Composite chelating plugging remover for oil fields and preparation method thereof

Abstract

The present invention belongs to the technical field of preparation of plugging removers, and specifically relates to a composite chelating plugging remover for oil fields and a preparation method thereof. The composite chelating plugging remover for oil fields of the present invention is composed of the following raw materials in percentage by mass: 7-9% of 1-butyl-3-methylimidazole dodecylsulfonate, 5-7% of erucamidopropyl hydroxypropyl sulfobetaine, 3-4% of sodium di-(2-ethylhexyl) sulfosuccinate, 4-5% of ethylenediamine di-o-hydroxyphenylacetic acid, 3-4% of N,N'-bis(2-hydroxybenzyl)ethylenediamine-N,N'-diacetic acid, 2-3% of O-(3-(benzyloxy)propyl)hydroxylamine, 1-2% of heptadecenyl hydroxyethylimidazoline quaternary ammonium salt, 1-1.5% of dimethyldiallylammonium chloride homopolymer, and the balance is water. The composite chelating plugging remover for oil fields of the present invention is applied to the deblocking of complex scale in oil fields and has excellent scale dissolution rate and wax prevention rate.

Description

Technical Field

[0001] The invention belongs to the technical field of preparation of plugging removers, and particularly relates to a composite chelating plugging remover for oil fields and a preparation method thereof. Background Art

[0002] During the polymer flooding development process in oil fields, long-term polymer injection can lead to concentrated polymer accumulation in the reservoir duct near the wellbore. Furthermore, as injection rates and pressures continue to increase, the blockage becomes increasingly dense, ultimately making polymer injection extremely difficult. During deblocking operations, the dense blockage prevents the deblocking agent from penetrating the core of the blockage, resulting in unsatisfactory deblocking results. Multi-component blockages contain not only polymers and colloidal asphaltene, but also mud and sand. These sand particles can form "bridges" in front of the screen perforations, making the blockage effect of multi-component blockages significantly stronger than that of ordinary blockages, and increasing the difficulty of deblocking.

[0003] The main reasons for the blockage of polymer injection wells include the following aspects: (1) During the injection process, polymers will be retained in the rock core due to adsorption and capture, reducing the rock permeability and causing formation damage; (2) In the wellbore area, polymers and inorganic scales are wrapped around each other, forming an organic-inorganic composite scale with inorganic scale as the core, which is difficult to remove; (3) High-valent metal ions (especially Fe 3+ ) Cross-linking with polymers to form flocs that are easily adsorbed and retained in pipelines, causing blockage of oil pipelines; (4) Scaling of clay minerals and calcium and magnesium ions, etc.

[0004] Patent CN103555307A discloses a plugging remover for oil production. The agent, calculated by weight, comprises 38-43 parts toluene, 8-13 parts xylene, 18-23 parts sodium dodecyl sulfate, and 13-18 parts ethylene glycol monobutyl ether. This plugging remover is used to remove blockages during the production of thin oil wells in the Tahe Oilfield. It primarily targets organic impurities such as colloids, asphaltenes, and waxes, and does not address inorganic scale impurities found in oilfield blockages.

[0005] Patent CN103881674B discloses a combined slug remover for polymer injection plugging, a preparation method and an application thereof, comprising a pre-treatment slug remover, an oxidative gel-breaking slug remover and a post-stage enhanced slug remover. The pre-treatment slug remover is composed of the following components in percentage by weight: 2-5% JHB-1 high-efficiency oil washing agent, 1-2% ammonium chloride, and the balance being water; the oxidative gel-breaking slug remover is composed of the following components in percentage by weight: 10-20% sodium percarbonate, 1-2% active agent, 0.5-2% corrosion inhibitor, 2-5% mutual solvent, and the balance being water; the post-stage enhanced slug remover is composed of the following components in percentage by weight: 5-10% sodium chlorite, 10-20% citric acid, 5-6% fluoroboric acid, 2-3% ammonium bifluoride, 1-2% ammonium chloride, JHB-1 The post-installed synergistic section of the aforementioned plugging remover contains a combination of fluoroboric acid and ammonium bifluoride. Under acidic conditions, these release free fluoride ions, which synergize with hydrogen ions to cause hydrofluoric acid corrosion of N80 steel. Sodium chlorite reacts with citric acid to produce chlorine dioxide, a highly oxidizing substance that exacerbates metal pitting and can lead to localized perforation of the downhole tubing. Furthermore, the rapid reaction of sodium chlorite and citric acid in the post-installed slug to produce chlorine dioxide releases significant heat, potentially causing localized high temperatures downhole, leading to polymer coking or formation mineral phase changes (such as montmorillonite to kaolinite), further exacerbating blockages.

