Composite plugging removing agent for shale gas reservoir and preparation method thereof

Abstract

This invention discloses a composite unblocking agent for shale gas reservoirs and its preparation method. The composite unblocking agent comprises the following raw materials in parts by weight: 5-15 parts oxidant, 0.1-1 parts corrosion inhibitor, 1-5 parts buffer, 1-5 parts co-solvent, 5-15 parts scale remover, 1-5 parts synergist, 1-5 parts dispersant, 0.1-1 parts regulator, 10-20 parts organic solvent, 0.1-0.5 parts gelling agent, and 50-70 parts water. This composite unblocking agent contains multiple unblocking components, can be used to unblock different types of plugs, and forms a synergistic effect, significantly improving the unblocking effect and rate while also increasing reservoir pressure and production. It is suitable for large-scale application in shale gas reservoir unblocking treatment.

Description

Technical Field

[0001] This invention relates to the field of oil and gas extraction technology, specifically to shale gas development technology, and particularly to a composite unblocking agent for shale gas reservoirs and its preparation method. Background Technology

[0002] Shale gas is a type of natural gas distributed in shale reservoirs, possessing enormous resource potential and economic value, and is an important component of future energy. However, due to the unique characteristics of shale reservoirs, such as low permeability, low porosity, and complex fracture networks, shale gas extraction is quite challenging, necessitating the use of hydraulic fracturing technology to increase reservoir permeability and improve gas production. However, while using hydraulic fracturing to increase reservoir permeability, several problems arise, such as low fracturing fluid recovery rates, the environmental impact of additives in the fracturing fluid, and reactions between the fracturing fluid and organic and inorganic matter in the reservoir. These problems can lead to the formation of various plugging materials in the reservoir, such as bitumen, wax, resin, calcium carbonate, calcium sulfate, and silicates. These plugging materials clog fractures and pores in the reservoir, reducing permeability and porosity, affecting gas flow and production, causing a drop in reservoir pressure and production, and even leading to reservoir failure and abandonment.

[0003] To address reservoir plugging issues, several unblocking agents have been developed and applied, such as oxidants, acidifiers, enzymes, and microbial agents. These agents primarily work through chemical reactions, physical processes, and biological mechanisms to destroy and eliminate plugging materials in the reservoir, restoring its permeability and increasing pressure and production. However, these unblocking agents also have some drawbacks, such as slow reaction rates, poor reaction effects, demanding reaction conditions, numerous reaction byproducts, high reaction costs, low reaction safety, and poor environmental impact. These shortcomings significantly limit the widespread application and promotion of existing unblocking agents.

[0004] Therefore, there is an urgent need for a new type of unblocking agent that can quickly, efficiently, safely, and environmentally unblock shale gas reservoirs under a wide range of applicable temperature and pressure conditions, thereby increasing reservoir pressure and production, extending reservoir life, and reducing extraction costs and risks. Summary of the Invention

[0005] The purpose of this invention is to address the aforementioned shortcomings of existing unblocking agents by proposing a composite unblocking agent for shale gas reservoirs and its preparation method.

[0006] To achieve the above-mentioned objective, this invention provides a composite unblocking agent for shale gas reservoirs, comprising the following raw materials in parts by weight: 5-15 parts of oxidant, 0.1-1 parts of corrosion inhibitor, 1-5 parts of buffer, 1-5 parts of co-solvent, 5-15 parts of scale remover, 1-5 parts of synergist, 1-5 parts of dispersant, 0.1-1 parts of regulator, 10-20 parts of organic solvent, 0.1-0.5 parts of gelling agent, and 50-70 parts of water.

