Block polymers for fluid loss control

Abstract

The present invention relates to the use of a block polymer as fluid loss control agent in a fluid injected under pressure into an oil-bearing rock, where: the fluid comprises solid particles and/or is brought into contact with solid particles within the oil-bearing rock subsequent to its injection, the polymer comprises: a first block which is adsorbed on at least a portion of the particles; and a second block with a composition distinct from that of the first and with a weight-average molecular weight of greater than 10 000 g/mol, for example of greater than 100 000 g/mol, and which is soluble in the fluid.

Claims

1. A process for controlling fluid loss, comprising injecting, under pressure into a subterranean formation, a fluid that comprises solid particles and/or is brought into contact with solid particles dispersed within a fluid downhole subsequent to the injecting and further comprises a block copolymer, wherein said block copolymer is prepared by controlled radical polymerization and comprises: a first polymer block composed of first monomer units, collectively having a weight-average molecular weight between 1,000 and 30,000 g/mol which, at the time of the injecting, is, and/or, after the time of the injecting, becomes adsorbed on at least a portion of the particles; and a second polymer block composed of second monomer units and bonded to the first polymer block, with a monomer composition distinct from that of said first polymer block, with a weight-average molecular weight of greater than 10,000 g/mol and up to 900,000 g/mol which is soluble in the fluid, where the second polymer block comprises at least predominantly monomer units selected from the group consisting of the monomer units U1 to U5 defined below, and mixtures thereof: monomer units U1, each comprising an acrylamide functional group, monomer units U2, each comprising a sulfonic acid or sulfonate functional group, neutral monomer units U3, monomer units U4, each comprising an ammonium group, acrylate monomer units U5, each comprising a COOH or COO group.

2. The process as claimed in claim 1, where the fluid comprises, before the injecting of the fluid into the formation, the block copolymer but does not comprise solid particles, and encounters said particles within the subterranean formation subsequent to the injecting of the fluid into the formation.

3. The process as claimed in claim 1, where the injected fluid comprises, before the injecting of the fluid into the formation, at least a portion of the particles combined with the block copolymer.

4. The process as claimed in claim 1, where the fluid is an aqueous fluid and where the second polymer block further comprises monomer units derived from hydrophobic monomers in a proportion of 0.05% to 10% by weight, with respect to the total weight of monomer units in the second block.

5. The process as claimed in claim 4, where: the particles are particles of calcium carbonate or cement; and the first polymer block is at least predominantly composed of monomer units U5 and/or U3 and/or U6; and the second polymer block is at least predominantly composed of units U1 and/or U2; or the particles are particles of carbonate of silica or sand; and the first polymer block is at least predominantly composed of monomer units U3 and/or U4 and/or U7; and the second polymer block is at least predominantly composed of monomer units U1 and/or U2 and/or U5; or the particles are particles of clay; and the first polymer block is at least predominantly composed of monomer units U4 and/or U6; and the second polymer block is at least predominantly composed of monomer units U1 and/or U2; or the particles are particles of carbon black; and the first polymer block is at least predominantly composed of hydrophobic monomer units U8; and the second polymer block is at least predominantly composed of monomer units U1 and/or U2 and/or U5; where: monomer units U6, each comprising phosphate, phosphonate or phosphinate groups, in the free acid form and/or in the saline form; (meth)acrylate monomer units U7, each functionalized by polydimethylsiloxanes; hydrophobic monomer units U8, including in particular esters of α, β-ethylenically unsaturated mono- or dicarboxylic acids with C1-C20 alcohols, vinylaromatic monomer units, such as styrene, for example, and fluorinated monomer units.

6. The process as claimed in claim 4, where the fluid is an oil cement grout which comprises the block copolymer as additive.

7. The process as claimed in claim 6, where: the second polymer block comprises monomer units U1 comprising an acrylamide functional groups; and the second polymer block has a weight-average molecular weight of between 150,000 and 750,000 g/mol.

8. The process as claimed in claim 7, wherein the second polymer block comprises dimethylacrylamide monomer units; and has a weight-average molecular weight of between 200,000 and 700,000 g/mol.

