Oil well optical cable for underground earthquake monitoring

Abstract

The invention provides an oil well optical cable for underground earthquake monitoring. The oil well optical cable comprises an optical fiber; the steel wire rope is coated with a rubber coating layer, the optical fiber is embedded in the surface of the rubber coating layer, and the optical fiber and the rubber coating layer are integrated; the outer layer of the optical fiber protection tube is coated with a sheath, and the steel wire rope is placed in the optical fiber protection tube; the high-temperature ointment is filled between the optical fiber protection tube and the rubber coating layer; and the outer-layer protection pipe adopts a high-strength seamless stainless steel pipe and is used for protecting internal elements. According to the oil well optical cable for underground earthquake monitoring, special packaging of the optical fibers is realized, mechanical protection of the optical fibers can be effectively realized, invasion of water, oil and other corrosive gases in an underground high-temperature and high-pressure environment can be avoided, the vibration sensing sensitivity of the optical fibers can be ensured, and the vibration sensing accuracy is improved. Effective physical and chemical protection can be achieved during optical fiber working, and hydrogen loss is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of oil well optical cables, and in particular to an oil well optical cable used for downhole seismic monitoring. Background Art

[0002] Oil well optical cables are mainly used in the fields of downhole detection, downhole seismic monitoring, geothermal logging and geological exploration during oil and gas extraction. They are widely used as carriers of downhole signal perception, downhole sensing equipment and measuring instruments, and signal transmission cables for downhole communications. Usually, the working environment of oil well optical cables is relatively harsh. They work in places with high pressure, high temperature, high oil and water content and full of corrosive gases all year round. In order to ensure the normal operation of downhole optical cables, oil well optical cables are made of corrosion-resistant and rigid materials.

[0003] Oil well optical cables used in the field of earthquake monitoring are not only used as signal transmission lines, but more importantly, they are distributed underground as vibration monitoring sensors. The distributed optical fiber vibration sensing technology can accurately detect earthquakes at different depths underground in the optical fiber distribution area. Conventional oil well optical cables are mostly composed of internal twisted steel wires and external steel pipes. Filling materials are added between the internal optical fiber, the steel wire and the external stainless steel pipe for protection and sealing. Although this method protects the internal optical fiber, it greatly increases the weight of the optical cable and reduces its strength. At the same time, due to the influence of its own structure, the oil well optical cable using distributed optical fiber vibration monitoring technology cannot guarantee the sensitivity of the optical fiber to external vibrations during underground earthquake monitoring, which greatly reduces the detection accuracy of the system. The optical fiber is usually placed directly inside the inner protective tube. The direct contact between the optical fiber and the protective tube can easily cause damage to the optical fiber, resulting in an increase in the number of subsequent inspections and maintenance.

[0004] In the Chinese patent application with application number: CN201420369181.0, there is a fiber optic cable for oil and gas wells, the fiber optic cable comprises a cable core and a protective layer wrapped around the outside of the cable core, the protective layer comprises a stainless steel tube outer protective layer (1) which is tightly fitted to the inside, a high temperature resistant intermediate protective layer (2) and a stainless steel tube inner protective layer (3), the cable core comprises a fiber paste (4) and a high temperature resistant optical fiber (5) filled in the fiber paste (4), and the fiber paste (4) is in contact with the stainless steel tube inner protective layer (3), and the high temperature resistant optical fiber (5) is not in contact with the stainless steel tube inner protective layer (3). The utility model fiber optic cable has the characteristics of corrosion resistance, high temperature resistance and water immersion resistance, as well as low hydrogen loss, high vibration resistance and collision resistance, that is, the fiber optic cable can adapt to the needs of harsh environments such as high temperature, high pressure, water immersion, hydrogen invasion, collision and vibration in oil wells, can be used for a long time in the well, and when it is used in optical fiber sensors, it can improve the accuracy and stability of optical fiber sensor measurements.

