Polymer oil-displacing agent for fractured-vuggy carbonate reservoir and preparation method of polymer oil-displacing agent

Abstract

The preparation method comprises the following steps: step 1, taking a mixed solution of acetone and ethanol as a solvent, adding N, N-dimethyl propane diamine, diethyl ether and perfluorononanoic acid into the mixed solution of acetone and ethanol, after complete reaction, adding chloropropene, continuing reaction, and after the reaction is finished, evaporating to remove the solvent to obtain a polymer oil-displacing agent; the fluorine-carbon cation hydrophobic monomer CF-1 is obtained; step 2, uniformly mixing white oil and an emulsifier Span80 and Tween 80 in a mass ratio of (35-45): (1-3): (1-2) to obtain an oil phase; the preparation method comprises the following steps: dissolving AM, sodium p-styrenesulfonate and a fluorocarbon cation hydrophobic monomer CF-1 in deionized water, adding sodium hydrogen sulfite, and uniformly stirring to obtain an aqueous solution; and adding the aqueous solution into the oil phase to obtain a uniform emulsion, adding ammonium persulfate, and reacting to obtain the high-molecular oil-displacing agent. The oil-displacing agent has high temperature resistance and salt resistance, and the adsorption of carbonate reservoirs to the oil-displacing agent is greatly reduced.

Description

Technical Field

[0001] The invention belongs to the field of crude oil production increase, and relates to a polymer oil displacement agent for carbonate fracture-cavity oil reservoirs and a preparation method thereof. Background Art

[0002] Typical carbonate fracture-cave reservoirs in China are mainly concentrated in the Tarim Oilfield and the Tahe Oilfield. Their water drive recovery rate is less than 20%, and the remaining oil is abundant. It is urgent to improve the crude oil recovery rate of fracture-cave reservoirs. Carbonate fracture-cave reservoirs are different from sandstone reservoirs. They are mostly complex combinations of caves and fractures. The scale is complex and varied, mainly caves and large fractures. The caves are large in scale and have various forms of connection. The spatial distribution is complex and the heterogeneity is extremely strong. In addition, carbonate fracture-cave reservoirs are buried deep and have extremely harsh formation conditions. For example, the Tahe fracture-cave reservoir is buried very deep (well depth greater than 5000m), with ultra-high temperature and high pressure (temperature greater than 150 degrees, pressure greater than 60MPa), and the mineralization is greater than 20×10 4 mg / L, which seriously restricts the research and development of oil displacement agents.

[0003] At present, the purpose of studying the oil displacement agent flooding method is mainly for sandstone reservoirs, but it has been shown that oil-wet fractured carbonate reservoirs have great potential for the use of oil displacement agents to improve oil recovery. Assuming that water can be naturally imbibed in fractured reservoirs and crude oil can be discharged from the rock matrix into the fractures for oil recovery, the use of oil displacement agents is attractive for improving oil recovery by changing wettability (becoming mixed wet / water wet) and promoting the imbibition process. Especially for carbonate reservoirs, the application effects of different types of oil displacement agents are different. Anionic oil displacement agents have high interfacial activity and good temperature resistance. At present, the industrialized anionic oil displacement agents in my country include petroleum sulfonates, alkylbenzene sulfonates, petroleum carboxylates, etc. However, most anionic oil displacement agents have poor salt tolerance, carbonate rocks are positively charged, anionic oil displacement agents have large adsorption losses, and cannot effectively desorb organic carboxylates adsorbed on the surface of carbonate rocks to change the wettability of rocks. Anionic-nonionic amphoteric oil displacement agents are those that introduce a certain amount of ethylene oxide or propylene oxide into the hydrophilic head group of anionic oil displacement agents, so that the molecular structure has both anionic and nonionic hydrophilic head groups. Its temperature and salt resistance depends on the type of anionic group, the type and size of alkoxy groups, and the type and size of lipophilic groups. Compared with conventional anionic oil displacement agents, its biggest feature is its strong salt resistance and small formation adsorption loss. Especially in high-temperature, high-salt, positively charged carbonate reservoirs, its use effect is better than that of anionic oil displacement agents. Anionic-nonionic oil displacement agents are a type of oil displacement agent that can be used in tertiary oil recovery in carbonate reservoirs. Their application in carbonate rocks requires effective changes in the wettability and oil recovery rate of carbonate rocks, and requires appropriate lipophilic chain lengths, alkoxy types, and group numbers.

