MXPA00005119A - Cementation auxiliary agent - Google Patents

Abstract

The invention relates to copolymers consisting of a) 1-99 wt.%structural units of formula (1), wherein R1=hydrogen or methyl, R4=C1-C22 alkylene, R5=C1-C22 alkyl or hydrogen and X=ammonium, lithium, sodium, potassium, an amine or a mixture of these substances and b) 99-1 wt.%structural units of formula (2), wherein R1=hydrogen or methyl and R2 and R3 represent C2-C22 alkyl independently of each other. The inventive copolymers are characterised in that component b) is not hydrolysed and in that the copolymers are produced by a solution-precipitation polymerisation in a non-aqueous solvent or a water-miscible organic solvent with a low water-content which represents a precipitating agent for the copolymer. The invention also relates to a method for cementing deep well drill holes using a cement slurry containing the following components:a) water of varying salinity, b) cement and c) the inventive copolymer in a concentration of 0.01-5%by weight of cement, preferably 0.05-0.09%by weight of cement.

Description

AUXILIARY OF CEMENTATION FOR WELLS DESCRIPTIVE MEMORY The present invention relates to water-soluble copolymers, to processes for their preparation and to their use to reduce the loss of water in cement slurries for cementing underground wells. The use of drilling fluids and cement slurries in underground wells to recover oil and natural gas deposits has been known for some time. When the perforation has reached a certain depth, a case is introduced into the hole. For this purpose, the case must be secured, that is, a cement slurry is pumped into the space between the formation and the case and hardens to form a solid rock. The hardened cement must be impermeable to gases and liquids so that no gas and / or oil can flow out of the carrier rock into other sections or up to the surface. The cement grout that will be pumped is subject to high demands. It must be easily pumpable, that is, have the lowest possible viscosity and yet it must not be separated. The release of water from the cement slurry to the porous rock must be low during the pumping operation, so that thick filter cakes are not formed in the perforation wall; the thick filter cakes would increase the pumping pressure so much, due to the constriction of the annular space, that the porous rock would disintegrate. In addition, the cement slurry would not be properly fixed and would become permeable to gases and oil if the release of water were excessive. On the other hand, the formation of cement cover must reach some resistance as fast as possible in the annular space, and shrinkage should not occur during fixing, since this would result in flow channels for gas, oil and water. The optimum establishment of the properties of the cement slurry is only possible through additives. The most important additives are retarders, accelerators, dispersants and water loss reducers. The effective water loss reducers used in the practice of cement and gypsum slurries are a wide variety of polymers, copolymers and combinations thereof. The first effective products, which are still currently used, were the cellulose ethers based on hydroxyethylcellulose and carboxymethylhydroxyethylcellulose. Due to thermal instability, they lose their efficiency at drilling temperatures of more than 100 ° C. As a result, many completely synthetic and different heat-stabilized polymers have been developed, and are currently still used at the different temperatures and salinities of the cement slurry. Polymers as additives to reduce water loss in cement slurries are well known from the literature. Many water loss reducers have an activity that is largely restricted to high temperatures. US-2,614,998 discloses the use of partially hydrolyzed polyacrylamide poly (acrylamido-co-acrylic acid) as reducing polymers of water loss. However, these polymers can cause a considerable retardation of the cement fixing time and only have low effectiveness at high temperatures. US-2,865,876, US-2,905,565 and US-3,052,628 describe the use of sulfonated polymers as additives. The polymers and copolymers described there are significantly different in their composition from the copolymers according to the present invention and have achieved absolutely no industrial importance. US-5,472,051 describes copolymers of AMPS and acrylic acid having molecular weights of less than 5000 g / mol. US-4,015,991 describes a polymer of AMPS and acrylamide, wherein at least 20% of the acrylamide units must subsequently be hydrolyzed to acrylic acid or to an acrylic acid salt. The reclaimed polymer consists of AMPS, acrylamide and acrylic acid or an acrylic acid salt. US 4,015,991 claims in this way the following copolymer: where x is 10-90 mole percent and is 10-90 mole percent z, depending on y, is 2 - 90 mole percent, where, if z is 0, inadequate water loss reduction properties were found in the test carried out. However, the disadvantage of this polymer is an undesired effect on the properties of the cement (reduction in the strength of the hardened cement) and retardation of the cement fixation. A further problem is the restricted temperature scale to be used as a water loss reducing polymer. TO 177 ° C is demonstrably inactive. No. 4,015,991 showed that suitable copolymers can not be prepared by the aqueous polymerization of AMPS and acrylamide without a hydrolysis step. EP 0 116 671 (= DE 3302168) describes the introduction of 5-60% by weight of a new additional comonomer, viz. A vinylamide (for example, N-vinylmethylacetamide). This allows to significantly expand the application scale at high temperatures, but these polymers exhibit worse application properties at temperatures of less than about 38 ° C. US-5,025,040 discloses copolymers of AMPS, acrylamide and at least 20% of N-vinylimidazole as novel vinoilamide components. US-4,931,489 discloses copolymers of substituted acrylamides and N-vinylimidazoles without the use of AMPS as the comonomer.