[0007] This invention provides a composite unblocking agent for shale gas reservoirs, containing multiple unblocking components. It not only reacts with organic and inorganic matter in shale gas reservoirs under high temperature and pressure conditions to produce large amounts of gas and water, thereby destroying the sealing materials and achieving unblocking, but also reacts with organic and inorganic matter in shale gas reservoirs under low temperature and pressure conditions through complexation, decomposition, and dissolution reactions, thereby eliminating sediments, scale, and colloids in the reservoir and enhancing the unblocking effect. Simultaneously, the contained organic solvent can dissolve, diffuse, and permeate with organic and inorganic matter in shale gas reservoirs within a wide applicable temperature and pressure range. The compound unblocking agent of this invention has a permeability-enhancing effect, thereby increasing the effective porosity and permeability of the reservoir and further enhancing the unblocking effect. The gelling agent it contains can undergo a cross-linking reaction with polymer unblocking agents and multifunctional formation unblocking agents under high temperature and pressure conditions, forming a gel with high elasticity and high sealing properties. This gel can effectively fill and seal fractures and pores in the reservoir, preventing gas leakage and loss, and increasing reservoir pressure and production. The compound unblocking agent of this invention contains multiple unblocking components, which can be used to unblock different types of plugs, and form a synergistic effect, significantly improving the unblocking effect and rate while also increasing reservoir pressure and production. It is suitable for large-scale application in the unblocking treatment of shale gas reservoirs.

[0008] The oxidant provides oxidizing power and can react with organic and inorganic matter in the shale gas reservoir to produce a large amount of gas and water, thereby destroying the plugging material in the reservoir and achieving the purpose of unblocking. Preferably, the oxidant is at least one of sodium persulfate, potassium persulfate, ammonium persulfate, and hydrogen peroxide. The preferred oxidant can provide sufficient oxidizing power and has good thermal stability and safety.

[0009] The corrosion inhibitor can effectively protect the metal materials of the reservoir and pipeline and prevent corrosion caused by oxidants; preferably, the corrosion inhibitor is at least one of benzotriazole, pyridine, and imidazole.

[0010] The buffer can adjust the pH value of the unblocking agent and maintain suitable reaction conditions for the unblocking agent; preferably, the buffer is at least one of sodium carbonate, potassium carbonate, and sodium phosphate.

[0011] The co-solvent can increase the solubility and flowability of the unblocking agent, reduce its viscosity and friction coefficient, and improve its injection efficiency; preferably, the co-solvent is at least one of polyethylene glycol, polypropylene glycol, and polyvinylpyrrolidone.

[0012] The descaling agent can effectively remove calcium carbonate, calcium sulfate, and silicate inorganic scale from the reservoir; preferably, the descaling agent is at least one of polycarboxylic acid, polyphosphoric acid, and polyacrylic acid; the preferred descaling agent has excellent descaling effect, good biodegradability, and environmental friendliness.

[0013] The synergist can effectively reduce the surface tension and contact angle of the unblocking agent, increase the wettability and permeability of the unblocking agent to the reservoir, and improve its unblocking effect; preferably, the synergist is at least one of sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, and dodecyltrimethylammonium bromide.

[0014] The dispersant can effectively disperse and suspend solid particles in the unblocking agent, preventing them from settling and agglomerating, and improving their stability and uniformity; preferably, the dispersant is at least one of polyacrylamide, polyvinyl alcohol, and sodium polyacrylate.

[0015] The regulator can effectively adjust the pH value of the unblocking agent and maintain suitable reaction conditions for the unblocking agent; preferably, the regulator is at least one of citric acid, acetic acid, and lactic acid.

[0016] The organic solvent can effectively dissolve organic matter in the reservoir and improve the unblocking effect; preferably, the organic solvent is at least one of ethanol, methanol, isopropanol, and acetone; preferably, the organic solvent is a mixed solution of ethanol, methanol, isopropanol, and acetone in a mass ratio of 5-10:2-5:1-3:1-2; the preferred organic solvent can effectively dissolve asphalt, wax, and resin organic matter in the reservoir, and at the same time has good volatility and biodegradability, and will not cause secondary pollution to the reservoir.

