Copolymer with water loss reduction function, preparation method thereof and method for reducing water loss of metakaolin-based geopolymer slurry

Abstract

The invention relates to the field of oil field well cementation, and discloses a copolymer with a water loss reduction function, a preparation method of the copolymer and a method for reducing the water loss of metakaolin-based geopolymer slurry. The copolymerization comprises a structural unit m, a structural unit n and a structural unit p. The copolymer with the water loss reduction function has good alkali resistance, and when the copolymer with the water loss reduction function is used as a metakaolin-based geopolymer slurry additive, the water loss of metakaolin-based geopolymer slurry can be effectively reduced. # imgabs0 #

Description

Technical Field

[0001] The invention relates to the field of oilfield cementing, and in particular to a copolymer with a water loss reducing function and a preparation method thereof, as well as a method for reducing the water loss of a metakaolin-based geopolymer slurry. Background Art

[0002] Cement and other industries will soon be included in the national carbon emissions trading system, which will have a significant and far-reaching impact on my country's cement industry and its operations. 9 t, accounting for about 55% of the world's total, and emitting about 1.4×10 9 t, accounting for approximately 14.3% of China's total carbon emissions. CO2 emissions per ton of cement and per ton of cement clinker are approximately 616.6 kg and 865.8 kg, respectively. The cement industry faces significant pressure to reduce emissions, and the task is arduous. As a specialty cement, reducing carbon emissions from oil well cement is bound to have a significant impact on the cementing industry. Geopolymer gelling systems are a more suitable cementing fluid besides oil well cement slurry. Compared to oil well cement slurry, geopolymers have outstanding low-carbon properties. Furthermore, metakaolin-based geopolymers exhibit excellent stability in corrosive environments, making them suitable for sealing acidic gas formations and CCUS wells. They also possess outstanding high-temperature resistance, low shrinkage, and high shear strength, ensuring long-term sealing integrity.

[0003] Currently, research on metakaolin-based geopolymer fluid loss additives is limited, primarily due to the strong alkalinity of the metakaolin-based geopolymer slurry. Paiva et al. (Journal of Petroleum Science and Engineering, 2018, 169:748-759) studied the fluid loss performance of a metakaolin-potassium hydroxide-potassium silicate geopolymer system. Without a fluid loss additive, the system's API water loss was 120 mL (at 27°C). With the addition of silica fume and the retarder p(AMPS-co-AA), the water loss at 31°C was reduced to 66 mL, suggesting that silica fume reduces filter cake porosity and permeability. However, this system is applicable at relatively low temperatures and cannot meet the high-temperature requirements of cementing environments.

[0004] Therefore, there is an urgent need for a fluid loss reducer that has good alkali resistance, is adaptable to high temperatures, and can effectively reduce the water loss of metakaolin-based geopolymer slurry. Summary of the Invention

[0005] The present invention aims to overcome the problems in the prior art of low applicable temperature and a need to improve the effect of reducing the water loss of a metakaolin-based geopolymer slurry. The present invention provides a copolymer with a water loss reduction function and a preparation method thereof, as well as a method for reducing the water loss of a metakaolin-based geopolymer slurry. The copolymer with a water loss reduction function has good alkali resistance and can maintain structural stability in a metakaolin slurry. Under the action of a pore solution in the metakaolin slurry, the copolymer can form a spherical conformation and can block the pores of a filter cake of the metakaolin-based geopolymer slurry.

[0006] In order to achieve the above object, the first aspect of the present invention provides a copolymer having a fluid loss reducing function, wherein the copolymer comprises a structural unit m, a structural unit n and a structural unit p.

[0007]

[0008] A second aspect of the present invention provides a method for preparing a copolymer having a fluid loss reducing function, wherein the preparation method comprises the following steps: mixing a comonomer and an initiator in the presence of a solvent to carry out a polymerization reaction; wherein the comonomer comprises an acrylic acid monomer, a 2-acrylamide-2-methylpropanesulfonic acid monomer, and an N-(isobutyloxy)methacrylamide monomer.

[0009] The third aspect of the present invention provides a copolymer with a fluid loss reduction function obtained by the preparation method provided by the present invention.

