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Multi-fractal distribution analysis for pore structure characterization of tight sandstone in the Southern Songliao Basin, China


Owing to the strong pore structure heterogeneity in tight sandstone reservoirs, quantitative evaluation of the microscopic pore structures of tight sandstone reservoirs has become a challenging effort. In addition the systematically characterized of pore structure under different primary depositional conditions and subsequent diagenesis is still ignored. This study focuses on the Lower Cretaceous Quan 4th member in central depression of the Southern Songliao Basin, with lithology is mainly characterized by grey lithic arkose sandstone interbedded by thin dark mudstone and burial depth of more than 2000m. As a result of intensive compaction and cementation triggered by sedimentary, diagenetic and tectonic factors, the reservoir densified significantly and underwent strong heterogeneity with the mean porosity of 8.5% and the mean permeability of 0.157×10-3μm2. In this study, various analytical techniques are conducted, including thin section petrography, scanning electronic microscope (SEM), high-pressure mercury injection porosimetry (HPMIP), rate-controlled mercury injection porosimetry (RMIP), nuclear magnetic resonance (NMR), fractal geometry and etc. By integrating the data and results above, pores of different genetic types were firstly recognized, furthermore the size distribution and fractal geometry of multiple pore and throat types are systematically presented. Additionally, the heterogeneity of pore structure and its controlling factors under different primary depositional conditions and subsequent diagenesis is specified. As such, the result will contribute to the microscopic reservoir characterization research and are of great importance for maintaining and enhancing petroleum recovery.