Oil well unblocking composition, preparation method thereof and targeted formation pore controlled-release unblocking method

Abstract

The invention relates to the technical field of oil field operation, and particularly discloses an oil well unblocking composition, a preparation method thereof and a targeted formation pore controlled-release unblocking method. Compared with a traditional unblocking means, the oil well unblocking composition can go deep into a stratum when used for unblocking operation, secondary pollution is little, various blockages in stratum pores are accurately removed, the pore permeability is improved, the life cycle of an oil well is prolonged, the unblocking effect of deep stratum pores is remarkably improved, and the oil well unblocking composition is suitable for being used in the deep stratum. The yield and the economic benefit of an oil field are increased.

Description

Technical Field

[0001] The present application relates to the technical field of oilfield operation, and more specifically, to an oil well deblocking composition and a preparation method thereof, and a targeted formation pore controlled-release deblocking method. Background Art

[0002] Oil has the characteristics of high energy density and easy transportation. It is mainly used as fuel and gasoline. It is known as the most important driving energy today. At present, most of the transportation energy is obtained from oil. In addition, oil is also the raw material for chemical industrial products such as fertilizers, solutions, pesticides and plastics. Therefore, oil is called "the blood of industry". In recent years, with the continuous consumption of oil resources, the scope of oil field exploration and development has gradually expanded, the degree has gradually deepened, and the difficulty of oil extraction has gradually increased. Therefore, how to further improve the recovery rate of crude oil will be a key problem to be overcome in the future.

[0003] Among the proven oil field reserves in my country, low-permeability oil reservoirs account for a large proportion. The original oil layer structure of this oil field is dense, and it is difficult for crude oil to penetrate from the oil layer into the wellbore. Generally, it requires the help of fracturing and other means to achieve effective development. Under the action of external fracturing forces, the original structure of the oil layer will be changed. The external fracturing force will cause cracks to form in the oil layer, and crude oil can easily flow into the wellbore through the side walls of the cracks. The speed at which crude oil passes through the cracks depends on the permeability of the cracks. The cracks with high permeability also have a fast speed at which crude oil passes through the cracks. Therefore, the energy consumption of crude oil flowing to the wellbore has also been reduced, allowing the fluid to flow to the wellbore at a higher capacity. In this way, not only can the production of oil wells be effectively increased, but also the oil wells can maintain a certain self-flowing ability.

[0004] With the long-term exploitation of oil wells, the temperature and pressure of the oil layer also decrease, which makes the near-well area very easy to precipitate wax and scale; some well formations are sensitive to flow rate. Due to the high flow rate or large pressure difference fluctuation, the inherent particles in the formation fall off and move with the fluid, which easily forms "bridge blockage" accumulation in the pore channel; the mismatch between the injected water and the formation fluid will lead to the formation of salt scale and emulsion blockage in the formation. These precipitates are deposited in the pore throats that the injected water can reach, causing the pore throat flow section to continue to shrink. Under such conditions, if the fracturing fluid is not completely debonded after the fracturing construction is completed, a large amount of polymer fragments will be generated. These fragments will be retained in the pore throats, thereby causing serious damage to the propped fractures and formation permeability, and severely hindering the flow of fluids in the propped fractures, so the oil well production will be significantly reduced.

[0005] With respect to the above-mentioned related technologies, the inventors believe that, although some methods for removing blockages have been developed to address the problem of oil well blockages, these methods are still inadequate for dealing with blockages between pores in deep formations. It is difficult to completely remove the blockages in the pores, and they often only treat the symptoms but not the root cause or are prone to cause secondary pollution. Summary of the invention

[0006] The unblocking methods in the related art are difficult to completely remove the blockages in the pores, and often only treat the symptoms but not the root cause or easily cause secondary pollution. In order to improve this defect, the present application provides an oil well unblocking composition and a preparation method thereof and a controlled release unblocking method for targeted formation pores.

