A core-shell sustained-release viscosity enhancer and its preparation method and application

Abstract

The present invention discloses a core-shell slow-release tackifier and a preparation method and application thereof, relating to the field of oilfield chemical technology. The core-shell slow-release tackifier comprises a core material and a shell material, wherein the core material is prepared from a raw material I comprising 2-acrylamido-2-methylpropanesulfonic acid (AMPS), acrylic acid (AA), a hydrophobic monomer, and laponite; and the shell material is prepared from a raw material II comprising a styrene monomer. The core-shell slow-release tackifier having a thermal tackifying effect is used as a suspension stabilizer for high-density cement slurry, can meet high-temperature construction environments of 150°C to 210°C, and the density difference of the cement slurry after curing is less than 0.03g / cm3 after standing for two hours. 3 .

Description

Technical Field

[0001] The present invention relates to the technical field of oilfield chemistry, and in particular to a core-shell slow-release tackifier, a preparation method thereof, and an application thereof. Background Art

[0002] As oil exploration and development continues to advance toward deep and ultra-deep wells, high-temperature, high-pressure formation environments have become an inevitable challenge for cementing projects. High temperatures intensify the Brownian motion of cement particles, leading to a decrease in viscosity and subsequent sedimentation. High-temperature, high-pressure environments often require high-density cement slurries containing large amounts of weighting materials such as iron powder, making sedimentation stability difficult to control. Excessive retarder additions in high-temperature environments often lead to increased dispersion in the slurry, further compromising sedimentation stability.

[0003] Currently, on-site construction often uses methods such as reducing the water-cement ratio and reducing the amount of retarders and dispersants to improve the high-temperature stability of cement slurries. However, this method can result in excessively high initial viscosity, hindering proper pumping of the slurry. Researchers have found that optimizing the particle size composition of the solid phase in the cement slurry and increasing the solid content per unit volume can improve slurry stability. However, this method is costly and complex, and is difficult to implement due to limitations in cementing materials and site requirements. It also has certain limitations in improving the settling stability of cement slurries. In addition, the addition of inorganic suspension stabilizers, including silica fume, metakaolin, hollow microspheres, microsilica, fine sand, volcanic ash, lime, mineral fillers, clay, and nanomaterials, can improve slurry suspension stability. However, the addition of some inorganic materials can negatively impact the strength development of the cement paste. Furthermore, polymer stabilizers are currently widely used and offer excellent suspension stability. However, polymer viscosity enhancers tend to thicken the slurry at low temperatures, making it difficult to pump. At high temperatures, polymer materials decompose, thinning the slurry (thickening at low temperatures and thinning at high temperatures), but this still fails to solve the problem of settlement instability in high-temperature, high-density cement slurries. Therefore, the development of intelligent thickeners that "do not thicken at low temperatures but increase viscosity at high temperatures" is urgent.

[0004] At present, there are very few domestic sedimentation stabilizer products, most of which have a temperature resistance of around 150°C, and begin to have a viscosity-increasing effect at low temperatures, resulting in poor overall performance of cement slurry with the addition of sedimentation stabilizers.

[0005] Li Xiaolin and others designed and developed a new type of thermal viscosity-increasing copolymer containing hydrophobic monomers, and developed a high-temperature stabilizer for high-density cement slurry based on the thermal viscosity-increasing copolymer. The apparent viscosity of the thermal viscosity-increasing copolymer solution gradually increases with increasing temperature, reaching a maximum value at 1151125℃. As the temperature continues to rise, the apparent viscosity decreases slightly, but the apparent viscosity at 150℃ can still be maintained at 214 times the initial apparent viscosity, showing a good thermal viscosity-increasing effect. 1% thermal viscosity-increasing copolymer was introduced into 2.50g / cm 3In high-density cement slurry, the density difference of cement slurry at 150℃ is 0.58g / cm 3 , reduced to 0.07g / cm 3 , the density difference of cement stone is reduced to 0.08g / cm 3 The comprehensive performance can meet the requirements of on-site construction. However, the system has a temperature resistance of only 150°C, which is far from the actual ultra-high temperature target, and the polymer has a certain viscosity at low temperatures. For details, see [Li Xiaolin, Li Jianhua, Yang Hongbin, et al. High-temperature stabilizer for high-density cement slurry based on thermal viscosity-increasing copolymer [J]. Drilling Fluids and Completion Fluids, 2022, 39(1): 76-81.]

[0006] Xiong Zhengqiang et al. proposed using hectorite as an ultra-high-temperature viscosifier for water-based drilling fluids. Experimental results revealed that synthetic hectorite H-6 exhibits excellent viscosifying properties and thermal stability, with a temperature resistance of up to 240°C. Its high-temperature viscosifying performance surpasses existing domestic and international high-temperature viscosifiers. When 1% H-6 was added to a 4% sodium bentonite-based slurry, the apparent viscosity of the slurry before and after aging at 240°C for 16 hours remained at 16.5 mPa·s. However, a sodium bentonite-based slurry containing 1% high-temperature viscosifier HE300 exhibited a viscosity reduction of over 92% after aging at 240°C for 16 hours. These results demonstrate that synthetic hectorite exhibits good compatibility with other treatment agents, making it suitable for use as an ultra-high-temperature viscosifier and promising for application in ultra-high-temperature water-based drilling fluids. However, no research has been conducted on its use in high-temperature cement slurries. For details, see [Xiong Zhengqiang, Li Xiaodong, Fu Fan, et al. Experimental study on the use of synthetic hectorite as a viscosifier for ultra-high temperature water-based drilling fluids [J]. Drilling Fluids and Completion Fluids, 2018, 35(5): 19-25.]

[0007] Chinese patent CN106967397B discloses a hydrophobically modified cellulose thermal thickener. Cellulose is dissolved in an alkaline solution, stirred evenly, and a soluble salt is added to precipitate the high-molecular-weight cellulose. Alkylene oxide is then added for etherification, and the product is then hydrophobically modified with a long-chain halogenated alkane to produce the hydrophobically modified cellulose thermal thickener. This product exhibits a viscosity-increasing effect at around 40°C. The system was tested at a temperature of 150°C and a water-cement ratio of 0.4, which is a conventional density system. High-temperature, high-density systems are difficult to achieve.

[0008] Chinese patent CN108586671B discloses an anionic thermally thickening water-soluble polymer and its preparation method. Using acrylamide, acrylic acid, and Pluronic triblock polymers for inverse emulsion polymerization, the molecular weight of the thermally thickening polymer is increased by the high reactivity of acrylamide and inverse emulsion polymerization, resulting in a significant thermally thickening effect at low concentrations, which can reduce application costs. The resulting polymer emulsion dissolves significantly faster than the polymer powder. After a small amount of inverse agent is added to the resulting emulsion dilution, it exhibits strong thermally thickening behavior. As the amount of inverse agent added increases, the emulsion dilution exhibits different thermally thickening behaviors. However, the viscosity of the thickener begins to increase at around 40°C, which makes low-temperature pumping difficult.

