A modified silica plugging agent based on multiple cross-linking and a preparation method and application thereof

Abstract

The present application belongs to the technical field of water plugging and profile control, and particularly relates to a modified silica plugging agent based on multiple cross-linking, a preparation method and application thereof. The modified silica plugging agent based on multiple cross-linking is a PAM-AMPS@SiO2 composite microsphere emulsion prepared from an oil phase and an aqueous phase; the mass ratio of the oil phase to the aqueous phase is 3: (1-2); the aqueous phase comprises grafted and modified SiO2, monomers, an initiator and deionized water; the monomers are acrylamide and 2-acrylamide-2-methylpropanesulfonic acid; the grafted and modified SiO2 is VTES silica ball with a vinyl functional group; and the oil phase comprises an emulsifier and white oil. The multiple cross-linking forms a composite microsphere emulsion structure, which can effectively fill channels such as pores and cracks, and has good plugging capacity for different scales of seepage channels in environments such as oil reservoirs.

Description

Technical Field

[0001] This invention belongs to the field of water plugging and profile control technology, specifically relating to a modified silica plugging agent based on multiple crosslinking, its preparation method, and its application. Background Technology

[0002] Currently used profile control and water shut-off methods include inorganic plugging agents, organic profile control and water shut-off agents, and inorganic / organic polymer microsphere profile control agents. Each of these agents has its own drawbacks, resulting in less than ideal profile control and water shut-off effects. Specifically: Inorganic plugging agents have high water-blocking strength and can seal high-permeability layers, but the seal is too solid, cannot be moved, is easy to bypass, and has a short lifespan, making repeated driving operations difficult and not conducive to deep profile control. The advantage of organic profile control and water shut-off agents is that they can shut off without completely blocking the water, and they can migrate to achieve deep profile control. However, their strength is not high, they cannot seal high-permeability layers, they are easily breached by injected water, and their effective time is relatively short. Inorganic / organic polymer microsphere profile control technology is a deep profile control and water shut-off technology that has been developed in recent years. It combines the high sealing strength of inorganic components with the water absorption, expansion, migration, and deformation capabilities of organic components. It has a stable structure and good application potential.

[0003] A search revealed that patent application number 202011120924.7 discloses a composite material with oil displacement function and its application. This composite material contains silica nanoparticles with phenyl-modified surfaces and an acrylamide multi-component copolymer. The composite material exhibits good stability, water solubility, aqueous phase thickening, and oil displacement effects. However, this patent involves physically mixing the phenyl-modified silica nanoparticles with the acrylamide multi-component copolymer. Acrylamide polymer microsphere plugging agents lack sufficient rigidity and strength, requiring repeated profile adjustments. Furthermore, the inorganic nanoparticles have poor swelling properties, resulting in poor plugging performance in complex formations. Summary of the Invention

[0004] The purpose of this invention is to provide a modified silica plugging agent based on multiple crosslinking, its preparation method and application, which solves the problems of insufficient rigidity and poor sealing performance of acrylamide polymer microsphere plugging agents.

[0005] This invention is achieved through the following technical solution: This invention discloses a modified silica plugging agent based on multiple crosslinking, which is a PAM-AMPS@SiO2 composite microsphere emulsion prepared from an aqueous phase and an oil phase; The mass ratio of the oil phase to the water phase is 3:(1-2); The aqueous phase includes grafted SiO2, monomers, initiators, and deionized water; The monomers are acrylamide and 2-acrylamide-2-methylpropanesulfonic acid; the grafted SiO2 is VTES silica spheres with vinyl functional groups; The oil phase includes emulsifiers and white oil.

[0006] Furthermore, the grafted SiO2 is obtained by modifying vinyltriethoxysilane and sodium dodecylbenzenesulfonate.

[0007] Furthermore, the mass ratio of acrylamide, 2-acrylamide-2-methylpropanesulfonic acid and grafted modified SiO2 is 1:(0.1-1):(0.4-0.8).

[0008] Furthermore, the emulsifier used is Span-80 and Tween-80, and the mass ratio of Span-80 to Tween-80 is 2:1 to 5:1; The initiator is ammonium persulfate, potassium persulfate, azobisisobutylimidazolium hydrochloride, azobisisobutyronitrile, or azobisisoheptanenitrile.

