Surfactants, processes for their preparation and use, and methods for reducing the viscosity of heavy oil

Abstract

The application relates to the technical field of thick oil emulsification viscosity reduction, and discloses a surfactant and a preparation method and application thereof, and a thick oil viscosity reduction method, wherein the surfactant comprises a compound with a structure shown in formula (I), wherein each R2 is independently selected from H, C1-C4 alkyl, R5 and R6 are independently substituted or unsubstituted C8-C 22 alkenyl, C8-C 22 alkyl or heteroalkyl, each R4 is independently selected from H, C1-C4 alkyl, and at least one R2 or R4 is R1 and R3 are independently selected from substituted or unsubstituted C1-C 20 alkylene; in the surfactant, the average value of s is 1-100. The surfactant shows obvious stimulus response 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] This invention relates to the field of heavy oil emulsification and viscosity reduction technology, specifically to a surfactant, its preparation method and application, and a method for reducing the viscosity of heavy oil. Background Technology

[0002] Improving the recovery rate of heavy oil has become a key national scientific and technological research direction. New oil displacement technologies such as chemical flooding and CO2 flooding have become research hotspots and have begun large-scale field applications. Recent studies have shown that oil displacement technology combining chemical and CO2 flooding can overcome the shortcomings of single technologies and is expected to enter field applications in the near future. The key to this combined oil displacement technology lies in developing surfactants that work synergistically with CO2. Patent CN111088025A discovered that a combination system of anionic and nonionic surfactants can effectively synergistically drive oil with CO2, but the binary system presents chromatographic separation problems during application. Furthermore, surfactants adsorb at the oil-water interface in the produced fluid, making it difficult to demulsify the oil-water emulsion and increasing the energy consumption of the demulsification and dehydration process.

[0003] The stimuli-responsiveness of surfactants is generally achieved by converting hydrophilic groups into nonpolar or weakly polar groups. Introducing tertiary amine groups into the molecule has been shown to impart CO2 responsiveness to the agent. CN107686723A discloses a CO2-responsive system using an anionic surfactant and a hydrocarbon-based polyamine composite, which enables in-situ gelation of hydrophobically modified polyacrylamide (HPAM) polymer solutions, increasing the gas-driven sweep volume. However, the composite system still suffers from limitations in chromatographic separation. CN111229121A discloses a method that achieves intelligent switching between "nonpolar" and "strongly polar" properties of the hydrophobic tail-chain tertiary amine group of the surfactant by adjusting the pH of the solution with acid or alkali. The tertiary amine group is located at the tail end of the molecule, providing a good pH-responsive site. CN114773212A discloses a single-chain dihydroxy CO2-responsive surfactant. This surfactant exhibits excellent CO2 stimuli responsiveness and can be used as a CO2-stimulated cleaning fracturing fluid, responding rapidly and quickly breaking down upon air introduction. However, its preparation process requires the use of bromine-containing hydrocarbon raw materials, which remain in the product and are difficult to remove completely, exacerbating pipeline corrosion. Currently, oilfield displacement agents standards all require the absence of chlorine / bromine, making this product difficult to apply industrially. CN109868066A discloses a rosin-based CO2 / N2-responsive polymerizable surfactant. This surfactant is responsive to CO2 / N2 and can be used as an emulsifier for nanoparticles; however, due to the large steric hindrance of the rosin group, its oil-water interfacial activity is theoretically unsatisfactory.

[0004] Therefore, it is necessary to design a novel responsive surfactant that exhibits excellent oil-water interfacial activity upon contact with CO2, thereby reducing interfacial tension, emulsifying and reducing viscosity, and achieving efficient synergistic viscosity reduction and oil displacement between the agent and CO2. Simultaneously, when the CO2 content in the produced fluid is low, it should be able to spontaneously demulsify in response, achieving energy saving and consumption reduction in the produced fluid post-treatment process. Summary of the Invention

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

[0006] To achieve the above objectives, a first aspect of the present invention provides a surfactant comprising a compound having the structure shown in formula (I).

