Emulsion polymer as well as preparation method and application thereof

Abstract

The invention discloses an emulsion polymer which contains a structural unit A, a structural unit B, a structural unit C and a structural unit D. The structural unit A has a structural unit shown in a formula (1), the structural unit B has a structural unit shown in a formula (2), the structural unit C has a structural unit shown in a formula (3), and the structural unit D has a structural unit shown in a formula (4). The weight percentage of the structural unit A is 5-15%, the weight percentage of the structural unit B is 2-40%, the weight percentage of the structural unit C is 10-70%, the weight percentage of the structural unit D is 1-80%, and the viscosity average molecular weight of the emulsion polymer is 30 million to 30 million; wherein R is an alkyl group, preferably a straight chain alkyl group or a branched chain alkyl group of C6-C18.

Description

Technical Field

[0001] This invention belongs to the field of low-permeability heavy oil reservoir exploitation, specifically relating to an emulsion polymer and its preparation method and application. Background Technology

[0002] Low-permeability heavy oil reservoirs have abundant reserves, but their development is often hampered by reservoir conditions and engineering technology, resulting in challenges such as low energy and low fluid levels. This is mainly due to the difficulty of reservoir seepage, which leads to slow pressure transmission and poor fluid supply. At the same time, the narrow rock pores and throats make them susceptible to damage, making the injection and production problems even more significant.

[0003] Hydraulic fracturing technology combines hydraulic fracturing equipment with water injection development, using high pressure (wellhead injection pressure generally greater than 35 MPa) and high speed (daily water injection rate per well generally greater than 1000 m³ / s). 3 / d), to achieve rapid replenishment of reservoir energy and increase reservoir pressure in a short period of time, thereby increasing the production pressure differential, fluid production, and oil production of the oil well. For example, Chinese invention patent application CN115306359A discloses a stratified pressure drive process tubing and method. The stratified pressure drive process tubing includes a compensator, hydraulic slips, an upper packer, an upper injection valve, a middle packer, a middle injection valve, a lower packer, a lower injection valve, a check valve, and a guide head. The two ends of the compensator are connected to tubing. The tubing at the lower end of the compensator is installed and clamped to the inner wall of the casing by hydraulic slips. The upper injection valve is connected to the tubing in the upper oil layer, the middle injection valve is connected to the tubing in the middle oil layer, and the lower injection valve is connected to the tubing in the lower oil layer. A check valve and a guide head are provided at the bottom of the tubing.

[0004] Currently, the application of pressure-driven technology in mining is in a stage of rapid large-scale promotion. How to utilize this technology to further and efficiently utilize low-permeability oil reservoir resources requires further in-depth research on its adaptability conditions.

[0005] For low-permeability heavy oil reservoirs, it is necessary to explore the "pressure drive+" technology model. To address the issues of slow pressure transmission between injection and production wells and uneven effect on production wells during pressure drive implementation, it is necessary to explore the "pressure drive + viscosity reducer" synergistic effect technology. However, the viscosity reducers currently used are mainly surfactants. For example, Chinese invention patent CN 1778862B discloses a heavy oil emulsification viscosity reducer, which includes the following components: a) anionic surfactant; b) nonionic-anionic surfactant; c) demulsifier; d) water. The weight ratio of a, b, and c is 1:0.1-50:0.01-20, and the water volume is 0.2-5000 times the total weight of a, b, and c. The anionic surfactant is a sodium or calcium salt of petroleum sulfonate formaldehyde condensate and sulfonated lignin. The nonionic-anionic surfactant is selected from phosphate, sulfate, carboxyl, and sulfonate salts of alkylphenols or fatty alcohol polyoxyethylene ethers. The demulsifier is an alkyl halide ammonium type cationic demulsifier, a polyoxyethylene polyoxypropylene polyol ether type nonionic demulsifier, or a polyoxyethylene polyoxypropylene polyethylene polyamine block copolymer. However, the above technical solution has the following shortcomings: 1. The aqueous solution has low viscosity and is prone to finger-like flow; 2. The on-site preparation time is long, which cannot meet the high-speed dispensing requirements of viscosity-reducing pressure drive technology.

[0006] Chinese invention patent CN103232573B discloses a method for preparing a polyacrylamide emulsion. The steps are as follows: acrylamide, anionic monomer, grafted matrix, water quality stabilizer, molecular weight regulator, and initiator are added to water, the pH is adjusted, and an aqueous phase is obtained; an emulsifier is added to a hydrocarbon solvent to prepare an oil phase; the aqueous phase is added dropwise to the oil phase, and an emulsion is formed through one-step or multi-step emulsification; the emulsion is deoxygenated by purging with an inert gas, and an initiator is added to initiate polymerization. After polymerization, a branched anionic polyacrylamide water-in-oil reverse emulsion is obtained. This emulsion, when used in the modern papermaking industry, avoids the problem of inorganic fillers detaching again after retention. However, this invention cannot be used in the field of fracturing technology.

[0007] In 2023, Luo Chunzhi published an article titled "Synthesis and Evaluation of Temperature- and Salt-Resistant Emulsion Polymer Filtration Loss Reducer" in the Journal of Yangtze University (Natural Science Edition), which describes a reverse emulsion polymerization method for preparing a temperature- and salt-resistant emulsion polymer filtration loss reducer. The monomers involved are acrylamide, acrylic acid, 2-ethacrylamido-2-methylpropanesulfonic acid, and N-vinyl-2-pyrrolidone. This reverse emulsion polymer exhibits temperature resistance up to 200℃ in composite brine slurry, with a filtration loss reduction rate exceeding 80.6%, superior to similar products. However, because this polymer lacks heavy oil emulsification properties, it cannot be used for pressure flooding in heavy oil reservoirs.

[0008] In summary, developing viscosity reducers that are compatible with pressure-driven development technology for low-permeability heavy oil reservoirs has become an urgent problem to be solved. Summary of the Invention

[0009] Objective of the Invention: To address the shortcomings of the prior art, this invention provides an emulsion polymer, its preparation method, and its applications. The emulsion polymer disclosed in this invention not only possesses rapid dissolution and aqueous phase thickening properties, but also emulsifies heavy oils, achieving a viscosity reduction rate of ≥95% for both ordinary and extra-heavy oils at a concentration of 0.1%. Furthermore, it is easy to apply and can be prepared and used immediately, meeting the application requirements of pressure-driven development technology.

[0010] Technical solution: An emulsion polymer, the emulsion polymer containing structural unit A, structural unit B, structural unit C and structural unit D, structural unit A having the structural unit shown in formula (1), structural unit B having the structural unit shown in formula (2), structural unit C having the structural unit shown in formula (3), structural unit D having the structural unit shown in formula (4), based on the weight of the emulsion polymer, structural unit A accounts for 5-15% by weight, structural unit B accounts for 2-40% by weight, structural unit C accounts for 10-70% by weight, structural unit D accounts for 1-80% by weight, and the viscosity-average molecular weight of the emulsion polymer is 30 million-39 million;

[0011]

[0012] Wherein: R is an alkane group, preferably C6~C6. 18 alkyl group.

[0013] Furthermore, R is C 12 ~C 16 Straight-chain alkane groups or cycloalkane groups.

[0014] Furthermore, based on the weight of the emulsion polymer, structural unit A accounts for 6-10% by weight, structural unit B accounts for 5-35% by weight, structural unit C accounts for 15-65% by weight, structural unit D accounts for 10-70% by weight, and the viscosity-average molecular weight of the emulsion polymer is 31 million to 38 million.

[0015] A method for preparing the above-mentioned emulsion polymer, comprising the following steps:

[0016] (1) Under stirring conditions, monomer E (acrylamide), monomer F (2-acrylamido-2-methylpropanesulfonic acid), monomer G (acrylomorpholine), solvent and water-based surfactant are mixed evenly to obtain an aqueous solution;

[0017] (2) Under stirring conditions, monomer H (long-chain alkyl dimethylaminoethyl acrylate), solvent oil and oil-based surfactant are mixed evenly to obtain an oil phase solution;

[0018] (3) Under a nitrogen or inert gas atmosphere, the aqueous solution and the oil solution are mixed, then an initiator is added and a solution polymerization reaction is carried out under the action of the initiator. After the reaction is completed, an emulsion polymer is obtained.

[0019] The monomer E is a monomer having the structure shown in formula (5), the monomer F is a monomer having the structure shown in formula (6), the monomer G is a monomer having the structure shown in formula (7), and the monomer H is a monomer having the structure shown in formula (8); based on the sum of the masses of the monomer E, the monomer F, the monomer G, and the monomer H, the amount of monomer E is 5-15% by weight, the amount of monomer F is 2-40% by weight, the amount of monomer G is 10-70% by weight, and the amount of monomer H is 1-80% by weight; the conditions of the solution polymerization reaction are such that the viscosity-average molecular weight of the polymer obtained by the polymerization reaction is 30 million to 39 million.

[0020]

[0021] Wherein: R is an alkane group, preferably C6~C6. 18 alkyl group.

[0022] Furthermore, the solvent in step (1) is one or more of deionized water, ethanol, ethyl acetate, and toluene, and its amount is at least 10 times, preferably 10 to 30 times, the amount of monomer E.

