A method for preparing a pH-responsive nanoreservoir for corrosion inhibitor loading and pickering emulsion stabilization

Abstract

The application provides a hollow mesoporous silica (BTA@HMSNs-CS) material for metal material targeted corrosion inhibition and Pickering emulsion stabilization in an oil production well, a preparation method and an application. The material selects hollow mesoporous silica (HMSNs) as a nano container for loading corrosion inhibitors, cross-linked chitosan (CS) as a pH response valve for controlling corrosion inhibitor release and reducing interfacial tension to form a Pickering emulsion. The BTA@HMSNs-CS is assembled from an acid response cross-linked CS network and a large cavity HMSNs, the preparation method is simple and easy to implement, has good acid response and emulsion stabilization performance, and has great reference value and application prospect in the field of downhole metal corrosion prevention and emulsion stabilization.

Description

Technical Field

[0001] This invention relates to the field of oil and gas field chemical agents, and in particular to a method for preparing a multifunctional material for metal-targeted corrosion inhibition and the formation of stable emulsions. Background Technology

[0002] In oil drilling and production, acidizing is often used to enhance oil recovery. In acidizing operations, especially in high-temperature deep and ultra-deep wells, the primary task is to address the corrosion of casing equipment by the high-temperature acidizing fluids. Directly injecting corrosion inhibitors is a commonly used technique to suppress corrosion of downhole equipment; however, this method cannot actively identify severely corroded areas for targeted protection and suffers from issues such as easy failure and short effective lifespan under complex and harsh downhole environments. Drawing inspiration from targeted drug delivery systems in the biomedical field, this study utilizes nano-containers with environmental recognition and response capabilities to encapsulate corrosion inhibitors. In areas where metal corrosion occurs, the surrounding environment of the nano-container undergoes specific changes. In response to these environmental changes, the nano-container immediately or continuously releases the encapsulated corrosion inhibitor molecules, thereby achieving precise protection of the metal material.

[0003] Currently, the fabrication technology of nanocontainers is maturing, and numerous studies on container-loaded corrosion inhibitors in the field of metal corrosion protection have been reported recently. However, the reported nanocontainers currently only function as corrosion inhibitor loading devices; after the inhibitors are released, the nanocontainers can only be disposed of as waste, failing to realize the multifunctional utilization of nanocontainers. In oil drilling and production engineering, multiple technical tasks are involved, such as corrosion protection of metal equipment, oil emulsification to enhance oil recovery, and water treatment. Therefore, the development of multifunctional materials is currently a research hotspot in oil production engineering. Summary of the Invention

[0004] One aspect of the present invention provides a method for preparing a corrosion inhibitor and emulsifier with pH-responsive properties, which specifically includes the following steps:

[0005] 1) At room temperature, sonicate 4g BTA and 300mL deionized water for 30min. Pour the mixture into a 500mL single-necked flask, and add 0.3g HMSNs. Connect the flask with a PTFE double-stop stopcock, sealing the connection with a sealing film to prevent air leakage, and then sonicate again. Connect the apparatus to a water-type vacuum pump using a white tubing, and evacuate until no more bubbles appear in the mixture. Stir the vacuum apparatus magnetically at room temperature. Finally, centrifuge the resulting product and wash three times with ethanol. Dry the final product, BTA@HMSNs, in a vacuum drying oven at 60℃ for 12h.

[0006] 2) Crosslinking of BTA@HMSNs with CS was carried out in a buffer solution. 400 mg of BTA@HMSNs was placed in a beaker, followed by 120 mL of buffer solution. After sonication for 15 min, the mixture was fully dispersed. Then, a surfactant was added to the beaker and stirred for 1 h, followed by 6 mL of a 1 wt% CS acetic acid solution. After reacting at room temperature for 4 h, the crosslinking agent was added. After 4 h, the product was centrifuged, washed three times with deionized water and ethanol, and dried under vacuum at 60 °C for 12 h to obtain BTA@HMSNs-CS.

[0007] In one specific embodiment, in step 1), the mixture of BTA and HMSNs is sonicated for 15 minutes, and the solution is stirred under vacuum for 30 minutes. This process is repeated three times.

