Polymer and method of making same and gelling acid composition

Abstract

The application relates to the technical field of carbonatite reservoir acid fracturing, and discloses a polymer, a preparation method thereof and a composition for gelled acid. The polymer comprises a structural unit shown in formula A, a structural unit shown in formula B and a structural unit shown in formula C, the viscosity-average molecular weight of the polymer is 5-8 million g / mol, the molecular weight distribution is 3-5, the weight ratio of the structural unit shown in formula A, the structural unit shown in formula B and the structural unit shown in formula C is 1:1.2-1.8:0.1-0.2. When the polymer is used as an acid liquid thickening agent, the polymer has the characteristics of high temperature resistance, shear resistance, low initial viscosity and low gel breaking liquid residue content.

Description

Technical Field

[0001] This invention relates to the field of acid fracturing technology for carbonate reservoirs, specifically to a polymer, its preparation method, and a composition for gelling acids. Background Technology

[0002] Thickeners are an important component of fracturing fluids. Compared to water-based fracturing fluids, acid-based fracturing fluids (i.e., acid fluids) have higher performance requirements for thickeners, mainly in terms of temperature resistance in strong acid environments. Depending on reservoir and process requirements, acid-based fracturing fluids are classified into systems such as gelling acid and crosslinking acid. Crosslinking acid thickeners need to be used in conjunction with crosslinking agents to be effective with acid fluids, while gelling acid thickeners can be used directly with acid fluids without the need for crosslinking agents.

[0003] Ultra-deep carbonate reservoirs are old and deeply buried, and generally exhibit high temperature and high pressure characteristics. For example, ultra-deep carbonate rock reservoirs are characterized by ultra-deep (>8000m), high closure pressure (>150MPa), and ultra-high temperature (>180℃), which places higher demands on the temperature resistance of acid solutions. However, existing acid thickeners have the following problems: (1) poor high temperature resistance, viscosity decreases at high temperatures, acid-rock reaction speed is fast, and effective action distance is short; (2) the viscosity of acid solution at high temperatures is often increased by increasing the amount of thickener, but this will result in a high initial viscosity of acid solution (at room temperature), which is not conducive to acid solution preparation and large-volume pumping on site, and increases the difficulty of construction; moreover, a higher initial viscosity will result in high friction and high pressure during the construction of acid fracturing tubing, especially for high-pressure reservoirs, which poses a safety risk. For example, CN114085315A discloses a high-temperature resistant emulsion-type acid thickener and its preparation method, wherein the quaternary polymer monomers in the thickener include acrylamide, methacrylpropyltrimethylammonium chloride, dimethyldiallylammonium chloride, and N. Vinylpyrrolidone. Although this thickener can withstand temperatures up to 220°C, the amount of thickener added to the acid solution is only 2%, resulting in an initial viscosity of 120 mPa·s for the base solution. This is very unfavorable for large-volume pumping of acid solution in on-site construction.

[0004] Therefore, for acid fracturing stimulation of ultra-deep carbonate reservoirs, how to reduce the initial viscosity of the acid while taking into account the rheological viscosity at high temperatures (temperature resistance and shear resistance to reduce the acid-rock reaction rate) and improve the efficiency of carbonate reservoir stimulation has become an urgent problem to be solved. Summary of the Invention

[0005] The purpose of this invention is to overcome the problems of high initial viscosity (at room temperature) and low rheological viscosity at high temperatures in existing technologies, and to provide a polymer, its preparation method, and a composition for gelling acids. This polymer can act as a thickener for acids without the use of crosslinking agents, giving the acids a lower initial viscosity for easier on-site application; it also exhibits higher rheological viscosity at high temperatures, improving the temperature resistance of the acids.

[0006] To achieve the above objectives, the present invention provides a polymer comprising structural units shown in Formula A, Formula B, and Formula C, wherein the structural unit shown in Formula B comprises at least one of the structural units shown in Formula B-1, Formula B-2, and Formula B-3; the polymer has a viscosity-average molecular weight of 5-8 million g / mol and a molecular weight distribution of 3-5; the weight ratio of the structural units shown in Formula A, Formula B, and Formula C is 1:1.2-1.8:0.1-0.2. Formula A; Formula B-1; Formula B-2; Formula B-3; Formula C; Among them, R 11 R 12 R 13 R 14 The same or different and each independently selected from H or C1-C4 alkyl groups; R 21 R 22 R 23 The same or different and independently selected from C1-C4 alkyl, C2-C4 alkenyl, and hydroxylated C1-C4 alkyl groups; R 31 R 32 The same or different and each independently selected from H or C1-C4 alkyl groups; R 41 Selected from C1-C4 alkylene groups or L1 and L2 are the same or different and are each independently selected from -SO3- or -COO-; M1 and M2 are the same or different and are each independently selected from H or alkali metals; X is selected from halogens; m, n and p are each independently selected from 0-3.

[0007] A second aspect of this invention provides a method for preparing a polymer, the method comprising: mixing compound A, compound B, and compound C with water; then, in the presence of an initiator, a complexing agent, a cosolvent, and a molecular weight regulator, causing compound A, compound B, and compound C to undergo a polymerization reaction; and then granulating and drying the product of the polymerization reaction; wherein compound B includes at least one of compound B1, compound B2, and compound B3; the amounts of compounds A, B, and C are such that the weight ratio of structural units of formula A, formula B, and formula C in the obtained polymer is 1:1.2-1.8:0.1-0.2; the initiator includes an oxidizing initiator, a reducing initiator, and an azo initiator; the molecular weight regulator is selected from C4-C15 alkyl thiols; and the cosolvent is selected from urea and / or thiourea. Compound A; Compound B1; Compound B2; Compound B3; Compound C; The definitions of R1, R2, R3, R4, L, M, X, m, n, and p are the same as those described in the first aspect of this invention.

[0008] A third aspect of the present invention provides a polymer prepared by the method described in the second aspect.

[0009] A fourth aspect of the present invention provides a gelling acid thickener, the gelling acid thickener comprising the polymers described in the first aspect and / or the third aspect of the present invention.

[0010] A fifth aspect of the present invention provides a composition comprising the polymer and additives described in the first aspect and / or the third aspect of the present invention.

[0011] Through the above technical solution, the present invention achieves the following beneficial effects: (1) Compared with existing acrylamide polymers, the polymer of the present invention comprises structural units of formulas A, B, and C in specific weight ratios, and has specific viscosity-average molecular weight and specific molecular weight distribution. When used in gelling acid systems, it exhibits lower initial viscosity and higher temperature resistance (high rheological viscosity at high temperatures). Preferably, the polymer of the present invention can reduce the amount of thickener used, so that the amount of thickener used can meet the requirement of high rheological viscosity (≥20 mPa·s) of acid solution at high temperature (200°C) with a lower amount of thickener.

[0012] (2) The polymer preparation method of the present invention is simple, the raw materials are readily available and of few types, which facilitates industrial production and can reduce the production cost of thickeners. The polymer of the present invention uses compounds A, B, and C in a specific weight ratio, and under the synergistic effect of three initiators—oxidative initiator, reductive initiator, and azo initiator—as well as specific types of cosolvents and molecular weight regulators, a polymer with a narrow molecular weight distribution range and a specific viscosity-average molecular weight is prepared. The polymer prepared by this method has a low initial viscosity and high temperature resistance (high rheological viscosity at high temperatures) when used in gelling acid systems.

[0013] (3) Compared with cross-linking acid systems, the gelling acid system of the present invention does not require a cross-linking agent, thus avoiding the problems of difficult debonding and excessive residue caused by the cross-linking reaction, and effectively reducing the damage of acid to the reservoir. The gelling acid system has a low residue content in the debonding liquid after reacting with marble (<170mg / L), which reduces the damage of the liquid to the reservoir.

