A zwitterionic surfactant with double head and a preparation method and application thereof

Abstract

The application provides a double-head betaine surfactant and a preparation method and application thereof. The double-head betaine surfactant has the following structure shown in structural formula I: wherein 10<=n<=16, X is halogen, and M is Na or K. The double-head betaine surfactant compound connects two betaine structure groups at both ends of a chain alkyl group, is used for oil displacement agent, has small interfacial tension when being in contact with oil and water, can greatly reduce capillary action of a formation, and especially due to the carboxylate structure, has good wetting reverse performance, reduces adhesion work required for stripping crude oil, and improves oil washing efficiency.

Description

Technical Field

[0001] This invention relates to the field of chemical enhanced oil recovery in oilfields, and more specifically, to a bisbenzyl betaine surfactant, its preparation method, and its application. Background Technology

[0002] In current oil recovery processes, primary oil recovery relying on formation energy has a low recovery rate. Subsequent water injection significantly improves oil recovery, but prolonged water injection can lead to problems such as water contamination and flooding. To further stabilize and increase production, oilfields have adopted other tertiary oil recovery technologies, such as CO2 flooding, N2 flooding, chemical flooding, and biological flooding. In recent years, with the decline in international oil prices, major oilfields have reduced the drilling and production of new wells and focused more on tapping the potential of older wells. Chemical flooding has gained acceptance among major oilfields due to its low input-output ratio. After secondary oil recovery, the water cut is as high as 80% or more, and the oil saturation of the reservoir is reduced, with residual oil and blind-end oil being the majority. Secondly, due to the capillary force in low-permeability layers, the starting pressure is high, making water flooding difficult to reach; and water flow channels are formed in high-permeability layers. However, the application effect of chemical flooding alone is not significant. Therefore, tertiary oil recovery requires accurate understanding of the reservoir and water injection conditions, and the combined use of multiple chemical flooding technologies to achieve good production enhancement and ultimately maximize the input-output ratio.

[0003] Technologies to improve sweep efficiency include polymer flooding, gel flooding, and viscoelastic polymer microsphere flooding; technologies to improve oil washing efficiency include surfactant flooding, molecular membrane flooding, and microbial flooding. According to the principles of chemical flooding, both sweep efficiency and oil washing efficiency need to be improved simultaneously to significantly increase oil recovery. This is typically achieved by combining polymers and surfactants, or by combining gel flooding with surfactant flooding. However, these combined approaches are costly. Using only surfactant-based oil displacement agents could simplify the process and reduce operating costs. However, existing oil displacement agents are not ideal in reducing interfacial tension, and improvements in both sweep efficiency and oil washing efficiency are needed. Summary of the Invention

[0004] The main objective of this invention is to provide a bisbenzamine surfactant, its preparation method, and its application, in order to solve the problem of insufficient oil washing efficiency of existing oil displacement agents.

[0005] To achieve the above objectives, according to one aspect of the present invention, a bisbenzinetine surfactant is provided, which has the structure shown in structural formula I:

[0006]

[0007] Where 10≤n≤16, X is a halogen, and M is Na or K.

[0008] Furthermore, X is Cl or Br, and preferably the value range of n is 12≤n≤16.

[0009] According to another aspect of this application, a method for preparing the above-mentioned bisbenzyl betaine surfactant is provided, the method comprising: subjecting tetramethylalkyldiamine and haloacetate to a bimolecular nucleophilic substitution reaction under alkaline conditions to obtain the bisbenzyl betaine surfactant, wherein the haloacetate is a sodium salt or a potassium salt.

[0010] Furthermore, the molar ratio of tetramethylalkyldiamine to haloacetate is 1:2 to 1:2.3. Preferably, the bimolecular nucleophilic substitution reaction is carried out under conditions of pH 9 to 12. More preferably, alkaline conditions are formed by using an alkaline solution when carrying out the bimolecular nucleophilic substitution reaction. The alkaline solution is selected from any one or more of sodium hydroxide aqueous solution and potassium hydroxide aqueous solution. Even more preferably, the bimolecular nucleophilic substitution reaction is carried out at 60 to 90°C.

[0011] Furthermore, the above preparation method also includes: purifying the reaction solution after the nucleophilic reaction is completed, preferably the purification includes: adding acetone to the reaction solution to crystallize and obtain a crystalline product; washing and drying the crystalline product to obtain a purified bisbenzyl betaine surfactant.

[0012] According to another aspect of this application, an oil displacement agent is provided, comprising, by weight: 5-10 parts of bisbenzaline surfactant, 5-10 parts of alkylpropylhydroxysulfonyl betaine surfactant, 30-45 parts of alcohol, and 20-50 parts of water; wherein the bisbenzaline surfactant is any one or more of the aforementioned bisbenzaline surfactants.

[0013] Furthermore, the alkylpropyl hydroxysulfonyl betaine surfactant is any one or more compounds having the structure shown in Formula II below:

[0014]

[0015] Where 12≤m≤24.

[0016] Furthermore, the alcohol is a monohydric alcohol with 1 to 8 carbon atoms, preferably a monohydric alcohol with 2 to 4 carbon atoms.

[0017] According to another aspect of this application, the application of any of the above-mentioned oil displacement agents in the field of crude oil extraction is provided, the application comprising dispersing the oil displacement agent in formation water to form an oil displacement agent solution, wherein the formation water has a salinity of 10,000 to 150,000 mg / L and the mass concentration of the oil displacement agent in the oil displacement agent solution is 0.3% to 1.5%.

[0018] Furthermore, the viscosity of the oil displacement agent solution is 0–30 mPa·s, and the interfacial tension value is ≤0.01 mN / m.

[0019] Applying the technical solution of this invention, the bisaccharide betaine surfactant compound has two betaine-structured groups attached to both ends of the chain alkyl group. Used as an oil displacement agent, it exhibits low interfacial tension when in contact with oil and water, significantly reducing formation capillary action. In particular, its carboxylate structure provides excellent wetting reversal properties, reducing the adhesion work required to strip crude oil and improving washing efficiency. Simultaneously, this bisaccharide betaine surfactant possesses a certain thickening ability, increasing the water-oil mobility ratio and sweep efficiency. Therefore, when used as an oil displacement agent, it can significantly improve oil recovery. Furthermore, this bisaccharide betaine surfactant can inhibit corrosion of metal tubing by adsorbing and forming a film on metal surfaces. The strong polarity of the carboxyl groups in the molecule further increases the adsorption stability of the bisaccharide betaine surfactant molecules on metal surfaces, while the oriented arrangement of the central chain alkyl group forms a hydrophobic interfacial film, further enhancing its corrosion inhibition function. Detailed Implementation

[0020] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to embodiments and comparative examples.

