A plugging removal agent for formation pore channel based on diazonium salt, and a preparation method and application thereof

Abstract

The application discloses a plugging removing agent for stratum pore channels based on diazonium salt and a preparation method and application thereof, and belongs to the technical field of oil field plugging removal. The method comprises the following steps: reducing the surface tension of colloidal plugging material by using a surfactant, dispersing the colloidal plugging material in the pore channel and reducing the adhesion of the plugging material, so as to increase the wettability of the pore channel. The high-temperature condition of the stratum is utilized to make the p-aminobenzoic acid isooctyl ester cation group generated by the decomposition of the diazonium salt, the p-aminobenzoic acid isooctyl ester cation group and electron-rich sites (such as unsaturated carbon-carbon bonds and aromatic rings) in the plugging material are subjected to electrophilic addition or substitution reaction, the molecular structure of the plugging material is loosened, and the adhesion strength of the plugging material is further reduced; the weak acid can gently dissolve the inorganic mineral components in the colloidal plugging material, destroy the internal adhesion structure of the inorganic mineral components, and avoid the pipeline corrosion risk caused by strong acid. The nitrogen gas released by the decomposition of the diazonium salt forms pressure impact in the pore channel, the loosened plugging material is discharged from the pore channel, and the deep plugging removal effect is achieved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of oil field plugging removal, and particularly relates to a stratum pore channel plugging removal agent based on diazonium salt and a preparation method and application thereof. BACKGROUND

[0002] In the process of oil and gas exploitation, gelled plugging often forms in the stratum pore channel, hindering the seepage of fluid. These plugging materials are mainly composed of organic matter (such as oil, asphaltene) and inorganic minerals (such as silicate, carbonate, etc.), usually having the characteristics of viscosity and poor solubility, and easily depositing in the pore channel and closely adhering to the stratum wall. The formation of gelled plugging is caused by various reasons, including the residue of chemical reagents in the exploitation process, the polymerization reaction induced by oil and gas flow, the deposition of mineral particles, etc. The existence of these plugging materials can significantly reduce the permeability of the stratum, affect the smooth flow of oil and gas fluid, and reduce the recovery rate, and in severe cases, even completely block the fluid flow in some well sections. Therefore, removing gelled plugging and restoring the seepage capacity of the stratum pore channel is a key measure to improve the efficiency of oil and gas exploitation.

[0003] At present, the conventional method for removing gelled plugging mainly includes strong acid cleaning (such as hydrochloric acid, sulfuric acid, mud acid), organic solvent dissolution, or the combined use of strong acid and organic solvent. Strong acid cleaning can dissolve the inorganic mineral components in the plugging material to dredge the pore channel, and solvent is used to partially dissolve the organic plugging material. However, although strong acid can effectively dissolve the plugging material, it has strong corrosiveness to the pipeline structure, greatly shortening the service life of the pipeline; and although organic solvent cleaning can partially dissolve the organic components, the solubility is limited, the cost is high, the effect is not significant, and it is difficult to be applied on a large scale. Although the combined use of strong acid and solvent can improve the removal effect to some extent, it still has the disadvantages of strong corrosion, high environmental risk, and incomplete removal.

[0004] In view of the problems of strong corrosion, incomplete removal, and high environmental risk in the traditional stratum pore channel plugging removal method, it is necessary to find a mild, efficient, and environmentally friendly stratum pore channel plugging removal method to achieve the removal of gelled plugging in a mild, efficient, and environmentally friendly manner, so as to improve the seepage conditions in the oil production process and protect the stratum and the environment. SUMMARY

[0005] In order to overcome the above-mentioned shortcomings of the prior art, the purpose of the present application is to provide a stratum pore channel plugging removal agent based on diazonium salt and a preparation method and application thereof, so as to solve the technical problem of providing a mild, efficient, and environmentally friendly stratum pore channel plugging removal method to effectively remove gelled plugging and improve the seepage conditions in the oil production process.