[0014] (4) In a preferred embodiment, the gelling acid system prepared by the polymer provided by the present invention as a thickener has the characteristics of low initial viscosity (≤55mPa.s) and high rheological viscosity (≥20mPa.s) at high temperature (200℃), which can reduce the reaction rate of acid rock and is beneficial to deep acid fracturing. Attached Figure Description

[0015] Figure 1 The image shows the infrared characterization of the polymer prepared in Example 1. Figure 2 Here is a scanning electron microscope (SEM) image of the polymer prepared in Example 1; Figure 3 This is a scanning electron microscope (SEM) characterization of the polymer in Comparative Example 8; Figure 4 This is a graph showing the changes in dissolution time and initial viscosity of the polymer in Example 2 in a 20% HCl solution; Figure 5 The rheological curve of the gelling acid system prepared by the polymer in Example 1 at 200°C is shown. Figure 6 Comparison of rheological curves at 200°C for the gelling acid systems prepared by the polymer of Example 1 and the polymer of Comparative Example 8; Figure 7 This is a photograph of the gelling acid system prepared by the polymer in Example 1 after shearing at 200°C; Figure 8 This is a photograph of the gelling acid system prepared by the polymer in Comparative Example 8 after shearing at 200°C. Figure 9 This is a corrosion diagram of the steel sheet caused by the gelling acid system prepared by the polymer in Example 1; Figure 10This is a photograph of the gelling acid system prepared by the polymer in Example 1 after reacting with marble blocks. Detailed Implementation

[0016] The endpoints and any values ​​of the ranges 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 endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0017] The present invention provides a polymer comprising structural units shown in Formula A, Formula B, and Formula C, wherein the structural unit shown in Formula B includes at least one of the structural units shown in Formula B-1, Formula B-2, and Formula B-3; the polymer has a viscosity-average molecular weight of 5-8 million g / mol and a molecular weight distribution of 3-5; the weight ratio of the structural units shown in Formula A, Formula B, and Formula C is 1:1.2-1.8:0.1-0.2. Formula A; Formula B-1; Formula B-2; Formula B-3; Formula C; Among them, R 11 R 12 R 13 R 14 The same or different and each independently selected from H or C1-C4 alkyl groups; R 21 R 22 R 23 The same or different and independently selected from C1-C4 alkyl, C2-C4 alkenyl, and hydroxylated C1-C4 alkyl groups; R 31 R 32 The same or different and each independently selected from H or C1-C4 alkyl groups; R 41 Selected from C1-C4 alkylene groups or L1 and L2 are the same or different and are each independently selected from -SO3- or -COO-; M1 and M2 are the same or different and are each independently selected from H or alkali metals; X is selected from halogens; m, n and p are each independently selected from 0-3.

[0018] While meeting one or two of the polymer's viscosity-average molecular weight, molecular weight distribution, and weight ratio requirements of this invention may reduce the initial viscosity, it cannot simultaneously meet the rheological viscosity requirements of the acid. Only when the polymer's viscosity-average molecular weight, molecular weight distribution, and weight ratio all meet the requirements of this invention can a high rheological viscosity be maintained while reducing the initial viscosity. This allows the polymer, when used as an acid thickener, to not only meet the requirements for large-volume pumping at room temperature, reducing construction difficulty, decreasing friction during acid fracturing string construction, reducing construction pressure, and avoiding safety risks associated with high-pressure reservoirs, but also to improve the polymer's temperature resistance, giving the acid a higher high-temperature rheological viscosity, slowing down the acid-rock reaction rate, and increasing the effective action distance.

[0019] In this invention, " "" indicates the connection key between structural units.

[0020] In some embodiments of the present invention, preferably, R 11 R 12 R 13 R 14 They may be the same or different and are each independently selected from H or C1-C3 alkyl groups. More preferably, R 11 R 12 R 13 R 14 They may be the same or different and each independently selected from H or C1-C2 alkyl groups. More preferably, R... 11 R 12 R 13 R 14 They may be the same or different and are each independently selected from H or methyl.

[0021] In some embodiments of the present invention, preferably, R 21 R 22 R 23 The same or different and independently selected from C1-C3 alkyl, C2-C3 alkenyl, and hydroxyl-substituted C1-C3 alkyl groups. More preferably, R 21 R 22 R 23 The same or different and each independently selected is methyl, ethyl, C2-C3 alkenyl, hydroxymethyl, or hydroxyethyl. More preferably, R 21 R 22 R 23 They may be the same or different and are each independently selected from methyl, ethyl, vinyl, propenyl or hydroxymethyl.

[0022] In some embodiments of the present invention, preferably, R 31 R 32 They may be the same or different and are each independently selected from H or C1-C3 alkyl groups. More preferably, R31 R 32 They may be the same or different and each independently selected from H, methyl, or ethyl. More preferably, R... 31 R 32 They may be the same or different and are each independently selected from H or methyl.

[0023] In some embodiments of the present invention, preferably, the particle size of the polymer is 150-400 μm, more preferably 150-250 μm.

[0024] In some embodiments of the present invention, preferably, the molecular chain aggregation area of ​​the polymer is less than 50%, more preferably less than 10%. When the molecular chain aggregation area of ​​the polymer is limited to the above-mentioned preferred range, the rheological viscosity can be improved.

[0025] In some embodiments of the present invention, preferably, when the polymer concentration in the hydrochloric acid aqueous solution with a mass fraction of 15-25% by weight is 0.5-1 g / 100 mL, the number of undissolved and visible polymer solid particles in the hydrochloric acid aqueous solution is ≤12 / 200 mL, more preferably ≤2 / 200 mL.

[0026] In some embodiments of the present invention, preferably, the sulfur content in the polymer is 5-10% by weight, more preferably 7-9% by weight.

[0027] In some embodiments of the present invention, preferably, R 41 Selected from C1-C3 alkylene groups or More preferably, R 41 Selected from C1-C2 alkylene or .

[0028] In some embodiments of the present invention, preferably, L1 and L2 are -SO3-.

[0029] In some embodiments of the present invention, preferably, M1 and M2 are the same or different and are each independently Na, K, or H. More preferably, M1 and M2 are selected from H.

[0030] In some embodiments of the present invention, preferably, X is selected from Cl, Br, or I. More preferably, X is selected from Cl or Br.

[0031] In some embodiments of the present invention, preferably, m, n, and p are each independently selected from 0 to 2. More preferably, m and p are both 1. More preferably, n is 2.

[0032] In some embodiments of the present invention, in order to further improve the temperature and shear resistance of the polymer-formulated gelling acid system while reducing the initial viscosity, preferably, the structural unit shown in Formula A has the structural unit shown in Formula A-1, the structural unit shown in Formula B has the structural unit shown in Formula B-4, and the structural unit shown in Formula C has the structural unit shown in Formula C-1. Formula A-1; Formula C-1; Formula B-4.

[0033] In this invention, the weight ratio of the structural unit shown in Formula A to the structural unit shown in Formula B can be 1:1.2, 1:1.25, 1:1.3, 1:1.35, 1:1.4, 1:1.45, 1:1.5, 1:1.55, 1:1.6, 1:1.65, 1:1.7, 1:1.75, 1:1.8, or any two of the above ratios.

[0034] In this invention, the weight ratio of the structural unit shown in Formula A to the structural unit shown in Formula C can be 1:0.1, 1:0.11, 1:0.12, 1:0.13, 1:0.14, 1:0.15, 1:0.16, 1:0.17, 1:0.18, 1:0.19, 1:0.2, or any two of the above.

[0035] In some embodiments of the present invention, preferably, the weight ratio of the structural unit shown in Formula A, the structural unit shown in Formula B, and the structural unit shown in Formula C is 1:1.3-1.7:0.15-0.2, and more preferably 1:1.4-1.6:0.16-0.18.

[0036] In this invention, the weight ratio of the structural units can be determined by the ratio of the amount of polymer monomers fed into each structural unit.