[0007]

[0008] Each R2 is independently selected from H, C1-C4 alkyl groups, R5 and R6 are independently substituted or unsubstituted C8-C. 22 alkenyl, C8-C 22 Alkyl or heteroalkyl groups, each R4 being independently selected from H, C1-C4 alkyl groups or And at least one R2 or R4 is R1 and R3 are each independently selected from substituted or unsubstituted C1-C. 20 Alkylene;

[0009] The average value of the s value in the surfactant is 1-100.

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

[0011] (1) An amine compound is reacted with a 1,2-epoxide compound in a first ring-opening reaction to obtain an intermediate oligool;

[0012] The amine compound has the structure shown in formula (i).

[0013]

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

[0015] The structure of the 1,2-epoxide compound is represented as follows: R5 and R6 are independently substituted or unsubstituted C8-C. 22 alkenyl, C8-C 22 Alkyl or heteroalkyl groups;

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

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

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

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

[0020] The novel oligomeric surfactant provided by this invention exhibits significant stimuli-responsiveness to both pH and carbon dioxide. Upon contact with acidic environments or carbon dioxide, the surfactant becomes positively charged, exhibiting characteristics of a cationic oligomeric surfactant and possessing excellent interfacial activity. It can emulsify heavy oils with a viscosity reduction rate exceeding 90%. In neutral and alkaline environments, the product is electrically neutral, exhibiting characteristics of a nonionic surfactant, and its oil-water interfacial activity weakens. Based on this, by utilizing its pH or carbon dioxide responsiveness, the product can achieve emulsification and viscosity reduction of heavy oils and spontaneous demulsification of oil-water emulsions. Therefore, the oligomeric surfactant provided by this invention can be used as a carbon dioxide displacement synergist and has promising application prospects.

[0021] The method for preparing the stimulus-responsive oligomeric surfactant provided by this invention is simple and efficient. The preparation process does not require the use of halogenated hydrocarbon raw materials, meets the halogen-free requirements of the oilfield displacement agent standard, and is easy to scale up industrially. Attached Figure Description

[0022] Figure 1This is the MALDI-TOF mass spectrum of the intermediate tetrapolyol obtained in Example 1 of this invention;

[0023] Figure 2 It is the surfactant TE prepared in Example 1 of this invention. 1 H NMR spectrum;

[0024] Figure 3 This is the MALDI-TOF mass spectrum of the intermediate hexameric alcohol obtained in Example 2 of this invention;

[0025] Figure 4 The surfactant HE prepared in Example 2 of this invention 1 H NMR spectrum;

[0026] Figure 5 This is the MALDI-TOF mass spectrum of the intermediate dimer obtained in Example 3 of this invention;

[0027] Figure 6 The surfactant HE prepared in Example 3 of this invention 1 H NMR spectrum. Detailed Implementation

[0028] 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.

[0029] In this invention, the wavy line in the substituent, for example Indicates the bonding position of the R group.

[0030] A first aspect of the present invention provides a surfactant comprising a compound having the structure shown in formula (I).

[0031]

[0032] Each R2 is independently selected from H, C1-C4 alkyl groups, R5 and R6 are independently substituted or unsubstituted C8-C. 22 alkenyl, C8-C 22 Alkyl or heteroalkyl groups, each R4 being independently selected from H, C1-C4 alkyl groups or And at least one R2 or R4 is R1 and R3 are each independently selected from substituted or unsubstituted C1-C.20 Alkylene;

[0033] The average value of the s value in the surfactant is 1-100.

[0034] According to the present invention, each R2 in formula (I) is independently selected from H, C1-C4 alkyl groups, And at least one R2 or R4 is It is understood that in the surfactants provided by this invention, as long as at least one head group in the structure shown in formula (I) is Therefore, the selection range for the position of the substituent is relatively wide. In this invention, "C1-C4 alkyl" refers to an alkyl group with 1-4 carbon atoms, which can be a straight-chain or branched alkyl group, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, or isobutyl.

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

[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] Under the above-mentioned preferred conditions, it is beneficial for the synergistic effect between multiple nonionic amphiphilic motifs to obtain excellent oil-water interface performance.

