Caractérisation d'un milieu poreux colmaté par la méthode du potentiel spontané

Overview & Synopsis

Laboratory experiments are performed on the physical clogging of a porous medium by injecting polydispersive suspended particles ranged from 1.7 to 40 μm in a column filled with sand (d50=715 µm). Three suspensions have been injected (2g/l, 3g/l and 5g/l) at constant flow velocity in a saturated porous medium. Hydrodynamic effects on particles deposition and porous medium damage were investigated. Particles retentions are significant at the inlet and decreases with depth which induces the drop of permeability and porosity. The coupling between electric and hydraulic flows is electrokinetic in nature, the second objective of this work is to test the sensitivity of the method of self-potential (SP) and to show the usefulness of this method to understand the controlling parameters of the electrical field associated with the filtration of suspended particles through a porous medium. Electrodes have been used to record the SP signal which detect and quantify the clay particles in the porous medium during injection tests. The variations of the SP signals are linearly correlated to the piezometric level changes. SP signals are directly sensitive to deposition particles distribution, and it is high at the inlet of the column where the deposit is large and decreases with depth. For the test injection with 2g/l the SP signal varies between +16 mv and +13 mv for the test with 3g/l it varies between +12 mv and +8mv and that with 5g/l it varies between - 22mv to-19mv. When the concentration of clay injected in the porous medium increases, the SP signal decreases and changes from a positive sign to a negative sign. SP method confirmed the behavior of the porous medium clogging obtained by the hydraulic measurements. The obtained results show that SP signal is sensitive to clay particles, their immediate passage to the inlet of the column and the amount deposited particles in each section of the porous medium.