The monograph is a vivid illustration of the effectiveness of percolation approach to the modeling of various processes of underground hydromechanics. Examples of consideration of complex problems related to the description of fluid flows in porous media are presented. The results obtained are very interesting not only from the scientific point of view but as the scientific basis for a number of enhanced oil recovery technologies. A percolation model of electrolyte flow in a porous medium is constructed taking into account the effect of a double electric layer on the flow in microcapillaries. On the basis of this model necessary adjustments will be made to the hydrodynamic development models. Percolation model of the hysteresis of the relative permeabilities for any type of collector is presented. The analytic integral expressions obtained make it possible to trace the trends of their dependence on various flow parameters. The analysis of osmotic and ion-exchange processes in the fluids flow in a clay-containing porous medium is carried out. This allowed us to determine the reasons for the increase in oil recovery under the changing of hydrochemical regime of the reservoir.