Fixing device and geothermal well optical fiber temperature measurement and fixing method

Abstract

The application discloses a fixing device for an optical fiber end, a geothermal well optical fiber fixing method and a geothermal well optical fiber temperature measuring method, and relates to the technical field of geothermal well optical fiber temperature measurement. The fixing device comprises a positioning mechanism and a running-in mechanism. The running-in mechanism comprises a running-in barrel, a plug and a limiting assembly. The plug is installed in the running-in barrel, so that a chamber with a closed end is formed between the first end of the running-in barrel and the plug. The plug is configured to open the closed end of the chamber when the pressure in the chamber is greater than a predetermined value. The limiting assembly is arranged on the running-in barrel and is configured to limit the running-in barrel on the positioning mechanism during the running-in process. The fixing device realizes wellhead pumping of optical fiber fixing through cooperation of the positioning mechanism and the running-in mechanism, can realize running-in and fixing of the optical fiber in the horizontal section of a U-shaped well, and solves the technical problems of difficulty in running-in by using a counterweight method, existence of monitoring blank in the horizontal section, easy winding and the like in the current geothermal well optical fiber temperature measurement.

Description

Technical Field

[0001] This invention relates to the field of downhole monitoring technology for geothermal wells, and more particularly to a fixing device and a method for fixing geothermal well fiber optic temperature measurement. Background Technology

[0002] Geothermal energy, as a clean energy source, plays a significant role in replacing fossil fuels. Currently, the development and utilization of geothermal energy in my country mainly involves shallow geothermal energy and medium-deep hydrothermal energy. Both face several challenges. Shallow geothermal energy suffers from cold (hot) accumulation during development, requires large land areas, and conflicts with urban underground space construction, hindering its widespread adoption. Medium-deep hydrothermal geothermal energy has a low sandstone reservoir reinjection rate, leading to environmental pollution and other derivative problems. Furthermore, many local governments have issued policies requiring mandatory reinjection of tailwater from medium-deep geothermal development. Improving the extraction technology of medium-deep geothermal energy to achieve "heat extraction without water extraction" has become a new direction for exploring the sustainable development of geothermal resources.

[0003] To analyze the impact of geothermal extraction and utilization on the geothermal gradient, rationally allocate heat transfer parameters, and better utilize geothermal resources, it is necessary to deploy distributed temperature-sensing optical fibers within geothermal wells to collect data on heat exchange and the dynamic changes in the geothermal field. Typically, the optical fibers are deployed using a weight-based method, which presents the following problems: (1) If the well trajectory is poor, there may be a jam or inability to descend; (2) If the distributed temperature measurement fiber cannot be completely laid into the horizontal section, a monitoring blank area will be left; (3) During the pumping process, the temperature measuring optical fiber located in the well will become entangled due to the disturbance of the water flow.

[0004] Currently, fiber optic cables are often installed in U-shaped wells using coiled tubing. However, this method is expensive and occupies tubing space, resulting in a reduction in the cross-sectional area of ​​the water flow, an increase in flow velocity, a shortening of the effective heating time of the circulating water, and an impact on heat exchange efficiency.

[0005] Therefore, existing technologies still need improvement. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a fixing device for the end of an optical fiber, a method for fixing optical fibers in geothermal wells, and a method for measuring the temperature of optical fibers in geothermal wells, thereby resolving a series of issues existing in the prior art for monitoring the temperature of optical fibers in geothermal wells.

[0007] To address the aforementioned technical problems, some embodiments of the present invention disclose a fixing device for the end of an optical fiber, comprising a positioning mechanism and an insertion mechanism, wherein... The lowering mechanism includes a lowering cylinder, a plug, and a limiting assembly. The plug is installed inside the lowering cylinder, forming a closed chamber between the first end of the lowering cylinder and the plug. The plug is configured to open the closed end of the chamber when the pressure inside the chamber is greater than a predetermined value. The limiting component is disposed on the lower inlet cylinder and configured to limit the lower inlet cylinder on the positioning mechanism during the lowering process.

