Numerical Method of Coupled Deformation-Flow-Advection Analysis of Tracer Response in a Geothermal Reservoir with a Large Planar Dominant Flow Path

Abstract

Dominant fluid flow paths in geothermal reservoirs are deformable due to tectonic stresses and fluid pressure. A numerical method for analysing tracer response is proposed by taking account of deformation of flow path, fluid flow and advective diffusion of tracer concentration. The dominant fluid flow path is supposed as a planar horizontal plane and two wells (the injection and production wells) are connected to the planar flow path. The fluid flow is governed by two equations. One is the equation of continuity which includes two unknowns, i.e. fluid pressure and asperity height. The other is the equation concerning with the asperity height derived from the Hertzian theory of contact. These coupled equations are simultaneously solved by means of a finite difference method. Using the results of fluid flow analysis in the dominant fluid flow path, tracer concentration analysis is made to include the effects of diffusion and adsorption to rock. Total Variation Diminishing (TVD) scheme is applied to solve numerically the equation of tracer concentration. As numerical examples the effects of fluid pressure at the injection well, injection process and diffusion coefficient on the tracer response are discussed.