[0017] The gelling agent can undergo a cross-linking reaction with the unblocking agent raw material under certain conditions to form a gel with high elasticity and high sealing properties, effectively filling and sealing cracks and pores in the reservoir, preventing gas leakage and loss, and improving reservoir pressure and production; preferably, the gelling agent is at least one of aluminum sulfate or ferric sulfate; the preferred gelling agent can provide sufficient cross-linking ability, while having good thermal stability and safety.

[0018] Preferably, the pH value of the composite unblocking agent is 9.0-11.0.

[0019] Preferably, in the composite unblocking agent, the weight ratio of organic solvent to water is 1:4; with this preferred ratio, the unblocking agent has better solubility, wettability, and permeability, resulting in a better unblocking effect.

[0020] To achieve the above-mentioned objective, this invention further provides a method for preparing a composite unblocking agent for shale gas reservoirs, comprising the following steps:

[0021] (1) The oxidant, corrosion inhibitor, buffer, cosolvent, descaling agent, synergist, dispersant and regulator are mixed to obtain a first mixture; the organic solvent is mixed with water to obtain a second mixture;

[0022] (2) Add the first mixture to the second mixture, stir and mix to dissolve, and obtain the composite unblocking agent for shale gas reservoirs of the present invention.

[0023] Preferably, in step (2), the stirring speed during stirring and dissolving is 100-200 rpm, the dissolving temperature is 40-60℃, and the stirring and dissolving time is 20-30 min; the preferred parameter conditions result in faster dissolving speed and more uniform dissolving.

[0024] To achieve the above-mentioned objectives, this invention further provides a method for unblocking shale gas reservoirs using a composite unblocking agent, comprising the following steps:

[0025] S1 obtains the geological parameters of the gas well to be unblocked;

[0026] Based on the geological parameters of the gas well, S2 uses mathematical models and optimization algorithms to calculate the optimal formula and injection parameters of the composite unblocking agent.

[0027] S3 formulated a composite unblocking agent for rock gas reservoirs according to the optimal formula of the unblocking agent, and diluted it with water to obtain the unblocking agent working solution;

[0028] S4 According to the optimal injection parameters obtained in step S2, the unblocking agent working fluid is injected into the shale gas reservoir of the gas well to be unblocked.

[0029] After well sealing and fluid drainage, S5 completed the unblocking of the shale gas reservoir.

[0030] In step S1, the geological parameters include the reservoir's temperature, pressure, permeability, and porosity.

[0031] In step S2, the mathematical model is based on the reservoir's seepage equation and reaction kinetic equation, used to describe the migration and reaction process of the composite unblocking agent in the reservoir, as well as the changes in reservoir pressure and production, specifically:

[0032]

[0033] Where p is the reservoir pressure; t is time; φ is the partial derivative function, representing the rate of change of p with respect to t; k is the reservoir permeability; μ is the viscosity of the unblocking agent; φ is the reservoir porosity. It is the Laplace operator; q is the reservoir gas production; S p The pressure source term refers to the pressure change brought to the reservoir after the injection of the unblocking agent; x is the displacement of any point in space; c i is the concentration of the i-th component in the unblocking agent; u is the flow rate of the unblocking agent; r i S is the reaction rate of the i-th component of the unblocking agent; i It is the source term of the i-th component, referring to the component change brought to the reservoir after flowing into it.

[0034] Preferably, in step (2), the optimization algorithm is based on genetic algorithm and simulated annealing algorithm to determine the optimal ratio and injection parameters of the composite unblocking agent, so as to achieve the maximum unblocking effect and the minimum cost. The specific steps include:

[0035] A. Initialize the formulation and injection parameters of a composite unblocking agent as individuals in a population. Represent each individual in the population using binary encoding. The length of the encoding is n, where n is the total number of components and injection parameters.

[0036] B. For each individual, calculate the corresponding component and injection parameter values ​​according to its code, and then substitute them into the mathematical model to solve the changes in reservoir pressure and gas production, as well as the cost of composite unblocking agent. Based on these results, calculate its fitness function value as an evaluation index of its optimization objective.