[0006] In order to achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0007] The application discloses a preparation method of a stratum pore channel clearing agent based on diazonium salt.

[0008] Isooctyl p-aminobenzoate is dissolved in ethanol, a surfactant is added, and after stirring reaction, cooling and standing, a first intermediate is obtained; weak acid is slowly added dropwise into a sodium nitrite solution, and then a sodium bisulfite solution is added, and after uniform stirring, a second intermediate is obtained; the second intermediate is slowly added dropwise into the first intermediate under a nitrogen environment, and after heat preservation reaction and then temperature increasing reaction, the solvent is removed through rotary evaporation to obtain the stratum pore channel clearing agent based on diazonium salt.

[0009] Preferably, the mass ratio of isooctyl p-aminobenzoate, ethanol and the surfactant is 1:(2-2.5):(0.02-0.05); the mass ratio of the sodium nitrite solution, the weak acid and the sodium bisulfite solution is 1:(1-1.2):(0.2-0.4).

[0010] Preferably, the mass concentration of the sodium nitrite solution is 5%-12%; the mass concentration of the sodium bisulfite solution is 2%-6%.

[0011] Preferably, the mass ratio of the first intermediate and the second intermediate is 1:(1.5-1.8).

[0012] Preferably, the temperature for stirring reaction is 25-40 DEG C, and the time is 0.5-1.5 h.

[0013] Preferably, the temperature for heat preservation reaction is 0-10 DEG C, and the time is 1-2 h.

[0014] Preferably, the temperature for temperature increasing reaction is 15-25 DEG C, and the time is 1-2 h.

[0015] Preferably, the surfactant is any one of dodecanol polyoxyethylene ether, polyethylene glycol monooleate and OP-10; and the weak acid is any one of formic acid, acetic acid and fruit acid.

[0016] The application further discloses a stratum pore channel clearing agent based on diazonium salt, which is prepared by the preparation method.

[0017] The application further discloses application of the stratum pore channel clearing agent based on diazonium salt in oil exploitation.

[0018] Compared with the prior art, the application has the following beneficial effects:

[0019] This invention discloses a method for preparing a formation pore blockage remover based on diazonium salts, which can efficiently remove colloidal blockages in formation pores, thereby improving seepage conditions during oil production. The surfactant in the system reduces the surface tension of the colloidal blockages, dispersing them in the pores and reducing their adhesion, thus increasing the wettability of the pores. Secondly, high-temperature conditions cause the diazonium salt to decompose, generating isooctyl p-aminobenzoate cationic groups. These groups can undergo electrophilic addition or substitution reactions with electron-rich sites (such as unsaturated carbon-carbon bonds and aromatic rings) in the blockages, loosening the molecular structure and further reducing their bonding strength. The introduction of a weak acid gently dissolves the inorganic mineral components in the colloidal blockages, disrupting their internal bonding structure and avoiding the formation corrosion risk caused by strong acids. Finally, the nitrogen gas released from the decomposition of the diazonium salt creates a pressure shock within the pores, expelling the loosened blockages and achieving a deep-layer clearing effect. This invention achieves a mild, efficient, and environmentally friendly unclogging method through the synergistic effect of surfactants, isooctyl para-aminobenzoate cationic groups, weak acids, and nitrogen. It overcomes the shortcomings of traditional unclogging methods using strong acids and organic solvents, while effectively protecting the formation structure and surrounding ecological environment. It is applicable to unclogging formation channels in the oil and gas field, improving oil and gas permeability and production efficiency.

[0020] Furthermore, the mass ratio of isooctyl p-aminobenzoate, ethanol, and surfactant is 1:(2~2.5):(0.02~0.05). By precisely controlling this mass ratio, optimal synergistic effects among the components in the unblocking agent are ensured. This ratio not only allows isooctyl p-aminobenzoate to fully dissolve and exert its effect, but also guarantees the best effect of the surfactant in reducing the surface tension and adhesion of the blockage. Ethanol, as a solvent, also plays a good role in dissolving and dispersing. The mass ratio of sodium nitrite solution, weak acid, and sodium bisulfite solution is 1:(1~1.2):(0.2~0.4). By precisely adjusting this mass ratio, a gentle yet effective removal of both inorganic and organic components from the blockage is achieved. The synergistic effect of sodium nitrite and sodium bisulfite, combined with the gentle dissolving ability of the weak acid, allows the unblocking agent to target different components of the blockage more precisely, improving removal efficiency.