EP-A-0 217 608, US-4,555,269 and EP-A-0 157 055 describe a polymer of AMPS and dimethylacrylamide in a molar ratio of 1: 4 to 4: 1 as a flow loss additive for cement slurries containing salts (approximately 10% by weight) and the use of AMPS and acrylic acid in a molar ratio of 1: 4 to 4: 1 for the same purpose. According to US Pat. No. 5,294,651, the disadvantages of the process of US Pat. No. 4,015,991 are overcome by an improvement analogous to that of EP-A-0 116 671 using an additional comonomer, in this case a cyclic vinylamide (for example, N-vinylpyrrolidone). . The proposed solution does not differ significantly from the method indicated in EP-A-0 116 671. To date, a technically satisfactory solution for a temperature range of 4 to 205 ° C based on the monomers described in US Pat. No. 4,015,991 has not been described. or without the partial hydrolysis of acrylamide. The multiplicity of polymers developed to reduce the release of water makes it clear that it is always difficult to formulate a technically optimal cement slurry. A significant effect on its suitability is exerted by the temperature of the drilling section prepared for cementation. Polymers designed for different temperatures present considerable logistical problems, since a certain number of water-reducing polymers must always be maintained in places scattered throughout the world. The objective was therefore to develop polymers that could cover the full temperature scale (4 ° C - 205 ° C) and were suitable for a wide range of cement slurries, ie various qualities of cement, water salinities of mixing and densities of cement grout. Surprisingly, it has been found that the necessary technical properties can be achieved by means of an AMPS-acrylamide copolymer if the polymerization process is modified and the subsequent hydrolysis is omitted, giving a novel polymer that has not been described above. In addition, this polymer does not cause the retardation of the fixation to less than 40 ° C. The present invention relates to copolymers consisting of: a) 1-99% by weight of structural units of the formula (1) wherein R1 is hydrogen or methyl, R4 is C? -C22 alkylene, R5 is C1-C22 alkyl or hydrogen, and X is ammonium, lithium, potassium, an amine or a mixture of these substances, and b) 99-1 % by weight of structural units of the formula (2) in which R 1 is hydrogen or methyl, R 2 and R 3, independently of each other, are hydrogen or C 1 -C 22 alkyl; wherein component b) is not hydrolyzed and the copolymers have been prepared by a precipitation polymerization of solution in a non-aqueous solvent or a water-miscible organic solvent having a low water content and being a precipitant for the copolymer. R2 and R3 are preferably hydrogen. R4 is preferably C2-C6 alkylene or, in particular, C3 alkylene. R5 is preferably hydrogen or methyl. In particular, the following substituents are used: X + = NH 4 + or Na +, R 1 = H, R 5 = H and R 4 = -C (CH 3) 2 -CH 2 -, R 1 = CH 3, R 5 = H and R 4 = -C (CH 3) 2-CH2-, R1, R2 and R3 = H, R1 and R2 = H, R3 = -C (CH3) 3, R1 = CH3, R2 and R3 = H, or R1 and R2 = H, R3 = -C ( CH3) 3. The average molecular weight of these polymers is preferably from 10,000 to 10,000,000 g / mol, preferably from 500,000 to 5,000,000 g / mol, in particular from 1,000,000 to 4,000,000 g / mol. The molecular weight indicators are the relative viscosity and the k value. To determine the k-value, the copolymer dissolves to a certain concentration (typically 0.5%) and the efflux time at 25 ° C is determined using a Ubbeiohde capillary viscometer. This value gives the absolute viscosity in the solution (? c). The absolute viscosity of the solvent is? 0. The ratio between the two absolute viscosities gives the relative viscosity: z = ^? The value k can be determined from the relative viscosities as a function of concentration by means of the following equation: 75. k2 l? g Z: - + k l + 1.5 kc the value k of the