High-strength self-assembled gel foam oil displacement agent and preparation method thereof

Abstract

The application provides a high-strength self-assembled gel foam oil displacement agent and a preparation method thereof, and belongs to the field of chemical oil displacement. The high-strength self-assembled gel foam oil displacement agent is composed of the following components: a ternary amphiphilic hydrophobic association copolymer, a zwitterionic surfactant, a non-ionic surfactant, a heat-resistant polyacid, a counterion compound, a chelating agent and formation water. The self-assembled gel foam oil displacement agent forms four interactions among the molecules of each component, significantly increases the strength of the foaming liquid, produces fine and rich nitrogen gas foam, has good stability, can block large fractures and solution cavities in a fracture-cavity type reservoir, can effectively expand the swept volume, and significantly improves the oil recovery rate of the fracture-cavity type reservoir. The foam agent does not produce precipitation with calcium and magnesium ions, and also does not precipitate due to salt.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of chemical oil displacement, and particularly relates to a high-strength self-assembled gel foam oil displacement agent and a preparation method thereof. BACKGROUND

[0002] Carbonate fracture-cave type reservoirs have great resource potential, and karst modes can be divided into surface weathering crust karst, fault-controlled karst and ancient dark river karst, and reservoir spaces are mainly large caves, large fractures and dissolution pores, which have great scale difference from micron to meter and strong heterogeneity, and the recovery rate is generally low. At present, the main method for enhancing the recovery of the carbonate fracture-cave type reservoirs in Tahe is water injection, gas injection and matching efficiency technology. Since 60%-70% of the cave reservoirs are collapsed and filled, and the flow characteristics are greatly different in the fracture development area, the injected medium is easy to channel into the high-conductivity channel, resulting in low water flooding efficiency, and there is a high risk of gas channeling in nitrogen gas flooding, so it is necessary to find a more effective method and theoretical guidance for enhancing the recovery of the carbonate fracture-cave type reservoirs.

[0003] Based on the adjustment of the nitrogen gas flooding channel, the purpose of optimizing the profile control and flooding is achieved by optimizing the matching medium of the nitrogen gas injection. The nitrogen gas foam is mainly used as the adjustment medium, and the foam has the characteristics of selective plugging, plugging large channels but not small channels, and plugging water but not oil, which makes the foam flooding technology have great development prospects in oilfield development. The oil recovery is further improved through the mechanisms of improving the oil-water interfacial tension and plugging the injection of the advantage nitrogen gas migration high channel. Nitrogen gas is an inert gas, which is not easy to react with the formation fluid and rock, is safe and economical, and has low solubility in water, thereby reducing the adverse effects caused by emulsification and sedimentation plugging. Therefore, the test of the nitrogen gas foam flooding can further enrich and develop the theory of enhancing the recovery of carbonate reservoirs, and has important theoretical and practical significance. The nitrogen gas foam flooding technology is a tertiary oil recovery technology based on nitrogen gas flooding and diversified oil displacement mechanisms, which shows great advantages in the oil and gas field development process by virtue of its unique properties and oil displacement mechanisms, and has been widely concerned at home and abroad.

[0004] In view of the problems of poor gas flooding effect and advantage sweep in the carbonate fracture-cave type reservoirs, the gel foam flooding pilot test is carried out in Well TK647 in Tahe Oilfield, and the preliminary effect is obtained, and the feasibility of the foam profile control and flooding is verified.

[0005] The gel foam system has a viscosity of 24x10 4The adaptability of the high-salinity oil reservoir needs to be optimized, and the long-term stability (effective period of field application) of the gel foam system is not high enough during the field application process. The gel foam system developed in the early stage involves multiple agents in the forming process, and the system is relatively complex, resulting in high use cost. In addition, the field construction process of the gel foam system is slightly complicated, and needs to be further optimized. The optimization of the system and the simplification of the process will further improve the economic benefits of the field application of the gel foam system.

