Abstract: A process for the selective and controlled reduction of permeability to water in oil-bearing formations made up of sandstone or limestone, the process comprising the injection of a slug of polymer aqueous solutions having a polarity opposite to the polarity of the rock, followed by the injection of a spacing slug of alkaline halide and then a fresh slug of polymer aqueous solution, the polarity of which is opposite to the polarity of the first polymer slug, and then a slug of aqueous solution of trivalent metal crosslinking agent to effect the partial crosslinking of the polymer charges, the polymer layers being successively added until the injection pressure of the polymer aqueous solutions show that the desired Residual Resistance Factor RRF was attained, and well production may be resumed.

Abstract: A process and apparatus are provided to enhance the recovery of petroleum from onshore and offshore reservoirs. The process includes the simultaneous stimulation of the formation by elastic sound waves, created by a sonic source installed at the oil well so that the elastic sonic waves which are superimposed reduce the adherence forces in the layer between oil/water and the rock formation, and by the oscillating electrical stimulation of the same layer, as from the same wells subject to sonic treatment. The electricity heats the formation by using resistive heating, and thus increases the pressure, thus eliminating the surface tensions between the faces of the fluid as a consequence of the oscillatory action of the ions in the surfaces of the fluid and in addition, reducing the viscosity of the fluids.