CN114988556B - Method and device for enhancing migration of repairing agent in low-permeability area based on circulating well - Google Patents

Abstract

The invention relates to a method for enhancing migration of a remediation agent in a low-permeability area based on a circulating well, which at least comprises the following steps: a circulating well capable of pumping and injecting water in the same well is arranged in a range close to the low-permeability area; determining a low permeability zone and disposing at least one injection point at a location proximate to the low permeability zone; injecting a repairing agent into the injection point, and injecting a catalyst into the circulating well; under the hydraulic excitation of the circulation well, water output by the circulation well applies a vertical and/or inclined downward driving force to the low-permeability area, so that the repairing agent is strengthened to vertically migrate and permeate into the low-permeability area. Aiming at the difficulty that the repairing agent cannot permeate into the low-permeability area in the prior art, the invention mainly couples the circulating well technology and the in-situ chemical oxidation technology, can strengthen the penetrating of the repairing agent into the low-permeability area and keep the repairing agent for a long time, does not need to add polymers, and improves the possibility of contact between the oxidizing agent and pollutants in the low-permeability area.

Description

Method and device for strengthening the migration of repair agent in low permeability areas based on circulating wells

Technical field

The present invention relates to the technical field of in-situ remediation of groundwater pollution, and in particular to methods and devices based on circulating well-enhanced remediation agents to migrate in low-permeability areas.

Background technique

In-situ chemical oxidation (ISCO) is considered an effective technology for the remediation of organic pollutants in soil and groundwater and has been widely used due to its high treatment efficiency, cost-effectiveness, and easy operation. Injecting oxidants into the ground allows pollutants to be mineralized into carbon dioxide, water and other inorganics, or converted into compounds that are less mobile or toxic than their original form. The most commonly used oxidants include ozone, Fenton, permanganate and persulfate (PS).

The efficiency of pollutant removal in aquifers mainly depends on the uniform distribution of the remediation agent in the contaminated area and its contact with the pollutants. After the oxidant is injected into the formation, it is only affected by the horizontal migration of water flow, which makes the migration speed of the oxidant slow and the repair efficiency in the contaminated area is not high.

Subsurface environments are often heterogeneous formations, with preferential flow paths forming in areas of high permeability. Additionally, reagents may float or sink during their migration in the aquifer due to the density difference between the injection solution and the groundwater. This density effect causes The migration process of oxidants forms bypass phenomena, which is common in repair agent transportation and aquifer repair. In order to solve the preferential flow problem caused by heterogeneity and density effects, a common solution is to enhance the cross-flow between porous media with different permeabilities by injecting water-soluble and shear-thinning polymers. However, the additional polymer not only changes the migration path of the oxidant, but also changes the migration path of the pollutants, limiting the efficiency of the oxidant. Adding additional reagents to the formation not only increases construction costs but also affects the biogeochemical properties of the formation.

Chinese patent CN106186123A discloses a circulating and controllable groundwater remediation system for low-permeability contaminated sites, in which a pumping well is provided at the center of the groundwater pollution plume with a permeability coefficient of 1 to 0.01m/d, and the pumping well is connected to groundwater distribution through a pumping aqueduct. A number of water injection wells are set up around the groundwater pollution plume. Each water injection well is equipped with a water injection water conduit pipe. Each water injection water conduit pipe is connected to the groundwater distribution pool through a multi-stage pollution enhanced disposal unit. This invention affects the flow direction of ground stream water by setting up several water injection wells. However, setting up multiple water injection wells is not only labor-intensive and time-consuming. Since the water injection wells and pumping wells are both installed in the aquifer above the aquifer, they can only promote the lateral penetration of groundwater, but still cannot promote the vertical migration of groundwater.

Chinese patent CN109047302A discloses an in-situ aeration remediation method for groundwater contaminated by VOCs in low permeability areas. Based on the surfactant-enhanced aeration remediation method, point-controllable hydraulic splitting technology is used to carry out multi-point remediation in low permeability contaminated areas. Hydraulic splitting generates a large number of artificial cracks in the area. At the same time, the pressure solution used for splitting is a surfactant solution. It aims to enhance the gas permeability of low-permeability contaminated areas and strengthen the desorption capacity of pollutants from fine-grained soil. Solve the problem of low permeability contaminated areas that are difficult to repair. The hydraulic splitting technology used in this invention cooperates with the strengthening effect of surfactant. The pressure solution used in the splitting process is SDBS surfactant solution with a concentration of 200-400mg/L. The inside of the hydraulic splitting well is a coaxial double-pipeline. Multi-point hydraulic splitting in different areas is achieved by moving the inner tube. However, the problem with this invention is that a surfactant solution is injected into the ground at the same time as the repair, thereby introducing new polymers.

