A self-falling, drill-free, staged cementing device

Abstract

The utility model relates to oil and gas well cementing tool technical field especially, relates to a kind of self-shedding drill-free staged cementing device, to solve the technical problem of the damage risk of cement sheath and closing sleeve in related art due to the dependence on drilling operation to restore the inside diameter of pipe, and further destroy the integrity of wellbore and shorten the service life.The self-shedding drill-free staged cementing device comprises: connecting pipe, gravity plug, closing plug and sliding sleeve assembly.The self-shedding drill-free staged cementing device sets the inner core barrel and the outer pipe body as a split structure connected by pin, and by putting closing plug to pressure after two-stage circulation cementing is completed, the inside diameter of pipe is restored by triggering sliding sleeve assembly to block circulation passage and inner core barrel shear pin in turn and then falling into well, and further restore the inside diameter of pipe.The self-shedding drill-free staged cementing device overcomes the technical problem that the inside diameter of pipe is restored by drilling operation in the existing staged cementing device, which causes the damage risk of cement sheath and closing sleeve, and further destroys the integrity of wellbore and shortens the service life.

Description

Technical Field

[0001] This utility model relates to the field of oil and gas well cementing tools, and in particular to a self-detaching, drill-free, staged cementing device. Background Technology

[0002] In oil and gas exploration cementing operations, staged cementing units are typically used to achieve a seal between the tubing string and the wellbore. However, after cementing, traditional staged cementing units often rely on drilling operations to restore the tubing diameter. The vibrations caused by drilling operations pose a risk of damaging the integrity of the cement sheath. Furthermore, the direct action of the drill string on the shut-off sleeve during drilling can easily damage or deform the shut-off sleeve, thereby compromising the tool's sealing performance, leading to annular pressure issues, severely affecting wellbore integrity, and significantly shortening its service life.

[0003] Existing staged cementing devices have technical problems: relying on drilling operations to restore the pipe diameter poses a risk of damage to the cement sheath and shut-off sleeve, thereby compromising wellbore integrity and shortening service life. Utility Model Content

[0004] The purpose of this invention is to provide a self-detaching, drill-free, staged cement injector to solve the technical problem in related technologies where relying on drilling operations to restore the pipe diameter poses a risk of damage to the cement sheath and shut-off sleeve, thereby compromising the integrity of the wellbore and shortening its service life.

[0005] To solve the above-mentioned technical problems, the technical solution provided by this utility model is as follows:

[0006] The self-detaching, drill-free, graded cement injector provided by this utility model includes:

[0007] The system comprises a connecting pipe, a gravity plug, a closing plug, and a sliding sleeve assembly. The connecting pipe has a circulation channel, and the sliding sleeve assembly is fitted onto the connecting pipe and seals the circulation channel. The connecting pipe includes an outer pipe body, an inner core cylinder, and a first shear pin. The inner core cylinder is connected to the outer pipe body via the first shear pin. The gravity plug, seated on the inner core cylinder, drives the sliding sleeve assembly to open the circulation channel. The closing plug, seated on the inner core cylinder, drives the sliding sleeve assembly to seal the circulation channel and, by applying pressure, shears off the first shear pin, causing the inner core cylinder to detach from the outer pipe body and fall into the well.

[0008] Specifically, the sliding sleeve assembly includes an external piston cylinder unit, which includes a switch sleeve fitted onto the outer tube. The switch sleeve has a first through hole, and the sliding of the switch sleeve along the outer tube is used to switch between misalignment and alignment between the first through hole and the circulation channel, thereby controlling the opening and closing of the circulation channel.

[0009] Specifically, the external piston cylinder unit further includes an upper centralizing ring fixedly installed on the outer tube body, and the switch sleeve inserted into the upper centralizing ring. A liquid cavity is formed between the upper centralizing ring, the switch sleeve, and the outer tube body. In the initial state, the first perforation and the circulation channel are misaligned, with the first perforation located on the side of the circulation channel closer to the upper centralizing ring. The outer tube body also has a liquid inlet hole located on the side of the inner core cylinder closer to the ground and communicating with the liquid cavity. When the gravity plug is seated on the inner core cylinder, the pumped fluid flows through the liquid inlet hole into the liquid cavity, which pushes the switch sleeve to slide along the outer tube body away from the upper centralizing ring, thereby causing the first perforation and the circulation channel to switch from misalignment to alignment, thus opening the circulation channel.

