Reservoir Characteristics of Lacustrine Shale and Marine Shale: Examples from the Songliao Basin, Bohai Bay Basin and Qiannan Depression

AbstractLacustrine shale from the Qingshankou Formatin of Songliao basin and the Shahejie Formation of Bohai Bay basin, and marine shale from the lower Cambrian Jiumenchong Formation of Qiannan depression were analysed by using rock pyrolysis, TOC (total organic carbon), XRD (X‐ray diffraction), SEM (scanning electron microscope), FE‐SEM (field emission scanning electron microscope), high pressure mercury intrusion, and low pressure N2 and CO2 gas adsorption experiments, in aim to reveal their reservoir features. The results show that: (1) the width of micro‐pores of all the studied samples mainly ranges from 0.45 to 0.7 nm indicated by CO2 isotherms, and the width of meso‐pores is less than 10 nm, with type IV adsorption isotherms and type H2 hysteresis loop, indicative of “ink‐bottle”‐shaped pores. Good correlations exist among pore volume, surface area and averaged pore diameter, and a good positive correlation exists between micro‐pore volume and TOC content; however, there is no obvious correlation between meso‐pore volume and TOC content; (2) interparticle pores, pores among the edge of mineral grains and organic matter pores were all identified in marine and lacustrine shale, among which the interparticle pores may be influence by dissolution effect Not all bitumen develops organic matter pore, and only high to over mature bitumen present pores. Now the description methods of micrometer scale pores developed in shale are very lack. Micro‐fractures developed in Jiyang depression and dissolution interparticle pores developed in Songliao Basin should be the accumulation sites for shale oil in lacustrine shale, and can be as sweet spots.