Silicon quantum dot modified compositions, modified silicon quantum dots, viscosifiers, viscosifier systems, drilling and completion fluids

Abstract

This invention provides a silicon quantum dot modified composition, modified silicon quantum dots, a thickener, a thickener system, drilling fluid, and completion fluid. The silicon quantum dot modified composition comprises an organic solvent and two modifying agents. When the silicon quantum dots obtained by further modification of this silicon quantum dot modified composition are used as thickeners in high-salinity drilling and completion fluids, the thickener exhibits excellent high-temperature resistance and continues to provide good rheological and thixotropic properties even after aging.

Description

Technical Field

[0001] This invention belongs to the field of oilfield chemical technology, specifically relating to a silicon quantum dot modified composition, modified silicon quantum dots, thickener, thickener system, drilling fluid, and completion fluid. Background Technology

[0002] As oil and gas well drilling depths increase, geological conditions become more complex during drilling. High-temperature, high-pressure, and high-salinity formations make controlling drilling fluid performance more difficult, placing higher demands on drilling fluid technology. During drilling, solid particles in the drilling fluid invade the reservoir, clogging pores and channels, causing reservoir damage and hindering efficient oil and gas field development. Solids-free drilling fluids, which do not contain bentonite or barite and use polymers and soluble salts as main additives, are one of the main reservoir protection drilling fluids currently available. Because solids-free drilling fluids do not contain active bentonite, they cannot rely on the spatial networking ability of bentonite particles to provide basic viscosity-enhancing and shear-lifting capabilities. Therefore, the role of polymers in flow pattern regulation is crucial. Furthermore, since solids-free drilling fluids do not contain barite for weighting, their density can only be controlled by the type and concentration of dissolved inorganic salts, which places higher demands on the polymer's salt resistance and interaction capabilities.

[0003] The rheological properties of drilling fluids are mainly measured by two parameters: viscosity and shear stress. Viscosity is a macroscopic reflection of the frictional forces between the components of the drilling fluid, while shear stress is a macroscopic reflection of the strength of the network structure between the components. Currently, commonly used solids-free drilling fluid flow modifiers in industry include two categories: biopolymers and synthetic polymers. Biopolymers are xanthan gum and its modified products, which have good solubility, salt resistance, thickening, and shear stress properties. However, their temperature resistance is poor, making it difficult to meet the drilling requirements at high temperatures. Synthetic polymers are copolymers of monomers such as acrylamide, acrylic acid, and 2-acrylamido-2-methylpropanesulfonic acid. They have good thickening and temperature resistance properties, but their salt resistance and shear stress properties are poor, making it difficult to adjust them to meet the rheological properties required in the drilling field.

[0004] Existing technologies either graft natural polymers or utilize hydrophobic associations and electrostatic interactions between synthetic polymers to improve their viscosity and shear strength. However, these methods often suffer from the following drawbacks: the modified natural polymers exhibit poor temperature resistance, making them unsuitable for applications at temperatures of 150°C and above; acrylamide-based synthetic polymers lack sufficient molecular rigidity, tending to entangle in solution and primarily producing a viscosity-enhancing effect; and the synthetic polymers exhibit poor salt resistance, making them unsuitable for applications with divalent salts (Ca). 2+ Mg 2+Under conditions of very high concentrations, the side groups or main chain of the polymer inevitably degrade during high-temperature aging, resulting in poor resistance to long-term high-temperature aging. Furthermore, the strength of hydrophobic association and electrostatic interactions is weak, making it difficult to improve the strength of the intermolecular network structure at high temperatures. Therefore, it is necessary to provide a new functional drilling treatment agent to improve the above problems. Summary of the Invention

[0005] To address the aforementioned technical problems, the present invention aims to provide a silicon quantum dot modified composition, modified silicon quantum dots, a thickener, a thickener system, drilling fluid, and completion fluid. This thickener exhibits excellent high-temperature resistance and continues to provide good rheological and thixotropic properties even after aging.

[0006] To achieve the above objectives, the present invention provides a silicon quantum dot modified composition comprising an organic solvent, a first modifier, and a second modifier;

[0007] The structural formula of the first modifier is: R1 is a C1-C6 alkyl group; a is 1-4, b is 1-30, and c is 1-6;

[0008] The structural formula of the second modifier is: d ranges from 1 to 4, and e ranges from 1 to 20.

[0009] Furthermore, the organic solvent is selected from one or more of acetone, 2-butanone, methanol, ethanol, n-propanol, isopropanol, and ethylene glycol.

[0010] Further, the weight ratio of the first modifier, the second modifier, and the organic solvent is 0.01–2:0.2–10:1–100. Preferably, the weight ratio of the first modifier, the second modifier, and the organic solvent is 0.05–1.2:1–7.5:5–60. In some optional embodiments, the weight ratio of the first modifier, the second modifier, and the organic solvent is 0.1–1:1.5–5:10–20.

[0011] Furthermore, R1 is a C1 to C4 alkyl group; a is 1 to 4, b is 1 to 22, c is 2 to 3; d is 1 to 2, and e is 5 to 20.

[0012] The present invention also provides a modified silicon quantum dot, which is obtained by surface modification of silicon quantum dots with the aforementioned silicon quantum dot modification composition; the silicon quantum dot modification composition includes an organic solvent, a first modifier, and a second modifier.

[0013] Further, the weight ratio of silicon quantum dots, the first modifier, the second modifier, and the organic solvent is 1:0.01–2:0.2–10:1–100. Preferably, the weight ratio of silicon quantum dots, the first modifier, the second modifier, and the organic solvent is 1:0.05–1.2:1–7.5:5–60. In some optional embodiments, the weight ratio of silicon quantum dots, the first modifier, the second modifier, and the organic solvent is 1:0.15–1:1.5–5:10–20.

[0014] Further, the surface modification process includes: mixing silicon quantum dots, a first modifier, and an organic solvent, reacting them at a temperature of 20–80°C for 1–24 hours, and then adding a second modifier to the system and reacting for 1–18 hours. Preferably, the surface modification process includes: mixing silicon quantum dots, a first modifier, and an organic solvent, reacting them at a temperature of 30–80°C for 2–12 hours, and then adding a second modifier to the system and reacting for 2–8 hours.

[0015] In a preferred embodiment, silicon quantum dots are prepared by the following steps: mixing a silicon-containing compound, a reducing agent, and water to carry out a hydrothermal reaction to obtain silicon quantum dots.

[0016] Furthermore, the silicon-containing compound is selected from one or more combinations of 3-aminopropyltriethoxysilane, 3-aminopropylmethyldiethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropylmethyldimethoxysilane, 3-(2-aminoethylamino)propyltriethoxysilane, 3-(2-aminoethylamino)propylmethyldiethoxysilane, 3-(2-aminoethylamino)propyltrimethoxysilane and 3-(2-aminoethylamino)propylmethyldimethoxysilane.

[0017] Furthermore, the reducing agent is selected from one or more combinations of isoascorbic acid, sodium isoascorbate, ascorbic acid, sodium ascorbate, folic acid, urea, thiourea, hydroquinone, 2-aminophenol, 4-aminophenol, citric acid, monosodium citrate, disodium citrate, and trisodium citrate.

[0018] Further, the weight ratio of the silicon-containing compound, reducing agent, and water is 1:0.001–0.5:1–100. Preferably, the weight ratio of the silicon-containing compound, reducing agent, and water is 1:0.005–0.35:2–40. In some optional embodiments, the weight ratio of the silicon-containing compound, reducing agent, and water is 1:0.02–0.35:3–10.

[0019] Further, the hydrothermal reaction temperature is 30–100°C, and the time is 0.2–10 h. Preferably, the hydrothermal reaction temperature is 50–90°C, and the time is 0.5–6 h.

[0020] The present invention also provides a thickener comprising the aforementioned modified silicon quantum dots and silicon-containing polymer; the silicon-containing polymer is obtained by polymerization of nonionic monomers, anionic monomers and silicon-containing monomers.

[0021] Further, the weight ratio of modified silicon quantum dots to silicon-containing polymers is 1:2 to 200. Preferably, the weight ratio of modified silicon quantum dots to silicon-containing polymers is 1:3 to 100. In some optional embodiments, the weight ratio of modified silicon quantum dots to silicon-containing polymers is 1:5 to 25.

[0022] In a preferred embodiment, the silicon-containing polymer is obtained by polymerizing nonionic monomers, anionic monomers, and silicon-containing monomers. The polymerization process includes: mixing nonionic monomers, anionic monomers, silicon-containing monomers, water, reduction initiator-1, reduction initiator-2, azo initiator, oxidation initiator-1, and oxidation initiator-2, and then reacting them in an inert gas atmosphere at a pH of 6-11 (preferably pH 6.5-8) at a temperature of -5-15°C (preferably -2-8°C) for 1-10 hours (preferably 1-5 hours), followed by a reaction at a temperature of 60-80°C for 1-4 hours.

[0023] Furthermore, the nonionic monomer is selected from one or more of N-ethylacrylamide, N,N-dimethylacrylamide, N,N-diethylacrylamide, acrylomorpholine and vinylpyrrolidone.

[0024] Furthermore, the anionic monomer is selected from one or more of 2-acrylamido-2-methylpropanesulfonic acid, sodium styrene sulfonate, and sodium vinyl sulfonate.

[0025] Furthermore, the silicon-containing monomer is selected from one or more of vinyltrimethoxysilane, vinyltriethoxysilane, allyltrimethoxysilane, and allyltriethoxysilane.

[0026] Furthermore, the reducing initiator-1 is selected from ferrous sulfate, ferrous ammonium sulfate, ferrous chloride, or ferrous ammonium chloride.

[0027] Furthermore, the reducing initiator-2 is selected from sodium sulfite, sodium bisulfite, sodium thiosulfate, sodium dithionite, or sodium formaldehyde sulfoxylate.

[0028] Furthermore, the azo initiator is selected from azobisisobutylamidine hydrochloride, azobisisopropylimidazoline hydrochloride, or azobiscyanopentanoic acid.

[0029] Furthermore, the oxidation initiator-1 is selected from potassium persulfate, sodium persulfate, or ammonium persulfate.

[0030] Furthermore, the oxidation initiator-2 is selected from hydrogen peroxide or benzoyl peroxide.

[0031] Furthermore, the weight ratio of nonionic monomer to anionic monomer is 1:0.1 to 10, preferably 1:0.1 to 3. In some optional embodiments, the weight ratio of nonionic monomer to anionic monomer is 1:0.5 to 3.

