Induced seismicity in pressurised single fractures: a numerical approach

Abstract

The exploration and exploitation of deep geothermal reservoirs has significantly increased during the last years. These reservoirs use heat exchange to produce heat or electricity. The so-called Enhanced Geothermal Systems (EGS) are characterized by a stimulation phase that aims to increase fluid flow and heat transfer between wells by increasing the permeability and transitivity of the reservoir. This is achieved by injecting high-pressure fluids (normally water) in order to increase the apertures of existing fractures, enhancing their sliding and/or generating new ones. However, this technique induces low-magnitude seismicity that occasionally results in damage at the Earth's surface. Numerical simulations able to reproduce the hydro-thermo-mechanical behaviour of geological reservoirs are an essential tool for the evaluation and forecasting of induced seismicity in such systems. In this study, the numerical code CFRAC is used to systematically evaluate how the orientation of faults with respect to the stress field influences seismicity, the injection rate and the fracture sliding behaviour.