Modeling Induced Seismicity: Inter-Seismic Quasi-Static Triggering in A Discretely Fractured Poroelastic Medium

摘要

We present a quasi-static and hydro-mechanical fully coupled approach to the modeling of inter-seismic triggering of seismicity in an arbitrary fractured and fluid-saturated poroelastic solid. The discrete fracture network (DFN) we consider is hybrid and at a dual-scale consisting of large-scale deterministic fractures and small-scale stochastic fractures following certain distributions. The fracture-poro-elasticity fully coupled modeling is carried out using our Jin & Zoback (2017) nonlinear computational model by explicitly resolving the deterministic fractures only. This provides inputs for the subsequent seismicity modeling that accounts for the entire hybrid dual-scale DFN. A new stress updating algorithm is developed accounting for the competing poroelastic stress compensation and seismicity-induced stress loss on fractures. Our model can therefore naturally produce multiple cycles of seismicity triggering. As an example, we perform a numerical experiment and generate a synthetic catalog of induced seismic events, and then analyze (1) seismicity distribution in relation to the fluid pressure, poroelastic stress and fracture distribution, (2) event type, (3) spatial-temporal characteristics, (4) stress history, (5) seismic source parameters and their characteristics and (6) activated DFN and permeability changes. Our modeling provides explanations to some curious observations in real data and can serve as a physics-based tool for predicting induced seismicity in complex geological media.