Rapid Rock Nanoporosity Analysis Using Small Angle Scattering Fused with Imaging Data Based on Stochastic Reconstructions

Abstract

Through recent decade pore-scale modelling techniques matured enough to establish their robustness for relatively simple porous rocks, in particular porous media with a narrow pore-size distribution within the resolution window of the X-ray microtomography devices. But modelling of flow properties for rocks with significant amount of nano-scale porosity requires additional multi-scale structure studies. Current imaging techniques are too limited or time-consuming to cover necessary volumes of porous media. Thus, we are in search of a fast, yet robust methodology to assess nan-scale pore structure which can be used to inform pore-scale models and improve the accuracy of flow and transport predictions. In this work we report some preliminary results on the usage of the small angle scattering techniques to access the nano-scale structural properties for two complex rocks: chalk and Bazhenov formation siliceous rock (shale). The pore-size interpretation of X-ray small angle scattering results is compared against mercury porosimetry results and scanning electron microscopy. We argue that obtained results show qualitative agreement which provides an alley for future technology to combine small angle scattering with stochastic reconstructions. To further elucidate the power of such approach we perform 3D stochastic reconstructions based on 2D SEM images and simulate apparent gas permeability using pore-network model accounting for slip and (Knudsen) diffusion effects. Compared to laboratory measurements of gas permeability our results show surprisingly good agreement. We discuss obtained results and future developments of such a novel technology.