Plugging method for seepage channel of geothermal system

Abstract

The invention relates to the technical field of geothermal development, and provides a geothermal system seepage channel plugging method which comprises the steps that a precipitation solution containing a chemical precipitator is injected into hot dry rock of a geothermal system, and the precipitation temperature of the chemical precipitator is smaller than the first critical temperature of the geothermal system; the temperature of the seepage channel in the hot dry rock is lower than the first critical temperature, so that a precipitation layer is formed; and then biological bacterium liquid containing mineralized microorganisms is injected into the hot dry rock, the growth temperature of the mineralized microorganisms is lower than the first critical temperature, and therefore the mineralized microorganisms grow in the seepage channels, with the temperature lower than the first critical temperature, in the hot dry rock and are induced to form mineralized substances to be precipitated to form a mineral substance layer. According to the method, a multi-mechanism mutual promotion and complementation efficient plugging system is formed by utilizing chemical regulation and control of the chemical precipitant and microbial induced precipitation, accurate and controllable plugging of the seepage channel in the hot dry rock is achieved, and the terrestrial heat collection efficiency is effectively improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of geothermal development, in particular to a plugging method for a seepage channel of a geothermal system. BACKGROUND

[0002] High-temperature geothermal resources are a kind of clean and renewable energy with abundant reserves and wide distribution, most of which are stored in underground dry hot rock layers. At present, the enhanced geothermal system (EGS) is considered as the main technical approach to develop and utilize dry hot rock geothermal resources. In the development of dry hot rock geothermal resources by using the EGS technology, the heat is mainly extracted through the water-heat circulation in the fracture network formed by fracturing, which is largely dependent on the seepage heat transfer process in the fracture network. However, during the water-heat circulation, the dominant seepage channel is easily formed, which leads to seepage short circuit, limited water-heat exchange area, and sharp decrease of water temperature, thereby affecting the heat extraction efficiency and sustainability. Therefore, in order to alleviate the seepage short circuit and prolong the heat extraction life, it is necessary to dynamically regulate the fluid circulation process in the fractures, that is, to accurately plug the dominant seepage channel and promote the dispersion of fluid into the heat channel to improve the heat extraction efficiency. SUMMARY

[0003] Therefore, it is necessary to provide a plugging method for a seepage channel of a geothermal system, which realizes accurate plugging of the dominant seepage channel in the dry hot rock and intelligent regulation of the permeability by using the physical-chemical and biological synergistic regulation technology, thereby effectively improving the geothermal extraction efficiency.

[0004] The present application provides a plugging method for a seepage channel of a geothermal system, which comprises the following steps:

[0005] injecting a precipitation solution containing a chemical precipitant into a dry hot rock of the geothermal system, the precipitation temperature of the chemical precipitant being less than a first critical temperature of the geothermal system, so that the chemical precipitant is precipitated to form a precipitation layer in the seepage channel of the dry hot rock with a temperature less than the first critical temperature;

[0006] further injecting a biological bacteria solution containing mineralized microorganisms into the dry hot rock, the growth temperature of the mineralized microorganisms contained in the biological bacteria solution being less than the first critical temperature, so that the mineralized microorganisms grow in the seepage channel of the dry hot rock with a temperature less than the first critical temperature and induce the formation of mineralized substances to precipitate and form a mineral layer.

[0007] In some embodiments, the plugging method satisfies at least one of the following conditions:

[0008] (1) the first critical temperature is 80℃-100℃;

[0009] (2) the deposition temperature of the chemical precipitant is 10℃-100℃, and the growth temperature of the mineralized microorganisms is 10℃-80℃;

[0010] (3) the chemical precipitant comprises a first calcium salt;

[0011] (4) The mineralization microorganism includes at least one of Bacillus pasteurii, Bacillus licheniformis and Bacillus subtilis.

[0012] In some embodiments, the precipitation solution further contains a precipitation aid; or, after the precipitation solution is injected into the hot dry rock, the precipitation aid is further injected into the hot dry rock.

[0013] In some embodiments, the precipitation aid includes an alkaline material, and the alkaline material includes at least one of calcium hydroxide, sodium hydroxide, potassium hydroxide, calcium hydroxide, sodium carbonate and sodium bicarbonate.

