Stratum pore channel unblocking agent based on diazonium salt as well as preparation method and application of stratum pore channel unblocking agent

Abstract

The invention discloses a stratum pore channel blocking remover based on diazonium salt and a preparation method and application thereof, and belongs to the technical field of oil field blocking removal. The method comprises: using a surfactant to reduce the surface tension of the colloidal obstructions, dispersing them in the pore channels and reducing the adhesion of the obstructions, thereby increasing the wettability of the pore channels. 2-ethylhexyl p-aminobenzoate cationic groups generated by diazonium salt decomposition and electron-rich sites (such as unsaturated carbon-carbon bonds and aromatic rings) in the blockages are subjected to an electrophilic addition or substitution reaction under the formation high-temperature condition, so that the molecular structures of the blockages are loosened, and the bonding strength of the blockages is further reduced; the weak acid can mildly dissolve inorganic mineral components in the colloidal blockages and destroy internal bonding structures of the colloidal blockages, so that the risk of pipeline corrosion caused by strong acid is avoided. Nitrogen released by diazonium salt decomposition forms pressure impact in the pore channels, loose blockages are discharged out of the pore channels, and the effect of deep blockage clearing is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of oilfield blockage removal, and in particular relates to a formation pore blockage clearing agent based on diazonium salt, and a preparation method and application thereof. Background Art

[0002] During the oil and gas extraction process, colloid blockages often form in the pores of the formation, hindering the flow of fluids. These blockages are mainly composed of organic matter (such as oils and asphaltene) and inorganic minerals (such as silicates and carbonates). They are usually viscous and difficult to dissolve. They are easily deposited in the pores and tightly adhere to the formation wall. There are many reasons for the formation of colloid blockages, including the residue of chemical reagents during the extraction process, polymerization reactions caused by oil and gas flow, and the deposition of mineral particles. The presence of these blockages will significantly reduce the permeability of the formation, affect the smooth flow of oil and gas fluids, lead to a decrease in the recovery rate, and even completely block the flow of fluids in some sections of the well in severe cases. Therefore, removing colloid blockages and restoring the seepage capacity of the formation pores are key measures to improve the efficiency of oil and gas extraction.

[0003] At present, conventional methods for removing colloid blockages mainly include strong acid cleaning (such as hydrochloric acid, sulfuric acid, and earth acid), organic solvent dissolution, or the combined application of strong acid and organic solvent. Strong acid cleaning dredges the channels by dissolving the inorganic mineral components in the blockage, while solvents are used to partially dissolve organic blockages. However, although strong acids can effectively dissolve blockages, they are highly corrosive to the pipeline structure, greatly shortening the service life of the pipeline; and although organic solvent cleaning can partially dissolve organic components, its solubility is limited, the cost is high, the effect is not significant, and it is difficult to apply on a large scale. Although the method of using a combination of strong acids and solvents can improve the removal effect to a certain extent, it still has disadvantages such as strong corrosiveness, high environmental risks, and incomplete removal.

[0004] In view of the problems of strong corrosion, incomplete cleaning and high environmental risk in traditional formation pore clearing methods, it is necessary to find a gentle, efficient and environmentally friendly formation pore clearing method to achieve gentle, efficient and environmentally friendly removal of colloid blockages, aiming to improve oil production seepage conditions and protect the formation and the environment. Summary of the invention

[0005] In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a diazonium salt-based formation pore clearing agent and its preparation method and application, so as to solve the technical problem of how to provide a mild, efficient and environmentally friendly formation pore clearing method to effectively remove colloid blockages and improve seepage conditions during oil production.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions: The invention discloses a method for preparing a formation pore clearing agent based on diazonium salt, comprising the following steps: Dissolve isooctyl p-aminobenzoate in ethanol, add a surfactant, stir to react, cool and stand to obtain a first intermediate; slowly drop a weak acid into a sodium nitrite solution, then add a sodium bisulfite solution, stir evenly to obtain a second intermediate; slowly drop the second intermediate into the first intermediate under a nitrogen environment, keep warm to react, then heat to react, remove the solvent by rotary evaporation to obtain a diazonium salt-based formation pore clearing agent.

[0007] Preferably, 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).

[0008] Preferably, the mass concentration of the sodium nitrite solution is 5% to 12%; the mass concentration of the sodium bisulfite solution is 2% to 6%.

