Modified high-temperature-resistant filtrate reducer and preparation method thereof

Abstract

The invention provides a modified high-temperature-resistant filtrate reducer and a preparation method thereof, and the preparation method comprises the following steps: (1) adding modified nano calcium silicate, acrylamide, acrylic acid, a hyperbranched monomer, a salt-resistant monomer, a temperature-resistant monomer and an oxidizing agent into water, and uniformly stirring and mixing to obtain a water-phase solution; (2) adding the water-phase solution into the oil-phase solution, fully emulsifying, and adding a reducing agent to initiate a polymerization reaction to obtain a polymerization product emulsion; and (3) adding nano silicon dioxide into the polymerization product emulsion, and initiating a polymerization reaction in the presence of an oxidizing agent and a reducing agent to obtain the modified high-temperature-resistant filtrate reducer. The obtained modified high-temperature-resistant filtrate reducer has excellent filtrate reduction performance under high-temperature and high-salt conditions, specifically, at the temperature of 250 DEG C, the filter loss of composite brine base slurry is smaller than or equal to 10 mL, and the reduction rate of the filter loss of the composite brine base slurry is larger than or equal to 90%.

Description

Technical Field

[0001] This invention relates to the field of oilfield development technology, and in particular to a modified high-temperature resistant filtration reducer and its preparation method. Background Technology

[0002] As oil and gas exploration and development continue to advance into unconventional, deep-earth, and deep-water environments, the probability of encountering complex formations such as high-temperature and high-pressure brine layers is increasing. Drilling fluids face the severe challenge of uncontrolled filtration loss under high-temperature and high-pressure brine layer conditions. Therefore, the salt resistance and high-temperature resistance of drilling fluid filtration reducers are becoming increasingly important.

[0003] However, most current filtration loss reducers will cause the molecular chains to curl and deform under high temperature and high salinity conditions, which will greatly reduce the filtration loss reduction effect. The well wall may become unstable and collapse as a result, causing accidents such as stuck drill bit and wellbore diameter reduction.

[0004] Therefore, there is an urgent need to provide a modified high-temperature resistant filtration loss reducer and its preparation method. Summary of the Invention

[0005] This invention provides a modified high-temperature resistant filtration loss reducing agent and its preparation method, which can solve the problem that the filtration loss reducing effect of existing filtration loss reducing agents deteriorates under high temperature and high salt conditions.

[0006] In a first aspect, the present invention provides a method for preparing a modified high-temperature resistant filtration loss reducing agent, the preparation method comprising the following steps: (1) Add modified nano-calcium silicate, acrylamide, acrylic acid, hyperbranched monomer, salt-resistant monomer, heat-resistant monomer and oxidant to water and stir to obtain an aqueous solution; (2) The aqueous solution is added to the oil solution for emulsification, and a reducing agent is added to initiate the polymerization reaction to obtain a polymer product emulsion; (3) Add nano-silica to the emulsion of the polymer product and initiate the polymerization reaction under the presence of oxidant and reducing agent to obtain the modified high temperature resistant filtration loss reducer.

[0007] Preferably, in step (1), the modified nano-calcium silicate is prepared by the following method: the nano-calcium silicate is prepared into a slurry and its pH value is adjusted to 8.0-8.5, and then a silane coupling agent is added to carry out a polymerization reaction to obtain the modified nano-calcium silicate.

[0008] Preferably, in step (1), the silane coupling agent is 3-(2,3-epoxypropoxy)propyltrimethoxysilane.

[0009] Preferably, the mass ratio of the nano-calcium silicate to the silane coupling agent is (10~15):(3~10).

[0010] Preferably, the polymerization reaction is carried out under a nitrogen atmosphere, at a temperature of 40-50°C, for a time of 3-4 hours.

[0011] Preferably, in step (1), the hyperbranched monomer is pentaerythritol triacrylate; The salt-resistant monomer is one or both of sodium 2-acrylamido-2-methylpropanesulfonate and sodium p-styrenesulfonate. The heat-resistant monomer is one or both of ethyl 2-phenylacrylate and methacrylamide ethyl ethylene urea.

[0012] Preferably, in step (1), the modified nano-calcium silicate is 5-10 parts by mass, acrylamide is 150-170 parts, acrylic acid is 30-40 parts, hyperbranched monomer is 20-40 parts, salt-resistant monomer is 30-50 parts, heat-resistant monomer is 5-10 parts, and water is 300-500 parts.

[0013] More preferably, in step (1), the pH value of the aqueous solution is 6.5-6.8.

[0014] Preferably, in step (2), the oil phase solution is obtained by mixing white oil and an emulsifier; wherein the emulsifier is one or more of Tween 81, OP-10, and Span 80.

[0015] Preferably, in step (1), the white oil is 220-260 parts by mass and the emulsifier is 20-30 parts.

[0016] Preferably, in step (2), the mass ratio of the oil phase solution to the aqueous phase solution is (24~29):(54~82).

[0017] Preferably, in step (2), the polymerization reaction temperature is 15~18℃ and the time is 2~3h.