polymers according to the invention is between 100 and 300, preferably between 150 and 270 and in particular between 180 and 250. The amount of structural units of the formula (1) is preferably from 10 to 90% in weight, in particular from 30 to 70% by weight. The amount of structural amounts of the formula (2) is preferably from 90 to 10% by weight, in particular from 70 to 30% by weight. Subsequent hydrolysis as described in US Pat. No. 4,015,991 is not advantageous for the technical properties (see examples 1-7, tables 1 and 2) to allow use as a water loss reducer in the widest possible temperature range of 4. ° C to 205 ° C. In fact, it has been found that subsequent partial hydrolysis results in disadvantageous technical properties at low temperatures in the form of an extension of the cement fixation time, and that, at high temperatures of more than 120 ° C, the loss of water is difficult. to control. The novel polymers can be used as water loss reducers at 4 ° C to 205 ° C in drilling fluids, in particular in cement slurries and slurries for water-based drilling. Its effectiveness is guaranteed even at 4 ° C and 205 ° C. The polymer can be mixed in the dry state with other powdery additives. However, it can also be added in dissolved form, together with other liquid additives, to the mixing water. The copolymers are prepared by precipitation polymerization of solution (see H.G Elias, Makromoleküle, Struktur-Eigenschaften-Synthesse-Stoffe [Macromolecules, Structure-Properties-Synthesis-Materials], Hüthig &Wepf Verlag, 1972, page 487). The monomers are completely or partially soluble in the polymerization medium, while the polymer is insoluble. The reaction can be carried out at temperatures between -10 and 100 ° C, preferably between 20 and 70 ° C. Suitable polymerization initiators are all substances that form free radicals; Apart from typical diazo compounds and percompounds, initiation by an oxide-reduction initiator, a photoinitiator or by high energy radiation (UV, neutron or plasma) is also possible. The water content of the solvents employed herein should preferably not exceed 10%, in particular 5%. Unlike the free radical aqueous polymerization, the product shows only a minor dependence on the nature of the initiator system used. Preferred examples of the compounds from which the structural units of formula 1 are derived are acrylamido-2-methylpropanesulfonic acid and methylacrylamido-2-methylpropanesulfonic acid. Preferred examples of the compounds from which the structural units of the formula 2 are derived are acrylamide, methacrylamide, isopropylacrylamide and tert-butylacrylamide. The polymers are formed as a white and bulky precipitate in tert-bunanol. The polymer can be isolated by any conventional process of evaporation, drying and isolation. In particular, butanol can be separated from the product by pressure filtration or distillation. A slight residue of tert-butanol does not cause safety or technical problems. The invention further relates to a method for cementing underground wells using a cement slurry containing the novel copolymer in a concentration of 0.01-5% bwoc (by weight cement), preferably 0.05 to 0.9% bwoc. The additional components of the cement slurries are water of different salinities and cement. In addition, dispersing aids, retarders, accelerators, extenders, antifoams or silicate derivatives can be used as additives. The invention also relates to the use of novel copolymers in fluids for water-based drilling, these drilling fluids may contain additional additives in addition to the novel copolymers. Said additives are, for example, bentonites, clay stabilizers, lignin / lignosulfonates, pH stabilizers (for example hydroxides), heat stabilizers (for example monoethanolamine or sulphonated synthetic polymers) and barites (to establish the desired density). The following examples describe the practice of the invention in greater detail.