[0010] Specifically, the sliding sleeve assembly further includes a guide and limiting unit, which includes a lower stabilizing ring fixedly installed on the outer tube body at the end away from the upper stabilizing ring. When the closing plug is seated on the inner core cylinder and separates the circulation channel from the ground end, the pumped fluid flows to the liquid chamber to push the switch sleeve to continue sliding along the outer tube body away from the upper stabilizing ring, thereby causing the first perforation and the circulation channel to switch from alignment to misalignment, thus blocking the circulation channel.

[0011] Specifically, the guide limiting unit further includes a shearing ring and a second shear pin. The shearing ring is sleeved on the outer tube and located between the switch sleeve and the lower centralizing ring. The second shear pin is inserted into both the shearing ring and the outer tube. When the switch sleeve slides and abuts against the shearing ring, the first perforation is completely aligned with the circulation channel. The shearing strength of the second shear pin is lower than that of the first shear pin. When the switch sleeve drives the shearing ring to cut the second shear pin and pushes the shearing ring against the lower centralizing ring, the first perforation is misaligned with the circulation channel.

[0012] Specifically, the external piston cylinder unit further includes a third shear pin, which is simultaneously inserted into the switch sleeve and the outer tube. The shear strength of the third shear pin is lower than that of the first shear pin.

[0013] Specifically, the inner core cylinder is provided with a first plug seat and a second plug seat, the diameter of the second plug seat being larger than the diameter of the first plug seat. Along the surface end towards the downhole direction, the second plug seat, the circulation channel, and the first plug seat are arranged sequentially. The gravity plug and the first plug seat's setting seal are used to block the bottom opening of the inner core cylinder, thereby causing the pumped fluid to be pressurized in the liquid chamber. When the pressure in the liquid chamber reaches the set threshold of the third shear pin, the third shear pin is sheared, causing the switch sleeve to slide towards the lower centralizing ring. The closing plug and the second plug seat's setting seal are used to separate the surface end from the circulation channel, thereby causing the pumped fluid to be pressurized in the liquid chamber. When the pressure in the liquid chamber reaches the set threshold of the second shear pin, the second shear pin is sheared, causing the switch sleeve to continue sliding towards the lower centralizing ring.

[0014] Specifically, the initial insertion depth of the upper centralizing ring and the switching sleeve is greater than the maximum stroke of the switching sleeve, and the fluid chamber remains isolated from the wellbore annulus. When the switching sleeve, the shearing ring, and the lower centralizing ring abut in sequence, i.e., when the switching sleeve reaches its maximum stroke, the pumped fluid is pressurized on the side of the closing plug near the ground. When the fluid pressure reaches the set threshold of the first shear pin, the first shear pin is sheared, the inner core cylinder is released from the outer tube, and the inner core cylinder, the gravity plug, and the closing plug detach from the outer tube and fall to the bottom of the well under the action of pressure and gravity.

[0015] Specifically, the guiding and limiting unit includes a guide block, and the switch sleeve has a guide groove parallel to the axis of the outer tube. One end of the guide block is embedded in the outer wall of the outer tube, and the other end is slidably connected to the guide groove, which is used to limit the rotation of the switch sleeve around the outer tube.

[0016] Specifically, multiple first perforations and the same number of circulation channels are evenly distributed around the axis of the outer tube.

[0017] Based on the above technical solutions, the beneficial effects of this utility model are analyzed as follows:

[0018] This utility model provides a self-detaching, drill-free, graded cement injector, comprising:

[0019] The system comprises a connecting pipe, a gravity plug, a closing plug, and a sliding sleeve assembly. The connecting pipe has a circulation channel, and the sliding sleeve assembly is fitted onto the connecting pipe and seals the circulation channel. The connecting pipe includes an outer pipe body, an inner core cylinder, and a first shear pin. The inner core cylinder is connected to the outer pipe body via the first shear pin. The gravity plug is seated on the inner core cylinder to drive the sliding sleeve assembly to open the circulation channel. The closing plug is seated on the inner core cylinder to seal the circulation channel and, by applying pressure, shears off the first shear pin, causing the inner core cylinder to detach from the outer pipe body and fall into the well.

