Betaine type hydrophobic association polymer oil-displacing agent with cyclic structure and preparation method of betaine type hydrophobic association polymer oil-displacing agent

Abstract

The invention relates to a betaine type hydrophobic associated polymer oil-displacing agent with a cyclic structure and a preparation method thereof, the oil-displacing agent is prepared by the following steps: copolymerizing four monomers of acrylamide, 2-allyl methylamino sodium ethanesulfonate, N-vinylpyrrolidone and long-chain alkyl diallyl sulfoethyl betaine CnDASBA which is a hydrophobic monomer with a betaine structure to form gel, chopping the gel, adding a catalyst, and stirring to obtain the betaine type hydrophobic associated polymer oil-displacing agent with the cyclic structure. Hydrolyzing in a sodium carbonate solution, neutralizing after hydrolysis, and purifying to obtain a final product. The preparation method comprises the following steps: firstly adding distilled water, then adding acrylamide, sodium 2-allylmethylamino ethanesulfonate and other remaining raw materials, supplementing water, adjusting the total concentration, introducing N2 to remove oxygen, adding an initiator, reacting to prepare gel, chopping the gel, and hydrolyzing to obtain the oil-displacing agent. The oil-displacing agent disclosed by the invention has relatively good water solubility, shows good salt resistance in saline water of which the mineralization degree is greater than or equal to 30000 mg / L, shows a good oil-displacing effect in a simulated oil-displacing experiment under a heterogeneous core condition, and can improve the crude oil recovery rate by 10% or above.

Description

Technical Field

[0001] The present invention relates to an oil recovery auxiliary agent, in particular to a hydrophobically associating polymer oil-displacing agent having a cyclic betaine structure and a hydrophobic group, specifically to a betaine-type hydrophobically associating polymer oil-displacing agent having a cyclic structure. The present invention also relates to a preparation method of the betaine-type hydrophobically associating polymer oil-displacing agent having a cyclic structure. Background Art

[0002] In order to slow down the decline of old oil fields and the shortage of crude oil production, some oil companies have carried out polymer flooding on a large scale, and both the application scale and oil increase effect have reached a good level. Artificially synthesized partially hydrolyzed polyacrylamide (HPAM) has been the most widely used. As the main agent of polymer flooding in tertiary oil recovery, HPAM has been widely used in many domestic oil fields. HPAM has achieved excellent oil recovery effects in low-mineralization reservoirs, but it also has certain deficiencies and shortcomings. The salt and temperature resistance is poor, which seriously affects the application scope of polymer flooding technology. Therefore, it is urgent to develop heat-resistant, salt-resistant and shear-resistant polymers to meet the needs. The most commonly used method is to modify acrylamide copolymers to enable them to withstand harsh conditions. Hydrophobic associating polymers are one of the modified products. Hydrophobic associating polymers refer to a class of polymers with a small amount of hydrophobic groups on the hydrophilic chain of the polymer (Dai Leiyang, Guo Xinwei, Wang Jian, et al. Synthesis and properties of AM / AMPS / DM-16 hydrophobic associating polymers [J]. Fine Petrochemicals, 2015, 32(1): 10-14). In aqueous solution, due to the presence of hydrophobic groups, intramolecular and intermolecular associations can occur to form a spatial network structure with good viscosity enhancement, temperature resistance and salt resistance. At present, hydrophobic associating polymers have been successfully applied in the efficient development of offshore oil fields (Sun Fujie. Current status and prospects of efficient development and enhanced recovery technology of China's offshore oil fields [J]. China Offshore Oil and Gas, 2023, 35(5): 91-99).

[0003] Related patent literature: CN1405266A discloses a method for preparing a highly tackifying hydrophobically associating polymer oil-displacing agent, which is characterized in that acrylamide (AM)-sodium acrylate (NaAA)-N-p-butylphenyl acrylamide (BPAM) hydrophobically associating water-soluble polymer is prepared into a solution with a concentration of 0.1-0.3wt%, a surfactant concentration of 0.01-1mmol / L and a NaCl concentration of 0.5-1.5wt%, and then added into a mixing kettle with a stirrer and a thermometer, and stirred evenly at a temperature of 25-40°C to obtain a highly tackifying hydrophobically associating water-soluble polymer oil-displacing agent. It has unique solution properties such as tackifying, salt resistance and shear resistance, and has good prospects for implementation in the development of high-salinity and high-shear oil reservoirs. CN105199043A discloses a water-soluble hydrophobic associating polymer and a preparation method thereof. The polymer raw material formula is as follows: by mass percentage, 16% to 26% acrylamide, 0.08% to 0.1% hydrophobic monomer, 2.6% to 9% hydrophilic monomer, 0.03% to 0.08% persulfate, 3% to 5% sodium dodecyl sulfate, 0.002% to 0.004% defoamer, and 60% to 81.3% deionized water. The water-soluble hydrophobic associating polymer of the invention has better heat resistance, salt resistance and shear resistance than the existing polyacrylamide, and can be used as an tertiary oil recovery oil displacement agent. CN 110229272A discloses a hydrophobic associating polymer for oil field fracturing and improving oil recovery and a preparation method thereof. The technical scheme is as follows: (1) reacting a long carbon chain methacrylate with a dimethylamine aqueous solution at a molar ratio of 1:1-3 at 20-60°C for 12 hours, removing excess dimethylamine aqueous solution by rotary evaporation to obtain a long chain tertiary amine; adding the obtained tertiary amine and allyl chloride in a molar ratio of 2-3:1 to acetone, reacting at 20-60°C for 12 hours, and recrystallizing to obtain a hydrophobic monomer; (2) preparing a 20-30% solution with acrylamide and a hydrophobic monomer, passing nitrogen for 30 minutes, heating to 40-60°C, adding an initiator, reacting for 4-8 hours, separating, purifying, and drying to obtain a hydrophobic associating polymer. CN106986965A discloses a hydrophobic associating polymer for oilfield fracturing fluid and improving oil recovery and a preparation method thereof, wherein the hydrophobic associating polymer is a thickener. The preparation method comprises: (1) dissolving 0.2 mol of dibromoethane in acetone, adding 0.1 mol of dimethylaminoethyl methacrylate dropwise into the acetone solution under stirring conditions, reacting at room temperature for 4 hours to obtain an N,N-dimethylbromoethyl methacryloyloxyethyl ammonium bromide intermediate; (2) adding 0.05 mol of the intermediate and 0.055 mol of erucic acid amide propyl dimethyl tertiary amine into ethanol, reacting at room temperature for 24 hours to obtain a polymerizable hydrophobic monomer; (3) adding the hydrophobic monomer and acrylamide into deionized water, passing nitrogen for half an hour, heating to 45-60°C, adding an initiator, and performing a polymerization reaction for 6-8 hours to obtain a hydrophobic associating polymer.The associative polymer has good viscosity increasing ability and is easy to prepare, and has good application prospects in oil field fracturing fluid and improving oil recovery.