[0038] The inventors of this invention discovered in their research that the nonionic oligomeric surfactant prepared by this invention shortens the spatial distance between multiple amphiphilic units through linking groups, making its synergistic effect with CO2 stronger. This results in excellent interfacial activity, emulsification, viscosity reduction, and other physicochemical properties, and these macroscopic properties are influenced by CO2 or H2. + Responsiveness.

[0039] In a further preferred embodiment, the surfactant comprises at least one of 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 Alkylene.

[0043] In this invention, R1 and R3 can be the same or different. The C1-C... 12The alkylene group can be a straight-chain or branched alkylene group, for example, it can be any one of methylene, ethylene, propylene, butylene, pentylene, hexylene, heptylene, octylene, nonylene, decylene, or its isomers. One or more carbon atoms in the alkylene group may optionally be substituted by one or more of cycloalkyl, aryl, or heteroatoms, the heteroatoms being, for example, 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 formulas (1) to (16);

[0045]

[0046]

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

[0048] In this invention, "C8-C" 22 "Alkyl" refers to an alkyl group with 8-22 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 an 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 Alkoxymethyl. Preferably, R5 is n-octyl, n-decyl, n-dodecyl, n-tetradecyl, n-hexadecyl, n-octadecyl, (2-ethylhexyloxy)methyl, octenyl, or C8-C. 10 The alkoxymethyl group, where R6 is hydrogen, is preferred. In the above-mentioned preferred configuration, the amphiphilicity of the surfactant is improved, thereby further enhancing the surface activity of the product.

[0050] According to some preferred embodiments of the present invention, the average value of the s-value in the surfactant is 2-20. The inventors of the present invention have found that when the s-value is too large, the polyoxyethylene chain segments have a large spatial volume, which may be detrimental to the close arrangement of molecules at the oil-water interface; while when the s-value is too small, it may lead to poor molecular solubility. When the average value of the s-value in the surfactant is within the above-mentioned 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 10,000 g / mol, and more preferably 400-8,000 g / mol.

[0052] In this invention, the molecular weight of the surfactant is calculated based on the molecular weight of the intermediate oligohydric alcohol, combined with the average value of s. Particularly preferably, the molecular weight of the surfactant is 750-6000 g / mol. Controlling the molecular weight of the surfactant within this preferred range facilitates efficient synergistic effects between multiple amphiphilic units in the product, while avoiding problems such as poor solubility and unsatisfactory interfacial activity caused by excessively high molecular weight.

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

[0054] (1) An amine compound is reacted with a 1,2-epoxide compound in a first ring-opening reaction to obtain an intermediate oligool;

[0055] The amine compound has the structure shown in formula (i).

[0056]

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

[0058] The structure of the 1,2-epoxide compound is represented as follows: R5 and R6 are independently substituted or unsubstituted C8-C. 22 alkenyl, C8-C 22 Alkyl or heteroalkyl groups;

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

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

[0061] According to some preferred embodiments of the present invention, the amine compound is selected from at least one of the compounds with structures shown in formulas (17) to (43);

[0062]

[0063]

[0064] According to some preferred embodiments of the present invention, the 1,2-epoxide compound is selected from 1,2-epoxydecane, 1,2-epoxytetradecane, 1,2-epoxyhexadecane, 1,2-epoxyoctadecane, 1,2-epoxyeicosene, 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-epoxide compound to the amine compound is (1-10):1, more preferably (1.1-2):1, wherein the molar amount of the amine compound is expressed as the molar amount of NH bonds in the molecule.

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

[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 choices for the organic solvent, as long as it can dissolve and disperse the reactants. Commonly used organic solvents in the art can be used in the present invention. For example, the organic solvent can be at least one selected from 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 intermediate oligohydric 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 choices for the base. Preferably, the base is selected from alkali metal hydroxides, and more preferably sodium hydroxide and / or potassium hydroxide.

