Underground internal blowout prevention tool

Abstract

The invention relates to the technical field of well drilling devices, in particular to an underground internal blowout prevention tool which comprises a barrel, a filter screen and a check valve, an inlet flow channel, a flow guide flow channel and an outlet flow channel which are sequentially communicated from top to bottom in the axial direction are formed in the barrel, and the filter screen is arranged at the lower end of the flow guide flow channel and defines an in-net space communicated with the flow guide flow channel; the check valve can be freely and movably placed in the space in the net up and down; and the check valve leaves and opens the lower end port of the flow guide flow channel under the action of fluid entering from the inlet flow channel or contacts and seals the lower end port of the flow guide flow channel under the action of fluid entering from the outlet flow channel. The check valve is matched with the lower end of the flow guide flow channel to replace a spring, a disc and other damageable parts to form a one-way flow valve, the structure is greatly simplified, and reliability, stability, safety and adaptability are enhanced.

Description

Technical Field

[0001] The invention relates to the technical field of drilling devices, and in particular to an underground blowout prevention tool. Background Art

[0002] In oil drilling projects, well control is the core priority of drilling safety production. During the drilling construction process, when drilling into oil and gas layers, if the formation pressure is greater than the bottom hole pressure of the drill string, the formation fluid will enter the drill string, causing well slugging, blowouts and other accidents. Especially for offshore drilling construction, if there are no timely and effective well shut-in measures, it will cause more serious consequences. The downhole internal blowout preventer is a safety device used to shut down the well near the drill bit in the drill string. It closes the internal channel of the drill string to prevent the formation high-pressure fluid from rushing up. Based on the position near the drill bit, it can complete the well shut-in more timely and effectively at the bottom of the well to ensure safety.

[0003] Most of the existing blowout prevention tools in drilling tools have the defects of complex structure, inconvenient assembly and disassembly, or short tool life due to the use of vulnerable parts such as disc or spring check valves, and the damage of the tool cannot be discovered immediately during the drilling process. For example, the invention patent with announcement number CN113090219B discloses a downhole blowout preventer, which is a downhole blowout prevention tool using a spring piston valve. The downhole blowout preventer uses the pressure difference between the inside and outside of the drill string to drive the compression and release of the spring to achieve well closing and unsealing. Its structure has the disadvantage of complex structure like common tools of the same type, and the spring is a vulnerable part. When the spring is damaged during use and cannot work normally, the effect of automatic well closing cannot be achieved. Summary of the invention

[0004] In view of the above-mentioned defects in the prior art, the technical problem to be solved by the present invention is to provide a downhole internal blowout prevention tool with a simple structure and better reliability and stability.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0006] The present invention provides an underground blowout prevention tool, comprising a barrel, a filter screen and a check valve. The barrel is internally formed with an inlet flow channel, a guide flow channel and an outlet flow channel which are sequentially connected along the axial direction from top to bottom. The filter screen is arranged at the lower end of the guide flow channel and surrounds a net space connected to the guide flow channel. The check valve can be freely placed in the net space up and down. The check valve leaves and opens the lower end port of the guide flow channel under the action of the fluid entering from the inlet flow channel, or contacts and closes the lower end port of the guide flow channel under the action of the fluid entering from the outlet flow channel.

[0007] Preferably, the lower end port of the flow guide channel is circular, the check valve is spherical, and the diameter of the check valve is larger than the diameter of the lower end port of the flow guide channel.

[0008] Preferably, the lower end surface of the flow guide channel is in an upwardly concave hemispherical shape and is compatible with the check valve.

[0009] Preferably, the guide channel includes an intermediate channel extending axially and a plurality of bypass channels axially spaced outside the intermediate channel, the bypass channel having a lower bypass section and an upper bypass section, the lower bypass section extending obliquely from the intermediate channel in an upward direction and away from the intermediate channel, the lower end of the lower bypass section being connected to the intermediate channel, one end of the upper bypass section being connected to the upper end of the lower bypass section, and the other end being connected to the intermediate channel.

[0010] Preferably, the lower bypass section extends in a straight shape and / or the upper bypass section extends in an upwardly convex curved shape.

