Modeling Induced Microseismicity in an Enhanced Geothermal System

摘要

The analysis of induced microseismicity is one of few tools available for characterizing the effectiveness of hydraulic stimulation in an enhanced geothermal system (EGS). However, the way in which the size, location, and source mechanisms of these events relate to the stimulation process is poorly understood. Using the massively parallel multiphysics code GEOS developed at Lawrence Livermore National Laboratory, we model large-scale mechanical deformation, fluid and heat flow, and fracturing processes using a fully coupled 3D Finite Element model and model the corresponding small-scale microseismicity using a point approximation for a population of pre-existing discontinuities distributed throughout the model domain. In our analysis, we explore the generation of microseismic events at the EGS Demonstration Project site at the Newberry Volcano in Oregon. Because the rock mass at the Newberry EGS is naturally very impermeable, the project operators are borrowing hydraulic fracturing techniques from the oil and gas industry to stimulate the reservoir and maximize energy production. Using the GEOS microseismic model we investigate the competing influences of tectonic stress change and matrix fluid flow, anisotropy and heterogeneity in the surrounding rock mass, the population of pre-existing fractures, and the hydraulic stimulation treatment design.