[0004] The oil displacement agents used in tertiary oil recovery in my country's carbonate reservoirs are still in a development stage, and there is no widely applicable oil displacement agent system. To select a suitable oil displacement agent system, it is necessary to analyze the specific reservoir conditions. In view of the high temperature and high salt characteristics of carbonate reservoirs, the selected oil displacement agent should have good temperature and salt resistance, low adsorption loss and good interfacial activity. However, the performance of existing oil displacement agents in these aspects cannot meet the use requirements of carbonate reservoirs. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the above-mentioned prior art and provide a polymer oil-displacing agent for carbonate fracture-cavity oil reservoirs and a preparation method thereof, which has high temperature resistance and salt resistance and greatly reduces the adsorption of the oil-displacing agent by carbonate reservoirs.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A polymer oil displacement agent for carbonate fracture-cavity reservoirs, the molecular structure of which is as follows:

[0008]

[0009] In the formula, m=1~3, n=50~70, x=3~5.

[0010] A method for preparing a polymer oil displacement agent for carbonate fracture-vuggy reservoirs comprises the following steps:

[0011] Step 1, using a mixture of acetone and ethanol as a solvent, adding N,N-dimethylpropylenediamine, ether and perfluorononanoic acid to the acetone-ethanol mixture, after complete reaction, adding allyl chloride, continuing the reaction, and evaporating and removing the solvent after the reaction is completed to obtain a fluorocarbon cationic hydrophobic monomer CF-1;

[0012] The dosage of each raw material component is: 2-5 parts by weight of N,N-dimethylpropylenediamine, 9-23 parts by weight of perfluorononanoic acid, 3-8 parts by weight of allyl chloride, and 64-86 parts by weight of solvent, wherein the solvent includes acetone-ethanol mixed solution and ether;

[0013] Step 2, white oil, emulsifier Span80 and Tween80 are mixed evenly to obtain an oil phase, in which the mass ratio of white oil, Span80 and Tween80 is 35-45:1-3:1-2; AM, sodium p-styrene sulfonate and fluorocarbon cationic hydrophobic monomer CF-1 are dissolved in deionized water, sodium bisulfite is added, and stirred evenly to obtain an aqueous solution, in which the weight parts of AM are 17-40 weight parts, sodium p-styrene sulfonate is 1-6 weight parts, fluorocarbon cationic hydrophobic monomer CF-1 is 11-25 weight parts, water is 20-35 weight parts, and the amount of oil phase is 9-15 weight parts; the aqueous solution is added to the oil phase to obtain a uniform emulsion, and ammonium persulfate is added. After the reaction is completed, a polymer oil displacement agent is obtained.

[0014] Preferably, in step 1, acetone and ethanol are mixed in equal mass ratios in the solvent.

[0015] Preferably, in step 1, under the protection of inert gas, N,N-dimethylpropylenediamine, ether and perfluorononanoic acid are added to the acetone-ethanol mixture.

[0016] Preferably, in step 1, N,N-dimethylpropylenediamine, ether and perfluorononanoic acid are added to an acetone-ethanol mixture, reacted at a temperature of 25-35° C. for 2-5 hours, then heated to 65-85° C., and then allyl chloride is added.

[0017] Preferably, in step 1, after adding allyl chloride, the reaction is continued for 3-5 hours.