[0021] Furthermore, the mass concentration of the sodium nitrite solution is 5%–12%, and the mass concentration of the sodium bisulfite solution is 2%–6%. By controlling the mass concentrations of the sodium nitrite and sodium bisulfite solutions, the stability and effectiveness of the unblocking agent during the reaction process are ensured. Appropriate concentration ranges not only guarantee efficient reaction but also avoid problems such as incomplete reaction or excessive corrosion caused by excessively high or low concentrations.

[0022] Furthermore, the mass ratio of the first intermediate to the second intermediate is 1:(1.5~1.8); by precisely controlling the mass ratio of the first intermediate to the second intermediate, the preparation process of the unblocking agent is further optimized. This ratio ensures sufficient reaction and optimal effect among the intermediates, improving the overall performance and stability of the unblocking agent.

[0023] Furthermore, the stirring reaction was conducted at a temperature of 25–40 °C for 0.5–1.5 h. By controlling the temperature and time of the stirring reaction, the smooth progress of the reaction process and the stability of the product were ensured. Appropriate temperature and time ranges not only improved reaction efficiency but also avoided problems such as product decomposition or side reactions caused by excessively high temperatures or prolonged times.

[0024] Furthermore, the temperature of the heat preservation reaction was 0~10℃, and the time was 1~2h; by controlling the temperature and time of the heat preservation reaction, the preparation process of the unblocking agent was further optimized. The low-temperature heat preservation reaction helps to stabilize the structure and properties of the product, and improves the effectiveness and stability of the unblocking agent.

[0025] Furthermore, the heating reaction temperature is 15-25°C, and the time is 1-2 hours. By controlling the temperature and time of the heating reaction, this invention ensures sufficient reaction and optimal effect among the components in the unblocking agent. Appropriate heating helps accelerate the reaction rate and improve the purity and performance of the product.

[0026] Furthermore, the surfactant is any one of dodecyl alcohol polyoxyethylene ether, polyethylene glycol monooleate, and OP-10; the weak acid is any one of formic acid, acetic acid, and fruit acid. By selecting specific surfactants and weak acids, the targeting and effectiveness of the unblocking agent are further enhanced. These surfactants and weak acids have good solubility, dispersibility, and mildness, enabling them to more effectively remove different components in the blockage while protecting the formation and pipeline structure from damage.

[0027] This invention also discloses a diazonium salt-based formation pore unblocking agent, prepared using the aforementioned method. This unblocking agent is prepared using a unique method, and through its unique formulation and preparation process, it achieves efficient, gentle, and environmentally friendly removal of colloidal blockages in formation pores. This unblocking agent can significantly reduce the adhesion and bonding strength of the blockages, disrupt their internal structure, and simultaneously use nitrogen pressure impact to expel the blockages from the pores. This greatly improves the seepage conditions during oil production, enhances oil and gas permeability and production efficiency, and brings significant economic and environmental benefits to the oil and gas extraction field.

