Interpenetrating network polymer blocking agent for drilling fluid as well as preparation method and application of interpenetrating network polymer blocking agent

Abstract

The invention provides an interpenetrating network polymer plugging agent for drilling fluid and a preparation method and application thereof, and the preparation method comprises the following steps: 1) mixing water, an emulsifier A, an emulsifier B and a water-soluble monomer C to obtain a water phase; 2) mixing the water phase, an oil-soluble monomer A (hard monomer) and a cross-linking agent D, and emulsifying to obtain an emulsion reaction mixed solution; (3) mixing the emulsification reaction mixed solution with a section of initiator solution, and carrying out thermal insulation polymerization to obtain a polymerized emulsion; and 4) mixing the polymerized emulsion with an oil-soluble monomer B (soft monomers), a cross-linking agent E and a two-stage initiator solution, and continuing to carry out thermal insulation polymerization to obtain the interpenetrating network polymer plugging agent for the drilling fluid. The plugging agent prepared by the method can give consideration to elastic deformation, bonding effect and temperature resistance (200 DEG C), has good compatibility with oil-based drilling fluid and water-based drilling fluid, and has obvious filtrate loss reduction and plugging effects.

Description

Technical Field

[0001] This invention belongs to the technical field of drilling fluid treatment agents in oil drilling engineering, and particularly relates to an interpenetrating network polymer plugging agent for drilling fluid, its preparation method and application. Background Technology

[0002] In deep and ultra-deep well drilling, problems such as low-pressure leakage, unstable wellbore collapse, and wellbore instability due to stress are frequent. The risks of well leakage and stuck pipe are high, and the handling is difficult. Both water-based and oil-based drilling fluids have experienced these issues. For example, in the Hongxing block, the Wujiaping Formation has well-developed fractures, with both collapse and leakage occurring. In the Zigong and Weiyuan blocks, the Longmaxi Formation mudstone and shale formations, and the Dongyuemiao Formation of Well Xingye 7, the stress release is severe due to fracturing. The Shunbei Santamu Formation limestone and the Maokou Formation in the Southwest work area are also geologically fractured. When drilling encounters formations with well-developed micro- and nano-porous structures, drilling fluid loss and wellbore instability / collapse are likely to occur. Micro- and nano-sealing materials need to be added to form a tight sealing layer, reduce drilling fluid intrusion, and improve the formation's pressure-bearing capacity to prevent "collapse due to leakage." Simultaneously, to further improve the anti-collapse effect, the material needs to have a certain degree of adhesion to act as a bonding and protective layer for the wellbore.

[0003] Commonly used polymer sealing materials cannot simultaneously achieve the desired elastic deformation, bonding effect, and temperature resistance (200℃), thus failing to simultaneously meet the requirements for high-temperature sealing, leak prevention, and collapse prevention. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide an interpenetrating network polymer plugging agent for drilling fluid, its preparation method and application. The plugging agent prepared by this method has good temperature resistance, good compatibility with both oil-based and water-based drilling fluids, and significant filtration loss reduction and plugging effect.

[0005] This invention provides a method for preparing an interpenetrating network polymer plugging agent for drilling fluids, comprising the following steps:

[0006] 1) Mix water, emulsifier A, emulsifier B and water-soluble monomer C to obtain an aqueous phase;

[0007] 2) Mix the aqueous phase, oil-soluble monomer A, and crosslinking agent D, and emulsify to obtain an emulsified reaction mixture;

[0008] 3) Mix the emulsion reaction mixture with a first-stage initiator solution, and polymerize under heat to obtain the polymerized emulsion;

[0009] 4) The polymerized emulsion is mixed with oil-soluble monomer B, crosslinking agent E and second-stage initiator solution, and polymerization is continued at a constant temperature to obtain an interpenetrating network polymer plugging agent for drilling fluid.

