Surfactant, preparation method therefor and use thereof

Abstract

The present invention relates to the field of oilfield development, and in particular, to a surfactant, a preparation method therefor and a use thereof. The structural formula of the surfactant is: [formula 1], wherein R is selected from linear or branched alkyl groups, n is an integer from 1 to 8, and m is an integer from 1 to 10. The surfactant provided by the present invention increases the solubility of traditional long-chain alkyl amido betaine, can reduce the difficulty in liquid preparation during oilfield application construction, and is more conducive to stripping reservoir crude oil and improving the ability to block a high-permeability water channel. When the surfactant provided by the present invention is applied to oil displacement in an oilfield, the oil displacement efficiency can be increased by more than 18% compared with water flooding.

Description

Surfactant and its preparation method and application

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of Chinese patent application No. 202311272324.6 filed on September 28, 2023, the contents of which are incorporated herein by reference. Technical Field

[0003] The present invention relates to the field of oil field development, and in particular to a surfactant, a preparation method and an application thereof. Background Art

[0004] Surfactant flooding technology is a new oilfield recovery enhancement technology that has gradually emerged in recent years. Its working principle is that after the flooding surfactant enters the reservoir, it spontaneously emulsifies in the high permeability water channel to form a W / O emulsion. The Jamin effect of large-sized emulsion droplets and the high emulsion viscosity are used to block the high permeability water channel, achieving the purpose of "adjustment". The high interfacial activity characteristics are used to improve the oil washing efficiency, achieving the purpose of "displacement". The notable characteristics of surfactant flooding agents are that the higher the water content, the greater the emulsion viscosity, the stronger the ability to block the high permeability channels with high water content, the better the flooding selectivity, and the ability to achieve the "adjustment + displacement" effect in one system. The surface injection process is simple and low-cost, and has broad application prospects.

[0005] Although currently known surfactant flooding technologies have demonstrated promising results, they still have limitations. Zhang Yao et al., in their paper "Study on Reservoir Adaptability and Oil Displacement Efficiency of Block Polyether Surfactant Flooding Systems," published a block polyether surfactant flooding system. This system was field-tested in the Zhou 16 well area of ​​the Jianghan Oilfield in 2017, achieving significant results, with single-well production increasing from 3 t / d to 8.43 t / d and the overall water content dropping from 93.18% to 86.32%. However, evaluation results revealed that this system exhibited significant flooding effects only in reservoirs with a permeability range of 3.2-10.9, while significantly decreasing in reservoirs with a range greater than 35.6.

[0006] In the article "Research on Surfactant Flooding and Its Application in Wenliu Oilfield", Wang Yongmei et al. disclosed a flooding system with an anion-non-surfactant as the main component and a composite anion as the auxiliary component. In 2019, it was put into field application in Wen 16 East District of Wenliu Oilfield. The single well production increased from 6.2t / d to 8.4t / d, and the water content decreased from 80.6% to 72.4%. However, it is a compound of multiple systems, which is easy to be chromatographically separated in the reservoir, and needs to be used together with a viscosity reducer. The system is complex and the cost is high.

[0007] CN202110599274 discloses a salt-tolerant anionic and cationic surfactant composition containing polyether segments for flooding, wherein the anionic and cationic surfactant compositions are prepared by using the same precursors to form an anionic and cationic surfactant composition with similar structures. Under the condition of a concentration of 0.1wt%, in the field formation water with a salinity of 250,000 mg / L and a calcium and magnesium ion content of 2000 mg / L, after aging at 120°C for 72h, the composition can form a 10% cation-ion surfactant with underground crude oil. -3 ~10 -4 The ultra-low interfacial tension of mN / m can increase oil recovery by over 15%. However, since the formula contains cationic surfactants, and the surface of sandstone reservoirs generally has negative points, this will cause a large amount of adsorption loss of the cationic surfactant, thus affecting the overall performance of the composition.

[0008] Summary of the Invention

[0009] The purpose of the present invention is to overcome the problems of poor viscosity increasing effect, low interfacial activity and weak emulsifying ability of surfactants used for flooding in the prior art, and to provide a surfactant and its preparation method and application.

[0010] In order to achieve the above object, the first aspect of the present invention provides a surfactant, wherein the structural formula of the surfactant is:

[0011] Wherein, R is selected from a straight chain or branched chain alkyl group, n is an integer of 1-8, and m is an integer of 1-10.