[0037] C. Based on the fitness function value, a selection operation is performed on the population using the roulette wheel method, retaining 10 excellent individuals and eliminating 10 inferior individuals;

[0038] D. Perform crossover on the population using the single-point crossover method. Randomly select two individuals, randomly select a crossover point, and exchange the component codes of the two individuals to generate two new individuals.

[0039] E. Perform mutation operations on the population using simulated annealing. Randomly select an individual and a mutation point, and change the code of the mutation point with probability to generate a new individual.

[0040] F. Determine if the new individual meets the termination condition. If it does, output the optimal component and injection parameters and end the algorithm. If it does not meet the condition, return to step B and continue the iterative calculation.

[0041] Preferably, the fitness function is f(x) = a + bc, where f(x) is the fitness function value, a is the normalized pressure value for each individual, b is the normalized gas production value for each individual, and c is the normalized cost of the composite unblocking agent for each individual.

[0042] Preferably, the termination condition includes the maximum number of iterations or the minimum change in the fitness function.

[0043] Preferably, the injection parameters include: injection pressure, injection time, and injection flow rate.

[0044] Preferably, in step S3, the dilution ratio with water is 1:9.

[0045] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0046] 1. The present invention provides a composite unblocking agent for shale gas reservoirs that can react with organic and inorganic matter in shale gas reservoirs under high temperature and high pressure conditions to produce a large amount of gas and water, thereby destroying the plugging material in the reservoir and achieving the unblocking effect.

[0047] 2. The composite unblocking agent for shale gas reservoirs of the present invention can undergo complexation, decomposition and dissolution reactions with organic and inorganic matter in shale gas reservoirs under low temperature and low pressure conditions, thereby eliminating sediments, scale and colloidal matter in the reservoir and enhancing the unblocking effect.

[0048] 3. The organic solvent contained in the composite unblocking agent for shale gas reservoirs of the present invention can dissolve, diffuse, and permeate with organic and inorganic matter in shale gas reservoirs under a wide range of applicable temperature and pressure conditions, thereby increasing the effective porosity and permeability of the reservoir.

[0049] 4. The composite unblocking agent for shale gas reservoirs of the present invention contains a gelling agent that can undergo a cross-linking reaction with polymer unblocking agents and multifunctional formation unblocking agents under high temperature and high pressure conditions to form a gel with high elasticity and high sealing properties. This gel can effectively fill and seal cracks and pores in the reservoir, prevent gas leakage and loss, and improve reservoir pressure and production.

[0050] 5. The present invention discloses a method for unblocking shale gas reservoirs using a composite unblocking agent. The method utilizes mathematical models and optimization algorithms to optimize the formulation and injection parameters of the unblocking agent, thereby significantly improving the unblocking effect and reducing the unblocking cost, making it suitable for large-scale application. Detailed Implementation

[0051] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to experimental examples and specific embodiments. However, this should not be construed as limiting the scope of the above-mentioned subject matter of this invention to the following embodiments; all technologies implemented based on the content of this invention fall within the scope of this invention.

[0052] Status of shale gas wells awaiting unblocking:

[0053] Group 1: Located in the Sichuan Basin, the well has a depth of 3000 meters, a temperature of 150℃, a pressure of 30MPa, a reservoir permeability of 0.1mD, a porosity of 5%, and the plugging materials are mainly asphalt, wax, resin, and organic matter.

[0054] Group 2: Located in the Tarim Basin, the well has a depth of 2000 meters, a temperature of 80℃, a pressure of 10MPa, a reservoir permeability of 0.05mD, a porosity of 4%, and the plugging material is mainly calcium carbonate, calcium sulfate, and silicate inorganic matter.

[0055] Group 3: Located in the Ordos Basin, the well has a depth of 1000 meters, a temperature of 50℃, a pressure of 5MPa, a reservoir permeability of 0.02mD, a porosity of 3%, and the plugging materials are mainly asphalt, wax, resin, and organic matter.

