System and method for enhancing geothermal tailwater reinjection efficiency using electric fields

Abstract

The present application belongs to the technical field of geothermal water development, and particularly relates to a system and method for enhancing the reinjection efficiency of geothermal tail water by using an electric field. The present application provides a combined mode of external ions, an external direct current electric field and nanobubbles, and uses chelating resin CH-90Na, a calcium chloride acidizing fluid, an external direct current electric field and nanoscale bubbles to improve the reinjection efficiency in multiple ways. First, the addition of chelating resin CH-90Na and calcium chloride can indirectly and directly increase the number of calcium ions in the reinjection water and has a certain effect of expanding the pore volume of the rock core; then, a small amount of appropriate acidification of the reinjection water can reduce the generation of precipitates in the tail water reinjection and the resulting blockage; finally, the combination of the external direct current electric field and nanobubbles can effectively improve the connectivity of the reservoir, thereby improving the reinjection efficiency of the geothermal tail water.

Description

Technical Field

[0001] This invention belongs to the field of geothermal water development technology, specifically relating to a system and method for enhancing the reinjection efficiency of geothermal tailwater using an electric field. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] In the process of hydrothermal geothermal development, geothermal tailwater reinjection is a key technology to solve the problems of reservoir pressure deficit and environmental pollution, decreased permeability, suspended solids and chemical precipitation in tailwater, and pressure imbalance in the thermal reservoir caused by the arbitrary discharge of produced water during geothermal water extraction.

[0004] Geothermal tailwater reinjection refers to the treatment of used geothermal water and its reinjection back into the geothermal aquifer through reinjection wells. This method re-injects treated geothermal wastewater into the underground reservoir to achieve environmental protection. Geothermal tailwater reinjection enables the sustainable use of underground hot water resources and reduces dependence on other traditional energy sources. However, the complex composition of geothermal water makes the reinjection pattern unclear, severely restricting the development of geothermal water reinjection schemes. Therefore, improving tailwater reinjection efficiency is essential for the development and utilization of geothermal energy.

[0005] Low reinjection efficiency due to blockage is a common problem in current hot water reinjection processes. With prolonged reinjection time and the influence of groundwater flow, dissolved substances in the hot water gradually precipitate and form blockages, leading to a decrease in reinjection effectiveness. Conventional geothermal reinjection processes often employ methods such as well location selection, reinjection temperature, and acidification to increase the reinjection efficiency of geothermal tailwater, but these methods have the following drawbacks: (1) Severe blockage: High mineralization ions (such as Mg) in the effluent 2+ Salts such as CaCO3 and SiO2 are prone to forming chemical precipitates, leading to pore blockage. (2) Low permeability: Traditional acidification technology can only expand the pores to a limited extent and cannot inhibit the formation of new blockages; (3) Technical limitations: Existing methods have not systematically solved the problems of ion interference, physical blockage and reservoir structure deterioration.

[0006] Therefore, there is an urgent need for a multi-technology collaborative solution that can significantly improve reinjection efficiency during geothermal extraction to solve the above-mentioned technical problems. Summary of the Invention

[0007] To address the aforementioned problems, the present invention aims to provide a system and method for enhancing the reinjection efficiency of geothermal tailwater using an electric field. This invention integrates a composite technical solution of chelating resin ion exchange, acidification fluid calcium ion replenishment, nanobubble physical cleaning, and an external DC electric field. This solves the problems of blockage, low sandstone permeability, and reservoir structure deterioration in geothermal tailwater reinjection, thereby achieving efficient and sustainable geothermal resource development.

