Physical mechanism of pressure gradient influence on filtration processes in rocks with mixed type of wettability

The paper analyzes the features of the distribution of oil and water phases in the pore space of rocks with a mixed type of wettability. It is shown that when a two-phase fluid moves through an elementary micro-volume of a porous medium, the pore space of which is represented by both hydrophilic and hydrophobic channels, one of these adjacent channels can be saturated with only one of the phases in a mobile form. It is established that the change in the water saturation of the pore space over the area of productive formations during their flooding is the reason for the strong dependence of the residual oil saturation of the rock on the displacement pressure gradient. Hence, in particular, it follows that sealing drilling technologies used to increase oil recovery and increase the values of displacement pressure gradients in rocks with a mixed type of wettability will be more effective. Keywords: mixed type of wettability; flooding of productive formations; residual oil saturation.