[0028] This invention also discloses the application of the diazonium salt-based formation pore unblocking agent prepared by the above-mentioned method in oil extraction. By using surfactants to reduce the surface tension of the blockage, dispersing it and reducing adhesion, and simultaneously utilizing the cationic groups generated from the decomposition of diazonium salts to react with the electron-rich sites in the blockage, the molecular structure of the blockage becomes loose, further reducing its bonding strength. This synergistic effect allows the unblocking agent to efficiently remove colloidal blockages and significantly improve formation permeability. Compared with traditional strong acid cleaning methods, the weak acid component used in this invention can gently dissolve the inorganic mineral components in the blockage, avoiding the strong corrosiveness of strong acids to the formation and pipelines, and extending the service life of pipelines. Furthermore, the entire unblocking process is more environmentally friendly, reducing the negative impact on the surrounding ecological environment. Through deep unblocking, this invention effectively restores the seepage capacity of formation pores, allowing oil and gas fluids to flow more smoothly, thereby improving oil and gas permeability and production efficiency. This has a significant effect on improving the overall economic benefits of oil extraction. Because the unblocking agent of this invention has a simple preparation process, relatively low cost, and significant unblocking effect, it can significantly reduce the unblocking cost in the oil extraction process. Simultaneously, by extending the service life of pipelines and improving oil and gas production efficiency, it also indirectly reduces extraction costs. Through a gentle yet efficient unblocking method, this invention avoids the formation structure damage problems that may be caused by traditional strong acid cleaning methods, thus enhancing formation stability. This is of great significance for ensuring the long-term stability and safety of oil extraction. Attached Figure Description

[0029] Figure 1 The pressure difference test diagram of the inlet and outlet of the displacement device before and after using the formation pore unblocking agent based on diazonium salt prepared in Example 3 of the present invention;

[0030] Figure 2 The viscosity test diagrams are of the effluent obtained by the displacement device before and after use of the formation pore unblocking agent based on diazonium salt prepared in Example 3 of the present invention. Detailed Implementation

[0031] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0032] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0033] Unless otherwise specified, all technical and scientific terms used herein have the common meaning as understood by those skilled in the art in relation to the invention, and in the event of any conflict, the definitions in this specification shall prevail.

[0034] 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.

[0035] 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.

[0036] In this article, unless otherwise specified, “contains,” “includes,” “containing,” “has,” or similar terms cover the meanings of “composed of” and “mainly composed of,” for example, “A contains a” covers the meanings of “A contains a and others” and “A contains only a.”

[0037] 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.

[0038] 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.

[0039] The following examples use instruments and equipment conventional in the art. Experimental methods in the following examples, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. All raw materials used in the following examples are conventional commercially available products with specifications conventional in the art. In this specification and the following examples, unless otherwise specified, "%" refers to weight percentage, "parts" refers to parts by weight, and "ratio" refers to weight proportion.

[0040] This invention provides a method for preparing a formation pore-blocking agent based on diazonium salts, comprising the following steps:

[0041] S1: Dissolve isooctyl p-aminobenzoate in an appropriate amount of ethanol. After complete dissolution, add a surfactant and stir at 25-40°C for 0.5-1.5 hours. Then cool and allow to stand to obtain the first intermediate. In another container, slowly add a weak acid to a sodium nitrite solution, followed by a sodium bisulfite solution. Stir until homogeneous to obtain the second intermediate.

[0042] S2: Under nitrogen atmosphere, the second intermediate is slowly added dropwise to the first intermediate. After reacting at 0~10℃ for 1~2h, the reaction system is then raised to 15~25℃ for 1~2h. After the reaction is completed, the solvent is removed by rotary evaporation to obtain the formation pore unblocking agent based on diazonium salt.

[0043] As an optional option, in step S1, the surfactant is any one of dodecyl alcohol polyoxyethylene ether, polyethylene glycol monooleate, and OP-10.

[0044] As an optional option, in step S1, the mass ratio of isooctyl p-aminobenzoate, ethanol and surfactant is 1:(2~2.5):(0.02~0.05).

[0045] As an optional option, in step S1, the weak acid can be any one of formic acid, acetic acid, and fruit acid.

[0046] As an optional option, in step S1, the mass concentration of sodium nitrite solution is 5%~12%; the mass concentration of sodium bisulfite solution is 2%~6%.

[0047] As an optional option, in step S1, the mass ratio of sodium nitrite solution, weak acid and sodium bisulfite solution is 1:(1~1.2):(0.2~0.4).

[0048] As an optional option, in step S2, the mass ratio of the first intermediate to the second intermediate is 1:(1.5~1.8).

