A nano-sized heavy oil viscosity reducer and unblocking agent and its preparation method

Abstract

This application relates to the field of petroleum extraction additives technology, specifically disclosing a nano-sized heavy oil viscosity reducer and unblocking agent and its preparation method. The nano-sized heavy oil viscosity reducer and unblocking agent comprises the following raw materials: 10-18 parts of mineralized modified nano-silica carrier, 10-14 parts of cross-linked fluorocarbon surfactant, 0.1-0.3 parts of polyacrylamide, 1-3 parts of benzo[a]isothiazolinone, and 55-75 parts of deionized water. The mineralized modified nano-silica carrier is prepared by growing a hydroxyapatite-titanium dioxide composite shell on its surface through a mineralization process, using nano-silica as the core. This application effectively enhances the long-term stability of the viscosity-reducing and unblocking agent's viscosity-reducing effect under high-temperature and high-salt environments, and comprehensively improves the long-term service stability of the viscosity reducer and unblocking agent in deep oil reservoir environments.

Description

Technical Field

[0001] This application relates to the field of petroleum extraction additives technology, and more specifically, it relates to a nano-thick oil viscosity reducer and unblocking agent and its preparation method. Background Technology

[0002] Nano-sized heavy oil viscosity reducers and unblocking agents are a class of petroleum extraction aids designed based on the unique interfacial and small-size effects of nanomaterials. Their core function is to reduce the viscosity of heavy oil and remove blockages caused by the deposition of heavy oil colloids, asphaltenes, and waxes in reservoir pores through penetration, dispersion, emulsification, or catalytic cracking. This improves reservoir flow conditions and enhances heavy oil recovery. Against the backdrop of increasingly abundant global heavy oil reserves but ever-increasing extraction difficulties, the research and application of highly efficient nano-sized heavy oil viscosity reducers and unblocking agents can not only solve the core problems of "high viscosity, low fluidity, and easy blockage" in heavy oil extraction, but also improve the economics and environmental friendliness of reservoir development, thus having significant industrial application value for ensuring a stable supply of oil and gas resources.

[0003] Several nano-sized heavy oil viscosity reducers and unblocking agents have been disclosed in the prior art. Among them, Chinese patent application CN118027935A discloses a multifunctional nano-sized heavy oil viscosity reducer and unblocking agent, its preparation method, and its application. This viscosity reducer and unblocking agent is composed of the following components by mass percentage: HD-3 nonionic surfactant: 5%-10%; carboxylic acid anionic fluorocarbon surfactant: 10%-30%; water: 60%-70%; polyacrylamide: 0.01%; and modified phenylpropylisothiazolinone: 1%. The multifunctional nano-sized heavy oil viscosity reducer and unblocking agent provided by this technical solution has both viscosity reducing and unblocking functions, which can effectively improve the recovery rate of heavy oil reservoirs.

[0004] However, the aforementioned nano-viscosity reducers and unblocking agents for heavy oil still have significant drawbacks in actual deep heavy oil reservoir development scenarios. Specifically, they exhibit insufficient long-term stability of viscosity reduction effects and short viscosity reduction half-life. The main reasons for this drawback are: surfactant components are prone to hydrolysis or aggregation in the high-temperature and high-salinity environment of deep oil reservoirs, leading to a decrease in their emulsifying and dispersing abilities; and there is a lack of stable synergistic mechanisms among the components, resulting in easy loss of effective ingredients. Actual operating condition tests have verified that in deep oil reservoirs at 140℃ and 30,000 mg / L salinity, the initial viscosity reduction rate of this type of viscosity reducer and unblocking agent can reach over 65%, but after 72 hours of continuous action, the viscosity reduction rate rapidly decreases to below 30%, which is insufficient to meet the continuous viscosity reduction and unblocking requirements during long-term development of deep heavy oil reservoirs. The viscosity reduction half-life of existing products (i.e., the time it takes for the viscosity reduction rate to decrease to 50% of the initial value) is usually less than 48 hours, which cannot match the operational cycle of deep heavy oil reservoir development and limits its widespread application in deep and complex oil reservoirs. Summary of the Invention

[0005] To enhance the long-term stability of the viscosity-reducing and unblocking agent's effect under high temperature and high salinity conditions, this application provides a nano-thick oil viscosity-reducing and unblocking agent and its preparation method.

