A polymer and a lost circulation material mixture containing the polymer and applications thereof

Abstract

The present application relates to the technical field of drilling plugging, in particular to a polymer, a plugging agent mixture containing the polymer and application. The polymer is prepared by polymerization of monomer A, monomer B, monomer C, monomer D and monomer E. The chemical structural formula of monomer A is: the chemical structural formula of monomer B is: the chemical structural formula of monomer C is: the chemical structural formula of monomer D is: and the chemical structural formula of monomer E is: wherein the molar ratio of monomer A, monomer B, monomer C, monomer D and monomer E is (0.2-1):(0.3-1):(0.5-1):(0.2-1):(0.3-1). The polymer can effectively improve its adhesion in the formation, cooperate with rigid plugging material, flexible plugging material and the like to form a plugging agent mixture with certain adhesion, and meet the plugging of the formation in the drilling process.

Description

Technical Field

[0001] This invention relates to the field of well drilling plugging technology, and more specifically to a polymer and a plugging agent mixture containing the polymer and its applications. Background Technology

[0002] In the exploration, development, and extraction of oil and gas, the connecting passage between the surface and underground is called a wellbore. Wellbore drilling is a crucial step in oil and gas field development and one of the most economical and effective ways to obtain oil and gas. However, this process is often accompanied by the loss of circulating fluids. Depending on the geological structure, geological factors, rock properties, and lithology of the encountered formations, well leakage during drilling can be mainly classified into two forms: permeable leakage and fracture leakage. During drilling, the loss of circulating fluids, such as drilling fluid, due to factors such as geological structure, rock properties, drilling parameters, and tools, is a significant factor or cause of potential well control risks and wellbore structural damage. Therefore, materials are often added during drilling to seal the formation, suppress or reduce the risk of leakage, or seal existing fractures or pores.

[0003] Common drilling plugging materials often use rigid or flexible granular substances as the main sealing materials or plugging agents. Rigid materials, due to their brittleness, are easily broken after being pumped into the formation, or they may be swept in along with other rigid materials, creating a sealing effect at the ends of fractures or pores. This makes it difficult to pump the plugging material into the fractured or porous formation, leading to plugging failure. Furthermore, the influx of foreign fluids into the formation, such as drilling circulation fluid and plugging slurry, can cause excessive fluid in the wellbore in a short period, which the formation cannot absorb. This results in the backflow of drilling circulation fluid and plugging slurry into the wellbore, mixing the newly pumped rigid plugging material into the wellbore. This can also easily cause blockage of drilling equipment or tools such as drill strings, drill bits, blowout preventers, and well control safety devices, resulting in irreversible adverse effects.

[0004] Existing sealing polymers or plugging gels primarily rely on colloids or micelles to form a sealant within cracks or pores pumped into the formation, working in conjunction with rigid or flexible plugging materials to achieve a sealing effect. Chinese invention patent CN111961160B discloses an active polymer for a high-molecular-weight gel plugging agent, which is a polycondensable macromolecular polymer with hydroxymethyl groups on its surface; it is prepared by reverse microemulsion polymerization of hydrophobic monomers and acrylamide monomers in the presence of a functional crosslinking agent, chain extender, initiator, and ethylenediaminetetraacetic acid. However, when the sealing polymer cannot form adhesion to the rock surface, it cannot adhere to the rock surface and form a strong adhesive layer. This causes conventional hydrophilic polymers to slip in sandstone pores and microcracks, resulting in poor sealing performance. Furthermore, when encountering formation water or groundwater, it is easily diluted, causing a decrease in gel strength and resulting in the plugging gel losing its original sealing properties. In particular, when this type of gel is pumped into sandstone formations with high porosity and permeability and containing micro-fractures, it is more susceptible to intrusion by formation water, edge water, and bottom water.

[0005] Existing conventional hydrophilic polymer gels are used as deformable, flexible materials added to plugging materials, mixed with rigid materials, and pumped to the lost formation. For example, Chinese invention patent CN114621392B discloses a high-temperature resistant organosilicon polymer gel plugging agent, which is formed by crosslinking organosilicon polymers in water, polymerized from vinyl monomers and organosilicon monomers. Such plugging agents are affected by many factors, including their own molecular structure, the monomer properties of the synthesized polymer, and molecular charge, resulting in poor adhesion of existing polymer gels to rock surfaces. Especially in aquifers or after drilling to connect to water layers, hydrophilic polymer gels are easily diluted or dispersed, forming gel bodies that float on the surface or in the water layer, making it difficult for them to flow with the water or migrate with the formation water to the lost formation. This makes it difficult for the rigid or flexible materials encapsulated by the plugging gel to seal the cracks or pores in the lost formation, resulting in waste of plugging materials and plugging failure.

[0006] Therefore, it is essential to develop a polymer with strong formation adhesion ability to improve the adhesion and bonding ability of polymer gels in formations, especially in aquifers or water-swept formations, thereby improving the sealing effect of leak plugging in aquifers, water-swept formations, fractured formations, or porous formations. Summary of the Invention

[0007] In view of this, the present invention provides a polymer that can effectively improve its adhesion in the formation, and can be combined with rigid or flexible plugging materials to form a plugging agent mixture with a certain adhesive capacity, thereby meeting the requirements for formation sealing during drilling and better implementing well plugging operations. The present invention also provides a plugging agent mixture containing this polymer and its application.

[0008] To solve at least one of the above-mentioned technical problems, the present invention adopts the following technical solution: According to one aspect of the present invention, a polymer is provided, which is prepared by polymerization of monomers A, B, C, D, and E. The chemical structural formula of monomer A is:

[0009] The chemical structural formula of monomer B is:

[0010] The chemical structural formula of monomer C is:

[0011] The chemical structural formula of monomer D is:

[0012] The chemical structural formula of monomer E is:

[0013] The molar ratio of monomers A, B, C, D and E is (0.2~1):(0.3~1):(0.5~1):(0.2~1):(0.3~1).

[0014] According to one embodiment of the present invention, the polymer has a viscosity-average molecular weight of 15 million to 20 million.

[0015] According to one embodiment of the present invention, the polymer has a molecular weight distribution of 1.1 to 1.3.

[0016] According to another aspect of the present invention, a method for preparing the polymer of any of the above embodiments is provided, comprising the following steps: S1. Add the emulsifier to the water and stir at 500-600 r / min for 20-30 min; then add the alkali metal carbonate and / or alkali metal bicarbonate and continue stirring at 500-600 r / min until the three are mixed evenly to prepare the emulsifier mixture. S2. The emulsifier mixture obtained in step S1, along with monomers A, B, C, D, and E, are added to a reaction vessel. Inert gas is introduced into the reaction vessel at a flow rate of 0.3-0.5 L / min. The stirrer is turned on and stirred at a speed of 300-400 r / min for 15-20 min. Then, the temperature is raised to 40-50°C and stabilized for 8-10 min. The first part by weight of the initiator is added, and inert gas is introduced and stirred at a speed of 200-300 r / min for 15-20 min. The temperature is then raised to 50-60°C and stabilized for 5-8 min. The second part by weight of the initiator is added and stirred at a speed of 200-300 r / min for 20-30 min. The temperature is then raised to 60-70°C and the reaction is maintained for 6-8 h to obtain a reaction mixture. The first part by weight accounts for 1 / 5 to 1 / 3 of the sum of the first and second parts by weight. S3. Cool the reaction mixture obtained in step S2 to 40~45°C, add the alkali metal carbonate or alkali metal bicarbonate selected in step S1 to adjust its pH value to neutral, and further cool to 25~30°C to obtain the polymer.

[0017] According to one embodiment of the present invention, in step S1, the ratio of the amount of emulsifier to the volume of water is 0.4~0.6:100mol / L; the emulsifier is at least one selected from OP-50, Span60, polysorbate-85, OS-15, sodium dodecyl sulfonate, and sodium dodecyl diphenyl ether disulfonate.

[0018] According to one embodiment of the present invention, in step S1, the ratio of the amount of alkali metal carbonate and / or alkali metal bicarbonate to the volume of water is 0.2~0.5:100mol / L; the alkali metal carbonate is sodium carbonate and / or potassium carbonate; the alkali metal bicarbonate is sodium bicarbonate and / or potassium bicarbonate.

[0019] According to one embodiment of the present invention, in step S2, the heating rate is maintained at 2°C / min during each heating process; the reaction is carried out under the protection of an inert gas; the inert gas refers to a gas that does not participate in the polymerization reaction, such as nitrogen or helium, and the inert gas is introduced into the reaction vessel at a flow rate of 0.3~0.5L / min.

[0020] According to one embodiment of the present invention, in step S2, the sum of the amounts of monomers A, B, C, D and E to the volume of water is 3~5:100mol / L; the initiator is potassium persulfate or ammonium persulfate; the ratio of the total amount of initiator to the volume of water is 0.02~0.06:100mol / L; and the volume of water is the same as the volume of water used in step S1.

[0021] According to one embodiment of the present invention, in step S2, the liquid monomers among monomers A, B, C, D and E are directly mixed with the emulsifier mixture; the solid monomers among monomers A, B, C, D and E are first dissolved in distilled water to prepare a solution of 2-5 g / mL before being mixed with the emulsifier mixture.

[0022] According to another aspect of the present invention, a sealant mixture is provided, comprising the polymer according to any one of claims 1-9, wherein the sealant mixture comprises, by weight, the following components: 10-20 parts polymer, 10-20 parts waste polyvinyl chloride granules, 5-10 parts sawdust, 5-10 parts aluminum flakes, 5-10 parts ferric carbonate powder, 5-10 parts reed stalk fragments, 5-10 parts sponge blocks, 5-10 parts waste sheet metal, 5-10 parts waste cardboard, 5-10 parts waste steel wool, and 10-20 parts mussel shell fragments.

