Acid liquid inverse emulsion thickening agent for ultra-high-temperature gelled acid and preparation method of acid liquid inverse emulsion thickening agent

Abstract

The invention relates to the technical field of oil field chemicals, and provides an acid liquid inverse emulsion thickening agent for ultrahigh-temperature gelled acid and a preparation method thereof.The thickening agent is prepared from methacryloyloxyethyl trimethyl ammonium chloride monomers through inverse emulsion polymerization, and an inverse emulsion comprises a water phase and an oil phase, the water-phase raw materials comprise a methacryloyloxyethyl trimethyl ammonium chloride monomer, an initiator, an auxiliary reagent, secondary water and a water-phase emulsifier, the water-phase emulsifier is a combination of dodecyl trimethyl ammonium bromide and lauryl alcohol polyether, and the oil-phase raw materials comprise an oily medium and an oil-phase emulsifier. The problems that in the prior art, a methacryloyloxyethyl trimethyl ammonium chloride (DMC) pure homopolymerized inverse emulsion is difficult to synthesize, and a thickening agent is insufficient in tackifying effect and poor in temperature resistance in an ultra-high-temperature environment can be solved.

Description

Technical Field

[0001] The present invention relates to the technical field of oilfield chemicals, in particular to an acid liquid inverse emulsion thickener for ultra-high temperature gelled acid and a preparation method thereof. Background Art

[0002] During oil and gas extraction, especially in acidizing operations, acid is often used to dissolve carbonate minerals in rocks to increase the permeability of the reservoir. In order to increase the viscosity of the acid and slow down the penetration rate of the acid in the rock formation, it is usually necessary to add a thickener. However, existing acid thickeners often have problems such as poor solubility and poor temperature adaptability, which affect the effectiveness of the acid and the operation results. In recent years, in order to solve the problem of insufficient high-temperature resistance of polymers in hydrochloric acid environments, improving the cationicity of the polymer itself has become an effective solution. DMC is a commonly used cationic monomer. The higher the cationicity, the stronger the temperature resistance of the polymer. In theory, using DMC homopolymerization, a cationic homopolymer resistant to ultra-high temperatures can be obtained. However, in the industry, this solution only has cases of aqueous solution polymerization and then preparing dry powder, and there are no cases of using inverse emulsion polymerization to obtain a uniform emulsion. The advantages of inverse emulsion polymerization over dry powder preparation include: first, the product can be used directly without subsequent treatment; second, the solubility and dispersion of the product is significantly easier than with dry powder, resulting in a more uniform and stable acid solution. However, the lack of commercially available inverse emulsion polymerization products stems from the following key challenges: first, the strong hydrophilicity and high charge density of the DMC monomer itself conflict with the physicochemical requirements of the inverse emulsion system; and second, traditional Span / Tween nonionic emulsifiers (HLB 4-6) rely on steric stabilization, but charge repulsion between the hydrophilic segments (polyoxyethylene) and cationic groups reduces their adsorption efficiency at the oil-water interface. While a low HLB (4–6) is required for stable W / O emulsions, the strong hydrophilicity of DMC requires a high HLB (>10) to reduce interfacial tension. These incompatibilities render conventional emulsifier combinations ineffective, preventing the effective synthesis of the desired product and creating a technical bottleneck. Summary of the Invention

[0003] The present invention aims to provide an acid liquid inverse emulsion thickener for ultra-high temperature gelled acid, so as to solve the problems in the prior art of difficulty in synthesizing pure homopolymer inverse emulsion of methacryloyloxyethyltrimethylammonium chloride (DMC), insufficient viscosity-increasing effect of the thickener under ultra-high temperature environment, and poor temperature resistance.

[0004] Another object of the present invention is to provide a method for preparing an acid solution inverse emulsion thickener for ultrahigh temperature gelled acid.

[0005] The technical solution of the present invention is: In one aspect, the present invention provides an acid liquid inverse emulsion thickener for ultra-high temperature gelled acid, which is prepared from methacryloyloxyethyltrimethylammonium chloride monomer by inverse emulsion polymerization, wherein the inverse emulsion comprises an aqueous phase and an oil phase; The aqueous phase raw materials include, by weight, 350-450 parts of methacryloyloxyethyltrimethylammonium chloride monomer, 4-9 parts of initiator, 1-2 parts of auxiliary reagent, 220-260 parts of secondary water and an aqueous phase emulsifier; the aqueous phase emulsifier is a combination of 1-5 parts of dodecyltrimethylammonium bromide and 1-5 parts of lauryl alcohol polyether; The oil phase raw materials include 220-260 parts of oily medium and 25-50 parts of oil phase emulsifier.

