Modified corrosion inhibitor, capsule of alginate gel encapsulated corrosion inhibitor and preparation method and application of capsule

Abstract

The invention relates to the technical field of steel anti-corrosion materials in oil and gas field wells, in particular to a modified corrosion inhibitor, a capsule for encapsulating the corrosion inhibitor through alginate gel and a preparation method and application of the capsule. The corrosion inhibitor is a compound as shown in a structural formula I, and is prepared into a capsule of the corrosion inhibitor encapsulated by alginate gel; the capsule system is applied to a high-temperature oil and gas field well and Q235 carbon steel in an oil well causes serious CO2 corrosion to metal due to high temperature and a saturated CO2 acidic environment, and a corrosion inhibition film can be formed on the surface of the metal by applying the imidazole corrosion inhibitor so as to protect a carbon steel matrix. And furthermore, a long-chain alkyl modified imidazole corrosion inhibitor is encapsulated in the alginate capsule, so that higher sinking speed and longer protection time can be obtained. The corrosion inhibition capsule disclosed by the invention can realize intelligent response, is long-acting and durable, is high in cost performance, and has a remarkable application value and a wide market prospect. # imgabs0 #

Description

Technical Field

[0001] The invention relates to the technical field of steel anticorrosion materials in oil and gas field wells, and more specifically to a modified corrosion inhibitor, a capsule of an alginate gel encapsulated corrosion inhibitor, and a preparation method and application thereof. Background Art

[0002] At present, the energy required for industrial production in the world is mainly coal, oil and natural gas, and in the foreseeable future, oil and natural gas energy will still be the main source of energy and industrial by-products. At the same time, carbon steel has high strength and can withstand the huge pressure faced by various equipment during oil field exploitation. Therefore, as an important global energy resource, oil faces many challenges in its exploitation and production process, among which the corrosion problem of carbon steel equipment is particularly prominent. In oil field exploitation, since formation water contains a variety of corrosive media, such as dissolved oxygen, hydrogen sulfide, carbon dioxide, etc., as well as acidification, water injection and other processes used in the exploitation process, metal equipment will be severely corroded. Corrosion not only causes equipment damage and increased maintenance costs, but may also cause safety accidents and pollute the environment. Therefore, how to effectively control the corrosion of oil field equipment has become a key issue that needs to be solved in the development of the oil industry. However, corrosion protection in high-temperature oil and gas equipment is extremely difficult. The high-temperature wells here refer to oil and gas field wells with an operating temperature above 60°C. In such extreme environments, the commonly used corrosion inhibitors in the market (BTA, MBT, etc.) will dissociate and become ineffective due to their poor chemical structure stability. Therefore, there are few reports on corrosion protection of carbon steel in high-temperature wells.

[0003] Although there have been extensive reports on the use of microcapsules to encapsulate corrosion inhibitors to achieve controlled release of target molecules, most of them are limited to doping microcapsules in the coating and then coating it on the surface of the substrate. The disadvantage of this approach is that the response of the microcapsules to the primary corrosion site is mainly based on the stress cracking caused by the microcracks in the coating, and it cannot respond to other physical environmental changes, and the protection time is short when applied alone. On the other hand, the performance of the corrosion inhibitor is continuously lost due to the flow effect downhole in the oil and gas field, and the high temperature environment also causes the corrosion inhibitor molecules to decompose and become ineffective due to thermal decomposition. In addition, the bonding problem between the coating and the substrate caused by the difficulty of surface treatment of engineering structures downhole in oil wells will also make the application flexibility of the microcapsule corrosion inhibition system subject to multiple restrictions of environmental factors, and the corrosion inhibitor applied alone cannot sink into the working area of ​​the oil well. Moreover, in the existing microcapsule corrosion inhibition system, the loading efficiency of the corrosion inhibitor is low, usually less than 60%.

[0004] Generally speaking, a loaded corrosion inhibitor is a functional substance that uses a carrier material to fix, encapsulate or adsorb the corrosion inhibitor molecules, and through the synergistic effect of the carrier and the corrosion inhibitor, better achieves corrosion protection of metals and other materials. It aims to solve the problems that traditional corrosion inhibitors may have during use, such as difficult to control the release rate, short action time, and weak pertinence. It is the skeleton structure of the entire system, and common ones are organic gels (such as polyacrylamide gel, etc.) and inorganic gels (silicone gel, etc.). The gel has a three-dimensional network structure with a large number of pores and channels inside, which can accommodate and fix the corrosion inhibitor molecules and play the role of physical support and carrier. Among these materials, alginate is widely used in material encapsulation due to its non-toxicity, high mechanical strength, and porous internal structure. In addition, environmental response factors are doped in the capsule to achieve its intelligent response and controlled release ability; at present, alginate gel is mainly used in drug delivery, chemical sensors, catalysis, and drug delivery, and there are few related reports in the preparation of targeted corrosion inhibitors for oil well corrosion protection. Summary of the invention

[0005] The purpose of the present invention is to overcome the above problems and defects in the prior art and provide a modified corrosion inhibitor.

