A wellhead optical cable pressure relief device and its installation method

Abstract

This invention discloses a wellhead optical cable pressure relief device and its installation method. In a first aspect, the device is used to embed an optical cable having, from the outside in, an outer sheath, an outer protective tube, an optical fiber unit, and an optical fiber core. It includes an isolation plate for pre-sealing the optical fiber core, allowing the core to pass through both sides. One side of the isolation plate has a low-pressure cavity for sealing and placing the exposed optical fiber core connected to the optical fiber core on the isolation plate. The other side of the isolation plate, along the direction away from the isolation plate, has a second high-pressure cavity for sealing and placing the exposed optical fiber core connected to the optical fiber core on the isolation plate, and a first high-pressure cavity for sealing and placing the exposed optical fiber unit. In a second aspect, the device provides an installation method. This invention can provide early warning and diversion for leaked oil / gas within the wellhead optical cable, preventing safety accidents.

Description

Technical Field

[0001] This invention relates to the field of logging optical cable technology, specifically to a wellhead optical cable pressure relief device and its installation method. Background Technology

[0002] Currently, with the development of domestic petroleum technology and the continuous improvement of casing external optical cable installation technology, downhole optical cable installation technology has become the engineering foundation of optical fiber reservoir geophysics business. In order to realize long-term dynamic monitoring of oil wells, more and more new wells have carried out permanent installation of casing external optical cables.

[0003] Engineering accidents or other reasons can cause damage to underground optical cables, leading to the leakage of high-pressure fluids, especially toxic and harmful gases, to the surface through the optical fiber unit, posing a significant safety hazard. If this safety hazard is not effectively addressed, it will seriously hinder the development of this business. Summary of the Invention

[0004] The purpose of this invention is to provide a wellhead optical cable pressure relief device and its installation method, which can provide early warning and diversion for oil / gas leakage inside the wellhead optical cable, and prevent the occurrence of safety accidents.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following solution:

[0006] In a first aspect, a wellhead optical cable pressure relief device is provided for embedding an optical cable having an outer sheath, an outer protective tube, an optical fiber unit, and an optical fiber core arranged sequentially from the outside to the inside. The device includes an isolation plate for pre-sealing the optical fiber core, allowing the optical fiber core to pass through both sides of the device. One side of the isolation plate is provided with a low-pressure cavity for sealing and placing the optical cable with the exposed optical fiber core connected to the optical fiber core on the isolation plate. The other side of the isolation plate is provided with a second high-pressure cavity for sealing and placing the optical cable with the exposed optical fiber core connected to the optical fiber core on the isolation plate and a first high-pressure cavity for sealing and placing the optical cable with the exposed optical fiber unit in sequence along the direction away from the isolation plate. The first high-pressure cavity and the second high-pressure cavity are each connected to a pressure relief channel for pressure relief. Its function is to provide corresponding pressure relief operations for different parts of the optical cable when damaged, based on the cable's structure: When the outer protective tube of the downhole optical cable is damaged, the downhole gas / liquid, under high pressure, passes through the damaged area and reaches the first high-pressure chamber, where it is depressurized separately through its pressure relief channel; when the outer protective tube of the downhole optical cable is damaged, causing the fiber optic unit to break, the downhole gas / liquid, under high pressure, passes through the damaged area and reaches both the first and second high-pressure chambers, where it is depressurized through its respective pressure relief channel. The low-pressure chamber is used to install and place the downhole optical cable located in the low-pressure environment outside the well. The isolation plate facilitates the connection between the downhole optical cable that passes through the first and second high-pressure chambers and is partially located in the downhole high-pressure environment, and the downhole optical cable that passes through the low-pressure chamber and is located in the low-pressure environment outside the well.

[0007] Furthermore, it also includes a through-cavity equipped with an isolation plate. One end of the through-cavity is connected to a tail-end sealing cap, and the other end of the through-cavity is connected to a sealed double-cavity. The end of the sealed double-cavity away from the isolation plate is connected to an optical cable spool. The optical cable spool and the sealed double-cavity form a first high-pressure cavity, the sealed double-cavity and the through-cavity form a second high-pressure cavity, and the through-cavity and the tail-end sealing cap form a low-pressure cavity. Its function is to form the first high-pressure cavity through the optical cable spool and the sealed double-cavity, the second high-pressure cavity through the sealed double-cavity and the through-cavity, and the low-pressure cavity through the tail-end sealing cap and the through-cavity.

[0008] Furthermore, the isolation plate is threadedly connected to at least one third sealing element for sealingly connecting with the optical fiber core and allowing the optical fiber core to pass through both ends. The isolation plate has a through-hole connecting the second high-pressure chamber and the low-pressure chamber, and the third sealing element is connected within the through-hole. Its function is to pre-seal a section of the optical fiber core within the third sealing element, ensuring that both ends of the optical fiber core are located outside the opposite sides of the isolation plate; the threaded connection between the third sealing element and the isolation plate achieves a sealed connection.

[0009] Furthermore, a first protective tube hole for placing an outer protective tube is provided through the optical cable spool. At the end of the first protective tube hole away from the isolation plate, a first retaining sleeve is provided for fitting over the outer protective tube. At the end of the first protective tube hole facing the isolation plate, a first sealing element is provided for fitting over the outer protective tube and sealingly connecting with it. The inner diameter of the first retaining sleeve matches the outer diameter of the outer protective tube. Its function is to provide a basic seal between the outer protective tube and the optical cable spool through the first retaining sleeve, and to further seal between the outer protective tube and the optical cable spool through the first sealing element, preventing gas / oil from entering the first high-pressure chamber through the gap between the outer protective tube and the optical cable spool.

