A surfactant-based heterogeneous supramolecular inclusion synergistic system for CO2 flooding reservoirs, and its preparation method and application

Abstract

The present invention provides a surfactant-based CO2 flooding reservoir heterogeneous supramolecular inclusion synergistic system and its preparation method and application. The supramolecular inclusion synergistic system of the present invention comprises the following raw material compositions in parts by mass: 0.1-0.2 parts of acid-resistant hydrophobic polymer microspheres, 1-2 parts of acid-resistant cyclodextrin polymers, 1-3 parts of surfactants, and 800-1200 parts of water. The heterogeneous supramolecular inclusion synergistic system of the present invention has acid resistance and good stability, and is stable under supercritical CO2 acidic conditions (pH is about 2-3); it has shear recovery, and the viscosity of the system is reduced under high shear conditions during injection, making it easy to inject, and supramolecular action occurs underground to achieve in-situ viscosity increase. The heterogeneous supramolecular inclusion synergistic system of the present invention can effectively achieve the blocking of gas channeling channels, with good blocking effect, thereby being able to improve the swept volume and displacement efficiency of CO2.

Description

Technical Field

[0001] The present invention belongs to the technical field of oilfield chemistry, and in particular relates to a surfactant-based CO2 flooding reservoir heterogeneous supramolecular inclusion synergistic system, a preparation method and an application thereof. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance understanding of the overall background of the invention and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to those skilled in the art.

[0003] In recent years, gas injection-enhanced oil recovery (ERR) technology has garnered significant attention, and CO2 flooding-ERR technology is gaining increasing attention as an effective method for greenhouse gas resource utilization. This technology not only meets the needs of oilfield development but also addresses CO2 storage and protects the atmospheric environment. This technology is applicable not only to conventional reservoirs but also to low- and ultra-low-permeability reservoirs, significantly improving oil recovery.

[0004] Gas channeling is an inevitable consequence of gas flooding development at a certain stage. It is exacerbated by objective factors such as viscous CO2 fingering, gravity overprinting, and reservoir heterogeneity. Gas channeling leads to ineffective utilization of injected CO2, exacerbating challenges in CO2 flooding development. Furthermore, the large amounts of CO2 produced after channeling pose safety risks, ultimately preventing the desired enhanced oil recovery.

[0005] To address the problem of CO2 flooding gas channeling, the foam anti-channeling material mentioned in patent document CN 114989796 A has good high-temperature and salt resistance properties; however, foam is a thermodynamically unstable system and therefore has poor stability. The polymer anti-channeling material mentioned in patent document CN103497748A can effectively block large pores in the formation, reduce polymer output, and improve oil recovery; however, single polymers have disadvantages such as insufficient strength. The gel anti-channeling material mentioned in patent document CN 117304910A has good high-temperature stability and low damage to the reservoir; however, the gel system has a high initial viscosity and average injectability. Nanospheres are currently the fastest-growing and most widely used water flooding plugging agent, but conventional nanospheres are unstable and easily degraded under supercritical CO2 acidic conditions (pH approximately 2-3), limiting the effectiveness of deep gas flooding plugging.

[0006] The present invention is proposed to solve the above-mentioned problems. Summary of the Invention

[0007] In response to the deficiencies in the prior art, the present invention provides a surfactant-based heterogeneous supramolecular inclusion enhancement system for CO2 flooding oil reservoirs, as well as its preparation method and application. The heterogeneous supramolecular inclusion enhancement system of the present invention has acid resistance and good stability, and is stable under supercritical CO2 acidic conditions (pH of about 2 to 3); it has shear recovery, and the viscosity of the system decreases under high shear conditions during injection, making it easy to inject, and supramolecular effects occur underground to achieve in-situ viscosity increase. The heterogeneous supramolecular inclusion enhancement system of the present invention can effectively block gas channeling channels with good blocking effect, thereby increasing the swept volume and displacement efficiency of CO2.

[0008] The present invention is achieved through the following technical solutions:

[0009] A surfactant-based heterogeneous supramolecular inclusion synergistic system for CO2 flooding reservoirs comprises the following raw materials in parts by weight: 0.1-0.2 parts of acid-resistant hydrophobic polymer microspheres, 1-2 parts of acid-resistant cyclodextrin polymer, 1-3 parts of surfactant, and 800-1200 parts of water.

[0010] According to a preferred embodiment of the present invention, a surfactant-based heterogeneous supramolecular inclusion synergistic system for CO2 flooding reservoirs includes the following raw materials in parts by mass: 0.1 parts of acid-resistant hydrophobic polymer microspheres, 1.5 parts of acid-resistant cyclodextrin polymer, 2 parts of surfactant, and 1000 parts of water.

[0011] According to the present invention, preferably, the particle size of the acid-resistant hydrophobic polymer microspheres is 50 to 300 nm.