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

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

[0072] In a further preferred embodiment, the second ring-opening reaction includes: mixing the intermediate oligool with a base at a first isothermal temperature, and then adding ethylene oxide at a second isothermal temperature to carry out the reaction. The first isothermal temperature does not exceed 100°C, preferably 80-100°C, and the second isothermal temperature is 100-180°C, preferably 120-160°C. Using the above preferred embodiments is beneficial to 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 this invention provides the application 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 heavy oil under acidic conditions and / or in the presence of carbon dioxide; wherein the viscosity reducer comprises the surfactant described in the first aspect or a 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 method described in the second aspect exhibits significant irritant responsiveness to both pH and carbon dioxide. This surfactant becomes positively charged upon contact with an acidic environment or carbon dioxide, exhibiting characteristics of a cationic oligomeric surfactant, possessing excellent interfacial activity, capable of emulsifying heavy oils, and achieving a viscosity reduction rate of over 90%.

[0077] Preferably, the viscosity reducing and oil displacement agent further contains water as a solvent, 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 includes: first contacting the viscosity reducer with acid and / or carbon dioxide, and then mixing it with heavy oil.

[0079] In a further preferred embodiment, the amount of acid is such that the pH of the product after the viscosity reducer contacts the acid is below 7, preferably 2-5. For example, the pH can be typical but not limiting pH values ​​such as 2, 2.5, 3, 3.5, 4, 4.5, 5, or a range between the two. More preferably, the amount of acid is such that the pH of the product after the viscosity reducer contacts the acid is 2-4.

[0080] This invention does not have any particular requirements regarding the type of acid, as long as the pH of the contact product can be adjusted to meet the above-mentioned range requirements. Conventional organic or inorganic acids can be used in this 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, the carbon dioxide flow rate is 0.5-10 L / min, preferably 3-10 L / min, relative to 1 L of the viscosity reducer.

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

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

[0084] The raw materials used in the following examples are all commercially available, and the main sources of the raw materials are shown in Table 1.

[0085] Table 1

[0086]

[0087] Example 1

[0088] The preparation process is shown in the following formula:

[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 50 mL of anhydrous ethanol, 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 rotary evaporation. The crude product was dissolved in dichloromethane, purified by silica gel column chromatography with dichloromethane / methanol elution, and dried under vacuum to obtain 9.0 g of white powdered intermediate tetrapolyol, with a calculated yield of 99 wt%. (The yield here is the percentage of the actual yield relative to the theoretical yield calculated based on the complete reaction of ethylenediamine, the same applies below.)

[0091] The intermediate tetrapolymer was characterized by MALDI-TOF mass spectrometry, and the results are as follows: Figure 1 As shown in the spectrum, a peak at 910.364 appears, which is the molecular ion peak of the intermediate tetrapolymer, proving that the target structure has been obtained.

[0092] (2) Add 100 parts by weight of the intermediate tetrapolymer to a high-pressure reactor, then add 0.5 parts by weight of KOH catalyst. Seal the reactor body and use dry nitrogen to displace the air in the high-pressure reactor, feed vessel, and feed pipe. Start heating and stirring, while simultaneously using a vacuum pump to evacuate the system. Stop evacuating the system when the temperature reaches 100°C. Add 135 parts by weight of ethylene oxide to the feed vessel, pressurize to 0.4 MPa, start mechanical stirring, and then slowly feed the material through the feed valve. During the process, control the reaction temperature at 140°C and the pressure at 0.4 MPa. After the addition is complete, stop stirring after reacting for 6 hours and continue aging for 1 hour. Once the pressure inside the reactor has decreased to a constant level, cool and discharge the material. Neutralize the reaction product with acetic acid, allow it to stand and separate into layers, then remove the lower opaque layer, which yields 165 parts by weight of the product, denoted as TE. The calculated yield is 93 wt%. (Here, the yield is the percentage of the actual yield of the target product relative to the theoretical yield calculated based on the complete reaction of the intermediate tetrapolymer, the same below.)

[0093] The product is passed through 1 Characterization was performed by H NMR, and the results are as follows: Figure 2 As shown in the figure. The peaks in the figure are assigned as follows:

[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 peak area ratio of the spectrum, the average value of s in the product TE was found to be 4.

