Oil and gas well blocking remover and preparation method thereof

Abstract

The invention belongs to the technical field of oil and gas development, and particularly relates to an oil and gas well blocking remover and a preparation method thereof. The blocking remover comprises the following components: 5-8% of low-carbon composite organic acid, 5-7% of fluoboric acid, 6-9% of ammonium bifluoride, 4-6% of an anti-acid sludge mutual solvent, 2-4% of a corrosion inhibitor, 2-4% of polyoxypropylene polyoxyethylene propylene glycol ether, 8-12% of a permeation dispersion surfactant, 2-5% of a sulfur dissolving agent, 2-5% of a stable chlorine dioxide solution and the balance of water. The preparation method comprises the following steps: adding the low-carbon composite organic acid, the fluoboric acid and the ammonium bifluoride into water and stirring; adding an acid sludge resisting mutual solvent and a sulfur dissolving agent, and stirring; adding the corrosion inhibitor, the polyoxypropylene polyoxyethylene propylene glycol ether and the permeation dispersion surfactant, and stirring; and finally, reducing the stirring speed, adding the stable chlorine dioxide solution, and stirring to uniformly mix. The blocking remover provided by the invention is comprehensive in blocking removal function, very good in dissolving and dispersing performance on complex blocking substances, very small in corrosion damage to a shaft pipe wall and wide in applicability.

Description

Technical Field

[0001] This invention belongs to the field of oil and gas development technology, specifically relating to an oil and gas well unblocking agent and its preparation method. Background Technology

[0002] In some oil and gas well production processes, there are problems such as high salinity of produced water and high concentration of scale-forming ions, which leads to severe scaling inside the tubing string. Long-term accumulation of scale makes the space inside the tubing string narrow, which can easily cause wellbore blockage.

[0003] Some oil and gas wells contain corrosive media such as hydrogen sulfide, carbon dioxide, and sulfate-reducing bacteria. During daily production, corrosion inhibitors need to be added for long-term corrosion prevention. The corrosion inhibitors decompose and produce residues, which, together with the corrosion products of the tubing, the produced fluids of the oil and gas wells, and other well-entry agents, cause a complex blockage of organic and inorganic matter in the wellbore.

[0004] Some sulfur-containing gas wells, especially those with high sulfur content, also suffer from blockage problems caused by elemental sulfur deposition.

[0005] Oil sludge produced by some oil and gas wells can also adhere to the wellbore, causing wellbore blockage. In particular, high-viscosity emulsions formed due to incompatibility between external fluids and formation fluids have extremely strong adhesion, making demulsification very difficult.

[0006] Some oil and gas wells also suffer from blockage caused by the migration of formation particles and the accumulation of formation minerals (calcium carbonate, silica, etc.).

[0007] In summary, during the oil and gas extraction process, the blockages in oil and gas wells are not a single substance but a mixture of multiple substances. These include inorganic substances such as scale, formation minerals, and iron compounds, as well as organic substances such as sludge, polymers, and sealing grease, and even elemental sulfur. Moreover, due to different geographical locations and environmental conditions, the causes of blockages are complex, making oil and gas well blockage a widespread problem that is difficult to solve effectively.

[0008] In existing technologies, there are many types of unblocking agents used in oil and gas wells, mainly acid solutions, organic solvents, and surfactants, and the unblocking effect is improved by repeated alternating injections. For example, CN114316934B discloses a low-corrosion polyacrylamide unblocking agent that can be mixed with acid solutions, composed of ammonium persulfate, PBTCA, phosphoric acid, acidizing corrosion inhibitor, fluorocarbon surfactant, petrolatum, Span-80, and water, which degrades the polymer through oxidation. However, existing unblocking agents have the characteristic of single unblocking function, poor solubility and dispersibility for complex blockages, and some unblocking fluids are highly corrosive and easily damage the wellbore wall. Summary of the Invention

[0009] The purpose of this invention is to provide an oil and gas well unblocking agent to solve the problems mentioned in the background art.

[0010] To achieve the above objectives, the present invention provides the following technical solution: This application provides an oil and gas well unblocking agent, comprising the following components by mass percentage: 5-8% of a low-carbon complex organic acid, specifically a mixture of a low-carbon organic acid and a polychelated organic acid, wherein the mass ratio of the low-carbon organic acid to the polychelated organic acid is (10-45):(30-40). Furthermore, the low-carbon organic acid is at least one of formic acid and acetic acid; the polychelated organic acid is one or more of aminotrimethylphosphonic acid, hydroxyethylidene diphosphonic acid, ethylenediaminetetramethylidene phosphonic acid, and aminotrimethylene phosphonic acid.

[0011] Low-carbon composite organic acids exhibit weak corrosivity to tubing and have a dissolving effect on deposits such as calcium carbonate and iron oxides. Using low-carbon composite organic acids avoids the corrosion of the wellbore wall caused by strong acids during the unblocking process while achieving good unblocking results. Simultaneously, low-carbon composite organic acids contain multi-component chelated organic acids, which can form stable water-soluble complexes with metal ions (such as ferric ions and calcium ions) through chelation, preventing metal ions from combining with acid radicals and hydroxide ions to form precipitates (such as ferric hydroxide and calcium sulfate). Furthermore, multi-component chelated organic acids also have certain scale inhibition and corrosion inhibition effects. The low-carbon composite organic acid used in this application dissolves deposits such as calcium carbonate and iron oxides and chelates stable metal ions, ensuring that the blockage remains in a dissolved state.

[0012] The combination of 5-7% fluoroboric acid and 6-9% ammonium bifluoride has a synergistic effect, significantly improving the dissolution capacity of the unblocking agent on siliceous plugging materials in the formation.

