A side-tracking hydraulic unlocking and releasing device for a bare-eye whipstock

Abstract

The present invention relates to the technical field of downhole tools for oil drilling, and particularly relates to a hydraulic unlocking and releasing device for sidetracking in open hole whipstock, which comprises an upper sub, a central tube, an upper piston, an elastic claw piston, a cylinder barrel, a spline shaft, a sealing joint, a rotation prevention key head, a threaded gland, and a lower sub. The upper sub is connected to the upper tool string through the central tube, and the lower sub is connected to the lower tool string. Splines are machined on both the inner and outer sides of the internal spline shaft and are engaged with the cylinder barrel and the central rod, and the torque from the upper pipe string can be borne. After the open hole sidetracking tool string is lowered into the wellbore, the spline unlocking is first achieved through hydraulic pressure, and then the releasing action is achieved through the way of right-hand rotation and back-off. Compared with the traditional back-off and releasing structure, the safety is higher.

Description

Technical Field

[0001] The present invention relates to the technical field of downhole tools for oil drilling, and particularly relates to a hydraulic unlocking and releasing device for sidetracking with a whipstock in open hole. Background Art

[0002] In drilling operations, due to technological requirements or the need to handle downhole complex conditions, open-hole sidetracking operations are often required in the deep part of the wellbore. The traditional method is to perform cement plugging for sidetracking. When the open-hole sidetracking position is in a high-angle, small-diameter, deep, high-temperature and / or high-pressure well section or there is a diameter-reduced well section above the sidetracking position, cement plugging for sidetracking often cannot achieve the same effect as in shallow wells. Especially in the deep hard formation well section, the strength of the cement plug is generally not higher than the strength of the surrounding formation rock, which makes it very difficult to use the cement plug as a "sidetracking platform" and sidetracking will be very difficult. By lowering a whipstock into the open hole and fixing it to the wellbore wall, and relying on the steel inclined plane for sidetracking, the success rate of sidetracking at one time can be greatly improved.

[0003] Currently, the commonly used open-hole whipstock is connected to the inclined plane and the anchor by a pipe string sent into the wellbore. First, the anchor is fixed to the formation rock, and then the pipe string is reversed and released by unscrewing to lift the pipe string to the surface. The basic principle is that a reverse thread is processed at the lower part of the pipe string, and the reverse thread is achieved by rotating the pipe string forward. The patent "CN201120415989.4" and "CN201220664891.7" disclose this releasing mechanism with reverse threads. This releasing method can withstand a large axial tensile force, but the disadvantage is that the tool cannot be rotated forward after being lowered into the well and cannot withstand torque. Therefore, it is more suitable for use in the casing, rather than in the open-hole section.

[0004] "CN201220567229.X" discloses a mechanical-hydraulic dual-action releasing mechanism, which can release the tool in two ways, hydraulic and mechanical, reducing the construction risk of releasing failure. However, this releasing method also cuts the pin between the hydraulic releasing lock head and the elastic claw, first unlocks the elastic claw and the external lock pipe, and then reverses and unscrews to release the tool, without solving the disadvantage that the elastic claw cannot withstand a large torque.

[0005] "CN201310246044.8" discloses a hydraulically actuated reverse and release mechanism, which overcomes the defect that the conventional left-handed thread reverse and release mechanism cannot rotate the pipe string forward on the ground during the process of lowering the tool into the well and before the operation is completed, and also overcomes the disadvantage that the shear pin of the existing mechanical and hydraulic dual-action releasing tool is accidentally cut. However, in the disclosed patent, the upper piston is connected to the housing by a pin, and when the pressure loss is large, it is easy to cause the upper piston pin to be cut in advance, resulting in the failure of hydraulic unlocking, the spline cannot be unlocked, and thus the mechanical reverse thread action cannot be achieved, with a relatively high risk of releasing failure. Summary of the Invention

[0006] The object of the present invention is to provide a hydraulic unlocking and releasing device for side drilling with a bare-eye whipstock in view of the deficiencies in the prior art, which is applicable to side drilling with a bare-eye whipstock.