[0023] According to one embodiment of the present invention, the polymer is a particle with a particle size of 20 to 40 mesh.

[0024] According to one embodiment of the present invention, the sawdust is a mixture of 5-10 parts by weight of poplar sawdust with a particle size of 20-40 mesh, 10-20 parts by weight of birch sawdust with a particle size of 60-80 mesh, and 10-20 parts by weight of pine sawdust with a particle size of 100-120 mesh.

[0025] According to one embodiment of the present invention, the waste polyvinyl chloride granules are composed of 20-50 parts by weight of hexagonal prism-shaped granules and 20-50 parts by weight of cylindrical granules, wherein the hexagonal prism-shaped granules have a side length of 2-6 cm and a length of 2-10 cm; and the cylindrical granules have a diameter of 1-6 cm and a length of 2-10 cm.

[0026] According to one embodiment of the present invention, the aluminum sheet has a length of 1-5cm, a width of 1-3cm, and a thickness of 1-3mm.

[0027] According to one embodiment of the present invention, the reed straw fragments are a mixture of dried alkalized reed straw with a particle size of 10-30 mesh obtained by soaking in a 10-20 wt.% sodium carbonate or potassium carbonate solution for 72 hours and then drying for 120 hours.

[0028] According to one embodiment of the present invention, the waste steel wool ball is formed by curling up waste steel wool with a length of 5-10cm and a diameter of 2mm-10mm.

[0029] According to one embodiment of the present invention, the waste cardboard is a square cardboard with a side length of 2-5cm and a thickness of 0.5-5mm.

[0030] According to one embodiment of the present invention, the scrap iron sheet is a mixture formed by mixing square iron sheets with a side length of 2-5cm and a thickness of 0.5-2mm and parallelogram iron sheets with side lengths of 2-5cm and 3-10cm and a thickness of 1-5mm in a 1:1 ratio.

[0031] According to one embodiment of the present invention, the ferric carbonate has a particle size of 100~400nm, the mussel shell fragments have a particle size of 10~20 mesh, and the sponge block is a cubic block with a side length of 1~10cm.

[0032] According to another aspect of the present invention, an application of any of the above-mentioned plugging agent mixtures in oil and gas field exploration and development is provided.

[0033] By adopting the above technical solution, the present invention has at least one of the following advantages compared with the prior art: (1) The polymer according to the present invention forms a liquid with a certain viscosity through intermolecular association, interleaving and cross-linking of molecular chains, which can effectively increase the viscosity and shear force of the polymer used for plugging, and is beneficial for suspension, such as weighting materials, rock fragments in the strata, sand and other particulate materials.

[0034] (2) The polymer according to the present invention can be directly added to the prepared polymer for sealing. Alternatively, the solid product can be obtained by evaporating the emulsion at 25~30°C and then used for liquid preparation.

[0035] (3) During the pumping process, the polymer of the present invention has excellent recoverable deformation properties and forms a variable three-dimensional network structure due to the interlacing, crossing and entanglement of molecular chains in the physical space of the polymer used for plugging, which can reduce the pumping friction.

[0036] (4) Compared with the prior art, the sealant mixture according to the present invention has the viscosity of the sealant increased by the interaction of polymer molecules through interlacing, crossing and entanglement or other substances introduced from the outside. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to specific examples.

[0038] It should be understood that the embodiments of the invention shown in the exemplary embodiments are merely illustrative. Although only a few embodiments have been described in detail in this invention, those skilled in the art will readily recognize that various modifications are possible without substantially departing from the teachings of the invention. Accordingly, all such modifications should be included within the scope of the invention. Other substitutions, modifications, variations, and deletions can be made to the design, operating conditions, and parameters of the following exemplary embodiments without departing from the spirit of the invention.

[0039] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and 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. Unless otherwise specified, the room temperature of the present invention is 25 ± 2°C. Furthermore, unless otherwise specified, all materials used in the present invention are commercially available.

[0040] According to one aspect of the present invention, a polymer is provided, which is prepared by polymerization of monomers A, B, C, D, and E. The chemical structural formula of monomer A is:

[0041] The chemical structural formula of monomer B is:

[0042] The chemical structural formula of monomer C is:

[0043] The chemical structural formula of monomer D is:

[0044] The chemical structural formula of monomer E is:

[0045] In the embodiments of the present invention, the molar ratio of monomer A, monomer B, monomer C, monomer D and monomer E is (0.2~1):(0.3~1):(0.5~1):(0.2~1):(0.3~1); the viscosity-average molecular weight of the polymer is 15 million to 20 million; and the molecular weight distribution of the polymer is 1.1 to 1.3.

[0046] The catechol hydroxyl structure contained in the polymer of this invention can chemically react with silica to form a relatively stable adhesion, which is beneficial for the polymer to adhere to the solid surface containing silica. The phenolic hydroxyl structure it contains allows for internal cross-linking when iron ions, iron-containing solids or liquids are introduced from the outside, forming a more stable gel with a certain strength. Furthermore, because the polymer contains ester groups, after being heated upon entering the formation, it can penetrate into cracks or pores and remain within them, achieving the purpose of adhering to loose porous particles and filling cracks or microcracks. Moreover, the polymer contains carboxyl groups, which, after being pumped into the formation, can dissolve some substances in the rock, such as plugging materials containing calcium carbonate or magnesium carbonate, or acid-soluble carbonate components contained in the rock itself, helping the polymer to better penetrate the formation and embed the carried sealing material into the formation cracks or pores, thus achieving a sealing effect. In addition, the carboxylic acid structure contained in the polymer can also dissolve other acid-soluble substances, such as iron filings and rust, which helps to release more iron ions around the polymer, forming multiple cross-linking points between the polymer and iron ions, and playing a positive role in improving the gel strength of the polymer.

[0047] The high-strength gel formed by the polymer according to the present invention helps to encapsulate rigid, flexible, and other plugging materials. Through the encapsulation effect of the high-strength gel, these rigid, flexible, and other plugging materials do not settle, resulting in a better sealing effect on the formation. Furthermore, it can gradually form after entering the formation, increasing the strength of the gel. Therefore, the group structure and molecular configuration of the polymer help reduce the pumping resistance of the polymer, allowing it to be transported to the lost formation more effectively and deeply. In addition, after being pumped into the formation, the polymer gradually forms a cross-linked structure; with the continuous cross-linking of multiple cross-linking sites, the strength of the gel itself is increased. This prevents formation water, edge water, and bottom water that communicate after drilling loss from diluting and dispersing the plugging material, the polymer gel, the plugging material encapsulated by the polymer gel, or the plugging agent mixture. This facilitates the sealing of the formation by the plugging material, plugging agent mixture, and plugging gel.

[0048] The above polymer is prepared by the following steps: S1. Add the emulsifier to the water and stir at 500-600 r / min for 20-30 min; then add the alkali metal carbonate and / or alkali metal bicarbonate and continue stirring at 500-600 r / min until the three are mixed evenly to prepare the emulsifier mixture. S2. The emulsifier mixture obtained in step S1, along with monomers A, B, C, D, and E, are added to a reaction vessel. Inert gas is introduced into the reaction vessel at a flow rate of 0.3-0.5 L / min. The stirrer is turned on and stirred at a speed of 300-400 r / min for 15-20 min. Then, the temperature is raised to 40-50°C and stabilized for 8-10 min. The first part by weight of the initiator is added, and inert gas is introduced and stirred at a speed of 200-300 r / min for 15-20 min. The temperature is then raised to 50-60°C and stabilized for 5-8 min. The second part by weight of the initiator is added and stirred at a speed of 200-300 r / min for 20-30 min. The temperature is then raised to 60-70°C and the reaction is maintained for 6-8 h to obtain a reaction mixture. The first part by weight accounts for 1 / 5 to 1 / 3 of the sum of the first and second parts by weight. S3. Cool the reaction mixture obtained in step S2 to 40~45℃, add the alkali metal carbonate or alkali metal bicarbonate selected in step S1 to adjust its pH value to neutral, and further cool to 25~30℃ to obtain the polymer.

[0049] Specifically, in step S1, the molar ratio of emulsifier to water volume is 0.4~0.6:100mol / L; the emulsifier is at least one of OP-50, Span60, polysorbate-85, OS-15, sodium dodecyl sulfonate, and sodium dodecyl diphenyl ether disulfonate. The molar ratio of alkali metal carbonate and / or alkali metal bicarbonate to water volume is 0.2~0.5:100mol / L; the alkali metal carbonate is sodium carbonate and / or potassium carbonate; the alkali metal bicarbonate is sodium bicarbonate and / or potassium bicarbonate. In step S2, the heating rate is maintained at 2℃ / min during each heating process; the reaction is carried out under the protection of a non-reactive gas; the non-reactive gas refers to a gas that does not participate in the polymerization reaction, specifically such as nitrogen or helium, and the non-reactive gas is introduced into the reaction vessel at a flow rate of 0.3~0.5L / min. The sum of the moles of monomers A, B, C, D, and E, in volume of water, is 3-5:100 mol / L; the initiator is potassium persulfate or ammonium persulfate; the mole ratio of the initiator to the volume of water is 0.02-0.06:100 mol / L; the volume of water is the same as the volume of water used in step S1. When preparing the pre-emulsion, the liquid monomers of monomers A, B, C, D, and E are directly mixed with the emulsifier mixture; the solid monomers of monomers A, B, C, D, and E are first dissolved in distilled water to prepare a solution of 2-5 g / mL before being mixed with the emulsifier mixture.

[0050] In embodiments of the present invention, monomer C can be synthesized through the following steps: S21. Mix dopamine hydrochloride, sodium borate, sodium carbonate, and deionized water; S22. Add methacrylic anhydride solution dropwise to adjust the pH value to between 9 and 10 to obtain dopamine methacrylamide.

