A liner plug system for liner cementing operations

Abstract

The application provides a liner plug system for liner cementing construction, which comprises a drill pipe plug, a liner plug arranged below the drill pipe plug, and a liner plug nipple arranged below the liner plug, the drill pipe plug can be connected with the liner plug to form a first composite body after descending, the first composite body can descend and the liner plug in the first composite body can be connected with the liner plug nipple, so that the first composite body and the liner plug nipple form a second composite body, and the second composite body can continue to descend. The application can improve the liner scraping effect and effectively isolate the drilling fluid and the cement slurry.

Description

Technical Field

[0001] This invention relates to the field of cementing construction technology, and more specifically, to a tailpipe plug system for tailpipe cementing construction. Background Technology

[0002] In tailpipe cementing operations, after the cement slurry is injected, the drill pipe plug in the drill pipe cement head needs to be released, and then drilling fluid is injected to displace the cement slurry. The drill pipe plug serves two purposes: firstly, it isolates the cement slurry from the drilling fluid, preventing mixing; secondly, it scrapes away the cement slurry within the drill string. When the drill pipe plug reaches the tailpipe plug, the two plugs can combine, and the tailpipe plug can be sheared off. This allows the drill pipe plug and tailpipe plug to descend together, scraping away the cement slurry within the tailpipe, until the combined drill pipe plug and tailpipe plug reach the ball seat position for impact pressure.

[0003] Because the stub plug needs to be pressed into the stub by the weight of the stub hanger during on-site assembly, and the stub hanger weighs between 500 and 1000 kg, the interference fit between the stub plug cup and the stub cannot be designed to be too large. Too much friction will make it difficult to insert the stub plug. In addition, the stub hanger needs to be lifted to determine if it has been released. Conventional stub plug cups are reversed. If the friction is too large, the stub plug will be prematurely sheared off, causing premature cementing of the stub. Therefore, under normal circumstances, the interference fit between the stub plug and the stub hanger is small and the friction is small, resulting in poor scraping effect of the stub plug.

[0004] There are other solutions that avoid cement blockage by modifying the tailpipe plug structure. For example, Chinese invention patent CN107829707A relates to a tailpipe cementing tailpipe plug assembly, which includes a short connector, a sliding sleeve, a pawl sleeve, and a plug mandrel. An annular platform is integrally fixed on the inner side of the middle part of the short connector, and at least one arc-shaped annular groove is provided on the inner side of the upper part of the annular platform. Pawls are evenly fixed on the upper end of the pawl sleeve, and a flange is integrally fixed on the outer side of the upper end of the pawl. The flange on the pawl is engaged in the arc-shaped annular groove. The lower part of the short connector is fitted onto the pawl sleeve, and the lower part of the sliding sleeve is fixedly connected to the middle part of the pawl sleeve by at least one shear pin. This solution uses a combination of short joints, sliding sleeves, ratchet sleeves, and rubber plug mandrels to prevent the drill pipe rubber plug from detaching from the tailpipe rubber plug assembly during descent, which could lead to cement plugs, slurry mixing, and inability to press the pipe. However, the rubber cup of the tailpipe rubber plug short section cannot be designed with a large interference fit between it and the tailpipe, resulting in poor tailpipe scraping effect and inability to effectively isolate the drilling fluid from the cement slurry.

[0005] For example, Chinese invention patent with publication number CN102628347A relates to an oil drilling cementing tool, and in particular to a tailpipe cementing rubber plug composite pressing device. The drill pipe rubber plug of this device includes a fixing nut, a connecting rod, a small rubber cup, and a cup seat. The fixing nut, connecting rod, cup seat, and guide head are sequentially threaded together from top to bottom. The small rubber cup is fitted on the outside of the connecting rod, and a locking block is installed on the outside of the cup seat. A return spring is installed on the inside of the locking block. The tailpipe hollow rubber plug includes a hollow connecting body, a large rubber cup, and a hollow guide cup seat. The hollow connecting body is designed to be hollow, and a locking block groove matching the locking block is designed on the inner wall of the hollow connecting body. The lower end of the hollow connecting body is threaded to the hollow guide cup seat, and a large rubber cup is fitted on the outside of the hollow connecting body. This solution can overcome the disadvantages of low bearing pressure of cementing rubber plugs, unsafe use, easy cement backflow, low backflow outside the pipe, and cement plugs left inside the pipe. However, it also cannot make it impossible to design a large interference fit between the rubber cup of the tailpipe rubber plug short section and the tailpipe, resulting in poor tailpipe scraping effect and inability to effectively isolate drilling fluid and cement slurry.