[0006] In view of the actual problems and the characteristics of the fracture-vug type oil reservoir, through molecular structure design and repeated experiments, the high-strength self-assembled foam oil displacement agent suitable for the fracture-vug type oil reservoir can form ordered aggregates under high-temperature and high-salinity conditions, effectively improve the viscosity of the foaming liquid, increase the thickness of the foam interface film, effectively improve the stability of the foam, the formed foam has a longer stable time, the ability to block cracks and solution cavities is enhanced, and the sweep efficiency is more significantly expanded. SUMMARY

[0007] In view of the defects of the prior art, the application provides a high-strength self-assembled gel foam oil displacement agent suitable for a fracture-vug type oil reservoir and a preparation method thereof. Raw materials of various components can self-assemble to form ordered aggregates through four intermolecular interactions, greatly increasing the viscosity of the foaming liquid under high-temperature and high-salinity conditions. The gel foam oil displacement agent has the characteristics of no alkali and no corrosion, has good temperature resistance and salt resistance, can make the oil-water interfacial tension reach an ultralow value, and can produce fine, stable and abundant foam. In the fracture-vug oil reservoir, the gel foam oil displacement agent can block large cracks and solution cavities, expand the swept volume, and significantly improve the recovery rate.

[0008] A high-strength self-assembled gel foam oil displacement agent is composed of the following components in weight percentage:

[0009]

[0010] The balance is formation water,

[0011] The salinity of the formation water is 100000-300000 mg / L.

[0012] The ternary amphiphilic hydrophobic associating copolymer is obtained by copolymerization of acrylamide (AM), methacryloyloxyethyl-N,N-dimethylpropane sulfonate (DMAPS) and dioctadecyl methyl allyl ammonium chloride (DiC18DMAAC).

[0013] The mass ratio of acrylamide (AM), methacryloyloxyethyl-N,N-dimethylpropane sulfonate (DMAPS) and dioctadecyl methyl allyl ammonium chloride (DiC18DMAAC) monomer units in the ternary amphiphilic hydrophobic associating copolymer is 4-6:0.5-1:0.1-0.3.

[0014] The preparation method of the ternary amphiphilic hydrophobic association copolymer is described in (Synthesis, Characterization and Properties of Amphiphilic Water-Soluble Polymers, Doctoral Dissertation of Quan Wei, Shandong University, 2013).

[0015] The zwitterionic surfactant is erucyl amido propyl betaine (EAB);

[0016] The non-ionic surfactant is N,N-dimethyl hexadecyl amine oxide (NOB-2);

[0017] The heat-resistant polyacid is trimesic acid;

[0018] The counterion compound is sodium salicylate;

[0019] The chelating agent is EDTA;

[0020] The formation water contains inorganic salts, and the inorganic salts include one or more of sodium chloride, magnesium chloride, sodium sulfate, sodium bisulfate, sodium carbonate, potassium chloride, and calcium chloride.

[0021] The application also provides a preparation method of the high-strength self-assembled gel foam oil displacement agent, comprising the following steps:

[0022] (1) heating the formation water to 70-90 DEG C, adding the ternary copolymer hydrophobic association polymer, stirring and dissolving, then adding the zwitterionic surfactant, stirring and dissolving;

[0023] (2) adding the non-ionic surfactant and the chelating agent into the mixed solution obtained in step (1) in sequence, stirring and dissolving;

[0024] (3) adding the heat-resistant polyacid and the counterion compound into the mixed solution obtained in step (2), stirring and dissolving, and then obtaining the high-strength self-assembled gel foam oil displacement agent.

[0025] The application also provides a use method of the high-strength self-assembled gel foam oil displacement agent, and the use method is as follows:

[0026] The high-strength self-assembled gel foam oil displacement agent is used to prepare foam through a sand filling pipe model, and the specific operation is as follows: the high-strength self-assembled gel foam oil displacement agent is added into a piston container; the lower end of the piston container is connected with a double-cylinder pump, and the upper end of the piston container is connected with the inlet end of the sand filling pipe through a three-way valve, and a high-pressure nitrogen cylinder is connected with the inlet end of the sand filling pipe through a three-way valve; the outlet end of the sand filling pipe is connected with a soap bubble flow meter and a foam test tube in sequence; the upper space of the piston container is connected with a high-pressure nitrogen cylinder, filled with nitrogen gas and kept at the same pressure as the high-pressure cylinder; the output flow of the double-cylinder pump is 1 mL / min, and the gas-liquid ratio is 3:1 alternately injected; after continuous and stable rich and delicate foam is generated, the injectable high-strength self-assembled foam can be obtained; wherein the sand filling pipe is filled with 80-100 mesh quartz sand, and the double-cylinder pump is an ISCO constant pressure and constant flow double-cylinder pump.

