Subsea flexible pipe soft bottom drill for forming a methane channel and method of forming

Abstract

The application discloses a soft-bottom drill for forming a methane channel of a submarine flexible pipe and a forming method, and relates to the field of submarine flexible pipe drilling. The drill comprises a whole frame structure, a flexible continuous drill rod mechanism, a straightening and penetrating mechanism and a power head mechanism. The whole frame structure comprises a support frame and a guide rail. The flexible continuous drill rod mechanism comprises a flexible pipe storage roller, a flexible pipe and a roller driving device. One end of the flexible pipe is wound on the flexible pipe storage roller, and the other end is guided into the straightening and penetrating mechanism through the guide rail. The straightening and penetrating mechanism is connected to the support frame. The straightening and penetrating mechanism is provided with a shearing device. The power head mechanism comprises an outer drill bit, an inner drill bit, an inner drill bit restraining device, a drill bit driving device and an armored cable. The application is suitable for cold spring area surface sediments containing natural gas and biological resources, and provides a special in-situ artificial channel for methane seepage upwelling.

Description

Technical Field

[0001] This invention relates to the field of deep-sea drilling technology, and in particular to a flexible subsea drilling rig for forming methane channels and a method for forming such rigs. Background Technology

[0002] With social development, technological progress, and the increasing demand for various resources, modern submarine cold seeps and hydrothermal vent ecosystems associated with methane leaks, rich in oil, gas, and metal resources, have been discovered. Submarine methane leaks and hydrothermal vent systems not only have significant resource value but also serve as the primary medium for material and energy exchange between the lithosphere and the external spheres (biosphere, hydrosphere, and atmosphere), altering the seabed's topography. Therefore, studying the development and extension of cold seeps in soft-bottomed environments is crucial for understanding seabed geological changes.

[0003] Currently, because cold seeps are buried in the shallow bottom of the seabed, they require a long period of geological structural changes to seep to the seabed surface. Over the long term, this will have a huge impact on the biological communities that originally lived in the methane seepage area. Drilling machines are needed to help form methane seepage channels to facilitate the study of the early formation and evolution of life in the biosynthetic ecosystem. Summary of the Invention

[0004] The purpose of this invention is to provide a flexible subsea drilling rig and method for forming methane channels, in order to solve the problems existing in the prior art. It is applicable to surface sediments in cold seep areas containing natural gas and biological resources, and provides a special in-situ artificial channel for methane seepage and upwelling.

[0005] To achieve the above objectives, the present invention provides the following solution:

[0006] This invention provides a subsea flexible tube drilling rig for forming methane channels in soft seabed conditions, comprising an overall frame structure, a flexible continuous drill rod mechanism, a straightening and penetration mechanism, and a power head mechanism. The overall frame structure includes a support frame and a guide rail fixedly connected to the support frame. The flexible continuous drill rod mechanism includes a flexible tube storage roller, a flexible tube, and a roller drive device. The flexible tube storage roller is rotatably connected to the support frame and driven to rotate by the roller drive device. One end of the flexible tube is wound around the flexible tube storage roller, and the other end is guided into the straightening and penetration mechanism via the guide rail. The straightening and penetration mechanism is connected to the support frame and is used to straighten the flexible tube and drive the flexible tube. The flexible tube moves up and down; the straightening and penetration mechanism is equipped with a shearing device for cutting the flexible tube; the power head mechanism includes an outer drill bit, an inner drill bit, an inner drill bit restraint device, a drill bit drive device, and an armored cable. The outer drill bit is rotatably connected inside the drilling end of the flexible tube. The inner drill bit is restrained in the flexible tube by the inner drill bit restraint device. The inner drill bit is driven to rotate by the drill bit drive device. When the inner drill bit rotates forward, it can engage with the outer drill bit and drive the outer drill bit to rotate together. When the inner drill bit rotates backward, it can disengage from the outer drill bit. The armored cable is connected to the inner drill bit restraint device. Lifting the armored cable can release the restraint device on the inner drill bit to retrieve the inner drill bit.

[0007] Preferably, the system further includes a monitoring mechanism, which includes a sensor chain installed inside the flexible tube. The sensor chain includes a temperature chain, a multi-parameter sensor array, and a wellbore trajectory sensor. The flexible tube remaining in the formation constitutes the methane channel. The temperature chain is used to obtain the temperature distribution within the methane channel. The multi-parameter sensor array is used to obtain the methane and carbon dioxide concentrations at the bottom of the methane channel. The wellbore trajectory sensor is used to invert the wellbore trajectory parameters in real time.

