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Permeability anisotropy of methane hydrate-bearing sands: Insights from CT scanning and pore network modelling
Computers and Geotechnics ( IF 5.3 ) Pub Date : 2020-07-01 , DOI: 10.1016/j.compgeo.2020.103568
Cong Hu , Xiaolei Liu , Yonggang Jia , Zhibo Duan

Abstract Gas hydrate formation in porous media is random and inhomogeneous, which causes the permeability to be anisotropic. The absolute and relative anisotropic permeabilities of hydrate-bearing sands at different hydrate saturations were investigated using a CT scanning technique combined with a pore network modelling method. The absolute permeability is directly calculated based on the extracted pore network. The equivalent pore network extracted by a maximum ball (MB) method is used to calculate the relative permeability. The anisotropic permeability coefficient β2 becomes increasingly smaller than β1 with increasing hydrate saturation, which indicates that the absolute permeability decrease in the y direction is more significant than that in the x direction. The capillary pressure increases with increasing hydrate saturation. The relative permeability in the y direction is highest at 14% hydrate saturation. However, it becomes lowest at 51% hydrate saturation. The anisotropy evolution of the relative permeability is consistent with the evolution of the absolute permeability. Image analysis shows that more hydrates accumulate and distribute in the plane normal to y direction, which will induce the pores to be more irregular and increase the pore anisotropy in this direction. The pore anisotropy will cause the permeability to be anisotropic in different directions.

中文翻译:

含甲烷水合物砂岩的渗透率各向异性:CT 扫描和孔隙网络建模的见解

摘要 多孔介质中天然气水合物的形成具有随机性和非均质性,导致渗透率具有各向异性。使用CT扫描技术结合孔隙网络建模方法研究了不同水合物饱和度下含水合物砂岩的绝对和相对各向异性渗透率。根据提取的孔隙网络直接计算绝对渗透率。用最大球法提取的等效孔隙网络计算相对渗透率。随着水合物饱和度的增加,各向异性渗透系数β2越来越小于β1,这表明y方向的绝对渗透率下降比x方向更显着。毛细管压力随着水合物饱和度的增加而增加。y 方向的相对渗透率在 14% 水合物饱和度时最高。然而,它在 51% 水合物饱和度时变得最低。相对渗透率的各向异性演化与绝对渗透率的演化一致。图像分析表明,在垂直于 y 方向的平面内,更多的水合物聚集和分布,这将导致孔隙更加不规则,并增加该方向的孔隙各向异性。孔隙各向异性会导致渗透率在不同方向上呈各向异性。图像分析表明,在垂直于 y 方向的平面内,更多的水合物聚集和分布,这将导致孔隙更加不规则,并增加该方向的孔隙各向异性。孔隙各向异性会导致渗透率在不同方向上呈各向异性。图像分析表明,在垂直于 y 方向的平面内,更多的水合物聚集和分布,这将导致孔隙更加不规则,并增加该方向的孔隙各向异性。孔隙各向异性会导致渗透率在不同方向上呈各向异性。
更新日期:2020-07-01
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