Underground gas injection device and layered gas injection tubular column

Abstract

The invention provides an underground gas injection device and a layered gas injection tubular column. The underground gas injection device comprises an outer protection pipe; the upper connector and the lower connector are connected with the two ends of the outer protection pipe respectively, via holes are formed in the upper connector and the lower connector respectively, the upper connector, the lower connector and the outer protection pipe jointly form a gas injection channel, and a first gas outlet is formed in the lower connector; the gas injection assembly is arranged in the outer protection pipe and connected with the lower connector, the gas injection assembly communicates with the gas injection channel and the first gas outlet, the gas injection assembly comprises an adjusting mechanism, and the adjusting mechanism is movably arranged to open or close the first gas outlet; the control assembly is arranged in the outer protection pipe and electrically connected with the gas injection assembly. The problem that in the prior art, a gas injection device cannot effectively control the gas injection amount underground is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of oil and gas exploitation, and in particular to a downhole gas injection device and a layered gas injection string. Background Art

[0002] With the large-scale development of oil and natural gas resources, intact oil reservoirs with good formation porosity and permeability and good crude oil flowability have gradually entered the middle and late stages of development, with phenomena such as rapid production decline and high water content. Traditional natural development has caused many oil and gas wells to experience unfavorable phenomena such as insufficient formation energy, severe production decline, and high water content.

[0003] Injecting gas into the formation to replenish formation energy and displace crude oil in the reservoir pores is a popular and effective means of crude oil extraction in recent years. The effect of gas drive has far surpassed that of thermal extraction and chemical displacement methods.

[0004] In the existing oil and gas production, there is no working cylinder that can be placed underground to realize gas injection into the formation. Most of the time, gas is injected at the wellhead in a general way, and the actual injection volume and injection pressure of the formation cannot be measured.

[0005] As can be seen from the above, there is a problem in the prior art that the gas injection device cannot effectively control the gas injection volume underground. Summary of the invention

[0006] The main purpose of the present invention is to provide a downhole gas injection device and a layered gas injection string to solve the problem that the gas injection device in the prior art cannot effectively control the gas injection volume downhole.

[0007] In order to achieve the above-mentioned purpose, according to one aspect of the present invention, a downhole gas injection device is provided, comprising: an outer protective tube; an upper joint and a lower joint, the upper joint and the lower joint are respectively connected to the two ends of the outer protective tube, the upper joint and the lower joint are respectively provided with through holes, and together with the outer protective tube form a gas injection channel, and the lower joint is provided with a first gas outlet; a gas injection assembly, the gas injection assembly is arranged in the outer protective tube and connected to the lower joint, the gas injection assembly is respectively connected to the gas injection channel and the first gas outlet, the gas injection assembly includes an adjusting mechanism, and the adjusting mechanism is movably arranged to open or close the first gas outlet; a control assembly, the control assembly is arranged in the outer protective tube and is electrically connected to the gas injection assembly.

[0008] Furthermore, the downhole gas injection device also includes an intermediate joint, both ends of which are respectively connected to the gas injection assembly and the control assembly, and one end of the control assembly away from the intermediate joint is connected to the upper joint.

[0009] Furthermore, the downhole gas injection device also includes a first pressure sensor, which is arranged on the middle joint and electrically connected to the control component, and is used to detect the pressure in the gas injection channel.

[0010] Furthermore, the upper joint and the lower joint are respectively threadedly connected to the two ends of the outer protective tube; and / or the middle joint is respectively threadedly connected to the gas injection component and the control component.

[0011] Furthermore, the downhole gas injection device also includes a first sealed tube and a second sealed tube, the control component and the gas injection component are respectively accommodated in the first sealed tube and the second sealed tube, and the annulus between the first sealed tube and the second sealed tube and the outer protective tube is a part of the gas injection channel.

[0012] Furthermore, the downhole gas injection device also includes: a second pressure sensor, which is arranged on the outer surface of the lower joint and electrically connected to the control component for detecting the formation pressure; a temperature sensor, which is arranged at the control component and electrically connected to the control component for detecting the formation temperature.

