Sequenced polymers for monitoring the filtrate and the rheology

Abstract

The present invention relates to the use of a sequenced polymer as an agent for monitoring the filtrate and the rheology of a fluid injected under pressure into an oil rock, wherein the fluid comprises solid particles and/or is brought into contact with solid particles within the oil rock after being injected, the polymer comprising: a first block which is adsorbed onto at least some of the particles; and a second block having a composition other than that of the first block and a mean molecular weight of more than 10,000 g/mol, for example more than 100,000 g/mol, and which is soluble in the fluid.

Claims

1. A process comprising injecting a fluid (F) under pressure into a subterranean formation, wherein said fluid (F) comprises solid particles (p) and/or is brought into contact with solid particles (p) within the subterranean formation subsequent to its injection, and a fluid loss control and rheology agent, wherein the fluid loss control and rheology agent is a block polymer (P) comprising: a first block (A) comprising of (meth)acrylate monomer units carrying a COOH or COO— group or esters thereof, which is adsorbed on at least a portion of the particles (p); and a second block (B) with a composition distinct from that of said first block (A), with a weight-average molecular weight of greater than 10 000 g/mol and up to 1 000 000 g/mol, and which is soluble in the fluid (F); and wherein the block polymer (P) has a molecular weight-average weight of greater than 500,000 g/mol and less than 2,500,000 g/mol.

2. The process claimed in claim 1, wherein the polymer reduces or inhibits the sedimentation of the particles while providing a fluid loss control effect.

3. The process claimed in claim 1, wherein the injected fluid (F) does not comprise solid particles (p), and encounters said particles (p) within the subterranean formation subsequent to its injection.

4. The process claimed in claim 1, wherein the injected fluid (F) comprises, before the injection, at least a portion of the particles (p) combined with the polymer (P), the polymer being advantageously employed as dispersing and stabilizing agent for the dispersion of the particles (p).

5. The process claimed in claim 1, wherein the fluid (F) is an aqueous fluid and wherein the block (B) is a block at least predominantly composed of monomer units selected from the group consisting of the monomer units U1 to U5 defined below, and the mixtures of these monomer units: monomer units U1: monomer units comprising an acrylamide functional group, monomer units U2: monomer units comprising a sulfonic acid or sulfonate functional group, monomer units U3: neutral monomer units, monomer units U4: monomer units carrying ammonium groups, monomer units U5: acrylate monomer units carrying a COOH or COO— group, optionally, block (B) comprises hydrophobic monomers in small proportions.

6. The process claimed in claim 1, wherein the fluid (F) is an oil cement grout which comprises the polymer (P) as additive.

7. The process claimed in claim 6, wherein: the block (B) comprises monomer units U1 comprising an acrylamide functional group, and optionally units U2 comprising a sulfonic acid or sulfonate functional group, and the block (B) has the weight-average molecular weight of between 150 000 and 750 000 g/mol.

8. The process claimed in claim 1, wherein the fluid (F) is a drilling fluid or a fracturing fluid which comprises the polymer (P) combined with particles (p).

9. The process claimed in claim 1, wherein the polymer (P) is a polymer prepared by controlled radical polymerization.

10. The fluid claimed in claim 5, wherein the monomer units U3 are esters of α,β-ethylenically unsaturated mono- or dicarboxylic acids with C2-C30 alkanediols or polyethylene glycols, 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 or N-vinyl-7-ethyl-2-caprolactam.

11. The fluid claimed in claim 5, wherein the monomer units U4 are amides of α,β-ethylenically unsaturated mono- or dicarboxylic acids with diamines having at least one primary or secondary amine group; N,N-diallylamines or N,N-diallyl-N-alkylamines.

12. The fluid claimed in claim 5, wherein block (B) comprises hydrophobic monomers in a proportion of 0.05% to 10% by weight, with respect to the total weight of monomer units in the block (B).

13. The fluid claimed in claim 7, wherein block (B) comprises dimethylacrylamide DMA units.

14. The fluid claimed in claim 7, wherein block (B) comprises acrylamidomethylpropanesulfonic acid (AMPS) units.

15. The fluid claimed in claim 7, wherein block (B) has the weight-average molecular weight of between 200 000 and 700 000 g/mol.

16. The process claimed in claim 1, wherein: the particles (p) are particles of calcium carbonate or cement; and the block (A) is at least predominantly composed of monomer units U5; and the block (B) is at least predominantly composed of units U1 and/or U2; wherein: monomer units U1 are monomer units comprising an acrylamide functional group, monomer units U2 are monomer units comprising a sulfonic acid or sulfonate functional group, monomer units U5 are (meth)acrylate monomer units carrying a COOH or COO— group.

