Temperature measurement optical fiber counterweight assembly and geothermal well optical fiber temperature measurement system and method

Abstract

The invention relates to the technical field of geothermal well monitoring, in particular to a temperature measurement optical fiber counterweight assembly and a geothermal well optical fiber temperature measurement system and method.The temperature measurement optical fiber counterweight assembly comprises a counterweight column, the counterweight column comprises a counterweight front section and a counterweight tail section which are distributed at the two ends and coaxially arranged, the counterweight front section is of a fusiform structure with the surface provided with a curved surface, and the counterweight tail section is connected with a temperature measurement optical fiber; the conical structure is gradually enlarged from the tail end to the front end of the counterweight column; the mounting groove is formed in the counterweight column in the axial direction and matched with the temperature measuring optical fiber in shape, and a sealing structure is formed between the mounting groove and the temperature measuring optical fiber. According to the invention, through the mutual cooperation of the counterweight column and the mounting groove, the lowering of the temperature measurement optical fiber can be assisted, the passing performance is better in the lowering process, the effects of centralizing, pulling and straightening the optical fiber and sealing the optical fiber plug are achieved, and the temperature in the geothermal deep well can be conveniently monitored.

Description

Technical Field

[0001] This invention relates to the field of geothermal well monitoring technology, and in particular to a temperature-measuring fiber optic counterweight assembly, a geothermal well fiber optic temperature measurement system and method. Background Technology

[0002] Monitoring the wellbore temperature of deep geothermal wells is a fundamental task in the development and utilization of geothermal resources. It is of great significance for understanding the impact of deep geothermal reservoirs and surrounding geothermal reinjection activities on reservoir temperature, and for ensuring the long-term sustainable development and utilization of resources. Distributed fiber optic temperature measurement technology has been widely used in geothermal well temperature measurement, but it is mainly used in production wells such as extraction or reinjection wells. For example, Chinese patent CN108871606B discloses a distributed fiber optic temperature monitoring system and method for deep geothermal wells. It vertically and centrally lowers a high-temperature resistant armored fiber optic cable into the deep geothermal well, which can ensure that the distance between each collection point is equal, resulting in more ideal data and ensuring a linear temperature distribution in the vertical direction.

[0003] However, because geothermal wells are often quite deep (generally several kilometers), it creates many inconveniences for fiber optic temperature measurement, leading to inaccurate temperature data. For example... Figure 1 As shown (the horizontal axis represents the depth of the geothermal well, and the vertical axis represents the measured temperature; the blue curve represents the temperature curve measured using existing temperature measurement methods, and the black dashed line represents the actual bottom temperature curve detected by gradually lowering the temperature sensor), it was found that the temperature curve measured by the existing temperature-measuring fiber optic cable exhibits an abnormal downward bend at the end relative to the actual value (i.e., the measured value near the end is lower than the actual value). Analysis of the cause of this abnormal end-data reveals that the fiber optic cable is affected by geothermal environmental factors over a long period, leading to a certain attenuation of the optical signal during transmission. This is particularly problematic as it results in inaccurate temperature measurement data at the fiber optic end, thus necessitating a more precise temperature calibration method.

[0004] To improve temperature measurement accuracy, the temperature-sensing optical fiber needs to be inserted straight down into the geothermal well without obstruction. There are two main methods for placing the existing temperature-sensing optical fiber into deep geothermal wells: one is to tie it to the pump pipe with a strap, which can be reused, but cannot avoid physical damage such as bumps during the pipe-down process, as well as situations where it gets stuck and cannot be lowered further; the other is to tie it to the casing with a casing coupling protector and a strap during well completion and lower it to monitor the temperature of the well wall. This method also cannot avoid physical damage such as bumps during the pipe-down process, and once buried, it cannot be retrieved, and once damaged, it cannot be repaired. Summary of the Invention

[0005] In this section, as well as in the abstract and title of this application, some simplifications or omissions may be made to avoid obscuring the purpose of this section, the abstract, and the title of this application, and such simplifications or omissions shall not be used to limit the scope of the invention.

[0006] To address the shortcomings of existing technologies, one objective of this invention is to provide a temperature-measuring fiber optic counterweight assembly.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: a temperature-sensing fiber optic counterweight assembly, comprising,

[0008] The counterweight column includes a front counterweight section and a tail counterweight section distributed at both ends and coaxially arranged.

[0009] The front section of the counterweight is a spindle-shaped structure with a curved surface.

[0010] The tail section of the counterweight is connected to a temperature-measuring optical fiber and is a tapered structure that gradually increases in size from the tail end to the front end of the counterweight column; and,

[0011] The mounting slot is axially positioned within the counterweight column and is adapted to the shape of the temperature-sensing optical fiber.

[0012] The mounting groove and the temperature measuring optical fiber form a sealed structure.

[0013] In a preferred embodiment of the temperature-measuring fiber optic counterweight assembly of the present invention, the tail section of the counterweight is a split structure that can be separated along the axial cross-section.

[0014] The split structure comprises at least two parts.

[0015] The mounting groove is formed by assembling the various separate structural components.

[0016] The various parts of the structure are detachably connected.

[0017] In a preferred embodiment of the temperature-measuring fiber optic counterweight assembly of the present invention, the end of the front section of the counterweight is an arc surface.

[0018] The beneficial effects of the temperature-sensing fiber optic counterweight assembly of the present invention are as follows: The present invention, through the cooperation between the counterweight column and the mounting groove, can assist in the lowering of the temperature-sensing fiber optic cable, and has excellent performance during the lowering process. It also has the effects of straightening, pulling, straightening the fiber optic cable and sealing the fiber optic plug, which facilitates the monitoring of temperature in deep geothermal wells.

[0019] Based on the same inventive concept, another objective of this invention is to provide a geothermal well fiber optic temperature measurement system.

[0020] To achieve the above objectives, the present invention adopts the following technical solution: a geothermal well fiber optic temperature measurement system, comprising the aforementioned temperature measurement fiber optic counterweight assembly, wherein the relationship between the maximum width M of any cross-sectional shape of the counterweight column along the axial direction, the width L of the geothermal well's variable-diameter step, and the minimum diameter N of the geothermal well's water inlet section satisfies: 2L <M<N。

[0021] As a preferred embodiment of the geothermal well fiber optic temperature measurement system of the present invention, it further includes:

[0022] Temperature-sensing optical fiber; and,

[0023] A fiber optic temperature measurement and processing device, wherein the fiber optic temperature measurement and processing device is connected to the end of the temperature measuring fiber away from the counterweight column;

[0024] The fiber optic temperature measurement processing device includes a laser emitting module for sending laser signals to the temperature measuring fiber, and an analysis and processing module for receiving Raman scattered light signals carrying temperature information returned by the temperature measuring fiber.

[0025] As a preferred embodiment of the geothermal well fiber optic temperature measurement system of the present invention, it further includes a constant temperature chamber, wherein the temperature measuring fiber has at least one calibration section that is always located inside the constant temperature chamber.

[0026] The constant temperature chamber is equipped with a temperature control module, and the temperature control module and the analysis and processing module have a bidirectional communication connection.

[0027] As a preferred embodiment of the geothermal well fiber optic temperature measurement system of the present invention, the calibration section is located above the geothermal liquid surface, or / and at the automatic water level sensor probe located below the geothermal liquid surface.

