Invisible packer and setting method thereof

Abstract

The present invention provides an invisible packer and a setting method thereof. The packer comprises a central tube and a stopper, and a setting push tube, a sealing protective sleeve, a sealing element and an anti-burst sand isolation tube which are sequentially sleeved on the outer wall of the central tube from top to bottom. The setting method is implemented by using the above-mentioned invisible packer. The present invention can protect the integrity of the sealing element before setting, prevent the packer from being accidentally set, and set normally when setting is required, and the setting is controllable.

Description

Technical Field

[0001] The present invention relates to the field of downhole operation tool technology and equipment for oil and gas field drilling engineering, and in particular to an invisible packer and a setting method thereof, which are used for well cementing, well completion or production enhancement and transformation operations in oil and gas fields. Background Art

[0002] As an important tool for construction, oil and gas well packers are used to achieve permanent mechanical isolation of the annulus during cementing construction to prevent oil, gas, water and other channels from entering the well and improve cementing quality; during completion or production enhancement, they are used to achieve isolation between pipe strings, between pipe strings and open holes, or between layers to ensure the pertinence of production enhancement or ensure that oil and gas are produced from the desired channel. Therefore, reliable isolation of the packer is extremely critical.

[0003] At present, the sealing elements of all oil and gas well packers are directly installed on the center tube of the packer, and their outer cylindrical surfaces are exposed. During the lowering process, the packer may get stuck with the upper casing wall or the well wall, and the sealing element may be scratched or expand prematurely. In addition, during the circulation displacement or well washing process, the bottom sand, the well wall mud cake and plugging materials are brought to the packer position together with the drilling fluid (completion fluid), and bridge blockage may also occur. More serious bridge blockage will cause the packer sealing component to expand prematurely. The above two situations are the problems currently faced by the packer, and the resulting downhole accidents or failures will cause construction work time and economic losses.

[0004] The Chinese patent with the publication number CN114439409A discloses a packer, which includes a cylindrical main body and a packer assembly sleeved on the outer wall of the main body, wherein the packer assembly has an elastic packer and an actuating device located radially inside the elastic packer, the actuating device can disperse the force on the elastic packer to make the elastic packer deform decomposedly and adaptively pack. During use, the packer has the characteristic of being able to adapt to the expansion according to the irregular open hole wellbore to solve the problem of loose sealing of the open hole packer. However, the elastic packer of the packer is exposed to the outside, and during the lowering process, it may get stuck with the upper casing wall or the well wall, and the sealing element may be scratched.

[0005] Therefore, in view of the shortcomings of the existing packers, it is necessary to study and design an improved packer to solve the above technical problems or alleviate the impact of the above technical problems. Summary of the invention

[0006] In view of the deficiencies in the prior art, the present invention aims to solve one or more problems in the prior art. For example, one of the purposes of the present invention is to protect the integrity of the sealing element before setting to prevent the packer from accidentally setting; the second purpose is to set the packer normally when setting is required, and the setting is controllable.

[0007] In order to achieve the above objectives, the present invention provides an invisible packer on one hand.

[0008] The packer may include a center tube and a limiter, as well as a setting push tube, a sealing protective sleeve, a sealing element and an anti-burst sand isolation tube which are sequentially sleeved on the outer wall of the center tube from top to bottom. Among them, a plurality of circumferentially distributed steps may be provided at the connection between the outer wall of the center tube and the sealing protective sleeve; the lower end of the setting push tube is circumferentially cut into a plurality of equal parts to form a plurality of corresponding axial grooves, which correspond to the steps one by one, so that the lower end of the setting push tube and the step are staggered, and the setting push tube can be inserted into the step gap and slide downward relative to the step; the upper end of the sealing protective sleeve can be fixed outside the step, and a first annular cavity is formed between the lower end and the outer wall of the center tube; the sealing element can be arranged in the first annular cavity, and the lower end is connected to the upper end of the anti-burst sand isolation tube, and the limiter can limit the downward travel of the anti-burst sand isolation tube.