[0009] Chinese patent document CN115872647A discloses a suspension stabilizer, which is a composite calcined product made of attapulgite, sepiolite and nano-silica. The operating temperature of the stabilizer is 30°C to 1180°C, indicating that it begins to increase viscosity at low temperatures, which is not conducive to the pumping of cement slurry, and cannot be used at high temperatures (>200°C).

[0010] At present, the existing literature on cement slurry thickeners all have application environments below 200°C, and the problem of low-temperature thickening has not been solved. Summary of the Invention

[0011] The present invention addresses the problem of easy sedimentation in high-temperature, high-density cement slurry systems in the prior art, as well as the problems of existing tackifiers with insufficient temperature resistance, thickening at low temperatures, and thinning at high temperatures. The present invention proposes a core-shell sustained-release tackifier. First, through molecular structure design, high-temperature-resistant hydrophobic side chains (AMPS and hydrophobic monomers) are introduced to avoid the problem of high-temperature decomposition and thinning of polymer tackifiers. This tackifier is then encapsulated in a polymer shell with a certain degree of temperature resistance, resulting in a core-shell sustained-release tackifier that solves the low-temperature thickening problem.

[0012] To solve the above technical problems, the first aspect of the present invention provides a kind of core-shell slow-release tackifier, including core material and shell material, the core material is prepared from the raw material I including 2-acrylamide-2-methylpropane sulfonic acid (AMPS), acrylic acid (AA), hydrophobic monomer and laponite;The shell material is prepared from the raw material II including styrene monomer.Wherein, 2-acrylamide-2-methylpropane sulfonic acid has good temperature resistance, acrylic acid has good adsorption, and laponite enhances the temperature resistance of 2-acrylamide-2-methylpropane sulfonic acid as inorganic temperature-resistant material collaborative hydrophobic monomer;The present invention improves its own temperature resistance by optimizing tackifier molecular structure, and then uses the prepared tackifying polymer as core material, and then preferably forms the heat-resistant core-shell slow-release tackifier with core-shell structure by shell material, makes the core-shell slow-release tackifier decompose at more than 90 DEG C of shell material, slow-release kernel tackifier, avoids low temperature thickening.

[0013] According to some embodiments of the present invention, the mass ratio of the 2-acrylamido-2-methylpropanesulfonic acid, acrylic acid, hydrophobic monomer, and hectorite is (25-60):(20-50):(10-20):(1-5), for example, 25:25:12:5, 60:50:10:1, 50:20:20:2, 25:30:15:3, and 40:40:15:2.

[0014] According to some embodiments of the present invention, the hydrophobic monomer is selected from at least one of isooctyl acrylate, octadecyl acrylate, octadecyl polyoxyethylene methacrylate, behenyl polyoxyethylene ether methacrylate, and hexadecyl dimethyl allyl ammonium chloride (DMDAC-16).

[0015] According to some embodiments of the present invention, the raw material I further includes a first initiator; preferably, the first initiator is selected from at least one of ammonium persulfate and potassium persulfate.

[0016] According to some embodiments of the present invention, the raw material II further includes an emulsifier, a second initiator, and a demulsifier; preferably, the emulsifier is selected from at least one of sodium lauryl sulfate, sodium lauryl sulfonate, and hexadecyltrimethylammonium bromide, preferably sodium lauryl sulfate; the second initiator is selected from at least one of ammonium persulfate and potassium persulfate, preferably potassium persulfate; the demulsifier is selected from at least one of aluminum sulfate, calcium chloride, and magnesium chloride, preferably aluminum sulfate.

[0017] The second aspect of the present invention provides a method for preparing the above-mentioned core-shell sustained-release viscosity enhancer, comprising the following steps:

[0018] 1) Mixing raw material I with water to perform reaction I to obtain a core material;

[0019] 2) The core material obtained in step 1) is mixed with styrene monomer, and reacted in an inert atmosphere to obtain the core-shell sustained-release tackifier.

[0020] According to some embodiments of the present invention, in step 1), the ratio of raw material I to water is (184-292) g:250 mL, for example, 268 g:250 mL, 242 g:250 mL, 184 g:250 mL, 292 g:250 mL, and 194 g:250 mL.

[0021] According to some embodiments of the present invention, in step 1), the mixing obtains solution A, and the pH of solution A is adjusted to 7 using a pH adjuster; preferably, the pH adjuster is selected from at least one of a sodium hydroxide solution and a potassium hydroxide solution with a mass fraction of 10% to 30%, for example, 10%, 20%, or 30%.

[0022] According to some embodiments of the present invention, in step 1), a first initiator is further added to the reaction I; preferably, the amount of the first initiator added is 0.1% to 0.5% of the total mass of the raw material I, for example 0.1%, 0.2%, 0.3%, 0.5%.

[0023] According to some embodiments of the present invention, in step 1), the conditions of reaction I include: temperature of 30°C to 60°C, for example, 45°C, 60°C, 30°C, and time of 2h to 10h, for example, 2h, 4h, 5h, 6h, 10h.

[0024] According to some embodiments of the present invention, in step 1), the reaction I further comprises drying and crushing; preferably, the drying conditions include: temperature of 60° C., time of 1 h to 3 h, for example, 1 h, 2 h, 3 h.

[0025] According to some embodiments of the present invention, in step 2), the mass of the core material is 20% to 50% of the mass of the styrene monomer, for example, 20%, 30%, 40%, 45%, or 50%.

[0026] According to some embodiments of the present invention, in step 2), an emulsifier and a second initiator are further added to the reaction II; preferably, the amount of the emulsifier added is 1% to 8% of the mass of the styrene monomer, for example, 1%, 5%, 8%; the amount of the second initiator added is 0.1% to 0.5% of the mass of the styrene monomer, for example, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%.

[0027] According to some embodiments of the present invention, in step 2), after the reaction II, a demulsifier is further added; preferably, the amount of the demulsifier added is 0.05% to 0.2% of the mass of the styrene monomer, for example 0.05%, 0.1%, or 0.2%.

[0028] According to some embodiments of the present invention, in step 2), the conditions of reaction II include: reaction temperature of 70°C to 80°C, such as 75°C, 70°C, 80°C, and reaction time of 2h to 5h, such as 3h.

[0029] According to some embodiments of the present invention, in step 2), the inert atmosphere is selected from nitrogen.

[0030] According to some embodiments of the present invention, the core material further comprises a modification step; preferably, the modification step comprises adding a surfactant to the core material aqueous solution, and performing reaction III to obtain the modified core material.

[0031] According to some embodiments of the present invention, the water-soluble mass fraction of the core material is 10% to 50%, for example, 10%, 20%, 30%, 40%, 50%.

[0032] According to some embodiments of the present invention, the added amount of the surfactant is 10% to 40% of the mass of the core material, for example 10%, 20%, 30%, 40%; preferably, the surfactant is selected from at least one of sodium dodecyl sulfate, sodium dodecyl sulfonate, hexadecyltrimethylammonium bromide (CTAB), sodium hexadecyl sulfonate, and sodium hexadecylbenzenesulfonate.