[0010] This invention mixes water, emulsifier A, emulsifier B, and water-soluble monomer C to obtain an aqueous phase. Emulsifier A is selected from one or more of sodium alkyl sulfate, sodium alkylbenzene sulfonate, sodium dialkyl-2-sulfosuccinate, and sodium alkylallyloxy polyoxyethylene phosphate; emulsifier B is selected from one or more of polyoxyethylene alkyl ether, polyoxyethylene phenolic ether, polyoxyethylene sorbitan ether stearate, and polyoxyethylene sorbitan monooleate; and water-soluble monomer C is selected from one or more of methacrylic acid, acrylamide, acrylic acid, and AMPS. The water-soluble monomer C enhances the hydrophilicity of the plugging agent. The pH of the aqueous phase is preferably adjusted to 7.5–8.5 using a 20% NaOH aqueous solution.

[0011] After obtaining the aqueous phase, the present invention mixes the aqueous phase, oil-soluble monomer A, and crosslinking agent D, and emulsifies them to obtain an emulsified reaction mixture. The emulsification reaction time in the present invention is 25–35 min, preferably 28–32 min; in a specific embodiment, the emulsification time is 30 min. Emulsification in the present invention is carried out under stirring conditions; the stirring rate is 580–620 rpm, preferably 590–610 rpm; in a specific embodiment, the stirring rate is 600 rpm. The present invention achieves complete emulsification under a N2 atmosphere.

[0012] The oil-soluble monomer A described in this invention is a hard monomer with a homopolymer glass transition temperature greater than -20°C, which can improve the rigidity and hardness of the plugging agent; the oil-soluble monomer A is selected from hard monomers such as styrene and / or methyl methacrylate; the crosslinking agent D is selected from one or more of N,N'-methylenebisacrylamide, polyvinyl alcohol diacrylate, 1,3-butadiene and 1,4-divinylbenzene.

[0013] In this invention, the initiator is dissolved in deionized water, resulting in a first-stage initiator solution and a second-stage initiator solution; the first-stage initiator solution comprises 60%–80% of the total initiator solution. The mass concentration of the initiator solution is 4%–10%.

[0014] The emulsion reaction mixture is obtained. In this invention, the emulsion reaction mixture is mixed with a first-stage initiator solution and polymerized at a controlled temperature to obtain a polymerized emulsion. Preferably, the emulsion reaction mixture is heated from room temperature to the temperature required for polymerization, and the polymerization temperature is maintained at 70–80°C. After emulsification, the stirring speed is reduced to 430–470 rpm for polymerization, preferably 440–460 rpm; in a specific embodiment, it is reduced to 450 rpm. Preferably, the first-stage initiator solution is added dropwise to the emulsion reaction mixture. The polymerization time is 55–65 min, preferably 60 min.

[0015] After obtaining the polymerized emulsion, the present invention mixes the polymerized emulsion with oil-soluble monomer B, crosslinking agent E, and a second-stage initiator solution, and continues polymerization at a controlled temperature to obtain an interpenetrating network polymer plugging agent for drilling fluids. In the present invention, the temperature for continued polymerization is 70–80°C. Preferably, the oil-soluble monomer B, crosslinking agent E, and second-stage initiator solution are added dropwise to the polymerized emulsion.

[0016] The oil-soluble monomer B described in this invention is a soft monomer, that is, the glass transition temperature of the homopolymer is less than -20°C, which can improve the flexibility of the plugging agent; the oil-soluble monomer B is selected from one or more of butyl methacrylate, methyl acrylate, vinyl acetate, butyl acrylate and isooctyl acrylate.

[0017] Based on the total mass of oil-soluble monomer A, oil-soluble monomer B, and water-soluble monomer C, the present invention uses 2% to 3% of emulsifier A and emulsifier B as the basis, 0.1% to 0.5% of crosslinking agent, and 0.5% to 2.0% of initiator.

[0018] Based on the total mass of oil-soluble monomer A, oil-soluble monomer B, and water-soluble monomer C as 100%, the water-soluble monomer C accounts for 10% to 20%; the oil-soluble monomer A accounts for 50% to 70%; and the oil-soluble monomer B accounts for 20% to 40%.

[0019] This invention improves the rigidity and hardness of polymers by using oil-soluble monomer A (hard monomer), oil-soluble monomer B (soft monomer) to improve polymer elasticity, water-soluble monomer to improve polymer hydrophilicity, and interpenetrating network structure to improve temperature resistance. The plugging agent prepared by this method can take into account elastic deformation, bonding effect and temperature resistance (200℃), and has good compatibility with both oil-based and water-based drilling fluids. It also has significant effects on reducing filtration loss and plugging.

