Preparation of multilayer coated gelatin particles, and multilayer coated gelatin particles, and methods and uses thereof

Abstract

The present application relates to the technical field of oilfield chemical profile control and water plugging, and discloses a composition for preparing multilayer film-coated gel particles, the multilayer film-coated gel particles, a preparation method thereof and application, wherein the multilayer film-coated gel particles comprise one layer of film-coated gel liquid particles and two layers of films coated on the outer surface of the one layer of film-coated gel liquid particles; the two layers of films are formed by the one layer of film-coated gel liquid particles and a dichloromethane solution containing a two-layer film agent and a dispersant aid, wherein the two-layer film agent is polylactic acid, and the dispersant aid is polyethylene glycol. When the multilayer film-coated gel particles are injected into a stratum, the two layers of films on the outside gradually degrade, the one layer of film-coated gel liquid particles on the inside is exposed, and the one layer of film-coated gel liquid particles agglomerate to form aggregates, thereby forming a seal in the deep part of the stratum.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of oilfield chemical profile control and water shutoff, and particularly relates to a composition for preparing multilayer coated gel particles, and the multilayer coated gel particles, a preparation method therefor, and applications thereof. BACKGROUND

[0002] Unconventional oil and gas resources are important positions for protecting national energy security by controlling water and increasing oil in China. With the development of unconventional oil and gas resources in China, the exploitation technology of deep fracture-cave type oil and gas reservoirs is becoming more and more perfect. Fracture-cave type carbonate reservoirs (fracture-cave type reservoirs) are mainly distributed in the Tarim Basin. Among them, the proven total reserves of oil and gas in the Tahe oilfield, the Lungu oilfield, the Halahatang oilfield, the Funan oilfield, and the Shunbei oil and gas field have exceeded 20.0 x 10 8 t, and the annual production has reached 700 x 10 4 t. They are important strategic replacement resources. In the current development technology of high-temperature and high-salinity fracture-cave type oil and gas reservoirs, water injection is the most widely used, but the extreme heterogeneity of fracture-cave type reservoirs leads to water channeling, which becomes an important factor affecting the development of high-temperature and high-salinity fracture-cave type oil and gas reservoirs. Unlike traditional pore type reservoirs, many wells in fracture-cave type reservoirs will be shut down due to rapid and violent water flooding (water cut close to 100%) after water injection. The regulation effect of the near-wellbore region is increasingly declining, and the regulation of the deep region of the fracture-cave type reservoir becomes an effective way to help the development of high-temperature and high-salinity fracture-cave type oil and gas reservoirs. The core is the research and development of the regulating agent. The gel type regulating agent has stable gelation effect, controllable gel performance, temperature resistance, salt resistance, and simple preparation, and becomes a widely used regulating agent. However, the high-viscosity gelation liquid and the short gelation time make it difficult for the gel to migrate to the deep region.

[0003] CN116333704A discloses a gel system capable of rapid gelation under high-temperature and high-salinity conditions and a preparation method thereof. The raw materials of the gel system include, by weight percentage, 2-4% phenolic pre-polymer, 0.1-0.2% polyethylene glycol, 0.6-1% polymer, and salt water system. The polymer is an acrylamide / 2-acrylamide-2-methylpropanesulfonic acid copolymer with a molecular weight of 8 million. The gel system can rapidly gel in a short time, solves the problem of poor gel strength or no gelation caused by the dilution of the gel by formation water in high-temperature and high-salinity fracture-cave type oil reservoirs, and is suitable for oil reservoirs with a formation temperature of <150℃ and a salinity of >20 x 10 4 mg / L. However, the gelation time of the gel is 1-1.5h, which is too fast to migrate to the deep region.

[0004] CN118772447A discloses an elastic gel particle and a preparation method thereof. The gel particle is prepared by granulating a gel prepared from silicate, a crosslinking agent, sulfonated phenolic resin, and polyvinyl alcohol under the action of an acid catalyst, and has a particle size of 1 x 10 1 to 3 x 10 6nm, can be aged at 130 DEG C, salinity 214812.46 mg / L for 90 d, the deformation recovery rate of 5 times extrusion is 60 to 87%, the dehydration rate is 15% to 30%, the volume shrinkage rate is 29% to 45%, but the gel particle does not consider the particle coalescence rate of the particle at high temperature and high salt, and the deep migration ability cannot be determined.

[0005] CN113897189A discloses a gel system suitable for high temperature and high salt fracture and cave type oil reservoir profile control and application, which is composed of AM / AMPS copolymer, non-ionic polyacrylamide, urotropine, hydroquinone and the balance of water, and the temperature is as high as 130 DEG C, and the formation water salinity is as high as 220000 mg / L to ensure the stability and strength of the gel, speed up the crosslinking reaction speed, and reduce the adverse effects of formation water dilution on the gel, but the effect of avoiding dilution of formation water is limited, and the effect of deep injection is affected.

[0006] Therefore, it is urgent to develop a gel system that can deep flow control to meet the heterogeneity control of high temperature and high salt fracture and cave type oil and gas reservoirs. SUMMARY

[0007] The purpose of the present application is to overcome the problems that the existing high temperature and high salt fracture and cave type oil and gas reservoir gel type control agent cannot be deep injected due to too fast gelation speed, and cannot be deep plugged due to dilution of the gelation liquid by formation water, and to provide a composition for preparing multi-layer coated gel particles, and the multi-layer coated gel particles and the preparation method and application thereof, which can form aggregates by mutual adhesion of the one-layer coated gel liquid particle exposed by the gradual degradation of the outer two-layer coating in the injected formation, and form a deep plugging in the formation.

[0008] In order to achieve the above-mentioned purpose, the first aspect of the present application provides a multi-layer coated gel particle, wherein the multi-layer coated gel particle comprises one-layer coated gel liquid particles and two-layer coating on the outer surface of the one-layer coated gel liquid particles; the two-layer coating is formed by the one-layer coated gel liquid particles and a dichloromethane solution containing a two-layer coating agent and a dispersant aid, wherein the two-layer coating agent is polylactic acid, and the dispersant aid is polyethylene glycol.

[0009] The second aspect of the present application provides a composition for preparing multi-layer coated gel particles, wherein the composition comprises a gelation liquid, a salt solution containing calcium ions, and a dichloromethane solution containing a two-layer coating agent and a dispersant aid, which are independently stored;

[0010] The gelation liquid comprises one or more of the following: liquid water, polyacrylamide, phenolic resin and one-layer coating agent;

[0011] The one-layer coating agent is one or more of fructose, carrageenan, sodium alginate, xanthan gum, carboxymethyl cellulose, sodium carboxymethyl starch, chitosan, sodium polyacrylate, and polyacrylic acid.

