Temperature-responsive gel plugging agent and its preparation method and application

Abstract

The present invention provides a method for preparing a temperature-responsive gel plugging agent, a temperature-responsive gel plugging agent, and applications thereof. The method comprises: adding hydroxybutyl chitosan to water, dissolving, heating, and allowing the mixture to stand to obtain the temperature-responsive gel plugging agent; wherein the mass fraction of the hydroxybutyl chitosan is 0.05% to 0.8%, preferably 0.2% to 0.6%, and more preferably 0.3% to 0.5%. The gel system is prepared by physical crosslinking without the need for any crosslinking agent, thereby improving the phase separation and precipitation, injection difficulties, and poor gelling ability of conventional gel plugging agents caused by dilution and diffusion, thereby achieving the purpose of diverting deep fluid flow, expanding the swept volume, and improving the recovery rate.

Description

Technical Field

[0001] The present invention relates to the technical field of oilfield chemistry, and in particular to a temperature-responsive gel plugging agent and a preparation method and application thereof. Background Art

[0002] Due to the heterogeneity of the formations and the complexity of the reservoir stratigraphy, water injection profiles in oil fields undergoing waterflooding development increase with increasing water injection rates, leading to significant water production in wells. Currently, most domestic oil fields are entering the middle and late stages of development, with average water cuts exceeding 80% in wells. Some older oil fields in eastern China have water cuts exceeding 90%. Consequently, the workload and difficulty of water plugging and profile control are increasing. A wide variety of water plugging and profile control agents are available, among which polyacrylamide gels offer strong controllability, simple application, and excellent adaptability. They preferentially penetrate water-producing and high-permeability zones, making them suitable for water plugging and profile control in low-permeability sandstone reservoirs and reservoirs with fractures and large flow channels. They can also adjust the water absorption profile within the formation and seal large pores. Due to these advantages, polyacrylamide gels have become widely recognized in high-water-cut and large-pore oil fields, becoming a key tool for unlocking the potential of these fields and stabilizing production. They have been widely used in oil fields such as Tahe and Shengli, achieving excellent results.

[0003] The plugging mechanism of polyacrylamide gel is that the polyacrylamide molecular chain contains numerous active groups, which cross-link with a cross-linking agent to form a network structure. This network structure can contain water within the lattice structure, forming a viscoelastic gel. This gel forms a physical blockage within the porous medium of the formation, preventing water from flowing through or redirecting it to achieve the purpose of plugging. Polymer gels primarily block water through physical blocking, with adsorption and dynamic capture functions. Currently, conventional polyacrylamide gel gelling fluids are prone to phase separation and precipitation during injection due to the dilution and diffusion of formation water, resulting in injection difficulties and reduced gelling capacity. Currently, there are few reports on methods to improve the dilution and diffusion of polyacrylamide gel plugging agents. These methods mainly rely on shortening the gelling time of the gelling fluid to mitigate the effects of dilution and diffusion. However, the negative impact of shortening the gelling time is that the gelling fluid cannot penetrate deep into the formation for deep plugging, significantly reducing the plugging effect.

[0004] In summary, conventional polyacrylamide gel has problems of difficulty in injection and low transaction capacity, which affects the blocking and adjustment effect. Summary of the Invention

[0005] In view of the above background technology, in order to solve the problems of injection difficulty and low gelling ability of the existing water plugging and profile control gel, the present invention provides a temperature-responsive gel plugging agent and its preparation method and application. The gel system is prepared by physical cross-linking and does not require the addition of any additional cross-linking agent, thereby improving the problems of phase separation and precipitation, injection difficulty and poor gelling ability caused by dilution and diffusion of current conventional gel plugging agents, thereby achieving the purpose of deep liquid flow diversion, expanding the swept volume and improving the recovery rate.

[0006] According to a first aspect of the present invention, a method for preparing a temperature-responsive gel plugging agent is provided, comprising adding hydroxybutyl chitosan to water, dissolving the mixture, heating the mixture, and allowing the mixture to stand to obtain a temperature-responsive gel plugging agent; wherein the mass fraction of the hydroxybutyl chitosan is 0.05% to 0.8%, preferably 0.2% to 0.6%, and more preferably 0.3% to 0.5%.

