Controllable phase inversion polymer as well as preparation method and application thereof

Abstract

The invention discloses a controllable phase inversion polymer which is composed of a structural unit A and a structural unit B. The structural unit A is provided by an acrylamide monomer. The structural unit B is provided by a temperature-resistant and salt-resistant monomer; on the basis of the weight of the controllable phase inversion polymer, the content of the structural unit A is 80-99 wt%, the balance is the structural unit B, and the viscosity average molecular weight of the controllable phase inversion polymer is 25,000,000-35,000,000. The invention discloses a preparation method of a controllable phase inversion polymer. According to the invention, water-soluble polymers are temporarily bound together through a controllable weak cross-linking technical means, so that the gel dispersion phase / solution continuous phase conversion is controllable, and the purposes of double effects of one agent and high-efficiency oil displacement are achieved. The dispersed-phase gel particles protect polymer macromolecules, are high in degradation resistance, and play a role in deformed particle profile control and displacement in a near wellbore area; the weak cross-linking effect is gradually hydrolyzed under the change of formation conditions to release the tackifying polymer, slow release and tackifying are realized in the deep part of an oil reservoir, and the crude oil recovery rate is improved.

Description

Technical Field

[0001] The invention relates to the technical field of oilfield exploitation, and in particular to a controllable phase transition polymer and a preparation method and application thereof. Background Art

[0002] As the oil field enters the high water content / extra-high water content development stage, the water drive development effect becomes worse. Due to long-term water injection and flushing, the remaining oil in the oil field shows the characteristics of "high dispersion and local enrichment", the oil saturation near the wellbore is low, and the water drive spread problem extends from the near-wellbore area in the early and middle stages of development to the deep far wellbore and even to the entire injection and production flow field. Realizing the efficient potential of the remaining oil and significantly improving the recovery rate is a major problem that needs to be solved urgently for the sustainable development of high-water-content old oil fields at home and abroad.

[0003] Polymer flooding technology is one of the chemical flooding technologies that can significantly increase the recovery rate of old oil fields. It has been promoted and applied in high-water-content oil fields in China, such as Daqing Oilfield and Shengli Oilfield, and has achieved good oil recovery effects, making important contributions to the sustained and stable production of China's old oil fields.

[0004] The viscosity of polymer solution is the key to improving the water-oil mobility ratio, expanding the volume of injected fluid, and significantly increasing the oil recovery rate, and it is the key to ensuring the economic benefits of polymer flooding. As the polymer flooding successor position gradually shifts to harsh oil reservoirs with higher temperatures and higher mineralization, polymer flooding technology faces two major technical challenges: (1) Partially hydrolyzed polyacrylamide (HPAM) is used as a chemical flooding technology. Under the conditions of high temperature and high mineralization in the formation, the viscosity of HPAM solution will drop significantly due to hydrolysis, degradation, precipitation and other losses. Simply increasing the concentration and dosage on site to ensure the injection viscosity will cause polymer waste and affect the economic benefits of polymer flooding development; (2) Conventional polymer solutions are prepared on the ground, transported through pipelines, and then injected into the formation through wellbore blastholes. Under various shear effects, the viscosity will be greatly reduced, which will have an adverse effect on the viscosity increase and mobility control in the deep reservoir. Therefore, how to significantly reduce the viscosity loss during the polymer injection process, achieve in-situ viscosity increase inside the reservoir, improve the deep viscosity increase performance and fluidity control ability of the polymer reservoir, and achieve the goal of significantly expanding the water drive swept volume is a key technical problem that needs to be urgently solved in polymer oil recovery.

[0005] In order to improve polymer viscosity, reduce polymer dosage, and expand the application scope of polymer flooding, domestic and foreign scholars have improved polymer viscosity enhancement and oil displacement performance through the research and development of heat-resistant and salt-resistant polymers and the injection process of polymer viscosity loss control. The main way to improve the heat-resistant and salt-resistant performance of polymers is to increase the relative molecular weight of polymers and introduce functional monomers with special structural functional groups on the molecular chain. Simply increasing the relative molecular weight of polymers can improve the viscosity enhancement performance of polymers, but polymers with higher molecular weights are more susceptible to shear mechanical degradation, causing viscosity loss and injection difficulties in lower permeability layers. Introducing functional monomers with special structural functional groups to improve heat-resistant and salt-resistant performance Measures to improve viscosity: First, introduce groups such as sulfonic acid with strong hydration ability to enhance the solubility of polymers, while avoiding the precipitation and separation of polymers caused by high calcium and magnesium ions, such as 2-acrylamide-2-methylpropanesulfonic acid (AMPS) as a commonly used heat-resistant and salt-resistant monomer; second, introduce ring structures to increase the steric hindrance, rigidity and hydrodynamic volume of polymer chains to avoid the curling and entanglement of molecular chains. Monomers with cyclic structures, such as N-vinyl pyrrolidone (NVP) and sodium p-styrene sulfonate, can improve the anti-curling performance of polymer molecular chains, make the molecular chains more stretched, reduce the probability of molecular chains entangled into clusters, and facilitate passing through reservoir pore throats; third, the introduction of hydrophobic groups such as long-chain alkyl groups can increase the steric hindrance of the molecular chains while producing intermolecular association effects, greatly increasing the viscosity; fourth, the introduction of zwitterions will show an "anti-polyelectrolyte effect" within a certain range as the salt concentration increases; fifth, the introduction of hydrophobic thermosensitive monomers with lower critical solution temperature (LCST) characteristics on the polymer molecular chain to form thermosensitive polymers by block or grafting. Common thermosensitive monomers include poly(ethylene oxide)-poly(propylene oxide) (PEO-PPO), poly(N-isopropylacrylamide) (PNI-PAM) and macromonomer copolymers based on acrylamide diacetone (MPAD).

[0006] The above-mentioned research and development ideas for temperature-resistant and salt-resistant polymers all adopt technical methods to greatly increase the initial viscosity of polymers, but they still cannot overcome the technical difficulties of polymer viscosity loss during the injection process and weak viscosity enhancement ability in deep reservoirs. Therefore, in order to slightly increase the initial viscosity, delay viscosity enhancement after entering the deep formation, compensate for factors such as dilution and degradation, and greatly increase the viscosity retention rate of the polymer solution, Wang Tao (2020) et al. designed a delayed viscosity-enhancing polyacrylamide molecular structure with slow-release cationic groups. When the polymer solution is under high temperature conditions, the potential cationic groups expose cations through hydrolysis and other reactions, and interact with the anions on the polymer chain through electrostatic supramolecular interactions to form multi-molecular associations, increase the hydrodynamic volume of the polymer, and greatly increase the apparent viscosity of the polymer solution. New paths have been explored to reduce the concentration of polymers and develop new high-viscosity and high-stability polymers. Xie Kemin (2020) et al. synthesized nano-microsphere delayed viscosity-increasing polymers with a core-shell structure to meet the oil recovery needs of high-temperature, high-salt, and low-permeability reservoirs. At room temperature, the polymer gel is wrapped in an oily shell. After being injected into the formation, as the temperature and pH value continue to increase, the outer shell gradually disintegrates and releases the effective substances inside, thereby achieving a delayed viscosity-increasing effect.