[0013] Fluoroboric acid hydrolyzes to produce hydrofluoric acid, which reacts with silicon dioxide to form soluble hexafluorosilicic acid. Hydrofluoric acid can also dissolve iron oxides to form soluble fluoride-iron complexes. Meanwhile, ammonium bifluoride releases fluoride ions under acidic conditions, increasing the fluoride ion concentration and synergistically dissolving silicates and metal oxides. Simultaneously, ammonium bifluoride provides ammonium ions, buffering the pH and preventing localized corrosion caused by the rapid consumption of hydrofluoric acid. Fluoroboric acid and ammonium bifluoride have a synergistic effect as a fluoride source; fluoroboric acid hydrolyzes to produce HF, and ammonium bifluoride provides a buffer of fluoride ions, forming a dynamic fluoride supply system. In existing technologies, due to the extremely corrosive nature of hydrofluoric acid, its use requires stringent conditions and strict control over concentration and dosage, making practical use inconvenient and requiring careful calculations by operators. This application, however, significantly reduces the risk of explosive fluoride ion release by using fluoroboric acid to slowly release hydrofluoric acid, combined with the pH buffering effect of ammonium bifluoride ions. Therefore, fluoroboric acid and ammonium bifluoride together provide fluoride ions, which can efficiently dissolve silicon-based and iron-based deposits, while controlling the reaction rate and reducing corrosion of pumping equipment and tubing.

[0014] The solution contains 4-6% of an acid-resistant slag miscible solvent, which is one or more of ethylene glycol monobutyl ether, ethylene glycol ethyl ether, diethylene glycol monobutyl ether, and triethylene glycol monobutyl ether. As an organic ether liquid, the acid-resistant slag miscible solvent is miscible with sulfur solvents such as toluene, ethylbenzene, and cyclohexene, avoiding the insolubility and stratification problems caused by directly introducing sulfur solvents such as toluene, ethylbenzene, and cyclohexene into the unblocking agent.

[0015] Meanwhile, using an acid-resistant sludge miscible solvent can also avoid the problem of secondary blockage caused by acid sludge during the oil well unblocking process. Its miscibility also enhances the dissolving ability of the unblocking agent for oil-soluble blockages such as sludge and sealing grease. The acid-resistant sludge miscible solvent has high polarity, which can dissolve intermediate products generated by the reaction of acids and minerals (such as colloidal silica), preventing them from agglomerating into sludge. Furthermore, it reduces the adsorption of surfactants at the oil-water interface, making it easier for droplets formed when acidic substances dissolve blockages to coalesce, avoiding emulsification between the oil and water phases. Therefore, it promotes the miscibility of the oil and water phases, preventing the precipitation of organic-inorganic complexes. It maintains the homogeneity of the reaction system and prevents the formation of secondary precipitation.

[0016] 2-4% corrosion inhibitor, specifically one or more of aldehyde-ketone-amine condensate, quinoline quaternary ammonium salt, and propynyl alcohol.

[0017] Corrosion inhibitors significantly reduce the corrosiveness of deblocking agents on the tubing. This application uses aldehyde-ketone-amine condensates, quinoline quaternary ammonium salts, and propargyl alcohol as corrosion inhibitors, which can form a dense adsorption film in acidic environments and preferentially adsorb onto the metal surface rather than the surface of the blockage, thus achieving selective corrosion inhibition.

[0018] 2-4% polyoxypropylene polyoxyethylene propylene glycol ether acts as a demulsifier, exhibiting good demulsification properties for emulsions containing waxes and asphalt, and also has a viscosity-reducing effect.

[0019] Polyoxypropylene polyoxyethylene propylene glycol ether is a block copolymer that combines demulsification (breaking up water-in-oil emulsions) and wetting and penetration functions; it realizes the demulsification and separation of oil sludge and emulsion, which facilitates subsequent dissolution.

[0020] 8-12% of a penetrating and dispersing surfactant, wherein the penetrating and dispersing surfactant is one or more of sodium dioctyl sulfosuccinate, dodecyl alcohol polyoxyethylene polyoxypropylene ether, and sec-octyl alcohol polyoxyethylene ether.

[0021] The combined use of polyoxypropylene polyoxyethylene propylene glycol ether and penetrating dispersing surfactants synergistically enhances the dissolution and dispersion of blockages by unblocking agents on dense blockages. Specifically, the penetrating dispersing surfactants reduce interfacial tension, enhancing the ability of the unblocking agent to penetrate into the interior of the blockage (such as sludge and sealant), and can disperse colloidal particles (such as elemental sulfur and FeS) and inorganic particles (such as calcium carbonate particles) through electrostatic repulsion and steric hindrance, preventing their re-aggregation. The combined use of penetrating dispersing surfactants and demulsifiers can improve the contact efficiency of the unblocking agent on organic-inorganic composite blockages.

[0022] The solution contains 2-5% sulfur solvent, which is one or more of toluene, ethylbenzene, and cyclohexene. This type of sulfur solvent is miscible with acid-resistant sludge, stable in the unblocking agent system, and avoids the problems of acid neutralization, consumption of effective components, and reduced unblocking effect caused by using basic amine sulfur solvents. The non-polar sulfur solvent selected in this application not only dissolves elemental sulfur, but cyclohexene also participates in the oxidation reaction to assist in the decomposition of stubborn organic matter; therefore, it also has a good dissolving effect on long-chain hydrocarbons (oil sludge) and esters (sealing esters).

[0023] A 2-5% stable chlorine dioxide solution, preferably with a mass fraction of 2-6%, is used in this application. The stable chlorine dioxide solution used in this application has strong oxidizing properties, slowly releases chlorine dioxide, and exhibits a mild reaction, enabling it to oxidatively degrade polymers; it can also decompose large molecular organic matter (such as asphaltenes and gums), reducing sludge viscosity; simultaneously, it can oxidize elemental sulfur to soluble sulfate ions, promoting the decomposition of blockages containing multiple components. When used in combination with other components, it can also effectively inhibit sulfate-reducing bacteria, preventing biofilm regeneration and further development of blockages.

[0024] The remainder is water.

[0025] This application also provides a method for preparing an oil and gas well unblocking agent, including the following steps: S1. Add water, low-carbon composite organic acid, fluoroboric acid, and ammonium bifluoride to the reaction vessel and stir to mix them evenly. S2. Add the anti-acid slag solvent and sulfur dissolving agent, and continue stirring to mix them evenly; S3. Add corrosion inhibitor, polyoxypropylene polyoxyethylene propylene glycol ether, and penetrating and dispersing surfactant, and continue stirring to mix evenly. S4. Reduce the stirring speed, add the stable chlorine dioxide solution, and stir to mix it evenly.