[0010] A fourth aspect of the present invention provides a method for reducing water loss in a metakaolin-based geopolymer slurry, wherein the method comprises: mixing the copolymer with water loss reduction function provided by the present invention with a metakaolin-based geopolymer slurry.

[0011] Through the above technical solution, the beneficial effects of the present invention include at least:

[0012] The fluid loss reduction copolymer of the present invention has excellent alkali resistance and good compatibility with geopolymer systems, without significantly affecting the rheology, thickening time, and strength of the geopolymer system. The fluid loss reduction copolymer of the present invention can significantly reduce the water loss of metakaolin-based geopolymer slurries, meeting cementing construction requirements, and is suitable for temperatures between 20°C and 80°C.

[0013] In preferred embodiments, the water loss of a metakaolin-based geopolymer slurry can be controlled to below 50 mL at a 1 wt% addition. Furthermore, by selecting the appropriate weight ratio of the polymerizable monomers, the amount of initiator used, and the polymerization reaction conditions, the water loss of the metakaolin-based geopolymer slurry after the addition of the copolymer with a water loss reduction function can be further reduced, and the compressive strength and fluidity of the metakaolin-based geopolymer slurry after the addition of the copolymer with a water loss reduction function can be further improved. DETAILED DESCRIPTION

[0014] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0015] The first aspect of the present invention provides a copolymer having a fluid loss reducing function, wherein the copolymer comprises a structural unit m, a structural unit n and a structural unit p.

[0016]

[0017] The copolymer with a water loss reduction function of the present invention is suitable for metakaolin-based geopolymers, has good alkali resistance, and can maintain structural stability in metakaolin slurry. Under the action of the pore solution of the metakaolin slurry, the copolymer can form a spherical conformation. When the copolymer is used as an additive for the metakaolin-based geopolymer slurry, the copolymer can block the pores of the metakaolin-based geopolymer slurry filter cake, thereby playing a role in regulating the water loss of the metakaolin-based geopolymer slurry.

[0018] The present invention has no particular restriction on the weight ratio of the structural units provided by the comonomer, as long as a structurally stable copolymer can be formed. In order to further reduce the water loss of the metakaolin-based geopolymer slurry to which the polymer is added, preferably, in the copolymer, the weight ratio of the structural unit m, the structural unit n and the structural unit p is 7:(1-5):(0.3-1).

[0019] In the present invention, the content of each structural unit in the polymer can be tested by conventional methods in the prior art, such as infrared spectroscopy, nuclear magnetic resonance, and the amount of monomers fed during the polymerization process. Preferably, the content of each structural unit in the polymer is determined by the amount of monomers fed. Specifically, the feed ratio of each monomer actually participating in the polymerization is determined by testing the content of unreacted monomers, thereby determining the content of each structural unit in the polymer. Furthermore, in the present invention, the content of each unreacted monomer in the tested polymer is less than 0.5wt%, indicating that substantially all monomers participate in the polymerization reaction. Specifically, the content of the residual monomers is determined by liquid chromatography.

[0020] The present invention has no particular limitation on the weight-average molecular weight of the copolymer, as long as it can form a stable spherical conformation under the action of the pore solution of the metakaolin-based geopolymer slurry and has an appropriate size to reduce the pores of the metakaolin-based geopolymer slurry filter cake. In order to further reduce the water loss of the metakaolin-based geopolymer slurry to which the polymer is added, preferably, the weight-average molecular weight of the copolymer is 420,000-490,000 g / mol.

[0021] According to the present invention, preferably, the molecular weight distribution index of the copolymer is 1.7-2.5.

[0022] The present invention has no particular limitation on the size of the copolymer, as long as it can reduce the porosity of the metakaolin-based geopolymer slurry filter cake. In order to further improve the blocking effect on the pores of the slurry filter cake and thus further regulate the water loss of the metakaolin-based geopolymer slurry, preferably, the average particle size of the copolymer is less than or equal to 180 μm, more preferably 130-165 μm.

[0023] A second aspect of the present invention provides a method for preparing a copolymer having a fluid loss reducing function, wherein the preparation method comprises the following steps: subjecting a comonomer to a polymerization reaction in the presence of an initiator and a solvent; wherein the comonomer comprises an acrylic acid monomer, a 2-acrylamide-2-methylpropanesulfonic acid monomer, and an N-(isobutyloxy)methacrylamide monomer.

