Offshore oilfield heavy oil thermal production well high-temperature optical fiber pressure monitoring system

Abstract

The invention discloses a high-temperature optical fiber pressure monitoring system for an offshore oilfield thickened oil thermal production well. The high-temperature optical fiber pressure monitoring system comprises an underground process pipe column and a high-temperature optical fiber pressure sensor arranged in the underground process pipe column. The high-temperature optical fiber pressure sensor is connected with a pressure demodulator arranged on the ground through an underground monitoring optical cable; the high-temperature optical fiber pressure sensor comprises a sealing body, and an optical fiber pressure sensing chip and an optical fiber leading-out end assembly which are arranged in the sealing body. The underground process pipe column comprises a tubing hanger, an upper oil pipe, a high-temperature annulus safety packer, a heat insulation oil pipe, a jet pump working barrel, a high-temperature deep well safety valve and a lower oil pipe which are sequentially connected. The optical fiber pressure sensor can resist the temperature of 370 DEG C and the pressure of 26 MPa, a set of optical fiber pressure monitoring system suitable for the offshore heavy oil thermal production well is provided by being matched with an underground monitoring optical cable and demodulation equipment, two sets of process pipe columns are designed according to different offshore monitoring requirements, and the purpose of monitoring the annular pressure and the pressure in the pipe by the heavy oil thermal production well is achieved.

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 monitoring system for a heavy oil thermal recovery well in an offshore oil field. Background Art

[0002] In the process of heavy oil thermal recovery, recording the dynamic parameters of downhole temperature and pressure of thermal recovery wells has become a necessary means of production design. By monitoring the real-time test data of temperature and pressure, we can qualitatively and quantitatively understand the steam absorption status of each production layer in the well, monitor the quality of steam injection, and judge the effect of steam injection, so as to provide a scientific basis for timely understanding the development dynamics of heavy oil reservoirs, adjusting thermal recovery plans, and improving the effect of steam injection development. Therefore, the dynamic monitoring technology of downhole temperature and pressure for heavy oil thermal recovery plays a vital role in heavy oil thermal recovery production. However, due to the complex structure of the high-temperature injection and production integrated process string of Bohai heavy oil and the high temperature and pressure parameters of steam injection (≥350℃, ≥17MPa), there is no mature online pressure technology at present, which leads to the great limitations of the injection and production parameter control and reservoir parameter evaluation of the high-temperature injection and production integrated technology, and it is impossible to understand the real situation in the well.

[0003] Fiber optic sensing test technology is very suitable for heavy oil thermal recovery monitoring due to its inherent safety, high precision, anti-electromagnetic interference, and corrosion resistance. At present, the fiber optic pressure monitoring technology used more often at home and abroad includes FP type, diaphragm type (FBG), and stress strain type (FBG) pressure sensors. The above pressure sensors are all subject to technical limitations because they cannot solve the sealing problem under high temperature and high pressure conditions of 350℃ and 26Mpa. At present, the highest temperature resistance of pressure sensors in the domestic and foreign markets does not exceed 300℃, so they cannot meet the high temperature and high pressure working conditions of heavy oil thermal recovery wells.

[0004] Therefore, a high-temperature optical fiber pressure monitoring system for offshore heavy oil thermal recovery wells is needed to meet the pressure monitoring needs of offshore thermal recovery wells under integrated injection and production conditions and solve the technical limitations of the existing single monitoring parameters for offshore heavy oil thermal recovery. Summary of the invention

[0005] The present invention is proposed to solve the problems existing in the prior art, and its purpose is to provide a high-temperature optical fiber pressure monitoring 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 monitoring system for heavy oil thermal recovery wells in an offshore oil field comprises a downhole process pipe string and a high-temperature optical fiber pressure sensor arranged in the downhole process pipe string; the high-temperature optical fiber pressure sensor is connected to a pressure demodulator arranged on the ground through a downhole monitoring optical cable; the high-temperature optical fiber pressure sensor comprises a sealing body, an optical fiber pressure sensing chip arranged in the sealing body, and an optical fiber lead-out end assembly; the downhole process pipe string comprises an oil pipe hanger, an upper oil pipe, a high-temperature annular space safety packer, an insulated oil pipe, a jet pump working cylinder, a high-temperature deep well safety valve and a lower oil pipe connected in sequence, and a round plug is arranged at the free end of the lower oil pipe; the downhole process pipe string and the downhole monitoring optical cable are integrated in an external pipe bundling manner or an external pipe to internal pipe transfer manner.

