Surfactant, preparation method and application thereof, and method for reducing viscosity of thickened oil

Abstract

The invention relates to the technical field of thick oil emulsification and viscosity reduction, and discloses a surfactant, a preparation method and application thereof, and a thick oil viscosity reduction method, the surfactant comprises a compound having a structure represented by formula (I) # imgabs0 #, each R2 is independently selected from H, C1-C4 alkyl groups, # imgabs1 # R5 and R6 are independently substituted or unsubstituted C8-C22 alkenyl groups, C8-C22 alkyl groups or heteroalkyl groups, each R4 is independently selected from H, C1-C4 alkyl groups or # imgabs2 # and at least one R2 or R4 is # imgabs3 # R1 and R3 are independently selected from substituted or unsubstituted C1-C20 alkylene groups; in the surfactant, the average value of the s value is 1-100. The surfactant shows obvious stimulation responsiveness to pH value and carbon dioxide, has excellent interfacial activity, and can realize emulsification viscosity reduction of thick oil and spontaneous demulsification of oil-water emulsion.

Description

Technical Field

[0001] The invention relates to the technical field of heavy oil emulsification and viscosity reduction, and in particular to a surfactant and a preparation method and application thereof, and a method for heavy oil viscosity reduction. Background Art

[0002] How to effectively improve the recovery rate of heavy oil has become a key national scientific and technological research direction. New oil recovery technologies such as chemical flooding and CO2 flooding have become research hotspots and have begun large-scale field applications. Research in recent years has shown that the oil recovery technology that combines chemical flooding with CO2 flooding can overcome the shortcomings of a single technology and is expected to enter field applications in the short term. The key to composite oil recovery technology lies in the development of surfactants that are highly efficient with CO2. Patent CN111088025A found that the compound system of anionic surfactants and non-ionic surfactants can effectively synergize with CO2 for oil recovery, but the binary system has the problem of chromatographic separation during application. In addition, the surfactant is adsorbed at the oil-water interface in the produced fluid, making the oil-water emulsion difficult to demulsify, which increases the energy consumption of the produced fluid demulsification and dehydration process.

[0003] The stimulus responsiveness of surfactants is generally achieved by converting hydrophilic groups into non-polar or weakly polar groups. The introduction of tertiary amine groups in the molecule has been proven to make the agent properties CO2 responsive. CN107686723A discloses the CO2 responsiveness of an anionic surfactant and a hydrocarbon polyamine composite system, which makes the hydrophobically modified polyacrylamide (HPAM) polymer solution gel in situ and increases the gas drive swept volume. However, the composite system still has the disadvantage of chromatographic separation. CN111229121A discloses a method of intelligently converting the hydrophobic tail chain tertiary amine group of the surfactant between "non-polar" and "strong polarity" by adding acid and alkali to adjust the pH of the solution. The tertiary amine group of the molecule is located at the tail end, which is a good pH responsive site. CN114773212A discloses a single-chain dihydroxy CO2 responsive surfactant, which has good CO2 stimulus responsiveness and can be used as a CO2 stimulus responsive clean fracturing fluid, with rapid response and rapid gel breaking when air is introduced. However, its preparation process requires the use of brominated hydrocarbon raw materials, which are difficult to remove from the product and aggravate the corrosion of pipelines. At present, the oil field oil displacement agent standards all require that the product does not contain chlorine / bromine elements, so it is difficult for this product to enter industrial application. CN109868066A discloses a rosin-based CO2 / N2 responsive polymerizable surfactant, which has responsive performance to CO2 / N2 and can be used as an emulsifier for nanoparticles, but due to the large steric hindrance of the rosin group, its oil-water interfacial activity is not ideal in theory.

[0004] Therefore, it is necessary to design a new type of responsive surfactant that exhibits excellent oil-water interfacial activity when it encounters CO2, thereby reducing interfacial tension, emulsifying and reducing viscosity, and achieving efficient synergistic viscosity reduction and oil displacement between the agent and CO2. At the same time, when the CO2 content in the produced fluid is low, it can spontaneously break the emulsion responsively, achieving energy saving and consumption reduction in the post-processing process of the produced fluid. Summary of the invention

[0005] The purpose of the present invention is to overcome the problems of insufficient oil-water interfacial activity and poor emulsification viscosity reduction effect of the surfactant in the above-mentioned prior art, and to provide a surfactant and its preparation method and application, and a method for reducing the viscosity of heavy oil. The surfactant has good stimulus response ability, has excellent interfacial activity under CO2 or acidic conditions, and has excellent emulsification viscosity reduction effect when used as a viscosity reduction oil displacement agent. When CO2 is replaced by nitrogen, or the acidity is neutralized, and the system is neutral / weakly alkaline, the water-in-oil emulsion formed by the surfactant and the heavy oil can spontaneously demulsify and separate water.

[0006] In order to achieve the above object, the present invention provides, in a first aspect, a surfactant comprising a compound having a structure shown in formula (I),

[0007]

[0008] Wherein, each R2 is independently selected from H, C1-C4 alkyl, R5 and R6 are each independently substituted or unsubstituted C8-C 22 Alkenyl, C8-C 22 alkyl or heteroalkyl, each R4 is independently selected from H, C1-C4 alkyl or and at least one R2 or R4 is R1 and R3 are each independently selected from substituted or unsubstituted C1-C 20 of alkylene;

[0009] In the surfactant, the average value of s value is 1-100.

