Self-healing gel plugging system with strong wall face binding capacity and use method and application

Abstract

The present application relates to the technical field of oilfield exploitation, and proposes a self-healing gel plugging system with strong wall surface combination capacity, a use method and application. The plugging system is composed of a self-healing gel, a wall surface bonding agent and a self-healing inducer. The wall surface bonding agent acts as a bridge as an intermediate, the catechol group on one side of the wall surface bonding agent interacts with the active sites on the rock surface in multiple ways, and the amino group on the other side forms a Schiff base bond with the aldehyde group of the crosslinking agent, thereby constructing a "wall-nanosheet-gel" bridging structure to firmly anchor the gel network on the rock wall. The gel network can be recrosslinked to realize self-healing after damage due to the dynamic reversible bond between the amino group and the aldehyde group. The self-healing inducer gradually releases acidic components under formation conditions, adjusts the local pH, promotes the condensation crosslinking of the aldehyde group-amino group, and improves the long-term stability of the system. The system can effectively inhibit particle channeling and improve waterflood sweep volume, thereby improving the recovery of crude oil.

Description

Technical Field

[0001] This invention relates to the field of oilfield development technology, and more specifically, to a self-healing gel sealing system with strong wall adhesion, its usage method, and its application. Background Technology

[0002] As the main oilfields continue to be developed and gradually enter the middle and late stages, long-term water injection has intensified the heterogeneity of the formation, leading to increasingly serious problems such as the flow of displaced phases along high-permeability channels. This results in ineffective circulation of injected water, increased water cut in the oilfield, and severely restricts the development effect of crude oil.

[0003] Profile control technology is a key means to address water channeling in oil reservoirs. Its core lies in sealing high-permeability channels, balancing the water absorption profile, and driving the injected fluid towards medium- and low-permeability layers, thereby expanding the swept volume and improving oil recovery. Currently, commonly used profile control systems mainly fall into two categories: gel-based and particulate-based. Gel-based systems inject polymers and cross-linking agents into the formation to form a three-dimensional network structure underground, achieving chemical sealing of high-permeability zones. Particulate-based systems rely on injecting rigid or flexible particulate materials, which bridge and block at the pore throat, forming an effective barrier. However, both systems have significant limitations—gel-based sealing materials have weak adhesion to the rock wall, making them prone to surface channeling under long-term water erosion and gel dehydration, reducing sealing stability; particulate-based systems, due to insufficient interparticle bonding strength, are prone to particle migration or the creation of interparticle channeling under high-flow-rate injection conditions, leading to sealing failure. As oilfield development enters the high water-cut stage, the heterogeneity of formations and the complexity of flow fields are becoming increasingly severe. Existing profile control systems face serious challenges in terms of long-term effectiveness and adaptability, making it difficult to meet the needs of efficient development. There is an urgent need to develop new profile control systems with stronger cohesion and higher scour resistance.

[0004] Patent CN201510037441.3, "A Low-Temperature Gelation and Controllable Profile Control and Water Plugging System, Its Preparation Method and Method," uses hydrolyzed polyacrylamide, paraformaldehyde, resorcinol, and m-phenylenediamine as its main components. It boasts advantages such as simple formulation and controllable gelation time and gel strength under low-temperature conditions. Patent CN202411406183.7, "UCST Gel Particles for Profile Control and Water Plugging, Its Preparation Method and Application," proposes a temperature-responsive gel particle that effectively enhances the reservoir adaptability of the plugging system by improving the particle's elastic deformation capacity. Simultaneously, it enables smooth migration into deep formations while maintaining good mechanical properties. However, problems such as weak interfacial adhesion between the gel and the rock wall, leading to cross-flow, and poor particle adhesion causing desorption and interparticle cross-flow, remain unresolved. Summary of the Invention

[0005] To address the aforementioned issues, this invention provides a self-healing gel sealing system with strong wall-to-wall bonding capabilities, along with its usage and applications. This system comprises a dynamically reversible gel sealing body constructed from carboxymethyl chitosan and a multi-aldehyde crosslinking agent, bifunctional Janus magnesium hydroxide nanosheets, and a self-healing inducer. Through the synergistic effect of multiple systems, it significantly enhances the bonding strength with the rock surface, exhibits excellent self-repairing performance and long-term stability, effectively inhibits inter-particle and gel-wall crosslinking behavior, and efficiently seals high-water-content channels.

[0006] In a first aspect, the present invention provides a self-healing gel sealing system with strong wall bonding ability, the self-healing gel sealing system comprising 1.0-2.0 wt% of self-healing gel, 0.05-0.1 wt% of wall bonding agent and 0.05-0.1 wt% of self-healing inducer;

[0007] The self-healing gel is obtained by forming a dynamic reversible gel network from carboxymethyl chitosan and a polyaldehyde crosslinking agent through an amino-aldehyde Schiff base reaction.

[0008] The wall binder is a bifunctional Janus-modified magnesium hydroxide nanosheet, and its preparation includes the following process:

[0009] Magnesium hydroxide nanosheets were modified with γ-aminopropyltriethoxysilane to introduce an amino group, and a Janus structure was formed by paraffin single-sided coating to obtain paraffin-coated magnesium hydroxide nanosheets; 3,4-dihydroxybenzoic acid was activated with carbodiimide / N-carboxysuccinimide and condensed with the amino group, and catechol groups were grafted; the paraffin was removed to obtain bifunctional Janus-modified magnesium hydroxide nanosheets.

[0010] The self-healing inducer is obtained by mixing hexamethylenetetramine with ammonium chloride and dissolving it in water.

[0011] Furthermore, the multi-aldehyde crosslinking agent is prepared by condensation of pentaerythritol and 4-formylbenzoic acid under the catalysis of 4-dimethylaminopyridine / dicyclohexylcarbodiimide, and it has a multi-branched aldehyde structure.

[0012] Further, the mass ratio of pentaerythritol to 4-formylbenzoic acid is 1.0:(4.16-6.0); the mass ratio of 4-formylbenzoic acid to 4-dimethylaminopyridine is (1.25-3.0):1.0; and the mass ratio of 4-formylbenzoic acid to dicyclohexylcarbodiimide is 1.0:(6.0-8.8).

[0013] Furthermore, the preparation of the polyaldehyde crosslinking agent includes the following steps:

[0014] The pentaerythritol and 4-formylbenzoic acid were dissolved in anhydrous toluene at 150-250 rpm; after cooling to 0°C, 4-dimethylaminopyridine was added and stirred for 15-20 min; dicyclohexylcarbodiimide was added and stirred for 30-40 min; the temperature was raised to 25°C and stirred for 12-13 h; the temperature was raised to 40°C and stirred for 24-26 h to obtain the polyaldehyde crosslinking agent.

[0015] Furthermore, in the amino-aldehyde Schiff base reaction, the molar ratio of carboxymethyl chitosan to polyaldehyde crosslinking agent is (1.0-1.2):1.0; the reaction pH is 5.5-6.0; the reaction temperature is 45-60℃; the stirring speed is 200-300 rpm; and the reaction time is 6-12 h.

