Oil displacement agent, its preparation method and application

Abstract

The present application relates to the field of oilfield chemistry, and discloses an oil displacement agent and a preparation method and application thereof.The oil displacement agent contains anionic surfactant, cationic surfactant, zwitterionic surfactant, auxiliary agent and water; wherein the anionic surfactant, cationic surfactant and zwitterionic surfactant each independently contains a chemical structure shown in formula (I), wherein A is selected from at least one of C8-C 14 alkyl and C8-C 14 alkenyl; D is C2-C4 alkyl; E is -H or -SO3M; n is an integer of 2-15; and M is an alkali metal element.The oil displacement agent has high surface activity, strong temperature resistance and salt resistance, and excellent stability.Under a use concentration of 0.1wt%, in saturated brine with a calcium ion content of 4000mg / L, after aging at 120℃ for 72h, the oil displacement agent can still form an ultra-low interfacial tension of 2.5×10 ‑4 -8.5×10 ‑3 mN / m with underground crude oil, and can improve the recovery rate by more than 20%.

Description

Technical Field

[0001] This invention relates to the field of oilfield chemistry, specifically to an oil displacement agent, its preparation method, and its application. Background Technology

[0002] Currently, medium- and low-permeability oil reservoirs account for 60-70% of my country's total oil reserves, and these reservoirs will be the main resource base for increasing reserves and production for a considerable period to come. Compared to high-permeability reservoirs, residual oil droplets in medium- and low-permeability reservoirs exist in pores with very small throat radii. Under the same conditions, the capillary resistance of these residual oil droplets is much greater than that of high-permeability reservoirs. Therefore, activating these residual oil droplets requires lower oil-water interfacial tension. Secondly, medium- and low-permeability reservoirs have high flow resistance, and liquid can only flow under relatively high displacement pressure. However, high water injection pressure easily causes microfractures to open, allowing water to rush along the fractures, resulting in a small swept volume and reduced oil displacement efficiency.

[0003] Single surfactants have limited interfacial tension properties. Currently, a common method is to use a combination of different types of surfactants to achieve lower oil-water interfacial tension. However, this method suffers from drawbacks such as high surfactant concentrations, poor economic efficiency, and chromatographic separation effects when different types of surfactants are used in combination, affecting the overall performance. Anionic and cationic surfactants can achieve lower oil-water interfacial tension at lower concentrations and have strong salt resistance. Using anionic and cationic surfactants in combination can significantly improve oil displacement efficiency. However, the use of anionic and cationic surfactants in combination still has some problems. For example, under strong anionic-cationic pair interactions, precipitation of the anionic and cationic surfactants can occur. This not only fails to reduce interfacial tension but also clogs pores, causing formation damage.

[0004] Therefore, the oil displacement agent needs to be redesigned to have high surface activity, strong temperature and salt resistance, and strong stability to meet the performance requirements of low-to-medium permeability oil reservoir development. Summary of the Invention

[0005] The purpose of this invention is to address the problem that existing oil displacement agents cannot meet the performance requirements of surface activity, temperature and salt resistance, and stability during use in the development of low-permeability oil reservoirs at low dosages, and to provide an oil displacement agent, its preparation method, and its application.

[0006] To achieve the above objectives, a first aspect of the present invention provides an oil displacement agent comprising anionic surfactant, cationic surfactant, amphoteric surfactant, an additive, and water; wherein...

[0007] The anionic surfactant, cationic surfactant, and zwitterionic surfactant each independently contain the chemical structure shown in formula (I).

[0008]

[0009] Where A is selected from C8-C 14 Alkyl and C8-C 14 At least one of the alkenyl groups; D is a C2-C4 alkyl group; E is -H or -SO3M; n is an integer from 2 to 15; M is an alkali metal element.

[0010] A second aspect of the present invention provides a method for preparing the oil displacement agent described in the first aspect, comprising:

[0011] (1) Prepare anionic surfactants, cationic surfactants, and amphoteric surfactants respectively; among which...

[0012] (1-1) The precursor shown in formula (V) is carboxylated with a carboxylating agent, followed by an optional neutralization reaction to obtain an anionic surfactant;

[0013] (1-2) In the presence of a first catalyst, the precursor shown in formula (V) is subjected to a first hydroamination reaction with hydrogen and dimethylamine to obtain a first intermediate; then the first intermediate is subjected to a first quaternization reaction with a first haloalkane to obtain a cationic surfactant.

[0014] (1-3) In the presence of a second catalyst, the precursor shown in formula (V) is subjected to a second hydroamination reaction with hydrogen and dimethylamine to obtain a second intermediate; then the second intermediate is subjected to a second quaternization reaction with a second haloalkane to obtain a third intermediate; the third intermediate is subjected to a sulfonation reaction with a sulfonating agent, followed by a neutralization reaction to obtain an amphoteric surfactant.

[0015]

[0016] (2) The anionic surfactant, cationic surfactant, amphoteric surfactant, additives and water are mixed to obtain the oil displacement agent;

[0017] The definitions of A, D, and n are the same as those involved in the first aspect mentioned above.

[0018] The third aspect of this invention provides the application of the oil displacement agent described in the first aspect in the exploitation of medium- and low-permeability oil reservoirs.

[0019] Through the above technical solution, the present invention has the following beneficial effects:

[0020] (1) The oil displacement agent provided by this invention adopts a mixed system including anionic surfactants, cationic surfactants and amphoteric surfactants, which have intramolecular and intermolecular anion-cation pair interactions, giving the oil displacement agent the advantages of high surface activity, strong temperature and salt resistance and low adsorption loss; at a usage concentration of 0.1wt%, in saturated brine with a calcium ion content of 4000 mg / L, after aging at 120℃ for 72 hours, the oil displacement agent can still form 2.5 × 10⁻⁶ ppm with underground crude oil. -4 -8.5×10 -3 With an ultra-low interfacial tension of mN / m, the recovery rate can be increased by more than 20% compared to water drive, and up to 33% in some cases.

[0021] (2) The introduction of zwitterionic surfactants can buffer the direct interaction between anionic and cationic surfactants, thereby enhancing the stability of the entire oil displacement agent system and preventing precipitation during use.

[0022] (3) In the oil displacement agent provided by the present invention, the anionic surfactant, cationic surfactant and amphoteric surfactant have similar molecular structures, which can reduce or even avoid the chromatographic separation of different components in the formation channels and enhance the oil displacement effect in the reservoir. Detailed Implementation

[0023] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0024] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0025] In a first aspect, the present invention provides an oil displacement agent comprising anionic surfactant, cationic surfactant, amphoteric surfactant, an additive, and water; wherein,

[0026] The anionic surfactant, cationic surfactant, and zwitterionic surfactant each independently contain the chemical structure shown in formula (I).

