Double-layer continuous pipe tool joint structure and assembly method thereof

Abstract

The present invention discloses a double-layer continuous pipe tool joint structure and an assembly method thereof, belonging to the technical field of drilling devices; the structure comprises an outer pipe connecting device and an inner pipe connecting device, the inner pipe connecting device is connected to the inner pipe, the outer pipe connecting device is connected to the outer pipe, a first flow channel is arranged in the inner pipe connecting device, the first flow channel is connected to the inner pipe to form a first liquid channel, the inner pipe is sleeved in the outer pipe, there is a gap between the outer side wall of the inner pipe and the inner side wall of the outer pipe to form a pipe sandwich, the inner pipe connecting device where the outer side of the first flow channel is located is provided with a second flow channel, the second flow channel is connected to the pipe sandwich to form a second liquid channel; the present invention solves the problem that traditional continuous pipes often adopt a single-layer structure, and effectively realizes the effect of the structure having a double flow channel by means of the design of the inner and outer pipes, and at the same time, effectively realizes the input and discharge of liquid by means of the double flow channel and the independently designed flow channel.

Description

Technical Field

[0001] The invention relates to a double-layer continuous pipe tool joint structure and belongs to the technical field of drilling devices. Background Art

[0002] Coiled tubing has been widely used in oil and gas field workover, acidizing, fracturing, perforating, logging, completion, drilling, plugging relief and other fields. Downhole tools are connected to coiled tubing through coiled tubing connectors. Single-layer coiled tubing has been applied on site, while double-layer coiled tubing is still in the research stage.

[0003] The connector for double-layer coiled tubing operations is used to connect the double-layer coiled tubing and downhole tools during double-layer coiled tubing downhole operations. The tool connector can simultaneously connect the inner tube, outer tube and downhole tools of the double-layer coiled tubing, and can be used in double-layer coiled tubing drilling, logging, unblocking and other occasions, especially in the application of offshore drilling devices. Adding a separate liquid recovery / discharge device will greatly increase the cost of the device and the difficulty of the device construction. The environment is also not a conventional environment, and its requirements are relatively higher.

[0004] The double-layer coiled tubing device and its supporting tools have the characteristics of negative pressure, independent loop circulation channel, and no interference with the wellbore and wellbore fluid. They are particularly suitable for horizontal wells, low-pressure reservoirs, loose sand layer reservoirs, heavy oil and extra-heavy oil, serious leakage, long well section open hole or screen completion and other well conditions. The use of double-layer coiled tubing operations for drilling and unblocking coalbed methane wells can effectively protect coal reservoirs; negative pressure sand flushing in horizontal wells can make the sand flushing operation effective and thorough; using the separate circulation loop of the double-layer coiled tubing, the wellbore accumulated fluid can be discharged smoothly to restore production. Applied to drilling technology, it can achieve pressure operation or underbalanced drilling. Summary of the invention

[0005] The object of the present invention is to provide a double-layer coiled tubing tool joint structure and an assembly method thereof in view of the above-mentioned problems. The tool joint can simultaneously connect the inner tube, outer tube and downhole tool of the double-layer coiled tubing, and can be used in double-layer coiled tubing drilling, logging, unblocking and other occasions. It has the advantages of simple structure, easy installation, simple operation and good process feasibility.

[0006] The technical solution adopted by the present invention is as follows:

[0007] A double-layer continuous pipe tool joint structure comprises an outer pipe connecting device and an inner pipe connecting device, wherein the inner pipe connecting device is connected to an inner pipe, and the outer pipe connecting device is connected to an outer pipe, wherein a first flow channel is arranged in the inner pipe connecting device, and the first flow channel is connected to the inner pipe to form a first liquid channel, wherein the inner pipe is sleeved in the outer pipe, and there is a gap between the outer side wall of the inner pipe and the inner side wall of the outer pipe to form a pipe sandwich, and a second flow channel is arranged in the inner pipe connecting device where the outer side of the first flow channel is located, and the second flow channel is connected to the pipe sandwich to form a second liquid channel.

[0008] Furthermore, the outer tube connecting device comprises an outer tube connector and an outer tube assembly structure for assembling the outer tube, and the inner tube connecting device is an inner tube connector, and the outer tube connector is assembled and connected with the inner tube connector.