[0037] In this invention, the viscosity-average molecular weight of the polymer can be 5 million g / mol, 5.2 million g / mol, 5.5 million g / mol, 5.8 million g / mol, 6 million g / mol, 6.2 million g / mol, 6.5 million g / mol, 6.8 million g / mol, 7 million g / mol, 7.2 million g / mol, 7.5 million g / mol, 7.8 million g / mol, 8 million g / mol, or any two of the above.

[0038] In this invention, the molecular weight distribution of the polymer can be 3, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 5, or any two of the above.

[0039] In some embodiments of the present invention, preferably, the polymer has a viscosity-average molecular weight of 7-8 million g / mol, more preferably 7-7.5 million g / mol, and a molecular weight distribution of 3-4.

[0040] A second aspect of this invention provides a method for preparing a polymer, the method comprising: mixing compound A, compound B, and compound C with water; then, in the presence of an initiator, a complexing agent, a cosolvent, and a molecular weight regulator, causing compound A, compound B, and compound C to undergo a polymerization reaction; and then granulating and drying the product of the polymerization reaction; wherein compound B includes at least one of compound B1, compound B2, and compound B3; the amounts of compounds A, B, and C are such that the weight ratio of structural units of formula A, formula B, and formula C in the obtained polymer is 1:1.2-1.8:0.1-0.2; the initiator includes an oxidizing initiator, a reducing initiator, and an azo initiator; the molecular weight regulator is selected from C4-C15 alkyl thiols; and the cosolvent is selected from urea and / or thiourea. Compound A; Compound B1; Compound B2; Compound B3; Compound C; Among them, R 11 R 12 R 13 R 14 R 21 R 22 R 23 R 31 R 32 R 41 The definitions of L1, L2, M1, M2, X, m, n, and p are the same as those described in the first aspect of this invention.

[0041] This invention prepares a polymer with a specific molecular weight and molecular weight distribution by using compounds A, B, and C in specific weight ratios under the synergistic effect of three initiators (oxidative initiator, reductive initiator, and azo initiator) as well as specific types of cosolvents and molecular weight regulators. The gel acid system prepared with a thickener containing this polymer has a low initial viscosity and a high rheological viscosity at high temperatures.

[0042] When the types and weight ratios of compounds A, B, and C are not within the range defined in this invention, the viscosity-average molecular weight will be too low or too high, the molecular weight distribution will be widened, the initial viscosity will increase, the rheological viscosity will decrease, and the viscosity retention rate will decrease, which will not meet the requirement of high rheological viscosity (≥20 mPa.s) of acid solution at high temperature (200°C).

[0043] The polymers of the present invention do not contain N,N-methylenebisacrylamide, methacrylamide, etc. during the preparation process.

[0044] In some embodiments of the present invention, preferably, the amounts of compounds A, B, and C are such that the weight ratio of structural units of formula A, formula B, and formula C in the resulting polymer is 1:1.3-1.7:0.15-0.2, more preferably 1:1.4-1.6:0.16-0.18. Limiting the amounts of compounds A, B, and C within the above-mentioned preferred range can further reduce the initial viscosity of the acid solution and increase the high-temperature rheological viscosity of the acid solution.

[0045] In this invention, the total amount of the initiator relative to every 10 grams of compound A can be 0.05g, 0.055g, 0.06g, 0.065g, 0.07g, 0.075g, 0.08g, 0.085g, 0.09g, 0.095g, 0.1g, or any two of the above.

[0046] In some embodiments of the present invention, preferably, the total amount of the initiator is 0.05-0.1g relative to 10g of the compound A, more preferably 0.05-0.07g, and even more preferably 0.06-0.07g.

[0047] In some embodiments of the present invention, the azo initiator is selected from azo initiators well known to those skilled in the art. Preferably, the azo initiator is a water-soluble azo compound. More preferably, the water-soluble azo compound is at least one of azobisisobutyramidine hydrochloride and azobisisobutyramidine hydrochloride.

[0048] In this invention, the oxidation initiator is selected from oxidants well known to those skilled in the art. The oxidation initiator is preferably selected from peroxides and / or permanganates, and more preferably from at least one of ammonium persulfate, sodium persulfate, potassium permanganate and hydrogen peroxide.

[0049] In this invention, the reduction initiator is selected from reducing agents well known to those skilled in the art. The reduction initiator is preferably selected from at least one of sulfite, sodium bisulfite, metabisulfite and thiosulfate, and more preferably from at least one of sodium sulfite, sodium metabisulfite and sodium thiosulfate.

[0050] The inventors of this invention have further discovered that the combination of the oxidizing initiator, the reducing initiator, and the azo initiator of this invention can improve the conversion rate of monomers, control the molecular weight distribution of polymers, further slow down the degradation of polymers at high temperatures, and improve the temperature resistance of polymers.

[0051] In some embodiments of the present invention, preferably, the weight ratio of the oxidizing initiator, the reducing initiator, and the azo initiator is 1-1.5:1-1.5:1. Using three initiators in a specific weight ratio in the present invention can further improve the temperature resistance of the polymer.

[0052] In some embodiments of the present invention, preferably, the molecular weight regulator is dodecyl mercaptan and / or butyl mercaptan, more preferably dodecyl mercaptan. Using the preferred molecular weight regulator of the present invention can further reduce the initial viscosity of the acid solution and increase its high-temperature rheological viscosity.

[0053] In some embodiments of the present invention, preferably, the complexing agent is selected from amino acid complexing agents, and more preferably from at least one of ethylenediaminetetraacetic acid, diethyltriaminepentaacetic acid, and aziridinetriacetic acid.

[0054] In this invention, the amount of molecular weight regulator relative to 10 grams of compound A can be 0.03g, 0.035g, 0.04g, 0.045g, 0.05g, 0.055g, 0.06g, 0.065g, 0.07g, 0.075g, 0.08g, or any two of the above.

[0055] In some embodiments of the present invention, preferably, the amount of molecular weight regulator used is 0.03-0.08g, more preferably 0.3-0.6g, and even more preferably 0.4-0.55g, relative to 10g of compound A.

[0056] In this invention, the amount of complexing agent used relative to 10 grams of compound A can be 0.1g, 0.11g, 0.12g, 0.13g, 0.14g, 0.15g, 0.16g, or any two of the above.

[0057] In some embodiments of the present invention, preferably, the amount of complexing agent used is 0.1-0.16g relative to 10g of compound A, more preferably 0.13-0.16g.

[0058] In this invention, the amount of cosolvent used relative to 10 grams of compound A can be 0.1g, 0.2g, 0.3g, 0.4g, 0.5g, 0.6g, 0.7g, 0.8g, 0.9g, 1g, or any combination of the above.

[0059] In some embodiments of the present invention, preferably, the amount of cosolvent used is 0.1-1g relative to 10g of compound A, more preferably 0.6-0.8g.

[0060] In some embodiments of the present invention, preferably, the step of mixing compound A, compound B, and compound C with water includes: mixing compound A and compound C with water, then using a pH adjuster to adjust the pH of the resulting mixture to 7-10, and then adding compound B. More preferably, the pH of the system is 8-9, and even more preferably 8.5-9. Compared to directly mixing compound A, compound B, and compound C with water and then adjusting the pH of the system, the polymer prepared using the above-mentioned preferred mixing steps of the present invention exhibits better temperature resistance.

[0061] In some embodiments of the present invention, preferably, the pH adjuster is selected from inorganic alkaline substances, more preferably from at least one of alkali metal hydroxides, alkali metal weak acid salts and ammonia water, and more preferably from at least one of sodium hydroxide, sodium carbonate, sodium bicarbonate and ammonia water.

[0062] In some embodiments of the present invention, preferably, the amount of water used is such that the total concentration of monomers in the mixture of compound A, compound B, compound C and water is 20-30% by weight. The monomers refer to compound A, compound B, and compound C.