[0007] The technical solution is as follows:

[0008] A hydraulic unlocking and releasing device for side drilling with a bare-eye whipstock includes an upper sub (10), a central tube (11), an upper piston (14), an elastic claw piston (16), a cylinder barrel (17), a spline shaft (18), a sealing joint (20), a rotation prevention key head (21), a threaded gland (22), a lower sub (23), and a shear pin (24);

[0009] The upper sub (10), the cylinder barrel (17), the sealing joint (20), and the lower sub (23) are sequentially connected to form an outer barrel string;

[0010] The central tube (11) is placed inside the outer barrel string and is threadedly connected to the upper sub (10) and the rotation prevention key head (21) at both ends respectively;

[0011] The rotation prevention key head (21) is inserted into the sealing joint (20) through a spline, and the lower part is pressed tightly by the threaded gland (22); the threaded gland (22) is threadedly connected to the sealing joint (20) and is placed in the inner cavity formed by the sealing joint (20) and the lower sub (23);

[0012] The upper piston (14), the elastic claw piston (16), and the spline shaft (18) are sleeved on the central tube (11) from top to bottom in sequence;

[0013] The spline shaft (18) is in spline fit with the cylinder barrel (17) and the central tube (11) respectively, and the lower part of the spline shaft (18) and the cylinder barrel (17) are connected by a shear pin (24);

[0014] The inner end face of the lower part of the elastic claw piston (16) is freely pressed against the upper end face of the spline shaft (18).

[0015] Furthermore, an elastic claw release cavity (30) is provided inside the cylinder barrel (17), and the outer dimension of the elastic claw at the lower part of the elastic claw piston (16) is larger than the inner diameter of the cylinder barrel (17) and smaller than the inner diameter of the elastic claw release cavity (30).

[0016] Furthermore, a sealing O-ring (12) and a sealing element A (13) are respectively provided on the inner and outer sides of the upper piston (14), and the two side end faces are limited by the inner end face of the upper sub (10) and the step on the inner cavity of the cylinder barrel (17).

[0017] Further, a pressure transmission hole (29) is provided in the upper part of the central tube (11). The pressure transmission hole (29) is a radial through hole. The upper piston (14) and the elastic claw piston (16) form a pressure cavity (27) with the cylinder barrel (17), and are communicated with the inner hole of the central tube (11) through the pressure transmission hole (29).

[0018] Further, a spline shaft downward displacement drainage and breathing hole (25) and an elastic claw piston downward displacement drainage and breathing hole (26) are provided in the middle of the cylinder barrel (17) body. The spline shaft downward displacement drainage and breathing hole (25) and the elastic claw piston downward displacement drainage and breathing hole (26) are radial through holes.

[0019] Further, an external spline is provided on the outer side of the spline shaft (18) to be in spline fit with the cylinder barrel (17), and an internal spline is provided on the inner side of the spline shaft (18) to be in spline fit with the central tube (11).

[0020] Further, the length of the external spline of the spline shaft (18) is greater than the length of the internal spline. When the shear pin (24) is cut off and the lower end face of the spline shaft (18) fits with the upper end face of the sealing joint (20), the spline shaft (18) and the cylinder barrel (17) are still meshed through splines, and the spline meshing between the spline shaft (18) and the central tube (11) is disengaged.

[0021] Further, an annular groove (28) is provided in the lower part of the spline shaft (18). The annular groove (28) cooperates with the pin hole machined on the cylinder barrel (17) body to jointly accommodate the shear pin (24).

[0022] Further, 4 rectangular splines are machined on the anti-rotation key head (21) and inserted into the corresponding spline grooves of the sealing joint (20).

[0023] Further, sealing elements B (15) are pressed on the inner and outer sides of the elastic claw piston (16).

[0024] The beneficial effects of the present invention are as follows:

[0025] The torque of the open-hole sidetracking tool string is transmitted by the meshing splines between the central tube, the spline shaft and the cylinder barrel, so it can withstand a large torque value. It overcomes the limitation that the conventional back-off and releasing mechanism cannot rotate the pipe string forward after the tool enters the wellbore, and has a wider application range. The weight of the lower pipe string is transmitted to the central tube through the thread and can also withstand a large weight. Therefore, when the open-hole sidetracking tool string encounters resistance when being lowered into the wellbore, it can be solved by rotating forward and moving up and down, and the use safety of the tool is higher.