[0006] Another object of the present invention is to provide a capsule containing the alginate gel encapsulated corrosion inhibitor.

[0007] Another object of the present invention is to provide a method for preparing the alginate gel-encapsulated corrosion inhibitor capsules.

[0008] The fourth object of the present invention is to provide the application of the alginate gel capsule encapsulating the corrosion inhibitor.

[0009] To achieve the above purpose, the following technical solutions are used:

[0010] A modified corrosion inhibitor, the corrosion inhibitor is a compound as shown in structural formula 1,

[0011]

[0012] The compound shown in formula 1 is a mixture of 4-aminobenzimidazole [4,5] [1,2-a] pyrimidine-2(1H)-1 and octadecyloxybenzoic acid in a molar ratio of 1-1.2:1; the mixture is dissolved in a DMSO analytical pure solution and reacted under the catalysis of N,N'-carbonyldiimidazole (CDI) to obtain the compound.

[0013] Further, the compound shown in formula 1 is prepared by adding 4-aminobenzimidazole [4,5] [1,2-a] pyrimidine-2(1H)-1 and octadecyloxybenzoic acid to a DMSO solution at 150-160° C. and stirring and mixing, and then reacting with N,N'-carbonyldiimidazole (CDI) to obtain a catalytic reaction product. 2 The atmosphere is fully reacted for 2 to 2.5 hours to obtain a long-chain alkoxybenzimidazole pyrimidone corrosion inhibitor.

[0014] The loading content of the modified corrosion inhibitor can reach 11.1-13.2%, and the loading efficiency is 91.22-93.41%. Both the loading content and the efficiency are not lower than those of the existing gel capsule corrosion inhibition system.

[0015] An application of the modified corrosion inhibitor is the application of the corrosion inhibitor in high temperature (above 60° C.) protection of corrosion-inducing areas of carbon steel products in high-temperature oil and gas field wells.

[0016] The corrosion inhibitor has a stronger corrosion inhibition effect; however, since the N atom in 4-aminobenzimidazole [4,5] and [1,2-a] pyrimidine-2 (1H) -1 contains a conjugated large π bond, it can produce π-π stacking, making the compound have extremely strong coordination to metal ions. In addition, the SP2 hybridized N atom contains a lone pair of electrons. At this time, the metal iron ion, as an acidic center, will accept electrons from the N and O atoms, so that the entire corrosion inhibitor molecule tends to maintain electrical neutrality and thus reduce corrosiveness.

[0017] Preferably, the corrosion inhibitor is an imidazole corrosion inhibitor modified with a long-chain alkyl group; since the imidazole corrosion inhibitor has a strong coordination property to metal ions, it has poor thermal stability and will dissociate in a solution at 50°C, losing 80% of its corrosion inhibition performance, thus failing to provide metal protection in a high-temperature solution. Long-chain alkyl groups with more than 12 carbon atoms can be combined with it to improve the thermal stability of the corrosion inhibitor, thereby making the structure of the imidazole corrosion inhibitor more stable, thereby avoiding the dissociation and desorption of the adsorption film of the corrosion inhibitor in common high-temperature solutions, thereby achieving the modification of the high-temperature thermodynamic properties of the imidazole corrosion inhibitor. At the same time, in actual engineering applications, sodium alginate and polyacrylamide can produce certain scale inhibition properties, thereby achieving comprehensive integrated corrosion protection for high-temperature downhole environments.

[0018] The corrosion inhibitor has a strong coordination property to metal ions, and its thermal stability is poor. It will dissociate in a solution at 50°C, and lose 80% of its corrosion inhibition performance, so that it cannot achieve the function of protecting metals in high-temperature solutions. The present invention modifies it with a long-chain alkyl group to improve the thermal stability of the corrosion inhibitor, thereby making the structure of the imidazole corrosion inhibitor more stable, thereby avoiding the dissociation and desorption of the adsorption film of the corrosion inhibitor in common high-temperature solutions, and then realizing the modification of the high-temperature thermodynamic properties of the imidazole corrosion inhibitor.

[0019] A capsule of an alginate gel encapsulated corrosion inhibitor, the capsule comprises a shell and an inner filling, the shell is an alginate gel containing a dopant, and the inner filling is the corrosion inhibitor according to claim 1; the molar ratio between the corrosion inhibitor and the alginate gel material is 5 to 8:1.