[0056] Example 1:

[0057] The method for unblocking includes the following steps:

[0058] S1 obtains the geological parameters of the gas well to be unblocked;

[0059] Based on the geological parameters of the gas well, S2 uses mathematical models and optimization algorithms to calculate the optimal formula and injection parameters of the unblocking agent.

[0060] The mathematical model is as follows:

[0061]

[0062] Where p is the reservoir pressure; t is time; φ is the partial derivative function, representing the rate of change of p with respect to t; k is the reservoir permeability; μ is the viscosity of the unblocking agent; φ is the reservoir porosity. It is the Laplace operator; q is the reservoir gas production; S p The pressure source term refers to the pressure change brought to the reservoir after the injection of the unblocking agent; x is the displacement of any point in space; c i is the concentration of the i-th component in the unblocking agent; u is the flow rate of the unblocking agent; r i S is the reaction rate of the i-th component of the unblocking agent; i It is the source term of the i-th component, which refers to the component change brought to the reservoir after flowing into it;

[0063] The optimized algorithm is as follows:

[0064] A. Initialize a compound unblocking agent formulation (5 parts oxidant, 0.1 parts corrosion inhibitor, 1 part buffer, 1 part co-solvent, 5 parts scale remover, 1 part synergist, 1 part dispersant, 0.1 part regulator, 10 parts organic solvent, 0.1 parts gelling agent, 50 parts water) and injection parameters (injection pressure 30 MPa, injection time 2 h, injection flow rate 1 m³ / h). 3 / min) is an individual in the population. Each individual in the population is represented by a binary code with a length of n, where n is the total number of components and injection parameters;

[0065] B. For each individual, calculate the corresponding component and injection parameter values ​​according to its code, and then substitute them into the mathematical model to solve the changes in reservoir pressure and gas production, as well as the cost of composite unblocking agent. Based on these results, calculate its fitness function value as an evaluation index of its optimization objective.

[0066] C. Based on the fitness function value, a selection operation is performed on the population using the roulette wheel method, retaining 10 excellent individuals and eliminating 10 inferior individuals;

[0067] D. Perform crossover on the population using the single-point crossover method. Randomly select two individuals, randomly select a crossover point, and exchange the component codes of the two individuals to generate two new individuals.

[0068] E. Perform mutation operations on the population using simulated annealing. Randomly select an individual and a mutation point, and change the code of the mutation point with probability to generate a new individual.

[0069] F. Determine if the new individual meets the termination condition. If it does, output the optimal component and injection parameters and end the algorithm. If it does not meet the condition, return to step B and continue the iterative calculation.

[0070] S3 formulated a composite unblocking agent for rock and gas reservoirs according to the optimal formula of the unblocking agent, and diluted it with water at a ratio of 1:9 to obtain the unblocking agent working solution.

[0071] S4 According to the optimal injection parameters obtained in step S2, the unblocking agent working fluid is injected into the shale gas reservoir of the gas well to be unblocked.

[0072] After simmering (48 hours) and draining the fluid, S5 completed the unblocking of the shale gas well.

[0073] Based on the condition of the shale gas well to be unblocked, the optimal unblocking agent formula and injection parameters are obtained using the above unblocking methods, as follows:

[0074] Group 1: The optimal formula for the unblocking agent is: 10 parts sodium persulfate, 0.5 parts benzotriazole, 3 parts sodium carbonate, 1.5 parts polyethylene glycol, 10 parts polycarboxylic acid, 3 parts sodium dodecylbenzenesulfonate, 1 part polyacrylamide, 1 part citric acid, 7.5 parts ethanol, 3.5 parts methanol, 2 parts isopropanol, 2 parts acetone, 0.3 parts aluminum sulfate, and 54.7 parts water; injection parameters include: 2m 3 Injection rate of / min, injection time of 1.5h, injection pressure of 40MPa;

