Hollow polymer microspheres and methods of making and using the same

Abstract

The application provides a hollow polymer microsphere and a preparation method and application thereof. The preparation method of the hollow polymer microsphere comprises the following steps: (1) polymerizing a second monomer and a prepolymer of a first monomer by adopting an emulsion polymerization method to obtain a polymer emulsion; (2) performing spray drying on the polymer emulsion obtained in the step (1) to obtain the hollow polymer microsphere; wherein the first monomer comprises a styrene monomer and / or an acrylate monomer; and the second monomer comprises one or a combination of two or more than two of acrylamide, 2-acrylamido-2-methyl-1-propane sulfonic acid, dimethyldiallyl ammonium chloride and maleic anhydride. The hollow polymer microsphere can reduce heat exchange between a drilling fluid and a formation, and simultaneously serves as a plugging agent to reduce the leakage of a water-based drilling fluid to the formation.

Description

Technical Field

[0001] This invention belongs to the field of oilfield chemistry, specifically relating to hollow polymer microspheres as a sealing and heat-insulating agent for water-based drilling fluids and their preparation method. Background Technology

[0002] As conventional oil and gas resources are gradually depleted, unconventional oil and gas resources, such as deep and ultra-deep oil and gas resources and high-temperature geothermal resources in deep dry hot rocks, have become one of the main alternative energy sources.

[0003] During drilling, the high-temperature formation comes into contact with the ambient-temperature drilling fluid. Due to the significant temperature difference between the drilling fluid and the rock, the drilling fluid undergoes a material and energy exchange as it flows through the wellbore, causing the drilling fluid temperature to rise while the formation temperature decreases. The cooling process of the high-temperature rock can lead to low-temperature induced thermal stress cracking. These thermal stress-induced cracks can further propagate after the drilling fluid enters, reducing the rock's mechanical strength. If the drilling fluid's plugging and inhibition performance is poor, formation hydration and expansion may occur, potentially leading to a series of wellbore instability problems such as rockfall, enlargement, or even well collapse. Furthermore, as the drilling fluid temperature gradually rises to the formation temperature, the high temperature can cause drilling fluid treatment agents to undergo high-temperature hydrolysis and become ineffective, necessitating the replenishment of drilling fluid treatment agents.

[0004] Therefore, effectively reducing heat exchange between water-based drilling fluid and high-temperature formations and improving the plugging performance of water-based drilling fluid are of great significance for improving wellbore stability, extending the service life of drilling fluid, and reducing the occurrence of complex downhole conditions.

[0005] Currently, there are no research reports on heat insulation materials for water-based drilling fluids, while there is a considerable amount of research on high-temperature heat-insulating coatings. For example, CN102030540A discloses a high-temperature heat-insulating coating composed of inorganic high-temperature refractory mortar, silica aerogel, potassium hexatitanate whiskers, mica flakes, and acetone / anhydrous ethanol; CN105860790A discloses a high-temperature heat-insulating coating composed of solvent, organosilicon resin, and high-temperature filler; CN103725074A discloses a high-temperature heat-insulating coating composed of high-reflectivity pigment, heat-insulating powder, toughening agent, high-temperature binder, water, and additives. However, the high-temperature heat-insulating coatings disclosed above only have simple heat insulation and high-temperature resistance properties and cannot be applied to the drilling fluid field. Therefore, it is necessary to develop a heat insulation material specifically for water-based drilling fluids to reduce heat exchange between the drilling fluid and the formation. Since air has a very low thermal conductivity, developing a material with a hollow structure as a drilling fluid wall-forming material can significantly reduce heat transfer between the formation and the drilling fluid. Summary of the Invention

[0006] To address the aforementioned problems, the present invention aims to provide a hollow polymer microsphere, its preparation method, and its application. This hollow polymer microsphere can reduce heat exchange between drilling fluid and formation, and simultaneously act as a plugging agent to reduce leakage of water-based drilling fluid into the formation.

[0007] To achieve the above objectives, the present invention provides a method for preparing hollow polymer microspheres, comprising the following steps:

[0008] (1) The second monomer and the prepolymer of the first monomer are polymerized by emulsion polymerization to obtain a polymer emulsion;

[0009] (2) The polymer emulsion obtained in step (1) is spray-dried to obtain the hollow polymer microspheres; wherein the first monomer includes styrene monomers and / or acrylate monomers; the second monomer includes one or more of acrylamide, 2-acryloylamino-2-methyl-1-propanesulfonic acid, dimethyldiallylammonium chloride, and maleic anhydride.