[0009] Preferably, the mass ratio of the first intermediate to the second intermediate is 1:(1.5-1.8).

[0010] Preferably, the stirring reaction temperature is 25-40° C. and the time is 0.5-1.5 h.

[0011] Preferably, the temperature of the insulation reaction is 0-10°C and the time is 1-2h.

[0012] Preferably, the temperature of the temperature-raising reaction is 15-25° C. and the time is 1-2 h.

[0013] Preferably, the surfactant is any one of lauryl alcohol polyoxyethylene ether, polyethylene glycol monooleate and OP-10; and the weak acid is any one of formic acid, acetic acid and fruit acid.

[0014] The invention also discloses a diazonium salt-based formation pore clearing and plugging agent, which is prepared by adopting the preparation method of the diazonium salt-based formation pore clearing and plugging agent.

[0015] The invention also discloses the application of the diazonium salt-based formation pore clearing agent prepared by the preparation method of the diazonium salt-based formation pore clearing agent in petroleum production.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The invention discloses a preparation method of a formation pore clearing agent based on diazonium salt, which can efficiently clear the colloid blockage in the formation pore, thereby improving the seepage conditions in the oil production process. The surface tension of the colloid blockage is reduced by using the surfactant in the system, so that it is dispersed in the pore and the adhesion of the blockage is reduced, thereby increasing the wettability of the pore. Secondly, the diazonium salt is decomposed under high temperature conditions to produce isooctyl aminobenzoate cationic groups, which can react with the electron-rich sites (such as unsaturated carbon-carbon bonds, aromatic rings) in the blockage by electrophilic addition or substitution reactions, so that the molecular structure of the blockage is loosened, and its bonding strength is further reduced; the introduction of weak acid gently dissolves the inorganic mineral components in the colloid blockage, destroys its internal bonding structure, and avoids the risk of formation corrosion caused by strong acid. Finally, the nitrogen released by the decomposition of the diazonium salt forms a pressure shock in the pore, discharges the loose blockage from the pore, and achieves the effect of deep clearing. This invention realizes a gentle, efficient and environmentally friendly clearing method through the synergistic effect of surfactants, isooctyl p-aminobenzoate cationic groups, weak acids and nitrogen, overcoming the shortcomings of traditional clearing methods using strong acids and organic solvents, while effectively protecting the formation structure and surrounding ecological environment. It is suitable for clearing formation pores in the oil and gas field and improving oil and gas permeability and production efficiency.

[0017] Furthermore, the mass ratio of isooctyl p-aminobenzoate, ethanol and surfactant is 1: (2~2.5): (0.02~0.05); by precisely controlling the mass ratio of isooctyl p-aminobenzoate, ethanol and surfactant, the best synergy between the components in the plugging agent is ensured. This ratio not only allows isooctyl p-aminobenzoate to fully dissolve and play its role, but also ensures the best effect of surfactant in reducing the surface tension and adhesion of the blockage. At the same time, ethanol as a solvent also plays a good dissolving and dispersing role. 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 the mass ratio of sodium nitrite solution, weak acid and sodium bisulfite solution, the inorganic mineral components and organic components in the blockage are gently and effectively removed. The synergistic effect of sodium nitrite and sodium bisulfite, combined with the mild dissolving ability of weak acid, enables the plugging agent to act more accurately on different components of the blockage, thereby improving the removal efficiency.

[0018] Furthermore, the mass concentration of sodium nitrite solution is 5%~12%; the mass concentration of sodium bisulfite solution is 2%~6%; by controlling the mass concentration of sodium nitrite solution and sodium bisulfite solution, the stability and effect of the plugging agent during the reaction are ensured. The appropriate concentration range not only ensures the efficient progress of the reaction, but also avoids problems such as insufficient reaction or excessive corrosion caused by too high or too low concentration.

[0019] 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 plugging agent is further optimized. This ratio ensures sufficient reaction and optimal effect between the intermediates, and improves the overall performance and stability of the plugging agent.

[0020] Furthermore, the stirring reaction temperature is 25-40°C and the time is 0.5-1.5h; by controlling the stirring reaction temperature and time, the smooth progress of the reaction process and the stability of the product are ensured. The appropriate temperature and time range not only improves the reaction efficiency, but also avoids problems such as product decomposition or side reactions caused by excessively high temperature or excessively long time.