[0007] In the first aspect, the present application provides an oil well plugging removal composition, which adopts the following technical solution: An oil well plugging removal composition comprises the following components in parts by weight: 16-18 parts of oxidant microcapsules, 6-8 parts of plugging removal aids, 0.6-0.8 parts of surfactants, 3-5 parts of clay stabilizers, 0.7-0.9 parts of ion stabilizers, 6-8 parts of demulsifiers, 2-4 parts of drainage aids, and 70-80 parts of water; the oxidant microcapsules contain persulfate, and the components of the plugging removal aids include alkali metal hydroxides.

[0008] By adopting the above technical scheme, the present application selects microcapsules containing strong oxidant persulfate as the main component of the unblocking composition, and adds an unblocking aid containing alkali metal hydroxide for coordination. Alkali metal hydroxide can dissolve mineral components such as silica in the stratum shedding, and has a certain dissolving effect on asphaltene and colloid in the oil well blockage, which promotes the disintegration of the blockage. The persulfate released by the oxidant microcapsules can further crack the polymer fragments, and the surfactant can reduce the aggregation of these cracking products. Through the synergistic effect of oxide microcapsules and unblocking aids, the main components of the oil well blockage can be effectively eliminated. In this process, clay stabilizers and ion stabilizers can reduce the interference of clay and formation ions, demulsifiers destroy the emulsion formed by fracturing fluid and formation fluid, and reduce the viscosity of the entire unblocking system, while drainage aids can reduce the interfacial tension of the unblocking system, reducing the obstruction caused by the formation to the backflow operation. Compared with traditional unblocking methods, the use of the oil well unblocking composition of the present application for unblocking operations can not only penetrate deep into the formation, but also has less secondary pollution, and can accurately remove various blockages in the formation pores, thereby improving pore permeability and extending the life cycle of the oil well; it significantly improves the unblocking effect of deep formation pores and increases the output and economic benefits of the oil field.

[0009] Preferably, the oxidant microcapsules are prepared according to the following method: Persulfate, stabilizer, ethanol and butanol are added to chloroform and stirred to mix, then acetic acid is added, and then a mixture of pyrrole and glycerol is dropped, and the reaction is continued under continuous stirring. After the reaction is completed, the remaining solid matter is washed and then vacuum dried to obtain oxidant microcapsules.

[0010] By adopting the above technical solution, the method of the present application makes the pyrrole monomer and the persulfate in the same continuous phase, and uses the oxidizing property of the persulfate to initiate the polymerization of the pyrrole monomer to form insoluble polypyrrole. The polypyrrole precipitates from the continuous phase and coats the persulfate to finally form microcapsules. The stabilizer provides good dispersibility for the microcapsules in this process, avoiding excessive concentration of the microcapsules.

[0011] Preferably, the stabilizer is a mixture of sodium lauryl sulfate and polyethylene glycol.

[0012] By adopting the above technical scheme, the compound of sodium dodecyl sulfate and polyethylene glycol can effectively promote the adsorption and polymerization of pyrrole monomer on the surface of ammonium persulfate, improve the dispersion effect of microcapsules, and help to improve the unblocking efficiency of the unblocking composition.

[0013] Preferably, the alkali metal hydroxide in the plugging-removing aid is one of sodium hydroxide and potassium hydroxide.

[0014] By adopting the above technical solution, the present application preferably uses sodium hydroxide and potassium hydroxide, two alkali metal hydroxides, both of which can effectively improve the unblocking effect of the unblocking composition.

[0015] Preferably, the blocking-removing aid further comprises triethanolamine.

[0016] By adopting the above technical solution, triethanolamine itself also has a certain alkalinity and good compatibility with the alkaline environment of the plugging-removing composition. In addition, triethanolamine can catalyze the oxidative decomposition reaction of persulfate, which helps to enhance the plugging-removing effect of the plugging-removing composition.

[0017] Preferably, the amount of triethanolamine used accounts for 18-26% of the total weight of the plugging-removing auxiliary agent.

[0018] By adopting the above technical solution, the present application optimizes the dosage of triethanolamine, which helps to improve the unblocking effect of the unblocking composition.

[0019] Preferably, the components of the blocking-removing aid further include a persulfate activator, and the persulfate activator is prepared according to the following method: (1) mixing cobalt nitrate hexahydrate and 2-methylimidazole, and calcining the mixture under the protection of an inert atmosphere to obtain solid particles; (2) The solid particles are washed with a sulfuric acid solution, then washed with methanol and filtered, and finally washed with water to obtain a persulfate activator.

