Alkali-free betaine type oil-displacing agent composition and preparation method thereof

Abstract

The invention belongs to the field of chemical oil recovery in the petroleum industry, and specifically relates to an alkali-free betaine type oil recovery agent composition and a preparation method thereof, which comprises the following raw materials by weight: 55-65 parts of a novel betaine type surfactant, 35-45 parts of polyoxyethylene ether, and 20-30 parts of a solvent, wherein the novel betaine type surfactant has a structure in which three betaine side chains are connected to a benzene ring. The alkali-free betaine type oil recovery agent composition provided by the invention has excellent temperature resistance and salt resistance, and can effectively reduce oil-water interfacial tension to improve oil recovery efficiency.

Description

Technical Field

[0001] The invention belongs to the field of chemical oil displacement in the petroleum industry, and particularly relates to an alkali-free betaine type oil displacement agent composition and a preparation method thereof. Background Art

[0002] Oil is known as the "blood of industry" and plays a vital role in modern industry, transportation, power generation and the chemical industry. It accounts for a large proportion of global energy consumption, far exceeding other energy sources. Oil is not only an important transportation and power generation fuel, but also a basic raw material for many chemical products and synthetic materials. At present, some oil fields in my country are in the tertiary oil recovery stage, mainly through chemical, thermal, microbial and miscible methods to further improve crude oil recovery. Among them, chemical method is the most promising technology for tertiary oil recovery and has been widely studied.

[0003] Patent CN105482797A discloses an organic composite alkali ternary composite oil displacement agent and its preparation method, including surfactant, organic base, inorganic weak base, polymer and water, using a composite base of organic base and inorganic weak base to replace inorganic strong base, reducing the amount of strong base, reducing the damage to the formation to a certain extent, reducing the amount of scaling in the formation and the entire injection and production system, but the alkali-containing formula is difficult to apply to high-mineralization and low-permeability oil reservoirs, and the promotion potential is limited. Patent CN109810685A discloses an oil displacement agent composition and its application, wherein the oil displacement agent composition contains cationic surfactant, gas, amphoteric surfactant, alcohol, polymer and water, the oil displacement agent composition has ultra-low interfacial tension, good emulsification performance, strong foaming ability, can increase the flow resistance of the water phase, effectively improve the sweep efficiency and increase the recovery rate of the oil reservoir, but when applied, it is necessary to alternately inject the mixture of non-gas components in the oil displacement agent composition with the gas into the oil layer, which is very inconvenient to operate.

[0004] Therefore, there is an urgent need to prepare an oil displacement agent composition that has excellent temperature resistance and salt resistance, can effectively reduce the oil-water interfacial tension, and improve the oil displacement efficiency. Summary of the invention

[0005] In order to overcome the above-mentioned deficiencies of the prior art, the present invention provides an alkali-free betaine type oil displacement agent composition and a preparation method thereof. The oil displacement agent has excellent temperature resistance and salt resistance, can effectively reduce the oil-water interfacial tension, and improve the oil displacement efficiency.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] The first aspect of the present invention provides an alkali-free betaine-type oil-displacing agent composition, which comprises the following raw materials by weight: 55-65 parts of a novel betaine-type surfactant, 35-45 parts of polyoxyethylene ether, and 20-30 parts of a solvent, wherein the novel betaine-type surfactant has a structure of three betaine side chains connected to a benzene ring, and the structural formula is as follows:

[0008]

[0009] Among them, in the compound structure shown in formula (I), the structure of R is as follows:

[0010]

[0011] Among them, in the compound structure shown in formula (II), 2≤x+z <y,12≤y≤18,R 1 is a sulfonate group or a carboxylate group, and * is a connection point with the compound represented by formula (I).

[0012] In the present invention, polyoxyethylene ether is used in combination with a betaine-type surfactant. The ether bonds in the polyoxyethylene ether molecules are not easily destroyed by acids and alkalis, have high stability, good water solubility, are electrolyte-resistant, are easily biodegradable, and have small foams. The combination with the betaine-type surfactant further reduces the interfacial tension between oil and water, thereby enhancing the oil washing ability of the oil displacement agent.

[0013] In some embodiments, the preparation method of the novel betaine-type surfactant comprises the following steps: adding acrylamide to ethanol under the condition of an initiator, stirring and reacting at 65-75°C for 0.5-1.5h, then adding styrene and continuing the reaction for 0.5-1.5h, then adding an inner salt compound and reacting for 1-2h, washing and drying, and obtaining a novel betaine-type surfactant.