[0009] Furthermore, the modified silica plugging agent based on multiple crosslinking can achieve a salt mineralization resistance of 100,000 mg / L and a plugging rate of 87.2%-92.5%.

[0010] Furthermore, the modified silica plugging agent based on multiple crosslinking achieves a microsphere particle size of 1.5µm at 70°C.

[0011] This invention also discloses a method for preparing the modified silica plugging agent based on multiple crosslinking, comprising the following steps: S1. Mix the emulsifier and white oil to prepare the oil phase; The grafted SiO2, monomer, and deionized water were mixed to prepare an initial aqueous phase mixture. S2. The oil phase and the initial aqueous phase are mixed evenly under stirring to obtain a mixed phase; After deoxygenation and nitrogen purging, the initiator was added dropwise to the mixed phase under nitrogen atmosphere and constant temperature water bath conditions to initiate polymerization. The reaction was carried out continuously under nitrogen atmosphere to obtain PAM-AMPS@SiO2 composite microsphere emulsion.

[0012] Furthermore, the method for preparing the grafted and modified SiO2 is as follows: Vinyltriethoxysilane and sodium dodecylbenzenesulfonate were added to water under stirring until an emulsion was formed; Ammonia solution was added dropwise to the emulsion until the pH reached 10-12, yielding the reaction mixture. The reaction mixture was kept at 40-60°C to obtain a uniform colloidal dispersion; The colloidal dispersion was centrifuged, and the resulting precipitate was repeatedly washed with water to obtain VTES silica spheres with vinyl functional groups.

[0013] Furthermore, in S2, the stirring is carried out under a constant temperature water bath, specifically the constant temperature water bath conditions are: a constant temperature reaction at 40-60℃ for 2-10 hours; The stirring speed is 500-1500 r / min.

[0014] The present invention also discloses the application of the modified silica plugging agent based on multiple crosslinking in water plugging and profile control.

[0015] Compared with the prior art, the present invention has the following beneficial technical effects: This invention discloses a modified silica plugging agent based on multiple crosslinking, which is a novel SiO2 / P(AM-AMPS) composite microsphere profile control agent. Grafted modified SiO2 is introduced into the raw materials. The grafted modified SiO2 and two monomers can undergo a polymerization reaction under the action of an initiator. The oil phase and the water phase form a water-in-oil emulsion through the emulsifier in the oil phase. The water-in-oil droplets are equivalent to small reactors. The water-soluble monomers undergo a polymerization reaction in the water phase of the droplets through the initiator to form SiO2 / P(AM-AMPS) with smaller particle size.

[0016] The monomer contains 2-acrylamide-2-methylpropanesulfonic acid (AMPS), which possesses strong anionic properties, good hydration ability, and resistance to temperature and salt. Under complex reservoir conditions with high temperature and high salinity, its sulfonic acid groups are not easily affected by temperature and salt ions, thus preventing them from losing activity or undergoing structural damage. This allows the entire plugging agent system to maintain good performance, ensuring the continuous effectiveness of the plugging action and broadening the applicable environmental range of this plugging agent.

[0017] Utilizing VTES silica spheres (grafted SiO2) with vinyl functional groups in the polymerization reaction allows for better grafting and crosslinking with monomers such as acrylamide, enhancing the stability of the entire microsphere structure and making it less susceptible to dispersion by formation fluids. The grafted SiO2, as a crucial structural component, possesses inherent rigidity and stability. Combined with crosslinking to form a network structure, it creates a robust sealing system that maintains its sealing effect over a long period, reducing production problems caused by subsequent sealing failure. One crosslinking method involves covalent crosslinking between the CC bonds in acrylamide, the CC bonds in AMPS, and the CC bonds in grafted SiO2. Another method involves hydrogen bonding between polyacrylamide and polyAMPS chains. Through multiple crosslinking processes, a composite microsphere emulsion structure is formed, effectively filling pores and fractures, providing good sealing capabilities for seepage channels of different scales in oil reservoirs and other environments. During oil extraction, it effectively prevents ineffective crossflow of injected water and other fluids, improving sweep efficiency and allowing the displacing fluid to better displace crude oil, thereby increasing oil recovery.