[0013] Furthermore, the gas injection component is a balanced gas pressure type gas injection switch structure.

[0014] Furthermore, the gas injection assembly also includes a cylinder having a hollow cavity, the adjustment mechanism includes an adjustment rod and a sealing piston, the sealing piston is connected to the end of the adjustment rod, the adjustment rod and the sealing piston are movably arranged in the hollow cavity for blocking or avoiding the hollow cavity.

[0015] Furthermore, an air inlet and a second air outlet are spaced apart axially on the peripheral side wall of the cylinder, the air inlet is connected to the air injection channel, the second air outlet is arranged corresponding to the first air outlet, and the sealing piston moves axially in the hollow cavity to adjust the opening of the air inlet.

[0016] Furthermore, the lower joint has a containing cavity, the cylinder is contained in the containing cavity, and the portion of the cylinder having the air inlet and the second air outlet is a reduced diameter section, so that an annular space is provided between the cylinder and the containing cavity.

[0017] Further, there are multiple air inlets, which are spaced apart along the circumference of the cylinder; and / or there are multiple second air outlets, which are spaced apart along the circumference of the cylinder.

[0018] Furthermore, the downhole gas injection device also includes a flow meter assembly, which is arranged at the second gas outlet and is used to measure the gas injection volume of the downhole gas injection device.

[0019] Furthermore, the gas injection assembly also includes a driving mechanism, which is drivingly connected to the adjusting rod and is used to drive the adjusting rod to drive the sealing piston to move axially.

[0020] Furthermore, the ends of the upper joint and / or the lower joint are of a gradually changing arc-shaped structure.

[0021] According to another aspect of the present invention, a layered gas injection string is provided, comprising the above-mentioned downhole gas injection device.

[0022] By applying the technical solution of the present invention, a downhole gas injection device comprises an outer protective tube, an upper joint, a lower joint, a gas injection assembly and a control assembly. The upper joint and the lower joint are respectively connected to two ends of the outer protective tube, and the upper joint and the lower joint are respectively provided with through holes to form a gas injection channel together with the outer protective tube. The lower joint is provided with a first gas outlet. The gas injection assembly is arranged in the outer protective tube and connected to the lower joint. The gas injection assembly is respectively connected to the gas injection channel and the first gas outlet. The gas injection assembly comprises an adjusting mechanism, and the adjusting mechanism is movably arranged to open or close the first gas outlet. The control assembly is arranged in the outer protective tube and electrically connected to the gas injection assembly. In this way, the control assembly can control the adjusting mechanism in real time underground according to actual needs, thereby controlling the opening and closing of the first gas outlet, thereby realizing effective regulation of the gas injection amount, and solving the problem that the gas injection device in the prior art cannot effectively control the gas injection amount underground. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The drawings constituting a part of the present application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0024] Figure 1 A schematic diagram showing the gas flow structure of a downhole gas injection device in a specific embodiment of the present invention is shown;

[0025] Figure 2 A schematic structural diagram showing an angle of a downhole gas injection device in a specific embodiment of the present invention;

[0026] Figure 3 A schematic structural diagram of a downhole gas injection device without an outer protective pipe installed in a specific embodiment of the present invention is shown;

[0027] Figure 4 A partial cross-sectional view of a downhole gas injection device in a specific embodiment of the present invention is shown;

[0028] Figure 5 A schematic structural diagram of a gas injection assembly in a specific embodiment of the present invention is shown;

[0029] Figure 6 A schematic diagram showing the structure of an adjustment mechanism in a specific embodiment of the present invention is shown;

[0030] Figure 7 A partial cross-sectional view of a lower joint in a specific embodiment of the present invention is shown;

[0031] Figure 8 A cross-sectional view of a lower joint in a specific embodiment of the present invention is shown;

[0032] Fig. 9A schematic diagram of the structure of a vertical well layered gas injection string in a specific embodiment of the present invention is shown;

[0033] Fig.10 A schematic structural diagram of a horizontal well layered gas injection string in a specific embodiment of the present invention is shown.

