Polymer gel particles, methods of making and using the same

Abstract

This invention provides a polymer gel particle, its preparation method, and its application. The polymer gel particle consists of a hydrophilic polymer backbone and a lipophilic polymer interpenetrating to form a semi-interpenetrating network structure. The hydrophilic polymer backbone is spherical with a rough surface and uniformly distributed porous structure, with interconnected pores. The polymer gel particle of this invention possesses both oil / water swelling capabilities and exhibits excellent swelling and plugging performance in both water-based drilling fluids and / or water-based completion fluids, as well as oil-based drilling fluids and / or oil-based completion fluids. It offers advantages such as good plugging effect and low filtration loss, which is of great significance for developing new multifunctional drilling fluids and / or completion fluids and ensuring energy exploration and development.

Description

Technical Field

[0001] This invention relates to oil and gas field drilling technology, specifically to a polymer gel particle, its preparation method, and its application. Background Technology

[0002] my country has entered a new stage of developing oil and gas resources in both old and new oil and gas fields. Accelerating the stable production and potential tapping in old fields while increasing reserves and building production in new fields is a crucial measure to ensure national energy security and safeguard the energy supply. Old oil and gas fields are the ballast and foundation of my country's oil and gas production. Due to long-term, multi-round development, formation pressure decays rapidly, and severe leakage occurs frequently in new wells in old fields, making the goal of stable production and potential tapping extremely challenging. In recent years, unconventional new oil and gas fields, represented by Changqing tight gas and Sichuan shale gas, have gradually become growth poles for oil and gas production. However, during exploration well construction in these new fields, unknown and abnormal formations are often encountered, resulting in extremely high leakage risks. Optimizing the sealing performance of drilling and completion fluids, especially improving leakage prevention and control capabilities during drilling, has become an inevitable choice for ensuring stable production in old fields and building production in new fields.

[0003] Gel-based materials, such as gel particles, gel particles, and polymer microspheres, exhibit swelling characteristics. In recent years, through continuous improvement and optimization, gel-based materials have gradually entered the ranks of drilling fluid and completion fluid treatment agents. During drilling, they can swell in the drilling fluid, changing from hard to soft, effectively filling and sealing formation fractures and pores, and effectively improving the mud cake, making it denser and reducing drilling fluid loss to the formation. However, most gel-based materials are prepared based on hydrogels, which means that gel-based plugging materials can only swell in aqueous environments, that is, they can only play a plugging role in water-based drilling fluids and cannot be applied to oil-based drilling fluid systems. With the gradual expansion of the application and market share of oil-based drilling fluids, the economic losses caused by formation loss and formation water inflow each year are enormous, while there is a lack of effective plugging materials to address formation loss or formation water inflow. Therefore, there is a need to develop gel-based plugging agents that can swell in both oil-phase and aqueous phases when dealing with formation loss and formation water inflow—in other words, drilling and completion fluid gel-based plugging agents with environmentally responsive swelling capabilities. The development of such plugging agents would not only fill the gap in oil-based drilling fluid gel-based plugging agent materials but would also be applicable to water-based drilling fluids, achieving the effects of "one agent for multiple uses" and "one agent for all applications."

[0004] Conventional gel materials are hydrogels formed by the cross-linking polymerization of hydrophilic monomers such as acrylamide and acrylic acid in aqueous solution. The hydrophilic monomers and the aqueous solution dictate that they can only swell in water. To prepare gel materials with oil-swelling properties, lipophilic monomers, such as hexyl methacrylate and lauryl methacrylate, need to be added to the polymerization reaction. However, lipophilic monomers with long hydrocarbon chains have very poor water solubility and cannot enter the aqueous solution to react with the hydrophilic monomers. In recent years, researchers have used surfactants such as sodium dodecyl sulfate and sodium dodecylbenzene sulfonate as solubilizers to promote the participation of lipophilic monomers in the polymerization reaction. However, the main chain of these polymers is still dominated by hydrophilic monomers, limiting the swelling effect of the lipophilic monomers in the oil phase environment. Therefore, to develop environmentally responsive gel materials that exhibit both oil and water swelling, it is necessary to break through the existing polymerization methods of hydrophilic and lipophilic monomers. This requires not only ensuring the participation of lipophilic monomers in the polymerization reaction but also guaranteeing the independence of the molecular chains formed by these monomers, promoting their full distribution and diffusion in the oil phase environment, and absorbing oil solvents to create a swelling effect. However, current research reports are still lacking, making it difficult to provide effective references and guidance. Summary of the Invention

[0005] The purpose of this invention is to overcome the problem that existing gel materials are difficult to combine oil / water swelling functions, and to provide a polymer gel particle, its preparation method and application. This polymer gel particle has both oil and water swelling functions and exhibits excellent swelling and plugging performance in water-based drilling fluids and / or water-based completion fluids, as well as oil-based drilling fluids and / or oil-based completion fluids. It has the advantages of good plugging effect and low filtration loss, which is of great significance for the development of new multifunctional drilling fluids and / or completion fluids and for ensuring energy exploration and development.

[0006] To achieve the above objectives, the present invention provides a polymer gel particle, wherein the polymer gel particle is a semi-interpenetrating network structure formed by the interpenetration of a hydrophilic polymer backbone and an oleophilic polymer; wherein the hydrophilic polymer backbone is spherical, with a rough surface and uniformly distributed porous structure, and the pores are interconnected.

[0007] A second aspect of the present invention provides a method for preparing polymer gel particles, the method comprising: freeze-drying a hydrophilic polymer dispersion to obtain a hydrophilic polymer skeleton, the freeze-drying step comprising: pre-freezing in liquid nitrogen, followed by freeze-drying; and emulsion polymerization of the hydrophilic polymer skeleton and the lipophilic monomer in the presence of an initiator 1, a crosslinking agent 1 and an emulsifier 1.

[0008] A third aspect of the present invention provides polymer gel particles prepared by the preparation method described herein.

[0009] A fourth aspect of the present invention provides the application of polymer gel particles as drilling fluid plugging agents and / or completion fluid plugging agents, wherein the polymer gel particles are the polymer gel particles described in the present invention.

[0010] The polymer gel particles of this invention have both oil and water swelling functions, exhibiting excellent swelling and plugging performance in water-based drilling fluids and / or water-based completion fluids, as well as oil-based drilling fluids and / or oil-based completion fluids. They have the advantages of good plugging effect and low filtration loss, which is of great significance for developing new multifunctional drilling fluids and / or completion fluids and ensuring energy exploration and development. Attached Figure Description

[0011] Figure 1 This is a schematic diagram of the preparation process of the polymer gel particles of the present invention; Figure 2 This is a scanning electron microscope image of the hydrophilic polymer skeleton in Preparation Example 1 of the present invention; Figure 3 This is a scanning electron microscope image of the hydrophilic polymer skeleton in Preparation Example 2 of the present invention; Figure 4 This is a scanning electron microscope image of the hydrophilic polymer skeleton in Preparation Example 3 of the present invention; Figure 5 This is a scanning electron microscope image of the hydrophilic polymer skeleton in Preparation Example 4 of the present invention; Figure 6 This is a scanning electron microscope image of the polymer gel particles in Example 1 of the present invention; Figure 7 This is a particle size distribution diagram of the polymer gel particles in Example 1 of the present invention; Figure 8 This is the microstructure of the polymer gel particles in Example 1 of the present invention; Figure 9 This is a Raman spectral imaging of the polymer gel particles in Example 1 of the present invention; Figure 10 This refers to the Raman spectrum of region 1 in the polymer gel particles of Example 1 of the present invention; Figure 11 This refers to the Raman spectrum of region 2 in the polymer gel particles of Example 1 of the present invention; Figure 12 The curves showing the average particle size variation of the polymer gel particles in Example 1 of this invention under three environments: high temperature aqueous phase (200°C, deionized water), high temperature oil phase (200°C, No. 3 white oil), and high temperature and high salt (200°C, 300000 mg / L NaCl solution). Figure 13 This refers to the surface wettability of the polymer gel particles in Example 1 of this invention when immersed in water; Figure 14This refers to the surface wettability of the polymer gel particles in Example 1 of this invention immersed in n-dodecane; Figure 15 This is a scanning electron microscope image of the polymer gel particles in Comparative Example 1 of the present invention. Detailed Implementation

[0012] 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.

[0013] This invention provides a polymer gel particle, wherein the polymer gel particle is a semi-interpenetrating network structure formed by the interpenetration of a hydrophilic polymer backbone and an oleophilic polymer; wherein: the hydrophilic polymer backbone is spherical, with a rough surface and uniformly distributed porous structure, and the pores are interconnected.

[0014] In this invention, polymer gel particles having the aforementioned structure can achieve the objectives of this invention. The range of selectable mass ratios of the hydrophilic polymer backbone to the lipophilic polymer is relatively wide. The following is an illustrative description, but it does not limit the scope of this invention. According to a preferred embodiment of this invention, the mass ratio of the hydrophilic polymer backbone to the lipophilic polymer is 1:0.5-2. Using the aforementioned technical solution, the polymer gel particles possess both oil / water swelling capabilities, exhibiting excellent swelling and plugging performance in water-based drilling fluids and / or water-based completion fluids, as well as oil-based drilling fluids and / or oil-based completion fluids.

[0015] In this invention, polymer gel particles with the aforementioned technical features can achieve the purpose of this invention. The range of selectable properties such as morphology, number-average molecular weight, and average particle size of polymer gel particles is relatively wide. The following is an illustrative description, but it does not limit the scope of this invention. According to a preferred embodiment of this invention, the polymer gel particles are spherical and have a smooth surface.

[0016] According to a preferred embodiment of the present invention, the number-average molecular weight of the polymer gel particles is 3.5 million to 9 million.

[0017] According to a preferred embodiment of the present invention, the average particle size of the polymer gel particles is 1.0-5.5 μm. Using the aforementioned technical solution, the polymer gel particles possess both oil / water swelling capabilities, exhibiting excellent swelling and plugging performance in water-based drilling fluids and / or water-based completion fluids, as well as oil-based drilling fluids and / or oil-based completion fluids.