[0009] Furthermore, the packer may also include a back-stop mechanism fixedly connected to the upper end of the sealing push tube, and the back-stop mechanism may be provided with internal back-stop teeth; the outer wall of the center tube may be provided with external back-stop teeth, and the internal back-stop teeth of the back-stop mechanism cooperate with the external back-stop teeth on the center tube to have a back-stop effect.

[0010] Furthermore, the upper end of the setting push cylinder and the anti-retraction mechanism can be fixedly connected by screws and / or threads.

[0011] Furthermore, the length of the axial groove is greater than the total stroke of the downward distance of the sealing element and the downward distance of the sealing element during the process of being compressed and fully expanded.

[0012] Furthermore, the packer may also include an anti-outburst fence, which may be installed in the first annular cavity of the sealing protection sleeve and disposed closely against the upper end surface of the sealing element.

[0013] Furthermore, the upper end of the anti-outburst fence may be a cylinder, the lower end may be an inclined surface, a deep groove is opened in the middle, and the lower end inclined surface and the middle deep groove are evenly cut into several parts in the circumferential direction.

[0014] Furthermore, the shape structure of the upper end portion of the anti-outburst sand isolation tube is mirror-symmetrical to the shape structure of the anti-outburst fence, and the lower end portion thereof may be a cylinder and connected to the upper end of the limiting member.

[0015] Furthermore, the outer diameter of the lower end cylinder of the anti-burst sand isolation tube is the same as the outer diameter of the sealing protection sleeve, and its inner diameter is loosely matched with the outer diameter of the upper end of the limiting member; a second annular cavity is formed between the inner wall of the lower end cylinder of the anti-burst sand isolation tube, the outer wall of the central tube and the upper end of the limiting member.

[0016] Furthermore, a plurality of radial screw holes distributed axially may be provided on the wall of the mating portion of the anti-burst sand isolation tube and the limiting member for installing limiting nails.

[0017] Furthermore, the outer walls of the upper and lower ends of the sealing element can be set to a certain curvature to match the inclined surfaces of the anti-outburst fence and the anti-outburst sand isolation tube, and the upper end outer wall is close to the inner side of the inclined surface of the anti-outburst fence, and the lower end outer wall is close to the inner side of the inclined surface of the anti-outburst sand isolation tube.

[0018] Furthermore, the sealing protective sleeve may be fixed to the step in a connection manner of a slot or a threaded connection.

[0019] Furthermore, the upper end of the limiting member may be provided with an internal thread, which is fixedly connected to a corresponding external thread provided on the central tube.

[0020] In order to achieve the above object, the present invention provides a method for setting a stealth packer on the other hand.

[0021] The sealing method can be implemented by using the invisible packer as described above.

[0022] Compared with the prior art, the beneficial effects of the present invention may include at least one of the following:

[0023] (1) The present invention uses a sealing protective sleeve to completely protect the sealing element of the packer, thereby preventing it from being scratched or prematurely set due to external reasons during the lowering or circulation process. When setting is required, the sealing element is pushed out of the sealing protective sleeve to implement the setting. The design is simple in structure and ingenious in design, making the lowering process of the packer safer and the sealing more reliable.

[0024] (2) The present invention adopts a multi-petal anti-blowout fence and an anti-blowout sand isolation tube that are easy to deform and have strong bearing capacity to support and protect the sealing element, which is compressed and expanded under the push of the sealing force to complete the sealing of the packer. This design can ensure the integrity of the sealing element during operation and construction, and the sealing action is safe and controllable, making the sealing more reliable.

[0025] (3) The present invention can protect the integrity of the sealing element before setting and prevent the packer from being accidentally set, and can also set the packer normally when it is needed, and the setting is controllable, thereby ensuring the integrity and effectiveness of the packer during operation.

