A cationic clay stabilizer and its preparation method

Abstract

This invention belongs to the field of oilfield development technology, specifically relating to a cationic clay stabilizer and its preparation method. The clay stabilizer comprises the following components by weight: 10-20 parts of a copolymer of 3-chloro-2-hydroxypropylmethyldiallyl ammonium chloride / dimethyldiallyl ammonium chloride, and 3-10 parts of vinyl phosphate-modified silica. The preparation method is as follows: the copolymer and modified silica are added together to a stirrer, heated to 50-60°C and stirred at 100-300 r / min, then cooled to 40-45°C and stirred again at 300-600 r / min to obtain the clay stabilizer. The clay stabilizer of this invention exhibits excellent comprehensive performance, high anti-swelling rate (greater than 92% even at 150°C, and higher than 93% after three water washes), good salt and acid / alkali resistance, and significantly improves the hydrophobicity of clay surfaces, making it suitable for complex oil reservoir conditions such as high temperature and high salinity.

Description

Technical Field

[0001] This invention belongs to the field of oilfield exploitation technology, specifically relating to a cationic clay stabilizer and its preparation method. Background Technology

[0002] Clay minerals are widely present in oil and gas reservoirs. When they come into contact with external fluids such as drilling fluids, fracturing fluids, and injected water, they are prone to hydration, swelling, and dispersion migration, leading to blockage of reservoir pore throats, decreased permeability, and reduced oil and gas production. Therefore, clay stabilizers have become an indispensable key chemical agent in oil and gas field development. An ideal clay stabilizer needs to possess comprehensive properties such as excellent anti-swelling effect, water washability, salt and acid / alkali resistance, high temperature resistance, and hydrophobicity and anti-wetting properties to adapt to complex formation environments (such as high temperature, high salinity, and strong acid / alkali conditions) and long-term development needs.

[0003] However, existing clay stabilizers have many technical defects and are difficult to meet the above-mentioned comprehensive performance requirements. Existing clay stabilizers mainly include inorganic salts, inorganic polynuclear polymers, cationic surfactants, cationic polymers, and zwitterionic polymers. Among them, inorganic salts (such as KCl and CaCl2) are low in cost but have a short shelf life and are not resistant to erosion; inorganic polynuclear polymers (such as aluminum hydroxide) have poor acid resistance; cationic surfactants tend to make the formation oleophilic, reducing the permeability of the oil and gas phases; cationic polymers are easily degraded at high temperatures; although zwitterionic polymers have good temperature resistance, salt resistance, and acid and alkali resistance, they still have insufficient long-term effectiveness and limited high-temperature resistance; in composite stabilizers containing nano-silica, the nano-silica is not effectively modified or the modification method is unreasonable, resulting in the nano-silica being prone to agglomeration, poor dispersibility, and weak synergistic effect with organic components.

[0004] Therefore, there is an urgent need to develop a clay stabilizer that combines strong water resistance, salt resistance, acid and alkali resistance, high temperature resistance, long-lasting anti-swelling properties, and excellent hydrophobic properties. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and to provide a cationic clay stabilizer and its preparation method. This stabilizer, through synergistic compounding, aims to simultaneously achieve the following comprehensive properties: highly efficient and long-lasting anti-swelling, excellent water washability, broad salt and acid / alkali resistance, outstanding high-temperature stability, and effective reservoir hydrophobic modification capability, thereby meeting the protection requirements of complex and demanding oil and gas reservoirs such as deep, ultra-deep, and high-salinity reservoirs.

[0006] To achieve the above-mentioned objectives, the present invention adopts the following technical solution: A cationic clay stabilizer comprises the following raw materials in parts by weight: 10-20 parts of 3-chloro-2-hydroxypropylmethyldiallylammonium chloride / dimethyldiallylammonium chloride copolymer and 3-10 parts of vinyl phosphate modified silica.

[0007] Furthermore, the clay stabilizer comprises the following raw materials in parts by weight: 15 parts of 3-chloro-2-hydroxypropylmethyldiallylammonium chloride / dimethyldiallylammonium chloride copolymer and 5 parts of vinyl phosphate modified silica.

[0008] Furthermore, in the 3-chloro-2-hydroxypropylmethyldiallylammonium chloride / dimethyldiallylammonium chloride copolymer, the molar ratio of the two structural monomers is (2~20):(80~98).