[0008] In one specific embodiment, in step 2), the buffer solution is a mixture of 5.1 g sodium acetate and 20 mL acetic acid. After adding a certain amount of water, 250 mL of a solution with pH = 3.6 is obtained.

[0009] In one specific embodiment, in step 2), the surfactant is sodium dodecylbenzenesulfonate and the crosslinking agent is glutaraldehyde.

[0010] In one specific embodiment, in step 2), 1 wt% CS acetic acid solution is 1 g CS added to 10 mL acetic acid, and the acetic acid concentration is 1% (v / v).

[0011] In one specific embodiment, in step 2), 20 mL of sodium dodecylbenzenesulfonate surfactant with a concentration of 0.025 mol / L is added, and 6 mL of glutaraldehyde crosslinking agent with a mass fraction of 25 wt% is added.

[0012] The beneficial effects of this invention are:

[0013] The corrosion inhibitor emulsifier prepared by this invention can achieve rapid release of corrosion inhibitor under acidic conditions, providing precise protection for corroded areas. At the same time, it can also stabilize at the oil-water interface of paraffin oil and reduce interfacial tension under acidic conditions to achieve emulsification of paraffin oil. Under neutral and alkaline conditions, oil and water can be separated, making it suitable for application scenarios in oilfields. Attached Figure Description

[0014] Figure 1 The scanning electron microscope (SEM) and transmission electron microscope (TEM) images of the corrosion-inhibiting emulsifier are shown.

[0015] Figure 2 The infrared spectrum of the corrosion-inhibiting emulsifier is shown.

[0016] Figure 3 The thermogravimetric analysis (TGA) curve of the corrosion inhibitor emulsifier is shown.

[0017] Figure 4 The UV spectrum of corrosion inhibitor release is shown.

[0018] Figure 5 Electrochemical test graphs of corrosion inhibitor emulsifiers at different addition amounts are shown.

[0019] Figure 6 Electrochemical test graphs of the corrosion inhibitor emulsifier at different time points are shown.

[0020] Figure 7 The stability test graphs of the paraffin oil-deionized water emulsion formed by the emulsifier at different addition amounts are shown.

[0021] Figure 8 The graph shows the stability test results of the emulsifier at different pH values. Detailed Implementation

[0022] The present invention will be further described below with reference to the embodiments. However, the embodiments of the present invention are merely illustrative examples and should not be construed as limiting the present invention under any circumstances.

[0023] Example 1

[0024] Synthesis method of pH-responsive corrosion inhibitor emulsifier:

[0025] (1) First, ultrasonically mix 4g BTA with 300mL deionized water for 30min. Then, add 0.3g HMSNs to the ultrasonically mixed solution and ultrasonically mix for 15min. Pour the mixture into a 500mL single-necked flask. Connect the flask with a PTFE double-stop stopcock and seal the connection with a sealing film to prevent air leakage. Then, connect the device to a water-type vacuum pump with a white tubing and evacuate until no more water bubbles appear in the mixed solution. Then, preserve the solution in tin under vacuum and stir for 30min. To ensure that the corrosion inhibitor is fully loaded into the HMSNs, repeat the above operation three times. Finally, centrifuge the obtained product and wash it three times with ethanol. Place the BTA@HMSNs product in a vacuum drying oven at 60℃ and dry for 12h.

[0026] (2) 5.1 g of sodium acetate was mixed with 20 mL of acetic acid, and a certain amount of water was added to obtain 250 mL of a buffer solution with pH = 3.6. 400 mg of HMSNs loaded with the BTA obtained above was placed in a beaker, and then 120 mL of the above buffer solution was added. After sonication for 15 min, the mixture was fully dispersed. Then, 20 mL of 0.025 mol / L sodium dodecylbenzenesulfonate solution was added to the beaker as a surfactant. After stirring for 1 h, 6 mL of 1 wt% CS acetic acid solution was added. After reacting at room temperature for 4 h, 6 mL of glutaraldehyde was added as a crosslinking agent. After 4 h, the product was centrifuged, washed three times with deionized water and ethanol, and dried under vacuum at 60 °C for 12 h to obtain the final product BTA@HMSNs-CS.

