四川盆地须家河组泥(页)岩储层孔隙特征

Pore characteristics of shale from Upper Triassic Xujiahe Formation in Sichuan Basin,China

研究四川盆地上三叠统须家河组黑色泥(页)岩的微孔隙特征及其控制因素。对须家河组泥(页)岩储层的井下岩心进行系统采样,进行场发射扫描电镜/能谱分析、比表面积和孔径、总有机碳含量、有机质成熟度、生油岩热解分析、X射线全岩和黏土矿物含量等一系列分析测试。结果显示,须家河组泥(页)岩的主要孔隙类型为粒间孔、粒缘缝、有机质气孔、粒间溶孔、黏土矿物晶间隙以及微裂缝等。其中有少数粒间微孔、粒间溶孔和粒缘缝的孔径可达到微米级。比表面积和孔径分析的孔径主要分布在0.895～19.907nm,以微孔为主;微孔和中孔的体积占孔隙总体积的92.5%。影响孔隙发育的因素主要有埋深、成岩演化、矿物、有机质丰度和热演化。埋深增大会造成微孔和中孔的体积减小,但成岩演化的溶蚀作用和黏土矿物组合的变化有利于大孔的体积增加;总有机碳含量与微孔和中孔的体积、比表面积以及微米级孔径正相关,起到主控作用;有机质成熟度对孔径和孔体积的控制作用较弱。

This paper adopts a series of measures, including SEM, mineral surface area, pore volume, pore diameters, total organic carbon （TOC）, vitrinite reflectivity （Ro）, source rock pyrolysis and X- ray mineral analysis, to research the pore characteristics and the main controlling factors of the black shale from the Upper Triassic Xujiahe Formation of Sichuan Basin. The results show that the main pore types are intergranular pores, grain boundary fractures, organic gas pores, intergranular dissolved pores, clay minerals intergranular pores and micro-fractures. The diameters of intergranular pores, intergranular dissolved pores and grain boundary fractures can reach micron level. The pore diameters are 0. 895%19. 907 nm. They are mainly micropores. The micropore and mesopore volume accounts for 92.5% of the total volume. The main controlling factors of the shale pores are the depth, diagenetic evolution, mineral, organic matter and the thermal evolution. The increasing of buried depth can decrease the micropore and mesopore volume, but the dissolution and the change of clay mineral assemblages in the diagenetic evolution stage can increase the macropore volume. TOC is a key controlling factor which has a positive correlation with micropore and mesopore volume, surface area, and micron pore diameter （SEM）. Ro has week control over the pore diameter and volume.