Numerical formulation for a simulator (CODE_BRIGHT) for the coupled analysis of saline media

Abstract

Salt rocks are being considered as potential recipients for geologic disposal of nuclear waste because of their favourable hydraulic and mechanical properties. In essence, processes controlling the behaviour of salt rocks are similar to those occurring in other media, except that they take place at unusually fast rates. The high solubility of salt in water is one of the causes of these high rates. In fact, creep deformation of wet salts takes place much faster than under dry conditions. This can be explained by means of a mechanism of creep deformation based on salt dissolution, molecular diffusion and precipitation at the pore scale caused by stress concentration[...]. The complex behaviour of saline media requires new theoretical and numerical developments. The study of the basic mechanisms has revealed that coupling between thermal, hydraulic and mechanical problems may be required in some cases. We have developed the governing equations for nonisothermal multiphase flow of brine and gas in deformable saline media. These include mass balance equations for the species in the system (salt, water and air), energy balance equation and stress equilibrium equation. Equilibrium restrictions complete the theoretical formulation. This paper presents a numerical formulation required for solving this complex problem in a practical way. An example of its application is also included.