Bonding wall-protecting polymer plugging agent for drilling fluid as well as preparation method and application of bonding wall-protecting polymer plugging agent

Abstract

The invention provides an adhesive wall-protecting polymer plugging agent for drilling fluid. The adhesive wall-protecting polymer plugging agent has a structure as shown in a formula I or a formula II. The polymer comprises polymer blocks with different glass transition temperatures, can be subjected to phase change at different temperatures, has cohesiveness, and is wide in leakage layer temperature range; the drilling fluid has good compatibility with oil-based drilling fluid and water-based drilling fluid; the well wall plugging agent can give consideration to deformability, bonding effect and high-temperature stability, has compact plugging and bonding wall protection effects, and achieves the purposes of effectively plugging micro-nano pores and improving well wall stability.

Description

Technical Field

[0001] This invention belongs to the technical field of drilling fluid treatment agents in oil drilling engineering, and particularly relates to a drilling fluid bonding and wall-protecting polymer plugging agent, its preparation method and application. Background Technology

[0002] During oil and gas 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 drill bits are high, and the handling is difficult. Both water-based and oil-based drilling fluids have been involved. 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 formation, and the Dongyuemiao Formation of Well Xingye 7, show severe stress release due to fracture. The Shunbei Santamu Formation limestone and the Maokou Formation in the Southwest work area also exhibit geological fractures.

[0003] 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 are needed to form a tight sealing layer, reduce drilling fluid intrusion, and improve the formation's pressure-bearing capacity, preventing collapse due to leakage. Simultaneously, to further enhance the anti-collapse effect, the material needs to possess a certain degree of adhesion, acting as a bond and protector for the wellbore. Commonly used polymer sealing materials cannot simultaneously achieve both elastic deformation and adhesion, thus failing to meet the required sealing, leakage prevention, and collapse prevention effects. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a bonding and wall-protecting polymer plugging agent for drilling fluid, its preparation method and application, which has excellent temperature resistance and can overcome the plugging problem of oil-based and water-based drilling fluids in deep wells at temperatures above 150°C.

[0005] This invention provides a bonding and wall-protecting polymer plugging agent for drilling fluids, having a structure of Formula I or Formula II:

[0006]

[0007] The value of m is 500 to 10000, the value of n is 1000 to 10000, and the value of p is 500 to 10000.

[0008] In formula I, R1 is selected from -H or C1~C 12 hydrocarbon group;

[0009] In Equations I and II, R3 and R5 are independently selected from -H or C1 to C 12 hydrocarbon group;

[0010] R2 is selected from C2~C 12 Hydrocarbon group; R4 is selected from -H, -NH2 or -NHC(CH3)2CHSO3H.

[0011] Preferably, R1 is selected from -H, -CH3, -CH2CH3, or -CH2CH2CH3;

[0012] In Formulas I and II, R3 and R5 are independently selected from -H, -CH3, -CH2CH3 or -CH2CH2CH3; R2 is selected from -CH2CH3 or -CH2CH2CH3.

[0013] This invention provides a method for preparing a bonding and wall-protecting polymer plugging agent for drilling fluids, comprising the following steps:

[0014] Emulsifier A, emulsifier B, water-soluble organic monomer C, and water are mixed to obtain an aqueous phase;

[0015] The aqueous phase and oil-soluble monomer A are mixed and emulsified to obtain an emulsified reaction mixture; oil-soluble monomer A is selected from styrene or methyl methacrylate;

[0016] Mix the initiator with water until fully dissolved to obtain an initiator solution;

[0017] The emulsion reaction mixture is mixed with 65-70% of the initiator solution, and a polymerization reaction is carried out to obtain the polymerized emulsion.

[0018] The polymerized emulsion and oil-soluble monomer B, along with the remaining 30-35% of the initiator aqueous solution, are mixed and polymerized further to obtain a drilling fluid bonding and wall-protecting polymer plugging agent having the structure shown in Formula I or Formula II.

[0019] Preferably, the water-soluble organic monomer C is selected from one or more of methacrylic acid, acrylamide, acrylic acid, and AMPS;

[0020] The amount of water-soluble monomer C added is 10% to 20% of the total mass of oil-soluble monomer A, oil-soluble monomer B and water-soluble monomer C.