[0006] Therefore, there is an urgent need for a tailpipe plug system for tailpipe cementing operations that can solve the technical drawbacks of existing tailpipe plug systems, such as poor tailpipe scraping effect and ineffective separation of drilling fluid and cement slurry. Summary of the Invention

[0007] One objective of this invention is to provide a tailpipe plug system for tailpipe cementing operations to improve tailpipe scraping effect and effectively isolate drilling fluid from cement slurry.

[0008] According to the present invention, a tailpipe plug system for tailpipe cementing is provided, comprising a drill pipe plug, a tailpipe plug disposed below the drill pipe plug, and a tailpipe plug sub disposed below the tailpipe plug. The drill pipe plug can connect with the tailpipe plug after descent to form a first composite. The first composite can descend and the tailpipe plug therein can connect with the tailpipe plug sub, so that the first composite and the tailpipe plug sub form a second composite, and the second composite can continue to descend.

[0009] In a preferred embodiment, the tailpipe plug system for tailpipe cementing further includes a ball seat disposed in the horizontal well section, the ball seat being capable of connecting to the tailpipe plug subsection of the second composite entering the horizontal well section.

[0010] In a preferred embodiment, the tailpipe rubber plug sub includes multiple rubber cups. During the descent of the tailpipe rubber plug sub in the vertical well section, the rubber cups can fit against the inner wall of the casing, and during the operation of the tailpipe rubber plug sub in the horizontal well section, the rubber cups can fit against the inner wall of the tailpipe string.

[0011] In a preferred embodiment, the tailpipe plug subsection includes five rubber cups arranged from top to bottom, wherein the first rubber cup is configured as a protrusion with an arc surface, the second and third rubber cups are both configured as strips and inclined upwards, and the fourth and fifth rubber cups are configured as strips and inclined downwards.

[0012] In a preferred embodiment, the tailpipe plug sub-section includes a first anti-reverse serration, and the tailpipe plug includes a first anti-reverse retaining spring, which can engage with the first anti-reverse serration to connect the first composite to the tailpipe plug sub-section.

[0013] In a preferred embodiment, the tailpipe plug sub-section further includes a retaining ring disposed at and in contact with the lower end of the rubber cup, wherein the end face of the retaining ring on the side in contact with the rubber cup is configured as a plane, and the end face on the side opposite to the plane is configured as a bevel.

[0014] In a preferred embodiment, the tailpipe plug sub-section further includes a second anti-reverse retaining spring, which is disposed below and opposite to the inclined surface, and the ball seat includes a second anti-reverse serration, the second anti-reverse retaining spring being used to connect with the second anti-reverse serration.

[0015] In a preferred embodiment, the tailpipe plug sub-section further includes a guide head disposed at the lower end.

[0016] In a preferred embodiment, the tailpipe plug sub also includes a housing fixed to the casing, a locking sleeve disposed within the housing, a fixing part, and a main body. The fixing part fixes the locking sleeve to the housing. The fixing part can be sheared so that the locking sleeve together with the main body can detach from the housing. The second composite can then descend and connect with the ball seat in the horizontal well section.

[0017] In a preferred embodiment, the locking sleeve, rubber cup, retaining ring, second anti-reverse snap ring, and guide head are all disposed on the outer periphery of the main body.

[0018] In a preferred embodiment, the first anti-retraction serration is disposed on the body.

[0019] The present invention also provides a tailpipe cementing construction method, comprising:

[0020] S1. The drill pipe rubber plug is lowered and connected to the tailpipe rubber plug to form the first composite;

[0021] S2, the first composite is moved downward and the tailpipe plug therein is connected to the tailpipe plug short section, so that the first composite and the tailpipe plug short section form a second composite.

[0022] S3, the second descending composite, and in the horizontal well section, the tailpipe plug sub-section therein is connected to the ball seat.

