Permeability-porosity Relationships in Rocks Subjected to Various Evolution Processes

Bernabé, Yves; Mok, Ulrich; Evans, Brian

doi:10.1007/pl00012574

Cited by 233 publications

(197 citation statements)

References 45 publications

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“…Then, just before the failure, the permeability increased to ∼ 10 −18 m 2 in the both experiments. There are a lot of studies dealing with permeability-porosity relationship and permeability-stress relationship (e.g., [43][44][45]). In our experiment, permeability reduction is approximately an exponential function of effective mean stress [45] and mainly attributed to elastic crack closure [43].…”

Section: Resultsmentioning

confidence: 99%

Changes in Electrokinetic Coupling Coefficients of Granite under Triaxial Deformation

Kuwano

Yoshida²

2012

International Journal of Geophysics

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Electrokinetic phenomena are believed to be the most likely origin of electromagnetic signals preceding or accompanying earthquakes. The intensity of the source current due to the electrokinetic phenomena is determined by the fluid flux and the electrokinetic coupling coefficient called streaming current coefficient; therefore, how the coefficient changes before rupture is essential. Here, we show how the electrokinetic coefficients change during the rock deformation experiment up to failure. The streaming current coefficient did not increase before failure, but continued to decrease up to failure, which is explained in terms of the elastic closure of capillary. On the other hand, the streaming potential coefficient, which is the product of the streaming current coefficient and bulk resistivity of the rock, increased at the onset of dilatancy. It may be due to change in bulk resistivity. Our result indicates that the zeta potential of the newly created surface does not change so much from that of the preexisting fluid rock interface.

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Section: Resultsmentioning

confidence: 99%

Changes in Electrokinetic Coupling Coefficients of Granite under Triaxial Deformation

Kuwano

Yoshida²

2012

International Journal of Geophysics

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“…Such connectivity threshold was studied by Bernabé et al [2003] revealing surprising correspondence between loss of effective porosity and reduced connectivity at n c . The range of critical porosity values for rocks n c (for which k becomes effectively zero) was found to be between 0.02 and 0.05 [Mavko and Nur, 1997;Bernabé et al, 2003].…”

Section: Models For Estimating Permeabilitymentioning

confidence: 99%

“…Recognizing the diversity of porosity-modifying mechanisms shaping pore size distribution, connectivity and tortuosity parameters, and consequently noneffective pore space, led Bernabé et al [2003] to conclude that k-n relationships for rocks resulting from different evolution processes should be process specific.…”

Section: Models For Estimating Permeabilitymentioning

confidence: 99%

“…Hence, equations (14) and (15) could offer potential relationships between ( G G o ) À1 and ( n n o ). However, we must recognize that such relationships are likely to depend on the nature of the densification process [Bernabé et al, 2003]. Pore evolution in hot-pressed calcite [Zhu et al, 1999] and in seafloor vent deposits [Zhu et al, 2007] showed that pore shape, tortuosity and connectivity can be affected simultaneously during the densification process.…”

Section: Modeling Effects Of Compaction On Kmentioning

confidence: 99%

“…The range of critical porosity values for rocks n c (for which k becomes effectively zero) was found to be between 0.02 and 0.05 [Mavko and Nur, 1997;Bernabé et al, 2003]. Timur [1968] introduced dependency on irreducible water saturation, S wi into the k-n relationships:…”

Section: Models For Estimating Permeabilitymentioning

confidence: 99%

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Air entry–based characteristic length for estimation of permeability of variably compacted earth materials

Assouline

Or²

2008

Water Resources Research

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[1] The permeability k of a porous medium is a geometrical pore space attribute required for quantifying fluid flows and transport processes for hydrological, civil, agriculture, and petroleum engineering applications. Permeability is often expressed as proportional to a characteristic length squared and inversely proportional to factors accounting for porosity, pore shape, and tortuosity effects. Compaction and diagenesis reduce porosity, mean pore size, and connectivity, resulting in decrease in k. Permeability prediction relies on suitable selection of a characteristic length that may vary from simple hydraulic radius approximation of Kozeny-Carman to more complex critical path analysis to identify flow-limiting pore size. For porous media undergoing significant changes in pore space (e.g., compaction due to anthropogenic activities), the proper choice of a robust characteristic length is particularly challenging. We propose using the air entry pressure, a natural characteristic length that gauges the largest drainable pore size. This choice of a characteristic length is compatible with the Aissen formula that provides robust estimates of k for complex pore shapes. Additionally, the model considers geometrical (tortuosity) factors and links relative changes in porosity to concurrent changes in k. The model was tested against experimental data for sands, sandstones with different cementing agents, and unconsolidated soils. For unconsolidated sands and soils the model provides reasonable predictions of permeability for the entire range of porosities determined in laboratory or field experiments. However, for sandstones, and especially those containing cementing agents such as clay, the model is valid up to a critical porosity where hydraulic connectivity is lost, resulting in drastic reduction in k. The geometrical factor for soils was influenced by silt-to-clay ratio, while for sands, it was correlated with mean grain diameter. The model offers improvement in predicting k and provides a means for incorporating critical pore size and connectivity information in addition to porosity.

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Microstructural controls on the physical and mechanical properties of edifice‐forming andesites at Volcán de Colima, Mexico

et al. 2014

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The reliable assessment of volcanic unrest must rest on an understanding of the rocks that form the edifice. It is their microstructure that dictates their physical properties and mechanical behavior and thus the response of the edifice to stress perturbations during unrest. We evaluate the interplay between microstructure and rock properties for a suite of edifice-forming rocks from Volcán de Colima (Mexico). Microstructural analyses expose (1) a pervasive, isotropic microcrack network, (2) a high, subspherical vesicle density, and (3) a wide vesicle size distribution. This complex microstructure severely impacts their physical and mechanical properties. In detail, porosities are high and range from 8 to 29%. As a consequence, elastic wave velocities, Youngs moduli, and uniaxial compressive strengths are low, and permeabilities are high. All of the rock properties demonstrate a wide range. For example, strength decreases by a factor of 8 and permeability increases by 4 orders of magnitude over the porosity range. Below a porosity of 11-14%, the permeability-porosity trend follows a power law with a much higher exponent. Microstructurally, this represents a critical vesicle content that efficiently connects the microcrack population and permits a much more direct path through the sample, rather than restricting flow to long and tortuous microcracks. Values of tortuosity inferred from the Kozeny-Carman permeability model support this hypothesis. However, we find that the complex microstructure precludes a complete description of their mechanical behavior through micromechanical modeling. We urge that the findings of this study be considered in volcanic hazard assessments at andesitic stratovolcanoes.

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Permeability-porosity Relationships in Rocks Subjected to Various Evolution Processes

Cited by 233 publications

References 45 publications

Changes in Electrokinetic Coupling Coefficients of Granite under Triaxial Deformation

Changes in Electrokinetic Coupling Coefficients of Granite under Triaxial Deformation

Air entry–based characteristic length for estimation of permeability of variably compacted earth materials

Microstructural controls on the physical and mechanical properties of edifice‐forming andesites at Volcán de Colima, Mexico

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