[0018] This invention enables microspheres to possess high rigidity while retaining their swelling properties, thus solving the problems of insufficient rigidity and strength of acrylamide polymer microsphere plugging agents, which require repeated profile adjustments; and the poor swelling performance of inorganic nanoparticles, which result in poor plugging performance in complex formations.

[0019] Furthermore, by configuring the oil phase and water phase at a reasonable mass ratio of 3:(1-2), a stable emulsion system is formed. This emulsion structure is beneficial for the storage, transportation, and uniform dispersion of the plugging agent during injection, avoiding aggregation and precipitation that could affect its effectiveness. On the other hand, it can also maintain a stable state in the underground environment, gradually exerting its plugging effect.

[0020] Furthermore, the performance of the plugging agent can be altered by adjusting the mass ratio of acrylamide, 2-acrylamide-2-methylpropanesulfonic acid, and grafted modified SiO2 (1:(0.1-1):(0.4-0.8)). Appropriately increasing the proportion of 2-acrylamide-2-methylpropanesulfonic acid can further improve its salt resistance; changing the amount of SiO2 can regulate the particle size, hardness, and other physical properties of the microspheres, thereby adapting them to formations with different permeabilities and pore structures to meet diverse plugging requirements.

[0021] Furthermore, the simultaneous addition of Tween and Span can effectively promote the emulsification of the water-oil mixture, achieving uniform dispersion of water and oil and forming a stable emulsion structure.

[0022] This invention discloses a method for preparing a modified silica plugging agent based on multiple crosslinking. By mixing the oil and aqueous phases uniformly under stirring, the method ensures good dispersion of each raw material component in the system, avoiding excessive local concentration differences. This lays the foundation for the subsequent polymerization reaction to generate a PAM-AMPS@SiO2 composite microsphere emulsion with uniform structure and stable performance. The final plugging agent product has a more uniform microsphere particle size distribution and better chemical composition consistency. In practical applications, the plugging effect is more stable and reliable, avoiding problems such as plugging leaks due to uneven product quality.

[0023] Deoxygenation and nitrogen purging, along with conducting the reaction under a nitrogen atmosphere, effectively eliminates oxygen from the system. Oxygen often interferes with the polymerization reaction, leading to incomplete polymerization or the formation of byproducts that affect the performance of the plugging agent. In an oxygen-free nitrogen environment, the polymerization reaction can proceed more smoothly as expected, improving the purity of the product. Furthermore, the stability of the resulting composite microsphere emulsion is enhanced, making it less prone to deterioration and decomposition during storage and subsequent use, thus ensuring long-term effectiveness.

[0024] By introducing inorganic silica into organic polymer microspheres, a novel, structurally stable SiO2 / P (AM-AMPS) composite microsphere profile control agent was developed. This agent combines the high-strength sealing properties of inorganic components with the expansion, deformation, and transport capabilities of organic components to improve the profile control and water shut-off effect.

[0025] Furthermore, during the mineralization experiment, when the mineralization degree increased from 0 mg / L to 10000 mg / L, the microsphere particle size increased from 870 nm to 1392 nm. When the mineralization degree was further increased to 20000 mg / L, the microsphere particle size reached a peak of 1606 nm. After increasing the mineralization degree to 100000 mg / L, the particle size stabilized at around 1350 nm, indicating that the PAM-AMPS@SiO2 composite microspheres have strong salt resistance.

[0026] Furthermore, during the temperature resistance test, as the temperature increased from 40℃ to 60℃, the microsphere particle size increased from 801nm to 1770nm. Further increasing the swelling temperature to 70℃ reduced the microsphere particle size to 1485nm. Even at high temperatures, the microsphere particle size remained around 1.5µm, indicating that the composite microspheres can still effectively seal corresponding pores or cracks at high temperatures, demonstrating good temperature resistance. Attached Figure Description