[0014] In some embodiments, the inner salt compound is a sulfonic acid inner salt or a carboxylic acid inner salt.

[0015] In some embodiments, the molar ratio of acrylamide, styrene, and inner salt compound is 1:(4-6):1.

[0016] Preferably, the molar ratio of acrylamide, styrene and inner salt compound is 1:5:1.

[0017] The polymer flooding method in the chemical method is the main technical method for tertiary oil recovery. It is favored because of its convenient operation and easy availability of raw materials. At present, polymers represented by partially hydrolyzed polyacrylamide and its derivatives are the most commonly used. The hydrolyzed polyacrylamide molecules are flexible chains, which show irregular coil conformations in aqueous solutions. They are easily affected by conditions such as salt and temperature in the solution. The temperature and salt resistance are not ideal. The viscosity drops sharply in the presence of salt. The molecular chain breaks under shear, resulting in a decrease in its viscosity-increasing ability, which limits its application conditions. The applicant has found that the thermal stability of partially hydrolyzed polyacrylamide can be improved by adding a ring structure to the molecular chain, and the rigidity can be increased by introducing a branched chain into the structure, thereby The anti-shearing ability is improved. Styrene is cheap and the raw materials are easily available. In the present invention, acrylamide is polymerized with styrene to introduce a cyclic structure to prepare a copolymer with good thermal stability. In addition, a hydrophilic side chain containing betaine is introduced, which, on the one hand, increases the anti-shearing performance. On the other hand, the number of positive and negative charge groups on the betaine side chain is equal. When the salt concentration increases, the viscosity also increases, so that the anti-salt viscosity-increasing performance of the oil displacement agent is improved. At the same time, the feeding sequence is set so that the lipophilic polystyrene chain segments and the hydrophilic chain segments cross each other, so that water molecules are more likely to enter the interior of the molecule, the water solubility of the polymer is increased, the length of the hydrophilic chain segment and the lipophilic chain segment is controlled, the contact area between the oil displacement agent and the oil is larger, and the oil recovery rate is improved.

[0018] In some embodiments, the structural formula of the inner salt compound is as follows:

[0019] R 1 It is a sulfonate or carboxylate.

[0020] In some embodiments, the method for preparing the inner salt compound comprises the following steps:

[0021] (1) Compound A is mixed with a halogenated olefin and reacted at 75-85° C. for 5-7 hours to obtain an intermediate;

[0022] (2) mixing the intermediate obtained in step (1) with 1,3,5-tri(chloromethyl)benzene, and reacting at 80-90° C. for 11-13 hours to obtain an inner salt compound;

[0023] The compound A is sodium N-methyltaurate or sodium N-methylaminoacetate; when the compound A is sodium N-methyltaurate, the inner salt compound is a sulfonic acid inner salt; when the compound A is sodium N-methylaminoacetate, the inner salt compound is a carboxylic acid inner salt.

[0024] Preferably, in step (2), the molar ratio of the intermediate to 1,3,5-tri(chloromethyl)benzene is 3:1.

[0025] In some embodiments, the molar ratio of compound A to halogenated olefin in step (1) is 1:(1-1.2).

[0026] Preferably, the molar ratio of compound A to halogenated olefin in step (1) is 1:1.1

[0027] The invention utilizes the halogen of halogenated olefin to replace the hydrogen atom on the nitrogen atom of sodium N-methyl taurate or sodium N-methylamino acetate, so that the molar ratio of halogenated olefin is slightly greater than that of sodium N-methyl taurate or sodium N-methylamino acetate, so that the hydrogen atom is more completely replaced and the yield of the intermediate is increased. Then, the tertiary amine of the intermediate is used to react with the chlorine atom of 1,3,5-tri(chloromethyl)benzene to generate a sulfonic acid inner salt or a carboxylic acid inner salt having a double bond and a betaine structure, and then the sulfonic acid inner salt or the carboxylic acid inner salt is copolymerized with acrylamide and styrene to generate a star-shaped copolymer with a regular structure. The hydrophilic and lipophilic segments of the polymer chain segments repel each other, so that the curling and winding of the molecular chain is reduced, the temperature and salt resistance are further improved, and the application range is wide.

[0028] In some embodiments, the solvent is one or more of water, ethanol, methanol, and ethylene glycol.

[0029] Preferably, the solvent is water.

