Double-tailed hydrophobic association polymer oil-displacing agent with cyclic structure and preparation method of oil-displacing agent

Abstract

The invention relates to a double-tailed hydrophobic associated polymer oil-displacing agent with a cyclic structure and a preparation method thereof. The oil-displacing agent is formed by copolymerization of four monomers, namely acrylamide, sodium 2-allylmethylamino ethanesulfonate, dihydroxyethyl diallyl ammonium chloride and double-tailed long-chain alkyl methyl (4-vinyl benzyl) ammonium chloride with a hydrophobic monomer with a cyclic structure. The preparation method comprises the following steps: firstly adding distilled water, sequentially adding the rest raw materials such as acrylamide, 2-allylmethylamino sodium ethanesulfonate and dihydroxyethyl diallyl ammonium chloride, supplementing water, adjusting the total concentration, introducing N2 to remove oxygen, adding an initiator, and reacting at a certain temperature to obtain the quadripolymer. The prepared polymer oil-displacing agent has good water solubility and good temperature resistance and shear resistance, shows good salt resistance in saline water with the mineralization degree larger than or equal to 30000 mg / L, shows a good oil-displacing effect in heterogeneous rock cores, 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 hydrophobic associating polymer oil-displacing agent containing a cyclic hydrophobic group, specifically a hydrophobic associating polymer oil-displacing agent with a cyclic double tail. The present invention also relates to a preparation method of the hydrophobic associating polymer oil-displacing agent with a cyclic double tail. Background Art

[0002] Extracting as much oil as possible from underground under existing conditions is the main task of oil field exploitation. However, the domestic reservoir structure is complex. After the oil fields are developed through water injection, the water content of most oil fields exceeds 90%, but there is still about 60% of crude oil underground that cannot be extracted (Zhu Rui. Synthesis and properties of heat-resistant and salt-resistant hydrophobic associating polymer AM / AMPS / OA [D]. 2015). In order to improve the recovery rate of crude oil, the most widely used technology in my country is polymer flooding, which has been widely used in Daqing Oilfield, Shengli Oilfield, and Henan Oilfield, and plays an important role in stabilizing the production of old oil fields. So far, the use of ordinary partially hydrolyzed polyacrylamide for domestic Class I oil reservoirs has achieved relatively good results, but for Class II and Class III oil reservoirs, the main problem is that under high shear, high mineralization ion concentration> 20000mg / L, high-valent mineral ions (Ca 2+ ,Mg 2+ In order to improve the heat and salt resistance of polymers, meet the conditions of high temperature and high salt reservoirs, and carry out production increase measures such as polymer flooding, composite flooding, profile adjustment and deep liquid flow diversion technology, the research and development of heat and salt resistant polymers has become one of the research topics of tertiary oil recovery workers at home and abroad in recent years, among which hydrophobic associating polymers are one of the products.

[0003] In the 1950s, Strauss et al. synthesized a polymer with both polysoap and hydrophobicity, and proposed the concept of hydrophobic associating polymer for the first time (Strauss UP, Jackson EG, Polysoaps I. Viscosity and solubilization studies on an n-dodecylbromide addition compound of poly-2-vinylpyridine [J]. J Polym Sci, 1951, 6 (5): 649-659). Later, Dubin synthesized a hydrophobic associating polymer using maleic acid and alkyl vinyl ether. In 1987, Evani and Roes used maleic anhydride / styrene copolymers to partially esterify long-chain alkyl polyvinyl ethers to prepare hydrophobically modified aqueous solution polymers, and used hydrophobic associating polymers in oil field production and studied their temperature and salt resistance. The results showed that these copolymers all showed relatively obvious viscosity increase and salt resistance (Evani S, Rose G D. Water soluble hydrophobe association polymers [J]. Polymer Material Science Engineering, 1987, 57: 477-481). Many experts and scholars in my country have also studied hydrophobic associating polymers. In China, Dong Lijian and others took the lead in the research on hydrophobically associating polymers in 1993. They synthesized a terpolymer using acrylamide, acrylic acid and hydrophobic monomer dodecyl methacrylate, and studied the oil displacement performance of the copolymer. They found that the polymer had excellent properties of temperature resistance, salt resistance and shear resistance, and could be used for oil displacement (Dong Lijian, Wang Biao. AST copolymer for oil displacement and indoor performance evaluation [J]. Oilfield Chemistry, 1993, 10 (4): 325-330 + 341). Zhou Hui and others synthesized acrylamide-octyl acrylate hydrophobically associating water-soluble polymer, but the viscosity of the obtained water-soluble polymer was very low and the critical association concentration was very high (Zhou Hui, Huang Ronghua. Solution properties of hydrophobically associating water-soluble acrylamide-octyl acrylate copolymer [J]. Oilfield Chemistry, 1997, 14 (3): 52-256). Luo Kaifu et al. prepared water-soluble acrylamide / (2-methacryloyl)oxyethyl dimethyl dodecyl ammonium bromide (AM / MEDMDA) copolymers by free radical aqueous solution copolymerization and evaluated their performance. The experiment showed that the synthesized hydrophobic associating polymer had a low viscosity.Academician Luo Pingya of Southwest Petroleum University designed a hydrophobic associative water-soluble polymer for crude oil development based on the actual needs of oil and gas production projects and combined the basic principles of polymer science and colloid chemistry (Zheng Yan. Synthesis and Solution Properties of Associative Polymers for Oil and Gas Development [D]. Doctoral Dissertation of Southwest Petroleum University, 1999.6). At present, hydrophobic associative polymerization has been developed and applied in many offshore and onshore oil fields, and has achieved good results.