[0006] Acidizing plugging removal is a common method for increasing oilfield production. Common acidizing technologies include soil acidizing, organic acidizing, foam acidizing, micellar acidizing, and CO2 acidizing. However, acidic solutions can easily corrode pipes, causing secondary damage. Fluorides can easily produce secondary precipitation (such as calcium fluoride and fluorosilicates), causing formation damage. Furthermore, acidizing plugging removers are limited in their effectiveness, being effective only against inorganic or organic scale and unable to address organic-inorganic composite blockages.

[0007] Therefore, it is necessary to explore a new type of composite chelating plugging remover for oil fields. Summary of the Invention

[0008] The purpose of the present invention is to provide a composite chelating plugging remover for oil fields. The composite chelating plugging remover has good scale dissolving rate and wax prevention rate. The present invention also provides a preparation method thereof.

[0009] The composite chelating plugging remover for oil fields of the present invention is composed of the following raw materials, calculated by mass percentage: 7-9% of 1-butyl-3-methylimidazole dodecylsulfonate, 5-7% of erucamidopropyl hydroxypropyl sulfobetaine, 3-4% of sodium di-(2-ethylhexyl)sulfosuccinate, 4-5% of ethylenediamine di-o-hydroxyphenylacetic acid, 3-4% of N,N'-bis(2-hydroxybenzyl)ethylenediamine-N,N'-diacetic acid, 2-3% of O-(3-(benzyloxy)propyl)hydroxylamine, 1-2% of heptadecenyl hydroxyethylimidazoline quaternary ammonium salt, 1-1.5% of dimethyldiallylammonium chloride homopolymer, and the balance being water.

[0010] Preferably, the composite chelating plugging remover for oil fields described in the present invention is composed of the following raw materials, measured by mass percentage: 8% of 1-butyl-3-methylimidazole dodecylsulfonate, 6% of erucamidopropyl hydroxypropylsulfobetaine, 3.5% of sodium di-(2-ethylhexyl)sulfosuccinate, 4.5% of ethylenediamine di-o-hydroxyphenylacetic acid, 3.5% of N,N'-bis(2-hydroxybenzyl)ethylenediamine-N,N'-diacetic acid, 2.5% of O-(3-(benzyloxy)propyl)hydroxylamine, 1.5% of heptadecenyl hydroxyethylimidazoline quaternary ammonium salt, 1.3% of dimethyldiallylammonium chloride homopolymer, and the balance is water.

