Corrosion inhibitor for pipe string of carbon dioxide huff and puff well and preparation method of corrosion inhibitor

Abstract

The invention provides a corrosion inhibitor for a carbon dioxide huff and puff well pipe column and a preparation method of the corrosion inhibitor. The preparation method comprises the following steps: modifying n-SiO2 by adopting KH792 to obtain KH792 (at) n-SiO2, and then introducing an imidazole compound and the KH792 (at) n-SiO2 into a ring-opening reaction of an intermediate polysuccinimide or epoxy succinic acid to obtain the corrosion inhibitor for the carbon dioxide huff and puff well pipe string. The corrosion inhibitor disclosed by the invention is excellent in corrosion inhibition effect, is suitable for oil fields which apply a CO2-EOR technology and are relatively serious in equipment corrosion condition and relatively harsh in corrosion condition, and has a relatively wide application prospect.

Description

Technical Field

[0001] The present invention relates to a corrosion inhibitor for a carbon dioxide huff and puff well string and a preparation method thereof, belonging to the technical field of oil exploitation. Background Art

[0002] With the development of carbon capture, utilization and storage (CCUS) science and technology, the CO 2 -EOR technology has become an economical and environmentally friendly enhanced oil recovery method, which has been applied to many oil fields and achieved certain economic benefits. However, the wide application of CO 2 flooding has also caused a series of oil field equipment corrosion problems. For example, some oil and gas fields contain high concentrations of CO 2 and have the characteristics of high pressure, high temperature and high flow rate. Under high temperature, high pressure and high flow rate conditions, corrosion and erosion-corrosion cause serious corrosion damage to the oil production and transportation system. Therefore, developing new environmentally friendly and efficient corrosion inhibitors with special resistance to high flow rate and high temperature and high pressure is of great significance for controlling corrosion under extreme conditions of CO 2 huff and puff.

[0003] Injecting a corrosion inhibitor into an oil well is one of the most commonly used methods to control CO 2 corrosion, which has the advantages of simple operation and low price. Polyaspartic acid (PASP) / polyepoxysuccinic acid (PESA) are polymers with good biocompatibility and biodegradability, which are obtained by ring-opening of intermediate polysuccinimide and epoxysuccinic acid respectively. Current research shows that both PASP / PESA can form an effective protective film on the substrate surface and can alleviate CO 2 -induced corrosion to a certain extent. Imidazoline-based corrosion inhibitors have been widely used to solve oil field corrosion problems. They can form a dense protective film on the substrate surface, effectively reduce the corrosion rate, and have good corrosion inhibition effects.

[0004] n-SiO 2 As a new type of inorganic material, due to its high specific surface area, excellent optical, electrical and thermal properties and other characteristics, it has been widely studied and applied. n-SiO 2 can combine with the metal surface to form a dense nano protective film, which can effectively isolate the corrosion medium of the external environment from catalytic activation of the object, thereby playing a role in protecting the metal. Secondly, due to the extremely small particle size of n-SiO 2 , it is easy to penetrate into the microscale pores on the metal surface or the cracks generated by corrosion to form a more stable coating layer, thereby reducing the corrosion rate. In addition, due to the relatively high hardness of n-SiO 2 itself, it can also enhance the mechanical properties of the protective film and still be able to persistently protect the substrate surface under high temperature, high pressure and high flow rate conditions. Summary of the Invention

[0005] To solve the problem that the current corrosion inhibitor has a sharp decrease in corrosion inhibition efficiency in a harsh corrosion environment of high temperature, high pressure and high flow rate, the purpose of the present invention is to provide a corrosion inhibitor for a carbon dioxide huff and puff well string applicable to a harsh corrosion environment and a preparation method thereof.