[0012] The two-layer coating agent is polylactic acid.

[0013] The dispersing aid is polyethylene glycol.

[0014] The third aspect of the present application provides a method for preparing the multi-layer coated gel particles using the composition of claim 4 or 5, wherein the method comprises:

[0015] (1) mixing the liquid water with the polyacrylamide under stirring to obtain a polymer solution;

[0016] (2) mixing the polymer solution with the phenolic resin to obtain a gel-forming solution;

[0017] (3) contacting the gel-forming solution with the one-layer coating agent to perform a cross-linking reaction, thereby obtaining a reinforced gel-forming solution;

[0018] (4) dropping the reinforced gel-forming solution into a salt solution containing calcium ions to obtain one-layer coated gel particles;

[0019] (5) placing the one-layer coated gel particles into a dichloromethane solution containing a two-layer coating agent and a dispersing aid to obtain multi-layer coated gel particles.

[0020] The fourth aspect of the present application provides the multi-layer coated gel particles prepared by the method described above.

[0021] The fifth aspect of the present application provides the application of the multi-layer coated gel particles described above as a plugging agent in high-temperature and high-salt fracture-cave type oil and gas reservoirs.

[0022] Through the above technical solution, the present application has the following advantages:

[0023] (1) The multi-layer coated gel particles of the present application have good dispersing effect, stable gel-forming performance, high plugging strength after particle coalescence, and strong long-term thermal stability.

[0024] (2) The multi-layer coated gel particles of the present application have good compatibility between each component, simple preparation of the gel-forming solution, and the presence of the one-layer coating agent, the two-layer coating agent, and the dilution-resistant aid does not affect the gel-forming effect.

[0025] (3) The raw materials of each component in the multi-layer coated gel particle composition of the present application are widely available, suitable for industrialized production and large-scale on-site preparation.

[0026] (4) The hydrophilic ether bond (-O-) and the linked hydroxyl group (-OH) of polyethylene glycol used in this invention give the surface of the multilayer coated gel particles of this invention a certain degree of hydrophilicity, which can maintain a good dispersion effect in the aqueous phase.

[0027] (5) The methyl group (-CH3) in polylactic acid, the two-layer coating agent used in this invention, makes the coating on the outside of the multi-layer coated gel particles of this invention dense and hydrophobic, which can avoid the dilution of the gelling solution by the formation water.

[0028] (6) When the multilayer coated gel particles of the present invention are injected into the formation, the outer two layers of coating gradually degrade, exposing the inner layer of coating gel particles to form aggregates that form a blockage deep in the formation. Attached Figure Description

[0029] Figure 1 This is a schematic diagram illustrating the preparation of the multilayer coated gel particles of the present invention;

[0030] Figure 2 This is a schematic diagram of the deep migration and sealing of multilayer coated gel particles according to the present invention;

[0031] Figure 3 This is a macroscopic schematic diagram of the multilayer coated gel particles prepared in Example 1 of the present invention;

[0032] Figure 4 This is a macroscopic image of the multilayer coated gel particles prepared in Example 1 of the present invention after agglomeration under high temperature, high salinity and formation water conditions;

[0033] Figure 5 This is a SEM image of the micro-network structure of the multilayer coated gel particles prepared in Example 2 of the present invention after agglomeration under high temperature, high salt and formation water conditions;

[0034] Figure 6 This is a macroscopic image of the ordinary gel prepared in Comparative Example 1 before and after gelation under high temperature, high salinity and formation water conditions. Detailed Implementation

[0035] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0036] As described above, the first aspect of the present application provides a multi-layer coated gel particle, wherein the multi-layer coated gel particle comprises a one-layer coated gel liquid particle and a two-layer coating on the outer surface of the one-layer coated gel liquid particle; the two-layer coating is formed by the one-layer coated gel liquid particle and a dichloromethane solution containing a two-layer coating agent and a co-dispersant, wherein the two-layer coating agent is polylactic acid, and the co-dispersant is polyethylene glycol.

[0037] The inventors of the present application found that a one-layer coating formed by a one-layer coating agent and calcium ions is a dense viscoelastic protective film that can isolate water and initially form a one-layer coated gel liquid particle; further, a two-layer coating is coated on the outer surface of the one-layer coated gel liquid particle, which can adhere to the surface of the one-layer coating agent and isolate water by its own hydrophobicity, forming a gel liquid particle that completely isolates formation water; the co-dispersant can be interspersed in the two-layer coating agent, improving the hydrophilicity of the particle, increasing the surface negative charge, and forming a dilution-resistant gel liquid particle dispersed in water; the above dilution-resistant gel liquid particle internally gels at high temperature and high salinity, the outer coating gradually degrades, exposing the internal gel particles, and the particles adhere to each other to form a plug in the deep formation.

[0038] According to the present application, the one-layer coating agent is selected from one or more of fructose, carrageenan, sodium alginate, xanthan gum, carboxymethyl cellulose, sodium carboxymethyl starch, chitosan, sodium polyacrylate, and polyacrylic acid; preferably, the one-layer coating agent is selected from one or more of fructose, carrageenan, sodium alginate, xanthan gum, and sodium polyacrylate.

[0039] According to the present application, the outer surface of the one-layer coated gel liquid particle is formed by a one-layer coating agent and calcium ions, and the interior of the one-layer coated gel liquid particle is formed by polyacrylamide, phenolic resin, and a one-layer coating agent.

[0040] According to the present application, the thickness of the one-layer coating is 50-500 μm, preferably 60-500 μm.

[0041] According to the present application, the thickness of the two-layer coating is 10-50 μm, preferably 18-42 μm.

[0042] According to the present application, the average particle size of the multi-layer coated gel particle is 0.5 mm-10 cm.

[0043] According to the present application, the polyacrylamide is an AM / AMPS copolymer, wherein AM (water-soluble acrylamide (AM), AMPS (sodium 2-acrylamido-2-methylpropanesulfonate); and the content of AM is 60-70 wt%, and the content of AMPS is 30-40 wt% based on the total weight of the AM / AMPS copolymer.

[0044] According to the present application, the relative molecular weight of the AM / AMPS copolymer is 5-12 million, preferably 8-9 million.

[0045] According to the present application, the hydrolysis degree of the AM / AMPS copolymer is 1-10%, preferably 1-3%.