EXAMPLES The first four examples describe typical procedures for the preparation of the novel polymer. In the examples, the counterion and the copolymer composition were varied. In the first four examples, the analytical and spectroscopic efforts did not detect any significant amount of acrylic acid or acrylates (products of acrylamide hydrolysis). As expected, hydrolysis of acrylamide did not occur at these temperatures and pH values (see also example 7). The technical effect is therefore attributable to poly (AMPS-co-acrylamide).

EXAMPLE 1 Copolymer comprising 70% by weight of AMPS and 30% by weight of AM, ammonium salt A 3-liter Quickfit flask equipped with anchor stirrer, reflux condenser with gas scrubber, combined thermometer / pH meter and gas inlet tube is charged with 1700 g of a rectified tert-butanol and 50 ml of distilled water. The reaction flask is placed in a heat-set heating bath. This reaction flask is covered with nitrogen gas, and 245 g of acrylamido-2-methylpropane-sufonic acid (AMPS 2404® (registered trademark of Lubrizol)) is introduced under a gentle countercurrent of nitrogen. The AMPS does not dissolve completely in the tert-butanol and is partially in the form of a solid dispersion. The pH of this mixture is less than 1. Aqueous ammonia is passed above the liquid phase through the tube for gas entry until the pH and dispersion is between 7 and 8. After the scale has been reached At the desired pH, the mixture is stirred for an additional hour and the pH is continuously recorded. The reaction flask is again covered with nitrogen and 105 g of acrylamide are introduced. After the introduction of acrylamide, the pH is revised again and if necessary it is corrected to the pH 7-8 scale. A constant stream of nitrogen is passed through the solution for at least 1 hour. After this time of inertia, the residual oxygen content is checked by means of an oxygen electrode. If the residual oxygen value measured in the liquid phase exceeds 1 ppm, the inertia must be repeated until this value is achieved. Then 1.5 g of AIBN are added under a gentle stream of nitrogen and the reaction flask is heated to 60 ° C. Just after an internal temperature of 60 ° C has been reached, the introduction of nitrogen gas is concluded and the polymerization reaction typically starts after a few minutes, which is evident from an increase in temperature from 10 to 15 ° C. Approximately 30 minutes after the start of the polymerization reaction, the maximum temperature is passed and the temperature in the reaction flask is raised to the boiling point of the tert-butanol by means of the heating bath. The mixture, which is now viscous, is stirred for an additional two hours under gentle reflux. The reaction product, which is in the form of a viscous polymer suspension in tert-butanol, is isolated by filtering the tert-butanol followed by drying in a vacuum drying cabinet. Yield: 365 g of polymer 1 Poly (acrylamido-2-methylpropanesulfonic acid-co-acrylamide) ammonium salt Dry content: 96% by weight (2.5% tert-butanol, 1.5% water). K value of a 0.5% by weight solution: 212 EXAMPLE 2 Copolymer comprising 70% by weight of AMPS and 30% by weight of AM, sodium salt The polymer is prepared analogously to Example 1. Instead of adding a corresponding amount of ammonia, 140.5 g of sodium carbonate are metered in after the addition of AMPS. The pH of the dispersion is then in the range of between 7 and 8. Yield: 380 g of polymer 2, sodium salt of poly (acrylamido-2-methylpropanesulfonic acid-co-acrylamide) Dry content: 94% by weight K value of a 0.5% by weight solution: 207 EXAMPLE 3 Copolymer comprising 60% by weight of AMPS and 40% by weight of AM, ammonium salt The polymer is prepared analogously to Example 1. Instead of the amounts given in Example 1, 21 Og of AMPS 2404 and 140 g of acrylamide are used. Yield: 362 g of polymer 3 Ammonium salt of poly (acrylamide-2-methylpropanesulfonic acid-co-acrylamide) Dry content: 97% by weight (2.5% g of tert-butanol, 1.5% of water) Value k of a 0.5% by weight solution: 210 EXAMPLE 4 Copolymer comprising 80% by weight of AMPS and 20% by weight of AM, ammonium salt The polymer is prepared analogously to Example 1. Instead of the amounts given in Example 1, 280 g of AMPS 2404 and 70 g of acrylamide are used. Yield: 368 g of polymer 4 Poly (acrylamido-2-methylpropanesulfonic acid-co-acrylamide) ammonium salt Dry content: 94% by weight (2.5% tert-butanol, 1.5% water) Solution k value 0.5 Weight%: 205 Similar to US-4,015,991, partial hydrolysis of the product was carried out, but for the purpose of comparing the technical properties of the product before and after the hydrolysis. The technical test makes clear that the subsequent partial hydrolysis of the product offers no advantage, but makes the procedure significantly more complex and expensive. In example 7 the effect of the dissolution and the subsequent rolling drying is investigated. No step of the process results in any change in the novel polymer.