[0004] The hydrophobic associating polymers synthesized (or prepared) by the above technology have certain temperature and salt resistance, and have good viscosity increasing ability below the mineralization degree of 30000 mg / L, but their salt resistance is poor when the mineralization degree is ≥30000 mg / L. Some hydrophobic associating polymers contain ester groups that are easily hydrolyzed at high temperature and high mineralization, and have poor long-term stability. Summary of the invention

[0005] The purpose of the present invention is to provide a betaine-type hydrophobic associating polymer oil-displacing agent with a cyclic structure, which has good performance, good viscosity increasing ability under high temperature and high salinity, and good shear resistance, can achieve a higher recovery rate, and can meet the technical requirements of a polymer oil-displacing agent with a wide range of uses on the market, thereby ensuring the smooth progress of oil production in high-temperature and high-salinity oil fields, and solving the problems that the existing hydrophobic associating polymer has poor temperature and salt resistance in brine with high salinity (mineralization ≥30000 mg / L), is easily hydrolyzed underground, and has a low crude oil recovery rate.

[0006] To this end, another object of the present invention is to provide a method for preparing a betaine-type hydrophobically associating polymer oil-displacing agent having a cyclic structure.

[0007] In order to solve the above technical problems, the technical solution adopted by the present invention is as follows:

[0008] A betaine-type hydrophobic associating polymer oil-displacing agent with a ring structure, the technical scheme of which is that it is composed of acrylamide AM, 2-allylmethylaminoethylsulfonic acid sodium AMES-Na, N-vinyl pyrrolidone (i.e. N-vinyl pyrrolidone) NVP and a betaine-structured hydrophobic monomer long-chain alkyl diallyl sulfoethyl betaine C n The four monomers of DASBA are copolymerized to form a gel. After the reaction is completed, the gel is chopped and hydrolyzed in an appropriate amount of sodium carbonate solution. After the hydrolysis, the final product is neutralized and purified to obtain the polymer oil-displacing agent. The structural formula of the polymer oil-displacing agent is as follows:

[0009]

[0010] In the above structural formula, x, y, z, p, q are the molar percentage ranges of the structural units: x = 63% to 84.5%, y = 10% to 20%, z = 5% to 15%, p = 0.3% to 1%, q = 0.2% to 1%, x + y + z + p + q = 100%. Wherein n = 12, 14, 16, 18, 20.

[0011] In the betaine-type hydrophobic associating polymer oil-displacing agent having a cyclic structure, the molar proportions of the monomer additions (ratios) are as follows (i.e., the oil-displacing agent is made of the following molar proportions of monomers): 83-94.5 parts of acrylamide AM, 5-15 parts of 2-allylmethylaminoethylsulfonic acid sodium AMES-Na, 0.3-1 parts of N-vinylpyrrolidone NVP, 0.1-0.2 parts of long-chain alkyl diallyl sulfoethyl betaine C having a betaine structure hydrophobic monomer, n DASBA 0.2~1 part.

[0012] The preparation method of the 2-allylmethylaminoethanesulfonic acid sodium AMES-Na comprises the following process steps: adding an appropriate amount of anhydrous ethanol as a solvent to a (500 mL) three-necked flask equipped with a thermometer, a reflux condenser with a Soxhlet extractor and a magnetic rotor, adding 65-95 g of sodium 2-chloroethylsulfonate at room temperature, then slowly adding 30-43 g of N-methylallylamine under stirring, adding 0.15-0.21 g of methylhydroquinone as an inhibitor, and charging 32-47 g of an acid binding agent wrapped with filter paper into the Soxhlet extractor, raising the temperature to reflux, reacting at a constant temperature for 20-25 hours, and removing the solvent and excess N-methylallylamine by reduced pressure distillation using a rotary evaporator to obtain 2-allylmethylaminoethanesulfonic acid sodium AMES-Na.

[0013] The above-mentioned hydrophobic monomer long-chain alkyl diallyl sulfoethyl betaine C having a betaine structure n The preparation method of DASBA comprises the following process steps: (1) adding an appropriate amount of anhydrous ethanol as a solvent to a three-necked flask (500 mL) equipped with a thermometer, a reflux condenser with a Soxhlet extractor and a magnetic rotor, adding 80 to 105 g of a chlorinated long-chain alkane at room temperature (23 to 25° C.) and with magnetic stirring on, then slowly adding 33 to 45 g of diallylamine under stirring, adding 0.14 to 0.25 g of a polymerization inhibitor methyl hydroquinone, placing 30 to 36 g of an acid binding agent wrapped with filter paper in the Soxhlet extractor, raising the temperature to reflux, reacting at constant temperature for 20 to 25 hours, removing the solvent and excess diallylamine by reduced pressure distillation using a rotary evaporator, and taking The polymerization inhibitor is separated by distilled water and dried to obtain a long-chain alkyl diallylamine; (2) in a three-necked flask (500 mL) equipped with a thermometer, a reflux condenser and a magnetic rotor, an appropriate amount of anhydrous ethanol is added as a solvent, 80-100 g of the long-chain alkyl diallylamine is added at room temperature and with magnetic stirring, and then 45-60 g of sodium 2-chloroethylsulfonate is slowly added under stirring, and 0.16-0.3 g of the polymerization inhibitor methyl hydroquinone is added, the temperature is raised to reflux, and the reaction is carried out at a constant temperature for 10-15 hours, and the solvent is removed by reduced pressure distillation using a rotary evaporator, and acetone is used for separation and purification to obtain a long-chain alkyl diallyl sulfoethyl betaine C having a betaine structure hydrophobic monomer nDASBA.

[0014] The preparation method of the betaine-type hydrophobic associating polymer oil-displacing agent with a ring structure comprises the following process steps: firstly, 1000-1500 mole parts of distilled water are added into a reactor, and 83-94.5 mole parts of acrylamide AM, 5-15 mole parts of 2-allylmethylaminoethylsulfonic acid sodium AMES-Na, 0.3-1 mole part of N-vinylpyrrolidone NVP, long-chain alkyl diallyl sulfoethyl betaine C having a betaine structure hydrophobic monomer are added in sequence under stirring. n DASBA 0.2-1 molar part, and then distilled water is added to control the total mass percentage concentration of the reaction monomers to be between 15% and 30% (the total mass percentage concentration of the reaction monomers is the mass percentage concentration of the above four monomers combined, the same below), and after stirring evenly (stirring the solution until the solution is a nearly transparent homogeneous system), N2 is passed for 30-35 minutes, and then an initiator is added, and N2 is continued to be passed, and the reaction is carried out for 4-10 hours under nitrogen protection and 30-60°C. The above reaction monomers are the above four monomers; after the reaction, the obtained gel-like product, i.e., the copolymer, is chopped, sodium carbonate solution is added, and then distilled water is added to dilute the copolymer to a mass percentage of 5%-8%, and the hydrolysis reaction is carried out at a temperature of 85-90°C for 1.5-2.5 hours. After the reaction, dilute hydrochloric acid is used for neutralization; then the product is washed with anhydrous ethanol, and the product is crushed and dried to obtain partially hydrolyzed AM / AMES / NVP / C n The DASBA tetrapolymer is a betaine-type hydrophobic associating polymer oil displacement agent having a ring structure after hydrolysis.

