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Lookup NU author(s): Dr Tom CharltonORCiD, Dr Mohamed Rouainia
This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).
© 2021. The Authors.This study investigates the nano to core-scale geomechanical properties of a maturity series of organic-rich, calcareous shales buried to 100°C–180°C, with a focus on: (a) the mechanical properties of organic matter; (b) the elastic response and anisotropy of the shale composite at micro and core scale; and (c) the creep response. Atomic force microscopy was used to target kerogen at nanoscale resolution, and it was found that the elastic stiffness increased with thermal maturity from 5.8 GPa in an immature sample to 11.3 GPa in a mature sample. Nanoindentation testing of the shale matrix showed that diagenesis is a key factor in determining the bulk elasticity, with increasingly intense carbonate cementation at higher thermal maturities contributing to a stiffer response. A multiscale model was formulated to upscale the elastic properties from nanoscale solid clay minerals to a microcracked composite at core scale, with good predictions of the micro and core-scale stiffness in comparison to indentation and triaxial results. A negative correlation was found between the creep modulus and clay/kerogen content, with greater creep displacement observed in nanoindentation tests in the immature clay- and kerogen-rich sample compared to samples of higher thermal maturity.
Author(s): Charlton TS, Goodarzi M, Rouainia M, Aplin AC, Cubillas P
Publication type: Article
Publication status: Published
Journal: Journal of Geophysical Research: Solid Earth
Year: 2021
Volume: 126
Issue: 7
Print publication date: 30/06/2021
Online publication date: 30/06/2021
Acceptance date: 08/06/2021
Date deposited: 07/10/2021
ISSN (print): 2169-9313
ISSN (electronic): 2169-9356
Publisher: John Wiley and Sons Inc
URL: https://doi.org/10.1029/2020JB021365
DOI: 10.1029/2020JB021365
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