Optical fiber oil and gas well casing pipe string structure and full life cycle real-time monitoring method

Abstract

The present application belongs to the technical field of oil well monitoring, and particularly relates to a kind of optical fiber oil and gas well casing string structure and full life cycle real-time monitoring method.A kind of optical fiber oil and gas well casing string structure, from bottom to top, includes sequentially connected float shoe, first casing, first float collar, second casing, second float collar, first optical fiber casing, second optical fiber casing, cable-through casing head, first optical fiber casing and second optical fiber casing are both double-layer pipe structures, including inner layer steel pipe and outer layer shrinkable steel pipe closely attached to the outer side of the inner layer steel pipe, and a plurality of optical fiber sensors are uniformly arranged on the outer side of the inner layer steel pipe in the circumferential direction.The present application can master the technical condition of oil and gas well casing string in real time through the optical fiber oil and gas well casing string structure, provide technical basis for workover decision, ensure the safe, environmentally friendly and stable production of oil and gas wells, and provide technical basis for casing inspection work of fracturing and other stimulation and injection measures.

Description

Technical Field

[0001] This invention belongs to the field of oil well monitoring technology, and specifically relates to a fiber optic oil and gas well casing string structure and a real-time monitoring method for its entire life cycle. Background Technology

[0002] Most casing damage monitoring technologies rely on in-casing inspections, only implementing preventative measures after damage is detected. This approach cannot provide real-time monitoring of casing deformation and stress processes, hindering timely problem detection and resolution. Furthermore, effective pressure system monitoring is lacking during oilfield development. Methods for detecting formation pressure are limited to in-casing pressure measurement, involving periodic testing by perforating the casing and formation and inserting pressure measuring equipment within the casing. This approach fails to provide real-time monitoring of formation pressure changes within the development block, thus failing to offer timely and effective technical data for dynamic adjustments.

[0003] In recent years, fiber optic monitoring technology has been developed outside the casing. Fiber optic sensors are deployed in two ways: in non-oil layers, they are deployed at a certain angle outside the casing; in oil layers, to avoid damage from perforation guns, downhole positioning technology is used to deploy the sensors at fixed points. However, since the positioning connector can only be fixed at one point, and the casing will rotate during the running-in process, there is a problem of large azimuth measurement errors over long distances. Summary of the Invention

[0004] To address the aforementioned problems, the purpose of this invention is to provide a real-time monitoring method for the structure and lifecycle of oil and gas well casing strings using optical fiber. This method enables real-time monitoring of the technical status of oil and gas well casing strings, providing a technical basis for well workover decisions and ensuring safe, environmentally friendly, and stable production of oil and gas wells. It also provides a technical basis for casing inspection work during fracturing and other production enhancement and injection measures.

[0005] The technical solution of the present invention is as follows: a fiber optic oil and gas well casing string structure, comprising, from bottom to top, a float shoe, a first casing, a first float collar, a second casing, a second float collar, a first fiber optic casing, a second fiber optic casing, and a cable-accessible casing head connected in sequence. The first fiber optic casing and the second fiber optic casing are both double-layer pipe structures, including an inner steel pipe and an outer diameter-reducing steel pipe tightly attached to the outside of the inner steel pipe. Multiple fiber optic sensors are uniformly arranged circumferentially on the outer side of the inner steel pipe.

[0006] The outer diameter of the floating shoe, the first floating hoop, and the second floating hoop is 158mm, the outer diameter of the first sleeve and the second sleeve is 139.7mm, and the length is 9.6m.

[0007] The first optical fiber sheath is located in the oil layer section. The outer diameter of the inner steel tube of the first optical fiber sheath is 139.7 mm, and the outer diameter of the outer shrinkable steel tube is 146 mm and the inner diameter is 140 mm. 24 optical fiber sensors are evenly arranged on the outer circumference of the inner steel tube. The length of the optical fiber sensor is the same as the length of the inner steel tube, and optical fiber sensor connectors are provided at both ends.

