A chemical blocking optimization method for interwell channeling prevention

Abstract

The application discloses a chemical blocking optimization method for interwell channeling prevention, and belongs to the field of oilfield development and enhanced oil recovery. The application adjusts and optimizes from the aspects of ensuring the gelation quality, the injection pressure of the chemical blocking well, whether there is a channeling channel between the wells after the chemical blocking, and the liquid level of the chemical blocking well. The chemical blocking optimization method can adjust and optimize the problems, such as poor injection and production quality, discontinuous injection, excessively high or low plugging strength and the like, which occur in the implementation process of the chemical blocking, effectively guarantees the injection quality of the blocking agent after the implementation, ensures continuous injection, blocks the channeling channel, and improves the production level of the potential layer.

Description

Technical Field

[0001] This invention belongs to the field of oilfield development and enhanced oil recovery, and relates to a chemical plugging optimization method for inter-well cross-flow prevention, and more specifically, a method for optimizing injection and production quality and plugging effect after chemical plugging is implemented in an oil reservoir. Background Technology

[0002] Chemical plugging technology is mainly used to solve the problems of uneven utilization and prominent inter-layer and planar contradictions in heterogeneous oil reservoirs during crude oil extraction. By injecting plugging agents into the formation, high-permeability layers and dominant channels are blocked, the sweep area and displacement efficiency are increased, low-permeability layers are activated, and the utilization level is improved.

[0003] During the implementation of chemical plugging, problems frequently arise such as poor injection quality, discontinuous injection, and excessively high or low plugging strength, leading to poor injection-production quality and an unsatisfactory injection-production relationship, resulting in reduced effectiveness of the measures. Typical problems include the following:

[0004] 1. Due to factors such as the quality of the solution, the properties of the reagents, and the injection process, the gel quality of the plugging agent cannot be guaranteed to meet the requirements of the scheme, which in turn affects the implementation effect of chemical plugging.

[0005] 2. If the viscosity of the plugging agent is too high, the injection pressure will gradually increase, making subsequent injection more difficult or impossible.

[0006] 3. Some wells have cross-flow channels, and the plugging agent reaches other production wells along the cross-flow channels, failing to achieve the purpose of sealing and profile adjustment;

[0007] 4. High fluid levels in some wells result in high bottom-hole flowing pressure and low production pressure differential, leading to low fluid production capacity in low-permeability layers (the main potential layers for chemical plugging), which affects development results.

[0008] Since many factors affect the effectiveness of chemical plugging in oilfields, oilfield development urgently needs to adjust and optimize the injection and production quality and relationship of chemical plugging to improve the effectiveness of the measures. Summary of the Invention

[0009] To overcome the shortcomings of existing technologies, this invention provides an optimized chemical plugging method for inter-well cross-flow prevention, specifically an optimized method for chemical plugging injection and production quality and plugging effect. This method can adjust and optimize problems such as poor injection and production quality, discontinuous injection, and excessively high or low plugging strength that occur during the implementation of chemical plugging, thereby ensuring the effectiveness of the measures.

[0010] The technical solution of this invention is: a chemical plugging optimization method for inter-well cross-flow prevention, comprising the following steps:

[0011] First, assess the quality of the sealant gel formation, and ensure gel quality using one or more of the following methods:

[0012] Detection of Fe in the prepared solution 2+ S 2- Check whether the SRB (sulfate-reducing bacteria) or oxygen content exceeds the standard and adjust it accordingly; or use polymers and crosslinking agents to improve the gel quality when preparing the plugging agent; or use a low-shear profile control pump and a paddle mixer on site for chemical plugging.

[0013] Second, determine the injection pressure of the chemical plugging well and use oxidants or inorganic acids to unplug and reduce pressure;

[0014] Third, determine whether there is a flow channel problem between wells after chemical plugging, and use mechanical plugging and sealing methods to make adjustments;

[0015] Fourth, determine the fluid level in the chemical plugging well and adopt different methods of increasing fluid output based on the formation's fluid supply capacity, daily fluid production level, and expected stable production time.

[0016] To ensure the quality of the gel, physical or chemical methods are used to remove Fe from the water used for preparation. 2+ S 2- The SRB or oxygen content can be regulated.