[0011] The composite chelating plugging remover for oil fields described herein comprises 1-butyl-3-methylimidazole dodecyl sulfonate and erucamidopropyl hydroxypropyl sulfobetaine, which work synergistically to remove polymer and asphaltene micelles. The addition of sodium di-(2-ethylhexyl) sulfosuccinate enhances the permeability of the prepared composite chelating plugging remover. 1-butyl-3-methylimidazole dodecyl sulfonate forms a π-π stacking interaction with polar groups in polymers or asphaltene. Its polar solvent properties penetrate and disrupt hydrogen bonds between polymer chains. The sulfonate groups in its molecular structure bind to polar groups on the asphalt surface, preventing their aggregation through steric hindrance, thereby dissolving and stripping the polymer and asphaltene impurities. At low concentrations, erucamidopropyl hydroxypropyl sulfobetaine forms critical micelles, penetrating and disrupting the gel structure formed by polymers. By reducing hydrogen bonds and van der Waals forces between polymer chains, it promotes the disentanglement of polymer chains, allowing the prepared composite chelating plugging remover to restore formation permeability. Erucamidopropyl hydroxypropyl sulfobetaine can also disrupt the oil-in-water emulsion interface film that stabilizes asphaltene, promoting oil-water separation while carrying asphaltene particles into the aqueous phase for discharge. The addition of erucamidopropyl hydroxypropyl sulfobetaine allows the prepared composite chelating plugging remover to maintain high activity, avoiding the problem of activity loss caused by metal ion precipitation. Furthermore, the addition of sodium di-(2-ethylhexyl) sulfosuccinate reduces the surface tension of the system, allowing it to quickly migrate to the interface, enhancing the penetration ability of the composite chelating plugging remover, disrupting the emulsion interface film, and dispersing the polymer and asphaltene particles.

[0012] The composite chelating plugging remover for oil fields of the present invention is a compound of ethylenediamine di-o-hydroxyphenylacetic acid and N,N'-bis(2-hydroxybenzyl)ethylenediamine-N,N'-diacetic acid. By forming a stable multivalent metal chelate with the metal ions in the inorganic scale, a large amount of inorganic scale is dissolved, thereby removing the inorganic scale in the blockage. Among them, the molecular structure of ethylenediamine di-o-hydroxyphenylacetic acid contains two o-hydroxyphenyl groups and an ethylenediamine skeleton, which has a multi-dentate coordination ability. By chelating calcium ions and magnesium ions in oilfield water, it prevents the deposition of scales such as calcium carbonate and calcium sulfate. N,N'-bis(2-hydroxybenzyl)ethylenediamine-N,N'-diacetic acid can effectively chelate Fe in oilfield water. 3+ , preventing iron oxide deposition, thereby alleviating pipe blockage. In addition, ethylenediamine di-o-hydroxyphenylacetic acid and N,N'-bis(2-hydroxybenzyl)ethylenediamine-N,N'-diacetic acid can also destroy the metal cross-linking points of high molecular weight polymers (such as polyacrylamide) through coordination, indirectly promoting degradation.

[0013] The composite chelating plugging remover for oil fields described in the present invention combines O-(3-(benzyloxy)propyl)hydroxylamine and heptadecenylhydroxyethylimidazoline quaternary ammonium salt to inhibit corrosion. The heptadecenylhydroxyethylimidazoline quaternary ammonium salt forms a hydrophobic film on the metal surface through electrostatic adsorption of the quaternary ammonium salt cation. The amino group and ether bond in the O-(3-(benzyloxy)propyl)hydroxylamine chemically coordinate with the metal (such as Fe) to form a dense passivation film. The two act synergistically, forming a double-layer protective film through the hydrophobicity of the quaternary ammonium salt and the chemical adsorption of the hydroxylamine. Furthermore, when the two are used in combination, the imidazoline quaternary ammonium salt preferentially inhibits the cathode reaction, while the hydroxylamine derivative inhibits anodic dissolution through amino group coordination, jointly reducing the corrosion current density. This combination of the two provides excellent corrosion inhibition performance in the complex environment of oil well blockages.

[0014] The composite chelating plugging remover for oil fields of the present invention uses dimethyldiallyl ammonium chloride homopolymer as a clay stabilizer. Dimethyldiallyl ammonium chloride homopolymer neutralizes the negative charge on the surface of clay minerals through electrostatic action, compresses and diffuses the double electric layer, reduces the electrostatic repulsion between clay particles, and thus improves the anti-swelling rate.

