A sapphire fiber optic sensor for downhole operations

Abstract

The application discloses a sapphire optical fiber sensor for downhole operation, which comprises a sapphire sensor (1), wherein the sapphire sensor (1) comprises a sapphire sensor unit (1-0) adopting a sapphire structure Fabry-Perot cavity structure, and the sapphire sensor unit (1-0) comprises a sapphire pressure-resistant diaphragm (1-0-1), a sapphire pressure-resistant cavity (1-0-2), a sapphire temperature-resistant diaphragm (1-0-3), a sapphire Perot cavity body (1-0-4), a collimator (1-0-5) and a high-temperature optical fiber (1-6) connected with the collimator; the sapphire pressure-resistant diaphragm and the sapphire temperature-resistant diaphragm are respectively welded on two ends of the sapphire pressure-resistant cavity through ceramic powder sintering on respective sides of the sapphire pressure-resistant diaphragm and the sapphire temperature-resistant diaphragm, so as to form a pressure sensing cavity (1-0-6); the other side of the sapphire temperature-resistant diaphragm is welded on one end of the sapphire Perot cavity body through ceramic powder sintering; and the collimator is fixed in an inner chamber of the sapphire Perot cavity body.

Description

Technical Field

[0001] This invention relates to the field of petroleum exploration technology, and more specifically to a sapphire fiber optic sensor for downhole operations. Background Technology

[0002] In the process of oil extraction, downhole temperature and pressure are essential measurement parameters. Accurate downhole temperature and pressure measurements play a crucial role in oil well monitoring. After an oil field is put into development, as the extraction time increases, the reservoir pressure continuously decreases, the underground crude oil undergoes significant degassing, its viscosity increases, and oil well production decreases considerably, sometimes even leading to shutdown. To compensate for the underground deficit caused by crude oil extraction, maintain or increase reservoir pressure, and achieve high and stable oil production, water / gas injection wells are used to inject water / gas into the reservoir to supplement and maintain reservoir pressure. However, these operations must be carried out only after a comprehensive understanding of the downhole conditions.

[0003] In other words, during the development of an oil field, people need to know detailed information about the properties and state of the fluid in the well during production or water injection. This requires the use of oil well logging, and its reliability and accuracy are of paramount importance.

[0004] Currently, downhole temperature and pressure monitoring systems primarily rely on capillary pressure measurement and electronic sensing technologies to measure these parameters. However, electronic sensors suffer from short lifespans, are prone to electrical sparking, and require annual surface calibration, limiting their application to routine and short-term logging operations. They are unsuitable for long-term monitoring of gas storage wells. Capillary pressure measurement, on the other hand, can only measure pressure, not temperature, which is its biggest drawback. Furthermore, capillary pressure measurement systems require continuous nitrogen replenishment during downhole operations to maintain a full nitrogen supply in the capillary, significantly increasing operation time and costs. Downhole temperature variations cause changes in nitrogen density within the capillary nitrogen tank and capillary, necessitating surface temperature correction to adjust nitrogen replenishment. This is often achieved through delayed surface temperature compensation and the use of thermocouples for temperature detection, a complex structure that hinders safe and stable operation. During installation, determining proper installation relies solely on back pressure observation, making it difficult to diagnose damage at depth.

[0005] Therefore, new equipment and technologies are needed to overcome the problems existing in the existing technology. Summary of the Invention

[0006] Studies have shown that fiber optic sensors have several advantages, such as insensitivity to electromagnetic interference and the ability to withstand extreme conditions, including high temperature, high pressure, and strong shocks and vibrations. They can measure wellbore and well site environmental parameters with high precision. Furthermore, fiber optic sensors have distributed measurement capabilities, allowing them to measure the spatial distribution of certain parameters and provide profile information. In addition, fiber optic sensors have a small cross-sectional area and short shape, requiring minimal space within the wellbore.

[0007] More specifically, sapphire fiber optic sensors have the characteristics of long lifespan, long sensing distance, high temperature resistance, multiple measurement points, good scalability, strong shock resistance, anti-interference, and low safety risks.

[0008] Sapphire fiber optic sensors have a significantly longer lifespan than electronic sensors. Typically, sapphire fiber optic temperature and pressure sensors can last 10-15 years, while electronic sensors only have an average lifespan of 1-3 years. Therefore, sensors often fail before the oil well is depleted, requiring replacement to continue obtaining temperature and pressure data. Removing old equipment and installing new equipment in oil and gas wells hundreds to thousands of meters deep is extremely labor-intensive and costly, impacting production and increasing the risk of accidents due to the increased number of operations. Combined with the cost of purchasing new equipment, sapphire fiber optic sensors are more economically viable than electronic sensors overall.