[0010] Furthermore, the sealed dual-cavity body is provided with an optical fiber unit hole for placing the optical fiber unit. A second sealing element is provided at the end of the optical fiber unit hole facing the isolation plate, for fitting over the optical fiber unit and sealingly connecting with it. Its function is to seal the optical fiber unit and the sealed dual-cavity body, preventing gas / oil from entering the second high-pressure chamber through the gap between the optical fiber unit and the sealed dual-cavity body.

[0011] Furthermore, the tail-end sealing cap has a second protective tube hole for placing the outer protective tube. At the end of the second protective tube hole away from the isolation plate, there is a second retainer for fitting over the outer protective tube. At the end of the second protective tube hole facing the isolation plate, there is a fourth sealing element for fitting over the outer protective tube and sealingly connecting with it. Its function is to seal the outer protective tube and the tail-end sealing cap, preventing external impurities from entering the low-pressure chamber through the gap between the outer protective tube and the tail-end sealing cap.

[0012] Furthermore, both the sealed dual-cavity body and the tail-end sealing cap have buffer cavities at the ends facing the isolation plate. Their function is that when the optical cable is installed in the second high-pressure or low-pressure cavity, the two optical fiber cores within the second high-pressure or low-pressure cavity need to be fused together before connecting the sealed dual-cavity body to the through-cavity or connecting the tail-end sealing cap to the through-cavity. Therefore, a relatively long optical fiber core needs to be reserved in the second high-pressure or low-pressure cavity. To avoid the long optical fiber core becoming tangled and messy, the optical fiber core needs to be spirally coiled within the second high-pressure or low-pressure cavity. To prevent the optical fiber core from bending directly from the exit point during coiling, which could easily break, buffer cavities are provided at the ends of both the sealed dual-cavity body and the tail-end sealing cap facing the isolation plate. These buffer cavities provide a buffer distance at the exit point for the optical fiber core, preventing bending.

[0013] Furthermore, the pressure relief channel includes a first mounting hole and a second mounting hole. A first mounting hole, connected to the first high-pressure chamber, is provided on the side wall of the sealed dual-chamber for sealing and mounting a pressure gauge with a normally closed pressure relief valve. A second mounting hole, connected to the second high-pressure chamber, is provided on the side wall penetrating the chamber for sealing and mounting a pressure gauge with a pressure relief valve. Its function is to control and maintain the high-pressure state of the first and second high-pressure chambers and to perform pressure relief operations through the normally closed pressure relief valve. The pressure gauge facilitates the observation of the pressure in the first and second high-pressure chambers, thereby understanding the damage status of the optical cable, serving as an early warning system, and preventing safety accidents.

[0014] Furthermore, the optical cable shaft includes a first end cap and a first embedded portion arranged sequentially towards the isolation plate; the sealed dual-cavity body includes a first mounting cavity, a second end cap, and a second embedded portion arranged sequentially towards the isolation plate; the through cavity includes a second mounting cavity facing the sealed dual-cavity body with the isolation plate as the boundary and a third mounting cavity facing the tail end sealing cover; the tail end sealing cover includes a third end cap and a third embedded portion arranged sequentially towards the isolation plate; the outer diameter of the first embedded portion matches the inner diameter of the first mounting cavity; the outer diameter of the second embedded portion matches the inner diameter of the second mounting cavity; and the outer diameter of the third embedded portion matches the inner diameter of the third mounting cavity. The inner diameters of the mounting cavities are matched. The outer walls of the first, second, and third embedding parts are all surrounded by annular grooves for installing O-rings. Sealing gaskets are provided on the contact surfaces between the first end cap and the sealed double cavity, the second end cap and the through cavity, and the third end cap and the through cavity. Annular mounting grooves for placing sealing gaskets are provided on the end faces of the sealed double cavity and / or the optical cable spool and / or the through cavity and / or the tail end sealing cap. Each sealing gasket is connected to the contacting objects by annularly distributed bolts. Its function is to achieve a sealed connection between the optical cable spool and the sealed double cavity, between the sealed double cavity and the through cavity, and between the through cavity and the tail end sealing cap through the annular grooves for installing O-rings and the annular mounting grooves for installing sealing gaskets; and to achieve a fixed connection between the optical cable spool and the sealed double cavity, between the sealed double cavity and the through cavity, and between the through cavity and the tail end sealing cap through the bolts.

[0015] Secondly, a method for installing a wellhead optical cable pressure relief device includes the following steps:

[0016] Step S1: Seal and install optical fiber cores that penetrate both sides of the isolation plate on the isolation plate;

[0017] Step S2: Strip the outer sheath and outer protective tube of the optical cable to expose the optical fiber unit, so that the section of the optical cable exposing the optical fiber unit is located in the first high-voltage cavity.

[0018] Step S3: Strip the optical fiber unit of the optical cable extending from the first high-voltage cavity to expose the optical fiber core, and fusion splice the optical fiber core with the optical fiber core on the side of the isolation plate facing the second high-voltage cavity so that the section of the optical cable with the exposed optical fiber core is located in the second high-voltage cavity.

