Amphiphilic nano-metal catalyst for reducing viscosity of thickened oil while drilling as well as preparation method and application of amphiphilic nano-metal catalyst

Abstract

The invention provides an amphiphilic nano-metal catalyst for reducing viscosity of thickened oil while drilling as well as a preparation method and application of the amphiphilic nano-metal catalyst, and belongs to the field of oilfield chemistry in the petroleum industry. The preparation method of the catalyst comprises the following steps: dispersing nano silicon dioxide in absolute ethyl alcohol, adding a hydrophilic monomer and deionized water, and reacting to obtain modified nano silicon dioxide; mixing the modified nano silicon dioxide, a hydrophobic monomer and an ester monomer, and reacting to obtain amphiphilic modified nano silicon dioxide; the preparation method comprises the following steps: dispersing transition metal salt and amphiphilic modified nano silicon dioxide in ethanol, dropwise adding a reducing agent solution, and reacting. The catalyst disclosed by the invention is formed by loading transition metal nanoparticles on the surface of amphiphilic modified nano silicon dioxide, has good compatibility with an oil phase and a water phase, can realize high-efficiency viscosity reduction of heavy oil at a relatively low temperature, can adapt to the temperature lower than 150 DEG C in a shaft environment, can also keep a lasting high-efficiency viscosity reduction effect of the heavy oil, and has a good application prospect. Meanwhile, the heat stability is good.

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 during drilling, a preparation method thereof, and an application thereof. Background Art

[0002] Carbonate reservoirs are important oil and gas producing formations. However, the carbonate reservoirs have well-developed fractures and caves, and heavy oil is likely to flow into the wellbore along the fractures and caves during drilling. Since the density of heavy oil is lower than that of the drilling fluid, the heavy oil that enters the wellbore will gradually float upward. As the temperature in the wellbore gradually decreases from bottom to top, the floating heavy oil will condense in the upper part of the wellbore, resulting in problems such as wellbore blockage, pipe freezing, and stuck pipe, which seriously restricts the safe and efficient development of heavy oil.

[0003] At present, for the problem of heavy oil invading the wellbore, the following three treatment methods are mainly adopted. First, by increasing the density of the drilling fluid to balance or exceed the formation pressure to prevent heavy oil from invading the wellbore; second, using high-density heavy mud to push the invaded heavy oil back into the formation from the wellbore; third, heating the wellbore to reduce the viscosity of heavy oil and make it easier to be discharged. However, these methods have some obvious disadvantages. For example, increasing the density or using heavy mud to push horizontally will exacerbate the loss of drilling fluid into the formation, especially in carbonate reservoirs with developed fractures and pores. This not only wastes a large amount of drilling fluid, increases the drilling cost, but also may damage the reservoir permeability. And the method of heating to reduce viscosity requires a long operation time. Especially for ultra-heavy oil, heating to reduce viscosity requires a large amount of energy, making the energy consumption and cost problems more prominent. Therefore, it is urgent to develop an efficient heavy oil viscosity reducer for use during drilling to prevent complex problems such as wellbore blockage, pipe freezing, and stuck pipe, improve the drilling efficiency, and ensure the safe and efficient development of heavy oil in carbonate reservoirs.

[0004] The heavy oil catalytic viscosity reduction technology is a kind of chemical viscosity reduction. Its greatest advantage lies in being able to achieve irreversible viscosity reduction of heavy oil. At the same time, it can also significantly reduce the viscosity of heavy oil at a small dosage, improve its fluidity, ensure the smooth drilling of heavy oil reservoirs, and is of great significance for the drilling of heavy oil, especially extra-heavy oil.

[0005] Patent document CN117683527A discloses a heavy oil catalytic viscosity reducer composition, a preparation method thereof, and an application thereof. The composition of the composition is as follows: Schiff base-nickel complex, ethylene tar fraction. The provided heavy oil catalytic viscosity reducer composition can reduce the content of resins and asphaltenes in heavy oil at 200-250 °C, crack macromolecules into small molecules, lighten heavy oil, and achieve irreversible viscosity reduction of heavy oil.

[0006] Patent document CN107880866A discloses a preparation method of a viscosity reducer for in-situ catalytic upgrading of heavy oil with metal nanocrystals. Using an inorganic or organic solution as a reducing agent, under certain temperature and anaerobic conditions, a mixture of organic nickel, organic amine, and organic acid is reduced to a metal nanocolloid solution to obtain a 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 preparation method of a viscosity reducer for catalytic cracking of heavy oil by nanocopper in thermal recovery of heavy oil: adding a reducing agent, an organic ether protecting agent, an alkali solution, and a dispersant to a copper salt, and finally obtaining a product. Reacting at 270°C, the viscosity reduction rate can reach 95.84%.