Chinese patent CN103043862 A discloses a groundwater in-situ restoration device based on synchronous fracture hydrodynamic circulation, including more than two hydrodynamic fracture wells and more than one pneumatic stripping circulation well. The pneumatic stripping circulation well is double-layered. Well, an upper screen and a lower screen are arranged in the well, the inner well is connected to an air pump, the outer well is connected to an extraction pump, and is connected to a gas treatment device outside the well through a pipeline; the hydrodynamic fracture well is located in low-permeability soil There is a fracture layer produced by hydraulic fracturing in the layer, and fracturing proppant is injected into the fracture; the fracture is generated by simultaneous hydraulic fracturing of two paired hydraulic fracture wells; the device also includes a hydraulic fracturing pump and a surface Active agent dosing tank, etc. This invention uses physical methods (shock cracking) to destroy low-permeability soil layers, increase the stripping efficiency of VOCs in groundwater, and achieve repair efficiency. Compared with the present invention, this technology is more destructive to the formation and has no repair effect on non-volatile pollutants. Based on this defect, the present invention uses the hydraulic driving effect of the circulating well to drive the repair agent to migrate to the low permeability area in the groundwater, and has a concentration accumulation effect, which can repair the pollutants remaining in the low permeability area.

Chinese patent CN113714271A discloses a groundwater circulation well-coupled in-situ chemical oxidation process for environmental restoration, which includes the following steps: S1. Preparation of oxidant; in the oxidation process, the raw materials used for the oxidant first need to be prepared in the laboratory, etc. Prepare for the next step of oxidation. S2. Extract groundwater for laboratory analysis; extract groundwater from wells at different depths or in different contaminated areas, and conduct laboratory analysis on different groundwaters. S3. Selection of oxidants for in-situ repair; the four main oxidants used for in-situ repair are permanganate, persulfate, hydrogen peroxide and ozone. Although this invention proposes the use of circulation wells for repair, the oxidant is injected through the circulation well, and the oxidant migrates based on water flow. Its purpose is to spread the repair range of the oxidant rather than to accumulate the concentration of the oxidant in the low-permeability area. effect. Since the low-permeability area only has a good repair effect on low-concentration repair agents, it is difficult for repair agents without step concentration differences to accumulate in low-permeability areas. Not only that, because the distance between the circulation well and the low permeability area is uncertain, the oxidant circulating from the circulation well first migrates laterally and then vertically. The concentration of the oxidant remains unchanged or becomes smaller, resulting in the oxidant reaching the low permeability area. It will also flow out with water. The oxidant migrates obliquely downward, and the vertical migration effect is poor. On the basis that the oxidant is gradually diluted with circulation, the cumulative effect of concentration cannot be achieved. Based on this defect, the present invention sets the injection point of the repair agent above the low-permeability area, and uses the hydraulic action of the circulation well to vertically migrate the low-concentration repair agent in the low-permeability area. The hydraulic force drives a certain concentration of the repair agent every time. The repair agent vertically migrates into the low permeability area, that is, the concentration of the oxidant entering the low permeability area will not be diluted and the concentration will not get lower and lower each time. This ensures the stability of the penetration concentration of the repair agent, so that the oxidant can be maintained at low Concentration accumulation effects occur in the penetration area.

In summary, the prior art does not provide a method to promote the migration of enhanced remediation agents in low-permeability areas without injecting additional polymer into the ground or setting up multiple water injection wells.

In addition, on the one hand, there are differences in the understanding of those skilled in the art; on the other hand, the applicant studied a large number of documents and patents when making the present invention, but due to space limitations, all details and contents are not listed in detail. However, this is by no means The present invention does not have these features of the prior art. On the contrary, the present invention already has all the features of the prior art, and the applicant reserves the right to add relevant prior art to the background art.

Contents of the invention

In the existing technology, the difficulties in the application of in-situ chemical remediation to low permeability areas include: first, the repair agent cannot penetrate into the low permeability area, making the treatment of contaminated low permeability areas a major problem in site remediation; second, due to Only affected by groundwater flow and its own gravity, the vertical migration of the repair agent is greatly restricted. The repair agent is already carried by the water flow before it reaches the middle and lower layers of the formation, and the scope of influence is limited.

In view of the shortcomings in the existing technology, the present invention couples the circulation well with the in-situ chemical oxidation technology, which can strengthen the penetration of the repair agent into the low permeability area and maintain it for a long time without the need for additional polymers, and improve the degradation efficiency of pollutants in the low permeability area. Under the hydraulic excitation of the circulating well, the invention increases the vertical migration distance of the repair agent and expands the influence range of the repair agent in the formation.

The invention provides a method based on circulating wells to enhance the migration of repair agents in low permeability areas. The method at least includes: setting up a circulating well close to the low permeability area that can complete water pumping and injection in the same well; determining the low permeability area. And set up at least one injection point close to the low permeability area; inject repair agent into the injection point, and inject catalyst into the circulation well; under the hydraulic excitation of the circulation well, the water output from the circulation well flows into The low permeability area exerts a vertical and/or oblique downward driving force, so that the repair agent is enhanced to migrate vertically and penetrate into the low permeability area.

