System and method for enhancing geothermal tail water recharge efficiency by using electric field

Abstract

The invention belongs to the technical field of geothermal water development, and particularly relates to a system and method for enhancing geothermal tail water recharge efficiency through an electric field. The invention provides a combination mode of additional ions, an additional direct-current electric field and nano-bubbles, and the recharge efficiency is improved in multiple aspects by adopting the chelating resin TulsimerCH-90Na, the calcium chloride acidizing fluid, the additional direct-current electric field and the nano-bubbles. Firstly, chelating resin TulsimerCH-90Na and calcium chloride are added, so that the number of calcium ions in recharge water can be indirectly and directly increased, and a certain expansion effect on the pore volume of a rock core is achieved; then, the recharge water is slightly and properly acidified to reduce blockage caused by precipitates generated in tail water recharge; and finally, through the combination of the external direct-current electric field and the nano bubbles, the connectivity of the reservoir can be effectively improved, so that the recharge efficiency of the geothermal tail water is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of geothermal water development, and in particular relates to a system and method for enhancing the efficiency of geothermal tail water recharge by utilizing an electric field. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance understanding of the overall background of the invention and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to those skilled in the art.

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

[0004] Geothermal tailwater reinjection involves treating used geothermal water and then injecting it back into the geothermal aquifer through a reinjection well. This method reinjects treated geothermal wastewater into the underground reservoir, thereby protecting the environment. Geothermal tailwater reinjection enables the sustainable utilization of underground hot water resources while reducing reliance on other traditional energy sources. However, the complex composition of geothermal water currently makes the principles of geothermal tailwater reinjection unclear, severely restricting the development of geothermal tailwater reinjection plans. Therefore, improving tailwater reinjection efficiency is essential for geothermal energy development and utilization.

[0005] In current hot water reinjection processes, low reinjection efficiency due to blockage is a common problem. As reinjection time increases and groundwater flow is affected, dissolved substances in the hot water gradually precipitate and form blockages, resulting in 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. However, these methods present the following challenges: (1) Serious blockage: High mineralization ions in the tail water (such as Mg 2+ ) and insoluble salts (CaCO3, SiO2) are prone to chemical precipitation, leading to pore blockage; (2) Low permeability: Traditional acidizing technology can only expand pores to a limited extent and cannot inhibit the formation of new blockages; (3) Technical limitations: Existing methods do not systematically address the problems of ion interference, physical blockage, and reservoir structural degradation.

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

[0007] To address these issues, the present invention aims to provide a system and method for enhancing the efficiency of geothermal tailwater recharge using an electric field. This system integrates a composite technology solution using chelating resin ion exchange, calcium ion supplementation with an acidizing fluid, nanobubble physical cleaning, and an applied DC electric field. This solution addresses issues such as blockage, low sandstone permeability, and reservoir structural degradation during geothermal tailwater recharge, thereby enabling efficient and sustainable geothermal resource development.

[0008] Specifically, the present invention provides the following technical solutions: In a first aspect, the present invention provides a system for enhancing the efficiency of geothermal tailwater reinjection using an electric field, comprising a geothermal tailwater production 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 disposed in the production well and the reinjection well and a current supply device; The inlet end of the cyclone desander is connected to the geothermal tail water production well. A first electric regulating valve is provided between the cyclone desander and the production well, and the first electric regulating valve enables one-way communication between the geothermal tail water production well and the cyclone desander. A second electric regulating valve is provided between the filter and the exhaust device, and the second electric regulating valve enables one-way 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 pressure pump; the outlet end of the ion exchange tank is connected to the inlet end of the acidification tank via a connecting pipeline; and the outlet end of the nanobubble generator is connected to the recharge well via a connecting pipeline.

[0009] Preferably, the sand discharge port of the cyclone desander is arranged at the conical bottom, the overflow port is arranged 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 in the multi-stage filter element structure is 10~50 μm, it is a coarse filtration stage, and the material is set to 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 to ceramic filter membrane, which is used to remove microbial clusters 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 reservoir microbial activity or pollutant type.