[0008] The second optical fiber sheath is located in the non-oil layer section. The outer diameter of the inner steel tube of the second optical fiber sheath is 139.7 mm, and the outer diameter of the outer shrinkable steel tube is 146 mm and the inner diameter is 140 mm. Eight optical fiber sensors are evenly arranged on the outer circumference of the inner steel tube. The length of the optical fiber sensor is the same as the length of the inner steel tube, and optical fiber sensor connectors are provided at both ends.

[0009] The fiber optic sensor adopts a three-layer structure: an inner layer of silicon dioxide, a middle layer of corundum, and an outer layer of capillary seamless steel tube.

[0010] The fiber optic sensors include temperature fiber optic sensors and strain fiber optic sensors.

[0011] The first and second fiber optic sleeves at the fiber optic sensor connector are each equipped with a protective straightener. The protective straightener has a spiral structure with multiple spiral straightening ridges. The upper inner side of the straightener body is provided with a slot, which matches the size of the sleeve coupling of the first and second fiber optic sleeves.

[0012] The protective straightener has 5 spiral straightening ridges, and the angle between the spiral straightening ridges and the straightener body is 72°.

[0013] A method for real-time monitoring of the entire lifecycle of fiber optic oil and gas well casing strings, using any of the fiber optic oil and gas well casing string structures described above, includes the following steps: S1: According to the downhole tubing design requirements, the tubing is connected at the wellhead. When connecting the first fiber optic sleeve and the second fiber optic sleeve, the fiber optic sensor and the optical cable are connected first, and three layers of epoxy resin and glass fiber are wrapped around them. Then, a protective stabilizer is installed on the outside of the sleeve. The three adjacent fiber optic sensors in the first fiber optic sleeve are connected to the one fiber optic sensor in the second fiber optic sleeve. S2: After the tubing is installed, connect the fiber optic sensor to the monitoring optical cable. The monitoring optical cable is led out from the cable conduit head and the monitoring signal is transmitted to the demodulator for decoding and monitoring. S3: The spiral perforation process is adopted, with a maximum of 8 holes on each casing to ensure that the perforating bullets do not destroy the 3 continuous fiber optic sensors at the same time. During the whole well monitoring process, the multi-arm caliper logging data is compared, and the first imaging result after well completion is used as the benchmark to compare and analyze the changes in well conditions at different time periods.

[0014] The technical advantages of this invention are as follows: 1. This invention, through its fiber optic oil and gas well casing string structure, enables real-time online monitoring of the technical condition of the oil and gas well casing string, providing early warning and technical support for selecting well workover timing; it can generate service status reports for the oil and gas well casing string, providing technical support for process optimization and well formation optimization for oilfield development and production enhancement measures; it can perform real-time, continuous monitoring, providing technical support for the full life cycle management of the wellbore; 2. This invention, through its protective centralizer, ensures that the spiral structure always contacts the well wall during casing installation, preventing scratches to the fiber optic sensors and providing protection; 3. This invention, through the first fiber optic casing with 24 fiber optic sensors installed in the oil layer section, adopts a spiral perforation process, with a maximum of 8 holes on each casing, ensuring that the perforating bullet does not simultaneously damage 3 continuous fiber optic sensors, so that the entire string always has 8 penetrating fiber optic sensors; ensuring the accuracy of the monitoring data; 4. This invention employs a three-layer encapsulation structure for the fiber optic sensor: an inner layer of silicon dioxide, a middle layer of corundum, and an outer layer of capillary seamless steel tube. This ensures that the fiber optic sensor can adapt to harsh downhole operating conditions and guarantees the stability of casing damage monitoring.

[0015] The following will provide further explanation in conjunction with the accompanying drawings. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of a fiber optic oil and gas well casing string structure according to an embodiment of the present invention.

[0017] Figure 2 This is a schematic diagram of the structure of the protective stabilizer according to an embodiment of the present invention.