[0019] Step S4: Strip the outer sheath, outer protective tube, and fiber unit of the other optical cable to expose the fiber core. Then, fusion splice the fiber core with the fiber core on the side of the isolation plate facing the low-pressure cavity, so that the section of the other optical cable with the exposed fiber core is located inside the low-pressure cavity.

[0020] Furthermore, it also includes the following steps:

[0021] Step S1a: In step S1, the fiber core is passed through the third sealing member provided on the isolation plate, so that the two ends of the fiber core are respectively located on both sides of the isolation plate, and then the fiber core is sealed in the third sealing member with glue.

[0022] Step S1b: After step S1a, a pressure test is performed on the third seal to ensure the sealing performance of the pre-fabricated optical fiber core within the third seal.

[0023] Step S2a: In step S2, first peel off the outer sheath of an optical cable to expose the outer protective tube. Then, pass the outer protective tube through the first ferrule, the first protective tube hole on the optical cable shaft, and the first seal in sequence. Then, connect the first ferrule and the first seal to the optical cable shaft. Finally, weld and seal the outer protective tube and the first seal.

[0024] Step S2b: After step S2a, the outer protective tube of the optical cable passing through the first seal is stripped to expose the optical fiber unit. After inserting the tail end of the optical fiber unit into the optical fiber unit hole of the sealed dual cavity, an O-ring is installed in the annular groove on the side wall of the first embedded part. The first embedded part on the optical cable shaft is installed into the first mounting cavity on the sealed dual cavity. After setting a sealing gasket between the first end cap on the optical cable shaft and the facing surfaces of the sealed dual cavity, the first end cap is brought into contact with the sealed dual cavity. Then, the first end cap is connected to the sealed dual cavity by the annularly distributed bolts to achieve a sealed connection between the optical cable shaft and the sealed dual cavity. The optical fiber unit passes through the optical fiber unit hole. Then, the optical fiber unit passing through the optical fiber unit hole passes through the second seal and the second seal is connected to the sealed dual cavity. Then, the optical fiber unit and the second seal are welded and sealed so that the section of the optical cable exposing the optical fiber unit is located in the first high-pressure cavity formed by the optical cable shaft and the sealed dual cavity.

[0025] Step S3a: In step S3, the optical fiber unit of the optical cable passing through the second seal is stripped to expose the optical fiber core, and the optical fiber core is fused with the optical fiber core on the side of the isolation plate facing the second seal.

[0026] Step S3b: After step S3a, an O-ring is installed in the annular groove on the side wall of the second embedded part. The second embedded part on the sealed double cavity is installed into the second mounting cavity on the through cavity. After a sealing gasket is placed between the second end cap on the sealed double cavity and the facing surfaces of the through cavity, the second end cap is brought into contact with the through cavity. Then, the second end cap is connected to the through cavity by the annularly distributed bolts, so that the sealed double cavity and the through cavity are sealed together, and the section of the optical cable with the exposed fiber core is located in the second high-voltage cavity formed by the sealed double cavity and the through cavity.

[0027] Step S4a: In step S4, first strip the outer sheath of the other optical cable to expose the outer protective tube. Then, pass the outer protective tube through the second ferrule, the second protective tube hole on the tail end sealing cap, and the fourth sealing element in sequence. Then, connect the second ferrule and the fourth sealing element to the tail end sealing cap. Finally, weld the outer protective tube and the fourth sealing element to seal them.

[0028] Step S4b: After step S4a, strip the outer protective tube and fiber unit of the optical cable passing through the fourth seal to expose the fiber core, and fusion splice the fiber core with the fiber core on the side of the isolation plate facing the fourth seal.

[0029] Step S4c: After step S4b, an O-ring is installed in the annular groove on the side wall of the third embedded part. The third embedded part on the tail end sealing cover is installed into the third mounting cavity on the through cavity. After a sealing gasket is placed between the facing surfaces of the third end cover and the through cavity, the third end cover is brought into contact with the through cavity. Then, the second end cover is connected to the through cavity by the annularly distributed bolts to achieve a sealed connection between the tail end sealing cover and the through cavity, so that the section of the other optical cable with the exposed fiber core is located in the low-pressure cavity formed by the tail end sealing cover and the through cavity.

[0030] Step S4d: After step S4c, install pressure gauges with normally closed pressure relief valves in both the first mounting hole and the second mounting hole.

[0031] The beneficial effects of this invention are as follows:

[0032] 1. Based on the structure of the optical cable, a first high-pressure chamber and a second high-pressure chamber are set up to perform corresponding pressure relief operations for damage to different parts of the optical cable: When the outer protective tube of the underground optical cable is damaged, the underground gas / liquid under high pressure passes through the damaged area to reach the first high-pressure chamber, and the pressure relief channel in the first high-pressure chamber is used to relieve pressure separately; when the outer protective tube of the underground optical cable is damaged and causes the optical fiber unit to be damaged, the underground gas / liquid under high pressure passes through the damaged area to reach the first high-pressure chamber and the second high-pressure chamber respectively, and the pressure is relieved through their respective pressure relief channels;

[0033] 2. The low-pressure chamber is used to install and place optical cables located in the low-pressure environment outside the well.