[0046] According to the present application, the phenolic resin crosslinking agent is selected from one or more of phenol type phenolic resin, p-benzenediol type phenolic resin and m-benzenediol type phenolic resin.

[0047] The second aspect of the present application provides a composition for preparing multi-layer coated gel particles, wherein the composition comprises a gel-forming solution, a calcium ion-containing salt solution, a dichloromethane solution containing a two-layer coating agent and a dispersant aid, which are independently stored;

[0048] The gel-forming solution comprises one or more of liquid preparation water, polyacrylamide, phenolic resin and a one-layer coating agent;

[0049] The one-layer coating agent is one or more of fructose, carrageenan, sodium alginate, xanthan gum, carboxymethyl cellulose, sodium carboxymethyl starch, chitosan, sodium polyacrylate and polyacrylic acid;

[0050] The two-layer coating agent is polylactic acid;

[0051] The dispersant aid is polyethylene glycol.

[0052] According to the present application, the calcium ion-containing salt solution is one or more of calcium chloride, calcium bicarbonate and calcium hydroxide, preferably calcium chloride; in the present application, the concentration of calcium ions in the calcium ion-containing salt solution is 0.5-2%;

[0053] According to the present application, the content of the polyacrylamide is 0.3-1.5 wt% based on the total weight of the gel-forming solution; the content of the phenolic resin crosslinking agent is 0.4-1.2 wt%, and the content of the one-layer coating agent is 0.2-5 wt%, and the balance is liquid preparation water; preferably, the content of the polyacrylamide is 0.5-1.2 wt% based on the total weight of the gel-forming solution; the content of the phenolic resin crosslinking agent is 0.6-1.0 wt%, and the content of the one-layer coating agent is 0.3-0.6 wt%, and the balance is liquid preparation water.

[0054] According to the application, the concentration of the double-layer coating agent is 5-30%, the concentration of the auxiliary dispersing agent is 0.1-0.6%, and the rest is dichloromethane; preferably, the concentration of the double-layer coating agent is 10%-20%, the concentration of the auxiliary dispersing agent is 0.2-0.3%, and the rest is dichloromethane.

[0055] The third aspect of the application provides a method for preparing the multi-layer coated gel particles by using the composition described above, wherein the method comprises:

[0056] (1) mixing the solution water and the polyacrylamide under stirring to obtain a polymer solution;

[0057] (2) mixing the polymer solution and the phenolic resin to obtain a gel-forming solution;

[0058] (3) contacting the gel-forming solution with a one-layer coating agent to perform a cross-linking reaction, thereby obtaining a reinforced gel-forming solution;

[0059] (4) dropping the reinforced gel-forming solution into a salt solution containing calcium ion-containing salt to obtain one-layer coated gel-forming solution particles;

[0060] (5) putting the one-layer coated gel-forming solution particles into a dichloromethane solution containing a double-layer coating agent and an auxiliary dispersing agent to obtain multi-layer coated gel particles.

[0061] According to the application, the first mixing condition comprises: temperature of 20±5℃, time of 60-90min, preferably 50-60min;

[0062] According to the application, the second mixing condition comprises: temperature of 20±5℃, time of 10-20min, preferably 10-15min.

[0063] According to the application, in step (3), the calcium ion and the one-layer coating agent perform a cross-linking reaction, wherein the cross-linking reaction condition comprises: temperature of 20±5℃, time of 20-60min, preferably 30-50min.

[0064] The fourth aspect of the application provides the multi-layer coated gel particles prepared by the method described above.

[0065] The fifth aspect of the application provides the application of the multi-layer coated gel particles described above as a plugging agent in high-temperature and high-salt fracture-cave type oil and gas reservoirs.

[0066] According to the present application, the conditions of the high-temperature and high-salinity fracture-cave type oil and gas reservoir include: temperature ≥ 110℃, salinity ≥ 200,000 mg / L, and calcium and magnesium ion content ≥ 5000 mg / L; preferably, the temperature is 110-150℃, the salinity is 200,000-300,000 mg / L, and the calcium and magnesium ion content is 5000-15000 mg / L.

[0067] According to the present application, the weight ratio of the multilayer coated gel particles to the amount of the formation water is 1:(1-9), preferably 1:(1-4).

[0068] According to the present application, the multilayer coated gel particles are aged for 48-96 hours to form aggregates, preferably the multilayer coated gel particles are aged for 48-72 hours to form aggregates.

[0069] The present application will be described in detail below through examples.

[0070] In the following examples and comparative examples:

[0071] The strength parameters of the gel particle aggregates after coalescence are measured by the rheometer elasticity test method;

[0072] The core plugging rate parameters are measured by the high-temperature and high-salinity core displacement experiment method;

[0073] The SEM is purchased from Hitachi, model Hitachi S-4800;

[0074] The AM / AMPS copolymer raw material is a commercially available product of Nore Biotech Co., Ltd.

[0075] The phenol type, hydroquinone type, and catechol type phenolic resin crosslinking agent raw materials are commercially available products of Lifeng New Material Co., Ltd.

[0076] Example 1

[0077] This example is to illustrate the preparation of multilayer coated gel particles using a composition for preparing multilayer coated gel particles and its application.

[0078] The composition for preparing multilayer coated gel particles includes: a gel-forming solution, a calcium ion-containing salt solution, and a dichloromethane solution containing a two-layer coating agent (polylactic acid) and a dispersant aid (polyethylene glycol); wherein the gel-forming solution includes a liquid preparation water, polyacrylamide, a phenolic resin (hydroquinone type phenolic resin), and a one-layer coating agent (carrageenan).

[0079] The polyacrylamide (AM / AMPS copolymer) has a relative molecular mass of 10 million, a hydrolysis degree of 3%, an AM content of 60% by weight, and an AMPS content of 40% by weight.

[0080] The content of polyacrylamide is 1.0% based on the total weight of the gelling liquid; the content of the hydroquinone type phenolic resin crosslinking agent is 0.6%; the content of the one-layer coating agent carrageenan is 0.3%; the balance is liquid preparation water, and the content is 98.1%; the total content of each component is 100%.

[0081] The calcium ion-containing salt solution is calcium chloride (CaCl2), and the concentration of calcium ions in the calcium ion-containing salt solution is 1%;

[0082] The concentration of the two-layer coating agent polylactic acid is 20%, the concentration of polyethylene glycol is 0.3%, and the balance is dichloromethane, and the concentration of dichloromethane is 79.7%.

