Geochemical and geomechanical alteration of siliciclastic reservoir rock by supercritical CO2-saturated brine formed during geological carbon sequestration

Samantha J. Fuchs, D. Nicholas Espinoza, Christina L. Lopano, Ange-Therese Akono, Charles J. Werth*

*Corresponding author for this work

Research output: Contribution to journalArticle

Abstract

Geologic carbon sequestration (GCS) is an approach for storing CO2 and mitigating greenhouse gas emissions. During GCS, carbon dioxide dissolves into pore water, resulting in a low-pH brine that can react with reservoir rock minerals. This work evaluates the effects of geochemical reactions on geomechanical integrity of representative siliciclastic reservoir samples obtained from the Mt. Simon formation. Rock samples were aged 4 or 8 weeks in CO2-saturated brine under reservoir conditions, and in N2-saturated brine as a control. Post-aging, CT scans revealed more extensive micro-fracture development along horizontal bedding planes at grain edges in CO2 versus N2-aged samples. Digital analysis of CO2-aged samples showed porosity increase from 8.1% to 15.8%. Scanning electron microscopy revealed the loss of clay cementation, greater exposure of quartz and K-feldspar grains, and apparent surface roughening (confirmed by laser profilometry) in CO2-aged samples, but not in N2-aged samples. Fracture toughness as evaluated by scratch testing was reduced by 32.1% after 4 weeks in scCO2-saturated brine and 69.5% after 8 weeks. The primary reason for weakening appears to be detachment of clays from quartz and feldspar grain surfaces, resulting in weakening of the rock matrix. Rock weakening may alter the geomechanical stability of storage formations.

Original languageEnglish (US)
Pages (from-to)251-260
Number of pages10
JournalInternational Journal of Greenhouse Gas Control
Volume88
DOIs
StatePublished - Sep 1 2019

Fingerprint

reservoir rock
carbon sequestration
brine
Rocks
Feldspar
Carbon
feldspar
Quartz
Clay
rock
quartz
clay
Profilometry
fracture toughness
Computerized tomography
bedding plane
cementation
Gas emissions
Greenhouse gases
Fracture toughness

Keywords

  • Fracture toughness
  • Geochemistry
  • Geologic carbon sequestration
  • Geomechanics
  • Mt. Simon

ASJC Scopus subject areas

  • Pollution
  • Energy(all)
  • Industrial and Manufacturing Engineering
  • Management, Monitoring, Policy and Law

Cite this

@article{a24a3537bffd4c9fbc41b0b157d2c594,
title = "Geochemical and geomechanical alteration of siliciclastic reservoir rock by supercritical CO2-saturated brine formed during geological carbon sequestration",
abstract = "Geologic carbon sequestration (GCS) is an approach for storing CO2 and mitigating greenhouse gas emissions. During GCS, carbon dioxide dissolves into pore water, resulting in a low-pH brine that can react with reservoir rock minerals. This work evaluates the effects of geochemical reactions on geomechanical integrity of representative siliciclastic reservoir samples obtained from the Mt. Simon formation. Rock samples were aged 4 or 8 weeks in CO2-saturated brine under reservoir conditions, and in N2-saturated brine as a control. Post-aging, CT scans revealed more extensive micro-fracture development along horizontal bedding planes at grain edges in CO2 versus N2-aged samples. Digital analysis of CO2-aged samples showed porosity increase from 8.1{\%} to 15.8{\%}. Scanning electron microscopy revealed the loss of clay cementation, greater exposure of quartz and K-feldspar grains, and apparent surface roughening (confirmed by laser profilometry) in CO2-aged samples, but not in N2-aged samples. Fracture toughness as evaluated by scratch testing was reduced by 32.1{\%} after 4 weeks in scCO2-saturated brine and 69.5{\%} after 8 weeks. The primary reason for weakening appears to be detachment of clays from quartz and feldspar grain surfaces, resulting in weakening of the rock matrix. Rock weakening may alter the geomechanical stability of storage formations.",
keywords = "Fracture toughness, Geochemistry, Geologic carbon sequestration, Geomechanics, Mt. Simon",
author = "Fuchs, {Samantha J.} and Espinoza, {D. Nicholas} and Lopano, {Christina L.} and Ange-Therese Akono and Werth, {Charles J.}",
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Geochemical and geomechanical alteration of siliciclastic reservoir rock by supercritical CO2-saturated brine formed during geological carbon sequestration. / Fuchs, Samantha J.; Espinoza, D. Nicholas; Lopano, Christina L.; Akono, Ange-Therese; Werth, Charles J.

In: International Journal of Greenhouse Gas Control, Vol. 88, 01.09.2019, p. 251-260.

Research output: Contribution to journalArticle

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T1 - Geochemical and geomechanical alteration of siliciclastic reservoir rock by supercritical CO2-saturated brine formed during geological carbon sequestration

AU - Fuchs, Samantha J.

AU - Espinoza, D. Nicholas

AU - Lopano, Christina L.

AU - Akono, Ange-Therese

AU - Werth, Charles J.

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AB - Geologic carbon sequestration (GCS) is an approach for storing CO2 and mitigating greenhouse gas emissions. During GCS, carbon dioxide dissolves into pore water, resulting in a low-pH brine that can react with reservoir rock minerals. This work evaluates the effects of geochemical reactions on geomechanical integrity of representative siliciclastic reservoir samples obtained from the Mt. Simon formation. Rock samples were aged 4 or 8 weeks in CO2-saturated brine under reservoir conditions, and in N2-saturated brine as a control. Post-aging, CT scans revealed more extensive micro-fracture development along horizontal bedding planes at grain edges in CO2 versus N2-aged samples. Digital analysis of CO2-aged samples showed porosity increase from 8.1% to 15.8%. Scanning electron microscopy revealed the loss of clay cementation, greater exposure of quartz and K-feldspar grains, and apparent surface roughening (confirmed by laser profilometry) in CO2-aged samples, but not in N2-aged samples. Fracture toughness as evaluated by scratch testing was reduced by 32.1% after 4 weeks in scCO2-saturated brine and 69.5% after 8 weeks. The primary reason for weakening appears to be detachment of clays from quartz and feldspar grain surfaces, resulting in weakening of the rock matrix. Rock weakening may alter the geomechanical stability of storage formations.

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