Gemini surfactant for thickened oil recovery and preparation method thereof

Abstract

The invention relates to a gemini surfactant for thickened oil recovery and a preparation method thereof, and belongs to the technical field of thickened oil recovery. The preparation method of the gemini surfactant for thickened oil recovery comprises the following steps: dissolving ethylene glycol dihydric alcohol and paratoluensulfonyl chloride in a tetrahydrofuran solvent, and carrying out substitution reaction under an alkaline condition to obtain an intermediate I; adding nonyl phenol and the intermediate I into a mixed solvent of tetrahydrofuran and N, N-dimethylformamide, and carrying out etherification reaction under an alkaline condition to obtain a gemini precursor II; and mixing an alkylphenol polyoxyethylene ether surfactant, the gemini precursor II and a formaldehyde aqueous solution, and carrying out a phenolic aldehyde condensation polymerization reaction under an acidic condition to obtain the gemini surfactant. The gemini surfactant prepared by the preparation method has good temperature resistance and salt tolerance, the preparation method is simple, the synthesis cost is low, and the gemini surfactant has good economical efficiency and is beneficial to realizing large-scale industrial production.

Description

Technical Field

[0001] The present invention belongs to the technical field of heavy oil exploitation, and particularly relates to a gemini surfactant for heavy oil exploitation and a preparation method thereof. Background Art

[0002] At present, conventional oil reserves only account for 30% of the world's oil reserves, and most of the remaining are heavy oil, extra-heavy oil, oil sands and bitumen. The current global energy demand highly depends on the exploitation of existing oil reservoirs, and the effective development of heavy oil and bitumen resources will have an important impact on the world's energy supply. However, their inherent high viscosity and low fluidity characteristics, combined with complex reservoir configurations, have greatly restricted their exploitation and utilization. The key to heavy oil exploitation is to reduce viscosity and improve fluidity. For this purpose, various viscosity reduction methods such as physical viscosity reduction, microbial viscosity reduction, and chemical viscosity reduction have been developed. The current important way to exploit heavy oil is to use steam injection thermal recovery technology in combination with a displacement agent. This method is easy to operate, has a small amount of displacement agent used, low cost, and good viscosity reduction effect, so it has received wide attention.

[0003] Gemini surfactants are considered to be one of the surfactants most likely to overcome the bottleneck of existing surfactants for oil displacement due to their excellent properties such as higher surface activity, lower critical micelle concentration, good water solubility, and temperature and salt resistance. The application of gemini surfactants in tertiary oil recovery has been studied earlier abroad and later in China. The gemini surfactants studied at home and abroad currently include cationic gemini surfactants, anionic gemini surfactants, and anionic-nonionic gemini surfactants, etc. Among them, although a lot of research has been done on the application of cationic gemini surfactants at home and abroad, the formation is generally negatively charged. If the cationic gemini surfactant is injected into the formation as a displacement agent, it is very easy to have electrostatic adsorption with the formation, resulting in a relatively high use cost and limited use effect; while the synthesis process of anionic gemini surfactants and anionic-nonionic gemini surfactants is cumbersome and the purification difficulty is large. Therefore, there are more reports on their synthesis research, and relatively fewer reports on their physicochemical properties and structure-activity relationships.

[0004] Therefore, how to provide a gemini surfactant with good temperature and salt resistance and low cost to meet the heavy oil exploitation requirements of offshore high-temperature and high-salt oil reservoirs is a technical problem that needs to be solved urgently at present. Summary of the Invention

[0005] Aiming at the above technical problems, the present invention provides a gemini surfactant for heavy oil exploitation and a preparation method thereof. The obtained gemini surfactant has good temperature and salt resistance, and the preparation method is simple, the synthesis cost is low, and it has good economy, which is conducive to realizing large-scale industrial production.

[0006] The present invention provides a preparation method of a gemini surfactant for heavy oil exploitation, comprising the following steps:

[0007] Dissolve ethylene glycol-based diols and p-toluenesulfonyl chloride in a tetrahydrofuran solvent, and carry out a substitution reaction under alkaline conditions so that the p-toluenesulfonyl group derived from p-toluenesulfonyl chloride substitutes the hydroxyl group of the ethylene glycol-based diols to obtain intermediate I;

[0008] Add nonylphenol and intermediate I into a mixed solvent of tetrahydrofuran and N,N-dimethylformamide, and carry out an etherification reaction under alkaline conditions so that two molecules of the nonylphenol are linked through intermediate I to obtain gemini precursor II;

[0009] Mix an alkylphenol polyoxyethylene ether surfactant, gemini precursor II and an aqueous formaldehyde solution, and carry out a phenolic aldehyde condensation reaction under acidic conditions so that two molecules of the alkylphenol polyoxyethylene ether surfactant are linked through gemini precursor II to obtain the gemini surfactant.

[0010] In some embodiments, the ethylene glycol-based diols are selected from any one of ethylene glycol, diethylene glycol, triethylene glycol and tetraethylene glycol.

[0011] In some embodiments, the alkylphenol polyoxyethylene ether surfactant is selected from any one of OP-6, OP-10, OP-15 and OP-20.

[0012] In some embodiments, in the step of synthesizing intermediate I, the molar ratio of the ethylene glycol-based diols to p-toluenesulfonyl chloride is 1:2.

[0013] In some embodiments, in the step of synthesizing intermediate I, the substitution reaction is carried out in an ice-water bath, the pH of the reaction solution is 13, and the reaction time is 7 h.

[0014] In some embodiments, in the step of synthesizing gemini precursor II, the molar ratio of the nonylphenol to intermediate I is 2:1, and the volume ratio of tetrahydrofuran to N,N-dimethylformamide in the mixed solvent is 1:9.

[0015] In some embodiments, in the step of synthesizing gemini precursor II, the reaction temperature of the etherification reaction is 105 °C, the pH of the reaction solution is 13, the etherification reaction is carried out in a reflux manner, and the reflux time is 8 h.

