TY - GEN
T1 - Shear-induced permeability enhancement
AU - Im, Kyungjae
AU - Elsworth, Derek
AU - Fang, Yi
N1 - Funding Information:
This work is the result of support provided by U.S. Department of Energy (DOE) under Grant No. DE-FE0023354. This support is gratefully acknowledged
Publisher Copyright:
© 2017 by Korean Society for Rock Mechanics.
PY - 2017
Y1 - 2017
N2 - Shear induced permeability evolution is a crucial mechanism in understanding changes in the subsurface hydraulic system driven by natural seismic events and in the stimulation for subsurface energy recovery. We investigate permeability response during aseismic-through-seismic shear deformation on saw-cut fractures of varying low-order roughness. We report shear-instability-permeability direct shear experiments on Westerly granite in a triaxial pressure cell that concurrently and continuously measures friction and permeability during multiple sequential slide and hold events. We observe two clearly different responses in permeability evolution representing end-of-spectrum behaviors. These are (i) shear induced permeability reduction which is dominant in the initial stage of shear slip to a shear offset of several millimeters and (ii) gradual permeability enhancement with further shear offset. When the sample is static (experimental hold period), permeability continuously decreases and follows a power law decay with time. We observe that, with a given (~1mm) shear displacement, the normalized permeability enhancement Δq/qinitial is greater after a longer hold period. This observation implies that the permeability of natural pre-existing faults that are locked over long durations can be significantly enhanced by shear deformations. The result suggests that permeability can be engineered in reservoirs by reactivated shear deformation and also suggests that the well-documented seismicity-associated permeability increase in natural hydraulic systems (e.g., Elkhoury et. al., 2006) may also be contributed to by systematic shear deformations.
AB - Shear induced permeability evolution is a crucial mechanism in understanding changes in the subsurface hydraulic system driven by natural seismic events and in the stimulation for subsurface energy recovery. We investigate permeability response during aseismic-through-seismic shear deformation on saw-cut fractures of varying low-order roughness. We report shear-instability-permeability direct shear experiments on Westerly granite in a triaxial pressure cell that concurrently and continuously measures friction and permeability during multiple sequential slide and hold events. We observe two clearly different responses in permeability evolution representing end-of-spectrum behaviors. These are (i) shear induced permeability reduction which is dominant in the initial stage of shear slip to a shear offset of several millimeters and (ii) gradual permeability enhancement with further shear offset. When the sample is static (experimental hold period), permeability continuously decreases and follows a power law decay with time. We observe that, with a given (~1mm) shear displacement, the normalized permeability enhancement Δq/qinitial is greater after a longer hold period. This observation implies that the permeability of natural pre-existing faults that are locked over long durations can be significantly enhanced by shear deformations. The result suggests that permeability can be engineered in reservoirs by reactivated shear deformation and also suggests that the well-documented seismicity-associated permeability increase in natural hydraulic systems (e.g., Elkhoury et. al., 2006) may also be contributed to by systematic shear deformations.
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M3 - Conference contribution
AN - SCOPUS:85048856045
T3 - 4th ISRM Young Scholars Symposium on Rock Mechanics, YSS 2017
SP - 383
EP - 385
BT - 4th ISRM Young Scholars Symposium on Rock Mechanics, YSS 2017
PB - International Society for Rock Mechanics
T2 - 4th ISRM Young Scholars Symposium on Rock Mechanics, YSS 2017
Y2 - 10 May 2017 through 13 May 2017
ER -