Reservoir repairing-shaft cleaning integrated agent for natural gas well and preparation method of reservoir repairing-shaft cleaning integrated agent

Abstract

The invention relates to a reservoir repairing-shaft cleaning integrated agent for a natural gas well and a preparation method thereof.The preparation method comprises the steps that 15-30 parts by weight of alkyl sulfate and 10-20 parts by weight of a stabilizer are added into water with the feeding weight being 1-2 times that of the stabilizer to be evenly stirred, then 5-15 parts by weight of alkyl dimethyl amine oxide is sequentially added, and the mixture is stirred to be uniform; and finally, supplementing water to 100 parts by weight, and uniformly mixing to obtain a liquid medicine which is the reservoir repairing-shaft cleaning integrated agent for the natural gas well. According to the invention, through compounding of the adaptive surfactant and the auxiliary agent, the low emulsification performance of the system is improved by utilizing a synergistic effect, and the problem that a large amount of emulsion is generated during foam drainage of a traditional foam scrubbing agent is solved.

Description

Technical Field

[0001] This invention relates to the field of foaming agents for natural gas wells, and specifically to a method for preparing an integrated reservoir repair and wellbore cleaning agent for natural gas wells. Background Technology

[0002] During natural gas well development, as gas production progresses, formation energy gradually depletes, and the well's gas production falls below the critical fluid-carrying capacity. The produced gas is insufficient to carry the produced formation water or condensate to the surface, causing the produced fluid to accumulate at the well bottom. This severely impacts normal well production and can even lead to production shutdowns. In my country, a significant number of natural gas reservoirs have entered the middle to late stages of extraction, and most natural gas wells have experienced bottom fluid accumulation. Therefore, removing bottom fluid is crucial for stabilizing and increasing natural gas well production.

[0003] Drainage gas production technology reduces the fluid pressure gradient in the wellbore, improves the fluid inflow conditions near the bottom of the well, clears the natural gas migration channels, and increases the gas reservoir recovery rate. It is an effective way to solve the problem of liquid accumulation in gas wells, increase gas well production, and extend the self-flowing period of gas wells. Currently, the more commonly used drainage gas production technologies mainly include foam drainage gas production, plunger gas lift drainage gas production, and velocity tubing drainage gas production.

[0004] Foam drainage gas production is widely used in most gas field developments due to its low investment cost, ease of operation, and good field application results. In foam drainage gas production, a foaming agent is injected into the wellbore through the annulus of the tubing. Because the foaming agent has excellent foaming properties, it reduces the interfacial tension between gas and water. After being agitated within the fluid at the bottom of the well, it generates a large amount of stable foam, resulting in a large amount of discontinuous high-quality foam composed of oil, water, and condensate. This alters the original two-phase structure of gas-liquid separation at the bottom of the well, transforming it into a foam structure composed of gas and liquid mixtures, significantly reducing the fluid density within the wellbore. The reduction in the relative density of the fluid within the wellbore leads to a decrease in bottombore back pressure, increasing gas lift capacity, increasing the pressure differential, and gradually restoring gas well production. The accumulated fluid at the bottom of the well is partially or completely discharged from the wellbore. Simultaneously, some of the agent enters the near-wellbore reservoir, adjusting the reservoir's wettability through adsorption and restoring gas phase permeability, thus achieving the effect of reservoir repair.

[0005] Furthermore, injected foaming agents often have good emulsifying properties, forming water-in-oil (W / O), oil-in-water (O / W), or other more complex emulsions with condensate in the gas well. These emulsions are difficult to treat using conventional methods, and the dosage of foaming agent has a significant impact on the condensate emulsion, increasing production costs. Simultaneously, these emulsions adhere to the wellbore and enter reservoir pores, significantly reducing permeability and leading to a decrease in gas well productivity. Therefore, it is necessary to coordinate and control the foaming and emulsifying properties of the foaming agent to create a low-emulsification foaming agent for natural gas well production that has good foaming activity and does not easily form stable emulsions with condensate. Summary of the Invention

[0006] Therefore, the purpose of this invention is to provide an integrated reservoir repair and wellbore cleaning agent for natural gas wells and its preparation method. By combining suitable surfactants and additives, the low emulsification performance of the system is improved by utilizing the synergistic effect, thus solving the problem of large amounts of emulsion generated during foam drainage of traditional foaming agents.

[0007] Unlike existing technologies, the above technical solution provides an integrated reservoir repair and wellbore cleaning agent for natural gas wells, which includes the following components in parts by weight: 15-30 parts of alkyl sulfate, 5-15 parts of alkyl dimethyl amine oxide, 1-3 parts of fluorocarbon surfactant, 10-20 parts of stabilizer, and the remainder is made up to 100 parts by weight with water.

[0008] Preferably, the alkyl sulfate is one of the following: sodium dodecyl sulfate, potassium dodecyl sulfate, ammonium dodecyl sulfate, sodium hexadecyl sulfate, potassium hexadecyl sulfate, ammonium hexadecyl sulfate, sodium octadecyl sulfate, potassium octadecyl sulfate, or ammonium octadecyl sulfate. This invention enhances the foaming and foam-stabilizing effects of the integrated agent by adding alkyl sulfates.

[0009] Preferably, the alkyl dimethyl amine oxide is one of the following: dodecyl dimethyl amine oxide, tetradecyl dimethyl amine oxide, hexadecyl dimethyl amine oxide, and octadecyl dimethyl amine oxide.