[0034] The above drawings include the following reference numerals:

[0035] 1. Upper joint; 2. Outer protective tube; 3. Lower joint; 4. First air outlet; 5. Control assembly; 6. Intermediate joint; 7. First pressure sensor; 8. Air injection assembly; 81. Cylinder; 9. Controller; 10. Second air outlet; 11. First flow meter; 12. Second flow meter; 13. First sealing tube; 14. Second sealing tube; 15. Third sealing tube; 16. Adapter; 17. Sealing piston; 18. Air inlet; 19. Second air outlet; 20. Adjusting rod; 30. Air injection channel; 100. Centralizer; 200. Packer; 300. Safety joint; 400. Downhole gas injection device. DETAILED DESCRIPTION

[0036] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0037] It should be noted that, unless otherwise specified, all technical and scientific terms used in this application have the same meanings as commonly understood by ordinary technicians in the technical field to which this application belongs.

[0038] In the present invention, unless otherwise specified, the directional words used, such as "up, down, top, bottom", usually refer to the directions shown in the drawings, or to the components themselves in the vertical, perpendicular or gravity directions; similarly, for ease of understanding and description, "inside and outside" refer to the inside and outside relative to the outline of each component itself, but the above-mentioned directional words are not used to limit the present invention.

[0039] Obviously, the above-described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0040] In order to solve the problem in the prior art that the gas injection device cannot effectively control the gas injection volume underground, the present invention provides an underground gas injection device and a layered gas injection string.

[0041] like Figures 1 to 4 , Figures 7 and 8As shown, the downhole gas injection device includes an outer protective tube 2, an upper joint 1, a lower joint 3, a gas injection assembly 8 and a control assembly 5. The upper joint 1 and the lower joint 3 are respectively connected to the two ends of the outer protective tube 2, and the upper joint 1 and the lower joint 3 are respectively provided with through holes, and together with the outer protective tube 2, form a gas injection channel 30. The lower joint 3 is provided with a first gas outlet 4. The gas injection assembly 8 is arranged in the outer protective tube 2 and connected to the lower joint 3. The gas injection assembly 8 is communicated with the gas injection channel 30 and the first gas outlet 4, respectively, and the gas injection assembly 8 includes an adjustment mechanism, and the adjustment mechanism is movably arranged to open or close the first gas outlet 4. The control assembly 5 is arranged in the outer protective tube 2 and is electrically connected to the gas injection assembly 8.

[0042] The downhole gas injection device includes an outer protective tube 2, an upper joint 1, a lower joint 3, a gas injection assembly 8 and a control assembly 5. The upper joint 1 and the lower joint 3 are respectively connected to the two ends of the outer protective tube 2, and the upper joint 1 and the lower joint 3 are respectively provided with through holes, and together with the outer protective tube 2, a gas injection channel 30 is formed, and the lower joint 3 is provided with a first gas outlet 4. The gas injection assembly 8 is arranged in the outer protective tube 2 and connected to the lower joint 3. The gas injection assembly 8 is communicated with the gas injection channel 30 and the first gas outlet 4 respectively. The gas injection assembly 8 includes an adjustment mechanism, and the adjustment mechanism is movably arranged to open or close the first gas outlet 4. The control assembly 5 is arranged in the outer protective tube 2 and is electrically connected to the gas injection assembly 8. In this way, the control assembly 5 can control the adjustment mechanism in real time underground according to actual needs, thereby controlling the opening and closing of the first gas outlet 4, and realizing effective regulation of the gas injection amount.

[0043] In this embodiment, the gas injection assembly 8 and the lower joint 3 are fixed by bolt connection.

[0044] like Figure 3 As shown, the downhole gas injection device also includes an intermediate joint 6. The two ends of the intermediate joint 6 are respectively connected to the gas injection component 8 and the control component 5, and the end of the control component 5 away from the intermediate joint 6 is connected to the upper joint 1. Specifically, the upper joint 1 has a sealing hole, and the control component 5, the intermediate joint 6 and the gas injection component 8 are connected as an integral short section, and are inserted into the sealing hole of the upper joint 1 by plugging to achieve a sealed connection with the upper joint 1.