[0005] In the Chinese patent application with application number: CN202221652414.9, a well-sealed oil well optical cable is involved, which is characterized by comprising an outer seamless stainless steel tube, an inner seamless stainless steel tube and steel wire; the steel wire is twisted in an S-shaped unidirectional layer on the periphery of the inner seamless stainless steel tube, and an optical fiber bundle consisting of 2 to 4 optical fibers is arranged at the inner center of the inner seamless stainless steel tube, and the space gap between the optical fiber bundle and the inner seamless stainless steel tube is filled with grease, and the outer wall of the inner seamless stainless steel tube and the inner wall of the outer seamless stainless steel tube are both provided with a waterproof layer; the utility model adopts high-strength steel wire as a reinforcement, which can overcome the problem that the strength of the steel tube cannot be increased due to the seamless steel tube welding process, and through the hardening and dehydrogenation treatment of the steel wire, the optical cable reinforcement effectively reduces the influence of hydrogen embrittlement, improves the mechanical strength and corrosion resistance of the oil well optical cable, and further improves the adaptability of the optical fiber in the oil well.

[0006] In the Chinese patent application with application number: CN201910764750.9, a sensor optical cable for oil and gas wells installed outside the casing is involved, including a central optical cable, a steel wire rope and a sheath. The sheath is flat and extruded and arranged outside the central optical cable and the steel wire rope. Steel wire ropes are arranged on both sides of the central optical cable. The central optical cable includes a sheath steel pipe, at least one steel pipe optical fiber unit and a plurality of reinforcements. The reinforcements and the steel pipe optical fiber unit are twisted to form a cable-like structure. The cable-like structure is arranged in the sheath steel pipe and fits tightly with the inner side of the sheath steel pipe. The utility model provides a sensor optical cable for oil and gas wells installed outside the casing, which has a simple and compact structure, sensitive perception, and high lateral pressure resistance, making underground construction outside the casing safer and more reliable.

[0007] In the Chinese patent application with application number: CN02211272.3, the rubber wire rope is a wire rope made of rubber composite. It is composed of rubber, steel wire and high elongation rubber. The high elongation rubber is immersed between the steel wires, and the rubber is applied to the outer layer of the steel wire. It can be used in marine ships, marine drilling, military underwater mine laying, underwater optical cables, dam gate ropes, mine derricks, oil derrick ropes, dock hoist ropes, building hoist ropes, various cranes and other industries.

[0008] The above existing technologies are greatly different from the present invention and fail to solve the technical problem we want to solve. For this reason, we have invented a new oil well optical cable for downhole seismic monitoring. Summary of the invention

[0009] The object of the present invention is to provide an oil well optical cable for downhole seismic monitoring which solves the problems of vibration sensing accuracy and optical fiber protection faced by oil well optical cables in the prior art during downhole seismic monitoring.

[0010] The purpose of the present invention can be achieved by the following technical measures: an oil well optical cable for downhole seismic monitoring, the oil well optical cable for downhole seismic monitoring comprising:

[0011] optical fiber;

[0012] A steel wire rope, the steel wire rope is covered with a rubber coating layer, the optical fiber is embedded in the surface of the rubber coating layer, and the optical fiber and the rubber coating layer are integrated;

[0013] An optical fiber protective tube, the outer layer of which is covered with an outer sheath, and the steel wire rope is placed in the optical fiber protective tube;

[0014] High temperature grease, which is filled in the light protection tube;

[0015] An outer protective tube protects the above-mentioned parts.

[0016] The purpose of the present invention can also be achieved by the following technical measures:

[0017] The diameter of the rubber coating layer is between 2 and 3 mm.

[0018] The rubber coating should contain at least one high-strength steel wire rope with a diameter of 1 mm to withstand tensile stress.

[0019] The steel wire rope is made of 304 stainless steel or high-strength galvanized steel or alloy-coated steel.

[0020] The steel wire rope is a soft steel wire rope made of multiple strands of fine steel wires twisted together.

[0021] The optical fiber is vulcanized and fixed together with the rubber coating layer during the molding process, and the rubber completely wraps the optical fiber.

[0022] The optical fiber comprises a core, a cladding and a coating layer, and the coating layer is made of a high temperature resistant material.

[0023] The coating layer is made of polyimide with a maximum temperature resistance of 350°C.

[0024] The outer protective tube is made of a thermoplastic elastic material, which may be one of thermoplastic polyolefin elastomer TPO, thermoplastic polyester elastomer TOEE, and thermoplastic polyurethane elastomer rubber TPU. The outer protective tube is in a wrapping manner.

[0025] The optical fiber is any one or more of single-mode optical fiber, multi-mode optical fiber, multi-core single-mode optical fiber, few-mode optical fiber, grating optical fiber, and microstructure optical fiber.

[0026] The material of the optical fiber protective tube is 316L stainless steel or 825 high nickel-chromium alloy steel.

