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Pore-scale hydraulic properties of virtual sandstone microstructures: spatial variations and voxel scale effects
Archives of Civil and Mechanical Engineering ( IF 4.4 ) Pub Date : 2022-11-10 , DOI: 10.1007/s43452-022-00566-7
Zhi Zhao, Xiao-Ping Zhou, Jun-Wei Chen

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.



中文翻译:

虚拟砂岩微结构的孔隙尺度水力特性:空间变化和体素尺度效应

本文旨在研究小尺度砂岩储层数字渗透率的空间变化和体素尺度效应。X 射线 μ-CT 成像用于捕获各种孔隙结构。数字孔隙尺度分析用于定量分析体素尺度对具有连通孔隙空间和无效孔隙的微观结构的影响。耦合多点统计行进立方体(MPS-MC)三维(3D)重建用于构建具有连通渗流通道的3D虚拟微通道模型。进行具有有效现实几何形状的孔隙网络数值模拟,以深入了解体素尺度对砂岩储层微观水力特性的影响。结果表明,当体素尺度大于300时,数字孔隙率、微孔和微晶粒度逐渐趋于稳定。3 . 渗透率和体素尺度效应的空间变化与渗流指数和数字孔隙度密切相关。当数字孔隙度小于 30% 时,渗流指数以指数方式增加,当数字孔隙度大于 30% 时,它以对数方式减小。通过建立渗透率与渗流指数的对数关系,渗透率易于评价,相对误差均小于5%。在数字分析框架中提出的渗透率-渗流指数为有效评估岩石储层的水力特性提供了极好的方法。

更新日期:2022-11-11
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