[0018] Preferably, in step 2, the aqueous solution is added to the oil phase, and an inert gas is introduced to obtain a uniform emulsion.

[0019] Preferably, in step 2, after obtaining a uniform emulsion, an inert gas is introduced, the emulsion is heated to 30-40° C., and then ammonium persulfate is added.

[0020] Furthermore, the inert gas is nitrogen.

[0021] Preferably, in step 2, after adding ammonium persulfate, stirring and constant temperature reaction are carried out for 2-6 hours.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The present invention provides a synthetic fluorine-containing surface active polymer oil-displacing agent. First, a new type of fluorine-containing intermediate is synthesized by amidation reaction using excess N, N-dimethylpropylenediamine and perfluorononanoic acid, and then reacted with allyl chloride. The purpose of this step is to introduce double bonds into the fluorine-containing intermediate to obtain a fluorocarbon cationic monomer CF-1, and finally obtain the final fluorine-containing polymer oil-displacing agent product by ternary copolymerization. The advantage of this synthesis method is that the molecular weight of the synthesis is relatively high, and the molecule can obtain better activity through modification and adjustment of specific groups. At the same time, the introduction of fluorine-containing active groups and anionic and cationic groups into the main structure can greatly reduce the oil-water interfacial tension, reduce the adsorption of carbonate formations, and greatly improve the temperature resistance and salt resistance of the oil-displacing agent. The fluorine-containing polymer oil-displacing agent is also a supramolecule. Through the interaction of anions and cations in an aqueous solution, the viscosity of the solution can be effectively increased, and the flow channel adjustment function can be played in the oil displacement process, so as to achieve the purpose of adjusting and displacing, and further improve the oil recovery rate; at the same time, the interaction of anions and cations can also greatly reduce the adsorption of the carbonate reservoir to the oil-displacing agent, so that its action distance is farther. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is the infrared spectrum of the oil displacing agent prepared in Example 1 of the present invention;

[0025] Figure 2 A fracture-cavity structure model diagram designed for a typical carbonate fracture-cavity structure of the present invention. DETAILED DESCRIPTION

[0026] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments; based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0027] It should be noted that the words "front", "rear", "left", "right", "up" and "down" used in the following description refer to directions in the drawings, and the words "inside" and "outside" refer to directions toward or away from the geometric center of a specific component, respectively.

[0028] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0029] The polymer oil displacement agent for carbonate fracture-cavity reservoirs provided by the present invention is a fluorine-containing polymer surfactant, and the molecular structure is as follows:

[0030]

[0031] In the formula, m=1~3, n=50~70, x=3~5.

[0032] The preparation method steps of the above oil displacing agent:

[0033] Step 1: Synthesis of fluorinated monomers:

[0034] Acetone-ethanol mixed liquid is used as solvent, acetone and ethanol are mixed in equal mass ratios, N, N-dimethylpropylenediamine, ether and perfluorononanoic acid are added to the acetone-ethanol mixed liquid under nitrogen protection, react at 25-35°C for 2-5h, then the temperature is raised to 65-85°C, allyl chloride is added dropwise, and the reaction is continued for 3-5h. After the reaction is completed, the solvent is evaporated and removed to obtain a fluorocarbon cationic hydrophobic monomer CF-1; wherein the amount of each component is: 2-5 parts by weight of N, N-dimethylpropylenediamine, 9-23 parts by weight of perfluorononanoic acid, 3-8 parts by weight of allyl chloride, and 64-86 parts by weight of solvent (acetone-ethanol mixed liquid, ether); the mass ratio of acetone-ethanol to ether is 10:1.