[0008] The above patents are mainly used in the field of heavy oil exploitation, and the required reaction temperature is relatively high (>200°C), which does not match the temperature in the wellbore during the drilling process (lower than 150°C), resulting in poor or even ineffective catalytic viscosity reduction in the wellbore, and cannot be used for the catalytic viscosity reduction while drilling of the heavy oil invading the wellbore. Therefore, it is of great significance to study an amphiphilic nanometal catalyst for viscosity reduction while drilling to solve the problem of heavy oil invading the wellbore during the drilling process. Summary of the Invention

[0009] Aiming at the deficiencies of the existing technology, the present invention provides an amphiphilic nanometal catalyst for viscosity reduction while drilling, its preparation method and application. The catalyst of the present invention is a transition metal nanoparticle loaded on the surface of amphiphilic modified nanosilica, and the preparation method is simple and easy for industrial production. The catalyst of the present invention has good compatibility with the oil phase and the water phase, can achieve efficient viscosity reduction of heavy oil at a lower temperature, can not only adapt to the temperature below 150°C in the wellbore environment, but also maintain a persistent and efficient heavy oil viscosity reduction effect, and has good thermal stability.

[0010] The technical solution of the present invention is as follows: A preparation method of an amphiphilic nanometal catalyst for viscosity reduction while drilling, comprising the steps of: (1) Fully disperse nanosilica in absolute ethanol, add a hydrophilic monomer and deionized water, react, separate the solid and liquid, and wash to obtain modified nanosilica; mix the modified nanosilica, a hydrophobic monomer, and an ester monomer, react, centrifuge, wash, and dry to obtain amphiphilic modified nanosilica; (2) Fully disperse a transition metal salt and amphiphilic modified nanosilica in ethanol, dropwise add a reducing agent solution, then react, filter, wash, dry, and grind to obtain an amphiphilic nanometal catalyst for viscosity reduction while drilling.

[0011] According to the preference of the present invention, in step (1), the particle size of the nanosilica is 15nm - 1μm.

[0012] Preferably according to the present invention, in step (1), the mass ratio of nano-silica to the volume of absolute ethanol is 0.01 - 0.13 g / mL, preferably 0.0546 g / mL.

[0013] Preferably according to the present invention, in step (1), the hydrophilic monomer is one or a combination of two or more of 3 - isocyanatopropyltriethoxysilane, 3 - aminopropyltriethoxysilane, 3 - mercaptopropyltrimethoxysilane, or ethylenediaminepropyltriethoxysilane; the mass ratio of the hydrophilic monomer to nano-silica is 0.009 - 0.2:1, preferably 0.018 - 0.1:1, and more preferably 0.018:1.

[0014] Preferably according to the present invention, in step (1), the volume ratio of deionized water to absolute ethanol is 1:150 - 250.

[0015] Preferably according to 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.

[0016] Preferably according to 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 more preferably 0.0092:1.

[0017] Preferably according to 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.

[0018] Preferably according to the present invention, in step (1), the reaction temperature after mixing the modified nano-silica, hydrophobic monomer, and ester monomer is 30 °C to 60 °C, preferably 50 °C; the reaction time is 3 - 6 h; the reaction is carried out under stirring conditions.

[0019] Preferably according to the present invention, in step (2), the transition metal salt is one of ferric chloride, copper sulfate, or nickel sulfate; the molar ratio of the transition metal salt to the amphiphilic modified nano-silica is 0.5 - 2:1, preferably 1:1.

[0020] Preferably according to the present invention, in step (2), the molar amount of the transition metal salt and the volume ratio of ethanol is 0.2 - 0.6 mol / L, preferably 0.45 mol / L.

[0021] 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, the solvent is a mixed solvent of ethanol and deionized water, wherein the volume ratio of ethanol to deionized water is 3-5:1; the concentration of the reducing agent solution is 0.1-0.3 g / mL.

[0022] Preferably according to 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.

[0023] Preferably according to the present invention, in step (2), the dropping rate is 6-12 mL / min, preferably 8 mL / min; the dropping is carried out under room temperature and stirring conditions.

[0024] Preferably according to the present invention, in step (2), the reaction condition is stirring reaction at room temperature for 20-40 min.

[0025] An amphiphilic nano metal catalyst for viscosity reduction of heavy oil while drilling is prepared by the above method.

[0026] Preferably according to the present invention, the amphiphilic nano metal catalyst for viscosity reduction of heavy oil while drilling is a transition metal nano particle loaded on the surface of amphiphilic modified nano silica.

