A blockage unblocking agent, its preparation method and application

Abstract

This invention relates to the field of oilfield chemistry, specifically to a plugging agent, its preparation method, and its application. The plugging agent comprises the following components by weight percentage: 10-25% amide compound, 15-25% ester compound, 5-50% co-solvent, 5-50% shale inhibitor, and 5-50% drainage aid. A method for preparing the plugging agent involves the optimized synthesis of conventional amides and small-molecule esters, introducing hydroxyl groups and hydrogen-bonding groups to maintain good permeability, dissolution and dispersion capabilities against plugging materials, improve water solubility, and further enhance operational safety by lowering the flash point. The plugging agent system not only has a flash point above 90℃, ensuring safety during use in natural gas wells, but also maintains stable performance in high-temperature environments up to 150℃ at the bottom of the well, meeting the stringent conditions of deep shale gas extraction and providing strong support for the development of deep oil and gas resources.

Description

Technical Field

[0001] This invention relates to the field of oilfield chemistry, and more specifically, to a deblocking agent, its preparation method, and its application. Background Technology

[0002] The bottom-hole temperature of deep shale gas wells generally exceeds 135℃, posing challenges to the temperature resistance and reliability of injected chemicals. Currently widely used room-temperature chemicals are unsuitable for the needs of deep shale gas development. Deep shale gas production is characterized by "high flowback, short stable production period, and rapid decline," with over 70% of the final recoverable reserves (EUR) of a gas well being produced during the low-pressure, low-production stage. During well production and maintenance, chemicals such as corrosion inhibitors, bactericides, and foaming agents are added. Under the high-temperature conditions at the bottom of the well… Volatile and soluble components in the reagents can be carried out of the wellbore by gas flow, liquid flow, or gas-liquid mixtures, leaving behind some insoluble or poorly soluble substances, which generally have high viscosity and easily form adhesive deposits that adhere to the pipe walls and well bottom. Simultaneously, oil-based drilling fluids that have seeped into the formation during the initial drilling process, or oil sludge produced during production, can emulsify and flocculate with some components of the reagents in a high-temperature environment. This sludge can then bind with gravel, corrosion products, and other solid phases in the well, forming emulsion blockages and complex blockages, affecting normal gas well production and the implementation of gas well process measures. Currently, there is considerable research and development on technologies for unblocking complex blockages in natural gas wells, but research on unblocking fluids and technologies for complex unblocking and bottom-hole emulsion blockage removal in deep shale gas wells with high temperature, low pressure, and low production is relatively lacking.

[0003] Chinese Invention Patent: Wellbore Unblocking Agent for Gas Wells, Design Method, Preparation Method and Application (Application No.: CN202310591992.9); The design method described in this patent first analyzes the wellhead conditions, reservoir water lock analysis, and wellbore contamination analysis, and then designs a targeted wellbore unblocking agent based on the analysis results. It includes: a solvent functional section, a solubilizing functional section, a dispersing functional section, a permeation functional section, a surface-active functional section, a complexing functional section, and a corrosion-inhibiting functional section; wherein the solvent functional section is water, and the solubilizing functional section is an organic solvent; since the reservoir's miscibility critical temperature is generally around 31.1℃, the boiling point of the organic solvent should be greater than 31.1℃ and lower than the reservoir temperature. Under reservoir temperature and pressure conditions, it should exist in a gaseous state or a miscible phase of gas and liquid, and be completely discharged from the wellbore during wellhead venting, without causing water retention in the producing layer due to measures. Shale gas wells typically employ single-well separation or centralized separation at well sites for production. Gas field water is discharged into non-enclosed sewage ponds at well sites, and the use of low-boiling-point solvents can easily lead to safety and environmental accidents. However, this invention patent, when there is liquid accumulation in the wellbore, causes the solubilizing solvent to vaporize prematurely during the well-clogging process, making it difficult to reach the blockage point and negatively impacting the dispersion of the blockage.

[0004] Chinese Invention Patent: A Method for Using Unblocking Fluid in Oil and Gas Wells (Application No.: CN202210740959.3); This patent involves drying a sample of plugging material from an oil and gas well to constant weight; extracting the dried sample; and dissolving the dried sample separately in an unblocking fluid system to obtain the dosages of organic unblocking agent A, inorganic unblocking agent B, and reactive unblocking agent C. Organic unblocking agent A is a mixture of low-molecular-weight ether, ethylene glycol, polyoxyethylene ether castor oil, surfactant a, and solvent oil. This invention addresses the technical problem of unclear selection criteria for existing unblocking agents, making it difficult to effectively remove plugging. Deep shale gas wells face sampling difficulties; obtaining samples of the plugging material before construction reduces the applicable scope. Furthermore, the solvent oil in the system contains alkanes and aromatics, and low-pressure gas wells suffer from leakage and flowback difficulties. After unblocking, the solvent oil remaining in the wellbore may re-emulsify with foaming agents added during the production process, forming secondary emulsion blockages, making it difficult to unblock the bottom-well emulsification problem in deep shale gas wells. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing unblocking agents in the cleaning and unblocking of deep shale gas wells, such as poor safety during on-site construction using volatile agents, poor applicability under high-temperature conditions, and the tendency of agent component residues to form secondary emulsion blockages. This invention provides an unblocking agent, its preparation method, and its application, solving problems such as sludge and bottom emulsion blockage of production tubing generated during the production process of deep shale gas wells. It is an unblocking agent that cleans and unblocks the wellbore, solubilizes bottom emulsions, reduces viscosity, and is suitable for high-temperature conditions at the bottom of deep shale gas wells, effectively maintaining normal production in deep shale gas wells.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0007] A blockage remover comprising the following components by weight percentage: 10-25% of an amide compound, 15-25% of an ester compound, 5-50% of a co-solvent, 5-50% of a shale inhibitor, and 5-50% of a drainage aid, with the balance being water;

[0008] The structural unit of the amide compound is: Wherein: R1 is any one of H, C1-C5 alkyl or C2-C5 olefin; R2 and R3 are any one of H or C1-C3 alkyl;

[0009] The structural unit of the ester compound is: Wherein: R4 is any one of methyl or vinyl; R5 is any one of polyol or polyol.

