Pore throat structure characteristics of tight sandstone reservoirs and their influence on movable fluid occurrence:Taking the Chang-7 Member of Qingcheng area of Ordos Basin as an example
Pore throat structure characteristics of tight sandstone reservoirs and their influence on movable fluid occurrence:Taking the Chang-7 Member of Qingcheng area of Ordos Basin as an example
[Objective]The analysis of pore structure and movable fluid distribution characteristics is the key ele-ment of reservoir research and is also the focus and hotspot of current research.It is of great significance for explo-ring tight sandstone oil and gas and improving oil and gas recovery.[Methods]The Chang-7 Member tight sand-stone reservoir in the Qingcheng area of Ordos Basin was selected as the research object in this paper.Combined with fractal theory,through physical property tests,casting thin section,scanning electron microscopy(SEM),high-pressure mercury injection,and nuclear magnetic resonance(NMR)experiments,the pore throat structure,heterogeneity,and movable fluid distribution characteristics of tight sandstone reservoirs were analysed,and the in-fl uence of the pore throat structure and heterogeneity on movable fluid occurrence was discussed.[Results]The results show that the reservoir space of the Chang-7 Member reservoir in the study area is mainly contributed by mi-cro-nanopores,which have poor pore connectivity.The pore throat radius is mainly 0.050-0.500 μm.The hetero-geneity of the pore throat structure is strong,and the fractal dimension distribution is between 2.65 and 2.90.The fluid mobility is poor,and the movable fluid saturation is distributed between 16.68％and 51.74％,the movable fluid is mostly distributed in medium and small pores.The Chang-7 Member reservoirs in the study area can be di-vided into three types.From the type I reservoir to the type Ⅲ reservoir,the development of residual intergranular pores and intergranular dissolution pores decreases,and the pore connectivity becomes poorer,and the pore throat size decreases,and the content of larger pore throats decreases,and the heterogeneity becomes stronger,and the fluid mobility is worse,and the movable fluid content in the medium and large pores tends to decrease,and mova-ble fluid tends to occur in the small pores.[Conclusion]This study provides a theoretical basis for tight sandstone oil and gas exploration and improving oil and gas recovery.
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