[0016] In some embodiments, in the step of synthesizing the gemini surfactant, the molar ratio of the alkylphenol polyoxyethylene ether surfactant, gemini precursor II and formaldehyde is (2-4):1:(2-3).

[0017] In some of these embodiments, in the step of synthesizing the gemini surfactant, the reaction temperature of the phenolic condensation polymerization reaction is 95 - 125 °C, the pH of the reaction solution is 3, and the reaction time is 6 - 12 h.

[0018] In addition, the present invention also provides a gemini surfactant for heavy oil exploitation prepared by the preparation method described in any one of the above technical solutions.

[0019] Compared with the prior art, the advantages and beneficial effects of the present invention are as follows:

[0020] 1. In the preparation method of the gemini surfactant for heavy oil exploitation provided by the present invention, the hydroxyl groups of ethylene glycol - type diols are first protected by substitution of tosyl groups. Furthermore, using ethylene glycol - type diols as linkers, two molecules of nonylphenol are connected through etherification reaction to obtain a gemini precursor II containing aromatic rings. Then, using this gemini precursor II containing aromatic rings as a linker and alkylphenol polyoxyethylene ether - type surfactants as raw materials, through phenolic condensation polymerization, a functional group oxyethylene chain segment (EO chain segment) is introduced into the framework of the gemini precursor II, thereby obtaining a non - ionic gemini surfactant containing an aromatic linker group. The gemini surfactant prepared in this way introduces two rigid benzene ring structures and multiple active sites through the gemini precursor II, which can enhance aromaticity, making the surfactant molecular structure closer to heavy petroleum molecules, facilitating the adsorption of molecules at the oil - water interface. At the same time, the introduced functional group oxyethylene chain segment contains more polar groups, further enhancing the ability to interact with various components in heavy oil. Through the synergistic effect of each part, the temperature and salt tolerance performance is improved, and the molecular weight of the surfactant molecules is increased, which is beneficial to improving the molecular structure stability, can adapt to the harsh geological conditions of oil reservoirs, and meet the requirements of heavy oil exploitation in offshore high - temperature and high - salinity oil reservoirs;

[0021] 2. For the preparation method of the gemini surfactant for heavy oil exploitation provided by the present invention, the raw materials for each step are easily available. Using the industrially mature substitution reaction, etherification reaction, and phenolic condensation polymerization reaction, the synthesis method is simple, the synthesis cost is low, it has good economy, and is conducive to realizing large - scale industrial production;

[0022] 3. The gemini surfactant for heavy oil exploitation provided by the present invention, as a flooding agent, can significantly reduce the viscosity of heavy oil, can withstand a maximum salinity of 100 g / L, and after aging treatment at 300 °C for 24 h, it can still maintain a viscosity reduction rate of more than 96% for heavy oil, has good high - temperature resistance performance, and the emulsion formed by it and heavy oil has a certain stability, with little impact on the demulsification and dehydration of subsequent crude oil, which is conducive to large - scale promotion at the site of heavy oil exploitation in offshore high - temperature and high - salinity oil reservoirs. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1IR spectrum of the gemini surfactant prepared in Example 2 of the present invention;

[0024] Figure 2 of the gemini surfactant prepared in Example 2 of the present invention 1 1H NMR spectrum;

[0025] Figure 3 Thermogravimetric analysis spectrum of the gemini surfactant prepared in Example 2 of the present invention;

[0026] Figure 4 Measurement results of the interfacial tension between the gemini surfactants prepared in Examples 2, 6 - 10 of the present invention and heavy oil at different NaCl concentrations;

[0027] Figure 5 Measurement results of the interfacial tension between the gemini surfactants prepared in Examples 2, 6 - 10 of the present invention and heavy oil at different CaCl2 concentrations. Detailed implementation manners

[0028] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Apparently, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0029] The embodiment of the present invention provides a preparation method of a gemini surfactant for heavy oil exploitation, including the following steps:

[0030] S1. Dissolve ethylene glycol - type diol and p - toluenesulfonyl chloride in a tetrahydrofuran solvent, and carry out a substitution reaction under alkaline conditions to enable the p - toluenesulfonyl group derived from p - toluenesulfonyl chloride to substitute the hydroxyl group of the ethylene glycol - type diol, obtaining intermediate Ⅰ;

[0031] S2. Add nonylphenol and intermediate Ⅰ into a mixed solvent of tetrahydrofuran and N,N - dimethylformamide, and carry out an etherification reaction under alkaline conditions to enable two molecules of nonylphenol to be connected through intermediate Ⅰ, obtaining gemini precursor Ⅱ;

[0032] S3. Mix an alkylphenol polyoxyethylene ether - type surfactant, gemini precursor Ⅱ, and an aqueous formaldehyde solution, and carry out a phenolic - aldehyde condensation reaction under acidic conditions to enable two molecules of the alkylphenol polyoxyethylene ether - type surfactant to be connected through gemini precursor Ⅱ, obtaining the gemini surfactant.

