URTeC: 2154641 Characterizing the Dynamic Growth of a Fracture Network Ted Urbancic *, Lindsay Smith Boughner, John W. Crowley, Adam M. Baig, and Eric von Lunen + Engineering Seismology Group Canada, + Nexen Energy ULC Copyright 2015, Unconventional Resources Technology Conference (URTeC) DOI 10.15530/urtec-2015-2154714 This paper was prepared for presentation at the Unconventional Resources Technology Conference held in San Antonio, Texas, USA, 20-22 July 2015. The URTeC Technical Program Committee accepted this presentation on the basis of information contained in an abstract submitted by the author(s). The contents of this paper have not been reviewed by URTeC and URTeC does not warrant the accuracy, reliability, or timeliness of any information herein. All information is the responsibility of, and, is subject to corrections by the author(s). Any person or entity that relies on any information obtained from this paper does so at their own risk. The information herein does not necessarily reflect any position of URTeC. Any reproduction, distribution, or storage of any part of this paper without the written consent of URTeC is prohibited. Summary In this paper, we discuss an approach that utilizes microseimicity associated with hydraulic fracture stimulations to characterize the evolution of deformation over time and the behavior of the rock mass. In applying these concepts through examples we look at moving beyond conventional static interpretations to reveal processes that play important roles in the dynamic expansion of a fracture network. Here, we introduce a parameterization that considers the diffusivity of the observed microseismicity that can be related to the ease in which the inelastic seismic deformation field can diffuse (Difusivity Index), the degree of deformation for a given stress and therefore the susceptibility of a rock mass to fracturing (Fracability Index), and the Seismic Efficiency, which is related to the energy budget of the failure process as related to the presence of fluids as opposed to stress-induced failures. Based on our observations, we suggest that Fracability Index can be used to identify regions of deformation and high stress associated with potential barriers to flow. Further, heterogeneity in the Diffusivity Index can be related to the advancement of the frac whereas Seismic Efficiency is a good indicator of stimulation extent, defining differences between stress induced and fluid induced fracturing. Our observations suggest that these dynamic parameters can be used to characterize the dynamic growth of fracture networks and assess design stimulation effectiveness. Introduction At the most basic level microseismic analysis reveals the position of events in space and provides a snapshot of what is happening at any given time. Some of these events are directly related to the injection of fluid/proppant and others are due to changes in the far-field stress. Both the engineering (treatment) parameters and the stress field are dynamic and change with time and as such, there is a great deal of information that can be obtained by considering the spatiotemporal dynamics of the processes involved. With the start of hydraulic fracturing microseismic events tend to occur at increasing distance from the perf zone and can be considered to mimic a diffusive process. The introduction of proppant can result in an increased proportion of events further from the perf zone as well as localized events behind the extending frac near the perf zone. Generally, the total lateral extent of growth and the success of a hydraulic fracture depends on the characteristics of the rock formation, the pre-existing fracture network, the treatment program, and the underlying physics of hydraulic fracturing. Generally, as deformation proceeds in a rock mass the amount of stress required for a given strain (stiffness) can change. End member cases include a purely brittle material (stress drops to zero at failure) and elastic-plastic material (stress remains constant past the yield stress and strain increases). Strain-hardening (stiffness increases) or softening (stiffness decreases) may occur past the yield stress of a given material due to changes occurring on the from increased deformation, poro-elastic effects, due to the response of the enclosed fluid, as well as the matrix