A cross-linked polymer and a method for preparing and using the same

Abstract

The application relates to the technical field of oil field chemistry, in particular to a cross-linked polymer and a preparation method and application thereof. The cross-linked polymer comprises structural unit A, structural unit B, structural unit C and a cross-linking unit; wherein the structural unit A is the structural unit B is the structural unit C is wherein M represents a metal combined with a phosphonic acid group in the form of an ionic bond, and m is the valence state of M. The random terpolymer obtained by optimizing the cross-linking system can significantly improve the viscosity retention rate of the cross-linked polymer at high temperature, can enhance the salt resistance (resistance to NaCl saturation and resistance to CaCl2 saturation), and has good proppant carrying performance.

Description

Technical Field

[0001] This invention relates to the field of oilfield chemical technology, and in particular to a crosslinked polymer, its preparation method, and its application. Background Technology

[0002] my country's drilling depth has reached 9,000 meters, with bottom hole temperatures ranging from 180 to 260°C. In many areas, there are long sections of salt-gypsum layers. As exploration extends into deeper strata, the drilled formations become increasingly complex, with more high-temperature, high-pressure, and high-salt formations. This places higher demands on the performance of drilling fluid treatment agents.

[0003] Viscosifiers are a class of treatment agents used in large quantities in drilling and completion fluids. They are usually composed of high molecular weight polymers, characterized by long molecular chains and good water solubility. Besides their viscosity-increasing effect, viscosifiers often also function as shale inhibitors (coating agents), filtration loss reducers, and flow pattern modifiers. Therefore, the use of viscosifiers is generally beneficial for improving the rheological properties of drilling fluids and for wellbore stability.

[0004] In the prior art, CN102127401A discloses a high-temperature resistant thickener for drilling fluids and its preparation method. It is made by mixing starch, guar gum, alkaline hydroxide, epoxide, and alcohol solvent in a certain proportion, followed by stirring, drying, and pulverizing. This product has a temperature resistance of up to 150℃ in freshwater drilling fluids and up to 140℃ in seawater drilling fluids. CN101955564A discloses a method for preparing a high-temperature resistant and salt-resistant thickener for drilling fluids. This method uses 2-acrylamido-2-methylpropanesulfonic acid, acrylic acid, and acrylamide as raw materials, polymerized via aqueous solution polymerization. This thickener exhibits good stability at a formation temperature of 150℃ and still retains some effectiveness in a 10% salt solution. CN104293325A discloses a viscosity reducer for drilling fluids and its preparation method. This method introduces acrylic acid, a sulfonating agent, a cationic monomer, and an organophosphonate into the reaction system, effectively reducing the viscosity of high-density polymer drilling fluids while maintaining good viscosity-reducing performance at 200℃. However, its optimization direction lies in viscosity reduction; further improvement is still possible while considering viscosity-enhancing properties, high-temperature resistance, and salt resistance.

[0005] It is evident that the temperature resistance of domestically produced high-temperature tackifiers is typically around 150–180℃, and this resistance increases when the system has a high degree of mineralization (especially Ca). 2+ Concentration higher than 1.4 × 10 4 When the concentration of a thickener (mg / L) is insufficient, molecular chain coiling and entanglement can occur, leading to product failure. Conventional aqueous solution polymerization methods have certain limitations. There is an urgent need in this field to develop a thickener product that can maintain good performance under high temperature and high salt conditions. Summary of the Invention

[0006] The present application aims to provide a cross-linked polymer and its preparation method and application, which overcomes the defects of the prior art that it is difficult to balance the tackifying performance, high temperature resistance and salt resistance, and realizes a cross-linked polymer which still has good tackifying effect under the condition of 180 DEG C, and is resistant to NaCl saturation and CaCl2 saturation.

[0007] In a first aspect, the present application first provides a cross-linked polymer, which comprises structural unit A, structural unit B, structural unit C and cross-linking unit.

[0008] The structural unit A is The structural unit B is The structural unit C is

[0009] The M represents a metal combined with the phosphonic acid group in the form of ionic bond, and m represents the valence of M.

[0010] The present application surprisingly finds that the molecular structure containing the above structural units can effectively increase the temperature resistance of the product, and adjust the rheological property of the drilling fluid system; at the same time, the combination of the carboxylic acid group and the phosphonic acid group can enhance the water solubility of the cross-linked polymer, and reduce the hydration time; the introduction of the phosphonic acid group and the increase of the polarity of the salt solution result in the enhancement of the hydrophobic association, which can significantly improve the calcium resistance and salt resistance of the cross-linked polymer.

[0011] As a preferred, the polymerization degree of the structural units A, B and C is 2000-5000, which is the same or different.

[0012] As a preferred, the M is one of monovalent metal, divalent metal, trivalent metal or tetravalent metal.

[0013] More preferably, the M is one of the Group IA metal, and m is 1; further preferably, the M is sodium or potassium; most preferably, the M is sodium.