[0033] In the above preparation method of the gemini surfactant for heavy oil exploitation, the hydroxyl groups of ethylene glycol-based diols are first protected by substitution of tosyl groups. Then, using ethylene glycol-based diols as linkers, two molecules of nonylphenol are connected through etherification reaction to obtain the aromatic-containing gemini precursor II. Further, using this aromatic-containing gemini precursor II as the linker group and alkylphenol polyoxyethylene ether surfactants as raw materials, through phenolic aldehyde condensation polymerization, a functional group oxyethylene group segment (EO segment) is introduced into the framework of the gemini precursor II, thereby obtaining a nonionic gemini surfactant containing an aromatic linker group. The gemini surfactant prepared in this way introduces two rigid benzene ring structures and multiple active sites through the gemini precursor II, which can enhance the aromaticity, make the surfactant molecular structure closer to heavy petroleum molecules, facilitate the adsorption of molecules at the oil-water interface. At the same time, the introduced functional group oxyethylene group segment contains more polar groups, further enhancing the ability to interact with various components in heavy oil. Through the synergistic effect of each part, the temperature and salt resistance performance is improved, and the molecular weight of the surfactant molecule is increased, which is beneficial to improving the molecular structure stability and can adapt to the harsh geological conditions of the oil reservoir, meeting the needs of heavy oil exploitation in offshore high-temperature and high-salt oil reservoirs. Moreover, in the above preparation method of the gemini surfactant for heavy oil exploitation, the raw materials for each step are easily available, and the substitution reaction, etherification reaction, and phenolic aldehyde condensation polymerization reaction, which are mature in industry, are adopted. The synthesis method is simple, the synthesis cost is low, and it has good economic efficiency, which is conducive to realizing large-scale industrial production.

[0034] In a preferred embodiment, the ethylene glycol-based diol is selected from any one of ethylene glycol, diethylene glycol, triethylene glycol, and tetraethylene glycol. Several specific ethylene glycol-based diols are listed in this preferred embodiment. Using these ethylene glycol-based diols as linkers, the gemini skeleton structure of the obtained gemini precursor II is more stable. It can be understood that the embodiments of the present invention are not limited to the several ethylene glycol-based diols listed above, and those skilled in the art can also select other suitable ethylene glycol-based diols.

[0035] In a preferred embodiment, the alkylphenol polyoxyethylene ether surfactant is selected from any one of OP-6, OP-10, OP-15, and OP-20. Several specific alkylphenol polyoxyethylene ether surfactants are listed in this preferred embodiment. The molecular chains of these alkylphenol polyoxyethylene ether surfactants all have an appropriate number of oxyethylene groups, which is beneficial to obtaining a gemini surfactant with stronger surface activity and stronger salt resistance. It can be understood that the embodiments of the present invention are not limited to the several alkylphenol polyoxyethylene ether surfactants listed above, and those skilled in the art can also select other suitable alkylphenol polyoxyethylene ether surfactants.

[0036] It should be noted that when the above-mentioned preferred ethylene glycol-based diols and alkylphenol polyoxyethylene ether-based surfactants are used, the reaction equation of the preparation method of the gemini surfactant for heavy oil recovery is as follows:

[0037] (1) The substitution reaction equation is:

[0038] HO(CH2CH2O) m + TsCl → TsO(CH2CH2O) m Ts (Intermediate Ⅰ);

[0039] (2) The etherification reaction equation is:

[0040]

[0041] (3) The phenolic aldehyde polycondensation reaction equation is:

[0042]

[0043] In the above reaction equations, m = 1 or 2 or 3 or 4, n = 6 or 10 or 15 or 20, R1 = C9H 19 , R2 = C8H 17 .

[0044] In a preferred embodiment, in the step of synthesizing the Intermediate Ⅰ, the molar ratio of the ethylene glycol-based diol to the p-toluenesulfonyl chloride is 1:2. This preferred embodiment specifically defines the molar ratio of the ethylene glycol-based diol to the p-toluenesulfonyl chloride during the substitution reaction, which can ensure that the p-toluenesulfonyl group fully substitutes the hydroxyl group of the ethylene glycol-based diol.

[0045] In a preferred embodiment, in the step of synthesizing the Intermediate Ⅰ, the substitution reaction is carried out in an ice-water bath, the pH of the reaction solution is 13, and the reaction time is 7 h. This preferred embodiment specifically defines the reaction temperature, the pH of the reaction solution, and the reaction time during the substitution reaction, which is beneficial to ensuring a complete reaction. It should be noted that in the step of synthesizing the Intermediate Ⅰ, the pH of the reaction solution is adjusted to 13 by dropping a potassium hydroxide aqueous solution.

[0046] In a preferred embodiment, in the step of synthesizing the gemini precursor Ⅱ, the molar ratio of nonylphenol to the Intermediate Ⅰ is 2:1, and the volume ratio of tetrahydrofuran to N,N-dimethylformamide in the mixed solvent is 1:9. This preferred embodiment specifically defines the molar ratio of nonylphenol to the Intermediate Ⅰ and the volume ratio of tetrahydrofuran to N,N-dimethylformamide in the mixed solvent during the etherification reaction, which can ensure the formation of a stable gemini precursor Ⅱ structure and improve the yield and purity of the gemini precursor Ⅱ.

[0047] In a preferred embodiment, in the step of synthesizing the gemini precursor II, the reaction temperature of the etherification reaction is 105 °C, the pH of the reaction solution is 13, the etherification reaction is carried out in a reflux manner, and the reflux time is 8 h. This preferred embodiment specifically defines the reaction temperature, the pH of the reaction solution, the reaction mode and the reaction time during the etherification reaction, which is beneficial to ensuring the full reaction. It should be noted that in the step of synthesizing the gemini precursor II, the pH of the reaction solution is adjusted to 13 by adding sodium hydroxide to the reaction solution.

[0048] In a preferred embodiment, in the step of synthesizing the gemini surfactant, the molar ratio of the alkylphenol polyoxyethylene ether surfactant, the gemini precursor II and formaldehyde is (2-4):1:(2-3). This preferred embodiment gives the preferred range of the ratio of the alkylphenol polyoxyethylene ether surfactant, the gemini precursor II and formaldehyde. This preferred ratio range can ensure that the prepared gemini surfactant has good temperature resistance, salt resistance and surface activity at the same time. It can be understood that those skilled in the art can select a suitable reaction ratio within the above preferred ratio range. For example, the molar ratio of the alkylphenol polyoxyethylene ether surfactant, the gemini precursor II and formaldehyde can be 2:1:2, 2.5:1:2, 3:1:2, 3.5:1:2, 4:1:2, 2:1:2.5, 2.5:1:2.5, 3:1:2.5, 3.5:1:2.5, 4:1:2.5, 2:1:3, 2.5:1:3, 3:1:3, 3.5:1:3 or 4:1:3, etc.