[0007] In short, the research and development of different types of temperature-resistant and salt-resistant polymers can improve the viscosity-increasing performance under reservoir conditions, and delayed / time-delayed viscosity-increasing polymers can also improve the viscosity retention rate during use to a certain extent, improve water-oil fluidity and expand the water drive swept volume, and broaden the application range of polymer drive reservoirs. However, as the oil field enters the high water content development stage, due to long-term water injection scouring, the dominant seepage channels develop, and the contradictions between layers, within layers and planes intensify, which can easily cause the seepage channels of the displacement solution to advance and cause crossflow. Therefore, a simple continuous phase viscosity-increasing solution is difficult to overcome the "liquid absorption profile reversal" phenomenon caused by reservoir heterogeneity and polymer retention, which is not conducive to improving the degree of crude oil utilization in relatively low and medium permeability layers, and the ability to expand the swept volume is limited, and it cannot meet the needs of significantly improving crude oil recovery. Summary of the invention

[0008] Purpose of the invention: In view of the fact that a simple continuous phase thickening solution is difficult to overcome the phenomenon of "liquid absorption profile reversal" caused by reservoir heterogeneity and polymer retention, the first purpose of the present invention is to disclose a controllable phase inversion polymer. The second purpose of the present invention is to disclose a method for preparing a controllable phase inversion polymer. The third purpose of the present invention is to disclose an application of a controllable phase inversion polymer.

[0009] The basic idea of ​​the present invention is: using controllable weak cross-linking technology to temporarily "bundle" water-soluble polymers together. The initial stage is a gel particle dispersion. After being injected into the formation, it is gradually hydrolyzed to release the viscosity-enhancing polymer under reservoir conditions, and the gradient viscosity-enhancing is slowly released in the deep reservoir. By controlling the degree of unsaturated grafting modification of the viscosity-enhancing polymer amide group, the phase transformation of the dispersed phase gel particles and the continuous phase viscosity polymer viscosity-enhancing solution can be controlled, so as to achieve the purpose of gel adjustment of the plugging flow line in the near-well section, viscosity-enhancing and expansion of the solution in the far-well section and efficient oil displacement.

[0010] Technical solution: A controllable phase inversion polymer, which is composed of a structural unit A and a structural unit B, wherein:

[0011] The structural unit A is provided by an acrylamide monomer represented by formula (1);

[0012]

[0013] Structural unit B is provided by temperature-resistant and salt-resistant monomers;

[0014] Based on the weight of the controllable phase inversion polymer, the content of structural unit A is 80-99% by weight, and the content of structural unit B is 1-20% by weight;

[0015] The viscosity average molecular weight of the controllable phase transition polymer is 25 million to 35 million.

[0016] Furthermore, based on the weight of the controllable phase inversion polymer, the content of structural unit A is 80 to 95% by weight, and the content of structural unit B is 5 to 20% by weight;

[0017] The viscosity average molecular weight of the controllable phase transition polymer is 30 million to 35 million.

[0018] Furthermore, the temperature-resistant and salt-resistant monomer is at least one of the 2-acrylamide-2-methylpropanesulfonic acid monomer shown in formula (2), the sodium styrene sulfonate monomer shown in formula (3), and the N-vinyl-2-pyrrolidone monomer shown in formula (4);

[0019]

[0020] A method for preparing a controllable phase inversion polymer, comprising the following steps:

[0021] (1) Preparation of viscosity-enhancing heat-resistant and salt-resistant polymer particles

[0022] (11) dissolving acrylamide monomer and temperature-resistant and salt-resistant monomer in an appropriate amount of water, and passing an inert gas or nitrogen into the water for at least 20 minutes to obtain a mixed solution;

[0023] (12) rapidly adding a free radical initiator to the mixed solution obtained in step (11) under low temperature conditions, continuing to pass an inert gas or nitrogen for at least 5 minutes, sealing the mixture, and reacting for at least 2 hours to obtain a viscosity-enhanced heat-resistant and salt-resistant polymer block;

[0024] (13), taking out and crushing the viscosity-enhancing heat-resistant and salt-resistant polymer block obtained in step (12) to obtain viscosity-enhancing heat-resistant and salt-resistant polymer particles;

[0025] (2) Preparation of controllable phase inversion polymers

[0026] (21), placing the viscosity-enhancing heat-resistant and salt-resistant polymer particles obtained in step (1) in a reactor, adding a strong organic base catalyst and an unsaturated halogenated hydrocarbon compound in sequence, stirring evenly, and then reacting at 30 to 50° C. for at least 1 hour to obtain amide-unsaturated graft-modified viscosity-enhancing polymer particles;

[0027] (22) Spraying an azo initiator system onto the surface of the amide-unsaturated grafted viscosity-enhancing polymer particles, reacting at 50-75° C. for at least 2 hours, then adding a hydrolysis agent thereto, and hydrolyzing for at least 90 minutes to obtain a controllable phase inversion polymer.

[0028] Furthermore, the temperature-resistant and salt-resistant monomer in step (11) is one or more of 2-acrylamido-2-methylpropanesulfonic acid, sodium styrene sulfonate, and N-vinyl-2-pyrrolidone.

[0029] Furthermore, in step (11), based on the total weight of the acrylamide monomer and the heat-resistant and salt-resistant monomer, the content of the acrylamide monomer is 80wt% to 99wt%, and the content of the heat-resistant and salt-resistant monomer is 1wt% to 20wt%.

[0030] Furthermore, in step (11), based on the total weight of the acrylamide monomer and the heat-resistant and salt-resistant monomer, the content of the acrylamide monomer is 80wt% to 85wt%, and the content of the heat-resistant and salt-resistant monomer is 5wt% to 20wt%.

[0031] Furthermore, based on the total weight of the acrylamide monomer and the temperature-resistant and salt-resistant monomer, the amount of water used in step (11) is 250 wt% to 400 wt%.

[0032] Furthermore, the inert gas in step (11) and step (12) is one of helium, neon and argon.

[0033] Furthermore, the low temperature condition in step (12) is 3°C to 9°C.

[0034] Furthermore, the free radical initiator in step (12) is one or more of an organic peroxide initiator, an azo initiator, and a redox initiator.

[0035] Furthermore, the organic peroxide initiator is one or more of benzoyl peroxide, lauroyl peroxide, cumene hydroperoxide, and tert-butyl hydroperoxide.

[0036] Furthermore, the azo initiator is one or more of azobisisobutyronitrile, azobisisoheptanenitrile, and azobisisobutylimidazoline hydrochloride.

[0037] Furthermore, the redox initiator is one or more of ammonium persulfate / sodium bisulfite, potassium persulfate / sodium bisulfite, hydrogen peroxide / tartaric acid, hydrogen peroxide / bleaching powder, ammonium persulfate / ferrous sulfate, hydrogen peroxide / ferrous sulfate, benzoyl peroxide / N,N-diethylaniline.

[0038] Furthermore, based on the total weight of the acrylamide monomer and the temperature-resistant and salt-resistant monomer in step (11), the amount of the free radical initiator used in step (12) is 0.001% to 0.5%.

[0039] Furthermore, the strong organic base catalyst described in step (21) is one or more of tert-butyl lithium, potassium tert-butoxide, sodium tert-butoxide, sodium amide, and tetrabutylammonium hydroxide.

[0040] Furthermore, based on the total weight of the acrylamide monomer and the temperature-resistant and salt-resistant monomer in step (11), the amount of the strong organic base catalyst used in step (21) is 0.1% to 5%.

[0041] Furthermore, the unsaturated halogenated hydrocarbon compound in step (21) is one or more of allyl chloride and allyl bromide.

[0042] Furthermore, based on the total weight of the acrylamide monomer and the temperature-resistant and salt-resistant monomer in step (11), the amount of the unsaturated halogenated hydrocarbon compound in step (21) is 0.1-5%.

[0043] Furthermore, the azo initiator system in step (22) is an aqueous solution of azobisisobutylimidazoline hydrochloride, wherein:

[0044] The mass ratio of azobisisobutylimidazoline hydrochloride to water is 1:(1-10).

[0045] Furthermore, the azo initiator system in step (22) is a mixture of azobisisobutyronitrile or azobisisoheptanenitrile, a nonionic surfactant and water, wherein:

[0046] The mass ratio of azobisisobutyronitrile or azobisisoheptanenitrile: water is 1:(1-10);

[0047] The mass ratio of the nonionic surfactant to water is (0.002-0.01):1, preferably 0.003:1.

