Description of Geothermal Simulator Geotherm: A Finite Difference Model of Three-Dimensional, Single- and Two-Phase Heat Transport in a Porous Medium

摘要

Characterization of multiphase geothermal reservoir behavior generally requires a three-dimensional description of the system, because of the significant effects of gravity segregation between steam and water. In this study we have developed two approaches for simulating the three-dimensional behavior of geothermal reservoirs. The more general model is based on full three-dimensional numerical approximations to the governing equations. These equations, describing the behavior of both one- and two-phase geothermal reservoirs, were derived from the balance equations for mass, momentum, and energy in porous media. This development yielded two nonlinear partial differential equations posed in terms of fluid pressure and enthalpy. Unfortunately, three-dimensional models are expensive in terms of both computer execution time and data requirements. To obtain a more economical, though less general, alternative, the three-dimensional equations were partially integrated in the vertical dimension, resulting in a quasi-three-dimensional areal model posed in terms of depth-averaged pressure and enthalpy. The vertically averaged parameters in the areal model were evaluated by assuming either depth-uniform properties or vertical equilibrium, that is, gravity segregation. The areal model included effects of an inclined variable-thickness reservoir and mass and energy leakage to confining beds. (ERA citation 13:003276)