[0020] In practical application, the connecting pipe is installed on the casing string and lowered into the well along with it. At this time, the sliding sleeve assembly keeps the circulation channel of the connecting pipe blocked. After the connecting pipe reaches the set cementing position, the first-stage cementing operation begins. After the first-stage cementing operation is completed, the gravity plug is inserted and seated on the inner core cylinder, thereby driving the sliding sleeve assembly to open the circulation channel through pressure buildup. The drilling fluid pumped in from the surface flows into the wellbore annulus through the circulation channel, establishing a second-stage circulation, and the second-stage cementing operation begins. After cementing is completed, the closing plug is inserted and seated on the inner core cylinder, blocking the circulation channel, thereby creating pressure buildup again to drive the sliding sleeve assembly to block the circulation channel, and the second-stage cementing operation ends. At this time, the pressure buildup is used to shear off the first shear pin between the outer casing and the inner core cylinder, thereby causing the inner core cylinder to detach from the well and the outer casing to return to full borehole.

[0021] As can be seen, compared with existing technologies, this self-detaching, drill-free staged cementing device sets the inner core and outer tube as a separate structure connected by pins. After the two-stage circulation cementing is completed, the closing plug is inserted to pressurize the well, thereby sequentially triggering the sliding sleeve assembly to seal the circulation channel and the inner core to shear the pin and detach, thus restoring the inner tube diameter. This overcomes the technical problem of existing staged cementing devices that rely on drilling operations to restore the inner tube diameter, which poses a risk of damage to the cement sheath and closing sleeve, thereby compromising wellbore integrity and shortening service life. Attached Figure Description

[0022] To more clearly illustrate the specific embodiments of this utility model or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this utility model. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0023] Figure 1 A schematic diagram of the initial state of the self-detaching, drill-free, graded cement injector provided in this embodiment of the utility model;

[0024] Figure 2 This is a schematic diagram of the structure when the gravity plug is deployed;

[0025] Figure 3 This is a schematic diagram of the structure when the circulation channel is open;

[0026] Figure 4 This is a schematic diagram of the structure when the shut-off plug is engaged;

[0027] Figure 5 This is a schematic diagram of the structure when the circulation channel is blocked;

[0028] Figure 6 This is a schematic diagram of the structure where the inner core tube has detached.

[0029] icon:

[0030] 100. Connecting pipe; 101. Circulation channel; 110. Outer tube body; 102. Liquid inlet; 1011. Second perforation; 120. Inner core cylinder; 103. First plug seat; 104. Second plug seat; 1012. Third perforation; 130. First shear pin;

[0031] 200. Gravity plug;

[0032] 300. Close the plug;

[0033] 400. Sliding sleeve assembly; 410. External piston cylinder unit; 411. Switch sleeve; 401. First through hole; 402. Guide groove; 412. Upper straightening ring; 413. Third shear pin; 420. Guide limiting unit; 421. Lower straightening ring; 422. Shear ring; 423. Second shear pin; 424. Guide block. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, and not all embodiments. The components of the embodiments of this utility model described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0035] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0036] The following detailed description, in conjunction with the accompanying drawings, outlines some embodiments of the present invention. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0037] Existing staged cementing devices have technical problems: relying on drilling operations to restore the pipe diameter poses a risk of damage to the cement sheath and shut-off sleeve, thereby compromising wellbore integrity and shortening service life.

[0038] In view of this, the present invention provides a self-detaching, drill-free, graded cement injector, comprising:

[0039] The system comprises a connecting pipe 100, a gravity plug 200, a closing plug 300, and a sliding sleeve assembly 400. The connecting pipe 100 has a circulation channel 101, and the sliding sleeve assembly 400 is fitted onto the connecting pipe 100 and blocks the circulation channel 101. The connecting pipe 100 includes an outer pipe body 110, an inner core cylinder 120, and a first shear pin 130. The inner core cylinder 120 is pinned to the outer pipe body 110 via the first shear pin 130. The gravity plug 200 is seated on the inner core cylinder 120 to drive the sliding sleeve assembly 400 to open the circulation channel 101. The closing plug 300 is seated on the inner core cylinder 120 to drive the sliding sleeve assembly 400 to block the circulation channel 101, and by applying pressure, shears the first shear pin 130, causing the inner core cylinder 120 to detach from the outer pipe body 110 and fall into the well.

