上扬子地区下寒武统高演化页岩微观孔隙特征

Micropore characteristics of high thermal evolution shale in the Lower Cambrian series in Upper Yangtze area

为揭示高演化页岩储层微观孔隙特征及储集性能,采用全岩X-射线衍射、有机碳测定、氦气孔隙度测试、低温氮气吸附、高压压汞—吸附联合测定及氩离子抛光—扫描电镜等多种技术方法,开展了上扬子地区下寒武统高演化页岩微观孔隙结构、类型及其特征研究。结果表明:页岩比表面积介于0.46~34.70m^2/g之间,平均为12.36m^2/g,总孔容介于(0.43~11.29)×10^(-3)cm^3/g之间,平均为4.65×10^(-3)cm^3/g,孔径以小孔(2~10nm)为主,其次为中孔(10~50nm),小孔孔容、TOC与比表面积呈正线性关系;页岩发育有机质孔、粒间孔、粒内孔、黏土矿物层间孔、黄铁矿晶间孔、构造微裂缝及成岩微裂缝7种孔隙类型,其中微裂缝全区普遍发育,四川盆地内部以粒间孔、黏土矿物层间孔及有机质孔为主,四川盆地之外仅发育有机质孔,形态以不规则形、狭缝形为主,无机矿物质孔欠发育,认为两者孔隙类型的差异与有机质含量高低密切相关。

In order to reveal the microscopic pore characteristics and reservoir performance of high thermal evolution shale reservoir,according tothe tests of whole rock X-ray diffraction,organic carbon,helium porosity,nitrogen adsorption at low temperature,joint tests of high pressure mercury and adsorption,argon ion polishing,scanning electron microscopy and other tests,micro pore structure,type and their characteristics of high thermal evolution shale in the Lower Cambrian are studied.The results show that the specific surface area of shale is from 0.46m^2/g to 34.70m^2/g with an average of 12.36m^2/g,the total pore volumepergram shale is from 0.43×10^（-3）cm^3/g to 11.29×10^（-3）cm^3/g with an average of 4.65×10^（-3）cm^3/g,and the pore diameteris mainly small（2-10nm）and followed by medium（10-50nm）.The relationship among total pore volumepergram,TOCand specific surface area is positive and linear.Shale developed 7 types of pores,i.e.,organic pore,intergranular pore,intragranular pore,clay interlayer pore,pyrite intergranular pore,structural micro fracture and diagenetic micro fracture.Micro cracks generally developed in all study area,organic pore,intergranular pore and clay interlayer pore mainly developed in Sichuan Basin,the pore outside Sichuan Basin mainly is organic pore,whose shape is irregular and narrow.Inorganic mineral poresundeveloped outside Sichuan Basin.It is believed that the difference of the pore type is closely related to the content of organic matter.