[0021] Preferably, the emulsifier is selected from emulsifier A and / or emulsifier B;

[0022] The emulsifier A is selected from one or more of sodium alkyl sulfate, sodium alkylbenzene sulfonate, sodium dialkyl-2-sulfosuccinate, and sodium alkylallyloxypolyoxyethylene phosphate.

[0023] The emulsifier B is selected from one or more of polyoxyethylene alkyl ether, polyoxyethylene phenolic ether, polyoxyethylene sorbitan ether stearate, and polyoxyethylene sorbitan monooleate.

[0024] Preferably, the amount of emulsifier A added is 2% to 3% of the total mass of oil-soluble monomer A, oil-soluble monomer B and water-soluble monomer C;

[0025] The amount of emulsifier B added is 2% to 3% of the total mass of the oil-soluble monomer A, oil-soluble monomer B and water-soluble monomer C.

[0026] Preferably, the amount of oil-soluble monomer A added is 50% to 75% of the total mass of oil-soluble monomer A, oil-soluble monomer B and water-soluble monomer C;

[0027] The oil-soluble monomer B can be one or more of butyl methacrylate, methyl acrylate, vinyl acetate, butyl acrylate, and isooctyl acrylate.

[0028] The amount of oil-soluble monomer B added is 25% to 40% of the total mass of oil-soluble monomer A, oil-soluble monomer B and water-soluble monomer C.

[0029] Preferably, the polymerization reaction is carried out at a temperature of 70–80°C for a time of 55–65 min.

[0030] The polymerization reaction continues at a temperature of 70–80°C for 60–300 min.

[0031] Preferably, the particle size distribution of the drilling fluid binder and wall-protecting polymer plugging agent is 0.05–50 μm, D 50 ≤15μm.

[0032] Preferably, the drilling fluid bonding and wall-protecting polymer plugging agent is applied to oil-based drilling fluid or water-based drilling fluid;

[0033] The application temperature of the drilling fluid bonding and wall-protecting polymer plugging agent shall not exceed 150°C.

[0034] This invention provides a polymeric plugging agent for drilling fluids, having a structure of Formula I or Formula II. The polymer comprises polymer blocks with different glass transition temperatures, allowing for phase transitions at various temperatures. It exhibits adhesive properties and a wide operating temperature range for leaky zones. It demonstrates good compatibility with both oil-based and water-based drilling fluids. It balances deformability, adhesiveness, and high-temperature stability, providing both sealing and plugging effects to effectively seal micro- and nano-pores and improve wellbore stability. Attached Figure Description

[0035] Figure 1 This is a particle size distribution diagram of the drilling fluid bonding and wall-protecting polymer plugging agent prepared in Example 1 of the present invention;

[0036] Figure 2 The infrared spectrum of the drilling fluid bonding and wall-protecting polymer plugging agent prepared in Example 1 of this invention;

[0037] Figure 3 The nuclear magnetic resonance spectrum of the drilling fluid bonding and wall-protecting polymer plugging agent prepared in Example 1 of the present invention;

[0038] Figure 4 The DSC spectrum of the drilling fluid bonding and wall-protecting polymer plugging agent prepared in Example 1 of this invention;

[0039] Figure 5 This is a scanning electron microscope image of the drilling fluid bonding and wall-protecting polymer plugging agent prepared in Example 1 of the present invention;

[0040] Figure 6 The diagram shows the wettability test results of the drilling fluid bonding and wall-protecting polymer plugging agent prepared according to an embodiment of the present invention and water. Detailed Implementation

[0041] This invention provides a bonding and wall-protecting polymer plugging agent for drilling fluids, having a structure of Formula I or Formula II:

[0042]

[0043] The value of m is 500-10000, preferably 2000-7000, more preferably 4000-6000; the value of n is 1000-10000, preferably 1500-5000, more preferably 1500-2500; the value of p is 500-10000, preferably 1000-5000, more preferably 1200-1600.

[0044] In formula I, R1 is selected from -H or C1~C 12 Hydrocarbon group, preferably -H or C1 to C4 hydrocarbon group;

[0045] In Equations I and II, R3 and R5 are independently selected from -H or C1 to C 12 Hydrocarbon group, preferably -H or C1 to C4 hydrocarbon group;

[0046] R2 is selected from C2~C 12 Hydrocarbon group; preferably C2-C5 hydrocarbon group;

[0047] R4 is selected from -H, -NH2, or -NHC(CH3)2CHSO3H.

