Nano thick oil viscosity-reducing blocking remover and preparation method thereof

Abstract

The invention relates to the technical field of oil exploitation aids, and particularly discloses a nano thick oil viscosity-reducing blocking remover and a preparation method thereof. The invention relates to a nano thick oil viscosity-reducing blocking remover, which is prepared from the following raw materials in parts by weight: 10 to 18 parts of mineralized modified nano silicon carrier, 10 to 14 parts of cross-linked fluorocarbon surfactant, 0.1 to 0.3 part of polyacrylamide, 1 to 3 parts of styrene-acrylic isothiazolinone and 55 to 75 parts of deionized water, the mineralized modified nano silicon carrier is prepared by taking nano silicon dioxide as a core and growing a hydroxyapatite-titanium dioxide composite shell layer on the surface of the core through a mineralization process. The long-term stability of the viscosity reduction effect of the viscosity reduction blocking remover in the high-temperature and high-salt environment is effectively enhanced, and the long-term service stability of the viscosity reduction blocking remover in the deep reservoir environment is comprehensively improved.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of oil exploitation aids, in particular to a nano thickened oil viscosity-reducing and plug-removing agent and a preparation method thereof. BACKGROUND

[0002] The nano thickened oil viscosity-reducing and plug-removing agent is a kind of oil exploitation aid designed based on the unique interface effect and small size effect of nano materials. The core function thereof is to reduce the viscosity of thickened oil and remove the blockage formed by the deposition of gum and asphaltene and the precipitation of wax in the oil reservoir pore through the effects of penetration, dispersion, emulsification or catalytic cracking, thereby improving the seepage condition of the oil reservoir and increasing the recovery rate of thickened oil. In the background of increasing reserves of thickened oil resources and increasing difficulty in exploitation, the research and application of the efficient nano thickened oil viscosity-reducing and plug-removing agent can not only solve the core problems of high viscosity, low flowability and easy blockage in the process of thickened oil exploitation, but also improve the economy and environmental protection of oil reservoir development, which has important industrial application significance for guaranteeing the stable supply of oil and gas resources.

[0003] A variety of nano thickened oil viscosity-reducing and plug-removing agent related schemes have been disclosed in the prior art. The Chinese patent application file with the publication number CN118027935A discloses a multifunctional nano thickened oil viscosity-reducing and plug-removing agent, a preparation method and application thereof. The viscosity-reducing and plug-removing agent is mixed by the following components in percentage by mass: HD-3 non-ionic surfactant: 5%-10%; carboxylic acid anionic fluorocarbon surfactant: 10%-30%; water: 60%-70%; polyacryl: 0.01%; modified benzene propyl isothiazolinone: 1%. The multifunctional nano thickened oil viscosity-reducing and plug-removing agent provided by the technical scheme has the functions of viscosity reduction and plug removal, and can effectively improve the recovery rate of thickened oil reservoirs.

[0004] However, the nano thickened oil viscosity-reducing and plug-removing agent in the above prior art still has obvious defects in the actual deep thickened oil reservoir exploitation scene, specifically, the long-term stability of the viscosity reduction effect is insufficient, and the viscosity reduction half-life is short. The main reason for the defect is that the surfactant components are prone to hydrolysis or aggregation in the high-temperature and high-salt environment of deep oil reservoirs, resulting in the attenuation of their emulsification and dispersion capacity; and there is a lack of stable synergistic mechanism among the components, and the effective components are prone to loss. According to actual working condition test verification, the initial viscosity reduction rate of this kind of viscosity-reducing and plug-removing agent can reach more than 65% in the deep oil reservoir environment of 140℃ and 30000mg / L salinity, but after 72h of continuous action, the viscosity reduction rate will quickly decay to less than 30%, which is difficult to meet the demand for continuous viscosity reduction and plug removal in the long-term exploitation process of deep thickened oil reservoirs; the viscosity reduction half-life (i.e. the time when the viscosity reduction rate decays to 50% of the initial value) of the existing product is usually less than 48h, which cannot match the operation cycle of deep thickened oil reservoir exploitation, limiting its popularization and application in deep complex oil reservoirs. SUMMARY

[0005] In order to enhance the long-term stability of the viscosity reduction effect of the viscosity-reducing and plug-removing agent in a high-temperature and high-salt environment, the application provides a nano thickened oil viscosity-reducing and plug-removing agent and a preparation method thereof.

[0006] The application provides a nano thickened oil viscosity-reducing and plug-removing agent. The nano thickened oil viscosity-reducing and plug-removing agent comprises the following raw materials in parts by weight: 10-18 parts of a mineralized modified nano silicon carrier; 10-14 parts of a cross-linked fluorocarbon surfactant; 0.1-0.3 parts of polyacrylamide; 1-3 parts of benzylpropylisothiazolinone; 55-75 parts of deionized water; The mineralized modified nano silicon carrier is prepared by taking nano silicon dioxide as a core and growing a hydroxyapatite-titanium dioxide composite shell layer on the surface of the core through a mineralization process.

[0007] By adopting the above technical scheme, the mineralized modified nano silicon carrier and the cross-linked fluorocarbon surfactant are used as core functional components, and the polyacrylamide and the benzylpropylisothiazolinone are used to construct a composite system, so that the bottleneck of poor viscosity reduction stability of the prior art is broken from the root.

