Use of encapsulated polyamines for limiting fluid loss

1. A method for sealing a subterranean environment, wherein a polyurethane encapsulated polyamine is injected into the subterranean environment, and is released in situ in the presence of a reactive species able to form a gel or a precipitate by a physical association and/or a chemical reaction with the released polyamine; wherein the reactive species is a crosslinkable component able to react with the polyamine and form a tridimensional network.

2. The method of claim 1 , wherein the reactive species comprises more than 2 functional groups able to react with an amine group for forming a chemical bond.

3. The method of claim 2 , wherein the reactive species is selected from the group consisting of polyacrylamide, a partially hydrolysed polyacrylamide, and derivatives thereof.

4. The method of claim 3 , wherein the reactive species is modified with ester functions.

5. The method of claim 4 , wherein the reactive species is modified with t-butylacrylate or methylmethacrylate.

6. The method of claim 2 , wherein the more than 2 functional groups are selected from the group consisting of carbonyl, aldehyde, ketone, carboxylic acid, ester and amide groups.

7. The method of claim 1 , wherein the reactive species is an epoxy compound.

8. The method of claim 1 , wherein the amine groups carried by the polyamine are primary or secondary amine groups.

9. The method of claim 1 , wherein the polyurethane encapsulated polyamine is obtained by a process comprising the steps of:

(E1) providing a reverse emulsion containing:

an oil phase comprising a curable mixture of

isocyanate; and

polyalkyldiene hydroxylated or polyol

dispersed in said oil phase, drops of a water solution or dispersion containing the polyamine,

(E2) pouring the reverse emulsion of step (E1) in a second water phase to make a multiple emulsion water/oil/water, containing, as the internal water phase, drops including the non-amine hydrophilic compound and, then,

(E3) curing into polyurethane all or part of the heat curable mixture contained in the oil phase of the multiple emulsion obtained in step (E2), either at high temperature or at lower temperature.

10. The method of claim 9 , wherein step (E3) is conducted between 50 and 95° C.

11. The method of claim 9 , wherein step (E3) is conducted between 15 and 30° C.

12. The method of claim 9 , wherein step (E3) is conducted at room temperature.