[0008] In some embodiments, the limiting component includes a first limiting member and a second limiting member, the second limiting member being installed on the outer wall of the lower inlet cylinder, and the limiting component being configured such that the second limiting member expands after passing through the positioning mechanism, so that the first limiting member and the second limiting member are respectively limited to both sides of the positioning mechanism.

[0009] In some embodiments, the second limiting member is an elastic member.

[0010] In some embodiments, the positioning mechanism includes a positioning step; The elastic element includes at least two arc-shaped spring pieces that are circumferentially and uniformly installed on the outer wall of the lowering cylinder. The first end of the arc-shaped spring piece is fixedly connected to the lowering cylinder, and the second end of the arc-shaped spring piece extends toward the first end of the lowering cylinder. Furthermore, the second ends of the multiple curved spring pieces, after being expanded, are engaged with the positioning step.

[0011] In some embodiments, the positioning mechanism further includes a positioning cylinder and an annular positioning component, the positioning component being located on the inner wall of the positioning cylinder, and a positioning step being formed on one side of the positioning component, and a positioning inclined surface being provided on the other side of the positioning component; Along the direction away from the positioning step, the inner diameter formed by the positioning ramp gradually increases; The second limiting member is located on the positioning step, and the first limiting member is located on the positioning inclined surface.

[0012] In some embodiments, the first limiting member is a limiting cylinder, the first end of which is connected to the first end or outer wall of the lower entry cylinder, and the end of which extends away from the second end of the lower entry cylinder. Along the direction from the first end to the end of the limiting cylinder, the outer diameter of the limiting cylinder gradually increases. Furthermore, the outer diameter of the limiting cylinder is adapted to be located within the inner wall of the positioning inclined surface; The end of the optical fiber is connected to the limiting cylinder or the lowering cylinder.

[0013] In some embodiments, the lowering mechanism further includes a connecting assembly through which the plug is mounted at a second end of the lowering cylinder, and the connecting assembly is configured to break when the pressure in the chamber exceeds a predetermined value, causing the plug to disengage from the lowering cylinder.

[0014] In some embodiments, the connecting component is a connecting pin.

[0015] In some embodiments, the second end of the lower inlet cylinder is provided with at least two pin holes, and the outer wall of the plug is circumferentially arranged with connecting holes corresponding to the pin holes, and at least two connecting pins are connected one-to-one between the pin holes and the connecting holes.

[0016] On the other hand, embodiments of the present invention also disclose a method for fixing optical fibers in geothermal wells, which uses the aforementioned fixing device for the end of the optical fiber for fixing.

[0017] In some embodiments, the fiber optic fixing method includes horizontal well fixing, the horizontal well fixing comprising: Install the positioning mechanism at the predetermined position of the horizontal well; Fix one end of the optical fiber to the lower inlet cylinder; The lowering mechanism is inserted into the geothermal well from the wellhead, the circulation pump is started, the fluid flows into the chamber and pushes the lowering mechanism to move until the limiting component of the lowering mechanism is limited on the positioning mechanism; Continue pressurizing using a circulating pump until the plug opens, allowing the closed end of the chamber to open.

[0018] In some embodiments, the fiber optic fixing method includes vertical well fixing, wherein a counterweight is connected to one end of the fiber optic cable and the cable is lowered to a designated position by gravity.

[0019] In some embodiments, a universal joint is provided at the first end of the lower inlet cylinder, and the optical fiber is connected to the universal joint.

[0020] Some embodiments of the present invention also disclose a method for measuring temperature with optical fiber in geothermal wells, which uses the aforementioned fixing device for fixing the end of the optical fiber to fix the end of the optical fiber.

[0021] In some embodiments, the aforementioned method for fixing optical fibers in geothermal wells is used for fixing the optical fibers.