[0096] Based on the molecular weight and S-value data of the intermediate tetrapolyol, the molecular weight of the surfactant was calculated to be 1613.34 g / mol.

[0097] Example 2

[0098] The preparation process is shown in the following formula:

[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 50 mL of anhydrous ethanol and reacted at 50 °C for 24 h. After the reaction was completed, the anhydrous ethanol solvent was removed by rotary evaporation, the crude product was dissolved in dichloromethane, purified by silica gel column chromatography with dichloromethane / methanol elution and vacuum drying to obtain 13.9 g of intermediate hexapolyol, with a calculated yield of 98 wt%.

[0102] The intermediate hexameric alcohol was characterized by MALDI-TOF mass spectrometry, and the results are as follows: Figure 3 As shown in the spectrum, a peak at 1421.030 appears, which is the molecular ion peak of the intermediate hexameric alcohol, proving that the target structure has been obtained.

[0103] (2) 100 parts by weight of the intermediate hexapolyol were added to a high-pressure reactor, followed by 1 part by weight of KOH catalyst. The reactor was sealed, and the air in the high-pressure reactor, feed vessel, and feed pipe was displaced by dry nitrogen. The reactor was heated and stirred, while a vacuum pump was used to evacuate the system. The vacuum pumping was stopped when the temperature reached 100°C. 185 parts by weight of ethylene oxide were added to the feed vessel, pressurized to 0.4 MPa, and mechanical stirring was started. Then the feed valve was opened and the material was fed slowly. During the process, the reaction temperature was controlled at 160°C and the pressure at 0.4 MPa. After the addition was completed, the reaction was stopped after 8 hours of reaction, and the mixture was aged for another 1 hour. The reactor was cooled and discharged after the pressure dropped to a constant level. The reaction product was neutralized with acetic acid, and after standing and separating into layers, the lower opaque layer was taken to obtain 190.4 parts by weight of the product, denoted as HE. The yield was calculated to be 90 wt%.

[0104] The product is passed through 1 Characterization was performed by H NMR, and the results are as follows: Figure 4 As shown in the figure. The peaks in the figure are assigned as follows:

[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 peak area ratio of the spectrum, it can be found that the average s value of the product HE is 6.

[0107] Based on the molecular weight and S-value data of the intermediate hexapolyol, the molecular weight of the surfactant was calculated to be 3004.38 g / mol.

[0108] Example 3

[0109] The preparation process is shown in the following formula:

[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 50 mL of anhydrous ethanol and reacted at 30 °C for 24 h. After the reaction was completed, the anhydrous ethanol solvent was removed by rotary evaporation. The crude product was dissolved in dichloromethane, purified by elution with dichloromethane / methanol using a silica gel column, and dried under vacuum to obtain 4.6 g of intermediate dimerol, with a yield of 90%.

[0112] The intermediate dimerol was characterized by MALDI-TOF mass spectrometry, and the results are as follows: Figure 5 As shown in the spectrum, a peak at 513.5391 appears, which is the molecular ion peak of the intermediate dimerol, proving that the target structure has been obtained.

[0113] (2) 100 parts by weight of the intermediate dimerol were added to a high-pressure reactor, followed by 0.25 parts by weight of KOH catalyst. The reactor was sealed, and dry nitrogen was used to displace the air in the high-pressure reactor, feed vessel, and feed pipe. The mixture was heated and stirred, while a vacuum pump was used to evacuate the system. Vacuum evacuation was stopped when the temperature reached 100°C. 86 parts by weight of ethylene oxide were added to the feed vessel, pressurized to 0.4 MPa, and mechanical stirring was started. The feed valve was then opened to slowly feed the material, controlling the reaction temperature at 120°C and the pressure at 0.4 MPa. After the addition was complete, the reaction was stopped after 5 hours of reaction, and the mixture was aged for another hour until the pressure inside the reactor reached a constant level. The product was then cooled and discharged. The reaction product was neutralized with acetic acid, and after standing and separating into layers, the lower opaque layer was removed, yielding 138 parts by weight of the product, denoted as DE, with a yield of 91 wt%.