[0014] In some embodiments, the biological bacteria solution further contains a nutrient and a mineralization precipitation source; or, after the biological bacteria solution is injected into the hot dry rock, the nutrient and the mineralization precipitation source are further injected into the hot dry rock; or, before the biological bacteria solution is injected into the hot dry rock, the mineralization precipitation source is further injected into the hot dry rock.

[0015] In some embodiments, the plugging method satisfies at least one of the following conditions:

[0016] (1) The nutrient includes urea;

[0017] (2) The mineralization precipitation source includes a second calcium salt.

[0018] In some embodiments, before the precipitation solution is injected into the hot dry rock, the plugging method further includes: injecting support particles into the hot dry rock to partially block the seepage channels in the hot dry rock and provide reaction sites for the chemical precipitation agent and the mineralization microorganism.

[0019] In some embodiments, the plugging method further satisfies at least one of the following conditions:

[0020] (1) The average particle size of the support particles is 0.1 times to 1 times the fracture opening of the seepage channels in the hot dry rock;

[0021] (2) The fracture opening of the seepage channels in the hot dry rock is 1 μm to 5000 μm.

[0022] (3) The support particles include at least one of quartz sand, ceramic particles and resin-coated sand particles.

[0023] In some embodiments, after the precipitation layer or the mineral layer is formed in the seepage channels, the plugging method further includes: when the drainage temperature of the geothermal system is higher than the second critical temperature, injecting a dredging agent into the hot dry rock.

[0024] In some embodiments, the dredging agent includes at least one of hydrochloric acid, nitric acid and citric acid.

[0025] Compared with the conventional technology, the present application has at least the following beneficial effects:

[0026] The present application injects a precipitation solution into the hot dry rock, which can precipitate at a temperature lower than the first critical temperature, so that the precipitation solution precipitates when flowing through the dominant seepage channel, forming a precipitation layer to partially block the dominant seepage channel with a lower temperature, and reducing the flow of liquid through the dominant seepage channel. Further, the hot dry rock is injected with a biological bacteria solution that grows at a temperature lower than the first critical temperature. The local alkaline environment formed by the precipitation layer and the lower temperature of the dominant seepage channel are conducive to the activity of microbial urease, promoting the growth of mineralized microorganisms, thereby inducing the formation of a mineral layer to cooperatively block the dominant seepage channel with the precipitation layer. Since both the chemical precipitant and the mineralized microorganisms precipitate or grow at a temperature lower than the first critical temperature, other seepage channels with higher temperatures can be avoided, thereby achieving precise blocking of the hot dry rock, improving the heat extraction area, and prolonging the life of the hot dry rock.

[0027] In addition, the precipitation solution and the biological bacteria solution can be transported over a long distance with the fluid injected into the hot dry rock, and the blocking position is not limited to the injection position, but can be precisely blocked according to the temperature of the seepage channel. DETAILED DESCRIPTION

[0028] The present application will be further described below in conjunction with embodiments and examples. These embodiments and examples are only used to illustrate the present application and not intended to limit the scope of the present application. The purpose of providing these embodiments and examples is to make the disclosure of the present application more thoroughly understood. It should also be understood that the present application can be implemented in many different forms and is not limited to the embodiments and examples described herein. Those skilled in the art can make various modifications or changes without departing from the spirit and scope of the present application, and the equivalent forms obtained thereby also fall within the protection scope of the present application. In addition, in the following description, a large number of specific details are given in order to provide a more complete understanding of the present application. It should be understood that the present application can be implemented without one or more of these details.

[0029] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application belongs. The terminology used in the specification of the present application is only for the purpose of describing specific embodiments and is not intended to limit the present application.

[0030] Hot dry rock refers to a high-temperature rock mass buried deep underground, which has a high temperature, almost no fluid, and very low porosity and permeability. Developing hot dry rock requires forming a fracture network through artificial permeability enhancement to achieve fluid circulation and heat extraction.

