Monitoring sensing optical cable

Abstract

The application provides a monitoring sensing optical cable for being attached to a casing of a subterranean well, the monitoring sensing optical cable comprising an outer sheath and a strain monitoring unit. The outer sheath is configured to be attached to an outer peripheral wall of the casing, and the outer peripheral wall of the outer sheath and the outer peripheral wall of the casing are configured to be fixed in a fixed layer; the strain monitoring optical unit comprises a first optical fiber and a first protective structure, the first optical fiber being capable of monitoring a strain of the first protective structure, the first optical fiber and the first protective structure having the same length; the first protective structure comprises a first protective layer and a second protective layer, the first protective layer being wrapped around an outer periphery of the first optical fiber, the second protective layer being wrapped around an outer periphery of the first protective layer, and the outer sheath being wrapped around an outer periphery of the second protective layer; the first protective layer is made of a material comprising a high-temperature-resistant polymer, the second protective layer is made of a pressure-resistant material, and the monitoring sensing optical cable has a pressure collapse strength of greater than or equal to 120 MPa. The monitoring sensing optical cable is capable of monitoring a strain of the casing in an environment of an oil and gas well.

Description

Technical Field

[0001] This application relates to the field of fiber optic sensing technology, and more particularly to a monitoring sensing optical cable. Background Technology

[0002] In oil and gas wells, various factors such as fracturing, seismic activity, formation subsidence and compaction, pressure changes caused by sand production, and rock creep can all lead to deformation and damage of the downhole casing, thereby affecting oil and gas production, causing a decrease or shutdown of production, or even resulting in well abandonment and significant economic losses. Current downhole sensing optical cables are mainly used to monitor parameters such as temperature, acoustic / vibration, or pressure; however, existing downhole sensing optical cables, because the optical fiber is in a slack state within the cable's protective casing, cannot promptly sense strain in the cable and surrounding casing. Summary of the Invention

[0003] To address the difficulty in monitoring downhole strain in oil and gas wells, this application provides a monitoring sensing optical cable capable of monitoring downhole casing strain in oil and gas wells.

[0004] This application provides a monitoring sensing optical cable for bonding with a casing of an underground well. The monitoring sensing optical cable includes an outer sheath and a strain monitoring unit. The outer sheath is configured to bond with the outer peripheral wall of the casing, and the outer peripheral wall of the outer sheath and the outer peripheral wall of the casing are configured to be fixed within a fixed layer. The strain monitoring optical unit includes a first optical fiber and a first protective structure. The first optical fiber can monitor the strain of the first protective structure, and the first optical fiber and the first protective structure have the same length. The first protective structure includes a first protective layer and a second protective layer. The first protective layer covers the outer periphery of the first optical fiber, and the second protective layer covers the outer periphery of the first protective layer. The outer sheath covers the outer periphery of the second protective layer. The first protective layer is made of a material including a high-temperature resistant polymer, and the second protective layer is made of a pressure-resistant material. The crush resistance of the monitoring sensing optical cable is ≥120MPa.

[0005] In the aforementioned monitoring and sensing optical cable, the first protective layer is made of polymer, which allows the first protective layer to cover the first optical fiber and keep the first optical fiber straight, thereby improving the accuracy of the first optical fiber's length matching the length of the first protective layer. The strain of the sheath is sequentially transmitted to the first optical fiber through the outer sheath, the second protective layer, and the first protective layer, enabling the first optical fiber to monitor the strain of the monitoring and sensing optical cable and the sheath. The second protective layer has compressive strength, and the compressive strength of the monitoring and sensing optical cable is ≥120MPa, allowing the monitoring and sensing optical cable to operate in the high-pressure environment of underground oil and gas wells. This reduces the risk that the first protective structure may not provide sufficient protection for the first optical fiber under the influence of pressure in the oil and gas well environment, leading to deformation of the first optical fiber and failure of strain monitoring of the sheath. Therefore, the first optical fiber can effectively monitor the strain of the sheath.

[0006] In one embodiment, the second protective layer is made of a material including carbon fiber polymer composite material or metal.

[0007] In one embodiment, the strain monitoring unit further includes a third protective layer that covers the outer periphery of the second protective layer, and the third protective layer is made of a material including carbon fiber polymer composite material.

[0008] In one embodiment, the monitoring sensing optical cable further includes a first support member, which includes multiple strands of steel wires twisted around the outer periphery of the first protective structure, with each steel wire fitting against the first protective structure, and an outer sheath covering the first support member.

[0009] In one embodiment, the screening strain of the first optical fiber is greater than or equal to 2%.

[0010] In one embodiment, the first protective structure further includes a third protective layer that covers the second protective layer.

[0011] In one embodiment, the first protective structure further includes a first filling layer covering the outer periphery of the first protective layer, and a second protective layer covering the outer periphery of the first filling layer. The first filling layer is made of a material including a high-temperature resistant thermosetting resin sealant.