[0010] The second aspect of the present invention provides a method for preparing a stimulus-responsive oligomeric surfactant, comprising the following steps:

[0011] (1) subjecting an amine compound to a first ring-opening reaction with a 1,2-epoxy compound to obtain an intermediate oligomer alcohol;

[0012] Wherein, the amine compound has a structure shown in formula (i),

[0013]

[0014] Wherein, each R2' is independently selected from H, C1-C4 alkyl or Each R4' is independently selected from H or C1-C4 alkyl; R1 and R3 are independently selected from substituted or unsubstituted C1-C 20 Alkylene, C2-C 20 Heteroalkylene and C6-C 20 At least one of the arylene groups;

[0015] The structure of the 1,2-epoxide compound is represented by R5 and R6 are each independently substituted or unsubstituted C8-C 22 Alkenyl, C8-C 22 An alkyl or heteroalkyl group;

[0016] (2) In the presence of a base, the intermediate oligomeric alcohol is subjected to a second ring-opening reaction with ethylene oxide.

[0017] The third aspect of the present invention provides use of the surfactant described in the first aspect or the surfactant prepared by the preparation method described in the second aspect in heavy oil viscosity reduction production.

[0018] A fourth aspect of the present invention provides a method for reducing the viscosity of heavy oil, comprising: mixing a viscosity reducer with the heavy oil under acidic conditions and / or in the presence of carbon dioxide; the viscosity reducer comprises the surfactant described in the first aspect or the surfactant prepared by the preparation method described in the second aspect;

[0019] Preferably, the method comprises: first contacting the viscosity reducer with acid and / or carbon dioxide, and then mixing the mixture with the heavy oil.

[0020] The novel oligomeric surfactant provided by the present invention exhibits obvious stimulus responsiveness to both pH value and carbon dioxide. The surfactant is positively charged when encountering an acidic environment or carbon dioxide, exhibiting the characteristics of a cationic oligomeric surfactant, having excellent interfacial activity, and being able to emulsify heavy oil, and having a viscosity reduction rate of more than 90%. In neutral and alkaline environments, the product is electrically neutral, has the characteristics of a nonionic surfactant, and the oil-water interfacial activity becomes weak. Based on this, with the aid of pH or carbon dioxide responsiveness, the product can achieve emulsification and viscosity reduction of heavy oil and spontaneous demulsification of oil-water emulsions. Therefore, the oligomeric surfactant provided by the present invention can be used as a carbon dioxide flooding synergist, and has a good application prospect.

[0021] The preparation method of the stimulus-responsive oligomeric surfactant provided by the present invention is simple and efficient, and no halogenated hydrocarbon raw materials are needed in the preparation process, so the preparation method meets the halogen-free requirement stipulated in the oilfield displacement agent standard and is easy to scale up industrially. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1is the MALDI-TOF mass spectrum of the intermediate tetramer alcohol prepared in Example 1 of the present invention;

[0023] Figure 2 is the surfactant TE obtained in Example 1 of the present invention 1 H NMR spectra;

[0024] Figure 3 is the MALDI-TOF mass spectrum of the intermediate hexamer alcohol prepared in Example 2 of the present invention;

[0025] Figure 4 is the surfactant HE obtained in Example 2 of the present invention 1 H NMR spectra;

[0026] Figure 5 is the MALDI-TOF mass spectrum of the intermediate dimer alcohol prepared in Example 3 of the present invention;

[0027] Figure 6 is the surfactant HE obtained in Example 3 of the present invention 1 H NMR spectra. DETAILED DESCRIPTION

[0028] The endpoints and any values ​​of the ranges disclosed in this article 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 each range, the endpoint values ​​of each range and the 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 as specifically disclosed in this article.

[0029] In the present invention, the wavy line in a substituent, e.g. Indicates the bonding position of the R group.

[0030] The first aspect of the present invention provides a surfactant, which comprises a compound having a structure shown in formula (I),

[0031]

[0032] Wherein, each R2 is independently selected from H, C1-C4 alkyl, R5 and R6 are each independently substituted or unsubstituted C8-C 22 Alkenyl, C8-C 22 alkyl or heteroalkyl, each R4 is independently selected from H, C1-C4 alkyl or and at least one R2 or R4 is R1 and R3 are each independently selected from substituted or unsubstituted C1-C20 of alkylene;

[0033] In the surfactant, the average value of s value is 1-100.

[0034] According to the present invention, each R2 in formula (I) is independently selected from H, C1-C4 alkyl, and at least one R2 or R4 is It is understood that, in the surfactant provided by the present invention, as long as at least one head group in the structure shown in formula (I) is In the present invention, "C1-C4 alkyl" refers to an alkyl group having 1 to 4 carbon atoms, which may be a straight chain or branched chain alkyl group, for example, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group or an isobutyl group.

[0035] According to some preferred embodiments of the present invention, in formula (I), at least two R2 are The remaining R2 may be H or a C1-C4 alkyl group.

[0036] According to some other preferred embodiments of the present invention, in formula (I), at least two R2 are And in each R2, at least one R4 is

[0037] In the above preferred case, it is beneficial for multiple non-ionic amphiphilic units to cooperate with each other and obtain excellent oil-water interface performance.