[0018] Those skilled in the art will understand that the swelling ratio refers to the ratio of the average particle size of polymer gel particles after immersion in an oil / water solution to that before immersion, while the shrinkage ratio refers to the ratio of the average particle size of polymer gel particles after immersion in a brine solution, such as NaCl solution, to that before immersion. There are no special requirements for the immersion time; generally, the average particle size is tested after immersion for a sufficiently long time and its stability is maintained. The immersion time is selected according to the actual situation. In this invention, an immersion time of 120 hours is used as an example. The polymer gel particles of this invention have both oil / water swelling functions and exhibit excellent swelling and plugging performance in water-based drilling fluids and / or water-based completion fluids, as well as oil-based drilling fluids and / or oil-based completion fluids. The range of selectable values ​​for the swelling ratio of polymer gel particles in oil / water solutions and the shrinkage ratio in brine solutions, such as NaCl solutions, is relatively wide. The following is an example, but it does not limit the scope of this invention. According to a preferred embodiment of this invention, the swelling ratio of the polymer gel particles in an aqueous phase at 150-250°C is 2-4 times.

[0019] According to a preferred embodiment of the present invention, the polymer gel particles have a swelling ratio of 1.5-3.5 times in the oil phase at 150-250°C.

[0020] According to a preferred embodiment of the present invention, the shrinkage ratio of the polymer gel particles in a NaCl solution at 150-250°C and 250,000-350,000 mg / L is 0.5-0.9 times, for example, 0.6, 0.7 and 0.8 times.

[0021] In this invention, any hydrophilic polymer skeleton having the aforementioned structure can be used. The range of physicochemical properties of the hydrophilic polymer skeleton is relatively wide. The following is an illustrative description, but it does not limit the scope of this invention. According to a preferred embodiment of this invention, the number average molecular weight of the hydrophilic polymer skeleton is 1 million to 3 million.

[0022] According to a preferred embodiment of the present invention, the pore size of the hydrophilic polymer skeleton is 1-300 nm.

[0023] According to a preferred embodiment of the present invention, the specific surface area of ​​the hydrophilic polymer backbone is 10-300 m². 2 / g.

[0024] Those skilled in the art will understand that the hydrophilic polymer skeleton includes hydrophilic structural units, which are derived from hydrophilic monomers. Commonly used hydrophilic monomers can be used in this invention. For example, hydrophilic monomers may contain one or more of amide groups, pyrrolidone groups, caprolactam groups, sulfonic acid groups, and sodium sulfonate groups.

[0025] According to a preferred embodiment of the present invention, the hydrophilic monomer is selected from one or more of acrylamide, N-hydroxymethylacrylamide, N-ethylacrylamide, N-isopropylacrylamide, vinylpyrrolidone, vinylcaprolactam, 2-acrylamido-2-methylpropanesulfonic acid, sodium methpropylene sulfonate, and sodium styrene sulfonate.

[0026] According to a preferred embodiment of the present invention, the hydrophilic monomer is a mixture of acrylamide and sodium methpropylene sulfonate, with a mass ratio of 1:0.1-2. Using the aforementioned technical solution, the polymer gel particles possess both oil / water swelling capabilities, exhibiting excellent swelling and plugging performance in both water-based drilling fluids and / or water-based completion fluids, and oil-based drilling fluids and / or oil-based completion fluids.

[0027] In this invention, those skilled in the art will understand that the lipophilic polymer comprises lipophilic structural units derived from lipophilic monomers. The range of lipophilic monomers is wide as long as the objective of this invention can be achieved. The following is an illustrative description, but it does not limit the scope of this invention. According to a preferred embodiment of this invention, the lipophilic monomer has the structural formula shown in formula (i):

[0028] Formula (i), where R is a C4-C12 alkyl group.

[0029] According to a preferred embodiment of the present invention, in the structural formula shown by the lipophilic monomer formula (i), R is an alkyl group of C4, C6 or C12.

[0030] Those skilled in the art will know that in the structural formula shown in the lipophilic monomer formula (i), when R is a C4 alkyl group, the lipophilic monomer is butyl methacrylate; when R is a C6 alkyl group, the lipophilic monomer is hexyl methacrylate; and when R is a C12 alkyl group, the lipophilic monomer is lauryl methacrylate.

[0031] Using the aforementioned technical solution, the polymer gel particles have both oil and water swelling functions, and exhibit excellent swelling and plugging performance in water-based drilling fluids and / or water-based completion fluids, as well as oil-based drilling fluids and / or oil-based completion fluids.

[0032] In this invention, the lipophilic polymer may further include a crosslinking structural unit I, which is derived from a crosslinking agent 1. The range of crosslinking agents 1 is relatively wide. This invention illustrates one embodiment but does not limit the scope of the invention. According to a preferred embodiment of the invention, the crosslinking agent 1 is selected from one or more of ethylene glycol dimethacrylate and trimethylolpropane trimethacrylate.

[0033] In this invention, the hydrophilic polymer may further include a crosslinking structural unit II, wherein the crosslinking structural unit II of the hydrophilic polymer is derived from crosslinking agent 2. There are no special requirements for the selection of crosslinking agent 2. In this invention, the crosslinking agent 2 is selected from one or more of N,N-methylenebisacrylamide and ethylene glycol diacrylate to illustrate the advantages of the invention, but this does not limit the scope of the invention.

[0034] In this invention, the objective of the invention can be achieved by selecting the aforementioned lipophilic monomer and crosslinking agent 1. The mass ratio of the lipophilic monomer to crosslinking agent 1 can be selected within a wide range. This invention exemplifies one embodiment, but does not limit the scope of the invention. According to a preferred embodiment of the invention, the advantages of the invention are exemplified by a mass ratio of the lipophilic monomer to crosslinking agent 1 of 1:0.0006-0.015, but this does not limit the scope of the invention.

[0035] In this invention, the aforementioned hydrophilic monomer and crosslinking agent 2 can both achieve the purpose of this invention. There are no special requirements for the mass ratio of the hydrophilic monomer to the crosslinking agent 2. In this invention, the advantages of this invention are illustrated by the example of a mass ratio of the hydrophilic monomer to the crosslinking agent 2 of 1:0.0001-0.005, but this does not limit the scope of this invention.

[0036] Polymer gels possessing the aforementioned technical features can all achieve the objectives of this invention. There are no special requirements for the preparation method of the polymer gel. One embodiment is illustrated, but it does not limit the scope of this invention. According to a preferred embodiment of this invention, the preparation method of polymer gel particles includes: freeze-drying a hydrophilic polymer dispersion to obtain a hydrophilic polymer skeleton. The freeze-drying step includes: pre-freezing in liquid nitrogen, followed by freeze-drying; and emulsion polymerization of the hydrophilic polymer skeleton and the lipophilic monomer in the presence of initiator 1, crosslinking agent 1, and emulsifier 1.

[0037] A schematic diagram of the preparation process of the polymer gel particles of the present invention is shown below. Figure 1 As shown, a hydrophilic polymer skeleton is first prepared by freeze-drying a hydrophilic polymer dispersion, and then the hydrophilic polymer skeleton and lipophilic monomer are emulsion polymerized to obtain polymer gel particles.

[0038] Those skilled in the art will know that in the process of preparing polymer gel particles, after emulsion polymerization, in order to obtain polymer gel particles, organic solvents such as anhydrous ethanol are generally used to filter and wash the product, mainly to remove the reaction solvent and emulsifier, and then the polymer gel particles are obtained after drying. This operation is a conventional prior art and will not be described in detail in this invention.

[0039] In this invention, the aforementioned freeze-drying method can be used to achieve the purpose of this invention during the preparation of polymer gel particles. The range of freeze-drying conditions is relatively wide. The following is an illustrative description, but it does not limit the scope of this invention. According to a preferred embodiment of this invention, the solvent of the hydrophilic polymer dispersion includes alcohol and water. The alcohol is selected from one or more of tert-butanol, ethanol, methanol, and propanol. The mass ratio of alcohol to water is 1:1-5.

[0040] According to a preferred embodiment of the present invention, in the hydrophilic polymer dispersion, the mass ratio of solvent to hydrophilic polymer is 1:0.01-0.05.

[0041] In the freeze-drying step, there are no special requirements for the pre-freezing time in liquid nitrogen, as long as the hydrophilic polymer dispersion is frozen solid. For example, it is generally pre-frozen in liquid nitrogen for 0.5-1.5 hours. In this embodiment of the invention, pre-freezing in liquid nitrogen for 1 hour is used as an example to illustrate the advantages of the invention, but this does not limit the scope of the invention.

[0042] In the freeze-drying process, the commonly used freeze-drying temperatures can all be used in this invention, and there are no special requirements for the freeze-drying temperature. For example, the freeze-drying temperature is -60℃ to -80℃. In the embodiments of this invention, the freeze-drying temperature of -80℃ is used to illustrate the advantages of this invention, but this does not limit the scope of this invention.

[0043] In the freeze-drying step, according to a preferred embodiment of the present invention, the freeze-drying is carried out under vacuum conditions and the freeze-drying pressure is 0.5-1.5 Pa. In the embodiments of the present invention, the freeze-drying pressure is 1 Pa to illustrate the advantages of the present invention, but this does not limit the scope of the present invention.

[0044] In the freeze-drying process, the freeze-drying time is generally selected based on the freeze-drying temperature, freeze-drying pressure, etc. For example, the freeze-drying time is 36-60 hours. In this embodiment of the invention, a freeze-drying time of 48 hours is used to illustrate the advantages of the invention, but this does not limit the scope of the invention.

[0045] According to a preferred embodiment of the present invention, the solvent of the hydrophilic polymer dispersion includes tert-butanol, ethanol and water, wherein the mass ratio of tert-butanol, ethanol and water is 1:1-2:7-8.

[0046] According to a preferred embodiment of the present invention, in the hydrophilic polymer dispersion, the mass ratio of solvent to hydrophilic polymer is 1:0.01-0.02. Using the aforementioned technical solution, the polymer gel particles possess both oil / water swelling capabilities, exhibiting excellent swelling and plugging performance in both water-based drilling fluids and / or water-based completion fluids, and oil-based drilling fluids and / or oil-based completion fluids.