[0011] Preferably, the cross-sectional shape of the bypass flow channel on the radial cross-sectional area of ​​the flow guide flow channel is annular with the middle flow channel as the center.

[0012] Preferably, it also includes a guide structure for constructing a guide channel. The interior of the cylinder is axially penetrated to form an inlet channel, an intermediate cavity and an outlet channel that are sequentially connected from top to bottom. The guide structure is built into the intermediate cavity and connected to the cylinder.

[0013] Preferably, the upper end of the flow guiding structure is detachably connected to the upper end of the middle cavity.

[0014] Preferably, the cylinder body comprises an upper connecting tube and a lower connecting tube both of which are axially penetrated inside, and the lower end of the upper connecting tube is detachably connected to the upper end of the lower connecting tube at the middle cavity.

[0015] Preferably, the cylinder, the flow guiding structure, the filter screen and the check valve are all made of metal.

[0016] Compared with the prior art, the present invention has significant improvements:

[0017] The downhole internal blowout prevention tool of the present invention connects a filter screen at the lower end of the guide flow channel in the cylinder, and places a check valve with upward and downward movement freedom in the filter screen, so that the check valve can open or close the lower end port of the guide flow channel under the impact of the fluid coming from above or from below, thereby forming a one-way flow valve by replacing vulnerable parts such as a spring and a disc through the cooperation of the check valve and the lower end of the guide flow channel, greatly simplifying the structure, eliminating the risk of damage to the internal blowout prevention tool during drilling, ensuring the stable operation of the internal blowout prevention tool and the safety of drilling construction, and reducing the number of trips and drills caused by damage to the internal blowout prevention tool, thereby improving drilling efficiency. At the same time, the simplified structure can make the drilling fluid flow more smoothly in the cylinder, and the overall assembly and disassembly of the internal blowout prevention tool is very convenient, and it is convenient to select the appropriate axial length of the cylinder and the axial length of the internal flow channel according to the actual drilling tool combination requirements, and the adaptability is stronger. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic front view of a downhole blowout prevention tool according to an embodiment of the present invention.

[0019] Figure 2 yes Figure 1 Schematic cross-sectional view along AA.

[0020] Figure 3 It is a schematic front view of the downhole blowout prevention tool without the barrel according to an embodiment of the present invention.

[0021] Figure 4 yes Figure 3 Schematic cross-sectional view along direction BB.

[0022] Figure 5 It is a schematic diagram of the flow direction of the fluid entering from the inlet flow channel and passing through the diversion flow channel from top to bottom when the downhole internal blowout prevention tool according to an embodiment of the present invention is in use.

[0023] Figure 6 It is a schematic diagram of the flow direction of the fluid entering from the outlet flow channel and passing through the guide flow channel from bottom to top when the downhole internal blowout prevention tool according to an embodiment of the present invention is in use.

[0024] The reference numerals are described as follows:

[0025] 1 Cylinder

[0026] 101 Upper connection tube

[0027] 102 Lower connection tube

[0028] 11 Inlet channel

[0029] 12. Flow diversion channel

[0030] 121 Intermediate flow channel

[0031] 122 Bypass channel

[0032] 122a Lower bypass section

[0033] 122b Upper bypass section

[0034] 13 Outlet channel

[0035] 14 Middle cavity

[0036] 2 Filter

[0037] 3 Check valve

[0038] 4. Flow guide structure DETAILED DESCRIPTION

[0039] The specific embodiments of the present invention are further described in detail below in conjunction with the accompanying drawings. These embodiments are only used to illustrate the present invention, but not to limit the present invention.

[0040] In the description of the present invention, it should be noted that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.

[0041] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0042] Furthermore, in the description of the present invention, unless otherwise specified, “plurality” means two or more.

[0043] like Figures 1 to 6 FIG. 1 is an embodiment of the downhole blowout prevention tool provided by the present invention.

[0044] See also Figure 1 and Figure 2 The downhole blowout prevention tool of this embodiment includes a barrel 1, a filter screen 2 and a check valve 3.