[0012] A second aspect of the present invention provides a method for preparing a surfactant, wherein the method comprises the following steps:

[0013] (1) subjecting a monounsaturated fatty acid to a sulfation reaction with concentrated sulfuric acid to obtain a sulfated fatty acid;

[0014] (2) contacting the sulfated fatty acid with hydrochloric acid to perform a hydrolysis reaction to obtain monohydroxystearic acid;

[0015] (3) in the presence of catalyst I, polymerizing the monohydroxystearic acid with ethylene oxide to obtain polyoxyethylene ether stearic acid;

[0016] (4) in the presence of catalyst II, the polyoxyethylene ether stearic acid and N,N-dimethyl-1,3-propylenediamine are subjected to an acylation reaction to obtain polyoxyethylene ether fatty acid amide propyl dimethylamine;

[0017] (5) In the presence of a reaction solvent, the polyoxyethylene ether fatty acid amide propyl dimethylamine is subjected to an alkylation reaction with sodium 3-chloro-2-hydroxypropanesulfonate to obtain the surfactant.

[0018] The third aspect of the present invention provides a use of the surfactant described in the first aspect of the present invention or the surfactant prepared according to the method described in the second aspect of the present invention in oil field flooding.

[0019] Through the above technical solution, the beneficial technical effects achieved by the present invention are as follows:

[0020] 1) The surfactant provided by the present invention increases the solubility of traditional long-chain fatty amide betaine, which can reduce the difficulty of preparing the solution during oil field application and construction;

[0021] 2) The surfactant provided by the present invention increases the ability to spontaneously emulsify crude oil, enabling oil-water emulsification with minimal or no disturbance, which is more conducive to stripping formation crude oil and improving the ability to block hypertonic water flow channels;

[0022] 3) The surfactant provided by the present invention is conducive to the formation of worm-like micelles, which can increase the viscosity of the aqueous solution, preferably reduce the oil-water interfacial tension to 0.007 mN / m, and improve the flooding capability;

[0023] 4) The preparation method of the surfactant provided by the present invention is simple, the raw material source is wide, the production cost is low, and it is suitable for industrial promotion;

[0024] 5) The surfactant provided by the present invention is used in oil field flooding, and the oil flooding efficiency can be increased by more than 18% compared with water flooding;

[0025] 6) The surfactant provided by the present invention is used in oil field flooding to significantly improve the adaptability range of the reservoir permeability extremes. DETAILED DESCRIPTION

[0026] The endpoints of the ranges and any values ​​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 endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0027] The first aspect of the present invention provides a surfactant, wherein the structural formula of the surfactant is:

[0028] Wherein, R is selected from a straight chain or branched chain alkyl group, n is an integer of 1-8, and m is an integer of 1-10.

[0029] In a preferred embodiment of the present invention, said R is selected from C2-C 15The straight chain or branched chain alkyl group is preferably a C4-C8 straight chain or branched chain alkyl group, and more preferably one of a C4 straight chain alkyl group, a C6 straight chain alkyl group, and a C8 straight chain alkyl group. That is, R is preferably an n-butyl group, an n-hexyl group, or an n-octyl group.

[0030] In a preferred embodiment of the present invention, n can be 1, 2, 3, 4, 5, 6, 7, 8, preferably 4 or 6.

[0031] In a preferred embodiment of the present invention, m can be 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10, preferably 1, 4, 5, or 10.

[0032] In a preferred embodiment of the present invention, the structural formula of the surfactant is one of Formula 1-1 to Formula 1-4:

[0033] Among them, C8H 27 -, C4H9- and C6H 13 - are all straight-linked alkyl groups.

[0034] A second aspect of the present invention provides a method for preparing a surfactant, wherein the method comprises the following steps:

[0035] (1) subjecting a monounsaturated fatty acid to a sulfation reaction with concentrated sulfuric acid to obtain a sulfated fatty acid;

[0036] (2) contacting the sulfated fatty acid with hydrochloric acid to perform a hydrolysis reaction to obtain monohydroxystearic acid;

[0037] (3) in the presence of catalyst I, condensing the monohydroxystearic acid with ethylene oxide to obtain polyoxyethylene ether stearic acid;

[0038] (4) in the presence of catalyst II, the polyoxyethylene ether stearic acid and N,N-dimethyl-1,3-propylenediamine are subjected to an acylation reaction to obtain polyoxyethylene ether fatty acid amide propyl dimethylamine;

[0039] (5) In the presence of a reaction solvent, the polyoxyethylene ether fatty acid amide propyl dimethylamine is subjected to an alkylation reaction with sodium 3-chloro-2-hydroxypropanesulfonate to obtain the surfactant.