[0027] Characterization:

[0028] CS, BTA, BTA@HMSNs, and BTA@HMSNs-CS were characterized by Fourier transform infrared spectroscopy (FTIR). Using the KBr pellet method, each sample was vacuum-dried until constant mass. Approximately 200 mg of dried KBr powder and approximately 2 mg of sample powder were weighed and ground in an agate mortar to prepare powder analytes with an average particle size of approximately 2 μm. These powders were then compressed into tablets (approximately 12 MPa) to obtain transparent, sheet-like analytes for detection. Detection conditions: wavelength range 500-4000 cm⁻¹. -1 Resolution is 2cm -1 The results are shown below. Figure 1 For HMSNs and BTA@HMSNs, 1090cm -1 and 806cm -1 It is the bending and tensile vibration peak of Si-O-Si, 3462 cm⁻¹ -1 It is the characteristic absorption peak of Si-OH, 1633 cm⁻¹ -1 This is a characteristic absorption peak of BTA. It indicates that the BTA corrosion inhibitor was successfully loaded into HMSNs. For BTA@HMSNs-CS, 1658 cm⁻¹ is the characteristic absorption peak. -1 and 1573cm -1 The absorption band at this point is the NH2 group, indicating that the cross-linked CS network is successfully wrapped on the surface of BTA@HMSNs.

[0029] The morphology of BTA@HMSNs-CS was examined using scanning electron microscopy and transmission electron microscopy. Figure 2 As can be seen, both the prepared HMSNs and BTA@HMSNs-CS are uniform, hollow, single-shell spherical nanoparticles. After being coated with cross-linked CS, the presence of CS on the surface of HMSNs can be observed. The size and wall thickness of BTA@HMSNs-CS are significantly increased compared to HMSNs, resulting in a decrease in the transparency of the nanoparticles.

[0030] The loading amount of corrosion inhibitor and the encapsulation amount of crosslinked CS were calculated based on the thermogravimetric curves. Figure 3 As can be seen, the BTA loading is approximately 12.80%, and the mass ratio of crosslinked CS on the HMSNs@BTA surface is 12.85%.

[0031] Example 2

[0032] BTA@HMSNs-CS pH response performance test:

[0033] The release percentage of BTA corrosion inhibitor under different pH conditions was determined using ultraviolet-visible spectroscopy. Results are shown below. Figure 4 .from Figure 4 As can be seen, the release rate of BTA was highest at pH 3, reaching 84.02% after 25 hours. In contrast, the release rates at pH 7 and 10 were only 21.45% and 11.02%, respectively. This indicates that BTA@HMSNs-CS exhibits good acid response performance. During cycling between pH 3 and 7, the release rate of BTA molecules changed with pH. At the initial pH of 7, the tightly cross-linked CS network restricted the release of BTA molecules. When the pH changed from 7 to 3, the release rate of BTA increased significantly, reaching 14.23% after 2 hours. When the pH returned to 7, the release rate of BTA decreased rapidly, reaching 96.55% after 3 cycles. This demonstrates that at higher pH values, the cross-linked CS network of BTA@HMSNs-CS becomes tighter, completely restricting the diffusion of BTA molecules. As the pH decreases, the repulsive forces between charges cause the cross-linked CS network to expand, allowing BTA molecules to diffuse into the solution through the mesopores of HMSNs. The release curves show that the "pH switch" is reversible and can be repeated several times. Based on the pH-reversible cross-linked CS network, the "release-stop-release" behavior of BTA in BTA@HMSNs-CS can automatically alternate with changes in pH.

[0034] Example 3

[0035] Electrochemical performance testing of BTA@HMSNs-CS

[0036] 1. Electrochemical performance testing at different concentrations:

[0037] To further investigate the corrosion inhibition behavior of BTA@HMSNs-CS at different concentrations and pH values, electrochemical experiments were conducted. Figure 5As shown, the Nyquist plot represents the capacitance arc; the larger the capacitance arc radius, the greater the corrosion resistance of the corrosion inhibitor to the metal. With increasing BTA@HMSNs-CS concentration, the capacitance arc radius increases, indicating that the corrosion inhibitor concentration affects the corrosion degree of the N80 sample. When the inhibitor concentration increases from 50 mg / L to 200 mg / L, the capacitance arc radius of BTA@HMSNs-CS in a 3.5 wt% NaCl solution at pH=3 is greater than that at pH=7 and pH=10. These results indicate that the cross-linked CS on the surface of BTA@HMSNs-CS decomposes under acidic conditions, releasing BTA molecules from the HMSNs cavities. The Bode plot further supports this conclusion. In a 3.5 wt% NaCl solution at pH=3, when the BTA@HMSNs-CS concentration increases from 50 mg / L to 200 mg / L, the |Z| of BTA@HMSNs-CS increases. 0.01 The Hz value is 1042.6 Ω·cm 2 It rapidly increased to 1792.2 Ω·cm 2 The efficiency was significantly improved compared to that under neutral and alkaline conditions; the relevant electrochemical parameters are shown in Table 1.

[0038] Table 1. Corrosion electrochemical parameters of N80 in 3.5 wt.% NaCl solutions containing different concentrations of BTA@HMSNs-CS in different pH systems: (a) pH=3, (b) pH=7, (c) pH=10.

[0039]

[0040]

[0041] 2. Electrochemical performance tests at different times:

[0042] Figure 6 Electrochemical tests showed that with increasing immersion time, the higher the concentration of BTA released in the three different pH systems, the better the corrosion inhibition effect. In the pH=3 system, due to the low pH value, BTA molecules in BTA@HMSNs-CS were rapidly released in the first 3 hours, reaching a maximum value of 2294.8 Ω·cm at 24 hours. 2 At this point, BTA molecules reached a sufficient concentration and adsorbed onto the surface of the N80 sample, significantly reducing the corrosion rate of the N80 sample. In the system at pH=7, the release rate of BTA molecules was significant in the first 10 hours, reaching 1657.1 Ω·cm at 24 hours (|Z| 0.01 Hz). 2 In the system with pH=10, the release rate of BTA molecules was low in the first 10 hours of corrosion, and the |Z|0.01Hz value increased slowly. The relevant electrochemical parameters are shown in Table 2.

[0043] Table 2. Electrochemical parameters of N80 corrosion in 3.5 wt.% NaCl at different pH systems: (a) pH=3, (b) pH=7, (c) pH=10

[0044]

[0045]

[0046] Example 4

[0047] Pickering emulsion performance test of BTA@HMSNs-CS:

[0048] Weigh out 0.0225 g, 0.045 g, 0.0675 g, and 0.09 g of emulsifier respectively and disperse them in 9 mL of deionized water (i.e., the mass fractions of emulsifier added are 0.25 wt%, 0.5 wt%, 0.75 wt%, and 1 wt%, respectively), and then add 1 mL of liquid paraffin. Figure 7 As shown, when BTA@HMSNs-CS is used as an emulsifier, the oil-water system containing 0.25 wt% BTA@HMSNs-CS forms a distinct oil-water (O / W) emulsion with an average particle size of 110 μm. When the amount of BTA@HMSNs-CS added to the oil-water system increases to 0.5 wt%, the average particle size of the emulsion decreases to 85 μm. When the mass fraction of BTA@HMSNs-CS in the oil-water system is 0.75 wt% and 1.0 wt%, respectively, the particle size of the emulsion decreases to 55 μm. Therefore, with the increase of the mass fraction of BTA@HMSNs-CS, the emulsion particle size decreases and gradually becomes more uniform, which is beneficial to the improvement of emulsion stability.

[0049] pH response behavior of pickering emulsions:

[0050] The pH response performance of Pickering emulsion was tested after adding 0.5 wt% BTA@HMSNs-CS. Figure 8 As shown, under acidic conditions, due to the presence of H+ in the solution... + At higher concentrations, the amino groups on the CS surface are completely protonated, forming -NH3 dissolved in the aqueous phase. + This significantly reduces the surface tension of the aqueous phase, and the remaining BTA@HMSNs-CS particles and CS polymer support the oil-water interface film, stabilizing it. At pH 3, the emulsion is macroscopically pale yellow because the emulsifier particles are adsorbed entirely at the oil-water interface. As the pH of the aqueous solution increases, the emulsion exhibits a demulsification trend. At pH 7 and 10, the emulsion droplets are very large, making it prone to breakage. This may be because the CS molecular chains shrink under neutral and alkaline conditions, thus losing surface activity, and the resulting emulsion cannot remain stable.