[0014] Or, the M is one of divalent metal, and m is 2; further preferably, the M is selected from one or more of magnesium, calcium, copper and iron.

[0015] Or, the M is one of trivalent metal, and m is 3; further preferably, the M is iron or aluminum.

[0016] Or, the M is one of tetravalent metal, and m is 4; further preferably, the M is titanium or zirconium.

[0017] As a preferred, the cross-linking unit is a linear alkyl group with C1-C 25 .

[0018] The present application discloses a cross-linking polymer, which comprises a cross-linking unit, a structure unit A, a structure unit B and a structure unit C.

[0019] More preferably, the cross-linking unit is a C6-C 10 linear alkyl.

[0020] Preferably, the cross-linking polymer has a structure formula as follows:

[0021]

[0022] wherein M represents a metal combined with a phosphonic acid group in the form of an ionic bond, m is the valence of M; n represents the number of carbon atoms, 1≤n≤25.

[0023] Preferably, the content of the cross-linking unit is 0.01-0.05wt% based on the total amount of the cross-linking polymer.

[0024] Preferably, the content of the structure unit A is 30-60wt% based on the total amount of the cross-linking polymer.

[0025] Preferably, the content of the structure unit B is 25-45wt% based on the total amount of the cross-linking polymer.

[0026] Preferably, the content of the structure unit C is 10-30wt% based on the total amount of the cross-linking polymer.

[0027] In a second aspect, the present application further provides a preparation method of the cross-linking polymer, which comprises: performing inverse emulsion polymerization on a diallyl aminomethyl phosphonate, acrylic acid and N-vinyl caprolactam to obtain a polymer; and then cross-linking the polymer by using a dihaloalkane as a cross-linking agent, thereby obtaining the cross-linking polymer.

[0028] The present application discloses a cross-linking polymer, which comprises a cross-linking unit, a structure unit A, a structure unit B and a structure unit C.

[0029] As a preference, the dihaloalkane is selected from the group consisting of 1,2-dichloroethane, 1,2-dichloropropane, 1,3-dichloropropane, 1,2-dichlorobutane, 1,3-dichlorobutane, 1,4-dichlorobutane, 1,2-dichloropentane, 1,3-dichloropentane, 1,4-dichloropentane, 1,5-dichloropentane, 1,2-dichlorohexane, 1,3-dichlorohexane, 1,4-dichlorohexane, 1,5-dichlorohexane, 1,6-dichlorohexane, 1,2-dichloroheptane, 1,3-dichloroheptane, 1,4-dichloroheptane, 1,5-dichloroheptane, 1,6-dichloroheptane, 1,7-dichloroheptane, 1,2-dichlorooctane, 1,3-dichlorooctane, 1,4-dichlorooctane, 1,5-dichlorooctane, 1,6-dichlorooctane, 1,7-dichlorooctane, 1,8-dichlorooctane, 1,2-dichlorononane, 1,3-dichlorononane, 1,4-dichlorononane, 1,5-dichlorononane, 1,6-dichlorononane, 1,7-dichlorononane, 1,8-dichlorononane, 1,9-dichlorononane, 1,2-dichlorodecane, 1,3-dichlorodecane, 1,4-dichlorodecane, 1,5-dichlorodecane, 1,6-dichlorodecane, 1,7-dichlorodecane, 1,8-dichlorodecane, 1,9-dichlorodecane, 1,10-dichlorodecane; 1,2-diiodoethane, 1,2-diiodopropane, 1,3-diiodopropane, 1,2-diiodobutane, 1,3-diiodobutane, 1,4-diiodobutane, 1,2-diiodopentane, 1,3-diiodopentane, 1,4-diiodopentane, 1,5-diiodopentane, 1,2-diiodohexane, 1,3-diiodohexane, 1,4-diiodohexane, 1,5-diiodohexane, 1,6-diiodohexane, 1,2-diiodoheptane, 1,3-diiodoheptane, 1,4-diiodoheptane, 1,5-diiodoheptane, 1,6-diiodoheptane, 1,7-diiodoheptane, 1,2-diiodooctane, 1,3-diiodooctane, 1,4-diiodooctane, 1,5-diiodooctane, 1,6-diiodooctane, 1,7-diiodooctane, 1,8-diiodooctane, 1,2-diiodononane, 1,3-diiodononane, 1,4-diiodononane, 1,5-diiodononane, 1,6-diiodononane, 1,7-diiodononane, 1,8-diiodononane, 1,9-diiodononane, 1,2-diiododecane, 1,3-diiododecane, 1,4-diiododecane, 1,5-diiododecane, 1,6-diiododecane, 1,7-diiododecane, 1,8-diiododecane, 1,9-diiododecane, 1,10-diiododecane.1,2-dibromoethane, 1,2-dibromopropane, 1,3-dibromopropane, 1,2-dibromobutane, 1,3-dibromobutane, 1,4-dibromobutane, 1,2-dibromopentane, 1,3-dibromopentane, 1,4-dibromopentane, 1,5-dibromopentane, 1,2-dibromohexane, 1,3-dibromohexane, 1,4-dibromohexane, 1,5-dibromohexane, 1,6-dibromohexane, 1,2-dibromoheptane, 1,3-dibromoheptane, 1,4-dibromoheptane, 1,5-dibromoheptane, 1,6-dibromoheptane, 1,7-dibromoheptane, 1,2-dibromo-octane, 1,3-dibromo-octane, 1,4-dibromo-octane, 1,5-dibromo-octane, 1,6-dibromo-octane, 1,7-dibromo-octane, 1,8-dibromo-octane, 1,2-dibromononane, 1,3-dibromononane, 1,4-dibromononane, 1,5-dibromononane, 1,6-dibromononane, 1,7-dibromononane, 1,8-dibromononane, 1,9-dibromononane, 1,2-dibromodecane, 1,3-dibromodecane, 1,4-dibromodecane, 1,5-dibromodecane, 1,6-dibromodecane, 1,7-dibromodecane, 1,8-dibromodecane, 1,9-dibromodecane, 1,10-dibromodecane; 1,2-difluoroethane, 1,2-difluoropropane, 1,3-difluoropropane, 1,2-difluorobutane, 1,3-difluorobutane, 1,4-difluorobutane, 1,2-difluoropentane, 1,3-difluoropentane, 1,4-difluoropentane, 1,5-difluoropentane, 1,2-difluorohexane, 1,3-difluorohexane, 1,4-difluorohexane, 1,5-difluorohexane, 1,6-difluorohexane, 1,2-difluoroheptane, 1,3-difluoroheptane, 1,4-difluoroheptane, 1,5-difluoroheptane, 1,6-difluoroheptane, 1,7-difluoroheptane, 1,2-difluoro-octane, 1,3-difluoro-octane, 1,4-difluoro-octane, 1,5-difluoro-octane, 1,6-difluoro-octane, 1,7-difluoro-octane, 1,8-difluoro-octane, 1,2-difluorononane, 1,3-difluorononane, 1,4-difluorononane, 1,5-difluorononane, 1,6-difluorononane, 1,7-difluorononane, 1,8-difluorononane, 1,9-difluorononane, 1,2-difluorodecane, 1,3-difluorodecane, 1,4-difluorodecane, 1,5-difluorodecane, 1,6-difluorodecane, 1,7-difluorodecane, 1,8-difluorodecane, 1,9-difluorodecane, 1,10-difluorodecane.