[0004] Related patent literature: CN1513890A discloses a non-ionic ternary hydrophobic associating polymer and its synthesis method. Its preparation scheme: (1) Using ethanol as solvent, allyl chloride and hexadecylamine as raw materials, AHAC is synthesized at 40-70°C; (2) AM is added to the AHAC aqueous solution, and then an initiator is added, the total monomer concentration is 10-20%, the initiation system concentration is 40-120 mg / L, the temperature is 40-60°C, and the time is 2-8h to prepare an AM / AHAC binary copolymer; (3) NaOH solution is added to the binary copolymer for hydrolysis to obtain an AM / NaAA / AHAC ternary polymer. The polymer has good viscosity and salt resistance. The synthesis method is simple and feasible, the conditions are mild, the yield is high, and it is easy to purify and separate. CN102391417A discloses a water-soluble hydrophobic associating polymer oil displacement agent and its preparation method. The technical scheme is as follows: the monomers used and the monomer mass percentages are: acrylamide AM 53.5-59.9%; sodium acrylate NaAA 40-45%; N-allyl oleamide NAO 0.1-1.5%; the preparation method is: firstly add NAO into the reactor, then add OP-10 and water, add AM, AA and NaOH after complete emulsification to prepare a solution with a total monomer mass percentage concentration of 10-25%, adjust the pH to 7.5-11, and pass N2 for 20 minutes; then add an initiator, continue to pass N2 for 20 minutes, react at 30-70°C for 4-12 hours; wash with anhydrous ethanol, dry and crush to obtain AM / NaAA / NAO ternary polymer. CN102850489A discloses a method for preparing a water-soluble hydrophobically associating polymer by a normal phase microemulsion polymerization method. The preparation scheme includes: dissolving a certain amount of sodium dodecyl sulfate in deionized water, adding acrylamide and octadecyl methacrylate, and stirring evenly to obtain a transparent or translucent microemulsion, wherein the mass ratio of acrylamide to octadecyl methacrylate is 10:0.5-2.0, the mass ratio of acrylamide, sodium dodecyl sulfate and deionized water is 1-15:1-15:100, and then adding 1% acrylamide. and 0.2% to 2.0% of the total weight of octadecyl methacrylate monomer, an oil-soluble initiator or an oil-soluble redox initiator, stirring and dissolving, gradually heating to 50 to 75°C, constant temperature reaction for 2 to 5 hours, precipitation, washing, extraction and drying after the microemulsion polymerization, the critical associative concentration of the water-soluble hydrophobic associating polymer obtained is 0.5 to 0.8 g / dL, and the apparent viscosity of the hydrophobic associating polymer at a concentration of 1% is 500 to 2500 mPa·s, which can be widely used in the fields of tertiary oil recovery of crude oil and sewage treatment. CN103641950A discloses an anionic hydrophobic associating partially hydrolyzed polyacrylamide, and its technical scheme is: first prepare a hydrophobic monomer-octyl acrylate. Then, it is synthesized with anionic monomers 2-acrylamido-2-methylpropanesulfonic acid, acrylic acid and acrylamide to synthesize anionic hydrophobic associating partially hydrolyzed polyacrylamide.The anionic hydrophobically associated partially hydrolyzed polyacrylamide can be used as an oil displacement agent in the tertiary oil recovery process. Compared with existing polyacrylamide and hydrophobically associated polymers, the anionic hydrophobically associated partially hydrolyzed polyacrylamide in this technology has better temperature resistance, salt resistance and shear resistance, and can be used as an oil displacement agent for tertiary oil recovery to improve crude oil recovery, especially under high temperature and high salt conditions.

[0005] The hydrophobic associating polymers synthesized 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. On the other hand, some hydrophobic associating polymers contain ester-based hydrophobic monomers, which are easily hydrolyzed at high temperatures and lose their hydrophobic associating effect. Summary of the invention

[0006] The purpose of the present invention is to provide a double-tailed hydrophobic associating polymer oil-displacing agent with a ring 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 polymers have poor temperature and salt resistance in brine with high salinity (mineralization ≥30000 mg / L), are easily hydrolyzed underground, and have a low crude oil recovery rate.

[0007] To this end, another object of the present invention is to provide a method for preparing an oil-displacing agent having a double-tail hydrophobic associating polymer with a cyclic structure.

[0008] In order to solve the above technical problems, the technical solution adopted by the present invention is as follows:

[0009] A (water-soluble) double-tailed 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, dihydroxyethyldiallylammonium chloride DHEDAAC and a double-tailed long-chain alkylmethyl (4-vinylbenzyl) ammonium chloride DC with a ring structure hydrophobic monomer n MVBAC is formed by copolymerization of four monomers, and the structural formula of the polymer oil displacement agent is as follows:

[0010]

[0011] In the above structural formula, x, y, z, and p are the molar percentage ranges of the structural units: x = 71% to 83.9%, y = 15% to 25%, z = 1% to 3%, p = 0.1% to 1.0%, and x + y + z + p = 100%. Where n = 8, 10, 12, or 14, and the long-chain alkyl group is an alkane with the same carbon number.