[0007] According to some embodiments of the present invention, a method for preparing a temperature-responsive gel plugging agent comprises the following steps:

[0008] Step a) dispersing chitosan in an alkaline aqueous solution and performing an alkalization treatment to obtain an alkaline chitosan aqueous solution;

[0009] Alkalinization is a pretreatment before the chitosan grafting modification reaction, the purpose of which is to fully swell and activate the chitosan. Specifically, the hydroxyl groups of the chitosan are activated so that they can subsequently undergo a nucleophilic reaction with butylene oxide.

[0010] Step b) adding the organic solution to the aqueous solution of alkalized chitosan obtained in step a) and stirring to obtain an organic solution of alkalized chitosan;

[0011] Step c) adding 1,2-butylene oxide dropwise into the organic solution of the alkalized chitosan in step b), heating for reaction, then cooling and adjusting the pH to neutral, and drying to obtain hydroxybutyl chitosan.

[0012] Furthermore, the preparation of the temperature-responsive gel plugging agent further comprises: step d) adding the hydroxybutyl chitosan obtained in step c) into water, dissolving it, heating it, and allowing it to stand to obtain the temperature-responsive gel plugging agent.

[0013] According to some embodiments of the present invention, the amount of chitosan in step a) relative to the alkaline aqueous solution is 5-15 g:100 ml, preferably 6-13 g:100 ml, more preferably 7-10 g:100 ml; and / or the alkaline aqueous solution includes an alkali metal aqueous solution, preferably a NaOH aqueous solution; the concentration of the NaOH aqueous solution is 30-70 weight %, preferably 30-60 weight %, more preferably 30-50 weight %.

[0014] According to some embodiments of the present invention, in step a), the chitosan is dispersed in an alkaline aqueous solution for alkalization treatment, stirred under nitrogen protection, and filtered; the stirring time is 12 to 48 hours, and the stirring speed is 1500 rpm to 5000 rpm.

[0015] Preferably, the step a) further comprises: filtering after the alkalization treatment to obtain alkalized chitosan.

[0016] According to some embodiments of the present invention, the organic solution in step b) comprises an alcohol aqueous solution, preferably an isopropyl alcohol aqueous solution; the volume of the organic solution in step b) is 20-100% of the aqueous solution of the alkalized chitosan, preferably 30-90%, more preferably 40-80%; the concentration of the isopropyl alcohol aqueous solution is 10-40% by weight, preferably 15-35% by weight, more preferably 15-30% by weight; the stirring time is 18-48 hours, and the stirring speed is 1500 rpm-5000 rpm.

[0017] According to some embodiments of the present invention, the molar ratio of 1,2-butylene oxide to the alkalized chitosan in step c) is 20-50, preferably 25-45, more preferably 30-40:1; and / or in step c), 1,2-butylene oxide is added dropwise to the alkalized chitosan isopropanol solution in step b), reacted at room temperature for 1-8 hours, and heated for 1-8 hours, with the heating temperature being 80-120°C.

[0018] According to some embodiments of the present invention, in step c), the reaction solution obtained by the heating reaction is cooled to room temperature, an acidic solution is added dropwise to the cooled reaction solution, the pH is adjusted to neutral, and then filtered, centrifuged, and dried to obtain hydroxybutyl chitosan; preferably, the acidic solution includes an HCl solution with a concentration of 6 to 15%, and the dropwise addition volume is 5 to 15 mL; preferably, the centrifugal precipitation speed is 8000 rpm to 15000 rpm, and the centrifugation time is 10 to 30 minutes.

[0019] According to some embodiments of the present invention, the preparation method further comprises standing at a temperature of 70 to 140°C.

[0020] According to a second aspect of the present invention, a temperature-responsive gel plugging agent prepared by the method described above is also provided, wherein the temperature-responsive gel plugging agent comprises a hydroxybutyl chitosan aqueous solution; wherein the weight average molecular weight of the hydroxybutyl chitosan is 4×10 6 ~12×10 6 g / mol, preferably 6×10 6 ~8×10 6 g / mol.

[0021] According to a third aspect of the present invention, a method for preparing the temperature-responsive gel plugging agent as described above or application of the temperature-responsive gel plugging agent as described above in the field of oilfield chemical technology is also provided.

[0022] According to some embodiments of the present invention, it is applied in deep profile control and water plugging of oil reservoirs.