[0028] In a preferred embodiment of the geothermal well fiber optic temperature measurement system of the present invention, the distance between at least two calibration sections is 300 meters to 500 meters.

[0029] As a preferred embodiment of the geothermal well fiber optic temperature measurement system of the present invention, it further includes a component located outside the geothermal well.

[0030] A reversing assembly, comprising a pulley mounted above the wellhead, wherein the temperature-sensing optical fiber bypasses the pulley and is redirected to extend into the geothermal well; and,

[0031] A traction component, which is connected to a temperature-sensing optical fiber outside the geothermal well, is used to retract or release the temperature-sensing optical fiber.

[0032] The beneficial effects of the geothermal well fiber optic temperature measurement system of the present invention are as follows: The present invention, through the cooperation of the temperature-sensing fiber counterweight component, the temperature-sensing fiber, the reversing component, and the traction component, can achieve protective load-bearing fixation of the fiber, allowing the temperature-sensing fiber to be stably lowered deep into the geothermal well, ultimately realizing distributed temperature measurement throughout the entire well section, and solving the problem of easy impact and damage to the temperature-sensing fiber during lowering; the counterweight can straighten the temperature-sensing fiber and accurately drop it to the bottom of the geothermal well, which is helpful for subsequent accurate temperature measurement and calibration calculations; and by setting up a constant temperature chamber and calibration section, automatic calibration of fiber optic temperature measurement can be achieved, avoiding the limitations of long-term use after one-time calibration, especially allowing for recalibration of measurement data at the fiber end, improving the accuracy of the measurement values.

[0033] Based on the same inventive concept, the third objective of this invention is to provide a method for optical fiber temperature measurement in geothermal wells.

[0034] To achieve the above objectives, the present invention adopts the following technical solution: a geothermal well fiber optic temperature measurement method, applied to the aforementioned geothermal well fiber optic temperature measurement system, comprising the following steps:

[0035] Connect the first end of the temperature-measuring optical fiber to the optical fiber temperature measurement and processing device.

[0036] Before the temperature-sensing fiber optic cable is inserted into the well, signal detection and calibration are performed to confirm that the temperature-sensing fiber optic cable is working properly.

[0037] The temperature-sensing optical fiber with a counterweight column at its end is lowered to the target depth position of the geothermal well using a traction component.

[0038] The signal is detected regularly using a fiber optic temperature measurement and processing device to collect temperature information at different depths within the geothermal well.

[0039] As a preferred embodiment of the geothermal well fiber optic temperature measurement method of the present invention, the calibration method includes:

[0040] Select at least one calibration section of the temperature-measuring fiber and place it in a constant temperature chamber;

[0041] Periodically drive the temperature control module inside the constant temperature chamber to adjust the temperature inside the chamber to the preset calibration point;

[0042] The temperature measurement data of the temperature measuring fiber is obtained by the analysis and processing module and compared with the actual temperature of the calibration section in the constant temperature chamber, and the calibration parameters are automatically adjusted.

[0043] The temperature T at the adjusted temperature measuring point z is:

[0044]

[0045] Where R(T, z) is the ratio of the Stokes light intensity to the anti-Stokes light intensity at the temperature measurement point, α is the fiber signal attenuation coefficient, K is the temperature sensitivity coefficient, and C is the temperature compensation value.

[0046] As a preferred embodiment of the geothermal well fiber optic temperature measurement method of the present invention, the calibration method further includes compensating for the optical switching loss of the temperature measuring fiber, and the method for calculating the optical switching loss coefficient Q is as follows:

[0047] Measure the Stokes light intensity r1, r2 and the anti-Stokes light intensity R1, R2 before and after the optical switch;

[0048] Calculate the optical switching loss factor using the following formula:

[0049]

[0050] The new temperature calculation formula is as follows:

[0051]

[0052] Where d(z) is the distance from position z to the optical switch.

[0053] As a preferred embodiment of the geothermal well fiber optic temperature measurement method of the present invention, the calibration method further includes:

[0054] Based on the actual temperatures T1 and T2 measured at any two calibration sections z1 and z2, and the fiber optic measurement value T z1 T z2 The data was corrected for the terminal temperature T3, and the signal strength ratios of the two were as follows:

[0055]

[0056] Next, calculate the difference in fiber optic signal attenuation coefficients along the path:

[0057]

[0058] Then the initial temperature T measured at the end of the temperature-sensing optical fiber was... z3 After correction, the terminal temperature compensation formula can be obtained as follows:

[0059]

[0060] Z3 represents the end position of the temperature-sensing optical fiber.

[0061] The beneficial effects of the fiber optic temperature measurement method for geothermal wells of the present invention are the same as those of the fiber optic temperature measurement system for geothermal wells, so they will not be described in detail here. Attached Figure Description

[0062] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. 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.

[0063] Figure 1 This is a schematic diagram of the temperature curve measured using existing technology.

[0064] Figure 2 This is a three-dimensional structural diagram of the temperature-measuring fiber optic counterweight component of the present invention.

[0065] Figure 3 This is a schematic diagram of the internal structure of the temperature-measuring fiber optic counterweight component of the present invention.

[0066] Figure 4 This is a schematic diagram of the structure of the geothermal well fiber optic temperature measurement system after the fiber optic counterweight has been lowered.

[0067] Figure 5 This is a schematic diagram illustrating the structural principle of the fiber optic temperature measurement processing device of the present invention.

[0068] Figure 6 This is a partially enlarged structural diagram of the counterweight column of the present invention located at the diameter-changing step of the geothermal well.

[0069] Figure 7 This is a schematic diagram of the structure at the wellhead of the geothermal well lowering device of the present invention.

[0070] Figure 8 This is a schematic diagram showing the preferred location distribution of the constant temperature chamber in the geothermal well fiber optic temperature measurement method of the present invention.

[0071] Figure 9 This is a schematic diagram of the temperature curve obtained by the fiber optic temperature measurement method for geothermal wells according to the present invention. Detailed Implementation

[0072] To make the objectives, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0073] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0074] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0075] Example 1

[0076] Reference Figure 2 and Figure 3 This is the first embodiment of the present invention, which provides a temperature-sensing fiber optic counterweight assembly capable of straightening and aligning the temperature-sensing fiber optic cable. It includes a counterweight column 100 and a mounting groove 200. The mounting groove 200 is adapted to the shape of the temperature-sensing fiber optic cable 300 and is located within the counterweight column 100. The temperature-sensing fiber optic cable 300 is connected to the counterweight column 100 through the mounting groove 200. The working principle of the temperature-sensing fiber optic cable 300 is as follows: a pulsed laser signal is emitted into the fiber optic channel of a high-temperature armored optical cable under the control of a data acquisition and control circuit; a wavelength division multiplexer divides the Raman scattered light signal carrying temperature in the high-temperature armored optical cable into Stokes light and anti-Stokes light according to wavelength; a photoelectric converter (i.e., an optical switch) converts the Stokes light signal and the anti-Stokes light signal into voltage signals respectively; the data acquisition and control circuit completes the data acquisition of the voltage signal; the industrial control computer interprets the data, converts it into temperature information, and saves and displays it. In this embodiment, distributed measurement is adopted, and temperature can be sensed in the entire fiber optic segment. The monitoring interval is 0.5m. The weight of the counterweight column 100 is used to straighten and tighten the temperature sensing fiber 300 so that the temperature sensing part of the temperature sensing fiber 300 can be lowered into the appropriate depth of the geothermal well, thereby realizing temperature monitoring.