[0010] The organic components in deep shale gas wells, such as sludge, emulsions, and solid cement, are mainly insoluble esters, aromatic hydrocarbons, alkanes, and nitrogen-containing heterocyclic substances—high-molecular-weight organic compounds. This invention uses modified small-molecule amides and small-molecule esters as the main body of water-soluble, highly permeable solvents. These solvents exhibit strong permeability to oil sludge, polymers, and other organic components, good solubility and dispersibility, and can effectively reduce the elasticity and viscosity of the emulsion interface film, thus achieving demulsification and solving the bottom-hole emulsification problem. The selected amides and esters have high flash points and are safe to use. Combined with co-solvents, drainage aids, shale inhibitors, and other additives, they form a water-soluble, neutral cleaning and unblocking agent suitable for use in deep shale gas wells.

[0011] A structural unit is a combination of atoms that make up a polymer chain and determine the polymer structure by connecting them in a certain way. C1-C5 alkyl groups refer to: methane, ethane, propane, n-butane, isobutane, n-pentane, isopentane, and neopentane.

[0012] Preferably, the co-solvent is any one or more of sodium dodecyl sulfate, sodium fatty alcohol polyoxyethylene ether sulfate, cocamidopropyl hydroxysulfonyl betaine, polyoxyethylene fatty alcohol ether, and amide-based gemini quaternary ammonium salt.

[0013] Preferably, the co-solvent is an amide-based quaternary ammonium salt gemini surfactant, which can form micelles in solution at low concentrations. It can solubilize insoluble or slightly soluble organic matter in water. During the backflow process, the cleaning and unblocking agent will be diluted by the gas field water. Through its co-solubilizing and solubilizing effects, it prevents the dissolved organic components of the blockage from precipitating out during the backflow process.

[0014] Preferably, the shale inhibitor is one or more of polydimethyldiallylammonium chloride, polytrimethylallylammonium chloride, dimethyldiallylammonium chloride, and trimethylallylammonium chloride.

[0015] Preferably, the shale inhibitor is a small molecule cationic compound, dimethyl diallyl ammonium chloride, which adsorbs onto clay particles, keeping them in a compact or non-dispersed state. It can effectively inhibit the hydration swelling, dispersion and migration of shale clay minerals, and has long-term stability. It is also effective in acidic, alkaline and neutral media.

[0016] Preferably, the drainage aid is one or more of the following: OP series alkylphenol polyoxyethylene ether, SPAN series sorbitan fatty acid ester, and Tween series polyoxyethylene sorbitan ester.

[0017] The OP series of alkylphenol polyoxyethylene ethers includes: OP-4, OP-7, OP-10, OP-15, and OP-20; the Span series of dehydrated sorbitan fatty acid esters includes: Span-20, Span-40, Span-60, and Span-80.

[0018] Preferably, the drainage aid is a Tween series polyoxyethylene sorbitan ester, which not only reduces the surface tension of the entire system, but also has good water solubility, making it easy to drain back and not easy to remain at the bottom of the well.

[0019] The Tween series of polyoxyethylene sorbitan esters includes: Tween-20, Tween-40, Tween-60, and Tween-80; the preferred variety in this invention is Tween-60.

[0020] Preferably, the amide compound is at least one of N,N-dimethylformamide, N,N-dimethylacetamide, 3-hydroxy-N,N-dimethylpropionamide, N,N-dimethylacrylamide, N,N-dimethylpentanamide, or N-methylpentanamide.

[0021] If R1 is H and R2 and R3 are -CH3, then the amide compound is: N,N-dimethylformamide;

[0022] If R1 is -CH3, and R2 and R3 are -CH3, then the amide compound is: N,N-dimethylacetamide;

[0023] If R1 is -CH2-CH2-OH and R2 and R3 are -CH3, then the amide compound is: 3-hydroxy-N,N-dimethylpropionamide;

[0024] If R1 is -CH=CH2 and R2 and R3 are -CH3, then the amide compound is: N,N-dimethylacrylamide;

[0025] If R1 is -CH2-CH2-CH2-CH3, and R2 and R3 are -CH3, then the amide compound is: N,N-dimethylpentanamide;

[0026] If R1 is -CH2-CH2-CH2-CH3, R2 is H, and R3 is -CH3, then the amide compound is: N-methylpentanamide.

[0027] Preferably, the ester compound is at least one selected from ethylene glycol monoacetate, hydroxypropyl acrylate, diethylene glycol monoacetate, diethylene glycol diacetate, triethylene glycol monoacetate, or triethylene glycol diacetate.