[0016] Further, the mass ratio of the magnesium hydroxide nanosheets to the γ-aminopropyltriethoxysilane is (3.5-10.0):1.0; the mass ratio of the paraffin-coated magnesium hydroxide nanosheets to the 3,4-dihydroxybenzoic acid is (1.16-2.5):1.0; and the mass ratio of the 3,4-dihydroxybenzoic acid, the carbodiimide, and the N-carboxysuccinimide is (1.0-2.0):(2.0-3.0):1.0.

[0017] Further, the magnesium hydroxide nanosheets have a mass fraction of 3.5-5%; the γ-aminopropyltriethoxysilane has a mass fraction of 0.5-1.0%; the paraffin-coated magnesium hydroxide nanosheets have a mass fraction of 3.5-5%; the 3,4-dihydroxybenzoic acid has a mass fraction of 2.0-3.0%; the carbodiimide has a mass fraction of 4.0-6.0%; and the N-carboxysuccinimide has a mass fraction of 1.5-2.0%.

[0018] Furthermore, the mass ratio of hexamethylenetetramine to ammonium chloride is 1.0:(1.5-1.7), and the mass fraction dissolved in water is 1.0-1.5%.

[0019] Secondly, based on the same inventive concept, the present invention provides a method of using the self-healing gel sealing system described in any one of the first aspects, comprising the following steps:

[0020] Dissolve 0.05-0.1 wt% of the wall binder in water to form a wall binder dispersion, and continuously inject 0.2-0.3 PV slugs into the high-permeability channels of the reservoir; mix self-healing gel with water to form a self-healing gel particle dispersion, then mix 1.0-2.0 wt% of the self-healing gel particle dispersion with 0.05-0.1 wt% of the self-healing inducer, and continuously inject 0.2-0.3 PV slugs into the high-permeability channels of the reservoir.

[0021] Thirdly, based on the same inventive concept, the present invention provides an application of the self-healing gel plugging system described in any one of the first aspects in the exploitation of heterogeneous oil reservoirs.

[0022] Compared with the prior art, the embodiments of the present invention have at least the following advantages or beneficial effects:

[0023] 1. The self-healing gel sealing system provided by the present invention can achieve in-situ cross-linking, effectively block high water-content channels, significantly improve the sweep range, and achieve efficient oil displacement.

[0024] 2. Carboxymethyl chitosan reacts with polyaldehyde crosslinking agents via an amino-aldehyde Schiff base reaction (R-CHO + H2N-R′). The R-CH=NR′+H2O structure forms a dynamic, reversible gel network with self-healing properties. After rupture or structural damage under external forces, this system can autonomously repair its internal network structure and restore its sealing performance.

[0025] 3. The self-healing inducer formulated with a combination of hexamethylenetetramine and ammonium chloride produces NH4 under pyrolysis / hydrolysis. + NH4 + H is released under hydrothermal conditions + This provides a favorable acidic environment for gel self-healing; the use of a self-healing crosslinking agent with a multi-branched aldehyde structure helps to form a denser gel network, further enhancing the stability of the system.

[0026] 4. Bifunctional Janus magnesium hydroxide nanosheets rapidly adsorb onto rock walls due to their high surface energy, acting as an intermediate bridging agent. On one side, the catechol groups, designed based on mussel biomimicry principles, exhibit strong adhesion to active sites on the rock surface (containing hydroxyl / metal oxygen sites) through multiple interactions such as hydrogen bonding and coordination. On the other side, amino groups and cross-linking agent aldehyde groups participate in Schiff base reactions to construct a "wall-nanosheet-gel" bridging structure, firmly anchoring the gel to the pore throat wall.

[0027] 5. This system can form a plug with strong wall bonding ability in situ in the formation, effectively suppressing the flow phenomenon between particles and on the wall, and achieving efficient plugging of high water-cut channels, thereby successfully achieving the goals of fluid flow diversion, expanding the swept volume and improving crude oil recovery. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. 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.

[0029] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0030] To address the technical problems existing in the prior art, according to one aspect of the embodiments of this disclosure, a self-healing gel sealing system with strong wall bonding ability is provided, the system comprising 1.0-2.0 wt% of self-healing gel, 0.05-0.1 wt% of wall bonding agent and 0.05-0.1 wt% of self-healing inducer.

[0031] The self-healing gel is obtained by forming a dynamic reversible gel network from carboxymethyl chitosan and a polyaldehyde crosslinking agent through an amino-aldehyde Schiff base reaction.

[0032] The preparation method of this self-healing gel includes the following steps:

[0033] Carboxymethyl chitosan (CMCS) and deionized water were added to a flask, and dilute hydrochloric acid (6%) was added to adjust the pH. A self-healing gel crosslinking agent was added, and the mixture was slowly stirred at a certain speed for a certain period of time. The temperature was gradually increased and the mixture was stirred for a period of time. The stirring was stopped, and the mixture was allowed to stand for a period of time to obtain a gel product. The gel product was placed in a 60°C oven to dry and then ground into powder to obtain a self-healing gel.

[0034] It should be noted that the self-healing gel crosslinking agent is a polyaldehyde crosslinking agent.

[0035] In some examples, the quality score of CMCS is 15-20%.

[0036] In some examples, the pH range is 5.5–6.0.

[0037] In some examples, the mass fraction of the self-healing gel crosslinking agent is 0.1-0.3%.

[0038] In some examples, the rotational speed is 50-100 rpm.

[0039] In some examples, the stirring time is 10-15 minutes.

[0040] In some examples, the temperature is 45-60℃.

[0041] In some examples, the reaction time is 2-3 hours.

[0042] Furthermore, the preparation method of the above-mentioned self-healing gel crosslinking agent includes the following steps:

[0043] A certain amount of 3Å molecular sieve was dried and activated at 300℃ for a period of time. After cooling to room temperature, it was added to a flask along with 150 mL of toluene. A certain amount of pentaerythritol and a certain amount of 4-formylbenzoic acid were added, and the mixture was stirred and dissolved under nitrogen protection. The system was then placed in an ice-water bath and stirred continuously at 150-250 rpm until 0℃. A certain amount of 4-dimethylaminopyridine (DMAP) was added, and the mixture was stirred for 15-20 min under ice-water bath conditions. A certain amount of dicyclohexylcarbodiimide (DCC) was added, and the mixture was stirred for 30-4 min under ice-water bath conditions. The temperature was gradually increased to 25℃, and the reaction was continued with stirring for a period of time. The temperature was gradually increased to 40℃, and the reaction was continued with stirring for a period of time to obtain the reaction product. The product was filtered, washed, and dried to obtain a self-healing gel crosslinking agent.

[0044] In some examples, the molecular sieve has a mass of 15-20g.

[0045] In some examples, the drying time is 6-8 hours.