[0009] Furthermore, the outer tube assembly structure includes a slip disposed inside the outer tube connector and used for assembling the outer tube, and a bushing is further disposed between the slip and the inner tube connector.

[0010] Furthermore, the inner side of one end of the outer tube connector is tapered for the assembly of the slips, and the slips clamp the outer tube through the cooperation between the tapered shape and the slips, and the other end of the outer tube connector is assembled and connected with the inner tube connector.

[0011] Furthermore, a gasket is provided between the slip and the bushing. The gasket is an annular spring gasket. The gasket includes an outer ring and two inner rings. The contact surface between the outer ring and the inner ring is a conical surface.

[0012] Furthermore, the bushing includes a first bushing and a second bushing, the second bushing is arranged between the first bushing and the gasket, the first bushing is arranged between the second bushing and the end of the inner tube connector, the first bushing is semi-cylindrical, and the two first bushings are used in pairs.

[0013] Furthermore, the outer tube connector and the inner tube connector are assembled by threaded connection, and after being assembled and connected, the outer tube connector and the inner tube connector are fixedly assembled by set screws.

[0014] Furthermore, the other end of the inner tube connector is also provided with a thread for connecting a downhole tool.

[0015] Furthermore, the outer structure of the slip is conical, a section of cylinder is arranged at the large end of the cone, and axial slip teeth and circumferential slip teeth are processed inside the slip.

[0016] Furthermore, the first flow channel is a through hole that passes through the middle of the inner tube connector, and the second flow channel is a plurality of strip-shaped flow channels evenly distributed outside the first flow channel, and the second flow channel passes through the inner tube connector.

[0017] A method for assembling a double-layer coiled tubing tool joint structure comprises the following steps:

[0018] a. Assemble the outer tube connection device: select the outer tube, and insert the outer tube connector, slip, gasket, and second bushing with sealing device from the lower end of the outer tube in sequence;

[0019] b. Assemble the inner tube and the inner tube connector, align the upper shoulder surface of the inner tube connector with the lower end surface of the inner tube, and keep the position of the inner tube connector fixed; then use a tool to press the inner tube into the annular groove of the inner tube connector to complete the connection between the inner tube connector and the inner tube;

[0020] c. Install the first bushing, install the semicircular first bushing onto the outside of the assembled inner tube, and move the second bushing downward so that the lower end surface of the second bushing contacts the upper end surface of the first bushing, and the lower end surface of the first bushing contacts the upper shoulder surface of the inner tube connector;

[0021] Then, the gasket and the slip are moved downward in sequence, so that the lower end surface of the gasket contacts the upper end surface of the second bushing, and the lower end surface of the slip contacts the upper end surface of the gasket;

[0022] Then move the outer tube connector downward so that the lower end surface of the outer tube connector is below the lower end surface of the first bushing, and preliminarily complete the installation of the bushing;

[0023] d. Install the outer tube connector, continue to move the outer tube connector downward, and connect it with the threads of the inner tube connector through the threads on it until the thread tightening torque reaches the design requirement;

[0024] e. Install the set screws. After the threaded connection between the outer tube connector and the inner tube connector is completed, install the set screws at the axially evenly distributed openings at the lower end of the outer tube connector to prevent the threads from being reversed.

[0025] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0026] 1. The double-layer coiled tubing tool joint structure of the present invention solves the problem that the conventional coiled tubing often adopts a single-layer structure. By means of the design of the inner and outer tubes, the structure effectively realizes the effect of having a double flow channel. At the same time, by means of the double flow channels and independently designed flow channels, the liquid input and discharge are effectively realized. The structure is easy to assemble and has better adaptability to the coiled tubing, which reduces the difficulty of on-site construction and the production cost of the device.