[0027] The steel wire rope covered with the rubber coating layer is located at the center of the outer protective tube.

[0028] The optical fiber, the rubber coating layer embedded with the steel wire rope, the high temperature grease and the optical fiber protective tube together form an optical unit, and the outer protective tube protects the optical unit.

[0029] The oil well optical cable for underground seismic monitoring in the present invention comprises an optical fiber, a rubber coating layer with a high-strength steel wire rope embedded therein, a high-temperature grease, an optical fiber protective tube and an outer protective tube. The outer protective tube is a high-strength seamless stainless steel tube with strong pressure resistance and corrosion resistance, and can protect the internal optical fiber unit to meet the normal working requirements in the underground high-temperature, high-pressure and highly corrosive gas environment. The rubber coating is the main body of the optical fiber unit, and its core is a high-strength twisted steel wire rope. Due to the characteristics of the rubber material, the optical fiber structure has a strong impact resistance and is more sensitive to seismic sound waves. The present invention is suitable for the field of underground seismic monitoring.

[0030] By applying the technical solution of the present invention, before the vulcanization process of the rubber, a high-strength stainless steel wire rope with a wire diameter of 1 mm is placed in the core, and the surface is prefabricated with a polyimide-coated optical fiber in a spiral winding manner. During the vulcanization process of the rubber, the three will be combined together. Due to the elastic properties of the rubber itself, it can assist the optical fiber to greatly improve its perception of vibration sound waves, and at the same time provide excellent mechanical protection for the optical fiber. However, due to the influence of its own weight, the rubber coating will produce a large tensile deformation along the vertical axial direction, which will cause the optical fiber to elongate or even break its own structure for a long time. Therefore, the internal high-strength steel wire rope can greatly reduce the possibility of this happening. The rough surface of the twisted steel wire rope can make the rubber layer more firmly attached to it, avoiding the occurrence of structural peeling. The optical fiber is spirally wound on the rubber coating, which increases the redundant length of the optical fiber and improves the reliability of the optical unit.

[0031] The optical fiber protective tube can provide the first mechanical protection for the internal optical fiber. The optical fiber protective tube and the internal structure are filled with high-temperature grease, which can prevent moisture erosion in the air, reduce external environmental disturbances and reduce hydrogen loss, and can effectively protect the internal optical fiber. The above parts constitute an optical unit. At the same time, the outer surface of the optical fiber protective tube is wrapped with a thermoplastic elastomer sheath. The sheath material can be one of TPO, TPEE, and TPU. This type of material has a good sound absorption effect, which can greatly reduce the reflection loss of vibration sound waves during seismic detection and improve the sensitivity of the optical cable for downhole seismic signal monitoring. At the same time, the elastic plastic material has strong elasticity and can provide good mechanical protection for the internal optical unit. The outer high-strength seamless stainless steel protective tube can prevent the intrusion of water, oil and other corrosive gases in the high-temperature and high-pressure environment underground, and can resist external mechanical shock to ensure the normal operation of the internal optical unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1The figure is a structural diagram of a specific embodiment of an oil well optical cable for downhole seismic monitoring according to the present invention. DETAILED DESCRIPTION

[0033] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0034] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations and / or combinations thereof.

[0035] Most existing oil well optical cables are composed of internal twisted steel wires and external steel pipes, with filling materials added between the internal optical fiber, the steel wires and the external stainless steel pipe for protection and sealing. Although this method protects the internal optical fiber, it greatly increases the weight of the optical cable and reduces its own strength. At the same time, due to the influence of its own structure, the oil well optical cable using distributed optical fiber vibration monitoring technology cannot guarantee the sensitivity of the optical fiber to external vibrations during downhole seismic monitoring, which greatly reduces the detection accuracy of the system. To solve this problem, the present application provides a new optical cable structure.

[0036] The oil well optical cable for downhole seismic monitoring comprises: a rubber coating layer with a steel wire rope embedded therein, an optical fiber fixed thereon in a spiral manner, an optical fiber protective tube and high-temperature grease filled inside, an elastic body protective layer wrapped around the outside of the optical fiber protective tube, and an outer protective tube providing mechanical protection.

[0037] The rubber coating layer should have strong oil resistance, water resistance and corrosion resistance under the premise of ensuring its own elasticity and strength, and should also be resistant to aging and impact.

