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  • C08F220/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical or a salt, anhydride ester, amide, imide or nitrile thereof
  • C08F220/02—Monocarboxylic acids having less than ten carbon atoms; Derivatives thereof
  • C08F220/10—Esters
  • C08F220/26—Esters containing oxygen in addition to the carboxy oxygen
  • C08F220/28—Esters containing oxygen in addition to the carboxy oxygen containing no aromatic rings in the alcohol moiety
  • C08F220/285—Esters containing oxygen in addition to the carboxy oxygen containing no aromatic rings in the alcohol moiety and containing a polyether chain in the alcohol moiety
  • C08F220/286—Esters containing oxygen in addition to the carboxy oxygen containing no aromatic rings in the alcohol moiety and containing a polyether chain in the alcohol moiety and containing polyethylene oxide in the alcohol moiety, e.g. methoxy polyethylene glycol (meth)acrylate
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  • C08G65/00—Macromolecular compounds obtained by reactions forming an ether link in the main chain of the macromolecule
  • C08G65/02—Macromolecular compounds obtained by reactions forming an ether link in the main chain of the macromolecule from cyclic ethers by opening of the heterocyclic ring
  • C08G65/26—Macromolecular compounds obtained by reactions forming an ether link in the main chain of the macromolecule from cyclic ethers by opening of the heterocyclic ring from cyclic ethers and other compounds
  • C08G65/2603—Macromolecular compounds obtained by reactions forming an ether link in the main chain of the macromolecule from cyclic ethers by opening of the heterocyclic ring from cyclic ethers and other compounds the other compounds containing oxygen
  • C08G65/2606—Macromolecular compounds obtained by reactions forming an ether link in the main chain of the macromolecule from cyclic ethers by opening of the heterocyclic ring from cyclic ethers and other compounds the other compounds containing oxygen containing hydroxyl groups
  • C08G65/2609—Macromolecular compounds obtained by reactions forming an ether link in the main chain of the macromolecule from cyclic ethers by opening of the heterocyclic ring from cyclic ethers and other compounds the other compounds containing oxygen containing hydroxyl groups containing aliphatic hydroxyl groups
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  • C09K8/00—Compositions for drilling of boreholes or wells; Compositions for treating boreholes or wells, e.g. for completion or for remedial operations
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  • C09K8/00—Compositions for drilling of boreholes or wells; Compositions for treating boreholes or wells, e.g. for completion or for remedial operations
  • C09K8/58—Compositions for enhanced recovery methods for obtaining hydrocarbons, i.e. for improving the mobility of the oil, e.g. displacing fluids
  • C09K8/588—Compositions for enhanced recovery methods for obtaining hydrocarbons, i.e. for improving the mobility of the oil, e.g. displacing fluids characterised by the use of specific polymers
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  • C09K8/00—Compositions for drilling of boreholes or wells; Compositions for treating boreholes or wells, e.g. for completion or for remedial operations
  • C09K8/60—Compositions for stimulating production by acting on the underground formation
  • C09K8/602—Compositions for stimulating production by acting on the underground formation containing surfactants
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  • C09K8/00—Compositions for drilling of boreholes or wells; Compositions for treating boreholes or wells, e.g. for completion or for remedial operations
  • C09K8/60—Compositions for stimulating production by acting on the underground formation
  • C09K8/62—Compositions for forming crevices or fractures
  • C09K8/66—Compositions based on water or polar solvents
  • C09K8/68—Compositions based on water or polar solvents containing organic compounds
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  • C09K8/00—Compositions for drilling of boreholes or wells; Compositions for treating boreholes or wells, e.g. for completion or for remedial operations
  • C09K8/60—Compositions for stimulating production by acting on the underground formation
  • C09K8/84—Compositions based on water or polar solvents
  • C09K8/86—Compositions based on water or polar solvents containing organic compounds
  • C09K8/88—Compositions based on water or polar solvents containing organic compounds macromolecular compounds
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  • C09K8/00—Compositions for drilling of boreholes or wells; Compositions for treating boreholes or wells, e.g. for completion or for remedial operations
  • C09K8/60—Compositions for stimulating production by acting on the underground formation
  • C09K8/92—Compositions for stimulating production by acting on the underground formation characterised by their form or by the form of their components, e.g. encapsulated material
  • C09K8/94—Foams
• • C—CHEMISTRY; METALLURGY
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  • C08F220/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical or a salt, anhydride ester, amide, imide or nitrile thereof
  • C08F220/02—Monocarboxylic acids having less than ten carbon atoms; Derivatives thereof
  • C08F220/52—Amides or imides
  • C08F220/54—Amides, e.g. N,N-dimethylacrylamide or N-isopropylacrylamide
  • C08F220/56—Acrylamide; Methacrylamide

Definitions

• the present invention relates to the use of a water-soluble hydrophobically associating copolymer as an additive in the development, exploitation and completion of underground mineral oil and natural gas deposits and in deep drillings.
• a copolymer of the above mentioned type is described in WO 201 1/015520 A1 with priority of 06.08.2009, published on 10.02.201 1 .
• That international patent application concerns a water-soluble, hydrophobically associating copolymer which is obtained in the presence of an non-polymerizable tenside, and processes for the preparation thereof and uses thereof.
• the specific applications und uses as described and claimed in this present patent application have not been recognized and described in that prior international patent application.
• Water-soluble thickening polymers are used in many fields of industry, for example in the field of cosmetics, in foods, for production of detergents, printing inks and emulsion paints, but especially in mineral oil production.
• hydro- phobically associating polymers are water-soluble polymers which have lateral or terminal hydrophobic groups, for example relatively long alkyl chains. In aqueous solution, such hydrophobic groups can associate with each other or with other substances having hydrophobic groups. This forms an associative network by which the medium is thickened.
• hydrophobically associating polymers are water-soluble polymers that contain a small number (less than one mole percent) of hydrophobic groups attached directly to the polymer backbone. This definition shall be adhered to for the purpose of the present patent application, keeping in mind, however, that one mole percent can be as much as ten or even twenty percent by weight of that hydrophobic groups.