[0031] Enhanced Geothermal System (EGS): A development method for low-permeability, high-temperature geothermal resources such as dry hot rock. It mainly uses methods such as hydraulic fracturing to artificially create or enhance the network of underground fractures, inject fluids to form a closed hydrothermal cycle, and extract geothermal energy for power generation or heating.

[0032] Because hot dry rock reservoirs are typically located in high-temperature, high-pressure, and high-stress environments, the stability of general plugging materials is insufficient. Furthermore, the plugging process requires high selectivity to avoid accidentally sealing uncooled channels and affecting thermal recovery efficiency. Therefore, traditional methods for plugging hot dry rock reservoirs include: 1. Physical plugging materials and microencapsulation methods. Physical plugging has certain advantages in terms of plugging selectivity, but generally lacks reversibility and has weak far-well plugging capabilities. Additionally, although microencapsulation can achieve a certain degree of long-distance delivery and controlled release, it suffers from high costs, strong dependence on plugging timing, and insufficient controllability. 2. Ionic liquid control methods. High-viscosity ionic liquid technology has potential in precise flow path control and reversibility, but its high viscosity significantly increases injection pressure and operating costs, and may also introduce risks such as induced earthquakes. 3. Thermally responsive proppant control method: This technology adjusts fracture permeability based on the volume or morphological changes of proppant particles under temperature changes. At present, it is difficult to achieve effective plugging of distant well sections, and the research and development of related materials are mostly in the laboratory stage, with a large gap before large-scale application.

[0033] One embodiment of this application provides a method for sealing seepage channels in a geothermal system. The sealing method includes:

[0034] A precipitation solution containing a chemical precipitant is injected into the dry hot rock of the geothermal system. The precipitation temperature of the chemical precipitant is lower than the first critical temperature of the geothermal system, so that the chemical precipitant precipitates in the seepage channels in the dry hot rock where the temperature is lower than the first critical temperature to form a precipitation layer.

[0035] Then, a biological solution containing mineralizing microorganisms is injected into the hot dry rock. The growth temperature of the mineralizing microorganisms in the biological solution is lower than the first critical temperature, so that the mineralizing microorganisms can grow in the seepage channels in the hot dry rock where the temperature is lower than the first critical temperature and induce the formation of minerals to precipitate and form a mineral layer.

[0036] This application uses a chemical precipitant with a precipitation temperature lower than the first critical temperature of the geothermal system. After the chemical precipitant is injected into the dry hot rock, it flows with the fluid into the dominant seepage channel. Due to the high flow velocity and small heat exchange area of ​​the fluid in the dominant seepage channel, the fluid temperature in the dominant seepage channel is relatively low (below the first critical temperature of the geothermal system). When the chemical precipitant flows to this area, it will precipitate, thereby forming a precipitation layer in the dominant seepage channel, which hinders the fluid flow and increases the heat exchange area between the channel and the fluid, effectively improving the heat exchange effect of the fluid in the channel. Furthermore, this application also employs mineralizing microorganisms with growth temperatures below the first critical temperature. After being injected into the hot dry rock, these microorganisms flow with the fluid, utilizing their self-limiting nature and temperature gradient within the seepage channels to grow in the lower-temperature dominant seepage channels, selectively and autonomously blocking the low-temperature seepage channels. Moreover, since the sediment layer creates a local alkaline environment within the seepage channels, it is conducive to the activity of microbial urease, thereby promoting the growth of mineralizing microorganisms in the area where the sediment layer is located. Working in synergy with the sediment layer, they hinder the flow of fluid within the channels and increase the tortuosity of the flow channels, effectively achieving precise blocking of seepage channels in the hot dry rock and improving the heat exchange effect of the fluid.

[0037] It is understood that the first critical temperature of the geothermal system in this application is an artificially set value, determined based on the temperature of the hot dry rock, the temperature of the seepage channels, the drainage temperature, and the required drainage volume. If the water temperature in the seepage channel is lower than the first critical temperature, it indicates that the seepage channel is a dominant seepage channel, meaning that the flow velocity within the channel is high and the water-heat exchange area is reduced, resulting in underutilization of heat energy and a lower fluid temperature. Consequently, the drainage temperature of the geothermal system may not meet the preset usage requirements. Therefore, it is necessary to seal the seepage channels with lower fluid temperatures to increase the water-heat exchange area and thus raise the fluid temperature within those channels.