[0015] The preparation method of the composite chelating plugging remover for oil fields of the present invention comprises the following steps:

[0016] (1) 1-Butyl-3-methylimidazolium dodecylsulfonate, erucamidopropyl hydroxypropylsulfobetaine and water are stirred evenly to form a homogeneous micellar solution;

[0017] (2) adding sodium di-(2-ethylhexyl) sulfosuccinate, ethylenediamine di-o-hydroxyphenylacetic acid, and N,N'-bis(2-hydroxybenzyl)ethylenediamine-N,N'-diacetic acid to the homogeneous micellar solution prepared in step (1), and stirring until completely dissolved;

[0018] (3) Add O-(3-(benzyloxy)propyl)hydroxylamine, heptadecenylhydroxyethylimidazoline quaternary ammonium salt and dimethyldiallyl ammonium chloride homopolymer to the mixture prepared in step (2), stirring and dissolving the mixture until a homogeneous system is formed, thereby preparing a composite chelating plugging remover for oil fields.

[0019] in:

[0020] In step (1), the stirring and mixing temperature is 44-46° C., and the stirring and mixing time is 30 min.

[0021] In step (2), the stirring and mixing temperature is 44-46° C., and the stirring and mixing time is 60 min.

[0022] In step (3), the stirring and mixing temperature is 28-30° C., and the stirring and mixing time is 20 min.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] (1) The composite chelating plugging remover for oil fields of the present invention is a compound of 1-butyl-3-methylimidazole dodecylsulfonate and erucamidopropyl hydroxypropyl sulfobetaine, which is used to remove high molecular weight polymers and asphaltene micelles in the blockage, and sodium di-(2-ethylhexyl) sulfosuccinate is added as a penetrant to improve the effective permeability of the composite chelating plugging remover. Ethylenediamine di-o-hydroxyphenylacetic acid and N,N'-bis(2-hydroxybenzyl)ethylenediamine-N,N'-diacetic acid are combined to form a specific chelating reaction with metal ions, destroying the crystal structure of inorganic scale and thus removing it. A mixture of O-(3-(benzyloxy)propyl)hydroxylamine and heptadecenylhydroxyethylimidazoline quaternary ammonium salt serves as a corrosion inhibitor. Through a dual mechanism of film-forming protection and electrochemical inhibition, it prevents corrosion damage to metal equipment caused by high-mineralization media during the plugging process. Dimethyldiallylammonium chloride homopolymer acts as a clay stabilizer, inhibiting the hydration, expansion, and dispersion migration of clay minerals in the reservoir, thereby protecting the permeation channels of the oil well. This synergistic effect between the raw materials ensures that the prepared composite chelating plugging remover has excellent performance.

[0025] (2) The composite chelating plugging remover for oil fields of the present invention has excellent scale dissolving rate and wax prevention rate when used in complex scale plugging removal in oil fields.

[0026] (3) The preparation method of the composite chelating plugging remover for oil fields of the present invention has a simple process, and the parameters in the preparation process are easy to control. The prepared composite chelating plugging remover has stable performance. DETAILED DESCRIPTION

[0027] The present invention will be further described below with reference to the examples.

[0028] Example 1

[0029] The composite chelating plugging remover for oil fields described in Example 1 is composed of the following raw materials, calculated by mass percentage: 8% 1-butyl-3-methylimidazole dodecylsulfonate, 6% erucamidopropyl hydroxypropyl sulfobetaine, 3.5% sodium di-(2-ethylhexyl)sulfosuccinate, 4.5% ethylenediamine di-o-hydroxyphenylacetic acid, 3.5% N,N'-bis(2-hydroxybenzyl)ethylenediamine-N,N'-diacetic acid, 2.5% O-(3-(benzyloxy)propyl)hydroxylamine, 1.5% heptadecenyl hydroxyethylimidazoline quaternary ammonium salt, 1.3% dimethyldiallylammonium chloride homopolymer, and the balance being water.

