Modeling the permeability evolution of microcracked rocks from elastic wave velocity inversion at elevated isostatic pressure

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Modeling the permeability evolution of microcracked rocks from elastic wave velocity inversion at elevated isostatic pressure

Benson, P; Schubnel, A; Vinciguerra, S; Trovato, C; Meredith, P; Young, RP; (2006) Modeling the permeability evolution of microcracked rocks from elastic wave velocity inversion at elevated isostatic pressure. Journal of Geophysical Research. Solid Earth , 111 (B4) 10.1029/2005JB003710. Green open access

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Abstract

[1] A key consequence of the presence of microcracks within rock is their significant influence upon elastic anisotropy and transport properties. Here two rock types (a basalt and a granite) with contrasting microstructures, dominated by microcracks, have been investigated using an advanced experimental arrangement capable of measuring porosity, P wave velocity, S wave velocity, and permeability contemporaneously at effective pressures up to 100 MPa. Using the Kachanov (1994) noninteractive effective medium theory, the measured elastic wave velocities are inverted using a least squares fit, permitting the recovery of the evolution of crack density and aspect ratio with increasing isostatic pressure. Overall, the agreement between measured and predicted velocities is good, with average error less than 0.05 km/s. At larger scales and above the percolation threshold, macroscopic fluid flow also depends on the crack density and aspect ratio. Using the permeability model of Guéguen and Dienes (1989) and the crack density and aspect ratio recovered from the elastic wave velocity inversion, we successfully predict the evolution of permeability with pressure for direct comparison with the laboratory measurements. We also calculate the evolution of the crack porosity with increasing isostatic pressure, on the basis of the calculated crack density, and compare this directly with the experimentally measured porosity. These combined experimental and modeling results illustrate the importance of understanding the details of how rock microstructures change in response to an external stimulus when predicting the simultaneous evolution of rock physical properties.

Type:	Article
Title:	Modeling the permeability evolution of microcracked rocks from elastic wave velocity inversion at elevated isostatic pressure
Open access status:	An open access version is available from UCL Discovery
DOI:	10.1029/2005JB003710
Publisher version:	https://doi.org/10.1029/2005JB003710
Language:	English
Additional information:	This version is the author accepted manuscript. For information on re-use, please refer to the publisher’s terms and conditions.
Keywords:	Science & Technology, Physical Sciences, Geochemistry & Geophysics, SEISMIC VELOCITIES, ANISOTROPY, CRACKS, DRY, DEFORMATION, CRYSTALLINE, PERCOLATION, DILATANCY, FAILURE, SOLIDS
UCL classification:	UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Earth Sciences
URI:	https://discovery.ucl.ac.uk/id/eprint/10115785