Circulation wells have the function of promoting groundwater remediation. By combining the circulation well with the repair agent, the repair agent can effectively migrate vertically under the hydraulic stimulation of the circulation well, which greatly strengthens the scope of action of the repair agent. The specific scope of action is determined by the injection water flow rate. The higher the injection water flow rate, the higher the injection water flow rate. The larger the radius of influence is.

Preferably, the method further includes: the location close to the low permeability area includes an area vertically above the permeability area and an area between the low permeability area and the location of the circulation well. The closer the injection is to the low permeability area, the more conducive it is to the accumulation of the repair agent in the low permeability area. If the remediation agent is far away from the low permeability area, the circulation well cannot hydraulically stimulate the vertical migration of the remediation agent. Injecting the repair agent near the low permeability area can cause the repair agent to migrate vertically under the stimulation of hydraulic pressure.

Preferably, the method further includes: injecting a low-concentration repair agent from the injection point multiple times; the concentration range of the low-concentration repair agent is 1 to 10 mmol/L. The higher the concentration of the repair agent, the less favorable it is for its accumulation in low permeability areas. Therefore, for the treatment of low permeability areas, multiple injections of low-concentration repair agents should be considered to ensure that the repair agents in low-permeability areas accumulate at a higher concentration.

Preferably, the method further includes: when the repair site is a DNAPL site, injecting a high-concentration repair agent into the injection point, and under the hydraulic excitation of the circulation well, the water output from the circulation well flows into the DNAPL The site applies a vertical and/or inclined downward driving force so that the high-concentration repair agent effectively migrates vertically; the concentration range of the high-concentration repair agent is 10 to 20 mmol/L. The present invention optimizes the usage amount of the repair agent by injecting repair agents of different concentrations into different positions. High concentrations of repair agents favor their own vertical migration. For DNAPL site repair, one-time injection of high-concentration repair agents can be considered.

Preferably, the method further includes: in the experimental simulation equipment, setting the pumping water flow rate of the circulation well in a range of 0.58 to 1.74 mL/h.

Preferably, the interior of the low permeability area is less affected by the hydraulic stimulation of the circulation well, and the concentration of the repair agent in the low permeability area can be maintained for a longer repair time; the range of the longer repair time is : Not less than 9 hours. Compared with the difficulty of impermeability in low-permeability areas in the prior art, the repair agent of the present invention not only easily penetrates into low-permeability areas, but can also be maintained in low-permeability areas at a certain concentration for a long time, which is effective for low-permeability areas. The area has been significantly repaired.

Preferably, the concentration of the repair agent injected at the injection point is positively correlated with the distance between the injection point and the low permeability area, wherein the distance between the injection point and the low permeability area becomes smaller Under the trend, the concentration of the repair agent injected at the injection point tends to become lower. According to the characteristics of the influence radius of the circulation well and the characteristics of the low-permeability area, the present invention selects a low-concentration repair agent for multiple injections at the injection point close to the low-permeability area, and selects a high-concentration repair agent once for the injection point far away from the low-permeability area. Sexual injection not only improves the repair effect of low-permeability areas and saves the use of repair agents, but also improves the repair effect of ground-penetration areas.

Preferably, the method further includes: increasing the influence radius of the repair agent by increasing the flow rate of water pumped and injected into the circulation well, and the influence radius is centered on the circulation well. The greater the injection water velocity of the circulating well, the greater its influence radius. Compared with the defect in the prior art that the migration of the repair agent is uncontrollable after the repair agent is injected into the ground, the present invention changes the influence radius of the repair agent by changing the injection water flow rate of the circulation well, so that the repair range of the repair agent can be realized It is initially controllable, so the influence radius of the remediation agent can be adjusted in a targeted manner according to the degree of pollution in the contaminated area.

Preferably, the method further includes: setting up at least one monitoring well in a specific contaminated area, and sampling soil from the monitoring well according to a preset remediation cycle to monitor the concentration of pollutants.

Preferably, the method further includes: measuring the effluent of the circulation well according to a preset period to monitor the removal efficiency of pollutants.

The present invention monitors the repair status of contaminated areas and the removal efficiency of pollutants through regular monitoring, effectively improves the difficulty of treating pollutants in low-permeability areas, rationalizes the repair cycle, reduces repair costs, and accelerates the repair process of contaminated sites.

The invention also provides a device for enhancing the migration of repair agent in a low permeability area, which at least includes a circulation well and a first injection component. The circulation well capable of completing water pumping and injection in the same well is arranged close to the low permeability area; At least one injection component is provided at the position of the low permeability area; a low-concentration repair agent is injected into the injection component, and a catalyst is injected into the circulation well; under the hydraulic excitation of the circulation well, the water output from the circulation well flows to The low permeability area exerts a vertical and/or oblique downward driving force, so that the repair agent is enhanced to migrate vertically and penetrate into the low permeability area.