EXAMPLE 5 Controlled hydrolysis of the polymer prepared in example 1 50 g of polymer 1 are dissolved in 1500 ml of distilled water with stirring. After complete dissolution of the polymer, 6.3 g of potassium hydroxide which had previously been dissolved in 20 ml of water are added. The mixture is heated to 60 ° C and stirred at this temperature for one hour. The product is dried with the aid of a rolling dryer. The process hydrolyzes 50% of the acrylamide to acrylic acid.

EXAMPLE 6 Controlled hydrolysis of the polymer prepared in example 1 50 g of polymer 1 of example 1 are dissolved in 1500 ml of distilled water with stirring. After complete dissolution of the polymer, 3.8 g of potassium hydroxide which had previously been dissolved in 20 ml of water are added. The mixture is heated to 60 ° C and stirred at this temperature for one hour. The product is dried with the aid of a rolling dryer. The process hydrolyzes 30% of the acrylamide to acrylic acid.

EXAMPLE 7 Review of hydrolysis reaction and drying conditions The polymer is prepared in a manner similar to that of Example 1, by dissolving 50 g of the polymer in 1500 ml of distilled water with stirring. The mixture is heated to 60 ° C and stirred at this temperature for one hour. The product is dried with the aid of a rolling dryer. No hydrolysis has occurred. An additional essential factor for successful technical tests is the highest possible molecular weight. Direct measurement of absolute molecular weight is not easy, since, for example, gel permeation chromatography, like many other methods, is a comparative method based on the use of polymer standards. Said model substances can not be prepared for these systems by anionic polymerization. For this reason, the relative viscosity was used as a measure of molecular weight. In the present process, only low molecular weights can very easily occur as a result of an impurity. Particularly important impurities are those which have a high free radical chain transfer constant, such as, for example, aldehydes and oximes, but also heavy metal or oxygen impurities. An impurity of this type is simulated by the addition of dodecyl mercaptan, which, as it is known, has a relatively broad free radical chain transfer constant. Such compounds can cause considerable interference with the polymerization even on the ppm scale. The examples serve to revise the minimum necessary relative viscosity (lower molecular weight-weight limit) that gives the desired properties. In Examples 8 and 9, low molecular weight polymers of this type were prepared.

EXAMPLE 8 Copolymer comprising 70% by weight of AMPS and 30% by weight of AM, ammonium salt The polymer is prepared in a manner similar to that of Example 1. Before the addition of the AIBN, 0.035 g dodecyl mercaptan is added. The product is soluble in butanol and has a high free radical chain transfer constant. Yield: 362 g of the polymer 7 Ammonium salt of poly (acrylamido-2-methylpropanesulfonic acid-co-acrylamide) acid. Dry content: 95% by weight K value of a 0.5% by weight solution: 169EXAMPLE 9 Copolymer comprising 70% by weight of AMPS and 30% by weight of AM, sodium salt The polymer is prepared in a manner similar to that of Example 1. Before the addition of the AIBN, 0.07 g dodecyl mercaptan is added. The product is soluble in butanol and has a high free radical chain transfer constant. Yield: 369 g of polymer 1 Poly (acrylamido-2-methylpropanesulfonic acid-co-acrylamide) ammonium salt Dry content: 93% by weight (2.5% tert-butanol, 1.5% water) K value of a solution 0.5% by weight: 148 The first examples show that the precipitation polymerization of solution in organic solvents is a suitable procedure for the preparation of reducing polymers of water loss. For a comparison with the technical properties of these novel polymers, the compound described in US Pat. No. 4,015,991 was prepared and tested.