[0075] Group 2: The optimal formula for the unblocking agent is: 5 parts hydrogen peroxide, 0.1 parts pyridine, 1 part sodium phosphate, 3.9 parts polypropylene glycol, 15 parts polycarboxylic acid, 1 part sodium dodecylbenzene sulfate, 2 parts polyvinyl alcohol, 1 part acetic acid, 5 parts ethanol, 2.5 parts methanol, 1.5 parts isopropanol, 1 part acetone, 0.2 parts aluminum sulfate, and 60.8 parts water; injection parameters include: 1m 3 Injection rate of / min, injection time of 1h, injection pressure of 30MPa;

[0076] Group 3: The optimal formula for the unblocking agent is: 15 parts ammonium persulfate, 1 part imidazole, 2 parts potassium carbonate, 2 parts polyvinylpyrrolidone, 5 parts polyphosphoric acid, 2 parts dodecyltrimethylammonium bromide, 1 part sodium polyacrylate, 0.1 parts lactic acid, 20 parts ethanol, 0.4 parts ferric sulfate, and 51.5 parts water; injection parameters include: 0.5m 3 Injection rate: / min; injection time: 0.5h; injection pressure: 15MPa.

[0077] Example 2:

[0078] A composite unblocking agent for shale gas reservoirs comprises the following raw materials in parts by weight: 10 parts sodium persulfate, 0.5 parts benzotriazole, 3 parts sodium carbonate, 1.5 parts polyethylene glycol, 15 parts polycarboxylic acid, 1 part sodium dodecylbenzene sulfate, 2 parts polyvinyl alcohol, 1 part acetic acid, 5 parts ethanol, 2.5 parts methanol, 1.5 parts isopropanol, 1 part acetone, 0.2 parts aluminum sulfate, and 70 parts water.

[0079] The unblocking method includes: diluting the composite unblocking agent with water at a ratio of 1:10 to obtain the unblocking agent working solution; and injecting it according to the following parameters: 1m 3 The unblocking agent working fluid is injected into the shale gas reservoir of the well to be unblocked at a flow rate of / min, an injection time of 1 hour, and an injection pressure of 30MPa. After well shut-in (48 hours) and fluid drainage, the unblocking of the shale gas well is completed.

[0080] Example 3

[0081] A composite unblocking agent for shale gas reservoirs comprises the following raw materials in parts by weight: 15 parts ammonium persulfate, 1 part imidazole, 2 parts potassium carbonate, 2 parts polyvinylpyrrolidone, 10 parts polycarboxylic acid, 3 parts sodium dodecylbenzenesulfonate, 1 part polyacrylamide, 1 part citric acid, 20 parts methanol, 0.3 parts aluminum sulfate, and 50 parts water.

[0082] The unblocking method includes: diluting the composite unblocking agent with water at a ratio of 1:5 to obtain the unblocking agent working solution; and injecting it according to the following parameters: 1m 3 The unblocking agent working fluid is injected into the shale gas reservoir of the well to be unblocked at a flow rate of / min, an injection time of 1 hour, and an injection pressure of 30MPa. After well shut-in (48 hours) and fluid drainage, the unblocking of the shale gas well is completed.

[0083] Comparative Example 1

[0084] The existing unblocking agent consists of: 15 parts ammonium persulfate, 2 parts imidazole, 2 parts each of polyethylene glycol and polypropylene glycol, 12 parts polyacrylic acid, 5 parts each of sodium dodecylbenzenesulfonate and sodium dodecyl sulfate, 2 parts citric acid, 2 parts ethanol, 2 parts methanol, 2 parts isopropanol, 2 parts acetone, and 50 parts water.

[0085] The unblocking method includes: diluting the composite unblocking agent with water at a ratio of 1:10 to obtain the unblocking agent working solution; and injecting it according to the following parameters: 1m 3 The unblocking agent working fluid is injected into the shale gas reservoir of the well to be unblocked at a flow rate of / min, an injection time of 1 hour, and an injection pressure of 30MPa. After well shut-in (48 hours) and fluid drainage, the unblocking of the shale gas well is completed.