[0008] The introduction of the mineralized modified nano silicon carrier restructures the bearing mechanism of the active components, effectively solves the defects of weak combination of the traditional carrier and the surfactant and easy desorption under high temperature and high salt, the hydroxyapatite-titanium dioxide composite shell layer grown on the surface of the carrier not only has strong high-temperature resistance and salt erosion resistance and can maintain structural integrity in harsh deep reservoir environments, but also forms strong interaction with the cross-linked fluorocarbon surfactant through rich polar functional groups in the shell layer, so that the active components are firmly anchored, and the risk of loss of effective components is significantly reduced.

[0009] The design of the cross-linked fluorocarbon surfactant solves the problems of easy hydrolysis and aggregation of the traditional surfactant from the molecular level. Unlike the existing linear structure surfactant, the surfactant forms a stable spatial network structure through dynamic covalent cross-linking, retains the excellent interfacial activity of the fluorocarbon chain to ensure the emulsification and viscosity reduction effect, and enhances the rigidity and anti-degradation ability of the molecular chain through the cross-linked structure, so as to effectively resist the erosion of the high-temperature and high-salt environment and avoid the attenuation of the interfacial activity.

[0010] In addition, the technical scheme of the present application realizes synergistic effect of the system by reasonably regulating the allocation ratio of each component. The introduction of polyacrylamide can form a three-dimensional network structure with the core component to further lock the active ingredients; benzylisothiazolinone can inhibit the damage of microorganism breeding at high temperature to the active ingredients, and the homogeneous system constructed with deionized water can effectively enhance the long-term stability of the viscosity reduction effect of the viscosity reduction and plugging agent in a high-temperature and high-salt environment, and comprehensively improve the long-term service stability of the product in a deep reservoir environment, so as to ensure that the viscosity reduction effect continuously matches the production operation cycle.

[0011] Optionally, the mineralized modified nanosilicon carrier is prepared by the following method: A1, dispersing nanosilica in a Tris-HCl buffer solution, ultrasonic dispersion for 60-90 min to obtain a dispersion A, adding a calcium chloride solution and a sodium dihydrogen phosphate solution to the dispersion A, and then adding tetrabutyl titanate, stirring for 40-60 min to obtain a mixed liquid B; A2, placing the mixed liquid B in a constant temperature water bath at 35-45 DEG C, and stirring and reacting for 12-24 h, during which the Tris-HCl buffer solution is supplemented every 4 h to maintain the pH of the reaction system at 8.5-9.0; after the reaction is completed, the precipitate is centrifuged and washed with deionized water and anhydrous ethanol for 3-5 times, respectively, and dried at 110-120 DEG C for 8-12 h to obtain the mineralized modified nanosilicon carrier.

[0012] By using the above technical scheme, in the preparation method, the selection of the Tris-HCl buffer solution and the pH maintenance strategy provide a stable chemical environment for the directional growth of the hydroxyapatite-titanium dioxide composite shell, avoiding uneven growth or shedding of the shell; the ultrasonic dispersion and the staged temperature maintaining reaction process ensure the close combination of the nanosilica core and the composite shell, further improving the structural stability and active component loading capacity of the carrier. The carrier prepared by the method can stably play the "anchoring-anti-deterioration" function, providing a reliable carrier guarantee for the long-term stability of the viscosity reduction system.

[0013] Optionally, the mass ratio of the nanosilica to the Tris-HCl buffer solution is 1: (10-20); the mass concentration of the calcium chloride solution is 5%-8%; the concentration of the sodium dihydrogen phosphate solution is 3%-5%; and the mass ratio of the nanosilica, the calcium chloride solution and the sodium dihydrogen phosphate solution is 1: (8-12): (5-8).

[0014] By adopting the above technical solutions, the reasonable ratio of nano-silica to buffer solution ensures the uniform dispersion of nanoparticles and avoids carrier function failure caused by particle agglomeration; the specific concentration of calcium chloride and sodium dihydrogen phosphate solution and the precise ratio ensure the orderly growth of hydroxyapatite shell and ensure a reasonable shell pore structure, which not only provides sufficient loading sites for surfactants, but also helps to achieve the slow release of active components; the synergistic ratio of each component improves the bonding strength between the composite shell and the core, enhances the carrier's resistance to erosion in high temperature and high salt environment, and indirectly ensures the long-term stability of the viscosity reduction system.

[0015] Optionally, in step A1, the amount of tetrabutyl titanate added is 1%-1.5% of the total mass of the calcium chloride solution and the sodium dihydrogen phosphate solution.

[0016] Optionally, the cross-linked fluorocarbon surfactant is prepared by free radical polymerization of perfluorooctyl acrylate, N-(2-hydroxyethyl)acrylamide, and 2-acryloyloxyethyl isocyanate to obtain a fluorocarbon copolymer precursor containing hydroxyl and isocyanate groups, and then by intramolecular dynamic covalent cross-linking reaction.