[0033] According to some embodiments of the present invention, the core material aqueous solution further comprises a heating step; preferably, the heating temperature is 50°C to 70°C, for example, 50°C, 60°C, or 70°C.

[0034] According to some embodiments of the present invention, the conditions of reaction III include: reaction temperature of 80° C., reaction time of 2 h to 5 h, for example, 2 h, 3 h, 4 h, or 5 h.

[0035] According to some embodiments of the present invention, after the reaction III, the step of filtering the reaction solution, adding a precipitant to the filtrate to generate a precipitate, and drying the precipitate is further included; preferably, the amount of the precipitant added is 30% to 50% of the mass of the core material, preferably 40%; further preferably, the precipitant is at least one of an AgNO3 solution and a polyaluminum chloride solution; further preferably, the concentration of the AgNO3 solution or the polyaluminum chloride solution is 0.05 mol / L to 0.2 mol / L, for example, 0.05 mol / L, 0.1 mol / L, or 0.02 mol / L.

[0036] A third aspect of the present invention provides a use of the core-shell slow-release tackifier in oil and gas well cementing.

[0037] According to some embodiments of the present invention, the core-shell slow-release tackifier is used as a suspension stabilizer in high-density cement slurries used for oil and gas well cementing. More preferably, the core-shell slow-release tackifier is added to the high-density cement slurry at an amount of 1% to 5% based on the total weight of the cement. Low temperatures have no significant effect on the consistency of the cement slurry. The core-shell slow-release tackifier of the present invention begins to increase viscosity at 90°C and has a maximum temperature resistance of 210°C. The density difference of the cured cement slurry after standing for two hours is less than 0.03g / cm 3 .

[0038] Beneficial effects:

[0039] The present invention provides a core-shell slow-release tackifier with a thermal tackifying effect. The core-shell slow-release tackifier is used as a suspension stabilizer for high-density cement slurry and can meet the high-temperature construction environment of 150°C to 1210°C. The density difference of the cement slurry after curing is less than 0.03g / cm2 after standing for two hours. 3 .

[0040] The present invention provides a core-shell slow-release viscosity enhancer with thermal viscosity enhancing effect, which can overcome the problem of traditional suspension stabilizers thickening at low temperatures and thinning at high temperatures, and can improve cementing quality and safety.

[0041] The core-shell slow-release tackifier provided by the present invention has a size of micron-level microspheres (1 μm-5 μm), is simple to ash at room temperature, and has little effect on the consistency of the slurry. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 This is a SEM photograph of the core-shell sustained-release viscosity enhancer D1 prepared in Example 1 of the present invention.

[0043] Figure 2 This is a SEM photograph of the core-shell sustained-release viscosity enhancer D6 prepared in Example 6 of the present invention.

[0044] Figure 3 This is a TEM photograph of the core-shell sustained-release viscosity enhancer D1 prepared in Example 1 of the present invention.

[0045] Figure 4 This is a TEM photo of the core-shell sustained-release viscosity enhancer D6 prepared in Example 6 of the present invention.

[0046] Figure 5 This is the thermogravimetric curve of the core-shell sustained-release tackifier D11D6 prepared in Examples 1-6 of the present invention.

[0047] Figure 6 This is the thermogravimetric curve of the tackifiers M11M3 prepared in Comparative Examples 1-3 of the present invention.

[0048] Figure 7 This is the thickening curve when the core-shell sustained-release thickener D1 prepared in Example 1 of the present invention is added.

[0049] Figure 8 This is the thickening curve without the addition of the core-shell sustained-release thickener D1 prepared in Example 1 of the present invention.

[0050] Figure 9 This is the thickening curve of the viscosity enhancer M1 prepared in Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0051] The present invention will be further described below with reference to the following examples, but the present invention is not limited to these examples.

[0052] The 2-acrylamido-2-methylpropanesulfonic acid in the present invention was purchased from Beijing Wokai Biotechnology Co., Ltd., with a model / specification of 500 g.

[0053] Acrylic acid in the present invention was purchased from Beijing Yinuokai Technology Co., Ltd., with a model / specification of 100 mL.

[0054] The hexadecyl dimethyl allyl ammonium chloride in the present invention was purchased from Chongqing Ruiya Biotechnology Co., Ltd., with a model / specification of 25 kg.

[0055] The hectorite in the present invention was purchased from Shanghai Myrrel Biochemical Technology Co., Ltd., with a model / specification of 100 g.

[0056] Isooctyl acrylate in the present invention was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., with a model / specification of 100 mL.

[0057] The octadecyl acrylate in the present invention was purchased from Shanghai Myril Biochemical Technology Co., Ltd., with a model / specification of 500 mL.

[0058] The octadecyl polyoxyethylene methacrylate in the present invention was purchased from Wuhan Hongde Yuexin Pharmaceutical Technology Co., Ltd. The model / specification is 25 kg.

[0059] The surfactant CTAB in the present invention was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., with a model / specification of 100 g.

[0060] The styrene monomer in the present invention was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., with a model / specification of 500 mL.

[0061] The three-necked flask, four-necked flask, vacuum drying oven and crusher in the present invention are all common commercial products unless otherwise specified.

[0062] The present invention uses a thermogravimetric analyzer (Shanghai Aitisen Instrument Technology Co., Ltd., ATS-TGA-1200Q) and a pressurized thickener (Shenyang Aerospace University Application Technology Co., Ltd., double-kettle pressurized thickener).

[0063] The SEM photographs of the core-shell sustained-release tackifier material of the present invention are taken using a scanning electron microscope.

[0064] The TEM photograph of the core-shell sustained-release tackifier material of the present invention is taken using a transmission electron microscope.

[0065] Example 1

[0066] This embodiment provides a core-shell sustained-release viscosity enhancer.

[0067] The preparation method is as follows:

[0068] (1) 100 g of 2-acrylamido-2-methylpropanesulfonic acid (AMPS), 100 g of acrylic acid (AA), 48 g of hexadecyldimethylallylammonium chloride, and 20 g of laponite were dissolved in 250 mL of water to obtain solution A. The pH of solution A was adjusted to 7 using a 20% by mass sodium hydroxide solution. Solution A was then transferred into a three-necked flask, 0.804 g of ammonium persulfate was added, and the mixture was reacted at a constant temperature of 45° C. for 5 h. The reaction product was placed in a vacuum drying oven at 60° C. for 2 h and then crushed into powder using a crusher to obtain a core material.

[0069] (2) 50 g of the core material prepared in step (1) was mixed with water to form a suspension solution with a mass fraction of 30%, and the temperature was raised to 60° C. to fully swell the core material. Then, 15 g of a surfactant, CTAB, was added. The mixture was stirred at 80° C. and reacted at a rate of 800 r / min for 3 h. After filtration, 20 g of a 0.1 mol / L AgNO3 solution was added to the filtrate to form a precipitate. The precipitate was dried at 80° C. for 2 h to obtain a modified core material.