[0006] To achieve the above purpose, the present invention provides a preparation method of a corrosion inhibitor for a carbon dioxide huff and puff well string, which includes:

[0007] Using KH792 (3-(2-aminoethyl)-aminopropyltrimethoxysilane) to modify n-SiO 2 to obtain KH792-modified n-SiO 2 (KH792@n-SiO 2 ), and then introducing an imidazole compound and KH792@n-SiO 2 in the ring-opening reaction of the intermediate to obtain the corrosion inhibitor for the carbon dioxide huff and puff well string;

[0008] Wherein, the mass ratio of n-SiO 2 to KH792 is (1-3):1;

[0009] The mass of the KH792@n-SiO 2 is 0.6-1.2% of the total mass of the intermediate and the imidazole compound;

[0010] The mass ratio of the imidazole compound to the intermediate is 1:(1-1.6)

[0011] The intermediate is polysuccinimide and / or epoxy succinic acid.

[0012] According to a specific embodiment of the present invention, preferably, using KH792 to modify n-SiO 2 includes the following steps:

[0013] Disperse n-SiO 2 in a solvent, add KH792, after ultrasonic dispersion, raise the temperature for reaction, and then through separation, washing and drying, obtain KH792@n-SiO 2 .

[0014] According to a specific embodiment of the present invention, preferably, the particle size of the n-SiO 2 is 10-30nm.

[0015] According to a specific embodiment of the present invention, preferably, the reaction temperature of the temperature-raising reaction is 60-80°C, and the reaction time is 6-8 hours.

[0016] According to a specific embodiment of the present invention, preferably, this preparation method further includes the following steps:

[0017] Disperse KH792@n-SiO 2 in water, add poly(succinimide) or epoxy succinic acid and imidazole compounds to react, then add an appropriate amount of alkaline substance for ring-opening reaction. After the reaction is completed, adjust the pH value to 7, and purify and dry the product to obtain the corrosion inhibitor for the carbon dioxide huff and puff well string.

[0018] According to a specific embodiment of the present invention, preferably, the preparation method includes the following steps:

[0019] Disperse n-SiO 2 in a solvent, add KH792, after ultrasonic dispersion, raise the temperature for reaction, and then separate, wash, and dry to obtain KH792@n-SiO 2 ;

[0020] Disperse KH792@n-SiO 2 in water, add poly(succinimide) or epoxy succinic acid and imidazole compounds to react, then add an appropriate amount of alkaline substance for ring-opening reaction. After the reaction is completed, adjust the pH value to 7, and purify and dry the product to obtain the corrosion inhibitor for the carbon dioxide huff and puff well string.

[0021] According to a specific embodiment of the present invention, preferably, the imidazole compounds include N-(3-aminopropyl)imidazole or 1-aminoimidazolidinone.

[0022] According to a specific embodiment of the present invention, preferably, the reaction temperature of the ring-opening reaction is 60°C - 70°C, and the reaction time is 2 hours - 8 hours.

[0023] According to a specific embodiment of the present invention, preferably, the alkaline substance is NaOH.

[0024] The present invention also provides a corrosion inhibitor for the carbon dioxide huff and puff well string, which is prepared by the above preparation method.

[0025] The putative structure of the corrosion inhibitor is shown in Formula I:

[0026]

[0027] n-SiO 2 represents nano-silica.

[0028] According to a specific embodiment of the present invention, preferably, the preparation method of the corrosion inhibitor for the carbon dioxide huff and puff well string provided by the present invention includes:

[0029] Step 1: Modification of nano-silica

[0030] Disperse an appropriate amount of dried n-SiO2 (with a particle size of 15 nm) was dispersed in a certain amount of toluene solvent, and a certain amount of KH792 was added. It was dispersed by shaking with an SK5200H ultrasonic disperser for 0.5 - 1 h. The ultrasonically dispersed mixed solution was added to a three-necked flask equipped with a thermometer and a condenser tube, and stirred and reacted at 60 - 80 °C for 6 - 8 h. Then, it was centrifuged, washed repeatedly with ethanol, dried under vacuum, and then ground to obtain modified nano-silica, named KH792@n-SiO 2 .