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

[0013] Preferably, the system for improving the geothermal tail water recharge efficiency further includes a water quality monitoring sensor, which is arranged at the outlet of the ion exchange tank and the outlet of the acidification tank for real-time detection of Ca2+ Mg 2+ concentration and pH value, and feed the data back to the control unit.

[0014] Further preferably, the water quality monitoring sensor arranged 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 arranged 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 geothermal tail water recharge efficiency also includes a resistivity sensor, a conductivity sensor, and an ion sensor. The resistivity sensor is arranged in the reservoir to detect the reservoir resistivity ρ in real time; the conductivity sensor and the ion sensor are arranged at the outlet end of the nanobubble generator, and the conductivity sensor is used to determine the water quality conductivity σ; the ion sensor is used to detect the water quality ion concentration C, and finally the data is integrated and fed back to the control unit.

[0016] Preferably, the external electric field module and the nanobubble generator are connected to a control unit for adjusting 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 (per second) is controlled by an external electric field module and a nanobubble generator. The corresponding adjustment formula for bubble generation parameters is as follows:

[0017] in, is the initial bubble generation rate, in pieces per second, are the baseline thresholds of reservoir resistivity, water conductivity and ion concentration, respectively, while ρ, σ and C are the real-time reservoir resistivity, real-time water conductivity and real-time ion concentration, with units of Ω·m, S / m and mol / L respectively, and k1, k2 and k3 are weight coefficients used to optimize the experiment to meet ; is the voltage regulation coefficient, which is positively correlated with the voltage of the applied electric field.

[0018] Specifically, a resistivity sensor installed in the reservoir of the recharge well monitors the reservoir resistivity in real time, evaluates the range of action and intensity requirements of the electric field, and simultaneously activates the electric field to expand pore connectivity and the nanobubble generator to clear released blockages at the initial stage of recharge. Combined with the real-time monitoring of the reservoir resistivity, a pressure sensor is installed in the wellbore of the recharge well to monitor the changes in pore pressure around the recharge well. Through the above multi-angle coordinated control, the operation of the external electric field module and the nanobubble generator is controlled.

[0019] A second aspect of the present invention provides a method for improving the geothermal tail water reinjection efficiency of the system utilizing electric field to enhance the geothermal tail water reinjection efficiency, comprising the following steps: S1. Send the pretreated geothermal tail water into the ion exchange tank to perform ion exchange reaction; S2. Sending the tail water after ion exchange into an acidification tank containing calcium salt solution for acidification treatment; S3. The tail water after acidification treatment is sent to the reinjection well, and geothermal tail water reinjection is carried out under the action of an external DC electric field and a nano bubble generator.

[0020] Preferably, in step S1, the pretreatment is to pass the produced geothermal tail water through a cyclone desander, a filter and an exhaust device in sequence to remove large particle impurities, suspended matter and bubbles in the geothermal tail water.

[0021] Preferably, in step S1, the material in the ion exchange tank includes chelating resin Tulsimer® CH-90Na to selectively adsorb Mg in the tail water. 2+ and heavy metal ions.

[0022] Preferably, in step S2, the material in the acidification tank is a calcium salt solution acidified with hydrochloric acid, the calcium salt is selected from one or more of calcium chloride and calcium nitrate, and the concentration of the acidified calcium salt solution is 1.5-2.5 g / mL.

[0023] Preferably, in step S3, the voltage range of the applied DC electric field is 2-10 V, and is dynamically adjusted according to the reservoir resistivity to increase the porosity by 3%-20%.

[0024] Preferably, in step S3, the diameter of the bubbles generated by the nanobubble generator is 50-200 nm, and the microjets generated by the collapse of the bubbles are used to clear pore blockages.

[0025] Preferably, in step S3, the external DC electric field and the nanobubble generator act alternately, first applying the external DC electric field for 12 to 24 hours, and then starting the nanobubble generator for 12 to 24 hours.

[0026] A third aspect of the present invention provides an application of the method for improving geothermal tail water reinjection efficiency of the above-mentioned system for enhancing geothermal tail water reinjection efficiency by utilizing an electric field in the field of geothermal tail water reinjection.