[0063] In some embodiments of the present invention, preferably, the temperature of the polymerization reaction is 25-45°C, more preferably 25-40°C; and the time is 8-25h, more preferably 10-12h.

[0064] In some embodiments of the present invention, preferably, the polymerization reaction includes a first polymerization reaction and a second polymerization reaction; wherein the temperature of the second polymerization reaction is higher than the temperature of the first polymerization reaction (e.g., 10-30°C higher). More preferably, the temperature of the first polymerization reaction is 15-35°C, and the temperature of the second polymerization reaction is 30-50°C. More preferably, the time of the first polymerization reaction is 1-10 hours, and the time of the second polymerization reaction is 8-30 hours. The inventors of the present invention have further discovered that by employing a two-step polymerization and controlling the temperature of the second polymerization reaction to be higher than that of the first polymerization reaction, the molecular weight distribution can be further reduced, the viscosity-average molecular weight can be increased, and the rheological viscosity and viscosity retention rate can be further improved.

[0065] In some embodiments of the present invention, preferably, the polymerization reaction is carried out under an inert atmosphere provided by nitrogen and / or an inert gas (helium, neon, argon).

[0066] In some embodiments of the present invention, preferably, after the polymerization reaction, the colloid obtained by the polymerization reaction is sheared, granulated, dried, and pulverized.

[0067] In some embodiments of the present invention, preferably, the drying (baking) is carried out under a vacuum of 0.1-0.5 mbar. In the present invention, 1 mbar = 0.0001 MPa.

[0068] In some embodiments of the present invention, preferably, the drying temperature is 30-80°C, more preferably 40-70°C, and even more preferably 50-60°C.

[0069] The drying is preferably carried out under oxygen-free conditions, and more preferably in a vacuum or protective atmosphere in this invention; the protective atmosphere can be any protective atmosphere known to those skilled in the art, and there are no special limitations, but nitrogen is preferred in this invention.

[0070] In some embodiments of the present invention, preferably, the drying time is 4-10 hours, more preferably 5-8 hours, and even more preferably 6-7 hours.

[0071] According to a particularly preferred embodiment of the present invention, the drying conditions include: a temperature of 50-60°C, a time of 6-7 hours, and a vacuum degree of 0.3-0.5 mbar. When the drying conditions are limited to the above range, polymer self-polymerization can be further avoided, the initial viscosity of the polymer-prepared gel acid system can be reduced, and the drag reduction rate of the gel acid system can be improved.

[0072] In some embodiments of the present invention, preferably, the pulverization refers to pulverizing the dried product into particles with a particle size of 150-400 μm, more preferably 150-250 μm. If the particle size is too small, the composition will dissolve too quickly in acid, resulting in "fish eyes"; if the particle size is too large, the composition will dissolve too slowly, affecting the efficiency of on-site solution preparation. However, the inventors of the present invention have further discovered that the polymer of the present invention can further reduce the number of "fish eyes"; in particularly preferred cases, the polymer of the present invention can reduce the number of "fish eyes" while reducing the dissolution time, or even avoid the formation of "fish eyes". "Fish eyes" refer to polymer solid particles in hydrochloric acid solution. Polymer particles refer to polymer particles with a particle size of 2 mm or more.

[0073] In this invention, the dried product is pulverized and then sieved to obtain particles with a particle size of 150-400μm, preferably 150-250μm.

[0074] In some embodiments of the present invention, preferably, the preparation method of the polymer includes: mixing compound A and compound C with water, then using a pH adjuster to adjust the pH of the mixed system to 7-10, and then adding compound B; then adding a complexing agent, a cosolvent, and a molecular weight regulator, and lowering the temperature of the system, and then adding an initiator to cause a polymerization reaction of compound A, compound B, and compound C, and then granulating and drying the product of the polymerization reaction. The temperature of the system is lowered to 5-12°C.

[0075] A third aspect of the present invention provides a polymer prepared by the method described in the second aspect.

[0076] A fourth aspect of the present invention provides a gelling acid thickener, the gelling acid thickener comprising the polymers described in the first aspect and / or the third aspect of the present invention.

[0077] A fifth aspect of the present invention provides a composition comprising the polymer and additives described in the first aspect and / or the third aspect of the present invention.

[0078] In some embodiments of the present invention, preferably, the additive is selected from corrosion inhibitors, corrosion synergists, iron ion stabilizers, drainage aids, and demulsifiers.

[0079] In some embodiments of the present invention, preferably, the corrosion inhibitor is selected from organic quaternary ammonium salts, more preferably from at least one of linear alkane quaternary ammonium salts, imidazoline quaternary ammonium salts, and quinoline quaternary ammonium salts, and more preferably from at least one of dodecyltrimethylammonium bromide, dodecyltrimethylammonium chloride, dodecyldimethylbenzylammonium bromide, tetradecyltrimethylammonium bromide, hexadecyltrimethylammonium bromide, palmitic imidazoline quaternary ammonium salt, linoleic imidazoline quaternary ammonium salt, n-capric imidazoline quaternary ammonium salt, lauric imidazoline quaternary ammonium salt, stearic imidazoline quaternary ammonium salt, quinoline quaternary ammonium salt, isoquinoline quaternary ammonium salt, methylquinoline quaternary ammonium salt, hydroxyquinoline quaternary ammonium salt, and aminoquinoline quaternary ammonium salt.

[0080] In some embodiments of the present invention, preferably, the mass ratio of the straight-chain alkane quaternary ammonium salt, the imidazoline quaternary ammonium salt, and the quinoline quaternary ammonium salt in the corrosion inhibitor is 1.33-3:0.6-2:1.

[0081] The corrosion inhibitor described in this invention is prepared according to the method disclosed in patent application 202111185235.9. For example, the corrosion inhibitor may include tetradecyltrimethylammonium bromide, imidazoline palmitate quaternary ammonium salt, and isoquinoline quaternary ammonium salt. The weight ratio of tetradecyltrimethylammonium bromide, imidazoline palmitate quaternary ammonium salt, and isoquinoline quaternary ammonium salt in the corrosion inhibitor may be 2-3:1-2:1.

[0082] In some embodiments of the present invention, preferably, the corrosion inhibitor is added in the form of an aqueous solution. More preferably, the content of the corrosion inhibitor in the aqueous solution is 0.4-0.55 g / mL.

[0083] In some embodiments of the present invention, preferably, the amount of corrosion inhibitor used is 22-44g relative to 8g of polymer, more preferably 27.5-38.5g.

[0084] In some embodiments of the present invention, preferably, the corrosion inhibitor is selected from at least one of alcohols, metal salts, and metal oxides, more preferably from C2-C. 10 Enols and / or metal oxides, more preferably propenols and antimony trioxide.

[0085] In some embodiments of the present invention, preferably, the mass ratio of the enol to the metal oxide in the corrosion inhibitor is 1.6-5:1, more preferably 2-3.5:1, and even more preferably 2.5:1. The corrosion inhibitor added in this invention can produce a significant synergistic effect with the corrosion inhibitor, enhancing the temperature resistance and barrier effect at the interface of the corrosion inhibitor, thereby reducing the corrosion of metal pipes by acid at high temperatures.

[0086] In some embodiments of the present invention, preferably, the amount of corrosion inhibitor is 5-20g, more preferably 5-15g, relative to 8g of polymer.

[0087] In some embodiments of the present invention, preferably, the iron ion stabilizer is selected from a compound of a complexing agent and a reducing agent, more preferably a compound of disodium ethylenediaminetetraacetate (a complexing agent) and isoascorbic acid (a reducing agent).

[0088] In some embodiments of the present invention, preferably, the mass ratio of the iron ion chelating agent to the reducing agent in the iron ion stabilizer is 2-4:1, more preferably 2-3.5:1, and even more preferably 2-3:1. The iron ion stabilizer of the present invention can complex, reduce, and disperse iron ions, inhibiting the phenomenon of free iron precipitating in the form of ferric hydroxide and clogging the reservoir.