[0012] In the (water-soluble) hydrophobic associating polymer oil-displacing agent with a cyclic structure, the molar fractions of each monomer are as follows (i.e., the oil-displacing agent is made of the following molar fractions of monomers): 71-83.9 parts of acrylamide AM, 15-25 parts of 2-allylmethylaminoethylsulfonic acid sodium AMES-Na, 1-3 parts of dihydroxyethyldiallylammonium chloride DHEDAAC, and a hydrophobic monomer with a cyclic structure and a long-chain alkylmethyl (4-vinylbenzyl) ammonium chloride DC n MVBAC 0.1~1 parts.

[0013] 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, adding an appropriate amount of anhydrous ethanol as a solvent, adding 65-95g of 2-chloroethylsulfonic acid sodium at room temperature (temperature is 23-25°C), then slowly adding 30-43g of N-methylallylamine under stirring, adding 0.15-0.21g of inhibitor methylhydroquinone, and charging 32-47g 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.

[0014] The preparation method of the salt-resistant monomer dihydroxyethyl diallyl ammonium chloride DHEDAAC 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 to 90 g of allyl chloride at a temperature of 5 to 8° C., then slowly adding 42 to 60 g of diethanolamine under stirring, adding 0.16 to 0.23 g of methyl hydroquinone as an inhibitor, and loading 35 to 50 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 to 22 hours, removing the solvent and excess allyl chloride by reduced pressure distillation using a rotary evaporator, and recrystallizing using anhydrous ethanol to obtain the salt-resistant monomer dihydroxyethyl diallyl ammonium chloride DHEDAAC.

[0015] The above hydrophobic monomer with a ring structure has a double-tail long-chain alkyl methyl (4-vinyl benzyl) ammonium chloride DC nThe preparation method of MVBAC comprises the following process steps: adding an appropriate amount of anhydrous ethanol as a solvent to a three-necked flask (500 mL) equipped with a thermometer, a reflux condenser and a magnetic rotor, adding 90 to 150 g of N,N-di-tail long-chain alkylmethyl tertiary amine at room temperature (temperature of 23 to 25° C.), then slowly adding 35 to 60 g of 4-vinylbenzyl chloride (i.e., 4-vinylbenzyl chloride) under stirring, adding 0.2 to 0.3 g of methyl hydroquinone as an inhibitor, raising the temperature to reflux, reacting at a constant temperature for 10 to 15 hours, removing the solvent by reduced pressure distillation using a rotary evaporator, and separating and purifying using acetone to obtain a hydrophobic monomer di-tail long-chain alkylmethyl (4-vinylbenzyl) ammonium chloride DC with a ring structure. n MVBAC monomers.

[0016] The preparation method of the 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 71-83.9 mole parts of acrylamide AM, 15-25 mole parts of 2-allylmethylaminoethylsulfonic acid sodium AMES-Na, 1-3 mole parts of dihydroxyethyldiallylammonium chloride DHEDAAC, an emulsifier, a hydrophobic monomer with a ring structure and a long-chain alkylmethyl (4-vinylbenzyl) ammonium chloride DC are added in sequence under stirring. n MVBAC 0.1-1 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 under nitrogen protection at 30-60°C for 4-10 hours; after the reaction, the obtained gel product is washed with anhydrous ethanol, and the product is dried and crushed to obtain AM / AMES / DHEDAAC / DC n MVBAC tetrapolymer is a double-tailed hydrophobic associating polymer oil displacement agent with a ring structure.

[0017] In the above technical scheme, the preferred technical scheme may be that the acid binding agent may be potassium carbonate or sodium carbonate. The emulsifier may be hexadecyltrimethylammonium bromide, and the amount of hexadecyltrimethylammonium bromide added is 0.06% to 0.1% of the total mass of the reaction solution. The emulsifier may also be OP-10 and the like. The amount of the above 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 described above. The initiator may be 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 1:1-1.5; 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 of the combination is arbitrary; in the composite initiator, the mass ratio of the oxidation-reduction system initiator to the water-soluble azo initiator is 1:1-2.

[0018] In the above technical solution, the preferred technical solution can also be that the hydrophobic monomer with a ring structure has a double-tail long-chain alkyl methyl (4-vinyl benzyl) ammonium chloride DC n In the MVBAC monomer, the long-chain alkyl group can be selected from decyl groups; the N,N-di-tail long-chain alkyl methyl tertiary amine in the preparation method is N,N-decyl methyl tertiary amine (i.e. didecyl methyl tertiary amine, CAS No. 7396-58-9), and the final product is didecyl methyl (4-vinyl benzyl) ammonium chloride DC 10 MVBAC. See Example 1.

[0019] In the above technical solution, the preferred technical solution can also be that the hydrophobic monomer with a ring structure has a double-tail long-chain alkyl methyl (4-vinyl benzyl) ammonium chloride DC n In the MVBAC monomer, the long-chain alkyl group can be selected from dodecyl groups. The N,N-double-tail long-chain alkyl methyl tertiary amine in the preparation method is N,N-dodecyl methyl tertiary amine (i.e. dodecyl dimethyl tertiary amine, CAS No. 112-18-5), and the final product is didodecyl methyl (4-vinyl benzyl) ammonium chloride DC 12 MVBAC. See Example 2.

[0020] Among the above technical solutions, a preferred technical solution may also be Embodiment 1 of the present invention.