[0008] Preferably, the internal drill bit restraint device includes a piston chamber and a locking tongue. The piston chamber is fixedly connected to the housing at the upper end of the drill bit drive device, and the lower end of the drill bit drive device is connected to the internal drill bit. A piston end cap is provided at the end of the piston chamber near the internal drill bit, and a piston is slidably disposed within the piston chamber. The piston includes a protruding section and a sliding section connected to each other. The protruding section protrudes outward through the piston end cap, and the sliding section is slidably disposed within the piston chamber. A piston rod is connected to the end of the sliding section away from the protruding section, and the piston rod passes through the piston chamber and is connected to the armored cable. A limiting step is formed between the protruding section and the sliding section. When the limiting step contacts the piston end cap, the piston end cap restricts the piston from continuing to move inward. As the drill bit moves in a certain direction, a spring is fitted on the piston rod. The spring is located inside the piston chamber, and its two ends abut against the sliding section and the inner wall of the piston chamber, respectively. The spring is in a compressed state. The housing of the drill bit drive device has multiple circumferentially distributed sliding holes. The flexible tube wall has locking tongue grooves corresponding to each of the sliding holes. A locking tongue is slidably disposed in each of the sliding holes. The radially inward end of the locking tongue abuts against the outer peripheral surface of the protruding section, and the radially outward end of the locking tongue extends into the locking tongue groove. When the armored cable is lifted, the protruding section can move upward to release the radial restriction on the locking tongue. At the same time, under the action of the locking tongue and the locking tongue groove, the locking tongue can move inward to disengage from the locking tongue groove.

[0009] Preferably, the locking tongue includes a radially arranged prism segment and a frustum segment, wherein the area of ​​the radially inward end of the frustum segment is larger than the area of ​​the radially outward end and equal to the cross-sectional area of ​​the prism segment, and the radially outward end of the frustum segment extends into the locking tongue groove; a limiting disc is provided at the radially inward end of the prism segment, the limiting disc is located inside the housing of the drill bit drive device, the limiting disc cannot pass through the sliding hole, and the radially outward end of the prism segment is connected to the radially inward end of the frustum segment.

[0010] Preferably, the inner drill bit is provided with a locking block, and the outer drill bit is provided with a locking groove that cooperates with the locking block. When the inner drill bit rotates forward, the locking block can engage with the locking groove, and when the inner drill bit rotates in reverse, the locking block disengages from the locking groove.

[0011] Preferably, the straightening and insertion mechanism includes a frame, within which two straightening and insertion assemblies are symmetrically arranged. Each straightening and insertion assembly includes a top sprocket, a bottom sprocket, an insertion chain, and a chain guide tensioner. The insertion chain is driven by the top sprocket and the bottom sprocket. The two insertion chains are in the same vertical plane. The flexible tube passes through the gap between the two insertion chains. The chain guide tensioner is located inside the insertion chain. The chain guide tensioners on both sides of the flexible tube are connected by clamping cylinders. The clamping cylinders can clamp the insertion chain and the flexible tube, thereby driving the flexible tube to move up and down through the friction between the insertion chain and the flexible tube.

[0012] Preferably, the shearing device is installed inside the frame and located below the straightening and penetration assembly. The shearing device includes two symmetrically arranged cutters. The flexible tube passes through the gap between the two cutters, and the flexible tube is cut by the relative movement of the two cutters.

[0013] Preferably, both the roller drive device and the drill bit drive device are oil-filled motors, and the top of the support frame is provided with lifting lugs.

[0014] The present invention also provides a method for forming a methane channel, based on the above-described subsea flexible pipe soft bottom drilling rig for forming a methane channel, comprising the following steps:

[0015] S1: Place the entire drilling rig structure on the seabed, start the drill bit drive device, and drill through the outer drill bit and the inner drill bit. At the same time, start the roller drive device and the straightening and penetration mechanism, release the flexible tube, straighten the flexible tube through the straightening and penetration mechanism and drive the flexible tube to move downward, and penetrate the flexible tube into the seabed.

