Ammonium halide 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 polyethylene imine capable of cross-linking the water-soluble polymer;
• (c) an ammonium halide;
• 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, wherein the bottomhole temperature of the portion of the subterranean formation is equal to or greater than 250° F. (121° C.);
• (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 east one non-acidic ethylenically unsaturated polar monomer;
• (ii) an organic crosslinker capable of crosslinking the water-soluble polymer;
• (iii) an ammonium halide;
• and
• (iv) water;
• (d) selecting the water-soluble polymer, the crosslinker, the ammonium halide, and the water, and the proportions thereof, such that the gelation time of the treatment fluid is at least 2 hours when tested under the estimated treatment conditions;
• and
• (e) injecting the treatment fluid through the wellbore into the portion of the subterranean formation.