[0021] The polymer oil displacement agent of the present invention is composed of acrylamide AM, 2-allylmethylaminoethylsulfonic acid sodium AMES-Na, dihydroxyethyldiallylammonium chloride DHEDAAC and a hydrophobic monomer with a ring structure and a double-tailed long-chain alkylmethyl (4-vinylbenzyl) ammonium chloride DC. n MVBAC is made by copolymerizing four monomers. Preparation method: Add an appropriate amount of distilled water into the reactor, and then add acrylamide AM, 2-allylmethylaminoethylsulfonic acid sodium AMES-Na, dihydroxyethyldiallyl ammonium chloride DHEDAAC, emulsifier hexadecyltrimethylammonium bromide, and hydrophobic monomer with a ring structure, double-tailed long-chain alkylmethyl (4-vinylbenzyl) ammonium chloride DC. n MVBAC, then add distilled water to make the total concentration of the reaction monomer reach the designed concentration, continue to stir the solution until the solution is a nearly transparent homogeneous system, after nitrogen is passed through to deoxygenate, add the initiator, and react at a certain temperature to obtain AM / AMES / DHEDAAC / DC n The MVBAC tetrapolymer is the polymer oil-displacing agent. The present invention introduces a double hydrophobic chain and a benzene ring structure into the polymer chain to improve the polymer's viscosity-increasing ability and temperature resistance, and increases the rigidity of the molecular chain by introducing a ring structure, thereby improving the polymer's thermal stability and shear resistance. 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 injection water with a mineralization of ≥30,000 mg / L on site. The polymer oil-displacing agent prepared by the present invention has good water solubility, shows good temperature and salt resistance in brine with a mineralization of ≥30,000 mg / L, and the oil displacement experiment shows a good oil displacement effect, which can increase the crude oil recovery rate by more than 10%.

[0022] Compared with the prior art, the present invention has the following effects: (1) by introducing a double-tailed hydrophobic long chain and a benzene ring, the rigidity of the polymer molecular chain is greatly enhanced and the hydrophobic association between copolymer molecules is increased, thereby greatly increasing the viscosity and rheological properties of the polymer and significantly improving the temperature resistance of the polymer; (2) by introducing a sulfonic acid group, the water solubility and salt resistance of the polymer are improved; (3) the polymer exhibits good temperature resistance, salt resistance and shear thinning resistance, and can better improve the crude oil recovery rate.

[0023] Referring to the experimental (test) part of the present invention below, in summary, the present invention provides a water-soluble double-tailed hydrophobic associating polymer oil-displacing agent with a ring structure, which has good performance, good viscosity increasing ability at high temperature and high salinity, and good shear resistance, and can achieve a higher recovery rate, meeting 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

[0024] Figure 1 This is the infrared spectrum of the copolymer (oil-displacing agent) synthesized (prepared) in Example 1 of the present invention.

[0025] Figure 2 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 concentration.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] 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

[0030] 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.

[0031] Example 1: The (water-soluble) hydrophobic associating polymer oil displacement agent with a ring structure of the present invention is prepared from the following monomers in molar fractions (copolymerized from four monomers): 80.13 parts of acrylamide AM, 18.04 parts of 2-allylmethylaminoethylsulfonic acid sodium AMES-Na, 1.52 parts of dihydroxyethyldiallylammonium chloride DHEDAAC, and a hydrophobic monomer with a ring structure and a long-chain alkylmethyl (4-vinylbenzyl) ammonium chloride DC n MVBAC 0.31 parts. The structural formula of the polymer oil displacement agent is as follows:

[0032]

[0033] In the structural formula, x, y, z, and p are the molar percentage ranges of the structural units: x=80.13%, y=18.04%, z=1.52%, p=0.31%, x+y+z+p=100%, wherein n=8, 10, 12, 14, and in this embodiment, n=8.

[0034] The long-chain alkyl group is selected from alkanes with the same carbon number. The above-mentioned hydrophobic monomer with a ring structure, double-tailed long-chain alkyl methyl (4-vinylbenzyl) ammonium chloride DC n In the MVBAC monomer, the long-chain alkyl group is decyl; the N,N-di-tail long-chain alkyl methyl tertiary amine in the following preparation method is N,N-decylmethyl tertiary amine (i.e., didecylmethyl tertiary amine), and the final product is didecylmethyl (4-vinylbenzyl) ammonium chloride DC 10 MVBAC.

[0035] The preparation method of the above-mentioned 2-allylmethylaminoethanesulfonate 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, 68g of sodium 2-chloroethylsulfonate is added at 25°C, and then 31g of N-methylallylamine is slowly added under stirring, 0.18g of methylhydroquinone as an inhibitor is added, 34g 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 22 hours, the solvent and excess N-methylallylamine are removed by reduced pressure distillation using a rotary evaporator to obtain 2-allylmethylaminoethanesulfonate sodium AMES-Na.

[0036] The preparation method of the dihydroxyethyl diallyl ammonium chloride DHEDAAC comprises the following process steps: adding 180 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 70 g of allyl chloride at a temperature of 5° C., then slowly adding 46 g of diethanolamine under stirring, adding 0.18 g of methyl hydroquinone as an inhibitor, and loading 38 g of potassium carbonate (acid binding agent) wrapped with filter paper into the Soxhlet extractor, raising the temperature to reflux, reacting at a constant temperature for 21 hours, removing the solvent and excess allyl chloride by reduced pressure distillation using a rotary evaporator, and recrystallizing using anhydrous ethanol to obtain the salt-resistant monomer dihydroxyethyl diallyl ammonium chloride DHEDAAC.