[0030] More preferably, the dihaloalkane is selected from 1,6-dibromohexane, 1,7-dibromoheptane, 1,8-dibromo-octane, 1,9-dibromononane or 1,10-dibromodecane.

[0031] As preferred, the amount of the dihaloalkane is 0.1-0.5 wt‰ of the total mass of the diallyl aminomethyl phosphonate, the acrylic acid and the N-vinyl caprolactam; in particular, the amount of the dihaloalkane can be 0.1 wt‰, 0.2 wt‰, 0.3 wt‰, 0.4 wt‰, 0.5 wt‰ of the total mass of the diallyl aminomethyl phosphonate, the acrylic acid and the N-vinyl caprolactam.

[0032] As preferred, the mass ratio of the diallyl aminomethyl phosphonate, the acrylic acid and the N-vinyl caprolactam is 0.5-3:1-5:0.1-1.

[0033] As preferred, the preparation method of the cross-linked polymer comprises:

[0034] S1: mixing the diallyl aminomethyl phosphonate, the acrylic acid, the N-vinyl caprolactam and water to obtain an aqueous phase;

[0035] S2: mixing the emulsifier with white oil to obtain the oil phase; then mixing the oil phase with the aqueous phase and stirring to obtain an emulsion;

[0036] S3: mixing the emulsion with an aqueous initiator solution under a nitrogen atmosphere and at a temperature of 40-80℃ to obtain a reaction liquid;

[0037] S4: mixing the reaction liquid with a dihaloalkane under a nitrogen atmosphere and at a temperature of 40-80℃ to obtain a product, which is the cross-linked polymer.

[0038] As preferred, in the S1, the mass ratio of the total mass of the diallyl aminomethyl phosphonate, the acrylic acid and the N-vinyl caprolactam to the water is (0.3-1.3):1.

[0039] As preferred, in the S2, the emulsifier is selected from one or more of op10, span80 and tween60.

[0040] More preferably, the emulsifier is a composite emulsifier of span80 and op10 with a mass ratio of (5-10):1; or, the emulsifier is a composite emulsifier of span80 and tween60 with a mass ratio of (5-10):1.

