A method for removing plugging of near-well reservoirs contaminated by polymer sewage

Abstract

The present application relates to a kind of to release near well reservoir polymer-containing sewage pollution plugging method.The main problem solved is that polymer and other impurities are easy to be adsorbed again after the existing composite plugging remover is used, and the plugging method has short effective period and poor specificity.The characteristics are as follows: first, inject organic cleaning agent to remove oil stains in wellbore, perforation and near well zone;then inject new environment-friendly degrading agent to remove dissolved, adsorbed and trapped polymers in the formation;then inject acid to dissolve inorganic plugging materials in near well zone and deep reservoir;finally, inject protective fluid to prevent polymer from being adsorbed again, remove the pollution of polymer-containing sewage to the reservoir and restore the permeability of the reservoir.The plugging method effectively removes the damage of polymer-containing sewage to the formation by sequentially injecting organic cleaning agent, new environment-friendly degrading agent, acid and protective fluid, which can reduce the injection pressure of water well, restore the injection volume, ultimately remove the pollution of polymer-containing sewage to the reservoir and is suitable for plugging in polymer-containing sewage reinjection well.

Description

Technical Field

[0001] This invention relates to the field of oil production engineering technology, and in particular to a method for unblocking near-wellbore reservoirs contaminated with polymer-containing wastewater. Background Technology

[0002] As the scale of polymer flooding in continental sandstone reservoirs continues to expand, the difficulty of producing fluid treatment is increasing year by year. Even after treatment, residual polymers and crude oil remain in the wastewater, leading to severe blockage of the relatively poor-permeability Class III oil layers after reinjection, making remediation extremely difficult. For example, in Daqing Oilfield, where waterflooding primarily targets low-permeability, thin-walled oil layers, polymer-containing wastewater is frequently reinjected into these layers, resulting in severe formation blockage. Conventional acid flooding systems, primarily using hydrochloric acid and hydrofluoric acid, easily cause flocculation and precipitation with polymers adhering to the formation, resulting in secondary damage to the reservoir, reduced effectiveness, and shorter lifespan. Composite unblocking agents composed of degradative agents, surfactants, and acids can alleviate complex reservoir blockage; however, polymer-containing wastewater reinjection is a long-term project. Existing composite unblocking agents easily re-adsorb polymers and other impurities after unblocking, resulting in short-term effectiveness and poor targeting. Therefore, there is an urgent need for a method to remove polymer-containing wastewater pollution from near-wellbore reservoirs, relieving the damage caused by the wastewater, restoring reservoir permeability, extending the effectiveness of measures, and providing long-term, effective reservoir protection. Summary of the Invention

[0003] The technical problem to be solved by this invention is to overcome the problems of existing composite unblocking agents being prone to re-adsorption of polymers and other impurities after unblocking, and the unblocking methods having short effective periods and poor targeting. This invention provides a method for removing polymer-containing wastewater pollution from near-wellbore reservoirs. This method involves sequentially injecting an organic cleaning agent, a novel environmentally friendly degrading agent, acid, and a protective fluid to effectively remove the damage to the formation caused by polymer-containing wastewater. It can reduce the injection pressure of the water well, restore the injection volume, and ultimately remove the pollution of the reservoir caused by polymer-containing wastewater. This method is suitable for unblocking polymer-containing wastewater reinjection wells.

[0004] The present invention solves its problem through the following technical solution: The unblocking method for removing polymer-containing wastewater pollution from near-wellbore reservoirs includes the following steps: S1. Prepare an organic cleaning agent solution; S2. Inject the prepared organic cleaning agent solution into the formation damaged by the polymer-containing wastewater; S3. Prepare the degradation agent solution; S4. Inject the prepared degradation agent solution into the formation damaged by polymer-containing wastewater; S5. Prepare acid solution; S6. Inject the prepared acid solution into the formation to carry out acidizing operations; S7. Prepare the protective agent; S8. Inject the prepared protective agent into the formation to complete the unblocking process.

[0005] Furthermore, the preparation method of the organic cleaning agent solution includes: Prepare an organic cleaning agent solution by mixing and stirring a 2% high-efficiency well washing fluid and a 0.8% anti-swelling agent aqueous solution according to the mass ratio.

[0006] Furthermore, the process of injecting the prepared organic cleaning agent solution into the formation damaged by the polymer-containing wastewater is as follows: The prepared organic cleaning agent solution was diluted with 0.3 ml of water. 3 After the organic cleaning agent solution is pumped into the formation damaged by the polymer-containing wastewater at a flow rate of / min, the well is shut in for a 2-hour reaction period.

[0007] Furthermore, the method for preparing the degradation agent solution includes: Prepare an 8% novel environmentally friendly degradation agent and a 2% ammonium chloride aqueous solution by mass ratio, mix and stir to obtain the degradation agent solution.

