Viscosifier agent for oilfield fluids in hard conditions

Abstract

The invention relates to aviscosifier useful for oilfield fluids, especially high TDS fluids and heavy brines, comprising: at least a zwitterionic polymer, prepared by inverse emulsion polymerization of: monomers A comprising a betaine group; nonionic monomers B monomers C including a metal ion crosslinkable group with a molar ratio of the monomers A to the monomers B between 4/96 and 40/60; and at least a metal ion compound leading to the crosslinking of the groups carried by monomers C.

Claims

1. A viscosifier for oilfield fluids, comprising: at least one zwitterionic polymer, prepared by inverse emulsion polymerization of: monomers A, each comprising a betaine group; nonionic monomers B; and monomers C, each comprising a metal ion-crosslinkable group, wherein monomers C are each selected from the group consisting of acrylate monomers bearing COOH or COO.sup. groups, monoesters of C4-C10 monoethylenically unsaturated dicarboxylic acids, and mixtures thereof, wherein the polymer comprises from 1 to 10% by weight of monomers C, based on the total weight of the polymer; with a molar ratio of the monomers A to the monomers B between 4/96 and 40/60; and at least one metal ion compound for crosslinking the metal ion-crosslinkable groups of monomers C.

2. The viscosifier of claim 1, wherein the polymer exhibits an intrinsic viscosity greater than 600 mL/g.

3. The viscosifier of claim 1, wherein the monomers A are monomers selected from the group consisting of the following monomers and their mixtures: alkylsulphonates or phosphonates of dialkylammonioalkyl acrylates, dialkylammonioalkyl methacrylates, dialkylammonioalkyl acrylamides, or dialkylammonioalkyl methacrylamides, each comprising a betaine group, heterocyclic betaine monomers, betaines resulting from the reaction of ethylenically unsaturated anhydrides and dienes, and phosphobetaines.

4. The viscosifier of claim 3, wherein the monomers A comprise monomers having one of the following formulae: ##STR00022## in which: R.sup.1 is hydrogen or methyl, R.sup.2 and R.sup.3, which are identical or different, are hydrogen or alkyls having from 1 to 6 carbon atoms, Y.sub.1 is a divalent group of formula O or NR.sub.2, Z.sup.is SO.sub.3.sup., m is 2 or 3, and n is 1-6.

5. The viscosifier of claim 4, wherein the monomers A comprise monomers having one of the following formulae: ##STR00023##

6. The viscosifier of claim 5, wherein the monomers A are SPP and/or SPE monomers.

7. The viscosifier of claim 1, wherein the monomers B are selected from the group consisting in the following monomers and the mixtures thereof: hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate hydroxypropyl methacrylate, acrylamide, methacrylamide, N-methylolacrylamide, dimethylacrylamide, dimethylmethacrylamide, poly(ethylene and/or propylene oxide), if appropriate random or in the block form, -methacrylates, vinyl alcohol, and vinylpyrrolidone.

8. The viscosifier of claim 7, wherein the monomers B are acrylamide.

9. The viscosifier of claim 1, wherein the monomers A are SPP and/or SPE and the nonionic monomers B are acrylamide, with a AM/SPP molar ratio of between 85/15 and 95/5.

10. The viscosifier of claim 1, wherein the at least one metal ion compound comprises a cation of Fe(III) or Al(III).

11. The viscosifier of claim 1, wherein the at least one metal ion compound comprises a cation of Zr(IV) or Ti(IV), or a borate.

12. The viscosifier of claim 1, wherein monomers C are each selected from the group consisting of acrylic acid, methacrylic acid, ethacrylic acid, [alpha]-chloro-acrylic acid, crotonic acid, maleic acid, itaconic acid, citraconic acid, mesaconic acid, glutaconic acid, aconitic acid, fumaric acid, monomethyl maleate, and mixtures thereof.

