Characterization of dynamic mechanical alterations of supercritical CO2-interacted coal through gamma-ray attenuation, ultrasonic and X-ray computed tomography techniques

K. H.S.M. Sampath, M. S. A. Perera, Dong-yin Li, P. G. Ranjith, S. K. Matthai

Research output: Contribution to journalArticleResearchpeer-review

Abstract

Coal-Supercritical CO2 (S-CO2) interaction causes severe mechanical alterations in coal that can possibly affect the mechanical competency and the coal seam integrity. Conventional static mechanical testings often fail to conduct repetitive and temporal measurements on coal specimens in the process of coal-S-CO2 interaction, thus unable to attain at decisive and reliable conclusions. Moreover, the said techniques fail to capture the mechanical anisotropies of heterogeneous coal mass that arise due to complex spatial distribution of mineral/maceral phases and fracture network. We combine three non-destructive techniques, viz. gamma-ray attenuation, ultrasonic technique and micro computed tomography to evaluate the S-CO2 interaction induced localized and anisotropic micro-structural alterations and the consequent mechanical response of a heterogeneous coal core specimen. Dynamic moduli were computed at radial and axial directions at natural condition, after 14 days and 45 days of S-CO2 interaction, and the resultant mechanical alterations were elucidated with the 3D-reconstructed micro-CT data collected at the same stages. Visualization and quantification of coal micro-structure emphasize that S-CO2-interacted coal mass is subjected to severe micro-cracking due to differential and free swelling, drying induced shrinkage and surface energy reduction, which can possibly lead to mechanical degradation. Spatial distribution of minerals and fractures at specific orientations significantly affects the gamma and ultrasonic wave propagation, thus can be successfully utilized to reflect the mechanical anisotropies. For same interaction condition and period, coal mass exhibits mechanical anisotropies and strength alterations at different levels, in which more heterogeneous mineral/maceral distribution causes significant localized mechanical alterations in mineral-rich areas, compared to that of comparatively homogeneous coal-rich regions. Temporal evaluation of strength parameters suggests that regardless of the considered orientations, significant strength alterations occur at initial stage of the coal-S-CO2 interaction process and the longer interaction causes only a slight strength reduction. Overall results conclude that S-CO2 induced mechanical property alterations in heterogeneous coal are highly localized and anisotropic, thus should be carefully evaluated in CO2 sequestration and ECBM extraction processes.

Original languageEnglish
Pages (from-to)268-280
Number of pages13
JournalJournal of Petroleum Science and Engineering
Volume174
DOIs
Publication statusPublished - 1 Mar 2019

Keywords

  • Anisotropy
  • Coal seam
  • Dynamic moduli
  • Heterogeneity
  • Supercritical CO

Cite this

@article{41f6988cf2304485afe98c5d0b0e8d01,
title = "Characterization of dynamic mechanical alterations of supercritical CO2-interacted coal through gamma-ray attenuation, ultrasonic and X-ray computed tomography techniques",
abstract = "Coal-Supercritical CO2 (S-CO2) interaction causes severe mechanical alterations in coal that can possibly affect the mechanical competency and the coal seam integrity. Conventional static mechanical testings often fail to conduct repetitive and temporal measurements on coal specimens in the process of coal-S-CO2 interaction, thus unable to attain at decisive and reliable conclusions. Moreover, the said techniques fail to capture the mechanical anisotropies of heterogeneous coal mass that arise due to complex spatial distribution of mineral/maceral phases and fracture network. We combine three non-destructive techniques, viz. gamma-ray attenuation, ultrasonic technique and micro computed tomography to evaluate the S-CO2 interaction induced localized and anisotropic micro-structural alterations and the consequent mechanical response of a heterogeneous coal core specimen. Dynamic moduli were computed at radial and axial directions at natural condition, after 14 days and 45 days of S-CO2 interaction, and the resultant mechanical alterations were elucidated with the 3D-reconstructed micro-CT data collected at the same stages. Visualization and quantification of coal micro-structure emphasize that S-CO2-interacted coal mass is subjected to severe micro-cracking due to differential and free swelling, drying induced shrinkage and surface energy reduction, which can possibly lead to mechanical degradation. Spatial distribution of minerals and fractures at specific orientations significantly affects the gamma and ultrasonic wave propagation, thus can be successfully utilized to reflect the mechanical anisotropies. For same interaction condition and period, coal mass exhibits mechanical anisotropies and strength alterations at different levels, in which more heterogeneous mineral/maceral distribution causes significant localized mechanical alterations in mineral-rich areas, compared to that of comparatively homogeneous coal-rich regions. Temporal evaluation of strength parameters suggests that regardless of the considered orientations, significant strength alterations occur at initial stage of the coal-S-CO2 interaction process and the longer interaction causes only a slight strength reduction. Overall results conclude that S-CO2 induced mechanical property alterations in heterogeneous coal are highly localized and anisotropic, thus should be carefully evaluated in CO2 sequestration and ECBM extraction processes.",
keywords = "Anisotropy, Coal seam, Dynamic moduli, Heterogeneity, Supercritical CO",
author = "Sampath, {K. H.S.M.} and Perera, {M. S. A.} and Dong-yin Li and Ranjith, {P. G.} and Matthai, {S. K.}",
year = "2019",
month = "3",
day = "1",
doi = "10.1016/j.petrol.2018.11.044",
language = "English",
volume = "174",
pages = "268--280",
journal = "Journal of Petroleum Science and Engineering",
issn = "0920-4105",
publisher = "Elsevier",

}

Characterization of dynamic mechanical alterations of supercritical CO2-interacted coal through gamma-ray attenuation, ultrasonic and X-ray computed tomography techniques. / Sampath, K. H.S.M.; Perera, M. S. A.; Li, Dong-yin; Ranjith, P. G.; Matthai, S. K.