[0045] The interior of the cylinder 1 is constituted with an inlet flow channel 11, a guide flow channel 12 and an outlet flow channel 13 which are sequentially connected from top to bottom along the axial direction. The inlet flow channel 11 and the outlet flow channel 13 are respectively located at the upper and lower ends of the cylinder 1 and have relatively short axial extension dimensions; the guide flow channel 12 is located in the middle of the cylinder 1 and has a relatively long axial extension dimension. The upper end of the cylinder 1 is used to connect with the drill string so that the internal channel of the drill string is connected with the upper end of the inlet flow channel 11; the lower end of the cylinder 1 is used to connect with the drill bit or the rotary guide tool so that the lower end of the outlet flow channel 13 leads to the drill bit or the rotary guide tool.

[0046] The filter screen 2 is arranged at the lower end of the diversion channel 12, and the filter screen 2 forms an inner mesh space connected to the diversion channel 12 at the lower end of the diversion channel 12, so the filter screen 2 is located between the diversion channel 12 and the outlet channel 13, and the diversion channel 12 and the outlet channel 13 are connected through the filter holes on the filter screen 2.

[0047] The check valve 3 can be freely moved up and down and placed in the net space formed by the filter screen 2. The check valve 3 is used to move upward to contact with the lower end of the diversion channel 12 to close the lower end port of the diversion channel 12, or move downward to leave the lower end of the diversion channel 12 to open the lower end port of the diversion channel 12. Under the action of the fluid entering from the inlet channel 11, the check valve 3 can move downward to leave and open the lower end port of the diversion channel 12. At this time, the diversion channel 12 and the outlet channel 13 are in a connected state; under the action of the fluid entering from the outlet channel 13, the check valve 3 can move upward to contact and close the lower end port of the diversion channel 12. At this time, the connection between the diversion channel 12 and the outlet channel 13 is blocked.

[0048] When the downhole blowout prevention tool of this embodiment is connected between the drill string and the drill bit or the rotary guide tool for drilling operations, in the initial state where the drilling fluid has not entered, the check valve 3 is pressed at the lower end of the diversion flow channel 12 under the action of the bottom seawater; when the drilling operation is drilling normally, the drilling fluid enters the inlet flow channel 11 from the upper end of the cylinder 1, and moves downward along the diversion flow channel 12, and impacts the check valve 3 after reaching the lower end of the diversion flow channel 12. The check valve 3 moves downward under the impact of the drilling fluid, leaves the lower end of the diversion flow channel 12, and finally falls on the bottom of the filter screen 2, thereby opening the lower end port of the diversion flow channel 12, allowing the drilling fluid to enter the well. It enters the filter screen 2 and enters the outlet flow channel 13 through the filter holes on the filter screen 2, and then flows out from the lower end of the outlet flow channel 13 to act on the drill bit or the rotary guide tool; when a blowout occurs at the bottom of the well, the bottom hole fluid enters the outlet flow channel 13 from the lower end of the barrel 1 under the action of the bottom hole high pressure, and then enters the filter screen 2 through the filter holes on the filter screen 2, and at the same time impacts the check valve 3 that falls on the bottom of the filter screen 2. The check valve 3 moves upward under the impact of the bottom hole fluid until it contacts the lower end of the diversion flow channel 12 and closes the lower end port of the diversion flow channel 12, so that the bottom hole fluid cannot continue to flow upward into the diversion flow channel 12, thereby preventing the bottom hole fluid from rising and completing a blowout prevention.

[0049] The downhole internal blowout preventer tool of the present embodiment is connected with a filter screen 2 at the lower end of the flow guide channel 12 in the cylinder 1, and a check valve 3 with the freedom of upward and downward movement is placed in the filter screen 2, so that the check valve 3 can open or close the lower end port of the flow guide channel 12 under the impact of the fluid coming from above or from below, so that the check valve 3 and the lower end of the flow guide channel 12 cooperate to replace the spring, disc and other vulnerable parts to form a one-way flow valve, which greatly simplifies the structure, eliminates the risk of damage to the internal blowout preventer tool during drilling, ensures the stable operation of the internal blowout preventer tool and the safety of drilling construction, and can also reduce the number of trips caused by damage to the internal blowout preventer tool, thereby improving the drilling efficiency. At the same time, the simplified structure can make the drilling fluid flow in the cylinder 1 more smoothly, and the overall assembly and disassembly of the internal blowout preventer tool is very convenient, and it is convenient to select the axial length of the cylinder 1 and the axial length of the internal flow channel according to the actual drilling tool combination requirements, and the adaptability is stronger.

