A permanent fixing device for downhole optical fiber and its installation method

Abstract

The present application provides a downhole optical fiber permanent fixing device and an installation method thereof. During the drilling process, the optical fiber is permanently fixed downhole by an outer tube and a casing, and the monitoring optical fiber is permanently placed in the injection well, which can monitor the entire life cycle. The optical fiber can be placed in the outer tube, and the casing is arranged on the outside of the outer tube, and the casing is connected to the well wall. A filler can be injected into the annular space formed between the casing and the outer tube to reinforce the outer tube and the well wall, effectively protecting the optical fiber from damage during the subsequent carbon dioxide injection process. Since the outer tube of the device and the optical fiber are not directly connected, the outer tube is fixed in the well by the filler, so the optical fiber can be recovered and reused after the monitoring is stopped.

Description

Technical Field

[0001] The present application relates to the technical field of oil and gas field development, and in particular to a downhole optical fiber permanent fixing device and an installation method thereof. Background Art

[0002] Pressure and temperature are fundamental reservoir engineering parameters in oil and gas resource development. Their real-time, high-precision measurement is crucial for determining the location and thickness of oil reservoirs, the depth of aquifers, and the operational pipelines for water / gas zones. Currently, fiber optic logging is the most promising logging method, offering high measurement accuracy, fast signal response, no electrical charge, and immunity to electromagnetic interference. It also offers a high operating temperature of up to 300°C, high-temperature and high-pressure resistance, corrosion resistance, and long transmission distances of tens of kilometers. It can be connected in series, enabling layered monitoring, permanent real-time online monitoring, and distributed monitoring. It also enables integrated monitoring of temperature, pressure, and even flow.

[0003] During the geological storage of carbon dioxide (CO2), monitoring wells are typically drilled alongside the injection well to monitor the distribution of the CO2 plume and changes in underground temperature and pressure. Optical fibers are placed in these wells for permanent or periodic monitoring. This approach typically requires drilling monitoring wells some distance from the injection well, resulting in high costs and inability to monitor the actual temperature and pressure below the injection well or the plume distribution. This impacts the optical fiber's lifespan, particularly at temperatures above 300°C, where hydrogen loss is exacerbated, shortening the fiber's lifespan.

[0004] In the existing technology, if the optical fiber is to be replaced, the oil well tubing must be pulled out. Moreover, for long-term injection wells, the downhole tubing cannot be replaced. Once the optical fiber fails, downhole data cannot be obtained. Therefore, a permanent optical fiber fixing device has been invented. After installation, the optical fiber can be directly replaced without pulling out the downhole tubing, which has become an urgent problem to be solved in this field. Summary of the Invention

[0005] To address the above issues, the present application provides a downhole optical fiber permanent fixture and usage method, which places the monitoring optical fiber in the injection well casing to achieve the purpose of monitoring the distribution of carbon dioxide plume and underground temperature and pressure changes.

[0006] To solve the above technical problems, this application provides the following technical solutions:

[0007] In a first aspect, the present application provides a downhole optical fiber permanent fixing device and an installation method thereof, comprising:

[0008] An outer tube, wherein the outer tube is an annular structure, and the optical fiber is arranged in a space formed by the outer tube;

[0009] The casing is disposed outside the outer tube, the outer tube wall of the casing is connected to the well wall, and the annular space formed by the casing and the outer tube can accommodate fillers for reinforcing the well wall and the outer tube.

[0010] Preferably, an optical fiber sleeve is provided on the outside of the optical fiber, one end of the optical fiber sleeve is provided with an internal thread, and the other end is provided with an external thread matching the internal thread, and the outer tube can be freely combined to a set length.

[0011] Preferably, a plurality of fixing members and supporting members are provided on the outside of the outer tube. The fixing members are coaxially arranged with the outer tube and are detachably connected to the outer tube. The supporting members connect the fixing members and the sleeve. The angle formed by the supporting members and the fixing members is adjustable, and the distance between the outer tube and the sleeve can be adjusted.

[0012] Preferably, the distances between each of the fixing members are equal.

[0013] Preferably, one end of the support member is connected to the fixing member via a rotating shaft, and the other end of the support member abuts against the sleeve.

