渤海湾盆地沧东凹陷孔二段页岩油资源丰富,但对于页岩油的储层特征、油气赋存、可动性及其关联性研究较少。为此,采用氩离子抛光-场发射扫描电镜、中子散射、高压压汞、低温氮气吸附等实验,对孔二段页岩油储层开展微观孔隙结构描述,对比抽提前后的孔体积之差与饱和-离心核磁共振结果,揭示了页岩油赋存及可动性特征。研究结果表明:孔二段页岩主要发育纳米级的粒间孔、溶蚀孔、有机质孔及微米级的微裂缝等储集空间;页岩油主要赋存于直径为20～40 nm和80～200 nm的孔隙中;长英质页岩具有较高的可动油饱和度,表明其具有更好的孔隙连通性和渗流能力,有利于页岩油的运移。页岩储层中矿物含量和孔隙结构共同控制了页岩油的可流动性。孔径小于50 nm的孔隙具有较大的比表面积,对页岩油的吸附能力较强,不利于页岩油的流动。该研究成果对页岩油的勘探开发具有重要指导意义。
The shale oil resources in Member 2 of Kongdian Formation of Cangdong Sag, Bohai Bay Basin are abundant, but there are few studies on the reservoir characteristics, occurrence, mobility and its correlation. To this end, the argon ion polishing field emission scanning electron microscopy, neutron scattering, high pressure mercury injection and low-temperature nitrogen adsorption experiments are adopted to describe the microscopic pore structure of the shale oil reservoir in Member 2 of Kongdian Formation, to compare the difference in pore volume before and after extraction with the saturation-centrifugal NMR results, and to reveal the characteristics of shale oil occurrence and mobility. The results of the study show that in the shale oil in Member 2 of Kongdian Formation, the nanometer-sized intra-granular pores, dissolution pores, organic pores and micron-sized micro-fracture and other reservoir spaces are mainly developed; the shale oil is mainly occurred in the pores with diameters ranging from 20-40 nm and 80-200 nm; the high saturation of movable oil in the felsic shale indicates that it has better pore connectivity and seepage capacity, which is conducive to the transportation of shale oil. The mineral content and pore structure in shale reservoirs jointly control the mobility of shale oil. Pores with a pore size less than 50 nm have a larger specific surface area and have a stronger adsorption capacity for shale oil, which is not conducive to the flow of shale oil. The study results have important guidance for the exploration and development of shale oil.
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