[0018] Preferably, in step (3), the amount of nano-silica is 15 to 20 parts by mass.

[0019] Preferably, in step (3), the polymerization reaction temperature is 15~18℃ and the time is 2~3h.

[0020] Preferably, the oxidant is one or two of potassium persulfate and cumene hydroperoxide; the reducing agent is one or two of sodium sulfite and sodium metabisulfite.

[0021] Preferably, the oxidant is 0.2 to 0.8 parts by mass and the reducing agent is 0.3 to 1.0 parts by mass.

[0022] Preferably, in step (3), after the polymerization reaction, a step of adding a phase inversion agent is further included; wherein the phase inversion agent is one or both of hexaethylene glycol dodecyl ether and octylphenol polyoxyethylene ether.

[0023] Secondly, embodiments of the present invention also provide a modified high-temperature resistant filtration loss reducing agent, which is prepared by any of the preparation methods described in the first aspect above.

[0024] Compared with the prior art, the present invention has at least the following beneficial effects: (1) In this invention, during the preparation of the filtration loss reducer, the nano-calcium silicate is modified beforehand and then copolymerized with various functional monomers (acrylamide, acrylic acid, salt-resistant monomer, heat-resistant monomer and hyperbranched monomer) to prepare a modified high-temperature resistant filtration loss reducer. During use, the polymer backbone of the filtration loss reducer is strongly adsorbed onto the well wall and clay particles through amide groups to form an initial filter cake. The modified nano-calcium silicate particles can not only effectively block the micropores in the formation, but the active silicate ions on their surface can also react with calcium and magnesium ions or clay minerals in the formation. The polymer undergoes a cementation reaction to form a dense, tough, and low-permeability high-quality filter cake, thereby significantly reducing filtration loss under high temperature and high pressure and effectively preventing formation hydration expansion and wellbore instability. At the same time, the hyperbranched monomer has a highly branched three-dimensional structure and a large number of modifiable end groups, which endow the polymer with a unique three-dimensional network structure. This not only effectively improves the shear dilution and leveling properties of drilling fluid, but also further enhances the filtration loss reduction performance of the entire polymer network under high temperature and high salt conditions through synergistic effects with temperature- and salt-resistant monomers and modified nano-calcium silicate. (2) In this invention, by further introducing nano-silica, it can interact with the active groups on the copolymer molecular chain to form a micro-crosslinked structure. This structure can effectively restrict the thermal motion of the polymer molecular chain at high temperature, so that it can maintain the liquid phase viscosity of the drilling fluid in a high temperature and high pressure environment, thereby reducing the filtration loss. In addition, the large amount of Si-OH carried by nano-silica can undergo a condensation reaction with Si-OH on the clay surface, producing a strong adsorption effect, thereby increasing the adsorption strength of the polymer on the clay surface, making the hydration film on the surface of clay particles thicker, increasing the repulsion of the hydration film, effectively preventing the aggregation between clay particles, which is conducive to maintaining a reasonable particle size distribution in the drilling fluid. Finally, a denser mud cake with lower permeability is formed on the well wall, thereby further improving the filtration loss reduction performance. (3) The modified high-temperature resistant filtration loss reducer prepared in this invention has excellent filtration loss reduction performance under high temperature and high salt conditions. Specifically, at a temperature of 250℃, the filtration loss of the composite salt water-based slurry is ≤10mL and the filtration loss reduction rate of the composite salt water-based slurry is ≥90%. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] This invention provides a method for preparing a modified high-temperature resistant filtration loss reducing agent, the method comprising the following steps: (1) Add modified nano-calcium silicate, acrylamide, acrylic acid, hyperbranched monomer, salt-resistant monomer, heat-resistant monomer and oxidant to water and stir to obtain an aqueous solution; (2) The aqueous solution is added to the oil solution for emulsification, and a reducing agent is added to initiate the polymerization reaction to obtain a polymer product emulsion; (3) Add nano-silica to the emulsion of the polymer product and initiate the polymerization reaction under the presence of oxidant and reducing agent to obtain the modified high temperature resistant filtration loss reducer.

[0027] In this embodiment of the invention, during the preparation of the filtration loss reducer, nano-calcium silicate is modified beforehand and then copolymerized with various functional monomers (acrylamide, acrylic acid, salt-resistant monomers, heat-resistant monomers, and hyperbranched monomers) to prepare a modified high-temperature resistant filtration loss reducer. During use, the polymer backbone of the filtration loss reducer is strongly adsorbed onto the well wall and clay particles through amide groups, forming an initial filter cake. The modified nano-calcium silicate particles can not only effectively seal the micropores in the formation, but the active silicate ions on their surface can also react with calcium and magnesium ions or clay minerals in the formation. The polymer undergoes a cementation reaction to form a dense, tough, and low-permeability high-quality filter cake, thereby significantly reducing filtration loss under high temperature and high pressure and effectively preventing formation hydration expansion and wellbore instability. At the same time, the hyperbranched monomers have a highly branched three-dimensional structure and a large number of modifiable end groups, which endow the polymer with a unique three-dimensional network structure. This not only effectively improves the shear dilution and leveling properties of drilling fluid, but also further enhances the filtration loss reduction performance of the entire polymer network under high temperature and high salt conditions through synergistic effects with temperature- and salt-resistant monomers and modified nano-calcium silicate.