[0023] The beneficial effects of the present invention are:

[0024] The temperature-responsive gel plugging agent provided by the present invention for oil reservoir profile control and water plugging forms a gel by hydrogen bonding within and between molecules, without the need for any cross-linking agent. It exists in the form of a sol at normal ambient temperature, transforms into a gel when a certain temperature is reached, and can return to a sol when the temperature is lowered again. By repeating the heating-cooling process, the system can switch between sol-gel-sol multiple times. In the field of water plugging and profile control, the temperature-responsive thermally reversible phase transition gel provided by the present invention can effectively utilize the temperature field changes and distribution of the oil reservoir during injection and production to achieve selective deep plugging, improve the problems of phase separation precipitation, injection difficulties, and poor gelling ability caused by dilution and diffusion of current conventional gel plugging agents, and achieve "blocking without killing", thereby avoiding technical risks such as oil well scrapping. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is the chitosan modification reaction mechanism of an exemplary embodiment of the present invention. DETAILED DESCRIPTION

[0026] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0027] Thermosensitive thermoreversible gel is a kind of gel synthesized through physical cross-linking (such as van der Waals forces or hydrogen bonding). Its volume does not change, but it undergoes phase transition (sol-gel-sol) under certain conditions. This type of gel exists in the form of a solution at normal ambient temperature and transforms into a gel state when a certain temperature is reached. This process is reversible. The technical features of the thermosensitive thermoreversible gel plugging and adjustment system are as follows: 1. It can effectively utilize the temperature field changes and distribution of the oil reservoir during injection and production to achieve selective plugging; 2. For granular plugging agents and resin plugging agents, there may be a risk of "blocking" the seepage channel and even causing the oil well to be scrapped. However, thermosensitive thermoreversible gel can "effectively adjust the profile" and "block without killing", so the thermosensitive thermoreversible gel plugging and adjustment system has no technical risks.

[0028] Chitosan, composed of 2-glucosamine and 2-acetylglucosamine linked by β-1,4-glycosidic bonds, is the only cationic amino polysaccharide found in nature. Its widespread availability, simple preparation methods, and ease of derivatization provide a foundation for its application. Due to its highly stable crystalline structure, chitosan molecules are insoluble in most solvents and can only be dissolved in acidic solutions, which greatly limits its application. Chemical modification of chitosan molecules can improve chitosan's water solubility and form derivatives with various structures and functions. In recent years, a new chitosan derivative, hydroxybutyl chitosan, has begun to attract attention. The modified product is readily soluble in water, and its aqueous solution, without the crosslinking action of a crosslinking agent, forms a hydrogel with a network structure through the entanglement of hydroxybutyl chitosan polymer chains and hydrogen bonding between molecular chains.

[0029] In the present invention, chitosan is modified by using chitosan as the main agent, 1,2-butylene oxide as the etherifying agent, and isopropyl alcohol aqueous solution as the dispersion system to obtain a modified water-soluble chitosan derivative - hydroxybutyl chitosan. The factors affecting the gelation temperature and gelation time of hydroxybutyl chitosan hydrogel and its thermal reversible behavior are investigated.

[0030] The specific implementation of the present invention is described in detail below with reference to specific embodiments.

[0031] Figure 1 This is the chitosan modification reaction mechanism of an exemplary embodiment of the present invention.

[0032] It should be noted that the reagents used in the embodiments of the present invention are all commercially available conventional products, and are all of analytical or chemical purity.

[0033] Example 1

[0034] 1. Alkalization of Chitosan: 1 g of chitosan powder (chemically pure, CAS: 9012-76-4, Laizhou Haili Biological Products Co., Ltd., Shandong Province) was dispersed in 20 mL of 30% NaOH (chemically pure, CAS: 1310-73-2, Beijing Chemical Reagent Factory) aqueous solution for alkalization. The mixture was stirred magnetically at 1200 rpm under N2 protection at room temperature for 12 h. The excess alkali solution was filtered and squeezed out.

[0035] 2. Dispersion of alkalized chitosan: Add 4 mL of a 10% aqueous solution of isopropanol (Beijing Chemical Reagent Factory, chemically pure, CAS No.: 67-63-0) to the alkalized chitosan and stir magnetically at 1500 rpm for 18 h until the alkalized chitosan is completely dispersed in the isopropanol system.

