High-temperature-resistant and anti-shearing oil-base-free clean fracturing fluid and preparation method thereof

Abstract

The invention relates to the technical field of fracturing fluid materials, in particular to high-temperature-resistant and anti-shearing oil-base-free clean fracturing fluid and a preparation method thereof. Each liter of the oil-base-free clean fracturing fluid comprises the following raw materials: 2.5-6 g of a modified quaternary ammonium salt surfactant, 1-5 g of low-carbon alcohol, 3-5.5 g of counter ion salt and the balance of water. The oil-base-free clean fracturing fluid prepared by the preparation method disclosed by the invention is further improved in high-temperature resistance and shear resistance, also has good antibacterial performance and excellent applicability, and is oil-base-free and more environment-friendly.

Description

Technical Field

[0001] The present invention relates to the technical field of fracturing fluid materials, and particularly relates to a high-temperature resistant and shear-resistant oil-free clean fracturing fluid and a preparation method thereof. Background Art

[0002] With the continuous growth of global energy demand, petroleum engineering, as an important field of energy exploitation, the development and innovation of its technologies are particularly crucial. And fracturing technology, as an important technology, is widely used in oil and gas well exploitation. By injecting fracturing fluid into the formation, the fractures in the formation are enlarged and new fractures are created and filled with proppants, thereby improving the permeability of the formation. With the continuous development of fracturing technology and environmental protection requirements, more and more new types of fracturing fluids have been developed. The commonly used fracturing fluids in the prior art mainly include oil-based fracturing fluids, water-based fracturing fluids, active fracturing fluids, and foam fracturing fluids, etc. Among them, oil-based fracturing fluids are fracturing fluids prepared with oil as a solvent or dispersion medium, and have extremely high advantages in high-temperature resistance. However, in the current situation where more attention is paid to environmental protection, due to the easy pollution of the formation and environment caused by the oil phase residue, oil-free and cleaner fracturing fluids have gradually developed.

[0003] Clean fracturing fluid is a low-viscosity cationic gelling fluid formed by adding surfactants to brine. The invention patent CN116622361B discloses a clean fracturing fluid composition, a clean fracturing fluid, a preparation method thereof and an application. The clean fracturing fluid composition disclosed in this invention includes erucyl propyl dimethylamine, amino acids, sodium erucyl acyl amino acid, and erucyl amide propyl betaine. Through compounding, each component crosslinks with each other to form a surfactant system based on a supramolecular structure, so that while each component fully exerts its effect, a synergistic effect is generated, making the fracturing fluid system have excellent viscoelastic properties, stability properties, rheological properties, and shear resistance properties. However, the amino acids used in its compounding may decompose at high temperatures, which will further lead to poor high-temperature resistance of the composition, greatly limiting its practical application. Summary of the Invention

[0004] Aiming at the defects of the prior art, the present invention discloses a high-temperature resistant and shear-resistant oil-free clean fracturing fluid and a preparation method thereof. The high-temperature resistance performance and shear resistance performance of the oil-free clean fracturing fluid prepared by the present invention are further improved, and it also has good antibacterial properties, excellent applicability, and is oil-free and more environmentally friendly.

[0005] In order to achieve the above object, the technical scheme adopted by the present invention is as follows:

[0006] The first aspect of the present invention provides a high-temperature resistant and shear-resistant oil-free clean fracturing fluid. Each liter of the oil-free clean fracturing fluid contains the following raw materials: 2.5 - 6 g of a modified quaternary ammonium salt surfactant, 1 - 5 g of a lower alcohol, 3 - 5.5 g of an anti-ion salt, and the balance of water.

[0007] In some embodiments of the present invention, the preparation steps of the modified quaternary ammonium salt surfactant are as follows:

[0008] (1) Add alkylphenol and dibromoalkane to absolute ethanol, then add a catalyst, heat to 60 - 70 °C, react for 1 - 2 h, then add the secondary aminoalkane compound, and stir and react at 80 - 90 °C for 2 - 4 h. After washing, an intermediate product is obtained;

[0009] (2) Dissolve the intermediate product of step (1) and chlorosulfonic acid in absolute dichloromethane and mix. React at 25 - 30 °C for 8 - 12 h. After neutralization, drying, washing, filtration and recrystallization, a modified quaternary ammonium salt surfactant is obtained.

[0010] In some embodiments of the present invention, the dibromoalkane in step (1) is dibromoethane or dibromobutane.

[0011] Preferably, the alkylphenol is nonylphenol.

