An amphiphilic nanometal catalyst for reducing viscosity of heavy oil while drilling, and its preparation method and application

Abstract

The present invention provides an amphiphilic nanometal catalyst for viscosity reduction of heavy oil while drilling, as well as its preparation method and application, belonging to the field of oilfield chemistry in the petroleum industry. The catalyst preparation method of the present invention comprises the following steps: dispersing nanosilica in anhydrous ethanol, adding a hydrophilic monomer and deionized water, and reacting to obtain modified nanosilica; mixing the modified nanosilica, a hydrophobic monomer, and an ester monomer, and reacting to obtain amphiphilic-modified nanosilica; and dispersing a transition metal salt and the amphiphilic-modified nanosilica in ethanol, dropwise adding a reducing agent solution, and reacting to obtain the catalyst. The catalyst of the present invention comprises amphiphilic-modified nanosilica with transition metal nanoparticles loaded on its surface. The catalyst has good compatibility with both oil and water phases, can achieve efficient viscosity reduction of heavy oil at relatively low temperatures, can adapt to temperatures below 150°C in wellbore environments, maintains a long-lasting and efficient heavy oil viscosity reduction effect, and exhibits good thermal stability.

Description

Technical Field

[0001] The present invention belongs to the field of oilfield chemistry in the petroleum industry, and particularly relates to an amphiphilic nano-metal catalyst for viscosity reduction of heavy oil while drilling, and a preparation method and application thereof. Background Art

[0002] Carbonate reservoirs are important oil and gas producing strata. However, they are heavily porous and prone to fractures and holes, which can lead to heavy oil flowing into the wellbore during drilling. Because heavy oil has a lower density than drilling fluid, it gradually rises after entering the wellbore. As the temperature in the wellbore gradually decreases from bottom to top, the rising heavy oil condenses in the upper part of the wellbore, leading to wellbore blockage, pipe congealment, and drill bit sticking, severely hampering the safe and efficient development of heavy oil.

[0003] Currently, three main approaches are used to address the problem of heavy oil intrusion into the wellbore. First, increasing the density of the drilling fluid to balance or exceed the formation pressure and prevent heavy oil from invading the wellbore; second, using high-density heavy slurry to push the invaded heavy oil back into the formation; and third, heating the wellbore to reduce the viscosity of the heavy oil, making it easier to drain. However, these methods have significant drawbacks. For example, increasing the density or using heavy slurry to push the oil horizontally can increase drilling fluid loss into the formation, especially in carbonate reservoirs with well-developed fractures and pores. This not only wastes a large amount of drilling fluid and increases drilling costs, but can also damage reservoir permeability. Furthermore, heating to reduce viscosity requires a long operation time, especially for ultra-heavy oil. Heat-based viscosity reduction consumes a large amount of energy, further exacerbating energy consumption and cost issues. Therefore, there is an urgent need to develop efficient while-drilling heavy oil viscosity reducers to prevent complex problems such as wellbore blockage, pipe freezing, and pipe sticking, improve drilling efficiency, and ensure the safe and efficient development of heavy oil in carbonate reservoirs.

[0004] Heavy oil catalytic viscosity reduction technology is a type of chemical viscosity reduction. Its greatest advantage is that it can achieve irreversible viscosity reduction of heavy oil. At the same time, it can significantly reduce the viscosity of heavy oil with a small addition amount, improve its fluidity, and ensure smooth drilling of heavy oil reservoirs. It is of great significance to the drilling of heavy oil, especially extra-heavy oil.

[0005] Patent document CN117683527A discloses a heavy oil catalytic viscosity reducer composition, its preparation method, and its use. The composition comprises a Schiff base-nickel complex and an ethylene tar fraction. The composition can reduce the content of colloids and asphaltene in heavy oil at 200-250°C, breaking down large molecules into smaller ones, lightening the heavy oil and achieving irreversible viscosity reduction.

[0006] Patent document CN107880866A discloses a method for preparing a metal nanocrystal viscosity reducer for in-situ catalytic modification of heavy oil. Using an inorganic or organic solvent as a reducing agent, organic nickel, an organic amine, and an organic acid are mixed and reduced to a metal nanocolloid solution under anaerobic conditions at a specific temperature to produce the metal nanocrystal viscosity reducer. After reacting at 250°C for 36 hours, the viscosity reduction rate of Bohai heavy oil measured at 30°C can reach 93.3%.

[0007] Patent document CN116836693A discloses a method for preparing a copper-based viscosity reducer for heavy oil thermal catalytic cracking. The method involves adding a reducing agent, an organic ether protective agent, an alkaline solution, and a dispersant to a copper salt to obtain the product. The reaction temperature is 270°C, and the viscosity reduction rate can reach 95.84%.

[0008] The aforementioned patent is primarily used in the field of heavy oil extraction, and the required reaction temperature is relatively high (>200°C), which is inconsistent with the temperature inside the wellbore during drilling (less than 150°C). This results in poor or even ineffective catalytic viscosity reduction within the wellbore, making it unsuitable for while-drilling catalytic viscosity reduction of heavy oil invading the wellbore. Therefore, the development of an amphiphilic nanometal catalyst for while-drilling heavy oil viscosity reduction is of great significance to addressing the problem of heavy oil intrusion during drilling. Summary of the Invention

[0009] To address the shortcomings of existing technologies, the present invention provides an amphiphilic nanometal catalyst for heavy oil viscosity reduction while drilling, as well as its preparation method and application. The catalyst comprises amphiphilic-modified nanosilica with transition metal nanoparticles loaded on its surface. The preparation method is simple and amenable to industrial production. The catalyst exhibits excellent compatibility with both oil and water phases, enabling efficient heavy oil viscosity reduction at relatively low temperatures. It can withstand wellbore temperatures below 150°C while maintaining a long-lasting, efficient heavy oil viscosity reduction effect. It also exhibits excellent thermal stability.