[0026] Fluid breathing holes are provided on both the cylinder barrels where the elastic claw piston and the spline shaft move downward. When the elastic claw piston and the spline shaft move under the action of liquid pressure, the liquid in the inner cavity of the cylinder barrel can be discharged in time.

[0027] Through the anti-rotation function achieved by the anti-rotation key head, the threaded gland, and the threaded fit with the central tube, compared with directly threading the central tube to the outer housing, the assembly is more convenient. Brief Description of the Drawings

[0028] The present invention will be described below with reference to the accompanying drawings.

[0029] Figure 1 It is an overall schematic diagram of the open-hole sidetracking tool string used in conjunction with the open-hole whipstock sidetracking hydraulic unlocking and releasing device of the present invention.

[0030] Figure 2 It is a schematic structural diagram of the open-hole whipstock sidetracking hydraulic unlocking and releasing device of the present invention.

[0031] Figure 3 It is a schematic diagram of the spline fit between the spline shaft, the central tube, and the outer cylinder of the open-hole whipstock sidetracking hydraulic unlocking and releasing device of the present invention.

[0032] Figure 4 It is a schematic diagram of the spline fit between the anti-rotation key head of the central tube and the spline of the open-hole whipstock sidetracking hydraulic unlocking and releasing device of the present invention.

[0033] In the figure:

[0034] 1. Feed rod, 2. Deflecting body, 3. Formation, 4. Releasing device, 5. Anchor, 6. Slip teeth, 7. Anti-rotation treated drill pipe, 8. Cement diversion hole, 9. Anti-rotation cross bar, 10. Upper sub, 11. Central tube, 12. Sealing O-ring, 13. Sealing element A, 14. Upper piston, 15. Sealing element B, 16. Elastic claw piston, 17. Cylinder barrel, 18. Spline shaft, 19. Sealing element C, 20. Sealing joint, 21. Anti-rotation key head, 22. Threaded gland, 23. Lower sub, 24. Shearing pin, 25. Drainage and breathing hole for downward movement of the spline shaft, 26. Drainage and breathing hole for downward movement of the elastic claw piston, 27. Pressure cavity, 28. Annular groove, 29. Pressure transmission hole, 30. Elastic claw release cavity. Detailed Description of the Preferred Embodiments

[0035] The following combines the attached Figures 1-4 drawings and specific embodiments to further elaborate on the present invention in detail.

[0036] Embodiment 1:

[0037] An open-hole whipstock sidetracking hydraulic unlocking and releasing device includes an upper sub 10, a central tube 11, an upper piston 14, an elastic claw piston, a cylinder barrel 17, a spline shaft, a sealing joint 20, an anti-rotation key head 21, a threaded gland 22, and a lower sub 23. The upper sub 10, the cylinder barrel 17, the sealing joint 20, and the lower sub 23 are sequentially connected by threads to form an outer cylinder string. The upper sub 10 is connected to the deflecting body 2 by threads, and the lower sub 23 is connected to the open-hole anchor 5 by threads.

[0038] The central pipe 11 is placed at the center inside the outer barrel string. The lower part is connected to the anti-rotation key head 21 through reverse-threaded connection, and the upper part is connected to the feeding rod 1 through right-hand threaded connection. The anti-rotation key head 21 is inserted into the spline groove of the sealing joint 20 through 4 rectangular splines, bearing the torque force from the upper drill string, and the lower part is pressed tightly by the threaded gland 22. The threaded gland 22 is connected to the sealing joint 20 through threads and is placed in the inner cavity formed by the sealing joint 20 and the lower joint 23. Its main purpose is to bear the downward pressure from the central pipe 11.

