Composite corrosion inhibitor for oil field and preparation method thereof

Abstract

The invention relates to the technical field of corrosion inhibitors, in particular to a composite corrosion inhibitor for an oil field and a preparation method of the composite corrosion inhibitor. The problems that the corrosion inhibitor for the oil field is poor in scale inhibition effect, sterilization performance, high temperature resistance, oxygen removal capacity and corrosion inhibition effect are solved. According to the invention, by changing the type, dosage and component proportion of the scale inhibitor, the corrosion inhibitor has a very good scale inhibition effect; by changing the ratio of different components in the bacteriostatic agent and the dosage of the bacteriostatic agent, the bactericidal performance of the corrosion inhibitor is improved; by changing the component proportion of the modifier, the components in the modifier form poly (butylene succinate) at high temperature, a protective layer is formed on the metal surface, and the high temperature resistance of the corrosion inhibitor is improved; by changing the type and dosage of the deoxidant, dissolved oxygen in a medium is consumed, and the deoxidizing performance of the corrosion inhibitor is improved; the corrosion inhibition performance of the corrosion inhibitor is improved by preparing oleic acid imidazoline and Mannich base and controlling the ratio of the oleic acid imidazoline and the Mannich base and utilizing the good compatibility of the oleic acid imidazoline and the Mannich base.

Description

Technical Field

[0001] The present invention relates to the technical field of corrosion inhibitors, in particular to a composite corrosion inhibitor for oil fields and a preparation method thereof. Background Art

[0002] As a very important strategic energy source, every link in the oil extraction process is crucial. During oilfield extraction, due to factors such as the downhole environment and acid injection production, water injection systems, oil and gas wells, and gathering pipelines are exposed to oily wastewater, high salinity, high mineralization, and complex microbial environments for a long time, making them extremely susceptible to corrosion. Corrosion can lead to the rapid failure of metal pipes and equipment, causing serious economic losses and production safety risks. The use of corrosion inhibitors is a common anti-corrosion measure in oilfields. Corrosion inhibitor anti-corrosion technology has the advantages of good anti-corrosion effect, ease of use, and low overall cost. In oilfield development, many processes such as acid fracturing, wellbore lifting, and crude oil transportation require corrosion inhibitors to protect equipment and pipelines.

[0003] Currently, commonly used corrosion inhibitors include amides, pyridines, quaternary ammonium salts, and imidazolines, with imidazolines being the most studied. Imidazoline molecules can form a stable protective film by adsorbing on metal surfaces via unshared nitrogen atoms and groups containing large π bonds. The steric hindrance and hydrophobicity of the benzene ring enhance their adsorption capacity, effectively protecting the metal and inhibiting corrosion. However, the poor water solubility of imidazoline corrosion inhibitors limits their application to a certain extent, and the corrosion inhibition effect of single-component corrosion inhibitors in actual use is not ideal. To further improve the corrosion inhibition performance of corrosion inhibitors, the combination of multiple corrosion-inhibiting components to form composite corrosion inhibitors has gradually become a research focus. The synergistic effect between different corrosion-inhibiting components can promote each other, significantly improving the overall performance of composite corrosion inhibitors.

[0004] Chinese patent CN114350336B discloses a composite corrosion inhibitor for oil fields and its preparation method. This invention uses a natural plant modifier to modify an imidazoline corrosion inhibitor, and then combines the modified imidazoline with adenosine and purine as the main slow-release ingredients. The three ingredients work synergistically, resulting in an excellent corrosion-inhibiting composite corrosion inhibitor. Compared with existing technologies, this composite corrosion inhibitor is simple to prepare, has a high corrosion inhibition rate, and is produced from a wide range of raw materials at low cost. However, the composite corrosion inhibitor prepared by this invention has poor scale inhibition performance and cannot achieve controlled deposition of scale-causing salts in water.

[0005] Chinese patent CN108796507B discloses a composite acidification corrosion inhibitor. Using soybean meal, rapeseed meal, and kelp as raw materials, the compound is subjected to enzymatic hydrolysis and microbial fermentation to produce a solution rich in amino acids such as glutamic acid and lysine. The solution also contains a certain amount of glucose. During use, the compound acidification corrosion inhibitor adheres well to metal surfaces due to the adhesion of the amino acids. Simultaneously, due to the increase in temperature in the oil well, the amino acids in the compound solution polymerize with the glutamic acid to form a polyaspartimide polymer, which forms a protective layer on the pipeline surface to prevent metal corrosion. This invention addresses the current problem of corrosion and perforation of oilfield pipelines during the acidification process for oil extraction in oil fields. However, the compound acidification corrosion inhibitor prepared by this invention has poor bactericidal properties.

[0006] Chinese patent CN117585821B discloses a composite scale and corrosion inhibitor, its preparation method, and its use. The composite scale and corrosion inhibitor comprises the following raw materials by weight: 20-30 parts polyaspartic acid, 10-15 parts modified polyacrylamide, 1-5 parts inorganic metal salt, 5-10 parts sodium gluconate, 2-4 parts triazole derivative, and 1-3 parts quaternary ammonium salt dispersant. The composite scale and corrosion inhibitor prepared by this invention contains no phosphorus or zinc salt components, is environmentally friendly, and exhibits excellent scale and corrosion inhibition properties. It also has multiple bactericidal and algaecidal effects, effectively preventing bacterial corrosion and algae growth in circulating water systems. However, polyaspartic acid undergoes thermal degradation under high temperature conditions or when exposed to high temperature for extended periods, resulting in poor high-temperature resistance.

[0007] Although the composite corrosion inhibitors for oil fields prepared in the prior art have made certain progress, they still have some shortcomings. Their scale inhibition effect is not good; their bactericidal performance is poor, which leads to the massive proliferation of bacteria breeding in the oil field and corrosion of metal equipment; their high temperature resistance is poor, and they are easily decomposed or ineffective at high temperatures; their deoxygenation capacity is poor, which leads to the oxidation reaction of oxygen in the injected gas and crude oil to generate a large amount of CO2, which reacts with water to cause corrosion of the pipe column; and their corrosion inhibition effect is not good.