[0027] One or more embodiments of the present invention have at least the following beneficial effects: (1) The present invention combines multiple methods to improve the efficiency of tail water recharge. It can not only prevent heavy metal ions from invading the formation and reduce the ions that have an inhibitory effect on the recharge 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 tail water recharge and promoting sustainable development.

[0028] (2) The present invention can indirectly and directly increase the amount of calcium ions in the reinjection water by first adding the 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 formation of precipitation and blockage during the tail water reinjection; finally, the combination of an external DC electric field and nanobubbles can effectively improve the connectivity of the reservoir, thereby improving the reinjection efficiency of the geothermal tail water.

[0029] (3) This invention combines the addition of a direct current electric field with nanobubble technology. The applied electric field increases porosity, allowing bubbles to occupy pore space and reduce the deposition of suspended matter. During high-pressure recharge, the bubbles compress and release energy, flushing the pores. Nanobubbles reduce fluid viscous resistance, while 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. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The accompanying drawings, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0031] Figure 1 A schematic diagram of a device for improving recharge efficiency provided by the present invention; Figure 2 This is a test diagram of the change in core permeability before and after the action of Example 1 and Comparative Examples 1 to 4 of the present invention; Figure 3 This is a test diagram of the reinjection efficiency gain of the core permeability involved in Example 1 and Comparative Examples 1 to 4 of the present invention; Among them, 1. Geothermal tailwater extraction well; 2. First electric regulating valve; 3. Cyclone desander; 4. Filter; 5. Second electric regulating valve; 6. Exhaust device; 7. Pressure 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; 20. Pressure sensor. DETAILED DESCRIPTION

[0032] It should be noted that the following detailed description is illustrative and is intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meaning as commonly understood by those skilled in the art to which the present invention belongs.

[0033] The present invention will be further described in detail below with reference to specific embodiments. It should be noted that the specific embodiments are intended to explain the present invention rather than to limit it.

[0034] Example 1 : like Figure 1 As shown, this embodiment provides a system for enhancing the efficiency of geothermal tailwater recharge by utilizing an electric field. The system includes a geothermal tailwater production well 1, a cyclone desander 3, a filter 4, an exhaust device 6, an ion exchange tank 8, an acidification tank 9, a recharge well 10, a nanobubble generator 11, and an external electric field module. The external electric field module includes a positive electrode 13 disposed in the geothermal tailwater production well 1, a negative electrode 12 disposed in the recharge well 10, and a current supply device 14. When the recharge rate of the recharge well 10 is greater than or equal to the water intake of the geothermal tailwater production well 1, the water intake of the geothermal tailwater production well 1 is sequentially delivered to the recharge well 10 through the geothermal tailwater production well 1, the cyclone desander 3, the filter 4, the exhaust device 6, the ion exchange tank 8, and the acidification tank 9.

[0035] In this embodiment, the cyclone desander has a sand discharge port located at the bottom of the cone, an overflow port located at the top of the device, and 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, which allows one-way communication between the geothermal tailwater extraction well and the cyclone desander. The discharged geothermal tailwater enters the cyclone desander through a recharge pipe, where solid-liquid separation is performed using the principle of centrifugal force. When the water flows under a pressure of 1.1 MPa, sand particles are thrown toward the outer wall of the device and fall along the wall to the conical bottom of the device. A sand discharge port is provided at the bottom to allow sand particles to be discharged, while the treated clean water is discharged through the upper overflow port of the device, thereby achieving the purpose of effectively desanding the geothermal tailwater containing sand particles.

[0036] In this embodiment, a second electric regulating valve is provided between the filter and the exhaust device, and the second electric regulating valve enables the filter to be connected to the exhaust device in one direction; after the geothermal tail water with sand removed enters the filter, it is physically intercepted by the surface or pores of the filter element to further remove impurities such as suspended matter and colloids. The present invention sets the filter to adopt 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 can not only filter the suspended matter in the reinjection fluid, but also filter out some microorganisms, effectively preventing physical blockage and biological blockage during reinjection in the well. In order to effectively reduce various blockages and improve filtration efficiency. The present invention adopts a composite filtration technology that combines cyclone sand removal with a filter with a multi-stage filter element structure, which reduces the workload of the filter, performs filtration in stages, maximizes the filtration effect, and reduces the probability of clogging caused by traditional direct filtration with a primary filter.