[0083] The method for preparing the multi-layer coated gel particles by using the above composition comprises:

[0084] (1) At room temperature (20±5℃), 0.8g of AM / AMPS copolymer is added in clean water under stirring at a speed of 600rpm for the first mixing, and stirred for 60 minutes to obtain a polymer solution;

[0085] (2) 0.6g of the hydroquinone type phenolic resin crosslinking agent is added under stirring for the second mixing, and stirred for 10 minutes to obtain a gelling liquid;

[0086] (3) 0.3g of the one-layer coating agent carrageenan is slowly added under stirring for crosslinking reaction, and stirred for 30 minutes until it is fully dissolved to obtain a reinforced gelling liquid;

[0087] (4) Then, the reinforced gelling liquid is dropped into a 990g aqueous solution containing 10g of CaCl2 to obtain one-layer coated gelling liquid particles;

[0088] (5) The one-layer coated gelling liquid particles are added into a 797g dichloromethane solution containing 200g of polylactic acid and 3g of polyethylene glycol, and stirred at a speed of 600rpm for 60 minutes, and then filtered to obtain multi-layer coated gel particles.

[0089] In addition, the prepared multi-layer coated gel particles are characterized, and the results are shown in Table 1.

[0090] In addition, 50g of the multi-layer coated gel particles are placed in 50g of formation water with a salinity of 220,000mg / L (100,000mg / L Ca 2+ , Mg 2+ divalent salt ions and the balance is NaCl), sealed in a pressure-resistant bottle, and aged at 140℃ for 48h, and then the particles are coalesced to form large-scale gel particle aggregates. The strength of the gel particle aggregates is 9.6Pa.

[0091] Figure 1is a schematic diagram of preparation of the multilayer film-coated gel particles of the present application, from Figure 1 It can be seen that: first, the characteristics of rapid cross-linking of the first layer of film-coating agent with calcium ions are used to form a layer of film on the surface of the gel-forming liquid, and initially form the shaped gel-forming liquid particles; the hydrogen bonds and hydrophobic interactions between the second layer of film-coating agent and the first layer of film are used to form a dense surface coating of the second layer of film, wherein SA is the calcium-sensitive polymer of the first layer of film-coating agent, and PLA is the polylactic acid of the second layer of film-coating agent, forming the multilayer film-coated gel particles; the first layer of film and the second layer of film adhere to each other by hydrogen bonds and hydrophobic interactions to prevent desorption; the gel particles are water-based dispersion, and have the characteristics of low viscosity, controllable particle size, high temperature stability, and dense film resistance to dilution.

[0092] Figure 2 is a schematic diagram of deep migration plugging of the multilayer film-coated gel particles of the present application, from Figure 2 It can be seen that: in the first stage, after the water-based dispersion gel-forming liquid particles are injected into the formation, they remain dispersed in the near-well region, are injected near the well, and continuously migrate to the deep part of the formation; in the second stage, the gel-forming liquid gels under the action of high temperature, and the gel is formed in the film, but due to the dispersion effect of the second layer of film, the particles still remain in a dispersed state with each other; in the third stage, after the film degrades (interfacial film degradation) during migration to the deep part of the formation, the internal gel particles are exposed, the particles adhere to each other to form large-scale gel particle aggregates, deep coalescence plugging, and effective plugging is formed. In addition, it should be noted that, in order to more clearly read the figure, the water-based dispersion gel-forming liquid particles injected into the formation wall in the first stage are enlarged, and the enlarged figure is used for representation; in the second stage, the gel-forming liquid gels, and the gel formed in the film is enlarged, and the enlarged figure is used for representation; in the third stage, after the film degrades (interfacial film degradation) to expose the internal gel particles, the enlarged figure is used for representation.

[0093] Figure 3 is a macroscopic schematic diagram of the multilayer film-coated gel particles prepared in Example 1 of the present application, from Figure 3 It can be seen that: the multilayer film-coated gel particles prepared in Example 1 of the present application have good dispersibility in formation water, which is conducive to stable and continuous injection.

[0094] Figure 4 is a macroscopic diagram of the multilayer film-coated gel particles prepared in Example 1 of the present application after coalescence under high temperature, high salt, and formation water conditions, from Figure 4 It can be seen that: after aging at high temperature, the multilayer film-coated gel particles prepared in Example 1 of the present application degrade the film, exposing the internal gel particles, which adhere to each other to form large-scale gel particle aggregates; the gel particle aggregates have a dense network structure, which can effectively plug the cracks.

[0095] Figure 5 is a SEM photo of the micro network structure of the multilayer film-coated gel particles prepared in Example 2 of the present application after coalescence under high temperature, high salt, and formation water conditions, fromFigure 5 It can be seen that the aggregate formed by the agglomeration of the multilayer coated gel particles prepared in Example 2 has a dense network structure, which can effectively plug the fractures.

[0096] Example 2

[0097] This example is to illustrate the preparation of multilayer coated gel particles using the composition for preparing multilayer coated gel particles and its application.

[0098] The composition for preparing multilayer coated gel particles includes: a gel-forming solution, a calcium ion-containing salt solution, and a dichloromethane solution containing a two-layer coating agent (polylactic acid) and a dispersant aid (polyethylene glycol); wherein the gel-forming solution includes a liquid preparation water, polyacrylamide, a phenolic resin (catechol type phenolic resin), and a one-layer coating agent (sodium alginate).

[0099] Among them, the relative molecular mass of polyacrylamide (AM / AMPS copolymer) is 8 million, the degree of hydrolysis is 2.4%, the content of AM is 65% by weight, and the content of AMPS is 35% by weight.

[0100] Among them, the content of polyacrylamide is 1.2% based on the total weight of the gel-forming solution; the content of catechol type phenolic resin crosslinking agent is 0.7%; the content of one-layer coating agent sodium alginate is 0.2%; the balance is liquid preparation water, the content is 97.9%, and the total content of each component is 100%.

[0101] Among them, the calcium ion-containing salt solution is calcium chloride (CaCl2), and the concentration of calcium ions in the calcium ion-containing salt solution is 1%;

[0102] Among them, the concentration of two-layer coating agent polylactic acid is 20%, the concentration of polyethylene glycol is 0.3%, and the balance is dichloromethane, the concentration of dichloromethane is 79.7%.