[0040] In step (1),

[0041] In a preferred embodiment of the present invention, the monounsaturated fatty acid is selected from C6-C 24 Straight-chain or branched monounsaturated fatty acids, preferably C 14 -C 22The straight-chain or branched monounsaturated fatty acid is more preferably one or more of erucic acid, oleic acid, myristic acid, palmitic acid, and ricinoleic acid. In the present invention, the monounsaturated fatty acid refers to a fatty acid containing one double bond.

[0042] In a preferred embodiment of the present invention, the mass concentration of the concentrated sulfuric acid is 92%-98.3%, preferably 95%-98.3%.

[0043] In a preferred embodiment of the present invention, the mass ratio of the monounsaturated fatty acid to concentrated sulfuric acid is 1:1-2, preferably 1:1.2-1.6.

[0044] In a preferred embodiment of the present invention, the sulfation reaction is carried out in an ice bath, and the reaction time of the sulfation reaction is 2-10 h, preferably 4-6 h.

[0045] In the present invention, the monounsaturated fatty acid and concentrated sulfuric acid are preferably cooled in an ice bath before the acidification reaction to reduce the temperature to about 0°C (eg, -5°C to 5°C).

[0046] In step (2),

[0047] In a preferred embodiment of the present invention, the molar concentration of the hydrochloric acid is 1-5 mol / L, preferably 2-4 mol / L.

[0048] In a preferred embodiment of the present invention, the volume ratio of the sulfated fatty acid to hydrochloric acid is 1:1-3, preferably 1:1.5-2.5.

[0049] In a preferred embodiment of the present invention, the reaction temperature of the hydrolysis is 60-110° C., preferably 75-95° C.; the reaction time of the hydrolysis is 20-80 min, preferably 30-60 min.

[0050] In a preferred embodiment of the present invention, after the hydrolysis is completed, sodium hydroxide is first added for neutralization, and then petroleum ether is added for extraction to obtain monohydroxystearic acid.

[0051] In step (3),

[0052] In a preferred embodiment of the present invention, the catalyst I is selected from sodium hydroxide and / or potassium hydroxide, preferably sodium hydroxide.

[0053] In a preferred embodiment of the present invention, the mass ratio of the monohydroxystearic acid, the catalyst I and the ethylene oxide is 1:0.01-0.1:1-15, preferably 1:0.02-0.05:1-10.

[0054] In a preferred embodiment of the present invention, the order of adding the monohydroxystearic acid, catalyst I and ethylene oxide is: first, the monohydroxystearic acid is heated and melted, and then the catalyst I is added to the molten monohydroxystearic acid, and then the temperature is raised to 110-140° C. under nitrogen protection, and ethylene oxide is added to react.

[0055] In a preferred embodiment of the present invention, the reaction temperature of the polymerization reaction is 110-140° C., preferably 120-130° C.; the reaction pressure is 0.1-0.5 MPa, preferably 0.1-0.3 MPa.

[0056] In the present invention, the polymerization reaction is carried out in a reactor. As the polymerization reaction proceeds, ethylene oxide is continuously consumed, and nitrogen needs to be continuously introduced to maintain a constant reaction pressure. When the pressure in the reactor is no longer fluctuating, that is, when nitrogen is no longer required, the polymerization reaction is completed. At this point, heating can be stopped and the temperature can be lowered to obtain polyoxyethylene ether stearic acid.

[0057] In step (4),

[0058] In a preferred embodiment of the present invention, the catalyst II is selected from one or more of boric acid, formic acid, and acetic acid, preferably boric acid.

[0059] In a preferred embodiment of the present invention, the mass ratio of the polyoxyethylene ether stearic acid, N,N-dimethyl-1,3-propylenediamine and catalyst II is 1:1-1.35:0.005-0.035; preferably 1:1-1.15:0.01-0.02.

[0060] In a preferred embodiment of the present invention, the reaction temperature of the acylation reaction is 130-180° C., preferably 140-165° C.; the reaction time of the acylation reaction is 2-12 h, preferably 5-10 h.

