Numerical Modeling of Liquid-Vapor Coupled Heat and Fluid Flow in Geothermal Reservoirs

Abstract

Liquid-vapor two phase flows in porous media are complex dynamic processes involving phase transitions and phase production due to concurrent processes. The coupled thermo fluid flow with liquid-vapor phase change has received increasing concern recently due to the highly nonlinear behaviors and drastic changes of physical properties. A numerical model is developed for simulating liquid/vapor two-phase coupled fluid and heat flow in porous media, particularly towards hydrothermal/geothermal reservoirs. The model is formulated by two nonlinear equations with pressure and enthalpy as the primary variables. The nonlinearities in the coupled partial differential equations as well as the severe oscillations and instabilities existing in the numerical modeling are investigated. The coupled highly nonlinear equations are solved simultaneously using a Newton based nonlinear finite element technique with the support of a phase change control module and an automatic time step control module. Numerical results are presented to illustrate the effectiveness and usefulness of the proposed model and algorithms.