Double-layer pipe reverse circulation drilling downhole mechanical three-channel plugging safety valve

Abstract

The application discloses a downhole mechanical three-channel blocking safety valve of a double-layer pipe reverse circulation drilling, and relates to the technical field of reverse circulation drilling. The application utilizes the phenomenon that a large amount of high-speed drilling fluid generated at the bottom of a well during blowout drives the power when the high-speed drilling fluid returns upward through the flow passage mutation, sets a soft rubber core outside the safety valve, sets an end face sealing structure in the annulus of the double-layer pipe, installs a torsional spring and a valve cover on the inner pipe, sets a throttling protrusion between the wellbore and the double-layer pipe drill string, and sets a throttling pipe in the inner pipe of the double-layer pipe, which are respectively used as the driving force for blocking the annulus of the wellbore and the double-layer pipe and the inner pipe of the double-layer pipe, so that the three channels in the downhole can be simultaneously blocked when the upflowing fluid in the downhole exceeds the design value, and the problem that the current downhole blowout preventer does not have the function of multi-channel blocking is solved. The throttling effect of the high-speed fluid is used to set the blocking structure of the inner pipe, so that the cuttings migration passage is effectively reserved, and the problem that the inner pipe migration passage of the current downhole blowout preventer is too small is solved.

Description

Technical Field

[0001] This invention relates to the field of reverse circulation drilling technology, and more specifically to a downhole mechanical three-channel plugging safety valve for double-wall reverse circulation drilling. Background Technology

[0002] Dual-tube reverse circulation drilling technology has significant technical advantages in oil and gas exploration and development due to its unique flow channel distribution and fluid circulation process. Compared with conventional drilling, it offers higher drilling speed, faster wellbore cleaning efficiency, and can effectively reduce drilling fluid loss in easily lost formations, effectively protecting the reservoir. The fully enclosed circulation of drilling fluid enables safe drilling in hydrogen sulfide-containing formations. Reverse circulation drilling technology has been applied in many fields such as coal mining, geothermal exploration and development, hydrogeological drilling, geology, metallurgy, construction, and water conservancy. In oil and gas exploration, deep well drilling is required, and the geological conditions are more complex. It is necessary to ensure the safety of the wellhead in the event of accidents such as blowouts and well kicks, and to achieve rapid response and control of dangerous conditions such as blowouts. There is an urgent need to design a downhole safety valve that completely seals the three drilling fluid flow channels downhole, thereby ensuring the safe operation of dual-tube reverse circulation drilling.

[0003] The existing problems with downhole safety valves include:

[0004] ① The existing blowout preventer can only block two channels in the double-layer pipe at most. Moreover, the blowout preventer consists of a set of separate blowout preventer valves, which block the annular channel and the inner channel of the double-layer pipe respectively. They need to be opened separately during use. When a dangerous working condition occurs, it is not possible to block the two channels in the double-layer pipe at the same time.

[0005] ② The existing double-layer pipe blowout preventer uses the pressure difference between blowout and normal drilling as the driving force. It requires the installation of a partition plate with a large stress surface in the inner pipe channel, which reduces the size of the inner pipe channel and seriously affects the movement of rock cuttings in the inner pipe.

[0006] ③ Existing blowout preventers for double-layered tubing utilize the pressure difference between blowout and normal drilling as the driving force. When the bottom hole pressure fluctuates, the blowout preventer will open and close intermittently, resulting in incomplete sealing and poor sealing effect.

[0007] ④ Existing double-layer pipe blowout preventers use a hydraulic drive method, but the reliability of this method decreases significantly with increasing drilling depth, and its stability is poor.

[0008] ⑤ The existing bottom blowout preventer does not meet the conditions for subsequent well control operations after the sealing is completed. Summary of the Invention

[0009] In order to overcome the defects existing in the prior art, the application discloses a double-layer pipe reverse circulation drilling downhole mechanical three-channel plugging safety valve.