[0027] The application of the above amphiphilic nano metal catalyst for viscosity reduction of heavy oil while drilling is used as a viscosity reducer while drilling for viscosity reduction of heavy oil invading the wellbore.

[0028] Preferably according to the present invention, the mass ratio of the amphiphilic nano metal catalyst for viscosity reduction of heavy oil while drilling to the volume of the drilling fluid is 0.003-0.01 g / mL, preferably 0.006-0.01 g / mL.

[0029] Preferably according to the present invention, the applicable temperature range of the amphiphilic nano metal catalyst for viscosity reduction of heavy oil while drilling is 130°C-300°C.

[0030] The technical features and beneficial effects of the present invention are as follows: 1. The preparation method of the nano metal catalyst of the present invention is simple and easy to industrialize. The present invention uses hydrophilic monomers, hydrophobic monomers, ester monomers and nano silicon dioxide as main raw materials. First, the amphiphilic silicon dioxide carrier is prepared by amphiphilic modification of silicon dioxide. The surface of the carrier contains hydrophilic groups, which enables it to achieve good dispersion in polar solvents. At the same time, after modification, the surface of silicon dioxide is covered with organic compounds such as hydrophobic monomers and ester monomers, thereby changing it from polar to weak polarity. This polarity change makes the nano metal catalyst easier to approach the heavy oil, and then the catalytic center can better approach the target reaction molecule, thereby significantly improving the catalytic reaction efficiency. Then, a reduction method is adopted, and a reducing agent is used to react with a transition metal salt to generate a nano metal element loaded on the surface of the amphiphilic modified nano silicon dioxide to achieve good catalytic effect. According to organic chemistry theory and catalytic theory, the d orbital of the transition metal catalytic center interacts with the target reaction molecule to reduce the activation energy of the reaction, and the d electrons in the zero-valent transition metal are the most abundant, so the transition metal has the best catalytic effect on organic compounds. When the foreign polar atomic nucleus (transition metal element) approaches the reaction molecule, it coordinates with the heteroatoms in the heavy oil, promotes electron transfer and weakens the corresponding CC, CO, CS and CN bonds, and water attacks the intermediates to cause the molecular chain to break, thereby generating smaller molecules and reducing the viscosity of the oil. The nano metal catalyst obtained by the present invention is a nano transition metal element loaded on the surface of amphiphilic silica. As a high temperature stable material, silica can enhance the thermal stability of the catalytic viscosity reducer in a high temperature environment.

[0031] 2. The core of the present invention is to construct an amphiphilic silica carrier and optimize the transition metal loading process through the synergistic modification of hydrophilic monomers, hydrophobic monomers and ester monomers. The present invention uses a specific type and amount of hydrophilic monomers to ensure that the carrier is stably dispersed in a polar solvent; if the hydrophilic monomer is omitted or the amount is inappropriate, the silica will agglomerate, and subsequent uniform modification and metal loading cannot be achieved. The types and molar ratios of the hydrophobic monomers and ester monomers of the present invention need to be appropriate to balance the surface polarity and the metal anchoring sites; if the hydrophobic monomer is missing, the surface polarity of the carrier is too strong, and the compatibility with heavy oil is significantly reduced; if the ester monomer is missing, the transition metal (such as Fe³⁺) is difficult to load uniformly through coordination, resulting in agglomeration of active centers. The transition metal is preferably Fe or Ni, which has significant advantages in cost performance and catalytic efficiency, and forms 5~20 nm metal particles after reduction.

[0032] 3. The nano-metal catalyst obtained in the present invention can significantly reduce the operating temperature. This is because making the metal catalyst into nano-particles can significantly increase its surface area and reaction activity, enabling the reaction to achieve efficient viscosity reduction at a lower temperature. Moreover, the silica support helps to improve the dispersion of metal particles and provides more reaction contact opportunities with heavy oil, thereby enhancing the catalytic reaction efficiency. Combining the excellent electron supply ability of transition metal nano-particles with the high dispersion performance of amphiphilic silica and the excellent heavy oil contact efficiency, the nano-metal catalyst can not only adapt to the temperature below 150 °C in the wellbore environment during the catalytic cracking viscosity reduction of heavy oil, but also maintain a persistent high-efficiency viscosity reduction effect, overcoming the problem that the previous viscosity reducers had a relatively high operating temperature and could not maintain a good viscosity reduction rate at the wellbore temperature.

