Connecting microstructural attributes and permeability from 3D tomographic images of in situ shear-enhanced compaction bands using multiscale computations.

WaiChing Sun and John W. Rudnicki
Department of Civil and Environmental Engineering, Northwestern University, Evanston, Illinois, USA.

José E. Andrade
Division of Engineering and Applied Science, California Institute of Technology, Pasadena, California, USA.

Peter Eichhubl
Jackson School of Geosciences, The University of Texas at Austin, Austin, Texas, USA.

Abstract. Tomographic images taken inside and outside a compaction band in a field specimen of Aztec sandstone are analyzed by using numerical methods such as graph theory, level sets, and hybrid lattice Boltzmann/finite element techniques. The results reveal approximately an order of magnitude permeability reduction within the compaction band. This is less than the several orders of magnitude reduction measured from hydraulic experiments on compaction bands formed in laboratory experiments and about one order of magnitude less than inferences from two-dimensional images of Aztec sandstone. Geometrical analysis concludes that the elimination of connected pore space and increased tortuosities due to the porosity decrease are the major factors contributing to the permeability reduction. In addition, the multiscale flow simulations also indicate that permeability is fairly isotropic inside and outside the compaction band.