[0024] The present invention has no particular restriction on the usage ratio of the comonomers, as long as a structurally stable copolymer can be formed. In order to further reduce the water loss of the metakaolin-based geopolymer slurry to which the polymer is added, according to the present invention, preferably, in the comonomers, the weight ratio of the acrylic acid monomer, the 2-acrylamide-2-methylpropanesulfonic acid monomer and the N-(isobutyloxy)methacrylamide monomer is 7:(1-5):(0.3-1).

[0025] The present invention has no particular limitation on the amount of the initiator, as long as it can initiate the polymerization reaction of acrylic acid monomer, 2-acrylamide-2-methylpropanesulfonic acid monomer and N-(isobutyloxy)methacrylamide monomer to proceed smoothly. In order to further reduce the water loss of the metakaolin-based geopolymer slurry to which the present polymer is added, preferably, the amount of the initiator is 0.3-2 wt % based on the total weight of the comonomers.

[0026] The present invention is not particularly limited to the type of initiator, and free radical initiators conventional in the art for initiating monomer polymerization reactions can be used. For example, peroxide initiators can be used, and the peroxide initiators can be organic peroxide initiators such as acyl peroxides, hydroperoxides, dialkyl peroxides, ester peroxides, ketone peroxides, and dicarbonate peroxides, and persulfate inorganic peroxide initiators such as potassium persulfate, sodium persulfate, and ammonium persulfate can also be used. For example, azo initiators can also be used, and the azo initiators can be azobisisobutyronitrile, azobisisoheptonitrile, dimethyl azobisisobutyrate, etc. For example, redox initiators can also be used, and can be an oxidant (ammonium persulfate) and a reducing agent (sodium bisulfite) system initiator.

[0027] In order to further reduce the water loss of the metakaolin-based geopolymer slurry to which the present polymer is added, in a preferred embodiment of the present invention, the initiator is a peroxide initiator, more preferably a persulfate inorganic peroxide initiator, and even more preferably ammonium persulfate.

[0028] The present invention has no particular limitation on the amount of solvent used, as long as the polymerization reaction can be smoothly carried out after the comonomer and initiator are mixed. In order to further reduce the water loss of the metakaolin-based geopolymer slurry to which the polymer is added, preferably, the amount of the solvent is such that the weight ratio of the solvent to the comonomer is 100:(10-50), preferably 100:(15-30).

[0029] According to the present invention, preferably, the solvent is water.

[0030] The present invention has no particular limitation on the temperature and time of the polymerization reaction. It suffices that the initiator can initiate the polymerization reaction at the polymerization temperature. In order to further reduce the water loss of the metakaolin-based geopolymer slurry to which the polymer is added, preferably, the polymerization reaction temperature is 45-55° C. and the time is 4-8 hours.

[0031] According to the present invention, in order to further improve the blocking effect on the pores of the slurry filter cake and reduce the water loss of the metakaolin-based geopolymer slurry to which the polymer is added, preferably, the preparation method further comprises: drying and pulverizing the product obtained by the polymerization reaction, and the pulverization conditions are such that the average particle size of the copolymer having the water loss reduction function is less than or equal to 180 μm, more preferably 130-165 μm.

[0032] The present invention has no particular restrictions on the equipment and drying conditions for drying the polymerization product, as long as the moisture in the polymerization product can be removed. For example, an electric heated blast constant temperature drying oven can be used to dry the polymerization product at 60-100°C for 30-60 hours.

[0033] The third aspect of the present invention provides a copolymer with a fluid loss reduction function obtained by the preparation method provided by the present invention.

[0034] A fourth aspect of the present invention provides a method for reducing water loss in a metakaolin-based geopolymer slurry, wherein the method comprises: mixing the copolymer with water loss reduction function provided by the present invention with a metakaolin-based geopolymer slurry.

[0035] The present invention has no particular restriction on the amount of the copolymer with a fluid loss reducing function added to the metakaolin-based geopolymer slurry. In order to further reduce the fluid loss of the metakaolin-based geopolymer slurry, preferably, the amount of the copolymer added is 0.5-1.5wt%, preferably 1-1.5wt%, based on the total weight of the metakaolin-based geopolymer slurry.