[0037] In this embodiment, an exhaust tank device is provided to release the gas trapped in the bubbles before re-injection. The outlet of the exhaust device 6 is connected to the inlet of the ion exchange tank via a pressure pump. As the geothermal tailwater enters the tank, the flow rate rapidly decreases due to the change in pipe diameter, causing a drop in pressure. This creates a pressure differential between the pressure within the bubbles and the pressure within the tank, forcing the bubbles to burst and releasing the gas. The exhaust tank effectively releases excess gases, such as methane and carbon dioxide, from the re-injection tailwater, thereby effectively preventing problems such as gas blockage, chemical reactions, and pipeline corrosion that may arise during the re-injection process.

[0038] In this embodiment, the material in the ion exchange tank is set to include chelating resin Tulsimer® CH-90Na to selectively adsorb Mg in the tail water. 2+ The geothermal tail water enters the ion exchange tank with the chelating resin Tulsimer® CH-90Na as the raw material through a pressure pump. The solution containing the target metal ions flows through the exchange column filled with Tulsimer® 90Na resin. The metal ions interact with the IDA functional groups on the resin to form a strong complex and are adsorbed by the resin particles. In this process, divalent metal ions show a higher affinity than monovalent ions, so selective adsorption can be achieved. The heavy metal ions and Mg in the tail water are adsorbed using ion exchange technology. 2+ .

[0039] In this embodiment, the outlet of the ion exchange tank is connected to the inlet of the acidizing tank through a connecting pipe, and the acidizing fluid is used to improve the permeability of the geothermal reservoir, especially in carbonate reservoirs. The acidizing fluid dissolves the carbonate minerals in the rock, expands the natural cracks and pores, thereby increasing the effective volume of the reservoir and improving the production capacity of the geothermal well, while also increasing the Ca in the solution. 2＋, which can expand the porosity of the formation, improve the reinjection efficiency, and solve the blockage problem, achieving a dual effect.

[0040] In this embodiment, the outlet of the nanobubble generator is directly connected to the recharge well via a connecting pipe. The bubbles produced by the nanobubble generator have a diameter of 50 to 200 nm and support a variety of gas inputs, including at least one of O2, N2, and CO2. The gas type is automatically switched based on reservoir microbial activity or contaminant type. Specifically, the high surface energy of the nanobubbles disrupts the adhesion of sediment to the rock wall. The collapse of these bubbles generates microjets that clear blockages within tiny pores and decompose organic matter and suspended particles. Bubble type can also be selected based on actual needs. For example, oxygen-enriched nanobubbles inhibit sulfate-reducing bacteria, while ozone-enriched nanobubbles degrade organic contaminants, both of which can reduce contamination of the formation during the recharge process.

[0041] In this embodiment, electrodes are installed in the reservoir within the recharge well, powered by a DC power supply. The voltage applied to the electric field is adjusted based on the soil resistivity and recharge requirements, enabling on-demand regulation in real-world scenarios. Furthermore, the electric field and bubbles act synergistically, enhancing both bubble stability and electrostatic adsorption of contaminants. The higher the voltage, the stronger the electroosmotic effect. Care must be taken not to exceed the soil's pressure limit, as the porosity of the rock changes with the action of the electric field.

[0042] In this embodiment, a water quality monitoring sensor is also included, which is set 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 water quality monitoring sensor installed at the outlet of the ion exchange tank is a selective electrode (ISE) 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.

[0043] In this embodiment, a resistivity sensor, a conductivity sensor, and an ion sensor are also included. The resistivity sensor is set in the reservoir to detect the reservoir resistivity ρ in real time; the conductivity sensor and the ion sensor are set at the outlet of the nanobubble generator, and the conductivity sensor is used to determine the water quality conductivity σ; the ion sensor is used to detect the water quality ion concentration C, and finally the data is integrated and fed back to the control unit.