[0034] 3. The isolation plate facilitates the connection between the underground optical cable that passes through the first high-pressure chamber and the second high-pressure chamber and is partially located in the underground high-pressure environment, and the underground optical cable that passes through the low-pressure chamber and is located in the underground low-pressure environment. Attached Figure Description

[0035] Figure 1 A three-dimensional structural diagram of a wellhead optical cable pressure relief device equipped with optical cables;

[0036] Figure 2 A cross-sectional schematic diagram of a wellhead optical cable pressure relief device equipped with an optical cable;

[0037] Figure 3 for Figure 2 A cross-sectional schematic diagram of the optical cable shaft and the sealed double cavity that constitute the first high-voltage cavity;

[0038] Figure 4 for Figure 2 A cross-sectional schematic diagram of the sealed double cavity and the through cavity that constitute the second high-pressure cavity;

[0039] Figure 5 for Figure 2 A cross-sectional view of the through cavity that forms the low-pressure chamber and the tail-end sealing cap.

[0040] The reference numerals in the attached drawings are explained as follows: 1. Outer sheath; 2. Outer protective tube; 3. Fiber optic unit; 4. Fiber optic core; 5. Isolation plate; 6. Low-pressure cavity; 7. First high-pressure cavity; 8. Second high-pressure cavity; 9. Through cavity; 10. Tail end sealing cap; 11. Sealed double cavity; 12. Optical cable reel; 13. First sealing element; 14. Second sealing element; 15. Third sealing element; 16. Fourth sealing element; 17. First protective tube hole; 18. Second protective tube hole; 19. First ferrule; 20. Second ferrule; 21. Fiber optic unit hole; 22. Buffer cavity; 23. First mounting hole; 24. Second mounting hole. Detailed Implementation

[0041] The present invention will be further described in detail below with reference to the embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto.

[0042] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "longitudinal," "lateral," "horizontal," "inner," "outer," "front," "rear," "top," and "bottom," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this invention is in use. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0043] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set up," "have," "install," "connect," and "connect" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0044] Example 1

[0045] Firstly, such as Figure 2As shown, a wellhead optical cable pressure relief device is used to embed an optical cable having an outer sheath 1, an outer protective tube 2, an optical fiber unit 3, and an optical fiber core 4 arranged sequentially from the outside to the inside. The device includes an isolation plate 5 for pre-sealing the optical fiber core 4, allowing the optical fiber core 4 to pass through both sides of itself. One side of the isolation plate 5 has a low-pressure cavity 6 for sealing and placing the optical cable with exposed optical fiber core 4 connected to the optical fiber core 4 on the isolation plate 5. The other side of the isolation plate 5, along a direction away from the isolation plate 5, has a second high-pressure cavity 8 for sealing and placing the optical cable with exposed optical fiber core 4 connected to the optical fiber core 4 on the isolation plate 5, and a first high-pressure cavity 7 for sealing and placing the optical cable with exposed optical fiber unit 3. The first high-pressure cavity 7 and the second high-pressure cavity 8 are each connected to a pressure relief channel for pressure relief. Its function is to provide corresponding pressure relief operations for different parts of the optical cable when the outer protective tube 2 of the underground optical cable is damaged, based on the structure of the optical cable: When the outer protective tube 2 of the underground optical cable is damaged, the underground gas / liquid under high pressure passes through the damaged area, along the gap between the outer protective tube 2 and the optical fiber unit 3, and reaches the first high-pressure chamber 7, where it is depressurized separately through the pressure relief channel; when the outer protective tube 2 of the underground optical cable is damaged, causing the optical fiber unit 3 to be damaged, the underground gas / liquid under high pressure passes through the damaged area, along the gap between the outer protective tube 2 and the optical fiber unit 3 and the gap between the optical fiber unit 3 and the optical fiber core 4, respectively, and reaches the first high-pressure chamber 7 and the second high-pressure chamber 8, where it is depressurized through its respective pressure relief channel. The low-pressure chamber 6 is used to install and place the underground optical cable located in the low-pressure environment outside the well. The isolation plate 5 facilitates the connection between the underground optical cable that passes through the first high-pressure chamber 7 and the second high-pressure chamber 8 and is partially located in the underground high-pressure environment, and the underground optical cable that passes through the low-pressure chamber 6 and is located in the underground low-pressure environment.

[0046] Specifically, such as Figure 1 , Figure 2As shown, it also includes a through cavity 9 with an isolation plate 5. One end of the through cavity 9 is connected to a tail end sealing cap 10, and the other end of the through cavity 9 is connected to a sealed double cavity 11. The end of the sealed double cavity 11 away from the isolation plate 5 is connected to an optical cable shaft 12. The optical cable shaft 12 and the sealed double cavity 11 form a first high-pressure cavity 7 after being connected, and the sealed double cavity 11 and the through cavity 9 form a second high-pressure cavity 8 after being connected. The through cavity 9 and the tail end sealing cap 10 form a low-pressure cavity 6 after being connected. The outer contours of the through cavity 9, the tail end sealing cap 10, the sealed double cavity 11, and the optical cable shaft 12 are all in the shape of a rotating body. The axes of the through cavity 9, the tail end sealing cap 10, the sealed double cavity 11, and the optical cable shaft 12 are all located on the same straight line. The through cavity 9 has a cylindrical cavity that runs through the front and rear end faces of the through cavity 9 and is coaxially arranged with the through cavity 9. The cylindrical cavity is divided into a second mounting cavity and a third mounting cavity in the middle by the isolation plate 5. Its function is to form a first high-pressure chamber 7 by means of the optical cable shaft 12 and the sealed double cavity 11, to form a second high-pressure chamber 8 by means of the sealed double cavity 11 and the through cavity 9, and to form a low-pressure chamber 6 by means of the tail end sealing cover 10 and the through cavity 9.