[0010] The technical solutions of the present invention are as follows:

[0011] A method for preparing an amphiphilic nano-metal catalyst for reducing the viscosity of heavy oil while drilling comprises the following steps:

[0012] (1) Nano-silica is fully dispersed in anhydrous ethanol, and a hydrophilic monomer and deionized water are added. After reaction, solid-liquid separation, and washing, modified nano-silica is obtained. Modified nano-silica, a hydrophobic monomer, and an ester monomer are mixed, reacted, centrifuged, washed, and dried to obtain amphiphilic-modified nano-silica.

[0013] (2) The transition metal salt and amphiphilic modified nano-silica are fully dispersed in ethanol, and a reducing agent solution is added dropwise. After the reaction, the catalyst is filtered, washed, dried, and ground to obtain an amphiphilic nano-metal catalyst for viscosity reduction of heavy oil while drilling.

[0014] Preferably, according to the present invention, in step (1), the particle size of the nano-silicon dioxide is 15 nm-1 μm.

[0015] According to the preferred embodiment of the present invention, in step (1), the volume ratio of the mass of nano-silica to anhydrous ethanol is 0.01-0.13 g / mL, preferably 0.0546 g / mL.

[0016] According to the present invention, preferably, in step (1), the hydrophilic monomer is one or a combination of two or more of 3-isocyanatepropyltriethoxysilane, 3-aminopropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane or ethylenediaminepropyltriethoxysilane; the mass ratio of the hydrophilic monomer to the nano-silica is 0.009-0.2:1, preferably 0.018-0.1:1, and more preferably 0.018:1.

[0017] According to the preferred embodiment of the present invention, in step (1), the volume ratio of deionized water to anhydrous ethanol is 1:150-250.

[0018] According to the preferred embodiment of the present invention, in step (1), the reaction temperature after adding the hydrophilic monomer and deionized water is 50-70° C., the reaction time is 2-6 h, and the reaction is carried out under stirring conditions.

[0019] According to the preferred embodiment of the present invention, in step (1), the hydrophobic monomer is one or a combination of two or more of hexadecyltrimethoxysilane, vinyltriethoxysilane or vinyltrimethoxysilane; the mass ratio of the hydrophobic monomer to nano-silica is 0.004-0.1:1, preferably 0.009-0.05:1, and further preferably 0.0092:1.

[0020] According to the preferred embodiment of the present invention, in step (1), the ester monomer is one or a combination of two or more of methyl methacrylate, methyl acrylate or tert-butyl acrylate; the mass ratio of the ester monomer to nano-silica is 0.01-0.2:1, preferably 0.01-0.06:1, and more preferably 0.027:1.

[0021] According to the preferred embodiment of the present invention, in step (1), the reaction temperature after the modified nano-silica, hydrophobic monomer and ester monomer are mixed is 30°C to 60°C, preferably 50°C; the reaction time is 3 to 6 hours; and the reaction is carried out under stirring conditions.

[0022] According to the preferred embodiment of the present invention, in step (2), the transition metal salt is one of ferric chloride, copper sulfate or nickel sulfate; and the molar ratio of the transition metal salt to the amphiphilic modified nano-silica is 0.5-2:1, preferably 1:1.

[0023] According to the preferred embodiment of the present invention, in step (2), the volume ratio of the molar amount of the transition metal salt to ethanol is 0.2-0.6 mol / L, preferably 0.45 mol / L.

[0024] Preferably, according to the present invention, in step (2), the reducing agent in the reducing agent solution is one of sodium borohydride, sodium hypophosphite or lithium aluminum hydride, and the solvent is a mixed solvent of ethanol and deionized water, wherein the volume ratio of ethanol to deionized water is 3-5:1; and the concentration of the reducing agent solution is 0.1-0.3 g / mL.

[0025] According to the preferred embodiment of the present invention, in step (2), the molar ratio of the transition metal salt to the reducing agent is 1:1-8, preferably 1:3.7.

[0026] According to the preferred embodiment of the present invention, in step (2), the dropping rate is 6-12 mL / min, preferably 8 mL / min; the dropping is carried out at room temperature under stirring conditions.

[0027] According to the preferred embodiment of the present invention, in step (2), the reaction conditions are stirring at room temperature for 20-40 minutes.

[0028] An amphiphilic nano-metal catalyst for reducing the viscosity of heavy oil while drilling is prepared by the above method.

[0029] According to a preferred embodiment of the present invention, the amphiphilic nano-metal catalyst for viscosity reduction of heavy oil while drilling is amphiphilic modified nano-silica with surface-loaded transition metal nanoparticles.

[0030] The above-mentioned amphiphilic nano metal catalyst for reducing the viscosity of heavy oil while drilling is used as a viscosity reducer while drilling to reduce the viscosity of heavy oil invading the wellbore.