9. The process as claimed in claim 8, wherein the second polymer block further comprises acrylamidomethylpropanesulfonic acid monomer units.

10. The process as claimed in claim 7, wherein the second polymer block comprises monomer units U1 comprising an acrylamide functional group, and monomer units U2 comprising a sulfonic acid or sulfonate functional group.

11. The process of claim 4, wherein: the neutral monomer units U3 comprise monomer units selected from selected from the group consisting of esters of α, β-ethylenically unsaturated mono- or dicarboxylic acids with C.sub.2-C.sub.30 alkanediols or polyethylene glycols, and tetrahydrofurfuryl acrylate, vinylacetamide, vinylpyrrolidone, N-vinylpiperidone, N-vinylcaprolactam, N-vinyl-5-methyl-2-pyrrolidone, N-vinyl-5-ethyl-2-pyrrolidone, N-vinyl-6-methyl-2-piperidone, N-vinyl-6-ethyl-2-piperidone, N-vinyl-7-methyl-2-caprolactam, and N-vinyl-7-ethyl-2-caprolactam, and the monomer units U4 comprise monomeric units selected from the group consisting of amides of α, β-ethylenically unsaturated mono- or dicarboxylic acids with diamines having at least one primary or secondary amine group; N,N-diallylamines, and N,N-diallyl-N-alkylamines.

12. The process as claimed in claim 4, wherein the second polymer block further comprises monomer units derived from hydrophobic monomers in in a proportion of 0.05% to 10% by weight, with respect to the total weight of monomer units in the second block.

13. The process as claimed in claim 1, where the second polymer block has a molecular weight of greater than 150,000 g/mol.

14. The process as claimed in claim 13, wherein the second polymer block has a molecular weight of between 200,000 and 900,000 g/mol.

15. The process as claimed in claim 1, where the fluid is a drilling fluid or a fracturing fluid which comprises the block copolymer combined with particles.

16. The polymer as claimed in claim 1, wherein the polymer is a block copolymer that comprises only the first and second polymer blocks.

17. The process of claim 1, wherein the second polymer block has a weight-average molecular weight of greater than 100,000 g/mol.

Description

EXAMPLE 1

Synthesis of poly(acrylic Acid)-b-poly(N,N-dimethylacrylamide-co-AMPS) Diblock Copolymers

(1) 1.1: Synthesis of Living Poly(Acrylic Acid) Blocks Having a Xanthate Ending

(2) (Short Blocks A1 to A4)

(3) 30 g of acrylic acid in an aqueous solvent (namely 70 g of distilled water for the blocks A1-A3—a mixture of 35 g of distilled water and 28 g of ethanol for the block A4) and O-ethyl S-(1-(methoxycarbonyl)ethyl) xanthate of formula (CH.sub.3CH(CO.sub.2CH.sub.3))S(C═S)OEt (in the amounts shown in table 1 below, where the value of the theoretical number-average molecular weight expected (M.sub.n, th), calculated by the ratio of the amount of monomer to the amount of xanthate, is also shown) and 312 mg of 2,2′-azobis(2-methylpropionamidine) dihydrochloride were introduced into a 250 ml round-bottomed flask at ambient temperature. The mixture was degassed by bubbling with nitrogen for 20 minutes.

(4) The round-bottomed flask was subsequently placed in an oil bath thermostatically controlled at 60° C. and the polymerization medium was left stirring at 60° C. for 4 hours.

(5) On conclusion of these four hours, the conversion was determined by .sup.1H NMR.

(6) An analysis by size exclusion chromatography in a mixture of water and acetonitrile (80/20) additivated with NaNO.sub.3 (0.1N) with an 18-angle MALS detector provides the weight-average molar mass (M.sub.w) and polydispersity index (M.sub.w/M.sub.n) values given in table 1 below.