[0049] In a preferred embodiment, in the step of synthesizing the gemini surfactant, the reaction temperature of the phenolic condensation polymerization reaction is 95-125 °C, the pH of the reaction solution is 2-3, and the reaction time is 6-12 h. This preferred embodiment gives the preferred range of the reaction temperature, the pH of the reaction solution and the reaction time during the polycondensation, which is beneficial to controlling the degree of polymerization, ensuring the full reaction and avoiding the occurrence of side reactions at the same time. It should be noted that due to the relatively high reaction temperature, to maintain the temperature of the reaction system, the temperature can be first raised to 40 °C and maintained for 30 min, and then raised to the required reaction temperature. It can be understood that those skilled in the art can select a suitable reaction temperature, the pH of the reaction solution and the reaction time within the above preferred range. For example, the reaction temperature can be 95 °C, 105 °C, 115 °C or 125 °C, etc., the pH of the reaction solution can be 2, 2.5 or 3, etc., and the reaction time can be 6 h, 8 h, 10 h or 12 h, etc.

[0050] The embodiments of the present invention also provide a gemini surfactant for heavy oil exploitation prepared by the above preparation method. As a flooding agent, the gemini surfactant for heavy oil exploitation can greatly reduce the viscosity of heavy oil, can withstand a maximum salinity of 100 g / L, and after aging treatment at 300 °C for 24 h, it can still maintain a viscosity reduction rate of more than 96% for heavy oil, has good high-temperature resistance, and the emulsion formed by it and heavy oil has a certain stability, with little impact on the demulsification and dehydration of subsequent crude oil, which is conducive to large-scale promotion at the heavy oil exploitation site of offshore high-temperature and high-salinity oil reservoirs.

[0051] In order to introduce the gemini surfactant for heavy oil exploitation and its preparation method provided by the embodiments of the present invention more clearly and in detail, the following will be described in combination with specific embodiments.

[0052] Example 1

[0053] The preparation method of the gemini surfactant for heavy oil exploitation includes the following steps:

[0054] (1) Under an ice-water bath, add triethylene glycol (38.8 g, 200 mmol), p-toluenesulfonyl chloride (76 g, 400 mmol) and 80 mL of the solvent tetrahydrofuran to a 500 mL three-necked flask and stir mechanically, then slowly dropwise add an aqueous potassium hydroxide solution (preparation method: weigh 44.8 g of potassium hydroxide and dissolve it in 60 mL of water). After the addition is complete, the solution changes from clear and colorless to turbid white, with a pH of 13. React for 7 h to obtain intermediate I;

[0055] (2) Add 10 mL of tetrahydrofuran, 90 mL of N,N-dimethylformamide to a 250 mL three-necked flask, and add sodium hydroxide (1.6 g, 40 mmol), 4-nonylphenol (8.8 g, 40 mmol), and intermediate I (10.4 g, 20 mmol). The pH of the reaction solution is 13, and reflux reaction is carried out at 105 °C for 8 h to obtain gemini precursor II;

[0056] (3) Add OP-10 (12.9 g, 20 mmol), gemini precursor II (6 g, 10 mmol), concentrated sulfuric acid and aqueous formaldehyde solution to the reaction kettle. Among them, the addition amount of formaldehyde is 3 times the molar amount of OP-10, and the pH of the reaction solution is 3; heat up to 40 °C and keep it for 30 min, then heat up to 95 °C for polycondensation reaction for 6 h to obtain the gemini surfactant.

[0057] Example 2

[0058] The preparation method of the gemini surfactant for heavy oil exploitation includes the following steps:

[0059] (1) Under an ice - water bath, add triethylene glycol tetraether (38.8 g, 200 mmol), p - toluenesulfonyl chloride (76 g, 400 mmol) and 80 mL of the solvent tetrahydrofuran into a 500 - mL three - necked flask, and stir mechanically. Then slowly dropwise add an aqueous potassium hydroxide solution (preparation method: weigh 44.8 g of potassium hydroxide and dissolve it in 60 mL of water). After the addition is complete, the solution changes from clear and colorless to turbid white, with a pH of 13. React for 7 h to obtain intermediate I;

[0060] (2) Add 10 mL of tetrahydrofuran, 90 mL of N,N - dimethylformamide into a 250 - mL three - necked flask, and add sodium hydroxide (1.6 g, 40 mmol), 4 - nonylphenol (8.8 g, 40 mmol), intermediate I (10.4 g, 20 mmol). The pH of the reaction solution is 13. Reflux and react at 105 °C for 8 h to obtain gemini precursor II;

[0061] (3) Add OP - 10 (16.2 g, 25 mmol), gemini precursor II (6 g, 10 mmol), concentrated sulfuric acid and aqueous formaldehyde solution into a reaction kettle. Among them, the addition amount of formaldehyde is 3 times the molar amount of OP - 10, and the pH of the reaction solution is 3. Heat up to 40 °C and keep it for 30 min, then heat up to 105 °C for polycondensation reaction for 8 h to obtain the gemini surfactant.