[0010] Preferably, the fluorocarbon surfactant is a polyethylene glycol ester of perfluorohexanoic acid, perfluorooctanoic acid, or perfluorodecanoic acid, with a degree of polymerization of 200-10000. By adding a fluorocarbon surfactant, this invention enables the integrated agent to possess hydrophilic and lipophilic properties.

[0011] Preferably, the stabilizer is glycerol or ethylene glycol.

[0012] This invention also discloses a method for preparing the integrated reservoir repair and wellbore cleaning agent for natural gas wells, which includes the following steps: adding 15-30 parts by weight of alkyl sulfate and 10-20 parts by weight of stabilizer to water with a weight of 1-2 times that of stabilizer and stirring evenly; then adding 5-15 parts by weight of alkyl dimethyl amine oxide and 1-3 parts by weight of fluorocarbon surfactant in sequence; and finally adding water to 100 parts by weight. The solution obtained after mixing evenly is the integrated reservoir repair and wellbore cleaning agent for natural gas wells.

[0013] Preferably, when adding 5-15 parts by weight of alkyl dimethyl amine oxide and 1-3 parts by weight of fluorocarbon surfactant, the alkyl dimethyl amine oxide is added while stirring, and the fluorocarbon surfactant is added after the alkyl dimethyl amine oxide is completely dissolved or evenly dispersed, and stirring is continued to form a uniform drug solution.

[0014] Unlike existing technologies, this invention has the following advantages:

[0015] 1. Low emulsification and self-demulsification effect: The integrated reservoir repair and wellbore cleaning agent for natural gas wells described in this invention utilizes a synergistic compounding of fluorocarbon surfactants and alkyl dimethyl amine oxide (an amphoteric surfactant). This effectively reduces interfacial tension and ensures foaming performance while significantly minimizing the formation of stable emulsions between the agent and condensate oil. In particular, the addition of glycerol or ethylene glycol stabilizers not only enhances the agent's resistance to temperature and salt but also achieves a "self-demulsification" effect, enabling the formed emulsion to demulsify and separate into water within a short time (no more than 12 hours), greatly reducing the difficulty and cost of subsequent oil-gas-water separation.

[0016] 2. Excellent foaming performance and drainage effect: The integrated reservoir repair and wellbore cleaning agent for natural gas wells described in this invention exhibits excellent foaming performance when prepared as a 0.5-1% concentration of foaming agent in gas well water (evaluated according to SY / T 6465-2000). Simultaneously, the foaming agent partially penetrates the reservoir into the wellbore, effectively restoring reservoir permeability, demonstrating that the foaming agent has the ability to effectively drain bottom-hole fluid and improve near-wellbore flow conditions.

[0017] 3. Synergistic formulation optimization, balancing performance and cost: The surfactants and additives used in the integrated reservoir repair and wellbore cleaning agent for natural gas wells described in this invention are of industrial grade or higher purity, with readily available raw materials and controllable costs. The components are compounded through a specific addition sequence and process, forming a stable system with synergistic performance enhancement. While ensuring efficient drainage, it fundamentally solves the subsequent treatment problems caused by the strong emulsification of traditional foaming agents.

[0018] In summary, the integrated reservoir repair and wellbore cleaning agent for natural gas wells described in this invention exhibits good foaming properties and low emulsification. When 0.5-1% of the low-emulsification foaming agent is prepared using gas well water, its foaming performance is evaluated according to SY / T 6465-2000 "Evaluation Method for Foaming Agents for Foam Drainage and Gas Production," with a Roche foam height of 16.8-18.9 cm. Its stability with gas well condensate emulsion is evaluated according to SY / T 5761-2016 "Performance Evaluation Method for Surfactants for Oil Displacement," with the emulsion stability lasting no more than 7 hours. According to GB / T 29172-2012 "Method for Determining Rock Permeability," the permeability of reservoir cores damaged by the injection of more than 1 PV of the aforementioned foaming agent solution can recover to over 65%. Detailed Implementation

[0019] To explain in detail the technical content, structural features, objectives, and effects of the technical solution, the following detailed description is provided in conjunction with specific embodiments.

[0020] Example 1

[0021] A reservoir repair and wellbore cleaning agent for natural gas wells comprises: 15 parts by weight of alkyl sulfate, 5 parts by weight of alkyl dimethyl amine oxide, 1 part by weight of fluorocarbon surfactant and 10 parts by weight of stabilizer, with the remainder made up to 100 parts by weight by water.

[0022] The alkyl sulfate is industrial-grade sodium dodecyl sulfate;

[0023] The alkyl dimethyl amine oxide is industrial-grade dodecyl dimethyl amine oxide;

[0024] The fluorocarbon surfactant is polyethylene glycol 200 of perfluorohexanoic acid with industrial-grade purity.

[0025] The stabilizer is glycerol of industrial grade.

[0026] The foaming agent prepared for use in the natural gas well reservoir repair-wellbore cleaning integrated agent in this embodiment is referred to as ASF-1.