[0030] The preparation method of the composite chelating plugging remover for oil fields described in Example 1 comprises the following steps:

[0031] (1) 1-Butyl-3-methylimidazolium dodecylsulfonate, erucamidopropyl hydroxypropylsulfobetaine and water are stirred evenly to form a homogeneous micellar solution;

[0032] (2) adding sodium di-(2-ethylhexyl) sulfosuccinate, ethylenediamine di-o-hydroxyphenylacetic acid, and N,N'-bis(2-hydroxybenzyl)ethylenediamine-N,N'-diacetic acid to the homogeneous micellar solution prepared in step (1), and stirring until completely dissolved;

[0033] (3) Add O-(3-(benzyloxy)propyl)hydroxylamine, heptadecenylhydroxyethylimidazoline quaternary ammonium salt and dimethyldiallyl ammonium chloride homopolymer to the mixture prepared in step (2), stirring and dissolving the mixture until a homogeneous system is formed, thereby preparing a composite chelating plugging remover for oil fields.

[0034] in:

[0035] The stirring and mixing temperature in step (1) is 45° C., and the stirring and mixing time is 30 min.

[0036] The stirring and mixing temperature in step (2) is 45° C., and the stirring and mixing time is 60 min.

[0037] In step (3), the stirring and mixing temperature is 29° C., and the stirring and mixing time is 20 min.

[0038] Example 2

[0039] The composite chelating plugging remover for oil fields described in Example 2 is composed of the following raw materials, calculated by mass percentage: 9% 1-butyl-3-methylimidazole dodecylsulfonate, 5% erucamidopropyl hydroxypropyl sulfobetaine, 3% sodium di-(2-ethylhexyl) sulfosuccinate, 5% ethylenediamine di-o-hydroxyphenylacetic acid, 4% N,N'-bis(2-hydroxybenzyl)ethylenediamine-N,N'-diacetic acid, 2% O-(3-(benzyloxy)propyl)hydroxylamine, 1% heptadecenyl hydroxyethylimidazoline quaternary ammonium salt, 1.5% dimethyldiallylammonium chloride homopolymer, and the balance being water.

[0040] The preparation method of the composite chelating plugging remover for oil fields described in Example 2 comprises the following steps:

[0041] (1) 1-Butyl-3-methylimidazolium dodecylsulfonate, erucamidopropyl hydroxypropylsulfobetaine and water are stirred evenly to form a homogeneous micellar solution;

[0042] (2) adding sodium di-(2-ethylhexyl) sulfosuccinate, ethylenediamine di-o-hydroxyphenylacetic acid, and N,N'-bis(2-hydroxybenzyl)ethylenediamine-N,N'-diacetic acid to the homogeneous micellar solution prepared in step (1), and stirring until completely dissolved;

[0043] (3) Add O-(3-(benzyloxy)propyl)hydroxylamine, heptadecenylhydroxyethylimidazoline quaternary ammonium salt and dimethyldiallyl ammonium chloride homopolymer to the mixture prepared in step (2), stirring and dissolving the mixture until a homogeneous system is formed, thereby preparing a composite chelating plugging remover for oil fields.

[0044] in:

[0045] The stirring and mixing temperature in step (1) is 46° C., and the stirring and mixing time is 30 min.

[0046] In step (2), the stirring and mixing temperature is 46° C., and the stirring and mixing time is 60 min.

[0047] In step (3), the stirring and mixing temperature is 28° C., and the stirring and mixing time is 20 min.

[0048] Example 3

[0049] The composite chelating plugging remover for oil fields described in Example 3 is composed of the following raw materials, calculated by mass percentage: 7% 1-butyl-3-methylimidazole dodecylsulfonate, 7% erucamidopropyl hydroxypropyl sulfobetaine, 4% sodium di-(2-ethylhexyl)sulfosuccinate, 4% ethylenediamine di-o-hydroxyphenylacetic acid, 3% N,N'-bis(2-hydroxybenzyl)ethylenediamine-N,N'-diacetic acid, 3% O-(3-(benzyloxy)propyl)hydroxylamine, 2% heptadecenyl hydroxyethylimidazoline quaternary ammonium salt, 1% dimethyldiallylammonium chloride homopolymer, and the balance being water.