[0008] Therefore, a composite corrosion inhibitor for oil fields and a preparation method thereof are proposed. Summary of the Invention

[0009] The purpose of the present invention is to provide a composite corrosion inhibitor for oil fields and a preparation method thereof. The composite corrosion inhibitor for oil fields is prepared by mixing a main corrosion inhibitor, a corrosion inhibitor synergist, a modifier, an antibacterial agent, an oxygen scavenger, a scale inhibitor, a surfactant and deionized water. By changing the type, dosage and component ratio of the scale inhibitor, the scale-causing salt calcium carbonate in the water can be deposited in a controlled manner in the cathode area of the metal surface, and the prepared composite corrosion inhibitor for oil fields has a good scale inhibition effect; by changing the ratio of different components in the antibacterial agent and the dosage of the antibacterial agent, the sulfate-reducing bacteria, iron bacteria, heterotrophic bacteria and other bacteria that grow in the oil field are sterilized to prevent them from multiplying in large quantities and causing corrosion to metal equipment; by changing the component ratio of the modifier, the components in the modifier are formed into polybutylene succinate under the action of high temperature. Diol esters further form a protective layer on the metal surface and are compounded with corrosion inhibitors to improve the high-temperature resistance of the composite corrosion inhibitor for oil fields. By changing the type and dosage of the deoxidizer, the dissolved oxygen in the medium is consumed, and a dense protective film can be formed on the metal surface through multiple adsorption centers, thereby improving the deoxidation performance of the composite corrosion inhibitor for oil fields. By preparing oleic acid imidazoline and Mannich base and controlling the ratio of the two, and utilizing the good compatibility between oleic acid imidazoline and Mannich base, the two are synergistically enhanced to improve the corrosion inhibition performance of the composite corrosion inhibitor for oil fields.

[0010] To achieve the above object, the present invention provides the following technical solutions:

[0011] On one hand, the present invention provides a method for preparing a composite corrosion inhibitor for oil fields. The composite corrosion inhibitor for oil fields is prepared by the following steps: weighing 28-40 parts of a main corrosion inhibitor, 4-8 parts of a corrosion inhibitor synergist, 25 parts of a modifier, 6-10 parts of an antibacterial agent, 10-15 parts of an oxygen scavenger, 8-12 parts of a scale inhibitor, and 3 parts of a surfactant, and adding the mixture to a reactor containing 60 parts of deionized water to obtain a first reactant; heating the first reactant to 45° C. and stirring the mixture for reaction for 1 hour to obtain a second reactant; and cooling the second reactant to 18° C. and then allowing the mixture to stand and be discharged to obtain the composite corrosion inhibitor for oil fields.

[0012] The main corrosion inhibitor comprises 10-18 parts of an oleic acid imidazoline corrosion inhibitor and 15-22 parts of a di-Mannich base corrosion inhibitor.

[0013] Preferably, the preparation method of the oleic acid imidazoline is as follows: oleic acid, diethylenetriamine, and xylene are added to a three-necked flask, and reacted at 150-180° C. for 2 hours to obtain an intermediate; the intermediate is heated to 220-240° C. and reacted for 4 hours to obtain an imidazoline intermediate; the imidazoline intermediate is cooled to 60° C. and thiourea solution is added dropwise, and the reaction is continued for 3 hours to obtain the oleic acid imidazoline.

[0014] Oleic acid imidazoline has a high amine value and cyclization rate, and can form a single-molecule adsorption film on the metal surface to slow down corrosion. This adsorption film can change the charge distribution and interface properties of the metal surface, stabilize the energy state of the metal surface, thereby increasing the activation energy of the corrosion reaction and slowing down the corrosion rate; at the same time, the non-polar groups on the corrosion inhibitor can also form a hydrophobic protective film on the metal surface, hindering the transfer of charges or substances related to the corrosion reaction, further slowing down the corrosion rate.

[0015] Preferably, the preparation method of the Mannich base is as follows: adding benzotriazole and anhydrous ethanol to a reactor to obtain a mixed solution; adding 20wt% hydrochloric acid dropwise to the mixed solution until the pH is 2-3 to obtain an acidic mixed solution; adding benzaldehyde, piperazine and a dispersant octadecenamine acetate to the acidic mixed solution, stirring, heating to 120°C, and then refluxing for 24 hours to obtain a reaction solution; continuously stirring the reaction solution until it cools to room temperature to obtain the Mannich base.

[0016] The Mannich base molecule contains multiple nitrogen atoms or oxygen atoms with lone pairs of electrons, and there are 2 or 3 non-coordinating atoms between nitrogen, nitrogen or oxygen, nitrogen. The polar groups in the molecule will be adsorbed on the surface of the metal, and the non-polar groups in the molecule will be arranged on the metal surface, which will change the structure of the metal double layer. At this time, the activation energy will increase accordingly during the metal ionization process, so that the energy state of the metal matrix surface gradually approaches the steady state, which increases the energy barrier of the corrosion reaction and thus slows down the corrosion process.

[0017] Preferably, the corrosion inhibitor and synergist is prepared by mixing propargyl alcohol, 8-hydroxyquinoline and sodium dodecylbenzenesulfonate in a mass ratio of 2:3:1.

[0018] Preferably, the modified product is prepared by stirring and mixing 10-15 parts of succinic acid, 8-13 parts of 1,4-butanediol and 6-10 parts of tetrabutyl titanate.

[0019] Preferably, the preparation method of the antibacterial agent is as follows: dissolving carboxymethyl chitosan in water, and adding 2-ethylimidazole and sodium lauryl sulfate to the water and mixing evenly to obtain a mixture one; adding fluoroethylene oxide dropwise to the mixture one to obtain a mixture two; reacting the mixture two at 5-12° C. for 3-6 hours and then purifying to obtain the antibacterial agent; the mass ratio of the carboxymethyl chitosan, the 2-ethylimidazole, the sodium lauryl sulfate and the fluoroethylene oxide is 0.8:1-5:0.2-0.4:1.5-5.