[0012] According to a preferred embodiment of the present invention, a method for preparing acid-resistant hydrophobic polymer microspheres comprises the steps of:

[0013] (1) white oil, Span80, and Tween80 are mixed uniformly to obtain an oil phase;

[0014] (2) Acrylamide (AM), hexadecyl dimethyl allyl ammonium chloride (C 16 DMAAC) and dimethyldiallylammonium chloride (DMDAAC) were fully dissolved in water, the pH value of the system was adjusted, and N,N-methylenebisacrylamide (MBA) was added and mixed uniformly to obtain an aqueous phase;

[0015] (3) The aqueous phase is added dropwise to the oil phase, and then an aqueous ammonium persulfate solution and an aqueous sodium bisulfite solution are added dropwise in sequence. After reaction, washing, drying, and grinding, the acid-resistant hydrophobic polymer microspheres are obtained.

[0016] Preferably, in step (1), the mass ratio of white oil, Span80, and Tween80 is 35-40:2-3:0.5-1.5, preferably 39:2.7:0.9.

[0017] Preferably, in step (2), acrylamide (AM), hexadecyldimethylallyl ammonium chloride (C 16 The mass ratio of DMAAC), dimethyldiallylammonium chloride (DMDAAC), N,N-methylenebisacrylamide (MBA) and water is 5-6:0.1-0.2:0.1-0.2:0.04-0.06:15-30, preferably 5.25:0.105:0.105:0.0546:21.

[0018] Preferably, in step (2), a sodium hydroxide aqueous solution with a mass concentration of 10%-50% is used to adjust the pH value of the system to 7.

[0019] Preferably, in step (3), the aqueous phase is added at a rate of 1-5 drops per second, and the addition is carried out under stirring and under the protection of a protective gas. Further preferably, the protective gas is nitrogen or argon.

[0020] Preferably, in step (3), the mass ratio of acrylamide in the aqueous phase to the oil phase is 5-6:40-45.

[0021] Preferably, in step (3), the rate of addition of the aqueous ammonium persulfate solution and the aqueous sodium bisulfite solution is 1-5 drops per second, and the addition is carried out under stirring and under the protection of a protective gas. Further preferably, the protective gas is nitrogen or argon.

[0022] Preferably, in step (3), the mass concentrations of the ammonium persulfate aqueous solution and the sodium bisulfite aqueous solution are both 0.02%-0.2%, wherein the mass ratio of ammonium persulfate to sodium bisulfite is 1:1; and the mass ratio of ammonium persulfate to acrylamide in the aqueous phase is 1:475-785.

[0023] Preferably, in step (3), the reaction temperature is 25-40°C, the reaction time is 2-6 hours, and the reaction is carried out under stirring and protective gas. More preferably, the protective gas is nitrogen or argon.

[0024] According to the present invention, the structure of the acid-resistant hydrophobic polymer microspheres is shown as follows:

[0025]

[0026] Preferably, according to the present invention, the acid-resistant cyclodextrin polymer is prepared by including the following raw materials in parts by weight: 5-15 parts of hydrophilic polymerization monomer, 0.1-1 part of hydrophobic monomer, 0.1-1 part of acid-resistant monomer, 0.01-0.1 part of initiator, 0.01-0.1 part of chain transfer agent containing cyclodextrin group, and 10-20 parts of water.

[0027] Preferably, the acid-resistant cyclodextrin polymer is prepared by the following raw materials in parts by weight: 10 parts of hydrophilic polymerization monomer, 0.2 parts of hydrophobic monomer, 0.3 parts of acid-resistant monomer, 0.022 parts of initiator, 0.022 parts of chain transfer agent containing cyclodextrin group, and 15 parts of water.

[0028] Preferably, the hydrophilic polymerizable monomers are acrylamide and acrylic acid, and the mass ratio of acrylamide to acrylic acid is 5-9:3.

[0029] Preferably, the hydrophobic monomer is N-octadecyl acrylamide.

[0030] Preferably, the acid-resistant monomer is dimethyldiallylammonium chloride.

[0031] Preferably, the initiators are potassium persulfate and sodium bisulfite, and the mass ratio of potassium persulfate to sodium bisulfite is 2-4:1.

[0032] Preferably, the chain transfer agent containing a cyclodextrin group is a RAFT chain transfer agent, and the structural formula is as follows:

[0033]

[0034] Preferably, the preparation method of the acid-resistant cyclodextrin polymer comprises the steps of:

[0035] The hydrophilic polymerization monomer, the hydrophobic monomer, the acid-resistant monomer and the chain transfer agent containing the cyclodextrin group are fully dispersed in water, and the pH of the system is adjusted to be weakly alkaline; an initiator aqueous solution is added, reacted, and then purified by precipitation, dried, and granulated to obtain an acid-resistant cyclodextrin polymer.

[0036] More preferably, a sodium hydroxide aqueous solution with a mass concentration of 30-50% is used to adjust the pH of the system to 7-8, preferably 7.3-7.6.