[0012] In one embodiment, the monitoring sensing optical cable further includes a temperature monitoring optical unit, which includes a second optical fiber and a second protective structure. The second optical fiber is disposed within the second protective structure, and the length of the second optical fiber is greater than the length of the second protective structure. The second optical fiber is configured to monitor the temperature change of the environment in which the monitoring sensing optical cable is located.

[0013] In one embodiment, the excess length of the second optical fiber relative to the second protective structure is greater than or equal to 0.5%.

[0014] In one embodiment, the second protective structure includes a pressure-resistant component and a second filling layer. The second filling layer covers the outer periphery of the second optical fiber and is made of a material including high-temperature resistant fiber paste or aramid yarn. The pressure-resistant component covers the outer periphery of the second filling layer and is made of a pressure-resistant material.

[0015] In one embodiment, the temperature resistance of the first optical fiber and the second optical fiber is greater than or equal to 150°C.

[0016] In one embodiment, the monitoring sensing optical cable further includes an armored component located inside the outer sheath. The armored component is made of a corrosion-resistant alloy, has a wall thickness of 0.5~1.5mm, and a crush resistance of not less than 120MPa. A temperature monitoring optical unit is located inside the armored component. And / or a strain monitoring optical unit and a temperature monitoring optical unit are respectively disposed inside the armored component. The monitoring sensing optical cable further includes a third filling layer, which covers the strain monitoring optical unit and the temperature monitoring optical unit. The armored component covers the third filling layer.

[0017] In one embodiment, the monitoring sensing optical cable further includes a second support member located inside the outer sheath. The second support member includes multiple strands of steel wires twisted together to form a column structure, and the tensile strength of the second support member is greater than or equal to 1770 MPa.

[0018] In one embodiment, the outer sheath is made of a high-temperature resistant polymer material reinforced with fiber filler. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the monitoring and sensing optical cable and sheath installed in a fixed layer according to an embodiment of this application.

[0021] Figure 2 This is a schematic diagram of a first embodiment of the monitoring sensor optical cable provided in this application.

[0022] Figure 3 This is a schematic diagram of a strain monitoring optical unit of a monitoring sensing optical cable provided in an embodiment of this application.

[0023] Figure 4 for Figure 3 A schematic diagram of the strain monitoring optical unit of the monitoring sensing optical cable shown in another embodiment.

[0024] Figure 5 This is a schematic diagram of a temperature monitoring optical unit in a monitoring sensing optical cable provided in an embodiment of this application.

[0025] Figure 6 This is a schematic diagram of a second embodiment of the monitoring sensing optical cable provided in one embodiment of this application.

[0026] Figure 7 This is a schematic diagram of a third embodiment of the monitoring sensing optical cable provided in this application.

[0027] Figure 8 This is a schematic diagram of Embodiment 4 of the monitoring sensing optical cable provided in one embodiment of this application.

[0028] Figure 9 This is a schematic diagram of Embodiment 5 of the monitoring sensing optical cable provided in an embodiment of this application.

[0029] Figure 10 This is a schematic diagram of a sixth embodiment of the monitoring sensing optical cable provided in this application.

[0030] Explanation of key component symbols: 100, monitoring and sensing optical cable; 1, outer sheath; 2, strain monitoring optical unit; 21, first optical fiber; 22, first protective structure; 221, first protective layer; 222, second protective layer; 223, third protective layer; 224, first filling layer; 3, temperature monitoring optical unit; 31, second optical fiber; 32, second protective structure; 321, pressure-resistant tube; 322, second filling layer; 6, armor; 7, third filling layer; 8, first support member; 9, second support member; 200, sleeve; 300, fixing layer. Detailed Implementation

[0031] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments.

[0032] It should be noted that when a component is said to be "fixed to" another component, it can be directly on the other component or there may be an intervening component. When a component is said to be "connected to" another component, it can be directly connected to the other component or there may be an intervening component. When a component is said to be "set on" another component, it can be directly set on the other component or there may be an intervening component. The terms "vertical," "horizontal," "left," "right," and similar expressions used in this document are for illustrative purposes only.

[0033] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used herein in the specification of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "or / and" as used herein includes any and all combinations of one or more of the associated listed items.

[0034] Some embodiments of this application are described in detail. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0035] like Figure 1 As shown, this application embodiment provides a monitoring sensing optical cable 100, which is used to monitor changes in an underground casing 200, such as the strain of the casing 200. The underground casing 200 is a casing structure for oil and gas wells. The monitoring sensing optical cable 100 is attached to the outer peripheral wall of the casing 200. The casing 200 and the monitoring sensing optical cable 100 are placed within a fixing layer 300. The fixing layer 300 covers the outer periphery of the casing 200 and the monitoring sensing optical cable 100. The fixing layer 300 is generally made of cement mortar and fills the outer periphery of the casing 200 and the monitoring sensing optical cable 100, so that the casing 200 and the monitoring sensing optical cable 100 form a tight fit. When the sleeve 200 undergoes elongation strain, the monitoring and sensing optical cable 100 will simultaneously generate strain. That is, the strain of the sleeve 200 is transmitted to the monitoring and sensing optical cable 100, thereby enabling the monitoring and sensing optical cable 100 to monitor the strain of the sleeve 200 in real time.