[0070] (3) 45 g of the modified core material and 100 g of styrene monomer were added to a four-necked flask and stirred at a speed of 800 r / min to fully disperse the modified core material in the styrene monomer. Then, 0.3 g of potassium persulfate and 5 g of sodium lauryl sulfate were added while continuing to stir at a speed of 800 r / min to obtain a stable emulsion. The emulsion polymerization reaction was carried out at a temperature of 75°C under nitrogen atmosphere for 3 h. Then, 0.1 g of aluminum sulfate was added to the polymerization product under stirring to break the emulsion. The resulting precipitate was washed and dried to obtain a core-shell type tackifier material D1. The SEM photograph of D1 is shown in FIG. Figure 1 , TEM photos see Figure 3 ,from Figure 1It can be seen that the core-shell sustained-release thickener D1 has a distinct core-shell structure and a uniform size of about 1 μm to 5 μm.

[0071] Example 2

[0072] This embodiment provides a core-shell sustained-release viscosity enhancer.

[0073] The preparation method is as follows:

[0074] (1) 120 g of 2-acrylamido-2-methylpropanesulfonic acid (AMPS), 100 g of acrylic acid (AA), 20 g of isooctyl acrylate, and 2 g of hectorite were dissolved in 250 mL of water to obtain solution A. The pH of solution A was adjusted to 7 using a 10% by mass sodium hydroxide solution. Solution A was then transferred into a three-necked flask, 0.242 g of ammonium persulfate was added, and the mixture was reacted at a constant temperature of 30° C. for 2 h. The reaction product was placed in a vacuum drying oven at 60° C. for 1 h and then crushed into powder using a crusher to obtain a core material.

[0075] (2) 50 g of the core material prepared in step (1) was mixed with water to form a suspension solution with a mass fraction of 10%, and the temperature was raised to 50° C. to fully swell the core material. Then, 5 g of a surfactant, CTAB, was added. The mixture was stirred at 80° C. and reacted at a rate of 800 r / min for 2 h. After filtration, 15 g of a 0.05 mol / L AgNO3 solution was added to the filtrate to form a precipitate. The precipitate was dried at 80° C. for 2 h to obtain a modified core material.

[0076] (3) 20 g of the above-mentioned modified core material and 100 g of styrene monomer were added to a four-necked flask, and stirred at a speed of 800 r / min to fully disperse the modified core material in the styrene monomer. Then, stirring was continued at a speed of 800 r / min and 0.1 g of potassium persulfate and 8 g of sodium lauryl sulfate were added to obtain a stable emulsion. The emulsion polymerization reaction was carried out at a temperature of 70°C and under nitrogen atmosphere protection for 3 h. Then, 0.05 g of aluminum sulfate was added to the polymerization reaction product under stirring to break the emulsion. The resulting precipitate was washed and dried to obtain the core-shell type tackifier material D2.

[0077] Example 3

[0078] This embodiment provides a core-shell sustained-release viscosity enhancer.

[0079] The preparation method is as follows:

[0080] (1) 100 g of 2-acrylamido-2-methylpropanesulfonic acid (AMPS), 40 g of acrylic acid (AA), 40 g of octadecyl acrylate, and 4 g of laponite were dissolved in 250 mL of water to obtain solution A. The pH of solution A was adjusted to 7 using a 30% by mass potassium hydroxide solution. Solution A was then transferred into a three-necked flask, 0.92 g of ammonium persulfate was added, and the mixture was reacted at a constant temperature of 60° C. for 10 h. The reaction product was placed in a vacuum drying oven at 60° C. and dried for 3 h. The product was then crushed into powder using a crusher to obtain a core material.

[0081] (2) 50 g of the core material prepared in step (1) was mixed with water to form a suspension solution with a mass fraction of 30%, and the temperature was raised to 70° C. to fully swell the core material. Then, 20 g of a surfactant CTAB was added. The mixture was stirred at 80° C. and reacted at a rate of 800 r / min for 3 h. After filtration, 25 g of 0.1 mol / L polyaluminum chloride was added to the filtrate to form a precipitate. The precipitate was dried at 80° C. for 2 h to obtain a modified core material.

[0082] (3) 50 g of the modified core material and 100 g of styrene monomer were added to a four-necked flask, and stirred at a speed of 800 r / min to fully disperse the modified core material in the styrene monomer. Then, stirring was continued at a speed of 800 r / min and 0.5 g of potassium persulfate and 8 g of sodium lauryl sulfate were added to obtain a stable emulsion. The emulsion polymerization reaction was carried out at a temperature of 80°C and under nitrogen atmosphere protection for 3 h. Then, 0.2 g of aluminum sulfate was added to the polymerization reaction product under stirring to break the emulsion. The resulting precipitate was washed and dried to obtain the core-shell type tackifier material D3.

[0083] Example 4

[0084] This embodiment provides a core-shell sustained-release viscosity enhancer.

[0085] The preparation method is as follows:

[0086] (1) 100 g of 2-acrylamido-2-methylpropanesulfonic acid (AMPS), 120 g of acrylic acid (AA), 60 g of octadecyl polyoxyethylene methacrylate, and 12 g of laponite were dissolved in 250 mL of water to obtain solution A. The pH of solution A was adjusted to 7 using a 20% by mass sodium hydroxide solution. Solution A was then transferred into a three-necked flask, 0.584 g of potassium persulfate was added, and the reaction was carried out at a constant temperature of 45° C. for 6 h. The reaction product was placed in a vacuum drying oven and dried at a temperature of 60° C. for 1 h. The product was crushed into powder using a crusher to obtain a core material.

[0087] (2) 50 g of the core material prepared in step (1) was mixed with water to form a suspension solution with a mass fraction of 20%, and the temperature was raised to 70° C. to fully swell the core material. Then, 15 g of a surfactant CTAB was added. The mixture was stirred at 80° C. and reacted at a rate of 800 r / min for 5 h. After filtration, 20 g of a 0.2 mol / L AgNO3 solution was added to the filtrate to form a precipitate. The precipitate was dried at 80° C. for 2 h to obtain a modified core material.

[0088] (3) 30 g of the modified core material and 100 g of styrene monomer were added to a four-necked flask, and stirred at a speed of 800 r / min to fully disperse the modified core material in the styrene monomer. Then, stirring was continued at a speed of 800 r / min and 0.2 g of potassium persulfate and 1 g of sodium lauryl sulfate were added to obtain a stable emulsion. The emulsion polymerization reaction was carried out at a temperature of 75°C and under nitrogen atmosphere protection for 3 h. Then, 0.1 g of aluminum sulfate was added to the polymerization reaction product under stirring to break the emulsion. The resulting precipitate was washed and dried to obtain the core-shell type tackifier material D4.

[0089] Example 5

[0090] This embodiment provides a core-shell sustained-release viscosity enhancer.

[0091] The preparation method is as follows:

[0092] (1) 80 g of 2-acrylamido-2-methylpropanesulfonic acid (AMPS), 80 g of acrylic acid (AA), 30 g of hexadecyldimethylallylammonium chloride, and 4 g of laponite were dissolved in 250 mL of water to obtain solution A. The pH of solution A was adjusted to 7 using a 20% by mass sodium hydroxide solution. Solution A was then transferred into a three-necked flask, 0.582 g of potassium persulfate was added, and the mixture was reacted at a constant temperature of 45° C. for 4 h. The reaction product was placed in a vacuum drying oven at a temperature of 60° C. and dried for 3 h. The product was then crushed into powder using a crusher to obtain a core material.

