US 6,474,413 B1Granted

Process for the reduction of the relative permeability to water in oil-bearing formations

AssigneePetroleo Brasileiro S.A. - Petrobras

InventorsLuiz Cesar Ferreira Barbosa, Sérgio Luiz Pereira De Freitas Coelho, Carlos Roberto Carvalho De Holleben, Geraldo Maria Ramos De Godoy

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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.

Claims22

Dependent claims

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 45° C. and 110° 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.

5 more elements

(a) injecting a slug of an anionic polymer aqueous solution in the required amount for adsorption in a certain penetration radius in the formation, a portion of said aqueous solution creating a polymer layer adsorbed to the formation and containing residual free negative charges, while another portion remains non-adsorbed to be displaced by successive layers of brine and polymer until the required penetration radius;
(b) injecting a spacing slug of aqueous brine solution to displace said non-adsorbed portion of the anionic polymer aqueous solution towards the interior of the formation, whereby will be spaced said slug of anionic polymer previously injected and the slug of cationic polymer solution to be injected;
(c) injecting a slug of aqueous solution of cationic polymer, in an amount sufficient to form a layer of cationic polymer adsorbed to the said layer of anionic polymer previously adsorbed to the formation rock;
(d) injecting a spacing slug of aqueous brine solution for spacing between polymer slugs and displacement of the cationic polymer solution towards the interior of the formation;
(e) repeating the alternating injection of slug of anionic and cationic polymer aqueous solution, the slugs being spaced by the injection of brine slug, and provided that the last layer is always made of a cationic polymer, until the injection pressure of the aqueous solution attains a value such that it meets the desired value of the Residual Resistance Factor to water (RRFw);
(f) closing the well during the time required for the slug of polymer aqueous solution to be adsorbed to the formation rock;
and
(g) resuming well production.

5 more elements

Dependencies are inferred from the claim text.

Facts

Application: 09/666,542Filed 21 Sep 2000
Priority: BR 990429422 Sep 1999
Granted: 5 Nov 2002
Term ends: Not estimatedThe source records don’t support an estimate.

Classification5 codes

C09K 8/501
Compositions for plastering borehole walls, i.e. compositions for temporary consolidation of borehole walls: using spacer compositions
C09K 8/512
Macromolecular compounds: containing cross-linking agents
E21B 33/138
Methods or devices for cementing, for plugging holes, crevices or the like: plastering the borehole wall; Injecting into the formation
C09K
Materials for miscellaneous applications, not provided for elsewhere