[0050] In this embodiment, preferably, the lower end port of the diversion channel 12 is circular, the check valve 3 is spherical, and the diameter of the check valve 3 is larger than the diameter of the lower end port of the diversion channel 12. Therefore, when the check valve 3 contacts the lower end of the diversion channel 12, the lower end port of the diversion channel 12 can be completely closed without any gap, thereby ensuring the anti-blowout effect. Preferably, the lower end face of the diversion channel 12 is hemispherical and concave upward and matched with the check valve 3, thereby increasing the contact area when the check valve 3 contacts the lower end of the diversion channel 12, thereby further increasing the closure of the lower end port of the diversion channel 12 and enhancing the anti-blowout effect.

[0051] When a blowout occurs at the bottom of the well and the check valve 3 moves upward in the filter screen 2 under the impact of the bottom hole fluid, that is, before the check valve 3 completely closes the lower end port of the diversion flow channel 12, a small amount of bottom hole fluid may enter the diversion flow channel 12. In order to prevent this part of the bottom hole fluid entering the diversion flow channel 12 from continuing to rise, the structure of the diversion flow channel 12 is designed in this embodiment. Figure 3 and Figure 4Preferably, the flow guide channel 12 includes an intermediate channel 121 and a bypass channel 122. The intermediate channel 121 extends axially, and the upper end and the lower end of the intermediate channel 121 are respectively connected to the inlet channel 11 and the outlet channel 13. A plurality of bypass channels 122 are provided, and the plurality of bypass channels 122 are axially spaced outside the intermediate channel 121. Each bypass channel 122 has a lower bypass section 122a and an upper bypass section 122b. The lower bypass section 122a extends obliquely from the intermediate channel 121 in a direction upward and deviating from the intermediate channel 121, the lower end of the lower bypass section 122a is connected to the intermediate channel 121, and the upper end of the lower bypass section 122a deviates from the intermediate channel 121 in the radial direction. The lower bypass section 122a preferably extends in a straight shape. One end of the upper bypass section 122b is connected to the upper end of the lower bypass section 122a, and the other end of the upper bypass section 122b is connected to the middle flow channel 121. The upper bypass section 122b preferably extends in an upwardly convex curved shape.

[0052] Hence, see Figure 5 When the drilling fluid enters the inlet flow channel 11 from the upper end of the cylinder 1 and then moves downward along the diversion flow channel 12 from top to bottom, the flow direction of the drilling fluid in the diversion flow channel 12 is as follows: Figure 5 As shown by the solid arrow, a part of the drilling fluid will flow directly downward along the middle flow channel 121, and the other part of the drilling fluid will enter the bypass flow channel 122 from the upper bypass section 122b at the bypass flow channel 122, and then flow back to the middle flow channel 121 from the lower bypass section 122a of the bypass flow channel 122, and finally merge with the drilling fluid in the middle flow channel 121 and flow out from the lower end port of the diversion flow channel 12. The bypass flow channel 122 will not hinder the drilling fluid flowing from top to bottom in the middle flow channel 121, and the drilling fluid can flow smoothly from top to bottom along the diversion flow channel 12 as a whole, and can obtain an acceleration effect due to the flow pressure.