[0016] S2: When drilling reaches the specified depth, shut down the roller drive device and the straightening and penetration mechanism, drive the inner drill bit to reverse, disengage the inner drill bit from the outer drill bit, then lift the armored cable to release the inner drill bit constraint device from the inner drill bit, and continue to lift the armored cable to retrieve the inner drill bit back to the drilling machine body.

[0017] S3: The flexible tube is cut by the shearing device, and the cut flexible tube remains in the formation to form the methane channel.

[0018] The present invention achieves the following technical effects compared to the prior art:

[0019] The present invention provides a submarine flexible pipe drilling rig and method for forming methane channels in soft seabed. The inner drill bit can engage with the outer drill bit when rotating forward and disengage from the outer drill bit when rotating backward, thus preventing accidental disengagement of the drill bit. The straightening and penetration mechanism can insert the flexible pipe into the seabed of the cold seep area as the drill bit advances, and the shearing device can retain the flexible pipe in the formation to form a sleeve wall, providing a special in-situ artificial channel for the soft seabed cold seep and assisting in the formation of methane leakage channels.

[0020] Furthermore, the present invention can invert the channel trajectory in real time on the host computer based on the wellbore trajectory sensor in the sensor chain; and realize the real-time monitoring of multiple parameters of the methane channel through the temperature chain and multi-parameter sensor array. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a schematic diagram of the overall structure of the submarine flexible pipe soft bottom drilling rig for forming methane channels provided by the present invention.

[0023] Figure 2 This is a schematic diagram of the straightening penetration mechanism and shearing device in this invention;

[0024] Figure 3 This is a schematic diagram of the power head mechanism in this invention;

[0025] Figure 4 This is a schematic diagram of the internal drill bit restraint device in this invention;

[0026] Figure 5 This is a schematic diagram of the internal and external drill bit disengagement in this invention;

[0027] Figure 6 This is a schematic diagram of the recovery of the internal drill bit via an armored cable in this invention;

[0028] Figure 7 This is a schematic diagram of the methane channel operation in this invention;

[0029] In the diagram: 1-Drilling rig overall frame structure, 2-Flexible continuous drill rod mechanism, 3-Straightening and penetration mechanism, 4-Power head mechanism, 5-Support frame, 6-Guide rail, 7-Flexible tube storage roller, 8-Flexible tube, 9-Roller drive device, 10-Shearing device, 11-Outer drill bit, 12-Inner drill bit, 13-Inner drill bit restraint device, 14-Drill bit drive device, 15-Armored cable, 16-Sensor chain, 17-Piston chamber, 18-Lock tongue, 19-Shell, 20-Piston end cap, 21- - Piston, 22- Protruding section, 23- Sliding section, 24- Piston rod, 25- Limiting step, 26- Spring, 27- Sliding hole, 28- Locking tongue groove, 29- Quadrilateral prism section, 30- Quadrilateral pyramidal section, 31- Limiting plate, 32- Locking block, 33- Locking groove, 34- Frame, 35- Straightening and penetration assembly, 36- Top sprocket, 37- Bottom sprocket, 38- Penetration chain, 39- Chain guide tensioner, 40- Clamping cylinder, 41- Cutter, 42- Lifting lug, 43- Submarine cold seep. Detailed Implementation

[0030] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] The purpose of this invention is to provide a flexible subsea drilling rig and method for forming methane channels, in order to solve the problems existing in the prior art. It is applicable to surface sediments in cold seep areas containing natural gas and biological resources, and provides a special in-situ artificial channel for methane seepage and upwelling.