[0010] The application utilizes the phenomenon that a large amount of high-speed drilling fluid generated at the well bottom during blowout drives the power when returning upward through the flow passage mutation, sets a soft rubber core on the outer layer of the safety valve, sets an end face sealing structure in the annulus of the double-layer pipe, installs a torsional spring and a valve cover on the inner pipe, sets a throttling protrusion between the wellbore and the double-layer pipe drill string, and sets a throttling pipe in the inner pipe of the double-layer pipe, which respectively serve as the driving force for plugging the annulus between the wellbore and the double-layer pipe, the annulus of the double-layer pipe and the inner pipe of the double-layer pipe, so that the three channels in the downhole can be simultaneously plugged when the downhole returning fluid exceeds the design value, and the problem that the current downhole blowout preventer does not have the function of multi-channel plugging is solved; the throttling effect of high-speed fluid is used to set the inner pipe plugging structure, the cuttings transport channel is effectively reserved, and the problem that the inner pipe transport channel of the current downhole blowout preventer is too small is solved; the C-shaped ring positioning mode is used to ensure that the throttling pipe does not open the plugging mechanism due to the fluctuation of the well bottom pressure when reaching the preset position, the problem that the current downhole blowout preventer is not tightly plugged due to the fluctuation of the well bottom pressure is solved, and the C-shaped ring positioning can open the two channels in the double-layer pipe after the plugging is completed, the heavy mud injection in the double-layer pipe is completed, the well killing is completed, and the problem that the current downhole blowout preventer does not have the well killing function is solved.

[0011] In order to achieve the above object, the technical scheme adopted by the application is:

[0012] A double-layer pipe reverse circulation drilling downhole mechanical three-channel plugging safety valve comprises an outer plugging structure, an inner plugging structure and a centralizing structure located between the outer plugging structure and the inner plugging structure.

[0013] The outer plugging structure comprises an outer pipe upper joint, an outer shear cylinder, an outer connecting pipe and an outer pipe lower joint arranged in sequence from top to bottom, and a soft rubber core, an extrusion cylinder and a large-stiffness spring are sequentially arranged on the outer wall of the outer connecting pipe from top to bottom, and the extrusion cylinder is fixed with the outer connecting pipe through a shear pin II; when the downhole returning fluid exceeds the design value, the high-speed fluid drives the extrusion cylinder to move upward to shear the shear pin II, and the extrusion cylinder drives the soft rubber core to deform to plug the annulus between the double-layer pipe and the wellbore.

[0014] The inner layer blocking structure comprises, from top to bottom, an inner pipe upper joint, an inner pipe positioning cylinder I, an inner pipe positioning cylinder II, an inner shearing cylinder, an inner connecting pipe, an inner pipe lower joint, the inner pipe upper joint, the inner pipe positioning cylinder I and the inner pipe positioning cylinder II are internally fitted with a throttle pipe, the throttle pipe is limited on the inner pipe positioning cylinder I by a C-shaped ring, the inner pipe positioning cylinder II is internally provided with an inner pipe blocking mechanism for blocking the inner pipe of the double-layer pipe, the outer wall of the inner pipe upper joint and the inner pipe positioning cylinder I is provided with an annulus blocking short pipe for blocking the annulus of the double-layer pipe; when the downhole backflow fluid exceeds the design value, the high-speed fluid drives the throttle pipe to move upward and separate from the limit, the throttle pipe drives the annulus blocking short pipe to move upward to block the annulus of the double-layer pipe; at the same time, after the throttle pipe moves upward, the inner pipe blocking mechanism acts to block the inner pipe of the double-layer pipe.

[0015] Preferably, the centralizing structure comprises upper and lower centralizing rings, the upper centralizing ring is arranged between the outer pipe upper joint and the inner pipe upper joint, and the lower centralizing ring is arranged between the outer pipe lower joint and the inner pipe lower joint.

[0016] Preferably, the inner pipe upper joint is connected with the inner pipe positioning cylinder I through threads, and the upper centralizing ring is fixed at the same time.

[0017] Preferably, the inner pipe positioning cylinder I is provided, at the upper part, with a positioning shoulder I, at the middle part, with a guide groove, and at the lower part, with a positioning groove I and a positioning groove II.

[0018] Preferably, the throttle pipe is provided, at the upper part, with a throttle port, at the middle part, with a pin hole, and at the lower part, with a mounting groove.

[0019] Preferably, the C-shaped ring is mounted in the mounting groove of the throttle pipe, passes through the inner pipe positioning cylinder I from the lower part, and is axially and radially fixed under the action of the C-shaped ring, the positioning groove I and the positioning shoulder I.

[0020] Preferably, the annulus blocking short pipe is connected with the throttle pipe through a connecting pin and moves axially along the guide groove with the throttle pipe.

[0021] Preferably, the inner pipe blocking mechanism comprises a valve cover, a valve seat, a torsional spring and a connecting pin; the valve cover is mounted on the valve seat through the connecting pin and the torsional spring, the valve seat is mounted on the inner pipe positioning cylinder II through a positioning pin, and the inner pipe positioning cylinder II is connected with the inner pipe positioning cylinder I through threads.

[0022] Preferably, the upper part of the inner connecting pipe penetrates into the inner shearing cylinder and is mounted on the inner shearing cylinder through a shearing pin III; the inner pipe lower joint is fixed with the inner connecting pipe through threads.