[0103] The method for preparing multilayer coated gel particles using the above composition includes:

[0104] (1) At room temperature (20±5℃), 1.2g of AM / AMPS copolymer is added in clean water at a stirring speed of 600rpm, and stirred for 60 minutes to obtain a polymer solution;

[0105] (2) While stirring, 0.7g of catechol type phenolic resin crosslinking agent is added, and stirred for 10 minutes to obtain a gel-forming solution;

[0106] (3) While stirring, 0.2g of one-layer coating agent sodium alginate is slowly added, and stirred for 30 minutes until it is fully dissolved to obtain a reinforced gel-forming solution;

[0107] (4) Then the reinforced gel solution droplets are added into a 990 g water solution containing 10 g CaCl2 to obtain a coated gel solution particle;

[0108] (5) The coated gel solution particle is added into a 797 g dichloromethane solution containing 200 g polylactic acid and 3 g polyethylene glycol, stirred at a stirring rate of 600 rpm for 60 min, and filtered to obtain a multi-coated gel particle.

[0109] In addition, the multi-coated gel particle is characterized, and the results are shown in Table 1.

[0110] In addition, 30 g of the multi-coated gel particle is placed in 70 g of formation water with a salinity of 200,000 mg / L (8000 mg / L Ca 2+ , Mg 2+ divalent salt ions and the rest is NaCl), sealed in a pressure-resistant bottle, and aged at 130℃ for 60 h, and the particle coagulates to form a large-scale gel particle aggregate. The strength of the gel particle aggregate is 9.2 Pa.

[0111] Example 3

[0112] This embodiment is to illustrate the preparation of a multi-coated gel particle using a composition for preparing a multi-coated gel particle and the application thereof.

[0113] The composition for preparing a multi-coated gel particle comprises a gel solution, a salt solution containing calcium ions, and a dichloromethane solution containing a two-layer coating agent (polylactic acid) and a dispersant aid (polyethylene glycol); wherein the gel solution comprises a solution water, polyacrylamide, a phenolic resin (a catechol type phenolic resin crosslinking agent and a pyrocatechol type phenolic resin crosslinking agent), and a one-layer coating agent (xanthan gum).

[0114] The polyacrylamide (AM / AMPS copolymer) has a relative molecular mass of 12 million and a hydrolysis degree of 3%, and the content of AM is 65% by weight and the content of AMPS is 35% by weight.

[0115] The content of the polyacrylamide is 0.6% based on the total weight of the gel solution; the contents of the catechol type phenolic resin crosslinking agent and the pyrocatechol type phenolic resin crosslinking agent are 0.3% and 0.3%, respectively; the content of the one-layer coating agent xanthan gum is 0.6%; and the rest is solution water, and the content of the solution water is 98.2%. The total content of the components is 100%.

[0116] The salt solution containing calcium ions is calcium chloride (CaCl2), and the concentration of calcium ions in the salt solution containing calcium ions is 1%.

[0117] The concentration of the two-layer coating agent polylactic acid is 20%, the concentration of the dispersant aid polyethylene glycol is 0.3%, and the rest is dichloromethane, and the concentration of dichloromethane is 79.7%.

[0118] The method for preparing the multi-layer coated gel particles using the above composition comprises:

[0119] (1) 0.6 g of AM / AMPS copolymer was added into clean water at room temperature (20±5℃) under stirring at a speed of 600 rpm, and stirred for 60 min to obtain a polymer solution;

[0120] (2) 0.3 g of p-phenylenediamine type phenolic resin crosslinking agent and 0.3 g of o-phenylenediamine type phenolic resin crosslinking agent were added under stirring, and stirred for 10 min to obtain a gel solution;

[0121] (3) 0.6 g of one-layer coating agent xanthan gum was slowly added under stirring, and stirred for 30 min until it was fully dissolved to obtain a reinforced gel solution;

[0122] (4) Then, the reinforced gel solution was added dropwise into a 990 g aqueous solution containing 10 g of CaCl2 to obtain one-layer coated gel particle solution;

[0123] (5) The one-layer coated gel particle solution was added into a 797 g dichloromethane solution containing 200 g of polylactic acid and 3 g of polyethylene glycol, and stirred for 60 min under stirring at a speed of 600 rpm, and filtered to obtain multi-layer coated gel particles.

[0124] In addition, the prepared multi-layer coated gel particles were characterized, and the results are shown in Table 1.

[0125] In addition, 30 g of the multi-layer coated gel particles were placed in 70 g of formation water with a salinity of 150,000 mg / L (6000 mg / L Ca 2+ , Mg 2+ divalent salt ions and the rest is NaCl), sealed in a pressure-resistant bottle, and aged at 130℃ for 60 h, and the particles were coagulated to form large-scale gel particle aggregates. The strength of the gel particle aggregates was 7.2 Pa.

[0126] Example 4

[0127] This embodiment is to illustrate the preparation of multi-layer coated gel particles using the composition for preparing multi-layer coated gel particles and its application.

[0128] The composition for preparing multi-layer coated gel particles comprises: a gel solution, a solution containing calcium ion salt, a dichloromethane solution containing two-layer coating agent (polylactic acid) and auxiliary dispersant (polyethylene glycol); wherein the gel solution comprises solution water, polyacrylamide, phenolic resin (phenol type phenolic resin), and one-layer coating agent (xanthan gum).

[0129] The polyacrylamide (AM / AMPS copolymer) has a relative molecular weight of 6 million, a hydrolysis degree of 1.8%, an AM content of 90% by weight, and an AMPS content of 10% by weight.

[0130] The polyacrylamide has a content of 1.2% by weight, the phenol type phenolic resin crosslinking agent has a content of 1.0% by weight, the one-layer coating agent xanthan gum has a content of 0.6% by weight, and the balance is the liquid preparation water, which has a content of 97.2% by weight, and the total content of the components is 100%.

[0131] The calcium ion-containing salt solution is calcium chloride (CaCl2), and the concentration of calcium ions in the calcium ion-containing salt solution is 1%.

[0132] The concentration of the two-layer coating agent polylactic acid is 20%, the concentration of the polyethylene glycol is 0.3%, and the balance is dichloromethane, and the concentration of dichloromethane is 79.7%.