[0012] In some embodiments of the present invention, the mass ratio of alkylphenol, dibromoalkane and secondary aminoalkane compound in step (1) is 1:(2 - 3):(0.8 - 1.5).

[0013] Preferably, the mass ratio of alkylphenol, dibromoalkane and secondary aminoalkane compound in step (1) is 1:2.5:1.2.

[0014] In some embodiments of the present invention, the mass ratio of the intermediate product and chlorosulfonic acid in step (2) is 1:(2 - 3.5).

[0015] Preferably, the mass ratio of the intermediate product and chlorosulfonic acid in step (2) is 1:3.

[0016] Preferably, the catalyst in step (1) is triethylamine or sodium hydroxide.

[0017] In some embodiments of the present invention, the preparation steps of the secondary aminoalkane compound in step (1) are as follows:

[0018] Add monobromoalkane and triethylenetetramine to absolute ethanol and mix. Stir and react at 80 - 90 °C for 8 - 10 h. After filtration, neutralization, washing and recrystallization, the secondary aminoalkane compound is obtained.

[0019] In some embodiments of the present invention, the mass ratio of monobromoalkane and triethylenetetramine is (0.7 - 1):1.

[0020] Preferably, the mass ratio of monobromoalkane and triethylenetetramine is 0.8:1.

[0021] Preferably, the bromoalkane is 1-bromotetradecane or 1-bromohexadecane.

[0022] More preferably, the bromoalkane is 1-bromotetradecane.

[0023] In the present invention, an oil-free clean fracturing fluid is obtained by mixing a modified quaternary ammonium salt surfactant, a lower alcohol, and an anti-ion salt in water. Among them, the modified quaternary ammonium salt surfactant prepared in the present invention effectively improves the temperature resistance by introducing a benzene ring and a sulfonic acid group into the quaternary ammonium salt. At the same time, the phenolic hydroxyl group that may remain on the benzene ring also synergistically plays a better antibacterial role with the quaternary ammonium salt, which can effectively inhibit the growth of formation microorganisms, prevent the biofilm generated by microbial contamination from blocking the formation, avoid affecting the use effect of the oil-free clean fracturing fluid and the fracturing process, and improve the functionality of the oil-free clean fracturing fluid.

[0024] Specifically, in the present invention, a bromoalkane and triethylenetetramine are first used as raw materials to obtain a secondary aminoalkane compound through a substitution reaction, and then a dibromoalkane is added to substitute the active hydrogen on its secondary amino group, and at the same time, an alkylphenol with a specific number of carbon chains is linked to synthesize an intermediate product. Then, the intermediate product is mixed with chlorosulfonic acid for a sulfonation reaction to obtain the final product, namely a modified quaternary ammonium salt surfactant. This modified quaternary ammonium salt surfactant simultaneously introduces a phenyl group and a sulfonic acid group, greatly enhancing the temperature resistance performance.

[0025] In the preparation process of the present invention, by controlling the introduction length of the functional chain segment, the phenomenon of loose molecular structure caused by the possible curling and folding of the molecular chain on the modified quaternary ammonium salt surfactant is avoided. When it is added to the oil-free fracturing fluid system, it can form a stable micelle structure, greatly improving the cohesive force, further enhancing the self-healing ability and anti-shearing performance of the modified quaternary ammonium salt surfactant, avoiding the adverse effect on the anti-shearing performance of the system when it is added to the oil-free clean fracturing fluid, and enabling the fracturing fluid to still exhibit good viscosity retention and temperature resistance at high temperatures, meeting the application requirements.

[0026] In some embodiments of the present invention, the lower alcohol is at least one of n-octanol, n-decanol, or 2-decanol.

[0027] Preferably, the lower alcohol is n-decanol.

[0028] In some embodiments of the present invention, the anti-ion salt is salicylate.

[0029] Preferably, the salicylate is sodium salicylate.

[0030] On the other hand, the present invention also provides a preparation method of an oil-free clean fracturing fluid with high temperature resistance and anti-shearing performance, comprising the following steps:

[0031] Mix the modified quaternary ammonium salt surfactant and lower alcohol, add them to water, stir until homogeneous, then add the counterion salt and continue stirring until homogeneous to obtain the product.

[0032] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0033] (1) By mixing the modified quaternary ammonium salt surfactant, lower alcohol, and counterion salt and adding them to water, the present invention obtains an oil-free clean fracturing fluid, whose high-temperature resistance and shear resistance are further improved. At the same time, it also has good antibacterial properties, excellent applicability, is oil-free, and is more environmentally friendly.