[0031] According to the present invention, preferably, the mass ratio of the amphiphilic nano-metal catalyst for viscosity reduction of heavy oil while drilling to the volume ratio of the drilling fluid is 0.003-0.01 g / mL, preferably 0.006-0.01 g / mL.

[0032] According to the preferred embodiment of the present invention, the applicable temperature range of the amphiphilic nano-metal catalyst for heavy oil viscosity reduction while drilling is 130°C-300°C.

[0033] The technical features and beneficial effects of the present invention are as follows:

[0034] 1. The preparation method of the nanometal catalyst of the present invention is simple and easy to industrialize. The present invention uses hydrophilic monomers, hydrophobic monomers, ester monomers and nanosilica as the main raw materials. First, silica is treated with amphiphilic modification to prepare an amphiphilic silica carrier. The carrier surface contains hydrophilic groups, which enables it to achieve good dispersion in polar solvents. At the same time, after modification, the silica surface is covered with organic compounds such as hydrophobic monomers and ester monomers, thereby converting it from polar to weakly polar. This polarity change makes it easier for the nanometal catalyst to approach heavy oil, thereby allowing the catalytic center to better approach the target reaction molecules, thereby significantly improving the efficiency of the catalytic reaction. Then, a reduction method is adopted to use a reducing agent to react with the transition metal salt to generate a nanometal element loaded on the amphiphilic modified nanosilica surface to achieve good catalytic efficacy. According to organic chemistry theory and catalysis theory, the d orbitals of the transition metal catalytic center interact with the target reaction molecules to reduce the activation energy of the reaction. Since zero-valent transition metals have the most abundant d electrons, transition metals have the best catalytic effect on organic compounds. When foreign polar atomic nuclei (transition metal elements) approach the reacting molecules, they coordinate with heteroatoms in the heavy oil, promoting electron transfer and weakening the corresponding C-C, C-O, C-S, and C-N bonds. Water attacks the intermediates, breaking the molecular chains and generating smaller molecules, thus reducing the oil's viscosity. The nanometal catalyst obtained in this invention consists of nanotransition metal elements supported on an amphiphilic silica surface. As a high-temperature stable material, silica can enhance the thermal stability of the catalytic viscosity reducer in high-temperature environments.

[0035] 2. The core of this invention lies in constructing an amphiphilic silica support through the synergistic modification of hydrophilic, hydrophobic, and ester monomers, and optimizing the transition metal loading process. This invention utilizes specific types and amounts of hydrophilic monomers to ensure stable dispersion of the support in polar solvents. Omission of the hydrophilic monomer or its inappropriate amount will result in silica agglomeration, making subsequent uniform modification and metal loading impossible. The types and molar ratios of the hydrophobic and ester monomers in this invention must be appropriate to balance surface polarity and metal anchoring sites. The absence of the hydrophobic monomer results in excessively polar support surfaces, significantly reducing compatibility with heavy oil. The absence of the ester monomer makes it difficult to uniformly load transition metals (such as Fe⁺) through coordination, leading to agglomeration of active sites. Fe or Ni are preferred transition metals, as they offer significant cost-effectiveness and catalytic efficiency, forming 5-20 nm metal particles upon reduction.

[0036] 3. The nanometal catalyst obtained by the present invention can significantly reduce the operating temperature. This is because making the metal catalyst into nanoparticles can significantly increase its surface area and reaction activity, allowing the reaction to achieve efficient viscosity reduction at a lower temperature. In addition, the silica carrier helps to improve the dispersibility of the metal particles and provide more opportunities for reaction contact with the heavy oil, thereby improving the efficiency of the catalytic reaction. Combining the excellent electron supply capacity of the transition metal nanoparticles with the efficient dispersion performance and excellent heavy oil contact efficiency of the amphiphilic silica, the nanometal catalyst can adapt to temperatures below 150°C in the wellbore environment during the catalytic cracking and viscosity reduction of heavy oil, while maintaining a long-lasting and efficient viscosity reduction effect. This overcomes the problem that previous viscosity reducers had to be used at higher temperatures and could not maintain a good viscosity reduction rate at wellbore temperatures.

[0037] 4. The nano-metal catalyst obtained by the present invention can play a certain role in reducing the viscosity of heavy oil, improve the low-temperature catalytic performance of the catalyst, and has good compatibility with both oil phase and water phase. It can be applied to various types of drilling fluids and can be used for catalytic viscosity reduction of heavy oil invading the wellbore while drilling; at the same time, the nano-metal catalyst has good high-temperature stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 The nano-silicon dioxide (SiO2), amphiphilic modified nano-silicon dioxide (AmphiphilicSiO2), amphiphilic nano-metal catalyst (Fe 0 / Amphiphilic SiO2) and the catalyst prepared in Comparative Example 6 (Fe 0 / SiO2) infrared spectrum;

[0039] Figure 2 Transmission electron microscopy and dispersion X-ray spectra of the amphiphilic nanometal catalyst prepared in Example 1. DETAILED DESCRIPTION

[0040] The technical solutions of the present invention are described clearly and completely below. Obviously, the embodiments described are only a portion of the embodiments of the present invention, not all of them. All other examples improved or modified by those skilled in the art based on the embodiments of the present invention are within the scope of protection of the present invention.