[0006] Furthermore, the purity of the methacryloyloxyethyltrimethylammonium chloride monomer is 78%-80%.

[0007] Furthermore, the initiator includes a combination of 3-5 parts of an oxidative initiator and 1-4 parts of an azo initiator by mass, the oxidative initiator includes one or more of potassium persulfate, ammonium persulfate, and sodium persulfate, and the azo initiator includes one or more of 2,2'-azabis(2-imidazoline) dihydrochloride, azobisisobutyronitrile, and azobisisobutylamidine.

[0008] Furthermore, the auxiliary reagent is disodium EDTA.

[0009] Furthermore, the oily medium includes one or more of 3# white oil, 10# white oil, and 15# white oil.

[0010] Furthermore, the oil phase emulsifier includes a combination of 20-35 parts of Span 80 and 5-15 parts of Tween emulsifiers by mass, and the Tween emulsifier includes one or more of Tween 80, Tween 81, and Tween 60.

[0011] Furthermore, it is characterized in that the reverse emulsion polymerization reaction is initiated by dripping an aqueous solution of a reducing initiator, and the reducing initiator includes one or more of ammonium sulfite, sodium sulfite, sodium metabisulfite, and potassium metabisulfite.

[0012] In another aspect, the present invention provides a method for preparing an acid liquid inverse emulsion thickener for ultrahigh temperature gelled acid, comprising the following steps: S1. The aqueous phase components are mixed and stirred uniformly, and deoxygenated to obtain an aqueous phase; S2. Stirring the oil phase component until the oil phase is clear and homogeneous to obtain an oil phase; S3. The aqueous phase was added to the oil phase and emulsified to a viscosity of the reaction system of 2200cp-2500cp to obtain a uniform emulsion; S4. The homogeneous emulsion is deoxygenated and a 1-5% aqueous solution of a reducing initiator is added to initiate a polymerization reaction to obtain an acid solution inverse emulsion thickener for ultrahigh temperature gelled acid.

[0013] Furthermore, in step S1, ultrasound combined with mechanical stirring is used at a rotation speed of 300 rpm; deoxygenation treatment is carried out by introducing nitrogen gas for a deoxygenation time of 2-3 hours.

[0014] Furthermore, in step S4, the deoxygenation treatment is to introduce nitrogen for 20-30 minutes while stirring at a stirring speed of 150-250 rpm; the reduced initiator aqueous solution is injected through a microinjection pump at an injection rate of 5-10 mL / h, the reaction temperature is controlled at 35-60 ° C, and the reaction time is 3-5 hours. Compared with the prior art, the embodiments of the present invention have at least the following advantages or beneficial effects: 1. Through the synergistic effect of dodecyltrimethylammonium bromide and lauryl alcohol polyether, the essential conflict between the strong hydrophilicity of DMC and the physical and chemical requirements of the inverse emulsion system is compensated, the droplet aggregation and premature gelation phenomena are effectively inhibited, and the stable synthesis of pure DMC homopolymer inverse emulsion is achieved, overcoming the technical bottleneck of poor emulsion stability in traditional processes.

[0015] 2. In 20% HCl acid solution, the viscosity of this thickener increases significantly with increasing dosage, far outperforming existing products without the addition of specific aqueous emulsifiers, and can flexibly meet the acid solution viscosity requirements of different acidizing operations.

[0016] 3. Even in ultra-high temperature environments of 140-200°C, the thickener can still maintain stable viscosity and a uniform state, without stratification or agglomeration; while existing products have shown severe stratification and agglomeration under the same conditions, proving that the product of the present invention is suitable for extreme high-temperature working conditions such as deep and ultra-deep wells.