[0047] Specifically, such as Figure 2 As shown, the isolation plate 5 is threadedly connected to at least one third sealing element 15 for sealingly connecting with the optical fiber core 4 and allowing the optical fiber core 4 to pass through both ends of itself. The isolation plate 5 has a through-hole connecting the second high-pressure chamber 8 and the low-pressure chamber 6, and the third sealing element 15 is connected within the through-hole. Its function is to pre-seal a section of the optical fiber core 4 within the third sealing element 15, ensuring that both ends of the optical fiber core 4 are located outside the opposite sides of the isolation plate 5; the threaded connection between the third sealing element 15 and the isolation plate 5 achieves a sealed connection.

[0048] Specifically, such as Figure 3 As shown, the optical cable spool 12 has a first protective tube hole 17 for placing the outer protective tube 2. At the end of the first protective tube hole 17 away from the isolation plate 5, there is a first retaining sleeve 19 for fitting over the outer protective tube 2. At the end of the first protective tube hole facing the isolation plate 5, there is a first sealing element 13 for fitting over the outer protective tube 2 and sealingly connecting with it. The inner diameter of the first retaining sleeve 19 matches the outer diameter of the outer protective tube 2. The first retaining sleeve 19 is threadedly connected to the optical cable spool 12 and communicates with the first protective tube hole 17. The first sealing element 13 is threadedly connected to the optical cable spool 12 and communicates with the first protective tube hole 17. Its function is to provide a basic seal between the outer protective tube 2 and the optical cable spool 12 through the first retaining sleeve 19, and to further seal between the outer protective tube 2 and the optical cable spool 12 through the first sealing element 13, preventing gas / oil from entering the first high-pressure chamber 7 through the gap between the outer protective tube 2 and the optical cable spool 12.

[0049] Specifically, such as Figure 4 As shown, the sealed dual-cavity body 11 has a through-hole 21 for placing the optical fiber unit 3. At the end of the optical fiber unit hole 21 facing the isolation plate 5, a second sealing element 14 is provided for fitting over the optical fiber unit 3 and sealingly connecting with it. The second sealing element 14 is threadedly connected to the sealed dual-cavity body 11 and communicates with the optical fiber unit hole 21. Its function is to seal the space between the optical fiber unit 3 and the sealed dual-cavity body 11, preventing gas / oil from entering the second high-pressure chamber 8 through the gap between the optical fiber unit 3 and the sealed dual-cavity body 11.

[0050] Specifically, such as Figure 5 As shown, the tail-end sealing cap 10 has a second protective tube hole 18 for placing the outer protective tube 2. At the end of the second protective tube hole 18 away from the isolation plate 5, there is a second retaining sleeve 20 for fitting over the outer protective tube 2. At the end of the second protective tube hole 18 facing the isolation plate 5, there is a fourth sealing element 16 for fitting over the outer protective tube 2 and sealingly connecting with it. The inner diameter of the second retaining sleeve 20 matches the outer diameter of the outer protective tube 2. The second retaining sleeve 20 is threadedly connected to the tail-end sealing cap 10 and communicates with the second protective tube hole 18. The fourth sealing element 16 is threadedly connected to the tail-end sealing cap 10 and communicates with the second protective tube hole 18. Its function is to seal the space between the outer protective tube 2 and the tail-end sealing cap 10 through the gap between them, preventing external impurities from entering the low-pressure chamber 6.

[0051] Specifically, such as Figure 4 , Figure 5 As shown, both the sealed dual-cavity body 11 and the tail-end sealing cap 10 have buffer cavities 22 at the ends facing the isolation plate 5. Their function is that when the optical cable is installed in the second high-pressure cavity 8 or the low-pressure cavity 6, the two optical fiber cores 4 in the second high-pressure cavity 8 or the low-pressure cavity 6 need to be fused together before connecting the sealed dual-cavity body 11 to the through-cavity 9 or connecting the tail-end sealing cap 10 to the through-cavity 9. Therefore, a longer optical fiber core 4 needs to be reserved in the second high-pressure cavity 8 or the low-pressure cavity 6. To avoid the longer optical fiber core 4 becoming tangled and messy, the optical fiber core 4 needs to be spirally coiled in the second high-pressure cavity 8 or the low-pressure cavity 6. To prevent the optical fiber core 4 from bending directly from the exit point during coiling, which could easily break, buffer cavities 22 are provided at the ends facing the isolation plate 5 of both the sealed dual-cavity body 11 and the tail-end sealing cap 10 to provide a buffer distance at the exit point of the optical fiber core 4, preventing bending.