[0017] By adopting the above technical solution and selecting perfluorooctyl acrylate, N-(2-hydroxyethyl)acrylamide, and 2-acryloyloxyethyl isocyanate as comonomers, the orderly introduction of fluorocarbon chains and active functional groups into the surfactant molecule is ensured. This not only guarantees efficient emulsification and dispersion capabilities but also provides sufficient active sites for dynamic covalent crosslinking. The process route of preparing copolymer precursors through free radical polymerization followed by intramolecular crosslinking enables the surfactant to form a crosslinked structure with both stability and dynamic repair functions. Under high temperature and high salt conditions, structural damage can be compensated through reversible breaking and recombination of covalent bonds, inhibiting hydrolysis and aggregation at the molecular level and solving the defect of insufficient long-term stability of traditional surfactants.

[0018] Optionally, the cross-linked fluorocarbon surfactant is prepared by the following method: B1. Perfluorooctyl acrylate, N-(2-hydroxyethyl)acrylamide, and 2-acryloyloxyethyl isocyanate were added to ethyl acetate solvent, and then azobisisobutyronitrile initiator was added. The mixture was polymerized at 70-80℃ for 6-8 hours under a nitrogen atmosphere to obtain the fluorocarbon copolymer precursor. B2. Dissolve the fluorocarbon copolymer precursor in N,N-dimethylformamide, add dibutyltin dilaurate catalyst, heat to 90-100℃, and maintain the temperature for 4-6 hours. After the reaction is completed, pour the product into deionized water to precipitate, filter and collect the precipitate, and dry it under vacuum to obtain the cross-linked fluorocarbon surfactant.

[0019] By adopting the above technical solutions, precise control of process parameters ensures the stability of product structure and performance. The nitrogen-atmospheric polymerization process effectively suppresses oxidative side reactions during free radical polymerization, ensuring the structural uniformity of the copolymer precursor. The selection of specific solvent systems and catalysts provides a suitable reaction environment for dynamic covalent crosslinking reactions, ensuring sufficient and controllable crosslinking and avoiding excessive crosslinking that leads to decreased surfactant solubility or loss of interfacial activity. Post-treatment processes such as precipitation and drying effectively remove unreacted monomers and impurities, improving product purity and ensuring that the surfactant stably plays its emulsifying and dispersing role in the viscosity-reducing system, guaranteeing long-term stability of the viscosity-reducing effect.

[0020] Optionally, in step B1, the mass ratio of perfluorooctyl acrylate, N-(2-hydroxyethyl)acrylamide, 2-acryloyloxyethyl isocyanate and ethyl acetate solvent is 5:(3-4):(1-2):(20-30).

[0021] By adopting the above technical solution, a specific ratio of comonomers can ensure a balanced distribution of fluorocarbon chains, hydroxyl groups, and isocyanate groups in the molecular chain. This not only ensures the interfacial activity of the surfactant but also provides sufficient active sites for the subsequent dynamic crosslinking reaction, avoiding insufficient crosslinking due to uneven functional group distribution. A reasonable solvent ratio ensures the full dissolution of the monomers and the smooth progress of the polymerization reaction, avoiding uneven polymerization caused by excessively high local monomer concentrations, and ensuring a uniform copolymer precursor structure. This ratio design further enhances the structural stability and anti-deterioration ability of the crosslinked product, enabling the surfactant to maintain excellent emulsification and viscosity reduction properties under high temperature and high salt conditions.

[0022] Optionally, in step B1, the amount of the azobisisobutyronitrile initiator added is 1%-3% of the total mass of the comonomer.

[0023] Optionally, in step B2, the mass ratio of the fluorocarbon copolymer precursor to N,N-dimethylformamide is 1:(5-8); the amount of the dibutyltin dilaurate catalyst added is 0.5%-1.2% of the mass of the fluorocarbon copolymer precursor.

[0024] Secondly, this application provides a method for preparing a nano-thick oil viscosity reducer and unblocking agent, which adopts the following technical solution: A method for preparing a nano-thick oil viscosity reducer and unblocking agent includes the following steps: S1. Mix polyacrylamide with deionized water, heat to 45-55℃ and stir for 20-30 minutes to obtain an aqueous solution of polyacrylamide. Then add mineralized modified nano-silicon carrier and cross-linked fluorocarbon surfactant, heat to 65-75℃ and keep warm and stir for 2-3 hours. S2. After the reaction is complete, cool the system to 30-40℃, add phenylisothiazolinone, and continue stirring at 150-200r / min for 40-60min. Cool to room temperature to obtain nano-thick oil viscosity reducer and unblocking agent.

[0025] By adopting the above technical solution, the stepwise heating and stirring process ensures the complete dissolution of polyacrylamide, avoiding uneven dispersion of the system due to insufficient dissolution, and laying the foundation for the uniform dispersion of the core components. The heat preservation reaction process at a specific temperature provides suitable conditions for the interaction between the mineralized modified nano-silicon carrier and the cross-linked fluorocarbon surfactant, promoting the formation of a stable synergistic interface layer and enhancing the anchoring effect of the active components. The subsequent cooling and addition of phenylisothiazolinone process design avoids the destruction of the antibacterial activity by high temperature, ensuring its effective microbial inhibition. The entire preparation process is logically coherent and the parameters are well-matched, ensuring the uniform structure and stable performance of the final product, enabling the viscosity reducer and unblocking agent to continuously exert excellent performance in the high-temperature and high-salinity environment of deep oil reservoirs.