[0008] In the above technical solution, the sealing body includes a pressure-conducting end head, an annular end cover and an optical cable connector which are connected in sequence; the pressure-conducting end head is a sleeve-type structure with two open ends, and the outer walls at both ends form external threads, the middle outer wall forms an external convex ring, and the inner wall at one end close to the pressure-conducting end head forms an internal convex platform; the annular end cover is composed of a sleeve portion and a frustum portion, both of which are hollow and open at both ends. The inner wall of the sleeve portion of the annular end cover forms an internal thread, and the small-diameter end of the frustum portion of the annular end cover is connected to the optical cable connector.

[0009] In the above technical solution, the optical fiber pressure-sensing chip includes a pressure-sensitive diaphragm, a single-mode optical fiber, and a temperature-measuring optical fiber Bragg grating and a pressure-measuring optical fiber Bragg grating etched on the single-mode optical fiber; the pressure-sensitive diaphragm is fixed inside the end of the pressure-conducting end away from the annular end cover, and the outer circumferential wall of the pressure-sensitive diaphragm is fixedly connected to the inner wall of the pressure-conducting end by laser welding; one end of the single-mode optical fiber is connected to the pressure-sensitive diaphragm, and the other end extends out of the optical cable connector; the temperature-measuring optical fiber Bragg grating is arranged on the single-mode optical fiber between the inner boss and the optical cable connector; the pressure-measuring optical fiber Bragg grating is arranged on the single-mode optical fiber close to the pressure-sensitive diaphragm.

[0010] In the above technical scheme, the optical fiber pressure-sensitive chip also includes a grating fixing mechanism and an optical fiber supporting mechanism; the grating fixing mechanism includes support bridge No. I and support bridge No. II; support bridge No. I is fixed to the inner side of the pressure-sensitive diaphragm, and the material of support bridge No. I is consistent with that of the pressure-sensitive diaphragm; support bridge No. II is fixed to the top of the inner boss by laser welding; the optical fiber supporting mechanism includes capillary steel tube No. I and capillary steel tube No. II, capillary steel tube No. I is sleeved on the outside of one end where the single-mode optical fiber is connected to the pressure-sensitive diaphragm, and capillary steel tube No. I is fixed to support bridge No. I by laser welding; capillary steel tube No. II is sleeved on the outside of the middle section of the single-mode optical fiber, and is fixed to support bridge No. II by laser welding.

[0011] In the above technical solution, the No. I support bridge, No. II support bridge and the cavity of the sealing body are located on the same axis.

[0012] In the above technical solution, the optical fiber lead-out end assembly is arranged inside the optical cable connector, which includes a capillary glass tube sleeved on the outside of the single-mode optical fiber and a soft metal sealing ring sleeved on the outside of the capillary glass tube; the single-mode optical fiber and the capillary glass tube are fixed by laser welding.

[0013] In the above technical solution, when the integration mode of the downhole process pipe string and the downhole monitoring optical cable 2 is the external bundling mode, the high-temperature optical fiber pressure sensor is arranged outside the lower oil pipe near one end of the round plug, and the downhole monitoring optical cable is arranged outside the oil pipe and connected to the oil pipe through the optical cable shield;

[0014] In the above technical scheme, when the integration method of the downhole process tubing and the downhole monitoring optical cable is the outside-to-inside-tube method, the downhole process tubing also includes an optical cable crossing Y-joint, the optical cable crossing Y-joint is arranged between the high-temperature deep well safety valve and the lower oil pipe, the high-temperature optical fiber pressure sensor is arranged inside the lower oil pipe near one end of the round plug, the downhole monitoring optical cable above the optical cable crossing Y-joint is arranged outside the oil pipe, and the downhole monitoring optical cable passes through the optical cable crossing Y-joint and then extends into the lower oil pipe.