[0049] This invention provides an application of a diazonium salt-based formation pore unblocking agent prepared according to the above-described method in the petrochemical field. When used as a pore unblocking agent in oilfields, it offers a highly efficient, mild, and environmentally friendly unblocking solution through the synergistic effect of surfactants, isooctyl p-aminobenzoate cationic groups, weak acids, and nitrogen, exhibiting significant advantages. This invention not only achieves highly efficient unblocking but also extends the service life of related equipment, reduces maintenance costs, and minimizes downtime. By improving oil recovery, reducing maintenance costs, extending equipment life, and reducing losses due to production stoppages, the application of this pore unblocking agent can significantly enhance the economic benefits of oilfields.

[0050] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0051] Example 1

[0052] A method for preparing a formation pore-blocking agent based on diazonium salts includes the following steps:

[0053] S1: Dissolve 10 g of isooctyl p-aminobenzoate in 25 g of ethanol. After complete dissolution, add 0.3 g of polyethylene glycol monooleate. Stir at 28°C for 1 h, then cool and allow to stand to obtain the first intermediate. In another container, slowly add 5 g of formic acid to 5 g of 5% sodium nitrite solution, then add 1.8 g of 5% sodium bisulfite solution. Stir until homogeneous to obtain the second intermediate.

[0054] S2: Under nitrogen atmosphere, 18g of the second intermediate was slowly added dropwise to 10g of the first intermediate. The reaction was maintained at 7°C for 1.5 h, and then the reaction system was raised to 18°C ​​for 1.5 h. After the reaction was completed, the solvent was removed by rotary evaporation to obtain a formation pore-blocking agent based on diazonium salt.

[0055] Example 2

[0056] A method for preparing a formation pore-blocking agent based on diazonium salts includes the following steps:

[0057] S1: 12 g of isooctyl p-aminobenzoate was dissolved in 30 g of ethanol. After complete dissolution, 0.35 g of OP-10 was added, and the mixture was stirred at 32°C for 1.2 h, then cooled and allowed to stand to obtain the first intermediate. In another container, 6 g of acetic acid was slowly added dropwise to 6 g of 8.5% sodium nitrite solution, followed by 2 g of 4% sodium bisulfite solution. After stirring until homogeneous, the second intermediate was obtained.

[0058] S2: Under nitrogen atmosphere, 12g of the second intermediate was slowly added dropwise to 8g of the first intermediate. The reaction was maintained at 6°C for 1.2 h, and then the reaction system was raised to 22°C for 2 h. After the reaction was completed, the solvent was removed by rotary evaporation to obtain a formation pore-blocking agent based on diazonium salt.

[0059] Example 3

[0060] A method for preparing a formation pore-blocking agent based on diazonium salts includes the following steps:

[0061] S1: Dissolve 11.5 g of isooctyl p-aminobenzoate in 28 g of ethanol. After complete dissolution, add 0.28 g of polyethylene glycol monooleate. Stir at 35°C for 0.8 h, then cool and allow to stand to obtain the first intermediate. In another container, slowly add 5.5 g of formic acid to 5.5 g of 12% sodium nitrite solution, then add 1.9 g of 5% sodium bisulfite solution. Stir until homogeneous to obtain the second intermediate.

[0062] S2: Under nitrogen atmosphere, 24g of the second intermediate was slowly added dropwise to 15g of the first intermediate. The reaction was maintained at 10°C for 1.4 h, and then the reaction system was raised to 19°C for 1.6 h. After the reaction was completed, the solvent was removed by rotary evaporation to obtain a formation pore-blocking agent based on diazonium salt.

[0063] Example 4

[0064] A method for preparing a formation pore-blocking agent based on diazonium salts includes the following steps:

[0065] S1: Dissolve 9.5 g of isooctyl p-aminobenzoate in 22 g of ethanol. After complete dissolution, add 0.25 g of polyethylene glycol monooleate. Stir at 33°C for 1 h, then cool and allow to stand to obtain the first intermediate. In another container, slowly add 5.2 g of fruit acid to 5.2 g of 10% sodium nitrite solution, then add 1.7 g of 6% sodium bisulfite solution. Stir until homogeneous to obtain the second intermediate.