[0048] Furthermore, the nonionic surfactant is one of a polyoxyethylene nonionic surfactant, a polyol nonionic surfactant, an alkanolamide nonionic surfactant, and a polyether nonionic surfactant.

[0049] Furthermore, the post-hydrolysis reagent in step (22) is one or more of sodium hydroxide, potassium hydroxide, and calcium hydroxide.

[0050] Furthermore, based on the total weight of the acrylamide monomer and the temperature-resistant and salt-resistant monomer in step (11), the amount of the hydrolysis agent used in step (22) is 0.5-10%.

[0051] Application of any of the above controllable phase inversion polymers as a polymer oil displacement agent.

[0052] Application of the controllable phase inversion polymer prepared by any of the above controllable phase inversion polymer preparation methods as a polymer oil displacement agent.

[0053] Beneficial effects: The controllable phase inversion polymer disclosed in the present invention and its preparation method and application have the following beneficial effects:

[0054] 1. Conventional polymers are completely dissolved and then injected into the formation, which makes them susceptible to mechanical shearing by valves, pipelines and blastholes during the injection process. After entering the formation, the viscosity is retained at a low level, and the ability to adjust the profile is reduced. During the migration of the formation, the polymer molecules are further sheared, and the oil recovery effect is reduced. However, when the controlled phase transition polymer is injected into the formation, it is mainly in the gel particle phase, with strong shear resistance, and has a good ability to adjust the profile of the near-well high permeability layer. As the particles migrate, they gradually transform into the solution phase to achieve oil recovery from far wells, greatly improving the utilization rate and oil recovery efficiency of the polymer.

[0055] 2. The initial state of the controllable phase transition polymer is a gel phase, which can reduce the chemical degradation of the polymer by divalent ions such as sulfur and iron in the injection water. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Figure 1 The flowchart of the method for preparing a controllable phase inversion polymer disclosed in the present invention is shown. Specific implementation method:

[0057] The specific embodiments of the present invention are described in detail below.

[0058] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0059] In this application document, the viscosity is measured by the rotation method in the viscosity measurement method of GB-T 10247-2008.

[0060] Example 1

[0061] A method for preparing a controllable phase inversion polymer, comprising the following steps:

[0062] (1) Preparation of viscosity-enhancing heat-resistant and salt-resistant polymer particles

[0063] (11) acrylamide monomer and 2-acrylamide-2-methylpropanesulfonic acid (monomer) in a mass ratio of 90:10 were dissolved in water (accounting for 250% of the total mass of the polymerized monomers), and nitrogen (purity 99.999%) was introduced for 30 minutes to remove the oxygen dissolved in the water to obtain a mixed solution;

[0064] (12) At 8°C, quickly add initiator benzoyl peroxide and benzoyl peroxide / N,N-diethylaniline (the mass ratio of the three is 2:1:1, and the total accounts for 0.001% of the total mass of the polymerized monomers) into the mixed solution, continue to pass nitrogen (purity 99.999%) for 5 minutes, and seal the mixture;

[0065] (13) After 3 hours of reaction, the rubber block is taken out and crushed using a crusher to obtain viscosity-enhancing heat-resistant and salt-resistant polymer particles;

[0066] (2) Preparation of controllable phase inversion polymers

[0067] (21) placing the viscosity-enhancing heat-resistant and salt-resistant polymer particles in a reactor, adding tert-butyl lithium (accounting for 0.1% of the total mass of the polymerized monomers), stirring thoroughly, adding allyl chloride (accounting for 0.2% of the total mass of the polymerized monomers), stirring thoroughly, and reacting at 45° C. for 1.5 hours to obtain viscosity-enhancing polymer particles modified by amide unsaturated grafting;

[0068] (22) Spray azobisisobutyronitrile (accounting for 0.001% of the total mass of the polymer monomer) dispersion onto the surface of the amide-unsaturated grafted viscosity-enhancing polymer particles, react at 65°C for 3 hours, and finally add sodium hydroxide (accounting for 2% of the total mass of the polymer monomer) and hydrolyze for 90 minutes, and dry at 80°C for 1 hour to obtain a controllable phase inversion polymer powder.

[0069] Furthermore, the azobisisobutyronitrile dispersion is composed of azobisisobutyronitrile, water, and a polyoxyethylene nonionic surfactant, wherein:

[0070] The mass ratio of azobisisobutyronitrile, water and polyoxyethylene nonionic surfactant is 1:1:0.003.

[0071] The synthetic route of step (2) is as follows:

[0072]

[0073]

[0074] The controllable phase inversion polymer prepared by the preparation method of the controllable phase inversion polymer is used as a polymer oil displacement agent.

[0075] Example 2

[0076] A method for preparing a controllable phase inversion polymer, comprising the following steps:

[0077] (1) Preparation of viscosity-enhancing heat-resistant and salt-resistant polymer particles

[0078] (11) dissolving acrylamide monomer and sodium styrene sulfonate (mass ratio 95:5) in water (accounting for 400% of the total mass of the polymerized monomers), introducing argon gas (purity 99.999%) for 30 minutes to remove the oxygen dissolved in the water to obtain a mixed solution;

[0079] (12) At 3°C, quickly add initiators ammonium persulfate / sodium bisulfite and azobisisobutyronitrile (the mass ratio of the three is 1:1:1, and the total mass accounts for 0.001% of the total mass of the polymerized monomers), continue to pass argon (purity 99.999%) for 5 minutes, and seal the container.

[0080] (13) After 3 hours of reaction, the rubber block is taken out and crushed using a crusher to obtain viscosity-enhancing heat-resistant and salt-resistant polymer particles;

[0081] (2) Preparation of controllable phase inversion polymers

[0082] (21) placing a viscosity-enhancing heat-resistant and salt-resistant polymer granules in a reactor, adding tert-butyl lithium (accounting for 0.5% of the total mass of the polymerized monomers), stirring thoroughly, adding allyl bromide (accounting for 1.0% of the total mass of the polymerized monomers), stirring thoroughly, and reacting at 50° C. for 2 hours to obtain a viscosity-enhancing polymer granules modified by an amide unsaturated grafting;

[0083] (22) Spray azobisisoheptanenitrile (accounting for 0.002% of the total mass of the polymer monomers) dispersion onto the surface of the amide-unsaturated grafted viscosity-enhancing polymer particles, react at 70°C for 3 hours, and finally add sodium hydroxide (accounting for 2% of the total mass of the polymer monomers) and hydrolyze for 120 minutes, and dry at 80°C for 1 hour to obtain granulated controllable phase inversion polymer dry powder.

[0084] Furthermore, the azobisisoheptanitrile dispersion in step (22) is a mixture of azobisisoheptanitrile dispersion, a polyether nonionic surfactant and water, wherein:

[0085] The mass ratio of azobisisoheptanenitrile dispersion: water is 1:10;

[0086] Polyether nonionic surfactant: water is 0.002:1.

[0087] The controllable phase inversion polymer prepared by the preparation method of the controllable phase inversion polymer is used as a polymer oil displacement agent.