[0022] By adopting the above technical solution, the present invention has at least the following beneficial effects: This invention provides a fixing device for the end of an optical fiber, a method for fixing optical fibers in geothermal wells, and a method for measuring the temperature of optical fibers in geothermal wells. By using a positioning mechanism in conjunction with a lowering mechanism, the wellhead pumping for fixing optical fibers is realized. It can realize the lowering and fixing of optical fibers in the horizontal section of a U-shaped well, and solves the technical problems of the counterweight method commonly used in geothermal well temperature measurement, such as difficulty in lowering the fiber, monitoring gaps in the horizontal section, and easy entanglement. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a usage diagram of a fixing device for optical fiber ends disclosed in some embodiments of the present invention; Figure 2 This is a schematic diagram of the lowering mechanism of the fixing device for the end of an optical fiber disclosed in some embodiments of the present invention; Figure 3 This is a schematic diagram of the positioning mechanism of a fixing device for optical fiber ends disclosed in some embodiments of the present invention; Figure 4 These are state diagrams illustrating the fixing process of the geothermal well optical fiber fixing method disclosed in some embodiments of the present invention. Figure 5 for Figure 2 Cross-sectional view at point AA; Figure 6 for Figure 2 Cross-sectional view at BB.

[0025] Explanation of reference numerals in the attached figures: 1. Positioning mechanism; 11. Positioning step; 12. Positioning cylinder; 13. Positioning inclined surface; 2. Lowering mechanism; 21. Lowering cylinder; 22. Plug; 23. Limiting cylinder; 24. Arc-shaped spring; 25. Chamber; 26. Connecting pin; 27. Universal joint; 3. Circulation pump; 4. Horizontal well tubing string; 5. Vertical well tubing string; 6. Vertical well fiber optic cable; 7. Horizontal well fiber optic cable; 8. Counterweight; 100. Horizontal well; 101. Horizontal section; 200. Vertical well. Detailed Implementation

[0026] The embodiments of this disclosure will be further described in detail below with reference to the accompanying drawings and examples. The detailed description of the embodiments and the accompanying drawings are used to illustrate the principles of this disclosure by way of example, but should not be used to limit the scope of this disclosure. This disclosure can be implemented in many different forms and is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

[0027] These embodiments are provided to make the disclosure thorough and complete, and to fully express the scope of the disclosure to those skilled in the art. It should be noted that, unless otherwise specifically stated, the relative arrangement of components and steps, material composition, numerical expressions, and values ​​set forth in these embodiments should be interpreted as exemplary only and not as limiting.

[0028] Furthermore, the terms "first," "second," and similar terms used in this disclosure do not indicate any order, quantity, or importance, but are merely used to distinguish different parts. Terms such as "including" or "contains" mean that the element preceding the word covers the element listed after the word, and do not exclude the possibility of covering other elements as well.

[0029] It should also be noted that, in the description of this disclosure, unless otherwise expressly specified and limited, the specific meaning of each term in this disclosure can be understood by those skilled in the art as appropriate. All terms used in this disclosure have the same meaning as understood by those skilled in the art to which this disclosure pertains, unless otherwise specifically defined. It should also be understood that terms defined in general dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant art, and should not be interpreted with an idealized or highly formalized meaning, unless expressly defined herein.

[0030] Techniques, methods, and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, they should be considered part of the specification.