[0036] According to the present invention, preferably, the metakaolin-based geopolymer slurry comprises the following components in parts by weight: 400 parts of metakaolin, 400-500 parts of water glass, 60-100 parts of water and 25-35 parts of retarder.

[0037] The present invention has no particular limitation on the type of retarder, and conventional substances in the art that can reduce the hydration rate and hydration heat of metakaolin and prolong the setting time can be used, such as hydroxyl compounds, hydroxycarboxylates and their derivatives, high-sugar lignin sulfonates, etc.

[0038] In a preferred embodiment of the present invention, the retarder is selected from at least one of glucose, sucrose and fructose.

[0039] According to the present invention, the metakaolin-based geopolymer slurry is alkaline, and the copolymer with fluid loss reduction function of the present invention has a good fluid loss reduction effect on the metakaolin-based geopolymer slurry with a pH value of 13-14 and a temperature of 20-80°C.

[0040] In a preferred embodiment of the present invention, the copolymer with fluid loss reducing function of the present invention has a good fluid loss reducing effect on a metakaolin-based geopolymer slurry with a pH value of 13.2-13.6 and a temperature of 45-60°C.

[0041] According to the present invention, the pH of the metakaolin-based geopolymer slurry can be controlled by adding a pH adjuster, such as sodium hydroxide. In a preferred embodiment of the present invention, the amount of sodium hydroxide added to the metakaolin-based geopolymer slurry is 40-50 parts by weight, based on 400 parts by weight of metakaolin.

[0042] The present invention will be described in detail below through examples and comparative examples. In the following examples and comparative examples, unless otherwise specified, all methods are conventional; and all reagents and materials used, unless otherwise specified, can be obtained from commercial sources.

[0043] The following examples and comparative examples are used to illustrate the preparation method of the copolymer having a fluid loss reducing function (i.e., a fluid loss reducer).

[0044] Example 1

[0045] A three-necked flask was sequentially charged with 100 g of distilled water, 14 g of acrylic acid, 2 g of 2-acrylamido-2-methylpropanesulfonic acid, and 1 g of N-(isobutyloxy)methacrylamide. Nitrogen was then introduced into the flask to expel air from the flask. After stirring for 20 minutes, 0.34 g of ammonium persulfate was added and stirred evenly. The flask was then placed in a 50°C waterbath for 4 hours. The polymer product was then dried at 80°C for 48 hours and pulverized to obtain a metakaolin-based geopolymer fluid loss additive P1. Laser particle size analyzer measurements revealed an average particle size of 150 μm. Gel permeation chromatography revealed a weight-average molecular weight of 423,626 g / mol and a molecular weight distribution index of 1.74.

[0046] Example 2

[0047] A three-necked flask was sequentially added with 100g of distilled water, 14g of acrylic acid, 4g of 2-acrylamido-2-methylpropanesulfonic acid, and 0.7g of N-(isobutyloxy)methacrylamide. Nitrogen was then introduced into the flask to expel air from the flask. After stirring for 20 minutes, 0.28g of ammonium persulfate was added and stirred evenly. The flask was then placed in a 50°C waterbath for 8 hours. The polymer was then dried at 80°C for 48 hours and pulverized to obtain a metakaolin-based geopolymer fluid loss additive P2 with an average particle size of 150μm. The weight-average molecular weight of fluid loss additive P2 was 439,888g / mol, and the molecular weight distribution index was 2.06.

[0048] Example 3

[0049] A three-necked flask was sequentially added with 100g of distilled water, 14g of acrylic acid, 6g of 2-acrylamido-2-methylpropanesulfonic acid, and 0.8g of N-(isobutyloxy)methacrylamide. Nitrogen was then introduced into the flask to expel air from the flask. After stirring for 20 minutes, 0.208g of ammonium persulfate was added and stirred evenly. The flask was then placed in a 45°C waterbath to react for 6 hours. The polymer product was then dried at 80°C for 48 hours and pulverized to obtain a metakaolin-based geopolymer fluid loss additive P3 with an average particle size of 150μm. The weight-average molecular weight of fluid loss additive P3 was 450304g / mol, and the molecular weight distribution index was 2.44.