In: Journal of Petroleum Science and Engineering, Vol. 174, 01.03.2019, p. 268-280.

Research output: Contribution to journalArticleResearchpeer-review

TY - JOUR

T1 - Characterization of dynamic mechanical alterations of supercritical CO2-interacted coal through gamma-ray attenuation, ultrasonic and X-ray computed tomography techniques

AU - Sampath, K. H.S.M.

AU - Perera, M. S. A.

AU - Li, Dong-yin

AU - Ranjith, P. G.

AU - Matthai, S. K.

PY - 2019/3/1

Y1 - 2019/3/1

N2 - Coal-Supercritical CO2 (S-CO2) interaction causes severe mechanical alterations in coal that can possibly affect the mechanical competency and the coal seam integrity. Conventional static mechanical testings often fail to conduct repetitive and temporal measurements on coal specimens in the process of coal-S-CO2 interaction, thus unable to attain at decisive and reliable conclusions. Moreover, the said techniques fail to capture the mechanical anisotropies of heterogeneous coal mass that arise due to complex spatial distribution of mineral/maceral phases and fracture network. We combine three non-destructive techniques, viz. gamma-ray attenuation, ultrasonic technique and micro computed tomography to evaluate the S-CO2 interaction induced localized and anisotropic micro-structural alterations and the consequent mechanical response of a heterogeneous coal core specimen. Dynamic moduli were computed at radial and axial directions at natural condition, after 14 days and 45 days of S-CO2 interaction, and the resultant mechanical alterations were elucidated with the 3D-reconstructed micro-CT data collected at the same stages. Visualization and quantification of coal micro-structure emphasize that S-CO2-interacted coal mass is subjected to severe micro-cracking due to differential and free swelling, drying induced shrinkage and surface energy reduction, which can possibly lead to mechanical degradation. Spatial distribution of minerals and fractures at specific orientations significantly affects the gamma and ultrasonic wave propagation, thus can be successfully utilized to reflect the mechanical anisotropies. For same interaction condition and period, coal mass exhibits mechanical anisotropies and strength alterations at different levels, in which more heterogeneous mineral/maceral distribution causes significant localized mechanical alterations in mineral-rich areas, compared to that of comparatively homogeneous coal-rich regions. Temporal evaluation of strength parameters suggests that regardless of the considered orientations, significant strength alterations occur at initial stage of the coal-S-CO2 interaction process and the longer interaction causes only a slight strength reduction. Overall results conclude that S-CO2 induced mechanical property alterations in heterogeneous coal are highly localized and anisotropic, thus should be carefully evaluated in CO2 sequestration and ECBM extraction processes.

AB - Coal-Supercritical CO2 (S-CO2) interaction causes severe mechanical alterations in coal that can possibly affect the mechanical competency and the coal seam integrity. Conventional static mechanical testings often fail to conduct repetitive and temporal measurements on coal specimens in the process of coal-S-CO2 interaction, thus unable to attain at decisive and reliable conclusions. Moreover, the said techniques fail to capture the mechanical anisotropies of heterogeneous coal mass that arise due to complex spatial distribution of mineral/maceral phases and fracture network. We combine three non-destructive techniques, viz. gamma-ray attenuation, ultrasonic technique and micro computed tomography to evaluate the S-CO2 interaction induced localized and anisotropic micro-structural alterations and the consequent mechanical response of a heterogeneous coal core specimen. Dynamic moduli were computed at radial and axial directions at natural condition, after 14 days and 45 days of S-CO2 interaction, and the resultant mechanical alterations were elucidated with the 3D-reconstructed micro-CT data collected at the same stages. Visualization and quantification of coal micro-structure emphasize that S-CO2-interacted coal mass is subjected to severe micro-cracking due to differential and free swelling, drying induced shrinkage and surface energy reduction, which can possibly lead to mechanical degradation. Spatial distribution of minerals and fractures at specific orientations significantly affects the gamma and ultrasonic wave propagation, thus can be successfully utilized to reflect the mechanical anisotropies. For same interaction condition and period, coal mass exhibits mechanical anisotropies and strength alterations at different levels, in which more heterogeneous mineral/maceral distribution causes significant localized mechanical alterations in mineral-rich areas, compared to that of comparatively homogeneous coal-rich regions. Temporal evaluation of strength parameters suggests that regardless of the considered orientations, significant strength alterations occur at initial stage of the coal-S-CO2 interaction process and the longer interaction causes only a slight strength reduction. Overall results conclude that S-CO2 induced mechanical property alterations in heterogeneous coal are highly localized and anisotropic, thus should be carefully evaluated in CO2 sequestration and ECBM extraction processes.

KW - Anisotropy

KW - Coal seam

KW - Dynamic moduli

KW - Heterogeneity

KW - Supercritical CO

UR - http://www.scopus.com/inward/record.url?scp=85056822245&partnerID=8YFLogxK

U2 - 10.1016/j.petrol.2018.11.044

DO - 10.1016/j.petrol.2018.11.044

M3 - Article

VL - 174

SP - 268

EP - 280

JO - Journal of Petroleum Science and Engineering

JF - Journal of Petroleum Science and Engineering

SN - 0920-4105

ER -