[0026] In summary, this application has the following beneficial effects: 1. This application effectively addresses the shortcomings of existing technologies, such as weak bonding between the carrier and active ingredients and easy desorption and loss under high temperature and high salt conditions, by using mineralized modified nano-silicon carriers as one of the core components, thus significantly improving the long-term stability of the viscosity-reducing effect. The carrier uses nano-silica as the core and a hydroxyapatite-titanium dioxide composite shell as the surface. The composite shell not only possesses extremely strong high-temperature resistance and salt erosion resistance, maintaining structural integrity even in the harsh environment of deep oil reservoirs, but also forms strong interactions with the active ingredients through the abundant polar functional groups of the shell, achieving firm anchoring of the active ingredients. Simultaneously, the porous structure of the composite shell helps to achieve the slow release of active ingredients, prolonging the effective ingredient's action period and providing reliable carrier support for the long-term stability of the viscosity-reducing system.

[0027] 2. This application selects a cross-linked fluorocarbon surfactant as another core component, solving the problem at the molecular level that traditional linear surfactants are prone to hydrolysis and aggregation under high temperature and high salt conditions, leading to a decline in interfacial activity. This surfactant is prepared by free radical polymerization and intramolecular dynamic covalent cross-linking reaction of specific comonomers, forming a stable spatial network structure. This structure retains the excellent interfacial activity of the fluorocarbon chain to ensure efficient emulsification and viscosity reduction, while the cross-linking structure enhances the rigidity and resistance to degradation of the molecular chain. More importantly, the dynamic covalent cross-linking structure has a self-healing function, which can quickly reorganize and restore performance when local structural damage is caused by environmental stress, effectively inhibiting the decline in interfacial activity and ensuring stable long-term emulsification and viscosity reduction effects.

[0028] 3. The viscosity-reducing and unblocking agent preparation method of this application achieves efficient synergistic integration of various components through a process design of stepwise heating and stirring, precise temperature control reaction, and cooling addition of antibacterial agents. Stepwise heating and stirring ensures the full dissolution of polyacrylamide and uniform dispersion of the core components, while the temperature-controlled reaction promotes the formation of a stable synergistic interface layer of the core components. The cooling addition of antibacterial agents ensures the antibacterial activity of benzo[a]isothiazolinone. The entire preparation process is logically coherent and highly adaptable, effectively avoiding problems such as uneven component dispersion and active ingredient deactivation, ensuring the uniform structure and stable performance of the final product. This allows the product to continuously exert excellent viscosity-reducing and unblocking effects in the high-temperature and high-salinity environment of deep oil reservoirs, demonstrating good prospects for industrial application. Detailed Implementation

[0029] The present application will be further described in detail below with reference to the embodiments.

[0030] Preparation example of mineralized modified nano-silicon carrier Preparation Example 1 The mineralized modified nano-silicon carrier was prepared using the following method: A1. Disperse 10 kg of nano-silica in 100 kg of Tris-HCl buffer solution and sonicate for 60 min to obtain dispersion A. Add 80 kg of 5% calcium chloride solution and 50 kg of 3% sodium dihydrogen phosphate solution to dispersion A, then add 1.3 kg of tetrabutyl titanate and stir for 40 min to obtain mixture B. A2. Place the mixture B in a 35℃ constant temperature water bath and stir for 12 hours. During this period, add Tris-HCl buffer solution every 4 hours to maintain the pH of the reaction system between 8.5 and 9.0. After the reaction is completed, centrifuge to separate the precipitate, wash it three times with deionized water and three times with anhydrous ethanol, and dry it at 110℃ for 8 hours to obtain the mineralized modified nano-silicon carrier.

[0031] Preparation Example 2 The mineralized modified nano-silicon carrier was prepared using the following method: A1. Disperse 10 kg of nano-silica in 150 kg of Tris-HCl buffer solution and sonicate for 75 min to obtain dispersion A. Add 100 kg of calcium chloride solution with a mass concentration of 6.5% and 65 kg of sodium dihydrogen phosphate solution with a mass concentration of 4% to dispersion A, then add 1.98 kg of tetrabutyl titanate and stir for 50 min to obtain mixture B. A2. Place the mixture B in a 40℃ constant temperature water bath and stir for 18 hours. During this period, add Tris-HCl buffer solution every 4 hours to maintain the pH of the reaction system between 8.5 and 9.0. After the reaction is completed, centrifuge to separate the precipitate, wash it 4 times with deionized water and anhydrous ethanol respectively, and dry it at 115℃ for 10 hours to obtain the mineralized modified nano-silicon carrier.