[0023] Preferably, the upper part of the outer connecting pipe penetrates into the outer shearing cylinder and is connected through a shearing pin I, a soft rubber core penetrates through the outer connecting pipe, and a squeezing cylinder is mounted on the outer connecting pipe through a shearing pin II to simultaneously complete axial fixation of the soft rubber core.

[0024] Preferably, the large stiffness spring is installed in the annular space between the extrusion cylinder and the outer connecting pipe, the lower joint of the outer pipe is connected with the outer connecting pipe through threads, and the lower joint realizes pre-compression of the large stiffness spring, and the upper joint of the outer pipe is connected with the outer shear cylinder through threads.

[0025] Preferably, the upper outer wall of the upper joint of the outer pipe is provided with a positioning boss I, the middle inner wall is provided with a guide inclined surface, and the lower part is provided with a connecting thread I.

[0026] Preferably, the upper part of the outer shear cylinder is provided with a connecting thread II, the lower part is uniformly provided with pin hole I and shaft shoulder I.

[0027] Preferably, the extrusion cylinder is uniformly provided with pin hole II, the upper outer wall is provided with a throttling protrusion, and the circumferential direction is uniformly provided with a booster groove.

[0028] Preferably, the upper part of the outer connecting pipe is provided with a shaft shoulder II and a pin hole III, the middle part is provided with a pin hole IV, and the lower part is provided with a thread III.

[0029] Preferably, the inner pipe positioning cylinder II is provided with a positioning pin hole in the upper part, and a boss in the lower part.

[0030] Preferably, the annular space sealing short joint is provided with a sealing inclined surface in the upper part and a connecting pin hole in the lower part.

[0031] The beneficial effects of the present application are as follows:

[0032] (1) When overflow and blowout occur in the double-layer pipe reverse circulation drilling process, the throttling pressure difference effect of high-speed drilling fluid at the flow passage mutation is utilized, the sealing structure of the two passages between the drill pipe wellbore annulus and the double-layer pipe is designed, and the sealing of the three passages under the well can be automatically completed, thereby ensuring the safety of the wellhead.

[0033] (2) The throttling pressure difference effect of high-speed drilling fluid at the flow passage mutation is utilized, the valve cover sealing form is adopted, and a large rock debris migration passage is left in the inner pipe of the double-layer pipe, thereby not affecting the normal drilling.

[0034] (3) The C-shaped ring positioning and the large stiffness spring setting mode are adopted, the sealing effect of the three passages after the sealing of the safety valve is ensured, the influence of the bottom hole pressure fluctuation is avoided, and the reliable sealing performance is ensured.

[0035] (4) The sealing and unsealing processes of the safety valve are mechanical operations, and are not affected by the well depth.

[0036] (5) After the sealing is completed, the two passages in the double-layer pipe can be reopened by changing the heavy mud pressure of the annular passage of the double-layer pipe, and the heavy mud injection and well killing are realized. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 The open state schematic diagram of the safety valve of the present application;

[0038] Figure 2 The closed state schematic diagram of the safety valve of the present application;

[0039] Figure 3 The quarter cross-section three-dimensional schematic diagram of the upper joint of the outer pipe of the present application;

[0040] Figure 4 The quarter cross-section three-dimensional schematic diagram of the outer shearing cylinder of the present application;

[0041] Figure 5 The quarter cross-section three-dimensional schematic diagram of the outer connecting pipe of the present application;

[0042] Figure 6 The quarter cross-section three-dimensional schematic diagram of the inner throttling pipe of the present application;

[0043] Figure 7 The open state schematic diagram of the plugging mechanism of the inner pipe of the present application;

[0044] Figure 8 The closed state schematic diagram of the plugging mechanism of the inner pipe of the present application;

[0045] Figure 9 The quarter cross-section three-dimensional schematic diagram of the inner pipe positioning cylinder I of the present application;

[0046] Figure 10 The quarter cross-section three-dimensional schematic diagram of the inner pipe positioning cylinder II of the present application;

[0047] Figure 11 The quarter cross-section three-dimensional schematic diagram of the extruding cylinder of the present application;

[0048] Figure 12 The three-dimensional structure schematic diagram of the centralizing ring of the present application;

[0049] Reference signs:

[0050] 1-Upper connector of outer tube, 101-Positioning boss I, 102-Guide bevel, 103-Thread I, 2-Straightening ring, 3-Annular seal plug short connector, 301-Seal bevel, 302-Connecting pin hole, 4-Outer shearing cylinder, 401-Thread II, 402-Shoulder I, 403-Pin hole I, 5-Shearing pin I, 6-Valve seat, 7-Torsion spring, 8-Connecting pin, 9-Valve cover, 10-Shearing pin II, 11-Outer connecting tube, 1101-Shoulder II, 1102-Pin hole III, 1103-Pin hole IV, 1104-Thread III, 12-High stiffness spring, 13-Lower connector of outer tube, 14-Lower connector of inner tube 15-Inner connecting pipe, 16-Shearing pin III, 17-Inner shearing cylinder, 18-Extrusion cylinder, 1801-Throttling protrusion, 1802-Pressure boosting groove, 1803-Pin hole II, 19-Inner tube positioning cylinder II, 1901-Positioning pin hole, 1902-Boss, 20-Soft rubber core, 21-Positioning pin, 22-C-ring, 23-Inner tube positioning cylinder I, 2301-Positioning shoulder I, 2302-Guide groove, 2303-Positioning groove I, 2304-Positioning groove II, 24-Connecting pin, 25-Throttling pipe, 2501-Throttling port, 2502-Pin hole, 2503-Mounting groove, 26-Upper connector of inner tube. Detailed Implementation

[0051] The following will provide a clear and complete description of the concept, specific structure, and technical effects of the present invention in conjunction with the embodiments and accompanying drawings, so as to fully understand the purpose, features, and effects of the present invention.

[0052] A double-walled reverse circulation drilling downhole mechanical three-channel plugging safety valve, such as Figures 1-12 As shown, it includes an outer sealing structure, an inner sealing structure, and a straightening structure located between the outer sealing structure and the inner sealing structure;

[0053] The outer sealing structure includes, from top to bottom, an upper outer pipe connector 1, an outer shearing cylinder 4, an outer connecting pipe 11, and a lower outer pipe connector 13. On the outer wall of the outer connecting pipe 11, from top to bottom, are arranged a soft rubber core 20, a compression cylinder 18, and a high-stiffness spring 12. The compression cylinder 18 is fixed to the outer connecting pipe 11 by a shear pin II 10. When the upflow fluid from the well exceeds the design value, the high-speed fluid drives the compression cylinder 18 upwards, shearing the shear pin II 10. The compression cylinder 18 then pushes the soft rubber core 20 to deform and seal the annulus between the double-layer pipe and the wellbore (one-channel sealing).

[0054] The inner sealing structure includes, from top to bottom, an inner tube upper connector 26, an inner tube positioning cylinder I 23, an inner tube positioning cylinder II 19, an inner shearing cylinder 17, an inner connecting pipe 15, and an inner tube lower connector 14. A throttling tube 25 is installed inside the inner tube upper connector 26, inner tube positioning cylinder I 23, and inner tube positioning cylinder II 19. The throttling tube 25 is limited on the inner tube positioning cylinder I 23 by a C-ring 22. The inner tube positioning cylinder II 19 is equipped with a mechanism for sealing the inner tube of the double-layer pipe. The inner tube plugging mechanism includes annular plugging short-circuit 3 on the outer wall of the inner tube upper connector 26 and the inner tube positioning cylinder I 23 for plugging the annulus of the double-layer tube. When the upflow fluid from the well exceeds the design value, the high-speed fluid drives the choke pipe 25 to move upward and break away from the limit. The choke pipe 25 drives the annular plugging short-circuit 3 to move upward and plug the annulus of the double-layer tube (two-channel plugging). At the same time, after the choke pipe 25 moves upward, the inner tube plugging mechanism activates to plug the inner tube of the double-layer tube (three-channel plugging). This embodiment ensures wellhead safety by setting the above-mentioned three-channel plugging.

[0055] like Figure 1 As shown, the straightening structure includes upper and lower straightening rings 2. The upper straightening ring 2 is positioned between the upper connector 1 of the outer tube and the upper connector 26 of the inner tube, while the lower straightening ring 2 is positioned between the lower connector 13 of the outer tube and the lower connector 14 of the inner tube. The upper straightening ring 2 is used to straighten the inner tube. The upper connector 26 of the inner tube is connected to the inner tube positioning cylinder I 23 by threads, and simultaneously fixes the upper straightening ring 2.

[0056] like Figure 9 As shown, the upper part of the inner tube positioning cylinder I23 is provided with a positioning shoulder I2301 for positioning with the upper connector 26 of the inner tube, the middle part is provided with a guide groove 2302, and the lower part is provided with positioning grooves I2303 and positioning grooves II2304 for fitting with the C-shaped ring 22.

