Numerical simulation of fluid flow and energy transport in liquid- and vapor-dominated hydrothermal systems

A mathematical model for simulating the pressure, temperature and phase-saturation behavior of geothermal reservoirs was derived on the basis of the balance equations for mass, momentum, and energy in porous media. With appropriate assumptions these equations were combined, and they reduced to two nonlinear partial-differential equations in which the dependent, unknown variables were fluid pressure and enthalpy. These resulting equations were valid for both single- and two-phase hydrothermal systems. Two alternative numerical models (Galerkin, finite-element and finite-difference) were developed for solving the combined pressure-enthalpy equations.