Composite chelating blocking remover for oil field and preparation method of composite chelating blocking remover

Abstract

The invention belongs to the technical field of preparation of blocking removers, and particularly relates to a composite chelating blocking remover for an oil field and a preparation method of the composite chelating blocking remover. The composite chelating blocking remover for the oil field is prepared from the following raw materials in percentage by mass: 7 to 9 percent of 1-butyl-3-methylimidazole dodecyl sulfonate, 5 to 7 percent of erucamide propyl hydroxypropyl sulfobetaine, 3 to 4 percent of di-(2-ethylhexyl) sodium sulfosuccinate, 4 to 5 percent of ethylenediamine di-o-hydroxyphenylacetic acid, 5 to 7 percent of N, N '-di (2-hydroxybenzyl) ethylenediamine-N, N'-bis (2-hydroxybenzyl)-N, N '-bis (2-ethylhexyl)-N, N'-bis (2-hydroxybenzyl)-N, N '-bis (2-hydroxybenzyl)-N, N'-bis (2-hydroxyphenyl)-N, N '-bis (2-hydroxyphenyl)-N, N'-bis (2-hydroxyphenyl)-N The cleaning agent is prepared from the following components in percentage by weight: 3 to 4 percent of N, N '-diacetic acid, 2 to 3 percent of O-(3-(benzyloxy) propyl) hydroxylamine, 1 to 2 percent of heptadecenyl hydroxyethyl imidazoline quaternary ammonium salt, 1 to 1.5 percent of dimethyl diallyl ammonium chloride homopolymer and the balance of water. The composite chelating blocking remover for the oil field has excellent scale dissolution rate and paraffin inhibition rate when being applied to complex scale blocking removal of the oil field.

Description

Technical Field

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

[0002] During the development of polymer flooding in oil fields, after long-term polymer injection, polymer concentration and aggregation will occur at the throats of the reservoirs in the near-wellbore zones of polymer injection wells. Moreover, with the continuous increase in the injection volume and the injection pressure, the plugging substances become denser and denser, ultimately making polymer injection very difficult. During the plugging removal operation, the dense plugging substances prevent the plugging removal agent from penetrating into the inner core of the plugging substances, resulting in an unsatisfactory plugging removal effect. The multi-component plugging substances not only contain polymers and asphaltenes, but also contain mud and sand. The mud and sand particles can form a "bridge plug" in front of the screen holes, making the plugging effect of the multi-component plugging substances significantly stronger than that of ordinary plugging substances, and the difficulty of plugging removal also increases accordingly.

[0003] The main reasons for the plugging of polymer injection wells include the following aspects: (1) During the polymer injection process in polymer injection wells, polymers will be retained in the rock cores under the action of adsorption and trapping, reducing the rock permeability and thus causing formation damage; (2) In the inlet zone, polymers and inorganic scales are wrapped and intertwined with each other, forming an organic-inorganic composite scale with the inorganic scale as the core, which is difficult to remove; (3) High-valent metal ions (especially Fe 3+ ) crosslink with polymers to form flocs that are easily adsorbed and retained in the pipeline, causing the tubing to be plugged; (4) Clay minerals and scaling of calcium and magnesium ions, etc.

[0004] Patent CN103555307A discloses a plugging removal agent for oil production. By weight, the plugging removal agent includes 38-43 parts of toluene, 8-13 parts of xylene, 18-23 parts of sodium dodecyl sulfonate, and 13-18 parts of ethylene glycol monobutyl ether. This plugging removal agent is used for removing plugging substances during the production process of thin oil wells in the Tahe Oilfield, mainly targeting organic impurities such as asphaltenes and waxes, and does not involve inorganic scale impurities in oil field plugging substances.