[0020] By adopting the above technical solution, the present application prepares a persulfate activator using cobalt nitrate hexahydrate and 2-methylimidazole as raw materials, which can further improve the oxidation ability of persulfate and improve the declogging effect of the declogging composition.

[0021] Preferably, the weight ratio of the cobalt nitrate hexahydrate to 2-methylimidazole is (2.5-3.5):(6.5-7.5).

[0022] By adopting the above technical solution, the present application optimizes the weight ratio of cobalt nitrate hexahydrate and 2-methylimidazole, which helps to improve the unblocking effect of the unblocking composition.

[0023] In a second aspect, the present application provides a method for preparing an oil well declogging composition, which adopts the following technical solution.

[0024] A method for preparing an oil well plugging-releasing composition comprises the following steps: (1) mixing oxidant microcapsules, a plugging-removing aid, a clay stabilizer, an ion stabilizer, a demulsifier, and a drainage aid to obtain a mixture for later use; mixing a surfactant and water to obtain a dispersion for later use; (2) Mixing the mixed material and the dispersion to obtain an oil well plugging removal composition.

[0025] In a third aspect, the present application provides a method for targeted formation pore controlled release and unblocking, which adopts the following technical solution.

[0026] A method for targeted formation pore controlled release plugging removal comprises the following steps: (1) preparing any one of the above-mentioned oil well plugging removal compositions for use; (2) Inject the plugging-removing composition into the perforation blasthole, wait for the plugging-removing composition to completely dissolve the blockage in the oil well, and then perform the flowback operation.

[0027] In summary, this application has the following beneficial effects: 1. Compared with traditional unblocking methods, the oil well unblocking composition of the present application can not only penetrate deep into the formation, but also has less secondary pollution, and can accurately remove various blockages in the formation pores, thereby improving pore permeability and extending the life cycle of the oil well; it significantly improves the unblocking effect of deep formation pores and increases the output and economic benefits of the oil field.

[0028] 2. In the present application, triethanolamine is preferably used as the unblocking aid. Triethanolamine itself also has a certain alkalinity and is compatible with the alkaline environment of the unblocking composition. In addition, triethanolamine can catalyze the oxidative decomposition reaction of persulfate, which helps to enhance the unblocking effect of the unblocking composition.

[0029] 3. The present application uses cobalt nitrate hexahydrate and 2-methylimidazole as raw materials to prepare a persulfate activator, which can further enhance the oxidizing ability of persulfate and improve the declogging effect of the declogging composition. DETAILED DESCRIPTION

[0030] The present application is further described in detail below in conjunction with embodiments, preparation examples and comparative examples. The raw materials involved in the present application can all be obtained commercially.

[0031] Preparation Example of Oxidant Microcapsules The following is an explanation using Preparation Example 1.

[0032] Preparation Example 1 In this preparation example, ammonium persulfate is used as the persulfate, and sodium dodecyl sulfate is used as the stabilizer.

[0033] In this preparation example, the oxidant microcapsules were prepared according to the following method: Persulfate, stabilizer, ethanol, butanol and chloroform were weighed in a ratio of 5kg:0.52kg:0.24kg:0.16g:40L, and persulfate, stabilizer, ethanol and butanol were added to chloroform at 25°C and stirred for 1 hour, and then acetic acid was added to adjust the pH to 4.5, and then a mixture of pyrrole and glycerol (the weight ratio of pyrrole to glycerol was 1:0.85, and the weight ratio of pyrrole to ammonium persulfate was 1:3) was added, and the reaction was continued for 4 hours under continuous stirring. After the reaction, the remaining solid matter was washed twice with distilled water and once with ethanol, and then vacuum dried at 50°C for 24 hours to obtain oxidant microcapsules.

[0034] Preparation Example 2 The difference between this preparation example and preparation example 1 is that the stabilizer is a mixture of sodium lauryl sulfate and polyethylene glycol, and the weight ratio of sodium lauryl sulfate to polyethylene glycol is 5:8. Preparation Example of Persulfate Activator The following is an explanation using Preparation Example 3.