[0028] By further introducing nano-silica, it can interact with the active groups on the copolymer molecular chains to form a micro-crosslinked structure. This structure can effectively restrict the thermal motion of the polymer molecular chains at high temperatures, allowing it to maintain the liquid phase viscosity of the drilling fluid even in high-temperature and high-pressure environments, thereby reducing filtration loss. Furthermore, the large amount of Si-OH carried by the nano-silica can undergo a condensation reaction with the Si-OH on the clay surface, producing a strong adsorption effect. This increases the adsorption strength of the polymer on the clay surface, thickens the hydration film on the clay particle surface, and increases the repulsive force of the hydration film, effectively preventing the aggregation between clay particles. This helps maintain a reasonable particle size distribution in the drilling fluid, ultimately forming a denser mud cake with lower permeability on the well wall, thereby further improving the filtration loss reduction performance.

[0029] According to some preferred embodiments, in step (1), the modified nano-calcium silicate is prepared by the following method: the nano-calcium silicate is prepared into a slurry and its pH value is adjusted to 8.0-8.5, and then a silane coupling agent is added to carry out a polymerization reaction to obtain the modified nano-calcium silicate; the silane coupling agent is 3-(2,3-epoxypropoxy)propyltrimethoxysilane.

[0030] According to some preferred embodiments, the mass ratio of the nano-calcium silicate to the silane coupling agent is (10~15):(3~10) (for example, it can be 10:3, 10:5, 10:10, 12:3, 12:5, 12:10, 15:3, 15:5 or 15:10); the polymerization reaction is carried out under a nitrogen atmosphere, the temperature of the polymerization reaction is 40~50℃ (for example, it can be 40℃, 42℃, 45℃, 48℃ or 50℃), and the time is 3~4h (for example, it can be 3h, 3.5h or 4h).

[0031] In this embodiment of the invention, nano-calcium silicate is first added to thionyl chloride and mixed to prepare a slurry of a certain mass concentration (e.g., 10%). Then, the pH of the slurry is adjusted to alkaline using sodium hydroxide. After nitrogen deoxygenation, a certain amount of the above-mentioned silane coupling agent is added to carry out a polycondensation reaction to form modified nano-calcium silicate. This allows the modified nano-calcium silicate to not only be added through physical doping, but also to participate in the copolymerization reaction as a functional monomer and be directly bonded to the three-dimensional network structure of the polymer. This makes the nano-calcium silicate more stable in the polymer and less likely to fall off in high temperature, high speed shear or solvent environment, thereby exerting the blocking effect of nano-calcium silicate for a long time and stably.

[0032] According to some preferred embodiments, in step (1), the hyperbranched monomer is pentaerythritol triacrylate; the salt-resistant monomer is one or two of sodium 2-acrylamido-2-methylpropanesulfonate and sodium p-styrenesulfonate; and the heat-resistant monomer is one or two of ethyl 2-phenylacrylate and methacrylamidoethyl ethylene urea.

[0033] In this embodiment of the invention, by introducing heat-resistant monomers and salt-resistant monomers during the polymerization reaction, the heat-resistant monomers can enhance the rigidity of the polymer skeleton, which is beneficial to inhibiting molecular chain breakage and coiling degradation at high temperatures. The salt-resistant monomers have strong hydration ability with sulfonic acid groups and are not sensitive to high-valence cations, which helps to ensure that the filtration loss reducer product can still maintain excellent hydration and stretching ability and filtration loss control performance in drilling fluid systems with high salinity and high calcium and magnesium ion concentrations. At the same time, the introduced hyperbranched monomers have highly branched three-dimensional structures and contain a large number of modifiable end groups. After participating in polymerization, they can endow the polymer with a unique three-dimensional network structure, which can not only effectively improve the shear dilution and leveling properties of drilling fluid, but also further enhance the network structure and sealing layer strength of the entire polymer system through synergistic effect with modified nano-calcium silicate.

[0034] According to some preferred embodiments, in step (1), by mass parts, the modified nano-calcium silicate is 5-10 parts (e.g., 5, 6, 7, 8, 9, or 10 parts), acrylamide is 150-170 parts (e.g., 150, 155, 160, 165, or 170 parts), acrylic acid is 30-40 parts (e.g., 30, 32, 35, 38, or 40 parts), and hyperbranched monomer is 20-40 parts (e.g., ...). For example, the amount can be 20 parts, 25 parts, 30 parts, 35 parts or 40 parts; the amount of salt-resistant monomer is 30 to 50 parts (for example, 30 parts, 35 parts, 40 parts, 45 parts or 50 parts); the amount of heat-resistant monomer is 5 to 10 parts (for example, 5 parts, 6 parts, 7 parts, 8 parts, 9 parts or 10 parts); and the amount of water is 300 to 500 parts (for example, 300 parts, 350 parts, 400 parts, 450 parts or 500 parts); the pH value of the aqueous phase solution is 6.5-6.8.