[0008] Specifically, the present invention provides the following technical solution: In a first aspect, the present invention provides a system for enhancing the reinjection efficiency of geothermal tailwater using an electric field, comprising a geothermal tailwater extraction well, a cyclone desander, a filter, an exhaust device, an ion exchange tank, an acidification tank, a reinjection well, a nanobubble generator, and an external electric field module, wherein the external electric field module includes electrodes and a current supply device disposed in the extraction well and the reinjection well. The inlet end of the hydrocyclone desander is connected to the geothermal tailwater extraction well. A first electric regulating valve is provided between the hydrocyclone desander and the extraction well, allowing unidirectional communication between the geothermal tailwater extraction well and the hydrocyclone desander. A second electric regulating valve is provided between the filter and the exhaust device, allowing unidirectional communication between the filter and the exhaust device. The outlet end of the exhaust device is connected to the inlet end of the ion exchange tank via a pressurization pump. The outlet end of the ion exchange tank is connected to the inlet end of the acidification tank via a connecting pipeline. The outlet end of the nanobubble generator is connected to the reinjection well via a connecting pipeline.

[0009] Preferably, the sand discharge port of the cyclone separator is located at the bottom of the cone, the overflow port is located at the top of the device, and the centrifugal separation efficiency is ≥95%.

[0010] Preferably, the filter adopts a multi-stage filter element structure with a pore size range of 1~50 μm; when the pore size range of the multi-stage filter element structure is 10~50 μm, it is a coarse filtration stage, and the material is set as sintered metal fiber, which is used to intercept fine sand and colloidal particles; when the pore size range is 1~10 μm, it is a fine filtration stage, and the material is set as ceramic filter membrane, which is used to remove microbial flocs and clay colloids.

[0011] Preferably, the nanobubble generator supports multiple gas inputs, including at least one of O2, N2, and CO2, and the gas type is automatically switched according to the activity of reservoir microorganisms or the type of pollutants.

[0012] Preferably, the electrodes are made of inert material, the spacing is 1.2 to 1.5 times the radius of influence of the reinjection well, and the electrode burial depth is aligned with the reservoir permeability zone.

[0013] Preferably, the system for improving the reinjection efficiency of geothermal tailwater further includes water quality monitoring sensors installed at the outlets of the ion exchange tank and the acidification tank for real-time detection of Ca.2+ Mg 2+ The concentration and pH value are recorded and the data is fed back to the control unit.

[0014] Further preferably, the water quality monitoring sensor installed at the outlet of the ion exchange tank is a selective electrode (ISE) or an online spectrometer to detect the concentration of ions in real time; the water quality monitoring sensor installed at the outlet of the acidification tank is a pH sensor to detect the pH value of the liquid in real time.

[0015] Preferably, the system for improving the efficiency of geothermal tailwater reinjection further includes a resistivity sensor, a conductivity sensor, and an ion sensor. The resistivity sensor is installed in the reservoir to detect the reservoir resistivity ρ in real time; the conductivity sensor and the ion sensor are installed at the outlet of the nanobubble generator. The conductivity sensor is used to determine the water conductivity σ; the ion sensor is used to detect the water ion concentration C. Finally, the data are integrated and fed back to the control unit.

[0016] Preferably, the external electric field module and the nanobubble generator are connected to the control unit to adjust the voltage and bubble generation parameters in real time according to the reservoir resistivity and water quality parameters, specifically: Based on the reservoir resistivity ρ, conductivity σ, and ion concentration C (water quality parameters), the bubble generation rate Q (numbers / second) is used as the control target and is regulated by an external electric field module and a nanobubble generator.

[0017] Specifically, the resistivity of the reservoir is monitored in real time by a resistivity sensor installed in the reinjection well reservoir to assess the range and intensity requirements of the electric field. At the initial stage of reinjection, the electric field is activated simultaneously to expand pore connectivity, and a nanobubble generator is activated to clear the released blockages. In conjunction with the real-time monitoring of reservoir resistivity, a pressure sensor is installed in the reinjection wellbore to monitor changes in pore pressure around the reinjection well. The operation of the external electric field module and the nanobubble generator is controlled through the above multi-angle coordinated control.

[0018] A second aspect of the present invention provides a method for improving the reinjection efficiency of geothermal tailwater in the above-mentioned system for enhancing geothermal tailwater reinjection efficiency using an electric field, comprising the following steps: S1. The pretreated geothermal tailwater is sent into an ion exchange tank to carry out an ion exchange reaction. S2. The tailwater after ion exchange is sent to an acidification tank containing calcium salt solution for acidification treatment. S3. The acid-treated tailwater is sent into the reinjection well, and geothermal tailwater is reinjected under the action of an external DC electric field and a nano bubble generator.

