川东北牛蹄塘组页岩孔隙结构特征及其控制因素

PORE STRUCTURAL CHARACTERISTICS AND THEIR CONTROLLING FACTORS OF NIUTITANG-FORMATION SHALE IN NORTHEAST SICHUAN BASIN

海相页岩气勘探在四川盆地周缘取得重要进展。通过X射线全岩衍射、氩离子抛光扫描电镜、二氧化碳和氮气吸附实验及有机地化实验等,对川东北地区下寒武统牛蹄塘组页岩的孔隙发育特征及其控制因素进行了研究。结果表明:川东北地区牛蹄塘组页岩有机质丰度较高,石英矿物和黏土矿物是主要造岩矿物;孔隙类型主要为有机质孔隙、脆性矿物粒间孔隙、黏土矿物层间缝等,有机质孔隙呈蜂窝状,在有机质内部发育,有机质孔数量较少,无机矿物孔隙以孔状、夹板状等μm级孔径为主;页岩孔容与比表面积随着有机质和黏土矿物含量的升高而变大。

The exploration of the marine facies shale in the margins of Sichuan Basin has made significant progress. With the help of XRD of the whole rocks,SEM of the polished argon ion,carbon dioxide( CO_2) and nitrogen( N2) adsorptions and the other organic geochemical tests,the pore developing characteristics and their controlling factors were researched for Niutitang-Formation Shale in Lower Cambrian Series of Northeast Sichuan Basin.The achievements show that the organic matters are well developed,the quartz and clay minerals are the key minerals; the key pore types are shown as follows: organic pore,intergranular pore among the brittle minerals,clay-mineral interbedded crack,etc. The honeycomb pore is mainly developed in the organic matters,which is hardly found; the inorganic-matter pore is mainly presented by the forms of the pore and plate,which the size is μmgrade; the specific surface area and pore volume of the shale become larger with the rise of the contents of the organic matters and clay minerals.