[0035] In this invention, by synergistically controlling the content of each monomer, the monomers complement each other, ultimately resulting in a filtration loss reducer product that simultaneously possesses extremely low filtration loss and temperature and salt resistance, effectively addressing the drilling challenges of complex formations. Experiments have confirmed that any imbalance in the content of any component will disrupt this synergistic effect, leading to performance degradation. For example, if the content of salt-resistant or temperature-resistant monomers is too low, the filtration loss reducer product will have insufficient salt and temperature resistance; while excessively high content will result in excessive cost and may affect solubility due to the introduction of too many hydrophobic structures. Furthermore, if the content of hyperbranched monomers is too low, it will hinder the improvement of drilling fluid shear dilution and leveling properties, and will not be able to form a synergistic effect with modified nano-calcium silicate to further enhance the network structure and sealing layer strength of the entire polymer system; while excessively high content can easily cause excessive polymer cross-linking, resulting in poor solubility of the filtration loss reducer product. Meanwhile, if the content of modified nano-calcium silicate is too low, the nano-blocking and reinforcing effects will not be obvious; however, if the content is too high, it will easily cause nanoparticle agglomeration, which will not only cause uneven dispersion in the polymer and form defects, but also deteriorate the rheological properties of the drilling fluid.

[0036] According to some preferred embodiments, in step (2), the oil phase solution is obtained by mixing white oil and an emulsifier; wherein the emulsifier is one or more of Tween 81, OP-10, and Span 80; by mass parts, the white oil is 220-260 parts (for example, 220 parts, 240 parts, 250 parts or 260 parts), and the emulsifier is 20-30 parts (for example, 20 parts, 25 parts or 30 parts).

[0037] According to some preferred embodiments, in step (2), the mass ratio of the oil phase solution to the aqueous phase solution is (24~29):(54~82) (for example, it can be 24:54, 24:60, 24:70, 24:82, 25:54, 25:60, 25:70, 25:82, 29:54, 29:60, 29:70 or 24:82); the polymerization temperature is 15~18℃ (for example, it can be 15℃, 16℃, 17℃ or 18℃), and the time is 2~3h (for example, it can be 2h, 2.5h or 3h).

[0038] According to some preferred embodiments, in step (3), the amount of nano-silica is 15 to 20 parts by mass (e.g., 15, 16, 17, 18, 19 or 20 parts); the mass ratio of nano-silica to modified nano-calcium silicate is preferably (1 to 2): (3 to 4); the temperature of the polymerization reaction is 15 to 18°C ​​(e.g., 15°C, 16°C, 17°C or 18°C), and the time is 2 to 3 hours (e.g., 2 hours, 2.5 hours or 3 hours).

[0039] In this embodiment of the invention, by further reacting nano-silica with the above-mentioned polymer product emulsion under a nitrogen atmosphere, the nano-silica and the polymer product form a micro-crosslinked structure. This structure can restrict the thermal motion of polymer molecular chains at high temperatures, effectively preventing their degradation and failure, so that the final filtration loss reducer product maintains good filtration loss reduction performance under high temperature and high pressure environment. Furthermore, the nano-silica can synergistically work with the modified nano-calcium silicate to form a dense, tough, and low-permeability filter cake on the well wall, thereby greatly reducing filtration loss. The experiments of this invention have confirmed that if the content of nano-silica is too low, it will not only be detrimental to the formation of a continuous micro-crosslinked network with the polymer product, thus limiting the improvement of the temperature resistance of the filtration loss reducer, but also will not form an effective gradation synergistic effect with the modified nano-calcium silicate, thereby failing to significantly improve the filtration loss reduction performance of the filtration loss reducer product at high temperatures. On the other hand, if the content of nano-silica is too high, it will not only cause the nano-silica particles to agglomerate and form large aggregates, but also lead to excessive crosslinking of the polymer network, resulting in poor solubility and slowed hydration rate of the filtration loss reducer product.

[0040] It should be noted that in the embodiments of the present invention, the nano-calcium silicate can be prepared by the preparation method in the prior art, and the particle size can be selected as 50-80nm, and the particle size of the nano-silica is 1~100nm.

[0041] According to some preferred embodiments, the oxidant is one or two of potassium persulfate and cumene hydroperoxide; the reducing agent is one or two of sodium sulfite and sodium metabisulfite; by mass parts, the oxidant is 0.2 to 0.8 parts (for example, 0.2 parts, 0.5 parts or 0.8 parts), and the reducing agent is 0.3 to 1.0 parts (for example, 0.3 parts, 0.5 parts, 0.8 parts or 1 part).