[0051] The reaction equation is as follows:

[0052] The weight ratio of dopamine hydrochloride, sodium borate, sodium carbonate, deionized water, and methacrylic anhydride is 3:15:2:6; the reaction temperature can be controlled at 40~80℃, and the reaction time can be controlled at 20±5h; the pH value is adjusted using 1.0mol / L sodium hydroxide solution.

[0053] It should be understood that there are no particular restrictions on the preparation and formulation methods of the polymer or other liquids used for plugging. Preparation methods well known to those skilled in the art can be used, and will not be elaborated here. Furthermore, the specific operations listed below should not be construed as limitations on the present invention.

[0054] The polymers according to the present invention will be further described below with reference to specific embodiments and test examples.

[0055] Example 1 The polymer according to this embodiment is prepared by the following steps: S1. Add 1 mol sodium dodecyl sulfonate, 1 mol sodium carbonate and 1 mol OP-50 to 500 mL distilled water and stir at high speed (500 r / min~550 r / min) for 30 min to obtain an emulsifier mixture; S2. Add monomers A, B, C, D, and E dropwise to the emulsifier mixture over 15 minutes in the following molar ratio of 0.2:0.3:0.5:0.2:0.3. During this time, purge with nitrogen at a rate of 0.3 L / min and stir the emulsion at a shear rate of 300 r / min using a shear emulsifier until the mixture is homogeneous. S3. Transfer the emulsion obtained in step S2 to a reaction vessel and purge with nitrogen at a rate of 0.3 L / min. Heat the emulsion to 45°C at a stirring speed of 300 r / min and a heating rate of 1°C / min and keep it at that temperature. After keeping it at that temperature for 5 min, add 1 / 4 of the weight of potassium persulfate. Continue stirring at 300 r / min and introduce nitrogen gas at a rate of 0.3 L / min for 15 min. Then, heat the emulsion to 50°C at a rate of 1°C / min and keep it at that temperature for 5 min. After that, add the remaining 3 / 4 of the weight of potassium persulfate. Continue stirring at 300 r / min and nitrogen gas is introduced at a rate of 0.2 L / min for 15 min. Then, heat the emulsion to 60 °C at a heating rate of 1 °C / min and keep it at that temperature. Stop the nitrogen gas introduction, close the reaction vessel, and keep the reaction at that temperature for 6 h. Stop the reaction and continue stirring at a rate of 150 r / min. After the reaction product cools down to 50°C naturally, add Na2CO3 to adjust the pH to 7. Continue cooling to 40°C and then stop stirring to obtain an emulsion containing polymer.

[0056] In step S3, potassium persulfate is dissolved in water to prepare a solution, which is then added to the reactor. Specifically, the ratio of the amount of potassium persulfate to the volume of water is 0.02:100.

[0057] S4. The solid obtained by evaporating the emulsion obtained in step S3 at a constant temperature of 30°C is the polymer.

[0058] To accurately characterize the properties of the polymer, it was washed with anhydrous ethanol and then dried.

[0059] Testing showed that the polymer prepared in Example 1 had a viscosity-average molecular weight of 15 million and a molecular weight distribution coefficient of 1.2. Furthermore, according to the 1H NMR spectrum, no proton peaks for olefin double bonds were found in the range of 5.5–6.5 ppm, indicating that monomers A, B, C, D, and E formed the polymer through a polymerization reaction. Infrared spectroscopy showed peaks in the 1650–1700 cm⁻¹ range. -1 The presence of characteristic peaks for carboxylic acids indicates the presence of monomer A in the polymer; the peaks are located in the 3500–3300 cm⁻¹ range. -1 1360~1020cm -1 The presence of characteristic peaks for amine groups indicates the presence of monomer B in the polymer; at 1500 cm⁻¹ -1 Left and right, 700~800cm -1 The presence of characteristic peaks for phenol indicates that the polymer contains the monomer C structure; 1740~1750 cm⁻¹ -1 The presence of characteristic peaks for ester groups indicates that the polymer contains monomer D; 1350~1260 cm⁻¹ -1 Characteristic peaks of alcohols appear, 3330-3060 cm⁻¹ -1 The presence of a characteristic peak for secondary amide indicates that the polymer contains the structure of monomer E.

[0060] Example 2 The polymer according to this embodiment is prepared by the following steps: S1. Add 1 mol sodium dodecyl sulfonate, 1 mol sodium carbonate and 1 mol OP-50 to 500 mL distilled water and stir at high speed (500 r / min~550 r / min) for 30 min to obtain an emulsifier mixture; S2. Add monomers A, B, C, D, and E dropwise to the emulsifier mixture over 15 minutes in the following molar ratio of 0.5:0.5:0.7:0.5:0.6. During this time, purge with nitrogen at a rate of 0.3 L / min and stir the emulsion at a shear rate of 300 r / min using a shear emulsifier until the mixture is homogeneous. S3. Transfer the emulsion obtained in step S2 to a reaction vessel and purge with nitrogen at a rate of 0.3 L / min. Heat the emulsion to 45°C at a stirring speed of 300 r / min and a heating rate of 1°C / min and keep it at that temperature. After keeping it at that temperature for 5 min, add 1 / 4 of the weight of potassium persulfate. Continue stirring at 300 r / min and introduce nitrogen gas at a rate of 0.3 L / min for 15 min. Then, heat the emulsion to 50°C at a rate of 1°C / min and keep it at that temperature for 5 min. After that, add the remaining 3 / 4 of the weight of potassium persulfate. Continue stirring at 300 r / min and nitrogen gas is introduced at a rate of 0.2 L / min for 15 min. Then, heat the emulsion to 60 °C at a heating rate of 1 °C / min and keep it at that temperature. Stop the nitrogen gas introduction, close the reaction vessel, and keep the reaction at that temperature for 6 h. Stop the reaction and continue stirring at a rate of 150 r / min. After the reaction product cools down to 50°C naturally, add Na2CO3 to adjust the pH to 7. Continue cooling to 40°C and then stop stirring to obtain an emulsion containing polymer.

[0061] In step S3, potassium persulfate is dissolved in water to prepare a solution, which is then added to the reactor. Specifically, the ratio of the amount of potassium persulfate to the volume of water is 0.05:100.

[0062] S4. The solid obtained by evaporating the emulsion obtained in step S3 at a constant temperature of 30°C is the polymer.

[0063] To accurately characterize the properties of the polymer, it was purified by washing with anhydrous ethanol and then dried.

[0064] Testing showed that the polymer prepared in Example 2 had a viscosity-average molecular weight of 15 million and a molecular weight distribution coefficient of 1.2. Furthermore, according to the 1H NMR spectrum, no proton peaks for olefin double bonds were found in the range of 5.5–6.5 ppm, indicating that monomers A, B, C, D, and E formed the polymer through a polymerization reaction. Infrared spectroscopy showed peaks in the 1650–1700 cm⁻¹ range. -1 The presence of characteristic peaks for carboxylic acids indicates the presence of monomer A in the polymer; the peaks are located in the 3500–3300 cm⁻¹ range. -1 1360~1020cm -1 The presence of characteristic peaks for amine groups indicates the presence of monomer B in the polymer; at 1500 cm⁻¹ -1 Left and right, 700~800cm -1 The presence of characteristic peaks for phenol indicates that the polymer contains the monomer C structure; 1740~1750 cm⁻¹ -1 The presence of characteristic peaks for ester groups indicates that the polymer contains monomer D; 1350~1260 cm⁻¹ -1 Characteristic peaks of alcohols appear, 3330-3060 cm⁻¹ -1 The presence of a characteristic peak for secondary amide indicates that the polymer contains the structure of monomer E.

[0065] Example 3 The polymer according to this embodiment is prepared by the following steps: S1. Add 1 mol sodium dodecyl sulfonate, 1 mol sodium carbonate and 1 mol OP-50 to 500 mL distilled water and stir at high speed (500 r / min~550 r / min) for 30 min to obtain an emulsifier mixture; S2. Add monomers A, B, C, D and E dropwise to the emulsifier mixture in the following molar ratio of 1:1:1:1:1 over 15 min. During this time, nitrogen gas is introduced at a rate of 0.3 L / min for protection, and the emulsion is stirred with a shear emulsifying stirrer at a shear rate of 300 r / min until the mixture is homogeneous. S3. Transfer the emulsion obtained in step S2 to a reaction vessel and purge with nitrogen at a rate of 0.3 L / min. Heat the emulsion to 45°C at a stirring speed of 300 r / min and a heating rate of 1°C / min and keep it at that temperature. After keeping it at that temperature for 5 min, add 1 / 4 of the weight of potassium persulfate. Continue stirring at 300 r / min and introduce nitrogen gas at a rate of 0.3 L / min for 15 min. Then, heat the emulsion to 50°C at a rate of 1°C / min and keep it at that temperature for 5 min. After that, add the remaining 3 / 4 of the weight of potassium persulfate. Continue stirring at 300 r / min and nitrogen gas is introduced at a rate of 0.2 L / min for 15 min. Then, heat the emulsion to 60 °C at a heating rate of 1 °C / min and keep it at that temperature. Stop the nitrogen gas introduction, close the reaction vessel, and keep the reaction at that temperature for 6 h. Stop the reaction and continue stirring at a rate of 150 r / min. After the reaction product cools down to 50°C naturally, add Na2CO3 to adjust the pH to 7. Continue cooling to 40°C and then stop stirring to obtain an emulsion containing polymer.

[0066] In step S3, ammonium persulfate is dissolved in water to prepare a solution, which is then added to the reactor. Specifically, the ratio of the amount of ammonium persulfate to the volume of water is 0.06:100.

[0067] S4. The solid obtained by evaporating the emulsion obtained in step S3 at a constant temperature of 30°C is the polymer.

