קולוקוויום בחוג לגאופיזיקה: Models for Reservoir-Induced Seismicity

Zoom: https://tau-ac-il.zoom.us/j/86769967727?pwd=25OfJE7Na6lWggNsBNRbl7H8bnW56x.1

Abstract:

Compared to other kinds of fluid-related seismicity, reservoir-induced seismicity (RIS) is usually characterized by higher magnitudes. Seismic and water level monitoring and statistical modelling, however, do not provide, however, a comprehensive understanding of the RIS mechanism and controls. Here I present two 2D FEM models specifically designed for RIS simulations: 1) poro-visco-elasto-plastic fully dynamic earthquake model with frictional coefficient rate-and-state dependence; 2) poro-visco-elastic model with low-dimensional (infinitely thin) fault. In the first model, normal fault with enhanced porosity is generated in the Earth’s crust with Drucker-Prager plasticity. Poroelastic part of the model is verified by simulating fast Biot compressional wave propagation, which determines the mesh and time step sizes used in the simulations; plasticity is verified by modelling shear wave inclination in extension and compression, both showing a good agreement with theoretical predictions. RIS is modelled under typical reservoir impoundment dynamics, producing four seismic sequences, triggered by pore pressure increase at the fault at shallow depth below the reservoir. Coseismic crack opening in a dilatant regime, induces porosity and permeability hikes. In the second model (under construction), the fault is modelled as infinitely thin frictional contact modelled by Mohr-Coulomb failure criterion, allowing for displacement and pore pressure discontinuities at seismic events. Stick-slip instability (demonstrating characteristic displacements, rates, friction coefficient, and state variable patterns) is modelled and verified on a block-slider example. Seismic slip at the fault indicates velocity peaks at the propagating rupture tips. Both models allow investigation of spatio-temporal RIS characteristics and their controls.

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מארגן האירוע: ד"ר ליאור רובננקו