[0114] The product DE was passed through 1 Characterization was performed by H NMR, and the results are as follows: Figure 6 As shown in the figure. The peaks in the figure are assigned as follows:

[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] By calculating the peak area ratio of the spectrum, it can be found 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 dimerol.

[0118] Example 4

[0119] The method of Example 1 was followed, except that in step (2), ethylene oxide was added in an amount of 1080 parts by weight. The resulting product was designated as TE-2. After calculating the peak area ratio of the spectrum, the average value of the s value in product TE was found to be 32. Based on the molecular weight and s value data of the intermediate tetrapolyol, the molecular weight of the surfactant was calculated to be 6544.28 g / mol.

[0120] Comparative Example 1

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

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

[0123] The oil-water interfacial tension of the oligomeric surfactant and the similar single-chain surfactant Brij35 prepared in the examples was measured under different conditions using a TX-500C interfacial tensiometer with the rotating droplet method. The oil used in the experiment was crude oil from a Shengli oilfield (its viscosity at 50℃ was measured to be 1053 mPa·s using a Haake VT550 rotational viscometer). The water used in the experiment was formation mineralized water with a salinity of 20000 mg / L. The test temperature was controlled at 50℃ and the rotation speed at 5000 rpm. The mass concentration of the surfactant aqueous solutions prepared in the experiment was 2000 mg / L.

[0124] (A) The interfacial tension measured when the surfactant is directly dissolved in formation water (pH 8.15) during the experiment is the interfacial tension under condition A.

[0125] (B) Dissolve the surfactant in the formation water, add hydrochloric acid, adjust the pH of the aqueous solution to 3.0, and then measure the interfacial tension, which is the interfacial tension under condition B.

[0126] (C) Dissolve the surfactant in formation water, add hydrochloric acid to adjust the pH of the aqueous solution to 3.0, then add sodium hydroxide to adjust the pH of the solution to 7.0, and then measure the interfacial tension. This is the interfacial tension under condition C.

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

[0128] (E) Dissolve the surfactant in 5L of formation water, introduce carbon dioxide at a flow rate of 1L / min for 5min, then introduce nitrogen at a flow rate of 1L / min for 10min, and then measure the interfacial tension. 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 this invention exhibits good interfacial activity under acidic conditions (condition B) or in the presence of carbon dioxide (condition D), and can reduce the oil-water interfacial tension of the target crude oil to 10. -2 Within the mN / m range, under neutral (condition A) and alkaline (condition C) conditions, or after replacing carbon dioxide with nitrogen (condition E), the interfacial activity of the oligomeric surfactant deteriorates, and the interfacial tension becomes higher. Therefore, the surfactant provided by this invention has a lower interfacial tension than H... + Carbon dioxide may exhibit a significant stimuli-responsiveness.

[0133] In contrast, the interfacial tension of polyoxyethylene lauryl ether (Brij35) in the comparative example was between (0.72-0.88) mN / m under acidic, alkaline, or neutral conditions, or after the introduction of carbon dioxide followed by nitrogen, and it showed no stimuli response.

[0134] Test Example 2: Stimulus Response Emulsification and Demulsification

[0135] The test oil and mineralized water used were the same as those used in the interfacial activity test. The test procedure for the viscosity reduction rate of heavy oil is as follows:

[0136] (a) Take 20g of the test oil and place it in a distillation flask;

[0137] (b) Prepare aqueous solutions of 1000 mg / L of the surfactants in the examples and comparative examples, and after treatment under different conditions (AE), take 10 mL of each solution and add it to a distillation flask containing the test oil.

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

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

[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 the oil-water mixture (mPa·s); and M is the viscosity reduction rate.

[0142] The method for treating the surfactant aqueous solution mentioned in step (b) is as follows:

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

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

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

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

[0147] Condition E: Carbon dioxide is introduced into 5L of surfactant aqueous solution at a flow rate of 1L / min for 5min, followed by nitrogen at a flow rate of 1L / min for 10min.

