Gelled aqueous composition for oil extraction
The present invention relates to the field of oil extraction. More specifically, it relates to a particular polymerization process, which provides access to formulations of polymers that may be used in particular for modifying rheology and fluid loss control during extraction operations and that have a better heat stability.
1. A process for preparing a polymer, the process comprising a micellar radical polymerization step (E) wherein the following are brought into contact, in an aqueous medium (M):
monomers (m1), dissolved or dispersed in said aqueous medium (M), termed hydrophilic monomers (m1);
monomers (m2) in the form of a micellar solution, namely a solution containing, in dispersed form in the aqueous medium (M), micelles comprising these monomers (m2), termed hydrophobic monomers (m2);
wherein said monomers (m1) and/or (m2) comprise crosslinking monomers (mR) comprising at least two ethylenic unsaturations, wherein the crosslinking monomers (mR) comprise hydrophilic crosslinking monomers (mR1) and/or hydrophobic crosslinking monomers (mR2);
at least one radical polymerization initiator; and
optionally, at least one radical polymerization control agent
wherein the concentration of crosslinking monomers (mR) is from 100 ppm to 1000 ppm, by weight relative to the total weight of all the monomers present in the aqueous medium (M).
2. The process as claimed in claim 1 , wherein step (E) is carried out in the presence of hydrophobic monomers (m2) which comprise, hydrophobic crosslinking monomers (mR2).
3. The process as claimed in claim 1 , wherein step (E) is carried out in the presence of hydrophilic monomers (m1), only a part of which consists of hydrophilic crosslinking monomers (mR1).
4. The process as claimed in claim 1 , wherein the process comprises a step (E2) after step (E), wherein the polymers obtained at the end of step (E) are milled, as a result of which the polymers are obtained in the form of dispersed particles.
5. The process as claimed in claim 1 , wherein the mole ratio (mR)/(m1), corresponding to the amount of crosslinking monomers (mR) relative to the total amount of hydrophilic monomers, is between 0.01 and 0.1%.
6. The process as claimed in claim 1 , wherein the radical polymerization control agent is a compound which comprises a thiocarbonylthio —S(C═S)— group.
7. The process as claimed in claim 1 , wherein the hydrophobic crosslinking monomers (mR2) are selected from the group consisting of divinylbenzene (DVB), and derivatives thereof.
8. The process according to claim 1 , wherein the hydrophilic crosslinking monomers (mR1) are chosen from selected from the group consisting of N,N′-methylenebisacrylamide (MBA), polyethylene glycol (PEG) diacrylate, triacrylate, divinyl ether, and derivatives thereof.
9. The process as claimed in claim 2 , wherein step (E) is carried out in the presence of hydrophobic monomers (m2) which consist exclusively of hydrophobic crosslinking monomers (mR2).
10. The process as claimed in claim 5 claim 1 , wherein the concentration of monomers (mR) is from 200 to 600 ppm by weight relative to the total weight of all the monomers present in the medium (E).
11. The process as claimed in claim 6 , wherein the radical polymerization control agent is a compound which comprises a xanthate group.
12. The process as claimed in claim 1 , wherein the at least one radical polymerization initiator is water-soluble or water-dispersible.