[0041] Further preferably, the amount of the emulsifier is 2-10 wt% of the total mass of the diallyl aminomethyl phosphonate, the acrylic acid and the N-vinyl caprolactam.

[0042] As preferred, in the S2, the white oil is an industrial white oil; more preferably, the industrial white oil is selected from one or more of No. 3 industrial white oil, No. 5 industrial white oil, No. 7 industrial white oil, No. 10 industrial white oil, No. 15 industrial white oil, No. 20 industrial white oil, No. 22 industrial white oil, No. 26 industrial white oil, No. 32 industrial white oil, No. 48 industrial white oil and No. 64 industrial white oil.

[0043] Further preferably, the mass ratio of the white oil to the water in the S1 is (0.8-1.2):1.

[0044] As preferred, in the S3, the initiator is selected from inorganic peroxide initiator and / or azo initiator.

[0045] More preferably, the inorganic peroxide initiator includes one or more of potassium persulfate, sodium persulfate and ammonium persulfate; the azo initiator includes one or more of azobis isobutylonitrile, azobis isoheptylonitrile, azobis dimethyl isobutyrate, azobis isobutyl amide hydrochloride and azobis isobutyl imidazole hydrochloride.

[0046] Further preferably, the initiator is used in an amount of 0.5-5 wt‰ of the total mass of the diallyl aminomethyl phosphonate, acrylic acid and N-vinyl caprolactam.

[0047] In a third aspect, the present application also provides a preparation method of the diallyl aminomethyl phosphonate, comprising:

[0048] S1: mixing phosphorous acid and an organic solvent under a contacting condition, adjusting the pH of the mixture to be no more than 7, and then slowly adding diallyl amine for reaction to obtain a first reaction system;

[0049] S2: adding an aldehyde to the first reaction system for reaction to obtain a second reaction system;

[0050] S3: adjusting the pH of the second reaction system to be 6-8, and then continuing the reaction, and separating the reaction product to obtain a solid phase, which is dried to obtain the diallyl aminomethyl phosphonate.

[0051] As preferred, in the S1, the organic solvent is selected from one or more of alcohol, ester, ether and ketone.

[0052] More preferably, the organic solvent is selected from alcohol, ester, ether and ketone with carbon atom number of 1-12.

[0053] Further preferably, the organic solvent is selected from one or more of methanol, ethanol, butanol, ethyl acetate, butyl acetate, isoamyl acetate, diethyl ether, butyl ether, acetone and methyl ethyl ketone.

[0054] As preferred, in the S1, the volume ratio of the organic solvent to phosphorous acid is 1-2:1-15, more preferably 1-2:1-8.

[0055] As preferred, in the S1, the pH value of the mixed stream is adjusted to 1-6.8; further preferably, the pH value is adjusted to 1-4, more preferably, the pH value is adjusted to 1-3.

[0056] In the present application, the pH value of the mixed stream in the S1 is adjusted by adding an acidic substance; the acidic substance can be inorganic acid and / or organic acid, which can be selected from one or more of hydrochloric acid, sulfuric acid, nitric acid, oxalic acid, glacial acetic acid, carbonic acid, hydrofluoric acid, citric acid, malic acid, tartaric acid and succinic acid.

[0057] As preferred, in the S1, the reaction temperature is -20-10℃, more preferably -10-5℃.

[0058] As preferred, the diene amine is added in the form of dropwise addition; further preferably, the dropwise addition is carried out at a rate of 10-200 mL / h.

[0059] As preferred, in the S2, the aldehyde is selected from one or more of formaldehyde, dimeric formaldehyde, trimeric formaldehyde and polymeric formaldehyde, more preferably formaldehyde.

[0060] As preferred, the aldehyde is added in the form of liquid, such as when formaldehyde is used, it can be directly added in the form of liquid; when dimeric formaldehyde, trimeric formaldehyde or polymeric formaldehyde is used, it can be first dissolved in a solvent and then added in the form of liquid; the solvent can be one or more of alcohol, ester, ether and ketone; further, the alcohol, ester, ether and ketone can have 1-12 carbon atoms, which can be selected from one or more of methanol, ethanol, butanol, ethyl acetate, butyl acetate, isoamyl acetate, diethyl ether, butyl ether, acetone and methyl ethyl ketone.

[0061] As preferred, in the S2, the aldehyde can be added in the form of dropwise addition, further preferably, the dropwise addition is carried out at a rate of 10-200 mL / h.

[0062] As preferred, in the S2, the reaction temperature is -20-10℃, more preferably -10-5℃.

[0063] As preferred, in the S3, the pH value of the second reaction system is adjusted to 6-8, which can be adjusted by adding alkaline substances, the alkaline substances can be inorganic bases and / or alkaline inorganic salts, the metal in the inorganic bases and / or alkaline inorganic salts is selected from one or more of monovalent, divalent, trivalent and tetravalent metal elements, and can be further selected from one or more of sodium hydroxide, potassium hydroxide, sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate, magnesium hydroxide, magnesium carbonate, calcium carbonate, calcium hydroxide, iron hydroxide, copper hydroxide, titanium hydroxide, zirconium hydroxide, and the like, and preferably one or more of sodium hydroxide and potassium hydroxide.