[0021] Furthermore, the temperature of the heat preservation reaction is 0-10°C and the time is 1-2 hours; by controlling the temperature and time of the heat preservation reaction, the preparation process of the plugging removal agent is further optimized. The low-temperature heat preservation reaction helps to stabilize the structure and performance of the product and improves the effect and stability of the plugging removal agent.

[0022] Furthermore, the temperature of the temperature-raising reaction is 15-25°C and the time is 1-2 hours. By controlling the temperature and time of the temperature-raising reaction, the present invention ensures the full reaction and the best effect between the components in the plugging removal agent. The appropriate temperature-raising process helps to accelerate the reaction rate and improve the purity and performance of the product.

[0023] Furthermore, the surfactant is any one of lauryl 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 pertinence and effect of the plugging agent are further enhanced. These surfactants and weak acids have good solubility, dispersibility and mildness, and can more effectively remove different components in the blockage, while protecting the formation and pipeline structure from damage.

[0024] The present invention also discloses a diazonium salt-based formation pore clearing agent, which is prepared by the preparation method of the diazonium salt-based formation pore clearing agent; the clearing agent is prepared by a unique preparation method, and through its unique formula and preparation process, it realizes efficient, gentle and environmentally friendly removal of colloid blockages in formation pores. This clearing agent can significantly reduce the adhesion and bonding strength of the blockage, destroy its internal structure, and use nitrogen pressure shock to discharge the blockage from the pore, thereby greatly improving the seepage conditions in the oil production process, improving oil and gas permeability and output efficiency, and bringing significant economic and environmental benefits to the field of oil and gas production.

[0025] The present invention also discloses the application of the formation pore clearing agent based on diazonium salt prepared by the preparation method of the formation pore clearing agent based on diazonium salt in oil production. The surface tension of the blockage is reduced by a surfactant, so that it is dispersed and the adhesion is reduced. At the same time, the cationic groups generated by the decomposition of the diazonium salt react with the electron-rich sites in the blockage to loosen the molecular structure of the blockage and further reduce the bonding strength. This synergistic effect enables the clearing agent to efficiently remove the colloid blockage and significantly improve the permeability of the formation. Compared with the traditional strong acid cleaning method, the weak acid component used in the present invention can gently dissolve the inorganic mineral components in the blockage, avoid the strong corrosion of the strong acid to the formation and the pipeline, and extend the service life of the pipeline. In addition, the entire clearing process is more environmentally friendly and reduces the negative impact on the surrounding ecological environment. Through deep clearing, the present invention effectively restores the seepage capacity of the formation pores, allowing the oil and gas fluid to flow more smoothly, thereby improving the permeability and output efficiency of oil and gas. This has a significant effect on improving the overall economic benefits of oil production. Since the preparation process of the plugging removal agent of the present invention is simple, the cost is relatively low, and the plugging removal effect is significant, it can significantly reduce the plugging removal cost in the oil production process. At the same time, since the service life of the pipeline is extended and the oil and gas output efficiency is improved, the production cost is also indirectly reduced. Through a gentle and efficient plugging removal method, the present invention avoids the problem of formation structure damage that may be caused by traditional strong acid cleaning methods and enhances the stability of the formation. This is of great significance for ensuring the long-term stability and safety of oil production. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a test diagram of the pressure difference between the inlet and outlet of the displacement device before and after the use of the diazonium salt-based formation pore clearing agent prepared in Example 3 of the present invention; Figure 2 This is a viscosity test chart of the discharge fluid obtained by the displacement device before and after the use of the diazonium salt-based formation pore clearing agent prepared in Example 3 of the present invention. DETAILED DESCRIPTION

[0027] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0028] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0029] Unless otherwise specified, all technical and scientific terms used herein have the common meanings understood by those skilled in the art for the present invention. In case of conflict, the definitions in this specification shall prevail.

[0030] 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.

[0031] In this article, 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).

[0032] In this document, unless otherwise specified, “includes,” “including,” “contains,” “has,” or similar terms cover the meanings of “consisting of” and “mainly consisting of,” for example, “A includes a” covers the meanings of “A includes a and other” and “A only includes a.”

[0033] 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.

[0034] 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.

[0035] The following examples use conventional instruments and equipment in the art. The experimental methods in the following examples where specific conditions are not specified are usually carried out under conventional conditions or under conditions recommended by the manufacturer. The various raw materials used in the following examples are conventional commercial products unless otherwise specified, and their specifications are conventional specifications in the art. In the specification of the present invention and the following examples, unless otherwise specified, "%" means weight percentage, "part" means weight part, and ratio means weight ratio.