[0062] Example 3

[0063] A preparation method of a gemini surfactant for heavy oil recovery, comprising the following steps:

[0064] (1) Under an ice - water bath, add triethylene glycol tetraether (38.8 g, 200 mmol), p - toluenesulfonyl chloride (76 g, 400 mmol) and 80 mL of the solvent tetrahydrofuran into a 500 - mL three - necked flask, and stir mechanically. Then slowly dropwise add an aqueous potassium hydroxide solution (preparation method: weigh 44.8 g of potassium hydroxide and dissolve it in 60 mL of water). After the addition is complete, the solution changes from clear and colorless to turbid white, with a pH of 13. React for 7 h to obtain intermediate I;

[0065] (2) Add 10 mL of tetrahydrofuran, 90 mL of N,N - dimethylformamide into a 250 - mL three - necked flask, and add sodium hydroxide (1.6 g, 40 mmol), 4 - nonylphenol (8.8 g, 40 mmol), intermediate I (10.4 g, 20 mmol). The pH of the reaction solution is 13. Reflux and react at 105 °C for 8 h to obtain gemini precursor II;

[0066] (3) Add OP-10 (19.4 g, 30 mmol), gemini precursor II (6 g, 10 mmol), concentrated sulfuric acid and aqueous formaldehyde solution into a reaction kettle. Among them, the addition amount of formaldehyde is 3 times the molar amount of OP-10, and the pH of the reaction solution is 3. Heat up to 40 °C and keep for 30 min, then heat up to 115 °C for polycondensation reaction for 10 h to obtain the gemini surfactant.

[0067] Example 4

[0068] A preparation method of a gemini surfactant for heavy oil exploitation, comprising the following steps:

[0069] (1) Under an ice-water bath, add triethylene glycol (38.8 g, 200 mmol), p-toluenesulfonyl chloride (76 g, 400 mmol) and 80 mL of the solvent tetrahydrofuran into a 500 mL three-necked flask and stir mechanically. Then slowly dropwise add an aqueous potassium hydroxide solution (preparation method: weigh 44.8 g of potassium hydroxide and dissolve it in 60 mL of water). After the dropping is completed, the solution changes from clear and colorless to turbid white, the pH is 13, and react fully for 7 h to obtain intermediate I;

[0070] (2) Add 10 mL of tetrahydrofuran, 90 mL of N,N-dimethylformamide into a 250 mL three-necked flask, and add sodium hydroxide (1.6 g, 40 mmol), 4-nonylphenol (8.8 g, 40 mmol), intermediate I (10.4 g, 20 mmol). The pH of the reaction solution is 13, and reflux reaction is carried out at 105 °C for 8 h to obtain gemini precursor II;

[0071] (3) Add OP-10 (22.6 g, 35 mmol), gemini precursor II (6 g, 10 mmol), concentrated sulfuric acid and aqueous formaldehyde solution into a reaction kettle. Among them, the addition amount of formaldehyde is 3 times the molar amount of OP-10, and the pH of the reaction solution is 3. Heat up to 40 °C and keep for 30 min, then heat up to 125 °C for polycondensation reaction for 12 h to obtain the gemini surfactant.

[0072] Example 5

[0073] A preparation method of a gemini surfactant for heavy oil exploitation, comprising the following steps:

[0074] (1) Under an ice-water bath, add triethylene glycol (38.8 g, 200 mmol), p-toluenesulfonyl chloride (76 g, 400 mmol) and 80 mL of the solvent tetrahydrofuran into a 500 mL three-necked flask and stir mechanically. Then slowly dropwise add an aqueous potassium hydroxide solution (preparation method: weigh 44.8 g of potassium hydroxide and dissolve it in 60 mL of water). After the dropping is completed, the solution changes from clear and colorless to turbid white, the pH is 13, and react fully for 7 h to obtain intermediate I;

[0075] (2) Add 10 mL of tetrahydrofuran and 90 mL of N,N-dimethylformamide into a 250 mL three-necked flask, and then add sodium hydroxide (1.6 g, 40 mmol), 4-nonylphenol (8.8 g, 40 mmol), and intermediate Ⅰ (10.4 g, 20 mmol). The pH of the reaction solution is 13. Reflux the reaction solution at 105 °C for 8 h to obtain gemini precursor Ⅱ.

[0076] (3) Add OP-10 (12.9 g, 20 mmol), gemini precursor II (6 g, 10 mmol), concentrated sulfuric acid and aqueous formaldehyde solution into a reaction kettle. Among them, the addition amount of formaldehyde is 3 times the molar amount of OP-10, and the pH of the reaction solution is 3. Heat up to 40 °C and keep it for 30 min, then heat up to 125 °C for polycondensation reaction for 6 h to obtain the gemini surfactant.

[0077] Example 6

[0078] A preparation method of a gemini surfactant for heavy oil exploitation, comprising the following steps:

[0079] (1) Under an ice-water bath, add tris(tetraethylene glycol) (38.8 g, 200 mmol), p-toluenesulfonyl chloride (76 g, 400 mmol) and 80 mL of the solvent tetrahydrofuran into a 500 mL three-necked flask, and stir mechanically. Then slowly dropwise add an aqueous potassium hydroxide solution (preparation method: weigh 44.8 g of potassium hydroxide and dissolve it in 60 mL of water). After the dropping is completed, the solution changes from clear and colorless to turbid white, and the pH is 13. React fully for 7 h to obtain intermediate Ⅰ.

[0080] (2) Add 10 mL of tetrahydrofuran and 90 mL of N,N-dimethylformamide into a 250 mL three-necked flask, and then add sodium hydroxide (1.6 g, 40 mmol), 4-nonylphenol (8.8 g, 40 mmol), and intermediate Ⅰ (10.4 g, 20 mmol). The pH of the reaction solution is 13. Reflux the reaction solution at 105 °C for 8 h to obtain gemini precursor Ⅱ.

[0081] (3) Add OP-6 (11.8 g, 25 mmol), gemini precursor II (6 g, 10 mmol), concentrated sulfuric acid and aqueous formaldehyde solution into a reaction kettle. Among them, the addition amount of formaldehyde is 3 times the molar amount of OP-10, and the pH of the reaction solution is 3. Heat up to 40 °C and keep it for 30 min, then heat up to 105 °C for polycondensation reaction for 8 h to obtain the gemini surfactant.