[0008] Furthermore, the degradation agent solution injection method includes: The prepared degradation agent solution was poured into a 0.5m solution. 3 The solution is injected at a rate of / min into the formation damaged by the polymer-containing wastewater. After the degradation agent solution is pumped out, the well is shut in for a 1-hour reaction.

[0009] Furthermore, the acid preparation method includes: Prepare an aqueous solution of 11.5% hydrochloric acid, 2% ammonium fluoride, and 1.5% glacial acetic acid by mass ratio, mix and stir to obtain an acid solution.

[0010] Furthermore, methods for injecting prepared acid solutions into the formation for acidizing operations include: The prepared acid solution was poured into a 0.5m solution. 3 Injected into the formation at a rate of / min, it treats inorganic blockages in the near-wellbore zone and deep reservoir, thereby improving matrix permeability.

[0011] Furthermore, methods for preparing the protective agent include: Prepare an aqueous solution of 0.5% surfactant and 1% anti-swelling agent by mass ratio, mix and stir to obtain a protective agent.

[0012] Furthermore, the method for injecting the protective agent includes: The prepared protective agent was mixed at 0.3m 3 The polymer is injected into the formation at a rate of / min. Through competitive adsorption, hydrophobic effect and solubilization, an ultra-thin film is formed on the surface of the oil layer pores to prevent polymer re-adsorption, thereby reducing the injection pressure and completing the unblocking process.

[0013] Furthermore, the high-efficiency well-washing fluid is GXXJ high-efficiency well-washing fluid; the anti-swelling agent is a chlorine-free clay anti-swelling agent; the surfactant is HRX-01 alkyl polyglycoside; and the environmentally friendly degrading agent is a non-oxidizing degrading agent.

[0014] This method for unblocking near-wellbore reservoirs contaminated with polymer-containing wastewater utilizes the following solvents and their components, each with its own role or synergistic effect: The GXXJ high-efficiency well-washing fluid in the organic cleaning agent removes oil contamination from the wellbore, boreholes, and near-wellbore area. Simultaneously, the chlorine-free clay anti-swelling agent prevents clay mineral particles from hydrating and swelling or migrating after oil removal. The degrading agent and acid work synergistically; the non-oxidizing degrading agent effectively degrades dissolved, adsorbed, and trapped polymers in the formation, while the acid dissolves inorganic blockages in the near-wellbore area and deep reservoir. This systemic action ensures the effective removal of both polymers and inorganic blockages. When the rock surface is exposed to water, the chlorine-free clay anti-swelling agent in the protective fluid prevents clay mineral particles from hydrating and swelling or migrating. The surfactant HRX-01 alkyl polyglycoside adsorbs onto the rock surface, preventing polymer re-adsorption and secondary damage to the reservoir. These chemical agents work synergistically to achieve unblocking and protection, eliminating contamination of the reservoir by polymer-containing wastewater, reducing injection pressure, and restoring reservoir permeability.

[0015] Compared with the above-mentioned background technology, the present invention has the following beneficial effects: This invention provides a method for unclogging near-wellbore reservoirs contaminated with polymer-containing wastewater. The method involves first injecting an organic cleaning agent to remove oil contamination from the wellbore, boreholes, and near-wellbore area; then injecting a novel environmentally friendly degradation agent to remove dissolved, adsorbed, and trapped polymers from the formation; next, injecting acid to dissolve inorganic blockages in the near-wellbore area and deep reservoir; and finally, injecting a protective liquid to prevent polymer re-adsorption, thereby removing the contamination of the reservoir by the polymer-containing wastewater, reducing injection pressure, and restoring reservoir permeability.

[0016] This invention effectively removes the damage to the formation caused by polymer-containing wastewater by sequentially injecting organic cleaning agent, novel environmentally friendly degrading agent, acid, and protective liquid. It successfully solves the problem of formation pollution caused by polymer-containing wastewater reinjection, reduces well injection pressure, restores injection volume, and ultimately removes the pollution of the reservoir caused by polymer-containing wastewater. It is suitable for unblocking polymer-containing wastewater reinjection wells. Attached Figure Description