[0050] Example 4

[0051] A three-necked flask was sequentially added with 100 g of distilled water, 14 g of acrylic acid, 8 g of 2-acrylamido-2-methylpropanesulfonic acid, and 0.9 g of N-(isobutyloxy)methacrylamide. Nitrogen was then introduced into the flask to expel air from the flask. After stirring for 20 minutes, 0.183 g of ammonium persulfate was added and stirred evenly. The flask was then placed in a 50°C waterbath to react for 5 hours. The polymer product was then dried at 80°C for 48 hours and pulverized to obtain a metakaolin-based geopolymer fluid loss additive P4 with an average particle size of 150 μm. The weight-average molecular weight of P4 was 463,567 g / mol, and the molecular weight distribution index was 2.47.

[0052] Example 5

[0053] A three-necked flask was sequentially added with 100g of distilled water, 14g of acrylic acid, 10g of 2-acrylamido-2-methylpropanesulfonic acid, and 0.6g of N-(isobutyloxy)methacrylamide. Nitrogen was then introduced into the flask to expel air from the flask. After stirring for 20 minutes, 0.074g of ammonium persulfate was added and stirred evenly. The flask was then placed in a 55°C waterbath for 5 hours. The polymer product was then dried at 80°C for 48 hours and pulverized to obtain a metakaolin-based geopolymer fluid loss additive P5 with an average particle size of 150μm. The weight-average molecular weight of P5 was 467,854g / mol, and the molecular weight distribution index was 1.86.

[0054] Example 6

[0055] A fluid loss additive was prepared according to the method of Example 2, except that the weight ratio of the polymerized monomers was changed. Specifically, "14 g acrylic acid, 4 g 2-acrylamido-2-methylpropanesulfonic acid, 0.7 g N-(isobutoxy)methacrylamide" was replaced with "4 g acrylic acid, 14 g 2-acrylamido-2-methylpropanesulfonic acid, 0.7 g N-(isobutoxy)methacrylamide." The resulting metakaolin-based geopolymer fluid loss additive P6 had an average particle size of 150 μm, a weight-average molecular weight of 485,940 g / mol, and a molecular weight distribution index of 1.73.

[0056] Example 7

[0057] A fluid loss additive was prepared according to the method of Example 2, except that the amount of initiator used was different. Specifically, "add 0.28 g of ammonium persulfate" was replaced with "add 0.5 g of ammonium persulfate." The resulting metakaolin-based geopolymer fluid loss additive P7 had an average particle size of 150 μm, a weight-average molecular weight of 307,106 g / mol, and a molecular weight distribution index of 3.25.

[0058] Example 8

[0059] A fluid loss additive was prepared according to the method of Example 2, except that the polymerization reaction conditions were different. Specifically, "Place the three-necked flask in a 65°C waterbath for 3 hours" was substituted for "Place the three-necked flask in a 50°C waterbath for 8 hours." The resulting metakaolin-based geopolymer fluid loss additive P8 had an average particle size of 150 μm, a weight-average molecular weight of 277,901 g / mol, and a molecular weight distribution index of 2.8.

[0060] Comparative Example 1

[0061] A fluid loss additive was prepared according to the method of Example 2, except that 0.7 g of N-(isobutyloxy)methacrylamide was replaced with 0.7 g of acrylamide. Copolymer D1 was obtained, having an average particle size of 150 μm, a weight-average molecular weight of 533,989 g / mol, and a molecular weight distribution index of 1.77.

[0062] Comparative Example 2

[0063] A fluid loss additive was prepared according to the method of Example 2, except that 2-acrylamide-2-methylpropanesulfonic acid was used instead of an equal weight of N-(isobutyloxy)methacrylamide. The resulting copolymer D2 had an average particle size of 150 μm, a weight-average molecular weight of 454,719 g / mol, and a molecular weight distribution index of 1.78.

[0064] Comparative Example 3

[0065] A fluid loss additive was prepared according to the method of Example 2, except that allyl sulfonic acid was used instead of an equal weight of 2-acrylamide-2-methylpropanesulfonic acid. Copolymer D3 was obtained, having an average particle size of 150 μm, a weight-average molecular weight of 241,949 g / mol, and a molecular weight distribution index of 1.66.