[0020] Carboxymethyl chitosan is an important derivative of chitosan. After the carboxymethyl group is introduced through chemical modification, its water solubility is greatly enhanced, while retaining many excellent properties of chitosan and giving it new functional properties. Carboxymethyl chitosan has a broad spectrum of antibacterial activity against a variety of bacteria, fungi and microorganisms, which is mainly due to the positively charged groups in its molecular structure (such as -NH3 + ) can interact with the negatively charged cell membrane of microorganisms, destroy the integrity of the cell membrane, and cause the leakage of cell contents, thereby achieving an antibacterial or bactericidal effect.

[0021] Preferably, the oxygen scavenger is one of hydrazine, acetone oxime and isoascorbic acid.

[0022] Preferably, the scale inhibitor is one or two of aminotrimethylenephosphonic acid, polyepoxysuccinic acid and hydroxyethylidene diphosphonic acid.

[0023] Preferably, the surfactant is octadecyldimethylbenzyl ammonium chloride.

[0024] The addition of surfactants can effectively increase the dispersibility, wettability and permeability of the composite corrosion inhibitor. At the same time, it can be adsorbed on the surface of the coupon to form a three-dimensional network film, filling the gaps in the film layer, causing the film layer to thicken, further hindering the charge and material transfer on the surface of the corroded substrate, and reducing its corrosion rate. At the same time, the foaming performance of the surfactant can also inhibit acid mist and slow down the corrosion reaction rate.

[0025] On the other hand, the present invention provides a composite corrosion inhibitor for oil fields, wherein the raw materials used in the production of the composite corrosion inhibitor for oil fields include a corrosion inhibitor main agent, a corrosion inhibitor synergist, a modifier, an antibacterial agent, an oxygen scavenger, a scale inhibitor, a surfactant and deionized water; the composite corrosion inhibitor for oil fields is prepared by any one of the preparation methods described above; the CaCO3 scale inhibition rate of the composite corrosion inhibitor for oil fields is 97.8%, and the CaSO4 scale inhibition rate is 98.5%; the heterotrophic bacteria killing rate of the composite corrosion inhibitor for oil fields is 99.7%, the iron bacteria killing rate is 99.6%, and the sulfate-reducing bacteria killing rate is 99.8%; the corrosion inhibition rate of the composite corrosion inhibitor for oil fields at 250°C is 98.2%; the dissolved oxygen content of the composite corrosion inhibitor for oil fields is 1.00 mg / L, and the oxygen deoxidation rate is 90.33%; the corrosion rate of the composite corrosion inhibitor for oil fields is 0.023 mm / a.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] 1. The present invention controls the type, dosage and component ratio of the scale inhibitor, which can not only form stable complexes with various metal ions such as iron, copper and zinc, but also dissolve oxides on the metal surface and enable the scale-causing salt calcium carbonate in the water to be deposited in a controlled manner in the cathode area of the metal surface. The resulting composite corrosion inhibitor for oil fields has an excellent scale inhibition effect, with a scale inhibition rate of 97.8% for CaCO3 scale and 98.5% for CaSO4 scale.

[0028] 2. The present invention sterilizes sulfate-reducing bacteria, iron bacteria, heterotrophic bacteria and other bacteria that grow in oil fields by changing the ratio of different components in the antibacterial agent and the dosage of the antibacterial agent to prevent their massive reproduction and corrosion of metal equipment, thereby affecting the production work of the oil field. The obtained composite corrosion inhibitor for oil fields has a sterilization rate of 99.6% for heterotrophic bacteria, 99.6% for iron bacteria, and 99.8% for sulfate-reducing bacteria, showing significantly improved sterilization performance.

[0029] 3. The present invention changes the component ratio of the modifier, so that the components in the modifier form polybutylene succinate under high temperature, further forming a protective layer on the metal surface. Due to the effect of titanium, it can self-nucleate and crystallize, thereby improving the stability. In addition, it is compounded with the corrosion inhibitor to improve the high temperature resistance of the composite corrosion inhibitor for oil fields. The corrosion inhibition rate at 250°C is 98.2%.

[0030] 4. The present invention can consume the dissolved oxygen in the medium by controlling the type and amount of the deoxidizer, and can form a dense protective film on the metal surface through multiple adsorption centers. The prepared composite corrosion inhibitor for oil fields has a dissolved oxygen content of 1.00 mg / L and an oxygen removal rate of 90.33%, showing significantly improved deoxidation performance.

[0031] 5. The present invention prepares oleic acid imidazoline and Mannich base and controls the ratio of the two. The good compatibility between oleic acid imidazoline and Mannich base is utilized to make the two synergistically enhance the effect. The organic corrosion inhibitor molecules can form a hydrophobic protective film on the metal surface through adsorption and directional arrangement, thereby reducing the corrosion rate. The corrosion rate of the prepared composite corrosion inhibitor for oil fields is 0.023 mm / a, showing significantly improved corrosion inhibition performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a graph showing the deoxygenation performance test results of the composite corrosion inhibitor for oil fields according to Example 47 of the present invention. DETAILED DESCRIPTION

[0033] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0034] See also Figure 1 The present invention provides a composite corrosion inhibitor for oil fields and a preparation method thereof. The technical solution is as follows:

[0035] The substance information involved in the present invention is as follows:

[0036] Oleic acid CAS: 112-80-1; diethylenetriamine CAS: 111-40-0; xylene CAS: 1330-20-7; thiourea CAS: 62-56-6; benzotriazole CAS: 95-14-7; anhydrous ethanol CAS: 64-17-5; hydrochloric acid CAS: 7647-01-0; benzaldehyde CAS: 100-52-7; piperazine CAS: 110-85-0; carboxymethyl chitosan CAS: 83512-85-0; 2-ethylimidazole CAS: 1072-62-4; sodium dodecyl sulfate CAS: 151-21-3; fluoroethylene oxide CAS: 503-09-3; propargyl alcohol CAS: 107-19-7; 8-hydroxyquinoline CAS: 148-24-3; sodium dodecylbenzenesulfonate CAS: 25155-30-0; succinic acid CAS: 110-15-6; 1,4-butanediol CAS: 110-63-4; tetrabutyl titanate CAS: 5593-70-4; hydrazine CAS: 302-01-2; acetone oxime CAS: 127-06-0; isoascorbic acid CAS: 89-65-6; sodium sulfite CAS: 7757-83-7; aminotrimethylenephosphonic acid CAS: 6419-19-8; polyepoxysuccinic acid CAS: 1528-98-7; hydroxyethylidene diphosphonic acid CAS: 2809-21-4; octadecyldimethylbenzyl ammonium chloride CAS: 122-19-0.

