High-temperature optical fiber pressure permanent testing system for offshore oilfield heavy oil thermal production well

Abstract

The invention discloses an offshore oilfield heavy oil thermal production well high-temperature optical fiber pressure permanent test system which comprises a high-temperature all-silica optical fiber pressure sensor arranged underground and a ground pressure demodulator arranged above the well, and the high-temperature all-silica optical fiber pressure sensor is connected with the ground pressure demodulator through a monitoring optical cable; the high-temperature all-silica optical fiber pressure sensor comprises a sealing shell, a pressure measuring chip arranged in the sealing shell, a single-mode optical fiber, a temperature compensation mechanism and an optical fiber leading-out mechanism. One end of the single-mode fiber is connected with the pressure measuring chip, and the other end extends out of the sealing shell; the temperature compensation mechanism is arranged on the single-mode fiber; and the optical fiber leading-out mechanism is arranged in the leading-out part of the sealing shell. According to the all-quartz optical fiber FP pressure sensor, all the pressure sensing chips adopt all-quartz structures, laser welding is combined, no sealant material exists in the overall sealing process of a pressure gauge, all the pressure sensing chips adopt a glass-metal soft sealing process, and the temperature resistance level of the pressure sensor is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of offshore heavy oil thermal recovery, and in particular relates to a high-temperature optical fiber pressure permanent testing system for a heavy oil thermal recovery well in an offshore oil field. Background Art

[0002] During the heat injection period, heavy oil thermal recovery wells have high downhole temperature and pressure parameters. In addition to the complex working conditions downhole, there is currently no mature online pressure monitoring technology that can meet the long-term, online monitoring needs of downhole pressure in heavy oil thermal recovery wells. Fiber optic sensing testing technology is very suitable for the field of heavy oil thermal recovery monitoring due to its inherent safety, high precision, anti-electromagnetic interference, and corrosion resistance. In addition to the characteristics of optical fiber itself, fiber optic pressure testing technology also has the characteristics of small size, easy integration, multiplexing, and easy to form various forms of fiber optic sensing networks, which can realize the measurement of multi-point pressure in complex downhole environments.

[0003] Fiber optic pressure sensors can be divided into FBG and FP types according to the testing principle. Due to the limitation of packaging method, the temperature resistance level of FBG type sensors cannot exceed 300°C. The manufacturing methods of FP type pressure sensors include MEMS technology and arc welding photonic crystal fiber technology, but these methods have disadvantages such as complex manufacturing process, high cost and poor temperature resistance.

[0004] Therefore, a high-temperature optical fiber pressure permanent test system for heavy oil thermal recovery wells in offshore oil fields is required to improve its temperature and pressure resistance levels in terms of manufacturing process and packaging method to meet the monitoring needs of heavy oil thermal recovery wells in offshore oil fields and solve the technical limitations of the existing single parameter of heavy oil thermal recovery monitoring. Summary of the invention

[0005] The present invention is proposed to solve the technical problem that the temperature resistance level of the optical fiber pressure testing technology in the prior art cannot exceed 300°C, and its purpose is to provide a high-temperature optical fiber pressure permanent testing system for heavy oil thermal recovery wells in offshore oil fields.

[0006] The present invention is achieved through the following technical solutions:

[0007] A high-temperature optical fiber pressure permanent test system for heavy oil thermal recovery wells in offshore oil fields, comprising a high-temperature all-quartz optical fiber pressure sensor arranged downhole and a ground pressure demodulator arranged above the well, wherein the high-temperature all-quartz optical fiber pressure sensor and the ground pressure demodulator are connected via a monitoring optical cable; the high-temperature all-quartz optical fiber pressure sensor comprises a sealed housing, a pressure measuring chip arranged in the sealed housing, a single-mode optical fiber, a temperature compensation mechanism and an optical fiber lead-out mechanism; one end of the single-mode optical fiber is connected to the pressure measuring chip, and the other end extends out of the pressure measuring chip and is connected to the monitoring optical cable; the temperature compensation mechanism is arranged on the single-mode optical fiber; and the optical fiber lead-out mechanism is arranged between the single-mode optical fiber and the inner wall of the sealed housing.