[0026] (4) The present invention can effectively solve the technical problem that the sealing elements of the existing packers may be accidentally scratched or expanded prematurely during construction. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solution of the present invention, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0028] Figure 1 A structural schematic diagram of the invisible packer of the present invention is shown;

[0029] Figure 2 A schematic structural diagram of the anti-outburst fence of the present invention is shown;

[0030] Figure 3 Another schematic structural diagram of the anti-outburst fence of the present invention is shown;

[0031] Figure 4 The present invention shows Figure 3 A magnified schematic diagram of the local M in the middle;

[0032] Figure 5 A structural schematic diagram of the anti-burst sand isolation tube of the present invention is shown;

[0033] Figure 6 The present invention shows Figure 5 BB cross-sectional view;

[0034] Figure 7 A schematic structural diagram of the setting push cylinder of the present invention is shown;

[0035] Figure 8 The present invention shows Figure 7 CC section view;

[0036] Fig. 9 A structural schematic diagram of the sealing protective sleeve of the present invention is shown;

[0037] Fig.10 The present invention shows Fig. 9 DD cross-sectional view.

[0038] Description of main reference numerals:

[0039] 1-center tube, 101-step; 2-retraction mechanism; 3-setting seal push cylinder, 301-axial slot; 4-sealing protection sleeve, 401-first annular cavity; 5-anti-burst fence, 501-cylinder, 502-inclined surface, 503-deep groove; 6-sealing element; 7-anti-burst sand isolation tube, 701-cylinder, 702-second annular cavity; 8-limiting member. DETAILED DESCRIPTION

[0040] The following is a clear and complete description of the technical solutions of the embodiments of the present invention in conjunction with the accompanying drawings of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work belong to the protection scope of the present invention. The contents not described in detail in the embodiments of the present invention belong to the prior art known to professional and technical personnel in this field.

[0041] It should be noted that “first”, “second”, “third”, etc. are only for the convenience of description and distinction, and should not be understood as indicating or implying relative importance. “upper”, “lower”, “front”, “back”, “left”, “right”, “inner”, “outer”, etc. are only for the convenience of description and to constitute a relative orientation or position relationship, and should not indicate or imply that the referred component must have such a specific orientation or position.

[0042] Exemplary Embodiment 1

[0043] This exemplary embodiment provides an invisible packer. Figures 1 to 10 Describe it.

[0044] like Figure 1 As shown, the packer may include a central pipe 1 and a stopper 8, and a setting push tube 3, a sealing protective sleeve 4, a sealing element 6 and an anti-burst sand isolation tube 7 which are sequentially sleeved on the outer wall of the central pipe 1 from top to bottom. The upper end of the central pipe 1 is connected to the upstream tool string, and the lower end is fixedly connected to the stopper 8. The stopper 8 can be set as a stopper coupling.

[0045] Among them, a plurality of steps 101 distributed circumferentially may be provided at the connection between the outer wall of the central tube 1 and the sealing protective sleeve 4. Figure 1 , Figure 7 and Figure 8 As shown, the lower end of the setting push tube 3 is circumferentially cut into several equal parts to form a corresponding number of axial grooves 301, and the axial grooves 301 correspond to the steps 101 one by one, so that the lower end of the setting push tube 3 and the step 101 are staggered and installed, and the setting push tube 3 can be stuck in the gap of the step 101 and slide downward relative to the step 101. The upper end of the sealing protection sleeve 4 can be fixed outside the step 101, and a first annular cavity 401 is formed between the lower end and the outer wall of the center tube 1. The sealing element 6 can be arranged in the first annular cavity 401, and the lower end is connected to the upper end of the anti-burst sand isolation tube 7, the inner wall of the sealing element 6 is close to the outer wall of the center tube 1, and its outer wall is close to the inner wall of the sealing protection sleeve 4. The lower end of the anti-burst sand isolation tube 7 is connected to the limiter 8, and the limiter 8 can limit the downward stroke of the anti-burst sand isolation tube 7.