[0027] 2. The double-layer coiled tubing tool joint structure of the present invention effectively realizes the assembly of the outer tube through the design of the outer tube connecting device, and at the same time effectively ensures the clamping effect of the clamping part on the outer tube in the axial direction, avoiding the problem of the outer tube loosening and falling off or poor sealing effect during use;

[0028] 3. The double-layer coiled tubing tool joint structure of the present invention effectively realizes the modularization of each connection part in its structural design, which can effectively reduce the difficulty of assembling the coiled tubing tool structure and facilitate the processing of the entire structure, effectively breaking through the double-layer coiled tubing tool problem. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The present invention will now be described by way of example with reference to the accompanying drawings, in which:

[0030] Figure 1 It is a schematic diagram of the structure of the present invention;

[0031] Figure 2 It is a schematic structural diagram of the outer tube connector of the present invention;

[0032] Figure 3 It is a schematic structural diagram of the inner tube connector of the present invention;

[0033] Figure 4 is a schematic cross-sectional view of the inner tube connector of the present invention;

[0034] Figure 5 It is a schematic diagram of the structure of the slip of the present invention;

[0035] Figure 6 is a schematic cross-sectional view of the slip of the present invention;

[0036] Figure 7 It is a structural schematic diagram of the gasket ring of the present invention;

[0037] Figure 8 It is a schematic diagram of the enlarged structure of the sealing ring assembly of the present invention.

[0038] Markings in the figure: 1-outer tube, 2-inner tube, 3-outer tube connector, 4-inner tube connector, 5-first flow channel, 6-second flow channel, 7-slip, 71-axial slip tooth, 72-circumferential slip tooth, 8-gasket, 81-outer ring, 82-inner ring, 9-first bushing, 10-second bushing, 11-fastening screw, 12-sealing ring, 13-retaining ring. DETAILED DESCRIPTION

[0039] All features disclosed in this specification, or steps in all methods or processes disclosed, except mutually exclusive features and / or steps, can be combined in any manner.

[0040] Any feature disclosed in this specification, unless otherwise stated, can be replaced by other equivalent or alternative features with similar purposes. That is, unless otherwise stated, each feature is only an example of a series of equivalent or similar features.

[0041] Example 1

[0042] A double-layer continuous pipe tool joint structure, such as Figures 1 to 8 As shown, it includes an outer tube connecting device and an inner tube connecting device, the inner tube connecting device is connected to the inner tube 2, the outer tube connecting device is connected to the outer tube 1, a first flow channel 5 is arranged in the inner tube connecting device, the first flow channel 5 is connected with the inner tube to form a first liquid channel, the inner tube is sleeved in the outer tube, there is a gap between the outer side wall of the inner tube and the inner side wall of the outer tube to form a tube sandwich, the inner tube connecting device where the outer side of the first flow channel is located is provided with a second flow channel 6, the second flow channel is connected with the tube sandwich to form a second liquid channel.

[0043] In this embodiment, in terms of structural design, the outer tube connection device can be designed to realize the assembly of the outer tube 1, and the inner tube connection device can realize the assembly of the inner tube 3. In the assembly process, the outer diameter of the inner tube 3 is smaller than the inner diameter of the outer tube 1, so as to realize a certain gap between the outer tube 1 and the inner tube 3, thereby forming a tube sandwich. In terms of specific structural design, the inner tube 3 and the tube sandwich are connected with the first flow channel 5 and the second flow channel 6 provided on the inner tube connection device respectively to realize two independent liquid channels, wherein the first liquid channel is a liquid inlet channel, and the second liquid channel is a liquid discharge channel. With the help of this structural design, the design of the double-layer continuous tube is effectively realized, and the assembly problem of the double-layer continuous tube is solved.

[0044] As a more specific design, further designs are made for the outer tube connection device and the inner tube connection device, the outer tube connection device includes an outer tube connector 3 and an outer tube assembly structure for assembling the outer tube, the inner tube connection device is an inner tube connector 4, and the outer tube connector 3 is assembled and connected with the inner tube connector 4. In the overall structural design, it is necessary to integrate all components into one, and in this design, the assembly of the overall structure is achieved by assembling the outer tube connector 3 and the inner tube connector 4.

[0045] As a more optimized design, the outer tube assembly structure includes a slip 7 disposed inside the outer tube connector 3 and used to assemble the outer tube 1, and a bushing and a gasket are further disposed between the slip 7 and the inner tube connector 4. The design of the bushing can effectively transmit the axial force, and the design of the gasket can alleviate the axial impact force.

