Patent ID: 6474413
Filing Date: 2002-11-05
Classification: C09K,E21B

Abstract:
A process for the selective and controlled reduction of the permeability to water in oil-bearing formations of average to high permeability and temperature between 45Â° C. and 110Â° C. traversed by a well for the production of oil and/or gas, wherein said process comprises, for said production well:(a) injecting a slug of cationic polymer aqueous solution in an amount required for adsorption in a certain radius of penetration in the formation, a portion of said aqueous solution creating a polymer layer adsorbed to the formation and containing free positive residual charges, while another portion remains non adsorbed and may be displaced by successive slugs of brine and polymer up to the required radius of penetration; (b) injecting a spacing slug of an aqueous brine solution, so as to displace said non-adsorbed portion of the slug of cationic polymer aqueous solution towards the interior of the formation, whereby will be separated the slug of cationic polymer solution already injected and the slug of anionic polymer aqueous solution to be injected; (c) injecting a slug of anionic polymer aqueous solution in an amount sufficient to create a layer of anionic polymer adsorbed to the said layer of cationic polymer previously adsorbed to the formation rock; (d) injecting a spacing slug of an aqueous brine solution for spacing the polymer slugs and displacing the slug of anionic polymer aqueous solution towards the interior of the formation; (e) repeating the alternating injection of slug of cationic and anionic polymer aqueous solution, the slugs being spaced by the injection of a slug of brine, and provided that the last layer is always a cationic polymer, until the injection pressure of polymer aqueous solution attains the desired value of Residual Resistance Factor to water (RRFw); (f) closing the well for the required time so that the aqueous solution of polymer slug is adsorbed to the formation rock; and (g) resuming well production.