[0015] The beneficial effects of the present invention are:

[0016] The present invention provides a high-temperature optical fiber pressure monitoring system for offshore heavy oil thermal recovery wells. Based on the downhole high-temperature and high-pressure working conditions of heavy oil thermal recovery wells, and the importance of real-time pressure data monitoring to thermal recovery well parameter analysis and production system regulation, a high-temperature optical fiber pressure sensor with a temperature resistance of 370°C and a pressure resistance of 26MPa is innovatively designed. The optical fiber unit, the pressure-sensitive chip structure, and the glass-metal sealing process are innovatively optimized in three aspects, respectively, to solve the sealing problem that the current optical fiber pressure sensor cannot withstand a temperature of more than 300°C. At the same time, a set of optical fiber pressure monitoring systems suitable for offshore heavy oil thermal recovery wells is proposed in conjunction with downhole monitoring optical cables and ground demodulation equipment. In view of different monitoring needs at sea, two sets of process pipe strings are designed respectively, to achieve the purpose of monitoring the annular pressure and the pressure inside the pipe of the heavy oil thermal recovery wells. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of the structure of the high temperature optical fiber pressure sensor of the present invention;

[0018] Figure 2 It is a structural schematic diagram of the downhole process pipe string and the downhole monitoring optical cable of the present invention when they are integrated by bundling outside the pipe;

[0019] Figure 3 It is a structural schematic diagram of the downhole process pipe column and the downhole monitoring optical cable of the present invention when they are integrated in a way of turning from outside the pipe to inside the pipe.

[0020] in:

[0021] 1. High temperature optical fiber pressure sensor;

[0022] 11. Pressure-conducting terminal; 12. Annular end cap; 13. Optical cable connector; 14. Inner boss; 15. Outer convex ring; 16. Pressure-sensitive diaphragm; 17. Single-mode optical fiber; 18. Temperature-measuring fiber Bragg grating; 19. Pressure-measuring fiber Bragg grating; 110. Support bridge No. Ⅰ; 111. Support bridge No. Ⅱ; 112. Capillary steel tube No. Ⅰ; 113. Capillary steel tube No. Ⅱ; 114. Capillary glass tube; 115. Soft metal sealing ring;

[0023] 2. Downhole monitoring optical cable;

[0024] 3. Pressure demodulator;

[0025] 41. Tubing hanger; 42. Upper tubing; 43. High-temperature annular safety packer; 44. Insulated tubing; 45. Jet pump working cylinder; 46. High-temperature deep well safety valve; 47. Lower tubing; 48. Round plug; 49. Optical cable crossing Y-joint.

[0026] For ordinary technicians in this field, other relevant drawings can be obtained based on the above drawings without any creative work. DETAILED DESCRIPTION

[0027] 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.

[0028] like Figures 1 to 3 As shown, a high-temperature optical fiber pressure monitoring system for a heavy oil thermal recovery well in an offshore oil field comprises a downhole process pipe string and a high-temperature optical fiber pressure sensor 1 arranged in the downhole process pipe string; the high-temperature optical fiber pressure sensor 1 is connected to a pressure demodulator 3 arranged on the ground through a downhole monitoring optical cable 2;

[0029] The high temperature optical fiber pressure sensor 1 comprises a sealing body, an optical fiber pressure sensing chip and an optical fiber lead-out end assembly arranged in the sealing body;

[0030] The sealing body comprises a pressure-conducting end head 11, an annular end cap 12 and an optical cable connector 13 which are connected in sequence; the sealing body is used to isolate the downhole medium from the optical fiber pressure-sensitive chip, and the pressure-conducting end head is mainly used to transmit the external pressure to the pressure-sensitive diaphragm, causing the pressure-sensitive diaphragm to produce axial deformation.