[0026] Step S4 requires reducing the stirring speed to 100-200 rpm to maintain the stability of the unblocking agent system and ensure the unblocking effect. If the stirring speed is not reduced, the excessively high speed will cause the added stable chlorine dioxide solution to volatilize chlorine dioxide gas, resulting in waste of the effective ingredients and affecting the effectiveness of the unblocking agent.

[0027] Furthermore, the stirring speed in step S1 is 100-400 rpm, and the stirring speed in step S4 is 100-200 rpm.

[0028] Compared with the prior art, the beneficial effects of this application are: 1. The unblocking agent provided in this application has good dissolving and dispersing ability for inorganic substances such as scale, formation minerals, and iron compounds, as well as organic substances such as sludge, polymers, and sealant grease, and elemental sulfur blockages and their mixtures, which solves the problems of narrow applicability and general unblocking effect of the unblocking agent in the prior art. 2. The unblocking agent provided in this application has very low corrosivity to tubing. Under conditions of 25-150℃, the corrosion rate of N80 carbon steel is 6.0-36.0 g / (㎡·h). 3. The unblocking agent provided in this application does not produce secondary precipitation of iron and calcium after dissolving and dispersing the blockage, and will not cause secondary damage to the formation or secondary blockage of the wellbore. 4. The unblocking agent provided in this application has a wide applicable temperature range, and is suitable for oil and gas well blockages from room temperature to high temperature of 150℃, which is very convenient for actual industrial application. 5. The preparation method of the unblocking agent provided in this application is simple and easy to operate, with low requirements for equipment and facilities, making production more convenient. It can be made directly on-site when needed, and has greater application value. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with embodiments. The illustrative embodiments and descriptions of this application are for explanation only and are not intended to limit the scope of this application. Any product identical or similar to this application, derived by any person based on the teachings of this application or by combining features of this application with other prior art, falls within the protection scope of this application.

[0030] For any experimental steps or conditions not specified in the examples, the procedures or conditions described in the conventional experimental procedures in the art can be followed. Reagents and other instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0031] This application provides an oil and gas well unblocking agent, comprising the following components by mass percentage: 5-8% of a low-carbon complex organic acid, specifically a mixture of a low-carbon organic acid and a polychelated organic acid, wherein the mass ratio of the low-carbon organic acid to the polychelated organic acid is (10-45):(30-40). Furthermore, the low-carbon organic acid is at least one of formic acid and acetic acid; the polychelated organic acid is one or more of aminotrimethylphosphonic acid, hydroxyethylidene diphosphonic acid, ethylenediaminetetramethylidene phosphonic acid, and aminotrimethylene phosphonic acid.

[0032] The combination of 5-7% fluoroboric acid and 6-9% ammonium bifluoride significantly enhances the dissolution capacity of the unblocking agent against siliceous plugging materials in the formation.

[0033] The solution contains 4-6% of an acid-resistant slag miscible solvent, which is one or more of ethylene glycol monobutyl ether, ethylene glycol ethyl ether, diethylene glycol monobutyl ether, and triethylene glycol monobutyl ether. As an organic ether liquid, the acid-resistant slag miscible solvent is miscible with sulfur solvents such as toluene, ethylbenzene, and cyclohexene, avoiding the insolubility and stratification problems caused by directly introducing sulfur solvents such as toluene, ethylbenzene, and cyclohexene into the unblocking agent.

[0034] 2-4% corrosion inhibitor, specifically one or more of aldehyde-ketone-amine condensate, quinoline quaternary ammonium salt, and propynyl alcohol.

[0035] 2-4% polyoxypropylene polyoxyethylene propylene glycol ether acts as a demulsifier, exhibiting good demulsification properties for emulsions containing waxes and asphalt, and also has a viscosity-reducing effect.

[0036] 8-12% of a penetrating and dispersing surfactant, wherein the penetrating and dispersing surfactant is one or more of sodium dioctyl sulfosuccinate, dodecyl alcohol polyoxyethylene polyoxypropylene ether, and sec-octyl alcohol polyoxyethylene ether.

[0037] 2-5% of a sulfur solvent, which is at least one of toluene, ethylbenzene and cyclohexene. This type of sulfur solvent is miscible with acid-resistant slag, has stable properties in the unblocking agent system, and avoids the problems of neutralization with acid, consumption of effective components and reduced unblocking effect caused by using basic amine sulfur solvents.

[0038] A 2-5% stable chlorine dioxide solution, preferably with a mass fraction of 2-6%.

[0039] The remainder is water.

[0040] This application also provides a method for preparing an oil and gas well unblocking agent, including the following steps: S1. Add measured water to the reaction vessel and stir at a constant speed. Then add measured amounts of low-carbon composite organic acid, fluoroboric acid, and ammonium hydrogen fluoride. Stir to mix thoroughly and evenly to form a uniform mixture. The preferred stirring speed is 100-400 rpm, and the preferred stirring time is 30-40 min.

[0041] S2. Add the measured amount of anti-acid slag solvent and sulfur dissolving agent, and continue stirring to ensure thorough and uniform mixing; the stirring time is preferably 40-50 minutes.

[0042] S3. Add the measured amount of corrosion inhibitor, polyoxypropylene polyoxyethylene propylene glycol ether, and penetrating dispersant surfactant, and continue stirring to ensure thorough and uniform mixing; the stirring time is preferably 30-60 minutes.

[0043] S4. Reduce the stirring speed to 100-200 rpm, add the measured amount of stable chlorine dioxide solution, and stir thoroughly to make it evenly mixed; then stop stirring to obtain the oil and gas well unblocking agent; the stirring time is preferably 10-30 min.

[0044] The technical solution of this application will be further described below with reference to embodiments and comparative examples.

[0045] Example 1: The oil and gas well unblocking agent provided in Example 1 comprises the following components by mass percentage: 1% formic acid, 4% aminotrimethylphosphonic acid, 5% fluoroboric acid, 6% ammonium bifluoride, 4% ethylene glycol monobutyl ether, 2% ketone aldehyde amine condensate corrosion inhibitor, 2% polyoxypropylene polyoxyethylene propylene glycol ether, 8% sodium dioctyl sulfonate succinate, 2% toluene, 2% stable chlorine dioxide solution with a mass fraction of 2%, and the balance being water.