[0040] In summary, the self-detaching, drill-free, staged cement injector provided by this utility model can achieve the following technical effects:

[0041] This self-detaching, drill-free staged cementing tool features a split structure where the inner core cylinder 120 and outer tube 110 are connected by pins. After the secondary circulation cementing is completed, the shut-off plug 300 is inserted to create pressure, which sequentially triggers the sliding sleeve assembly 400 to block the circulation channel 101 and the inner core cylinder 120 to shear off the pins and detach from the well, thus restoring the inner diameter of the tube. This overcomes the technical problem of existing staged cementing tools that rely on drilling operations to restore the inner diameter, which poses a risk of damage to the cement sheath and shut-off sleeve, thereby compromising wellbore integrity and shortening service life.

[0042] The following combination Figures 1 to 6 The structure and shape of the self-detaching, drill-free, graded cement injector provided in this embodiment are described in detail below:

[0043] Specifically, regarding how the sliding sleeve assembly 400 achieves the blocking and opening of the circulation channel 101:

[0044] The sliding sleeve assembly 400 includes an external piston cylinder unit 410, which includes a switch sleeve 411 fitted onto the outer tube body 110. The switch sleeve 411 has a first through hole 401. The sliding of the switch sleeve 411 along the outer tube body 110 is used to switch between misalignment and alignment between the first through hole 401 and the circulation channel 101, thereby controlling the opening and closing of the circulation channel 101.

[0045] Regarding how the gravity plug 200 drives the switch sleeve 411 to slide along the outer tube 110 and open the circulation channel 101, specifically:

[0046] The external piston cylinder unit 410 also includes an upper centralizing ring 412 fixedly installed on the outer tube 110, and a switch sleeve 411 inserted into the upper centralizing ring 412. A liquid cavity is formed between the upper centralizing ring 412, the switch sleeve 411, and the outer tube 110. In the initial state, the first perforation 401 and the circulation channel 101 are misaligned, with the first perforation 401 located on the side of the circulation channel 101 closer to the upper centralizing ring 412. The outer tube 110 also has a liquid inlet hole 102, located on the side of the inner core cylinder 120 closer to the ground and communicating with the liquid cavity. When the gravity plug 200 is seated on the inner core cylinder 120, the pumped fluid flows into the liquid cavity through the liquid inlet hole 102 to push the switch sleeve 411 to slide away from the upper centralizing ring 412 along the outer tube 110, thereby causing the first perforation 401 and the circulation channel 101 to switch from misalignment to alignment, thus opening the circulation channel 101.

[0047] Regarding how the closing plug 300 drives the switch sleeve 411 to slide along the outer tube body 110 and block the circulation channel 101, specifically:

[0048] The sliding sleeve assembly 400 also includes a guide limiting unit 420, which includes a lower stabilizing ring 421. The lower stabilizing ring 421 is fixedly installed on the outer tube 110 at the end away from the upper stabilizing ring 412. When the closing plug 300 is seated on the inner core cylinder 120 and separates the circulation channel 101 from the ground end, the pumped fluid flows to the liquid chamber to push the switch sleeve 411 to continue sliding along the outer tube 110 away from the upper stabilizing ring 412, thereby causing the first perforation 401 and the circulation channel 101 to switch from alignment to misalignment, thereby blocking the circulation channel 101.