[0036] The present invention provides a method for preparing a formation pore clearing agent based on diazonium salt, comprising the following steps: S1: Dissolve isooctyl p-aminobenzoate in an appropriate amount of ethanol, add a surfactant after it is completely dissolved, control the temperature to be 25-40°C and stir for 0.5-1.5 hours, then cool and stand to obtain the first intermediate. In another container, slowly drop a weak acid into the sodium nitrite solution, then add the sodium bisulfite solution, and stir evenly to obtain the second intermediate.

[0037] S2: In a nitrogen environment, slowly add the second intermediate to the first intermediate, maintain the reaction at 0-10°C for 1-2 hours, then raise the temperature of the reaction system to 15-25°C for 1-2 hours. After the reaction, remove the solvent by rotary evaporation to obtain a diazonium salt-based formation pore clearing agent.

[0038] As an optional solution, in step S1, the surfactant is any one of polyoxyethylene lauryl alcohol ether, polyethylene glycol monooleate and OP-10.

[0039] As an optional scheme, in step S1, the mass ratio of isooctyl p-aminobenzoate, ethanol and surfactant is 1:(2~2.5):(0.02~0.05).

[0040] As an optional solution, in step S1, the weak acid is any one of formic acid, acetic acid and fruit acid.

[0041] As an optional solution, in step S1, the mass concentration of the sodium nitrite solution is 5% to 12%; the mass concentration of the sodium bisulfite solution is 2% to 6%.

[0042] As an optional solution, in step S1, 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).

[0043] As an optional solution, in step S2, the mass ratio of the first intermediate to the second intermediate is 1:(1.5~1.8).

[0044] The present invention provides an application of a diazonium salt-based formation pore clearing agent prepared according to the above-mentioned preparation method in the field of petrochemical industry. When used as a pore clearing agent in the field of oil fields, through the synergistic effect of surfactants, isooctyl p-aminobenzoate cationic groups, weak acids and nitrogen, an efficient, mild and environmentally friendly clearing scheme is provided, which has significant advantages. The present invention not only achieves efficient clearing, but also can extend the service life of related equipment, reduce maintenance costs and downtime. By improving recovery, reducing maintenance costs, extending equipment life and reducing losses caused by shutdowns, the application of the pore clearing agent can significantly improve the economic benefits of oil fields.

[0045] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. The components of the embodiments of the present invention described and shown in the drawings here can usually be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0046] Example 1 A method for preparing a formation pore clearing agent based on diazonium salt comprises the following steps: S1: Dissolve 10 g of isooctyl p-aminobenzoate in 25 g of ethanol, add 0.3 g of polyethylene glycol monooleate after complete dissolution, control stirring at 28°C for 1 h, and then cool and stand to obtain the first intermediate. In another container, slowly drop 5 g of formic acid into 5 g of 5% sodium nitrite solution, then add 1.8 g of 5% sodium bisulfite solution, and stir evenly to obtain the second intermediate.

[0047] S2: In a nitrogen environment, 18 g of the second intermediate was slowly added dropwise to 10 g of the first intermediate, and the reaction temperature was maintained at 7 °C for 1.5 h. The reaction temperature was then raised to 18 °C for 1.5 h. After the reaction, the solvent was removed by rotary evaporation to obtain a diazonium salt-based formation pore clearing agent.

[0048] Example 2 A method for preparing a formation pore clearing agent based on diazonium salt comprises the following steps: S1: Dissolve 12 g of isooctyl p-aminobenzoate in 30 g of ethanol, add 0.35 g of OP-10 after complete dissolution, control stirring at 32°C for 1.2 h, and then cool and stand to obtain the first intermediate. In another container, slowly drop 6 g of acetic acid into 6 g of 8.5% sodium nitrite solution, then add 2 g of 4% sodium bisulfite solution, and stir evenly to obtain the second intermediate.

[0049] S2: In a nitrogen environment, 12 g of the second intermediate was slowly added dropwise to 8 g of the first intermediate, and the reaction temperature was maintained at 6 °C for 1.2 h. The reaction temperature was then raised to 22 °C for 2 h. After the reaction, the solvent was removed by rotary evaporation to obtain a diazonium salt-based formation pore clearing agent.