[0028] If R4 is -CH3 and R5 is -CH2-CH2-OH, then the ester compound is: ethylene glycol monoacetate;

[0029] If R4 is -CH=CH2 and R5 is -CH(CH3)-CH2-OH, then the ester compound is: hydroxypropyl acrylate;

[0030] If R4 is -CH3 and R5 is -CH2-CH2-O-CH2-CH2-OH, then the ester compound is: diethylene glycol monoacetate;

[0031] If R4 is -CH3 and R5 is -CH2-CH2-O-CH2-CH2-O-CO-CH3, then the ester compound is: diethylene glycol diacetate;

[0032] If R4 is -CH3 and R5 is -CH2-CH2-O-CH2-CH2-O-CH2-CH2-OH, then the ester compound is: triethylene glycol monoacetate;

[0033] If R4 is -CH3 and R5 is -CH2-CH2-O-CH2-CH2-O-CH2-CH2-O-CO-CH3, then the ester compound is: triethylene glycol diacetate.

[0034] Preferably, the unblocking agent has a system flash point greater than 90°C, and the unblocking agent has a solubility rate of greater than 90% for complex blockages. The unblocking agent formulated with this composition has a system flash point greater than 90°C, providing high safety for use in natural gas wells. The agent system is temperature resistant to 150°C, meeting the high-temperature conditions at the bottom of deep shale gas wells. The solubility rate for complex blockages can reach over 90%, and the apparent viscosity of the emulsion can be significantly reduced after use.

[0035] Preferably, the unblocking agent comprises the following components: 10-25% 3-hydroxy-N,N-dimethylpropionamide, 15-25% triethylene glycol monoacetate, 5-10% amide-gemini quaternary ammonium salt, 1-7% dimethyl diallyl ammonium chloride, 4-6% polyoxyethylene sorbitan ester, and the balance being water.

[0036] A method for preparing the above-mentioned unblocking agent includes the following steps:

[0037] Preparation of amide compounds: A chlorinating agent is added dropwise to the carboxylic acid monomer R1-COOH at a molar ratio of carboxylic acid to chlorinating agent of 1:1.1-1.5, the temperature is controlled at 30-60℃, and the reaction time is 60-120 min to obtain the intermediate acyl chloride; wherein the chlorinating agent is any one of SOCl2, (COCl)2, POCl3 or PCl5;

[0038] The intermediate acyl chloride was added dropwise to organic amine R2-NH2 at a molar ratio of 1:1.0.5-1.2. The temperature during the dropwise addition was controlled at 10-30℃ and the reaction time was 90-150 min. The pH was adjusted to 7-9 with an alkaline compound to obtain the amide compound.

[0039] Preparation of ester compounds: Carboxylic acid monomer R3-COOH and organic alcohol monomer R4-OH are mixed in a molar ratio of 1:1.1-1.5, and 2-15% of a catalyst (by mass) of the reaction system is added. The reaction temperature is controlled at 90-150℃, and the reaction time is 120-160 min. Finally, the catalyst and the organic alcohol are separated to obtain ester compounds. The catalyst is any one of concentrated sulfuric acid, sulfonic acid, or solid heteropolyacid.

[0040] The prepared amide compound and ester compound are mixed, and then a cosolvent, shale inhibitor and drainage aid are added to obtain the unblocking agent.

[0041] The main structural factors affecting the flash point of organic compounds are molecular size, degree of branching, and electrostatic effects. Specifically, the flash point increases with increasing molecular volume; the flash point also increases with increasing degree of molecular branching and structural complexity; and the flash point also increases with enhanced electrostatic effects.

[0042] This invention introduces hydroxyl groups with more branched chains, thereby increasing the degree of branching of the compound and forming intermolecular hydrogen bonds to enhance intermolecular attraction, reducing the volatility of organic compounds and thus increasing the flash point of the synthesized compound.

[0043] Conventional amides and small-molecule esters are characterized by low flash points. Flash point is an important parameter for measuring the flammability of a compound and a crucial safety indicator for flammable liquids during storage, transportation, and use. Flash point prediction for organic compounds often employs quantitative structure-activity relationship (QSPR) models. The more heavy atoms in a molecule, the higher the flash point; the more branched the molecule, the greater the intermolecular distance, the smaller the intermolecular forces, and the lower the flash point; the greater the degree of unsaturation of the molecule, the greater the molecular polarity, the greater the orientation force, and the higher the flash point; the larger the molecular volume, the higher the flash point, and volume is closely related to the number of atoms constituting the molecule—that is, the more atoms a molecule contains, or the greater its relative molecular mass, the higher the flash point; compounds with intermolecular hydrogen bonds also have high flash points.

[0044] QSPR model analysis and calculation can be used to optimize the synthesis of conventional amides and small molecule esters, and introduce hydroxyl groups, hydrogen bonding groups, etc., while retaining good permeability, dissolution and dispersion ability for blockages, improving water solubility and flash point, and further improving the safety of construction operations.

[0045] Preferably, the chlorinating agent is oxalyl chloride (COCl)2, the alkaline compound is an aqueous solution of potassium hydroxide, and the catalyst is a solid heteropolyacid.

[0046] In the early stage of the reaction, the excess chlorinating agent (COCl)2 reacts with the potassium hydroxide aqueous solution to form potassium chloride and potassium oxalate. Finally, calcium chloride aqueous solution is added to the system until no calcium oxalate precipitate is formed, and an aqueous solution of potassium chloride and amide compound is obtained. Potassium chloride is the shale inhibitor material added during the construction of shale gas wells. The entire system does not have the environmental protection problem of waste liquid treatment. Heteropolyacid (HPA) is an oxygen-containing polyacid composed of heteroatoms and polyatoms connected by oxygen atom coordination bridging in a certain structure. It is a bifunctional green catalyst with both acid-base and redox properties.

[0047] Preferably, the co-solvent is an amide-based gemini quaternary ammonium salt, the shale inhibitor is dimethyl diallyl ammonium chloride, and the drainage aid is Tween series polyoxyethylene sorbitan ester.