[0041] The raw materials used in the examples are all conventional raw materials and can be obtained commercially; the methods described are all based on existing technologies unless otherwise specified.

[0042] Example 1

[0043] A method for preparing an amphiphilic nano-metal catalyst for reducing the viscosity of heavy oil while drilling comprises the following steps:

[0044] (1) The preparation method of amphiphilic modified nano-silica is as follows:

[0045] 10.925 g (0.18 mol) of 15 nm nanosilica particles were thoroughly dispersed in 200 mL of anhydrous ethanol and stirred vigorously for 30 minutes. 0.2 g of the hydrophilic monomer 3-aminopropyltriethoxysilane and 1 mL of deionized water were added, and the mixture was stirred for 4 hours at 60°C. Solid-liquid separation was performed, and the particles were washed with anhydrous ethanol to remove unreacted 3-aminopropyltriethoxysilane and other residues, yielding modified nanosilica. 0.1 g of the hydrophobic monomer hexadecyltrimethoxysilane and 0.3 g of the ester monomer methyl methacrylate were added to the modified nanosilica, and the mixture was stirred at 50°C for 3 hours. The product was washed three times with anhydrous ethanol by centrifugation to remove residual modifiers and impurities such as ammonia. Finally, the product was vacuum-dried at 70°C for 12 hours to yield amphiphilic-modified nanosilica.

[0046] (2) The preparation method of the nanometal catalyst is as follows:

[0047] 48.66 g (0.18 mol) of ferric chloride hexahydrate and the amphiphilic-modified nano-silica obtained above were mixed and placed in a 1000 mL three-necked flask, and then 400 mL of ethanol was added under mechanical stirring for 10 minutes to completely disperse the mixture to obtain a mixed solution.

[0048] 24.97 g (0.66 mol) of sodium borohydride was dissolved in 100 ml of ethanol and deionized water (ethanol:deionized water, volume ratio: 80:20) and added dropwise to the mixture via a constant pressure dropping funnel (addition rate: 8 mL / min) while the reaction mixture in the flask was vigorously stirred at ambient temperature. After the addition of the sodium borohydride solution, the reaction mixture was stirred at room temperature for an additional 30 minutes and then filtered through a 0.2 μm filter. The filter cake was washed twice with industrial-grade ethanol to prevent rusting during subsequent filtration, then vacuum-dried overnight and ground with a spatula to yield a fine black powder of the target product: an amphiphilic nanometal catalyst for viscosity reduction of heavy oil while drilling, namely, an amphiphilic SiO2 / Fe catalyst.

[0049] pass Figure 1 As you can see, 1100cm -1 Represents Si-O-Si stretching, which is the main peak of SiO2. 3438cm -1 The OH stretching comes from the surface Si-OH, and this characteristic peak appears in all four sample curves. SiO2 reacts with the hydrophilic monomer 3-aminopropyltriethoxysilane to introduce -NH2, and the NH characteristic peak in the amino group on its surface is generated at 1524 cm -1 The sample containing amphiphilic SiO2 produces a characteristic peak here, while Fe 0 / The NH characteristic peak of amphiphilic SiO2 is slightly shifted to 1512cm -1 Nearby. 2920 and 2855cm -1 The -CH3, -CH2 stretching vibration peaks are brought by the hydrophobic monomer hexadecyltrimethoxysilane. 0 / Obvious characteristic peaks appeared in amphiphilic SiO2. 1610cm -1 Fe-OH, Fe-O stretching vibration, in Fe 0 / SiO2 and Fe 0 / exists in amphiphilic SiO2, proving the existence of Fe. -1 It is the C=O stretching peak, representing the successful grafting of the ester group in methyl methacrylate.

[0050] Transmission electron microscopy and energy dispersive X-ray spectroscopy Figure 2 The distribution of Fe and Si elements can be seen, among which the distribution of SiO2 is relatively uniform, but the arrangement of Fe is slightly agglomerated.

[0051] The application process of nano metal catalyst is as follows:

[0052] 0.6 g of nano-metal catalyst was mixed with 100 mL of drilling fluid (composition: 3.25 g bentonite, 0.25 g caustic soda, 0.15 g soda ash, 0.35 g polymer fluid loss reducer, 0.4 g polyanionic cellulose, 2.5 g sulfonated phenolic resin, 2.5 g asphalt anti-slump agent, 1.5 g calcium carbonate, 88.1 g water) and placed in an aging tank. 30 g of heavy oil (1862 g / mol) was added and the aging tank was placed in a roller heating furnace and rolled at 130°C or 250°C for 10 hours. The viscosity of the liquid after hot rolling treatment was tested to calculate the viscosity reduction rate.

[0053] Example 2

[0054] A method for preparing an amphiphilic nanometal catalyst for viscosity reduction of heavy oil while drilling is as described in Example 1, except that in step (1), the nanosilica particles with a particle size of 15 nm are replaced with nanosilica particles with a particle size of 1 μm; the other steps and conditions are the same as those in Example 1.

[0055] The application process of the nano metal catalyst is the same as that in Example 1.

[0056] Example 3

[0057] A method for preparing an amphiphilic nanometal catalyst for viscosity reduction of heavy oil while drilling is as described in Example 1, except that in step (1), the amount of nanosilica particles with a particle size of 15 nm is 5.46 g (0.09 mol); the other steps and conditions are the same as in Example 1.