[0036] 3. Synthesis of Hydroxybutyl Chitosan: 1.92 mL of 1,2-butylene oxide (Analytical Grade, CAS No.: 106-88-7, Beijing Bailingwei Technology Co., Ltd.) was added dropwise to the above alkalinized chitosan dispersion. The reaction was maintained at room temperature for 1 h while stirring at the same speed as in step 2. The temperature was then raised to 80°C and the reaction was continued for 1 h.

[0037] 4. Purification of Hydroxybutyl Chitosan: After the reaction is complete, cool to room temperature and add 15 mL of 6% HCl (chemically pure, Beijing Chemical Reagent Factory, CAS No. 7647-01-0) dropwise to the reaction mixture to adjust the pH to neutral. Once the mixture becomes clear, filter out the insoluble material and allow to precipitate overnight with alcohol. Centrifuge at 8000 rpm for 30 minutes, collect the precipitate, and dry it as usual.

[0038] 5. Preparation of hydroxybutyl chitosan hydrogel: Take 0.03g hydroxybutyl chitosan powder, add it to 30ml deionized water, let it stand at room temperature overnight until it is fully dissolved, and then heat it to 70℃ and let it stand to form a gel.

[0039] The reaction mechanisms of the above steps are as follows Figure 1 shown.

[0040] The molecular weight of the hydroxybutyl chitosan prepared by the present invention is 5.5×10 6 .

[0041] Example 2

[0042] 1. Alkalization of chitosan: Weigh 1.6 g of chitosan powder and disperse it in 20 mL of a 40% NaOH aqueous solution for alkalization. Stir magnetically at 2500 rpm under N2 protection at room temperature for 20 h. Filter and squeeze out the excess alkali solution.

[0043] 2. Dispersion of alkalized chitosan: Add 8 mL of 18% isopropanol aqueous solution to the alkalized chitosan and stir magnetically at 2500 rpm for 25 h until the alkalized chitosan is completely dispersed in the isopropanol system;

[0044] 3. Synthesis of hydroxybutyl chitosan: 3.08 mL of 1,2-butylene oxide was added dropwise to the above-mentioned alkalized chitosan dispersion, and the reaction was carried out at room temperature for 3 h while maintaining the stirring speed of step 2. The reaction was then continued at 90°C for 3 h.

[0045] 4. Purification of Hydroxybutyl Chitosan: After the reaction is complete, cool to room temperature and add 12.5 mL of 8% HCl solution dropwise to adjust the pH to neutral. Once the mixture becomes clear, filter out the insoluble matter and allow to precipitate overnight with alcohol. Centrifuge at 9500 rpm for 15 minutes, collect the precipitate, and dry it as usual.

[0046] 5. Preparation of hydroxybutyl chitosan hydrogel: Take 0.075g hydroxybutyl chitosan powder, add it to 30ml deionized water, let it stand at room temperature overnight until it is fully dissolved, and then heat it to 90℃ and let it stand to form a gel.

[0047] Similarly to the above example, the molecular weight of the hydroxybutyl chitosan prepared by the present invention was 4.3×10 6 .

[0048] Example 3

[0049] 1. Alkalization of chitosan: Weigh 2 g of chitosan powder and disperse it in 20 mL of 50% NaOH aqueous solution for alkalization. Stir magnetically at 3300 rpm for 30 h at room temperature under N2 protection. Filter and squeeze out excess alkali solution.

[0050] 2. Dispersion of alkalized chitosan: Add 12 mL of 25% isopropanol aqueous solution to the alkalized chitosan and stir magnetically at 3300 rpm for 33 h until the alkalized chitosan is completely dispersed in the isopropanol system;

[0051] 3. Synthesis of hydroxybutyl chitosan: 4.48 mL of 1,2-butylene oxide was added dropwise to the above alkalinized chitosan dispersion, and the reaction was carried out at room temperature for 4.5 h while maintaining the stirring speed of step 2. The reaction was then continued at 100°C for another 4.5 h.

[0052] 4. Purification of Hydroxybutyl Chitosan: After the reaction is complete, cool to room temperature and add 10 mL of 10.5% HCl solution dropwise to adjust the pH to neutral. Once the mixture becomes clear, filter out the insoluble matter and allow to precipitate overnight with alcohol. Centrifuge at 11,000 rpm for 20 minutes, collect the precipitate, and dry it as usual.