[0009] Furthermore, the molar ratio of 3-chloro-2-hydroxypropylmethyldiallylammonium chloride monomer to dimethyldiallylammonium chloride monomer in the 3-chloro-2-hydroxypropylmethyldiallylammonium chloride / dimethyldiallylammonium chloride copolymer is 8:85.

[0010] Furthermore, the preparation process of the vinylphosphoric acid-modified silica specifically includes the following steps: S1. Mix isopentenyloxy polyethylene glycol, acetic acid, hydrogen peroxide and triethoxyvinylsilane to obtain solution A; S2. Mix vitamin C, vinyl phosphate, mercaptopropionic acid and water to obtain solution B; S3. Add solution B from step S2 to solution A from step S1 to obtain solution C; S4. The solution C described in step S3 is mixed and reacted with the nano silica gel under alkaline conditions to obtain vinyl phosphate modified silica.

[0011] Further, in step S1, the mass ratio of isopentenyloxy polyethylene glycol, acetic acid, hydrogen peroxide and triethoxyvinylsilane is 180~220:0.4~0.6:1.8~2.2:4~6.

[0012] Further, in step S2, the mass ratio of vitamin C, vinyl phosphate, mercaptopropionic acid, and water is 0.7~0.9:18~20:0.7~0.9:45~55.

[0013] Furthermore, the average particle size of the nano-silica gel is 10 nm.

[0014] This invention also provides a method for preparing a cationic clay stabilizer, comprising: weighing 3-chloro-2-hydroxypropylmethyldiallylammonium chloride / dimethyldiallylammonium chloride copolymer and vinyl phosphate-modified silica together and adding them to a stirrer, then heating to 50-60°C and stirring at a speed of 100-300 r / min. Subsequently, cooling to 40-45°C and stirring at a speed of 300-600 r / min for 30 min to obtain the clay stabilizer.

[0015] The beneficial effects of this invention are: The clay stabilizer of this invention has the advantages of simple preparation process and operation, small dosage, and strong adaptability to oil reservoirs. Therefore, it can be widely promoted and applied to meet the needs of oilfield development.

[0016] The cationic clay stabilizer of this invention has excellent comprehensive performance, possessing characteristics such as high efficiency in preventing swelling, long-term stability, high temperature resistance, water washing resistance, high salt resistance, and acid and alkali resistance. At a high temperature of 150℃, the swelling rate remains above 92%, and after three water washings, the swelling rate is higher than 93%. Under a mineralization of 35000mg / L, the swelling rate is greater than 92%, and the swelling rate exceeds 90% within an acid-base range of pH=3 to 13. It is suitable for complex oil and gas reservoir environments such as deep, high temperature, and high mineralization.

[0017] The cationic clay stabilizer of the present invention can form a dense hydrophobic film on the clay surface through the synergistic effect of copolymer and vinyl phosphate modified silica, significantly increasing the contact angle to 54.65°, effectively inhibiting water molecule intrusion, fundamentally reducing the tendency of clay hydration and swelling, and improving reservoir wettability, which is beneficial to oil and gas flow. Attached Figure Description

[0018] Figure 1 This is a scanning electron microscope (SEM) image of sodium-based bentonite treated with clay stabilizer solution in Comparative Example 1 of the present invention. Figure 2 This is a scanning electron microscope (SEM) image of sodium-based bentonite treated with clay stabilizer solution in Comparative Example 2 of the present invention. Figure 3 This is a scanning electron microscope (SEM) image of sodium-based bentonite after treatment with clay stabilizer solution in Example 3 of the present invention; Figure 4 The image shows the contact angle test results of sodium-based bentonite and distilled water after treatment with clay stabilizer solution in Comparative Example 1 of this invention. Figure 5 The image shows the contact angle test results of sodium-based bentonite and distilled water after treatment with clay stabilizer solution in Comparative Example 2 of this invention. Figure 6 This is a contact angle test image of sodium-based bentonite and distilled water after treatment with clay stabilizer solution in Example 3 of the present invention. Detailed Implementation

[0019] The technical solutions in the embodiments of the present invention will be clearly and completely described below. 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 are within the scope of protection of the present invention.

