Istopore seminar from Mariangeles Soldi

Dissolution and precipitation processes modify the structure of the porous media at microscale which significantly affects the macroscopic properties of the media. These variations in the pore geometry result in changes in the hydraulic properties that control the groundwater flow and also in the electrokinetic properties associated to the displacement of electrical charges carried by the flow. Therefore the evolution of the streaming potential during dissolution and precipitation can be estimated from the changes in the electrokinetic properties. Under the hypothesis of a uniform dissolution or precipitation of the pores and based on the effective excess charge density approach, we developed a physically-based theoretical model for estimating the effective excess charge density as function of time. The model is derived based on the assumption that the pore structure can be represented by an ensemble of capillary tubes with a smooth periodic variation of their radius and a fractal pore size distribution. The analytical expressions obtained to describe the effective excess charge density also depend on chemical parameters of the fluid and on petrophysical properties and geometrical parameters of the medium. In addition, the periodic variations assumed in the pore geometry allow us to include the hysteresis phenomenon on the electrokinetic properties. The expressions of the proposed model have been compared against available experimental laboratory data.