[0027] During preparation, 15 parts by weight of alkyl sulfate and 10 parts by weight of stabilizer are added to 10 parts by weight of water and stirred until homogeneous. Then, 5 parts by weight of alkyl dimethyl amine oxide and 1 part of fluorocarbon surfactant are added sequentially, and finally, water is added to a final volume of 100 parts by weight. The reagents are added while stirring during the preparation process, ensuring each reagent is completely dissolved or evenly dispersed before adding the next, until a homogeneous solution is formed. This is the integrated reservoir repair and wellbore cleaning agent for natural gas wells.

[0028] When applying, prepare 1% low-emulsification foaming agent with gas well water and stir until uniformly mixed. Measure the surface tension according to the following standards: SY / T 5370-2018 "Method for Determination of Surface and Interfacial Tension" (Petroleum and Natural Gas Industry Standard); SY / T 5153.3-1995 "Method for Determination of Contact Angle of Reservoir Rock Wettability" (Contact Angle Method); SY / T 6465-2000 "Evaluation Method for Foaming Agents for Foam Drainage and Gas Production" (Evaluation Method); SY / T 5761-2016 "Method for Evaluation of Performance of Surfactants for Oil Displacement" (Evaluation Method); and GB / T 29172-2012 "Method for Determination of Rock Permeability" (Determination Method). Measure the permeability of the reservoir core after damage caused by injecting a foaming agent solution of 1 PV or higher.

[0029] Testing revealed that the surface tension of the low-emulsification foaming agent in this embodiment was 20.5 mN / m, the interfacial tension with crude oil was 0.012 mN / m, the contact angle between the foaming agent and water was 125°, and the contact angle with oil was 75°. The initial foam height of the low-emulsification foaming agent was 18.9 cm, the foam height after 5 minutes was 17.0 cm, the height was greater than 10.0 cm, the emulsion stability lasted for 6 hours, and the permeability recovery rate of the reservoir core after the injection of 1 PV of low-emulsification foaming agent solution was 69%.

[0030] Example 2

[0031] A reservoir repair and wellbore cleaning agent for natural gas wells comprises: 18 parts by weight of alkyl sulfate, 8 parts by weight of alkyl dimethyl amine oxide, 1 part by weight of fluorocarbon surfactant and 12 parts by weight of stabilizer, with the remainder made up to 100 parts by weight by water.

[0032] The alkyl sulfate is chemically pure potassium dodecyl sulfate;

[0033] The alkyl dimethyl amine oxide is chemically pure tetradecyl dimethyl amine oxide;

[0034] The fluorocarbon surfactant is polyethylene glycol 500 of perfluorooctanoic acid with a chemical purity of 500 or higher.

[0035] The stabilizer is chemically pure glycerol.

[0036] The foaming agent prepared for use in the natural gas well reservoir repair-wellbore cleaning integrated agent in this embodiment is referred to as ASF-2.

[0037] During preparation, 18 parts by weight of alkyl sulfate and 12 parts by weight of stabilizer are added to 12 parts by weight of water and stirred until homogeneous. Then, 8 parts by weight of alkyl dimethyl amine oxide and 1 part of fluorocarbon surfactant are added sequentially, and finally, water is added to a final volume of 100 parts by weight. The reagents are added while stirring during the preparation process, ensuring each reagent is completely dissolved or evenly dispersed before adding the next, until a homogeneous solution is formed. This is the integrated reservoir repair and wellbore cleaning agent for natural gas wells.

[0038] When applying, prepare 0.7% low-emulsification foaming agent with gas well water and stir until uniformly mixed. Surface tension is measured according to the following standards: SY / T 5370-2018 "Method for Determination of Surface and Interfacial Tension" (Petroleum and Natural Gas Industry Standard); Contact angle on the rock surface is measured according to SY / T 5153.3-1995 "Method for Determination of Contact Angle of Reservoir Rock Wettability" (Oil Reservoir Rock Wettability Determination); foaming performance is evaluated according to SY / T 6465-2000 "Evaluation Method for Foaming Agents for Foam Drainage and Gas Production" (Foaming Performance Evaluation Method); stability with gas well condensate emulsion is evaluated according to SY / T 5761-2016 "Performance Evaluation Method for Surfactants Used for Oil Displacement" (Oil Displacement) (Standard Method); and permeability of reservoir cores after damage caused by injection of the above-mentioned foaming agent solution at a concentration of 1 PV or higher is determined according to GB / T 29172-2012 "Method for Determination of Rock Permeability".

[0039] Testing revealed that the surface tension of the low-emulsification foaming agent in this embodiment was 20.9 mN / m, the interfacial tension with crude oil was 0.018 mN / m, the contact angle between the foaming agent and water was 110°, and the contact angle with oil was 68°. The initial foam height of the low-emulsification foaming agent was 18.1 cm, and the foam height after 5 minutes was 16.8 cm, exceeding 10.0 cm. The emulsion stability lasted for 5 hours, and the permeability recovery rate of the reservoir core after damage caused by injecting 1.2 PV of the low-emulsification foaming agent solution was 65%.

[0040] Example 3

[0041] A reservoir repair and wellbore cleaning agent for natural gas wells comprises: 20 parts by weight of alkyl sulfate, 6 parts by weight of alkyl dimethyl amine oxide, 2 parts by weight of fluorocarbon surfactant and 15 parts by weight of stabilizer, with the remainder made up to 100 parts by weight by water.

