Oligomeric cationic surfactants, processes for their preparation and use

Abstract

The application relates to the technical field of polymer surfactants, in particular to an oligomeric cationic surfactant and a preparation method and application thereof. The preparation method of the oligomeric cationic surfactant comprises the following steps: dimer acid and N,N-dimethylethanolamine are reacted under first reaction conditions to generate a tertiary amine intermediate; the tertiary amine intermediate, hydrochloric acid and epichlorohydrin are reacted under second reaction conditions to generate a hydrochloride intermediate; and the tertiary amine intermediate and the hydrochloride intermediate are reacted under third reaction conditions to generate the oligomeric cationic surfactant. The oligomeric cationic surfactant has a hydrophilic quaternary ammonium salt structure and a hydrophobic alkyl carbon chain structure, forms a viscous liquid with viscoelasticity after being dissolved in water, and can be used as a viscoelastic surfactant to carry sand for fracturing operations.

Description

Technical Field

[0001] This invention belongs to the field of polymeric surfactant technology, specifically relating to an oligomeric cationic surfactant, its preparation method, and its application. Background Technology

[0002] In oilfield development, primary recovery utilizes reservoir pressure for extraction, while secondary recovery uses water injection to replenish formation energy and recover oil via reverse flow. Primary and secondary recovery typically only extract 10%-20% of the crude oil reserves, leaving a large amount of unextracted crude oil dispersed within the formation. Because crude oil in the formation is difficult to accumulate, extraction is challenging, necessitating tertiary recovery. In tertiary recovery, fracturing is a method of artificially creating fractures in the reservoir. After fracturing, proppant-carrying fluid is injected. This fluid carries sand and gravel, filling the fractures to prevent closure. The crude oil then flows and accumulates within the fractures before being extracted.

[0003] Tertiary oil recovery is an important method for increasing oil production in oilfields. Fracturing fluid carrying proppant is a crucial measure to improve formation conductivity, requiring high viscosity and good temperature and salt resistance. Surfactants are an important type of fracturing fluid; they primarily increase the viscosity of the aqueous solution by self-assembling into worm-like micelles in water, thereby achieving proppant-carrying fracturing.

[0004] However, the surfactants currently used are generally small molecule structures. Small molecule surfactants have disadvantages such as large usage and poor temperature resistance. Due to the poor temperature resistance of small molecule surfactants, the length of the worm-like micelles formed under high formation temperature conditions is reduced, which in turn leads to a decrease in fracturing fluid viscosity, a decrease in sand carrying capacity, and a decrease in tertiary oil recovery rate. Summary of the Invention

[0005] The purpose of this application is to address the shortcomings of existing surfactants, such as poor temperature resistance, unstable viscosity, and poor sand-carrying capacity, by providing an oligomeric cationic surfactant, its preparation method, and its application. The embodiments of this application are implemented as follows:

[0006] A first aspect of this application provides an oligomeric cationic surfactant having the following structural formula:

[0007]

[0008] Where n = 1 to 10.

[0009] A second aspect of this application provides a method for preparing an oligomeric cationic surfactant, the method comprising:

[0010] Dimer acid and N,N-dimethylethanolamine react under the first reaction conditions to generate a tertiary amine intermediate;

[0011] The tertiary amine intermediate, hydrochloric acid, and epichlorohydrin react under the second reaction conditions to generate a hydrochloride intermediate;

[0012] The tertiary amine intermediate reacts with the hydrochloride intermediate under a third reaction condition to generate an oligomeric cationic surfactant.

[0013] In some embodiments, the first reaction conditions include a reaction temperature of 140°C-180°C, a reaction time of 4h-8h, and a catalyst of p-toluenesulfonic acid or potassium hydroxide, wherein the molar ratio of dimer acid to N,N-dimethylethanolamine is 1:2-2.4, and the amount of catalyst used is 0.1%-0.5% of the sum of the mass of dimer acid and N,N-dimethylethanolamine.

[0014] In some embodiments, the second reaction conditions include a reaction temperature of 68°C-80°C and a reaction time of 6h-12h, wherein the molar ratio of the tertiary amine intermediate, epichlorohydrin, and hydrochloric acid is 1:2-2.2:2-2.3.

[0015] In some embodiments, the third reaction conditions include a reaction temperature of 60°C-80°C, a reaction time of 6h-12h, and a pH of 4-5, wherein the molar ratio of the tertiary amine intermediate to the hydrochloride intermediate is 1:1-1.2.

[0016] A third aspect of this application provides an application of an oligomeric cationic surfactant, including:

[0017] Oligomeric cationic surfactants are mixed with water to prepare an aqueous solution;

[0018] The aqueous solution is thoroughly mixed with the sand particles to form a sand-carrying solution;

[0019] The sand-carrying fluid is injected into the wellbore.