[0038] The first critical temperature can be defined based on the water temperature in the seepage channels of different hot dry rocks. Optionally, the first critical temperature can be 50% to 90% of the initial water temperature in the seepage channel. For example, if the initial water temperature in the seepage channel is 100℃ during the initial operation of the geothermal system, then the first critical temperature can be 50℃ to 90℃. Alternatively, the first critical temperature can also be defined based on the drainage temperature of the geothermal system. A decrease in the drainage temperature indicates a decrease in the water temperature in the seepage channels, with some channels reaching below the first critical temperature. Therefore, the water temperature in the seepage channels can be estimated from the drainage temperature of the geothermal system. Optionally, the first critical temperature can be 70% to 90% of the initial drainage temperature of the geothermal system.

[0039] In some embodiments, the first critical temperature is 80°C to 100°C, for example, it can be 80°C, 82°C, 84°C, 86°C, 88°C, 90°C, 92°C, 94°C, 96°C, 98°C or 100°C.

[0040] In some embodiments, the initial temperature of the hot dry rock is 150°C to 250°C, for example, it can be 150°C, 160°C, 170°C, 180°C, 190°C, 200°C, 210°C, 220°C, 230°C, 240°C or 250°C.

[0041] In some embodiments, the deposition temperature of the chemical precipitant is 10°C to 100°C, for example, 10°C, 20°C, 30°C, 40°C, 50°C, 60°C, 70°C, 80°C, 90°C, or 100°C. The growth temperature of the mineralizing microorganisms is 10°C to 80°C, for example, 10°C, 20°C, 30°C, 40°C, 50°C, 60°C, 70°C, or 80°C.

[0042] In some embodiments, the chemical precipitant can induce mineral deposition using ions in a fluid, for example, it can precipitate at least one of calcium salt precipitates and silicate precipitates. The precipitate may be at least one of magnesium silicate, calcium silicate, and calcium carbonate. Optionally, the chemical precipitant includes a first calcium salt. For example, the first calcium salt may be at least one of calcium chloride, calcium nitrate, calcium hydroxide, calcium sulfate, and calcium gluconate, preferably calcium chloride.

[0043] Optionally, the temperature of the precipitation solution can be 40℃~80℃, and the pH can be 5~9, thereby avoiding precipitation of the precipitation solution before injection.

[0044] Understandably, the content and amount of chemical precipitant in the precipitation solution can be selected based on the fracture volume and seepage rate in the hot dry rock. Furthermore, the reaction time for injecting the chemical precipitant can also be selected based on the fluid temperature and ion concentration in the hot dry rock.

[0045] In some embodiments, the mineralizing microorganisms can survive at dry, hot rock temperatures and grow below a first critical temperature, forming mineral deposits during growth to seal seepage channels. Optionally, the mineralizing microorganisms include at least one of Bacillus pasteurellii, Bacillus licheniformis, and Bacillus subtilis. Further, the temperature of the bio-solution is 40°C to 70°C, and the pH is 5 to 9, thereby ensuring microbial activity and maintaining the metabolic environment for the microorganisms.

[0046] Understandably, the content and amount of mineralizing microorganisms in the biological solution can be selected based on the fracture volume and seepage rate in the hot dry rock. Furthermore, nutrients or pH adjusters can be injected into the hot dry rock to ensure a suitable growth environment for the mineralizing microorganisms.

[0047] In some embodiments, the precipitation solution further contains a precipitant aid; or, after injecting the precipitation solution into the hot dry rock, a precipitant aid is also injected into the hot dry rock. This application further enhances the precipitation effect of the chemical precipitant by combining it with a precipitant aid, thereby improving the plugging efficiency.

[0048] Optionally, the precipitant may include an alkaline material. For example, the alkaline material may include at least one of calcium hydroxide, sodium hydroxide, potassium hydroxide, sodium carbonate, and sodium bicarbonate. Among these, the carbonate-containing alkaline precipitant may also provide carbonate ions, thereby promoting the precipitation formation in the precipitate solution.