[0038] The inventors of the present invention have found in their research that the nonionic oligomeric surfactant prepared by the present invention shortens the spatial distance between multiple amphiphilic moieties through the linking group, making the synergistic effect between it and CO2 stronger, showing excellent interfacial activity, emulsification and viscosity reduction and other physicochemical properties, and these macroscopic properties have CO2 or H + Responsiveness.

[0039] In a further preferred embodiment, the surfactant comprises at least one of the compounds having the structure shown in the following formula:

[0040]

[0041]

[0042] According to some preferred embodiments of the present invention, R1 and R3 are each independently selected from substituted or unsubstituted C1-C 12 of alkylene.

[0043] In the present invention, R1 and R3 may be the same or different. 12The alkylene group may be a straight chain or branched alkylene group, for example, a methylene group, an ethylene group, a propylene group, a butylene group, a pentylene group, a hexylene group, a heptylene group, an octylene group, a nonylene group, a decylene group or any one of their isomers. One or more carbon atoms in the alkylene group may also be optionally substituted by one or more of a cycloalkyl group, an aryl group or a heteroatom, and the heteroatom may be selected from at least one of O, S and N.

[0044] According to some preferred embodiments of the present invention, R1 and R3 are selected from any one of the structures shown in formula (1) to formula (16);

[0045]

[0046]

[0047] In some preferred embodiments of the present invention, in formula C, R1 and R3 are preferably

[0048] In the present invention, "C8-C 22 "Alkyl" refers to an alkyl group having 8 to 22 carbon atoms, such as n-octyl, n-decyl, n-dodecyl, n-tetradecyl, n-hexadecyl, n-octadecyl, etc. "Heteroalkyl" refers to a group formed by replacing at least one carbon atom in the alkyl group with a heteroatom, such as O, S or N.

[0049] According to some preferred embodiments of the present invention, R5 and R6 are each independently n-octyl, n-decyl, n-dodecyl, n-tetradecyl, n-hexadecyl, n-octadecyl, (2-ethylhexyloxy)methyl, octenyl or C8-C 10 Preferably, R5 is n-octyl, n-decyl, n-dodecyl, n-tetradecyl, n-hexadecyl, n-octadecyl, (2-ethylhexyloxy)methyl, octenyl or C8-C 10 Alkoxymethyl, R6 is hydrogen. In the above preferred case, it is beneficial to improve the oil-water amphiphilicity of the surfactant, thereby further improving the surface activity of the product.

[0050] According to some preferred embodiments of the present invention, the average value of s in the surfactant is 2-20. The inventors of the present invention have found in their research that when the s value is too large, the space volume of the polyoxyethylene segment is large, which may be unfavorable for the close arrangement of molecules at the oil-water interface; and when the s value is too small, it may lead to poor molecular solubility. When the average value of s in the surfactant is within the above preferred range, it is beneficial to further improve the interfacial activity of the surfactant.

[0051] According to the present invention, the surfactant is an oligomeric surfactant, preferably, the molecular weight of the surfactant does not exceed 10000 g / mol, preferably 400-8000 g / mol.

[0052] In the present invention, the molecular weight of the surfactant is calculated based on the molecular weight of the intermediate oligomer alcohol and the average number of s. Particularly preferably, the molecular weight of the surfactant is 750-6000 g / mol. Controlling the molecular weight of the surfactant within the above preferred range is conducive to the efficient synergistic effect between multiple amphiphilic units in the product, while avoiding the problems of poor solubility and unsatisfactory interfacial activity caused by too high molecular weight.

[0053] A second aspect of the present invention provides a method for preparing a surfactant, comprising the following steps:

[0054] (1) subjecting an amine compound to a first ring-opening reaction with a 1,2-epoxy compound to obtain an intermediate oligomer alcohol;

[0055] Wherein, the amine compound has a structure shown in formula (i),

[0056]

[0057] Wherein, each R2' is independently selected from H, C1-C4 alkyl or Each R4' is independently selected from H or C1-C4 alkyl; R1 and R3 are independently selected from substituted or unsubstituted C1-C 20 Alkylene, C2-C 20 Heteroalkylene and C6-C 20 At least one of the arylene groups;

[0058] The structure of the 1,2-epoxide compound is represented by R5 and R6 are each independently substituted or unsubstituted C8-C 22 Alkenyl, C8-C 22 An alkyl or heteroalkyl group;

[0059] (2) In the presence of a base, the intermediate oligomeric alcohol is subjected to a second ring-opening reaction with ethylene oxide.

[0060] According to the present invention, in formula (i), the definitions of R1, R3, R5 and R6 are the same as those in formula (I), and are not repeated here.

[0061] According to some preferred embodiments of the present invention, the amine compound is selected from at least one of the compounds having structures represented by formula (17) to formula (43);

[0062]

[0063]

[0064] According to some preferred embodiments of the present invention, the 1,2-epoxy compound is selected from 1,2-epoxydecane, 1,2-epoxytetradecane, 1,2-epoxyhexadecane, 1,2-epoxyoctadecane, 1,2-epoxyeicosane, 2-ethylhexyl glycidyl ether, 1,2-epoxy-9-decene and C8-C 10 At least one of alkyl glycidyl ethers.