COMPARATIVE EXAMPLE 1 (Not according to the invention, prepared as described in US Pat. No. 4,015,991, copolymer prepared by polymerization of the aqueous, 88% by weight of AMPS and 12% by weight of acrylamide 328 g of distilled and degassed water are introduced into a 2-liter Quickfit flask equipped with anchor stirrer, reflux condenser with gas scrubber, combined thermometer / pH meter and gas inlet tube, and then 116.4 g of acid are added acrylamide-2-methylpropanesulfonic acid (AMPS 2404®). The AMPS is neutralized by the addition of 45 g of a 50% solution of sodium hydroxide (NaOH). The neutralization reaction gives a clear solution having a pH of between 7 and 8. 14.7 g of acrylamide are slowly dissolved in the solution neutralized in this manner. Nitrogen gas is again passed through the reaction solution for one hour. Then 0.69 g of tert-butyl peroxypivalate and 1.0 ml of an iron sodium ammoniosulfate are added as an oxide-reduction initiator pair. The iron ammoniosulfate solution is prepared by dissolving 0.098 g of Fe (NH) 2 (S0) 2 in 500 g of water. This mixture is further stirred at room temperature until it initiates a polymerization reaction, after 1-2 hours. The exothermic polymerization reaction increases the temperature to 50-60 ° C in the adiabatic polymerization. After the maximum temperature has been passed, the internal temperature is set to 60 ° C by the thermostat. A transparent gel of high viscosity is formed. The gel is mechanically sprayed and dried on a rolling dryer. Yield: 149 g of the comparative polymer 1 PoIi (acrylamide-2-methylpropanesulfonic acid-co-acrylamide acid sodium salt) According to the test, this base polymer had only a deficient water loss reducing action. In contrast, partially hydrolyzed products must have adequate technical properties at a low temperature of 28 ° C. These products were prepared and tested as described in Comparative Examples 2 and 3.

COMPARATIVE EXAMPLE 2 (Not according to the invention, prepared as described in US Pat. No. 4,015,991). Controlled hydrolysis of the polymer prepared in comparative example 1 45. 3 g of comparative polymer 1 are dissolved in 1500 ml of distilled water with stirring. After the complete dissolution of the polymer, 1.68 g of potassium hydroxide dissolved in 20 ml of water are added. The mixture is heated to 60 ° C and stirred at this temperature for one hour. The reaction product is dried again with the aid of a rolling dryer. This produces 50% hydrolysis of the acrylamide.

COMPARATIVE EXAMPLE 3 (Not according to the invention, prepared as described in US Pat. No. 4,015,991). Controlled hydrolysis of the polymer prepared in comparative example 1 The hydrolysis is carried out in a manner similar to that of comparative example 2. However, a reduced amount of 1.0 g of KOH is used. A hydrolysis of 30% of the acrylamide is thus achieved. By means of analytical and spectroscopic methods, the functionalities of acrylic acid (acrylic acid or salts thereof) were found in the correct order of magnitude.