[0027] Figure 1 This is a flowchart illustrating a method for preparing a modified silica plugging agent based on multiple crosslinking according to the present invention; Figure 2 Figure 1 shows the experimental results of mineralization performance of the PAM-AMPS@SiO2 composite microsphere emulsion prepared in Example 2. Figure 3 The figure shows the results of the blocking experiment of the PAM-AMPS@SiO2 composite microsphere emulsion prepared in Example 2; Figure 4 Figure 1 shows the results of a temperature resistance test on the PAM-AMPS@SiO2 composite microsphere emulsion prepared in Example 2. Figure 5 The image shows the results of a shear test on the PAM-AMPS@SiO2 composite microsphere emulsion prepared in Example 2. Figure 6 This is a reaction process diagram of the preparation of a modified silica plugging agent based on multiple crosslinking according to the present invention; Figure 7 This is a diagram of the reaction process of grafted SiO2. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of the present invention clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention; that is, the described embodiments are only a part of the embodiments of the present invention, and not all of them.

[0029] The components described and illustrated in the accompanying drawings and embodiments of this invention can be arranged and designed in various different configurations. Therefore, the detailed description of the embodiments of the invention provided in the following drawings is not intended to limit the scope of the claimed invention, but merely to illustrate one selected embodiment of the invention. All other embodiments obtained by those skilled in the art based on the accompanying drawings and embodiments of this invention without inventive effort are within the scope of protection of this invention.

[0030] It should be noted that the terms “comprising,” “including,” or any other variations are intended to cover non-exclusive inclusion, such that a process, element, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to the process, element, method, article, or apparatus.

[0031] The experimental reagents used in this invention are shown in the table below.

[0032] Experimental reagents

[0033] This invention discloses a modified silica plugging agent based on multiple crosslinking, wherein the modified silica plugging agent based on multiple crosslinking is a PAM-AMPS@SiO2 composite microsphere emulsion prepared from an aqueous phase and an oil phase; The mass ratio of the oil phase to the water phase is 3:(1-2); The aqueous phase includes grafted SiO2, monomers, initiators, and deionized water; The monomers are acrylamide and 2-acrylamide-2-methylpropanesulfonic acid; the grafted SiO2 is VTES silica spheres with vinyl functional groups; The oil phase includes emulsifiers and white oil.

[0034] Specifically, the method for preparing the grafted and modified SiO2 is as follows: Vinyltriethoxysilane and sodium dodecylbenzenesulfonate were added to water under stirring until an emulsion was formed; Ammonia solution was added dropwise to the emulsion until the pH reached 10-12, yielding the reaction mixture. The reaction mixture was kept at 40-60°C to obtain a uniform colloidal dispersion; The colloidal dispersion was centrifuged, and the resulting precipitate was repeatedly washed with water to obtain VTES silica spheres with vinyl functional groups.

[0035] More preferably, the mass ratio of acrylamide, 2-acrylamide-2-methylpropanesulfonic acid and grafted modified SiO2 is 1:(0.1-1):(0.4-0.8).

[0036] More preferably, the emulsifier is a mixture of Span-80 and Tween-80, with a mass ratio of Span-80 to Tween-80 of 2:1 to 5:1; The initiator is ammonium persulfate, potassium persulfate, azobisisobutylimidazolium hydrochloride, azobisisobutyronitrile, or azobisisoheptanenitrile.

[0037] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0038] Example 1 This embodiment discloses a modified silica plugging agent based on multiple crosslinking, which is prepared from an aqueous phase, an oil phase and an initiator; The mass ratio of the oil phase to the water phase is 3:2; The aqueous phase includes grafted modified SiO2, monomers, and deionized water; the monomers are acrylamide and 2-acrylamide-2-methylpropanesulfonic acid; the grafted modified SiO2 is VTES silica spheres with vinyl functional groups. The oil phase includes emulsifiers and white oil; The mass ratio of acrylamide, 2-acrylamide-2-methylpropanesulfonic acid and grafted modified SiO2 is 1:0.1:0.4.