[0037] The above-mentioned didecylmethyl (4-vinylbenzyl) ammonium chloride DC 10 The preparation method of MVBAC includes the following process steps: 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 100 g of N,N-decylmethyl tertiary amine (i.e., didecylmethyl tertiary amine) at a temperature of 25° C., then slowly adding 48 g of 4-vinylbenzyl chloride under stirring, adding 0.2 g of methyl hydroquinone as an inhibitor, raising the temperature to reflux, reacting at a constant temperature for 14 hours, removing the solvent by reduced pressure distillation using a rotary evaporator, and separating and purifying with acetone to obtain didecylmethyl (4-vinylbenzyl) ammonium chloride DC with a ring structure hydrophobic monomer. 10 MVBAC monomers.

[0038] The preparation method of the double-tailed hydrophobic associating polymer oil displacement agent with a ring structure (i.e. AM / AMES / DHEDAAC / DC 10 The synthesis process of MVBAC hydrophobically associating polymer oil displacement agent comprises the following process steps: firstly, 1000 mole parts of distilled water are added into a reactor, and then 80.13 mole parts of acrylamide AM, 18.04 mole parts of 2-allylmethylaminoethanesulfonic acid sodium AMES-Na, 1.52 mole parts of dihydroxyethyldiallylammonium chloride DHEDAAC, 0.07% of the total mass of the reaction solution of the emulsifier hexadecyltrimethylammonium bromide, and the hydrophobic monomer didecylmethyl (4-vinylbenzyl) ammonium chloride DC having a cyclic structure are added in sequence under stirring. 10MVBAC 0.31 molar parts, and then distilled water was added to control the total mass percentage concentration of the reaction monomers to 20%. After stirring evenly, N2 was passed for 30 minutes, and then 0.1% of the initiator of the total mass of the reaction monomers was added, and N2 was continued to be passed. The reaction was carried out under nitrogen protection and 50°C for 7 hours. The total mass of the reaction monomers is the total mass of the above four monomers. After the reaction, the obtained gel product was washed with anhydrous ethanol, and the product was dried and crushed to obtain AM / AMES / DHEDAAC / DC 10 The MVBAC tetrapolymer is a double-tailed hydrophobic associating polymer oil displacement agent with a ring structure.

[0039] 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 1:2; in the composite initiator, the mass ratio of the oxidation-reduction system initiator to the water-soluble azo initiator is 1:1.5.

[0040] Preparation Comparative Example: For the convenience of presentation in the experimental part of the present invention, the above-mentioned AM / AMES / DHEDAAC / DC 10 The MVBAC tetrapolymer is abbreviated as PAADD (ie, the polymer oil displacement agent of the present invention). Under the same conditions, acrylamide AM and acrylic acid AA are used to synthesize partially hydrolyzed polyacrylamide HPAM (comparative example).

[0041] Example 2: The hydrophobic associating polymer oil displacement agent with a ring structure of the present invention is prepared from the following monomers in molar fractions (copolymerized from four monomers): 77.55 parts of acrylamide AM, 20.81 parts of 2-allylmethylaminoethylsulfonic acid sodium AMES-Na, 1.41 parts of dihydroxyethyldiallylammonium chloride DHEDAAC, and a hydrophobic monomer with a ring structure and a long-chain alkylmethyl (4-vinylbenzyl) ammonium chloride DC n MVBAC 0.23 parts.

[0042] The structural formula of the polymer oil displacement agent is the same as that of Example 1. In the structural formula, x, y, z, and p are the molar percentage ranges of the structural units: x=77.55%, y=20.81%, z=1.41%, p=0.23%, x+y+z+p=100%, wherein n=8, 10, 12, 14, and in this embodiment, n=10. The long-chain alkyl group is selected from alkanes with the same carbon number.

[0043] The above-mentioned hydrophobic monomer with a ring structure has a double-tail long-chain alkyl methyl (4-vinyl benzyl) ammonium chloride DC n In the MVBAC monomer, the long-chain alkyl group is selected from dodecyl. The N,N-double-tail long-chain alkyl methyl tertiary amine in the following preparation method is N,N-dodecylmethyl tertiary amine (i.e., dodecyldimethyl tertiary amine), and the final product is didodecylmethyl (4-vinylbenzyl) ammonium chloride DC 12 MVBAC.

[0044] 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, adding an appropriate amount of anhydrous ethanol as a solvent, adding 75g of sodium 2-chloroethylsulfonate at 25°C, then slowly adding 34g of N-methylallylamine under stirring, adding 0.21g of inhibitor methylhydroquinone, and charging 37g of potassium carbonate (acid binding agent) wrapped with filter paper into the Soxhlet extractor, raising the temperature to reflux, and reacting at a constant temperature for 23 hours, using a rotary evaporator to remove the solvent and excess N-methylallylamine by reduced pressure distillation, and using anhydrous ethanol for recrystallization to obtain 2-allylmethylaminoethanesulfonic acid sodium AMES-Na.

[0045] The preparation method of the dihydroxyethyl diallyl ammonium chloride DHEDAAC comprises the following process steps: 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 76 g of allyl chloride at a temperature of 5° C., then slowly adding 50 g of diethanolamine under stirring, adding 0.20 g of methyl hydroquinone as an inhibitor, and loading 41 g of potassium carbonate (acid binding agent) wrapped with filter paper into the Soxhlet extractor, raising the temperature to reflux, reacting at a constant temperature for 22 hours, removing the solvent and excess allyl chloride by reduced pressure distillation using a rotary evaporator, and recrystallizing using anhydrous ethanol to obtain the salt-resistant monomer dihydroxyethyl diallyl ammonium chloride DHEDAAC.