[0031] Step 2: Preparation of the corrosion inhibitor for the string of huff and puff wells 2 The preparation of the corrosion inhibitor for the string of huff and puff wells

[0032] An appropriate amount of KH792@n-SiO 2 was ultrasonically dispersed in water for 0.5 - 1 h, and then an appropriate amount of PSI was added and mixed evenly to obtain a suspension. The suspension was added to a three-necked flask equipped with a thermometer and a condenser tube, and an appropriate amount of N-(3-aminopropyl)imidazole or 1-aminoimidazolidinone was slowly dropped into the suspension, and stirred and heated at 60 °C for 2 h. Then, an appropriate amount of NaOH was added to the mixed solution for ring-opening reaction (ring-opening of PASP under alkaline conditions), and reacted at 60 - 70 °C for 2 - 8 h; at the end of the reaction, the pH was adjusted to 7, and then washed, purified, dried with ethanol, and ground to obtain an orange-yellow solid powder, namely the corrosion inhibitor for the string of huff and puff wells CO 2 .

[0033] Through molecular structure design, the present invention can achieve the goals of cost reduction and environmental protection and high efficiency. During the ring-opening process of the intermediate poly(succinimide) or epoxy succinic acid, the imidazole group and n-SiO 2 are introduced into the molecular chain segments of PASP / PESA. N-(3-aminopropyl)imidazole / 1-aminoimidazolidinone and KH792@n-SiO 2 are introduced into the molecular chain segments of PASP / PESA polymer by forming -CONH- through substituting -COOH after ring-opening. Thus, by combining the excellent performance of imidazole, n-SiO 2 and PASP / PESA, a corrosion inhibitor CO for the string of huff and puff wells suitable for harsh corrosion environments is obtained 2 .

[0034] In the molecular structure of the corrosion inhibitor of the present invention, PASP / PESA main chain has multiple adsorption sites and can form a large passivation isolation film on the metal surface to prevent carbon steel from being corroded, so it is widely used to inhibit CO 2 corrosion. At the same time, both N atoms on the imidazole ring have lone pairs of electrons, which can form coordination bonds with Fe to produce adsorption. This coordination bond is a chemical bond, and the adsorption force is very strong and not easy to desorb, which is sufficient to displace the corrosive medium from the metal surface. In addition, the highly rigid n-SiO2 Maintain the original structure under high load conditions, and have good temperature, pressure and high flow rate resistance performance, and can be applied to harsh thermal / chemical conditions. At the same time, the introduction of n-SiO 2 enhances the film roughness and greatly improves the hydrophobic performance of the film, which can further prevent water molecules and other erosive ions from invading the substrate surface.

[0035] The advantages and positive effects of the present invention are as follows:

[0036] The CO 2 corrosion inhibitor for CO2 huff and puff well string is synthesized on the basis of PASP / PESA by introducing n-SiO 2 and imidazole groups. The finally obtained PASP / PESA derivative chemical agent takes into account the advantages of imidazole, n-SiO 2 and PASP to a certain extent. At the same time, the structures cooperate with each other, so as to realize the innovation of the corrosion inhibition mechanism and the innovation of the synthesis technology. The molecular structure of the CO 2 corrosion inhibitor for CO2 huff and puff well string formed by the present invention plays a decisive role in corrosion inhibition under harsh corrosion environments. The relationship between the molecular structure and the corrosion inhibition performance of the CO 2 corrosion inhibitor for CO2 huff and puff well string formed by the present invention will enrich the understanding of the relationship between the molecular structure and the corrosion inhibition performance of PASP / PESA-based chemical agents, deepen the understanding of the corrosion inhibition mechanism, and form theoretical innovation.

[0037] In the harsh corrosion environment of CO 2 huff and puff wells, the corrosion inhibitor of the present invention has excellent corrosion inhibition effect. Under the conditions of temperature 90 °C, CO 2 partial pressure 1 MPa, 3 MPa, 5 MPa, rotation speed 800 r / min, corrosion inhibitor concentration 150 mg / L, and 240 h, the corrosion inhibition rate can reach more than 90%. It is suitable for oilfields applying CO 2 -EOR technology with relatively serious equipment corrosion and relatively harsh corrosion conditions, and has a relatively broad application prospect. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is the infrared spectrogram before and after KH792@n-SiO 2 .

[0039] Figure 2 It is the infrared spectrogram of the corrosion inhibitor for CO 2 huff and puff well string.

[0040] Figure 3 It is the electrochemical test results of the corrosion inhibitor for CO 2 huff and puff well string (150 mg / L) at different temperatures.