[0036] Please continue reading. Figure 2 and Figure 3 The monitoring sensing optical cable 100 includes an outer sheath 1 and a strain monitoring optical unit 2. The outer sheath 1 is fitted to the outer peripheral wall of the sleeve 200, and the outer peripheral wall of the outer sheath 1 and the outer peripheral wall of the sleeve 200 are fixed within the fixing layer 300. The strain monitoring optical unit 2 is located inside the outer sheath 1 and includes a first optical fiber 21 and a first protective structure 22. The first protective structure 22 covers the outer periphery of the first optical fiber 21, and the first protective structure 22 and the first optical fiber 21 are in a tight fit. The first optical fiber 21 can monitor the strain of the first protective structure 22. The first optical fiber 21 and the first protective structure 22 have the same length. The first protective structure 22 is disposed inside the outer sheath 1 and is in a tight fit with the outer sheath 1. The strain of the sleeve 200 is transmitted to the first optical fiber 21 through the outer sheath 1 and the first protective structure 22.

[0037] The first protective structure 22 includes a first protective layer 221 and a second protective layer 222. The first protective layer 221 covers the outer periphery of the first optical fiber 21. The second protective layer 222 covers the outer periphery of the first protective layer 221. The outer sheath 1 covers the outer periphery of the second protective layer 222. The length of the first optical fiber 21 is the same as the length of the first protective layer 221, and the length of the second protective layer 222 is the same as the length of the first protective layer 221, thereby making the length of the first optical fiber 21 the same as the length of the first protective structure 22.

[0038] Since the outer sheath 1, the second protective layer 222, and the first protective layer 221 are sequentially wrapped around the first optical fiber 21, and the outer peripheral wall of the outer sheath 1 and the outer peripheral wall of the sleeve 200 are fixed within the fixing layer 300, the outer sheath 1 and the sleeve 200 are stably attached. This allows the deformation of the sleeve 200 to be synchronously transmitted to the first optical fiber 21 through the outer sheath 1, the second protective layer 222, and the first protective layer 221 when the sleeve 200 experiences minor strain, causing minor strain in the first optical fiber 21. The first optical fiber 21 adopts the Brillouin distributed optical fiber monitoring principle. When the first optical fiber 21 deforms, the frequency of the Brillouin scattered light changes accordingly, realizing the strain monitoring of the sleeve 200 by the first optical fiber 21.

[0039] In one embodiment, the first protective layer 221 is made of a material including a high-temperature resistant polymer, and the second protective layer 222 is made of a pressure-resistant material, which can improve the circumferential crush resistance of the monitoring sensor optical cable 100, making the crush resistance of the monitoring sensor optical cable 100 ≥120MPa, thereby improving the pressure resistance performance of the monitoring sensor optical cable 100.

[0040] The first protective layer 221 is made of polymer, which allows it to cover the first optical fiber 21 and keep the first optical fiber 21 straight, thereby improving the accuracy of the length of the first optical fiber 21 being the same as the length of the first protective layer 221. The second protective layer 222 has compressive strength, with the compressive strength of the monitoring and sensing optical cable 100 being ≥120MPa. This allows the monitoring and sensing optical cable 100 to operate in the working environment of underground oil and gas wells, reducing the risk that the first protective structure 22 may not provide sufficient protection for the first optical fiber 21 under the influence of pressure and other factors in the oil and gas well environment, thus preventing damage or breakage of the first optical fiber 21 during installation and operation of the optical cable.

[0041] In one embodiment, the first protective layer 221 may be continuously extruded from at least one of ETFE (ethylene-tetrafluoroethylene copolymer), PFA (perfluoroalkoxy resin), and PEEK (polyether ether ketone).

[0042] In one embodiment, the second protective layer 222 is made of a material including carbon fiber polymer composite material or metal. Both carbon fiber polymer composite material and metal material have high compressive and tensile strength. For example, the second protective layer 222 is a tubular structure made of stainless steel. The second protective layer 222 can be formed by longitudinally wrapping stainless steel strips and continuously laser welding to form a stainless steel tube, which is then drawn and reduced in diameter before being tightly bonded to the first protective layer 221. The use of stainless steel or carbon fiber polymer composite material for the second protective layer 222 can enhance the compressive strength of the strain monitoring optical unit 2.

[0043] When the second protective layer 222 is made of carbon fiber polymer composite material, the second protective layer 222 can be formed by composite curing of carbon fiber bundles and epoxy resin, and tightly wrapped around the periphery of the first protective layer 221 to enhance the tensile and compressive strength of the strain monitoring optical unit 2.