[0133] The method for preparing the multi-layer coated gel particles by using the above composition comprises the following steps:

[0134] (1) At room temperature (20±5°C), 1.2 g of AM / AMPS copolymer is added in water under stirring at a stirring speed of 600 rpm, and stirred for 60 minutes to obtain a polymer solution;

[0135] (2) While stirring, 1.0 g of phenol type phenolic resin crosslinking agent is added, and stirred for 10 minutes to obtain a gel solution;

[0136] (3) While stirring, 0.6 g of one-layer coating agent xanthan gum is slowly added, and stirred for 30 minutes until it is fully dissolved to obtain a reinforced gel solution;

[0137] (4) Then, the reinforced gel solution is added dropwise into a 990 g aqueous solution containing 10 g of CaCl2 to obtain one-layer coated gel particle solution;

[0138] (5) The one-layer coated gel particle solution is added into a 797 g dichloromethane solution containing 200 g of polylactic acid and 3 g of polyethylene glycol, and stirred for 60 minutes under stirring at a stirring speed of 600 rpm, and then filtered to obtain multi-layer coated gel particles.

[0139] In addition, the prepared multi-layer coated gel particles are characterized, and the results are shown in Table 1.

[0140] In addition, 50 g of the multi-layer coated gel particles are placed in 50 g of water with a mineralization degree of 150,000 mg / L (6000 mg / L Ca 2+ , Mg 2+The gel particles aggregate to form large-scale gel particle aggregates after aging for 96 hours at 110°C in a pressure-resistant bottle sealed in a formation water (NaCl as the main ion, with divalent salt ions being NaCl) to form large-scale gel particle aggregates. The strength of the gel particle aggregates is 8.2 Pa.

[0141] Example 5

[0142] This embodiment is directed to the preparation of multilayer coated gel particles using a composition for preparing multilayer coated gel particles and the application thereof.

[0143] The composition for preparing multilayer coated gel particles comprises: a gel-forming solution, a calcium ion-containing salt solution, and a dichloromethane solution containing a two-layer coating agent (polylactic acid) and a dispersant aid (polyethylene glycol); wherein the gel-forming solution comprises a solution water, polyacrylamide, a phenolic resin (phenol type phenolic resin), and a one-layer coating agent (fructose).

[0144] The polyacrylamide (AM / AMPS copolymer) has a relative molecular mass of 6 million and a degree of hydrolysis of 1.8%, and the content of AM is 90% by weight and the content of AMPS is 10% by weight;

[0145] The content of the polyacrylamide is 1.2% based on the total weight of the gel-forming solution; the content of the phenol type phenolic resin crosslinking agent is 1.0%; the content of the one-layer coating agent fructose is 1.0%; the balance is solution water, and the content of the solution water is 96.8%; and the total content of the components is 100%.

[0146] The calcium ion-containing salt solution is calcium chloride (CaCl2), and the concentration of calcium ions in the calcium ion-containing salt solution is 1%;

[0147] The concentration of the two-layer coating agent polylactic acid is 8%, the concentration of the polyethylene glycol is 0.3%, and the balance is dichloromethane, and the concentration of the dichloromethane is 91.7%.

[0148] The method for preparing multilayer coated gel particles using the above composition comprises:

[0149] (1) At room temperature (20±5°C), 1.2g of AM / AMPS copolymer is added to clean water under stirring at a stirring speed of 600 rpm, and stirred for 60 minutes to obtain a polymer solution;

[0150] (2) While stirring, 1.0g of a phenol type phenolic resin crosslinking agent is added, and stirred for 10 minutes to obtain a gel-forming solution;

[0151] (3) While stirring, 1.0g of a one-layer coating agent fructose is slowly added, and stirred for 30 minutes until it is fully dissolved to obtain a strengthened gel-forming solution;

[0152] (4) Then the reinforced gel solution was added dropwise to 990g of aqueous solution containing 10g CaCl2 to obtain a layer of coated gel solution particles.

[0153] (5) Add a layer of coated gel particles to a solution of 917g dichloromethane containing 80g polylactic acid and 3g polyethylene glycol, stir at a stirring rate of 600 rpm for 60 minutes, and filter to obtain multi-layer coated gel particles.

[0154] In addition, the prepared multilayer coated gel particles were characterized, and the results are shown in Table 1.

[0155] In addition, 50g of multilayer coated gel particles were placed in 50g of mineralization with a concentration of 150,000 mg / L (6000 mg / L Ca). 2+ Mg 2+ In formation water containing divalent salt ions (the remainder being NaCl), the particles were placed in a pressure-resistant bottle and sealed. After aging at 110℃ for 48 hours, the particles agglomerated to form large-scale gel particle aggregates. The strength of the gel particle aggregates was 7.9 Pa.

[0156] Example 6

[0157] This embodiment illustrates the preparation of multilayer coated gel particles using a composition for preparing multilayer coated gel particles and its application.

[0158] The composition for preparing multilayer coated gel particles includes: a gelling solution, a calcium ion salt solution, and a dichloromethane solution containing a second coating agent (polylactic acid) and a dispersant (polyethylene glycol); wherein the gelling solution includes a solution of water, polyacrylamide, phenolic resin (phenolic resin type), and a first coating agent (sodium polyacrylate).

[0159] The polyacrylamide (AM / AMPS copolymer) has a relative molecular mass of 6 million, a degree of hydrolysis of 1.8%, an AM content of 90% by weight, and an AMS content of 10% by weight.

[0160] Based on the total weight of the gelling solution, the content of polyacrylamide is 1.2%; the content of phenolic resin crosslinking agent is 1.0%; the content of sodium polyacrylate as a coating agent is 0.6%; and the balance is water for dispensing, with a content of 97.2%, and the sum of the contents of all components is 100%.

[0161] The calcium ion-containing salt solution is calcium chloride (CaCl2), and the concentration of calcium ions in the calcium ion-containing salt solution is 1%.

[0162] The secondary coating agent, polylactic acid, has a concentration of 25%, polyethylene glycol has a concentration of 0.3%, and the remainder is dichloromethane with a concentration of 74.7%.

[0163] The method for preparing the multi-layer coated gel particles using the above composition comprises:

[0164] (1) 1.2 g of AM / AMPS copolymer was added into clean water under stirring at a speed of 600 rpm at room temperature (20±5℃), and stirred for 60 minutes to obtain a polymer solution;

[0165] (2) 1.0 g of phenol type phenolic resin crosslinking agent was added while stirring, and stirred for 10 minutes to obtain a gel solution;

[0166] (3) 0.6 g of one layer of coated agent, sodium polyacrylate, was slowly added while stirring, and stirred for 30 minutes until it was fully dissolved to obtain a reinforced gel solution;

[0167] (4) The reinforced gel solution was then added dropwise into a solution of 10 g of CaCl2 in 990 g of water to obtain one layer of coated gel solution particles;

[0168] (5) The one layer of coated gel solution particles was added into a solution of 250 g of polylactic acid and 3 g of polyethylene glycol in 747 g of dichloromethane, and stirred for 60 minutes at a speed of 600 rpm, and filtered to obtain multi-layer coated gel particles.