[0027] The high-strength self-assembled gel foam oil displacement agent is injected into a full-size core (L x d = 300 mm * 100 mm) to perform oil displacement experiment, and the full-size core is vertically installed with the inlet at the bottom and the outlet at the top. The full-size core is prepared by laser carving the fracture, hole and pore of the carbonate outcrop according to the characteristics of the fracture, hole and pore of the fracture-cave reservoir, and the specific operation is as follows: under certain high temperature and high pressure conditions, the full-size core saturated with high salinity formation water is placed in a vertical core holder, and a confining pressure is added, the sealing property of the system is checked, if the sealing property is good, the experiment is continued; crude oil is injected into the core through an intermediate container until the outlet is all crude oil, the original oil saturation is established; the crude oil is water-flooding to the economic limit (the water cut is stable to 98%), the water-flooding reservoir model is established, and the water-flooding recovery rate is calculated; the valve is opened, the foam prepared by the sand filling pipe is connected, and the crude oil is displaced by 0.5 PV high-strength self-assembled foam, after the foam slug is injected, the subsequent water flooding is performed to the economic limit, and the high-strength self-assembled gel foam oil displacement agent is used to improve the recovery rate of crude oil.

[0028] The high-strength self-assembled gel foam oil displacement agent system formula of the application, the mutual association of the hydrophobic group of the ternary amphiphilic hydrophobic association copolymer enhances the spatial network structure of the polymer molecules in the solution, so that the viscosity of the polymer increases, and the positive charge in the ternary amphiphilic hydrophobic association copolymer and the negative charge of the ionized carboxyl group in the polybasic acid benzenetricarboxylic acid can produce strong electrostatic interaction, the electrostatic interaction shortens the relative distance of the hydrophobic groups on different molecular chains, enhances the hydrophobic association between the molecular chains, and makes the polymer more easily form a spatial network structure in the solution, thereby improving the viscosity-increasing effect. In addition, the addition of the erucic acid amide betaine amphoteric surfactant and the N,N-dimethyl hexadecyl amine nonionic surfactant promotes the association of the polymer, so that the viscosity is further increased, and the main reason is that the ternary amphiphilic hydrophobic association polymer forms a hydrophobic micro zone through the hydrophobic effect of itself, the addition of a low mass concentration of surfactant interacts with the hydrophobic micro zone to form a mixed micelle, promotes the aggregation between the associated molecules, and macroscopically exhibits increased viscosity. In addition, the erucic acid amide betaine amphoteric surfactant can self-assemble into complex worm-like micelles under the action of the counterion compound sodium salicylate, and the contour length of the complex worm-like micelles can be from 1000 nanometers to even 100 micrometers; in the solution, when the complex worm-like micelles reach a certain length and density, the micelles begin to intertwine and overlap with each other to form a network structure with viscoelasticity, and the addition of the ternary copolymer makes the intertwining and overlapping more intense. Therefore, it can be seen that the following four interactions exist between the molecules in the foaming agent solution: 1) the ternary amphiphilic hydrophobic association copolymer itself has a hydrophobic association; 2) the ternary amphiphilic hydrophobic association copolymer and the polybasic acid have electrostatic interaction; 3) the ternary amphiphilic hydrophobic association copolymer and the surfactant form a mixed micelle to promote the association and aggregation of the polymer molecules; and 4) the erucic acid amide betaine amphoteric surfactant and the counterion compound sodium salicylate self-assemble into complex worm-like micelles, and the micelles intertwine with each other to form a network structure with viscoelasticity. Under the four interactions between the molecules and the molecules, the viscosity of the foaming system increases a lot under high-temperature conditions.

[0029] Unlike existing polymer solutions, the high polymer prepared in the application is a long-chain molecular structure connected by covalent bonds, and the foaming agent system has association between macromolecules, electrostatic interaction between macromolecules and small molecules, and molecular ordered assemblies formed by the aggregation of small molecules under intermolecular force, and the molecular ordered assemblies and the polymer intertwine to form a complex.

[0030] The application adopts the association structure, complex worm-like micelle structure, aggregation structure, intertwining structure formed by the ternary amphiphilic hydrophobic association copolymer, surfactant molecules, polybasic acid and sodium salicylate counterion, and the process of dissociation and recombination, so the whole system is a dynamic and balanced network structure.

