Ultrasonic descaling device and method for a tower geothermal production well

Abstract

The application provides a tower type geothermal production well ultrasonic descaling device and method, and belongs to the technical field of geothermal energy development. The descaling device comprises: a subterranean well shaft located below the ground and a ground well shaft located above the ground, the subterranean well shaft and the ground well shaft being sealingly connected through a connecting assembly; an ultrasonic detection device arranged outside the ground well shaft and used for detecting and feeding back the attachment condition of calcium scale in the ground well shaft; and an ultrasonic descaling device arranged outside the ground well shaft and used for removing the calcium scale in the ground well shaft. After the device and method are adopted, the positioning and removal of the entire calcium scale do not need to stop the production well, the geothermal power generation time can be greatly prolonged, more economic benefits can be created, the calcium scale generation position can be accurately positioned and removed, the descaling work efficiency is greatly improved, the descaling cost is saved, and energy is saved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of geothermal energy development, and particularly relates to a tower type geothermal production well ultrasonic descaling device and method. BACKGROUND

[0002] Geothermal energy is a clean energy with great reserves and wide distribution, and has very high utilization value. Dry hot rock geothermal resources are a kind of geothermal resources, and compared with water-heat type geothermal resources, the dry hot rock geothermal resources are more stable and have higher temperature, and are more suitable for the design of stable power generation. However, the disadvantage is that the buried depth is large, and the current main development means is to drill production wells and injection wells according to a certain distance, and to manufacture an artificial heat reservoir through hydraulic fracturing and other means. The cold water injected from the injection well can be used for power generation and heating after being heated in the heat reservoir.

[0003] When the geothermal fluid rises to the vicinity of the wellhead of the production well, the pressure rapidly decreases, and the flash evaporation phenomenon occurs, and the dissolved CO2 in the fluid is rapidly released into the air, and the product of the concentration of Ca2+ and the concentration of CO32- in the fluid is greater than the solubility product of CaCO3, so that CaCO3 is precipitated from the fluid, and adheres to the well wall to form calcium scale, and it can be known through principle analysis that the depth of the calcium scale formation is generally within 100m downward from the wellhead. 2+ The product of the concentration of Ca2+ and the concentration of CO32- in the fluid is greater than the solubility product of CaCO3, so that CaCO3 is precipitated from the fluid, and adheres to the well wall to form calcium scale, and it can be known through principle analysis that the depth of the calcium scale formation is generally within 100m downward from the wellhead. 2- The product of the concentration of Ca2+ and the concentration of CO32- in the fluid is greater than the solubility product of CaCO3, so that CaCO3 is precipitated from the fluid, and adheres to the well wall to form calcium scale, and it can be known through principle analysis that the depth of the calcium scale formation is generally within 100m downward from the wellhead.

[0004] A large amount of calcium scale adheres to the surface of the well wall, which can reduce the diameter of the wellbore of the production well, not only causing the temperature of the high-temperature water to decrease and the flow to decrease, but also causing the production well to be blocked or even scrapped. The current conventional method for removing calcium scale from the well wall is to inject chemical drugs into the production well or to use a physical method for descaling.

[0005] The Chinese patent publication CN112696175A discloses a geothermal wellhead device for geothermal energy, comprising: a device body, a mounting plate, the bottom of the device body is provided with the mounting plate, and the inner top of the device body is provided with a steam turbine, the inner middle ends of the device body are provided with screening devices on both sides, and the bottom of the screening device is provided with a sand removal device. By continuously rotating the guide block at the bottom of the reverse osmosis membrane, a certain oscillation can be caused, and the guide block can make one end of the reverse osmosis membrane protrude upward, so that the sand on the reverse osmosis membrane can be guided to fall into the groove for collection, thereby avoiding the blockage of the reverse osmosis membrane due to too much sand. At the same time, the rotation of the guide block can drive the rotating disc to rotate through the first and second conical wheels, so that the rotating disc cooperates with the limiting block to drive the scraper rod to swing back and forth, thereby avoiding the scaling of the inner wall of the arc-shaped plate. At the same time, the arc-shaped plate can rotate according to the flowing direction of the geothermal water, so that the scraper plate can fully contact the inner wall of the arc-shaped plate for further descaling. However, since the calcium scale is generated at a position far from the ground surface, the descaling efficiency is low when using conventional mechanical descaling methods to remove the deep calcium scale. At the same time, if the conventional mechanical method is used for descaling, production needs to be stopped, so the calcium scale removed from the inner wall of the production well will continue to deposit downward, which may block part of the well section.