[0093] (2) 50 g of the core material prepared in step (1) was mixed with water to form a suspension solution with a mass fraction of 30%, and the temperature was raised to 60° C. to fully swell the core material. Then, 15 g of a surfactant, CTAB, was added. The mixture was stirred at 80° C. and reacted at a rate of 800 r / min for 4 h. After filtration, 15 g of 0.1 mol / L polyaluminum chloride was added to the filtrate to form a precipitate. The precipitate was dried at 80° C. for 2 h to obtain a modified core material.

[0094] (3) 40 g of the modified core material and 100 g of styrene monomer were added to a four-necked flask and stirred at a speed of 800 r / min to fully disperse the modified core material in the styrene monomer. Then, 0.3 g of potassium persulfate and 5 g of sodium lauryl sulfate were added while continuing to stir at a speed of 800 r / min to obtain a stable emulsion. The emulsion polymerization reaction was carried out at a temperature of 75 ° C. under nitrogen atmosphere protection for 3 h. Then, 0.1 g of aluminum sulfate was added to the polymerization reaction product under stirring to break the emulsion. The resulting precipitate was washed and dried to obtain the core-shell type tackifier material D5.

[0095] Example 6

[0096] This embodiment provides a core-shell sustained-release viscosity enhancer.

[0097] The preparation method is as follows:

[0098] (1) 100 g of 2-acrylamido-2-methylpropanesulfonic acid (AMPS), 100 g of acrylic acid (AA), 48 g of hexadecyldimethylallylammonium chloride, and 20 g of laponite were dissolved in 250 mL of water to obtain solution A. The pH of solution A was adjusted to 7 using a 20% by mass sodium hydroxide solution. Solution A was then transferred into a three-necked flask, 0.804 g of ammonium persulfate was added, and the mixture was reacted at a constant temperature of 45° C. for 5 h. The reaction product was placed in a vacuum drying oven at 60° C. for 2 h and crushed into powder using a crusher to obtain a core material.

[0099] (2) 50 g of the core material prepared in step (1) was mixed with water to form a suspension solution with a mass fraction of 30%, and the temperature was raised to 60° C. to fully swell the core material. Then, 15 g of a surfactant CTAB was added. The mixture was stirred at 80° C. and reacted at a rate of 800 r / min for 3 h. After filtration, 25 g of a 0.1 mol / L AgNO3 solution was added to the filtrate to form a precipitate. The precipitate was dried at 80° C. for 2 h to obtain a modified core material.

[0100] (3) 20 g of the modified core material and 100 g of styrene monomer were added to a four-necked flask and stirred at a speed of 800 r / min to fully disperse the modified core material in the styrene monomer. Then, 0.4 g of potassium persulfate and 5 g of sodium lauryl sulfate were added while continuing to stir at a speed of 800 r / min to obtain a stable emulsion. The emulsion polymerization reaction was carried out at a temperature of 75°C under nitrogen atmosphere for 3 h. Then, 0.1 g of aluminum sulfate was added to the polymerization product under stirring to break the emulsion. The resulting precipitate was washed and dried to obtain a core-shell type tackifier material D6. The SEM photograph of D6 is shown in FIG. Figure 2 , TEM photos see Figure 4 ,from Figure 2It can be seen that the core-shell sustained-release thickener D6 has a distinct core-shell structure and a uniform size of about 1 μm to 5 μm.

[0101] Comparative Example 1

[0102] This comparative example provides a tackifier.

[0103] The preparation method is as follows:

[0104] 100 g of 2-acrylamido-2-methylpropanesulfonic acid (AMPS), 100 g of acrylic acid (AA), 48 g of hexadecyldimethylallylammonium chloride, and 20 g of hectorite were dissolved in 250 mL of water to obtain solution A. The pH of solution A was adjusted to 7 using a 20% mass fraction sodium hydroxide solution. Then, solution A was transferred into a three-necked flask, 0.804 g of ammonium persulfate was added, and the reaction was carried out at a constant temperature of 45° C. for 5 h. The reaction product was placed in a vacuum drying oven at 60° C. and dried for 2 h. It was then crushed into powder using a crusher to obtain an unmodified core material viscosity enhancer M1.

[0105] Comparative Example 2

[0106] This comparative example provides a tackifier.

[0107] The preparation method is as follows:

[0108] (1) 100 g of 2-acrylamido-2-methylpropanesulfonic acid (AMPS), 100 g of acrylic acid (AA), 48 g of hexadecyldimethylallylammonium chloride, and 20 g of laponite were dissolved in 250 mL of water to obtain solution A. The pH of solution A was adjusted to 7 using a 20% by mass sodium hydroxide solution. Solution A was then transferred into a three-necked flask, 0.804 g of ammonium persulfate was added, and the mixture was reacted at a constant temperature of 45° C. for 5 h. The reaction product was placed in a vacuum drying oven at 60° C. for 2 h, and then crushed into powder using a crusher to obtain a core material viscosity enhancer.

[0109] (2) 50 g of the core material prepared in step (1) was mixed with water to form a suspension solution with a mass fraction of 30%, and the temperature was raised to 60° C. to fully swell the core material. Then, 15 g of surfactant CTAB was added. The mixture was stirred at 80° C. and reacted at a rate of 800 r / min for 3 h. After filtration, 20 g of a 0.1 mol / L AgNO3 solution was added to the filtrate to form a precipitate. The precipitate was dried at 80° C. for 2 h to obtain the modified core material viscosity enhancer M2.

[0110] Comparative Example 3

[0111] This comparative example provides a tackifier.

[0112] The preparation method is as follows:

[0113] (1) 100 g of 2-acrylamido-2-methylpropanesulfonic acid (AMPS), 100 g of acrylic acid (AA), 48 g of hexadecyldimethylallylammonium chloride, and 24 g of laponite were dissolved in 250 mL of water to obtain solution A. The pH of solution A was adjusted to 7 using a 20% by mass sodium hydroxide solution. Solution A was then transferred into a three-necked flask, 0.804 g of ammonium persulfate was added, and the mixture was reacted at a constant temperature of 45° C. for 5 h. The reaction product was placed in a vacuum drying oven at 60° C. for 2 h and then crushed into powder using a crusher to obtain a core material.

[0114] (2) 50 g of the core material prepared in step (1) was mixed with water to form a suspension solution with a mass fraction of 30%, and the temperature was raised to 60° C. to fully swell the core material. Then, 15 g of a surfactant, CTAB, was added. The mixture was stirred at 80° C. and reacted at a rate of 800 r / min for 3 h. After filtration, 20 g of a 0.1 mol / L AgNO3 solution was added to the filtrate to form a precipitate. The precipitate was dried at 80° C. for 2 h to obtain a modified core material.