EXAMPLES Test results The test is carried out according to API spec. 10. In an atmospheric consistency meter, the cement slurry is agitated / conditioned at the test temperature, and then the rheology is measured at the same temperature using a FANN Model 35SA viscometer (at high temperature, the conditioning is carried out at 93 ° C and the viscosity is measured) and the water loss is measured at less than 120 ° C using a Baroid HTHP filter press or at more than 120 ° C using the agitation fluid loss test apparatus. The fixation time is determined using an HTHP consistency meter. Table 1 shows the properties of water loss reduction in the previous examples according to API spec. 10 to 35 ° C in the static filtration test on a Baroid HTHP filter press. It is clear that the novel copolymers allow a very adequate reduction of water loss at low temperatures to be achieved. Naturally, the partially hydrolyzed acrylamide-AMPS-based polymers (= acrylic acid-acrylamide-AMPS copolymer) of US Pat. No. 4,015,991 and prepared in Comparative Examples 2 and 3 also reduce the loss of water at these low temperatures. However, Table 1 clearly shows the adverse effect on fixation time. The comparative example 1 confirms the situation found in US-4,015,991 that the partial hydrolysis of the acrylamide-co-AMPS polymers is necessary in the aqueous polymerization process in order to maintain the water loss of the cement slurries in suitable limits and practically acceptable (<100ml / 30 min) at low temperatures. The novel polymers have no effect on the fixing time of the cement slurries, as long as the acrylamide has not been partially hydrolyzed subsequently as described in US Pat. No. 4,015,991. Example 5 and Example 6 describe novel copolymers that have subsequently been partially hydrolyzed. The partial hydrolysis immediately has an adverse effect on an undesired extension of the fixation time. Example 7 makes clear that the partial hydrolysis of the acrylamide does not occur under the above polymerization conditions. Examples 8 and 9 show the effect of the preferred molecular weight scale (k-value). Formulation of cement slurries: 15.8 ppg of Dyckerhoff G 0.3% bwoc of polymer 0.065 3.78 l / of PNS 0.05 3.78 l / sk of anti-foam agent TABLE 1 % bwoc Concentration in weight of cement BC Units of Bearden consistency The point of relaxation, plastic viscosity and water loss are referred to conditioned cement slurry at 35 ° C. Table 2 shows the water loss reduction properties of the previous examples according to API spec. 10 to 176 ° C in the agitation fluid loss test apparatus. It is clear here that novel copolymers allow a very adequate reduction of water loss even at high temperatures. At these high temperatures, the polymers of US Pat. No. 4,015,991 based on partially hydrolyzed acrylamide-AMPS (= acrylic acid-acrylamide-copolymer AMPS) no longer reduce water loss in a suitable, ie economic (comparative examples 1 2 and 3). Formulation of cement slurries: 15.8 ppg Dyckerhoff G 0.7% polymer bwoc 0.20 3.78 l / sk of PNS 1.5 3.78 l / sk of HT retarder 35% bwoc of silica fluor 0.05 3.78 l / sk of antifoaming agent TABLE 2 % bwoc Concentration in weight of cement BC Units of Bearden consistency The point of relaxation and plastic viscosity refer to cement slurry conditioned at 93 ° C. The water loss was determined at 176 ° C. Table 3 shows the properties of water loss reduction of novel polymers on a wide range of temperatures (4 ° C to 205 ° C) in cement slurries of various densities, salinities and based on cement qualities of different origin. The universal application capacity of novel polymers represents an important contribution towards simplifying the grout formulations used worldwide. The cement slurries were prepared and tested by a standardized method known to the person skilled in the art., in accordance with API spec.10, and in addition to the water loss reducing polymers, contain additional additives common to those skilled in the art which are used as a standard to produce an optimum cement slurry. The following abbreviations are used:% bwoc: Concentration in weight of cement ppg: Density of cement slurries in pounds per gallon = 0.1198 kg / l 3.78 l / sk: Concentration in 3.785 liters of liquid additive per bag of cement (corresponds to 8,879 l / 100kg of cement) PNS: Polysaphthalene sulfonate DMS: Polymelamine sulfonate TABLE 3 00 t lO The experimental results given in Table 4 show that the novel copolymer has very suitable water loss reduction properties as an additive for conventional water-based drilling fluids, even at a high temperature of 190 ° C.