[0008] In the above technical scheme, the sealed shell includes a pressure-sensing part, a pressure-measuring part, a main body and a lead-out part which are connected in sequence; the pressure-sensing part is a sleeve structure with a stepped through hole formed in the middle, and the stepped through hole is composed of a connecting section, a limiting section, a pressure-conducting section and a pressure-sensing section with inner diameters decreasing in sequence; the pressure-measuring part is a stepped cylindrical section with small diameters at both ends and a large diameter in the middle, and a through hole is formed in the middle, which is connected to the pressure-conducting section and the pressure-sensing section of the pressure-sensing part; one end of the main body is sleeved on the outside of the small-diameter section of the pressure-measuring part, and the other end is threadedly connected to the lead-out part; the lead-out part is composed of a hollow cylindrical section and a hollow truncated cone section which are connected in sequence, and the large-diameter end of the truncated cone section is connected to the main body.

[0009] In the above technical solution, the inner wall of the limiting section forms an inner convex ring; a pressure-sensitive deformation tube is sleeved inside the pressure-sensitive section, and a pressure-conducting fluid is encapsulated in the pressure-sensitive deformation tube.

[0010] In the above technical solution, the components of the sealed housing are connected by mechanical sealing and then laser welding is used to achieve secondary sealing.

[0011] In the above technical solution, the pressure measuring chip is arranged in the pressure measuring part, which includes an optical fiber FP cavity and a sealing end.

[0012] In the above technical solution, the temperature compensation mechanism includes a fiber Bragg grating and a protection tube. The fiber Bragg grating is etched on the single-mode optical fiber using femtosecond laser etching technology; and the protection tube is sleeved on the outside of the fiber Bragg grating.

[0013] In the above technical solution, the temperature compensation mechanism and the inner wall of the sealed housing are sealed by a soft metal sealing method.

[0014] In the above technical solution, the optical fiber lead-out mechanism includes a capillary glass tube and a metal soft seal. The capillary glass tube is sleeved outside the single-mode optical fiber, and the metal soft seal is arranged between the capillary glass tube and the inner wall of the sealing shell.

[0015] In the above technical solution, the monitoring optical cable includes a high-temperature optical fiber and an outer armored protection tube arranged inside and outside; the high-temperature optical fiber is a pure silicon core modified polyimide optical fiber.

[0016] In the above technical scheme, the monitoring optical cable and the high-temperature all-quartz optical fiber pressure sensor are connected by equal-diameter ring welding. The single-mode optical fiber of the high-temperature all-quartz optical fiber pressure sensor and the high-temperature optical fiber of the monitoring optical cable are first fusion-spliced ​​by an optical fiber fusion splicer, and a high-temperature protective tube is sheathed at the fusion point; the optical cable tube sheathed on the outside of the single-mode optical fiber and the outer armored protective tube of the monitoring optical cable are connected by laser welding.

[0017] The beneficial effects of the present invention are:

[0018] The present invention provides a high-temperature optical fiber pressure permanent test system for heavy oil thermal recovery wells in offshore oil fields, and innovatively designs an all-quartz optical fiber FP pressure sensor. The pressure sensing chips of the sensor all adopt an all-quartz structure and are connected in combination with laser welding. There is no sealant material in the overall sealing process of the pressure gauge, and all glass-metal soft sealing processes are used, which greatly improves the temperature resistance level of the pressure sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of the structure of the high-temperature all-quartz optical fiber pressure sensor in the present invention;

[0020] Figure 2 It is a schematic diagram of the equal-diameter ring welding structure of the high-temperature all-quartz optical fiber pressure sensor and the monitoring optical cable in the present invention.

[0021] Figure 3 It is a schematic diagram of the structure of the optical fiber FP cavity in the present invention.

[0022] in:

[0023] 1. High temperature all-quartz optical fiber pressure sensor;

[0024] 11. Sealed housing; 111. Pressure sensing part; 112. Pressure measuring part; 113. Main body; 114. Leading part; 115. Inner convex ring

[0025] 12. Pressure measuring chip; 121. Optical fiber FP cavity; 1211. Cavity sheath; 1212. Reflection surface No. I; 1213. Reflection surface No. II; 122. Sealing end;

[0026] 13. Single-mode optical fiber; 131. Optical cable tube;

[0027] 14. Temperature compensation mechanism;

[0028] 15. Optical fiber lead-out mechanism; 151. Capillary glass tube; 152. Metal soft seal;

[0029] 2. Monitoring optical cable; 21. High temperature optical fiber; 22. Outer armored protection tube;

[0030] 3. High temperature protective tube.

[0031] For ordinary technicians in this field, other relevant drawings can be obtained based on the above drawings without any creative work. DETAILED DESCRIPTION

[0032] In order to enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention is further described below with reference to the accompanying drawings and through specific implementation methods.