[0031] Compared with the invention patents CN110776893A and ZL201710864250.3, the counter ion of the present application has a small molecular weight, the self-assembled complex worm-like micelles are longer, and the viscosity is higher under the same amount in macroscopic. The concentration required to form worm-like micelles of the same length with hydrophobic associating polymer is greatly reduced, thereby reducing the amount of surfactant. The formation of complex worm-like micelles can effectively prevent the generation of calcium carbonate crystal nucleus and the growth of crystal. The double electric layer is thinned due to the extrusion of calcium and magnesium ions on the complex worm-like micelles, the hydrodynamics of the complex worm-like micelles is reduced, the size is reduced, the generated foam is fine and uniform, and the stability is good. At the same time, the synergistic effect of erucylamide betaine surfactant and amine oxide nonionic surfactant leads to more closely arranged surfactant molecules on the oil-water interface, stronger reduction of oil-water interfacial tension, and can make the oil-water interfacial tension reach ultra-low value. In addition, erucylamide betaine surfactant, N,N-dimethylhexadecyl amine oxide nonionic surfactant and dioctadecyl methyl allyl ammonium chloride (DiC18DMAAC) monomer unit in the ternary amphiphilic hydrophobic associating copolymer all have long chain hydrophobic groups, which are all conducive to enhancing the hydrophobic association. Benzoic acid and dioctadecyl methyl allyl ammonium chloride (DiC18DMAAC) monomer unit in the ternary amphiphilic hydrophobic associating copolymer are all conducive to improving the temperature resistance of the foaming fluid. Erucylamide betaine surfactant, N,N-dimethylhexadecyl amine oxide nonionic surfactant and ternary amphiphilic hydrophobic associating copolymer can all significantly improve the salt resistance of the foaming fluid.

[0032] Compared with the prior art, the present application has the following advantages:

[0033] (1) The foaming oil displacement agent described in the present application, the ternary copolymer hydrophobic associating polymer and the erucylamide betaine, the trimesic acid and the sodium salicylate in the brine have four intermolecular interactions, which can form a complex with a multi-level structure and have a higher viscosity. Under the same conditions, the viscosity of the system formed by adding the same amount of sodium salicylate is much higher than that of the system formed by adding the same amount of sodium dodecyl sulfate; the viscosity of the system formed by adding trimesic acid is much higher than that of the system formed by adding glutaric acid. After nitrogen is introduced and foaming, the generated foam is abundant, delicate and has a long half-life; when nitrogen foam is injected into the high-temperature and high-salt fracture-cave type reservoir in the northwest oilfield, it not only has salt resistance and temperature resistance, but also has good foaming and foam stability, and can make the oil-water interfacial tension reach 10-3mN / m order of magnitude.

[0034] (2) The foam oil displacement agent described in the application does not contain alkali, avoiding the problems of reducing the viscoelasticity of the system, producing precipitation between alkali and formation water, increasing injection process and difficulty in treating produced fluid, increasing cost and the like in application, and simultaneously adding a terpolymer to improve the viscosity increasing ability of the foam liquid under high temperature conditions, the hydrodynamic radius of the random coil formed after the terpolymer is dissolved in the formation water is large, the viscosity is high, the foam liquid film is thick, and the foam liquid can effectively plug the solution cavity and large cracks in the fracture-vug type oil reservoir.

[0035] (3) The stability of the foam after foaming is significantly improved, the oil-water two-phase flowability is improved, the swept volume is expanded, the oil-water interfacial tension is significantly reduced, the oil washing efficiency is improved, the formation energy is increased, and the seepage capacity of the oil phase liquid is improved, thereby significantly improving the crude oil recovery rate of the high-temperature high-salt fracture-vug type oil reservoir. DETAILED DESCRIPTION

[0036] Example 1: A high-strength self-assembled gel foam oil displacement agent and a preparation method thereof

[0037] consists of the following components by weight percentage:

[0038]

[0039] The terpolymer amphiphilic hydrophobic association copolymer is obtained by copolymerization of acrylamide (AM), methacryloyloxyethyl-N,N-dimethylpropane sulfonate (DMAPS) and dioctadecyl methyl allyl ammonium chloride (DiC18DMAAC), and the mass ratio of the acrylamide (AM), methacryloyloxyethyl-N,N-dimethylpropane sulfonate (DMAPS) and dioctadecyl methyl allyl ammonium chloride (DiC18DMAAC) monomer units is 5:1:0.1.