[0046] In some examples, the mass of pentaerythritol is 2.5-3g.

[0047] In some examples, the mass of 4-formylbenzoic acid is 12.5-15 g.

[0048] In some examples, the mass of DMAP is 1-2g.

[0049] In some examples, the mass of DCC is 18-22g.

[0050] In some examples, the reaction time at 25°C is 12-13 hours.

[0051] In some examples, the reaction time at 40°C is 24-26 hours.

[0052] The wall binder is bifunctional Janus-modified magnesium hydroxide nanosheets, and its preparation includes the following process:

[0053] Magnesium hydroxide nanosheets were modified with γ-aminopropyltriethoxysilane to introduce amino groups, and a Janus structure was formed by paraffin single-sided coating to obtain paraffin-coated magnesium hydroxide nanosheets; 3,4-dihydroxybenzoic acid was activated with carbodiimide / N-carboxysuccinimide and condensed with amino groups, and catechol groups were grafted; the paraffin was removed to obtain bifunctional Janus-modified magnesium hydroxide nanosheets.

[0054] It is worth noting that the bifunctional Janus-modified magnesium hydroxide nanosheets serve as an intermediate to connect the gel to the rock wall. One side contains catechol groups, which form hydrogen bonds or coordination interactions with hydroxyl or metal oxygen sites on the rock surface; the other side contains amino groups, which react with the polyaldehyde crosslinking agent to form Schiff base bonds.

[0055] Furthermore, the preparation method of magnesium hydroxide nanosheets includes the following steps:

[0056] A certain amount of magnesium chloride hexahydrate (MgCl2·6H2O) was added to deionized water and ultrasonically vibrated for 30 min to ensure complete dispersion. The mixture was then continuously magnetically stirred at a certain speed and heated to a certain temperature. A certain amount of sodium hydroxide (NaOH) was slowly added dropwise at a speed of 1.5 mL / min, and stirring was continued at a certain speed for a certain time to form a white suspension. Stirring was stopped, and the suspension was allowed to cool naturally at room temperature. After centrifugation and washing several times, the suspension was dried in a vacuum drying oven at 60℃ for 12 h to obtain Mg(OH)2 nanosheets.

[0057] In some examples, the mass fraction of MgCl2·6H2O is 3.5-5%.

[0058] In some examples, the stirring speed is 300-500 rpm.

[0059] In some examples, the stirring time is 3-5 hours.

[0060] In some examples, the temperature is 45-60℃.

[0061] In some examples, the mass fraction of NaOH is 1.0-1.5%.

[0062] Furthermore, the γ-aminopropyltriethoxysilane-modified magnesium hydroxide nanosheets include the following steps:

[0063] Magnesium hydroxide nanosheets were added to deionized water and ultrasonically vibrated for 30 min to ensure thorough dispersion. A certain mass of γ-aminopropyltriethoxysilane (KH550) was added to ethanol and slowly added dropwise to the magnesium hydroxide nanosheet dispersion aqueous solution at a rate of 1.5 mL / min. The solution was stirred at room temperature for a certain period of time. After stirring was stopped, the suspension was allowed to cool naturally at room temperature. After centrifugation and washing several times, the suspension was dried in a vacuum drying oven at 60 °C for 12 h to obtain amino-modified Mg(OH)2 nanosheets.

[0064] In some examples, the mass fraction of Mg(OH)2 nanosheets is 3.5-5%.

[0065] In some examples, the mass fraction of KH550 is 0.5-1.0%.

[0066] In some examples, the rotation speed is 300-400 rpm.

[0067] In some examples, the stirring time is 3-5 hours.

[0068] Furthermore, the preparation of paraffin-coated magnesium hydroxide nanosheets includes the following steps:

[0069] A certain mass of amino-modified Mg(OH)₂ nanosheets was added to deionized water and ultrasonically vibrated for 30 min to ensure full dispersion. Magnetic stirring was then continuously performed at 300 rpm. A certain mass of solid paraffin was added to the above solution. The reaction environment temperature was gradually increased to 70℃ under water bath conditions to fully melt the paraffin. The stirring speed was gradually increased to 800 rpm and continuously stirred for 30 min to ensure full emulsification of the reaction system. The emulsified solution was quickly transferred to an ice-water bath for rapid cooling. The resulting paraffin particles were removed and rinsed with deionized water to remove surface impurities, yielding paraffin-coated magnesium hydroxide nanosheets.

[0070] In some examples, the mass fraction of amino-modified Mg(OH)2 nanosheets is 3.5-5%.

[0071] In some examples, the mass fraction of solid paraffin is 30-40%.

[0072] Furthermore, grafting catechol groups includes the following steps:

[0073] Magnesium hydroxide nanosheets coated with paraffin were added to deionized water and magnetically stirred at a certain speed under ice-water bath conditions (4℃) to ensure uniform dispersion in the water for later use. Under ice-water bath conditions (4℃), a certain mass of 3,4-dihydroxybenzoic acid (PCA) was dissolved in 30 mL of buffer solution, and a certain mass of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) and N-hydroxysuccinimide (NHS) were added to the buffer solution. The mixture was stirred continuously for a period of time to fully activate PCA. The activated solution was added to the paraffin particle dispersion and stirred continuously at a certain speed under ice-water bath conditions (4℃) for a period of time. After the solution temperature was restored to room temperature, a certain mass of 2-mercaptoethanol was added and stirred continuously for a period of time. After centrifugation and washing, paraffin-coated Janus-modified Mg(OH)2 nanosheets were obtained.

[0074] In some examples, the stirring speed was 200-300 rpm.

[0075] In some examples, the buffer solution is 1.5 wt% 2-(N-morpholino)ethanesulfonic acid (MES).

[0076] In some examples, the quality fraction of PCA is 2.0-3.0%.

[0077] In some examples, the quality score of EDC is 4.0-6.0%.

[0078] In some examples, the NHS quality fraction is 1.5-2.0%.

[0079] In some examples, the stirring time for activating PCA is 15-20 min.

[0080] In some examples, the stirring time between the activated solution and the paraffin particle dispersion was 16-24 hours.

[0081] In some examples, the mass fraction of 2-mercaptoethanol is 4.0-6.0%.

[0082] In some examples, the stirring time after the addition of 2-mercaptoethanol is 30-50 min.

[0083] Further, removing paraffin wax includes the following steps:

[0084] Janus-modified Mg(OH)₂ nanosheets coated with paraffin were placed in a centrifuge tube and gradually heated to 50°C in a water bath. A certain amount of chloroform / toluene mixed solution was added to a beaker to fully dissolve the solid paraffin. The mixture was centrifuged at 8000 rpm for 10 min, and the nanosheet precipitate was removed. It was washed twice each with acetone, ethanol, and water, and then dried in a vacuum drying oven at 60°C for 12 h to obtain bifunctional Janus-modified magnesium hydroxide nanosheets, i.e., wall binders.

[0085] In some examples, the chloroform / toluene mixing ratio is 1.0:1.0.