[0046] This oil and gas well unblocking agent is prepared by the following method: S1. Add 64 kg of water to the reactor. Under stirring at 100 rpm, add 1 kg of formic acid, 4 kg of aminotrimethylphosphonic acid, 5 kg of fluoroboric acid, and 6 kg of ammonium bifluoride. Stir for 30 minutes to mix thoroughly. S2. Add 4 kg of ethylene glycol monobutyl ether and 2 kg of toluene, and continue stirring for 40 minutes to ensure thorough mixing. S3. Add 2 kg of ketone aldehyde amine condensate corrosion inhibitor, 2 kg of polyoxypropylene polyoxyethylene propylene glycol ether, and 8 kg of sodium dioctyl sulfonate succinate, and continue stirring for 30 minutes to ensure thorough mixing. S4. Add 2 kg of 2% stable chlorine dioxide solution and continue stirring for 10 minutes to mix evenly. Stop stirring to obtain the oil and gas well unblocking agent.

[0047] Example 2: The oil and gas well unblocking agent provided in Example 2 comprises the following components by mass percentage: 1% acetic acid, 4% hydroxyethylidene diphosphonic acid, 5% fluoroboric acid, 6% ammonium bifluoride, 4% ethylene glycol ethyl ether, 2% quinoline quaternary ammonium salt, 2% polyoxypropylene polyoxyethylene propylene glycol ether, 8% dodecyl alcohol polyoxyethylene polyoxypropylene ether, 2% ethylbenzene, 2% 4% stable chlorine dioxide solution by mass, and the balance being water.

[0048] This oil and gas well unblocking agent is prepared by the following method: S1. Add 64 kg of water to the reactor. Under stirring at 200 rpm, add 1 kg of acetic acid, 4 kg of hydroxyethylidene diphosphonic acid, 5 kg of fluoroboric acid, and 6 kg of ammonium bifluoride. Stir for 35 min to ensure thorough mixing. S2. Add 4 kg of ethylene glycol ethyl ether and 2 kg of ethylbenzene, and continue stirring for 45 minutes to ensure thorough mixing. S3. Add 2 kg of quinoline quaternary ammonium salt, 2 kg of polyoxypropylene polyoxyethylene propylene glycol ether, and 8 kg of dodecyl alcohol polyoxyethylene polyoxypropylene ether, and continue stirring for 40 minutes to ensure thorough and uniform mixing. S4. Reduce the rotation speed to 150 rpm, add 2 kg of 4% stable chlorine dioxide solution, stir for 20 minutes to mix thoroughly, and then stop stirring to obtain the oil and gas well unblocking agent.

[0049] Example 3: The oil and gas well unblocking agent provided in Example 3 comprises the following components by mass percentage: 3% formic acid, 3% ethylenediaminetetramethylenephosphonic acid, 6% fluoroboric acid, 7% ammonium bifluoride, 5% diethylene glycol monobutyl ether, 3% propargyl alcohol, 3% polyoxypropylene polyoxyethylene propylene glycol ether, 10% sec-octyl alcohol polyoxyethylene ether, 3% cyclohexene, 3% 4% stable chlorine dioxide solution by mass, and the balance being water.

[0050] This oil and gas well unblocking agent is prepared by the following method: S1. Add 54 kg of water to the reactor. Under stirring at 300 rpm, add 3 kg of formic acid, 3 kg of ethylenediaminetetramethylenephosphonic acid, 6 kg of fluoroboric acid, and 7 kg of ammonium bifluoride. Stir for 40 minutes to ensure thorough mixing. S2. Add 5 kg of diethylene glycol monobutyl ether and 3 kg of cyclohexene, and continue stirring for 50 minutes to ensure thorough mixing. S3. Add 3 kg of propargyl alcohol, 3 kg of polyoxypropylene polyoxyethylene propylene glycol ether, and 10 kg of 2-octyl alcohol polyoxyethylene ether, and continue stirring for 60 minutes to ensure thorough mixing. S4. Reduce the rotation speed to 200 rpm, add 3 kg of 4% stable chlorine dioxide solution, stir for 30 minutes to mix thoroughly, and then stop stirring to obtain the oil and gas well unblocking agent.

[0051] Example 4: The oil and gas well unblocking agent provided in Example 4 comprises the following components by mass percentage: 2% formic acid, 2% acetic acid, 2% aminotrimethylene phosphonic acid, 2% hydroxyethylidene diphosphonic acid, 7% fluoroboric acid, 9% ammonium bifluoride, 3% diethylene glycol monobutyl ether, 3% triethylene glycol monobutyl ether, 2% ketone-aldehyde-amine condensate corrosion inhibitor, 2% propargyl alcohol, 4% polyoxypropylene-polyoxyethylene propylene glycol ether, 6% sodium dioctyl sulfonate succinate, 6% sec-octyl alcohol polyoxyethylene ether, 2.5% toluene, 2.5% ethylbenzene, 5% 3% stable chlorine dioxide solution, and the balance being water.

[0052] This oil and gas well unblocking agent is prepared by the following method: S1. Add 40 kg of water to the reactor. Under stirring at 400 rpm, add 2 kg of formic acid, 2 kg of acetic acid, 2 kg of aminotrimethylene phosphonic acid, 2 kg of hydroxyethylidene diphosphonic acid, 7 kg of fluoroboric acid, and 9 kg of ammonium bifluoride. Stir for 35 min to ensure thorough mixing. S2. Add 3 kg of diethylene glycol monobutyl ether, 3 kg of triethylene glycol monobutyl ether, 2.5 kg of toluene, and 2.5 kg of ethylbenzene, and continue stirring for 45 minutes to ensure thorough mixing. S3. Add 2 kg of ketone aldehyde amine condensate corrosion inhibitor, 2 kg of propargyl alcohol, 4 kg of polyoxypropylene polyoxyethylene propylene glycol ether, 6 kg of sodium dioctyl sulfonate succinate, and 6 kg of sec-octyl alcohol polyoxyethylene ether, and continue stirring for 50 minutes to ensure thorough mixing. S4. Reduce the rotation speed to 150 rpm, add 5 kg of 3% stable chlorine dioxide solution, stir for 29 minutes to mix thoroughly, and then stop stirring to obtain the oil and gas well unblocking agent.