[0048] Amide-based quaternary ammonium salt gemini surfactants can form micelles in solution at low concentrations, which can solubilize insoluble or slightly soluble organic matter in water. During the flowback process, the cleaning and unblocking agent is diluted by gas field water, and its solubilizing and enlarging effects prevent the dissolved organic components of the blockage from precipitating out during the flowback process. Dimethyl diallyl ammonium chloride small molecule cationic compounds adsorb onto clay particles, keeping them in a compact or non-dispersed state, which can effectively inhibit the hydration swelling, dispersion and migration of shale clay minerals. It has long-term stability and is equally effective in acidic, alkaline and neutral media. Tween series polyoxyethylene sorbitan esters not only reduce the surface tension of the entire system, but also have good water solubility, are easy to flowback and do not easily remain at the bottom of the well.

[0049] An application of the above-mentioned unblocking agent, wherein the unblocking agent is used in one or more scenarios of high temperature, low pressure or low production wells in deep shale gas formations.

[0050] Given the unique characteristics of shale formations, the unblocking agent exhibits exceptional dispersion, inhibition, and anti-swelling properties. It effectively prevents cleaning agents from seeping into the formation during operations, thus avoiding contamination of tight shale reservoirs and ensuring the purity and efficient extraction of oil and gas resources. The unblocking agent system not only has a flash point above 90℃, ensuring safety during use in natural gas wells, but also maintains stable performance in the high-temperature environment of the well bottom, reaching up to 150℃, meeting the stringent conditions of deep shale gas extraction and providing strong support for the development of deep oil and gas resources.

[0051] Preferably, the unblocking agent has a flash point greater than 110℃.

[0052] More preferably, the unblocking agent has a flash point greater than 120°C.

[0053] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0054] 1. This invention protects a deblocking agent whose components are composed of water-soluble materials, eliminating solid components and achieving a highly efficient and rapid demulsification effect. It significantly reduces the viscosity of the liquid and exhibits excellent oil dispersion and removal capabilities. Particularly noteworthy is the strong inhibitory and anti-swelling function of this deblocking agent on the dispersion behavior of shale, effectively preventing the potential contamination of tight shale reservoirs caused by the penetration of cleaning agents into the formation.

[0055] 2. Regarding safety, the unblocking agent system of this invention has an overall flash point above 90℃, ensuring a high degree of safety in natural gas well applications. Furthermore, this agent system exhibits excellent temperature resistance, capable of withstanding high-temperature environments up to 150℃, perfectly meeting the application requirements under extreme high-temperature conditions at the bottom of deep shale gas wells.

[0056] 3. This unblocking agent fully complies with environmental standards. It is non-fluorescent, non-toxic, harmless, and does not contain flammable or explosive solvents or mineral oil components. It is biodegradable and environmentally friendly. Furthermore, it has no corrosive effect on various rubber materials and downhole tools, ensuring the long-term stable operation of the equipment.

[0057] 4. The unblocking agent also has strong compatibility, and can be compatible with a variety of media such as flowback fluid, fracturing fluid, and brine. There is no need to worry about operational obstacles caused by compatibility issues, which further improves the flexibility and efficiency of operations.

[0058] 5. To further enhance practicality and flexibility, the unblocking method of this invention is versatile and can be adjusted according to the specific conditions of the gas well blockage on site. Specifically, it includes multiple efficient cleaning modes such as slug cleaning, full wellbore cleaning, and near-wellbore cleaning, ensuring accurate and effective unblocking operations regardless of the type of blockage. Attached Figure Description

[0059] Figure 1 This is a schematic diagram of the on-site construction process for slug cleaning in Example 6.

[0060] Figure 2 This is a schematic diagram of the on-site construction process for cleaning the entire wellbore and the near-well zone in Example 6.

[0061] Figure 3 The production data curve of well WY25-3HF in Example 6. Detailed Implementation

[0062] To more clearly describe the inventive objectives, technical solutions, and advantages of the specific embodiments of this invention, the solutions in the specific embodiments will be described in detail below with reference to the accompanying drawings. The specific technical solutions involved in the following embodiments are merely for the purpose of clearly and completely describing the innovative technical solutions of this invention. They are only a part of the specific implementation methods that this invention can adopt, not all embodiments, and should not be construed as limiting the innovative solutions of this invention. Any solution that adopts the same inventive concept as this invention should be included within the protection scope of this invention.

[0063] Secondly, the descriptions of the accompanying drawings in the specific embodiments of the present invention are merely for the purpose of facilitating the understanding of the present invention by those skilled in the art. Some details in the drawings are shown to facilitate a clear presentation of the technical solution. It should not be assumed that all technical features in the drawings must be included in the specific implementation cases, nor should the detailed features in the drawings be regarded as additional limitations on the innovative technical solution of the present invention.

[0064] For those skilled in the art, when understanding the solutions described in the specific embodiments of the present invention, conventional technical manuals in the field can be consulted. At the same time, appropriate understandings or adjustments can be made to the above-mentioned terms to deduce the same or similar technical solutions without creative effort.

[0065] Example 1

[0066] A blockage remover and its preparation method are disclosed. The raw materials of the blockage remover are composed of the following components by weight: 10% 3-hydroxy-N,N-dimethylpropionamide, 20% triethylene glycol monoacetate, 5% amide-based gemini quaternary ammonium salt, 5% dimethyl diallyl ammonium chloride, 5% polyoxyethylene sorbitan ester, and the remainder being water.