[0044] In this embodiment, the external electric field module and the nanobubble generator are connected to a control unit for adjusting 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 (per second) is controlled by an external electric field module and a nanobubble generator. The corresponding adjustment formula for bubble generation parameters is as follows:

[0045] in, is the initial bubble generation rate, are the baseline thresholds of reservoir resistivity, water conductivity and ion concentration, respectively, while ρ, σ and C are the real-time reservoir resistivity, real-time water conductivity and real-time ion concentration, with units of Ω·m, S / m and mol / L respectively, and k1, k2 and k3 are weight coefficients used to optimize the experiment to meet ; is the voltage regulation coefficient, which is positively correlated with the voltage of the applied electric field.

[0046] Specifically, a resistivity sensor installed in the reservoir of the recharge well monitors the reservoir resistivity in real time, evaluates the range of action and intensity requirements of the electric field, and simultaneously activates the electric field to expand pore connectivity and the nanobubble generator to clear released blockages at the initial stage of recharge. Combined with the real-time monitoring of the reservoir resistivity, a pressure sensor is installed in the wellbore of the recharge well to monitor the changes in pore pressure around the recharge well. Through the above multi-angle coordinated control, the operation of the external electric field module and the nanobubble generator is controlled.

[0047] The system of the present invention can be equipped with pressure gauges, thermometers, flow meters and other equipment in some places of the reinjection pipeline as needed, so as to facilitate access to the intelligent operation and maintenance system and realize automatic optimization reinjection of the system.

[0048] Specifically: the pressure sensor monitors the pressure changes in the reinjection pipeline in real time. When the pressure is abnormal, it indicates that a blockage may occur. The intelligent operation and maintenance system will automatically adjust the opening of the first electric control valve and the second electric control valve to reduce the tail water delivery speed. At the same time, it will enhance the working intensity of the nano bubble generator and use the micro jet generated by the collapse of nano bubbles to clear the blockage. The thermometer monitors the tail water temperature in real time. If the temperature deviates from the range suitable for reinjection, the control unit will make timely adjustments. The flow meter measures the flow of tail water in real time. Combined with the pressure and temperature data, the control unit can accurately calculate the reinjection rate. When the reinjection rate is lower than the set threshold, the voltage of the external DC electric field will be increased (within the range of 2~10 V). The effect of the electric field will increase the reservoir porosity, thereby increasing the reinjection rate and ensuring that the system is always in a state of efficient reinjection.

[0049] The above-mentioned method for improving the geothermal tail water reinjection efficiency by utilizing an electric field to enhance the geothermal tail water reinjection efficiency comprises the following steps: (1) The process of removing large particles of sand by a cyclone desander; (2) The filter further removes fine impurities; (3) Release excess gas in the recharged tailwater through the exhaust device; (4) Entering the ion exchange tank to replace ions harmful to the formation; (5) Expanding formation porosity through acidizing tanks; (6) Inject a DC electric field into the geothermal tail gas production well and the recharge well (the voltage of the DC electric field is set to 10 V; the electrodes are made of titanium alloy, the spacing is 1.5 times the influence radius of the recharge well, and the buried depth of the electrodes is aligned with the reservoir permeability zone); (7) Before recharging, set the nanobubble generator (set the bubble concentration to 1×10 9 number / ml); In this embodiment, the DC power supply generating device and the nanobubble generating device are set to be turned on at the same time, and the nanobubble and electric field treatment times are both 24 hours.

[0050] Comparative Example 1 : The difference between this comparative example and Example 1 is that the nanobubble generator is not provided, and the connection of other devices and the method of enhancing the geothermal tail water reinjection efficiency are consistent with those in Example 1.

[0051] Comparative Example 2 : The difference between this comparative example and Example 1 is that the external electric field module is not provided, and the methods of connecting other devices and enhancing the geothermal tail water reinjection efficiency are consistent with those in Example 1.

[0052] Comparative Example 3 : The difference between this comparative example and Example 1 is that the external electric field module and the nanobubble generator are not provided, and the connection of other devices and the method of enhancing the geothermal tail water reinjection efficiency are consistent with those in Example 1.

[0053] Comparative Example 4 : The difference between this comparative example and Example 1 is that in this comparative example, the external DC electric field is applied and the nanobubble generator is started intermittently; the methods of connecting other devices and enhancing the geothermal tail water recharge efficiency are consistent with those in Example 1.