[0053] 5. Preparation of hydroxybutyl chitosan hydrogel: Take 0.12g hydroxybutyl chitosan powder, add it to 30ml deionized water, let it stand at room temperature overnight until it is fully dissolved, and then heat it to 110℃ and let it stand to form a gel.

[0054] Similarly to the above example, the molecular weight of the hydroxybutyl chitosan prepared by the present invention was 6.8×10 6 .

[0055] Example 4

[0056] 1. Alkalization of chitosan: Weigh 2.6 g of chitosan powder and disperse it in 20 mL of 60% NaOH aqueous solution for alkalization. Stir magnetically at 4200 rpm under N2 protection at room temperature for 40 h. Filter and squeeze out excess alkali solution.

[0057] 2. Dispersion of alkalized chitosan: Add 16 mL of 32% isopropanol aqueous solution to the alkalized chitosan and stir magnetically at 4200 rpm for 40 h until the alkalized chitosan is completely dispersed in the isopropanol system;

[0058] 3. Synthesis of hydroxybutyl chitosan: 6.12 mL of 1,2-butylene oxide was added dropwise to the above-mentioned alkalized chitosan dispersion, and the reaction was carried out at room temperature for 6 h while maintaining the stirring speed of step 2. The reaction was then continued at 110°C for 6 h.

[0059] 4. Purification of Hydroxybutyl Chitosan: After the reaction is complete, cool to room temperature and add 7.5 mL of 12.5% ​​HCl solution dropwise to adjust the pH to neutral. Once the mixture becomes clear, filter out insoluble matter and allow to precipitate overnight in alcohol. Centrifuge at 13,000 rpm for 25 minutes, collect the precipitate, and dry it as usual.

[0060] 5. Preparation of hydroxybutyl chitosan hydrogel: Take 0.165g of hydroxybutyl chitosan powder, add it to 30ml of deionized water, let it stand at room temperature overnight until it is fully dissolved, and then heat it to 125℃ and let it stand to form a gel.

[0061] Similarly to the above example, the molecular weight of the hydroxybutyl chitosan prepared by the present invention was 9.9×10 6 .

[0062] Example 5

[0063] 1. Alkalization of chitosan: Weigh 3 g of chitosan powder and disperse it in 20 mL of 70% NaOH aqueous solution for alkalization. Stir magnetically at 5000 rpm under N2 protection at room temperature for 48 h. Filter and squeeze out excess alkali solution.

[0064] 2. Dispersion of alkalized chitosan: Add 20 mL of 40% isopropanol aqueous solution to the alkalized chitosan and stir magnetically at 5000 rpm for 48 hours until the alkalized chitosan is completely dispersed in the isopropanol system;

[0065] 3. Synthesis of hydroxybutyl chitosan: 8 mL of 1,2-butylene oxide was added dropwise to the above-mentioned alkalized chitosan dispersion, and the reaction was carried out at room temperature for 8 h while maintaining the stirring speed of step 2. The reaction was then continued at 120°C for another 8 h.

[0066] 4. Purification of Hydroxybutyl Chitosan: After the reaction is complete, cool to room temperature and add 5 mL of 15% HCl solution dropwise to adjust the pH to neutral. Once the mixture becomes clear, filter out insoluble matter and allow to precipitate overnight in alcohol. Centrifuge at 15,000 rpm for 30 minutes, collect the precipitate, and dry it as usual.

[0067] 5. Preparation of hydroxybutyl chitosan hydrogel: Take 0.21g hydroxybutyl chitosan powder, add it to 30ml deionized water, let it stand at room temperature overnight until it is fully dissolved, and then heat it to 140℃ and let it stand to form a gel.

[0068] Similarly to the above example, the molecular weight of the hydroxybutyl chitosan prepared by the present invention was 11.5×10 6 .

[0069]

Performance test

[0070] 1. Viscosity test

[0071] A certain mass fraction of the temperature-responsive gel plugging agent aqueous solution prepared in each of the above examples was prepared using room temperature water, stirred for 1 hour, and allowed to stand for 1 hour to remove bubbles dissolved in the solution. Finally, its viscosity was measured using a DVⅡ+ Brookfield rotary viscometer, and the average of three measurements was taken as its viscosity value.