[0169] In addition, the prepared multi-layer coated gel particles were characterized, and the results are shown in Table 1.

[0170] In addition, 50 g of the multi-layer coated gel particles were placed in 50 g of formation water with a salinity of 150,000 mg / L (6000 mg / L Ca 2+ , Mg 2+ divalent salt ions and the rest was NaCl), sealed in a pressure-resistant bottle, and aged at 110℃ for 108 hours, after which the particles coagulated to form large-scale gel particle aggregates. The strength of the gel particle aggregates was 7.6 Pa.

[0171] Comparative Example 1

[0172] The coated gel particles were prepared according to the same method as in Example 1, except that no one layer of coated agent was added and no two layers of coating were performed, to obtain gel blocking agents, which were gelled at 140℃ for 3.5 hours.

[0173] In addition, the prepared gel blocking agents were characterized, and the results are shown in Table 1.

[0174] Figure 6 are macroscopic pictures of the ordinary gel prepared in Comparative Example 1 before and after gelling under high temperature, high salinity and formation water conditions, from which Figure 6 it can be seen that when the gel solution prepared in Comparative Example 1 just contacted the formation water, there was a clear boundary between the gel solution and the formation water due to the difference in density and viscosity (the left picture in FIG. 1), and after the gel solution was gelled, the gel solution and the formation water were mixed together (the right picture in FIG. 1). Figure 6The first picture from left to right in Figure 1); due to both are water-based system and no physical and chemical barrier, the gel-forming fluid is diluted by formation water (the second picture from left to right in Figure 1); finally, after aging at certain temperature, it results in very low gel strength of the frozen gel, which leads to poor plugging effect (the third picture from left to right in Figure 1). Figure 6 Figure 6

[0175] Comparative Example 2

[0176] The coated frozen gel particles were prepared according to the same method as Example 2, except that one layer of coating agent was not added and two layers of coating were not performed, to obtain a frozen gel plugging agent, which was gelled at 130°C for 6 hours.

[0177] In addition, the prepared frozen gel plugging agent was characterized, and the results are shown in Table 1.

[0178] Comparative Example 3

[0179] The coated frozen gel particles were prepared according to the same method as Example 3, except that one layer of coating agent was not added and two layers of coating were not performed, to obtain a frozen gel plugging agent, which was gelled at 130°C for 4 hours.

[0180] In addition, the prepared frozen gel plugging agent was characterized, and the results are shown in Table 1.

[0181] Comparative Example 4

[0182] The coated frozen gel particles were prepared according to the same method as Example 4, except that one layer of coating agent was not added and two layers of coating were not performed, to obtain a frozen gel plugging agent, which was gelled at 110°C for 6 hours.

[0183] In addition, the prepared frozen gel plugging agent was characterized, and the results are shown in Table 1.

[0184] Comparative Example 5

[0185] The gel-forming fluid was prepared according to the same method as Example 1, except that two layers of coating were not performed, to obtain a frozen gel particle plugging agent, which was aged at 140°C for 8 hours and obvious coalescence occurred.

[0186] In addition, the prepared frozen gel particle plugging agent was characterized, and the results are shown in Table 1.

[0187] Comparative Example 6

[0188] The coated frozen gel particles were prepared according to the same method as Example 2, except that two layers of coating were not performed, to obtain a frozen gel particle plugging agent, which was aged at 130°C for 12 hours and obvious coalescence occurred.

[0189] In addition, the prepared frozen gel particle plugging agent was characterized, and the results are shown in Table 1. ​​

[0190] Comparative Example 7

[0191] The coated gel particles were prepared in the same manner as in Example 3, except that the second coating was not performed, to obtain gel particle plugs, which were significantly coalesced after aging at 130°C for 12 hours.

[0192] In addition, the prepared gel particle plugs were characterized, and the results are shown in Table 1.

[0193] Comparative Example 8

[0194] The coated gel particles were prepared in the same manner as in Example 4, except that the second coating was not performed, to obtain gel particle plugs, which were significantly coalesced after aging at 110°C for 24 hours.

[0195] In addition, the prepared gel particle plugs were characterized, and the results are shown in Table 1.

[0196] Comparative Example 9

[0197] The coated gel particles were prepared in the same manner as in Example 1, except that, in step (5), "polylactic acid" was replaced with "polyimide".

[0198] Gel particle plugs were obtained, which were not coalesced after aging at 130°C for 72 hours.

[0199] In addition, the prepared gel particle plugs were characterized, and the results are shown in Table 1.

[0200] Comparative Example 10

[0201] The coated gel particles were prepared in the same manner as in Example 1, except that, in step (4), "10 g of a CaCl2 solution in 990 g of water" was replaced with "10 g of a MaCl2 solution in 990 g of water".

[0202] Gel particle plugs were not obtained.

[0203] In addition, the prepared product was characterized, and the results are shown in Table 1.

[0204] Comparative Example 11

[0205] The coated gel particles were prepared in the same manner as in Example 1, except that, in step (5), "polyethylene glycol" was replaced with "sodium dodecyl sulfate".

[0206] Gel particle plugs were obtained, which were significantly coalesced after aging at 130°C for 36 hours.

[0207] In addition, the prepared gel particle plugs were characterized, and the results are shown in Table 1.

[0208] Comparative Example 12

[0209] The film-coated gel particles were prepared in the same manner as in Example 1, except that in step (5), "200 g of polylactic acid" was replaced by "50 g of polylactic acid".

[0210] The gel particle plugging agent was obtained, and obvious coalescence occurred after aging at 130℃ for 24 hours.

[0211] In addition, the prepared gel particle plugging agent was characterized, and the results are shown in Table 1.

[0212] Table 1

[0213]

[0214] As can be seen from the above results, the multilayer film-coated gel particle plugging agent prepared by the present application can form a shaped first film with calcium ions in water through rapid cross-linking of the first film agent in the gel-forming liquid, and the dense second film can protect the gel-forming liquid inside the gel particle from being diluted by formation water during migration. The gel-forming liquid inside the gel particle cross-links and gels under the action of high temperature during migration in the formation, and the film protects the gel-forming liquid from being diluted by formation water during this process. The hydrophilicity of the gel particle is improved by the dispersing aid in the film, so that the gel particle has good dispersibility. After migration to the deep formation, the film gradually degrades, the gel particle is exposed and coalesces with each other to form a gel particle aggregate.