[0021] As analyzed in the background section, existing technologies suffer from problems such as high surface tension of oil displacement agents and insufficient oil washing efficiency. To address this issue, this application provides a bis-headed betaine surfactant, its preparation method, and its application.

[0022] In a typical embodiment of this application, a bisbenzilate surfactant is provided, which has the structure shown in Formula I:

[0023]

[0024] Where 10≤n≤16, X is a halogen, and M is Na or K.

[0025] This bisaccharide betaine surfactant compound has two betaine groups attached to both ends of a chain alkyl group. Used as an oil displacement agent, it exhibits low interfacial tension when in contact with oil and water, significantly reducing formation capillary action. In particular, its carboxylate structure provides excellent wetting reversal properties, reducing the adhesion work required to strip crude oil and improving washing efficiency. Simultaneously, this bisaccharide betaine surfactant possesses thickening capabilities, increasing the water-to-oil mobility ratio and sweep efficiency. Therefore, when used as an oil displacement agent, it can significantly improve oil recovery. Furthermore, this bisaccharide betaine surfactant can inhibit corrosion of metal tubing by adsorbing and forming a film on metal surfaces. The strong polarity of the carboxyl groups in the molecule further increases the adsorption stability of the bisaccharide betaine surfactant molecule on metal surfaces, while the oriented alignment of the central chain alkyl group forms a hydrophobic interfacial film, further enhancing its corrosion inhibition function.

[0026] The halide ion X in the above-mentioned bisbenzitaine surfactant molecule can be any one of F, Cl, Br, and I. In some preferred embodiments of this application, X is Cl or Br. In the above structural formula I, n represents the number of methylene groups in the carbon chain between the two N atoms. In some preferred embodiments, 12 ≤ n ≤ 16, that is, n is 12, 13, 14, 15, or 16. When n is the above value, the corresponding bisbenzitaine surfactant, when used as an oil displacement agent, has a smaller interfacial tension when in contact with oil and water, which can further improve the oil washing efficiency.

[0027] In another typical embodiment of this application, a method for preparing the above-mentioned bisbenzyl betaine surfactant is provided. The method includes: subjecting tetramethylalkyldiamine and haloacetate to a bimolecular nucleophilic substitution reaction under alkaline conditions to obtain the bisbenzyl betaine surfactant, wherein the haloacetate is a sodium salt or a potassium salt.

[0028] The bis-terminated betaine surfactant obtained by this preparation method has two betaine-structured groups attached to both ends of the chain alkyl group. Used as an oil displacement agent, it exhibits low interfacial tension when in contact with oil and water, significantly reducing formation capillary action. In particular, its carboxylate structure gives it excellent wetting reversal properties, reducing the adhesion work required to strip crude oil and improving oil washing efficiency. Simultaneously, this bis-terminated betaine surfactant has a certain thickening ability, increasing the water-oil mobility ratio and sweep efficiency. Therefore, this anionic bis-quaternary ammonium salt, when used as an oil displacement agent, can significantly improve oil recovery. On the other hand, this bis-terminated betaine surfactant can inhibit the corrosion of metal tubing by adsorbing and forming a film on the metal surface. Furthermore, the strong polarity of the carboxyl group in the molecule increases the adsorption stability of the bis-terminated betaine surfactant molecule on the metal surface, while the oriented arrangement of the central chain alkyl group forms a hydrophobic interfacial film, further enhancing its corrosion inhibition function.

[0029] The above preparation method is based on the Menschutkin reaction mechanism, which can be used to determine the reaction conditions. In some embodiments of this application, since one tetramethylalkyldiamine reacts with two molecules of haloacetate, the molar ratio of tetramethylalkyldiamine to haloacetate is 1:2 to 1:2.3. That is, the haloacetate is slightly in excess to ensure that the tertiary amine can be fully quaternized and reduce the formation of byproducts.

[0030] In some embodiments of this application, the bimolecular nucleophilic substitution reaction is carried out at a pH of 9–12, which facilitates the formation of the transition state and the target compound. For example, an alkaline solution is used to create alkaline conditions during the bimolecular nucleophilic substitution reaction, and the alkaline solution is selected from any one or more of aqueous sodium hydroxide and potassium hydroxide solutions. Preferably, the bimolecular nucleophilic substitution reaction is carried out at 60–90°C, which provides a suitable reaction rate and helps to improve the yield of the bis-betaine surfactant.

[0031] The bisbenzacetin surfactant prepared by the above method can be post-processed according to existing purification methods. In some embodiments of this application, the reaction solution after the nucleophilic reaction is completed is purified, preferably by: adding acetone to the reaction solution to crystallize and obtain a crystalline product; washing and drying the crystalline product to obtain the purified bisbenzacetin surfactant. It should be noted that acetone has lower solubility for the above-mentioned bisbenzacetin surfactant at low temperatures. Therefore, cooling the reaction solution, for example, to room temperature, before adding acetone, and ensuring that the added acetone is below room temperature, helps to improve the purification effect. Similarly, the crystalline product can be washed with low-temperature acetone. The washing method can be based on existing technology and will not be described in detail here.

[0032] In one typical embodiment of this application, an oil displacement agent is provided, comprising, by weight: 5-10 parts of bisbenzidine surfactant, 5-10 parts of alkylpropyl hydroxysulfonyl betaine surfactant, 30-45 parts of alcohol, and 20-50 parts of water; wherein the bisbenzidine surfactant is any one or more of the above-mentioned bisbenzidine surfactants.