[0086] Comparative Example 2

[0087] A composite unblocking agent for shale gas reservoirs comprises the following raw materials in parts by weight: 10 parts sodium persulfate, 0.5 parts benzotriazole, 3 parts sodium carbonate, 1.5 parts polyethylene glycol, 15 parts polycarboxylic acid, 1 part sodium dodecylbenzene sulfate, 2 parts polyvinyl alcohol, 1 part acetic acid, 5 parts ethanol, 2.5 parts methanol, 1.5 parts isopropanol, 1 part acetone, and 70 parts water.

[0088] The unblocking method includes: diluting the composite unblocking agent with water at a ratio of 1:10 to obtain the unblocking agent working solution; and injecting it according to the following parameters: 1m 3 The unblocking agent working fluid is injected into the shale gas reservoir of the well to be unblocked at a flow rate of / min, an injection time of 1 hour, and an injection pressure of 30MPa. After well shut-in (48 hours) and fluid drainage, the unblocking of the shale gas well is completed.

[0089] Comparative Example 3

[0090] A composite unblocking agent for shale gas reservoirs comprises the following raw materials in parts by weight: 10 parts sodium persulfate, 0.5 parts benzotriazole, 3 parts sodium carbonate, 1.5 parts polyethylene glycol, 15 parts polycarboxylic acid, 1 part sodium dodecylbenzene sulfate, 2 parts polyvinyl alcohol, 1 part acetic acid, 0.2 parts aluminum sulfate, and 70 parts water.

[0091] The unblocking method includes: diluting the composite unblocking agent with water at a ratio of 1:10 to obtain the unblocking agent working solution; and injecting it according to the following parameters: 1m 3 The unblocking agent working fluid is injected into the shale gas reservoir of the well to be unblocked at a flow rate of / min, an injection time of 1 hour, and an injection pressure of 30MPa. After well shut-in (48 hours) and fluid drainage, the unblocking of the shale gas well is completed.

[0092] The unblocking agents prepared in the above examples and comparative examples were used to unblock oil and gas wells in groups 1, 2, and 3 in sequence. The unblocking effect and cost were statistically analyzed, and the results are as follows:

[0093] Statistical results of the first group of traffic congestion relief experiments

[0094]

[0095] Statistical results of the second group of traffic congestion relief experiments

[0096]

[0097]

[0098] Statistical results of the third group of traffic congestion relief experiments

[0099]

[0100] Analysis of the above results shows that the composite unblocking agent of the present invention can significantly improve the unblocking effect of gas wells, especially when the unblocking method of the present invention is used, it has a better unblocking effect and can significantly reduce the unblocking cost. The above embodiments only illustrate specific implementation methods of this application, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of protection of this application. It should be noted that for those skilled in the art, several modifications and improvements can be made without departing from the concept of the technical solution of this application, and these all fall within the scope of protection of this application.

Claims

1. A composite unblocking agent for shale gas reservoirs, characterized in that, It comprises the following raw materials in parts by weight: 5-15 parts oxidant, 0.1-1 parts corrosion inhibitor, 1-5 parts buffer, 1-5 parts cosolvent, 5-15 parts descaling agent, 1-5 parts synergist, 1-5 parts dispersant, 0.1-1 parts regulator, 10-20 parts organic solvent, 0.1-0.5 parts gelling agent, and 50-70 parts water.

2. The composite unblocking agent for shale gas reservoirs according to claim 1, characterized in that, The oxidant is at least one of sodium persulfate, potassium persulfate, ammonium persulfate, and hydrogen peroxide; and / or the corrosion inhibitor is at least one of benzotriazole, pyridine, and imidazole; and / or the buffer is at least one of sodium carbonate, potassium carbonate, and sodium phosphate; and / or the co-solvent is at least one of polyethylene glycol, polypropylene glycol, and polyvinylpyrrolidone; and / or the descaling agent is at least one of polycarboxylic acid, polyphosphoric acid, and polyacrylic acid; and / or the synergist is at least one of sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, and dodecyltrimethylammonium bromide; and / or the dispersant is at least one of polyacrylamide, polyvinyl alcohol, and sodium polyacrylate; and / or the regulator is at least one of citric acid, acetic acid, and lactic acid; and / or the organic solvent is at least one of ethanol, methanol, isopropanol, and acetone; and / or the gelling agent is at least one of aluminum sulfate or ferric sulfate.