[0066] S2: Under nitrogen atmosphere, 23g of the second intermediate was slowly added dropwise to 14g of the first intermediate. The reaction was maintained at 8°C for 1.5 h, and then the reaction system was raised to 21°C for 1.8 h. After the reaction was completed, the solvent was removed by rotary evaporation to obtain a formation pore-blocking agent based on diazonium salt.

[0067] Example 5

[0068] A method for preparing a formation pore-blocking agent based on diazonium salts includes the following steps:

[0069] S1: 13 g of isooctyl p-aminobenzoate was dissolved in 32 g of ethanol. After complete dissolution, 0.38 g of dodecyl alcohol polyoxyethylene ether was added. The mixture was stirred at 38°C for 1.5 h and then cooled and allowed to stand to obtain the first intermediate. In another container, 6.2 g of acetic acid was slowly added dropwise to 6.2 g of 9% sodium nitrite solution, followed by 2.1 g of 4% sodium bisulfite solution. After stirring until homogeneous, the second intermediate was obtained.

[0070] S2: Under nitrogen atmosphere, 17g of the second intermediate was slowly added dropwise to 11g of the first intermediate. The reaction was maintained at 4°C for 1.8 h, and then the reaction system was raised to 23°C for 2 h. After the reaction was completed, the solvent was removed by rotary evaporation to obtain a formation pore-blocking agent based on diazonium salt.

[0071] Example 6

[0072] A method for preparing a formation pore-blocking agent based on diazonium salts includes the following steps:

[0073] S1: 10.8 g of isooctyl p-aminobenzoate was dissolved in 27 g of ethanol. After complete dissolution, 0.324 g of OP-10 was added, and the mixture was stirred at 30°C for 1 h, then cooled and allowed to stand to obtain the first intermediate. In another container, 6 g of fruit acid was slowly added dropwise to 6 g of a 10% sodium nitrite solution, followed by 2 g of a 3% sodium bisulfite solution. After stirring until homogeneous, the second intermediate was obtained.

[0074] S2: Under nitrogen atmosphere, 21g of the second intermediate was slowly added dropwise to 13g of the first intermediate. The reaction was maintained at 5°C for 1.5 h, and then the reaction system was raised to 20°C for 1.5 h. After the reaction was completed, the solvent was removed by rotary evaporation to obtain a formation pore-blocking agent based on diazonium salt.

[0075] Example 7

[0076] A method for preparing a formation pore-blocking agent based on diazonium salts includes the following steps:

[0077] S1: Dissolve 10 g of isooctyl p-aminobenzoate in 20 g of ethanol. After complete dissolution, add 0.2 g of polyethylene glycol monooleate. Stir at 25 °C for 1 h, then cool and allow to stand to obtain the first intermediate. In another container, slowly add 6 g of acetic acid to 5 g of 5% sodium nitrite solution, then add 1 g of 2% sodium bisulfite solution. Stir until homogeneous to obtain the second intermediate.

[0078] S2: Under nitrogen atmosphere, 18g of the second intermediate was slowly added dropwise to 10g of the first intermediate. The reaction was maintained at 0℃ for 1 h, and then the reaction system was raised to 15℃ for 1 h. After the reaction was completed, the solvent was removed by rotary evaporation to obtain a formation pore-blocking agent based on diazonium salt.

[0079] Example 8

[0080] A method for preparing a formation pore-blocking agent based on diazonium salts includes the following steps:

[0081] S1: Dissolve 10 g of isooctyl p-aminobenzoate in 25 g of ethanol. After complete dissolution, add 0.5 g of dodecyl alcohol polyoxyethylene ether. Stir at 40°C for 0.5 h, then cool and allow to stand to obtain the first intermediate. In another container, slowly add 8.8 g of fruit acid to 5 g of 8% sodium nitrite solution, then add 2 g of 3% sodium bisulfite solution. Stir until homogeneous to obtain the second intermediate.