• hydrophobically associating polymers An important area of use of these hydrophobically associating polymers is in the field of mineral oil production, especially of tertiary mineral oil production (enhanced oil recovery, EOR). Details of the use of hydrophobically associating copolymers for tertiary mineral oil production are described, for example, in the review article by Taylor, K.C. and Nasr-EI-Din, H.A. in J. Petr. Sci. Eng. 1998, 19, 265-280.
• polymer flood- ing Another of the techniques of tertiary mineral oil production is known as "polymer flood- ing".
• a mineral oil deposit is not an underground “lake of mineral oil”, but rather the mineral oil is held in tiny pores of the mineral oil-bearing rock. The diameter of the pores in the formation is typically only a few micrometers.
• polymer flooding an aqueous solution of a thickening polymer is injected through injection boreholes into a mineral oil deposit. The injection of the polymer solution forces the mineral oil through said cavities in the formation from the injection borehole proceeding in the direction of the production borehole, and the mineral oil is produced via the production borehole.
• aqueous polymer solution as opposed to pure water prevents channels of different permeability from forming in the course of flooding of the underground for- mation (known as "fingering"), as a result of which the other underground regions would not be flooded.
• fingering channels of different permeability from forming in the course of flooding of the underground for- mation
• the addition of the polymer to the aqueous phase reduces the mobility thereof and leads as a result to a more homogeneous flooding operation.
• hydroaulic fracturing A further technique in mineral oil production is known as "hydraulic fracturing".
• hy- draulic fracturing for example, a high-viscosity aqueous solution is injected under high pressure into the oil- or gas-bearing formation layer. The high pressure gives rise to cracks in the rock, which facilitates the production of oil or gas.
• the thickeners used here are in particular guar and the more thermally stable derivatives thereof, for example hydroxypropylguar or carboxymethylhydroxypropylguar (J. K. Fink, Oil Field Chemi- cals, Elsevier 2003, p. 240 ff).
• Foamed fluids are used in hydraulic fracturing, both as “proppants” and as “diverting agents” (Burman et al., 1986, DOI: 10.21 18/15575-MS; Parlar et al., 1995, DOI:
• the foam is said to remain stable over the entire treatment. Differ- ent factors influence the stability of the foam, including the viscosity, the chemical composition of the foam formers, the formation temperature and the gas phase.
• the aqueous polymer solution contains no gel particles at all. This is because even small gel particles with dimensions in the micrometer range can block the fine pores in the formation and hence stop the mineral oil production. Hydrophobically associating copolymers for mineral oil production should therefore have a minimum proportion of gel particles.
• the aim is for the polymers to achieve an increase in the viscosity of the water, which ideally corresponds to the viscosity of the hydrocarbons to be produced.
• Hydrophobically associating water-soluble copolymers are frequently prepared by what is known as micellar copolymerization. This involves solvating water-insoluble comonomers by the addition of surfactants in the aqueous reaction medium and reacting them with hydrophilic comonomers, for example acrylamide, to give a water-soluble hydrophobically associating copolymer.
• hydrophilic comonomers for example acrylamide
• the surfactant used in both cases is sodium dodecylsulphonate (SDS).
• SDS sodium dodecylsulphonate
• a further example of a micellar copolymerization is given by J. Colloid Interf. Sci. 2009, 333, 152-163. Acrylamide is reacted here with a polypropylene glycol methacrylate in the presence of SDS.
• WO 85/03510 describes water-soluble hydrophobically associating copolymers of an ethylenically unsaturated water-soluble monomer and of an ethylenically unsaturated amphiphilic monomer with hydrophobic groups. These copolymers are ob- tained by reaction of water-soluble monomers, for example acrylamide, and amphiphilic monomers, for example dodecylpolyoxyethylene (10) methacrylate.
• the amphiphilic comonomers are characterized as water-soluble at room temperature but water-insoluble at elevated temperature or the temperature used in the preparation of the copolymers, for example of 60°C.
• a surfactant or emulsifier is added here too if re- quired, i.e. when the polymerization is effected at elevated temperature, in order to ensure the solubility of the amphiphilic comonomer under the polymerization conditions.
• the monomer is then no longer a water-soluble variant.
• a further method for preparation of water-soluble hydrophobically associating copoly- mers is the use of surface-active water-soluble comonomers. These comonomers have a hydrophobic component which brings about the hydrophobically associating effect in the copolymer, and a hydrophilic component which ensures the water solubility of the comonomer.
• the advantage of this process is that no additional surfactant is needed for solvation of the hydrophobically associating monomer.
• J. Appl. Polym. Sci. 1999, 74, 21 1-217 discusses the use of a cationic wa- ter-soluble hydrophobically associating comonomer which has been obtained by reacting 2-methacryloyloxyethyldimethylamine with 1 -bromododecane.
• Canadian patent 2,196,908 is concerned with associating monomers and polymers.
• At the forefront of this document are essentially emulsion polymers of methacrylic acid, ethyl acrylate and a monomer which has been obtained by reaction of dimethyl-m- isoprenylbenzyl isocyanate (DMI) and EIM or polybutylene oxide or polybutylene oxide- co-polyethylene oxide.
• DMI dimethyl-m- isoprenylbenzyl isocyanate
• EIM polybutylene oxide or polybutylene oxide- co-polyethylene oxide.
• water-insoluble and nonhydro- philic monomers for example ethyl acrylate.
• hydrophobically associating copolymers when used as thickeners in the field of mineral oil production have the disadvantage that the viscosity decreases with rising temperature. Since the use of these polymers in mineral oil production usually takes place at elevated temperature, this is a particularly serious disadvantage.
• a further disadvantage of the above-described and commercially available hydrophobically associative polymers is the high gel content thereof, which forms in the course of dissolution and can block porous formations.
• This problem has already been partly solved with copolymers according to our prior international patent application WO 2010/133527 A2 with priority of 20.05.2009, published 25.1 1.2010. The gel contents were reduced markedly therein, but not avoided entirely.
• hydrophobically associative polymers with improved properties compared to the already known hydrophobically associating copolymers.
• Our above mentioned prior international patent application WO 201 1/015520 A1 provides a hydrophobically associating copolymer with low or undetectable gel content.