[0115] (3) 45 g of the modified core material and 100 g of styrene monomer were added to a four-necked flask, and stirred at a speed of 800 r / min to fully disperse the modified core material in the styrene monomer. Then, stirring was continued at a speed of 800 r / min and 0.3 g of potassium persulfate and 5 g of sodium lauryl sulfate were added to obtain a stable emulsion. The emulsion polymerization reaction was carried out at a temperature of 75 ° C. under nitrogen atmosphere protection for 3 h. Then, 0.1 g of aluminum sulfate was added to the polymerization reaction product under stirring to break the emulsion. The resulting precipitate was washed and dried to obtain the core-shell type thickener material M3.

[0116] Comparative Example 4

[0117] This comparative example provides a tackifier.

[0118] The preparation method is as follows:

[0119] (1) 100 g of 2-acrylamido-2-methylpropanesulfonic acid (AMPS), 100 g of acrylic acid (AA), 120 g of hexadecyldimethylallylammonium chloride, and 20 g of hectorite were dissolved in 250 mL of water to obtain solution A. The pH of solution A was adjusted to 7 using a 20% by mass sodium hydroxide solution. Solution A was then transferred into a three-necked flask, 0.804 g of ammonium persulfate was added, and the mixture was reacted at a constant temperature of 45° C. for 5 h. The reaction product was placed in a vacuum drying oven at 60° C. for 2 h and then crushed into powder using a crusher to obtain a core material.

[0120] (2) 50 g of the core material prepared in step (1) was mixed with water to form a suspension solution with a mass fraction of 30%, and the temperature was raised to 60° C. to fully swell the core material. Then, 15 g of a surfactant, CTAB, was added. The mixture was stirred at 80° C. and reacted at a rate of 800 r / min for 3 h. After filtration, 15 g of a 0.1 mol / L AgNO3 solution was added to the filtrate to form a precipitate. The precipitate was dried at 80° C. for 2 h to obtain a modified core material.

[0121] (3) 45 g of the modified core material and 100 g of styrene monomer were added to a four-necked flask, and stirred at a speed of 800 r / min to fully disperse the modified core material in the styrene monomer. Then, stirring was continued at a speed of 800 r / min and 0.3 g of potassium persulfate and 5 g of sodium lauryl sulfate were added to obtain a stable emulsion. The emulsion polymerization reaction was carried out at a temperature of 75 ° C. under nitrogen atmosphere protection for 3 h. Then, 0.1 g of aluminum sulfate was added to the polymerization reaction product under stirring to break the emulsion. The resulting precipitate was washed and dried to obtain the core-shell type tackifier material M4.

[0122] In order to further illustrate the performance of the core-shell sustained-release tackifiers prepared in Examples 1-6 and Comparative Examples 1-4 of the present invention, the following tests were performed.

[0123] (1) The core-shell sustained-release tackifiers D11D6 and M11M4 prepared in Examples 1-6 of the present invention and Comparative Examples 1-4 were respectively subjected to a thermogravimetric analyzer ATS-TGA-1200Q produced by Shanghai Aitisen Instrument Technology Co., Ltd. The samples were heated from room temperature to 300° C. at a heating rate of 10° C. / min under a nitrogen atmosphere. The test environment was consistent. The thermogravimetric curves of the core-shell sustained-release tackifiers D11D6 and M1 to M4 prepared in Examples 1-6 of the present invention and Comparative Examples 1-4 were recorded as follows: Figure 5 and Figure 6 .

[0124] from Figure 5 and Figure 6 It can be seen that the core-shell slow-release thickeners D11D6 gradually decomposed with the increase of temperature, and both showed two obvious weight losses. Taking D1 as an example, when the temperature rose to 90°C, the thickener began to lose weight for the first time, indicating that the shell polystyrene began to decompose and lose weight. As the temperature continued to rise, the core material gradually decomposed. When the temperature rose to 300°C, 80% of the mass of the core-shell slow-release thickener had not been decomposed, indicating that the core-shell slow-release thickener had good high temperature resistance.

[0125] However, when the temperature rises to 60°C, comparative examples M1 and M2 begin to lose weight, indicating that the core material gradually decomposes. When the temperature rises to 300°C, only 40% of the mass of the core-shell sustained-release thickener is not decomposed, indicating that the unmodified or non-core-shell thickener has insufficient high temperature resistance. In addition, when the monomer ratio in the core-shell sustained-release thickener exceeds or falls below the specified range, the temperature resistance of the thickener also decreases (M3 and M4).

[0126] (2) Cement slurry preparation

[0127] Based on the mass of the dry powder of oil well cement, the solid phase and liquid phase to be added were weighed and the cement slurry was prepared according to the API standard (American Petroleum Institute). The solid phase and the liquid phase were mixed evenly before preparation. The weighed liquid phase was poured into the mixer and the speed was set to 4000 r / min. -1 Pour the weighed solid phase into the mixer within 15 seconds and then adjust the mixer speed to 12000 r / min. -1 , continue stirring for 35s.

[0128] 1. Sedimentation stability test

[0129] First, set the target temperature of the pressurized viscosifier to 210°C, the target pressure to 90 MPa, and the heating time to 90 minutes. Immediately place the prepared cement slurry into the pressurized viscosifier's kettle. Once the temperature and pressure reach the target values, continue stirring the slurry at the set temperature and pressure for 30 minutes. Slowly release the pressure. Once the temperature drops to 90°C, remove the slurry cup from the viscosifier and remove any residual oil from the upper layer of the slurry using a syringe or paper towel. Then, use a densitometer to measure the density of the upper, middle, and lower portions of the slurry cup.

[0130] Test Example 1

[0131] Density is 2.5g / cm 3 The cement slurry formula is: G-grade cement + 90wt% silica fume + 345wt% iron powder + 10wt% polycarboxylic acid high-temperature retarder + 18wt% AMPS high-temperature fluid loss additive + 1wt% modified wood sulfonate dispersant + 1wt% tributyl ester defoamer + 1wt% core-shell slow-release viscosity enhancer D1 + 120wt% water, wherein the density of the iron powder is 6.0g / cm 3, the system is C1 (in this system, based on the mass of grade G cement as 100%, the amount of silica fume added is 90% of the mass of grade G cement, the amount of iron powder added is 345% of the mass of grade G cement, the amount of polycarboxylic acid high-temperature retarder added is 10% of the mass of grade G cement, the amount of AMPS high-temperature fluid loss additive added is 18% of the mass of grade G cement, the amount of modified wood sulfonate dispersant added is 1% of the mass of grade G cement, the amount of tributyl ester defoamer added is 1% of the mass of grade G cement, the amount of core-shell slow-release viscosity enhancer D1 added is 1% of the mass of grade G cement, and the amount of water added is 120% of the mass of grade G cement. The component selection in the cement slurry formula in the following test examples 2-14 is the same as that in test example 1).