[0045] In this embodiment, the upper joint 1 and the lower joint 3 are respectively threadedly connected to the two ends of the outer protective tube 2. Similarly, the middle joint 6 is respectively threadedly connected to the gas injection component 8 and the control component 5.

[0046] like Figure 4As shown, the downhole gas injection device also includes a first sealing tube 13 and a second sealing tube 14. The control assembly 5 and the gas injection assembly 8 are respectively accommodated in the first sealing tube 13 and the second sealing tube 14, and the annulus between the first sealing tube 13 and the second sealing tube 14 and the outer protective tube 2 is a part of the gas injection channel 30. Specifically, the first sealing tube 13 is connected to the upper joint 1 and the middle joint 6 respectively, and the second sealing tube 14 is connected to the lower joint 3 and the middle joint 6 respectively. Further, the first sealing tube 13 and the second sealing tube 14 are coaxially arranged. The sealing tube seals and isolates the pressure of the gas in the tube to prevent the components of the control assembly 5 and the gas injection assembly 8 from being damaged by pressure.

[0047] Further, such as Figure 5 As shown, the downhole gas injection device further includes a third sealing tube 15. The third sealing tube 15 is nested inside and outside the second sealing tube 14, and at least a part of the gas injection assembly 8 is accommodated in the third sealing tube 15. That is, this embodiment uses a double-layer sealing tube to protect the gas injection assembly 8.

[0048] like Figure 3 As shown, the downhole gas injection device also includes a first pressure sensor 7. The first pressure sensor 7 is arranged on the intermediate joint 6 and is electrically connected to the control component 5, and is used to detect the pressure in the gas injection channel 30. Specifically, a threaded mounting hole is provided on the intermediate joint 6, and the first pressure sensor 7 is connected to the intermediate joint 6 through the threaded mounting hole. It can be understood that the intermediate joint 6 is located in the gas injection channel 30, so the first pressure sensor 7 can be directly located in the gas injection channel 30 and measure the pressure in the channel. In this embodiment, the downhole gas injection device also includes a second pressure sensor and a temperature sensor. The second pressure sensor is arranged on the outer surface of the lower joint 3 and is electrically connected to the control component 5, and is used to detect the formation pressure. The temperature sensor is arranged at the control component 5 and is electrically connected to the control component 5, and is used to detect the formation temperature.

[0049] In this embodiment, the control component 5 is electrically connected to the surface equipment through a communication cable. The upper connector 1 and the lower connector 3 are both provided with cable communication holes. The power supply control data sent by the surface equipment enters the downhole gas injection device through the cable communication hole on the upper connector 1, and is introduced into the gas injection component 8 through the interface of the control component 5. The lead wire of the gas injection component 8 is connected to the lower connector 3 through the gap between the second sealing tube 14 and the gas injection component 8, and then transmitted to the next-level instrument through the cable communication hole on the lower connector 3.

[0050] like Figure 5 As shown, the gas injection assembly 8 further includes a cylinder 81. The cylinder 81 has a hollow cavity, and the adjustment mechanism includes an adjustment rod 20 and a sealing piston 17, the sealing piston 17 is connected to the end of the adjustment rod 20, and the adjustment rod 20 and the sealing piston 17 are movably arranged in the hollow cavity for blocking or avoiding the hollow cavity.

[0051] like Figures 5 and 6 As shown, the circumferential side wall of the cylinder 81 is axially spaced apart with an air inlet 18 and a second air outlet 19 , the air inlet 18 is connected to the air injection channel 30 , the second air outlet 19 is arranged corresponding to the first air outlet 4 , and the sealing piston 17 moves axially in the hollow cavity to adjust the opening of the air inlet 18 .