13. The viscosifier of claim 1, wherein the monomers A are monomers selected from the group consisting of the following monomers and their mixtures: ##STR00024##

14. A process for increasing the viscosity of an oilfield fluid, comprising adding to the fluid: at least one zwitterionic polymer, prepared by inverse emulsion polymerization of: monomers A, each comprising a betaine group; nonionic monomers B; and monomers C each comprising a metal ion-crosslinkable group, wherein monomers C are each selected from the group consisting of acrylate monomers bearing COOH or COO.sup. groups, monoesters of C4-C10 monoethylenically unsaturated dicarboxylic acids, and mixtures thereof; with a molar ratio of the monomers A to the monomers B between 4/96 and 40/60, wherein the polymer comprises from 1 to 10% by weight of monomers C, based on the total weight of the polymer, and at least one metal ion compound for crosslinking the metal ion-crosslinkable groups of monomers C.

15. The process of claim 14, wherein the oilfield fluid is a high total dissolved solids fluid.

16. The process of claim 15, wherein the oilfield fluid is a heavy brine.

17. The process of claim 14, wherein the molar ratio of the monomers A to the monomers B is between 7/93 and 30/70.

Description

EXAMPLES

(1) Part I: Polymer Synthesis

Example 1

(2) The synthesis is performed in two stages: preparation of an emulsion comprising the monomers and the surfactants, followed by a copolymerization.

(3) Preparation of the Emulsion:

(4) 360.42 g of Exxsol D100S (Exxon mobil), 33.97 g of Alkamuls S80 (Solvay), 11.88 g of Alkamuls S20 (Solvay), 7.44 g of Rhodibloc RS (Solvay) and 3.23 g of Hypermer B261 (Croda) are added to a 600 ml glass beaker with magnetic stirring. The mixing is maintained until the solution is clear (Mixture 1). 496.17 g of 50% acrylamide in water, 113.44 g of SPP (Raschig), 29.02 g of acrylic acid sodium salt at 19.74%, 1.82 g of Versene 100E (Dow) and 54.55 g of water are added to a 1000 ml glass beaker with magnetic stirring. The mixing is maintained until the solution is clear (Mixture 2). The mixture 2 is subsequently introduced into the mixture 1 under a magnetic stirring. The stirring is maintained for 10 min and then all the liquid is added to a mixer of rotor/stator type in order to be mixed for 18 min (10000 rpm). The stable emulsion is thus obtained.

(5) Copolymerization:

(6) All the emulsion prepared immediately above is added to a 2 liter jacketed reactor equipped with a nitrogen inlet, a mechanical stirrer, a reflux condenser and a temperature regulation via a thermostatically controlled bath. The temperature of the reaction medium is brought to 30 C. while flushing with nitrogen. 0.36 g of Trigonox 99C75 (Akzo Nobel) is added at 30 C. 4hours after this addition the temperature is increased to 50 C. An additional 0.129 g of Trigonox 99C75 is added during the temperature ramp at 45 C. The temperature of the reaction medium is maintained at 50 C. for 1 h 30. 0.836 g of sodium metabisulfite partially solubilized in 2.057 g of water is subsequently added after 1 hour at 50 C. The combined mixture is collected at ambient temperature.

Example 2

(7) The synthesis is performed in two stages: preparation of an emulsion comprising the monomers and the surfactants, followed by a copolymerization.

(8) Preparation of the Emulsion:

(9) 360.42 g of Exxsol D100S (Exxon mobil), 33.97 g of Alkamuls S80 (Solvay), 11.88 g of Alkamuls S20 (Solvay), 7.44 g of Rhodibloc RS (Solvay) and 3.23 g of Hypermer B261 (Croda) are added to a 600 ml glass beaker with magnetic stirring. The mixing is maintained until the solution is clear (Mixture 1). 496.17 g of 50% acrylamide in water, 113.44 g of SPP (Raschig), 74.87 g of acrylic acid sodium salt at 19.74%, 1.82 g of Versene 100E (Dow) and 8.7 g of water are added to a 1000 ml glass beaker with magnetic stirring. The mixing is maintained until the solution is clear (Mixture 2). The mixture 2 is subsequently introduced into the mixture 1 under a magnetic stirring. The stirring is maintained for 10 min and then all the liquid is added to a mixer of rotor/stator type in order to be mixed for 18 min (10000 rpm). The stable emulsion is thus obtained.