[0027]

[0028] Where A is selected from C8-C 14 Alkyl and C8-C 14At least one of the alkenyl groups; D is a C2-C4 alkyl group; E is -H or -SO3M; n is an integer from 2 to 15; M is an alkali metal element.

[0029] According to the present invention, in the oil displacement agent, the anionic surfactant, cationic surfactant, and amphoteric surfactant have similar molecular structures and all contain... Structure. Wherein, for the anionic surfactant and cationic surfactant, E is -H in the structure contained therein; for the zwitterionic surfactant, E is -SO3M in the structure contained therein.

[0030] According to the present invention, in formula (I), preferably, A is selected from C8-C 14 Straight-chain alkyl and C8-C 14 At least one of the straight-chain alkenyl groups.

[0031] According to the present invention, in formula (I), more preferably, A is selected from C9-C 12 Straight-chain alkyl and C9-C 12 At least one of the straight-chain alkenyl groups, more preferably C9-C 12 Straight-chain alkyl groups.

[0032] According to the present invention, in formula (I), preferably, D is a C2-C3 alkyl group.

[0033] According to the present invention, in formula (I), preferably, n is an integer from 3 to 12.

[0034] According to the present invention, in formula (I), preferably, M is Na or K.

[0035] According to the present invention, based on the chemical structure shown in formula (I), specifically, the structural formula of the anionic surfactant is shown in formula (II):

[0036]

[0037] Among them, R1 is selected from C8-C 14 Alkyl and C8-C 14 At least one of the alkenyl groups; R2 is a C2-C4 alkyl group; G is an alkali metal element; i is an integer from 2 to 15.

[0038] According to the present invention, for the anionic surfactant, in formula (II), preferably, R1 is selected from C8-C 14 Straight-chain alkyl and C8-C 14 At least one of the straight-chain alkenyl groups.

[0039] According to the present invention, in formula (II), more preferably, R1 is selected from C9-C12 Straight-chain alkyl and C9-C 12 At least one of the straight-chain alkenyl groups, more preferably C9-C 12 Straight-chain alkyl groups.

[0040] According to the present invention, in formula (II), preferably, R2 is a C2-C3 alkyl group.

[0041] According to the present invention, in formula (II), preferably, G is Na or K.

[0042] According to the present invention, in formula (II), preferably, i is an integer from 3 to 12.

[0043] In this invention, the anionic surfactant has good temperature and salt resistance and low interfacial tension.

[0044] According to the present invention, based on the chemical structure shown in formula (I), specifically, the structural formula of the cationic surfactant is shown in formula (III):

[0045]

[0046] R3 is selected from C8-C 14 Alkyl and C8-C 14 At least one of the alkenyl groups; R4 is a C2-C4 alkyl group; R5 is methyl or benzyl; X is a halogen; q is an integer from 2 to 15.

[0047] According to the present invention, for the cationic surfactant, in formula (III), preferably, R3 is selected from C8-C 14 Straight-chain alkyl and C8-C 14 At least one of the straight-chain alkenyl groups.

[0048] According to the present invention, in formula (III), more preferably, R3 is selected from C9-C 12 Straight-chain alkyl and C9-C 12 At least one of the straight-chain alkenyl groups, more preferably C9-C 12 Straight-chain alkyl groups.

[0049] According to the present invention, in formula (III), preferably, R4 is a C2-C3 alkyl group.

[0050] According to the present invention, in formula (III), preferably, R5 is benzyl.

[0051] According to the present invention, in formula (III), preferably, X is Cl or Br, and more preferably Cl.

[0052] According to the present invention, in formula (III), preferably, q is an integer from 3 to 12.

[0053] In this invention, when the cationic surfactant and the anionic surfactant are used in combination, they can generate ultra-low interfacial tension through intermolecular cation-anion pair interactions. At the same time, since the cationic surfactant and the anionic surfactant have similar structures, they can significantly reduce chromatographic separation phenomena in the formation.

[0054] According to the present invention, based on the chemical structure shown in formula (I), specifically, the structural formula of the zwitterionic surfactant is shown in formula (IV):

[0055]

[0056] R6 is selected from C8-C 14 Alkyl and C8-C 14 At least one of the alkenyl groups; R7 is a C2-C4 alkyl group; R8 is methyl or benzyl; Z is a halogen; t is an integer from 2 to 15; M is an alkali metal element.

[0057] According to the present invention, for the zwitterionic surfactant, in formula (IV), preferably, R6 is selected from C8-C. 14 Straight-chain alkyl and C8-C 14 At least one of the straight-chain alkenyl groups.

[0058] According to the present invention, in formula (IV), more preferably, R6 is selected from C9-C 12 Straight-chain alkyl and C9-C 12 At least one of the straight-chain alkenyl groups, more preferably C9-C 12 Straight-chain alkyl groups.

[0059] According to the present invention, in formula (IV), preferably, R7 is a C2-C3 alkyl group.

[0060] According to the present invention, in formula (IV), preferably, R8 is benzyl.

[0061] According to the present invention, in formula (IV), preferably, Z is Cl or Br.

[0062] According to the present invention, in formula (IV), preferably, t is an integer from 3 to 12.

[0063] According to the present invention, in formula (IV), preferably, M is Na or K.

[0064] In this invention, the zwitterionic surfactant can further generate intermolecular ion pairs with the cationic surfactant and anionic surfactant, further improving the system's temperature and salt resistance and reducing interfacial tension. At the same time, since the three have similar structures, chromatographic separation problems can be greatly reduced when they are used in combination.

[0065] According to the present invention, in the oil displacement agent, the anionic surfactant, cationic surfactant, and zwitterionic surfactant satisfy a specific quantitative relationship. Preferably, the molar ratio of (anionic surfactant + cationic surfactant) to zwitterionic surfactant is 1:(0.25-4), more preferably 1:(0.5-2).

[0066] According to the present invention, in the oil displacement agent, the molar ratio of anionic surfactant to cationic surfactant is 1:(0.1-10), preferably 1:(0.2-5).

[0067] In this invention, while the individual effects of anionic surfactants, cationic surfactants, and zwitterionic surfactants can be considered, the oil displacement agent provided by this invention, when containing the three surfactants with the specific structures described above and satisfying the quantitative relationship, can produce a synergistic effect. This results in the oil displacement agent possessing high surface activity, strong temperature and salt resistance, and excellent stability, significantly improving oil displacement efficiency. Outside of the above-defined range, the obtained oil displacement agent cannot possess the aforementioned comprehensive properties.

[0068] According to the present invention, in the oil displacement agent, the amount of (anionic surfactant + cationic surfactant + amphoteric surfactant) is 25-130 parts by weight relative to 100 parts by weight of water, and the amount of additives is 1-60 parts by weight.

[0069] According to the present invention, preferably, the (anionic surfactant + cationic surfactant + amphoteric surfactant) is 40-100 parts by weight relative to 100 parts by weight of water, and the additives are 5-40 parts by weight.