[0064] As preferred, in the S3, the reaction temperature is 0-90℃, and more preferably 20-40℃; the reaction time is 0.5-6h, and more preferably 1-3h.

[0065] As preferred, in the S3, the separation is solid-liquid separation, and the solid-liquid separation can be achieved by any means that can realize the separation of solid and liquid phases, the selection of the liquid-solid separation means belongs to the basic skills of the person skilled in the art, and can be reasonably selected according to the actual situation, and one or more of filtration separation, centrifugal separation and the like can be used.

[0066] As preferred, in the S3, the liquid phase obtained by separation can be recycled back to S1 for continuous use, and other raw materials can be supplemented for continuous reaction.

[0067] As preferred, in the S3, the drying temperature is 60-120℃, and the drying time is 6-12h.

[0068] As preferred, the molar ratio of the diallylamine, phosphorous acid and aldehyde is diallylamine: phosphorous acid: aldehyde = 1: (1-2): (1-2); and more preferably 1: (1-1.5): (1-1.5).

[0069] In the present application, the entire reaction process for preparing the diallyl aminomethyl phosphonate is carried out under anhydrous conditions.

[0070] In the present application, the organic solvent is used as the reaction solvent in the preparation process of the diallyl aminomethyl phosphonate, and the reaction process is carried out under anhydrous conditions, which can improve the reaction efficiency, reduce the occurrence of side reactions, and improve the purity of the obtained product. At the same time, the diallyl aminomethyl phosphonate is water-soluble, and the use of the organic solvent reaction system in the preparation is beneficial to the subsequent separation of the product, and the product can be clearly separated by using conventional separation means such as filtration or centrifugal separation, and the target product can be obtained by further drying at low temperature. The entire process is green, pollution-free, non-toxic and harmless.

[0071] In a fourth aspect, the present application provides the use of the crosslinked polymer in drilling fluid or completion fluid.

[0072] In the present application, the cross-linked polymer can be used in oilfield polymers for viscosity increase, cut point raising, drilling and completion, and in water treatment, papermaking industry, fiber industry, coating industry, water-absorbing materials, printing and dyeing auxiliaries, biological medicine and other fields.

[0073] As a preference, the cross-linked polymer is used as a viscosity increasing agent.

[0074] As a preference, the cross-linked polymer is used as a viscosity increasing agent.

[0075] As a preference, the cross-linked polymer is used as a viscosity increasing agent.

[0076] In a fifth aspect, the present application provides a drilling fluid containing the cross-linked polymer described above.

[0077] In a sixth aspect, the present application provides a completion fluid containing the cross-linked polymer described above.

[0078] Based on the above technical solutions, the present application has the following advantages:

[0079] The random terpolymer obtained by optimizing the cross-linking system can significantly improve the viscosity retention rate of the cross-linked polymer at high temperature, and can enhance the salt resistance (resistance to NaCl saturation, resistance to CaCl2 saturation), and also has good rock carrying performance. DETAILED DESCRIPTION

[0080] To make the objectives, technical solutions and advantages of the present application clearer, the technical solutions in the present application will be described clearly and completely below. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0081] Unless otherwise specified, the various raw materials used in the embodiments are commercially available conventional raw materials, and the technical means used is conventional means well known to those skilled in the art.

[0082] Embodiment 1

[0083] This embodiment provides a cross-linked polymer, the structural formula of which is as follows:

[0084]

[0085] This embodiment further provides a preparation method of the cross-linked polymer described above, comprising the following steps:

[0086] In a flask, 20 g of acrylic acid, 10 g of sodium diallyl aminomethyl phosphonate, 2 g of N-vinyl caprolactam, 70 g of water were added, and stirred well to obtain a uniform solution to obtain an aqueous phase. 64 g of 7 # The white oil was added to a beaker, 0.54 g of Span 80, 0.1 g of Tween 60 were added, and stirred well to obtain an oil phase. Then the oil phase was added to the flask, mixed with the aqueous phase, and stirred well for 30 min to obtain an emulsion. 0.016 g of potassium persulfate was completely dissolved in 10 g of water, and the emulsion was mixed with the aqueous solution of potassium persulfate under a nitrogen atmosphere at 45°C to obtain a reaction solution. When the temperature of the reaction solution dropped to 45°C, 0.0032 g of 1,6-dibromohexane was added to the reaction solution, and the reaction was continued for 2 h, and then the reaction was stopped. The obtained product was a cross-linked polymer.