[0049] To improve the alignment accuracy between the first perforation 401 and the circulation channel 101, thereby maximizing the effective diameter of the circulation channel 101, in this embodiment, the guide limiting unit 420 further includes a shearing ring 422 and a second shear pin 423. The shearing ring 422 is sleeved on the outer tube 110 and located between the switch sleeve 411 and the lower straightening ring 421. The second shear pin 423 is simultaneously inserted into both the shearing ring 422 and the outer tube 110. When the switch sleeve 411 slides and abuts against the shearing ring 422, the first perforation 401 and the circulation channel 101 are completely aligned. To prevent the first perforation 401 from not being completely misaligned with the circulation channel 101 when the switch sleeve 411 reaches its maximum stroke, thus preventing the circulation channel 101 from closing properly, when the switch sleeve 411 drives the shearing ring 422 to cut the second shear pin 423 and pushes the shearing ring 422 against the lower straightening ring 421, the first perforation 401 and the circulation channel 101 are in a misaligned state. The shear strength of the second shear pin 423 is lower than that of the first shear pin 130, ensuring that when the closing plug 300 is engaged for pressurization, the second shear pin 423 is cut off before the first shear pin 130.

[0050] To prevent the switch sleeve 411 from being prematurely triggered by slight pressure fluctuations downhole, in this embodiment, the external piston cylinder unit 410 further includes a third shear pin 413, which is simultaneously inserted into the switch sleeve 411 and the outer tube 110. The third shear pin 413 will only be sheared when the fluid chamber pressure reaches a set threshold, thereby triggering the sliding action of the switch sleeve 411. The shear strength of the third shear pin 413 is lower than that of the first shear pin 130, ensuring that when the gravity plug 200 is deployed for pressurization, the third shear pin 413 is sheared before the first shear pin 130.

[0051] Regarding the structure of the inner core cylinder 120, specifically:

[0052] The inner core cylinder 120 is provided with a first plug seat 103 and a second plug seat 104, the diameter of the second plug seat 104 being larger than the diameter of the first plug seat 103. The second plug seat 104, the circulation channel 101, and the first plug seat 103 are arranged sequentially from the surface end towards the downhole. The gravity plug 200 and the first plug seat 103 are used to seal the bottom opening of the inner core cylinder 120, thereby causing the pumped fluid to be pressurized in the liquid chamber. When the pressure in the liquid chamber reaches the set threshold of the third shear pin 413, the third shear pin 413 is sheared, causing the switch sleeve 411 to slide downward towards the centralizing ring 421. The closing plug 300 and the second plug seat 104 are used to separate the surface end from the circulation channel 101, thereby causing the pumped fluid to be pressurized in the liquid chamber. When the pressure in the liquid chamber reaches the set threshold of the second shear pin 423, the second shear pin 423 is sheared, causing the switch sleeve 411 to continue sliding downward towards the centralizing ring 421.

[0053] Specifically, regarding how the inner core cylinder 120 cuts off the first shear pin 130 and separates from the outer tube 110:

[0054] The initial insertion depth of the upper centralizing ring 412 and the switch sleeve 411 is greater than the maximum stroke of the switch sleeve 411, and the fluid chamber remains isolated from the wellbore annulus. When the switch sleeve 411, shear ring 422, and lower centralizing ring 421 abut in sequence, that is, when the switch sleeve 411 reaches its maximum stroke, the pumped fluid is pressurized on the side of the shut-off plug 300 near the ground. When the fluid pressure reaches the set threshold of the first shear pin 130, the first shear pin 130 is sheared, the inner core cylinder 120 is released from the outer tube 110, and the inner core cylinder 120, gravity plug 200, and shut-off plug 300 detach from the outer tube 110 and fall to the bottom of the well under the action of pressure and gravity. The internal diameter of the outer tube 110 is quickly restored by the spontaneous detachment and entry of the inner core cylinder 120 into the well, saving the cost and time of drilling and removing related components, while avoiding the risk of damaging the wellbore integrity and shortening its service life.

[0055] To limit the rotation of the switch sleeve 411 around the outer tube 110, thereby ensuring that each first perforation 401 is always aligned with the corresponding circulation channel 101 along the axial direction of the outer tube 110, in this embodiment, the guide limiting unit 420 includes a guide block 424, and the switch sleeve 411 has a guide groove 402 parallel to the axis of the outer tube 110. One end of the guide block 424 is embedded in the outer wall of the outer tube 110, and the other end is slidably connected to the guide groove 402, which is used to limit the rotation of the switch sleeve 411 around the outer tube 110, thereby ensuring that when the switch sleeve 411 slides and abuts against the shear ring 422, each first perforation 401 can be aligned with a circulation channel 101, and no misalignment due to the rotation angle will occur.