[0044] In one embodiment, the screening strain of the first optical fiber 21 is greater than or equal to 2%. For example, the first optical fiber 21 can be a high-strength single-mode optical fiber, and its screening strain can be 2%, 2.5%, 3%, etc., but is not limited to the values ​​listed above. Other values ​​not listed are also within the protection scope of this application if the screening strain of the first optical fiber 21 is greater than or equal to 2%.

[0045] In one embodiment, the first optical fiber 21 may be a high-temperature resistant optical fiber, and the coating material of the fiber may include high-temperature resistant acrylate, silicone resin and / or polyimide, with a temperature resistance rating of 150°C, 200°C, 300°C, etc., but not limited to the values ​​listed above. Other values ​​not listed in this range are also within the protection scope of this application.

[0046] Please see Figure 4 In other embodiments, when higher tensile and compressive strength requirements are met, the strain monitoring optical unit 2 further includes a third protective layer 223. The third protective layer 223 is made of carbon fiber tow and epoxy resin composite and cured, and covers the outer periphery of the second protective layer 222. When the second protective layer 222 is made of stainless steel, the first protective structure 22 further includes a first filling layer 224. The first filling layer 224 covers the outer periphery of the first protective layer 221, and the second protective layer 222 covers the outer periphery of the first filling layer 224. The first filling layer 224 is made of a material including high-temperature resistant thermosetting resin sealant. The first filling layer 224 is tightly bonded to the first protective layer 221 and the second protective layer 222, which helps to improve the accuracy of the strain transmission sleeve 200 of the first protective structure 22. In another embodiment, the first filling layer 224 can also be omitted. The third protective layer 223 covers the outer periphery of the second protective layer 222.

[0047] In one embodiment, when the second protective layer 222 is made of stainless steel pipe, a third protective layer 223 may be provided outside the second protective layer 222. When the second protective layer 222 is made of carbon fiber polymer composite material, the third protective layer 223 may not be provided. The third protective layer 223 tightly wraps around the outer periphery of the second protective layer 222 (stainless steel pipe).

[0048] It is understood that in other embodiments, the third protective layer 223 may also be omitted. When the second protective layer 222 is made of a material including carbon fiber polymer composite material, the thickness of the second protective layer 222 is increased, which can also increase the tensile and compressive strength of the strain monitoring optical unit 2 to meet higher tensile and compressive strength requirements.

[0049] It is understood that the first protective structure 22 includes multiple layers of protection. The first protective layer 221 is a high-temperature resistant polymer, the second protective layer 222 is a carbon fiber polymer composite material or a stainless steel pipe, and the third protective layer 223 is a carbon fiber polymer composite material. This enables the strain monitoring optical unit 2 to not only have high-temperature resistance, but also strong resistance to flattening, corrosion and tensile strength, making it suitable for high-temperature, high-pressure and highly corrosive application environments in oil and gas wells.

[0050] In one embodiment, the monitoring sensing optical cable 100 further includes a first support member 8. The first support member 8 includes multiple strands of steel wire, which are twisted around the outer periphery of the first protective structure 22, and each steel wire is attached to the first protective structure 22. An outer sheath 1 covers the first support member 8. The first support member 8 forms a support around the strain monitoring optical unit 2, which mainly improves the tensile and impact resistance of the strain monitoring optical unit 2, reduces the risk of damage to the monitoring sensing optical cable 100 due to mechanical external forces during construction, and improves the construction safety of the monitoring sensing optical cable 100. In addition, the first support member 8 surrounding the outer periphery of the strain monitoring optical unit 2 can also further improve the crush resistance of the monitoring sensing optical cable 100.

[0051] Please see Figure 2 and Figure 5 The ambient temperature of the sheath 200 affects the Brillouin scattering frequency of the first optical fiber 21, making the strain monitoring of the sheath 200 by the first optical fiber 21 susceptible to temperature influence. To eliminate the influence of temperature on the strain monitoring of the sheath 200, the monitoring sensing optical cable 100 also includes a temperature monitoring optical unit 3. The temperature monitoring optical unit 3 is located inside the outer sheath 1 and includes a second optical fiber 31 and a second protective structure 32. The second optical fiber 31 is disposed within the second protective structure 32, and the length of the second optical fiber 31 is greater than the length of the second protective structure 32. The second protective structure 32 has tensile and compressive strength, enabling the second optical fiber 31 to operate in the environment where the sheath 200 is located. The second optical fiber 31 can monitor the temperature changes of the environment where the monitoring sensing optical cable 100 is located, which also means it can monitor the temperature changes of the environment where the sheath 200 is located.

[0052] Since the length of the second optical fiber 31 is greater than the length of the second protective structure 32, the second optical fiber 31 has excess fiber length. When the second protective structure 32 experiences minimal strain, even if the second protective structure 32 comes into contact with the second optical fiber 31, the second optical fiber 31 inside the temperature monitoring optical unit 3 remains in a relaxed state. The second optical fiber 31 has no strain, and the frequency of Brillouin scattering light in the second optical fiber 31 is only affected by temperature changes and is not affected by the strain of the sleeve 200.

