PERMEABILITY OF GRANITE UNDER HIGH PRESSURE
PERMEABILITY OF GRANITE UNDER HIGH PRESSURE
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DOI：
10.1029/jb073i006p02225
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发表时间：
1968-01-01
影响因子：
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通讯作者：
FRANGOS, WT
中科院分区：
文献类型：
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作者：
BRACE, WF;WALSH, JB;FRANGOS, WT
测量了Westerly花岗岩的渗透率作为有效压力的函数，直到4kb。使用了一种瞬态方法，在这种方法中，观察到了压力的小增量变化的衰减;衰减特性，当与样品的尺寸和流体（水或氩气）的压缩性和粘度相结合时，得到了花岗岩的渗透率，k. k的范围从100 bar压力下的350 nd（毫达西= 10 − 17 cm 2）到4000 bar压力下的4 nd。根据线性衰减特性，达西定律显然甚至在这个最低值也成立。西风花岗岩的k和电阻率ρ s都随压力显著变化，两者关系密切，k = C ρ s − 1.5 ± 0.1，其中C为常数。根据这种关系，在10千帕压力下的k1的外推值约为0.5 nd。该值大致等于溶质扩散中涉及的流速，但仍比体积扩散快得多。测得的渗透率和孔隙度使水力半径，因此，在花岗岩中的孔隙空间的形状进行估计。形状（在低压下的平缝，在高压下的等维孔隙）是一致的，从岩石的弹性特性推断。由于有效压力对孔压的依赖性很强，因此高孔隙压力下的岩石可能具有相对的渗透性。
The permeability of Westerly granite was measured as a function of effective pressure to 4 kb. A transient method was used, in which the decay of a small incremental change of pressure was observed; decay characteristics, when combined with dimensions of the sample and compressibility and viscosity of the fluid (water or argon) yielded permeability,k.kof the granite ranged from 350 nd (nanodarcy = 10−17cm2) at 100‐bar pressure to 4 nd at 4000 bars. Based on linear decay characteristics, Darcy's law apparently held even at this lowest value. Bothkand electrical resistivity, ρs, of Westerly granite vary markedly with pressure, and the two are closely related byk=Cρs−1.5±0.1, whereCis a constant. With this relationship, an extrapolated value ofkat 10‐kb pressure would be about 0.5 nd. This value is roughly equivalent to flow rates involved in solute diffusion but is still a great deal more rapid than volume diffusion. Measured permeability and porosity enable hydraulic radius and, hence, the shape of pore spaces in the granite to be estimated. The shapes (flat slits at low pressure, equidimensional pores at high pressure) are consistent with those deduced from elastic characteristics of the rock. From the strong dependence ofkon effective pressure, rocks subject to high pore pressure will probably be relatively permeable.