[0035] Preparation Example 3 In this preparation example, the persulfate activator was prepared according to the following method: (1) mixing cobalt nitrate hexahydrate and 2-methylimidazole in a weight ratio of 1:10, and calcining the mixture at 920° C. for 2 h under argon atmosphere to obtain solid particles; (2) The solid particles are washed with a 10 wt % sulfuric acid solution, then washed with methanol and filtered, and finally washed with water to obtain a persulfate activator.

[0036] Preparation Example 4 The difference between this preparation example and preparation example 3 is that the weight ratio of cobalt nitrate hexahydrate to 2-methylimidazole is 2.5:7.5.

[0037] Preparation Example 5 The difference between this preparation example and preparation example 3 is that the weight ratio of cobalt nitrate hexahydrate to 2-methylimidazole is 3:7.

[0038] Preparation Example 6 The difference between this preparation example and preparation example 3 is that the weight ratio of cobalt nitrate hexahydrate to 2-methylimidazole is 3.5:6.5. Example

[0039] Examples 1-5 The following description is given by taking Example 1 as an example.

[0040] Example 1 In this embodiment, the oxidant microcapsules are prepared according to the method of Preparation Example 1, the blocking aid is sodium hydroxide, the surfactant is sodium dodecylbenzene sulfonate, the clay stabilizer is China Building Materials Zhongyan TD-1 anti-mud agent, the ion stabilizer is tetrasodium ethylenediaminetetraacetic acid, the demulsifier is a mixture of demulsifier TA-1031 and demulsifier SP-169 in a weight ratio of 3:1, and the drainage aid is CT5-4 drainage aid.

[0041] This embodiment provides an oil well declogging composition, comprising the following components in parts by weight: 16 kg of oxidant microcapsules, 6 kg of declogging aid, 0.6 kg of surfactant, 3 kg of clay stabilizer, 0.7 kg of ion stabilizer, 6 kg of demulsifier, 2 kg of drainage aid, and 70 kg of water.

[0042] This embodiment provides a method for preparing an oil well plugging-releasing composition, comprising the following steps: (1) mixing oxidant microcapsules, a plugging-removing aid, a clay stabilizer, an ion stabilizer, a demulsifier, and a drainage aid to obtain a mixture for later use; mixing a surfactant and water to obtain a dispersion for later use; (2) Mixing the mixed material and the dispersion to obtain an oil well plugging removal composition.

[0043] This embodiment provides a method for targeted formation pore controlled release plugging removal, comprising the following steps: (1) preparing an oil well plugging-removing composition for standby use; (2) Inject the plugging-removing composition into the perforation blasthole, wait for the plugging-removing composition to completely dissolve the blockage in the oil well, and then perform the flowback operation.

[0044] As shown in Table 1, the main difference between Examples 1-5 is that the raw material ratios of the oil well plugging removal composition are different.

[0045] Table 1 Raw material ratio of oil well plugging removal composition sample Example 1 Example 2 Example 3 Example 4 Example 5 Oxidant microcapsules / kg 16 16.5 17 17.5 18 Blockage-relieving agent / kg 6 6.5 7 7.5 8 Surfactant / kg 0.6 0.65 0.7 0.75 0.8 Clay stabilizer / kg 3 3.5 4 4.5 5 Ion stabilizer / kg 0.7 0.75 0.8 0.85 0.9 Demulsifier / kg 6 6.5 7 7.5 8 Drainage aid / kg 2 2.5 3 3.5 4 Water / kg 70 72 75 78 80 Example 6 The difference between this embodiment and embodiment 5 is that the oxidant microcapsules are prepared according to the method of preparation example 2.

[0046] Example 7 The difference between this embodiment and embodiment 6 is that potassium hydroxide is used as the blocking-removing auxiliary agent.

[0047] Example 8 The difference between this embodiment and embodiment 7 is that the component of the blocking-removing aid further includes triethanolamine, and the amount of triethanolamine used accounts for 15% of the total weight of the blocking-removing aid.

[0048] Example 9 The difference between this embodiment and embodiment 8 is that the amount of triethanolamine used accounts for 18% of the total weight of the plugging-removing auxiliary agent.