[0053] The Brillouin scattered light frequencies of the first fiber 21 of the strain monitoring optical unit 2 and the second fiber 31 of the temperature monitoring optical unit 3 are monitored by a ground-based Brillouin fiber optic monitoring demodulator. The difference in their variation reflects the actual strain that occurs in the sleeve 200, thereby timely reflecting the strain of the sleeve 200 and realizing timely monitoring of the strain of the sleeve 200.

[0054] The strain monitoring optical unit 2 and the temperature monitoring optical unit 3 can be arranged at intervals and are encapsulated by the outer sheath 1.

[0055] In one embodiment, the strain monitoring optical unit 2 and the temperature monitoring optical unit 3 are arranged linearly, and the outer sheath 1 is generally a rectangular column structure, but not limited thereto. For example, in another embodiment, the strain monitoring optical unit 2 and the temperature monitoring optical unit 3 can also be arranged in a curved manner so that the outer sheath 1 is an arc-shaped column structure. For example, the surface of the outer sheath 1 that contacts the sleeve 200 is a curved surface.

[0056] In one embodiment, the outer sheath 1 is made of a fiber-filled high-temperature resistant polymer composite material. For example, the fiber can be glass fiber or carbon fiber. The polymer composite material can be selected according to the downhole environment. For example, at least one of the following polymer composite materials can be selected: ETFE (ethylene-tetrafluoroethylene copolymer), FEP (fluorinated ethylene propylene copolymer), PFA (perfluoroalkoxy resin), etc. The glass fiber filling ratio is 3% to 15%. Specifically, the glass fiber filling ratio can be 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, etc., but is not limited to the values ​​listed above. Other values ​​not listed within this range are also within the scope of protection of this application. The outer sheath 1 uses a high-temperature resistant polymer material containing glass fiber filling, which can enhance the tensile strength, wear resistance, impact resistance, and deformation resistance of the outer sheath 1. It can effectively reduce the risk of the optical cable being damaged, scratched, or flattened by mechanical external forces during construction and improve its ability to resist deformation under high-temperature downhole environments.

[0057] Understandably, distributed fiber optic sensing technology can be used to monitor the deformation of the casing in oil and gas wells in real time. When the deformation exceeds the design threshold, an early warning can be issued in a timely manner, allowing for timely preventive measures to be taken, adjusting mining conditions, preventing further deterioration of the casing deformation, or timely repairs to avoid irreparable losses. By setting up strain monitoring optical unit 2 and temperature monitoring optical unit 3, the temperature and strain at different locations in the oil and gas well can be sensed. When the casing 200 deforms, the outer sheath 1 and the first protective structure 22 of the monitoring sensing optical cable 100 undergo elongation or compressive strain. The strain of the casing 200 is promptly transmitted to the first optical fiber 21 in the strain monitoring optical unit 2. Therefore, the first optical fiber 21 can promptly and sensitively sense the strain occurring in the optical cable. Since the temperature monitoring optical unit 3 has excess fiber length, when the monitoring sensing optical cable 100 undergoes a small strain due to the deformation of the sleeve 200, the second optical fiber 31 remains in a relaxed state and will not be subjected to force or strain. It can only sense the temperature change around the monitoring sensing optical cable 100. Thus, the temperature monitoring optical unit 3 and the strain monitoring optical unit 2 work together to accurately measure the strain of the sleeve 200.

[0058] In one embodiment, the excess length of the second optical fiber 31 is greater than or equal to 0.5%. The excess length of the second optical fiber 31 can be 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, etc., but is not limited to the values ​​listed above. Other unlisted values ​​within this range are also within the scope of protection of this application. The excess length of the second optical fiber 31 ensures that when the second protective structure 32 experiences minimal strain, the second optical fiber 31 remains in a relaxed state and will not be subjected to stress or strain. Therefore, it cannot promptly detect the strain occurring in the second protective structure 32; it can only sense temperature changes around the monitoring sensing optical cable 100. The Brillouin scattering frequency in the second optical fiber 31 is only affected by temperature changes, allowing it to coordinate with the Brillouin scattering frequency of the first optical fiber 21 in the strain monitoring optical unit 2 to obtain the sleeve strain monitoring result.

[0059] It is understood that, in one embodiment, the first optical fiber 21 and the second optical fiber 31 are both high-temperature resistant optical fibers, so as to be able to adapt to the high-temperature and harsh environment downhole in oil and gas wells. The temperature resistance of the first optical fiber 21 and the second optical fiber 31 is greater than or equal to 150°C. Their temperature resistance can be 150°C, 200°C, 300°C, etc., but is not limited to the values ​​listed above. Other values ​​not listed in this range are also within the protection scope of this application.

[0060] In one embodiment, two second optical fibers 31 are located within the second protective structure 32 of the temperature monitoring optical unit 3.