Description

EXAMPLE 1

Synthesis of poly(acrylic acid)-b-poly(N,N-di methylacrylamide-co-AMPS) Diblock Copolymers

(1) 1.1: Synthesis of living poly(acrylic acid) blocks having a xanthate ending

(2) (Short Block A)

(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 reaction 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 short block A Block Xanthate Conversion M.sub.w synthesized M.sub.n, th (g) (.sup.1H NMR) (g/mol) M.sub.w/M.sub.n A 1000 6.24 >99.9% 2100 1.8
1.2: Synthesis of Diblock Copolymers from the Short Block A
Polymers P1 to P7

(8) The block A prepared as shown in section 1.1 was employed in its reaction medium obtained, without purification, with a weight of polymer w.sub.A given in table 2 below. The block 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 P7: amounts of reactants employed during the synthesis w of AA Target short Reference M block w.sub.DMA w.sub.AMPS w.sub.water w.sub.persulf w.sub.sfs polymer (kg/mol) (g) (g) (g) (g) (g) (g) P7 10 12.5 28.7 33.2 171.4 2.04 2.04 P6 25 42.5 243.5 281.5 1403 5.76 5.76 P5 50 5.33 25.3 29.3 138.7 0.5 0.5 P4 100 0.709 25.3 29.3 138.7 3.0 3.0 P3 200 0.287 25.6 29.6 139 3.0 3.0 P2 500 0.177 31.7 36.6 157.5 12.0 12.0 P1 1000 0.14 31.6 36.6 180.4 0.4 0.82 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 characterization by SEC of the polymers P1 to P7 Reference Target M M.sub.w polymer (kg/mol) (kg/mol) PI P7 10 33 1.8 P6 25 66 1.5 P5 50 121 1.8 P4 100 286 2.0 P3 200 394 1.4 P2 500 1090 2.2 P1 1000 2500 2.1

EXAMPLE 2

Synthesis of poly(acrylic acid)-b-poly(acrylamide-co-N,N-di methylacrylamide-co-AMPS) Diblock Copolymers

(15) 1.1: Synthesis of Living Poly(Acrylic Acid) Blocks Having a Xanthate Ending

(16) (Short Block A)

(17) 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.

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

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

(20) 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.

(21) TABLE-US-00004 TABLE 1 short block A Block Xanthate Conversion M.sub.w synthesized M.sub.n, th (g) (.sup.1H NMR) (g/mol) M.sub.w/M.sub.n A 1000 6.24 >99.9% 2100 1.8
1.2: Synthesis of Diblock Copolymers from the Short Block A
Polymers P8 to P15

(22) The block A prepared as shown in section 1.1 was employed in its reaction medium obtained, without purification, with a weight of polymer w.sub.A given in table 2 below. The block was introduced into a 250 ml round-bottomed flask at ambient temperature and then a 50% by weight aqueous acrylamide solution, N,N-dimethylacrylamide DMA, a 50% by weight aqueous AMPS solution 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).

(23) 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).

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

(25) 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.

(26) TABLE-US-00005 TABLE 2 polymers P8 to P15: amounts of reactants employed during the synthesis w of AA Target short Reference M block w.sub.Am w.sub.DMA w.sub.AMPS w.sub.water w.sub.persulf w.sub.sfs polymer (kg/mol) (g) (g) (g) (g) (g) (g) (g) P10 200 1.63 67.8 15.8 72.93 269.5 1.29 5.17 P12 200 1.63 43.0 30.0 69.3 283.6 1.29 5.17 P13 200 1.63 20.5 42.9 66.1 296.5 1.29 5.17 P14 200 1.63 10.1 48.9 64.6 302.5 1.29 5.17 P15 200 1.63 4.95 51.8 63.8 305.4 1.29 5.17 w of AA Target short Reference M block w.sub.Am w.sub.DMA w.sub.AMPS w.sub.water w.sub.persulf W.sub.smb polymer (kg/mol) (g) (g) (g) (g) (g) (g) (g) P8 50 2.49 29.7 6.9 32.0 115.5 0.56 2.87 P9 100 1.25 49.6 6.9 32.0 96.9 0.56 2.87 P11 300 0.36 29.7 6.9 32.0 117.6 0.56 2.87 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 0.25% by weight aqueous sodium formaldehyde sulfoxylate solution W.sub.sbm: weight of the 0.25% by weight aqueous sodium metabisulfite solution

(27) TABLE-US-00006 TABLE 3 characterization by SEC of the polymers P8 to P11 Reference Target M M.sub.w polymer (kg/mol) (kg/mol) PI P8 50 94 1.3 P9 100 185 1.3 P10 200 320 1.3 P11 300 630 1.4

EXAMPLE 3

(28) Evaluation of the Diblock Polymers in Cement Grouts

(29) The diblock polymers P2 to P7 prepared in example 1 and the control prepared in example 2 were used to prepare oil cement grouts with a conventional density of 15.8 ppg (1 ppg=0.1205 kg/I) having the following formulation: Municipal water: 334.4 g Diblock polymer (at 20% in aqueous solution): 19.5 g Organic antifoaming agent: 2.1 g Dykheroff black label cement (API Class G): 781.5 g

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

(31) 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).