[0047] In this invention, conventional emulsion polymerization can achieve the purpose of this invention in the process of preparing polymer gel particles. The conditions for emulsion polymerization can be selected according to the prior art. The following is an illustrative description, but it does not limit the scope of this invention. According to a preferred embodiment of this invention, the conditions for emulsion polymerization include: the initiator 1 is selected from one or more of 2,2-dioxyacetophenone and 2-(2-hydroxyethoxy)ethyl oxy(phenyl)acetic acid ester.

[0048] According to a preferred embodiment of the present invention, the conditions for emulsion polymerization include: the emulsifier 1 is selected from one or more of inulin lauryl carbamate, cocoyl diethanolamide, and lauryl polyoxyethylene ether sulfate.

[0049] According to a preferred embodiment of the present invention, the conditions for emulsion polymerization include: an emulsion polymerization temperature of 40-70°C. In this embodiment of the invention, an emulsion polymerization temperature of 65°C is used to illustrate the advantages of the present invention, but this does not limit the scope of the present invention.

[0050] In this invention, the emulsion polymerization time is generally adjusted according to the emulsion polymerization temperature, etc. For example, the emulsion polymerization time is 2-8 hours. In this embodiment of the invention, the emulsion polymerization time is 5 hours to illustrate the advantages of the invention, but this does not limit the scope of the invention.

[0051] In this invention, the emulsion polymerization is generally carried out in an inert gas, such as nitrogen.

[0052] In this invention, the emulsion polymerization is generally carried out under ultraviolet light irradiation, using the crosslinking agent and initiator selected according to the invention.

[0053] In this invention, the emulsion polymerization is generally carried out dynamically, with no special requirements on the rotation speed, such as 50-200 rpm. In this embodiment, the rotation speed of 100 rpm is used to illustrate the advantages of the invention, but this does not limit the scope of the invention.

[0054] In this invention, there are no special requirements for the method of adding each raw material in the emulsion polymerization. It can be selected according to the existing technology. An embodiment is illustrated, but it does not limit the scope of the invention. For example, the method of emulsion polymerization includes: adding an oil phase containing the hydrophilic polymer backbone, the lipophilic monomer and the crosslinking agent 1 to an aqueous phase containing emulsifier 1, and then adding initiator 1 to carry out polymerization.

[0055] In this invention, there are no special requirements for the amount of oil phase solvent, water and initiator 1 in the emulsion polymerization process. They can be selected according to the prior art. The following is an illustrative description, but it does not limit the scope of the invention. According to a preferred embodiment of the invention, the mass ratio of the aqueous phase containing emulsifier 1 to the oil phase containing hydrophilic molecular chain backbone, lipophilic monomer and crosslinking agent 1 is 1:0.2-0.5.

[0056] According to a preferred embodiment of the present invention, in the aqueous phase containing emulsifier 1, the mass ratio of emulsifier 1 to water is 1:10-40.

[0057] According to a preferred embodiment of the present invention, in an oil phase containing a hydrophilic molecular chain backbone, a lipophilic monomer, and a crosslinking agent 1, the total mass ratio of the hydrophilic molecular chain backbone, the lipophilic monomer, and the crosslinking agent 1 to the mass ratio of the oil phase solvent is 1:1-10.

[0058] According to a preferred embodiment of the present invention, the mass ratio of the oil phase solvent to the initiator 1 is 1:0.0001-0.0005.

[0059] In this invention, as long as the hydrophilic polymer dispersion can be freeze-dried to obtain the hydrophilic polymer skeleton during the preparation of polymer gel particles, there are no special requirements for the preparation method of the hydrophilic polymer in the hydrophilic polymer dispersion. This invention illustrates one embodiment, but does not limit the scope of the invention. According to a preferred embodiment of the invention, the preparation method of the hydrophilic polymer in the hydrophilic polymer dispersion includes: performing reverse emulsion polymerization of the hydrophilic monomer in the presence of initiator 2, crosslinking agent 2 and emulsifier 2.

[0060] Those skilled in the art will know that in the process of preparing hydrophilic polymers, after reverse emulsion polymerization, in order to obtain hydrophilic polymer products, organic solvents such as anhydrous ethanol are generally used to filter and wash the products, mainly to remove the reaction solvents and emulsifiers, and then the products are dried to obtain hydrophilic polymers. This operation is a conventional prior art and will not be described in detail in this invention.

[0061] In this invention, the preparation method of the hydrophilic polymer does not have special requirements for the conditions of the reverse emulsion polymerization. The conditions can be selected according to the prior art. The following is an illustrative description, but it does not limit the scope of the invention. According to a preferred embodiment of the invention, the conditions of the reverse emulsion polymerization include: the initiator 2 is selected from one or more of potassium persulfate and ammonium persulfate.

[0062] According to a preferred embodiment of the present invention, the conditions for the reverse emulsion polymerization include: the crosslinking agent 2 is selected from one or more of N,N-methylenebisacrylamide and ethylene glycol diacrylate.

[0063] According to a preferred embodiment of the present invention, the conditions for the reverse emulsion polymerization include: the emulsifier 2 is selected from one or more of Span80, OP-4 and Span-60.

[0064] According to a preferred embodiment of the present invention, the conditions for the reverse emulsion polymerization include: a reverse emulsion polymerization temperature of 40-70°C. In this embodiment of the invention, a reverse emulsion polymerization temperature of 65°C is used to illustrate the advantages of the present invention, but this does not limit the scope of the present invention.

[0065] In this invention, the reverse emulsion polymerization time is generally adjusted according to the reverse emulsion polymerization temperature, etc. For example, the reverse emulsion polymerization time is 2-8 hours. In this embodiment of the invention, the reverse emulsion polymerization time is 4 hours to illustrate the advantages of the invention, but this does not limit the scope of the invention.

[0066] In this invention, the reverse emulsion polymerization is generally carried out under alkaline conditions, for example, pH 8-9.

[0067] In this invention, the reverse emulsion polymerization is generally carried out in an inert gas, such as nitrogen.

[0068] In this invention, the reverse emulsion polymerization is generally carried out dynamically, with no special requirements on the rotation speed, such as 100-600 rpm. In this embodiment of the invention, a rotation speed of 300 rpm is used to illustrate the advantages of the invention, but this does not limit the scope of the invention.

[0069] In this invention, there are no special requirements for the method of adding each raw material in the reverse emulsion polymerization. It can be selected according to the existing technology. One embodiment is illustrated, but it does not limit the scope of the invention. According to a preferred embodiment of the invention, the method of reverse emulsion polymerization includes: adding an aqueous phase containing the hydrophilic monomer and crosslinking agent 2 to an oil phase containing emulsifier 2, and then adding initiator 2 to carry out polymerization.

[0070] In this invention, there are no special requirements for the amount of water, oil phase solvent, initiator 2 and crosslinking agent 2 used in the reverse emulsion polymerization process. They can be selected according to the prior art. The following is an illustrative description, but it does not limit the scope of the invention. According to a preferred embodiment of the invention, the mass ratio of the oil phase containing emulsifier 2 to the aqueous phase containing hydrophilic monomer and crosslinking agent 2 is 1:0.2-0.5.

[0071] According to a preferred embodiment of the present invention, in the oil phase containing emulsifier 2, the mass ratio of emulsifier 2 to oil phase solvent is 1:10-40.

[0072] According to a preferred embodiment of the present invention, in the aqueous phase containing hydrophilic monomer and crosslinking agent 2, the mass ratio of the total mass of hydrophilic monomer and crosslinking agent 2 to the mass of water is 1:1-5.

[0073] According to a preferred embodiment of the present invention, the mass ratio of water to initiator 2 is 1:0.001-0.005.

[0074] In this invention, the aforementioned hydrophilic monomer and crosslinking agent 2 can both achieve the purpose of this invention. There are no special requirements for the mass ratio of the hydrophilic monomer to the crosslinking agent 2. In this invention, the advantages of this invention are illustrated by the example of a mass ratio of the hydrophilic monomer to the crosslinking agent 2 of 1:0.0001-0.005, but this does not limit the scope of this invention.

[0075] In this invention, there are no special requirements for the oil phase solvent. Commonly used oil phase solvents can achieve the purpose of this invention. For example, one or more selected from No. 3 white oil, No. 5 white oil, No. 10 white oil, cyclohexane or liquid paraffin are used. In the embodiments of this invention, No. 3 white oil and No. 10 white oil are used to illustrate the advantages of this invention, but this does not limit the scope of this invention.

[0076] This invention provides polymer gel particles prepared by the preparation method described herein.

[0077] This invention provides an application of polymer gel particles as a drilling fluid plugging agent and / or completion fluid plugging agent, wherein the polymer gel particles are the polymer gel particles described in this invention.

[0078] The polymer gel particles of the present invention have good effects when used as a plugging agent for water-based drilling fluids and / or oil-based drilling fluids.

[0079] The polymer gel particles of this invention have both oil and water swelling functions, exhibiting excellent swelling and plugging performance in water-based drilling fluids and / or water-based completion fluids, as well as oil-based drilling fluids and / or oil-based completion fluids. They have the advantages of good plugging effect and low filtration loss, which is of great significance for developing new multifunctional drilling fluids and / or completion fluids and ensuring energy exploration and development.

[0080] The present invention will be described in detail below through embodiments.

[0081] In the following examples and comparative examples: Scanning electron microscope (SEM) images of polymer gel particles and hydrophilic polymer backbones were obtained using a FEI Quanta 200F SEM. Before measurement, the sample surface was coated with gold.

[0082] The number-average molecular weights of the polymer gel particles and the hydrophilic polymer backbone were determined by an integrated gel permeation chromatograph, specifically using tetrahydrofuran as the eluent and setting the flow rate to 1.0 mL / min.

[0083] Characterization method of polymer gel particles by scanning electron microscopy-Raman spectroscopy: The microstructure is viewed in the field of view of the scanning electron microscope, the area to be analyzed is selected, Raman spectroscopy imaging is performed on the corresponding area, and the Raman spectrum of the corresponding area is output.