[0019] Preferably, in step S1, the pretreatment involves passing the extracted geothermal tailwater through a cyclone separator, a filter, and an exhaust device in sequence to remove large particulate impurities, suspended solids, and air bubbles from the geothermal tailwater.

[0020] Preferably, in step S1, the material in the ion exchange tank includes the chelating resin Tulsimer® CH-90Na to selectively adsorb Mg from the effluent. 2+ and heavy metal ions.

[0021] Preferably, in step S2, the material in the acidification tank is a calcium salt solution acidified with hydrochloric acid, and the calcium salt is selected from one or more of calcium chloride and calcium nitrate.

[0022] Preferably, in step S3, the voltage range of the applied DC electric field is 2~10 V, and it is dynamically adjusted according to the reservoir resistivity to increase porosity by 3%~20%.

[0023] Preferably, in step S3, the diameter of the bubbles generated by the nanobubble generator is 50~200 nm, and the microjet generated by their collapse is used to remove pore blockages.

[0024] Preferably, in step S3, the applied DC electric field and the nanobubble generator work alternately, with the applied DC electric field being applied for 12-24 hours first, and then the nanobubble generator being started for 12-24 hours.

[0025] A third aspect of the present invention provides an application of the above-described system for enhancing the reinjection efficiency of geothermal tailwater using an electric field in the field of geothermal tailwater reinjection.

[0026] One or more embodiments of the present invention have at least the following beneficial effects: (1) This invention combines multiple methods to improve the efficiency of geothermal tailwater reinjection. It can not only prevent heavy metal ions from invading the formation and reduce ions that inhibit reinjection efficiency, but also improve the porosity and permeability of the formation by strengthening the electric field and using nanobubble technology, thereby improving the efficiency of geothermal tailwater reinjection and promoting sustainable development.

[0027] (2) The present invention can indirectly and directly increase the number of calcium ions in the reinjection water by first adding chelating resin Tulsimer® CH-90Na and calcium chloride, which has a certain effect on expanding the pore volume of the core; then, the reinjection water is acidified in a small amount to reduce the precipitation and blockage in the tailwater reinjection; finally, the combination of external DC electric field and nanobubbles can effectively improve the connectivity of the reservoir, thereby improving the reinjection efficiency of geothermal tailwater.

[0028] (3) This invention combines the addition of a DC electric field with nanobubble technology. The external electric field increases porosity, and the bubbles occupy the pore space, reducing the deposition of suspended matter. During high-pressure reinjection, the bubbles compress and release energy, flushing the pores. The nanobubbles reduce fluid viscous resistance, and the electric field provides directional driving force. The combination of the two significantly improves the penetration depth and uniformity of water flow, making it particularly suitable for underground reservoirs. Attached Figure Description

[0029] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0030] Figure 1 A schematic diagram of the device for improving recharge efficiency provided by the present invention; Figure 2 These are test graphs showing the changes in core permeability before and after the action of the present invention in Embodiment 1 and Comparative Examples 1-4. Figure 3 The graphs show the recharge efficiency gain test results of core permeability involved in Embodiment 1 and Comparative Examples 1-4 of this invention. The components include: 1. Geothermal tailwater extraction well; 2. First electric regulating valve; 3. Cyclone desander; 4. Filter; 5. Second electric regulating valve; 6. Exhaust device; 7. Pressurization pump; 8. Ion exchange tank; 9. Acidification tank; 10. Recharge well; 11. Nanobubble generator; 12. Negative electrode; 13. Positive electrode; 14. Current supply device; 15. Selective electrode; 16. pH sensor; 17. Conductivity sensor; 18. Ion sensor; 19. Resistivity sensor; and 20. Pressure sensor. Detailed Implementation

[0031] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0032] The present invention will be further described in detail below with reference to specific embodiments. It should be noted that the specific embodiments are explanations of the present invention and not limitations thereof.