[0050] The preparation method of the composite chelating plugging remover for oil fields described in Example 3 is composed of the following steps:

[0051] (1) 1-Butyl-3-methylimidazolium dodecylsulfonate, erucamidopropyl hydroxypropylsulfobetaine and water are stirred evenly to form a homogeneous micellar solution;

[0052] (2) adding sodium di-(2-ethylhexyl) sulfosuccinate, ethylenediamine di-o-hydroxyphenylacetic acid, and N,N'-bis(2-hydroxybenzyl)ethylenediamine-N,N'-diacetic acid to the homogeneous micellar solution prepared in step (1), and stirring until completely dissolved;

[0053] (3) Add O-(3-(benzyloxy)propyl)hydroxylamine, heptadecenylhydroxyethylimidazoline quaternary ammonium salt and dimethyldiallyl ammonium chloride homopolymer to the mixture prepared in step (2), stirring and dissolving the mixture until a homogeneous system is formed, thereby preparing a composite chelating plugging remover for oil fields.

[0054] in:

[0055] The stirring and mixing temperature in step (1) is 44° C., and the stirring and mixing time is 30 min.

[0056] In step (2), the stirring and mixing temperature is 44° C., and the stirring and mixing time is 60 min.

[0057] In step (3), the stirring and mixing temperature is 30° C., and the stirring and mixing time is 20 min.

[0058] Comparative Example 1

[0059] The preparation method of the composite chelating plugging remover for oil fields described in Comparative Example 1 is the same as that of Example 1, the only difference being that the raw material composition of the composite chelating plugging remover for oil fields is different. The composite chelating plugging remover for oil fields described in Comparative Example 1 is composed of the following raw materials, measured by mass percentage: 3.5% sodium di-(2-ethylhexyl) sulfosuccinate, 4.5% ethylenediamine di-o-hydroxyphenylacetic acid, 3.5% N,N'-bis(2-hydroxybenzyl)ethylenediamine-N,N'-diacetic acid, 2.5% O-(3-(benzyloxy)propyl)hydroxylamine, 1.5% heptadecenyl hydroxyethyl imidazoline quaternary ammonium salt, 1.3% dimethyl diallyl ammonium chloride homopolymer, and the balance being water.

[0060] Comparative Example 2

[0061] The preparation method of the composite chelating plugging remover for oil fields described in Comparative Example 2 is the same as that of Example 1, the only difference being that the raw material composition of the composite chelating plugging remover for oil fields is different. The composite chelating plugging remover for oil fields described in Comparative Example 2 is composed of the following raw materials, measured by mass percentage: 6% erucamidopropyl hydroxypropyl sulfobetaine, 3.5% sodium di-(2-ethylhexyl) sulfosuccinate, 4.5% ethylenediamine di-o-hydroxyphenylacetic acid, 3.5% N,N'-bis(2-hydroxybenzyl)ethylenediamine-N,N'-diacetic acid, 2.5% O-(3-(benzyloxy)propyl)hydroxylamine, 1.5% heptadecenyl hydroxyethyl imidazoline quaternary ammonium salt, 1.3% dimethyl diallyl ammonium chloride homopolymer, and the balance being water.

[0062] Comparative Example 3

[0063] The preparation method of the composite chelating plugging remover for oil fields described in Comparative Example 3 is the same as that of Example 1, the only difference being that the raw material composition of the composite chelating plugging remover for oil fields is different. The composite chelating plugging remover for oil fields described in Comparative Example 3 is composed of the following raw materials, by mass percentage: 8% 1-butyl-3-methylimidazole dodecylsulfonate, 6% erucamidopropyl hydroxypropyl sulfobetaine, 3.5% N,N'-bis(2-hydroxybenzyl)ethylenediamine-N,N'-diacetic acid, 2.5% O-(3-(benzyloxy)propyl)hydroxylamine, 1.5% heptadecenyl hydroxyethylimidazoline quaternary ammonium salt, 1.3% dimethyldiallylammonium chloride homopolymer, and the balance being water.