[0072] 2. Determination of gel point temperature

[0073] A certain volume and mass fraction of the temperature-responsive gel plugging agent aqueous solution prepared in each of the above examples was transferred into an ampoule bottle, which was placed in an oven at a certain temperature. The solution was taken out every 20 minutes to observe the changes in the solution. When the solution turned into a milky white gel, the temperature at that time was recorded as the gelation temperature.

[0074] 3. Determination of plugging performance:

[0075] (1) Core preparation

[0076] Using quartz sand as a reference, the core tube was vacuumed and set to -0.1 MPa. After stabilization for 0.5 hours, the tube was saturated with water for 24 hours. The actual porosity was then calculated, and the permeability of the core tube was then measured using water. Core tube model parameters included: quartz sand, 60.00 cm in length, 2.5 cm in diameter, and 4.91 cm² of interface agent.

[0077] (2) Injecting the temperature-responsive gel plugging agent aqueous solution prepared in the above embodiments

[0078] At room temperature, a certain mass fraction of the temperature-responsive gel plugging agent aqueous solution prepared in the above examples at a concentration of 1.5 to 2 PV was injected into the simulated core tube, and then the device system was heated to a certain temperature and kept at this temperature for 3 hours.

[0079] (3) Use hot water of the same temperature for displacement, record the pressure difference at both ends of the core tube, and analyze the plugging effect.

[0080] The gel point temperatures of the temperature-responsive gel plugging agents prepared in the above examples were evaluated through indoor tests. The results are shown in Table 1.

[0081] Table 1 Viscosity and gelation of each example at different temperatures

[0082]

[0083] Based on Table 1, the temperature-responsive gel plugging agents prepared in Examples 1-5 exhibit low viscosity and a sol state at temperatures below 60°C. When the temperature rises to 65°C, they partially gel, forming a milky white, filamentous gel. When the temperature rises to 70°C, they reach a completely gelled state. The system does not transform into a gel at 70°C, but gradually does so as the temperature rises above 70°C. This is because some hydroxyl groups on the hydroxybutyl chitosan molecular chains bind to water molecules, while others form intramolecular and intermolecular hydrogen bonds, indirectly connecting the molecular chains to the water molecules and separating them from each other. Furthermore, the mobility of the hydroxybutyl chitosan molecular chains decreases at low temperatures, allowing the system to maintain a sol state at low temperatures. However, as the temperature rises, the intramolecular and intermolecular hydrogen bonds weaken, releasing water molecules from the hydroxybutyl chitosan molecular chains. Furthermore, the increased temperature increases the mobility of the hydroxybutyl chitosan molecular chains, enhancing hydrophobic interactions and causing the polymer chains to entangle with each other, forming a three-dimensional network-like gel structure.

[0084] The plugging performance of the temperature-responsive gel plugging agents prepared in Examples 1-5 was evaluated through indoor tests, and the results are shown in Table 2.

[0085] Table 2 Plugging rate of temperature-responsive gel plugging agent prepared in each example at 80°C

[0086] Original permeability / mD Permeability after plugging / mD Blockage rate / % Example 1 1989.61 34.88 98.25 Example 2 1999.26 28.65 98.57 Example 3 2028.57 19.69 99.03 Example 4 1996.69 32.79 98.36 Example 5 2042.85 37.82 98.15

[0087] As shown in Table 2, the temperature-responsive gel plugging agents prepared in Examples 1-5 have a plugging rate of over 98% at 80°C, demonstrating that they have strong plugging strength and plugging capacity and can meet the water plugging requirements of sandstone reservoirs.

[0088] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, under the technical enlightenment provided by the present invention, as common knowledge in the art, other equivalent variations and improvements can be made, which should also be considered as the scope of protection of the present invention.

Claims

1. Application of a temperature-responsive gel plugging agent in the field of oilfield chemical technology, characterized in that: Adding hydroxybutyl chitosan into water, dissolving, heating and standing to obtain the temperature-responsive gel plugging agent; Wherein, the mass fraction of the hydroxybutyl chitosan is 0.05%~0.8%; The preparation method of the hydroxybutyl chitosan comprises the following steps: Step a) dispersing chitosan in an alkaline aqueous solution and performing an alkalization treatment to obtain an alkaline chitosan aqueous solution; Step b) adding the organic solution to the aqueous solution of alkalized chitosan obtained in step a) and stirring to obtain an organic solution of alkalized chitosan; Step c) adding 1,2-butylene oxide dropwise to the organic solution of the alkalized chitosan in step b), heating for reaction, then cooling and adjusting the pH to neutral, and drying to obtain hydroxybutyl chitosan; Wherein, the application is the application in deep profile control and water plugging of oil reservoirs; In step c), the molar ratio of 1,2-butylene oxide to the alkalized chitosan is 20-50:1; In step c), the 1,2-butylene oxide is added dropwise to the alkalized chitosan isopropanol solution in step b), reacting at room temperature for 1 to 8 hours, and then heating for 1 to 8 hours at a temperature of 80 to 120° C.; Keep it at a temperature of 70~140℃.