[0077] Specifically, the counterweight column 100 includes a front counterweight section 101 and a rear counterweight section 102 distributed at both ends and coaxially arranged. After the temperature-sensing optical fiber 300 is lowered, the counterweight column 100 is connected to the temperature-sensing optical fiber 300 through the rear counterweight section 102. The front counterweight section 101 of the counterweight column 100 automatically droops to its lowest point under the action of gravity. In this embodiment, the counterweight column 100 is cylindrical in shape. The front counterweight section 101, the rear counterweight section 102, and the entire counterweight column 100 are coaxial, and the center of gravity of the counterweight column 100 is also located on its axis. After the temperature-sensing optical fiber 300 is straightened, it is collinear with the axis of the center of gravity of the counterweight column 100.

[0078] Furthermore, the front section 101 of the counterweight has a spindle-shaped structure with a curved surface, where "spindle-shaped" is generally defined as a shape that is "pointed at both ends and thick in the middle." For example... Figure 3As shown, the front section 101 of the counterweight may contain only a part of the spindle-shaped structure. In this embodiment, the front section 101 of the counterweight has at least one tip of the spindle shape, and the tip is located at the end of the front section 101 of the counterweight. The surface from the tip to the thicker part in the middle is curved, and the diameter of the thicker part is the maximum diameter of the entire counterweight column 100. The other end of the spindle shape is used to connect with the other parts of the counterweight column 100. During the process of the temperature-sensing optical fiber 300 being lowered through the counterweight column 100, the front section 101 of the counterweight is at the forefront during the downward movement. During its movement, since the thicker part of the spindle shape is more easily blocked by obstacles, the curved surface of the spindle shape on the surface of the front section 101 of the counterweight will sweep across the obstacles during the downward movement. In particular, when the temperature-sensing optical fiber 300 swings during the lowering of the counterweight column 100, the thicker part of the spindle shape of the front section 101 of the counterweight can also be the first to touch the obstacle and rebound, thereby playing a corrective role.

[0079] In a preferred embodiment, the end of the front section 101 of the counterweight is an arc surface. Since the spindle-shaped structure has at least one tip, setting the tip as an arc surface makes it less likely to get stuck in the well wall steps, rusted pits or grooves during its movement. After setting the arc surface, the tip becomes relatively smooth and can easily glide over the above-mentioned obstacles by means of the inertia of the downward movement.

[0080] The counterweight tail section 102 is connected to the temperature-sensing optical fiber 300 and is a tapered structure that gradually increases in size from the tail end of the counterweight column 100 to the front end. That is, the end of the counterweight tail section 102 closest to the temperature-sensing optical fiber 300 cable is smaller, and the other end is larger. In this embodiment, the side of the tapered structure is also a relatively smooth curved surface. In this way, when the temperature-sensing optical fiber 300 is lifted, the smaller end of the counterweight tail section 102 is located at the front end in the direction of travel, and its probability of hitting obstacles is smaller. When the side of the counterweight tail section 102 or the larger front section 101 of the counterweight touches an obstacle, it can also slide over the obstacle through the curved surface of the side in the inertia of displacement, thereby smoothly realizing the upward movement of the temperature-sensing optical fiber 300.

[0081] Furthermore, the mounting groove 200 is axially positioned within the counterweight column 100 and is adapted to the shape of the temperature-sensing optical fiber 300, forming a sealed structure between the mounting groove 200 and the temperature-sensing optical fiber 300. The centers of gravity of the mounting groove 200 and the counterweight column 100 are coaxial in the vertical direction. The front diameter of the mounting groove 200 is slightly larger than the rear diameter, facilitating the placement of a plug with a diameter slightly larger than the optical fiber, while also enhancing the anti-slip effect. Specifically, it includes a groove body 201 adapted to the temperature-sensing optical fiber 300, and a groove body 202 adapted to the plug of the temperature-sensing optical fiber 300. The groove body 201 is connected to the end of the counterweight tail section 102. When the temperature-sensing optical fiber 300 is lowered, the groove body 202 and its adapted plug portion are positioned below, allowing the plug of the temperature-sensing optical fiber 300 to stably support the counterweight column 100, preventing the counterweight column 100 from slipping off the temperature-sensing optical fiber 300 under significant gravity. The mounting groove 200 is slightly larger than the temperature measuring fiber 300. After installation, it can be filled with industrial sealant to achieve a seal after solidification.

[0082] The plug of the temperature-sensing fiber optic cable 300 is mainly used to protect the fiber optic interface, prevent dust from entering, or achieve specific fiber optic connection functions. The plug is located at the end of the temperature-sensing fiber optic cable 300, and its diameter is slightly larger than that of the temperature-sensing fiber optic cable 300. After the temperature-sensing fiber optic cable 300 is placed in the mounting groove 200, the groove body 202 and the plug of the temperature-sensing fiber optic cable 300 are sealed with industrial sealant to prevent dust, corrosive liquids, etc., from entering the temperature-sensing fiber optic cable 300 through the plug and affecting the temperature measurement accuracy. At the same time, the connection through the industrial sealant can improve the connection strength between the temperature-sensing fiber optic cable 300 and the counterweight column 100, further preventing the counterweight column 100 from slipping out of the temperature-sensing fiber optic cable 300 due to excessive weight.

[0083] Furthermore, the counterweight column 100 includes a connecting section 103 disposed between the front counterweight section 101 and the rear counterweight section 102, and a mounting groove 200 disposed within the rear counterweight section 102 and the connecting section 103. The connecting section 103 connects the front counterweight section 101 and the rear counterweight section 102. The connecting section 103 is also cylindrical, and its central axis is collinear with the central axes of the front counterweight section 101 and the rear counterweight section 102, thereby increasing the distance between them. In this embodiment, the mass of the front counterweight section 101 is set to be greater than that of both the connecting section 103 and the rear counterweight section 102, thereby lowering the center of gravity of the counterweight column 100 when the temperature-sensing fiber optic cable 300 is lowered, promoting the verticality of both the counterweight column 100 and the temperature-sensing fiber optic cable 300. Simultaneously, the connecting section 103 facilitates the detachable connection and installation of the front counterweight section 101 and the rear counterweight section 102.

[0084] The counterweight tail section 102 and the connecting middle section 103 are both detachable split structures that can be separated along the axial cross section. Each split structure includes at least two parts, and the mounting groove 200 is formed by combining the various split structures. The various split structures are detachably connected. In this embodiment, the split structure includes two parts, which can be fixed by bolts through pre-reserved bolt slots. Each part has half of the mounting groove 200, which facilitates the quick installation of the temperature measuring fiber optic cable 300 into one half of the mounting groove 200 after disassembly. After applying industrial sealant to the mounting groove 200, the other half of the split structure is covered, and finally the two split structures are connected and fixed by bolts to complete the installation.

[0085] In one optional embodiment, the front section 101 of the counterweight and the connecting middle section 103 are detachably connected and can be installed and disassembled using a threaded connection structure. This threaded connection mechanism allows for the replacement of the front section 101 of the counterweight with different shapes, sizes, and masses to adapt to more application scenarios. Any cross-sectional shape of the front section 101 along the axial direction is circular or elliptical, and the center of the circle or ellipse is located on the central axis of the front section 101.