[0005] Patent CN103881674B discloses a plugging removal agent for slug combination in polymer injection plugged well sections, a preparation method and an application thereof, including a pretreatment slug plugging removal agent, an oxidation gel-breaking slug plugging removal agent and a post-treatment synergistic slug plugging removal agent. The pretreatment slug plugging removal agent is composed of the following components in weight percentage: 2-5% of JHB-1 type high-efficiency oil washing agent, 1-2% of ammonium chloride, and the balance is water. The oxidation gel-breaking slug plugging removal agent is composed of the following components in weight percentage: 10-20% of sodium percarbonate, 1-2% of surfactant, 0.5-2% of corrosion inhibitor, 2-5% of mutual solvent, and the balance is water. The post-treatment synergistic slug plugging removal agent is composed of the following components in weight percentage: 5-10% of sodium chlorite, 10-20% of citric acid, 5-6% of fluoboric acid, 2-3% of ammonium bifluoride, 1-2% of ammonium chloride, 2-3% of JHB-1 type high-efficiency oil washing agent, 0.5-2% of corrosion inhibitor, 2-5% of mutual solvent, and the balance is water. In the post-treatment synergistic section of the above plugging removal agent, fluoboric acid and ammonium bifluoride are selected to be used in combination, and free fluoride ions are released under acidic conditions, and they act synergistically with hydrogen ions to cause hydrofluoric acid corrosion to N80 steel. Moreover, sodium chlorite reacts with citric acid to generate chlorine dioxide, and its strong oxidizing property intensifies pitting corrosion of metals, resulting in local perforation of downhole pipe strings. In addition, after sodium chlorite and citric acid are mixed in the post-treatment slug, they react quickly to generate chlorine dioxide, releasing a large amount of heat, which may cause local high temperature downhole, resulting in polymer coking or formation mineral phase transformation (such as the transformation of montmorillonite into kaolinite), exacerbating the plugging.

[0006] Acidizing plugging removal is a commonly used production-increasing means in oilfield production. Commonly used acidizing plugging removal technologies include: mud acidizing, organic acidizing, foam acid, micellar acid, CO2 acidizing, etc. However, acid solution is easy to corrode pipe strings, causing secondary damage. Fluoride is easy to generate secondary precipitates (such as calcium fluoride, fluorosilicate), causing formation damage, or the function of the acidizing plugging removal agent is single, only effective for inorganic scale or organic scale, and unable to deal with organic-inorganic composite plugging substances.

[0007] Therefore, it is necessary to explore a new type of composite chelating plugging removal agent for oilfields. Summary of the Invention

[0008] The object of the present invention is to provide a composite chelating plugging removal agent for oilfields. The composite chelating plugging removal agent has a good scale dissolution rate and paraffin prevention rate. The present invention also provides a preparation method thereof at the same time.

[0009] The composite chelating plugging removal agent for oil fields according to the present invention is composed of the following raw materials in terms of mass percentage: 7-9% of 1-butyl-3-methylimidazolium dodecylsulfonate, 5-7% of erucic acid amide propyl hydroxypropyl sulfobetaine, 3-4% of bis-(2-ethylhexyl) sulfosuccinate sodium, 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 hydroxyethyl imidazoline quaternary ammonium salt, 1-1.5% of dimethyldiallylammonium chloride homopolymer, and the balance being water.

[0010] Preferably, the composite chelating plugging removal agent for oil fields according to the present invention is composed of the following raw materials in terms of mass percentage: 8% of 1-butyl-3-methylimidazolium dodecylsulfonate, 6% of erucic acid amide propyl hydroxypropyl sulfobetaine, 3.5% of bis-(2-ethylhexyl) sulfosuccinate sodium, 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 hydroxyethyl imidazoline quaternary ammonium salt, 1.3% of dimethyldiallylammonium chloride homopolymer, and the balance being water.