[0039] The formulation system is shown in Table 1: Table 1

[0040] like Figure 1 As shown, the preparation method of the modified silica plugging agent based on multiple crosslinking includes the following steps: S1. Mix 0.45g of emulsifier and 78g of white oil to prepare the oil phase; The emulsifiers include Span-80 and Tween-80 in a mass ratio of 2:1. 8g of grafted modified SiO2, 20g of acrylamide, 2g of 2-acrylamide-2-methylpropanesulfonic acid and 16.7g of deionized water were mixed to prepare an initial aqueous phase mixture; S2. The oil phase and the initial aqueous phase are mixed evenly under stirring to obtain a mixed phase; After deoxygenation and nitrogen purging, under nitrogen atmosphere and constant temperature water bath conditions of 60℃, stirring at 1500 rpm for 30 minutes, then... 5 Initiator g was added dropwise to the mixed phase to initiate polymerization. The reaction was carried out continuously for 2 hours under nitrogen purging to obtain PAM-AMPS@SiO2 composite microsphere emulsion.

[0041] The PAM-AMPS@SiO2 composite microsphere emulsion prepared in Example 1 was subjected to mineralization performance experiments. The particle size of the multi-crosslinked PAM-AMPS@SiO2 varied with the degree of mineralization, as follows: Figure 2 As shown, the details are as follows: When the mineralization increased from 0 mg / L to 10000 mg / L, the microsphere size increased from 870 nm to 1392 nm. When the mineralization was further increased to 20000 mg / L, the microsphere size reached a peak of 1606 nm. After increasing the mineralization to 100000 mg / L, the particle size stabilized at around 1350 nm, indicating that the PAM-AMPS@SiO2 composite microspheres have strong salt resistance.

[0042] Comparative Example Based on Example 1, a PAM-AMPS composite microsphere emulsion was prepared without adding grafted modified SiO2 to the aqueous phase.

[0043] Blocking experiments were conducted on the PAM-AMPS@SiO2 composite microsphere emulsion prepared in Example 1 and the PAM-AMPS composite microsphere emulsion prepared in the comparative example. Figure 3As shown, the set of columns on the left is a comparative example, and the set of columns on the right is Example 1. It can be clearly seen that the permeability of the sand-filled tube on the left before injection was 289 mD. After injecting 0.5 PV of PAM-AMPS microspheres, the permeability became 37 mD, and the blocking rate was 87.2%. The permeability of the sand-filled tube on the right before injection was 301 mD. After injecting 0.5 PV of PAM-AMPS@SiO2 composite microspheres, the permeability became 23 mD, and the blocking rate was 92.5%. It can be clearly seen that the composite microspheres of the present invention have a better blocking rate under the same injection pressure.

[0044] When the injection amount of the PAM-AMPS@SiO2 composite microsphere emulsion prepared in Example 1 was 0.5 PV, the permeability before injection was 301 mD. After injection of the PAM-AMPS@SiO2 composite microsphere emulsion prepared in Example 1, the permeability was 23 mD, and the blocking rate could reach 92.5%, as shown in Table 4.

[0045] The PAM-AMPS@SiO2 composite microsphere emulsion prepared in Example 1 was subjected to a temperature resistance test, such as... Figure 4 As shown, the details are as follows: As the temperature increased from 40℃ to 60℃, the particle size of the PAM-AMPS@SiO2 composite microspheres increased from 801nm to 1770nm. Further increasing the swelling temperature to 70℃ reduced the microsphere particle size to 1485nm. Even at high temperatures, the microsphere particle size remained around 1.5µm, indicating that the composite microspheres could still effectively seal corresponding pores or cracks at high temperatures, demonstrating good temperature resistance.

[0046] The PAM-AMPS@SiO2 composite microsphere emulsion prepared in Example 1 was subjected to a shearing experiment, as follows: Figure 5 As shown, the details are as follows: The rheological curves formed a closed loop based on the top and bottom equilibrium flow experiments, indicating that the rheology of the microsphere dispersion system is reversible. The microsphere structure was not destroyed under high shear rates, demonstrating the good shear resistance of the microsphere system.

[0047] The reaction process of this invention is as follows: Figure 6 As shown, grafted modified SiO2, acrylamide, and 2-acrylamide-2-methylpropanesulfonic acid undergo polymerization under the action of an initiator. The oil phase and the water phase form a water-in-oil emulsion through the emulsifier in the oil phase. The water-in-oil droplets are equivalent to small reactors. Water-soluble monomers undergo polymerization in the water phase of the droplets through the initiator to form polymers with smaller particle sizes.