[0020] The interpenetrating network polymer plugging agent for drilling fluid prepared by this invention has a particle size distribution of 0.05–50 μm, D 50 ≤15μm.

[0021] This invention provides an interpenetrating network polymer plugging agent for drilling fluids, which is prepared by the method described in the above technical solution.

[0022] The present invention also provides an application of the interpenetrating network polymer plugging agent for drilling fluid prepared by the preparation method described above in oil-based drilling fluids, water-based drilling fluids, or high-temperature formations above 200°C.

[0023] The preparation method provided by this invention uses oil-soluble monomers A and B, which have different glass transition temperatures. The uncrosslinked portions of the oil-soluble polymer blocks A and B formed by oil-soluble monomers A and B can undergo phase transitions at different temperatures, exhibiting adhesiveness and adapting to a wide range of lost circulation temperatures. The crosslinked portions can elastically deform, providing deformation and filling effects. The elastic deformation and adhesiveness of the plugging agent form a strong and dense adhesive plugging layer, effectively preventing lost circulation and sealing the wellbore. Through the combined action of oil-soluble and water-soluble monomers, the plugging agent exhibits good compatibility with both oil-based and water-based drilling fluids. The crosslinked portions form an interpenetrating network, exhibiting good temperature resistance, capable of withstanding temperatures above 200°C.

[0024] This invention provides a method for preparing an interpenetrating network polymer plugging agent for drilling fluids, comprising the following steps: 1) mixing water, emulsifier A, emulsifier B, and water-soluble monomer C to obtain an aqueous phase; 2) mixing the aqueous phase, oil-soluble monomer A, and crosslinking agent D, and emulsifying to obtain an emulsion reaction mixture; 3) mixing the emulsion reaction mixture with a first-stage initiator solution, and polymerizing at a controlled temperature to obtain a polymerized emulsion; 4) mixing the polymerized emulsion with oil-soluble monomer B, crosslinking agent E, and a second-stage initiator solution, and continuing to polymerize at a controlled temperature to obtain an interpenetrating network polymer plugging agent for drilling fluids. The plugging agent prepared by this method can balance elastic deformation, bonding effect, and temperature resistance (200℃), exhibiting good temperature resistance, good compatibility with both oil-based and water-based drilling fluids, and significant filtration loss reduction and plugging effects. Attached Figure Description

[0025] Figure 1 This is a particle size distribution diagram of the plugging agent prepared in Example 1 of the present invention;

[0026] Figure 2 This is a schematic diagram of the interpenetrating network polymer structure of the plugging agent prepared in Example 1 of the present invention;

[0027] Figure 3 The structural formulas of the first network polymer A (Formula A), the second network polymer B (Formula B), and the polymer C (Formula C) in the blocking agent prepared in Example 1 of the present invention are:

[0028] Figure 4 The infrared spectrum of the blocking agent prepared in Example 1 of this invention;

[0029] Figure 5 This is a morphology diagram of the API medium-pressure filter cake of the plugging agent prepared in Example 1 of the present invention;

[0030] Figure 6 This is a graph showing the API medium-pressure filter cake wettability test of the sealing agent prepared in Example 1 of the present invention. Detailed Implementation

[0031] To further illustrate the present invention, the following detailed description, in conjunction with embodiments, provides an interpenetrating network polymer plugging agent for drilling fluid, its preparation method, and its application. However, these descriptions should not be construed as limiting the scope of protection of the present invention.

[0032] Example 1

[0033] The preparation method of the interpenetrating network polymer plugging agent for drilling fluid according to the present invention includes the following steps:

[0034] The mixture of 20g styrene and 0.04g 1,4-divinylbenzene, and the mixture of 10g butyl methacrylate and 0.2g 1,4-divinylbenzene were washed three times with 20% NaOH aqueous solution and set aside for later use.

[0035] Dissolve 0.24g of initiator (ammonium persulfate) in 6g of deionized water to make two initiator solutions (2 / 3 and 1 / 3 respectively) for later use.