[0035] Step 2, weigh white oil, emulsifier Span80, Tween80, stir and mix evenly at high speed to obtain an oil phase. In the oil phase, the mass ratio of white oil, Span80, and Tween80 is 35-45:1-3:1-2. Dissolve AM, sodium p-styrene sulfonate and fluorocarbon cationic hydrophobic monomer CF-1 in deionized water, add sodium bisulfite, stir evenly to obtain an aqueous solution. In the aqueous solution, 17-40 parts by weight of AM, 1-6 parts by weight of sodium p-styrene sulfonate, 11-25 parts by weight of fluorocarbon cationic hydrophobic monomer CF-1, and 20-35 parts by weight of water. Add the aqueous solution dropwise to 9-15 parts by weight of the oil phase, pass nitrogen, obtain a uniform emulsion, continue to pass nitrogen, heat the emulsion to 30-40°C, add ammonium persulfate, stir, and react at a constant temperature for 2-6 hours to obtain a polymer oil displacement agent.

[0036] Example 1

[0037] A method for preparing a polymer oil displacement agent, i.e. a fluorine-containing polymer surfactant, for use in carbonate fracture-cavity oil reservoirs:

[0038] Step 1: In a three-necked flask equipped with a stirring and condensing device, add 12 g of N, N-dimethylpropylenediamine and 16.5 g of ether, then add 148.5 g of a mixture of acetone and ethanol, slowly add 55 g of perfluorononanoic acid, introduce nitrogen, and react at 30°C for 3 h; then heat to 80°C, add 18 g of allyl chloride dropwise, continue to react for 4 h, use a rotary evaporator to remove the solvent in the system, and obtain a fluorocarbon cationic hydrophobic monomer CF-1.

[0039] Step 2: Weigh 59g white oil and 3g Span80, 1.5g Tween80 emulsifier, stir at 1000r / min on an electromagnetic stirrer for 10min to mix evenly to obtain an oil phase. Weigh 92g AM, 13.7g sodium p-styrene sulfonate and 69g functional monomer CF-1, add 100g deionized water, add 1.5g sodium bisulfite, stir evenly to obtain an aqueous solution; add the aqueous solution dropwise to the oil phase, pass nitrogen, and obtain a uniform emulsion; set the reaction temperature to 40°C, pass nitrogen, add 1g ammonium persulfate, continue stirring, and react at a constant temperature for 6h to obtain a polymer oil displacement agent.

[0040] The structure of the oil displacement agent prepared in Example 1 was characterized using a Fourier transform infrared spectrometer. The infrared spectrum is shown in FIG. Figure 1 As shown. The absorption band is 2893cm -1 、2629cm -1 The stretching vibration absorption peaks of methyl and methylene are at 1640cm -1 No characteristic peak was observed at 3035cm -1 The characteristic peaks at 782 cm are the stretching vibration of the unsaturated benzene ring =CH, -1 The characteristic peak at 1034cm is caused by the out-of-plane bending of the benzene ring hydrogen =CH, and -1 (-S=O symmetrical expansion), 1166cm -1 (-S=O asymmetric expansion), 618cm -1 (SO stretching) These all indicate that sodium p-styrene sulfonate is copolymerized into the structure of the oil displacement agent; 1375 cm -1 The characteristic peak at 3473cm is the stretching vibration of CF; -1 The peak at 1681 cm is the stretching vibration absorption peak of the NH single bond. -1 It is the stretching vibration absorption peak of -C=O in -CONH (amide), 1508cm -1 Characteristic peaks at -NH in-plane bending, 1375cm -1 The characteristic peak at is CN stretching. The existence of the above peaks proves that the oil displacement agent prepared in Example 1 has the expected molecular structure.

[0041] The basic performance test of the oil displacement agent prepared in Example 1 is shown in Table 1.

[0042] Table 1. Performance test results of the oil displacement agent obtained in Example 1

[0043] Serial number project result 1 Appearance Light yellow viscous liquid 2 pH 8.0 3 Surface tension (0.2wt%), mN / m 21.8 4 Interfacial tension (0.2wt%), mN / m 0.000421 5 Effective content, % 51

[0044] In the table, the surface tension and interfacial tension are measured by dissolving the oil displacing agent in water to form an aqueous solution with a mass percentage concentration of 0.2%.