[0048] In a specific embodiment of the present invention, R1 is selected from -H, -CH3, -CH2CH3, or -CH2CH2CH3;

[0049] In Formulas I and II, R3 and R5 are independently selected from -H, -CH3, -CH2CH3 or -CH2CH2CH3; R2 is selected from -CH2CH3 or -CH2CH2CH3.

[0050] The aforementioned polymers include polymer blocks with different glass transition temperatures, which can undergo phase transitions at different temperatures, exhibit adhesive properties, and have a wide operating temperature range for lost circulation. They also have good compatibility with both oil-based and water-based drilling fluids. Their elastic deformation and adhesive properties form a strong and dense adhesive sealing layer, effectively preventing lost circulation and sealing the wellbore for wall protection.

[0051] The aforementioned drilling fluid adhesive wall-blocking polymer has a micro-nano particle size.

[0052] In a specific embodiment of the present invention, the drilling fluid adhesive wall-sealing polymer plugging agent shown has a structure of Formula I, wherein R1, R2, R3, R4 and R5 are -H, -CH2CH2CH3, -CH3, -NH2 and -H, respectively; the values ​​of m, n and p are 4100, 1500 and 1200, respectively, and m:n:p = 41:15:12;

[0053] Alternatively, the drilling fluid adhesive wall-sealing polymer plugging agent shown may have the structure of Formula I, wherein R1, R2, R3, R4 and R5 are -H, -CH2CH2CH3, -H, -H and -H, respectively; the values ​​of m, n and p are 5100, 2100 and 1500, and m:n:p = 17:7:5;

[0054] Or the drilling fluid binder wall-sealing polymer plugging agent shown has the structure of Formula II, wherein R2, R3, R4 and R5 are -CH2CH2CH3, -CH3, -NH2 and -H respectively; the values ​​of m, n and p are 5700, 2000 and 1600 respectively, and m:n:p = 57:20:16.

[0055] This invention provides a method for preparing the drilling fluid bonding and wall-protecting polymer plugging agent described in the above-mentioned technical solution, comprising the following steps:

[0056] Emulsifier A, emulsifier B, water-soluble organic monomer C, and water are mixed to obtain an aqueous phase;

[0057] The aqueous phase and oil-soluble monomer A are mixed and emulsified to obtain an emulsified reaction mixture; oil-soluble monomer A is selected from styrene or methyl methacrylate;

[0058] Mix the initiator with water until fully dissolved to obtain an initiator solution;

[0059] The emulsion mixture is mixed with 65% to 70% of the initiator solution, and a polymerization reaction is carried out to obtain the polymerized emulsion.

[0060] The polymerized emulsion and oil-soluble monomer B, along with the remaining 30%–35% of the initiator aqueous solution, are mixed and polymerized further to obtain a drilling fluid bonding and wall-protecting polymer plugging agent having the structure shown in Formula I or Formula II.

[0061] If the oil-soluble monomer A is selected from styrene, then the drilling fluid adhesive wall-protecting polymer plugging agent has the structure of Formula I; if the oil-soluble monomer A is selected from methyl methacrylate, then the drilling fluid adhesive wall-protecting polymer plugging agent has the structure of Formula II.

[0062] The oil-soluble monomers A and B used in this invention have different glass transition temperatures, and the oil-soluble polymer blocks A and B can undergo phase transitions at different temperatures, exhibiting adhesive properties and adapting to a wide range of lost circulation temperatures. Through the combined action of the oil-soluble monomers and water-soluble organic monomers, the plugging agent exhibits good compatibility with both oil-based and water-based drilling fluids. Through the elastic deformation and adhesive effect of the plugging agent, a strong and dense adhesive plugging layer is formed, effectively preventing lost circulation and achieving the purpose of sealing and protecting the well wall.

[0063] This invention involves mixing an emulsifier, a water-soluble organic monomer, and water to obtain an aqueous phase. The emulsifier used in this invention is selected from emulsifier A and / or emulsifier B; emulsifier A is selected from one or more of sodium alkyl sulfate, sodium alkylbenzene sulfonate, sodium dialkyl-2-sulfosuccinate, and sodium alkylallyloxypolyoxyethylene phosphate; emulsifier B is selected from one or more of polyoxyethylene alkyl ether, polyoxyethylene phenolic ether, polyoxyethylene sorbitan ether stearate, and polyoxyethylene sorbitan monooleate. Preferably, the water-soluble organic monomer is added after the water, emulsifier A, and emulsifier B are thoroughly mixed.