[0082] Example 7

[0083] A preparation method of a gemini surfactant for heavy oil exploitation, comprising the following steps:

[0084] (1) Under an ice-water bath, add triethylene glycol tetraether (38.8 g, 200 mmol), p-toluenesulfonyl chloride (76 g, 400 mmol) and 80 mL of the solvent tetrahydrofuran to a 500 mL three-necked flask, stir mechanically, and then slowly add an aqueous potassium hydroxide solution (preparation method: weigh 44.8 g of potassium hydroxide and dissolve it in 60 mL of water). After the addition is complete, the solution changes from clear and colorless to turbid white, with a pH of 13. React for 7 h to obtain intermediate I;

[0085] (2) Add 10 mL of tetrahydrofuran, 90 mL of N,N-dimethylformamide to a 250 mL three-necked flask, and add sodium hydroxide (1.6 g, 40 mmol), 4-nonylphenol (8.8 g, 40 mmol), and intermediate I (10.4 g, 20 mmol). The pH of the reaction solution is 13. Reflux and react at 105 °C for 8 h to obtain gemini precursor II;

[0086] (3) Add OP-15 (21.7 g, 25 mmol), gemini precursor II (6 g, 10 mmol), concentrated sulfuric acid and aqueous formaldehyde solution to the reaction kettle. Among them, the addition amount of formaldehyde is 3 times the molar amount of OP-10. The pH of the reaction solution is 3; heat up to 40 °C and keep it for 30 min, then heat up to 105 °C for polycondensation reaction for 8 h to obtain the gemini surfactant.

[0087] Example 8

[0088] A preparation method of a gemini surfactant for heavy oil exploitation, comprising the following steps:

[0089] (1) Under an ice-water bath, add triethylene glycol tetraether (38.8 g, 200 mmol), p-toluenesulfonyl chloride (76 g, 400 mmol) and 80 mL of the solvent tetrahydrofuran to a 500 mL three-necked flask, stir mechanically, and then slowly add an aqueous potassium hydroxide solution (preparation method: weigh 44.8 g of potassium hydroxide and dissolve it in 60 mL of water). After the addition is complete, the solution changes from clear and colorless to turbid white, with a pH of 13. React for 7 h to obtain intermediate I;

[0090] (2) Add 10 mL of tetrahydrofuran, 90 mL of N,N-dimethylformamide to a 250 mL three-necked flask, and add sodium hydroxide (1.6 g, 40 mmol), 4-nonylphenol (8.8 g, 40 mmol), and intermediate I (10.4 g, 20 mmol). The pH of the reaction solution is 13. Reflux and react at 105 °C for 8 h to obtain gemini precursor II;

[0091] (3) Add OP-20 (27.2 g, 25 mmol), Gemini precursor II (6 g, 10 mmol), concentrated sulfuric acid, and aqueous formaldehyde solution into a reaction kettle. Among them, the addition amount of formaldehyde is 3 times the molar amount of OP-10, and the pH of the reaction solution is 3. Heat up to 40 °C and keep for 30 min, then heat up to 105 °C for polycondensation reaction for 8 h to obtain the Gemini surfactant.

[0092] Example 9

[0093] A preparation method of a Gemini surfactant for heavy oil exploitation, comprising the following steps:

[0094] (1) Under an ice-water bath, add ethylene glycol (12.4 g, 200 mmol), p-toluenesulfonyl chloride (76 g, 400 mmol), and 80 mL of the solvent tetrahydrofuran into a 500 mL three-necked flask and stir mechanically. Then slowly dropwise add an aqueous potassium hydroxide solution (preparation method: weigh 44.8 g of potassium hydroxide and dissolve it in 60 mL of water). After the addition is complete, the solution changes from clear and colorless to turbid white, with a pH of 13. React fully for 7 h to obtain intermediate I.

[0095] (2) Add 10 mL of tetrahydrofuran, 90 mL of N,N-dimethylformamide into a 250 mL three-necked flask, and add sodium hydroxide (1.6 g, 40 mmol), 4-nonylphenol (8.8 g, 40 mmol), and intermediate I (10.4 g, 20 mmol). The pH of the reaction solution is 13. Reflux and react at 105 °C for 8 h to obtain Gemini precursor II.

[0096] (3) Add OP-10 (16.2 g, 25 mmol), Gemini precursor II (6 g, 10 mmol), concentrated sulfuric acid, and aqueous formaldehyde solution into a reaction kettle. Among them, the addition amount of formaldehyde is 3 times the molar amount of OP-10, and the pH of the reaction solution is 3. Heat up to 40 °C and keep for 30 min, then heat up to 105 °C for polycondensation reaction for 8 h to obtain the Gemini surfactant.

[0097] Example 10

[0098] A preparation method of a Gemini surfactant for heavy oil exploitation, comprising the following steps:

[0099] (1) Under an ice-water bath, add triethylene glycol (30 g, 200 mmol), p-toluenesulfonyl chloride (76 g, 400 mmol), and 80 mL of the solvent tetrahydrofuran into a 500 mL three-necked flask and stir mechanically. Then slowly dropwise add an aqueous potassium hydroxide solution (preparation method: weigh 44.8 g of potassium hydroxide and dissolve it in 60 mL of water). After the addition is complete, the solution changes from clear and colorless to turbid white, with a pH of 13. React fully for 7 h to obtain intermediate I.

[0100] (2) Add 10 mL of tetrahydrofuran and 90 mL of N,N-dimethylformamide into a 250 mL three-necked flask, and then add sodium hydroxide (1.6 g, 40 mmol), 4-nonylphenol (8.8 g, 40 mmol), and intermediate Ⅰ (10.4 g, 20 mmol). The pH of the reaction solution is 13. Reflux the reaction at 105 °C for 8 h to obtain gemini precursor Ⅱ;

[0101] (3) Add OP-10 (16.2 g, 25 mmol), gemini precursor II (6 g, 10 mmol), concentrated sulfuric acid and formaldehyde aqueous solution into the reaction kettle. Among them, the addition amount of formaldehyde is 3 times the molar amount of OP-10, and the pH of the reaction solution is 3; Heat up to 40 °C and keep it for 30 min, then heat up to 105 °C for polycondensation reaction for 8 h to obtain the gemini surfactant.