[0009] Sapphire sensors have a longer transmission distance than electronic sensors. Electronic sensors, due to significant signal attenuation in cables, typically have a maximum sensing distance of less than 5 km. For deep wells exceeding 5 km in depth, complex active devices must be installed for signal amplification to ensure signal quality. This limits the use of electronic sensors in deep wells, especially in the now widespread oil and gas wells. Because optical signals experience very little attenuation in fiber optic cables, optical sensors can achieve an effective sensing distance of up to 20 km, making them suitable for deep well sensing and significantly exceeding the application range of electronic sensors.

[0010] For electronic sensors, the operating temperature is generally limited to below 175℃ due to the constraints of their electronic components. This makes them unsuitable for long-term use in high-temperature oil and gas wells where temperatures exceed 175℃. Electronic sensors also have a higher failure rate under prolonged high-temperature conditions, making high temperature a bottleneck for them. Quartz sensors face the same issue. In contrast, sapphire fiber optic sensors utilize integrated temperature and pressure measurement sapphire Fabry-Perot cavity optics in their downhole portion. These devices exhibit excellent performance at high temperatures. Therefore, given the prevalence of high-temperature oil wells today, sapphire sensing devices can operate normally for extended periods under high-temperature conditions, significantly outperforming both electronic and quartz sensors, making them well-suited for high-temperature wells.

[0011] Electronic sensors typically have no more than 10 measurement points; otherwise, the system becomes complex and bulky, making installation difficult. Ordinary single-point electronic temperature and pressure sensors require four copper wires for signal transmission; while sapphire fiber optic sensors similarly require only a single-mode fiber to transmit temperature and pressure signals. Furthermore, fiber optic cables can serve as a scalable technology platform, simultaneously performing single-point temperature and pressure measurements, distributed temperature measurement, multi-directional flow measurement, and distributed acoustic wave measurement, achieving multi-purpose functionality and increasing design flexibility.

[0012] Sapphire sensors have smaller sensor heads, resulting in less impact during vibration and superior shock resistance. Electronic sensors, on the other hand, contain numerous electronic components, and their core parts are significantly larger and heavier than sapphire sensors. These components are subjected to greater impact during vibration and shock, making fiber optic sensors superior in shock resistance. Since vibration is unavoidable during sensor transportation, installation, and underground use, it is also an important indicator of sensor performance.

[0013] Electronic sensors, due to their use of electronic components and circuitry, are susceptible to electromagnetic interference. Sapphire sensors, however, are completely unaffected by electromagnetic interference. Furthermore, electronic sensors operating in flammable and explosive environments underground are actively powered devices. While measures such as increased protection levels and safer circuit designs can be implemented, the possibility of electrical arcing due to equipment failure still exists. In contrast, all active components of a sapphire sensor are located in the equipment room at the wellhead, completely eliminating the risk of electrical arcing.

[0014] According to one aspect of the present invention, a sapphire fiber optic sensor for downhole operations is provided, comprising a sapphire sensor (1), wherein the sapphire sensor (1) includes a sapphire sensor unit (1-0), the sapphire sensor unit (1-0) being constructed of sapphire to form a Fabry-Perot cavity structure, including a sapphire pressure-resistant diaphragm (1-0-1), a sapphire pressure-resistant cavity (1-0-2), a sapphire heat-resistant diaphragm (1-0-3), a sapphire Paro cavity body (1-0-4), a collimator (1-0-5), and a high-temperature optical fiber (1-6) connected to the collimator (1-0-5).

[0015] Among them, the sapphire pressure-resistant diaphragm (1-0-1) and the sapphire heat-resistant diaphragm (1-0-3) are respectively sintered and welded to both ends of the sapphire pressure-resistant cavity (1-0-2) by ceramic powder, thereby forming the pressure-sensitive cavity (1-0-6). One end of the sapphire Paro cavity body (1-0-4) is sintered and welded to the sapphire heat-resistant diaphragm (1-0-3) by ceramic powder. Thus, the sapphire heat-resistant diaphragm (1-0-3) is set between the sapphire Paro cavity body (1-0-4) and the sapphire pressure-resistant cavity (1-0-2). The collimator (1-0-5) is fixed in the internal cavity of the sapphire Paro cavity body (1-0-4).