[0050] Example 3 A method for preparing a formation pore clearing agent based on diazonium salt comprises the following steps: S1: Dissolve 11.5 g of isooctyl p-aminobenzoate in 28 g of ethanol, add 0.28 g of polyethylene glycol monooleate after it is completely dissolved, control stirring at 35°C for 0.8 h, then cool and stand to obtain the first intermediate. In another container, slowly drop 5.5 g of formic acid into 5.5 g of 12% sodium nitrite solution, then add 1.9 g of 5% sodium bisulfite solution, and stir evenly to obtain the second intermediate.

[0051] S2: Under nitrogen environment, 24 g of the second intermediate was slowly added dropwise to 15 g of the first intermediate, and the reaction temperature was maintained at 10°C for 1.4 h. The reaction temperature was then raised to 19°C for 1.6 h. After the reaction, the solvent was removed by rotary evaporation to obtain a diazonium salt-based formation pore clearing agent.

[0052] Example 4 A method for preparing a formation pore clearing agent based on diazonium salt comprises the following steps: S1: Dissolve 9.5 g of isooctyl p-aminobenzoate in 22 g of ethanol, add 0.25 g of polyethylene glycol monooleate after complete dissolution, control stirring at 33°C for 1 h, and then cool and 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, and stir evenly to obtain the second intermediate.

[0053] S2: Under nitrogen environment, 23g of the second intermediate was slowly added dropwise to 14g of the first intermediate, and the reaction temperature was maintained at 8°C for 1.5 hours. Then, the reaction system was heated to 21°C and reacted for 1.8 hours. After the reaction, the solvent was removed by rotary evaporation to obtain a diazonium salt-based formation pore clearing agent.

[0054] Example 5 A method for preparing a formation pore clearing agent based on diazonium salt comprises the following steps: S1: Dissolve 13 g of isooctyl p-aminobenzoate in 32 g of ethanol, add 0.38 g of dodecanol polyoxyethylene ether after complete dissolution, control stirring at 38°C for 1.5 h, then cool and stand to obtain the first intermediate. In another container, slowly drop 6.2 g of acetic acid into 6.2 g of 9% sodium nitrite solution, then add 2.1 g of 4% sodium bisulfite solution, and stir evenly to obtain the second intermediate.

[0055] S2: Under nitrogen environment, 17g of the second intermediate was slowly added dropwise to 11g of the first intermediate, and the reaction was maintained at 4°C for 1.8 hours. The reaction system was then heated to 23°C for 2 hours. After the reaction, the solvent was removed by rotary evaporation to obtain a diazonium salt-based formation pore clearing agent.

[0056] Example 6 A method for preparing a formation pore clearing agent based on diazonium salt comprises the following steps: S1: Dissolve 10.8 g of isooctyl p-aminobenzoate in 27 g of ethanol, add 0.324 g of OP-10 after it is completely dissolved, control stirring at 30°C for 1 h, and then cool and stand to obtain the first intermediate. In another container, slowly add 6 g of fruit acid to 6 g of 10% sodium nitrite solution, then add 2 g of 3% sodium bisulfite solution, and stir evenly to obtain the second intermediate.

[0057] S2: Under nitrogen environment, 21g of the second intermediate was slowly added dropwise to 13g of the first intermediate, and the reaction temperature was maintained at 5°C for 1.5 hours. Then, the reaction temperature was raised to 20°C and the reaction temperature was raised to 20°C for 1.5 hours. After the reaction, the solvent was removed by rotary evaporation to obtain a diazonium salt-based formation pore clearing agent.

[0058] Example 7 A method for preparing a formation pore clearing agent based on diazonium salt comprises the following steps: S1: Dissolve 10 g of isooctyl p-aminobenzoate in 20 g of ethanol, add 0.2 g of polyethylene glycol monooleate after it is completely dissolved, control stirring at 25°C for 1 h, and then cool and stand to obtain the first intermediate. In another container, slowly drop 6 g of acetic acid into 5 g of 5% sodium nitrite solution, then add 1 g of 2% sodium bisulfite solution, and stir evenly to obtain the second intermediate.

[0059] S2: In a nitrogen environment, 18 g of the second intermediate was slowly added dropwise to 10 g of the first intermediate, and the reaction was maintained at 0°C for 1 hour. The reaction system was then heated to 15°C for 1 hour. After the reaction, the solvent was removed by rotary evaporation to obtain a diazonium salt-based formation pore clearing agent.