[0023] Further, the water-based surfactant mentioned in step (1) is one or more of Tween60, Tween80, Span40, Span60, OP-10, OP-13, OP-15, OP-20, OP-30, OP-40, and OP-50, and its amount is at least 0.1 wt% of the amount of monomer E, preferably 0.1 to 0.5 wt%.

[0024] Furthermore, in step (1), heating is performed simultaneously during stirring, and the heating temperature is controlled at at least 25°C, preferably 25–50°C, and / or

[0025] The stirring conditions in step (1) are as follows: the stirring speed is at least 200 rpm, preferably 200 to 400 rpm.

[0026] Further, the solvent oil mentioned in step (2) is a dearomatic solvent oil with a flash point higher than 60°C, preferably one of D40 solvent oil, D60 solvent oil, and D80 solvent oil, and its amount is at least 40 wt% of the amount of monomer E, preferably 40 to 80 wt%.

[0027] Further, the oil-based surfactant mentioned in step (2) is one or more of castor oil polyoxyethylene ether, isotretinoin polyoxyethylene ether, alkylphenol polyoxyethylene ether, and lauryl alcohol polyoxyethylene ether, and its amount is at least 0.05 wt% of the amount of monomer E, preferably 0.05 to 0.1 wt%.

[0028] Furthermore, in step (2), the stirring bar is as follows: the stirring speed is at least 200 rpm, preferably 200 to 500 rpm.

[0029] Furthermore, in step (3), nitrogen or an inert gas is continuously introduced throughout the process, and / or

[0030] Step (3) involves continuous stirring at a speed of at least 400 rpm, preferably 400 to 1000 rpm.

[0031] Further, the initiator mentioned in step (3) is a mixture of substance A, substance B, and substance C, with a mixing ratio of 1:(1~2):(0.5~1.2), wherein:

[0032] The total amount of the initiator is at least 0.01 wt% of the amount of monomer E, preferably 0.01 to 0.5%;

[0033] Substance A is one or more of ammonium persulfate, sodium persulfate, and potassium persulfate;

[0034] Substance B is one or more of sodium bisulfite, potassium bisulfite, and ammonium bisulfite;

[0035] The substance C is one or more of azobisisobutyronitrile and azobisisoheptanenitrile.

[0036] Furthermore, the reaction temperature of the solution polymerization reaction in step (3) is at least 50°C, preferably 50–80°C;

[0037] The reaction time for the solution polymerization reaction in step (3) is at least 5 hours, preferably 5-10 hours.

[0038] The emulsion polymer is prepared by any of the methods described above.

[0039] The application of the emulsion polymer described in any of the above-mentioned methods as a viscosity reducer in pressure drive production of low-permeability heavy oil reservoirs.

[0040] Invention principle:

[0041] The emulsion polymer provided by this invention belongs to the quaternary emulsion copolymer. The emulsion polymer is obtained by emulsion polymerization reaction with acrylamide and 2-acrylamido-2-methylpropanesulfonic acid as the main monomers, supplemented by hydrophobic monomers and monomers containing cyclic groups.

[0042] Making emulsion polymers into emulsion form does not affect the molecular polymerization length, allowing them to maintain high viscosity in aqueous solutions. On the other hand, the unique solubility of emulsions enables on-site preparation during pressure drive construction.

[0043] Introducing lipophilic long chains R into the molecules of emulsion polymers can effectively insert into the interior of heavy oils and easily adsorb onto the oil-water interface;

[0044] The hydrophilic groups such as sulfonic acid groups, amide groups, and morpholine groups introduced into the molecules of emulsion polymers can adsorb water molecules at the oil-water interface through hydrogen bonding, thus adsorbing a water film on the outer layer of the oil and achieving the emulsification function.

[0045] The special introduction of morpholine groups into the emulsion polymer of the present invention can significantly improve the molecule's ability to inhibit hydrolysis and enhance the aging stability of the molecule during reservoir oil displacement.

[0046] After emulsion polymerization, the product is not refined, so the unreacted lipophilic and hydrophilic surfactants can still play a role in the oil displacement process, enhancing the stability of the emulsion.

[0047] Beneficial effects: Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0048] (1) It has the characteristics of simple preparation process, low cost and strong adaptability;

[0049] (2) The emulsion polymer of the present invention has a significant thickening effect, with a viscosity-average molecular weight of 30 million to 39 million, and an apparent viscosity of ≥100 mPa·s at a mineralization of 10,000 mg / L and a temperature of 50°C.

[0050] (3) The emulsion polymer of the present invention has a good effect of rapid emulsification and viscosity reduction at low concentration. At a concentration of 0.1wt%, the viscosity reduction rate for ordinary heavy oil and extra-heavy oil reaches more than 95%, and it can achieve rapid dissolution with a dissolution time of ≤300s.

[0051] (4) The emulsion polymer of the present invention has the advantages of simple on-site construction, no need for pre-preparation, and easy dissolution, and can meet the requirements of low-permeability heavy oil pressure drive technology. Attached Figure Description

[0052] Figure 1 The infrared spectrum of the emulsion polymer Q1 prepared in Example 1 is shown. Detailed Implementation

[0053] The specific embodiments of the present invention are described in detail below.

[0054] The "range" disclosed in this invention is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if a range of 10–50 is listed for a specific parameter, it is also expected that ranges of 10–40 and 20–50 are also included. Furthermore, if the minimum range values ​​are 1 and 2, and the maximum range values ​​are 3, 4, and 5, then the following ranges are all expected: 1–3, 1–4, 1–5, 2–3, 2–4, and 2–5. In this application, unless otherwise stated, the numerical range "a–b" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0–5" means that all real numbers between "0–5" have been listed herein; "0–5" is merely a shortened representation of these numerical combinations.

[0055] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0056] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0057] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0058] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0059] Unless otherwise specified, the reaction will proceed under normal temperature and pressure conditions.

[0060] Unless otherwise specified, all parts or percentages are by weight or by weight percentage.

[0061] In this invention, all the substances used are known substances that can be purchased or synthesized by known methods.

[0062] In this invention, all the devices or equipment used are conventional devices or equipment known in the art and are readily available.

[0063] The emulsion polymer synthesis route of the present invention is as follows:

[0064]

[0065]

[0066] First aspect of the invention:

[0067] An emulsion polymer comprising structural unit A, structural unit B, structural unit C and structural unit D, wherein structural unit A has a structural unit as shown in formula (1), structural unit B has a structural unit as shown in formula (2), structural unit C has a structural unit as shown in formula (3), and structural unit D has a structural unit as shown in formula (4), wherein, based on the weight of the emulsion polymer, structural unit A accounts for 5-15% by weight, structural unit B accounts for 2-40% by weight, structural unit C accounts for 10-70% by weight, and structural unit D accounts for 1-80% by weight, and the viscosity-average molecular weight of the emulsion polymer is 30 million to 39 million;

[0068]

[0069] Wherein: R is an alkane group, preferably C6~C6. 18 alkyl group.

[0070] Furthermore, R is C 12 ~C 16 Straight-chain alkane groups or cycloalkane groups.

[0071] Furthermore, based on the weight of the emulsion polymer, structural unit A accounts for 6-10% by weight, structural unit B accounts for 5-35% by weight, structural unit C accounts for 15-65% by weight, structural unit D accounts for 10-70% by weight, and the viscosity-average molecular weight of the emulsion polymer is 31 million to 38 million.

[0072] The second aspect of the invention:

[0073] A method for preparing an emulsion polymer, comprising the following steps:

[0074] (1) Under stirring conditions, monomer E (acrylamide), monomer F (2-acrylamido-2-methylpropanesulfonic acid), monomer G (acrylomorpholine), solvent and water-based surfactant are mixed evenly to obtain an aqueous solution;

[0075] (2) Under stirring conditions, monomer H (long-chain alkyl dimethylaminoethyl acrylate), solvent oil and oil-based surfactant are mixed evenly to obtain an oil phase solution;

[0076] (3) Under a nitrogen or inert gas atmosphere, the aqueous solution and the oil solution are mixed, then an initiator is added and a solution polymerization reaction is carried out under the action of the initiator. After the reaction is completed, an emulsion polymer is obtained.

[0077] The monomer E is a monomer having the structure shown in formula (5), the monomer F is a monomer having the structure shown in formula (6), the monomer G is a monomer having the structure shown in formula (7), and the monomer H is a monomer having the structure shown in formula (8); based on the sum of the masses of the monomer E, the monomer F, the monomer G, and the monomer H, the amount of monomer E is 5-15% by weight, the amount of monomer F is 2-40% by weight, the amount of monomer G is 10-70% by weight, and the amount of monomer H is 1-80% by weight; the conditions of the solution polymerization reaction are such that the viscosity-average molecular weight of the polymer obtained by the polymerization reaction is 30 million to 39 million.

[0078]

[0079] Wherein: R is an alkane group, preferably C6~C6. 18 alkyl group.

[0080] Furthermore, R is C 12 ~C 16 Straight-chain alkane groups or cycloalkane groups.

[0081] Furthermore, based on the weight of the emulsion polymer, structural unit A accounts for 6-10% by weight, structural unit B accounts for 5-35% by weight, structural unit C accounts for 15-65% by weight, structural unit D accounts for 10-70% by weight, and the viscosity-average molecular weight of the emulsion polymer is 31 million to 38 million.

