Polymer composition for inhibiting the formation of inorganic and/or organic deposits in underground formations

Abstract

The invention relates to compositions for inhibiting the formation of deposits in underground formations such as oil wells, comprising, in a solvent medium, polymers P resulting from the radical copolymerization, preferably controlled and in solution, of a mixture including: monomers having an ethylenically unsaturated structure, selected from monomers that form, by polymerization, a polymer that has an effect of inhibiting the formation of organic and/or inorganic deposits; and polyethylenically unsaturated, cross-linking monomers carrying at least one group that can be cleaved between two ethylene unsaturations, said polymers P being present in the solvent in the form of dispersed nanogels.

Claims

1. A composition comprising, in a solvent medium S, chemically crosslinked polymers P resulting from the radical copolymerization of a mixture of monomers including: structuring monomers comprising ethylenically unsaturated monomers m1, selected from monomers which induce the chemically crosslinked polymer P to have an effect of inhibiting organic and/or inorganic deposit formation; and polyethylenically unsaturated monomers m2, bearing at least one group which is cleavable between two ethylenic unsaturations, and a polymerization control agent, wherein the polymerization control agent comprises a thiocarbonylthio group S(CS), wherein the amount of control agent relative to the total amount of monomers (control agent)/(m1+m2) is between 0.1% and 10%; and where said polymers P are present in the solvent medium S in the form of dispersed objects having sizes of less than 100 nm, wherein the monomers m1 are selected from the group consisting of acrylic acid, sodium vinyl sulfonate, styrenesulfonic acid and vinylphosphonic acid; wherein the monomers m2 are acrylic esters, methacrylic esters, diallyl ethers or divinyl ethers of the following dihydric alcohols: 1,2-ethanediol; 1,2-propanediol; 1,3-propanediol; 1,2-butanediol; 1,3-butanediol; 2,3-butanediol; 1,4-butanediol; but-2-ene-1,4-diol; 1,2-pentanediol; 1,5-pentanediol; diethylene glycol; triethylene glycol; tetraethylene glycol; dipropylene glycol; tripropylene glycol; tetrapropylene glycol; 3-thiapentane-1,5-diol; polyethylene glycols and/or polypropylene glycols; and polytetrahydrofurans, these polyols having a molecular weight of between 200 and 10 000; mixtures of two or more of these alcohols.

2. The composition as claimed in claim 1, which is prepared according to a process which comprises a step (E) in which the following are brought together: the ethylenically unsaturated monomers m1; the polyethylenically unsaturated monomers m2 bearing the cleavable function; a source of free radicals; and the polymerization control agent, with a degree of crosslinking, defined by the molar ratio m2/(m1+m2), corresponding to the amount of monomers m2 relative to the total amount of monomers, of between 0.05% and 25%.

3. The composition as claimed in claim 1, wherein the polymers P are obtained via a radical polymerization of the monomers m1 and m2 carried out in solution.

4. The composition as claimed in claim 1, wherein the polymers P comprise cleavable groups, introduced via the use of the monomers m2, which are divalent groups selected from -ester-; -amide-; -ether-; -ether phosphate-; and/or -ether sulfate-groups.

5. The composition as claimed in claim 4, wherein the cleavable groups are ester or amide groups.

6. The composition as claimed in claim 1, wherein the polymers P are present in the form of objects having a radius of gyration of less than 100 nm.

7. The composition as claimed in claim 1, wherein the monomers m2 are diethylene glycol diacrylate (DiEGDA), wherein the polymers P comprise cleavable -ester-groups.

8. A composition comprising, in a solvent medium S, chemically crosslinked polymers P resulting from the radical copolymerization of a mixture of monomers including: structuring monomers comprising ethylenically unsaturated monomers m1, selected from monomers which induce the chemically crosslinked polymer P to have an effect of inhibiting organic and/or inorganic deposit formation, wherein the monomers m1 are selected from the group consisting of acrylic acid, sodium vinyl sulfonate, styrenesulfonic acid and vinylphosphonic acid; and polyethylenically unsaturated monomers m2, bearing at least one group which is cleavable between two ethylenic unsaturations, wherein the monomers m2 are selected from the group consisting of diethylene glycol diacrylate (DiEGDA) and N,N-methylenebisacrylamide (MBA), and a polymerization control agent, wherein the polymerization control agent comprises a thiocarbonylthio group S(CS), wherein the amount of control agent relative to the total amount of monomers (control agent)/(m1+m2) is between 0.1% and 10%; and where said polymers P are present in the solvent medium S in the form of dispersed objects having sizes of less than 100 nm.