[0065] According to the present invention, preferably, in step (1), the molar ratio of the 1,2-epoxy compound to the amine compound is (1-10):1, preferably (1.1-2):1, wherein the molar amount of the amine compound is based on the molar amount of the NH bond in the molecule.

[0066] Preferably, the conditions of the first ring-opening reaction include: temperature of 30-150° C., preferably 30-80° C.; time of 4-72 h, preferably 12-18 h.

[0067] According to the present invention, preferably, the first ring-opening reaction is carried out in the presence of an organic solvent. The present invention has a wide range of selection for the organic solvent. As long as it can dissolve and disperse the reactants, any organic solvent commonly used in the art can be applied to the present invention. For example, the organic solvent can be at least one of methanol, ethanol, isopropanol and dichloromethane.

[0068] According to some preferred embodiments of the present invention, in step (2), the mass ratio of ethylene oxide to the intermediate oligomeric alcohol is (20-1000):100, preferably (50-500):100.

[0069] According to the present invention, the second ring-opening reaction in step (2) is carried out in the presence of a base. The present invention has a wide range of selection for the base. Preferably, the base is selected from alkali metal hydroxides, preferably sodium hydroxide and / or potassium hydroxide.

[0070] According to some preferred embodiments of the present invention, the mass ratio of the base to the intermediate oligomeric alcohol is (0.1-2):100, preferably (0.25-1):100.

[0071] According to the present invention, preferably, the conditions of the second ring-opening reaction include: reaction temperature of 80-180°C, reaction time of 4-10h, and reaction pressure of 0.3-1MPa.

[0072] In a further preferred embodiment, the second ring-opening reaction comprises: mixing the intermediate oligomeric alcohol with a base at a first constant temperature, and then adding ethylene oxide to react at a second constant temperature, wherein the first constant temperature does not exceed 100° C., preferably 80-100° C., and the second constant temperature is 100-180° C., preferably 120-160° C. The above preferred embodiment is advantageous in improving the efficiency of the ring-opening reaction between the alcohol hydroxyl group and ethylene oxide.

[0073] Preferably, the second ring-opening reaction is carried out under stirring conditions.

[0074] The third aspect of the present invention provides use of the surfactant described in the first aspect or the surfactant prepared by the preparation method described in the second aspect in heavy oil recovery.

[0075] A fourth aspect of the present invention provides a method for reducing the viscosity of heavy oil, comprising: mixing a viscosity reducer with the heavy oil under acidic conditions and / or in the presence of carbon dioxide; the viscosity reducer comprises the surfactant described in the first aspect or the surfactant prepared by the preparation method described in the second aspect.

[0076] According to the present invention, the surfactant described in the first aspect or the surfactant prepared by the preparation method described in the second aspect exhibits obvious stimulus responsiveness to pH value and carbon dioxide. The surfactant is positively charged when encountering an acidic environment or carbon dioxide, exhibits the characteristics of a cationic oligomeric surfactant, has excellent interfacial activity, can emulsify heavy oil, and has a viscosity reduction rate of more than 90%.

[0077] Preferably, the viscosity reducing oil displacement agent further contains solvent water, and the concentration of the surfactant in the viscosity reducing agent is 500-5000 mg / L, preferably 1000-3000 mg / L.

[0078] According to some preferred embodiments of the present invention, the method comprises: first contacting the viscosity reducer with acid and / or carbon dioxide, and then mixing the contact with the heavy oil.

[0079] In a further preferred embodiment, the amount of acid used is such that the pH of the product after the viscosity reducer and the acid are in contact is lower than 7, preferably 2-5, for example, the pH may be 2, 2.5, 3, 3.5, 4, 4.5, 5, or other typical but non-limiting pH values ​​or a range therebetween. More preferably, the amount of acid used is such that the pH of the product after the viscosity reducer and the acid are in contact is 2-4.

[0080] The present invention has no particular requirements for the type of the acid, as long as the pH of the contact product can be adjusted to meet the above range requirements, conventional organic acids or inorganic acids can be applied to the present invention. For example, the acid can be at least one of hydrochloric acid, sulfuric acid, phosphoric acid and glacial acetic acid.

[0081] In a further preferred embodiment, relative to 1 L of the viscosity reducer, the amount of carbon dioxide introduced is 0.5-10 L / min, preferably 3-10 L / min.

[0082] In a further preferred embodiment, the amount of the viscosity reducer is 0.43-2.3 L, preferably 0.5-1.5 L, relative to 1 L of the heavy oil.

[0083] The present invention will be described in detail below through examples.

[0084] The raw materials involved in the following examples are all purchased from commercial sources, and the main sources of raw materials are shown in Table 1.

[0085] Table 1

[0086]

[0087] Example 1

[0088] The preparation process is shown below:

[0089]

[0090] (1) 0.6 g (10 mmol) of ethylenediamine was added to a solution of 12.7 g (60 mmol) of 1,2-epoxytetradecane in anhydrous ethanol (50 mL), and the mixture was heated to 78.5°C and refluxed for 24 h. After the reaction was completed, the anhydrous ethanol solvent was removed by a rotary evaporator, the crude product was dissolved in dichloromethane, and then purified by eluting with dichloromethane / methanol on a silica gel column and vacuum dried to obtain 9.0 g of a white powdery intermediate tetramer alcohol, with a calculated yield of 99 wt%. (The yield here is: the percentage of the actual yield to the theoretical yield calculated based on the complete reaction of ethylenediamine, the same below)

[0091] The intermediate tetramer alcohol was characterized by MALDI-TOF mass spectrometry. Figure 1 A peak of 910.364 appeared in the spectrum, which was the molecular ion peak of the intermediate tetramer alcohol, proving that the target structure was obtained.