[0049] In some embodiments, the bio-fluid also contains nutrients and mineralization sources; or, after injecting the bio-fluid into the hot dry rock, nutrients and mineralization sources are also injected into the hot dry rock; or, before injecting the bio-fluid into the hot dry rock, mineralization sources are also injected into the hot dry rock. Here, nutrients refer to the nutrients required for the growth of mineralizing microorganisms, and can be selected according to the different growth conditions of the mineralizing microorganisms; mineralization sources refer to the mineral elements required for the mineralization induced by the mineralizing microorganisms. This application, by injecting nutrients and mineralization sources into the hot dry rock, further ensures the growth of mineralizing microorganisms and promotes the induced formation of minerals, effectively improving the plugging effect. Furthermore, this application can also inject mineralizing microorganisms first, and then inject mineralization sources, so that the mineralizing microorganisms flow with the fluid to the distal end, attach, grow, and induce deposition, achieving directional plugging control in the distal well section.

[0050] In the case of urease activity by mineralizing microorganisms, the nutrient can be urea. The source of mineralization precipitation can be a second calcium salt. For example, the second calcium salt includes at least one of calcium chloride, calcium nitrate, calcium hydroxide, calcium sulfate, and calcium gluconate, preferably calcium chloride.

[0051] Furthermore, after sealing the seepage channels for a period of time, the fluid heat exchange effect is improved. When the temperature in the seepage channels exceeds the growth temperature of the mineralizing microorganisms, the microorganisms become inactive and cease inducing deposition to form mineralized substances, thus achieving precise sealing of the low-temperature seepage channels without completely blocking them. In addition, some of the deposited mineralized substances will gradually dissolve at high temperatures, enabling reversible sealing of the seepage channels.

[0052] Taking Bacillus as an example, it can secrete urease to catalyze the hydrolysis of urea to generate carbonate ions, which combine with calcium ions injected into the solution to form calcium carbonate precipitate. Bacillus can grow and induce the deposition of calcium carbonate precipitate in seepage channels with temperatures below the first critical temperature, but cannot grow and deposit calcium carbonate precipitate in seepage channels with temperatures above the first critical temperature, thus achieving precise sealing of low-temperature seepage channels. Furthermore, after the seepage channel is sealed, when the temperature is raised above the growth temperature of Bacillus or the supply of nutrients and oxygen is stopped, the activity of Bacillus decreases or even becomes inactive, thereby stopping the deposition of calcium carbonate and preventing the continuous growth and deposition of calcium carbonate to completely seal the seepage channel. In addition, the deposited calcium carbonate precipitate will gradually dissolve upon heating, thus achieving reversible sealing of the seepage channel.

[0053] It is understandable that during the artificial permeability enhancement of hot dry rock to form seepage channels, some proppant particles are injected into the hot dry rock to ensure the formation of seepage channels. These proppant particles can form an accumulation structure within the seepage channels, slowing down the high-velocity seepage and weakening the preferential flow effect. In this application, the chemical precipitant and mineralizing microorganisms can adhere to and precipitate on the proppant particles.

[0054] In some embodiments, before injecting the precipitation solution into the hot dry rock, the sealing method further includes injecting support particles into the hot dry rock to partially block the seepage channels and provide reaction sites for chemical precipitants and mineralizing microorganisms. For example, the support particles can be injected into the seepage channels by pumping. This application can also inject support particles into the target sealing location based on flow field distribution and temperature monitoring data in the hot dry rock. Due to their own weight, flow velocity difference, and inter-particle accumulation effect, the support particles form physical barriers in the seepage channels, reducing local permeability, blocking high-permeability channels, and achieving rapid sealing of the seepage channels. Furthermore, the support particles can increase the surface roughness and specific surface area inside the seepage channels, providing more reaction interfaces for subsequent chemical precipitation and microbial attachment. Working synergistically with the precipitation layer and mineral layer, the spatial distribution of the sealing is more uniform, and the sealing efficiency is higher.

