Numerical Simulation of Geothermal Reservoir Systems with Multiphase Fluids

Abstract

This paper describes a modular framework for simulating geothermal well and reservoir performance. The numerical model is able to account for transient, three-dimensional, single- or two-phase fluid flow in normal heterogeneous or fractured-matrix formations. Both conductive and convective heat flow are accounted for and fluid states in the reservoir can range between liquid phase, two-phase steam-water mixtures to superheated steam. Both short term well reaction and long term reservoir performance can be monitored as dynamic mass/heat flow processes. Equations-of-state (EOS) for water and CO2 are integrated as part of the fully-coupled nonlinear finite element simulator. In this paper, the code has been applied for use in geotechnical risk assessments for mine developments in geothermal areas. Comparison of EGS-CO2 and EGS-water is demonstrated in the paper and results show that the simulator PANDAS/ThermoFluid can be used for both conventional geothermal fields and enhanced geothermal systems.