Fractal analysis and spatial disposition of porosity in major indian gas shales using low-pressure nitrogen adsorption and advanced image segmentation

Abstract

Pore surface heterogeneities and their associated lacunarity of major Indian shale gas reservoirs were analyzed using both gas adsorption and advanced image analysis. The experiments were carried on samples from priority Indian gas shales namely Cambay, Cauvery, Krishna-Godavari and Damodar Valley. An advanced watershed segmentation was adopted on the SEM images to understand the control of pore size on the porosity of shale formations. Further, 3D as well as 2D surface intensity maps were plotted from the SEM images applying the distance transformation technique. The fractal dimension D ranged from 2.55 to 2.78 for LPN2GA suggesting a high degree of complexity in their fractal pattern. The 3D surface intensity map is found to be useful in picturizing the anisotropy in shale brought about by preferential orientation of clay minerals. The results can be extended in understanding the behavior of gas flow within the complex pore systems as exhibited by shale.