[0070] According to the present invention, in the oil displacement agent, the auxiliary agent is an alcohol, which can play a solubilizing role, enabling the surfactant to be rapidly dispersed and dissolved in water. Preferably, it is at least one selected from ethanol, n-propanol, isopropanol, and n-butanol.

[0071] The oil displacement agent provided by this invention employs a mixed system comprising specific anionic surfactants, cationic surfactants, and amphoteric surfactants. The presence of intramolecular and intermolecular anion-cation pair interactions significantly enhances its interaction with oil and water, resulting in high surface activity and strong temperature and salt resistance. The introduction of amphoteric surfactants effectively buffers the direct anion-cation pair interactions between anionic and cationic surfactants, ensuring system stability and preventing precipitation. Furthermore, the three surfactants are designed to have similar molecular structures, reducing or even eliminating chromatographic separation during use and enhancing the oil displacement effect in the reservoir. The oil displacement agent provided by this invention achieves the aforementioned effects even at low concentrations, exhibiting high oil displacement efficiency. For example, when this oil displacement agent is added to saturated brine with a calcium ion content of 4000 mg / L to prepare a 0.1 wt% aqueous solution, after aging at 120°C for 72 hours, it can still form a 2.5 × 10⁻⁶ ppm reaction with underground crude oil. -4 -8.5×10 -3 With an ultra-low interfacial tension of mN / m, the recovery rate can be increased by more than 20%, and up to 33% in some cases.

[0072] According to a preferred embodiment of the present invention, in the oil displacement agent, in the structural formula (II) of the anionic surfactant, R1 is selected from C9-C6. 12 The linear alkyl group, R2 is a C2-C3 alkyl group, G is Na or K, and i is an integer from 3 to 12; in the structural formula (III) of the cationic surfactant, R3 is selected from C9-C 12 The linear alkyl group, R4 is a C2-C3 alkyl group, R5 is benzyl, X is Cl or Br, and q is an integer from 3 to 12; in the structural formula (IV) of the zwitterionic surfactant, R6 is selected from C9-C6. 12 The straight-chain alkyl group, R7 is a C2-C3 alkyl group, R8 is benzyl, Z is Cl or Br, t is an integer from 3 to 12, and M is Na or K (for example, anionic surfactants are...). Cationic surfactants are and amphoteric surfactants are Or anionic surfactants are Cationic surfactants are and amphoteric surfactants are Or anionic surfactants are Cationic surfactants are and amphoteric surfactants are (Anionic surfactant + cationic surfactant): The molar ratio of amphoteric surfactant is 1:(0.5-2); The molar ratio of anionic surfactant to cationic surfactant is 1:(0.2-5); Relative to 100 parts by weight of water, (anionic surfactant + cationic surfactant + amphoteric surfactant) is 40-100 parts by weight, and the auxiliary agent is 5-40 parts by weight. It can achieve a 3×10 formation with underground crude oil after aging at 120℃ for 72 hours in saturated brine with a calcium ion content of 4000 mg / L at a usage concentration of 0.1 wt% and underground crude oil. -4 -9×10 -4 With an ultra-low interfacial tension of mN / m, it can improve the recovery rate by 25-33% compared to water drive.

[0073] A second aspect of the present invention provides a method for preparing the oil displacement agent described in the first aspect, comprising:

[0074] (1) Prepare anionic surfactants, cationic surfactants, and amphoteric surfactants respectively; among which...

[0075] (1-1) The precursor shown in formula (V) is carboxylated with a carboxylating agent, followed by an optional neutralization reaction to obtain an anionic surfactant;

[0076] (1-2) In the presence of a first catalyst, the precursor shown in formula (V) is subjected to a first hydroamination reaction with hydrogen and dimethylamine to obtain a first intermediate; then the first intermediate is subjected to a first quaternization reaction with a first haloalkane to obtain a cationic surfactant.

[0077] (1-3) In the presence of a second catalyst, the precursor shown in formula (V) is subjected to a second hydroamination reaction with hydrogen and dimethylamine to obtain a second intermediate; then the second intermediate is subjected to a second quaternization reaction with a second haloalkane to obtain a third intermediate; the third intermediate is subjected to a sulfonation reaction with a sulfonating agent, followed by a neutralization reaction to obtain an amphoteric surfactant.

[0078]

[0079] (2) The anionic surfactant, cationic surfactant, amphoteric surfactant, additives and water are mixed to obtain the oil displacement agent;

[0080] The definitions of A, D, and n are the same as those involved in the first aspect mentioned above.

[0081] According to the present invention, in step (1), the numbers of steps (1-1), (1-2), and (1-3) are only used to distinguish the preparation processes of different surfactants and do not represent the order of preparation. The preparation method of the present invention does not limit the preparation order of the different surfactants used and can be carried out in any order.

[0082] According to the present invention, the precursor is an alkylphenol polyoxyethylene ether, which can be obtained by conventional methods in-house or by using commercially available products, as long as it meets the limiting conditions for A, D and n in the formula (V).

[0083] According to the present invention, in step (1-1), the carboxylating agent is capable of reacting with the hydroxyl group in the precursor shown in formula (V) and introducing a carboxyl group into the structure. Preferably, the carboxylating agent can be chloroacetic acid and / or sodium chloroacetate.

[0084] According to the present invention, in step (1-1), the molar ratio of the precursor to the carboxylating agent is 1:(1.05-1.2).

[0085] According to the present invention, in step (1-1), the conditions for the carboxylation reaction include: a temperature of 50-90°C and a time of 2-6 hours.

[0086] According to the present invention, in step (1-1), if the carboxylating agent is sodium chloroacetate, no neutralization reaction is required after the carboxylation reaction, and the product obtained by the carboxylation reaction is the anionic surfactant. If the carboxylating agent is chloroacetic acid, an alkali is added to the product system after the carboxylation reaction to perform a neutralization reaction, and the pH of the system is adjusted to 9-10 to obtain the cationic surfactant. Preferably, the alkali used in the neutralization reaction is selected from sodium hydroxide and / or potassium hydroxide.

[0087] According to the present invention, in steps (1-2), the first catalyst is an amination catalyst, the active components of which include copper and nickel, and the support includes, but is not limited to, at least one of alumina, silica, and titanium dioxide. In the present invention, the first catalyst can be prepared in-house using conventional methods, or it can be a commercially available product, such as the NCH6-2A catalyst from the Research Institute of Sinopec Nanjing Chemical Group.

[0088] According to the present invention, in step (1-2), the molar ratio of the precursor: hydrogen: dimethylamine is 1:(0.2-3.5):(2.5-6).

[0089] According to the present invention, in step (1-2), the conditions for the first hydroamination reaction include: a temperature of 180-250°C, a pressure of 1-5.5 MPa, and a time of 2-8 h.