[0089] In some embodiments of the present invention, preferably, the amount of iron ion stabilizer used is 1.5-4.5g relative to 8g of polymer, more preferably 2.4-3.6g, and even more preferably 2.7-3.3g.

[0090] In some embodiments of the present invention, preferably, the iron ion stabilizer is added in the form of an aqueous solution; more preferably, the content of the iron ion stabilizer in the aqueous solution is 0.2-0.3 g / mL.

[0091] In some embodiments of the present invention, preferably, the demulsifier is selected from surfactants, more preferably from nonionic surfactants, and even more preferably from polyoxyethylene polyoxypropylene propylene glycol ether.

[0092] In some embodiments of the present invention, preferably, the amount of demulsifier used is 1-4g relative to 8g of polymer, more preferably 2-3g; and even more preferably 2.25-2.75g.

[0093] In some embodiments of the present invention, preferably, the demulsifier is added in the form of an aqueous solution. More preferably, the content of the demulsifier in the aqueous solution is 0.25-0.3 g / mL.

[0094] In some embodiments of the present invention, preferably, the drainage aid is selected from surfactants and C1-C 18 Alcohols, more preferably selected from fluorocarbon surfactants, polyethers, and C1-C... 12 At least one of the alcohols.

[0095] In some embodiments of the present invention, preferably, the amount of the drainage aid is 0.5-2.5g relative to 8g of polymer, more preferably 1.2-1.8g, and even more preferably 1.35-1.65g.

[0096] In some embodiments of the present invention, preferably, the drainage aid is added in the form of an aqueous solution. More preferably, the content of the drainage aid in the aqueous solution is 0.1-0.15 g / mL.

[0097] In some embodiments of the present invention, preferably, the amount of corrosion inhibitor aqueous solution used is 40-80 mL, corrosion inhibitor synergist used is 5-20 g, iron ion stabilizer aqueous solution used is 5-15 mL, drainage aid aqueous solution used is 5-15 mL, and demulsifier aqueous solution used is 5-15 mL, relative to each 8 g of polymer. More preferably, the amount of corrosion inhibitor aqueous solution used is 50-70 mL, corrosion inhibitor synergist used is 5-15 g, iron ion stabilizer aqueous solution used is 8-12 mL, drainage aid aqueous solution used is 8-12 mL, and demulsifier aqueous solution used is 8-12 mL, relative to each 8 g of polymer. More preferably, relative to each 8g of polymer, the amount of corrosion inhibitor aqueous solution is 50-60mL, the amount of corrosion inhibitor synergist is 8-12g, the amount of iron ion stabilizer aqueous solution is 9-11mL, the amount of drainage aid aqueous solution is 9-11mL, and the amount of demulsifier aqueous solution is 9-11mL.

[0098] The present invention also provides a method for preparing a gelling acid system, the method comprising mixing the above composition with a solvent. The solvent may be a dilute hydrochloric acid solution, such as a 20% HCl aqueous solution. The amount of the composition is such that the content of the polymer described in the first aspect in the gelling acid system is less than 1% (e.g., 0.1%wt, 0.2%wt, 0.3%wt, 0.4%wt, 0.5%wt, 0.6%wt, 0.7%wt, 0.9%wt, 0.9%wt, 1%wt), preferably 0.6-0.9%wt.

[0099] When preparing gelling acid systems, the compositions of the present invention do not require the use of crosslinking agents.

[0100] The present invention will be described in detail below through embodiments. In the following embodiments, Example 1 10g of acrylamide and 1.8g of methacryloyloxyethyltrimethylammonium chloride were dissolved in deionized water and stirred until homogeneous. Sodium hydroxide was added to adjust the pH to 8.5, followed by the addition of 16g ​​of 2-acrylamido-2-methylpropanesulfonic acid, resulting in an aqueous solution with a total monomer concentration of 27.8% by weight. Then, 0.05g of dodecyl mercaptan, 0.15g of diethyltriaminepentaacetic acid, and 0.8g of urea were added sequentially to the aqueous solution. The mixture was stirred with N2 for 20 minutes and cooled to 10°C. Next, 0.025g of sodium persulfate, 0.025g of sodium bisulfite, and 0.02g of azobisisobutyramidine hydrochloride were added. N2 was continuously purged for 10 minutes, and the polymerization reaction was carried out at 25°C for 2 hours and then at 40°C for 10 hours under stirring. The polymer was then sheared, granulated, dried under vacuum of 0.5 mbar at 50°C for 7 hours, and finally pulverized to a particle size of 150-250 μm.

[0101] The infrared characterization image of the polymer prepared in Example 1 is shown below. Figure 1 As shown, by Figure 1 Analysis shows that at 3432.5cm -1 The peak at 1594.8 cm⁻¹ corresponds to the characteristic peaks of the symmetric and asymmetric stretching vibrations of the NH bond in the -NH₂ group within the structural unit provided by the acrylamide monomer; -1 The peak at 3432.5 cm⁻¹ is a characteristic peak of the amide group -NH₂. -1 The peak at 1594.8 cm -1 The peak at 1034.6 cm⁻¹ proves that the polymer contains amide groups; -1 The peak at 2805.3 cm⁻¹ is a characteristic peak of the symmetric stretching vibration of the sulfonic acid group. -1 and 1354.2cm -1 The characteristic absorption peak of CH3-N in the structural unit of methacryloyloxyethyltrimethylammonium chloride was provided.

[0102] Example 2 10g of acrylamide and 1.6g of methacryloyloxyethyltrimethylammonium chloride were dissolved sequentially in deionized water. After stirring until homogeneous, sodium hydroxide was added to adjust the pH to 8.5. Then, 14.5g of 2-acrylamido-2-methylpropanesulfonic acid was added to obtain an aqueous solution with a total monomer concentration of 26.1% by weight. Next, 0.06g of dodecyl mercaptan, 0.14g of ethylenediaminetetraacetic acid, and 0.6g of thiourea were added sequentially to the aqueous solution. The mixture was stirred with N2 for 20 minutes and cooled to 10°C. Finally, 0.02g of ammonium persulfate, 0.02g of sodium metabisulfite, and 0.02g of azobisisobutyrazoline hydrochloride were added. N2 was continuously purged for 10 minutes, and the polymerization reaction was carried out at 20°C for 4 hours and then at 35°C for 18 hours under stirring. The polymer was then sheared, granulated, dried under vacuum of 1 mbar at 60°C for 6 hours, and pulverized to a particle size of 150-250 μm to obtain the polymer.

[0103] Example 3 10g of acrylamide and 1.7g of methacryloyloxyethyltrimethylammonium chloride were dissolved sequentially in deionized water and stirred until homogeneous. Sodium hydroxide was added to adjust the pH to 8, followed by the addition of 13g of 2-acrylamido-2-methylpropanesulfonic acid, resulting in an aqueous solution with a total monomer concentration of 24.7% by weight. Then, 0.03g of dodecyl mercaptan, 0.12g of diethyltriaminepentaacetic acid, and 0.8g of urea were added sequentially to the aqueous solution. The mixture was stirred with N2 for 20 minutes and cooled to 10°C. Finally, 0.025g of sodium persulfate, 0.025g of sodium bisulfite, and 0.02g of azobisisobutyramidine hydrochloride were added, and N2 was continuously purged for 10 minutes. The polymer was then polymerized at 25°C for 2 hours and at 40°C for 10 hours under stirring. The polymer was then sheared, granulated, dried under vacuum of 5 mbar at 55°C for 6 hours, and pulverized to a particle size of 150-250 μm.

[0104] Example 4 The method of Example 1 was followed, except that "2-acrylamide-2-methylpropanesulfonic acid" was replaced with an equal weight of "sodium 2-acrylamide-2-methylpropanesulfonate" to obtain the polymer.