[0132] Test Example 2

[0133] Density is 2.5g / cm 3 The cement slurry formula is: G-grade cement + 90wt% silica fume + 345wt% iron powder + 10wt% high-temperature retarder + 18wt% high-temperature fluid loss additive + 1wt% dispersant + 1wt% defoamer + 2wt% core-shell slow-release viscosity enhancer D2 + 120wt% water, where the density of the iron powder is 6.0g / cm 3 , the system is C2.

[0134] Test Example 3

[0135] Density is 2.5g / cm 3 The cement slurry formula is: G-grade cement + 90wt% silica fume + 345wt% iron powder + 10wt% high-temperature retarder + 18wt% high-temperature fluid loss additive + 1wt% dispersant + 1wt% defoamer + 3wt% core-shell slow-release viscosity enhancer D3 + 120wt% water, where the density of the iron powder is 6.0g / cm 3 , the system is C3.

[0136] Test Example 4

[0137] Density is 2.5g / cm 3 The cement slurry formula is: G-grade cement + 90wt% silica fume + 345wt% iron powder + 10wt% high-temperature retarder + 18wt% high-temperature fluid loss additive + 1wt% dispersant + 1wt% defoamer + 4wt% core-shell slow-release viscosity enhancer D4 + 120wt% water, where the density of the iron powder is 6.0g / cm 3 , the system is C4.

[0138] Test Example 5

[0139] Density is 2.5g / cm 3The cement slurry formula is: G-grade cement + 90wt% silica fume + 345wt% iron powder + 10wt% high-temperature retarder + 18wt% high-temperature fluid loss additive + 1wt% dispersant + 1wt% defoamer + 5wt% core-shell slow-release viscosity enhancer D5 + 120wt% water, where the density of the iron powder is 6.0g / cm 3 , the system is C5.

[0140] Test Example 6

[0141] Density is 2.5g / cm 3 The cement slurry formula is: G-grade cement + 90wt% silica fume + 345wt% iron powder + 10wt% high-temperature retarder + 18wt% high-temperature fluid loss additive + 1wt% dispersant + 1wt% defoamer + 1wt% core-shell slow-release viscosity enhancer D6 + 120wt% water, where the density of the iron powder is 6.0g / cm 3 , the system is C6.

[0142] Test Example 7

[0143] Density is 2.5g / cm 3 The cement slurry formula is: G-grade cement + 90wt% silica fume + 345wt% iron powder + 10wt% high-temperature retarder + 18wt% high-temperature fluid loss additive + 1wt% dispersant + 1wt% defoamer + 3wt% core-shell slow-release viscosity enhancer D1 + 120wt% water, where the density of the iron powder is 6.0g / cm 3 , the system is C7.

[0144] Test Example 8

[0145] Density is 2.2g / cm 3 The cement slurry formula is: G-grade cement + 90wt% silica fume + 345wt% iron powder + 10wt% high-temperature retarder + 18wt% high-temperature fluid loss additive + 1wt% dispersant + 1wt% defoamer + 5wt% core-shell slow-release viscosity enhancer D1 + 120wt% water, where the density of the iron powder is 6.0g / cm 3 , the system is C8.

[0146] Test Example 9

[0147] Density is 2.5g / cm 3 The cement slurry formula is: G-grade cement + 90wt% silica fume + 345wt% iron powder + 10wt% high-temperature retarder + 18wt% high-temperature fluid loss additive + 1wt% dispersant + 1wt% defoamer + 120wt% water, where the density of iron powder is 6.0g / cm 3 , the system is C9.

[0148] Test Example 10

[0149] Density is 2.2g / cm 3 The cement slurry formula is: G-grade cement + 90wt% silica fume + 300wt% iron powder + 10wt% high-temperature retarder + 18wt% high-temperature fluid loss additive + 1wt% dispersant + 1wt% defoamer + 1wt% core-shell slow-release viscosity enhancer D1 + 120wt% water, where the density of the iron powder is 6.0g / cm 3 , the system is C10.

[0150] Test Example 11

[0151] Density is 2.5g / cm 3 The cement slurry formula is: G-grade cement + 90wt% silica fume + 345wt% iron powder + 10wt% high-temperature retarder + 18wt% high-temperature fluid loss additive + 1wt% dispersant + 1wt% defoamer + 3wt% viscosity enhancer M1 + 120wt% water, where the density of iron powder is 6.0g / cm 3 , the system is C11.

[0152] Test Example 12

[0153] Density is 2.5g / cm 3 The cement slurry formula is: G-grade cement + 90wt% silica fume + 345wt% iron powder + 10wt% high-temperature retarder + 18wt% high-temperature fluid loss additive + 1wt% dispersant + 1wt% defoamer + 3wt% viscosity enhancer M2 + 120wt% water, where the density of iron powder is 6.0g / cm 3 , the system is C12.

[0154] Test Example 13

[0155] Density is 2.5g / cm 3 The cement slurry formula is: G-grade cement + 90wt% silica fume + 345wt% iron powder + 10wt% high-temperature retarder + 18wt% high-temperature fluid loss additive + 1wt% dispersant + 1wt% defoamer + 3wt% core-shell slow-release viscosity enhancer M3 + 120wt% water, where the density of the iron powder is 6.0g / cm 3 , the system is C13.

[0156] Test Example 14

[0157] Density is 2.5g / cm 3 The cement slurry formula is: G-grade cement + 90wt% silica fume + 345wt% iron powder + 10wt% high-temperature retarder + 18wt% high-temperature fluid loss additive + 1wt% dispersant + 1wt% defoamer + 3wt% core-shell slow-release viscosity enhancer M4 + 120wt% water, where the density of the iron powder is 6.0g / cm 3 , the system is C14.

[0158] Table 1 Test results of cement slurry properties described in Test Examples 1-14

[0159]

[0160] It can be seen from the results in Table 1 that when the core-shell sustained-release thickener prepared by the present invention is not added (C9), the density is 2.5 g / cm 3 The cement slurry settled seriously after high temperature curing, and the density difference between the upper and lower parts reached 0.4g / cm 3 The density difference of the cement slurry system with the core-shell slow-release tackifier prepared in Examples 1-6 of the present invention was improved, and the density difference after curing was less than 0.03 g / cm 3 When the addition amount of the core-shell slow-release tackifier of the present invention reaches 5wt%, the cement slurry system has basically no sedimentation; In addition, the density is 2.2g / cm 3 The cement slurry system (C10) has no settlement after curing and has good stability;

[0161] However, the cement slurry systems to which the viscosity enhancers M1 to M4 prepared in Comparative Examples 1 to 4 of the present invention were added had poor temperature resistance and decomposed prematurely, resulting in poor slurry sedimentation stability.

[0162] 2. Thickening curve test

[0163] The cement slurry preparation complies with API standards, with the target temperature of the pressurized thickener being 210°C, the target pressure being 90 MPa, and the heating time being 90 min.

[0164] Cement slurry thickening performance testing was conducted in accordance with the test requirements of GB / T 19139-2012, "Test Methods for Oil Well Cement." The prepared cement slurry was poured into the cylindrical rotating slurry cup of the pressurized viscometer. After ensuring a tight seal, the target temperature and pressure were set. During the test, the slurry cup rotated at 150 (±15) r / min, and the instrument measured its torque to generate the cement slurry's consistency curve.