[0042] The alkyl sulfate is analytical grade sodium octadecyl sulfate;

[0043] The alkyl dimethyl amine oxide is analytically pure tetradecyl dimethyl amine oxide;

[0044] The fluorocarbon surfactant is polyethylene glycol 6000 of industrial-grade purity perfluorooctanoic acid.

[0045] The stabilizer is analytical grade ethylene glycol.

[0046] The foaming agent prepared for use in the natural gas well reservoir repair-wellbore cleaning integrated agent in this embodiment is referred to as ASF-3.

[0047] To prepare the solution, add 20 parts by weight of alkyl sulfate and 15 parts by weight of stabilizer to 30 parts by weight of water and stir until homogeneous. Then, add 6 parts by weight of alkyl dimethyl amine oxide and 2 parts by weight of fluorocarbon surfactant, and finally add water to a final volume of 100 parts by weight. During preparation, add the reagents while stirring, ensuring each reagent is completely dissolved or evenly dispersed before adding the next, until a homogeneous solution is formed. This is the integrated reservoir repair and wellbore cleaning agent for natural gas wells.

[0048] When applying, prepare 0.6% of the low-emulsification foaming agent with gas well water and stir until uniformly mixed. Surface tension is measured according to the following standards: SY / T 5370-2018 "Method for Determination of Surface and Interfacial Tension" (Petroleum and Natural Gas Industry Standard); Contact angle on the rock surface is measured according to SY / T 5153.3-1995 "Method for Determination of Contact Angle of Reservoir Rock Wettability" (Oil Reservoir Rock Wettability Determination); foaming performance is evaluated according to SY / T 6465-2000 "Evaluation Method for Foaming Agents for Foam Drainage and Gas Production" (Evaluation Method); stability with gas well condensate emulsion is evaluated according to SY / T 5761-2016 "Performance Evaluation Method for Surfactants for Oil Displacement" (Method); and permeability of reservoir cores after damage caused by injection of the above-mentioned foaming agent solution at a concentration of 1 PV or higher is determined according to GB / T 29172-2012 "Method for Determination of Rock Permeability".

[0049] Testing revealed that the surface tension of the low-emulsification foaming agent in this embodiment was 21.0 mN / m, the interfacial tension with crude oil was 0.023 mN / m, the contact angle between the foaming agent and water was 105°, the contact angle with oil was 60°, the initial foam height of the low-emulsification foaming agent was 17.5 cm, the foam height after 5 minutes was 16.8 cm (greater than 10.0 cm), the emulsion stability duration was 5.5 hours, and the permeability recovery rate of the reservoir core after damage caused by injection of 1.4 PV of the low-emulsification foaming agent solution was 70%.

[0050] Example 4

[0051] A reservoir repair and wellbore cleaning agent for natural gas wells comprises: 24 parts by weight of alkyl sulfate, 10 parts by weight of alkyl dimethyl amine oxide, 1 part by weight of fluorocarbon surfactant and 20 parts by weight of stabilizer, with the remainder made up to 100 parts by weight by water.

[0052] The alkyl sulfate is industrial-grade hexadecyl ammonium sulfate;

[0053] The alkyl dimethyl amine oxide is analytically pure octadecyl dimethyl amine oxide;

[0054] The fluorocarbon surfactant is polyethylene glycol 10000 of industrial grade perfluorooctanoic acid.

[0055] The stabilizer is analytical grade glycerol.

[0056] The foaming agent prepared for use in the natural gas well reservoir repair-wellbore cleaning integrated agent in this embodiment is referred to as ASF-4.

[0057] To prepare the solution, add 24 parts by weight of alkyl sulfate and 20 parts by weight of stabilizer to 40 parts by weight of water and stir until homogeneous. Then, add 10 parts by weight of alkyl dimethyl amine oxide and 1 part of fluorocarbon surfactant sequentially. Finally, add water to a final volume of 100 parts by weight. During preparation, add the reagents while stirring, ensuring each reagent is completely dissolved or evenly dispersed before adding the next, until a homogeneous solution is formed. This is the integrated reservoir repair and wellbore cleaning agent for natural gas wells.

[0058] When applying, prepare 0.8% of the low-emulsification foaming agent with gas well water and stir until uniformly mixed. Surface tension is measured according to the following standards: SY / T 5370-2018 "Method for Determination of Surface and Interfacial Tension" (Petroleum and Natural Gas Industry Standard); Contact angle on the rock surface is measured according to SY / T 5153.3-1995 "Method for Determination of Contact Angle of Reservoir Rock Wettability" (Oil Reservoir Rock Wettability Determination); foaming performance is evaluated according to SY / T 6465-2000 "Evaluation Method for Foaming Agents for Gas Production Foam Drainage" (Evaluation Method); stability with gas well condensate emulsion is evaluated according to SY / T 5761-2016 "Performance Evaluation Method for Surfactants for Oil Displacement" (Method); and permeability of reservoir cores after damage caused by injection of the above-mentioned foaming agent solution at a concentration of 1 PV or higher is determined according to GB / T 29172-2012 "Method for Determination of Rock Permeability".

[0059] Testing revealed that the surface tension of the low-emulsification foaming agent in this embodiment was 20.3 mN / m, the interfacial tension with crude oil was 0.010 mN / m, the contact angle between the foaming agent and water was 128°, and the contact angle with oil was 80°. The initial foam height of the low-emulsification foaming agent was 18.4 cm, the foam height after 5 minutes was 17.2 cm, and the height was greater than 10.0 cm. The emulsion stability lasted for 6 hours, and the permeability recovery rate of the reservoir core after the injection of 1 PV of the low-emulsification foaming agent solution was 72%.