[0090] In this invention, the structural formula of the first intermediate obtained in step (1-2) is shown in formula (VI):

[0091]

[0092] According to the present invention, in step (1-2), the first haloalkane is a halomethane and / or benzyl halide, preferably chloromethane, bromomethane, benzyl chloride or benzyl bromide.

[0093] According to the present invention, in step (1-2), in the first quaternization reaction, the molar ratio of the first intermediate to the first haloalkane is 1:(1.1-1.3).

[0094] According to the present invention, in step (1-2), the conditions for the first quaternization reaction include: a temperature of 60-150°C and a time of 6-12 h.

[0095] According to the present invention, in steps (1-3), the second catalyst is the same as the first catalyst.

[0096] According to the present invention, in steps (1-3), the molar ratio of the precursor: hydrogen: dimethylamine is 1:(0.2-3.5):(2.5-6.0).

[0097] According to the present invention, in steps (1-3), the conditions for the second hydroamination reaction include: a temperature of 180-250°C, a pressure of 1-5.5 MPa, and a time of 2-8 h.

[0098] According to the present invention, in steps (1-3), the obtained second intermediate has the structural formula shown in formula (VI) above.

[0099] According to the present invention, in steps (1-3), the second haloalkane is a halomethane and / or benzyl halide, preferably chloromethane, bromomethane, benzyl chloride or benzyl bromide.

[0100] According to the present invention, in steps (1-3), in the second quaternization reaction, the molar ratio of the second intermediate to the second haloalkane is 1:(1.1-1.3).

[0101] According to the present invention, in steps (1-3), the conditions for the second quaternization reaction include: a temperature of 60-150°C and a time of 6-12 h.

[0102] According to the present invention, in steps (1-3), the sulfonating agent is at least one of sulfuric acid, fuming sulfuric acid and sulfur trioxide.

[0103] According to the present invention, in steps (1-3), in the sulfonation reaction, the molar ratio of the third intermediate to the sulfonating agent is 1:(1.2-2).

[0104] According to the present invention, in steps (1-3), the sulfonation reaction conditions include: a temperature of 80-170°C and a time of 2-10 hours.

[0105] According to the present invention, in steps (1-3), after the sulfonation reaction, an alkali is added to the product system to carry out a neutralization reaction, and the pH value of the system is adjusted to 7-9 to obtain the zwitterionic surfactant. Preferably, the alkali used in the neutralization reaction is selected from sodium hydroxide and / or potassium hydroxide.

[0106] According to the present invention, in step (2), the auxiliary agent is an alcohol, preferably at least one of ethanol, n-propanol, isopropanol and n-butanol.

[0107] According to the present invention, there is no particular limitation on the mixing method in step (2), as long as it is possible to mix the anionic surfactant, cationic surfactant and amphoteric surfactant obtained in step (1) with the auxiliary agent and water to obtain a uniform oil displacement agent. Preferably, the anionic surfactant, cationic surfactant and amphoteric surfactant can be mixed first, and then mixed with the auxiliary agent and water.

[0108] According to the present invention, in step (2), the molar ratio of (anionic surfactant + cationic surfactant) to zwitterionic surfactant is 1:(0.25-4), preferably 1:(0.5-2).

[0109] According to the present invention, in step (2), the molar ratio of anionic surfactant to cationic surfactant is 1:(0.1-10), preferably 1:(0.2-5).

[0110] According to the present invention, in step (2), relative to 100 parts by weight of water, (anionic surfactant + cationic surfactant + amphoteric surfactant) is 25-130 parts by weight, and the auxiliary agent is 1-60 parts by weight.

[0111] According to the present invention, in step (2), preferably, for 100 parts by weight of water, (anionic surfactant + cationic surfactant + amphoteric surfactant) is 40-100 parts by weight, and the additive is 5-40 parts by weight.

[0112] The third aspect of this invention provides the application of the oil displacement agent described in the first aspect in the exploitation of medium- and low-permeability oil reservoirs.

[0113] According to the present invention, the permeability of the medium-low permeability reservoir is 0.01-50 mD.

[0114] The oil displacement agent provided by this invention is particularly suitable for oil displacement operations in low-permeability reservoirs. It has high surface activity, strong temperature and salt resistance and excellent stability, which can bring about higher recovery rates.

[0115] The present invention will be described in detail below through examples. Unless otherwise specified, the following examples and comparative examples are all conventional methods; the reagents and materials mentioned are commercially available unless otherwise specified.

[0116] First catalyst and second catalyst: grade NCH6-2A, Sinopec Nanjing Chemical Group Research Institute;

[0117] Precursor: Purchased from Shandong Maofa Chemical Co., Ltd.

[0118] Example 1

[0119] This embodiment illustrates the preparation of oil displacement agents.

[0120] Precursor structure formula:

[0121] (1-1) The precursor (in the above structural formula, A is...) D is (n=3) was reacted with sodium chloroacetate in a carboxylation reaction (the molar ratio of precursor to sodium chloroacetate was 1:1.05; the carboxylation reaction temperature was 50℃, and the reaction time was 6h) to obtain an anionic surfactant (n=3). Where R1 is R2 is G is Na, i is 3);

[0122] (1-2) In the presence of the first catalyst, the precursor (in the above structural formula, A is...) D is ethyl, n is 12) undergoes a first hydroamination reaction with hydrogen and dimethylamine (molar ratio of precursor: hydrogen: dimethylamine is 1:0.2:2.5; reaction temperature is 180℃, reaction pressure is 1MPa, reaction time is 8h) to obtain a first intermediate; then the obtained first intermediate undergoes a first quaternization reaction with benzyl chloride (molar ratio of first intermediate: benzyl chloride is 1:1.1; reaction temperature is 60℃, reaction time is 12h) to obtain a cationic surfactant ( Among them, R3 is R4 is ethyl, R5 is benzyl, X is Cl, and q is 12);

[0123] (1-3) In the presence of a second catalyst, the precursor (in the above structural formula, A is...) D is ethyl, n is 8) undergoes a second hydroamination reaction with hydrogen and dimethylamine (molar ratio of precursor:hydrogen:dimethylamine is 1:0.2:2.5; reaction temperature is 180℃, reaction pressure is 1MPa, reaction time is 8h) to obtain a second intermediate; then the obtained second intermediate undergoes a second quaternization reaction with benzyl chloride (molar ratio of second intermediate:benzyl chloride is 1:1.1; reaction temperature is 60℃, reaction time is 12h) to obtain a third intermediate; the obtained third intermediate is further subjected to a sulfonation reaction with fuming sulfuric acid (molar ratio of third intermediate:fuming sulfuric acid is 1:1.2; reaction temperature is 80℃, reaction time is 10h), then sodium hydroxide is added to the sulfonation product system for neutralization reaction, and the pH of the system is adjusted to 8 to obtain an amphoteric surfactant. Among them, R6 is R7 is ethyl, R8 is benzyl, Z is Cl, t is 8, M is Na;

[0124] (2) The anionic surfactant and cationic surfactant prepared above are mixed evenly at a molar ratio of 1:0.2 to obtain surfactant mixture-1; then surfactant mixture-1 is mixed evenly with the zwitterionic surfactant prepared above at a molar ratio of 1:0.5 to obtain surfactant mixture-2.

