Permeability of Triaxially Compressed Sandstone: Influence of Deformation and Strain-rate on Permeability
Permeability of Triaxially Compressed Sandstone: Influence of Deformation and Strain-rate on Permeability
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DOI：
10.1007/pl00012571
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发表时间：
2003-05
影响因子：
2
通讯作者：
Juliane Heiland
中科院分区：
文献类型：
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作者：
Juliane Heiland
研究了差应力对下二叠统砂岩渗透率的影响。采用直径为50 mm、长度为100 mm的细粒（平均粒径为0.2 mm）、低孔隙度（6-9%）砂岩试件，研究了差应力、岩石变形、岩石破坏与水力特性之间的关系，重点研究了岩石三轴变形破坏前和破坏区水力特性的变化。试验在围压20 MPa以下进行，轴向力由侧向应变控制，应变速率为10- 6 ~ 10-7sec-1。在使样品变形的同时，通过稳态技术测定渗透率，其中在样品长度上的压力梯度为1 MPa，并且流体压力水平在围压的40%至90%之间。结果表明，低孔隙度砂岩在三轴应力增加条件下，渗透率首先由于压实作用而降低，在压实作用开始后渗透率开始增加。这种渗透率演化与结晶岩的渗透率演化相似。渗透率演化对应变率的显著依赖性被发现。渗透率与体积应变的比较表明，渗透率的增加后，发病的渗透性不足以恢复到初始渗透率的破坏的标本。在实验之前确定的初始渗透率通常在破坏后区域恢复。在渗透性开始后，渗透率的增加与体积应变呈线性关系
The influence of differential stress on the permeability of a Lower Permian sandstone was investigated. Rock cylinders of 50 mm in diameter and 100 mm length of a fine-grained (mean grain size 0.2 mm), low-porosity (6-9%) sandstone were used to study the relation between differential stress, rock deformation, rock failure and hydraulic properties, with a focus on the changes of hydraulic properties in the pre-failure and failure region of triaxial rock deformation. The experiments were conducted at confining pressures up to 20 MPa, and axial force was controlled by lateral strain with a rate ranging from 10-6to 10-7sec-1. While deforming the samples, permeability was determined by steady-state technique with a pressure gradient of 1 MPa over the specimen length and a fluid pressure level between 40 and 90% of the confining pressure. The results show that permeability of low-porosity sandstones under increasing triaxial stress firstly decreases due to compaction and starts to increase after the onset of dilatancy. This kind of permeability evolution is similar to that of crystalline rocks. A significant dependence of permeability evolution on strain rate was found. Comparison of permeability to volumetric strain demonstrates that the permeability increase after the onset of dilatancy is not sufficient to regain the initial permeability up to failure of the specimen. The initial permeability, which was determined in advance of the experiments, usually was regained in the post-failure region. After the onset of dilatancy, the permeability increase displays a linear dependence on volumetric strain