[0084] The method for determining the surface wettability of polymer gel particles immersed in water / n-dodecane is the contact angle method.

[0085] The particle size distribution of the polymer gel particles was determined using a laser particle size analyzer. Specifically, in anhydrous ethanol solution, the average particle size and particle size distribution of the samples were determined using a Microtrac S3500 particle size analyzer based on laser diffraction; in corresponding aqueous, oil, and salt solutions, the average particle size and particle size distribution of the swollen samples were determined. Prior to measurement, the suspension was gently sonicated to aid in proper sample dispersion; particle size testing was conducted at room temperature, and the mass concentration of the measured particles was 0.05%.

[0086] The test method for the average particle size variation curves of polymer gel particles under high-temperature aqueous phase, high-temperature oil phase, and high-temperature high-salt environments is as follows: Prepare the corresponding aqueous phase, oil phase, and salt solutions: Mix 5g of polymer gel particles with 500mL of deionized water; mix 5g of polymer gel with 500mL of NaCl brine with salt contents of 50000, 100000, 150000, 2000000, 250000, and 300000 mg / L; mix 5g of polymer gel particles with 500mL of No. 3 white oil; inject the mixed polymer gel particles-deionized water, polymer gel particles-salt water, and polymer gel particles-white oil into a hydrothermal synthesis reactor, and place the hydrothermal synthesis reactor in a constant temperature chamber at 200℃ to simulate the high-temperature environment of a wellbore. Take them out at intervals and use a laser particle size analyzer to measure the particle size of the polymer gel particles, thereby observing and measuring the change in average particle size.

[0087] The performance evaluation method for polymer gel particles as plugging agents in water-based and oil-based drilling fluids is as follows: the test is conducted according to the method in national standard GB / T 16783.1-2014, using a high-temperature and high-pressure plugging performance tester, a ceramic sand disc with a gas permeability of 750 mD, and a temperature set at 200℃. The amount of plugging agent added is calculated as a volume percentage of the prepared water-based / oil-based drilling fluid. in, The water-based drilling fluid is prepared as follows: Based on a water volume of 100 mL, add 2.0 g of bentonite, 0.05 g of coating agent, 0.05 g of flow pattern modifier, 4.0 g of filtration loss reducer, 1.0 g of inhibitor stabilizer, 1.0 g of inhibitor lubricant, 7.0 g of potassium chloride, 23.0 g of type I organic salt, and 76.7 g of barite, resulting in a fluid with a density of approximately 1.60 g / cm³. 3 Water-based drilling fluid; The preparation method for oil-based drilling fluid is as follows: Dissolve 9.0g of primary emulsifier and 4.5g of secondary emulsifier in 240mL of No. 3 white oil. Then, under high-speed stirring at 11000rpm, gradually add 12.0g of organic clay, 60.0mL of 20% calcium chloride aqueous solution, 9.0g of alkalinity adjuster, 15g of filtration loss reducer, and 320.0g of barite powder to form a solution with a density of approximately 1.6g / cm³. 3 Oil-based drilling fluid.

[0088] The present invention will be further illustrated below through examples.

[0089] Preparation Example 1 Preparation of hydrophilic polymer backbone: The first step is to prepare a hydrophilic polymer. 200g of No. 10 white oil and 8g of Span80 were added to a three-necked glass flask equipped with a stirrer, nitrogen purging tube, and thermometer for emulsification to obtain an oil phase containing emulsifier. The emulsification temperature was 30℃, the emulsification time was 30min, and the stirring speed was controlled at 300rpm. 10g of acrylamide, 5g of sodium methacrylate, 0.015g of N,N-methylenebisacrylamide, and 30g of deionized water were mixed and added dropwise to the oil phase containing emulsifier. After stirring until all raw materials were dissolved, nitrogen gas was purged for 30min, the pH was controlled at 8.5, the temperature was controlled at 65℃, and then 0.12g of potassium persulfate was added. The reaction was carried out for 4h, cooled to room temperature, and the product was filtered and washed with anhydrous ethanol. After drying, a hydrophilic polymer was obtained.

[0090] The second step is freeze drying. The 15g hydrophilic polymer prepared above was dispersed in a 1000g mixed solution of tert-butanol / ethanol / deionized water, wherein the mass of tert-butanol in the mixed solution was 100g, the mass of ethanol was 200g, and the mass of deionized water was 700g. After uniform dispersion, the polymer was frozen in liquid nitrogen for 60min, and then freeze-dried at -80℃ and 1Pa for 48h, before being restored to room temperature and atmospheric pressure.

[0091] The prepared sample was observed using a scanning electron microscope, and the results are as follows: Figure 2 As shown in the scanning electron microscope images, it appears to be spherical with a rough surface and a uniformly distributed porous structure with interconnected pores. Its number-average molecular weight is measured to be 1.68-2.2 million, pore size to be 9-189 nm, and specific surface area to be 76-188 m². 2 / g.

[0092] Preparation Example 2 Preparation of hydrophilic polymer backbone: The first step is to prepare a hydrophilic polymer. 200g of No. 10 white oil and 8g of Span80 were added to a three-necked glass flask equipped with a stirrer, nitrogen purging tube, and thermometer for emulsification to obtain an oil phase containing emulsifier. The emulsification temperature was 30℃, the emulsification time was 30min, and the stirring speed was controlled at 300rpm. 10g of acrylamide, 1g of sodium methacrylate, 0.001g of ethylene glycol diacrylate, and 30g of deionized water were mixed and added dropwise to the oil phase containing emulsifier. After stirring until all raw materials were dissolved, nitrogen gas was purged for 30min, the pH was controlled at 8.3, the temperature was controlled at 65℃, and then 0.15g of potassium persulfate was added. The reaction was carried out for 4h, cooled to room temperature, and the product was filtered and washed with anhydrous ethanol. After drying, a hydrophilic polymer was obtained.

[0093] The second step is freeze drying. The 10g hydrophilic polymer prepared above was dispersed in a 1000g mixed solution of tert-butanol / ethanol / deionized water, wherein the mass of tert-butanol, ethanol, and deionized water in the mixed solution was 100g, 100g, and 800g. After uniform dispersion, the polymer was frozen in liquid nitrogen for 60min, followed by freeze-drying at -80℃ and 1Pa for 48h, and then restored to room temperature and atmospheric pressure.

[0094] The prepared sample was observed using a scanning electron microscope, and the results are as follows: Figure 3 As shown in the scanning electron microscope images, its morphology is similar to that of Preparation Example 1, exhibiting a spherical shape, a rough surface, and a uniformly distributed porous structure with interconnected pores. Compared to Preparation Example 1, the pores are slightly larger, and the framework structure is slightly looser. Its number-average molecular weight was measured to be 1.18-1.86 million, pore size to be 37-250 nm, and specific surface area to be 36-146 m². 2 / g.

[0095] Preparation Example 3 Preparation of hydrophilic polymer backbone: The first step is to prepare a hydrophilic polymer. 200g of No. 10 white oil and 8g of Span80 were added to a three-necked glass flask equipped with a stirrer, nitrogen purging tube, and thermometer for emulsification to obtain an oil phase containing emulsifier. The emulsification temperature was 30℃, the emulsification time was 30min, and the stirring speed was controlled at 300rpm. 10g of acrylamide, 20g of sodium methpropylene sulfonate, 0.015g of N,N-methylenebisacrylamide, and 30g of deionized water were mixed and added dropwise to the oil phase containing emulsifier. After stirring until all raw materials were dissolved, nitrogen gas was purged for 30min, the pH was controlled at 8.8, the temperature was controlled at 65℃, and then 0.03g of potassium persulfate was added. The reaction was carried out for 4h, cooled to room temperature, and the product was filtered and washed with anhydrous ethanol. After drying, a hydrophilic polymer was obtained.

[0096] The second step is freeze drying. The 20g hydrophilic polymer prepared above was dispersed in a 1000g mixed solution of tert-butanol / ethanol / deionized water, wherein the mass of tert-butanol, ethanol, and deionized water in the mixed solution was 100g, 100g, and 800g. After uniform dispersion, the polymer was frozen in liquid nitrogen for 60min, followed by freeze-drying at -80℃ and 1Pa for 48h, and then restored to room temperature and atmospheric pressure.

[0097] The prepared parent sample was observed using a scanning electron microscope, and the results are as follows: Figure 4 As shown in the scanning electron microscope images, its morphology is similar to that of Preparation Example 1 and Preparation Example 2, exhibiting a spherical shape, a rough surface, and a uniformly distributed porous structure with interconnected pores. Compared to Preparation Example 1, the pores are slightly smaller, and the framework structure is more compact. Its number-average molecular weight was measured to be 2.18-2.66 million, the pore size to be 2-69 nm, and the specific surface area to be 154-269 m². 2 / g.

[0098] Preparation Example 4 Preparation of hydrophilic polymer backbone: The first step is to prepare a hydrophilic polymer. 200g of No. 10 white oil and 8g of Span80 were added to a three-necked glass flask equipped with a stirrer, nitrogen purging tube, and thermometer for emulsification to obtain an oil phase containing emulsifier. The emulsification temperature was 30℃, the emulsification time was 30min, and the stirring speed was controlled at 300rpm. 10g of acrylamide, 5g of sodium methacrylate, 0.015g of N,N-methylenebisacrylamide, and 30g of deionized water were mixed and added dropwise to the oil phase containing emulsifier. After stirring until all raw materials were dissolved, nitrogen gas was purged for 30min, the pH was controlled at 8.5, the temperature was controlled at 65℃, and then 0.12g of potassium persulfate was added. The reaction was carried out for 4h, cooled to room temperature, and the product was filtered and washed with anhydrous ethanol. After drying, a hydrophilic polymer was obtained.

[0099] The second step is freeze drying. The 15g hydrophilic polymer prepared above was dispersed in a 1000g mixed solution of tert-butanol / ethanol / deionized water, wherein the mass of tert-butanol in the mixed solution was 100g, the mass of ethanol was 200g, and the mass of deionized water was 700g. After uniform dispersion, the solution was frozen in a -80℃ freezer for 60min, and then freeze-dried at -80℃ and 1Pa for 48h, before being restored to room temperature and atmospheric pressure.