[0058] The application process of the nano metal catalyst is the same as that in Example 1.

[0059] Example 4

[0060] A method for preparing an amphiphilic nanometal catalyst for reducing the viscosity of heavy oil while drilling is the same as that in Example 1.

[0061] The application process of the nano-metal catalyst is the same as that described in Example 1, except that the amount of drilling fluid used is 200 mL; the other steps and parameters are the same as those in Example 1.

[0062] Example 5

[0063] A method for preparing an amphiphilic nanometal catalyst for viscosity reduction of heavy oil while drilling is as described in Example 1, except that in step (2), the amount of sodium borohydride used is 10 g (0.26 mol); the other steps and conditions are the same as in Example 1.

[0064] The application process of the nano metal catalyst is the same as that in Example 1.

[0065] Example 6

[0066] A method for preparing an amphiphilic nanometal catalyst for viscosity reduction of heavy oil while drilling is as described in Example 1, except that in step (1), the amount of hydrophilic monomer is changed to 0.1 g, the amount of hydrophobic monomer is changed to 0.05 g, and the amount of ester monomer is changed to 0.15 g; the other steps and conditions are the same as those in Example 1.

[0067] The application process of the nano metal catalyst is the same as that in Example 1.

[0068] Example 7

[0069] A method for preparing an amphiphilic nanometal catalyst for viscosity reduction of heavy oil while drilling is as described in Example 1, except that in step (2), the transition metal salt is replaced by nickel sulfate in the same molar amount instead of ferric chloride; the other steps and conditions are the same as those in Example 1.

[0070] The application process of the nano metal catalyst is the same as that in Example 1.

[0071] Example 8

[0072] A method for preparing an amphiphilic nanometal catalyst for viscosity reduction of heavy oil while drilling is as described in Example 1, except that in step (2), the amount of ferric chloride hexahydrate used is 24.33 g (0.09 mol); the other steps and conditions are the same as those in Example 1.

[0073] The application process of the nano metal catalyst is the same as that in Example 1.

[0074] Example 9

[0075] A method for preparing an amphiphilic nanometal catalyst for viscosity reduction of heavy oil while drilling is as described in Example 1, except that in step (1), the amount of hydrophilic monomer is changed to 0.1 g, and the amount of ester monomer is changed to 0.15 g; the other steps and conditions are the same as those in Example 1.

[0076] The application process of the nano metal catalyst is the same as that in Example 1.

[0077] Example 10

[0078] A method for preparing an amphiphilic nanometal catalyst for viscosity reduction of heavy oil while drilling is as described in Example 1, except that in step (1), the amount of hydrophilic monomer is changed to 0.1 g, and the amount of hydrophobic monomer is changed to 0.05 g; the other steps and conditions are the same as those in Example 1.

[0079] The application process of the nano metal catalyst is the same as that in Example 1.

[0080] Example 11

[0081] A method for preparing an amphiphilic nanometal catalyst for viscosity reduction of heavy oil while drilling is as described in Example 1, except that in step (1), the amount of hydrophobic monomer is changed to 0.05 g, and the amount of ester monomer is changed to 0.15 g; the other steps and conditions are the same as those in Example 1.

[0082] The application process of the nano metal catalyst is the same as that in Example 1.

[0083] Example 12

[0084] A method for preparing an amphiphilic nanometal catalyst for viscosity reduction of heavy oil while drilling is as described in Example 1, except that in step (1), the hydrophilic monomer is ethylenediaminepropyltriethoxysilane; and the other steps and conditions are the same as in Example 1.

[0085] The application process of the nano metal catalyst is the same as that in Example 1.

[0086] Example 13

[0087] A method for preparing an amphiphilic nanometal catalyst for viscosity reduction of heavy oil while drilling is as described in Example 1, except that in step (1), the hydrophobic monomer is vinyltriethoxysilane; the other steps and conditions are the same as in Example 1.

[0088] The application process of the nano metal catalyst is the same as that in Example 1.

[0089] Example 14

[0090] A method for preparing an amphiphilic nanometal catalyst for viscosity reduction of heavy oil while drilling is as described in Example 1, except that in step (1), the ester monomer is methyl acrylate; the other steps and conditions are the same as in Example 1.

[0091] The application process of the nano metal catalyst is the same as that in Example 1.

[0092] Comparative Example 1

[0093] A method for preparing a viscosity reducer is as described in Example 1, except that: step (1) is omitted; amphiphilic-modified nano-silica is not added in step (2); and the other steps and conditions are the same as in Example 1.

[0094] The viscosity reducer application process is the same as in Example 1.

[0095] Comparative Example 2

[0096] A method for preparing an amphiphilic nanometal catalyst for reducing the viscosity of heavy oil while drilling is the same as that in Example 1.

[0097] The process of applying the nano-metal catalyst is the same as that described in Example 1, except that the drilling fluid is replaced with deionized water; the other steps and parameters are the same as those in Example 1.

[0098] Comparative Example 3

[0099] A method for preparing a viscosity reducer is as described in Example 1, except that no hydrophilic monomer is added in step (1); the specific steps are as follows:

[0100] To 10.925 g (0.18 mol) of 15 nm nanosilica particles, 0.1 g of the hydrophobic monomer hexadecyltrimethoxysilane and 0.3 g of the ester monomer methyl methacrylate were added. The mixture was stirred at 50°C for 3 hours. The product was washed three times with anhydrous ethanol by centrifugation to remove residual modifiers and impurities such as ammonia. Finally, the product was vacuum-dried at 70°C for 12 hours to obtain the modified nanosilica.