[0010] According to a specific embodiment of the present invention, preferably, the styrene monomer has the structure shown in Formula I:

[0011]

[0012] In Formula I, R1 is selected from H, C1-C5 alkyl groups and their derivatives, and C6-C18 phenyl groups and their derivatives; preferably selected from methyl, ethyl, and phenyl groups.

[0013] The acrylate monomer has the structure shown in Formula II:

[0014]

[0015] In Equation II, R2 is selected from C1-C 10 alkyl groups and their derivatives; R3 is selected from H or methyl.

[0016] According to a specific embodiment of the present invention, preferably, step (1) includes the following steps:

[0017] (a) Preparation of prepolymer solution: Dissolve the first monomer, the first crosslinking agent and the first initiator in an organic solvent, raise the temperature to the first reaction temperature of 15-40℃, and react for 2-10 h (preferably 4-8 h) to obtain the prepolymer solution;

[0018] (b) Preparation of stable phase solution: After dissolving the stabilizer in water, add the second monomer, the second crosslinking agent, and the emulsifier to obtain the stable phase solution;

[0019] (c) Emulsion polymerization: The stable phase solution is added to the prepolymer solution, emulsified, and then the temperature is raised to the second reaction temperature of 40-80°C. A second initiator is added, and the reaction is carried out for 1-6 hours (preferably 3-5 hours) to obtain the polymer emulsion.

[0020] According to a specific embodiment of the present invention, preferably, in step (a), the first crosslinking agent includes one or more of divinylbenzene, dimethyldiimide, and ethylene glycol dimethacrylate.

[0021] According to a specific embodiment of the present invention, preferably, the first initiator includes one or a combination of two or more of benzoyl peroxide, azobisisobutyronitrile, and azobisisobutyramidine.

[0022] According to a specific embodiment of the present invention, preferably, the organic solvent includes one or more of dichloromethane, toluene, white oil, ethyl acetate, and cyclohexane.

[0023] According to a specific embodiment of the present invention, preferably, in step (b), the stabilizer includes one or more of polyvinyl alcohol, polyethylene glycol, hydroxymethyl cellulose, hydroxypropyl cellulose, hydroxyethyl cellulose, and carboxymethyl cellulose.

[0024] According to a specific embodiment of the present invention, preferably, the second crosslinking agent includes one or more of N,N-methylenebisacrylamide, formaldehyde, acetaldehyde, furfural, and urea-formaldehyde.

[0025] According to a specific embodiment of the present invention, preferably, the emulsifier includes one or more of Span 60, Span 80, Span 85, Tween 60, and Tween 80.

[0026] According to a specific embodiment of the present invention, preferably, in step (c), the second initiator includes one or more of potassium persulfate, ammonium persulfate, sodium bisulfite, and hydrogen peroxide.

[0027] According to a specific embodiment of the present invention, preferably, in step (a), the amount of the first monomer added is 20-40 g / 100 mL, more preferably 25-35 g / 100 mL.

[0028] According to a specific embodiment of the present invention, preferably, in step (a), the amount of the first crosslinking agent added is 0.5-2.5 g / 100 mL, more preferably 1-1.5 g / 100 mL.

[0029] According to a specific embodiment of the present invention, preferably, in step (a), the amount of the first initiator added is 0.1-0.6 g / 100 mL, more preferably 0.3-0.4 g / 100 mL.

[0030] According to a specific embodiment of the present invention, preferably, in step (b), the amount of stabilizer added is 1-5 g / 100 mL, more preferably 2-3 g / 100 mL.

[0031] According to a specific embodiment of the present invention, preferably, in step (b), the amount of the second monomer added is 5-15 g / 100 mL, more preferably 8-12 g / 100 mL.

[0032] According to a specific embodiment of the present invention, preferably, in step (b), the amount of the second crosslinking agent added is 0.5-2.5 g / 100 mL, more preferably 1-1.5 g / 100 mL.

[0033] According to a specific embodiment of the present invention, preferably, in step (b), the amount of emulsifier added is 1-5 g / 100 mL, more preferably 2-3 g / 100 mL.