[0064] The water-soluble organic monomers used in this invention are selected from one or more of methacrylic acid, acrylamide, acrylic acid, and AMPS; the amount of water-soluble monomers added is 10% to 20% of the total mass of oil-soluble monomer A, oil-soluble monomer B, and water-soluble monomer C. These water-soluble monomers can provide hydrophilic groups, improve the hydrophilicity of the product, and enhance its compatibility and plugging performance with water-based drilling fluids.

[0065] After obtaining the aqueous phase, the present invention mixes the aqueous phase with oil-soluble monomer A and emulsifies it to obtain an emulsified reaction mixture. Preferably, the aqueous phase and oil-soluble monomer A are added sequentially to a four-necked flask equipped with a condenser, stirrer, and N2 gas channel. Before use, the oil-soluble monomer A is preferably washed three times with a 20% NaOH aqueous solution. The amount of oil-soluble monomer A added in the present invention is 50% to 75% of the total mass of oil-soluble monomer A, oil-soluble monomer B, and water-soluble monomer C. The oil-soluble monomer A in the present invention is selected from styrene and / or methyl methacrylate.

[0066] After obtaining the emulsion reaction mixture, the present invention mixes the emulsion reaction mixture with a 2 / 3 initiator solution comprising 65%–70% of the total mixture and performs a polymerization reaction to obtain a polymerized emulsion. The initiator used in the present invention is selected from one or more of potassium persulfate, ammonium persulfate, and sodium persulfate. The polymerization reaction temperature in the present invention is 70–80°C, and the time is 55–65 min. The initiator solution used in the first stage of polymerization accounts for 65%–70% of the total initiator dosage, preferably 2 / 3.

[0067] After obtaining the polymerized emulsion, the present invention mixes the polymerized emulsion with oil-soluble monomer B and the remaining 30%–35% of the 1 / 3 initiator solution, and continues polymerization to obtain a bonding and wall-protecting polymer plugging agent for drilling fluids. In the present invention, the amount of oil-soluble monomer B added is 25%–40% of the total monomer addition. The oil-soluble monomer B in the present invention is selected from one or more of butyl methacrylate, methyl acrylate, vinyl acetate, butyl acrylate, and isooctyl acrylate. The remaining initiator solution is a two-stage initiator, accounting for 30%–35% of the total initiator solution, preferably 1 / 3.

[0068] In this invention, the polymerization temperature is 70–80°C and the polymerization time is 60–300 min.

[0069] The drilling fluid bonding and wall-protecting polymer plugging agent provided by this invention has a particle size distribution of 0.05–50 μm, D 50 ≤15μm.

[0070] The drilling fluid bonding and wall-protecting polymer plugging agent described in the above-mentioned technical solution provided by the present invention is applied to oil-based drilling fluid or water-based drilling fluid; the application temperature of the drilling fluid bonding and wall-protecting polymer plugging agent is not higher than 150°C.

[0071] The oil-based drilling fluid of this invention comprises diesel oil and a 20% calcium chloride aqueous solution in a volume ratio of 80:20. Based on the total amount of diesel oil and the 20% calcium chloride aqueous solution, the oil-based drilling fluid also includes 4% emulsifier, 4% calcium oxide, 3% organic clay, and 4% filtration reducer. The bonding and wall-protecting polymer plugging agent used in the drilling fluid accounts for 1% to 3% of the oil-based drilling fluid mass.

[0072] The water-based drilling fluid is a slurry. The bonding and wall-protecting polymer plugging agent used in the drilling fluid accounts for 1-3% of the water-based drilling fluid's mass.

[0073] To further illustrate the present invention, the following detailed description, in conjunction with embodiments, provides a drilling fluid bonding and wall-protecting polymer plugging agent, its preparation method, and its application. However, these descriptions should not be construed as limiting the scope of protection of the present invention.

[0074] Example 1

[0075] The preparation method of the drilling fluid bonding and wall-protecting polymer plugging agent of the present invention includes the following steps:

[0076] Wash 20g of styrene and 10g of butyl methacrylate three times with 20% NaOH aqueous solution and set aside; dissolve 0.75g of initiator (ammonium persulfate) in 7.5g of deionized water and divide it into two portions: a first-stage initiator and a second-stage initiator, and set aside for later use.