Description of the drawings

Figure 1 is a simplified structural schematic diagram of the operation of the sand box simulation tank and circulation well from one angle;

Figure 2 is a simplified structural schematic diagram of the operation of the sand box simulation tank and circulation well from another angle;

Figure 3 is a schematic diagram of the simulated water flow field line driven by a circulating well;

Figure 4 shows the hydrogen peroxide concentration distribution diagram when driving without circulation well;

Figure 5 shows the hydrogen peroxide concentration distribution chart driven by a 10 rpm circulating well;

Figure 6 shows the concentration distribution diagram of 5mM hydrogen peroxide driven by a 10rpm circulating well;

Figure 7 shows the concentration distribution diagram of 20mM hydrogen peroxide driven by a 10rpm circulating well;

Figure 8 is a distribution diagram of hydrogen peroxide concentration driven by a 10 rpm circulating well;

Figure 9 shows the sampling points ⑩ and ⑩ of the low permeability area with or without circulation well driving. Schematic diagram of changes in hydrogen peroxide concentration;

Figure 10 shows the low permeability area sampling points ⑩ and Schematic diagram of changes in hydrogen peroxide concentration.

List of reference signs

1: Driving mechanism; 2: Circulation well; 3: Sand box; 21: Water pumping pipe; 22: Packing plate; 23: Water injection pipe; 31: Groundwater input mechanism; 32: Groundwater outlet; 33: Sampling port; 34: Groundwater Entrance.

Detailed ways

A detailed description will be given below with reference to the accompanying drawings.

The present invention provides a method based on circulating wells to enhance the migration of repair agents in low permeability areas. The present invention can also provide a method for adjusting the influence range of repair agents in low permeability areas.

In the present invention, the repair agent is an oxidizing agent used in in-situ chemical oxidation technology. Oxidizing agents include permanganate, persulfate, hydrogen peroxide and ozone. The first three oxidants are usually injected in liquid form, although ozone is a strong oxidant.

In the present invention, the low permeability area is mainly composed of clay (illite, montmorillonite, etc.) and has a permeability coefficient of about 1×10 ^-6 ~ 9×10 ^-7 m/s. Due to its low permeability coefficient, the pores The flow rate is greatly restricted and the water permeability is extremely poor.

In the simulation experiment of the present invention, hydrogen peroxide is used as a repair agent to conduct simulation experiments to verify the technical effect of the technical solution of the present invention.

The present invention is assisted by an experimental simulation device capable of displaying the migration process of the repair agent.

As shown in Figure 1, the experimental simulation equipment of the present invention is shown in Figures 1 and 2.

The experimental simulation equipment at least includes a circulation well 2 and a sand box 3. The circulation well 2 is arranged in the sand box 3 in a manner of longitudinally pumping and injecting water. The circulation well 2 is connected to the driving mechanism 1 so that the driving mechanism 1 can pump and inject water in the circulation well 2 .

The circulation well 2 in the present invention has the same structure as a real circulation well and is a reduced version of the circulation well, which can realize the circulation of groundwater by the circulation well. The driving mechanism 1 is a pump, which provides driving force for pumping and injecting water into the circulation well. The circulation well 2 at least includes a water pumping pipe 21 , a water injection pipe 23 and a isolation plate 22 . The isolation plate 22 isolates the well body into upper and lower parts. The bottom of the well body is provided with several screen holes to allow groundwater to enter the well body through the screen holes. The water pumping pipe penetrates the isolation plate 22 and pumps out the groundwater at the bottom of the well body and injects it into the upper part of the well body. The upper part of the well body is provided with several screen holes that communicate with the outside world, and the injected water flows into the gravel from the screen holes. The water flowing out of the screen holes flows in downward and inclined directions due to gravity. Since the driving mechanism 1 drives the water pumping pipe 21 to extract groundwater and form a negative pressure, the groundwater in the gravel gathers to the bottom of the circulation well based on the underground negative pressure and enters the bottom of the circulation well again through the sieve hole at the bottom of the circulation well, forming a groundwater flow. cycle.

The sand box 3 is a box with gravel inside and is used to simulate the underground environment. A groundwater inlet 34 is provided on one side of the sand box 3 . The simulated groundwater is input into the sandbox through the groundwater input mechanism 32 and the groundwater inlet 34 of the sandbox 3 . The groundwater input mechanism 32 is preferably a water pump. The groundwater inlet 34 is located at the bottom of one side of the sand box 3 .

The groundwater outlet 32 is located on the other side of the sand box 3 near the top. That is, there is a height difference between the groundwater inlet 34 and the groundwater outlet 32 , and the height of the groundwater inlet 34 is lower than the height of the groundwater outlet 32 . Such an arrangement enables the flow of simulated groundwater to form virtual groundwater in the sand box 3, so as to observe the circulation influence and repair effect of the circulation well 2 on the groundwater.

Preferably, several groundwater inlets 34 are provided on one side of the sand box 3 . A number of groundwater outlets 32 are provided on the other side of the sand box 3 to construct simulated groundwater with lateral migration at different height differences. Both the groundwater inlet 34 and the groundwater outlet 32 are provided with sealing covers, which can be removed when needed and used to seal the ports when not in use.