[0061] In a preferred embodiment of the present invention, after the acylation reaction is completed, vacuum distillation is first performed, and then recrystallization is performed using ethanol to obtain polyoxyethylene ether fatty acid amide propyl dimethylamine.

[0062] In step (5),

[0063] In a preferred embodiment of the present invention, the reaction solvent is selected from one or more of isopropanol, water, methanol, and ethanol, preferably isopropanol and water. Further preferably, the volume ratio of isopropanol to water is 1:1.5-2.5.

[0064] In a preferred embodiment of the present invention, the sodium 3-chloro-2-hydroxypropanesulfonate may be a commercially available product or may be synthesized according to a known method, which is not particularly limited in the present invention.

[0065] In a preferred embodiment of the present invention, the mass ratio of the polyoxyethylene ether fatty acid amide propyl dimethylamine, sodium 3-chloro-2-hydroxypropanesulfonate and the reaction solvent is 1:1-1.5:1-15, preferably 1:1.1-1.3:3-10.

[0066] In a preferred embodiment of the present invention, the reaction temperature of the alkylation reaction is 40-100° C., preferably 50-90° C.; the reaction time of the alkylation reaction is 1-7 h, preferably 3-6 h.

[0067] In the present invention, after the alkylation reaction is completed, the reaction liquid obtained after the alkylation reaction can be separated and purified to separate the alkylation product to obtain a surfactant, or the reaction liquid containing the surfactant obtained after the alkylation reaction can be directly used as a surfactant for oil displacement.

[0068] The third aspect of the present invention provides a use of the surfactant described in the first aspect of the present invention or the surfactant prepared according to the method described in the second aspect of the present invention in oil field flooding.

[0069] The surfactant provided in the present invention can be diluted with water and then injected into the oil reservoir alone, or it can be used in combination with other chemical agents such as polymers, nanospheres, etc. and then injected into the oil reservoir, which can significantly improve the oil displacement effect and increase the recovery rate.

[0070] The present invention will be described in detail below through examples, wherein the mass concentration of concentrated sulfuric acid is 98%.

[0071] Preparation of sodium 3-chloro-2-hydroxypropanesulfonate: 1 g of sodium bisulfite, 0.015 g of ethylenediaminetetraacetic acid, and 3 g of water were added to a reactor equipped with a condenser and a stirrer. The temperature was raised to 70°C, and 3 g of epichlorohydrin was slowly added dropwise. The temperature was further raised to 90°C and the reaction was carried out for 3 h. Then, heating was stopped and the mixture was allowed to stand for 3 h. The mixture was then filtered and dried to obtain sodium 3-chloro-2-hydroxypropanesulfonate.

[0072] Example 1

[0073] (1) Erucic acid and concentrated sulfuric acid were placed in an ice bath and cooled to 0°C. Then, 1.6 g of concentrated sulfuric acid was added to 1 g of erucic acid in an ice bath to carry out a sulfation reaction. The reaction was stirred for 6 h to obtain sulfated erucic acid.

[0074] (2) The sulfated erucic acid was mixed with 4 mol / L hydrochloric acid in a volume ratio of 1:2.5, heated to 95°C for hydrolysis, stirred for 30 minutes, then NaOH was added to neutralize the excess acid, and extracted with petroleum ether to obtain monohydroxy erucic acid;

[0075] (3) heating the monohydroxy erucic acid until it is completely melted, adding sodium hydroxide, and then transferring the mixture into a high-pressure reactor. Nitrogen is introduced to remove the air in the reactor, and then ethylene oxide is added. The temperature is raised to 130° C., and a polymerization reaction is carried out at 0.3 MPa. During the reaction, the reaction pressure is monitored in real time, and nitrogen is continuously introduced to maintain a constant pressure. After the reaction pressure no longer changes, heating is stopped and the mixture is cooled to obtain polyoxyethylene ether erucic acid; wherein the mass ratio of monohydroxy erucic acid, sodium hydroxide, and ethylene oxide is 1:0.05:1;

[0076] (4) Add the above-mentioned polyoxyethylene ether erucic acid, N,N-dimethyl-1,3-propylenediamine and boric acid in a mass ratio of 1:1.15:0.02 to a reactor equipped with a condenser, a stirrer and a temperature measuring device, and carry out an acylation reaction after nitrogen is introduced to replace the air. The reaction is carried out at 165°C for 10 hours. After the reaction is completed, vacuum distillation is first performed to separate the excess N,N-dimethyl-1,3-propylenediamine, and then recrystallized from ethanol to obtain polyoxyethylene ether erucic acid amide propyl dimethylamine;