[0087] The preparation method of the sodium diallyl aminomethyl phosphonate comprises the following steps:

[0088] In a reaction vessel, 15 g of phosphorous acid, 14 mL of anhydrous ethanol, and 6 mL of concentrated sulfuric acid (98 wt%) were added in sequence to adjust the pH of the system to 1, and then the reaction vessel was placed in an ice water bath. A constant drop funnel was used to add 8.6 mL of diallylamine dropwise, and the addition was completed in 45 min. After the addition was completed, the reaction was continued for 3 h. Then a mixture of 15 g of trioxane and 14 mL of anhydrous ethanol was added to the constant drop funnel, and the addition was completed in 40 min. After the addition was completed, the reaction was continued for 4 h. 6.0 g of NaOH was added to the system to adjust the pH of the system to 7, and the reaction was continued at 20°C for 3 h. After further centrifugal separation, the obtained solid material was further dried at 90°C for 10 h to obtain the target product, sodium diallyl aminomethyl phosphonate solid powder.

[0089] Example 2

[0090] This example provides a cross-linked polymer, the structural formula of which is as follows:

[0091]

[0092] This example further provides a preparation method of the cross-linked polymer, comprising the following steps:

[0093] In a flask, 20 g of acrylic acid, 20 g of calcium diallyl aminomethyl phosphonate, 10 g of N-vinyl caprolactam, 73 g of water were added, and stirred well to obtain a uniform solution to obtain an aqueous phase. 83 g of 5 #White oil into a beaker, add 2.2g Span80, 0.3g Tween60, stir until uniform, get oil phase. Then the oil phase into the flask, mixed with water phase, fully stirred 30min, get emulsion. 0.05g ammonium persulfate completely dissolved in 10g water, under the condition of nitrogen atmosphere, 60℃, the emulsion mixed with ammonium persulfate solution to react, get reaction liquid. When the temperature of the reaction liquid dropped to 50℃, 0.01g 1,7 dibromoheptane was added to the reaction liquid, continue to react 2h, stop the reaction, the product is crosslinked polymer.

[0094] The preparation method of the calcium diallyl aminomethyl phosphonate is the same as that of the sodium diallyl aminomethyl phosphonate, and the only difference is that the alkaline reagent used for adjusting the pH of the system to neutral is Ca(OH)2.

[0095] Example 3

[0096] This example provides a crosslinked polymer, the structural formula of which is as follows:

[0097]

[0098] This example further provides a preparation method of the crosslinked polymer, comprising the following steps:

[0099] In a flask, add 10g acrylic acid, 30g sodium diallyl aminomethyl phosphonate, 10g N-vinyl caprolactam, 40g water, fully stirred until the solution is uniform, get water phase. Weigh 48g 7 # White oil into a beaker, add 4.5g Span80, 0.5g op10, stir until uniform, get oil phase. Then the oil phase into the flask, mixed with water phase, fully stirred 30min, get emulsion. 0.25g azobisdimethylimidazole hydrochloride completely dissolved in 10g water, under the condition of nitrogen atmosphere, 45℃, the emulsion mixed with azobisdimethylimidazole hydrochloride solution to react, get reaction liquid. When the temperature of the reaction liquid dropped to 60℃, 0.025g 1,8 dibromo octane was added to the reaction liquid, continue to react 2h, stop the reaction, the product is crosslinked polymer.

[0100] Example 4

[0101] This example provides a crosslinked polymer, the structural formula of which is the same as that of example 1, and the preparation method thereof comprises the following steps:

[0102] In a flask, add 20g acrylic acid, 10g sodium diallyl aminomethyl phosphonate, 2g N-vinyl caprolactam, 85g water, fully stirred until the solution is uniform, get water phase. Weigh 75g 7 #White oil into a beaker, add 1.4g Span80, 0.2g Tween60, stirring evenly, get oil phase. Then the oil phase into a flask, mixed with water, stirring for 30min, get emulsion. 0.064g potassium persulfate completely dissolved in 10g water, under the condition of nitrogen atmosphere, 45℃, the emulsion and potassium persulfate solution mixed with reaction, get reaction liquid. When the temperature of the reaction liquid dropped to 45℃, 0.0032g 1,6 dibromohexane was added to the reaction liquid, continue to react 2h, stop the reaction, the product is crosslinked polymer.

[0103] Example 5

[0104] The comparative example provides a crosslinked polymer, its preparation method is the same with example 1, the difference is only: 1,6 dibromohexane is replaced by N,N methylene bisacrylamide.

[0105] Comparative example 1

[0106] The comparative example provides a crosslinked polymer, its preparation method is the same with example 1, the difference is only: phosphonate monomer is replaced by dimethyl diallyl ammonium chloride.

[0107] In order to further illustrate the technical effect of the present application, the above examples and comparative examples are also given in the effect test in practical application.