[0016] According to an embodiment of the present invention, the sapphire sensor (1) further includes a sapphire sensor body (1-2), the sapphire sensor body (1-2) includes an outlet end and a pressure inlet end, the sapphire sensor unit (1-0) is disposed in the inner cavity of the sapphire sensor body (1-2), the sapphire pressure-resistant diaphragm (1-0-1) faces the pressure inlet end, and the sapphire Paro cavity body (1-0-4) is sealed and fixed in the inner cavity on the side of the outlet end.

[0017] According to an embodiment of the present invention, the sapphire sensor (1) further includes a sensor pressure inlet (1-1) connected to the pressure inlet end of the sapphire sensor body (1-2).

[0018] According to an embodiment of the present invention, the sapphire sensor (1) further includes a connector, a high-temperature optical fiber (1-6) passes through the outlet end and through the connector, the connector includes a connecting shaft (1-5), two sensor connecting studs (1-4) and two limiting rings (1-3), the two sensor connecting studs (1-4) are respectively sleeved on both sides of the connecting shaft (1-5) and the thread directions of the two sensor connecting studs are respectively facing both sides, the two ends of the connecting shaft (1-5) are threaded to the two limiting rings (1-3), and one end of the connector is sealed to the outlet end of the sapphire sensor body (1-2) through the threaded connection of a sensor connecting stud (1-4).

[0019] According to an embodiment of the present invention, the sapphire fiber optic sensor for downhole operations further includes a sensor protector (2), which is hermetically connected to the other end of the connector, so that the splice point (5-2) where the high-temperature fiber (1-6) and the fiber (5-1) in the armored cable (5) passing through the sensor protector (2) are fused together can be protected within the sensor protector (2).

[0020] According to an embodiment of the present invention, the sensor protector (2) includes a sensor solder joint protector front connector (2-1) that is hermetically connected to the other end of the connector, a sensor solder joint protector intermediate tube (2-2), and a sealing connection assembly.

[0021] Among them, the front end connector (2-1) of the sensor solder joint protector is connected to one end of the middle tube (2-2) of the sensor solder joint protector by sealing welding, and the sealing connection assembly is sealed to the other end of the middle tube (2-2) of the sensor solder joint protector. The fusion point (5-1) is located in the middle tube (2-2) of the sensor solder joint protector.

[0022] The sealing connection assembly includes the tail end of the splice point protector (2-3), the tail end sealing stud (2-7), the tail end connector (2-11), and the tail end clamping stud (2-12).

[0023] The right end of the protector tail end (2-3) is sealed and welded to the left end of the middle tube (2-2) of the sensor solder joint protector; and the right end of the connecting inner cavity of the protector tail end (2-3) has a conical surface.

[0024] The outer periphery of the tail-end sealing stud (2-7) is formed with a first shoulder, a first annular groove, and a second shoulder from right to left. The first sealing ring (2-6), the first semi-circular spacer (2-8), and the second sealing ring (2-10) are respectively installed on the first shoulder, the first annular groove, and the second tail shoulder. A first wire retaining ring (2-9) is installed in the middle of the outer surface of the first semi-circular spacer (2-8). A first flange retaining sleeve (2-5) is provided at the right end of the tail-end sealing stud (2-7). A first metal cone sealing assembly (2-4) is provided between the first flange retaining sleeve (2-5) and the conical surface of the tail end (2-3) of the protector. Thus, the connecting inner cavity of the tail end (2-3) of the protector is connected to the tail-end sealing stud (2-7) through a threaded seal.

[0025] The outer periphery of the tail connector (2-11) is formed with a second annular groove and a third shoulder from right to left. The second semicircular spacer (2-13) and the third sealing ring (2-14) are respectively installed on the second annular groove and the third shoulder. A second wire retaining ring (2-15) is installed in the middle of the outer surface of the second semicircular spacer (2-13). A second metal cone sealing assembly (2-16) is provided between the right end of the tail connector (2-11) and the tapered surface formed by the right end of the connecting inner cavity of the tail sealing stud (2-7). Thus, the connecting inner cavity of the tail sealing stud (2-7) is connected to the tail connector (2-11) through a threaded seal.

[0026] The right end of the connecting cavity of the tail end connector (2-11) is formed with a conical surface, and the third metal cone sealing assembly (2-17) is disposed between the conical surface and the right end of the tail end clamping stud (2-12), thereby the connecting cavity of the tail end connector (2-11) is connected to the tail end clamping stud (2-12) in a threaded seal.

[0027] According to an embodiment of the present invention, the sapphire fiber optic sensor for downhole operations further includes a sensor sleeve (3) configured to encapsulate the sensor protector (2) and the sapphire sensor (1).

