Oligomeric cationic surfactant as well as preparation method and application thereof

Abstract

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

Description

Technical Field

[0001] The invention belongs to the technical field of polymer surfactants, and specifically relates to an oligomeric cationic surfactant and a preparation method and application thereof. Background Art

[0002] In the process of oilfield exploitation, primary oil recovery is to exploit the oil and gas reservoir pressure, and secondary oil recovery is to use water injection to supplement the formation energy and reverse oil recovery. Primary and secondary oil recovery can generally only produce 10%-20% of crude oil reserves. A large amount of unexploited crude oil is scattered in the formation. Because the crude oil in the formation is difficult to gather, it is difficult to exploit, so tertiary oil recovery is required. In tertiary oil recovery, fracturing is to artificially fractur e the reservoir to create cracks. After fracturing, sand-carrying fluid needs to be injected. The sand-carrying fluid carries sand and gravel and fills the gravel into the cracks to prevent the gap from closing. The crude oil flows and accumulates in the cracks before being exploited.

[0003] Tertiary oil recovery is an important method for increasing oilfield production. Fracturing sand-carrying fluid is an important measure to improve the formation conductivity, which requires the sand-carrying fluid to have high viscosity and good temperature and salt resistance. Surfactant is an important fracturing fluid, which mainly forms worm-like micelles by self-assembling in water to increase the viscosity of the aqueous solution and achieve the purpose of sand-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 by them in the high temperature environment of the formation is reduced, which in turn leads to a decrease in the viscosity of the fracturing fluid, a decrease in sand carrying capacity, and a decrease in the tertiary oil recovery rate. Summary of the invention

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

[0006] The first aspect of the embodiments of the present application provides an oligomeric cationic surfactant having the following structural formula:

[0007]

[0008] Among them, n=1~10.

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

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

[0011] The tertiary amine intermediate, hydrochloric acid and epichlorohydrin react under the second reaction condition 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 the catalyst is 0.1%-0.5% of the sum of the masses 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 condition includes a reaction temperature of 60°C-80°C, a reaction time of 6h-12h and a pH of 4-5, and the molar ratio of the tertiary amine intermediate to the hydrochloride intermediate is 1:1-1.2.

[0016] The third aspect of the present application provides an application of an oligomeric cationic surfactant, comprising:

[0017] The oligomeric cationic surfactant is mixed with water to prepare an aqueous solution;

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

[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 aqueous solution and the sand particles are mixed in a ratio of 70:30-50:50.

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

[0023] Beneficial effects of this application:

[0024] The oligomeric cationic surfactant of the present application has a hydrophilic quaternary ammonium salt structure and a hydrophobic alkyl carbon chain structure, so the oligomeric cationic surfactant exhibits the performance of reducing surface tension, and the polymer molecules cross-link and entangle in water, so that the aqueous solution has a certain viscosity, and 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. When the temperature rises, the worm-like micelles are destroyed and the viscosity decreases rapidly. However, the oligomeric cationic surfactants of the present application are dissolved in water to form a viscous liquid, and the polymer molecules form stable chemical bonds through chemical reactions. When the temperature rises, the chemical bonds can exist stably, and the cross-linking and entanglement between the polymers is not destroyed, which has better temperature resistance.

[0026] Furthermore, the oligomeric cationic surfactant of the present application has a hydrophilic quaternary ammonium salt structure and a hydrophobic alkyl carbon chain structure. The hydrocarbon long chain structure has a tendency to escape from the water phase and enter the oil phase. The hydrophilic structure of the quaternary ammonium salt dissolves in the water phase, reducing the cohesion of the two phases at the oil-water interface, thereby reducing the oil-water interfacial tension and having a certain oil displacement effect.

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

[0028] In order to enable those skilled in the art to understand the characteristics and effects of the present invention, the following is a general description and definition of the terms and expressions mentioned in the specification and claims. Unless otherwise specified, all technical and scientific terms used in the text are the common meanings understood by those skilled in the art for the present invention. In the event of a conflict, the definition in this specification shall prevail.

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

[0030] Herein, all features such as values, quantities, contents and concentrations defined in the form of numerical ranges or percentage ranges are for simplicity and convenience only. Accordingly, the description of numerical ranges or percentage ranges should be considered to have included and specifically disclosed all possible secondary ranges and individual values ​​within the range (including integers and fractions).

[0031] In this document, in order to make the description concise, not all possible combinations of various technical features in various embodiments or examples are described. Therefore, as long as there is no contradiction in the combination of these technical features, the various technical features in various embodiments or examples can be combined arbitrarily, and all possible combinations should be considered to be within the scope of this specification.

[0032] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0033] The oligomeric cationic surfactant, the preparation and application of the oligomeric cationic surfactant provided in the present application are further described below in conjunction with specific examples.

[0034] The first aspect of the embodiments of the present application provides an oligomeric cationic surfactant having the following structural formula:

[0035]

[0036] Among them, n=1-10.

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

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

[0039] The tertiary amine intermediate, hydrochloric acid and epichlorohydrin react under the second reaction condition 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 expressed by the reaction equation as follows:

[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 the catalyst is 0.1% to 0.5% of the sum of the masses 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 condition includes a reaction temperature of 68°C-80°C, a reaction time of 6h-12h and a pH of 4-5, and the molar ratio of the tertiary amine intermediate to the hydrochloride intermediate is 1:1-1.2.

