A Study of Progressive Failure in Porous Rocks Using Numerical and Experimental Modeling

Abstract

Physical mechanisms governing natural and induced earthquakes are still poorly understood and, despite the relevance, this lack of knowledge limits the usefulness of Geoenergy projects and severely undermines their societal acceptance. Due to the difficulty in retrieving direct measurements and observations to understand these important processes, we study laboratory acoustic emissions in combination with numerical models to shed light on the physics governing seismicity. A dry sample of Berea sandstone was tested to failure under a confining pressure of 40 MPa in a triaxial machine (LabQuake). Using in-house developed conical-type piezo-electric transducers, which are absolutely calibrated and exhibit a flat, broadband response between 100 kHz and 1.5 MHz, we are able to investigate the generated acoustic emission clouds by locating the single events and by inverting for their moment tensor solutions. Furthermore, numerical simulations are performed using a finite difference two-dimensional continuum-based fully coupled thermo-mechanical visco-elasto-plastic numerical modeling tool. We are able to image and locate regions of high stress and strain and, thus, to identify potential nucleation zones of seismic events and compare them at a first order with our experimental results.