[0020] The alginate gel containing dopants is a mixture of polyacrylamide particles, alginate solution and barium sulfate solid, wherein the molar ratio of each component is 10-12:5-8:11-13.

[0021] The alginate is one or more of sodium alginate, polyacrylamide, barium sulfate, and calcium alginate, preferably sodium alginate with a viscosity of 2000.

[0022] A method for preparing alginate gel encapsulated corrosion inhibitor capsules, comprising mixing the corrosion inhibitor solution described in claim 1 with polyacrylamide particles and barium sulfate solid, adding a sodium alginate solution preheated to 70-80°C, dropping a 15wt% CaCl2 solution into the mixed solution, and obtaining alginate gel encapsulated corrosion inhibitor capsules by a one-pot synthesis method.

[0023] The molar ratio of the corrosion inhibitor solution, the polyacrylamide particles, the alginate solution and the barium sulfate solid is 1:10-12:5-8:11-13.

[0024] The one-pot synthesis is to place the mixed solution on a constant temperature stirring table at 800-1200 rpm (preferably 1000 rpm) and mix for 20-30 min (preferably 25 min), and the reaction temperature is 60° C.-80° C. (preferably 75° C.).

[0025] An application of the alginate gel encapsulated corrosion inhibitor capsule, the alginate gel encapsulated corrosion inhibitor capsule is used in the high temperature (above 60° C.) protection of the corrosion inducing area of ​​carbon steel products in high-temperature oil and gas field wells.

[0026] Furthermore, the alginate gel capsule is used in the preparation of a directional controlled-release corrosion inhibitor.

[0027] Furthermore, alginate gel capsules are used in the preparation of corrosion inhibitors for heavy directional temperature-sensitive seawater oil well carbon steel or metal products.

[0028] The present invention also provides the use of the alginate gel-encapsulated corrosion inhibitor capsule in the directional protection of the corrosion-inducing area of ​​carbon steel or metal products in the oil and gas underground working area; the alginate shell in the corrosion inhibitor capsule can respond to the temperature of the metal CO2 corrosion environment caused by the high-temperature circulation process in the oil and gas underground working area, thereby implementing the directional release of the corrosion inhibitor and long-term protection at the corrosion sites in the deeper oil well working area.

[0029] Specifically, the capsules of the alginate gel encapsulated corrosion inhibitor are directly placed in the produced water pipeline of the oil and gas field for protection. It can be widely used in produced water circulation systems, oil and gas gathering pipelines, high-temperature oil well pumps and various equipment in high-temperature oil and gas field acidic solutions or acidic marine environments. Compared with traditional methods, it has a wider range of applications and more significant effects.

[0030] Specifically, the pH range of the weakly acidic environment generated by CO2 corrosion of the carbon steel in the oil well working area is 3.5 to 4.5.

[0031] The main working principle of the capsule of the present invention is that carbon steel produces serious CO in the well of oil and gas field. 2 Corrosion, and the water film with extremely high oxygen content formed on the surface of carbon steel in the corrosion area further combines with the metal matrix to produce serious local metal defects, resulting in high temperature and acidic environment, and then the corrosion inhibitor composite is obtained based on the problems that the corrosion inhibitor can adapt to high temperature and is acid-resistant. The imidazole corrosion inhibitor is thermodynamically modified from a long-chain alkyl group, and a specific combination of loose and porous alginate gel materials is used as a carrier to internally encapsulate the corrosion inhibitor (long-chain alkoxy-modified imidazole corrosion inhibitor) molecules to obtain capsules. When the high temperature and acidic environment in the working area of ​​the oil well is in contact with the gel corrosion inhibition capsule, it has The thermosensitive dissociative gel capsule responds to the temperature rise stimulus generated by the operation in the oil well, and produces structural dissociation to release the corrosion inhibitor encapsulated inside. The barium sulfate in the capsule acts as a role in increasing the density of the corrosion-inhibiting capsule, thereby achieving directional delivery of the capsule to areas deep underground to achieve severe corrosion areas, and forms an insoluble protective film on the surface of the corrosion substrate to achieve the corrosion inhibitor protection effect. In the absence of high-temperature corrosion, the alginate / polyacrylamide shell stores and protects the active groups of the corrosion inhibitor from degradation in the oil and gas field solution, thereby achieving the sensitized anti-corrosion performance of the corrosion inhibitor composite system. At the same time, in actual engineering applications, sodium alginate and polyacrylamide can produce certain scale inhibition properties, thereby further achieving comprehensive integrated corrosion protection for high-temperature underground environments. Compared with the prior art, the present invention has the following beneficial effects:

[0032] (1) The capsules of the alginate gel loaded with corrosion inhibitors of the present invention have the characteristics of directional sinking, temperature response and long-term protection; when metal products are exposed to high-temperature CO in high-temperature oil and gas fields, 2 During corrosion, the alginate shell of the corrosion inhibitor capsule of the present invention will sink to the working area and dissociate to deliver the corrosion inhibitor to the metal corrosion area, realize directional recognition and release, and form an insoluble protective film on the surface of the corroded substrate to achieve corrosion inhibition effect. The alginate shell used has heavy sinking and temperature sensitivity that other gels do not have, so it is very suitable for the corrosive environment of oil and gas fields. At its temperature dissociation critical point, alginate can sink to the designated area in time to deal with the high temperature and CO in the deep working area of ​​the oil well.2 It responds to the corrosive environment and can quickly release corrosion inhibitors to act on the corrosive area.

[0033] (2) In the preparation process of the alginate gel-loaded corrosion inhibitor capsule of the present invention, polyacrylamide (PAM) is innovatively used to fill the pores of the alginate gel to play a temperature responsive role, such as Figure 6 The polyacrylamide shown in the figure effectively reduces the capsule pores, thereby achieving temperature-controlled capsule release. Barium sulfate is added to the alginate gel to increase the density of the gel capsule, so that it can quickly sink into the corrosion working area. The three interact with each other to jointly address the technical defects of flow failure, high temperature failure, and redundant deployment of the oil and gas downhole corrosion inhibition system.

[0034] (3) The loading rate of the corrosion inhibitor in the alginate gel-loaded corrosion inhibitor capsule of the present invention is 11.1-18.3%, and the loading efficiency is 91.22-93.41%, which is much higher than the loading efficiency (<60%) of the corrosion inhibitor encapsulation system studied in the past. When the oil well water production and other physical effects are destroyed, the corrosion inhibitor will act on the insoluble protective film formed on the surface of the corroded substrate. At this time, the sufficient corrosion inhibitor in the loose and porous structure of the alginate can continuously protect the metal substrate and has a long-term effect.

[0035] (4) The alginate gel-loaded corrosion inhibitor capsules of the present invention are highly efficient and durable, have high yields, and are used in small amounts. They can be added in large quantities to the oil well water production circulation system. The corrosion inhibition complex encapsulated in the capsules can respond to and release in a high temperature environment, thereby maintaining a high anti-corrosion efficiency in a high temperature environment for a long time.

[0036] (5) When the alginate gel-loaded corrosion inhibitor capsule of the present invention releases the imidazole corrosion inhibitor in response to the corrosive environment, the alginate and polyacrylamide components in the capsule shell material are also dissociated in a high temperature environment and complexed with the metal material to produce a complex that has a certain scale inhibition effect.

[0037] (6) The alginate gel-loaded corrosion inhibitor capsules of the present invention have the characteristics of high cost performance. The effective ingredient of the corrosion inhibitor is 4-aminobenzimidazol[4,5][1,2-a]pyrimidin-2(1H)-one modified with a long-chain alkyl group. The raw materials for the synthesis of the complex are widely available, the preparation method is simple, the yield is high, and mass production can be carried out, so the comprehensive application cost is low.

[0038] (7) The alginate gel-loaded corrosion inhibitor capsule 4-aminobenzimidazole [4,5] [1,2-a] pyrimidine-2(1H)-1 of the present invention is widely used as a pharmaceutical intermediate. At the same time, the shell materials used in the alginate gel capsule carrier are all biologically active ingredients, which are safe, green and non-toxic, and are in line with the development trend of green corrosion inhibition systems.

[0039] (8) The alginate gel-loaded corrosion inhibitor capsules of the present invention have strong universality and are suitable for oil well CO 2 Corrosion will only take effect when it occurs in a corresponding high-temperature environment, and it has excellent stability to various external conditions such as salinity and pressure. Therefore, this material is widely used in corrosion protection in various underground working areas of oil and gas fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 The molecular structure diagram of the synthetic octadecyloxybenzimidazolopyrimidone-quaternary ammonium salt (OBIP) provided in the embodiment of the present invention.

[0041] Figure 2 The invention provides a synthetic route of octadecyloxybenzimidazolopyrimidone-quaternary ammonium salt (OBIP) in accordance with an embodiment of the present invention.

[0042] Figure 3 FT-IR (a) and H-NMR (b) spectra of octadecyloxybenzimidazolopyrimidone-quaternary ammonium salt (OBIP) provided in an embodiment of the present invention.

[0043] Figure 4 This is a synthetic schematic diagram of the alginate gel-loaded corrosion inhibitor capsule provided in an embodiment of the present invention.