[0020] In some embodiments, the mass ratio of the oligomeric cationic surfactant to water is 3-100:1000.

[0021] In some embodiments, the ratio of the aqueous solution to the sand particles is 70:30-50:50.

[0022] In some embodiments, the concentration of the aqueous solution is 0.3%-1%.

[0023] The beneficial effects of this application are:

[0024] The oligomeric cationic surfactant of this application has a hydrophilic quaternary ammonium salt structure and a hydrophobic alkyl carbon chain structure. Therefore, the oligomeric cationic surfactant exhibits the property of reducing surface tension. Furthermore, the polymer molecules cross-link and entangle in water, giving its aqueous solution a certain viscosity, which forms a viscous sand-carrying liquid after mixing with sand particles.

[0025] Furthermore, conventional VES fracturing fluids rely on molecular self-assembly to form worm-like micelles to increase viscosity. As temperature rises, these worm-like micelles are destroyed, causing a rapid decrease in viscosity. In contrast, the oligomeric cationic surfactant of this application dissolves in water to form a viscous liquid. The polymer molecules form stable chemical bonds through a chemical reaction. These chemical bonds remain stable even at elevated temperatures, and the cross-linking and entanglement between polymers are not disrupted, resulting in better temperature resistance.

[0026] Furthermore, the oligomeric cationic surfactant of this application has a hydrophilic quaternary ammonium salt structure and a hydrophobic alkyl carbon chain structure. The long hydrocarbon chain structure has a tendency to escape from the aqueous phase and enter the oil phase. The hydrophilic structure of the quaternary ammonium salt dissolves in the aqueous phase, reducing the cohesive force between the two phases at the oil-water interface. Therefore, it can reduce the interfacial tension between the oil and water and has a certain oil displacement effect.

[0027] Furthermore, the preparation mechanism of the oligomeric cationic surfactant of this application is clear, the reaction conditions are simple, and it is easy to scale up production. Detailed Implementation

[0028] To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

[0029] The theories or mechanisms described and disclosed herein, whether right or wrong, should not in any way limit the scope of the invention, that is, the contents of the invention can be implemented without being limited by any particular theory or mechanism.

[0030] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0031] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0032] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0033] The following specific embodiments further illustrate the oligomeric cationic surfactants provided in this application, their preparation, and their applications.

[0034] A first aspect of this application provides an oligomeric cationic surfactant having the following structural formula:

[0035]

[0036] Where n = 1 - 10.

[0037] A second aspect of this application provides a method for preparing an oligomeric cationic surfactant, the method comprising the following steps:

[0038] Dimer acid and N,N-dimethylethanolamine react under the first reaction conditions to generate a tertiary amine intermediate;

[0039] The tertiary amine intermediate, hydrochloric acid, and epichlorohydrin react under the second reaction conditions to generate a hydrochloride intermediate;

[0040] The tertiary amine intermediate reacts with the hydrochloride intermediate under a third reaction condition to generate an oligomeric cationic surfactant.

[0041] The above steps are represented by the following reaction equations:

[0042]

[0043] In some embodiments, the first reaction conditions include a reaction temperature of 140°C-180°C, a reaction time of 4h-8h, and a catalyst of p-toluenesulfonic acid or potassium hydroxide, wherein the molar ratio of dimer acid to N,N-dimethylethanolamine is 1:2-2.4, and the amount of catalyst used is 0.1% to 0.5% of the sum of the mass of dimer acid and N,N-dimethylethanolamine.

[0044] In some embodiments, the second reaction conditions include a reaction temperature of 68°C-80°C and a reaction time of 6h-12h, wherein the molar ratio of the tertiary amine intermediate, epichlorohydrin, and hydrochloric acid is 1:2-2.2:2-2.3.

[0045] In some embodiments, the third reaction conditions include a reaction temperature of 68°C-80°C, a reaction time of 6h-12h, and a pH of 4-5, wherein the molar ratio of the tertiary amine intermediate to the hydrochloride intermediate is 1:1-1.2.

[0046] A third aspect of this application provides an application of an oligomeric cationic surfactant, the application comprising:

[0047] Oligomeric cationic surfactants are mixed with water to prepare a solution;

[0048] The solution is thoroughly mixed with the sand particles to form a sand-carrying liquid;

[0049] The sand-carrying fluid is injected into the wellbore.

[0050] In some embodiments, the mass ratio of the oligopionic surfactant to water is 3-10:1000. For example, the mass ratio of the oligopionic surfactant to water is 3:1000, 5:1000, 7:1000, and 9:1000.

[0051] In some embodiments, the ratio of the solution to the sand particles is 70:30 to 50:50. For example, the ratios of the solution to the sand particles are 70:30, 60:40, and 50:50.