[0017] 4. Compared with the difficulty of preparing liquids with traditional dry powder thickeners, the inverse emulsion thickener of the present invention can be directly mixed with acid liquid, has good dispersibility and high liquid preparation efficiency, and can effectively improve the construction efficiency of oil and gas field acidizing operations. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0019] Figure 1 This is a diagram of the acid solution product prepared from the product of Example 1 of the present invention; Figure 2This is a state diagram of the product of Example 1 after the heat resistance test of the present invention; Figure 3 This is a state diagram of the product of Comparative Example 4 after the heat resistance test of the present invention; Figure 4 This is a product diagram prepared in Example 1 of the present invention; Figure 5 This is the infrared spectrum characterization diagram of the product of Example 1 of the present invention; Figure 6 This is the 1H-NMR spectrum of the deuterated water phase of the product of Example 1 of the present invention; Figure 7 Schematic diagram of optical microscopy after premature gelation; Figure 8 Schematic diagram of the emulsion state under a 50x optical microscope. DETAILED DESCRIPTION

[0020] To make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer are used. Where the manufacturer of the reagents or instruments is not specified, all are conventional products that can be purchased commercially.

[0021] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below with reference to specific embodiments.

[0022] The present invention provides a method for preparing an acid liquid inverse emulsion thickener for ultra-high temperature gelled acid. The thickener is prepared from methacryloyloxyethyltrimethylammonium chloride monomer (DMC) through an inverse emulsion polymerization reaction. The inverse emulsion includes an aqueous phase and an oil phase. The preparation method comprises the following steps: S1. The aqueous phase components are mixed and stirred uniformly by ultrasonic combined mechanical stirring at a speed of 300 rpm, and deoxygenated for 2-3 hours by nitrogen to obtain an aqueous phase; the aqueous phase components include 350-450 parts by mass of methacryloyloxyethyltrimethylammonium chloride monomer with a purity of 78%-80%, 4-9 parts of initiator, 1-2 parts of auxiliary reagent, 220-260 parts of secondary water and an aqueous emulsifier; the aqueous emulsifier is a combination of 1-5 parts of dodecyltrimethylammonium bromide and 1-5 parts of lauryl alcohol polyether, the initiator includes a combination of 3-5 parts of an oxidative initiator and 1-4 parts of an azo initiator, the oxidative initiator includes one or more of potassium persulfate, ammonium persulfate, and sodium persulfate, the azo initiator includes one or more of 2,2'-azabis(2-imidazoline) dihydrochloride, azobisisobutyronitrile, and azobisisobutylamidine, and the auxiliary reagent is disodium EDTA; S2. The oil phase component is mechanically stirred at a speed of 300 rpm until the oil phase is clear and uniform to obtain an oil phase; the oil phase component comprises 220-260 parts by mass of an oily medium and 25-50 parts of an oily emulsifier, the oily medium comprising one or more of 3# white oil, 10# white oil, and 15# white oil, the oily emulsifier comprising 20-35 parts of Span 80 and 5-15 parts of a Tween emulsifier, the Tween emulsifier comprising one or more of Tween 80, Tween 81, and Tween 60; S3. The aqueous phase was added to the oil phase and emulsified using a high-speed homogenizer until the viscosity of the reaction system reached 2200cp-2500cp to obtain a uniform emulsion; S4. Deoxygenate the homogeneous emulsion by passing nitrogen gas for 20-30 minutes while stirring at a speed of 150-250 rpm. Add a 1-5% aqueous solution of a reducing initiator to initiate polymerization to obtain an acid inverse emulsion thickener for ultrahigh temperature gelling acid. The reducing initiator aqueous solution is injected via a microinjection pump at a rate of 5-10 mL / h. The reaction temperature is controlled at 35-60°C and the reaction time is 3-5 hours.

[0023] The features and performance of the present invention are further described in detail below with reference to the embodiments.

[0024] Example 1 This embodiment provides a method for preparing an acid liquid inverse emulsion thickener for ultra-high temperature gelled acid, comprising the following steps: S1. Dissolve 420 parts of DMC, 230 parts of secondary water, 1 part of potassium persulfate, 1 part of sodium persulfate, 1 part of 2,2'-azabis(2-imidazoline) dihydrochloride, 2 parts of dodecyltrimethylammonium bromide, 2 parts of lauryl alcohol polyether, and 1 part of EDTA2Na in a mixture at 300 rpm using ultrasonic and mechanical stirring. Deoxygenate by passing nitrogen for 2 h to obtain an aqueous phase. S2 using mechanical stirring, 90 parts 3 # white oil, 30 parts 10 # white oil, 110 parts 15 # white oil were added to the reaction flask at 300 rpm, and then 28 parts of Span 80, 3 parts of soil temperature 81, 1 part of soil temperature 80 were added and stirred until the oil phase was clear and uniform to obtain an oil phase; S3. The aqueous phase was poured into the oil phase and emulsified using a high-speed homogenizer at a speed of 20,000 rpm for 15 minutes. The viscosity of the reaction system was finally emulsified to 2330 cp to obtain a uniform emulsion. S4. Connect the homogeneous emulsion to the reactor, introduce nitrogen to the emulsion surface, and continue deoxygenation for 30 minutes. During this period, use a mechanical stirrer to continuously stir at 250 rpm. Prepare a 5% solution of sodium sulfite and ammonium sulfite in a ratio of 2:1. Use a microinjection pump to inject it into the reaction system at a rate of 1 mL / h. Control the reaction temperature to 35°C and continue the reaction for 5 hours to obtain the product.