(10) Copolymerization:

(11) All the emulsion prepared immediately above is added to a 2 liter jacketed reactor equipped with a nitrogen inlet, a mechanical stirrer, a reflux condenser and a temperature regulation via a thermostatically controlled bath. The temperature of the reaction medium is brought to 30 C. while flushing with nitrogen. 0.36 g of Trigonox 99C75 (Akzo Nobel) is added at 30 C. 4hours after this addition the temperature is increased to 50 C. An additional 0.129 g of Trigonox 99C75 is added during the temperature ramp at 45 C. The temperature of the reaction medium is maintained at 50 C. for 1 h 30. 0.836 g of sodium metabisulfite partially solubilized in 2.057 g of water is subsequently added after 1 hour at 50 C. The combined mixture is collected at ambient temperature.

Example 3

(12) The synthesis is performed in two stages: preparation of an emulsion comprising the monomers and the surfactants, followed by a copolymerization.

(13) Preparation of the Emulsion:

(14) 398.86 g of Exxsol D100S (Exxon mobil), 37.59 g of Alkamuls S80 (Solvay), 13.15 g of Alkamuls S20 (Solvay), 8.23 g of Rhodibloc RS (Solvay) and 3.57 g of Hypermer B261 (Croda) are added to a 600 ml glass beaker with magnetic stirring. The mixing is maintained until the solution is clear (Mixture 1). 496.17 g of 50% acrylamide in water, 113.44 g of SPP (Raschig), 157.7 g of acrylic acid sodium salt at 19.74% and 1.82 g of Versene 100E (Dow) are added to a 1000 ml glass beaker with magnetic stirring. The mixing is maintained until the solution is clear (Mixture 2). The mixture 2 is subsequently introduced into the mixture 1 under a magnetic stirring. The stirring is maintained for 10 min and then all the liquid is added to a mixer of rotor/stator type in order to be mixed for 18 min (10000 rpm). The stable emulsion is thus obtained.

(15) Copolymerization:

(16) All the emulsion prepared immediately above is added to a 2 liter jacketed reactor equipped with a nitrogen inlet, a mechanical stirrer, a reflux condenser and a temperature regulation via a thermostatically controlled bath. The temperature of the reaction medium is brought to 30 C. while flushing with nitrogen. 0.36 g of Trigonox 99C75 (Akzo Nobel) is added at 30 C. 4hours after this addition the temperature is increased to 50 C. An additional 0.129 g of Trigonox 99C75 is added during the temperature ramp at 45 C. The temperature of the reaction medium is maintained at 50 C. for 1 h 30. 0.836 g of sodium metabisulfite partially solubilized in 2.057 g of water is subsequently added after 1 hour at 50 C. The combined mixture is collected at ambient temperature.

Example 4

(17) The synthesis is performed in two stages: preparation of an emulsion comprising the monomers and the surfactants, followed by a copolymerization.

(18) Preparation of the Emulsion:

(19) 379.56 g of Exxsol D100S (Exxon mobil), 35.77 g of Alkamuls S80 (Solvay), 12.51 g of Alkamuls S20 (Solvay), 7.84 g of Rhodibloc RS (Solvay) and 3.4 g of Hypermer B261 (Croda) are added to a 600 ml glass beaker with magnetic stirring. The mixing is maintained until the solution is clear (Mixture 1). 496.17 g of 50% acrylamide in water, 113.44 g of SPP (Raschig), 120.48 g of maleic acid sodium salt at 19.74% and 1.82 g of Versene 100E (Dow) are added to a 1000 ml glass beaker with magnetic stirring. The mixing is maintained until the solution is clear (Mixture 2). The mixture 2 is subsequently introduced into the mixture 1 under a magnetic stirring. The stirring is maintained for 10 min and then all the liquid is added to a mixer of rotor/stator type in order to be mixed for 18 min (10000 rpm). The stable emulsion is thus obtained.