[0033] The oil displacement agent provided in this application possesses excellent wetting reversal properties, ultra-low interfacial tension, reduces the adhesion work required for crude oil stripping, and improves oil washing efficiency. It also increases the water-oil mobility ratio and sweep efficiency, thus significantly improving oil recovery. The bis-capped betaine surfactant in this oil displacement agent can inhibit the corrosion of metal tubing by adsorbing and forming a film on the metal surface. Furthermore, the strong polarity of the carboxyl groups in the molecule increases the adsorption stability of the bis-capped betaine surfactant molecules on the metal surface, while the directional arrangement of the central chain alkyl groups forms a hydrophobic interfacial film, further enhancing its corrosion inhibition function. The alkylpropyl hydroxysulfonyl betaine surfactant contained in this oil displacement agent further reduces the interfacial tension between oil and water, and the alcohol in it can accelerate the oil-water interfacial equilibrium. Simultaneously, this oil displacement agent exhibits high temperature resistance, high salinity, and the ability to inhibit tubing corrosion. Compared to the complex process of using two or three oil displacement technologies, the operation process is greatly simplified by using this oil displacement agent, which can significantly reduce operating costs. Furthermore, the oil displacement agent provided in this application has a relatively simple composition, and only a few types of chemicals are needed to achieve the functions of improving crude oil recovery and corrosion inhibition, which helps to save operating and usage costs.

[0034] The alkylpropyl hydroxysulfonate betaine surfactant in this oil displacement agent can be selected from various alkylpropyl hydroxysulfonate betaine surfactants in the prior art. Adding it to the oil displacement agent can further reduce interfacial tension. In some embodiments of this application, the alkylpropyl hydroxysulfonate betaine surfactant is any one or more compounds having the structure shown in Formula II below, which has better performance and exerts a greater synergistic effect with the bis-headed betaine surfactant of this application.

[0035]

[0036] In the structural formula, 12≤m≤24, for example, m is 13, 14, 15, 16, 17, 18, 19, 20, 21 or 22.

[0037] The alcohol in the oil displacement agent can be selected from alcohols in the prior art. In some embodiments of this application, the alcohol is a monohydric alcohol with 1 to 8 carbon atoms, preferably a monohydric alcohol with 2 to 4 carbon atoms, such as ethanol, propanol, isopropanol, n-butanol, isobutanol, tert-butanol, and more preferably ethanol, isopropanol, and n-butanol.

[0038] The water in this oil displacement agent is used to dissolve the bis-betaine surfactant, which is beneficial for the mixing of the components to form a homogeneous solution. It can be obtained from tap water, distilled water or deionized water, preferably deionized water.

[0039] In one typical embodiment of this application, the application of any of the above-mentioned oil displacement agents in the field of crude oil extraction is provided. The application includes dispersing the oil displacement agent in formation water to form an oil displacement agent solution, wherein the salinity of the formation water is 10,000 to 150,000 mg / L, and the mass concentration of the oil displacement agent in the oil displacement agent solution is 0.3% to 1.5%.

[0040] The preparation method of this oil displacement agent solution is simple, which can significantly improve the oil recovery rate and inhibit tubing corrosion. At the same time, the operation process will be greatly simplified by using this oil displacement agent, which can significantly reduce operating costs. Furthermore, the oil displacement agent provided in this application has a relatively simple composition, using only a few types of chemicals to achieve the functions of improving oil recovery rate and corrosion inhibition, which is conducive to saving operating and usage costs.

[0041] In some embodiments of this application, the mass concentration of the oil displacement agent in the oil displacement agent solution is 0.6%–1.5%, 0.6%–1.2%, or 0.6%–0.9%, which has a high oil recovery rate and good corrosion inhibition function. Preferably, the mass concentration of the oil displacement agent in the oil displacement agent solution is 0.9%–1.5%, 0.6%–1.2%, or 0.9%–1.2%, and more preferably, the mass concentration of the oil displacement agent in the oil displacement agent solution is 1.2%–1.5%, which significantly improves the oil recovery rate and corrosion inhibition function.

[0042] In some embodiments of this application, by adjusting the above-mentioned mass concentration, the viscosity of the above-mentioned oil displacement agent solution is made to be 0-30 mPa·s, and the interfacial tension value is ≤0.01 mN / m. The oil displacement agent solution at this viscosity meets the injection viscosity requirements. Preferably, the viscosity of the oil displacement agent solution is 15-30 mPa·s, which has a better oil displacement effect.

[0043] The beneficial effects that this application can achieve will be further illustrated below with reference to embodiments and comparative examples.

[0044] The chemical reagents used in the embodiments of this application, such as tetradecyltetramethyldiamine, sodium chloroacetate, sodium bromoacetate, erucamide propyl hydroxysulfonate surfactant, oleamide propyl hydroxysulfonate surfactant, and cocamidopropyl hydroxysulfonate surfactant, were all purchased from Sinopharm Group.

[0045] In the following examples and comparative examples, the formation water salinity is 1×10⁻⁶. 4 ~15×10 4 mg / L, the simulated oil used was a mixture of formation crude oil and neutral refined oil in a 1:10 ratio. Performance testing was conducted according to the following method:

[0046] Interfacial tension test: According to SY / T 5370-2018 "Method for determination of surface and interfacial tension", the interfacial tension between the oil displacement agent aqueous solution and the formation crude oil was tested. The testing equipment used was a German dataphysis SVT20N, the test temperature was 60℃, and the rotation speed was 6000r / min.

[0047] Viscosity test: According to the method in Chapter 4 of GB / T 10247-2008 "Viscosity Measurement Method", the viscosity of different concentrations of oil displacement agent aqueous solutions prepared with formation water was tested by rotational viscosity measurement method.

[0048] Core Physical Simulation Displacement Test: The physical simulation displacement effect was tested according to the methods in Chapter 9 of SY / T 6424-2014 "Performance Test Methods for Composite Oil Displacement Systems". The cores used in the core physical simulation displacement test were artificial cores with dimensions of 4.5mm × 4.5mm × 300mm, permeability ≤ 10mD ≤ 100mD, and porosity approximately 17%. During the test, the cores were first dried, vacuum-saturated with water, and saturated with simulated oil at 60℃ for 48 hours. Then, water was injected at a rate of 1 mL / min to a water cut of 98%. Next, at a rate of 1 mL / min, a 1% displacement agent solution was injected at a volume greater than 1 PV. Finally, water was injected to a water cut of 98%, and the oil recovery rate was calculated.

[0049] Corrosion Inhibition Performance Test: The corrosion inhibition performance of the oil displacement agent solution was tested according to SY / T 5273-2014 "Performance Inhibitors and Evaluation Methods for Oilfield Produced Water Treatment". J55 or N80 coating material was selected, the test temperature was 60 degrees Celsius, the medium was a 0.5% oil displacement agent solution prepared from formation water, and the test duration was 96 hours for a static coating test. Based on the static coating test conditions, a dynamic coating test was conducted with a sample linear velocity of 0.5 m / s.