9. A method of using a composition as claimed in claim 1, comprising placing the composition into an underground formation containing oil to inhibit formation of inorganic or organic deposits in the underground formation in the context of an oil extraction.

10. The composition as claimed in claim 1, wherein the polymers are present in the solvent in the form of dispersed nanogels having a radius of gyration of 1 to 75 nm.

11. The composition as claimed in claim 1, wherein the polymers are present in the solvent in the form of dispersed nanogels having a radius of gyration of 1 to 50 nm.

12. The composition as claimed in claim 11, wherein the chemically crosslinked polymers P have a degree of crosslinking, defined by the molar ratio m2/(m1+m2), corresponding to the amount of monomers m2 relative to the total amount of monomers, of between 0.05% and 25%.

13. The composition of claim 12, wherein the control agent is O-ethyl-S-(1-methoxycarbonylethyl)xanthate (CH.sub.3CH(CO.sub.2CH.sub.3))S(CS)OEt, and the polymers have chains of approximately the same size, wherein the monomers m2 are diethylene glycol diacrylate (DiEGDA), wherein the polymers P comprise cleavable -ester-groups.

14. The composition as claimed in claim 1, wherein the polymerization control agent comprises a compound of formula (I): ##STR00002## wherein Z is selected from the group consisting of H, Cl, an optionally substituted alkyl or optionally substituted aryl radical, an optionally substituted heterocycle, an optionally substituted alkylthio radical, an optionally substituted arylthio radical, an optionally substituted alkoxy radical, an optionally substituted aryloxy radical, an optionally substituted amino radical, an optionally substituted hydrazine radical, an optionally substituted alkoxycarbonyl radical, an optionally substituted aryloxycarbonyl radical, an optionally substituted carboxyl, acyloxy radical, an optionally substituted aroyloxy radical, an optionally substituted carbamoyl radical, a cyano radical, a dialkyl- or diaryl-phosphonato radical, a dialkyl-phosphinato or diaryl-phosphinato radical, or a polymer chain, and R.sub.1 represents an optionally substituted alkyl, acyl, aryl, aralkyl, alkene or alkyne group, a saturated or unsaturated, aromatic, optionally substituted carbocycle or heterocycle, or a hydrophilic polymer chain, wherein the groups R.sub.1 or Z, when they are substituted, may be substituted with optionally substituted phenyl groups, optionally substituted aromatic groups, saturated or unsaturated carbocycles, saturated or unsaturated heterocycles, or groups selected from alkoxycarbonyl or aryloxycarbonyl (COOR), carboxyl (COOH), acyloxy (O.sub.2CR), carbamoyl (CONR.sub.2), cyano (CN), alkylcarbonyl, alkylarylcarbonyl, arylcarbonyl, arylalkylcarbonyl, phthalimido, maleimido, succinimido, amidino, guanidimo, hydroxyl (OH), amino (NR.sub.2), halogen, perfluoroalkyl C.sub.nF.sub.2n+1, allyl, epoxy, alkoxy (OR), S-alkyl, S-aryl, alkali metal salts of carboxylic acids, alkali metal salts of sulfonic acid, polyethylene oxide, polypropylene oxide, quaternary ammonium salts, R representing an alkyl or aryl group, or a polymer chain; wherein the optionally substituted alkyl, acyl, aryl, aralkyl or alkyne groups generally contain 1 to 20 carbon atoms which are linear or branched and optionally substituted with oxygen atoms.

15. The composition of claim 1, wherein the control agent is O-ethyl-S-(1-methoxycarbonylethyl)xanthate (CH.sub.3CH(CO.sub.2CH.sub.3))S(CS)OEt, and the polymers have chains of approximately the same size.

Description

EXAMPLE 1

(1) Synthesis of an AA-Based Homopolymer (Comparative)

(2) The following are introduced, at ambient temperature, into a 250 ml three-necked round-bottomed flask surmounted by a reflux condenser and equipped with a magnetic stirrer: 2.061 g of O-ethyl-S-(1-methoxycarbonyl ethyl) xanthate, (CH.sub.3CH(CO.sub.2CH.sub.3))S(CS)OEt, Rhodixan A1 manufactured by Rhodia 9.28 g of deionized water 9.28 g of ethanol.

(3) The reaction medium is degassed under nitrogen bubbling for 30 minutes, then the nitrogen stream is maintained above the reaction medium while the polymerization is carried out.

(4) The reaction medium is brought to 70 C. with stirring.