[0105] Example 5 The method of Example 1 was followed, except that "methacryloyloxyethyltrimethylammonium chloride" was replaced with an equal weight of "acryloyloxyethyltrimethylammonium chloride" to obtain the polymer.

[0106] Example 6 The method of Example 1 was followed, except that "dodecyl mercaptan" was replaced with an equal weight of "butyl mercaptan" to obtain the polymer.

[0107] Example 7 The process was carried out according to Example 1, except that "polymerization reaction at 25°C for 2 hours and polymerization reaction at 40°C for 10 hours" was replaced with "polymerization reaction at 30°C for 12 hours" to obtain the polymer.

[0108] Example 8 The method of Example 1 was followed, except that "drying at a vacuum of 0.5 mbar and a temperature of 50°C for 7 hours" was replaced with "drying at a vacuum of 0.5 mbar and a temperature of 70°C for 7 hours".

[0109] Comparative Example 1 The method of Example 1 was followed, except that "acrylamide" was replaced with an equal weight of "N-isopropylacrylamide" to obtain the polymer.

[0110] Comparative Example 2 The method of Example 1 was followed, except that "2-acrylamide-2-methylpropanesulfonic acid" was replaced with an equal weight of "sodium allyloxypropanesulfonate" to obtain the polymer.

[0111] Comparative Example 3 The procedure was carried out according to Example 1, except that "azobisisobutyramidine hydrochloride" was replaced with "0.01g sodium persulfate and 0.01g sodium bisulfite".

[0112] Comparative Example 4 The procedure was carried out according to Example 1, except that "dodecyl mercaptan" was replaced with an equal weight of "sodium formate".

[0113] Comparative Example 5 The procedure was carried out according to Example 1, except that “urea” was replaced with an equal weight of “nonylphenol polyoxyethylene ether”.

[0114] Comparative Example 6 The polymer was prepared according to Example 1 of CN103146372A.

[0115] Comparative Example 7 The method of Example 1 was followed, except that the weight ratio of acrylamide, 2-acrylamide-2-methylpropanesulfonic acid, and methacryloyloxyethyltrimethylammonium chloride was 1:0.2:0.2 to obtain the polymer.

[0116] Comparative Example 8 A commercially available gelling acid thickener was used instead of the polymer in Example 1.

[0117] Test Example 1 The viscosity-average molecular weight and molecular weight distribution, sulfur content, degree of polymer chain aggregation, number of "fish eyes", and dissolution time of the polymers in the above examples and comparative examples were tested. The test results are shown in Table 1.

[0118] The molecular weight determination method is the viscosity method, specifically: 20g of a 58.5g / L sodium chloride solution is mixed with 0.1g of the polymer to prepare a dilute solution, and then its intrinsic viscosity [η] is measured at 30℃ using an Ubbelohde viscometer. The intrinsic viscosity is then determined according to the Mark-Houwink empirical formula [η] = K × M. a Calculate its viscosity-average molecular weight, where K represents the Mark-Howwink constant (K = 4.75 × 10⁻⁶). -3 M This represents the viscosity-average molecular weight, and a is the conformation index (a=0.8).

[0119] The molecular weight distribution index (PDI) was determined by gel permeation chromatography. Specifically, the polymer was dissolved in a 0.1 mol / L NaNO3 aqueous solution, filtered, and injected. Separation was performed using a hydrophilic gel chromatography column with 0.1 mol / L NaNO3 solution as the mobile phase (30°C, 0.8 mL / min), and the chromatographic peaks were recorded using a differential refractive index detector. The weight-average molecular weight (Mw) and number-average molecular weight (Mn) were calculated by combining the narrow distribution standard calibration curve, and the molecular weight distribution index (PDI) was obtained as PDI = Mw / Mn.

[0120] Test method for sulfur content in polymers: The sulfur content is determined using an X-ray fluorescence spectrometer. First, the powder is compressed into a tablet. After preheating the instrument, the sample is placed on the stage. A voltage of 30-50 kV and a current of 50-100 μA are set, and the measurement time is 30-120 seconds. Three parallel tests are performed, and the average value is taken. RSD ≤ 5%.

[0121] Method for testing the degree of polymer molecular chain aggregation: 0.05g of polymer was mixed with 100mL of saline solution (2wt% sodium chloride aqueous solution) to obtain an aqueous solution. The degree of polymer molecular chain aggregation in the aqueous solution was then tested under an electron microscope. The degree of aggregation was divided into three levels: I, II, and III. Level I indicates that the polymer molecular chain aggregation area is less than 10%, Level II indicates that the polymer molecular chain aggregation area is between 10% and 30%, and Level III indicates that the polymer molecular chain aggregation area is between 30% and 50%. The polymer molecular chain aggregation area was calculated as follows: within any 100μm × 100μm region of the SEM image, the area occupied by polymer molecular chains forming a backbone with a thickness greater than 2μm. The smaller the polymer molecular chain aggregation area, the better the flexibility of the polymer.

[0122] The scanning electron microscope (SEM) characterization image of the polymer prepared in Example 1 is shown below. Figure 2 As shown, the scanning electron microscope (SEM) characterization image of the polymer in Comparative Example 8 is as follows. Figure 3 As shown, Figure 2 and Figure 3 The comparison shows that, Figure 3 The polymer exhibits severe molecular chain aggregation in solution; Figure 2 The polymers exhibit minimal molecular chain aggregation in solution, indicating that the polymers of this invention have higher flexibility and flowability.

[0123] The test method for the number of "fish eyes" is as follows: Measure 200 ml of 20% HCl solution into a 500 ml beaker, set the stirring speed to 120 rpm, and uniformly add 1.6 g of polymer within 5 seconds. Stir until the polymer dissolves. After the polymer is completely dissolved, record the dissolution time and count the number of visible "fish eyes". The faster the dissolution and the fewer the number of "fish eyes", the better the polymer's solubility.

[0124] The graph showing the changes in dissolution time and initial viscosity of the polymer in Example 2 in a 20% HCl solution is shown below. Figure 4 As shown, by Figure 4 It can be seen that the initial viscosity of the polymer in Example 2 of the present invention remains basically unchanged after 20 minutes, indicating that the polymer can be dissolved in about 20 minutes. The dissolution time is short, and on-site solution preparation can be completed in a short time. Moreover, the initial viscosity of the polymer after dissolution is low, which is convenient for on-site pumping.

[0125] Table 1

[0126] Test Example 2 The high-temperature resistance, shear resistance, and corrosion resistance of the polymers prepared in the above examples and comparative examples in the gelling acid system were tested. Preparation of gelling acid system: Take 920 mL of 20% HCl in a mixer, turn on the stirrer, add 50 mL of corrosion inhibitor aqueous solution, 10 g of corrosion inhibitor synergist and 8 g of polymer in sequence, stir for 30 min, and then add 10 mL of iron ion stabilizer aqueous solution, 10 mL of demulsifier aqueous solution and 10 mL of drainage aid aqueous solution. After stirring evenly, the gelling acid system is obtained.

[0127] The corrosion inhibitor aqueous solution was provided by Southwest Petroleum University and prepared according to Example 4 in application number 202111185235.9.

[0128] The corrosion inhibitor is a composition of propylene alcohol and antimony trioxide in a mass ratio of 5:2, provided by Tianjin Hengzhixin Technology Co., Ltd.

[0129] The iron ion stabilizer aqueous solution is an aqueous solution of a compound of disodium ethylenediaminetetraacetate and isoascorbic acid in a mass ratio of 2:1 (the total content of disodium ethylenediaminetetraacetate and isoascorbic acid in the aqueous solution of the compound is 0.3 g / mL), provided by Beijing Baofengchun Petroleum Technology Co., Ltd.

[0130] The demulsifier aqueous solution is an aqueous solution of polyoxyethylene polyoxypropylene propylene glycol ether (the content of polyoxyethylene polyoxypropylene propylene glycol ether in the aqueous solution is 0.25g / mL), provided by Puyang Dongpu Technology Development Co., Ltd.