[0060] Example 5

[0061] A reservoir repair and wellbore cleaning agent for natural gas wells comprises: 25 parts by weight of alkyl sulfate, 15 parts by weight of alkyl dimethyl amine oxide, 3 parts by weight of fluorocarbon surfactant and 17 parts by weight of stabilizer, with the remainder made up to 100 parts by weight by water.

[0062] The alkyl sulfate is analytical grade potassium octadecyl sulfate;

[0063] The alkyl dimethyl amine oxide is industrial grade hexadecyl dimethyl amine oxide;

[0064] The fluorocarbon surfactant is chemically pure polyethylene glycol 200 of perfluorodecanoic acid.

[0065] The stabilizer is glycerol of industrial grade.

[0066] The foaming agent prepared for use in the natural gas well reservoir repair-wellbore cleaning integrated agent in this embodiment is referred to as ASF-5.

[0067] To prepare the solution, add 25 parts by weight of alkyl sulfate and 17 parts by weight of stabilizer to 34 parts by weight of water and stir until homogeneous. Then, add 15 parts by weight of alkyl dimethyl amine oxide and 3 parts by weight of fluorocarbon surfactant, and finally add water to a final volume of 100 parts by weight. During preparation, add the reagents while stirring, ensuring each reagent is completely dissolved or evenly dispersed before adding the next, until a homogeneous solution is formed. This is the integrated reservoir repair and wellbore cleaning agent for natural gas wells.

[0068] When applying, prepare 0.5% of the low-emulsification foaming agent with gas well water and stir until uniformly mixed. Measure the surface tension according to the following standards: SY / T 5370-2018 "Method for Determination of Surface and Interfacial Tension" (Petroleum and Natural Gas Industry Standard); SY / T 5153.3-1995 "Method for Determination of Contact Angle of Reservoir Rock Wettability" (Method for Determination of Contact Angle); SY / T 6465-2000 "Evaluation Method for Foaming Agents for Foam Drainage and Gas Production" (Evaluation Method); SY / T 5761-2016 "Method for Evaluation of Performance of Surfactants for Oil Displacement" (Evaluation Method); and GB / T 29172-2012 "Method for Determination of Rock Permeability" (Determination Method). Measure the permeability of the reservoir core after damage caused by injecting a foaming agent solution of 1 PV or higher.

[0069] Testing revealed that the surface tension of the low-emulsification foaming agent in this embodiment was 20.4 mN / m, the interfacial tension with crude oil was 0.012 mN / m, the contact angle between the foaming agent and water was 120°, the contact angle with oil was 70°, the initial foam height of the low-emulsification foaming agent was 18.6 cm, the foam height after 5 minutes was 16.9 cm (greater than 10.0 cm), the emulsion stability lasted for 7 hours, and the permeability recovery rate of the reservoir core after damage caused by injection of 1.2 PV of the low-emulsification foaming agent solution was 68%.

[0070] Example 6

[0071] A reservoir repair and wellbore cleaning agent for natural gas wells comprises: 30 parts by weight of alkyl sulfate, 13 parts by weight of alkyl dimethyl amine oxide, 1 part by weight of fluorocarbon surfactant and 18 parts by weight of stabilizer, with the remainder made up to 100 parts by weight by water.

[0072] The alkyl sulfate is industrial-grade sodium octadecyl sulfate;

[0073] The alkyl dimethyl amine oxide is analytically pure dodecyl dimethyl amine oxide;

[0074] The fluorocarbon surfactant is analytical grade polyethylene glycol 5000 of perfluorodecanoic acid;

[0075] The stabilizer is industrial-grade ethylene glycol.

[0076] The foaming agent prepared for use in the natural gas well reservoir repair-wellbore cleaning integrated agent in this embodiment is referred to as ASF-6.

[0077] To prepare the solution, add 30 parts by weight of alkyl sulfate and 18 parts by weight of stabilizer to 36 parts by weight of water and stir until homogeneous. Then, add 13 parts by weight of alkyl dimethyl amine oxide and 1 part of fluorocarbon surfactant sequentially. Finally, add water to a final volume of 100 parts by weight. During preparation, add the reagents while stirring, ensuring each reagent is completely dissolved or evenly dispersed before adding the next, until a homogeneous solution is formed. This is the integrated reservoir repair and wellbore cleaning agent for natural gas wells.

[0078] When applying, prepare 0.5% of the low-emulsification foaming agent with gas well water and stir until uniformly mixed. Measure the surface tension according to the following standards: SY / T 5370-2018 "Method for Determination of Surface and Interfacial Tension" (Petroleum and Natural Gas Industry Standard); SY / T 5153.3-1995 "Method for Determination of Contact Angle of Reservoir Rock Wettability" (Method for Determination of Contact Angle); SY / T 6465-2000 "Evaluation Method for Foaming Agents for Foam Drainage and Gas Production" (Evaluation Method); SY / T 5761-2016 "Method for Evaluation of Performance of Surfactants for Oil Displacement" (Evaluation Method); and GB / T 29172-2012 "Method for Determination of Rock Permeability" (Determination Method). Measure the permeability of the reservoir core after damage caused by injecting a foaming agent solution of 1 PV or higher.