[0046] The above-mentioned didodecylmethyl (4-vinylbenzyl) ammonium chloride DC 12The preparation method of MVBAC includes the following process steps: 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 125 g of N,N-dodecylmethyl tertiary amine (i.e., dodecyldimethyl tertiary amine) at a temperature of 25° C., then slowly adding 50 g of 4-vinylbenzyl chloride under stirring, adding 0.25 g of methyl hydroquinone as an inhibitor, raising the temperature to reflux, reacting at a constant temperature for 15 hours, removing the solvent by reduced pressure distillation using a rotary evaporator, and separating and purifying with acetone to obtain a hydrophobic monomer didodecylmethyl (4-vinylbenzyl) ammonium chloride DC with a ring structure. 12 MVBAC monomers.

[0047] The preparation method of the double-tailed hydrophobic associating polymer oil displacement agent with a ring structure (i.e. AM / AMES / DHEDAAC / DC 12 The synthesis process of MVBAC hydrophobically associating polymer oil displacement agent comprises the following process steps: firstly, 1200 mole parts of distilled water are added into a reactor, and then 77.55 mole parts of acrylamide AM, 20.81 mole parts of 2-allylmethylaminoethanesulfonic acid sodium AMES-Na, 1.41 mole parts of dihydroxyethyldiallylammonium chloride DHEDAAC, 0.08% of the total mass of the reaction solution of the emulsifier hexadecyltrimethylammonium bromide, and the hydrophobic monomer didodecylmethyl (4-vinylbenzyl) ammonium chloride DC having a cyclic structure are added in sequence under stirring. 12 MVBAC 0.23 molar parts, and then distilled water was added to control the total mass percentage concentration of the reaction monomers to 25%. After stirring evenly, N2 was passed for 30 minutes, and then 0.12% of the initiator of the total mass of the reaction monomers was added, and N2 was continued to be passed. The reaction was carried out under nitrogen protection and 45°C for 8 hours. The total mass of the reaction monomers is the total mass of the above four monomers. After the reaction, the obtained gel product was washed with anhydrous ethanol, and the product was dried and crushed to obtain AM / AMES / DHEDAAC / DC 12 MVBAC tetrapolymer, the tetrapolymer is a double-tailed hydrophobic associating polymer oil displacement agent with a ring structure. 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 azobisisobutylimidazoline hydrochloride (VA-044); 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: AM / AMES / DHEDAAC / DC 10 Structural characterization of the MVBAC tetrapolymer oil-displacing agent (ie, the polymer oil-displacing agent of the present invention).

[0050] The polymer PAADD prepared in Example 1 (i.e., the polymer oil-displacing agent of the present invention, the same below) was subjected to structural analysis, as follows: The FTIR spectrum of the polymer is as follows: Figure 1 Shown: 3700~3332cm -1 -OH and -NH (antisymmetric) stretching vibration absorption peak; 3195cm -1 is the stretching vibration absorption peak of -NH (symmetric); 2932cm -1 and 2857cm -1 They are the asymmetric and symmetric stretching vibration absorption peaks of methylene respectively; 1659cm -1 It is -C=O stretching vibration absorption peak; 1605cm -1 Benzene ring skeleton vibration absorption peak; 1451cm -1 The absorption peaks are the in-plane bending vibration absorption peaks of methylene and the vibration absorption peaks of benzene skeleton; 1416cm -1 is the absorption peak of amide CN stretching vibration; 1338cm -1 The stretching vibration absorption peaks of amine and quaternary ammonium salt CN are at 1184cm -1 and 1040cm -1 It is the characteristic absorption peak of -SO3; 844cm -1 It is the absorption peak of the out-of-plane bending vibration of the benzene ring. The infrared spectrum confirms that the product contains structures such as -CONH2, -SO3, -CH2-, -CH3, -C6H4-tertiary amine and quaternary ammonium salt. From the infrared spectrum data, it can be proved that the target product is AM / AMES / DHEDAAC / DC 10 MVBAC tetrapolymer.

[0051] Experiment 2: AM / AMES / DHEDAAC / DC 10 Viscosity test experiment of MVBAC tetrapolymer oil-displacing agent (i.e., polymer oil-displacing agent of the present invention).

[0052] At room temperature (25±1°C), the apparent viscosities of the polymer PAADD and HPAM solutions (prepared with distilled water) prepared in Example 1 with different concentrations were measured using an NDJ-5S digital rotational viscometer to investigate the relationship between the apparent viscosities of the two polymers and the polymer concentration. Figure 2 .Depend on Figure 2It can be seen that at 1000 mg / L, the two polymers PAADD and HPAM can reach 46.7 mPa·s and 26.8 mPa·s, respectively, at 2000 mg / L, they can reach 234.2 mPa·s and 98.7 mPa·s, respectively, and at 4000 mg / L, they can reach 1234 mPa·s and 216.8 mPa·s, respectively. The results show that compared with HPAM, when the concentration exceeds 1000 mg / L, the synthesized tetrapolymer exhibits good viscosity-increasing ability.

[0053] Experiment 3: AM / AMES / DHEDAAC / DC 10 Experimental test on the temperature resistance of the MVBAC tetrapolymer oil-displacing agent (i.e., the polymer oil-displacing agent of the present invention).