[0031] The pressure-conducting end head 11 is a sleeve-type structure with open ends, with external threads formed on the outer walls of both ends, an outer convex ring 15 formed on the middle outer wall, and an inner convex platform 14 formed on the inner wall of the end close to the pressure-conducting end head 11; the pressure-conducting end head 11 is threadedly connected to the annular end cover 12, and the connection is laser welded for secondary sealing;

[0032] The annular end cap 12 is composed of a sleeve portion and a truncated cone portion, both of which are hollow and open at both ends. The inner wall of the sleeve portion of the annular end cap 12 forms an internal thread, which is threadedly connected to the pressure-guiding end head 11, and the small-diameter end of the truncated cone portion of the annular end cap 12 is connected to the optical cable connector 13;

[0033] The optical cable connector 13 is used to connect to the monitoring optical cable;

[0034] The optical fiber pressure-sensitive chip includes a pressure-sensitive diaphragm 16, a single-mode optical fiber 17, and a temperature-measuring optical fiber grating 18 and a pressure-measuring optical fiber grating 19 etched on the single-mode optical fiber 17;

[0035] The pressure-sensitive diaphragm 16 is fixed inside the end of the pressure-conducting terminal 11 away from the annular end cover 12, and the outer circumferential wall of the pressure-sensitive diaphragm 16 is fixedly connected to the inner wall of the pressure-conducting terminal 11 by laser welding;

[0036] The single-mode optical fiber 17 is a polyimide pure silica core optical fiber, one end of which is connected to the pressure-sensitive diaphragm 16, and the other end extends out of the optical cable connector 13;

[0037] The temperature measuring fiber Bragg grating 18 is arranged on the single mode optical fiber 17 between the inner boss 14 and the optical cable connector 13; the pressure measuring fiber Bragg grating 19 is arranged on the single mode optical fiber 17 close to the pressure sensing diaphragm 16;

[0038] The temperature-measuring fiber Bragg grating 18 and the pressure-measuring fiber Bragg grating 19 are both etched on the single-mode optical fiber 17 by femtosecond laser etching technology. This technology does not need to remove the optical fiber coating layer and retains the original mechanical strength of the optical fiber. The maximum temperature resistance of the temperature-measuring fiber Bragg grating 18 and the pressure-measuring fiber Bragg grating 19 is 370°C. The temperature-measuring fiber Bragg grating 18 is used for temperature compensation of the pressure-measuring fiber Bragg grating 19, and the pressure-measuring fiber Bragg grating 19 is used for testing the external pressure. The optical fiber structural unit using this technology has a maximum temperature resistance of 370°C.

[0039] The optical fiber pressure sensing chip also includes a grating fixing mechanism and an optical fiber supporting mechanism;

[0040] The grating fixing mechanism includes a No. I support bridge 110 and a No. II support bridge 111; the No. I support bridge 110 is fixed to the inner side of the pressure-sensitive diaphragm 16, and the No. I support bridge 110 and the pressure-sensitive diaphragm 16 are made of the same material, which has a low elastic modulus temperature coefficient and good wave velocity consistency;

[0041] The No. II support bridge 111 is fixed to the top of the inner boss 14 by laser welding;

[0042] The No. Ⅰ supporting bridge 110, No. Ⅱ supporting bridge 111 and the cavity of the sealing body are located on the same axis;

[0043] The optical fiber support mechanism includes a capillary steel tube No. 112 and a capillary steel tube No. 213. The capillary steel tube No. 112 is sleeved outside the end where the single-mode optical fiber 17 is connected to the pressure-sensitive membrane 16, and the capillary steel tube No. 112 is fixed to the support bridge No. 110 by laser welding; the capillary steel tube No. 213 is sleeved outside the middle section of the single-mode optical fiber 17, and is fixed to the support bridge No. 211 by laser welding;