[0046] Specifically, when the sealing push cylinder 3 is subjected to the downward axial sealing force, the sealing push cylinder 3 passes through the gap between the steps 101, enters the first annular cavity 401, and pushes the sealing element 6 and the anti-burst sand isolation cylinder 7 downward, until the sealing element 6 is pushed out of the first annular cavity 401 of the sealing protection sleeve 4, and at the same time, the anti-burst sand isolation cylinder 7 is restricted by the limit member 8 and stops descending. The sealing push cylinder 3 continues to descend and will begin to squeeze the sealing element 6. The sealing element 6 is subjected to the downward thrust of the sealing push cylinder 3 and the upward reaction force of the anti-burst sand isolation cylinder 7, and expands and deforms to fill the annulus, thereby implementing sealing.

[0047] In this embodiment, if Figure 1 , Figures 7 and 8 As shown, several steps 101 on the outer wall of the center tube 1 are evenly distributed circumferentially, and the lower end of the sealing push tube 3 is evenly cut into corresponding equal parts circumferentially to form several axial grooves 301 evenly distributed circumferentially, so as to achieve better staggered installation between the lower end of the sealing push tube 3 and the steps 101.

[0048] In this embodiment, if Figure 1 As shown, the packer may also include a backstop mechanism 2 fixedly connected to the upper end of the sealing push tube 3, and the backstop mechanism 2 may be provided with internal backstop teeth; the outer wall of the center pipe 1 may be provided with external backstop teeth, and the internal backstop teeth of the backstop mechanism 2 cooperate with the external backstop teeth on the center pipe 1 to have a backstop effect.

[0049] Specifically, when the packer is set, the stop mechanism 2 and the setting push tube 3 push the sealing element 6 downward to seal. After the sealing element 6 is fully expanded and sealed in place, the stop teeth of the stop mechanism 2 and the center pipe 1 form a self-locking stop. This can not only remove the axial setting force applied to the packer after the packer is set, but also prevent the packer from being accidentally unsealed.

[0050] Furthermore, the upper end of the setting push cylinder 3 and the anti-retraction mechanism 2 can be fixedly connected by screws and / or threads. For example, an internal thread is provided at the lower end of the anti-retraction mechanism 2, and a matching external thread is provided at the upper end of the setting push cylinder 3, or the lower end of the anti-retraction mechanism 2 and the upper end of the setting push cylinder 3 are fixed by screws evenly distributed in the circumference, or they are fixed by screws after being connected by threads to prevent the threaded connection from loosening. Of course, the present invention is not limited to this, and any other method that can fix the two together to achieve integrated movement is acceptable.

[0051] In this embodiment, if Figure 1 As shown, the length of the axial groove 301 is greater than the total travel distance of the sealing element 6 and the downward distance of the sealing element 6 during the process of being compressed and fully expanded. The length of the axial groove 301 is set in this way to ensure that the sealing element 6 can fully expand and deform, fully fill the annulus, and achieve effective sealing. The length of the axial groove 301 is sufficient to ensure the sealing effect of the packer.

[0052] In this embodiment, if Figure 1 As shown, the packer may further include an anti-bump fence 5, which may be installed in the first annular cavity 401 of the sealing protective sleeve 4 and arranged close to the upper end surface of the sealing element 6. Before setting, the upper end of the anti-bump fence 5 may reach below the step 101 of the central pipe 1.

[0053] In this embodiment, if Figures 1 to 4 As shown, the upper end of the anti-burst fence 5 can be a cylinder 501, the lower end can be a slope 502, and a deep groove 503 is opened in the middle, and the lower end slope 502 and the middle deep groove 503 are evenly cut into several parts in the circumferential direction, forming a multi-petal structure. Among them, in order to fully demonstrate the structural characteristics of the anti-burst fence 5, Figure 3 The left part corresponds to Figure 2 AA section view, Figure 4 yes Figure 3 A magnified schematic diagram of the local M in the figure.

[0054] Furthermore, if Figures 1 to 6 As shown, the shape and structure of the upper end portion of the anti-burst sand isolation tube 7 is mirror-symmetrical to the shape and structure of the anti-burst fence 5, and also presents a multi-petal structure, and its lower end portion can be a cylinder 701, and is connected to the upper end of the limit member 8.