[0034] According to a specific embodiment of the present invention, preferably, in step (c), the volume ratio of the prepolymer solution to the stable phase solution is 75:25-90:10, more preferably 80:20-85:15.

[0035] According to a specific embodiment of the present invention, preferably, in step (c), the amount of the second initiator added is 0.1-0.6 g / 100 mL, more preferably 0.3-0.4 g / 100 mL.

[0036] According to a specific embodiment of the present invention, preferably, the first reaction temperature is 25-30°C.

[0037] According to a specific embodiment of the present invention, preferably, the second reaction temperature is 50-70°C.

[0038] According to a specific embodiment of the present invention, preferably, the shear emulsification rate of the emulsion is 5000-10000 rpm.

[0039] According to a specific embodiment of the present invention, preferably, the inlet temperature during the spray drying process is 120-180℃, more preferably 125-135℃.

[0040] According to a specific embodiment of the present invention, preferably, the outlet temperature during the spray drying process is 55-85°C, more preferably 65-80°C.

[0041] According to a specific embodiment of the present invention, preferably, the feeding rate during the spray drying process is 150-300 mL / h, more preferably 200-250 mL / h.

[0042] According to a specific embodiment of the present invention, preferably, before spray drying, the concentration of the polymer in the polymer emulsion is diluted to 2-10 wt%, more preferably 3-8 wt%.

[0043] According to a specific embodiment of the present invention, the above preparation method includes the following specific steps:

[0044] (1) Preparation of prepolymer solution:

[0045] Weigh out an appropriate amount of the first monomer, the first crosslinking agent and the first initiator, dissolve them in 100 mL of organic solvent, stir evenly, raise the temperature to the first reaction temperature, and react at a constant temperature for 2-10 h to obtain a prepolymer solution.

[0046] (2) Preparation of stable phase solution:

[0047] Add an appropriate amount of stabilizer to 100 mL of deionized water. After the stabilizer is completely dissolved, weigh an appropriate amount of the second monomer, the second crosslinking agent, and the emulsifier to obtain a stable phase solution.

[0048] (3) Emulsion polymerization:

[0049] The stable phase solution is added to the prepolymer solution according to a certain ratio, and shear emulsification is performed for 20 minutes using a shear emulsifier. After emulsification is completed, the emulsion is transferred to a three-necked flask, heated to the second reaction temperature, and then the second initiator is added. The temperature is maintained and the reaction continues for 1-6 hours.

[0050] (4) Spray drying:

[0051] The emulsion prepared in step (3) is diluted in a certain proportion and added to a spray dryer. Hollow polymer microspheres are obtained after spraying by setting the inlet and outlet temperatures and the feeding speed.

[0052] The present invention also provides hollow polymer microspheres prepared by the above preparation method.

[0053] This invention also provides the application of the above-mentioned hollow polymer microspheres as a sealing and heat-insulating agent in drilling fluid.

[0054] The present invention has the following beneficial effects:

[0055] (1) Compared with inorganic materials, polymers have a lower thermal conductivity. The synthesized hollow polymer microspheres can be used as thermal insulation materials for water-based drilling fluids to reduce the rock strength reduction caused by thermal stress cracking in the formation.

[0056] (2) The synthesized hollow polymer microspheres can delay the heat exchange between drilling fluid and high-temperature formation, and extend the service life of drilling fluid;

[0057] (3) The synthesized hollow polymer microspheres can be used as a plugging agent to reduce the leakage of water-based drilling fluid into the formation. Detailed Implementation

[0058] In order to provide a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solution of the present invention will now be described in detail below, but it should not be construed as limiting the scope of implementation of the present invention.

[0059] Example 1

[0060] This embodiment provides hollow polymer microspheres, which are prepared by the following steps:

[0061] (1) Weigh 25g of styrene, 1g of divinylbenzene and 0.3g of benzoyl peroxide and dissolve them in 100mL of dichloromethane. After stirring evenly, heat to 25℃ and react at a constant temperature for 5h to obtain a prepolymer solution.

[0062] (2) Weigh 3g of polyvinyl alcohol and add it to 100mL of deionized water. After it is completely dissolved, weigh 8g of acrylamide, 2g of 2-acrylamido-2-methyl-1-propanesulfonic acid, 1g of N,N-methylenebisacrylamide and 2g of Span 80 to obtain a stable phase solution.