[0020] The present invention provides a cationic clay stabilizer comprising the following raw materials in parts by weight: 10-20 parts of 3-chloro-2-hydroxypropylmethyldiallylammonium chloride / dimethyldiallylammonium chloride copolymer and 3-10 parts of vinyl phosphate modified silica.

[0021] In this invention, the cationic clay stabilizer comprises the following raw materials in parts by weight: 10 parts of 3-chloro-2-hydroxypropylmethyldiallylammonium chloride / dimethyldiallylammonium chloride copolymer and 5 parts of vinyl phosphate modified silica.

[0022] In this invention, the preferred molar ratio of the two structural monomers in the 3-chloro-2-hydroxypropylmethyldiallylammonium chloride / dimethyldiallylammonium chloride copolymer is (2~20):(80~98). More preferably, the molar ratio is (5~15):(85~95), and even more preferably, it is 8:92. In this copolymer, the dimethyldiallylammonium chloride unit is the core that provides a high density of permanent positive charge. Its quaternary ammonium salt cation can be rapidly adsorbed onto the negatively charged clay mineral surface through strong electrostatic interaction, effectively neutralizing its surface charge. This is the first line of defense and the basis for immediate action in inhibiting clay hydration swelling and crystal layer dispersion. The introduced 3-chloro-2-hydroxypropylmethyldiallylammonium chloride has active chlorine atoms at the end of its side chain that can serve as potential chemical reaction sites. Under alkaline or high-temperature conditions, it can interact with hydroxyl groups at the clay edge or groups on the surface of functionalized nano-silica, thereby converting physical adsorption into partial covalent bonding and improving its resistance to water washing and erosion. The relatively long hydroxypropyl side chain of this unit has certain hydrophobicity and steric hindrance effects, which helps to form a hydrophobic protective film on the clay surface, changing the wettability of the reservoir rock, thereby inhibiting the intrusion of the aqueous phase and facilitating the seepage of the oil and gas phases. By controlling its molar ratio with DMDAAC, it is possible to... Without significantly weakening the overall positive charge density, the hydrophilic / hydrophobic balance, adsorption conformation, and molecular chain flexibility of the polymer are adjusted to facilitate its spread on clay surfaces and the formation of a dense adsorption layer. This also imparts better environmental adaptability (e.g., salinity, pH). Furthermore, the hydrophobic alkyl chains of the 3-chloro-2-hydroxypropylmethyldiallylammonium chloride / dimethyldiallylammonium chloride copolymer and the isopentenyl hydrophobic ends of vinylphosphoric acid-modified silica spontaneously tend to align and aggregate at the clay-water interface after adsorption onto the clay surface through intermolecular interactions (e.g., hydrophobic association, van der Waals forces). This intelligent self-assembly behavior ultimately constructs a dense, low-surface-energy composite hydrophobic film on the exterior of the clay particles, fundamentally transforming the hydrophilic clay surface into a hydrophobic surface. This hydrophobic film physically blocks water molecules from approaching the clay crystal layer, thereby significantly inhibiting hydration swelling and enhancing water wash resistance.

[0023] In this invention, the preparation process of the vinyl phosphate-modified silica specifically includes the following steps: S1. Mix isopentenyloxy polyethylene glycol, acetic acid, hydrogen peroxide and triethoxyvinylsilane to obtain solution A; S2. Mix vitamin C, vinyl phosphate, mercaptopropionic acid and water to obtain solution B; S3. Add solution B from step S2 to solution A from step S1 to obtain solution C; S4. The solution C described in step S3 is mixed and reacted with the nano silica gel under alkaline conditions to obtain vinyl phosphate modified silica.