[0054] Test Example 1 : This test example compares the core permeability of the devices and methods involved in Example 1 and Comparative Examples 1 to 4. The test process is as follows: For Example 1: a sandstone core from the geothermal reservoir was collected and cut into a cylinder with a length of 5 cm and a diameter of 2.5 cm. The cylindrical core was placed in a constant temperature box and treated at 105°C for 12 h to completely remove moisture. The dried core was then passed through a permeability measuring device to test the permeability in the core to indicate the recharge capacity without external influence. The DC power supply generator and the nanobubble generator were simultaneously turned on to inject an electric field and nanobubbles into the core at the same time. The electric field strength was 10 V and the bubble concentration was 1×10 9 The nanobubble and electric field treatment time were both 24 h, and the permeability test was carried out on the treated cores to indicate the recharge capacity after the simultaneous effect of electric field and nanobubbles.

[0055] For Comparative Example 1: Compared with the test process of Example 1, nanobubble injection was not performed, that is, the DC power generation device was directly turned on, and the electric field was injected into the core with an electric field intensity of 10 V and a treatment time of 24 h. The permeability test of the core after electric field treatment was carried out to indicate the recharge capacity after the influence of the electric field.

[0056] For Comparative Example 2: Compared with the test process of Example 1, the DC power supply was not turned on, that is, the nanobubble generating device was directly turned on, and the nanobubbles were injected into the core with a bubble concentration of 1×10 9 The number of nanobubbles / ml was 24 h, and the permeability test of the core treated with nanobubbles was carried out to show the recharge capacity after the effect of nanobubbles.

[0057] For Comparative Example 3: Compared with the test process of Example 1, the injection of nanobubbles and the turning on of the DC power supply were not performed, and the permeability test was carried out directly on the core, indicating the recharge capacity after the influence of the intermittent action of the electric field and nanobubbles.

[0058] For Comparative Example 4: Compared with the test process of Example 1, the DC power supply generating device is first turned on, and an electric field is injected into the core with an electric field strength of 10 V for 24 hours; then the nanobubble generating device is turned on, and nanobubbles are injected into the core for 24 hours; the permeability test of the treated core is carried out to indicate the recharge capacity after the intermittent action of the electric field and nanobubbles.

[0059] Core permeability indicates the ability of fluid to flow through the core and, therefore, reflects changes in reinjection efficiency. The higher the permeability, the better the reinjection efficiency. The change in permeability is used to calculate the geothermal tailwater reinjection efficiency gain using the following formula: Reinjection Efficiency Gain = (Permeability after treatment - Permeability before treatment) / Permeability before treatment × 100%. The reinjection efficiency gain results for different comparative examples and Example 1 are shown in Table 1: Table 1

[0060] As shown in Table 1, Figures 2 and 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 tail water reinjection efficiency can achieve an increase in the porosity and permeability of the formation, thereby improving the geothermal tail water reinjection efficiency and promoting sustainable development.

[0061] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A system for enhancing geothermal tailwater recharge efficiency using an electric field, characterized in that: Specifically, it includes a geothermal tailwater production well, a cyclone desander, a filter, an exhaust device, an ion exchange tank, an acidification tank, a recharge well, a nanobubble generator and an external electric field module. The external electric field module includes electrodes and a current providing device arranged in the production well and the recharge well; The inlet end of the cyclone desander is connected to the geothermal tail water production well. A first electric regulating valve is provided between the cyclone desander and the production well, and the first electric regulating valve enables one-way communication between the geothermal tail water production well and the cyclone desander. A second electric regulating valve is provided between the filter and the exhaust device, and the second electric regulating valve enables one-way 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 pressure pump; the outlet end of the ion exchange tank is connected to the inlet end of the acidification tank via a connecting pipeline; and the outlet end of the nanobubble generator is connected to the recharge well via a connecting pipeline.

2. The system for enhancing geothermal tailwater recharge efficiency by utilizing electric field according to claim 1, characterized in that: 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 centrifugal separation efficiency is ≥95%; Preferably, the filter adopts a multi-stage filter element structure with a pore size range of 1-50 μm; when the pore size range in the multi-stage filter element structure is 10-50 μm, it is a coarse filtration stage, and the material is set to 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 to ceramic filter membrane, which is used to remove microbial clusters and clay colloids; 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 reservoir microbial activity or pollutant type.