[0031] like Figures 1 to 6As shown, some embodiments of the present invention disclose a fixing device for the end of an optical fiber, including a positioning mechanism 1 and a lowering mechanism 2. The positioning mechanism needs to be fixed at a predetermined position in a geothermal well. The lowering mechanism 2 includes a lowering cylinder 21, a plug 22, and a limiting component. The plug 22 is installed inside the lowering cylinder 21, forming a closed chamber 25 between the first end of the lowering cylinder 21 and the plug 22. The plug 22 is configured to open the closed end of the chamber 25 when the pressure inside the chamber 25 is greater than a predetermined value. The limiting component is disposed on the lowering cylinder 21 and configured to limit the lowering cylinder 21 to the positioning mechanism 1 during the lowering process. In this embodiment, the positioning mechanism 1 works in conjunction with the lowering mechanism 2. By setting a plug 22, a chamber 25 is formed inside the lowering cylinder 21. This allows the fluid to be driven by the circulating pump 3 and pressed down into the geothermal well. During use, the circulating pump 3 continuously pressurizes the fluid from the opening of the chamber 25 into the chamber 25, thereby moving the lowering mechanism 2 along the geothermal well until it reaches the position of the positioning mechanism 1. The limiting component cooperates with the positioning mechanism 1 to form a limit, and then the pressure is continued until the closed end of the chamber 25 opens. This achieves wellhead pumping with fixed optical fiber, enabling the lowering and fixing of the optical fiber in the horizontal section 101 of the U-shaped well. It solves the technical problems of the current method of using counterweights for optical fiber temperature measurement in geothermal wells, such as difficulty in lowering the fiber, monitoring gaps in the horizontal section 101, and easy entanglement.

[0032] Some embodiments of the present invention disclose a fixing device for the end of an optical fiber. Based on the above embodiments, to limit the lowering mechanism 2 in both front and rear directions, the limiting component may include a first limiting member and a second limiting member. The second limiting member is installed on the outer wall of the lowering cylinder 21. The limiting component is configured such that the second limiting member expands after passing through the positioning mechanism 1, so that the first limiting member and the second limiting member are respectively limited to both sides of the positioning mechanism 1. The second limiting member may be an elastic element to achieve the above function.

[0033] To facilitate the positioning of the elastic element, the positioning mechanism 1 may include a positioning step 11; the elastic element may include at least two circumferentially uniformly installed arc-shaped spring pieces 24 on the outer wall of the lowering cylinder 21, the first end of the arc-shaped spring piece 24 being fixedly connected to the lowering cylinder 21, and the second end of the arc-shaped spring piece 24 extending towards the first end of the lowering cylinder 21; and, after expansion, the second ends of the plurality of arc-shaped spring pieces 24 are engaged on the positioning step 11. Generally, at least three arc-shaped spring pieces 24 may be provided, circumferentially arranged on the outer wall of the lowering cylinder 21. During the lowering process, the arc-shaped spring pieces 24 contact the casing of the geothermal well, which can effectively maintain the centering of the lowering mechanism 2 and effectively reduce the lowering resistance.

[0034] To achieve the limiting between the first limiting member and the positioning mechanism 1, in the above embodiment, the positioning mechanism 1 may further include a positioning cylinder 12 and an annular positioning component. The positioning component is located on the inner wall of the positioning cylinder 12, and a positioning step 11 is formed on one side of the positioning component, while a positioning inclined surface 13 is formed on the other side. Along the direction away from the positioning step 11, the inner diameter formed by the positioning inclined surface 13 gradually increases. The second limiting member is limited by the positioning step 11, and the first limiting member is limited by the positioning inclined surface 13. In use, the positioning cylinder 12 needs to be fixed at a predetermined position in the geothermal well, which determines the final position of the fiber optic end. The first limiting member can generally be set as a limiting cylinder 23, which can achieve the cooperating limiting with the positioning inclined surface 13. Specifically, the first end of the limiting cylinder 23 can be connected to the first end or the outer wall of the lower entry cylinder 21, and the last end of the limiting cylinder 23 extends away from the second end of the lower entry cylinder 21. Along the direction from the first end to the last end of the limiting cylinder 23, the outer diameter of the limiting cylinder 23 gradually increases; and the outer diameter of the limiting cylinder 23 is adapted to be limited to the inner wall of the positioning inclined surface 13; the end of the optical fiber is connected to the limiting cylinder 23 or the lower entry cylinder 21. In this structure, a universal joint 27 can be installed at the end of the limiting cylinder 23, and the end of the optical fiber can be inserted into the universal joint 27 so that the optical fiber can be lowered into the predetermined position along with the lower entry cylinder 21.