[0048] Example 2 This embodiment discloses a modified silica plugging agent based on multiple crosslinking, which is prepared from an aqueous phase, an oil phase and an initiator; The mass ratio of the oil phase to the aqueous phase is 3:1.5; The aqueous phase includes grafted modified SiO2, monomers, and deionized water; the monomers are acrylamide and 2-acrylamide-2-methylpropanesulfonic acid; the grafted modified SiO2 is VTES silica spheres with vinyl functional groups. The oil phase includes emulsifiers and white oil; The mass ratio of acrylamide, 2-acrylamide-2-methylpropanesulfonic acid and grafted modified SiO2 is 1:0.2:0.6.

[0049] The formulation system is shown in Table 2: Table 2

[0050] like Figure 1 As shown, the preparation method of the modified silica plugging agent based on multiple crosslinking includes the following steps: S1. Mix 0.6g of emulsifier and 80g of white oil to prepare the oil phase; The emulsifiers include Span-80 and Tween-80 in a mass ratio of 3:1. 7.92g of grafted modified SiO2, 13.2g of acrylamide, 2.64g of 2-acrylamide-2-methylpropanesulfonic acid and 14.5g of deionized water were mixed to prepare an initial aqueous phase mixture; S2. The oil phase and the initial aqueous phase are mixed evenly under stirring to obtain a mixed phase; After deoxygenation and nitrogen purging, under nitrogen atmosphere and constant temperature water bath at 50℃, stirring at 1200 r / min for 60 min, 6 g of initiator was added dropwise to the mixed phase to initiate polymerization. The reaction was continued for 5 h under continuous nitrogen purging to obtain PAM-AMPS@SiO2 composite microsphere emulsion.

[0051] When the injection volume is 0.5 PV, the permeability before injection is 296 mD. After injection of the PAM-AMPS@SiO2 composite microsphere emulsion prepared in Example 2, the permeability is 32 mD and the blocking rate can reach 89.2%, as shown in Table 4.

[0052] Example 3 This embodiment discloses a modified silica plugging agent based on multiple crosslinking, which is prepared from an aqueous phase, an oil phase and an initiator; The mass ratio of the oil phase to the water phase is 3:1; The aqueous phase includes grafted modified SiO2, monomers, and deionized water; the monomers are acrylamide and 2-acrylamide-2-methylpropanesulfonic acid; the grafted modified SiO2 is VTES silica spheres with vinyl functional groups. The oil phase includes emulsifiers and white oil; The mass ratio of acrylamide, 2-acrylamide-2-methylpropanesulfonic acid and grafted modified SiO2 is 1:0.5:0.8.

[0053] The formulation system is shown in Table 3: Table 3

[0054] like Figure 1 As shown, the preparation method of the modified silica plugging agent based on multiple crosslinking includes the following steps: S1. Mix 0.75g of emulsifier and 100g of white oil to prepare the oil phase; The emulsifiers include Span-80 and Tween-80 in a mass ratio of 5:1. 8g of grafted modified SiO2, 10g of acrylamide, 5g of 2-acrylamide-2-methylpropanesulfonic acid and 10g of deionized water were mixed to prepare an initial aqueous phase mixture; S2. The oil phase and the initial aqueous phase are mixed evenly under stirring to obtain a mixed phase; After deoxygenation and nitrogen purging, and stirring at 1000 r / min for 90 min in a constant temperature water bath at 40℃, 4.5 g of initiator was added dropwise to the mixed phase to initiate polymerization. The reaction was continued for 8 h under continuous nitrogen purging to obtain PAM-AMPS@SiO2 composite microsphere emulsion.

[0055] When the injection volume is 0.5 PV, the permeability before injection is 289 mD. After injection of the PAM-AMPS@SiO2 composite microsphere emulsion prepared in Example 3, the permeability is 37 mD and the blocking rate can reach 87.2%, as shown in Table 4.