The sand box 3 can be see-through or non-see-through. Preferably, the sand box 2 is configured to be see-through, that is, a sand box made of see-through material is used to facilitate observation of the water circulation process of the circulation well. Preferably, as can be seen from the bird's eye view of the sand box shown in Figure 2, a number of sampling ports 33 are respectively provided on the two sides of the sand box 3 that are not provided with groundwater inlets and underground water outlets for the penetration of the repair agent. Take samples.

The top of the sand box 3 is open and used for injecting the repair agent at different distances from the circulation well.

Preferably, the sampling ports 33 are arranged at different distances from the circulation well 2 . For example, several sampling ports 33 are arranged in a row laterally. Preferably, several sampling ports 33 can also be arranged in two or three rows with different heights. Preferably, the two rows of sampling ports 33 can also be disposed in a staggered manner so that sampling can be carried out from different locations in the gravel.

Preferably, as shown in FIG. 1 , at least one low-permeability material with a different density from the gravel is provided in the sand box 3 as an underground low-permeability area 4 . The low permeability area 4 is arranged near the circulation well 2 so that the penetration of the repair agent in the low permeability area by the circulation well can be clearly tested.

Preferably, in the experimental simulation equipment, the distance between the low permeability area 4 and the circulation well 2 is 0.16m~0.35m.

In actual site applications, the distance between the circulation well and the low permeability area is 0 to 20m. Further preferably, when the distance between the circulation well and the low permeability area is 3 to 10 m, the strengthening effect of the circulation well is better. Furthermore, the circulation well performs positive circulation at a medium flow rate, which is more conducive to the enhanced repair of low permeability areas. The medium flow rate of the circulation well ranges from 1 to 3L/h.

It should be noted that in the present invention, the circulation well is arranged in a non-vertical upper area of the low permeability area, so that the circulation well driving water can exert an oblique downward or vertical downward driving force on the low permeability area. In the existing technology, the circulation well is placed above the low permeability area or directly inserted into the low permeability area, which can only destroy the structure of the low permeability area, and the water from the circulation well cannot exert a vertical downward driving force on the low permeability area. Naturally, The repair agent cannot be continuously migrated vertically downward.

The location of the low permeability area 4 corresponds to at least two sampling points, which facilitates sampling of the penetration conditions of the repair agent at at least two locations in the low permeability area.

The present invention selects two injection points close to the circulation well area (ie, the left and right sides of the circulation well) to inject 75 mL of 10 mM hydrogen peroxide solution respectively. The groundwater input mechanism 31 simulates the groundwater flow velocity at a speed of 0.046m/d. The driving mechanism 1 uses 10 rpm (34.7 mL/min) as the injection water flow rate of the circulation well 2. In the simulation experiment, the hydrogen peroxide migration process was reflected by measuring the concentration of 32 sampling points at 3, 6, 9, and 12 hours after the start of the experiment.

As shown in Figures 3 and 9, when the circulation well is not started, hydrogen peroxide accumulates above the low permeability area 4 due to the blocking effect of the low permeability area, and the hydrogen peroxide part moves to the right due to the action of water flow. In some concentration accumulation areas, it can be proved that the water flow is the main influencing factor of the lateral migration of hydrogen peroxide, and the effect of its own gravity affects the vertical migration. In the four time periods, the hydrogen peroxide concentration was not detected in the low permeability area 4. This is because the permeability of the low permeability area is greatly different from that of the surrounding areas, and it only relies on the natural downward penetration of water flow and the oxidant itself. , it is difficult for hydrogen peroxide to enter low permeability areas.

In the current existing technology, the difficulties in applying in-situ chemical remediation to low-permeability areas include: first, the repair agent cannot penetrate into the low-permeability area, making the treatment of contaminated low-permeability areas a major problem in site remediation; second, Because it is only affected by groundwater flow and its own gravity, the vertical migration of the repair agent is greatly restricted. The repair agent has been taken away by the water flow before it reaches the middle and lower layers of the formation, which limits the range of influence of the repair agent. .

In order to solve the deficiencies of the prior art, the present invention also provides a device for enhancing the migration of repair agent in low permeability areas, which at least includes a circulation well and a first injection component. The first injection component is used to inject a low concentration of repair agent into the low permeability area and its vicinity.

Circulation wells capable of pumping and injecting water in the same well are located close to low permeability areas. At least one first injection component is positioned adjacent to the low permeability area. Inject a low concentration of repair agent into the injection component. Inject catalyst into the circulation well. Under the hydraulic excitation of the circulation well, the water output from the circulation well exerts a vertical and/or oblique downward driving force to the low permeability area, so that the repair agent is strengthened to migrate vertically and penetrate into the low permeability area.

The device for enhancing the migration of the repair agent in the low permeability area also includes a second injection component. The second injection component is used to inject a high concentration of repair agent into the DNAPL site.

Preferably, the first injection components are distributed around the low permeability area. The first injection component can be divided into multiple groups of positions for injecting the repair agent.