[0034] (2) By introducing a benzene ring and a sulfonic acid group into the quaternary ammonium salt, the present invention effectively improves the temperature resistance of the modified quaternary ammonium salt surfactant. At the same time, the phenolic hydroxyl group that may remain on the benzene ring also synergistically plays a better antibacterial role with the quaternary ammonium salt, which can effectively inhibit the growth of formation microorganisms and avoid affecting the use effect of the oil-free clean fracturing fluid and the fracturing process, jointly improving the functionality of the oil-free clean fracturing fluid.

[0035] (3) During the preparation process, the present invention also controls the introduction length of the functional chain segment, avoiding the phenomenon of loose molecular structure caused by the coiling and folding of the molecular chain on the modified quaternary ammonium salt surfactant, and avoiding the adverse effect on the shear resistance of the system when it is added to the oil-free clean fracturing fluid, so that the fracturing fluid still shows good viscosity retention rate and temperature resistance under high-temperature conditions, meeting the application requirements. Specific Embodiments

[0036] The following will describe the present invention in combination with specific implementation examples. It should be noted that the following examples are examples of the present invention, only used to illustrate the present invention, and not to limit the present invention. At the same time, all professional terms mentioned below have the same meaning as commonly understood by those skilled in the art. The professional terms used in this article are only for the purpose of describing specific embodiments, and are not intended to limit the protection scope of the present invention. Other combinations and various improvements within the concept of the present invention can be made without departing from the main idea or scope of the present invention.

[0037] Unless otherwise specified, the reagents used below can be easily obtained from commercial companies.

[0038] Unless otherwise specified, the post-treatment steps such as "neutralization", "washing", "recrystallization", "drying", "filtration", etc. used below are conventional operations of those skilled in the art and can be selected according to actual operations.

[0039] Preparation Example 1

[0040] The preparation steps of the secondary aminoalkane compound are as follows:

[0041] 4 g of 1-bromotetradecane and 5 g of triethylenetetramine were added to 20 mL of absolute ethanol and mixed. The mixture was stirred and reacted at 85 °C for 9 h. After filtration, neutralization, washing and recrystallization, the secondary aminoalkane compound was obtained.

[0042] Preparation Example 2

[0043] The preparation steps of the secondary aminoalkane compound were the same as those in Preparation Example 1, except that the amount of 1-bromotetradecane added in this preparation example was 6 g.

[0044] Preparation Example 3

[0045] The preparation steps of the modified quaternary ammonium salt surfactant were as follows:

[0046] (1) 1 g of nonylphenol and 2.5 g of dibromoethane were added to 20 mL of absolute ethanol, and then 0.05 g of triethylamine was added. The temperature was raised to 65 °C and reacted for 1.5 h. Then 1.2 g of the secondary aminoalkane compound was added, and the mixture was stirred and reacted at 85 °C for 3 h. After washing, an intermediate product was obtained;

[0047] (2) 1 g of the intermediate product from step (1) and 3 g of chlorosulfonic acid were dissolved in 50 mL of anhydrous dichloromethane and mixed. The reaction was carried out at 28 °C for 10 h. After neutralization, drying, washing, filtration and recrystallization, the modified quaternary ammonium salt surfactant was obtained.

[0048] The secondary aminoalkane compound used in this preparation example was obtained from Preparation Example 1.

[0049] Preparation Example 4

[0050] The preparation steps of the modified quaternary ammonium salt surfactant were the same as those in Preparation Example 3, except that the amount of the secondary aminoalkane compound added in step (1) of this preparation example was 2 g.

[0051] Preparation Example 5

[0052] The preparation steps of the modified quaternary ammonium salt surfactant were the same as those in Preparation Example 3, except that the amount of dibromoethane added in step (1) of this preparation example was 3.5 g.

[0053] Preparation Example 6

[0054] The preparation steps of the modified quaternary ammonium salt surfactant were the same as those in Preparation Example 3, except that the amount of chlorosulfonic acid added in step (2) of this preparation example was 4 g.

[0055] Preparation Example 7

[0056] The preparation steps of the modified quaternary ammonium salt surfactant were the same as those in Preparation Example 3, except that the secondary aminoalkane compound used in step (1) of this preparation example was obtained from Preparation Example 2.