[0006] The paper "Analysis of Scaling in Ganzi Geothermal Wells and Countermeasures" (New Energy Progress, June 2015, Vol. 3, No. 3) introduces that scaling is one of the most important problems in the process of geothermal utilization, which has an important influence on the optimal design and safe operation of geothermal power stations. A geothermal well in Ganzi area is selected as the research object, and the water quality of the geothermal water during discharge is analyzed. The corrosion and scaling trend is judged according to the Langelier index (LI) and Ryznar index (RI). At the same time, XRD analysis is carried out on the scaling composition, and the scaling reason and scaling prevention measures are determined. The research results show that the RI of geothermal water is 5.58, and the LI is 0.19, which indicates that the geothermal water has a scaling trend, and the scaling degree is moderate. The scaling composition is CaCO3, and the scaling reason is that the reduction of fluid pressure causes CO2 to escape from water, leading to the precipitation of CaCO3 scaling. The descaling method is chemical well washing, and the scale inhibition measure is recommended to use chemical inhibitors. Since the calcium scale is generated at a position far from the ground surface, the uniformity of the distribution of the chemical medicine is not controlled to a great extent when the chemical medicine is injected for descaling. Increasing the dosage of the injected chemical medicine will increase the additional economic cost.

[0007] Therefore, it is of great significance to find a method to solve the above problems to ensure the duration of geothermal power generation, the stable extraction and utilization of geothermal resources, and the yield and efficiency of geothermal power generation.

[0008] The method of ultrasonic scale removal has been applied in many cases in oil pipelines. However, oil pipelines are all set on the ground surface or buried very shallowly, while geothermal wells are all below the ground surface and have a relatively large depth. Therefore, the environment for ultrasonic scale removal operations in geothermal wells is greatly restricted. The existing ultrasonic plugging removal devices for the calcium scale blockage problem in geothermal wells can only lift the ultrasonic plugging removal device into the well for scale removal and plugging removal operations when the normal production of the production well is stopped. Frequent production stoppages will greatly reduce the power generation duration of the normal operation of the geothermal system. Summary of the Invention

[0009] The object of the present invention is to solve the problems existing in the above-mentioned prior art, and provide a tower-type geothermal production well ultrasonic scale removal device and method. By adopting a high tower-type geothermal production well, the position where calcium scale is generated is transferred above the ground surface, providing sufficient working space for ultrasonic positioning of the calcium scale position and ultrasonic fixed-point removal of calcium scale, and finally achieving accurate positioning and fixed-point removal of the calcium scale position in the production well without affecting normal geothermal production.

[0010] The present invention is achieved through the following technical solutions:

[0011] In the first aspect of the present invention, a tower-type geothermal production well ultrasonic scale removal device is provided, including:

[0012] An underground wellbore located below the ground and a ground wellbore located above the ground, and the underground wellbore and the ground wellbore are hermetically connected through a connecting component;

[0013] An ultrasonic detection device, arranged outside the ground wellbore, for detecting and feeding back the attachment condition of calcium scale in the ground wellbore;

[0014] An ultrasonic scale removal device, arranged outside the ground wellbore, for removing calcium scale in the ground wellbore.

[0015] The further improvement of the present invention lies in:

[0016] The height of the ground wellbore is determined according to the position where calcium scale is generated in the underground wellbore when the ground wellbore was not originally set. The height H2 of the ground wellbore should be greater than the distance H1 from the lowest position where calcium scale is generated in the underground wellbore to the ground surface when the ground wellbore was not originally set, that is, the relationship H1 < H2 should be satisfied.

[0017] The further improvement of the present invention is as follows:

[0018] The connecting component is a cylindrical barrel with both ends open. A first groove is provided along the circumference at the top of the cylindrical barrel. A plurality of first through holes are evenly provided along the circumferential direction on the two opposite side walls of the first groove. First bolts sequentially pass through the opposite first through holes on the two side walls of the first groove;

[0019] The bottom of the cylindrical tube is provided with a second groove along the circumference. Multiple second through holes are evenly provided along the circumference on the two opposite side walls of the second groove. The second bolt passes through the two opposite second through holes on the two side walls of the second groove in sequence.