[0037] Example 1

[0038] Preparation of oleic acid imidazoline: oleic acid, diethylenetriamine, and xylene are added to a 250 mL three-necked flask, and the mixture is reacted at 150-180° C. for 2 hours to obtain an intermediate; the intermediate is heated to 220-240° C. and reacted for 4 hours to obtain an imidazoline intermediate; the imidazoline intermediate is cooled to 60° C., thiourea solution is added dropwise, and the reaction is continued for 3 hours to obtain the oleic acid imidazoline.

[0039] Preparation of a Mannich base: adding benzotriazole and anhydrous ethanol to a reactor to obtain a mixed solution; adding 20 wt % hydrochloric acid dropwise to the mixed solution until the pH is 2-3 to obtain an acidic mixed solution; adding benzaldehyde, piperazine, and a dispersant, octadecenamine acetate, to the acidic mixed solution, stirring, heating to 120° C., and then refluxing for 24 hours to obtain a reaction solution; continuously stirring the reaction solution until it cools to room temperature to obtain the Mannich base.

[0040] Preparation of an antibacterial agent: dissolving carboxymethyl chitosan in water, adding 2-ethylimidazole and sodium dodecyl sulfate to the water and mixing uniformly to obtain a first mixture; adding fluoroethylene oxide dropwise to the first mixture to obtain a second mixture; reacting the second mixture at 5-12° C. for 3-6 hours and then purifying to obtain the antibacterial agent; wherein the mass ratio of carboxymethyl chitosan, 2-ethylimidazole, sodium dodecyl sulfate and fluoroethylene oxide is 0.8:1:0.2:1.5.

[0041] Preparation of a composite corrosion inhibitor for oil fields: 28 parts of a main corrosion inhibitor, 4 parts of a corrosion inhibitor synergist, 25 parts of a modifier, 6 parts of an antibacterial agent, 10 parts of an oxygen scavenger, 8 parts of a scale inhibitor and 3 parts of a surfactant are weighed and added into a reactor containing 60 parts of deionized water to obtain reactant one; the reactant one is heated to 45°C and stirred for reaction for 1 hour to obtain reactant two; the reactant two is cooled to 18°C and then allowed to stand and discharged to obtain the composite corrosion inhibitor for oil fields; the 28 parts of the main corrosion inhibitor include 10 parts of an oleic acid imidazoline corrosion inhibitor and 18 parts of a diMannich base corrosion inhibitor; the modifier is prepared by stirring and mixing 10 parts of succinic acid, 8 parts of 1,4-butanediol and 6 parts of tetrabutyl titanate; the oxygen scavenger is hydrazine; the scale inhibitor is aminotrimethylenephosphonic acid; and the surfactant is octadecyldimethylbenzyl ammonium chloride.

[0042] Examples 2-14

[0043] Refer to the preparation method and parameter conditions of Example 1, the specific differences are shown in Table 1.

[0044] Table 1 Preparation conditions of Examples 2-14

[0045] Example Types of scale inhibitors Antiscalant ratio Antiscalant dosage / portion Example 2 Aminotrimethylenephosphonic acid / 10 Example 3 Aminotrimethylenephosphonic acid / 12 Example 4 Polyepoxysuccinic acid / 10 Example 5 Hydroxyethylidene diphosphonic acid / 10 Example 6 Aminotrimethylenephosphonic acid + polyepoxysuccinic acid 1：1 10 Example 7 Aminotrimethylenephosphonic acid + polyepoxysuccinic acid 1：2 10 Example 8 Aminotrimethylenephosphonic acid + polyepoxysuccinic acid 2：1 10 Example 9 Aminotrimethylenephosphonic acid + hydroxyethylidene diphosphonic acid 1：1 10 Example 10 Aminotrimethylenephosphonic acid + hydroxyethylidene diphosphonic acid 1：2 10 Example 11 Aminotrimethylenephosphonic acid + hydroxyethylidene diphosphonic acid 2：1 10 Example 12 Polyepoxysuccinic acid + hydroxyethylidene diphosphonic acid 1：1 10 Example 13 Polyepoxysuccinic acid + hydroxyethylidene diphosphonic acid 1：2 10 Example 14 Polyepoxysuccinic acid + hydroxyethylidene diphosphonic acid 2：1 10

[0046] Comparative Example 1

[0047] A composite corrosion inhibitor for oil fields was prepared according to the method of Example 1, except that no scale inhibitor was added.

[0048] Example 15 Scale inhibition performance test

[0049] The scale inhibition performance of the composite corrosion inhibitors prepared in Examples 1-14 and Comparative Example 1 was tested. The main indicators of the test water quality were total hardness 756 mg / L, calcium hardness 522 mg / L, pH = 8.45, and alkalinity 375 mg / L. The scale inhibition performance test method was carried out in accordance with GB / T16632-2008 "Determination of scale inhibition performance of water treatment agents - Calcium carbonate precipitation method"; the results are shown in Table 2.