[0015] In the above technical scheme, the preferred technical scheme may be that the initiator is a composite initiator, including an oxidation-reduction system initiator and a water-soluble azo initiator. In the oxidation-reduction system initiator, the oxidant is potassium persulfate or ammonium persulfate, the reductant is sodium bisulfite, and the molar ratio of the oxidant to the reductant is 1:1 to 1.5; the water-soluble azo initiator is one or a combination of azobisisobutylamidine hydrochloride (V-50), azobisisobutylimidazoline hydrochloride (VA-044), and azobis(N-2-carboxyethyl-2-methylpropionamidine) hydrate (VA-057), and the ratio is arbitrary when combined; in the composite initiator, the mass ratio of the oxidation-reduction system initiator to the water-soluble azo initiator is 1:1 to 2.

[0016] In the above technical solution, the preferred technical solution can also be that the hydrophobic monomer long-chain alkyl diallyl sulfoethyl betaine C having a betaine structure nIn DASBA, the long-chain alkyl group is hexadecyl; the chlorinated long-chain alkane in step (1) is hexadecyl chloride, the intermediate long-chain alkyl diallylamine is hexadecyl diallylamine, and the final product in step (2) is hexadecyl diallyl sulfoethyl betaine C having a betaine structure hydrophobic monomer 16 DASBA. See Example 1.

[0017] In the above technical solution, the preferred technical solution can also be that the hydrophobic monomer long-chain alkyl diallyl sulfoethyl betaine C having a betaine structure n In DASBA, the long-chain alkyl group is octadecyl; in step (1), the chlorinated long-chain alkane is octadecyl chloride, the intermediate long-chain alkyl diallylamine is octadecyl diallylamine, and the final product in step (2) is octadecyl diallyl sulfoethyl betaine C having a betaine structure hydrophobic monomer 18 DASBA. See Example 2.

[0018] In the above technical scheme, a preferred technical scheme can also be that the acid binding agent is potassium carbonate or sodium carbonate, etc.; the added amount of the above initiator is 0.05% to 0.2% of the total mass of the reaction monomers, and the total mass of the reaction monomers is the total mass of the four monomers mentioned above; the mass fraction of the above dilute hydrochloric acid can be 5%; the added amount of the above sodium carbonate solution is 45% to 75% of the weight (mass) of the acrylamide monomer, and the sodium carbonate solution is a sodium carbonate aqueous solution with a mass percentage concentration of 15% to 20%.

[0019] Among the above technical solutions, a preferred technical solution may also be Embodiment 1 of the present invention.

[0020] The polymer oil displacement agent of the present invention is composed of acrylamide AM, 2-allylmethylaminoethylsulfonate AMES-Na, N-vinylpyrrolidone NVP and a long-chain alkyl diallyl sulfoethyl betaine C having a betaine structure hydrophobic monomer. nThe four monomers of DASBA are copolymerized to form a gel. After the reaction is completed, the gel is chopped and hydrolyzed in an appropriate amount of sodium carbonate solution. After the hydrolysis, it is neutralized and purified to obtain the final product. Preparation method: First add an appropriate amount of distilled water to the reactor, then add acrylamide, sodium 2-allylmethylaminoethanesulfonate, N-vinyl pyrrolidone, and a long-chain alkyl diallyl sulfoethyl betaine, a hydrophobic monomer with a betaine structure, in sequence, and then add the remaining water. After stirring evenly, after deoxygenation through N2, an initiator is added, and at a certain temperature, the copolymer gel is reacted to obtain the copolymer gel. After the reaction is completed, the gel is chopped and hydrolyzed in an appropriate amount of sodium carbonate solution. After the hydrolysis, it is neutralized and purified to obtain the final product. The present invention introduces a hydrophobic chain with a ring structure into the polymer chain, which improves the viscosity increasing ability, temperature resistance, and salt resistance of the polymer; by introducing a ring structure to increase the rigidity of the molecular chain, the thermal stability and shear resistance of the polymer are improved. Sulfonic acid groups are introduced into the molecular chain to improve the water solubility and salt resistance of the polymer, meeting the actual construction needs of the injection water with a salinity of ≥30000 mg / L on site. The polymer oil-displacing agent prepared by the present invention has good water solubility, exhibits good salt resistance in salt water with a salinity of ≥30000 mg / L, and shows good oil-displacing effect in oil-displacing experiments, which can increase the crude oil recovery rate by more than 10%.

[0021] Compared with the prior art, the present invention has the following effects: (1) by introducing the five-membered ring, the rigidity of the polymer molecular chain is greatly enhanced and the hydrophobic association between the copolymer molecules is increased, thereby greatly increasing the viscosity-increasing performance of the polymer and greatly improving the temperature resistance and shear resistance of the polymer; (2) the introduction of the sulfonic acid group improves the water solubility and salt resistance of the polymer; (3) the polymer exhibits good temperature resistance, salt resistance and shear resistance, and can better improve the crude oil recovery rate.

[0022] Referring to the experimental (test) part of the present invention below, in summary, the present invention provides a (water-soluble) betaine-type hydrophobic associating polymer oil-displacing agent with a cyclic structure, which has good performance, good viscosity increasing ability at high temperature and high salinity, and good shear resistance, can achieve a higher recovery rate, and meets the technical requirements of polymer oil-displacing agents with a wide range of uses on the market, thereby ensuring the smooth progress of oil production in high-temperature and high-salinity oil fields, and solving the problems of poor temperature and salt resistance of existing hydrophobic associating polymers in brine with high salinity (mineralization ≥30000 mg / L), easy hydrolysis underground, and low crude oil recovery rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is the infrared spectrum of the copolymer (oil-displacing agent) synthesized (prepared) in Example 1 of the present invention.

[0024] Figure 2Graph showing the relationship between the apparent viscosity of the copolymer (oil displacing agent) synthesized in Example 1 of the present invention and the change in concentration.

[0025] Figure 3 Graph showing the relationship between the apparent viscosity of the copolymer (oil displacing agent) synthesized in Example 1 of the present invention and the change in temperature.