[0086] Reference Figure 3 In this embodiment, each part of the counterweight column 100 is a columnar shape formed by rotation along the central axis. This ensures that the distance to which it touches obstacles in each direction during use is not changed by its own rotation. Therefore, the shape of any cross-section of the counterweight front section 101 along the axial direction is the same. The axial cross-section of the spindle-shaped structure with a curved surface includes circles, ellipses, and other shapes. Any cross-section shape of the counterweight front section 101 along the axial direction can be a circle, an ellipse, or a part thereof. The counterweight front section 101 structure composed of circular and elliptical cross-sections is stable and easy to process. Preferably, it is an elliptical cross-section. The curvature variation of the outer curved surface of the counterweight front section 101 with an elliptical cross-section is smaller than that of a circle, which provides better passability when lowered. In addition, for the same mass and density, the center of gravity of the counterweight front section 101 with an elliptical cross-section is relatively lower than that of the counterweight front section 101 with a circular cross-section.

[0087] Working principle: The counterweight tail section 102 and the connecting middle section 103 are separated along the axial section, exposing the mounting groove 200 inside the counterweight column 100. The dust, oil, rust, etc. on the surface of the mounting groove 200 are cleaned. Then, the temperature measuring fiber 300 and its plug are installed into the groove 1 201 and groove 2 202 respectively, and the bolt grooves of the separated structures are aligned. Next, the gap between the temperature measuring fiber 300 and the mounting groove 200 is self-filled with industrial sealant. After solidification, a seal is achieved. Then, the various parts of the structure are connected and fixed with bolts. Finally, the counterweight front section 101 and the connecting middle section 103 are connected by threaded rotation to complete the assembly between the temperature measuring fiber 300 and the counterweight column 100.

[0088] Example 2

[0089] Referring to Figures 2-6 , which is the second embodiment of the present invention. Different from the previous embodiment, this embodiment provides a geothermal well optical fiber temperature measurement system, which includes the temperature measurement optical fiber weight component and the temperature measurement optical fiber 300 in Embodiment 1, and also includes an optical fiber temperature measurement processing device 700. As Figure 5 shown, the optical fiber temperature measurement processing device 700 adopts an existing technology device, which is a DTS device. The parameters are adjusted through the upper computer software. It is connected to the end of the temperature measurement optical fiber 300 far away from the weight column 100. It includes a laser emission module 701 for sending laser signals to the temperature measurement optical fiber 300, and an analysis and processing module 702 for receiving the Raman scattered light signals carrying temperature information returned by the temperature measurement optical fiber 300. The laser emission module 701 is used to send laser signals to the temperature measurement optical fiber 300, and the analysis and processing module 702 receives the Raman scattered light signals carrying temperature information returned by the temperature measurement optical fiber 300 and performs analysis and display. After the temperature measurement optical fiber 300 is lowered to the target measurement depth position of the geothermal well, by processing and protecting the tail fiber, making an optical cable joint, and connecting the optical fiber temperature measurement processing device 700 through the optical cable joint, it is determined that the geothermal well optical fiber temperature measurement system can work normally.

[0090] In this embodiment, the geothermal well is a special geothermal monitoring well, which includes a geothermal well wall 601, an optical fiber entry hole 602 provided at the wellhead, a reduced diameter step 603 located on the geothermal well wall 601, and a water intake section 604 located deep in the geothermal well. The overall shape of the geothermal well is approximately cylindrical. The optical fiber entry hole 602 is located at the center of the top of the geothermal well, and its size is adapted to the outer shape size of the weight column 100; the reduced diameter step 603 is formed when the drilling times and the bit size are changed during the drilling of the geothermal well; the water intake section 604 of the geothermal well refers to the hydraulic connection channel between the geothermal well and the heat reservoir layer, and the deep underground hot water enters the geothermal well from this part and rises to the side pressure height of the heat reservoir pressure.

[0091] Preferably, in this embodiment, the maximum width M of any cross-sectional shape of the weight column 100 of the temperature measurement optical fiber weight component along the axial direction, the width L of the reduced diameter step 603 of the geothermal well, and the minimum diameter N of the water intake section 604 of the geothermal well satisfy the relationship 2L < M < N. Referring to Figure 6The largest diameter part of the counterweight column 100 is located at the front section 101 of the counterweight. Any cross-section of the front section 101 along the axial direction is elliptical, and the maximum width of the cross-section is M / 2. The distance from the outer contour to the central axis is limited to M / 2 > L, so that the end of the front section 101 of the counterweight column 100 will not be directly blocked by the geothermal well diameter-changing step 603 when the counterweight column 100 is lowered. Even if the counterweight column 100 is blocked by the geothermal well diameter-changing step 603 when it swings, it will slide over the diameter-changing step 603 through the curved surface on the side. The maximum width M of any cross-section of the counterweight column 100 along the axial direction is smaller than the minimum diameter N of the geothermal well water inlet section 604, so as to ensure that the counterweight column 100 can be submerged in the geothermal well water inlet section 604 for temperature monitoring and will not be stuck in this section.

[0092] The rest of the structure is the same as in Example 1.

[0093] Example 3

[0094] Reference Figures 2-7 This is the third embodiment of the present invention. Unlike the previous embodiment, this embodiment provides a reversing assembly 400 and a traction assembly 500 located outside the geothermal well, solving the problem of easy impact and damage to the temperature-sensing optical fiber 300 during the lowering process. The traction assembly 500 enables the lifting and lowering of the temperature-sensing optical fiber 300 and the counterweight assembly, while the reversing assembly 400 ensures that the temperature-sensing optical fiber 300 can be stably lowered into the geothermal well.

[0095] Specifically, the reversing assembly 400 includes a pulley 401 installed above the wellhead. The temperature-sensing optical fiber 300 bypasses the pulley 401 and is redirected to enter the geothermal well. To ensure the propagation quality of the optical signal, the reversing bending radius of the cable is preferably no more than 20 cm. The pulley 401 is installed at the geothermal wellhead via a mounting bracket. During the extension and retraction process, the temperature-sensing optical fiber 300 drives the pulley 401 to rotate, which is a rolling connection method. This method results in less wear compared to the direct sliding between the optical fiber and the geothermal well in existing technologies. Since the temperature-sensing optical fiber 300 needs to be lowered vertically into the geothermal well, the reversing via the pulley 401 allows for easy pulling of the temperature-sensing optical fiber 300 in other directions on the ground, facilitating operation.

[0096] Furthermore, the traction component 500 is connected to the temperature-sensing optical fiber 300 outside the geothermal well for winding and unwinding the optical fiber 300. In this embodiment, the traction component 500 uses an existing winch, winding the optical fiber 300 around the ground winch within the bending radius of the optical fiber 300. The winch is fixed to the ground using expansion bolts and includes a traction part for winding and unwinding the temperature-sensing optical fiber 300 cable, and a braking part for preventing the winding and unwinding of the temperature-sensing optical fiber 300 cable. The traction part has a forward and reverse drive structure via a motor, thereby realizing the lifting and lowering of the temperature-sensing optical fiber 300. The braking part is an electric brake structure for precise control.