[0035] This invention discloses a fixing device for optical fiber ends. Based on the above embodiments, to enable the plug 22 to open the sealing end of the lower insertion cylinder 21 under sufficient pressure, the plug 22 can be made of a material with appropriate pressure resistance, allowing it to tear or pop out under sufficient pressure. Alternatively, the plug 22 can be connected to the lower insertion cylinder 21 via a connecting component with a predetermined strength. By controlling the pressure resistance of the connecting component, the pressure at which the plug 22 detaches from the lower insertion cylinder 21 can be controlled. Specifically, the plug 22 is installed at the second end of the lower insertion cylinder 21 via the connecting component, and the connecting component is configured to break when the pressure in the chamber 25 exceeds a predetermined value, causing the plug 22 to detach from the lower insertion cylinder 21. This connecting component can be a connecting pin 26. Specifically, the second end of the lower insertion cylinder 21 can be provided with at least two pin holes, and the outer wall of the plug 22 is circumferentially arranged with connecting holes corresponding to the pin holes. At least two connecting pins 26 connect the pin holes and the connecting holes in a one-to-one correspondence. Generally, two to three connecting pins 26 can be set to achieve a stable connection and avoid excessive strength that would make it difficult for the plug 22 to come out.

[0036] Some embodiments of the present invention also disclose a method for fixing optical fibers in a geothermal well, which uses the aforementioned fixing device for the end of the optical fiber for fixing. Taking a U-shaped geothermal well as an example, it generally includes a horizontal well 100 and a vertical well 200, the bottoms of which are connected to form a heat exchange medium circulation channel. The circulating medium can enter the well casing from the horizontal well 100, be heated in the well casing, and then return to the surface from the vertical well 200 for use in building heating, etc. Conversely, the heat exchange medium can also enter from the vertical well 200 and return from the horizontal well 100. Correspondingly, it includes fixing the horizontal well 100 and the vertical well 200, as well as fixing the optical fiber 7 in the horizontal well and the optical fiber 6 in the vertical well. Due to its direct structural characteristics, the fixing of the vertical well 200 can be achieved by directly selecting a counterweight 8 to connect one end of the optical fiber, and lowering it to a designated position by gravity from the vertical well pipe string 5. The fixing of the horizontal well 100 needs to be implemented using the fixing device for the end of the optical fiber disclosed in the aforementioned embodiments, which may specifically include: The positioning mechanism 1 is installed at a predetermined position in the horizontal well 100, generally at the end of the horizontal well 100. Specifically, the positioning cylinder 12 of the positioning mechanism 1 can be connected to the casing of the horizontal well 100 by a thread. The positioning mechanism 1 forms a channel inside which the lowering mechanism 2 can pass through. In this embodiment, the positioning mechanism 1 also includes an annular positioning component fixedly installed inside the positioning cylinder 12. One side of the positioning component forms a positioning step 11, and the other side forms a cylindrical shape with one end larger than the other. As the distance between the positioning component and the positioning step 11 increases, its inner diameter gradually increases.

[0037] Then, one end of the optical fiber is fixed to the lowering cylinder 21 or the limiting component of the lowering mechanism 2 via a universal joint 27. In this embodiment, the limiting component includes the arc-shaped spring piece 24 described in the previous embodiment as a limiting member, and a limiting cylinder 23 extending from the first end of the lowering cylinder 21 away from the lowering cylinder 21. The limiting cylinder 23 has a large outer diameter at one end and a small outer diameter at the other end, and is fitted and snapped into the cylindrical adapter of the positioning component. That is, the minimum inner diameter of the cylinder of the positioning component should be greater than the maximum outer diameter of the limiting cylinder 23. Generally, in order to ensure the stability of positioning, the minimum inner diameter of the cylinder is the same as the minimum outer diameter of the limiting cylinder 23, and the maximum inner diameter of the cylinder is the same as the maximum outer diameter of the limiting cylinder 23, which can ensure stable and reliable limiting. In addition, a connecting pipe with the same minimum inner diameter as the cylinder can be provided between the minimum end of the cylinder and the positioning step 11. The side of the connecting pipe away from the cylinder forms a positioning step 11 between it and the inner diameter of the positioning cylinder 12. The length of the connecting tube corresponds to the distance between the second end of the matching arc-shaped spring 24 and the limiting cylinder 23, thereby enabling stable positioning of the lowering mechanism 2.