[0054] The polymer PAADD (i.e., the polymer oil-displacing agent of the present invention) and HPAM (comparative example) prepared in Example 1 were prepared into 2000 mg / L aqueous solutions with distilled water, and the relationship between the apparent viscosity of the two polymer solutions and the temperature was measured at 25°C to 90°C. 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 PAADD shows better temperature resistance. When the temperature reaches 90℃, the apparent viscosity of PAADD and HPAM solutions are 127.0mPa·s and 33.3mPa·s, respectively. Compared with the viscosity at 25℃, the viscosity retention rates of the two polymer solutions are 54.23% and 33.74%, respectively. The results show that compared with HPAM, the synthesized tetrapolymer shows better temperature resistance.

[0055] Experiment 4: AM / AMES / DHEDAAC / DC 10 Experimental test on the salt resistance of the MVBAC tetrapolymer oil-displacing agent (i.e., the polymer oil-displacing agent of the present invention).

[0056] PAADD (i.e., the polymer oil-displacing agent of the present invention) and HPAM prepared in Example 1 were prepared into 2000 mg / L polymer 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, mass ratio). The apparent viscosities of the two polymer solutions were measured at 25°C. Figure 4 .Depend on Figure 4It can be seen that when the mineralization of the brine increases, the apparent viscosity of the two polymers increases first and then decreases. PAADD exhibits better salt resistance, showing salt thickening below a mineralization of 7000 mg / L, while HPAM shows salt thickening below a mineralization of 1000 mg / L. When the brine content increases to 50000 mg / L, the apparent viscosities of PAADD and HPAM solutions are 98.9 mPa·s and 12.5 mPa·s, respectively, and their viscosity retention rates are 42.23% and 12.66%, respectively; the results show that compared with HPAM, the synthesized tetrapolymer exhibits better salt resistance.

[0057] Experiment 5: AM / AMES / DHEDAAC / DC 10 Shear resistance test experiment of MVBAC tetrapolymer (i.e., polymer oil displacement agent of the present invention).

[0058] The polymer PAADD (i.e., the polymer oil displacement agent of the present invention) and HPAM prepared in Example 1 were prepared into a target solution of 2000 mg / L using distilled water, and the polymer solutions were sheared at different speeds in a Wu Yin stirrer. 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 two polymer PAADD and HPAM solutions is 199.3mPa·s and 63.4mPa·s respectively; their viscosity retention rates are 85.10% and 64.24% respectively; when the speed reaches 17000r / min, the apparent viscosity of the two polymer solutions is 98.6mPa·s and 11.7mPa·s respectively, and their viscosity retention rates are 42.10% and 11.85% respectively. The results show that compared with HPAM, the synthesized tetrapolymer exhibits better shear resistance.

[0059] Experiment 6: AM / AMES / DHEDAAC / DC 10 Indoor core flooding experiment of MVBAC tetrapolymer (i.e., the polymer oil-displacing agent of the present invention).

[0060] The polymer PAADD 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 80.2 mPa·s, a three-layer heterogeneous core of 4.5×4.5×30.0 cm, and an average permeability of 1197×10 -3 μm2 . 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 43.70%. Through indoor oil recovery experiments, it was calculated that the polymer can increase the recovery rate by 13.18%. 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 increasing property, shows good salt resistance in mixed brine with salinity ≥30000mg / L, and shows good oil displacement effect in indoor oil displacement experiment, which can increase crude oil recovery rate by more than 10%. The present invention provides a water-soluble double-tailed hydrophobic associating polymer oil-displacing agent with a ring structure, which has good performance, good viscosity increasing ability under high temperature and high salinity, and good shear resistance, achieves a high recovery rate, and can meet the technical requirements of polymer oil-displacing agents with a wide range of uses in the market, thereby ensuring the smooth progress of oil exploitation in high-temperature and high-salinity oil fields, and solving the problems of poor temperature and salt resistance of existing hydrophobic associating polymers in saline with high salinity (mineralization ≥30000mg / L), easy hydrolysis underground, and low crude oil recovery rate.

Claims

1. A double-tailed hydrophobic associating polymer oil-displacing agent with a ring structure, characterized in that It is composed of acrylamide AM, 2-allylmethylaminoethanesulfonic acid sodium AMES-Na, dihydroxyethyldiallyl ammonium chloride DHEDAAC and a hydrophobic monomer with a ring structure and a double-tailed long-chain alkylmethyl (4-vinylbenzyl) ammonium chloride DC n MVBAC is formed by copolymerization of four monomers, and the structural formula of the polymer oil displacement agent is as follows: In the above structural formula, x, y, z, and p are the molar percentage ranges of the structural units: x=71% to 83.9%, y=15% to 25%, z=1% to 3%, p=0.1% to 1.0%, x+y+z+p=100%, wherein n=8, 10, 12, or 14.

2. The oil-displacing agent of the double-tailed hydrophobically associating polymer with a ring structure according to claim 1, characterized in that The molar fractions of each monomer are as follows: acrylamide AM 71-83.9 parts, 2-allylmethylaminoethylsulfonic acid sodium AMES-Na 15-25 parts, dihydroxyethyldiallylammonium chloride DHEDAAC 1-3 parts, and a hydrophobic monomer with a ring structure, double-tailed long-chain alkylmethyl (4-vinylbenzyl) ammonium chloride DC n MVBAC 0.1~1 parts.

