Pore‑scale hydraulic properties of virtual sandstone microstructures: spatial variations and voxel scale effects

This paper aims at studying spatial variations and voxel scale effects on digital-permeability of sandstone reservoirs at small-scale. X-ray μ-CT imaging is applied to capture various pore-structures. Digital pore-scale analysis is employed to quantitatively analyze voxel scale effects on microstructures with connective pore space and invalid pores. The coupling multipoint statistics-marching cube (MPS-MC) three-dimensional (3D) reconstruction is used to construct 3D virtual micro-channel models with connective seepage channels. Pore network numerical simulations with valid realistic geometries are conducted to deeply understand voxel scale effects on microscopic hydraulic properties of sandstone reservoirs. The results show that digital porosity, micro-pore and micro-grain size gradually become stable with a voxel scale larger than 3003. The spatial variation of permeability and voxel scale effects relates extremely to the seepage index and digital porosity. As digital porosity is less than 30%, the seepage index increases with an exponential manner, and as digital porosity is larger than 30%, it decreases with a logarithm manner. The permeability is easy to evaluate by the established logarithm relation between the permeability and seepage index with relative errors all less than 5%. The proposed permeability-seepage index in the digital analysis framework provides excellent approaches to effectively evaluate the hydraulic properties of rock reservoirs.

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Opracowanie rekordu ze środków MEiN, umowa nr SONP/SP/546092/2022 w ramach programu "Społeczna odpowiedzialność nauki" - moduł: Popularyzacja nauki i promocja sportu (2022-2023)