Permeability, porosity and pore geometry evolution during compaction of Neogene sedimentary rocks
Permeability, porosity and pore geometry evolution during compaction of Neogene sedimentary rocks
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DOI：
10.1016/j.jsg.2013.12.010
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发表时间：
2014-05
影响因子：
3.1
通讯作者：
K. Okazaki;H. Noda;S. Uehara;T. Shimamoto
中科院分区：
文献类型：
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作者：
K. Okazaki;H. Noda;S. Uehara;T. Shimamoto
渗透率 k 表示为水力半径 Rh（= 孔体积 Vp/样品表面积 S）平方、孔隙率 和无量纲几何因子 1/G 的乘积。G 通常根据模型假设为常数，部分原因是其测量很困难。我们提出了一种在不假设任何微观结构模型的情况下测量 G 的方法，并展示了沉积岩在压实过程中的演化过程，因为沉积岩的颗粒太细，无法观察和量化微观结构。我们测量了日本 Horonobe 的 Koetoi 组硅藻泥岩 (Kdm, phi= 0.53–0.64) 和 Wakkanai 组硅质泥岩 (Wsm, phi= 0.28–0.33) 在围压高达 100 MPa 的压实过程中的 S、k、Vp 和颗粒体积 Vg。它们是类似的沉积岩，但成岩作用的等级不同。Vp和SyieldRh，因此我们可以估计G。Kdm的G在压实过程中几乎保持不变，在1.3到6之间变化，而来自较少孔隙的Wsm的一些样品的G随着压实而不可逆地增加，从大约0.1到10。G增加2个数量级可能表明主要流体通道从沿裂缝集中流动到普遍流动的变化。
Permeabilitykis expressed as a product of the hydraulic radiusRh(=pore volumeVp/sample surface areaS) squared, porosityϕ, and a nondimensional geometrical factors 1/G.Gis often assumed constant depending on the model, partly because its measurement is difficult. We propose a method to measureGwithout assuming any microstructural model, and present its evolution during compaction of sedimentary rocks that are too fine-grained to observe and quantify microstructures. We measuredS,k,Vp, and grain volumeVgduring compaction with confining pressure up to 100 MPa of diatomaceous mudstone from Koetoi Formation (Kdm,ϕ= 0.53–0.64) and siliceous mudstone from Wakkanai Formation (Wsm,ϕ= 0.28–0.33), Horonobe, Japan. They are similar sedimentary rocks, but are different in the grade of diagenesis.VpandSyieldRh, and thus we can estimateG.Gfor Kdm remains nearly constant during compaction and varies from 1.3 to 6, whereasGfor some samples from less porous Wsm increases irreversibly with compaction from about 0.1 to 10. The increase inGby 2 orders of magnitude probably indicates the change in the dominant fluid conduit from concentrated flow along fractures to pervasive flow.