Probabilistic Evaluation of Susceptibility to Fluid Injection-Induced Seismicity Based on Statistics of Fracture Criticality

Abstract Fault reactivation and associated microseismicity pose a potential threat to industrial processes involving fluid injection into the subsurface. In this research, fracture criticality, defined as gradient of critical pressure change trigger seismicity (Δ p c / h ), is proposed novel reservoir depth-independent metric fault slip susceptibility. Based on statistics probabilistic evaluation framework for susceptibility injection-induced was developed by integrating seismic observations hydrogeological modelling operations faulted reservoirs. The method considers injection-driven increase, variability regional density. Utilising methodology, distribution criticality obtained evaluate in both off-fault zones at Hellisheiði geothermal site, Iceland. It has been found that within shows natural (mostly ranging between 0.001 2.0 bar/km), tend be characterised larger values than off-faut zones. Fracture estimated each zone roughly follow Gaussian distribution. around five re-injection wells site were have relatively high probability event occurrence, these regions experienced levels induced over microseismic monitoring period. seismotectonic state generally consistent with forecasted based criticality.