[0092] (2) Add 100 parts by weight of the intermediate tetramer alcohol to the autoclave, then add 0.5 parts by weight of KOH catalyst, seal the autoclave, displace the air in the autoclave, feed kettle and feed pipe with dry nitrogen, start heating and stirring, and evacuate with a vacuum pump at the same time. Stop evacuating when the temperature reaches 100°C. Add 135 parts by weight of ethylene oxide to the feed kettle, pressurize to 0.4MPa, start mechanical stirring, and then open the feed valve to slowly feed. During the process, control the reaction temperature at 140°C and the pressure at 0.4MPa. After the addition is completed, react for 6 hours and stop stirring. Continue aging for 1 hour. When the pressure in the autoclave drops to a constant level, cool and discharge the material. The reaction product is neutralized with acetic acid, and after standing and stratification, the lower layer of opaque material is taken to obtain 165 parts by weight of the product, recorded as TE, with a calculated yield of 93wt%. (The yield here is: the actual yield of the target product as a percentage of the theoretical yield calculated based on the complete reaction of the intermediate tetramer alcohol, the same below)

[0093] The product is passed through 1 H NMR characterization results are shown in Figure 2 As shown. The peaks in the figure belong to the following:

[0094] 1 H NMR (CDCl3, 400MHz): δ=0.880(-CH3), 1.259(CH3-(CH2) 11 -CH-), 2.430-2.675(-N-CH2-), 3.606-3.703(-O-CH2-CH2-O-).

[0095] After calculating the spectrum peak area ratio, the average value of s value in the product TE was obtained to be 4.

[0096] The molecular weight of the surfactant was calculated to be 1613.34 g / mol based on the molecular weight and s value data of the intermediate tetraol.

[0097] Example 2

[0098] The preparation process is shown below:

[0099]

[0100]

[0101] (1) 1.5 g (10 mmol) of tris(2-aminoethyl)amine was added to a solution of 19.1 g (90 mmol) of 1,2-epoxytetradecane in anhydrous ethanol (50 mL) and reacted at 50° C. for 24 h. After the reaction, the anhydrous ethanol solvent was removed by a rotary evaporator, and the crude product was dissolved in dichloromethane, and then purified by silica gel chromatography with dichloromethane / methanol and vacuum dried to obtain 13.9 g of the intermediate hexamer alcohol, with a calculated yield of 98 wt%.

[0102] The intermediate hexamer alcohol was characterized by MALDI-TOF mass spectrometry. Figure 3 A peak of 1421.030 appeared in the spectrum, which was the molecular ion peak of the intermediate hexamer alcohol, proving that the target structure was obtained.

[0103] (2) Add 100 parts by weight of the intermediate hexamer alcohol to the autoclave, then add 1 part by weight of KOH catalyst, seal the autoclave, displace the air in the autoclave, feed kettle and feed pipe with dry nitrogen, start heating and stirring, and evacuate with a vacuum pump at the same time. Stop evacuating when the temperature rises to 100°C. Add 185 parts by weight of ethylene oxide to the feed kettle, pressurize to 0.4MPa, start mechanical stirring, and then open the feed valve to slowly feed. During the process, control the reaction temperature at 160°C and the pressure at 0.4MPa. After the addition is completed, stop stirring for 8 hours, continue aging for 1 hour, wait until the pressure in the kettle drops to a constant, and cool and discharge. The reaction product is neutralized with acetic acid, and after standing and stratification, take out the opaque material of the lower layer to obtain 190.4 parts by weight of the product, recorded as HE, with a calculated yield of 90wt%.

[0104] The product is passed through 1 H NMR characterization results are shown in Figure 4 As shown. The peaks in the figure belong to the following:

[0105] 1 H NMR (CDCl3, 400MHz): δ=0.880(-CH3), 1.258-1.451(CH3-(CH2) 11 -CH-), 2.554(-N-CH2-, -N-CH2-CH-), 3.648-3.716(-O-CH2-CH2-O-).

[0106] By calculating the spectrum peak area ratio, it can be seen that the average s value of the product HE is 6.

[0107] The molecular weight of the surfactant was calculated to be 3004.38 g / mol based on the molecular weight and s value data of the intermediate hexamer alcohol.

[0108] Example 3

[0109] The preparation process is shown below:

[0110]

[0111] (1) 0.9 g (10 mmol) of N,N'-dimethylethylenediamine was added to a solution of 6.4 g (30 mmol) of 1,2-epoxytetradecane in anhydrous ethanol (50 mL) and reacted at 30°C for 24 h. After the reaction, the anhydrous ethanol solvent was removed by a rotary evaporator, the crude product was dissolved in dichloromethane, and then purified by silica gel chromatography with dichloromethane / methanol and vacuum dried to obtain 4.6 g of the intermediate dimer alcohol with a yield of 90%.