[0033] Example 1 : like Figure 1As shown, this embodiment provides a system for enhancing the reinjection efficiency of geothermal tailwater using an electric field. The system includes a geothermal tailwater extraction well 1, a cyclone desander 3, a filter 4, an exhaust device 6, an ion exchange tank 8, an acidification tank 9, a reinjection well 10, a nanobubble generator 11, and an external electric field module. The external electric field module includes a positive electrode 13 located in the geothermal tailwater extraction well 1, a negative electrode 12 located in the reinjection well 10, and a current supply device 14. When the reinjection volume of the reinjection well 10 is greater than or equal to the water intake volume of the geothermal tailwater extraction well 1, the water intake volume of the geothermal tailwater extraction well 1 is sequentially fed into the reinjection well 10 via the geothermal tailwater extraction well 1, the cyclone desander 3, the filter 4, the exhaust device 6, the ion exchange tank 8, and the acidification tank 9.

[0034] In this embodiment, the sand discharge port of the cyclone desander is located at the bottom of the cone, and the overflow port is located at the top of the device. The inlet end of the cyclone desander is connected to the geothermal tailwater extraction well. A first electric regulating valve is provided between the cyclone desander and the extraction well, allowing one-way communication between the geothermal tailwater extraction well and the cyclone desander. The discharged geothermal tailwater enters the cyclone desander device through a reinjection pipe, where solid-liquid separation is performed using the principle of centrifugal force. When the water flow is under a pressure of 1.1 MPa, the sand particles are thrown against the outer wall of the device and fall down the wall to the bottom of the cone. At the bottom, a sand discharge port is provided to allow the sand particles to be discharged, while the treated clean water is discharged through the overflow port at the top of the device, thereby achieving the purpose of effectively removing sand from the geothermal tailwater containing sand particles.

[0035] In this embodiment, a second electrically operated regulating valve is provided between the filter and the exhaust device, allowing the filter to communicate unidirectionally with the exhaust device. After the geothermal tailwater with sand particles removed enters the filter, it is further filtered by the physical interception of the filter element's surface or pores, removing suspended solids and colloids. This invention employs a multi-stage filter element structure, including a coarse filter element with a filtration accuracy of 50 μm and a fine filter element with a filtration accuracy of 10 μm. The fine filter element not only filters suspended solids in the reinjection fluid but also removes some microorganisms, effectively preventing physical and biological blockages during well reinjection. To effectively reduce various blockages and improve filtration efficiency, this invention uses a composite filtration technology combining cyclone sand removal and a filter with a multi-stage filter element structure. This reduces the filter's workload, performs tiered filtration, maximizes the filtration effect, and reduces the probability of blockage caused by traditional direct primary filter filtration.

[0036] In this embodiment, an exhaust tank device is installed to release the gas in the bubbles before reinjection. The outlet of the exhaust device 6 is connected to the inlet of the ion exchange tank via a pressurized pump. When geothermal tailwater enters the tank, the flow rate decreases rapidly due to the change in pipe diameter, causing a pressure drop. The pressure difference between the pressure inside the bubbles and the pressure inside the tank forces the bubbles to burst, releasing the gas. The exhaust tank effectively releases excess gases such as methane and carbon dioxide from the reinjection tailwater, thereby effectively preventing problems such as gas blockage, chemical reactions, and pipe corrosion during the reinjection process.

[0037] In this embodiment, the material in the ion exchange tank is set to include the chelating resin Tulsimer® CH-90Na to selectively adsorb Mg from the effluent. 2+ And heavy metal ions. Geothermal wastewater is pumped into an ion exchange tank using Tulsimer® CH-90Na chelating resin as raw material. The solution containing the target metal ions flows through an exchange column packed with Tulsimer® 90Na resin. The metal ions interact with the IDA functional groups on the resin to form strong complexes, which are then adsorbed by the resin particles. In this process, divalent metal ions show a higher affinity than monovalent ions, thus achieving selective adsorption. Ion exchange technology is used to adsorb heavy metal ions and Mg in the wastewater. 2+ .