[0100] The prepared sample was observed using a scanning electron microscope, and the results are as follows: Figure 5 As shown in the scanning electron microscope images, its morphology is non-spherical, with a smooth surface, lacking a connected porous structure and a skeletal structure; its number-average molecular weight is measured to be 1.55-2.32 million, and its specific surface area is 1.2-2.3 m². 2 / g.

[0101] Preparation Example 5 Preparation of hydrophilic polymer backbone: The first step is to prepare a hydrophilic polymer. 200g of No. 10 white oil and 8g of Span80 were added to a three-necked glass flask equipped with a stirrer, nitrogen purging tube, and thermometer for emulsification to obtain an oil phase containing emulsifier. The emulsification temperature was 30℃, the emulsification time was 30min, and the stirring speed was controlled at 300rpm. 10g of N-hydroxymethylacrylamide, 5g of vinylpyrrolidone, 0.015g of N,N-methylenebisacrylamide, and 30g of deionized water were mixed and added dropwise to the oil phase containing emulsifier. After stirring until all raw materials were dissolved, nitrogen gas was purged for 30min, the pH was controlled at 8.5, the temperature was controlled at 65℃, and then 0.12g of potassium persulfate was added. The reaction was carried out for 4h, cooled to room temperature, and the product was filtered and washed with anhydrous ethanol. After drying, a hydrophilic polymer was obtained.

[0102] The second step is freeze drying. The 15g hydrophilic polymer prepared above was dispersed in a 1000g mixed solution of tert-butanol / ethanol / deionized water, wherein the mass of tert-butanol in the mixed solution was 100g, the mass of ethanol was 200g, and the mass of deionized water was 700g. After uniform dispersion, the polymer was frozen in liquid nitrogen for 60min, and then freeze-dried at -80℃ and 1Pa for 48h, before being restored to room temperature and atmospheric pressure.

[0103] The scanning electron microscope (SEM) images of the prepared samples were similar to those of Preparation Example 1. They exhibited a spherical morphology, a rough surface, and a uniformly distributed porous structure with interconnected pores. Their number-average molecular weight was measured to be 1.56-2.36 million, pore size to be 26-167 nm, and specific surface area to be 84-194 m². 2 / g.

[0104] Example 1 The hydrophilic polymer backbone obtained in Preparation Example 1 was used as a raw material; 200g of deionized water and 8g of inulin lauryl carbamate were added to a three-necked glass flask equipped with a stirrer, a nitrogen purging tube, and a thermometer for emulsification to obtain an aqueous phase containing emulsifier. The emulsification temperature was 30℃, the emulsification time was 30min, and the stirring speed was controlled at 100rpm. 5g of hydrophilic polymer backbone, 2g of butyl methacrylate, 3g of lauryl methacrylate, 0.02g of ethylene glycol dimethacrylate, 0.02g of trimethylolpropane trimethacrylate, and 32g of No. 3 white oil were mixed and added dropwise to the aqueous phase containing emulsifier. Nitrogen gas was purged for 30min, the stirring speed was controlled at 100rpm, and the temperature was controlled at 65℃. Then, 0.01g of 2,2-dioxyacetophenone was added, and the reaction was carried out under ultraviolet light for 5h. After cooling to room temperature, the product was filtered and washed with anhydrous ethanol, and dried to obtain polymer gel particles.

[0105] The number-average molecular weight of the prepared polymer gel particles was 5.78-6.3 million.

[0106] Scanning electron microscope images of the prepared polymer gel particles are shown below. Figure 6 As shown in the figure, the polymer gel particles have a regular spherical structure with a smooth surface. There is no aggregation or adhesion between the polymer gel particles, and the dispersion is good.

[0107] The particle size distribution of the prepared polymer gel particles is shown in the figure. Figure 7 As shown in the figure, the particle size range of the polymer gel particles is 1.51-4.35 μm, with an average particle size of 2.51 μm. The particle size exhibits a normal distribution, narrow particle size distribution, and good monodispersity.

[0108] The structure and chemical composition of the prepared polymer gel particles were characterized by scanning electron microscopy-Raman spectroscopy, and the results are shown in the figure. Figure 8-11 , Figure 8 The microstructure of the prepared polymer gel particles (including region 1 and region 2) is shown. Figure 9 Raman spectral imaging of the prepared polymer gel particles (including region 1 and region 2). Figure 10 To obtain the region 1 Raman spectrum of the prepared polymer gel particles, Figure 11To analyze the Raman spectra of region 2 in the prepared polymer gel particles, it was found that: Scanning electron microscopy revealed multiple polymer strands intertwining and entangled within the microscopic polymer gel particles, indicating that the hydrophilic polymer backbone and the lipophilic polymer backbone are independent yet intertwined; significant differences in Raman spectral colors corresponding to different polymers at the microscopic level indicate that the chemical composition of the polymer gel particles is heterogeneous. Based on the imaging colors, the polymers in the polymer gel particles can be divided into two categories: one category appears red or dark red, and the other appears yellow or bright yellow; the Raman spectra of the two types of polymers are significantly different: the polymers in region 1, which appear yellow or bright yellow, have Raman spectra in the range of 3163-3583 cm⁻¹. -1 The presence of distinct absorption peaks within this range indicates the presence of numerous polar hydrophilic groups in this type of polymer, suggesting that it belongs to a hydrophilic polymer backbone. The Raman spectra of the red and dark red molecular chains in region 2 are located between 3163 and 3583 cm⁻¹. -1 The absence of obvious absorption peaks within the range indicates that the molecular chain does not contain hydrophilic polar groups, but is dominated by lipophilic nonpolar groups with long hydrocarbon chains. This suggests that the polymer is a lipophilic polymer. This further proves that the hydrophilic polymer backbone and the lipophilic polymer in the polymer gel particles are independent of each other and intertwine with each other.

[0109] The average particle size variation curves of the prepared polymer gel particles under three environments—high-temperature aqueous phase (200℃, deionized water), high-temperature oil phase (200℃, No. 3 white oil), and high-temperature high-salt (200℃, 300,000 mg / L NaCl solution)—are shown below. Figure 12 As can be seen from the figure: First, the polymer gel particles exhibit swelling capabilities in both water and white oil, meaning they possess both oil / water swelling properties. Furthermore, the swelling trend in both solutions is consistent: with increasing swelling time, the average particle size of the polymer gel particles initially increases rapidly and then gradually stabilizes, showing a similar trend. Specifically, in a high-temperature aqueous phase (200℃, deionized water) environment, from the start of swelling to 24 hours, the average particle size of the polymer gel particles increases rapidly, from 2.52 μm to 6.31 μm. After 84 hours, with further time, the average particle size of the polymer gel particles... The average particle size of the gel particles gradually stabilized. In a high-temperature oil phase (200℃, No. 3 white oil) environment, from the start of swelling to the 12th hour, the average particle size of the polymer gel particles increased rapidly, from 2.61 μm to 4.05 μm. After 72 hours, the average particle size of the polymer gel particles gradually stabilized with the extension of time. From the start of swelling to the 120th hour, the swelling ratios of the polymer gel particles were 3.7 times and 2.6 times in a high-temperature aqueous phase (200℃, deionized water) environment and a high-temperature oil phase (200℃, No. 3 white oil) environment, respectively. Second, the polymer gel particles have excellent salt resistance and very slight shrinkage effect. Specifically, in a high-temperature and high-salt environment (200℃, 300,000 mg / L NaCl solution), the average particle size of the polymer gel particles remains basically stable within 48 hours, changing from the initial average particle size of 2.41 μm to 2.38 μm. After 48 hours, the average particle size only decreases slightly, and after 120 hours, the average particle size decreases to 1.9 μm, with a shrinkage factor of 0.79.

[0110] The average particle size variation trends of the prepared polymer gel particles under different temperature aqueous phases (deionized water at 50℃, 100℃, 150℃ and 200℃), different temperature oil phases (No. 3 white oil at 50℃, 100℃, 150℃ and 200℃), and different concentrations of high temperature salt solutions (NaCl solution at 200℃, 50000 mg / L, 200℃, 100000 mg / L, 200℃, 150000 mg / L, 200℃, 200000 mg / L, 200℃, 250000 mg / L, 200℃, 300000 mg / L) were basically the same. The specific swelling ratio and shrinkage ratio are shown in Table 1.

[0111] The hydrophilic polymer backbone and lipophilic molecular chains in polymer gel particles endow them with swelling properties in both aqueous and oily environments. Figure 13 The surface wettability of polymer gel particles when immersed in water. Figure 14 The surface wettability of polymer gel particles immersed in n-dodecane was investigated. Results showed that when the polymer gel particles were immersed in water, the contact angle between n-dodecane and their surface reached 155.4°, indicating that the polymer gel particles swelled in water, and the polar molecular chains in the hydrophilic polymer backbone expanded outwards, encapsulating the lipophilic backbone structure and resisting contact with the non-polar n-dodecane liquid, resulting in superoleophobicity. When the polymer gel particles were immersed in n-dodecane, the contact angle between water and their surface reached 154.8°, exhibiting superhydrophobic properties. This indicates that when the polymer gel particles swelled in n-dodecane, the non-polar molecular chains in the lipophilic backbone diffused outwards, encapsulating the hydrophilic backbone structure internally, preventing it from contacting the polar water, thus producing superhydrophobicity. This also demonstrates that the environmental swelling characteristics of polymer gel particles depend on the solvent they first come into contact with, and their surface wettability is determined by the solvent environment.

[0112] The performance evaluation results of the prepared polymer gel particles as plugging agents in water-based drilling fluids are shown in Table 2, and the performance evaluation results in oil-based drilling fluids are shown in Table 3.