[0017] Appendix Figure 1 This is a schematic diagram of the unblocking process of the present invention; Appendix Figure 2 This is the injection curve of well M in embodiment of the present invention after treating the polymer-containing wastewater that caused damage to the reservoir. Detailed Implementation The present invention will be further described below with reference to the accompanying drawings: As attached Figure 1 As shown, the present invention provides a method for unblocking near-wellbore reservoirs contaminated with polymer-containing wastewater, comprising: S1. Prepare organic cleaning agent solution: Prepare 2% high-efficiency well washing fluid and 0.8% anti-swelling agent aqueous solution according to the mass ratio, mix and stir to obtain organic cleaning agent solution; S2, Organic cleaning agent solution injection: Add the prepared organic cleaning agent solution at a rate of 0.3m... 3 The organic cleaning agent solution is injected into the formation damaged by the polymer-containing wastewater at a rate of / min. After the injection is completed, the well is shut in for a 2-hour reaction. S3, Preparation of degradation agent solution: Prepare 8% new environmentally friendly degradation agent and 2% ammonium chloride aqueous solution according to the mass ratio, mix and stir to obtain degradation agent solution; S4, Injection of Degrading Agent Solution: Inject the prepared degradation agent solution at a rate of 0.5m... 3 The solution is injected at a rate of / min into the formation damaged by the polymer-containing wastewater. After the degradation agent solution is pumped out, the well is shut in for a 1-hour reaction. S5, Prepare acid solution: Prepare an aqueous solution of 11.5% hydrochloric acid, 2% ammonium fluoride and 1.5% glacial acetic acid according to the mass ratio, mix and stir to obtain acid solution; S6, Acidification Construction: Pour the prepared acid solution at a rate of 0.5m... 3 / min is injected into the formation to treat inorganic blockages in the near-wellbore zone and deep reservoir, thereby improving matrix permeability; S7, Preparation of protective agent: Prepare an aqueous solution of 0.5% surfactant and 1% anti-swelling agent according to the mass ratio, mix and stir to obtain the protective agent; S8, Protective agent injection: Add the prepared protective agent at a concentration of 0.3m... 3 The polymer is injected into the formation at a rate of / min. Through competitive adsorption, hydrophobic effect and solubilization, an ultra-thin film is formed on the surface of the oil layer pores to prevent polymer re-adsorption, thereby reducing the injection pressure and completing the unblocking process.

[0018] Example 1 The Daqing Oilfield Fifth Oil Production Plant's waterflooding development primarily utilizes low-permeability, thin, and poor-permeability reservoirs. With the continuous expansion of polymer flooding, the amount of polymer-containing wastewater reinjected into these thin, poor-permeability reservoirs is increasing, leading to severe formation blockage. This has further deteriorated the injection conditions of water wells in the Xing-13 wastewater reinjection block of the Fifth Oil Production Plant, making remediation extremely difficult. Currently, well M in the Xing-13 area is prone to reservoir blockage and severe pollution due to the large amount of polymers, suspended solids, and other impurities contained in the reinjected wastewater. This invention employs a deblocking method to remove near-wellbore reservoir pollution caused by polymer-containing wastewater, relieving the damage to the reservoir, restoring reservoir permeability, and extending the effectiveness of the measures, thus providing long-term effective protection for the reservoir. Figure 1 As shown, the specific process is as follows: S1. Prepare organic cleaning agent solution: Prepare 2% GXXJ high-efficiency well washing fluid and 0.8% chloride-free clay anti-swelling agent aqueous solution according to the mass ratio, mix and stir to obtain organic cleaning agent solution; S2, Organic cleaning agent solution injection: Add the prepared organic cleaning agent solution at a rate of 0.3m... 3 The organic cleaning agent solution is injected into the formation damaged by the polymer-containing wastewater at a rate of / min. After the injection is completed, the well is shut in for a 2-hour reaction. S3, Preparation of degradation agent solution: Prepare 8% non-oxidizing degradation agent KHXS and 2% ammonium chloride aqueous solution according to the mass ratio, mix and stir to obtain degradation agent solution; S4, Injection of Degrading Agent Solution: Inject the prepared degradation agent solution at a rate of 0.5m... 3 The solution is injected at a rate of / min into the formation damaged by the polymer-containing wastewater. After the degradation agent solution is pumped out, the well is shut in for a 1-hour reaction. S5, Prepare acid solution: Prepare an aqueous solution of 11.5% hydrochloric acid, 2% ammonium fluoride and 1.5% glacial acetic acid according to the mass ratio, mix and stir to obtain acid solution; S6, Acidification Construction: Pour the prepared acid solution at a rate of 0.5m... 3 / min is injected into the formation to treat inorganic blockages in the near-wellbore zone and deep reservoir, thereby improving matrix permeability; S7, Preparation of protective agent: Prepare an aqueous solution of 0.5% surfactant HRX-01 alkyl polyglycoside and 1% chlorine-free clay anti-swelling agent according to the mass ratio, mix and stir to obtain the protective agent; S8, Protective agent injection: Add the prepared protective agent at a concentration of 0.3m... 3 The polymer is injected into the formation at a rate of / min. Through competitive adsorption, hydrophobic effect and solubilization, an ultra-thin film is formed on the surface of the oil layer pores to prevent polymer re-adsorption, thereby reducing the injection pressure and completing the unblocking process.

[0019] The injection curve of well M after reservoir damage was relieved in Example 1 is shown below. Figure 2 The application of the method of this invention demonstrates that the well regained formation permeability, improved injection capacity, and was able to complete the injection volume.

