Modified Theoretical Model for Temperature-Dependent Electro-Kinetic Properties of Porous Media

I report theoretical modelling of streaming potential coefficient C sp and zeta potential ζ in porous media with NaCl electrolytes as a function of temperature up to 150°C. The modelling captures the essential behaviour of both C sp and ζ as a function of both temperature, salinity and pH, the latter of which also depends on temperature and salinity. The modelling also shows ζ which is negative, decreasing in magnitude with temperature, and as pH becomes smaller. It also shows that C sp is also negative but has a complex temperature and pH dependence. These behaviours are controlled mainly by the temperature dependence of pH, but also depend on the temperature dependence of the density, viscosity, relative permittivity and electrical conductivity of the pore solution. The model has been compared to experimental data for sandstones up to 150°C, and describes the data reasonably well when using physically reasonable values for the electro-chemical parameters describing the electrical double layer. This modelling has implications for the calculation of electro-kinetic parameters in geothermal reservoirs, CCUS targets and radioactive storage underground.