[0088] Example 3

[0089] A method for preparing a controllable phase inversion polymer, comprising the following steps:

[0090] (1) Preparation of viscosity-enhancing heat-resistant and salt-resistant polymer particles

[0091] (11) dissolving acrylamide monomer and N-vinyl-2-pyrrolidone (mass ratio 95:5) in water (300% of the total mass of the polymerizable monomers), introducing nitrogen (purity 99.999%) for 30 minutes to remove oxygen dissolved in water to obtain a mixed solution;

[0092] (12) At 9°C, quickly add initiators benzoyl peroxide and azobisisobutyronitrile (the mass ratio of the two is 2:1, and the total mass accounts for 0.001% of the total mass of the polymerized monomers), continue to pass argon gas (purity 99.999%) for 5 minutes, and seal the tube;

[0093] (13) After reacting for 3 hours, the rubber block is taken out and crushed using a crusher to obtain viscosity-enhancing heat-resistant and salt-resistant polymer particles;

[0094] (2) Preparation of controllable phase inversion polymers

[0095] (21) placing a viscosity-enhancing heat-resistant and salt-resistant polymer granules in a reactor, adding sodium tert-butoxide (accounting for 1.0% of the total mass of the polymerized monomers), stirring thoroughly, adding allyl bromide (accounting for 2.0% of the total mass of the polymerized monomers), stirring thoroughly, and reacting at 50° C. for 2 hours to obtain a viscosity-enhancing polymer granules modified by an amide unsaturated grafting;

[0096] (22) Spray azobisisoheptanenitrile (accounting for 0.002% of the total mass of the polymer monomers) dispersion onto the surface of the amide-unsaturated grafted viscosity-enhancing polymer particles, react at 75°C for 3 hours, and finally add potassium hydroxide (accounting for 5% of the total mass of the polymer monomers) and hydrolyze for 100 minutes, and dry at 80°C for 1 hour to obtain granulated controllable phase inversion polymer dry powder.

[0097] Furthermore, the azobisisoheptanitrile dispersion in step (22) is a mixture of azobisisoheptanitrile dispersion, a polyether nonionic surfactant and water, wherein:

[0098] The mass ratio of azobisisoheptanenitrile dispersion: water is 1:10;

[0099] Polyether nonionic surfactant: water is 0.002:1.

[0100] The controllable phase inversion polymer prepared by the preparation method of the controllable phase inversion polymer is used as a polymer oil displacement agent.

[0101] Example 4

[0102] A controllable phase inversion polymer, the controllable phase inversion polymer is composed of a structural unit A and a structural unit B, wherein:

[0103] The structural unit A is provided by an acrylamide monomer represented by formula (1);

[0104]

[0105] Structural unit B is provided by temperature-resistant and salt-resistant monomers;

[0106] Based on the weight of the controllable phase inversion polymer, the content of structural unit A is 80% by weight, and the content of structural unit B is 20% by weight;

[0107] And the viscosity average molecular weight of the controllable phase transition polymer is 25.1 million.

[0108] Furthermore, the temperature-resistant and salt-resistant monomer is a 2-acrylamide-2-methylpropanesulfonic acid monomer represented by formula (2);

[0109]

[0110] Application of the above controllable phase transition polymer as a polymer oil displacement agent.

[0111] Example 5

[0112] A controllable phase inversion polymer, the controllable phase inversion polymer is composed of a structural unit A and a structural unit B, wherein:

[0113] The structural unit A is provided by an acrylamide monomer represented by formula (1);

[0114]

[0115] Structural unit B is provided by temperature-resistant and salt-resistant monomers;

[0116] Based on the weight of the controllable phase inversion polymer, the content of structural unit A is 99% by weight, and the content of structural unit B is 20% by weight;

[0117] And the viscosity average molecular weight of the controllable phase transition polymer is 34.89 million.

[0118] Furthermore, the temperature-resistant and salt-resistant monomer is a sodium styrene sulfonate monomer represented by formula (3);

[0119]

[0120] Application of any of the above controllable phase inversion polymers as a polymer oil displacement agent.

[0121] Example 6

[0122] A controllable phase inversion polymer, the controllable phase inversion polymer is composed of a structural unit A and a structural unit B, wherein:

[0123] The structural unit A is provided by an acrylamide monomer represented by formula (1);

[0124]

[0125] Structural unit B is provided by temperature-resistant and salt-resistant monomers;

[0126] Based on the weight of the controllable phase inversion polymer, the content of structural unit A is 95% by weight, and the content of structural unit B is 5% by weight;

[0127] And the viscosity average molecular weight of the controllable phase transition polymer is 29.98 million.

[0128] Furthermore, the temperature-resistant and salt-resistant monomer is composed of equal weights of 2-acrylamido-2-methylpropanesulfonic acid monomer represented by formula (2), sodium styrene sulfonate monomer represented by formula (3), and N-vinyl-2-pyrrolidone monomer represented by formula (4);

[0129]

[0130]

[0131] Application of the above controllable phase transition polymer as a polymer oil displacement agent.

[0132] Example 7

[0133] A controllable phase inversion polymer, the controllable phase inversion polymer is composed of a structural unit A and a structural unit B, wherein:

[0134] The structural unit A is provided by an acrylamide monomer represented by formula (1);

[0135]

[0136] Structural unit B is provided by temperature-resistant and salt-resistant monomers;

[0137] Based on the weight of the controllable phase inversion polymer, the content of structural unit A is 85% by weight, and the content of structural unit B is 15% by weight;

[0138] The viscosity average molecular weight of the controllable phase transition polymer is 32 million.

[0139] Furthermore, the temperature-resistant and salt-resistant monomer is a mixture of equal masses of a 2-acrylamide-2-methylpropanesulfonic acid monomer represented by formula (2) and a sodium styrene sulfonate monomer represented by formula (3);

[0140]

[0141] Application of the above controllable phase transition polymer as a polymer oil displacement agent.

[0142] Example 8

[0143] A method for preparing a controllable phase inversion polymer, comprising the following steps:

[0144] (1) Preparation of viscosity-enhancing heat-resistant and salt-resistant polymer particles

[0145] (11) dissolving acrylamide monomer and temperature-resistant and salt-resistant monomer in an appropriate amount of water, and passing an inert gas into the water for 20 minutes to obtain a mixed solution;

[0146] (12) rapidly adding a free radical initiator to the mixed solution obtained in step (11) under low temperature conditions, continuing to pass an inert gas for 5 minutes, sealing the mixture, and reacting for 2 hours to obtain a viscosity-enhanced heat-resistant and salt-resistant polymer block;

[0147] (13), taking out and crushing the viscosity-enhancing heat-resistant and salt-resistant polymer block obtained in step (12) to obtain viscosity-enhancing heat-resistant and salt-resistant polymer particles;

[0148] (2) Preparation of controllable phase inversion polymers

[0149] (21), placing the viscosity-enhancing heat-resistant and salt-resistant polymer particles obtained in step (1) in a reactor, adding a strong organic base catalyst and an unsaturated halogenated hydrocarbon compound in sequence, stirring evenly, and then reacting at 30° C. for 5 hours to obtain amide-unsaturated graft-modified viscosity-enhancing polymer particles;

[0150] (22) Spraying an azo initiator system onto the surface of the amide-unsaturated grafted viscosity-enhancing polymer particles, reacting at 50° C. for 5 hours, and then adding a hydrolysis agent thereto. After hydrolysis for 90 minutes, a controllable phase inversion polymer is obtained.

[0151] Furthermore, the temperature-resistant and salt-resistant monomer in step (11) is 2-acrylamide-2-methylpropanesulfonic acid.

[0152] Furthermore, in step (11), based on the total weight of the acrylamide monomer and the heat-resistant and salt-resistant monomer, the content of the acrylamide monomer is 80 wt %, and the content of the heat-resistant and salt-resistant monomer is 20 wt %.

[0153] In another embodiment, in step (11), based on the total weight of the acrylamide monomer and the heat-resistant and salt-resistant monomer, the content of the acrylamide monomer is 85 wt %, and the content of the heat-resistant and salt-resistant monomer is 15 wt %.

[0154] Furthermore, based on the total weight of the acrylamide monomer and the temperature-resistant and salt-resistant monomer, the amount of water used in step (11) is 250 wt%.

[0155] Furthermore, the inert gas in step (11) and step (12) is neon.

