Axial and Radial Permeability Evolutions of Compressed Sandstones: End Effects and Shear-band Induced Permeability Anisotropy
Axial and Radial Permeability Evolutions of Compressed Sandstones: End Effects and Shear-band Induced Permeability Anisotropy
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DOI：
10.1007/s00024-009-0495-0
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发表时间：
2009-07-01
影响因子：
2
通讯作者：
Raphanel, Jean L.
中科院分区：
文献类型：
--
作者：
Dautriat, Jeremie;Gland, Nicolas;Raphanel, Jean L.
研究了静水应力和单轴应力状态对砂岩孔隙度和渗透率的影响。实验过程中使用一个特殊的三轴细胞，允许渗透率测量在轴向和径向方向。芯套配备了两个远离末端放置的压力取样器。它们提供中等长度的轴向渗透率测量，而不是总渗透率测量，总渗透率测量基于通过三轴单元的活塞施加的流量。芯套还配备有在横向于样品轴线的两个方向上进行流动的装置。两个独立的措施，从而获得轴向和互补的径向渗透率。已测试了孔隙度约为5.8%至8%、渗透率范围为2.5 mD至30 mD的枫丹白露砂岩样品和孔隙度为24%、渗透率为3D的Bentheimer砂岩样品。对于枫丹白露砂岩，通过每种方法获得的初始轴向渗透率值非常一致。Bentheimer砂岩样品的轴向中等长度渗透率比总渗透率高1.6倍。在径向方向上也观察到类似的差异，它也基本上与径向流引起的流线形状有关。所有受试样品的总渗透率和径向渗透率的应力依赖性均高于中长渗透率。在活塞/样品和径向端口/样品接口的压实损伤的影响进行了讨论。在Bentheimer砂岩上，在连续单轴压缩载荷过程中，定向渗透率测量的相关性已被证明，直到样品破坏。我们可以有效地测量脆性破坏相关的渗透率的影响：它往往会增加在故障传播方向和强烈的横向方向上减少。
The influence of hydrostatic and uniaxial stress states on the porosity and permeability of sandstones has been investigated. The experimental procedure uses a special triaxial cell which allows permeability measurements in the axial and radial directions. The core sleeve is equipped with two pressure samplers placed distant from the ends. They provide mid-length axial permeability measure as opposed to the overall permeability measure, which is based on the flow imposed through the pistons of the triaxial cell. The core sleeve is also equipped to perform flows in two directions transverse to the axis of the sample. Two independent measures of axial and complementary radial permeability are thus obtained. Both Fontainebleau sandstone specimens with a porosity of about 5.8% to 8% and low permeability ranging from 2.5 mD to 30 mD and Bentheimer sandstone with a porosity of 24% and a high permeability of 3D have been tested. The initial axial permeability values obtained by each method are in good agreement for the Fontainebleau sandstone. The Bentheimer sandstone samples present an axial mid-length permeability 1.6 times higher than the overall permeability. A similar discrepancy is also observed in the radial direction, also it relates essentially to the shape of flow lines induced by the radial flow. All the tested samples have shown a higher stress dependency of overall and radial permeability than mid-length permeability. The effect of compaction damage at the pistons/sample and radial ports/sample interfaces is discussed. The relevance of directional permeability measurements during continuous uniaxial compression loadings has been shown on the Bentheimer sandstone until the failure of the sample. We can efficiently measure the influence of brittle failure associated to dilatant regime on the permeability: It tends to increase in the failure propagation direction and to decrease strongly in the transverse direction.