[0215] In Comparative Examples 1-4, no first film agent was added, no second film was formed, the gel-forming liquid was diluted by formation water, the gelation speed was too fast, and the gelation effect was not good and the migration distance was too short.

[0216] In Comparative Examples 5-8, only a first film agent was added, no second film was formed, and the formed gel-forming liquid had good resistance to dilution by formation water. However, due to the absence of a second film and a dispersing aid, the coalescence speed of the particles was fast and the migration distance was short.

[0217] In Comparative Example 9, the polyimide was stable at high temperatures and could not be degraded, so the gel particle could not be exposed and the particles could not coalesce to form a gel particle aggregate.

[0218] In Comparative Example 10, the first film agent had low sensitivity to magnesium ions and could not react with magnesium ions to form a first film.

[0219] In Comparative Example 11, the molecular weight of sodium dodecyl sulfate was low and the thermal stability was poor, so it could not exist stably on the surface of the particle at high temperatures.

[0220] In Comparative Example 12, the concentration of polylactic acid is low, the two-layer coating is unstable, and the degradation rate is accelerated, resulting in faster exposure of the gel particles.

[0221] The above describes the preferred embodiments of the present application, but the present application is not limited thereto. Within the technical concept of the present application, various simple modifications can be made to the technical solutions of the present application, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be considered as disclosed by the present application and belong to the protection scope of the present application.

Claims

1. A multilayer coated gel granule, characterized in that, The multilayer coated gel particles include a layer of coated gel particles and a second layer of coating covering the outer surface of the layer of coated gel particles; the second layer of coating is formed by the layer of coated gel particles and a dichloromethane solution containing a second layer coating agent and a dispersant, wherein the second layer coating agent is polylactic acid and the dispersant is polyethylene glycol. The coating agent is one or more of fructose, carrageenan, sodium alginate, xanthan gum, carboxymethyl cellulose, sodium carboxymethyl starch, chitosan, sodium polyacrylate, and polyacrylic acid; The outer surface of the coated gel particles is formed by a coating agent and calcium ions, and the interior of the coated gel particles is formed by polyacrylamide, phenolic resin and a coating agent.

2. The multilayer coated gel particles according to claim 1, wherein, The coating agent is selected from one or more of fructose, carrageenan, sodium alginate, xanthan gum, and sodium polyacrylate.

3. The multilayer coated gel particles according to claim 1 or 2, wherein, The thickness of the coating film is 50-500 μm; And / or, the thickness of the two-layer coating film is 10-50 μm; And / or, the average particle size of the multilayer coated gel particles is 0.5mm-10cm.

4. A composition for preparing multilayer coated gel particles, characterized in that, The composition includes separately stored gelling liquid, calcium ion-containing salt solution, and dichloromethane solution containing a two-layer coating agent and a dispersant; The gelling solution includes a solution of water, polyacrylamide, phenolic resin, and a coating agent. The coating agent is one or more of fructose, carrageenan, sodium alginate, xanthan gum, carboxymethyl cellulose, sodium carboxymethyl starch, chitosan, sodium polyacrylate, and polyacrylic acid. The second-layer coating agent is polylactic acid; The dispersant is polyethylene glycol.

5. The composition according to claim 4, wherein, The calcium-containing salt solution is one or more of calcium chloride, calcium bicarbonate, and calcium hydroxide. And / or, the concentration of calcium ions in the calcium-containing salt solution is 0.5-2%; And / or, based on the total weight of the gelling solution, the content of the polyacrylamide is 0.3-1.5% by weight; the content of the phenolic resin crosslinking agent is 0.4-1.2% by weight; the content of the first layer coating agent is 0.2-5% by weight; and the balance is water for dissolving the solution. And / or, the concentration of the second-layer coating agent is 5-30%, the concentration of the dispersant is 0.1-0.6%, and the balance is dichloromethane.

6. The composition according to claim 5, wherein, The calcium-containing salt solution is calcium chloride; And / or, the concentration of the second-layer coating agent is 10%-20%, the concentration of the dispersant is 0.2-0.3%, and the balance is dichloromethane.

7. A method for preparing multilayer coated gel particles using the composition according to any one of claims 4-6, characterized in that, The method includes: (1) Under stirring conditions, the water and polyacrylamide were mixed for the first time to obtain a polymer solution; (2) The polymer solution is mixed with phenolic resin for a second time to obtain a gelling solution; (3) The gelling solution is brought into contact with a coating agent to carry out a crosslinking reaction, thereby obtaining a reinforced gelling solution; (4) The reinforced gel solution is dropped into a salt solution containing calcium ions to obtain a layer of coated gel solution particles; (5) The first layer of coated gel particles is placed in a dichloromethane solution containing a second layer coating agent and a dispersant to obtain multi-layer coated gel particles.

8. The method according to claim 7, wherein, The conditions for the first mixing include: a temperature of 20±5℃ and a time of 60-90 min; And / or, the conditions for the second mixing include: a temperature of 20±5℃ and a time of 10-20 min; And / or, the conditions for the crosslinking reaction include: a temperature of 20±5℃ and a time of 20-60 min.

9. The method according to claim 8, wherein, The conditions for the first mixing include: a time of 50-60 minutes; And / or, the conditions for the second mixing include: a time of 10-15 minutes; And / or, the conditions for the crosslinking reaction include: a time of 30-50 min.

10. A multilayer coated gel particle prepared by the method according to any one of claims 7-9.

11. The application of the multilayer coated gel particles as a plugging agent according to any one of claims 1-3 and 10 in high-temperature, high-salinity fractured-vuggy oil and gas reservoirs; wherein, The conditions for the high-temperature, high-salinity fracture-vuggy oil and gas reservoir include: temperature ≥110℃, mineralization ≥200,000 mg / L, and calcium and magnesium ions ≥5,000 mg / L.

12. The application according to claim 11, wherein, The conditions for the high-temperature, high-salinity fracture-vuggy oil and gas reservoir include: a temperature of 110-150℃, a mineralization of 200,000 mg / L-300,000 mg / L, and a calcium and magnesium ion content of 5,000 mg / L-15,000 mg / L.

13. The application according to claim 11 or 12, wherein, The weight ratio of the multilayer coated gel particles to the formation water is 1:(1-9). And / or, the multilayer coated gel particles agglomerate to form aggregates after aging for 48-96 hours.

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