[0156] Furthermore, the low temperature condition in step (12) is 3°C.

[0157] Furthermore, the free radical initiator in step (12) is a mixture of equal masses of an organic peroxide initiator, an azo initiator, and a redox initiator.

[0158] Furthermore, the organic peroxide initiator is a mixture of equal masses of benzoyl peroxide, lauroyl peroxide, cumene hydroperoxide and tert-butyl hydroperoxide.

[0159] Furthermore, the azo initiator is a mixture of equal masses of azobisisobutyronitrile, azobisisoheptanenitrile and azobisisobutylimidazoline hydrochloride.

[0160] Furthermore, the redox initiator is a mixture of equal masses of ammonium persulfate / sodium bisulfite, potassium persulfate / sodium bisulfite, hydrogen peroxide / tartaric acid, hydrogen peroxide / bleaching powder, ammonium persulfate / ferrous sulfate, hydrogen peroxide / ferrous sulfate, and benzoyl peroxide / N,N-diethylaniline.

[0161] Furthermore, based on the total weight of the acrylamide monomer and the temperature-resistant and salt-resistant monomer in step (11), the amount of the free radical initiator used in step (12) is 0.2%.

[0162] Furthermore, the strong organic base catalyst in step (21) is tert-butyl lithium.

[0163] Furthermore, based on the total weight of the acrylamide monomer and the temperature-resistant and salt-resistant monomer in step (11), the amount of the strong organic base catalyst used in step (21) is 0.1%.

[0164] Furthermore, the unsaturated halogenated hydrocarbon compound in step (21) is allyl chloride.

[0165] Furthermore, based on the total weight of the acrylamide monomer and the temperature-resistant and salt-resistant monomer in step (11), the amount of the unsaturated halogenated hydrocarbon compound in step (21) is 0.1.

[0166] Furthermore, the azo initiator system in step (22) is an aqueous solution of azobisisobutylimidazoline hydrochloride, wherein:

[0167] The mass ratio of azobisisobutylimidazoline hydrochloride to water is 1:1.

[0168] In another embodiment, the azo initiator system in step (22) is a mixture of azobisisobutyronitrile, a nonionic surfactant and water, wherein:

[0169] The mass ratio of azobisisobutyronitrile: water is 1:1;

[0170] The mass ratio of nonionic surfactant to water is 0.002:1.

[0171] Furthermore, the nonionic surfactant is a polyoxyethylene nonionic surfactant.

[0172] In another embodiment, the azo initiator system in step (22) is a mixture of azobisisoheptanonitrile, a nonionic surfactant and water, wherein:

[0173] The mass ratio of azobisisoheptanonitrile: water is 1:1;

[0174] The mass ratio of nonionic surfactant to water is 0.002:1.

[0175] Furthermore, the nonionic surfactant is a polyoxyethylene nonionic surfactant.

[0176] Furthermore, the post-hydrolysis reagent in step (22) is sodium hydroxide.

[0177] Furthermore, based on the total weight of the acrylamide monomer and the temperature-resistant and salt-resistant monomer in step (11), the amount of the hydrolysis agent used in step (22) is 0.5-10%.

[0178] Application of the controllable phase inversion polymer prepared by any of the above controllable phase inversion polymer preparation methods as a polymer oil displacement agent.

[0179] Example 9

[0180] A method for preparing a controllable phase inversion polymer, comprising the following steps:

[0181] (1) Preparation of viscosity-enhancing heat-resistant and salt-resistant polymer particles

[0182] (11) dissolving acrylamide monomer and temperature-resistant and salt-resistant monomer in an appropriate amount of water, and passing an inert gas into the water for 60 minutes to obtain a mixed solution;

[0183] (12) rapidly adding a free radical initiator to the mixed solution obtained in step (11) under low temperature conditions, continuing to pass an inert gas for 20 minutes, sealing the mixture, and reacting for 5 hours to obtain a viscosity-enhancing heat-resistant and salt-resistant polymer block;

[0184] (13), taking out and crushing the viscosity-enhancing heat-resistant and salt-resistant polymer block obtained in step (12) to obtain viscosity-enhancing heat-resistant and salt-resistant polymer particles;

[0185] (2) Preparation of controllable phase inversion polymers

[0186] (21), placing the viscosity-enhancing heat-resistant and salt-resistant polymer particles obtained in step (1) in a reactor, adding a strong organic base catalyst and an unsaturated halogenated hydrocarbon compound in sequence, stirring evenly, and then reacting at 50° C. for 1 hour to obtain amide-unsaturated graft-modified viscosity-enhancing polymer particles;

[0187] (22) Spraying an azo initiator system onto the surface of the amide-unsaturated grafted viscosity-enhancing polymer particles, reacting at 75° C. for 2 hours, and then adding a hydrolysis agent thereto. After hydrolysis for 120 minutes, a controllable phase inversion polymer is obtained.

[0188] Furthermore, the temperature-resistant and salt-resistant monomer in step (11) is a mixture of equal masses of 2-acrylamido-2-methylpropanesulfonic acid, sodium styrenesulfonate and N-vinyl-2-pyrrolidone.

[0189] Furthermore, in step (11), based on the total weight of the acrylamide monomer and the heat-resistant and salt-resistant monomer, the content of the acrylamide monomer is 99 wt %, and the content of the heat-resistant and salt-resistant monomer is 1 wt %.

[0190] In another embodiment, in step (11), based on the total weight of the acrylamide monomer and the heat-resistant and salt-resistant monomer, the content of the acrylamide monomer is 84 wt %, and the content of the heat-resistant and salt-resistant monomer is 16 wt %.

[0191] Furthermore, based on the total weight of the acrylamide monomer and the temperature-resistant and salt-resistant monomer, the amount of water used in step (11) is 400 wt%.

[0192] Furthermore, the inert gas in step (11) and step (12) is neon.

[0193] Furthermore, the low temperature condition in step (12) is 9°C.

[0194] Furthermore, the free radical initiator in step (12) is an organic peroxide initiator.

[0195] Furthermore, the organic peroxide initiator is benzoyl peroxide.

[0196] Furthermore, based on the total weight of the acrylamide monomer and the temperature-resistant and salt-resistant monomer in step (11), the amount of the free radical initiator used in step (12) is 0.5%.

[0197] Furthermore, the strong organic base catalyst in step (21) is potassium tert-butoxide.

[0198] Furthermore, based on the total weight of the acrylamide monomer and the temperature-resistant and salt-resistant monomer in step (11), the amount of the strong organic base catalyst used in step (21) is 5%.

[0199] Furthermore, the unsaturated halogenated hydrocarbon compound in step (21) is allyl bromide.

[0200] Furthermore, based on the total weight of the acrylamide monomer and the temperature-resistant and salt-resistant monomer in step (11), the amount of the unsaturated halogenated hydrocarbon compound in step (21) is 5%.

[0201] Furthermore, the azo initiator system in step (22) is an aqueous solution of azobisisobutylimidazoline hydrochloride, wherein:

[0202] The mass ratio of azobisisobutylimidazoline hydrochloride to water is 1:10.

[0203] In another embodiment, the azo initiator system in step (22) is a mixture of azobisisobutyronitrile, a nonionic surfactant and water, wherein:

[0204] The mass ratio of azobisisobutyronitrile: water is 1:10;

[0205] The mass ratio of nonionic surfactant to water is 0.01:1.

[0206] Furthermore, the nonionic surfactant is a polyol type nonionic surfactant.

[0207] In another embodiment, the azo initiator system in step (22) is a mixture of azobisisoheptanonitrile, a nonionic surfactant and water, wherein:

[0208] The mass ratio of azobisisoheptanonitrile: water is 1:10;

[0209] The mass ratio of nonionic surfactant to water is 0.01:1.

[0210] Furthermore, the nonionic surfactant is a polyol type nonionic surfactant.