[0086] In some examples, the volume of the chloroform / toluene mixture is 1.5 to 2.0 times the volume of the melted paraffin.

[0087] It should be noted that the wall binder is bifunctional Janus-modified magnesium hydroxide nanosheets, the dispersed phase is water, and the concentration is 0.05-0.1wt%.

[0088] The self-healing inducer is obtained by mixing hexamethylenetetramine with ammonium chloride and dissolving it in water.

[0089] It is worth noting that the self-healing inducer gradually releases acidic components under formation conditions, adjusting the local pH to improve the gel cross-linking effect.

[0090] Furthermore, the preparation of the self-healing inducer includes the following steps:

[0091] Hexamethylenetetramine and ammonium chloride were mixed in a ratio of 1:(1.5-1.7), and the mixture was dissolved in water at a certain mass fraction to obtain a self-healing inducer.

[0092] In some examples, the mass fraction of the mixture is 1.0-1.5%.

[0093] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Experimental methods in the following embodiments, unless otherwise specified, are generally performed according to national standards. If no corresponding national standard exists, then generally accepted international standards, conventional conditions, or conditions recommended by the manufacturer are followed.

[0094] Example 1

[0095] This embodiment provides a self-healing gel sealing system with strong wall bonding ability, which is composed of 0.05wt% wall bonding agent 1, 0.05wt% self-healing inducer and 1.0wt% self-healing gel 1. The preparation method includes the following steps:

[0096] The wall bonding agent 1 is prepared as follows:

[0097] 3.5 g of magnesium chloride hexahydrate (MgCl2·6H2O) was added to 95.5 g of deionized water and ultrasonically vibrated for 30 min to disperse it fully. The mixture was then continuously magnetically stirred at 300 rpm and heated to 45 °C. 1 g of sodium hydroxide (NaOH) was slowly added dropwise at a rate of 1.5 mL / min. The mixture was stirred at 300 rpm for 3 h to form a white suspension. The stirring was stopped and the suspension was allowed to cool naturally at room temperature. The suspension was centrifuged and washed several times and then dried in a vacuum drying oven at 60 °C for 12 h to obtain Mg(OH)2 nanosheets.

[0098] 3.5g of the above nanosheets were added to 96g of deionized water and ultrasonically vibrated for 30min to ensure full dispersion. 0.5g of γ-aminopropyltriethoxysilane (KH550) was added to ethanol and slowly added dropwise to the nanosheet dispersion aqueous solution at a rate of 1.5mL / min. The solution was stirred continuously at 300rpm for 3h at room temperature. After stirring was stopped, the suspension was allowed to cool naturally at room temperature. After centrifugation and washing several times, the suspension was dried in a vacuum drying oven at 60℃ for 12h to obtain amino-modified Mg(OH)2 nanosheets.

[0099] 3.5g of amino-modified Mg(OH)2 nanosheets were added to 66.5g of deionized water and ultrasonically vibrated for 30min to fully disperse them. Magnetic stirring was continuously performed at 300rpm. 30g of solid paraffin was added to the above solution. The reaction environment temperature was gradually increased to 70℃ under water bath conditions to fully melt the paraffin. The stirring speed was gradually increased to 800rpm and continuously stirred for 30min to fully emulsify the reaction system. The emulsified solution was quickly transferred to an ice-water bath environment for rapid cooling. The resulting paraffin particles were removed after cooling and rinsed with deionized water to remove surface impurities, yielding paraffin-coated nanosheets.

[0100] The above-mentioned paraffin-coated nanosheets were added to 58.5g of deionized water and magnetically stirred at 200rpm under ice-water bath conditions (4℃) to ensure uniform dispersion in the water for later use. 2g of 3,4-dihydroxybenzoic acid (PCA) was dissolved in 30g of MES buffer, and 4g of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) and 1.5g of N-hydroxysuccinimide (NHS) were added to the buffer. The mixture was stirred continuously at 200rpm for 15min under ice-water bath conditions (4℃) to fully activate PCA. The activated solution was added to the paraffin particle dispersion and stirred continuously at 200rpm for 16h under ice-water bath conditions (4℃). 4g of 2-mercaptoethanol was added and the mixture was stirred continuously at room temperature for 30min. After centrifugation and washing, paraffin-coated Janus nanosheets were obtained.

[0101] Janus nanosheets coated with paraffin were placed in a centrifuge tube and gradually heated to 50°C in a water bath. 54 mL of chloroform / toluene mixed solution was added to a beaker to fully dissolve the solid paraffin. The mixture was centrifuged at 8000 rpm for 10 min, and the nanosheet precipitate was removed. It was washed twice each with acetone, ethanol, and water, and then dried in a vacuum drying oven at 60°C for 12 h to obtain wall binder 1.

[0102] The self-healing gel 1 is prepared as follows:

[0103] 15g of 3Å molecular sieve was dried at 300℃ for 6h for activation treatment. After cooling to room temperature, it was added to a flask and 150mL of toluene was added.

[0104] Add 2.5g of pentaerythritol and a certain amount of 12.5g of 4-formylbenzoic acid. After stirring and dissolving under nitrogen protection, place the system in an ice-water bath and stir continuously at 200rpm until 0℃.

[0105] Add 1 g of 4-dimethylaminopyridine (DMAP) to the above system and continue stirring for 15 min under ice-water bath conditions;

[0106] Add 18g of dicyclohexylcarbodiimide (DCC) to the above system and continue stirring for 30min under ice-water bath conditions;

[0107] Gradually heat the system to 25°C and continue stirring for 12 hours;

[0108] Gradually heat the system to 40°C and continue stirring for 24 hours;

[0109] Filter, wash, and dry to obtain a self-healing gel crosslinking agent;

[0110] Add 15g of carboxymethyl chitosan (CMCS) and 85g of deionized water to a flask, and adjust the pH to 6 with dilute hydrochloric acid (6%).

[0111] Add 0.1g of self-healing gel crosslinking agent and stir slowly at 50rpm for 10min;

[0112] Gradually increase the temperature to 45℃ and continue stirring for 2 hours;

[0113] Stop stirring and let the reaction stand for 2 hours to obtain the gel product;

[0114] The gel product was dried in a 60°C oven and then ground into powder to obtain self-healing gel 1, hereinafter referred to as sealing system 1.

[0115] The self-healing inducer is prepared as follows:

[0116] Hexamethylenetetramine and ammonium chloride were mixed at a mass ratio of 1:1.5, and the mixture was dissolved in water at a mass fraction of 1% to obtain a self-healing inducer.