[0028] According to an embodiment of the present invention, the tail end (2-3) of the protector further includes a first detection hole (2-18) formed on the side wall for detecting the sealing performance between the tail end sealing stud (2-7) and the tail end (2-3) of the protector.

[0029] According to an embodiment of the present invention, the tail end sealing stud (2-7) further includes a second detection hole (2-19) formed on the side wall for detecting the sealing performance between the tail end sealing stud (2-7) and the tail end connector (2-11).

[0030] According to an embodiment of the present invention, the sapphire fiber optic sensor for downhole operations further includes a demodulator connected to the armored optical cable (5). Attached Figure Description

[0031] The following description will detail some specific embodiments of the invention by way of example and not limitation, with reference to the accompanying drawings. The same reference numerals in the drawings denote the same or similar parts or portions. Those skilled in the art will understand that these drawings are not necessarily drawn to scale. The objectives and features of the invention will become more apparent from the following description taken in conjunction with the accompanying drawings, in which:

[0032] Figure 1 This is a schematic diagram of the structure of a sapphire sensor unit for a sapphire fiber optic sensor for downhole operations according to an embodiment of the present invention.

[0033] Figure 2 This is a cross-sectional schematic diagram of a portion of the structure of a sapphire fiber optic sensor for downhole operations according to an embodiment of the present invention.

[0034] Figure 3 This is a cross-sectional schematic diagram of another part of the structure of a sapphire fiber optic sensor for downhole operations according to an embodiment of the present invention.

[0035] Figure 4 A schematic cross-sectional view of a sapphire fiber optic sensor with a sensor tube according to an embodiment of the present invention;

[0036] Figure 5 A diagram illustrating the pressure change displayed by a digital pressure gauge when monitoring pressure using a sapphire fiber optic sensor according to an embodiment of the present invention;

[0037] Figure 6 To and Figure 5 The diagram shows the result of the cavity length change corresponding to the pressure change.

[0038] Figure 7 A calibration curve of pressure versus cavity length for a sapphire fiber optic sensor according to an embodiment of the present invention; and

[0039] Figure 8 This is a calibration curve of the temperature versus the thickness of the sapphire heat-resistant diaphragm of the sapphire fiber optic sensor according to an embodiment of the present invention. Detailed Implementation

[0040] The present invention can be better understood from the accompanying drawings and the following embodiments. However, those skilled in the art will readily understand that the descriptions in the embodiments are for illustrative purposes only and should not, and will not, limit the scope of the invention.

[0041] Figure 4 This is a schematic cross-sectional view of a sapphire fiber optic sensor with a sensor tube according to an embodiment of the present invention. (Reference) Figure 4 The sapphire fiber optic sensor of the implementation scheme may include a sapphire sensor (1), a sensor protector (2), a sensor tube (3), and an armored optical cable (5). The sapphire sensor (1) and the armored optical cable (5) are securely and safely connected by the sensor protector (2). The sapphire sensor (1) and the sensor protector (2) are both placed in the sensor tube (3), and the sensor tube (3) is fixed to the pipeline, thereby providing further protection for the sensor through the sensor tube (3). The tube itself is not sealed and does not hinder the sapphire sensor (1) from measuring environmental parameters.

[0042] Figure 1 This is a schematic diagram of the sapphire sensor unit of a sapphire fiber optic sensor for downhole operations according to an embodiment of the present invention. (Reference) Figure 1The sapphire sensor (1) of the implementation scheme includes a sapphire sensor unit 1-0, wherein the sapphire sensor unit 1-0 may include a sapphire pressure-resistant diaphragm (1-0-1), a sapphire pressure-resistant cavity (1-0-2), a sapphire heat-resistant diaphragm (1-0-3), a sapphire Paro cavity body (1-0-4), a collimator (1-0-5), and a high-temperature optical fiber (1-6) connected to the collimator (1-0-5); wherein, one side of the sapphire pressure-resistant diaphragm (1-0-1) and the sapphire heat-resistant diaphragm (1-0-3) are respectively welded to both ends of the sapphire pressure-resistant cavity (1-0-2) by ceramic powder sintering, thereby forming a pressure-sensitive cavity (1-0-6). The other side of the sapphire heat-resistant diaphragm (1-0-3) is sintered and welded to one end of the sapphire Paro cavity body (1-0-4) via ceramic powder, and the collimator (1-0-5) is fixed in the internal chamber of the sapphire Paro cavity body (1-0-4). Thus, the sapphire sensor unit (1-0) with a Fabry-Perot cavity structure is formed using sapphire.