[0033] like Figures 1 to 3As shown, a high-temperature optical fiber pressure permanent test system for heavy oil thermal recovery wells in offshore oil fields comprises a high-temperature all-quartz optical fiber pressure sensor 1 arranged downhole and a ground pressure demodulator arranged above the well, and the high-temperature all-quartz optical fiber pressure sensor 1 is connected to the ground pressure demodulator via a monitoring optical cable 2;

[0034] The high temperature all-quartz optical fiber pressure sensor 1 comprises a sealed housing 11, a pressure measuring chip 12 arranged in the sealed housing 11, a single-mode optical fiber 13, a temperature compensation mechanism 14 and an optical fiber lead-out mechanism 15;

[0035] The sealed housing 11 comprises a pressure sensing part 111, a pressure measuring part 112, a main body 113 and a lead-out part 114 which are connected in sequence by a mechanical seal; the connection positions between the pressure sensing part 111, the pressure measuring part 112, the main body 113 and the lead-out part 114 are connected by mechanical seal and then laser welded to achieve secondary sealing, thereby ensuring the temperature and pressure resistance performance;

[0036] The pressure sensing portion 111 is a sleeve structure with a stepped through hole formed in the middle, and the stepped through hole is composed of a connecting section, a pressure conducting section and a pressure sensing section with successively decreasing inner diameters; an inner convex ring 115 is formed in the middle of the inner wall of the pressure conducting section;

[0037] A pressure-sensitive deformation tube is set inside the pressure-sensitive section, and a certain pressure-conducting fluid is encapsulated in the pressure-sensitive deformation tube; the pressure-sensitive deformation tube realizes the isolation of the inner cavity of the optical fiber pressure sensor from the external medium;

[0038] The pressure-conducting section is used to connect the pressure-sensing section with the pressure-measuring chip 12, and to guide the pressure-conducting fluid in the pressure-sensing section to the pressure-measuring end of the optical fiber FP cavity 121, so that the length of the FP cavity changes;

[0039] The pressure sensing chamber and the inner cavity of the optical fiber pressure sensor are sealed at the pressure conducting cavity by metal sealing to prevent the pressure conducting fluid from entering the interior of the optical fiber pressure sensor.

[0040] The pressure measuring part 112 is a stepped cylinder with small diameters at both ends and a large diameter in the middle, and a through hole is formed in the middle, which is connected to the pressure-conducting section and the pressure-sensing section of the pressure-sensing part 111;

[0041] One end of the main body 113 is sleeved on the outside of the small diameter section of the pressure measuring part 112, and the other end is threadedly connected to the lead-out part 114; the main body 113 is used to protect the temperature compensation mechanism, and adopts a metal soft seal to achieve sealing between it and the temperature compensation mechanism. At the same time, the connection between the pressure measuring part 112 and the lead-out part 114 is achieved. The pressure measuring part 112 is used to protect the pressure measuring chip, and the two ends of the pressure measuring part adopt metal soft seals to respectively achieve the sealing of the pressure measuring chip 12 and the pressure sensing part 111, and at the same time, the connection between the pressure sensing part 111 and the main body 113 is achieved.

[0042] The lead-out portion 114 is composed of a hollow cylindrical section and a hollow truncated cone section connected to each other, and the large diameter end of the truncated cone section is connected to the main body 113;

[0043] The components of the sealing housing 11 are connected by mechanical sealing and then laser welding to achieve secondary sealing, thereby ensuring its temperature and pressure resistance. The sealing housing 11 achieves overall sealing between the interior of the high-temperature all-quartz optical fiber pressure sensor 1 and the downhole medium.

[0044] The pressure measuring chip 12 is arranged in the pressure measuring part 112, and comprises an optical fiber FP cavity 121 and a sealing end 122;

[0045] The optical fiber FP cavity 121 includes a cavity sheath 1211 and a No. I reflection surface 1212 and a No. II reflection surface 1213 disposed on both end faces of the cavity sheath 1211; one end of the No. I reflection surface 1212 is connected to the single-mode optical fiber 13 through a monitoring pigtail;

[0046] The reflection surface No. 1 1212 and the reflection surface No. 2 1213 are both pure silica optical fibers, and the diameter after removing the coating layer is 125um. The reflection surface No. 1 1212 is a single-mode pure silica optical fiber with a specification of 9 / 125um, and the reflection surface No. 2 1213 is a multi-mode pure silica optical fiber with a specification of 50 / 125um. The reflection surface No. 1 1212 and the reflection surface No. 2 1213 serve as the two end faces of the optical fiber FP cavity. The optical fiber forms an interference spectrum after multiple reflections between these two end faces. The cavity sheath 1211 is a capillary glass tube, which is used to connect and fix the two optical fiber reflection surfaces. The inner and outer diameters of the capillary glass tube match the dimensions of the optical fiber core and cladding.