• the object of this present invention was to examine whether this copolymer is suitable for use as an additive in the development, exploitation and completion of underground mineral oil and natural gas deposits and in deep drillings, for example in hydraulic fracturing, as a thickener or stabilizer of foams, and as a thickener of completion fluids, spa- cer fluids and drilling muds under the conditions customary in underground formations.
• This object is achieved by the features of the independent claim.
• the dependent claims relate to preferred embodiments.
• the copolymer described in our above mentioned prior international patent application WO 201 1/015520 A1 has an advantageous viscosity profile and is particularly suitable, for example, as a thickener for completion fluids, spacer fluids and drilling muds, hydraulic fracturing and foams, since the viscosity of this copolymer increases with rising temperature up to a maximum at approx. 60 °C.
• the present invention thus provides for the use of a hydrophobically associating copolymer as an additive in the development, exploitation and completion of underground mineral oil and natural gas deposits and in deep drillings, wherein the copolymer comprises
• H 2 C C(R 1 )-R 4 -0-(-CH2-CH2-0-)k-(-CH 2 -CH(R 3 )-0-)i-R 5 (I), and/or
• R1 H or methyl
• R2 an aliphatic and/or aromatic, straight-chain or branched hydrocarbyl radical having 8 to 40 carbon atoms
• R3 each independently a hydrocarbyl radical having at least 2 carbon atoms
• R4 a single bond or a divalent linking group selected from the group of -(C n H 2n )- [R 4a ], -0-(Cn-H 2 n')- [R 4b ] and -C(0)-0-(C n "H 2n ")- [R 4c L where n, n' and n" are each integers from 1 to 6,
• R5 H or a Ci-3o-hydrocarbyl radical, preferably H or a Ci-5-alkyl radical and particu- larly H,
• the copolymer is obtainable through copolymerization of the monomers (a) and (b) in the presence of at least one surfactant (c).
• the term "nonpoly- merizable surfactant" as used herein has been chosen for clarity reasons. Surfactants, as a rule, are nonpolymerizable compounds. By using this term, it is meant to clarify that the surfactant (c) will not become chemically bound to, in or by the copolymer of the invention.
• hydrophobically associating copolymers can be prepared without the addition of a surfactant, since all comonomers used therein are water-soluble. It was therefore all the more surprising that, in the copolymer according to WO 201 1/ 015520 A1 , the addition of a surfactant during the aqueous solution polymerization of hydrophilic monomers with a water-soluble hydrophobically associating co- monomer achieved a distinct improvement in the polymer properties, especially the thickening action, and also significantly reduced the gel content. Without wanting to be bound by theory, this effect can probably be explained as follows:
• the hydrophobically associating comonomer forms micels in the aqueous reaction medium.
• the effect of this is that the hydrophobically associating regions are incorporated blockwise into the polymer.
• an additional nonpolymerizable surfactant is present in the course of preparation of the co- polymer, preferably already before the initiation of the polymerization reaction, mixed micelles form. These mixed micelles thus contain polymerizable comonomer and nonpolymerizable sufractant.
• the hydrophobically associating monomers are then incorporated in shorter blocks. At the same time, the number of these shorter blocks per polymer chain is greater.
• the polymer constitution of the copolymer according to WO 201 1/015520 A1 differs distinctly from the prior art copolymers, as a result of which the performance properties thereof also improve significantly.
• the inventive hydrophobically associating copolymers are water-soluble copolymers which contain a small number of hydrophobic groups.
• the hydro- phobic groups can associate with themselves or with other substances having hydrophobic groups, and thicken the aqueous medium by virtue of this interaction.
• water- soluble especially also includes alkali-soluble dispersions of polymers, i.e. polymers which are present as dispersions in the acidic pH range and only in the alkaline pH range dissolve in water and display their thickening action.
• the copolymers of the invention should be miscible with water in any ratio. According to the invention, however, it is sufficient when the copolymers are water-soluble at least at the desired use concentration and at the desired pH.
• the solubility in distilled water at room temperature (20 °C) should be at least 20 g/l, preferably at least 50 g/l and more preferably at least 100 g/l.
• inventive hydrophobically associating copolymers therefore comprise, in addition to the hydrophobic groups already mentioned, hydrophilic groups in such an amount that the water solubility outlined is ensured at least in the pH range envisaged for the particular use.
• the inventive hydrophobically associating copolymer comprises at least one mono- ethylenically unsaturated monomer (a) which imparts hydrophobically associating properties to the copolymer of the invention and is therefore referred to hereinafter as "hydrophobically associating monomer".
• the at least one monoethylenically unsaturated water-soluble monomer (a) is at least one compound of the general formulas (I) and/or (II) as defined hereinabove.
• the polyoxy- alkylene radical may thus have a terminal OH group.
• R 1 is H or a methyl group.
• R 4 is a single bond or a divalent linking group selected from the group of -(C n H 2n )- [R 4a ], -0-(C n 'H 2n ')- [R 4b ] and -C(0)-0-(Cn"H 2n ")- [R 4c ]-
• n, n' and n" are each natural numbers from 1 to 6.
• the -(C n H 2n )-, -(C n 'H 2n ')- and -(C n "H 2n ")- groups are preferably linear aliphatic hydrocarbyl groups.
• R 4a is preferably a group selected from -CH 2 -, -CH 2 -CH 2 - and -CH 2 -CH 2 -CH 2 -, more preferably a methylene group -CH 2 -.
• R 4b is preferably a group selected from -0-CH 2 -CH 2 -, -0-CH 2 -CH 2 -CH 2 - and -0-CH 2 - CH 2 -CH 2 -CH 2 -, more preferably -0-CH 2 -CH 2 -CH 2 -CH 2 -.
• R 4c is preferably a group selected from -C(0)-0-CH 2 -CH 2 -, -C(0)0-CH(CH 3 )-CH 2 -, -C(0)0-CH 2 -CH(CH 3 )-, -C(0)0-CH2-CH 2 -CH2-CH 2 - and -C(0)0-CH2-CH 2 -CH2-CH 2 - CH2-CH2-, more preferably -C(0)-0-CH 2 -CH 2 - and -C(0)0-CH2-CH 2 -CH2-CH 2 - and most preferably -C(0)-0-CH 2 -CH 2 -.