[0050] Table 2 Scale inhibition performance test of Examples 1-14 and Comparative Example 1

[0051] Example <![CDATA[Calcium carbonate scale inhibition / %]]> <![CDATA[Calcium sulfate scale inhibition / % <!-- 5 -->]]> Example 1 95.3 95.6 Example 2 96.4 96.4 Example 3 96.2 96.3 Example 4 96.6 96.1 Example 5 97.2 97.7 Example 6 97.1 98.3 Example 7 97.4 98.3 Example 8 97.8 98.5 Example 9 96.8 96.2 Example 10 97.0 96.9 Example 11 96.7 96.6 Example 12 96.9 97.2 Example 13 97.1 97.5 Example 14 97.3 97.8 Comparative Example 1 82.3 80.5

[0052] Aminotrimethylenephosphonic acid belongs to an organic phosphine-based scale inhibitor. It inhibits scale by slowing down the growth rate of crystals and causing the CaCO3 lattice to become warped. It also has a significant threshold effect. As can be seen from Table 2, in Examples 1-3, as the amount of scale inhibitor increases, the ability of aminotrimethylenephosphonic acid to inhibit CaCO3 scale and CaSO4 scale first increases to a threshold value and then decreases. According to Examples 1-5, it can be seen that among the single scale inhibitors, hydroxyethylidene diphosphonic acid has the best scale inhibition effect. In Examples 6-8, when inhibiting CaCO3 scale and CaSO4 scale, aminotrimethylenephosphonic acid and polyepoxysuccinic acid have a synergistic effect at any addition ratio, and the scale inhibition effect is better than when used alone. In Example 8, aminotrimethylenephosphonic acid and polyepoxysuccinic acid are mixed in a ratio of 2:1 to obtain a composite scale inhibitor. When 10 parts of the composite scale inhibitor are added to the composite corrosion inhibitor, the scale inhibition effect is the best, and the scale inhibition rate for CaCO3 scale reaches 97.8%, and the scale inhibition rate for CaSO4 scale reaches 97.8%. The scale inhibition rate of SO4 scale reaches 98.5%; in Examples 9-11, there is no synergistic effect between aminotrimethylenephosphonic acid and hydroxyethylidene diphosphonic acid, and the scale inhibition effect of the composite scale inhibitor is not as good as the scale inhibition effect when hydroxyethylidene diphosphonic acid is used alone; in Examples 12-14, there is a synergistic effect when polyepoxysuccinic acid and hydroxyethylidene diphosphonic acid are added in a ratio of 2:1; in Comparative Example 1, no scale inhibitor is added to the composite corrosion inhibitor, and the scale inhibition performance of the corrosion inhibitor is greatly reduced, the scale inhibition rate for CaCO3 scale is reduced to 82.3%, and the scale inhibition rate for CaSO4 scale is only 80.5%.

[0053] Example 16

[0054] Oleic acid imidazoline and Mannich base were prepared according to the method of Example 1.

[0055] Preparation of an antibacterial agent: dissolving carboxymethyl chitosan in water, adding 2-ethylimidazole and sodium dodecyl sulfate to the water and mixing uniformly to obtain a first mixture; adding fluoroethylene oxide dropwise to the first mixture to obtain a second mixture; reacting the second mixture at 5-12° C. for 3-6 hours and then purifying to obtain the antibacterial agent; wherein the mass ratio of carboxymethyl chitosan, 2-ethylimidazole, sodium dodecyl sulfate and fluoroethylene oxide is 0.8:1:0.2:1.5.

[0056] Preparation of a composite corrosion inhibitor for oil fields: 28 parts of a main corrosion inhibitor, 4 parts of a corrosion inhibitor synergist, 25 parts of a modifier, 8 parts of an antibacterial agent, 10 parts of an oxygen scavenger, 10 parts of a scale inhibitor and 3 parts of a surfactant are weighed and added into a reactor containing 60 parts of deionized water to obtain reactant one; the reactant one is heated to 45°C and stirred for reaction for 1 hour to obtain reactant two; the reactant two is cooled to 18°C and then allowed to stand and discharged to obtain the composite corrosion inhibitor for oil fields; the 28 parts of the main corrosion inhibitor include 10 parts of an oleic acid imidazoline corrosion inhibitor and 18 parts of a di-Mannich base corrosion inhibitor; the modifier is prepared by stirring and mixing 10 parts of succinic acid, 8 parts of 1,4-butanediol and 6 parts of tetrabutyl titanate; the oxygen scavenger is hydrazine; the scale inhibitor includes aminotrimethylenephosphonic acid and polyepoxysuccinic acid, and the mixing ratio of the two is 2:1; the surfactant is octadecyldimethylbenzyl ammonium chloride.

[0057] Examples 17-24

[0058] The preparation method and parameter conditions of Example 16 are referred to, and the specific differences are shown in Table 3. The four substances in Table 3 are carboxymethyl chitosan, 2-ethylimidazole, sodium lauryl sulfate and fluoroethylene oxide.

[0059] Comparative Example 2

[0060] A composite corrosion inhibitor for oil fields was prepared according to the method of Example 16, except that no antibacterial agent was added.

[0061] Example 25 Sterilization Performance Test

[0062] Oilfield produced water was collected, and the composite corrosion inhibitors for oilfields prepared in Examples 8, 16-24, and Comparative Example 2 were added to the water samples. After the water samples were kept in contact at 35±2°C for a certain period of time, the number of residual heterotrophic bacteria in the water samples was determined by the plate count method according to the methods in HG / T 3609-2000 and GB / T 14643.5-2009. The number of sulfate-reducing bacteria and iron bacteria in the water samples was determined by the dilution culture method. A blank sample was also prepared, and the sterilization rate was calculated. The results are shown in Table 3.

