A model for deep geothermal brines : state space description and thermodynamic properties : a thesis presented in partial fulfilment of the requirements for the degree of Ph.D. in Mathematics at Massey University
To facilitate the simulation of heat and fluid transport in deep geophysical environments, this thesis proposes correlations for calculation of density, enthalpy and viscosity values for brine (H2O + NaCl) over a wide range of temperature T, pressure p and mass fraction of sodium chloride X. Although geothermal fluids are not pure H2O-NaCl systems, they are mainly composed of H2O and NaCl and in this thesis we model geothermal fluids as brines. Firstly T-p-X state space delineations of such a model fluid are described. Then using experimental and calculated data, approximate correlations for the three properties are given in terms of the primary variables T, p and X. These correlations cover the entire T-p-X state space and can be used in subroutines suitable for use in numerical simulation programs. The case of one-dimensional, steady vertical flows is described and our correlations for the state space delineations and the thermodynamic properties are tested on such flows.