[0068] To accurately characterize the properties of the polymer, it was purified by washing with anhydrous ethanol and then dried.

[0069] Testing showed that the polymer prepared in Example 3 had a viscosity-average molecular weight of 15 million and a molecular weight distribution coefficient of 1.2. Furthermore, according to the 1H NMR spectrum, no proton peaks for olefin double bonds were found in the range of 5.5–6.5 ppm, indicating that monomers A, B, C, D, and E formed the polymer through a polymerization reaction. Infrared spectroscopy showed peaks in the 1650–1700 cm⁻¹ range. -1 The presence of characteristic peaks for carboxylic acids indicates the presence of monomer A in the polymer; the peaks are located in the 3500–3300 cm⁻¹ range. -1 1360~1020cm -1 The presence of characteristic peaks for amine groups indicates the presence of monomer B in the polymer; at 1500 cm⁻¹ -1 Left and right, 700~800cm -1 The presence of characteristic peaks for phenol indicates that the polymer contains the monomer C structure; 1740~1750 cm⁻¹ -1 The presence of characteristic peaks for ester groups indicates that the polymer contains monomer D; 1350~1260 cm⁻¹ -1 Characteristic peaks of alcohols appear, 3330-3060 cm⁻¹ -1 The presence of a characteristic peak for secondary amide indicates that the polymer contains the structure of monomer E.

[0070] The polymer according to the present invention can be applied to the sealant mixture in the form of solid particles, or it can be diluted with a diluent to form a premixed slurry before being applied to the sealant mixture. The diluent can be water, bentonite slurry, or other similar substances. In embodiments of the present invention, when water is used as the diluent, the polymer's proportion in the premixed slurry is preferably 10 wt.% to 40 wt.%.

[0071] Test Example 1 The polymer prepared in Example 3 was added at a rate of 20 wt.% and thoroughly mixed with deionized water to form a mixture. Polyacrylamide with a viscosity-average molecular weight of 15 million was added at a rate of 20 wt.% and thoroughly mixed with deionized water to form a mixture. Hydroxypropyl guar gum was added at a rate of 20 wt.% and thoroughly mixed with deionized water to form a mixture. A constant flow pump was used to pump the mixture at a flow rate of 3 ml / min. The clamp temperature was 80 degrees Celsius. The viscosity and flowability of the three polymers in a sand-filled tube were tested. The sand-filled tube was filled with quartz sand with a mesh size of 200-400. The experimental results are shown in Table 1.

[0072] Table 1. Flowability test of three polymers in sand-filled pipes

[0073] As shown in Table 1, hydroxypropyl guar gum exhibited the lowest pumping pressure differential in the initial 30 minutes. This is because its molecular structure, still composed of macromolecular chains of mannose and galactose, lacks groups capable of adhering to or sticking with silica in the quartz sand. Its ability to maintain a certain pressure differential is also attributed to the strong rigidity of its ring-like structure, which scrapes against the quartz sand surface. Furthermore, compared to the multi-molecular chain structure and direct-connection structure of Example 3 and polyacrylamide, it also exhibited lower flow resistance in the sand-filled pipe.

[0074] In Example 3, the presence of o-phenolic hydroxyl groups allows for adhesion and bonding with silica in the quartz sand, thereby increasing the pumping pressure differential. Example 3 is also more easily adhered to in the sand-filled pipe, achieving a sealing and blocking effect.

[0075] According to Drilling Fluid Technology (Revised Edition), sandstone surfaces exhibit negative electrical charge. When amino groups are hydrolyzed and protonated, positively charged cationic structures can be formed, thereby increasing the adhesion properties of Example 3 on sandstone surfaces.

[0076] In addition, the ester groups in Example 3 can also cause the polymer to melt after being heated and flow into the gaps between the quartz sand particles in the sand filling pipe, thereby sticking the quartz sand together.

[0077] As time progressed, the three polymers were pumped into the sand-filled tube. With prolonged heating time, all three polymers adhered to the sand-filled tube to a certain extent. Compared to Example 3, the ester, ortho-phenolic hydroxyl, and amino groups present exhibited better adhesion and bonding effects, while the other two polymers showed poor adhesion and sealing capabilities.

[0078] Test Example 2 The polymer prepared in Example 3 was added at a rate of 20 wt.% and thoroughly mixed with deionized water to form a mixture, which was designated as premixed slurry-1. The polymer prepared in Example 3 was added at a rate of 45 wt.% and thoroughly mixed with deionized water to form a mixture, which was designated as premixed slurry-2. The sealing properties of the mixtures were then tested.

[0079] Six sandstone cores were taken and placed in core holders. Premixed slurry solutions, designated Premixed Slurry-1 and Premixed Slurry-2, were injected using a constant flow pump at a rate of 3 ml / min. The holder temperature was maintained at 80 degrees Celsius. The pressure gauge readings at the liquid inflow ports were observed to determine the sealing effect. The experimental results are shown in Table 2.

[0080] Table 2 Polymer plugging performance test for leak sealing

[0081] The polymer prepared in Example 3 was added at a rate of 20 wt.% and thoroughly mixed with deionized water to form Mixture-1; Polyacrylamide with a viscosity-average molecular weight of 15 million was added at a rate of 20 wt.% and thoroughly mixed with deionized water to form Mixture-2. The two mixtures were then injected into the rock core.

[0082] Four sandstone cores were taken and placed in core holders. The two mixtures were injected using a constant flow pump at a rate of 3 ml / min. The holder temperature was 80 degrees Celsius. The pressure gauge readings at the liquid inlet were observed to determine the sealing effect. The experimental results are shown in Table 3.

[0083] Table 3 Polymer plugging performance test for leak sealing

[0084] As can be seen from Tables 2 and 3, the polymer of this invention exhibits superior sealing performance compared to polyacrylamide in both high-permeability and low-permeability rock cores. Table 2 shows that the sealing pressure-bearing capacity decreases significantly with decreasing sandstone permeability; however, the sealing pressure-bearing capacity significantly improves with increasing concentration in Example 3. The sealing effect is even better in high-permeability rock cores.

[0085] As can be seen from Table 3, both the mixture of Example 3 and polyacrylamide of the same concentration exhibited a certain sealing ability in cores with different permeabilities; however, in cores with the same permeability, the sealing effect of Example 3 was better.

[0086] Test Example 3 The polymer prepared in Example 3 was added at a rate of 20 wt.% and thoroughly mixed with deionized water to form a mixture. 100 ml of this mixture was then added to ferric carbonate powder, the mixture was heated to 60°C, and allowed to stand for 30 minutes.

[0087] After 30 minutes, the liquid in the beaker containing the polymer mixture was observed to change from colorless to red. The mixture was then stirred clockwise with a glass rod; as the stirring amplitude increased, the viscosity of the mixture increased significantly.

[0088] This indicates that the aqueous solution formed after the polymer dissolves in water is somewhat acidic, capable of dissolving acid-soluble substances such as ferric carbonate powder. As the ferric carbonate powder gradually releases iron ions, these ions form cross-linking points with the phenolic hydroxyl groups in the polymer, creating cross-linked structures between the polymer molecular chains, thereby increasing the polymer's strength.

[0089] Test Example 4 The polymer particles prepared in Example 3 were spread on a sandstone sample (permeability 300 mD, size 3 cm × 3 cm × 1 cm) and the sandstone sample was heated. After the polymer was completely melted, it was found that the polymer penetrated between the sandstone particles in the sample and no polymer was found to seep out from the other side of the sample.

[0090] This demonstrates that polymer particles, when heated, exhibit excellent fluidity, allowing them to penetrate the pores of sandstone and embed themselves within the sandstone slab.

[0091] When the rock slab was broken, it was found that the areas where the polymer had flowed remained intact and lumpy. This indicates that the polymer was embedded in the pores of the sandstone, binding the loose sandstone particles together.

[0092] Take two more sandstone slabs from the same stratum, spread the polymer particles prepared in Example 3 on the sandstone sample (permeability 300mD, size 3cm×3cm×1cm), and heat the sandstone slab. After the polymer is completely melted, it is tightly bonded to the other slab.

[0093] One hour later, one of the sandstone slabs was fixed, and the other slab was pulled with a tensile tester. A significant reading was observed on the tester. Repeating the experiment, it was clearly observed that as the mass of the polymer particles increased, the tensile tester reading gradually increased. This indicates that the polymer forms a high-strength adhesion between the sandstone slabs.

[0094] According to another aspect of the present invention, a sealant mixture containing the polymer of any of the above embodiments is provided, which generally comprises the following components in parts by weight: 10-20 parts polymer, 10-20 parts waste polyvinyl chloride granules, 5-10 parts sawdust, 5-10 parts aluminum flakes, 5-10 parts ferric carbonate powder, 5-10 parts reed stalk fragments, 5-10 parts sponge blocks, 5-10 parts waste sheet metal, 5-10 parts waste cardboard, 5-10 parts waste steel wool, and 10-20 parts mussel shell fragments.

[0095] In a preferred embodiment of the present invention, the sawdust is a mixture of 5-10 parts by weight of poplar sawdust with a particle size of 20-40 mesh, 10-20 parts by weight of birch sawdust with a particle size of 60-80 mesh, and 10-20 parts by weight of pine sawdust with a particle size of 100-120 mesh; wherein, the poplar sawdust is dried alkalized poplar sawdust obtained by soaking in a 10-20 wt.% sodium bicarbonate or potassium bicarbonate solution for 72 hours and then drying for 72 hours; the birch sawdust is dried alkalized birch sawdust obtained by soaking in a 5-10 wt.% sodium hydroxide or potassium hydroxide solution for 24 hours and then drying for 72 hours; and the pine sawdust is dried alkalized pine sawdust obtained by soaking in a 15-20 wt.% sodium carbonate or potassium carbonate solution for 48 hours and then drying for 48 hours.