[0112] The intermediate dimer alcohol was characterized by MALDI-TOF mass spectrometry. Figure 5 A peak of 513.5391 appeared in the spectrum, which was the molecular ion peak of the intermediate dimer alcohol, proving that the target structure was obtained.

[0113] (2) Add 100 parts by weight of the intermediate dimer alcohol to the autoclave, then add 0.25 parts by weight of KOH catalyst, seal the autoclave, displace the air in the autoclave, feed kettle and feed pipe with dry nitrogen, start heating and stirring, and evacuate with a vacuum pump at the same time. Stop evacuating when the temperature rises to 100°C. Add 86 parts by weight of ethylene oxide to the feed kettle, pressurize to 0.4MPa, start mechanical stirring, and then open the feed valve to slowly feed. During the process, control the reaction temperature at 120°C and the pressure at 0.4MPa. After the addition is completed, react for 5 hours and stop stirring. Continue aging for 1 hour. When the pressure in the autoclave drops to a constant level, cool and discharge. The reaction product is neutralized with acetic acid, and after standing and stratification, the lower layer of opaque material is removed to obtain 138 parts by weight of product, recorded as DE, with a yield of 91wt%.

[0114] The product DE was passed through 1 H NMR characterization results are shown in Figure 6 As shown. The peaks in the figure belong to the following:

[0115] 1 H NMR (CDCl3, 400MHz): δ=0.879(-CH3), 1.259(CH3-(CH2) 11 -CH-), 2.267-2.308(-N-CH2-, -N-CH3), 3.647(-O-CH2-CH2-O-).

[0116] After calculating the spectrum peak area ratio, it can be seen that the average s value of the product DE is 3.

[0117] The molecular weight of the surfactant was calculated to be 776.69 g / mol based on the molecular weight and s value data of the intermediate dimer alcohol.

[0118] Example 4

[0119] The method of Example 1 was followed, except that the amount of ethylene oxide added in step (2) was 1080 parts by weight. The obtained product was recorded as TE-2, and the average value of the s value in the product TE was 32 after calculating the peak area ratio of the spectrum. The molecular weight of the surfactant was calculated to be 6544.28 g / mol through the molecular weight and s value data of the intermediate tetramer alcohol.

[0120] Comparative Example 1

[0121] Commercially available polyoxyethylene lauryl ether (Brij35) was used as a surfactant.

[0122] Test Example 1: Stimulus-Response Interface Activity

[0123] The oil-water interfacial tension of the oligomeric surfactant prepared in the embodiment and the single-chain surfactant Brij35 of the same type under different conditions was measured using a TX-500C interfacial tension meter using a rotating drop method. The test oil was crude oil from a Shengli oil field (its viscosity at 50°C was 1053 mPa·s measured using a Haake VT550 rotational viscometer). The test water was formation mineralized water with a mineralization of 20000 mg / L. The test process controlled the test temperature to 50°C and the rotation speed to 5000 rpm. The mass concentration of the surfactant aqueous solutions configured in the test was 2000 mg / L.

[0124] (A) During the test, the interfacial tension was measured by dissolving the surfactant directly in formation water (pH 8.15). This is the interfacial tension under condition A.

[0125] (B) The surfactant is dissolved in formation water, hydrochloric acid is added, and the pH value of the aqueous solution is adjusted to 3.0. The interfacial tension then measured is the interfacial tension under condition B;

[0126] (C) The surfactant is dissolved in formation water, hydrochloric acid is added to adjust the pH value of the aqueous solution to 3.0, and then sodium hydroxide is added to adjust the pH value of the solution to 7.0. The interfacial tension is then measured, which is the interfacial tension under condition C;

[0127] (D) The surfactant was dissolved in 5 L of formation water, and carbon dioxide was introduced at a gas flow rate of 1 L / min for 5 min. The interfacial tension was then measured. This is the interfacial tension under condition D.

[0128] (E) The surfactant was dissolved in 5 L of formation water, carbon dioxide was introduced at a flow rate of 1 L / min for 5 min, and nitrogen was introduced at a flow rate of 1 L / min for 10 min. The interfacial tension was then measured. This is the interfacial tension under condition E.

[0129] The results are shown in Table 2.

[0130] Table 2

[0131]

[0132] As can be seen from Table 2, the surfactant provided by the present invention has good interfacial activity under acidic conditions (condition B) or carbon dioxide presence conditions (condition D), and can reduce the oil-water interfacial tension of the target crude oil to 10 -2 mN / m range, under neutral (A condition) and alkaline conditions (C condition), or after replacing carbon dioxide with nitrogen (E condition), the interfacial activity of the oligomeric surfactant becomes poor and the interfacial tension is high. + Or carbon dioxide has obvious stimulus responsiveness.

[0133] In contrast, the interfacial tension values ​​of polyoxyethylene lauryl ether (Brij35) in the comparative example were between (0.72-0.88) mN / m under acidic, alkaline or neutral conditions, or after the introduction of carbon dioxide and then nitrogen, and showed no stimulus responsiveness.