[0055] Specifically, the upper end portion of the anti-burst sand isolation tube 7 and the anti-burst fence 5 are symmetrical in upper and lower directions relative to the sealing element 6. The anti-burst fence 5 comprises a cylinder 501, a deep groove 503 and a slope 502 from top to bottom, while the upper end portion of the anti-burst sand isolation tube 7 comprises a slope 502, a deep groove 503 and a cylinder 501 from top to bottom.

[0056] In this embodiment, if Figure 1 As shown, the outer diameter of the lower end cylinder 701 of the anti-burst sand isolation tube 7 is the same as the outer diameter of the sealing protection sleeve 4, and the inner diameter is gap-matched with the outer diameter of the upper end of the limiter 8; a second annular cavity 702 is formed between the inner wall of the lower end cylinder 701 of the anti-burst sand isolation tube 7, the outer wall of the central tube 1 and the upper end of the limiter 8.

[0057] Specifically, if the outer diameter of the lower end cylinder 701 of the anti-burst sand isolation tube 7 is too large, it may get stuck or scratched with the upper casing wall or the well wall during the process of going down the well, and if the outer diameter is too small, the sediment at the bottom of the well, the mud cake on the well wall and the plugging material may be brought to the position of the sealing protective sleeve 4 together with the drilling fluid (completion fluid) to cause blockage, so the outer diameter of the lower end cylinder 701 of the anti-burst sand isolation tube 7 is the most suitable to be the same as the outer diameter of the sealing protective sleeve 4. The inner diameter of the lower end cylinder 701 of the anti-burst sand isolation tube 7 and the clearance of the upper end outer diameter of the limiter 8 are matched to ensure that the anti-burst sand isolation tube 7 can go down a certain distance relative to the limiter 8, so that the sealing element 6 can be pushed out of the sealing protective sleeve 4 to prevent sediment, mud cake on the well wall and plugging material from entering the second annular cavity 702 and causing blockage.

[0058] In this embodiment, if Figure 1 As shown, the wall of the mating part of the anti-burst sand isolation tube 7 and the limiting member 8 may be provided with a plurality of radial screw holes distributed axially for installing the limiting nails. The position where the limiting nails are installed determines the distance that the anti-burst sand isolation tube 7 can go down, and the downward distance of the anti-burst sand isolation tube 7 is more suitable when the sealing element 6 just starts to expand and deform after being completely pushed out of the sealing protective sleeve 4. Of course, the present invention is not limited to this, and the installation position of the limiting nails can be adjusted and set according to the actual construction needs on site.

[0059] In this embodiment, if Figure 1 , Figures 3 to 6 As shown, the outer walls of the upper and lower ends of the sealing element 6 can be set to have a certain curvature, matching the inclined surfaces 502 of the anti-burst fence 5 and the anti-burst sand isolation tube 7, and the upper end outer wall is close to the inner side of the inclined surface 502 of the anti-burst fence 5, and the lower end outer wall is close to the inner side of the inclined surface 502 of the anti-burst sand isolation tube 7. This setting is to ensure that when the sealing element 6 expands and deforms during the setting process, the inclined surfaces 502 of the anti-burst fence 5 and the anti-burst sand isolation tube 7 are stretched together, and can fully wrap the sealing element 6 to protect the sealing element 6.

[0060] In this embodiment, if Figure 1 , Figures 9 and 10 As shown, the connection method of the sealing protective sleeve 4 fixed to the step 101 can be a slot or a threaded connection. That is, the fixed connection method can be a slot matching the step 101 of the central tube 1 is provided at the upper end of the sealing protective sleeve 4; or an internal thread is provided at the upper end of the sealing protective sleeve 4, and a matching external thread is provided on the step 101 of the central tube 1. Of course, the present invention is not limited to this, and other methods that can achieve fixed connection between the two are also possible.