[0039] The torque transmission between the central pipe 11 and the outer barrel string is achieved through the cooperation of the internal and external splines of the spline shaft with the keys between the central pipe 11 and the cylinder barrel 17. For convenient installation and positioning, the number of internal and external splines of the spline shaft is usually the same, but the numbers can also be different. There is a groove at the lower part of the spline shaft, and it is suspended on the cylinder barrel 17 through a certain number of shear pins 24. The cylinder barrel 17 is usually machined with 8 - 12 pin holes, and the installation number of the pins is determined by calculating the actual required hydraulic pressure.

[0040] The elastic claw piston 16 is placed between the cylinder barrel 17 and the central pipe 11, and sealing elements B15 are pressed on the inner and outer sides. The lower inner end face of the elastic claw piston is freely pressed against the upper end face of the spline shaft. The upper piston 14 is placed between the cylinder barrel 17 and the central pipe 11 and sealing elements A13 are pressed on the inner and outer sides. The two end faces are limited by the lower inner end face of the upper joint 10 and the inner cavity step of the cylinder barrel 17. The upper piston 14 and the elastic claw piston form a sealed chamber with the cylinder barrel 17 and the central pipe 11, and are connected to the inside of the central pipe 11 through the pressure transmission hole 29.

[0041] Embodiment 2:

[0042] A hydraulic unlocking and releasing device for open-hole whipstock sidetracking, the upper part is connected to the whipstock body 2 and the feeding rod 1 through threads, and the lower part is connected to the anchor 5 and the anti-rotation pipe through threads.

[0043] There is a shearable plug in the anchor 5, and the shear pressure is greater than the shear pressure of the pins in the releasing device 4.

[0044] After the open-hole sidetracking tool string is lowered to the designed well depth, the pressure is built up inside the central pipe 11 by pumping drilling fluid through the wellhead. The pressure inside the central pipe 11 acts on the upper end face of the elastic claw piston through the pressure transmission hole 29, pushing the elastic claw piston to squeeze the spline shaft downward. When the designed pressure value is reached, the shear pins 24 are broken, and the spline engagement between the central pipe 11 and the spline shaft is disengaged, enabling the central pipe 11 to be released by rotating it forward.

[0045] The lower end of the elastic claw piston is a petal-shaped elastic claw, and the outer diameter of the claw tip is greater than the inner diameter of the cylinder barrel 17 and less than the inner diameter of the elastic claw release cavity 30. When the elastic claw piston moves down to the position of the elastic claw release cavity 30, the petal-shaped elastic claw opens.

[0046] Continue to increase the pressure inside the central tube 11, and the anchor 5 starts to work, firmly inserting the slips 6 into the rock formation 3 to prevent the rotation of the whipstock 2. When the pressure inside the central tube 11 reaches the shear pressure of the shear plug, the plug opens and the pressure inside the tube is relieved. At this time, the rebound force caused by the instantaneous release of pressure may cause the spline shaft to pop up, resulting in the separation and re-engagement of the central tube 11 and the spline shaft after separation, making the central tube unable to rotate counterclockwise to unscrew and the release of the tool joint to fail. The flap-shaped elastic claw at the lower end of the elastic claw piston can prevent this situation from occurring.

[0047] The spline length of the spline shaft engaged with the cylinder barrel 17 is longer than the spline length of the spline shaft engaged with the central tube 11. After the spline shaft moves down in place, the spline engagement with the central tube 11 is completely disengaged, and the spline engaged with the cylinder barrel 17 is still partially engaged. When the central tube 11 is rotated counterclockwise to unscrew, the spline shaft does not rotate.

[0048] Embodiment 3:

[0049] The overall structure of the open-hole whipstock sidetracking tool string used in conjunction with the open-hole sidetracking hydraulic unlocking and releasing device of the present invention is referred to in the appendix Figure 1 。

[0050] The releasing device 4 is assembled between the whipstock 2 and the anchor 5. At the upper end of the releasing device 4, the central tube 11 is threadedly connected to the running-in string 1 through a right-hand thread. The upper end of the running-in string 1 is connected to the relevant work string including the drill pipe. The upper joint 10 of the present releasing device is threadedly connected to the whipstock 2. A through hole is machined in the whipstock 2 to allow the running-in string 1 to pass freely. The lower joint 23 of the releasing mechanism is threadedly connected to the anchor 5 through a thread. Three or four slips 6 are provided in the middle of the anchor 5, and the lower end is threadedly connected to the anti-rotation treated drill pipe 7.