[0038] The steel wire ropes should include at least one high-strength steel wire rope to withstand tensile stress.

[0039] The optical fiber and the rubber coating are integrated as a whole, and preferably the optical fiber is spirally wound and embedded inside the surface of the rubber.

[0040] The optical fiber comprises a core, a cladding and a coating layer, and the coating layer is preferably made of a high temperature resistant material, preferably a polyimide coating layer.

[0041] The outside of the optical fiber and the rubber coating layer is an optical fiber protective tube, and the inside of the optical fiber protective tube is preferably filled with high-temperature grease.

[0042] The outer side of the optical fiber protective tube is surrounded by an elastic protective layer.

[0043] The outermost layer of the optical cable is an outer protective tube, and preferably the outer protective tube is a high-strength seamless stainless steel tube.

[0044] The optical fiber is any one or more of single-mode optical fiber, multi-mode optical fiber, multi-core single-mode optical fiber, few-mode optical fiber, grating optical fiber, and microstructure optical fiber.

[0045] The following are several specific embodiments of the present invention.

[0046] Example 1

[0047] In a specific embodiment 1 of the present invention, Figure 1 As shown, the optical cable consists of a rubber coating 4 with an embedded steel wire rope 3, an optical fiber 1 spirally fixed thereon, an optical fiber protective tube 2 and a high-temperature grease 5 filled inside, an elastomer protective layer 6 wrapped around the outside of the optical fiber protective tube, and an outer protective tube 7 for providing mechanical protection.

[0048] The present application provides effective mechanical and chemical protection for the optical fiber by tightly combining the optical fiber with rubber during the vulcanization process of the rubber. At the same time, the elasticity of the rubber and the structure of the optical fiber protective tube can ensure the effective monitoring of earthquakes by the optical fiber. The optical fiber protective tube, the elastomeric protective layer on the optical fiber protective tube and the outer protective tube can prevent the optical cable from intrusion of external hazardous substances in the harsh working environment underground, ultimately ensuring the normal operation of the internal optical fiber.

[0049] The rubber material can be selected from materials with good wear resistance, anti-aging, stable physical and chemical properties, and good high and low temperature resistance. In this embodiment, the material of the rubber coating layer 4 is nitrile rubber with a diameter of 2 to 3 mm. Nitrile rubber has the characteristics of oil resistance, high and low temperature resistance, wear resistance, good air tightness, etc., good mechanical properties, stable chemical properties, and is commonly used in various sealing components. Its vulcanization temperature is about 150°C.

[0050] Before the vulcanization process of the rubber, a high-strength stainless steel wire rope with a wire diameter of 1mm is placed in the core. The preferred material is 304 stainless steel or high-strength galvanized steel or alloy-coated steel, and more preferably a soft steel wire rope with multiple strands of fine steel wires twisted together. During the vulcanization process, the rubber will be combined with the steel wire rope. Due to the elastic properties of the rubber itself, it can assist the optical fiber in greatly improving its perception of vibration sound waves, and at the same time provide excellent mechanical protection for the optical fiber. However, due to the influence of its own weight, the rubber coating will produce a large tensile deformation along the vertical axial direction. If this continues for a long time, it will cause the optical fiber to elongate or even break its own structure. Therefore, the internal high-strength steel wire rope can greatly reduce the possibility of this happening. The rough surface of the twisted steel wire rope can make the rubber layer adhere to it more firmly, avoiding the occurrence of structural peeling.

[0051] Example 2

[0052] In a specific embodiment 2 of the present invention, the optical fiber is prefabricated on the surface of the rubber layer in a spiral winding manner during the vulcanization process of the rubber layer. The optical fiber includes a core, a cladding and a coating layer, and the coating layer is preferably made of a high temperature resistant material, and further preferably the coating layer material is polyimide with a maximum temperature tolerance of 350°C, and its normal working temperature is 300°C, which meets the high temperature working environment requirements underground, and can ensure that the optical fiber is not damaged during the rubber vulcanization process.

[0053] On the one hand, the rubber wrapping the optical fiber can effectively protect the optical fiber, and on the other hand, it can play a role of mechanical buffering for the optical fiber. In particular, when high-intensity vibration causes excessive displacement of the optical fiber under normal working conditions, it can prevent the optical fiber from directly colliding with the steel casing and causing damage to the optical fiber.