[0032] Further, the total weight ratio of nonionic monomers to anionic monomers is 1:0.001 to 0.05, i.e., (weight of nonionic monomers + weight of anionic monomers) ÷ weight of silicon-containing monomers = 1:0.001 to 0.05. Preferably, the total weight ratio of nonionic monomers to anionic monomers is 1:0.005 to 0.05, i.e., (weight of nonionic monomers + weight of anionic monomers) ÷ weight of silicon-containing monomers = 1:0.005 to 0.05. In some optional embodiments, the total weight ratio of nonionic monomers to anionic monomers is 1:0.01 to 0.05, i.e., (weight of nonionic monomers + weight of anionic monomers) ÷ weight of silicon-containing monomers = 1:0.01 to 0.05.

[0033] Further, the total weight ratio of nonionic monomers, anionic monomers, and silicon-containing monomers to water is 1:0.5 to 20, i.e., (weight of nonionic monomers + weight of anionic monomers + weight of silicon-containing monomers) ÷ weight of water = 1:0.5 to 20. Preferably, the total weight ratio of nonionic monomers, anionic monomers, and silicon-containing monomers to water is 1:1 to 10, i.e., (weight of nonionic monomers + weight of anionic monomers + weight of silicon-containing monomers) ÷ weight of water = 1:1 to 10.

[0034] Further, the weight ratio of water, reducing initiator-1, reducing initiator-2, azo initiator, oxidation initiator-1, and oxidation initiator-2 is 1:0.000001~0.0001:0.00001~0.0002:0.00002~0.0005:0.00001~0.0003:0.000001~0.00005, preferably 1:0.000005~0.00006:0.00002~0.00012:0.00005~0.0005:0.00003~0.0002:0.000005~0.00003.

[0035] The present invention also provides a thickener system comprising the aforementioned thickener and brine.

[0036] Further, the weight ratio of the silicone polymer to the brine in the thickener is 1:10 to 500. Preferably, the weight ratio of the silicone polymer to the brine is 1:15 to 200. In some optional embodiments, the weight ratio of the silicone polymer to the brine is 1:20 to 70.

[0037] In some alternative embodiments, the brine is an aqueous solution of a salt compound, which may be calcium chloride, sodium chloride, potassium chloride, etc., and the weight fraction of the salt compound in the brine may be 15-35%.

[0038] In some optional embodiments, the thickener system may further include an oxygen scavenger, such as thiourea. This application does not impose any specific limitations on the oxygen scavenger; inventors may select the oxygen scavenger based on actual operating conditions. In some optional embodiments, the amount of oxygen scavenger may be 0.1% to 1% of the thickener system.

[0039] The present invention also provides a drilling fluid comprising the aforementioned thickener. Furthermore, the present invention also provides a completion fluid comprising the aforementioned thickener.

[0040] Based on the above scheme, the present invention can achieve the following technical effects: the raw materials of the present invention are readily available, the preparation process is simple and safe, and the production cost is low. The present invention can prepare silicon quantum dots with high surface amino density and small particle size through hydrothermal reaction, which can improve the utilization of functional groups on the particle surface and facilitate good interaction between the particles and silicon-containing polymers. The present invention can inhibit the condensation between silicate esters and improve the dispersibility of silicon quantum dots by surface modification of silicon quantum dots in organic solvents; by introducing polyoxyethylene, sulfonic acid, and other groups onto silicon quantum dots using a first and a second modifier, the dispersion performance of silicon quantum dots under high temperature and high salt conditions is improved. Moreover, the modified silicon quantum dots and silicon-containing polymer molecular chains interact to form an inorganic / organic composite structure, which can improve the high-temperature stability of the polymer side groups and main chain. The surface of the modified silicon quantum dots has a silicate ester structure, which can react with the silicate esters on the silicon-containing polymer molecular chains to form siloxane-type dynamic covalent bonds, improving the network structure strength of the thickener system, thereby achieving a good lifting effect. The thickener of this invention has the advantages of rapid dispersion and dissolution, and excellent temperature and salt resistance, which can significantly improve the shear strength of solid-free water-based drilling fluids. Furthermore, the product prepared by this invention is easy to store and meets environmental protection requirements. Detailed Implementation

[0041] 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.

[0042] Example 1

[0043] This embodiment provides a method for preparing a thickener system, which includes the following steps:

[0044] (1) Preparation of aminosilicon quantum dots

[0045] 50g of 3-aminopropyltrimethoxysilane, 3.5g of thiourea, and 500g of deionized water were added to a three-necked glass flask equipped with a stirrer, a condenser, and a thermometer. The mixture was stirred until all the raw materials were dissolved. The temperature was controlled at 80℃ and the reaction was carried out for 3 hours. The product was then filtered, dried, and pulverized to obtain aminosilicon quantum dots.

[0046] (2) Preparation of modified silicon quantum dots

[0047] 10g of aminosilicon quantum dots, 3g of the first modifier (R1 is ethyl, a is 1, b is 16, c is 3) and 120g of ethanol were added to a three-necked glass bottle equipped with a stirrer, a condenser and a thermometer. The aminosilicon quantum dots were stirred to disperse them evenly. The temperature was controlled at 45℃ and the reaction was carried out for 8 hours. Then 25g of the second modifier (d is 1, e is 7) was added and the reaction was carried out for 6 hours to obtain modified silicon quantum dots.

[0048] (3) Preparation of silicon-containing polymers

[0049] 10g of N,N-dimethylacrylamide, 19.5g of 2-acrylamido-2-methylpropanesulfonic acid, 0.5g of allyltriethoxysilane, and 150g of deionized water were added to a three-necked glass flask equipped with a stirrer, a nitrogen purging tube, and a thermometer. After stirring until all the raw materials were dissolved, nitrogen gas was purged for 30 minutes, the pH was controlled at 7.5, and the temperature was controlled at 0℃. Then, 0.003g of ferrous sulfate, 0.01g of sodium sulfite, 0.025g of azobisisobutylamidine hydrochloride, 0.015g of potassium persulfate, and 0.002g of hydrogen peroxide were added. The reaction was carried out for 4 hours, and then the temperature was raised to 60℃ and the reaction was carried out for 1 hour. The product was dried and pulverized to obtain a silicon-containing polymer.

[0050] (4) Preparation of thickener system

[0051] Add 1g of modified silicon quantum dots, 13g of silicon-containing polymer, and thiourea (0.5wt% of the system) to 600g of brine (a CaCl2 aqueous solution with a CaCl2 weight fraction of 30%), stir and dissolve to obtain the thickener system.

[0052] Example 2

[0053] This embodiment provides a method for preparing a thickener system, which includes the following steps:

[0054] (1) Preparation of aminosilicon quantum dots

[0055] 75g of 3-aminopropyltrimethoxysilane, 25g of 3-aminopropylmethyldimethoxysilane, 3.5g of thiourea, and 500g of deionized water were added to a three-necked glass flask equipped with a stirrer, a condenser, and a thermometer. The mixture was stirred until all the raw materials were dissolved. The temperature was controlled at 80℃ and the reaction was carried out for 3 hours. The product was then filtered, dried, and pulverized to obtain aminosilicon quantum dots.

[0056] (2) Preparation of modified silicon quantum dots

[0057] 10g of aminosilicon quantum dots, 3g of the first modifier (R1 is ethyl, a is 1, b is 16, c is 3) and 120g of ethanol were added to a three-necked glass bottle equipped with a stirrer, a condenser and a thermometer. The aminosilicon quantum dots were stirred to disperse them evenly. The temperature was controlled at 45℃ and the reaction was carried out for 8 hours. Then 25g of the second modifier (d is 1, e is 7) was added and the reaction was carried out for 6 hours to obtain modified silicon quantum dots.

[0058] (3) Preparation of silicon-containing polymers

[0059] 10g of N,N-dimethylacrylamide, 19.5g of 2-acrylamido-2-methylpropanesulfonic acid, 0.5g of allyltriethoxysilane, and 150g of deionized water were added to a three-necked glass flask equipped with a stirrer, a nitrogen purging tube, and a thermometer. After stirring until all the raw materials were dissolved, nitrogen gas was purged for 30 minutes, the pH was controlled at 7.5, and the temperature was controlled at 0℃. Then, 0.003g of ferrous sulfate, 0.01g of sodium sulfite, 0.025g of azobisisobutylamidine hydrochloride, 0.015g of potassium persulfate, and 0.002g of hydrogen peroxide were added. The reaction was carried out for 4 hours, and then the temperature was raised to 60℃ and the reaction was carried out for 1 hour. The product was dried and pulverized to obtain a silicon-containing polymer.

[0060] (4) Preparation of thickener system

[0061] Add 1g of modified silicon quantum dots, 13g of silicon-containing polymer, and thiourea (0.5wt% of the system) to 600g of brine (a CaCl2 aqueous solution with a CaCl2 weight fraction of 30%), stir and dissolve to obtain the thickener system.

[0062] Example 3

[0063] This embodiment provides a method for preparing a thickener system, which includes the following steps:

[0064] (1) Preparation of aminosilicon quantum dots

[0065] 80g of 3-aminopropyltriethoxysilane, 50g of 3-(2-aminoethylamino)propyltriethoxysilane, 3.5g of thiourea, and 500g of deionized water were added to a three-necked glass flask equipped with a stirrer, a condenser, and a thermometer. The mixture was stirred until all the raw materials were dissolved. The temperature was controlled at 80℃ and the reaction was carried out for 3 hours. The product was then filtered, dried, and pulverized to obtain aminosilicon quantum dots.

[0066] (2) Preparation of modified silicon quantum dots

[0067] 10g of aminosilicon quantum dots, 3g of the first modifier (R1 is ethyl, a is 1, b is 16, c is 3) and 120g of ethanol were added to a three-necked glass bottle equipped with a stirrer, a condenser and a thermometer. The aminosilicon quantum dots were stirred to disperse them evenly. The temperature was controlled at 45℃ and the reaction was carried out for 8 hours. Then 25g of the second modifier (d is 1, e is 7) was added and the reaction was carried out for 6 hours to obtain modified silicon quantum dots.

[0068] (3) Preparation of silicon-containing polymers

[0069] 10g of N,N-dimethylacrylamide, 19.5g of 2-acrylamido-2-methylpropanesulfonic acid, 0.5g of allyltriethoxysilane, and 150g of deionized water were added to a three-necked glass flask equipped with a stirrer, a nitrogen purging tube, and a thermometer. After stirring until all the raw materials were dissolved, nitrogen gas was purged for 30 minutes, the pH was controlled at 7.5, and the temperature was controlled at 0℃. Then, 0.003g of ferrous sulfate, 0.01g of sodium sulfite, 0.025g of azobisisobutylamidine hydrochloride, 0.015g of potassium persulfate, and 0.002g of hydrogen peroxide were added. The reaction was carried out for 4 hours, and then the temperature was raised to 60℃ and the reaction was carried out for 1 hour. The product was dried and pulverized to obtain a silicon-containing polymer.