[0046] As a more specific design, the inner side of one end of the outer pipe connector 3 is tapered for the assembly of the slip 7. The slip clamps the outer pipe through the cooperation of the taper and the slip 7. The other end of the outer pipe connector 3 is assembled and connected to the inner pipe connector 4. With the tapered structure, of course, the slip 7 is also of a tapered structure. When the outer pipe connector 3 is assembled and axially moved, the tapered structure will generate a uniform force on the slip 7 to cause the slip to contract inward, realizing the clamping function. More specifically, the tapered length inside the outer pipe connector 3 is greater than the tapered length of the slip 7 to reserve assembly allowance for assembly.

[0047] To better achieve the axial buffering effect, in a more specific design, a spacer ring 8 is further provided between the slip and the bushing. The spacer ring 8 is an annular spring washer. The spacer ring includes 1 outer ring 81 and 2 inner rings 82. The contact surface between the outer ring 81 and the inner rings 82 is a conical surface. Taking the attached drawing as an illustration, the 2 inner rings 82 are assembled facing each other to form a structure similar to the Chinese character "工" with an annular conical groove. The outer ring 81 is assembled in the conical groove and the conical surface assembly is realized. More specifically, the spacer ring 8 is used to transmit the working axial load, compensate for axial deformation, and bear the impact load that may occur during work.

[0048] For further design of the bushing, the bushing includes a first bushing 9 and a second bushing 10. The second bushing 10 is arranged between the first bushing 9 and the spacer ring. The first bushing 9 is arranged between the second bushing 10 and the end of the inner pipe connector. The first bushing 9 is semi-cylindrical and 2 first bushings 9 are used in pairs.

[0049] For a specific description of the second bushing 10, the second bushing 10 is located below the metal spacer ring and is within the internal space formed by the outer pipe connector 3 and the coiled tubing outer pipe 1. It is used to transmit the axial load and seal the drilling fluid in the annulus space of the double-layer coiled tubing tool joint. The second bushing 10 is cylindrical, and sealing grooves are provided on both its inner wall side and outer wall side. Sealing rings 12 and retaining rings 13 are arranged in the sealing grooves. More specifically, 2 annular sealing grooves are respectively provided on its inner wall side and outer wall side.

[0050] More specifically, the length of the outer pipe 1 extends to the section where the first bushing 9 and the second bushing 10 match. Specifically, the end face of the outer pipe 1 matches the second bushing 10. Among them, the pipe sandwich, the gap between the inner side wall of the first bushing 9 and the outer side wall of the inner pipe 2, and the second flow channel 6 communicate to form a second liquid channel. As more specific, the first bushing 9 includes 2 semi-cylindrical structures. During installation, the lower end face of the second bushing 10 contacts the upper end face of the first bushing 9, and the lower end face of the first bushing 9 contacts the upper shoulder face of the inner pipe connector 4.

[0051] In terms of specific structural design, the outer tube connector 3 and the inner tube connector 4 are assembled by threaded connection, and the outer tube connector 3 and the inner tube connector 4 are fixedly assembled by a set screw 11 after being assembled and connected. As a specific description, in this design, the outer tube connector 3 is provided with an internal thread, and the inner tube connector 4 is provided with an external thread. The internal thread and the end of the outer tube connector 3 have a spacing for the assembly of the set screw. The specific assembly of the set screw 11 is: a plurality of threaded holes are evenly distributed on the circumference of the outer tube connector 3 and the inner tube connector 4, and the set screw 11 is assembled in the threaded hole to prevent the thread from being reversed. As a more specific description, the other end of the inner tube connector 4 is also provided with a thread for connecting downhole tools.

[0052] As a more specific design, as a specific structural design, the external structure of the slip 7 is conical, and a section of cylinder is arranged at the large end of the cone, and the inside of the slip 7 is processed with axial slip teeth 71 and annular slip teeth 72. Among them, the axial slip teeth 71 are used to bear torque, and the annular slip teeth 72 are used to bear axial load. Considering the uniform force, in addition, the slip 8 is evenly grooved in the circumferential direction. The effect of its grooves is specifically as follows: strip grooves are opened at both ends of the slip 8, and the strip grooves are distributed in a circumferential array, and the strip grooves at both ends are cross-arranged. Considering that the slip 7 needs to be deformed in the annular direction and the slip teeth need to have a higher hardness, 20CrMnTi is selected as the material of the slip 7. The axial tooth profile segment and the annular tooth profile segment of the slip 7 can be segmented and independent in the axial direction of the slip or interpenetrate and intersect with each other. This embodiment only lists the axial teeth and annular teeth that are segmented and independent in the axial direction of the slip.