[0044] Figure 5 Scanning electron microscope and energy dispersive spectrometer element distribution diagram of alginate gel loaded corrosion inhibitor capsule (b) and blank capsule (a) provided in the embodiment of the present invention

[0045] Figure 6 BET isothermal adsorption curves (a) and pore size distribution diagrams (b) of alginate gel-loaded corrosion inhibitor capsules, blank capsules, and comparative capsules provided in the embodiments of the present invention DETAILED DESCRIPTION

[0046] The present invention is further described below in conjunction with the accompanying drawings and specific examples, but the examples do not limit the present invention in any form. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the art.

[0047] Unless otherwise specified, the reagents and materials used in the following examples are commercially available.

[0048] The present invention uses a capsule SA@PAM@OBIP loaded with corrosion inhibitors in alginate gel to illustrate the intention of the present invention. A carbon steel corrosion inhibitor is used as a carrier using a specific combination material containing a temperature-responsive alginate gel and a long-chain alkyl-modified 4-aminobenzimidazole [4,5] and [1,2-a] pyrimidine-2(1H)-1 (OBIP) as a loading object. The carrier contains polyacrylamide (PAM) and barium sulfate, and the three are specifically combined and synergistic. Polyacrylamide (PAM) and sodium alginate gel are modified with temperature-sensitive factors, thereby realizing temperature-responsive encapsulation of carbon steel corrosion inhibitor in alginate gel. The corrosion inhibition system is used in high-temperature areas underground in oil and gas fields. Carbon steel or metal products are exposed to acidic CO2 due to the alternating high temperature of the oil field production cycle. 2 The environment causes the alginate capsules to dissociate and release corrosion inhibitors, which can achieve directional protection of the oil well working area. 2 The adsorption orientation of alkyl imidazole corrosion inhibitors changes under high temperature and acidic environment, and can also improve the thermal stability of the corrosion inhibitor adsorption film and enhance the hydrophobicity of the substrate. The corrosion inhibition capsules of the present invention can respond intelligently, be long-lasting, and have high cost performance, and have significant application value and broad market prospects.

[0049] The corrosion inhibition capsule system is based on the protective effect of the porous structure of alginate gel on the activity of the guest and the property of releasing the guest molecules due to the difference in expansion of alginate and polyacrylamide when heated. By constructing a core-shell structure system (SA@PAM@OBIP) of OBIP in alginate (SA) porous structure composite polyacrylamide, the adaptability of OBIP to the harsh corrosion environment in the sea-high temperature oil well production solution area on the surface of carbon steel is enhanced. At the same time, the adsorption orientation of OBIP changes under high temperature conditions, thereby improving its thermal stability, thereby adapting to the environment, protecting alloys such as carbon steel, and inhibiting CO 2 Integration of corrosion capabilities.

[0050] The present invention adopts two electrochemical methods, electrochemical impedance spectroscopy and potentiodynamic polarization, to characterize the rust inhibition performance. Although the rust inhibition efficiency obtained by the two methods is different, the electrochemical impedance spectroscopy tests the corrosion efficiency over a period of time, and the potentiodynamic polarization method tests the corrosion efficiency in a transient process, but the overall change trend of various methods is consistent. It can be seen that the compound has excellent rust inhibition performance under different corrosion inhibitor concentrations, temperatures, and pH conditions. The experimental test method adopted is from the following national standards: [1] ISO 16773-4-2009, Paints and varnishes. Electrochemical impedance spectroscopy (EIS) of high impedance coating samples. Part 4: Spectral examples of polymer coated samples [S]. (Weight loss experiment, electrochemical impedance spectroscopy experiment to determine the rust inhibition efficiency) [2] GB / T 24196-2009, Electrochemical test methods for corrosion of metals and alloys - Guide for constant potential and potentiodynamic polarization measurements [S]. (Determination of rust inhibition efficiency by potentiodynamic polarization curve experiment).

[0051] Example 1

[0052] Preparation of corrosion inhibitor composite (octadecyloxybenzimidazolopyrimidone-quaternary ammonium salt (OBIP)):

[0053] The reaction substrates 4-aminobenzo[4,5]imidazole[1,2-a]pyrimidine-2(1H)-1, 4-(octadecyloxy)benzoic acid and DMSO were added into a round-bottom flask at a molar ratio of 1:1. 2 Under protection, co-heat and stir at 150°C for 3 hours to obtain a crystalline brown liquid. The solution is distilled and dried under reduced pressure at 80°C to obtain a precipitate. The precipitate is filtered, washed three times with ethanol, vacuum dried, and recrystallized from anhydrous ethanol to obtain a pure product of the OBIP intermediate. The product is co-heated with epichlorohydrin at 85°C for 24 hours to obtain an OBIP solution. The solution is distilled and dried under reduced pressure at 80°C to obtain OBIP. The precipitate is then filtered, washed three times with ethanol, vacuum dried, and recrystallized from ethanol to obtain a pure product of OBIP (see the chemical structure). Figure 1 And synthetic route to participate Figure 2 ) The structure of the synthesized product was verified by Fourier transform infrared spectroscopy and nuclear magnetic resonance hydrogen spectrum characterization, such as Figure 3 shown.