[0131] The drainage aid aqueous solution is an aqueous solution of perfluorohexyl sulfonamide polyoxyethylene ether (the content of perfluorohexyl sulfonamide polyoxyethylene ether in the aqueous solution is 0.15 g / mL), provided by Zhongyuan Downhole Special Operations Company.

[0132] Initial viscosity test method: At room temperature (25℃), the viscosity of the above gelling acid system at 100 rpm is measured using a six-speed rotational viscometer. This viscosity is denoted as η. 初 .

[0133] The viscosity retention rate test method is as follows: referring to the method in standard Q / SH CG0149-2021 "Technical Requirements for Thickeners for Gelatinous Acids", the high temperature resistance and shear resistance of the gelling acid system are tested using an RS6000 high temperature and high pressure acid rheometer. During the test, the viscosity retention rate is 170s. -1 The shear rate was measured, and continuous shearing at 200℃ for 30 min was performed. The average viscosity for the first 3 min was recorded as viscosity η1, and the average viscosity for the last 3 min was recorded as the final rheological viscosity η2, denoted as η. 流变 The test results are shown in Table 2.

[0134] The viscosity retention rate is calculated as follows: η2 ÷ η1 × 100%.

[0135] The temperature and shear resistance of the gelling acid system prepared by the polymer in Example 1 is as follows: Figure 5 As shown, the gelled acid system exhibits good temperature and shear resistance, which can meet the requirements of acid fracturing stimulation of high-temperature reservoirs; specifically... Figure 5 The medium curve represents 170s -1 Curves showing the changes in shear rate and rheological viscosity over time at 200℃.

[0136] Figure 6This graph compares the temperature and shear resistance of the gelling acid systems prepared from the polymer of Example 1 (this product) and the polymer of Comparative Example 8 (an existing product). As can be seen from the graph, the rheological viscosity of the polymer in Comparative Example 8 decreases sharply with increasing shear time, falling below 20 mPa·s after 30 minutes of shearing, failing to meet the acid requirements. In contrast, the polymer of Example 1 shows a less significant decrease in rheological viscosity with increasing shear time, and its rheological viscosity remains above 20 mPa·s even after 30 minutes of shearing at 200°C.

[0137] Figure 7 and Figure 8 The gelling acid systems prepared from the polymers of Example 1 and Comparative Example 8, respectively, were heated to 170s. -1 By comparing the shear rate and the state after continuous shearing at 200°C for 50 min, it can be seen that the gelling acid system of Example 1 of the present invention exhibits a uniform liquid state and no micelles after continuous shearing at high temperature; while the gelling acid system of Comparative Example 8 shows polymer hydration and the presence of micelles after continuous shearing at high temperature. Therefore, the polymer of the present invention can effectively slow down the acid salt reaction rate and achieve deep acid fracturing.

[0138] The corrosion rate was determined using a high-temperature, high-pressure dynamic corrosion rate tester. The mass loss of PS110 steel sheets was measured after 4 hours of corrosion in a gelling acid system at 200℃, 60 r / min, and 16 MPa. The mass loss per unit area (m²) was calculated. 2 The corrosion rate is the mass (g) of steel sheet lost per unit time (1h), and the test results are shown in Table 2.

[0139] Figure 9 The figure shows the corrosion of steel sheets by the gelling acid system prepared by the polymer in Example 1 of the present invention. As can be seen from the figure, the gelling acid system in Example 1 of the present invention causes less corrosion to the steel sheets, which can effectively slow down the corrosion of the tubing and ensure construction safety.

[0140] Table 2

[0141] Test Example 3 The results of the debonding residue performance tests of the polymers prepared in each embodiment and comparative example are shown in Table 3.

[0142] The method for determining the residue content of the gelling liquid is as follows: at 90℃, 100g of gelling acid system is reacted with 150g of marble block until the pH value is neutral, then washed with water, centrifuged, dried and the residue content is calculated.

[0143] Figure 10The image shows a photograph of the gelling acid system prepared by the polymer in Example 1 of this invention reacting with marble blocks. As can be seen from the image, the liquid is homogeneous and leaves low residue after gelation. Therefore, the polymer of this invention can effectively reduce the damage of acid to the reservoir and facilitate liquid backflow.

[0144] Table 3

[0145] As can be seen from the results in Tables 2-3, compared with the comparative examples, the acid solutions prepared using the polymers of the embodiments of the present invention as thickeners have the advantages of low initial viscosity and high rheological viscosity at high temperature (200℃). Furthermore, the rheological viscosity of the acid solutions prepared using the polymers of the present invention as thickeners is above 20 mPa·s, and the initial viscosity is below 60 mPa·s; preferably, the rheological viscosity of the acid solutions in Examples 1-2 of the present invention is above 25 mPa·s, and the initial viscosity is below 50 mPa·s. Simultaneously, the gelling acid system of the present invention exhibits a low residue content after reacting with marble.

[0146] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A polymer, characterized in that, The polymer comprises structural units shown in Formula A, Formula B, and Formula C, wherein the structural unit shown in Formula B includes at least one of the structural units shown in Formula B-1, Formula B-2, and Formula B-3; the polymer has a viscosity-average molecular weight of 5-8 million g / mol and a molecular weight distribution of 3-5; the weight ratio of the structural units shown in Formula A, Formula B, and Formula C is 1:1.2-1.8:0.1-0.

2. Formula A; Formula B-1; Formula B-2; Formula B-3; Formula C; Among them, R 11 R 12 R 13 R 14 The same or different and each independently selected from H or C1-C4 alkyl groups; R 21 R 22 R 23 The same or different and independently selected from C1-C4 alkyl, C2-C4 alkenyl, and hydroxylated C1-C4 alkyl groups; R 31 R 32 The same or different and each independently selected from H or C1-C4 alkyl groups; R 41 Selected from C1-C4 alkylene groups or L1 and L2 are the same or different and are each independently selected from -SO3- or -COO-; M1 and M2 are the same or different and are each independently selected from H or alkali metals; X is selected from halogens; m, n and p are each independently selected from 0-3.

2. The polymer according to claim 1, wherein, R 11 , R 12 , R 13 , R 14 are identical or different and each independently selected from H or C1-C3alkyl; and / or, R 21 , R 22 , R 23 are identical or different and each independently selected from the group consisting of Ci-C3-alkyl, C2-C3-alkenyl, hydroxy-substituted Ci-C3-alkyl; and / or, R 31 , R 32 are identical or different and each independently selected from H or C1-C3 alkyl; And / or, R 41 Selected from C1-C3 alkylene groups or ; And / or, X is selected from Cl, Br, or I; And / or, m, n and p are each independently selected from 0 to 2.

3. The polymer according to claim 1 or 2, wherein, R 11 R 12 R 13 R 14 They may be the same or different and are each independently selected from H or C1-C2 alkyl groups; And / or, R 21 R 22 R 23 They may be the same or different and are each independently selected from methyl, ethyl, C2-C3 alkenyl, hydroxymethyl or hydroxyethyl; And / or, R 31 R 32 They may be the same or different and are each independently selected from H, methyl or ethyl; And / or, R 41 Selected from C1-C2 alkylene or ; And / or, both m and p are 1; And / or, n is 2.

4. The polymer according to any one of claims 1-3, wherein, R 11 R 12 R 13 R 14 They may be the same or different and are each independently selected from H or methyl; And / or, R 21 R 22 R 23 They may be the same or different and are each independently selected from methyl, ethyl, vinyl, propenyl or hydroxymethyl; And / or, the polymer has a particle size of 150-400 μm, preferably 150-250 μm; And / or, the molecular chain aggregation area of ​​the polymer is less than 50%, preferably less than 10%; And / or, when the polymer concentration is 0.5-1 g / 100 mL in a hydrochloric acid aqueous solution with a mass fraction of 15-25% by weight, the number of polymer solid particles in the hydrochloric acid aqueous solution is ≤12 / 200 mL, preferably ≤2 / 200 mL; And / or, the sulfur content in the polymer is 5-10% by weight, preferably 7-9% by weight.