[0024] In the above preparation process, the proportions of each raw material and the reaction conditions have a significant impact on the performance of the final product. The preferred mass ratio of isopentenyloxy polyethylene glycol, acetic acid, hydrogen peroxide, and triethoxyvinylsilane in step S1 is 180~220:0.4~0.6:1.8~2.2:4~6, more preferably 200:0.5:2:4. In this step, isopentenyloxy polyethylene glycol and triethoxyvinylsilane serve as polymerizable monomers, hydrogen peroxide as an oxidant, and acetic acid is used to adjust the system to a weakly acidic environment, stabilize the monomers, and assist in subsequent reactions. Each component coexists in its original form in the mixture; the mass ratio of vitamin C, vinyl phosphoric acid, mercaptopropionic acid and water in step S2 is preferably 0.7~0.9:18~20:0.7~0.9:45~55, more preferably 0.8:1.8:0.8:51. In this step, vitamin C acts as a reducing agent and forms a redox initiation system with hydrogen peroxide in solution A; vinyl phosphoric acid is a functional monomer; mercaptopropionic acid acts as a chain transfer agent. In step S3, vitamin C reacts with hydrogen peroxide to generate free radicals, which initiate the copolymerization of three monomers: isopentenyloxy polyethylene glycol, triethoxyvinylsilane and vinyl phosphoric acid, to form a copolymer whose molecular chain simultaneously contains polyethylene glycol segments, siloxane end groups and phosphonic acid groups. The siloxane end groups in this copolymer are subsequently hydrolyzed under alkaline conditions and chemically grafted onto the silanol groups on the surface of silica with an average particle size of 10 nm to obtain modified silica. The modified nano-silica forms a rigid core, fundamentally endowing the system with the ability to resist high-temperature thermal degradation. The grafted isopentenyloxy polyethylene glycol is a long-chain nonionic hydrophilic polymer, providing excellent water solubility and steric hindrance, effectively preventing the aggregation of nanoparticles in complex, highly saline environments. This ensures stable dispersion as primary nanoparticles, allowing them to penetrate into the nanoscale pores and interlayer domains of clay, forming a nanoscale physical barrier that mechanically prevents further separation and migration of clay layers. Its performance is unaffected by the charge shielding effect of high-concentration salt ions, thus ensuring the system's superior salt resistance in ultra-high salinity environments. The phosphonic acid groups introduced into the copolymer maintain high charge stability and coordination ability under different pH conditions, making them less susceptible to the salt ion shielding effect. The phosphate groups, negatively charged in solution, can form electrostatic interactions or ion pairs with the quaternary ammonium salt groups (positively charged) in the cationic copolymer, promoting their bonding and enhancing the binding force with clay minerals through coordination. The modified silica, when compounded with cationic copolymers, forms a denser organic-inorganic hybrid network within the system. The modified silica not only disperses uniformly within the polymer matrix, enhancing overall mechanical strength and thermal stability, but also physically fills the spaces between polymer chains, further preventing the intrusion of water molecules and salt ions. This synergistic effect ultimately results in a significant improvement in the overall performance of the clay stabilizer, particularly in its resistance to washing, salt, acids and alkalis, and high temperatures.

[0025] The present invention also provides a method for preparing the above-mentioned cationic clay stabilizer, the method comprising: weighing (3-chloro-2-hydroxypropyl)methyldiallylammonium chloride / dimethyldiallylammonium chloride copolymer and vinyl phosphate modified silica together and adding them to a stirrer, then heating to 50-60°C and stirring at a speed of 100-300 r / min. Subsequently, cooling to 40-45°C and stirring again at a speed of 300-600 r / min to obtain the clay stabilizer.

[0026] Preparation Example Preparation method of vinyl phosphate modified silica S1. Mix 200g of isopentenyloxy polyethylene glycol, 0.5g of acetic acid, 2g of hydrogen peroxide, and 4g of triethoxyvinylsilane to obtain solution A. S2. Mix 0.8g vitamin C, 18g vinyl phosphate, 0.8g mercaptopropionic acid, and 51g water to obtain solution B. S3. Add solution B from step S2 to solution A from step S1 to obtain solution C; S4. Mix 7.8g of the solution C from step S3 with 100g of silica gel with an average particle size of 100nm at pH 9.5, 40℃ in a water bath, and 500r / min. Then, dialyze the resulting solution in deionized water for about 3 days until the total organic carbon analyzer can no longer detect any obvious residual organic matter in the water, thus obtaining vinyl phosphate modified silica.

[0027] Example 1 A method for preparing a cationic clay stabilizer Ten parts by weight of (3-chloro-2-hydroxypropyl)methyldiallylammonium chloride / dimethyldiallylammonium chloride copolymer and ten parts by weight of the vinyl phosphoric acid modified silica prepared in the preparation example were weighed and added to a stirrer. The mixture was then heated to 50°C and stirred at 100 r / min. Subsequently, the temperature was lowered to 40°C and stirred at 300 r / min for 30 min to obtain the clay stabilizer.

