鄂尔多斯盆地延长组长7_(3)亚段纹层型页岩油储层孔隙结构特征与影响因素

Pore structure characteristics and impact factors of laminated shale oil reservoir in Chang 7_(3) sub-member of Ordos Basin

以鄂尔多斯盆地延长组长7_(3)亚段纹层型页岩油储层为研究对象,综合运用TOC分析、岩石热解分析、X射线衍射分析、偏光和荧光显微镜观察、场发射扫描电镜观察和低压氮气吸附分析,对纹层型页岩的岩相类型、孔隙微观定性特征和定量结构参数,以及孔隙结构的主控因素进行了系统研究。根据沉积、地球化学和矿物组成特征和差异,长7_(3)亚段可划分出凝灰质—有机质纹层页岩、黏土质—有机质纹层页岩和长英质—黏土质纹层页岩3种岩相类型,孔隙主体分别以有机质生烃增压缝、黏土矿物—长英质晶间粒间复合孔以及长英质粒间孔缝系统为主。样品中介孔最为发育,“凝灰质—有机质”“黏土质—有机质”“长英质—黏土质”的孔隙体积和比表面积依次增加,孔隙网络非均质性和孔隙表面粗糙程度则分别呈逐渐减弱和增强的趋势。有机质孔隙整体发育有限,以有机质—黄铁矿—黏土矿物复合孔为主,是微孔的主要组成部分,与石英刚性颗粒相关的原生粒间孔缝系统是介孔和宏孔的主要组成部分,也是整个孔隙网络的主体,长石溶蚀孔发育局限,对于孔隙网络贡献较小。

Taking the laminated shale oil reservoir in Chang 7_(3) sub-section of Yanchang Formation in Ordos Basin as the research object,the lithofacies type,micro qualitative and quantitative pore structure parameters and the main controlling factors of the pore structure of laminated shale were systematically studied by comprehensive analysis of TOC,rock-eval,X-ray diffraction,polarized light and fluorescence microscope observation,field emission scanning electron microscope observation and low-pressure N2 adsorption analysis.According to the characteristics and differences of sedimentation,geochemistry and mineral composition,the Chang 7_(3) laminated shale can be divided into three lithofacies types:Tuffaceous-organic lamellar shale,clayey-organic lamellar shale and felsic-clayey lamellar shale.The pore network are mainly composed of organic hydrocarbon generation pressurization fractures,clay mineral felsic intergranular composite pores and felsic plasmid intergranular pore fracture systems,respectively.The samples are most developed in mesopores.The pore volume and specific surface area of“tuffaceous-organic matter”“clayey-organic matter”“felsic-clay”increase in turn,while the heterogeneity of the pore network and the roughness of the pore surface are gradually weakened and enhanced,respectively.The overall development of organic matter pores is limited,mainly organic matter-pyrite-clay mineral composite pores,which are the main components of micropores.The primary intergranular pore system related to rigid quartz particles is the main component of mesopores and macropores,and also the mainstay of the entire pore network.The development of feldspar dissolution pores is limited,which makes little contribution to the pore network.