[0125] 40 parts by weight of the above surfactant mixture, 2 and 5 parts by weight of isopropanol, and 100 parts by weight of water are mixed to obtain an oil displacement agent (denoted as S1).

[0126] Example 2

[0127] This embodiment illustrates the preparation of oil displacement agents.

[0128] Precursor structure formula:

[0129] (1-1) The precursor (in the above structural formula, A is...) D is an ethyl group, n is 12) and chloroacetic acid are reacted with chloroacetic acid (the molar ratio of precursor to chloroacetic acid is 1:1.2; the carboxylation reaction temperature is 90℃, and the reaction time is 2h). Then, potassium hydroxide is added to the resulting product system for neutralization, and the pH of the system is adjusted to 10 to obtain an anionic surfactant. Where R1 is R2 is ethyl, G is K, and i is 12);

[0130] (1-2) In the presence of the first catalyst, the precursor (in the above structural formula, A is...) D is (n=3) reacts with hydrogen and dimethylamine in a first hydroamination reaction (molar ratio of precursor:hydrogen:dimethylamine:1:3.5:6; reaction temperature:250℃, reaction pressure:5.5MPa, reaction time:2h) to obtain a first intermediate; then the obtained first intermediate is reacted with benzyl bromide in a first quaternization reaction (molar ratio of first intermediate:benzyl bromide:1:1.3; reaction temperature:150℃, reaction time:6h) to obtain a cationic surfactant. Among them, R3 is R4 is R5 is benzyl, X is Br, and q is 3);

[0131] (1-3) In the presence of a second catalyst, the precursor (in the above structural formula, A is...) D is (n=3) undergoes a second hydroamination reaction with hydrogen and dimethylamine (molar ratio of precursor:hydrogen:dimethylamine:1:3.5:6; reaction temperature:250℃, reaction pressure:5.5MPa, reaction time:2h) to obtain a second intermediate. The obtained second intermediate then undergoes a second quaternization reaction with benzyl bromide (molar ratio of second intermediate:benzyl bromide:1:1.3; reaction temperature:150℃, reaction time:6h) to obtain a third intermediate. The obtained third intermediate is further subjected to a sulfonation reaction with sulfur trioxide (molar ratio of third intermediate:sulfur trioxide:1:2; reaction temperature:170℃, reaction time:2h). Potassium hydroxide is then added to the sulfonation product system for neutralization, and the pH of the system is adjusted to 8 to obtain an amphoteric surfactant. Among them, R6 is R7 is R8 is benzyl, Z is Br, t is 3, M is K);

[0132] (2) The anionic surfactant and cationic surfactant prepared above are mixed evenly at a molar ratio of 1:5 to obtain surfactant mixture-1; then surfactant mixture-1 is mixed evenly with the zwitterionic surfactant prepared above at a molar ratio of 1:2 to obtain surfactant mixture-2.

[0133] Mix 100 parts by weight of the above surfactant mixture-2, 40 parts by weight of ethanol and 100 parts by weight of water to obtain an oil displacement agent (denoted as S2).

[0134] Example 3

[0135] This embodiment illustrates the preparation of oil displacement agents.

[0136] Precursor structure formula:

[0137] (1-1) The precursor (in the above structural formula, A is...) D is an ethyl group, n is 7) and sodium chloroacetate undergoes a carboxylation reaction (the molar ratio of precursor to sodium chloroacetate is 1:1.1; the carboxylation reaction temperature is 70℃, and the reaction time is 4h) to obtain an anionic surfactant ( Where R1 is R2 represents ethyl, G represents sodium, and i represents 7);

[0138] (1-2) In the presence of the first catalyst, the precursor (in the above structural formula, A is...) D is ethyl, n is 8) undergoes a first hydroamination reaction with hydrogen and dimethylamine (molar ratio of precursor:hydrogen:dimethylamine is 1:1.5:4.5; reaction temperature is 210℃, reaction pressure is 4MPa, reaction time is 5h) to obtain a first intermediate; then the obtained first intermediate undergoes a first quaternization reaction with benzyl chloride (molar ratio of first intermediate:benzyl chloride is 1:1.2; reaction temperature is 110℃, reaction time is 9h) to obtain a cationic surfactant ( Among them, R3 is R4 is ethyl, R5 is benzyl, X is Cl, and q is 8);

[0139] (1-3) In the presence of a second catalyst, the precursor (in the above structural formula, A is...) D is ethyl, n is 12) undergoes a second hydroamination reaction with hydrogen and dimethylamine (molar ratio of precursor:hydrogen:dimethylamine is 1:2:4; reaction temperature is 220℃, reaction pressure is 3.5MPa, reaction time is 4h) to obtain a second intermediate; then the obtained second intermediate undergoes a second quaternization reaction with benzyl chloride (molar ratio of second intermediate:benzyl chloride is 1:1.2; reaction temperature is 120℃, reaction time is 8h) to obtain a third intermediate; the obtained third intermediate is further subjected to a sulfonation reaction with sulfuric acid (molar ratio of third intermediate:sulfuric acid is 1:1.5; reaction temperature is 120℃, reaction time is 5h), then sodium hydroxide is added to the sulfonation product system for neutralization reaction, and the pH of the system is adjusted to 8 to obtain an amphoteric surfactant. Among them, R6 is R7 is ethyl, R8 is benzyl, Z is Cl, t is 12, M is Na;

[0140] (2) The anionic surfactant and cationic surfactant prepared above are mixed evenly in a molar ratio of 1:1 to obtain surfactant mixture-1; then surfactant mixture-1 is mixed evenly with the zwitterionic surfactant prepared above in a molar ratio of 1:1 to obtain surfactant mixture-2.

[0141] Mix 60 parts by weight of the above surfactant mixture-2, 10 parts by weight of n-butanol, and 100 parts by weight of water to obtain an oil displacement agent (denoted as S3).

[0142] Example 4

[0143] This embodiment illustrates the preparation of oil displacement agents.