[0040] The salinity of the formation water is:

[0041] sodium ion potassium ion calcium ion magnesium ion chloride ion bicarbonate ion total mineralization mg / L 40452.5 13315 10665 8042.5 88242.5 3135.0 163852.5

[0042] Preparation method:

[0043] (1) The formation water is heated to 80℃, the terpolymer hydrophobic association polymer is added, and after stirring and dissolving, the erucylamide propyl betaine is added and stirred and dissolved;

[0044] (2) The non-ionic surfactant N,N-dimethylhexadecyl amine oxide and the chelating agent are sequentially added to the mixed solution obtained in step (1) and stirred and dissolved;

[0045] (3) The trimesic acid and sodium salicylate are added to the mixed solution obtained in step (2) and stirred and dissolved, and the self-assembled gel foam oil displacement agent is obtained.

[0046] Example 2: A high-strength self-assembled gel foam oil displacement agent and a preparation method thereof

[0047] consists of the following components by weight percentage:

[0048]

[0049] The ternary amphiphilic hydrophobic association copolymer is obtained by copolymerization of acrylamide (AM), methacryloyloxyethyl-N,N-dimethylpropane sulfonate (DMAPS) and dioctadecyl methyl allyl ammonium chloride (DiC18DMAAC), and the mass ratio of acrylamide (AM), methacryloyloxyethyl-N,N-dimethylpropane sulfonate (DMAPS) and dioctadecyl methyl allyl ammonium chloride (DiC18DMAAC) monomer units is 6:1:0.3.

[0050] The salinity of the formation water is:

[0051] sodium ion potassium ion calcium ion magnesium ion chloride ion bicarbonate ion total mineralization mg / L 50161.1 16510.6 13224.6 9972.7 109420.7 3887.4 203177.1

[0052] Preparation method:

[0053] (1) The formation water is heated to 80℃, and the ternary copolymer hydrophobic association polymer is added, stirred and dissolved, and then erucylamide propyl betaine is added and stirred and dissolved;

[0054] (2) The non-ionic surfactant N,N-dimethylhexadecyl amine oxide and the chelating agent are sequentially added to the mixed solution obtained in step (1) and stirred and dissolved;

[0055] (3) The mixed solution obtained in step (2) is added with trimesic acid and sodium salicylate, stirred and dissolved, and then the self-assembled gel foam oil displacement agent is obtained.

[0056] Example 3 A high-strength self-assembled gel foam oil displacement agent and a preparation method thereof

[0057] consists of the following components by weight percentage:

[0058]

[0059]

[0060] The ternary amphiphilic hydrophobic association copolymer is obtained by copolymerization of acrylamide (AM), methacryloyloxyethyl-N,N-dimethylpropane sulfonate (DMAPS) and dioctadecyl methyl allyl ammonium chloride (DiC18DMAAC), and the mass ratio of acrylamide (AM), methacryloyloxyethyl-N,N-dimethylpropane sulfonate (DMAPS) and dioctadecyl methyl allyl ammonium chloride (DiC18DMAAC) monomer units is 6:1:0.3.

[0061] The salinity of the formation water is:

[0062] sodium ion potassium ion calcium ion magnesium ion chloride ion bicarbonate ion total mineralization mg / L 55015.4 17108.4 14165.0 10437.8 119009.8 4263.6 220000.0

[0063] Preparation method:

[0064] (1) The formation water is heated to 80℃, and the terpolymer hydrophobic associating polymer is added, stirred and dissolved, and then the erucylamide propyl betaine is added and stirred and dissolved;

[0065] (2) The nonionic surfactant N, N-dimethylhexadecylamine oxide and the chelating agent are sequentially added to the mixed solution obtained in step (1) and stirred and dissolved;

[0066] (3) The trimesic acid and sodium salicylate are added to the mixed solution obtained in step (2) and stirred and dissolved, and the foam flooding agent is obtained.

[0067] Performance test:

[0068] 1. Viscosity, interfacial tension, foaming property and half-life of the foam flooding agent under high temperature and high pressure

[0069] Test method:

[0070] (1) The viscosity of the foam flooding agent prepared in the above Examples 1-3 under the conditions of temperature 150℃ and pressure 40Mpa is determined by a high temperature and high pressure HAKEE rheometer, and the oil-water interfacial tension under the conditions of temperature 150℃ and pressure 40Mpa is determined by a high temperature and high pressure Tax500 ultra-low rotation interfacial tension meter, and the results are shown in Table 1.