[0044] The optical fiber pressure sensing chip 12 is the optical fiber pressure sensing unit of the high temperature optical fiber pressure sensor 1, which adopts the optical fiber Bragg grating pressure measurement principle and realizes the test of external pressure by demodulating the change of the central wavelength of the optical fiber Bragg grating; the pressure sensing diaphragm 16 generates axial deformation after direct contact with the external medium, and transmits its force to the pressure measuring optical fiber Bragg grating 19, so that the pressure measuring optical fiber Bragg grating 19 produces periodic changes in the grating fringes; the No. Ⅰ support bridge 110 and the No. Ⅱ support bridge 111 are used to fix the corresponding pressure measuring optical fiber Bragg grating 19 and the temperature measuring optical fiber Bragg grating 18 respectively;

[0045] The optical fiber lead-out end assembly is arranged inside the optical cable connector 13, and includes a capillary glass tube 114 sleeved outside the single-mode optical fiber 17 and a soft metal sealing ring 115 sleeved outside the capillary glass tube 114; the single-mode optical fiber 17 is fixed to the capillary glass tube 114 by laser welding;

[0046] The optical fiber lead-out end assembly is used to achieve the sealing between the single-mode optical fiber 17 and the annular end cap 12. After the single-mode optical fiber 17 passes through the No. II capillary steel tube 113, it passes through the capillary glass tube 114 again, and the single-mode optical fiber 17 and the capillary glass tube 114 are welded and fixed by a laser welding process, and then they are passed through the optical cable connector 13 together. At the same time, a soft metal sealing ring 115 is used to achieve the sealing between the single-mode optical fiber 17, the capillary glass tube 114, and the optical cable connector. At the same time, a high-temperature sealant is used at the position where the single-mode optical fiber 17 passes through the optical cable connector for secondary sealing, thereby improving the safety performance of the high-temperature optical fiber pressure sensor;

[0047] Since the optical fiber is made of glass and the optical cable connector 13 is made of metal, sealants are currently widely used to achieve the seal between the two, 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 be able to play the role of sealing and isolation. The single-mode optical fiber is inserted into the inner diameter of the capillary glass tube, and the single-mode optical fiber is welded to the capillary glass tube by laser welding. The capillary glass tube and the optical cable connector 13 are glass-metal sealed, and the sealing method uses a soft metal sealing ring to achieve mechanical sealing.

[0048] The downhole monitoring optical cable 2 is used for downhole pressure signal transmission, and includes high-temperature optical fibers and an outer armored protection tube arranged inside and outside. The high-temperature optical fiber is a pure silicon core modified polyimide optical fiber, and 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 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. The downhole monitoring optical cable 2 is connected to the high-temperature optical fiber pressure sensor 1 by a metal ferrule and laser welding. The downhole monitoring optical cable 2 is connected to the pressure demodulator 3 by a pigtail.

[0049] The pressure demodulator 3 is used to convert the downhole pressure signal into an electrical signal and then demodulate and output it into pressure data;

[0050] The downhole process string includes a tubing hanger 41, an upper tubing 42, a high-temperature annular safety packer 43, an insulated tubing 44, a jet pump mandrel 45, a high-temperature deep well safety valve 46 and a lower tubing 47, which are connected in sequence. A round plug 48 is provided at the free end of the lower tubing 47.

[0051] The integration method of the downhole process pipe string and the downhole monitoring optical cable 2 is an outside-pipe bundling method or an outside-pipe-inside-pipe transfer method;

[0052] When the downhole process pipe string and the downhole monitoring optical cable 2 are integrated in an external bundling manner, the high-temperature optical fiber pressure sensor 1 is arranged outside the lower oil pipe 47 near one end of the round plug 48, and the downhole monitoring optical cable 2 is arranged outside the oil pipe and connected to the oil pipe through the optical cable shield;

[0053] When the downhole process pipe string and the downhole monitoring optical cable 2 are integrated in an outside-pipe-inside-pipe manner, the downhole process pipe string also includes an optical cable crossing Y-joint 49, and the optical cable crossing Y-joint 49 is arranged between the high-temperature deep well safety valve 46 and the lower oil pipe 47. The high-temperature optical fiber pressure sensor 1 is arranged inside the lower oil pipe 17 near one end of the round plug 48. The downhole monitoring optical cable 2 above the optical cable crossing Y-joint 49 is arranged outside the oil pipe, and the downhole monitoring optical cable 2 passes through the optical cable crossing Y-joint 49 and then extends into the lower oil pipe 47.