[0117] Example 2

[0118] This embodiment provides a self-healing gel sealing system with strong wall bonding ability, which is composed of 0.075wt% wall bonding agent 2, 0.075wt% self-healing inducer and 1.5wt% self-healing gel 2. The preparation method includes the following steps:

[0119] The wall bonding agent 2 is prepared as follows:

[0120] 4g of magnesium chloride hexahydrate (MgCl2·6H2O) was added to 94.8g of deionized water and ultrasonically vibrated for 30min to disperse it fully. The mixture was then magnetically stirred continuously at 500rpm and heated to 50℃. 1.2g of sodium hydroxide (NaOH) was slowly added dropwise at a rate of 1.5mL / min. The mixture was stirred at 400rpm for 4h to form a white suspension. The stirring was stopped and the suspension was allowed to cool naturally at room temperature. The suspension was centrifuged and washed several times and then dried in a vacuum drying oven at 60℃ for 12h to obtain Mg(OH)2 nanosheets.

[0121] 4g of the above nanosheets were added to 95.25g of deionized water and ultrasonically vibrated for 30min to ensure full dispersion. 0.75g of γ-aminopropyltriethoxysilane (KH550) was added to ethanol and slowly added dropwise to the nanosheet dispersion aqueous solution at a rate of 1.5mL / min. The solution was stirred continuously at 350rpm for 4h at room temperature. After stirring was stopped, the suspension was allowed to cool naturally at room temperature. After centrifugation and washing several times, the suspension was dried in a vacuum drying oven at 60℃ for 12h to obtain amino-modified Mg(OH)2 nanosheets.

[0122] 4g of amino-modified Mg(OH)2 nanosheets were added to 61g of deionized water and ultrasonically vibrated for 30min to fully disperse them. Magnetic stirring was continuously performed at 250rpm. 35g of solid paraffin was added to the above solution. The reaction environment temperature was gradually increased to 70℃ under water bath conditions to fully melt the paraffin. The stirring speed was gradually increased to 800rpm and continuously stirred for 30min to fully emulsify the reaction system. The emulsified solution was quickly transferred to an ice-water bath environment for rapid cooling. The resulting paraffin particles were removed after cooling and rinsed with deionized water to remove surface impurities, yielding paraffin-coated nanosheets.

[0123] The above-mentioned paraffin-coated nanosheets were added to 55.75 g of deionized water and magnetically stirred at 300 rpm under ice-water bath conditions (4 °C) to disperse them evenly in the water for later use. 2.5 g of 3,4-dihydroxybenzoic acid (PCA) was dissolved in 30 g of MES buffer, and 5 g of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) and 1.75 g of N-hydroxysuccinimide (NHS) were added to the buffer. The mixture was stirred continuously at 250 rpm for 17.5 min under ice-water bath conditions (4 °C) to fully activate PCA. The activated solution was added to the paraffin particle dispersion and stirred continuously at 250 rpm for 24 h under ice-water bath conditions (4 °C). Then, 5 g of 2-mercaptoethanol was added and the mixture was stirred for another 40 min at room temperature. After centrifugation and washing, paraffin-coated Janus nanosheets were obtained.

[0124] Janus nanosheets coated with paraffin were placed in a centrifuge tube and gradually heated to 50°C in a water bath. 63 mL of chloroform / toluene mixed solution was added to a beaker to fully dissolve the solid paraffin. The mixture was centrifuged at 8000 rpm for 10 min, and the nanosheet precipitate was removed. It was washed twice each with acetone, ethanol, and water, and then dried in a vacuum drying oven at 60°C for 12 h to obtain wall binder 2.

[0125] The self-healing gel 2 is prepared as follows:

[0126] 17.5 g of 3 Å molecular sieve was dried at 300 °C for 7 h to activate it. After cooling to room temperature, it was added to a flask and 150 mL of toluene was added.

[0127] Add 2.75g of pentaerythritol and 13.75g of 4-formylbenzoic acid, stir and dissolve under nitrogen protection, then place the system in an ice-water bath and stir continuously at 200rpm until 0℃.

[0128] Add 1.5 g of 4-dimethylaminopyridine (DMAP) to the above system and continue stirring for 15 min under ice-water bath conditions;

[0129] Add 20g of dicyclohexylcarbodiimide (DCC) to the above system and continue stirring for 30min under ice-water bath conditions;

[0130] Gradually raise the temperature of the system to 25°C and continue stirring for 12.5 hours;

[0131] Gradually heat the system to 40°C and continue stirring for 25 hours;

[0132] Filter, wash, and dry to obtain a self-healing gel crosslinking agent;

[0133] Add 17.5g of carboxymethyl chitosan (CMCS) and 82.5g of deionized water to a flask, and add dilute hydrochloric acid (6%) to adjust the pH to 5.8;

[0134] Add 0.2g of self-healing gel crosslinking agent and stir slowly at 750rpm for 12.5min;

[0135] Gradually increase the temperature to 60℃ and then continue stirring for 2.5 hours;

[0136] Stop stirring and let the reaction stand for 2.5 hours to obtain the gel product;

[0137] The gel product was dried in a 60°C oven and then ground into powder to obtain self-healing gel 2, hereinafter referred to as sealing system 2.

[0138] The self-healing inducer is prepared as follows:

[0139] Hexamethylenetetramine and ammonium chloride were mixed at a mass ratio of 1:1.5, and the mixture was dissolved in water at a mass fraction of 1% to obtain a self-healing inducer.

[0140] Example 3

[0141] This embodiment provides a self-healing gel sealing system with strong wall bonding ability, which is composed of 0.1 wt% wall bonding agent 3, 0.1 wt% self-healing inducer and 2.0 wt% self-healing gel 3. The preparation method includes the following steps:

[0142] The wall bonding agent 3 is prepared as follows:

[0143] 5g of magnesium chloride hexahydrate (MgCl2·6H2O) was added to 93.5g of deionized water and ultrasonically vibrated for 30min to disperse it fully. The mixture was then magnetically stirred continuously at 500rpm and heated to 60℃. 1.5g of sodium hydroxide (NaOH) was slowly added dropwise at a rate of 1.5mL / min. The mixture was stirred at 500rpm for 5h to form a white suspension. The stirring was stopped and the suspension was allowed to cool naturally at room temperature. After centrifugation and washing several times, the suspension was dried in a vacuum drying oven at 60℃ for 12h to obtain Mg(OH)2 nanosheets.

[0144] 5g of the above nanosheets were added to 94g of deionized water and ultrasonically vibrated for 30min to ensure full dispersion. 1g of γ-aminopropyltriethoxysilane (KH550) was added to ethanol and slowly added dropwise to the nanosheet dispersion aqueous solution at a rate of 1.5mL / min. The solution was stirred continuously at 400rpm for 5h at room temperature. After stirring was stopped, the suspension was allowed to cool naturally at room temperature. After centrifugation and washing several times, the suspension was dried in a vacuum drying oven at 60℃ for 12h to obtain amino-modified Mg(OH)2 nanosheets.