[0053] Example 5: The oil and gas well unblocking agent provided in Example 5 comprises the following components by mass percentage: 4.5% formic acid, 3% hydroxyethylidene diphosphonic acid, 6% fluoroboric acid, 8% ammonium bifluoride, 3% ethylene glycol monobutyl ether, 2% diethylene glycol monobutyl ether, 2% quinoline quaternary ammonium salt, 2% propargyl alcohol, 3.5% polyoxypropylene polyoxyethylene propylene glycol ether, 3% sodium dioctyl sulfonate succinate, 3% dodecyl alcohol polyoxyethylene polyoxypropylene ether, 4% sec-octyl alcohol polyoxyethylene ether, 2% toluene, 2% cyclohexene, 5% 2% stable chlorine dioxide solution by mass, and the balance being water.

[0054] This oil and gas well unblocking agent is prepared by the following method: S1. Add 47 kg of water to the reactor. Under stirring at 250 rpm, add 4.5 kg of formic acid, 3 kg of hydroxyethylidene diphosphonic acid, 6 kg of fluoroboric acid, and 8 kg of ammonium bifluoride. Stir for 35 minutes to ensure thorough mixing. S2. Add 3 kg of ethylene glycol monobutyl ether, 2 kg of diethylene glycol monobutyl ether, 2 kg of toluene, and 2 kg of cyclohexene, and continue stirring for 40 minutes to ensure thorough mixing. S3. Reduce the rotation speed to 150 rpm, add 2 kg of quinoline quaternary ammonium salt, 2 kg of propargyl alcohol, 3.5 kg of polyoxypropylene polyoxyethylene propylene glycol ether, 3 kg of sodium dioctyl sulfonate succinate, 3 kg of dodecyl alcohol polyoxyethylene polyoxypropylene ether, and 4 kg of sec-octyl alcohol polyoxyethylene ether, and stir for 40 minutes to make it fully mixed. S4. Add 5 kg of 2% stable chlorine dioxide solution and continue stirring for 15 minutes to ensure thorough mixing. Stop stirring to obtain the oil and gas well unblocking agent.

[0055] Example 6: The oil and gas well unblocking agent provided in Example 6 comprises the following components by mass percentage: 2% formic acid, 2% acetic acid, 1% aminotrimethylphosphonic acid, 1% hydroxyethylidene diphosphonic acid, 1% ethylenediaminetetramethylphosphonic acid, 6% fluoroboric acid, 7.5% ammonium bifluoride, 1% ethylene glycol monobutyl ether, 1% ethylene glycol ethyl ether, 1.5% diethylene glycol monobutyl ether, 1.5% triethylene glycol monobutyl ether, and 1%... The composition consists of a ketone-aldehyde-amine condensate corrosion inhibitor, 1% quinoline quaternary ammonium salt, 1.5% propargyl alcohol, 3.5% polyoxypropylene polyoxyethylene propylene glycol ether, 3% sodium dioctyl sulfonate succinate, 3% dodecyl alcohol polyoxyethylene polyoxypropylene ether, 3% sec-octyl alcohol polyoxyethylene ether, 1% toluene, 1% ethylbenzene, 1.5% cyclohexene, 3.5% 6% stable chlorine dioxide solution, and the balance being water.

[0056] This oil and gas well unblocking agent is prepared by the following method: S1. Add 51.5 kg of water to the reactor. Under stirring at 200 rpm, add 2 kg of formic acid, 2 kg of acetic acid, 1 kg of aminotrimethylphosphonic acid, 1 kg of hydroxyethylidene diphosphonic acid, 1 kg of ethylenediaminetetramethylphosphonic acid, 6 kg of fluoroboric acid, and 7.5 kg of ammonium bifluoride. Stir for 30 minutes to ensure thorough mixing. S2. Add 1 kg of ethylene glycol monobutyl ether, 1 kg of ethylene glycol ethyl ether, 1.5 kg of diethylene glycol monobutyl ether, 1.5 kg of triethylene glycol monobutyl ether, 1 kg of toluene, 1 kg of ethylbenzene, and 1.5 kg of cyclohexene, and continue stirring for 40 minutes to ensure thorough mixing. S3. Add 1 kg of ketone aldehyde amine condensate corrosion inhibitor, 1 kg of quinoline quaternary ammonium salt, 1.5 kg of propargyl alcohol, 3.5 kg of polyoxypropylene polyoxyethylene propylene glycol ether, 3 kg of sodium dioctyl sulfonate succinate, 3 kg of dodecyl alcohol polyoxyethylene polyoxypropylene ether, and 3 kg of sec-octyl alcohol polyoxyethylene ether, and continue stirring for 40 minutes to ensure thorough mixing. S4. Reduce the rotation speed to 100 rpm, add 3.5 kg of 6% stable chlorine dioxide solution, stir for 15 minutes to mix thoroughly, and then stop stirring to obtain the oil and gas well unblocking agent.

[0057] Comparative Example 1: An oil and gas well unblocking agent was prepared according to the method, raw materials, and dosage of Example 1, except that hydrofluoric acid with a mass concentration of 50% was used to replace fluoroboric acid and ammonium bifluoride to obtain the product.

[0058] That is, the oil and gas well unblocking agent in Comparative Example 1 includes the following components by mass percentage: 1% formic acid, 4% aminotrimethylphosphonic acid, 11% hydrofluoric acid with a mass concentration of 50%, 4% ethylene glycol monobutyl ether, 2% ketone aldehyde amine condensate corrosion inhibitor, 2% polyoxypropylene polyoxyethylene propylene glycol ether, 8% sodium dioctyl sulfonate succinate, 2% toluene, 2% stable chlorine dioxide solution with a mass fraction of 2%, and the balance being water.

[0059] Comparative Example 2: Except for the absence of dodecyl alcohol polyoxyethylene polyoxypropylene ether, an oil and gas well unblocking agent was prepared according to the method, raw materials and dosage of Example 2 to obtain the product.