[0053] See also Figure 6 When the bottom hole fluid enters the outlet flow channel 13 from the lower end of the cylinder 1 under the action of the bottom hole high pressure, before the check valve 3 completely closes the lower end port of the diversion flow channel 12, a small amount of bottom hole fluid enters the diversion flow channel 12 and returns from bottom to top along the diversion flow channel 12. The flow direction of the bottom hole fluid in the diversion flow channel 12 is as follows: Figure 6As shown by the dotted arrow, when the bottom hole fluid passes through the connecting port between the lower bypass section 122a of the bypass flow channel 122 and the middle flow channel 121, it will be divided into two branches through the lower bypass section 122a, one of which continues to flow upward along the middle flow channel 121, and the other branch enters the bypass flow channel 122 from the lower bypass section 122a, and flows back to the middle flow channel 121 from the upper bypass section 122b of the bypass flow channel 122. The branch flowing back to the middle flow channel 121 from the upper bypass section 122b of the bypass flow channel 122 impacts and collides with the branch flowing upward along the middle flow channel 121, which will hinder the bottom hole fluid from flowing upward. The bypass flow channel 122 hinders the bottomhole fluid flowing from bottom to top in the intermediate flow channel 121, and the bottomhole fluid flowing upward in the intermediate flow channel 121 will be offset by the tributary that flows back from the upper bypass section 122b after being diverted to the bypass flow channel 122 each time it passes through a bypass flow channel 122, thereby having a pressure relief and flow blocking effect on the bottomhole fluid flowing from bottom to top along the diversion flow channel 12, hindering the bottomhole fluid from flowing upward, and a small amount of bottomhole fluid entering the diversion flow channel 12 loses its impact force in repeated offset consumption, and ultimately cannot reach the upper end of the diversion flow channel 12, thereby achieving a thorough blowout prevention effect and ensuring safety.

[0054] Therefore, through the above-mentioned structural design of the diversion flow channel 12, this embodiment can realize the unimpeded flow of drilling fluid from top to bottom along the diversion flow channel 12 as a whole, while effectively preventing the bottom hole fluid entering the diversion flow channel 12 from flowing from bottom to top along the diversion flow channel 12.

[0055] In this embodiment, preferably, the cross-sectional shape of the bypass flow channel 122 on the radial cross-section of the diversion flow channel 12 is annular with the middle flow channel 121 as the center, thereby increasing the overall flow area of ​​the diversion flow channel 12, which can increase the smoothness of the drilling fluid flowing from top to bottom along the diversion flow channel 12, and can also increase the hedging consumption and pressure relief and flow resistance effects of the bottom hole fluid flowing from bottom to top along the diversion flow channel 12.

[0056] See also Figures 2 to 4 Preferably, the downhole blowout prevention tool of this embodiment also includes a flow guiding structure 4 for constructing a flow guiding channel 12, and the middle flow channel 121 of the flow guiding channel 12 axially penetrates the flow guiding structure 4. The flow guiding structure 4 preferably has a conformal profile similar to the structural shape of the flow guiding channel 12. The interior of the cylinder 1 is axially penetrated to form an inlet flow channel 11, an intermediate cavity 14 and an outlet flow channel 13 that are sequentially connected from top to bottom. The flow guiding structure 4 is built into the intermediate cavity 14 and connected to the cylinder 1, and the upper and lower ends of the flow guiding channel 12 that penetrates the flow guiding structure 4 are respectively connected to the inlet flow channel 11 and the outlet flow channel 13. The filter screen 2 is connected to the lower end of the flow guiding structure 4, so that the filter screen 2 is located at the lower end of the flow guiding channel 12. Preferably, the filter screen 2 is welded to the lower end of the flow guiding structure 4.

[0057] Preferably, the upper end of the flow guiding structure 4 is detachably connected to the upper end of the middle cavity 14. Preferably, the upper end of the middle cavity 14 of the cylinder 1 is a threaded hole with internal threads, and the upper end of the flow guiding structure 4 is provided with external threads. The upper end of the flow guiding structure 4 is connected by the external threads and the internal threads of the threaded hole at the upper end of the middle cavity 14, so that the flow guiding structure 4 is connected and fixed to the cylinder 1. The threaded connection has the advantages of convenient assembly and disassembly, and stable and reliable connection.

[0058] Further, the barrel 1 includes an upper connecting tube 101 and a lower connecting tube 102, both of which are axially connected inside. The lower end of the upper connecting tube 101 is detachably connected to the upper end of the lower connecting tube 102 at the middle cavity 14, that is, the upper connecting tube 101 is axially connected inside to form an inlet flow channel 11 and a part of the middle cavity 14, and the lower connecting tube 102 is axially connected inside to form another part of the middle cavity 14 and an outlet flow channel 13. The upper connecting tube 101 and the lower connecting tube 102 are connected to form a complete barrel 1 and the inlet flow channel 11, the middle cavity 14 and the outlet flow channel 13 connected from top to bottom in sequence inside the barrel 1. By setting the barrel 1 as a split part in which the upper connecting tube 101 and the lower connecting tube 102 are detachably connected, the assembly of the guide structure 4 inside the barrel 1 can be facilitated. Preferably, the lower end of the upper connecting tube 101 and the upper end of the lower connecting tube 102 are detachably connected by threaded connection.