[0079] Testing revealed that the surface tension of the low-emulsification foaming agent in this embodiment was 20.6 mN / m, the interfacial tension with crude oil was 0.014 mN / m, the contact angle between the foaming agent and water was 115°, the contact angle with oil was 76°, the initial foam height of the low-emulsification foaming agent was 18.5 cm, the foam height after 5 minutes was 16.8 cm (greater than 10.0 cm), the emulsion stability lasted for 6 hours, and the permeability recovery rate of the reservoir core after damage caused by injection of 1.4 PV of the low-emulsification foaming agent solution was 74%.

[0080] Example 7

[0081] A reservoir repair and wellbore cleaning agent for natural gas wells comprises: 26 parts by weight of alkyl sulfate, 14 parts by weight of alkyl dimethyl amine oxide, 2 parts by weight of fluorocarbon surfactant and 15 parts by weight of stabilizer, with the remainder made up to 100 parts by weight by water.

[0082] The alkyl sulfate is industrial-grade octadecyl ammonium sulfate;

[0083] The alkyl dimethyl amine oxide is analytically pure dodecyl dimethyl amine oxide;

[0084] The fluorocarbon surfactant is ethylene glycol ester 10000 of perfluorodecanoic acid with industrial-grade purity.

[0085] The stabilizer is industrial-grade ethylene glycol.

[0086] The foaming agent prepared for use in the natural gas well reservoir repair-wellbore cleaning integrated agent in this embodiment is referred to as ASF-7.

[0087] To prepare the solution, add 26 parts by weight of alkyl sulfate and 15 parts by weight of stabilizer to 15 parts by weight of water and stir until homogeneous. Then, add 10 parts by weight of alkyl dimethyl amine oxide and 2 parts by weight of fluorocarbon surfactant, and finally add water to a final volume of 100 parts by weight. During preparation, add the reagents while stirring, ensuring each reagent is completely dissolved or evenly dispersed before adding the next, until a homogeneous solution is formed. This is the integrated reservoir repair and wellbore cleaning agent for natural gas wells.

[0088] When applying, prepare 0.8% of the low-emulsification foaming agent with gas well water and stir until uniformly mixed. Surface tension is measured according to the following standards: SY / T 5370-2018 "Method for Determination of Surface and Interfacial Tension" (Petroleum and Natural Gas Industry Standard); Contact angle on the rock surface is measured according to SY / T 5153.3-1995 "Method for Determination of Contact Angle of Reservoir Rock Wettability" (Oil Reservoir Rock Wettability Determination); foaming performance is evaluated according to SY / T 6465-2000 "Evaluation Method for Foaming Agents for Gas Production Foam Drainage" (Evaluation Method); stability with gas well condensate emulsion is evaluated according to SY / T 5761-2016 "Performance Evaluation Method for Surfactants for Oil Displacement" (Method); and permeability of reservoir cores after damage caused by injection of the above-mentioned foaming agent solution at a concentration of 1 PV or higher is determined according to GB / T 29172-2012 "Method for Determination of Rock Permeability".

[0089] Testing revealed that the surface tension of the low-emulsification foaming agent in this embodiment was 21.2 mN / m, the interfacial tension with crude oil was 0.019 mN / m, the contact angle between the foaming agent and water was 122°, and the contact angle with oil was 77°. The initial foam height of the low-emulsification foaming agent was 18.3 cm, the foam height after 5 minutes was 17.1 cm, and the height was greater than 10.0 cm. The emulsion stability lasted for 6.5 hours, and the permeability recovery rate of the reservoir core after damage caused by the injection of 1.4 PV of the low-emulsification foaming agent solution was 72%.

[0090] Example 8

[0091] A reservoir repair and wellbore cleaning agent for natural gas wells comprises: 16 parts by weight of alkyl sulfate, 13 parts by weight of alkyl dimethyl amine oxide, 1 part by weight of fluorocarbon surfactant and 20 parts by weight of stabilizer, with the remainder made up to 100 parts by weight by water.

[0092] The alkyl sulfate is analytical grade potassium hexadecyl sulfate;

[0093] The alkyl dimethyl amine oxide is chemically pure tetradecyl dimethyl amine oxide;

[0094] The fluorocarbon surfactant is analytical grade polyethylene glycol 5000 of perfluorohexanoic acid;

[0095] The stabilizer is glycerol of industrial grade.

[0096] The foaming agent prepared for use in the natural gas well reservoir repair-wellbore cleaning integrated agent in this embodiment is referred to as ASF-8.

[0097] To prepare the solution, add 16 parts by weight of alkyl sulfate and 20 parts by weight of stabilizer to 20 parts by weight of water and stir until homogeneous. Then, add 13 parts by weight of alkyl dimethyl amine oxide and 1 part of fluorocarbon surfactant sequentially. Finally, add water to a final volume of 100 parts by weight. During preparation, add the reagents while stirring, ensuring each reagent is completely dissolved or evenly dispersed before adding the next, until a homogeneous solution is formed. This is the integrated reservoir repair and wellbore cleaning agent for natural gas wells.