[0057] like Figure 6 As shown, the throttling tube 25 has a throttling port 2501 at the top, a pin hole 2502 in the middle, and an installation groove 2503 at the bottom.

[0058] like Figure 1 As shown, the C-ring 22 is installed in the mounting groove 2503 of the throttling tube 25, passing through the inner tube positioning cylinder I23 from the bottom. Under the action of the C-ring 22, the positioning groove I2303, and the positioning shoulder I2301, the throttling tube 25 is fixed axially and radially.

[0059] like Figure 1 As shown, the annular sealing short-circuit 3 is connected to the throttling pipe 25 through the connecting pin 24 passing through the guide groove 2302, and moves axially along the guide groove 2302 with the throttling pipe 25.

[0060] like Figure 7 and 8As shown, the inner tube blocking mechanism includes valve cover 9, valve seat 6, torsion spring 7 and connecting pin 8; valve cover 9 is installed on valve seat 6 through connecting pin 8 and torsion spring 7, valve seat 6 is installed on inner tube positioning cylinder II 19 through positioning pin 21, and inner tube positioning cylinder II 19 is connected with inner tube positioning cylinder I 23 through threads.

[0061] As shown in FIG. 1, the upper part of outer connecting pipe 11 penetrates into outer shearing cylinder 4 and is connected through shearing pin I 5, soft rubber core 20 penetrates through outer connecting pipe 11, and extrusion cylinder 18 is installed on outer connecting pipe 11 through shearing pin II 10, and at the same time, axial fixation of soft rubber core 20 is completed. Figure 1 As shown in FIG. 1, the upper part of outer connecting pipe 11 penetrates into outer shearing cylinder 4 and is connected through shearing pin I 5, soft rubber core 20 penetrates through outer connecting pipe 11, and extrusion cylinder 18 is installed on outer connecting pipe 11 through shearing pin II 10, and at the same time, axial fixation of soft rubber core 20 is completed.

[0062] As shown in FIG. 1, the upper part of outer connecting pipe 11 penetrates into outer shearing cylinder 4 and is connected through shearing pin I 5, soft rubber core 20 penetrates through outer connecting pipe 11, and extrusion cylinder 18 is installed on outer connecting pipe 11 through shearing pin II 10, and at the same time, axial fixation of soft rubber core 20 is completed. Figure 1 As shown in FIG. 1, the upper part of outer connecting pipe 11 penetrates into outer shearing cylinder 4 and is connected through shearing pin I 5, soft rubber core 20 penetrates through outer connecting pipe 11, and extrusion cylinder 18 is installed on outer connecting pipe 11 through shearing pin II 10, and at the same time, axial fixation of soft rubber core 20 is completed.

[0063] Figure 1 As shown in FIG. 1, the upper part of outer connecting pipe 11 penetrates into outer shearing cylinder 4 and is connected through shearing pin I 5, soft rubber core 20 penetrates through outer connecting pipe 11, and extrusion cylinder 18 is installed on outer connecting pipe 11 through shearing pin II 10, and at the same time, axial fixation of soft rubber core 20 is completed.

[0064] As shown in FIG. 1, the upper part of outer connecting pipe 11 penetrates into outer shearing cylinder 4 and is connected through shearing pin I 5, soft rubber core 20 penetrates through outer connecting pipe 11, and extrusion cylinder 18 is installed on outer connecting pipe 11 through shearing pin II 10, and at the same time, axial fixation of soft rubber core 20 is completed. Figure 3 As shown in FIG. 1, the upper part of outer connecting pipe 11 penetrates into outer shearing cylinder 4 and is connected through shearing pin I 5, soft rubber core 20 penetrates through outer connecting pipe 11, and extrusion cylinder 18 is installed on outer connecting pipe 11 through shearing pin II 10, and at the same time, axial fixation of soft rubber core 20 is completed.

[0065] Figure 4 As shown in FIG. 1, the upper part of outer connecting pipe 11 penetrates into outer shearing cylinder 4 and is connected through shearing pin I 5, soft rubber core 20 penetrates through outer connecting pipe 11, and extrusion cylinder 18 is installed on outer connecting pipe 11 through shearing pin II 10, and at the same time, axial fixation of soft rubber core 20 is completed.

[0066] As shown in FIG. 1, the upper part of outer connecting pipe 11 penetrates into outer shearing cylinder 4 and is connected through shearing pin I 5, soft rubber core 20 penetrates through outer connecting pipe 11, and extrusion cylinder 18 is installed on outer connecting pipe 11 through shearing pin II 10, and at the same time, axial fixation of soft rubber core 20 is completed. Figure 11 As shown in FIG. 1, the upper part of outer connecting pipe 11 penetrates into outer shearing cylinder 4 and is connected through shearing pin I 5, soft rubber core 20 penetrates through outer connecting pipe 11, and extrusion cylinder 18 is installed on outer connecting pipe 11 through shearing pin II 10, and at the same time, axial fixation of soft rubber core 20 is completed.