[0032] Preparation Example 3 The mineralized modified nano-silicon carrier was prepared using the following method: A1. Disperse 10 kg of nano silica in 200 kg of Tris-HCl buffer solution and sonicate for 90 min to obtain dispersion A. Add 120 kg of calcium chloride solution with a mass concentration of 8% and 80 kg of sodium dihydrogen phosphate solution with a mass concentration of 5% to dispersion A. Then add 3 kg of tetrabutyl titanate and stir for 60 min to obtain mixture B. A2. Place the mixture B in a 45℃ constant temperature water bath and stir for 24 hours. During this period, add Tris-HCl buffer solution every 4 hours to maintain the pH of the reaction system between 8.5 and 9.0. After the reaction is completed, centrifuge to separate the precipitate, wash it 5 times with deionized water and 5 times with anhydrous ethanol, and dry it at 120℃ for 12 hours to obtain the mineralized modified nano-silicon carrier.

[0033] Preparation Example 4 The mineralized modified nano-silicon carrier was prepared using the following method: A1. Disperse 10 kg of nano-silica in 200 kg of Tris-HCl buffer solution and sonicate for 90 min to obtain dispersion A. Add 120 kg of calcium chloride solution with a mass concentration of 8% and 80 kg of sodium dihydrogen phosphate solution with a mass concentration of 5% to dispersion A and stir for 60 min to obtain mixture B. A2. Place the mixture B in a 45℃ constant temperature water bath and stir for 24 hours. During this period, add Tris-HCl buffer solution every 4 hours to maintain the pH of the reaction system between 8.5 and 9.0. After the reaction is completed, centrifuge to separate the precipitate, wash it 5 times with deionized water and 5 times with anhydrous ethanol, and dry it at 120℃ for 12 hours to obtain the mineralized modified nano-silicon carrier.

[0034] Preparation example of cross-linked fluorocarbon surfactants Preparation Example 5 Crosslinked fluorocarbon surfactants are prepared using the following method: B1. Add 5 kg of perfluorooctyl acrylate, 3 kg of N-(2-hydroxyethyl)acrylamide, and 1 kg of 2-acryloyloxyethyl isocyanate to 20 kg of ethyl acetate solvent, and then add 0.09 kg of azobisisobutyronitrile initiator. Polymerize at 70 °C for 6 h under nitrogen atmosphere to obtain fluorocarbon copolymer precursor. B2. Dissolve 10 kg of fluorocarbon copolymer precursor in 50 kg of N,N-dimethylformamide, add 0.05 kg of dibutyltin dilaurate catalyst, heat to 90 °C, and keep the temperature for 4 h. After the reaction is complete, pour the product into deionized water to precipitate, filter and collect the precipitate, and dry it under vacuum to obtain the cross-linked fluorocarbon surfactant.

[0035] Preparation Example 6 Crosslinked fluorocarbon surfactants are prepared using the following method: B1. Add 5 kg of perfluorooctyl acrylate, 3.5 kg of N-(2-hydroxyethyl)acrylamide, and 1.5 kg of 2-acryloyloxyethyl isocyanate to 25 kg of ethyl acetate solvent, and then add 0.2 kg of azobisisobutyronitrile initiator. Polymerize at 75 °C for 7 h under a nitrogen atmosphere to obtain the fluorocarbon copolymer precursor. B2. Dissolve 10 kg of fluorocarbon copolymer precursor in 65 kg of N,N-dimethylformamide, add 0.08 kg of dibutyltin dilaurate catalyst, heat to 95 °C, and keep the temperature for 5 h. After the reaction is complete, pour the product into deionized water to precipitate, filter and collect the precipitate, and dry it under vacuum to obtain the cross-linked fluorocarbon surfactant.

[0036] Preparation Example 7 Crosslinked fluorocarbon surfactants are prepared using the following method: B1. Add 5 kg of perfluorooctyl acrylate, 4 kg of N-(2-hydroxyethyl)acrylamide, and 2 kg of 2-acryloyloxyethyl isocyanate to 30 kg of ethyl acetate solvent, and then add 0.33 kg of azobisisobutyronitrile initiator. Polymerize at 75 °C for 7 h under nitrogen atmosphere to obtain fluorocarbon copolymer precursor. B2. Dissolve 10 kg of fluorocarbon copolymer precursor in 65 kg of N,N-dimethylformamide, add 0.08 kg of dibutyltin dilaurate catalyst, heat to 95 °C, and keep the temperature for 5 h. After the reaction is complete, pour the product into deionized water to precipitate, filter and collect the precipitate, and dry it under vacuum to obtain the cross-linked fluorocarbon surfactant.

[0037] Example Example 1 A nano-thick oil viscosity reducer and unblocking agent, the raw material components and formulations of which are shown in Table 1, wherein the mineralized modified nano-silicon carrier is the mineralized modified nano-silicon carrier prepared in Preparation Example 1; the cross-linked fluorocarbon surfactant is the cross-linked fluorocarbon surfactant prepared in Preparation Example 5; and the effective solid content of the polyacrylamide is 90%, and the number average molecular weight is 800W.

[0038] A method for preparing a nano-thick oil viscosity reducer and unblocking agent includes the following steps: S1. Mix polyacrylamide with deionized water, heat to 45°C and stir for 20 min to obtain an aqueous solution of polyacrylamide. Then add mineralized modified nano-silicon carrier and cross-linked fluorocarbon surfactant, heat to 65°C and stir for 2 h. S2. After the reaction is complete, the system is cooled to 30°C, phenylisothiazolinone is added, and the mixture is stirred at 150 r / min for 40 min. After cooling to room temperature, a nano-thick oil viscosity reducer and unblocking agent is obtained.