[0036] In a 250 mL four-necked flask equipped with a condenser, stirrer, and N2 gas channel, 60 g of water, 0.8 g of sodium alkylbenzene sulfonate, 0.8 g of polyoxyethylene alkyl ether, and 4 g of acrylamide were added and dissolved. Then, a mixture of 20 g of styrene and 0.04 g of 1,4-divinylbenzene was added. The mixture was stirred at 600 rpm for 30 min under N2 atmosphere, then the temperature was raised from room temperature to 70 °C. The stirring speed was reduced to 450 rpm, and a first-stage initiator solution was slowly added dropwise. The mixture was kept at this temperature for 1 h. Then, a mixture of 10 g of butyl methacrylate and 0.02 g of 1,4-divinylbenzene was slowly added dropwise over 1 h. After the addition was complete, stirring was continued for 2 h. Finally, a second-stage initiator solution was added dropwise, and the mixture was kept at this temperature and stirred for 3 h. Heating was then stopped, and the mixture was cooled to obtain an interpenetrating network polymer plugging agent for drilling fluids.

[0037] Figure 2 The diagram shows the interpenetrating polymer network structure of the plugging agent prepared in Example 1 of the present invention, including a first network crosslinked polymer A, a second network crosslinked polymer B, and a polymer C; wherein, the first network crosslinked polymer A is formed by polymerization of oil-soluble monomer A, the second network crosslinked polymer B is formed by polymerization of oil-soluble monomer B, and polymer C is formed by polymerization of water-soluble monomer C; they interpenetrate to form a network polymer structure.

[0038] Example 2:

[0039] The preparation method of the interpenetrating network polymer plugging agent for drilling fluid according to the present invention includes the following steps:

[0040] The mixture of 20g styrene and 0.04g 1,4-divinylbenzene, and the mixture of 10g butyl acrylate and 0.02g 1,4-divinylbenzene were washed three times with 20% NaOH aqueous solution and set aside for later use.

[0041] Dissolve 0.24g of initiator (ammonium persulfate) in 6g of deionized water to make two initiator solutions (2 / 3 and 1 / 3 respectively) for later use.

[0042] In a 250 mL four-necked flask equipped with a condenser, stirrer, and N2 gas channel, 60 g of water, 0.8 g of sodium alkylbenzene sulfonate, 0.8 g of polyoxyethylene alkyl ether, and 4 g of acrylamide were added and dissolved. Then, a mixture of 20 g of styrene and 0.04 g of 1,4-divinylbenzene was added. The mixture was stirred at 600 rpm for 30 min under N2 atmosphere, then the temperature was raised from room temperature to 70 °C. The stirring speed was reduced to 450 rpm, and a first-stage initiator solution was slowly added dropwise. Polymerization was maintained at this temperature for 1 h. Then, a mixture of 10 g of butyl acrylate and 0.02 g of 1,4-divinylbenzene was slowly added dropwise over 1 h. After the addition was complete, stirring was continued for 2 h. Finally, a second-stage initiator solution was added dropwise, and the mixture was stirred at this temperature for 3 h. Heating was then stopped, and the mixture was cooled to obtain an interpenetrating network polymer plugging agent for drilling fluids.

[0043] Example 3:

[0044] The preparation method of the interpenetrating network polymer plugging agent for drilling fluid according to the present invention includes the following steps:

[0045] The mixture of 20g methyl methacrylate and 0.04g 1,4-divinylbenzene, and the mixture of 10g butyl methacrylate and 0.02g 1,4-divinylbenzene were washed three times with 20% NaOH aqueous solution and set aside for later use.

[0046] Dissolve 0.24g of initiator (ammonium persulfate) in 6g of deionized water to make two initiator solutions (2 / 3 and 1 / 3 respectively) for later use.

[0047] In a 250 mL four-necked flask equipped with a condenser, stirrer, and N2 gas channel, 60 g of water, 0.8 g of sodium alkylbenzene sulfonate, 0.8 g of polyoxyethylene alkyl ether, and 4 g of acrylamide were added and dissolved. Then, 20 g of methyl methacrylate and 0.04 g of 1,4-divinylbenzene mixture were added. The mixture was stirred at 600 rpm for 30 min under N2 atmosphere, then the temperature was raised from room temperature to 70 °C. The stirring speed was reduced to 450 rpm, and a first-stage initiator solution was slowly added dropwise. The mixture was kept at this temperature for 1 h. Then, 10 g of butyl methacrylate and 0.02 g of 1,4-divinylbenzene mixture were slowly added dropwise over 1 h. After the addition was complete, stirring was continued for 2 h. Finally, a second-stage initiator solution was added dropwise, and the mixture was kept at this temperature and stirred for 3 h. Heating was then stopped, and the mixture was cooled to obtain an interpenetrating network polymer plugging agent for drilling fluid.