[0101] Other steps and conditions are the same as in Example 1.

[0102] The viscosity reducer application process is the same as in Example 1.

[0103] Comparative Example 4

[0104] A method for preparing a viscosity reducer is as described in Example 1, except that no hydrophobic monomer is added in step (1); the specific steps are as follows:

[0105] 10.925 g (0.18 mol) of 15 nm nanosilica particles were thoroughly dispersed in 200 mL of anhydrous ethanol and stirred vigorously for 30 minutes. 0.2 g of the hydrophilic monomer 3-aminopropyltriethoxysilane and 1 mL of deionized water were added, and the mixture was stirred for 4 hours at 60°C. Solid-liquid separation was performed, and the particles were washed with anhydrous ethanol to remove unreacted 3-aminopropyltriethoxysilane and other residues, yielding modified nanosilica. 0.3 g of the ester monomer methyl methacrylate was added to the modified nanosilica, and the mixture was stirred at 50°C for 3 hours. The product was washed three times with anhydrous ethanol by centrifugation to remove residual modifiers and impurities such as ammonia. Finally, the product was vacuum dried at 70°C for 12 hours to yield the modified nanosilica.

[0106] Other steps and conditions are the same as in Example 1.

[0107] The viscosity reducer application process is the same as in Example 1.

[0108] Comparative Example 5

[0109] A method for preparing a viscosity reducer is as described in Example 1, except that no ester monomer is added in step (1); the specific steps are as follows:

[0110] 10.925 g (0.18 mol) of 15 nm nanosilica particles were thoroughly dispersed in 200 mL of anhydrous ethanol and stirred vigorously for 30 minutes. 0.2 g of the hydrophilic monomer 3-aminopropyltriethoxysilane and 1 mL of deionized water were added, and the mixture was stirred for 4 hours at 60°C. Solid-liquid separation was performed, and the particles were washed with anhydrous ethanol to remove unreacted 3-aminopropyltriethoxysilane and other residues, yielding modified nanosilica. 0.1 g of the hydrophobic monomer hexadecyltrimethoxysilane was added to the modified nanosilica, and the mixture was stirred at 50°C for 3 hours. The product was washed three times with anhydrous ethanol by centrifugation to remove residual modifiers and impurities such as ammonia. Finally, the product was vacuum-dried at 70°C for 12 hours to yield amphiphilic-modified nanosilica.

[0111] Other steps and conditions are the same as in Example 1.

[0112] The viscosity reducer application process is the same as in Example 1.

[0113] Comparative Example 6

[0114] A method for preparing a viscosity reducer is as described in Example 1, except that: step (1) is omitted; in step (2), the amphiphilic-modified nano-silica is replaced by 10.925 g (0.18 mol) of nano-silica particles with a particle size of 15 nm; and the other steps and conditions are the same as in Example 1.

[0115] The viscosity reducer application process is the same as in Example 1.

[0116] Test example

[0117] The following performance evaluations were performed on the nanometal catalysts prepared in Examples 1-14 and Comparative Examples 1-6.

[0118] 1. Evaluation of heavy oil viscosity reduction performance

[0119] Evaluating the viscosity reduction performance of heavy oil is the most intuitive and effective method for testing the performance of nanometal catalysts. To directly evaluate the catalyst's effect on heavy oil viscosity, the heavy oil cracked by the nanometal catalysts in the examples and comparative examples was left at 50°C for 24 hours. The oil and water were then separated by centrifugation. The remaining oil was then tested for viscosity using a Haake rheometer at room temperature. The viscosity reduction rate was then measured and compared to determine the viscosity reduction effect.

[0120] Table 1 Viscosity reduction of each group of heavy oil after catalytic reaction at 130℃

[0121]

[0122] Table 2 Viscosity reduction of each group of heavy oil after catalytic reaction at 250℃

[0123]

[0124] In Example 1, which reacted at 130°C, the viscosity reduction reached 77.3%, demonstrating excellent results. In comparison, the viscosity reduction in Example 1, which reacted at 250°C, was further improved, reaching 97.5%. Comparison of Example 1 at 130°C and 250°C demonstrates that the present invention can be used in both low- and high-temperature applications, exhibiting excellent thermal stability and achieving high-temperature performance comparable to other commercially available high-temperature catalytic viscosity reducers.

[0125] 2. Evaluation of heavy oil molecular weight

[0126] Evaluating the molecular weight of heavy oil is the simplest and most direct method for testing the catalytic cracking effect of nanometal catalysts. To directly evaluate the effect of nanometal catalysts on heavy oil viscosity, the heavy oil cracked at 130°C by the nanometal catalysts in the Examples and Comparative Examples was left at 50°C for 24 hours. The oil and water were then separated by centrifugation. The remaining oil was then tested for weight-average molecular weight using gel permeation chromatography. The molecular weight change before and after the reaction was measured, allowing comparison of the catalytic cracking effect.