[0039] Example 2 A nano-thick oil viscosity reducer and unblocking agent, the raw material components and formulations of which are shown in Table 1, wherein the mineralized modified nano-silicon carrier is the mineralized modified nano-silicon carrier prepared in Preparation Example 1; the cross-linked fluorocarbon surfactant is the cross-linked fluorocarbon surfactant prepared in Preparation Example 6; the effective solid content of the polyacrylamide is 90%, and the number average molecular weight is 1000W.

[0040] A method for preparing a nano-thick oil viscosity reducer and unblocking agent includes the following steps: S1. Mix polyacrylamide with deionized water, heat to 50°C and stir for 25 min to obtain an aqueous solution of polyacrylamide. Then add mineralized modified nano-silicon carrier and cross-linked fluorocarbon surfactant, heat to 70°C and keep warm and stir for 2.5 h. S2. After the reaction is complete, the system is cooled to 35°C, phenylisothiazolinone is added, and the mixture is stirred at 180 r / min for 50 min. After cooling to room temperature, a nano-thick oil viscosity reducer and unblocking agent is obtained.

[0041] Example 3 A nano-thick oil viscosity reducer and unblocking agent, the raw material components and formulations of which are shown in Table 1, wherein the mineralized modified nano-silicon carrier is the mineralized modified nano-silicon carrier prepared in Preparation Example 1; the cross-linked fluorocarbon surfactant is the cross-linked fluorocarbon surfactant prepared in Preparation Example 7; and the effective solid content of the polyacrylamide is 90%, and the number average molecular weight is 1200W.

[0042] A method for preparing a nano-thick oil viscosity reducer and unblocking agent includes the following steps: S1. Mix polyacrylamide with deionized water, heat to 55°C and stir for 30 min to obtain an aqueous solution of polyacrylamide. Then add mineralized modified nano-silicon carrier and cross-linked fluorocarbon surfactant, heat to 75°C and stir for 3 h. S2. After the reaction is complete, the system is cooled to 40°C, phenylisothiazolinone is added, and the mixture is stirred at 200 r / min for 50 min. After cooling to room temperature, a nano-thick oil viscosity reducer and unblocking agent is obtained.

[0043] Table 1. Raw material components and proportions (kg) of the viscosity-reducing and unblocking agents in Examples 1-3

[0044] Example 4 A nano-thick oil viscosity reducer and unblocking agent, which differs from Example 2 in that the mineralized modified nano-silicon carrier in this example is the mineralized modified nano-silicon carrier prepared in Preparation Example 2.

[0045] Example 5 A nano-thick oil viscosity reducer and unblocking agent, which differs from Example 2 in that the mineralized modified nano-silicon carrier in this example is the mineralized modified nano-silicon carrier prepared in Preparation Example 3.

[0046] Example 6 A nano-thick oil viscosity reducer and unblocking agent, which differs from Example 2 in that the number-average molecular weight of the polyacrylamide in this example is 1600W.

[0047] Comparative Example Comparative Example 1 A nano-heavy oil viscosity reducer and unblocking agent was prepared according to Example 1 in the patent application document with publication number CN118027935A, entitled "A Multifunctional Nano Heavy Oil Viscosity Reducer and Unblocking Agent, Preparation Method and Application Thereof".

[0048] Comparative Example 2 A nano-thick oil viscosity reducer and unblocking agent, which differs from Example 2 in that an equal amount of nano-silica is used instead of the mineralized modified nano-silica carrier in this comparative example.

[0049] Comparative Example 3 A nano-thick oil viscosity reducer and unblocking agent, which differs from Example 2 in that a carboxylic acid-based anionic fluorocarbon surfactant is used instead of a cross-linked fluorocarbon surfactant in this comparative example.

[0050] Comparative Example 4 A nano-thick oil viscosity reducer and unblocking agent, which differs from Example 2 in that the mineralized modified nano-silicon carrier in this comparative example is the mineralized modified nano-silicon carrier prepared in Preparation Example 4.

[0051] Performance testing 1. Experimental materials and environmental simulation (1) Test oil: The actual crude oil sample of the deep heavy oil reservoir was selected, and the kinematic viscosity at 50℃ was measured to be 2500 mPa·s (which is consistent with the high viscosity characteristics of deep heavy oil). (2) Simulated reservoir environment: Prepare simulated formation water with a salinity of 30,000 mg / L (prepared by mixing NaCl, CaCl2 and MgCl2 in a mass ratio of 5:3:2), and control the test temperature at 140℃ (simulating the high temperature and high salinity conditions of deep reservoirs). (3) Sample preparation: The viscosity reducing and unblocking agents of each embodiment and comparative example are diluted with simulated formation water at a mass ratio of 1:100 to prepare the test working solution.