[0061] In this embodiment, if Figure 1 As shown, the upper end of the limiter 8 may be provided with an internal thread, which is fixedly connected with the corresponding external thread provided on the central tube 1. In this way, the upper end surface of the limiter 8 can also be used to cooperate in limiting the downward stroke of the anti-burst sand isolation tube 7. Of course, the present invention is not limited to this, and other methods that can achieve fixed connection between the two are also possible.

[0062] Exemplary Embodiment 2

[0063] This exemplary embodiment provides a method for setting a stealth packer. Figures 1 to 10 Describe it.

[0064] The setting method may be implemented by using the invisible packer as in exemplary embodiment 1, and may include the following steps:

[0065] During the process of lowering the tool into the well and after the packer is lowered to the designed position, the sealing element 6 is always in the sealing protection sleeve 4 and is always in a protected state;

[0066] When the packer needs to be set, the axial setting force is applied to push the stop mechanism 2 to drive the setting push cylinder 3 downward. The setting push cylinder 3 passes through the first annular cavity 401 between the sealing protection sleeve 4 and the central tube 1, and presses down the anti-blowout fence 5. At this time, the anti-blowout fence 5, the sealing element 6 and the anti-blowout sand isolation tube 7 are pushed downward together.

[0067] Until the anti-burst sand isolation tube 7 reaches the limit piece 8 and stops, at this time, the anti-burst fence 5 and the sealing element 6 are completely exposed from the sealing protection sleeve 4, and the setting push tube 3 is pushed down continuously. At this time, the anti-burst fence 5 and the inclined surface 502 of the anti-burst sand isolation tube 7 are squeezed and deformed, supporting and protecting the sealing element 6, so that they are squeezed and expanded together;

[0068] When the sealing element 6 is radially thickened and deformed to completely fill the annular space, the packer is in place, and at the same time, the stop mechanism 2 and the center pipe 1 are self-locked and stop, and the packer setting action is completed.

[0069] In this embodiment, before the tool is lowered into the well, the packer is connected to the upstream sealing mechanism and other tool strings through the upper end of the central pipe 1, and the lower end is connected to the downstream tool string through the limiter 8 to form a complete tool string, and then the string is lowered from the wellhead in sequence.

[0070] In order to better understand the above exemplary embodiments of the present invention, the working principle and structural features of the invisible packer are further described below.

[0071] The working principle and structural features of the invisible packer of the present invention include at least the following points:

[0072] (1) The present invention uses a sealing protective sleeve to completely protect the sealing element of the packer. During the lowering or circulation process (when the packer does not need to be set), the sealing element is always in the sealing protective sleeve and will not be scratched or set prematurely due to external reasons. When it is necessary to set the seal, the sealing element is pushed out of the sealing protective sleeve by a setting push cylinder that is offset and assembled with the center tube of the packer. Under the action of the axial setting force, the sealing element cooperates with the anti-burst fence and the anti-burst sand isolation cylinder to achieve normal setting like the sealing element of a conventional packer. The structural design is simple and ingenious, the setting action is convenient and controllable, and the packer seal is safer and more reliable.

[0073] (2) The present invention adopts a multi-petal structure of an anti-burst fence and an anti-burst sand isolation tube that is easy to deform and has strong bearing capacity to protect the sealing element. The deep groove and the inclined surface part in the middle of the anti-burst fence and the anti-burst sand isolation tube are evenly divided into several parts in the circumferential direction. When pushed and squeezed by the sealing force, the deep groove with a thin middle wall is deformed, the angle between the inclined surface part and the axis increases, and the inclined surface opens like an umbrella, the maximum outer diameter increases, and it is close to the outer wall of the annulus to be sealed, supporting and wrapping the sealing element. At this time, the outer anti-burst fence and anti-burst sand isolation tube play the role of protecting the inner sealing element, and deform together with the sealing element during the sealing to complete the annulus isolation. This structural design makes the sealing element safer and the isolation more reliable.