(7) TABLE-US-00001 TABLE 1 blocks A1-A4 Block Xanthate Conversion M.sub.w synthesized M.sub.n, th (g) (.sup.1H NMR) (g/mol) M.sub.w/M.sub.n A1 10 000   0.624 99.5% 22 000   1.8 A2 5000 1.25 99.7% 10 000   1.7 A3 2500 2.50 99.6% 5000 1.7 A4 1000 6.24 >99.9% 2100 1.8
1.2: Synthesis of Diblock Copolymers from the Blocks A1 to A5
Polymers P1 to P17

(8) The blocks A1 to A4 prepared as shown in section 1.1 were employed in their reaction medium obtained, without purification, with a weight of polymer w.sub.A given in table 2 below. The chosen block, in its reaction mixture without purification, was introduced into a 250 ml round-bottomed flask at ambient temperature and then N,N-dimethylacrylamide DMA, a 50% by weight aqueous AMPS solution (25% by molar ratio to the amount of N,N-dimethylacrylamide) and distilled water, with a final solids content of approximately 20% by weight, and ammonium persulfate as a 5.0% by weight aqueous solution were added (in amounts given in table 2 below).

(9) The mixture was degassed by bubbling with nitrogen for 20 minutes. Sodium formaldehyde sulfoxylate, in the form of a 1.0% by weight aqueous solution, was added to the medium, the same weight of this solution being introduced as that of the ammonium persulfate solution (see table 2).

(10) The polymerization reaction was allowed to take place without stirring at ambient temperature (20° C.) for 24 hours.

(11) On conclusion of the 24 hours of reaction, the conversion was measured by .sup.1H NMR (results in table 3).

(12) An analysis by size exclusion chromatography in a mixture of water and acetonitrile (80/20 v/v) additivated with NaNO.sub.3 (0.1N) with a refractive index detector provides the number-average molar mass (M.sub.n) and polydispersity index (M.sub.w/M.sub.n) values which are listed in table 3.

(13) TABLE-US-00002 TABLE 2 polymers P1 to P17: amounts of reactants employed during the synthesis Polymer Short block w.sub.A w.sub.DMA w.sub.AMPS w.sub.water w.sub.persulf w.sub.sfs synthesized (g) (g) (g) (g) (g) (g) P1 A1 0.835 15.3 17.7 75.6 6.0 6.0 P2 A1 1.65 15.2 17.6 75.7 6.0 6.0 P3 A1 1.65 6.16 7.12 29.1 3.0 3.0 P4 A1 2.68 5.06 5.85 25.4 3.0 3.0 P5 A1 3.99 5.60 6.47 27.9 3.0 3.0 P6 A1 5.51 5.19 6.00 27.3 3.0 3.0 P7 A2 0.426 15.2 17.6 75.6 6.0 6.0 P8 A2 0.847 15.2 17.6 75.6 6.1 6.3 P9 A2 0.840 6.28 7.27 29.6 3.0 3.0 P10 A2 1.59 5.93 6.86 29.6 3.0 3.0 P11 A2 2.13 5.98 6.91 29.0 3.0 3.0 P12 A2 3.05 5.67 6.55 28.8 3.0 3.0 P13 A3 0.703 25.6 29.6 138.1 3.0 3.0 P14 A3 1.74 25.3 29.3 137.6 3.0 3.0 P15 A4 0.177 31.7 36.6 157.5 12.0 12.0 P16 A4 0.287 25.6 29.6 139 3.0 3.0 P17 A4 0.709 25.3 29.3 138.7 3.0 3.0 P18 A4 5.33 25.3 29.3 138.7 0.5 0.5 w.sub.water: weight of distilled water added, with the exclusion of the water added in the other solutions w.sub.persulf: weight of the 5% by weight aqueous ammonium persulfate solution added w.sub.sfs: weight of the 1% by weight aqueous sodium formaldehyde sulfoxylate solution

(14) TABLE-US-00003 TABLE 3 polymers P1 to P17 Polymer Short Conversion M.sub.w synthesized block DMA AMPS (kg/mol) M.sub.w/M.sub.n P1 A1 99.4% 98.0% 620 5.2 P2 A1 99.7% 99.2% 420 3.2 P3 A1 >99.9%  >99.9%  P4 A1 >99.9%  >99.9%  P5 A1 >99.9%  >99.9%  P6 A1 >99.9%  >99.9%  P7 A2 99.6% 99.8% 600 3.0 P8 A2 99.8% 99.2% 390 3.3 P9 A2 >99.9%  >99.9%  P10 A2 >99.9%  >99.9%  P11 A2 >99.9%  >99.9%  P12 A2 >99.9%  >99.9%  P13 A3 99.7% 98.7% 450 2.3 P14 A3 >99.9%  >99.9%  210 1.9 P15 A4 99.4% 99.6% 760 2.5 P16 A4 99.8% 99.5% 410 2 P17 A4 99.7% 99.4% 180 1.9 P18 A4  >99%  >99% 47.5 1.5