[0030] The second aspect of the present invention provides a method for preparing an alkali-free betaine type oil-displacing agent composition, comprising the following steps: stirring a novel betaine type surfactant, polyoxyethylene ether and a solvent at 25-35° C. for 25-35 min to obtain an alkali-free betaine type oil composition.

[0031] The third aspect of the present invention provides an application of an alkali-free betaine type oil-displacing agent composition, wherein the addition amount of the alkali-free betaine type oil-displacing agent composition during use is 0.2-0.4 wt %.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] 1. The present invention prepares an alkali-free betaine-type oil displacement agent composition by using a new betaine-type surfactant and polyoxyethylene ether, which has excellent temperature resistance and salt resistance, can effectively reduce the oil-water interfacial tension and thus improve the oil displacement efficiency.

[0034] 2. In the present invention, a copolymer with good thermal stability is prepared by polymerizing acrylamide and styrene and introducing a cyclic structure. In addition, a hydrophilic side chain containing betaine is introduced, which increases its shear resistance on the one hand, and on the other hand, the number of positive and negative charge groups on the betaine side chain is equal. When the salt concentration increases, the viscosity also increases, thereby improving the salt resistance and viscosity-increasing performance of the oil displacement agent.

[0035] 3. In the present invention, the oleophilic polystyrene chain segments and the hydrophilic chain segments are cross-linked, so that water molecules can more easily enter the interior of the molecule, thereby increasing the water solubility of the polymer, controlling the length of the hydrophilic chain segments and the oleophilic chain segments, increasing the contact area between the oil displacement agent and the oil, and improving the oil recovery rate.

[0036] 4. The present invention generates a star-shaped copolymer with a regular structure by copolymerizing sulfonic acid inner salt or carboxylic acid inner salt, acrylamide and styrene, and the hydrophilic and lipophilic segments between the polymer segments repel each other, reducing the curling and entanglement of the molecular chain, further improving the temperature and salt resistance, and having a wide range of applications. DETAILED DESCRIPTION

[0037] The present invention will be described below in conjunction with specific embodiments. It should be noted that the following examples and comparative examples are examples of the present invention and are only used to illustrate the present invention, but not to limit the present invention. Other combinations and various modifications within the concept of the present invention may be performed without departing from the spirit or scope of the present invention.

[0038] In order to facilitate those skilled in the art to implement the present invention, some raw materials and manufacturers of the embodiments and comparative examples are described as follows: the compounds and reagents used can be purchased commercially, among which AEO-9 fatty alcohol polyoxyethylene ether was purchased from Jinan Xinke Chemical Co., Ltd.

[0039] Preparation Example 1

[0040] The preparation method of sulfonic acid inner salt-1 comprises the following steps:

[0041] (1) Dissolve 16.1 g of sodium N-methyltaurate and 8.4 g of allyl chloride in 60 g of DMF and react at 80° C. for 6 hours to obtain an intermediate;

[0042] (2) 60.3 g of the intermediate obtained in step (1) and 22.4 g of 1,3,5-tri(chloromethyl)benzene were dissolved in 200 g of anhydrous ethanol and reacted at 85° C. for 12 h to obtain the sulfonic acid inner salt-1, the structural formula of which is as follows:

[0043]

[0044] Preparation Example 2

[0045] The preparation method of the carboxylic acid inner salt comprises the following steps:

[0046] (1) Dissolve 11.1 g of sodium N-methylaminoacetate and 8.4 g of allyl chloride in 60 g of DMF and react at 80° C. for 6 hours to obtain an intermediate;

[0047] (2) 45.3 g of the intermediate obtained in step (1) and 22.4 g of 1,3,5-tri(chloromethyl)benzene were dissolved in 200 g of anhydrous ethanol and reacted at 85° C. for 12 h to obtain the carboxylic acid inner salt, the structural formula of which is as follows:

[0048]

[0049] Preparation Example 3

[0050] The preparation method of sulfonic acid inner salt-2 comprises the following steps:

[0051] (1) 16.1 g of sodium N-methyltaurate and 10 g of 4-chloro-1-butene were dissolved in 60 g of DMF and reacted at 80° C. for 6 hours to obtain an intermediate;

[0052] (2) 64.5 g of the intermediate obtained in step (1) and 22.4 g of 1,3,5-tri(chloromethyl)benzene were dissolved in 200 g of anhydrous ethanol and reacted at 85° C. for 12 h to obtain the sulfonic acid inner salt-2, the structural formula of which is as follows:

[0053]

[0054] Preparation Example 4

[0055] The preparation method of sulfonate inner salt-3 is the same as that of Preparation Example 1, except that an equimolar amount of benzyl chloride is used in step (2) to replace 1,3,5-tri(chloromethyl)benzene. The structural formula of sulfonate inner salt-3 is as follows:

[0056]

[0057] Preparation Example 5

[0058] The preparation method of the novel betaine surfactant-1 comprises the following steps: adding 0.01 g of azobisisobutyronitrile and 7.1 g of acrylamide to 500 g of anhydrous ethanol, stirring and reacting at 70° C. for 1 h, then adding 52 g of styrene and continuing the reaction for 1 h, then adding 65.1 g of sulfonic acid inner salt-1 and reacting for 1.5 h, washing and drying, and obtaining the novel betaine surfactant-1, the structural formula of which is as follows:

[0059]

[0060] Preparation Example 6

[0061] The preparation method of the novel betaine surfactant-2 comprises the following steps: adding 0.01 g of azobisisobutyronitrile and 7.1 g of acrylamide to 500 g of anhydrous ethanol, stirring and reacting at 70° C. for 1 h, then adding 52 g of styrene and continuing the reaction for 1 h, then adding 79.1 g of sulfonic acid inner salt-2 and reacting for 1.5 h, washing and drying, and obtaining the novel betaine surfactant-2, the structural formula of which is as follows:

[0062]

[0063] Preparation Example 7

[0064] The preparation method of the novel betaine surfactant-3 comprises the following steps: adding 0.01 g of azobisisobutyronitrile and 7.1 g of acrylamide to 500 g of anhydrous ethanol, stirring and reacting at 70° C. for 1 h, then adding 52 g of styrene and continuing the reaction for 1 h, then adding 54.3 g of carboxylic acid inner salt and reacting for 1.5 h, washing and drying, and obtaining the novel betaine surfactant-3, the structural formula of which is as follows:

[0065]

[0066] Preparation Example 8

[0067] The preparation method of the novel betaine surfactant-4 comprises the following steps: adding 0.01 g of azobisisobutyronitrile and 7.1 g of acrylamide to 500 g of anhydrous ethanol, stirring and reacting at 70° C. for 1 h, then adding 52 g of styrene and continuing the reaction for 1 h, then adding 130.2 g of sulfonic acid inner salt-1 and reacting for 1.5 h, washing and drying, and obtaining the novel betaine surfactant-4, the structural formula of which is as follows:

[0068]

[0069] Preparation Example 9

[0070] The preparation method of the novel betaine surfactant-5 comprises the following steps: adding 0.01 g of azobisisobutyronitrile and 7.1 g of acrylamide to 500 g of anhydrous ethanol, stirring and reacting at 70° C. for 1 h, then adding 52 g of styrene and continuing the reaction for 1 h, then adding 65.1 g of sodium vinyl sulfonate and reacting for 1.5 h, washing and drying, and obtaining the novel betaine surfactant-5, the structural formula of which is as follows:

[0071]

[0072] Preparation Example 10

[0073] The preparation method of the novel betaine surfactant-6 comprises the following steps: adding 0.01 g of azobisisobutyronitrile and 7.1 g of acrylamide to 500 g of anhydrous ethanol, stirring and reacting at 70° C. for 1 h, then adding 52 g of styrene and continuing the reaction for 1 h, then adding 80.7 g of sulfonic acid inner salt-3 and reacting for 1.5 h, washing and drying, and obtaining the novel betaine surfactant-6, the structural formula of which is as follows:

[0074]

[0075] Example 1

[0076] This embodiment provides an alkali-free betaine-type oil-displacing agent composition, which includes the following raw materials by weight: 60 parts of a novel betaine-type surfactant-1, 40 parts of AEO-9 fatty alcohol polyoxyethylene ether, and 25 parts of water;

[0077] In this embodiment, a method for preparing an alkali-free betaine type oil composition comprises the following steps: stirring a novel betaine type surfactant-1, AEO-9 fatty alcohol polyoxyethylene ether and water at 30° C. for 30 minutes to obtain an alkali-free betaine type oil composition.