[0043] As shown in the figure, external pressure (P0) applies pressure to the sapphire sensor unit (1-0), causing a change in the cavity length (L0) of the pressure-sensing cavity (1-0-6). The greater the external pressure (P0), the shorter the cavity length (L0); the smaller the external pressure (P0), the longer the cavity length (L0). Through calibration, a correspondence between external pressure (P0) and cavity length (L0) can be established.

[0044] During use, by accurately detecting the cavity length (L0), the external pressure (P0) can be determined through the calibration curve. Figure 5 Figure 6 shows the pressure changes displayed by the digital pressure gauge according to the implementation scheme, and Figure 6 shows the corresponding cavity length changes according to the implementation scheme. Figure 5 and 6 As shown, when the external pressure increases, the length (L0) of the pressure-sensing cavity (1-0-6) decreases; when the external pressure decreases, the length (L0) of the pressure-sensing cavity (1-0-6) increases. Therefore, there is an inverse relationship between the magnitude of the external pressure P and the cavity length d of the Fabry-Perot cavity. The calibration curve of the pressure sensor can be obtained through calibration, as shown in the figure. Figure 7 As shown, this demonstrates the good linearity and accuracy of the pressure sensor of the present invention.

[0045] Furthermore, the ambient temperature causes changes in the thickness (H0) of the sapphire heat-resistant film (1-0-3). Higher temperatures result in greater thickness, while lower temperatures result in less thickness. Calibration establishes a correlation between temperature and film thickness (H0). During use, the film thickness (H0) is precisely measured, for example, by calculating the phase difference between the sine waves of the reflected light from the first surface of the sapphire heat-resistant film (1-0-3) and the reflected light from the second surface. The temperature can then be determined using a calibration curve. Figure 8 The calibration curves of the temperature versus the thickness of the sapphire heat-resistant diaphragm for the sapphire fiber optic sensor according to the embodiments of the present invention show that the temperature sensor of the present invention has good linearity and accuracy.

[0046] Figure 2 This is a cross-sectional schematic diagram of a portion of the structure of a sapphire fiber optic sensor for downhole operations according to an embodiment of the present invention. (Reference) Figure 2 The sapphire sensor (1) further includes a sapphire sensor body (1-2) and a sensor pressure inlet component (1-1) and a connector respectively connected to the pressure inlet and outlet ends of the sapphire sensor body (1-2). The sapphire sensor body (1-2) is a cylinder with an inner cavity, including an outlet end and a pressure inlet end (in the attached figure, the right side is the pressure inlet end and the left side is the outlet end). The sapphire sensor unit (1-0) is disposed in the inner cavity of the sapphire sensor body (1-2), the sapphire pressure-resistant diaphragm (1-0-1) faces the pressure inlet end, and the sapphire Paro cavity body (1-0-4) is sealed and fixed in the inner cavity on the outlet end side. For example, a high-temperature resistant adhesive such as epoxy adhesive can be used to seal and bond the sapphire Paro cavity body (1-0-4) in the inner cavity of the sapphire sensor body (1-2) near the outlet end, thereby sealingly separating the sapphire Paro cavity body (1-0-4) from the pressure inlet and outlet ends of the sapphire sensor body (1-2).

[0047] As shown in the figure, the sensor pressure inlet (1-1) is connected to the pressure inlet end of the sapphire sensor body (1-2). A passage is formed in the sensor pressure inlet (1-1) to guide fluid from the external environment into the sapphire sensor body (1-2). For example, the connecting end of the sensor pressure inlet (1-1) has a protrusion, while the pressure inlet end has a recess. The protrusion and the recess can be joined together by thread or by welding.

[0048] refer to Figure 2The outlet end of the sapphire sensor body (1-2) is connected to the connector. The high-temperature optical fiber (1-6) of the sapphire sensor unit (1-0) passes through the outlet end and through the connector. The connector includes a connecting shaft (1-5), two sensor connecting studs (1-4), and two limiting rings (1-3). The two sensor connecting studs (1-4) are respectively fitted on both sides of the connecting shaft (1-5), and threads are formed on the outer surfaces of the two sensor connecting studs, with the thread directions facing both sides. The two ends of the connecting shaft (1-5) are connected to the two limiting rings (1-3) through threads. One end of the connector is connected to the thread on the inner surface of the outlet end of the sapphire sensor body (1-2) through the thread of one sensor connecting stud (1-4), thereby connecting to the outlet end of the sapphire sensor body (1-2). More specifically, the outlet end of the sapphire sensor body (1-2) is formed with a concave conical surface, while the connecting shaft (1-5) is formed with a corresponding convex conical surface. The two components are in close contact under the action of the sensor connecting stud (1-4), thereby achieving a seal.