[0061] The second optical fiber 31 has at least one single-mode fiber. When there are multiple optical fibers, they can be multiple single-mode fibers, or a combination of single-mode and multi-mode fibers. In addition to monitoring temperature, the second optical fiber 31 may also include a single-mode fiber for monitoring sound waves / vibrations. The second optical fiber 31 is a high-temperature resistant fiber, with a temperature resistance of 150℃, 200℃, 300℃, etc., but not limited to the values ​​listed above. Other unlisted values ​​within this range are also within the scope of protection of this application. The coating material of the second optical fiber 31 can be a high-temperature resistant acrylate, silicone resin, or polyimide.

[0062] In one embodiment, the second protective structure 32 includes a pressure-resistant tube 321 and a second filling layer 322. The pressure-resistant tube 321 is located inside the outer sheath 1, the second optical fiber 31 is located inside the pressure-resistant tube 321, and the second filling layer 322 fills the space between the second optical fiber 31 and the pressure-resistant tube 321. The pressure-resistant tube 321 is made of a material including corrosion-resistant materials. The second filling layer 322 may be made of a material including high-temperature resistant fiber paste or aramid yarn.

[0063] In one embodiment, the pressure-resistant tube 321 is made of stainless steel, such as 304 or 316L stainless steel. A second filling layer 322 may be formed between the second optical fiber 31 and the pressure-resistant tube 321, which may be made of high-temperature resistant fiber paste or aramid yarn.

[0064] In this embodiment, the inner diameter of the pressure-resistant tube 321 is larger than the outer diameter of the second optical fiber 31, and the excess length of the second optical fiber 31 is greater than or equal to 0.5%, which means that the axial length of the second optical fiber 31 after being straightened exceeds the axial length of the pressure-resistant tube 321 by at least 0.5%, so that when the second optical fiber 31 is completely located inside the pressure-resistant tube 321, the second optical fiber 31 is in a relaxed state (i.e., the second optical fiber 31 is partially in a bent state).

[0065] In other embodiments, the second filling layer 322 may not be provided between the second optical fiber 31 and the pressure-resistant tube 321.

[0066] Please see Figure 2 In one embodiment, the monitoring sensing optical cable 100 further includes an armor 6, which is located inside the outer sheath 1. The temperature monitoring optical unit 3 is located inside the armor 6. The material of the armor 6 includes a corrosion-resistant alloy. The wall thickness of the armor 6 is 0.5~1.5mm, and the crush resistance of the armor 6 is not less than 120MPa.

[0067] The armor component 6 can be tubular, specifically made of corrosion-resistant alloy materials such as 316L stainless steel, 825 (iron-nickel based corrosion-resistant alloy), and 625 (nickel-based high-temperature alloy). The wall thickness of the armor component 6 can be 0.5mm, 0.71mm, 0.89mm, 1.24mm, 1.5mm, etc., but is not limited to the values ​​listed above. Other values ​​not listed within this range are also within the scope of protection of this application. The crush resistance of the armor component 6 can be 120MPa, 138MPa, 180MPa, 207MPa, etc., but is not limited to the values ​​listed above. Other values ​​not listed within this range are also within the scope of protection of this application.

[0068] Understandably, the armor 6 provides good mechanical protection for the temperature monitoring optical unit 3, effectively preventing damage to the temperature monitoring optical unit 3 from external forces, resisting corrosion in the downhole environment, and improving the crush resistance and long-term operational reliability of the monitoring sensor optical cable 100.

[0069] In one embodiment, a third filler layer 7 is provided between the armor 6 and the temperature monitoring optical unit 3, the material of the third filler layer 7 comprising a high-temperature resistant polymer.

[0070] In this embodiment, the third filler layer 7 can be a sealing filler layer, and the material of the third filler layer 7 can be ETFE (ethylene-tetrafluoroethylene copolymer), FEP (fluorinated ethylene propylene copolymer) or PFA (perfluoroalkoxy resin).

[0071] In other embodiments, the third filling layer 7 may not be provided between the armor 6 and the temperature monitoring optical unit 3.

[0072] In one embodiment, the monitoring sensing optical cable 100 further includes a second support member 9. The second support member 9 is located inside the outer sheath 1, the outer diameter of the second support member 9 is larger than the outer diameter of the armor 6, and the tensile strength of the second support member 9 is not less than 1770 MPa.

[0073] In one embodiment, the second support member 9 may be a round high-strength galvanized steel wire or stainless steel wire, or a steel wire rope formed by twisting multiple strands of round high-strength galvanized steel wire or stainless steel wire. The second support member 9 is arranged at intervals from the strain monitoring optical unit 2 and the temperature monitoring optical unit 3.

[0074] In one embodiment, the tensile strength of the first support member 8 and the second support member 9 may be 1770MPa, 1870MPa, 1960MPa, 2160MPa, etc., respectively, but is not limited to the values ​​listed above. Other values ​​not listed in this range are also within the protection scope of this application.