[0144] Precursor structure formula:

[0145] (1-1) The precursor (in the above structural formula, A is...) D is (n=2) was reacted with sodium chloroacetate in a carboxylation reaction (the molar ratio of precursor to sodium chloroacetate was 1:1.05; the carboxylation reaction temperature was 50℃, and the reaction time was 6h) to obtain an anionic surfactant (n=2). Where R1 is R2 is G is Na, i is 2);

[0146] (1-2) In the presence of the first catalyst, the precursor (in the above structural formula, A is...) D is (n=13) reacts with hydrogen and dimethylamine in a first hydroamination reaction (molar ratio of precursor:hydrogen:dimethylamine:1:0.2:2.5; reaction temperature:180℃; reaction pressure:1MPa; reaction time:8h) to obtain a first intermediate; then the obtained first intermediate is reacted with chloromethane in a first quaternization reaction (molar ratio of first intermediate:chloromethane:1:1.1; reaction temperature:60℃; reaction time:12h) to obtain a cationic surfactant. Among them, R3 is R4 is R5 is methyl, X is Cl, and q is 13);

[0147] (1-3) In the presence of a second catalyst, the precursor (in the above structural formula, A is...) D is (n=15) undergoes a second hydroamination reaction with hydrogen and dimethylamine (molar ratio of precursor:hydrogen:dimethylamine:1:0.2:2.5; reaction temperature:180℃; reaction pressure:1MPa; reaction time:8h) to obtain a second intermediate. The obtained second intermediate then undergoes a second quaternization reaction with chloromethane (molar ratio of second intermediate:chloromethane:1:1.1; reaction temperature:60℃; reaction time:12h) to obtain a third intermediate. The obtained third intermediate is further subjected to a sulfonation reaction with fuming sulfuric acid (molar ratio of third intermediate:fuming sulfuric acid:1:1.2; reaction temperature:80℃; reaction time:10h). Potassium hydroxide is then added to the sulfonation product system for neutralization, and the pH of the system is adjusted to 8 to obtain an amphoteric surfactant. Among them, R6 is R7 is R8 represents methyl, Z represents Cl, t represents 15, and M represents K.

[0148] (2) The anionic surfactant and cationic surfactant prepared above are mixed evenly at a molar ratio of 1:0.1 to obtain surfactant mixture-1; then surfactant mixture-1 is mixed evenly with the zwitterionic surfactant prepared above at a molar ratio of 1:0.25 to obtain surfactant mixture-2.

[0149] 25 parts by weight of the above surfactant mixture-2, 1 part by weight of isopropanol and 100 parts by weight of water are mixed to obtain an oil displacement agent (denoted as S4).

[0150] Example 5

[0151] This embodiment illustrates the preparation of oil displacement agents.

[0152] Precursor structure formula:

[0153] (1-1) The precursor (in the above structural formula, A is...) D is (n=13) was reacted with chloroacetic acid in a carboxylation reaction (the molar ratio of precursor to chloroacetic acid was 1:1.2; the carboxylation reaction temperature was 90℃, and the reaction time was 2h). Then, potassium hydroxide was added to the resulting product system for neutralization, and the pH of the system was adjusted to 10 to obtain an anionic surfactant. Where R1 is R2 is G is K, i is 13);

[0154] (1-2) In the presence of the first catalyst, the precursor (in the above structural formula, A is...) D is (n=15) reacts with hydrogen and dimethylamine in a first hydroamination reaction (molar ratio of precursor:hydrogen:dimethylamine:1:3.5:6; reaction temperature:250℃, reaction pressure:5.5MPa, reaction time:2h) to obtain a first intermediate; then the obtained first intermediate is reacted with chloromethane in a first quaternization reaction (molar ratio of first intermediate:chloromethane:1:1.3; reaction temperature:150℃, reaction time:6h) to obtain a cationic surfactant. Among them, R3 is R4 is R5 is methyl, X is Cl, and q is 15);

[0155] (1-3) In the presence of a second catalyst, the precursor (in the above structural formula, A is...) D is (n=2) reacts with hydrogen and dimethylamine in a second hydroamination reaction (molar ratio of precursor:hydrogen:dimethylamine:1:3.5:6; reaction temperature:250℃, reaction pressure:5.5MPa, reaction time:2h) to obtain a second intermediate. The obtained second intermediate is then reacted with chloromethane in a second quaternization reaction (molar ratio of second intermediate:chloromethane:1:1.3; reaction temperature:150℃, reaction time:6h) to obtain a third intermediate. This third intermediate is further reacted with sulfur trioxide in a sulfonation reaction (molar ratio of third intermediate:sulfur trioxide:1:2; reaction temperature:170℃, reaction time:2h). Potassium hydroxide is then added to the sulfonation product system for neutralization, and the pH of the system is adjusted to 8 to obtain an amphoteric surfactant. Among them, R6 is R7 is R8 represents methyl, Z represents Cl, t represents 2, and M represents K.

[0156] (2) The anionic surfactant and cationic surfactant prepared above are mixed evenly at a molar ratio of 1:10 to obtain surfactant mixture-1; then surfactant mixture-1 is mixed evenly with the amphoteric surfactant prepared above at a molar ratio of 1:4 to obtain surfactant mixture-2.

[0157] Mix 130 parts by weight of the above surfactant mixture-2, 60 parts by weight of ethanol and 100 parts by weight of water to obtain an oil displacement agent (denoted as S5).

[0158] Example 6

[0159] This embodiment illustrates the preparation of oil displacement agents.

[0160] Precursor structure formula:

[0161] (1-1) The precursor (in the above structural formula, A is...) D is (n=15) was reacted with sodium chloroacetate in a carboxylation reaction (the molar ratio of precursor to sodium chloroacetate was 1:1.1; the carboxylation reaction temperature was 70℃, and the reaction time was 4h) to obtain an anionic surfactant (n=15). Where R1 is R2 is G is Na, i is 15);

[0162] (1-2) In the presence of the first catalyst, the precursor (in the above structural formula, A is...) D is (n=2) reacts with hydrogen and dimethylamine in a first hydroamination reaction (molar ratio of precursor:hydrogen:dimethylamine:1:1.5:4.5; reaction temperature:210℃, reaction pressure:4MPa, reaction time:5h) to obtain a first intermediate; then the obtained first intermediate is reacted with chloromethane in a first quaternization reaction (molar ratio of first intermediate:chloromethane:1:1.2; reaction temperature:90℃, reaction time:9h) to obtain a cationic surfactant. Among them, R3 is R4 is R5 is methyl, X is Cl, and q is 2);

[0163] (1-3) In the presence of a second catalyst, the precursor (in the above structural formula, A is...) D is (n=13) undergoes a second hydroamination reaction with hydrogen and dimethylamine (molar ratio of precursor:hydrogen:dimethylamine:1:2:4; reaction temperature:220℃; reaction pressure:3.5MPa; reaction time:4h) to obtain a second intermediate. The obtained second intermediate is then subjected to a second quaternization reaction with chloromethane (molar ratio of second intermediate:chloromethane:1:1.2; reaction temperature:120℃; reaction time:8h) to obtain a third intermediate. The obtained third intermediate is further subjected to a sulfonation reaction with sulfuric acid (molar ratio of third intermediate:sulfuric acid:1:1.5; reaction temperature:120℃; reaction time:5h). Sodium hydroxide is then added to the sulfonation product system for neutralization, and the pH of the system is adjusted to 8 to obtain an amphoteric surfactant. Among them, R6 is R7 is R8 is methyl, Z is Cl, t is 13, M is Na);

[0164] (2) The anionic surfactant and cationic surfactant prepared above are mixed evenly at a molar ratio of 1:8 to obtain surfactant mixture-1; then surfactant mixture-1 is mixed evenly with the zwitterionic surfactant prepared above at a molar ratio of 1:3 to obtain surfactant mixture-2.