[0017] When using polymers and crosslinking agents to improve the gel quality in the formulation of plugging agents, the choice of crosslinking agent can be based on different reservoir temperature blocks, using either organic chromium crosslinking agents or phenolic resin crosslinking agents. For the polymer selection, anionic or amphoteric polyacrylamide should be used when formulating the plugging agent.

[0018] The paddle agitator has minimal mechanical shear, and the mixing time does not exceed 2 hours. The principle for determining the mixing speed is that the linear velocity at the blade tip is generally 1.7-2.5 m / s.

[0019] The high injection pressure in chemically plugged wells is mainly due to the accumulation of plugging agent flocculents, clay, mechanical impurities, etc., in the near-wellbore area. The specific method for unblocking and reducing pressure using oxidants or inorganic acids is as follows: the construction process is designed with two slugs. After injecting the oxidant, the well is shut in for 4 hours, and then inorganic acid is injected. The treatment radius of the oxidant and inorganic acid is designed to be 3-5m.

[0020] Furthermore, to determine whether there are crossflow channels between wells after chemical plugging, a mechanical method for locating and sealing crossflow is used for adjustment, including:

[0021] (1) When the polymer concentration in the traversed well is 5%-10% of the injection concentration, the layers in which the well’s production capacity reaches more than 40% shall be plugged.

[0022] (2) When the polymer concentration in the traversed well is 10%-20% of the injection concentration, the layers in which the well’s production capacity reaches more than 30% shall be plugged.

[0023] (3) When the polymer concentration in the traversed well is more than 20% of the injection concentration, the layers in which the fluid production capacity of the well reaches more than 20% shall be sealed.

[0024] Furthermore, to determine the fluid level in chemically plugged wells, different methods of fluid extraction and discharge are employed, specifically:

[0025] (1) The submersion depth is between 200-600m, and the expected daily liquid production level is 70-130m. 3 Submersible electric pumps are installed in the production wells;

[0026] (2) The submersion depth is less than 200m, and the expected daily liquid production level is 40-70m. 3 Large pumps were used to increase drainage at the production wells.

[0027] Compared with the prior art, the beneficial effects of the present invention are:

[0028] The chemical plugging optimization method provided by this invention can adjust and optimize the chemical plugging process to address problems such as poor injection and production quality, discontinuous injection, and excessively high or low plugging strength. After implementation, it can effectively ensure the quality of plugging agent injection, ensure continuous injection, block crossflow channels, and improve the production level of potential layers. Detailed Implementation

[0029] The present invention will be described in detail below through specific embodiments. It should be understood that the description of the embodiments is intended to explain and illustrate the overall concept of the present invention, and should not be construed as limiting the present invention. Unless otherwise defined, the technical or scientific terms used in the present invention should have the ordinary meaning understood by those skilled in the art. Unless otherwise specified, the experimental methods used in the present invention are all conventional methods, and the experimental equipment, materials, reagents, etc. used are all commercially available. The terms "first," "second," and similar terms used in the present invention do not indicate any order, quantity, or importance, but are only used to distinguish different components. The present invention will select appropriate technical means and implementation order according to the corresponding problems encountered during on-site implementation.

[0030] Example 1

[0031] A chemical plugging optimization method for inter-well cross-flow prevention includes the following steps:

[0032] First, assess the quality of the sealant gel formation, and ensure gel quality using one or more of the following methods:

[0033] Detection of Fe in the prepared solution 2+ S 2- Check whether the SRB or oxygen content exceeds the standard and adjust it accordingly; or use polymers and crosslinking agents to improve the gel quality when preparing the plugging agent; or use a low-shear profile control pump and a paddle agitator on site for chemical plugging.

[0034] Second, determine the injection pressure of the chemical plugging well and use oxidants or inorganic acids to unplug and reduce pressure;

[0035] Third, determine whether there is a flow channel problem between wells after chemical plugging, and use mechanical plugging and sealing methods to make adjustments;

[0036] Fourth, determine the fluid level in the chemical plugging well and adopt different methods of increasing fluid output based on the formation's fluid supply capacity, daily fluid production level, and expected stable production time.

[0037] The following is a more detailed explanation of each step:

[0038] 1. Assess the quality of the sealant gelation to ensure its quality.