[0038] Next, the sealing end of the lowering mechanism 2 is inserted downwards into the geothermal well through the wellhead. The surface circulation pump 3 is started, and the circulation pump 3 is connected to the inlet pipeline of the horizontal well 100 and the return pipeline of the vertical well 200. Fluid flows into the chamber 25 along the horizontal well string 4 and pushes the lowering mechanism 2 until the limiting component of the lowering mechanism 2 is limited on the positioning mechanism 1. After entering the positioning mechanism 1, the elastic element (arc-shaped spring 24) of the lowering mechanism 2 is compressed and retracted until it passes through the positioning step 11 and then rebounds and opens and locks on the positioning step 11 to prevent the lowering mechanism 2 from moving backwards. At the same time, the end of the lowering mechanism 2 with the larger outer diameter is locked on the cylinder of the positioning device, preventing the lowering mechanism 2 from moving forward.

[0039] Continue pressurizing using the circulation pump 3 until the plug 22 opens, opening the closed end of the chamber 25. Specifically, increase the pressure of the circulation pump 3 until the pin of the plug 22 at the end of the lowering cylinder 21 breaks, and the plug 22 disengages from the lowering cylinder 21. The two sides of the lowering cylinder 21 are connected, and the lowering and positioning of the horizontal well fiber optic cable 7 is completed.

[0040] Embodiments of the present invention also disclose a method for optical fiber temperature measurement in geothermal wells, which uses the fixing device for optical fiber ends described in the foregoing embodiments to fix the optical fiber ends. The optical fiber fixing method for geothermal wells described in the foregoing embodiments is used for optical fiber fixing.

[0041] In summary, the fiber optic end fixing device, geothermal well fiber optic fixing method, and geothermal well fiber optic temperature measurement method disclosed in the embodiments of the present invention, compared with the prior art, can realize the insertion and fixing of the 101 fiber optic cable in the horizontal section of the U-shaped well through the fiber optic end fixing device and the wellhead pumping process. The process is simple, economical, feasible, highly operable, less likely to have monitoring blank areas, no cable entanglement, and does not affect heat exchange efficiency, and has good application prospects.

[0042] The embodiments of this disclosure have now been described in detail. To avoid obscuring the concept of this disclosure, some details known in the art have not been described. Those skilled in the art can fully understand how to implement the technical solutions disclosed herein based on the above description.

[0043] While specific embodiments of this disclosure have been described in detail by way of examples, those skilled in the art should understand that the examples are for illustrative purposes only and not intended to limit the scope of this disclosure. Those skilled in the art should understand that modifications can be made to the above embodiments or equivalent substitutions can be made to some technical features without departing from the scope and spirit of this disclosure. In particular, as long as there is no structural conflict, the technical features mentioned in the various embodiments can be combined in any manner.

Claims

1. A fixing device for the end of an optical fiber, characterized in that, Includes a positioning mechanism and a lowering mechanism, among which, The lowering mechanism includes a lowering cylinder, a plug, and a limiting assembly. The plug is installed inside the lowering cylinder, forming a closed chamber between the first end of the lowering cylinder and the plug. The plug is configured to open the closed end of the chamber when the pressure inside the chamber is greater than a predetermined value. The limiting component is disposed on the lower inlet cylinder and configured to limit the lower inlet cylinder on the positioning mechanism during the lowering process.

2. The fixing device for the end of an optical fiber according to claim 1, characterized in that, The limiting component includes a first limiting member and a second limiting member. The second limiting member is installed on the outer wall of the lower inlet cylinder. The limiting component is configured such that the second limiting member expands after passing through the positioning mechanism, so that the first limiting member and the second limiting member are respectively limited to both sides of the positioning mechanism.

