A Three-Dimensional Poroelastic Model for Naturally Fractured Geothermal Reservoir Stimulation

Abstract

One of the most important tasks for geothermal reservoir development is engineering a fractured reservoir and predicting its future performance. For this purpose, numerical modeling of fluid flow and deformation of fractured rock is necessary. This work focuses on utilizing a stochastic fracture network to simulate the thermal-hydro-mechanical response of the reservoir during the stimulation process, and to assess the permeability enhancement in the stimulated zone. The reservoir stimulation process is simulated using a system of rock blocks some of which contain stochastically-distributed fractures and fractured zones. The effect of the fractures on permeability is introduced into the model by using the equivalent permeability approach. The rocks matrix is assumed to be poroelastic and the fractures are allowed to deform and to slip. Heat transport within the fractures, and heat conduction between adjacent rock mass and the fluid in the fracture are also considered. A series of simulations are carried out to analyze the rock mechanical response and permeability evolution for a Newberry-type reservoir. Results show the significant role of fracture distribution and its mechanical deformation in EGS design and development. This model provides a tool to predict the performance of natural fracture networks, and to analyze the stimulation response and future production performance.