[0070] (4) Preparation of thickener system

[0071] Add 1g of modified silicon quantum dots, 13g of silicon-containing polymer, and thiourea (0.5wt% of the system) to 600g of brine (a CaCl2 aqueous solution with a CaCl2 weight fraction of 30%), stir and dissolve to obtain the thickener system.

[0072] Example 4

[0073] This embodiment provides a method for preparing a thickener system, which includes the following steps:

[0074] (1) Preparation of aminosilicon quantum dots

[0075] 50g of 3-aminopropyltrimethoxysilane, 1.5g of sodium isoascorbate, and 500g of deionized water were added to a three-necked glass flask equipped with a stirrer, a condenser, and a thermometer. The mixture was stirred until all the raw materials were dissolved. The temperature was controlled at 80℃ and the reaction was carried out for 3 hours. The product was then filtered, dried, and pulverized to obtain aminosilicon quantum dots.

[0076] (2) Preparation of modified silicon quantum dots

[0077] 10g of aminosilicon quantum dots, 3g of the first modifier (R1 is ethyl, a is 1, b is 16, c is 3) and 120g of ethanol were added to a three-necked glass bottle equipped with a stirrer, a condenser and a thermometer. The aminosilicon quantum dots were stirred to disperse them evenly. The temperature was controlled at 45℃ and the reaction was carried out for 8 hours. Then 25g of the second modifier (d is 1, e is 7) was added and the reaction was carried out for 6 hours to obtain modified silicon quantum dots.

[0078] (3) Preparation of silicon-containing polymers

[0079] 10g of N,N-dimethylacrylamide, 19.5g of 2-acrylamido-2-methylpropanesulfonic acid, 0.5g of allyltriethoxysilane, and 150g of deionized water were added to a three-necked glass flask equipped with a stirrer, a nitrogen purging tube, and a thermometer. After stirring until all the raw materials were dissolved, nitrogen gas was purged for 30 minutes, the pH was controlled at 7.5, and the temperature was controlled at 0℃. Then, 0.003g of ferrous sulfate, 0.01g of sodium sulfite, 0.025g of azobisisobutylamidine hydrochloride, 0.015g of potassium persulfate, and 0.002g of hydrogen peroxide were added. The reaction was carried out for 4 hours, and then the temperature was raised to 60℃ and the reaction was carried out for 1 hour. The product was dried and pulverized to obtain a silicon-containing polymer.

[0080] (4) Preparation of thickener system

[0081] Add 1g of modified silicon quantum dots, 13g of silicon-containing polymer, and thiourea (0.5wt% of the system) to 600g of brine (a CaCl2 aqueous solution with a CaCl2 weight fraction of 30%), stir and dissolve to obtain the thickener system.

[0082] Example 5

[0083] This embodiment provides a method for preparing a thickener system, which includes the following steps:

[0084] (1) Preparation of aminosilicon quantum dots

[0085] 50g of 3-aminopropyltrimethoxysilane, 7g of disodium citrate, and 500g of deionized water were added to a three-necked glass flask equipped with a stirrer, a condenser, and a thermometer. The mixture was stirred until all the raw materials were dissolved. The temperature was controlled at 80℃ and the reaction was carried out for 3 hours. The product was then filtered, dried, and pulverized to obtain aminosilicon quantum dots.

[0086] (2) Preparation of modified silicon quantum dots

[0087] 10g of aminosilicon quantum dots, 3g of the first modifier (R1 is ethyl, a is 1, b is 16, c is 3) and 120g of ethanol were added to a three-necked glass bottle equipped with a stirrer, a condenser and a thermometer. The aminosilicon quantum dots were stirred to disperse them evenly. The temperature was controlled at 45℃ and the reaction was carried out for 8 hours. Then 25g of the second modifier (d is 1, e is 7) was added and the reaction was carried out for 6 hours to obtain modified silicon quantum dots.

[0088] (3) Preparation of silicon-containing polymers

[0089] 10g of N,N-dimethylacrylamide, 19.5g of 2-acrylamido-2-methylpropanesulfonic acid, 0.5g of allyltriethoxysilane, and 150g of deionized water were added to a three-necked glass flask equipped with a stirrer, a nitrogen purging tube, and a thermometer. After stirring until all the raw materials were dissolved, nitrogen gas was purged for 30 minutes, the pH was controlled at 7.5, and the temperature was controlled at 0℃. Then, 0.003g of ferrous sulfate, 0.01g of sodium sulfite, 0.025g of azobisisobutylamidine hydrochloride, 0.015g of potassium persulfate, and 0.002g of hydrogen peroxide were added. The reaction was carried out for 4 hours, and then the temperature was raised to 60℃ and the reaction was carried out for 1 hour. The product was dried and pulverized to obtain a silicon-containing polymer.

[0090] (4) Preparation of thickener system

[0091] Add 1g of modified silicon quantum dots, 13g of silicon-containing polymer, and thiourea (0.5wt% of the system) to 600g of brine (a CaCl2 aqueous solution with a CaCl2 weight fraction of 30%), stir and dissolve to obtain the thickener system.

[0092] Example 6

[0093] This embodiment provides a method for preparing a thickener system, which includes the following steps:

[0094] (1) Preparation of aminosilicon quantum dots

[0095] 50g of 3-aminopropyltrimethoxysilane, 3.5g of thiourea, and 850g of deionized water were added to a three-necked glass flask equipped with a stirrer, a condenser, and a thermometer. The mixture was stirred until all the raw materials were dissolved. The temperature was controlled at 80℃ and the reaction was carried out for 3 hours. The product was then filtered, dried, and pulverized to obtain aminosilicon quantum dots.

[0096] (2) Preparation of modified silicon quantum dots

[0097] 10g of aminosilicon quantum dots, 3g of the first modifier (R1 is ethyl, a is 1, b is 16, c is 3) and 120g of ethanol were added to a three-necked glass bottle equipped with a stirrer, a condenser and a thermometer. The aminosilicon quantum dots were stirred to disperse them evenly. The temperature was controlled at 45℃ and the reaction was carried out for 8 hours. Then 25g of the second modifier (d is 1, e is 7) was added and the reaction was carried out for 6 hours to obtain modified silicon quantum dots.

[0098] (3) Preparation of silicon-containing polymers

[0099] 10g of N,N-dimethylacrylamide, 19.5g of 2-acrylamido-2-methylpropanesulfonic acid, 0.5g of allyltriethoxysilane, and 150g of deionized water were added to a three-necked glass flask equipped with a stirrer, a nitrogen purging tube, and a thermometer. After stirring until all the raw materials were dissolved, nitrogen gas was purged for 30 minutes, the pH was controlled at 7.5, and the temperature was controlled at 0℃. Then, 0.003g of ferrous sulfate, 0.01g of sodium sulfite, 0.025g of azobisisobutylamidine hydrochloride, 0.015g of potassium persulfate, and 0.002g of hydrogen peroxide were added. The reaction was carried out for 4 hours, and then the temperature was raised to 60℃ and the reaction was carried out for 1 hour. The product was dried and pulverized to obtain a silicon-containing polymer.

[0100] (4) Preparation of thickener system

[0101] Add 1g of modified silicon quantum dots, 13g of silicon-containing polymer, and thiourea (0.5wt% of the system) to 600g of brine (a CaCl2 aqueous solution with a CaCl2 weight fraction of 30%), stir and dissolve to obtain the thickener system.

[0102] Example 7

[0103] This embodiment provides a method for preparing a thickener system, which includes the following steps:

[0104] (1) Preparation of aminosilicon quantum dots

[0105] 50g of 3-aminopropyltrimethoxysilane, 3.5g of thiourea, and 500g of deionized water were added to a three-necked glass flask equipped with a stirrer, a condenser, and a thermometer. The mixture was stirred until all the raw materials were dissolved. The temperature was controlled at 65℃ and the reaction was carried out for 1.5 hours. The product was then filtered, dried, and pulverized to obtain aminosilicon quantum dots.

[0106] (2) Preparation of modified silicon quantum dots

[0107] 10g of aminosilicon quantum dots, 3g of the first modifier (R1 is ethyl, a is 1, b is 16, c is 3) and 120g of ethanol were added to a three-necked glass bottle equipped with a stirrer, a condenser and a thermometer. The aminosilicon quantum dots were stirred to disperse them evenly. The temperature was controlled at 45℃ and the reaction was carried out for 8 hours. Then 25g of the second modifier (d is 1, e is 7) was added and the reaction was carried out for 6 hours to obtain modified silicon quantum dots.

[0108] (3) Preparation of silicon-containing polymers

[0109] 10g of N,N-dimethylacrylamide, 19.5g of 2-acrylamido-2-methylpropanesulfonic acid, 0.5g of allyltriethoxysilane, and 150g of deionized water were added to a three-necked glass flask equipped with a stirrer, a nitrogen purging tube, and a thermometer. After stirring until all the raw materials were dissolved, nitrogen gas was purged for 30 minutes, the pH was controlled at 7.5, and the temperature was controlled at 0℃. Then, 0.003g of ferrous sulfate, 0.01g of sodium sulfite, 0.025g of azobisisobutylamidine hydrochloride, 0.015g of potassium persulfate, and 0.002g of hydrogen peroxide were added. The reaction was carried out for 4 hours, and then the temperature was raised to 60℃ and the reaction was carried out for 1 hour. The product was dried and pulverized to obtain a silicon-containing polymer.

[0110] (4) Preparation of thickener system

[0111] Add 1g of modified silicon quantum dots, 13g of silicon-containing polymer, and thiourea (0.5wt% of the system) to 600g of brine (a CaCl2 aqueous solution with a CaCl2 weight fraction of 30%), stir and dissolve to obtain the thickener system.

[0112] Example 8

[0113] This embodiment provides a method for preparing a thickener system, which includes the following steps:

[0114] (1) Preparation of aminosilicon quantum dots

[0115] 50g of 3-aminopropyltrimethoxysilane, 3.5g of thiourea, and 500g of deionized water were added to a three-necked glass flask equipped with a stirrer, a condenser, and a thermometer. The mixture was stirred until all the raw materials were dissolved. The temperature was controlled at 80℃ and the reaction was carried out for 3 hours. The product was then filtered, dried, and pulverized to obtain aminosilicon quantum dots.

[0116] (2) Preparation of modified silicon quantum dots

[0117] 10g of aminosilicon quantum dots, 7g of the first modifier (R1 is methyl, a is 2, b is 22, c is 3) and 120g of ethanol were added to a three-necked glass flask equipped with a stirrer, a condenser and a thermometer. The aminosilicon quantum dots were dispersed evenly by stirring, and the temperature was controlled at 45℃. The reaction was carried out for 8 hours. Then 25g of the second modifier (d is 1, e is 7) was added and the reaction was carried out for 6 hours to obtain modified silicon quantum dots.