[0097] The reversing assembly 400 also includes a ground pulley 402 located outside the geothermal well. The temperature-sensing optical fiber 300, located between the traction assembly 500 and the top pulley 401, is tumblingly connected to the ground pulley 402. The number of ground pulleys 402 can be adjusted according to the distance between the winch and the top pulley 401 and the terrain. However, since multiple reversals are not conducive to light propagation, this embodiment sets up a set of ground pulleys 402. By setting up the cooperation between the ground pulleys 402 and the top pulley 401, the traction direction of the temperature-sensing optical fiber 300 can be further adjusted to facilitate operation, and the support for the middle section of the temperature-sensing optical fiber 300 cable can be increased, thereby improving the safety during traction.

[0098] Furthermore, the counterweight column 100 is made of a material resistant to the high temperatures of geothermal wells. The temperature range within a geothermal well varies considerably depending on geological conditions, depth, and intended use, requiring selection and configuration based on actual conditions. Additionally, the weight of the counterweight column 100 is greater than its buoyancy relative to the geothermal liquid, ensuring that the counterweight column 100 is submerged in the geothermal liquid within the inlet section 604 and subsequently submerges the connected temperature-sensing fiber optic cable 300, facilitating temperature monitoring. In this embodiment, the surface of the counterweight column 100 is made of stainless steel, which is resistant to the high temperatures of geothermal wells and the corrosive properties of the geothermal liquid.

[0099] The rest of the structure is the same as in Example 2.

[0100] Counterweight installation process: When installing the counterweight column 100, the counterweight column 100 is split along the axial section to expose the mounting groove 200 inside the counterweight column 100; after cleaning the impurities on the surface of the mounting groove 200, the temperature measuring fiber 300 is adaptively installed into the mounting groove 200, and the split counterweight column 100 is reassembled and aligned; the gap between the temperature measuring fiber 300 and the mounting groove 200 is adaptively filled with industrial sealant to achieve a seal; the split counterweight columns 100 are re-fixed with bolts; the front section 101 of the counterweight with a suitable shape and mass is connected and fixed to the middle section 103 to complete the assembly between the temperature measuring fiber 300 and the counterweight column 100.

[0101] Counterweight lowering process: Install counterweight column 100 on one end of temperature measuring fiber 300, and converge the end close to fiber temperature measuring processing device 700 to traction component 500. After temperature measuring fiber 300 passes around reversing component 400, lower counterweight column 100 from the center of geothermal well into geothermal well. Gradually lower counterweight column 100 to the bottom of geothermal well using traction component 500. Temperature can be sensed throughout the entire fiber optic section. In this embodiment, a monitoring interval of 0.5m is set and temperature monitoring is activated.

[0102] Example 4

[0103] Reference Figures 2-8This is the fourth embodiment of the present invention. Unlike the previous embodiment, this embodiment provides a constant temperature chamber 800 and a calibration section 301 located inside the constant temperature chamber 800, which can realize automatic calibration of fiber optic temperature measurement and avoid the limitation of long-term use after one-time calibration.

[0104] Specifically, the temperature-measuring optical fiber 300 has at least one calibration section 301 that is always located inside the constant temperature chamber 800. The constant temperature chamber 800 is equipped with a temperature control module 801, which has a bidirectional communication connection with the analysis and processing module 702. The constant temperature chamber 800 is existing technology and can be filled with heat media such as oil and water. The temperature control module 801 includes a microcontroller, a temperature sensor, and a thermoelectric cooler, achieving precise temperature regulation (±0.01℃). The thermoelectric cooler is a Peltier semiconductor with a response time of <5s. The microcontroller is controlled by a PID algorithm, and the data processor is an embedded ARM Cortex-A7+FPGA, supporting real-time signal demodulation (>100Hz per channel). It can control and measure the real-time temperature of the heat medium inside the constant temperature chamber 800 and transmit the temperature data to the analysis and processing module 702. The analysis and processing module 702 periodically drives the temperature control module 801 to adjust the temperature inside the constant temperature chamber 800 to the preset calibration point according to the set automatic calibration program. By acquiring the temperature measurement data of the optical fiber in the calibration section 301 at this time, and comparing it with the actual temperature inside the constant temperature chamber 800, the calibration parameters are automatically adjusted to achieve automatic calibration.

[0105] Furthermore, the calibration section 301 is located outside the geothermal well. It is more convenient to set up the constant temperature chamber 800 on the temperature measuring fiber 300 outside the geothermal well. Generally, the first section of the temperature measuring fiber 300 and the section before the temperature measuring fiber 300 enters the geothermal well can be selected as the calibration section 301. The first section is chosen because it is close to the fiber optic temperature measuring and processing device 700, which is convenient for operation. The section before entering the geothermal well is the farthest position outside the geothermal well from the fiber optic temperature measuring and processing device 700. Relatively speaking, the temperature data measured by the temperature measuring fiber 300 in the constant temperature chamber 800 will be closer to the actual error value inside the geothermal well.

[0106] The remaining structure is the same as in Example 3.

[0107] Example 5

[0108] Reference Figures 1-8 This is the fifth embodiment of the present invention. Unlike the previous embodiment, this embodiment provides a geothermal well fiber optic temperature measurement method, which is applied to the geothermal well fiber optic temperature measurement system in embodiment 4, and can realize the automatic calibration and adjustment of the temperature measuring fiber 300.

[0109] Specifically, the process includes the following steps: First, the head end of the temperature-sensing fiber optic cable 300 is connected to the fiber optic temperature processing device 700; then, signal detection and calibration of the temperature-sensing fiber optic cable 300 are performed before it enters the well to ensure that the temperature-sensing fiber optic cable 300 is working properly; then, the temperature-sensing fiber optic cable 300 with the counterweight column 100 at its end is lowered to the target depth position of the geothermal well using the traction component 500; during detection, signal detection is carried out periodically by the fiber optic temperature processing device 700 to collect temperature information at different depths within the geothermal deep well.

[0110] Furthermore, the calibration method includes: firstly, selecting at least one calibration segment 301 of the temperature-sensing optical fiber 300 and placing it inside the constant temperature chamber 800; then periodically driving the temperature control module 801 inside the constant temperature chamber 800 to adjust the temperature inside the constant temperature chamber 800 to a preset calibration point; then, obtaining the temperature measurement data of the temperature-sensing optical fiber 300 at this time through the analysis and processing module 702, comparing it with the actual temperature of the calibration segment 301 inside the constant temperature chamber 800, and automatically adjusting the calibration parameters. The temperature T at the temperature measurement point z after adjustment is given by Formula 1:

[0111]

[0112] Where R(T, z) is the ratio of the Stokes light intensity to the anti-Stokes light intensity at the temperature measurement point z, which can be measured by analyzing the Stokes light and anti-Stokes light signals in the optical signal received by the analysis and processing module 702. α is the fiber optic signal attenuation coefficient, K is the temperature sensitivity coefficient, and C is the temperature compensation value. Adjusting the fiber optic signal attenuation coefficient α is to flatten the entire curve. If it is too large, the curve will tilt upwards; if it is too small, the curve will tilt downwards. The typical value is around 0.1. Adjusting the temperature sensitivity coefficient K is to ensure that the fiber optic temperature difference measured by the fiber optic temperature measurement and processing device 700 matches the actual temperature difference measured by the thermometer. The typical value of K is around 560. The temperature compensation value C is to shift the entire curve upwards or downwards to match the actual temperature value. The typical value of C is 0.