[0041] Figure 4 Under the conditions of 0 °C and 90 °C for CO 2 SEM image of the film-forming property of the corrosion inhibitor for the tubing string of huff and puff wells on the surface of N80 steel sheet.

[0042] Figure 5 Under 5 MPa CO 2 SEM image of N80 steel sheet after high-temperature and high-pressure dynamic corrosion test under partial pressure. Specific implementation manners

[0043] The content of the present invention will be described in detail below in conjunction with specific drawings and embodiments. The following examples are only the preferred embodiments of the present invention. It should be noted that the following description is only for explaining the present invention and does not impose any form of limitation on the present invention. Any simple modifications, equivalent changes and modifications made to the embodiments according to the technical essence of the present invention all fall within the scope of the technical solution of the present invention. In the following embodiments, the materials, reagents, etc. used are all obtained from commercial channels unless otherwise specified.

[0044] Example 1:

[0045] This example provides a corrosion inhibitor for the tubing string of carbon dioxide huff and puff wells, and its preparation method includes the following steps:

[0046] S101: Disperse 3 g of n-SiO 2 (with a particle size of 15 nm) in 90 mL of toluene solvent, add 1.4 g of KH792, and disperse it by shaking with an SK5200H ultrasonic disperser for 1 h. Add the ultrasonically dispersed mixed solution to a three-necked flask equipped with a thermometer and a condenser, stir and react at 60 °C for 8 h, then centrifuge, wash repeatedly with ethanol, dry in vacuum, and finally dry and grind at 60 °C to obtain modified n-SiO 2 , named KH792@n-SiO 2 .

[0047] S102: Ultrasonically disperse 0.03 g of KH792@n-SiO 2 in 25 mL of water for 0.5 h, then add 1.19 g of PSI and mix evenly to obtain a suspension. Add the suspension to a three-necked flask equipped with a thermometer and a condenser, and slowly drop 1.81 g of N-(3-aminopropyl)imidazole into the suspension, stir and heat at 60 °C for 2 h. Then add 0.6 g of NaOH to the mixed solution and react at 60 °C for 2 h. At the end of the reaction, adjust the pH to 7, then wash, purify and dry with ethanol and grind to obtain an orange-yellow solid powder, obtaining a corrosion inhibitor for the tubing string of CO 2 huff and puff wells.

[0048] At a temperature of 90 °C, CO 2Under the harsh corrosion environment with partial pressures of 1 MPa, 3 MPa, and 5 MPa and a rotation speed of 800 r / min, the corrosion inhibition performance of the corrosion inhibitor for the CO2 huff and puff well string obtained in this example was evaluated by the dynamic weight loss method. The test results are shown in Table 1. The experimental results show that when the concentration is 150 mg / L, the corrosion inhibition rate can reach more than 90%. This indicates that the corrosion inhibitor obtained in this example has excellent corrosion inhibition performance in the harsh CO2 huff and puff corrosion environment. 2 Under the harsh corrosion environment with partial pressures of 1 MPa, 3 MPa, and 5 MPa and a rotation speed of 800 r / min, the corrosion inhibition performance of the corrosion inhibitor for the CO2 huff and puff well string obtained in this example was evaluated by the dynamic weight loss method. The test results are shown in Table 1. The experimental results show that when the concentration is 150 mg / L, the corrosion inhibition rate can reach more than 90%. This indicates that the corrosion inhibitor obtained in this example has excellent corrosion inhibition performance in the harsh CO2 huff and puff corrosion environment. 2 huff and puff corrosion environment.

[0049] Example 2:

[0050] This example provides a corrosion inhibitor for a CO2 huff and puff well string, and its preparation method includes the following steps:

[0051] S101: Disperse 3 g of n-SiO2 (with a particle size of 15 nm) in 90 mL of toluene solvent, add 1.4 g of KH792, and disperse it by shaking with a SK5200H ultrasonic disperser for 1 h. Add the ultrasonically dispersed mixed solution to a three-necked flask equipped with a thermometer and a condenser, stir and react at 60 °C for 8 h, then centrifuge, wash repeatedly with ethanol, dry under vacuum, and finally dry and grind at 60 °C to obtain modified n-SiO2, named KH792@n-SiO2. 2 (with a particle size of 15 nm) in 90 mL of toluene solvent, and add 1.4 g of KH792. Disperse it by shaking with a SK5200H ultrasonic disperser for 1 h. Add the ultrasonically dispersed mixed solution to a three-necked flask equipped with a thermometer and a condenser, stir and react at 60 °C for 8 h, then centrifuge, wash repeatedly with ethanol, dry under vacuum, and finally dry and grind at 60 °C to obtain modified n-SiO2, named KH792@n-SiO2. 2 and named KH792@n-SiO2. 2 .