[0098] When applying, prepare 1% low-emulsification foaming agent with gas well water and stir until uniformly mixed. Surface tension is measured according to the following standards: SY / T 5370-2018 "Method for Determination of Surface and Interfacial Tension" (Petroleum and Natural Gas Industry Standard); Contact angle on the rock surface is measured according to SY / T 5153.3-1995 "Method for Determination of Contact Angle of Reservoir Rock Wettability" (Method for Determination of Contact Angle); foaming performance is evaluated according to SY / T 6465-2000 "Evaluation Method for Foaming Agents for Foam Drainage and Gas Production" (Method for Evaluation of Foaming Agents for Foam Drainage and Gas Production); stability with gas well condensate emulsion is evaluated according to SY / T 5761-2016 "Method for Evaluation of Performance of Surfactants for Oil Displacement" (Method for Evaluation of Surfactant Performance); and permeability of reservoir cores after damage caused by injection of the above-mentioned foaming agent solution at a concentration of 1.2 PV or higher is determined according to GB / T 29172-2012 "Method for Determination of Rock Permeability".

[0099] Testing revealed that the surface tension of the low-emulsification foaming agent in this embodiment was 20.8 mN / m, the interfacial tension with crude oil was 0.020 mN / m, the contact angle between the foaming agent and water was 112°, and the contact angle with oil was 69°. The initial foam height of the low-emulsification foaming agent was 18.1 cm, the foam height after 5 minutes was 16.8 cm (greater than 10.0 cm), the emulsion stability lasted for 6 hours, and the permeability recovery rate of the reservoir core after damage caused by injection of 1.4 PV of the low-emulsification foaming agent solution was 70%.

[0100] Example 9

[0101] A reservoir repair and wellbore cleaning agent for natural gas wells comprises: 22 parts by weight of alkyl sulfate, 11 parts by weight of alkyl dimethyl amine oxide, 3 parts by weight of fluorocarbon surfactant and 16 parts by weight of stabilizer, with the remainder made up to 100 parts by weight by water.

[0102] The alkyl sulfate is industrial-grade sodium hexadecyl sulfate;

[0103] The alkyl dimethyl amine oxide is industrial-grade hexadecyl dimethyl amine oxide;

[0104] The fluorocarbon surfactant is analytical grade polyethylene glycol 10000 of perfluorohexanoic acid;

[0105] The stabilizer is industrial-grade ethylene glycol.

[0106] The foaming agent prepared for use in the natural gas well reservoir repair-wellbore cleaning integrated agent in this embodiment is referred to as ASF-9.

[0107] During preparation, 22 parts by weight of alkyl sulfate and 16 parts by weight of stabilizer are added to 32 parts by weight of water and stirred until homogeneous. Then, 11 parts by weight of alkyl dimethyl amine oxide and 3 parts by weight of fluorocarbon surfactant are added sequentially. Finally, water is added to a final volume of 100 parts by weight. The reagents are added while stirring, ensuring each reagent is completely dissolved or evenly dispersed before adding the next, until a homogeneous solution is formed. This is the integrated reservoir repair and wellbore cleaning agent for natural gas wells.

[0108] When applying, prepare 0.7% low-emulsification foaming agent with gas well water and stir until uniformly mixed. Surface tension is measured according to the following standards: SY / T 5370-2018 "Method for Determination of Surface and Interfacial Tension" (Petroleum and Natural Gas Industry Standard); Contact angle on the rock surface is measured according to SY / T 5153.3-1995 "Method for Determination of Contact Angle of Reservoir Rock Wettability" (Oil Reservoir Rock Wettability Determination); foaming performance is evaluated according to SY / T 6465-2000 "Evaluation Method for Foaming Agents for Foam Drainage and Gas Production" (Foaming Performance Evaluation Method); stability with gas well condensate emulsion is evaluated according to SY / T 5761-2016 "Performance Evaluation Method for Surfactants Used for Oil Displacement" (Oil Displacement) (Standard Method); and permeability of reservoir cores after damage caused by injection of the above-mentioned foaming agent solution at a concentration of 1 PV or higher is determined according to GB / T 29172-2012 "Method for Determination of Rock Permeability".

[0109] Testing revealed that the surface tension of the low-emulsification foaming agent in this embodiment was 20.7 mN / m, the interfacial tension with crude oil was 0.021 mN / m, the contact angle between the foaming agent and water was 111°, and the contact angle with oil was 81°. The initial foam height of the low-emulsification foaming agent was 18.7 cm, the foam height after 5 minutes was 17.0 cm, the height was greater than 10.0 cm, the emulsion stability lasted for 7 hours, and the permeability recovery rate of the reservoir core after damage caused by the injection of 1.4 PV of the low-emulsification foaming agent solution was 67%.

[0110] The results of the foaming and emulsification effects of the low-emulsification foaming agents in Examples 1-9 are shown in Table 1.

[0111] Table 1. Foaming and emulsifying effects of low-emulsifying foaming agents in the examples.

[0112]

[0113] As can be seen from the table above, the integrated reservoir repair and wellbore cleaning agent for natural gas wells described in this invention has good foaming properties and low emulsification. When 0.5-1% of the low-emulsification foaming agent is prepared with gas well water, its foaming performance is evaluated according to SY / T 6465-2000 "Evaluation Method for Foaming Agents for Foam Drainage and Gas Production," with a Roche foam height of 16.8-18.9 cm. Its stability with gas well condensate emulsion is evaluated according to SY / T 5761-2016 "Performance Evaluation Method for Surfactants for Oil Displacement," with the emulsion stability lasting no more than 7 hours. According to GB / T 29172-2012 "Method for Determining Rock Permeability," the permeability of the reservoir core after injection of more than 1 PV of the above-mentioned foaming agent solution can recover more than 65%.

