Fracturing fluids based on associative polymers and on labile surfactants

1. A process for recovery of hydrocarbons in a hydrocarbon reservoir, comprising a step where a fracturing fluid comprising, in an aqueous medium:

an associative polymer suitable for increasing the viscosity of the aqueous medium; and

a labile surfactant, wherein the labile surfactant comprises an ethoxylated fatty acid ester, in an amount sufficient to reduce or inhibit the effect of increasing the viscosity induced by said associative polymer; is injected into a hydrocarbon reservoir where the temperature and/or pH conditions are suitable for lyzing all or some of the labile surfactant;

wherein the associative polymer is made by micellar radical polymerization in which the following are placed in contact, in an aqueous medium:

hydrophilic monomers, dissolved or dispersed in said aqueous medium;

hydrophobic monomers, in the form of a micellar solution that comprises micelles of such hydrophobic monomers dispersed in the aqueous medium;

at least one radical polymerization initiator; and

at least one radical polymerization control agent.

2. The process according to claim 1 , wherein the labile surfactant comprises an ethoxylated fatty acid ester of formula R—COO—(CH 2 —CH 2 —O—) n —H, where R is a linear or branched hydrocarbon chain.

3. The process according to claim 1 , wherein the associative polymer is present in an amount of 0.1% to 3% by weight relative to the total weight of the fracturing fluid.

4. The process according to claim 1 , wherein the micelles further comprise at least one surfactant.

5. The process according to claim 1 , wherein the initiator comprises a water-soluble or water-dispersible initiator.

6. The process according to claim 1 , wherein the radical polymerization control agent comprises a thiocarbonylthio group.

7. The process according to claim 6 , wherein the radical polymerization control agent is a xanthate compound.