[0127] Table 3 Molecular weight of each group of heavy oil after being placed at 50℃ for 24 hours

[0128]

[0129] 3. Performance evaluation of four components of heavy oil

[0130] Evaluating the properties of four components of heavy oil is a common method for examining changes within the oil after catalytic cracking. To visually assess the effect of nanometal catalysts on heavy oil viscosity, the heavy oils cracked at 130°C using nanometal catalysts in the Examples and Comparative Examples were left at 50°C for 24 hours. The oil and water were then separated by centrifugation. The four components in the separated heavy oil were then tested.

[0131] Table 4 Four components of each group of heavy oil after being placed at 50℃ for 24h

[0132]

[0133] By comparing Examples 1 and 2, it is found that the viscosity reduction rate decreases. This is because silicon dioxide plays an important role in the dispersibility of viscous oil as a carrier, and increases the force with viscous oil through hydrophobicity, thereby improving the contact probability of catalyst with viscous oil. When particle size increases, specific surface area decreases, and the chance of catalyst contacting oil molecules decreases, causing the viscosity reduction effect to decrease. Larger particles may cause the dispersibility of catalyst in oil to deteriorate, and aggregation increases, thereby reducing the overall viscosity reduction effect. The above can also be reflected from the molecular weight and four components of Examples 1 and 2.

[0134] In Example 3, however, the amount of carrier used was reduced, which directly reduced the total surface area of ​​the catalyst, i.e., the number of active sites. The effectiveness of a catalyst depends on the active sites on its surface, which participate in reactions with molecules in the heavy oil. Reducing the amount means less opportunity for effective catalytic reaction, and the viscosity reduction effect will inevitably be significantly reduced.

[0135] Example 4 The amount of drilling fluid used is too high. The increase in the amount of base slurry will dilute the concentration of the catalyst in the system, resulting in a decrease in the contact efficiency between the catalyst and the heavy oil. The rate and effect of the catalytic reaction will also be weakened, which will greatly reduce the viscosity reduction rate.

[0136] In Example 5, the amount of reducing agent was reduced, so that the product contained a large amount of Fe 3+ And a small amount of Fe element. It is Fe element that plays the main catalytic cracking role in the catalytic reaction. The reduction of Fe element causes the main component of the catalytic reaction to be missing, resulting in a decrease in the viscosity reduction rate.

[0137] In Example 6, the amount of modified monomer was reduced, so that during the reaction, polar and non-polar repulsive forces existed between the catalyst and the heavy oil molecules, making it difficult to fully mix them, resulting in a lower viscosity reduction rate.

[0138] In Examples 7 and 8, the transition metal salt was modified, and the catalytic effect of nickel metal decreased compared with that of iron alone. The reduction of the catalytic main metal alone resulted in a decrease in catalytic efficiency and a decrease in viscosity reduction rate.

[0139] Changing the monomer ratio in Examples 9-11 and changing the monomer type in Examples 12-14 will affect the viscosity reduction effect of the catalyst.

[0140] Comparative Example 1 does not add amphiphilic silica, that is, nano-Fe as a catalytic viscosity reducer. The unsupported catalyst has poor compatibility with heavy oil and has a strong hydrophilic surface, which makes it difficult to form a good interaction with the hydrophobic heavy oil molecules, resulting in poor viscosity reduction effect.

[0141] In Comparative Example 2, deionized water was used as the solvent instead of drilling fluid. The bentonite in the drilling fluid absorbs water and swells, dispersing into tiny particles and forming a suspension. This suspension improves the dispersibility of the catalyst, facilitating contact between the catalyst and the heavy oil through the solubilization and dispersion of the bentonite. Deionized water, on the other hand, has poor dispersibility, reducing the efficiency of the catalytic reaction.

[0142] In Comparative Examples 3-5, if no monomer is added, the viscosity reduction effect of the obtained materials will be greatly reduced; in Comparative Example 6, if the amphiphilic modified nano-silica is replaced with nano-silica particles, the viscosity reduction effect thereof will also be greatly reduced.

[0143] 4. Evaluation in drilling fluid system

[0144] The properties of the water-based drilling fluid were tested according to the latest national standard, "GB / T 16783.1-2014 Field Testing of Drilling Fluids in the Petroleum and Natural Gas Industry—Part 1: Water-Based Drilling Fluids." The prepared water-based drilling fluid was then aged at 200°C for 16 hours. The properties of the water-based drilling fluid were again tested according to the same standard. The results are shown in Table 5.

[0145] The drilling fluid consists of the following components in percentage by mass: 4000 mL of fresh water, 160 g of bentonite, 6 g of caustic soda, 12 g of soda ash, 9 g of polyanionic cellulose, 120 g of lignite resin, and barite weighted to a density of 2.0 g / cm 3 The amount of nano metal catalyst added is 24 g.

[0146] Table 5 Drilling fluid properties

[0147]

[0148] Table 5 shows that compared to water-based drilling fluids without viscosity reducers, the addition of a catalyst (Example 1) slightly reduces the plastic viscosity, but has minimal impact on fluid loss, thus not affecting normal use of the drilling fluid. Reducing the amount of reducing agent (Example 5) and catalytic metal salt (Example 8) weakens the viscosity reduction effect, resulting in lower fluid loss compared to Example 1. Regarding the changes in monomer dosage (Examples 6, 9-11), the reduction in hydrophilic monomers weakens the effect of the catalyst (Example 1) on the apparent viscosity of the water-based drilling fluid, while this effect is not as pronounced with the reduction in hydrophobic and ester monomers. The catalytic viscosity reducer with a hydrophilic silica carrier (Comparative Example 6) has the greatest impact on plastic viscosity due to the strong affinity of the hydrophilic catalyst for the water-based drilling fluid, allowing for full contact. Overall, this nano-metal catalytic viscosity reducer for heavy oil drilling while maintaining excellent viscosity reduction properties does not affect the normal use of water-based drilling fluids.