Preferably, several first injection components can be positioned at different distances with the low permeability area as the center. For example, the distance between the first group of first injection components and the center of the low permeability area is L1, and the concentration of the injected repair agent is C1. The distance between the second group of first injection components and the center of the low permeability area is L2, and the concentration of the injected repair agent is C2. When L1 is smaller than L2, C1 ≤ C2. By analogy, the distance between the first injection component of the Nth group and the center of the low permeability area is LN, and the concentration of the injected repair agent is CN. When L(N-1) is smaller than LN, C(N-1) ≤ CN.

A device for enhancing the migration of a repair agent in a low permeability area can be used to implement a method for enhancing the migration of a repair agent in a low permeability area. The method includes at least:

S1: Set up a circulation well close to the low permeability area that can complete water pumping and injection in the same well;

S2: Determine the low permeability area and set at least one injection point close to the low permeability area;

S3: Inject repair agent into the injection point and inject catalyst into the circulation well;

S4: Under the hydraulic excitation of the circulation well, the water output from the circulation well exerts a vertical and/or oblique downward driving force to the low permeability area, so that the repair agent is strengthened to migrate vertically and penetrate into the low permeability area.

Preferably, the location close to the low permeability area includes an area vertically above the permeability area and an area between the low permeability area and the location of the circulation well.

As shown in Figure 4, driven by the circulation well 2, the hydraulic excitation of the circulation well increases the vertical component force, allowing hydrogen peroxide to effectively penetrate into the low permeability area 4. As shown in Figures 6 to 8, as the circulation well continues to operate, the hydrogen peroxide in the low permeability zone 4 can be maintained at a higher concentration. Driven by a pumping water flow rate of 10 rpm in the circulation well, hydrogen peroxide has filled the entire sand box after 6 hours, as shown in Figure 4. Under the hydraulic stimulation of the circulation well, the vertical migration of hydrogen peroxide is effectively improved. As the running time continues, due to the greater number of cycles, the hydraulic strength in the area close to the circulation well is greater than in the area far away from the circulation well, causing the hydrogen peroxide to be diluted many times, and the concentration around circulation well 2 is significantly lower than that far away from the circulation well. Concentration in the well area.

Preferably, different concentrations of repair agents have different penetration effects on the low permeability area 4 . Choosing the correct concentration of repair agent can improve the effectiveness of repairs in low permeability areas.

The present invention selects two injection points close to the circulation well area (ie, the left and right sides of the circulation well) to inject 75mM and 5mM/20mM hydrogen peroxide solutions respectively. The groundwater input mechanism simulates the groundwater flow rate at 0.046m/d, and uses 10rpm (34.7mL/min) as the pumping and injection water flow rate in the circulating well. The water velocity here is the artificially simulated normal flow velocity of groundwater. The present invention reflects the migration process of hydrogen peroxide by measuring the concentration of 32 sampling points respectively at 3, 6, 9 and 12 hours after the circulation well is operated.

When the circulation well enhances the migration of hydrogen peroxide with a concentration of 5mM, as shown in Figures 5 and 10, the right area of the circulation well 2 has a more obvious water pumping process, indicating that the right area is affected by water pumping and injection from the circulation well. The impact is greater, and the left area is dominated by hydrogen peroxide accumulating in the low permeability area.

When the circulation well enhances the migration of hydrogen peroxide with a concentration of 20mM, as shown in Figure 6, there is an obvious pumping curve on the left side of the circulation well 2 at the 6th hour. The higher the concentration, the less conducive it is to the accumulation of the repair agent in the low permeability area 4. During the migration process of the repair agent for 3 hours, hydrogen peroxide with a concentration of 20mM was distributed throughout the sandbox, which shows that a higher concentration of hydrogen peroxide is more beneficial to the vertical migration efficiency in non-low permeability areas.

Circulation wells strengthen that different concentrations of hydrogen peroxide have different migration effects. It can be proven that high concentrations of hydrogen peroxide are conducive to its own vertical migration. The higher the concentration of hydrogen peroxide, the less conducive it is to its accumulation in low permeability areas. Therefore, in actual low permeability areas, multiple injections of low concentrations can be considered to ensure higher concentration accumulation in low permeability areas.

In view of the penetration characteristics and vertical migration characteristics of the low-permeability area affected by the concentration of the repair agent, the present invention injects a low-concentration repair agent into the low-permeability area and a high-concentration repair agent into the non-low-permeability area.

Preferably, a low-concentration repair agent is injected from the injection point in multiple injections. The concentration range of low-concentration repair agents is 1 to 10mmol/L.

When the repair site is a DNAPL site, a high concentration of repair agent is injected into the injection point. DNAPL sites refer to non-aqueous phase liquids that are denser than water. Due to the influence of their own gravity, they tend to accumulate at the bottom of the aquifer. Therefore, DNAPL sites focus on treating lower-layer pollutants as the focus of restoration.