[0071] (2) 200mL of the foam flooding agent prepared in the above Examples 1-3 is placed in a high temperature and high pressure visual foaming device (patent No. ZL201010130488.1), the stirring device is closed and connected to nitrogen, heated to 150℃, pressurized to 40MPa, stirred at a speed of 4000r / min for 60s, the initial foam volume V0 is immediately read, and the timing is started; the time t required for half of the foam to be eliminated is recorded, which is the foam half-life, and finally the foam comprehensive index FCI (FCI = 0.75 x V0 x t) is calculated. 1 / 2 1 / 2

[0072] Table 1 Influence of viscosity, interfacial tension, foaming property and half-life of the foam flooding agent under high temperature and high pressure

[0073]

[0074] ​​Compared with the invention patent ZL201710864250.3, the present application does not use triethanolamine and urea; the viscosity and foam comprehensive index FCI of the foam oil displacement agent of the present application examples 1, 2 and 3 are significantly increased compared with the corresponding examples of the invention patent ZL201710864250.3.

[0075] According to the detection data in Table 1 above, the oil-water interfacial tension of the three examples of the invention patent ZL201710864250.3 cannot reach 10 -3 mN.m -1 orders of magnitude (ultra-low value), while the oil-water interfacial tension of the present application examples 1 and 2 reaches 10 - 3 mN.m -1 orders of magnitude, so the oil displacement agent of the present application has stronger oil-water interfacial tension reduction.

[0076] In the case where the total amount (0.66-1.36%) of the main agent (including ternary copolymer hydrophobic associating polymer, erucylamide propyl betaine, N,N-dimethylhexadecyl amine oxide, trimesic acid, sodium salicylate, chelating agent EDTA) used in the present application is far less than the total amount (30-80%) of the main agent (anionic and cationic surfactants, betaine surfactant and nonionic surfactant) of the invention patent CN110776893A, compared with the 9 examples of the invention patent ZL201810856435.4, ZL201810856435.4 does not have any half-life data, which is seriously missing, and the repeated test determines that its half-life is only 3-5 min, which is far lower than the data 17-22 min in the above table of the present application, so the foam comprehensive index value of the present application is larger, the self-assembly ability is stronger, and the foam comprehensive performance is better.

[0077] 2, the foam oil displacement agent prepared by the present application is prepared into foam through a sand filling pipe, injected into a full-size core, and the crude oil recovery is detected

[0078] The specific operation is: the high-strength self-assembled gel foam oil displacement agent is added into a piston container; the lower end of the piston container is connected with a double-cylinder pump, and the upper end of the piston container is connected with the inlet end of the sand filling pipe through a three-way valve, and a nitrogen high-pressure gas cylinder is connected with the inlet end of the sand filling pipe through a three-way valve; the outlet end of the sand filling pipe is connected with a soap bubble flowmeter and a foam test tube in sequence; the upper space of the piston container is connected with a nitrogen high-pressure gas cylinder, filled with nitrogen gas and kept at the same pressure as the nitrogen high-pressure gas cylinder; the output flow of the double-cylinder pump is 1 mL / min, and the gas-liquid ratio is 3:1 alternately injected, after waiting for continuous and stable rich and delicate foam to be generated, the high-strength self-assembled foam which can be injected into a full-size core is obtained; wherein the sand filling pipe is filled with 80-100 mesh quartz sand, and the double-cylinder pump is an ISCO constant pressure and constant flow double-cylinder pump;

[0079] The high-strength self-assembled gel foam oil displacement agent is injected into a full-size core (L x d = 300 mm * 100 mm) to perform an oil displacement experiment. The full-size core is vertically installed, with the inlet at the bottom and the outlet at the top. The full-size core is prepared according to the characteristics of fractures, holes and pores of the fracture-vug reservoir by laser engraving the carbonate outcrop. The specific operation is as follows: under certain high-temperature and high-pressure conditions, the full-size core saturated with high salinity formation water is placed in a vertical core holder, and a confining pressure is applied. The sealing property of the system is checked. If the sealing property is good, the experiment is continued. Crude oil is injected into the core through an intermediate container until the outlet is completely filled with crude oil, and the initial oil saturation is established. The crude oil is water-flooded to the economic limit (the water cut is stabilized to 98%), and a water-flooded reservoir model is established. The water-flooded recovery rate is calculated. The valve is opened, and the foam prepared by the front sand filling pipe is connected. The crude oil is displaced by 0.5 PV of the high-strength self-assembled foam. After the foam slug is completely injected, the subsequent water flooding is performed to the economic limit, and the high-strength self-assembled gel foam oil displacement agent is used to improve the recovery rate of crude oil.