[0050] Example 1

[0051] 40 mL of a NaOH aqueous solution with a pH of 10 was added to a three-necked flask, followed by 20 g of dodecyltetramethyldiamine. The mixture was stirred until homogeneous. Then, 20 g of sodium chloroacetate was added to the flask, and the mixture was heated to 60 °C. After reacting for 6 hours, heating was stopped. After cooling to room temperature, 30 mL of acetone was added to the flask, and the mixture was stirred for half an hour. A white precipitate formed in the solution. The precipitate was filtered through a suction funnel and washed to obtain the white precipitate. The white crystals were dried in an oven at 60 °C to obtain 28 g of dodecyl dibenzene betaine surfactant.

[0052] Take 5g of the prepared dodecyl bibenzyl betaine surfactant and erucamide propyl hydroxysulfonyl betaine surfactant (molecular formula C 30 H60 5g of N2O5S, 45g of isopropanol, and 45g of deionized water were added to beakers and stirred until a light yellow oil displacement agent was obtained.

[0053] The above-mentioned oil displacement agent was mixed with formation water to prepare oil displacement agent solutions with concentrations of 0.3%, 0.6%, 0.9%, 1.2%, and 1.5%, respectively. The viscosity of the oil displacement agent solutions with different concentrations and their interfacial tension with the formation crude oil were tested, and the results are shown in Table 1.

[0054] Table 1

[0055] Concentration (wt%) 0.3％ 0.6％ 0.9％ 1.2％ 1.5％ <![CDATA[Interfacial tension (×10 -3 mN / m)]]> 5.8 4.2 3.1 3 1.3 Viscosity (mPa·s) 14 17 22 25 30

[0056] As shown in Table 1, the oil displacement agent can form an ultra-low interfacial tension with the formation crude oil within a concentration range of 0.3% to 1.5%, and the concentration range is relatively wide, which meets the requirements for the use of oil displacement agents. From the viscosity data, the oil displacement agent has a good thickening effect, which can improve the water-oil mobility ratio and thus expand the water drive sweep area.

[0057] The core physical simulation oil displacement experiment results provided in this embodiment show that the water flooding recovery rate is 42.5%; after the oil displacement agent is injected, the water cut decreases from 98% to 89%, and the volume decreases by 9%; the recovery rate increases to 60.2%, which is an increase in recovery rate of 17.7%.

[0058] Using the oil displacement agent solution with an oil displacement agent content of 0.6% in this embodiment, a dynamic plate-coating test was conducted on N80 steel sheets, and the test results are shown in Table 2.

[0059] Table 2

[0060]

[0061] Using the oil displacement agent solution with an oil displacement agent content of 0.6% in this embodiment, a static coating test was conducted on N80 steel sheets, and the test results are shown in Table 3.

[0062] Table 3

[0063]

[0064] As shown in Tables 2 and 3, the static corrosion inhibition rate of the oil displacement agent solution with a content of 0.6% for N80 coated tubing is higher than that of the dynamic corrosion inhibition rate of the oil displacement agent solution with a content of 0.6% in this embodiment. This is because, under dynamic conditions, the corrosion product film detaches, causing localized corrosion and leading to an increased corrosion rate. This indicates that the oil displacement agent provided in this embodiment not only improves crude oil recovery but also has good corrosion inhibition performance for tubing during use.

[0065] Example 2

[0066] 50 mL of a NaOH aqueous solution with a pH of 9 was added to a three-necked flask, followed by 20 g of hexadecyltetramethyldiamine. The mixture was stirred until homogeneous. Then, 24 g of sodium chloroacetate was added to the flask, and the mixture was heated to 80 °C for 3 hours. Heating was then stopped. After cooling to room temperature, 45 mL of acetone was added to the flask, and the mixture was stirred for half an hour. A white precipitate formed in the solution. The precipitate was filtered and washed using a suction funnel. The white crystals were dried in an oven at 60 °C to obtain 27 g of hexadecyl dibenzene betaine surfactant.

[0067] Take 10g of the prepared hexadecyl bicapsid betaine surfactant and erucamide propyl hydroxysulfonyl betaine surfactant (molecular formula C 30 H 60 10g of N2O5S, 40g of isopropanol, and 40g of deionized water were added to beakers and stirred until a light yellow oil displacement agent was obtained.

[0068] The oil displacement agent was prepared into aqueous solutions with formation water at concentrations of 0.3%, 0.6%, 0.9%, 1.2%, and 1.5%, respectively. The viscosity of the oil displacement agent solutions at different concentrations and their interfacial tension with the formation crude oil were tested, and the results are shown in Table 4.

[0069] Table 4

[0070] Concentration (wt%) 0.3％ 0.6％ 0.9％ 1.2％ 1.5％ <![CDATA[Interfacial tension (×10 -3 mN / m)]]> 10.4 8.6 4.2 3.0 1.9 Viscosity (mPa·s) 6 10 14 17 22

[0071] As shown in Table 4, the oil displacement agent can form an ultra-low interfacial tension with the formation crude oil in the concentration range of 0.6% to 1.5%. From the viscosity data, the oil displacement agent has a good thickening effect, which can improve the water-oil mobility ratio and thus expand the water drive sweep area.

[0072] The results of the core physical simulation oil displacement experiment using the oil displacement agent provided in Example 2 are as follows: the water flooding recovery rate is 39.4%; after the oil displacement agent is injected, the water cut decreases from 98% to 91%, a decrease of 7%; the recovery rate increases to 57.8%, an increase in recovery rate of 18.4%.

[0073] Using the oil displacement agent solution with an oil displacement agent content of 0.6% in this embodiment, a dynamic plate-hanging test was conducted on J55 steel sheets, and the test results are shown in Table 5.

[0074] Table 5

[0075]

[0076] Using the oil displacement agent solution with an oil displacement agent content of 0.6% in this embodiment, a static plate hanging test was conducted on J55 steel sheets, and the test results are shown in Table 6.

[0077] Table 6

[0078]

[0079] As shown in Tables 5 and 6, the oil displacement agent solution with a content of 0.6% in this embodiment showed good corrosion inhibition effect on both dynamic and static coating experiments of J55 coatings, thus exhibiting good corrosion inhibition performance on the tubing during use.