[0052] Specifically, the first air outlet 4 is arranged on the lower joint 3, the first air inlet 18 is located below the second air outlet 19, the second air outlet 19 is connected to the first air outlet 4, and the controller 9 in the control component 5 controls the movement of the adjusting rod 20. The movement of the sealing piston 17 is driven by the movement of the adjusting rod 20, so as to realize the movement of the sealing piston 17 in the cylinder 81 and then realize the sealing piston 17 to seal and adjust the opening size of the air inlet 18.

[0053] In this embodiment, the lower joint 3 has a receiving cavity, the cylinder 81 is received in the receiving cavity, and the portion of the cylinder 81 having the air inlet 18 and the second air outlet 19 is a reduced diameter section, so that there is an annular space between the cylinder 81 and the receiving cavity. Furthermore, the cylinder section of the cylinder 81 located between the air inlet 18 and the second air outlet 19 is a sealing section, and the sealing section is sealed and connected to the inner wall of the receiving cavity, so that the injected gas can only flow through the hollow cavity of the cylinder 81. It should be noted that the above-mentioned reduced diameter section is only for the outer diameter of the cylinder 81, that is, the inner diameter of the sealing section is the same as the inner diameter at the air inlet 18 and the second air outlet 19. The lower joint 3 has a flow passage, and the flow passage is connected to the injection channel 30 and the injection assembly 8 respectively. That is to say, the air inlet 18 is connected to the injection channel 30 through the flow passage, and the injected gas enters the annular space at the air inlet 18 through the flow passage.

[0054] In this embodiment, there are multiple air inlets 18, and the multiple air inlets 18 are arranged at intervals along the circumference of the cylinder 81. Similarly, there are multiple second air outlets 19, and the multiple second air outlets 19 are arranged at intervals along the circumference of the cylinder 81. Through the above arrangement, the flow area of ​​the air injection assembly 8 can be increased, thereby improving the air injection efficiency.

[0055] In this embodiment, the gas injection assembly 8 is a balanced gas pressure type gas injection switch structure. Figure 6 As shown, the areas of the pressure surface A and the pressure surface B in the air inlet 18 of the air injection assembly 8 are equal. Regardless of whether the air injection assembly 8 is open or closed, the forces on the pressure surfaces on both sides can be offset. When the adjusting rod 20 drives the sealing piston 17 to move left and right, force-free movement can be achieved, thereby achieving the air inlet 18 being opened or closed without being affected by the unilateral downhole high pressure and the wellhead injection pressure.

[0056] In this embodiment, the downhole gas injection device further includes a flow meter assembly, which is disposed at the second gas outlet 19 and is used to measure the gas injection volume of the downhole gas injection device. Figure 4 As shown, the flow meter assembly includes a first flow meter 11 and a second flow meter 12. The first flow meter 11 and the second flow meter 12 are arranged at an interval, and the gas injection volume is calculated by the difference between the first flow meter 11 and the second flow meter 12.

[0057] In this embodiment, the gas injection assembly 8 further includes a driving mechanism, which is drivingly connected to the adjusting rod 20, and is used to drive the adjusting rod 20 to drive the sealing piston 17 to move axially. Specifically, the controller 9 controls the movement of the driving mechanism, and then controls the adjusting rod 20 to drive the axial movement of the sealing piston 17. The cylinder 81 is connected to the third sealing tube 15 through the adapter 16, and the driving mechanism is located in the third sealing tube 15. Further, the adjusting rod 20 passes through the adapter 16 and is drivingly connected to the driving mechanism in the third sealing tube 15.

[0058] In this embodiment, the ends of the upper joint 1 and the lower joint 3 are gradually curved. Specifically, during the installation and movement of the upper joint 1 and the lower joint 3, the ends of the gradually curved structures can effectively prevent the upper joint 1 and the lower joint 3 from scratching and hanging against the well wall when passing through a steep slope during the process of going down the well.