[0108] Test example

[0109] The crosslinked polymer prepared by the above examples and comparative examples is evaluated as follows:

[0110] 1, tackifying and temperature resistance performance test

[0111] Preparation of polymer solution: 3.5g crosslinked polymer prepared by example or comparative example was added into 350mL deionized water, stirring at 8000r / min for 20min, to get polymer solution sample.

[0112] Performance test: the apparent viscosity of polymer solution was measured by six speed viscometer at room temperature according to the method specified in national standard GB / T 16783.1-2006. After the measurement, the polymer solution was transferred to high temperature roller furnace, and aged at 180℃ for 16h. After aging, the apparent viscosity of polymer solution after aging was measured after stirring at 8000r / min for 20min when the solution temperature dropped to room temperature. The apparent viscosity data before and after aging is shown in table 1.

[0113] Table 1 polymer tackifying and temperature resistance performance test results

[0114]

[0115]

[0116] 2. Salt resistance test

[0117] Preparation of polymer saturated salt solution: under stirring, NaCl was added into 350 mL deionized water until the solution could not dissolve NaCl any more, and then a saturated NaCl solution was obtained. 3.5 mL polymer sample was added into 350 mL saturated NaCl solution, and stirred at 8000 r / min for 20 min to obtain a polymer saturated NaCl solution. The polymer saturated CaCl2 solution was prepared in the same way as the polymer saturated NaCl solution.

[0118] Performance test: the apparent viscosity of the polymer solution was determined at room temperature by using a six-speed viscometer according to the method specified in GB / T 16783.1-2006. After the determination, the polymer solution was transferred into a high-temperature roller oven, and aged at 180℃ for 16 h. After the aging, the apparent viscosity of the polymer solution after aging was determined after the solution temperature was reduced to room temperature and stirring at 8000 r / min for 20 min. The apparent viscosity data of the polymer saturated NaCl solution and the polymer saturated CaCl2 solution before and after aging are shown in Tables 2 and 3, respectively.

[0119] Table 2. Polymer anti-NaCl performance test results

[0120]

[0121]

[0122] Table 3. Polymer anti-CaCl2 performance test results

[0123]

[0124] From the data in Tables 1-3, it can be seen that the crosslinked polymer prepared in the application has excellent tackifying, salt resistance and gel strength performance, and still has a high viscosity retention rate after aging at 180℃ for 16 h. The polymer can maintain good tackifying performance in the saturated salt solution, and the apparent viscosity of the solution after aging is much higher than that of the data in the comparative examples. In addition, the shear force of the polymer aqueous solution remains at a high level before and after aging, indicating that the crosslinked polymer prepared in the application has good proppant carrying performance.

[0125] It should be pointed out finally that the above embodiments are only used to illustrate the technical solutions of the present application, but not to limit the same; and although the present application has been described in detail with reference to the foregoing embodiments, it should be appreciated by those skilled in the art that the technical solutions recorded in the foregoing embodiments can be modified, or some technical features thereof can be replaced equivalently; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A crosslinked polymer, characterized in that, The crosslinked polymer includes structural unit A, structural unit B, structural unit C, and crosslinking unit; Wherein, structural unit A is Structural unit B is ; Structural unit C is ; Wherein, M represents a metal bonded to a phosphonic acid group in the form of an ionic bond, and m is the valence state of M; based on the total amount of the crosslinked polymer, the content of the crosslinking unit is 0.01wt%~0.05wt%, the content of structural unit A is 30wt%~60wt%, the content of structural unit B is 25wt%~45wt%, and the content of structural unit C is 10wt%~30wt%.

2. The crosslinked polymer according to claim 1, characterized in that, The structural formula of the crosslinked polymer is: ； Where M represents a metal bonded to a phosphonic acid group by an ionic bond, m represents the valence state of M, and n represents the number of carbon atoms, 1≤n≤25; The method for preparing the crosslinked polymer includes: performing reverse emulsion polymerization of diallylaminomethylphosphonate, acrylic acid and N-vinylcaprolactam to obtain a polymer; and then using a dihaloalkane as a crosslinking agent to crosslink the polymer to obtain the crosslinked polymer.

3. The crosslinked polymer according to claim 1, characterized in that, M is one of a monovalent metal, a divalent metal, a trivalent metal, or a tetravalent metal.

4. The crosslinked polymer according to claim 3, characterized in that, M is a metal in group IA, and m is 1.

5. The crosslinked polymer according to claim 4, characterized in that, M represents sodium or potassium.

6. The crosslinked polymer according to claim 3, characterized in that, M is a divalent metal, and m is 2.

7. The crosslinked polymer according to claim 6, characterized in that, M is selected from one or more of magnesium, calcium, copper, and iron.