[0077] (5) The polyoxyethylene ether erucic acid amide propyl dimethylamine, sodium 3-chloro-2-hydroxypropanesulfonate and reaction solvent (a mixture of isopropyl alcohol and water with a volume ratio of 1:2.5) were mixed evenly in a mass ratio of 1:1.3:10, and then an alkylation reaction was carried out at 90°C for 6 hours. After the reaction was completed, the alkylation product was separated to obtain the surfactant polyoxyethylene ether erucic acid amide propyl hydroxysulfobetaine represented by formula 1-1.

[0078] Example 2

[0079] (1) Oleic acid and concentrated sulfuric acid were placed in an ice bath and cooled to 0°C. Then, 1.4 g of concentrated sulfuric acid was added to 1 g of oleic acid in an ice bath for sulfation reaction. The reaction was stirred for 4 h to obtain sulfated oleic acid.

[0080] (2) The sulfated oleic acid was mixed with 2 mol / L hydrochloric acid in a volume ratio of 1:2, heated to 90°C for hydrolysis, stirred for 50 minutes, and then NaOH was added to neutralize the excess acid, and extracted with petroleum ether to obtain monohydroxy oleic acid;

[0081] (3) heating the monohydroxy oleic acid until it is completely melted, adding sodium hydroxide, and then transferring the mixture into a high-pressure reactor. Nitrogen is introduced to remove the air in the reactor, and then ethylene oxide is added. The temperature is raised to 125° C., and a polymerization reaction is carried out at 0.2 MPa. During the reaction, the reaction pressure is monitored in real time, and nitrogen is continuously introduced to maintain a constant pressure. After the reaction pressure no longer changes, heating is stopped and the mixture is cooled to obtain polyoxyethylene ether oleic acid; wherein the mass ratio of monohydroxy oleic acid, sodium hydroxide, and ethylene oxide is 1:0.04:4;

[0082] (4) Add the above-mentioned polyoxyethylene ether oleic acid, N,N-dimethyl-1,3-propylenediamine and boric acid in a mass ratio of 1:1:0.015 to a reactor equipped with a condenser, a stirrer and a temperature measuring device, and then introduce nitrogen to replace the air for acylation reaction, and react at 145°C for 8 hours; after the reaction is completed, first perform vacuum distillation to separate the excess N,N-dimethyl-1,3-propylenediamine, and then recrystallize with ethanol to obtain polyoxyethylene ether oleic acid amide propyl dimethylamine;

[0083] (5) The polyoxyethylene ether oleic acid amidopropyl dimethylamine, sodium 3-chloro-2-hydroxypropanesulfonate and reaction solvent (a mixture of isopropyl alcohol and water with a volume ratio of 1:1.5) were mixed evenly in a mass ratio of 1:1.1:8, and then an alkylation reaction was carried out at 80°C for 5 hours. After the reaction was completed, the alkylation product was separated to obtain the surfactant polyoxyethylene ether oleic acid amidopropyl hydroxysulfobetaine represented by formula 1-2.

[0084] Example 3

[0085] (1) Myristic acid and concentrated sulfuric acid were placed in an ice bath and cooled to 0°C. Then, 1.2 g of concentrated sulfuric acid was added to 1 g of myristic acid in an ice bath to carry out a sulfation reaction. The reaction was stirred for 4 h to obtain sulfated myristic acid.

[0086] (2) The sulfated myristic acid was mixed with 2 mol / L hydrochloric acid in a volume ratio of 1:1.5, heated to 75°C for hydrolysis, stirred for 30 minutes, and then NaOH was added to neutralize the excess acid, and extracted with petroleum ether to obtain monohydroxymyristic acid;

[0087] (3) heating the monohydroxymyristic acid until it is completely melted, adding sodium hydroxide, and then transferring it into a high-pressure reactor. Nitrogen is introduced to remove the air in the reactor, and then ethylene oxide is added. The temperature is raised to 120° C., and a polymerization reaction is carried out at 0.1 MPa. During the reaction, the reaction pressure is monitored in real time, and nitrogen is continuously introduced to maintain a constant pressure. After the reaction pressure no longer changes, heating is stopped and cooling is carried out to obtain polyoxyethylene ether myristic acid; wherein the mass ratio of monohydroxymyristic acid, sodium hydroxide, and ethylene oxide is 1:0.03:10;