[0060] Example 8 A method for preparing a formation pore clearing agent based on diazonium salt comprises the following steps: S1: Dissolve 10 g of isooctyl p-aminobenzoate in 25 g of ethanol, add 0.5 g of dodecanol polyoxyethylene ether after complete dissolution, control stirring at 40°C for 0.5 h, then cool and stand to obtain the first intermediate. In another container, slowly drop 8.8 g of fruit acid into 5 g of 8% sodium nitrite solution, then add 2 g of 3% sodium bisulfite solution, and stir evenly to obtain the second intermediate.

[0061] S2: In a nitrogen environment, 17 g of the second intermediate was slowly added dropwise to 10 g of the first intermediate, and the reaction temperature was maintained at 3 °C for 2 h. The reaction temperature was then raised to 25 °C for 2 h. After the reaction, the solvent was removed by rotary evaporation to obtain a diazonium salt-based formation pore clearing agent.

[0062] Characterization and Testing: In order to evaluate the effect of the formation pore clearing agent, the clearing agent synthesized in Example 3 was tested. In order to evaluate the effect of the clearing agent on the clearing of colloid blockages, the pressure difference test of the displacement device was carried out to monitor the pressure changes at the inlet and outlet before and after the application of the clearing agent. Since the blockage is a bond of organic matter and inorganic minerals, the significant reduction in pressure difference indicates that the colloid blockage has been partially removed, which means that the clearing agent effectively improves the fluidity of the pores and enhances the permeability of the fluid. Test method: Add 20 g of a colloid solution with a solid content of 0.6% to the displacement equipment, carry out swelling treatment for 2 hours, then start the displacement test and record the inlet and outlet pressure difference at this time. During this process, 10 g, 20 g, 30 g, 40 g and 50 g of the clearing agent were gradually injected into the displacement device for 12 hours, and then the displacement test was continued, and the inlet and outlet pressure difference was recorded again. For detailed test results, see Figure 1 .

[0063] Figure 1 This is a test diagram of the pressure difference between the inlet and outlet of the displacement device before and after the diazonium salt-based formation pore clearing agent prepared in Example 3 of the present invention is used; Figure 1 It can be seen that with the increase in the amount of plugging agent used, the pressure difference between the inlet and outlet gradually decreases, which indicates that with the increase in the amount of plugging agent, the amount of dissolution and removal of colloid plugging gradually increases, and the pore dredging effect is gradually enhanced. This is because the increase in the amount of plugging agent makes the colloid structure looser, and the increase in nitrogen release produces a pressure effect and causes more plugging to be discharged from the pores, thereby effectively improving the formation permeability.

[0064] In order to evaluate the effect of the formation pore clearing agent, the clearing agent synthesized in Example 3 was tested against the colloid blockages. The pressure difference test of the displacement device was used to monitor the viscosity change of the discharge fluid after clearing. Since the colloid blockages will be partially dissolved in the discharge fluid after being removed, resulting in an increase in the viscosity of the discharge fluid, the clearing effect can be reflected to a certain extent from the viscosity change of the discharge fluid. Test method: Add 20 g of a colloid solution with a solid content of 0.6% to the displacement equipment, carry out swelling treatment for 2 hours, then start the displacement test and record the inlet and outlet pressure difference at this time. During this process, 10 g, 20 g, 30 g, 40 g and 50 g of the clearing agent were gradually injected into the displacement device for 12 hours, and then the displacement test was continued, and the viscosity value of the discharge fluid was recorded again. For detailed test results, see Figure 2 .

[0065] Figure 2 This is a viscosity test diagram of the discharge fluid obtained by the displacement device before and after the use of the diazonium salt-based formation pore clearing agent prepared in Example 3 of the present invention; Figure 2 It can be seen that as the amount of the clearing agent used increases, the viscosity of the discharged liquid shows an increasing trend. This phenomenon shows that the increase in the amount of the clearing agent promotes the breaking and dissolution of the colloid blockage. The clearing agent loosens and softens the colloid structure in the formation, and these softened colloid molecules are discharged through the pressure difference formed by nitrogen, resulting in an increase in the viscosity of the discharged liquid. The higher the viscosity means that more colloid is discharged, and the effect of clearing the formation pores is more significant. This excellent performance provides a reliable technical guarantee for the blockage of formation pores under complex working conditions, and further verifies the potential value of the present invention in practical applications.