[0014] Preferably, springs are provided on the outer side of one end of the fixing member close to the supporting member and on the inner side of one end of the supporting member close to the fixing member.

[0015] Preferably, the end of the support member close to the well wall is located above the end close to the fixing member.

[0016] Preferably, an air pipe is provided outside the outer tube for injecting carbon dioxide.

[0017] Preferably, the injection wellhead is provided with a conduit for introducing the filler.

[0018] In a second aspect, the present application provides an application of the above-mentioned downhole optical fiber permanent fixing device, characterized in that it includes:

[0019] According to the depth of the injection well, the optical fiber is placed in the outer tube;

[0020] A casing is arranged in the injection well, wherein the outer wall of the casing is connected to the wall of the injection well, and the casing forms an annular space;

[0021] placing the outer tube into the annular space;

[0022] Filling material is injected into the annular space to reinforce the well wall and the outer pipe.

[0023] It can be seen from the above technical solution that the present application provides a permanent downhole optical fiber fixing device and an installation method thereof. During the drilling process, the optical fiber is permanently fixed underground by an outer tube and a casing, and the monitoring optical fiber is permanently placed in the injection well, which can monitor the entire life cycle. The optical fiber can be placed in the outer tube, and the casing is arranged on the outside of the outer tube, and the casing is connected to the well wall. The annular space formed between the casing and the outer tube can be injected with fillers to reinforce the outer tube and the well wall, effectively protecting the optical fiber from damage during the subsequent carbon dioxide injection process. Since the outer tube of the device and the optical fiber are not directly connected, the outer tube is fixed in the well by the filler, so the optical fiber can be recovered and reused after the monitoring is stopped.

[0024] In order to make the above and other objects, features and advantages of the present invention more obvious and easy to understand, preferred embodiments are given below and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0026] Figure 1 This is a schematic structural diagram of a downhole optical fiber permanent fixing device in an embodiment of the present application.

[0027] Figure 2 This is a schematic diagram of the outer tube structure of the downhole optical fiber permanent fixing device in an embodiment of the present application.

[0028] Figure 3 Schematic diagram of the application process of the downhole optical fiber permanent fixing device in an embodiment of the present application.

[0029] Figure numerals: 1. catheter; 2. cement slurry; 3. casing; 4. production casing; 5. air pipe; 6. optical fiber sleeve; 7. optical fiber; 8. outer tube; 9. fixing piece; 10. internal thread; 11. external thread. DETAILED DESCRIPTION

[0030] To make the purpose, technical solutions, and advantages of the embodiments of this application more clear, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the drawings in the embodiments of this application. Obviously, the described embodiments are part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0031] During the geological storage of carbon dioxide (CO2), monitoring wells are typically drilled alongside the injection well to monitor the distribution of the CO2 plume and changes in underground temperature and pressure. Optical fibers are placed in these wells for permanent or periodic monitoring. This approach typically requires drilling monitoring wells some distance from the injection well, resulting in high costs and inability to measure the actual temperature and pressure below the injection well or the distribution of the plume below it.

[0032] Based on the above content, the present application provides an embodiment of a downhole optical fiber permanent fixing device, see Figure 1 The downhole optical fiber permanent fixing device includes: an outer tube 8, the outer tube 8 is a ring-shaped structure, and the optical fiber 7 is arranged in the space formed by the outer tube 8;

[0033] The casing 3 is arranged outside the outer tube 8, and the outer tube wall of the casing 3 is connected to the well wall. The annular space formed by the casing 3 and the outer tube 8 can accommodate fillers for reinforcing the well wall and the outer tube 8.

[0034] In this embodiment, an optical fiber 7 can be placed in the outer tube 8, and the casing 3 is mounted on the outside of the outer tube and connected to the well wall. A filler can be injected into the annular space formed between the casing 3 and the outer tube 8. A conduit 1 is provided at the wellhead for injecting the filler. The filler can be used to reinforce the outer tube and the well wall, and to seal off oil, gas, and water layers, effectively protecting the optical fiber from damage during the subsequent carbon dioxide injection process. Since the outer tube of the device and the optical fiber are not directly connected, the outer tube is fixed in the well by the filler, so the optical fiber can be recovered and reused after stopping monitoring. The filler can be cement slurry 2. The tube body of the casing 3 close to the well wall is the surface casing, and the tube body close to the outer tube is the production casing 4.

