Multi-layer coated gel particle and application thereof

Abstract

The invention provides a multi-layer coated gel particle and application thereof. The multi-layer film-coated gel particle comprises a polymer gel particle and more than two film-coated layers coated on the surface of the polymer gel particle, and the melting temperatures of the film-coated layers are different. The multi-layer coated gel particles provided by the invention have non-uniform expansibility, including non-uniformity of the expansion times of the gel particles and non-uniformity of the expansion time of the gel particles, and can present different melting states in the migration and temperature rise process of a reservoir; and finally, non-uniform expansion of the gel particles and whole-process plugging from the injection end to the deep part of the reservoir are caused. According to the multi-layer coated gel particles, the coating melting temperature can be designed according to the reservoir temperature, and targeted profile control and displacement of a target reservoir are achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of oil extraction, and in particular relates to a method for preparing non-uniform swelling gel particles suitable for deep flooding of low-permeability reservoirs and an application thereof. Background Art

[0002] The injection fluid flows along the dominant seepage channels such as fractures, high permeability layers or high permeability strips, which will cause inefficient and ineffective circulation of the injected fluid, greatly reducing the oil and gas recovery rate. At the same time, the problem of crossflow in the reservoir is an inevitable problem accompanying the reservoir fracturing transformation, the full production cycle of oil and gas field development and the full generation measures. Therefore, solving the crossflow of the injected fluid and expanding the swept volume are the keys to improving the oil and gas recovery rate. Polymers, functional polymers, etc. can play a role in fluidity control by increasing the viscosity of the water phase, which can inhibit the formation and expansion of the dominant seepage channel. However, polymers are still homogeneous fluids, and their effect on improving the injection and production profile is limited; in addition, although underground gels have the advantage of high plugging strength, they have the disadvantages of uncontrollable gelation and pollution of low permeability layers. Therefore, granular plugging agents such as pre-crosslinked gel particles and polymer microspheres have been widely studied, which have the advantages of selective plugging of high permeability strips and deep plugging of elastic deformation. However, gel particles are solid-liquid dispersion systems. Once they absorb water and swell, their particle size will increase significantly, limiting their injectability. Therefore, it is necessary to study a reservoir condition-responsive gel particle, which maintains a small particle size and easy injection state before water absorption and swelling during the injection process, and absorbs water and swells based on physical changes under reservoir conditions, thereby playing a role in pore throat plugging.

[0003] Common reservoir response conditions include temperature, salinity, pressure, etc. At present, the technologies for reservoir responsive gel mainly include: temperature-resistant and salt-resistant viscoelastic polymer gel particles and displacement agents and their preparation methods and applications (CN111087536B), a temperature-responsive self-assembled displacement system and its application (CN112898958B), a temperature-sensitive polymer nano-microsphere for displacement and its preparation method (CN113801267A), a temperature-responsive gel plugging agent and its preparation method and application (CN115490882A), a temperature-responsive bulk-expanding particle and its preparation method and application (CN115678054A), etc. The above technologies focus on advanced modification methods and the improvement of temperature resistance. Although they can achieve temperature response, they are one-time responses and do not have the characteristics of multi-layer response and non-uniform expansion of elastic particles. For example, the "Temperature-responsive gel plugging agent and its preparation method and application" (CN202110678564.0) applied by Sinopec on June 18, 2021. The patent adds hydroxybutyl chitosan to water, melts, heats up and stands to obtain a temperature-responsive gel plugging agent; wherein the mass fraction of the hydroxybutyl chitosan is 0.05% to 0.8%, preferably 0.2 to 0.6%, and more preferably 0.3 to 0.5%. This kind of gel system can improve the problems of phase precipitation, injection difficulties and poor gelling ability caused by dilution and diffusion of conventional gel plugging agents, thereby achieving the purpose of deep liquid flow diversion, expanding the swept volume and improving the recovery rate. The main disadvantage of this type of technology is that the temperature response of the gel plugging agent is a one-time response, and the gel particles expand explosively, that is, once the gel particles respond, their injection performance will be greatly reduced.