[0054] Example 2

[0055] Capsule shell preparation

[0056] 0.6 g sodium alginate (SA) and 1.2 g BaSO 4 Heat and mix in 15 ml (99 wt%) solution. Stir the solution at 70 °C for 15 minutes. Draw the reaction solution into a 5 ml syringe, then add 15 wt% CaCl 2After standing for 10 minutes, light yellow transparent particles with clear outlines were obtained. The granular products were collected by centrifugation and dried in an oven at 60°C for 24 hours to obtain the pure product of SA blank capsules.

[0057] Comparative Example 1

[0058] Preparation of alginate gel capsule shell doped with polyacrylamide / barium sulfate

[0059] By using a one-pot synthesis method in alginate gel capsule shell doped with polyacrylamide / barium sulfate,

[0060] 0.6 g sodium alginate (SA), 0.5 g polyacrylamide (PAM) and 1.2 g BaSO 4 Mix in 15 ml (99 wt%) solution. Stir the solution at 70 °C for 15 minutes. Draw the reaction solution into a 5 ml syringe, then add 15 wt% CaCl 2 After standing for 10 minutes, light yellow transparent particles with clear outlines were obtained. The granular products were collected by centrifugation and dried in an oven at 60°C for 24 hours to obtain the pure product of SA@PAM capsules.

[0061] The pure product of SA@PAM capsules was washed four times with ethanol solution and dried under vacuum at 60°C (1 h) to obtain alginate encapsulated imidazole corrosion inhibitor capsule shell.

[0062] Example 3

[0063] Preparation of alginate gel capsules encapsulating corrosion inhibitors

[0064] A long-chain alkyl-modified imidazole corrosion inhibitor (OBIP) was in situ encapsulated in polyacrylamide / barium sulfate-doped alginate gel using a one-pot synthesis method, where the alginate gel synthesis mode is as follows: Figure 3 : 0.26 g of OBIP obtained in Example 1, 0.6 g of sodium alginate (SA), 0.5 g of polyacrylamide (PAM) and 1.2 g of BaSO 4 Mix in 15 ml (99 wt%) solution. Stir the solution at 70 °C for 15 minutes. Draw the reaction solution into a 5 ml syringe, then add 15 wt% CaCl 2 After standing for 10 minutes, light yellow transparent particles with clear outlines were obtained. The granules were collected by centrifugation and dried in an oven at 60°C for 24 hours to obtain the pure product of SA@OBIP@OBIP capsules. The synthesis process is as follows Figure 4 shown.

[0065] The pure product of SA@PAM@OBIP corrosion inhibitor capsules was washed four times with ethanol solution and dried in vacuum at 60°C (1 h) to obtain alginate encapsulated imidazole corrosion inhibitor capsules, wherein the loading content of the latter corrosion inhibitor in the capsules was 18.3% and the loading efficiency was 92.4%.

[0066] The changes of N element in pure product of SA@PAM capsule and pure product of SA@PAM@OBIP corrosion inhibitor capsule were analyzed by scanning electron microscope and energy dispersive spectrometer. Figure 5 As shown in Figure 2, it is confirmed that the OBIP corrosion inhibitor is loaded in the gel capsule. The isothermal adsorption curves and pore size changes of SA, SA@PAM, and SA@PAM@OBIP are shown in Figure 2. Figure 6 As shown, it is confirmed that the addition of PAM effectively reduces the capsule pores, thereby achieving the temperature control response function.

[0067] Performance Testing

[0068] 1. Laboratory uniform corrosion full immersion test method for metal materials The corrosion inhibition efficiency of the corrosion inhibitor OBIP is determined by the following conditions: the experimental material is carbon steel (Fe: 99.5%, Mn: 0.4-0.5%, C: 0.1-0.2%); the corrosion inhibition environment is to add the corrosion inhibitor composite prepared in Example 1 to the medium, wherein the amount of the corrosion inhibitor composite added is 0.0002 mol / L-0.001 mol / L; the medium is CO shown in Table 1 2 Saturated oil and gas field production solution, the dosage is 500mL; the Q235 carbon steel material is immersed in a medium environment with the corrosion inhibitor complex added, the concentration equivalent of the corrosion inhibitor complex is about 130mg / L~650mg / L, the temperature is 25, 50, 90℃, pH=3.5~4.5, the immersion time is 1 day, specifically, 12 test groups are set, and the conditions are shown in Table 2; the corrosion inhibition efficiency is obtained through experimental tests according to the above-mentioned determination method, and the results are shown in Table 3; at the same time, the medium without the corrosion inhibitor complex is used as a blank control, and the medium with 4-aminobenzo[4,5]imidazole[1,2-a]pyrimidine-2(1H)-1 added as a corrosion inhibitor is used as a comparative test group.