[0023] This invention has at least the following effects:

[0024] This invention comprises a drill pipe rubber plug, a tailpipe rubber plug located below the drill pipe rubber plug, and a tailpipe rubber plug short section located below the tailpipe rubber plug. The drill pipe rubber plug can connect with the tailpipe rubber plug after descent to form a first composite. The first composite can descend, and the tailpipe rubber plug within it can connect with the tailpipe rubber plug short section, thereby forming a second composite. Since the second composite, consisting of the drill pipe rubber plug, tailpipe rubber plug, and tailpipe rubber plug short section, can descend together, the tailpipe rubber plug short section can be pre-positioned below the tailpipe hanger, ensuring that the tailpipe rubber plug short section is not connected to the tailpipe hanger. This eliminates the impact on the tailpipe rubber plug short section during on-site assembly and tailpipe hanger release and lifting operations. Therefore, a larger interference fit can be designed between the rubber cup of the tailpipe rubber plug short section and the tailpipe, increasing the friction between the tailpipe rubber plug and the tailpipe, thereby improving the effect of the tailpipe rubber plug in scraping the cement slurry inside the tailpipe and effectively preventing cement plug residue at the top of the tailpipe rubber plug.

[0025] The present invention includes a ball seat disposed in the horizontal well section, which can be connected to a tailpipe rubber plug short section of the second composite entering the horizontal well section. This allows the second composite to isolate drilling fluid from cement slurry. At the same time, the second composite, composed of drill pipe rubber plug, tailpipe rubber plug and tailpipe rubber plug short section, can scrape the cement slurry inside the tailpipe string wall together, thereby improving scraping efficiency.

[0026] The tailpipe rubber plug short section of the present invention includes multiple rubber cups. During the descent of the tailpipe rubber plug short section in the vertical well section, the rubber cups can fit against the inner wall of the casing. During the operation of the tailpipe rubber plug short section in the horizontal well section, the rubber cups can fit against the inner wall of the tailpipe string. Thus, by having the multiple rubber cups of the tailpipe rubber plug short section fit against the inner wall of the casing and the inner wall of the tailpipe string in sequence, the scraping efficiency of the tailpipe rubber plug short section is improved.

[0027] The present invention improves the scraping efficiency by constructing the first rubber cup as a protruding body with an arc surface, thereby increasing the contact area with the inner wall of the sleeve. Furthermore, by constructing the second and third rubber cups as strips and tilting upwards, and the fourth and fifth rubber cups as strips and tilting downwards, the wear resistance of the second, third, fourth, and fifth rubber cups can be improved.

[0028] The present invention includes a retaining ring disposed at the lower end of the rubber cup and in contact with it. The end face of the retaining ring on the side in contact with the rubber cup is constructed as a plane, which can support the rubber cup and prevent the rubber cup from bending. The end face on the side opposite to the plane is constructed as a slope, which facilitates the bonding of the tailpipe rubber plug short section with the ball seat.

[0029] This invention utilizes a tailpipe rubber plug short section comprising a housing fixed to the casing, a locking sleeve disposed within the housing, a fixing part, and a main body. The fixing part secures the locking sleeve to the housing, and the fixing part can be sheared off so that the locking sleeve, along with the main body, can detach from the housing. This allows the second composite to descend and connect with the ball seat in a horizontal well section. After the first composite and the tailpipe rubber plug short section are connected to form the second composite, the second composite can descend and contact and combine with the ball seat in a horizontal well section. This allows the second composite, composed of the drill pipe rubber plug, the tailpipe rubber plug, and the tailpipe rubber plug short section, to jointly scrape the inner wall of the casing and the inner wall of the tailpipe string, improving scraping efficiency. Attached Figure Description

[0030] Figure 1 A schematic diagram of a tailpipe plug system for tailpipe cementing, including the present invention, is shown.

[0031] Figure 2 A schematic diagram of the tailpipe plug section of the tailpipe plug system for tailpipe cementing construction according to the present invention is shown.

[0032] Figure 3 A schematic diagram of the structure of the first composite of the tailpipe plug system for tailpipe cementing construction of the present invention is shown.

[0033] Figure 4 A schematic diagram of the structure of the second composite of the tailpipe plug system for tailpipe cementing construction of the present invention is shown.

[0034] Figure 5 The diagram schematically illustrates the structure of the second composite of the tailpipe plug system for tailpipe cementing of the present invention after it is connected to the ball seat.

[0035] In this application, all drawings are schematic and are used only to illustrate the principles of the invention, and are not drawn to scale. Detailed Implementation

[0036] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention. It should be noted that, unless otherwise specified, the embodiments and features described in this application can be arbitrarily combined with each other.