[0088] (4) Adding the above-mentioned polyoxyethylene ether myristic acid, N,N-dimethyl-1,3-propylenediamine and boric acid in a mass ratio of 1:1:0.01 to a reactor equipped with a condenser, a stirrer and a temperature measuring device, and introducing nitrogen to replace the air to carry out an acylation reaction, and reacting at 140°C for 5 hours; after the reaction is completed, first performing reduced pressure distillation to separate the excess N,N-dimethyl-1,3-propylenediamine, and then recrystallizing with ethanol to obtain polyoxyethylene ether myristic acid amidopropyl dimethylamine;

[0089] (5) The polyoxyethylene ether myristyl oleic acid amidopropyl dimethylamine, sodium 3-chloro-2-hydroxypropanesulfonate and reaction solvent (a mixture of isopropyl alcohol and water with a volume ratio of 1:1.5) were mixed evenly in a mass ratio of 1:1.1:3 and then subjected to an alkylation reaction at 50°C for 6 hours. After the reaction was completed, the alkylation product was separated to obtain the surfactant polyoxyethylene ether myristyl oleic acid amidopropyl hydroxysulfobetaine represented by formula 1-3.

[0090] Example 4

[0091] (1) Palmitoleic acid and concentrated sulfuric acid were placed in an ice bath and cooled to 0°C. Then, 1.5 g of concentrated sulfuric acid was added to 1 g of palmitoleic acid in an ice bath to carry out a sulfation reaction. The reaction was stirred for 5.5 h to obtain sulfated palmitoleic acid.

[0092] (2) The sulfated palmitoleic acid was mixed with 3 mol / L hydrochloric acid in a volume ratio of 1:2.5, heated to 85°C for hydrolysis, stirred for 45 minutes, and then NaOH was added to neutralize the excess acid, and extracted with petroleum ether to obtain monohydroxypalmitoleic acid;

[0093] (3) heating the monohydroxypalmitoleic acid until it is completely melted, adding sodium hydroxide, and then transferring it into a high-pressure reactor, introducing nitrogen to remove the air in the reactor, and then adding ethylene oxide, raising the temperature to 120° C., and conducting a polymerization reaction at 0.1 MPa. During the reaction, the reaction pressure is monitored in real time, and nitrogen is continuously introduced to maintain a constant pressure. After the reaction pressure no longer changes, heating is stopped to obtain polyoxyethylene ether palmitoleic acid; wherein the mass ratio of monohydroxypalmitoleic acid, sodium hydroxide, and ethylene oxide is 1:0.05:5;

[0094] (4) Adding the above-mentioned polyoxyethylene ether palmitoleic acid, N,N-dimethyl-1,3-propylenediamine and boric acid in a mass ratio of 1:1:0.02 to a reactor equipped with a condenser, a stirrer and a temperature measuring device, and introducing nitrogen to replace the air to carry out an acylation reaction, and reacting at 140°C for 5 hours; after the reaction is completed, first performing reduced pressure distillation to separate the excess N,N-dimethyl-1,3-propylenediamine, and then recrystallizing with ethanol to obtain polyoxyethylene ether palmitoleic acid amidopropyl dimethylamine;

[0095] (5) The polyoxyethylene ether oleic acid amidopropyl dimethylamine, sodium 3-chloro-2-hydroxypropanesulfonate and reaction solvent (a mixture of isopropyl alcohol and water with a volume ratio of 1:1.5) were mixed evenly in a mass ratio of 1:1.1:4, and then an alkylation reaction was carried out at 50°C for 3 hours. After the reaction was completed, the alkylation product was separated to obtain the surfactant polyoxyethylene ether palmitoleic acid amidopropyl hydroxysulfobetaine represented by formula 1-4.

[0096] Comparative Example 1

[0097] (1) In a reactor equipped with a condenser, a stirrer and a temperature measuring device, erucic acid, N,N-dimethyl-1,3-propylenediamine and boric acid are added in a mass ratio of 1:1.15:0.015, and nitrogen is introduced to replace the air for acylation reaction, and the reaction is carried out at 145°C for 8 hours. After the reaction is completed, vacuum distillation is first performed to separate the excess N,N-dimethyl-1,3-propylenediamine, and then recrystallized from ethanol to obtain erucamidopropyl dimethylamine;

[0098] (2) The above-mentioned erucamidopropyl dimethylamine, sodium 3-chloro-2-hydroxypropanesulfonate and reaction solvent (a mixture of isopropyl alcohol and water with a volume ratio of 1:2.5) were mixed uniformly in a mass ratio of 1:1.3:10 and then subjected to an alkylation reaction at 90°C for 6 hours. After the reaction was completed, the alkylation product was separated to obtain the surfactant erucamidopropyl hydroxysulfobetaine represented by formula 1-5.