2. The use according to claim 1, characterized in that The mass fraction of the hydroxybutyl chitosan is 0.2-0.6%.

3. The use according to claim 1 or 2, characterized in that The mass fraction of the hydroxybutyl chitosan is 0.3-0.5%.

4. The use according to claim 1 or 2, characterized in that In step a), the amount of chitosan relative to the alkaline aqueous solution is 5-15 g:100 ml; and / or The alkaline aqueous solution includes an alkali metal hydroxide aqueous solution.

5. The use according to claim 1 or 2, characterized in that: In step a), the amount of chitosan relative to the alkaline aqueous solution is 6-13 g:100 ml; and / or The alkaline aqueous solution is a NaOH aqueous solution, and the concentration of the NaOH aqueous solution is 30-70% by weight.

6. The use according to claim 5, characterized in that In step a), the amount of chitosan relative to the alkaline aqueous solution is 7-10 g:100 ml; and / or The concentration of the NaOH aqueous solution is 30-60 wt %.

7. The use according to claim 5, characterized in that The concentration of the NaOH aqueous solution is 30-50 wt %.

8. The use according to claim 1 or 2, characterized in that In step a), the chitosan is dispersed in the alkaline aqueous solution and subjected to alkalization treatment under stirring and nitrogen protection.

9. The use according to claim 1 or 2, characterized in that: The stirring time is 12 to 48 hours, and the stirring speed is 1500 rpm to 5000 rpm.

10. The use according to claim 1 or 2, characterized in that: The step a) further comprises: filtering after the alkalization treatment to obtain alkalized chitosan.

11. The use according to claim 1 or 2, characterized in that: The organic solution in step b) comprises an alcohol aqueous solution; The volume of the organic solution in step b) is 20-100% of the aqueous solution of the alkalized chitosan; The concentration of the isopropyl alcohol aqueous solution is 10 to 40% by weight; The stirring time is 18 to 48 hours, and the stirring speed is 1500 rpm to 5000 rpm.

12. The use according to claim 11, characterized in that The organic solution in step b) is an isopropyl alcohol aqueous solution; The volume of the organic solution in step b) is 30-90% of the aqueous solution of the alkalized chitosan; The concentration of the isopropyl alcohol aqueous solution is 15 to 35% by weight.

13. The use according to claim 12, characterized in that The volume of the organic solution in step b) is 40-80% of the aqueous solution of the alkalized chitosan; The concentration of the isopropyl alcohol aqueous solution is 15 to 30% by weight.

14. The use according to claim 1 or 2, characterized in that: In step c), the molar ratio of 1,2-butylene oxide to the alkalized chitosan is 25-45:

1.

15. The use according to claim 14, characterized in that In step c), the molar ratio of 1,2-butylene oxide to the alkalized chitosan is 30-40:

1.

16. The use according to claim 1 or 2, characterized in that: In step c), the reaction solution obtained by the heating reaction is cooled to room temperature, an acidic solution is added dropwise to the cooled reaction solution, the pH is adjusted to neutral, and then the solution is filtered, centrifuged and dried to obtain hydroxybutyl chitosan.

17. The use according to claim 16, characterized in that The acidic solution includes HCl solution with a concentration of 6-15% and a dropwise addition volume of 5-15 mL.

18. The use according to claim 16, characterized in that The centrifugal precipitation speed is 8000rpm~15000rpm, and the centrifugation time is 10~30 minutes.

19. The use according to claim 1 or 2, characterized in that: in, The weight average molecular weight of the hydroxybutyl chitosan is 4×10 6 ~12×10 6 g / mol.

20. The use according to claim 19, characterized in that in, The weight average molecular weight of the hydroxybutyl chitosan is 6×10 6 ~8×10 6 g / mol.

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