[0047] The pressure measuring chip 12 adopts the optical fiber FP cavity pressure measuring principle and realizes the test of external pressure by demodulating the cavity length of the FP cavity. The preparation method of the optical fiber FP cavity 121 is as follows: after cutting a flat end face of the capillary glass tube with a cutting knife, the two cut end faces of the No. Ⅰ reflection surface and the capillary glass tube are placed inside the welding machine for welding. After the welding is completed, the capillary glass tube is cut with a cutting knife to reserve a specific length, which is the cavity length of the FP cavity. Then, one end of the No. Ⅱ reflection surface is cut flat with an ultrasonic cutting knife and then welded with the other end of the capillary glass tube through a welding machine to form the other reflection end face of the FP cavity; the No. Ⅰ reflection surface 1212 serves as a reflection end face of the optical fiber FP cavity 121; the No. Ⅱ reflection surface 1213 also serves as another reflection end face and lead-out end of the optical fiber FP cavity 121. The No. Ⅱ reflection surface 1213 is connected to the single-mode optical fiber 13 through a monitoring pigtail to detect the reflection spectrum of the FP cavity.

[0048] A sealing end 122 is arranged outside the single-mode optical fiber 13 connected to the No. Ⅰ reflection surface 1212 of the optical fiber FP cavity 121, and the sealing end 122 includes a capillary glass tube sleeved outside the single-mode optical fiber 13 and a metal soft seal arranged between the capillary glass tube and the inner wall of the pressure measuring part 112; the single-mode optical fiber 13 and the capillary glass tube are fixed by laser welding, and the metal soft seal realizes the sealing between the capillary glass tube and the pressure measuring part 112;

[0049] The capillary glass tube is used to protect the single-mode optical fiber led out of the optical fiber FP cavity. The metal soft seal is used to achieve the seal between the capillary glass tube and the sealing body. The capillary glass tube and the sealing body are glass-metal seals. The seal between the two is currently more commonly used sealants, including epoxy resin glue and inorganic glue. The maximum temperature resistance of this type of sealant is 300°C. If the temperature exceeds 300°C, it will not play a role in sealing and isolation. Therefore, the present application adopts a soft metal sealing method, which can not only achieve the sealing between glass and metal, but also greatly improve its temperature resistance level, with a maximum temperature resistance of 370°C.

[0050] One end of the single-mode optical fiber 13 is connected to the pressure measuring chip 12, and the other end extends from the lead-out portion 114 of the sealed housing 11. The single-mode optical fiber 13 extending from the sealed housing 11 is sheathed with an optical cable tube 131;

[0051] A temperature compensation mechanism 14 is arranged outside the single-mode optical fiber 13 located inside the main body 113 of the sealed housing 11; the temperature compensation mechanism 14 includes an optical fiber grating and a protection tube, the optical fiber grating is etched on the single-mode optical fiber 13 by using a femtosecond laser etching technology, and the protection tube is sleeved outside the optical fiber grating; the femtosecond laser etching technology does not need to remove the optical fiber coating layer, retains the original mechanical strength of the optical fiber, and the maximum temperature resistance of the optical fiber grating is 370°C; the protection tube is used to improve the mechanical strength of the optical fiber grating; the temperature compensation mechanism 14 and the inner wall of the sealed housing 11 are sealed by a soft metal sealing method;

[0052] The temperature compensation mechanism 14 adopts the fiber Bragg grating temperature measurement principle. When the downhole ambient temperature changes, the central wavelength of the fiber Bragg grating will change. Temperature compensation is achieved by demodulating the change in the central wavelength of the grating to eliminate the change in the fiber FP cavity length caused by temperature change.