Under the hydraulic excitation of the circulation well, the water output from the circulation well exerts a vertical and/or oblique downward driving force on the DNAPL site, causing the high-concentration repair agent to effectively migrate vertically. The concentration range of high-concentration repair agents is 10 to 20mmol/L.

In the present invention, the interior of the low permeability area is less affected by the hydraulic stimulation of the circulation well, and the concentration of the repair agent in the low permeability area can be maintained for a longer repair time. The longer repair time range that the present invention can achieve is more than 9 hours.

For example, the present invention also simulates the impact of enhanced hydrogen peroxide transport in circulation wells at different injection points.

In order to reflect the impact of different injection sites on the enhanced hydrogen peroxide transmission in circulation wells, a circulation well driving test was conducted: hydrogen peroxide solutions with concentrations of 75mM and 10mM were selected above the low permeability area and its symmetrical positions, respectively, at 0.046m/ dSimulate the groundwater flow rate, and use 10rpm (34.7mL/min) as the pumping and injection water flow rate in the circulating well. The migration process of hydrogen peroxide was reflected by measuring the concentration of 32 sampling points at 3, 6, 9 and 12 hours respectively.

Regarding the impact of different injection sites on enhanced hydrogen peroxide transmission in circulation wells, as shown in Figure 3, hydrogen peroxide can effectively penetrate into low-permeability areas. As shown in Figure 6, the hydraulic excitation effect of the circulation well has left and downward components, and as the circulation well continues to operate, the hydrogen peroxide accumulated in the low permeability area can remain for a long time. The time range in which the hydrogen peroxide in the low permeability area can be maintained is more than 9 hours. Among them, in the first 6 hours of penetration, the transmission is mainly from the high permeability area to the low permeability area, and the second six hours is mainly due to the decomposition of clay in the low permeability area. The attenuation rate increases with the increase of hydrogen peroxide concentration. Concentrated hydrogen peroxide only decays by 5% in the last six hours, and high-concentration hydrogen peroxide only decays by 10% in the next six hours. Therefore, the low-permeability area can maintain the incoming hydrogen peroxide for a longer period of time.

Compared with the existing technology that requires continuous or frequent injection of repair agent, the present invention improves the relative position control between the circulation well and the low permeability area and changes the injection position of the repair agent, so that the low permeability area has the effect of the repair agent. Due to the cumulative effect of concentration, when the repair agent can be maintained for a long time (more than 9 hours) in low permeability areas, there is no need to inject the repair agent frequently, which not only saves the usage of the repair agent, but also reduces the injection work of the repair agent. quantity, simplifying the operation process of the repair agent.

In the present invention, injecting hydrogen peroxide above the low permeability area can strengthen the aggregation of the low permeability area. As shown in Figure 6, at four times, a higher hydrogen peroxide concentration can be detected by the injection method above the low permeability area. .

In the present invention, the closer the injection point of the repair agent is to the low permeability area, the more obvious the effect of the circulation well on strengthening the repair agent in the low permeability area.

Preferably, based on the above-mentioned influence of the injection concentration and injection point position of the repair agent represented by hydrogen peroxide on the migration effect of the repair agent in the low permeability area, the present invention can strengthen the low permeability area by injecting repair agents of different concentrations. and the repair effect of DNAPL sites.

The concentration of the repair agent injected at the injection point is positively related to the distance between the injection point and the low permeability area. As the distance between the injection point and the low permeability area becomes smaller, the concentration of the repair agent injected at the injection point tends to become lower, so that the repair agent is more likely to accumulate in the low permeability area and strengthen the repair effect.

For example, the closer the injection point is to the low permeability area, the concentration of the injected repair agent can become relatively lower as the distance becomes closer. The farther the injection point is from the low permeability area, the higher the concentration of the injected repair agent.

For example, there are three injection points at horizontal distances from far to near low permeability areas. The concentrations at the three injection points become stepwise lower as the distance from the middle of the low permeability region becomes smaller.

With this arrangement, low-concentration repair agents can better vertically migrate to low-permeability areas under the hydraulic stimulation of the circulation well, and high-concentration repair agents at the DNAPL site can also migrate vertically based on their own gravity.

In the present invention, the influence radius of the repair agent is increased by increasing the flow rate of pumping and injection water in the circulating well, and the influence radius is centered on the circulating well. The flow rate of pumping and injection water in circulating wells increases, and its radius of influence also becomes relatively larger. Therefore, by increasing the flow rate of the pumping and injection water in the circulating well and increasing the vertical migration distance of the repair agent, the radius of influence of the repair agent can be relatively expanded, further improving the repair effect of the repair agent on the contaminated area.

Preferably, the present invention sets at least one monitoring well in a specific contaminated area. Soils are sampled from monitoring wells according to preset remediation cycles to monitor the concentration of contaminants to ensure the effectiveness of in-situ chemical oxidation remediation.

Preferably, in the present invention, the effluent from the circulation well is measured according to a preset period to monitor the removal efficiency of pollutants.