[0004] The following technologies can solve the problem of one-time explosive response, for example: multi-layer core-shell structure polymer microspheres, drive-adjusting agents and their preparation methods and applications (CN111087553B), a sustained-release polymer microsphere extraction agent with a core-shell heterogeneous structure and its preparation method (CN115806813A), and modified slow-swelling particle profile control agent and its preparation method and application (CN103205247A). Among them, the "Multi-layer Core-Shell Structure Polymer Microspheres, Drive-Adjusting Agents and Their Preparation Methods and Applications" (patent, CN111087553A) applied by China Petrochemical Corporation on October 23, 2018. This patent is aimed at the existing technology that the preparation of core-shell microspheres is mostly prepared by dispersion polymerization, the reaction system contains a large amount of volatile substances, there are safety hazards, the product particle size is large and easy to settle, and it needs to be distilled and purified into dry powder for use; a few of the products obtained by the reverse emulsion method are spherical products, which cannot be proved to be core-shell structures, and there are problems such as low effective content and poor stability. A multilayer core-shell polymer microsphere was prepared, including a core, an inner shell and an outer shell, with an average particle size of 100-1000nm, a particle size dispersion index ≤0.5, and a single-peak distribution. It can be directly added to the injected water for deep profile adjustment, water plugging, oil displacement and other oil field applications to enhance oil recovery. The main disadvantage of this type of technology is that the multilayer core-shell structure cannot achieve quantitative temperature response, that is, it cannot achieve personalized design according to the reservoir temperature; at the same time, the particle size of this type of polymer microsphere is small, and it cannot achieve the plugging of large-size advantageous channels such as cracks. Summary of the invention

[0005] In view of the deficiencies of the prior art, the present invention discloses a non-uniform swelling gel particle, a displacement agent using the particle, and a reservoir targeted displacement method.

[0006] The first aspect of the present invention provides a multi-layer coated gel particle, comprising a polymer gel particle and a coating layer coated on the surface of the polymer gel particle, wherein the coating layer has two or more layers, and each layer of the coating layer has a different melting temperature.

[0007] According to one embodiment of the present invention, the melting temperature of the inner coating layer in the multi-layer coated gel particles is higher than the melting temperature of the outer coating layer.

[0008] According to another embodiment of the present invention, the melting temperature of the coating layer is 70°C-150°C.

[0009] According to another embodiment of the present invention, the coating layer includes stearate.

[0010] According to another embodiment of the present invention, the stearate is calcium stearate or sodium stearate.

[0011] According to another embodiment of the present invention, the particle size of the polymer gel particles is 3 to 70 μm, and the thickness of the coating layer is 1 to 10 μm.

[0012] The second aspect of the present invention provides a displacement agent, comprising polymer gel particles coated with different numbers of coating layers, wherein the number of coating layers is 1 to 5 layers.

[0013] According to one embodiment of the present invention, when the displacement agent comprises polymer gel particles coated with two or more coating layers, the melting temperatures of different coating layers are different.

[0014] According to another embodiment of the present invention, the melting temperature of the inner coating layer of the polymer gel particles coated with two or more coating layers is higher than the melting temperature of the outer coating layer.

[0015] According to another embodiment of the present invention, the melting temperature of the coating layer is 70°C-150°C.

[0016] According to another embodiment of the present invention, the regulating agent includes polymer gel particles coated with one coating layer and polymer gel particles coated with two coating layers, the melting point temperature of the coating layer of the polymer gel particles coated with one coating layer is the same as the melting point temperature of the outer coating layer of the polymer gel particles coated with two coating layers, and the coating layer includes stearate.

[0017] According to another embodiment of the present invention, the particle size of the polymer gel particles is 3 to 70 μm, and the thickness of the coating layer is 1 to 10 μm.

[0018] A third aspect of the present invention provides a reservoir fluid flow diversion method, which uses the above-mentioned displacement agent.