[0082] Furthermore, the solvent in step (1) is one or more of deionized water, ethanol, ethyl acetate, and toluene, and its amount is at least 10 times, preferably 10 to 30 times, the amount of monomer E.

[0083] Further, the water-based surfactant mentioned in step (1) is one or more of Tween60, Tween80, Span40, Span60, OP-10, OP-13, OP-15, OP-20, OP-30, OP-40, and OP-50, and its amount is at least 0.1 wt% of the amount of monomer E, preferably 0.1 to 0.5 wt%.

[0084] Furthermore, in step (1), heating is performed simultaneously during stirring, and the heating temperature is controlled at at least 25°C, preferably 25–50°C, and / or

[0085] The stirring conditions in step (1) are as follows: the stirring speed is at least 200 rpm, preferably 200 to 400 rpm.

[0086] Further, the solvent oil mentioned in step (2) is a dearomatic solvent oil with a flash point higher than 60°C, preferably one of D40 solvent oil, D60 solvent oil, and D80 solvent oil, and its amount is at least 40 wt% of the amount of monomer E, preferably 40 to 80 wt%.

[0087] Further, the oil-based surfactant mentioned in step (2) is one or more of castor oil polyoxyethylene ether, isotretinoin polyoxyethylene ether, alkylphenol polyoxyethylene ether, and lauryl alcohol polyoxyethylene ether, and its amount is at least 0.05 wt% of the amount of monomer E, preferably 0.05 to 0.1 wt%.

[0088] Furthermore, in step (2), the stirring bar is as follows: the stirring speed is at least 200 rpm, preferably 200 to 500 rpm.

[0089] Furthermore, in step (3), nitrogen or an inert gas is continuously introduced throughout the process, and / or

[0090] Step (3) involves continuous stirring at a speed of at least 400 rpm, preferably 400 to 1000 rpm.

[0091] Further, the initiator mentioned in step (3) is a mixture of substance A, substance B, and substance C, with a mixing ratio of 1:(1~2):(0.5~1.2), wherein:

[0092] The total amount of the initiator is at least 0.01 wt% of the amount of monomer E, preferably 0.01 to 0.5%;

[0093] Substance A is one or more of ammonium persulfate, sodium persulfate, and potassium persulfate;

[0094] Substance B is one or more of sodium bisulfite, potassium bisulfite, and ammonium bisulfite;

[0095] The substance C is one or more of azobisisobutyronitrile and azobisisoheptanenitrile.

[0096] Furthermore, the reaction temperature of the solution polymerization reaction in step (3) is at least 50°C, preferably 50–80°C;

[0097] The reaction time for the solution polymerization reaction in step (3) is at least 5 hours, preferably 5-10 hours.

[0098] According to a more specific preferred embodiment, a method for preparing an emulsion polymer specifically includes the following steps:

[0099] S1 aqueous phase preparation

[0100] In a reaction vessel, monomers E (acrylamide), F (2-acrylamido-2-methylpropanesulfonic acid), and G (acrylomorpholine) are added sequentially. Then, an appropriate amount of deionized water is added as a solvent. The heating temperature is controlled at 25–50°C, and the stirring speed is controlled at 200–400 rpm. After complete dissolution, a water-based surfactant is added, and the mixture is stirred for 10–20 minutes to obtain a mixed solution. The pH of the reaction solution (e.g., sodium hydroxide solution) is then adjusted to 6.5–8.0, and the solution is cooled to room temperature to obtain an aqueous phase solution.

[0101] S2 oil phase preparation

[0102] Solvent oil and monomer H (long-chain alkyl dimethylaminoethyl acrylate) were added to a reaction vessel. An oil-based surfactant was continuously added while stirring at a speed of 200-500 rpm. After complete dissolution, an oil phase solution was obtained.

[0103] S3 emulsion polymerization

[0104] Nitrogen or inert gas is introduced into the reaction vessel. Then, the stirring speed of the oil phase solution obtained in step (2) is adjusted to 500-1000 rpm. The aqueous phase solution obtained in step (1) is then slowly added into the reaction vessel. After it is completely added, stirring is continued to form a stable reverse emulsion. Then, the temperature is raised to 50-80℃ and an initiator is added. The mixture is stirred at a constant temperature for 5-10 hours. Then, the temperature is lowered to obtain the emulsion polymer.

[0105] Further, the water-based surfactant mentioned in step S1 is one or more of Tween60, Tween80, Span40, OP-10, OP-13 and OP-15, and its amount is at least 0.1 wt% of the amount of monomer E, preferably 0.1 to 0.5 wt%.

[0106] Furthermore, the solvent oil mentioned in step S2 is a dearomatic solvent oil with a flash point higher than 60°C, preferably one of D60 solvent oil and D80 solvent oil, and its amount is at least 40 wt% of the amount of monomer E, preferably 40 to 80 wt%.

[0107] Further, the oil-based surfactant mentioned in step S2 is one or more of castor oil polyoxyethylene ether and isotridecyl alcohol polyoxyethylene ether, and its amount is at least 0.05 wt% of the amount of monomer E, preferably 0.05 to 0.1 wt%.

[0108] Further, the initiator mentioned in step S3 is a mixture of ammonium persulfate, sodium bisulfite and azobisisobutyronitrile, with a mixing ratio of 1:(1-2):(0.5-1.2), and the total amount of the initiator is at least 0.01 wt% of the amount of monomer E, preferably 0.01-0.5%.

[0109] The emulsion polymer is prepared by any of the methods described above.

[0110] The application of the emulsion polymer described in any of the above-mentioned methods as a viscosity reducer in pressure drive production of low-permeability heavy oil reservoirs.

[0111] In one embodiment:

[0112] An emulsion polymer comprising structural unit A, structural unit B, structural unit C and structural unit D, wherein structural unit A has a structural unit as shown in formula (1), structural unit B has a structural unit as shown in formula (2), structural unit C has a structural unit as shown in formula (3), and structural unit D has a structural unit as shown in formula (4), wherein, based on the weight of the emulsion polymer, structural unit A accounts for 10% by weight, structural unit B accounts for 20% by weight, structural unit C accounts for 30% by weight, and structural unit D accounts for 40% by weight, and the viscosity-average molecular weight of the emulsion polymer is 35 million;

[0113]

[0114] Where: R is C 14 Straight-chain alkane groups.

[0115] A method for preparing the above-mentioned emulsion polymer, comprising the following steps:

[0116] (1) Under stirring conditions, monomer E (acrylamide), monomer F (2-acrylamido-2-methylpropanesulfonic acid), monomer G (acrylomorpholine), solvent and water-based surfactant are mixed evenly to obtain an aqueous solution;

[0117] (2) Under stirring conditions, monomer H (long-chain alkyl dimethylaminoethyl acrylate), solvent oil and oil-based surfactant are mixed evenly to obtain an oil phase solution;

[0118] (3) Under a nitrogen atmosphere, the aqueous solution and the oil solution are mixed, then an initiator is added and a solution polymerization reaction is carried out under the action of the initiator. After the reaction is completed, an emulsion polymer is obtained, wherein...

[0119] The monomer E is a monomer having the structure shown in formula (5), the monomer F is a monomer having the structure shown in formula (6), the monomer G is a monomer having the structure shown in formula (7), and the monomer H is a monomer having the structure shown in formula (8); based on the sum of the masses of the monomer E, the monomer F, the monomer G, and the monomer H, the amount of monomer E is 10% by weight, the amount of monomer F is 20% by weight, the amount of monomer G is 30% by weight, and the amount of monomer H is 40% by weight; the conditions of the solution polymerization reaction are such that the viscosity-average molecular weight of the polymer obtained by the polymerization reaction is 35 million.

[0120]

[0121] Where: R is C 14 Straight-chain alkane groups.

[0122] Furthermore, the solvent in step (1) is deionized water, and its amount is 20 times that of monomer E.

[0123] Further, the water-based surfactant mentioned in step (1) is Tween60, and its amount is 0.3 wt% of the amount of monomer E.

[0124] Furthermore, in step (1), heating is performed simultaneously during stirring, with the heating temperature controlled at 40°C, and / or

[0125] The stirring conditions in step (1) are as follows: the stirring speed is 300 rpm.

[0126] Furthermore, the solvent oil mentioned in step (2) is a dearomatic solvent oil with a flash point higher than 60°C, preferably D60 solvent oil, and its amount is 60wt% of the amount of monomer E.

[0127] Further, the oil-based surfactant mentioned in step (2) is castor oil polyoxyethylene ether, and its amount is 0.08 wt% of the amount of monomer E.

[0128] Furthermore, in step (2), the stirring bar is as follows: the stirring speed is 300 rpm.

[0129] Furthermore, nitrogen gas is continuously introduced throughout step (3), and / or

[0130] Step (3) involves continuous stirring at a speed of 800 rpm.

[0131] Further, the initiator mentioned in step (3) is a mixture of ammonium persulfate, sodium bisulfite and azobisisobutyronitrile, with a mixing ratio of 1:1.5:1, and the total amount of the initiator is 0.3% of the amount of monomer E.

[0132] Furthermore, the reaction temperature of the solution polymerization reaction in step (3) is 60°C;

[0133] The reaction time for the solution polymerization reaction in step (3) is 8 hours.