[0211] Furthermore, the post-hydrolysis reagent in step (22) is potassium hydroxide.

[0212] Furthermore, based on the total weight of the acrylamide monomer and the temperature-resistant and salt-resistant monomer in step (11), the amount of the hydrolysis agent used in step (22) is 10%.

[0213] Application of the controllable phase inversion polymer prepared by any of the above controllable phase inversion polymer preparation methods as a polymer oil displacement agent.

[0214] Example 10

[0215] A method for preparing a controllable phase inversion polymer, comprising the following steps:

[0216] (1) Preparation of viscosity-enhancing heat-resistant and salt-resistant polymer particles

[0217] (11) dissolving acrylamide monomer and temperature-resistant and salt-resistant monomer in an appropriate amount of water, and passing an inert gas into the water for 40 minutes to obtain a mixed solution;

[0218] (12) The mixed solution obtained in step (11) is controlled to be under low temperature conditions, and a free radical initiator is quickly added, and the inert gas is continuously passed for 10 minutes, and the mixture is sealed and reacted for 3 hours to obtain a viscosity-enhancing heat-resistant and salt-resistant polymer block;

[0219] (13), taking out and crushing the viscosity-enhancing heat-resistant and salt-resistant polymer block obtained in step (12) to obtain viscosity-enhancing heat-resistant and salt-resistant polymer particles;

[0220] (2) Preparation of controllable phase inversion polymers

[0221] (21), placing the viscosity-enhancing heat-resistant and salt-resistant polymer particles obtained in step (1) in a reactor, adding a strong organic base catalyst and an unsaturated halogenated hydrocarbon compound in sequence, stirring evenly, and then reacting at 40° C. for 2 hours to obtain amide-unsaturated graft-modified viscosity-enhancing polymer particles;

[0222] (22) Spraying an azo initiator system onto the surface of the amide-unsaturated grafted viscosity-enhancing polymer particles, reacting at 70° C. for 3 hours, and then adding a hydrolysis agent thereto. After hydrolysis for 130 minutes, a controllable phase inversion polymer is obtained.

[0223] Furthermore, the temperature-resistant and salt-resistant monomer in step (11) is N-vinyl-2-pyrrolidone.

[0224] Furthermore, in step (11), based on the total weight of the acrylamide monomer and the heat-resistant and salt-resistant monomer, the content of the acrylamide monomer is 90 wt %, and the content of the heat-resistant and salt-resistant monomer is 10 wt %.

[0225] Furthermore, based on the total weight of the acrylamide monomer and the temperature-resistant and salt-resistant monomer, the amount of water used in step (11) is 300 wt%.

[0226] Furthermore, the inert gas in step (11) and step (12) is argon.

[0227] Furthermore, the low temperature condition in step (12) is 8°C.

[0228] Furthermore, the free radical initiator in step (12) is an azo initiator.

[0229] Furthermore, the azo initiator is azobisisobutyronitrile.

[0230] Furthermore, based on the total weight of the acrylamide monomer and the temperature-resistant and salt-resistant monomer in step (11), the amount of the free radical initiator used in step (12) is 0.2%.

[0231] Furthermore, the strong organic base catalyst in step (21) is sodium tert-butoxide.

[0232] Furthermore, based on the total weight of the acrylamide monomer and the temperature-resistant and salt-resistant monomer in step (11), the amount of the strong organic base catalyst used in step (21) is 0.5%.

[0233] Furthermore, the unsaturated halogenated hydrocarbon compound in step (21) is a mixture of propyl chloride and allyl bromide in equal amounts.

[0234] Furthermore, based on the total weight of the acrylamide monomer and the temperature-resistant and salt-resistant monomer in step (11), the amount of the unsaturated halogenated hydrocarbon compound in step (21) is 0.5%.

[0235] Furthermore, the azo initiator system in step (22) is an aqueous solution of azobisisobutylimidazoline hydrochloride, wherein:

[0236] The mass ratio of azobisisobutylimidazoline hydrochloride to water is 1:5.

[0237] In another embodiment, the azo initiator system in step (22) is a mixture of azobisisobutyronitrile, a nonionic surfactant and water, wherein:

[0238] The mass ratio of azobisisobutyronitrile: water is 1:5;

[0239] The mass ratio of nonionic surfactant to water is 0.003:1.

[0240] Furthermore, the nonionic surfactant is an alkanolamide type nonionic surfactant.

[0241] In another embodiment, the azo initiator system in step (22) is a mixture of azobisisoheptanonitrile, a nonionic surfactant and water, wherein:

[0242] The mass ratio of azobisisoheptanonitrile: water is 1:5;

[0243] The mass ratio of nonionic surfactant to water is 0.003:1.

[0244] Furthermore, the nonionic surfactant is an alkanolamide type nonionic surfactant.

[0245] Furthermore, the post-hydrolysis reagent in step (22) is calcium hydroxide.

[0246] Furthermore, based on the total weight of the acrylamide monomer and the temperature-resistant and salt-resistant monomer in step (11), the amount of the hydrolysis agent used in step (22) is 1%.

[0247] Application of the controllable phase inversion polymer prepared by any of the above controllable phase inversion polymer preparation methods as a polymer oil displacement agent.

[0248] Embodiment 11

[0249] A method for preparing a controllable phase inversion polymer, comprising the following steps:

[0250] (1) Preparation of viscosity-enhancing heat-resistant and salt-resistant polymer particles

[0251] (11) dissolving acrylamide monomer and temperature-resistant and salt-resistant monomer in an appropriate amount of water, and passing nitrogen gas into the water for 50 minutes to obtain a mixed solution;

[0252] (12) rapidly adding a free radical initiator to the mixed solution obtained in step (11) under low temperature conditions, continuing to pass nitrogen for 20 minutes, sealing, and reacting for 3 hours to obtain a viscosity-enhanced heat-resistant and salt-resistant polymer block;

[0253] (13), taking out and crushing the viscosity-enhancing heat-resistant and salt-resistant polymer block obtained in step (12) to obtain viscosity-enhancing heat-resistant and salt-resistant polymer particles;

[0254] (2) Preparation of controllable phase inversion polymers

[0255] (21), placing the viscosity-enhancing heat-resistant and salt-resistant polymer particles obtained in step (1) in a reactor, adding a strong organic base catalyst and an unsaturated halogenated hydrocarbon compound in sequence, stirring evenly, and then reacting at 40° C. for 2 hours to obtain amide-unsaturated graft-modified viscosity-enhancing polymer particles;

[0256] (22) Spraying an azo initiator system onto the surface of the amide-unsaturated grafted viscosity-enhancing polymer particles, reacting at 60° C. for 3 hours, and then adding a hydrolysis agent thereto. After hydrolysis for 180 minutes, a controllable phase inversion polymer is obtained.

[0257] Furthermore, the temperature-resistant and salt-resistant monomer in step (11) is sodium styrene sulfonate.

[0258] Furthermore, in step (11), based on the total weight of the acrylamide monomer and the heat-resistant and salt-resistant monomer, the content of the acrylamide monomer is 88 wt %, and the content of the heat-resistant and salt-resistant monomer is 12 wt %.

[0259] Furthermore, based on the total weight of the acrylamide monomer and the temperature-resistant and salt-resistant monomer, the amount of water used in step (11) is 280 wt%.

[0260] Furthermore, the low temperature condition in step (12) is 5°C.

[0261] Furthermore, the free radical initiator in step (12) is a redox initiator.

[0262] Furthermore, the redox initiator is ammonium persulfate / sodium bisulfite.

[0263] Furthermore, based on the total weight of the acrylamide monomer and the temperature-resistant and salt-resistant monomer in step (11), the amount of the free radical initiator used in step (12) is 0.2%.