[0033] 4. The nano-metal catalyst obtained in 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 the oil phase and the water phase. It can be applied to various types of drilling fluids and can be used for catalytic viscosity reduction while drilling to invade the heavy oil in the wellbore. At the same time, the nano-metal catalyst has good high-temperature stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 Infrared spectra of nano-silica (SiO2), amphiphilic modified nano-silica (AmphiphilicSiO2), amphiphilic nano-metal catalyst (Fe 0 / Amphiphilic SiO2) prepared in Example 1, and the catalyst (Fe 0 / SiO2) prepared in Comparative Example 6; Figure 2 Transmission electron microscope and energy-dispersive X-ray spectra of the amphiphilic nano-metal catalyst prepared in Example 1. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0035] The technical solutions of the present invention will be described clearly and completely below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of them. Based on the embodiments of the present invention, all other examples modified or polished by those of ordinary skill in the art belong to the scope of protection of the present invention.

[0036] The raw materials used in the examples are all conventional raw materials and can be obtained commercially; the methods are all prior art unless otherwise specified.

[0037] Example 1 A preparation method of an amphiphilic nano-metal catalyst for viscosity reduction of heavy oil while drilling, comprising the steps: (1) The preparation method of amphiphilic modified nano-silica is as follows: 10.925 g (0.18 mol) of nano-silica particles with a particle size of 15 nm were fully dispersed in 200 mL of absolute ethanol, and stirred vigorously for 30 minutes. Then, 0.2 g of hydrophilic monomer 3-aminopropyltriethoxysilane and 1 mL of deionized water were added, and the mixture was stirred for 4 hours at a temperature controlled at 60 °C. After solid-liquid separation and washing the particles with absolute ethanol to remove unreacted 3-aminopropyltriethoxysilane, etc., modified nano-silica was obtained. 0.1 g of hydrophobic monomer cetyltrimethoxysilane and 0.3 g of ester monomer methyl methacrylate were added to the modified nano-silica, and the mixture was stirred at 50 °C for 3 hours. The product was centrifugally washed with absolute ethanol 3 times to remove residual modifiers and impurities such as ammonia water. Finally, the product was vacuum dried at 70 °C for 12 hours to obtain amphiphilic modified nano-silica.

[0038] (2) The preparation method of the nano-metal catalyst is as follows: 48.66 g (0.18 mol) of ferric chloride hexahydrate and the above-mentioned amphiphilic modified nano-silica were mixed and placed in a 1000 mL three-necked flask. Then, 400 mL of ethanol was added under mechanical stirring for 10 minutes to completely disperse them to obtain a mixed solution.

[0039] 24.97 g (0.66 mol) of sodium borohydride was dissolved in 100 ml of ethanol-deionized water (the volume ratio of ethanol to deionized water was 80:20), and was added dropwise to the above mixed solution through a constant pressure dropping funnel (dropping rate: 8 mL / min), while the reaction solution in the flask was stirred vigorously at ambient temperature. After the addition of the sodium borohydride solution was completed, the reaction mixture was stirred at room temperature for 30 minutes, and then filtered through a 0.2 μm filter. The filter cake was washed twice with industrial grade ethanol to prevent rusting immediately during subsequent filtration, and then vacuum dried overnight and ground with a spatula to obtain the target product, the amphiphilic nano-metal catalyst for viscosity reduction of heavy oil during drilling, namely amphiphilic SiO2 / Fe catalyst.

[0040] It can be seen that 1100 cm Figure 1 represents Si-O-Si stretching, which is the main peak of SiO2. 3438 cm -1 is for O-H stretching, coming from surface Si-OH, and this group of characteristic peaks appeared in the curves of all four groups of samples. When SiO2 reacts with the hydrophilic monomer 3-aminopropyltriethoxysilane, -NH2 is introduced, and the N-H characteristic peak in its surface amino group is generated at 1524 cm -1 . Samples containing amphiphilic SiO2 produced characteristic peaks here, while the N-H characteristic peak of Fe -1 / amphiphilic SiO2 was slightly shifted to 1512 cm 0 -1Nearby. 2920 and 2855 cm -1 are the -CH3 and -CH2 stretching vibration peaks brought by the hydrophobic monomer cetyltrimethoxysilane, and obvious characteristic peaks appear in both amphiphilic SiO2 and Fe 0 / amphiphilic SiO2. 1610 cm -1 Fe-OH and Fe-O stretching vibrations exist in both Fe 0 / SiO2 and Fe 0 / amphiphilic SiO2, proving the existence of Fe. And 1740 cm -1 is the C=O stretching peak, representing the successful grafting of the ester group in methyl methacrylate.

[0041] Through transmission electron microscopy and energy-dispersive X-ray spectroscopy Figure 2 the distributions of Fe and Si elements can be seen. Among them, the distribution of SiO2 is relatively uniform, but the arrangement of Fe is slightly agglomerated.