[0054] The invention proposes a high-temperature optical fiber pressure monitoring system for offshore oilfield heavy oil thermal recovery wells. The optical fiber pressure sensor used in the system adopts the femtosecond laser fiber Bragg grating pressure measurement principle, combined with a pre-tensioned diaphragm structure, and innovatively adopts a high-temperature resistant glass-metal sealing process. The optical fiber pressure sensing chip design, the sealing body design, the optical fiber lead-out end design and other aspects are optimized respectively, so as to improve the overall temperature and pressure resistance level of the pressure gauge, reach a temperature resistance of 370°C and a pressure resistance of 26MPa, and solve the design problem that the maximum temperature resistance of the optical fiber pressure sensor does not exceed 300°C; and for the complex medium environment of high temperature, high pressure and strong corrosion of offshore heavy oil thermal recovery wells, targeted solutions are proposed from two aspects of test cable and ground demodulation; at the same time, in order to meet different pressure monitoring requirements at sea, for the complex process string structure of high-temperature injection and production integration of offshore heavy oil wells, under the premise of not changing the existing process and tool working conditions, two test process strings of oil pipe pressure and annulus pressure are proposed, which respectively meet the requirements of offshore heavy oil thermal recovery wells for monitoring the pressure inside the oil pipe and the annulus of the oil casing, and solve the problem of long-term and real-time online monitoring of downhole pressure in offshore heavy oil thermal recovery wells.

[0055] 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 monitoring system for heavy oil thermal recovery wells in offshore oil fields, characterized by: The invention comprises a downhole process pipe string and a high-temperature optical fiber pressure sensor (1) arranged in the downhole process pipe string; the high-temperature optical fiber pressure sensor (1) is connected to a pressure demodulator (3) arranged on the ground through a downhole monitoring optical cable (2); the high-temperature optical fiber pressure sensor (1) comprises a sealing body, an optical fiber pressure sensing chip arranged in the sealing body, and an optical fiber lead-out end assembly; the downhole process pipe string comprises an oil pipe hanger (41), an upper oil pipe (42), a high-temperature annular space safety packer (43), an insulated oil pipe (44), a jet pump working cylinder (45), a high-temperature deep well safety valve (46), and a lower oil pipe (47) connected in sequence, and a round plug (48) is arranged at the free end of the lower oil pipe (47); the downhole process pipe string and the downhole monitoring optical cable (2) are integrated in an external pipe bundling manner or an external pipe to internal pipe transfer manner.

2. The high-temperature optical fiber pressure monitoring system for heavy oil thermal recovery wells in offshore oil fields according to claim 1, characterized in that: The sealing body comprises a pressure-conducting end head (11), an annular end cover (12) and an optical cable connector (13) which are connected in sequence; the pressure-conducting end head (11) is a sleeve-type structure with open ends, the outer walls of both ends thereof are formed with external threads, the middle outer wall forms an external convex ring (15), and the inner wall of one end close to the pressure-conducting end head (11) forms an inner convex platform (14); the annular end cover (12) is composed of a sleeve portion and a truncated cone portion, both of which are hollow and open at both ends, the inner wall of the sleeve portion of the annular end cover (12) is formed with internal threads, and the small-diameter end of the truncated cone portion of the annular end cover (12) is connected to the optical cable connector (13).