[0049] Example 10 The difference between this embodiment and embodiment 8 is that the amount of triethanolamine used accounts for 22% of the total weight of the plugging-removing auxiliary agent.

[0050] Embodiment 11 The difference between this embodiment and embodiment 8 is that the amount of triethanolamine used accounts for 26% of the total weight of the plugging-removing auxiliary agent.

[0051] Example 12 The difference between this embodiment and embodiment 11 is that the components of the blocking-removing aid further include a persulfate activator, the blocking-removing aid is prepared according to the method of preparation example 3, and the amount of the persulfate activator accounts for 5% of the total weight of the blocking-removing aid.

[0052] Example 13 The difference between this embodiment and embodiment 12 is that the blocking-removing aid is prepared according to the method of preparation example 4.

[0053] Embodiment 14 The difference between this embodiment and embodiment 12 is that the blocking-removing aid is prepared according to the method of preparation example 5.

[0054] Embodiment 15 The difference between this embodiment and embodiment 12 is that the blocking-removing aid is prepared according to the method of preparation example 6.

[0055] Comparative Example Comparative Example 1 The difference between this comparative example and Example 1 is that the components of the oil well plugging removal composition do not include oxidant microcapsules.

[0056] Comparative Example 2 The difference between this comparative example and Example 3 is that the components of the oil well plugging removal composition do not include a plugging removal aid.

[0057] Performance test method Test environment: An oil field was selected for field testing, and samples of blockages in the perforation holes were collected. After analysis, it was found that the blockages contained the following components in weight percentage: wax 67.9%, asphaltene 12.6%, colloid 13.1%, and the remainder were formation impurities.

[0058] Remove the blockage of the blasthole and nearby formations in the perforation section. According to the formula V = φ × d × π × (R 2 -r 2 )+n×d×(Rr)×π×r0 2 The amount of the deblocking composition is calculated, where V is the total volume of the deblocking composition, φ is the physical porosity of the oil layer, d is the length of the perforation section, R is the perforation radius of the oil well, r is the radius of the oil layer casing, n is the perforation density, and r0 is the perforation hole diameter.

[0059] Referring to the targeted formation pore controlled-release unblocking method of each embodiment and comparative example, the unblocking composition was added according to the calculated amount, and timing was performed at the same time. After the unblocking composition was added, the well was shut down for 10 hours, and the return flow was continuous and stable until the return liquid flow rate was continuous and stable, and the pH value of the return liquid was lower than 8, and production was arranged. Stable production indicated that the liquid flow channel had been connected, the oil layer was adequately supplied with liquid, and the unblocking was successful. The timing reading at this time was recorded, which was the unblocking time. The unblocking time of each embodiment and comparative example is shown in Table 2.

[0060] Table 2 Unblocking time Combining Examples 1-5 and Comparative Examples 1-2 and Table 2, it can be seen that the unblocking time measured in Examples 1-5 is shorter. This is because the present application uses the synergistic effect of oxide microcapsules and unblocking aids to effectively dissolve the main components that form oil well blockages, thereby fully dissolving the blockages. Comparative Example 1 lacks oxidant microcapsules. Although a certain unblocking effect can be achieved through the alkaline components in the unblocking aid, the unblocking effect is relatively poor because the polymer fragments cannot be fully cracked. Although Comparative Example 2 can achieve the cracking of polymer fragments, it lacks a unblocking aid and cannot dissolve components such as silica, asphaltene, and colloid, so the unblocking effect is also poor.

[0061] Combining Example 5 and Example 6 with Table 2, it can be seen that the unblocking time measured in Example 6 is shorter, indicating that the compound of sodium dodecyl sulfate and polyethylene glycol can effectively promote the adsorption and polymerization of pyrrole monomer on the surface of ammonium persulfate, improve the dispersion effect of microcapsules, and help to improve the unblocking efficiency of the unblocking composition.

[0062] It can be seen from Example 6 and Example 7 and Table 2 that when potassium hydroxide is used as a component of the blocking-removing auxiliary agent, the blocking-removing composition has a better blocking-removing effect.