[0264] Further, the strong organic base catalyst described in step (21) is a mixture of equal masses of tert-butyl lithium, potassium tert-butoxide, sodium tert-butoxide, sodium amide, and tetrabutylammonium hydroxide. In another embodiment, the strong organic base catalyst described in step (21) is tetrabutylammonium hydroxide. In yet another embodiment, the strong organic base catalyst described in step (21) is sodium amide.

[0265] Furthermore, based on the total weight of the acrylamide monomer and the temperature-resistant and salt-resistant monomer in step (11), the amount of the strong organic base catalyst used in step (21) is 2%.

[0266] Furthermore, the unsaturated halogenated hydrocarbon compound in step (21) is allyl chloride.

[0267] Furthermore, based on the total weight of the acrylamide monomer and the temperature-resistant and salt-resistant monomer in step (11), the amount of the unsaturated halogenated hydrocarbon compound in step (21) is 3%.

[0268] Furthermore, the azo initiator system in step (22) is an aqueous solution of azobisisobutylimidazoline hydrochloride, wherein:

[0269] The mass ratio of azobisisobutylimidazoline hydrochloride to water is 1:8.

[0270] In another embodiment, the azo initiator system in step (22) is a mixture of azobisisobutyronitrile, a nonionic surfactant and water, wherein:

[0271] The mass ratio of azobisisobutyronitrile: water is 1:4;

[0272] The mass ratio of nonionic surfactant to water is 0.005:1.

[0273] Furthermore, the nonionic surfactant is a polyether nonionic surfactant.

[0274] In another embodiment, the azo initiator system in step (22) is a mixture of azobisisobutyronitrile or azobisisoheptanenitrile, a nonionic surfactant and water, wherein:

[0275] The mass ratio of azobisisobutyronitrile or azobisisoheptanenitrile: water is 1:4;

[0276] The mass ratio of nonionic surfactant to water is 0.008:1.

[0277] Furthermore, the nonionic surfactant is a polyether nonionic surfactant.

[0278] Furthermore, the post-hydrolysis reagent in step (22) is a mixture of equal masses of sodium hydroxide, potassium hydroxide and calcium hydroxide.

[0279] Furthermore, based on the total weight of the acrylamide monomer and the temperature-resistant and salt-resistant monomer in step (11), the amount of the hydrolysis agent used in step (22) is 3%.

[0280] Application of the controllable phase inversion polymer prepared by any of the above controllable phase inversion polymer preparation methods as a polymer oil displacement agent.

[0281] Examples 12-15

[0282] It is substantially the same as Example 9, except that the organic peroxide initiator is different:

[0283]

[0284] Examples 16-18

[0285] It is roughly the same as Example 10, except that the azo initiator is different:

[0286]

[0287] Examples 19-25

[0288] The same as Example 11, the only difference is the redox initiator:

[0289]

[0290]

[0291] Comparative Example 1

[0292] A method for preparing a polymer, comprising the following steps:

[0293] Acrylamide monomer and 2-acrylamido-2-methylpropanesulfonic acid (mass ratio 90:10) were dissolved in water, and nitrogen (purity 99.999%) was introduced for 30 minutes to remove the dissolved oxygen in the water.

[0294] At 8°C, initiator benzoyl peroxide and benzoyl peroxide / N,N-diethylaniline (the mass ratio of the three is 2:1:1, and the total accounts for 0.001% of the total mass of the polymerized monomers) were quickly added, and nitrogen (purity 99.999%) was continued to flow for 5 minutes, and the mouth was sealed.

[0295] After 3 hours of reaction, the rubber block was taken out and crushed by a crusher to obtain polymer particles. Finally, sodium hydroxide (accounting for 2% of the total weight of the polymer monomer) was added for hydrolysis, and the mixture was dried at 80°C for 1 hour and granulated to obtain polymer dry powder.

[0296] Comparative Example 2

[0297] A method for preparing a polymer, comprising the following steps:

[0298] Acrylamide monomer and sodium styrene sulfonate (SSS) (mass ratio 95:5) were dissolved in water, and argon gas (purity 99.999%) was introduced for 30 minutes to remove the dissolved oxygen in the water.

[0299] At 9° C., initiators ammonium persulfate, ferrous sulfate, and azobisisobutyronitrile (mass ratio 2:1:1, accounting for 0.001% of the total mass of the polymerized monomers) were quickly added, and argon (purity 99.999%) was continued to flow for 5 minutes, and the port was sealed.

[0300] After 3 hours of reaction, the rubber block was taken out and crushed by a crusher to obtain polymer particles. Finally, sodium hydroxide (accounting for 2% of the total weight of the polymer monomer) was added for hydrolysis, and the mixture was dried at 80°C for 1 hour and granulated to obtain polymer dry powder.

[0301] Comparative Example 3

[0302] A method for preparing a polymer, comprising the following steps:

[0303] Acrylamide monomer and N-vinyl-2-pyrrolidone (mass ratio 95:5) were dissolved in water, and nitrogen (purity 99.999%) was introduced for 30 minutes to remove the oxygen dissolved in the water.

[0304] At 9° C., initiators benzoyl peroxide and azobisisobutyronitrile (mass ratio 2:1, total accounting for 0.001% of the total mass of the polymerized monomers) were quickly added, and argon (purity 99.999%) was continued to flow for 5 minutes, and the port was sealed.

[0305] After 3 hours of reaction, the rubber block was taken out and crushed by a crusher to obtain polymer particles. Finally, sodium hydroxide (accounting for 2% of the total weight of the polymer monomer) was added for hydrolysis, and the mixture was dried at 80°C for 1 hour and granulated to obtain polymer dry powder.

[0306] Verification test:

[0307] 0.5 g of the controllable phase inversion polymer powder obtained in Examples 1-3 and the polymer powder obtained in Comparative Examples 1-3 were accurately weighed and dissolved in 1000 mL of sodium chloride solution (sodium chloride concentration: 10000 mg / L). The mixture was stirred until no colloid particles were left. The viscosity of the polymer solution was measured. The results are shown in the following table:

[0308]

[0309] From the results in Table 1, it can be seen that the controllable phase transition polymers prepared by Examples 1-3 have a good elastic modulus when swollen, and the dissolution time is controlled to be 42 to 36 hours to achieve the transformation from the discontinuous gel phase to the continuous solution phase. After complete dissolution, the viscosity of the polymer solution is basically the same as that of the conventional polymer comparative examples 1-3.

[0310] From the above, it can be seen that the controllable weak cross-linking technical means of the method of the present invention is used to temporarily "bundle" the water-soluble polymers together. The initial stage is a gel particle dispersion. After being injected into the formation, it is gradually hydrolyzed to release the viscosity-enhancing polymer under reservoir conditions, and the gradient viscosity enhancement is slowly released in the deep reservoir. By controlling the degree of unsaturated grafting modification of the amide group of the viscosity-enhancing polymer, the phase conversion of the dispersed phase gel particles to the continuous phase polymer solution can be controlled, so as to achieve the purpose of gel adjustment of the plugging flow line in the near-well section, viscosity enhancement and expansion of the solution in the far-well section and efficient oil displacement.

[0311] The above describes the embodiments of the present invention in detail. However, the present invention is not limited to the above embodiments, and various changes can be made within the knowledge of ordinary technicians in the relevant technical field without departing from the purpose of the present invention.

Claims

1. A controllable phase inversion polymer, characterized in that: The controllable phase inversion polymer consists of a structural unit A and a structural unit B, wherein: The structural unit A is provided by an acrylamide monomer represented by formula (1); Structural unit B is provided by temperature-resistant and salt-resistant monomers; Based on the weight of the controllable phase inversion polymer, the content of structural unit A is 80-99% by weight, and the content of structural unit B is 1-20% by weight; The viscosity average molecular weight of the controllable phase transition polymer is 25 million to 35 million.