[0077] In a 250 mL four-necked flask equipped with a condenser, stirrer, and N2 gas channel, 72.5 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 to obtain an aqueous phase. Then, 20 g of styrene was added, and the mixture was stirred at 600 rpm for 30 min under N2 atmosphere. The temperature was then raised from room temperature to 70 °C, and the stirring speed was reduced to 450 rpm. A first-stage initiator solution (accounting for 2 / 3 of the total initiator) was slowly added dropwise, and the mixture was kept at this temperature for 1 h for polymerization. Then, 10 g of butyl methacrylate and a second-stage initiator solution (accounting for 1 / 3 of the total initiator) were slowly added dropwise over 1 h. The mixture was kept at this temperature and stirred for another 3 h. After that, the heating was stopped, and the mixture was cooled to obtain a drilling fluid bonding and wall-protecting polymer plugging agent. R1, R2, R3, R4, and R5 are -H, -CH2CH2CH3, -CH3, -NH2, and -H, respectively. The values ​​of m, n, and p are 4100, 1500, and 1200, respectively, and the ratio of m:n:p is 41:15:12.

[0078] Figure 1 The particle size distribution of the product; Figure 2 The infrared spectrum of the product; Figure 3 The NMR spectrum of the product; Figure 4 The differential scanning calorimetry (DSC) spectrum of the product; Figure 4 The two valleys indicate that they softened at different temperatures.

[0079] Example 2:

[0080] The preparation method of the drilling fluid bonding and wall-protecting polymer plugging agent of the present invention includes the following steps:

[0081] Wash 20g of styrene and 10g of butyl acrylate three times with 20% NaOH aqueous solution and set aside; dissolve 0.75g of initiator (ammonium persulfate) in 7.5g of deionized water and divide it into two portions: a first-stage initiator and a second-stage initiator, and set aside for later use.

[0082] In a 250 mL four-necked flask equipped with a condenser, stirrer, and N2 gas channel, 72.5 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 to obtain an aqueous phase. Then, 20 g of styrene was added to adjust the pH to 7.5. 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 primary initiator solution (accounting for 2 / 3 of the total initiator volume) was slowly added dropwise. Polymerization was maintained at this temperature for 1 h. Then, 10 g of butyl acrylate and a secondary initiator solution (accounting for 1 / 3 of the total initiator volume) were slowly added dropwise over 1 h. The mixture was then stirred and maintained at this temperature for another 3 h. Heating was stopped, and the mixture was cooled to obtain a drilling fluid bonding and wall-protecting polymer plugging agent. R1, R2, R3, R4, and R5 are -H, -CH2CH2CH3, -H, -H, and -H, respectively. The values ​​of m, n, and p are 5100, 2100, and 1500, respectively, and the ratio of m:n:p is 17:7:5.

[0083] Example 3:

[0084] The preparation method of the drilling fluid bonding and wall-protecting polymer plugging agent of the present invention includes the following steps:

[0085] Wash 20g of methyl methacrylate and 10g of butyl methacrylate three times with 20% NaOH aqueous solution and set aside; dissolve 0.75g of initiator (ammonium persulfate) in 7.5g of deionized water and divide it into two portions: a first-stage initiator and a second-stage initiator, and set aside for later use.

[0086] In a 250 mL four-necked flask equipped with a condenser, stirrer, and N2 gas channel, 72.5 g of water, 0.8 g of sodium alkylbenzene sulfonate, 0.8 g of polyoxyethylene alkyl ether, and 4 g of acrylamide (AM) were added and dissolved. 20 g of methyl methacrylate was added, and the mixture was stirred at 600 rpm for 30 min under N2 atmosphere. The temperature was then raised from room temperature to 70 °C, and the stirring speed was reduced to 450 rpm. A first-stage initiator solution (accounting for 2 / 3 of the total initiator) was slowly added dropwise. Polymerization was maintained at this temperature for 1 h. Then, 10 g of butyl methacrylate and a second-stage initiator solution (accounting for 1 / 3 of the total initiator) were slowly added dropwise over 1 h. After stirring at this temperature for another 3 h, heating was stopped, and the mixture was cooled to obtain a drilling fluid bonding and wall-protecting polymer plugging agent. R2, R3, R4, and R5 are -CH2CH2CH3, -CH3, -NH2, and -H, respectively. The values ​​of m, n, and p are 5700, 2000, and 1600, respectively, and the ratio of m:n:p is 57:20:16.