In summary, the present invention's method of coupling circulating well technology and in-situ chemical oxidation technology can enhance the penetration of oxidants into low permeability areas and maintain them for a long time without the need for additional polymers, thereby increasing the possibility of contact between oxidants and pollutants in low permeability areas. Under the hydraulic excitation of the circulation well, the vertical migration distance of the oxidant is increased and the influence range of the oxidant in the formation is expanded. Therefore, according to the actual site conditions, the optimization method of the present invention at least includes: first, for efficient repair of low permeability areas, select the injection point closer to the low permeability areas; second, high concentration of hydrogen peroxide is conducive to its own vertical migration, The injection of high-concentration oxidants can be considered for DNAL site remediation; thirdly, the higher the concentration, the less conducive it is to its accumulation in low-permeability areas. Therefore, multiple injections of low-concentration oxidants can be considered in actual sites to ensure higher concentrations in low-permeability areas. Concentration accumulation.

It should be noted that the above specific embodiments are exemplary, and those skilled in the art can come up with various solutions inspired by the disclosure of the present invention, and these solutions also belong to the disclosure scope of the present invention and fall within the scope of the present invention. within the scope of protection of the invention. Those skilled in the art should understand that the description of the present invention and the accompanying drawings are illustrative and do not constitute limitations on the claims. The scope of protection of the present invention is defined by the claims and their equivalents. The description of the present invention contains multiple inventive concepts, such as "preferably", "according to a preferred embodiment" or "optionally" means that the corresponding paragraph discloses an independent concept, and the applicant reserves the right to propose a division based on each inventive concept. The right to apply.

Claims (9)

1. A method based on circulating wells to strengthen the migration of repair agents in low permeability areas, characterized in that the method at least includes: Set up a circulation well close to the low permeability area that can complete water pumping and injection in the same well; Determine a low permeability area and set at least one injection point close to the low permeability area, the location close to the low permeability area including a vertically upper area of the low permeability area and the low permeability area and the The area between circulation well locations; Inject repair agent into the injection point and inject catalyst into the circulation well; In the case of hydraulic excitation of the circulation well to increase the vertical component, the water output from the circulation well exerts a vertical and/or oblique downward driving force to the low permeability area, so that the repair agent is strengthened Migrate vertically and penetrate into the low permeability areas. 2. The method based on the migration of circulating well-enhanced repair agent in low permeability areas according to claim 1, characterized in that the method further includes: Inject a low-concentration repair agent from the injection point in multiple injections; The concentration range of the low-concentration repair agent is 1~10 mmol/L. 3. The method based on the migration of circulating well-enhanced repair agent in low permeability areas according to claim 1 or 2, characterized in that the method further includes: When the repair site is a DNAPL site, a high-concentration repair agent is injected into the injection point, Under the hydraulic excitation of the circulation well, the water output from the circulation well exerts a vertical and/or oblique downward driving force on the DNAPL site, causing the high-concentration repair agent to effectively migrate vertically; The concentration range of the high-concentration repair agent is 10~20 mmol/L. 4. The method for strengthening the migration of repair agents in low permeability areas based on circulating wells according to claim 1, characterized in that, The interior of the low permeability area is less affected by the hydraulic stimulation of the circulation well, and the concentration of the repair agent in the low permeability area can be maintained for a longer repair time; The range of the longer repair time is: not less than 9 hours. 5. The method of strengthening the migration of repair agent in the low permeability area based on circulating wells according to claim 2, characterized in that, The concentration of the repair agent injected at the injection point is positively related to the distance between the injection point and the low permeability area, where, As the distance between the injection point and the low permeability area becomes smaller, the concentration of the repair agent injected at the injection point tends to become lower. 6. The method based on the migration of circulating well-enhanced repair agent in low permeability areas according to claim 1, characterized in that the method further includes: By increasing the flow rate of water pumping and injection in the circulation well, the influence radius of the repair agent is increased, The influence radius is centered on the circulation well. 7. The method based on the migration of circulating well-enhanced repair agent in low permeability areas according to claim 6, characterized in that the method further includes: Set up at least one monitoring well in a specific contaminated area, Soil is sampled from the monitoring well according to a preset remediation cycle to monitor the concentration of contaminants. 8. The method based on the migration of circulating well-enhanced repair agent in low permeability areas according to claim 7, characterized in that the method further includes: The effluent from the circulation well is measured according to a preset period to monitor the removal efficiency of pollutants. 9. A device for enhancing the migration of repair agents in low-permeability areas, characterized by at least including a circulation well and a first injection component, Circulation wells capable of pumping and injecting water in the same well are set up close to low permeability areas; At least one injection component is disposed close to the low permeability area, and the location close to the low permeability area includes a vertically upper area of the low permeability area and between the low permeability area and the circulation well location. Area; Inject a low-concentration repair agent into the injection component, and inject a catalyst into the circulation well; In the case of hydraulic excitation of the circulation well to increase the vertical component, the water output from the circulation well exerts a vertical and/or oblique downward driving force to the low permeability area, so that the repair agent is strengthened Migrate vertically and penetrate into the low permeability areas.