鄂尔多斯盆地正宁地区长7段页岩层系致密储层物性下限研究OACHSSCD

The pure shale of the Chang 7 member in the Zhengning area of the Ordos Basin is a favorable lithology for shale-type shale oil exploration.To clarify the enrichment and distribution patterns of shale oil in this region,based on core analysis,high-pressure mercury intrusion,nuclear magnetic resonance(NMR)and other data,this study systematically determined,for the first time,the lower limits of physical properties of tight reservoirs in the Chang 71,Chang 72,and Chang 73sub-members using empirical statistics,irreducible water saturation,mercury intrusion parameters,and minimum flow pore throat radius methods.The results show that the lower porosity limits for the Chang 71,Chang 72,and Chang 73 sub-members are 6.51％,6.55％,and 4.99％,respectively;the lower permeability limits are 0.033 mD,0.048 mD,and 0.060 mD,respectively;and the minimum flow pore throat radii are 0.007 1 μm,0.01 μm,and 0.006 9 μm,respectively.Significant differences in the lower limits of physical properties exist among the sub-members,with no positive correlation between porosity and permeability or pore throat radius.The enrichment and production of shale-type shale oil are primarily controlled by pore throat structure and fluid mobility,rather than static storage capacity characterized solely by porosity.Among them,the Chang 72 sub-member exhibits the optimal configuration of reservoir conditions and microscopic flow properties,making it the most favorable exploration interval in the study area.The Chang 73 sub-member can form reservoirs with low porosity but has a higher threshold for fluid production,while the Chang 71 sub-member shows outstanding flow potential in its high-porosity intervals.The research results provide a quantitative basis for identifying effective reservoirs and optimizing sweet spots in the area.