微多孔介质迂曲度与孔隙结构关系

Study on the relationship of tortuosity with pore structure in micro-porous media

采用四参数随机生成(QSGS)、随机堆积和随机裂缝生成等算法,构建了各向异性、非均质性和不同孔隙形状的二维多孔介质;并改进QSGS算法,构建了二维裂缝—孔隙双重介质。结合标准反弹边界条件,运用多弛豫时间格子Boltzmann(MRT-LB)模型研究了微多孔介质迂曲度与孔隙结构的关系。结果表明:现有迂曲度模型均不适用于复杂多孔介质;多孔介质迂曲度与孔隙度、各向异性、非均质性、孔隙形状和裂缝等有关,其中孔隙度、各向异性、孔隙形状和裂缝的影响更显著;圆形孔多孔介质的迂曲度普遍大于裂缝性多孔介质,粒间孔多孔介质的迂曲度居于二者之间;裂缝开度和裂缝走向均显著影响裂缝—孔隙双重介质的迂曲度。最后,基于模拟结果,分别建立了多孔介质迂曲度与孔隙度和各向异性的关系式。该研究有助于进一步认识多孔介质迂曲度。

Two-dimensional anisotropy,heterogeneity and different pore shape of micro-porous media were generated by adopting the quartet structure generation set（QSGS）method,randomly distributed particles method and random fracture generation method,while the improved QSGS method was utilized to generate two-dimensional fracture-pore dual media.By applying bounce-back wall boundary condition,a multirelaxation-time lattice Boltzmann（MRT-LB）model was adopted to simulate fluid flow in porous media for analyzing the correlation of tortuosity with pore structure in micro-porous media.The simulation results show that porosity,anisotropy,heterogeneity,pore shape and fracture all affect tortuosity,while porosity,anisotropy,pore shapeand fracture play a more significant role.The tortuosity of the circular pore media is generally greater than that of the fractured porous media,while the tortuosity of the intergranular pore media is basically in the middle.The aperture and strike of fracture significantly affect the tortuosity of fracture-pore dual media.Meanwhile,the existing tortuosity models are not suitable for complex porous media.Finally,the relations of tortuosity with anisotropy and porosity are established respectively based on the simulation results.This workis helpful to further reveal the relationshipbetweentortuosity and pore structurein micro-porous media.