[0087] Comparative Example 1:

[0088] Add 30g of methyl methacrylate to a beaker, wash three times with 20% NaOH aqueous solution, and transfer to a four-necked flask to obtain the oil phase;

[0089] In a 250 mL four-necked flask equipped with a condenser, stirrer, and N2 gas channel, 72.5 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 an initiator solution (0.75 g of ammonium persulfate dissolved in 7.5 g of deionized water) 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 is Comparative Example 1.

[0090] Comparative Example 2:

[0091] Add 30g of butyl methacrylate to a beaker, wash three times with 20% NaOH aqueous solution, and transfer to a four-necked flask to obtain the oil phase; add 72.5g of water, 0.8g of sodium alkylbenzene sulfonate, 0.8g of polyoxyethylene alkyl ether, and 4g of AM to a 250mL four-necked flask equipped with a condenser, stirrer, and N2 gas channel, mix and dissolve, stir at 600rpm for 30min under N2 atmosphere, then raise the temperature from room temperature to 70℃, reduce the stirring speed to 450rpm, and slowly add the initiator solution (0.75g of ammonium persulfate dissolved in 7.5g of deionized water), keep at the temperature for 4h to polymerize, and obtain the product as Comparative Example 2.

[0092] The products prepared according to the embodiments of the present invention were evaluated, and the results are as follows:

[0093] (1) Particle size analysis

[0094] The binder wall-protecting polymer plugging agents obtained in the examples and comparative examples were measured using a laser particle size analyzer, and the results are shown in Table 1. Table 1 shows that the binder wall-protecting 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.

[0095] Table 1. Particle size D of the products from the examples and comparative examples. 50

[0096] Serial Number <![CDATA[Particle size D 50 , μm]]> Example 1 6.25 Example 2 7.21 Example 3 6.43 Comparative Example 1 2.58 Comparative Example 2 2.61

[0097] (2) Blocking performance evaluation

[0098] ① Oil-based drilling fluid

[0099] The drilling fluid obtained from the reaction in the example was added to an oil-based drilling fluid using a bonding and wall-protecting polymer plugging agent. After aging at 150°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 bonding and wall-protecting polymer plugging agent has good compatibility with oil-based drilling fluids and exhibits good plugging and filtration loss reduction performance.

[0100] Table 2 Evaluation of Product Dosage and Drilling Fluid Compatibility in Examples

[0101]

[0102]

[0103] Note: Diesel fuel + 20% calcium chloride aqueous solution (0# diesel fuel: 20% calcium chloride aqueous solution = 80:20) + 4% emulsifier + 4% calcium oxide + 3% organic clay + 4% filtration reducer (density 1.7g / cm³) 3 The 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).

[0104] ② Water-based drilling fluid

[0105] The drilling fluid obtained from the reaction in the example was added to 4% shale slurry with a bonding and wall-protecting polymer plugging agent and aged at 150°C for 16 hours. Rheological properties were measured at room temperature using a six-speed rotational viscometer, and API filtration loss (FL) was measured using an API medium-pressure fluid loss meter. API The results are shown in Table 3. As can be seen from Table 3, the product of this invention can effectively reduce drilling fluid filtration loss in water-based drilling fluids.

[0106] Table 3 Evaluation of Product Dosage and Drilling Fluid Compatibility in Examples

[0107]

[0108]

[0109] The experimental results show that this product has the following characteristics: temperature resistance up to 150℃, 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.

[0110] (2) Adhesion and wall protection

[0111] The drilling fluid obtained from the reaction in Example 1 (2% of the binder and wall-protecting polymer sealant) was added to 4% shale slurry and aged at 150°C for 16 hours. The pressure filtration loss in API was measured. After the filter cake was dried at room temperature, its state was observed using an electron scanning microscope (see [link]). Figure 3 Add water to the filter cake and observe its wettability (see...). Figure 4 The polymer reacts with bentonite to form a dense, bonded filter cake. Evaluation of its wettability with clean water shows that this filter cake exhibits reduced hydrophilicity, and the polymer can delay the wetting of the filter cake by clean water, thus providing a bonding and protective effect on the filter cake wall.