[0060] That is, the oil and gas well unblocking agent in Comparative Example 2 includes the following components by mass percentage: 1% acetic acid, 4% hydroxyethylidene diphosphonic acid, 5% fluoroboric acid, 6% ammonium bifluoride, 4% ethylene glycol ethyl ether, 2% quinoline quaternary ammonium salt, 2% polyoxypropylene polyoxyethylene propylene glycol ether, 2% ethylbenzene, 2% stable chlorine dioxide solution with a mass fraction of 4%, and the balance being water.

[0061] Comparative Example 3: The oil and gas well unblocking agent was prepared according to the method, raw materials, and dosage of Example 3, except that a 40% ammonium persulfate solution was used to replace the stable chlorine dioxide solution to obtain the product.

[0062] That is, the oil and gas well unblocking agent in Comparative Example 3 includes the following components by mass percentage: 3% formic acid, 3% ethylenediaminetetramethylenephosphonic acid, 6% fluoroboric acid, 7% ammonium bifluoride, 5% diethylene glycol monobutyl ether, 3% propargyl alcohol, 3% polyoxypropylene polyoxyethylene propylene glycol ether, 10% 2-octyl alcohol polyoxyethylene ether, 3% cyclohexene, 3% ammonium persulfate solution with a mass concentration of 40%, and the balance being water.

[0063] Comparative Example 4: The oil and gas well unblocking agent was prepared according to the method, raw materials and dosage of Example 4, except that diphenylmethane diamine was used to replace toluene and ethylbenzene to obtain the product.

[0064] That is, the oil and gas well unblocking agent in Comparative Example 4 includes the following components by mass percentage: 2% formic acid, 2% acetic acid, 2% aminotrimethylene phosphonic acid, 2% hydroxyethylidene diphosphonic acid, 7% fluoroboric acid, 9% ammonium bifluoride, 3% diethylene glycol monobutyl ether, 3% triethylene glycol monobutyl ether, 2% ketone aldehyde amine condensate corrosion inhibitor, 2% propargyl alcohol, 4% polyoxypropylene polyoxyethylene propylene glycol ether, 6% sodium dioctyl sulfonate succinate, 6% sec-octyl alcohol polyoxyethylene ether, 5% diphenylmethane diamine, 5% 3% stable chlorine dioxide solution by mass, and the balance being water.

[0065] Comparative Example 5: An oil and gas well unblocking agent was prepared according to the method, raw materials, and dosage of Example 5, except that industrial hydrochloric acid with a mass concentration of 31% was used to replace formic acid and hydroxyethylidene diphosphonic acid to obtain the product.

[0066] That is, the oil and gas well unblocking agent in Comparative Example 5 comprises the following components by mass percentage: 7.5% industrial hydrochloric acid with a mass concentration of 31%, 6% fluoroboric acid, 8% ammonium bifluoride, 3% ethylene glycol monobutyl ether, 2% diethylene glycol monobutyl ether, 2% quinoline quaternary ammonium salt, 2% propargyl alcohol, 3.5% polyoxypropylene polyoxyethylene propylene glycol ether, 3% sodium dioctyl sulfonate succinate, 3% dodecyl alcohol polyoxyethylene polyoxypropylene ether, 4% sec-octyl alcohol polyoxyethylene ether, 2% toluene, 2% cyclohexene, 5% stable chlorine dioxide solution with a mass fraction of 2%, and the balance being water.

[0067] Comparative Example 6: The oil and gas well unblocking agent was prepared according to the method, raw materials, and dosage of Example 6, except that ethylene glycol monobutyl ether, ethylene glycol ethyl ether, diethylene glycol monobutyl ether, and triethylene glycol monobutyl ether in the formulation of Example 6 were all replaced with alkylbenzene sulfonic acid to obtain the product.

[0068] That is, the oil and gas well unblocking agent in Comparative Example 6 includes the following components by mass percentage: 2% formic acid, 2% acetic acid, 1% aminotrimethylphosphonic acid, 1% hydroxyethylidene diphosphonic acid, 1% ethylenediaminetetramethylidene phosphonic acid, 6% fluoroboric acid, 7.5% ammonium hydrogen fluoride, 5% alkylbenzene sulfonic acid, 1% ketone aldehyde amine condensate corrosion inhibitor, 1% quinoline quaternary ammonium salt, 1.5% propargyl alcohol, 3.5% polyoxypropylene polyoxyethylene propylene glycol ether, 3% sodium dioctyl sulfonate succinate, 3% dodecyl alcohol polyoxyethylene polyoxypropylene ether, 3% sec-octyl alcohol polyoxyethylene ether, 1% toluene, 1% ethylbenzene, 1.5% cyclohexene, 3.5% stable chlorine dioxide solution with a mass fraction of 6%, and the balance being water.

[0069] The performance of the oil and gas well unblocking agents obtained in Examples 1-6 and Comparative Examples 1-6 will be tested below.

[0070] Test index 1, dissolution and dispersion ability: Dissolution and dispersion ability is a core indicator for evaluating unblocking agents, reflecting their ability to dissolve and disperse blockages. Before testing, several identical, clean, and dry beakers and eight different blockage samples were prepared. The unblocking agent provided in this application was used to conduct the dissolution and dispersion ability test.

[0071] The eight types of blockage samples were: marble, block sulfur, sealant, oil-based mud, rust, ferrous sulfide, silica particles, and on-site blockage (which, after testing, included rock fragments, carbonate scale, organic polymers, iron corrosion products, sludge, sealant, elemental sulfur, etc.).

[0072] The specific testing method is as follows: First, weigh the dry beakers separately and record the mass as m0; then place the blockage in the beaker and weigh it together with the beaker, and record the mass as m1; then the mass of the blockage is m1-m0; then add 80 times the amount of unblocking agent to the beaker.