[0099] Test Example 1

[0100] 0.3 g of the surfactants prepared in Examples 1-4 and Comparative Example 1 were respectively added to 100 g of formation water from a block of Changqing Oilfield (mineralization of 42 g / L, calcium and magnesium ion content of 2 g / L) to obtain test samples, and the solubility of the surfactants was observed.

[0101] Among them, it can be seen from observation that the surfactants prepared in Examples 1-4 can be completely dissolved in formation water and have good solubility. However, the surfactant prepared in Comparative Example 1 cannot be completely dissolved in formation water and has poor solubility.

[0102] With reference to SY / T 6424-2014 composite flooding system performance test method, the viscosity of the test sample was tested at 50°C, and the interfacial tension between the sample and crude oil from a block of Changqing Oilfield (reservoir temperature of 50°C) was tested. The emulsifying power of the test sample was tested with reference to the colorimetric method for determination of emulsifying power of surfactants in GB T 6369-2008. The test results are shown in Table 1.

[0103] Table 1

[0104] As can be seen from Table 1, the surfactant provided in the present invention can significantly increase the viscosity of the water phase, while significantly reducing the oil-water interfacial tension and emulsifying crude oil with an emulsification power of more than 85.4%.

[0105] Test Example 2

[0106] An oil displacement experiment was carried out by simulating the reservoir conditions of a block in the Changqing Oilfield. The experimental method was based on the SY / T6424-2014 composite oil displacement system performance test method. The oil displacement efficiency of the surfactants prepared in different embodiments and comparative examples at an effective concentration of 0.3% was investigated. The test results are shown in Table 2.

[0107] Table 2

[0108] It can be seen from Table 2 that, under the same conditions, the oil displacement efficiency of the surfactant aqueous solution prepared in the present invention can be increased by at least 18.3% compared with water displacement.

[0109] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A surfactant, characterized in that The structural formula of the surfactant is: Wherein, R is selected from a straight chain or branched chain alkyl group, n is an integer of 1-8, and m is an integer of 1-10.

2. The surfactant according to claim 1, wherein The R is selected from C2-C 15 A straight chain or branched chain alkyl group.

3. The surfactant according to claim 2, wherein The R is a C4-C8 straight chain or branched chain alkyl.

4. The surfactant according to claim 3, wherein The R is one of a C4 straight chain alkyl group, a C6 straight chain alkyl group, and a C8 straight chain alkyl group.

5. The surfactant according to claim 2, wherein The structural formula of the surfactant is one of Formula 1-1 to Formula 1-4: Among them, C8H 27 -, C4H9- and C6H 13 - are all straight-linked alkyl groups.

6. A method for preparing a surfactant, characterized in that: The method comprises the following steps: (1) subjecting a monounsaturated fatty acid to a sulfation reaction with concentrated sulfuric acid to obtain a sulfated fatty acid; (2) contacting the sulfated fatty acid with hydrochloric acid to carry out a hydrolysis reaction to obtain monohydroxystearic acid; (3) in the presence of a catalyst I, polymerizing the monohydroxystearic acid with ethylene oxide to obtain polyoxyethylene ether stearic acid; (4) Under the action of catalyst II, the polyoxyethylene ether stearic acid and N,N-dimethyl-1,3-propylenediamine are subjected to acylation reaction to obtain polyoxyethylene ether fatty acid amide propyl dimethylamine; (5) In the presence of a reaction solvent, the polyoxyethylene ether fatty acid amide propyl dimethylamine is subjected to an alkylation reaction with sodium 3-chloro-2-hydroxypropanesulfonate to obtain the surfactant.

7. The preparation method according to claim 6, wherein: The monounsaturated fatty acid is selected from C8-C 36 Straight-chain or branched monounsaturated fatty acids; And / or, the mass concentration of the concentrated sulfuric acid is 92%-98.3%; And / or, the mass ratio of the monounsaturated fatty acid to concentrated sulfuric acid is 1:1-2; And / or, the sulfation reaction is carried out in an ice bath, and the reaction time of the sulfation reaction is 2-10 hours.