[0102] Structure characterization

[0103] Perform structure characterization on the gemini surfactant prepared in Example 2. Its IR spectrum is as Figure 1 shown, and its 1 1H NMR spectrum is as Figure 2 shown.

[0104] It can be seen from the IR spectrum (i.e., Figure 1 ) that: the broad peak at 3475 cm -1 is the stretching vibration peak of O-H; the absorption peaks at 2924 cm -1 , 2872 cm -1 are the absorption peaks of long-chain alkyl groups; the stretching vibration peaks of the benzene ring skeleton are at 1608 cm -1 , 1510 cm -1 ; the characteristic absorption peak of the ester group is at 1256 cm -1 ; the antisymmetric stretching vibration absorption peak of the characteristic group C-O-C of polyoxyethylene ether is at 1110 cm -1 , and the symmetric stretching vibration absorption peak of C-O-C is at 950 cm -1 .

[0105] It can be seen from the 1 1H NMR spectrum (i.e., Figure 2 ) that: the peak at the chemical shift δ = 6.5 - 7.0 ppm is the proton peak on the benzene ring, the proton peak on the hydrophobic alkyl chain is at the chemical shift δ = 0.5 - 1.5 ppm, the proton peak on the oxyethylene group of polyoxyethylene ether is at the chemical shift δ = 3.5 ppm, the peak at the chemical shift δ = 4.0 ppm is the proton peak on the linking group, and the peak at the chemical shift δ = 3.8 ppm is the proton peak of the methylene group in the benzyl group, which is one of the evidences for the condensation of formaldehyde on the benzene ring.

[0106] Viscosity reduction experiment

[0107] According to the enterprise standard Q / SH1020 2193-2013 "General Technical Conditions for High-Temperature Viscosity Reducers for Heavy Oil" of Shengli Petroleum Administration Bureau, Sinopec Group, the gemini surfactants prepared in Examples 1-10 and the commercially available oil displacement agent (sodium dodecylbenzenesulfonate) were used for viscosity reduction evaluation of Bohai heavy oil (viscosity of 3500 mPa·s at 50 °C). The steps for viscosity reduction evaluation are as follows:

[0108] (1) Prepare aqueous solutions with a concentration of 1 wt% of the gemini surfactants prepared in Examples 1-10 and sodium dodecylbenzenesulfonate. Take 10 mL of each sample and age it at a high temperature of 300 °C for 24 h to obtain the high-temperature active aqueous solutions of each sample.

[0109] (2) Mix the high-temperature active aqueous solutions of the above samples with heavy oil at a volume ratio of 3:7 and stir well with a glass rod at 50 °C.

[0110] (3) Measure the viscosity of the oil-water mixture system with an RVDV-IIIU type rotational viscometer at a temperature of 50 °C and a rotation speed of 200 r / min. The test results are shown in Table 1.

[0111] Table 1 Viscosity Reduction Test Results

[0112] Sample Viscosity / mPa·s Viscosity reduction rate / % Example 1 97.30 97.22 Example 2 43.04 98.77 Example 3 57.76 98.35 Example 4 66.50 98.10 Example 5 90.66 97.41 Example 6 127.04 96.37 Example 7 39.00 98.89 Example 8 85.02 97.57 Example 9 100.10 97.14 Example 10 67.88 98.06 Sodium dodecylbenzenesulfonate Not emulsified Not emulsified

[0113] As can be seen from Table 1, after high-temperature treatment, the gemini surfactants prepared in each example of the present invention have a viscosity reduction rate of more than 96% for Bohai heavy oil with a viscosity of 3500 mPa·s at a relatively low concentration (1 wt%), while the commercially available oil displacement agent sodium dodecylbenzenesulfonate cannot emulsify Bohai heavy oil with a viscosity of 3500 mPa·s. It can be seen that the gemini surfactant prepared by the preparation method provided by the present invention for heavy oil exploitation has a high heavy oil viscosity reduction rate and exhibits excellent temperature resistance.

[0114] High Temperature Resistance Performance Test

[0115] The thermogravimetric analysis of the gemini surfactant prepared in Example 2 of the present invention is as Figure 3 shown. It can be seen that: the weight loss is relatively slow before 150 °C, and the weight loss is nearly 14%; the weight loss accelerates around 354 °C, and the weight loss is the largest; when the temperature reaches 400 °C, the residue of the sample is still as high as more than 10%. This shows that the gemini surfactant prepared in Example 2 of the present invention has strong temperature resistance and exhibits good thermal stability, and it can withstand a high temperature of 300 °C.

[0116] Salt Resistance Experiment

[0117] Add a certain amount of NaCl to deionized water to prepare different salinities (2×10 4mg / L, 4×10 4 mg / L, 6×10 4 mg / L, 8×10 4 mg / L, 10×10 4 mg / L, 12×10 4 mg / L, 16×10 4 mg / L and 20×10 4 mg / L), a series of brines. Using the above series of brines, the gemini surfactants obtained in Examples 2 and 6 - 10 were respectively formulated into a series of surfactant aqueous solutions with a concentration of 1 wt%, and their dissolution conditions are shown in Table 2.

[0118] Table 2 Dissolution conditions of the gemini surfactants obtained in Examples 2 and 6 - 10 in a series of brines

[0119]

[0120] As can be seen from Table 2, when the concentration of NaCl in the system is 10×10 4 mg / L, except that the solution of Example 6 was turbid at room temperature, the gemini surfactants of Examples 2, 7 - 10 did not precipitate from the solution and showed good solubility.