[0028] In the 3-chloro-2-hydroxypropylmethyldiallylammonium chloride / dimethyldiallylammonium chloride copolymer, the molar ratio of 3-chloro-2-hydroxypropylmethyldiallylammonium chloride monomer to dimethyldiallylammonium chloride monomer is 2:90. Example 2 20 parts by weight of (3-chloro-2-hydroxypropyl)methyldiallylammonium chloride / dimethyldiallylammonium chloride copolymer and 3 parts by weight of the vinyl phosphoric acid modified silica prepared in the preparation example were weighed and added to a stirrer. The mixture was then heated to 60°C and stirred at 300 r / min. Subsequently, the temperature was lowered to 45°C and stirred at 600 r / min for 30 min to obtain the clay stabilizer.

[0029] The molar ratio of 3-chloro-2-hydroxypropylmethyldiallylammonium chloride monomer to dimethyldiallylammonium chloride monomer in the chloro-2-hydroxypropylmethyldiallylammonium chloride / dimethyldiallylammonium chloride copolymer is 20:80.

[0030] Example 3 15 parts by weight of (3-chloro-2-hydroxypropyl)methyldiallylammonium chloride / dimethyldiallylammonium chloride copolymer and 5 parts by weight of the vinyl phosphoric acid modified silica prepared in the preparation example were weighed and added to a stirrer. The mixture was then heated to 55°C and stirred at 150 r / min. Subsequently, the temperature was lowered to 42°C and stirred at 500 r / min for 30 min to obtain the clay stabilizer.

[0031] The molar ratio of 3-chloro-2-hydroxypropylmethyldiallylammonium chloride monomer to dimethyldiallylammonium chloride monomer in the chloro-2-hydroxypropylmethyldiallylammonium chloride / dimethyldiallylammonium chloride copolymer is 8:85.

[0032] Comparative Example 4 Except for the absence of vinyl phosphate-modified silica, the other conditions were the same as in Example 3.

[0033] Comparative Example 5 Except for the absence of (3-chloro-2-hydroxypropyl)methyldiallylammonium chloride / dimethyldiallylammonium chloride copolymer, the other conditions were the same as in Example 3.

[0034] Test case Temperature resistance test Take 0.5g of sodium bentonite and place it in a 10mL centrifuge tube. Add 10mL of the 1.5% (w / w) solution prepared with the clay stabilizer from Examples 1-3 and Comparative Examples 1-2, respectively. Shake well and place in water baths at 25℃, 100℃, and 150℃ for 2 hours. After cooling, centrifuge and measure the anti-swelling rate according to SY / T59702016. The results are shown in Table 1 below: Table 1 Evaluation results of temperature resistance test of clay stabilizer As shown in Table 1, Examples 1-3 exhibited excellent anti-swelling properties at different temperatures of 25℃, 100℃, and 150℃, with anti-swelling rates all exceeding 92%. Furthermore, these rates remained above 92% even at 150℃, demonstrating the outstanding high-temperature stability of the clay stabilizer of this invention. In contrast, Comparative Examples 1 and 2 showed a significant decrease in anti-swelling rates at high temperatures, particularly at 150℃, dropping to 58.3% and 45.6% respectively. This indicates that the anti-swelling ability of the single vinylphosphoric acid modified silica and the (3-chloro-2-hydroxypropyl)methyldiallylammonium chloride / dimethyldiallylammonium chloride copolymer is poor, making it unsuitable for field application.

[0035] Water wash resistance evaluation test The long-lasting effect of the stabilizer was evaluated according to the water wash resistance test method in SY / T5970-2016.

[0036] The specific experimental steps are as follows: (a) Prepare a 1.5% (w / w) solution of the clay stabilizers from Examples 1-3 and Comparative Examples 1-2, and determine the initial anti-swelling rate of the clay stabilizers using centrifugation. (b) Discard the supernatant after centrifugation in the centrifuge tube, add 10 mL of distilled water, shake well and let stand for 2 hours, and determine the anti-swelling rate after one water wash again using centrifugation. (c) Repeat step (b) to determine the anti-swelling rate after two water washes and the anti-swelling rate after three water washes. The results are shown in [the table below]. Figure 1 And Table 2.