[0069] Table 1

[0070] Inorganic salt NaCl KCl <![CDATA[MgCl 2 ·6H2O]]> <![CDATA[CaCl 2 ]]> <![CDATA[Na 2 SO 4 ]]> <![CDATA[NaHCO 3 ]]> Content (g / L) 62.36 3.4 4.46 0.57 0.64 0.52

[0071] Table 2

[0072]

[0073]

[0074] Table 3

[0075] Electrochemical impedance spectroscopy Potentiodynamic polarization curve Blank test group 1 0％ 0％ Test Group 1 73.73％ 87.65％ Test Group 2 87.16％ 94.75％ Test Group 3 91.38％ 93.34％ Test Group 4 92.48％ 95.46％ Blank test group 2 0％ 0％ Test Group 5 64.3％ 85.71％ Test Group 6 75.98％ 92.15％ Test Group 7 87.39％ 92.45％ Test Group 8 88.89％ 94.42％ Blank test group 3 0％ 0％ Test Group 9 58.7％ 74.14％ Test Group 10 67.3％ 79.01％ Test Group 11 85.00％ 85.07％ Test Group 12 87.4％ 92.26％ Comparative test group 1 35.24％ 36.33％ Comparative test group 2 24.52％ 23.28％ Comparative test group 3 14.26％ 15.74％

[0076] 2. Simulate the circulating water dynamics of the oil well water production area to test the real-time process of carbon steel corrosion to determine the corrosion inhibition effect of the composite

[0077] First, select Q235 carbon steel sheet as the metal to be tested (Fe: 99.5%, Mn: 0.4-0.5%, C: 0.1-0.2%). Use it as the working electrode of the electrochemical experiment with a specification of 10mm×10mm×10mm. Seal the carbon steel with epoxy resin to expose a working area of ​​10mm×10mm. Polish the test piece with 400-1200 sandpaper, then rinse with deionized water, and then ultrasonically clean it with anhydrous ethanol for 5 minutes, then blow dry with nitrogen, and finally store it in a desiccator for use.

[0078] The experimental medium is a solution, which is the CO used in performance test 1. 2 Saturated oil and gas field produced solution; the concentration of OBIP added to the oil and gas field produced water solution is 0.0008mol / L~0.0024mol / L, and the concentration of OBIP added to the SA@PAM@OBIP capsule is 0.0008mol / L. Cyclic hydrodynamic experiment: The treated electrode sample is immersed in two experimental media at 363K for 48h. Every hour, 50ml of liquid is extracted from 500mL of test solution and 50ml of liquid without corrosion inhibitor is added. One test cycle is 1~2h, and this cycle is repeated.

[0079] Electrochemical test: A three-electrode system was used, with a saturated calomel electrode (SCE) as the reference electrode and a platinum electrode (Pt) as the counter electrode. The area of ​​Pt was 4 cm 2 The working electrode was immersed in the above two media until the open circuit potential (OCP) was stable. The excitation signal used in the electrochemical impedance spectroscopy (EIS) test was a sine wave with an amplitude of 10mV and a scanning frequency range of 100KHz to 10mHz. The test time was 48 hours of immersion of the test piece and the first hour after each addition and extraction cycle immersion time. The test was carried out in the addition and extraction test solution.

[0080] Specifically:

[0081] Conditions: The experimental material is carbon steel (Fe: 99.5%, Mn: 0.4-0.5%, C: 0.1-0.2%), the corrosion inhibition environment is to add pure OBIP and SA@PAM@OBIP capsules to the medium, and the medium is the CO used in the performance test 1 above. 2The saturated oil and gas field produced solution is used in an amount of 500mL, wherein the amount of capsule added to each 500mL of the solution to be tested is 1.98g; the concentration equivalent of the corrosion inhibitor in the capsule under the condition of full release is about 0.0008mol / L, the temperature is 90℃, and the extraction and addition cycle is carried out 47 times according to the above simulation experiment record (the pH of the corrosion product liquid layer on the surface of the metal substrate is 3.6-4.5). Specifically, 21 test groups are set up, and the conditions are set as shown in Table 4; the corrosion inhibition efficiency is obtained through experimental testing according to the above-mentioned determination method, and the results are shown in Table 5;

[0082] Table 4

[0083]

[0084]