[0052] In some embodiments, the concentration of the aqueous solution is 0.3%-1%.

[0053] The preparation of oligomeric cationic surfactants is described below with reference to specific examples.

[0054] Example 1

[0055] First, dimer acid (Guangzhou Yuanda New Material Co., Ltd., 561g, 1mol) and N,N-dimethylethanolamine (213.6g, 2.4mol) were added to a small high-pressure reactor. Esterification reaction was carried out under the catalysis of p-toluenesulfonic acid (3.8g, 0.5%). The temperature in the reactor was 170℃, the pressure was 0.5MPa, and the reaction time was 8h, generating a tertiary amine intermediate.

[0056] Then, under normal pressure, the tertiary amine intermediate (351 g, 1 mol) and a methanol / water mixed solvent (mass ratio 2:2, 400 g) were added to a four-necked flask. Hydrochloric acid (220 g, 36.5% content, 2.2 mol) was slowly added dropwise to neutralize to pH 5. Then epichlorohydrin (212.7 g, 2.3 mol) was added, and the second step reaction was carried out at 70 °C for 10 h to generate the hydrochloride intermediate.

[0057] Then, add 351 g, 1 mol of tertiary amine intermediate to the four-necked flask and continue the reaction at 80 °C for 10 h. After the reaction is completed, the product is a yellow to reddish-brown viscous liquid, which is the oligomeric cationic surfactant.

[0058] Example 2

[0059] First, dimer acid (Guangzhou Yuanda New Material Co., Ltd., 561g, 1mol) and N,N-dimethylethanolamine (204.7g, 2.3mol) were added to a small high-pressure reactor. Esterification reaction was carried out under the catalysis of p-toluenesulfonic acid (3.0g, 0.4%). The temperature in the reactor was 160℃, the pressure was 0.5MPa, and the reaction time was 7h, generating a tertiary amine intermediate.

[0060] Then, under normal pressure, the tertiary amine intermediate (351 g, 1 mol) and a methanol / water mixed solvent (mass ratio 2:2, 400 g) were added to a four-necked flask. Hydrochloric acid (200 g, 36.5% content, 2 mol) was slowly added dropwise to neutralize to pH 5. Then epichlorohydrin (203.5 g, 2.2 mol) was added, and the second step reaction was carried out at 80 °C for 9 h to generate the hydrochloride intermediate.

[0061] Then, add 351 g, 1 mol of tertiary amine intermediate to the four-necked flask and continue the reaction at 80 °C for 8 h. After the reaction is complete, the product is a yellow to reddish-brown viscous liquid, which is the oligomeric cationic surfactant.

[0062] Example 3

[0063] First, dimer acid (Guangzhou Yuanda New Material Co., Ltd., 561g, 1mol) and N,N-dimethylethanolamine (195.8g, 2.2mol) were added to a small high-pressure reactor. Esterification reaction was carried out under the catalysis of p-toluenesulfonic acid (2.3g, 0.3%). The temperature in the reactor was 150℃, the pressure was 0.5MPa, and the reaction time was 8h, generating a tertiary amine intermediate.

[0064] Then, under normal pressure, the tertiary amine intermediate (351 g, 1 mol) and a mixed solvent of ethanol / water (mass ratio 3:1, total 400 g) were added to a four-necked flask. Hydrochloric acid (220 g, 36.5% content, 2.2 mol) was slowly added dropwise to neutralize to pH 5. Then epichlorohydrin (194.2 g, 2.1 mol) was added, and the second step reaction was carried out at 80 °C for 8 h to generate the hydrochloride intermediate.

[0065] Then, add 351 g, 1 mol of tertiary amine intermediate to the four-necked flask and continue the reaction at 70 °C for 8 h. After the reaction is complete, the product is a yellow to reddish-brown viscous liquid, which is the oligomeric cationic surfactant.

[0066] Example 4

[0067] First, dimer acid (Guangzhou Yuanda New Material Co., Ltd., 561g, 1mol) and N,N-dimethylethanolamine (178g, 2.0mol) were added to a small high-pressure reactor. Esterification reaction was carried out under the catalysis of p-toluenesulfonic acid (1.5g, 0.2%). The temperature in the reactor was 140℃, the pressure was 0.5MPa, and the reaction time was 6h, generating a tertiary amine intermediate.

[0068] Then, under normal pressure, the tertiary amine intermediate (351 g, 1 mol) and a mixed solvent of isopropanol / water (mass ratio 2:2, total 400 g) were added to a four-necked flask. Hydrochloric acid (200 g, 36.5% content, 2 mol) was slowly added dropwise to neutralize to pH 5. Then epichlorohydrin (185 g, 2 mol) was added, and the second step reaction was carried out at 70 °C for 7 h to generate the hydrochloride intermediate.