[0052] Specifically, such as Figure 2As shown, the pressure relief channel includes a first mounting hole 23 and a second mounting hole 24. The side wall of the sealed double-cavity 11 has a first mounting hole 23 for sealing and installing a pressure gauge with a pressure relief valve, which is connected to the first high-pressure cavity 7. The side wall passing through the cavity 9 has a second mounting hole 24 for sealing and installing a pressure gauge with a pressure relief valve, which is connected to the second high-pressure cavity 8. Both the first mounting hole 23 and the second mounting hole 24 are threaded holes. Their function is to control and maintain the high-pressure state of the first high-pressure cavity 7 and the second high-pressure cavity 8 and to perform pressure relief operations through the normally closed pressure relief valve. The pressure gauge facilitates the observation of the pressure in the first high-pressure cavity 7 and the second high-pressure cavity 8, thereby understanding the damage status of the optical cable, serving as an early warning system, and preventing safety accidents.

[0053] Specifically, such as Figure 2 , Figure 3 , Figure 4 , Figure 5As shown, the optical cable shaft 12 includes a first end cap and a first embedded part arranged sequentially toward the isolation plate 5. The sealed double cavity 11 includes a first mounting cavity, a second end cap, and a second embedded part arranged sequentially toward the isolation plate 5. The through cavity 9 includes a second mounting cavity toward the sealed double cavity 11 with the isolation plate 5 as the boundary and a third mounting cavity toward the tail end sealing cover 10. The tail end sealing cover 10 includes a third end cap and a third embedded part arranged sequentially toward the isolation plate 5. The outer diameter of the first embedded part matches the inner diameter of the first mounting cavity, the outer diameter of the second embedded part matches the inner diameter of the second mounting cavity, and the outer diameter of the third embedded part matches the inner diameter of the third mounting cavity. The outer walls of the first embedded part, the second embedded part, and the third embedded part are all surrounded by annular grooves for installing O-ring seals. Sealing gaskets are provided on the contact surfaces between the first end cap and the sealed double cavity 11, between the second end cap and the through cavity 9, and between the third end cap and the through cavity 9. Each sealing gasket is connected to the two contacting objects by bolts arranged in a ring. The outer diameter of the first end cap is larger than the outer diameter of the first embedded part, the outer diameter of the second end cap is larger than the outer diameter of the second embedded part, and the outer diameter of the third end cap is larger than the outer diameter of the third embedded part. Annular mounting grooves for placing sealing gaskets are provided on the end faces of the sealed double cavity 11 that contact the optical cable shaft 12, the end faces of the through cavity 9 that contact the sealed double cavity 11, and the end faces of the through cavity 9 that contact the tail end sealing cap 10. The annular mounting grooves are concentrically arranged with their respective mounting cavities on their respective end faces, and their inner diameters are larger than the inner diameters of their respective mounting cavities. Its function is to achieve a sealed connection between the optical cable spool 12 and the sealed double cavity 11, between the sealed double cavity 11 and the through cavity 9, and between the through cavity 9 and the tail end sealing cover 10 by setting an annular groove for installing an O-ring and an annular mounting groove for installing a sealing gasket; and to achieve a fixed connection between the optical cable spool 12 and the sealed double cavity 11, between the sealed double cavity 11 and the through cavity 9, and between the through cavity 9 and the tail end sealing cover 10 by setting bolts.

[0054] Secondly, a method for installing a wellhead optical cable pressure relief device includes the following steps:

[0055] Step S1: Seal and install optical fiber cores 4 that penetrate both sides of the isolation plate 5 on the isolation plate 5;

[0056] Step S2: Strip the outer sheath 1 and outer protective tube 2 of the optical cable to expose the optical fiber unit 3, so that the section of the optical cable exposing the optical fiber unit 3 is located in the first high-voltage cavity 7.

[0057] Step S3: Strip the optical fiber unit 3 of the optical cable extending from the first high-voltage cavity 7 to expose the optical fiber core 4, and fusion splice the optical fiber core 4 with the optical fiber core 4 on the side of the isolation plate 5 facing the second high-voltage cavity 8 so that the section of the optical cable exposing the optical fiber core 4 is located inside the second high-voltage cavity 8.

[0058] Step S4: Strip off the outer sheath 1, outer protective tube 2, and optical fiber unit 3 of the other optical cable to expose the optical fiber core 4. Then, fusion splice the optical fiber core 4 with the optical fiber core 4 on the side of the isolation plate 5 facing the low-pressure cavity 6, so that the section of the other optical cable exposing the optical fiber core 4 is located inside the low-pressure cavity 6.

[0059] Specifically, it also includes the following steps:

[0060] Step S1a: In step S1, the optical fiber core 4 is passed through the third sealing member 15 provided on the isolation plate 5, so that the two ends of the optical fiber core 4 are respectively located on both sides of the isolation plate 5, and then the optical fiber core 4 is sealed in the third sealing member 15 with glue.

[0061] Step S1b: After step S1a, a pressure test is performed on the third sealing element 15 to ensure the sealing performance of the pre-fabricated optical fiber core 4 within the third sealing element 15.

[0062] Step S2a: In step S2, first peel off the outer sheath 1 of an optical cable to expose the outer protective tube 2. Then, pass the outer protective tube 2 through the first clamp 19, the first protective tube hole 17 on the optical cable shaft 12, and the first seal 13 in sequence. Then, connect the first clamp 19 and the first seal 13 to the optical cable shaft 12. After that, weld and seal the outer protective tube 2 and the first seal 13.