[0073] Unblocking ability tests were conducted at different temperatures. Specifically, when the test temperature was ≤95℃, the beaker mouth was sealed with a beaker sealing film, and then placed in an oven for dissolution and dispersion. When the test temperature was >95℃, all the blockage material and unblocking agent in the beaker were poured into a high-temperature aging tank lined with polytetrafluoroethylene, sealed, and then placed in an oven for dissolution and dispersion. All samples were dissolved for 4 hours, i.e., the blockage material was dissolved and dispersed in the unblocking agent for 4 hours. Then, the mixture in the beaker or high-temperature aging tank was poured out and filtered through a 20-mesh sieve. The residue in the beaker or aging tank was also rinsed with water and filtered through a 20-mesh sieve to obtain all the residue. All the residue was transferred to another dry beaker (this beaker was pre-dried and weighed, and its mass was recorded as m2). Then, the beaker containing the residue was placed open in a drying oven at 25℃ and allowed to dry for 12 hours. The beaker and the residue were weighed together, and the mass was recorded as m. 3， The mass of the residue after drying is m3-m2.

[0074] Dissolution and dispersion rate = [(m1-m0)-(m3-m2)] / (m1-m0)×100%. After experimental verification, the dissolution and dispersion rates of the oil and gas well unblocking agents obtained in Examples 1-6 and Comparative Examples 1-6 are shown in the table below.

[0075] Table 1 shows the dissolution and dispersion rates (%) of the oil and gas well unblocking agents obtained in Examples 1-6 and Comparative Examples 2-4 and 6 at 70℃. marble Block sulfur Sealing grease Oil-based mud rust Ferrous sulfide Silica particles On-site blockage Example 1 100 83.1 93.0 94.2 100 100 96.0 90.6 Example 2 100 84.1 93.4 94.1 100 100 96.3 91.0 Comparative Example 2 96.5 74.0 72.8 72.1 95.8 94.7 91.2 70.3 Example 3 100 85.2 94.2 94.3 97.5 100 96.3 92.7 Comparative Example 3 100 82.6 83.7 82.1 96.6 100 95.8 81.3 Example 4 100 86.3 94.3 94.5 100 100 96.4 92.9 Comparative Example 4 53.1 13.2 67.8 64.5 47.8 37.2 22.1 60.0 Example 5 100 85.5 94.2 94.4 100 100 96.3 92.8 Example 6 100 85.3 94.2 94.4 100 100 96.3 92.8 Comparative Example 6 100 84.8 86.0 84.9 100 100 95.8 85.3 As shown in Table 1, Examples 1-6 exhibited high dissolution and dispersion rates for all eight types of blockages, with some blockages achieving 100% dissolution and dispersion. Particularly for stubborn on-site blockages containing multiple components, the unblocking agents provided in Examples 1-6 achieved dissolution and dispersion rates of 90-93%, demonstrating excellent unblocking effects. Among the unblocking agents provided in the six examples, the unblocking agent provided in Example 4 showed the best dissolution and dispersion effect. These data demonstrate that the unblocking agent of this application possesses stable and excellent unblocking effects.

[0076] A comparison of the data from Comparative Example 2 and Example 2 shows that the unblocking agent provided in Comparative Example 2 has a generally poor unblocking effect on organic materials or polymers such as sealant grease, oil-based mud, and sludge, as well as on-site blockages including sealant grease, oil-based mud, and sludge, with a reduction in dissolution and dispersion rate of more than 20%. Because the dodecyl alcohol polyoxyethylene polyoxypropylene ether in Example 2 has a better dissolution and dispersion effect on dense blockages, and the unblocking agent in Comparative Example 2 does not include this component, the unblocking effect is significantly reduced. Comparative Example 3 replaced the stable chlorine dioxide solution with ammonium persulfate solution, which resulted in poorer degradation of organic materials and polymers, leading to a reduction in the dissolution and dispersion rate of blockages containing organic materials and polymers (such as sealant grease, oil-based mud, and on-site blockages) of more than 10%. However, for blockages without organic materials or polymers, the effect on the dissolution and dispersion rate was relatively small.

[0077] In Comparative Example 4, toluene and ethylbenzene used in Example 4 were completely replaced with diphenylmethane diamine. Diphenylmethane diamine, as a polyamine-based sulfur solvent, causes an acid-base neutralization reaction between the acidic components (low-carbon complex organic acids, fluoroboric acid) in the unblocking agent and alkaline substances like diphenylmethane diamine, resulting in partial consumption of the effective components and a significant decrease in dissolution and dispersion rates. In Example 6, ethylene glycol monobutyl ether, ethylene glycol ethyl ether, diethylene glycol monobutyl ether, and triethylene glycol monobutyl ether not only have anti-acid slag properties but are also miscible solvents. They reduce the adsorption of surfactants at the oil-water interface, making it easier for droplets formed when acidic substances dissolve blockages to coalesce, preventing oil-water emulsification and resulting in better unblocking effects. However, in Comparative Example 6, these components were completely replaced with alkylbenzene sulfonic acid. Alkylbenzene sulfonic acid does not have miscible solvent properties, thus reducing the dissolution and dispersion rates of blockages containing oil or organic matter, such as sealing grease, oil-based mud, and on-site blockages.

[0078] Table 2 shows the dissolution and dispersion rates (%) of the oil and gas well unblocking agents obtained in Examples 1-6 at 110℃. marble Block sulfur Sealing grease Oil-based mud rust Ferrous sulfide Silica particles On-site blockage Example 1 97.5 83.5 93.3 94.4 100 100 96.2 91.0 Example 2 100 84.4 93.7 94.5 100 100 96.4 91.5 Example 3 100 85.4 94.5 94.5 100 100 96.4 93.4 Example 4 100 86.6 94.7 95.0 100 100 96.4 93.2 Example 5 100 86.5 94.5 94.7 100 100 96.3 93.1 Example 6 100 85.5 94.6 94.6 100 100 96.4 93.4 As can be seen from the above data, the unblocking agents provided in Examples 1-6 still exhibit excellent unblocking capabilities at 110℃.

