Comparison of Discrete Fracture Network with Equivalent Continuum Models for Thermal- Mechanical- Hydraulic Processes in Enhanced Geothermal System, A Benchmark Study

Abstract:

One of the major challenges on simulating of thermal transfer in enhanced geothermal system (EGS) is the determination of geo- structure of the simulated area. The common approaches can be divided into Discrete Fracture Network (DFN) and Equivalent Continuum model (ECM). The DFN employs numbers of fractures whose properties are obviously different than surrounding matrix, while ECM uses the equivalent value from fractures and surrounding matrix as the properties of the simulated domain. In this paper, the 2D thermal- mechanical- hydraulic (THM) model with the geometry of DFN and ECM are built, the influences from stress and thermal induced changes for porosity and permeability are considered. The thermal distribution and temperature at abstraction well are compared. A sensitive study is also done for the DFN for the determination of the influences from fracture density, distribution and connectivity.