[0042] According to some preferred embodiments, in step (3), after the polymerization reaction, a step of adding a phase inversion agent is also included; wherein the phase inversion agent is one or two of hexaethylene glycol dodecyl ether and octylphenol polyoxyethylene ether.

[0043] In this embodiment of the invention, after the polymerization reaction, 19 to 23 parts of a phase-inverting agent are added to transform the polymer emulsion from an oil-in-water type to an oil-in-water type, ultimately obtaining a filtration loss reducer product that can be rapidly dispersed and dissolved in an aqueous system.

[0044] This invention also provides a modified high-temperature resistant filtration loss reducer obtained by any of the above preparation methods.

[0045] The modified high-temperature resistant filtration loss reducer prepared in the embodiments of the present invention has excellent filtration loss reduction performance under high temperature and high salt conditions. Specifically, at a temperature of 250°C, the filtration loss of the composite brine-based slurry is ≤10mL, and the filtration loss reduction rate of the composite brine-based slurry is ≥90%.

[0046] To more clearly illustrate the technical solution and advantages of the present invention, the following examples provide a detailed description of a modified high-temperature resistant filtration loss reducer and its preparation method; in the following examples, the content of each component is expressed in parts by mass.

[0047] Example 1: (1) Preparation of modified nano-calcium silicate: 13 parts of nano-calcium silicate were dissolved in 130 parts of thionyl chloride to prepare a slurry with a mass concentration of 10%. The pH value of the slurry was adjusted to 8.5 with sodium hydroxide. Then it was transferred to a reaction vessel, and nitrogen gas was passed through to remove oxygen for 30 min. The temperature was raised to 45℃, and 8 parts of silane coupling agent (3-(2,3-epoxypropoxy)propyltrimethoxysilane) were added. The polymerization reaction was carried out for 3 h. After the reaction was completed, the reaction product was washed with 70 parts of ethanol and dried to obtain modified nano-calcium silicate. Eight parts of modified nano-calcium silicate, 160 parts of acrylamide, 35 parts of acrylic acid, 30 parts of hyperbranched monomer (pentaerythritol triacrylate), 40 parts of salt-resistant monomer (sodium 2-acrylamide-2-methylpropanesulfonate), 8 parts of heat-resistant monomer (ethyl 2-phenylacrylate), and 0.3 parts of oxidant (potassium persulfate) were dissolved in 400 parts of water and stirred until homogeneous. The pH of the mixed solution was then adjusted to 6.6 with sodium hydroxide to obtain an aqueous solution. (2) Mix 230 parts of white oil and 25 parts of emulsifier (Span-80) evenly to obtain an oil phase solution; add the aqueous phase solution to the oil phase solution and fully emulsify it, then transfer it to the reactor, purge with nitrogen for 30 min, add 0.3 parts of reducing agent (sodium sulfite) and initiate the polymerization reaction at 15℃ for 3 h to obtain the polymerization product emulsion; (3) Add 18 parts of nano silica to the emulsion of the polymerization product and mix well. Then add 0.3 parts of oxidant (potassium persulfate) and stir evenly. Purge with nitrogen for 30 min to remove oxygen. Add 0.3 parts of reducing agent (sodium sulfite) and initiate the polymerization reaction at 15°C for 3 h. After the reaction is complete, add 20 parts of phase inversion agent (octylphenol polyoxyethylene ether) and mix well to obtain the modified high temperature resistant filtration loss reducer.

[0048] Example 2: (1) Preparation of modified nano-calcium silicate: 13 parts of nano-calcium silicate were dissolved in 130 parts of thionyl chloride to prepare a slurry with a mass concentration of 10%. The pH value of the slurry was adjusted to 8.5 with sodium hydroxide. Then it was transferred to a reaction vessel, and nitrogen gas was passed through to remove oxygen for 30 min. The temperature was raised to 45℃, and 8 parts of silane coupling agent (3-(2,3-epoxypropoxy)propyltrimethoxysilane) were added. The polymerization reaction was carried out for 3 h. After the reaction was completed, the reaction product was washed with 70 parts of ethanol and dried to obtain modified nano-calcium silicate. Nine parts of modified nano-calcium silicate, 170 parts of acrylamide, 30 parts of acrylic acid, 25 parts of hyperbranched monomer (pentaerythritol triacrylate), 40 parts of salt-resistant monomer (sodium 2-acrylamide-2-methylpropanesulfonate), 7 parts of heat-resistant monomer (ethyl 2-phenylacrylate), and 0.3 parts of oxidant (potassium persulfate) were dissolved in 400 parts of water and stirred until homogeneous. The pH of the mixed solution was then adjusted to 6.6 with sodium hydroxide to obtain an aqueous solution. (2) Mix 230 parts of white oil and 25 parts of emulsifier (Span-80) evenly to obtain an oil phase solution; add the aqueous phase solution to the oil phase solution and fully emulsify it, then transfer it to the reactor, purge with nitrogen for 30 min, add 0.3 parts of reducing agent (sodium sulfite) and initiate the polymerization reaction at 15℃ for 3 h to obtain the polymerization product emulsion; (3) Add 16 parts of nano silica to the emulsion of the polymerization product and mix well. Then add 0.3 parts of oxidant (potassium persulfate) and stir evenly. Purge with nitrogen for 30 min to remove oxygen. Add 0.3 parts of reducing agent (sodium sulfite) and initiate the polymerization reaction at 15°C for 3 h. After the reaction is complete, add 20 parts of phase inversion agent (octylphenol polyoxyethylene ether) and mix well to obtain the modified high temperature resistant filtration loss reducer.