[0038] In this embodiment, the outlet of the ion exchange tank is connected to the inlet of the acidizing tank via a connecting pipeline. The acidizing fluid is used to improve the permeability of geothermal reservoirs, especially in carbonate reservoirs. The acidizing fluid dissolves carbonate minerals in the rock, expanding natural fractures and pores, thereby increasing the effective volume of the reservoir and improving the productivity of the geothermal well. It also enhances the Ca content in the solution. 2＋ This can increase formation porosity, thereby improving reinjection efficiency and solving blockage problems, achieving a dual effect.

[0039] In this embodiment, the outlet of the nanobubble generator is directly connected to the reinjection well via a connecting pipeline. The nanobubble generator produces bubbles with a diameter of 50-200 nm, supporting multiple gas inputs, including at least one of O2, N2, and CO2. The gas type automatically switches based on reservoir microbial activity or pollutant type. Specifically, the high surface energy of the nanobubbles disrupts the adhesion between sediments and the rock wall. The collapse of these bubbles generates microjets that can remove blockages in micropores and decompose organic matter and suspended particles. The bubble type can also be selected according to actual needs; for example, oxygen-enriched nanobubbles inhibit sulfate-reducing bacteria, while ozone nanobubbles degrade organic pollutants, both of which can reduce formation contamination during reinjection.

[0040] In this embodiment, electrodes are installed at the reservoir within the reinjection well, powered by a DC power supply. The voltage applied to the electric field is adjusted according to the soil resistivity and reinjection requirements, allowing for on-demand control in specific scenarios. Furthermore, the electric field and air bubbles have a synergistic effect; the electric field enhances bubble stability and electrostatic adsorption of contaminants. Higher voltage results in stronger electroosmosis; care must be taken not to exceed the soil's compressive strength limit. The porosity of the rock changes with the action of the electric field.

[0041] In this embodiment, a water quality monitoring sensor is also included, installed at the outlet of the ion exchange tank and the outlet of the acidification tank, for real-time detection of Ca. 2+ Mg 2+ The system monitors ion concentration and pH value, and feeds the data back to the control unit. Specifically, the water quality monitoring sensor at the outlet of the ion exchange tank is a selective electrode (ISE) to detect the ion concentration in real time; the water quality monitoring sensor at the outlet of the acidification tank is a pH sensor to detect the pH value of the liquid in real time.

[0042] In this embodiment, a resistivity sensor, a conductivity sensor, and an ion sensor are also included. The resistivity sensor is installed in the reservoir to detect the reservoir resistivity ρ in real time. The conductivity sensor and the ion sensor are installed at the outlet of the nanobubble generator. The conductivity sensor is used to determine the water conductivity σ. The ion sensor is used to detect the water ion concentration C. Finally, the data are integrated and fed back to the control unit.

[0043] In this embodiment, the external electric field module and the nanobubble generator are connected to the control unit to adjust the voltage and bubble generation parameters in real time according to the reservoir resistivity and water quality parameters, specifically: Based on the reservoir resistivity ρ and water quality parameters (conductivity σ, ion concentration C), the bubble generation rate Q (numbers / second) is used as the control target and is regulated by an external electric field module and a nanobubble generator.

[0044] Specifically, the resistivity of the reservoir is monitored in real time by a resistivity sensor installed in the reinjection well reservoir to assess the range and intensity requirements of the electric field. At the initial stage of reinjection, the electric field is activated simultaneously to expand pore connectivity, and a nanobubble generator is activated to clear the released blockages. In conjunction with the real-time monitoring of reservoir resistivity, a pressure sensor is installed in the reinjection wellbore to monitor changes in pore pressure around the reinjection well. The operation of the external electric field module and the nanobubble generator is controlled through the above multi-angle coordinated control.

[0045] The system of this invention can be equipped with pressure gauges, thermometers, flow meters and other devices in certain parts of the reinjection pipeline as needed, which facilitates connection to the intelligent operation and maintenance system and realizes automatic optimization of reinjection.