[0067] The specific preparation method is as follows:

[0068] (COCl)₂ was added dropwise to the carboxylic acid monomer HO-CH₂-CH₂-COOH at a molar ratio of carboxylic acid to chlorinating reagent of 1:1.1, with the temperature controlled at 60℃ and the reaction time at 60 min, to obtain the intermediate acyl chloride. The intermediate acyl chloride was then added dropwise to the organic amine CH₃-NH₂ at a molar ratio of 1:1, with the temperature controlled at 10℃ and the reaction time at 90 min. The pH was adjusted to 7 with 6 mol / L potassium hydroxide to prepare 3-hydroxy-N,N-dimethylpropionamide.

[0069] The carboxylic acid monomer CH3-COOH and the organic alcohol monomer CH3-OH were mixed in a molar ratio of 1:1.1, and 2% of the mass of solid heteropoly acid was added to the reaction system. The reaction temperature was controlled at 90℃ and the reaction time was 120 min. Finally, the catalyst and the organic alcohol were separated to obtain triethylene glycol monoacetate.

[0070] Unblocking agent A is prepared by mixing 10% by weight of 3-hydroxy-N,N-dimethylpropionamide, 20% triethylene glycol monoacetate, 5% amide-gemini quaternary ammonium salt, 5% dimethyl diallyl ammonium chloride and 5% polyoxyethylene sorbitan ester in 55% water.

[0071] Example 2

[0072] A blockage remover and its preparation method are disclosed. The blockage remover comprises: 15% 3-hydroxy-N,N-dimethylpropionamide, 15% triethylene glycol monoacetate, 10% amide-based gemini quaternary ammonium salt, 2% dimethyl diallyl ammonium chloride, 5% polyoxyethylene sorbitan ester, and the remainder being water.

[0073] The specific preparation method is as follows:

[0074] (COCl)₂ was added dropwise to the carboxylic acid monomer HO-CH₂-CH₂-COOH at a molar ratio of carboxylic acid to chlorinating reagent of 1:1.1, with the temperature controlled at 60℃ and the reaction time at 60 min, to obtain the intermediate acyl chloride. The intermediate acyl chloride was then added dropwise to the organic amine CH₃-NH₂ at a molar ratio of 1:1, with the temperature controlled at 10℃ and the reaction time at 90 min. The pH was adjusted to 7 with 6 mol / L potassium hydroxide to prepare 3-hydroxy-N,N-dimethylpropionamide.

[0075] Carboxylic acid monomer CH3-COOH and organic alcohol monomer CH3-OH were mixed in a molar ratio of 1:1.1, and 2% of solid heteropoly acid by mass of the reaction system was added. The reaction temperature was controlled at 90℃ and the reaction time was 120 min. Finally, the catalyst and organic alcohol were separated to obtain triethylene glycol monoacetate.

[0076] Unblocking agent B was prepared by mixing 15% by weight of 3-hydroxy-N,N-dimethylpropionamide, 15% triethylene glycol monoacetate, 10% amide-gemini quaternary ammonium salt, 2% dimethyl diallyl ammonium chloride, and 5% polyoxyethylene sorbitan ester in 53% water.

[0077] Example 3

[0078] A blockage remover and its preparation method are disclosed. The blockage remover comprises: 20% 3-hydroxy-N,N-dimethylpropionamide, 20% triethylene glycol monoacetate, 5% amide-based gemini quaternary ammonium salt, 5% dimethyl diallyl ammonium chloride, 5% polyoxyethylene sorbitan ester, and the remainder being water.

[0079] The specific preparation method is as follows:

[0080] (COCl)2 was added dropwise to the carboxylic acid monomer HO-CH2-CH2-COOH at a molar ratio of carboxylic acid to chlorinating agent of 1:1.5, with the temperature controlled at 60℃ and the reaction time at 120 min, to obtain the intermediate acyl chloride. The intermediate acyl chloride was then added dropwise to the organic amine CH3-NH2 at a molar ratio of 1.2, with the temperature controlled at 30℃ and the reaction time at 150 min. The pH was adjusted to 9 with 6 mol / L potassium hydroxide to prepare 3-hydroxy-N,N-dimethylpropionamide.

[0081] The carboxylic acid monomer CH3-COOH and the organic alcohol monomer CH3-OH were mixed in a molar ratio of 1:1.1-1.5, and 15% of the mass of solid heteropoly acid was added to the reaction system. The reaction temperature was controlled at 150℃ and the reaction time was 160 min. Finally, the catalyst and the organic alcohol were separated to obtain triethylene glycol monoacetate.

[0082] Unblocking agent C was prepared by mixing 20% ​​by weight of 3-hydroxy-N,N-dimethylpropionamide, 20% triethylene glycol monoacetate, 5% amide-gemini quaternary ammonium salt, 5% dimethyl diallyl ammonium chloride and 5% polyoxyethylene sorbitan ester in 45% water.

[0083] Example 4

[0084] A blockage remover and its preparation method are disclosed. The blockage remover comprises: 15% 3-hydroxy-N,N-dimethylpropionamide, 25% triethylene glycol monoacetate, 5% amide-based gemini quaternary ammonium salt, 5% dimethyl diallyl ammonium chloride, 5% polyoxyethylene sorbitan ester, and the remainder being water.

[0085] The specific preparation method is as follows:

[0086] (COCl)2 was added dropwise to the carboxylic acid monomer HO-CH2-CH2-COOH at a molar ratio of carboxylic acid to chlorinating reagent of 1:1.5, with the temperature controlled at 30℃ and the reaction time at 120 min, to obtain the intermediate acyl chloride. The intermediate acyl chloride was then added dropwise to the organic amine CH3-NH2 at a molar ratio of 1.2, with the temperature controlled at 10℃ and the reaction time at 150 min. The pH was adjusted to 9 with 6 mol / L potassium hydroxide to prepare 3-hydroxy-N,N-dimethylpropionamide.