[0134] Test Example 2: Stimulus-responsive emulsification and demulsification

[0135] The test oil and mineralized water are consistent with those in the surface activity test. The test steps for the viscosity reduction rate of heavy oil are as follows:

[0136] (a) Place 20 g of test oil in a distillation flask;

[0137] (b) The surfactants in the examples and comparative examples were prepared into 1000 mg / L aqueous solutions, and after being treated under different conditions (AE), 10 mL was taken and added to a distillation flask containing the test oil;

[0138] (c) Stir gently for 1 min at 50 °C, let stand for 2 h, and then measure the viscosity of the oil-water mixture at 50 °C using a Haake VT550 rotational viscometer;

[0139] (d) Calculate the viscosity reduction rate using the following formula based on the measured viscosity data:

[0140] M=[(η1-η2) / η1]×100%;

[0141] In the above formula, η1 refers to the viscosity of crude oil (mPa·s); η2 refers to the viscosity of oil-water mixture (mPa·s); and M is the viscosity reduction rate.

[0142] Wherein, the surfactant aqueous solution treatment method mentioned in step (b) is:

[0143] Condition A: directly dissolved in formation water without other treatment;

[0144] Condition B: Add hydrochloric acid to adjust the pH value of the aqueous solution to 3.0;

[0145] Condition C: sodium hydroxide was added to the surfactant aqueous solution with a pH value of 3.0 to adjust the solution pH value to 7.0;

[0146] Condition D: Carbon dioxide was introduced into 5 L of surfactant aqueous solution at a gas flow rate of 1 L / min for 5 min;

[0147] Condition E: Carbon dioxide was introduced into 5 L of the surfactant aqueous solution at a gas flow rate of 1 L / min for 5 min, and then nitrogen was introduced at a gas flow rate of 1 L / min for 10 min.

[0148] The viscosity reduction effect is shown in Table 3.

[0149] Table 3

[0150]

[0151] It can be seen from the test data in Table 3 that, on the one hand, the surfactant provided in the embodiments of the present invention encounters H + After external stimulation by carbon dioxide, they all have strong emulsification and viscosity reduction effects, and can emulsify the target heavy oil into water-in-oil emulsions to achieve efficient viscosity reduction of heavy oil, and the viscosity reduction rate of heavy oil is higher than 90%. The single-chain surfactant Brij35 used in the comparative example has no stimulus responsiveness, and its emulsification and viscosity reduction effect on the target heavy oil is not good.

[0152] On the other hand, the surfactant provided in the embodiment of the present invention has basically no emulsification and viscosity reduction effect under neutral or alkaline conditions, or after nitrogen is introduced to replace carbon dioxide, and the oil-water mixture is re-phased in a relatively short time. Sodium hydroxide aqueous solution is further added to the oil-water emulsion obtained under condition B to adjust the pH value of the system to 7.0; nitrogen or air is introduced into the oil-water mixed emulsion obtained under condition D at a ventilation rate of 1 L / min, and the demulsification of the mixed emulsion is observed, and the time required for demulsification is recorded. The results are shown in Table 4:

[0153] Table 4

[0154]

[0155] Combining the results of Table 3 and Table 4, it can be seen that the surfactant provided by the present invention is also stimuli-responsive to the reduced viscosity heavy oil (water-in-oil emulsion) obtained after emulsification of the target heavy oil. When the pH value is adjusted to neutral, or air or nitrogen is introduced into the oil-water mixture to replace carbon dioxide, the oil-water interfacial activity of the surfactant is weak and the oil-in-water emulsion cannot be stabilized, thereby achieving spontaneous demulsification.

[0156] The results of the above test examples show that the new oligomeric surfactant provided by the present invention exhibits obvious stimulus responsiveness to both pH value and carbon dioxide. When the oligomeric surfactant encounters hydrogen ions and carbon dioxide in water, it has excellent interfacial activity and can reduce the interfacial tension of the target heavy oil to 10 -2 mN / m range, and the viscosity reduction rate of the target heavy oil is higher than 90%. At the same time, by utilizing the stimulus responsiveness of the oligomeric surfactant, the spontaneous demulsification of the displacement produced fluid can be achieved by adjusting the pH value or introducing nitrogen / air to replace carbon dioxide. This makes the oligomeric surfactant provided by the present invention usable as a carbon dioxide oil recovery synergist, and has a good application prospect.

[0157] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A surfactant, characterized in that The surfactant includes a compound having a structure shown in formula (I), Wherein, each R2 is independently selected from H, C1-C4 alkyl, R5 and R6 are each independently substituted or unsubstituted C8-C 22 Alkenyl, C8-C 22 alkyl or heteroalkyl, each R4 is independently selected from H, C1-C4 alkyl or and at least one R2 or R4 is R1 and R3 are each independently selected from substituted or unsubstituted C1-C 20 of alkylene; In the surfactant, the average value of s value is 1-100.

2. The surfactant according to claim 1, wherein At least two R2 Or, at least two R2 are And in each R2, at least one R4 is 3. The surfactant according to claim 1 or 2, wherein The surfactant comprises at least one of the compounds having the following structural formula, 4. The surfactant according to any one of claims 1 to 3, wherein R1 and R3 are each independently selected from substituted or unsubstituted C1-C 12 of alkylene; Preferably, R1 and R3 are selected from any one of the structures shown in formula (1) to formula (16); 5. The surfactant according to any one of claims 1 to 4, wherein R5 and R6 are each independently n-octyl, n-decyl, n-dodecyl, n-tetradecyl, n-hexadecyl, n-octadecyl, (2-ethylhexyloxy)methyl, octenyl or C8-C 10 Alkoxymethyl; Preferably, R5 is n-octyl, n-decyl, n-dodecyl, n-tetradecyl, n-hexadecyl, n-octadecyl, (2-ethylhexyloxy)methyl, octenyl or C8-C 10 Alkoxymethyl, R6 is hydrogen; And / or, in the surfactant, the average value of s value is 2-20.