[0020] A further improvement of the present invention is that:

[0021] The widths of the first and second grooves are the same as the wall thicknesses of the surface well and the underground well, respectively.

[0022] The lower part of the ground well is provided with a plurality of through holes that correspond to the first through hole evenly in the circumferential direction. The bottom of the ground well is inserted into the first groove, and the first bolt passes through the first through hole and the through hole on the ground well for fixing.

[0023] The upper part of the underground shaft is evenly provided with multiple through holes corresponding to the second through hole along the circumference. The top of the underground shaft is inserted into the second groove, and the second bolt passes through the second through hole and the through hole on the underground shaft for fixation.

[0024] A further improvement of the present invention is that:

[0025] The surface well casing is equipped with an external protective structure, which surrounds the outer wall of the surface well casing and presents an overall shape that is narrower at the top and wider at the bottom, meaning that the diameter of the top section is smaller than the diameter of the bottom section.

[0026] A further improvement of the present invention is that:

[0027] Thermal insulation material is filled between the external protective structure and the ground well shaft.

[0028] A further improvement of the present invention is that:

[0029] The ultrasonic detection device is tightly fitted to the outer wall of the external protective structure.

[0030] A further improvement of the present invention is that:

[0031] The ultrasonic descaling device is tightly fitted to the outer wall of the external protective structure.

[0032] A further improvement of the present invention is that:

[0033] The descaling device also includes a filtration device, which is installed in a pipe connected to the surface well shaft.

[0034] A second aspect of the present invention provides an ultrasonic descaling method for tower-type geothermal production wells, specifically comprising the following steps:

[0035] Step 1: Install a surface well on top of the existing underground well, and seal the surface well with the underground well using a connecting component; install an external protective structure on the outside of the surface well.

[0036] Step 2: With the production well operating normally, attach the ultrasonic detection device tightly to the outer wall of the external protective structure to detect the entire surface wellbore and determine the precise location of calcium scale adhesion.

[0037] Step 3: Fit the ultrasonic descaling device tightly onto the outer wall of the external protective structure and perform ultrasonic descaling on the precise location where the calcium scale adheres. The calcium scale that peels off from the well wall of the ground well is discharged through the pipeline along with the high-temperature water in the production well during normal operation. Finally, it is filtered by the filtration device, thus completing the ultrasonic descaling operation for all high-tower geothermal production wells.

[0038] Compared with the prior art, the beneficial effects of the present invention are:

[0039] 1. By adopting the method of the present invention, the construction environment for descaling work changes from below the ground surface to above the ground surface, providing the necessary space and convenient conditions for descaling work.

[0040] 2. With the method of the present invention, the entire process of locating and removing calcium scale does not require the production well to be shut down. Compared with the previous ultrasonic descaling method for geothermal wells, the present invention can greatly extend the duration of geothermal power generation and create more economic benefits.

[0041] 3. By using the method of the present invention, the location of calcium scale formation can be accurately located and removed, which greatly improves the efficiency of scale removal. At the same time, compared with general scale removal operations, the method of the present invention can greatly shorten the time required for scale removal operations, save scale removal costs, and save energy. Attached Figure Description

[0042] Figure 1 This is a structural diagram of the high-tower geothermal production well in the ultrasonic descaling device of the present invention;

[0043] Figure 2 This is a schematic diagram showing the connection between the surface wellbore and the underground wellbore of a high-tower geothermal production well;

[0044] Figure 3 This is a top view of the connecting components;

[0045] Figure 4 This is a structural diagram of the underground well shaft before the surface well shaft was installed;

[0046] Figure 5 This is a top view of the surface well shaft;

[0047] Figure 6 This is a flow chart of an ultrasonic descaling method for tower-type geothermal production wells according to the present invention.