[0039] To address the issue of gelation quality in plugging agents, this invention employs a gelation assurance method to optimize injection quality. It fully considers three factors: solution quality, agent performance, and injection process. One or more of the following methods are used to ensure gelation quality:

[0040] 1. Detection of Fe in the prepared solution water 2+ S 2- Check if SRB or oxygen content exceeds the standard and adjust accordingly:

[0041] Important indicators affecting gel quality in the solution preparation water include Fe 2+ S 2- SRB, oxygen. Among them, Fe in the prepared solution... 2+ S 2- The normal standards for SRB are shown in Table 1. In this optimized method, physical or chemical methods are used to reduce Fe in the prepared water. 2 + S 2- The SRB or oxygen content is regulated; as a preferred embodiment of the present invention, the physical method is: using an anti-corrosion process or adding oxygen to the water to remove Fe. 2+ S 2- The effect of SRB on gelation, and then the release of oxygen from the water through stirring. The anti-corrosion process refers to applying an internal coating for corrosion protection to the on-site solution preparation equipment, preventing the inner wall of the equipment from contacting the blockage agent and eliminating Fe... 2+ Regarding the effect of the sealant on gelation, the preferred material used is epoxy zinc-rich paint.

[0042] Furthermore, the chemical method involves using bactericides, oxygen scavengers, and stabilizers to ensure the quality of the gel. For example, formaldehyde, glutaraldehyde, and / or dichloroisocyanuric acid are used as bactericides, acetone oxime as an oxygen scavenger, and thiourea as a stabilizer. As a preferred embodiment, glutaraldehyde concentrations of 50-200 mg / L, thiourea concentrations of 20-100 mg / L, and acetone oxime concentrations of 50-100 mg / L are used.

[0043] Table 1. Statistical Table of Water Quality Standards for Deep Surface Dredging

[0044]

[0045] 2. Using polymers and crosslinking agents in the formulation of plugging agents improves the quality of the gel formation:

[0046] When the formulation of the plugging agent uses polymers and crosslinking agents to improve the gelation quality, the polymer mass concentration is 0.2%-0.4%, and the crosslinking agent mass concentration is 0.2%-0.7%. Regarding the selection of the crosslinking agent, depending on the reservoir temperature zone, an organochromium crosslinking agent or a phenolic resin crosslinking agent can be used; preferably, for reservoirs with temperatures between 30-70°C, an organochromium crosslinking agent is used; preferably, for reservoirs with temperatures between 70-120°C, a phenolic resin crosslinking agent is used. When using a phenolic resin crosslinking agent, the gelation performance can be improved by selecting a catalyst used in the crosslinking agent generation process. The catalyst includes sodium hydroxide, ammonia, or barium hydroxide, etc.

[0047] To more clearly describe the present invention, the preparation process of the phenolic resin crosslinking agent is described below:

[0048] Phenolic resins are condensation polymers synthesized from phenols and aldehydes under acidic or alkaline conditions via a two-step catalytic process. The preparation process is as follows:

[0049] Weigh an appropriate amount of phenol and pour it into a reaction vessel, heating it to 50°C to melt it into a liquid. Weigh a catalyst according to a ratio of 5% of the total amount of phenol and formaldehyde (pure substances), dividing it into two portions: 3.5% and 1.5%. Add the 3.5% catalyst to the reaction vessel containing the molten phenol, reserving the remaining 1.5%. Maintain the reaction vessel temperature at 50°C and stir the reaction for 20 minutes. Weigh 80% of the required amount of formaldehyde according to a phenol:formaldehyde ratio of 1:3 (molar ratio) and pour it into the reaction vessel. Raise the reaction vessel temperature to 60°C and continue stirring the reaction for 50 minutes. Add the remaining 1.5% catalyst to the reaction vessel, raise the reaction vessel temperature to 70°C, and stir the reaction for 20 minutes. Finally, add the remaining 20% ​​formaldehyde, raise the reaction temperature to 90°C, and stir the reaction for 30 minutes.

[0050] For polymer selection, anionic or amphoteric polyacrylamide is used when preparing plugging agents. Anionic polyacrylamide is generally used; however, amphoteric polyacrylamide can be used if the water quality in the solution is poor. The molecular weight of the aforementioned anionic or amphoteric polyacrylamide is determined based on its matching relationship with the pore throat radius and permeability.