• the R 4 group is more preferably an R 4a or R 4b group, more preferably an R 4b group.
• R 4 is more preferably a group selected from -CH2- and -O-CH2-CH2-CH2- CH2-, most preferably -O-CH2-CH2-CH2-CH2-.
• the monomers of the formula (I) also have a polyoxyalkylene radical which consists of the units -(-Chb-Chb-O- - and -(-CH2-CH(R 3 )-0-)i- where the units are arranged in block structure in the sequence shown in formula (I). The transition between the two blocks may be abrupt or else continuous.
• the number of alkylene oxide units k is a number from 6 to 150, preferably 12 to 100, more preferably 15 to 80, even more preferably 20 to 30 and, for example, approx. 22 to 25.
• the R 3 radicals are each independently hydrocarbyl radicals of at least 2 carbon atoms, preferably at least 3 and more preferably 3 to 10 carbon atoms. This may be an aliphatic and/or aromatic, linear or branched carbon radical. It is preferably an aliphatic radical.
• R 3 radicals comprise ethyl, n-propyl, n-butyl, n-pentyl, n-hexyl, n- heptyl, n-octyl, n-nonyl or n-decyl, and phenyl.
• suitable R 3 radicals comprise n-propyl, n-butyl, n-pentyl, particular preference being given to an n-propyl radical.
• the -(-CH2-CH(R 3 )-0-)i- block is thus a block which consists of alkylene oxide units having at least 4 carbon atoms, preferably at least 5 carbon atoms, and/or glycidyl ethers having an ether group of at least 2, preferably at least 3, carbon atoms.
• Preferred R 3 radicals are the hydrocarbyl radicals mentioned; the units of the second terminal block are more preferably alkylene oxide units comprising at least 5 carbon atoms, such as pentene oxide units or units of higher alkylene oxides.
• the number of alkylene oxide units I is a number from 5 to 25, preferably 6 to 20, more preferably 8 to 18, even more preferably 10 to 15 and, for example, approx. 12.
• a monoethylenic group is joined to a polyoxyal- kylene group with block structure, specifically firstly to a hydrophilic block having polyethylene oxide units, which is in turn joined to a second terminal hydrophobic block formed at least from butene oxide units, preferably at least pentene oxide units, or units of higher alkylene oxides, for example dodecene oxide.
• the second block has a terminal OH group.
• the end group is thus not etherified with a hydrocarbyl radical for the hydrophobic assocation, but rather the terminal -(-CH2-CH(R 3 )-0-)i- block with the R 3 radicals is itself responsible for the hydrophobic association of the copolymers prepared using the monomers (a) of the formula (I).
• the R 5 radical is H or a preferably aliphatic hydrocarbyl radical having 1 to 30 carbon atoms, preferably 1 to 10 and more preferably 1 to 5 carbon atoms.
• R 5 is preferably H, methyl or ethyl, more preferably H or methyl and most preferably H.
• the monomer representatives (I) and (II) may be involved in any proportions in the structure of the copolymer.
• the first block -(-CH 2 -CH 2 0-)k- When the block boundary is fixed at the middle of the transition zone, it is possible for the first block -(-CH 2 -CH 2 0-)k- to have small amounts of -CH 2 -CH(R 3 )-0- units and for the second block -(-CH 2 -CH(R 3 )-0-)i- to have small amounts of -CH 2 -CH 2 -0- units, although these units are not arranged randomly over the block but are arranged in the transition zone mentioned.
• the monomers (a) are water-soluble.
• the solubil- ity of the monomers (a) in distilled water at room temperature (20 °C) should be at least 10 g/l, preferably at least 50 g/l and more preferably at least 100 g/l.
• the amount of the monoethylenically unsaturated, hydrophobically associating monomers (a) is guided by the particular end use of the inventive copolymer and is generally 0.1 to 20% by weight based on the total amount of all monomers in the copolymer. The amount is preferably 0.5 to 15% by weight.
• the inventive hydrophobically associating copolymer comprises at least one different monoethylenically unsaturated hydrophilic mono- mer (b). It is of course also possible to use mixtures of a plurality of different hydrophilic monomers (b).
• the hydrophilic monomers (b) comprise, in addition to an ethylenically unsaturated group, one or more hydrophilic groups.
• the hydrophilic groups are especially functional groups which comprise oxygen and/or nitrogen atoms. They may additionally comprise especially sulphur and/or phosphorus atoms as heteroatoms.
• the monomers (b) should be miscible with water in any ratio, but it is sufficient for execution of the invention that the hydrophobically associating copolymer of the invention has the water solubility mentioned at the outset.
• the term "hydrophilic" in connection with monomer (b) means that the solubility of monomer (b) in distilled water at room temperature (20 °C) should be at least 100 g/l, preferably at least 200 g/l and more preferably at least 500 g/l.
• acidic groups such as carboxyl groups -COOH, sulpho groups -SO3H, phosphonic acid groups -PO3H2 or phosphoric acid groups -OP(OH)3.
• Examples of preferred functional groups include hydroxyl groups -OH, carboxyl groups -COOH, sulpho groups -SO3H, carboxamide groups -C(0)-NH2, amide groups
• n is preferably a number from 1 to 200.
• the functional groups may be attached directly to the ethylenically unsaturated group, or else joined to the ethylenically unsaturated group via one or more linking hydrocarbyl groups.
• the at least one hydrophilic monomer (b) is preferably a monomer comprising acidic groups, where the acidic groups, in accordance with the invention, comprise at least one group selected from the group of -COOH, -SO3H and -PO3H2. Preference is also given to monomers of the general formula where R 7 is H or methyl and R 8 is a hydrophilic group or a group comprising one or more hydrophilic groups.
• the R 8 groups are groups which comprise heteroatoms in such an amount that the water solubility defined at the outset is attained.