[0046] Specifically: a pressure sensor monitors pressure changes in the reinjection pipeline in real time. When the pressure is abnormal, it indicates a possible blockage. The intelligent operation and maintenance system automatically adjusts the opening of the first and second electric regulating valves to reduce the tailwater delivery speed. At the same time, it increases the working intensity of the nanobubble generator, using the micro-jet generated by the collapse of nanobubbles to clear the blockage. A thermometer monitors the tailwater temperature in real time. If the temperature deviates from the suitable reinjection range, the control unit will adjust it in time. A flow meter measures the tailwater flow rate in real time. Combined with pressure and temperature data, the control unit can accurately calculate the reinjection rate. When the reinjection rate is lower than the set threshold, it will increase the voltage of the external DC electric field (within the range of 2~10 V) to increase the reservoir porosity by using the electric field, thereby increasing the reinjection rate and ensuring that the system is always in a state of efficient reinjection.

[0047] The above-mentioned system for enhancing geothermal tailwater reinjection efficiency using an electric field includes the following steps: (1) The process of removing large particles of mud and sand by a hydrocyclone separator; (2) The filter further removes fine impurities; (3) Release excess gas in the recharge tailwater through the exhaust device; (4) Entering the ion exchange tank to replace ions harmful to the formation; (5) Increase formation porosity by using an acidizing tank; (6) Inject DC electric field into the geothermal tail gas extraction well and reinjection well (set the voltage of the external DC electric field to 10 V; the electrodes are made of titanium alloy, the spacing is 1.5 times the influence radius of the reinjection well, and the electrode burial depth is aligned with the reservoir permeability zone). (7) Set up a nanobubble generator before reinjection (set bubble concentration to 1×10⁻⁶). 9 (number / ml) In this embodiment, the DC power generation device and the nanobubble generation device are set to be turned on simultaneously, and the nanobubble and electric field treatment time is 24 hours each.

[0048] Comparative Example 1 : The difference between this comparative example and Example 1 is that the nanobubble generator was not installed, but the connection of other devices and the method of enhancing the efficiency of geothermal tailwater reinjection are the same as in Example 1.

[0049] Comparative Example 2 : The difference between this comparative example and Example 1 is that no external electric field module was installed, but the connection of other devices and the method of enhancing the efficiency of geothermal tailwater reinjection are the same as in Example 1.

[0050] Comparative Example 3 : The difference between this comparative example and Example 1 is that no external electric field module and nanobubble generator were installed. The connection of other devices and the method of enhancing the efficiency of geothermal tailwater reinjection are the same as in Example 1.

[0051] Comparative Example 4 : The difference between this comparative example and Example 1 is that this comparative example intermittently applies an external DC electric field and starts a nanobubble generator; the connection of other devices and the method of enhancing the geothermal tailwater reinjection efficiency are the same as in Example 1.

[0052] Experimental Example 1 : This test example compares the core permeability of the apparatus and methods involved in Example 1 and Comparative Examples 1-4. The test process is as follows: For Example 1: A sandstone core from a geothermal reservoir was collected and cut to obtain a cylinder 5 cm long and 2.5 cm in diameter. The cylindrical core was placed in a constant temperature chamber and treated at 105°C for 12 hours to completely remove moisture. The dried core was then tested for permeability using a permeability measuring device to indicate the reinjection capacity without external influence. Simultaneously, a DC power supply generator and a nanobubble generator were activated to inject an electric field and nanobubbles into the core. The electric field strength was 10 V and the bubble concentration was 1 × 10⁻⁶. 9 The number of nanobubbles per milliliter and the treatment time for both the nanobubbles and the electric field were 24 h. The permeability of the treated core was then tested to demonstrate the reinjection capacity under the combined influence of the electric field and the nanobubbles.

[0053] For Comparative Example 1: Compared to the test process of Example 1, no nanobubbles were injected. Instead, the DC power generation device was directly turned on, and an electric field was injected into the core with an electric field strength of 10 V for 24 h. The core treated with the electric field was then subjected to permeability testing to demonstrate the reinjection capacity after the electric field effect.