[0059] The gas injection process of the downhole gas injection device in this embodiment is as follows:

[0060] The injected gas flows from the through hole of the upper joint 1 into the gas injection channel 30 in the annulus between the outer protective tube 2 and the first sealing tube 13, the middle joint 6, and the second sealing tube 14, and then enters the flow channel on the lower joint 3. After flowing out of the flow channel of the lower joint 3, the injected gas is divided into two. When the gas injection assembly 8 is open, a part of the injected gas enters the gas injection assembly 8, and enters the formation through the gas inlet 18, the second gas outlet 19 and the first gas outlet 4 in sequence, and the remaining injected gas flows directly into the next layer through the connecting oil pipe. In this process, the regulating mechanism adjusts the opening of the gas inlet 18 according to the actual gas injection demand.

[0061] like Figures 9 and 10 As shown, the present invention further provides a layered gas injection string, which includes the above-mentioned downhole gas injection device 400.

[0062] Specifically, the layered gas injection string further includes a centralizer 100, a packer 200 and a safety joint 300. Fig. 9 As shown, during the vertical well gas injection process, two packers 200 are vertically spaced apart, and a downhole gas injection device 400 is provided between the two packers 200 to inject gas into the formation between the two packers 200. A downhole gas injection device 400 is also provided at the lower end of the second packer 200 to inject gas into the next layer.

[0063] like Fig.10As shown, during the process of injecting gas into the horizontal well, a safety joint 300 is provided in the bending section of the layered gas injection string, and a stabilizer 100 is provided between the packer 200 and the safety joint 300 to protect the communication cable in the layered gas injection string. A stabilizer 100 is also provided between the packer 200 and the downhole gas injection device 400 near the safety joint 300. The horizontal placement of the layered gas injection string is achieved by the two stabilizers 100.

[0064] In the above-ground part, the layered gas injection string is also provided with a remote control terminal, which includes a PC and a ground control device. The PC and the ground control device are connected wirelessly or wired, and the ground control device is connected to various electronic components through communication cables. In the specific implementation project, the user is located in the control room, pays attention to the gas injection situation in real time through the PC, and sends control instructions through the PC.

[0065] From the above description, it can be seen that the above embodiment of the present invention achieves the following technical effects: the downhole gas injection device includes an outer protective tube 2, an upper joint 1, a lower joint 3, a gas injection assembly 8 and a control assembly 5. The upper joint 1 and the lower joint 3 are respectively connected to the two ends of the outer protective tube 2, and the upper joint 1 and the lower joint 3 are respectively provided with through holes, and together with the outer protective tube 2, a gas injection channel 30 is formed, and the lower joint 3 is provided with a first gas outlet 4. The gas injection assembly 8 is arranged in the outer protective tube 2 and connected to the lower joint 3. The gas injection assembly 8 is connected to the gas injection channel 30 and the first gas outlet 4 respectively. The gas injection assembly 8 includes an adjustment mechanism, and the adjustment mechanism is movably arranged to open or close the first gas outlet 4. The control assembly 5 is arranged in the outer protective tube 2 and is electrically connected to the gas injection assembly 8. In this way, the control assembly 5 can control the adjustment mechanism in real time underground according to actual needs, thereby controlling the opening and closing of the first gas outlet, and realizing effective regulation of the gas injection amount.

[0066] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0067] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the numbers used in this way can be interchanged where appropriate, so that the embodiments of the present application described herein can be implemented in an order other than those illustrated or described herein.

[0068] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A downhole gas injection device, characterized in that: include: Outer protective tube (2); An upper joint (1) and a lower joint (3), wherein the upper joint (1) and the lower joint (3) are respectively connected to two ends of the outer protective tube (2), the upper joint (1) and the lower joint (3) are respectively provided with through holes, and together with the outer protective tube (2) form a gas injection channel (30), and the lower joint (3) is provided with a first gas outlet (4); an air injection assembly (8), the air injection assembly (8) being arranged in the outer protective tube (2) and connected to the lower joint (3), the air injection assembly (8) being communicated with the air injection channel (30) and the first air outlet (4) respectively, the air injection assembly (8) comprising an adjustment mechanism, the adjustment mechanism being movably arranged to open or close the first air outlet (4); A control component (5), wherein the control component (5) is arranged in the outer protective tube (2) and is electrically connected to the gas injection component (8).