[0037] More preferably, the mass concentration of the initiator aqueous solution is 0.01-0.05 g / mL.

[0038] Further preferably, the reaction conditions are as follows: under protective gas protection, stirring the reaction at 40-70°C until the system becomes viscous, and then under protective gas protection, standing the reaction at 40-70°C for 4-7h; preferably, the protective gas is nitrogen or argon, the reaction temperature is 45°C, and the standing reaction time is 6h.

[0039] According to the present invention, the surfactant is preferably a gemini betaine surfactant, the structural formula of which is as follows:

[0040]

[0041] The preparation method of the surfactant-based CO2 flooding reservoir heterogeneous supramolecular inclusion synergistic system comprises the following steps:

[0042] Acid-resistant hydrophobic polymer microspheres are fully dispersed in water, and a microsphere dispersion is obtained through an expansion reaction; an acid-resistant cyclodextrin polymer and a surfactant are added, fully mixed and dispersed evenly, and an aging reaction is performed to obtain a surfactant-based CO2 flooding reservoir heterogeneous supramolecular inclusion enhancement system.

[0043] Preferably, according to the present invention, the acid-resistant hydrophobic polymer microspheres are dispersed in water and stirred at 200-400 r / min at room temperature for 4-6 hours to be fully dispersed; preferably, the stirring rate is 300 r / min and the stirring time is 5 hours.

[0044] According to the preferred embodiment of the present invention, the expansion reaction temperature is 40-60°C, the expansion reaction time is 24-36h, and the expansion reaction is carried out at 50-200r·min -1 The expansion reaction is carried out under stirring conditions; preferably, the expansion reaction temperature is 40° C. and the expansion reaction time is 24 h.

[0045] According to the present invention, preferably, the aging reaction temperature is 40-50° C., and the aging reaction time is 36-72 h; preferably, the aging reaction temperature is 40° C., and the aging reaction time is 72 h.

[0046] The above surfactant-based heterogeneous supramolecular inclusion enhancement system for CO2 flooding reservoirs is applied to plug gas channeling in CO2 flooding reservoirs.

[0047] The technical features and beneficial effects of the present invention are:

[0048] 1. The core components of the heterogeneous supramolecular inclusion enhancement system for CO2 flooding oil reservoirs of the present invention, the hydrophobic polymer microspheres and the cyclodextrin polymer themselves, both have good acid resistance and stability: the microspheres are swellable under acidic conditions, and the polymer has good apparent viscosity under acidic conditions, so that the heterogeneous supramolecular inclusion enhancement system of the present invention can be used stably under supercritical CO2 acidic conditions (pH of about 2 to 3).

[0049] 2. The synthesis of the cyclodextrin polymer of the present invention introduces a new RAFT polymerization method, which can control the molecular weight and molecular structure, reduce shear loss, and the low molecular weight polymer has a low initial viscosity and is easy to inject. The supramolecular effect occurs underground to achieve in-situ viscosity enhancement. The chain transfer agent of the present invention introduces cyclodextrin groups, so that the cyclodextrin groups can be introduced to both ends of the polymer during application, which is convenient for the host-guest inclusion complex with the hydrophobic long chain on the surface of the microsphere. The amount of the RAFT chain transfer agent of the present invention needs to be appropriate; if the amount is too much, the polymer chain will be very short and the molecular weight will be too low, which will cause the viscosity to decrease and affect the effect of the supramolecular inclusion enhancement system; if the amount is too little, the host-guest inclusion complex will be too weak, the viscosity enhancement effect will not be obvious, and the effect of the supramolecular inclusion enhancement system will be affected.

[0050] 3. Conventional polymer microspheres are unstable and easily degraded under acidic conditions, resulting in a short shelf life and limited expansion performance and deep channel sealing. The present invention introduces acid-resistant monomers into the polymer microspheres, enhancing their acid resistance. The hydrophobic polymer microspheres of the present invention can form a host-guest inclusion complex with the cyclodextrin polymer of the present invention, making the polymer network structure denser and thus increasing viscosity. Furthermore, this can block gas channeling, thereby increasing the swept volume and displacement efficiency of CO2.

[0051] 4. The Gemini betaine surfactant introduced in this invention can hydrophobically associate with the hydrophobic groups on the surface of the hydrophobic polymer microspheres and the hydrophobic groups on the cyclodextrin polymer, enhancing the viscosity of the medium between the particles in the heterogeneous supramolecular inclusion synergistic system. It can also impart surface and interfacial activity to the heterogeneous supramolecular inclusion synergistic system as a whole, facilitating the emulsification or displacement of residual oil in porous media. Therefore, the use of a specific type of surfactant in this invention allows for both hydrophobic association and reduced interfacial tension.