[0037] Table 2 Evaluation results of the water wash resistance of clay stabilizers As can be seen from Table 2, after three washes, the anti-swelling rate of Examples 1-3 can still be maintained above 93%, while the anti-swelling rate of Comparative Examples 1 and 2 decreased significantly under the same washing conditions, reaching only 77.4% and 53.4% ​​respectively after three washes, which is significantly lower than that of the Example group. This indicates that the clay stabilizer of the present invention has good long-lasting effect and water erosion resistance.

[0038] Salt resistance test A standard brine solution with a mineralization of 35000 mg / L was prepared by maintaining a CaCl2:MgCl2:NaCl mass ratio of 3:2:15. Using this brine solution as a solvent, stabilizer solutions of Examples 1-3 and Comparative Examples 1-2 with a mass fraction of 1.5% were prepared. The anti-swelling rate was determined according to the "Anti-Swelling Rate Test" method, and the results are shown in Table 3. Table 3 Evaluation results of salt resistance test of clay stabilizers As shown in Table 3, in a high-salinity (35000 mg / L) brine environment, the anti-swelling rate of Example 13 remained above 92%, reaching a maximum of 95.4%, demonstrating superior salt resistance. In contrast, the anti-swelling rates of Comparative Examples 1 and 2 under the same salinity conditions were only 75.2% and 60.1%, respectively, significantly lower than the Example group. This indicates that the clay stabilizer of the present invention has good anti-swelling ability under a salinity of 35000 mg / L.

[0039] Acid and alkali resistance test The anti-swelling rate of clay stabilizer under pH conditions was determined. The specific steps are as follows: A 25% hydrochloric acid and sodium hydroxide solution was prepared, and a 1.5% clay stabilizer solution was adjusted to pH=3 and pH=13. Its anti-swelling effect was then measured, and the results are shown in Table 4. Table 4 Evaluation results of acid and alkali resistance tests of clay stabilizers As shown in Table 4, under extreme conditions of strong acid (pH=3) and strong alkali (pH=13), the anti-swelling rate of Example 13 remained above 90%, demonstrating excellent acid and alkali resistance. In contrast, the anti-swelling rates of Comparative Examples 1 and 2 decreased significantly in acidic and alkaline environments, especially at pH=13, where they were only 65.1% and 61.1%, respectively. This indicates that the introduction of modified silica into the clay stabilizer of this invention, through its stable chemical structure and synergistic effect with the copolymer, significantly enhances the system's adaptability over a wide pH range, making it suitable for reservoir environments with complex acidity and alkalinity.

[0040] Scanning electron microscopy analysis Bentonite was soaked in clay stabilizer solutions containing 1.5% of those used in Examples 3 and Comparative Examples 1-2 for at least 12 hours. The supernatant was discarded, excess water was removed by filtration, and the clay was dried in an oven. The dried clay minerals were then ground into powder using an agate mortar. The clay powder was analyzed by scanning electron microscopy, and the results are shown below. Figures 1-3 .

[0041] SEM images of sodium-based bentonite treated with clay stabilizer solutions in Comparative Examples 1, 2, and 3 show that the sodium-based bentonite particles treated with clay stabilizer solutions in Comparative Examples 1 and 2 have larger gaps between particles, are loose and disordered, and have a loose structure, making them prone to water absorption, swelling, and dispersion. In contrast, the sodium-based bentonite particles treated with clay stabilizer solutions in Example 3 are larger and have a denser structure, with a large number of bentonite particles agglomerated into a single unit. This reduces the probability of contact with water and inhibits hydration swelling. Furthermore, the larger bentonite particles are encapsulated by the clay stabilizer, making them less susceptible to water erosion and dispersion. The SEM images of sodium-based bentonite treated with clay stabilizer solutions in Comparative Examples 1, 2, and 3 clearly demonstrate the stabilizing effect of the clay stabilizer.

[0042] Contact angle analysis The wetting of clay particles with aqueous phase after treatment with clay stabilizer solutions in Examples 3 and 1-2 was observed using a contact angle meter. Specifically, 1.5% (w / w) of clay stabilizer solutions from Examples 3 and 1-2 were added to a 1% (w / w) sodium montmorillonite suspension, respectively. After shaking and ultrasonic dispersion, thoroughly dried clay slices were prepared using glass slides, and their contact angles with distilled water were measured. The results are shown below. Figures 4-6 .