[0051] According to indoor studies, when the median pore radius r of the oil layer... h Blockage will not occur when the molecular radius of curvature is greater than 10 times that of the polymer molecule. That is:

[0052]

[0053] In the formula: r h —Core pore throat radius, μm

[0054] r p —Polymer gyrocoel radius, μm

[0055] Polymer gyroradius r p It is calculated using the following formula:

[0056]

[0057] In the formula: [η]——polymer intrinsic viscosity, dL / g

[0058] M – Relative molecular mass of the polymer, 10 6

[0059] Therefore, the formula for calculating the polymer molecular weight M is as follows:

[0060]

[0061] Meanwhile, based on indoor experimental data, the matching relationship between polymer molecular weight and permeability is as follows:

[0062] Table 2. Matching Relationship between Polymer Molecular Weight and Permeability

[0063]

[0064] 3. Low-shear profile control pumps are used at the chemical plugging site, and paddle agitators are used for stirring. The mechanical shear of the paddle agitator is minimized, and the mixing time does not exceed 2 hours. The principle for determining the stirring speed is: the linear velocity of the blade tip is generally 1.7-2.5 m / s.

[0065] 2. Determine the injection pressure of chemically plugged wells and use oxidants or inorganic acids to de-plug and reduce pressure.

[0066] The high injection pressure in chemically plugged wells is mainly due to the accumulation of plugging agent flocculents, clay, and mechanical impurities in the near-wellbore zone. The specific method for unblocking and reducing pressure using oxidants or inorganic acids is as follows: the oxidant degrades the polymer through oxidation, releasing the plugging agent flocculents; the inorganic acid degrades mechanical impurities and scale through acidification. The construction process involves two slugs. After injecting the oxidant, the well is left to stand for 4 hours, followed by continued injection of inorganic acid. The treatment radius for both the oxidant and inorganic acid is designed to be 3-5 meters. As a preferred embodiment, sodium hypochlorite, which has high safety and good degradation effect, is used as the oxidant, with a treatment radius designed to be 0.5-1.5 meters; a soil acid is used as the inorganic acid, with a treatment radius designed to be 3.5-4.5 meters.

[0067] Third, determine whether there are crossflow channels between wells after chemical plugging, and adjust using mechanical plugging methods.

[0068] To address the issue of crossflow channels between wells after chemical plugging, a mechanical sealing method was employed for adjustment. The mechanically sealed tubing was then used for layer-by-layer production. By analyzing the production situation, the crossflow channels were identified, and the crossflow layers were sealed. Specifically:

[0069] (1) When the polymer concentration in the traversed well is 5%-10% of the injection concentration, the layers in which the well’s production capacity reaches more than 40% shall be plugged.

[0070] (2) When the polymer concentration in the traversed well is 10%-20% of the injection concentration, the layers in which the well’s production capacity reaches more than 30% shall be plugged.

[0071] (3) When the polymer concentration in the traversed well is more than 20% of the injection concentration, the layers in which the fluid production capacity of the well reaches more than 20% shall be sealed.

[0072] IV. Determine the fluid level in chemically plugged wells and adopt different methods of fluid extraction and discharge enhancement based on the formation's fluid supply capacity, daily fluid production level, and expected stable production time.

[0073] To address the issue of low fluid production capacity in potential formations due to high fluid levels in chemically plugged wells, different methods for increasing fluid output are employed based on formation fluid supply capacity, daily fluid production level, and expected stable production time. Specifically:

[0074] (1) The submersion depth is between 200-600m, and the expected daily liquid production level is 70-130m. 3 Submersible electric pumps are installed in the production wells;

[0075] (2) The submersion depth is less than 200m, and the expected daily liquid production level is 40-70m. 3 Large pumps were used to increase drainage at the production wells.

[0076] Example 2

[0077] Chemical plugging was implemented in a heterogeneous reservoir of an oilfield. During implementation, the average gelation viscosity was 1389 mPa·s, and the gelation rate was 53.7%, failing to meet the design requirements. Injection was stopped in four chemical plugging wells when the injection pressure exceeded 18 MPa; inter-well flow also occurred. In this example, a total of 12 production wells were involved, with some having polymer concentrations exceeding 300 mg / L, and others exhibiting high fluid levels, resulting in no significant effect from the chemical plugging implementation. To address the injection-production mismatch observed in this block, the method provided by this invention is applied for improvement. The specific optimization method is as follows:

