TY - GEN
T1 - Weakening effects of microstructural tribological films in CO2-altered reservoirs and caprocks
AU - Wang, Chaoyi
AU - Elsworth, Derek
AU - Fang, Yi
AU - Liu, Keru
AU - Jia, Yunzhong
N1 - Funding Information:
This work is the result of support provided by DOE Grant DE-FE0023354. This support is gratefully acknowledged.
Publisher Copyright:
© 2017 ARMA, American Rock Mechanics Association.
PY - 2017
Y1 - 2017
N2 - Where supercritical CO2 is injected into aquifers, the subsequent dissolution of CO2 into the brine may result in substantial reaction and chemical transformation of the minerals comprising the reservoir and caprock and disturb the stress field, and alter the permeability These combined effects may result in weakening of pre-existing faults, transformation of permeability and the triggering of induced-seismicity, via weakening. Pristine and CO2-alterd rocks from the Crystal Geyser (Major et al. 2014) define the evolution of Fe-coating (hematite) into altered tribological films (goethite) surrounding the grains with different strength and stability properties. We use this transformed microstructural form to examine the ensemble strength and structural stability. We use a 2-D Distinct Element Model (DEM) to simulate fault gouge materials under slip events. The mechanical response of grain-grain contacts is represented by a linear-elastic contact model with rotational resistance and a slip-weakening friction law. Goethite and hematite coating configurations are represented using tiny particles surrounding quartz analog particles with different contact properties. Numerical shear experiments are performed on simulated fault gouge with unaltered (hematite coating) and altered (goethite coating) configurations. CO2 altered gouge shows lower friction coefficient (~0.4) than unaltered gouge (~0.65). However, the weakening effect of the goethite coating is not enhanced by increasing relative coating concentration. Results of end-member (unaltered and altered gouge materials) behaviors show that the goethite film may serve as the main mechanism of weakening and creep behavior in these CO2 altered faults.
AB - Where supercritical CO2 is injected into aquifers, the subsequent dissolution of CO2 into the brine may result in substantial reaction and chemical transformation of the minerals comprising the reservoir and caprock and disturb the stress field, and alter the permeability These combined effects may result in weakening of pre-existing faults, transformation of permeability and the triggering of induced-seismicity, via weakening. Pristine and CO2-alterd rocks from the Crystal Geyser (Major et al. 2014) define the evolution of Fe-coating (hematite) into altered tribological films (goethite) surrounding the grains with different strength and stability properties. We use this transformed microstructural form to examine the ensemble strength and structural stability. We use a 2-D Distinct Element Model (DEM) to simulate fault gouge materials under slip events. The mechanical response of grain-grain contacts is represented by a linear-elastic contact model with rotational resistance and a slip-weakening friction law. Goethite and hematite coating configurations are represented using tiny particles surrounding quartz analog particles with different contact properties. Numerical shear experiments are performed on simulated fault gouge with unaltered (hematite coating) and altered (goethite coating) configurations. CO2 altered gouge shows lower friction coefficient (~0.4) than unaltered gouge (~0.65). However, the weakening effect of the goethite coating is not enhanced by increasing relative coating concentration. Results of end-member (unaltered and altered gouge materials) behaviors show that the goethite film may serve as the main mechanism of weakening and creep behavior in these CO2 altered faults.
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M3 - Conference contribution
AN - SCOPUS:85047893484
T3 - 51st US Rock Mechanics / Geomechanics Symposium 2017
SP - 1047
EP - 1054
BT - 51st US Rock Mechanics / Geomechanics Symposium 2017
PB - American Rock Mechanics Association (ARMA)
T2 - 51st US Rock Mechanics / Geomechanics Symposium 2017
Y2 - 25 June 2017 through 28 June 2017
ER -