[0006] The nano-heavy oil viscosity reducer and unblocking agent provided in this application adopts the following technical solution:

[0007] A nano-thick oil viscosity reducer and unblocking agent comprises the following raw materials in parts by weight:

[0008] 10-18 parts of mineralized modified nano-silicon carrier;

[0009] 10-14 parts of cross-linked fluorocarbon surfactant;

[0010] Polyacrylamide 0.1-0.3 parts;

[0011] 1-3 parts of phenylisothiazolinone;

[0012] 55-75 parts deionized water;

[0013] The mineralized modified nano-silicon carrier is prepared by growing a hydroxyapatite-titanium dioxide composite shell on its surface through a mineralization process, with nano-silicon dioxide as the core.

[0014] By adopting the above technical solution, mineralized modified nano-silicon carrier and cross-linked fluorocarbon surfactant are used as the core functional components, and a composite system is constructed in conjunction with polyacrylamide and phenylisothiazolinone, fundamentally overcoming the bottleneck of poor viscosity reduction stability in existing technologies. Its core advantage lies in achieving a dual improvement in the stable loading of active components and resistance to degradation, providing a core guarantee for the long-term stability of the viscosity reduction effect.

[0015] The introduction of mineralized modified nano-silica carriers reconstructs the carrier mechanism of active components, effectively solving the defects of traditional carriers such as weak binding force with surfactants and easy desorption under high temperature and high salt conditions. This carrier uses nano-silica as the core, and the hydroxyapatite-titanium dioxide composite shell grown on the surface not only has extremely strong high temperature resistance and salt erosion resistance, maintaining structural integrity in the harsh environment of deep oil reservoirs, but also achieves strong anchoring of active components through the strong interaction between the abundant polar functional groups of the shell and cross-linked fluorocarbon surfactants, significantly reducing the risk of loss of effective ingredients.

[0016] The design of cross-linked fluorocarbon surfactants solves the problems of easy hydrolysis and aggregation of traditional surfactants at the molecular level. Unlike existing linear surfactants, this surfactant forms a stable spatial network structure through dynamic covalent cross-linking. It retains the excellent interfacial activity of fluorocarbon chains to ensure emulsification and viscosity reduction, while the cross-linking structure enhances the rigidity and resistance to degradation of the molecular chains. It can effectively resist the corrosion of high temperature and high salt environments and avoid the decay of interfacial activity.

[0017] Furthermore, the technical solution of this application achieves synergistic effect of the system by reasonably adjusting the distribution ratio of each component. The introduction of polyacrylamide can form a three-dimensional network structure with the core components through physical entanglement, further locking in the effective components; phenylisothiazolinone can inhibit the destruction of effective components by microbial growth under high temperature environment. Combined with the homogeneous system constructed by deionized water, it effectively enhances the long-term stability of the viscosity-reducing and unblocking agent in high temperature and high salinity environment, comprehensively improves the long-term service stability of the product in deep oil reservoir environment, and ensures that the viscosity-reducing effect continuously matches the production operation cycle.

[0018] Optionally, the mineralized modified nano-silicon support is prepared using the following method:

[0019] A1. Disperse nano-silica in Tris-HCl buffer solution and sonicate for 60-90 min to obtain dispersion A. Add calcium chloride solution and sodium dihydrogen phosphate solution to dispersion A, then add tetrabutyl titanate and stir for 40-60 min to obtain mixture B.

[0020] A2. Place the mixture B in a constant temperature water bath at 35-45℃ and stir for 12-24 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 with deionized water and anhydrous ethanol 3-5 times respectively, and dry it at 110-120℃ for 8-12 hours to obtain the mineralized modified nano-silicon carrier.

[0021] By employing the above-mentioned technical solution, the selection of Tris-HCl buffer solution and the strategy of continuous pH maintenance provide a stable chemical environment for the directional growth of the hydroxyapatite-titanium dioxide composite shell, avoiding uneven shell growth or detachment. The ultrasonic dispersion and segmented heat-preservation reaction process ensures the tight bonding between the nano-silica core and the composite shell, further enhancing the structural stability and active component loading capacity of the carrier. The carrier prepared by this method can stably perform its "anchoring-anti-deterioration" function, providing a reliable carrier guarantee for the long-term stability of the viscosity-reducing system.

[0022] Optionally, the mass ratio of the nano-silica 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 nano-silica, calcium chloride solution, and sodium dihydrogen phosphate solution is 1:(8-12):(5-8).

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] Optionally, the cross-linked fluorocarbon surfactant is prepared by the following method:

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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).

[0032] 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.

[0033] Optionally, in step B1, the amount of the azobisisobutyronitrile initiator added is 1%-3% of the total mass of the comonomer.

[0034] 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.