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

[0149] Table 3

[0150]

[0151] As can be seen from the test data in Table 3, on the one hand, the surfactant provided in the embodiments of the present invention reacts with H + Both the target heavy oil and the target heavy oil exhibit strong emulsification and viscosity reduction effects after external stimulation with carbon dioxide. They can emulsify the target heavy oil into an oil-in-water emulsion, achieving efficient viscosity reduction of the heavy oil, with viscosity reduction rates exceeding 90%. In contrast, the single-chain surfactant Brij35 used in the comparative example showed no irritation response, and its emulsification and viscosity reduction effect on the target heavy oil was poor.

[0152] On the other hand, the surfactant provided in the embodiments of the present invention has virtually no emulsifying and viscosity-reducing effect under neutral or alkaline conditions, or after nitrogen is introduced to replace carbon dioxide, and the oil-water mixture re-separates in a short time. Further, sodium hydroxide aqueous solution was added to the oil-water emulsion obtained under condition B to adjust the pH of the system to 7.0; nitrogen or air was introduced into the oil-water emulsion obtained under condition D at a rate of 1 L / min, and the demulsification of the mixed emulsion was observed and the time required for demulsification was recorded. The results are shown in Table 4.

[0153] Table 4

[0154]

[0155] The results in Tables 3 and 4 show that the surfactant provided by this invention also exhibits stimuli-responsiveness to the viscosity-reducing heavy oil (oil-in-water emulsion) obtained after emulsifying the target heavy oil. When the pH is adjusted to neutral, or when air or nitrogen is introduced into the oil-water mixture to replace carbon dioxide, the surfactant's interfacial activity with the water is weakened, making it unable to stabilize the water-in-oil emulsion, thus enabling spontaneous demulsification.

[0156] The results of the above test examples show that the novel oligomeric surfactant provided by this invention exhibits significant irritant response to both pH and carbon dioxide. When the oligomeric surfactant encounters hydrogen ions and carbon dioxide in water, it possesses excellent interfacial activity, capable of reducing the interfacial tension of the target heavy oil to 10. -2 The viscosity reduction rate for the target heavy oil is above 90% within the mN / m range. Furthermore, by utilizing the stimuli-responsiveness of the oligomeric surfactant, spontaneous demulsification of the produced fluid can be achieved by adjusting the pH value or by introducing nitrogen / air to replace carbon dioxide. This makes the oligomeric surfactant provided by this invention a promising candidate for use as a carbon dioxide flooding enhancer.

[0157] 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. A surfactant, characterized in that, The surfactant is a compound having the structure shown in formula (I). Equation (I), Each R2 is independently selected from C1-C4 alkyl groups. or R5 is selected from n-octyl, n-decyl, n-dodecyl, n-tetradecyl, n-hexadecyl, or n-octadecyl; R6 is hydrogen; each R4 is independently selected from C1-C4 alkyl groups or... And at least one R2 or R4 is R1 and R3 are each independently selected from any of the structures shown in the following formula; The average value of the s value in the surfactant is 2-20.

2. The surfactant according to claim 1, wherein, At least two R2 values ​​are ; Or, at least two R2 values ​​are And in each R2, at least one R4 is .

3. The surfactant according to claim 1, wherein, The surfactant is at least one of the compounds having the following structural formulas. Formula A, Formula B, Formula C.

4. The surfactant according to any one of claims 1-3, wherein, The molecular weight of the surfactant does not exceed 10,000 g / mol.

5. The surfactant according to claim 4, wherein, The molecular weight of the surfactant does not exceed 400-8000 g / mol.

6. A method for preparing a surfactant according to any one of claims 1-5, characterized in that, Includes the following steps: (1) An amine compound is subjected to a first ring-opening reaction with a 1,2-epoxide compound to obtain an intermediate oligool; The amine compound has the structure shown in formula (i). Equation (i), Each R2' is independently selected from C1-C4 alkyl groups or... Each R4' is independently selected from C1-C4 alkyl groups; The structure of the 1,2-epoxide compound is represented as follows: ; (2) In the presence of a base, the intermediate oligohydric alcohol is subjected to a second ring-opening reaction with ethylene oxide; The base is selected from alkali metal hydroxides.