[0078] 1. Laboratory tests revealed that the Fe content in the prepared solution was [missing information]. 2+The levels of Fe and SRB exceeded the limits by 1.2 mg / L and 1800 cells / mL, respectively. Physical methods, such as adding oxygen to the water, were used on-site to reduce Fe levels. 2+ The SRB content was adjusted, and the polymer type was changed to zwitterionic polyacrylamide with a molecular weight of 18 million. The catalyst used for the phenolic resin crosslinking agent was optimized to barium hydroxide. The on-site injection pump was changed to a low-shear profile control pump, and a paddle agitator was used. The mixing time was 1.5 hours, and the stirring speed was 28 rpm (blade tip linear velocity 2.1 m / s). After implementation, the gel viscosity increased to 4818 mPa·s, and the gelation rate increased to 95.2%.

[0079] 2. For high-pressure chemically plugged wells, deplugging and pressure reduction were implemented. The formulation system used 2% oxidant and 12% terrine acid by mass, with an optimized treatment radius of 5m. After implementation, the average pressure decreased by 8.3MPa, and the chemical plugging was restored in all wells.

[0080] 3. Using a polymer concentration of 200 mg / L as a dividing line, two production wells around the chemically plugged well had polymer concentrations of 100-200 mg / L, and one production well had a polymer concentration exceeding 200 mg / L (the actual measured polymer concentration exceeded 300 mg / L, indicating severe cross-flow). By using mechanical methods to locate and seal the cross-flowing layers, the production layers of the cross-flowing wells were segmented and sampled. Layers with polymer concentrations exceeding 30% of the injected concentration were plugged. After implementation, the polymer concentrations in all three wells decreased to 0-50 mg / L.

[0081] 4. In the chemical plugging well group, there were two production wells with a dynamic fluid level of less than 200m. Submersible electric pumps were installed in these wells, resulting in an average daily production of 105m³. 3 There are three wells with dynamic fluid levels between 200-600m. Large pumps were used to increase drainage in these wells, primarily Φ57mm and Φ70mm pumping pumps. After implementation, the average daily production reached 58m³. 3 .

[0082] After applying the above optimization methods, the injection and production quality and relationship of the chemical plugging well group were significantly improved, and the daily oil production increased from 3.2 tons to 16.9 tons.

[0083] Example 3

[0084] In a heterogeneous reservoir in the Huandong Shuang Oilfield, chemical plugging was implemented on 8 well groups (30 production wells) to enhance oil recovery after long-term waterflooding. During implementation, the designed gel viscosity was 4500 mPa·s, the average gel viscosity was 2585 mPa·s, and the gelation rate was 42.9%, failing to meet the design requirements. Five of the chemical plugging wells experienced injection pressures exceeding 18 MPa, requiring either water injection or cessation of injection. Simultaneously, six production wells exhibited excessively high polymer concentrations in the produced fluid, indicating inter-well cross-flow. To address the injection-production mismatch observed during implementation in this reservoir, the method provided in this invention is applied for improvement, as follows:

[0085] 1. Laboratory testing revealed that the SRB concentration in the prepared solution exceeded the standard by 2500 cells / mL. On-site chemical methods (using formaldehyde as a bactericide) were employed to eliminate the SRB. Simultaneously, the polymer type was adjusted to a zwitterionic polyacrylamide with a molecular weight of 15 million. Given the formation temperature of 60℃, an organic chromium crosslinking agent was used, and the stabilizer thiourea was optimized to improve gel stability. The on-site injection pump was adjusted to a low-shear profile control pump, and a paddle agitator was used. The mixing time was 2 hours, and the stirring speed was 28 rpm. After implementation, the gel viscosity increased to 5647 mPa·s, and the gelation rate increased to 92.8%.

[0086] 2. For high-pressure chemically plugged wells, deplugging and pressure reduction were implemented. The formulation system used 3% oxidant + 10% soil acid, and the treatment radius was optimized to 4m. After implementation, the average pressure decreased by 7.2MPa, and the chemical plugging was restored in all wells.