[0113] Example 2 The hydrophilic polymer framework obtained in Preparation Example 2 was used as a raw material; 200g of deionized water and 8g of inulin lauryl carbamate were added to a three-necked glass flask equipped with a stirrer, a nitrogen purging tube and a thermometer for emulsification to obtain an aqueous phase containing emulsifier. The emulsification temperature was 30℃, the emulsification time was 30min, and the stirring speed was controlled at 100rpm. 5g of hydrophilic polymer backbone, 2g of butyl methacrylate, 1g of hexyl methacrylate, 2g of lauryl methacrylate, 0.05g of ethylene glycol dimethacrylate, 0.025g of trimethylolpropane trimethacrylate, and 32g of No. 3 white oil were mixed and then added dropwise to the aqueous phase containing emulsifier. Nitrogen gas was purged for 30 minutes, the stirring speed was controlled at 100 rpm, and the temperature was controlled at 65℃. Then, 0.016g of 2-(2-hydroxyethoxy)ethyl oxy(phenyl)acetic acid ester was added, and the reaction was carried out under ultraviolet light for 5 hours. After cooling to room temperature, the product was filtered and washed with anhydrous ethanol, and dried to obtain polymer gel particles.

[0114] The number-average molecular weight of the prepared polymer gel particles was 4.91-5.63 million.

[0115] The scanning electron microscope (SEM) image of the prepared polymer gel particles is similar to that of the polymer gel particles in Example 1. The polymer gel particles have a regular spherical structure, a smooth surface, and no aggregation or adhesion between them, indicating good dispersibility.

[0116] The particle size distribution of the prepared polymer gel particles is similar to that of the polymer gel particles in Example 1. The particle size range of the polymer gel particles is 1.61-4.21 μm, the average particle size is 2.62 μm, the particle size is normally distributed, the particle size distribution is narrow, and the monodispersity is good.

[0117] The scanning electron microscopy-Raman spectroscopy characterization results of the prepared polymer gel particles are similar to those of the polymer gel particles in Example 1. The hydrophilic polymer backbone and the lipophilic polymer of the polymer gel particles are independent of each other and intertwine with each other.

[0118] The average particle size variation curves of the prepared polymer gel particles under three environments—high temperature aqueous phase (200℃, deionized water), high temperature oil phase (200℃, No. 3 white oil), and high temperature and high salt (200℃, 300,000 mg / L NaCl solution)—are similar to those of the polymer gel particles in Example 1 under the same three environments. Table 1 shows the swelling or shrinkage ratios of the polymer gel particles under the same environments.

[0119] The surface wettability of the prepared polymer gel particles when immersed in water and when immersed in n-dodecane is similar to that of the polymer gel particles in Example 1 when immersed in water and when immersed in n-dodecane. The environmental swelling characteristics of the polymer gel particles depend on which solvent they first come into contact with, and the surface wettability is determined by the solvent environment.

[0120] The performance evaluation results of the prepared polymer gel particles as plugging agents in water-based drilling fluids are shown in Table 2, and the performance evaluation results in oil-based drilling fluids are shown in Table 3.

[0121] Example 3 The hydrophilic polymer backbone obtained in Preparation Example 3 was used as a raw material; 200g of deionized water and 8g of inulin lauryl carbamate were added to a three-necked glass flask equipped with a stirrer, nitrogen purging tube, and thermometer for emulsification to obtain an aqueous phase containing emulsifier. The emulsification temperature was 30℃, the emulsification time was 30min, and the stirring speed was controlled at 100rpm. 5g of hydrophilic polymer backbone, 2g of butyl methacrylate, 1g of hexyl methacrylate, 2g of lauryl methacrylate, 0.0005g of ethylene glycol dimethacrylate, 0.0025g of triallyl isocyanurate, and 32g of No. 3 white oil were mixed and then added dropwise to the aqueous phase containing emulsifier. Nitrogen gas was purged for 30min, the stirring speed was controlled at 100rpm, and the temperature was controlled at 65℃. Then, 0.0032g of 2,2-dioxyacetophenone was added, and the reaction was carried out under ultraviolet light for 5h. After cooling to room temperature, the product was filtered and washed with anhydrous ethanol, and dried to obtain polymer gel particles.

[0122] The number-average molecular weight of the prepared polymer gel particles was 6.4-6.93 million.

[0123] The scanning electron microscope (SEM) image of the prepared polymer gel particles is similar to that of the polymer gel particles in Example 1. The polymer gel particles have a regular spherical structure, a smooth surface, and no aggregation or adhesion between them, indicating good dispersibility.

[0124] The particle size distribution of the prepared polymer gel particles is similar to that of the polymer gel particles in Example 1. The particle size range of the polymer gel particles is 1.48-4.51 μm, the average particle size is 2.74 μm, the particle size is normally distributed, the particle size distribution is narrow, and the monodispersity is good.

[0125] The scanning electron microscopy-Raman spectroscopy characterization results of the prepared polymer gel particles are similar to those of the polymer gel particles in Example 1. The hydrophilic polymer backbone and the lipophilic polymer of the polymer gel particles are independent of each other and intertwine with each other.

[0126] The average particle size variation curves of the prepared polymer gel particles under three environments—high temperature aqueous phase (200℃, deionized water), high temperature oil phase (200℃, No. 3 white oil), and high temperature and high salt (200℃, 300,000 mg / L NaCl solution)—are similar to those of the polymer gel particles in Example 1 under the same three environments. Table 1 shows the swelling or shrinkage ratios of the polymer gel particles under the same environments.

[0127] The surface wettability of the prepared polymer gel particles when immersed in water and when immersed in n-dodecane is similar to that of the polymer gel particles in Example 1 when immersed in water and when immersed in n-dodecane. The environmental swelling characteristics of the polymer gel particles depend on which solvent they first come into contact with, and the surface wettability is determined by the solvent environment.

[0128] The performance evaluation results of the prepared polymer gel particles as plugging agents in water-based drilling fluids are shown in Table 2, and the performance evaluation results in oil-based drilling fluids are shown in Table 3.

[0129] Example 4 The method of Example 1 was followed, except that the mass of ethylene glycol dimethacrylate was 0.06 g and the mass of trimethylolpropane trimethacrylate was 0.03 g, while the other raw materials and conditions were the same.

[0130] The number-average molecular weight of the prepared polymer gel particles was 6.27-6.85 million.

[0131] The scanning electron microscope (SEM) image of the prepared polymer gel particles is similar to that of the polymer gel particles in Example 1. The polymer gel particles have a regular spherical structure, a smooth surface, and no aggregation or adhesion between them, indicating good dispersibility.

[0132] The particle size distribution of the prepared polymer gel particles is similar to that of the polymer gel particles in Example 1. The particle size range of this polymer gel is 1.34-4.79 μm, the average particle size is 2.81 μm, the particle size is normally distributed, the particle size distribution is narrow, and the monodispersity is good.

[0133] The scanning electron microscopy-Raman spectroscopy characterization results of the prepared polymer gel particles are similar to those of the polymer gel particles in Example 1. The hydrophilic polymer backbone and the lipophilic polymer of the polymer gel particles are independent of each other and intertwine with each other.

[0134] The average particle size variation curves of the prepared polymer gel particles under three environments—high temperature aqueous phase (200℃, deionized water), high temperature oil phase (200℃, No. 3 white oil), and high temperature and high salt (200℃, 300,000 mg / L NaCl solution)—are similar to those of the polymer gel particles in Example 1 under the same three environments. Table 1 shows the swelling or shrinkage ratios of the polymer gel particles under the same environments.

[0135] The surface wettability of the prepared polymer gel particles when immersed in water and when immersed in n-dodecane is similar to that of the polymer gel particles in Example 1 when immersed in water and when immersed in n-dodecane. The environmental swelling characteristics of the polymer gel particles depend on which solvent they first come into contact with, and the surface wettability is determined by the solvent environment.

[0136] The performance evaluation results of the prepared polymer gel as a plugging agent in water-based drilling fluid are shown in Table 2, and the performance evaluation results in oil-based drilling fluid are shown in Table 3.

[0137] Example 5 The method of Example 1 was followed, except that the mass of ethylene glycol dimethacrylate was 0.0003 g and the mass of trimethylolpropane trimethacrylate was 0.002 g, while the other raw materials and conditions were the same.

[0138] The number-average molecular weight of the prepared polymer gel particles was 5.32-5.91 million.

[0139] The scanning electron microscope (SEM) image of the prepared polymer gel particles is similar to that of the polymer gel particles in Example 1. The polymer gel particles have a regular spherical structure, a smooth surface, and no aggregation or adhesion between them, indicating good dispersibility.

[0140] The particle size distribution of the prepared polymer gel particles is similar to that of the polymer gel particles in Example 1. The particle size range of this polymer gel is 1.28-4.46 μm, with an average particle size of 2.68 μm and an average particle size of 2.74 μm. The particle size shows a normal distribution, a narrow particle size distribution, and good monodispersity.

[0141] The scanning electron microscopy-Raman spectroscopy characterization results of the prepared polymer gel particles are similar to those of the polymer gel particles in Example 1. The hydrophilic polymer backbone and the lipophilic polymer of the polymer gel particles are independent of each other and intertwine with each other.

[0142] The average particle size variation curves of the prepared polymer gel particles under three environments—high temperature aqueous phase (200℃, deionized water), high temperature oil phase (200℃, No. 3 white oil), and high temperature and high salt (200℃, 300,000 mg / L NaCl solution)—are similar to those of the polymer gel particles in Example 1 under the same three environments. Table 1 shows the swelling or shrinkage ratios of the polymer gel particles under the same environments.

[0143] The surface wettability of the prepared polymer gel particles when immersed in water and when immersed in n-dodecane is similar to that of the polymer gel particles in Example 1 when immersed in water and when immersed in n-dodecane. The environmental swelling characteristics of the polymer gel particles depend on which solvent they first come into contact with, and the surface wettability is determined by the solvent environment.

[0144] The performance evaluation results of the prepared polymer gel as a plugging agent in water-based drilling fluid are shown in Table 2, and the performance evaluation results in oil-based drilling fluid are shown in Table 3.

[0145] Example 6 The method is the same as in Example 1, except that the mass ratio of the hydrophilic polymer backbone to the lipophilic monomer is 1:2. Specifically, the ingredients are: 5g hydrophilic polymer backbone, 4g butyl methacrylate, 6g lauryl methacrylate, 0.08g ethylene glycol dimethacrylate, and no trimethylolpropane trimethacrylate is added. All other raw materials and conditions are the same.