[0011] In the composite chelating plugging removal agent for oil fields according to the present invention, 1-butyl-3-methylimidazolium dodecylsulfonate and erucic acid amide propyl hydroxypropyl sulfobetaine act synergistically to remove high molecular polymers and asphaltene micelles. The addition of bis-(2-ethylhexyl) sulfosuccinate sodium enhances the permeability of the prepared composite chelating plugging removal agent. Among them: 1-butyl-3-methylimidazolium dodecylsulfonate undergoes π-π stacking with polar groups in high molecular polymers or asphaltenes. Its polar solvent characteristics can penetrate and break the hydrogen bonds between high molecular polymer chains. The sulfonate group in its molecular structure binds to the polar groups on the asphaltene surface, preventing their aggregation through steric hindrance effects, and then dissolving and stripping high molecular polymers and asphaltene impurities. Erucic acid amide propyl hydroxypropyl sulfobetaine can form critical micelles at low concentrations, penetrate and break the gel structure formed by high molecular polymers, promote the disentanglement of polymer chains by reducing the hydrogen bonds and van der Waals forces between high molecular polymer chains, enabling the prepared composite chelating plugging removal agent to restore formation permeability. Erucic acid amide propyl hydroxypropyl sulfobetaine can also destroy the interfacial film of the asphaltene-stabilized water-in-oil emulsion, promote oil-water separation while carrying asphaltene particles into the aqueous phase for discharge. The addition of erucic acid amide propyl hydroxypropyl sulfobetaine keeps the prepared composite chelating plugging removal agent highly active, avoiding the problem of activity failure caused by metal ion precipitation. In addition, the addition of bis-(2-ethylhexyl) sulfosuccinate sodium reduces the surface tension of the system, can quickly migrate to the interface, enhances the penetration ability of the composite chelating plugging removal agent, destroys the emulsion interfacial film, and plays a dispersing role on high molecular polymers and asphaltene particles.

[0012] The composite chelating plugging remover for oil fields described in the present invention uses ethylenediamine di(o-hydroxyphenyl)acetic acid and N,N'-bis(2-hydroxybenzyl)ethylenediamine-N,N'-diacetic acid in combination. By forming stable polyvalent metal chelates with metal ions in inorganic scales, it can dissolve a large amount of inorganic scales and remove the inorganic scales in the blockage. Among them, the molecular structure of ethylenediamine di(o-hydroxyphenyl)acetic acid contains two o-hydroxyphenyl groups and an ethylenediamine backbone, and has multidentate coordination ability. By chelating calcium ions and magnesium ions in oil field water, it can prevent the deposition of scales such as calcium carbonate and calcium sulfate. N,N'-bis(2-hydroxybenzyl)ethylenediamine-N,N'-diacetic acid can efficiently chelate Fe 3+ , preventing the deposition of iron oxides, thereby alleviating pipeline blockage. In addition, ethylenediamine di(o-hydroxyphenyl)acetic acid and N,N'-bis(2-hydroxybenzyl)ethylenediamine-N,N'-diacetic acid can also destroy the metal cross-linking points of high molecular polymers (such as polyacrylamide) through coordination, indirectly promoting degradation.

[0013] The composite chelating plugging remover for oil fields described in the present invention uses O-(3-(benzyloxy)propyl)hydroxylamine and heptadecenyl hydroxyethyl imidazoline quaternary ammonium salt in combination to play an anti-corrosion role. The heptadecenyl hydroxyethyl imidazoline quaternary ammonium salt forms a hydrophobic film on the metal surface through the electrostatic adsorption of quaternary ammonium salt cations. The amino group and ether bond in O-(3-(benzyloxy)propyl)hydroxylamine form a dense passivation film with the metal (such as Fe) through chemical coordination. The two work together to form a double-layer protective film through the hydrophobicity of the quaternary ammonium salt and the chemical adsorption of hydroxylamine. Moreover, when the two are used in combination, the imidazoline quaternary ammonium salt preferentially inhibits the cathodic reaction, and the hydroxylamine derivative inhibits the anodic dissolution through amino coordination, jointly reducing the corrosion current density. The combined use of the two gives it excellent anti-corrosion performance in the complex environment of oil well blockages.

[0014] The composite chelating plugging remover for oil fields described in the present invention uses poly(diallyldimethylammonium chloride) homopolymer as a clay stabilizer. The poly(diallyldimethylammonium chloride) homopolymer neutralizes the negative charge on the surface of clay minerals through electrostatic action, compresses the diffuse double 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 described in the present invention comprises the following steps: (1) Stir 1-butyl-3-methylimidazolium dodecylsulfonate, erucic acid amide propyl hydroxypropyl sulfobetaine and water evenly to form a homogeneous micelle solution; (2) Add sodium bis(2-ethylhexyl)sulfosuccinate, ethylenediamine di(o-hydroxyphenyl)acetic acid and N,N'-bis(2-hydroxybenzyl)ethylenediamine-N,N'-diacetic acid to the homogeneous micelle solution prepared in step (1), and stir until completely dissolved; (3) Add O-(3-(benzyloxy)propyl)hydroxylamine, heptadecenyl hydroxyethyl imidazoline quaternary ammonium salt and dimethyldiallylammonium chloride homopolymer to the mixture prepared in step (2), and stir to dissolve until a homogeneous system is formed to prepare a composite chelating plugging removal agent for oil fields.