[0080] Example 3

[0081] 60 mL of a NaOH aqueous solution with a pH of 11 was added to a three-necked flask, followed by 20 g of tetradecyltetramethyldiamine. The mixture was stirred until homogeneous. Then, 25 g of sodium chloroacetate was added to the flask, and the mixture was heated to 70°C for 5 hours. Heating was then stopped. After cooling to room temperature, 40 mL of acetone was added to the flask, and the mixture was stirred for half an hour. A white precipitate formed in the solution. The precipitate was filtered through a suction funnel and washed to obtain the white precipitate. The white crystals were dried in an oven at 60°C to obtain 30 g of tetradecyl dibenzene betaine surfactant.

[0082] Take 8g of the prepared tetradecyl bicapsid betaine surfactant and oleamidopropyl hydroxysulfonyl betaine surfactant (molecular formula C...). 26 H 51 8g of N2O5S, 36g of ethanol, and 48g of deionized water were added to beakers and stirred until a pale yellow oil displacement agent was obtained.

[0083] The oil displacement agent provided in Example 3 was mixed with formation water to prepare aqueous solutions with concentrations of 0.3%, 0.6%, 0.9%, 1.2%, and 1.5%, respectively. The viscosity of the aqueous solutions of different concentrations of oil displacement agent and their interfacial tension with the formation crude oil were tested, and the results are shown in Table 7.

[0084] Table 7

[0085] Concentration (wt%) 0.3％ 0.6％ 0.9％ 1.2％ 1.5％ <![CDATA[Interfacial tension (×10 -3 mN / m)]]> 41 21 24 4.6 5 Viscosity (mPa·s) 3 7 11 16 20

[0086] As shown in Table 7, the concentration range of the oil displacement agent that forms an ultra-low interfacial tension with the formation crude oil is 1.2% to 1.5%. The oil displacement agent has a significant viscosity-enhancing effect, which can improve the water-oil mobility ratio and thus improve the sweep efficiency.

[0087] The results of the core physical simulation oil displacement experiment using the oil displacement agent provided in Example 3 showed that the water flooding recovery rate was 41.6%; after injecting the oil displacement agent, the water cut decreased from 98% to 90%, a decrease of 8%; the recovery rate increased to 58.8%, an increase of 17.2%. This also indicates that the range of ultra-low interfacial tension between the oil displacement agent provided in this example and the formation crude oil is too narrow. Because the bound water in the core can further dilute the oil displacement agent solution, the oil displacement effect of the oil displacement agent is greatly affected.

[0088] Example 4

[0089] 60 mL of a NaOH aqueous solution with a pH of 9 was added to a three-necked flask, followed by 20 mL of dodecyltetramethyldiamine. The mixture was stirred until homogeneous. Then, 23 g of sodium chloroacetate was added to the flask, and the mixture was heated to 70°C for 5 hours. Heating was then stopped. After cooling to room temperature, 40 mL of acetone was added to the flask, and the mixture was stirred for half an hour. A white precipitate formed in the solution. The precipitate was filtered and washed using a suction funnel. The white crystals were dried in an oven at 60°C to obtain 27 g of dodecyl dibenzene betaine surfactant.

[0090] Take 6g of the prepared dodecyl bibenzyl betaine surfactant and cocamidopropyl hydroxysulfonyl betaine surfactant (molecular formula C... 20 H 42 6g of N2O5S), 38g of n-butanol, and 50g of deionized water were added to beakers and stirred until a pale yellow oil displacement agent was obtained.

[0091] The above-mentioned oil displacement agent was prepared into aqueous solutions with formation water at concentrations of 0.3%, 0.6%, 0.9%, 1.2%, and 1.5%, respectively. The viscosity of the aqueous solutions of different concentrations of oil displacement agent and their interfacial tension with the formation crude oil were tested, and the results are shown in Table 8.

[0092] Table 8

[0093]

[0094]

[0095] The results of the core physical simulation oil displacement experiment using the oil displacement agent provided in Example 4 are as follows: the water flooding recovery rate is 40.8%; after the oil displacement agent is injected, the water cut decreases from 98% to 87%, a decrease of 11%; the recovery rate increases to 55.9%, an increase in recovery rate of 15.1%.

[0096] Example 5

[0097] This embodiment provides an oil displacement agent comprising: 12g of hexadecyl dicapeptide betaine surfactant provided in Example 2, and cocamidopropyl hydroxysulfonate betaine surfactant (molecular formula C). 20 H 42 12g of N2O5S, 36g of n-butanol, and 48g of deionized water were added to beakers and stirred until homogeneous to obtain a pale yellow oil displacement agent.

[0098] The oil displacement agent was prepared into aqueous solutions with formation water at concentrations of 0.3%, 0.6%, 0.9%, 1.2%, and 1.5%, respectively. The viscosity of the aqueous solutions of different concentrations of oil displacement agent and their interfacial tension with the formation crude oil were tested, and the results are shown in Table 9.

[0099] Table 9

[0100] Concentration (wt%) 0.3％ 0.6％ 0.9％ 1.2％ 1.5％ <![CDATA[Interfacial tension (×10 -3 mN / m)]]> 20 16 9.3 7.5 6.8 Viscosity (mPa·s) 8 12 16 20 26

[0101] The results of the core physical simulation oil displacement experiment using the oil displacement agent provided in Example 5 are as follows: the water flooding recovery rate is 43.2%; after the oil displacement agent is injected, the water cut decreases from 98% to 87%, a decrease of 12%; the recovery rate increases to 59.1%, an increase in recovery rate of 15.9%.

[0102] Example 6

[0103] This embodiment provides an oil displacement agent comprising: 8g of the dodecyl bibenzyl betaine surfactant provided in Example 1, and oleamide propyl hydroxysulfonyl betaine surfactant (molecular formula C). 26 H 51 8g of N2O5S, 34g of ethanol and 50g of deionized water were added to beakers and stirred until a light yellow oil displacement agent was obtained.

[0104] The oil displacement agent was prepared into aqueous solutions with formation water at concentrations of 0.3%, 0.6%, 0.9%, 1.2%, and 1.5%, respectively. The viscosity of the aqueous solutions of different concentrations of oil displacement agent and their interfacial tension with the formation crude oil were tested, and the results are shown in Table 10.