[0146] The number-average molecular weight of the prepared polymer gel particles was 6.44-7.06 million.

[0147] The scanning electron microscope (SEM) image of the prepared polymer gel particles is similar to that of the polymer gel particles in Example 1. The polymer gel particles have a regular spherical structure, a smooth surface, and no aggregation or adhesion between them, indicating good dispersibility.

[0148] The particle size distribution of the prepared polymer gel particles is similar to that of the polymer gel particles in Example 1. The particle size range of the polymer gel particles is 1.44-4.56 μm, the average particle size is 2.63 μm, the particle size is normally distributed, the particle size distribution is narrow, and the monodispersity is good.

[0149] The scanning electron microscopy-Raman spectroscopy characterization results of the prepared polymer gel particles are similar to those of the polymer gel particles in Example 1. The hydrophilic polymer backbone and the lipophilic polymer of the polymer gel particles are independent of each other and intertwine with each other.

[0150] The average particle size variation curves of the prepared polymer gel particles under three environments—high temperature aqueous phase (200℃, deionized water), high temperature oil phase (200℃, No. 3 white oil), and high temperature and high salt (200℃, 300,000 mg / L NaCl solution)—are similar to those of the polymer gel particles in Example 1 under the same three environments. Table 1 shows the swelling or shrinkage ratios of the polymer gel particles under the same environments.

[0151] The surface wettability of the prepared polymer gel particles when immersed in water and when immersed in n-dodecane is similar to that of the polymer gel particles in Example 1 when immersed in water and when immersed in n-dodecane. The environmental swelling characteristics of the polymer gel particles depend on which solvent they first come into contact with, and the surface wettability is determined by the solvent environment.

[0152] The performance evaluation results of the prepared polymer gel as a plugging agent in water-based drilling fluid are shown in Table 2, and the performance evaluation results in oil-based drilling fluid are shown in Table 3.

[0153] Example 7 The method is the same as in Example 1, except that the mass ratio of the hydrophilic polymer backbone to the lipophilic monomer is 1:0.5. Specifically, the mass of the hydrophilic polymer backbone is 5g, the mass of butyl methacrylate is 1g, the mass of lauryl methacrylate is 1.5g, ethylene glycol dimethacrylate is not added, the mass of trimethylolpropane trimethacrylate is 0.02g, and the other raw materials and conditions are the same.

[0154] The number-average molecular weight of the prepared polymer gel particles was 4.72-5.38 million.

[0155] The scanning electron microscope (SEM) image of the prepared polymer gel particles is similar to that of the polymer gel particles in Example 1. The polymer gel particles have a regular spherical structure, a smooth surface, and no aggregation or adhesion between them, indicating good dispersibility.

[0156] The particle size distribution of the prepared polymer gel particles is similar to that of the polymer gel particles in Example 1. The particle size range of the polymer gel particles is 1.40-4.68 μm, the average particle size is 2.57 μm, the particle size is normally distributed, the particle size distribution is narrow, and the monodispersity is good.

[0157] The scanning electron microscopy-Raman spectroscopy characterization results of the prepared polymer gel particles are similar to those of the polymer gel particles in Example 1. The hydrophilic polymer backbone and the lipophilic polymer of the polymer gel particles are independent of each other and intertwine with each other.

[0158] The average particle size variation curves of the prepared polymer gel particles under three environments—high temperature aqueous phase (200℃, deionized water), high temperature oil phase (200℃, No. 3 white oil), and high temperature and high salt (200℃, 300,000 mg / L NaCl solution)—are similar to those of the polymer gel particles in Example 1 under the same three environments. Table 1 shows the swelling or shrinkage ratios of the polymer gel particles under the same environments.

[0159] The surface wettability of the prepared polymer gel particles when immersed in water and when immersed in n-dodecane is similar to that of the polymer gel particles in Example 1 when immersed in water and when immersed in n-dodecane. The environmental swelling characteristics of the polymer gel particles depend on which solvent they first come into contact with, and the surface wettability is determined by the solvent environment.

[0160] The performance evaluation results of the prepared polymer gel as a plugging agent in water-based drilling fluid are shown in Table 2, and the performance evaluation results in oil-based drilling fluid are shown in Table 3.

[0161] Example 8 The method is the same as in Example 1, except that the mass ratio of the hydrophilic polymer backbone to the lipophilic monomer is 1:2.2. Specifically, the mass of the hydrophilic polymer backbone is 5g, the mass of butyl methacrylate is 4.4g, the mass of lauryl methacrylate is 6.6g, the mass of ethylene glycol dimethacrylate is 0.044g, the mass of trimethylolpropane trimethacrylate is 0.044g, and the remaining raw materials and conditions are the same.

[0162] The number-average molecular weight of the prepared polymer gel particles was 6.53-7.1 million.

[0163] The scanning electron microscope (SEM) image of the prepared polymer gel particles is similar to that of the polymer gel particles in Example 1. The polymer gel particles have a regular spherical structure, a smooth surface, and no aggregation or adhesion between them, indicating good dispersibility.

[0164] The particle size distribution of the prepared polymer gel particles is similar to that of the polymer gel particles in Example 1. The particle size range of the polymer gel particles is 1.40-4.61 μm, the average particle size is 2.78 μm, the particle size is normally distributed, the particle size distribution is narrow, and the monodispersity is good.

[0165] The scanning electron microscopy-Raman spectroscopy characterization results of the prepared polymer gel particles are similar to those of the polymer gel particles in Example 1. The hydrophilic polymer backbone and the lipophilic polymer of the polymer gel particles are independent of each other and intertwine with each other.

[0166] The average particle size variation curves of the prepared polymer gel particles under three environments—high temperature aqueous phase (200℃, deionized water), high temperature oil phase (200℃, No. 3 white oil), and high temperature and high salt (200℃, 300,000 mg / L NaCl solution)—are similar to those of the polymer gel particles in Example 1 under the same three environments. Table 1 shows the swelling or shrinkage ratios of the polymer gel particles under the same environments.

[0167] The surface wettability of the prepared polymer gel particles when immersed in water and when immersed in n-dodecane is similar to that of the polymer gel particles in Example 1 when immersed in water and when immersed in n-dodecane. The environmental swelling characteristics of the polymer gel particles depend on which solvent they first come into contact with, and the surface wettability is determined by the solvent environment.

[0168] The performance evaluation results of the prepared polymer gel as a plugging agent in water-based drilling fluid are shown in Table 2, and the performance evaluation results in oil-based drilling fluid are shown in Table 3.

[0169] Example 9 The method is the same as in Example 1, except that the mass ratio of the hydrophilic polymer backbone to the lipophilic monomer is 1:0.4. Specifically, the mass ratio of the hydrophilic polymer backbone is 5g, the mass ratio of butyl methacrylate is 0.8g, the mass ratio of lauryl methacrylate is 1.2g, the mass ratio of ethylene glycol dimethacrylate is 0.008g, the mass ratio of trimethylolpropane trimethacrylate is 0.008g, and the other raw materials and conditions are the same.

[0170] The number-average molecular weight of the prepared polymer gel particles was 4.62-5.23 million.

[0171] The scanning electron microscope (SEM) image of the prepared polymer gel particles is similar to that of the polymer gel particles in Example 1. The polymer gel particles have a regular spherical structure, a smooth surface, and no aggregation or adhesion between them, indicating good dispersibility.

[0172] The particle size distribution of the prepared polymer gel particles is similar to that of the polymer gel particles in Example 1. The particle size range of the polymer gel particles is 1.44-4.92 μm, the average particle size is 2.62 μm, the particle size is normally distributed, the particle size distribution is narrow, and the monodispersity is good.

[0173] The scanning electron microscopy-Raman spectroscopy characterization results of the prepared polymer gel particles are similar to those of the polymer gel particles in Example 1. The hydrophilic polymer backbone and the lipophilic polymer of the polymer gel particles are independent of each other and intertwine with each other.

[0174] The average particle size variation curves of the prepared polymer gel particles under three environments—high temperature aqueous phase (200℃, deionized water), high temperature oil phase (200℃, No. 3 white oil), and high temperature and high salt (200℃, 300,000 mg / L NaCl solution)—are similar to those of the polymer gel particles in Example 1 under the same three environments. Table 1 shows the swelling or shrinkage ratios of the polymer gel particles under the same environments.

[0175] The surface wettability of the prepared polymer gel particles when immersed in water and when immersed in n-dodecane is similar to that of the polymer gel particles in Example 1 when immersed in water and when immersed in n-dodecane. The environmental swelling characteristics of the polymer gel particles depend on which solvent they first come into contact with, and the surface wettability is determined by the solvent environment.

[0176] The performance evaluation results of the prepared polymer gel as a plugging agent in water-based drilling fluid are shown in Table 2, and the performance evaluation results in oil-based drilling fluid are shown in Table 3.

[0177] Example 10 The method of Example 1 was followed, except that the hydrophilic polymer skeleton obtained in Preparation Example 5 was used as the raw material, while the other raw materials and conditions were the same.

[0178] The number-average molecular weight of the prepared polymer gel particles was 5.16-5.75 million.

[0179] The scanning electron microscope (SEM) image of the prepared polymer gel particles is similar to that of the polymer gel particles in Example 1. The polymer gel particles have a regular spherical structure, a smooth surface, and no aggregation or adhesion between them, indicating good dispersibility.

[0180] The particle size distribution of the prepared polymer gel particles is similar to that of the polymer gel particles in Example 1. The particle size range of the polymer gel particles is 1.33-4.25 μm, the average particle size is 3.05 μm, the particle size is normally distributed, the particle size distribution is narrow, and the monodispersity is good.

[0181] The scanning electron microscopy-Raman spectroscopy characterization results of the prepared polymer gel particles are similar to those of the polymer gel particles in Example 1. The hydrophilic polymer backbone and the lipophilic polymer of the polymer gel particles are independent of each other and intertwine with each other.

[0182] The average particle size variation curves of the prepared polymer gel particles under three environments—high temperature aqueous phase (200℃, deionized water), high temperature oil phase (200℃, No. 3 white oil), and high temperature and high salt (200℃, 300,000 mg / L NaCl solution)—are similar to those of the polymer gel particles in Example 1 under the same three environments. Table 1 shows the swelling or shrinkage ratios of the polymer gel particles under the same environments.