[0020] In this embodiment, the high-efficiency well-washing fluid is GXXJ high-efficiency well-washing fluid, manufactured by Daqing Huaying Chemical Co., Ltd.; the surfactant is HRX-01 alkyl polyglycoside, manufactured by Daqing High-tech Zone Hualongxiang Chemical Co., Ltd.; and the environmentally friendly degradation agent is non-oxidizing degradation agent KHXS, manufactured by Shandong Binzhou Yucheng Chemical Technology Co., Ltd.

Claims

1. A method for unblocking near-wellbore reservoirs contaminated with polymer-containing wastewater, comprising the following steps: S1. Preparation of organic cleaning agent solution; preparation methods include: Prepare an organic cleaning agent solution by mixing and stirring a 2% high-efficiency well washing fluid and a 0.8% anti-swelling agent aqueous solution according to the mass ratio. S2. Inject the prepared organic cleaning agent solution into the formation damaged by the polymer-containing wastewater; S3. Prepare the degradation agent solution; preparation methods include: Prepare an 8% novel environmentally friendly degradation agent and a 2% ammonium chloride aqueous solution by mass ratio, mix and stir to obtain the degradation agent solution; S4. Inject the prepared degradation agent solution into the formation damaged by polymer-containing wastewater; S5. Prepare acid solution; the methods for preparing acid solution include: Prepare an aqueous solution of 11.5% hydrochloric acid, 2% ammonium fluoride, and 1.5% glacial acetic acid according to the mass ratio, mix and stir to obtain an acid solution; S6. Inject the prepared acid solution into the formation to carry out acidizing operations; S7. Preparation of the protective agent; methods for preparing the protective agent include: Prepare an aqueous solution of 0.5% surfactant and 1% anti-swelling agent by mass ratio, mix and stir to obtain a protective agent; S8. Inject the prepared protective agent into the formation to complete the unblocking process; The high-efficiency well-washing fluid is GXXJ high-efficiency well-washing fluid; the anti-swelling agent is a chlorine-free clay anti-swelling agent; the surfactant is HRX-01 alkyl polyglycoside; and the environmentally friendly degrading agent is a non-oxidizing degrading agent. The GXXJ high-efficiency well-washing fluid in the organic cleaning agent can remove oil stains from the wellbore, boreholes, and near-wellbore area. Simultaneously, the chlorine-free clay anti-swelling agent prevents clay mineral particles from hydrating and swelling or migrating after oil removal. The degrading agent and acid work synergistically; the non-oxidizing degrading agent effectively degrades dissolved, adsorbed, and trapped polymers in the formation, while the acid dissolves inorganic blockages in the near-wellbore area and deep reservoir. This systemic action ensures that both polymers and inorganic blockages are effectively removed. When the rock surface is exposed to water, the chlorine-free clay anti-swelling agent in the protective fluid prevents clay mineral particles from hydrating and swelling or migrating, while the surfactant HRX-01 alkyl polyglycoside adsorbs onto the rock surface, preventing polymer re-adsorption and secondary damage to the reservoir. These chemical agents work synergistically to achieve both unblocking and protection, eliminating pollution of the reservoir by polymer-containing wastewater, reducing injection pressure, and restoring reservoir permeability.

2. The method for unblocking near-wellbore reservoirs contaminated with polymer-containing wastewater according to claim 1, characterized in that: The process of injecting the prepared organic cleaning agent solution into the formation damaged by polymer-containing wastewater is as follows: The prepared organic cleaning agent solution was diluted with 0.3 ml of water. 3 After the organic cleaning agent solution is pumped into the formation damaged by the polymer-containing wastewater at a flow rate of / min, the well is shut in for a 2-hour reaction period.

3. The method for unblocking near-wellbore reservoirs contaminated with polymer-containing wastewater according to claim 1, characterized in that: Method for injecting degradation agent solution: Inject the prepared degradation agent solution into a 0.5m solution. 3 The solution is injected at a rate of / min into the formation damaged by the polymer-containing wastewater. After the degradation agent solution is pumped out, the well is shut in for a 1-hour reaction.

4. The method for unblocking near-wellbore reservoirs contaminated with polymer-containing wastewater according to claim 1, characterized in that: Methods for acidizing operations by injecting prepared acid solutions into the formation include: The prepared acid solution was poured into a 0.5m solution. 3 Injected into the formation at a rate of / min, it treats inorganic blockages in the near-wellbore zone and deep reservoir, thereby improving matrix permeability.

5. The method for unblocking near-wellbore reservoirs contaminated with polymer-containing wastewater according to claim 1, characterized in that: Methods for injecting protective agents include: The prepared protective agent was mixed at 0.3m 3 The solution is injected into the formation at a rate of / min to complete the unblocking process.

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