[0048] In the diagram, 1. Calcium scale, 2. Surface well shaft, 3. External protective structure, 4. Thermal insulation material, 5. Underground well shaft, 6. Connecting components, 7. Ultrasonic detection device, 8. Precise location of calcium scale adhesion, 9. Ultrasonic descaling device, 10. Filtration device, 11. Power generation device. Detailed Implementation

[0049] The present invention will now be described in further detail with reference to the accompanying drawings:

[0050] This invention discloses an ultrasonic descaling device and method for tower-type geothermal production wells. By adopting a high-tower geothermal production well, the location of calcium scale formation is transferred to above the ground surface, providing sufficient working space for ultrasonic positioning and targeted removal of calcium scale. Ultimately, it achieves precise positioning and targeted removal of calcium scale in the production well without affecting normal geothermal production.

[0051]

Example 1

[0052] This invention provides an ultrasonic descaling device for tower-type geothermal production wells, comprising:

[0053] like Figure 1 As shown, the underground shaft 5 is located below ground level and the surface shaft 2 is located above ground level, as... Figure 2 As shown, the underground shaft 5 and the surface shaft 2 are sealed together by a connecting assembly 6;

[0054] An ultrasonic detection device 7 is installed on the outside of the surface wellbore 2 to detect and provide feedback on the adhesion of calcium scale inside the surface wellbore 2.

[0055] An ultrasonic descaling device 9 is installed on the outside of the surface well 2 to remove calcium scale inside the surface well 2.

[0056] It should be noted that the ultrasonic detection device 7 is an existing product. For example, patents and related products such as ultrasonic flaw detection and ultrasonic pipe wall thickness measurement can monitor the thickness of calcium scale in the well. The ultrasonic descaling device 9 is also an existing product. Any device that can directionally emit high-frequency sound waves for descaling can remove calcium scale from the well.

[0057] The underground wellbore 5 and the surface wellbore 2 are sealed together by a connecting assembly 6, ensuring the integrity of both production well sections (i.e., surface wellbore 2 and underground wellbore 5). This allows for a shift in the location of the critical flash pressure. Because the water in the geothermal well experiences a pressure drop upon reaching the surface, dissolved CO2 in the fluid is rapidly released into the air, and the Ca in the fluid... 2+ Concentration and CO3 2-The product of concentrations is greater than the solubility product of CaCO3, causing CaCO3 to precipitate from the fluid and form calcium scale that adheres to the well wall. Adding the surface wellbore 2 raises the wellhead position and increases the pressure within the wellbore. The increase in pressure within the underground wellbore 5 due to the addition of the surface wellbore 2 is ρ. 水 gH2 (H2 is the height of the surface wellbore 2), in the underground wellbore 5, where calcium scale would normally form, CO2 remains dissolved in the water due to increased pressure, and no calcium scale is formed. When the water in the geothermal production well reaches the wellhead of the surface wellbore 2, the pressure decreases, and calcium scale forms. Based on this, the location of calcium scale formation can be transferred from below the surface to the surface wellbore 2.

[0058] like Figure 2 and Figure 3 As shown, the connecting component 6 is a cylindrical tube with openings at both the top and bottom. The top of the cylindrical tube has a first groove along its circumference. Multiple first through holes are evenly distributed along the circumference on the two opposite side walls of the first groove. A first bolt passes through the two opposite first through holes on the two side walls of the first groove in sequence. The bottom of the cylindrical tube has a second groove along its circumference. Multiple second through holes are evenly distributed along the circumference on the two opposite side walls of the second groove. A second bolt passes through the two opposite second through holes on the two side walls of the second groove in sequence. The widths of the first and second grooves are the same as the wall thicknesses of the surface well 2 and the underground well 5, respectively. The lower part of the surface well 2 has multiple through holes evenly distributed along its circumference, corresponding to the first through holes. The bottom of the surface well 2 is inserted into the first groove, and the first bolt passes through the first through hole and the through hole on the surface well 2 to fix it. The upper part of the underground well 5 has multiple through holes evenly distributed along its circumference, corresponding to the second through holes. The top of the underground well 5 is inserted into the second groove, and the second bolt passes through the second through hole and the through hole on the underground well 5 to fix it. During installation, the underground well shaft 5 is inserted into the second groove and fixed with the second bolt, the surface well shaft 2 is inserted into the first groove and fixed with the first bolt, and then waterproof sealing is performed at the gap between the underground well shaft 5 and the second groove, and at the gap between the surface well shaft 2 and the first groove.