[0063] Table 3 Bactericidal performance test of Examples 8, 16-24 and Comparative Example 2

[0064]

[0065]

[0066] As can be seen from Table 3, in Examples 8, 16-18, as the amount of antibacterial agent added increases, the bactericidal effect is also enhanced. This is because more antibacterial agent molecules can interact with microbial cells, destroying their cell structure or function, thereby achieving a better bactericidal effect; when the amount of antibacterial agent added exceeds a certain limit, due to the solvent effect, the bactericidal effect no longer increases significantly, and may even decrease. For example, in Example 18, when the amount of antibacterial agent added is increased to 10 parts, its bactericidal rate decreases. Since carboxymethyl chitosan has good biocompatibility and biodegradability, it has antibacterial and antibacterial characteristics, and imidazole compounds also belong to broad-spectrum antifungal compounds. After cross-linking the two, the antibacterial properties are improved. At the same time, the toxicity of the imidazole compounds is also reduced. In Example 22, 9 parts of antibacterial agents are added, and the mass ratio of the four substances in the antibacterial agent is 0.8:5:0.4:1.5. The obtained composite corrosion inhibitor for oil fields has the best bactericidal performance. At this time, the bactericidal rate of heterotrophic bacteria is 99.6%, the bactericidal rate of iron bacteria is 99.6%, and the bactericidal rate of sulfate-reducing bacteria reaches 99.8%, which can avoid the proliferation of bacteria and corrosion of metal equipment. In Comparative Example 2, no antibacterial agent is added, and the obtained composite corrosion inhibitor for oil fields has poor bactericidal performance. The bactericidal rate of heterotrophic bacteria is 68.3%, the bactericidal rate of iron bacteria is 71.2%, and the bactericidal rate of sulfate-reducing bacteria is 70.6%, which is far inferior to the composite corrosion inhibitor for oil fields prepared by the present invention.

[0067] Example 26

[0068] According to the method of Example 16 above, oleic acid imidazoline, Mannich base and antibacterial agent were prepared.

[0069] Preparation of a composite corrosion inhibitor for oil fields: 28 parts of a main corrosion inhibitor, 4 parts of a corrosion inhibitor synergist, 25 parts of a modifier, 9 parts of an antibacterial agent, 10 parts of an oxygen scavenger, 10 parts of a scale inhibitor and 3 parts of a surfactant are weighed and added into a reactor containing 60 parts of deionized water to obtain reactant one; the reactant one is heated to 45°C and stirred for reaction for 1 hour to obtain reactant two; the reactant two is cooled to 18°C and then allowed to stand and discharged to obtain the composite corrosion inhibitor for oil fields; the 28 parts of the main corrosion inhibitor include 10 parts of an oleic acid imidazoline corrosion inhibitor and 18 parts of a di-Mannich base corrosion inhibitor; the modifier is prepared by stirring and mixing 12 parts of succinic acid, 8 parts of 1,4-butanediol and 6 parts of tetrabutyl titanate; the oxygen scavenger is hydrazine; the scale inhibitor includes aminotrimethylenephosphonic acid and polyepoxysuccinic acid, and the mixing ratio of the two is 2:1; the surfactant is octadecyldimethylbenzyl ammonium chloride.

[0070] Examples 27-33

[0071] Referring to the preparation method and parameter conditions of Example 26, the specific differences are shown in Table 4.

[0072] Comparative Example 3

[0073] A composite corrosion inhibitor for oil fields was prepared according to the method of Example 26, except that no modifier was added.

[0074] Example 34 High temperature resistance test

[0075] The corrosion inhibition rate of the corrosion inhibitor at 250°C was determined according to GB / T 18175-2014 “Determination of corrosion inhibition performance of water treatment agents—Rotating coupon method”. The test specimen was 20# carbon steel, the coupon rotation speed was 75 r / min, and the test time was 24 h. The test results are shown in Table 4.

[0076] Table 4 High temperature resistance test of Examples 22, 26-33 and Comparative Example 3

[0077] Example Succinic acid dosage / portion 1,4-Butanediol dosage / part Tetrabutyl titanate dosage / part Corrosion inhibition rate / % Example 22 10 8 6 96.4 Example 26 12 8 6 96.8 Example 27 14 8 6 97.4 Example 28 15 8 6 97.1 Example 29 14 10 6 98.2 Example 30 14 13 6 97.5 Example 31 14 10 8 98.0 Example 32 14 10 9 97.3 Example 33 14 10 10 97.0 Comparative Example 3 0 0 0 80.9

[0078] The components in the modifier form polybutylene succinate under high temperature, which can form a protective layer on the metal surface. Due to the effect of titanium, it can self-nucleate and crystallize, improving its stability. When compounded with the corrosion inhibitor, the high-temperature resistance of the composite corrosion inhibitor is improved, so that it will not decompose and fail at high temperatures. In Example 29, when the modifier is made by stirring and mixing 14 parts of succinic acid, 10 parts of 1,4-butanediol, and 9 parts of tetrabutyl titanate, the obtained composite corrosion inhibitor for oil fields has the best high-temperature resistance, and the corrosion inhibition rate can reach 98.2% at a high temperature of 250°C. In Comparative Example 3, the composite corrosion inhibitor for oil fields prepared without adding the modifier is prone to coking, stratification, and poor solubility and dispersibility at high temperatures, resulting in poor corrosion inhibition effect, and the corrosion inhibition rate drops to 80.9%.

[0079] Example 35

[0080] According to the method of Example 16 above, oleic acid imidazoline, Mannich base and antibacterial agent were prepared.

[0081] Preparation of a composite corrosion inhibitor for oil fields: 28 parts of a main corrosion inhibitor, 4 parts of a corrosion inhibitor synergist, 25 parts of a modifier, 9 parts of an antibacterial agent, 12 parts of an oxygen scavenger, 10 parts of a scale inhibitor and 3 parts of a surfactant are weighed and added into a reactor containing 60 parts of deionized water to obtain reactant one; the reactant one is heated to 45°C and stirred for reaction for 1 hour to obtain reactant two; the reactant two is cooled to 18°C and then allowed to stand and discharged to obtain the composite corrosion inhibitor for oil fields; the 28 parts of the main corrosion inhibitor include 10 parts of an oleic acid imidazoline corrosion inhibitor and 18 parts of a diMannich base corrosion inhibitor; the modifier is prepared by stirring and mixing 14 parts of succinic acid, 10 parts of 1,4-butanediol and 6 parts of tetrabutyl titanate; the oxygen scavenger is hydrazine; the scale inhibitor includes aminotrimethylenephosphonic acid and polyepoxysuccinic acid, and the mixing ratio of the two is 2:1; the surfactant is octadecyldimethylbenzyl ammonium chloride.