[0019] According to one embodiment of the present invention, the proportion of polymer gel particles having different numbers of coating layers in the displacement agent, and / or the particle size of the polymer gel, and / or the melting temperature of each coating layer are selected according to the reservoir temperature distribution.

[0020] According to another embodiment of the present invention, the method comprises: preparing a dispersion containing the displacement agent; mixing the dispersion with an injection liquid and pumping the mixture into the formation together; wherein the solvent of the dispersion is clean water, salt water, injection water or reinjection water.

[0021] According to another embodiment of the present invention, the mass fraction of the dispersion is 0.1-5wt%, and the viscosity is lower than 2mPa.s.

[0022] According to another embodiment of the present invention, the injection fluid includes fracturing fluid and an oil displacement system.

[0023] The multi-layer coated gel particles of the present invention have non-uniform expansion properties: including the non-uniformity of the gel particle expansion multiple and the non-uniformity of the gel particle expansion time, which can present different melting states during the reservoir migration and heating process, ultimately leading to non-uniform expansion of the gel particles and full-process plugging from the injection end to the deep reservoir. The multi-layer coated gel particles of the present invention can be coated with a melting temperature designed according to the reservoir temperature to achieve targeted regulation and displacement of the target reservoir. The present invention does not increase the operation time, does not require additional on-site staff, and has better economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 and Figure 2 It is a curve chart of the test results of the effect of the addition ratio of the monomers added to synthesize the gel particles on the particle size in the embodiment of the present invention.

[0025] Figure 3 1 is a graph showing the melting point test results of the modified stearate coating layer according to an embodiment of the present invention.

[0026] Figure 4 3 is a curve diagram of the expansion volume change of the multi-layer coated gel particles at different temperatures according to an embodiment of the present invention. DETAILED DESCRIPTION

[0027] The present invention is described in detail below in conjunction with specific implementation modes.

[0028] The first aspect of the present invention provides a multi-layer coated gel particle, comprising a polymer gel particle and a coating layer coated on the surface of the polymer gel particle. The coating layer has two or more layers, and the melting temperatures of the coating layers are different. The coating layer is temperature responsive and can melt and release the internal gel particles during the reservoir migration process.

[0029] In an optional embodiment, the melting temperature of the inner coating layer in the multi-layer coated gel particles is higher than the melting temperature of the outer coating layer. The melting temperature of each coating layer is preferably 70°C-150°C, and it can be applied to common reservoirs as a displacement agent. The melting temperature of the coating layer can be achieved at a predetermined value by any suitable substance. For example, but not limited to, the coating layer includes stearate. The stearate can be sodium stearate or calcium stearate.

[0030] In an optional embodiment, the particle size of the polymer gel particles is 3 to 70 μm, and the thickness of the coating layer is 1 to 10 μm.

[0031] The core polymer gel particles in the multi-layer film-coated gel particles of the present invention can be any appropriate gel particles, such as but not limited to acrylamide gel particles, cellulose gel particles, nano gel particles, etc. The coating method can also be any appropriate method, such as but not limited to, emulsion method, implosion method, reverse emulsion method, etc. The following is an example of forming polyacrylamide gel particles by reverse emulsion method and forming multi-layer coatings on the surface by stearic acid coating method to illustrate the preparation process of the multi-layer film-coated gel particles of the present invention. Of course, the multi-layer film-coated gel particles of the present invention are not limited to the following method.

[0032] The preparation method of polymer gel particles may include: (1) adding acrylamide, acrylic acid, 2-propylene-2-methylpropanesulfonic acid monomer, crosslinking agent stabilizer, and pH regulator into deionized water, and stirring to obtain an aqueous solution; (2) preparing an initiator aqueous solution; (3) mixing the aqueous solution with an emulsifier, an oil phase, and an initiator solution, and stirring to emulsify into a microemulsion; (4) subjecting the microemulsion to a polymerization reaction to obtain a dispersion of gel particles in the oil phase; (5) separating the gel particles from the oil phase, washing with anhydrous ethanol, and drying to obtain gel particles. The crosslinking agent may be one of N,N'-methylenebisacrylamide, polyethylene glycol dimethacrylate, glutaraldehyde, urotropine phenolic resin, polyethylene glycol diacrylate, or a combination thereof. The oil phase may be n-hexane, liquid paraffin, phenyl silicone oil, n-decane, caprylic / decanoic acid triglyceride, or the like.