[0118] (3) Preparation of silicon-containing polymers

[0119] 10g of N,N-dimethylacrylamide, 19.5g of 2-acrylamido-2-methylpropanesulfonic acid, 0.5g of allyltriethoxysilane, and 150g of deionized water were added to a three-necked glass flask equipped with a stirrer, a nitrogen purging tube, and a thermometer. After stirring until all the raw materials were dissolved, nitrogen gas was purged for 30 minutes, the pH was controlled at 7.5, and the temperature was controlled at 0℃. Then, 0.003g of ferrous sulfate, 0.01g of sodium sulfite, 0.025g of azobisisobutylamidine hydrochloride, 0.015g of potassium persulfate, and 0.002g of hydrogen peroxide were added. The reaction was carried out for 4 hours, and then the temperature was raised to 60℃ and the reaction was carried out for 1 hour. The product was dried and pulverized to obtain a silicon-containing polymer.

[0120] (4) Preparation of thickener system

[0121] Add 1g of modified silicon quantum dots, 13g of silicon-containing polymer, and thiourea (0.5wt% of the system) to 600g of brine (a CaCl2 aqueous solution with a CaCl2 weight fraction of 30%), stir and dissolve to obtain the thickener system.

[0122] Example 9

[0123] This embodiment provides a method for preparing a thickener system, which includes the following steps:

[0124] (1) Preparation of aminosilicon quantum dots

[0125] 50g of 3-aminopropyltrimethoxysilane, 3.5g of thiourea, and 500g of deionized water were added to a three-necked glass flask equipped with a stirrer, a condenser, and a thermometer. The mixture was stirred until all the raw materials were dissolved. The temperature was controlled at 80℃ and the reaction was carried out for 3 hours. The product was then filtered, dried, and pulverized to obtain aminosilicon quantum dots.

[0126] (2) Preparation of modified silicon quantum dots

[0127] 10g of aminosilicon quantum dots, 1.5g of the first modifier (R1 is butyl, a is 1, b is 12, c is 2) and 120g of ethanol were added to a three-necked glass flask equipped with a stirrer, a condenser and a thermometer. The aminosilicon quantum dots were stirred to disperse them evenly. The temperature was controlled at 45℃ and the reaction was carried out for 8 hours. Then 25g of the second modifier (d is 1, e is 7) was added and the reaction was carried out for 6 hours to obtain modified silicon quantum dots.

[0128] (3) Preparation of silicon-containing polymers

[0129] 10g of N,N-dimethylacrylamide, 19.5g of 2-acrylamido-2-methylpropanesulfonic acid, 0.5g of allyltriethoxysilane, and 150g of deionized water were added to a three-necked glass flask equipped with a stirrer, a nitrogen purging tube, and a thermometer. After stirring until all the raw materials were dissolved, nitrogen gas was purged for 30 minutes, the pH was controlled at 7.5, and the temperature was controlled at 0℃. Then, 0.003g of ferrous sulfate, 0.01g of sodium sulfite, 0.025g of azobisisobutylamidine hydrochloride, 0.015g of potassium persulfate, and 0.002g of hydrogen peroxide were added. The reaction was carried out for 4 hours, and then the temperature was raised to 60℃ and the reaction was carried out for 1 hour. The product was dried and pulverized to obtain a silicon-containing polymer.

[0130] (4) Preparation of thickener system

[0131] Add 1g of modified silicon quantum dots, 13g of silicon-containing polymer, and thiourea (0.5wt% of the system) to 600g of brine (a CaCl2 aqueous solution with a CaCl2 weight fraction of 30%), stir and dissolve to obtain the thickener system.

[0132] Example 10

[0133] This embodiment provides a method for preparing a thickener system, which includes the following steps:

[0134] (1) Preparation of aminosilicon quantum dots

[0135] 50g of 3-aminopropyltrimethoxysilane, 3.5g of thiourea, and 500g of deionized water were added to a three-necked glass flask equipped with a stirrer, a condenser, and a thermometer. The mixture was stirred until all the raw materials were dissolved. The temperature was controlled at 80℃ and the reaction was carried out for 3 hours. The product was then filtered, dried, and pulverized to obtain aminosilicon quantum dots.

[0136] (2) Preparation of modified silicon quantum dots

[0137] 10g of aminosilicon quantum dots, 2.5g of the first modifier (R1 is ethyl, a is 2, b is 1, c is 2), and 120g of ethanol were added to a three-necked glass flask equipped with a stirrer, a condenser, and a thermometer. The aminosilicon quantum dots were stirred to disperse them evenly. The temperature was controlled at 45℃ and the reaction was carried out for 8 hours. Then, 25g of the second modifier (d is 1, e is 7) was added and the reaction was carried out for 6 hours to obtain modified silicon quantum dots.

[0138] (3) Preparation of silicon-containing polymers

[0139] 10g of N,N-dimethylacrylamide, 19.5g of 2-acrylamido-2-methylpropanesulfonic acid, 0.5g of allyltriethoxysilane, and 150g of deionized water were added to a three-necked glass flask equipped with a stirrer, a nitrogen purging tube, and a thermometer. After stirring until all the raw materials were dissolved, nitrogen gas was purged for 30 minutes, the pH was controlled at 7.5, and the temperature was controlled at 0℃. Then, 0.003g of ferrous sulfate, 0.01g of sodium sulfite, 0.025g of azobisisobutylamidine hydrochloride, 0.015g of potassium persulfate, and 0.002g of hydrogen peroxide were added. The reaction was carried out for 4 hours, and then the temperature was raised to 60℃ and the reaction was carried out for 1 hour. The product was dried and pulverized to obtain a silicon-containing polymer.

[0140] (4) Preparation of thickener system

[0141] Add 1g of modified silicon quantum dots, 13g of silicon-containing polymer, and thiourea (0.5wt% of the system) to 600g of brine (a CaCl2 aqueous solution with a CaCl2 weight fraction of 30%), stir and dissolve to obtain the thickener system.

[0142] Example 11

[0143] This embodiment provides a method for preparing a thickener system, which includes the following steps:

[0144] (1) Preparation of aminosilicon quantum dots

[0145] 50g of 3-aminopropyltrimethoxysilane, 3.5g of thiourea, and 500g of deionized water were added to a three-necked glass flask equipped with a stirrer, a condenser, and a thermometer. The mixture was stirred until all the raw materials were dissolved. The temperature was controlled at 80℃ and the reaction was carried out for 3 hours. The product was then filtered, dried, and pulverized to obtain aminosilicon quantum dots.

[0146] (2) Preparation of modified silicon quantum dots

[0147] 10g of aminosilicon quantum dots, 5g of the first modifier (R1 is butyl, a is 4, b is 6, c is 3) and 120g of ethanol were added to a three-necked glass flask equipped with a stirrer, a condenser and a thermometer. The aminosilicon quantum dots were stirred to disperse them evenly. The temperature was controlled at 45℃ and the reaction was carried out for 8 hours. Then 25g of the second modifier (d is 1, e is 7) was added and the reaction was carried out for 6 hours to obtain modified silicon quantum dots.

[0148] (3) Preparation of silicon-containing polymers

[0149] 10g of N,N-dimethylacrylamide, 19.5g of 2-acrylamido-2-methylpropanesulfonic acid, 0.5g of allyltriethoxysilane, and 150g of deionized water were added to a three-necked glass flask equipped with a stirrer, a nitrogen purging tube, and a thermometer. After stirring until all the raw materials were dissolved, nitrogen gas was purged for 30 minutes, the pH was controlled at 7.5, and the temperature was controlled at 0℃. Then, 0.003g of ferrous sulfate, 0.01g of sodium sulfite, 0.025g of azobisisobutylamidine hydrochloride, 0.015g of potassium persulfate, and 0.002g of hydrogen peroxide were added. The reaction was carried out for 4 hours, and then the temperature was raised to 60℃ and the reaction was carried out for 1 hour. The product was dried and pulverized to obtain a silicon-containing polymer.

[0150] (4) Preparation of thickener system

[0151] Add 1g of modified silicon quantum dots, 13g of silicon-containing polymer, and thiourea (0.5wt% of the system) to 600g of brine (a CaCl2 aqueous solution with a CaCl2 weight fraction of 30%), stir and dissolve to obtain the thickener system.

[0152] Example 12

[0153] This embodiment provides a method for preparing a thickener system, which includes the following steps:

[0154] (1) Preparation of aminosilicon quantum dots

[0155] 50g of 3-aminopropyltrimethoxysilane, 3.5g of thiourea, and 500g of deionized water were added to a three-necked glass flask equipped with a stirrer, a condenser, and a thermometer. The mixture was stirred until all the raw materials were dissolved. The temperature was controlled at 80℃ and the reaction was carried out for 3 hours. The product was then filtered, dried, and pulverized to obtain aminosilicon quantum dots.

[0156] (2) Preparation of modified silicon quantum dots

[0157] 10g of aminosilicon quantum dots, 3g of the first modifier (R1 is ethyl, a is 1, b is 16, c is 3) and 120g of ethanol were added to a three-necked glass bottle equipped with a stirrer, a condenser and a thermometer. The aminosilicon quantum dots were stirred to disperse them evenly. The temperature was controlled at 45℃ and the reaction was carried out for 8 hours. Then, 15g of the second modifier (d is 1, e is 12) was added and the reaction was carried out for 6 hours to obtain modified silicon quantum dots.

[0158] (3) Preparation of silicon-containing polymers

[0159] 10g of N,N-dimethylacrylamide, 19.5g of 2-acrylamido-2-methylpropanesulfonic acid, 0.5g of allyltriethoxysilane, and 150g of deionized water were added to a three-necked glass flask equipped with a stirrer, a nitrogen purging tube, and a thermometer. After stirring until all the raw materials were dissolved, nitrogen gas was purged for 30 minutes, the pH was controlled at 7.5, and the temperature was controlled at 0℃. Then, 0.003g of ferrous sulfate, 0.01g of sodium sulfite, 0.025g of azobisisobutylamidine hydrochloride, 0.015g of potassium persulfate, and 0.002g of hydrogen peroxide were added. The reaction was carried out for 4 hours, and then the temperature was raised to 60℃ and the reaction was carried out for 1 hour. The product was dried and pulverized to obtain a silicon-containing polymer.

[0160] (4) Preparation of thickener system

[0161] Add 1g of modified silicon quantum dots, 13g of silicon-containing polymer, and thiourea (0.5wt% of the system) to 600g of brine (a CaCl2 aqueous solution with a CaCl2 weight fraction of 30%), stir and dissolve to obtain the thickener system.