[0082] Examples 36-45

[0083] Referring to the preparation method and parameter conditions of Example 35, the specific differences are shown in Table 5.

[0084] Comparative Example 4

[0085] A composite corrosion inhibitor for oil fields was prepared according to the method of Example 35, except that no deoxidizer was added.

[0086] Example 46 Deoxygenation Performance Test

[0087] The dissolved oxygen content of the simulated oilfield wastewater sample was 10.35 mg / L. The type and dosage of the deoxidizer were changed, and the dissolved oxygen content was measured using a fixed portable dissolved oxygen meter. The deoxidation rate of various deoxidizers was obtained based on the changes in the dissolved oxygen content. The results are shown in Table 5.

[0088] Table 5 Deoxygenation Performance Test of Examples 29, 35-45 and Comparative Example 4

[0089] Example Deoxidizer Type Deoxidizer dosage / portion Dissolved oxygen content / mg / L Deoxygenation rate / % Example 29 Hydrazine 10 3.20 69.08 Example 35 Hydrazine 12 1.98 80.87 Example 36 Hydrazine 13 1.00 90.33 Example 37 Hydrazine 15 1.05 89.86 Example 38 Acetone oxime 10 9.24 10.72 Example 39 Acetone oxime 12 9.13 11.79 Example 40 Acetone oxime 13 9.06 12.46 Example 41 Acetone oxime 15 9.07 12.36 Example 42 Erythorbic acid 10 9.26 10.53 Example 43 Erythorbic acid 12 8.34 19.42 Example 44 Erythorbic acid 13 7.64 26.18 Example 45 Erythorbic acid 15 7.74 25.22 Comparative Example 4 / / 10.03 3.09

[0090] Hydrazine is a strong reducing agent in alkaline environment, which can reduce dissolved oxygen in water to nitrogen and water. Figure 1As shown, in Examples 29, 35-45, when hydrazine is used as a deoxidizer, the obtained composite corrosion inhibitor for oil fields has the best deoxidation effect. Compared with acetone oxime and isoascorbic acid, hydrazine can reduce the oxygen content of the simulated liquid faster, achieving the purpose of deoxidation. In Examples 29, 35-37, as the amount of hydrazine used as the deoxidizer increases, deoxidation first increases and then decreases. When the amount of hydrazine used is too little, it cannot effectively react with the oxygen dissolved in the water, resulting in a decrease in the deoxidation rate; when the amount of hydrazine used is too much, hydrazine will decompose to produce nitrogen and ammonia, thereby increasing the dissolved oxygen content and reducing the deoxidation rate. Therefore, in Example 36, when hydrazine is used as a deoxidizer and the amount of hydrazine added is 13 parts, the obtained composite corrosion inhibitor for oil fields has the best deoxidation effect, with a dissolved oxygen content of only 1.00 mg / L and an oxygen removal rate of 90.33%. In Comparative Example 4, no deoxidizer was added to the composite corrosion inhibitor for oil fields, and the deoxidation performance was poor. The measured dissolved oxygen content was as high as 10.03 mg / L, and the deoxidation rate was only 3.09%.

[0091] Example 47

[0092] According to the method of Example 16 above, oleic acid imidazoline, Mannich base and antibacterial agent were prepared.

[0093] Preparation of a composite corrosion inhibitor for oil fields: 28 parts of a main corrosion inhibitor, 4 parts of a corrosion inhibitor synergist, 25 parts of a modifier, 9 parts of an antibacterial agent, 13 parts of an oxygen scavenger, 10 parts of a scale inhibitor and 3 parts of a surfactant are weighed and added into a reactor containing 60 parts of deionized water to obtain reactant one; the reactant one is heated to 45°C and stirred for reaction for 1 hour to obtain reactant two; the reactant two is cooled to 18°C and then allowed to stand and discharged to obtain the composite corrosion inhibitor for oil fields; the 28 parts of the main corrosion inhibitor include 13 parts of an oleic acid imidazoline corrosion inhibitor and 15 parts of a di-Mannich base corrosion inhibitor; the modifier is prepared by stirring and mixing 14 parts of succinic acid, 10 parts of 1,4-butanediol and 6 parts of tetrabutyl titanate; the oxygen scavenger is hydrazine; the scale inhibitor includes aminotrimethylenephosphonic acid and polyepoxysuccinic acid, and the mixing ratio of the two is 2:1; the surfactant is octadecyldimethylbenzyl ammonium chloride.

[0094] Examples 48-54

[0095] Referring to the preparation method and parameter conditions of Example 47, the specific differences are shown in Table 6.

[0096] Comparative Example 5

[0097] A composite corrosion inhibitor for oil fields was prepared according to the method of Example 47, except that no Mannich base was added.

[0098] Comparative Example 6

[0099] A composite corrosion inhibitor for oil fields was prepared according to the method of Example 47, except that oleic acid imidazoline was not added.

[0100] Example 55 Corrosion Inhibition Performance Test

[0101] The corrosion rate of the corrosion inhibitor was determined according to GB / T 18175-2014 “Determination of corrosion inhibition performance of water treatment agents - Rotating coupon method”. 20# carbon steel was used as the test coupon, the coupon rotation speed was 75 r / min, and the test time was 24 h. The test results are shown in Table 6.

