Geothermal reservoir simulation: 2. Numerical solution techniques for liquid‐ and vapor‐dominated hydrothermal systems

摘要: Two numerical models are introduced for simulating three-dimensional, two-phase fluid flow and heat transport in geothermal reservoirs. The first model is based on a three-dimensional formulation of the governing equations Since resulting two partial differential equations, posed terms pressure enthalpy, highly nonlinear inhomogeneous, they require solution. uses finite difference approximations, with fully implicit Newton-Raphson treatment block (vertical slice) successive iterative technique matrix permits use large time steps, while robust method reduces computer execution storage problems. An alternative derived by integration (in vertical dimension) equations. This second explicitly assumes equilibrium (gravity segregation) between steam water can be applied to reservoirs good communication. depth-averaged enthalpy solved two-dimensional that stable sequential solution technique, direct methods, iteration accumulation source terms. quasi-three-dimensional areal should used whenever possible, because it significantly requires less data preparation. includes effects an inclined, variable-thickness reservoir mass energy leakage confining beds. works best thin (<500 m) high permeability. It also problems horizontal anisotropy when permeability sufficiently high. Comparisons higher-order finite, element approximations show some advantage using techniques single-phase In general, upstream weighting diagonal lumping These lead lower-order tend obviate any method.