(5) 4.37 g of a solution containing 10% by weight of initiator V50 are then added all at once. Immediately following this, 87.71 g of a solution containing 51% by weight of acrylic acid are continuously added over the course of 3 hours. Simultaneously, 50 g of a solution containing 13.1 g of a solution containing 10% by weight of initiator V50 and 36.9 g of deionized water are continuously added over the course of 3 h 10. Once the addition of the reagents is complete, the reaction medium is maintained at 70 C. with stirring for 1 hour. The heating is then stopped and the reaction medium is allowed to reach ambient temperature before discharging it.

(6) The molar mass measured by .sup.1H NMR is 8761 g/mol. The solids content (115 C., 1 h) is 34.6 w/w %. The degree of conversion measured by HPLC is 100%. The average molar mass measured by GPC-MALLS is 5200 g/mol.

EXAMPLE 2

(7) Synthesis of an AA-Based Homopolymer (Comparative)

(8) The following are introduced, at ambient temperature, into a 250 ml three-necked round-bottomed flask surmounted by a reflux condenser and equipped with a magnetic stirrer: 1.339 g of O-ethyl-S-(1-methoxycarbonyl ethyl)xanthate, (CH.sub.3CH(CO.sub.2CH.sub.3))S(CS)OEt, Rhodixan A1 manufactured by Rhodia 6.02 g of deionized water 6.02 g of ethanol.

(9) The reaction medium is degassed under nitrogen bubbling for 30 minutes, then the nitrogen stream is maintained above the reaction medium while the polymerization is carried out.

(10) The reaction medium is brought to 70 C. with stirring.

(11) 2.84 g of a solution containing 10% by weight of initiator V50 are then added all at once. Immediately following this, 92.02 g of a solution containing 49% by weight of acrylic acid are continuously added over the course of 3 hours. Simultaneously, 50 g of a solution containing 8.51 g of a solution containing 10% by weight of initiator V50 and 41.5 g of deionized water are continuously added over the course of 3 h 10. Once the addition of the reagents is complete, the reaction medium is maintained at 70 C. with stirring for 1 hour. The heating is then stopped and the reaction medium is allowed to reach ambient temperature before discharging it.

(12) The molar mass measured by .sup.1H NMR is 11 691 g/mol. The solids content (115 C., 1 h) is 35.1 w/w %. The degree of conversion measured by HPLC is 100%. The average molar mass measured by GPC-MALLS is 9100 g/mol.

EXAMPLE 3

(13) Synthesis of an AA-Based Nanogel

(14) The following are introduced, at ambient temperature, into a 250 ml three-necked round-bottomed flask surmounted by a reflux condenser and equipped with a magnetic stirrer: 2.061 g of O-ethyl-S-(1-methoxycarbonyl ethyl)xanthate, (CH.sub.3CH(CO.sub.2CH.sub.3))S(CS)OEt, Rhodixan A1 manufactured by Rhodia 9.3 g of deionized water 9.3 g of ethanol.

(15) The reaction medium is degassed under nitrogen bubbling for 30 minutes, then the nitrogen stream is maintained above the reaction medium while the polymerization is carried out.

(16) The reaction medium is brought to 70 C. with stirring.

(17) 4.4 g of a solution containing 10% by weight of initiator V50 are then added all at once. Immediately following this, 107.1 g of an aqueous solution containing 45 g of acrylic acid, 10.7 g of diethylene glycol diacrylate and 51.4 g of deionized water are continuously added over the course of 3 hours. Simultaneously, 60 g of a solution containing 13.1 g of a solution containing 10% by weight of initiator V50 and 46.9 g of deionized water are continuously added over the course of 3 h. Once the addition of the reagents is complete, the reaction medium is maintained at 70 C. with stirring for 1 hour. The heating is then stopped and the reaction medium is allowed to reach ambient temperature before discharging it.

(18) The solids content (115 C., 1 h) is 26.5 w/w %. The degree of acrylic acid conversion measured by HPLC is 100%. The average molar mass measured by GPC-MALLS is 144 400 g/mol.

EXAMPLE 4

(19) Synthesis of an AA-Based Nanogel

(20) The following are introduced, at ambient temperature, into a 250 ml three-necked round-bottomed flask surmounted by a reflux condenser and equipped with a magnetic stirrer: 1.190 g of O-ethyl-S-(1-methoxycarbonyl ethyl)xanthate, (CH.sub.3CH(CO.sub.2CH.sub.3))S(CS)OEt, Rhodixan A1 manufactured by Rhodia 5.4 g of deionized water 5.4 g of ethanol.

(21) The reaction medium is degassed under nitrogen bubbling for 30 minutes, then the nitrogen stream is maintained above the reaction medium while the polymerization is carried out.

(22) The reaction medium is brought to 70 C. with stirring.