[0035] In a specific embodiment, see Figure 2 A fiber optic sleeve 6 is provided on the outside of the optical fiber. One end of the fiber optic sleeve 6 is provided with an internal thread 10, and the other end is provided with an external thread 11 matching the internal thread 10. The fiber optic sleeve 6 can be freely combined to a set length. After measuring the depth of the injection well, the outer tube 8 is assembled to an appropriate length according to the depth.

[0036] For instructions on how to use this device, see Figure 3 ,S1: Assemble the actual length of the optical fiber sleeve according to the drilling depth of the injection well.

[0037] In this step, according to the depth of the injection well, an appropriate number of optical fiber sleeves 6 are selected, two optical fiber sleeves 6 are connected end to end, multiple downhole optical fiber sleeve external threads and internal threads are assembled respectively, the monitoring optical fiber is placed in the optical fiber sleeve, and the optical fiber sleeve is assembled.

[0038] S2: Before the cementing process, the optical fiber sleeve is placed in the annular space between the production casing 4 of the downhole injection well and the wellbore.

[0039] In this step, the casing 3 is installed inside the injection well, thereby forming an annular space between the casing 3 and the wellbore, and the outer tube 8 is installed in the annular space formed between the casing 3 and the wellbore, thereby also forming an annular space between the outer tube 8 and the casing 3, and then the assembled optical fiber sleeve 6 is placed in the outer tube 8.

[0040] S3: Inject cement slurry for cementing. Cement is injected into the annular space formed between the outer tube 8 and the casing 3 to fill the annular space, thereby permanently fixing the outer tube 8. The optical fiber in the outer tube 8 can be replaced or removed normally.

[0041] From the above description, it can be seen that the present application provides a permanent downhole optical fiber fixing device and an installation method thereof. During the drilling process, the optical fiber is permanently fixed underground by an outer tube and a casing, and the monitoring optical fiber is permanently placed in the injection well, which can monitor the entire life cycle. The optical fiber can be placed in the outer tube, and the casing is arranged on the outside of the outer tube, and the casing is connected to the well wall. The annular space formed between the casing and the outer tube can be injected with fillers to reinforce the outer tube and the well wall, effectively protecting the optical fiber from damage during the subsequent carbon dioxide injection process. Since the outer tube of the device and the optical fiber are not directly connected, the outer tube is fixed in the well by the filler, so the optical fiber can be recovered and reused after the monitoring is stopped.

[0042] In a specific embodiment, see Figure 2 A plurality of fixing members 9 and supporting members are provided on the outside of the outer tube 8. The fixing member 9 is coaxially arranged with the outer tube 8 and is detachably connected to the outer tube 8. The supporting member connects the fixing member and the sleeve 3. The angle formed by the supporting member and the fixing member 9 is adjustable, and the distance between the outer tube 8 and the sleeve 3 can be adjusted.

[0043] In this embodiment, the optical fiber 7 is placed in an outer tube 8. Fixing members 9 and supports are provided on the outside of the outer tube 8. The spacing between each fixing member 9 is equal to strengthen the stability of the outer tube 8. The fixing member 9 and the support member are movably connected to adjust the angle between the support member and the fixing member 9. In this application, in order for the outer tube 8 to effectively protect the optical fiber, the material selected for the outer tube 8 should have a certain degree of hardness and high temperature resistance, while not affecting the optical fiber data acquisition.

[0044] In a specific embodiment, one end of the support member is connected to the fixing member 9 through a rotating shaft, and the other end of the support member is in contact with the sleeve 3. A spring is provided on the outer side of the end of the fixing member 9 close to the support member and on the inner side of the end of the support member close to the fixing member 9. Due to the provision of the spring, the angle between the support member and the fixing member 9 can only be adjusted within a set range. At the same time, the end of the support member close to the fixing member 9 is located below the end away from the fixing member 9. Therefore, the support member is fixed to the well wall in the direction toward the well (that is, it can enter the well smoothly and cannot move toward the outside of the well, which plays a fixing role), which can ensure that the outer tube where the optical fiber is located remains in the center of the sleeve.