[0055] In some embodiments, the particle size and injection volume of the proppant particles can be selected based on the aperture size and permeability of the seepage channels in the hot dry rock, ensuring that the proppant particles can enter the seepage channels and accumulate to seal them after injection. Optionally, the average particle size of the proppant particles is 0.1 to 1 times the fracture aperture of the seepage channels in the hot dry rock, for example, it can be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.92, or 1.0 times. The fracture aperture of the seepage channels in the hot dry rock can be 1 μm to 5000 μm, for example, it can be 100 μm, 200 μm, 300 μm, 400 μm, 500 μm, 600 μm, 700 μm, 800 μm, 900 μm, or 5000 μm.

[0056] In some embodiments, the supporting particles include at least one of quartz sand, ceramsite, and resin-coated sand particles.

[0057] This application utilizes a combination of physical sealing with supporting particles, chemical precipitation with chemical precipitants, and microbial mineralization deposition. These three methods complement and work together to effectively delay thermal breakthrough, improve heat exchange efficiency, extend reservoir service life, and adapt to complex underground high-temperature, high-pressure, and fracture heterogeneous conditions.

[0058] In some embodiments, after a sedimentary layer or mineral layer forms in the seepage channel, the sealing method further includes: injecting a clearing agent into the hot dry rock after the drainage temperature of the geothermal system exceeds a second critical temperature. When the fluid flow rate in the hot dry rock is slow or the drainage temperature is high, i.e., the sealing volume in the seepage channel is large, requiring an increase in fluid flow rate and a decrease in drainage temperature, a clearing agent can be injected into the hot dry rock to dissolve part of the sedimentary layer and mineral layer, reducing the blockage of the seepage channel and achieving unblocking and reversible regulation of the seepage channel.

[0059] It is understood that the second critical temperature in this application is an artificially set value, which can be set according to the dry hot rock temperature, drainage temperature, and drainage volume requirements of the geothermal system. For example, the second critical temperature is 1 to 1.2 times the pre-approved drainage temperature.

[0060] In some embodiments, the drain cleaner may include organic and inorganic acids to dissolve the deposits and mineral layers that form the blockage, thereby reducing the degree of blockage. For example, the drain cleaner includes at least one of hydrochloric acid, nitric acid, and citric acid.

[0061] The following embodiments use a simulated geothermal system, wherein the opening of the seepage channels in the hot dry rock is 0.1mm~5mm, the initial temperature of the hot dry rock is 150℃~250℃, the flow rate of the injected water is 30kg / s, and the temperature of the water before injection is 50℃. The first critical temperature can be 100℃.

[0062] Example 1

[0063] S1. Inject support particles with an average particle size of 0.01mm~1mm, made of quartz sand, into the dry hot rock. The support particles enter the seepage channel and accumulate and block it, thus physically sealing the seepage channel.

[0064] S2. Inject a calcium chloride-containing precipitation solution into the hot dry rock. The precipitation solution enters the seepage channel of the hot dry rock along with the fluid and deposits a calcium carbonate precipitation layer in the seepage channel at a temperature of 50℃~100℃ and on the supporting particles, thereby chemically sealing the seepage channel.

[0065] S3. Inject a biological solution containing Bacillus pasteurellii and urea into the hot dry rock. The precipitated solution enters the seepage channel of the hot dry rock along with the fluid and deposits a calcium carbonate mineral layer in the seepage channel at a temperature of 50℃~80℃, on the supporting particles and on the precipitate layer, thereby biologically inducing deposition and sealing the seepage channel.

[0066] This application improves the drainage temperature of the geothermal system by sealing the seepage channels of hot dry rock in Example 1.

[0067] In summary, the supporting particles of this application can form a stable particle skeleton in the seepage channel, providing an attachment interface and improving the efficiency of chemical sealing precipitation and microbial mineralization. Both chemical deposition and microbial deposition can form a composite seal between the supporting particles; using silica solution as a chemical sealing agent, its controllable precipitation reaction under specific conditions inside the fracture fills small pores or coats the supporting particle accumulation, achieving chemically enhanced sealing. Moreover, the local alkaline environment brought about by chemical deposition is conducive to the activity of microbial urease, forming a "chemical-biological" synergistic mechanism. In addition, both the precipitation layer and the mineral layer in this application can be dissolved by injecting a dredging agent, thereby achieving reversible sealing. Therefore, this application aims to achieve precise and controllable sealing of the fracture seepage heat transfer process in high-temperature reservoirs such as hot dry rocks. Based on the physical-chemical-biological synergistic sealing and control technology, it uses multiple measures such as the rational design of supporting particles, chemical sealing with chemical precipitants, and microbial-induced precipitation to organically cooperate at different stages, dynamically adjust the fracture seepage channel, effectively suppress thermal breakthrough, and has reversible adjustment capabilities.

