Effect of faceting on pore geometry in texturally equilibrated rocks: implications for low permeability at low porosity
Effect of faceting on pore geometry in texturally equilibrated rocks: implications for low permeability at low porosity
复制标题
DOI：
10.1007/s00410-006-0099-y
复制
发表时间：
2006-06
影响因子：
3.5
通讯作者：
T. Yoshino;J. Price;D. Wark;E. Watson
中科院分区：
文献类型：
--
作者：
T. Yoshino;J. Price;D. Wark;E. Watson
结构平衡岩石的孔隙几何形状受晶界和固液界界面能比的控制。孔隙壁面状分布是岩石孔隙网络的共同特征，对液体分布有强烈的影响。通过对几种具有不同程度的面形和二面角的体系的图像分析，研究了面形对平衡孔隙几何形状的影响。用f值（孔壁平面界面长度与固液总界面边界长度之比）来评价面化程度。随着液体体积分数的增加，f值有增大的趋势。小面体系显示相对均匀的液体分布。中等多面体系具有较高的二面角（~ 55°），其特征是被多面壁包围的大孔隙发育和三结管的互补收缩，而低二面角的强多面体系没有显示出三结管收缩的证据，尽管大多数孔隙被多面孔壁包围。由于平面和曲面之间界面能的差异，多面体系往往在孔壁上产生更多的小面边界。在面化程度相同的体系中，液体分布的非均质性随二面角的增大而减小。对于面状体系，低液分数的结构平衡岩石的渗透率会因三重结体积的相对减小或由于面状壁的截断而导致沿粒边通道的关闭而显著降低。
The pore geometry of texturally equilibrated rocks is controlled by the interfacial energy ratio between grain boundaries and solid–liquid boundaries. Faceting at pore walls, which is a common feature of pore networks in rocks, strongly affects the liquid distribution. We investigated the effects of faceting on the equilibrium pore geometries based on image analysis of several systems with various degrees of faceting and dihedral angles. The degree of faceting was assessed by theFvalue, which is the ratio of the flat interface length at the pore wall to the length of total interfacial boundary between solid and liquid. TheFvalues tend to increase with increasing liquid volume fraction. Little-faceted systems show relatively homogeneous liquid distribution. Moderately-faceted systems with a higher dihedral angle (∼55°) are characterized by development of large pores surrounded by faceted walls and complementary shrinkage of triple junction tubes, whereas strongly faceted systems with a low dihedral angle show no evidence of shrinking triple junction tubes, although most pores are surrounded by faceted pore walls. The faceted systems tend to produce more facet boundaries at the pore walls due to the difference of interfacial energies between the flat and curved surfaces. In the systems with the same degree of faceting, heterogeneity of liquid distribution tends to decrease with dihedral angle. For faceting systems, the permeability of texturally equilibrated rocks with low liquid fraction would be significantly decreased by the relative reduction of triple junction volumes or by closure of channels along grain edge due to the truncation of facet walls.