[0102] Table 6 Corrosion inhibition performance test of Examples 36, 47-54 and Comparative Examples 5-6

[0103]

[0104]

[0105] As shown in Table 6, Examples 36 and 47-54 contain both oleic acid imidazoline and Mannich base, which synergistically enhance the corrosion inhibition effect of the composite corrosion inhibitor. In Example 52, the corrosion inhibition effect of the main corrosion inhibitor composed of 15 parts of oleic acid imidazoline and 20 parts of Mannich base is the best, and the corrosion rate of the obtained composite corrosion inhibitor for oil fields is only 0.023 mm / a; compared with the embodiments, Comparative Examples 5-6 do not contain Mannich base and oleic acid imidazoline respectively, and the corrosion inhibition effect is poor, especially Comparative Example 6, in the absence of oleic acid imidazoline, even if the amount of Mannich base is increased, it is difficult to achieve the ideal corrosion rate; in Comparative Example 5, only oleic acid imidazoline is used as the corrosion inhibition main agent, and the corrosion rate of the obtained composite corrosion inhibitor for oil fields reaches 0.088 mm / a; in Comparative Example 6, only Mannich base is used as the corrosion inhibition main agent, and the corrosion rate of the obtained composite corrosion inhibitor for oil fields is as high as 0.095 mm / a.

[0106] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a composite corrosion inhibitor for oil fields, characterized in that: The composite corrosion inhibitor for oil fields is prepared by the following steps: weighing 28-40 parts by weight of a main corrosion inhibitor, 4-8 parts of a corrosion inhibitor synergist, 25 parts of a modifier, 6-10 parts of a bacteriostat, 10-15 parts of an oxygen scavenger, 8-12 parts of a scale inhibitor, and 3 parts of a surfactant, and adding the mixture to a reactor containing 60 parts of deionized water to obtain a first reactant; heating the first reactant to 45° C. and stirring the mixture for reaction for 1 hour to obtain a second reactant; and cooling the second reactant to 18° C. and then allowing the mixture to stand and be discharged to obtain the composite corrosion inhibitor for oil fields; The main corrosion inhibitor comprises 10-18 parts of an oleic acid imidazoline corrosion inhibitor and 15-22 parts of a di-Mannich base corrosion inhibitor.

2. The method for preparing a composite corrosion inhibitor for oil fields according to claim 1, wherein: The preparation method of the oleic acid imidazoline is as follows: oleic acid, diethylenetriamine, and xylene are added to a three-necked flask, and reacted at 150-180° C. for 2 hours to obtain an intermediate; the intermediate is heated to 220-240° C. and reacted for 4 hours to obtain an imidazoline intermediate; After the imidazoline intermediate was cooled to 60° C., thiourea solution was added dropwise and the reaction was continued for 3 h to obtain the oleic acid imidazoline.

3. The method for preparing a composite corrosion inhibitor for oil fields according to claim 1, wherein: The preparation method of the Mannich base is as follows: adding benzotriazole and anhydrous ethanol to a reactor to obtain a mixed solution; adding 20wt% hydrochloric acid dropwise to the mixed solution until the pH is 2-3 to obtain an acidic mixed solution; adding benzaldehyde, piperazine and a dispersant to the acidic mixed solution, stirring, heating to 120°C and then refluxing for 24 hours to obtain a reaction solution; and continuously stirring the reaction solution until it cools to room temperature to obtain the Mannich base.

4. The method for preparing a composite corrosion inhibitor for oil fields according to claim 1, wherein: The corrosion inhibitor and synergist is prepared by mixing propargyl alcohol, 8-hydroxyquinoline and sodium dodecylbenzenesulfonate in a mass ratio of 2:3:

1.

5. The method for preparing a composite corrosion inhibitor for oil fields according to claim 1, wherein: The modified material is prepared by stirring and mixing 10-15 parts of succinic acid, 8-13 parts of 1,4-butanediol and 6-10 parts of tetrabutyl titanate.

6. The method for preparing a composite corrosion inhibitor for oil fields according to claim 5, characterized in that: The preparation method of the antibacterial agent is as follows: dissolving carboxymethyl chitosan in water, adding 2-ethylimidazole and sodium lauryl sulfate to the water and mixing evenly to obtain a first mixture; adding fluoroethylene oxide dropwise to the first mixture to obtain a second mixture; reacting the second mixture at 5-12° C. for 3-6 hours and then purifying to obtain the antibacterial agent; the mass ratio of the carboxymethyl chitosan, the 2-ethylimidazole, the sodium lauryl sulfate and the fluoroethylene oxide is 0.8:1-5:0.2-0.4:1.5-5.

7. The method for preparing a composite corrosion inhibitor for oil fields according to claim 1, wherein: The oxygen scavenger is one of hydrazine, acetone oxime and isoascorbic acid.

8. The method for preparing a composite corrosion inhibitor for oil fields according to claim 1, wherein: The scale inhibitor is one or two of aminotrimethylene phosphonic acid, polyepoxysuccinic acid and hydroxyethylidene diphosphonic acid.

9. The method for preparing a composite corrosion inhibitor for oil fields according to claim 1, wherein: The surfactant is octadecyldimethylbenzyl ammonium chloride.

10. A composite corrosion inhibitor for oil fields, characterized by: The raw materials for producing the composite corrosion inhibitor for oil fields include a main corrosion inhibitor, a corrosion inhibitor synergist, a modifier, an antibacterial agent, an oxygen scavenger, a scale inhibitor, a surfactant and deionized water; the composite corrosion inhibitor for oil fields is prepared by the preparation method according to any one of claims 1 to 9; the CaCO3 scale inhibition rate of the composite corrosion inhibitor for oil fields is 97.8%, and the CaSO4 scale inhibition rate is 98.5%; the heterotrophic bacteria killing rate of the composite corrosion inhibitor for oil fields is 99.7%, the iron bacteria killing rate is 99.6%, and the sulfate-reducing bacteria killing rate is 99.8%; the corrosion inhibition rate of the composite corrosion inhibitor for oil fields at 250° C. is 98.2%; the dissolved oxygen content of the composite corrosion inhibitor for oil fields is 1.00 mg / L, and the oxygen removal rate is 90.33%; The corrosion rate of the composite corrosion inhibitor for oil fields is 0.023 mm / a.

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