[0049] See Figure 2 and 3 The sapphire fiber optic sensor for downhole operations according to the implementation scheme may further include a sensor protector (2), which includes a sensor solder joint protector front connector (2-1), a sensor solder joint protector intermediate tube (2-2), and a sealing connection assembly. One end of the sensor solder joint protector front connector (2-1) is sealed to the other end of the connector, and the connection method can be the same as the connection method between the connector and the sapphire sensor body (1-2), so it will not be described in detail. The other end of the sensor solder joint protector front connector (2-1) is sealed to the sensor solder joint protector intermediate tube (2-2), for example, by welding. Thus, the high-temperature optical fiber (1-6) can pass through the connector and the sensor solder joint protector front connector (2-1) in a sealed manner and enter the sensor solder joint protector intermediate tube (2-2).

[0050] like Figure 3 As shown, the sealed connection assembly is sealed to the other end of the intermediate tube (2-2) of the sensor solder joint protector. The armored optical cable (5) passes through the sealed connection assembly and enters the intermediate protection tube (2-2). Thus, the optical fiber (5-1) and the high-temperature optical fiber (1-6) are fused together in the intermediate tube (2-2) of the sensor solder joint protector and are protected.

[0051] refer to Figure 3The sealing connection assembly of the implementation scheme may include a tail end of the splice point protector (2-3), a tail end sealing stud (2-7), a tail end connector (2-11), and a tail end clamping stud (2-12); the right end of the protector tail end (2-3) is sealed and welded to the left end of the sensor solder joint protector intermediate tube (2-2); and the right end of the connecting inner cavity of the protector tail end (2-3) has a conical surface.

[0052] More specifically, the right end of the protector tail end (2-3) has a protruding structure, and the left end of the sensor solder joint protector intermediate tube (2-2) has a matching recessed structure. The two fit together, and the right end of the protector tail end (2-3) can be welded to the left end of the sensor solder joint protector intermediate tube (2-2) for a sealed fit. A connecting cavity is formed in the protector tail end (2-3), with its inner diameter gradually decreasing from left to right. A thread for the tail end sealing stud (2-7) for connection is formed in the connecting cavity, and a tapered surface is formed at the right end of the connecting cavity.

[0053] The outer periphery of the tail-end sealing stud (2-7) is threaded to mate with the threaded inner cavity of the protector tail end (2-3), and the outer periphery also has a first shoulder, a first annular groove, and a second shoulder formed sequentially from right to left; the first sealing ring (2-6), the first semi-circular spacer (2-8), and the second sealing ring (2-10) are respectively installed on the first shoulder, the first annular groove, and the second tail shoulder, and the first semi-circular spacer (2-8) is adjacent to the second sealing ring (2-10); a first wire retaining ring (2-9) is installed in the middle of the outer surface of the first semi-circular spacer (2-8); a first flange retaining sleeve (2-5) is provided at the right end of the tail-end sealing stud (2-7). A first metal cone sealing assembly (2-4) is provided between the tapered surface of the protector tail end (2-3) and the tapered surface of the protector tail end (2-3), thereby connecting the tail end sealing stud (2-7) to the connecting inner cavity of the protector tail end (2-3) through a threaded seal; in addition, a connecting inner cavity is formed in the tail end sealing stud (2-7), the inner diameter of the connecting inner cavity gradually decreases from left to right, a thread for connecting the tail end connector (2-11) is formed in the connecting inner cavity, and a tapered surface is formed at the right end of the connecting inner cavity.

[0054] The outer periphery of the tail-end connector (2-11) is formed with threads that mate with the threads in the inner cavity of the tail-end sealing stud (2-7). A second annular groove and a third shoulder are formed sequentially from right to left on the outer periphery. A second semi-circular spacer (2-13) and a third sealing ring (2-14) are respectively installed on the second annular groove and the third shoulder, with the second semi-circular spacer (2-13) adjacent to the third sealing ring (2-14). A second wire retainer (2-15) is installed in the middle of the outer surface of the second semi-circular spacer (2-13). A second metal cone sealing assembly (2-16) is provided between the right end of the tail-end connector (2-11) and the conical surface formed by the right end of the inner cavity of the tail-end sealing stud (2-7). Thus, the inner cavity of the tail-end sealing stud (2-7) is threadedly and securely connected to the tail-end connector (2-11).