[0080] The core parameters of the cores used in examples 1-3 are shown in Table 2, and the displacement experiment results of the high-strength self-assembled gel foam oil displacement agent used in examples 1-3 are shown in Table 3.

[0081] Table 2 Basic parameters of the fracture-vug full-diameter core used in the experiment

[0082]

[0083] Table 3 Experimental results of the high-strength self-assembled foam

[0084] core number waterflood efficiency / % Steady flow pressure differential / Mpa.m -1 ]] foam flooding EOR / % example 1 43.14 3.1 24.7 example 2 40.76 3.4 26.8 example 3 38.66 3.6 29.3

[0085] According to the detection data in Table 3 above, the foam system prepared by using the main agent (including the ternary amphiphilic hydrophobic association copolymer, erucyl amido propyl betaine, N, N-dimethyl hexadecyl amine oxide, trimesic acid, sodium salicylate and chelating agent EDTA) used in the application improves the recovery rate by 24.7%, 26.8% and 29.3% respectively in the above three examples. Compared with the oil displacement efficiency of 16.2%, 20.5%, 18.9%, 17.3%, 18.1%, 18.5%, 19.1%, 20.7% and 18.8% in examples 1-9 of the invention patent ZL201810856435.4, the minimum and maximum oil displacement efficiencies of the oil displacement agent of the application are 8.5% and 8.6% higher respectively, and thus the oil displacement agent has higher oil displacement capacity.

[0086] Finally, it should be noted that the above is only to illustrate the technical solutions of the present application, and is not a limitation on the scope of protection of the present application, and simple modifications or equivalent replacements of the technical solutions of the present application by those skilled in the art do not deviate from the essence and scope of the technical solutions of the present application.

Claims

1. A high-strength self-assembling gel foam oil-displacing agent, characterized by: consists of the following components by weight percentage: ternary amphiphilic hydrophobic associating copolymer 0.2-0.3%, zwitterionic surfactant 0.2-0.3%, nonionic surfactant 0.1-0.35%, heat-resistant polybasic acid 0.1-0.2%, counterion compound 0.02-0.07%, chelating agent 0.04-0.14%, the rest is formation water, the salinity of the formation water is 100000-300000 mg / L; the ternary amphiphilic hydrophobic associating copolymer is acrylamide, methacryloyloxyethyl-N,N-dimethylpropane sulfonate, dioctadecyl methyl allyl ammonium chloride copolymer; the zwitterionic surfactant is erucylamide propyl betaine; the nonionic surfactant is N,N-dimethyl hexadecyl amine oxide; the heat-resistant polybasic acid is trimesic acid; the counterion compound is sodium salicylate; the chelating agent is EDTA; the formation water contains inorganic salts, and the inorganic salts include one or more of sodium chloride, magnesium chloride, sodium sulfate, sodium bisulfate, sodium carbonate, potassium chloride, and calcium chloride.

2. The high-strength self-assembling gel foam oil displacement agent of claim 1, wherein: The mass ratio of acrylamide, methacryloyloxyethyl-N,N-dimethylpropane sulfonate, and dioctadecyl methyl allyl ammonium chloride monomer units in the ternary amphiphilic hydrophobic associating copolymer is 4-6:0.5-1:0.1-0.

3.

3. A process for the preparation of a high-strength self-assembling gel foam oil displacement agent according to any one of claims 1-2, characterized in that: comprising the following steps: (1) heating the formation water to 70-90℃, adding the ternary copolymer hydrophobic associating polymer, stirring and dissolving, then adding the zwitterionic surfactant, stirring and dissolving; (2) adding the nonionic surfactant and the chelating agent to the mixed solution obtained in step (1) in sequence, stirring and dissolving; (3) adding the heat-resistant polybasic acid and the counterion compound to the mixed solution obtained in step (2), stirring and dissolving, to obtain the product.

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