[0053] As a more specific design for the inner tube connector, the first flow channel 5 is a through hole that runs through the middle of the inner tube connector, and the second flow channel 6 is a plurality of strip-shaped flow channels evenly distributed outside the first flow channel, and the second flow channel 6 runs through the inner tube connector. In this design, the second flow channels 6 are distributed in a circumferential array to ensure the overall rigidity of the inner tube connector 4, as illustrated in the accompanying drawings.

[0054] On the basis of the above-mentioned specific structural design, as an assembly method of the outer tube 1, by tightening the connecting thread between the outer tube connector 3 and the inner tube connector 4, the inner conical surface of the upper part of the outer tube connector 3 is pressed against the outer conical surface of the slip 7, thereby causing the slip teeth to be pressed into the outer tube 1, relying on the friction between the inner conical surface of the outer tube connector 3 and the outer conical surface of the slip 7, and the friction between the inner wall surface of the slip 7 and the outer tube 1 of the double-layer coiled tube, the axial load and working torque of the double-layer coiled tube tool joint are borne when the double-layer coiled tube tool joint is working, so as to realize the connection between the slip and the outer tube of the double-layer coiled tube, and the connection between the outer tube and the double-layer coiled tube tool joint.

[0055] Secondly, as a method of assembling the inner tube 2, the inner tube 2 is pressed into the annular groove on the upper part of the inner tube connector 4 by a special tool, and the annular groove is supplemented with sealing grooves on both sides, and a sealing ring 12 and a retaining ring 13 are installed therein to seal the drilling fluid. As a specific description, the end of the inner tube connector 4 used to connect the outer tube connector 3 is also provided with an assembly part for assembling the inner tube 2, and a plurality of annular grooves are provided on the assembly part, and the inner tube 2 is assembled on the assembly part. In a more specific design, sealing grooves are also provided on both sides of the annular groove, and a sealing ring 12 and a retaining ring 13 are assembled in the annular groove. With this method, the sealing effect of the structure is effectively achieved.

[0056] As a more specific description, according to the actual situation, Figure 1 The upper middle end is the upper part when in use, and the lower end is the lower part when in use. Describing the outer tube connector 3, the inner conical surface in the middle of the outer tube connector 3 is pressed against the outer conical surface of the slip 7, so that the slip teeth are pressed against the outer tube 1, and the slip 7 is connected to the outer tube 1. A gasket 8 (metal gasket), a first bushing 9 and a second bushing 10 are installed in the cylindrical structure in the middle of the outer tube connector 3, which are used to transfer axial loads and compensate for axial deformation. The connecting thread at the lower end of the outer tube connector 3 cooperates with the connecting thread at the upper end of the inner tube connector, so that the outer tube connector 3 is pressed against the slip 7, and the slip 7 is pressed against the outer tube 1, so as to realize the function of the slip 7 clamping the outer tube 1. The threaded lower end of the outer tube connector 3 has threaded holes evenly distributed along the circumference, which are used to install the retaining screws 11 to prevent the threads from being reversed.

[0057] Example 2

[0058] Based on the embodiment 1, the inner tube connector 4 is further designed, and the upper part of the inner tube connector 4 is provided with evenly distributed annular grooves for connecting the inner tube 2. At the same time, sealing grooves are provided on both sides of the annular groove for installing the sealing ring 12 and the retaining ring 13 to seal the drilling fluid.

[0059] In its more specific structural design, the inner tube connector 4 is provided with a trapezoidal thread in the middle for connecting the outer tube connector 3. Sealing grooves are provided on both sides of the female thread for installing a sealing ring 12 and a retaining ring 13 to seal the drilling fluid. A circumferential groove is provided at the lower part of the sealing groove on the lower side of the female thread for installing a set screw 11. As a specific description, the outer tube connector 3 is provided with a female thread matching the inner tube connector.

[0060] As a more specific design, the inner tube connector 4 is provided with a digital thread at the bottom for connecting the downhole tool. A cylindrical part is also provided at the bottom of the digital thread for matching with the downhole tool, and a sealing groove is provided on the cylindrical part, in which a sealing ring 12 and a retaining ring 13 can be installed to seal the drilling fluid and form a drilling fluid input circulation channel.