[0121] Furthermore, at 50 °C, the interfacial tension between the above series of surfactant aqueous solutions and heavy oil was measured, and the results are as Figure 4 shown. It can be Figure 4 seen that: the oil - water interfacial tension of each example system first gradually decreased and reached the minimum value with the increase of the NaCl concentration, and then further increased with the increase of the NaCl concentration. Within the range of NaCl concentration used in this experiment, the oil - water interfacial tension of each example system could reach the lowest, indicating that there was an optimal salinity for the gemini surfactants of each example within the range of NaCl concentration used in this experiment; except that the optimal NaCl concentration of the gemini surfactant of Example 6 was 6×10 4 mg / L, the optimal NaCl concentrations of the gemini surfactants of Examples 2, 7 - 10 were all in the range of 8×10 4 ~12×10 4 mg / L; among them, the oil - water systems formed by the surfactants of Examples 2, 8 and 10 could reach an ultra - low interfacial tension (in the order of 10 -3 mN / m), and the anti - salt effect was the best.

[0122] Furthermore, a brine with a salinity of 10×10 4An aqueous solution of NaCl at mg / L, and different concentrations of inorganic salt CaCl2 (2000 mg / L, 4000 mg / L, 6000 mg / L, 8000 mg / L and 10000 mg / L) were added to obtain a series of Ca-containing 2+ brines. Using the above series of Ca-containing 2+ brines, the gemini surfactants prepared in Examples 2, 6-10 were respectively formulated into a series of surfactant-containing Ca 2+ aqueous solutions with a concentration of 1 wt%. At 50 °C, the interfacial tension between the above series of surfactant-containing Ca 2+ aqueous solutions and heavy oil was measured. The results are as Figure 5 shown. It can be Figure 5 seen that the increase in the concentration of inorganic salt CaCl2 has a significantly smaller effect on the oil-water interfacial tension of each example system than NaCl, but the addition of inorganic salt CaCl2 generally reduces the interfacial activity of each example system. As the concentration of CaCl2 in the solution increases, the oil-water interfacial tension of each example system generally shows a trend of gradually increasing with the increase in the concentration of CaCl2; the optimal CaCl2 concentration of the gemini surfactants prepared in Examples 2, 6-10 is between 2000 and 4000 mg / L. At this concentration, the interfacial tension is relatively the lowest. Although the ultra-low interfacial tension cannot be achieved, it still remains in the order of 10 -2 mN / m.

[0123] It can be seen from the above salt resistance experiment that the gemini surfactants prepared in Examples 2, 6-10 of the present invention have good salt resistance.

Claims

1. Preparation method of gemini surfactant for heavy oil exploitation, characterized in that, It includes the following steps: Dissolve ethylene glycol-based diol and p-toluenesulfonyl chloride in a tetrahydrofuran solvent, and carry out a substitution reaction under alkaline conditions so that the p-toluenesulfonyl group derived from the p-toluenesulfonyl chloride substitutes the hydroxyl group of the ethylene glycol-based diol to obtain Intermediate Ⅰ; Add nonylphenol and Intermediate Ⅰ into a mixed solvent of tetrahydrofuran and N,N-dimethylformamide, and carry out an etherification reaction under alkaline conditions so that two molecules of the nonylphenol are linked through Intermediate Ⅰ to obtain Gemini precursor Ⅱ; Mix an alkylphenol polyoxyethylene ether surfactant, Gemini precursor Ⅱ and an aqueous formaldehyde solution, and carry out a phenolic aldehyde condensation reaction under acidic conditions so that two molecules of the alkylphenol polyoxyethylene ether surfactant are linked through Gemini precursor Ⅱ to obtain a Gemini surfactant.

2. The preparation method of the gemini surfactant for heavy oil recovery according to claim 1, characterized in that, The ethylene glycol-based diol is selected from any one of ethylene glycol, diethylene glycol, triethylene glycol and tetraethylene glycol.

3. The preparation method of the gemini surfactant for heavy oil recovery according to claim 1, characterized in that, The alkylphenol polyoxyethylene ether surfactant is selected from any one of OP-6, OP-10, OP-15 and OP-20.

4. The preparation method of the gemini surfactant for heavy oil recovery according to claim 1, characterized in that, In the step of synthesizing Intermediate Ⅰ, the molar ratio of the ethylene glycol-based diol to the p-toluenesulfonyl chloride is 1:

2.

5. The preparation method of the gemini surfactant for heavy oil recovery according to claim 1 or 4, characterized in that, In the step of synthesizing Intermediate Ⅰ, the substitution reaction is carried out in an ice-water bath, the pH of the reaction solution is 13, and the reaction time is 7 h.

6. The preparation method of the gemini surfactant for heavy oil recovery according to claim 1, characterized in that, In the step of synthesizing Gemini precursor Ⅱ, the molar ratio of the nonylphenol to Intermediate Ⅰ is 2:1, and the volume ratio of tetrahydrofuran to N,N-dimethylformamide in the mixed solvent is 1:

9.

7. The preparation method of the gemini surfactant for heavy oil recovery according to claim 1 or 6, characterized in that, In the step of synthesizing Gemini precursor Ⅱ, the reaction temperature of the etherification reaction is 105 °C, the pH of the reaction solution is 13, the etherification reaction is carried out in a reflux manner, and the reflux time is 8 h.

8. The preparation method of the gemini surfactant for heavy oil recovery according to claim 1, characterized in that, In the step of synthesizing the Gemini surfactant, the molar ratio of the alkylphenol polyoxyethylene ether surfactant, Gemini precursor Ⅱ and formaldehyde is (2-4):1:(2-3).

9. The preparation method of the gemini surfactant for heavy oil recovery according to claim 1 or 8, characterized in that, In the step of synthesizing the Gemini surfactant, the reaction temperature of the phenolic aldehyde condensation reaction is 95-125 °C, the pH of the reaction solution is 3, and the reaction time is 6-12 h.

10. A Gemini surfactant for heavy oil recovery prepared by the preparation method according to any one of claims 1-9.

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