8. The crosslinked polymer according to claim 3, characterized in that, M is one of the trivalent metals, and m is 3.

9. The crosslinked polymer according to claim 8, characterized in that, M represents iron or aluminum.

10. The crosslinked polymer according to claim 3, characterized in that, M is one of the tetravalent metals, and m is 4.

11. The crosslinked polymer according to claim 10, characterized in that, M represents titanium or zirconium.

12. The crosslinked polymer according to any one of claims 2 to 11, characterized in that, The crosslinking units are C1~C 25 Straight-chain alkyl groups.

13. The crosslinked polymer according to claim 12, characterized in that, The crosslinking unit is C6~C 10 Straight-chain alkyl groups.

14. The crosslinked polymer according to claim 2, characterized in that, The dihaloalkane is selected from one of 1,6-dibromohexane, 1,7-dibromoheptane, 1,8-dibromooctane, 1,9-dibromononane, and 1,10-dibromodecane.

15. The crosslinked polymer according to claim 14, characterized in that, The amount of the dihaloalkane used is 0.1 wt‰ to 0.5 wt‰ of the total mass of diallylaminomethylphosphonate, acrylic acid, and N-vinylcaprolactam.

16. The crosslinked polymer according to claim 2, characterized in that, The mass ratio of diallylaminomethylphosphonate, acrylic acid, and N-vinylcaprolactam is (0.5~3):(1~5):(0.1~1).

17. The crosslinked polymer according to claim 2, characterized in that, The method for preparing the crosslinked polymer includes: S1: Diallylaminomethylphosphonate, acrylic acid, N-vinylcaprolactam and water are mixed to obtain an aqueous phase; S2: Mix the emulsifier with white oil to obtain an oil phase; then mix the oil phase with the aqueous phase and stir to obtain an emulsion; S3: Under a nitrogen atmosphere and at a temperature of 40℃~80℃, the emulsion is mixed with an initiator aqueous solution to react and obtain a reaction solution; S4: Under a nitrogen atmosphere and at a temperature of 40℃~80℃, the reaction solution is mixed with a dihaloalkanes and reacted. The product obtained after the reaction is complete is the cross-linked polymer.

18. The crosslinked polymer according to claim 17, characterized in that, In S1, the total mass ratio of diallylaminomethylphosphonate, acrylic acid, and N-vinylcaprolactam to the mass ratio of water is (0.3~1.3):

1.

19. The crosslinked polymer according to claim 17, characterized in that, In S2, the emulsifier is selected from one or more of OP10, Span80, and Tween60.

20. The crosslinked polymer according to claim 19, characterized in that, In S2, the emulsifier is a composite emulsifier of span80 and op10 in a mass ratio of (5~10):1; or, the emulsifier is a composite emulsifier of span80 and tween60 in a mass ratio of (5~10):

1.

21. The crosslinked polymer according to claim 19, characterized in that, The amount of emulsifier used is 2 wt% to 10 wt% of the total mass of diallylaminomethylphosphonate, acrylic acid and N-vinylcaprolactam.

22. The crosslinked polymer according to any one of claims 17 to 21, characterized in that, In S2, the white oil is industrial white oil.

23. The crosslinked polymer according to claim 22, characterized in that, The industrial white oil is selected from one or more of the following: No. 3 industrial white oil, No. 5 industrial white oil, No. 7 industrial white oil, No. 10 industrial white oil, No. 15 industrial white oil, No. 20 industrial white oil, No. 22 industrial white oil, No. 26 industrial white oil, No. 32 industrial white oil, No. 48 industrial white oil, and No. 64 industrial white oil.

24. The crosslinked polymer according to claim 22, characterized in that, The mass ratio of the white oil to the water in S1 is (0.8~1.2):

1.

25. The crosslinked polymer according to any one of claims 17 to 21, characterized in that, In S3, the initiator is selected from inorganic peroxide initiators and / or azo initiators.

26. The crosslinked polymer according to claim 25, characterized in that, The inorganic peroxide initiator includes one or more of potassium persulfate, sodium persulfate, and ammonium persulfate; the azo initiator includes one or more of azobisisobutyronitrile, azobisisoheptanenitrile, dimethyl azobisisobutyrate, azobisisobutyramidine hydrochloride, and azobisisobutyramidazole hydrochloride.

27. The crosslinked polymer according to claim 25, characterized in that, The initiator is used in an amount of 0.5 wt‰ to 5 wt‰ of the total mass of diallylaminomethylphosphonate, acrylic acid, and N-vinylcaprolactam.

28. The use of the crosslinked polymer according to any one of claims 1 to 27 in drilling fluid or completion fluid.

29. The application according to claim 28, characterized in that, The cross-linked polymer serves as a thickener.

30. The application according to claim 29, characterized in that, When used as a thickener, the crosslinked polymer is used in drilling or completion fluids at amounts of 3 to 30 g / L, which may be the same or different.

31. A drilling fluid, characterized in that, It contains the crosslinked polymer as described in any one of claims 1 to 27.

32. A completion fluid, characterized in that, It contains the crosslinked polymer as described in any one of claims 1 to 27.

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