川东南地区X1井自流井组富有机质页岩储集空间发育特征与主控因素

The development characteristics of reservoir space structure and associated major controlling factors for Jurassic Ziliujing Formation organic-rich shale in Well X1,southeastern Sichuan,China

研究川东南地区X1井下侏罗统自流井组富有机质页岩储集空间结构特征及影响因素。综合应用有机地球化学、X射线衍射、扫描电镜、液氮吸附、高压压汞等手段,对自流井组页岩层系的基本地质特征、储集空间结构特征进行分析。自流井组富有机质页岩的干酪根以Ⅱ_(2)型为主,热演化程度处于成熟阶段;矿物成分以黏土矿物和石英为主,黏土矿物的平均质量分数为41%,石英的平均质量分数为33.41%;储集空间类型主要为有机质孔隙、无机质孔隙和微裂缝,其中粒/晶内孔、粒/晶间孔、微裂缝较为发育;孔隙直径的范围较大,有20~50 nm和1μm左右两个峰值,微孔和介孔分别提供了页岩储层的主要比表面积和孔体积。自流井组富有机质页岩的有机质孔隙不发育,石英含量对储集空间的发育有一定的积极作用,黏土矿物层状晶体结构的发育以及黏土矿物转化过程促进有机质生烃作用,产生的烃类和CO_(2)有利于溶蚀孔的形成,说明黏土矿物含量对页岩的比表面积、孔隙体积起主要控制作用。

By means of organic geochemistry,X-ray diffraction,scanning electron microscopy,liquid nitrogen adsorption and high-pressure mercury injection,the basic geological characteristics and reservoir space structure characteristics of the Lower Jurassic Ziliujing Formation shale in Well X1 in southeast Sichuan are analyzed,aiming to reveal the reservoir space structure characteristics and influencing factors of organic-rich shale.The results show that the kerogen of organic-rich shale in Ziliujing Formation is mainly typeⅡ_(2),and the degree of thermal evolution is in mature stage.Clay minerals and quartz are dominant in the mineral composition and the average mass fraction of clay minerals and quartz is 41%and 33.41%respectively.The reservoir space types of Ziliujing Formation organic-rich shale mainly include organic pores,inorganic pores and microfractures,among which middle grained/intragranular pores,grain/intergranular pores and microfractures are well developed,with two varied peak values of pore diameters of 20~50 nm and 1μm.It is recognized that the micropores and mesopores provide the main specific surface area and pore volume of shale reservoirs respectively.However,the organic pores of organic-rich shale in Ziliujing Formation are poorly developed,and the quartz content has a positive effect on the development of reservoir space.It is considered that the clay mineral content plays a major role in controlling the specific surface area and pore volume of shale,since the development of layered crystal structure of clay minerals and the transformation process of clay minerals promote the hydrocarbon generation of organic matter,and the generated hydrocarbons and CO_(2) are conducive to the formation of dissolution pores.