[0064] The composite chelating plugging remover for oil fields prepared in Examples 1-3 and Comparative Examples 1-3 were weighed and mixed evenly with distilled water to obtain an aqueous solution of the composite chelating plugging remover for oil fields with a concentration of 10 wt%. 13.0 g of calcium carbonate / magnesium carbonate / ferric hydroxide / aluminum hydroxide was then added to 100 mL of the aqueous solution of the chelating plugging remover for oil fields and shaken at 40 ° C. The mixture was then placed in a constant temperature incubator at 40 ° C. for 24 h. The sample was taken out and filtered using medium-speed qualitative filter paper, and then dried at 105 ° C. Finally, the scale dissolution rate was calculated by the mass difference before and after the experiment.

[0065] The test process of asphalt dissolution rate is as follows:

[0066] (1) Weigh the N80 steel sheet and record m1 to the nearest 0.001g;

[0067] (2) Soak the steel sheet (below the hole end) evenly in preheated asphalt (10# asphalt), take about 2g of asphalt, weigh and record m2, accurate to 0.001g, and set aside;

[0068] (3) Take 200 mL of oilfield composite chelating plugging remover and place the asphalt hanging piece into the lower part of the thread-mouth bottle;

[0069] (4) Place the experimental thread-mouth bottle in a 45°C water bath for 24 hours, then remove the coupon and record the mass m3 of the coupon removed to the nearest 0.001 g.

[0070] (5) Asphalt dissolution rate = (m 3- m2) / (m 2- m1)*100%.

[0071] Organic-inorganic mixed blockage sample: Sampled from an oil well in Shengli Oilfield, composed of 35.7% crude oil, 6.5% polymer, 32.5% inorganic minerals, and 25.3% water. Of this, colloids and asphaltenes accounted for 26.9% of the crude oil; the polymer was polyacrylamide; and the inorganic minerals were 31% calcium carbonate, 19% magnesium carbonate, 33% iron hydroxide, and 17% clay minerals.

[0072] The composite chelating plugging remover for oil fields prepared in Examples 1-3 and Comparative Examples 1-3 were weighed and mixed evenly with distilled water to obtain an aqueous solution of the composite chelating plugging remover for oil fields with a concentration of 5 wt%. The organic-inorganic composite blockage was placed in the aqueous solution of the composite chelating plugging remover for oil fields at 45° C. and normal pressure. The reaction was carried out for 24 hours, and the degradation rate was calculated.

[0073] The viscosity after high temperature treatment (72 hours at 75°C) was measured using a rotational viscometer, and the viscosity retention rate was calculated. The higher the viscosity retention rate, the better the high temperature stability.

[0074] The above test results are shown in Table 1 below.

[0075] Table 1 Scale dissolution rate test results of composite chelating plugging remover for oilfield use

[0076]

[0077] As shown in Table 1, the composite chelating plugging remover for oil fields prepared in Examples 1-3 has a good removal rate for inorganic scale, organic scale and organic-inorganic composite scale, and has high stability. Compared with Example 1, Comparative Example 1 omitted 1-butyl-3-methylimidazole dodecyl sulfonate and erucamidopropyl hydroxypropyl sulfobetaine in the raw materials, resulting in a significant decrease in the removal rate of organic scale; Compared with Comparative Example 1, Comparative Example 2 omitted 1-butyl-3-methylimidazole dodecyl sulfonate in the raw materials. Compared with Comparative Example 1, the removal rate of organic scale increased, but was still far worse than that of Example 1; Compared with Example 1, Comparative Example 3 omitted di-(2-ethylhexyl) sodium sulfosuccinate and ethylenediamine di-o-hydroxyphenylacetic acid in the raw materials, resulting in a significant decrease in the removal rate of inorganic scale. In addition, due to the lack of some raw materials in Comparative Examples 1-3, the removal ability of the prepared plugging remover for organic-inorganic composite scale decreased, and the high-temperature stability also decreased. It can be seen from this that the raw materials of the composite chelating plugging remover for oil fields described in this application have a synergistic relationship.

