Pore and fracture scale characterization of oil shale at different microwave temperatures

Abstract

. The spatial complexity of oil shale systems is manifested by microstructure, pore space randomness and extensive heterogeneity. A microwave pyrolysis device developed for this study was used to pyrolyze oil shale, and the microstructure before and after pyrolysis was visually examined and quantified. The internal structure of the rock and the extent of pore and fracture expansion are more accurately determined in this way. The microstructure of oil shale at different temperatures before and after microwave pyrolysis is identified by X-ray microcomputed tomography (μCT) with automatic ultra-high-resolution scanning electron microscopy (SEM), to observe the heterogeneous state of oil shale on 2D and 3D scales and define the distribution of internal pores and fractures by post-processing μCT visualization. The study found that fractures sized from microns to millimeters along with pore fractures were observed at increasing microwave temperatures. The fractures gradually expanded with increasing temperature in the direction of horizontal or vertical laminae and generated a more connected pore network. The kerogen gradually decreased with a rise in temperature. The porosity increased from 0.26% to 13.69% at the initial temperature. This research is essential for the qualitative as well as quantitative analysis of the internal structure of oil shales under microwave radiation.