[0016] Among them: In step (1), the stirring and mixing temperature is 44 - 46 °C, and the stirring and mixing time is 30 min.

[0017] In step (2), the stirring and mixing temperature is 44 - 46 °C, and the stirring and mixing time is 60 min.

[0018] In step (3), the stirring and mixing temperature is 28 - 30 °C, and the stirring and mixing time is 20 min.

[0019] Compared with the prior art, the present invention has the following beneficial effects: (1) For the composite chelating plugging removal agent for oil fields of the present invention, 1-butyl-3-methylimidazolium dodecylsulfonate and erucic acid amide propyl hydroxypropyl sulfobetaine are used in combination to strip and remove the high molecular polymers and asphaltene micelles in the plugging substances. Di-(2-ethylhexyl)sulfosuccinate is added as a penetrant to improve the effective permeability of the composite chelating plugging removal agent. Ethylenediamine di-o-hydroxyphenylacetic acid and N,N'-bis(2-hydroxybenzyl)ethylenediamine-N,N'-diacetic acid are used in combination to undergo a specific chelation reaction with metal ions to destroy the crystal structure of inorganic scale, thereby removing the inorganic scale. A mixture of O-(3-(benzyloxy)propyl)hydroxylamine and heptadecenyl hydroxyethyl imidazoline quaternary ammonium salt is used as a corrosion inhibitor. Through the dual mechanisms of film formation protection and electrochemical inhibition, it prevents the corrosion and damage of metal equipment by high salinity media during the plugging removal process. Dimethyldiallylammonium chloride homopolymer is used as a clay stabilizer to inhibit the hydration swelling and dispersion migration of clay minerals in the reservoir, thereby protecting the oil well penetration channels. Thus, through the synergistic effect between the raw materials, it ensures that the prepared composite chelating plugging removal agent has excellent performance.

[0020] (2) The composite chelating plugging removal agent for oil fields of the present invention has excellent scale dissolution rate and paraffin prevention rate when applied to the plugging removal of complex scales in oil fields.

[0021] (3) The preparation method of the composite chelating plugging removal agent for oil fields of the present invention has a simple process, the parameters during the preparation process are easy to control, and the performance of the prepared composite chelating plugging removal agent is stable. Specific Embodiments

[0022] The present invention will be further described below in conjunction with embodiments.

[0023] Example 1 The composite chelating plugging removal agent for oil fields described in Example 1 is composed of the following raw materials in terms of mass percentage: 8% of 1-butyl-3-methylimidazolium dodecylsulfonate, 6% of erucic acid amide propyl hydroxypropyl sulfobetaine, 3.5% of bis(2-ethylhexyl) sulfosuccinate, 4.5% of ethylenediamine di(o-hydroxyphenyl)acetic 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 hydroxyethyl imidazoline quaternary ammonium salt, 1.3% of dimethyldiallylammonium chloride homopolymer, and the balance is water.

[0024] The preparation method of the composite chelating plugging removal agent for oil fields described in Example 1 consists of the following steps: (1) Stir 1-butyl-3-methylimidazolium dodecylsulfonate, erucic acid amide propyl hydroxypropyl sulfobetaine and water evenly to form a homogeneous micelle solution; (2) Add bis(2-ethylhexyl) sulfosuccinate, ethylenediamine di(o-hydroxyphenyl)acetic acid and N,N'-bis(2-hydroxybenzyl)ethylenediamine-N,N'-diacetic acid to the homogeneous micelle solution prepared in step (1), and stir until completely dissolved; (3) Add O-(3-(benzyloxy)propyl)hydroxylamine, heptadecenyl hydroxyethyl imidazoline quaternary ammonium salt and dimethyldiallylammonium chloride homopolymer to the mixture prepared in step (2), stir and dissolve until a homogeneous system is formed, and prepare the composite chelating plugging removal agent for oil fields.