[0052] 5. There are interactions between the components of the heterogeneous supramolecular inclusion enhancement system for CO2 flooding reservoirs of the present invention: manifested in the host-guest inclusion interaction between the hydrophobic polymer microspheres and the cyclodextrin polymer, the hydrophobic association interaction between the hydrophobic polymer microspheres and the surfactant, and the hydrophobic association interaction between the cyclodextrin polymer and the surfactant.

[0053] 6. The heterogeneous supramolecular inclusion synergistic system of the present invention is stronger than the traditional particle synergistic system. The medium between the traditional particles in the stratum is water, which is easily broken through by gas. However, in the heterogeneous supramolecular inclusion synergistic system of the present invention, the medium between the particles in the stratum is a composite synergistic system with a higher viscosity such as cyclodextrin polymers and surfactants. In addition, both the cyclodextrin polymers and the surfactants can interact with the surface of the particles and act as a cross-linking agent, bonding the particles together. Surfactants and cyclodextrin polymers can also undergo hydrophobic association, but this effect is not strong. Under certain strong shearing effects, they can be shear-thinned and easily injected. However, this shearing is reversible. When the shear disappears, the viscosity is restored due to the self-assembly effect. The heterogeneous supramolecular inclusion synergistic system of the present invention has better blocking performance for gas channeling, thereby being able to improve the swept volume and displacement efficiency of CO2. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 This is the blocking effect data of the supramolecular inclusion synergistic system prepared in Example 1;

[0055] Figure 2 This is the blocking effect data of the supramolecular inclusion synergistic system prepared in Example 4. DETAILED DESCRIPTION

[0056] The present invention will be further described below in conjunction with specific examples. It should be understood that these examples are intended to illustrate the present invention only and are not intended to limit the scope of the invention. The experimental methods in the following examples, for which specific conditions are not specified, are generally performed under conventional conditions or as recommended by the manufacturer.

[0057] A RAFT chain transfer agent containing cyclodextrin groups is prepared according to existing methods as follows: 1 g of allyl β-cyclodextrin and 2.33 g of thiolactic acid are dissolved in 15 mL of deionized water. 1.85 g of carbon disulfide is slowly added dropwise to the mixture in an ice-water bath. After stirring and reacting for 6 hours at 30°C, 2.62 g of benzyl bromide is added dropwise. The reaction is continued for 18 hours. After completion of the reaction, the reaction solution is added dropwise to anhydrous ethanol to produce a large precipitate. The precipitate is filtered and rinsed 2-3 times with anhydrous ethanol. The product is then dried in a 45°C oven until the mass remains constant, pulverized, and granulated to obtain a RAFT chain transfer agent containing cyclodextrin groups.

[0058] The preparation method of the surfactant is as follows: adding palmitic acid and N,N-dimethyl-1,3-propylenediamine in a molar ratio of 1:1 to a three-necked flask, keeping the mixture in an oil bath at 150° C. for 10 hours until the pH value is less than 6, and then vacuuming to remove excess N,N-dimethyl-1,3-propylenediamine to obtain palmitic acid amidopropyl dimethyl tertiary amine (PKO); pouring equimolar amounts of PKO, sodium 3-chloro-2-hydroxypropanesulfonate (CHPS-Na), and an ethanol-water mixed solvent (the volume ratio of ethanol to water is 1:1, and the molar amount of sodium 3-chloro-2-hydroxypropanesulfonate (CHPS-Na) and the volume ratio of the mixed solvent is 0.2 mol / L) into the three-necked flask, reacting at 80° C. for 8 hours, and distilling under reduced pressure. The mixture is washed with petroleum ether to remove PKO to obtain a palmitic acid amidopropyl-N-dimethylsulfonate betaine (AS-22) surfactant; and adding 5 g of the mixture into the three-necked flask. AS-22 was completely dissolved in dimethylformamide and then heated to 40°C. 1 g of isophorone diisocyanate was added dropwise and allowed to react for 2 h to obtain a gemini betaine surfactant.

[0059]

[0060] Example 1

[0061] A method for preparing a surfactant-based heterogeneous supramolecular inclusion synergistic system for CO2 flooding reservoirs comprises the following steps:

[0062] (1) Synthesis of acid-resistant hydrophobic polymer microspheres

[0063] Weigh 39g of white oil, 2.7g of Span80, and 0.9g of Tween80 into a four-necked flask equipped with a thermometer, stirrer, and reflux apparatus. Stir and mix thoroughly at 600 rpm. Flow nitrogen through the system for at least 30 minutes to remove dissolved oxygen.

[0064] Weigh 0.105 g of dimethyldiallyl ammonium chloride (DMDAAC), 5.25 g of acrylamide (AM), 0.105 g of hexadecyldimethylallyl ammonium chloride (C 16 DMAAC) was dissolved in 21 g of deionized water and stirred evenly using a magnetic stirrer. After stirring and dissolving, the pH value of the system was adjusted to 7 with NaOH (aqueous solution, 20 wt%). 0.0546 g of N,N-methylenebisacrylamide was weighed and added to the beaker and stirred evenly. After each agent was completely dissolved, stirring was continued for 5 minutes before dissolving other agents. After all agents were evenly dissolved, nitrogen was passed for 15 minutes and ultrasonic oscillation was performed for 15 minutes to fully remove oxygen in the aqueous phase.