[0087] 3. Using a polymer concentration of 200 mg / L as a dividing line, three production wells around the chemically plugged well had polymer concentrations of 100-200 mg / L, two production wells had polymer concentrations of 200-300 mg / L, and one production well had a polymer concentration exceeding 300 mg / L. By using mechanical methods to plug the flow channels, the production layers of the flow-prone wells were segmented and samples were taken. Layers with polymer concentrations exceeding 30% of the injected concentration were plugged. After implementation, the polymer concentrations in all six wells decreased to below 100 mg / L.

[0088] After applying the above optimization methods, the injection and production quality and relationship of the chemical plugging well group were significantly improved, and the daily oil production increased from 5.8 tons to 23.7 tons.

[0089] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A chemical plugging optimization method for inter-well cross-flow prevention, characterized in that, Includes the following steps: To determine the gelation quality of the plugging agent, one or more of the following methods can be used to ensure gelation quality: Detecting the Fe content in the solution water. 2+ S 2- Check whether the SRB or oxygen content exceeds the standard and adjust it accordingly; or use polymers and crosslinking agents to improve the gel quality when preparing the plugging agent; or use a low-shear profile control pump and a paddle agitator on site for chemical plugging. Determine the injection pressure of chemically plugged wells and use oxidants or inorganic acids to unplug and reduce pressure; To determine whether there are crossflow channels between wells after chemical plugging, a mechanical method for finding and sealing crossflow channels is used for adjustment; The mechanical sealing and cross-linking method is specifically as follows: (1) When the polymer concentration in the traversed well is 5%-10% of the injection concentration, the wells with a production capacity of more than 40% should be sealed. (2) If the polymer concentration in the well is 10%-20% of the injection concentration, then the wells with a production capacity of more than 30% should be sealed. (3) If the polymer concentration in the well is more than 20% of the injected concentration, then all formations with a well production capacity of more than 20% shall be blocked. Determine the fluid level in chemical plugging wells and adopt different methods of fluid extraction and discharge based on the formation fluid supply capacity, daily fluid production level, and expected stable production time. The specific method for increasing fluid excretion is as follows: (1) The submersion depth is between 200-600m, and the expected daily liquid production level is 70-130m. 3 Submersible electric pumps are installed in the production wells; (2) The submersion depth is less than 200m, and the expected daily liquid production level is 40~70m. 3 Large pumps were used to increase drainage at the production wells.

2. The method according to claim 1, characterized in that, Using physical or chemical methods to remove Fe from the prepared water 2 + S 2- The SRB or oxygen content can be regulated.

3. The method according to claim 2, characterized in that, The physical method involves removing Fe using an anti-corrosion process or by adding oxygen to the water. 2+ S 2- The effect of SRB on gel formation, and then the oxygen in the water is released through stirring.

4. The method according to claim 2, characterized in that, The chemical method involves using bactericides, oxygen absorbers, and stabilizers to ensure the quality of the gel.

5. The method according to claim 4, characterized in that, The bactericide is formaldehyde, glutaraldehyde, and / or dichloroisocyanuric acid; the oxygen scavenger is acetone oxime; and the stabilizer is thiourea.

6. The method according to claim 1, characterized in that, To ensure the quality of the gel, organic chromium crosslinking agents or phenolic resin crosslinking agents are used depending on the different reservoir temperature blocks.

7. The method according to claim 6, characterized in that, For oil reservoirs with temperatures between 30-70℃, use an organic chromium crosslinking agent; for oil reservoirs with temperatures between 70-120℃, use a phenolic resin crosslinking agent.

8. The method according to claim 6, characterized in that, When using phenolic resin crosslinking agents, the gelation performance is improved by using catalysts in the crosslinking agent generation process.

9. The method according to claim 8, characterized in that, The catalyst includes sodium hydroxide, ammonia, or barium hydroxide.

10. The method according to claim 1, characterized in that, When preparing plugging agents, anionic or amphoteric polyacrylamide is used, and the molecular weight is determined based on its matching relationship with the pore throat radius and permeability.

11. The method according to claim 1, characterized in that, The mixing time of the paddle agitator shall not exceed 2 hours, and the principle for determining the mixing speed is: the linear velocity of the blade tip is 1.7-2.5 m / s.

12. The method according to claim 1, characterized in that, The construction process of unblocking and depressurizing using oxidants or inorganic acids is divided into two stages. After injecting oxidant into the chemical plugging well, the well is simmered for 4 hours, and then inorganic acid is injected. The treatment radius of the oxidant and inorganic acid is designed to be 3-5m.

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