[0035] Secondly, this application provides a method for preparing a nano-thick oil viscosity reducer and unblocking agent, which adopts the following technical solution:

[0036] A method for preparing a nano-thick oil viscosity reducer and unblocking agent includes the following steps:

[0037] 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.

[0038] 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.

[0039] 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.

[0040] In summary, this application has the following beneficial effects:

[0041] 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.

[0042] 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.

[0043] 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

[0044] The present application will be further described in detail below with reference to the embodiments.

[0045] Preparation example of mineralized modified nano-silicon carrier

[0046] Preparation Example 1

[0047] Mineralized modified nano-silicon supports were prepared using the following method:

[0048] 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.

[0049] 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.

[0050] Preparation Example 2

[0051] Mineralized modified nano-silicon supports were prepared using the following method:

[0052] 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.

[0053] 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.

[0054] Preparation Example 3

[0055] Mineralized modified nano-silicon supports were prepared using the following method:

[0056] 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.

[0057] 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.

[0058] Preparation Example 4

[0059] Mineralized modified nano-silicon supports were prepared using the following method:

[0060] 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.

[0061] 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.

[0062] Preparation example of cross-linked fluorocarbon surfactants

[0063] Preparation Example 5

[0064] Crosslinked fluorocarbon surfactants are prepared using the following method:

[0065] 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.

[0066] 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.

[0067] Preparation Example 6

[0068] Crosslinked fluorocarbon surfactants are prepared using the following method:

[0069] 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.

[0070] 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 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.

[0071] Preparation Example 7

[0072] Crosslinked fluorocarbon surfactants are prepared using the following method:

[0073] 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.

[0074] 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 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.

[0075] Example

[0076] Example 1

[0077] 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.

[0078] A method for preparing a nano-thick oil viscosity reducer and unblocking agent includes the following steps:

[0079] 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.

[0080] 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.

[0081] Example 2

[0082] 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; and the effective solid content of the polyacrylamide is 90%, and the number average molecular weight is 1000W.

[0083] A method for preparing a nano-thick oil viscosity reducer and unblocking agent includes the following steps:

[0084] 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 stir for 2.5 h.

[0085] 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.

[0086] Example 3

[0087] 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.

[0088] A method for preparing a nano-thick oil viscosity reducer and unblocking agent includes the following steps:

[0089] 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.

[0090] 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.

[0091] Table 1. Raw material components and proportions (kg) of the viscosity-reducing and unblocking agents in Examples 1-3

[0092]

[0093] Example 4

[0094] 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.

[0095] Example 5

[0096] 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.

[0097] Example 6

[0098] 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.

[0099] Comparative Example

[0100] Comparative Example 1

[0101] 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".

[0102] Comparative Example 2

[0103] 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.

[0104] Comparative Example 3

[0105] 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.

[0106] Comparative Example 4

[0107] 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.

[0108] Performance testing

[0109] 1. Experimental materials and environmental simulation

[0110] (1) Test oil: The actual crude oil sample from 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).

[0111] (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).

[0112] (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.

[0113] 2. Methods for detecting initial viscosity reduction rate and long-term viscosity reduction rate (72h)

[0114] (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).

[0115] (2) Take the test oil and the working solution 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).

[0116] (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).

[0117] (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).

[0118] 3. Method for detecting viscosity reduction half-life

[0119] (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.

[0120] (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;

[0121] (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".

[0122] The test results are shown in Table 2.

[0123] Table 2 Experimental Results

[0124]

[0125] 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.

[0126] 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.

[0127] 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.

[0128] 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.