(23) 2.52 g of a solution containing 10% by weight of initiator V50 are then added all at once. Immediately following this, 83.7 g of an aqueous solution containing 40 g of acrylic acid, 6.3 g of diethylene glycol diacrylate and 37.3 g of deionized water are continuously added over the course of 3 hours. Simultaneously, 60 g of a solution containing 7.6 g of a solution containing 10% by weight of initiator V50 and 52.4 g of deionized water are continuously added over the course of 3 hours. Once the addition of the reagents is complete, the reaction medium is maintained at 70 C. with stirring for 1 hour. The heating is then stopped and the reaction medium is allowed to reach ambient temperature before discharging it.

(24) The solids content (115 C., 1 h) is 29.3 w/w %. The degree of acrylic acid conversion measured by HPLC is 100%. The average molar mass measured by GPC-MALLS is 65 220 g/mol.

EXAMPLE 5

(25) Synthesis of an AA-Based Nanogel

(26) The following are introduced, at ambient temperature, into a 250 ml three-necked round-bottomed flask surmounted by a reflux condenser and equipped with a magnetic stirrer: 2.061 g of O-ethyl-S-(1-methoxycarbonyl ethyl)xanthate, (CH.sub.3CH(CO.sub.2CH.sub.3))S(CS)OEt, Rhodixan A1 manufactured by Rhodia 9.3 g of deionized water 9.3 g of ethanol.

(27) The reaction medium is degassed under nitrogen bubbling for 30 minutes, then the nitrogen stream is maintained above the reaction medium while the polymerization is carried out.

(28) The reaction medium is brought to 70 C. with stirring.

(29) 4.4 g of a solution containing 10% by weight of initiator V50 are then added all at once. Immediately following this, 107.1 g of an aqueous solution containing 45 g of acrylic acid, 2.2 g of methylenebisacrylamide and 37.3 g of deionized water are continuously added over the course of 3 hours. Simultaneously, 60 g of a solution containing 13.1 g of a solution containing 10% by weight of initiator V50 and 46.9 g of deionized water are continuously added over the course of 3 h. Once the addition of the reagents is complete, the reaction medium is maintained at 70 C. with stirring for 1 hour. The heating is then stopped and the reaction medium is allowed to reach ambient temperature before discharging it.

(30) The solids content (115 C., 1 h) is 30.0 w/w %. The degree of acrylic acid conversion measured by HPLC is 100%. The average molar mass measured by GPC-MALLS is 116 700 g/mol.

EXAMPLE 6

(31) Synthesis of an AA-Based Nanogel

(32) The following are introduced, at ambient temperature, into a 250 ml three-necked round-bottomed flask surmounted by a reflux condenser and equipped with a magnetic stirrer: 2.061 g of O-ethyl-S-(1-methoxycarbonyl ethyl)xanthate, (CH.sub.3CH(CO.sub.2CH.sub.3))S(CS)OEt, Rhodixan A1 manufactured by Rhodia 9.3 g of deionized water 9.3 g of ethanol.

(33) The reaction medium is degassed under nitrogen bubbling for 30 minutes, then the nitrogen stream is maintained above the reaction medium while the polymerization is carried out.

(34) The reaction medium is brought to 70 C. with stirring.

(35) 4.4 g of a solution containing 10% by weight of initiator V50 are then added all at once. Immediately following this, 84.3 g of an aqueous solution containing 45 g of acrylic acid, 2.0 g of methylenebisacrylamide and 37.3 g of deionized water are continuously added over the course of 3 hours. Simultaneously, 60 g of a solution containing 13.1 g of a solution containing 10% by weight of initiator V50 and 46.9 g of deionized water are continuously added over the course of 3 h. Once the addition of the reagents is complete, the reaction medium is maintained at 70 C. with stirring for 1 hour. The heating is then stopped and the reaction medium is allowed to reach ambient temperature before discharging it.

(36) The solids content (115 C., 1 h) is 30.0 w/w %. The degree of acrylic acid conversion measured by HPLC is 100%. The average molar mass measured by GPC-MALLS is 116 700 g/mol.

EXAMPLE 7

(37) Synthesis of an AA-Based Nanogel

(38) The following are introduced, at ambient temperature, into a 250 ml three-necked round-bottomed flask surmounted by a reflux condenser and equipped with a magnetic stirrer: 2.061 g of O-ethyl-S-(1-methoxycarbonyl ethyl)xanthate, (CH.sub.3CH(CO.sub.2CH.sub.3))S(CS)OEt, Rhodixan A1 manufactured by Rhodia 9.3 g of deionized water 9.3 g of ethanol.

(39) The reaction medium is degassed under nitrogen bubbling for 30 minutes, then the nitrogen stream is maintained above the reaction medium while the polymerization is carried out.