[0048] Comparative Example 1:

[0049] Add 30g of methyl methacrylate and 0.06g of 1,4-divinylbenzene to a beaker, wash three times with 20% NaOH aqueous solution, and transfer to a four-necked flask to obtain the oil phase;

[0050] Dissolve 0.24g of initiator (ammonium persulfate) in 6g of deionized water to obtain an initiator solution for later use;

[0051] In a 250 mL four-necked flask equipped with a condenser, stirrer, and N2 gas channel, 60 g of water, 0.8 g of sodium alkylbenzene sulfonate, 0.8 g of polyoxyethylene alkyl ether, and 4 g of acrylic acid were added and dissolved. The pH was adjusted to 7.5 with 20% NaOH aqueous solution, and butyl methacrylate was added. The mixture was stirred at 600 rpm for 30 min under N2 atmosphere, then the temperature was raised from room temperature to 70 °C, the stirring speed was reduced to 450 rpm, and the initiator solution was slowly added dropwise. The mixture was kept at this temperature for 4 h for polymerization, then heating was stopped, and the mixture was cooled to obtain the product, which was Comparative Example 1.

[0052] Comparative Example 2:

[0053] Add 30g of butyl acrylate and 0.06g of 1,4-divinylbenzene to a beaker, wash three times with 20% NaOH aqueous solution, and transfer to a four-necked flask to obtain the oil phase;

[0054] Dissolve 0.24g of initiator (ammonium persulfate) in 6g of deionized water to obtain an initiator solution for later use;

[0055] In a 250 mL four-necked flask equipped with a condenser, stirrer, and N2 gas channel, add 60 g of water, 0.8 g of sodium alkylbenzene sulfonate, 0.8 g of polyoxyethylene alkyl ether, and 4 g of AM. Mix and dissolve the mixture, then add styrene. Stir at 600 rpm for 30 min under N2 atmosphere, then raise the temperature from room temperature to 70 °C, reduce the stirring speed to 450 rpm, and slowly add the initiator solution. Polymerize at this temperature for 4 h to obtain the product, which is Comparative Example 2.

[0056] The products prepared according to the embodiments of the present invention were evaluated, and the results are as follows:

[0057] (1) Particle size analysis

[0058] The interpenetrating network polymer plugging agent obtained in the examples was measured using a laser particle size analyzer, and the results are shown in Table 1. As can be seen from Table 1, the interpenetrating network polymer plugging agent for drilling fluid obtained in this invention has a particle size in the micro-nano range, making it suitable for use in drilling plugging and for sealing microfractures and pores.

[0059] Table 1. Particle size D of the products from the examples 50

[0060]

[0061]

[0062] (2) Blocking performance evaluation

[0063] ① Oil-based drilling fluid

[0064] The drilling fluid obtained from the reaction in the example was added to an oil-based drilling fluid using an interpenetrating network polymer plugging agent. After aging at 200°C for 16 hours, the rheological properties of the drilling fluid were measured using a six-speed rotational viscometer at 65°C. The high-temperature, high-pressure filtration loss of the drilling fluid was also measured, and the results are shown in Table 2. Table 2 shows that adding the product of this invention to the oil-based drilling fluid did not significantly change the rheological properties of the drilling fluid system; however, the high-temperature, high-pressure filtration loss decreased. This indicates that the interpenetrating network polymer plugging agent has good compatibility with oil-based drilling fluids and exhibits good filtration loss reduction and plugging performance.

