松辽盆地长岭断陷沙河子组页岩岩相特征及其对孔隙结构的控制

Lithofacies characteristics and impact on pore structure of the Shahezi Formation shale, Changling Fault Depression, Songliao Basin

依据松辽盆地长岭断陷沙河子组页岩特征、有机质丰度和矿物含量建立岩相划分方案,把研究区页岩划分为7种岩相,在此基础上开展扫描电镜、CO_2和N_2吸附以及高压压汞实验以分析孔隙结构。研究区沙河子组页岩孔隙发育,不同岩相发育的主要孔隙类型也不相同,有机质孔隙主要发育在黏土质页岩中。页岩孔径呈现多峰分布特征,中孔是孔体积的主要贡献者,平均占50.9%;微孔是比表面积的主要贡献者,平均占67.8%。微孔发育主要受黏土矿物控制,中孔发育受碳酸盐矿物控制,宏孔发育受脆性矿物和黏土矿物联合控制。富有机质黏土质页岩对比表面积和孔体积的影响明显,对沙河子组页岩孔隙发育起主要控制作用。

A lithofacies classification was established based on TOC and XRD data on cores of the Shahezi Formation in the Changling Fault Depression of the Songliao Basin.There are 7 lithofacies in the study area.Scanning electron microscopy,CO2 and N2 adsorption and high pressure mercury intrusion experiments were applied to quantitatively characterize pore structure.Shale pores were developed in the Shahezi Formation,and the pore types of different lithofacies were also different.Organic matter pores were mainly developed in argillaceous shale.Shale pore size exhibited a multi-peak distribution.Mesopores were the main contributors to pore volume,accounting for an average of 50.9%.Micropores were the main contributors to specific surface area,accounting for an average of 67.8%.The development of micropores was mainly controlled by clay minerals,the development of mesopores was controlled by carbonate minerals,while the development of macropores was controlled by the combination of siliceous and clay minerals.The organic-rich argillaceous rock influenced the surface area and pore volume,and played a major role in controlling shale pore development of the Shahezi Formation.