(40) The reaction medium is brought to 70 C. with stirring.

(41) 4.4 g of a solution containing 10% by weight of initiator V50 are then added all at once. Immediately following this, 84.3 g of an aqueous solution containing 45 g of acrylic acid, 5.5 g of diethylene glycol diacrylate, 0.5 g of methylenebisacrylamide and 43.6 g of deionized water are continuously added over the course of 3 hours. Simultaneously, 60 g of a solution containing 13.1 g of a solution containing 10% by weight of initiator V50 and 46.9 g of deionized water are continuously added over the course of 3 h. Once the addition of the reagents is complete, the reaction medium is maintained at 70 C. with stirring for 1 hour. The heating is then stopped and the reaction medium is allowed to reach ambient temperature before discharging it.

(42) The solids content (115 C., 1 h) is 29.0 w/w %. The degree of acrylic acid conversion measured by HPLC is 100%. The average molar mass measured by GPC-MALLS is 31 280 g/mol.

EXAMPLE 8

(43) Synthesis of a Nanogel Based on AA and on NaSS

(44) The following are introduced, at ambient temperature, into a 250 ml three-necked round-bottomed flask surmounted by a reflux condenser and equipped with a magnetic stirrer: 2.061 g of O-ethyl-S-(1-methoxycarbonyl ethyl)xanthate, (CH.sub.3CH(CO.sub.2CH.sub.3))S(CS)OEt, Rhodixan A1 manufactured by Rhodia 9.3 g of deionized water 9.3 g of ethanol.

(45) The reaction medium is degassed under nitrogen bubbling for 30 minutes, then the nitrogen stream is maintained above the reaction medium while the polymerization is carried out.

(46) The reaction medium is brought to 70 C. with stirring.

(47) 4.4 g of a solution containing 10% by weight of initiator V50 are then added all at once. Immediately following this, 94.8 g of an aqueous solution containing 45 g of acrylic acid, 9.4 g of diethylene glycol diacrylate and 40.4 g of deionized water are continuously added over the course of 3 hours. Simultaneously, 50 g of a solution containing 13.1 g of a solution containing 10% by weight of initiator V50 and 36.9 g of deionized water are continuously added over the course of 3 h. Once the addition of the reagents is complete, the reaction medium is maintained at 70 C. with stirring for 1 hour. The heating is then stopped and the reaction medium is allowed to reach ambient temperature before discharging it and then adjusting the pH thereof to 3.4 with sodium hydroxide at 50 wt %. This medium is then concentrated under reduced pressure using a rotary evaporator, until a solid concentration of 49.8 wt % is obtained (115 C., 60 min). This solution is reintroduced into the three-necked reactor, and 9.9 g of NaSS are added thereto. The reaction medium is degassed under nitrogen bubbling for 30 minutes, then the nitrogen stream is maintained above the reaction medium while the polymerization is carried out. The reaction medium is brought to 70 C. with stirring.

(48) 8.7 g of a solution containing 10% by weight of initiator V50 are then added all at once. The solution is maintained at 70 C. for 6 hours with stirring and a further 8.7 g of a solution containing 10% by weight of initiator V50 are then added all at once. Once the addition of the reagents is complete, the reaction medium is maintained at 70 C. with stirring for 12 hours. The heating is then stopped and the reaction medium is allowed to reach ambient temperature before discharging it.

(49) The solids content (115 C., 1 h) is 25.9 w/w %. The degree of acrylic acid conversion measured by HPLC is 100%. The average molar mass measured by GPC-MALLS is 105 000 g/mol.

EXAMPLE 9

(50) Synthesis of a Nanogel Based on AA and on VPARef 332

(51) The following are introduced, at ambient temperature, into a 250 ml three-necked round-bottomed flask surmounted by a reflux condenser and equipped with a magnetic stirrer: 2.061 g of O-ethyl-S-(1-methoxycarbonyl ethyl)xanthate, (CH.sub.3CH(CO.sub.2CH.sub.3))S(CS)OEt, Rhodixan A1 manufactured by Rhodia 9.3 g of deionized water 9.3 g of ethanol.

(52) The reaction medium is degassed under nitrogen bubbling for 30 minutes, then the nitrogen stream is maintained above the reaction medium while the polymerization is carried out.

(53) The reaction medium is brought to 70 C. with stirring.