[0053] The optical fiber lead-out mechanism 15 comprises a capillary glass tube 151 and a metal soft seal 152. The capillary glass tube 151 is sleeved on the outside of the single-mode optical fiber 13, and the metal soft seal 152 is arranged between the capillary glass tube 151 and the inner wall of the lead-out portion 114 of the sealed housing 11; the capillary glass tube 151 is used to protect the single-mode optical fiber, the single-mode optical fiber passes through the capillary tube and is fixed, and the metal soft seal 152 is used to achieve sealing between the capillary glass tube 151 and the lead-out portion 114 of the sealed housing 11;

[0054] The optical fiber lead-out mechanism 15 is arranged inside the lead-out portion 114 of the sealed housing 11. The optical fiber lead-out mechanism 15 is used to achieve sealing between the single-mode optical fiber 13 led out of the pressure measuring chip 12 and the inner wall of the lead-out position of the sealed housing 11, thereby ensuring isolation of the interior of the high-temperature all-quartz optical fiber pressure sensor 1 from the external medium.

[0055] The monitoring optical cable 2 is used for downhole pressure signal transmission, and includes a high-temperature optical fiber 21 and an outer armored protection tube 22 arranged inside and outside; the high-temperature optical fiber 21 is a pure silicon core modified polyimide optical fiber, the optical fiber core adopts a pure silicon process, and no doping is added to the core, so it has lower hydrogen loss characteristics and higher stability; the outer armored protection tube 22 is suitable for a variety of structures, including a single-layer tube structure, a multi-layer tube structure, an internal aluminum cladding structure, an internal steel wire twisted armor structure, etc.

[0056] The monitoring optical cable 2 and the high-temperature all-quartz optical fiber pressure sensor 1 are butt-jointed by equal-diameter ring welding. The single-mode optical fiber 13 and the high-temperature optical fiber 21 of the monitoring optical cable 2 are first fusion-joined by an optical fiber fusion splicer, and a high-temperature protective tube 23 is sheathed at the fusion joint for protection to improve the mechanical strength of the fusion joint. The optical cable tube 131 sheathed on the outside of the single-mode optical fiber 13 is laser welded to the outer armored protective tube 22 of the monitoring optical cable 2. The outer diameter of the optical cable tube and the outer armored protective tube 22 of the monitoring optical cable 2 are the same. The two are butt-welded by a fully automatic laser welding machine to achieve equal-diameter welding. The mechanical strength of the welding joint is basically the same as the strength of the body.

[0057] The surface demodulator is used to convert the downhole pressure signal into an electrical signal and then demodulate and output it into pressure data. The surface pressure demodulator is connected to the monitoring optical cable 2 via a pigtail.

[0058] The present invention is based on the Fabry-Perot cavity pressure measurement principle and adopts an all-quartz structure to innovatively design a high-temperature optical fiber pressure sensor with a temperature resistance of 370°C and a pressure resistance of 26MPa. The pressure sensor includes a pressure sensing chamber, a pressure conducting cavity, a pressure measuring chip, a temperature compensation slider, a sealing body, and an optical fiber lead-out end. The FP cavity of the pressure sensor is a pure quartz structure and is processed by laser welding. There is no sealant material in the overall sealing process, and all glass-metal soft sealing processes are adopted, which greatly improves the temperature resistance level of the pressure sensor and solves the design problem that the maximum temperature resistance of the optical fiber pressure sensor does not exceed 300°C. At the same time, it is equipped with downhole monitoring cables and ground pressure demodulators to form a high-temperature optical fiber pressure permanent test system for offshore heavy oil thermal recovery wells. In view of the complex process pipe column structure of high-temperature injection and production integration of offshore heavy oil thermal recovery wells, as well as the complex working conditions of high temperature and high pressure downhole, an innovative equal-diameter ring welding connection method of optical fiber pressure sensor and test cable is proposed. There is no other steel pipe sheath at the welding point, which brings certain convenience to on-site construction. In addition, the laser welding method is far superior to the metal sealing method in terms of welding strength, temperature and pressure resistance, and sealing, thus avoiding the leakage problem of optical fiber pressure sensor.

[0059] The applicant declares that the above is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention shall fall within the protection scope and disclosure scope of the present invention.

Claims

1. A high-temperature optical fiber pressure permanent test system for heavy oil thermal recovery wells in offshore oil fields, characterized by: The invention comprises a high-temperature all-quartz optical fiber pressure sensor (1) arranged underground and a surface pressure demodulator arranged above the well, wherein the high-temperature all-quartz optical fiber pressure sensor (1) and the surface pressure demodulator are connected via a monitoring optical cable (2); the high-temperature all-quartz optical fiber pressure sensor (1) comprises a sealed housing (11), a pressure measuring chip (12) arranged in the sealed housing (11), a single-mode optical fiber (13), a temperature compensation mechanism (14) and an optical fiber lead-out mechanism (15); one end of the single-mode optical fiber (13) is connected to the pressure measuring chip (12), and the other end thereof is connected to the monitoring optical cable (2) after extending out of the pressure measuring chip (12); the temperature compensation mechanism (14) is arranged on the single-mode optical fiber (13); and the optical fiber lead-out mechanism (15) is arranged between the single-mode optical fiber (13) and the inner wall of the sealed housing (11).