[0063] Combining Example 7, Example 8-11 and Table 2, it can be seen that the unblocking time measured in Example 8-11 is relatively short. This is because triethanolamine itself also has a certain alkalinity and is compatible with the alkaline environment of the unblocking composition. In addition, triethanolamine can catalyze the oxidative decomposition reaction of persulfate, which helps to enhance the unblocking effect of the unblocking composition. Combining Examples 9-11, it can be seen that when the amount of triethanolamine used accounts for 18-26% of the total weight of the unblocking aid, it helps to improve the unblocking effect of the unblocking composition.

[0064] It can be seen from Example 11, Examples 12-15 and Table 2 that the unblocking time measured in Examples 12-15 is relatively short, because the persulfate activator can further improve the oxidizing ability of the persulfate and improve the unblocking effect of the unblocking composition. Moreover, when the weight ratio of cobalt nitrate hexahydrate to 2-methylimidazole is (2.5-3.5): (6.5-7.5), the unblocking effect of the unblocking composition is better.

[0065] The above embodiments are merely explanations of the present application and are not limitations of the present application. After reading this specification, those skilled in the art may make modifications to the embodiments of the present application without any creative contribution as needed. However, as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. An oil well plugging removal composition, characterized in that: The invention comprises the following components in parts by weight: 16-18 parts of oxidant microcapsules, 6-8 parts of plugging-removing aid, 0.6-0.8 parts of surfactant, 3-5 parts of clay stabilizer, 0.7-0.9 parts of ion stabilizer, 6-8 parts of demulsifier, 2-4 parts of drainage aid and 70-80 parts of water; the oxidant microcapsules contain persulfate, and the components of the plugging-removing aid include alkali metal hydroxide.

2. The oil well plugging removal composition according to claim 1, characterized in that: The oxidant microcapsules are prepared according to the following method: Persulfate, stabilizer, ethanol and butanol are added to chloroform and stirred to mix, then acetic acid is added, and then a mixture of pyrrole and glycerol is dropped, and the reaction is continued under continuous stirring. After the reaction is completed, the remaining solid matter is washed and then vacuum dried to obtain oxidant microcapsules.

3. The oil well plugging removal composition according to claim 2, characterized in that: The stabilizer is a mixture of sodium lauryl sulfate and polyethylene glycol.

4. The oil well plugging removal composition according to claim 1, characterized in that: The alkali metal hydroxide in the blocking-removing auxiliary agent is one of sodium hydroxide and potassium hydroxide.

5. The oil well plugging removal composition according to claim 4, characterized in that: The components of the blocking-removing auxiliary agent also include triethanolamine.

6. The oil well plugging removal composition according to claim 5, characterized in that: The amount of triethanolamine used accounts for 18-26% of the total weight of the plugging-removing auxiliary agent.

7. The oil well plugging removal composition according to claim 4, characterized in that: The components of the blocking-removing aid also include a persulfate activator, and the persulfate activator is prepared according to the following method: (1) mixing cobalt nitrate hexahydrate and 2-methylimidazole, and calcining the mixture under an inert atmosphere to obtain solid particles; (2) The solid particles are washed with a sulfuric acid solution, then washed with methanol and filtered, and finally washed with water to obtain a persulfate activator.

8. The oil well plugging removal composition according to claim 7, characterized in that: The weight ratio of the cobalt nitrate hexahydrate to 2-methylimidazole is (2.5-3.5):(6.5-7.5).

9. The method for preparing the oil well plugging-releasing composition according to any one of claims 1 to 8, characterized in that: The following steps are involved: (1) Mixing oxidant microcapsules, plugging-removing aids, clay stabilizers, ion stabilizers, demulsifiers, and drainage aids to obtain a mixture, which is set aside; mixing surfactants and water to obtain a dispersion, which is set aside; (2) The mixed material and the dispersion are mixed to obtain an oil well plugging removal composition.

10. A method for targeted formation pore controlled release plugging removal, characterized in that: The following steps are involved: (1) preparing the oil well plugging removal composition according to any one of claims 1 to 8 for standby use; (2) Inject the plugging-removing composition into the perforation hole, wait for the plugging-removing composition to completely dissolve the blockage in the oil well, and then perform the flowback operation.

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