Qualitative and quantitative evaluation of the alteration of micro-fracture characteristics of supercritical CO2-interacted coal

Abstract

CO2 geo-sequestration necessitates injection of CO2 into coal reservoirs, in which CO2 becomes supercritical due to high pressure/temperature conditions. Consequently, the coal-supercritical CO2 (S−CO2) interaction triggers micro-structural alterations, inferring the necessity of temporal and spatial analyses. In this study, three imaging techniques were used to evaluate the S−CO2-induced micro-structural alterations in heterogeneous coal specimens. Results from the qualitative analysis indicate that S−CO2 interaction causes new fracture formation and extension/widening of existing fractures in coal. Quantitative analysis concludes that fracture fraction and fracture-matrix interface area in..