[0085] Table 5

[0086] Electrochemical impedance spectroscopy Test Group 1 83.85％ Test Group 2 84.89％ Test Group 3 82.7％ Test Group 4 77.18％ Test Group 5 74.86％ Test Group 6 69.3％ Test Group 7 64.23％ Test Group 8 86.9％ Test Group 9 86.7％ Test Group 10 84.8％ Test Group 11 80.7％ Test Group 12 77.6％ Test Group 13 71.9％ Test Group 14 66.3％ Test Group 15 76.2％ Test Group 16 78.1％ Test Group 17 84.5％ Test Group 18 87.2％ Test Group 19 84.9％ Test Group 20 78.1％ Test Group 21 74.9％

[0087] The above test results show that the imidazole corrosion inhibitor obtained by the present invention has obvious high temperature resistance, and the capsules of alginate gel loaded with imidazole corrosion inhibitor can be controlled by temperature and respond intelligently, have strong thermal stability, high cost performance, and have significant application value and broad market prospects. At the same time, the long-term high temperature corrosion inhibitor OBIP loaded by alginate gel further indicates its long-term protection ability, which further increases its corrosion protection time to 48h under the condition of achieving long-term effect when applied alone.

[0088] In summary, the present invention adopts polyacrylamide and barium sulfate as two factors to jointly modify alginate gel, and combines the performance of alginate gel. Polyacrylamide and sodium alginate produce pores of different sizes due to temperature changes to achieve temperature-controlled release, and barium sulfate enhances the density of the capsule to adapt to a deeper liquid environment. The three interact with each other to jointly address the technical defects of flow failure, high temperature failure, and redundant deployment of the corrosion inhibition system in oil and gas wells.

Claims

1. A modified corrosion inhibitor, characterized in that: The corrosion inhibitor is a compound as shown in structural formula 1, 2. The modified corrosion inhibitor according to claim 1, characterized in that: The compound shown in formula 1 is a mixture of 4-aminobenzimidazole [4,5] [1,2-a] pyrimidine-2(1H)-1 and octadecyloxybenzoic acid in a molar ratio of 1 to 1.2:1; the mixture is dissolved in a DMSO analytical pure solution and reacted under the catalysis of N,N'-carbonyldiimidazole (CDI) to obtain the compound.

3. The modified corrosion inhibitor according to claim 2, characterized in that: The compound shown in formula 1 is prepared by adding 4-aminobenzimidazole [4,5] [1,2-a] pyrimidine-2(1H)-1 and octadecyloxybenzoic acid into a DMSO solution at 150-160° C. and stirring to mix well. The mixture is fully reacted in a N2 atmosphere for 2-2.5 hours under the catalysis of N,N'-carbonyldiimidazole (CDI) to obtain a long-chain alkoxybenzimidazole pyrimidone corrosion inhibitor.

4. An application of the modified corrosion inhibitor according to claim 1, characterized in that: The corrosion inhibitor is used in high temperature protection of corrosion-inducing areas of carbon steel products in high temperature oil and gas field wells.

5. An alginate gel capsule encapsulating a corrosion inhibitor, characterized in that: The capsule comprises a shell and an inner filling, wherein the shell is an alginate gel containing an impurity, and the inner filling is the corrosion inhibitor according to claim 1; the molar ratio between the corrosion inhibitor and the alginate gel material is 5 to 8:

1.

6. The alginate gel-encapsulated corrosion inhibitor capsule according to claim 4, characterized in that: The alginate gel containing dopants is a mixture of polyacrylamide particles, alginate solution and barium sulfate solid, wherein the molar ratio of each component is 10-12:5-8:11-13.

7. A method for preparing alginate gel-encapsulated corrosion inhibitor capsules according to claim 4, characterized in that: The corrosion inhibitor solution of claim 1 is mixed with polyacrylamide particles and barium sulfate solid, and then a sodium alginate solution preheated to 70-80° C. is added, and the mixed solution is dripped into a 15wt% CaCl2 solution to obtain alginate gel-encapsulated corrosion inhibitor capsules through a one-pot synthesis method.

8. The method for preparing alginate gel-encapsulated corrosion inhibitor capsules according to claim 7, characterized in that: The molar ratio of the corrosion inhibitor solution, the polyacrylamide particles, the alginate solution and the barium sulfate solid is 1:10-12:5-8:11-13.

9. The method for preparing alginate gel-encapsulated corrosion inhibitor capsules according to claim 7, characterized in that: The one-pot synthesis is to place the mixed solution on a constant temperature stirring table at 800-1200 rpm and mix for 20-30 minutes, and the reaction temperature is 60°C-80°C.

10. An application of the alginate gel capsule encapsulating the corrosion inhibitor according to claim 1, characterized in that: The capsules of the alginate gel encapsulated corrosion inhibitor are used in high temperature protection of corrosion-inducing areas of carbon steel products in high temperature oil and gas field wells.

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