[0045] Example 2

[0046] A method for preparing a polymer oil displacement agent, i.e. a fluorine-containing polymer surfactant, for use in carbonate fracture-cavity oil reservoirs:

[0047] Step 1: In a three-necked flask equipped with a stirring and condensing device, add 20 g of N, N-dimethylpropylenediamine and 25.15 g of ether, then add 251.5 g of a mixture of acetone and ethanol, slowly add 73.4 g of perfluorononanoic acid, introduce nitrogen, and react at 25°C for 5 hours; then heat to 65°C, add 30 g of allyl chloride dropwise, continue to react for 5 hours, use a rotary evaporator to remove the solvent in the system, and obtain a fluorocarbon cationic hydrophobic monomer CF-1.

[0048] Step 2: Weigh 40g white oil and 2g Span80, 1g Tween80 emulsifier, stir at 1000r / min on an electromagnetic stirrer for 10min to mix evenly to obtain an oil phase. Weigh 41g AM, 5.95g sodium p-styrene sulfonate and 30.26g functional monomer CF-1, add 44g deionized water, add 0.5g sodium bisulfite, stir evenly to obtain an aqueous solution; add the aqueous solution dropwise to the oil phase, pass nitrogen, and obtain a uniform emulsion; set the reaction temperature to 37°C, pass nitrogen, add 0.7g ammonium persulfate, continue stirring, and react at a constant temperature for 2h to obtain a polymer oil displacement agent.

[0049] Example 3

[0050] A method for preparing a polymer oil displacement agent, i.e. a fluorine-containing polymer surfactant, for use in carbonate fracture-cavity oil reservoirs:

[0051] Step 1: In a three-necked flask equipped with a stirring and condensing device, add 24.52 g of N, N-dimethylpropylenediamine and 33.49 g of ether, then add 334.85 g of a mixture of acetone and ethanol, slowly add 75 g of perfluorononanoic acid, introduce nitrogen, and react at 35°C for 2 hours; then heat to 85°C, add 32.14 g of allyl chloride dropwise, continue to react for 3 hours, use a rotary evaporator to remove the solvent in the system, and obtain a fluorocarbon cationic hydrophobic monomer CF-1.

[0052] Step 2: Weigh 41g white oil and 2.5g Span80 and 1.2g Tween80 emulsifiers, stir them on an electromagnetic stirrer at 1000r / min for 10min to mix them evenly to obtain the oil phase. Weigh 39.6g AM, 4.8g sodium p-styrene sulfonate and 30g functional monomer CF-1, add them to 42.6g deionized water, add 0.4g sodium bisulfite, stir evenly to obtain an aqueous solution; add the aqueous solution dropwise to the oil phase, pass nitrogen, and obtain a uniform emulsion; set the reaction temperature to 30°C, pass nitrogen, add 0.5g ammonium persulfate, continue stirring, and react at a constant temperature for 5h to obtain a polymer oil displacement agent.

[0053] Example 4

[0054] An oil displacement agent (aqueous solution) for carbonate rock fracture-cavity oil reservoirs is composed of the following components by mass percentage: 0.2% of oil displacement agent and 99.8% of water.

[0055] The oil displacing agent is the oil displacing agent obtained in Example 1.

[0056] The oil displacement agent (aqueous solution) obtained in this example was subjected to a performance test at 150°C and a salinity of 200,000. The results are shown in Table 2:

[0057] Table 2. Performance test of oil displacement agent obtained in Example 2

[0058]

[0059]

[0060] Example 5

[0061] An oil displacement agent (aqueous solution) for carbonate rock fracture-cavity oil reservoirs is composed of the following components by mass percentage: 0.3% of the oil displacement agent and 99.7% of water.

[0062] The oil displacing agent is the oil displacing agent obtained in Example 1.

[0063] The oil displacement agent (aqueous solution) obtained in this example was subjected to a performance test at 170° C. and a salinity of 250,000. The results are shown in Table 3.