[0025] Example 2 This embodiment provides a method for preparing an acid liquid inverse emulsion thickener for ultra-high temperature gelled acid, comprising the following steps: S1. Dissolve 400 parts of DMC, 260 parts of secondary water, 2 parts of potassium persulfate, 2 parts of 2,2'-azabis(2-imidazoline) dihydrochloride, 2 parts of dodecyltrimethylammonium bromide, 1 part of lauryl alcohol polyether, and 1 part of EDTA2Na in a mixture at 300 rpm using ultrasonic and mechanical stirring. Deoxygenate with nitrogen for 2 h to obtain an aqueous phase. S2 using mechanical stirring, at 300rpm 130 parts 3 # white oil, 60 parts 10 # white oil, 80 parts 15 # white oil were added to the reaction flask, and then 30 parts of Span 80, 4 parts of soil temperature 81, 1 part of soil temperature 80 was stirred until the oil phase was clear and uniform to obtain an oil phase; S3. The aqueous phase was poured into the oil phase, using a high-speed homogenizer, controlling the speed to 20,000 rpm, emulsifying for 15 minutes, and finally emulsifying the viscosity of the reaction system to 2302cp to obtain a uniform emulsion; S4. Connect the homogeneous emulsion to the reactor, introduce nitrogen gas to the subsurface of the emulsion, and continue deoxygenation for 30 minutes. During this period, use a mechanical stirrer to continuously stir at 250 rpm. Prepare a 2% solution of sodium sulfite and ammonium sulfite in a ratio of 1:1. Use a microinjection pump to inject it into the reaction system at a rate of 4 mL / h. Control the reaction temperature to 45°C and continue the reaction for 3.5 hours to obtain the product.

[0026] Example 3 This embodiment provides a method for preparing an acid liquid inverse emulsion thickener for ultra-high temperature gelled acid, comprising the following steps: S1. Dissolve 400 parts of DMC, 260 parts of secondary water, 3 parts of potassium persulfate, 1 part of 2,2'-azabis(2-imidazoline) dihydrochloride, 2 parts of dodecyltrimethylammonium bromide, 2 parts of lauryl alcohol polyether, and 1 part of EDTA2Na in a mixture at 300 rpm using ultrasonic and mechanical stirring. Deoxygenate with nitrogen for 2 h to obtain an aqueous phase. S2 using mechanical stirring, at 300rpm 130 parts 3 # white oil, 60 parts 10 # white oil, 80 parts 15 # white oil were added to the reaction flask, and then 30 parts of Span 80, 4 parts of soil temperature 81, 1 part of soil temperature 80 was stirred until the oil phase was clear and uniform to obtain an oil phase; S3. The aqueous phase was poured into the oil phase, using a high-speed homogenizer, controlling the speed to 20,000 rpm, emulsifying for 15 minutes, and finally emulsifying the viscosity of the reaction system to 2302cp to obtain a uniform emulsion; S4. Connect the homogeneous emulsion to the reactor, introduce nitrogen to the emulsion surface, and continue deoxygenation for 30 minutes. During this period, use a mechanical stirrer to continuously stir at 250 rpm. Prepare a 5% solution of sodium sulfite and ammonium sulfite in a ratio of 1:1. Use a microinjection pump to inject it into the reaction system at a rate of 1 mL / h. Control the reaction temperature to 50°C and continue the reaction for 3 hours to obtain the product.

[0027] Comparative Example 1 This comparative example is basically the same as Example 1, except that dodecyltrimethylammonium bromide and lauryl alcohol polyether are not added, in order to verify the effect of cationic surfactant on the synthesis reaction of DMC system inverse emulsion thickener.

[0028] Comparative Example 2 This comparative example provides an existing inverse emulsion thickener product, manufactured by 835 of Shandong Noer Biotechnology Co., Ltd.

