Selective reduction of water permeability in petroleum rock formations by creation of adsorbed cross-linked polymers to form hydrophilic layers

摘要

Successive injections of plugs of cationic and anionic polymer solutions are effected in a production well to reduce the water permeability of the rock formation. Process for the selective reduction and control of the water permeability in petroleum rock formations with a high permeability and at temperatures between 45 and 110 deg C crossed by a petroleum and/or gas production well, which comprises the stages:- (1) Injection of an aqueous solution plug of a cationic polymer in an amount required for a given radius of penetration in the formation. Part of the aqueous solution creates a layer of adsorbed polymer with residual positive charges whilst another part remains non-adsorbed and can be displaced by further successive plugs of brine and polymer up to the penetration required; (2) Injection of a spacer lug of a solution of brine so as to displace the non-adsorbed part of the cationic polymer solution to the interior of the formation and to separate the polymer solution already injected from the anionic polymer to be injected; (3) Injection of an aqueous anionic polymer solution to create an adsorbed anionic polymer layer on the previous cationic layer; (4) Injection of an aqueous brine solution to space the two polymer solutions and displace the anionic polymer solution towards the interior of the formation; (5) Repetition of the injections of alternating plugs of cationic and anionic solutions with brine spacers, the last layer being a cationic layer, until the injection pressure of aqueous polymer solution attains the required value for the residual resistance factor (RRFw); (6) Shut-down of the well for the time necessary for the aqueous polymer plug to be adsorbed on the rock formation; (7) Re-start of well production.