[0056] In order to improve the fluid throughput efficiency of the secondary circulation, in this embodiment, multiple first perforations 401 and the same number of circulation channels 101 are evenly distributed around the axis of the outer tube 110.

[0057] In this embodiment, the outer tube 110 has a second through hole 1011, and the inner core tube 120 has a third through hole 1012. When the inner core tube 120 and the outer tube 110 are locked by the first shear pin 130, the second through hole 1011 and the third through hole 1012 are completely aligned and form a circulation channel 101.

[0058] In summary, the specific working process of the self-detaching, drill-free, graded cement injector provided in this embodiment is as follows:

[0059] The connecting pipe 100 is installed on the casing string and lowered into the well along with it. At this time, the switch sleeve 411 keeps the circulation channel 101 blocked. After the connecting pipe 100 reaches the set cementing position, the first-stage cementing operation begins. After the first-stage cementing operation is completed, the gravity plug 200 is inserted and set in the first plug seat 103. The drilling fluid pumped into the surface forms a pressure build-up in the fluid chamber. When the pressure in the fluid chamber reaches the set threshold of the second shear pin 423, the switch sleeve 411 is pushed to shear the second shear pin 423 and slides downward toward the shearing ring 421. When the switch sleeve 411 abuts against the shear ring 422, the first perforation 401 aligns with the circulation channel 101, and the circulation channel 101 is opened, establishing the second-stage circulation. After cementing is completed, the closing plug 300 is inserted and set in the second plug seat 104, blocking the circulation channel 101, thereby forming a pressure build-up in the fluid chamber again. When the pressure in the hydraulic chamber reaches the set threshold of the third shear pin 413, the switch sleeve 411 and shear ring 422 are pushed to cut the third shear pin 413 and slide towards the lower centralizing ring 421. When the switch sleeve 411, shear ring 422 and lower centralizing ring 421 abut in sequence, the first perforation 401 is misaligned with the circulation channel 101, the circulation channel 101 is blocked, and the secondary cementing operation ends. At this time, the shut-off plug 300 starts to pressurize again on the side near the ground. When the pressure reaches the set threshold of the first shear pin 130, the inner core cylinder 120 cuts the first shear pin 130 and falls to the bottom of the well together with the gravity plug 200 and the shut-off plug 300, and the outer tube 110 returns to full diameter.

[0060] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this utility model, and are not intended to limit it. Although the utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this utility model.

Claims

1. A self-detaching, drill-free, graded cement injector, characterized in that, include: Connecting pipe, gravity plug, closing plug and sliding sleeve assembly; The connecting pipe has a circulation channel, and the sliding sleeve assembly is fitted onto the connecting pipe and blocks the circulation channel. The connecting pipe includes an outer pipe body, an inner core cylinder, and a first shear pin. The inner core cylinder is connected to the outer pipe body through the first shear pin pin. A gravity plug is seated on the inner core cylinder to drive the sliding sleeve assembly to open the circulation channel. A closing plug is seated on the inner core cylinder to drive the sliding sleeve assembly to block the circulation channel, and the inner core cylinder is disengaged from the outer pipe body and falls into the well by shearing the first shear pin through pressure.

2. The self-detaching, drill-free, graded cement injector according to claim 1, characterized in that: The sliding sleeve assembly includes an external piston cylinder unit, which includes a switch sleeve fitted onto the outer tube body; The switch sleeve has a first through hole. The sliding of the switch sleeve along the outer tube body is used to switch between the first through hole and the circulation channel between misalignment and alignment, thereby controlling the opening and closing of the circulation channel.