[0069] Then, add 351 g, 1 mol of tertiary amine intermediate to the four-necked flask and continue the reaction at 70 °C for 6 h. After the reaction is complete, the product is a yellow to reddish-brown viscous liquid, which is the oligomeric cationic surfactant.

[0070] Sand-carrying performance test

[0071] Thickening tests were conducted on aqueous solutions of surfactants using the oligomeric cationic surfactants provided in the examples. The viscosity, temperature resistance, and interfacial tension of the aqueous solutions prepared with each surfactant were tested. This application also includes a comparative example, hexadecyltrimethylammonium chloride, which is a widely used surfactant for fracturing.

[0072] The thickening experiment of surfactant aqueous solutions was conducted as follows: First, the oligomeric cationic surfactants provided in each example and the comparative cetyltrimethylammonium chloride were diluted with water to 0.5%, then fully dissolved at room temperature for 30 minutes. Finally, the oil-water interfacial tension and viscosity at different temperatures were tested for each aqueous solution. The specific performance test results are shown in Table 1.

[0073] Table 1 Performance Test Results

[0074]

[0075] As shown in Table 1, the oligomeric cationic surfactant of this application has a viscosity of over 60 mPa·s in a 0.5% aqueous solution at room temperature (25°C), and maintains a viscosity of over 38 mPa·s when heated to 70°C, exhibiting high viscosity. Its aqueous solution also has an oil-water interfacial tension of up to 10. -2 The viscosity of hexadecyltrimethylammonium chloride (HMC) is mN / m, exhibiting good interfacial tension. In contrast, a 0.5% aqueous solution of hexadecyltrimethylammonium chloride at 25°C has a viscosity of only 25.3 mPa·s or higher, and its viscosity is essentially the same as water when heated to 70°C. Therefore, the oligomeric cationic surfactant of this application possesses good thickening and temperature resistance properties, making it suitable for use in oilfield thickening and fracturing.

[0076] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Anyone skilled in the art can make various modifications and alterations without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be determined by the claims.

Claims

1. An oligo-cationic surfactant, characterized in that, It has the following structural formula: Wherein, n = 1 ~ 10.

2. The method for preparing an oligomeric cationic surfactant according to claim 1, characterized in that, The preparation method comprises: Step 1, dimer acid and N, N-dimethyl ethanolamine are reacted under first reaction conditions to generate a tertiary amine intermediate; Step 2, the tertiary amine intermediate, hydrochloric acid and epichlorohydrin are reacted under second reaction conditions to generate a hydrochloride intermediate; Step 3, the tertiary amine intermediate and the hydrochloride intermediate are reacted under third reaction conditions to generate an oligomeric cationic surfactant; The reaction equation of step 1 is: The reaction equation of step 2 is The reaction equation of step 3 is:

3. The method for preparing an oligomeric cationic surfactant according to claim 2, characterized in that, The first reaction conditions include a reaction temperature of 140℃-180℃, a reaction time of 4h-8h, and a catalyst of p-toluenesulfonic acid or potassium hydroxide, wherein the molar ratio of dimer acid and N, N-dimethyl ethanolamine is 1:2-2.4, and the catalyst is used in an amount of 0.1%-0.5% of the sum of the mass of dimer acid and N, N-dimethyl ethanolamine.

4. The method for preparing an oligomeric cationic surfactant according to claim 2, characterized in that, The second reaction conditions include a reaction temperature of 68℃-80℃ and a reaction time of 6h-12h, wherein the molar ratio of the tertiary amine intermediate, epichlorohydrin and hydrochloric acid is 1:2-2.2:2-2.

3.

5. The method for preparing an oligomeric cationic surfactant according to claim 2, characterized in that, The third reaction conditions include a reaction temperature of 60℃-80℃, a reaction time of 6h-12h, and a pH of 4-5, and the molar ratio of the tertiary amine intermediate and the hydrochloride intermediate is 1:1-1.

2.

6. Use of an oligocationic surfactant according to claim 1, characterized in that, The application comprises: The oligomeric cationic surfactant is mixed with water to prepare an aqueous solution; The aqueous solution is mixed with sand particles to form a sand-carrying fluid; The sand-carrying fluid is injected into a wellbore.

7. Use of an oligocationic surfactant according to claim 6, characterised in that, The mass ratio of the oligomeric cationic surfactant to water is 3-100:1000.

8. Use of an oligocationic surfactant according to claim 6, characterised in that, The ratio of the aqueous solution to the sand particles when mixed is 70:30-50:

50.

9. Use of an oligocationic surfactant according to claim 6, characterised in that, The concentration of the aqueous solution is 0.3%-1%.

Images