[0056] Table 4 Comparison of Blocking Rates in Examples 1-3

[0057] The formulation system of the grafted and modified SiO2 in the above embodiments is shown in the table below:

[0058] Preparation process: 3.8 g VTES and 0.013 g SDBS were added to 30 mL of water under vigorous stirring until an emulsion was formed. 0.5 mL of ammonia was added dropwise to the emulsion to adjust the pH to 11.5. The reaction mixture was kept at 50°C for 48 h to obtain a homogeneous colloidal dispersion. To remove unreacted reactants and ammonia, the colloidal dispersion was centrifuged at high speed. The resulting precipitate was washed repeatedly with water to obtain VTES silica spheres (VSNPs) with vinyl functional groups. The reaction mechanism is as follows: Figure 7As shown.

[0059] 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 it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the protection scope of the present invention.

Claims

1. A modified silica plugging agent based on multiple crosslinking, characterized in that, The modified silica plugging agent based on multiple crosslinking is a PAM-AMPS@SiO2 composite microsphere emulsion prepared from an aqueous phase and an oil phase; The mass ratio of the oil phase to the water phase is 3:(1-2); The aqueous phase includes grafted SiO2, monomers, initiators, and deionized water; The monomers are acrylamide and 2-acrylamide-2-methylpropanesulfonic acid; the grafted SiO2 is VTES silica spheres with vinyl functional groups; The oil phase includes emulsifiers and white oil.

2. The modified silica plugging agent based on multiple crosslinking according to claim 1, characterized in that, The grafted SiO2 was obtained by modifying vinyltriethoxysilane and sodium dodecylbenzenesulfonate.

3. The modified silica plugging agent based on multiple crosslinking according to claim 1, characterized in that, The mass ratio of acrylamide, 2-acrylamide-2-methylpropanesulfonic acid and grafted modified SiO2 is 1:(0.1-1):(0.4-0.8).

4. The modified silica plugging agent based on multiple crosslinking according to claim 1, characterized in that, The emulsifier used is Span-80 and Tween-80, and the mass ratio of Span-80 to Tween-80 is 2:1 to 5:1; The initiator is ammonium persulfate, potassium persulfate, azobisisobutylimidazolium hydrochloride, azobisisobutyronitrile, or azobisisoheptanenitrile.

5. The modified silica plugging agent based on multiple crosslinking according to claim 1, characterized in that, The modified silica plugging agent based on multiple crosslinking can achieve a salt mineralization resistance of 100,000 mg / L and a plugging rate of 87.2%-92.5%.

6. The modified silica plugging agent based on multiple crosslinking according to claim 1, characterized in that, The modified silica plugging agent based on multiple crosslinking achieves a microsphere particle size of 1.5µm at 70℃.

7. The method for preparing the modified silica plugging agent based on multiple crosslinking as described in any one of claims 1-6, characterized in that, Includes the following steps: S1. Mix the emulsifier and white oil to prepare the oil phase; The grafted SiO2, monomer, and deionized water were mixed to prepare an initial aqueous phase mixture. S2. The oil phase and the initial aqueous phase are mixed evenly under stirring to obtain a mixed phase; After deoxygenation and nitrogen purging, the initiator was added dropwise to the mixed phase under nitrogen atmosphere and constant temperature water bath conditions to initiate polymerization. The reaction was carried out continuously under nitrogen atmosphere to obtain PAM-AMPS@SiO2 composite microsphere emulsion.

8. The method for preparing the modified silica plugging agent based on multiple crosslinking according to claim 7, characterized in that, The method for preparing the grafted and modified SiO2 is as follows: Vinyltriethoxysilane and sodium dodecylbenzenesulfonate were added to water under stirring until an emulsion was formed; Ammonia solution was added dropwise to the emulsion until the pH reached 10-12, yielding the reaction mixture. The reaction mixture was kept at 40-60°C to obtain a uniform colloidal dispersion; The colloidal dispersion was centrifuged, and the resulting precipitate was repeatedly washed with water to obtain VTES silica spheres with vinyl functional groups.

9. The method for preparing the modified silica plugging agent based on multiple crosslinking according to claim 7, characterized in that, In S2, the stirring is carried out under a constant temperature water bath. Specifically, the constant temperature water bath conditions are: a constant temperature reaction at 40-60℃ for 2-10 hours. The stirring speed is 500-1500 r / min.

10. The application of the modified silica plugging agent based on multiple crosslinking as described in any one of claims 1-6 in water shut-off and profile control.

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