• suitable monomers (b) include monomers comprising acidic groups, for example monomers comprising -COOH groups, such as acrylic acid or methacrylic acid, crotonic acid, itaconic acid, maleic acid or fumaric acid, monomers comprising sulpho groups, such as vinylsulphonic acid, allylsulphonic acid, 3-allyloxy-2-hydroxy- propanesulphonic acid, 2-acrylamido-2-methylpropanesulphonic acid (AMPS®), 2- methacrylamido-2-methylpropanesulphonic acid, 2-acrylamidobutanesulphonic acid, 3- acrylamido-3-methylbutanesulphonic acid or 2-acrylamido-2,4,4- trimethylpentanesulphonic acid, or monomers comprising phosphonic acid groups, such as vinylphosphonic acid, allylphosphonic acid,
• N-(meth)acrylamidoalkylphosphonic acids or (meth)acryloyloxyalkylphosphonic acids are N-(meth)acrylamidoalkylphosphonic acids or (meth)acryloyloxyalkylphosphonic acids.
• acrylamide and methacrylamide and derivatives thereof for example N-methyl(meth)acrylamide, N,N'-dimethyl(meth)acrylamide and N-methylolacrylamide, N-vinyl derivatives such as N-vinylformamide, N-vinylacetamide, N-vinylpyrrolidone or N-vinylcaprolactam, and vinyl esters such as vinyl formate or vinyl acetate.
• N-Vinyl derivatives can be hydrolysed after polymerization to vinylamine units, and vinyl esters to vinyl alcohol units.
• the R 9 radicals are each independently H, methyl or ethyl, preferably H or methyl, with the proviso that at least 50 mol% of the R 9 radicals are H. Preferably at least 75 mol% of the R 9 are H, more preferably at least 90 mol%, and they are most preferably exclusively H.
• the R 10 radical is H, methyl or ethyl, preferably H or methyl.
• the individual alkylene oxide units may be arranged randomly or in blocks. In the case of a block copolymer, the transition between the blocks may be abrupt or gradual.
• Suitable hydrophilic monomers (b) are also monomers having ammonium groups, especially ammonium derivatives of N-(co-aminoalkyl)(meth)acrylamides or co-aminoalkyl (meth)acrylic esters.
• the R 12 radicals are each independently Ci-C 4 -alkyl, preferably methyl, or a group of the general formula -R 14 -S03H, where R 14 is a preferably linear Ci-C 4 -alkylene group or a phenyl group, with the proviso that generally not more than one of the R 12 substitu- ents is a substituent having sulpho groups. More preferably, the three R 12 substituents are each methyl groups, i.e. the monomer has a -N(CH3)3 + group.
• X " in the above formula is a monovalent anion, for examople Ch Of course, X may also be a corresponding fraction of a polyvalent anion, though this is not preferred.
• suitable monomers (b) of the general formula (Va) or (Vb) include salts of 3-trimethylammonio- propylacrylamides or 2-trimethylammonioethyl (meth)acrylates, for example the corresponding chlorides such as 3-trimethylammoniopropylacrylamide chloride (DIMAPA- QUAT) and 2-trimethylammonioethyl methacrylate chloride (MADAME-QUAT).
• DIMAPA- QUAT 3-trimethylammoniopropylacrylamide chloride
• MADAME-QUAT 2-trimethylammonioethyl methacrylate chloride
• the monomer (b) may thus be an uncharged monomer (b1 ), and here especially a monomer selected from the group of (meth)acrylamide, A/-methyl(meth)acrylamide, A/,A/-dimethyl(meth)acrylamide, A/-methylol(meth)acrylamide, A/-vinylformamide or N- vinyl-2-pyrrolidone, and the monomer (b2) may be at least one selected from the group of (meth)acrylic acid, vinylsulphonic acid, allylsulphonic acid, 2-acrylamido-2- methylpropanesulphonic acid (AMPS®), 2-methacrylamido-2-methylpropanesulphonic acid, 2-acrylamidobutanesulphonic acid, 3-acrylamido-3-methylbutanesulphonic acid or 2-acrylamido-2,4,4-trimethylpentanesulphonic acid or vinylphosphonic acid.
• AMPS® 2-acrylamido-2-methylpropanesulphonic acid
• the copolymer may additionally also comprise at least one cationic monomer (b3) having ammonium groups, where the cationic monomer comprises salts of 3-tri- methylammoniopropyl(meth)acrylamides and 2-trimethylammonioethyl(meth)acrylates.
• hydrophilic monomers can of course be used not only in the acid or base form shown, but also in the form of corresponding salts. It is also possible to convert acidic or basic groups to corresponding salts after the formation of the polymer.
• the inventive copolymer comprises, in a preferred embodiment of the invention, at least one monomer (b) comprising acidic groups.
• monomers which comprise at least one group selected from the group of -COOH, - SO3H and -PO3H2, particular preference being given to monomers comprising COOH groups and/or -SO3H groups, and suitable salts thereof.
• At least one of the monomers (b) is preferably a monomer selected from the group of (meth)acrylic acid, vinylsulphonic acid, allylsulphonic acid and 2-acrylamido-2- methylpropanesulphonic acid (AMPS®), more preferably acrylic acid and/or AMPS® or salts thereof.
• AMPS® 2-acrylamido-2- methylpropanesulphonic acid
• inventive copolymers are advantageously prepared in the presence of at least one nonpolymerizable surfactant (c), which is preferably at least one nonionic surfactant.
• c nonpolymerizable surfactant
• anionic and cationic surfactants are also suitable, to the extent that they do not take part in the polymerization reaction.
• the nonionic surfactant is preferably an ethoxylated, long-chain aliphatic alcohol which may optionally contain aromatic components.
• examples include: Ci2-i4-fatty alcohol ethoxylates, Ci6-is-fatty alcohol ethoxylates, Ci3-oxo alcohol ethoxylates, Cio-oxo alcohol ethoxylates, C13-15-OXO alcohol ethoxylates, Cio-Guerbet alcohol ethoxylates and alkylphenol ethoxylates.
• a suitable surfactant is especially at least one representative selected from the group of the ethoxylated alkylphenols, the ethoxylated saturated iso-Ci3-alcohols and/or the ethoxylated Cio-Guerbet alcohols.
• inventive copolymers in addition to monomers (a) and (b), may optionally also comprise monomers (d) which possess two or more, preferably two, ethylenically unsaturated groups.
• monomers (d) which possess two or more, preferably two, ethylenically unsaturated groups.