[0061] A thickened cylinder is provided between the Axel thread and the digital thread to facilitate clamping the inner tube connector 4 when tightening the thread.

[0062] Example 3

[0063] On the basis of Example 1 and different from Example 1, based on the design of the present structure, theoretically, as applicable, the first liquid channel is a liquid discharge channel, and the second liquid channel is a liquid inlet channel.

[0064] As a specific description, the first liquid channel formed by the first flow channel 5 communicating with the inner tube 2 is a liquid discharge channel, and the second liquid channel formed by the second flow channel 6 communicating with the tube interlayer is a liquid inlet channel.

[0065] Example 4

[0066] Based on the structural design of Examples 1 to 3, a double-layer coiled tubing tool joint structure assembly method is provided. In the following description, according to the actual state, the attached Figure 1 For example, the upper end (the upper end of the outer tube connector) is the upper part when in use, and the lower end (the lower end of the inner tube connector connection tool) is the lower part when in use.

[0067] A method for assembling a double-layer coiled tubing tool joint structure comprises the following steps:

[0068] a. Assemble the outer tube connection device: select the outer tube 1, and insert the outer tube connector 3, slip 7, gasket 8, and the second bushing 10 with a sealing device from the lower end of the outer tube 1 in sequence;

[0069] b. Assembling the inner tube 2 and the inner tube connector 4, aligning the upper shoulder surface of the inner tube connector 4 with the lower end surface of the inner tube 2, and keeping the position of the inner tube connector 4 fixed; then using a tool, press the inner tube 2 into the annular groove of the inner tube connector 4 to complete the connection between the inner tube connector 4 and the inner tube 2;

[0070] c. Install the first bushing 9. Install the two semicircular first bushings 9 onto the outside of the assembled inner tube 2, and move the second bushing 10 downward so that the lower end surface of the second bushing 10 contacts the upper end surface of the first bushing 9, and the lower end surface of the first bushing 9 contacts the upper shoulder surface of the inner tube connector 4;

[0071] Then, the gasket 8 and the slip 7 are moved downward in sequence, so that the lower end surface of the gasket 8 contacts the upper end surface of the second bushing 10, and the lower end surface of the slip 7 contacts the upper end surface of the gasket 8;

[0072] Then move the outer tube connector 3 downwards so that the lower end surface of the outer tube connector 3 is below the lower end surface of the first bushing 10, and the installation of the bushing 1 is preliminarily completed;

[0073] d. Install the outer tube connector 3, continue to move the outer tube connector 3 downward, and connect it with the threads of the inner tube connector 4 through the threads on it until the thread tightening torque reaches the design requirement;

[0074] e. Install the set screws 11. After the threaded connection between the outer tube connector 3 and the inner tube connector 4 is completed, install the stop screws 11 at the axially evenly distributed openings at the lower end of the outer tube connector 3 to prevent the threads from being reversed.

[0075] In summary:

[0076] 1. The double-layer coiled tubing tool joint structure of the present invention solves the problem that the conventional coiled tubing often adopts a single-layer structure. By means of the design of the inner and outer tubes, the structure effectively realizes the effect of having a double flow channel. At the same time, by means of the double flow channels and independently designed flow channels, the liquid input and discharge are effectively realized. The structure is easy to assemble and has better adaptability to the coiled tubing, which reduces the difficulty of on-site construction and the production cost of the device.

[0077] 2. The double-layer coiled tubing tool joint structure of the present invention effectively realizes the assembly of the outer tube through the design of the outer tube connecting device, and at the same time effectively ensures the clamping effect of the clamping part on the outer tube in the axial direction, avoiding the problem of the outer tube loosening and falling off or poor sealing effect during use;

[0078] 3. The double-layer coiled tubing tool joint structure of the present invention effectively realizes the modularization of each connection part in its structural design, which can effectively reduce the difficulty of assembling the coiled tubing tool structure and facilitate the processing of the entire structure, effectively breaking through the double-layer coiled tubing tool problem.

[0079] The present invention is not limited to the above-mentioned specific embodiments, but extends to any new features or any new combination disclosed in this specification, as well as any new method or process steps or any new combination disclosed.

