Characteristics of pore differences between different lithofacies of continental mixed shale and the influencing mechanism:An example from the Permian Lucaogou Formation in the Jimusar Depression
The lithology plays a decisive role in the distribution of high-quality reservoirs and fa-vorable oil-bearing areas.In order to find out the reservoir characteristics and influencing mecha-nism of different lithofacies or lithofacies combinations of shale oil reservoirs in Permian Lucao-gou Formation of Jimsar Sag,the whole rock mineral X-ray diffraction analysis(XRD),total organic carbon content determination(TOC),rock thin section identification,vitrinite reflec-tance(Ro),field emission scanning electron microscope,low field nuclear magnetic resonance,high pressure mercury injection experiment,low temperature nitrogen adsorption experiment and physical property analysis were used to study the difference characteristics and influencing mechanism of different lithofacies pores in Lucaogou Formation.The results show that:The main lithofacies in the study area include high-carbon massive silty sandy dolomite(HK-Ⅱ1),high-carbon laminated silty shale(HW-Ⅰ2),carbon-rich massive silty sandy dolomite(RK-Ⅱ1),and carbon-rich massive argillaceous siltstone(RK-Ⅲ 2).The organic acid and carbonate dissolution associated with hydrocarbon generation of shale organic matter were significant,which promoted the scale development of intergranular pores,intragranular pores and dissolu-tion fractures.There are obvious differences in pore structure size and complexity of different shale lithofacies.The coupling and matching relationship between sedimentary environment and diagenesis is the key to the differential development of pores.
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