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

[0047] The oligomeric cationic surfactant is mixed with water to prepare a solution;

[0048] The solution is fully mixed with 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 oligomeric cationic surfactant to water is 3-10:1000. For example, the mass ratio of the oligomeric cationic 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 70:30-50:50, for example, the ratio of the solution to the sand particles is 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 the oligomeric cationic surfactant is described below in conjunction with specific examples.

[0054] Example 1

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

[0056] Then, 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 under normal pressure, and hydrochloric acid (220 g, 36.5% content, 2.2 mol) was slowly added dropwise to neutralize to a pH value of 5, and then epichlorohydrin (212.7 g, 2.3 mol) was added, and the second step reaction was carried out at 70°C for 10 hours to generate a hydrochloride intermediate;

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

[0058] Example 2

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

[0060] Then, 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 under normal pressure, and hydrochloric acid (200 g, 36.5% content, 2 mol) was slowly added dropwise to neutralize to a pH value of 5, and then epichlorohydrin (203.5 g, 2.2 mol) was added, and the second step reaction was carried out at 80°C for 9 hours to generate a hydrochloride intermediate;

[0061] Then, a tertiary amine intermediate (351 g, 1 mol) was added to the four-necked flask, and the reaction was continued at 80° C. for 8 h. After the reaction was completed, the product was a yellow to reddish brown viscous liquid, which was an oligomeric cationic surfactant.

[0062] Example 3

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

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

[0065] Then, a tertiary amine intermediate (351 g, 1 mol) was added to the four-necked flask, and the reaction was continued at 70° C. for 8 h. After the reaction was completed, the product was a yellow to reddish brown viscous liquid, which was an oligomeric cationic surfactant.

[0066] Example 4

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

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

[0069] Then, the tertiary amine intermediate (351 g, 1 mol) was added to the four-necked flask, and the reaction was continued at 70° C. for 6 h. After the reaction was completed, the product was a yellow to reddish brown viscous liquid, which was an oligomeric cationic surfactant.

[0070] Sand carrying performance test

[0071] The oligomeric cationic surfactants provided in the examples were used to perform surfactant aqueous solution thickening tests, and the viscosity, temperature resistance and interfacial tension of the aqueous solutions prepared by the surfactants were tested. The present application also provides a comparative example of hexadecyltrimethylammonium chloride, which is a widely used surfactant for fracturing.

[0072] The surfactant aqueous solution thickening experiment is specifically as follows: the oligomeric cationic surfactant provided in each embodiment and the comparative example hexadecyltrimethylammonium chloride are first diluted to 0.5% with clean water, and then fully dissolved at room temperature for 30 minutes, and finally the oil-water interfacial tension of each aqueous solution and the viscosity at different temperatures are tested. The specific performance test results are shown in Table 1.

[0073] Table 1 Performance test results

[0074]

[0075] As can be seen from Table 1, the viscosity of the 0.5% aqueous solution of the oligomeric cationic surfactant of the present application at room temperature of 25°C can reach above 60mPa.s, and the viscosity is maintained above 38mPa.s when heated to 70°C, which has a relatively high viscosity, and the oil-water interfacial tension of the aqueous solution can reach 10 -2 mN / m, with good interfacial tension. However, the viscosity of 0.5% aqueous solution of hexadecyltrimethylammonium chloride at room temperature of 25°C is only above 25.3mPa.s, and the viscosity is basically the same as that of water when heated to 70°C. Therefore, the oligomeric cationic surfactant of the present application has good thickening performance and temperature resistance, and can be used for oil field thickening and fracturing.

[0076] Although the present invention has been disclosed as above in the form of a preferred embodiment, it is not intended to limit the present invention. Anyone familiar with this technology can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be based on the definition of the claims.

Claims

1. An oligomeric cationic surfactant, characterized in that It has the following structural formula: Among them, n=1~10.

2. The method for preparing an oligomeric cationic surfactant according to claim 1, characterized in that: The preparation method comprises: The dimer acid and N,N-dimethylethanolamine react under the first reaction condition to generate a tertiary amine intermediate; The tertiary amine intermediate, hydrochloric acid and epichlorohydrin react under the second reaction condition to generate a hydrochloride intermediate; The tertiary amine intermediate reacts with the hydrochloride intermediate under a third reaction condition to generate an oligomeric cationic surfactant.

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°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 the catalyst is 0.1%-0.5% of the sum of the masses of dimer acid and N,N-dimethylethanolamine.

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° C.-80° C. and a reaction time of 6 h-12 h, 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° C.-80° C., a reaction time of 6 h-12 h, and a pH of 4-5, and a molar ratio of the tertiary amine intermediate to the hydrochloride intermediate of 1:1-1.

2.

6. An application of an oligomeric cationic surfactant, characterized in that: The applications include: The oligomeric cationic surfactant is mixed with water to prepare an aqueous solution; The aqueous solution is fully mixed with sand particles to form a sand-carrying liquid; The sand-carrying fluid is injected into the wellbore.

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

8. The use of an oligomeric cationic surfactant according to claim 6, characterized in that: The ratio of the aqueous solution to the sand particles when mixed is 70:30-50:

50.

9. The use of an oligomeric cationic surfactant according to claim 6, characterized in that: The concentration of the aqueous solution is 0.3%-1%.

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