[0134] According to a more specific preferred embodiment, a method for preparing an emulsion polymer specifically includes the following steps:

[0135] S1 aqueous phase preparation

[0136] In a reaction vessel, monomers E (acrylamide), F (2-acrylamido-2-methylpropanesulfonic acid), and G (acrylomorpholine) are added sequentially. Then, an appropriate amount of deionized water is added as a solvent. The heating temperature is controlled at 40°C, and the stirring speed is controlled at 300 rpm. After complete dissolution, a water-based surfactant is added, and the mixture is stirred for 15 minutes to obtain a mixed solution. The pH of the reaction solution (e.g., sodium hydroxide solution) is then adjusted to 7.0, and the solution is cooled to room temperature to obtain an aqueous phase solution.

[0137] S2 oil phase preparation

[0138] Solvent oil and monomer H (long-chain alkyl dimethylaminoethyl acrylate) were added to the reaction vessel. An oil-based surfactant was continuously added while stirring at a speed of 400 rpm. After complete dissolution, an oil phase solution was obtained.

[0139] S3 emulsion polymerization

[0140] Nitrogen gas was introduced into the reaction vessel, and the stirring speed of the oil phase solution obtained in step (2) was adjusted to 800 rpm. The aqueous phase solution obtained in step (1) was then slowly added into the reaction vessel. After it was completely added, stirring was continued to form a stable reverse emulsion. The temperature was then raised to 60°C, and an initiator was added. The mixture was stirred at a constant temperature for 8 hours. The emulsion polymer was then obtained by cooling.

[0141] Further, the water-based surfactant mentioned in step S1 is Tween60, and its amount is 0.3 wt% of the amount of monomer E.

[0142] Furthermore, the solvent oil mentioned in step S2 is a dearomatic solvent oil with a flash point higher than 60°C, preferably D60 solvent oil, and its amount is 60wt% of the amount of monomer E.

[0143] Further, the oil-based surfactant mentioned in step S2 is castor oil polyoxyethylene ether, and its amount is 0.08 wt% of the amount of monomer E.

[0144] Furthermore, the initiator mentioned in step S3 is a mixture of ammonium persulfate, sodium bisulfite, and azobisisobutyronitrile, with a mixing ratio of 1:1.5:1, and the total amount of the initiator is 0.3% of the amount of monomer E.

[0145] The emulsion polymer is prepared by any of the methods described above.

[0146] The application of the emulsion polymer described in any of the above-mentioned methods as a viscosity reducer in pressure drive production of low-permeability heavy oil reservoirs.

[0147] In yet another embodiment:

[0148] An emulsion polymer comprising structural unit A, structural unit B, structural unit C and structural unit D, wherein structural unit A has a structural unit as shown in formula (1), structural unit B has a structural unit as shown in formula (2), structural unit C has a structural unit as shown in formula (3), and structural unit D has a structural unit as shown in formula (4), wherein, based on the weight of the emulsion polymer, structural unit A accounts for 5% by weight, structural unit B accounts for 2% by weight, structural unit C accounts for 70% by weight, and structural unit D accounts for 23% by weight, and the viscosity-average molecular weight of the emulsion polymer is 30.5 million;

[0149]

[0150] Wherein: R is an isohexyl group. In another embodiment, R is C 12 Straight-chain alkane groups.

[0151] A method for preparing the above-mentioned emulsion polymer, comprising the following steps:

[0152] (1) Under stirring conditions, monomer E (acrylamide), monomer F (2-acrylamido-2-methylpropanesulfonic acid), monomer G (acrylomorpholine), solvent and water-based surfactant are mixed evenly to obtain an aqueous solution;

[0153] (2) Under stirring conditions, monomer H (long-chain alkyl dimethylaminoethyl acrylate), solvent oil and oil-based surfactant are mixed evenly to obtain an oil phase solution;

[0154] (3) Under a helium atmosphere, the aqueous solution and the oil solution are mixed, then an initiator is added and a solution polymerization reaction is carried out under the action of the initiator. After the reaction is completed, an emulsion polymer is obtained, wherein...

[0155] The monomer E is a monomer having the structure shown in formula (5), the monomer F is a monomer having the structure shown in formula (6), the monomer G is a monomer having the structure shown in formula (7), and the monomer H is a monomer having the structure shown in formula (8); based on the sum of the masses of the monomer E, the monomer F, the monomer G, and the monomer H, the amount of monomer E is 5% by weight, the amount of monomer F is 2% by weight, the amount of monomer G is 70% by weight, and the amount of monomer H is 23% by weight; the conditions of the solution polymerization reaction are such that the viscosity-average molecular weight of the polymer obtained by the polymerization reaction is 30.5 million.

[0156]

[0157] Wherein: R is an isohexyl group. In another embodiment, R is C 12 Straight-chain alkane groups.

[0158] Furthermore, the solvent in step (1) is ethanol, and its amount is 10 times that of monomer E.

[0159] Further, the water-based surfactant mentioned in step (1) is Tween80, and its amount is 0.1 wt% of the amount of monomer E.

[0160] Furthermore, in step (1), heating is performed simultaneously during stirring, with the heating temperature controlled at 25°C, and / or

[0161] The stirring conditions in step (1) are as follows: the stirring speed is 200 rpm.

[0162] Furthermore, the solvent oil mentioned in step (2) is a dearomatic solvent oil with a flash point higher than 60°C, preferably D80 solvent oil, and its amount is 40 wt% of the amount of monomer E.

[0163] Further, the oil-based surfactant mentioned in step (2) is isotridecyl alcohol polyoxyethylene ether, and its amount is 0.05 wt% of the amount of monomer E.

[0164] Furthermore, the stirring bar in step (2) is as follows: stirring speed 200 rpm.

[0165] Furthermore, in step (3), helium is continuously introduced throughout the process, and / or

[0166] Step (3) involves continuous stirring at a speed of 400 rpm.

[0167] Further, the initiator mentioned in step (3) is a mixture of substance A, substance B, and substance C, with a mixing ratio of 1:1:0.5, wherein:

[0168] The total amount of the initiator is 0.01 wt% of the amount of monomer E;

[0169] Substance A is sodium persulfate;

[0170] Substance B is potassium bisulfite;

[0171] The substance C is azobisisoheptanenitrile.

[0172] Furthermore, the reaction temperature of the solution polymerization reaction in step (3) is 50°C;

[0173] The reaction time for the solution polymerization reaction in step (3) is 10 hours.

[0174] According to a more specific preferred embodiment, a method for preparing an emulsion polymer specifically includes the following steps:

[0175] S1 aqueous phase preparation

[0176] In a reaction vessel, monomers E (acrylamide), F (2-acrylamido-2-methylpropanesulfonic acid), and G (acrylomorpholine) are added sequentially. Then, an appropriate amount of deionized water is added as a solvent. The heating temperature is controlled at 25°C, and the stirring speed is controlled at 200 rpm. After complete dissolution, a water-based surfactant is added, and the mixture is stirred for 20 minutes to obtain a mixed solution. The pH of the reaction solution (e.g., sodium hydroxide solution) is then adjusted to 6.5, and the solution is cooled to room temperature to obtain an aqueous phase solution.

[0177] S2 oil phase preparation

[0178] Solvent oil and monomer H (long-chain alkyl dimethylaminoethyl acrylate) were added to the reaction vessel. An oil-based surfactant was continuously added while stirring at a speed of 200 rpm. After complete dissolution, an oil phase solution was obtained.

[0179] S3 emulsion polymerization

[0180] Nitrogen or inert gas is introduced into the reaction vessel. Then the stirring speed of the oil phase solution obtained in step (2) is adjusted to 500 rpm. Then the aqueous phase solution obtained in step (1) is slowly added into the reaction vessel. After it is completely added, stirring is continued to form a stable reverse emulsion. Then the temperature is raised to 50°C and an initiator is added. The mixture is stirred at a constant temperature for 10 hours. Then the temperature is lowered to obtain the emulsion polymer.

[0181] Further, the water-based surfactant mentioned in step S1 is Tween80, and its amount is 0.1 wt% of the amount of monomer E.

[0182] Furthermore, the solvent oil mentioned in step S2 is a dearomatic solvent oil with a flash point higher than 60°C, preferably D80 solvent oil, and its amount is 40 wt% of the amount of monomer E.

[0183] Further, the oil-based surfactant mentioned in step S2 is isotridecyl alcohol polyoxyethylene ether, and its amount is 0.05 wt% of the amount of monomer E.

[0184] Further, the initiator mentioned in step S3 is a mixture of ammonium persulfate, sodium bisulfite and azobisisobutyronitrile, with a mixing ratio of 1:1:0.5, and the total amount of the initiator is 0.01 wt% of the amount of monomer E.

[0185] The emulsion polymer is prepared by any of the methods described above.

[0186] The application of the emulsion polymer described in any of the above-mentioned methods as a viscosity reducer in pressure drive production of low-permeability heavy oil reservoirs.