[0063] Step S2b: After step S2a, strip the outer protective tube 2 of the optical cable that passes through the first seal 13 to expose the optical fiber unit 3. Insert the tail end of the optical fiber unit 3 into the optical fiber unit hole 21 of the sealed dual cavity 11. Install an O-ring seal in the annular groove on the side wall of the first embedding part. By inserting the first embedding part on the optical cable shaft 12 into the first mounting cavity on the sealed dual cavity 11, and after setting a sealing gasket between the first end cap on the optical cable shaft 12 and the facing surfaces of the sealed dual cavity 11, the first end cap comes into contact with the sealed dual cavity 11. Then, the first end cap is connected to the sealed double cavity 11 by bolts arranged in a ring, so that the optical cable shaft 12 and the sealed double cavity 11 are sealed together, allowing the optical fiber unit 3 to pass through the optical fiber unit hole 21. Then, the optical fiber unit 3 passing through the optical fiber unit hole 21 is passed through the second sealing member 14, and the second sealing member 14 is connected to the sealed double cavity 11. Then, the optical fiber unit 3 and the second sealing member 14 are welded and sealed, so that the section of the optical cable exposed by the optical fiber unit 3 is located in the first high-pressure cavity 7 formed by the optical cable shaft 12 and the sealed double cavity 11.

[0064] Step S3a: In step S3, the optical fiber unit 3 of the optical cable passing through the second seal 14 is stripped to expose the optical fiber core 4, and the optical fiber core 4 is fused with the optical fiber core 4 on the side of the isolation plate 5 facing the second seal 14.

[0065] Step S3b: After step S3a, an O-ring is installed in the annular groove on the side wall of the second embedded part. The second embedded part on the sealed double cavity 11 is installed into the second mounting cavity on the through cavity 9. After a sealing gasket is placed between the second end cap on the sealed double cavity 11 and the facing surfaces of the through cavity 9, the second end cap is brought into contact with the through cavity 9. Then, the second end cap is connected to the through cavity 9 by the annularly distributed bolts, so that the sealed double cavity 11 and the through cavity 9 are sealed together, and the section of the optical cable with the exposed fiber core 4 is located in the second high-voltage cavity 8 formed by the sealed double cavity 11 and the through cavity 9.

[0066] Step S4a: In step S4, first peel off the outer sheath 1 of the other optical cable to expose the outer protective tube 2. Then, pass the outer protective tube 2 through the second ferrule 20, the second protective tube hole 18 on the tail end sealing cap 10, and the fourth sealing member 16 in sequence. Then, connect the second ferrule 20 and the fourth sealing member 16 to the tail end sealing cap 10. After that, weld and seal the outer protective tube 2 and the fourth sealing member 16.

[0067] Step S4b: After step S4a, strip the outer protective tube 2 and optical fiber unit 3 of the optical cable passing through the fourth seal 16 to expose the optical fiber core 4, and fused the optical fiber core 4 with the optical fiber core 4 on the side of the isolation plate 5 facing the fourth seal 16.

[0068] Step S4c: After step S4b, an O-ring is installed in the annular groove on the side wall of the third embedded part. The third embedded part on the tail end sealing cover 10 is installed into the third mounting cavity on the through cavity 9. After a sealing gasket is placed between the facing surfaces of the third end cover and the through cavity 9, the third end cover is brought into contact with the through cavity 9. Then, the second end cover is connected to the through cavity 9 by the annularly distributed bolts, so that the tail end sealing cover 10 and the through cavity 9 are sealed together, and the section of the other optical cable with the exposed fiber core 4 is located in the low-pressure cavity 6 formed by the tail end sealing cover 10 and the through cavity 9.

[0069] Step S4d: After step S4c, pressure gauges with normally closed pressure relief valves are installed in both the first mounting hole 23 and the second mounting hole 24.

[0070] The working principle of this embodiment is explained as follows: By setting the first sealing element 13, the second sealing element 14, the third sealing element 15, and the fourth sealing element 16, it is possible to avoid the difficulty in removing the previous welding points when the optical cable is welded to the optical cable shaft 12, the sealed double cavity 11, or the tail end sealing cover 10 and the optical cable, if an error occurs in the subsequent installation steps.

[0071] When the outer protective tube 2 of the downhole optical cable is damaged, the downhole gas / liquid under high pressure passes through the damaged area and along the gap between the outer protective tube 2 and the optical fiber unit 3 to reach the first high-pressure chamber 7. The first high-pressure chamber 7 is depressurized or diverted separately through the pressure relief valve installed in the first mounting hole 23 on the sealed double chamber 11. After leakage, the pressure can be detected in real time by the pressure gauge installed in the first mounting hole 23.

[0072] When the outer protective tube 2 of the underground optical cable is damaged, causing the optical fiber unit 3 to be damaged, the underground gas / liquid under high pressure will pass through the damaged area and along the gap between the outer protective tube 2 and the optical fiber unit 3 and the gap between the optical fiber unit 3 and the optical fiber core 4, respectively, into the first high-pressure chamber 7 and the second high-pressure chamber 8. The pressure will be released or diverted through the pressure relief valve in the first mounting hole 23 installed on the sealed double chamber 11 and the pressure relief valve in the second mounting hole 24 installed on the through chamber 9, respectively. After leakage, the pressure can be detected in real time by the pressure gauges installed in the first mounting hole 23 and the second mounting hole 24.