[0052] S102: Ultrasonically disperse 0.018 g of KH792@n-SiO2 in 25 mL of water for 0.5 h, then add 1.4 g of PSI and mix evenly to obtain a suspension. Add the suspension to a three-necked flask equipped with a thermometer and a condenser, and slowly drop 1.6 g of N-(3-aminopropyl)imidazole into the suspension. Stir and heat at 60 °C for 2 h, then add 0.6 g of NaOH to the mixed solution and react at 60 °C for 6 h. At the end of the reaction, adjust the pH to 7, then wash, purify, and dry with ethanol and grind to obtain an orange-yellow solid powder, obtaining a corrosion inhibitor for a CO2 huff and puff well string. 2 in 25 mL of water for 0.5 h, then add 1.4 g of PSI and mix evenly to obtain a suspension. Add the suspension to a three-necked flask equipped with a thermometer and a condenser, and slowly drop 1.6 g of N-(3-aminopropyl)imidazole into the suspension. Stir and heat at 60 °C for 2 h, then add 0.6 g of NaOH to the mixed solution and react at 60 °C for 6 h. At the end of the reaction, adjust the pH to 7, then wash, purify, and dry with ethanol and grind to obtain an orange-yellow solid powder, obtaining a corrosion inhibitor for a CO2 huff and puff well string. 2 huff and puff well string.

[0053] Based on Example 1, this example adjusted the dosage ratio of PSI to N-(3-aminopropyl)imidazole, the addition amount of KH792@n-SiO2, and the reaction time after adding NaOH. Under the harsh corrosion environment with a temperature of 90 °C, CO2 partial pressures of 1 MPa, 3 MPa, and 5 MPa, and a rotation speed of 800 r / min, the CO2 huff and puff well string corrosion inhibitor obtained in this example was evaluated by the dynamic weight loss method. 2 and the addition amount of KH792@n-SiO2, as well as the reaction time after adding NaOH. Under the harsh corrosion environment with a temperature of 90 °C, CO2 partial pressures of 1 MPa, 3 MPa, and 5 MPa, and a rotation speed of 800 r / min, the CO2 huff and puff well string corrosion inhibitor obtained in this example was evaluated by the dynamic weight loss method. 2 Under the harsh corrosion environment with a temperature of 90 °C, CO2 partial pressures of 1 MPa, 3 MPa, and 5 MPa, and a rotation speed of 800 r / min, the CO2 huff and puff well string corrosion inhibitor obtained in this example was evaluated by the dynamic weight loss method. 2Corrosion inhibition performance of the corrosion inhibitor for huff and puff well string. The test results are shown in Table 1. The experimental results show that when the concentration is 150 mg / L, the corrosion inhibition rate can reach more than 90%. Thus, it shows that the CO 2 The corrosion inhibitor for huff and puff well string 2 has excellent corrosion inhibition performance in a harsh CO

[0054] Example 3:

[0055] This example provides a corrosion inhibitor for carbon dioxide huff and puff well string, and its preparation method includes the following steps:

[0056] S101: Disperse 3 g of n-SiO 2 (with a particle size of 15 nm) in 90 mL of toluene solvent, add 1.4 g of KH792, and disperse it by shaking with a SK5200H ultrasonic disperser for 1 h. Add the ultrasonically dispersed mixed solution to a three-necked flask equipped with a thermometer and a condenser, stir and react at 60 °C for 8 h, then centrifuge and wash repeatedly with ethanol, vacuum dry, and finally dry and grind at 60 °C to obtain modified n-SiO 2 , named KH792@n-SiO 2 .