• This can achieve a certain level of crosslinking of the copolymer, provided that this does not have any undesired adverse effects in the intended use of the copolymer. Too high a degree of crosslinking should, however, be avoided in any case; more particularly, the required water solubility of the copolymer must not be impaired. Whether a low level of crosslinking may be advisable in the indi- vidual case is guided by the particular use of the copolymer, and the person skilled in the art makes an appropriate selection.
• Suitable monomers (d) include 1 ,4-butanediol di(meth)acrylate, 1 ,6-hex- anediol di(meth)acrylate, 1 ,3-butylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate or oligoethylene glycol di(meth)acrylates, for example polyethylene glycol bis(meth)acrylate, N,N'-methylenebis(meth)acrylamide, ethyl- ene glycol divinyl ether, triethylene glycol divinyl ether, triallylamine, triallylaminemeth- ammonium chloride, tetraallylammonium chloride or tris(2-hydroxyethyl) isocyanurate tri(meth)acrylate.
• crosslinking monomers (d) are used only in small amounts.
• the amount of the monomers (d) should not exceed 1.0% by weight based on the amount of all monomers used.
• the type and amount of the crosslinker are determined by the person skilled in the art according to the de- sired use of the copolymer.
• the copolymer is used as a thickening rheological additive for hydraulic fracturing.
• Said copolymer can also be used as a thickening rheological additive for completion fluids, spacer fluids and drilling fluids, or else as a thickening rheological additive and/or as a stabilizer for foams.
• the inventive use is effected preferably at a temperature in the range from 40 °C to 120 °C, more preferably at 50 °C to 100 °C.
• monomer component (a) should be present in amounts of 0.1 to 20.0% by weight, preferably of 0.1 to 5% by weight, monomer component (b) in amounts of 50.0 to 99.8% by weight, and surfactant (c) in amounts of 0.1 to 10.0% by weight, based in each case on the total amount of all components in the copolymer.
• the exact amount is guided by the type and the desired end use of the hydrophobically associating co- polymers and is determined correspondingly by the person skilled in the art.
• R 3 of monomer component (a) of the formula (I) is a hydrocarbyl radical having at least 3 carbon atoms. More preferably, with regard to monomer component (a) of the formula (I), R 1 is H and R 4 is a group selected from -CH 2 - and -O-CH2-CH2-CH2-CH2-.
• the at least one monomer (b) is preferably a monomer comprising acidic groups and/or salts thereof.
• the acidic groups are preferably at least one group selected from -COOH, -SO3H and -PO3H2, and salts thereof.
• the copolymer is a copolymer (A1 ) which comprises at least two different hydrophilic monomers (b), which comprise at least one uncharged hydrophilic monomer (b1 ), preferably acrylamide, and • at least one hydrophilic anionic monomer (b2) which comprises at least one acidic group selected from -COOH, -SO3H and -PO3H2, where the amount of the monomers (a) is 0.1 to 20% by weight and that of all monomers (b) together is 70 to 99.5% by weight, based on the amount of all monomers in the copolymer.
• A1 which comprises at least two different hydrophilic monomers (b), which comprise at least one uncharged hydrophilic monomer (b1 ), preferably acrylamide, and • at least one hydrophilic anionic monomer (b2) which comprises at least one acidic group selected from -COOH, -SO3H and -PO3H2, where the amount of the monomers (a) is 0.1 to 20% by weight and that of all
• the preferred uncharged monomers (b1 ) are (meth)acrylamide, A/-methyl(meth)acryla- mide, A/,A/-dimethyl(meth)acrylamide, A/-methylol(meth)acrylamide, A/-vinylformamide and A/-vinyl-2-pyrrolidone, and the monomer (b2) is at least one monomer selected from the group of (meth)acrylic acid, vinylsulphonic acid, allylsulphonic acid, 2- acrylamido-2-methylpropanesulphonic acid (AMPS ® ), 2-methacrylamido-2- methylpropanesulphonic acid, 2-acrylamidobutanesulphonic acid, 3-acrylamido-3- methylbutanesulphonic acid, 2-acrylamido-2,4,4-trimethylpentanesulphonic acid and vinylphosphonic acid.
• AMPS ® 2-methacrylamido-2- methylpropanesulphonic acid
• the inventive copolymer may additionally also comprise at least one cationic monomer (b3) having ammonium groups, more preferably salts of 3-trimethylammoniopro- pyl(meth)acrylamides and/or 2-trimethylammonioethyl (meth)acrylates.
• the copolymer is a copolymer (A2) which comprises at least two different hydrophilic monomers (b), which are at least
• the copolymer is a copolymer (A3) which comprises at least two different hydrophilic monomers (b), which are at least ⁇ 5 to 50% by weight of at least one uncharged hydrophilic monomer (b1 ), and
• the inventive copolymer also comprises up to 1 % by weight of the crosslinking monomer (d) which comprises at least two ethylenically unsaturated groups and has already been mentioned above, where monomer (d) comprises at least one monomer selected from the group of triallylamine, triallylmethylammonium chloride, tetraallylammonium chloride, ⁇ , ⁇ '-methylenebisacrylamide, triethylene glycol bis- methacrylate, triethylene glycol bisacrylate, polyethylene glycol(400) bismethacrylate and polyethylene glycol(400) bisacrylate.
• monomer (d) comprises at least one monomer selected from the group of triallylamine, triallylmethylammonium chloride, tetraallylammonium chloride, ⁇ , ⁇ '-methylenebisacrylamide, triethylene glycol bis- methacrylate, triethylene glycol bisacrylate, polyethylene glycol(400) bismethacrylate and polyethylene glycol(400) bisacrylate.
• inventive copolymers can be prepared by methods known in principle to those skilled in the art, by free-radical polymerization of the monomers (a), (b) and optionally (d), for example by solution or gel polymerization in the aqueous phase.
• the monomers (a) of the formula (I) used in accordance with the invention are more preferably provided by the above-described preparation process by alkoxylating ethylenically unsaturated alcohols, for example hydroxybutyl vinyl ether, optionally followed by an etherification.
• the preparation is undertaken by means of gel polymeriza- tion in the aqueous phase.