[0187] In another embodiment:

[0188] An emulsion polymer comprising structural unit A, structural unit B, structural unit C and structural unit D, wherein structural unit A has a structural unit as shown in formula (1), structural unit B has a structural unit as shown in formula (2), structural unit C has a structural unit as shown in formula (3), and structural unit D has a structural unit as shown in formula (4), wherein, based on the weight of the emulsion polymer, structural unit A accounts for 15% by weight, structural unit B accounts for 40% by weight, structural unit C accounts for 10% by weight, and structural unit D accounts for 35% by weight, and the viscosity-average molecular weight of the emulsion polymer is 39 million;

[0189]

[0190] Where: R is C 18 Straight-chain alkane groups.

[0191] In another embodiment, an emulsion polymer is provided, the emulsion polymer comprising structural unit A, structural unit B, structural unit C and structural unit D, structural unit A having a structural unit as shown in formula (1), structural unit B having a structural unit as shown in formula (2), structural unit C having a structural unit as shown in formula (3), and structural unit D having a structural unit as shown in formula (4), wherein, based on the weight of the emulsion polymer, structural unit A accounts for 10% by weight, structural unit B accounts for 35% by weight, structural unit C accounts for 15% by weight, and structural unit D accounts for 40% by weight, and the viscosity-average molecular weight of the emulsion polymer is 38 million;

[0192]

[0193] Where R represents cyclohexyl.

[0194] In another embodiment: an emulsion polymer comprising structural unit A, structural unit B, structural unit C and structural unit D, wherein structural unit A has a structural unit as shown in formula (1), structural unit B has a structural unit as shown in formula (2), structural unit C has a structural unit as shown in formula (3), and structural unit D has a structural unit as shown in formula (4), wherein, based on the weight of the emulsion polymer, structural unit A accounts for 6% by weight, structural unit B accounts for 5% by weight, structural unit C accounts for 65% by weight, and structural unit D accounts for 24% by weight, and the viscosity-average molecular weight of the emulsion polymer is 33 million;

[0195]

[0196] Where R is n-butyl.

[0197] In another embodiment: an emulsion polymer comprising structural unit A, structural unit B, structural unit C and structural unit D, wherein structural unit A has a structural unit as shown in formula (1), structural unit B has a structural unit as shown in formula (2), structural unit C has a structural unit as shown in formula (3), and structural unit D has a structural unit as shown in formula (4), wherein, based on the weight of the emulsion polymer, structural unit A accounts for 9% by weight, structural unit B accounts for 6% by weight, structural unit C accounts for 15% by weight, and structural unit D accounts for 70% by weight, and the viscosity-average molecular weight of the emulsion polymer is 31 million;

[0198]

[0199] Where R is a methyl group.

[0200] In another embodiment: an emulsion polymer comprising structural unit A, structural unit B, structural unit C and structural unit D, wherein structural unit A has a structural unit as shown in formula (1), structural unit B has a structural unit as shown in formula (2), structural unit C has a structural unit as shown in formula (3), and structural unit D has a structural unit as shown in formula (4), wherein, based on the weight of the emulsion polymer, structural unit A accounts for 10% by weight, structural unit B accounts for 35% by weight, structural unit C accounts for 45% by weight, and structural unit D accounts for 10% by weight, and the viscosity-average molecular weight of the emulsion polymer is 35 million;

[0201]

[0202] Where: R is C16 Straight-chain alkane groups.

[0203] A method for preparing the above-mentioned emulsion polymer, comprising the following steps:

[0204] (1) Under stirring conditions, monomer E (acrylamide), monomer F (2-acrylamido-2-methylpropanesulfonic acid), monomer G (acrylomorpholine), solvent and water-based surfactant are mixed evenly to obtain an aqueous solution;

[0205] (2) Under stirring conditions, monomer H (long-chain alkyl dimethylaminoethyl acrylate), solvent oil and oil-based surfactant are mixed evenly to obtain an oil phase solution;

[0206] (3) Under a neon atmosphere, the aqueous solution and the oil solution are mixed, then an initiator is added and a solution polymerization reaction is carried out under the action of the initiator. After the reaction is completed, an emulsion polymer is obtained, wherein...

[0207] The monomer E is a monomer having the structure shown in formula (5), the monomer F is a monomer having the structure shown in formula (6), the monomer G is a monomer having the structure shown in formula (7), and the monomer H is a monomer having the structure shown in formula (8); based on the sum of the masses of the monomer E, the monomer F, the monomer G, and the monomer H, the amount of monomer E is 15% by weight, the amount of monomer F is 40% by weight, the amount of monomer G is 10% by weight, and the amount of monomer H is 35% by weight; the conditions of the solution polymerization reaction are such that the viscosity-average molecular weight of the polymer obtained by the polymerization reaction is 39 million.

[0208]

[0209] Where: R is C 18 A straight-chain alkane group. In another embodiment, R is C 16 The linear alkane group. In another embodiment, R is methyl. In another embodiment, R is n-butyl. In another embodiment, R is cyclohexyl.

[0210] Furthermore, the solvent in step (1) is ethyl acetate, and its amount is 30 times that of monomer E. In another embodiment, the solvent in step (1) is a mixture of deionized water, ethanol, ethyl acetate, and toluene in equal mass ratios, and its amount is 25 times that of monomer E. In another embodiment, the solvent in step (1) is toluene, and its amount is 12 times that of monomer E.

[0211] Further, the water-based surfactant mentioned in step (1) is Span40, and its amount is 0.5 wt% of the amount of monomer E. In another embodiment, the water-based surfactant mentioned in step (1) is OP-10, and its amount is 0.2 wt% of the amount of monomer E. In another embodiment, the water-based surfactant mentioned in step (1) is OP-13, and its amount is 0.1 wt% of the amount of monomer E. In another embodiment, the water-based surfactant mentioned in step (1) is OP-15, and its amount is 0.4 wt% of the amount of monomer E. In another embodiment, the water-based surfactant mentioned in step (1) is a mixture of Tween60, Tween80, Span40, OP-10, OP-13 and OP-15 in equal mass ratios, and its amount is 0.5 wt% of the amount of monomer E. In another embodiment, the water-based surfactant mentioned in step (1) is a mixture of Tween60, Tween80, Span40, Span60, OP-10, OP-13, OP-15, OP-20, OP-30, OP-40, and OP-50 in equal mass ratios, and its amount is 0.5 wt% of the amount of monomer E. In another embodiment, the water-based surfactant mentioned in step (1) is Span60, and its amount is 0.3 wt% of the amount of monomer E. In another embodiment, the water-based surfactant mentioned in step (1) is OP-15, and its amount is 0.5 wt% of the amount of monomer E. In another embodiment, the water-based surfactant mentioned in step (1) is OP-20, and its amount is 0.4 wt% of the amount of monomer E. In another embodiment, the water-based surfactant mentioned in step (1) is OP-30, and its amount is 0.3 wt% of the amount of monomer E. In another embodiment, the water-based surfactant in step (1) is OP-40, and its amount is 0.3 wt% of the amount of monomer E. In another embodiment, the water-based surfactant in step (1) is OP-50, and its amount is 0.5 wt% of the amount of monomer E.

[0212] Furthermore, in step (1), heating is performed simultaneously during stirring, with the heating temperature controlled at 50°C, and / or

[0213] The stirring conditions in step (1) are as follows: stirring speed 400 rpm.

[0214] Furthermore, the solvent oil mentioned in step (2) is a dearomatic solvent oil with a flash point higher than 60°C, preferably D40 solvent oil, and its amount is 80 wt% of the amount of monomer E.

[0215] Further, the oil-based surfactant mentioned in step (2) is a mixture of castor oil polyoxyethylene ether, isotretinoin polyoxyethylene ether, alkylphenol polyoxyethylene ether, and lauryl alcohol polyoxyethylene ether in equal mass ratios, and its amount is 0.1 wt% of the amount of monomer E. In another embodiment, the oil-based surfactant mentioned in step (2) is alkylphenol polyoxyethylene ether, and its amount is 0.1 wt% of the amount of monomer E. In another embodiment, the oil-based surfactant mentioned in step (2) is lauryl alcohol polyoxyethylene ether, and its amount is 0.08 wt% of the amount of monomer E.

[0216] Furthermore, the stirring bar in step (2) is as follows: stirring speed 500 rpm.

[0217] Furthermore, in step (3), neon gas is continuously introduced throughout the process, and / or

[0218] Step (3) involves continuous stirring at a speed of 1000 rpm.

[0219] Further, the initiator mentioned in step (3) is a mixture of substance A, substance B, and substance C, with a mixing ratio of 1:2:1.2, wherein:

[0220] The total amount of the initiator is 0.5% of the amount of monomer E.

[0221] Substance A is potassium persulfate;

[0222] Substance B is ammonium bisulfite;

[0223] The substance C is azobisisobutyronitrile.

[0224] In another embodiment, the initiator mentioned in step (3) is a mixture of substances A, B, and C in a mixing ratio of 1:1.5:1, wherein:

[0225] The total amount of the initiator is 0.02 wt% of the amount of monomer E;

[0226] Substance A is a mixture of ammonium persulfate, sodium persulfate, and potassium persulfate in equal mass ratios;

[0227] Substance B is a mixture of sodium bisulfite, potassium bisulfite, and ammonium bisulfite in equal mass ratios.

[0228] The substance C is a mixture of azobisisobutyronitrile and azobisisoheptanenitrile in equal mass ratios.