[0042] The application process of the nano-metal catalyst is as follows: Mix 0.6 g of the nano-metal catalyst with 100 mL of drilling fluid (the composition is 3.25 g of bentonite, 0.25 g of caustic soda, 0.15 g of soda ash, 0.35 g of polymer filtrate reducer, 0.4 g of polyanionic cellulose, 2.5 g of sulfonated phenolic resin, 2.5 g of asphalt anti-collapse agent, 1.5 g of calcium carbonate, 88.1 g of water), stir and mix them, then load them into an aging tank, add 30 g of heavy oil (1862 g / mol), put the aging tank into a roller heating furnace, roll at 130 °C or 250 °C for 10 hours, test the viscosity of the liquid after heat rolling treatment, and calculate the viscosity reduction rate.

[0043] Example 2 A preparation method of an amphiphilic nano-metal catalyst for viscosity reduction of heavy oil while drilling, as described in Example 1, the difference is that: in step (1), the nano-silica particles with a particle size of 15 nm are replaced by nano-silica particles with a particle size of 1 μm; other steps and conditions are the same as in Example 1.

[0044] The application process of the nano-metal catalyst is the same as in Example 1.

[0045] Example 3 A preparation method of an amphiphilic nano-metal catalyst for viscosity reduction of heavy oil while drilling, as described in Example 1, the difference is that: in step (1), the dosage of the nano-silica particles with a particle size of 15 nm is 5.46 g (0.09 mol); other steps and conditions are the same as in Example 1.

[0046] The application process of the nano-metal catalyst is the same as in Example 1.

[0047] Example 4 The preparation method of an amphiphilic nano metal catalyst for viscosity reduction of heavy oil while drilling is the same as that in Example 1.

[0048] The application process of the nano metal catalyst is as described in Example 1, except that the dosage of the drilling fluid is 200 mL; other steps and parameters are the same as those in Example 1.

[0049] Example 5 The preparation method of an amphiphilic nano metal catalyst for viscosity reduction of heavy oil while drilling is as described in Example 1, except that in step (2), the dosage of sodium borohydride is 10 g (0.26 mol); other steps and conditions are the same as those in Example 1.

[0050] The application process of the nano metal catalyst is the same as that in Example 1.

[0051] Example 6 The preparation method of an amphiphilic nano metal catalyst for viscosity reduction of heavy oil while drilling is as described in Example 1, except that in step (1), the dosage of the hydrophilic monomer is changed to 0.1 g, the dosage of the hydrophobic monomer is changed to 0.05 g, and the dosage of the ester monomer is changed to 0.15 g; other steps and conditions are the same as those in Example 1.

[0052] The application process of the nano metal catalyst is the same as that in Example 1.

[0053] Example 7 The preparation method of an amphiphilic nano metal 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 from ferric chloride with nickel sulfate of the same molar amount; other steps and conditions are the same as those in Example 1.

[0054] The application process of the nano metal catalyst is the same as that in Example 1.

[0055] Example 8 The preparation method of an amphiphilic nano metal catalyst for viscosity reduction of heavy oil while drilling is as described in Example 1, except that in step (2), the dosage of ferric chloride hexahydrate is 24.33 g (0.09 mol); other steps and conditions are the same as those in Example 1.

[0056] The application process of the nano metal catalyst is the same as that in Example 1.

[0057] Example 9 The preparation method of an amphiphilic nano metal catalyst for viscosity reduction of heavy oil while drilling is as described in Example 1, except that in step (1), the dosage of the hydrophilic monomer is changed to 0.1 g and the dosage of the ester monomer is changed to 0.15 g; other steps and conditions are the same as those in Example 1.

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

[0059] Example 10 A preparation method of an amphiphilic nano metal catalyst for viscosity reduction of heavy oil while drilling, 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; other steps and conditions are the same as those in Example 1.

[0060] The application process of the nano metal catalyst is the same as that in Example 1.

[0061] Example 11 A preparation method of an amphiphilic nano metal catalyst for viscosity reduction of heavy oil while drilling, 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; other steps and conditions are the same as those in Example 1.

[0062] The application process of the nano metal catalyst is the same as that in Example 1.

[0063] Example 12 A preparation method of an amphiphilic nano metal catalyst for viscosity reduction of heavy oil while drilling, as described in Example 1, except that: in step (1), the hydrophilic monomer is ethylenediaminepropyltriethoxysilane; other steps and conditions are the same as those in Example 1.

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

[0065] Example 13 A preparation method of an amphiphilic nano metal catalyst for viscosity reduction of heavy oil while drilling, as described in Example 1, except that: in step (1), the hydrophobic monomer is vinyltriethoxysilane; other steps and conditions are the same as those in Example 1.