[0063] (3) According to the volume ratio of prepolymer solution to stable phase solution of 80:20, 20 mL of stable phase solution was added to 80 mL of prepolymer solution, and sheared emulsified for 20 min by shear emulsifier. After emulsification, the emulsion was transferred to a three-necked flask, heated to 50 °C, and then 0.3 g of potassium persulfate was added. The temperature was maintained and the reaction continued for 4 h.

[0064] (4) The emulsion prepared in step (3) is diluted to 5% (polymer concentration, wt%, the same below), added to a spray dryer, and hollow polymer microspheres S1 are obtained after spraying by setting the inlet and outlet temperatures and the feeding speed to 125℃, 65℃ and 200mL / h respectively.

[0065] Example 2

[0066] This embodiment provides hollow polymer microspheres, which are prepared by the following steps:

[0067] (1) Weigh 35g styrene, 1.5g divinylbenzene and 0.4g benzoyl peroxide and dissolve them in 100mL dichloromethane. After stirring evenly, heat to 25℃ and react at a constant temperature for 5h to obtain a prepolymer solution.

[0068] (2) Weigh 3g of polyvinyl alcohol and add it to 100mL of deionized water. After it is completely dissolved, weigh 10g of acrylamide, 2g of 2-acrylamido-2-methyl-1-propanesulfonic acid, 1.5g of N,N-methylenebisacrylamide and 3g of Span 80 to obtain a stable phase solution.

[0069] (3) According to the volume ratio of prepolymer solution to stable phase solution of 80:20, 20 mL of stable phase solution was added to 80 mL of prepolymer solution, and sheared emulsified for 20 min by shear emulsifier. After emulsification, the emulsion was transferred to a three-necked flask, heated to 70 °C, and then 0.3 g of potassium persulfate was added. The temperature was maintained and the reaction continued for 4 h.

[0070] (4) Dilute the emulsion prepared in step (3) to 3% concentration and add it to a spray dryer. By setting the inlet and outlet temperatures and the feeding speed to 125℃, 65℃ and 200mL / h respectively, hollow polymer microspheres S2 are obtained after spraying.

[0071] Example 3

[0072] This embodiment provides hollow polymer microspheres, which are prepared by the following steps:

[0073] (1) Weigh 25g of methyl methacrylate, 1g of dimethyl diimide ester and 0.3g of benzoyl peroxide and dissolve them in 100mL of dichloromethane. After stirring evenly, heat to 25℃ and react at a constant temperature for 5h to obtain a prepolymer solution.

[0074] (2) Weigh 3g of polyethylene glycol and add it to 100mL of deionized water. After it is completely dissolved, weigh 8g of acrylamide, 4g of 2-acrylamido-2-methyl-1-propanesulfonic acid, 1g of N,N-methylenebisacrylamide and 2g of Span 80 to obtain a stable phase solution.

[0075] (3) According to the volume ratio of prepolymer solution to stable phase solution of 85:15, 15 mL of stable phase solution was added to 85 mL of prepolymer solution, and shear emulsified for 20 min by shear emulsifier. After emulsification, the emulsion was transferred to a three-necked flask, heated to 60 °C, and then 0.3 g of potassium persulfate was added. The temperature was maintained and the reaction continued for 5 h.

[0076] (4) Dilute the emulsion prepared in step (3) to 5% concentration and add it to a spray dryer. By setting the inlet and outlet temperatures and the feeding speed to 125℃, 65℃ and 200mL / h respectively, hollow polymer microspheres S3 are obtained after spraying.

[0077] Example 4

[0078] This embodiment provides hollow polymer microspheres, which are prepared by the following steps:

[0079] (1) Weigh 35g of methyl methacrylate, 1.5g of dimethyl diimide ester and 0.4g of benzoyl peroxide and dissolve them in 100mL of dichloromethane. After stirring evenly, heat to 25℃ and react at a constant temperature for 5h to obtain a prepolymer solution.

[0080] (2) Weigh 3g of polyethylene glycol and add it to 100mL of deionized water. After it is completely dissolved, weigh 10g of acrylamide, 2g of 2-acrylamido-2-methyl-1-propanesulfonic acid, 1g of N,N-methylenebisacrylamide and 3g of Span 80 to obtain a stable phase solution.