[0054] Example 3

[0055] In a specific embodiment 3 of the present invention, the optical fiber protective tube can provide the first mechanical protection for the internal optical fiber. The optical fiber protective tube and the interior are filled with high-temperature grease. The high-temperature grease can prevent moisture erosion in the air, reduce external environmental disturbances and reduce hydrogen loss, and can effectively protect the internal optical fiber. The above parts constitute an optical unit. At the same time, the outer surface of the optical fiber protective tube is wrapped with a thermoplastic elastomer protective layer. The protective layer material can be one of TPO, TPEE, and TPU. This type of material has a good sound absorption effect, which can greatly reduce the reflection loss of vibration sound waves during seismic detection and improve the sensitivity of the optical cable for downhole seismic signal monitoring. At the same time, the elastic plastic material has strong elasticity and can provide good mechanical protection for the internal optical unit. The outer high-strength seamless stainless steel protective tube can prevent the intrusion of water, oil and other corrosive gases in the high-temperature and high-pressure environment underground, and can resist external mechanical shocks to ensure the normal operation of the internal optical unit.

[0056] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions recorded in the aforementioned embodiments or replace some of the technical features therein with equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

[0057] Except for the technical features described in the specification, all other technical features are known technologies to those skilled in the art.

Claims

1. Oil well optical cable for downhole seismic monitoring, characterized in that: The oil well optical cable for downhole seismic monitoring includes: optical fiber; A steel wire rope, the steel wire rope is covered with a rubber coating layer, the optical fiber is embedded in the surface of the rubber coating layer, and the optical fiber and the rubber coating layer are integrated; An optical fiber protective tube, the outer layer of which is covered with a sheath, and the steel wire rope is placed in the optical fiber protective tube; High temperature grease, which is filled between the optical fiber protective tube and the rubber coating layer; Outer protective tube, which is made of high-strength seamless stainless steel tube, is used to protect internal components.

2. The oil well optical cable for downhole seismic monitoring according to claim 1, characterized in that: The diameter of the rubber coating layer is between 2 and 3 mm.

3. The oil well optical cable for downhole seismic monitoring according to claim 1, characterized in that: The rubber coating should contain at least one high-strength steel wire rope with a diameter of 1 mm to withstand tensile stress.

4. The oil well optical cable for downhole seismic monitoring according to claim 1, characterized in that: The steel wire rope is made of 304 stainless steel or high-strength galvanized steel or alloy-coated steel.

5. The oil well optical cable for downhole seismic monitoring according to claim 1, characterized in that: The steel wire rope is a soft steel wire rope made of multiple strands of fine steel wires twisted together.

6. The oil well optical cable for downhole seismic monitoring according to claim 1, characterized in that: The optical fiber is vulcanized and fixed together with the rubber coating layer during the molding process, so that the rubber completely wraps the optical fiber.

7. The oil well optical cable for downhole seismic monitoring according to claim 1, characterized in that: The optical fiber comprises a core, a cladding and a coating layer, and the coating layer is made of a high temperature resistant material.

8. The oil well optical cable for downhole seismic monitoring according to claim 7, characterized in that: The coating layer is made of polyimide with a maximum temperature resistance of 350°C.

9. The oil well optical cable for downhole seismic monitoring according to claim 1, characterized in that: The outer protective tube is made of a thermoplastic elastic material, which may be one of thermoplastic polyolefin elastomer TPO, thermoplastic polyester elastomer TOEE, and thermoplastic polyurethane elastomer rubber TPU. The outer protective tube is in a wrapping manner.

10. The oil well optical cable for downhole seismic monitoring according to claim 1, characterized in that: The optical fiber is any one or more of single-mode optical fiber, multi-mode optical fiber, multi-core single-mode optical fiber, few-mode optical fiber, grating optical fiber, and microstructure optical fiber.

11. The oil well optical cable for downhole seismic monitoring according to claim 1, characterized in that: The material of the optical fiber protective tube is 316L stainless steel or 825 high nickel-chromium alloy steel.

12. The oil well optical cable for downhole seismic monitoring according to claim 1, characterized in that: The steel wire rope covered with the rubber coating layer is located at the center of the outer protective tube.

13. The oil well optical cable for downhole seismic monitoring according to claim 1, characterized in that: The optical fiber, the rubber coating layer embedded with the steel wire rope, the high temperature grease and the optical fiber protective tube together form an optical unit, and the outer protective tube protects the optical unit.

Images