(54) 4.4 g of a solution containing 10% by weight of initiator V50 are then added all at once. Immediately following this, 84.8 g of an aqueous solution containing 45 g of acrylic acid, 9.4 g of diethylene glycol diacrylate and 30.4 g of deionized water are continuously added over the course of 3 hours. Simultaneously, 60 g of a solution containing 13.1 g of a solution containing 10% by weight of initiator V50 and 46.9 g of deionized water are continuously added over the course of 3 h. Once the addition of the reagents is complete, the reaction medium is maintained at 70 C. with stirring for 1 hour. The heating is then stopped and the reaction medium is allowed to reach ambient temperature before discharging it and then adjusting the pH thereof to 2.6 with sodium hydroxide at 50 wt %. This medium is then concentrated under reduced pressure using a rotary evaporator, until a solid concentration of 44.7 wt % is obtained (115 C., 60 min). This solution is reintroduced into the three-necked reactor, and 4.9 g of VPA are added thereto. The reaction medium is degassed under nitrogen bubbling for 30 minutes, then the nitrogen stream is maintained above the reaction medium while the polymerization is carried out. The reaction medium is brought to 70 C. with stirring.

(55) 8.7 g of a solution containing 10% by weight of initiator V50 are then added all at once. The solution is maintained at 70 C. for 6 hours with stirring and a further 8.7 g of a solution containing 10% by weight of initiator V50 are then added all at once. Once the addition of the reagents is complete, the reaction medium is maintained at 70 C. with stirring for 12 hours. The heating is then stopped and the reaction medium is allowed to reach ambient temperature before discharging it.

(56) The solids content (115 C., 1 h) is 20.0 w/w %. The degree of acrylic acid conversion measured by HPLC is 100%. The average molar mass measured by GPC-MALLS is 72 270 g/mol.

(57) Part 2: Properties of the Polymers Prepared

(58) The properties of the polymers synthesized in the above examples were tested as follows:

EXAMPLE 10

(59) Evaluation Under Static Conditions of the (BaSO.sub.4) Scale Formation Inhibition Performance Levels

(60) The polymers prepared were evaluated under static conditions, according to the methodology known as the Jar test or Bottle test, which consists in measuring the level of precipitating cation (calcium or barium) soluble after mixing of two incompatible waters in a flask, then evolution of the mixture without stirring for a given time, and measurement of the soluble cations by a spectroscopic method (ICP-AES). The experiments comprise a controlled test without inhibitor and tests in the presence of inhibitors.

(61) This evaluation is carried out at 95 C. and pH 5.5 after mixing of two brines, one of which has the composition of formation water from the FORTIES field in the North Sea (contains barium) and the other of which has the composition of seawater (contains sulfate). The inhibitor is placed in the seawater. The inhibitor concentration is 15 ppm (of active material) relative to the final mixture.

(62) The pH of the seawater solution containing the inhibitor is brought to approximately 5.5 with a sodium acetate/acetic acid buffer solution.

(63) The compositions of the brines (FORTIES water and seawater) are the following:

(64) FORTIES Water

(65) TABLE-US-00001 Ion mg/l Na.sup.+ 31 275 Ca.sup.2+ 2000 Mg.sup.2+ 739 K.sup.+ 654 Ba.sup.2+ 269 Sr.sup.2+ 771 salt Salt (g/l) NaCl 79.50 CaCl.sub.22H.sub.2O 7.34 MgCl.sub.26H.sub.2O 6.18 KCl 1.25 BaCl.sub.22H.sub.2O 0.48 SrCl.sub.26H.sub.2O 2.35
Seawater

(66) TABLE-US-00002 Ion mg/l Na.sup.+ 10 890 Ca.sup.2+ 428 Mg.sup.2+ 1368 K.sup.+ 460 SO.sub.4.sup.2 2690 salt Salt (g/l) NaCl 24.40 CaCl.sub.22H.sub.2O 1.57 MgCl.sub.26H.sub.2O 11.44 KCl 0.88 Na.sub.2SO4 3.97

(67) 100 ml of each of these waters are conditioned in polyethylene flasks.

(68) After having equilibrated the temperature of the brines at 95 C. in an incubator, the content of the FORTIES water flask is poured into the flask containing the barium. Stirring is carried out manually, then the mixture is put back in the incubator at 95 C. for 2 h.

(69) For each test series, two control tests are carried out: Min blank: this is a test without inhibitor, the barium ion content will be the minimum (maximum precipitation of BaSO.sub.4). Max blank: this is a test without sulfate and without inhibitor, the seawater is replaced with purified water, the barium ion content will be the maximum, since there is no precipitation.

(70) After the 2 hours of the tests, the flasks are removed from the incubator and a 5 ml sample is taken, and then diluted in 5 ml of a soaking solution, the composition of which is: 5000 ppm of KCL/1000 ppm of PVS (sodium Poly(Vinyl Sulfonate)) adjusted to pH 8-8.5 (with 0.01 N NaOH). A barium assay is carried out on these samples (ICP-AES) and the inhibition efficiency, expressed according to the formula below, is deduced therefrom.