Claims

1. A hollow mesoporous silica (BTA@HMSNs-CS) material with cross-linked chitosan encapsulated and loaded with BTA corrosion inhibitor, characterized by targeted corrosion inhibition of metal materials in oil wells and Pickering emulsion stabilization, and characterized by the following: The material releases corrosion inhibitors and forms a Pickering emulsion under acidic conditions. It is prepared through the following key steps: 4g BTA is ultrasonically mixed with 300mL deionized water at room temperature for 30min. 0.3g HMSNs are added, followed by vacuum stirring, centrifugation, washing, and drying to obtain BTA@HMSNs. 400mg BTA@HMSNs are dispersed in 120mL of an acetate-sodium acetate buffer solution at pH 3.

6. 20mL of 0.025mol / L sodium dodecylbenzenesulfonate is added and stirred for 1h. Then, 6mL of 1wt% chitosan-acetic acid solution is added, and the mixture is reacted at room temperature for 4h. 6mL of 25wt% glutaraldehyde is added for crosslinking, followed by centrifugation, washing, and drying to obtain the target material.

2. The BTA@HMSNs-CS material according to claim 1, characterized in that, In the UV spectrum of the corrosion inhibitor release of the BTA@HMSNs-CS material, the release amount of the corrosion inhibitor reaches 84.02% at pH = 3, 21.45% at pH = 7, and 11.02% at pH = 10. Similarly, it can form a stable Pickering emulsion under acidic conditions and achieve demulsification under neutral and alkaline conditions.

3. A method for preparing the BTA@HMSNs-CS material according to claim 1 or 2, comprising the following steps: 1) At room temperature, 4 g BTA and 300 mL deionized water were ultrasonically mixed for 30 min. The mixture was then poured into a 500 mL single-necked flask, and 0.3 g HMSNs were added to the flask. The flask was connected with a polytetrafluoroethylene double-stop stopcock, and the connection was sealed with a sealing film to prevent air leakage. The mixture was then ultrasonically treated. The device was then connected to a water-type vacuum pump with a white tubing, and vacuum was applied until no more water bubbles appeared in the mixture. The vacuum device was then magnetically stirred at room temperature. Finally, the product was centrifuged, washed three times with ethanol, and the final product BTA@HMSNs was dried in a vacuum drying oven at 60 °C for 12 h. 2) Crosslinking of BTA@HMSNs with CS was carried out in a buffer solution. 400 mg of BTA@HMSNs was placed in a beaker, and then 120 mL of buffer solution was added. After sonication for 15 min, the mixture was fully dispersed. Then, a surfactant was added to the beaker and stirred for 1 h. Then, 6 mL of 1 wt% CS acetic acid solution was added and reacted at room temperature for 4 h. After that, the crosslinking agent was added. After 4 h, the product was centrifuged and washed three times with deionized water and ethanol. It was then vacuum dried at 60 °C for 12 h to obtain BTA@HMSNs-CS.

4. The preparation method according to claim 3, characterized in that, The mixture of BTA and HMSNs was sonicated for 15 minutes, and the solution was stirred under vacuum for 30 minutes. This process was repeated three times.

5. The preparation method according to claim 3, characterized in that, The buffer solution is a mixture of 5.1 g sodium acetate and 20 mL acetic acid, with the addition of a certain amount of water to obtain 250 mL of solution with pH = 3.

6.

6. The preparation method according to claim 3, characterized in that, The surfactant is sodium dodecylbenzenesulfonate, and the crosslinking agent is glutaraldehyde.

7. The preparation method according to claim 3, characterized in that, A 1 wt% CS acetic acid solution is prepared by adding 1 g of CS to 10 mL of acetic acid, resulting in an acetic acid concentration of 1% (v / v).

8. The preparation method according to claim 3, characterized in that, The surfactant sodium dodecylbenzenesulfonate was added in 20 mL at a concentration of 0.025 mol / L, and the crosslinking agent glutaraldehyde with a mass fraction of 25 wt% was added in 6 mL.

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