[0064] Table 3. Performance test of oil displacement agent obtained in Example 3

[0065]

[0066]

[0067] Embodiment 6:

[0068] The oil displacing agent (aqueous solution) is composed of the following components by mass percentage: 0.2% of the oil displacing agent and 99.8% of water.

[0069] The oil displacing agent is the oil displacing agent obtained in Example 1.

[0070] The oil displacement agent obtained in this example was used to carry out oil displacement experiments on a fracture-cavity structure model designed according to a typical carbonate fracture-cavity structure. Figure 2 shown.

[0071] The fracture-cavity structure model parameters and water injection displacement experiment parameters are determined based on the actual formation conditions and the following similarity criteria.

[0072] Table 4. Similarity criteria and their physical meanings

[0073]

[0074] According to the selected parameters, the initial oil-water distribution is established in the model, the injection and production wells are connected to simulate water injection and huff and puff until no oil is produced, and after the water drive residual oil is established, the injection and displacement agent huff and puff are simulated again (the huff and puff is performed 3 times) until no liquid is produced, and the experimental data are recorded; According to the selected parameters, the initial oil-water distribution is established in the model, the injection and production wells are connected to simulate water injection and production (1 injection and 1 production) until no oil is produced, and after the water drive residual oil is established, the injection and displacement agent production (1 injection and 1 production) are simulated again until no liquid is produced, and the experimental data are recorded. The data of the huff and puff model and the injection and production model are processed separately, and the average value is obtained. The results are shown in Table 5.

[0075] Table 5. Experimental results of improving oil recovery rate using fracture-cavity model of oil displacement agent in Example 4

[0076] project Throughput Model Injection-production model Water drive recovery, % 31.38 52.75 Recovery rate after measures, % 40.63 73.23 Oil recovery enhancement, % 9.25 20.48

[0077] Embodiment 7:

[0078] The structural location of the TK84XX well is on a slope. There was no emptying and leakage during the drilling process. The amplitude change rate and well logging showed that the reservoir was developed, and the acid fracturing showed that the fractures were extending normally. Comprehensive analysis shows that the reservoir type is fracture type. Before the oil displacement agent flooding measure, the well was injected with water for 5 rounds, with a total injection of 7904m 3 , cumulative liquid production 1.17×104m 3 , stratum deficit 4039m 3 , the average daily oil production in each round before the measures were implemented showed a significant downward trend.

[0079] The oil displacement agent prepared in Example 1 was used in the 6th to 8th rounds of water injection in the TK84XX well. The concentration was 0.2%. A total of 5000 m3 of oil displacement fluid was injected in the three rounds of water injection. 3 , with an effective period of 287 days, a cumulative oil production of 5,932 tons, a daily increase of 3.6 tons, a cumulative increase of 1,033.2 tons, and a good oil increase effect.

[0080] In summary, the fluorine-containing polymer oil-displacing agent provided by the present invention has both anionic and cationic groups, which can greatly reduce the oil-water interfacial tension and reduce the adsorption of carbonate formations, and has excellent temperature and salt resistance. It is also a supramolecule that can increase the viscosity of the solution through the entanglement of anions and cations, play a role in flow channel adjustment, and can play a role in regulating and displacing, thereby further improving the oil recovery rate.

[0081] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0082] It should be understood that the above description is for illustration and not for limitation. Many embodiments and many applications beyond the examples provided will be apparent to those skilled in the art upon reading the above description. Therefore, the scope of the present teachings should not be determined with reference to the above description, but rather with reference to the foregoing claims and the full scope of equivalents to which such claims are entitled. For the purpose of comprehensiveness, all articles and references, including disclosures of patent applications and publications, are incorporated herein by reference. The omission of any aspect of the subject matter disclosed herein in the foregoing claims is not intended to be a waiver of such subject matter, nor should it be considered that the applicant has not considered such subject matter to be part of the disclosed inventive subject matter.