[0065] Table 2 Evaluation of Product Dosage and Drilling Fluid Compatibility in Examples

[0066] Interpenetrating network polymer plugging agent / % PV / mPa·s YP / Pa FL HTHP / mL]]> base slurry 46 15 17.6 Base slurry + 1% of the product from Example 1 46 15 13.2 Base slurry + 2% of the product from Example 1 47 16 10.8 Base slurry + 3% of the product from Example 1 48 16 9.2 Base slurry + 2% of the product from Example 2 47 16 11.4 Base slurry + 2% of the product from Example 3 48 16 11.2 Base slurry + 2% of Comparative Example 1 product 46 15 15.6 Base slurry + 2% of Comparative Example 2 product 46 15 15.4

[0067] Note: Diesel fuel + 20% calcium chloride aqueous solution (0# diesel fuel: 20% calcium chloride aqueous solution = 90:10) + 5% emulsifier + 2% calcium oxide + 2% organic clay + 4% filtration reducer (density 1.8g / cm³) 3The emulsifier is a polyamide integrated emulsifier (LEMUL emulsifier for oil-based drilling fluids), Zhongyuan Petroleum Engineering Co., Ltd., patent number ZL.201711027059.X; organic soil, Zhejiang Fenghong New Material Co., Ltd. (BS-1C); filtration loss reducer is an oxidized asphalt filtration loss reducer, Shandong Deshunyuan Petroleum Technology Co., Ltd. (OFC).

[0068] ② Water-based drilling fluid

[0069] The drilling fluid obtained from the reaction in the example was added to a 4% bentonite-based slurry (prepared by adding 0.8g Na2CO3 and 16g bentonite to 400mL of clean water, stirring thoroughly, and curing at room temperature for 24h) using an interpenetrating network polymer plugging agent. The slurry was then aged at 200℃ for 16h. Rheological properties were measured using a six-speed rotational viscometer at room temperature, and API filtration loss was measured using an API medium-pressure fluid loss meter. The results are shown in Table 3. Table 3 shows that the product of this invention can effectively reduce drilling fluid filtration loss in water-based drilling fluids.

[0070] Table 3 Evaluation of Product Dosage and Drilling Fluid Compatibility in Examples

[0071] Interpenetrating network polymer plugging agent / % AV / mPa·s PV / mPa·s YP / mPa.s <![CDATA[FL API / mL]]> base slurry 8 7 1 32.4 Base slurry + 1% of the product from Example 1 8 7 1 26.2 Base slurry + 2% of the product from Example 1 8.5 7 1.5 22.8 Base slurry + 3% of the product from Example 1 8 7 1 18.6 Base slurry + 2% of the product from Example 2 8 7 1 23.4 Base slurry + 2% of the product from Example 3 8 7 1 24.0 Base slurry + 2% of Comparative Example 1 product 8 7 1 28.2 Base slurry + 2% of Comparative Example 2 product 8 7 1 28.8

[0072] The experimental results show that this product has the following characteristics: temperature resistance up to 200℃, good compatibility with both oil-based and water-based drilling fluids, significant reduction in filtration loss and plugging effect, and can be used for plugging of high-temperature formations.

[0073] (3) Adhesion and wall protection

[0074] 10% of the drilling fluid obtained in Example 1 was added to clean water with an interpenetrating network polymer plugging agent and subjected to static hot rolling at 200°C. The pressure filtration loss in API was measured at room temperature. After the filter cake was dried at room temperature, its state was observed under an electron scanning microscope (see...). Figure 5 Add water (containing methylene blue) to the filter cake and observe its wettability (see...). Figure 6 The medium-pressure filter cake surface has a dense film and some polymer microparticles, indicating that the material has the functions of particle blocking and wall bonding; the evaluation of water wettability shows that the hydrophilicity of the film is reduced, which can delay the water wetting of the filter cake.

[0075] As can be seen from the above embodiments, the present invention provides a method for preparing an interpenetrating network polymer plugging agent for drilling fluid, comprising the following steps: 1) mixing water, emulsifier A, emulsifier B and water-soluble monomer C to obtain an aqueous phase; 2) mixing the aqueous phase, oil-soluble monomer A and crosslinking agent D, and emulsifying to obtain an emulsion reaction mixture; 3) mixing the emulsion reaction mixture with a first-stage initiator solution, and polymerizing at a constant temperature to obtain a polymerized emulsion; 4) mixing the polymerized emulsion with oil-soluble monomer B, crosslinking agent E and a second-stage initiator solution, and continuing to polymerize at a constant temperature to obtain an interpenetrating network polymer plugging agent for drilling fluid. This invention improves the rigidity and hardness of polymers by using the above-mentioned oil-soluble monomer A (hard monomer), the above-mentioned oil-soluble monomer B (soft monomer) to improve the elasticity of polymers, and the above-mentioned water-soluble monomer C to improve the hydrophilicity of polymers. The interpenetrating network structure improves temperature resistance. The plugging agent prepared by this method can take into account elastic deformation, bonding effect and temperature resistance (200℃), and has good compatibility with both oil-based and water-based drilling fluids. It also has significant effects on reducing filtration loss and plugging.