6. The surfactant according to any one of claims 1 to 5, wherein The molecular weight of the surfactant is no more than 10000 g / mol, preferably 400-8000 g / mol.

7. A method for preparing a surfactant, characterized in that: The following steps are involved: (1) subjecting an amine compound to a first ring-opening reaction with a 1,2-epoxy compound to obtain an intermediate oligomer alcohol; Wherein, the amine compound has a structure shown in formula (i), Wherein, each R2' is independently selected from H, C1-C4 alkyl or Each R4' is independently selected from H or C1-C4 alkyl; R1 and R3 are independently selected from substituted or unsubstituted C1-C 20 Alkylene, C2-C 20 Heteroalkylene and C6-C 20 At least one of the arylene groups; The structure of the 1,2-epoxide compound is represented by R5 and R6 are each independently substituted or unsubstituted C8-C 22 Alkenyl, C8-C 22 An alkyl or heteroalkyl group; (2) In the presence of a base, the intermediate oligomeric alcohol is subjected to a second ring-opening reaction with ethylene oxide.

8. The preparation method according to claim 7, wherein: In formula (i), R1 and R3 are selected from linear or branched C1-C 12 Alkylene, C2-C 10 At least one of a heteroalkylene group and a disubstituted phenyl group; wherein the heteroatom in the heteroalkylene group is selected from at least one of O, S and N; Preferably, the amine compound is selected from at least one of the compounds having structures represented by formula (17) to formula (43); 9. The preparation method according to claim 7 or 8, wherein: R5 and R6 are each independently n-octyl, n-decyl, n-dodecyl, n-tetradecyl, n-hexadecyl, n-octadecyl, (2-ethylhexyloxy)methyl, octenyl or C8-C10 alkoxymethyl; Preferably, the 1,2-epoxy compound is selected from 1,2-epoxydecane, 1,2-epoxytetradecane, 1,2-epoxyhexadecane, 1,2-epoxyoctadecane, 1,2-epoxyeicosane, 2-ethylhexyl glycidyl ether, 1,2-epoxy-9-decene and C8-C 10 At least one of alkyl glycidyl ethers.

10. The preparation method according to any one of claims 7 to 9, wherein: In step (1), the molar ratio of the 1,2-epoxy compound to the amine compound is (1-10):1, preferably (1.1-2):1, wherein the molar amount of the amine compound is based on the molar amount of the NH bond in the molecule; Preferably, the conditions of the first ring-opening reaction include: temperature of 30-150°C, time of 4-72h; Preferably, the first ring-opening reaction is carried out in the presence of an organic solvent, and the organic solvent is preferably at least one of methanol, ethanol, isopropanol and dichloromethane.

11. The preparation method according to any one of claims 7 to 10, wherein: In step (2), the mass ratio of ethylene oxide to the intermediate oligomeric alcohol is (20-1000):100, preferably (50-500):100; Preferably, the base is selected from alkali metal hydroxides, preferably sodium hydroxide and / or potassium hydroxide; Preferably, the mass ratio of the base to the intermediate oligomeric alcohol is (0.1-2):100, preferably (0.25-1):

100.

12. The preparation method according to any one of claims 7 to 11, wherein: The conditions of the second ring-opening reaction include: reaction temperature of 80-180°C, reaction time of 4-10h, reaction pressure of 0.3-1MPa; Preferably, the second ring-opening reaction comprises: mixing the intermediate oligomeric alcohol with a base at a first constant temperature, and then adding ethylene oxide to react at a second constant temperature, wherein the first constant temperature does not exceed 100° C., preferably 80-100° C., and the second constant temperature is 100-180° C., preferably 120-160° C.; Preferably, the second ring-opening reaction is carried out under stirring conditions.

13. Use of the surfactant according to any one of claims 1 to 6 or the surfactant prepared by the preparation method according to any one of claims 7 to 12 in heavy oil viscosity reduction recovery.

14. A method for reducing the viscosity of heavy oil, comprising: Mixing the viscosity reducer with the heavy oil under acidic conditions and / or in the presence of carbon dioxide; The viscosity reducing agent comprises the surfactant described in any one of claims 1 to 6 or the surfactant prepared by the preparation method described in any one of claims 7 to 12; Preferably, the method comprises: first contacting the viscosity reducer with acid and / or carbon dioxide, and then mixing with the heavy oil; Preferably, the viscosity reducer further contains solvent water, the water is reservoir formation water or clean water, and the concentration of the surfactant in the viscosity reducer is 500-5000 mg / L; Preferably, the amount of acid used is such that the pH of the product after the viscosity reducer and the acid contact is lower than 7, preferably 2-5; Preferably, the amount of carbon dioxide introduced is 0.5-10 L relative to 1 L of the viscosity reducer; Preferably, the amount of the viscosity reducer is 0.43-2.3 L relative to 1 L of the heavy oil.

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