[0049] Example 3: (1) Preparation of modified nano-calcium silicate: 13 parts of nano-calcium silicate were dissolved in 130 parts of thionyl chloride to prepare a slurry with a mass concentration of 10%. The pH value of the slurry was adjusted to 8.5 with sodium hydroxide. Then it was transferred to a reaction vessel, and nitrogen gas was passed through to remove oxygen for 30 min. The temperature was raised to 45℃, and 9 parts of silane coupling agent (3-(2,3-epoxypropoxy)propyltrimethoxysilane) were added. The polymerization reaction was carried out for 3 h. After the reaction was completed, the reaction product was washed with 70 parts of ethanol and dried to obtain modified nano-calcium silicate. Eight parts of modified nano-calcium silicate, 160 parts of acrylamide, 35 parts of acrylic acid, 35 parts of hyperbranched monomer (pentaerythritol triacrylate), 38 parts of salt-resistant monomer (sodium 2-acrylamide-2-methylpropanesulfonate), 8 parts of heat-resistant monomer (methacrylamide ethyl ethylene urea), and 0.3 parts of oxidant (potassium persulfate) were dissolved in 420 parts of water and stirred until homogeneous. The pH of the mixed solution was then adjusted to 6.6 with sodium hydroxide to obtain an aqueous solution. (2) Mix 240 parts of white oil and 25 parts of emulsifier (OP-10) evenly to obtain an oil phase solution; add the aqueous phase solution to the oil phase solution and fully emulsify it, then transfer it to the reaction vessel, purge with nitrogen for 30 min, add 0.3 parts of reducing agent (sodium sulfite) and initiate the polymerization reaction at 15℃ for 3 h to obtain the polymerization product emulsion; (3) Add 16 parts of nano silica to the emulsion of the polymerization product and mix well. Then add 0.3 parts of oxidant (potassium persulfate) and stir evenly. Purge with nitrogen for 30 min to remove oxygen. Add 0.3 parts of reducing agent (sodium sulfite) and initiate the polymerization reaction at 15°C for 3 h. After the reaction is complete, add 20 parts of phase inversion agent (hexaethylene glycol dodecyl ether) and mix well to obtain the modified high temperature resistant filtration loss reducer.

[0050] Example 4: (1) Preparation of modified nano-calcium silicate: 13 parts of nano-calcium silicate were dissolved in 130 parts of thionyl chloride to prepare a slurry with a mass concentration of 10%. The pH value of the slurry was adjusted to 8.5 with sodium hydroxide. Then it was transferred to a reaction vessel, and nitrogen gas was passed through to remove oxygen for 30 min. The temperature was raised to 45℃, and 9 parts of silane coupling agent (3-(2,3-epoxypropoxy)propyltrimethoxysilane) were added. The polymerization reaction was carried out for 3 h. After the reaction was completed, the reaction product was washed with 70 parts of ethanol and dried to obtain modified nano-calcium silicate. 10 parts of modified nano-calcium silicate, 165 parts of acrylamide, 35 parts of acrylic acid, 32 parts of hyperbranched monomer (pentaerythritol triacrylate), 45 parts of salt-resistant monomer (sodium 2-acrylamide-2-methylpropanesulfonate), 6 parts of heat-resistant monomer (ethyl 2-phenylacrylate), and 0.3 parts of oxidant (potassium persulfate) were dissolved in 430 parts of water and stirred until homogeneous. The pH of the mixed solution was then adjusted to 6.6 with sodium hydroxide to obtain an aqueous solution. (2) Mix 240 parts of white oil and 27 parts of emulsifier (Tween 81) evenly to obtain an oil phase solution; add the aqueous phase solution to the oil phase solution and emulsify it fully, then transfer it to the reactor. After purging with nitrogen for 30 minutes, add 0.3 parts of reducing agent (sodium sulfite) and initiate the polymerization reaction at 15°C for 3 hours to obtain the polymerization product emulsion. (3) Add 16 parts of nano silica to the emulsion of the polymerization product and mix well. Then add 0.3 parts of oxidant (potassium persulfate) and stir evenly. Purge with nitrogen for 30 min to remove oxygen. Add 0.3 parts of reducing agent (sodium sulfite) and initiate the polymerization reaction at 15°C for 3 h. After the reaction is complete, add 20 parts of phase inversion agent (octylphenol polyoxyethylene ether) and mix well to obtain the modified high temperature resistant filtration loss reducer.