[0043] Depend on Figures 4-6 It can be seen that the contact angles between sodium-based bentonite treated with clay stabilizer solutions in Comparative Examples 1 and 2 and distilled water were 21.71° and 18.54°, respectively. The contact angle after treatment with clay stabilizer solution in Example 3 was 54.65°. This indicates that single-component clay stabilizers cannot effectively modify the clay surface, which still maintains strong hydrophilicity and easily contacts water molecules, resulting in hydration and swelling. However, the contact angle in Example 3 increased to 54.65°, indicating that the clay surface treated with the stabilizer of this invention can effectively repel the aqueous phase and inhibit the adsorption and intrusion of water molecules, thereby fundamentally reducing the tendency of clay hydration and swelling. This is mainly due to the synergistic effect of the 3-chloro-2-hydroxypropylmethyldiallylammonium chloride / dimethyldiallylammonium chloride copolymer and vinyl phosphate modified silica: the hydrophobic links in the copolymer and the isopentenyl hydrophobic ends of the modified silica are oriented and self-assembled on the clay surface to form a dense, low surface energy composite hydrophobic film. This hydrophobic film not only significantly enhances the clay's resistance to water washing and erosion, but also helps to change the wettability of reservoir rocks, reducing water lock damage and thus creating more favorable conditions for oil and gas flow.

[0044] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A cationic clay stabilizer, characterized in that, The clay stabilizer comprises the following raw materials in parts by weight: 10-20 parts of 3-chloro-2-hydroxypropylmethyldiallylammonium chloride / dimethyldiallylammonium chloride copolymer and 3-10 parts of vinyl phosphate modified silica.

2. The cationic clay stabilizer according to claim 1, characterized in that, The clay stabilizer comprises the following raw materials in parts by weight: 15 parts of 3-chloro-2-hydroxypropylmethyldiallylammonium chloride / dimethyldiallylammonium chloride copolymer and 5 parts of vinyl phosphate modified silica.

3. The cationic clay stabilizer according to claim 1, characterized in that, The molar ratio of 3-chloro-2-hydroxypropylmethyldiallylammonium chloride monomer to dimethyldiallylammonium chloride monomer in the 3-chloro-2-hydroxypropylmethyldiallylammonium chloride / dimethyldiallylammonium chloride copolymer is (2~20):(80~90).

4. The cationic clay stabilizer according to claim 3, characterized in that, The molar ratio of 3-chloro-2-hydroxypropylmethyldiallylammonium chloride monomer to dimethyldiallylammonium chloride monomer in the 3-chloro-2-hydroxypropylmethyldiallylammonium chloride / dimethyldiallylammonium chloride copolymer is 8:

85.

5. The cationic clay stabilizer according to claim 3, characterized in that, The preparation process of the vinyl phosphate modified silica specifically includes the following steps: S1. Mix isopentenyloxy polyethylene glycol, acetic acid, hydrogen peroxide and triethoxyvinylsilane to obtain solution A; S2. Mix vitamin C, vinyl phosphate, mercaptopropionic acid and water to obtain solution B; S3. Add solution B from step S2 to solution A from step S1 to obtain solution C; S4. The solution C described in step S3 is mixed and reacted with the nano silica gel under alkaline conditions to obtain vinyl phosphate modified silica.

6. The cationic clay stabilizer according to claim 5, characterized in that, The mass ratio of isopentenyl oxy polyethylene glycol, acetic acid, hydrogen peroxide and triethoxyvinylsilane in step S1 is 180~220:0.4~0.6:1.8~2.2:4~6.

7. The cationic clay stabilizer according to claim 5, characterized in that, The mass ratio of vitamin C, vinyl phosphate, mercaptopropionic acid and water in step S2 is 0.7~0.9:18~20:0.7~0.9:45~55.

8. The cationic clay stabilizer according to claim 5, characterized in that, The average particle size of the nano-silica gel is 10 nm.

9. The method for preparing the clay stabilizer according to any one of claims 1 to 8, characterized in that, The preparation method includes: weighing 3-chloro-2-hydroxypropylmethyldiallylammonium chloride / dimethyldiallylammonium chloride copolymer and vinyl phosphate modified silica together and adding them to a stirrer, then heating to 50~60℃ and stirring at a speed of 100~300 r / min. Subsequently, cooling to 40~45℃ and stirring at a speed of 300~600 r / min to obtain a clay stabilizer.

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