[0113] In Formula 1 above: the fiber optic signal attenuation coefficient α is adjusted to keep the entire temperature measurement curve horizontal. During calibration, the fiber optic cable is placed in a constant temperature environment, and the fiber optic signal attenuation coefficient α is adjusted until the temperature measurement curve is horizontal. The fiber optic signal attenuation coefficient α is adjusted in the DTS host computer software of the fiber optic temperature measurement processing device 700 to keep the entire temperature curve completely horizontal. By comparing the actual temperature difference with the temperature difference detected by the temperature measurement system, the system's sensitivity to temperature changes is matched with the actual situation. The temperature compensation value C is adjusted to shift the entire curve up or down, so that the temperature measurement result is consistent with the actual temperature value.

[0114] During continuous measurement, calibration section 301 remains within the constant temperature chamber 800. Analysis and processing module 702 continuously receives the temperature values ​​measured by the optical fiber within calibration section 301 and compares them with the actual values ​​within the constant temperature chamber 800. When the difference between these two values ​​exceeds a preset range, analysis and processing module 702 recalibrates through the aforementioned calibration steps to achieve automatic calibration. This facilitates timely response to changes in performance or environmental parameters of the temperature-measuring optical fiber 300 during continuous use, ensuring the temperature measurement system maintains a high-precision measurement standard. By calibrating the data differences measured at different locations of calibration section 301 and within their respective constant temperature chambers 800, errors caused by localized, random data changes are reduced. Furthermore, the values ​​from multiple calibration sections 301 can be cross-referenced for calibration. This unified calibration achieves optimal results when the measured values ​​from different locations of calibration section 301 show the same magnitude of difference from the actual values, ensuring the overall temperature curve maintains a high level of accuracy.

[0115] During the automatic calibration process, when the measured values ​​of calibration segments 301 at different locations differ from the actual values, it is considered whether the location of calibration segment 301 is near the optical switch. The calibration method also includes compensating for the optical switch loss of the temperature measuring fiber 300. The method for calculating the optical switch loss coefficient Q is to measure the Stokes light intensity r1, r2 and the anti-Stokes light intensity R1, R2 before and after the optical switch.

[0116] Next, calculate the optical switching loss coefficient using the following formula:

[0117]

[0118] The new temperature calculation formula three is as follows:

[0119]

[0120] Where d(z) is the distance from position z to the optical switch.

[0121] In this embodiment, to verify the effectiveness of the improved Formula 3 for calculating optical switch loss, the following experiment was conducted: S1. Setting up the experimental environment: First, prepare DTS equipment, optical fiber, optical switch, optical power meter, temperature control device, etc. Then, place the optical fiber in a temperature control environment to ensure uniform temperature. Next, introduce the optical switch into the optical fiber and measure the optical signal intensity before and after the optical switch. S2. Calibration process: First, adjust the optical fiber signal attenuation coefficient α, temperature sensitivity coefficient K, and temperature compensation value C to make the temperature measurement curve consistent with the actual temperature. Then, calculate the optical switch loss coefficient k based on the measured optical signal intensity. S3. Temperature measurement verification: First, calculate the temperature at various points along the optical fiber under different temperature conditions using the improved calibration Formula 3. Then, compare the calculated temperature with the actual temperature to verify the accuracy and reliability of Formula 3.

[0122] Furthermore, regarding the detailed method for adjusting the fiber optic signal attenuation coefficient α and temperature sensitivity coefficient K in S2 above: S2.1. Adjusting the fiber optic signal attenuation coefficient α: Experimental preparation: Place the fiber optic cable in a temperature-stable environment, such as a constant-temperature water bath or oil bath, ensuring the fiber optic cable is long enough, typically at least 3 meters, to meet the calibrated spatial resolution requirements. Then connect the DTS device, ensuring the device is operating normally, and open the host computer software; Initial measurement: In the host computer software, view the initial temperature curve. This curve reflects the temperature distribution along the fiber optic cable. If the curve is generally sloping, it indicates that the fiber optic signal attenuation coefficient needs adjustment; Adjusting the fiber optic signal attenuation coefficient α: Locate the fiber optic signal attenuation coefficient setting option in the DTS host computer software. Increase or decrease the fiber optic signal attenuation coefficient according to the slope direction of the curve: If the curve slopes upward, appropriately decrease the fiber optic signal attenuation coefficient; if the curve slopes downward, appropriately increase the fiber optic signal attenuation coefficient. After each adjustment, wait for the temperature curve to stabilize and observe the changes in the curve; Verifying the adjustment effect: Repeat the above adjustment process until the temperature curve remains horizontal. At this point, the fiber optic signal attenuation coefficient adjustment is complete, indicating that the fiber optic cable's own attenuation characteristics have been compensated.

[0123] S2.2. Adjusting the Temperature Sensitivity Coefficient K: Experimental Preparation: Prepare a high-precision thermometer to measure the actual temperature. Place a section of optical fiber (at least 3 meters) in an environment with a known temperature, such as a constant-temperature water bath or oil bath. Measure the Actual Temperature Difference: Use the high-precision thermometer to measure the actual temperature of the environment where the optical fiber is located. Simultaneously, record the temperature of the optical fiber section measured by the DTS device and calculate the difference between the actual temperature and the DTS measured temperature. Adjust the Temperature Sensitivity Coefficient: Find the temperature sensitivity coefficient (K value) setting option in the DTS host computer software. Adjust the K value according to the relationship between the actual temperature difference and the measured temperature difference: If the temperature difference measured by DTS is greater than the actual temperature difference, it indicates that the optical fiber is too sensitive and the K value needs to be increased to reduce sensitivity. If the temperature difference measured by DTS is less than the actual temperature difference, it indicates that the optical fiber is not sensitive enough and the K value needs to be decreased to increase sensitivity. After each adjustment, wait for the temperature curve to stabilize and observe the changes in the curve. Verify the Adjustment Effect: Repeat the above adjustment process until the temperature difference measured by DTS matches the actual temperature difference. At this point, the temperature sensitivity coefficient K is adjusted, indicating that the sensitivity of the optical fiber to temperature changes has been calibrated.

[0124] Then, simply adjust the temperature compensation value C to ensure accurate temperature adjustment (for example, if the indoor temperature measured by DTS becomes 22℃ and the fiber optic temperature in the oil tank becomes 62℃, then simply set the C value to -2℃. This will shift the entire curve downwards by 2℃, making the room temperature 20℃ and the fiber optic temperature in the oil tank 60℃, consistent with the actual temperature).

[0125] Table 1 below shows a set of temperature measurement data, including the optical switch loss coefficient, obtained by the above experimental method.

[0126] Table 1

[0127]

[0128] In the above experiment, the actual temperature T0 within the constant temperature device at different locations z of the optical fiber was measured using a high-precision thermometer. The optical switching loss coefficient k was calculated before the experiment by measuring the optical signal intensity before and after the optical switch. The Stokes light intensity ratio R was obtained by collecting the Stokes light and anti-Stokes light intensity ratios at various points along the optical fiber using a DTS device. The optical fiber signal attenuation coefficient α, temperature sensitivity coefficient K, and temperature compensation value C were parameters adjusted and determined during the calibration process. The calculated temperature T was obtained by using the improved calibration formula three, combined with the above parameters, to calculate the temperature at various points along the optical fiber. The error ΔT represents the difference between the calculated temperature and the actual temperature, and is used to evaluate the accuracy and reliability of the calibration formula.