(71) $\%\mathrm{efficiency}=\frac{\left[{\mathrm{Ba}}^{2+}\right]-{\left[{\mathrm{Ba}}^{2+}\right]}_{\min }}{{\left[{\mathrm{Ba}}^{2+}\right]}_{\max }-{\left[{\mathrm{Ba}}^{2+}\right]}_{\min }}*100$
with [Ba.sup.2+].sub.max=Ba.sup.2+ concentration in the Max blank [Ba.sup.2+].sub.min=Ba.sup.2+ concentration in the Min blank

(72) The table below groups together the performance levels obtained.

(73) TABLE-US-00003 % efficiency of % efficiency of BaSO.sub.4 inhibition BaSO.sub.4 inhibition inhibitor (15 ppm) (30 ppm) Example 1 p-AA 77 94 Example 2 p-AA 84 93 Example 3 AA-DiEGDA 43 56 nanogel Example 4 AA-DiEGDA 55 71 nanogel Example 5 AA-MBA nanogel 61 75 Example 6 AA-MBA nanogel 45 Example 7 AA-MBA-DiEGDA 73 72 nanogel Example 8 AA/NaSS DiEGDA 67 64 nanogel Example 9 AAA/PA DiEGDA 54 67 nanogel

EXAMPLE 11

(74) Release Capacity of the Nanogels Subjected to a Temperature Increase

(75) This example illustrates the capacity of the nanogels according to the invention to release polymeric units when they are subjected to a temperature increase. Depending on the heat sensitivity of the crosslinking agents present in the nanogel, the release will, for a given temperature, be more or less rapid.

(76) The aqueous solutions of nanogels resulting from the previous examples were tested under the following conditions.

(77) The aqueous solutions are introduced into glass flasks, at their end-of-synthesis pH, and then degassed under nitrogen bubbling for 20 minutes. After the flasks have been closed, they are placed in an incubator for one week at constant temperature (75 C., 85 C. and 95 C.).

(78) Samples are taken at regular time intervals and an analysis by the Gel Permation Chromatography-Multi Angle Laser Light Scattering (GPC-MALLS) method makes it possible to measure, on the samples, the weight-average molecular weight (Mw) of the species present.

(79) The conditions used for the GPC-MALLS are the following: A set of Aquagel-OH Mixed (3*(150*7 5 mm)) columns stationary phase: styrene/divinylbenzene which has been crosslinked mobile phase: buffer solution at pH=7: 100% water, 100 mM NaCl, 25 mM NaH.sub.2PO.sub.4, 25 mM Na.sub.2HPO.sub.4, 100 ppm NaN.sub.3 an RI refractometric detector (Agilent 1100) a MALLS Mini Dawn light scattering detector

(80) Since the pH also has an effect on the rate of hydrolysis of the points of crosslinking and therefore on the rate of release of the polymeric species, the table below specifies the pH of each heat-treated nanogel solution and recalls the weight-average molar mass measured by GPC-MALLS.

(81) TABLE-US-00004 Product Mw (kg/mol) pH Example 3 AA/DiEGDA 144 2.1 Example 7 AA/DiEGDA/MBA 31 2.0 Example 5 AA/MBA 117 2.0 Example 4: AA/DiEGDA 65 2.0 Example 8 AA/NaSS DiEGDA 105 4.9 Example 9: AAA/PA DiEGDA 72 3.2

(82) The tables below group together, for each starting nanogel and each sample, the weight-average molar mass values expressed in kg/mol. Also indicated, in the final column, is the weight-average molar mass corresponding to the noncrosslinked polymeric unit (examples 1 to 4).

(83) TABLE-US-00005 Example 3 Linear 1 2 3 7 10 polymer t = 0 6 h day days days days days Example 1 95 C. 144 85 32 21 18 11 12 5.2 85 C. 144 79 85 35 27 19 17 5.2 75 C. 144 69 55 43 / 35 / 5.2

(84) TABLE-US-00006 Example 4 1 2 3 4 6 Linear t = 0 6 h day days days days days polymer 95 C. 65 42 22 15 14 / / 9.1 85 C. 65 46 31 24 21 19 9.1 75 C. 65 52 36 32 / / 30 9.1

(85) TABLE-US-00007 Example 5 1 2 3 4 7 Linear t = 0 6 h day days days days days polymer 95 C. 117 44 16 14 / / / 7.6 85 C. 117 77 37 22 19 15 9 7.6 75 C. 117 90 61 45 / 28 22 7.6