[0032] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0033] like Figures 1-7As shown, this embodiment provides a submarine flexible pipe soft-bottom drilling rig for forming methane channels, including an overall drilling frame structure 1, a flexible continuous drill rod mechanism 2, a straightening and penetration mechanism 3, and a power head mechanism 4; the overall drilling frame structure 1 includes a support frame 5 and a guide rail 6 fixedly connected to the support frame 5; the flexible continuous drill rod mechanism 2 includes a flexible pipe storage roller 7, a flexible pipe 8, and a roller drive device 9. The flexible pipe storage roller 7 is rotatably connected to the support frame 5 and driven to rotate by the roller drive device 9. One end of the flexible pipe 8 is wound around the flexible pipe storage roller 7, and the other end is guided into the straightening and penetration mechanism 3 through the guide rail 6; the straightening and penetration mechanism 3 is connected to the support frame 5 and is used to straighten the flexible pipe 8 and drive the flexible pipe 8 up and down. The straightening and penetration mechanism 3 is equipped with a shearing device 10 for cutting the flexible tube 8. The power head mechanism 4 includes an outer drill bit 11, an inner drill bit 12, an inner drill bit restraint device 13, a drill bit drive device 14, and an armored cable 15. The outer drill bit 11 is rotatably connected to the inside of the drilling end of the flexible tube 8. The inner drill bit 12 is restrained in the flexible tube 8 by the inner drill bit restraint device 13. The inner drill bit 12 is driven to rotate by the drill bit drive device 14. When the inner drill bit 12 rotates forward, it can engage with the outer drill bit 11 and drive the outer drill bit 11 to rotate together. When the inner drill bit 12 rotates in reverse, it can disengage from the outer drill bit 11. The armored cable 15 is connected to the inner drill bit restraint device 13. Lifting the armored cable 15 can release the restraint of the inner drill bit restraint device 13 on the inner drill bit 12 so as to retrieve the inner drill bit 12.

[0034] In operation, the entire drilling rig is placed on the seabed, the drill bit drive device 14 is activated, and drilling is carried out through the outer drill bit 11 and the inner drill bit 12. At the same time, the roller drive device 9 and the straightening and penetration mechanism 3 are activated to release the flexible tube 8. The straightening and penetration mechanism 3 straightens the flexible tube 8 and drives it downward to penetrate the seabed. When the drilling reaches the designated depth, the roller drive device 9 and the straightening and penetration mechanism 3 are shut off, and the inner drill bit 12 is driven to reverse, disengaging the inner drill bit 12 from the outer drill bit 11. Then, the armored cable 15 is lifted to release the constraint of the inner drill bit constraint device 13 on the inner drill bit 12. The armored cable 15 is then lifted to retrieve the inner drill bit 12 back to the drilling rig body. The flexible tube 8 is cut by the shearing device 10, and the cut flexible tube 8 remains in the formation to form a methane channel. In this device, the inner drill bit 12 can engage with the outer drill bit 11 when rotating forward and disengage from the outer drill bit 11 when rotating backward, thus preventing accidental disengagement of the drill bit. The straightening and penetration mechanism 3 can insert the flexible tube 8 into the bottom sediment of the cold seep area as the drill bit advances, and the shearing device 10 can retain the flexible tube 8 in the formation to form a sleeve wall, providing a special in-situ artificial channel for the soft bottom sediment cold seep and assisting in the formation of a methane leakage channel.

[0035] In this embodiment, a monitoring mechanism is also included. This mechanism comprises a sensor chain 16 installed within the flexible tube 8. The sensor chain 16 includes a temperature chain, a multi-parameter sensor array, and a wellbore trajectory sensor. The flexible tube 8 remaining in the formation forms a methane channel. The temperature chain is used to obtain the temperature distribution within the methane channel, the multi-parameter sensor array is used to obtain the methane and carbon dioxide concentrations at the bottom of the methane channel, and the wellbore trajectory sensor is used to invert wellbore trajectory parameters in real time. When drilling reaches a designated depth, i.e., when the sensor chain 16 can detect the drill bit touching the seabed cold seep 43, drill bit retrieval can commence.

[0036] In this embodiment, the internal drill bit restraint device 13 includes a piston chamber 17 and a locking tongue 18. The piston chamber 17 is fixedly connected to the housing 19 at the upper end of the drill bit drive device 14. The lower end of the drill bit drive device 14 is connected to the internal drill bit 12. A piston end cap 20 is provided at the end of the piston chamber 17 near the internal drill bit 12. A piston 21 is slidably disposed inside the piston chamber 17. The piston 21 includes a protruding section 22 and a sliding section 23 connected to each other. The protruding section 22 protrudes outward through the piston end cap 20. The sliding section 23 is slidably disposed inside the piston chamber 17. A piston rod 24 is connected at the end of the sliding section 23 away from the protruding section 22. The piston rod 24 passes through the piston chamber 17 and is connected to the armored cable 15. A limiting step 25 is formed between the protruding section 22 and the sliding section 23. When the limiting step 25 contacts the piston end cap 20, the piston end cap 20 restricts the piston 21. As the drill bit 12 continues to move inward, a spring 26 is fitted onto the piston rod 24. The spring 26 is located inside the piston chamber 17, and its two ends abut against the sliding section 23 and the inner wall of the piston chamber 17, respectively. The spring 26 is in a compressed state. The housing 19 of the drill bit drive device 14 is provided with multiple circumferentially distributed sliding holes 27. The wall of the flexible tube 8 is provided with locking tongue grooves 28 corresponding to each sliding hole 27. A locking tongue 18 is slidably installed in each sliding hole 27. The radially inward end of the locking tongue 18 abuts against the outer peripheral surface of the protruding section 22, and the radially outward end of the locking tongue 18 extends into the locking tongue groove 28. When the armored cable 15 is lifted, the protruding section 22 can move upward to release the radial restriction on the locking tongue 18. At the same time, under the action of the locking tongue 18 and the locking tongue groove 28, the locking tongue 18 can move inward to disengage from the locking tongue groove 28. When drilling reaches the designated depth and the inner drill bit 12 needs to be retrieved, the inner drill bit 12 reverses, the armored cable 15 is lifted to release the radial limit on the locking tongue 18, and then the armored cable 15 is lifted to retrieve the inner drill bit 12 back to the drilling rig body.