[0018] Reference numerals: 1-Float shoe, 2-First sleeve, 3-First float clamp, 4-Second sleeve, 5-Second float clamp, 6-First fiber optic sleeve, 7-Second fiber optic sleeve, 8-Cable sleeve head, 9-Optical cable-, 10-Demodulator, 11-Spiral straightening ridge, 12-Straightener body, 13-Slot. Detailed Implementation

[0019] Example 1 like Figure 1 As shown, a fiber optic oil and gas well casing string structure includes, from bottom to top, a float shoe 1, a first casing 2, a first float collar 3, a second casing 4, a second float collar 5, a first fiber optic casing 6, a second fiber optic casing 7, and a cable-accessible casing head 8 connected in sequence. The first fiber optic casing 6 and the second fiber optic casing 7 are both double-layer pipe structures, including an inner steel pipe and an outer diameter-reducing steel pipe tightly attached to the outside of the inner steel pipe. Multiple fiber optic sensors are uniformly arranged circumferentially on the outer side of the inner steel pipe.

[0020] In practical use, both the first fiber optic sleeve 6 and the second fiber optic sleeve 7 of this invention have a double-layer pipe structure, including an inner steel pipe and an outer shrinkable steel pipe tightly attached to the outside of the inner steel pipe. Multiple fiber optic sensors are evenly arranged circumferentially on the outer side of the inner steel pipe. Through the fiber optic oil and gas well casing string structure, multiple fiber optic sensors can monitor the technical status of the oil and gas well casing string in real time, providing technical basis for well workover decisions and ensuring safe, environmentally friendly, and stable production of oil and gas wells; and providing technical basis for casing inspection work for production enhancement and injection measures such as fracturing.

[0021] Example 2 Preferably, based on Embodiment 1, in this embodiment, the outer diameter of the floating shoe 1, the first floating hoop 3, and the second floating hoop 5 is 158mm, the outer diameter of the first sleeve 2 and the second sleeve 4 is 139.7mm, and the length is 9.6m.

[0022] In actual use, the outer diameter of the floating shoe 1, the first floating hoop 3, and the second floating hoop 5 of the present invention is 139.7mm, the outer diameter of the first sleeve 2 and the second sleeve 4 is 139.7mm, and the length is 10m, to ensure that sufficient protective space is formed below the first optical fiber sleeve 6 during the lowering of the sleeve.

[0023] Example 3 Preferably, based on Embodiment 1 or Embodiment 2, in this embodiment, the first optical fiber sleeve 6 is located in the oil layer section, the outer diameter of the inner steel tube of the first optical fiber sleeve 6 is 139.7mm, the outer diameter of the outer shrinkable steel tube is 146mm and the inner diameter is 140mm, and 24 optical fiber sensors are uniformly arranged circumferentially on the outer side of the inner steel tube. The length of the optical fiber sensor is the same as the length of the inner steel tube, and optical fiber sensor connectors are provided at both ends.

[0024] In actual use, the first optical fiber sleeve 6 of the present invention is located in the oil layer section. The outer diameter of the inner steel tube of the first optical fiber sleeve 6 is 139.7mm, and the outer diameter of the outer shrinkable steel tube is 146mm and the inner diameter is 140mm. The first optical fiber sleeve 6 is connected to the inner steel tube, and a direct connection method is adopted, which is simple and quick.

[0025] Example 4 Preferably, based on Embodiment 1 or Embodiment 3, in this embodiment, the second optical fiber sleeve 7 is located in the non-oil layer section, the outer diameter of the inner steel tube of the second optical fiber sleeve 7 is 139.7mm, the outer diameter of the outer shrinkable steel tube is 146mm and the inner diameter is 140mm, and 8 optical fiber sensors are uniformly arranged circumferentially on the outer side of the inner steel tube. The length of the optical fiber sensor is the same as the length of the inner steel tube, and optical fiber sensor connectors are provided at both ends.

[0026] In actual use, the second optical fiber sleeve 7 is located in the non-oil layer section. The outer diameter of the inner steel tube of the second optical fiber sleeve 7 is 139.7mm, and the outer diameter of the outer shrinkable steel tube is 146mm and the inner diameter is 140mm. The second optical fiber sleeve 7 is connected to the inner steel tube, and a direct connection method is adopted, which is simple and quick.