TABLE 4

Claims (13)

NOVELTY OF THE INVENTION CLAIMS

1. - A copolymer having a k value of 100 to 300, measured in

0. 5% by weight in distilled water solution, consisting of: a) 1-99% by weight of structural units of the formula (1) wherein R 1 is hydrogen or methyl, R 4 is C 1 -C 22 alkylene, R 5 is C 1 -C 22 alkyl or hydrogen, and X is ammonium, lithium, potassium, an amine or a mixture of these substances, and b) 99-1% by weight of structural units of the formula (2) wherein R 1 is hydrogen or methyl, R 2 and R 3, independently of one another, are hydrogen or C 1 -C 22 alkyl; wherein component b) is not hydrolyzed and the copolymers have been prepared by a precipitation polymerization of solution in a non-aqueous solvent or a water-miscible organic solvent having a low water content and being a precipitant for the copolymer. 2. A copolymer according to claim 1, further characterized in that it has a molecular weight of 10,000 to 10,000,000 g / mol.

3. A copolymer according to claim 1 and / or 2, which consists of a) 90-10% by weight of units of the formula (1) and b) 10 -90% by weight of units of the formula 2).

4. A copolymer according to claim 3, which consists of a) 30-70% by weight of units of the formula (1) and b) 70-30% by weight of units of the formula (2).

5. A copolymer according to one or more of claims 1 to 4, further characterized in that the radicals in the formula (1) and the formula (2) have the following meanings, independently of one another: X + = NH + or Na \ R1 = H, R5 = H and R4 = -C (CH3) 2 -CH2-, R1 = CH3, R5 = H and R4 = -C (CH3) 2 -CH2-, R1, R2 and R3 = H, R1 and R2 = H, R3 = -C (CH3) 3, R1 = CH3 > R2 and R3 = H or R1 and R2 = H, R3 = -C (CH3) 3.

6. A copolymer according to one or more of claims 1 to 5, further characterized in that it has a value k of 150 to 270, measured in 0.5% by weight of solution in distilled water.

7. - A copolymer according to claim 2, further characterized in that it has a molecular weight of 500,000 to 5,000,000 g / mol.

8. A copolymer according to claim 2, further characterized in that it has a molecular weight of 1,000,000 to 4,000,000 g / mol.

9. A copolymer according to one or more of claims 1 to 8, further characterized in that it has a value k of 180 to 250, measured in 0.5% by weight of solution in distilled water.

10. A process for cementing underground wells using a cement slurry comprising the following components: a) water of several salinities, b) cement and c) a copolymer according to one or more of claims 1 to 6 in a concentration of 0.01 -5% by weight of cement (bwoc).

11. The method according to claim 10, further characterized in that the concentration of component c) is 0.05 to 0.9 bwoc.

12. The process according to claim 10, further characterized in that dispersants, retardants, accelerators, extenders, antifoams or silicate derivatives are used as auxiliary additives.

13. The use of a copolymer according to one or more of claims 1 to 9 in water-based drilling fluids. solution in a non-aqueous solvent or an organic solvent mcible in water with a low water content representing a precipitating agent for the copolymer; The invention also relates to a method for cementing drill holes in deep wells using a cement slurry containing the following components: a) water of variable salinity, b) cement and c) the copolymer of the invention in a concentration of 0.01- 5% by weight of cement, preferably 0.05-0.09% by weight of cement. JN / osu * avc * rcp * if P00 / 110F SUMMARY OF THE INVENTION The invention relates to copolymers consisting of a) 1 99% by weight of structural units of the formula (1) wherein R1 is hydrogen or methyl, R4 is alkylene of C -? - C22, R5 is C1-C22 alkyl or hydrogen and X is ammonium, lithium, potassium, an amine or a mixture of these substances and b) 99-1% by weight of structural units of the formula (2) wherein R is hydrogen or methyl and R2 and R3 represent C1-C22 alkyl independently from each other; the copolymers of the invention are characterized in that component b) is not hydrolyzed and that the copolymers are produced by a precipitation polymerization of solution in a non-aqueous solvent or a water-miscible organic solvent with a low water content representing an agent of precipitation for the copolymer; The invention also relates to a method for cementing drill holes in deep wells using a cement slurry containing the following components: a) water of variable salinity, b) cement and c) the copolymer of the invention in a concentration of 0.01- 5% by weight of cement, preferably 0.05-0.09% by weight of cement. P00 / 110F