[0029] Comparative Example 3 This comparative example provides an existing inverse emulsion thickener product, which is an emulsion produced by Guanghan Huaxing New Technology Development Institute.

[0030] Comparative Example 4 This comparative example is basically the same as Example 1, except that lauryl alcohol polyether and dodecyltrimethylammonium bromide are replaced by fatty alcohol polyoxyethylene ether AEO-9 and octadecyltrimethylammonium chloride to verify the effect of other cationic surfactants on the synthesis reaction of the DMC system inverse emulsion thickener.

[0031] In order to better understand the present invention, the following will further illustrate the present invention by testing the products of the above embodiments and comparative examples.

[0032] A 20% HCl acid solution was prepared, comprising 20% ​​HCl and 3% heterocyclic quaternary ammonium salt corrosion inhibitor, and 1%, 1.2%, 2.5%, and 3% of the products of Examples 1-3 and Comparative Examples 1-4 were added, respectively. The viscosity was tested using a viscometer at room temperature. The test results are shown in Table 1:

[0033] The heat resistance performance in 20% HCl acid solution is shown in Table 2:

[0034] Please refer to Figure 1 , Figure 1 The figure shows the acid product prepared from the product of Example 1. From the test results, it can be seen that Examples 1-3 can all produce effective products, among which Example 1 has the best viscosity-increasing effect and the best temperature resistance, which can reach 200°C. Comparative Examples 1 and 4 attempted to not use lauryl polyether and dodecyltrimethylammonium bromide as aqueous phase surfactants and replaced them with other cationic surfactants. However, due to the polymerization problem of the reaction, the reaction failed to obtain the target product. Comparative Examples 2 and 3 are existing products on the market. The viscosity of the products of Comparative Examples 2 and 3 decreased significantly when the temperature reached 160°C, and the temperature resistance was not as good as that of Examples 1-3. Please refer to Figure 2-3 , Figure 2 This is the product status diagram of Example 1 after the heat resistance test. Figure 3 This is a product state diagram of Comparative Example 2. It can be seen from the figure that the product of Example 1 has a stable shape and uniform appearance, while the product of Comparative Example 2 is severely stratified and agglomerated, and incompatibility has occurred, indicating that the temperature resistance of Comparative Example 2 is poor, while the product of the present invention has good temperature resistance.

[0035] The present invention solves the problem that the current DMC homopolymer emulsion cannot be effectively synthesized. The product prepared in Example 1 is as follows: Figure 4 As shown, its molecular formula is , infrared spectroscopy characterization such as Figure 5 As shown, the product deuterated water phase 1H-NMR diagram is as follows Figure 6 shown.

[0036] The core difficulty in industrializing the homopolymerization of pure DMC (methacryloyloxyethyltrimethylammonium chloride) as a single monomer in inverse emulsions stems from the monomer's inherent strong hydrophilicity and high charge density, which fundamentally conflict with the physical and chemical requirements of the inverse emulsion system. This technical bottleneck is comprehensively analyzed from the following three aspects: First, insufficient electrostatic repulsion and droplet coalescence: Each repeating unit in the DMC homopolymer chain carries a quaternary ammonium cationic group (+N(CH3)3), resulting in the surface zeta potential of the emulsion droplets often exceeding +50 mV. This high charge density should enhance electrostatic repulsion between droplets, but due to the low dielectric constant of the oil phase (ε≈2), the electrostatic shielding effect is significant, resulting in an actual repulsion energy barrier of less than 10 kT (far below the 25 kT required for stability). Consequently, the emulsified droplets are highly susceptible to coalescence during both the emulsification and reaction processes.

[0037] Second, the nucleation of inverse emulsions relies on monomer droplets as the reaction site, but the interfacial tension between the DMC aqueous solution and the oil phase is high (>40 mN / m), the droplet size distribution is wide (PDI>0.5), the reaction rate after initiation is uneven, and some droplets gel prematurely. Please refer to Figure 7-8 , Figure 7 This is an optical micrograph after premature gelation. Figure 8 This is the emulsion state under a 50x optical microscope. A large number of droplet coalescence phenomena can be observed from the figure.

[0038] Third, there's the emulsification issue: Traditional Span / Tween nonionic emulsifiers (HLB 4-6) rely on steric hindrance for stabilization, but charge repulsion between their hydrophilic segments (polyoxyethylene) and cationic groups reduces their adsorption efficiency at the oil-water interface. A low HLB (4–6) is required to stabilize W / O emulsions, but DMC's strong hydrophilicity requires a high HLB (>10) to reduce interfacial tension. These two factors are incompatible, rendering conventional emulsifier combinations ineffective.

