TY - JOUR
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.
N1 - Funding Information:
This work was supported as part of the Center for Geologic Storage of CO2, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences under Award # DE-SC0C12504. Data for this project were provided, in part, by work supported by the U.S. Department of Energy under award number DE-FC26-05NT42588 and the Illinois Department of Commerce and Economic Opportunity. This research was supported in part by an appointment to the U.S. Department of Energy (DOE) Postgraduate Research Program at the National Energy Technology Laboratory administered by the Oak Ridge Institute for Science and Education. We thank Luis Hernandez-Uribe, who provided the Matlab code used to analyze scratch test data and determine fracture toughness values. We acknowledge the Chevron Digital Petrophysics Laboratory https://faculty.engr.utexas.edu/espinoza/microct , where X-ray microfocus scanning was performed.
Publisher Copyright:
© 2019 Elsevier Ltd
PY - 2019/9
Y1 - 2019/9
N2 - 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.
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.
KW - Fracture toughness
KW - Geochemistry
KW - Geologic carbon sequestration
KW - Geomechanics
KW - Mt. Simon
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U2 - 10.1016/j.ijggc.2019.06.014
DO - 10.1016/j.ijggc.2019.06.014
M3 - Article
AN - SCOPUS:85067798948
SN - 1750-5836
VL - 88
SP - 251
EP - 260
JO - International Journal of Greenhouse Gas Control
JF - International Journal of Greenhouse Gas Control
ER -