[0067] Figure 5 As shown in FIG. 1, the upper part of outer connecting pipe 11 penetrates into outer shearing cylinder 4 and is connected through shearing pin I 5, soft rubber core 20 penetrates through outer connecting pipe 11, and extrusion cylinder 18 is installed on outer connecting pipe 11 through shearing pin II 10, and at the same time, axial fixation of soft rubber core 20 is completed.

[0068] As shown in FIG. 1, the upper part of outer connecting pipe 11 penetrates into outer shearing cylinder 4 and is connected through shearing pin I 5, soft rubber core 20 penetrates through outer connecting pipe 11, and extrusion cylinder 18 is installed on outer connecting pipe 11 through shearing pin II 10, and at the same time, axial fixation of soft rubber core 20 is completed. Figure 10 As shown in FIG. 1, the upper part of outer connecting pipe 11 penetrates into outer shearing cylinder 4 and is connected through shearing pin I 5, soft rubber core 20 penetrates through outer connecting pipe 11, and extrusion cylinder 18 is installed on outer connecting pipe 11 through shearing pin II 10, and at the same time, axial fixation of soft rubber core 20 is completed.

[0069] Figure 1 As shown in FIG. 1, the upper part of outer connecting pipe 11 penetrates into outer shearing cylinder 4 and is connected through shearing pin I 5, soft rubber core 20 penetrates through outer connecting pipe 11, and extrusion cylinder 18 is installed on outer connecting pipe 11 through shearing pin II 10, and at the same time, axial fixation of soft rubber core 20 is completed.

[0070] ​​​​In the present application, the large stiffness spring generates a large elastic force after pre-compression. The extrusion force required for deformation of the soft rubber core is lower than that of a conventional rubber core. The inner layer pipe of the safety valve is connected by insertion, and the outer layer pipe is connected by oil pipe taper thread, which can be quickly connected into a standard double-layer drill pipe. The shear force required for the rupture of shear pin II is lower than that of shear pin I and shear pin III.

[0071] The working process of the present application is as follows:

[0072] During normal drilling, the safety valve is in an open state, and drilling fluid is pumped from the double-layer pipe annulus. The drilling fluid flows into the upper double-layer pipe annulus, passes through the annulus between the inner and outer pipes of the safety valve, and then flows into the annulus of the double-layer pipe connected below the safety valve until the bottom of the well. After passing through the bottom drill bit, the drilling fluid carrying cuttings returns from the inner pipe passage of the double-layer pipe. When the drilling fluid carrying cuttings passes through the throttle pipe 25, the pressure at the large-diameter end of the variable-diameter section is greater than that at the small-diameter end due to the gradually decreasing flow passage at the variable-diameter section, thereby forming a pressure drop and generating an upward thrust at the variable-diameter section. Due to the presence of the C-shaped ring 22 and the positioning groove I 2303, the throttle pipe 25 will not be pushed, and the safety valve annulus and inner pipe sealing mechanism remain in an open state. The drilling fluid carrying cuttings returns from the inner pipe passage to the surface mud system. At the same time, during normal drilling, the annulus between the wellbore and the double-layer pipe is in a low flow rate state, and the pressure drop generated in the throttle passage formed by the extrusion cylinder 18 and the wellbore is not enough to shear the shear pin II 10, so the annulus between the double-layer pipe and the wellbore is in an open state.