[0073] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Based on the technical essence of the present invention, any simple modifications, equivalent substitutions, and improvements made to the above embodiments within the spirit and principles of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A wellhead optical cable pressure relief device, used for an optical cable with an outer sheath (1), an outer protective tube (2), an optical fiber unit (3), and an optical fiber core (4) arranged sequentially from the outside to the inside, characterized in that: Includes a pre-sealed optical fiber core (4) and an isolation plate (5) through which the optical fiber core (4) passes through both sides of itself. One side of the isolation plate (5) is provided with a low-pressure cavity (6) for sealing and placing an optical cable with exposed optical fiber core (4) and connected to the optical fiber core (4) on the isolation plate (5). On the other side of the isolation plate (5), along the direction away from the isolation plate (5), there are a second high-pressure cavity (8) for sealing and placing an optical cable with exposed optical fiber core (4) and connected to the optical fiber core (4) on the isolation plate (5) and a first high-pressure cavity (7) for sealing and placing an optical cable with exposed optical fiber unit (3). The first high-pressure cavity (7) and the second high-pressure cavity (8) are each connected to a pressure relief channel for pressure relief. It also includes a through cavity (9) with an isolation plate (5), one end of the through cavity (9) is connected to a tail end sealing cap (10), and the other end of the through cavity (9) is connected to a sealed double cavity (11). The end of the sealed double cavity (11) away from the isolation plate (5) is connected to an optical cable shaft (12). After the optical cable shaft (12) and the sealed double cavity (11) are connected, they form a first high-pressure cavity (7). After the sealed double cavity (11) and the through cavity (9) are connected, they form a second high-pressure cavity (8). After the through cavity (9) and the tail end sealing cap (10) are connected, they form a low-pressure cavity (6).

2. The wellhead optical cable pressure relief device according to claim 1, characterized in that: The isolation plate (5) is threaded with at least one third sealing element (15) for sealing connection with the optical fiber core (4) and allowing the optical fiber core (4) to pass through both ends of itself.

3. The wellhead optical cable pressure relief device according to claim 1, characterized in that: The optical cable shaft (12) is provided with a first protective tube hole (17) for placing the outer protective tube (2). The end of the first protective tube hole (17) away from the isolation plate (5) is provided with a first ferrule (19) for fitting outside the outer protective tube (2). The end of the first protective tube hole (17) facing the isolation plate (5) is provided with a first sealing element (13) for fitting outside the outer protective tube (2) and sealingly connected with the outer protective tube (2).

4. The wellhead optical cable pressure relief device according to claim 1, characterized in that: The sealed double cavity (11) is provided with an optical fiber unit hole (21) for placing the optical fiber unit (3). The end of the optical fiber unit hole (21) facing the isolation plate (5) is provided with a second sealing element (14) for being sleeved on the outside of the optical fiber unit (3) and sealed to the optical fiber unit (3).

5. The wellhead optical cable pressure relief device according to claim 1, characterized in that: The tail end sealing cap (10) is provided with a second protective tube hole (18) for placing the outer protective tube (2). The end of the second protective tube hole (18) away from the isolation plate (5) is provided with a second sleeve (20) for fitting outside the outer protective tube (2). The end of the second protective tube hole (18) facing the isolation plate (5) is provided with a fourth sealing element (16) for fitting outside the outer protective tube (2) and sealingly connected with the outer protective tube (2).

6. The wellhead optical cable pressure relief device according to claim 1, characterized in that: Both the sealed double cavity (11) and the tail sealing cap (10) have a buffer cavity (22) at the end facing the isolation plate (5).

7. The wellhead optical cable pressure relief device according to claim 1, characterized in that: The pressure relief channel includes a first mounting hole (23) and a second mounting hole (24). The side wall of the sealed double cavity (11) is provided with a first mounting hole (23) for sealing and installing a pressure gauge with a normally closed pressure relief valve. The first mounting hole (23) is connected to the first high pressure cavity (7). The side wall of the cavity (9) is provided with a second mounting hole (24) for sealing and installing a pressure gauge with a normally closed pressure relief valve. The second mounting hole (24) is connected to the second high pressure cavity (8).

8. A method for installing a wellhead optical cable pressure relief device, applicable to the wellhead optical cable pressure relief device as described in any one of claims 1 to 7, characterized in that: Includes the following steps: Step S1: Seal and install optical fiber cores (4) that penetrate both sides of the isolation plate (5) on the isolation plate (5); Step S2: Strip the outer sheath (1) and outer protective tube (2) of the optical cable to expose the optical fiber unit (3) so that the section of the optical cable exposing the optical fiber unit (3) is located in the first high-voltage cavity (7); Step S3: Strip the optical fiber unit (3) of the optical cable extending from the first high-pressure cavity (7) to expose the optical fiber core (4), and fusion splice the optical fiber core (4) with the optical fiber core (4) on the side of the isolation plate (5) facing the second high-pressure cavity (8) so that the section of the optical cable with exposed optical fiber core (4) is located in the second high-pressure cavity (8). Step S4: Peel off the outer sheath (1), outer protective tube (2), and fiber unit (3) of the other optical cable to expose the fiber core (4). Then, fusion splice the fiber core (4) with the fiber core (4) on the side of the isolation plate (5) facing the low-pressure cavity (6) so that the section of the other optical cable with exposed fiber core (4) is located in the low-pressure cavity (6).

Images