[0057] S102: Ultrasonically disperse 0.024 g of KH792@n-SiO 2 in water for 0.5 h, then add 1.33 g of PSI and mix evenly to obtain a suspension. Add the suspension to a three-necked flask equipped with a thermometer and a condenser, and slowly drop 1.67 g of N-(3-aminopropyl) imidazole into the suspension, stir and heat at 60 °C for 2 h. Then add 0.6 g of NaOH to the mixed solution and react at 60 °C for 8 h. At the end of the reaction, adjust the pH to 7, then wash, purify and dry with ethanol and grind to obtain an orange-yellow solid powder, obtaining the corrosion inhibitor for carbon dioxide huff and puff well string 2 .

[0058] Based on Example 1, this example adjusted the dosage ratio of PSI to N-(3-aminopropyl) imidazole, the addition amount of KH792@n-SiO 2 and the reaction time after adding NaOH. In a harsh corrosion environment with a temperature of 90 °C, a CO 2 partial pressure of 1 MPa, 3 MPa, 5 MPa, and a rotation speed of 800 r / min, the corrosion inhibition performance of the corrosion inhibitor for carbon dioxide huff and puff well string obtained in this example was evaluated by the dynamic weight loss method. The test results are shown in Table 1. The experimental results show that when the concentration is 150 mg / L, the corrosion inhibition rate can reach more than 90%. Thus, it shows that the corrosion inhibitor for carbon dioxide huff and puff well string obtained in this example 2 has excellent corrosion inhibition performance in a harsh CO 2 huff and puff corrosion environment2 It has excellent corrosion inhibition performance in the throughput corrosion environment.

[0059] Comparative Example 1:

[0060] The difference between this comparative example and Example 1 is that n-SiO was not added during the preparation process 2 , and the specific preparation method is as follows:

[0061] 1.19 g of PSI was dispersed evenly in 25 mL of water to obtain a suspension. The suspension was added to a three-necked flask equipped with a thermometer and a condenser, and 1.81 g of N-(3-aminopropyl)imidazole was slowly dropped into the suspension, and stirred and heated at 60 °C for 2 h. Then 0.6 g of NaOH was added to the mixed solution, and reacted at 60 °C for 2 h. At the end of the reaction, the pH was adjusted to 7, and then washed with ethanol, purified, dried and ground to obtain an orange-yellow solid powder.

[0062] Comparative Example 2:

[0063] The difference between this comparative example and Example 2 is that n-SiO was not added during the preparation process 2 .

[0064] Its preparation method is as follows:

[0065] 1.4 g of PSI was dispersed evenly in 25 mL of water to obtain a suspension. The suspension was added to a three-necked flask equipped with a thermometer and a condenser, and 1.6 g of N-(3-aminopropyl)imidazole was slowly dropped into the suspension, and stirred and heated at 60 °C for 2 h. Then 0.6 g of NaOH was added to the mixed solution, and reacted at 60 °C for 6 h. At the end of the reaction, the pH was adjusted to 7, and then washed with ethanol, purified, dried and ground to obtain an orange-yellow solid powder.

[0066] Comparative Example 3:

[0067] The difference between this comparative example and Example 3 is that n-SiO was not added during the preparation process 2 .

[0068] Its preparation method is as follows:

[0069] 1.33 g of PSI was dispersed evenly in water to obtain a suspension. The suspension was added to a three-necked flask equipped with a thermometer and a condenser, and 1.67 g of N-(3-aminopropyl)imidazole was slowly dropped into the suspension, and stirred and heated at 60 °C for 2 h. Then 0.6 g of NaOH was added to the mixed solution, and reacted at 60 °C for 8 h. At the end of the reaction, the pH was adjusted to 7, and then washed with ethanol, purified, dried and ground to obtain an orange-yellow solid powder.