[0027] Example 5 Preferably, based on Embodiment 1 or Embodiment 4, in this embodiment, the fiber optic sensor adopts a three-layer structure, with an inner layer of silicon dioxide, a middle layer of corundum, and an outer layer of capillary seamless steel tube.

[0028] In practical use, this invention uses a three-layer encapsulation structure for the fiber optic sensor: an inner layer of silicon dioxide, a middle layer of corundum, and an outer layer of capillary seamless steel tube. This ensures that the fiber optic sensor can adapt to harsh downhole operating conditions and guarantees the stability of casing damage monitoring.

[0029] Example 6 Preferably, based on Embodiment 1 or Embodiment 5, in this embodiment, the fiber optic sensor includes a temperature fiber optic sensor and a strain fiber optic sensor.

[0030] In practical use, the fiber optic sensor described in this invention includes a temperature fiber optic sensor and a strain fiber optic sensor, which can test both the temperature change of the entire wellbore and the stress change.

[0031] Example 7 Preferably, based on Embodiment 1 or Embodiment 6, in this embodiment, a protective straightener is provided on the outside of the first optical fiber sleeve 6 and the second optical fiber sleeve 7 at the optical fiber sensor connector. The protective straightener adopts a spiral structure and is provided with multiple spiral straightening ridges 11. A slot 13 is provided on the upper inner side of the straightener body 12. The slot 13 matches the size of the sleeve coupling of the first optical fiber sleeve 6 and the second optical fiber sleeve 7.

[0032] In actual use, the first fiber optic sleeve 6 and the second fiber optic sleeve 7 at the fiber optic sensor connector of the present invention are equipped with protective centralizers. The protective centralizers adopt a spiral structure. During the casing process, the spiral structure always contacts the well wall to prevent the fiber optic sensor from being scratched and thus play a protective role.

[0033] Example 8 Preferably, based on Embodiment 1 or Embodiment 7, in this embodiment, the protective straightener is provided with 5 spiral straightening ridges 11, and the angle between the spiral straightening ridges 11 and the straightener body 12 is 72°.

[0034] In actual use, the protective centralizer of the present invention is provided with 5 spiral centralizing ridges 11. The spiral centralizing ridges 11 and the centralizer body 12 have an angle of 72°. The 5 spiral centralizing ridges 11 ensure that the spiral structure always contacts the well wall during the casing process, preventing the fiber optic sensor from being scratched and playing a protective role. They also avoid the increased resistance of casing due to too many spiral centralizing ridges.

[0035] Example 9 A method for real-time monitoring of the entire lifecycle of fiber optic oil and gas well casing strings, using any of the fiber optic oil and gas well casing string structures described above, includes the following steps: S1: According to the downhole tubing design requirements, when connecting the downhole tubing at the wellhead, the first fiber optic sleeve 6 and the second fiber optic sleeve 7 are connected. First, connect the fiber optic sensor and the optical cable, and then wrap 3 layers of epoxy resin and glass fiber. Then, install a protective centralizer on the outside of the sleeve. The three adjacent fiber optic sensors in the first fiber optic sleeve 6 are connected to the one fiber optic sensor in the second fiber optic sleeve 7. S2: After the tubing is installed, connect the fiber optic sensor to the monitoring optical cable 9. The monitoring optical cable 9 is led out from the cable sleeve head 8 and the monitoring signal is transmitted to the demodulator 10 for decoding and monitoring. S3: The spiral perforation process is adopted, with a maximum of 8 holes on each casing to ensure that the perforating bullets do not destroy the 3 continuous fiber optic sensors at the same time. During the whole well monitoring process, the multi-arm caliper logging data is compared, and the first imaging result after well completion is used as the benchmark to compare and analyze the changes in well conditions at different time periods.