[0078] Example 2

[0079] This embodiment provides an alkali-free betaine-type oil-displacing agent composition, which includes the following raw materials by weight: 55 parts of a novel betaine-type surfactant-1, 35 parts of AEO-9 fatty alcohol polyoxyethylene ether, and 20 parts of water;

[0080] The preparation method of an alkali-free betaine type oil composition in this embodiment comprises the following steps: stirring a novel betaine type surfactant-1, AEO-9 fatty alcohol polyoxyethylene ether and water at 25° C. for 35 minutes to obtain an alkali-free betaine type oil composition.

[0081] Example 3

[0082] This embodiment provides an alkali-free betaine-type oil-displacing agent composition, which includes the following raw materials by weight: 65 parts of a new betaine-type surfactant-1, 45 parts of AEO-9 fatty alcohol polyoxyethylene ether, and 30 parts of water;

[0083] The preparation method of the alkali-free betaine type oil composition of this embodiment comprises the following steps: stirring the novel betaine type surfactant-1, AEO-9 fatty alcohol polyoxyethylene ether and water at 35° C. for 25 minutes to obtain the alkali-free betaine type oil composition.

[0084] Example 4

[0085] This embodiment provides an alkali-free betaine-type oil-displacing agent composition and a preparation method thereof. The specific implementation method is the same as that of Example 1, except that the new betaine-type surfactant-1 is replaced by the new betaine-type surfactant-2 in equal amounts.

[0086] Example 5

[0087] This embodiment provides an alkali-free betaine-type oil-displacing agent composition and a preparation method thereof. The specific implementation method is the same as that of Example 1, except that the new betaine-type surfactant-1 is replaced by the new betaine-type surfactant-3 in equal amounts.

[0088] Example 6

[0089] This embodiment provides an alkali-free betaine-type oil-displacing agent composition and a preparation method thereof. The specific implementation method is the same as that of Example 1, except that the new betaine-type surfactant-1 is replaced by the new betaine-type surfactant-4 in equal amounts.

[0090] Comparative Example 1

[0091] This comparative example provides an alkali-free betaine type oil-displacing agent composition and a preparation method thereof. The specific implementation manner is the same as that of Example 1, except that the new betaine type surfactant-1 is replaced by the new betaine type surfactant-5 in equal amounts.

[0092] Comparative Example 2

[0093] This comparative example provides an alkali-free betaine type oil-displacing agent composition and a preparation method thereof. The specific implementation manner is the same as that of Example 1, except that an equal amount of the new betaine type surfactant-1 is replaced by a new betaine type surfactant-6.

[0094] Performance Testing:

[0095] 1. Determination of interfacial tension

[0096] The interfacial tension between the oil displacement agent composition with a concentration of 0.3 wt% and the dehydrated crude oil of Jiangsu Shaqi Oilfield was tested using a TX500C full-range interfacial tension measuring instrument at a test temperature of 85° C. and a rotation speed of 5000 rpm.

[0097] 2. Anti-salt viscosity

[0098] Using NDJ-1 rotary viscometer, the viscosity of the oil displacement agent composition with a concentration of 0.3wt% and the water at the Jiangsu Shaqi Oilfield was measured at 85°C. The volume ratio of the two was 1:1. The concentrations of various substances in the water at the Jiangsu Shaqi Oilfield are shown in Table 1.

[0099] Table 1

[0100]

[0101] 3. Oil displacement effect

[0102] According to the physical simulation oil displacement effect test of the composite oil displacement system in the SY / T6424-2000 composite oil displacement system performance test method, a simulated oil displacement experiment was carried out at 87°C on a core with a length of 30 cm, a diameter of 2.5 cm and a permeability of 20 mD: first, water displacement was carried out to a water content of 98%, and the water displacement recovery rate was calculated according to the recovery rate calculation method formula. After the water displacement was completed, 0.3 pv (core pore volume) of 0.3 wt% of the oil displacement agent composition was injected, and then water displacement was carried out to a water content of 100%, and the oil displacement agent recovery rate was calculated according to the recovery rate calculation method formula. The enhanced crude oil recovery rate after water displacement = (oil displacement agent recovery rate - water displacement recovery rate) / water displacement recovery rate × 100%.

[0103] Each embodiment and comparative example was tested according to the above method, and the results are shown in Table 2.