3. The high-temperature optical fiber pressure monitoring system for heavy oil thermal recovery wells in offshore oil fields according to claim 1, characterized in that: The optical fiber pressure-sensitive chip comprises a pressure-sensitive diaphragm (16), a single-mode optical fiber (17), and a temperature-measuring optical fiber Bragg grating (18) and a pressure-measuring optical fiber Bragg grating (19) etched on the single-mode optical fiber (17); the pressure-sensitive diaphragm (16) is fixed inside the end of the pressure-conducting end head (11) away from the annular end cover (12), and the outer circumferential wall of the pressure-sensitive diaphragm (16) and the inner wall of the pressure-conducting end head (11) are fixedly connected by laser welding; one end of the single-mode optical fiber (17) is connected to the pressure-sensitive diaphragm (16), and the other end extends out of the optical cable connector (13); the temperature-measuring optical fiber Bragg grating (18) is arranged on the single-mode optical fiber (17) between the inner boss (14) and the optical cable connector (13); and the pressure-measuring optical fiber Bragg grating (19) is arranged on the single-mode optical fiber (17) close to the pressure-sensitive diaphragm (16).

4. The high-temperature optical fiber pressure monitoring system for heavy oil thermal recovery wells in offshore oil fields according to claim 3, characterized in that: The optical fiber pressure-sensitive chip further comprises a grating fixing mechanism and an optical fiber supporting mechanism; the grating fixing mechanism comprises a No. I supporting bridge (110) and a No. II supporting bridge (111); the No. I supporting bridge (110) is fixed to the inner side of the pressure-sensitive diaphragm (16), and the No. I supporting bridge (110) and the pressure-sensitive diaphragm (16) are made of the same material; the No. II supporting bridge (111) is fixed to the top of the inner boss (14) by laser welding; The optical fiber support mechanism comprises a capillary steel tube No. 1 (112) and a capillary steel tube No. 2 (113); the capillary steel tube No. 1 (112) is sleeved outside one end of the single-mode optical fiber (17) connected to the pressure-sensitive diaphragm (16), and the capillary steel tube No. 1 (112) is fixed to the support bridge No. 1 (110) by laser welding; the capillary steel tube No. 2 (113) is sleeved outside the middle section of the single-mode optical fiber (17), and is fixed to the support bridge No. 2 (111) by laser welding.

5. The high-temperature optical fiber pressure monitoring system for heavy oil thermal recovery wells in offshore oil fields according to claim 4, characterized in that: The No. I support bridge (110), the No. II support bridge (111) and the cavity of the sealing body are located on the same axis.

6. The high-temperature optical fiber pressure monitoring system for heavy oil thermal recovery wells in offshore oil fields according to claim 1, characterized in that: The optical fiber lead-out end assembly is arranged inside the optical cable connector (13), and comprises a capillary glass tube (114) sleeved outside the single-mode optical fiber (17) and a soft metal sealing ring (115) sleeved outside the capillary glass tube (114); the single-mode optical fiber (17) and the capillary glass tube (114) are fixed by laser welding.

7. The high-temperature optical fiber pressure monitoring system for heavy oil thermal recovery wells in offshore oil fields according to claim 1, characterized in that: When the downhole process pipe string and the downhole monitoring optical cable 2 are integrated in an external bundling manner, the high-temperature optical fiber pressure sensor (1) is arranged outside the lower oil pipe (47) near one end of the round plug (48), and the downhole monitoring optical cable (2) is arranged outside the oil pipe and connected to the oil pipe through an optical cable shield.

8. The high-temperature optical fiber pressure monitoring system for heavy oil thermal recovery wells in offshore oil fields according to claim 1, characterized in that: When the downhole process pipe string and the downhole monitoring optical cable (2) are integrated in an outside-pipe-inside-pipe manner, the downhole process pipe string further comprises an optical cable crossing Y-joint (49), the optical cable crossing Y-joint (49) is arranged between the high-temperature deep well safety valve (46) and the lower oil pipe (47), the high-temperature optical fiber pressure sensor (1) is arranged inside the lower oil pipe (17) near one end of the round plug (48), the downhole monitoring optical cable (2) above the optical cable crossing Y-joint (49) is arranged outside the oil pipe, and the downhole monitoring optical cable (2) passes through the optical cable crossing Y-joint (49) and then extends into the lower oil pipe (47).

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