[0183] The surface wettability of the prepared polymer gel particles when immersed in water and when immersed in n-dodecane is similar to that of the polymer gel particles in Example 1 when immersed in water and when immersed in n-dodecane. The environmental swelling characteristics of the polymer gel particles depend on which solvent they first come into contact with, and the surface wettability is determined by the solvent environment.

[0184] The performance evaluation results of the prepared polymer gel particles as plugging agents in water-based drilling fluids are shown in Table 2, and the performance evaluation results in oil-based drilling fluids are shown in Table 3.

[0185] Comparative Example 1 The method of Example 1 was followed, except that the hydrophilic polymer skeleton obtained in Preparation Example 4 was used as the raw material, while the other raw materials and conditions were the same.

[0186] Scanning electron microscope image of the prepared polymer gel particles is shown below. Figure 15 As shown in the figure, the polymer gel particles have an irregular structure.

[0187] Testing revealed that the prepared polymer gel particles lacked an accurate particle size distribution.

[0188] The prepared polymer gel particles do not exhibit swelling properties in high-temperature aqueous phase (200℃, deionized water) and high-temperature oil phase (200℃, No. 3 white oil) environments. During a continuous 120-hour swelling experiment, the particle size of the polymer particles remained essentially consistent with the initial particle size. Precipitation occurred in high-temperature and high-salt environments (200℃, 300,000 mg / L NaCl solution), resulting in excessive shrinkage and failure.

[0189] The performance evaluation results of the prepared polymer gel particles as plugging agents in water-based drilling fluids are shown in Table 2, and the performance evaluation results in oil-based drilling fluids are shown in Table 3.

[0190] Table 1

[0191] Table 2

[0192] Table 3

[0193] As can be seen from Tables 1, 2, and 3, the polymer gel particles in Examples 1-10 of this invention have both oil / water swelling functions. When used as a plugging agent, they have the advantages of good plugging effect and low filtration loss. Specifically, without the addition of plugging agent, the filtration loss of water-based drilling fluid and oil-based drilling fluid at 750mD PPA reached 40.4mL and 16.4mL, respectively. As the amount of plugging agent gradually increased in both water-based and oil-based drilling fluids, the filtration loss of 750mD PPA decreased significantly. The results show that the polymer gel particles of this invention have excellent swelling and plugging performance as a plugging agent in both water-based and oil-based drilling fluids.

[0194] The polymer gel particles in Comparative Example 1 were likely prepared with an irregular structure due to the use of an unsuitable and incomplete hydrophilic polymer skeleton. Tests showed that they did not have water-oil swelling properties, and the 750mD PPA filtration loss did not decrease significantly in water-based and oil-based drilling fluids at different dosages, indicating that the polymer gel particles did not have plugging ability.

[0195] The results above show that the embodiments of the present invention have the significant advantage of being applicable to both water-based and oil-based drilling fluids, and their swelling capacity in water and oil makes their plugging effect significantly better.

[0196] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A polymer gel particle, characterized in that, The polymer gel particles are formed by a semi-interpenetrating network structure consisting of a hydrophilic polymer backbone and an oleophilic polymer interpenetrating each other; wherein the hydrophilic polymer backbone is spherical, with a rough surface and uniformly distributed porous structure, and the pores are interconnected.

2. The polymer gel particles according to claim 1, characterized in that, The mass ratio of the hydrophilic polymer backbone to the lipophilic polymer is 1:0.5-2.

3. The polymer gel particles according to claim 1 or 2, characterized in that, The polymer gel particles are spherical with smooth surfaces; and / or The polymer gel particles have a number average molecular weight of 3.5 million to 9 million; and / or The average particle size of the polymer gel particles is 1.0-5.5 μm; and / or The polymer gel particles swell by 2-4 times in an aqueous phase at 150-250℃; and / or The polymer gel particles swell by 1.5-3.5 times in the oil phase at 150-250°C; and / or The polymer gel particles exhibit a shrinkage ratio of 0.5-0.9 times in a NaCl solution at 150-250℃ and 250,000-350,000 mg / L.

4. The polymer gel particles according to claim 1 or 2, characterized in that, The number-average molecular weight of the hydrophilic polymer backbone is 1 million to 3 million; and / or The pore size of the hydrophilic polymer framework is 1-300 nm; and / or The specific surface area of ​​the hydrophilic polymer skeleton is 10-300 m². 2 / g; and / or The hydrophilic polymer backbone includes hydrophilic structural units derived from hydrophilic monomers, wherein the hydrophilic monomers contain one or more of the following: amide groups, pyrrolidone groups, caprolactam groups, sulfonic acid groups, and sodium sulfonate groups.

5. The polymer gel particles according to claim 4, characterized in that, The hydrophilic monomer is selected from one or more of acrylamide, N-hydroxymethylacrylamide, N-ethylacrylamide, N-isopropylacrylamide, vinylpyrrolidone, vinylcaprolactam, 2-acrylamido-2-methylpropanesulfonic acid, sodium methpropylene sulfonate, and sodium styrene sulfonate.

6. The polymer gel particles according to claim 5, characterized in that, The hydrophilic monomer is a mixture of acrylamide and sodium methpropylene sulfonate, with a mass ratio of 1:0.1-2.

7. The polymer gel particles according to claim 1 or 2, characterized in that, The lipophilic polymer comprises lipophilic structural units derived from lipophilic monomers, wherein the lipophilic monomers have the structural formula shown in formula (i): Formula (i), where R is a C4-C12 alkyl group.

8. The polymer gel particles according to claim 7, characterized in that, In the structure shown in the lipophilic monomer formula (i), R is a C4, C6, or C12 alkyl group.

9. The polymer gel particles according to claim 1 or 2, characterized in that, The crosslinking structural unit I of the lipophilic polymer is derived from crosslinking agent 1, which is selected from one or more of ethylene glycol dimethacrylate and trimethylolpropane trimethacrylate; and / or The crosslinking structural unit II of the hydrophilic polymer is derived from crosslinking agent 2, which is selected from one or more of N,N-methylenebisacrylamide and ethylene glycol diacrylate.

10. The polymer gel particles according to claim 9, wherein, The mass ratio of the lipophilic monomer to crosslinking agent 1 is 1:0.0006-0.015; and / or The mass ratio of the hydrophilic monomer to the crosslinking agent 2 is 1:0.0001-0.

005.

11. A method for preparing polymer gel particles according to any one of claims 1-10, characterized in that, The method includes: The hydrophilic polymer dispersion was freeze-dried to obtain a hydrophilic polymer skeleton. The freeze-drying steps included: pre-freezing in liquid nitrogen, followed by freeze-drying. In the presence of initiator 1, crosslinking agent 1, and emulsifier 1, the hydrophilic polymer backbone and lipophilic monomer are subjected to emulsion polymerization.

12. The method according to claim 11, characterized in that, The freeze-drying conditions include: The solvent of the hydrophilic polymer dispersion includes an alcohol and water, wherein the alcohol is selected from one or more of tert-butanol, ethanol, methanol, and propanol, and the mass ratio of alcohol to water is 1:1-5; and / or In the hydrophilic polymer dispersion, the mass ratio of solvent to hydrophilic polymer is 1:0.01-0.05; and / or Pre-freeze in liquid nitrogen for 0.5–1.5 h; and / or The freeze-drying temperature is -60℃ to -80℃; and / or Freeze-drying is carried out under vacuum conditions at a pressure of 0.5-1.5 Pa; and / or The freeze-drying time is 36-60 hours.

13. The method according to claim 12, characterized in that, The solvent for the hydrophilic polymer dispersion includes tert-butanol, ethanol, and water, wherein the mass ratio of tert-butanol, ethanol, and water is 1:1-2:7-8; and / or In the hydrophilic polymer dispersion, the mass ratio of solvent to hydrophilic polymer is 1:0.01-0.

02.

14. The method according to claim 11, characterized in that, The conditions for emulsion polymerization include: The initiator 1 is selected from one or more of 2,2-dioxyacetophenone and 2-(2-hydroxyethoxy)ethyloxo(phenyl)acetate; and / or The emulsifier 1 is selected from one or more of inulin lauryl carbamate, cocoyl diethanolamide, and lauryl polyoxyethylene ether sulfate; and / or The emulsion polymerization temperature is 40-70℃; and / or The emulsion polymerization time is 2-8 hours; and / or Emulsion polymerization is carried out in an inert gas; and / or Emulsion polymerization is carried out under ultraviolet light irradiation; and / or Emulsion polymerization was carried out dynamically at a rotation speed of 50-200 rpm.

15. The method according to claim 11, characterized in that, The method for preparing the hydrophilic polymer in the hydrophilic polymer dispersion includes: The hydrophilic monomer is subjected to reverse emulsion polymerization in the presence of initiator 2, crosslinking agent 2 and emulsifier 2.

16. The method according to claim 15, characterized in that, The conditions for the reverse emulsion polymerization include: The initiator 2 is selected from one or more of potassium persulfate and ammonium persulfate; and / or The crosslinking agent 2 is selected from one or more of N,N-methylenebisacrylamide and ethylene glycol diacrylate; and / or The emulsifier 2 is selected from one or more of Span80, OP-4, and Span-60; and / or The reverse emulsion polymerization temperature is 40-70℃; and / or The reverse emulsion polymerization time is 2-8 hours; and / or Reverse emulsion polymerization at pH 8-9; and / or Inverse emulsion polymerization is carried out in an inert gas; and / or The reverse emulsion polymerization was carried out dynamically at a rotation speed of 100-600 rpm.

17. A polymer gel particle, characterized in that, The polymer gel particles are prepared according to the method described in any one of claims 11-16.

18. The application of a polymer gel particle as a drilling fluid plugging agent and / or completion fluid plugging agent, characterized in that, The polymer gel particles are any one of the polymer gel particles described in claims 1-10 and 17.

19. The application according to claim 18, characterized in that, The polymer gel particles are used as a water-based drilling fluid plugging agent and / or an oil-based drilling fluid plugging agent.

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