Quantifying nano-pore heterogeneity and anisotropy in gas shale by synchrotron radiation nano-CT

Abstract

As a tight reservoir, the majority of the pores in shale are nano pores. Compared to conventional reservoirs, the pore structure of shale presents strong heterogeneity and anisotropy. Quantitative characterization of nano-pore heterogeneity and anisotropy is of great significance for accurate assessment of gas reservoir capacity and the optimization of gas wells layout. In order to quantitatively characterize nano-pore heterogeneity and anisotropy in gas shale, experimental and images processing methods for gas shale nano-pore structure characterization by synchrotron radiation nano-CT were explored. The proposed method for quantitative characterization of nano-pore heterogeneity is independent of pore structure testing approach and sub-volumes number. Nano-pore anisotropy characteristics were quantitatively characterized by the eigenvalues and eigenvectors of permeability tensor, which was consistent with nano-pore geometrical morphology. Experimental and images processing methods in this paper can be references for other porous materials characterization by synchrotron radiation nano-CT. Methods for quantitative characterization of pores heterogeneity and anisotropy proposed in this paper are applicable for other porous media.