[0112] As can be seen from the above embodiments, the present invention provides a polymer plugging agent for drilling fluids, having a structure of Formula I or Formula II. The polymer comprises polymer blocks with different glass transition temperatures, allowing for phase transitions at different temperatures, exhibiting adhesive properties, and covering a wide range of leakage temperature zones. It has good compatibility with both oil-based and water-based drilling fluids; it balances deformability, adhesiveness, and high-temperature resistance, improving the density of the plugging layer and the adhesive wall-protecting effect, thereby effectively sealing micro- and nano-pores and improving wellbore stability. Experimental results show that adding 1-3% of the plugging agent to oil-based drilling fluid results in a flow rate (FL) of 4.8-6.0 mL; adding 1-3% of the plugging agent to water-based drilling fluid results in a FL of 11.4-13.2 mL.

[0113] 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 polymeric plugging agent for drilling fluids, having a structure of Formula I or Formula II: The value of m is 500 to 10000, the value of n is 1000 to 10000, and the value of p is 500 to 10000. In formula I, R1 is selected from -H or C1~C 12 hydrocarbon group; In Equations I and II, R3 and R5 are independently selected from -H or C1 to C 12 hydrocarbon group; R2 is selected from C2~C 12 Hydrocarbon group; R4 is selected from -H, -NH2 or -NHC(CH3)2CHSO3H.

2. The drilling fluid bonding and wall-protecting polymer plugging agent according to claim 1, characterized in that, R1 is selected from -H, -CH3, -CH2CH3 or -CH2CH2CH3; In Formulas I and II, R3 and R5 are independently selected from -H, -CH3, -CH2CH3 or -CH2CH2CH3; R2 is selected from -CH2CH3 or -CH2CH2CH3.

3. A method for preparing the drilling fluid bonding and wall-protecting polymer plugging agent as described in claim 1, comprising the following steps: Emulsifier A, emulsifier B, water-soluble organic monomer C, and water are mixed to obtain an aqueous phase; The aqueous phase and oil-soluble monomer A are mixed and emulsified to obtain an emulsified reaction mixture; oil-soluble monomer A is selected from styrene or methyl methacrylate; Mix the initiator with water until fully dissolved to obtain an initiator solution; The emulsion reaction mixture is mixed with 65-70% of the initiator solution, and a polymerization reaction is carried out to obtain the polymerized emulsion. The polymerized emulsion and oil-soluble monomer B, along with the remaining 30-35% of the initiator solution, are mixed and polymerized further to obtain a drilling fluid bonding and wall-protecting polymer plugging agent having the structure shown in Formula I or Formula II.

4. The preparation method according to claim 3, characterized in that, The water-soluble organic monomer C is selected from one or more of methacrylic acid, acrylamide, acrylic acid, and AMPS; The amount of water-soluble monomer C added is 10% to 20% of the total mass of oil-soluble monomer A, oil-soluble monomer B and water-soluble monomer C.

5. The preparation method according to claim 3, characterized in that, The emulsifier is selected from emulsifier A and / or emulsifier B; The emulsifier A is selected from one or more of sodium alkyl sulfate, sodium alkylbenzene sulfonate, sodium dialkyl-2-sulfosuccinate, and sodium alkylallyloxypolyoxyethylene 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.

6. The preparation method according to claim 3, characterized in that, The amount of emulsifier A added is 2% to 3% of the total mass of oil-soluble monomer A, oil-soluble monomer B and water-soluble monomer C; The amount of emulsifier B added is 2% to 3% of the total mass of the oil-soluble monomer A, oil-soluble monomer B and water-soluble monomer C.

7. The preparation method according to claim 3, characterized in that, The amount of oil-soluble monomer A added is 50% to 75% of the total mass of oil-soluble monomer A, oil-soluble monomer B and water-soluble monomer C. The oil-soluble monomer B is selected from one or more of butyl methacrylate, methyl acrylate, vinyl acetate, butyl acrylate, and isooctyl acrylate; The amount of oil-soluble monomer B added is 25% to 40% of the total mass of oil-soluble monomer A, oil-soluble monomer B and water-soluble monomer C.

8. The preparation method according to claim 3, characterized in that, The polymerization reaction is carried out at a temperature of 70–80°C for a time of 55–65 min. The polymerization reaction continues at a temperature of 70–80°C for 60–300 min.

9. The preparation method according to claim 3, characterized in that, The particle size distribution of the drilling fluid binder and wall-protecting polymer plugging agent is 0.05–50 μm, D 50 ≤15μm.

10. A drilling fluid bonding and wall-protecting polymer plugging agent according to any one of claims 1 to 2, applied to oil-based drilling fluid or water-based drilling fluid; The application temperature of the drilling fluid bonding and wall-protecting polymer plugging agent shall not exceed 150°C.

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