[0075] Understandably, the second support member 9 enhances the tensile strength, anti-flattening performance, and impact resistance of the monitoring and sensing optical cable 100, reduces the risk of damage to the monitoring and sensing optical cable 100 due to mechanical external forces during construction, and improves the construction safety of the monitoring and sensing optical cable 100.

[0076] In one embodiment, the crush resistance of the monitoring sensing optical cable 100 is ≥120MPa. For example, the crush resistance of the monitoring sensing optical cable 100 reaches 120MPa, 130MPa, 140MPa, 150MPa, 160MPa, etc., but is not limited to the values ​​listed above. Other values ​​not listed in this range are also within the protection scope of this application.

[0077] The following are several examples: Example 1: like Figure 2As shown, the first optical fiber 21 is a polyimide-coated single-mode optical fiber, and the first protective layer 221 is made of PEEK (polyetheretherketone) with an outer diameter of 1.0 mm. The second protective layer 222 is a carbon fiber epoxy resin composite material with an outer diameter of 2.5 mm. A first support member 8 is provided around the strain monitoring optical unit 2. The first support member 8 is composed of six steel wire reinforcements twisted together, each steel wire having a diameter of 2.4 mm. The six steel wires are evenly twisted around the strain monitoring optical unit 2. The temperature monitoring optical unit 3 has two second optical fibers 31, one single-mode fiber and one multimode fiber. The coating of the first optical fiber 21 and the second optical fiber 31 is polyimide, with a temperature resistance rating of 300℃. The pressure-resistant tube 321 is made of 316L steel, with an outer diameter of 3.2 mm and a wall thickness of 0.2 mm. A second filling layer 322 is provided between the pressure-resistant tube 321 and the second optical fiber 31, and the material of the second filling layer 322 is aramid yarn. The excess length of the second optical fiber 31 is 0.7%. The armor 6 is made of 316L steel, with an outer diameter of 6.35 mm and a wall thickness of 0.89 mm. The armor 6 is formed by continuous laser welding to create a sealed protective tube, with a crush resistance of not less than 160 MPa and a tensile strength of not less than 15 kN. A third filling layer 7 is provided between the interior of the armor 6 and the outer periphery of the temperature monitoring optical unit 3. The third filling layer 7 is made of PFA (perfluoroalkoxy resin), which is formed by high-temperature melt extrusion of PFA material. The outer diameter of the third filling layer 7 is 4.57 mm and the wall thickness is 0.68 mm. The monitoring and sensing optical cable 100 also includes a second support member 9, which is composed of seven steel wire reinforcements twisted together, each with a diameter of 2.5 mm. This second support member 9 is arranged in a straight line with the strain monitoring optical unit 2, which is surrounded by the first support member 8, and the armored member 6, which contains the temperature monitoring optical unit 3. The outer sheath 1 is wrapped with a polymer filled with glass fiber, the main component of which is PFA (perfluoroalkoxy resin), with 8% glass fiber added. The outer sheath 1 has a height of 26 mm and a width of 10 mm. The monitoring and sensing optical cable 100 has a crush resistance ≥120 MPa and a tensile strength ≥130 kN.

[0078] Example 2: like Figure 6 As shown, the difference from Embodiment 1 is that the strain monitoring optical unit 2 does not have a first support member 8 on its outer periphery, but instead has two second support members 9, each of which is formed by seven steel wire reinforcing members twisted together. The two second support members 9 are distributed on the outer sides of the temperature monitoring optical unit 3 and the strain monitoring optical unit 2, with the armor 6 and the internal temperature monitoring optical unit 3 and strain monitoring optical unit 2 located in the middle, and the two second support members 9 located on both sides. The monitoring sensing optical cable 100 has a crush resistance ≥120MPa and a tensile strength ≥145kN.

[0079] Example 3: like Figure 7 As shown, the difference from Embodiment 1 is that the second support member 9 is not provided. The crush resistance of this monitoring and sensing optical cable 100 is ≥120MPa, and the tensile strength is ≥75kN.

[0080] Example 4: like Figure 8 As shown, the difference from Embodiment 1 is that the temperature monitoring optical unit 3 and the strain monitoring optical unit 2 are spaced apart inside the armor 6, and the first support member 8 is omitted. The monitoring and sensing optical cable 100 has a crush resistance ≥160MPa and a tensile strength ≥90kN.

[0081] Example 5: like Figure 9 As shown, the difference from Embodiment 1 is that the strain monitoring optical unit 2 does not have a first support member 8 on its outer periphery, and the strain monitoring optical unit 2 has a third protective layer 223, which is a carbon fiber polymer composite material. The crush resistance of this monitoring sensing optical cable 100 is ≥160MPa, and the tensile strength is ≥160kN.

[0082] Example 6: like Figure 10 As shown, the difference from Embodiment 5 is that the monitoring sensor optical cable 100 does not have a second support member 9. The crush resistance of this monitoring sensor optical cable 100 is ≥160MPa, and the tensile strength is ≥105kN.