[0065] After the oil phase was stirred for 20 minutes, the aqueous phase was added dropwise at a rate of 1-2 drops per second under nitrogen protection under stirring conditions of 600 r / min. After the microemulsion became clear and transparent, the rotation speed was reduced to 350 r / min, and a 0.2% aqueous solution of ammonium persulfate (wherein the mass of ammonium persulfate was 0.01092 g) and a 0.2% aqueous solution of sodium bisulfite (wherein the mass of sodium bisulfite was 0.01092 g) were added to the microemulsion in sequence at a rate of 1-2 drops per second. After the addition was completed, the reaction was continued with stirring at 40° C. under nitrogen protection for 4 hours.

[0066] After the reaction is completed, cool and stand at room temperature; repeatedly wash the microemulsion with anhydrous ethanol for 3-5 times to fully remove the oil phase adhering to the solid surface of the microspheres, and separate the solid and liquid using filter paper; place the solid in a drying oven at 50°C for 24 hours to fully dry, and grind the solid microspheres to obtain acid-resistant hydrophobic polymer microspheres with an average particle size of 82 nm.

[0067] (2) Preparation of acid-resistant cyclodextrin polymer:

[0068] 7g acrylamide, 3g acrylic acid, 0.2g N-octadecylacrylamide, 0.3g dimethyldiallylammonium chloride, and 0.022g of the cyclodextrin-containing RAFT chain transfer agent prepared above were weighed and dissolved in 15g of deionized water. The mixture was placed in a 250mL three-necked flask and stirred continuously under nitrogen. The pH was adjusted to approximately 7.3-7.6 using a 40% aqueous sodium hydroxide solution, and the mixture was then transferred to the flask. The flask was placed in a thermostatic water bath at 45°C, continuously purged with nitrogen, and stirred at high speed for 1-2 hours until the solution clarified. Subsequently, 1mL of an aqueous solution of potassium persulfate and sodium bisulfite (the total mass of potassium persulfate and sodium bisulfite was 0.022g, with a mass ratio of 3:1) was injected using a syringe. The reaction was stirred at 45°C in a nitrogen atmosphere. When the reaction enhancement system became viscous, stirring was stopped and the three-necked flask was sealed and placed in a nitrogen atmosphere at 45°C for 6 hours to obtain a transparent colloidal product. The product was taken out and cut into small pieces, and purified by acetone precipitation three times. The cyclodextrin polymer particles were obtained by vacuum drying and granulation.

[0069] (3) Preparation method of surfactant-based heterogeneous supramolecular inclusion enhancement system for CO2 flooding reservoirs:

[0070] First, 0.01 g of acid-resistant hydrophobic polymer microspheres were weighed and slowly dispersed in 100 mL of distilled water at 300 r·min. -1 The speed was stirred at room temperature for 5 hours, so that the acid-resistant hydrophobic polymer microspheres could be well dispersed in water without aggregation. When the acid-resistant hydrophobic polymer microspheres were evenly dispersed, they were placed in a water bath, the stirring speed was reduced, and the mixture was stirred at 100 r·min at 40°C. -1 The mixture was stirred at 400°C for 24 hours and then expanded for 24 hours. Subsequently, 0.15 g of an acid-resistant cyclodextrin polymer and 0.2 g of the aforementioned Gemini betaine surfactant were added. After mixing evenly, the mixture was placed in a 40°C thermostat and aged for 72 hours to obtain a surfactant-based heterogeneous supramolecular inclusion synergistic system for CO2 flooding reservoirs.

[0071] Example 2

[0072] A method for preparing a surfactant-based heterogeneous supramolecular inclusion synergistic system for CO2 flooding reservoirs is as described in Example 1, except that the amount of acid-resistant hydrophobic polymer microspheres used is 0.005 g; the other steps and conditions are the same as in Example 1.

[0073] Example 3

[0074] A method for preparing a surfactant-based heterogeneous supramolecular inclusion synergistic system for CO2 flooding reservoirs is as described in Example 1, except that the amount of acid-resistant hydrophobic polymer microspheres used is 0.02 g; the other steps and conditions are the same as in Example 1.

[0075] Example 4

[0076] A method for preparing a surfactant-based heterogeneous supramolecular inclusion synergistic system for CO2 flooding reservoirs is as described in Example 1, except that the amount of acid-resistant cyclodextrin polymer used is 0.1 g; the other steps and conditions are the same as in Example 1.

[0077] Example 5

[0078] A method for preparing a surfactant-based heterogeneous supramolecular inclusion synergistic system for CO2 flooding reservoirs is as described in Example 1, except that the amount of acid-resistant cyclodextrin polymer used is 0.2 g; the other steps and conditions are the same as in Example 1.

