Computer axial tomography in geosciences: an overview

Computer axial tomography (CAT) is one of the most adequate non-destructive techniques for the investigation of the internal structure of a large cate gory of objects. This method, based on the attenuation of X- or gamma-ray, generates digital images which map the numerical values of the linear atten uation coefficient of a section or of the entire volume of the investigated sample. Depending on the energy of the utilized radiation as well as on th e effective atomic number of the sample, CAT can furnish, with a spatial re solution of 0.01-0.5 mm, quantitative as well as qualitative information co ncerning local density or chemical composition of the sample. In geoscience s, CAT has been successfully applied to the investigation of bulk density, moisture content or macroporosity of the soil, soil-plant-water system, oil sand or shales, small scale heterogeneities in siltstone or sandstone, dia monds in kimberlite, mineralization layers in manganese nodules, local stru cture of marine sediments or coal composition. The method has also been use d for the investigation of the rock mechanical properties, rock permeabilit y, fracture network, two or three-phase flow or residual oil distribution i n carbonate cores. A review of the actual applications of CAT in soil scien ce, sedimentology, coal geology as well as rock mechanics is presented. All these applications reveal the great potential of CAT in geoscience investi gations. (C) 1999 Elsevier Science B.V. All rights reserved.