；当成岩流体碱性逐渐变强时，蒙脱石蚀变形成伊利石和绿泥石。

Abstract: Clay minerals are the important fillings in clastic rocks, have important geological significance for oil and gas reservoir. In this paper, the characteristics, formation mechanism, alteration law and influence factors of the clay minerals in the new system of Jiyang Depression are studied by means of X diffraction, scanning electron microscopy, and electron microscopy. The results show: The Eocene Kongdian formation of clay minerals such as illite, kaolinite, chlorite and illite/smectite in Jiyang depression, Illite honeycomb, silk thread and ribbon shaped under the scanning electron microscope, a book like kaolinite, chlorite, wormlike, lobular flake, Illite/smectite irregular gra-nular, flake; The formation mechanism of clay minerals can be divided into mineral terrigenous detrital clay mineral formation mechanism and its mechanism of two kinds of clay. The formation mechanism of terrigenous detrital clay minerals associated with hydrodynamic intensity. The formation mechanism of the in-situ clay minerals is influenced by the temperature and the fluid properties. At a certain temperature, into the rock and fluid in the alkaline range to form mont-morillonite, illite and chlorite in the acidic range is conducive to kaolinite formation; The formation mechanism and alteration process of clay minerals are controlled by the paleo temperature and the formation of the fluid. When the temperature of the local temperature was 70 - 140, the montmorillonite and kaolinite altered to form illite; The local temperature rises to 100 - 140 DEG C, illite/smectite illite alteration; When the diagenetic fluid from acid to alkaline, kaolinite chlorite alteration was formed; When the alkaline diagenetic fluid gradually becomes stronger, montmo-rillonite alteration of illite and chlorite is formed.