Pore evolution model and diagenetic evolution sequence of the Mesoproterozoic Xiamaling shale in Zhangjiakou, Hebei

Current research on diagenesis and its evolution focuses mainly sandstone reservoirs. Conventional oil gas reservoir observation techniques for characterizing shale reservoirs are limited, comprehensive nanoscale pore variations, of reservoirs, especially immature low-maturity marine is relatively scarce. To reveal the shale, geochemical mineral analyses, quantitative characterization structure qualitative morphology were performed Xiamaling shale. With burial geothermal history, diagenetic sequence system studied. The results show that smectite continually transforms to an illite-smectite (I/S) mixed layer then quickly illite chlorite; kaolinite content gradually decreases as maturity increases. hydrocarbon expulsion threshold EqRo = 1.0%, porosity a minimum value 1.0% model shows volumes (PVs) micropores macropores decrease minima at approximately 0.92% 0.85%, respectively, increase; mesopore PVs continuously decrease. Micropore surface areas (SAs) their 0.85% simultaneously, macropore SAs main types compaction, dissolution, cementation, thermal maturation organic matter (OM), clay transformation; it reaches period B middle stage, determined. composition variation characteristics analysed, corresponding established.