[0070] The n-SiO before and after being modified by KH792 provided in the embodiments of the present invention 2 The infrared characterization results are as Figure 1 shown below:

[0071] The infrared spectra of the n-SiO before and after being modified by KH792 2 are respectively shown as (A) in Figure 1 and (B) in Figure 1 . A C-H stretching vibration peak appears at 2996 cm -1 , and a relatively strong absorption peak appearing at 1396 cm -1 is attributed to the stretching vibration peak of the -C-N- bond;

[0072] The asymmetric stretching vibration peak and symmetric stretching vibration peak of the Si-O-Si bond concentrate at the broad peak position at 1119 cm -1 . The stretching vibration peak of the Si-C bond appears at 807 cm -1 , and the characteristic absorption peak of C═C appears at 1634 cm -1 , indicating that the modification of n-SiO 2 by KH792 is successful.

[0073] The infrared characterization results of the corrosion inhibitor for the CO 2 huff and puff well string provided in Embodiment 3 of the present invention are as Figure 2 shown below:

[0074] The infrared spectra of PSI, PASP and n-SiO 2 @PASP are as Figure 2 shown. It can be clearly seen from Figure 2 that the carbonyl stretching vibration absorption peak corresponding to the imide in PSI at 1715 cm -1 disappears in PASP, indicating that PSI is successfully ring-opened. In the infrared spectrum of n-SiO 2 @PASP, the absorption peak near 1643 cm -1 has a relatively wide peak. It is analyzed that this is caused by the overlap of the stretching vibration peak of -C═N- and the carbonyl stretching vibration absorption peak of the amide. Among them, -C═N- is the characteristic peak of the imidazole ring. The absorption peak at 1397 cm -1 is the stretching vibration peak of the -C-N bond. The absorption peak near 1089 cm -1 has a relatively wide peak. It is analyzed that this is caused by the overlap of the stretching vibration peaks of the Si-O-Si bond and the carbon-carbon skeleton on the imidazole ring. The stretching vibration peak of the Si-C bond appears at 795 cm -1 . In summary, n-SiO 2 and the imidazole group are successfully introduced into the PASP molecular chain, indicating that n-SiO 2 @PASP(CO2 The corrosion inhibitor for the production-injection well string has been successfully synthesized.

[0075] The water solubility of the products synthesized in Examples 1-3 was tested. The test results showed good water solubility, and it could completely dissolve in pure water at a concentration of 1000 ppm.

[0076] The film-forming performance of the corrosion inhibitor synthesized in Example 1 on the surface of N80 steel sheets at different temperatures was tested by film-forming experiments. In a 3.5% wt NaCl aqueous solution of 1000 ppm corrosion inhibitor solution, after pre-filming at a constant temperature of 0 °C and 90 °C for 1 h, the SEM characterization results are as Figure 4 shown. In Figure 4 , a represents the blank sample + constant temperature of 0 °C; b represents the blank sample + constant temperature of 90 °C; c represents the 1000 ppm sample + constant temperature of 0 °C; d represents the 1000 ppm sample + constant temperature of 90 °C.

[0077] Combined with Figure 3 the electrochemical test results at different temperatures, and comparing the film-forming properties of the corrosion inhibitor on the surface of N80 steel sheets before and after adding the corrosion inhibitor ( Figure 4 ), it can be seen that the corrosion inhibitor pre-filming was successful under the conditions of 0 °C and 90 °C, indicating that the synthesized corrosion inhibitor CO 2 corrosion inhibitor for production-injection well string n-SiO 2 @PASP can achieve a corrosion inhibition effect both at low and high temperatures.

[0078] To prove the beneficial effects of the present invention, the present invention simulated the CO 2 oil displacement process, used CCUS oil well produced water, and tested the corrosion inhibition performance of the corrosion inhibitors prepared in Examples 1-3 in a high-temperature and high-pressure corrosion tester. At the same time, a blank experiment without adding a corrosion inhibitor was conducted. The test results are shown in Table 1 (the test results of the comparative examples are shown in Table 2).

[0079] Table 1 Corrosion inhibition performance of the corrosion inhibitor for the production-injection well string under different CO 2 partial pressures (Examples 1-3) 2

[0080]

[0081]

[0082] Table 2 Corrosion inhibition performance of the corrosion inhibitor for the production-injection well string under different CO 2 partial pressures (Comparative Examples 1-3) 2

[0083]

[0084] Note: Experimental conditions: N80, 90 °C, 240 h, flow rate of 800 r / min, inhibitor dosage of 150 mg / L.