[0057] Example 1

[0058] A high-temperature resistant and shear-resistant oil-free clean fracturing fluid, and each liter of the oil-free clean fracturing fluid contains the following raw materials: 4.2 g of a modified quaternary ammonium salt surfactant, 3 g of n-decanol, 4 g of sodium salicylate, and the balance of water.

[0059] The preparation method of the high-temperature resistant and shear-resistant oil-free clean fracturing fluid in this example comprises the following steps:

[0060] Mix the modified quaternary ammonium salt surfactant and n-decanol and add them to water. After stirring until uniform, add sodium salicylate and continue to stir until uniform to obtain the product.

[0061] The modified quaternary ammonium salt surfactant used in this example is obtained from Preparation Example 3.

[0062] Example 2

[0063] A high-temperature resistant and shear-resistant oil-free clean fracturing fluid, and each liter of the oil-free clean fracturing fluid contains the following raw materials: 2.5 g of a modified quaternary ammonium salt surfactant, 1 g of n-decanol, 3 g of sodium salicylate, and the balance of water.

[0064] The preparation method of the high-temperature resistant and shear-resistant oil-free clean fracturing fluid in this example is the same as that in Example 1 in specific steps.

[0065] The modified quaternary ammonium salt surfactant used in this example is obtained from Preparation Example 3.

[0066] Example 3

[0067] A high-temperature resistant and shear-resistant oil-free clean fracturing fluid, and each liter of the oil-free clean fracturing fluid contains the following raw materials: 6 g of a modified quaternary ammonium salt surfactant, 5 g of n-decanol, 5.5 g of sodium salicylate, and the balance of water.

[0068] The preparation method of the high-temperature resistant and shear-resistant oil-free clean fracturing fluid in this example is the same as that in Example 1 in specific steps.

[0069] The modified quaternary ammonium salt surfactant used in this example is obtained from Preparation Example 3.

[0070] Example 4

[0071] A high-temperature resistant and shear-resistant oil-free clean fracturing fluid and its preparation method, and the specific implementation manner is the same as that in Example 1, with the difference that the modified quaternary ammonium salt surfactant used is obtained from Preparation Example 4.

[0072] Example 5

[0073] A high-temperature resistant and shear-resistant oil-free clean fracturing fluid and its preparation method, and the specific implementation manner is the same as that in Example 1, with the difference that the modified quaternary ammonium salt surfactant used is obtained from Preparation Example 5.

[0074] Example 6

[0075] An oil-free clean fracturing fluid with high temperature resistance and shear resistance and its preparation method. The specific implementation manner is the same as that of Example 1, except that the modified quaternary ammonium salt surfactant used is obtained from Preparation Example 6.

[0076] Example 7

[0077] An oil-free clean fracturing fluid with high temperature resistance and shear resistance and its preparation method. The specific implementation manner is the same as that of Example 1, except that the modified quaternary ammonium salt surfactant used is obtained from Preparation Example 7.

[0078] Comparative Example 1

[0079] An oil-free clean fracturing fluid with high temperature resistance and shear resistance and its preparation method. The specific implementation manner is the same as that of Example 1, except that octadecyltrimethylammonium chloride is used to equally replace the modified quaternary ammonium salt surfactant.

[0080] Performance Test

[0081] Take the oil-free clean fracturing fluids obtained in Examples 1-7 and Comparative Example 1 above as samples for the following performance tests. The specific test results are shown in Table 1:

[0082] 1. High temperature resistance performance: Select a high temperature rheometer. Under the conditions of 130 °C and a shear rate of 170 s -1 , record the viscosity respectively to characterize the high temperature resistance performance of the oil-free clean fracturing fluid;

[0083] 2. Shear resistance performance test: Select a rheometer. Under the conditions of 25 °C and a shear rate of 170 s -1 , record the shear viscosities of each sample at 0 min and 60 min respectively, and calculate the shear viscosity drop value to characterize the shear resistance performance of the oil-free clean fracturing fluid;

[0084] 3. Antibacterial performance: Refer to the public patent CN116396741B, and use Escherichia coli as the test bacterium to test the antibacterial rate of each sample to characterize the antibacterial performance of the oil-free clean fracturing fluid.

[0085] Table 1

[0086]

[0087] As can be seen from Table 1, the oil-free clean fracturing fluids provided in Examples 1-3 of the present invention have excellent high temperature resistance performance, good shear resistance performance, and good antibacterial effect.