[0026] Figure 4 The figure is a relationship diagram of the apparent viscosity of the copolymer (oil displacement agent) synthesized in Example 1 of the present invention as a function of the salinity.

[0027] Figure 5 Graph showing the relationship between the apparent viscosity of the copolymer (oil displacing agent) synthesized in Example 1 of the present invention and the shear rate.

[0028] Figure 6 This is a diagram of the oil displacement efficiency of the copolymer (oil displacement agent) synthesized in Example 1 of the present invention. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described in conjunction with the embodiments below. Obviously, the described embodiments are part of the embodiments of the present invention, not all of them. Based on this embodiment, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of the present invention.

[0030] Example 1: The betaine-type hydrophobic associating polymer oil displacement agent with a cyclic structure of the present invention is composed of acrylamide AM, 2-allylmethylaminoethylsulfonate sodium AMES-Na, N-vinylpyrrolidone NVP and a long-chain alkyl diallyl sulfoethyl betaine C having a betaine structure hydrophobic monomer n The four monomers of DASBA are copolymerized to form a gel. After the reaction is completed, the gel is chopped and hydrolyzed in an appropriate amount of sodium carbonate solution. After the hydrolysis, the final product is neutralized and purified to obtain the polymer oil-displacing agent. The structural formula of the polymer oil-displacing agent is as follows:

[0031]

[0032] In the above structural formula, x, y, z, p, and q are the molar percentage ranges of the structural units: x = 63% to 84.5%, y = 10% to 20%, z = 5% to 15%, p = 0.3% to 1%, q = 0.2% to 1%, and x + y + z + p + q = 100%. Wherein n = 12, 14, 16, 18, 20. In this embodiment, n = 14.

[0033] Specifically, the (water-soluble) betaine-type hydrophobic associating polymer oil-displacing agent having a ring structure is prepared from the following monomers in molar fractions: 88.26 parts of acrylamide AM, 10.82 parts of 2-allylmethylaminoethylsulfonic acid sodium AMES-Na, 0.49 parts of N-vinylpyrrolidone NVP, and a long-chain alkyl diallyl sulfoethyl betaine C having a betaine structure hydrophobic monomer. n DASBA 0.43 parts.

[0034] The above-mentioned hydrophobic monomer long-chain alkyl diallyl sulfoethyl betaine C having a betaine structure n In DASBA, the long-chain alkyl group is hexadecyl; in the following step (1), the chlorinated long-chain alkane is hexadecyl chloride, the intermediate long-chain alkyl diallylamine is hexadecyl diallylamine, and the final product in the following step (2) is hexadecyl diallyl sulfoethyl betaine C having a betaine structure hydrophobic monomer 16 DASBA.

[0035] The preparation method of the above-mentioned 2-allylmethylaminoethanesulfonic acid sodium AMES-Na comprises the following process steps: in a 500mL three-necked flask equipped with a thermometer, a reflux condenser with a Soxhlet extractor and a magnetic rotor, 180mL of anhydrous ethanol is added as a solvent, 70g of sodium 2-chloroethylsulfonate is added at 25°C, and then 32g of N-methylallylamine is slowly added under stirring, 0.16g of methylhydroquinone as an inhibitor is added, 35g of potassium carbonate (acid binding agent) wrapped with filter paper is loaded into the Soxhlet extractor, the temperature is increased to reflux, and after constant temperature reaction for 23 hours, the solvent and excess N-methylallylamine are removed by reduced pressure distillation using a rotary evaporator to obtain 2-allylmethylaminoethanesulfonic acid sodium AMES-Na.

[0036] The above hydrophobic monomer hexadecyl diallyl sulfoethyl betaine C having a betaine structure 16The preparation method of DASBA comprises the following process steps: (1) adding 200 mL of anhydrous ethanol as a solvent to a 500 mL three-necked flask equipped with a thermometer, a reflux condenser with a Soxhlet extractor and a magnetic rotor, adding 95 g of chlorohexadecane at a temperature of 25° C. and with magnetic stirring on, then slowly adding 40 g of diallylamine under stirring, adding 0.18 g of methyl hydroquinone as an inhibitor, and placing 31 g of potassium carbonate (acid binding agent) wrapped with filter paper in the Soxhlet extractor, raising the temperature to reflux, reacting at a constant temperature for 24 hours, removing the solvent and excess diallylamine by reduced pressure distillation using a rotary evaporator, and using distilled water to obtain a slurry; Separate the polymerization inhibitor and dry to obtain hexadecyldiallylamine; (2) add 200 mL of anhydrous ethanol as a solvent to a 500 mL three-necked flask equipped with a thermometer, a reflux condenser and a magnetic rotor, add 90 g of hexadecyldiallylamine at a temperature of 25° C. and with magnetic stirring turned on, then slowly add 52 g of sodium 2-chloroethylsulfonate under stirring, add 0.19 g of polymerization inhibitor methylhydroquinone, raise the temperature to reflux, react at constant temperature for 13 hours, remove the solvent by reduced pressure distillation using a rotary evaporator, and separate and purify using acetone to obtain hexadecyldiallylsulfoethylbetaine C, a hydrophobic monomer having a betaine structure. 16 DASBA.

[0037] The preparation method of the betaine-type hydrophobic associating polymer oil-displacing agent with a ring structure comprises the following process steps: first, 1000 mole parts of distilled water are added to a reactor, and then 8.26 mole parts of acrylamide AM, 10.82 mole parts of 2-allylmethylaminoethylsulfonic acid sodium AMES-Na, 0.49 mole parts of N-vinylpyrrolidone NVP, hexadecyldiallylsulfoethyl betaine C having a betaine structure hydrophobic monomer are added in sequence under stirring. 16 DASBA 0.43 parts, and then distilled water is added to control the total mass percentage concentration of the reaction monomers to 20%. After stirring evenly, N2 is passed for 30 minutes, and then 0.12% of the initiator of the total mass of the reaction monomers is added, and N2 is continued to be passed. The reaction is carried out under nitrogen protection and 45°C for 9 hours. The above-mentioned reaction monomers are the four monomers mentioned above; after the reaction, the obtained gel-like product, i.e., the copolymer, is chopped, and sodium carbonate solution is added (the amount of sodium carbonate solution added is 60% of the weight of the acrylamide monomer, and the sodium carbonate solution is a sodium carbonate aqueous solution with a mass percentage concentration of 15%), and then distilled water is added to dilute the copolymer to a mass percentage concentration of 5%. The hydrolysis reaction is carried out at a temperature of 90°C for 2.0 hours. After the reaction is completed, dilute hydrochloric acid (mass fraction of 5%) is used for neutralization; the product is then washed with anhydrous ethanol, crushed and dried to obtain partially hydrolyzed AM / AMES / NVP / C 16DASBA tetrapolymer, the tetrapolymer after hydrolysis is a betaine type hydrophobic associating polymer oil-displacing agent with a cyclic structure (that is, the polymer oil-displacing agent of the present invention).