[0104] Table 2

[0105]

[0106]

[0107] It can be seen from the data table of Examples 1-3 in Table 2 that the oil displacement agent can maintain a low interfacial tension, good salt resistance and high enhanced oil recovery after water flooding; in Example 4, the new betaine-type surfactant-1 is replaced by a new betaine-type surfactant-2 in equal amounts, which increases the interfacial tension of the oil displacement agent, reduces the viscosity, and reduces the enhanced oil recovery after water flooding; in Example 5, the new betaine-type surfactant-1 is replaced by a new betaine-type surfactant-3 in equal amounts, which may be due to the acidity of carboxylic acid being less than that of sulfonic acid, which increases the interfacial tension of the oil displacement agent, reduces the viscosity, and reduces the enhanced oil recovery after water flooding; in Example 6 When the new betaine-type surfactant-1 is replaced by the new betaine-type surfactant-4 in equal amounts, the interfacial tension of the oil displacement agent increases, the viscosity decreases, and the enhanced crude oil recovery after water flooding decreases; in Comparative Example 1, the new betaine-type surfactant-1 is replaced by the new betaine-type surfactant-5 in equal amounts, the interfacial tension of the oil displacement agent increases, the salt resistance decreases, the viscosity decreases, and the enhanced crude oil recovery after water flooding decreases; in Comparative Example 2, the new betaine-type surfactant-1 is replaced by the new betaine-type surfactant-6 in equal amounts, the structure of the polymer is irregular, the interfacial tension of the oil displacement agent increases, the salt resistance and viscosity-increasing ability decreases, and the enhanced crude oil recovery after water flooding decreases.

[0108] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technician familiar with this profession can make some changes or modifications to equivalent embodiments of equivalent changes using the technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. An alkali-free betaine type oil-displacing agent composition, characterized in that: The raw materials include, by weight: 55-65 parts of a novel betaine-type surfactant, 35-45 parts of polyoxyethylene ether, and 20-30 parts of a solvent. The novel betaine-type surfactant has a structure of three betaine side chains connected to a benzene ring, and the structural formula is as follows: （Ⅰ） Among them, in the compound structure shown in formula (I), the structure of R is as follows: （Ⅱ） Among them, in the compound structure shown by formula (II), 2 ≤ x + z < y, 12 ≤ y ≤ 18, and R1 is CH2SO3 - or COO - , and * is the connection point with the compound shown by formula (I).

2. The alkali-free betaine type oil-displacing agent composition according to claim 1, characterized in that: The preparation method of the novel betaine type surfactant comprises the following steps: adding acrylamide to ethanol under the condition of an initiator, stirring and reacting at 65-75° C. for 0.5-1.5 hours, then adding styrene to continue reacting for 0.5-1.5 hours, then adding an inner salt compound to react for 1-2 hours, washing and drying to obtain the novel betaine type surfactant.

3. The alkali-free betaine type oil-displacing agent composition according to claim 2, characterized in that: The inner salt compound is a sulfonic acid inner salt or a carboxylic acid inner salt.

4. The alkali-free betaine type oil-displacing agent composition according to claim 2, characterized in that: The molar ratio of acrylamide, styrene and internal salt compound is 1:(4-6):

1.

5. The alkali-free betaine oil-displacing agent composition according to any one of claims 2 to 4, characterized in that: The structural formula of the inner salt compound is as follows: , R1 is CH2SO3 - or COO - .

6. The alkali-free betaine type oil-displacing agent composition according to claim 5, characterized in that: The preparation method of the inner salt compound comprises the following steps: (1) Compound A is mixed with a halogenated olefin and reacted at 75-85° C. for 5-7 hours to obtain an intermediate; (2) mixing the intermediate obtained in step (1) with 1,3,5-tri(chloromethyl)benzene, and reacting at 80-90° C. for 11-13 hours to obtain an inner salt compound; The compound A is sodium N-methyltaurate or sodium N-methylaminoacetate.

7. The alkali-free betaine type oil-displacing agent composition according to claim 6, characterized in that: In the step (1), the molar ratio of compound A to halogenated olefin is 1:(1-1.2).

8. The alkali-free betaine type oil-displacing agent composition according to claim 1, characterized in that: The solvent is one or more of water, ethanol, methanol and ethylene glycol.

9. A method for preparing the alkali-free betaine oil-displacing agent composition according to any one of claims 1 to 8, characterized in that: The following steps are involved: The novel betaine-type surfactant, polyoxyethylene ether and solvent are stirred at 25-35° C. for 25-35 minutes to obtain an alkali-free betaine-type oil composition.

10. An application of the alkali-free betaine oil-displacing agent composition according to any one of claims 1 to 8, characterized in that: The alkali-free betaine oil composition is added in an amount of 0.2-0.4 wt % when used.

Images