[0051] Refer to the appendix Figure 2 to further describe the construction process and the main functions of the open-hole sidetracking tool string where the present invention is located.

[0052] The open-hole sidetracking hydraulic unlocking and releasing mechanism of the present invention: includes an upper joint 10, a central tube 11, an upper piston 14, an elastic claw piston 16, a cylinder barrel 17, a spline shaft 18, a sealing joint 20, a rotation prevention key head 21, a threaded gland 22, and a lower joint 23.

[0053] The upper joint 1 is sequentially threadedly connected to the cylinder barrel 17, the sealing joint 20, and the lower joint 23 to form an outer tube string.

[0054] The central tube 11 is placed at the center inside the outer tube string and is connected to the rotation prevention key head 21 through a reverse thread at the lower part. The lower part of the central tube 11 is matched with the sealing joint 20 through a sealing element C19.

[0055] Refer to the appendix Figure 4, the anti-rotation key head 21 and the sealing joint 20 form a spline fit. Four rectangular splines are machined on the anti-rotation key head 21 and inserted into the corresponding spline grooves of the sealing joint 20. This spline fit mainly bears the torque force from the central tube 11 during the forward release.

[0056] The lower part of the central tube 11 is pressed tightly by the threaded gland 22. The threaded gland 22 is connected to the sealing joint 20 by threads and placed in the inner cavity formed by the sealing joint 20 and the lower joint 23. The main function of the threaded gland 22 is to bear the axial tensile force from the central tube 11 and the upper pipe string.

[0057] Refer to the appendix Figure 3 , a spline fit is formed between the central tube 11 and the spline shaft 18, and a spline fit is formed between the cylinder barrel 17 and the spline shaft 18. For convenient installation and positioning, the number of internal and external splines of the spline shaft 18 is usually the same, but the numbers can also be different.

[0058] The lower part of the spline shaft 18 and the cylinder barrel 17 are connected by shear pins 24. There is an annular groove 28 at the lower part of the spline shaft 18. The annular groove 28 cooperates with the pin holes machined on the body of the cylinder barrel 17 to jointly accommodate the shear pins 24. The number of pin holes in the cylinder barrel 17 is usually 8 - 12, but not all pin holes need to be installed with shear pins 24. The installation quantity is determined by calculating the actual required hydraulic pressure.

[0059] The elastic claw piston 16 is placed between the cylinder barrel 17 and the central tube 11, and sealing elements B15 are pressed on the inner and outer sides. The lower inner cavity end face of the elastic claw piston 16 is freely pressed against the upper end face of the spline shaft 18. There is an enlarged inner diameter cavity, the elastic claw release cavity 30, in the middle of the body of the cylinder barrel 17. The lower end of the elastic claw piston 16 is a petal-shaped elastic claw, and the outer diameter of its claw tip is larger than the inner diameter of the cylinder barrel 17 and smaller than the inner diameter of the elastic claw release cavity 30.

[0060] The upper piston 14 is placed between the cylinder barrel 17 and the central tube 11, and sealing O-rings 12 and sealing elements A13 are pressed on the inner and outer sides. The two end faces are limited by the lower end face inside the upper joint 10 and the inner cavity step of the cylinder barrel 17. There is a radial through-hole, the pressure transmission hole 29, in the upper part of the central tube 11. The upper piston 14 and the elastic claw piston 16 form a pressure cavity 27 with the cylinder barrel 17, and it is communicated with the inner hole of the central tube 11 through the pressure transmission hole 29.

[0061] There are a radial through-hole, the spline shaft downward displacement drainage and breathing hole 25, and the elastic claw piston downward displacement drainage and breathing hole 26 in the middle of the body of the cylinder barrel 17.

[0062] Specifically for the construction process of the release device:

[0063] Refer to the appendix Figure 1 At the wellhead, connect the open-hole sidetracking tool string, including connecting the central tube 11 with the running-in string 1, connecting the lower joint 23 with the anchor 5, and connecting the anchor 5 with the anti-rotation treated drill pipe 7.