[0081] (3) According to the volume ratio of prepolymer solution to stable phase solution of 85:15, 15 mL of stable phase solution was added to 85 mL of prepolymer solution, and sheared emulsified for 20 min by shear emulsifier. After emulsification, the emulsion was transferred to a three-necked flask, heated to 60 °C, and then 0.4 g of potassium persulfate was added. The temperature was maintained and the reaction continued for 5 h.

[0082] (4) Dilute the emulsion prepared in step (3) to 7% concentration and add it to a spray dryer. By setting the inlet and outlet temperatures and the feeding speed to 125℃, 65℃ and 200mL / h respectively, hollow polymer microspheres S4 are obtained after spraying.

[0083] Example 5

[0084] This embodiment provides hollow polymer microspheres, which are prepared by the following steps:

[0085] (1) Weigh 25g butyl acrylate, 1g ethylene glycol dimethacrylate and 0.3g azobisisobutyronitrile and dissolve them in 100mL dichloromethane. After stirring evenly, heat to 30℃ and react at a constant temperature for 7h to obtain a prepolymer solution.

[0086] (2) Weigh 2g of hydroxymethyl cellulose and add it to 100mL of deionized water. After it is completely dissolved, weigh 6g of acrylamide, 6g of 2-acrylamido-2-methyl-1-propanesulfonic acid, 1g of N,N-methylenebisacrylamide and 2g of Span 80 to obtain a stable phase solution.

[0087] (3) According to the volume ratio of prepolymer solution to stable phase solution of 80:20, 20 mL of stable phase solution was added to 80 mL of prepolymer solution, and sheared emulsified for 20 min by shear emulsifier. After emulsification, the emulsion was transferred to a three-necked flask, heated to 70 °C, and then 0.3 g of potassium persulfate was added. The temperature was maintained and the reaction continued for 4 h.

[0088] (4) Dilute the emulsion prepared in step (3) to 5% concentration and add it to a spray dryer. By setting the inlet and outlet temperatures and the feeding speed to 125℃, 65℃ and 200mL / h respectively, hollow polymer microspheres S5 are obtained after spraying.

[0089] Example 6

[0090] This embodiment provides hollow polymer microspheres, which are prepared by the following steps:

[0091] (1) Weigh 30g butyl acrylate, 1.3g ethylene glycol dimethacrylate and 0.4g azobisisobutyronitrile and dissolve them in 100mL dichloromethane. After stirring evenly, heat to 30℃ and react at a constant temperature for 5h to obtain a prepolymer solution.

[0092] (2) Weigh 2g of hydroxymethyl cellulose and add it to 100mL of deionized water. After it is completely dissolved, weigh 10g of acrylamide, 2g of maleic anhydride, 1g of N,N-methylenebisacrylamide and 2g of Span 80 to obtain a stable phase solution.

[0093] (3) According to the volume ratio of prepolymer solution to stable phase solution of 85:15, 15 mL of stable phase solution was added to 85 mL of prepolymer solution, and shear emulsified for 20 min by shear emulsifier. After emulsification, the emulsion was transferred to a three-necked flask, heated to 50 °C, and then 0.4 g of potassium persulfate was added. The temperature was maintained and the reaction continued for 5 h.

[0094] (4) The concentration of the emulsion prepared in step (3) is diluted to 4%, and added to a spray dryer. The inlet and outlet temperatures and the feeding speed are set to 125℃, 65℃ and 200mL / h, respectively. Hollow polymer microspheres S6 are obtained after spraying.

[0095] Comparative Example 1

[0096] This comparative example provides a polymer microsphere, which is produced according to the method of Example 1, except that the volume ratio of the prepolymer solution to the stable phase solution is 50:50 in step (3). Other conditions are the same as in Example 1, and sample D1 is obtained.

[0097] Comparative Example 2

[0098] This comparative example provides a polymer microsphere, which is produced according to the method of Example 1, except that in step (4), the inlet and outlet temperatures and the feeding rate of the spray dryer are 85°C, 45°C, and 500 mL / h, respectively. Other conditions are the same as in Example 1, and sample D2 is obtained.

[0099] Comparative Example 3

[0100] This comparative example provides a polymer microsphere, which is produced according to the method of Example 1, except that the first monomer added in step (1) is octadecyl methacrylate. Other conditions are the same as in Example 1, and sample D3 is obtained.