[0055] The tail connector (2-11) has a connecting cavity, and the connecting cavity has a thread for connecting the tail clamping stud (2-12). The right end of the connecting cavity has a conical surface. The third metal cone sealing assembly (2-17) is disposed between the conical surface and the right end of the tail clamping stud (2-12). The outer periphery of the tail clamping stud (2-12) has a thread that mates with the thread in the connecting cavity of the tail connector (2-11). Thus, the connecting cavity of the tail connector (2-11) is connected to the tail clamping stud (2-12) in a threaded seal.

[0056] like Figure 3 As shown, the positions where the mating threads are formed on the inner or outer walls of the tail end (2-3), tail end sealing stud (2-7), tail end connector (2-11), and tail end clamping stud (2-12) of the protector can be as shown by the dashed circles in the figure.

[0057] In addition, to test the sealing performance between various components, a first test hole (2-18) can be formed on the side wall of the tail end (2-3) of the protector to test the sealing performance between the tail end sealing stud (2-7) and the tail end (2-3) of the protector. Examples include the sealing effect of the first metal cone sealing assembly (2-4), the first flanged sleeve (2-5), and the first sealing ring (2-6); the first semi-circular spacer (2-8), the first wire retaining ring (2-9); and the sealing effect of the second sealing ring (2-10). A second test hole (2-19) can also be formed on the side wall of the tail end sealing stud (2-7) to test the sealing performance between the tail end sealing stud (2-7) and the tail end connector (2-11). Examples include the sealing effect of the second metal cone sealing assembly (2-16), the second semi-circular spacer (2-13), the third sealing ring (2-14), and the second wire retaining ring (2-15).

[0058] All of the above components are made of high temperature and high pressure resistant materials. For example, the intermediate tube (2-2), the tail end (2-3), the tail end sealing stud (2-7), the tail end connector (2-11), and the tail end clamping stud (2-12) of the sensor solder joint protector can be made of stainless steel. The sealing components in the middle can also be made of metal or other materials such as carbon materials.

[0059] In addition, the sapphire fiber optic sensor for downhole operations in the implementation scheme also includes a demodulator connected to the armored optical cable (5) for signal transmission, reception and analysis.

[0060] Specific implementation methods have been provided above, but the present invention is not limited to the implementation methods described above. The basic idea of ​​the present invention lies in the above basic scheme. For those skilled in the art, designing various modified models, formulas, and parameters based on the teachings of the present invention does not require creative effort. Changes, modifications, substitutions, and variations made to the implementation methods without departing from the principles and spirit of the present invention still fall within the protection scope of the present invention.

Claims

1. A sapphire fiber optic sensor for downhole operations, characterized in that: The system includes a sapphire sensor (1), which comprises a sapphire sensor unit (1-0). The sapphire sensor unit (1-0) is constructed of sapphire to form a Fabry-Perot cavity structure, including a sapphire pressure-resistant diaphragm (1-0-1), a sapphire pressure-resistant cavity (1-0-2), a sapphire heat-resistant diaphragm (1-0-3), a sapphire Paro cavity body (1-0-4), a collimator (1-0-5), and a high-temperature optical fiber (1-6) connected to the collimator (1-0-5). Among them, the sapphire pressure-resistant diaphragm (1-0-1) and the sapphire heat-resistant diaphragm (1-0-3) are respectively sintered and welded to both ends of the sapphire pressure-resistant cavity (1-0-2) by ceramic powder, thereby forming the pressure-sensitive cavity (1-0-6). One end of the sapphire Paro cavity body (1-0-4) is sintered and welded to the sapphire heat-resistant diaphragm (1-0-3) by ceramic powder, thereby the sapphire heat-resistant diaphragm (1-0-3) is set between the sapphire Paro cavity body (1-0-4) and the sapphire pressure-resistant cavity (1-0-2); the collimator (1-0-5) is fixed in the internal cavity of the sapphire Paro cavity body (1-0-4); The sapphire sensor (1) further includes a sapphire sensor body (1-2), which includes an outlet end and a pressure inlet end. The sapphire sensor unit (1-0) is disposed in the inner cavity of the sapphire sensor body (1-2), the sapphire pressure-resistant diaphragm (1-0-1) faces the pressure inlet end, and the sapphire Paro cavity body (1-0-4) is sealed and fixed in the inner cavity on the side of the outlet end. The sapphire sensor (1) also includes a sensor pressure inlet component (1-1) connected to the pressure inlet end of the sapphire sensor body (1-2). The sapphire sensor (1) further includes a connector. A high-temperature optical fiber (1-6) passes through the outlet end and through the connector. The connector includes a connecting shaft (1-5), two sensor connecting studs (1-4), and two limiting rings (1-3). The two sensor connecting studs (1-4) are respectively fitted on both sides of the connecting shaft (1-5), and the thread directions of the two sensor connecting studs are respectively facing both sides. The two ends of the connecting shaft (1-5) are connected to the two limiting rings (1-3) by threads. One end of the connector is sealed to the outlet end of the sapphire sensor body (1-2) by a threaded connection of a sensor connecting stud (1-4).