[0096] In a preferred embodiment of the present invention, the waste polyvinyl chloride granules are composed of 20-50 parts by weight of hexagonal prism-shaped granules and 20-50 parts by weight of cylindrical granules; wherein the hexagonal prism-shaped granules have a side length of 2-6 cm and a length of 2-10 cm; and the cylindrical granules have a diameter of 1-6 cm and a length of 2-10 cm.

[0097] The purpose of using aluminum sheets in this invention is that the catechol hydroxyl groups in the polymer can be adsorbed onto the surface of the aluminum sheet, thereby increasing the adhesion of the polymer in the plugging agent mixture and preventing dilution and dispersion by water, drilling fluid, etc. Additionally, aluminum sheets are easily deformed under pressure. When the aluminum sheet is pumped into the formation, it is compressed by the subsequently pumped fluid, causing deformation and allowing it to enter fractures, pores, or larger formation fissures. Upon encountering the polymer, the polymer can be adsorbed onto the surface of the aluminum sheet, forming a colloid with other materials in the plugging agent mixture, thereby sealing formation leakage fissures. Because the aluminum sheet can be embedded or compressed into formation fractures, pores, or larger formation fissures, the polymer colloids and plugging agent mixture can achieve a better sealing effect. In a preferred embodiment of this invention, the aluminum sheet has a length of 1-5 cm, a width of 1-3 cm, and a thickness of 1-3 mm.

[0098] In a preferred embodiment of the present invention, the reed straw fragments used are dried alkalized reed straw fragments obtained by soaking in a 10-20 wt.% sodium carbonate or potassium carbonate solution for 72 hours and then drying for 120 hours, with a particle size of 10-30 mesh.

[0099] In a preferred embodiment of the invention, the waste steel wool ball is formed by curling waste steel wire with a length of 5-10 cm and a diameter of 2 mm-10 mm. The waste cardboard is a square cardboard with a side length of 2-5 cm and a thickness of 0.5-5 mm. The waste sheet metal is a mixture formed by mixing square sheet metal with a side length of 2-5 cm and a thickness of 0.5-2 mm and parallelogram sheet metal with side lengths of 2-5 cm and 3-10 cm and a thickness of 1-5 mm in a 1:1 ratio. The ferric carbonate has a particle size of 100-400 nm. The mussel shell fragments have a particle size of 10-20 mesh. The sponge block is a cubic block with a side length of 1-10 cm.

[0100] The sealing agent mixture according to the present invention will be further described below with reference to specific embodiments and test examples.

[0101] Example 4 Weigh 10 parts of polymer granules from Example 1, 10 parts of waste polyvinyl chloride granules, 6 parts of sawdust, 7 parts of aluminum sheet, 8 parts of iron carbonate powder, 7 parts of reed straw fragments, 6 parts of sponge block, 7 parts of waste iron sheet, 6 parts of waste cardboard, 7 parts of waste steel wool, and 10 parts of mussel shell fragments, and mix them thoroughly to obtain sealant material composition A. Waste polyvinyl chloride granules are composed of 40 parts by weight of hexagonal prism-shaped granules and 30 parts by weight of cylindrical granules with a particle size of 30 parts by weight; wherein, the hexagonal prism-shaped granules have a side length of 3cm and a length of 5cm; the cylindrical granules have a diameter of 3cm and a length of 5cm. The aluminum sheet is 2cm long, 1cm wide, and 1mm thick; the iron carbonate powder is 200nm; the reed stalk fragments are 20 mesh; the sponge block is a cube with a side length of 3cm; the waste steel wool ball is formed by curling waste steel wire with a length of 6cm and a diameter of 3mm; the waste cardboard is a square cardboard with a side length of 3cm and a thickness of 1mm; the waste iron sheet is a mixture of square iron sheet with a side length of 3cm and a thickness of 1.5mm and a parallelogram with one side length of 3cm and the other side length of 5cm and a thickness of 3mm, in a 1:1 ratio; the mussel shell fragments are 15 mesh; the sawdust is a mixture of 7 parts by weight of poplar sawdust with a particle size of 30 mesh, 15 parts by weight of birch sawdust with a particle size of 70 mesh, and 15 parts by weight of pine sawdust with a particle size of 110 mesh.

[0102] Example 5 Weigh 15 parts of polymer particles from Example 2, 15 parts of waste polyvinyl chloride particles, 7 parts of sawdust, 8 parts of aluminum sheet, 7 parts of iron carbonate powder, 7 parts of reed straw fragments, 7 parts of sponge block, 7 parts of waste iron sheet, 8 parts of waste paperboard, 7 parts of waste steel wool, and 16 parts of mussel shell fragments, and mix them thoroughly to obtain sealant material composition B. Waste polyvinyl chloride granules are composed of 35 parts by weight of hexagonal prism-shaped granules and 45 parts by weight of cylindrical granules with a particle size of 45 parts by weight; wherein, the hexagonal prism-shaped granules have a side length of 5cm and a length of 7cm; the cylindrical granules have a diameter of 5cm and a length of 8cm. The aluminum sheet is 2cm long, 2cm wide, and 2mm thick; the iron carbonate powder is 300nm; the reed stalk fragments are 25 mesh; the sponge block is a cube with a side length of 4cm; the waste steel wool ball is formed by curling waste steel wire with a length of 8cm and a diameter of 7mm; the waste cardboard is a square cardboard with a side length of 4cm and a thickness of 1.5mm; the waste iron sheet is a mixture of square iron sheet with a side length of 4cm and a thickness of 1.5mm and a parallelogram with one side length of 4cm and the other side length of 7cm and a thickness of 4mm, in a 1:1 ratio; the mussel shell fragments are 15 mesh; the sawdust is a mixture of 9 parts by weight of poplar sawdust with a particle size of 30 mesh, 18 parts by weight of birch sawdust with a particle size of 70 mesh, and 17 parts by weight of pine sawdust with a particle size of 110 mesh.

[0103] Example 6 Weigh 20 parts of polymer particles from Example 3, 20 parts of waste polyvinyl chloride particles, 8 parts of sawdust, 10 parts of aluminum sheet, 9 parts of iron carbonate powder, 7 parts of reed straw fragments, 7 parts of sponge block, 9 parts of waste iron sheet, 7 parts of waste paperboard, 10 parts of waste steel wool, and 17 parts of mussel shell fragments, and mix them thoroughly to obtain sealant material composition C. Waste polyvinyl chloride granules are a mixture of 50 parts by weight of hexagonal prism-shaped granules and 50 parts by weight of cylindrical granules with a particle size of 50 parts by weight; wherein, the hexagonal prism-shaped granules have a side length of 6cm and a length of 10cm; the cylindrical granules have a diameter of 6cm and a length of 10cm. The aluminum sheet is 5cm long, 3cm wide, and 2mm thick; the iron carbonate powder is 400nm; the reed stalk fragments are 30 mesh; the sponge block is a cube with a side length of 5cm; the waste steel wool ball is formed by curling waste steel wire with a length of 10cm and a diameter of 10mm; the waste cardboard is a square cardboard with a side length of 5cm and a thickness of 5mm; the waste iron sheet is a mixture formed by mixing square iron sheet with a side length of 5cm and a thickness of 2mm with a parallelogram with one side length of 5cm and the other side length of 10cm and a thickness of 5mm in a 1:1 ratio; the mussel shell fragments are 20 mesh; the sawdust is a mixture formed by 10 parts by weight of poplar sawdust with a particle size of 40 mesh, 20 parts by weight of birch sawdust with a particle size of 80 mesh, and 20 parts by weight of pine sawdust with a particle size of 120 mesh.

[0104] Test Example 5 The sealing agent mixture described in Example 6 was prepared into a sealing test slurry with a concentration of 20%-50% (based on the mass-to-volume ratio of the mixture in Example 6 to the bentonite slurry). The bentonite slurry concentration was 5% (based on the mass-to-volume ratio of bentonite to water). The sealing test slurry was poured into a CYDL-II type high-temperature and high-pressure dynamic and static sealing tester. By changing the size of the crack-type and pore-type molds, the sealing effect was observed under the same pushing pressure (3MPa).

[0105] The test results are as follows: Table 4. Sealing effect of crack-type leakage

[0106] Table 4 shows that, under the same pressure, the sealing effect varies with different crack sizes. For crack sizes between 0.5mm and 1mm, all mixtures show a sealing effect. As the crack size increases, only high-concentration sealing mixtures achieve a better sealing effect.

[0107] Table 5. Pore-type leakage plugging effect

[0108] Table 5 yields similar conclusions to Table 4. It is evident that mixtures of sealing agents of various concentrations are effective at sealing leaks. However, as the size of pores or cracks increases, the concentration of the sealing agent should be increased to ensure a better sealing effect.

[0109] Note: A plus sign indicates a better sealing effect; a minus sign indicates that an effective seal cannot be formed.

[0110] Test Example 6 The sealing agent mixture described in Example 6 was prepared into a sealing test slurry with a concentration of 20%-50% (based on the mass-to-volume ratio of the mixture in Example 6 to the bentonite slurry). The bentonite slurry concentration was 5% (based on the mass-to-volume ratio of bentonite to water). Sandstone slabs and carbonate rock slabs with dimensions of 10cm × 3cm × 2cm were placed in clamps, respectively, and a confining pressure of 2MPa was maintained. Simultaneously, the clamps were heated to 60℃. The sealing test slurry was poured into a CYDL-II type high-temperature and high-pressure dynamic and static sealing tester. By changing the gap size between the rock slabs, under the same pushing pressure (5MPa), the outlet was closed for 60 minutes, and the sealing effect was observed.