[0037] In this embodiment, the locking tongue 18 includes a radially arranged quadrangular prism segment 29 and a quadrangular frustum segment 30. The area of ​​the radially inward end of the quadrangular frustum segment 30 is larger than the area of ​​the radially outward end and is equal to the cross-sectional area of ​​the quadrangular prism segment 29. The radially outward end of the quadrangular frustum segment 30 extends into the locking tongue groove 28. A limiting plate 31 is provided at the radially inward end of the quadrangular prism segment 29. The limiting plate 31 is located inside the housing 19 of the drill bit drive device 14. The limiting plate 31 cannot pass through the sliding hole 27. The radially outward end of the quadrangular prism segment 29 is connected to the radially inward end of the quadrangular frustum segment 30. The setting of the limiting plate 31 can prevent the locking tongue 18 from dislodging from the housing 19 of the drill bit drive device 14. The inclined setting of the side of the truncated pyramid section 30 can generate a radial force between the truncated pyramid section 30 and the locking tongue groove 28 when the armor cable 15 is lifted. Under the action of the radial force, the locking tongue 18 dislodges from the locking tongue groove 28.

[0038] In this embodiment, the inner drill bit 12 is provided with a locking block 32, and the outer drill bit 11 is provided with a locking groove 33 that cooperates with the locking block 32. When the inner drill bit 12 rotates clockwise, the locking block 32 can engage with the locking groove 33. When the inner drill bit 12 rotates counterclockwise, the locking block 32 disengages from the locking groove 33. When drilling is required, the inner drill bit 12 rotates clockwise to engage the locking block 32 with the locking groove 33; when the inner drill bit 12 needs to be retrieved, the inner drill bit 12 rotates counterclockwise to disengage the locking block 32 from the locking groove 33.

[0039] In this embodiment, the straightening and insertion mechanism 3 includes a frame 34, within which two straightening and insertion components 35 are symmetrically arranged. Each straightening and insertion component 35 includes a top sprocket 36, a bottom sprocket 37, an insertion chain 38, and a chain guide tensioner 39. The insertion chain 38 is drivingly connected to the top sprocket 36 and the bottom sprocket 37. The two insertion chains 38 are in the same vertical plane. The flexible tube 8 passes through the gap between the two insertion chains 38. The chain guide tensioner 39 is disposed inside the insertion chain 38. The chain guide tensioners 39 on both sides of the flexible tube 8 are connected by clamping cylinders 40. The clamping cylinders 40 can clamp the insertion chain 38 and the flexible tube 8 with the chain guide tensioners 39, thereby driving the flexible tube 8 to move up and down through the friction between the insertion chain 38 and the flexible tube 8. Each straightening and insertion component 35 is provided with a drive device to drive the top sprocket 36 to rotate. When it is necessary to insert the flexible tube 8, the two top sprockets 36 are driven to rotate inward, and at the same time, the clamping cylinder 40 presses the insertion chain 38 and the flexible tube 8 together, thereby driving the flexible tube 8 to move downward.