[0038] The above-mentioned initiator is a composite initiator, including an oxidation-reduction system initiator and a water-soluble azo initiator. In the above-mentioned oxidation-reduction system initiator, the oxidant is potassium persulfate, the reductant is sodium bisulfite, and the molar ratio of the oxidant to the reductant is 1:1; the above-mentioned water-soluble azo initiator is a combination of azobisisobutylimidazoline hydrochloride (VA-044) and azobisisobutylamidine hydrochloride (V-50), and the mass ratio of VA-044 to V-50 is 2:1; in the composite initiator, the mass ratio of the oxidation-reduction system initiator to the water-soluble azo initiator is 1:1.5.

[0039] Preparation of comparative example: In order to facilitate the experimental part of the present invention, the above-mentioned partially hydrolyzed AM / AMES / NVP / C 16 DASBA tetrapolymer is abbreviated as PAAANC (ie, the polymer oil displacement agent of the present invention). Under the same conditions, acrylamide AM and 2-allylmethylaminoethanesulfonic acid sodium AMES-Na were used to synthesize AM / AMES copolymer (comparative example).

[0040] Example 2: The betaine-type hydrophobic associating polymer oil displacement agent with a cyclic structure of the present invention is composed of acrylamide AM, 2-allylmethylaminoethylsulfonate AMES-Na, N-vinylpyrrolidone NVP and a betaine-structured hydrophobic monomer long-chain alkyl diallyl sulfoethyl betaine C n The four monomers of DASBA are copolymerized to form a gel. After the reaction is completed, the gel is chopped and hydrolyzed in an appropriate amount of sodium carbonate solution. After the hydrolysis, it is neutralized and purified to obtain the final product, which is the polymer oil-displacing agent. The structural formula of the polymer oil-displacing agent is the same as that of Example 1.

[0041] In the above structural formula, x, y, z, p, and q are the molar percentage ranges of the structural units: x = 63% to 84.5%, y = 10% to 20%, z = 5% to 15%, p = 0.3% to 1%, q = 0.2% to 1%, and x + y + z + p + q = 100%. Wherein n = 12, 14, 16, 18, 20. In this embodiment, n = 16.

[0042] Specifically, the betaine-type hydrophobic associating polymer oil displacement agent having a ring structure is prepared from the following monomers in molar fractions: 87.48 parts of acrylamide AM, 11.82 parts of 2-allylmethylaminoethylsulfonate AMES-Na, 0.38 parts of N-vinylpyrrolidone NVP, and a long-chain alkyl diallyl sulfoethyl betaine C having a betaine structure hydrophobic monomer. n DASBA 0.32 parts.

[0043] The preparation method of the above-mentioned 2-allylmethylaminoethanesulfonic acid sodium AMES-Na comprises the following process steps: in a 500mL three-necked flask equipped with a thermometer, a reflux condenser with a Soxhlet extractor and a magnetic rotor, 200mL of anhydrous ethanol is added as a solvent, 78g of sodium 2-chloroethylsulfonate is added at 25°C, and then 35g of N-methylallylamine is slowly added under stirring, 0.18g of methylhydroquinone as an inhibitor is added, 39g of potassium carbonate (acid binding agent) wrapped with filter paper is loaded into the Soxhlet extractor, the temperature is increased to reflux, and after constant temperature reaction for 24 hours, the solvent and excess N-methylallylamine are removed by reduced pressure distillation using a rotary evaporator to obtain 2-allylmethylaminoethanesulfonic acid sodium AMES-Na.

[0044] The above-mentioned hydrophobic monomer long-chain alkyl diallyl sulfoethyl betaine C having a betaine structure n In DASBA, the long-chain alkyl group is octadecyl; in the following step (1), the chlorinated long-chain alkane is octadecyl chloride, the intermediate long-chain alkyl diallylamine is octadecyl diallylamine, and the final product in the following step (2) is octadecyl diallyl sulfoethyl betaine C having a betaine structure hydrophobic monomer 18 DASBA.

[0045] The above hydrophobic monomer octadecyl diallyl sulfoethyl betaine C having a betaine structure 18 The preparation method of DASBA comprises the following process steps: (1) adding 200 mL of anhydrous ethanol as a solvent to a 500 mL three-necked flask equipped with a thermometer, a reflux condenser with a Soxhlet extractor and a magnetic rotor, adding 100 g of chlorooctadecane at a temperature of 25° C. and with magnetic stirring on, then slowly adding 38 g of diallylamine under stirring, adding 0.16 g of methyl hydroquinone as an inhibitor, placing 30 g of potassium carbonate (acid binding agent) wrapped with filter paper in the Soxhlet extractor, raising the temperature to reflux, reacting at constant temperature for 25 hours, removing the solvent and excess diallylamine by reduced pressure distillation using a rotary evaporator, and performing distillation to obtain a product; (2) adding 200 mL of anhydrous ethanol as a solvent to a 500 mL three-necked flask equipped with a thermometer, a reflux condenser and a magnetic rotor, adding 85 g of octadecyldiallylamine at a temperature of 25°C and with magnetic stirring, then slowly adding 45 g of sodium 2-chloroethylsulfonate under stirring, adding 0.16 g of methylhydroquinone as an inhibitor, raising the temperature to reflux, reacting at constant temperature for 14 hours, removing the solvent by reduced pressure distillation using a rotary evaporator, and separating and purifying with acetone to obtain octadecyldiallylsulfoethyl betaine C, a hydrophobic monomer having a betaine structure. 18 DASBA.

[0046] The preparation method of the betaine-type hydrophobic associating polymer oil-displacing agent with a ring structure comprises the following process steps: first, 1200 mole parts of distilled water are added to a reactor, and then 87.48 mole parts of acrylamide AM, 11.82 mole parts of 2-allylmethylaminoethylsulfonic acid sodium AMES-Na, 0.38 mole parts of N-vinylpyrrolidone NVP, octadecyldiallylsulfoethyl betaine C having a betaine structure hydrophobic monomer are added in sequence under stirring. 18 DASBA 0.32 parts, and then distilled water is added to control the total mass percentage concentration of the reaction monomers to 20%. After stirring evenly, N2 is passed for 30 minutes, and then 0.08% of the initiator of the total mass of the reaction monomers is added, and N2 is continued to be passed, and the reaction is carried out under nitrogen protection and 50°C for 8 hours. The above-mentioned reaction monomers are the four monomers mentioned above; after the reaction, the obtained gel-like product, i.e., the copolymer, is chopped, and sodium carbonate solution is added (the amount of sodium carbonate solution added is 50% of the weight of the acrylamide monomer, and the sodium carbonate solution is a sodium carbonate aqueous solution with a mass percentage concentration of 15%), and then distilled water is added to dilute the copolymer to a mass percentage concentration of 5%, and the hydrolysis reaction is carried out at a temperature of 90°C for 2.0 hours. After the reaction is completed, it is neutralized with dilute hydrochloric acid with a mass fraction of 5%; then the product is washed with anhydrous ethanol, and the product is crushed and dried to obtain partially hydrolyzed AM / AMES / NVP / C 18 DASBA tetrapolymer, the tetrapolymer after hydrolysis is a betaine type hydrophobic associating polymer oil-displacing agent with a cyclic structure (that is, the polymer oil-displacing agent of the present invention).