3. The system for enhancing geothermal tailwater recharge efficiency by utilizing electric field according to claim 1, characterized in that: The electrodes are made of titanium alloy, with a spacing of 1.2 to 1.5 times the influence radius of the recharge well, and the buried depth of the electrodes is aligned with the permeability zone of the reservoir.

4. The system for enhancing geothermal tailwater recharge efficiency by utilizing electric field according to claim 1, characterized in that: The system for improving geothermal tail water recharge efficiency also includes a water quality monitoring sensor, which is arranged at the outlet of the ion exchange tank and the outlet of the acidification tank for real-time detection of Ca 2+ Mg 2+ concentration and pH value, and feed the data back to the control unit.

5. The system for enhancing geothermal tailwater recharge efficiency by utilizing electric field according to claim 1, characterized in that: The system for improving the geothermal tailwater recharge efficiency also includes a resistivity sensor, a conductivity sensor, and an ion sensor. The resistivity sensor is set in the reservoir to detect the reservoir resistivity ρ in real time; the conductivity sensor and the ion sensor are set at the outlet of the nanobubble generator, and the conductivity sensor is used to determine the water conductivity σ; the ion sensor is used to detect the water ion concentration C, and finally the data is integrated and fed back to the control unit; Preferably, the external electric field module and the nanobubble generator are connected to a control unit for adjusting 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 controlled by an external electric field module and a nanobubble generator. The corresponding adjustment formula for bubble generation parameters is as follows: in, is the initial bubble generation rate, in pieces per second, are the baseline thresholds of reservoir resistivity, water conductivity and ion concentration, respectively, while ρ, σ and C are the real-time reservoir resistivity, real-time water conductivity and real-time ion concentration, with units of Ω·m, S / m and mol / L respectively, and k1, k2 and k3 are weight coefficients used to optimize the experiment to meet ; is the voltage regulation coefficient, which is positively correlated with the voltage of the applied electric field.

6. A method for improving geothermal tail water recharge efficiency by utilizing an electric field to enhance geothermal tail water recharge efficiency according to any one of claims 1 to 5, characterized in that: The following steps are involved: S1. Send the pretreated geothermal tail water into the ion exchange tank to perform ion exchange reaction; S2. Sending the tail water after ion exchange into an acidification tank containing calcium salt solution for acidification treatment; S3. The tail water after acidification treatment is sent to the reinjection well, and geothermal tail water reinjection is carried out under the action of an external DC electric field and a nano bubble generator.

7. The method for improving geothermal tail water recharge efficiency according to claim 6, wherein: In step S1, the pretreatment is to pass the produced geothermal tail water through a cyclone desander, a filter and an exhaust device in sequence to remove large particles of impurities, suspended matter and bubbles in the geothermal tail water; Preferably, the material in the ion exchange tank includes chelating resin Tulsimer® CH-90Na to selectively adsorb Mg in the tail water. 2+ and heavy metal ions.

8. The method for improving geothermal tail water recharge efficiency according to claim 6, wherein: In step S2, the material in the acidification tank is a calcium salt solution acidified with hydrochloric acid, the calcium salt is selected from one or more of calcium chloride and calcium nitrate, and the concentration of the acidified calcium salt solution is 1.5-2.5 g / mL.

9. The method for improving geothermal tail water recharge efficiency according to claim 6, wherein: In step S3, the voltage range of the applied DC electric field is 2-10 V and is dynamically adjusted according to the reservoir resistivity to increase the porosity by 3%-20%; Preferably, the size of the bubbles generated by the nanobubble generator is 50-200 nm, and the microjets generated by their collapse are used to clear pore blockages; Preferably, the external DC electric field and the nanobubble generator act alternately, first applying the external DC electric field for 12 to 24 hours, and then starting the nanobubble generator for 12 to 24 hours.

10. Application of the method for improving geothermal tail water reinjection efficiency of the system utilizing electric field to enhance geothermal tail water reinjection efficiency according to any one of claims 1 to 5 in the field of geothermal tail water reinjection.

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