[0052] 2. Methods for detecting initial viscosity reduction rate and long-term viscosity reduction rate (72h) (1) Referring to GB / T265-1988 "Determination of kinematic viscosity and calculation of dynamic viscosity of petroleum products", the initial viscosity of the test oil at 50℃ was determined by a rotational viscometer (denoted as μ0). (2) Take the test oil and the working liquid of the viscosity reducer and unblocking agent at a volume ratio of 10:1, place them in a high-pressure reactor, stir at 140℃ for 30 min (simulating full contact between the agent and crude oil), and measure the viscosity of the system after cooling to 50℃ (recorded as μ1, corresponding to the initial viscosity reduction rate). (3) Maintain a constant temperature environment of 140℃ in the high-pressure reactor and let it stand for 72 hours. Stir gently for 10 minutes every 24 hours during this period (simulating the actual stand-up production conditions of the oil reservoir). After 72 hours, cool to 50℃ and measure the viscosity of the system (recorded as μ2, corresponding to the long-term viscosity reduction rate of 72 hours). (4) Calculation of viscosity reduction rate: Viscosity reduction rate η = (μ0 - μ n ) / μ0×100% (when n=1, it is the initial viscosity reduction rate; when n=2, it is the viscosity reduction rate over 72 hours).

[0053] 3. Method for detecting viscosity reduction half-life (1) Take the test oil and the working liquid of the viscosity reducer and unblocking agent at a volume ratio of 10:1, place them in a high-pressure reactor, and keep them at a constant temperature of 140℃. At time points of 0h (i.e. after initial viscosity reduction), 12h, 24h, 36h, 48h, 60h, 72h, 96h, 120h, and 144h, cool to 50℃ and measure the viscosity of the system. (2) Calculate the viscosity reduction rate at each time point, and plot the viscosity reduction rate decay curve with time as the horizontal axis and viscosity reduction rate as the vertical axis; (3) Determination of viscosity reduction half-life: Read the time corresponding to the viscosity reduction rate decaying to 50% of the initial viscosity reduction rate from the decay curve, which is the viscosity reduction half-life. If the viscosity reduction rate is still higher than 50% of the initial value after 144h, it is recorded as ">144h".

[0054] The test results are shown in Table 2.

[0055] Table 2 Experimental Results

[0056] As shown in Table 2, the initial viscosity reduction rate of Comparative Example 1 was only 65.2%, which plummeted to 28.7% after 72 hours, with a viscosity reduction half-life of only 42 hours. This fully exposes the deficiency of existing technologies in terms of "insufficient long-term stability of viscosity reduction effect in high-temperature and high-salt environments." In contrast, the initial viscosity reduction rates of all embodiments in this application are as high as 95% or more, with Example 2 reaching 98.5%, and the viscosity reduction rate still remains above 87% after 72 hours, with a viscosity reduction half-life exceeding 128 hours. This difference in data stems from the synergistic system of mineralized modified nano-silicon carrier and cross-linked fluorocarbon surfactant used in this application, which enhances the anti-deterioration ability of active components from both the support mechanism and molecular structure levels, completely breaking through the performance bottleneck of existing technologies.

[0057] Comparative Example 2 used ordinary nano-silica instead of the mineralized modified nano-silica carrier, resulting in an initial viscosity reduction rate of 76.8%, a 72-hour viscosity reduction rate of only 35.1%, and a half-life of 55 hours, a significant decline in performance compared to Example 2. The core reason for the data difference is that ordinary nano-silica has weak binding force with the active component and is prone to desorption and loss under high temperature and high salt conditions, leading to a rapid decline in the viscosity reduction effect. In contrast, the mineralized modified nano-silica carrier of this application, with its strong high temperature and salt resistance and abundant polar functional groups in the hydroxyapatite-titanium dioxide composite shell, achieves firm anchoring of the active component, significantly reduces the risk of loss of effective ingredients, and ensures long-term maintenance of the viscosity reduction effect.

[0058] Comparative Example 3 used a common carboxylic acid anionic fluorocarbon surfactant instead of the cross-linked product, resulting in an initial viscosity reduction rate of 72.5%, a 72-hour viscosity reduction rate of only 32.4%, and a half-life of 48 hours, significantly lower than Example 2. This is because common linear surfactants are prone to hydrolysis and aggregation under high temperature and high salt conditions, leading to rapid decay of interfacial activity. In contrast, the cross-linked fluorocarbon surfactant of this application forms a spatial network structure through dynamic covalent cross-linking, retaining the excellent interfacial activity of the fluorocarbon chain while possessing self-healing capabilities. This allows it to resist harsh environmental corrosion and effectively inhibit the decay of interfacial activity.

[0059] The synergistic effect of the titanium dioxide component in the composite shell can be corroborated by the data analysis of Example 2 and Comparative Example 4. Comparative Example 4, using a modified carrier prepared without tetrabutyl titanate (without titanium dioxide component), showed an initial viscosity reduction rate of 79.5%, a 72-hour viscosity reduction rate of 42.6%, and a half-life of 78 hours. While superior to Comparative Examples 2 and 3, this was still significantly lower than Example 2. This indicates that the composite shell formed by hydroxyapatite and titanium dioxide has a synergistic effect, further enhancing the structural stability of the carrier and the loading capacity of the active components. Examples 2 and 5 exhibited the best overall performance due to their superior modified carrier and cross-linked surfactant ratios, optimized process parameters, and more complete synergistic effects among the components, resulting in an optimal balance between viscosity reduction and long-term stability.