5. The polymer according to any one of claims 1-4, wherein, The structural unit shown in Equation A has the structural unit shown in Equation A-1, the structural unit shown in Equation B has the structural unit shown in Equation B-4, and the structural unit shown in Equation C has the structural unit shown in Equation C-1. Formula A-1; Formula C-1; Formula B-4.

6. The polymer according to any one of claims 1-5, wherein, The weight ratio of the structural unit shown in Formula A, Formula B, and Formula C is 1:1.3-1.7:0.15-0.2, preferably 1:1.4-1.6:0.16-0.

18.

7. The polymer according to any one of claims 1-6, wherein, The polymer has a viscosity-average molecular weight of 7-8 million g / mol, preferably 7-7.5 million g / mol, and a molecular weight distribution of 3-4.

8. A method for preparing a polymer, characterized in that, The method includes: mixing compounds A, B, and C with water, then polymerizing compounds A, B, and C in the presence of an initiator, a complexing agent, a cosolvent, and a molecular weight regulator; and then granulating and drying the polymerization product. Compound B includes at least one of compounds B1, B2, and B3. The amounts of compounds A, B, and C are such that the weight ratio of structural units of formula A, B, and C in the resulting polymer is 1:1.2-1.8:0.1-0.

2. The initiator includes oxidative initiators, reductive initiators, and azo initiators. The molecular weight regulator is selected from C4-C15 alkyl thiols. The cosolvent is selected from urea and / or thiourea. Compound A; Compound B1; Compound B2; Compound B3; Compound C; Among them, R 11 R 12 R 13 R 14 R 21 R 22 R 23 R 31 R 32 R 41 The definitions of L1, L2, M1, M2, X, m, n, and p are the same as those in any one of claims 1-7.

9. The method according to claim 8, wherein, The amounts of compounds A, B, and C are such that the weight ratio of the structural units shown in formula A, B, and C in the resulting polymer is 1:1.3-1.7:0.15-0.2, more preferably 1:1.4-1.6:0.16-0.

18. And / or, relative to every 10 grams of compound A, the total amount of the initiator is 0.05-0.1 g, preferably 0.05-0.07 g, more preferably 0.06-0.07 g; And / or, the azo initiator is a water-soluble azo compound, preferably, the water-soluble azo compound is at least one of azobisisobutyramidine hydrochloride and azobisisobutyramidine hydrochloride; And / or, the reduction initiator is at least one of sulfite, metabisulfite and thiosulfate, preferably at least one of sodium sulfite, sodium bisulfite, sodium metabisulfite and sodium thiosulfate; And / or, the oxidation initiator is a peroxide and / or permanganate, preferably at least one of ammonium persulfate, sodium persulfate, potassium permanganate and hydrogen peroxide; And / or, the weight ratio of the oxidation initiator, reduction initiator and azo initiator is 1-1.5:1-1.5:

1.

10. The method according to claim 8 or 9, wherein, The molecular weight regulator is dodecyl mercaptan and / or butyl mercaptan; And / or, the complexing agent is selected from amino acid complexing agents, preferably from at least one of ethylenediaminetetraacetic acid, diethyltriaminepentaacetic acid, and aziridinetriacetic acid; And / or, relative to every 10 grams of compound A, the amount of molecular weight regulator is 0.03-0.06 g, the amount of complexing agent is 0.1-0.16 g, and the amount of cosolvent is 0.1-1 g.

11. The method according to any one of claims 8-10, wherein, The step of mixing compound A, compound B, compound C with water includes: mixing compound A and compound C with water, then using a pH adjuster to adjust the pH of the mixed system to 7-10, and then adding compound B; Preferably, the pH value of the system is 8-9, more preferably 8.5-9; Preferably, the pH adjuster is selected from inorganic alkaline substances, more preferably from at least one of alkali metal hydroxides, alkali metal weak acid salts and ammonia water, and more preferably from at least one of sodium hydroxide, sodium carbonate, sodium bicarbonate and ammonia water.

12. The method according to any one of claims 8-11, wherein, The polymerization reaction is carried out at a temperature of 25-45°C, preferably 25-40°C, for a time of 8-25 hours, preferably 10-12 hours; more preferably, the polymerization reaction includes a first polymerization reaction and a second polymerization reaction; wherein the temperature of the second polymerization reaction is higher than the temperature of the first polymerization reaction. And / or, the polymerization reaction is carried out under an inert atmosphere provided by nitrogen and / or an inert gas; And / or, the drying is carried out under a vacuum of 0.1-0.5 mbar; the drying temperature is 30-80°C, preferably 40-70°C, more preferably 50-60°C; the drying time is 4-10 h, preferably 5-8 h, more preferably 6-7 h.

13. The polymer prepared by the method according to any one of claims 8-12.

14. A gelling acid thickener, characterized in that, The gelling acid thickener comprises the polymer described in any one of claims 1-7 and 13.

15. A composition for gelling acid, characterized in that, The composition comprises the polymer and additives as described in any one of claims 1-7 and 13.

16. The composition according to claim 15, wherein, The additives are selected from corrosion inhibitors, corrosion synergists, iron ion stabilizers, drainage aids, and demulsifiers.

17. The composition according to claim 16, wherein, The corrosion inhibitor is selected from organic quaternary ammonium salts, preferably from at least one of straight-chain alkane quaternary ammonium salts, imidazoline quaternary ammonium salts, and quinoline quaternary ammonium salts; more preferably, the straight-chain alkane quaternary ammonium salt is selected from at least one of dodecyltrimethylammonium bromide, dodecyltrimethylammonium chloride, dodecyldimethylbenzylammonium bromide, tetradecyltrimethylammonium bromide, and hexadecyltrimethylammonium bromide; the imidazoline quaternary ammonium salt is selected from at least one of palmitic imidazoline quaternary ammonium salt, linoleic imidazoline quaternary ammonium salt, oleic imidazoline quaternary ammonium salt, n-capric imidazoline quaternary ammonium salt, lauric imidazoline quaternary ammonium salt, and stearic imidazoline quaternary ammonium salt; the quinoline quaternary ammonium salt is selected from at least one of quinoline quaternary ammonium salt, isoquinoline quaternary ammonium salt, methylquinoline quaternary ammonium salt, hydroxyquinoline quaternary ammonium salt, and aminoquinoline quaternary ammonium salt; Preferably, the corrosion inhibitor is selected from at least one of alcohols, metal salts and metal oxides, preferably from C2-C10 enols and / or metal oxides, and more preferably from propenols and antimony trioxide; Preferably, the iron ion stabilizer is selected from at least two of citric acid, acetic acid, ethylenediaminetetraacetic acid, hypozinogenin triacetic acid, ascorbic acid, and stannous chloride, and more preferably from at least two of citric acid, hypozinogenin triacetic acid, and ascorbic acid; Preferably, the demulsifier is selected from surfactants, more preferably from nonionic surfactants, and more preferably from polyoxyethylene polyoxypropylene propylene glycol ether; Preferably, the drainage aid is selected from surfactants and / or C1-C. 18 Alcohols, preferably selected from fluorocarbon surfactants, polyethers, and C1-C... 12 At least one of the alcohols; Preferably, the composition does not contain a crosslinking agent.

18. The composition according to any one of claims 15-17, wherein, For every 8g of polymer, the amount of corrosion inhibitor is 22-44g, the amount of corrosion inhibitor synergist is 5-20g, the amount of iron ion stabilizer is 1.5-4.5g, the amount of demulsifier is 1-4g, and the amount of drainage aid is 0.5-2.5g.

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