3. The self-detaching, drill-free, graded cement injector according to claim 2, characterized in that: The external piston cylinder unit also includes an upper centralizing ring fixedly installed on the outer tube body, and a switch sleeve inserted into the upper centralizing ring; A liquid cavity is formed between the upper stabilizing ring, the switch sleeve, and the outer tube; In the initial state, the first perforation and the circulation channel are misaligned, with the first perforation located on the side of the circulation channel closer to the upper straightening ring; The outer tube is also provided with a liquid inlet, which is located on the side of the inner core cylinder near the ground and is connected to the liquid cavity; When the gravity plug is seated in the inner core cylinder, the pump-pressurized fluid flows into the liquid chamber through the inlet hole, which pushes the switch sleeve to slide away from the upper aligning ring along the outer tube, thereby causing the first perforation and the circulation channel to switch from misalignment to alignment, thus opening the circulation channel.

4. The self-detaching, drill-free, graded cement injector according to claim 3, characterized in that: The sliding sleeve assembly also includes a guide and limiting unit, which includes a lower stabilizing ring, which is fixedly installed on the outer tube body at the end away from the upper stabilizing ring; When the stopper is sealed in the inner core and the circulation channel is separated from the ground end, the pumped fluid flows into the liquid chamber to push the switch sleeve to continue sliding along the outer tube away from the upper aligning ring, thereby causing the first perforation and the circulation channel to switch from alignment to misalignment, and thus block the circulation channel.

5. The self-detaching, drill-free, graded cement injector according to claim 4, characterized in that: The guide limiting unit also includes a shearing ring and a second shearing pin. The shearing ring is sleeved on the outer tube and located between the switch sleeve and the lower straightening ring. The second shearing pin is inserted into both the shearing ring and the outer tube. When the switch sleeve slides and abuts against the shear ring, the first perforation is perfectly aligned with the circulation channel; The shear strength of the second shear pin is lower than that of the first shear pin; When the switch sleeve drives the shearing ring to cut the second shear pin and pushes the shearing ring against the lower straightening ring, the first perforation and the circulation channel are misaligned.

6. The self-detaching, drill-free, graded cement injector according to claim 5, characterized in that: The external piston cylinder unit also includes a third shear pin, which is simultaneously inserted into the switch sleeve and the outer tube body; The shear strength of the third shear pin is lower than that of the first shear pin.

7. The self-detaching, drill-free, graded cement injector according to claim 6, characterized in that: The inner core cylinder is provided with a first plug seat and a second plug seat, the diameter of the second plug seat being larger than the diameter of the first plug seat; Along the surface end toward the well, the second plug seat, the circulation channel, and the first plug seat are arranged in sequence; The gravity plug and the first plug seat are used to seal the bottom opening of the inner core cylinder, so that the pumped fluid is pressurized in the liquid chamber. When the pressure in the liquid chamber reaches the set threshold of the third shear pin, the third shear pin is sheared, so that the switch sleeve slides downward towards the straightening ring. The setting seal of the closing plug and the second plug seat is used to isolate the ground end from the circulation channel, thereby causing the pumped fluid to be pressurized in the liquid chamber. When the pressure in the liquid chamber reaches the set threshold of the second shear pin, the second shear pin is sheared, thereby causing the switch sleeve to continue sliding downward towards the straightening ring.

8. The self-detaching, drill-free, graded cement injector according to claim 5, characterized in that: The initial insertion depth of the upper centralizing ring and the switch sleeve is greater than the maximum stroke of the switch sleeve, and the fluid chamber and the wellbore annulus are always kept isolated. When the switch sleeve, shear ring and lower centralizing ring abut in sequence, that is, when the switch sleeve reaches its maximum stroke, the pumped fluid is pressurized on the side of the shut-off plug near the ground. When the fluid pressure reaches the set threshold of the first shear pin, the first shear pin is sheared, the inner core cylinder is released from the outer tube, and the inner core cylinder, gravity plug and closing plug detach from the outer tube and fall to the bottom of the well under the action of pressure and gravity.

9. The self-detaching, drill-free, graded cement injector according to claim 4, characterized in that: The guide limiting unit includes a guide block, and the switch sleeve has a guide groove parallel to the axis of the outer tube body; One end of the guide block is embedded in the outer wall of the outer tube, and the other end is slidably connected to the guide groove to limit the rotation of the switch sleeve around the outer tube.

10. The self-detaching, drill-free, graded cement injector according to claim 1, characterized in that: Multiple first perforations and the same number of circulation channels are evenly distributed around the axis of the outer tube.

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