[0082] S2: Under nitrogen atmosphere, 17g of the second intermediate was slowly added dropwise to 10g of the first intermediate. The reaction was maintained at 3°C ​​for 2 hours, and then the reaction system was raised to 25°C for 2 hours. After the reaction was completed, the solvent was removed by rotary evaporation to obtain a formation pore-blocking agent based on diazonium salt.

[0083] Characterization and testing:

[0084] To evaluate the effectiveness of the formation pore clearing agent, the agent synthesized in Example 3 was tested. To assess its effectiveness against colloidal blockages, a pressure difference test was conducted using a displacement device to monitor the pressure changes at the inlet and outlet before and after the application of the agent. Since the blockage is a binder of organic and inorganic minerals, a significant decrease in pressure difference indicates that the colloidal blockage was partially removed, demonstrating that the agent effectively improved pore flow and enhanced fluid permeability. Test method: 20 g of a 0.6% solids colloidal solution was added to the displacement device and swollen for 2 hours. The displacement test was then initiated, and the inlet and outlet pressure differences were recorded. During this process, 10 g, 20 g, 30 g, 40 g, and 50 g of the agent were gradually injected into the displacement device for 12 hours. The displacement test was then continued, and the inlet and outlet pressure differences were recorded again. Detailed test results can be found in [link to test results]. Figure 1 .

[0085] Figure 1 This is a test diagram showing the pressure difference between the inlet and outlet of the displacement device before and after using the diazonium salt-based formation pore unblocking agent prepared in Example 3 of this invention; (The diagram is from...) Figure 1 It is evident that as the amount of unblocking agent used increases, the pressure difference between the inlet and outlet gradually decreases. This indicates that with increased dosage, the amount of colloidal blockage dissolved and removed gradually increases, thus enhancing the pore-clearing effect. This is because increasing the dosage of unblocking agent makes the colloidal structure more porous, and the increased nitrogen release generates a pressure effect that allows more blockage to be discharged from the pores, thereby effectively improving formation permeability.

[0086] To evaluate the effectiveness of the formation pore unblocking agent, the unblocking agent synthesized in Example 3 was tested against colloidal blockages. The viscosity change of the effluent after unblocking was monitored using a pressure difference test with a displacement device. Since the colloidal blockages partially dissolve in the effluent after removal, leading to an increase in viscosity, the viscosity change of the effluent can reflect the unblocking effect to some extent. Test method: 20 g of a colloidal solution with a solid content of 0.6% was added to the displacement device and subjected to swelling treatment for 2 hours. The displacement test was then initiated, and the inlet and outlet pressure difference was recorded. During this process, 10 g, 20 g, 30 g, 40 g, and 50 g of the unblocking agent were gradually injected into the displacement device for 12 hours. The displacement test was then continued, and the viscosity value of the effluent was recorded again. Detailed test results can be found in [link to test results]. Figure 2 .

[0087] Figure 2 The viscosity test diagrams of the effluent obtained by the displacement device before and after use of the diazonium salt-based formation pore unblocking agent prepared in Example 3 of this invention are shown. Figure 2It is evident that the viscosity of the effluent increases with the increase in the amount of unblocking agent used. This phenomenon indicates that the increased amount of unblocking agent promotes the dissolution and breaking down of colloidal blockages. The unblocking agent softens and loosens the colloidal structure in the formation; these softened colloidal molecules are expelled through the pressure difference created by nitrogen gas, leading to an increase in the viscosity of the effluent. Higher viscosity means more colloidal material is removed, resulting in a more significant unblocking effect on formation channels. This superior performance provides reliable technical support for unblocking formation channels under complex operating conditions, further validating the potential value of this invention in practical applications.