[0047] The above-mentioned initiator is a composite initiator, including an oxidation-reduction system initiator and a water-soluble azo initiator. In the above-mentioned oxidation-reduction system initiator, the oxidant is ammonium persulfate, the reductant is sodium bisulfite, and the molar ratio of the oxidant to the reductant is 1:1.2; the above-mentioned water-soluble azo initiator is azobisisobutylamidine hydrochloride V-50; in the composite initiator, the mass ratio of the oxidation-reduction system initiator to the water-soluble azo initiator is 1:1.7.

[0048] The following is the experimental (test) part of the present invention:

[0049] Experiment 1: Partial hydrolysis of AM / AMES / NVP / C 16 Structural characterization of DASBA tetrapolymer oil displacing agent (ie, polymer oil displacing agent of the present invention).

[0050] The structure of the polymer PAAANC (i.e., the polymer oil displacement agent of the present invention) prepared in Example 1 was analyzed as follows: The FTIR spectrum of the polymer is as follows: Figure 1 Shown: 3336cm-1 -NH (antisymmetric) stretching vibration absorption peak; 3190cm -1 is the stretching vibration absorption peak of -NH (symmetric); 2928cm -1 and 2856cm -1 They are the asymmetric and symmetric stretching vibration absorption peaks of methylene respectively; 1661cm -1 It is -C=O stretching vibration absorption peak; 1450cm -1 It is the absorption peak of the in-plane bending vibration of methylene; 1415cm -1 is the absorption peak of amide CN stretching vibration; 1351cm -1 The CN stretching vibration absorption peaks of amine and quaternary ammonium salts are at 1320cm -1 It is the CO stretching vibration absorption peak of carboxylic acid; 1184cm -1 and 1039cm -1 The infrared spectrum confirms that the product contains structures such as -CONH2, -SO3, -CH2-, -CH3, -COO-, tertiary amine, and quaternary ammonium salt. The infrared spectrum data proves that the target product is partially hydrolyzed AM / AMES / NVP / C 16 DASBA tetrapolymer.

[0051] Experiment 2: Partial hydrolysis of AM / AMES / NVP / C 16 Viscosity test experiment of DASBA tetrapolymer oil-displacing agent (ie, polymer oil-displacing agent of the present invention).

[0052] At room temperature (25±1°C), the apparent viscosities of the polymer PAAANC (i.e., the polymer oil displacement agent of the present invention) prepared in Example 1 and the AM / AMES copolymer solution (prepared with distilled water) of different concentrations were measured using a NDJ-5S digital rotational viscometer to investigate the changes in the apparent viscosities of the two solutions with the polymer concentration. Figure 2 .Depend on Figure 2 It can be seen that at 1000 mg / L, the two polymers PAAANC and AM / AMES copolymer can reach 55.8 mPa·s and 22.4 mPa·s respectively, 2000 mg / L can reach 265.4 mPa·s and 82.3 mPa·s respectively, and 4000 mg / L can reach 1575 mPa·s and 190.7 mPa·s respectively. The results show that when the concentration exceeds 1000 mg / L, the synthesized polymer exhibits better viscosity-increasing ability than the AM / AMES copolymer.

[0053] Experiment 3: Partial hydrolysis of AM / AMES / NVP / C 16 Experimental test on the temperature resistance of the DASBA tetrapolymer oil-displacing agent (i.e., the polymer oil-displacing agent of the present invention).

[0054] The polymer PAAANC (i.e., the polymer oil-displacing agent of the present invention) and AM / AMES prepared in Example 1 were prepared into 2000 mg / L aqueous solution with distilled water, and the apparent viscosity of the PAAANC and AM / AMES copolymer solutions was measured at 25°C to 90°C as a function of temperature. Figure 3 .Depend on Figure 3 It can be seen that the apparent viscosity of the two polymer solutions gradually decreases with the increase of temperature, and PAAANC exhibits better temperature resistance. When the temperature reaches 90℃, the apparent viscosities of PAAANC and AM / AMES copolymer solutions are 127.1mPa·s and 31.7mPa·s, respectively. Compared with the viscosity at 25℃, the viscosity retention rates of the two polymers are 47.89% and 38.52%, respectively. The results show that compared with AM / AMES copolymer, the synthesized polymer exhibits better temperature resistance.

[0055] Experiment 4: Partial hydrolysis of AM / AMES / NVP / C 16 Experimental test on salt resistance of DASBA tetrapolymer oil-displacing agent (i.e., polymer oil-displacing agent of the present invention).

[0056] The PAAANC (i.e., the polymer oil-displacing agent of the present invention) and the AM / AMES copolymer prepared in Example 1 were prepared into 2000 mg / L aqueous solutions using mixed brine of different concentrations (the ratio of various salts in the mixed brine was NaCl:KCl:CaCl2:MgCl2=7:2:0.6:0.4, by mass ratio). The apparent viscosities of the two polymer solutions were measured at 25°C. Figure 4 .Depend on Figure 4 It can be seen that when the mineralization of the brine increases, the apparent viscosity of the two polymers increases first and then decreases. PAAANC exhibits better salt resistance and shows salt thickening below a mineralization of 5000 mg / L, while AM / AMES copolymer shows salt thickening below a mineralization of 3000 mg / L. When the brine content increases to 50000 mg / L, the apparent viscosities of PAAANC and AM / AMES copolymer solutions are 106.2 mPa·s and 17.4 mPa·s, respectively, and their viscosity retention rates are 40.02% and 21.14%, respectively; the results show that compared with AM / AMES copolymer, the synthesized polymer exhibits better salt resistance.

[0057] Experiment 5: Partial hydrolysis of AM / AMES / NVP / C 16 Shear resistance test experiment of DASBA tetrapolymer oil displacing agent (ie, polymer oil displacing agent of the present invention).

