Content area
Résumé
When a pressure difference is applied to the two ends of a capillary tube containing an electrolyte, the fluid flow will induce an electric current flow. Streaming potential (STP) will result across the capillary tube when there is no net electrical current flow. Conversely when a voltage difference is applied to the two ends of a capillary tube containing an electrolyte, the electric current flow will induce the fluid flow. This is called Electroosmosis (ELO). The electroosmotic counter pressure will result when there is no net fluid flow. We investigated experimentally streaming potential and electroosmosis associated with brine flowing through porous media. Rock and sintered glass beads samples are made in the form of porous plugs which are then saturated with aqueous NaCl solutions.
The experimental set-up is automated through a computer interface. Lock-in amplification and FFT techniques are used and their advantages over conventional DC flow method are demonstrated. Streaming potential and electroosmosis coefficients are measured along with permeability and conductivity. These linear response coefficients give a complete description of electrical and fluid transport properties.
Onsager's relations are verified in our experimental data. We then propose a new way of measuring the throat size and the permeability of the porous materials. We also find when we change the electrolyte concentration, the surface properties of different samples show a different characteristics. We will propose a method to detect the thickness of a mudcake using STP frequency spectrum.