[0051] Example 5: Example 5 is basically the same as Example 1, except that in step (1), the amount of modified nano-calcium silicate is 15 parts.

[0052] Example 6: Example 6 is basically the same as Example 1, except that in step (1), the hyperbranched monomer is 45 parts.

[0053] Example 7: Example 7 is basically the same as Example 1, except that in step (3), the amount of nano-silica is 25 parts.

[0054] Comparative Example 1 Comparative Example 1 is basically the same as Example 1, except that: in step (1), no modified nano-calcium silicate is added; 160 parts of acrylamide, 35 parts of acrylic acid, 30 parts of hyperbranched monomer (pentaerythritol triacrylate), 40 parts of salt-resistant monomer (sodium 2-acrylamide-2-methylpropanesulfonate), 8 parts of heat-resistant monomer (ethyl 2-phenylacrylate) and 0.3 parts of oxidant (potassium persulfate) are dissolved in 408 parts of water and stirred until well mixed. Then, the pH of the mixed solution is adjusted to 6.6 with sodium hydroxide to obtain an aqueous solution.

[0055] Comparative Example 2 Comparative Example 2 is basically the same as Example 1, except that: in step (1), no hyperbranched monomer is added; 8 parts of modified nano calcium silicate, 160 parts of acrylamide, 35 parts of acrylic acid, 40 parts of salt-resistant monomer (sodium 2-acrylamide-2-methylpropanesulfonate), 8 parts of heat-resistant monomer (ethyl 2-phenylacrylate) and 0.3 parts of oxidant (potassium persulfate) are dissolved in 430 parts of water and stirred until well mixed. Then, the pH of the mixed solution is adjusted to 6.6 with sodium hydroxide to obtain an aqueous solution.

[0056] Comparative Example 3 Comparative Example 3 is basically the same as Example 1, except that step (3) is removed, that is, 20 parts of phase inversion agent (octylphenol polyoxyethylene ether) are added to the emulsion of the polymer product obtained after the reaction in step (2) and mixed to obtain a modified high temperature resistant filtration loss reducer.

[0057] Comparative Example 4 Comparative Example 4 is basically the same as Example 1, except that in step (1), the nano-calcium silicate is not modified. Instead, 8 parts of nano-calcium silicate, 160 parts of acrylamide, 35 parts of acrylic acid, 30 parts of hyperbranched monomer (pentaerythritol triacrylate), 40 parts of salt-resistant monomer (sodium 2-acrylamide-2-methylpropanesulfonate), 8 parts of heat-resistant monomer (ethyl 2-phenylacrylate) and 0.3 parts of oxidant (potassium persulfate) are dissolved in 400 parts of water and stirred until well mixed. Then, the pH of the mixed solution is adjusted to 6.6 with sodium hydroxide to obtain an aqueous solution.

[0058] Comparative Example 5 Comparative Example 5 is basically the same as Example 1, except that in step (1), 13 parts of nano-calcium carbonate were dissolved in 130 parts of thionyl chloride to prepare a slurry with a mass concentration of 10%, and the pH value of the slurry was adjusted to 8.5 with sodium hydroxide. Then it was transferred to a reaction vessel, purged with nitrogen for 30 min to remove oxygen, heated to 45°C, and 8 parts of silane coupling agent (3-(2,3-epoxypropoxy)propyltrimethoxysilane) were added. The polymerization reaction was carried out for 3 h. After the reaction was completed, the reaction product was treated with 70 The modified nano-calcium carbonate was obtained by washing with ethanol and drying. 8 parts of the modified nano-calcium carbonate, 160 parts of acrylamide, 35 parts of acrylic acid, 30 parts of hyperbranched monomer (pentaerythritol triacrylate), 40 parts of salt-resistant monomer (sodium 2-acrylamide-2-methylpropanesulfonate), 8 parts of heat-resistant monomer (ethyl 2-phenylacrylate), and 0.3 parts of oxidant (potassium persulfate) were dissolved in 400 parts of water and stirred until homogeneous. The pH of the mixed solution was then adjusted to 6.6 with sodium hydroxide to obtain an aqueous solution.