(86) TABLE-US-00008 Example 7 1 2 3 4 7 Linear t = 0 6 h day days days days days polymer 95 C. 31 24 14 12 / 10 / 7.5 85 C. 31 29 22 16 14 11 9 7.5 75 C. 31 / 28 24 21 / / 7.5

(87) TABLE-US-00009 Example 8 1 2 3 4 7 Linear t = 0 6 h day days days days days polymer 95 C. 105 44 23 16 13 12 9 6.7 85 C. 105 72 39 26 21 18 / 6.7 75 C. 105 89 58 41 34 29 / 6.7

(88) TABLE-US-00010 Example 9 Linear 1 2 3 4 7 polymer t = 0 6 h day days days days days Example 4 95 C. 72 45 27 19 16 / / 6.1 85 C. 72 54 34 26 / 18 13 6.1 75 C. 72 50 43 33 / 21 6.1

EXAMPLE 12

(89) Evaluation Under Static Conditions of the BaSO.sub.4 Inhibition Performance Levels of the Nanogels After Thermal Aging at 150 C.

(90) In this example, the inhibition efficiency of the nanogels was measured after a heat treatment, which once again demonstrates the release of the linear polymeric units, under the conditions hereinafter.

(91) Solutions containing 10% by weight of nanogels in deionized water are prepared, the pH of these solutions is adjusted to 6. These solutions are introduced into Teflon chambers, and then degassed for 30 minutes under nitrogen bubbling. After these Teflon chambers have been closed, they are placed in a steel system, called a Parr bomb, making it possible to work under hydrothermal conditions above 100 C.

(92) These Parr bombs are placed in an incubator at 150 C. for 5 days.

(93) At the end of this heat treatment, the nanogels are evaluated according to the procedure described in example 10 and the BaSO.sub.4 inhibition performance levels thereof are thus evaluated.

(94) The level of polymer in these jar tests is 15 ppm.

(95) The table below groups together the performance levels before and after aging. These results illustrate the capacity of the nanogels to release the linear polymeric species since the performance level of the linear species is found after aging.

(96) TABLE-US-00011 % efficiency of % efficiency of BaSO.sub.4 inhibi- BaSO.sub.4 inhibi- tion (15 ppm) after tion (15 ppm) aging at 150 C. inhibitor before aging for 5 days Example 1 linear pAA 77 81 Example 5 AA/MBA 61 85 nanogel Example 6 AA/MBA 45 80 nanogel

EXAMPLE 13

(97) Adsorption on Alumina and Kaolinite

(98) The clay used as adsorption support is kaolinite. Its specific surface area measured according to the nitrogen BET method is 12 m.sup.2/g.

(99) The alumina used as adsorption support has a specific surface area of 200 m.sup.2/g measured according to the nitrogen BET method.

(100) 1 liter of brine is prepared, the composition of which for 1 liter is the following 2.4 g of NaCl 5.7 g of MgCl.sub.2.6H.sub.2O 1.5 g of CaCl.sub.2.2H.sub.2O

(101) A solution containing 1000 ppm of polymer or nanogel is prepared from this brine. The pH of these solutions is controlled: it is, after adsorption, 5.0 for the alumina support and 3.1 for the kaolinite support.

(102) The solid and also 30 g of solution containing a variable concentration of polymer or nanogel are then placed in glass flasks. For the kaolinite, 2 g of solid are brought into contact with the 30 g of solution; for the alumina, 0.2 g of solid are brought into contact with the 30 g of solution.

(103) The flasks containing the solid and the solution are closed and then stirred by hand and placed in an incubator at 85 C., in which they remain for approximately 15 hours.

(104) After 15 hours of contacting, the supernatant is sampled hot, and the polymer concentration is measured on said supernatant by determining the amount of organic carbon by means of a TOC-meter (LabToc from Pollution & Process Monitoring). This level was also determined on the solutions before contacting.

(105) The level of polymer or of nanogel adsorbed at the surface of the solid is deduced therefrom, through the difference.

(106) The table below groups together the adsorptions measured, expressed in mg/g (mg of polymer or nanogel per g of solid); the C.sub.ini values represent the initial concentrations of polymer in the solution before adsorption, expressed in ppm.

(107) TABLE-US-00012 Amount Adsorbed Amount Adsorbed (mg additive/ (mg additive/ inhibitor g of clay) g of alumina) example 1 p-AA 7.6 115 example 2 p-AA (ref 303) 5.3 133 example 3 AA-DiEGDA 9.3 114 nanogel example 4 AA-DiEGDA 8.6 124 nanogel