[0066] Comparative Example 4

[0067] A fluid loss additive was prepared according to the method of Example 2, except that 2-(2-methacryloyloxy)ethyl 3-oxobutanoate was used in place of an equal weight of N-(isobutyloxy)methacrylamide. The resulting copolymer D4 had an average particle size of 150 μm, a weight-average molecular weight of 562,863 g / mol, and a molecular weight distribution index of 3.25.

[0068] Test Case

[0069] In order to evaluate the ability of the fluid loss additives prepared in the Examples and Comparative Examples to control water loss in a metakaolin-based geopolymer slurry, the water loss of the metakaolin-based geopolymer fluid loss additives prepared in the Examples and Comparative Examples was measured, and the compressive strength and fluidity of the metakaolin-based geopolymer slurry were also measured. The water loss test for metakaolin-based geopolymer slurry was conducted according to the "Static Fluid Loss Test for Cement Slurry" in the national standard "GB / T 19139-2012 Test Methods for Oil Well Cement" at a test temperature of 50°C. The compressive strength test for metakaolin-based geopolymer slurry was conducted according to the "Compressive Strength Test for Cement Paste" in the national standard "GB / T 19139-2012 Test Methods for Oil Well Cement" at a test temperature of 50°C and a curing period of 3 days. The fluidity test for metakaolin-based geopolymer slurry was conducted according to the "Fluidity of Cement Paste" in the national standard "GB / T 8077-2012 Test Methods for Homogeneity of Concrete Admixtures" at a test temperature of 25°C. The geopolymer slurry formula is: 400g metakaolin + 440g water glass + 45.4g sodium hydroxide + 80g water + 32g glucose. The amount of fluid loss additive added is based on the total weight of the metakaolin-based geopolymer slurry. The results are shown in Table 1.

[0070] Table 1

[0071] serial number Water loss, mL Compressive strength, MPa Fluidity, cm Slurry + 1wt% P1 30 23.2 24.8 Slurry + 1wt% P2 36 23.1 25.5 Slurry + 0.5wt% P2 78 23.9 26.4 Slurry + 1.5wt% P2 26 22.6 24.7 Slurry + 1wt% P3 38 23.6 25.3 Slurry + 1wt% P4 32 22.8 25.9 Slurry + 1wt% P5 34 22.6 24.5 Slurry + 1wt% P6 186 18.5 22.4 Slurry + 1wt% P7 148 19.2 25.5 Slurry + 1wt% P8 164 18.4 26.4 Slurry + 1wt% D1 238 20.7 21.5 Slurry + 1wt% D2 240 18.5 23.6 Slurry + 1wt% D3 242 19.8 25.1 Slurry + 1wt% D4 194 18.6 24.8 slurry 262 24.6 26.8

[0072] The results in Table 1 show that the water loss of a metakaolin-based geopolymer slurry without a fluid loss additive at 50°C was 262 mL, which does not meet cementing construction requirements. However, after adding the fluid loss additives P1-P5 prepared in the present invention, suitable for use with metakaolin-based geopolymer slurries, the water loss of the slurry can be controlled to below 50 mL at a 1 wt% dosage, demonstrating excellent water loss control and meeting cementing construction requirements. When the fluid loss additive P2 prepared in Example 2 was added at 0.5 wt%, 1 wt%, and 1.5 wt%, respectively, the water loss of the metakaolin-based geopolymer slurry gradually decreased with increasing fluid loss additive addition. When the fluid loss additive prepared in Example 2 was added at 1 wt%, the water loss of the metakaolin-based geopolymer slurry was 36 mL. In addition, in Comparative Example 1, acrylamide was used instead of an equal weight of N-(isobutoxy)methacrylamide, in Comparative Example 2, 2-acrylamide-2-methylpropanesulfonic acid was used instead of an equal weight of N-(isobutoxy)methacrylamide, in Comparative Example 3, allyl sulfonic acid was used instead of an equal weight of 2-acrylamide-2-methylpropanesulfonic acid, and in Comparative Example 4, 2-(2-methacryloyloxy)ethyl 3-oxobutyrate was used instead of an equal weight of N-(isobutoxy)methacrylamide. Compared with the addition of fluid loss additives P1-P8 to the metakaolin-based geopolymer slurry, the water loss after the addition of fluid loss additives D1-D4 to the metakaolin-based geopolymer slurry was significantly increased.