[0129] Experimental data shows that, under different fiber locations and actual temperature conditions, the temperature calculated using the improved calibration formula (Formula 3) is very close to the actual temperature with minimal error. For example, at 100m, the actual temperature is 60℃, and the calculated temperature is 60.0℃, with an error of 0℃; at 50m, the actual temperature is 50℃, and the calculated temperature is 50.1℃, with an error of only +0.1℃. These small errors demonstrate that the improved calibration formula, after compensating for optical switching losses, can accurately reflect temperature changes along the fiber, verifying the formula's accuracy and reliability.

[0130] In summary, the experimental data shows that the improved calibration formula three can effectively improve the temperature measurement accuracy of the distributed fiber optic temperature measurement system and can be reliably applied in actual temperature monitoring scenarios.

[0131] Example 6

[0132] Reference Figures 1-9 This is the sixth embodiment of the present invention. Unlike the previous embodiment, this embodiment provides at least two calibration segments 301 spaced apart, each located within an independent constant temperature chamber 800. Another factor contributing to the difference in measured values ​​between calibration segments 301 at different locations and their actual values ​​during automatic calibration is the varying distances between the calibration segments 301 and the tip of the temperature-measuring optical fiber 300. This causes interference to the optical signal in the geothermal environment as the propagation distance increases. This embodiment allows for recalibration of the end-point measurement data. The calibration method further includes: based on the actual temperatures T1 and T2 measured at any two calibration segments 301 (z1 and z2), and the optical fiber measurement value T... z1 T z2The data was corrected for the terminal temperature T3, and the signal strength ratios of the two were as follows:

[0133]

[0134] Next, calculate the difference in fiber optic signal attenuation coefficients along the path:

[0135]

[0136] Then, the initial temperature T measured at the end of the temperature-sensing fiber optic cable 300 was... z3 After correction, the fourth formula for terminal temperature compensation can be obtained:

[0137]

[0138] Z3 is the end position of the temperature measuring fiber optic cable 300.

[0139] Furthermore, to investigate the appropriate spacing between adjacent constant temperature chambers 800, the following experiment was conducted: The temperature of the first set of constant temperature chambers 800 was set to a fixed 25℃, while the temperature inside the other set of constant temperature chambers 800 was set to be variable. The actual end temperature temporarily measured below the temperature sensor was 75℃. The temperature measuring fiber optic cable 300 used in the experiment was of the high-temperature resistant OM4 type (attenuation @1550nm=2.5dB / km), and the noise level of the test environment was Gaussian white noise (σ=0.5dB). The experiment changed the spacing between the constant temperature chambers 800 and the temperature inside the variable constant temperature chambers 800. Ten sets of experimental data were measured, and the experimental data were compiled into Table 2 below.

[0140] Table 2

[0141]

[0142]

[0143] As shown in Table 2 above, when the spacing z2-z1 between the constant temperature chambers 800 is between 300 and 500 m, the signal-to-noise ratio (SNR) is greater than 20 dB, which meets the industrial accuracy requirements. Simultaneously, the end-compensation error is around 0.2℃, better than the 0.5℃ standard for deep well monitoring. When the spacing z2-z1 between the constant temperature chambers 800 is less than 300 m, the SNR drops sharply, and the end-compensation error amplifies to -1.7℃. Conversely, when the spacing z2-z1 between the constant temperature chambers 800 is greater than 500 m, overcompensation occurs due to the cumulative attenuation of the fiber optic signal, leading to a positive error. In summary, the optimal spacing between adjacent constant temperature chambers 800 is 300–500 m.

[0144] Example 7

[0145] Reference Figures 1-9This is the seventh embodiment of the present invention. Unlike embodiment 4, this embodiment provides an automatic water level sensor probe 900 located below the geothermal liquid surface 605. This can solve the problem of discrepancies between the data calibrated by the constant temperature chamber 800 outside the geothermal well and the actual data changes below the geothermal well. The temperature measuring fiber optic cable 300 near the automatic water level sensor probe 900 is used as the calibration section 301.

[0146] Specifically, since the geothermal fluid level 605 in the geothermal well fluctuates, an automatic water level sensor probe 900 is typically installed several tens of meters below the normally floating geothermal fluid level 605. Automatic water level sensors are existing technology; their principle is generally to detect the distance from the probe's current position to the geothermal fluid level 605 by measuring water pressure, thus determining the height of the geothermal fluid level 605. The automatic water level sensor probe 900 is lowered to a fixed position inside the well via a communication cable. The cable connects to a measuring head at the wellhead, which can read the water level, geothermal fluid level 605 depth, and temperature at the probe's location in real time. The temperature of the probe 900 below the water surface is different from that at the wellhead, and the temperature gradient below the geothermal fluid surface 605 is extremely small (<0.1℃ / m). The temperature fluctuation at the probe is ≤±0.3℃ / 24h (measured data), meaning that the temperature change at the probe location is relatively slow. At this time, the automatic water level probe 900, combined with the surrounding geothermal fluid, is equivalent to providing a constant temperature chamber 800 environment. Therefore, the temperature measuring fiber optic cable 300 at the automatic water level probe 900 can also obtain the measured value (measured by the calibration section 301 fiber optic cable at this location) and the actual value (directly measured by the automatic water level probe 900).

[0147] Here, the temperature at the location is obtained by the automatic water level probe 900, and the advantages of combining the surrounding geothermal fluid with the environment of the constant temperature box 800 are: (1) Compared with the constant temperature box 800 set outside the geothermal well, it can better represent the temperature change under the geothermal well. The distance from the automatic water level probe 900 as the "constant temperature box" to the geothermal fluid surface 605 is always accurate, and the real-time distance from the end of the optical fiber to the geothermal fluid surface 605 can also be confirmed. The accuracy of calibrating the temperature measurement data of the end of the optical fiber in the same geothermal environment is stronger; (2) Geothermal It is not convenient to set up a constant temperature chamber 800 downhole, but it is relatively simple to just lower the automatic water level probe 900 to the shallow layer with the cable; (3) Since the signal attenuation amplitude is small near the ground, the error caused by the change of the fiber optic signal attenuation coefficient α during the calibration of this part is small; (4) The automatic water level probe 900 is connected by a cable, and its height is adjustable. It can measure the height of the probe position from the geothermal liquid surface 605. The area below this position is in the geothermal liquid, and it is easy to confirm the changing trend of the fiber optic signal attenuation coefficient α, which helps to determine the end temperature data.

[0148] To investigate the suitable installation position of the automatic water level gauge probe 900, the following experiment was set up: First, the material of the temperature measuring fiber 300 was the same as in the previous experiment. By adjusting the installation distance D of the automatic water level gauge probe 900 relative to the geothermal liquid surface 605, the temperature gradient A, fiber signal attenuation coefficient α, light intensity ratio sensitivity B, and the relationship between the error E between the end-calculated calibration value and the actual value were measured, as shown in Table 3 below.