Claims

1. A polymer oil displacement agent for carbonate fracture-cavity reservoirs, characterized in that: Its molecular structure is as follows: In the formula, m=1~3, n=50~70, x=3~5.

2. A method for preparing a polymer oil displacement agent for carbonate fracture-cavity reservoirs according to claim 1, characterized in that: The following steps are involved: Step 1, using a mixture of acetone and ethanol as a solvent, adding N,N-dimethylpropylenediamine, ether and perfluorononanoic acid to the acetone-ethanol mixture, after complete reaction, adding allyl chloride, continuing the reaction, and evaporating and removing the solvent after the reaction is completed to obtain a fluorocarbon cationic hydrophobic monomer CF-1; The dosage of each raw material component is: 2-5 parts by weight of N,N-dimethylpropylenediamine, 9-23 parts by weight of perfluorononanoic acid, 3-8 parts by weight of allyl chloride, and 64-86 parts by weight of solvent, wherein the solvent includes acetone-ethanol mixed solution and ether; Step 2, white oil, emulsifier Span80 and Tween80 are mixed evenly to obtain an oil phase, in which the mass ratio of white oil, Span80 and Tween80 is 35-45:1-3:1-2; AM, sodium p-styrene sulfonate and fluorocarbon cationic hydrophobic monomer CF-1 are dissolved in deionized water, sodium bisulfite is added, and stirred evenly to obtain an aqueous solution, in which the weight parts of AM are 17-40 weight parts, sodium p-styrene sulfonate is 1-6 weight parts, fluorocarbon cationic hydrophobic monomer CF-1 is 11-25 weight parts, water is 20-35 weight parts, and the amount of oil phase is 9-15 weight parts; the aqueous solution is added to the oil phase to obtain a uniform emulsion, and ammonium persulfate is added. After the reaction is completed, a polymer oil displacement agent is obtained.

3. The method for preparing a polymer oil displacement agent for carbonate fracture-cavity reservoirs according to claim 2, characterized in that: In step 1, acetone and ethanol are mixed in equal mass ratios in the solvent.

4. The method for preparing a polymer oil displacement agent for carbonate fracture-cavity reservoirs according to claim 2, characterized in that: In step 1, under the protection of inert gas, N,N-dimethylpropylenediamine, ether and perfluorononanoic acid are added to an acetone-ethanol mixture.

5. The method for preparing a polymer oil displacement agent for carbonate fracture-cavity reservoirs according to claim 2, characterized in that: In step 1, N,N-dimethylpropylenediamine, ether and perfluorononanoic acid are added to an acetone-ethanol mixture, reacted at a temperature of 25-35° C. for 2-5 hours, then heated to 65-85° C., and then allyl chloride is added.

6. The method for preparing a polymer oil displacement agent for carbonate fracture-cavity reservoirs according to claim 2, characterized in that: In step 1, after adding allyl chloride, the reaction is continued for 3-5 hours.

7. The method for preparing a polymer oil displacement agent for carbonate fracture-cavity reservoirs according to claim 2, characterized in that: In step 2, the aqueous solution is added to the oil phase, and an inert gas is introduced to obtain a uniform emulsion.

8. The method for preparing a polymer oil displacement agent for carbonate fracture-cavity reservoirs according to claim 2, characterized in that: In step 2, after obtaining a uniform emulsion, an inert gas is introduced to heat the emulsion to 30-40° C., and then ammonium persulfate is added.

9. The method for preparing a polymer oil displacement agent for carbonate fracture-cavity reservoirs according to any one of claims 4, 7 and 8, characterized in that: The inert gas is nitrogen.

10. The method for preparing a polymer oil displacement agent for carbonate fracture-cavity reservoirs according to claim 2, characterized in that: In step 2, after adding ammonium persulfate, stir and react at a constant temperature for 2-6 hours.

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