[0111] The test results are as follows: Table 6. Sealing Effect of Crack-Type Leakage in Sandstone Slabs

[0112] Note: An increase in the number of plus signs indicates a better sealing effect; a result accompanied by minus signs indicates a poor sealing effect; a result with only minus signs indicates that an effective seal cannot be formed.

[0113] Table 7. Leakage sealing effect of carbonate rock slabs

[0114] Note: An increase in the number of plus signs indicates a better sealing effect; a result accompanied by minus signs indicates a poor sealing effect; a result with only minus signs indicates that an effective seal cannot be formed.

[0115] As shown in Table 6, after the sealing slurry is pumped into the sandstone slab and heated to a certain temperature, the polymer in the sealing agent mixture, mixed with other sealing agents, is pumped into the gaps in the sandstone slab. Over time, a high-strength viscous layer forms between the polymer and the sandstone slab, carrying the mixture of other sealing agents to fill the gaps between the slabs. The polymer also adheres well to the sandstone slabs, acting as a channel to inhibit the subsequent flow of the sealing agent mixture towards the outlet, thus achieving a good sealing effect. Furthermore, due to the polymer's own physical properties, it dissolves acid-soluble substances such as scrap iron and ferric carbonate in the sealing agent mixture, forming a high-strength gel between the polymers, which also increases the sealing ability of the sealing agent composition to some extent.

[0116] Table 6 further shows that, under the same confining pressure, displacement pressure, and holding temperature, different crack sizes exhibit different sealing effects as the concentration of the plugging agent mixture increases. The higher the concentration of the plugging agent mixture, the better the sealing effect.

[0117] As shown in Table 7, under the same confining pressure, displacement pressure, and holding temperature, different crack sizes exhibit varying sealing effects with increasing concentration of the plugging agent mixture. Compared to the sandstone slabs in Table 6, the sealing effect of the carbonate rock slabs is slightly inferior. This is mainly because the surface composition of carbonate rocks differs from that of sandstone samples; the polymer forms less adhesive force on the carbonate rock surface compared to sandstone. The better sealing effect data shown in Table 7 is primarily due to the interactions between the plugging agent mixtures. For example, during the dissolution of scrap iron and ferric carbonate, the iron ions released around the polymer crosslink it, forming a stable gel. This gel, together with other plugging agent mixtures, forms strong sealing aggregates, thereby inhibiting and hindering the flow of subsequent plugging slurry, resulting in a better sealing effect.

[0118] Test Example 7 The polymer particles obtained in Example 3 were thoroughly mixed with distilled water at a mass-to-volume ratio of 30% to form a polymer solution. 100 ml of the polymer solution was taken, and an aluminum sheet with a length of 1 cm, a width of 1 cm, and a thickness of 1 mm was added to the polymer solution. The mixture of polymer solution and aluminum sheet was then heated from room temperature to 60°C and held at that temperature for 30 minutes.

[0119] During the heating process, the polymer solution is continuously stirred.

[0120] Take 10 ml of the above polymer solution and add 0.1 mol / L sodium hydroxide solution to it. The polymer solution becomes turbid. Continue to add sodium hydroxide solution, and the turbidity gradually disappears and the solution becomes clear.

[0121] It was clearly observed that the viscosity of the polymer solution increased, making stirring more difficult. After 30 minutes, the aluminum sheet was removed with tweezers, revealing a large amount of polymer adhering to its surface, forming a tongue-shaped polymer gel. Shaking the tweezers did not easily remove the tongue-shaped polymer gel from the aluminum sheet surface.

[0122] This test example demonstrates that polymers can adsorb onto the surface of aluminum sheets, forming a stable adsorption layer. Due to the inherent properties of the polymer, aluminum ions released from the aluminum sheet can form cross-links with the polymer, creating micelles. Therefore, aluminum ions can effectively form micelles with polymers, and aluminum sheets are also a favorable substrate for polymer micelles or polymer adhesion.

[0123] According to another aspect of the present invention, an application of the plugging agent mixture of any of the above embodiments is provided in oil and gas field exploration and development. The plugging agent mixture according to the present invention will be further described below with reference to specific application examples.

[0124] Application Example 1 This application example focuses on well H5-5, a two-stage horizontal well with a depth of 2722 meters. The drilled formation is a coarse-fine siltstone stratum with geological structures such as microfractures. The drilled section has a high quartz content (silica content between 45% and 70%). The horizontal section is 1200 meters long with a well inclination of 35°, and the vertical section is 627 meters long.

[0125] From the perspective of geological structure and rock properties, the H5-5 well encountered a formation with brittle and fractured lithology, which is prone to leakage of drilling circulating fluids, such as drilling fluid.

[0126] The well used a water-based drilling fluid. The water-based drilling fluid system was formulated with bentonite slurry (a mixture of bentonite and water), and other treatment agents were added to the bentonite slurry according to a pre-established drilling design plan. The formation encountered during drilling, from the upper vertical section to the lower horizontal section, consisted of coarse- to fine-grained siltstone containing micro-fractured geological structures.

[0127] During drilling of well H5-5, due to factors such as geological structure, rock properties, and drill string oscillation, the drilling fluid tank alarm sounded after drilling to a depth of 1025 meters. The drilling fluid level in the tank dropped, indicating drilling fluid loss. As drilling continued, the drop in drilling fluid level became more pronounced, indicating that a fracture had been connected during the drilling process. Judging from the drilling fluid loss rate, the loss velocity at this point was 12 m / s². 3 / h. Quickly prepare plugging slurry at the drilling site and carry out the plugging operation.

[0128] Based on the current leakage rate, formation lithology, and drilling depth, the plugging agent mixture shown in Example 4 was used for plugging operations.

[0129] Prepare 50m of the sealing grout containing the sample from Example 4. 3 At this point, the concentration of the plugging agent mixture was 20% (based on the mass-to-volume ratio of the mass of the plugging agent mixture from Example 4 to the volume of the drilling fluid at this point). Pumping was performed into the well, drilling was stopped, the drilling fluid circulation system was shut off, and the well was allowed to stand for 30 minutes. The drilling fluid was then circulated at a pump rate of 10 L / s. The loss velocity was found to have decreased to 7 m³ / s. 3 / h. This indicates that the sealant mixture from Example 4 achieved a certain sealant effect.

[0130] The concentration of the plugging agent mixture from Example 4 was further increased to 28%. The plugging operation was carried out according to the plugging procedure. After circulating the drilling fluid at a pump rate of 12 L / s, the fluid level in the drilling fluid tank no longer dropped. The drilling fluid circulation rate was further increased to 15 L / s, and the fluid level in the drilling fluid tank still did not drop. This indicates that the plugging agent mixture at this point achieved a plugging effect, effectively sealing the formation. No further leakage occurred during the 2-hour drilling recovery period. After reaching the predetermined drilling level, the next drilling operation was carried out. This plugging operation was effective.

[0131] Application Example 2 The application example focuses on well W-7, a three-section vertical well with a depth of 3722 meters. The drilled formation is a muddy-fine siltstone formation with geological structures such as fractures and microfractures. The drilled section has a high quartz content (silica content between 55% and 75%).

[0132] From the perspectives of geological structure and rock properties, Well W-7 has a quartz content between 55% and 75%. The lithology of the strata encountered during drilling is brittle and has obvious fractures, which makes it easier for drilling circulating fluids, such as drilling fluid, to be lost.

[0133] The well used a water-based drilling fluid. The water-based drilling fluid system was formulated with bentonite slurry (a mixture of bentonite and water), and other treatment agents were added to the bentonite slurry according to a pre-established drilling design plan. The formation encountered during drilling, from the upper vertical section to the lower horizontal section, consisted of argillaceous to fine-grained sandstone containing microfractures and fractured geological structures.

[0134] During drilling of Well W-7, due to factors such as geological structure, rock properties, and drill string oscillation, the drilling fluid tank alarm sounded after reaching a depth of 3225 meters. The drilling fluid level in the tank dropped, indicating drilling fluid loss. As drilling continued, the drop in drilling fluid level became more pronounced, indicating that a fracture had been connected during the drilling process. Judging from the drilling fluid loss rate, the loss velocity at this point was 26 m / s². 3 / h. Quickly prepare plugging slurry at the drilling site and carry out the plugging operation.

[0135] Based on the current leakage rate, formation lithology, and drilling depth, the plugging agent mixture shown in Example 5 was used for plugging operations.

[0136] Prepare 100m³ of the sealing grout containing the sample from Example 5. 3At this point, the concentration of the plugging agent mixture was 35% (based on the mass-to-volume ratio of the mass of the plugging agent mixture from Example 5 to the volume of the drilling fluid at this point). Pumping was performed into the well, drilling was stopped, the drilling fluid circulation system was shut off, and the well was allowed to stand for 40 minutes. The drilling fluid was then randomly circulated at a pump speed of 12 L / s. The loss velocity was found to have decreased to 9 m / s. 3 / h. This indicates that the sealant mixture from Example 5 achieved a certain sealant effect.

[0137] The concentration of the plugging agent mixture from Example 5 was further increased to 45%. The plugging operation was carried out according to the plugging procedure. After circulating the drilling fluid at a pump rate of 16 L / s, the fluid level in the drilling fluid tank no longer dropped. The drilling fluid circulation rate was further increased to 18 L / s, and the fluid level in the drilling fluid tank still did not drop. This indicates that the plugging agent mixture at this point achieved a plugging effect, effectively sealing the formation. No further leakage occurred during the 2-hour drilling recovery period. After reaching the predetermined drilling level, the next drilling operation was carried out. This plugging operation was effective.

[0138] Application Example 3 This application example focuses on Well H-9, a two-stage horizontal well with a depth of 5722 meters. The drilled formation consists of coarse-fine siltstone with microfractures and other geological structures, and the encountered well section has a high quartz content. The horizontal section is 1500 meters long with a well inclination of 55°, and the vertical section is 1625 meters long.