[0033] In the above steps (1) and (3), stirring can be performed using a homogenizer at 5000 rpm. The pH value of the aqueous solution obtained in step (1) is 5.0-7.0. The pH regulator includes: sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, or a combination thereof. The conditions for the polymerization reaction in step (4) are: 70-140°C, nitrogen atmosphere; and the reaction time is 6-12 hours.

[0034] The coating step may include: (6) dissolving the gel particles, stearate b and initiator solution into deionized water, and heating and stirring to complete a primary coating reaction on the surface of the gel particles; (7) dissolving the coated gel particles, stearate a and initiator solution in step (6) into deionized water, and heating and stirring to complete a secondary coating reaction on the surface of the gel particles; (8) separating the gel particles by centrifugation, washing with anhydrous ethanol, and drying to obtain multi-layer coated gel particles.

[0035] The conditions for the polymerization reaction in steps (6) and (7) are: 80-140° C., nitrogen atmosphere; and reaction time is 6-12 hours.

[0036] The second aspect of the present invention provides a displacement agent, comprising polymer gel particles coated with different numbers of coating layers, wherein the number of coating layers is 1 to 5 layers. The displacement agent of the present invention comprises polymer gels coated with different numbers of coating layers, and the surface coatings (i.e., the outermost coatings) of the multi-layer coated gel particles with different numbers of coating layers have different melting temperatures, so the positions and degrees of melting in the reservoir are different, resulting in different degrees of water absorption and swelling of the internal gel particles, thereby achieving non-uniform expansion and non-explosive expansion of the gel particles. At the same time, the melting temperature of the coating can be quantitatively designed according to the reservoir temperature to achieve the regulation of the diversion of the reservoir fluid flow, that is, targeted displacement and reservoir fracturing can be achieved.

[0037] In the displacement agent of the present invention, the distribution of polymer gel particles with different numbers of coating layers in the displacement agent can be reasonably selected according to the actual situation of the temperature of the reservoir. For example, according to the actual situation of the reservoir, the displacement agent includes polymer gel particles coated with one coating layer and polymer gel particles coated with two coating layers; or the displacement agent includes polymer gel particles coated with one coating layer, polymer gel particles coated with two coating layers, and polymer gel particles coated with three coating layers; or the displacement agent includes polymer gel particles coated with one coating layer, polymer gel particles coated with three coating layers, and so on. The above are only examples and are not exhaustive. Those skilled in the art can select appropriate combinations of different numbers of coating layers according to the above concepts according to actual needs. It is also possible to reasonably select the proportion of polymer gel particles with different numbers of coating layers contained in the displacement agent, the particle size of the polymer gel, and the melting temperature of each coating layer according to the actual situation of the reservoir temperature.

[0038] In an optional embodiment, when the displacement agent comprises polymer gel particles coated with two or more coating layers, the melting temperatures of different coating layers are different. Preferably, the melting temperature of the inner coating layer of the polymer gel particles coated with two or more coating layers should be higher than the melting temperature of the outer coating layer.

[0039] In an optional embodiment, the melting temperature of the coating layer is 70° C.-150° C., which can be applicable to common reservoirs.

[0040] The coating layer can be formed of any suitable substance. For example, but not limited to, the coating layer includes calcium stearate and / or sodium stearate. Calcium stearate and sodium stearate can be coated on the surface of the polymer gel particles in any suitable manner.