[0229] Furthermore, the reaction temperature of the solution polymerization reaction in step (3) is 80°C;

[0230] The reaction time for the solution polymerization reaction in step (3) is 5 hours.

[0231] According to a more specific preferred embodiment, a method for preparing an emulsion polymer specifically includes the following steps:

[0232] S1 aqueous phase preparation

[0233] In a reaction vessel, monomers E (acrylamide), F (2-acrylamido-2-methylpropanesulfonic acid), and G (acrylomorpholine) are added sequentially. Then, an appropriate amount of deionized water is added as a solvent. The heating temperature is controlled at 50°C, and the stirring speed is controlled at 400 rpm. After complete dissolution, a water-based surfactant is added, and the mixture is stirred for 20 minutes to obtain a mixed solution. The pH of the reaction solution (e.g., sodium hydroxide solution) is then adjusted to 8.0, and the solution is cooled to room temperature to obtain an aqueous phase solution.

[0234] S2 oil phase preparation

[0235] Solvent oil and monomer H (long-chain alkyl dimethylaminoethyl acrylate) were added to the reaction vessel. An oil-based surfactant was continuously added while stirring at a speed of 500 rpm. After complete dissolution, an oil phase solution was obtained.

[0236] S3 emulsion polymerization

[0237] Nitrogen or inert gas is introduced into the reaction vessel. Then the stirring speed of the oil phase solution obtained in step (2) is adjusted to 1000 rpm. Then the aqueous phase solution obtained in step (1) is slowly added into the reaction vessel. After it is completely added, stirring is continued to form a stable reverse emulsion. Then the temperature is raised to 80°C and an initiator is added. The mixture is stirred at a constant temperature for 5 hours. Then the temperature is lowered to obtain the emulsion polymer.

[0238] Further, the water-based surfactant mentioned in step S1 is Span40, and its amount is 0.1 wt% of the amount of monomer E. In another embodiment, the water-based surfactant mentioned in step S1 is OP-10, and its amount is 0.5 wt% of the amount of monomer E. In another embodiment, the water-based surfactant mentioned in step S1 is OP-13, and its amount is 0.2 wt% of the amount of monomer E. In another embodiment, the water-based surfactant mentioned in step S1 is OP-15, and its amount is 0.5 wt% of the amount of monomer E. In yet another embodiment, the water-based surfactant mentioned in step S1 is a mixture of Tween60, Tween80, Span40, OP-10, OP-13, and OP-15 in equal mass ratios, and its amount is 0.5 wt% of the amount of monomer E.

[0239] Furthermore, the solvent oil mentioned in step S2 is a dearomatic solvent oil with a flash point higher than 60°C, preferably D60 solvent oil, and its amount is 80 wt% of the amount of monomer E.

[0240] Further, the oil-based surfactant mentioned in step S2 is a mixture of castor oil polyoxyethylene ether and isotretinoin polyoxyethylene ether in equal mass ratio, and its amount is 0.1 wt% of the amount of monomer E.

[0241] Furthermore, the initiator mentioned in step S3 is a mixture of ammonium persulfate, sodium bisulfite, and azobisisobutyronitrile, with a mixing ratio of 1:2:1.2, and the total amount of the initiator is 0.5% of the amount of monomer E.

[0242] The emulsion polymer is prepared by any of the methods described above.

[0243] The application of the emulsion polymer described in any of the above-mentioned methods as a viscosity reducer in pressure drive production of low-permeability heavy oil reservoirs.

[0244] Example 1

[0245] A method for preparing an emulsion polymer specifically includes the following steps:

[0246] S1 aqueous phase preparation

[0247] 1 mol acrylamide, 0.02 mol 2-acrylamido-2-methylpropanesulfonic acid, and 0.0001 mol acrylamide morpholine were added sequentially to a beaker, followed by 710 g of deionized water. The heating temperature was controlled at 30 °C, and the stirring speed was 200 rpm. After complete dissolution, 0.071 g Tween 60 was added, and the mixture was stirred for 10 min. The pH of the aqueous solution was adjusted to 7.0 with sodium hydroxide solution, and finally cooled to room temperature to obtain an aqueous solution.

[0248] S2 oil phase preparation

[0249] Add 28.4 g of D60 solvent oil and 0.0001 mol of long-chain alkyl dimethylaminoethyl acrylate to a three-necked flask. Continuously add 0.0355 g of castor oil polyoxyethylene ether while stirring at 200 rpm. After complete dissolution, an oil phase solution is obtained.

[0250] S3 emulsion polymerization

[0251] Nitrogen gas was introduced into a three-necked flask, and the stirring speed of the oil phase solution was adjusted to 500 rpm at room temperature. The aqueous phase solution obtained in step S1 was slowly added to the three-necked flask. After the solution was completely added, stirring was continued to form a stable reverse emulsion. The temperature was then raised to 50°C, and 0.0071 g of initiator was added. The initiator was a mixture of ammonium persulfate, sodium bisulfite, and azobisisobutyronitrile in a ratio of 1:1:0.5. The mixture was stirred at a constant temperature for 5 h. The temperature was then lowered to obtain a milky white emulsion, which is the emulsion polymer Q1.

[0252] Example 2

[0253] A method for preparing an emulsion polymer specifically includes the following steps:

[0254] S1 aqueous phase preparation

[0255] 1 mol acrylamide, 0.05 mol 2-acrylamido-2-methylpropanesulfonic acid, and 0.0005 mol acrylamide morpholine were added sequentially to a beaker, followed by 850 g of deionized water. The heating temperature was controlled at 35 °C, and the stirring speed was 250 rpm. After complete dissolution, 0.092 g Tween 80 was added, and the mixture was stirred for 15 min. The pH of the aqueous solution was adjusted to 6.5 with sodium hydroxide solution, and finally cooled to room temperature to obtain an aqueous solution.

[0256] S2 oil phase preparation

[0257] Add 35.3g of D80 solvent oil and 0.001mol of long-chain alkyl dimethylaminoethyl acrylate to a three-necked flask. Continuously add 0.0523g of isotridecyl polyoxyethylene ether while stirring at 300rpm. After complete dissolution, an oil phase solution is obtained.

[0258] S3 emulsion polymerization

[0259] Nitrogen gas was introduced into a three-necked flask, and the stirring speed of the oil phase solution was adjusted to 550 rpm at room temperature. The aqueous phase solution obtained in step S1 was slowly added to the three-necked flask. After it was completely added, stirring was continued to form a stable reverse emulsion. The temperature was raised to 60°C, and 0.05 g of initiator was added. The initiator was a mixture of ammonium persulfate, sodium bisulfite, and azobisisobutyronitrile in a mixing ratio of 1:2:0.8. The mixture was stirred at a constant temperature for 7 h. Then the temperature was lowered to obtain a milky white emulsion, which is the emulsion polymer Q2.

[0260] Example 3

[0261] A method for preparing an emulsion polymer specifically includes the following steps:

[0262] S1 aqueous phase preparation

[0263] 1 mol acrylamide, 0.1 mol 2-acrylamido-2-methylpropanesulfonic acid, and 0.001 mol acrylamide morpholine were added sequentially to a beaker, followed by 920 g of deionized water. The heating temperature was controlled at 40 °C, and the stirring speed was 200 rpm. After complete dissolution, 0.115 g Tween 60 was added, and the mixture was stirred for 12 min. The pH of the aqueous solution was then adjusted to 8.0 with sodium hydroxide solution, and finally cooled to room temperature to obtain an aqueous solution.

[0264] S2 oil phase preparation

[0265] Add 31.2 g of D80 solvent oil and 0.0005 mol of long-chain alkyl dimethylaminoethyl acrylate to a three-necked flask. Continuously add 0.0412 g of isotridecyl polyoxyethylene ether while stirring at 300 rpm. After complete dissolution, an oil phase solution is obtained.

[0266] S3 emulsion polymerization

[0267] Helium gas was introduced into a three-necked flask, and the stirring speed of the oil phase solution was adjusted to 600 rpm at room temperature. The aqueous phase solution obtained in step S1 was slowly added to the three-necked flask. After the solution was completely added, stirring was continued to form a stable reverse emulsion. The temperature was raised to 60°C, and 0.01 g of initiator was added. The initiator was a mixture of ammonium persulfate, sodium bisulfite, and azobisisobutyronitrile in a ratio of 1:1:0.6. The mixture was stirred at a constant temperature for 6 hours. The temperature was then lowered to obtain a milky white emulsion, which is the emulsion polymer Q3.

[0268] Example 4

[0269] A method for preparing an emulsion polymer specifically includes the following steps:

[0270] S1 aqueous phase preparation

[0271] 1 mol acrylamide, 0.2 mol 2-acrylamido-2-methylpropanesulfonic acid, and 0.005 mol acrylamide morpholine were added sequentially to a beaker, followed by 1160 g of deionized water. The mixture was heated to 36 °C and stirred at 300 rpm until completely dissolved. Then, 0.158 g of Tween 80 was added and stirred for 15 min. The pH of the aqueous solution was adjusted to 7.0 with sodium hydroxide solution, and finally cooled to room temperature to obtain an aqueous solution.

[0272] S2 oil phase preparation

[0273] Add 38.6 g of D60 solvent oil and 0.005 mol of long-chain alkyl dimethylaminoethyl acrylate to a three-necked flask. Continuously add 0.0578 g of isotridecyl polyoxyethylene ether while stirring at 400 rpm. After complete dissolution, an oil phase solution is obtained.