[0037] In the description of this invention, it should be understood that the terms "inner", "outer", "upper", "lower", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0038] It should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include one or more of that feature.

[0039] In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0040] In this invention, unless otherwise explicitly specified and limited, the terms "connection," "fixed," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0041] Figure 1 A schematic diagram of an overall structure of a tailpipe plug system 100 for tailpipe cementing construction, including the present invention, is shown. Figure 2 A schematic diagram of the tailpipe plug section of the tailpipe plug system for tailpipe cementing construction according to the present invention is shown. Figure 3 A schematic diagram of the structure of the first composite of the tailpipe plug system for tailpipe cementing construction of the present invention is shown. Figure 4 A schematic diagram of the structure of the second composite of the tailpipe plug system for tailpipe cementing construction of the present invention is shown. Figure 5 The diagram schematically illustrates the structure of the second composite of the tailpipe plug system for tailpipe cementing of the present invention after connection with the ball seat. Figures 1 to 5 As shown, the tailpipe plug system 100 for tailpipe cementing construction of the present invention includes a drill pipe plug 1, a tailpipe plug 4 disposed below the drill pipe plug 1, and a tailpipe plug sub 6 disposed below the tailpipe plug 4. Both the tailpipe plug 4 and the tailpipe plug sub 6 are disposed within the casing. The drill pipe plug 1 is lowered into the casing from the wellhead located on the surface. As the drill pipe plug 1 descends within the well, it connects with the tailpipe plug 4 to form a first composite. This first composite can descend further, and the tailpipe plug 4 can connect with the tailpipe plug sub 6, thereby forming a second composite. The second composite can continue to descend and enter the horizontal well section. It should be noted that before entering the horizontal well section, the second composite is located within the casing of the vertical well section; after entering the horizontal well section, it is located within the tailpipe string 7 of the horizontal well section.

[0042] Specifically, drill pipe plug 1 is inserted into the casing. Drill pipe plug 1 passes through drill string 2 and reaches tailpipe plug 4 below tailpipe hanger 3. The anti-reverse snap ring on drill pipe plug 1 can engage with the anti-reverse serrated structure on the locking seat in tailpipe plug 4 to achieve locking and anti-reverse, thereby forming a first composite with drill pipe plug 1 and tailpipe plug 4. Under hydraulic action, the shear pin on tailpipe plug 4 is sheared, and the first composite descends and reaches tailpipe plug short section 6 at the connection of casing 5. Tailpipe plug 4 and tailpipe plug short section 6 can be connected, thereby forming a second composite with drill pipe plug 1, tailpipe plug 4 and tailpipe plug short section 6. The second composite continues to descend in the vertical well section and then enters the horizontal well section.

[0043] This invention comprises a drill pipe rubber plug 1, a tailpipe rubber plug 4 disposed below the drill pipe rubber plug 1, and a tailpipe rubber plug short section 6 disposed below the tailpipe rubber plug 4. The drill pipe rubber plug 1 can connect with the tailpipe rubber plug 4 after descent to form a first composite. The first composite can descend, and the tailpipe rubber plug 4 can connect with the tailpipe rubber plug short section 6. This allows the first composite and the tailpipe rubber plug short section 6 to form a second composite. Since the second composite consisting of the drill pipe rubber plug 1, the tailpipe rubber plug 4, and the tailpipe rubber plug short section 6 can descend together, the second composite can descend together. This allows for the pre-installation of a short rubber plug 6 below the tailpipe hanger 3, ensuring that the short rubber plug 6 is not connected to the tailpipe hanger 3. This eliminates the impact of on-site assembly and tailpipe hanger 3 release and lifting operations on the short rubber plug 6. Consequently, a larger interference fit can be designed between the rubber cup of the short rubber plug 6 and the tailpipe, increasing the friction between the tailpipe plug 4 and the tailpipe. This enhances the effect of the tailpipe plug 4 in scraping the cement slurry inside the tailpipe, effectively preventing cement plugs from remaining on the upper part of the tailpipe plug 4.

[0044] In one or more embodiments, the tailpipe plug system 100 for tailpipe cementing of the present invention further includes a ball seat 8 disposed in the tailpipe string 7 in a horizontal well section, the second composite being able to descend and enter the horizontal well section, and the ball seat 8 being able to connect with the tailpipe plug short section 6 of the second composite entering the horizontal well section.