[0088] In summary, this invention discloses a formation pore unblocking agent based on diazonium salts and its preparation method. Isooctyl p-aminobenzoate is dissolved in an appropriate amount of ethanol. After complete dissolution, a surfactant is added, and the mixture is stirred at a controlled temperature T1 for a certain time t1, followed by cooling and settling to obtain a first intermediate. In another container, a weak acid is slowly added dropwise to a sodium nitrite solution, followed by a sodium bisulfite solution. After stirring until homogeneous, a second intermediate is obtained. Under a nitrogen atmosphere, the second intermediate is slowly added dropwise to the first intermediate, and the reaction is maintained at a certain temperature T2 for a certain time t2. The reaction system is then raised to a certain temperature T3 and reacted for a certain time t3. After the reaction is complete, the solvent is removed by rotary evaporation to obtain the formation pore unblocking agent based on diazonium salts. Firstly, the surfactant reduces the surface tension of the colloidal blockage, dispersing it in the pores and reducing its adhesion, thereby increasing the wettability of the pores. Secondly, the high-temperature conditions of the formation allow the isooctyl p-aminobenzoate cationic groups produced by the decomposition of diazonium salts to undergo electrophilic addition or substitution reactions with electron-rich sites (such as unsaturated carbon-carbon bonds and aromatic rings) in the blockage, loosening the molecular structure of the blockage and further reducing its bonding strength. The introduction of a weak acid gently dissolves the inorganic mineral components in the colloidal blockage, disrupting its internal bonding structure and avoiding the pipeline corrosion risk caused by strong acids. Finally, the nitrogen gas released from the decomposition of diazonium salts creates a pressure impact within the pores, expelling the loosened blockages and achieving a deep unblocking effect. The formation pore unblocking agent provided by this invention overcomes the shortcomings of traditional strong acid and organic solvent unblocking methods and has broad application prospects.

[0089] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a formation pore-blocking agent based on diazonium salts, characterized in that, Includes the following steps: Isooctyl p-aminobenzoate was dissolved in ethanol, a surfactant was added, the mixture was stirred and reacted, and then cooled and allowed to stand to obtain the first intermediate. A weak acid was slowly added dropwise to a sodium nitrite solution, followed by a sodium bisulfite solution. After stirring until homogeneous, a second intermediate was obtained. Under a nitrogen atmosphere, the second intermediate was slowly added dropwise to the first intermediate. After the reaction was kept at a constant temperature, the temperature was increased again. The solvent was removed by rotary evaporation to obtain a formation pore-blocking agent based on diazonium salts. The surfactant is any one of dodecyl alcohol polyoxyethylene ether, polyethylene glycol monooleate, and OP-10; the stirring reaction temperature is 25~40℃, and the time is 0.5~1.5h; The mass ratio of isooctyl p-aminobenzoate, ethanol, and surfactant is 1:(2~2.5):(0.02~0.05); the mass ratio of sodium nitrite solution, weak acid, and sodium bisulfite solution is 1:(1~1.2):(0.2~0.4). The sodium nitrite solution has a mass concentration of 5% to 12%; the sodium bisulfite solution has a mass concentration of 2% to 6%. The mass ratio of the first intermediate to the second intermediate is 1:(1.5~1.8).

2. The preparation method of the formation pore unblocking agent based on diazonium salt according to claim 1, characterized in that, The temperature of the heat preservation reaction is 0~10℃, and the time is 1~2h.

3. The preparation method of the formation pore unblocking agent based on diazonium salt according to claim 1, characterized in that, The heating reaction is carried out at a temperature of 15-25°C for 1-2 hours.

4. The preparation method of the formation pore unblocking agent based on diazonium salt according to claim 1, characterized in that, The weak acid is any one of formic acid, acetic acid, and fruit acid.

5. A formation pore-blocking agent based on diazonium salts, characterized in that, It is prepared by the method of preparation of formation pore unblocking agent based on diazonium salt as described in any one of claims 1 to 4.

6. The application of the diazonium salt-based formation pore unblocking agent prepared by the preparation method of any one of claims 1 to 4 in oil extraction.

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