[0129] 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-thick oil viscosity reducer and unblocking agent, characterized in that, The raw materials include the following parts by weight: 10-18 parts of mineralized modified nano-silicon carrier; 10-14 parts of cross-linked fluorocarbon surfactant; Polyacrylamide 0.1-0.3 parts; 1-3 parts of phenylisothiazolinone; 55-75 parts deionized water; The mineralized modified nano-silicon carrier is prepared by growing a hydroxyapatite-titanium dioxide composite shell on its surface through a mineralization process, with nano-silica as the core. The preparation method of mineralized modified nano-silica carrier is as follows: A1. Disperse nano-silica in Tris-HCl buffer solution and ultrasonically disperse for 60-90 min to obtain dispersion A. Add calcium chloride solution and sodium dihydrogen phosphate solution to dispersion A, then add tetrabutyl titanate and stir for 40-60 min to obtain mixture B. The mass ratio of nano-silica to Tris-HCl buffer solution is 1:(10-20); the mass concentration of calcium chloride solution is 5%-8%; the concentration of sodium dihydrogen phosphate solution is 3%-5%; nano-silica, calcium chloride solution and sodium dihydrogen phosphate... The mass ratio of the solution is 1:(8-12):(5-8); the amount of tetrabutyl titanate added is 1%-1.5% of the total mass of calcium chloride solution and sodium dihydrogen phosphate solution; A2, place the mixture B in a constant temperature water bath at 35-45℃ and stir for 12-24h. During this period, add Tris-HCl buffer solution every 4h to maintain the pH of the reaction system between 8.5-9.0; after the reaction is completed, centrifuge to separate the precipitate, wash it with deionized water and anhydrous ethanol 3-5 times respectively, and dry it at 110-120℃ for 8-12h to obtain the mineralized modified nano-silicon carrier; The preparation method of cross-linked fluorocarbon surfactant is as follows: B1, perfluorooctyl acrylate, N-(2-hydroxyethyl)acrylamide, and 2-acryloyloxyethyl isocyanate are added to ethyl acetate solvent, and then azobisisobutyronitrile initiator is added. The mixture is polymerized at 70-80℃ for 6-8h under a nitrogen atmosphere to obtain the fluorocarbon copolymer precursor. 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); B2, the fluorocarbon copolymer precursor is dissolved in N,N-dimethylformamide, dibutyltin dilaurate catalyst is added, the temperature is raised to 90-100℃, and the reaction is maintained for 4-6h. After the reaction, the product is poured into deionized water to precipitate, the precipitate is collected by filtration, and the cross-linked fluorocarbon surfactant is obtained after vacuum drying.

2. The nano-thick oil viscosity reducer and unblocking agent according to claim 1, characterized in that: In step B1, the amount of azobisisobutyronitrile initiator added is 1%-3% of the total mass of the comonomer.

3. The nano-thick oil viscosity reducer and unblocking agent according to claim 1, characterized in that: In step B2, the mass ratio of the fluorocarbon copolymer precursor to N,N-dimethylformamide is 1:(5-8); the amount of dibutyltin dilaurate catalyst added is 0.5%-1.2% of the mass of the fluorocarbon copolymer precursor.

4. A method for preparing a nano-thick oil viscosity reducer and deblocking agent, characterized in that, 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 150-200 r / min for 40-60 min. Cool to room temperature to obtain nano-heavy oil viscosity reducer and unblocking agent. The preparation method of mineralized modified nano-silica carrier is as follows: A1. Disperse nano-silica in Tris-HCl buffer solution and ultrasonically disperse for 60-90 min to obtain dispersion A. Add calcium chloride solution and sodium dihydrogen phosphate solution to dispersion A, then add tetrabutyl titanate and stir for 40-60 min to obtain mixture B. The mass ratio of nano-silica to Tris-HCl buffer solution is 1:(10-20); the mass concentration of calcium chloride solution is 5%-8%; the concentration of sodium dihydrogen phosphate solution is 3%-5%; nano-silica, calcium chloride solution and sodium dihydrogen phosphate... The mass ratio of the solution is 1:(8-12):(5-8); the amount of tetrabutyl titanate added is 1%-1.5% of the total mass of calcium chloride solution and sodium dihydrogen phosphate solution; A2, place the mixture B in a constant temperature water bath at 35-45℃ and stir for 12-24h. During this period, add Tris-HCl buffer solution every 4h to maintain the pH of the reaction system between 8.5-9.0; after the reaction is completed, centrifuge to separate the precipitate, wash it with deionized water and anhydrous ethanol 3-5 times respectively, and dry it at 110-120℃ for 8-12h to obtain the mineralized modified nano-silicon carrier; The preparation method of cross-linked fluorocarbon surfactant is as follows: B1, perfluorooctyl acrylate, N-(2-hydroxyethyl)acrylamide, and 2-acryloyloxyethyl isocyanate are added to ethyl acetate solvent, and then azobisisobutyronitrile initiator is added. The mixture is polymerized at 70-80℃ for 6-8h under a nitrogen atmosphere to obtain the fluorocarbon copolymer precursor. 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); B2, the fluorocarbon copolymer precursor is dissolved in N,N-dimethylformamide, dibutyltin dilaurate catalyst is added, the temperature is raised to 90-100℃, and the reaction is maintained for 4-6h. After the reaction, the product is poured into deionized water to precipitate, the precipitate is collected by filtration, and the cross-linked fluorocarbon surfactant is obtained after vacuum drying.

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