Evolution of Pore-Scale Morphology of Oil Shale During Pyrolysis: A Quantitative Analysis

摘要

Changes of morphological parameters of oil shale under thermal conditions are investigated. Analyses are based on 26 micro-computed tomography (micro-CT) images of Green River immature shale rock available under creative commons license. Several image processing and characterization algorithms are applied to sequential high-resolution micro-CT images of oil shale samples undergoing pyrolysis. Pore-scale morphology is extracted and quantified, providing results for pore size, throat size, grain size, specific surface, coordination number, and fracture aperture. The results demonstrate critical increases of porosity, coordination number and fracture aperture in the temperature range from 390 to 400 , which translates into step change in the transport properties of the shale after pyrolysis. It is further observed that the coordination spectrum, the pore and throat size distributions, become smoother during the pyrolysis process. Finally, the absolute permeability of the samples is calculated at each step in three principal directions, and it is demonstrated that samples' permeability is more correlated with the pore connectivity rather than the average pore size. The morphological characteristics presented here enable advanced microstructure-informed approaches to pore-scale modeling of transport for optimizing oil production.