3. The composite unblocking agent for shale gas reservoirs according to claim 2, characterized in that, The organic solvent is a mixed solution of ethanol, methanol, isopropanol and acetone in a mass ratio of 5-10:2-5:1-3:1-2.

4. The composite unblocking agent for shale gas reservoirs according to claim 1, characterized in that, The pH value of the composite unblocking agent is 9.0-11.

0.

5. The composite unblocking agent for shale gas reservoirs according to claim 1, characterized in that, In the composite unblocking agent, the weight ratio of organic solvent to water is 1:

4.

6. A method for unblocking shale gas reservoirs using the composite unblocking agent described in claims 1-5, characterized in that, Includes the following steps: S1 obtains the geological parameters of the gas well to be unblocked; the geological parameters include the reservoir's temperature, pressure, permeability, and porosity; Based on the geological parameters of the gas well, S2 calculates the optimal formulation and injection parameters of the composite unblocking agent using mathematical models and optimization algorithms; the injection parameters include: injection pressure, injection time, and injection flow rate; S3 formulated a composite unblocking agent for rock gas reservoirs according to the optimal formula of the unblocking agent, and diluted it with water to obtain the unblocking agent working solution; S4 According to the optimal injection parameters obtained in step S2, the unblocking agent working fluid is injected into the shale gas reservoir of the gas well to be unblocked. After well sealing and fluid drainage, S5 completed the unblocking of the shale gas reservoir.

7. The unblocking method according to claim 6, characterized in that, In step S2, the mathematical model is: where p is the pressure of the reservoir; t is time; k is the permeability of the reservoir; μ is the viscosity of the plugging remover; φ is the porosity of the reservoir; ▽ is the Laplace operator; q is the gas production rate of the reservoir; S p is the source term of pressure; x is the displacement of any point in space; c i is the concentration of the i-th component in the plugging remover; u is the flow rate of the plugging remover; r i is the reaction rate of the i-th component in the plugging remover; S i is the source term of the i-th component.

8. The unblocking method according to claim 6, characterized in that, The optimization algorithm includes the following steps: A. Initialize the formulation and injection parameters of a composite unblocking agent as individuals in a population. Represent each individual in the population using binary encoding. The length of the encoding is n, where n is the total number of components and injection parameters. B. For each individual, calculate the corresponding component and injection parameter values ​​according to its code, and then substitute them into the mathematical model to solve the changes in reservoir pressure and gas production, as well as the cost of composite unblocking agent. Based on these results, calculate its fitness function value as an evaluation index of its optimization objective. C. Based on the fitness function value, a selection operation is performed on the population using the roulette wheel method, retaining 10 excellent individuals and eliminating 10 inferior individuals; D. Perform crossover on the population using the single-point crossover method. Randomly select two individuals, randomly select a crossover point, and exchange the component codes of the two individuals to generate two new individuals. E. Perform mutation operations on the population using simulated annealing. Randomly select an individual and a mutation point, and change the code of the mutation point with probability to generate a new individual. F. Determine if the new individual meets the termination condition. If it does, output the optimal component and injection parameters and end the algorithm. If it does not meet the condition, return to step B and continue the iterative calculation.

9. The unblocking method according to claim 8, characterized in that, The fitness function mentioned in step C is f(x) = a + bc, where f(x) is the fitness function value, a is the normalized pressure value for each individual, b is the normalized gas production value for each individual, and c is the normalized cost of the composite unblocking agent for each individual.

10. The unblocking method according to claim 8, characterized in that, The termination conditions include the maximum number of iterations or the minimum change in the fitness function.

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