[0114] The foaming and emulsification effects of each component used in Example 1 were tested using the same method as the monoclonal agent test in Example 1. The test results are shown in Table 2. Meanwhile, the foaming and emulsification effects of the components used in Examples 2-9 were also tested using the same method as the monoclonal agent test in Example 1. The test results are shown in Tables 3-10.

[0115] Table 2. Foaming and emulsifying effects of each component added in Example 1

[0116]

[0117] Table 3. Foaming and emulsifying effects of each component added in Example 2

[0118]

[0119] Table 4. Foaming and emulsifying effects of each component added in Example 3

[0120]

[0121] Table 5. Foaming and emulsifying effects of each component added in Example 4

[0122]

[0123] Table 6. Foaming and emulsifying effects of each component added in Example 5

[0124]

[0125] Table 7. Foaming and emulsifying effects of each component added in Example 6

[0126]

[0127] Table 8. Foaming and emulsifying effects of each component added in Example 7

[0128]

[0129] Table 9. Foaming and emulsifying effects of each component added in Example 8

[0130]

[0131] Table 10. Foaming and emulsifying effects of each component added in Example 9

[0132]

[0133] A comparison of the data in Tables 2-10 and 1 shows that in Examples 1-9, the surface tension and other indicators of each individual component showed a certain degree of improvement compared to the low-emulsification foaming agent. However, in terms of key foaming performance and low emulsification, each individual component was significantly inferior to the foaming agent. Furthermore, the concentration of each individual component was higher than that of the foaming agent. In summary, it is clear that the individual components failed to achieve a synergistic effect of "1+1>2," and it is necessary to use a compound agent to simultaneously improve both foam drainage and low-emulsification effects.

[0134] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or terminal device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or terminal device. Unless otherwise specified, an element defined by the phrase "comprising..." or "including..." does not exclude the presence of additional elements in the process, method, article, or terminal device that includes said element. Additionally, in this document, "greater than," "less than," "exceeding," etc., are understood to exclude the stated number; "above," "below," "within," etc., are understood to include the stated number.

[0135] It should be noted that although the above embodiments have been described herein, this does not limit the scope of patent protection for this invention. Therefore, any changes and modifications made to the embodiments described herein based on the innovative concept of this invention, or any equivalent structural or procedural transformations made using the content of this specification, directly or indirectly applying the above technical solutions to other related technical fields, are all included within the scope of patent protection for this invention.

Claims

1. A reservoir repair and wellbore cleaning integrated agent for natural gas wells, characterized in that: It comprises the following components in parts by weight: 15-30 parts of alkyl sulfate, 5-15 parts of alkyl dimethyl amine oxide, 1-3 parts of fluorocarbon surfactant, 10-20 parts of stabilizer, and the remainder is made up to 100 parts by weight with water.

2. The integrated reservoir repair and wellbore cleaning agent for natural gas wells according to claim 1, characterized in that: The alkyl sulfate is one of the following: sodium dodecyl sulfate, potassium dodecyl sulfate, ammonium dodecyl sulfate, sodium hexadecyl sulfate, potassium hexadecyl sulfate, ammonium hexadecyl sulfate, sodium octadecyl sulfate, potassium octadecyl sulfate, and ammonium octadecyl sulfate.

3. The integrated reservoir repair and wellbore cleaning agent for natural gas wells according to claim 1, characterized in that: The alkyl dimethyl amine oxide is one of the following: dodecyl dimethyl amine oxide, tetradecyl dimethyl amine oxide, hexadecyl dimethyl amine oxide, or octadecyl dimethyl amine oxide.

4. The integrated reservoir repair and wellbore cleaning agent for natural gas wells according to claim 1, characterized in that: The fluorocarbon surfactant is a polyethylene glycol ester of perfluorohexanoic acid, perfluorooctanoic acid, or perfluorodecanoic acid, with a degree of polymerization of 200-10000.

5. The integrated reservoir repair and wellbore cleaning agent for natural gas wells according to claim 1, characterized in that: The stabilizer is glycerol or ethylene glycol.

6. The preparation method of the integrated reservoir repair and wellbore cleaning agent for natural gas wells according to any one of claims 1-5, characterized in that: Add 15-30 parts by weight of alkyl sulfate and 10-20 parts by weight of stabilizer to water with a weight of 1-2 times that of stabilizer and stir until homogeneous. Then add 5-15 parts by weight of alkyl dimethyl amine oxide and 1-3 parts by weight of fluorocarbon surfactant. Finally, add water to 100 parts by weight and mix thoroughly. The resulting solution is the integrated reservoir repair and wellbore cleaning agent for natural gas wells.

7. The preparation method of the integrated reservoir repair and wellbore cleaning agent for natural gas wells according to claim 6, characterized in that: It includes the following steps: When adding 5-15 parts by weight of alkyl dimethyl amine oxide and 1-3 parts by weight of fluorocarbon surfactant, the alkyl dimethyl amine oxide is added while stirring. After the alkyl dimethyl amine oxide is completely dissolved or evenly dispersed, the fluorocarbon surfactant is added, and stirring is continued to form a uniform drug solution.

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