[0145] 5g of amino-modified Mg(OH)2 nanosheets were added to 55g of deionized water and ultrasonically vibrated for 30min to fully disperse them. Magnetic stirring was continuously performed at 300rpm. 40g of solid paraffin was added to the above solution. The reaction environment temperature was gradually increased to 70℃ under water bath conditions to fully melt the paraffin. The stirring speed was gradually increased to 800rpm and continuously stirred for 30min to fully emulsify the reaction system. The emulsified solution was quickly transferred to an ice-water bath environment for rapid cooling. The resulting paraffin particles were removed after cooling and rinsed with deionized water to remove surface impurities, yielding paraffin-coated nanosheets.

[0146] The above-mentioned paraffin-coated nanosheets were added to 53g of deionized water and magnetically stirred at 200rpm under ice-water bath conditions (4℃) to ensure uniform dispersion in the water for later use. 3g of 3,4-dihydroxybenzoic acid (PCA) was dissolved in 30g of MES buffer, and 6g of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) and 2g of N-hydroxysuccinimide (NHS) were added to the buffer. The mixture was stirred continuously at 300rpm for 20min under ice-water bath conditions (4℃) to fully activate PCA. The activated solution was added to the paraffin particle dispersion and stirred continuously at 300rpm for 20h under ice-water bath conditions (4℃). Then, 6g of 2-mercaptoethanol was added and the mixture was stirred for another 50min at room temperature. After centrifugation and washing, paraffin-coated Janus nanosheets were obtained.

[0147] Janus nanosheets coated with paraffin were placed in a centrifuge tube and gradually heated to 50°C in a water bath. 72 mL of chloroform / toluene mixed solution was added to a beaker to fully dissolve the solid paraffin. The mixture was centrifuged at 8000 rpm for 10 min, and the nanosheet precipitate was removed. It was washed twice each with acetone, ethanol, and water, and then dried in a vacuum drying oven at 60°C for 12 h to obtain wall binder 3.

[0148] The self-healing gel 3 is prepared as follows:

[0149] 20g of 3Å molecular sieve was dried at 300℃ for 8h for activation treatment. After cooling to room temperature, it was added to a flask and 150mL of toluene was added.

[0150] Add 3g of pentaerythritol and 15g of 4-formylbenzoic acid, stir and dissolve under nitrogen protection, then place the system in an ice-water bath and stir continuously at 200 rpm until 0℃.

[0151] Add 2g of 4-dimethylaminopyridine (DMAP) to the above system and continue stirring for 15min under ice-water bath conditions;

[0152] Add 22g of dicyclohexylcarbodiimide (DCC) to the above system and continue stirring for 30min under ice-water bath conditions;

[0153] Gradually heat the system to 25°C and continue stirring for 13 hours;

[0154] Gradually heat the system to 40°C and continue stirring for 26 hours;

[0155] Filter, wash, and dry to obtain a self-healing gel crosslinking agent;

[0156] Add 20g of carboxymethyl chitosan (CMCS) and 80g of deionized water to a flask, and adjust the pH to 5.5 with dilute hydrochloric acid (6%).

[0157] Add 0.3g of self-healing gel crosslinking agent and stir slowly at 100rpm for 15min;

[0158] Gradually increase the temperature to 60℃ and stir continuously for 3 hours;

[0159] Stop stirring and let the reaction stand for 3 hours to obtain the gel product;

[0160] The gel product was dried in a 60°C oven and then ground into powder to obtain self-healing gel 3, hereinafter referred to as sealing system 3.

[0161] The self-healing inducer is prepared as follows:

[0162] Hexamethylenetetramine and ammonium chloride were mixed at a mass ratio of 1:1.5, and the mixture was dissolved in water at a mass fraction of 1% to obtain a self-healing inducer.

[0163] Comparative Example 1

[0164] This comparative example provides a self-healing gel sealing system, which consists of 0.05 wt% self-healing inducer and 1.0 wt% self-healing gel. Its preparation method is basically the same as that of Example 1, except that no wall bonding agent is added, in order to verify the effect of not adding a wall bonding agent on the technical effect.

[0165] Comparative Example 2

[0166] This comparative example provides a self-healing gel sealing system, which consists of 0.05 wt% wall bonding agent and 1.0 wt% self-healing gel. Its preparation method is basically the same as that of Example 1, except that no self-healing inducer is added, in order to verify the effect of not adding a self-healing inducer on the technical effect.

[0167] Comparative Example 3

[0168] This comparative example provides a self-healing gel sealing system, which consists of 0.05 wt% wall bonding agent, 1.0 wt% self-healing gel 4, and 0.05 wt% self-healing inducer. The preparation method is basically the same as in Example 1, except that the preparation of self-healing gel 4 is carried out in the following steps:

[0169] Add 15g of carboxymethyl chitosan (CMCS) and 85g of deionized water to a flask, and adjust the pH to 6 with dilute hydrochloric acid (6%).

[0170] Add 0.1g of glutaraldehyde and stir slowly at 50rpm for 10min;

[0171] Gradually increase the temperature to 45℃ and continue stirring for 2 hours;

[0172] Stop stirring and let the reaction stand for 2 hours to obtain the gel product;

[0173] The gel product was dried in a 60°C oven and then ground into powder to obtain self-healing gel 4, hereinafter referred to as sealing system 4.

[0174] To verify the impact of different self-healing gel systems on the technical effect.

[0175] Comparative Example 4

[0176] This comparative example provides a self-healing gel sealing system, which consists of a single self-healing gel 5, and the preparation method includes the following steps:

[0177] Add 5g of tetramethylethylenediamine and 35g of deionized water to a flask, add 10g of acrylic acid, stir well to obtain a crosslinking agent solution, weigh 1g of azobisisobutyramidine hydrochloride and add it to deionized water to prepare an initiator solution with a mass concentration of 5%.

[0178] Add 20g of hexadecyl dimethyl allyl ammonium chloride to a 200mL beaker containing 50g of deionized water. Stir the solution with a mechanical stirrer at 300r / min until the hexadecyl dimethyl allyl ammonium chloride is evenly dispersed in the deionized water. Then weigh 30g of acrylamide and add it to the solution and stir evenly.

[0179] Add 1 mL of crosslinking agent solution to the above solution, stir well, then add 0.5 mL of initiator solution and stir well.

[0180] The above solution was placed in an ultraviolet light initiation chamber and allowed to stand for 6 hours to obtain a gel product.

[0181] The gel product was dried in a 60°C oven and then ground into powder to obtain self-healing gel 5, hereinafter referred to as sealing system 5.

[0182] To verify the technical effectiveness of conventional self-healing gels without the addition of wall bonding agents and self-healing inducers.

[0183] To better understand the present invention, the following tests were performed on the products obtained in the embodiments and comparative examples.

[0184] Test Example 1

[0185] This test example examines the adhesion performance of the products obtained from the above embodiments and comparative examples. The test method is as follows:

[0186] The adhesion strength between rock and gel was studied by testing the separation strength between the rock and gel. The specific steps are as follows:

[0187] The test rock was pretreated with a wall bonding solution (immersed in the pretreatment solution for 30 minutes). A hook was attached to one side of the rock with epoxy adhesive, and the other side was attached to the gel. The gel and rock were then immersed in a self-healing inducer solution at 80°C. After the gel adhesion stabilized, the force required for the gel to separate from the rock was tested using a spring balance. The adhesion strength was calculated using the following formula:

[0188] P=F / A

[0189] Where F(N) is the maximum strength during the separation test, and A(m) is the maximum strength during the separation test. 2 ) represents the interaction area between the gel and the rock.