[0066] The application process of the nano metal catalyst is the same as that in Example 1.

[0067] Example 14 A preparation method of an amphiphilic nano metal catalyst for viscosity reduction of heavy oil while drilling, as described in Example 1, except that: in step (1), the ester monomer is methyl acrylate; other steps and conditions are the same as those in Example 1.

[0068] The application process of the nano metal catalyst is the same as that in Example 1.

[0069] Comparative Example 1 A preparation method of a viscosity reducer, as described in Example 1, except that: step (1) is omitted; amphiphilic modified nano silica is not added in step (2); other steps and conditions are the same as those in Example 1.

[0070] The application process of the viscosity reducer is the same as that in Example 1.

[0071] Comparative Example 2 The preparation method of an amphiphilic nano-metal catalyst for viscosity reduction of heavy oil during drilling is the same as that in Example 1.

[0072] The application process of the nano-metal catalyst is as described in Example 1, except that the drilling fluid is replaced with deionized water; other steps and parameters are the same as those in Example 1.

[0073] Comparative Example 3 The preparation method of 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: Add 0.1 g of hydrophobic monomer cetyltrimethoxysilane and 0.3 g of ester monomer methyl methacrylate to 10.925 g (0.18 mol) of nano-silica particles with a particle size of 15 nm, and stir and react at a temperature of 50 °C for 3 hours. The product is centrifugally washed 3 times with absolute ethanol to remove residual modifiers and impurities such as ammonia water, and finally the product is vacuum dried at 70 °C for 12 hours to obtain modified nano-silica.

[0074] Other steps and conditions are the same as those in Example 1.

[0075] The application process of the viscosity reducer is the same as that in Example 1.

[0076] Comparative Example 4 The preparation method of 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: Disperse 10.925 g (0.18 mol) of nano-silica particles with a particle size of 15 nm in 200 mL of absolute ethanol, stir vigorously for 30 minutes, add 0.2 g of hydrophilic monomer 3-aminopropyltriethoxysilane and 1 mL of deionized water, and stir for 4 hours at a temperature controlled at 60 °C. Separate the solid and liquid, wash the particles with absolute ethanol to remove unreacted 3-aminopropyltriethoxysilane, etc., to obtain modified nano-silica. Add 0.3 g of ester monomer methyl methacrylate to the modified nano-silica, and stir and react at a temperature of 50 °C for 3 hours. The product is centrifugally washed 3 times with absolute ethanol to remove residual modifiers and impurities such as ammonia water, and finally the product is vacuum dried at 70 °C for 12 hours to obtain modified nano-silica.

[0077] Other steps and conditions are the same as those in Example 1.

[0078] The application process of the viscosity reducer is the same as that in Example 1.

[0079] Comparative Example 5 The preparation method of 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: 10.925 g (0.18 mol) of nano-silica particles with a particle size of 15 nm were fully dispersed in 200 mL of absolute ethanol, and stirred vigorously for 30 minutes. Then, 0.2 g of hydrophilic monomer 3-aminopropyltriethoxysilane and 1 mL of deionized water were added, and the mixture was stirred for 4 hours at a temperature controlled at 60 °C. After solid-liquid separation and washing the particles with absolute ethanol to remove unreacted 3-aminopropyltriethoxysilane, etc., modified nano-silica was obtained. 0.1 g of hydrophobic monomer cetyltrimethoxysilane was added to the modified nano-silica, and the reaction was stirred at 50 °C for 3 hours. The product was centrifugally washed with absolute ethanol 3 times to remove residual modifiers and impurities such as ammonia water. Finally, the product was vacuum dried at 70 °C for 12 hours to obtain amphiphilic modified nano-silica.

[0080] Other steps and conditions were the same as in Example 1.

[0081] The application process of the viscosity reducer was the same as in Example 1.

[0082] Comparative Example 6 A preparation method of a viscosity reducer, as described in Example 1, except that: step (1) was omitted; in step (2), the amphiphilic modified nano-silica was replaced with 10.925 g (0.18 mol) of nano-silica particles with a particle size of 15 nm; other steps and conditions were the same as in Example 1.

[0083] The application process of the viscosity reducer was the same as in Example 1.

[0084] Test Example The following performance evaluations were carried out on the nano-metal catalysts prepared in Examples 1-14 and Comparative Examples 1-6.

