Salt of weak bronsted base and bronsted acid as gelation retarder for crosslinkable polymer compositions

A treatment fluid for use in a subterranean formation, wherein the treatment fluid comprises:

• (a) a water-soluble polymer comprising a copolymer of:
• (i) at least one non-acidic ethylenically unsaturated polar monomer, and
• (ii) at least one polymerizable ethylenically unsaturated ester;
• (b) a polyethyleneimine capable of cross-linking the water-soluble polymer;
• (c) a salt of a weak Bronsted base and a Bronsted acid, wherein the salt of a weak Bronsted base and a Bronsted acid is not a formate or a carbonate and is present in a concentration of at least about 0.1% by weight of water (10 lb/Mgal);
• and
• (d) water;
• wherein the treatment fluid is a crosslinkable polymer solution.

A method for blocking the permeability of a portion of a subterranean formation penetrated by a wellbore, the method comprising the steps of:

• (a) selecting the portion of the subterranean formation to be treated;
• (b) selecting estimated treatment conditions, wherein the estimated treatment conditions comprise temperature over a treatment time;
• (c) forming a treatment fluid that is a crosslinkable polymer composition comprising:
• (i) a water-soluble polymer, wherein the water-soluble polymer comprises a polymer of at least one non-acidic ethylenically unsaturated polar monomer;
• (ii) a polymeric organic crosslinker comprising amine groups, wherein the polymeric organic crosslinker is capable of crosslinking the water-soluble polymer;
• (iii) a salt of a weak Bronsted base and a Bronsted acid, wherein the salt of a weak Bronsted base and a Bronsted acid is not a formate or a carbonate and is present in a concentration of at least about 0.1% by weight of water (10 lb/Mgal);
• and
• (iv) water;
• (d) selecting the water-soluble polymer, the crosslinker, the salt of a weak Bronsted base and a Bronsted acid, and the water, and the proportions thereof, such that the gelation time of the treatment fluid is at least 1 hour when tested under the estimated treatment conditions;
• and
• (e) injecting the treatment fluid through the wellbore into the portion of the subterranean formation.

A method for blocking the permeability of a portion of a subterranean formation penetrated by a wellbore, the method comprising the steps of:

• (a) forming a treatment fluid that is a crosslinkable polymer composition comprising:
• (i) a water-soluble polymer, wherein the water-soluble polymer comprises a polymer of at least one non-acidic ethylenically unsaturated polar monomer;
• (ii) a polymeric organic crosslinker comprising amine groups, wherein the polymeric organic crosslinker is capable of crosslinking the water-soluble polymer;
• (iii) a salt of a weak Bronsted base and a Bronsted acid, wherein the salt of a weak Bronsted base and a Bronsted acid is not a formate or a carbonate and is present in a concentration of at least about 0.1% by weight of water (10 lb/Mgal);
• and
• (iv) water;
• (b) introducing the treatment fluid through the wellbore into the portion of the subterranean formation;
• and
• (c) allowing the crosslinkable polymer composition to form a crosslinked gel in the subterranean formation.