[0083] In the aforementioned monitoring and sensing optical cable 100, the first protective layer 221 is made of polymer and covers the first optical fiber 21. The second protective layer 222 has compressive strength. The compressive strength of the monitoring and sensing optical cable 100 is ≥120MPa. The monitoring and sensing optical cable 100 can work in the high-pressure working environment of underground oil and gas wells, avoiding the risk of failure of strain monitoring of the casing 200 due to damage to the first optical fiber 21 caused by the pressure of the oil and gas well.

[0084] The above embodiments are only used to illustrate the technical solutions of this application and are not intended to limit it. Although this application has been described in detail with reference to the above preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions to the technical solutions of this application should not depart from the spirit and scope of the technical solutions of this application.

Claims

1. A monitoring and sensing optical cable for bonding with the casing of an underground well, characterized in that, The monitoring and sensing optical cable includes: An outer sheath is configured to fit against the outer peripheral wall of the sleeve, and the outer peripheral wall of the outer sheath and the outer peripheral wall of the sleeve are configured to be fixed within a fixed layer. The strain monitoring optical unit includes a first optical fiber and a first protective structure. The first optical fiber can monitor the strain of the first protective structure. The first optical fiber and the first protective structure have the same length. The first protective structure includes a first protective layer and a second protective layer. The first protective layer covers the outer periphery of the first optical fiber, and the second protective layer covers the outer periphery of the first protective layer. An outer sheath covers the outer periphery of the second protective layer. The first protective layer is made of a material including a high-temperature resistant polymer, and the second protective layer is made of a pressure-resistant material. The crush resistance of the monitoring sensing optical cable is ≥120MPa.

2. The monitoring and sensing optical cable as described in claim 1, characterized in that, The second protective layer is made of materials including carbon fiber polymer composites or metals.

3. The monitoring and sensing optical cable as described in claim 1, characterized in that, The strain monitoring unit also includes a third protective layer, which covers the outer periphery of the second protective layer and is made of a material including carbon fiber polymer composite material.

4. The monitoring and sensing optical cable as described in claim 1, characterized in that, The monitoring and sensing optical cable also includes a first support member, which includes multiple strands of steel wires. The multiple strands of steel wires are twisted around the outer periphery of the first protective structure, and each steel wire is attached to the first protective structure. The outer sheath covers the first support member.

5. The monitoring and sensing optical cable as described in claim 1, characterized in that, The screening strain of the first optical fiber is greater than or equal to 2%.

6. The monitoring and sensing optical cable as described in claim 1, characterized in that, The first protective structure further includes a third protective layer, which covers the outer periphery of the second protective layer. The first protective structure also includes a first filling layer, which covers the outer periphery of the first protective layer. The second protective layer covers the outer periphery of the first filling layer. The first filling layer is made of a high-temperature resistant thermosetting resin sealant.

7. The monitoring and sensing optical cable as described in any one of claims 1 to 6, characterized in that, The monitoring sensing optical cable also includes a temperature monitoring optical unit, which includes a second optical fiber and a second protective structure. The second optical fiber is disposed within the second protective structure, and the length of the second optical fiber is greater than the length of the second protective structure. The second optical fiber is configured to monitor the temperature change of the environment in which the monitoring sensing optical cable is located.

8. The monitoring and sensing optical cable as described in claim 7, characterized in that, The excess length of the second optical fiber relative to the second protective structure is greater than or equal to 0.5%.

9. The monitoring and sensing optical cable as described in claim 7, characterized in that, The second protective structure includes a pressure-resistant component and a second filling layer. The second filling layer covers the outer periphery of the second optical fiber and is made of a material including high-temperature resistant fiber paste or aramid yarn. The pressure-resistant component covers the outer periphery of the second filling layer and is made of a pressure-resistant material.

10. The monitoring and sensing optical cable as described in claim 7, characterized in that, The temperature resistance of the first optical fiber and the second optical fiber is greater than or equal to 150°C.

11. The monitoring and sensing optical cable as described in claim 7, characterized in that, The monitoring and sensing optical cable also includes an armored component, which is located inside the outer sheath. The material of the armored component includes a corrosion-resistant alloy, the wall thickness of the armored component is 0.5~1.5mm, and the compressive strength of the armored component is not less than 120MPa. The temperature monitoring optical unit is located inside the armor; and / or The strain monitoring optical unit and the temperature monitoring optical unit are respectively disposed within the armor. The monitoring sensing optical cable also includes a third filling layer, which covers the strain monitoring optical unit and the temperature monitoring optical unit. The armor covers the third filling layer.

12. The monitoring sensing optical cable according to any one of claims 1 to 6, characterized in that, The monitoring and sensing optical cable also includes a second support member located inside the outer sheath. The second support member includes multiple strands of steel wire, which are twisted together to form a column structure. The tensile strength of the second support member is greater than or equal to 1770 MPa.

13. The monitoring and sensing optical cable according to any one of claims 1 to 6, characterized in that, The outer sheath is made of a high-temperature resistant polymer material containing fiber filling.

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