[0085] 1. Evaluation of the viscosity reduction performance of heavy oil The evaluation of the viscosity reduction performance of heavy oil is the most intuitive and effective method to test the performance of nano-metal catalysts. To visually evaluate the effect of the catalyst on the viscosity of heavy oil, after the heavy oil cracked by the nano-metal catalyst in the examples and comparative examples was placed at 50 °C for 24 hours, the heavy oil and water were separated by centrifugation. The remaining heavy oil was used to test the viscosity at room temperature with a Haake rheometer to obtain the change in the viscosity reduction rate and compare the viscosity reduction effects.

[0086] Table 1 Viscosity reduction rate of heavy oil in each group after catalytic reaction at 130 °C

[0087] Table 2 Viscosity reduction rate of heavy oil in each group after catalytic reaction at 250 °C

[0088] Example 1 with reaction at 130°C achieved a viscosity reduction rate of 77.3%, showing good results. In contrast, Example 1 with reaction at 250°C had a further increased viscosity reduction rate, reaching 97.5%. Comparing Example 1 at 130°C and 250°C shows that the present invention can be applied at low temperatures and used at high temperatures, has good thermal stability, and the effect at high temperatures is not inferior to other high-temperature catalytic viscosity reducers on the market.

[0089] 2. Evaluation of heavy oil molecular weight Evaluating the heavy oil molecular weight is the simplest and most direct method to test the catalytic cracking effect of nano-metal catalysts. To visually evaluate the influence of nano-metal catalysts on the viscosity of heavy oil, after the heavy oil cracked by the nano-metal catalyst in the examples and comparative examples was placed at 50°C for 24 hours, the heavy oil and water were separated by centrifugation. The remaining heavy oil was used to test the weight-average molecular weight by gel permeation chromatography to obtain the change in molecular weight before and after the reaction, and compare the catalytic cracking effect.

[0090] Table 3 Molecular weights of heavy oil in each group after being placed at 50°C for 24h

[0091] 3. Evaluation of the properties of four components of heavy oil Evaluating the properties of four components of heavy oil is a commonly used method to investigate the internal changes of heavy oil after catalytic cracking. To visually evaluate the influence of nano-metal catalysts on the viscosity of heavy oil, after the heavy oil cracked by the nano-metal catalyst in the examples and comparative examples was placed at 50°C for 24 hours, the heavy oil and water were separated by centrifugation. The content of the four components of the separated heavy oil was tested.

[0092] Table 4 Four components of heavy oil in each group after being placed at 50°C for 24h

[0093] By comparing Examples 1 and 2, it was found that the viscosity reduction rate decreased. This is because silica, as a carrier, plays an important role in the dispersion of heavy oil, and increases the interaction with heavy oil through hydrophobicity, improving the contact probability between the catalyst and heavy oil. When the particle size increases, the specific surface area decreases, and the chance of contact between the catalyst and oil molecules decreases, resulting in a reduction in the viscosity reduction effect. Larger particles may lead to poorer dispersion of the catalyst in oil and more aggregation phenomena, thus reducing the overall viscosity reduction effect. The above can also be reflected from the comparison of molecular weights and four components in Examples 1 and 2.

[0094] In Example 3, the amount of the carrier was reduced, directly reducing the total surface area of the catalyst, that is, the number of active sites. The effect of the catalyst depends on the active sites on its surface, and these sites participate in the reaction with the molecules in heavy oil. Reducing the amount means fewer opportunities for effective catalytic reactions, and the viscosity reduction effect will inevitably decrease significantly.

[0095] 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.

[0096] 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. The main catalytic cracking effect is played by Fe element. 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.

[0097] In Example 6, the amount of modified monomers 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 decrease in the viscosity reduction rate.

[0098] In Examples 7 and 8, the transition metal salts were 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 the catalytic efficiency and a decrease in the viscosity reduction rate.

[0099] Examples 9-11 change the monomer ratio, and Examples 12-14 change the monomer type, which will affect the viscosity reduction effect of the catalyst.

[0100] 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, has a strong surface hydrophilicity, and is difficult to form a good interaction with the hydrophobic heavy oil molecules, resulting in poor viscosity reduction effect.

[0101] In Comparative Example 2, deionized water is used as the solvent instead of drilling fluid. The bentonite in the drilling fluid absorbs water and swells, dispersing into tiny particles to form a suspension. This suspension can improve the dispersibility of the catalyst, and through the solubilization and dispersing effect of the bentonite, it is beneficial for the catalyst to contact with the heavy oil. However, deionized water has poor dispersibility, which reduces the efficiency of the catalytic reaction.

[0102] In Comparative Examples 3-5, if no monomer is added, the viscosity reduction effect of the obtained material 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.