[0101] The performance of the products prepared in Examples 1-6 and Comparative Examples 1-3 was evaluated:

[0102] In the following tests, 4g of the white powdery water-based drilling fluid obtained from the reaction was weighed out and added to 400mL of base slurry using sealing and heat insulation material to evaluate its rheological and filtration properties.

[0103] Drilling fluid rheology and filtration test

[0104] (1) Preparation of base slurry: Measure 400mL of distilled water and put it in a stirrer. Add 0.8g of sodium carbonate and stir to dissolve. While stirring, add 16g of drilling fluid bentonite. Stir at high speed for 20min and let it stand for more than 48h to hydrate. Then add 4g of PAC-LV and stir at high speed for 20min.

[0105] (2) Add 4g of the sealing and heat-insulating materials (S1-S6, D1-D3) prepared in Examples 1-6 and Comparative Examples 1-3 to the base slurry, stir at high speed for 30 minutes, and then put it into an aging tank for hot rolling at 260℃ for 16 hours. Measure its rheological parameters and API filtration loss at room temperature, and measure its high-temperature and high-pressure filtration loss at 200℃ and 3.5MPa. The results are shown in Table 1. The drilling fluid rheology and filtration loss tests are based on GB 16783.1-2014, and the specific test steps are as follows:

[0106] 1. Drilling fluid rheological testing:

[0107] (1) Pour drilling fluid sample into the sample cup up to the scale line, place the sample on the viscometer stand, and move the stand so that the sample liquid level just coincides with the scale line on the outer cylinder.

[0108] (2) Rotate the outer cylinder at 600 r / min. After the dial reading stabilizes, read and record the dial reading.

[0109] (3) Convert the rotation speed to 300 r / min, and after the dial reading stabilizes, read and record the dial reading;

[0110] Apparent viscosity (AV) = R600 / 2;

[0111] Plastic viscosity (PV) = R600 - R300;

[0112] Dynamic shear force (YP) = AV - PV

[0113] Where R600 is the dial reading at 600 r / min;

[0114] R300 is the dial reading at 300 r / min.

[0115] 2. API filtration loss test:

[0116] (1) Pour the drilling fluid sample into the drilling fluid cup, place the filter paper and install the filter loss meter;

[0117] (2) Place the dry graduated cylinder under the discharge tube to receive the filtrate, close the pressure relief valve and adjust the pressure regulator to make the pressure in the cup reach 690kPa±35kPa, and start timing while pressurizing;

[0118] (3) Measure the volume of the filtrate after 30 minutes.

[0119] 3. High Temperature and High Pressure (HTHP) Filtration Loss Test:

[0120] (1) Insert the thermometer into the thermometer socket on the heating jacket, heat the heating jacket to 240°C, and adjust the thermostat switch to maintain the required temperature.

[0121] (2) Close the bottom valve stem, pour the drilling fluid into the drilling fluid cup, place the filter paper in place, and close the drilling fluid cup;

[0122] (3) Connect the adjustable pressure source to the top valve stem and the bottom filtrate receiver respectively and lock them;

[0123] (4) With both the top and bottom valve stems closed, adjust the pressure regulators at the top and bottom to 2.5 MPa respectively, open the top valve stem, apply a pressure of 2.5 MPa to the drilling fluid, and maintain this pressure for 1 hour;

[0124] (5) Increase the top pressure to 6.0 MPa, open the bottom valve stem to measure the filtration loss, and collect the filtrate for 30 min.

[0125] 4. High-temperature and high-pressure sand table filtration loss test:

[0126] After replacing the high-temperature and high-pressure filter paper used in the high-temperature and high-pressure experiment with a sand disc, the high-temperature and high-pressure sand disc filtration loss (FL) of the drilling fluid was tested under the same test conditions. 砂盘 .

[0127] After the filter cake that had undergone drilling fluid API filtration loss test was dried at 80℃, the thermal conductivity of the filter cake was tested using a laser thermal conductivity meter, with a scanning temperature range of 40-300℃.

[0128] The manufacturer of the six-speed viscometer is Qingdao Tongchun Petroleum Instrument Co., Ltd., and the model number is ZNN-D6B.

[0129] The manufacturer of the low-speed mixer is Qingdao Tongchun Petroleum Instrument Co., Ltd., model D90;

[0130] The centrifuge is manufactured by Hunan Xiangyi Laboratory Instrument Development Co., Ltd., model TG16-WS;

[0131] The laser thermal conductivity meter is manufactured by NETZSCH of Germany, model LFA457.