[0105] Table 10

[0106] Concentration (wt%) 0.3％ 0.6％ 0.9％ 1.2％ 1.5％ <![CDATA[Interfacial tension (×10 -3 mN / m)]]> 6.3 5.7 4.6 4.3 2.8 Viscosity (mPa·s) 3 7 11 16 20

[0107] The results of the core physical simulation oil displacement experiment using the oil displacement agent provided in Example 6 are as follows: the water flooding recovery rate is 39.2%; after the oil displacement agent is injected, the water cut decreases from 98% to 92%, a decrease of 6%; the recovery rate increases to 57.4%, an increase in recovery rate of 18.2%.

[0108] Using the oil displacement agent provided in this embodiment, a dynamic coating test was conducted on J55 steel sheets. The test results are shown in Table 11.

[0109] Table 11

[0110]

[0111]

[0112] Using the oil displacement agent provided in this embodiment, a static coating test was conducted on J55 steel sheets. The test results are shown in Table 12.

[0113] Table 12

[0114]

[0115] As shown in Tables 11 and 12, the oil displacement agent solution with a content of 0.6% in this embodiment has good corrosion inhibition performance on J55 pads, indicating that the oil displacement agent solution has good anti-corrosion performance on the oil pipe during use.

[0116] Example 7

[0117] The difference from Example 2 is that, by weight, the oil displacement agent comprises: 5 parts of hexadecyl dicapeptide betaine surfactant, 10 parts of oleamide propyl hydroxysulfonate betaine surfactant, 45 parts of isopropanol, and 45 parts of deionized water.

[0118] The above-mentioned oil displacement agent was mixed with formation water to prepare oil displacement agent solutions with concentrations of 0.3%, 0.6%, 0.9%, 1.2%, and 1.5%, respectively. The viscosity of the oil displacement agent solutions with different concentrations and their interfacial tension with the formation crude oil were tested, and the results are shown in Table 13.

[0119] Table 13

[0120] Concentration (wt%) 0.3％ 0.6％ 0.9％ 1.2％ 1.5％ <![CDATA[Interfacial tension (×10 -3 mN / m)]]> 6.3 6.8 5.7 5.2 4.9 Viscosity (mPa·s) 10 16 20 24 32

[0121] The core physical simulation oil displacement experiment results provided in this embodiment show that the water flooding recovery rate is 42.3%; after the oil displacement agent is injected, the water cut decreases from 98% to 90.6%, a decrease of 7.4%; the recovery rate increases to 60%, an increase in recovery rate of 17.7%.

[0122] Example 8

[0123] The difference from Example 3 is that, by weight, the oil displacement agent comprises: 10 parts tetradecyl dicapeptide betaine surfactant, 5 parts erucamide propyl hydroxysulfonate betaine surfactant, 45 parts isopropanol, and 45 parts deionized water.

[0124] The above-mentioned oil displacement agent was mixed with formation water to prepare oil displacement agent solutions with concentrations of 0.3%, 0.6%, 0.9%, 1.2%, and 1.5%, respectively. The viscosity of the oil displacement agent solutions with different concentrations and their interfacial tension with the formation crude oil were tested, and the results are shown in Table 14.

[0125] Table 14

[0126] Concentration (wt%) 0.3％ 0.6％ 0.9％ 1.2％ 1.5％ <![CDATA[Interfacial tension (×10 -3 mN / m)]]> 13 8.4 7.1 6.8 6.6 Viscosity (mPa·s) 12 15 19 23 31

[0127] The core physical simulation oil displacement experiment results provided in this embodiment show that the water flooding recovery rate is 41%; after the oil displacement agent is injected, the water cut decreases from 98% to 89.5%, a decrease of 8.5%; the recovery rate increases to 57.3%, an increase in recovery rate of 16.3%.

[0128] Example 9

[0129] The difference from Example 3 is that sodium bromoacetate was used instead of sodium chloroacetate in the preparation of the tetradecyl dicapeptide surfactant, resulting in 30g of tetradecyl dicapeptide surfactant.

[0130] The above-mentioned oil displacement agent was mixed with formation water to prepare oil displacement agent solutions with concentrations of 0.3%, 0.6%, 0.9%, 1.2%, and 1.5%, respectively. The viscosity of the oil displacement agent solutions with different concentrations and their interfacial tension with the formation crude oil were tested, and the results are shown in Table 15.

[0131] Table 15

[0132] Concentration (wt%) 0.3％ 0.6％ 0.9％ 1.2％ 1.5％ <![CDATA[Interfacial tension (×10 -3 mN / m)]]> 5.3 5.0 4.7 4.5 3.8 Viscosity (mPa·s) 5 9 13 15 23

[0133] The core physical simulation oil displacement experiment results provided in this embodiment show that the water flooding recovery rate is 40.7%; after the oil displacement agent is injected, the water cut decreases from 98% to 88%, a decrease of 10%; the recovery rate increases to 60%, an increase in recovery rate of 19.3%.

[0134] Example 10

[0135] The difference from Example 1 is that, in preparing the dodecyl bibenzyl betaine surfactant, potassium hydroxide solution was used instead of sodium hydroxide solution, and potassium chloroacetate was used instead of sodium chloroacetate, resulting in 25g of dodecyl bibenzyl betaine surfactant.

[0136] The above-mentioned oil displacement agent was mixed with formation water to prepare oil displacement agent solutions with concentrations of 0.3%, 0.6%, 0.9%, 1.2%, and 1.5%, respectively. The viscosity of the oil displacement agent solutions with different concentrations and their interfacial tension with the formation crude oil were tested, and the results are shown in Table 16.

[0137] Table 16

[0138] Concentration (wt%) 0.3％ 0.6％ 0.9％ 1.2％ 1.5％ <![CDATA[Interfacial tension (×10 -3 mN / m)]]> 16 13 9.5 8.8 8.2 Viscosity (mPa·s) 3 6 11 14 19

[0139] The core physical simulation oil displacement experiment results provided in this embodiment show that the water flooding recovery rate is 41.6%; after the oil displacement agent is injected, the water cut decreases from 98% to 83.3%, a decrease of 14.7%; and the recovery rate increases to 55.9%, an increase of 14.3%.

[0140] Example 11

[0141] The difference from Example 2 is that the reaction temperature for preparing the hexadecyl dicapeptide betaine surfactant was 90°C, yielding 29g of hexadecyl dicapeptide betaine surfactant.