[0058] The polymer PAAANC (i.e., the polymer oil displacement agent of the present invention) prepared in Example 1 was prepared into a target solution of 2000 mg / L using distilled water and 10000 mg / L of composite brine, and the AM / AMES copolymer was prepared into a target solution of 2000 mg / L using distilled water. The polymer solutions were sheared at different speeds. The shear resistance of the two polymer solutions was investigated. Figure 5 .Depend on Figure 5 It can be seen that the apparent viscosity of the two polymer solutions decreases with the increase of shear rate. When the shear speed is 3500r / min, the apparent viscosity of the polymer PAAANC in distilled water and salt water is 208.2mPa·s and 111.8mPa·s, respectively, and the apparent viscosity of the AM / AMES copolymer is 56.1mPa·s; the viscosity retention rates of PAAANC in two water qualities are 78.45% and 48.97%, respectively, and the viscosity retention rate of AM / AMES copolymer is 68.17%; when the speed reaches 17000r / min, the apparent viscosity of the polymer PAAANC in distilled water and salt water is 99.5mPa·s and 47.2mPa·s, respectively, and the apparent viscosity of the AM / AMES copolymer is 16.3mPa·s; the viscosity retention rates of PAAANC in two water qualities are 37.49% and 20.67%, respectively, and the viscosity retention rate of AM / AMES copolymer is 19.81%. The results show that compared with AM / AMES copolymer, the synthesized polymer exhibits better shear resistance.

[0059] Experiment 6: Partial hydrolysis of AM / AMES / NVP / C 16 Indoor core flooding experiment of DASBA tetrapolymer oil-displacing agent (i.e., polymer oil-displacing agent of the present invention).

[0060] The polymer PAAANC prepared in Example 1 (i.e., the polymer oil-displacing agent of the present invention) was prepared into a 2000 mg / L aqueous solution using a mixed brine with a salinity of 30000 mg / L (the ratio of various salts in the mixed brine was NaCl: KCl: CaCl2: MgCl2 = 7:2:0.6:0.4, mass ratio), a simulated reservoir temperature of 70°C, a simulated oil viscosity of 83.8 mPa·s, and a three-layer heterogeneous core of 4.5×4.5×30.0 cm. The average water permeability was about 1237×10 -3 μm 2. The core saturated with simulated oil was displaced with brine at an injection rate of 1 mL / min. When the instantaneous water content exceeded 70%, polymer flooding was performed with an injection volume of 0.3 PV, followed by subsequent water flooding until the three instantaneous water content reached 95%. The final recovery was calculated. The same method was used for water flooding until the three instantaneous water content reached 95%. The experimental results show that the final recovery rate of water flooding is 30.52%, and the final recovery rate of polymer flooding is 46.84%. Through indoor oil recovery experiments, it was calculated that the polymer can increase the recovery rate by 16.32%. The polymer has a good oil recovery effect under high temperature and high mineralization.

[0061] In summary, the polymer oil-displacing agent prepared by the above embodiments of the present invention has good viscosity, temperature resistance and shear resistance; it shows good salt resistance in mixed brine with a salinity of ≥30000 mg / L; the indoor oil displacement experiment shows a good oil displacement effect, which can increase the crude oil recovery rate by more than 10%. The present invention provides a (water-soluble) betaine-type hydrophobic associating polymer oil-displacing agent with a cyclic structure, which has good performance, good viscosity-increasing ability at high temperature and high salinity, and good shear resistance, can achieve a higher recovery rate, and can meet the technical requirements of the polymer oil-displacing agent with a wide range of use in the market, thereby ensuring the smooth progress of oil exploitation in high-temperature and high-salinity oil fields, and solving the problems that the existing hydrophobic associating polymer has poor temperature and salt resistance in brine with high salinity (mineralization ≥30000 mg / L), is easily hydrolyzed underground, and has a low crude oil recovery rate.

Claims

1. A betaine-type hydrophobically associating polymer oil-displacing agent having a cyclic structure, characterized in that It is composed of acrylamide AM, 2-allylmethylaminoethylsulfonate AMES-Na, N-vinylpyrrolidone NVP and a long-chain alkyl diallyl sulfoethyl betaine C with a betaine structure hydrophobic monomer. n The four monomers of DASBA are copolymerized to form a gel. After the reaction is completed, the gel is chopped up and hydrolyzed in an appropriate amount of sodium carbonate solution. After the hydrolysis, the final product is neutralized and purified to obtain the polymer oil-displacing agent. The structural formula of the polymer oil-displacing agent is as follows: In the above structural formula, x, y, z, p, q are the molar percentage ranges of the structural units: x = 63% to 84.5%, y = 10% to 20%, z = 5% to 15%, p = 0.3% to 1%, q = 0.2% to 1%, x + y + z + p + q = 100%. Wherein n = 12, 14, 16, 18, 20.

2. The betaine type hydrophobically associating polymer oil-displacing agent having a cyclic structure according to claim 1, characterized in that The molar proportions of each monomer added are as follows: 83-94.5 parts of acrylamide AM, 5-15 parts of 2-allylmethylaminoethylsulfonate AMES-Na, 0.3-1 parts of N-vinylpyrrolidone NVP, and 0.1-1 parts of long-chain alkyl diallyl sulfoethyl betaine C having a betaine structure hydrophobic monomer. n DASBA 0.2~1 part.

3. The betaine type hydrophobically associating polymer oil-displacing agent having a cyclic structure according to claim 1 or 2, characterized in that The preparation method of 2-allylmethylaminoethanesulfonic acid sodium AMES-Na comprises the following process steps: adding an appropriate amount of anhydrous ethanol as a solvent to a three-necked flask equipped with a thermometer, a reflux condenser with a Soxhlet extractor and a magnetic rotor, adding 65-95 g of sodium 2-chloroethylsulfonate at room temperature, then slowly adding 30-43 g of N-methylallylamine under stirring, adding 0.15-0.21 g of methylhydroquinone as an inhibitor, and charging 32-47 g of an acid binding agent wrapped with filter paper into the Soxhlet extractor, raising the temperature to reflux, reacting at a constant temperature for 20-25 hours, and removing the solvent and excess N-methylallylamine by reduced pressure distillation using a rotary evaporator to obtain 2-allylmethylaminoethanesulfonic acid sodium AMES-Na.