(20) Copolymerization:

(21) All the emulsion prepared immediately above is added to a 2 liter jacketed reactor equipped with a nitrogen inlet, a mechanical stirrer, a reflux condenser and a temperature regulation via a thermostatically controlled bath. The temperature of the reaction medium is brought to 30 C. while flushing with nitrogen. 0.36 g of Trigonox 99C75 (Akzo Nobel) is added at 30 C. 4hours after this addition the temperature is increased to 50 C. An additional 0.129 g of Trigonox 99C75 is added during the temperature ramp at 45 C. The temperature of the reaction medium is maintained at 50 C. for 1 h 30. 0.836 g of sodium metabisulfite partially solubilized in 2.057 g of water is subsequently added after 1 hour at 50 C. The combined mixture is collected at ambient temperature.

Example 5 (COMPARATIVE)

Non Crosslinkable Copolymer

(22) The synthesis is performed in two stages: preparation of an emulsion comprising the monomers and the surfactants, followed by a copolymerization.

(23) Preparation of the Emulsion:

(24) 365.2 g of Exxsol D100S (Exxon mobil), 34.42 g of Alkamuls S80 (Solvay), 12.04 g of Alkamuls S20 (Solvay), 7.54 g of Rhodibloc RS (Solvay) and 3.27 g of Hypermer B261 (Croda) are added to a 600 ml glass beaker with magnetic stirring. The mixing is maintained until the solution is clear (Mixture 1). 496.17 g of 50% acrylamide in water, 113.44 g of SPP (Raschig) and 1.82 g of Versene 100E (Dow) are added to a 1000 ml glass beaker with magnetic stirring. The mixing is maintained until the solution is clear (Mixture 2). The mixture 2 is subsequently introduced into the mixture 1 under a magnetic stirring. The stirring is maintained for 10 min and then all the liquid is added to a mixer of rotor/stator type in order to be mixed for 18 min (10000 rpm). The stable emulsion is thus obtained.

(25) Copolymerization:

(26) All the emulsion prepared immediately above is added to a 2 liter jacketed reactor equipped with a nitrogen inlet, a mechanical stirrer, a reflux condenser and a temperature regulation via a thermostatically controlled bath. The temperature of the reaction medium is brought to 30 C. while flushing with nitrogen. 0.36 g of Trigonox 99C75 (Akzo Nobel) is added at 30 C. 4hours after this addition the temperature is increased to 50 C. An additional 0.129 g of Trigonox 99C75 is added during the temperature ramp at 45 C. The temperature of the reaction medium is maintained at 50 C. for 1 h 30. 0.836 g of sodium metabisulfite partially solubilized in 2.057 g of water is subsequently added after 1 hour at 50 C. The combined mixture is collected at ambient temperature.

(27) Part II-Rheological Performance: Application Test

Example 6

Evaluations of Polymer Gels Made from Purified Polymers

(28) The polymers are purified by precipitation in acetone and dried. The powders obtained are dissolved at 5 g/l with magnetic stirring. After full hydration of the polymer powder crosslinker is added under high speed magnetic stirring.

(29) The polymers have been used in the solutions of variable salinities described in Table 4 below.

(30) TABLE-US-00002 TABLE 4 Reference Ionic strength (mol/L) Density pH 40% CaCl2 15.2 1.7 3.9 20% CaCl2 6.7 1.19 5.4 20% NaCl 3.9 1.15 6.5

(31) Crosslinkers tested here are Titanium acetylacetonate and iron oxide. Titanium acetyl acetonate is available (commercially from Dorf Ketal under trade name Tyzor AA-75) at 75% active in solution in isopropanol and active TiO2 content is 16.5%.

(32) Iron oxide is solubilised from FeCl3 solid in presence of acetic acid. Solution concentration contains 1% active ferric ions and 1% acetic acid when used in NaCl. For use in CaCl2 brines, ferric or aluminum ions are dissolved in de-ionised water at 1%wt active cation prior use.

(33) Gel rheological properties in 20% NaCl at 95 C. are measured, viscosities at shear rate 0.1 s.sup.1 are reported in table below.