[0059] Preferably, the barrel 1 (upper connecting barrel 101 and lower connecting barrel 102), guide structure 4, filter screen 2 and check valve 3 of the downhole internal blowout preventer tool of the present embodiment are all made of metal, so that the downhole internal blowout preventer tool of the present embodiment is an all-metal component, which can be suitable for high-temperature and high-pressure well drilling operations, and can ensure the stable operation of the downhole internal blowout preventer tool and the safety of drilling construction.

[0060] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and substitutions can be made without departing from the technical principles of the present invention. These improvements and substitutions should also be regarded as the scope of protection of the present invention.

Claims

1. A downhole blowout prevention tool, characterized in that: The invention comprises a cylinder (1), a filter screen (2) and a check valve (3); the cylinder (1) is internally provided with an inlet flow channel (11), a guide flow channel (12) and an outlet flow channel (13) which are sequentially connected from top to bottom along the axial direction; the filter screen (2) is arranged at the lower end of the guide flow channel (12) and surrounds a net space connected to the guide flow channel (12); the check valve (3) can be freely placed in the net space so as to move up and down; the check valve (3) leaves and opens the lower end port of the guide flow channel (12) under the action of the fluid entering from the inlet flow channel (11) or contacts and closes the lower end port of the guide flow channel (12) under the action of the fluid entering from the outlet flow channel (13).

2. The downhole internal blowout prevention tool according to claim 1, characterized in that: The lower end port of the flow guide channel (12) is circular, the check valve (3) is spherical, and the diameter of the check valve (3) is larger than the diameter of the lower end port of the flow guide channel (12).

3. The downhole blowout prevention tool according to claim 2, characterized in that: The lower end surface of the flow guide channel (12) is in an upwardly concave hemispherical shape and is compatible with the check valve (3).

4. The downhole internal blowout prevention tool according to claim 1, characterized in that: The flow guide channel (12) comprises an intermediate channel (121) extending in the axial direction and a plurality of bypass channels (122) arranged outside the intermediate channel (121) in the axial direction at intervals. The bypass channel (122) comprises a lower bypass section (122a) and an upper bypass section (122b). The lower bypass section (122a) extends obliquely from the intermediate channel (121) in an upward direction and away from the intermediate channel (121). The lower end of the lower bypass section (122a) is connected to the intermediate channel (121). One end of the upper bypass section (122b) is connected to the upper end of the lower bypass section (122a), and the other end is connected to the intermediate channel (121).

5. The downhole internal blowout prevention tool according to claim 4, characterized in that: The lower bypass section (122a) extends in a straight shape and / or the upper bypass section (122b) extends in an upwardly convex curved shape.

6. The downhole internal blowout prevention tool according to claim 4, characterized in that: The cross-sectional shape of the bypass flow channel (122) on the radial cross-sectional area of ​​the flow guide flow channel (12) is annular with the intermediate flow channel (121) as the center.

7. The downhole internal blowout prevention tool according to claim 1 or 4, characterized in that: It also includes a flow guiding structure (4) for constructing the flow guiding channel (12); the interior of the cylinder (1) is axially penetrated to form the inlet channel (11), the middle cavity (14) and the outlet channel (13) which are sequentially connected from top to bottom; the flow guiding structure (4) is built into the middle cavity (14) and connected to the cylinder (1).

8. The downhole internal blowout prevention tool according to claim 7, characterized in that: The upper end of the flow-guiding structure (4) is detachably connected to the upper end of the middle cavity (14).

9. The downhole internal blowout prevention tool according to claim 8, characterized in that: The cylinder body (1) comprises an upper connecting tube (101) and a lower connecting tube (102) both of which are axially penetrated inside, and the lower end of the upper connecting tube (101) and the upper end of the lower connecting tube (102) are detachably connected at the middle cavity (14).

10. The downhole internal blowout prevention tool according to claim 7, characterized in that: The cylinder (1), the flow-guiding structure (4), the filter screen (2) and the check valve (3) are all made of metal.

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