• a mixture of the monomers (a), (b) and optionally (d), initiators, the surfactant (c) and other assistants with water is first provided.
• Acidic monomers can be neutralized completely or partially before the polymerization. Preference is given to a pH of approx. 4 to approx. 9.
• the concentration of all components except the solvents is typically approx. 20 to 60% by weight, pref- erably approx. 30 to 50% by weight.
• At least one hydrophobically associating monomer (a) and at least one hydrophilic monomer (b) is recommended to subject at least one hydrophobically associating monomer (a) and at least one hydrophilic monomer (b) to an aqueous solution polymerization in the presence of at least one surfactant (c), preferably by initially charging monomer com- ponent (a) and then successively adding monomer component (b) and component (c).
• a mixture containing monomer component (b) and component (c) to monomer component (a).
• the invention also includes addition of component (c) to monomer component (a), and subsequent addition of monomer component (b) to the mixture obtained.
• the polymerization should be per- formed especially at a pH in the range from 5.0 to 7.5 and preferably at a pH of 6.0.
• the mixture is subsequently polymerized thermally and/or photochemically, preferably at -5°C to 50°C. If polymerization is effected thermally, preference is given to using polymerization initiators which can initiate even at comparatively low temperature, for example redox initiators.
• the thermal polymerization can be undertaken even at room temperature or by heating the mixture, preferably to temperatures of not more than 50°C.
• the photochemical polymerization is typically undertaken at temperatures of -5°C to 10°C.
• photochemical and thermal polymerization can be combined with one another, by adding both initiators for the thermal and photochemical polymerization to the mixture.
• the polymerization is first initiated photochemically at low temperatures, preferably -5 to +10°C.
• the heat of reaction re- leased heats the mixture, which additionally initiates the thermal polymerization.
• the gel polymerization is generally effected without stirring. It can be effected batch- wise by irradiating and/or heating the mixture in a suitable vessel at a layer thickness of 2 to 20 cm. The polymerization gives rise to a solid gel.
• the polymerization can also be effected continuously.
• a polymerization apparatus is used, which possesses a conveyor belt to accommodate the mixture to be polymerized.
• the conveyor belt is equipped with devices for heating or for irradiating with UV radiation.
• the mixture is poured onto one end of the belt by means of a suitable appara- tus, the mixture is polymerized in the course of transport in belt direction, and the solid gel can be removed at the other end of the belt.
• the gel obtained is preferably comminuted and dried after the polymerization.
• the drying should preferably be effected at temperatures below 100°C.
• a suitable separating agent for this step. This gives the hydro- phobically associating copolymer as granules or powder.
• the inventive copolymers preferably possess a number-average molecular weight M n of 50 000 to 25 000 000 g/mol.
• the polymer powder or granules obtained are generally used in the form of an aqueous solution in the course of application at the site of use, the polymer has to be dissolved in water on site. This may result in undesired lumps with the high molecular weight polymers described.
• an assistant which accelerates or improves the dissolution of the dried polymer in water to the inventive polymer as early as in the course of synthesis.
• This assistant may, for example, be urea.
• the hydrophobically associating copolymer can, as already mentioned at the outset, be used in accordance with the invention for thickening of aqueous phases.
• the selection of the type and amount of the monomers (a), (b), (c) and (d) can be used to adjust the properties of the copolymers to the particular technical requirements.
• concentration of the copolymer is 0.05 to 5% by weight based on the aqueous phase, preferably 0.1 to 2% by weight and more preferably 0.15 to 1 % by weight.
• aqueous phases to be thickened are, as already mentioned above, for example, formulations for hydraulic fracturing, completion fluids, spacer fluids and drilling fluids, and also aqueous formulations to generate foam.
• copolymers can be used here alone, or else in combination with other thickening components, for example together with other thickening polymers. They can also be formulated, for example, together with surfactants to give a thickening system.
• the surfactants can form micelles in aqueous solution, and the hydrophobically associating copolymers can form, together with the micelles, a three-dimensional thickening network.
• the copolymer can be dissolved directly in the aqueous phase to be thickened. It is also conceivable to predissolve the copolymer and then to add the solution formed to the system to be thickened.
• Fig. 1 shows a graphical representation of the viscosity of an aqueous solution of a copolymer according to the invention over temperature
• Fig. 2 shows a graphical representation of rheological data measured at 300 rpm
• Fig. 3 shows a graphical representation of rheological data measured at 3 rpm
• Fig. 4 shows a graphical representation of foam buildup data on a SUA foam tester
• Fig. 5 shows a graphical representation of foam collapse data on a SUA foam tester
• Fig. 6 shows a graphical representation of Fann-35 data measured in HC02lMa brine
• Fig. 7 shows a graphical represent, of Fann-35 data measured in CaC /CaB ⁇ brine
• Fig. 8 shows a graphical representation of Fann-35 data measured in CaBr2 brine.
• a 3 I vessel with stirrer and thermometer is initially charged with 242.5 g of a 50% Na- AMPS® solution (AMPS® 2405, from Lubrizol). 295.8 g of water were added while stirring. Subsequently, 1 .2 g of Surfynol DF 58 and 0.4 g of Baysilone EN (from Bayer) as defoamers were added successively. After addition of 4.6 g of Pluriol A1 190V+12PeO (development product from BASF consisting of hydroxybutyl vinyl ether having 25 ethylene oxide units and 12 pentene oxide units), 228.8 g of a 50% acrylamide solution (from Cytec) were added.
• Pluriol A1 190V+12PeO development product from BASF consisting of hydroxybutyl vinyl ether having 25 ethylene oxide units and 12 pentene oxide units
• the pH was adjusted to 6.0 with a 20% NaOH solution and/or a 20% H2SO4 solution. During the inertization by purging with nitrogen for 30 minutes, the solution was cooled to approx. 20°C.
• the solution was transferred to a plastic vessel of dimensions (w * d * h) 15cm * 10cm * 20cm, and 16.0 g (200 ppm) of 10% 2,2'-azobis(2-amidinopropane) dihydrochloride, 0.5 g (10 ppm) of 1 % bisulphite solution, 8 g (6 ppm) of 0.1 % tert-butyl hydroperoxide solution and 4.0 g (5 ppm) of 1 % iron(ll) sulphate solution were added successively.