[0076] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing an interpenetrating network polymer plugging agent for drilling fluids, comprising the following steps: 1) Mix water, emulsifier A, emulsifier B and water-soluble monomer C to obtain an aqueous phase; 2) Mix the aqueous phase, oil-soluble monomer A, and crosslinking agent D, and emulsify to obtain an emulsified reaction mixture; 3) Mix the emulsion reaction mixture with a first-stage initiator solution, and polymerize under heat to obtain the polymerized emulsion; 4) The polymerized emulsion is mixed with oil-soluble monomer B, crosslinking agent E and second-stage initiator solution, and polymerization is continued at a constant temperature to obtain an interpenetrating network polymer plugging agent for drilling fluid.

2. The preparation method according to claim 1, characterized in that, In step 1), the emulsifier A is selected from one or more of sodium alkyl sulfate, sodium alkylbenzene sulfonate, sodium dialkyl-2-sulfosuccinate, and sodium alkylallyloxy polyoxyethylene phosphate. The emulsifier B is selected from one or more of polyoxyethylene alkyl ether, polyoxyethylene phenolic ether, polyoxyethylene sorbitan ether stearate and polyoxyethylene sorbitan monooleate. The water-soluble monomer C is selected from one or more of methacrylic acid, acrylamide, acrylic acid, and AMPS.

3. The preparation method according to claim 1, characterized in that, In step 2), the oil-soluble monomer A is selected from styrene and / or methyl methacrylate; The crosslinking agent D is selected from one or more of N,N'-methylenebisacrylamide, polyvinyl alcohol diacrylate, 1,3-butadiene, and 1,4-divinylbenzene.

4. The preparation method according to claim 1, characterized in that, The initiator in the first initiator solution in step 3) and the initiator in the second initiator solution in step 4) are independently selected from one or more of potassium persulfate, ammonium persulfate and sodium persulfate.

5. The preparation method according to claim 1, characterized in that, In step 4), the oil-soluble monomer B is selected from one or more of butyl methacrylate, methyl acrylate, vinyl acetate, butyl acrylate, and isooctyl acrylate. The crosslinking agent E is selected from one or more of N,N'-methylenebisacrylamide, polyvinyl alcohol diacrylate, 1,3-butadiene, and 1,4-divinylbenzene.

6. The preparation method according to claim 1, characterized in that, The temperatures for both heat preservation polymerization and continued heat preservation polymerization are 70–80℃.

7. The preparation method according to claim 1, characterized in that, Based on the total mass of oil-soluble monomer A, oil-soluble monomer B, and water-soluble monomer C as 100%, the water-soluble monomer C accounts for 10% to 20%; the oil-soluble monomer A accounts for 50% to 70%; and the oil-soluble monomer B accounts for 20% to 40%.

8. According to the preparation method of claim 1, based on the total mass of oil-soluble monomer A, oil-soluble monomer B and water-soluble monomer C, the total amount of crosslinking agent added is 0.1% to 0.5%; the total amount of initiator added is 0.5% to 2.0%; and the amounts of emulsifier A and emulsifier B are both 2% to 3%. The pH value of the aqueous phase was adjusted to 7.5–8.5 using a 20% NaOH aqueous solution.

9. An interpenetrating network polymer plugging agent for drilling fluid prepared by the preparation method according to any one of claims 1 to 8; The interpenetrating network polymer plugging agent for drilling fluid has a particle size of 0.05–50 μm, D 50 ≤15μm.

10. The application of an interpenetrating network polymer plugging agent for drilling fluid prepared by any one of claims 1 to 8 in oil-based drilling fluids, water-based drilling fluids, or high-temperature formations above 200°C.

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