[0066] In summary, the present invention discloses a formation pore clearing agent based on diazonium salt and a preparation method thereof, wherein isooctyl p-aminobenzoate is dissolved in an appropriate amount of ethanol, a surfactant is added after complete dissolution, and the mixture is stirred at a temperature T1 for a certain time t1 and then cooled and allowed to stand to obtain a first intermediate. In another container, a weak acid is slowly added dropwise to a sodium nitrite solution, and then a sodium bisulfite solution is added, and the second intermediate is obtained after stirring evenly. Under a nitrogen environment, the second intermediate is slowly added dropwise to the first intermediate, and after a certain time t2 of reaction is maintained at a certain temperature T2, the reaction system is then raised to a certain temperature T3 and reacted for a certain time t3. After the reaction is completed, the solvent is removed by rotary evaporation to obtain a formation pore clearing agent based on diazonium salt. First, a surfactant is used to reduce the surface tension of the colloid plug, so that it is dispersed in the pores and the adhesion of the plug is reduced, thereby increasing the wettability of the pores. Secondly, the high temperature conditions of the formation are used to decompose the diazonium salt to produce the isooctyl p-aminobenzoate cationic group, and the isooctyl p-aminobenzoate cationic group undergoes electrophilic addition or substitution reaction with the electron-rich parts (such as unsaturated carbon-carbon bonds, aromatic rings) in the blockage, so that the molecular structure of the blockage is loose, and its bonding strength is further reduced; the introduction of weak acid gently dissolves the inorganic mineral components in the colloid blockage, destroys its internal bonding structure, and avoids the risk of pipeline corrosion caused by strong acid. Finally, the nitrogen released by the decomposition of the diazonium salt forms a pressure shock in the pores, discharges the loose blockages from the pores, and achieves the effect of deep clearing. The formation pore clearing agent provided by the present invention overcomes the shortcomings of traditional strong acid and organic solvent clearing methods, and has broad application prospects.

[0067] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements 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 clearing agent based on diazonium salt, characterized in that: The following steps are involved: Dissolve isooctyl p-aminobenzoate in ethanol, add a surfactant, stir to react, cool and stand to obtain a first intermediate; Slowly drop a weak acid into a sodium nitrite solution, then add a sodium bisulfite solution, and stir evenly to obtain a second intermediate; under a nitrogen environment, slowly drop the second intermediate into the first intermediate, keep warm for reaction, then heat the reaction, remove the solvent by rotary evaporation, and obtain a formation pore clearing agent based on a diazonium salt.

2. The method for preparing the diazonium salt-based formation pore clearing agent according to claim 1, characterized in that: 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).

3. The method for preparing the diazonium salt-based formation pore clearing agent according to claim 1, characterized in that: The mass concentration of the sodium nitrite solution is 5% to 12%; the mass concentration of the sodium bisulfite solution is 2% to 6%.

4. The method for preparing the diazonium salt-based formation pore clearing agent according to claim 1, characterized in that: The mass ratio of the first intermediate to the second intermediate is 1:(1.5-1.8).

5. The method for preparing the diazonium salt-based formation pore clearing agent according to claim 1, characterized in that: The stirring reaction is carried out at a temperature of 25-40° C. and for a time of 0.5-1.5 h.

6. The method for preparing the diazonium salt-based formation pore clearing agent according to claim 1, characterized in that: The temperature of the heat preservation reaction is 0-10°C and the time is 1-2h.

7. The method for preparing the diazonium salt-based formation pore clearing agent according to claim 1, characterized in that: The temperature of the temperature-raising reaction is 15-25° C. and the time is 1-2 hours.

8. The method for preparing the diazonium salt-based formation pore clearing agent according to claim 1, characterized in that: The surfactant is any one of lauryl alcohol polyoxyethylene ether, polyethylene glycol monooleate and OP-10; the weak acid is any one of formic acid, acetic acid and fruit acid.

9. A formation pore clearing agent based on diazonium salt, characterized in that: The diazonium salt-based formation pore clearing agent is prepared by the preparation method of any one of claims 1 to 8.

10. Use of the diazonium salt-based formation pore clearing agent prepared by the preparation method of the diazonium salt-based formation pore clearing agent according to any one of claims 1 to 8 in oil production.

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