[0059] The apparent viscosity, stability, and dispersibility of the modified high-temperature resistant filtration loss reducing agent samples provided in the examples and comparative examples were compared and tested. The test results of the performance indicators are shown in Table 1 below: The specific testing method is as follows: (1) Test of filtration loss and filtration vector reduction rate of composite brine-based slurry: Preparation of composite brine-based slurry: Measure 400 mL of distilled water into a cup, add 18.0 g of sodium chloride, 2.0 g of anhydrous calcium chloride, and 5.2 g of magnesium chloride. After they dissolve, add 60.0 g of slurry conforming to SY / T5490. -2016 standard sodium bentonite and 3.6g anhydrous sodium carbonate; stir at high speed (11000r / min) for 20min, stopping at least twice to scrape off the clay adhering to the container wall, and cure in a sealed container at 25±3℃ for 24h to prepare a composite brine-based slurry. Determination of filtration loss of base slurry: Stir the cured composite brine base slurry at high speed for 20 min, place it in a furnace at a set temperature of 240℃ for aging for 16 h, then cool it to room temperature (25℃), and stir it at high speed (11000 r / min) for 5 min. Measure the filtration loss according to GB / T 16783.1. The filtration loss should be 80-110 mL. Otherwise, adjust the amount of sodium bentonite added. Determination of filtration loss after high-temperature aging: Add 12.0 g of filtration loss reducer sample to the composite brine-based slurry, stir at high speed (11000 r / min) for 20 min, place it in an oven at a set temperature of 240℃ for aging for 16 h, then cool to room temperature (25℃), stir at high speed for 5 min, and determine the pressure filtration loss according to GB / T16783.1. The reduction rate of filtrate loss in composite brine-based slurry was determined using the following formula: F = (F0 - F1) / F0 × 100% In the formula: F—reduction rate of filtrate loss of composite brine-based slurry, %; F0—filtrate loss of base slurry, in milliliters (mL); F1—filtrate loss of sample slurry, in milliliters (mL).

[0060] Table 1 As can be seen from the above embodiments, the modified high-temperature resistant filtration loss reducer prepared by the present invention not only has excellent temperature resistance, salt resistance and shear resistance, but also has excellent filtration loss reduction performance. At a temperature of 240℃, the filtration loss of the composite salt water-based slurry is ≤8mL, and the filtration loss reduction rate of the composite salt water-based slurry is ≥91%.

[0061] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a modified high-temperature resistant filtration loss reducing agent, characterized in that, The preparation method includes the following steps: (1) Add modified nano-calcium silicate, acrylamide, acrylic acid, hyperbranched monomer, salt-resistant monomer, heat-resistant monomer and oxidant to water and stir to obtain an aqueous solution; (2) The aqueous solution is added to the oil solution for emulsification, and a reducing agent is added to initiate the polymerization reaction to obtain a polymer product emulsion; (3) Add nano-silica to the emulsion of the polymer product and initiate the polymerization reaction under the presence of oxidant and reducing agent to obtain the modified high temperature resistant filtration loss reducer.

2. The preparation method according to claim 1, characterized in that, In step (1), the modified nano-calcium silicate is prepared by the following method: nano-calcium silicate is prepared into a slurry and its pH value is adjusted to 8.0-8.5, and then a silane coupling agent is added to carry out a polymerization reaction to obtain the modified nano-calcium silicate; Preferably, the silane coupling agent is 3-(2,3-epoxypropoxy)propyltrimethoxysilane.

3. The preparation method according to claim 2, characterized in that, The mass ratio of the nano-calcium silicate to the silane coupling agent is (10~15):(3~10); and / or The polymerization reaction is carried out under a nitrogen atmosphere at a temperature of 40-50°C for 3-4 hours.

4. The preparation method according to claim 1, characterized in that, In step (1), the hyperbranched monomer is pentaerythritol triacrylate; The salt-resistant monomer is one or both of sodium 2-acrylamido-2-methylpropanesulfonate and sodium p-styrenesulfonate. The heat-resistant monomer is one or both of ethyl 2-phenylacrylate and methacrylamide ethyl ethylene urea.

5. The preparation method according to claim 1, characterized in that, In step (1), by mass parts, the modified nano-calcium silicate is 5-10 parts, acrylamide is 150-170 parts, acrylic acid is 30-40 parts, hyperbranched monomer is 20-40 parts, salt-resistant monomer is 30-50 parts, heat-resistant monomer is 5-10 parts, and water is 300-500 parts; and / or The pH value of the aqueous solution is 6.5-6.

8.

6. The preparation method according to claim 1, characterized in that, In step (2), the oil phase solution is obtained by mixing white oil and an emulsifier; wherein the emulsifier is one or more of Tween 81, OP-10, and Span 80; By weight, the white oil is 220-260 parts and the emulsifier is 20-30 parts.

7. The preparation method according to claim 1, characterized in that, In step (2), the mass ratio of the oil phase solution to the aqueous phase solution is (24~29):(54~82); and / or The polymerization reaction is carried out at a temperature of 15-18℃ for 2-3 hours.

8. The preparation method according to claim 1, characterized in that, In step (3), the amount of nano-silica is 15-20 parts by mass; and / or The polymerization reaction is carried out at a temperature of 15-18℃ for 2-3 hours.

9. The preparation method according to any one of claims 1 to 8, characterized in that, The oxidizing agent is one or two of potassium persulfate and cumene hydroperoxide; the reducing agent is one or two of sodium sulfite and sodium metabisulfite. By mass, the oxidant comprises 0.2 to 0.8 parts, and the reducing agent comprises 0.3 to 1.0 parts; and / or In step (3), after the polymerization reaction, a phase inversion agent is added; wherein the phase inversion agent is one or both of hexaethylene glycol dodecyl ether and octylphenol polyoxyethylene ether.

10. A modified high-temperature resistant filtration loss reducing agent, characterized in that, It is prepared by any one of claims 1 to 9.

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