[0132] Table 1. Influence of Sealing and Insulation Materials on Drilling Fluid Performance in Water-Based Drilling Fluids

[0133]

[0134]

[0135] Note: S0 is the base grout without sealing and insulation material.

[0136] As shown in Table 1, the rheology and filtration loss of the base slurry S0 without sealing and insulation material changed significantly before and after high-temperature aging. The apparent viscosity decreased from 42 mPa·s to 21 mPa·s, the plastic viscosity decreased from 34 mPa·s to 11 mPa·s, and the filtration loss increased from 12.2 mL to 36.4 mL. The significant increase in filtration loss is due to the thermal degradation of PAC-LV in the drilling fluid after high-temperature aging, which leads to a decrease in polymer molecular weight, a decrease in drilling fluid viscosity, and a weakening of the filtration loss reduction effect. When 1% sealing and insulation material was added, the decrease in drilling fluid viscosity was smaller, and the filtration loss was also significantly reduced. This indicates that adding the sealing and insulation material of the present invention can improve the high-temperature resistance of the drilling fluid and has a certain sealing and filtration loss reduction ability.

[0137] In addition, the thermal conductivity of the mud cake was evaluated, and the results are shown in Table 2.

[0138] Table 2. Influence of sealing and insulation materials for water-based drilling fluids on the thermal insulation performance of drilling fluid mud cake.

[0139]

[0140]

[0141] As shown in Table 2, the thermal conductivity of the drilling fluid formed with the sealing and insulating material (hollow polymer microspheres) of this invention decreased from 0.986 W / (m·K) to 0.476 W / (m·K) compared to that without the sealing and insulating material, and the thermal diffusivity decreased from 0.362 mm² / k. 2 / s decreased to 0.147mm 2 The thermal conductivity decreases significantly with a value of / s, indicating that the material has good thermal insulation properties.

[0142] The foregoing description includes examples of one or more embodiments. Of course, those skilled in the art will recognize that the various embodiments can be further combined and arranged. Therefore, the embodiments described herein are intended to cover all such changes, modifications, and variations that fall within the scope of the appended claims. Furthermore, the term "comprising" as used in the specification or claims is interpreted in a manner similar to the term "including," just as "comprising" is interpreted as a conjunction in the claims. Additionally, the use of any term "or" in the specification of the claims is intended to mean "non-exclusive or."

[0143] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from the concept and scope of the invention. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for preparing hollow polymer microspheres, comprising the following steps: (a) Preparation of prepolymer solution: Dissolve the first monomer, the first crosslinking agent and the first initiator in an organic solvent, raise the temperature to the first reaction temperature of 15-40℃, and react for 2-10 h to obtain the prepolymer solution; (b) Preparation of stable phase solution: After dissolving the stabilizer in water, the second monomer, the second crosslinking agent, and the emulsifier are added to obtain the stable phase solution; (c) Emulsion polymerization: The stable phase solution is added to the prepolymer solution, and after emulsification, the temperature is raised to the second reaction temperature of 40-80°C, a second initiator is added, and the reaction is carried out for 1-6 h to obtain the polymer emulsion; the volume ratio of the prepolymer solution to the stable phase solution is 75:25-90:

10. (d) The polymer emulsion obtained in step (c) is spray-dried to obtain the hollow polymer microspheres; during the spray drying process, the inlet temperature is 120-180℃, the outlet temperature is 55-85℃, and the feeding rate is 150-300 mL / h. The first monomer includes styrene monomers and / or acrylate monomers; The second monomer includes one or more of acrylamide, 2-acrylamido-2-methyl-1-propanesulfonic acid, dimethyldiallylammonium chloride, and maleic anhydride. The styrene monomer has the structure shown in Formula I: Formula I, In Formula I, R1 is selected from H, C1-C5 alkyl groups and their derivatives, and C6-C18 phenyl groups and their derivatives; The acrylate monomer has the structure shown in Formula II: Formula II, In Formula II, R2 is selected from C1-C 10 alkyl groups and their derivatives; R3 is selected from H or methyl.

2. The preparation method according to claim 1, wherein, R1 is selected from methyl, ethyl, or phenyl.

3. The preparation method according to claim 1, wherein, In step (a), the first crosslinking agent includes one or more of divinylbenzene, dimethyldiimide, and ethylene glycol dimethacrylate.