4. The betaine type hydrophobically associating polymer oil-displacing agent having a cyclic structure according to claim 1 or 2, characterized in that The above-mentioned hydrophobic monomer long-chain alkyl diallyl sulfoethyl betaine C having a betaine structure n The preparation method of DASBA comprises the following process steps: (1) adding an appropriate amount of anhydrous ethanol as a solvent to a three-necked flask equipped with a thermometer, a reflux condenser with a Soxhlet extractor and a magnetic rotor, adding 80-105 g of a chlorinated long-chain alkane at room temperature and with magnetic stirring, then slowly adding 33-45 g of diallylamine under stirring, adding 0.14-0.25 g of a polymerization inhibitor methyl hydroquinone, placing 30-36 g of an acid binding agent wrapped with filter paper in the Soxhlet extractor, raising the temperature to reflux, reacting at a constant temperature for 20-25 hours, removing the solvent and excess diallylamine by reduced pressure distillation using a rotary evaporator, and using distilled water to obtain a 30-36 g acid binding agent; Separate the polymerization inhibitor and dry to obtain long-chain alkyl diallylamine; (2) add an appropriate amount of anhydrous ethanol as a solvent to a three-necked flask equipped with a thermometer, a reflux condenser and a magnetic rotor, add 80-100 g of long-chain alkyl diallylamine at room temperature and with magnetic stirring, then slowly add 45-60 g of sodium 2-chloroethylsulfonate under stirring, add 0.16-0.3 g of polymerization inhibitor methyl hydroquinone, raise the temperature to reflux, react at constant temperature for 10-15 hours, remove the solvent by reduced pressure distillation using a rotary evaporator, and separate and purify using acetone to obtain a long-chain alkyl diallyl sulfoethyl betaine C having a betaine structure hydrophobic monomer n DASBA.

5. The betaine type hydrophobically associating polymer oil-displacing agent having a cyclic structure according to claim 1, characterized in that The preparation method comprises the following process steps: firstly, 1000-1500 mole parts of distilled water are added into a reactor, and then 83-94.5 mole parts of acrylamide AM, 5-15 mole parts of 2-allylmethylaminoethylsulfonate AMES-Na, 0.3-1 mole parts of N-vinylpyrrolidone NVP, long-chain alkyl diallyl sulfoethyl betaine C having a betaine structure and a hydrophobic monomer are added in sequence under stirring. n DASBA 0.2-1 molar part, and then distilled water is added to control the total mass percentage concentration of the reaction monomers between 15% and 30%, and after stirring evenly, N2 is passed for 30-35 minutes, and then an initiator is added, and N2 is continued to be passed, and the reaction is carried out under nitrogen protection at 30-60°C for 4-10 hours. The above-mentioned reaction monomers are the four monomers mentioned above; after the reaction, the obtained gel-like product, i.e., the copolymer, is chopped, sodium carbonate solution is added, and then distilled water is added to dilute the copolymer to a mass percentage of 5%-8%, and the hydrolysis reaction is carried out at a temperature of 85-90°C for 1.5-2.5 hours. After the reaction, dilute hydrochloric acid is used for neutralization; then the product is washed with anhydrous ethanol, and the product is crushed and dried to obtain partially hydrolyzed AM / AMES / NVP / C n The DASBA tetrapolymer is a betaine-type hydrophobic associating polymer oil displacement agent having a ring structure after hydrolysis.

6. The betaine type hydrophobically associating polymer oil-displacing agent having a cyclic structure according to claim 5, characterized in that The above-mentioned initiator is a composite initiator, including an oxidation-reduction system initiator and a water-soluble azo initiator. In the oxidation-reduction system initiator, the oxidant is potassium persulfate or ammonium persulfate, the reductant is sodium bisulfite, and the molar ratio of the oxidant to the reductant is 1:1 to 1.5; the water-soluble azo initiator is one or more of azobisisobutylamidine hydrochloride V-50, azobisisobutylimidazoline hydrochloride VA-044, and azobis(N-2-carboxyethyl-2-methylpropionamidine) hydrate VA-057, and the ratio is arbitrary when combined; in the composite initiator, the mass ratio of the oxidation-reduction system initiator to the water-soluble azo initiator is 1:1 to 2.

7. The betaine type hydrophobically associating polymer oil-displacing agent having a cyclic structure according to claim 4, characterized in that The above-mentioned hydrophobic monomer long-chain alkyl diallyl sulfoethyl betaine C having a betaine structure n In DASBA, the long-chain alkyl group is hexadecyl; the chlorinated long-chain alkane in step (1) is hexadecyl chloride, and the final product in step (2) is hexadecyl diallyl sulfoethyl betaine C having a betaine structure hydrophobic monomer 16 DASBA; or The above-mentioned hydrophobic monomer long-chain alkyl diallyl sulfoethyl betaine C having a betaine structure n In DASBA, the long-chain alkyl group is octadecyl; the chlorinated long-chain alkane in step (1) is chlorooctadecane, and the final product in step (2) is octadecyldiallylsulfoethyl betaine C having a betaine structure hydrophobic monomer 18 DASBA.

8. The betaine type hydrophobically associating polymer oil-displacing agent having a cyclic structure according to claim 3 or 4, characterized in that The above-mentioned acid binding agent is potassium carbonate or sodium carbonate.

9. The betaine type hydrophobically associating polymer oil-displacing agent having a cyclic structure according to claim 5, characterized in that The amount of the initiator added is 0.05% to 0.2% of the total mass of the reaction monomers, and the total mass of the reaction monomers is the total mass of the four monomers mentioned above; the mass fraction of the dilute hydrochloric acid is 5%; the amount of the sodium carbonate solution added is 45% to 75% of the weight of the acrylamide monomers, and the sodium carbonate solution is a sodium carbonate aqueous solution with a mass percentage concentration of 15% to 20%.

10. A method for preparing the betaine type hydrophobically associating polymer oil-displacing agent having a cyclic structure according to claim 1, characterized in that The method comprises the following process steps: firstly, 1000-1500 mole parts of distilled water are added into a reactor, and then 83-94.5 mole parts of acrylamide AM, 5-15 mole parts of 2-allylmethylaminoethylsulfonate AMES-Na, 0.3-1 mole parts of N-vinylpyrrolidone NVP, long-chain alkyl diallyl sulfoethyl betaine C having a betaine structure and a hydrophobic monomer are added in sequence under stirring. n DASBA 0.2-1 molar part, and then distilled water is added to control the total mass percentage concentration of the reaction monomers between 15% and 30%, and after stirring evenly, N2 is passed for 30-35 minutes, and then an initiator is added, and N2 is continued to be passed, and the reaction is carried out under nitrogen protection at 30-60°C for 4-10 hours. The above-mentioned reaction monomers are the four monomers mentioned above; after the reaction, the obtained gel-like product, i.e., the copolymer, is chopped, sodium carbonate solution is added, and then distilled water is added to dilute the copolymer to a mass percentage of 5%-8%, and the hydrolysis reaction is carried out at a temperature of 85-90°C for 1.5-2.5 hours. After the reaction, dilute hydrochloric acid is used for neutralization; then the product is washed with anhydrous ethanol, and the product is crushed and dried to obtain partially hydrolyzed AM / AMES / NVP / C n The DASBA tetrapolymer is a betaine-type hydrophobic associating polymer oil displacement agent having a ring structure after hydrolysis.

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