[0059] In a preferred embodiment of the present invention, the diameter and function of the surface well 2 are the same as those of the underground well 5; the height of the surface well 2 can be determined based on the location of calcium scale formation in the underground well 5 when the surface well 2 was not installed, and the height H2 of the surface well 2 (e.g.) Figure 1 (As shown) should be greater than the distance H1 from the ground surface at the lowest point of calcium scale formation in the underground well 5 when the surface well 2 was not installed (e.g., Figure 4As shown, that is, the relationship H1 < H2 should be satisfied at least. After adding the surface wellbore 2, the calcium scale formation position will move upward. When H1 is equal to H2, after adding the surface wellbore 2, during the normal production process, the calcium scale formation position just moves upward from the position of H1 below the ground surface to near the ground surface at this time; when H1 < H2, it can ensure that the calcium scale formation position just moves upward completely into the surface wellbore 2. Only in this way can the subsequent calcium scale detection and removal operations on the ground surface be realized.

[0060] A preferred embodiment of the present invention is as Figure 1 shown. An external protection structure 3 is provided outside the surface wellbore 2. The external protection structure 3 surrounds the outer wall of the surface wellbore 2 and presents an overall frustum shape with a narrower top and a wider bottom, that is, the diameter of the top cross-section is smaller than that of the bottom cross-section, which plays a role in maintaining the stability of the entire high-tower geothermal production well, as Figure 5 shown. A heat-insulating material 4 is filled between the external protection structure 3 and the surface wellbore 2. Lightweight and low-thermal-conductivity materials such as heat-insulating aerogel, expanded perlite, polystyrene foam plastic, and polyurethane foam plastic can be used as the heat-insulating material for filling, which can minimize the heat loss of the high-temperature fluid in the production well due to the increase in the height of the production wellbore.

[0061] In a preferred embodiment of the present invention, the ultrasonic detection device 7 is closely attached to the outer wall of the external protection structure 3, and starts to detect the attachment condition of calcium scale in the surface wellbore 2 through the feedback of ultrasonic information. After monitoring the entire surface wellbore 2 from top to bottom, the range where the calcium scale thickness exceeds the limit (when the cumulative calcium scale thickness on the well wall is greater than half of the radius of the surface wellbore 2, the calcium scale seriously affects the normal production of the production well and calcium scale removal operations are required) is marked, that is, the height data of the calcium scale formation area is recorded, providing height information for the installation of the subsequent ultrasonic calcium scale removal equipment.

[0062] In a preferred embodiment of the present invention, the ultrasonic scale removal device 9 is closely attached to the outer wall of the external protection structure 3 and continuously emits ultrasonic waves to the surface wellbore 2, reasonably using the ultrasonic scale removal principle to remove the calcium scale inside the surface wellbore 2. During the whole process, the production well operates normally, and the calcium scale peeled off under the action of ultrasonic waves will be discharged from the production well together with the high-temperature water in the production well. At the same time, filtration treatment is carried out before using the high-temperature water for power generation, and the scale removal work of the production well can be completed.

[0063] In a preferred embodiment of the present invention, the ultrasonic descaling device for a tower-type geothermal production well further includes a filtration device 10. The filtration device 10 contains filter screens of different mesh sizes and activated carbon arranged along the water flow direction. The filter screens and activated carbon can filter out large-particle calcium scale impurities and adsorb small-particle suspended matter. After the water in the production well enters the filtration device 10 and passes through the filter screens and activated carbon, calcium scale fragments and suspended matter are filtered out. The filtration device 10 is installed in a pipe connected to the surface well shaft 2. The other end of the pipe can be connected to a power generation device. Calcium scale that is peeled off from the well wall by the ultrasonic descaling device 9 is discharged along with the high-temperature water in the production well during normal operation through the pipe. The calcium scale is filtered out in the filtration device 10, and the high-temperature water enters the power generation device to generate electricity. The filter materials (filter screens and activated carbon) in the filtration device 10 should be updated or replaced in a timely manner to prevent pipe blockage caused by incomplete calcium scale filtration.

