Abstract: This paper attempts an in-depth analysis on the hydrodynamic behavior of clays considering the multiple driving forces of pressure and induced electrical potential (IEP). Electrokinetics is employed to quantify the processes of ion migration, fluid motion, and potential distribution, which are described by the coupled equations of the Nernst-Planck (NP), the Navier-Stokes (NS), and the Poisson-Boltzmann (PB), respectively. The numerical investigation shows that employment of Debye-Huckel approximation may be inappropriate for clays in calculation of double layer potential since their relatively high surface charge density. IEP is caused by the requirement of electroneutrality for the clay-water system, and is directly proportional to the separation of cation-anion resulting from the differential hydraulic migratability between them. IEP contributes to decelerating cation, accelerating anion, and producing a negative electroosmosis that counteracts in partial the positive flow driven by pressure. At those conditions including low concentration, small porosity, and high surface charge density, double layer effects may be enhanced, leading to significant effects both in IEP and its flow reduction.

Key words: electrokinetics, coupling, electric double layer.