Evaluation of rock anisotropy using 3D X-ray computed tomography

Abstract The anisotropic nature of fabric and internal structures plays a significant role in fluid flow, heat transfer, and geomechanical behavior in rock. The existence and orientation of anisotropy in various rocks have been evaluated using laboratory experiments and image analyses to characterize anisotropic pore networks, micro-fractures, mineralogy, grain fabric, and stiffness from micro- to macro-scales. We present an assessment of anisotropy in rock by systematic and planar clustering of three-dimensional X-ray attenuation values and associated statistical analysis on the basis that X-ray CT numbers directly represent the internal density of the mineral fabric in the rock mass. Variation in voxel values across the slicing plane for a given orientation enables identification of the unique orientation of anisotropy in rock. The proposed concept is validated using a 3D virtual structure and is applied to four different rock types. The sensitivity of anisotropic features and the image noise effect are further explored to highlight the robustness of the proposed method for evaluating the anisotropy of rock fabrics.

[1]  R. Ketcham,et al.  Acquisition, optimization and interpretation of X-ray computed tomographic imagery: applications to the geosciences , 2001 .

[2]  S. Pietruszczak,et al.  Characterization of anisotropy in porous media by means of linear intercept measurements , 2003 .

[3]  Seokwon Jeon,et al.  Deformation and strength anisotropy of Asan gneiss, Boryeong shale, and Yeoncheon schist , 2012 .

[4]  D. Deming.  Estimation of the thermal conductivity anisotropy of rock with application to the determination of terrestrial heat flow , 1994 .

[5]  N. Christensen,et al.  Seismic anisotropy of shales , 1995 .

[6]  C. Celorio,et al.  Characterization by computed X-ray tomography of the evolution of the pore structure of a dolomite rock during freeze-thaw cyclic tests , 1999 .

[7]  W. Lowrie,et al.  Magnetic anisotropy, rock fabrics and finite strain in deformed sediments of SW Sardinia (Italy) , 1999 .

[8]  Richard A. Ketcham,et al.  Nondestructive high-resolution visualization and measurement of anisotropic effective porosity in complex lithologies using high-resolution X-ray computed tomography , 2005 .

[9]  Kwang Yeom Kim,et al.  Quantifying the distribution of paste-void spacing of hardened cement paste using X-ray computed tomography , 2012 .

[10]  Tae Sup Yun,et al.  Determination of air-void parameters of hardened cement-based materials using X-ray computed tomography , 2012 .

[11]  R. Ketcham.  Three-dimensional grain fabric measurements using high-resolution X-ray computed tomography , 2005 .

[12]  V. Cnudde,et al.  X-ray microtomography (μ-CT) to evaluate microstructure of mortars containing low density additions , 2012 .

[13]  Patrick Launeau,et al.  Magnetite grain shape fabric and distribution anisotropy vs rock magnetic fabric: a three-dimensional case study , 1998 .

[14]  B. Amadei.  Importance of anisotropy when estimating and measuring in situ stresses in rock , 1996 .

[15]  Z. Pros,et al.  Laboratory Approach to the Study of Elastic Anisotropy on Rock Samples , 1998 .

[16]  Carsten Raven,et al.  Numerical removal of ring artifacts in microtomography , 1998 .

[17]  D. Chapman,et al.  Thermal conductivity anisotropy of metasedimentary and igneous rocks , 2007 .

[18]  K. Min,et al.  Anisotropy of elastic moduli, P-wave velocities, and thermal conductivities of Asan Gneiss, Boryeong Shale, and Yeoncheon Schist in Korea , 2012 .

[19]  C. H. Scholz,et al.  Dilatancy anisotropy and the response of rock to large cyclic loads , 1979 .

[20]  Veerle Cnudde,et al.  High‐resolution X‐ray CT for 3D petrography of ferruginous sandstone for an investigation of building stone decay , 2011, Microscopy research and technique.

[21]  Tsukasa Nakano,et al.  Diffusion ellipsoids of anisotropic porous rocks calculated by X‐ray computed tomography‐based random walk simulations , 2008 .

[22]  Wei Sun,et al.  Magnetic anisotropy, scanning electron microscopy, and X ray pole figure goniometry study of inclination shallowing in a compacting clay‐rich sediment , 1992 .

[23]  M. Fuller,et al.  Anisotropy of magnetic susceptibility of rocks and minerals , 1963 .

[24]  D. Prior,et al.  Effects of crystallographic anisotropy on fracture development and acoustic emission in quartz , 2010 .

[25]  M. Nasseri,et al.  Analysis of fracture damage zone in anisotropic granitic rock using 3D X-ray CT scanning techniques , 2011 .

[26]  Veerle Cnudde,et al.  3D characterization of sandstone by means of X-ray computed tomography , 2011 .

[27]  Shengju Zhu,et al.  Impact of rock anisotropy on fracture development , 2008 .

[28]  F. Osborne.  Rift, grain, and hardway in some pre-Cambrian granites, Quebec , 1935 .

[29]  W. B. Lindquist,et al.  Pore and throat size distributions measured from synchrotron X-ray tomographic images of Fontaineble , 2000 .