8. The preparation method according to claim 7, wherein: The monounsaturated fatty acid is C 12 -C 22 Straight-chain or branched monounsaturated fatty acids; And / or, the mass concentration of the concentrated sulfuric acid is 95%-98.3%; And / or, the mass ratio of the monounsaturated fatty acid to concentrated sulfuric acid is 1:1.2-1.6; And / or, the reaction time of the sulfation reaction is 4-6h.

9. The preparation method according to claim 8, wherein: The monounsaturated fatty acid is one or more of erucic acid, oleic acid, myristic acid, palmitoleic acid and ricinoleic acid.

10. The preparation method according to any one of claims 6 to 9, wherein: The concentration of the hydrochloric acid is 1-5 mol / L; and / or, the volume ratio of the sulfated fatty acid to hydrochloric acid is 1:1-3; And / or, the reaction temperature of the hydrolysis is 60-110° C., and the reaction time of the hydrolysis is 20-80 min; And / or, after the hydrolysis reaction is completed, sodium hydroxide is first added for neutralization, and then petroleum ether is added for extraction to obtain the monohydroxystearic acid.

11. The preparation method according to claim 10, wherein: The concentration of the hydrochloric acid is 2-4 mol / L; and / or, the volume ratio of the sulfated fatty acid to hydrochloric acid is 1:1.5-2.5; And / or, the reaction temperature of the hydrolysis is 75-95° C., and the reaction time of the hydrolysis is 30-60 min.

12. The preparation method according to claim 6, wherein: The catalyst I is selected from sodium hydroxide and / or potassium hydroxide; and / or, the mass ratio of the monohydroxystearic acid, the catalyst I and the ethylene oxide is 1:0.01-0.08:1-15; And / or, the reaction temperature of the polymerization reaction is 110-140° C., and the reaction pressure is 0.1-0.5 MPa.

13. The preparation method according to claim 12, wherein: The catalyst I is sodium hydroxide; and / or, the mass ratio of the monohydroxystearic acid, the catalyst I and the ethylene oxide is 1:0.02-0.05:1-10; And / or, the reaction temperature of the polymerization reaction is 120-130° C., and the reaction pressure is 0.1-0.3 MPa.

14. The preparation method according to claim 6, wherein: The catalyst II is selected from one or more of boric acid, formic acid and acetic acid; and / or, the mass ratio of the polyoxyethylene ether stearic acid, N,N-dimethyl-1,3-propylenediamine and catalyst II is 1:1-1.35:0.005-0.035; And / or, the reaction temperature of the acylation reaction is 130-180°C, and the reaction time is 2-12h; And / or, after the acylation reaction is completed, vacuum distillation is first performed, and then recrystallization is performed with ethanol to obtain the polyoxyethylene ether fatty acid amide propyl dimethylamine.

15. The preparation method according to claim 14, wherein: The catalyst II is boric acid; And / or, the mass ratio of the polyoxyethylene ether stearic acid, N,N-dimethyl-1,3-propylenediamine and catalyst II is 1:1-1.15:0.01-0.02; And / or, the reaction temperature of the acylation reaction is 140-165° C., and the reaction time is 5-10 h.

16. The preparation method according to claim 6, wherein: The reaction solvent is selected from one or more of isopropanol, water, methanol and ethanol; And / or, the mass ratio of the polyoxyethylene ether fatty acid amide propyl dimethylamine, sodium 3-chloro-2-hydroxypropane sulfonate and the reaction solvent is 1:1-1.5:1-15; And / or, the reaction temperature of the alkylation reaction is 40-100° C., and the reaction time is 1-7 h.

17. The preparation method according to claim 16, wherein: The reaction solvent is isopropanol and water; And / or, the mass ratio of the polyoxyethylene ether fatty acid amide propyl dimethylamine, sodium 3-chloro-2-hydroxypropane sulfonate and the reaction solvent is 1:1.1-1.3:3-10; And / or, the reaction temperature of the alkylation reaction is 50-90° C., and the reaction time is 3-6 hours.

18. The preparation method according to claim 17, wherein: The volume ratio of the isopropanol to water is 1:1.5-2.

5.

19. Use of the surfactant according to any one of claims 1 to 5 or the surfactant prepared by the method according to any one of claims 6 to 18 in oil field flooding.

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