2. The sapphire fiber optic sensor for downhole operations according to claim 1, characterized in that, It also includes a sensor protector (2), which is hermetically connected to the other end of the connector, so that the splice point (5-2) where the high-temperature optical fiber (1-6) and the optical fiber (5-1) in the armored optical cable (5) passing through the sensor protector (2) are located in the sensor protector (2) and protected.

3. The sapphire fiber optic sensor for downhole operations according to claim 2, characterized in that, The sensor protector (2) includes a sensor solder joint protector front connector (2-1) that is sealed to the other end of the connector, a sensor solder joint protector intermediate tube (2-2), and a sealing connection assembly. Among them, the front end connector (2-1) of the sensor solder joint protector is connected to one end of the intermediate tube (2-2) of the sensor solder joint protector by sealing welding, and the sealing connection assembly is sealed to the other end of the intermediate tube (2-2) of the sensor solder joint protector. The fusion point (5-1) is located in the intermediate tube (2-2) of the sensor solder joint protector. The sealing connection assembly includes the tail end of the splice point protector (2-3), the tail end sealing stud (2-7), the tail end connector (2-11), and the tail end clamping stud (2-12). The right end of the protector tail end (2-3) is sealed and welded to the left end of the sensor solder joint protector intermediate tube (2-2); and the right end of the connecting inner cavity of the protector tail end (2-3) has a conical surface. The outer periphery of the tail-end sealing stud (2-7) is formed with a first shoulder, a first annular groove, and a second shoulder from right to left. The first sealing ring (2-6), the first semi-circular spacer (2-8), and the second sealing ring (2-10) are respectively installed on the first shoulder, the first annular groove, and the second tail shoulder. A first wire retaining ring (2-9) is installed in the middle of the outer surface of the first semi-circular spacer (2-8). A first flange retaining sleeve (2-5) is provided at the right end of the tail-end sealing stud (2-7). A first metal cone sealing assembly (2-4) is provided between the first flange retaining sleeve (2-5) and the conical surface of the tail end (2-3) of the protector. Thus, the connecting inner cavity of the tail end (2-3) of the protector is connected to the tail-end sealing stud (2-7) through a threaded seal. The outer periphery of the tail connector (2-11) is formed with a second annular groove and a third shoulder from right to left. The second semicircular spacer (2-13) and the third sealing ring (2-14) are respectively installed on the second annular groove and the third shoulder. A second wire retaining ring (2-15) is installed in the middle of the outer surface of the second semicircular spacer (2-13). A second metal cone sealing assembly (2-16) is provided between the right end of the tail connector (2-11) and the tapered surface formed by the right end of the connecting inner cavity of the tail sealing stud (2-7). Thus, the connecting inner cavity of the tail sealing stud (2-7) is connected to the tail connector (2-11) in a threaded seal. The right end of the connecting cavity of the tail connector (2-11) is formed with a conical surface, and the third metal cone sealing assembly (2-17) is disposed between the conical surface and the right end of the tail clamping stud (2-12), thereby the connecting cavity of the tail connector (2-11) is connected to the tail clamping stud (2-12) in a threaded seal.

4. The sapphire fiber optic sensor for downhole operations according to claim 2, characterized in that, It also includes a sensor tube (3) configured to encapsulate the sensor protector (2) and the sapphire sensor (1).

5. The sapphire fiber optic sensor for downhole operations according to claim 3, characterized in that, The tail end (2-3) of the protector also includes a first detection hole (2-18) formed on the side wall for detecting the sealing performance between the tail end sealing stud (2-7) and the tail end (2-3) of the protector.

6. The sapphire fiber optic sensor for downhole operations according to claim 3, characterized in that, The tail end sealing stud (2-7) also includes a second detection hole (2-19) formed on the side wall for detecting the sealing performance between the tail end sealing stud (2-7) and the tail end connector (2-11).

7. The sapphire fiber optic sensor for downhole operations according to claim 2, characterized in that, It also includes a demodulator connected to the armored optical cable (5).

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