[0079] Example 6

[0080] A method for preparing a surfactant-based heterogeneous supramolecular inclusion synergistic system for CO2 flooding reservoirs is as described in Example 1, except that the amount of gemini betaine surfactant used is 0.1 g; the other steps and conditions are the same as in Example 1.

[0081] Example 7

[0082] A method for preparing a surfactant-based heterogeneous supramolecular inclusion synergistic system for CO2 flooding reservoirs is as described in Example 1, except that the amount of gemini betaine surfactant used is 0.3 g; the other steps and conditions are the same as in Example 1.

[0083] Example 8

[0084] A method for preparing a surfactant-based heterogeneous supramolecular inclusion enhancement system for CO2 flooding reservoirs is as described in Example 1, except that: in step (1), in the preparation of acid-resistant hydrophobic polymer microspheres, the amount of dimethyldiallylammonium chloride added is 0.2 g; the other steps and conditions are the same as in Example 1.

[0085] Example 9

[0086] A method for preparing a surfactant-based heterogeneous supramolecular inclusion enhancement system for CO2 flooding reservoirs is as described in Example 1, except that: in the preparation of acid-resistant hydrophobic polymer microspheres in step (1), the amount of hexadecyldimethylallyl ammonium chloride added is 0.2 g; the other steps and conditions are the same as in Example 1.

[0087] Example 10

[0088] A method for preparing a surfactant-based heterogeneous supramolecular inclusion enhancement system for CO2 flooding reservoirs is as described in Example 1, except that: in the preparation of the acid-resistant cyclodextrin polymer in step (2), the amount of dimethyldiallylammonium chloride added is 1 g; the other steps and conditions are the same as in Example 1.

[0089] Example 11

[0090] A method for preparing a surfactant-based heterogeneous supramolecular inclusion synergistic system for CO2 flooding reservoirs is as described in Example 1, except that: in the preparation of the acid-resistant cyclodextrin polymer in step (2), the amount of N-octadecyl acrylamide added is 1 g; the other steps and conditions are the same as in Example 1.

[0091] Example 12

[0092] A method for preparing a surfactant-based heterogeneous supramolecular inclusion enhancement system for CO2 flooding reservoirs is as described in Example 1, except that: in the preparation of the acid-resistant cyclodextrin polymer in step (2), the added amount of a chain transfer agent containing a cyclodextrin group is 0.1 g; the other steps and conditions are the same as in Example 1.

[0093] Comparative Example 1

[0094] A method for preparing a supramolecular inclusion synergistic system is as described in Example 1, except that no surfactant is added; other steps and conditions are the same as in Example 1.

[0095] Comparative Example 2

[0096] A method for preparing a supramolecular inclusion synergistic system is as described in Example 1, except that the acid-resistant cyclodextrin polymer is replaced by an equal amount of HPAM; the other steps and conditions are the same as in Example 1.

[0097] Comparative Example 3

[0098] A method for preparing a supramolecular inclusion synergistic system is as described in Example 1, except that the surfactant is replaced by an equal amount of sodium lauryl sulfate; the other steps and conditions are the same as in Example 1.

[0099] Comparative Example 4

[0100] A method for preparing a supramolecular inclusion synergistic system, as described in Example 1, except that: the acid-resistant hydrophobic polymer microspheres are replaced with an equal amount of acrylamide microspheres; that is, in step (1), dimethyldiallylammonium chloride and hexadecyldimethylallylammonium chloride are replaced with an equal amount of acrylamide;

[0101] Other steps and conditions are the same as in Example 1.

[0102] Comparative Example 5

[0103] A method for preparing a supramolecular inclusion synergistic system is as described in Example 1, except that no acid-resistant cyclodextrin polymer is added; other steps and conditions are the same as in Example 1.

[0104] Comparative Example 6

[0105] A method for preparing a supramolecular inclusion synergistic system is as described in Example 1, except that: in step (2), dimethyldiallylammonium chloride is not added; the other steps and conditions are the same as in Example 1.

[0106] Comparative Example 7

[0107] A method for preparing a supramolecular inclusion synergistic system is as described in Example 1, except that in step (2), N-octadecyl acrylamide is replaced by N-hexadecyl acrylamide; the other steps and conditions are the same as in Example 1.

[0108] Test example

[0109] The performance of the supramolecular inclusion enhancement system was tested.

[0110] 1. Viscosity and shear recovery test

[0111] The ionic composition of the mineralized water is shown in Table 1. Acid was added to adjust the pH to 3 to simulate supercritical CO2 conditions. The water in the synergistic systems prepared in the Examples and Comparative Examples was replaced with the mineralized water in Table 1. Shearing was performed at 85°C and a mechanical shear rate of 1000 r / min for 3 minutes. The viscosity before and after shearing was measured using a rheometer at 85°C, and the viscosity retention was calculated as shown in Table 2 below.

