Numerical investigation of cyclic hydraulic stimulation and related induced seismicity in Pohang fractured geothermal reservoir

摘要

In this study we investigate numerically the flow rate controlled cyclic stimulation experiment performed in August 2017 at the Pohang EGS site using the finite element code FracMan. Per definition, a soft stimulation method aims to increase permeability while reducing the risk of inducing larger seismic events. The numerical code enables studying hydro-mechanical processes and investigating main characteristics of induced seismicity such as spatial evolution of events and their moment magnitude in relation to injected fluid volume in three dimensions. The analysis contributes to understanding the fracturing processes and induced seismicity in naturally compartmentalized fractured reservoir. The code can be also used for predicting the relationship between fluid injection volume and spatial extent of generated or reactivated fractures, i.e. the stimulated reservoir volume. The reservoir model will eventually allow different injection strategies to be investigated to design an optimal stimulation procedure ahead of future field application of soft stimulation. Furthermore, it may also serve as a basis for future numerical investigations.