[0165] Mix 120 parts by weight of the above surfactant mixture-2, 50 parts by weight of n-butanol, and 100 parts by weight of water to obtain an oil displacement agent (denoted as S6).

[0166] Comparative Example 1

[0167] This embodiment illustrates the preparation of oil displacement agents.

[0168] The method of Example 1 was followed, except that step (1-1) was omitted (i.e., the anionic surfactant was not prepared), and in step (2), the anionic surfactant was replaced with an equal weight of the cationic surfactant prepared in step (1-2) (i.e., "surfactant mixture-1" was replaced with a cationic surfactant). Other conditions were the same as in Example 1. An oil displacement agent (denoted as D1) was obtained.

[0169] Comparative Example 2

[0170] The method of Example 1 was followed, except that steps (1-2) were omitted (i.e., the cationic surfactant was not prepared), and in step (2), the cationic surfactant was replaced with an anionic surfactant prepared in step (1-1) by an equal weight (i.e., "surfactant mixture-1" was replaced with an anionic surfactant). Other conditions were the same as in Example 1. An oil displacement agent (denoted as D2) was obtained.

[0171] Comparative Example 3

[0172] The method of Example 1 was followed, except that steps (1-3) were omitted (i.e., the amphoteric surfactant was not prepared), and in step (2), surfactant mixture-2 was replaced with an equal weight of surfactant mixture-1. Other conditions were the same as in Example 1. An oil displacement agent (denoted as D3) was obtained.

[0173] Test case

[0174] The oil displacement agents S1-S6 and D1-D3 prepared in Examples 1-6 and Comparative Examples 1-3, as well as conventional oil displacement agent a (used in oilfields, main components: anionic gemini surfactant and amphoteric surfactant), were subjected to interfacial tension tests and simulated oil displacement tests, respectively.

[0175] 1. Interface tension test

[0176] A saturated saline solution with a calcium ion content of 4000 mg / L was prepared using sodium chloride and calcium chloride as a simulated saline solution. The above-mentioned S1-S6, D1-D3 and conventional oil displacement agent a were added to it respectively to obtain simulated saline solutions with an oil displacement agent concentration of 0.1 wt%. The appearance of the solution was observed to see if there were any insoluble substances or precipitates.

[0177] Using a rotating drop interfacial tensiometer (model TX-500C), the interfacial tension (i.e., the interfacial tension before aging) between a simulated brine solution with a displacement agent concentration of 0.1 wt% and dehydrated crude oil was measured at 85℃ and a rotation speed of 3000 rpm. The results are shown in Table 1. Subsequently, the simulated brine solution with a displacement agent concentration of 0.1 wt% was placed in an aging vessel and aged at 120℃ for 72 h. The interfacial tension (i.e., the interfacial tension after aging) between the simulated brine solution and dehydrated crude oil was tested again at 85℃ and a rotation speed of 3000 rpm. The results are shown in Table 1.

[0178] 2. Simulated oil displacement test

[0179] The core displacement test was conducted on an artificial core (permeability 5±1 mD) with a length of 30 cm and a diameter of 2.5 cm. The displacement test temperature was 90℃. First, the artificial core was displaced with simulated brine without the above-mentioned oil displacement agent until the water cut was 98%. The volume of oil displaced was read and the recovery rate was calculated (denoted as X1). Then, the artificial core was further displaced with simulated brine solution with the above-mentioned oil displacement agent concentration of 0.1 wt% until the water cut was 98%. The volume of oil displaced was read and the total recovery rate was calculated (denoted as X2). The enhanced recovery rate is X2-X1. The results are shown in Table 1.

[0180] Table 1

[0181]

[0182] As shown in Table 1, the oil displacement agents S1-S6 prepared in Examples 1-6 are highly stable and do not precipitate during use. Utilizing the intramolecular and intermolecular cation-anion pairings, S1-S6 exhibits high surface activity even at low concentrations and possesses strong temperature and salt resistance, resulting in significant oil displacement effects compared to conventional oil displacement agents. Furthermore, because the anionic, cationic, and zwitterionic surfactant components in S1-S6 have similar molecular structures, chromatographic separation during use can be reduced or even avoided, thereby enhancing the oil displacement effect in the reservoir.

[0183] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. The application of an oil displacement agent in improving the recovery rate of low-to-medium permeability oil reservoirs, characterized in that, The oil displacement agent contains anionic surfactants, cationic surfactants, amphoteric surfactants, additives, and water; wherein, The anionic surfactant, cationic surfactant, and amphoteric surfactant each independently contain the chemical structure shown in formula (I). Equation (I) Where A is selected from C8-C 14 Alkyl and C8-C 14 At least one of the alkenyl groups; D is a C2-C4 alkyl group; E is -H or -SO3M; n is an integer from 2 to 15; M is an alkali metal element.

2. The application according to claim 1, wherein, A is selected from C9-C 12 Straight-chain alkyl and C9-C 12 At least one of the straight-chain alkenyl groups; D is a C2-C3 alkyl group; n is an integer from 3 to 12; M is Na or K.

3. The application according to claim 2, wherein, A is C9-C 12 Straight-chain alkyl groups.

4. The application according to any one of claims 1-3, wherein, For the anionic surfactant and cationic surfactant, in formula (I), E is -H.

5. The application according to any one of claims 1-3, wherein, For the zwitterionic surfactant, in formula (I), E is -SO3M.

6. The application according to any one of claims 1-3, wherein, The structural formula of the anionic surfactant is shown in formula (II): Equation (II) Among them, R1 is selected from C8-C 14 Alkyl and C8-C 14 At least one of the alkenyl groups; R2 is a C2-C4 alkyl group; G is an alkali metal element; i is an integer from 2 to 15.

7. The application according to claim 6, wherein, R1 is selected from C9-C 12 Straight-chain alkyl and C9-C 12 At least one of the straight-chain alkenyl groups; R2 is a C2-C3 alkyl group; G is Na or K; i is an integer from 3 to 12.