[0025] Wherein: In step (1), the stirring and mixing temperature is 45 °C, and the stirring and mixing time is 30 min.

[0026] In step (2), the stirring and mixing temperature is 45 °C, and the stirring and mixing time is 60 min.

[0027] In step (3), the stirring and mixing temperature is 29 °C, and the stirring and mixing time is 20 min.

[0028] Example 2 The composite chelating plugging removal agent for oil fields described in Example 2 is composed of the following raw materials in terms of mass percentage: 9% of 1-butyl-3-methylimidazolium dodecylsulfonate, 5% of erucic acid amide propyl hydroxypropyl sulfobetaine, 3% of bis(2-ethylhexyl) sulfosuccinate, 5% of ethylenediamine di(o-hydroxyphenyl)acetic acid, 4% of N,N'-bis(2-hydroxybenzyl)ethylenediamine-N,N'-diacetic acid, 2% of O-(3-(benzyloxy)propyl)hydroxylamine, 1% of heptadecenyl hydroxyethyl imidazoline quaternary ammonium salt, 1.5% of dimethyldiallylammonium chloride homopolymer, and the balance is water.

[0029] The preparation method of the composite chelating plugging removal agent for oil fields described in Example 2 consists of the following steps: (1) Stir 1-butyl-3-methylimidazolium dodecylsulfonate, erucic acid amide propyl hydroxypropyl sulfobetaine and water evenly to form a homogeneous micelle solution; (2) Add sodium bis(2-ethylhexyl)sulfosuccinate, ethylenediamine di(o-hydroxyphenyl)acetic acid and N,N'-bis(2-hydroxybenzyl)ethylenediamine-N,N'-diacetic acid to the homogeneous micelle solution prepared in step (1), and stir until completely dissolved; (3) Add O-(3-(benzyloxy)propyl)hydroxylamine, heptadecenyl hydroxyethyl imidazoline quaternary ammonium salt and dimethyldiallylammonium chloride homopolymer to the mixture prepared in step (2), and stir and dissolve until a homogeneous system is formed to prepare a composite chelating plugging removal agent for oil fields.

[0030] Among them: In step (1), the stirring and mixing temperature is 46 °C, and the stirring and mixing time is 30 min.

[0031] In step (2), the stirring and mixing temperature is 46 °C, and the stirring and mixing time is 60 min.

[0032] In step (3), the stirring and mixing temperature is 28 °C, and the stirring and mixing time is 20 min.

[0033] Example 3 The composite chelating plugging removal agent for oil fields described in Example 3 consists of the following raw materials in mass percentage: 7% of 1-butyl-3-methylimidazolium dodecylsulfonate, 7% of erucic acid amide propyl hydroxypropyl sulfobetaine, 4% of sodium bis(2-ethylhexyl)sulfosuccinate, 4% of ethylenediamine di(o-hydroxyphenyl)acetic acid, 3% of N,N'-bis(2-hydroxybenzyl)ethylenediamine-N,N'-diacetic acid, 3% of O-(3-(benzyloxy)propyl)hydroxylamine, 2% of heptadecenyl hydroxyethyl imidazoline quaternary ammonium salt, 1% of dimethyldiallylammonium chloride homopolymer, and the balance is water.

[0034] The preparation method of the composite chelating plugging removal agent for oil fields described in Example 3 consists of the following steps: (1) Stir 1-butyl-3-methylimidazolium dodecylsulfonate, erucic acid amide propyl hydroxypropyl sulfobetaine and water evenly to form a homogeneous micelle solution; (2) Add sodium bis(2-ethylhexyl)sulfosuccinate, ethylenediamine di(o-hydroxyphenyl)acetic acid and N,N'-bis(2-hydroxybenzyl)ethylenediamine-N,N'-diacetic acid to the homogeneous micelle solution prepared in step (1), and stir until completely dissolved; (3) Add O-(3-(benzyloxy)propyl)hydroxylamine, heptadecenyl hydroxyethyl imidazoline quaternary ammonium salt, and dimethyldiallylammonium chloride homopolymer to the mixture prepared in step (2), and stir to dissolve until a homogeneous system is formed to prepare a composite chelating plugging remover for oil fields.

[0035] Among them: In step (1), the stirring and mixing temperature is 44°C, and the stirring and mixing time is 30 min.