[0036] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A fiber optic oil and gas well casing string structure, characterized in that: From bottom to top, the structure includes a floating shoe (1), a first sleeve (2), a first floating hoop (3), a second sleeve (4), a second floating hoop (5), a first fiber optic sleeve (6), a second fiber optic sleeve (7), and a cable-accessible sleeve head (8). Both the first fiber optic sleeve (6) and the second fiber optic sleeve (7) are double-layered tube structures, consisting of an inner steel pipe and an outer, retractable steel pipe tightly attached to the outside of the inner steel pipe. Multiple fiber optic sensors are evenly distributed circumferentially on the outer side of the inner steel pipe. The first fiber optic sleeve (6) is located in the oil layer section. The outer diameter of the inner steel pipe of the first fiber optic sleeve (6) is 139.7 mm, and the outer, retractable steel pipe has an outer diameter of 146 mm and an inner diameter of 140 mm after reduction. 24 fiber optic sensors are evenly distributed circumferentially on the outer side of the inner steel pipe. The length of each fiber optic sensor is the same as the length of the inner steel pipe, and fiber optic sensor connectors are provided at both ends. The second optical fiber sleeve (7) is located in the non-oil layer section. The outer diameter of the inner steel tube of the second optical fiber sleeve (7) is 139.7 mm, and the outer diameter of the outer shrinkable steel tube is 146 mm and the inner diameter is 140 mm. Eight optical fiber sensors are evenly arranged on the outer circumference of the inner steel tube. The length of the optical fiber sensor is the same as the length of the inner steel tube. Optical fiber sensor connectors are provided at both ends. Protective straighteners are provided on the outside of the first optical fiber sleeve (6) and the second optical fiber sleeve (7) at the optical fiber sensor connector. The protective straightener adopts a spiral structure and includes a straightener body (12). Multiple spiral straightening ridges (11) are provided on the outside of the straightener body (12). A slot (13) is provided on the upper inner side of the straightener body (12). The slot (13) matches the size of the sleeve coupling of the first optical fiber sleeve (6) and the second optical fiber sleeve (7).

2. The fiber optic oil and gas well casing string structure according to claim 1, characterized in that: The outer diameter of the floating shoe (1), the first floating hoop (3), and the second floating hoop (5) is 158 mm, the outer diameter of the first sleeve (2) and the second sleeve (4) is 139.7 mm, and the length is 9.6 m.

3. The fiber optic oil and gas well casing string structure according to claim 1, characterized in that: The fiber optic sensor adopts a three-layer structure: an inner layer of silicon dioxide, a middle layer of corundum, and an outer layer of capillary seamless steel tube.

4. The fiber optic oil and gas well casing string structure according to claim 1, characterized in that: The fiber optic sensors include temperature fiber optic sensors and strain fiber optic sensors.

5. The fiber optic oil and gas well casing string structure according to claim 1, characterized in that: The protective straightener has 5 spiral straightening ridges (11), and the spiral straightening ridges (11) and the straightener body (12) have an angle of 72°.

6. A method for real-time monitoring of the entire lifecycle of a fiber optic oil and gas well casing string, using the fiber optic oil and gas well casing string structure as described in claim 1, characterized in that: Includes the following steps: S1: According to the design requirements of the downhole tubing, the tubing is connected at the wellhead. When the first fiber optic sleeve (6) and the second fiber optic sleeve (7) are connected, the fiber optic sensors are connected first, and three layers of epoxy resin and glass fiber are wrapped around them. Then, a protective stabilizer is installed on the outside of the sleeve. The three adjacent fiber optic sensors in the first fiber optic sleeve (6) are connected to one fiber optic sensor in the second fiber optic sleeve (7). S2: After the tubing is installed, connect the fiber optic sensor to the monitoring optical cable (9). The monitoring optical cable (9) is led out from the cable sleeve head (8) and the monitoring signal is transmitted to the demodulator (10) for decoding and monitoring. S3: The spiral perforation process is adopted, with a maximum of 8 holes on each casing to ensure that the perforating bullets do not destroy the 3 continuous fiber optic sensors at the same time. During the whole well monitoring process, the multi-arm caliper logging data is compared, and the first imaging result after well completion is used as the benchmark to compare and analyze the changes in well conditions at different time periods.

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