[0088] It can be seen from the comparison between Example 4, Example 5, Example 6 and Example 1 that when the addition ratios of the secondary amino alkane compound, dibromoethane in step (1) and chlorosulfonic acid in step (2) are changed respectively during the preparation of the modified quaternary ammonium salt surfactant, the substitution reaction of the modified quaternary ammonium salt surfactant will be affected, the structural arrangement and micellization will be affected, and the rearrangement of micelles when the modified quaternary ammonium salt surfactant is sheared will be inhibited, resulting in a decrease in the viscosity of the oil-free clean fracturing fluid at high temperature, and the shear resistance and antibacterial effect will also decrease to varying degrees.

[0089] It can be seen from the comparison between Example 7 and Example 1 that changing the addition amount of 1-bromotetradecane during the preparation of the secondary amino alkane compound will cause the molecular chain of the obtained modified quaternary ammonium salt surfactant to be easily curled and folded, thereby affecting the high-temperature resistance and shear resistance of the oil-free clean fracturing fluid.

[0090] It can be seen from the comparison between Comparative Example 1 and Example 1 that when octadecyltrimethylammonium chloride is used to replace the modified quaternary ammonium salt surfactant in equal amount, the high-temperature resistance, shear resistance and antibacterial properties of the oil-free clean fracturing fluid will decrease to varying degrees.

[0091] The above are only the preferred embodiments of the present invention, and do not impose any formal limitations on the present invention. Although the present invention has been disclosed above with the preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some changes or modifications to equivalent embodiments by using the disclosed technical content within the scope of the technical solution of the present invention. However, as long as it does not depart from the technical solution content of the present invention, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A high-temperature resistant and shear-resistant oil-free clean fracturing fluid, characterized in that, Each liter of the oil-free base cleaning fracturing fluid contains the following raw materials: 2.5 - 6 g of modified quaternary ammonium salt surfactant, 1 - 5 g of lower alcohol, 3 - 5.5 g of counterion salt, and the balance of water.

2. The oil-free clean fracturing fluid with high temperature resistance and shear resistance according to claim 1, wherein The preparation steps of the modified quaternary ammonium salt surfactant are as follows: (1) Add alkylphenol and dibromoalkane into absolute ethanol, then add a catalyst, heat up to 60 - 70 °C, react for 1 - 2 h, then add secondary aminoalkane compound, and stir and react at 80 - 90 °C for 2 - 4 h. After washing, an intermediate product is obtained; (2) Mix the intermediate product from step (1) and chlorosulfonic acid in absolute dichloromethane, react at 25 - 30 °C for 8 - 12 h, and after neutralization, drying, washing, filtration, and recrystallization, a modified quaternary ammonium salt surfactant is obtained.

3. The oil-free base clean fracturing fluid with high temperature resistance and shear resistance according to claim 2, characterized in that, In step (1), the dibromoalkane is dibromoethane or dibromobutane.

4. The oil-free clean fracturing fluid with high temperature resistance and shear resistance according to claim 2, characterized in that, In step (1), the mass ratio of alkylphenol, dibromoalkane, and secondary aminoalkane compound is 1:(2 - 3):(0.8 - 1.5).

5. The oil-free clean fracturing fluid with high temperature resistance and shear resistance according to claim 2, characterized in that, In step (2), the mass ratio of the intermediate product and chlorosulfonic acid is 1:(2 - 3.5).

6. The oil-free clean fracturing fluid with high temperature resistance and shear resistance according to claim 2, wherein, The preparation steps of the secondary aminoalkane compound in step (1) are as follows: Add monobromoalkane and triethylenetetramine into absolute ethanol and mix them, stir and react at 80 - 90 °C for 8 - 10 h, and after filtration, neutralization, washing, and recrystallization, the secondary aminoalkane compound is obtained.

7. The oil-free clean fracturing fluid with high temperature resistance and shear resistance according to claim 6, wherein, The mass ratio of the monobromoalkane and triethylenetetramine is (0.7 - 1):

1.

8. The oil-free clean fracturing fluid with high temperature resistance and shear resistance according to claim 1, characterized in that The lower alcohol is at least one of n-octanol, n-decanol, or 2-decanol.

9. The oil-free clean fracturing fluid with high temperature resistance and shear resistance according to claim 1, characterized in that, The counterion salt is salicylate.

10. A method for preparing the oil-free clean fracturing fluid with high temperature resistance and shear resistance according to any one of claims 1-9, characterized in that, It includes the following steps: Mix the modified quaternary ammonium salt surfactant and the lower alcohol, add them into water, stir until uniform, then add the counterion salt, and continue to stir until uniform to obtain the product.

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