Claims

1. A composite chelating plugging remover for oil fields, characterized by: The invention is composed of the following raw materials in percentage by mass: 7-9% of 1-butyl-3-methylimidazole dodecylsulfonate, 5-7% of erucamidopropyl hydroxypropylsulfobetaine, 3-4% of sodium di-(2-ethylhexyl)sulfosuccinate, 4-5% of ethylenediamine di-o-hydroxyphenylacetic acid, 3-4% of N,N'-bis(2-hydroxybenzyl)ethylenediamine-N,N'-diacetic acid, 2-3% of O-(3-(benzyloxy)propyl)hydroxylamine, 1-2% of heptadecenyl hydroxyethylimidazoline quaternary ammonium salt, 1-1.5% of dimethyldiallylammonium chloride homopolymer, and the balance of water. The preparation method of the composite chelating plugging remover for oil fields comprises the following steps: (1) 1-Butyl-3-methylimidazolium dodecylsulfonate, erucamidopropyl hydroxypropylsulfobetaine and water are stirred evenly to form a homogeneous micellar solution; (2) adding sodium di-(2-ethylhexyl) sulfosuccinate, ethylenediamine di-o-hydroxyphenylacetic acid, and N,N'-bis(2-hydroxybenzyl)ethylenediamine-N,N'-diacetic acid to the homogeneous micellar solution prepared in step (1), and stirring until completely dissolved; (3) Add O-(3-(benzyloxy)propyl)hydroxylamine, heptadecenylhydroxyethylimidazoline quaternary ammonium salt and dimethyldiallyl ammonium chloride homopolymer to the mixture prepared in step (2), stirring and dissolving the mixture until a homogeneous system is formed, thereby preparing a composite chelating plugging remover for oil fields.

2. The composite chelating plugging remover for oil fields according to claim 1, characterized in that: The product is composed of the following raw materials in percentage by mass: 8% 1-butyl-3-methylimidazole dodecylsulfonate, 6% erucamidopropyl hydroxypropylsulfobetaine, 3.5% sodium di-(2-ethylhexyl)sulfosuccinate, 4.5% ethylenediamine di-o-hydroxyphenylacetic acid, 3.5% N,N'-bis(2-hydroxybenzyl)ethylenediamine-N,N'-diacetic acid, 2.5% O-(3-(benzyloxy)propyl)hydroxylamine, 1.5% heptadecenyl hydroxyethylimidazoline quaternary ammonium salt, 1.3% dimethyldiallylammonium chloride homopolymer, and the balance is water.

3. A method for preparing the composite chelating plugging remover for oil fields according to claim 1, characterized in that: It consists of the following steps: (1) 1-Butyl-3-methylimidazolium dodecylsulfonate, erucamidopropyl hydroxypropylsulfobetaine and water are stirred evenly to form a homogeneous micellar solution; (2) adding sodium di-(2-ethylhexyl) sulfosuccinate, ethylenediamine di-o-hydroxyphenylacetic acid, and N,N'-bis(2-hydroxybenzyl)ethylenediamine-N,N'-diacetic acid to the homogeneous micellar solution prepared in step (1), and stirring until completely dissolved; (3) Add O-(3-(benzyloxy)propyl)hydroxylamine, heptadecenylhydroxyethylimidazoline quaternary ammonium salt and dimethyldiallyl ammonium chloride homopolymer to the mixture prepared in step (2), stirring and dissolving the mixture until a homogeneous system is formed, thereby preparing a composite chelating plugging remover for oil fields.

4. The method for preparing the composite chelating plugging remover for oil fields according to claim 3, wherein: In step (1), the stirring and mixing temperature is 44-46° C., and the stirring and mixing time is 30 min.

5. The method for preparing the composite chelating plugging remover for oil fields according to claim 3, characterized in that: In step (2), the stirring and mixing temperature is 44-46° C., and the stirring and mixing time is 60 min.

6. The method for preparing the composite chelating plugging remover for oil fields according to claim 3, characterized in that: In step (3), the stirring and mixing temperature is 28-30° C., and the stirring and mixing time is 20 min.

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