EXAMPLE 2 (COMPARATIVE)

Synthesis of a poly(N,N-dimethylacrylamide-co-AMPS) Monoblock Polymer

(15) 15.3 g of N,N-dimethylacrylamide, 18 g of AMPS, 75.6 g of distilled water, 1.03 g of a 1% by weight ethanolic solution of O-ethyl S-(1-(methoxycarbonyl)ethyl) xanthate of formula (CH.sub.3CH(CO.sub.2CH.sub.3))S(C═S)OEt and 6.0 g of a 5% by weight aqueous ammonium persulfate solution were introduced into a 250 ml round-bottomed flask at ambient temperature. The mixture was degassed by bubbling with nitrogen for 20 minutes.

(16) 6.0 g of a 1% by weight aqueous sodium formaldehyde sulfoxylate solution were subsequently added. The two aqueous ammonium persulfate and sodium formaldehyde sulfoxylate solutions were degassed beforehand by bubbling with nitrogen.

(17) The polymerization reaction was then allowed to take place without stirring at ambient temperature (20° C.) for 24 hours.

(18) On conclusion of the 24 hours of reaction, a 99.8% conversion of N,N-dimethylacrylamide and a 99.6% conversion of AMPS, as determined by .sup.1H NMR, were obtained.

(19) An analysis by size exclusion chromatography in water additivated with NaNO.sub.3 (0.1N) with a refractive index detector provides the following number-average molar mass (M.sub.n) and polydispersity index (M.sub.w/M.sub.n) values (relative to the PEO standards):

(20) M.sub.w=1 070 000 g/mol

(21) M.sub.w/M.sub.n=2.8.

EXAMPLE 3

Evaluation of the Diblock Polymers in Cement Grouts

(22) The diblock polymers P1 to P17 prepared in example 1 and the control prepared in example 2 were used to prepare oil cement grouts having the following formulation:

(23) Municipal water:

(24) 334.4 g
Diblock polymer (at 20% in aqueous solution): 19.5 g
Dispersing agent (polymelamine sulfonate) (at 50% in aqueous solution): 8.6 g
Retarder (calcium lignosulfonate) (at 48% in aqueous solution): 4.4 g
Organic antifoaming agent: 2.1 g
Dykheroff black label cement (API Class G): 781.5 g

(25) The fluid loss control agent is mixed with the liquid additives and with the municipal water before incorporation of the cement.

(26) The formulation and the filtration test were carried out according to the standard of the American Petroleum Institute (API recommended practice for testing well cements, 10B, 2nd edition, April 2013).

(27) After mixing and dispersing all the constituents of the formulation, the grout obtained was conditioned at 88° C. for 20 minutes in an atmospheric consistometer (model 1250 supplied by Chandler Engineering Inc.), prestabilized at this temperature, which makes it possible to simulate the conditions experienced by the cement grout during descent in a well.

(28) The fluid loss control performance was determined by a static filtration at 88° C. in a double-ended cell with a capacity of 175 ml equipped with 325 mesh×60 mesh metal screens (supplied by Ofite Inc., reference 170-45). The performances of the polymers in the cement formulations are given in table 4 below:

(29) TABLE-US-00004 TABLE 4 performances Polymer tested API vol (ml) P18 54 P17 41 P16 40 P15 45 P14 35.8 P13 37.9 P12 193 P11 113 P10 72 P9 66.2 P8 59 P7 70 P6 174 P5 131 P4 67 P3 62 P2 68 P1 62 Comparative examples: Polymer of example 2 655 Polymer of example 2 + block A2 435 (similar composition to that of P8, with the two blocks non-bonded)