[0085] Figure 5 CO with a partial pressure of 5 MPa 2 SEM images of N80 steel sheets after high-temperature and high-pressure dynamic corrosion tests under a partial pressure of. In Figure 5 a represents the blank sample; b represents the sample with 150 mg / L inhibitor added.

[0086] As can be seen from Table 1 and Table 2, when the partial pressures of CO 2 are 1 MPa, 3 MPa, and 5 MPa respectively, and the n-SiO 2 @PASP inhibitor prepared in Examples 1-3 with a concentration of 150 mg / L is added, the corrosion rate is significantly lower than the blank corrosion rate, and the inhibition rates all reach over 90%. However, the inhibition effect of the inhibitor prepared in the comparative example is not good, indicating that the introduction of SiO 2 can effectively improve the inhibition rate under high-temperature and high-pressure conditions, and the introduction of SiO 2 may produce a synergistic effect with the polyaspartic acid chain and the imidazole group, thereby improving the inhibition efficiency. This shows that the n-SiO 2 @PASP inhibitor can effectively inhibit the corrosion of the N80 tubing by the produced water in CCUS oil wells under a certain partial pressure of CO 2 .

Claims

1. A preparation method of a corrosion inhibitor for a carbon dioxide huff and puff well string, which comprises: Using KH792 to modify n-SiO 2 to obtain KH792@n-SiO 2 , and then introducing an imidazole compound and KH792@n-SiO 2 in the ring-opening reaction of the intermediate to obtain the corrosion inhibitor for the carbon dioxide huff and puff well string; Among them, the mass ratio of n-SiO 2 to KH792 is (1 - 3):1; The KH792@n-SiO 2 has a mass of 0.6 - 1.2% of the total mass of the intermediate and the imidazole compound; The mass ratio of the imidazole compound to the intermediate is 1:(1 - 1.6); The intermediate is poly(succinimide) and / or epoxy succinic acid.

2. The preparation method according to claim 1, wherein, Modifying n-SiO with KH792 2 includes the following steps: Disperse n-SiO 2 in a solvent, add KH792, after ultrasonic dispersion, raise the temperature for reaction, and then through separation, washing, and drying, KH792@n-SiO 2 is obtained.

3. The preparation method according to claim 1 or 2, wherein, The n-SiO 2 has a particle size of 10 - 30 nm.

4. The preparation method according to claim 2, wherein, The reaction temperature of the temperature-raising reaction is 60 - 80 °C, and the reaction time is 6 - 8 hours.

5. The preparation method according to claim 1 or 2, wherein, This preparation method further comprises the following steps: Disperse KH792@n-SiO 2 in water, add polysuccinimide or epoxy succinic acid and imidazole compounds to react, then add an appropriate amount of alkaline substance for ring-opening reaction. After the reaction is completed, adjust the pH value to 7, purify and dry the product to obtain the corrosion inhibitor for the carbon dioxide huff and puff well string.

6. The preparation method according to claim 1, wherein, This preparation method comprises the following steps: Disperse n-SiO 2 in a solvent, add KH792, after ultrasonic dispersion, raise the temperature for reaction, and then through separation, washing, and drying, obtain KH792@n-SiO 2 ; Disperse KH792@n-SiO 2 in water, add polysuccinimide or epoxy succinic acid and imidazole compounds to carry out a reaction, then add an appropriate amount of alkaline substance to carry out a ring-opening reaction. After the reaction is completed, adjust the pH value to 7, purify and dry the product to obtain the corrosion inhibitor for the carbon dioxide huff and puff well string.

7. The preparation method according to claim 5 or 6, wherein, The imidazole compound includes N-(3-aminopropyl)imidazole or 1-aminoimidazolidinone.

8. The preparation method according to claim 5 or 6, wherein, The reaction temperature of the ring-opening reaction is 60 °C - 70 °C, and the reaction time is 2 hours - 8 hours.

9. The preparation method according to claim 5 or 6, wherein, The alkaline substance is NaOH.

10. A corrosion inhibitor for a carbon dioxide huff and puff well string, which is prepared by the preparation method according to any one of claims 1 - 9.

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