[0190] The test results are shown in Table 1:

[0191] Table 1 Adhesion performance test results

[0192] Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Pretreatment solution 0.05wt% Wall binder 1 dispersion 0.075wt% wall binder 2 dispersion 0.1wt% wall binder dispersion Deionized water 0.05wt% Wall binder 1 dispersion 0.05wt% Wall binder 1 dispersion Deionized water Testing System 1.0wt% plugging system 1 1.5wt% plugging system 2 2.0wt% plugging system 3 1.0wt% plugging system 1 1.0wt% plugging system 1 1.0wt% plugging system 4 Blocking System 5 Self-healing inducing solution 0.05wt% self-healing inducer 0.075wt% self-healing inducer 0.1wt% self-healing inducer 0.05wt% self-healing inducer Deionized water 0.05wt% self-healing inducer Deionized water Adhesion strength (Psi) 1.4 1.6 1.9 0.6 0.2 1.2 0.2

[0193] As shown in Table 1, the adhesion strength of Examples 1-3 is significantly higher than that of the conventional self-healing gel system in Comparative Example 3.

[0194] The adhesion strength of Examples 1-3 showed an increasing trend, indicating that the addition of components such as wall binders and self-healing gel crosslinking agents is beneficial to improving gel adhesion. Comparing Example 1 (with wall binder) and Comparative Example 1 (without wall binder), it can be seen that the wall binder significantly improves gel adhesion strength by forming stable anchor points between the rock surface and the gel. Comparing Example 1 (with self-healing inducer) and Comparative Example 2 (without self-healing inducer), it can be seen that the weakly acidic environment provided by the self-healing inducer helps inhibit the hydrolysis of C=N bonds, thereby improving gel strength. Comparing Example 1 (crosslinking agent is a self-healing gel crosslinking agent) and Comparative Example 3 (crosslinking agent is glutaraldehyde), it can be seen that more aldehyde branches help form a denser gel network structure, improving gel adhesion strength to some extent.

[0195] Test Example 2

[0196] This test example examines the self-healing performance of the products obtained in the above embodiments and comparative examples. The test method is as follows:

[0197] The self-healing gel was prepared into a dumbbell shape and divided into two pieces. One piece of gel was stained red with amaranth red. The two pieces of gel were then brought into contact with each other and immersed in a self-healing induction solution at 80°C. The healing process at the contact surface was observed. Healing was considered complete when the contact surface completely disappeared. The error time was within 10 minutes. The experimental results are shown in Table 2.

[0198] Table 2. Results of Self-Healing Performance Test

[0199] Example 1 Example 2 Example 3 Comparative Example 2 Comparative Example 3 Comparative Example 4 Testing System 1.0wt% plugging system 1 1.5wt% plugging system 2 2.0wt% plugging system 3 1.0wt% plugging system 1 1.0wt% plugging system 4 Blocking System 5 Self-healing inducing solution 0.05wt% self-healing inducer 0.075wt% self-healing inducer 0.1wt% self-healing inducer Deionized water 0.05wt% self-healing inducer Deionized water Healing time (min) 60-70 50-60 40-50 70-80 60-70 90-100

[0200] As shown in Table 2, the self-healing inducer can significantly increase the condensation rate of aldehyde and amino groups. The self-healing speed of Examples 1-3 is significantly faster than that of the conventional self-healing gel system in Comparative Example 3.

[0201] The adhesion strength of Examples 1-3 showed an increasing trend, indicating that increasing the amount of self-healing gel crosslinking agent is beneficial to improving the self-healing effect of the gel. A comparison of Example 1 (with self-healing inducer) and Comparative Example 2 (without self-healing inducer) shows that the weakly acidic environment provided by the self-healing inducer helps promote the condensation of aldehyde and amino groups, reducing healing time. The healing times of Example 1 (crosslinking agent is a self-healing gel crosslinking agent) and Comparative Example 3 (crosslinking agent is glutaraldehyde) are similar, indicating that the self-healing speed is mainly related to the total content of effective functional groups (aldehyde groups) of the crosslinking agent, and is less affected by the number of branches.

[0202] Test Example 3

[0203] This test example performs an elastic modulus test on the products obtained from the above embodiments and comparative examples. The test method is as follows:

[0204] The elastic modulus of the gel after gelation was tested using a HAAKE rheometer, and the elastic modulus was used to evaluate the strength of different embodiments. During testing, a flat plate sensor with a gap of 3 mm was used. The measurement was performed using an oscillation frequency curve mode, with a test frequency of 0.1 Hz to 20 Hz and a stress of 1 Pa. The elastic modulus (G') was then obtained. The experimental results are shown in Table 3.

[0205] Table 3 Elastic modulus test

[0206] Example 1 Example 2 Example 3 Comparative Example 3 Comparative Example 4 Testing System 1.0wt% plugging system 1 1.5wt% plugging system 2 2.0wt% plugging system 3 1.0wt% plugging system 4 Blocking System 5 Elastic modulus (Pa) 214.8 247.1 280.6 180.4 112.7

[0207] As shown in Table 3, the main component affecting the elastic modulus of the gel is the self-healing crosslinking agent. As can be seen from Examples 1-3, the elastic modulus increases with the increase of crosslinking agent content. By comparing Example 1 (crosslinking agent is a self-healing gel crosslinking agent) with Comparative Example 3 (crosslinking agent is glutaraldehyde), it can be seen that more aldehyde branches help to form a denser gel network structure, which to some extent affects the elastic modulus of the gel.

[0208] Test Example 4

[0209] This test example examines the sealing pressure-bearing performance of the products obtained in the above embodiments and comparative examples. The test method is as follows:

[0210] A cylindrical artificial rock core, 5 cm long and 2.5 cm in diameter, was selected and cut axially from the middle. Stainless steel pads were placed on both sides of the crack to provide support, creating an artificial crack with a width of 2 mm. The sealing effect of the gel system was evaluated. After injecting a certain amount of precursor solution, the gel sealing system was mixed with the self-healing inducing solution and injected into the rock core. The core was then aged at 70°C for 12 hours, and its breakthrough pressure was tested. The test results are shown in Table 4.