3. The fixing device for the end of an optical fiber according to claim 1, characterized in that, The second limiting element is an elastic element.

4. The fixing device for the end of a light beam according to claim 3, characterized in that, The positioning mechanism includes a positioning step; The elastic element includes at least two arc-shaped spring pieces that are circumferentially and uniformly installed on the outer wall of the lowering cylinder. The first end of the arc-shaped spring piece is fixedly connected to the lowering cylinder, and the second end of the arc-shaped spring piece extends toward the first end of the lowering cylinder. Furthermore, the second ends of the multiple curved spring pieces, after being expanded, are engaged with the positioning step.

5. The fixing device for the end of a light beam according to claim 2, characterized in that, The positioning mechanism further includes a positioning cylinder and an annular positioning component. The positioning component is located on the inner wall of the positioning cylinder, and a positioning step is formed on one side of the positioning component, while a positioning inclined surface is formed on the other side of the positioning component. Along the direction away from the positioning step, the inner diameter formed by the positioning ramp gradually increases; The second limiting member is located on the positioning step, and the first limiting member is located on the positioning inclined surface.

6. The fixing device for the end of an optical fiber according to claim 5, characterized in that, The first limiting member is a limiting cylinder. The first end of the limiting cylinder is connected to the first end or outer wall of the lower entry cylinder. The end of the limiting cylinder extends away from the second end of the lower entry cylinder. Along the direction from the first end to the end of the limiting cylinder, the outer diameter of the limiting cylinder gradually increases. Furthermore, the outer diameter of the limiting cylinder is adapted to be located within the inner wall of the positioning inclined surface; The end of the optical fiber is connected to the limiting cylinder or the lowering cylinder.

7. The fixing device for the end of an optical fiber according to claim 1, characterized in that, The lowering mechanism further includes a connecting assembly, through which the plug is mounted at the second end of the lowering cylinder, and the connecting assembly is configured to break when the pressure in the chamber exceeds a predetermined value, causing the plug to disengage from the lowering cylinder.

8. The fixing device for the end of an optical fiber according to claim 7, characterized in that, The connecting component is a connecting pin.

9. The fixing device for the end of an optical fiber according to claim 8, characterized in that, The second end of the lower inlet cylinder is provided with at least two pin holes, and the outer wall of the plug is circumferentially arranged with connecting holes corresponding to the pin holes. At least two connecting pins are connected one-to-one between the pin holes and the connecting holes.

10. A method for fixing optical fibers in a geothermal well, characterized in that, The fiber optic end is fixed using the fixing device described in any one of claims 1-9.

11. The method for fixing optical fibers in geothermal wells according to claim 10, characterized in that, Includes horizontal well fixing, wherein the horizontal well fixing includes: Install the positioning mechanism at the predetermined position of the horizontal well; Fix one end of the optical fiber to the lower inlet cylinder; The lowering mechanism is inserted into the geothermal well from the wellhead, the circulation pump is started, the fluid flows into the chamber and pushes the lowering mechanism to move until the limiting component of the lowering mechanism is limited on the positioning mechanism; Continue pressurizing using a circulating pump until the plug opens, allowing the closed end of the chamber to open.

12. The method for fixing optical fibers in geothermal wells according to claim 10, characterized in that, This includes a vertical well fixation system, wherein one end of the optical fiber is connected to a counterweight block and lowered to a designated position by gravity.

13. The method for fixing optical fibers in geothermal wells according to claim 11, characterized in that, The first end of the lower inlet cylinder is provided with a universal joint, and the optical fiber is connected to the universal joint.

14. A method for fiber optic temperature measurement in geothermal wells, characterized in that, The fiber optic end is fixed using the fixing device for fiber optic ends as described in any one of claims 1-9.

15. The method for fiber optic temperature measurement of geothermal wells according to claim 14, characterized in that, The optical fiber is fixed using the optical fiber fixing method for geothermal wells as described in any one of claims 10-13.

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