[0073] In addition, Example 6 changed the weight ratio of the polymerized monomers. Compared with Example 2, the water loss of the metakaolin-based geopolymer slurry after adding the fluid loss reducer P6 increased, and the compressive strength and fluidity also decreased. Example 7 increased the amount of initiator. Compared with Example 2, the water loss of the metakaolin-based geopolymer slurry after adding the fluid loss reducer P7 increased, and the compressive strength also decreased. Example 8 increased the polymerization temperature and shortened the polymerization time. Compared with Example 2, the water loss of the metakaolin-based geopolymer slurry after adding the fluid loss reducer P8 increased, and the compressive strength also decreased. This shows that when the weight ratio of the polymerized monomers, the amount of initiator, and the polymerization reaction conditions meet the optimal conditions, the water loss of the metakaolin-based geopolymer slurry after adding the fluid loss reducer can be further reduced, and the compressive strength and fluidity of the metakaolin-based geopolymer slurry after adding the fluid loss reducer can be further improved.

[0074] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A copolymer having a fluid loss reducing function, characterized in that: The copolymer includes structural unit m, structural unit n and structural unit p, 2. The copolymer according to claim 1, characterized in that In the copolymer, the weight ratio of the structural unit m, the structural unit n and the structural unit p is 7: (1-5): (0.3-1); and / or, the weight average molecular weight of the copolymer is 420,000-490,000 g / mol; And / or, the molecular weight distribution index of the copolymer is 1.7-2.

5.

3. The copolymer according to claim 1 or 2, characterized in that The average particle size of the copolymer is less than or equal to 180 μm, more preferably 130-165 μm.

4. A method for preparing a copolymer having a fluid loss reducing function, characterized in that: The preparation method comprises the following steps: in the presence of an initiator and a solvent, polymerizing comonomers; wherein the comonomers comprise acrylic acid monomers, 2-acrylamide-2-methylpropanesulfonic acid monomers and N-(isobutyloxy)methacrylamide monomers.

5. The preparation method according to claim 4, characterized in that Among the comonomers, the weight ratio of acrylic acid monomer, 2-acrylamide-2-methylpropanesulfonic acid monomer and N-(isobutyloxy)methacrylamide monomer is 7:(1-5):(0.3-1); And / or, based on the total weight of the comonomers, the amount of the initiator is 0.3-2 wt%.

6. The preparation method according to claim 4 or 5, characterized in that The amount of the solvent used is such that the weight ratio of the solvent to the comonomer is 100:(10-50), preferably 100:(15-30); Preferably, the solvent is water.

7. The preparation method according to any one of claims 4 to 6, characterized in that The polymerization reaction temperature is 45-55° C. and the reaction time is 4-8 hours.

8. The preparation method according to any one of claims 4 to 7, characterized in that The preparation method further comprises: drying and crushing the product obtained by the polymerization reaction, wherein the crushing conditions are such that the average particle size of the copolymer is less than or equal to 180 μm, more preferably 130-165 μm.

9. A copolymer with a fluid loss reducing function obtained by the preparation method according to any one of claims 4 to 8.

10. A method for reducing water loss of a metakaolin-based geopolymer slurry, characterized in that: The method comprises: mixing the copolymer having a fluid loss reducing function according to any one of claims 1 to 3 and 9 with a metakaolin-based geopolymer slurry; Preferably, the copolymer is added in an amount of 0.5-1.5 wt %, preferably 1-1.5 wt %, based on the total weight of the metakaolin-based geopolymer slurry; Preferably, the metakaolin-based geopolymer slurry comprises the following components in parts by weight: 400 parts of metakaolin, 400-500 parts of water glass, 60-100 parts of water and 25-35 parts of retarder; and / or, the pH value of the metakaolin-based geopolymer slurry is 13-14, preferably 13.2-13.6; The temperature is 20-80°C, preferably 45-60°C.

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