2. The downhole gas injection device according to claim 1, characterized in that: The downhole gas injection device also includes an intermediate joint (6), the two ends of which are respectively connected to the gas injection component (8) and the control component (5), and the end of the control component (5) away from the intermediate joint (6) is connected to the upper joint (1).

3. The downhole gas injection device according to claim 2, characterized in that: The downhole gas injection device further comprises a first pressure sensor (7), which is arranged on the intermediate joint (6) and electrically connected to the control component (5) and is used to detect the pressure in the gas injection channel (30).

4. The downhole gas injection device according to claim 2, characterized in that: The upper joint (1) and the lower joint (3) are respectively threadedly connected to two ends of the outer protective tube (2); and / or The intermediate joint (6) is threadedly connected to the gas injection component (8) and the control component (5) respectively.

5. The downhole gas injection device according to claim 1, characterized in that: The downhole gas injection device also includes a first sealed tube (13) and a second sealed tube (14), the control component (5) and the gas injection component (8) are respectively accommodated in the first sealed tube (13) and the second sealed tube (14), and the annulus between the first sealed tube (13) and the second sealed tube (14) and the outer protective tube (2) is a part of the gas injection channel (30).

6. The downhole gas injection device according to claim 1, characterized in that: The downhole gas injection device also includes: a second pressure sensor, which is arranged on the outer surface of the lower joint (3) and is electrically connected to the control component (5) and is used to detect formation pressure; A temperature sensor is arranged at the control component (5) and is electrically connected to the control component (5) and is used to detect formation temperature.

7. The downhole gas injection device according to claim 1, characterized in that: The gas injection component (8) is a balanced gas pressure type gas injection switch structure.

8. The downhole gas injection device according to claim 7, characterized in that: The gas injection assembly (8) also includes a cylinder (81), the cylinder (81) has a hollow cavity, the adjustment mechanism includes an adjustment rod (20) and a sealing piston (17), the sealing piston (17) is connected to the end of the adjustment rod (20), the adjustment rod (20) and the sealing piston (17) are movably arranged in the hollow cavity, and are used to block or avoid the hollow cavity.

9. The downhole gas injection device according to claim 8, characterized in that: The circumferential side wall of the cylinder (81) is provided with an air inlet (18) and a second air outlet (19) spaced apart along the axial direction, the air inlet (18) is connected to the air injection channel (30), the second air outlet (19) is arranged corresponding to the first air outlet (4), and the sealing piston (17) moves axially in the hollow cavity to adjust the opening of the air inlet (18).

10. The downhole gas injection device according to claim 9, characterized in that: The lower joint (3) has a receiving cavity, the cylinder (81) is received in the receiving cavity, and the portion of the cylinder (81) having the air inlet (18) and the second air outlet (19) is a reduced diameter section, so that an annular space is provided between the cylinder (81) and the receiving cavity.

11. The downhole gas injection device according to claim 10, characterized in that: There are a plurality of air inlets (18), and the plurality of air inlets (18) are arranged at intervals along the circumference of the cylinder (81); and / or There are a plurality of second air outlets (19), and the plurality of second air outlets (19) are arranged at intervals along the circumference of the cylinder (81).

12. The downhole gas injection device according to claim 9, characterized in that: The downhole gas injection device further comprises a flow meter assembly, which is arranged at the second gas outlet (19) and is used to measure the gas injection volume of the downhole gas injection device.

13. The downhole gas injection device according to claim 9, characterized in that: The gas injection assembly (8) further comprises a driving mechanism, which is drivingly connected to the adjusting rod (20) and is used to drive the adjusting rod (20) to drive the sealing piston (17) to move axially.

14. The downhole gas injection device according to any one of claims 1 to 13, characterized in that: The ends of the upper joint (1) and / or the lower joint (3) are of a gradually changing arc-shaped structure.

15. A layered gas injection string, characterized in that: A downhole gas injection device comprising the downhole gas injection device according to any one of claims 1 to 14.

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