[0073] When the well drilling process encounters dangerous working conditions such as blowout, the bottom of the well drilling fluid passes through the double-layer pipe and the annulus of the wellbore, the double-layer pipe annulus channel, and the inner pipe channel of the double-layer pipe upward rapidly, and the drilling fluid returning from the annulus between the double-layer pipe and the wellbore is even larger. When a large amount of drilling fluid returns upward at high speed in the throttling channel formed between the extrusion 18 cylinder and the wellbore, because of the throttling pressure drop of the fluid, the extrusion cylinder 18 upper end throttling protrusion 1801, the booster groove 1802 will be subjected to an upward thrust, when the return flow reaches the design threshold, that is, the upward thrust on the extrusion cylinder 18 upper end throttling protrusion 1801, the booster groove 1802 reaches the design value, the shear pin II 10 will be sheared under the combined action of the pre-compressed large stiffness spring 12 spring force and the thrust, and the soft rubber core 20 is deformed to block the annulus between the double-layer pipe and the wellbore under the extrusion of the extrusion cylinder 18. At the same time, the drilling fluid returning from the inner pipe of the double-layer pipe to the safety valve throttling pipe 25 forms a pressure drop at the throttling port 2501 of the throttling pipe 25, and an upward thrust is generated at the throttling port 2501. The generated thrust is used to overcome the resistance of the C-shaped ring 22 in the positioning groove I 2303. When the C-shaped ring 22 is deformed and contracted to the installation groove 2503 under the thrust, the throttling pipe 25 moves upward under the action of the thrust, and the annulus blocking short circuit 3 is driven by the throttling pipe 25 and moves upward under the throttling thrust generated by the drilling fluid in the annulus blocking short circuit. When the blocking slope coincides with the guide slope 102, the annulus blocking short circuit 3 and the throttling pipe 25 move to the axial limit position, and the C-shaped ring 22 is located in the positioning groove II 2304 at this time. The annulus of the double-layer pipe is blocked. Because the throttling pipe 25 moves upward, the valve cover 9 rebounds to the valve seat 6 under the action of the torsional spring 7 to complete the blocking of the inner pipe of the double-layer pipe. When the bottom hole pressure fluctuates, the double-layer pipe two channels will not be opened due to the positioning function of the C-shaped ring 22 and the action of the torsional spring 7.

[0074] Well killing and safety valve extraction process: when the downhole three channels are blocked, inject heavy mud into the double-layer pipe annulus channel from the ground. When the pressure on the upper end of the blocking annulus short circuit is greater than the pressure at the bottom of the well, the blocking annulus drives the throttling pipe 25 to move downward, and the C-shaped ring 22 is pushed out of the positioning groove II 2304 under the action of the thrust. The two channels of the double-layer pipe are opened, the heavy mud is injected from the double-layer pipe annulus, the bottom hole mud is returned to the ground from the double-layer pipe inner pipe, and the well killing is completed. When the well killing is completed, the drilling pressure is increased downward, the outer shear cylinder 4 shears the shear pin I 5, and the inner shear cylinder 17 shears the shear pin III 16. The drilling string is lifted, the soft rubber core 20 returns to its original state, the safety valve is unblocked, the outer shear cylinder 4 drives the outer connecting pipe 11, and the inner shear cylinder 17 drives the inner connecting pipe 15 to move upward and extract the wellbore. After replacing the shear pin, it will be used next time.

[0075] The above describes the embodiments of the present application in detail, but the present application is not limited to the above-mentioned embodiments, and those skilled in the art can make various equivalent modifications or replacements without departing from the spirit of the present application, and these equivalent modifications or replacements are all included in the scope defined by the claims of the present application.

Claims

1. A mechanical three-channel plugging safety valve for double-walled reverse circulation drilling wells, characterized in that, It includes an outer sealing structure, an inner sealing structure, and a straightening structure located between the outer sealing structure and the inner sealing structure; The outer sealing structure includes an upper outer pipe connector (1), an outer shearing cylinder (4), an outer connecting pipe (11), and an lower outer pipe connector (13) arranged sequentially from top to bottom. A soft rubber core (20), a compression cylinder (18), and a high-stiffness spring (12) are arranged sequentially from top to bottom on the outer wall of the outer connecting pipe (11). The compression cylinder (18) is fixed to the outer connecting pipe (11) by shear pin II (10). When the upflow fluid from the well exceeds the design value, the high-speed fluid drives the compression cylinder (18) to move upward and cuts the shear pin II (10). The compression cylinder (18) pushes the soft rubber core (20) to deform and seal the annulus between the double-layer pipe and the wellbore. The inner sealing structure includes, in descending order, an inner tube upper connector (26), an inner tube positioning cylinder I (23), an inner tube positioning cylinder II (19), an inner shearing cylinder (17), an inner connecting pipe (15), and an inner tube lower connector (14). A throttling tube (25) is installed inside the inner tube upper connector (26), inner tube positioning cylinder I (23), and inner tube positioning cylinder II (19). The throttling tube (25) is limited on the inner tube positioning cylinder I (23) by a C-ring (22), and the inner tube positioning cylinder II (19)... 19) An inner tube sealing mechanism is provided for sealing the inner tube of the double-layer pipe. The inner tube upper connector (26) and the outer wall of the inner tube positioning cylinder I (23) are provided with annular sealing short-circuit (3) for sealing the annulus of the double-layer pipe. When the upflow fluid in the well exceeds the design value, the high-speed fluid drives the throttle pipe (25) to move upward and break away from the limit. The throttle pipe (25) drives the annular sealing short-circuit (3) to move upward and seal the annulus of the double-layer pipe. At the same time, after the throttle pipe (25) moves upward, the inner tube sealing mechanism acts to seal the inner tube of the double-layer pipe. The straightening structure includes upper and lower straightening rings (2). The upper straightening ring (2) is located between the upper connector (1) of the outer tube and the upper connector (26) of the inner tube, and the lower straightening ring (2) is located between the lower connector (13) of the outer tube and the lower connector (14) of the inner tube. The upper connector (26) of the inner tube is connected to the inner tube positioning cylinder I (23) by thread, and at the same time the upper straightening ring (2) is fixed.