[0087] Carboxylic acid monomer CH3-COOH and organic alcohol monomer CH3-OH were mixed in a molar ratio of 1:1.1, and 2% of solid heteropoly acid was added by mass of the reaction system. The reaction temperature was controlled at 150℃ and the reaction time was 120 min. Finally, the catalyst and organic alcohol were separated to obtain triethylene glycol monoacetate.

[0088] Unblocking agent D was prepared by mixing 15% by weight of 3-hydroxy-N,N-dimethylpropionamide, 25% triethylene glycol monoacetate, 5% amide-gemini quaternary ammonium salt, 5% dimethyl diallyl ammonium chloride and 5% polyoxyethylene sorbitan ester in 45% water.

[0089] Example 5

[0090] A blockage remover and its preparation method are disclosed. The blockage remover comprises: 25% 3-hydroxy-N,N-dimethylpropionamide, 25% triethylene glycol monoacetate, 5% amide-based gemini quaternary ammonium salt, 5% dimethyl diallyl ammonium chloride, 5% polyoxyethylene sorbitan ester, and the remainder being water.

[0091] The specific preparation method is as follows:

[0092] (COCl)2 was added dropwise to the carboxylic acid monomer HO-CH2-CH2-COOH at a molar ratio of carboxylic acid to chlorinating reagent of 1:1.5, with the temperature controlled at 60℃ and the reaction time at 120 min, to obtain the intermediate acyl chloride. The intermediate acyl chloride was then added dropwise to the organic amine CH3-NH2 at a molar ratio of 1.2, with the temperature controlled at 30℃ and the reaction time at 150 min. The pH was adjusted to 7 with 6 mol / L potassium hydroxide to prepare 3-hydroxy-N,N-dimethylpropionamide.

[0093] Carboxylic acid monomer CH3-COOH and organic alcohol monomer CH3-OH were mixed in a molar ratio of 1:1.5, and 15% of solid heteropoly acid by mass of the reaction system was added. The reaction temperature was controlled at 150℃ and the reaction time was 120 min. Finally, the catalyst and organic alcohol were separated to obtain triethylene glycol monoacetate.

[0094] Unblocking agent E was prepared by mixing 25% by weight of 3-hydroxy-N,N-dimethylpropionamide, 25% triethylene glycol monoacetate, 5% amide-gemini quaternary ammonium salt, 5% dimethyl diallyl ammonium chloride and 5% polyoxyethylene sorbitan ester in 35% water.

[0095] Comparative Example

[0096] A blockage remover and its preparation method are disclosed. The blockage remover comprises: 5% amide-based gemini quaternary ammonium salt, 5% dimethyl diallyl ammonium chloride, 5% polyoxyethylene sorbitan ester, and the remainder being water.

[0097] The specific preparation method is as follows:

[0098] Unblocking agent X was prepared by mixing 5% by weight of amide-based gemini quaternary ammonium salt, 5% by weight of dimethyl diallyl ammonium chloride and 5% by weight of polyoxyethylene sorbitan ester in 85% water.

[0099] Test case

[0100] 1. Flash point test:

[0101] The flash points of the unblocking agents prepared in Examples 1-5 and the comparative examples were tested using the "Standard for Determination of Flash Point and Ignition Point of Petroleum Products - Cleveland Open Cup Method" (GB T 3536-2008).

[0102] 2. Emulsion viscosity reduction experiment:

[0103] Simulated emulsion preparation: Sampling of downhole emulsion blockages is difficult and not easy to obtain. Therefore, the laboratory experiment used white oil to simulate the oily components in the well and added an emulsifier to form a simulated emulsion blockage. The emulsion formed by mixing 50% No. 10 white oil, 15% Span 80 and 35% water at a stirring rate of 11000 r / min for 10 min has good stability and is not easy to break down after adding water.

[0104] Viscosity tests were performed on the unblocking agents prepared in Examples 1-5 and the comparative examples. 200g of the emulsified blockage material was weighed out, and its apparent viscosity before the experiment was tested. Then, 100ml of the unblocking agent was added to each, and the mixture was stirred at 300r / min for 2 minutes. The apparent viscosity was then tested again.

[0105] 3. Experiment on dissolving composite blockages:

[0106] Preparation of simulated composite plugging material: Use oil-based mud (80% diesel + 10% oxidized asphalt + 1.2% aluminum stearate + 0.8% lime (quicklime powder) + 4% organic soil + 2% sodium dodecyl sulfate + 2% Span 80) : fracturing sand (70-140 mesh) = 1:2 as simulated solid-phase composite plugging material.

[0107] The unblocking agent AE prepared in Examples 1-5 and the unblocking agent prepared in the comparative example were respectively subjected to unblocking experiments. The test method was as follows: W1 composite blockage material was weighed, and the total weight of the composite blockage material and the beaker was recorded as W2. Then, the unblocking agent was added at a ratio of blockage material: unblocking agent = 1:10. After stirring at a stirring speed of 300 r / min for 5 min, the mixture was filtered, and the weight of the residue and the weight of the beaker W3 were weighed. The solubility rate of the composite blockage material was calculated as %.

[0108] Calculation formula:

[0109] The test results are shown in Table 1.

[0110] Table 1. Experimental results of emulsion viscosity reduction and complex blockage dissolution.

