济阳坳陷沙河街组湖相页岩储层孔隙定性描述及全孔径定量评价

以济阳坳陷沙河街组纹层状页岩为例,采用大面积视域拼接扫描电镜、低温N₂/CO₂吸附和高压压汞实验,定性分析页岩有机质纹层、矿物与孔隙形态,定量评价孔隙大小与分布,同时对比洗油前后页岩孔隙分布特征,探讨页岩油可能的富集空间。研究样品中发育条带状和分散状分布的有机质和方解石,粘土矿物与石英分布样式复杂。尽管研究样品处于低熟—成熟生油阶段,其中仍然发育较多的有机质孔,可能是部分油气（尤其是轻质部分）流出/逃逸后结果,此外还发育大量粒间孔、粒内孔和微裂缝。采用低温N₂吸附（反映小于100 nm的孔隙）、高压压汞（反映100 nm至十几μm的孔隙）和大面积视域拼接SEM扫描可以有效全尺度反映湖相页岩富集空间。页岩连通储集空间由纳米级孔隙（小于300 nm）和微米尺度的微裂缝（0.5至十几μm）构成,页岩油则主要富集在小于100 nm的孔隙和大于1 μm尺度的微裂缝中。本文所采用的分析方法及结论可供其它生油阶段页岩的相关研究所借鉴。

Qualitative description and full-pore-size quantitative evaluation of pores in lacustrine shale reservoir of Shahejie Formation,Jiyang Depression

The organic matter lamina,mineral composition,and pore geometry of the lamellar shale from the Shahejie Formation,Jiyang Depression,were qualitatively analyzed and the size and distribution of pores were quantitatively studied,through combined experimental methods,such as the large-area visual field splicing scanning electron microscope(SEM) technology,low temperature N₂/CO₂ adsorption experiment,and high pressure mercury intrusion experiment.Meanwhile,the characteristics of pore distribution before and after core cleaning were compared,and the possible spaces for shale oil enrichment were analyzed.The organic matter and calcite in the samples studied are distributed in both banded and dispersed forms,and the distribution of clay minerals and quartz is complex.Although the shale samples studied are in the stage of low maturity-oil generation,organic pores are still well developed in them,which may be ascribed to the efflux or escape of some hydrocarbons(especially the light oil and gas).In addition,large number of intergranular pores,intragranular pores and micro-cracks are also developed.Low-temperature N₂ adsorption experiment(used to describe pores with diameter being less than 100 nm)and high-pressure mercury intrusion experiment(used to describe pores with diameter ranging from 100 nm to a dozen μm)and large-area visual field splicing SEM scanning can effectively reflect the full size of lacustrine shale reservoir space.Interconnected reservoir space of shale is composed of pores of nano-scale(with pore diameter being less than 300 nm)and micro-fractures(with the width of 0.5 to a dozen of μm)in micrometer scale.While shale oil mainly accumulates in pores less than about 100 nm and micro-cracks larger than about 1 μm.The analytical methods and conclusions presented in this study can be of referential value to the related studies on shale during its oil generation stage.