[0142] Comparative Example 1

[0143] The difference from Example 1 is that the oil displacement agent does not contain dodecyl dibenzyl betaine surfactant.

[0144] The above-mentioned oil displacement agent was mixed with formation water to prepare oil displacement agent solutions with concentrations of 0.3%, 0.6%, 0.9%, 1.2%, and 1.5%, respectively. The viscosity of the oil displacement agent solutions with different concentrations and their interfacial tension with the formation crude oil were tested, and the results are shown in Table 17.

[0145] Table 17

[0146] Concentration (wt%) 0.3％ 0.6％ 0.9％ 1.2％ 1.5％ <![CDATA[Interfacial tension (×10 -3 mN / m)]]> 80 75 76 68 67 Viscosity (mPa·s) 2 4 3 5 4

[0147] The core physical simulation oil displacement experiment results provided in this comparative example show that the water flooding recovery rate was 40.8%; after the oil displacement agent was injected, the water cut decreased from 98% to 94%, a decrease of 4%; and the recovery rate increased to 45.6%, an increase of 4.8%.

[0148] Using the oil displacement agent solution with an oil displacement agent content of 0.6% in this embodiment, N80 steel sheets were selected for dynamic plate hanging test, and the test results are shown in Table 18.

[0149] Table 18

[0150]

[0151] Using the oil displacement agent solution with a content of 0.6% as described in this comparative example, static coating tests were conducted on N80 steel sheets. The test results are shown in Table 19.

[0152] Table 19

[0153]

[0154] Comparative Example 2

[0155] The difference from Example 1 is that, by weight, the oil displacement agent comprises: 5 parts of dodecyl bibenzyl betaine surfactant, 2 parts of erucamide propyl hydroxysulfonyl betaine surfactant, 10 parts of isopropanol, and 10 parts of deionized water.

[0156] The above-mentioned oil displacement agent was mixed with formation water to prepare oil displacement agent solutions with concentrations of 0.3%, 0.6%, 0.9%, 1.2%, and 1.5%, respectively. The viscosity of the oil displacement agent solutions with different concentrations and their interfacial tension with the formation crude oil were tested, and the results are shown in Table 20.

[0157] Table 20

[0158] Concentration (wt%) 0.3％ 0.6％ 0.9％ 1.2％ 1.5％ <![CDATA[Interfacial tension (×10 -3 mN / m)]]> 38 36 36 32 32 Viscosity (mPa·s) 5 7 8 8 10

[0159] The core physical simulation oil displacement experiment results provided in this comparative example show that the water flooding recovery rate was 41.5%; after the oil displacement agent was injected, the water cut decreased from 98% to 92%, a decrease of 6%; the recovery rate increased to 48.9%, an increase of 7.4%.

[0160] Using the oil displacement agent solution with an oil displacement agent content of 0.6% in this embodiment, N80 steel sheets were selected for dynamic plate hanging test, and the test results are shown in Table 21.

[0161] Table 21

[0162]

[0163] Using the oil displacement agent solution with a content of 0.6% as described in this comparative example, static coating tests were conducted on N80 steel sheets. The test results are shown in Table 22.

[0164] Table 22

[0165]

[0166] Comparative Example 3

[0167] The difference from Example 1 is that, by weight, the oil displacement agent comprises: 15 parts of dodecyl bibenzyl betaine surfactant, 5 parts of erucamide propyl hydroxysulfonyl betaine surfactant, 45 parts of isopropanol, and 45 parts of deionized water.

[0168] The above-mentioned oil displacement agent was mixed with formation water to prepare oil displacement agent solutions with concentrations of 0.3%, 0.6%, 0.9%, 1.2%, and 1.5%, respectively. The viscosity of the oil displacement agent solutions with different concentrations and their interfacial tension with the formation crude oil were tested, and the results are shown in Table 23.

[0169] Table 23

[0170] Concentration (wt%) 0.3％ 0.6％ 0.9％ 1.2％ 1.5％ <![CDATA[Interfacial tension (×10 -3 mN / m)]]> 28 26 25 24 23 Viscosity (mPa·s) 12 16 19 23 30

[0171] The core physical simulation oil displacement experiment results provided in this comparative example show that the water flooding recovery rate was 42.1%; after the oil displacement agent was injected, the water cut decreased from 98% to 90%, a decrease of 8%; the recovery rate increased to 51.4%, an increase of 9.3%.

[0172] Comparative Example 4

[0173] The difference from Example 1 is that, by weight, the oil displacement agent comprises: 3 parts of dodecyl bibenzyl betaine surfactant, 5 parts of erucamide propyl hydroxysulfonyl betaine surfactant, 45 parts of isopropanol, and 45 parts of deionized water.

[0174] The above-mentioned oil displacement agent was mixed with formation water to prepare oil displacement agent solutions with concentrations of 0.3%, 0.6%, 0.9%, 1.2%, and 1.5%, respectively. The viscosity of the oil displacement agent solutions with different concentrations and their interfacial tension with the formation crude oil were tested, and the results are shown in Table 24.

[0175] Table 24

[0176] Concentration (wt%) 0.3％ 0.6％ 0.9％ 1.2％ 1.5％ <![CDATA[Interfacial tension (×10 -3 mN / m)]]> 15 13 13 8 6 Viscosity (mPa·s) 3 7 11 15 18

[0177] The core physical simulation oil displacement experiment results provided in this comparative example show that the water flooding recovery rate was 41.7%; after the oil displacement agent was injected, the water cut decreased from 98% to 93%, a decrease of 5%; the recovery rate increased to 52.7%, an increase of 11%.

[0178] Comparative Example 5

[0179] The difference from Example 1 is that, by weight, the oil displacement agent comprises: 5 parts of dodecyl bibenzyl betaine surfactant, 15 parts of erucamide propyl hydroxysulfonyl betaine surfactant, 45 parts of isopropanol, and 45 parts of deionized water.

[0180] The above-mentioned oil displacement agent was mixed with formation water to prepare oil displacement agent solutions with concentrations of 0.3%, 0.6%, 0.9%, 1.2%, and 1.5%, respectively. The viscosity of the oil displacement agent solutions with different concentrations and their interfacial tension with the formation crude oil were tested, and the results are shown in Table 25.