2. A controllable phase inversion polymer as claimed in claim 1, characterized in that: Based on the weight of the controllable phase inversion polymer, the content of structural unit A is 80-95% by weight, and the content of structural unit B is 5-20% by weight; The viscosity average molecular weight of the controllable phase transition polymer is 30 million to 35 million.

3. A controllable phase inversion polymer as claimed in claim 1, characterized in that: The temperature-resistant and salt-resistant monomer is at least one of a 2-acrylamide-2-methylpropanesulfonic acid monomer represented by formula (2), a sodium styrene sulfonate monomer represented by formula (3), and an N-vinyl-2-pyrrolidone monomer represented by formula (4); 4. A method for preparing a controllable phase inversion polymer, characterized in that: Here are the steps: (1) Preparation of viscosity-enhancing heat-resistant and salt-resistant polymer particles (11) dissolving acrylamide monomer and temperature-resistant and salt-resistant monomer in an appropriate amount of water, and passing an inert gas or nitrogen into the water for at least 20 minutes to obtain a mixed solution; (12) rapidly adding a free radical initiator to the mixed solution obtained in step (11) under low temperature conditions, continuing to pass an inert gas or nitrogen for at least 5 minutes, sealing the mixture, and reacting for at least 2 hours to obtain a viscosity-enhanced heat-resistant and salt-resistant polymer block; (13), taking out and crushing the viscosity-enhancing heat-resistant and salt-resistant polymer block obtained in step (12) to obtain viscosity-enhancing heat-resistant and salt-resistant polymer particles; (2) Preparation of controllable phase inversion polymers (21), placing the viscosity-enhancing heat-resistant and salt-resistant polymer particles obtained in step (1) in a reactor, adding a strong organic base catalyst and an unsaturated halogenated hydrocarbon compound in sequence, stirring evenly, and then reacting at 30 to 50° C. for at least 1 hour to obtain amide-unsaturated graft-modified viscosity-enhancing polymer particles; (22) Spraying an azo initiator system onto the surface of the amide-unsaturated grafted viscosity-enhancing polymer particles, reacting at 50-75° C. for at least 2 hours, then adding a hydrolysis agent thereto, and hydrolyzing for at least 90 minutes to obtain a controllable phase inversion polymer.

5. The method for preparing a controllable phase inversion polymer according to claim 4, characterized in that: The temperature-resistant and salt-resistant monomer in step (11) is one or more of 2-acrylamide-2-methylpropanesulfonic acid, sodium styrenesulfonate, and N-vinyl-2-pyrrolidone.

6. The method for preparing a controllable phase inversion polymer according to claim 4, characterized in that: In step (11), based on the total weight of the acrylamide monomer and the heat-resistant and salt-resistant monomer, the content of the acrylamide monomer is 80wt% to 99wt%, and the content of the heat-resistant and salt-resistant monomer is 1wt% to 20wt%.

7. The method for preparing a controllable phase inversion polymer according to claim 6, characterized in that: In step (11), based on the total weight of the acrylamide monomer and the heat-resistant and salt-resistant monomer, the content of the acrylamide monomer is 80wt% to 85wt%, and the content of the heat-resistant and salt-resistant monomer is 5wt% to 20wt%.

8. The method for preparing a controllable phase inversion polymer according to claim 4, characterized in that: The amount of water used in step (11) is 250 wt % to 400 wt % based on the total weight of the acrylamide monomer and the temperature-resistant and salt-resistant monomer.

9. The method for preparing a controllable phase inversion polymer according to claim 4, characterized in that: The inert gas in step (11) and step (12) is one of helium, neon and argon.

10. The method for preparing a controllable phase inversion polymer according to claim 4, characterized in that: The low temperature condition in step (12) is 3°C to 9°C.

11. The method for preparing a controllable phase inversion polymer according to claim 4, characterized in that: The free radical initiator in step (12) is one or more of an organic peroxide initiator, an azo initiator, and a redox initiator.

12. The method for preparing a controllable phase inversion polymer according to claim 11, characterized in that: The organic peroxide initiator is one or more of benzoyl peroxide, lauroyl peroxide, cumene hydroperoxide and tert-butyl hydroperoxide.

13. The method for preparing a controllable phase inversion polymer according to claim 11, characterized in that: The azo initiator is one or more of azobisisobutyronitrile, azobisisoheptanenitrile and azobisisobutylimidazoline hydrochloride.

14. The method for preparing a controllable phase inversion polymer according to claim 11, characterized in that: The redox initiator is one or more of ammonium persulfate / sodium bisulfite, potassium persulfate / sodium bisulfite, hydrogen peroxide / tartaric acid, hydrogen peroxide / bleaching powder, ammonium persulfate / ferrous sulfate, hydrogen peroxide / ferrous sulfate, benzoyl peroxide / N,N-diethylaniline.

15. The method for preparing a controllable phase inversion polymer according to claim 4, characterized in that: The amount of the free radical initiator in step (12) is 0.001% to 0.5% based on the total weight of the acrylamide monomer and the temperature-resistant and salt-resistant monomer in step (11).

16. The method for preparing a controllable phase inversion polymer according to claim 4, characterized in that: The strong organic base catalyst described in step (21) is one or more of tert-butyl lithium, potassium tert-butoxide, sodium tert-butoxide, sodium amide, and tetrabutylammonium hydroxide.

17. The method for preparing a controllable phase inversion polymer according to claim 4, characterized in that: The amount of the strong organic base catalyst used in step (21) is 0.1% to 5% based on the total weight of the acrylamide monomer and the temperature-resistant and salt-resistant monomer in step (11).

18. The method for preparing a controllable phase inversion polymer according to claim 4, characterized in that: The unsaturated halogenated hydrocarbon compound in step (21) is one or more of allyl chloride and allyl bromide.

19. The method for preparing a controllable phase inversion polymer according to claim 4, characterized in that: The amount of the unsaturated halogenated hydrocarbon compound in step (21) is 0.1-5% based on the total weight of the acrylamide monomer and the temperature-resistant and salt-resistant monomer in step (11).

20. The method for preparing a controllable phase inversion polymer according to claim 4, characterized in that: The azo initiator system in step (22) is an aqueous solution of azobisisobutylimidazoline hydrochloride, wherein: The mass ratio of azobisisobutylimidazoline hydrochloride to water is 1:(1-10).

21. The method for preparing a controllable phase inversion polymer according to claim 4, characterized in that: The azo initiator system in step (22) is a mixture of azobisisobutyronitrile or azobisisoheptanenitrile, a nonionic surfactant and water, wherein: The mass ratio of azobisisobutyronitrile or azobisisoheptanenitrile: water is 1:(1-10); The mass ratio of the nonionic surfactant to water is (0.002-0.01):1, preferably 0.003:

1.

22. The method for preparing a controllable phase inversion polymer according to claim 21, characterized in that: The nonionic surfactant is one of a polyoxyethylene nonionic surfactant, a polyol nonionic surfactant, an alkanolamide nonionic surfactant, and a polyether nonionic surfactant.

23. The method for preparing a controllable phase inversion polymer according to claim 4, characterized in that: The post-hydrolysis reagent in step (22) is one or more of sodium hydroxide, potassium hydroxide and calcium hydroxide.

24. The method for preparing a controllable phase inversion polymer according to claim 4, characterized in that: The amount of the hydrolysis agent used in step (22) is 0.5-10% based on the total weight of the acrylamide monomer and the temperature-resistant and salt-resistant monomer in step (11).

25. Use of the controllable phase inversion polymer according to any one of claims 1 to 3 as a polymer oil displacement agent.

26. Use of the controllable phase inversion polymer prepared by the method for preparing the controllable phase inversion polymer according to any one of claims 4 to 24 as a polymer oil displacement agent.

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