[0112] Table 1 Mineralization ion composition

[0113]

[0114] Table 2 Viscosity data

[0115]

[0116]

[0117] It can be seen from the data in Table 2 that the combination of the acid-resistant cyclodextrin polymer, the acid-resistant hydrophobic polymer microspheres and the gemini betaine surfactant in the present invention, and the use of the ratio in Example 1, can exert better viscosity increasing ability and shear resistance at the lowest cost.

[0118] 2. Oil-water interfacial tension test: an oil droplet (thin oil) was injected into a liquid glass capillary and suspended in a supramolecular inclusion enhancement system (where water was replaced with the mineralized water in Table 1 in equal amounts). The oil droplet was rotated at high speed (6000 r / min) and the suspension was suspended in a supramolecular inclusion enhancement system (where water was replaced with the mineralized water in Table 1 in equal amounts). -1), the oil drop was stretched and deformed, and its equilibrium interfacial tension was measured at 85°C. The test results are shown in Table 3 below.

[0119] Table 3 Interfacial tension data

[0120] sample <![CDATA[Interfacial tension / mN·m -1 > Example 1 0.022 Comparative Example 3 0.042

[0121] It can be seen from the data in Table 3 that Gemini betaine surfactants have a stronger ability to reduce interfacial tension than general surfactants.

[0122] 3. Gas drive sealing experiment: A core model with an artificial simulated fracture (Φ2.5cm×2.5cm×10cm, fracture width of 0.03mm) was placed in a core holder. The confining pressure was set to 15MPa and the back pressure was set to 7.6MPa. The flow rate of the constant speed pump was adjusted to 0.5mL·min -1 Perform CO2 gas flooding until the pressure is stable, record the injection pressure difference on both sides of the core holder, and calculate the permeability; inject 0.5PV of the enhancement system solution into the core at a rate of 0.5mL·min-1, heat the displacement device to 60-80℃, close the displacement device for 8-12h, and then inject the solution again at a rate of 0.5mL·min-1. -1 The CO2 gas drive was carried out at a rate of 100 nm until the pressure was stable. The injection pressure difference on both sides of the core holder was recorded, and the permeability and thus the plugging rate were calculated.

[0123] The test results are shown in Table 4. The blocking effect data of the supramolecular inclusion synergistic system prepared in Example 1 and Comparative Example 4 are shown in Table 4. Figure 1 and 2 shown.

[0124] Table 4 Plugging rate data

[0125] sample Blockage rate / % Example 1 98 Example 2 89 Example 3 91 Example 4 82 Example 5 97 Example 6 84 Example 7 88 Example 8 90 Example 9 89 Example 10 91 Example 11 88 Example 12 82 Comparative Example 1 80 Comparative Example 2 81 Comparative Example 3 83 Comparative Example 4 85 Comparative Example 5 78 Comparative Example 6 83 Comparative Example 7 87

[0126] As can be seen from the figure, the heterogeneous supramolecular inclusion synergistic system prepared by the present invention has a better blocking effect.

[0127] As described above, the heterogeneous supramolecular inclusion synergistic system prepared by the present invention has better viscosity increasing effect, stronger ability to reduce oil-water interfacial tension, and higher blocking rate.