[0054] For Comparative Example 2: Compared to the testing process in Example 1, the DC power supply was not turned on; instead, the nanobubble generation device was directly activated, and nanobubbles were injected into the rock core at a concentration of 1×10⁻⁶. 9 The permeability of the core sample treated with nanobubbles was measured at a concentration of 1000 μL for 24 hours to determine the reinjection capacity after the effect of nanobubbles.

[0055] For Comparative Example 3: Compared to the test process of Example 1, no nanobubbles were injected and the DC power supply was turned on. The permeability test was carried out directly on the core, indicating the reinjection capacity after the intermittent effect of the electric field and nanobubbles.

[0056] For Comparative Example 4: Compared to the test process of Example 1, the DC power generation device was first turned on, and an electric field was injected into the core with an electric field strength of 10 V for 24 h; then the nanobubble generation device was turned on, and nanobubbles were injected into the core for 24 h; the permeability of the core after treatment was tested to show the reinjection capacity after the intermittent effect of the electric field and nanobubbles.

[0057] Core permeability represents the fluid's seepage capacity within the core, thus reflecting changes in reinjection efficiency. Higher permeability indicates better reinjection efficiency. The change in permeability is used to calculate the reinjection efficiency gain of geothermal tailwater. The calculation formula is as follows: Reinjection efficiency gain = (Permeability after treatment - Permeability before treatment) / Permeability before treatment × 100%. The test results of reinjection efficiency gains for different comparative examples and Example 1 are shown in Table 1. Table 1

[0058] As shown in Table 1, the data and Figures 2-3 As shown, the permeability of the core after treatment in Example 1 of the present invention is significantly better than that in Comparative Examples 1 to 4, and the reinjection efficiency gain can reach 599.88%. That is, the combination of multiple methods to improve the reinjection efficiency of tailwater can improve the porosity and permeability of the formation, thereby improving the reinjection efficiency of geothermal tailwater and promoting sustainable development.

[0059] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A system for enhancing the reinjection efficiency of geothermal tailwater using an electric field, characterized in that, Specifically, it includes a geothermal tailwater extraction well, a hydrocyclone desander, a filter, an exhaust device, an ion exchange tank, an acidification tank, a reinjection well, a nanobubble generator, and an external electric field module. The external electric field module includes electrodes and a current supply device installed in the extraction well and the reinjection well. The inlet end of the hydrocyclone desander is connected to the geothermal tailwater extraction well. A first electric regulating valve is provided between the hydrocyclone desander and the extraction well, allowing unidirectional communication between the geothermal tailwater extraction well and the hydrocyclone desander. A second electric regulating valve is provided between the filter and the exhaust device, allowing unidirectional communication between the filter and the exhaust device. The outlet end of the exhaust device is connected to the inlet end of the ion exchange tank via a pressurization pump. The outlet end of the ion exchange tank is connected to the inlet end of the acidification tank via a connecting pipeline. The outlet end of the nanobubble generator is connected to the reinjection well via a connecting pipeline. The system also includes a resistivity sensor, a conductivity sensor, and an ion sensor. The resistivity sensor is installed in the reservoir to detect the reservoir resistivity ρ in real time. The conductivity sensor and the ion sensor are installed at the outlet of the nanobubble generator. The conductivity sensor is used to determine the water conductivity σ. The ion sensor is used to detect the water ion concentration C. Finally, the data are integrated and fed back to the control unit. The external electric field module and the nanobubble generator are connected to the control unit and are used to adjust the voltage and bubble generation parameters in real time according to the reservoir resistivity and water quality parameters. Specifically, based on the reservoir resistivity ρ, conductivity σ and ion concentration C, the bubble generation rate Q is used as the control target and is controlled by the external electric field module and the nanobubble generator. In the initial stage of reinjection, the control unit activates an electric field to expand pore connectivity and simultaneously activates a nanobubble generator to clear released blockages. Combined with real-time monitoring of reservoir resistivity, a pressure sensor is installed inside the reinjection well to monitor changes in pore pressure around the reinjection well. The operation of the external electric field module and the nanobubble generator is controlled in a multi-angle coordinated manner.