[0181] Table 25

[0182] Concentration (wt%) 0.3％ 0.6％ 0.9％ 1.2％ 1.5％ <![CDATA[Interfacial tension (×10 -3 mN / m)]]> 25 24 24 20 17 Viscosity (mPa·s) 10 14 17 19 20

[0183] The core physical simulation oil displacement experiment results provided in this comparative example show that the water flooding recovery rate was 41.4%; after the oil displacement agent was injected, the water cut decreased from 98% to 94%, a decrease of 4%; and the recovery rate increased to 47.9%, an increase of 6.5%.

[0184] Comparative Example 6

[0185] The difference from Example 1 is that the dodecyl bisbenzyl betaine surfactant in the oil displacement agent is replaced with n-hexylhexamethyldibromide.

[0186] The above-mentioned oil displacement agent was mixed with formation water to prepare oil displacement agent solutions with concentrations of 0.3%, 0.6%, 0.9%, 1.2%, and 1.5%, respectively. The viscosity of the oil displacement agent solutions with different concentrations and their interfacial tension with the formation crude oil were tested, and the results are shown in Table 26.

[0187] Table 26

[0188] Concentration (wt%) 0.3％ 0.6％ 0.9％ 1.2％ 1.5％ Interfacial tension (mN / m) 5 4 4 2 1 Viscosity (mPa·s) 2 3 3 5 5

[0189] The core physical simulation oil displacement experiment results provided in this comparative example show that the water flooding recovery rate was 42.8%; after the oil displacement agent was injected, the water cut decreased from 98% to 96%, a decrease of 3%; the recovery rate increased to 46.5%, an increase of 3.7%.

[0190] Using the oil displacement agent solution with an oil displacement agent content of 0.6% in this embodiment, N80 steel sheets were selected for dynamic plate hanging test, and the test results are shown in Table 27.

[0191] Table 27

[0192]

[0193] Using the oil displacement agent solution with a content of 0.6% as described in this comparative example, static coating tests were conducted on N80 steel sheets. The test results are shown in Table 28.

[0194] Table 28

[0195]

[0196] As can be seen from the above description, the embodiments of the present invention achieve the following technical effects: The oil displacement agent provided by this application has good wetting reversal performance, ultra-low interfacial tension, and can reduce the adhesion work required to strip crude oil, thereby improving the oil washing efficiency. It can also increase the water-oil mobility ratio and the sweep efficiency, thus significantly improving the oil recovery rate. The bisbenzyl betaine surfactant in this oil displacement agent can inhibit the corrosion of metal tubing by adsorbing and forming a film on the metal surface. Furthermore, the strong polarity of the carboxyl groups in the molecule increases the adsorption stability of the bisbenzyl betaine surfactant molecules on the metal surface, while the directional arrangement of the central chain alkyl groups forms a hydrophobic interfacial film, further enhancing its corrosion inhibition function. Meanwhile, the oil displacement agent contains alkylpropyl hydroxysulfonate betaine surfactant to further reduce the surface tension of the oil, and the alcohol in it can accelerate the oil-water interface equilibrium. Overall, it has the characteristics of high temperature resistance and high salinity, and can also inhibit the corrosion of oil pipes. Compared with the complex process of using two or three oil displacement technologies, the operation process will be greatly simplified when using this oil displacement agent, which can significantly reduce operating costs. In addition, the oil displacement agent provided in this application has a relatively simple composition, and only a few types of chemicals are needed to achieve the functions of improving crude oil recovery and corrosion inhibition, which is conducive to saving operating and usage costs.

[0197] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An oil displacement agent, characterized in that, The oil displacement agent comprises, by weight, 5-10 parts of bisbenzyl betaine surfactant, 5-10 parts of alkylpropyl hydroxysulfonyl betaine surfactant, 30-45 parts of alcohol, and 20-50 parts of water; The bicapsulated betaine surfactant has the structure shown in Formula I: Structural Formula I Where 12≤n≤16, X is Cl or Br, and M is Na or K.

2. The oil displacement agent according to claim 1, characterized in that, The alkylpropyl hydroxysulfonyl betaine surfactant is any one or more compounds having the structure shown in Formula II below: Structural Formula II Where 12≤m≤24.

3. The oil displacement agent according to claim 1, characterized in that, The alcohol is a monohydric alcohol with 1 to 8 carbon atoms.

4. The oil displacement agent according to claim 1, characterized in that, The alcohol is a monohydric alcohol with 2 to 4 carbon atoms.

5. The oil displacement agent according to claim 1, characterized in that, The preparation method of the bicapsulated betaine surfactant includes: Tetramethylalkyldiamine and haloacetate were subjected to a bimolecular nucleophilic substitution reaction under alkaline conditions to obtain the bisbenzyl betaine surfactant, wherein the haloacetate was a sodium or potassium salt.

6. The oil displacement agent according to claim 5, characterized in that, The molar ratio of the tetramethylalkyldiamine to the haloacetate is 1:2 to 1:2.

3.

7. The oil displacement agent according to claim 5, characterized in that, The bimolecular nucleophilic substitution reaction was carried out at a pH of 9–12.

8. The oil displacement agent according to claim 5, characterized in that, The alkaline conditions are formed by using an alkaline solution during the bimolecular nucleophilic substitution reaction. The alkaline solution is selected from any one or more of sodium hydroxide aqueous solution and potassium hydroxide aqueous solution.

9. The oil displacement agent according to claim 5, characterized in that, The bimolecular nucleophilic substitution reaction was carried out at 60–90 °C.

10. The oil displacement agent according to claim 5, characterized in that, The preparation method further includes purifying the reaction solution after the nucleophilic reaction is completed.

11. The oil displacement agent according to claim 10, characterized in that, The purification includes: Acetone was added to the reaction solution to induce crystallization, yielding a crystalline product. The crystalline product was washed and dried to obtain purified bisbenzyl betaine surfactant.

12. The application of the oil displacement agent according to any one of claims 1 to 11 in the field of crude oil extraction, characterized in that, The application includes dispersing the oil displacement agent in formation water to form an oil displacement agent solution, wherein the formation water has a salinity of 10,000 to 150,000 mg / L and the mass concentration of the oil displacement agent in the oil displacement agent solution is 0.3% to 1.5%.

13. The application according to claim 12, characterized in that, The viscosity of the oil displacement agent solution is 0~30 mPa·s, and the interfacial tension value is ≤0.01 mN / m.

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