[0162] Example 13

[0163] This embodiment provides a method for preparing a thickener system, which includes the following steps:

[0164] (1) Preparation of aminosilicon quantum dots

[0165] 50g of 3-aminopropyltrimethoxysilane, 3.5g of thiourea, and 500g of deionized water were added to a three-necked glass flask equipped with a stirrer, a condenser, and a thermometer. The mixture was stirred until all the raw materials were dissolved. The temperature was controlled at 80℃ and the reaction was carried out for 3 hours. The product was then filtered, dried, and pulverized to obtain aminosilicon quantum dots.

[0166] (2) Preparation of modified silicon quantum dots

[0167] 10g of aminosilicon quantum dots, 3g of the first modifier (R1 is ethyl, a is 1, b is 16, c is 3) and 120g of ethanol were added to a three-necked glass flask equipped with a stirrer, a condenser and a thermometer. The aminosilicon quantum dots were stirred to disperse them evenly. The temperature was controlled at 45℃ and the reaction was carried out for 8 hours. Then, 40g of the second modifier (d is 1, e is 18) was added and the reaction was carried out for 6 hours to obtain modified silicon quantum dots.

[0168] (3) Preparation of silicon-containing polymers

[0169] 10g of N,N-dimethylacrylamide, 19.5g of 2-acrylamido-2-methylpropanesulfonic acid, 0.5g of allyltriethoxysilane, and 150g of deionized water were added to a three-necked glass flask equipped with a stirrer, a nitrogen purging tube, and a thermometer. After stirring until all the raw materials were dissolved, nitrogen gas was purged for 30 minutes, the pH was controlled at 7.5, and the temperature was controlled at 0℃. Then, 0.003g of ferrous sulfate, 0.01g of sodium sulfite, 0.025g of azobisisobutylamidine hydrochloride, 0.015g of potassium persulfate, and 0.002g of hydrogen peroxide were added. The reaction was carried out for 4 hours, and then the temperature was raised to 60℃ and the reaction was carried out for 1 hour. The product was dried and pulverized to obtain a silicon-containing polymer.

[0170] (4) Preparation of thickener system

[0171] Add 1g of modified silicon quantum dots, 13g of silicon-containing polymer, and thiourea (0.5wt% of the system) to 600g of brine (a CaCl2 aqueous solution with a CaCl2 weight fraction of 30%), stir and dissolve to obtain the thickener system.

[0172] Example 14

[0173] This embodiment provides a method for preparing a thickener system, which includes the following steps:

[0174] (1) Preparation of aminosilicon quantum dots

[0175] 50g of 3-aminopropyltrimethoxysilane, 3.5g of thiourea, and 500g of deionized water were added to a three-necked glass flask equipped with a stirrer, a condenser, and a thermometer. The mixture was stirred until all the raw materials were dissolved. The temperature was controlled at 80℃ and the reaction was carried out for 3 hours. The product was then filtered, dried, and pulverized to obtain aminosilicon quantum dots.

[0176] (2) Preparation of modified silicon quantum dots

[0177] 10g of aminosilicon quantum dots, 3g of the first modifier (R1 is ethyl, a is 1, b is 16, c is 3), 150g of methanol and 50g of 2-butanone were added to a three-necked glass flask equipped with a stirrer, a condenser and a thermometer. The aminosilicon quantum dots were stirred to disperse them evenly. The temperature was controlled at 45℃ and the reaction was carried out for 8 hours. Then 25g of the second modifier (d is 1, e is 7) was added and the reaction was carried out for 6 hours to obtain modified silicon quantum dots.

[0178] (3) Preparation of silicon-containing polymers

[0179] 10g of N,N-dimethylacrylamide, 19.5g of 2-acrylamido-2-methylpropanesulfonic acid, 0.5g of allyltriethoxysilane, and 150g of deionized water were added to a three-necked glass flask equipped with a stirrer, a nitrogen purging tube, and a thermometer. After stirring until all the raw materials were dissolved, nitrogen gas was purged for 30 minutes, the pH was controlled at 7.5, and the temperature was controlled at 0℃. Then, 0.003g of ferrous sulfate, 0.01g of sodium sulfite, 0.025g of azobisisobutylamidine hydrochloride, 0.015g of potassium persulfate, and 0.002g of hydrogen peroxide were added. The reaction was carried out for 4 hours, and then the temperature was raised to 60℃ and the reaction was carried out for 1 hour. The product was dried and pulverized to obtain a silicon-containing polymer.

[0180] (4) Preparation of thickener system

[0181] Add 1g of modified silicon quantum dots, 13g of silicon-containing polymer, and thiourea (0.5wt% of the system) to 600g of brine (a CaCl2 aqueous solution with a CaCl2 weight fraction of 30%), stir and dissolve to obtain the thickener system.

[0182] Example 15

[0183] This embodiment provides a method for preparing a thickener system, which includes the following steps:

[0184] (1) Preparation of aminosilicon quantum dots

[0185] 50g of 3-aminopropyltrimethoxysilane, 3.5g of thiourea, and 500g of deionized water were added to a three-necked glass flask equipped with a stirrer, a condenser, and a thermometer. The mixture was stirred until all the raw materials were dissolved. The temperature was controlled at 80℃ and the reaction was carried out for 3 hours. The product was then filtered, dried, and pulverized to obtain aminosilicon quantum dots.

[0186] (2) Preparation of modified silicon quantum dots

[0187] 10g of aminosilicon quantum dots, 3g of the first modifier (R1 is ethyl, a is 1, b is 16, c is 3) and 120g of ethanol were added to a three-necked glass bottle equipped with a stirrer, a condenser and a thermometer. The aminosilicon quantum dots were stirred to disperse them evenly. The temperature was controlled at 60℃ and the reaction was carried out for 5h. Then 25g of the second modifier (d is 1, e is 7) was added and the reaction was carried out for 6h to obtain modified silicon quantum dots.

[0188] (3) Preparation of silicon-containing polymers

[0189] 10g of N,N-dimethylacrylamide, 19.5g of 2-acrylamido-2-methylpropanesulfonic acid, 0.5g of allyltriethoxysilane, and 150g of deionized water were added to a three-necked glass flask equipped with a stirrer, a nitrogen purging tube, and a thermometer. After stirring until all the raw materials were dissolved, nitrogen gas was purged for 30 minutes, the pH was controlled at 7.5, and the temperature was controlled at 0℃. Then, 0.003g of ferrous sulfate, 0.01g of sodium sulfite, 0.025g of azobisisobutylamidine hydrochloride, 0.015g of potassium persulfate, and 0.002g of hydrogen peroxide were added. The reaction was carried out for 4 hours, and then the temperature was raised to 60℃ and the reaction was carried out for 1 hour. The product was dried and pulverized to obtain a silicon-containing polymer.

[0190] (4) Preparation of thickener system

[0191] Add 1g of modified silicon quantum dots, 13g of silicon-containing polymer, and thiourea (0.5wt% of the system) to 600g of brine (a CaCl2 aqueous solution with a CaCl2 weight fraction of 30%), stir and dissolve to obtain the thickener system.

[0192] Example 16

[0193] This embodiment provides a method for preparing a thickener system, which includes the following steps:

[0194] (1) Preparation of aminosilicon quantum dots

[0195] 50g of 3-aminopropyltrimethoxysilane, 3.5g of thiourea, and 500g of deionized water were added to a three-necked glass flask equipped with a stirrer, a condenser, and a thermometer. The mixture was stirred until all the raw materials were dissolved. The temperature was controlled at 80℃ and the reaction was carried out for 3 hours. The product was then filtered, dried, and pulverized to obtain aminosilicon quantum dots.

[0196] (2) Preparation of modified silicon quantum dots

[0197] 10g of aminosilicon quantum dots, 3g of the first modifier (R1 is ethyl, a is 1, b is 16, c is 3) and 120g of ethanol were added to a three-necked glass bottle equipped with a stirrer, a condenser and a thermometer. The aminosilicon quantum dots were stirred to disperse them evenly. The temperature was controlled at 45℃ and the reaction was carried out for 8 hours. Then 25g of the second modifier (d is 1, e is 7) was added and the reaction was carried out for 6 hours to obtain modified silicon quantum dots.

[0198] (3) Preparation of silicon-containing polymers

[0199] 10g of N,N-dimethylacrylamide, 8g of acrylamide, 2g of vinylpyrrolidone, 19.5g of 2-acrylamido-2-methylpropanesulfonic acid, 0.5g of allyltriethoxysilane, and 150g of deionized water were added to a three-necked glass flask equipped with a stirrer, a nitrogen purging tube, and a thermometer. After stirring until all the raw materials were dissolved, nitrogen gas was purged for 30 minutes, the pH was controlled at 7.5, and the temperature was controlled at 0℃. Then, 0.003g of ferrous sulfate, 0.01g of sodium sulfite, 0.025g of azobisisobutylamidine hydrochloride, 0.015g of potassium persulfate, and 0.002g of hydrogen peroxide were added, and the reaction was carried out for 4 hours. Then, the temperature was raised to 60℃ and the reaction was carried out for 1 hour. The product was dried and pulverized to obtain a silicon-containing polymer.

[0200] (4) Preparation of thickener system

[0201] Add 1g of modified silicon quantum dots, 13g of silicon-containing polymer, and thiourea (0.5wt% of the system) to 600g of brine (a CaCl2 aqueous solution with a CaCl2 weight fraction of 30%), stir and dissolve to obtain the thickener system.

[0202] Example 17

[0203] This embodiment provides a method for preparing a thickener system, which includes the following steps:

[0204] (1) Preparation of aminosilicon quantum dots

[0205] 50g of 3-aminopropyltrimethoxysilane, 3.5g of thiourea, and 500g of deionized water were added to a three-necked glass flask equipped with a stirrer, a condenser, and a thermometer. The mixture was stirred until all the raw materials were dissolved. The temperature was controlled at 80℃ and the reaction was carried out for 3 hours. The product was then filtered, dried, and pulverized to obtain aminosilicon quantum dots.

[0206] (2) Preparation of modified silicon quantum dots

[0207] 10g of aminosilicon quantum dots, 3g of the first modifier (R1 is ethyl, a is 1, b is 16, c is 3) and 120g of ethanol were added to a three-necked glass bottle equipped with a stirrer, a condenser and a thermometer. The aminosilicon quantum dots were stirred to disperse them evenly. The temperature was controlled at 45℃ and the reaction was carried out for 8 hours. Then 25g of the second modifier (d is 1, e is 7) was added and the reaction was carried out for 6 hours to obtain modified silicon quantum dots.