[0165] The thickening curves of the core-shell sustained-release thickener D1 prepared in Example 1 of the present invention with and without the addition of the core-shell sustained-release thickener D1 are shown in FIG. Figure 6 and Figure 7 As shown, the thickening curve of the cement slurry system (C9) without the core-shell slow-release tackifier D1 prepared in Example 1 gradually decreases with increasing temperature, and the viscosity decreases significantly; the thickening curve of the cement slurry system (C7) with the core-shell slow-release tackifier D1 prepared in Example 1 does not change significantly with increasing temperature, indicating that the core material has a significant viscosity-enhancing effect at this temperature, and the core-shell slow-release tackifier D1 can withstand a temperature of 210°C, which is consistent with the results of the thermogravimetric curve.

[0166] The thickening curve of the cement slurry system (C11) to which the layered tackifier M1 prepared in Comparative Example 1 of the present invention is added is as follows: Figure 9As shown in the thickening curve of the cement slurry system (C11) with the thickener M1 described in Comparative Example 1, it can be seen that the initial viscosity of the thickening curve after adding M1 is too high, resulting in an unstable thickening curve. Therefore, it is easy to decompose without a shell structure and has poor temperature resistance.

[0167] It should be noted that the embodiments described above are only used to explain the present invention and do not constitute any limitation of the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory words, rather than restrictive words. The present invention may be modified as specified within the scope of the claims of the present invention, and the present invention may be revised without departing from the scope and spirit of the present invention. Although the present invention described therein relates to specific methods, materials and embodiments, it does not mean that the present invention is limited to the specific examples disclosed therein. On the contrary, the present invention can be extended to all other methods and applications with the same function.

Claims

1. A core-shell sustained-release thickener, characterized in that: The invention comprises a core material and a shell material, wherein the core material is prepared from a raw material I comprising 2-acrylamido-2-methylpropanesulfonic acid, acrylic acid, a hydrophobic monomer and hectorite; and the shell material is prepared from a raw material II comprising a styrene monomer. The mass ratio of the 2-acrylamido-2-methylpropanesulfonic acid, acrylic acid, hydrophobic monomer, and laponite is (25-60): (20-50): (10-20): (1-5); The hydrophobic monomer is selected from at least one of isooctyl acrylate, octadecyl acrylate, octadecyl polyoxyethylene methacrylate, behenyl polyoxyethylene ether methacrylate, and hexadecyl dimethyl allyl ammonium chloride; The core material further comprises a modification step; The modification step comprises mixing raw material I with water, reacting I to obtain a core material, adding a surfactant to the aqueous solution of the core material, and reacting III to obtain a modified core material; The mass fraction of the core material aqueous solution is 10% to 50%; The amount of surfactant added is 10% to 40% of the mass of the core material; The core material aqueous solution further comprises a heating step, the heating temperature being 50°C to 70°C; The conditions of the reaction III include: a reaction temperature of 80° C. and a reaction time of 2 h to 5 h.

2. The core-shell sustained-release thickener according to claim 1, characterized in that The raw material I also includes a first initiator; And / or, the raw material II further includes an emulsifier, a second initiator and a demulsifier.

3. The core-shell sustained-release thickener according to claim 2, characterized in that The first initiator is selected from at least one of ammonium persulfate and potassium persulfate; And / or, the emulsifier is selected from at least one of sodium lauryl sulfate, sodium lauryl sulfonate, and hexadecyltrimethylammonium bromide; the second initiator is selected from at least one of ammonium persulfate and potassium persulfate; and the demulsifier is selected from at least one of aluminum sulfate, calcium chloride, and magnesium chloride.

4. The core-shell sustained-release thickener according to any one of claims 1 to 3, characterized in that The surfactant is selected from at least one of sodium lauryl sulfate, sodium lauryl sulfonate, hexadecyltrimethylammonium bromide, sodium hexadecyl sulfonate, and sodium hexadecylbenzenesulfonate.

5. The core-shell sustained-release viscosity enhancer according to any one of claims 1 to 3, characterized in that: After the reaction III, the method further comprises filtering the reaction solution, adding a precipitant to the filtrate to generate a precipitate, and drying the precipitate.

6. The core-shell sustained-release thickener according to claim 5, characterized in that The amount of the precipitant added is 30% to 50% of the mass of the nuclear material.

7. The core-shell sustained-release thickener according to claim 6, characterized in that The precipitant is at least one of AgNO3 solution and polyaluminium chloride solution.

8. The core-shell sustained-release thickener according to claim 7, characterized in that The concentration of the AgNO3 solution or the concentration of the polyaluminium chloride solution is 0.05 mol / L to 0.2 mol / L.

9. A method for preparing the core-shell sustained-release tackifier according to any one of claims 1 to 8, characterized in that: The steps include: 1) Mixing raw material I with water to perform reaction I to obtain a core material; 2) The core material obtained in step 1) is mixed with styrene monomer, and reacted in an inert atmosphere to obtain the core-shell sustained-release tackifier.

10. The preparation method according to claim 9, characterized in that In step 1), the ratio of raw material I to water is (184-292) g: 250 mL; and / or, the mixing obtains solution A, and the pH of solution A is adjusted to 7 using a pH adjuster; And / or, a first initiator is further added to the reaction I; And / or, the conditions of reaction I include: temperature of 30°C to 60°C, time of 2h to 10h; And / or, the reaction I further includes drying and crushing.

11. The preparation method according to claim 10, characterized in that: The pH regulator is selected from at least one of a sodium hydroxide solution and a potassium hydroxide solution with a mass fraction of 10% to 30%; And / or, the amount of the first initiator added is 0.1% to 0.5% of the total mass of the raw material I.

12. The preparation method according to any one of claims 9 to 11, characterized in that: In step 2), the mass of the core material is 20% to 50% of the mass of the styrene monomer; And / or, an emulsifier and a second initiator are further added to the reaction II; And / or, after the reaction II, a demulsifier is further added; And / or, the conditions of reaction II include: reaction temperature of 70° C. to 80° C., reaction time of 2 h to 5 h; And / or, the inert atmosphere is selected from nitrogen.

13. The preparation method according to claim 12, characterized in that The amount of the emulsifier added is 1% to 8% of the mass of the styrene monomer; the amount of the second initiator added is 0.1% to 0.5% of the mass of the styrene monomer; And / or, the amount of the demulsifier added is 0.05% to 0.2% of the mass of the styrene monomer.

14. Use of the core-shell slow-release tackifier according to any one of claims 1 to 8 or the core-shell slow-release tackifier prepared by the preparation method according to any one of claims 9 to 13 in cementing of oil and gas wells.

15. The use according to claim 14, characterized in that The core-shell slow-release tackifier is used as a suspension stabilizer in high-density cement slurry for oil and gas well cementing.

16. The use according to claim 15, characterized in that The amount of the core-shell slow-release viscosity enhancer added to the high-density cement slurry is 1% to 5% based on the total mass of the cement.

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