[0041] In an optional embodiment, the displacement agent includes polymer gel particles coated with one coating layer and polymer gel particles coated with two coating layers, and the melting point temperature of the coating layer of the polymer gel particles coated with one coating layer is the same as the melting point temperature of the outer coating layer of the polymer gel particles coated with two coating layers. The melting point temperature of the outer coating layer of the polymer gel particles coated with two coating layers is lower than the temperature of its inner coating layer. When the displacement agent enters the reservoir, when the reservoir temperature reaches the melting point temperature of the outer coating layer of the gel polymer particles coated with two coating layers, the coating layer of the gel polymer particles coated with one coating layer melts to expose the gel polymer particles, and the gel polymer particles expand to achieve reservoir plugging. The outer coating layer of the gel polymer particles coated with two coating layers melts, and the inner coating layer is still coated on the outer surface of the gel polymer particles, and will not absorb water and swell, so that a smaller particle size can be maintained, and it still has good injectability, and can be further migrated until the temperature rises to the melting temperature of the inner coating layer again, and the gel polymer particles are released to achieve water absorption and swelling plugging.

[0042] In an optional embodiment, the particle size of the polymer gel particles is 3 to 70 μm, and the thickness of the coating layer is 1 to 10 μm.

[0043] The third aspect of the present invention provides a reservoir targeted displacement method using the above-mentioned displacement agent. The proportion of polymer gel particles containing different numbers of coating layers in the displacement agent, and / or the particle size of the polymer gel particles, and / or the melting temperature of each coating layer, etc. can be selected according to the temperature distribution of the reservoir. Since the displacement agent of the present invention contains different numbers of coating layers and the melting temperatures of the outer coating layers are different, after the displacement dispersion is pumped into the formation, it will not absorb water and swell due to the coating layer, and can maintain a small particle size, and it has good injectability. During the migration process in the reservoir, the temperature will gradually rise. When the temperature is higher than the melting temperature of the outer coating of the gel particles, some of the gel particles absorb water and swell to achieve reservoir plugging; and the other part of the double-layer coating or high-melting-temperature coating of the gel particles can be further migrated until the temperature rises to the melting temperature of the coating again, and the gel particles absorb water and swell to achieve plugging.

[0044] In an optional embodiment, the reservoir targeted flow diversion method includes: preparing a dispersion containing a displacement agent; mixing the dispersion with an injection liquid and pumping them into the formation together. The solvent of the dispersion is clean water, brine, injection water or reinjection water. The mass fraction of the dispersion is 0.1-5wt%, and the viscosity is less than 2mPa.s. When the viscosity of the dispersion is too high, the injectivity will be greatly affected.

[0045] In an optional embodiment, the injection fluid includes a fracturing fluid and an oil displacement system.

[0046] The present invention is further described below by specific examples. However, these examples are merely exemplary and do not constitute any limitation to the scope of the present invention. In the following examples and comparative examples, the reagents, materials and instruments used are all commercially available unless otherwise specified.

[0047] Example

[0048] (1) 100 mL of vegetable oil and a mixture of Span and Tween (mass ratio 1:1) were added to a four-necked reaction flask and then stirred at 50 °C under nitrogen atmosphere;

[0049] (2) acrylamide, acrylic acid, 2-acryl-2-methylpropanesulfonic acid monomer and crosslinking agent N,N'-methylenebisacrylamide were added in sequence according to the ratio in Table 1, and the pH of the solution was adjusted to 7 with sodium hydroxide solution. After nitrogen was injected to remove oxygen in the reaction bottle, ammonium persulfate and sodium bisulfite (mass ratio 1:1) with a concentration of 0.05% were added to the system as initiators;

[0050] Table 1 Gel particle synthesis formula parameters

[0051]

[0052]

[0053] (3) Use a separatory funnel to drip the solution in (2) into a four-necked reaction flask within 20 minutes. When the water phase is completely suspended in the oil phase, heat it to 80°C to initiate monomer polymerization. Place the four-necked reaction flask on a magnetic stirrer and stir at the speed in Table 1 for 4 hours, then turn off the heating device. Stop stirring after the emulsion cools to room temperature and let it stand for 1 hour;