[0149] Table 3

[0150]

[0151] As shown in Table 3 above, the temperature gradient A increases with increasing depth, and a smaller temperature gradient A is more conducive to temperature stability; the fiber signal attenuation coefficient α intensifies with increasing depth, while the intensity-to-sensitivity ratio B shows a more sensitive state with increasing temperature. Considering the influence of these three parameters on end-point calibration, and configuring different weights, the comprehensive error E is calculated using the following formula:

[0152] E = w1·e -2A +w2·α+w3 / B

[0153] In this calculation, weights w1 = 0.4, w2 = 0.3, and w3 = 0.3, resulting in the neutral error values ​​shown in Table 3. Based on the comprehensive error E values ​​in the table, installing the automatic water level sensor probe 900 within a range of 65-90m below the geothermal fluid surface 605 minimizes the error, making it the preferred value. Since the geothermal fluid surface 605 fluctuates, the automatic water level sensor probe 900 can be installed approximately 75m below it, ensuring that the normal fluctuation range of the geothermal fluid surface 605 falls within the aforementioned preferred range. Furthermore, after confirming the installation position of the automatic water level sensor probe 900, the optimal distance between adjacent constant temperature chambers 800, obtained in the previous embodiment, can be used to determine the placement of the constant temperature chamber 800 above the geothermal fluid surface 605. This significantly improves accuracy and provides guidance for practical installation. Figure 9 The figure shows a schematic diagram of the temperature curve obtained through the above temperature measurement calibration scheme. The curve distribution trend is consistent with the actual situation, especially the phenomenon of abnormal downward bending at the end has disappeared.

[0154] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A temperature-sensing fiber optic counterweight assembly, characterized in that: include, The counterweight column (100) includes a front section (101) and a tail section (102) of the counterweight, which are distributed at both ends and coaxially arranged. The front section (101) of the counterweight is a spindle-shaped structure with a curved surface. The tail section (102) of the counterweight is connected to the temperature-measuring optical fiber (300) and is a tapered structure that gradually increases in size from the tail end to the front end of the counterweight column (100); and, The mounting slot (200) is axially positioned within the counterweight column (100) and is adapted to the shape of the temperature-sensing fiber optic cable (300). The mounting groove (200) and the temperature measuring optical fiber (300) form a sealed structure.

2. The temperature-sensing fiber optic counterweight assembly as described in claim 1, characterized in that: The counterweight tail section (102) is a split structure that can be separated along the axial cross section. The split structure comprises at least two parts. The mounting groove (200) is formed by assembling the various separate structural parts. The various parts of the structure are detachably connected.

3. The temperature-sensing fiber optic counterweight assembly as described in claim 1 or 2, characterized in that: The end of the front section (101) of the counterweight is an arc surface.

4. A geothermal well fiber optic temperature measurement system, comprising a temperature-measuring fiber optic counterweight assembly as described in any one of claims 1 to 3, characterized in that: The relationship between the maximum width M of any cross-sectional shape of the counterweight column (100) along the axial direction, the width L of the geothermal well variable diameter step (603), and the minimum diameter N of the geothermal well inlet section (604) satisfies: 2L <M<N。 5. The geothermal well fiber optic temperature measurement system as described in claim 4, characterized in that: It also includes, Temperature-sensing fiber optic cable (300); and, Fiber optic temperature measurement processing device (700), wherein the fiber optic temperature measurement processing device (700) is connected to the end of the temperature measuring fiber (300) away from the counterweight column (100); The fiber optic temperature measurement processing device (700) includes a laser emitting module (701) for sending laser signals to the temperature measuring fiber (300), and an analysis and processing module (702) for receiving the Raman scattered light signal carrying temperature information returned by the temperature measuring fiber (300).

6. The geothermal well fiber optic temperature measurement system as described in claim 5, characterized in that: It also includes a constant temperature chamber (800), wherein at least one calibration section (301) of the temperature measuring fiber (300) is always located inside the constant temperature chamber (800); The constant temperature chamber (800) is equipped with a temperature control module (801), and the temperature control module (801) is bidirectionally connected to the analysis and processing module (702).

7. The geothermal well fiber optic temperature measurement system as described in claim 6, characterized in that: The calibration section (301) is located above the geothermal liquid surface (605) and / or at the automatic water level sensor probe (900) below the geothermal liquid surface (605).

8. The geothermal well fiber optic temperature measurement system as described in claim 6 or 7, characterized in that: The interval between at least two calibration sections (301) is 300 to 500 meters.

9. The geothermal well fiber optic temperature measurement system as described in any one of claims 4 to 7, characterized in that: This also includes those located outside the geothermal well. A reversing assembly (400) includes a pulley (401) mounted above the wellhead, wherein the temperature-sensing optical fiber (300) bypasses the pulley (401) and extends into the geothermal well; and, A traction assembly (500) is connected to a temperature-sensing optical fiber (300) outside the geothermal well and is used to retract or release the temperature-sensing optical fiber (300).

10. A method for fiber optic temperature measurement of geothermal wells, applied to the fiber optic temperature measurement system of geothermal wells as described in any one of claims 4 to 9, characterized in that: Includes the following steps: Connect the first end of the temperature-measuring optical fiber (300) to the optical fiber temperature measurement and processing device (700); Before the temperature-sensing fiber (300) is inserted into the well, signal detection and calibration are performed to confirm that the temperature-sensing fiber (300) is working properly. The temperature-measuring fiber (300) with a counterweight column (100) at its end is lowered to the target depth position of the geothermal well by the traction assembly (500); The signal detection is carried out periodically by the fiber optic temperature measurement and processing device (700) to collect temperature information at different depths in the geothermal deep well.

11. The method for fiber optic temperature measurement of geothermal wells as described in claim 10, characterized in that: The calibration method includes: Select at least one calibration section (301) of the temperature measuring fiber (300) and place it in a constant temperature chamber (800); The temperature control module (801) inside the constant temperature chamber (800) is periodically driven to adjust the temperature inside the constant temperature chamber (800) to the preset calibration point; The temperature measurement data of the temperature measuring fiber (300) is obtained by the analysis and processing module (702) and compared with the actual temperature of the calibration section (301) in the constant temperature chamber (800) to automatically adjust the calibration parameters. The temperature T at the adjusted temperature measuring point z is: Where R(T,z) is the ratio of the Stokes light intensity to the anti-Stokes light intensity at the temperature measurement point, α is the fiber signal attenuation coefficient, K is the temperature sensitivity coefficient, and C is the temperature compensation value.

12. The geothermal well fiber optic temperature measurement method as described in claim 11, characterized in that: The calibration method also includes compensation for the optical switching loss of the temperature-sensing fiber (300), and the method for calculating the optical switching loss coefficient Q is as follows: Measure the Stokes light intensity r1, r2 and the anti-Stokes light intensity R1, R2 before and after the optical switch; Calculate the optical switching loss factor using the following formula: The new temperature calculation formula is as follows: Where d(z) is the distance from position z to the optical switch.

13. The geothermal well fiber optic temperature measurement method as described in claim 11 or 12, characterized in that: The calibration method further includes: Based on the actual temperatures T1 and T2 measured at any two calibration segments (301) of z1 and z2, and the fiber optic measurement value T z1 T z2 The data was corrected for the terminal temperature T3, and the signal strength ratios of the two were as follows: Next, calculate the difference in fiber optic signal attenuation coefficients along the path: Then the initial temperature T measured at the end of the temperature-sensing fiber (300) is... z3 After correction, the terminal temperature compensation formula can be obtained as follows: Z3 is the end position of the temperature measuring fiber (300).

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