[0111]

[0112] In summary, all the unblocking agents in Examples 1-5 have flash points exceeding 110°C, indicating that these emulsion viscosity reducers have high safety during use and are not easily ignited. Example 4 has the highest flash point at 125.6°C, suggesting potentially superior stability and safety at high temperatures. While the unblocking agents in Examples 1, 2, 3, and 5 have slightly lower flash points, they still remain at a high level and meet the requirements for safe use.

[0113] The unblocking agents in Examples 1-5 all showed a solubility of over 90% for the composite blockage, while the solubility of the composite blockage in the comparative example without the addition of 3-hydroxy-N,N-dimethylpropionamide and triethylene glycol monoacetate was only 17%. The solubility of the composite blockage in Examples 1-5 was much greater than that in the comparative example. Therefore, the unblocking agent of the present invention can effectively enhance the solubility of the composite blockage, and the enhancement effect is significant.

[0114] In Examples 1-5, the viscosity of the emulsion before and after the addition of the unblocking agent was significantly different, and the viscosity was reduced from 95 mPas to about 20 mPas. In contrast, the comparative example could only reduce the viscosity from 98 mPas to 76 mPas.

[0115] Based on the data analysis of the embodiments and comparative examples, it can be determined that the unblocking agent protected by the present invention has strong safety performance, a high flash point, and a high solubility for complex blockages, with a solubility rate of up to 97.8%, which almost completely dissolves the complex blockages. Furthermore, it also has a significant effect on reducing the viscosity of emulsions.

[0116] Example 6

[0117] The application method of a blockage unblocking agent is as follows:

[0118] 1. Unblocking of oil pipes and casing annulus—slug cleaning

[0119] The implementation plan for deep shale gas well slug cleaning is as follows: "Tubing / casing pumping → tubing / casing gas lift push → shut-in and repressurization → gas injection and pressure build-up → well opening and flowback → gas lift and flowback". See the detailed process below. Figure 1 Specifically, the plan is as follows:

[0120] ① A pump truck is used to pump unblocking agent from the casing to flush and clean the inner wall of the tubing, the near-well wall, and the annulus, thus initially cleaning the wellbore.

[0121] ②The unblocking agent is pushed through the tubing via gas lift, further flushing the inner wall of the tubing, near the well wall, and the inner wall of the casing, allowing the agent to penetrate deep into the blockage point.

[0122] ③ Close the well and pressurize or inject gas to reduce pressure, so that the blockage and the unblocking agent can react and dissolve more fully, increase the unblocking agent's release area, and disperse and dissolve the blockage segment.

[0123] ④ Well run-out: Utilize the gas well's own energy to expel formation contaminants. When the gas well's energy is low, gas lift can be used to assist in well run-out, thereby achieving purification of deep shale gas wells.

[0124] 2. Cleaning of the entire wellbore and near-wellbore area

[0125] The implementation plan for cleaning the entire wellbore and near-wellbore zone of deep shale gas formations is as follows: "Reagent preparation → casing pumping → water displacement → well shut-in and soaking → well opening and flowback → gas lift flowback". For details, see [link to detailed process]. Figure 2 Specifically:

[0126] ① Prepare a well-washing fluid (unblocking agent dilution) with a concentration of not less than 10% on the ground using a liquid injection system, and then fully dissolve and disperse it using a mixer.

[0127] ② Pump the well-washing fluid from the casing, maintaining a flow rate of 2m³ / min. 3 The flow rate is above 1000 m / min, which flushes and cleans the annulus of the oil casing, thus playing a role in initially cleaning the wellbore and dissolving insoluble oily solids.

[0128] ③ The water in the casing is replaced by at least one wellbore volume of clean water, allowing the diluted unblocking agent to further penetrate the near-wellbore zone of the formation, thereby achieving deep purification of the near-wellbore zone of the producing formation.

[0129] ④ Close the well and pressurize or inject gas to reduce pressure, so that the blockage and the unblocking agent can react and dissolve more fully, increase the unblocking agent's release area, and disperse and dissolve the blockage segment.

[0130] ⑤ Well run-through: Utilize the gas well's own energy to expel formation contaminants. When the gas well's energy is low, gas lift can be used to assist in well run-through, thereby achieving purification of deep shale gas wells.

[0131] 3. Field application results (WY25-3HF well)

[0132] (1) Construction Overview

[0133] On the first day, after the gas well initially experienced pressure surges, production was maintained through measures such as air venting. Subsequently, these measures failed, and the gas well entered a low-pressure, low-production state, producing 0.2-0.8 million cubic meters of gas and 0-2 cubic meters of liquid per day.

[0134] On the 19th day, 30m was pumped from the casing. 3 Dilute unblocking fluid + 60m 3Use clean water, with a construction flow rate of 660-880 L / min. The construction pump pressure rises from 6.8 MPa to 8 MPa and then drops to 0 MPa. After pumping is completed, the well is kept closed for 1 day to remove blockages in the horizontal section and near-wellbore zone.

[0135] On the 20th day, gas was observed immediately after well opening and fluid discharge. The process was introduced, with an instantaneous production of 0.8-1.2 million cubic meters per day and an instantaneous fluid production of 6-8 cubic meters per day.

[0136] On the 21st day, 30m of fluid was drained with air lift assistance. 3 The oil pressure increased from 2.7MPa to 3.8MPa, the instantaneous production of the gas well fluctuated between 15,000 and 20,000 cubic meters, and the instantaneous fluid production was 10-18 cubic meters per day, which was introduced into the process production.