[0074] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed in the present invention should all fall within the protection scope of the technical solution of the present invention.

Claims

1. An invisible packer, characterized in that: The packer comprises a central tube and a stopper, and a setting push tube, a sealing protective sleeve, a sealing element and a burst prevention sand isolation tube which are sequentially sleeved on the outer wall of the central tube from top to bottom; wherein, A plurality of steps distributed circumferentially are provided at the connection between the outer wall of the central tube and the sealing protective sleeve; The lower end of the setting push cylinder is cut into several equal parts in the circumferential direction to form several corresponding axial grooves. The axial grooves correspond to the steps one by one, so that the lower end of the setting push cylinder and the step can be staggered and installed, and the setting push cylinder can be inserted into the step gap and slide downward relative to the step; The upper end of the sealing protective sleeve is fixed outside the step, and a first annular cavity is formed between the lower end and the outer wall of the central tube; The sealing element is arranged in the first annular cavity, and the lower end is connected to the upper end of the anti-burst sand isolation cylinder, and the limiter can limit the downward stroke of the anti-burst sand isolation cylinder; The length of the axial groove is greater than the total stroke of the downward distance of the sealing element and the downward distance of the sealing element during the process of being compressed and fully expanded.

2. The invisible packer according to claim 1, characterized in that: The packer further comprises a backstop mechanism fixedly connected to the upper end of the setting push tube, wherein the backstop mechanism is provided with internal backstop teeth; The outer wall of the central tube is provided with an outer stop tooth, and the inner stop tooth of the stop mechanism cooperates with the outer stop tooth on the central tube to have a stop function.

3. The invisible packer according to claim 2, characterized in that: The upper end of the setting push cylinder is fixedly connected to the anti-retraction mechanism by screws and / or threads.

4. The invisible packer according to claim 1, characterized in that: The packer further comprises an anti-outburst fence, which is installed in the first annular cavity of the sealing protection sleeve and is arranged close to the upper end surface of the sealing element.

5. The invisible packer according to claim 4, characterized in that: The upper end of the anti-outburst fence is a cylinder, the lower end is an inclined surface, a deep groove is opened in the middle, and the lower end inclined surface and the middle deep groove are evenly cut into several parts in the circumferential direction.

6. The invisible packer according to claim 5, characterized in that: The shape structure of the upper end portion of the anti-burst sand isolation tube is mirror-symmetrical to the shape structure of the anti-burst fence, and the lower end portion thereof is divided into a cylinder and connected to the upper end of the limiting member.

7. The invisible packer according to claim 6, characterized in that: The outer diameter of the lower end cylinder of the anti-burst sand isolation tube is the same as the outer diameter of the sealing protection sleeve, and its inner diameter is loosely matched with the outer diameter of the upper end of the limiting member; a second annular cavity is formed between the inner wall of the lower end cylinder of the anti-burst sand isolation tube, the outer wall of the central tube and the upper end of the limiting member.

8. The invisible packer according to claim 7, characterized in that: A plurality of radial screw holes distributed axially are arranged on the wall of the mating part of the anti-burst sand isolation tube and the limiting member for installing the limiting nails.

9. The invisible packer according to claim 6, characterized in that: The outer walls of the upper and lower ends of the sealing element are arranged with a certain curvature, matching the inclined surfaces of the anti-outburst fence and the anti-outburst sand isolation tube, and the upper end outer wall is close to the inner side of the inclined surface of the anti-outburst fence, and the lower end outer wall is close to the inner side of the inclined surface of the anti-outburst sand isolation tube.

10. The invisible packer according to claim 1, characterized in that: The sealing protective sleeve is fixed to the step in a slot or threaded connection.

11. The invisible packer according to claim 1, characterized in that: The upper end of the limiting member is provided with an internal thread, which is fixedly connected with a corresponding external thread provided on the central tube.

12. A method for setting an invisible packer, characterized in that: The sealing method is implemented by using the invisible packer as described in any one of claims 1 to 11.

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