[0054] (4) The solution in (3) is centrifuged and filtered to obtain a gel particle sample, a portion of the gel particle sample is washed with anhydrous ethanol and then dispersed in water to prepare an aqueous solution, and the particle size distribution of the gel particles is measured using a laser particle size analyzer;

[0055] (5) dissolving the remaining gel particles again in an organic hydrocarbon solvent and placing them in a four-necked reaction flask for later use;

[0056] (6) Take another four-necked reaction flask and add 100 mL of anhydrous ethanol, and keep the temperature at 70° C. under a nitrogen environment. Add a certain proportion of stearic acid and calcium carbonate / sodium carbonate particles in accordance with Table 2, add 10 mL of dilute sulfuric acid solution, and stir at a speed of 100 rpm to catalyze the stearic acid esterification reaction. After reacting for 8 hours, turn off the heating device and stop stirring after the solution cools down. Let it stand for 1 hour to obtain the modified stearate.

[0057] Table 2 Modified stearate formula

[0058] Modified stearate samples Stearic acid and carbonate and dosage ratio Melting temperature(℃) #a Stearic acid + sodium carbonate = 1:1 91 #b Stearic acid + calcium carbonate = 1:1 127

[0059] (7) Select the two stearates synthesized in Table 2 and the gel particles synthesized in Table 1 to react and coat at 70° C. The specific implementation example is shown in Table 3. After the reaction is completed, centrifugation, filtration, washing and drying can obtain coated gel particles, that is, multi-layer coated gel particles.

[0060] Table 3 Synthesis Example of Multilayer Film-coated Gel Particles

[0061]

[0062]

[0063] Experimental example

[0064] The median particle size of samples 1 to 6 in Table 1 was measured by a laser particle size analyzer. Figure 1 and Figure 2 shown. Figure 1 The gel particle sample synthesized in this patent has a particle size of about 30 to 70 μm. As the proportion of cross-linking agent added decreases, the particle size of the gel particles gradually decreases. As the stirring speed increases, the particle size of the gel particles gradually decreases. The gel particle synthesis parameters can be selected according to the compatibility of the reservoir and the particle size of the gel particles.

[0065] The melting points of the two modified stearates in Table 2 were tested using a calorimeter and compared. Figure 3 As shown in Figure 2, it can be found that the melting point of the modified stearate is significantly higher than that of stearic acid.

[0066] The melting property and temperature response characteristics of the double-layer coated gel particles obtained in the six examples in Table 3 were evaluated by the heating and melting method. 100 mL of water was added to a 250 mL measuring cylinder; 1 g of the coated gel particle sample was added to the water and the measuring cylinder was placed in an oil bath and heated to 80°C, 100°C, 120°C and 130°C in sequence, and the melting and expansion height of the gel particles after the temperature stabilized was observed and recorded.

[0067] Table 4 shows the expansion volume data of the double-layer coated gel particles G1 to G6 during the gradual heating process (the unit in the table is mL), and the corresponding plotted curve is shown in Figure 4As shown. The first coating of G1~G6 is modified stearate b, and the second coating is modified stearate a, and the melting temperatures of the two are 127℃ and 91℃, respectively. It can be found that the expansion volume of the sample is small at 80℃, indicating that the success rate of the two coatings is high; at 100℃, only the coating of the gel particles with successful second coating melts, and the internal particles absorb water and expand; at 120℃, the volume of water absorption and expansion increases slightly. On the one hand, the temperature increase promotes the internal water absorption and expansion of the particles, and on the other hand, it can further make the gel particles with incomplete first coating absorb water and expand. However, the overall expansion volume changes little, indicating that the success rate of the first coating is high; at 130℃, one layer of the gel particles melts, and the expansion volume of the gel particles increases significantly. The above process proves the characteristics of the temperature response layer by layer during the heating process of the gel particles, which can achieve the non-uniform expansion of the gel particles. Comparing the expansion volumes of G1~G6 at the same temperature, it can be found that the larger the particle size of the gel particle core, the larger its expansion volume.