(34) TABLE-US-00003 Sample Crosslinker Crosslinker Viscosity reference type concentration (mPa .Math. s) Example 5 Ref Tyzor AA-75 0 16 Example 5 Ref Tyzor AA-75 1 g/L 18 Example 3 10% AA Tyzor AA-75 0 42 Example 3 10% AA Tyzor AA-75 1 g/L 1200 Example 5 Ref Ferric ion 0 16 Example 5 Ref Ferric ion 50 mg/L 9.3 Example 1 2% AA Ferric ion 0 35 Example 1 2% AA Ferric ion 50 mg/L 720 Example 2 5% AA Ferric ion 0 42 Example 2 5% AA Ferric ion 50 mg/L 1200 Example 3 10% AA Ferric ion 0 42 Example 3 10% AA Ferric ion 50 mg/L 230 Example 4 5% MA Ferric ion 0 7 Example 4 5% MA Ferric ion 50 mg/L 500 Example 4 5% MA Ferric ion 100 mg/L 2300

(35) This series of results demonstrate the ability to crosslink and enhance rheological performance of polymers bearing crosslinkable units in concentrated sodium chloride solution.

(36) Gel rheological properties in 20% CaCl2 at 95 C. are measured; viscosities at shear rate 0.1 s.sup.1 are reported in table below.

(37) TABLE-US-00004 Sample Crosslinker Crosslinker Viscosity reference type concentration (mPa .Math. s) Example 5 Ref Tyzor AA-75 0 15 Example 5 Ref Tyzor AA-75 1 g/L 16 Example 2 5% AA Tyzor AA-75 0 50 Example 2 5% AA Tyzor AA-75 1 g/L 470 Example 3 10% AA Tyzor AA-75 0 35 Example 3 10% AA Tyzor AA-75 1 g/L 782 Example 4 5% MA Tyzor AA-75 0 25 Example 4 5% MA Tyzor AA-75 1 g/L 27 Example 5 Ref Ferric ion 0 15 Example 5 Ref Ferric ion 50 mg/L 20 Example 2 5% AA Ferric ion 0 50 Example 2 5% AA Ferric ion 50 mg/L 450 Example 3 10% AA Ferric ion 0 18 Example 3 10% AA Ferric ion 50 mg/L 200 Example 3 10% AA Ferric ion 100 mg/L 2700 Example 4 5% MA Ferric ion 0 25 Example 4 5% MA Ferric ion 50 mg/L 76 Example 4 5% MA Ferric ion 100 mg/L 1850

(38) This series of results illustrate the ability to crosslink and enhance rheological performance of polymers bearing crosslinkable units in concentrated calcium chloride solution.

Example 7

Evaluations of Polymer Gels Made Without Purification of the Polymer

(39) The polymers of Example 3 and 5, have been dispersed directly in CaCl2 40% brine.

(40) 2 g/L nonionic surfactant Antarox BL240 (Solvay) has been mixed into the brine before introduction of the polymer in inverse emulsion. The amount necessary to obtain 5 g/l of polymer has been dispersed in the brines. These preparations was, in a first step, stirred vigorously by hand for a few moments and then stirred with a magnetic bar for 15 minutes before crosslinker is added under high shear.

(41) Gel rheological properties in 40% CaCl2Cl at 95 C. are measured; viscosities at shear rate 0.1 s.sup.1 are reported in table below.

(42) TABLE-US-00005 Sample Crosslinker Viscosity reference Crosslinker type concentration (mPa .Math. s) Example 5 Ref No crosslinker 0 86 Example 5 Ref Ferric ion 200 mg/L 70 Example 5 Ref Aluminum ion 100 mg/L 80 Example 3 10% AA No crosslinker 0 390 Example 3 10% AA Ferric ion 100 mg/L 690 Example 3 10% AA Ferric ion 200 mg/L 690 Example 3 10% AA Aluminum ion 100 mg/L 1560

(43) These results show the dramatic increase of viscosity once appropriate crosslinker is added to the polymer brine solutions directly dispersed from invert emulsion even with extremely high ionic strength brine.