Claims

1. A double-layer coiled tubing tool joint structure, characterized in that: The invention comprises an outer tube connection device and an inner tube connection device, wherein the inner tube connection device is connected to the inner tube, the outer tube connection device is connected to the outer tube, a first flow channel is arranged in the inner tube connection device, the first flow channel is connected to the inner tube to form a first liquid channel, the inner tube is sleeved in the outer tube, there is a gap between the outer wall of the inner tube and the inner wall of the outer tube to form a tube sandwich, the inner tube connection device at the outer side of the first flow channel is provided with a second flow channel, the second flow channel is connected to the tube sandwich to form a second liquid channel; the outer tube connection device comprises an outer tube connector and an outer tube for assembling the outer tube Assembly structure, the inner tube connecting device is an inner tube connector, and the outer tube connector is assembled and connected with the inner tube connector; the outer tube assembly structure includes a slip that is arranged inside the outer tube connector and is used to assemble the outer tube, and a bushing is also arranged between the slip and the inner tube connector; the outer structure of the slip is conical, and a section of cylinder is arranged at the large end of the cone, and axial slip teeth and circumferential slip teeth are processed inside the slip; the first flow channel is a through hole that passes through the middle of the inner tube connector, and the second flow channel is a plurality of strip flow channels evenly distributed on the outside of the first flow channel, and the second flow channel passes through the inner tube connector.

2. A double-layer coiled tubing tool joint structure according to claim 1, characterized in that: The inner side of one end of the outer tube connector is tapered for the assembly of slips, and the slips clamp the outer tube through the cooperation between the tapered shape and the slips, and the other end of the outer tube connector is assembled and connected with the inner tube connector.

3. A double-layer coiled tubing tool joint structure according to claim 1, characterized in that: A gasket is also provided between the slip and the bushing. The gasket is an annular spring gasket. The gasket includes an outer ring and two inner rings. The contact surface between the outer ring and the inner ring is a conical surface.

4. A double-layer coiled tubing tool joint structure as claimed in claim 3, characterized in that: The bushing includes a first bushing and a second bushing, wherein the second bushing is arranged between the first bushing and the gasket, and the first bushing is arranged between the second bushing and the end of the inner tube connector. The first bushing is semi-cylindrical, and the two first bushings are used in pairs.

5. The double-layer coiled tubing tool joint structure according to claim 1, characterized in that: The outer tube connector and the inner tube connector are assembled by threaded connection. After being assembled and connected, the outer tube connector and the inner tube connector are fixed by set screws. The other end of the inner tube connector is also provided with threads for connecting downhole tools.

6. A method for assembling a double-layer coiled tubing tool joint structure, using a double-layer coiled tubing tool joint structure according to any one of claims 1 to 5, characterized in that: The following steps are involved: a. Assemble the outer tube connection device: select the outer tube, and insert the outer tube connector, slip, gasket, and second bushing with sealing device from the lower end of the outer tube in sequence; b. Assemble the inner tube and the inner tube connector, align the upper shoulder surface of the inner tube connector with the lower end surface of the inner tube, and keep the position of the inner tube connector fixed; then use a tool to press the inner tube into the annular groove of the inner tube connector to complete the connection between the inner tube connector and the inner tube; c. Install the first bushing, install the two semi-cylindrical first bushings outside the assembled inner tube, and move the second bushing downward so that the lower end surface of the second bushing contacts the upper end surface of the first bushing, and the lower end surface of the first bushing contacts the upper shoulder surface of the inner tube connector; Then, the gasket and the slip are moved downward in sequence, so that the lower end surface of the gasket contacts the upper end surface of the second bushing, and the lower end surface of the slip contacts the upper end surface of the gasket; Then move the outer tube connector downward so that the lower end surface of the outer tube connector is below the lower end surface of the first bushing, and preliminarily complete the installation of the bushing; d. Install the outer tube connector, continue to move the outer tube connector downward, and connect it with the threads of the inner tube connector through the threads on it until the thread tightening torque reaches the design requirement; e. Install the set screws. After the threaded connection between the outer tube connector and the inner tube connector is completed, install the set screws at the axially evenly distributed openings at the lower end of the outer tube connector to prevent the threads from being reversed.

Images