[0208] (3) Preparation of silicon-containing polymers

[0209] 10g of N,N-dimethylacrylamide, 20g of 2-acrylamido-2-methylpropanesulfonic acid, 5g of sodium styrene sulfonate, 0.5g of allyltriethoxysilane, and 150g of deionized water were added to a three-necked glass flask equipped with a stirrer, a nitrogen purging tube, and a thermometer. After stirring until all the raw materials were dissolved, nitrogen gas was purged for 30 minutes, the pH was controlled at 7.5, and the temperature was controlled at 0℃. Then, 0.003g of ferrous sulfate, 0.01g of sodium sulfite, 0.025g of azobisisobutylamidine hydrochloride, 0.015g of potassium persulfate, and 0.002g of hydrogen peroxide were added. The reaction was carried out for 4 hours, and then the temperature was raised to 60℃ and the reaction was carried out for 1 hour. The product was dried and pulverized to obtain a silicon-containing polymer.

[0210] (4) Preparation of thickener system

[0211] Add 1g of modified silicon quantum dots, 13g of silicon-containing polymer, and thiourea (0.5wt% of the system) to 600g of brine (a CaCl2 aqueous solution with a CaCl2 weight fraction of 30%), stir and dissolve to obtain the thickener system.

[0212] Example 18

[0213] This embodiment provides a method for preparing a thickener system, which includes the following steps:

[0214] (1) Preparation of aminosilicon quantum dots

[0215] 50g of 3-aminopropyltrimethoxysilane, 3.5g of thiourea, and 500g of deionized water were added to a three-necked glass flask equipped with a stirrer, a condenser, and a thermometer. The mixture was stirred until all the raw materials were dissolved. The temperature was controlled at 80℃ and the reaction was carried out for 3 hours. The product was then filtered, dried, and pulverized to obtain aminosilicon quantum dots.

[0216] (2) Preparation of modified silicon quantum dots

[0217] 10g of aminosilicon quantum dots, 3g of the first modifier (R1 is ethyl, a is 1, b is 16, c is 3) and 120g of ethanol were added to a three-necked glass bottle equipped with a stirrer, a condenser and a thermometer. The aminosilicon quantum dots were stirred to disperse them evenly. The temperature was controlled at 45℃ and the reaction was carried out for 8 hours. Then 25g of the second modifier (d is 1, e is 7) was added and the reaction was carried out for 6 hours to obtain modified silicon quantum dots.

[0218] (3) Preparation of silicon-containing polymers

[0219] 10g of N,N-dimethylacrylamide, 19.5g of 2-acrylamido-2-methylpropanesulfonic acid, 0.1g of vinyltrimethoxysilane, 0.2g of allyltrimethoxysilane, and 150g of deionized water were added to a three-necked glass flask equipped with a stirrer, a nitrogen purging tube, and a thermometer. After stirring until all the raw materials were dissolved, nitrogen gas was purged for 30 minutes, the pH was controlled at 7.5, and the temperature was controlled at 0℃. Then, 0.003g of ferrous sulfate, 0.01g of sodium sulfite, 0.025g of azobisisobutylamidine hydrochloride, 0.015g of potassium persulfate, and 0.002g of hydrogen peroxide were added. The reaction was carried out for 4 hours, and then the temperature was raised to 60℃ and the reaction was carried out for 1 hour. The product was dried and pulverized to obtain a silicon-containing polymer.

[0220] (4) Preparation of thickener system

[0221] Add 1g of modified silicon quantum dots, 13g of silicon-containing polymer, and thiourea (0.5wt% of the system) to 600g of brine (a CaCl2 aqueous solution with a CaCl2 weight fraction of 30%), stir and dissolve to obtain the thickener system.

[0222] Example 19

[0223] This embodiment provides a method for preparing a thickener system, which includes the following steps:

[0224] (1) Preparation of aminosilicon quantum dots

[0225] 50g of 3-aminopropyltrimethoxysilane, 3.5g of thiourea, and 500g of deionized water were added to a three-necked glass flask equipped with a stirrer, a condenser, and a thermometer. The mixture was stirred until all the raw materials were dissolved. The temperature was controlled at 80℃ and the reaction was carried out for 3 hours. The product was then filtered, dried, and pulverized to obtain aminosilicon quantum dots.

[0226] (2) Preparation of modified silicon quantum dots

[0227] 10g of aminosilicon quantum dots, 3g of the first modifier (R1 is ethyl, a is 1, b is 16, c is 3) and 120g of ethanol were added to a three-necked glass bottle equipped with a stirrer, a condenser and a thermometer. The aminosilicon quantum dots were stirred to disperse them evenly. The temperature was controlled at 45℃ and the reaction was carried out for 8 hours. Then 25g of the second modifier (d is 1, e is 7) was added and the reaction was carried out for 6 hours to obtain modified silicon quantum dots.

[0228] (3) Preparation of silicon-containing polymers

[0229] 10g of N,N-dimethylacrylamide, 19.5g of 2-acrylamido-2-methylpropanesulfonic acid, 0.6g of vinyltriethoxysilane, 0.3g of allyltriethoxysilane, and 150g of deionized water were added to a three-necked glass flask equipped with a stirrer, a nitrogen purging tube, and a thermometer. After stirring until all the raw materials were dissolved, nitrogen gas was purged for 30 minutes, the pH was controlled at 7.5, and the temperature was controlled at 0℃. Then, 0.003g of ferrous sulfate, 0.01g of sodium sulfite, 0.025g of azobisisobutylamidine hydrochloride, 0.015g of potassium persulfate, and 0.002g of hydrogen peroxide were added. The reaction was carried out for 4 hours, and then the temperature was raised to 60℃ and the reaction was carried out for 1 hour. The product was dried and pulverized to obtain a silicon-containing polymer.

[0230] (4) Preparation of thickener system

[0231] Add 1g of modified silicon quantum dots, 13g of silicon-containing polymer, and thiourea (0.5wt% of the system) to 600g of brine (a CaCl2 aqueous solution with a CaCl2 weight fraction of 30%), stir and dissolve to obtain the thickener system.

[0232] Example 20

[0233] This embodiment provides a method for preparing a thickener system, which includes the following steps:

[0234] (1) Preparation of aminosilicon quantum dots

[0235] 50g of 3-aminopropyltrimethoxysilane, 3.5g of thiourea, and 500g of deionized water were added to a three-necked glass flask equipped with a stirrer, a condenser, and a thermometer. The mixture was stirred until all the raw materials were dissolved. The temperature was controlled at 80℃ and the reaction was carried out for 3 hours. The product was then filtered, dried, and pulverized to obtain aminosilicon quantum dots.

[0236] (2) Preparation of modified silicon quantum dots

[0237] 10g of aminosilicon quantum dots, 3g of the first modifier (R1 is ethyl, a is 1, b is 16, c is 3) and 120g of ethanol were added to a three-necked glass bottle equipped with a stirrer, a condenser and a thermometer. The aminosilicon quantum dots were stirred to disperse them evenly. The temperature was controlled at 45℃ and the reaction was carried out for 8 hours. Then 25g of the second modifier (d is 1, e is 7) was added and the reaction was carried out for 6 hours to obtain modified silicon quantum dots.

[0238] (3) Preparation of silicon-containing polymers

[0239] 10g of N,N-dimethylacrylamide, 19.5g of 2-acrylamido-2-methylpropanesulfonic acid, 0.5g of allyltriethoxysilane, and 250g of deionized water were added to a three-necked glass flask equipped with a stirrer, a nitrogen purging tube, and a thermometer. After stirring until all the raw materials were dissolved, nitrogen gas was purged for 30 minutes, the pH was controlled at 7.5, and the temperature was controlled at 0℃. Then, 0.003g of ferrous sulfate, 0.01g of sodium sulfite, 0.025g of azobisisobutylamidine hydrochloride, 0.015g of potassium persulfate, and 0.002g of hydrogen peroxide were added. The reaction was carried out for 4 hours, and then the temperature was raised to 60℃ and the reaction was carried out for 1 hour. The product was dried and pulverized to obtain a silicon-containing polymer.

[0240] (4) Preparation of thickener system

[0241] Add 1g of modified silicon quantum dots, 13g of silicon-containing polymer, and thiourea (0.5wt% of the system) to 600g of brine (a CaCl2 aqueous solution with a CaCl2 weight fraction of 30%), stir and dissolve to obtain the thickener system.

[0242] Example 21

[0243] This embodiment provides a method for preparing a thickener system, which includes the following steps:

[0244] (1) Preparation of aminosilicon quantum dots

[0245] 50g of 3-aminopropyltrimethoxysilane, 3.5g of thiourea, and 500g of deionized water were added to a three-necked glass flask equipped with a stirrer, a condenser, and a thermometer. The mixture was stirred until all the raw materials were dissolved. The temperature was controlled at 80℃ and the reaction was carried out for 3 hours. The product was then filtered, dried, and pulverized to obtain aminosilicon quantum dots.

[0246] (2) Preparation of modified silicon quantum dots

[0247] 10g of aminosilicon quantum dots, 3g of the first modifier (R1 is ethyl, a is 1, b is 16, c is 3) and 120g of ethanol were added to a three-necked glass bottle equipped with a stirrer, a condenser and a thermometer. The aminosilicon quantum dots were stirred to disperse them evenly. The temperature was controlled at 45℃ and the reaction was carried out for 8 hours. Then 25g of the second modifier (d is 1, e is 7) was added and the reaction was carried out for 6 hours to obtain modified silicon quantum dots.

[0248] (3) Preparation of silicon-containing polymers

[0249] 10g of N,N-dimethylacrylamide, 19.5g of 2-acrylamido-2-methylpropanesulfonic acid, 0.5g of allyltriethoxysilane, and 150g of deionized water were added to a three-necked glass flask equipped with a stirrer, a nitrogen purging tube, and a thermometer. After stirring until all the raw materials were dissolved, nitrogen gas was purged for 30 minutes, the pH was controlled at 7.5, and the temperature was controlled at 0℃. Then, 0.0015g of ferrous ammonium sulfate, 0.012g of sodium thiosulfate, 0.04g of azodicyanovalerate, 0.011g of sodium persulfate, and 0.0025g of benzoyl peroxide were added. The reaction was carried out for 4 hours, and then the temperature was raised to 60℃ and the reaction was carried out for 1 hour. The product was dried and pulverized to obtain a silicon-containing polymer.

[0250] (4) Preparation of thickener system

[0251] Add 1g of modified silicon quantum dots, 13g of silicon-containing polymer, and thiourea (0.5wt% of the system) to 600g of brine (a CaCl2 aqueous solution with a CaCl2 weight fraction of 30%), stir and dissolve to obtain the thickener system.

[0252] Example 22

[0253] This embodiment provides a method for preparing a thickener system, which includes the following steps:

[0254] (1) Preparation of aminosilicon quantum dots

[0255] 50g of 3-aminopropyltrimethoxysilane, 3.5g of thiourea, and 500g of deionized water were added to a three-necked glass flask equipped with a stirrer, a condenser, and a thermometer. The mixture was stirred until all the raw materials were dissolved. The temperature was controlled at 80℃ and the reaction was carried out for 3 hours. The product was then filtered, dried, and pulverized to obtain aminosilicon quantum dots.