8. The application according to claim 7, wherein, R1 is selected from C9-C 12 Straight-chain alkyl groups.

9. The application according to any one of claims 1-3, wherein, The structural formula of the cationic surfactant is shown in Formula (III): Equation (III) R3 is selected from C8-C 14 Alkyl and C8-C 14 At least one of the alkenyl groups; R4 is a C2-C4 alkyl group; R5 is methyl or benzyl; X is a halogen; q is an integer from 2 to 15.

10. The application according to claim 9, wherein, R3 is selected from C9-C 12 Straight-chain alkyl and C9-C 12 At least one of the straight-chain alkenyl groups; R4 is a C2-C3 alkyl group; R5 is benzyl; X is Cl or Br; q is an integer from 3 to 12.

11. The application according to claim 10, wherein, R3 is selected from C9-C 12 Straight-chain alkyl groups.

12. The application according to any one of claims 1-3, wherein, The structural formula of the zwitterionic surfactant is shown in formula (IV): Formula (IV) R6 is selected from C8-C 14 Alkyl and C8-C 14 At least one of the alkenyl groups; R7 is a C2-C4 alkyl group; R8 is methyl or benzyl; Z is a halogen; t is an integer from 2 to 15; M is an alkali metal element.

13. The application according to claim 12, wherein, R6 is selected from C9-C 12 Straight-chain alkyl and C9-C 12 At least one of the straight-chain alkenyl groups; R7 is a C2-C3 alkyl group; R8 is a benzyl group; Z is Cl or Br; t is an integer from 3 to 12; M is Na or K.

14. The application according to claim 13, wherein R6 is selected from C9-C. 12 Straight-chain alkyl groups.

15. The application according to any one of claims 1-3, wherein, (Anionic surfactant + cationic surfactant): The molar ratio of zwitterionic surfactants is 1:(0.25-4).

16. The application according to claim 15, wherein, (Anionic surfactant + cationic surfactant): The molar ratio of zwitterionic surfactants is 1:(0.5-2).

17. The application according to any one of claims 1-3, wherein, The molar ratio of anionic surfactant to cationic surfactant is 1:(0.1-10).

18. The application according to claim 17, wherein, The molar ratio of anionic surfactant to cationic surfactant is 1:(0.2-5).

19. The application according to any one of claims 1-3, wherein, Relative to 100 parts by weight of water, (anionic surfactant + cationic surfactant + amphoteric surfactant) is 25-130 parts by weight, and the auxiliary agent is 1-60 parts by weight.

20. The application according to claim 19, wherein, Relative to 100 parts by weight of water, (anionic surfactant + cationic surfactant + amphoteric surfactant) is 40-100 parts by weight, and the additives are 5-40 parts by weight.

21. The application according to any one of claims 1-3, wherein, The additive is an alcohol.

22. The application according to claim 21, wherein, The auxiliary agent is at least one selected from ethanol, n-propanol, isopropanol, and n-butanol.

23. The application according to any one of claims 1-3, wherein, The method for preparing the oil displacement agent includes: (1) Prepare anionic surfactants, cationic surfactants, and amphoteric surfactants respectively; wherein, (1-1) The precursor shown in formula (V) is subjected to a carboxylation reaction with a carboxylating agent, followed by an optional neutralization reaction to obtain an anionic surfactant; (1-2) In the presence of a first catalyst, the precursor shown in formula (V) is subjected to a first hydroamination reaction with hydrogen and dimethylamine to obtain a first intermediate; then the first intermediate is subjected to a first quaternization reaction with a first haloalkane to obtain a cationic surfactant. (1-3) In the presence of a second catalyst, the precursor shown in formula (V) is subjected to a second hydroamination reaction with hydrogen and dimethylamine to obtain a second intermediate; then the second intermediate is subjected to a second quaternization reaction with a second haloalkane to obtain a third intermediate; the third intermediate is subjected to a sulfonation reaction with a sulfonating agent, followed by a neutralization reaction to obtain an amphoteric surfactant. Equation (V) (2) The anionic surfactant, cationic surfactant, amphoteric surfactant, additives and water are mixed to obtain the oil displacement agent; The definitions of A, D, and n are the same as those in claim 1.

24. The application according to claim 23, wherein, In step (1-1), the molar ratio of the precursor to the carboxylating agent is 1:(1.05-1.2).

25. The application according to claim 23, wherein, In step (1-1), the carboxylating agent is chloroacetic acid and / or sodium chloroacetate.

26. The application according to claim 23, wherein, In step (1-1), the conditions for the carboxylation reaction include: a temperature of 50-90℃ and a time of 2-6h.

27. The application according to claim 23, wherein, In step (1-1), the base used in the neutralization reaction is selected from sodium hydroxide and / or potassium hydroxide.

28. The application according to claim 23, wherein, In steps (1-2), the molar ratio of the precursor, hydrogen, and dimethylamine is 1:(0.2-3.5):(2.5-6).

29. The application according to claim 23, wherein, In steps (1-2), the first haloalkane is a halomethane and / or a benzyl halide.

30. The application according to claim 23, wherein, In steps (1-2), the molar ratio of the first intermediate to the first haloalkane is 1:(1.1-1.3).

31. The application according to claim 23, wherein, In steps (1-2), the conditions for the first hydroamination reaction include: a temperature of 180-250℃, a pressure of 1-5.5MPa, and a time of 2-8h.

32. The application according to claim 23, wherein, In steps (1-2), the conditions for the first quaternization reaction include: a temperature of 60-150℃ and a time of 6-12h.

33. The application according to claim 23, wherein, In steps (1-3), the molar ratio of the precursor: hydrogen: dimethylamine is 1:(0.2-3.5):(2.5-6).

34. The application according to claim 23, wherein, In steps (1-3), the second haloalkane is a halomethane and / or a benzyl halide.

35. The application according to claim 23, wherein, In steps (1-3), the sulfonating agent is at least one of sulfuric acid, fuming sulfuric acid, and sulfur trioxide.

36. The application according to claim 23, wherein, In steps (1-3), the molar ratio of the second intermediate to the second haloalkane is 1:(1.1-1.3).

37. The application according to claim 23, wherein, In steps (1-3), the molar ratio of the third intermediate to the sulfonating agent is 1:(1.2-2).

38. The application according to claim 23, wherein, In steps (1-3), the conditions for the second hydroamination reaction include: a temperature of 180-250℃, a pressure of 1-5.5MPa, and a time of 2-8h.

39. The application according to claim 23, wherein, In steps (1-3), the conditions for the second quaternization reaction include: a temperature of 60-150℃ and a time of 6-12h.

40. The application according to claim 23, wherein, In steps (1-3), the sulfonation reaction conditions include: a temperature of 80-170℃ and a time of 2-10h.

41. The application according to claim 23, wherein, In steps (1-3), the base used in the neutralization reaction is selected from sodium hydroxide and / or potassium hydroxide.

42. The application according to claim 1, wherein, The permeability of the medium-low permeability reservoir is 0.01-50 mD.

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