[0079] Table 3 shows the dissolution and dispersion rates (%) of the oil and gas well unblocking agents obtained in Examples 1-6 at 150℃. marble Block sulfur Sealing grease Oil-based mud rust Ferrous sulfide Silica particles On-site blockage Example 1 100 83.7 93.4 94.4 100 100 96.4 91.1 Example 2 100 84.6 93.7 94.6 100 100 96.4 91.6 Example 3 100 85.5 94.6 94.5 100 100 96.5 93.4 Example 4 100 86.8 94.8 95.0 100 100 96.5 93.4 Example 5 100 86.7 94.6 94.9 100 100 96.4 93.4 Example 6 100 85.8 94.8 94.8 100 100 96.4 93.7 As shown in Table 3, the unblocking agents provided in Examples 1-6 still exhibit excellent unblocking capabilities at 150℃. Furthermore, a comprehensive comparison of the data in Tables 1-3 shows that the unblocking agents provided in Examples 1-6 of this application all possess excellent dissolution and dispersion rates at different temperatures. This information proves that the unblocking agents provided in this application have stable unblocking performance and can meet the unblocking needs of oil and gas wells in various environments and situations.

[0080] Test index 2, corrosion rate: The static corrosion rate of N80 carbon steel under normal pressure at different temperatures was tested according to the method specified in SY / T 5886-2018. The corrosion rate is expressed in g / (m²·h), and the test results are shown in Table 4 below.

[0081] 25℃ 50℃ 75℃ 90℃ 120℃ 150℃ Example 1 6.0 9.3 11.2 18.5 26.2 34.8 Comparative Example 1 32.7 51.3 66.5 95.3 139.6 198.1 Example 2 6.1 9.2 11.4 18.7 26.5 34.6 Example 3 7.3 9.9 13.1 19.8 27.3 35.3 Example 4 6.6 9.6 11.8 18.9 27.0 35.8 Example 5 6.4 9.0 10.9 17.9 25.8 36.0 Comparative Example 5 13.2 19.8 23.6 38.8 61.5 83.5 Example 6 6.6 9.8 11.3 19.0 27.4 35.0

[0082] As shown in Table 4, at different temperatures ranging from 25 to 150°C, the corrosion rate of the unblocking agents provided in Examples 1-6 of this application increases with increasing temperature. This is logical; as temperature increases, molecular activity becomes more intense, and the active molecules of the unblocking agent come into contact with the N80 carbon steel molecules more frequently, thus macroscopically exhibiting a characteristic of accelerated corrosion with increasing temperature. However, from the actual numerical values ​​of the corrosion rate, the corrosion rates of the unblocking agents provided in Examples 1-6 are all relatively low, resulting in less corrosion damage to the wellbore wall.

[0083] Furthermore, the corrosion rate of Comparative Example 1 was significantly higher than that of Example 1. This is because Comparative Example 1 replaced all the pure fluoroboric acid and pure ammonium bifluoride in Example 1 with 50% hydrofluoric acid, resulting in a substantial decrease in concentration but a significant increase in corrosion rate. Hydrofluoric acid has a greater corrosive effect on carbon steel and cannot meet the low-corrosion requirements on site. Therefore, the combination of fluoroboric acid and ammonium bifluoride selected in this application achieves good unblocking effects while reducing corrosion damage, demonstrating its superiority. Meanwhile, Comparative Example 5, which replaced all the pure formic acid and hydroxyethylidene diphosphonic acid in Example 5 with 31% industrial hydrochloric acid, also exhibited the characteristic of faster corrosion despite using a lower concentration of acid, proving the superiority of formic acid and hydroxyethylidene diphosphonic acid selected in this application.

[0084] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. An oil and gas well unblocking agent, characterized in that, It includes the following components by weight percentage: 5-8% low-carbon complex organic acid, 5-7% fluoroboric acid, 6-9% ammonium bifluoride, 4-6% anti-acid slag mutual solvent, 2-4% corrosion inhibitor, 2-4% polyoxypropylene polyoxyethylene propylene glycol ether, 8-12% penetrating and dispersing surfactant, 2-5% sulfur solvent, 2-5% stable chlorine dioxide solution, and the balance being water.

2. The oil and gas well unblocking agent according to claim 1, characterized in that, The low-carbon composite organic acid is a mixture of low-carbon organic acid and polychelated organic acid, and the mass ratio of the low-carbon organic acid to the polychelated organic acid is (10-45):(30-40).

3. The oil and gas well unblocking agent according to claim 2, characterized in that, The low-carbon organic acid is at least one of formic acid and acetic acid, and the polycyclic chelated organic acid is one or more of aminotrimethylphosphonic acid, hydroxyethylidene diphosphonic acid, ethylenediaminetetramethylidene phosphonic acid, and aminotrimethylene phosphonic acid.

4. The oil and gas well unblocking agent according to claim 1, characterized in that, The anti-acid slag mutual solvent is one or more of ethylene glycol monobutyl ether, ethylene glycol ethyl ether, diethylene glycol monobutyl ether, and triethylene glycol monobutyl ether.

5. The oil and gas well unblocking agent according to claim 1, characterized in that, The corrosion inhibitor is one or more of the following: aldehyde-ketone-amine condensate, quinoline quaternary ammonium salt, and propynyl alcohol.

6. The oil and gas well unblocking agent according to claim 1, characterized in that, The penetrating and dispersing surfactant is one or more of sodium dioctyl sulfonate, dodecyl alcohol polyoxyethylene polyoxypropylene ether, and sec-octyl alcohol polyoxyethylene ether.

7. The oil and gas well unblocking agent according to claim 1, characterized in that, The sulfur solvent is one or more of toluene, ethylbenzene, and cyclohexene.

8. The oil and gas well unblocking agent according to claim 1, characterized in that, The mass fraction of the stable chlorine dioxide solution is 2-6%.

9. The method for preparing the oil and gas well unblocking agent according to claim 1, characterized in that, Includes the following steps: S1. Add water, low-carbon composite organic acid, fluoroboric acid, and ammonium bifluoride to the reaction vessel and stir to mix them evenly. S2. Add the anti-acid slag solvent and sulfur dissolving agent, and continue stirring to mix them evenly; S3. Add corrosion inhibitor, polyoxypropylene polyoxyethylene propylene glycol ether, and penetrating and dispersing surfactant, and continue stirring to mix evenly. S4. Reduce the stirring speed, add the stable chlorine dioxide solution, and stir to mix it evenly.

10. The preparation method according to claim 9, characterized in that, The stirring speed in step S1 is 100-400 rpm, and the stirring speed in step S4 is 100-200 rpm.