[0045] In some other embodiments, the support member may be an annular structure or a tubular structure. When the support member is an annular structure, each fixing member 9 is equipped with a support member, which is sleeved outside the fixing member 9, and the diameter of the upper opening of the support member is larger than the diameter of the lower opening. When the support member is a tubular structure, to further secure the position of the support casing in the well, each fixing member 9 is equipped with multiple support members, and the support members are arranged inclined toward the well.

[0046] In a specific embodiment, the distance between every two adjacent fixing members 9 on the outer tube 8 is equal. In the present application, the distance between the fixing members 9 is preferably 3 meters.

[0047] In a specific embodiment, an air pipe 5 is provided outside the outer tube for injecting carbon dioxide.

[0048] From the above description, it can be seen that the downhole optical fiber permanent fixing device and installation method provided by the present application can permanently fix the optical fiber underground through the outer tube and the casing during the drilling process, and permanently place the monitoring optical fiber in the injection well, so that the entire life cycle monitoring can be carried out. The optical fiber can be placed in the outer tube, and the casing is arranged on the outside of the outer tube, and the casing is connected to the well wall. The annular space formed between the casing and the outer tube can be injected with fillers to reinforce the outer tube and the well wall, effectively protecting the optical fiber from damage during the subsequent carbon dioxide injection process. Since the outer tube of the device and the optical fiber are not directly connected, the outer tube is fixed in the well by the filler, so the optical fiber can be recovered and reused after the monitoring is stopped.

[0049] In the description of this specification, reference to the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples" means that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the embodiment of this specification. In this specification, the exemplary expressions of the above terms do not necessarily refer to the same embodiment or example.

[0050] In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification, as well as the features of the different embodiments or examples, unless they are mutually inconsistent. The above description is merely an embodiment of the embodiment of this specification and is not intended to limit the embodiment of this specification. For those skilled in the art, various changes and modifications may be made to the embodiment of this specification. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the embodiment of this specification shall be included within the scope of the claims of the embodiment of this specification.

Claims

1. A permanent fixing device for downhole optical fiber, characterized in that: include: An outer tube, wherein the outer tube is an annular structure, and the optical fiber is arranged in a space formed by the outer tube; A casing, the casing being disposed outside the outer tube, the outer tube being placed in an annular space formed by the casing and the production casing, the outer tube wall of the casing being connected to the wall of the injection well, and the annular space formed by the casing and the production casing being capable of accommodating a filler for reinforcing the casing and the outer tube; The outer tube is provided with a plurality of fixing members and supporting members. The fixing members are coaxially arranged with the outer tube and are detachably connected to the outer tube. The supporting members abut against the sleeve and are connected to the fixing members. A spring is provided between the supporting members and the fixing members so that the angle formed by the supporting members and the fixing members can be adjusted within a set range, thereby adjusting the distance between the outer tube and the sleeve. The production casing is provided with an air pipe inside for injecting carbon dioxide; An optical fiber sleeve is provided on the outside of the optical fiber, one end of the optical fiber sleeve is provided with an internal thread, and the other end thereof is provided with an external thread matching the internal thread, and the outer tube can be freely assembled to a set length; The outer tube is fixed in the well by the filler, and the optical fiber can be recovered and reused after the monitoring is stopped.

2. The downhole optical fiber permanent fixing device according to claim 1, characterized in that: The distances between each of the fixing members are equal.

3. The downhole optical fiber permanent fixing device according to claim 1, characterized in that: One end of the supporting member is connected to the fixing member via a rotating shaft.

4. The downhole optical fiber permanent fixing device according to claim 3, characterized in that: One end of the support member close to the well wall is located above one end close to the fixing member.

5. The downhole optical fiber permanent fixing device according to claim 1, characterized in that: The injection wellhead is provided with a conduit for introducing the filler.

6. A method for installing a downhole optical fiber permanent fixture according to any one of claims 1 to 5, characterized in that: include: According to the depth of the injection well, the optical fiber is placed in the outer tube; A casing is arranged in the injection well, wherein the outer wall of the casing is connected to the wall of the injection well, and the casing and the production casing form an annular space; placing the outer tube into the annular space; Filling material is injected into the annular space to reinforce the well wall and the outer pipe.

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