[0060] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A nano-viscosity-reducing and plug-removing agent for thickened oil, characterized in that, The raw materials include the following weight parts: Mineralized modified nano-silicon carrier 10-18 parts; Cross-linked fluorocarbon surfactant 10-14 parts; Polyacrylamide 0.1-0.3 parts; Benzylpropylisothiazolinone 1-3 parts; Deionized water 55-75 parts; The mineralized modified nano-silicon carrier is prepared by taking nano-silicon dioxide as the core and growing a hydroxyapatite-titanium dioxide composite shell on the surface thereof through a mineralization process.

2. The nanoscale viscosity-reducing and blockage-removing agent according to claim 1, characterized in that, The mineralized modified nano-silicon carrier is prepared by the following method: A1. Disperse nano-silicon dioxide in a Tris-HCl buffer solution, and ultrasonically disperse for 60-90 min to obtain a dispersion A. Add a calcium chloride solution and a sodium dihydrogen phosphate solution to the dispersion A, and then add tetrabutyl titanate, and stir for 40-60 min to obtain a mixture B; A2. Place the mixture B in a 35-45℃ constant temperature water bath, and heat and stir for 12-24 h. During the reaction, supplement the Tris-HCl buffer solution every 4 h to maintain the pH of the reaction system at 8.5-9.

0. After the reaction, centrifugally separate the precipitate, and sequentially wash it with deionized water and anhydrous ethanol for 3-5 times. Dry the precipitate at 110-120℃ for 8-12 h to obtain the mineralized modified nano-silicon carrier.

3. The nanoscale viscosity-reducing and blockage-removing agent according to claim 2, characterized in that: In the step A1, the mass ratio of the nano-silicon dioxide to the Tris-HCl buffer solution is 1:(10-20). The mass concentration of the calcium chloride solution is 5%-8%. The concentration of the sodium dihydrogen phosphate solution is 3%-5%. The mass ratio of the nano-silicon dioxide, the calcium chloride solution and the sodium dihydrogen phosphate solution is 1:(8-12):(5-8).

4. The nanoscale viscosity-reducing and blockage-removing agent according to claim 2, characterized in that: In the step A1, the amount of the tetrabutyl titanate added is 1%-1.5% of the total mass of the calcium chloride solution and the sodium dihydrogen phosphate solution.

5. The nanoscale viscosity-reducing and blockage-removing agent according to claim 1, characterized in that: The cross-linked fluorocarbon surfactant is prepared by taking perfluorooctyl acrylate, N-(2-hydroxyethyl) acrylamide and 2-acryloyloxyethyl isocyanate as the comonomers, by free radical polymerization to obtain a fluorocarbon copolymer precursor containing hydroxyl and isocyanate groups, and by intramolecular dynamic covalent cross-linking reaction.

6. The nanoscale viscosity-reducing and blockage-removing agent according to claim 5, characterized in that, The cross-linked fluorocarbon surfactant is prepared by the following method: B1. Add perfluorooctyl acrylate, N-(2-hydroxyethyl) acrylamide and 2-acryloyloxyethyl isocyanate to ethyl acetate solvent, and then add azobisisobutyronitrile initiator. Polymerize at 70-80℃ for 6-8 h under nitrogen atmosphere to obtain a fluorocarbon copolymer precursor; B2. Dissolve the fluorocarbon copolymer precursor in N,N-dimethylformamide, and add dibutyltin dilaurate catalyst. Heat to 90-100℃, and heat and react for 4-6 h. After the reaction, pour the product into deionized water to precipitate, collect the precipitate by filtration, and vacuum dry to obtain the cross-linked fluorocarbon surfactant.

7. The nanoscale viscosity-reducing and plug-removing agent according to claim 6, characterized in that: In the step B1, the mass ratio of perfluorooctyl acrylate, N-(2-hydroxyethyl) acrylamide, 2-acryloyloxyethyl isocyanate and ethyl acetate solvent is 5:(3-4):(1-2):(20-30).

8. The nanoscale viscosity-reducing and plug-removing agent according to claim 6, characterized in that: In the step B1, the amount of the azobisisobutyronitrile initiator added is 1%-3% of the total mass of the comonomers.

9. The nanoscale viscosity-reducing and plug-removing agent according to claim 6, characterized in that: In the step B2, the mass ratio of the fluorocarbon copolymer precursor to N,N-dimethylformamide is 1: (5-8), and the amount of dibutyltin dilaurate catalyst added is 0.5%-1.2% of the mass of the fluorocarbon copolymer precursor.

10. A preparation method of a nano thickened oil viscosity reducing and plug removing agent, characterized in that, The method comprises the following steps: S1, polyacrylamide is mixed with deionized water, heated to 45-55℃ and stirred for 20-30min to obtain a polyacrylamide aqueous solution, then a mineralized modified nanosilicon carrier and a cross-linked fluorocarbon surfactant are added, heated to 65-75℃, and stirred for 2-3h; S2, after the reaction is completed, the system is cooled to 30-40℃, and benzylpropylisothiazolinone is added, and stirring is continued at a speed of 150-200r / min for 40-60min, and then cooled to room temperature to obtain a nanometer thick oil viscosity reducing and plugging removing agent.

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