[0274] S3 emulsion polymerization

[0275] Argon gas was introduced into a three-necked flask, and the stirring speed of the oil phase solution was adjusted to 650 rpm at room temperature. The aqueous phase solution obtained in step S1 was slowly added to the three-necked flask. After it was completely added, stirring was continued to form a stable reverse emulsion. The temperature was then raised to 70°C, and 0.10 g of initiator was added. The initiator was a mixture of ammonium persulfate, sodium bisulfite, and azobisisobutyronitrile in a mixing ratio of 1:1.5:1.0. The mixture was stirred at a constant temperature for 8 hours. The temperature was then lowered to obtain a milky white emulsion, which is the emulsion polymer Q4.

[0276] Example 5

[0277] A method for preparing an emulsion polymer specifically includes the following steps:

[0278] S1 aqueous phase preparation

[0279] 1 mol acrylamide, 0.5 mol 2-acrylamido-2-methylpropanesulfonic acid, and 0.01 mol acrylamide morpholine were added sequentially to a beaker, followed by 1280 g of deionized water. The mixture was heated to 48 °C and stirred at 350 rpm until completely dissolved. Then, 0.213 g of Span40 was added and stirred for 16 min. The pH of the aqueous solution was adjusted to 6.5 with sodium hydroxide solution, and finally cooled to room temperature to obtain an aqueous solution.

[0280] S2 oil phase preparation

[0281] Add 42.3g of D80 solvent oil and 0.01mol of long-chain alkyl acrylate dimethylaminoethyl ester to a three-necked flask. Continuously add 0.0623g of castor oil polyoxyethylene ether while stirring at 450rpm. After complete dissolution, an oil phase solution is obtained.

[0282] S3 emulsion polymerization

[0283] Neon gas was introduced into a three-necked flask, and the stirring speed of the oil phase solution was adjusted to 700 rpm at room temperature. The aqueous phase solution obtained in step S1 was slowly added to the three-necked flask. After it was completely added, stirring was continued to form a stable reverse emulsion. The temperature was then raised to 65°C, and 0.20 g of initiator was added. The initiator was a mixture of ammonium persulfate, sodium bisulfite, and azobisisobutyronitrile in a mixing ratio of 1:1.5:1.1. The mixture was stirred at a constant temperature for 9 h. The temperature was then lowered to obtain a milky white emulsion, which is the emulsion polymer Q5.

[0284] Example 6

[0285] A method for preparing an emulsion polymer specifically includes the following steps:

[0286] S1 aqueous phase preparation

[0287] 1 mol acrylamide, 1.0 mol 2-acrylamido-2-methylpropanesulfonic acid, and 0.01 mol acrylmorpholine were added sequentially to a beaker, followed by 1280 g of deionized water. The mixture was heated to 32 °C and stirred at 320 rpm until completely dissolved. Then, 0.258 g of OP-10 was added and stirred for 18 min. The pH of the aqueous solution was adjusted to 8.0 with sodium hydroxide solution, and finally cooled to room temperature to obtain an aqueous solution.

[0288] S2 oil phase preparation

[0289] Add 45.7g of D80 solvent oil and 0.05mol of long-chain alkyl acrylate dimethylaminoethyl ester to a three-necked flask. Continuously add 0.0685g of isotridecyl alcohol polyoxyethylene ether while stirring at 350rpm. After complete dissolution, an oil phase solution is obtained.

[0290] S3 emulsion polymerization

[0291] Nitrogen gas was introduced into a three-necked flask, and the stirring speed of the oil phase solution was adjusted to 800 rpm at room temperature. The aqueous phase solution obtained in step S1 was slowly added to the three-necked flask. After the solution was completely added, stirring was continued to form a stable reverse emulsion. The temperature was then raised to 60°C, and 0.25 g of initiator was added. The initiator was a mixture of ammonium persulfate, sodium bisulfite, and azobisisobutyronitrile in a ratio of 1:2:0.9. The mixture was stirred at a constant temperature for 5 h. The temperature was then lowered to obtain a milky white emulsion, which is the emulsion polymer Q6.

[0292] Example 7

[0293] A method for preparing an emulsion polymer specifically includes the following steps:

[0294] S1 aqueous phase preparation

[0295] 1 mol acrylamide, 2.0 mol 2-acrylamido-2-methylpropanesulfonic acid, and 0.1 mol acrylmorpholine were added sequentially to a beaker, followed by 1890 g of deionized water. The mixture was heated to 45 °C and stirred at 360 rpm until completely dissolved. Then, 0.317 g of OP-15 was added and stirred for 13 min. The pH of the aqueous solution was adjusted to 7.0 with sodium hydroxide solution, and finally cooled to room temperature to obtain an aqueous solution.

[0296] S2 oil phase preparation

[0297] Add 51.3g of D60 solvent oil and 0.1mol of long-chain alkyl acrylate dimethylaminoethyl ester to a three-necked flask. Continuously add 0.0478g of castor oil polyoxyethylene ether while stirring at 400rpm. After complete dissolution, an oil phase solution is obtained.

[0298] S3 emulsion polymerization

[0299] Nitrogen gas was introduced into a three-necked flask, and the stirring speed of the oil phase solution was adjusted to 1000 rpm at room temperature. The aqueous phase solution obtained in step S1 was slowly added to the three-necked flask. After the solution was completely added, stirring was continued to form a stable reverse emulsion. The temperature was then raised to 80°C, and 0.355 g of initiator was added. The initiator was a mixture of ammonium persulfate, sodium bisulfite, and azobisisobutyronitrile in a ratio of 1:2:1.2. The mixture was stirred at a constant temperature for 10 h. The temperature was then lowered to obtain a milky white emulsion, which is the emulsion polymer Q7.

[0300] Example 8

[0301] A method for preparing an emulsion polymer specifically includes the following steps:

[0302] S1 aqueous phase preparation

[0303] 1 mol acrylamide, 2.5 mol 2-acrylamido-2-methylpropanesulfonic acid, and 0.2 mol acrylmorpholine were added sequentially to a beaker, followed by 2130 g of deionized water. The mixture was heated to 50 °C and stirred at 400 rpm until completely dissolved. Then, 0.355 g of OP-10 was added and stirred for 20 min. The pH of the aqueous solution was adjusted to 7.0 with sodium hydroxide solution, and finally cooled to room temperature to obtain an aqueous solution.

[0304] S2 oil phase preparation

[0305] Add 56.8 g of D80 solvent oil and 0.3 mol of long-chain alkyl dimethylaminoethyl acrylate to a three-necked flask. Continuously add 0.071 g of isotridecyl polyoxyethylene ether while stirring at 500 rpm. After complete dissolution, an oil phase solution is obtained.

[0306] S3 emulsion polymerization

[0307] Nitrogen gas was introduced into a three-necked flask, and the stirring speed of the oil phase solution was adjusted to 1000 rpm at room temperature. The aqueous phase solution obtained in step S1 was slowly added to the three-necked flask. After the solution was completely added, stirring was continued to form a stable reverse emulsion. The temperature was then raised to 80°C, and 0.355 g of initiator was added. The initiator was a mixture of ammonium persulfate, sodium bisulfite, and azobisisobutyronitrile in a ratio of 1:2:1.2. The mixture was stirred at a constant temperature for 10 h. The temperature was then lowered to obtain a milky white emulsion, which is the emulsion polymer Q8.

[0308] Performance testing and characterization

[0309] Test Example 1: Infrared Test

[0310] The emulsion polymer Q1 prepared in Example 1 was subjected to infrared spectroscopy, and the test results are as follows: Figure 1 As shown. The test was conducted using a V33 infrared spectrometer (Bruker, Germany), from... Figure 1 As can be seen, 2923.47cm -1 It is at 3300cm -1 The wider peaks nearby should be OH and NH peaks; 1714.9 cm⁻¹ -1 It is the absorption peak of the C=O stretching vibration, 1608.6 cm⁻¹. -1 Characteristic peak of benzene ring C=C; 1300 cm⁻¹ -1 With 1400cm -1 The nearby peak is produced by the coupling of OH and CO; 1200 cm⁻¹ -1 and 1300cm -1 This is a characteristic peak for phenols; 1000 cm⁻¹ -1 ~1100cm -1 The interval is between the absorption peaks of the CN stretching vibration on the pyrrole ring, at 1608.6 cm⁻¹. -1 The peaks are characteristic of the C=C ring on the benzene ring. In summary, this indicates that the generated substance is the target emulsion polymer.

[0311] Test Example 2: Viscosity-average molecular weight and apparent viscosity test

[0312] The experiment selected the emulsion polymers Q1 to Q8 of the present invention and the Hanwha acrylic emulsion RW-116 product (with self-crosslinking characteristics) produced by Guangzhou Jingyi New Materials Co., Ltd. for comparison of molecular weight and apparent viscosity. The molecular weight was tested using the viscosity-average molecular weight test method.

[0313] The apparent viscosity test method is as follows: First, the test sample is diluted with saline solution with a mineralization of 20000 mg / L to a 0.5% solution, and the dissolution time is recorded. Then, the apparent viscosity of the prepared solution is tested using a Hacker rheometer at 50℃. The test results are shown in Table 1.