2. The safety valve as described in claim 1, characterized in that, The inner tube positioning cylinder I (23) is provided with a positioning shoulder I (2301) at the top, a guide groove (2302) in the middle, and positioning grooves I (2303) and II (2304) at the bottom.

3. The safety valve as described in claim 2, characterized in that, The throttling pipe (25) has a throttling port (2501) at the top, a pin hole (2502) in the middle, and an installation groove (2503) at the bottom.

4. The safety valve as described in claim 3, characterized in that, The C-ring (22) is installed in the mounting groove (2503) of the throttling tube (25) and passes through the inner tube positioning cylinder I (23) from the bottom. The axial and radial fixation of the throttling tube (25) is achieved under the action of the C-ring (22), positioning groove I (2303), and positioning shoulder I (2301).

5. The safety valve as described in claim 3, characterized in that, The annular sealing short circuit (3) is connected to the throttling pipe (25) through the guide groove (2302) via the connecting pin (24), and moves axially along the guide groove (2302) with the throttling pipe (25).

6. The safety valve as described in claim 1, characterized in that, The inner tube sealing mechanism includes a valve cover (9), a valve seat (6), a torsion spring (7), and a connecting pin (8); the valve cover (9) is installed on the valve seat (6) through the connecting pin (8) and the torsion spring (7), the valve seat (6) is installed on the inner tube positioning cylinder II (19) through the positioning pin (21), and the inner tube positioning cylinder II (19) and the inner tube positioning cylinder I (23) are connected by threads.

7. The safety valve as described in claim 1, characterized in that, The upper part of the inner connecting tube (15) is inserted into the inner shearing cylinder (17) and installed on the inner shearing cylinder (17) by shearing pin III (16); the lower connector (14) of the inner tube is fixed to the inner connecting tube (15) by threads.

8. The safety valve as described in claim 1, characterized in that, The upper part of the external connecting tube (11) is inserted into the external shearing cylinder (4) and connected by shearing pin I (5). The soft rubber core (20) passes through the external connecting tube (11). The extrusion cylinder (18) is installed on the external connecting tube (11) by shearing pin II (10) to simultaneously fix the soft rubber core (20) axially.

9. The safety valve as described in claim 1, characterized in that, The high-stiffness spring (12) is installed in the annular space between the extrusion cylinder (18) and the outer connecting pipe (11). The lower connector (13) of the outer pipe is connected to the outer connecting pipe (11) by a thread to achieve pre-compression of the high-stiffness spring (12). The upper connector (1) of the outer pipe is connected to the outer shear cylinder (4) by a thread.

10. The safety valve as claimed in claim 1, characterized in that, The upper outer wall of the outer tube connector (1) is provided with a positioning boss I (101), the middle inner wall is provided with a guide slope (102), and the lower part is provided with a connecting thread I (103).

11. The safety valve as claimed in claim 1, characterized in that, The upper part of the outer shear cylinder (4) is provided with connecting thread II (401), and the lower part is evenly distributed with pin holes I (403) and shoulder I (402).

12. The safety valve as claimed in claim 1, characterized in that, The extrusion cylinder (18) is provided with pin holes II (1803) evenly distributed, and the upper outer wall is provided with throttling protrusions (1801) and pressure-boosting grooves (1802) evenly distributed around the periphery.

13. The safety valve as claimed in claim 1, characterized in that, The external connecting pipe (11) is provided with a shoulder II (1101) and a pin hole III (1102) at the top, a pin hole IV (1103) in the middle, and a thread III (1104) at the bottom.

14. The safety valve as claimed in claim 1, characterized in that, The upper part of the inner tube positioning cylinder II (19) is provided with positioning pin holes (1901), and the lower part is provided with a boss (1902).

15. The safety valve as claimed in claim 1, characterized in that, The annular sealing short connector (3) shown has a sealing slope at the top and a connecting pin hole at the bottom.

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