[0139] From the perspectives of geological structure and rock properties, well H-9 has a boundary water layer at a depth of 3755-3777 meters and 200 meters to the northwest. The lithology of the encountered formation (silica content between 65% and 85%) is more brittle and fractured, which is prone to loss of drilling circulating fluids, such as drilling fluid.

[0140] The well used a water-based drilling fluid. The water-based drilling fluid system was formulated with bentonite slurry (a mixture of bentonite and water), and other treatment agents were added to the bentonite slurry according to a pre-established drilling design plan. The formation encountered during drilling, from the upper vertical section to the lower horizontal section, consisted of coarse- to fine-grained siltstone containing micro-fractured geological structures.

[0141] During drilling of well H-9, due to factors such as geological structure, rock properties, and drill string oscillation, the drilling fluid tank alarm sounded after reaching a depth of 3525 meters. The drilling fluid level in the tank dropped, indicating drilling fluid loss. As drilling continued, the drop in drilling fluid level became more pronounced, indicating that a fracture had been connected during the drilling process. Judging from the drilling fluid loss rate, the loss velocity at this point was 38 m / s². 3 / h. Quickly prepare plugging slurry at the drilling site and carry out the plugging operation.

[0142] Based on the current leakage rate, formation lithology, and drilling depth, the plugging agent mixture shown in Example 6 was used for plugging operations.

[0143] Prepare 100m of the sealing grout containing the sample from Example 6. 3 At this point, the concentration of the plugging agent mixture was 40% (based on the mass-to-volume ratio of the mass of the plugging agent mixture from Example 6 to the volume of the drilling fluid at this point). Pumping was performed into the well, drilling was stopped, the drilling fluid circulation system was shut off, and the well was allowed to stand for 30 minutes. The drilling fluid was then randomly circulated at a pump speed of 15 L / s. The loss velocity was found to have decreased to 28 m³ / s. 3 / h. This indicates that the sealant mixture from Example 6 achieved a certain sealant effect.

[0144] The concentration of the plugging agent mixture from Example 6 was further increased to 45%. The plugging operation was carried out according to the plugging procedure. After circulating the drilling fluid at a pump rate of 20 L / s, the fluid level in the drilling fluid tank stopped dropping. Drilling resumed for 2 hours. At this point, due to encountering a formation fracture, edge water entered the wellbore, diluting the drilling fluid and plugging slurry. This caused the fluid level in the drilling fluid tank to continue to drop.

[0145] At this point, increase the concentration of the plugging slurry from Example 6 to 50% and reduce the pumping rate. Pump all the plugging slurry into the wellbore at a pumping speed of 10 L / s, then shut down the drilling circulation equipment, stop drilling, and seal the well for 2 hours. Allow the plugging agent combination to take effect.

[0146] After well opening, drilling continued, and the drilling fluid circulation rate was increased to 16 L / s. After circulating the drilling fluid, the fluid level in the tank no longer dropped. The pump rate was further increased to 22 L / s, and the fluid level in the tank still did not drop. This indicates that the plugging agent mixture had achieved a sealing effect, effectively sealing the formation and preventing the intrusion of formation edge water. No further leakage occurred during the 2-hour continuation of drilling. After reaching the predetermined drilling level, the next drilling operation was carried out. This plugging operation was effective.

[0147] Application Example 4 This application example focuses on Well W7-5, a two-stage horizontal well with a depth of 1772 meters. The drilled formation is a coarse siltstone stratum with fracture-cavity geological structures such as fissures and karst caves. The drilled section has a high quartz content (silica content between 45% and 60%). The horizontal section is 800 meters long with a well inclination of 35°, and the vertical section is 327 meters long.

[0148] From the perspective of geological structure and rock properties, the W7-5 well encountered a formation with brittle lithology and a fracture-cavity geological structure, which is prone to leakage of drilling circulating fluids, such as drilling fluid.

[0149] The well used a water-based drilling fluid. The water-based drilling fluid system was formulated with bentonite slurry (bentonite + water), based on a pre-established drilling design plan, by adding other treatment agents to the bentonite slurry. The formation encountered during drilling, from the upper vertical section to the lower horizontal section, consisted of coarse siltstone, a fracture-cavity formation with geological structures such as fractures and karst caves.

[0150] During drilling of well W7-5, due to factors such as geological structure, rock properties, and drill string oscillation, the drilling fluid tank alarm sounded after drilling to 825 meters, indicating a drop in the drilling fluid level, suggesting drilling fluid loss. As drilling continued, the drop in the drilling fluid level became more pronounced, indicating that a fracture had been connected during the drilling process. Based on the drilling fluid loss rate, the loss velocity at this point was 15 m / s². 3 / h. Quickly prepare plugging slurry at the drilling site and carry out the plugging operation.

[0151] Based on the current leakage rate, formation lithology, and drilling depth, the plugging agent mixture shown in Example 5 was used for plugging operations.

[0152] Prepare 80m of the sealing grout containing Example 5 3 At this point, the concentration of the plugging agent mixture was 30% (based on the mass-to-volume ratio of the mass of the plugging agent mixture from Example 5 to the volume of the drilling fluid at this point). Pumping was performed into the well, drilling was stopped, the drilling fluid circulation system was shut off, and the well was allowed to stand for 30 minutes. The drilling fluid was then circulated at a pump rate of 12 L / s. The loss velocity was found to have decreased to 9 m / s. 3 / h. This indicates that the sealant mixture from Example 5 achieved a certain sealant effect.

[0153] The concentration of the plugging agent mixture from Example 5 was further increased to 38%. The plugging operation was carried out according to the plugging procedure. After circulating the drilling fluid at a pump rate of 14 L / s, the fluid level in the drilling fluid tank no longer dropped. The drilling fluid circulation rate was further increased to 16 L / s, and the fluid level in the drilling fluid tank still did not drop. This indicates that the plugging agent mixture at this point achieved a plugging effect, effectively sealing the formation. No further leakage occurred during the 2-hour drilling recovery period. After reaching the predetermined drilling level, the next drilling operation was carried out. This plugging operation was effective.

[0154] Application Example 5 This application example focuses on Well W8-5, a two-stage horizontal well with a depth of 2752 meters. The drilled formation is a fractured carbonate rock formation with geological structures such as microfractures and fractures. The encountered well section has a high dolomite content (between 60% and 90%). The horizontal section is 1200 meters long with a well inclination of 65°, and the vertical section is 627 meters long.

[0155] From the perspective of geological structure and rock properties, the W8-5 well encountered a fractured formation with a high content of carbonate minerals, which makes it more prone to loss of drilling circulating fluids, such as drilling fluid.

[0156] The well used a water-based drilling fluid. The water-based drilling fluid system was formulated with bentonite slurry (a mixture of bentonite and water), and other treatment agents were added to the bentonite slurry according to a pre-established drilling design plan. The formation encountered during drilling, from the upper vertical section to the lower horizontal section, was a fractured carbonate rock formation with microfractures and other geological structures.

[0157] During drilling of well W8-5, due to factors such as geological structure, rock properties, and drill string oscillation, the drilling fluid tank alarm sounded after reaching a depth of 1335 meters. The drilling fluid level in the tank dropped, indicating drilling fluid loss. As drilling continued, the drop in drilling fluid level became more pronounced, indicating that a fracture had been connected during the drilling process. Judging from the drilling fluid loss rate, the loss velocity at this point was 32 m / s². 3 / h. Quickly prepare plugging slurry at the drilling site and carry out the plugging operation.

[0158] Based on the current leakage rate, formation lithology, and drilling depth, the plugging agent mixture shown in Example 6 was used for plugging operations.

[0159] Prepare 200m of the sealing grout containing the sample from Example 6. 3 At this point, the concentration of the plugging agent mixture was 35% (based on the mass-to-volume ratio of the mass of the plugging agent mixture from Example 6 to the volume of the drilling fluid at this point). Pumping was performed into the well, drilling was stopped, the drilling fluid circulation system was shut off, and the well was allowed to stand for 60 minutes. The drilling fluid was then randomly circulated at a pump speed of 15 L / s. The loss velocity was found to have decreased to 10 m / s. 3 / h. This indicates that the sealant mixture from Example 6 achieved a certain sealant effect.

[0160] The concentration of the plugging agent mixture from Example 6 was further increased to 45%. The plugging operation was carried out according to the plugging procedure. After circulating the drilling fluid at a pump rate of 17 L / s, the fluid level in the drilling fluid tank no longer dropped. The drilling fluid circulation rate was further increased to 20 L / s, and the fluid level in the drilling fluid tank still did not drop. This indicates that the plugging agent mixture at this point achieved a plugging effect, effectively sealing the formation. No further leakage occurred during the 2-hour drilling recovery period. After reaching the predetermined drilling level, the next drilling operation was carried out. This plugging operation was effective.

[0161] Application Example 6 This application example focuses on Well W9-5, a three-section vertical well with a depth of 5585 meters. The drilled formation consists of coarse-fine siltstone and argillaceous siltstone, exhibiting geological structures such as microfractures and fractures. The drilled interval has a high quartz content (silica content between 55% and 75%). Furthermore, the oil and gas reservoir contains edge water and bottom water formations, and the well encountered these formations relatively close together. This makes it easy for edge water and bottom water to enter the wellbore through fractures and other geological structures.

[0162] From the perspectives of geological structure and rock properties, the W9-5 well encountered a formation with brittle and fractured lithology, which easily leads to the loss of circulating drilling fluids, such as drilling fluid. Furthermore, the formation contains edge water and bottom water layers, which can easily enter the wellbore along fractures, diluting the drilling fluid, reducing its density, and potentially causing wellbore instability, blowouts, and other downhole complications and drilling accidents.