[0256] (2) Preparation of modified silicon quantum dots

[0257] 10g of aminosilicon quantum dots, 3g of the first modifier (R1 is ethyl, a is 1, b is 16, c is 3) and 120g of ethanol were added to a three-necked glass bottle equipped with a stirrer, a condenser and a thermometer. The aminosilicon quantum dots were stirred to disperse them evenly. The temperature was controlled at 45℃ and the reaction was carried out for 8 hours. Then 25g of the second modifier (d is 1, e is 7) was added and the reaction was carried out for 6 hours to obtain modified silicon quantum dots.

[0258] (3) Preparation of silicon-containing polymers

[0259] 10g of N,N-dimethylacrylamide, 19.5g of 2-acrylamido-2-methylpropanesulfonic acid, 0.5g of allyltriethoxysilane, and 150g of deionized water were added to a three-necked glass flask equipped with a stirrer, a nitrogen purging tube, and a thermometer. After stirring until all the raw materials were dissolved, nitrogen gas was purged for 30 minutes, the pH was controlled at 7.5, and the temperature was controlled at 0℃. Then, 0.0045g of ferrous chloride, 0.009g of sodium dithionite, 0.015g of azodicyanovalerate, 0.002g of ammonium persulfate, and 0.001g of hydrogen peroxide were added. The reaction was carried out for 4 hours, and then the temperature was raised to 60℃ and the reaction was carried out for 1 hour. The product was dried and pulverized to obtain a silicon-containing polymer.

[0260] (4) Preparation of thickener system

[0261] Add 1g of modified silicon quantum dots, 13g of silicon-containing polymer, and thiourea (0.5wt% of the system) to 600g of brine (a CaCl2 aqueous solution with a CaCl2 weight fraction of 30%), stir and dissolve to obtain the thickener system.

[0262] Example 23

[0263] This embodiment provides a method for preparing a thickener system, which includes the following steps:

[0264] (1) Preparation of aminosilicon quantum dots

[0265] 50g of 3-aminopropyltrimethoxysilane, 3.5g of thiourea, and 500g of deionized water were added to a three-necked glass flask equipped with a stirrer, a condenser, and a thermometer. The mixture was stirred until all the raw materials were dissolved. The temperature was controlled at 80℃ and the reaction was carried out for 3 hours. The product was then filtered, dried, and pulverized to obtain aminosilicon quantum dots.

[0266] (2) Preparation of modified silicon quantum dots

[0267] 10g of aminosilicon quantum dots, 3g of the first modifier (R1 is ethyl, a is 1, b is 16, c is 3) and 120g of ethanol were added to a three-necked glass bottle equipped with a stirrer, a condenser and a thermometer. The aminosilicon quantum dots were stirred to disperse them evenly. The temperature was controlled at 45℃ and the reaction was carried out for 8 hours. Then 25g of the second modifier (d is 1, e is 7) was added and the reaction was carried out for 6 hours to obtain modified silicon quantum dots.

[0268] (3) Preparation of silicon-containing polymers

[0269] 10g of N,N-dimethylacrylamide, 19.5g of 2-acrylamido-2-methylpropanesulfonic acid, 0.5g of allyltriethoxysilane, and 150g of deionized water were added to a three-necked glass flask equipped with a stirrer, a nitrogen purging tube, and a thermometer. After stirring until all the raw materials were dissolved, nitrogen gas was purged for 30 minutes, the pH was controlled at 7.3, and the temperature was controlled at -1℃. Then, 0.003g of ferrous sulfate, 0.01g of sodium sulfite, 0.025g of azobisisobutylamidine hydrochloride, 0.015g of potassium persulfate, and 0.002g of hydrogen peroxide were added. The reaction was carried out for 3 hours, and then the temperature was raised to 60℃ and the reaction was carried out for 1 hour. The product was dried and pulverized to obtain a silicon-containing polymer.

[0270] (4) Preparation of thickener system

[0271] Add 1g of modified silicon quantum dots, 13g of silicon-containing polymer, and thiourea (0.5wt% of the system) to 600g of brine (a CaCl2 aqueous solution with a CaCl2 weight fraction of 30%), stir and dissolve to obtain the thickener system.

[0272] Example 24

[0273] This embodiment provides a method for preparing a thickener system, which includes the following steps:

[0274] (1) Preparation of aminosilicon quantum dots

[0275] 50g of 3-aminopropyltrimethoxysilane, 3.5g of thiourea, and 500g of deionized water were added to a three-necked glass flask equipped with a stirrer, a condenser, and a thermometer. The mixture was stirred until all the raw materials were dissolved. The temperature was controlled at 80℃ and the reaction was carried out for 3 hours. The product was then filtered, dried, and pulverized to obtain aminosilicon quantum dots.

[0276] (2) Preparation of modified silicon quantum dots

[0277] 10g of aminosilicon quantum dots, 3g of the first modifier (R1 is ethyl, a is 1, b is 16, c is 3) and 120g of ethanol were added to a three-necked glass bottle equipped with a stirrer, a condenser and a thermometer. The aminosilicon quantum dots were stirred to disperse them evenly. The temperature was controlled at 45℃ and the reaction was carried out for 8 hours. Then 25g of the second modifier (d is 1, e is 7) was added and the reaction was carried out for 6 hours to obtain modified silicon quantum dots.

[0278] (3) Preparation of silicon-containing polymers

[0279] 10g of N,N-dimethylacrylamide, 19.5g of 2-acrylamido-2-methylpropanesulfonic acid, 0.5g of allyltriethoxysilane, and 150g of deionized water were added to a three-necked glass flask equipped with a stirrer, a nitrogen purging tube, and a thermometer. After stirring until all the raw materials were dissolved, nitrogen gas was purged for 30 minutes, the pH was controlled at 6.8, and the temperature was controlled at 6℃. Then, 0.003g of ferrous sulfate, 0.01g of sodium sulfite, 0.025g of azobisisobutylamidine hydrochloride, 0.015g of potassium persulfate, and 0.002g of hydrogen peroxide were added. The reaction was allowed to proceed for 2.5 hours, and then the temperature was raised to 60℃ and the reaction was allowed to proceed for 1 hour. The product was dried and pulverized to obtain a silicon-containing polymer.

[0280] (4) Preparation of thickener system

[0281] Add 1g of modified silicon quantum dots, 13g of silicon-containing polymer, and thiourea (0.5wt% of the system) to 600g of brine (a CaCl2 aqueous solution with a CaCl2 weight fraction of 30%), stir and dissolve to obtain the thickener system.

[0282] Example 25

[0283] This embodiment provides a method for preparing a thickener system, which includes the following steps:

[0284] (1) Preparation of aminosilicon quantum dots

[0285] 50g of 3-aminopropyltrimethoxysilane, 3.5g of thiourea, and 500g of deionized water were added to a three-necked glass flask equipped with a stirrer, a condenser, and a thermometer. The mixture was stirred until all the raw materials were dissolved. The temperature was controlled at 80℃ and the reaction was carried out for 3 hours. The product was then filtered, dried, and pulverized to obtain aminosilicon quantum dots.

[0286] (2) Preparation of modified silicon quantum dots

[0287] 10g of aminosilicon quantum dots, 3g of the first modifier (R1 is ethyl, a is 1, b is 16, c is 3) and 120g of ethanol were added to a three-necked glass bottle equipped with a stirrer, a condenser and a thermometer. The aminosilicon quantum dots were stirred to disperse them evenly. The temperature was controlled at 45℃ and the reaction was carried out for 8 hours. Then 25g of the second modifier (d is 1, e is 7) was added and the reaction was carried out for 6 hours to obtain modified silicon quantum dots.

[0288] (3) Preparation of silicon-containing polymers

[0289] 10g of N,N-dimethylacrylamide, 19.5g of 2-acrylamido-2-methylpropanesulfonic acid, 0.5g of allyltriethoxysilane, and 150g of deionized water were added to a three-necked glass flask equipped with a stirrer, a nitrogen purging tube, and a thermometer. After stirring until all the raw materials were dissolved, nitrogen gas was purged for 30 minutes, the pH was controlled at 7.5, and the temperature was controlled at 0℃. Then, 0.003g of ferrous sulfate, 0.01g of sodium sulfite, 0.025g of azobisisobutylamidine hydrochloride, 0.015g of potassium persulfate, and 0.002g of hydrogen peroxide were added. The reaction was carried out for 4 hours, and then the temperature was raised to 60℃ and the reaction was carried out for 1 hour. The product was dried and pulverized to obtain a silicon-containing polymer.

[0290] (4) Preparation of thickener system

[0291] Add 2.5g of modified silicon quantum dots, 13g of silicon-containing polymer, and thiourea (0.5wt% of the system) to 600g of brine (a CaCl2 aqueous solution with a CaCl2 weight fraction of 30%), stir and dissolve to obtain the thickener system.

[0292] Example 26

[0293] This embodiment provides a method for preparing a thickener system, which includes the following steps:

[0294] (1) Preparation of aminosilicon quantum dots

[0295] 50g of 3-aminopropyltrimethoxysilane, 3.5g of thiourea, and 500g of deionized water were added to a three-necked glass flask equipped with a stirrer, a condenser, and a thermometer. The mixture was stirred until all the raw materials were dissolved. The temperature was controlled at 80℃ and the reaction was carried out for 3 hours. The product was then filtered, dried, and pulverized to obtain aminosilicon quantum dots.

[0296] (2) Preparation of modified silicon quantum dots

[0297] 10g of aminosilicon quantum dots, 3g of the first modifier (R1 is ethyl, a is 1, b is 16, c is 3) and 120g of ethanol were added to a three-necked glass bottle equipped with a stirrer, a condenser and a thermometer. The aminosilicon quantum dots were stirred to disperse them evenly. The temperature was controlled at 45℃ and the reaction was carried out for 8 hours. Then 25g of the second modifier (d is 1, e is 7) was added and the reaction was carried out for 6 hours to obtain modified silicon quantum dots.

[0298] (3) Preparation of silicon-containing polymers

[0299] 10g of N,N-dimethylacrylamide, 19.5g of 2-acrylamido-2-methylpropanesulfonic acid, 0.5g of allyltriethoxysilane, and 150g of deionized water were added to a three-necked glass flask equipped with a stirrer, a nitrogen purging tube, and a thermometer. After stirring until all the raw materials were dissolved, nitrogen gas was purged for 30 minutes, the pH was controlled at 7.5, and the temperature was controlled at 0℃. Then, 0.003g of ferrous sulfate, 0.01g of sodium sulfite, 0.025g of azobisisobutylamidine hydrochloride, 0.015g of potassium persulfate, and 0.002g of hydrogen peroxide were added. The reaction was carried out for 4 hours, and then the temperature was raised to 60℃ and the reaction was carried out for 1 hour. The product was dried and pulverized to obtain a silicon-containing polymer.