[0039] Based on this, the present invention adds two cationic monomers, dodecyltrimethylammonium bromide and lauryl alcohol polyether, to the aqueous phase, uses a polymerization method, adopts a homogenizer as a mechanical emulsification solution, and simultaneously combines multiple emulsifiers and a compound of multiple types of white oil to enhance the "core-shell structure stability" formed by the oil-in-water, greatly increase the viscosity of the emulsion, and improve the overall stability of the reaction system.

[0040] The embodiments described above are some, but not all, of the embodiments of the present invention. The detailed description of the embodiments of the present invention is not intended to limit the scope of the invention as claimed, but rather merely represents selected embodiments of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are also within the scope of protection of the present invention.

Claims

1. An acid liquid inverse emulsion thickener for ultra-high temperature gelled acid, characterized in that: The inverse emulsion is prepared by using methacryloyloxyethyltrimethylammonium chloride monomer through inverse emulsion polymerization, wherein the inverse emulsion comprises an aqueous phase and an oil phase; The aqueous phase raw materials include, by mass, 350-450 parts of methacryloyloxyethyltrimethylammonium chloride monomer, 4-9 parts of initiator, 1-2 parts of auxiliary reagent, 220-260 parts of secondary water and aqueous phase emulsifier; the aqueous phase emulsifier is a combination of 1-5 parts of dodecyltrimethylammonium bromide and 1-5 parts of lauryl alcohol polyether; The oil phase raw materials include 220-260 parts of oily medium and 25-50 parts of oil phase emulsifier.

2. The thickener according to claim 1, characterized in that The purity of the methacryloyloxyethyltrimethylammonium chloride monomer is 78%-80%.

3. The thickener according to claim 1, characterized in that The initiator comprises a combination of 3-5 parts of an oxidative initiator and 1-4 parts of an azo initiator by mass, wherein the oxidative initiator comprises one or more of potassium persulfate, ammonium persulfate, and sodium persulfate, and the azo initiator comprises one or more of 2,2'-azabis(2-imidazoline) dihydrochloride, azobisisobutyronitrile, and azobisisobutylamidine.

4. The thickener according to claim 1, characterized in that The auxiliary reagent is disodium EDTA.

5. The thickener according to claim 1, characterized in that The oily medium includes one or more of 3# white oil, 10# white oil, and 15# white oil.

6. The thickener according to claim 1, characterized in that The oil phase emulsifier comprises a combination of 20-35 parts of Span 80 and 5-15 parts of Tween emulsifiers by mass, and the Tween emulsifiers include one or more of Tween 80, Tween 81, and Tween 60.

7. The thickener according to claim 1, characterized in that The reverse emulsion polymerization reaction is initiated by dropwise addition of a reducing initiator aqueous solution, wherein the reducing initiator comprises one or more of ammonium sulfite, sodium sulfite, sodium metabisulfite, and potassium metabisulfite.

8. A method for preparing an acid liquid inverse emulsion thickener for ultrahigh temperature gelled acid, comprising the following steps: S1. The aqueous phase components are mixed and stirred uniformly, and deoxygenated to obtain an aqueous phase; S2. stirring the oil phase component until the oil phase is clear and homogeneous to obtain an oil phase; S3. The aqueous phase was added to the oil phase and emulsified to a viscosity of the reaction system of 2200cp-2500cp to obtain a uniform emulsion; S4. The homogeneous emulsion is deoxygenated and a 1-5% aqueous solution of a reducing initiator is added to initiate a polymerization reaction to obtain an acid solution inverse emulsion thickener for ultrahigh temperature gelled acid.

9. The method according to claim 8, characterized in that In the step S1, ultrasound combined with mechanical stirring is used at a rotation speed of 300 rpm; the deoxygenation treatment is carried out by introducing nitrogen gas for a deoxygenation time of 2-3 hours.

10. The method according to claim 8, characterized in that In step S4, the deoxygenation treatment is performed by introducing nitrogen for 20-30 minutes while stirring at a stirring speed of 150-250 rpm; the reduced initiator aqueous solution is injected through a microinjection pump at an injection rate of 5-10 mL / h, the reaction temperature is controlled at 35-60° C., and the reaction time is 3-5 hours.

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