[0040] In this embodiment, the shearing device 10 is installed inside the frame 34 and located below the straightening and penetration assembly 35. The shearing device 10 includes two symmetrically arranged cutters 41. The flexible tube 8 passes through the gap between the two cutters 41, and the flexible tube 8 is cut by the relative movement of the two cutters 41. After drilling into place, the downward movement of the flexible tube 8 is stopped, and the two cutters 41 are driven to move relative to each other to cut the flexible tube 8 in the middle.

[0041] In this embodiment, both the roller drive device 9 and the drill bit drive device 14 are oil-filled motors, and the top of the support frame 5 is provided with a lifting lug 42. The lifting lug 42 facilitates the hoisting of the support frame 5 and its placement on the seabed.

[0042] A method for forming a methane channel, based on the above-described subsea flexible pipe soft-bottom drilling rig for forming a methane channel, includes the following steps:

[0043] S1: Place the entire drilling rig on the seabed, start the drill bit drive device 14, and drill through the outer drill bit 11 and the inner drill bit 12. At the same time, start the roller drive device 9 and the straightening and penetration mechanism 3, release the flexible tube 8, straighten the flexible tube 8 through the straightening and penetration mechanism 3 and drive the flexible tube 8 to move downward, and penetrate the flexible tube 8 into the seabed.

[0044] S2: When drilling reaches the specified depth, shut down the roller drive device 9 and the straightening and penetration mechanism 3, drive the inner drill bit 12 to reverse, disengage the inner drill bit 12 from the outer drill bit 11, then lift the armored cable 15 to release the inner drill bit constraint device 13 from the inner drill bit 12, and continue to lift the armored cable 15 to retrieve the inner drill bit 12 back to the drilling machine body.

[0045] S3: The flexible tube 8 is cut by the shearing device 10, and the cut flexible tube 8 remains in the formation to form a methane channel.

[0046] Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this invention. Furthermore, those skilled in the art will recognize that, based on the ideas of this invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this invention.

Claims

1. A flexible subsea drilling rig for forming methane channels, characterized in that: The system includes an overall drilling rig frame structure, a flexible continuous drill rod mechanism, a straightening and penetration mechanism, and a power head mechanism. The overall drilling rig frame structure includes a support frame and a guide rail fixedly connected to the support frame. The flexible continuous drill rod mechanism includes a flexible tube storage roller, a flexible tube, and a roller drive device. The flexible tube storage roller is rotatably connected to the support frame and driven to rotate by the roller drive device. One end of the flexible tube is wound around the flexible tube storage roller, and the other end is guided into the straightening and penetration mechanism through the guide rail. The straightening and penetration mechanism is connected to the support frame and is used to straighten the flexible tube and drive it to move up and down. The straightening and penetration mechanism... The structure includes a shearing device for cutting the flexible tube; the power head mechanism includes an outer drill bit, an inner drill bit, an inner drill bit restraint device, a drill bit drive device, and an armored cable. The outer drill bit is rotatably connected inside the drilling end of the flexible tube. The inner drill bit is restrained in the flexible tube by the inner drill bit restraint device. The inner drill bit is driven to rotate by the drill bit drive device. When the inner drill bit rotates forward, it can engage with the outer drill bit and drive the outer drill bit to rotate together. When the inner drill bit rotates backward, it can disengage from the outer drill bit. The armored cable is connected to the inner drill bit restraint device. Lifting the armored cable can release the restraint device on the inner drill bit to retrieve the inner drill bit. The internal drill bit restraint device includes a piston chamber and a locking tongue. The piston chamber is fixedly connected to the housing at the upper end of the drill bit drive device, and the lower end of the drill bit drive device is connected to the internal drill bit. A piston end cap is provided at the end of the piston chamber near the internal drill bit, and a piston is slidably disposed within the piston chamber. The piston includes a protruding section and a sliding section connected to each other. The protruding section protrudes outward through the piston end cap, and the sliding section is slidably disposed within the piston chamber. A piston rod is connected to the end of the sliding section away from the protruding section, and the piston rod passes through the piston chamber and is connected to the armored cable. A limiting step is formed between the protruding section and the sliding section. When the limiting step contacts the piston end cap, the piston end cap restricts the piston from continuing to move towards the internal drill bit. The piston rod is fitted with a spring, which is located inside the piston chamber and its two ends abut against the sliding section and the inner wall of the piston chamber, respectively. The spring is in a compressed state. The housing of the drill bit drive device is provided with multiple circumferentially distributed sliding holes. The flexible tube wall is provided with locking tongue grooves corresponding to each sliding hole. A locking tongue is slidably disposed in each sliding hole. The radially inward end of the locking tongue abuts against the outer peripheral surface of the protruding section, and the radially outward end of the locking tongue extends into the locking tongue groove. When the armored cable is lifted, the protruding section can move upward to release the radial restriction on the locking tongue. At the same time, under the action of the locking tongue and the locking tongue groove, the locking tongue can move inward to disengage from the locking tongue groove. The latch includes a radially arranged prism segment and a frustum segment. The area of ​​the radially inward end of the frustum segment is larger than the area of ​​the radially outward end and is equal to the cross-sectional area of ​​the prism segment. The radially outward end of the frustum segment extends into the latch groove.