[0314] Table 1 Comparison of viscosity-average molecular weight and apparent viscosity of emulsion polymers and commercially available products

[0315] sample Viscosity-average molecular weight / 10,000 Apparent viscosity / mPa·s <![CDATA[Q1]]> 3650 108.5 <![CDATA[Q2]]> 3580 106.8 <![CDATA[Q3]]> 3700 123.6 <![CDATA[Q4]]> 3900 142.3 <![CDATA[Q5]]> 3560 118.4 <![CDATA[Q6]]> 3510 106.2 <![CDATA[Q7]]> 3800 126.8 <![CDATA[Q8]]> 3680 119.3 RW-116 22.3 113.6

[0316] As shown in Table 1, compared with the commercially available self-crosslinking polymer emulsion RW-116, the emulsion polymers Q1 to Q8 of the present invention have higher viscosity-average molecular weights, with a viscosity-average molecular weight greater than 35 million and reaching a maximum of 39 million (Q4). They also have higher apparent viscosity. At a high salinity of 20,000 mg / L, the apparent viscosity of the emulsion polymers Q1 to Q8 of the present invention at a concentration of 0.5% is all above 100 mPa·s, reaching a maximum of 142.3 mPa·s (Q4). They have a better thickening effect, can effectively suppress cross-flow problems, and meet the requirements of heavy oil viscosity reduction pressure drive technology.

[0317] Test Example 3: Viscosity Reduction and Dissolution Time Test

[0318] The experiment selected the emulsion polymers Q1 to Q8 of the present invention and the Hanwha acrylic emulsion RW-116 product (with self-crosslinking properties) produced by Guangzhou Jingyi New Materials Co., Ltd. to compare the solubility and viscosity reduction rate at different concentrations. The test methods for solubility and viscosity reduction rate were performed in accordance with Q / SH10201519-2016 "General Technical Conditions for Heavy Oil Viscosity Reducers".

[0319] The experimental oil was heavy oil from a deep, low-permeability reservoir in the Shengli Oilfield. The viscosity of the degassed crude oil at 50℃ was 26600 mPa·s, and the average permeability of the formation in this block was 56.8 × 10⁻⁶. -3 μm 2 The mineralization of the formation mineralized water was 10194 mg / L. The test results are shown in Table 2.

[0320] Table 2 Comparison of solubility and viscosity reduction rate of emulsion polymers and commercially available products

[0321]

[0322]

[0323] As can be seen from Table 2, the emulsion polymers Q1 to Q8 of the present invention have better solubility and a 1 / 3 reduction in dissolution time compared with the commercially available emulsion polymer RW-116, which fully meets the on-site liquid preparation requirements of the on-site pressure drive technology.

[0324] Furthermore, the emulsion polymers Q1 to Q8 of the present invention, when used at a concentration of 0.1%, achieve a viscosity reduction rate of over 95% for heavy oil, playing a very positive role in improving the flow properties of heavy oil in reservoirs. In contrast, commercially available products, due to their self-crosslinking function, only increase viscosity after crosslinking and do not emulsify or disperse heavy oil, thus making them unsuitable for heavy oil pressure-driven viscosity reduction extraction technology. Therefore, the emulsion polymers Q1 to Q8 of the present invention have a much wider range of applications.

[0325] The embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above embodiments, and various changes can be made within the scope of knowledge possessed by those skilled in the art without departing from the spirit of the present invention.

Claims

1. An emulsion polymer, characterized in that, The emulsion polymer contains structural unit A, structural unit B, structural unit C and structural unit D. Structural unit A has the structural unit shown in formula (1), structural unit B has the structural unit shown in formula (2), structural unit C has the structural unit shown in formula (3), and structural unit D has the structural unit shown in formula (4). Based on the weight of the emulsion polymer, structural unit A accounts for 5-15% by weight, structural unit B accounts for 2-40% by weight, structural unit C accounts for 10-70% by weight, and structural unit D accounts for 1-80% by weight. The viscosity-average molecular weight of the emulsion polymer is 30 million to 39 million. Wherein: R is an alkane group, preferably C6~C6. 18 alkane group.

2. The emulsion polymer as described in claim 1, characterized in that, R is C 12 ~C 16 Straight-chain alkane groups or cycloalkane groups.

3. The emulsion polymer as described in claim 1, characterized in that, Based on the weight of the emulsion polymer, structural unit A accounts for 6-10% by weight, structural unit B accounts for 5-35% by weight, structural unit C accounts for 15-65% by weight, structural unit D accounts for 10-70% by weight, and the viscosity-average molecular weight of the emulsion polymer is 31 million to 38 million.

4. A method for preparing the emulsion polymer according to claim 1, characterized in that, The steps are as follows: (1) Under stirring conditions, monomer E, monomer F, monomer G, solvent and water-based surfactant are mixed evenly to obtain an aqueous solution; (2) Under stirring conditions, monomer H, solvent oil and oil-based surfactant are mixed evenly to obtain an oil phase solution; (3) Under a nitrogen or inert gas atmosphere, the aqueous solution and the oil solution are mixed, then an initiator is added and a solution polymerization reaction is carried out under the action of the initiator. After the reaction is completed, an emulsion polymer is obtained. The monomer E is a monomer having the structure shown in formula (5), the monomer F is a monomer having the structure shown in formula (6), the monomer G is a monomer having the structure shown in formula (7), and the monomer H is a monomer having the structure shown in formula (8); based on the sum of the masses of the monomer E, the monomer F, the monomer G, and the monomer H, the amount of monomer E is 5-15% by weight, the amount of monomer F is 2-40% by weight, the amount of monomer G is 10-70% by weight, and the amount of monomer H is 1-80% by weight; the conditions of the solution polymerization reaction are such that the viscosity-average molecular weight of the polymer obtained by the polymerization reaction is 30 million to 39 million. Wherein: R is an alkane group, preferably C6~C6. 18 alkane group.

5. The method for preparing an emulsion polymer as described in claim 4, characterized in that, The solvent used in step (1) is one or more of deionized water, ethanol, ethyl acetate, and toluene, and its amount is at least 10 times, preferably 10 to 30 times, the amount of monomer E.

6. The method for preparing an emulsion polymer as described in claim 4, characterized in that, The water-based surfactant mentioned in step (1) is one or more of Tween60, Tween80, Span40, Span60, OP-10, OP-13, OP-15, OP-20, OP-30, OP-40, and OP-50, and its amount is at least 0.1 wt% of the amount of monomer E, preferably 0.1 to 0.5 wt%.

7. The method for preparing an emulsion polymer as described in claim 4, characterized in that, In step (1), heating is performed simultaneously with stirring, and the heating temperature is controlled at at least 25°C, preferably 25–50°C, and / or The stirring conditions in step (1) are as follows: the stirring speed is at least 200 rpm, preferably 200 to 400 rpm.

8. The method for preparing an emulsion polymer as described in claim 4, characterized in that, The solvent oil mentioned in step (2) is a dearomatic solvent oil with a flash point higher than 60°C, preferably one of D40 solvent oil, D60 solvent oil, or D80 solvent oil, and its amount is at least 40 wt% of the amount of monomer E, preferably 40 to 80 wt%.

9. The method for preparing an emulsion polymer as described in claim 4, characterized in that, The oil-based surfactant mentioned in step (2) is one or more of castor oil polyoxyethylene ether, isotretinoin polyoxyethylene ether, alkylphenol polyoxyethylene ether, and lauryl alcohol polyoxyethylene ether, and its amount is at least 0.05 wt% of the amount of monomer E, preferably 0.05 to 0.1 wt%.

10. The method for preparing an emulsion polymer as described in claim 4, characterized in that, In step (2), the stirring bar is as follows: the stirring speed is at least 200 rpm, preferably 200 to 500 rpm.

11. The method for preparing an emulsion polymer as described in claim 4, characterized in that, Step (3) Continuously purge with nitrogen or inert gas throughout the process, and / or Step (3) involves continuous stirring at a speed of at least 400 rpm, preferably 400 to 1000 rpm.

12. The method for preparing an emulsion polymer as described in claim 4, characterized in that, The initiator mentioned in step (3) is a mixture of substance A, substance B, and substance C, with a mixing ratio of 1:(1~2):(0.5~1.2), wherein: The total amount of the initiator is at least 0.01 wt% of the amount of monomer E, preferably 0.01 to 0.5%; Substance A is one or more of ammonium persulfate, sodium persulfate, and potassium persulfate; Substance B is one or more of sodium bisulfite, potassium bisulfite, and ammonium bisulfite; The substance C is one or more of azobisisobutyronitrile and azobisisoheptanenitrile.

13. The method for preparing an emulsion polymer as described in claim 4, characterized in that, The reaction temperature of the solution polymerization reaction in step (3) is at least 50°C, preferably 50–80°C, and / or The reaction time for the solution polymerization reaction in step (3) is at least 5 hours, preferably 5-10 hours.

14. An emulsion polymer, characterized in that, It is prepared by the preparation method according to any one of claims 4-13.

15. The application of the emulsion polymer of claim 1 or 14 as a viscosity reducer in pressure displacement production of low-permeability heavy oil reservoirs.

Images