[0045] The present invention includes a ball seat 8 disposed in the horizontal well section, and the ball seat 8 can be connected to the tailpipe rubber plug short section 6 of the second composite entering the horizontal well section. This allows the second composite to isolate drilling fluid from cement slurry. At the same time, the second composite, composed of drill pipe rubber plug 1, tailpipe rubber plug 4 and tailpipe rubber plug short section 6, can scrape the cement slurry inside the tailpipe string 7 together, thereby improving scraping efficiency.

[0046] In one or more embodiments, the tailpipe rubber plug short section 6 of the present invention includes a plurality of rubber cups 65. During the downward movement of the tailpipe rubber plug short section 6 in the vertical well section, the rubber cups 65 can fit against the inner wall of the casing, and during the operation of the tailpipe rubber plug short section 6 in the horizontal well section, the rubber cups 65 can fit against the inner wall of the tailpipe string.

[0047] The tailpipe rubber plug short section 6 of the present invention includes multiple rubber cups 65. During the descent of the tailpipe rubber plug short section 6 in the vertical well section, the rubber cups 65 can fit against the inner wall of the casing. During the operation of the tailpipe rubber plug short section 6 in the horizontal well section, the rubber cups 65 can fit against the inner wall of the tailpipe string. Thus, by having multiple rubber cups 65 of the tailpipe rubber plug short section 6 fit against the inner wall of the casing and the inner wall of the tailpipe string in sequence, the scraping efficiency of the tailpipe rubber plug short section 6 can be improved.

[0048] In one or more embodiments, the tailpipe plug short section 6 includes five rubber cups 65 arranged from top to bottom. The first rubber cup 65 is configured as a protruding body with an arcuate surface; the second and third rubber cups 65 are both configured as strips and inclined upwards; and the fourth and fifth rubber cups 65 are configured as strips and inclined downwards. For example, the second and third rubber cups 65 form an angle of 30°-60° with the centerline of the tailpipe plug short section 6, and the fourth and fifth rubber cups 65 form an angle of 120°-150° with the centerline of the tailpipe plug short section 6. It should be noted that the number of rubber cups 65 in the tailpipe plug short section 6 can be adjusted according to the sleeve length; either separate rubber cups or integrated rubber cups can be used.

[0049] The present invention constructs the first rubber cup 65 as a protruding body with an arc surface, which can increase the contact area with the inner wall of the sleeve, thereby giving the first rubber cup 65 a strong scraping ability and improving scraping efficiency. Furthermore, by constructing the second and third rubber cups 65 as strips and inclined upwards, and the fourth and fifth rubber cups 65 as strips and inclined downwards, the wear resistance of the second, third, fourth, and fifth rubber cups 65 can be improved.

[0050] In one or more embodiments, the tailpipe rubber plug 6 includes a first anti-reverse serration, and the tailpipe rubber plug 4 includes a first anti-reverse snap ring 46. During the downward movement of the tailpipe rubber plug 4 inside the sleeve, the anti-reverse snap ring 46 can engage with the first anti-reverse serration so that the first composite body is engaged and connected with the tailpipe rubber plug 6.

[0051] In one or more embodiments, the tailpipe plug stub 6 further includes a retaining ring 66 disposed at and in contact with the lower end of the cup 65. The retaining ring 66 has a flat end face on the side in contact with the cup 65 and a beveled end face on the side opposite to the flat end face.

[0052] The present invention includes a retaining ring 66 disposed at the lower end of the rubber cup 65 and in contact with it. The end face of the retaining ring 66 on the side in contact with the rubber cup 65 is constructed as a plane, which can support the rubber cup 65 and prevent the rubber cup 65 from bending. The end face on the side opposite to the plane is constructed as a slope, which facilitates the bonding of the tailpipe rubber plug 6 with the ball seat 8.

[0053] In one or more embodiments, the tailpipe plug stub 6 further includes a second anti-reverse retaining spring 67, which is disposed below and opposite to the inclined surface of the retaining ring 66, and the ball seat 8 includes a second anti-reverse serration, the second anti-reverse retaining spring 67 being used to connect with the second anti-reverse serration.

[0054] In one or more embodiments, the tailpipe rubber plug sub-section 6 further includes a guide head 68 disposed at the lower end. The guide head 68 adopts a double-sealing structure to improve the sealing performance of the tailpipe rubber plug sub-section 6 and the ball seat 8 after they are combined.