2. The high-temperature optical fiber pressure permanent test system for offshore oilfield heavy oil thermal recovery wells according to claim 1 is characterized in that: The sealed housing (11) comprises a pressure sensing portion (111), a pressure measuring portion (112), a main body portion (113) and a lead-out portion (114) which are connected in sequence; The pressure sensing portion (111) is a sleeve structure with a stepped through hole formed in the middle, and the stepped through hole is composed of a connecting section, a limiting section, a pressure guiding section and a pressure sensing section, the inner diameters of which decrease in sequence; The pressure measuring part (112) is a stepped cylindrical shape with small diameters at both ends and a large diameter in the middle, and a through hole is formed in the middle, which is connected to the pressure-conducting section and the pressure-sensing section of the pressure-sensing part (111); One end of the main body (113) is sleeved on the outside of the small diameter section of the pressure measuring part (112), and the other end is threadedly connected to the lead-out part (114); The lead-out portion (114) is composed of a hollow cylindrical section and a hollow truncated cone section which are connected to each other, and the large-diameter end of the truncated cone section is connected to the main body portion (113).

3. The high-temperature optical fiber pressure permanent test system for offshore oilfield heavy oil thermal recovery wells according to claim 2 is characterized in that: An inner convex ring is formed on the inner wall of the limiting section; a pressure-sensitive deformation tube is sleeved inside the pressure-sensitive section, and a pressure-conducting fluid is encapsulated in the pressure-sensitive deformation tube.

4. The high-temperature optical fiber pressure permanent test system for offshore oilfield heavy oil thermal recovery wells according to claim 2, characterized in that: The components of the sealing housing (11) are connected by mechanical sealing and then laser welding is used to achieve secondary sealing.

5. The high-temperature optical fiber pressure permanent test system for offshore oilfield heavy oil thermal recovery wells according to claim 1 is characterized in that: The pressure measuring chip (12) is arranged in the pressure measuring part (112), and comprises an optical fiber FP cavity (121) and a sealing end (122).

6. The high-temperature optical fiber pressure permanent test system for offshore oilfield heavy oil thermal recovery wells according to claim 1, characterized in that: The temperature compensation mechanism (14) comprises a fiber grating and a protection tube. The fiber grating is etched on the single-mode optical fiber (13) using a femtosecond laser etching technique. The protection tube is sleeved on the outside of the fiber grating.

7. The high-temperature optical fiber pressure permanent test system for offshore oilfield heavy oil thermal recovery wells according to claim 1, characterized in that: The temperature compensation mechanism (14) and the inner wall of the sealing housing (11) are sealed by a soft metal sealing method.

8. The high-temperature optical fiber pressure permanent test system for offshore oilfield heavy oil thermal recovery wells according to claim 1, characterized in that: The optical fiber lead-out mechanism (15) comprises a capillary glass tube (151) and a metal soft seal (152); the capillary glass tube (151) is sleeved outside the single-mode optical fiber (13); and the metal soft seal (152) is arranged between the capillary glass tube (151) and the inner wall of the sealing housing (11).

9. The high-temperature optical fiber pressure permanent test system for offshore oilfield heavy oil thermal recovery wells according to claim 1, characterized in that: The monitoring optical cable (2) comprises a high-temperature optical fiber (21) and an outer armored protection tube (22) arranged inside and outside the optical fiber; the high-temperature optical fiber (21) is a pure silicon core modified polyimide optical fiber.

10. The high-temperature optical fiber pressure permanent test system for offshore oilfield heavy oil thermal recovery wells according to claim 1, characterized in that: The monitoring optical cable (2) and the high-temperature all-quartz optical fiber pressure sensor (1) are butt-jointed by equal-diameter ring welding. The single-mode optical fiber (13) of the high-temperature all-quartz optical fiber pressure sensor (1) and the high-temperature optical fiber (21) of the monitoring optical cable (2) are first fusion-joined by an optical fiber fusion splicer, and a high-temperature protective tube (23) is sheathed at the fusion joint. The optical cable tube (131) sheathed outside the single-mode optical fiber (13) and the outer armored protective tube (22) of the monitoring optical cable (2) are connected by laser welding.

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