3. The oil-displacing agent of the disulfonate hydrophobically associating polymer 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 oil-displacing agent of the double-tailed hydrophobically associating polymer with a ring structure according to claim 1 or 2, characterized in that The preparation method of the salt-resistant monomer dihydroxyethyl diallyl ammonium chloride DHEDAAC 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 65-90g of allyl chloride at a temperature of 5-8°C, then slowly adding 42-60g of diethanolamine under stirring, adding 0.16-0.23g of methyl hydroquinone as an inhibitor, and loading 35-50g of an acid binding agent wrapped with filter paper into the Soxhlet extractor, raising the temperature to reflux, and reacting at a constant temperature for 20-22 hours, using a rotary evaporator to remove the solvent and excess allyl chloride under reduced pressure distillation, and using anhydrous ethanol for recrystallization to obtain the salt-resistant monomer dihydroxyethyl diallyl ammonium chloride DHEDAAC.

5. The oil-displacing agent of the double-tailed hydrophobically associating polymer with a ring structure according to claim 1 or 2, characterized in that The above hydrophobic monomer with a ring structure has a double-tail long-chain alkyl methyl (4-vinyl benzyl) ammonium chloride DC n The preparation method of MVBAC 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 and a magnetic rotor, adding 90-150 g of N,N-di-tail long-chain alkylmethyl tertiary amine at room temperature, then slowly adding 35-60 g of 4-vinylbenzyl chloride under stirring, adding 0.2-0.3 g of methyl hydroquinone as an inhibitor, raising the temperature to reflux, reacting at a constant temperature for 10-15 hours, removing the solvent by reduced pressure distillation using a rotary evaporator, and separating and purifying with acetone to obtain a hydrophobic monomer di-tail long-chain alkylmethyl (4-vinylbenzyl) ammonium chloride DC with a ring structure. n MVBAC monomers.

6. The oil-displacing agent of the double-tailed hydrophobically associating polymer with a ring 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 71-83.9 mole parts of acrylamide AM, 15-25 mole parts of 2-allylmethylaminoethylsulfonic acid sodium AMES-Na, 1-3 mole parts of dihydroxyethyldiallylammonium chloride DHEDAAC, an emulsifier, a hydrophobic monomer with a ring structure and a double-tailed long-chain alkylmethyl (4-vinylbenzyl) ammonium chloride DC are added in sequence under stirring. n MVBAC 0.1-1 molar part, and then distilled water is added to control the total mass percentage concentration of the reaction monomers between 15% and 30%. After stirring evenly, N2 is passed for 30-35 minutes, and then the initiator is added, and N2 is continued to be passed. The reaction is carried out under nitrogen protection at 30-60°C for 4-10 hours. After the reaction, the obtained gel product is washed with anhydrous ethanol, and the product is dried and crushed to obtain AM / AMES / DHEDAAC / DC n MVBAC tetrapolymer is a double-tailed hydrophobic associating polymer oil displacement agent with a ring structure.

7. The oil-displacing agent of the double-tailed hydrophobically associating polymer with a ring structure according to claim 6, characterized in that The emulsifier is hexadecyltrimethylammonium bromide, and the amount of hexadecyltrimethylammonium bromide added is 0.06% to 0.1% of the total mass of the reaction solution; 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 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.

8. The oil-displacing agent of the double-tailed hydrophobically associating polymer with a ring structure according to claim 5, characterized in that The above-mentioned hydrophobic monomer with a ring structure has a double-tail long-chain alkyl methyl (4-vinyl benzyl) ammonium chloride DC n In the MVBAC monomer, the long-chain alkyl group is selected from decyl; the N,N-double-tail long-chain alkyl methyl tertiary amine in the preparation method is N,N-decyl methyl tertiary amine, i.e. didecyl methyl tertiary amine, and the final product is didecyl methyl (4-vinyl benzyl) ammonium chloride DC 10 MVBAC; or The above-mentioned hydrophobic monomer with a ring structure has a double-tail long-chain alkyl methyl (4-vinyl benzyl) ammonium chloride DC n In the MVBAC monomer, the long-chain alkyl group is selected from dodecyl, and the N,N-double-tail long-chain alkyl methyl tertiary amine in the preparation method is N,N-dodecyl methyl tertiary amine, i.e., didodecyl methyl tertiary amine, and the final product is didodecyl methyl (4-vinyl benzyl) ammonium chloride DC 12 MVBAC.

9. The oil-displacing agent of the double-tailed hydrophobically associating polymer with a ring structure according to claim 3 or 4, characterized in that The above-mentioned acid binding agent is potassium carbonate or sodium carbonate.

10. A method for preparing the oil-displacing agent of the double-tailed hydrophobic associating polymer with a ring structure according to claim 1, characterized in that The method comprises the following process steps: firstly, adding 1000-1500 mole parts of distilled water into a reactor, and then sequentially adding 71-83.9 mole parts of acrylamide AM, 15-25 mole parts of 2-allylmethylaminoethylsulfonic acid sodium AMES-Na, 1-3 mole parts of dihydroxyethyldiallylammonium chloride DHEDAAC, an emulsifier, a hydrophobic monomer with a ring structure and a double-tailed long-chain alkylmethyl (4-vinylbenzyl) ammonium chloride DC under stirring; n MVBAC 0.1-1 molar part, and then distilled water is added to control the total mass percentage concentration of the reaction monomers between 15% and 30%. After stirring evenly, N2 is passed for 30-35 minutes, and then the initiator is added, and N2 is continued to be passed. The reaction is carried out under nitrogen protection at 30-60°C for 4-10 hours. After the reaction, the obtained gel product is washed with anhydrous ethanol, and the product is dried and crushed to obtain AM / AMES / DHEDAAC / DC n MVBAC tetrapolymer is a double-tailed hydrophobic associating polymer oil displacement agent with a ring structure.

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