2. The subsea flexible pipe soft-bottom drilling rig for forming methane channels according to claim 1, characterized in that: It also includes a monitoring mechanism, which includes a sensor chain installed inside the flexible tube. The sensor chain includes a temperature chain, a multi-parameter sensor array, and a wellbore trajectory sensor. The flexible tube remaining in the formation constitutes the methane channel. The temperature chain is used to obtain the temperature distribution within the methane channel. The multi-parameter sensor array is used to obtain the methane and carbon dioxide concentrations at the bottom of the methane channel. The wellbore trajectory sensor is used to invert the wellbore trajectory parameters in real time.

3. The subsea flexible pipe soft-bottom drilling rig for forming methane channels according to claim 1, characterized in that: The radially inward end of the quadrangular prism segment is provided with a limiting plate, which is located inside the housing of the drill bit drive device. The limiting plate cannot pass through the sliding hole. The radially outward end of the quadrangular prism segment is connected to the radially inward end of the quadrangular pyramid segment.

4. The subsea flexible pipe soft-bottom drilling rig for forming methane channels according to claim 1, characterized in that: The inner drill bit is provided with a locking block, and the outer drill bit is provided with a locking groove that cooperates with the locking block. When the inner drill bit rotates forward, the locking block can engage with the locking groove. When the inner drill bit rotates in reverse, the locking block disengages from the locking groove.

5. The subsea flexible pipe soft-bottom drilling rig for forming methane channels according to claim 1, characterized in that: The straightening and insertion mechanism includes a frame, within which two straightening and insertion assemblies are symmetrically arranged. Each straightening and insertion assembly includes a top sprocket, a bottom sprocket, an insertion chain, and a chain guide tensioner. The insertion chain is driven by the top sprocket and the bottom sprocket. The two insertion chains are in the same vertical plane. The flexible tube passes through the gap between the two insertion chains. The chain guide tensioner is located inside the insertion chain. The chain guide tensioners on both sides of the flexible tube are connected by clamping cylinders. The clamping cylinders can clamp the insertion chain and the flexible tube, thereby driving the flexible tube to move up and down through the friction between the insertion chain and the flexible tube.

6. The subsea flexible pipe soft-bottom drilling rig for forming methane channels according to claim 5, characterized in that: The shearing device is installed inside the frame and located below the straightening and penetration assembly. The shearing device includes two symmetrically arranged cutters. The flexible tube passes through the gap between the two cutters and is cut by the relative movement of the two cutters.

7. The subsea flexible pipe soft-bottom drilling rig for forming methane channels according to claim 1, characterized in that: Both the roller drive device and the drill bit drive device are oil-filled motors, and the top of the support frame is provided with lifting lugs.

8. A method for forming a methane channel, characterized in that, The subsea flexible pipe soft-bottom drilling rig for forming methane channels according to any one of claims 1 to 7 includes the following steps: S1: Place the entire drilling rig structure on the seabed, start the drill bit drive device, and drill through the outer drill bit and the inner drill bit. At the same time, start the roller drive device and the straightening and penetration mechanism, release the flexible tube, straighten the flexible tube through the straightening and penetration mechanism and drive the flexible tube to move downward, and penetrate the flexible tube into the seabed. S2: When drilling reaches the specified depth, shut down the roller drive device and the straightening and penetration mechanism, drive the inner drill bit to reverse, disengage the inner drill bit from the outer drill bit, then lift the armored cable to release the inner drill bit constraint device from the inner drill bit, and continue to lift the armored cable to retrieve the inner drill bit back to the drilling machine body. S3: The flexible tube is cut by the shearing device, and the cut flexible tube remains in the formation to form the methane channel.

Images