[0064] Based on the principle of calcium scale formation in geothermal well fluids, when dissolved CO2 in the fluid rises to the vicinity of the production wellhead, the pressure drops rapidly. When the pressure at a certain depth in the production well falls below the critical pressure for flash evaporation, flash evaporation occurs, and the dissolved CO2 is rapidly released into the air. At this point, the calcium in the fluid... 2+ Concentration and CO3 2- The product of concentrations is greater than the solubility product of CaCO3, causing CaCO3 to precipitate from the fluid and adhere to the well wall to form calcium scale.

[0065] Therefore, this invention adopts a high-tower geothermal production well design, raising the wellhead position from the original surface to a certain height, thereby shifting the location of flash evaporation from below the surface to above the surface, thus achieving the goal of shifting the location of calcium scale formation from below the surface to above the surface.

[0066] By taking advantage of the different propagation speeds of ultrasound in different media, information such as the location and thickness of calcium scale formation on the well wall can be obtained by changing the position of the sound wave emission.

[0067] Ultrasonic descaling mainly utilizes the cavitation effect, activation effect, and shearing effect of ultrasound. When the calcium scale adhering to the inner wall of the production well is in an ultrasonic field, the calcium scale, water, and well casing respond differently to the ultrasonic frequency, resulting in different vibrations among the three. This leads to high-speed relative motion, which ultimately causes the calcium scale layer to loosen and fall off, thus achieving the purpose of ultrasonic descaling.

[0068]

Example 2

[0069] This invention provides an ultrasonic descaling method for tower-type geothermal production wells, such as... Figure 6 As shown, the specific steps include:

[0070] Step 1, a surface wellbore 2 is set on the original underground wellbore 5, and the surface wellbore 2 and the underground wellbore 5 are hermetically connected through a connecting component 6; the diameter and function of the surface wellbore 2 are the same as those of the underground wellbore 5.

[0071] The underground wellbore 5 and the surface wellbore 2 are hermetically connected through the connecting component 6, which can ensure good integrity of the upper and lower parts of the production well wellbore (i.e., the surface wellbore 2 and the underground wellbore 5), so as to realize the upward shift of the position where the critical flashing pressure appears. Since the pressure of the water in the geothermal well decreases when it reaches the surface, the dissolved CO2 in the fluid is quickly released into the air, and the product of the Ca 2+ concentration and the CO3 2- concentration in the fluid is greater than the solubility product of CaCO3, making CaCO3 precipitate from the fluid and form calcium scale adhering to the well wall. After adding the surface wellbore 2, the position of the wellhead is raised, and the pressure in the wellbore is increased. Since the increased pressure in the underground wellbore 5 due to adding the surface wellbore 2 is ρ 水 gH2, at the position where calcium scale was originally generated in the underground wellbore 5, due to the increased pressure, CO2 remains dissolved in water and no calcium scale is generated. When the water in the geothermal production well reaches the wellhead of the surface wellbore 2, the pressure decreases and calcium scale is formed. Accordingly, the position where calcium scale is generated can be transferred from below the surface to the surface wellbore 2.

[0072] An external protection structure 3 is provided outside the surface wellbore 2. The external protection structure 3 surrounds the outer wall of the surface wellbore 2 and presents a frustum of a cone shape that is narrower at the top and wider at the bottom, that is, the diameter of the top cross-section is smaller than that of the bottom cross-section, which plays a role in maintaining the stability of the entire high-tower geothermal production well. At the same time, a heat insulation material 4 is filled between the external protection structure 3 and the surface wellbore 2. Lightweight and low-thermal-conductivity materials such as heat insulation aerogel, expanded perlite, polystyrene foam plastic, and polyurethane foam plastic can be used as the heat insulation material for filling, which can minimize the heat loss of the high-temperature fluid in the production well due to the increase in the wellbore height.

[0073] The height of the surface wellbore 2 can be determined according to the original calcium scale generation position in the underground wellbore. The height H2 of the surface wellbore 2 should be greater than the distance H1 from the lowest position where calcium scale was generated in the underground wellbore 5 to the surface before the surface wellbore 2 was not set, that is, at least the relationship H1 < H2 should be satisfied.

[0074] After the construction of the high-tower geothermal well is completed, the normal operation of the geothermal production well begins. As time goes by, when the calcium scale adhering to the inner wall of the surface wellbore 2 affects the normal and efficient operation of geothermal power generation, the scale removal operation starts.