[0128] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art will be able to modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein with equivalents. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A surfactant-based heterogeneous supramolecular inclusion synergistic system for CO2 flooding reservoirs, characterized in that: The invention comprises the following raw materials in parts by weight: 0.1-0.2 parts of acid-resistant hydrophobic polymer microspheres, 1-2 parts of acid-resistant cyclodextrin polymer, 1-3 parts of surfactant, and 800-1200 parts of water; The preparation method of acid-resistant hydrophobic polymer microspheres comprises the following steps: (1) Mix white oil, Span80, and Tween80 evenly to obtain an oil phase; (2) Acrylamide (AM), hexadecyl dimethyl allyl ammonium chloride (C 16 DMAAC) and dimethyldiallyl ammonium chloride (DMDAAC) are fully dissolved in water, the pH value of the system is adjusted, and N, N-methylenebisacrylamide (MBA) is added and mixed evenly to obtain an aqueous phase; (3) adding the aqueous phase dropwise to the oil phase, and then sequentially adding an aqueous solution of ammonium persulfate and an aqueous solution of sodium bisulfite, reacting, washing, drying, and grinding to obtain acid-resistant hydrophobic polymer microspheres; The acid-resistant cyclodextrin polymer is prepared by comprising the following raw materials in parts by weight: 5-15 parts of a hydrophilic polymerizable monomer, 0.1-1 parts of a hydrophobic monomer, 0.1-1 parts of an acid-resistant monomer, 0.01-0.1 parts of an initiator, 0.01-0.1 parts of a chain transfer agent containing a cyclodextrin group, and 10-20 parts of water; The hydrophilic polymerization monomers are acrylamide and acrylic acid, and the mass ratio of acrylamide to acrylic acid is 5-9:3; the hydrophobic monomer is N-octadecyl acrylamide; the acid-resistant monomer is dimethyl diallyl ammonium chloride; and the chain transfer agent containing a cyclodextrin group is a RAFT chain transfer agent, and the structural formula is as follows: The surfactant is a gemini betaine surfactant with the following structural formula: 。 2. The surfactant-based heterogeneous supramolecular inclusion synergistic system for CO2 flooding reservoirs according to claim 1, characterized in that: The method for preparing acid-resistant hydrophobic polymer microspheres includes one or more of the following conditions: i. In step (1), the mass ratio of white oil, Span80, and Tween80 is 35-40:2-3:0.5-1.5; ii. In step (2), acrylamide (AM), hexadecyldimethylallyl ammonium chloride (C 16 The mass ratio of DMAAC), dimethyldiallylammonium chloride (DMDAAC), N,N-methylenebisacrylamide (MBA) and water is 5-6:0.1-0.2:0.1-0.2:0.04-0.06:15-30; iii. In step (2), the pH value of the system is adjusted to 7 using a sodium hydroxide aqueous solution with a mass concentration of 10%-50%; iv. In step (3), the aqueous phase is added at a rate of 1-5 drops per second, and the addition is carried out under stirring and under the protection of a protective gas; the protective gas is nitrogen or argon; v. In step (3), the mass ratio of acrylamide in the aqueous phase to the oil phase is 5-6:40-45; vi. In step (3), the dropping rate of the aqueous ammonium persulfate solution and the aqueous sodium bisulfite solution is 1-5 drops per second, and the dropping is carried out under stirring conditions and protective gas protection; the protective gas is nitrogen or argon; vii. In step (3), the mass concentrations of the ammonium persulfate aqueous solution and the sodium bisulfite aqueous solution are both 0.02%-0.2%, wherein the mass ratio of ammonium persulfate to sodium bisulfite is 1:1; the mass ratio of ammonium persulfate to acrylamide in the aqueous phase is 1:475-785; viii. In step (3), the reaction temperature is 25-40°C, the reaction time is 2-6 hours, and the reaction is carried out under stirring and protective gas protection; the protective gas is nitrogen or argon.

3. The surfactant-based heterogeneous supramolecular inclusion synergistic system for CO2 flooding reservoirs according to claim 1, characterized in that: In the acid-resistant cyclodextrin polymer, the initiators are potassium persulfate and sodium bisulfite, and the mass ratio of potassium persulfate to sodium bisulfite is 2-4:

1.

4. The surfactant-based heterogeneous supramolecular inclusion synergistic system for CO2 flooding reservoirs according to claim 1, characterized in that: The preparation method of the acid-resistant cyclodextrin polymer comprises the following steps: The hydrophilic polymer monomer, the hydrophobic monomer, the acid-resistant monomer and the chain transfer agent containing the cyclodextrin group are fully dispersed in water, and the pH of the system is adjusted to be weakly alkaline; an initiator aqueous solution is added, reacted, and then purified by precipitation, dried, and granulated to obtain an acid-resistant cyclodextrin polymer; A sodium hydroxide aqueous solution with a mass concentration of 30-50% is used to adjust the pH of the system to 7-8; the mass concentration of the initiator aqueous solution is 0.01-0.05 g / mL; the reaction conditions are as follows: under protective gas protection, stir the reaction at 40-70°C until the system becomes viscous, and then under protective gas protection, stand the reaction at 40-70°C for 4-7 hours; the protective gas is nitrogen or argon.

5. The method for preparing the surfactant-based heterogeneous supramolecular inclusion synergistic system for CO2 flooding reservoirs according to any one of claims 1 to 4, comprising the steps of: Acid-resistant hydrophobic polymer microspheres are fully dispersed in water, and a microsphere dispersion is obtained through an expansion reaction; an acid-resistant cyclodextrin polymer and a surfactant are added, fully mixed and dispersed evenly, and an aging reaction is performed to obtain a surfactant-based CO2 flooding reservoir heterogeneous supramolecular inclusion enhancement system.

6. The method for preparing the surfactant-based heterogeneous supramolecular inclusion synergistic system for CO2 flooding reservoirs according to claim 5, characterized in that: Include one or more of the following conditions: i. Disperse the acid-resistant hydrophobic polymer microspheres in water and stir at room temperature at 200-400 rpm for 4-6 hours to fully disperse them; ii. The expansion reaction temperature is 40-60℃, the expansion reaction time is 24-36h, and the expansion reaction is at 50-200 r·min -1 Carried out under stirring conditions; iii. The aging reaction temperature is 40-50°C, and the aging reaction time is 36-72h.

7. The use of a surfactant-based heterogeneous supramolecular inclusion synergistic system for CO2 flooding reservoirs according to any one of claims 1 to 4, characterized in that: Used to seal gas channel in CO2 flooding reservoirs.

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