[0064] Lower the connected open-hole sidetracking tool string into the wellbore through the drill pipe to the designed well depth.

[0065] Build up pressure inside the central tube 11 by pumping drilling fluid through the wellhead.

[0066] The pressure inside the central tube 11 acts on the upper end face of the elastic jaw piston 16 through the pressure transmission hole 29, pushing the elastic jaw piston 16 to squeeze the spline shaft 18 downward. When the designed pressure value is reached, the shear pin 24 is broken.

[0067] At this time, continue to build up pressure. The elastic jaw piston 16 continues to move downward and pushes the spline shaft 18 to move to the upper end face of the seal joint 20. When the elastic jaw piston 16 and the spline shaft 18 move downward, the fluid in the inner cavity of the cylinder barrel 17 is discharged into the wellbore annulus through the downward displacement drainage breathing hole 25 of the spline shaft and the downward displacement drainage breathing hole 26 of the elastic jaw piston.

[0068] After the spline shaft 18 moves downward in place, the spline engagement between the central tube 11 and the spline shaft 18 is disengaged, and the central tube 11 rotates forward until the reverse-threaded connection between the central tube 11 and the anti-rotation key head 21 becomes loose, achieving releasing of the string.

[0069] The releasing process is completed, and the running-in string 1 is pulled out of the wellhead.

[0070] In addition, in the technical solution of the present invention:

[0071] There is a shear plug inside the anchor 5, and the shear pressure of the shear plug is greater than the shearing pressure of the shear pin 24 inside the releasing device 4.

[0072] Continue to increase the pressure inside the central tube 11. The anchor 5 starts to work, horizontally pushes the slip teeth 6 and bites into the formation rock 3 to prevent the deflecting sub 2 from rotating. When the pressure inside the central tube 11 reaches the shear pressure of the shear plug inside the anchor 5, the shear plug opens and the pressure inside the tube is relieved. At this time, the rebound force caused by the instantaneous release of the pressure may cause the spline shaft 18 to rebound upward, resulting in the re-engagement of the central tube 11 and the spline shaft 18 after separation, preventing the central tube 11 from rotating forward and reverse-threading, and causing the releasing to fail. The flap-type elastic jaw at the lower end of the elastic jaw piston 16 can prevent this situation from occurring. The elastic jaw piston 16 moves downward to the position of the elastic jaw release cavity 30, the flap-type elastic jaw opens and is limited within the elastic jaw release cavity 30, and the elastic jaw piston 16 is limited.

[0073] The length of the spline groove of the cylinder barrel 17 is greater than the length of the external spline of the spline shaft 18. When the lower end face of the spline shaft 18 contacts the upper end face of the seal joint 20, there is still a certain length of engagement of this spline.

[0074] The spline engagement length between the central pipe 11 and the spline shaft 18 is relatively short. After the spline shaft 18 moves down to the proper position, the spline fit engaged with the central pipe 11 is completely disengaged. When the central pipe 11 is rotated in a reverse buckling manner, the spline shaft 18 does not affect the rotation of the central pipe 11.

[0075] Refer to the appendix Figure 1 , usually 1-2 drill pipes 7 with anti-rotation treatment are connected to the lower end of the tool string. In order to prevent the whipstock 2 from rotating during the drilling process, it is more appropriate to select the cementing construction process. The drill pipe 7 with anti-rotation treatment is processed from ordinary oil drill pipes. Multiple groups of cement diversion holes 8 are processed on the side wall to provide a flow channel for the cement. The anti-rotation cross bar 9 is fixed to the drill pipe wall by welding or threading. The main purpose is that after the cement solidifies, the anti-rotation cross bar 9 can be more firmly consolidated into the cement sheath to prevent the rotation of the upper pipe string.