[0075] Step 2: With the production well operating normally, the ultrasonic detection device 7 is tightly attached to the outer wall of the external protective structure 3 of the high-tower geothermal production well. Ultrasonic detection is performed on the calcium scale adhesion in the surface wellbore 2 at different positions at the same horizontal height. The entire surface wellbore 2 is then detected from top to bottom. After the detection is completed, the precise location 8 of the calcium scale adhesion can be determined. This precise location 8 is also the working range of the ultrasonic descaling device 9.

[0076] Step 3: Use the ultrasonic descaling device 9 to remove calcium scale. The ultrasonic descaling device 9 is tightly attached to the outer wall of the external protective structure 3. Perform ultrasonic descaling operation on the precise location 8 where the calcium scale is attached. The calcium scale that peels off from the well wall is discharged through the pipeline along with the high-temperature water in the production well during normal operation. Then, the calcium scale is filtered out by the filter device 10, thus completing the ultrasonic descaling operation of all high-tower geothermal production wells.

[0077] Finally, it should be noted that the calcium scale is filtered out in the filter device 10, and the high-temperature water enters the power generation device 11 to generate electricity. The filter material in the filter device 10 needs to be updated or replaced in a timely manner to prevent pipe blockage caused by incomplete calcium scale filtration.

[0078] The following example of a dry hot rock geothermal power plant further illustrates the ultrasonic descaling method for tower-type geothermal production wells of the present invention.

[0079] In this dry hot rock geothermal power plant, using conventional production well settings, monitoring revealed that the lowest point of calcium scale formation was 40m from the wellhead, and the diameter of the underground well 5 was 450mm.

[0080] Based on the above information, the height H2 of the high-tower geothermal production well is determined to be 50m, and the diameter of the surface wellbore 2 and the underground wellbore 5 are exactly the same, both being 450mm. To ensure the stability of the high-tower geothermal production well, the specific dimensions of the external protective structure 3 are designed as follows: top diameter 1000mm and bottom diameter 2000mm. The space between the surface wellbore 2 and the external protective structure 3 is filled with thermal insulation material 4 with a thermal conductivity of 0.02W / (m·℃). A connecting component 6 is used to seal the connection between the surface wellbore 2 and the underground wellbore 5 of the high-tower geothermal production well. After the construction of the high-tower geothermal production well is completed, a filter device 10 is installed before the power generation unit 11, such as... Figure 2 As shown.

[0081] As geothermal power generation continues, calcium scale accumulates in surface wellbore 2. Monitoring of the production well's flow rate revealed that the calcium scale buildup in wellbore 2 was so severe that it was affecting normal geothermal power generation efficiency. Therefore, ultrasonic descaling of the wellbore was initiated. The ultrasonic descaling process for a high-tower geothermal production well is as follows: Figure 6As shown.

[0082] Step 1: With the production well operating normally, the ultrasonic detection device 7 is tightly attached to the outer wall of the external protective structure 3 of the high-tower geothermal production well to conduct ultrasonic detection. At different positions at the same horizontal height, the calcium scale adhesion in the inner well barrel 2 is detected by ultrasonic detection. The ultrasonic detection device is used to detect the entire surface well barrel 2 from top to bottom. After the detection is completed, the precise location 8 of the calcium scale adhesion can be determined.

[0083] Step 2: Use the ultrasonic descaling device 9 to remove calcium scale from the precise location 8 of the calcium scale adhesion determined in Step 1. The ultrasonic descaling device 9 is tightly attached to the outer wall of the external protective structure 3, and ultrasonic descaling is performed on the precise location 8 of the calcium scale adhesion. The calcium scale that peels off from the well wall is discharged along with the high-temperature water in the production well during normal operation through the pipeline. The calcium scale is filtered out in the filter device 10, and the high-temperature water enters the power generation device 11 to generate electricity.

[0084] The filter material in the filter device 10 needs to be updated or replaced in a timely manner to prevent pipe blockage caused by incomplete calcium scale filtration. This will complete the ultrasonic descaling operation for all high-tower geothermal production wells.

[0085] In the description of this invention, unless otherwise stated, the terms "upper," "lower," "left," "right," "inner," "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0086] Finally, it should be noted that the above technical solution is only one embodiment of the present invention. For those skilled in the art, based on the application methods and principles disclosed in the present invention, it is easy to make various types of improvements or modifications, and not limited to the methods described in the above specific embodiments of the present invention. Therefore, the methods described above are only preferred and have no limiting significance.