[0300] (4) Preparation of thickener system

[0301] Add 0.6g of modified silicon quantum dots, 13g of silicon-containing polymer, and thiourea (0.5wt% of the system) to 600g of brine (a CaCl2 aqueous solution with a CaCl2 weight fraction of 30%), stir and dissolve to obtain the thickener system.

[0302] Example 27

[0303] This embodiment provides a method for preparing a thickener system, which includes the following steps:

[0304] (1) Preparation of aminosilicon quantum dots

[0305] 50g of 3-aminopropyltrimethoxysilane, 3.5g of thiourea, and 500g of deionized water were added to a three-necked glass flask equipped with a stirrer, a condenser, and a thermometer. The mixture was stirred until all the raw materials were dissolved. The temperature was controlled at 80℃ and the reaction was carried out for 3 hours. The product was then filtered, dried, and pulverized to obtain aminosilicon quantum dots.

[0306] (2) Preparation of modified silicon quantum dots

[0307] 10g of aminosilicon quantum dots, 3g of the first modifier (R1 is ethyl, a is 1, b is 16, c is 3) and 120g of ethanol were added to a three-necked glass bottle equipped with a stirrer, a condenser and a thermometer. The aminosilicon quantum dots were stirred to disperse them evenly. The temperature was controlled at 45℃ and the reaction was carried out for 8 hours. Then 25g of the second modifier (d is 1, e is 7) was added and the reaction was carried out for 6 hours to obtain modified silicon quantum dots.

[0308] (3) Preparation of silicon-containing polymers

[0309] 10g of N,N-dimethylacrylamide, 19.5g of 2-acrylamido-2-methylpropanesulfonic acid, 0.5g of allyltriethoxysilane, and 150g of deionized water were added to a three-necked glass flask equipped with a stirrer, a nitrogen purging tube, and a thermometer. After stirring until all the raw materials were dissolved, nitrogen gas was purged for 30 minutes, the pH was controlled at 7.5, and the temperature was controlled at 0℃. Then, 0.003g of ferrous sulfate, 0.01g of sodium sulfite, 0.025g of azobisisobutylamidine hydrochloride, 0.015g of potassium persulfate, and 0.002g of hydrogen peroxide were added. The reaction was carried out for 4 hours, and then the temperature was raised to 60℃ and the reaction was carried out for 1 hour. The product was dried and pulverized to obtain a silicon-containing polymer.

[0310] (4) Preparation of thickener system

[0311] Add 1g of modified silicon quantum dots, 13g of silicon-containing polymer, and thiourea (0.5wt% of the system) to 350g of brine (a CaCl2 aqueous solution with a CaCl2 weight fraction of 30%), stir and dissolve to obtain the thickener system.

[0312] Example 28

[0313] This embodiment provides a method for preparing a thickener system, which includes the following steps:

[0314] (1) Preparation of aminosilicon quantum dots

[0315] 50g of 3-aminopropyltrimethoxysilane, 3.5g of thiourea, and 500g of deionized water were added to a three-necked glass flask equipped with a stirrer, a condenser, and a thermometer. The mixture was stirred until all the raw materials were dissolved. The temperature was controlled at 80℃ and the reaction was carried out for 3 hours. The product was then filtered, dried, and pulverized to obtain aminosilicon quantum dots.

[0316] (2) Preparation of modified silicon quantum dots

[0317] 10g of aminosilicon quantum dots, 3g of the first modifier (R1 is ethyl, a is 1, b is 16, c is 3) and 120g of ethanol were added to a three-necked glass bottle equipped with a stirrer, a condenser and a thermometer. The aminosilicon quantum dots were stirred to disperse them evenly. The temperature was controlled at 45℃ and the reaction was carried out for 8 hours. Then 25g of the second modifier (d is 1, e is 7) was added and the reaction was carried out for 6 hours to obtain modified silicon quantum dots.

[0318] (3) Preparation of silicon-containing polymers

[0319] 10g of N,N-dimethylacrylamide, 19.5g of 2-acrylamido-2-methylpropanesulfonic acid, 0.5g of allyltriethoxysilane, and 150g of deionized water were added to a three-necked glass flask equipped with a stirrer, a nitrogen purging tube, and a thermometer. After stirring until all the raw materials were dissolved, nitrogen gas was purged for 30 minutes, the pH was controlled at 7.5, and the temperature was controlled at 0℃. Then, 0.003g of ferrous sulfate, 0.01g of sodium sulfite, 0.025g of azobisisobutylamidine hydrochloride, 0.015g of potassium persulfate, and 0.002g of hydrogen peroxide were added. The reaction was carried out for 4 hours, and then the temperature was raised to 60℃ and the reaction was carried out for 1 hour. The product was dried and pulverized to obtain a silicon-containing polymer.

[0320] (4) Preparation of thickener system

[0321] Add 1g of modified silicon quantum dots, 13g of silicon-containing polymer, and thiourea (0.5wt% of the system) to 850g of brine (a CaCl2 aqueous solution with a CaCl2 weight fraction of 30%), stir and dissolve to obtain the thickener system.

[0322] Performance Evaluation: The rheological properties of the thickener system in the above examples were tested (before aging), and then further placed in an aging tank and aged at 170°C for 7 days. The rheological properties were then tested again (after aging). The rheological properties were determined according to the method specified in the national standard GB / T16783.1-2014, and the test temperature was 50°C. The test data are shown in Table 1.

[0323] Table 1

[0324]

[0325]

[0326] As shown in Table 1, the high-salinity drilling fluid and completion fluid thickener prepared by this invention exhibits high dynamic shear force (YP) under high calcium conditions. Furthermore, it demonstrates a low plastic viscosity (PV) / dynamic shear force (YP) ratio and suitable initial and final shear values, exhibiting excellent rheological and thixotropic properties. This provides good support for the dynamic carrying of rock cuttings and the static suspension of solid phases within the system. In particular, the system exhibits excellent temperature resistance, maintaining good rheological and thixotropic properties even after aging.

Claims

1. A silicon quantum dot modified composition, wherein, Includes organic solvents, a first modifier, and a second modifier; The structural formula of the first modifier is: R1 is a C1-C6 alkyl group; a is 1-4, b is 1-30, and c is 1-6; The structural formula of the second modifier is: d ranges from 1 to 4, and e ranges from 1 to 20.

2. The silicon quantum dot modified composition according to claim 1, wherein, The organic solvent is selected from one or more of acetone, 2-butanone, methanol, ethanol, n-propanol, isopropanol and ethylene glycol.

3. The silicon quantum dot modified composition according to claim 1, wherein, R1 is a C1-C4 alkyl group; a is 1-4; b is 1-22; c is 2-3; d is 1-2; and e is 5-20.

4. The silicon quantum dot modified composition according to claim 1, wherein, The weight ratio of the first modifier, the second modifier, and the organic solvent is 0.01–2:0.2–10:1–100.

5. A modified silicon quantum dot, wherein, The silicon quantum dot is obtained by surface modification of silicon quantum dots and the silicon quantum dot modified composition according to any one of claims 1 to 4; the silicon quantum dot modified composition includes an organic solvent, a first modifier, and a second modifier.

6. The modified silicon quantum dot according to claim 5, wherein, The weight ratio of the silicon quantum dots, the first modifier, the second modifier, and the organic solvent is 1:0.01-2:0.2-10:1-100.

7. The modified silicon quantum dot according to claim 5, wherein, The weight ratio of the silicon quantum dots, the first modifier, the second modifier, and the organic solvent is 1:0.15 to 1:1.5 to 5:10 to 20.

8. The modified silicon quantum dots according to claim 5, wherein, The surface modification process includes: mixing the silicon quantum dots, the first modifier, and the organic solvent, reacting them at a temperature of 20–80°C for 1–24 hours, and then adding the second modifier to the system and reacting for 1–18 hours.

9. The modified silicon quantum dot according to claim 5, wherein, The silicon quantum dots are obtained by a hydrothermal reaction of a silicon-containing compound, a reducing agent, and water.

10. The modified silicon quantum dot according to claim 9, wherein, The silicon-containing compound is selected from one or more combinations of 3-aminopropyltriethoxysilane, 3-aminopropylmethyldiethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropylmethyldimethoxysilane, 3-(2-aminoethylamino)propyltriethoxysilane, 3-(2-aminoethylamino)propylmethyldiethoxysilane, 3-(2-aminoethylamino)propyltrimethoxysilane, and 3-(2-aminoethylamino)propylmethyldimethoxysilane. The reducing agent is selected from one or more of isoascorbic acid, sodium isoascorbate, ascorbic acid, sodium ascorbate, folic acid, urea, thiourea, hydroquinone, 2-aminophenol, 4-aminophenol, citric acid, monosodium citrate, disodium citrate, and trisodium citrate. The weight ratio of the silicon-containing compound, the reducing agent, and water is 1:0.001 to 0.5:1 to 100.

11. A thickener, wherein, Includes the modified silicon quantum dots and silicon-containing polymers as described in any one of claims 5 to 10.

12. The thickener according to claim 11, wherein, The weight ratio of the modified silicon quantum dots to the silicon-containing polymer is 1:2 to 200.

13. The thickener according to claim 11, wherein, The weight ratio of the modified silicon quantum dots to the silicon-containing polymer is 1:5 to 25.

14. The thickener according to claim 11, wherein, The silicon-containing polymer is obtained by polymerizing nonionic monomers, anionic monomers and silicon-containing monomers; The nonionic monomer is selected from one or more of N-ethylacrylamide, N,N-dimethylacrylamide, N,N-diethylacrylamide, acrylmorpholine and vinylpyrrolidone; The anionic monomer is selected from one or more of 2-acrylamido-2-methylpropanesulfonic acid, sodium styrene sulfonate and sodium vinyl sulfonate; The silicon-containing monomer is selected from one or more of vinyltrimethoxysilane, vinyltriethoxysilane, allyltrimethoxysilane, and allyltriethoxysilane.

15. The thickener according to claim 14, wherein, The weight ratio of the nonionic monomer to the anionic monomer is 1:0.1 to 10; The total weight of the nonionic monomer and the anionic monomer is 1:0.001 to 0.05 of the weight of the silicon-containing monomer. The total weight ratio of the nonionic monomer, the anionic monomer, and the silicon-containing monomer to the weight ratio of water is 1:0.5 to 20.

16. A thickener system, wherein, It includes the thickener and brine as described in any one of claims 11 to 15.

17. A drilling fluid, wherein, The thickener included in any one of claims 11 to 15.

18. A completion fluid, wherein, The thickener included in any one of claims 11 to 15.

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