[0036] In step (2), the stirring and mixing temperature is 44°C, and the stirring and mixing time is 60 min.

[0037] In step (3), the stirring and mixing temperature is 30°C, and the stirring and mixing time is 20 min.

[0038] Comparative Example 1 The preparation method of the composite chelating plugging remover for oil fields described in this Comparative Example 1 is the same as that in Example 1. The only difference is 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 this Comparative Example 1 is composed of the following raw materials in mass percentage: sodium bis(2-ethylhexyl)sulfosuccinate 3.5%, ethylenediamine di(o-hydroxyphenyl)acetic acid 4.5%, N,N'-bis(2-hydroxybenzyl)ethylenediamine-N,N'-diacetic acid 3.5%, O-(3-(benzyloxy)propyl)hydroxylamine 2.5%, heptadecenyl hydroxyethyl imidazoline quaternary ammonium salt 1.5%, dimethyldiallylammonium chloride homopolymer 1.3%, and the balance is water.

[0039] Comparative Example 2 The preparation method of the composite chelating plugging remover for oil fields described in this Comparative Example 2 is the same as that in Example 1. The only difference is 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 this Comparative Example 2 is composed of the following raw materials in mass percentage: erucic acid amide propyl hydroxypropyl sulfobetaine 6%, sodium bis(2-ethylhexyl)sulfosuccinate 3.5%, ethylenediamine di(o-hydroxyphenyl)acetic acid 4.5%, N,N'-bis(2-hydroxybenzyl)ethylenediamine-N,N'-diacetic acid 3.5%, O-(3-(benzyloxy)propyl)hydroxylamine 2.5%, heptadecenyl hydroxyethyl imidazoline quaternary ammonium salt 1.5%, dimethyldiallylammonium chloride homopolymer 1.3%, and the balance is water.

[0040] Comparative Example 3 The preparation method of the composite chelating plugging removal agent for oil fields described in Comparative Example 3 is the same as that in Example 1. The only difference is that the raw material composition of the composite chelating plugging removal agent for oil fields is different. The composite chelating plugging removal agent for oil fields described in Comparative Example 3 is composed of the following raw materials in mass percentage: 8% of 1-butyl-3-methylimidazolium dodecylsulfonate, 6% of erucic acid amide propyl hydroxypropyl sulfobetaine, 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 hydroxyethyl imidazoline quaternary ammonium salt, 1.3% of dimethyldiallylammonium chloride homopolymer, and the balance is water.

[0041] Weigh the composite chelating plugging removal agents prepared in Examples 1-3 and Comparative Examples 1-3 and mix them evenly with distilled water to obtain an aqueous solution of the composite chelating plugging removal agent for oil fields with a concentration of 10 wt%. Then, add 13.0 g of calcium carbonate / magnesium carbonate / iron hydroxide / aluminum hydroxide to 100 mL of the aqueous solution of the chelating plugging removal agent for oil fields, shake well at 40 °C, then place it in a constant temperature incubator at 40 °C for 24 h. Take out the sample, filter it with medium-speed qualitative filter paper, then dry it at 105 °C, and finally calculate the scale dissolution rate through the mass difference before and after the experiment.

[0042] The test process of the asphalt dissolution rate is as follows: (1) Weigh the N80 steel sheet and record m1, accurate to 0.001 g; (2) Immerse the steel sheet (below the perforated end) evenly in the pre-heated asphalt (10# asphalt), dip about 2 g of asphalt, weigh and record m2, accurate to 0.001 g, for later use; (3) Take 200 mL of the composite chelating plugging removal agent for oil fields and place the asphalt hanging piece in the lower part of the screw-cap bottle; (4) After leaving the screw-cap bottle for the experiment to stand in a 45 °C water bath for 24 hours, take out the hanging piece and record the mass m3 of the taken-out hanging piece, accurate to 0.001 g; (5) Asphalt dissolution rate = (m 3- m2) / (m 2- m1)*100%.