Claims

1. An ultrasonic descaling device for tower-type geothermal production wells, characterized in that, The descaling device includes: An underground well shaft located below ground level and a surface well shaft located above ground level, wherein the underground well shaft and the surface well shaft are sealed together by a connecting assembly; An ultrasonic detection device is installed on the outside of the surface well casing to detect and provide feedback on the adhesion of calcium scale inside the surface well casing. An ultrasonic descaling device is installed on the outside of the surface well casing to remove calcium scale inside the surface well casing; The height of the surface wellbore is determined based on the location of calcium scale formation in the underground wellbore when no surface wellbore was installed. The height H2 of the surface wellbore should be greater than the distance H1 from the lowest point of calcium scale formation in the underground wellbore to the ground surface when no surface wellbore was installed, i.e., it should satisfy the relationship H1. <H2。 2. The ultrasonic descaling device for a tower-type geothermal production well according to claim 1, characterized in that, The connecting component is a cylindrical tube with openings at both ends. The top of the cylindrical tube has a first groove along the circumference. Multiple first through holes are evenly provided circumferentially on the two opposite side walls of the first groove. The first bolt passes through the opposite first through holes on the two side walls of the first groove in sequence. The bottom of the cylindrical tube is provided with a second groove along the circumference, and a plurality of second through holes are uniformly provided along the circumference on the two opposite side walls of the second groove. The second bolt passes through the two opposite second through holes on the two side walls of the second groove in sequence.

3. The ultrasonic descaling device for a tower-type geothermal production well according to claim 2, characterized in that, The widths of the first groove and the second groove are the same as the wall thicknesses of the surface well and the underground well, respectively. The lower part of the ground well cylinder is provided with a plurality of through holes that correspond to the first through hole evenly in the circumferential direction. The bottom of the ground well cylinder is inserted into the first groove, and the first bolt passes through the first through hole and the through hole on the ground well cylinder for fixing. The upper part of the underground well is provided with a plurality of through holes that correspond to the second through hole evenly in the circumferential direction. The top of the underground well is inserted into the second groove, and the second bolt passes through the second through hole and the through hole on the underground well for fixation.

4. The ultrasonic descaling device for a tower-type geothermal production well according to any one of claims 1-3, characterized in that, The surface well casing is provided with an external protective structure, which surrounds the outer wall of the surface well casing and has an overall shape that is narrower at the top and wider at the bottom, that is, the diameter of the top section is smaller than the diameter of the bottom section.

5. The ultrasonic descaling device for a tower-type geothermal production well as described in claim 4, characterized in that, The space between the external protective structure and the ground well casing is filled with thermal insulation material.

6. The ultrasonic descaling device for a tower-type geothermal production well according to claim 5, characterized in that, The ultrasonic detection device is tightly attached to the outer wall of the external protective structure.

7. The ultrasonic descaling device for a tower-type geothermal production well according to claim 5, characterized in that, The ultrasonic descaling device is tightly fitted to the outer wall of the external protective structure.

8. The ultrasonic descaling device for a tower-type geothermal production well according to any one of claims 5-7, characterized in that, The descaling device also includes a filtration device, which is installed in a pipe connected to the surface well shaft.

9. An ultrasonic descaling method using the ultrasonic descaling device for tower-type geothermal production wells according to any one of claims 1-8, characterized in that, Specifically, the following steps are included: Step 1: Install a surface well on top of the existing underground well, and seal the surface well with the underground well using a connecting component; install an external protective structure on the outside of the surface well. Step 2: With the production well operating normally, attach the ultrasonic detection device tightly to the outer wall of the external protective structure to detect the entire surface wellbore and determine the precise location of calcium scale adhesion. Step 3: Fit the ultrasonic descaling device tightly onto the outer wall of the external protective structure and perform ultrasonic descaling on the precise location where the calcium scale adheres. The calcium scale that peels off from the well wall of the ground well is discharged through the pipeline along with the high-temperature water in the production well during normal operation. Finally, it is filtered by the filtration device, thus completing the ultrasonic descaling operation for all high-tower geothermal production wells.

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