• the polymerization was initiated by irradiating with UV light (two Philips tubes; Cleo Performance 40 W). After approx. 2-3 h, the cut-resistant gel was removed from the plastic vessel and cut with scissors into gel cubes of approx. 5 cm * 5 cm * 5 cm in size. Before the gel cubes were comminuted with a conventional meat grinder, they were lubricated with the separating agent Sitren 595 (polydimethylsiloxane emulsion; from Goldschmidt). The separating agent is a polydimethylsiloxane emulsion which has been diluted 1 :20 with water. The gel granules obtained were subsequently distributed homogeneously on drying grids and dried to constant weight under reduced pressure at approx. 90-120°C in a forced-air drying cabinet. Approx. 500 g of white hard granules were obtained, which were converted to a pulverulent state with the aid of a centrifugal mill.
• Lutensol TO 15 but also other nonionic surfactants, and also anionic and cationic surfactants, can be used in the synthesis of the inventive copolymers.
• a mixed ionic copolymer was produced.
• This copolymer contains, in addition to AMPS®, acrylamide and Pluriol A1 190V+12PeO, the cationic monomer 3-trimethylammoniopropylmethacrylamide chloride (DIMAPAQUAT).
• DIMAPAQUAT the cationic monomer 3-trimethylammoniopropylmethacrylamide chloride
• the molar ratio of the monomers is AMPS®:acrylamide:DIMAPAQUAT:Pluriol
• AMPS® the sodium salt of acrylic acid was produced.
• the proportions by mass of the monomers were 28% sodium acrylate, 70% acrylamide and 2% Pluriol
• A1 190V+12PeO The surfactant added was 4.8 g of Lutensol AP 10 (BASF).
• the solids content of the polymerized gel was 19.5%.
• the measurement of the viscosity as de- scribed in use ex. 1 gave a value of 49 mPas.
• This example describes an alternative polymerization process to preparation example 5.
• a plastic bucket with magnetic stirrer, pH meter and thermometer was initially charged with 121.2 g of Na-AMPS® (50% solution) to which were subsequently added 155 g of distilled water, 0.6 g of Surfynol, 0.2 g of Baysilone, 2.3 g of Pluriol A1 190V + 12 PeO, 1 14.4 g of acrylamide (50% solution), 1 .2 g of Versenex (5% solution) and 2.4 g of Lutensol AP10.
• pH 6.0 with a 20% or 2% sulphuric acid solution and addition of the rest of the water (total amount of water minus the amount of water already added, minus the amount of acid required)
• the monomer solution was adjusted to the start temperature of 20°C.
• the solution was transferred into a thermos flask, the temperature sensor for temperature recording was mounted and the mixture was purged with nitrogen for 30 minutes. At the end of the nitrogen purging, the online measurement of the temperature was started, the start temperature was checked once more and adjusted, and 1 .6 ml of a 10% V50 solution, 0.12 ml of a 1 % t-BHPO solution and 0.24 ml of a 1 % sodium sulphite solution were added successively. As the monomer solution began to thicken, the nitrogen frit was removed from the monomer solution. Once the temperature of the gel block had attained its maximum, the temperature sensor was removed and the thermos flask was placed into a drying cabinet at 80°C for two hours.
• the gel block was removed from the thermos flask and approx. 0.5-1 cm of the surface was removed with scissors and discarded. The remainder was halved, painted with the separating agent Comperlan COD (coconut fatty acid dietha- nolamide) and comminuted with the aid of a meat grinder.
• the gel granules obtained were dried in a fluidized bed dryer at 55°C for two hours. This gave white hard granules which were converted to a pulverulent state by means of a centrifugal mill.
• the inventive polymers are not merely a physical mixture of the polymer from preparation ex. 1 and the surfactant, but that the polymer structure is cru- cially influenced during the polymerization reaction, the viscosities of mixtures of the polymer from preparation ex. 1 with the surfactant Lutensol TO 15 were also measured:
• the polymer from preparation example 3 was refluxed in a Soxhlet with toluene over a period of 48 h. This ex- tracted 90% of Lutensol TO 15 originally present from the copolymer. However, the high viscosity of the polymer was preserved even after the virtually complete extraction of the surfactant.
• the gel content is reduced significantly as a result of the surfactant addition. With rising amount of surfactant, it is possible to reduce the gel content down to below the detection limit.
• c 1200 ppm in 9% salt solution, measured at 6 rpm with Brookfield LV and UL adapter.
• the table below shows the rheological properties of a 0.6% solution of hydroxypropyl- guar (Galctasol® 40H4FDS1 , from Ashland Aqualon) at different temperatures and speeds (measured with Fann 35).
• Fig. 2 and Fig. 3 the values measured at 300 rpm and 3 rpm in tap water were summarized in Fig. 2 and Fig. 3, respectively.
• the viscosity values of the inventive copolymers at room temperature are firstly higher than those of the commercial polymers used to date; secondly, no significant decline in viscosity is observed with rising temperature, and it is even possible to observe a rise at the low shear rates.
• the comparatively high viscosity values at the low shear rates are particularly advantageous for use as a thickener in hydraulic fracturing, since proppants are generally pumped together with the polymer solution in this use. Thus, settling of these prop- pants is prevented. 4.
• test parameters of use examples 7 and 8 are reproduced in the table below, and the results are given in form of graphical representations in Fig 4 (foam buildup).
• the inventive polymers have a higher viscosity at the same dosage compared to Biovis® (Scleroglucan, from BASF) and particularly compared to Xanthan (Bioflow®, from BASF), especially after ageing. It is also of interest that flatter rheology can be
• the inventive polymer from preparation example 16 was tested in 4 different high-density salt solutions ("brines") which are used as solids-free completion fluids:
• the inventive polymers were added as a 1 .75% solution to the particular brines, and the viscosity of the resulting completion fluid was determined with the Fann-35 at room temperature.
• the completion fluids were aged dynamically in a roller kiln at the particular temperatures specified for 16 hours. Subsequently, the liquid was cooled to RT and determined again with the Fann-35.

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