[0211] Table 4. Results of the sealing pressure test

[0212] Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Precursor solution 0.05wt% Wall binder 1 dispersion 0.075wt% wall binder 2 dispersion 0.1wt% wall binder dispersion Deionized water 0.05wt% Wall binder 1 dispersion 0.05wt% Wall binder 1 dispersion Deionized water Testing System 1.0wt% plugging system 1 1.5wt% plugging system 2 2.0wt% plugging system 3 1.0wt% plugging system 1 1.0wt% plugging system 1 1.0wt% plugging system 4 Blocking System 5 Self-healing inducing solution 0.05wt% self-healing inducer 0.075wt% self-healing inducer 0.1wt% self-healing inducer 0.05wt% self-healing inducer Deionized water 0.05wt% self-healing inducer Deionized water Breakthrough pressure (MPa) 1.2 1.6 1.8 0.7 0.6 0.8 0.3

[0213] As shown in Table 4, the sealing strength of Examples 1-3 is significantly higher than that of the conventional self-healing gel system in Comparative Example 3.

[0214] A comparison of Examples 1-3 shows that, under confined space conditions, increasing the effective content can promote denser and more compact gel aggregates, significantly improving gel strength. Comparative Example 4 exhibits the lowest pressure-bearing capacity; its gel particles have weak agglomeration ability and poor adhesion to the wall surface, exhibiting cross-flow problems even at low pressures, leading to some particles being ejected. The experimental results of Examples 1 and Comparative Example 1 indicate that wall binders help improve the adhesion between gel aggregates and the wall surface, reducing cross-flow problems between the gel and the wall. However, limited by the pressure-bearing capacity of the gel aggregates, the aggregates break down when the pressure reaches a certain level, resulting in cross-flow between gel particles and a low breakthrough pressure.

[0215] As can be seen from the comparison of Example 1 and Comparative Example 2, the weakly acidic environment provided by the self-healing inducer can effectively inhibit the hydrolysis reaction of C=N bonds, improve the stability of the gel network, and thus increase the breakthrough pressure.

[0216] As can be seen from the comparison of Example 1 and Comparative Example 3, the increase in the number of crosslinking agent branches helps to form a denser gel crosslinking network, which can further improve the gel blocking strength and thus increase the breakthrough pressure.

[0217] Various embodiments of the present invention may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a hard limitation on the scope of the invention; therefore, it should be considered that the range description has specifically disclosed all possible subranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed subranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Furthermore, whenever a numerical range is referred to herein, it means including any referenced number (fraction or integer) within the range referred to.

[0218] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A self-healing gel plugging system with strong wall face bonding ability, characterized in that, The self-healing gel plugging system comprises 1.0-2.0 wt% of the self-healing gel, 0.05-0.1 wt% of the wall surface binding agent and 0.05-0.1 wt% of the self-healing inducer; The self-healing gel is formed by a dynamic reversible gel network through an amino-aldehyde Schiff base reaction of carboxymethyl chitosan and a polyaldehyde crosslinking agent; The polyaldehyde crosslinking agent is prepared by condensation of pentaerythritol and 4-formylbenzoic acid under catalysis of 4-dimethylaminopyridine / dicyclohexyl carbodiimide, and has a multi-branched aldehyde group structure; The wall surface binding agent is a bifunctional Janus modified magnesium hydroxide nanosheet, and its preparation comprises the following processes: The magnesium hydroxide nanosheet is modified by introducing amino groups through γ-aminopropyl triethoxysilane, and a Janus structure is formed by a paraffin single-side coating method to obtain paraffin single-side coated magnesium hydroxide nanosheet; 3,4-dihydroxybenzoic acid is activated by using carbodiimide / N-carboxy succinimide and condensed with the amino groups to graft catechol groups; and the paraffin is removed to obtain the bifunctional Janus modified magnesium hydroxide nanosheet; The self-healing inducer is obtained by mixing and dissolving urotropine and ammonium chloride in water.

2. The self-healing gel plug system of claim 1, wherein, The mass ratio of the pentaerythritol to the 4-formylbenzoic acid is 1.0:(4.16-6.0); the mass ratio of the 4-formylbenzoic acid to the 4-dimethylaminopyridine is (1.25-3.0):1.0; and the mass ratio of the 4-formylbenzoic acid to the dicyclohexyl carbodiimide is 1.0:(6.0-8.8).

3. The self-healing gel plug system of claim 2, wherein, The preparation of the polyaldehyde crosslinking agent comprises the following steps: The pentaerythritol and the 4-formylbenzoic acid are dissolved in anhydrous toluene at 150-250 rpm; 4-dimethylaminopyridine is added after cooling to 0℃ and stirred for 15-20 min; dicyclohexyl carbodiimide is added and stirred for 30-40 min; the temperature is raised to 25℃ and the reaction is carried out for 12-13 h; the temperature is raised to 40℃ and the reaction is carried out for 24-26 h to obtain the polyaldehyde crosslinking agent.

4. The self-healing gel plug system of claim 1, wherein, In the amino-aldehyde Schiff base reaction, the molar ratio of carboxymethyl chitosan to polyaldehyde crosslinking agent is (1.0-1.2):1.0; the reaction pH is 5.5-6.0; the reaction temperature is 45-60℃; the stirring speed is 200-300 rpm; and the reaction time is 6-12 h.

5. The self-healing gel plug system of claim 1, wherein, The mass ratio of the magnesium hydroxide nanosheet to the γ-aminopropyl triethoxysilane is (3.5-10.0):1.0; the mass ratio of the paraffin single-side coated magnesium hydroxide nanosheet to the 3,4-dihydroxybenzoic acid is (1.16-2.5):1.0; and the mass ratio of the 3,4-dihydroxybenzoic acid, the carbodiimide and the N-carboxy succinimide is (1.0-2.0):(2.0-3.0):1.

0.

6. The self-healing gel plug system of claim 1, wherein, The mass fraction of the magnesium hydroxide nanosheet is 3.5-5%; the mass fraction of the gamma-aminopropyltriethoxysilane is 0.5-1.0%; the mass fraction of the paraffin single-sided coated magnesium hydroxide nanosheet is 3.5-5%; the mass fraction of the 3,4-dihydroxybenzoic acid is 2.0-3.0%; the mass fraction of the carbodiimide is 4.0-6.0%; and the mass fraction of the N-carboxyl succinimide is 1.5-2.0%.

7. The self-healing gel plug system of claim 1, wherein, The mass ratio of the urotropin to the ammonium chloride is 1.0: (1.5-1.7), and the mass fraction dissolved in water is 1.0-1.5%.

8. A method of using the self-healing gel plugging system of any one of claims 1-7, characterized in that, The method comprises the following steps: 0.05-0.1wt% of the wall surface binding agent is dissolved in water to form a wall surface binding agent dispersion liquid, and a 0.2-0.3PV slug is continuously injected into the high-permeability channel of the oil reservoir; the self-healing gel is mixed with water to form a self-healing gel particle dispersion liquid, then 1.0-2.0wt% of the self-healing gel particle dispersion liquid is mixed with 0.05-0.1wt% of the self-healing inducer, and a 0.2-0.3PV slug is continuously injected into the high-permeability channel of the oil reservoir.

9. Application of the self-healing gel plugging system in any one of claims 1-7 in the exploitation of a heterogeneous oil reservoir.