[0103] 4. Evaluation in drilling fluid system The performance of water-based drilling fluid was determined according to the latest national standard GB / T 16783.1-2014 Field Test of Drilling Fluids in the Petroleum and Natural Gas Industry Part 1: Water-based Drilling Fluid. Then, the prepared water-based drilling fluid was aged at 200°C for 16 hours, and the performance of the water-based drilling fluid was determined again with reference to the above standard. The results are shown in Table 5.

[0104] The drilling fluid consists of the following components by mass percentage: the content of fresh water is 4000 mL, the content of bentonite is 160 g, the content of caustic soda is 6 g, the content of soda ash is 12 g, the content of polyanionic cellulose is 9 g, the content of lignite resin is 120 g, and barite is added to increase the density to 2.0 g / cm 3 . The addition amount of the nano-metal catalyst is 24 g.

[0105] Table 5 Drilling Fluid Properties

[0106] As can be seen from Table 5, compared with the water-based drilling fluid without a viscosity reducer, the plastic viscosity slightly decreases when the catalyst (Example 1) is added, but the influence on the filtration loss is very small and does not affect the normal use of the drilling fluid; reducing the amount of the reducing agent (Example 5) and the catalytic metal salt (Example 8) weakens the viscosity reduction effect, so the filtration loss is smaller compared with Example 1; in terms of changing the monomer amount (Examples 6, 9 - 11), the decrease in the hydrophilic monomer weakens the influence of the catalyst (Example 1) on the apparent viscosity of the water-based drilling fluid, while this is not obvious for the decrease in the hydrophobic monomer and the ester monomer. The catalytic viscosity reducer with hydrophilic silica as the carrier (Comparative Example 6) has the greatest influence on the plastic viscosity because the hydrophilic catalyst has a strong affinity with the water-based drilling fluid and can be fully contacted. Generally speaking, the nano-metal catalytic viscosity reducer for heavy oil during drilling does not affect the normal use of the water-based drilling fluid while maintaining good viscosity reduction for heavy oil.

Claims

1. A preparation method of an amphiphilic nano metal catalyst for viscosity reduction of heavy oil while drilling, characterized in that, It includes the steps: (1) Fully disperse nano-silica in absolute ethanol, add a hydrophilic monomer and deionized water, and after reaction, perform solid-liquid separation and washing to obtain modified nano-silica; mix the modified nano-silica, a hydrophobic monomer, and an ester monomer, and after reaction, perform centrifugation, washing, and drying to obtain amphiphilic-modified nano-silica; The hydrophilic monomer is one or a combination of two or more of 3-isocyanatopropyltriethoxysilane, 3-aminopropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, or ethylenediaminepropyltriethoxysilane; the mass ratio of the hydrophilic monomer to 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 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 nano-silica is 0.01 - 0.2:1; (2) Fully disperse a transition metal salt and amphiphilic-modified nano-silica in ethanol, dropwise add a reducing agent solution, and then after reaction, perform filtration, washing, drying, and grinding to obtain an amphiphilic nano-metal catalyst for viscosity reduction of heavy oil during drilling; The transition metal salt is one of ferric chloride, copper sulfate, or nickel sulfate; the molar ratio of the transition metal salt to 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.

2. The preparation method of the 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-silica is 15 nm - 1 μm.

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

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

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

6. The preparation method of the amphiphilic nano metal catalyst for viscosity reduction of heavy oil while drilling according to claim 1, characterized in that, In step (2), it includes one or more of the following conditions: i. The molar amount of the transition metal salt to the volume of 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, where the volume ratio of ethanol to deionized water is 3 - 5:1; the concentration of the reducing agent solution is 0.1 - 0.3 g / mL.

7. The preparation method of the amphiphilic nano metal catalyst for viscosity reduction of heavy oil while drilling according to claim 1, characterized in that, In step (2), the molar ratio of the transition metal salt to the reducing agent is 1:1 - 8.

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

9. An amphiphilic nano metal catalyst for viscosity reduction of heavy oil while drilling, characterized in that, Prepared by the method according to any one of claims 1-8; the amphiphilic nano-metal catalyst for viscosity reduction of heavy oil while drilling is a transition metal nanoparticle loaded on the surface of amphiphilic modified nano-silica.

10. The application of the amphiphilic nano metal catalyst for viscosity reduction of heavy oil while drilling according to any one of claims 1-8, characterized in that, Applied as a viscosity reducer while drilling for viscosity reduction of heavy oil invading the wellbore; the mass ratio of the amphiphilic nano-metal catalyst for viscosity reduction of heavy oil while drilling to the volume of the drilling fluid is 0.003-0.01 g / mL; the applicable temperature range of the amphiphilic nano-metal catalyst for viscosity reduction of heavy oil while drilling is 130°C-300°C.

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