7. The preparation method according to claim 6, wherein, In formula (i), the amine compound is selected from at least one of the compounds with the structure shown in the following formula.

8. The preparation method according to claim 6, wherein, The 1,2-epoxide compound is selected from at least one of 1,2-epoxydecane, 1,2-epoxytetradecane, 1,2-epoxyhexadecane, 1,2-epoxyoctadecane, and 1,2-epoxyeicosane.

9. The preparation method according to claim 6, wherein, In step (1), the molar ratio of the 1,2-epoxide compound to the amine compound is (1-10):1, wherein the molar amount of the amine compound is expressed as the molar amount of NH bonds in the molecule.

10. The preparation method according to claim 9, wherein, In step (1), the molar ratio of the 1,2-epoxide compound to the amine compound is (1.1-2):

1.

11. The preparation method according to any one of claims 6-10, wherein, The conditions for the first ring-opening reaction include: a temperature of 30-150℃ and a time of 4-72h.

12. The preparation method according to claim 11, wherein, The first ring-opening reaction was carried out in the presence of an organic solvent.

13. The preparation method according to claim 12, wherein, The organic solvent is at least one of methanol, ethanol, isopropanol, and dichloromethane.

14. The preparation method according to any one of claims 6-10, wherein, In step (2), the mass ratio of ethylene oxide to intermediate oligohydric alcohol is (20-1000):

100.

15. The preparation method according to claim 14, wherein, In step (2), the mass ratio of ethylene oxide to intermediate oligohydric alcohol is (50-500):

100.

16. The preparation method according to claim 6, wherein, The alkali is sodium hydroxide and / or potassium hydroxide.

17. The preparation method according to claim 6, wherein, The mass ratio of the alkali to the intermediate oligohydric alcohol is (0.1-2):

100.

18. The preparation method according to claim 17, wherein, The mass ratio of the alkali to the intermediate oligohydric alcohol is (0.25-1):

100.

19. The preparation method according to any one of claims 6-10, wherein, The conditions for the second ring-opening reaction include: a reaction temperature of 80-180℃, a reaction time of 4-10h, and a reaction pressure of 0.3-1MPa.

20. The preparation method according to claim 19, wherein, The second ring-opening reaction includes: mixing the intermediate oligool with an alkali at a first constant temperature, and then adding ethylene oxide at a second constant temperature to carry out the reaction. The first constant temperature does not exceed 100°C, and the second constant temperature is 100-180°C.

21. The preparation method according to claim 20, wherein, The first constant temperature is 80-100℃, and the second constant temperature is 120-160℃.

22. The preparation method according to claim 20, wherein, The second ring-opening reaction was carried out under stirring conditions.

23. The application of the surfactant according to any one of claims 1-5 or the surfactant prepared by any one of claims 6-22 in the viscosity reduction extraction of heavy oil.

24. A method for reducing the viscosity of heavy oil, comprising: The viscosity reducer is mixed with the heavy oil under acidic conditions and / or in the presence of carbon dioxide; The viscosity reducer includes the surfactant described in any one of claims 1-5 or the surfactant prepared by the preparation method described in any one of claims 6-22.

25. The method according to claim 24, wherein, The method includes: first contacting the viscosity reducer with acid and / or carbon dioxide, and then mixing it with heavy oil.

26. The method of claim 25, wherein, The viscosity reducer also contains water as a solvent, which is reservoir formation water or clean water, and the concentration of the surfactant in the viscosity reducer is 500-5000 mg / L.

27. The method of claim 25, wherein, The amount of acid used is such that the pH of the product after the viscosity reducer comes into contact with the acid is below 7.

28. The method according to claim 27, wherein, The amount of acid used is such that the pH of the product after the viscosity reducer comes into contact with the acid is 2-5.

29. The method according to claim 25, wherein, The amount of carbon dioxide introduced is 0.5-10L relative to 1L of the viscosity reducer.

30. The method according to claim 25, wherein, The amount of viscosity reducer used is 0.43-2.3L relative to 1L of the heavy oil.

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