[0137] On the 29th day, the gas well had discharged a cumulative total of 91m³ of fluid. 3 The gas well maintained stable production for three consecutive days, with oil pressure maintained at 4-4.2 MPa, daily gas production of 25,000-28,000 cubic meters / day, and daily liquid production of 5-7 cubic meters / day. It was determined that the gas well blockage was successfully resolved, and production resumed at 10 kg foam discharge.

[0138] (2) Implementation Results

[0139] For specific implementation results, please refer to Figure 3 .

[0140] The well effectively cleaned its wellbore by using a diluted unblocking agent, which resolved the issues of continuously rising casing pressure and well shutdown during the early stages of production. This restored stable production to the well. After the well was cleaned, the oil pressure increased from 2.8 MPa to 4.2 MPa, the oil-casing pressure difference decreased from 5.5 MPa to 1.2 MPa, and the well production recovered to 26,000-28,000 cubic meters per day, with an average daily increase of 25,000 cubic meters.

[0141] The above embodiments describe only the basic principles, main features and / or advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and the description of the invention content in the specification are only the principles or specific cases of the present invention. Without departing from the essence of the innovative idea of ​​the present invention, there are various changes and improvements to the innovative solution of the present invention, and all such changes and improvements fall within the scope of protection claimed by the present invention.

Claims

1. A blockage-removing agent, characterized in that, The unblocking agent comprises the following components by weight percentage: 10-25% amide compound, 15-25% ester compound, 5-50% cosolvent, 5-50% shale inhibitor and 5-50% drainage aid, with the balance being water; The structural unit of the amide compound is: Wherein: R1 is any one of H, C1-C5 alkyl or C2-C5 olefin; R2 and R3 are any one of H or C1-C3 alkyl; The structural unit of the ester compound is: Wherein: R4 is any one of methyl or vinyl; R5 is any one of polyol or polyol.

2. The unblocking agent according to claim 1, characterized in that, The co-solvent is any one or more of sodium dodecyl sulfate, sodium fatty alcohol polyoxyethylene ether sulfate, cocamidopropyl hydroxysulfonate betaine, polyoxyethylene fatty alcohol ether, and amide-based gemini quaternary ammonium salt.

3. The unblocking agent according to claim 1, characterized in that, The shale inhibitor is one or more of polydimethyldiallylammonium chloride, polytrimethylallylammonium chloride, dimethyldiallylammonium chloride, and trimethylallylammonium chloride; the drainage aid is one or more of OP series alkylphenol polyoxyethylene ethers, SPAN series dehydrated sorbitan fatty acid esters, and Tween series polyoxyethylene dehydrated sorbitan esters.

4. The unblocking agent according to claim 1, characterized in that, The amide compound is at least one of N,N-dimethylformamide, N,N-dimethylacetamide, 3-hydroxy-N,N-dimethylpropionamide, N,N-dimethylacrylamide, N,N-dimethylpentanamide, or N-methylpentanamide.

5. The unblocking agent according to claim 1, characterized in that, The ester compound is at least one of ethylene glycol monoacetate, hydroxypropyl acrylate, diethylene glycol monoacetate, diethylene glycol diacetate, triethylene glycol monoacetate, or triethylene glycol diacetate.

6. The unblocking agent according to claim 1, characterized in that, The flash point of the unblocking agent is greater than 90°C, and the solubility of the unblocking agent in the complex blockage is greater than 90%.

7. A blockage-removing agent according to claims 1-6, characterized in that, The unblocking agent comprises the following components: 10-25% 3-hydroxy-N,N-dimethylpropionamide, 15-25% triethylene glycol monoacetate, 5-10% amide-based gemini quaternary ammonium salt, 1-7% dimethyl diallyl ammonium chloride, 4-6% polyoxyethylene sorbitan ester, and the balance being water.

8. A method for preparing any one of the unblocking agents according to claims 1-7, characterized in that, Includes the following steps: Preparation of amide compounds: A chlorinating agent is added dropwise to the carboxylic acid monomer R1-COOH at a molar ratio of carboxylic acid to chlorinating agent of 1:1.1-1.

5. The chlorinating agent is any one of SOCl2, (COCl)2, POCl3, or PCl5. The temperature is controlled at 30-60℃ and the reaction time is 60-120 min to obtain the intermediate acyl chloride. The intermediate acyl chloride was added dropwise to organic amine R2-NH2 at a molar ratio of 1:1.0.5-1.

2. The temperature during the dropwise addition was controlled at 10-30℃ and the reaction time was 90-150 min. The pH was adjusted to 7-9 with an alkaline compound to obtain the amide compound. Preparation of ester compounds: Carboxylic acid monomer R3-COOH and organic alcohol monomer R4-OH are mixed in a molar ratio of 1:1.1-1.5, and 2-15% of a catalyst (by mass) of the reaction system is added. The catalyst is any one of concentrated sulfuric acid, sulfonic acid, or solid heteropoly acid. The reaction temperature is controlled at 90-150℃ and the reaction time is 120-160 min. Finally, the catalyst and organic alcohol are separated to obtain ester compounds. The prepared amide compound and ester compound are mixed, and then a cosolvent, shale inhibitor and drainage aid are added to obtain the unblocking agent.

9. The preparation method according to claim 8, characterized in that, The chlorinating agent is oxalyl chloride, the alkaline compound is an aqueous solution of potassium hydroxide, and the catalyst is a solid heteropolyacid.

10. An application of any one of the unblocking agents according to claims 1-6, characterized in that, Application of unblocking agents in one or more scenarios of high temperature, low pressure or low production wells in deep shale gas formations.

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