[0076] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A hydraulic unlocking and releasing device for side drilling with a naked-eye whipstock, characterized in that, It includes an upper sub (10), a central tube (11), an upper piston (14), an elastic claw piston (16), a cylinder barrel (17), a spline shaft (18), a sealing joint (20), an anti-rotation key head (21), a threaded gland (22), a lower sub (23), and a shear pin (24); The upper sub (10), the cylinder barrel (17), the sealing joint (20), and the lower sub (23) are sequentially connected to form an outer barrel string; The central tube (11) is placed inside the outer barrel string and is threadedly connected to the upper sub (10) and the anti-rotation key head (21) at both ends respectively; The anti-rotation key head (21) is inserted into the sealing joint (20) through splines, and the lower part is pressed tightly by the threaded gland (22); The threaded gland (22) is threadedly connected to the sealing joint (20) and is placed in the inner cavity formed by the sealing joint (20) and the lower sub (23); The upper piston (14), the elastic claw piston (16), and the spline shaft (18) are sleeved on the central tube (11) in sequence from top to bottom; The spline shaft (18) is in spline fit with the cylinder barrel (17) and the central tube (11) respectively, and the lower part of the spline shaft (18) and the cylinder barrel (17) are connected by a shear pin (24); The inner end face of the lower part of the elastic claw piston (16) is freely pressed against the upper end face of the spline shaft (18). An elastic claw release cavity (30) is provided inside the cylinder barrel (17). The outer dimension of the elastic claw at the lower part of the elastic claw piston (16) is larger than the inner diameter of the cylinder barrel (17) and smaller than the inner diameter of the elastic claw release cavity (30); Sealing O-rings (12) and sealing element A (13) are respectively provided on the inner and outer sides of the upper piston (14), and both end faces are limited by the inner end face of the upper sub (10) and the step on the inner cavity of the cylinder barrel (17).

2. The hydraulic unlocking and releasing device for side drilling with a naked-eye whipstock according to claim 1, characterized in that, A pressure transmission hole (29) is provided in the upper part of the central tube (11). The pressure transmission hole (29) is a radial through hole. The upper piston (14) and the elastic claw piston (16) form a pressure cavity (27) with the cylinder barrel (17) and are communicated with the inner hole of the central tube (11) through the pressure transmission hole (29).

3. The hydraulic unlocking and releasing device for side drilling with a naked-eye whipstock according to claim 1, characterized in that, A spline shaft downward displacement liquid drainage and breathing hole (25) and an elastic claw piston downward displacement liquid drainage and breathing hole (26) are provided in the middle of the cylinder barrel (17) body. The spline shaft downward displacement liquid drainage and breathing hole (25) and the elastic claw piston downward displacement liquid drainage and breathing hole (26) are radial through holes.

4. The hydraulic unlocking and releasing device for side drilling with a naked-eye whipstock according to claim 1, characterized in that, External splines are provided on the outer side of the spline shaft (18) for spline fit with the cylinder barrel (17), and internal splines are provided on the inner side of the spline shaft (18) for spline fit with the central tube (11).

5. The hydraulic unlocking and releasing device for side drilling with a naked-eye whipstock according to claim 4, characterized in that, The length of the external splines of the spline shaft (18) is greater than the length of the internal splines. When the shear pin (24) is cut off and the lower end face of the spline shaft (18) fits against the upper end face of the sealing joint (20), the spline shaft (18) and the cylinder barrel (17) are still meshed by splines, and the spline meshing between the spline shaft (18) and the central tube (11) is disengaged.

6. The hydraulic unlocking and releasing device for side drilling with a naked-eye whipstock according to claim 5, characterized in that, There is an annular groove (28) at the lower part of the spline shaft (18). The annular groove (28) cooperates with the pin hole machined on the cylinder barrel (17) body to jointly accommodate the shear pin (24).

7. The hydraulic unlocking and releasing device for side drilling with a naked-eye whipstock according to any one of claims 1-6, characterized in that, Four rectangular splines are machined on the anti-rotation key head (21) and are inserted into the corresponding spline grooves of the sealing joint (20).

8. The hydraulic unlocking and releasing device for side drilling with a naked-eye whipstock according to any one of claims 1-6, characterized in that, The elastic claw piston (16) presses the sealing element B (15) on the inner and outer sides.

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