4. The preparation method according to claim 1, wherein, The first initiator includes one or a combination of two or more of benzoyl peroxide, azobisisobutyronitrile, and azobisisobutylamidine.

5. The preparation method according to claim 1, wherein, The organic solvent includes one or more of dichloromethane, toluene, white oil, ethyl acetate, and cyclohexane.

6. The preparation method according to claim 1, wherein, In step (b), the stabilizer includes one or more of polyvinyl alcohol, polyethylene glycol, hydroxymethyl cellulose, hydroxypropyl cellulose, hydroxyethyl cellulose, and carboxymethyl cellulose.

7. The preparation method according to claim 1, wherein, The second crosslinking agent includes one or more of N,N-methylenebisacrylamide, formaldehyde, acetaldehyde, furfural, and urea-formaldehyde.

8. The preparation method according to claim 1, wherein, The emulsifier includes one or more of Span 60, Span 80, Span 85, Tween 60, and Tween 80.

9. The preparation method according to claim 1, wherein, In step (c), the second initiator includes one or more of potassium persulfate, ammonium persulfate, sodium bisulfite, and hydrogen peroxide.

10. The preparation method according to claim 1, wherein, In step (a), the amount of the first monomer added is 20-40 g / 100mL.

11. The preparation method according to claim 10, wherein, The amount of the first monomer added is 25-35 g / 100mL.

12. The preparation method according to claim 1, wherein, The amount of the first crosslinking agent added is 0.5-2.5 g / 100mL.

13. The preparation method according to claim 12, wherein, The amount of the first crosslinking agent added is 1-1.5 g / 100mL.

14. The preparation method according to claim 1, wherein, The amount of the first initiator added is 0.1-0.6 g / 100mL.

15. The preparation method according to claim 14, wherein, The amount of the first initiator added is 0.3-0.4 g / 100mL.

16. The preparation method according to claim 1, wherein, In step (b), the amount of stabilizer added is 1-5 g / 100mL.

17. The preparation method according to claim 16, wherein, In step (b), the amount of stabilizer added is 2-3 g / 100mL.

18. The preparation method according to claim 1, wherein, The amount of the second monomer added is 5-15 g / 100mL.

19. The preparation method according to claim 18, wherein, The amount of the second monomer added is 8-12 g / 100mL.

20. The preparation method according to claim 1, wherein, The amount of the second crosslinking agent added is 0.5-2.5 g / 100mL.

21. The preparation method according to claim 20, wherein, The amount of the second crosslinking agent added is 1-1.5 g / 100mL.

22. The preparation method according to claim 1, wherein, The amount of emulsifier added is 1-5 g / 100mL.

23. The preparation method according to claim 1, wherein, The amount of emulsifier added is 2-3 g / 100mL.

24. The preparation method according to claim 1, wherein, In step (c), the volume ratio of the prepolymer solution to the stable phase solution is 80:20-85:

15.

25. The preparation method according to claim 1, wherein, The amount of the second initiator added is 0.1-0.6 g / 100mL.

26. The preparation method according to claim 25, wherein, The amount of the second initiator added is 0.3-0.4 g / 100mL.

27. The preparation method according to claim 1, wherein, The first reaction temperature is 25-30℃.

28. The preparation method according to claim 1, wherein, The second reaction temperature is 50-70℃.

29. The preparation method according to claim 1, wherein, The shear emulsification rate of the emulsion is 5000-10000 rpm.

30. The preparation method according to claim 1, wherein, During the spray drying process, the inlet temperature is 125-135℃.

31. The preparation method according to claim 1, wherein, During the spray drying process, the outlet temperature is 65-80℃.

32. The preparation method according to claim 1, wherein, During the spray drying process, the feeding rate is 200-250 mL / h.

33. The preparation method according to claim 1, wherein, Before spray drying, the concentration of the polymer in the polymer emulsion is diluted to 2-10 wt%.

34. The preparation method according to claim 33, wherein, Before spray drying, the concentration of the polymer in the polymer emulsion is diluted to 3-8 wt%.

35. Hollow polymer microspheres prepared by the preparation method according to any one of claims 1-34.

36. The application of the hollow polymer microspheres of claim 35 as a sealing and insulating agent in drilling fluid.

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