Claims

1. A method for preparing an amphiphilic nanometal catalyst for viscosity reduction of heavy oil while drilling, comprising the steps of: (1) Nano-silica is fully dispersed in anhydrous ethanol, and a hydrophilic monomer and deionized water are added. After reaction, solid-liquid separation, and washing, modified nano-silica is obtained. Modified nano-silica, a hydrophobic monomer, and an ester monomer are mixed, reacted, centrifuged, washed, and dried to obtain amphiphilic-modified nano-silica. The hydrophilic monomer is one or a combination of two or more of 3-isocyanatepropyltriethoxysilane, 3-aminopropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane or ethylenediaminepropyltriethoxysilane; the mass ratio of the hydrophilic monomer to the nano-silica is 0.009-0.2:1; the hydrophobic monomer is one or a combination of two or more of hexadecyltrimethoxysilane, vinyltriethoxysilane or vinyltrimethoxysilane; the mass ratio of the hydrophobic monomer to the nano-silica is 0.004-0.1:1; the ester monomer is one or a combination of two or more of methyl methacrylate, methyl acrylate or tert-butyl acrylate; the mass ratio of the ester monomer to the nano-silica is 0.01-0.2:1; (2) The transition metal salt and amphiphilic modified nano-silica are fully dispersed in ethanol, and a reducing agent solution is added dropwise, followed by reaction, filtration, washing, drying, and grinding to obtain an amphiphilic nano-metal catalyst for viscosity reduction of heavy oil while drilling; The transition metal salt is one of ferric chloride and nickel sulfate; the molar ratio of the transition metal salt and the amphiphilic modified nano-silica is 0.5-2:1; the reducing agent in the reducing agent solution is one of sodium borohydride, sodium hypophosphite or lithium aluminum hydride; and the molar ratio of the transition metal salt and the reducing agent is 1:3.7-8.

2. The method for preparing an amphiphilic nano-metal catalyst for viscosity reduction of heavy oil while drilling according to claim 1, characterized in that: In step (1), the particle size of the nano-silicon dioxide is 15 nm-1 μm.

3. The method for preparing an amphiphilic nano-metal catalyst for viscosity reduction of heavy oil while drilling according to claim 1, characterized in that: In step (1), one or more of the following conditions are included: i. The mass ratio of nano-silica to anhydrous ethanol is 0.01-0.13 g / mL; ii. The volume ratio of deionized water to anhydrous ethanol is 1:150-250.

4. The method for preparing the amphiphilic nano-metal catalyst for viscosity reduction of heavy oil while drilling according to claim 1, characterized in that: In step (1), the reaction temperature after adding the hydrophilic monomer and deionized water is 50-70° C., the reaction time is 2-6 h, and the reaction is carried out under stirring conditions.

5. The method for preparing the amphiphilic nano-metal catalyst for viscosity reduction of heavy oil while drilling according to claim 1, characterized in that: In step (1), the reaction temperature after the modified nano-silica, hydrophobic monomer and ester monomer are mixed is 30°C to 60°C; the reaction time is 3 to 6 hours; and the reaction is carried out under stirring conditions.

6. The method for preparing the amphiphilic nano-metal catalyst for viscosity reduction of heavy oil while drilling according to claim 1, characterized in that: In step (2), one or more of the following conditions are included: i. The volume ratio of the transition metal salt to ethanol is 0.2-0.6 mol / L; ii. The solvent in the reducing agent solution is a mixed solvent of ethanol and deionized water, wherein the volume ratio of ethanol to deionized water is 3-5:1; and the concentration of the reducing agent solution is 0.1-0.3 g / mL.

7. The method for preparing the amphiphilic nano-metal catalyst for viscosity reduction of heavy oil while drilling according to claim 1, characterized in that: In step (2), the dropwise addition rate is 6-12 mL / min; the dropwise addition is carried out at room temperature with stirring; and the reaction conditions are stirring at room temperature for 20-40 minutes.

8. An amphiphilic nanometal catalyst for reducing the viscosity of heavy oil while drilling, characterized in that: Prepared by the method according to any one of claims 1 to 7; the amphiphilic nano-metal catalyst for viscosity reduction of heavy oil while drilling is amphiphilic modified nano-silica with transition metal nanoparticles loaded on its surface.

9. The use of the amphiphilic nano-metal catalyst for viscosity reduction of heavy oil while drilling according to any one of claims 1 to 7, characterized in that: As a viscosity reducer while drilling, it is used to reduce the viscosity of heavy oil invading the wellbore; the mass ratio of the amphiphilic nanometal catalyst for viscosity reduction of heavy oil while drilling to the volume ratio of drilling fluid is 0.006-0.01 g / mL; the applicable temperature range of the amphiphilic nanometal catalyst for viscosity reduction of heavy oil while drilling is 130℃-300℃.

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