(32) 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.

(33) The rheology of the cement grouts is subsequently evaluated using a Chandler rotary viscometer (Chan 35 model) at the conditioning temperature of the cement slag. The viscosity is measured as a function of the shear gradient and the rheological profile of the cement slag is interpreted by regarding it as being a Bingham fluid. The characteristic quantities extracted are thus the plastic viscosity (PV, expressed in mPa.Math.s) and the yield point (expressed in lb/100 ft.sup.2). 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:

(34) TABLE-US-00007 TABLE 4 performance levels Reference M.sub.w FL API vol PV Yield point polymer (kg/mol) (ml) (mPa .Math. s) (lb/100 ft.sup.2) P7 33 55 7.5 0 P6 66 55 23 0 P5 121 46 36 0 P4 286 58 81 5 P3 394 44 129 37 P2 1090 52 62 43

(35) The polymers with low molar masses act as dispersing agents with very low to zero viscosities and yield points. In contrast, polymers with high molar masses act as thickeners and reinforce the viscosity and the yield point. These rheology modifications are made while ensuring good control of fluid loss with an API volume which remains very low, approximately 50 ml.

EXAMPLE 4

(36) Evaluation of the Diblock Polymers as Suspending Agent in Low-Density Cement Grouts

(37) High-weight diblock polymers (P1 and P2) are formulated in low-density cement slags in order to evaluate their ability to control the rheology and prevent separation of the cement by settling, while ensuring good control of fluid loss. As in example 3, the slurries are prepared according to the standard of the American Petroleum Institute (API recommended practice for testing well cements, 10B, 2nd edition, April 2013). The formulations are produced using the weights reported in table 5 below.

(38) TABLE-US-00008 TABLE 5 low-density cement formulations Cement grout FLA w diblock density concentration w cement w water polymer (ppg) (% bwoc) (g) (g) (g) 15 0.5 756.9 407.6 3.78 13.75 0.5 614.9 453.1 3.07 12.5 0.5 472.5 498.7 2.36 12.5 0.75 472.5 498.3 3.54 12.5 1 472.5 498.6 4.72

(39) After mixing and dispersing all the constituents of the formulation, the grout obtained was conditioned at 25° C. for 20 minutes in an atmospheric consistometer (model 1250 supplied by Chandler Engineering Inc.), prestabilized at this temperature.

(40) The rheology of the cement grouts is subsequently evaluated using a Chandler rotary viscometer (Chan 35 model) at the conditioning temperature of the cement slag. The viscosity is measured as a function of the shear gradient and the rheological profile of the cement slag is interpreted by regarding it as being a Bingham fluid. The characteristic quantities extracted are thus the plastic viscosity (PV, expressed in mPa.$) and the yield point (expressed in lb/100 ft.sup.2).

(41) The prevention of the sedimentation within the cement slag is evaluated by a “free water” test, which consists in leaving the cement slag to settle out in a graduated measuring cylinder at the test temperature for 2 hours. The procedure for carrying out this test is referenced in the API standard, recommended practice for testing well cements, 10B (2nd edition, April 2013).

(42) The fluid loss control performance was determined by a static filtration at 25° 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 performance levels of the polymers in the cement formulations are given in table 4 below:

(43) TABLE-US-00009 TABLE 6 low-density cements diblock polymers performance levels Cement Yield Free grout FLA point fluid density concentration PV (lb/100 V.sub.API (ml/100 Polymer (ppg) (% bwoc) (mPa .Math. s) ft.sup.2) (ml) ml) P2 15 0.5 75 17 37 0 P2 13.75 0.5 48 4 42 1 P2 12.5 0.5 18 1 70 50 P2 12.5 0.75 27 3 47 40 P2 12.5 1 42 3 36 20 P1 12.5 0.5 27 3 91 15 P1 12.5 0.75 32 9 49 0 P1 12.5 1 39 12 38 0

(44) The example above makes it possible to demonstrate the capacity for suspension of the diblocks of high molar mass, making it possible to ensure a good suspension of the cement slag while making it possible to reduce or eliminate the free fluid on low-density cement slags. This suspension is produced while ensuring good control of fluid loss with low V API volumes.