[0163] The well used a water-based drilling fluid. The water-based drilling fluid system was formulated with bentonite slurry (bentonite + water), based on a pre-established drilling design plan, by adding other treatment agents to the bentonite slurry. The formation encountered during drilling, from the upper vertical section to the lower horizontal section, consisted of coarse-fine siltstone and argillaceous siltstone containing microfractures and fractured geological structures.

[0164] During drilling of well W9-5, due to factors such as geological structure, rock properties, and drill string oscillation, the drilling fluid tank alarm sounded after reaching a depth of 3725 meters. The drilling fluid level in the tank dropped, indicating drilling fluid loss. As drilling continued, the drop in the drilling fluid level became more pronounced, indicating that a fracture had been connected during the drilling process. Based on the drilling fluid loss rate, the loss velocity at this point was 52 m / s². 3 / h. Quickly prepare plugging slurry at the drilling site and carry out the plugging operation.

[0165] Based on the current leakage rate, formation lithology, and drilling depth, a conventional plugging agent mixture is used for plugging operations.

[0166] Prepare 50m of conventional sealing grout (10% composite sealing agent FD-1 + 10% SDL + 10% CDL + 12% DSA + 4% fine nutshell 60 mesh). 3 At this point, the concentration of the plugging agent mixture was 30% (based on the mass-to-volume ratio of the plugging material mixture to the current volume of drilling fluid). Pumping was initiated into the well, drilling was stopped, the drilling fluid circulation system was shut off, and the well was allowed to stand for 50 minutes. The drilling fluid was then randomly circulated at a pump rate of 15 L / s. The loss velocity was observed to decrease to 47 m³ / s. 3 / h. This indicates that the sealing effect of conventional sealing grout is not ideal.

[0167] At this point, affected by the previous formation loss, the drilled formation fractures were widened, connecting with the adjacent edge water layer and causing a large amount of water to invade the wellbore. With conventional plugging materials ineffective and edge water intrusion encountered, a composite plugging agent developed using two different embodiments was used for sealing.

[0168] Continue the plugging operation. Based on the plugging agent mixture of Example 5, add the plugging agent mixture of Example 6, with a higher concentration than that of Example 5. Pump both mixtures into the wellbore using an intermittent pumping method. Mix the plugging agent mixtures of Example 5 and Example 6 at a concentration of 20% + 30% to form a mixture. Prepare 200m³ of this plugging slurry. 3 Following the established procedures for plugging leaks, a sealing operation was performed. After circulating the drilling fluid at a pump rate of 15 L / s, the rate of drop in the drilling fluid tank slowed, prompting further pumping of the plugging agent mixture. After pumping the plugging slurry at a rate of 16 L / s, the well was shut in for 2 hours. After circulating the drilling fluid at a pump rate of 12 L / s, the drilling fluid tank level stopped dropping. The drilling fluid circulation rate was further increased, and after circulating the drilling fluid at a pump rate of 16 L / s, the drilling fluid tank level still did not drop. This indicates that the plugging agent mixture had achieved a sealing effect, effectively sealing the formation. No further leakage occurred during the 2-hour drilling resumption. After reaching the predetermined drilling depth, the next drilling operation was initiated. This plugging operation was effective.

[0169] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0170] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A polymer, characterized in that, It is prepared by polymerization reaction of monomers A, B, C, D and E, wherein, The chemical structural formula of monomer A is: The chemical structural formula of monomer B is: The chemical structural formula of monomer C is: The chemical structural formula of monomer D is: The chemical structural formula of monomer E is: The molar ratio of monomers A, B, C, D and E is (0.2~1):(0.3~1):(0.5~1):(0.2~1):(0.3~1).

2. The polymer according to claim 1, characterized in that, The polymer has a viscosity-average molecular weight of 15 million to 20 million.

3. The polymer according to claim 1, characterized in that, The polymer has a molecular weight distribution of 1.1 to 1.

3.

4. A method for preparing a polymer, characterized in that, The method for preparing the polymer according to any one of claims 1-3 comprises the following steps: S1. Add the emulsifier to the water and stir at 500-600 r / min for 20-30 min; then add the alkali metal carbonate and / or alkali metal bicarbonate and continue stirring at 500-600 r / min until the three are mixed evenly to prepare the emulsifier mixture. S2. The emulsifier mixture obtained in step S1, along with monomers A, B, C, D, and E, are added to a reaction vessel. Inert gas is introduced into the reaction vessel at a flow rate of 0.3-0.5 L / min. The stirrer is turned on and stirred at a speed of 300-400 r / min for 15-20 min. Then, the temperature is raised to 40-50°C and stabilized for 8-10 min. The first part by weight of the initiator is added, and inert gas is introduced and stirred at a speed of 200-300 r / min for 15-20 min. The temperature is then raised to 50-60°C and stabilized for 5-8 min. The second part by weight of the initiator is added and stirred at a speed of 200-300 r / min for 20-30 min. The temperature is then raised to 60-70°C and the reaction is maintained for 6-8 h to obtain a reaction mixture. The first part by weight accounts for 1 / 5 to 1 / 3 of the sum of the first and second parts by weight. S3. Cool the reaction mixture obtained in step S2 to 40~45°C, add the alkali metal carbonate or alkali metal bicarbonate selected in step S1 to adjust its pH value to neutral, and further cool to 25~30°C to obtain the polymer.

5. The method according to claim 4, characterized in that, In step S1, The ratio of the amount of emulsifier to the volume of water is 0.4~0.6:100mol / L; The emulsifier is at least one of OP-50, Span60, polysorbate-85, OS-15, sodium dodecyl sulfonate, and sodium dodecyl diphenyl ether disulfonate.

6. The method according to claim 4, characterized in that, In step S1, The molar ratio of alkali metal carbonates and / or alkali metal bicarbonates to the volume of water is 0.2~0.5:100mol / L; Alkali metal carbonates are sodium carbonate and / or potassium carbonate; Alkali metal bicarbonates are sodium bicarbonate and / or potassium bicarbonate.

7. The method according to claim 6, characterized in that, In step S2, During each heating process, the heating rate is maintained at 2℃ / min; the reaction is carried out under the protection of an inert gas; the inert gas includes nitrogen or helium, and the inert gas is introduced into the reaction vessel at a flow rate of 0.3~0.5L / min.

8. The method according to claim 6, characterized in that, In step S2, The sum of the amounts of monomers A, B, C, D, and E, and the volume ratio of water, are 3-5:100 mol / L; the initiator is potassium persulfate or ammonium persulfate; the total amount of initiator and the volume ratio of water are 0.02-0.06:100 mol / L; the volume of water is the volume of water used in step S1.

9. The method according to claim 6, characterized in that, In step S2, For the liquid monomers among monomers A, B, C, D, and E, they are directly mixed with the emulsifier mixture; For the solid monomers among monomers A, B, C, D, and E, the solid monomers are first dissolved in distilled water to prepare a solution of 2-5 g / mL before being mixed with the emulsifier mixture.

10. A sealant mixture, characterized in that, The sealant mixture contains the polymer according to any one of claims 1-3, and comprises the following components by weight: 10-20 parts of the polymer, 10-20 parts of waste polyvinyl chloride granules, 5-10 parts of sawdust, 5-10 parts of aluminum flakes, 5-10 parts of iron carbonate powder, 5-10 parts of reed stalk fragments, 5-10 parts of sponge blocks, 5-10 parts of waste sheet metal, 5-10 parts of waste cardboard, 5-10 parts of waste steel wool, and 10-20 parts of mussel shell fragments.

11. The sealant mixture according to claim 10, characterized in that, The polymer consists of particles with a particle size of 20-40 mesh.

12. The sealant mixture according to claim 10, characterized in that, The sawdust is a mixture of 5-10 parts by weight of poplar sawdust with a particle size of 20-40 mesh, 10-20 parts by weight of birch sawdust with a particle size of 60-80 mesh, and 10-20 parts by weight of pine sawdust with a particle size of 100-120 mesh.

13. The sealant mixture according to claim 10, characterized in that, The waste polyvinyl chloride granules are composed of 20-50 parts by weight of hexagonal prism-shaped granules and 20-50 parts by weight of cylindrical granules, wherein the hexagonal prism-shaped granules have a side length of 2-6 cm and a length of 2-10 cm; and the cylindrical granules have a diameter of 1-6 cm and a length of 2-10 cm.

14. The sealant mixture according to claim 10, characterized in that, The aluminum sheet has a length of 1-5cm, a width of 1-3cm, and a thickness of 1-3mm.

15. The sealant mixture according to claim 10, characterized in that, The reed straw fragments are a mixture of dried, alkalized reed straw with a particle size of 10-30 mesh, obtained by soaking in a 10-20 wt.% sodium carbonate or potassium carbonate solution for 72 hours and then drying for 120 hours.

16. The sealant mixture according to claim 10, characterized in that, The scrap iron sheet is a mixture formed by mixing square iron sheets with a side length of 2-5cm and a thickness of 0.5-2mm and parallelogram iron sheets with a side length of 2-5cm and a thickness of 3-10cm and a thickness of 1-5mm in a 1:1 ratio.

17. The sealant mixture according to claim 10, characterized in that, Waste cardboard is a square cardboard with a side length of 2-5cm and a thickness of 0.5-5mm.

18. The sealant mixture according to claim 10, characterized in that, The waste steel wool ball is formed by curling up waste steel wool with a length of 5-10cm and a diameter of 2mm-10mm.

19. The sealant mixture according to claim 10, characterized in that, The ferric carbonate has a particle size of 100~400nm, the mussel shell fragments have a particle size of 10~20 mesh, and the sponge block is a cubic block with a side length of 1~10cm.

20. The application of the plugging agent mixture according to any one of claims 10-19 in oil and gas field exploration and development.

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