[0068] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0069] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these modifications and improvements all fall within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the appended claims.

Claims

1. A method of plugging a geothermal system permeable channel, characterized by, The plugging method comprises: injecting a precipitation solution containing a chemical precipitant into hot dry rock of a geothermal system, the precipitation temperature of the chemical precipitant being less than a first critical temperature of the geothermal system, so that the chemical precipitant is precipitated to form a precipitation layer in a percolation channel of the hot dry rock at a temperature less than the first critical temperature; injecting a biological bacteria solution into the hot dry rock, the growth temperature of mineralizing microorganisms contained in the biological bacteria solution being less than the first critical temperature, so that the mineralizing microorganisms grow in the percolation channel of the hot dry rock at a temperature less than the first critical temperature and induce the formation of mineralization to precipitate and form a mineral layer.

2. The method of sealing a geothermal system permeable pathway of claim 1, wherein, The plugging method satisfies at least one of the following conditions: (1) the first critical temperature is 80-100°C; (2) the deposition temperature of the chemical precipitant is 10-100°C, and the growth temperature of the mineralizing microorganisms is 10-80°C; (3) the chemical precipitant comprises a first calcium salt; (4) the mineralizing microorganisms comprise at least one of Bacillus pasteurii, Bacillus licheniformis and Bacillus subtilis.

3. The method of sealing a geothermal system permeable pathway of claim 1, wherein, The precipitation solution further contains a precipitation aid; or, after injecting the precipitation solution into the hot dry rock, a precipitation aid is further injected into the hot dry rock.

4. The method of sealing a geothermal system permeable pathway of claim 3, wherein, The precipitation aid comprises an alkaline material, and the alkaline material comprises at least one of calcium hydroxide, sodium hydroxide, potassium hydroxide, calcium hydroxide, sodium carbonate and sodium bicarbonate.

5. The method of sealing a geothermal system permeable pathway of claim 1, wherein, The biological bacteria solution further contains nutrients and a mineralization precipitation source; or, after injecting the biological bacteria solution into the hot dry rock, nutrients and a mineralization precipitation source are further injected into the hot dry rock; or, before injecting the biological bacteria solution into the hot dry rock, a mineralization precipitation source is further injected into the hot dry rock.

6. The method of sealing a geothermal system permeable pathway of claim 5, wherein, The plugging method satisfies at least one of the following conditions: (1) the nutrients comprise urea; (2) the mineralization precipitation source comprises a second calcium salt.

7. The method of sealing a geothermal system permeable pathway of claim 1, wherein, Before injecting the precipitation solution into the hot dry rock, the plugging method further comprises: injecting support particles into the hot dry rock to partially block the percolation channel in the hot dry rock and provide reaction sites for the chemical precipitant and the mineralizing microorganisms.

8. The method of sealing a geothermal system permeable pathway of claim 7, wherein, The plugging method further satisfies at least one of the following conditions: (1) the average particle size of the support particles is 0.1-1 times the fracture opening of the percolation channel in the hot dry rock; (2) the fracture opening of the percolation channel in the hot dry rock is 1-5000 μm; (3) the support particles comprise at least one of quartz sand, ceramic particles and resin-coated sand particles.

9. A method of sealing a geothermal system permeable pathway according to any one of claims 1 to 8, wherein, After the precipitation layer or the mineral layer is formed in the percolation channel, the plugging method further comprises: when the drainage temperature of the geothermal system is higher than a second critical temperature, injecting a dredging agent into the hot dry rock.

10. The method of sealing a geothermal system permeable pathway of claim 9, wherein, The dredging agent comprises at least one of hydrochloric acid, nitric acid and citric acid.