2. The system for enhancing geothermal tailwater reinjection efficiency using an electric field as described in claim 1, characterized in that, The sand discharge port of the cyclone separator is located at the bottom of the cone, and the overflow port is located at the top of the device. The centrifugal separation efficiency is ≥95%.

3. The system for enhancing geothermal tailwater reinjection efficiency using an electric field as described in claim 1, characterized in that, The filter adopts a multi-stage filter element structure with a pore size range of 1~50 μm. When the pore size range of the multi-stage filter element structure is 10~50 μm, it is a coarse filtration stage, and the material is set as sintered metal fiber, which is used to intercept fine sand and colloidal particles. When the pore size range is 1~10 μm, it is a fine filtration stage, and the material is set as ceramic filter membrane, which is used to remove microbial flocs and clay colloids.

4. The system for enhancing geothermal tailwater reinjection efficiency using an electric field as described in claim 1, characterized in that, The nanobubble generator supports multiple gas inputs, including at least one of O2, N2, and CO2, and the gas type is automatically switched according to the activity of reservoir microorganisms or the type of pollutants.

5. The system for enhancing geothermal tailwater reinjection efficiency using an electric field as described in claim 1, characterized in that, The electrodes are made of titanium alloy, and the spacing between them is 1.2 to 1.5 times the radius of influence of the reinjection well. The electrode burial depth is aligned with the reservoir permeability zone.

6. The system for enhancing geothermal tailwater reinjection efficiency using an electric field as described in claim 1, characterized in that, The system also includes water quality monitoring sensors installed at the outlets of the ion exchange tank and the acidification tank for real-time detection of Ca. 2+ Mg 2+ The concentration and pH value are recorded, and the data is fed back to the control unit.

7. A method for improving the reinjection efficiency of geothermal tailwater based on the system for enhancing geothermal tailwater reinjection efficiency using an electric field as described in any one of claims 1 to 6, characterized in that, Includes the following steps: S1. The pretreated geothermal tailwater is sent into an ion exchange tank to carry out an ion exchange reaction. S2. The tailwater after ion exchange is sent to an acidification tank containing calcium salt solution for acidification treatment. S3. The acid-treated tailwater is sent into the reinjection well, and geothermal tailwater is reinjected under the action of an external DC electric field and a nano bubble generator.

8. The method for improving the reinjection efficiency of geothermal tailwater as described in claim 7, characterized in that, In step S1, the pretreatment involves passing the extracted geothermal tailwater through a cyclone separator, a filter, and an exhaust device in sequence to remove large particulate impurities, suspended solids, and air bubbles from the geothermal tailwater.

9. The method for improving the reinjection efficiency of geothermal tailwater as described in claim 7, characterized in that, In step S1, the material in the ion exchange tank includes the chelating resin Tulsimer® CH-90Na to selectively adsorb Mg from the effluent. 2+ and heavy metal ions.

10. The method for improving the reinjection efficiency of geothermal tailwater as described in claim 7, characterized in that, In step S2, the material in the acidification tank is a calcium salt solution acidified with hydrochloric acid, and the calcium salt is selected from one or more of calcium chloride and calcium nitrate.

11. The method for improving the reinjection efficiency of geothermal tailwater as described in claim 7, characterized in that, In step S3, the voltage range of the applied DC electric field is 2~10 V, and it is dynamically adjusted according to the reservoir resistivity to increase porosity by 3%~20%.

12. The method for improving the reinjection efficiency of geothermal tailwater as described in claim 7, characterized in that, In step S3, the size of the bubbles generated by the nanobubble generator is 50~200 nm, and the microjet generated by their collapse is used to remove pore blockages.

13. The method for improving the reinjection efficiency of geothermal tailwater as described in claim 7, characterized in that, In step S3, the applied DC electric field and the nanobubble generator work alternately. First, the applied DC electric field is applied for 12~24 hours, and then the nanobubble generator is started for 12~24 hours.

14. The application of the system for enhancing the reinjection efficiency of geothermal tailwater using an electric field as described in any one of claims 1 to 6 in the field of geothermal tailwater reinjection.

Images