[0043] Organic-inorganic mixed plugging sample: Sampled from a certain oil well in Shengli Oilfield, it is composed of 35.7% crude oil, 6.5% polymer, 32.5% inorganic minerals and 25.3% water. Among them, the content ratio of gum and asphaltene in the crude oil is 26.9%; the polymer is polyacrylamide; the inorganic minerals are composed of 31% calcium carbonate, 19% magnesium carbonate, 33% iron hydroxide and 17% clay minerals.

[0044] Weigh the oilfield composite chelating plugging removers prepared in Examples 1-3 and Comparative Examples 1-3, and mix them evenly with distilled water to obtain an oilfield composite chelating plugging remover aqueous solution with a concentration of 5 wt%. Place the organic-inorganic composite plugging in the oilfield composite chelating plugging remover aqueous solution at 45°C under normal pressure, react for 24 h, and calculate the degradation rate.

[0045] Use a rotary viscometer to measure the viscosity after high-temperature treatment (placed at 75°C for 72 h), and calculate the viscosity retention rate. The higher the viscosity retention rate, the better its high-temperature stability.

[0046] The above test results are shown in Table 1 below.

[0047] Table 1 Scaling removal rate test results of the oilfield composite chelating plugging remover

[0048] As can be seen from Table 1, the oilfield composite chelating plugging removers prepared in Examples 1-3 have good removal rates for inorganic scale, organic scale, and organic-inorganic composite scale, and have high stability. Compared with Example 1, in Comparative Example 1, 1-butyl-3-methylimidazolium dodecylsulfonate and erucic acid amide propyl hydroxypropyl sulfobetaine were omitted from the raw materials, resulting in a significant decrease in the removal rate of organic scale; compared with Comparative Example 1, in Comparative Example 2, 1-butyl-3-methylimidazolium dodecylsulfonate was omitted from the raw materials. Compared with Comparative Example 1, the removal rate of organic scale increased, but it was still far worse than that of Example 1; compared with Example 1, in Comparative Example 3, sodium bis-(2-ethylhexyl) sulfosuccinate and ethylenediamine di-o-hydroxyphenylacetic acid were omitted from 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 that there is a synergistic relationship among the raw materials of the oilfield composite chelating plugging remover described in this application.

Claims

1. A composite chelating plugging removal agent for oil fields, characterized in that: By mass percentage, it is composed of the following raw materials: 7-9% of 1-butyl-3-methylimidazolium dodecylsulfonate, 5-7% of erucic acid amide propyl hydroxypropyl sulfobetaine, 3-4% of bis(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 hydroxyethyl imidazoline quaternary ammonium salt, 1-1.5% of dimethyldiallylammonium chloride homopolymer, and the balance is water.

2. The composite chelating plugging removal agent for oil fields according to claim 1, wherein: By mass percentage, it is composed of the following raw materials: 8% of 1-butyl-3-methylimidazolium dodecylsulfonate, 6% of erucic acid amide propyl hydroxypropyl sulfobetaine, 3.5% of bis(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 hydroxyethyl imidazoline quaternary ammonium salt, 1.3% of dimethyldiallylammonium chloride homopolymer, and the balance is water.

3. A preparation method of the composite chelating plugging removal agent for oil fields according to claim 1, characterized in that: It consists of the following steps: (1) Stir 1-butyl-3-methylimidazolium dodecylsulfonate, erucic acid amide propyl hydroxypropyl sulfobetaine and water evenly to form a homogeneous micelle solution; (2) Add bis(2-ethylhexyl) sulfosuccinate, ethylenediamine di-o-hydroxyphenylacetic acid and N,N'-bis(2-hydroxybenzyl)ethylenediamine-N,N'-diacetic acid to the homogeneous micelle solution prepared in step (1), and stir until completely dissolved; (3) Add O-(3-(benzyloxy)propyl)hydroxylamine, heptadecenyl hydroxyethyl imidazoline quaternary ammonium salt and dimethyldiallylammonium chloride homopolymer to the mixture prepared in step (2), stir and dissolve until a homogeneous system is formed, and prepare a composite chelating plugging removal agent for oil fields.

4. The preparation method of the composite chelating plugging removal agent for oil fields according to claim 3, characterized in that: In step (1), the stirring and mixing temperature is 44-46 °C, and the stirring and mixing time is 30 min.

5. The preparation method of the composite chelating plugging removal agent 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 preparation method of the composite chelating plugging removal agent 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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