Injection‐Induced Moment Release Can Also Be Aseismic

Abstract

The cumulative seismic moment is a robust measure of the earthquake response to fluid injection for injection volumes ranging from 3,100 to about 12 million m3. Over this range, the moment release is limited to twice the product of the shear modulus and the volume of injected fluid. This relation also applies at the much smaller injection volumes of the field experiment in France reported by Guglielmi et al. (2015, https://doi.org/10.1126/science.aab0476) and laboratory experiments to simulate hydraulic fracturing described by Goodfellow et al. (2015, https://doi.org/10.1002/2015GL063093). In both of these studies, the relevant moment release for comparison with the fluid injection was aseismic and consistent with the scaling that applies to the much larger volumes associated with injection‐induced earthquakes with magnitudes extending up to 5.8. Neither the microearthquakes, at the site in France, nor the acoustic emission in the laboratory samples contributed significantly to the deformation due to fluid injection.

Earthquakes Induced by Hydraulic Fracturing Are Pervasive in Oklahoma

“…The cumulative moment and volumes at HF wells associated with induced earthquake sequences are in general agreement with the relationship identified by McGarr and Barbour (; Figure S10). Nearly all HF sequences had cumulative moments within the range expected for the volumes injected at the corresponding well with assumed shear moduli <30 GPa.…”

“…The most notable exception to this are the total volumes of fluids used in stimulating HF wells, which we obtained from FracFocus and by digitizing well records. Previously, volume of fluid injected at HF wells has been found to influence the likelihood of induced seismicity in Canada (Schultz et al, ) and could be associated with the maximum expected moment release (McGarr, ; McGarr & Barbour, ).…”

“…Nearly all HF sequences had cumulative moments within the range expected for the volumes injected at the corresponding well with assumed shear moduli <30 GPa. Our analysis only considered volumes injected at the individual HF well and therefore ignored the volume from other wells within 10 km that was considered by McGarr and Barbour (); if other nearby wells were considered in the volume calculation, there were would be a stronger agreement. From the McGarr and Barbour () relationship, a M > 4 earthquake could be a possibility for HF wells with volumes >~10 5 bbls.…”

“…Our analysis only considered volumes injected at the individual HF well and therefore ignored the volume from other wells within 10 km that was considered by McGarr and Barbour (); if other nearby wells were considered in the volume calculation, there were would be a stronger agreement. From the McGarr and Barbour () relationship, a M > 4 earthquake could be a possibility for HF wells with volumes >~10 5 bbls. Since a majority of HF wells associated with seismicity had volumes greater than this value, a M > 4 earthquake induced by HF could have been a possibility in Oklahoma if the McGarr and Barbour () relationship is applicable.…”

“…From the McGarr and Barbour () relationship, a M > 4 earthquake could be a possibility for HF wells with volumes >~10 5 bbls. Since a majority of HF wells associated with seismicity had volumes greater than this value, a M > 4 earthquake induced by HF could have been a possibility in Oklahoma if the McGarr and Barbour () relationship is applicable.…”