[0068] Table 4 Volume changes of multilayer coated gel particles during melting and expansion layer by layer (G1-G6)

[0069]

[0070]

[0071] Special note: The examples only consider the effects of the monomer addition ratio, stirring speed and monomer addition ratio in the gel particle synthesis reaction as well as the stearic acid modification process. The reaction temperature, dilute sulfuric acid addition, reaction time in the gel particle synthesis process as well as the stirring speed, reaction temperature and reaction time in the stearic acid modification process will affect the coating results and the gel particle expansion multiples. The above factors are all within the scope of consideration of this patent and need to be protected by the patent.

[0072] The preferred embodiments of the present invention disclosed above are only used to help illustrate the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to the specific implementation methods described. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A multi-layer coated gel particle, characterized in that: The invention comprises polymer gel particles and a coating layer coated on the surface of the polymer gel particles. The coating layer has two or more layers, and the melting temperatures of the layers of the coating layer are different.

2. The multi-layer coated gel particles according to claim 1, characterized in that: The melting temperature of the inner coating layer in the multi-layer coating gel particles is higher than the melting temperature of the outer coating layer.

3. The multi-layer coated gel particles according to claim 1, characterized in that: The melting temperature of the coating layer is 70°C-150°C.

4. The multi-layer coated gel particles according to claim 1, characterized in that: The coating layer includes stearate.

5. The multi-layer coated gel particles according to claim 4, characterized in that: The stearate is calcium stearate or sodium stearate.

6. The multi-layer coated gel particles according to claim 1, characterized in that: The particle size of the polymer gel particles is 3 to 70 μm, and the thickness of the coating layer is 1 to 10 μm.

7. A displacement agent, characterized in that: The invention comprises polymer gel particles coated with different numbers of coating layers, wherein the number of coating layers is 1 to 5 layers.

8. The control agent according to claim 7, characterized in that: When the displacement agent comprises polymer gel particles coated with two or more coating layers, the melting temperatures of different coating layers are different.

9. The control agent according to claim 8, characterized in that: The melting temperature of the inner coating layer of the polymer gel particles coated with two or more coating layers is higher than the melting temperature of the outer coating layer.

10. The control agent according to claim 9, characterized in that: The melting temperature of the coating layer is 70°C-150°C.

11. The control agent according to claim 10, characterized in that: The regulating agent includes polymer gel particles coated with one coating layer and polymer gel particles coated with two coating layers. The melting point temperature of the coating layer of the polymer gel particles coated with one coating layer is the same as the melting point temperature of the outer coating layer of the polymer gel particles coated with two coating layers, and the coating layer includes stearate.

12. The control agent according to claim 7, characterized in that: The particle size of the polymer gel particles is 3 to 70 μm, and the thickness of the coating layer is 1 to 10 μm.

13. A reservoir fluid flow diversion method, characterized in that: Use the control agent according to any one of claims 7 to 12.

14. The reservoir fluid flow diversion method according to claim 13, characterized in that: The proportion of polymer gel particles having different numbers of coating layers in the displacement agent, and / or the particle size of the polymer gel, and / or the melting temperature of each coating layer are selected according to the reservoir temperature distribution.

15. The reservoir fluid flow diversion method according to claim 13, characterized in that: include: preparing a dispersion containing the displacement agent; The dispersion liquid is mixed with the injection liquid and pumped into the formation together; Wherein, the solvent of the dispersion liquid is clean water, salt water, injection water or reinjection water.

16. The reservoir fluid flow diversion method according to claim 15, characterized in that: The mass fraction of the dispersion is 0.1-5wt%, and the viscosity is lower than 2mPa.s.

17. The reservoir fluid flow diversion method according to claim 15, characterized in that: The injection fluid includes fracturing fluid and oil displacement system.

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