[0055] In one or more embodiments, the tailpipe rubber plug sub 6 further includes a housing 61 fixedly connected to the casing, a locking sleeve 62 disposed within the housing 61, a fixing part 63, and a main body 64. The fixing part 63 fixes the locking sleeve 62 to the housing 61. The housing 61 is fixedly connected to the casing. After the anti-retraction snap ring 46 on the tailpipe rubber plug 4 engages with the anti-retraction serrations on the main body 64 of the tailpipe rubber plug sub 6, the tailpipe rubber plug 4 and the tailpipe rubber plug sub 6 are locked and anti-retraction. The first composite body and the tailpipe rubber plug sub 6 are connected to form a second composite body. Under hydraulic action, the fixing part 63 can be sheared so that the locking sleeve 62 together with the main body 64 can detach from the housing 61. The second composite body can then descend and contact and combine with the ball seat 8 in the horizontal well section. Optionally, the fixing part can be a shear pin.

[0056] The present invention comprises a shell 61 fixed to the casing, a locking sleeve 62 disposed within the shell 61, a fixing part 63, and a main body 64. The fixing part 63 fixes the locking sleeve 62 to the shell 61, and the fixing part 63 can be cut off so that the locking sleeve 62 together with the main body 64 can detach from the shell 61. The second composite can then descend and connect with the ball seat 8 in the horizontal well section. After the first composite and the tailpipe rubber plug 6 are connected to form the second composite, the second composite can descend and contact and combine with the ball seat 8 in the horizontal well section. Thus, the second composite composed of the drill pipe rubber plug 1, the tailpipe rubber plug 4, and the tailpipe rubber plug 6 can jointly scrape the inner wall of the casing and the inner wall of the tailpipe string 7, thereby improving the scraping efficiency.

[0057] In one or more embodiments, the locking sleeve 62, the rubber cup 65, the retaining ring 66, the second anti-reverse snap ring 67, and the guide head 68 are all disposed on the outer periphery of the main body 64, and the first anti-reverse serration is disposed on the main body 64.

[0058] Based on the aforementioned tailpipe cementing system 100 for tailpipe cementing construction, the present invention also provides a tailpipe cementing construction method, comprising:

[0059] S1. The down-feeding drill pipe rubber plug 1 is connected to the tailpipe rubber plug 4 to form the first composite;

[0060] S2, the first composite is moved downward and the tailpipe plug 4 therein is connected to the tailpipe plug short section 6, so that the first composite and the tailpipe plug short section 6 form a second composite.

[0061] S3, the second descending composite, and in the horizontal well section, the tailpipe rubber plug 6 is connected to the ball seat 8.

[0062] This invention has at least the following effects:

[0063] This invention comprises a drill pipe rubber plug 1, a tailpipe rubber plug 4 disposed below the drill pipe rubber plug 1, and a tailpipe rubber plug short section 6 disposed below the tailpipe rubber plug 4. The drill pipe rubber plug 1 can connect with the tailpipe rubber plug 4 after descent to form a first composite. The first composite can descend, and the tailpipe rubber plug 4 can connect with the tailpipe rubber plug short section 6. This allows the first composite and the tailpipe rubber plug short section 6 to form a second composite. Since the second composite consisting of the drill pipe rubber plug 1, the tailpipe rubber plug 4, and the tailpipe rubber plug short section 6 can descend together, the second composite can descend together. This allows for the pre-installation of a short rubber plug 6 below the tailpipe hanger 3, ensuring that the short rubber plug 6 is not connected to the tailpipe hanger 3. This eliminates the impact of on-site assembly and tailpipe hanger 3 release and lifting operations on the short rubber plug 6. Consequently, a larger interference fit can be designed between the rubber cup of the short rubber plug 6 and the tailpipe, increasing the friction between the tailpipe plug 4 and the tailpipe. This enhances the effect of the tailpipe plug 4 in scraping the cement slurry inside the tailpipe, effectively preventing cement plugs from remaining on the upper part of the tailpipe plug 4.

[0064] The tailpipe rubber plug short section 6 of the present invention includes multiple rubber cups 65. During the descent of the tailpipe rubber plug short section 6 in the vertical well section, the rubber cups 65 can fit against the inner wall of the casing. During the operation of the tailpipe rubber plug short section 6 in the horizontal well section, the rubber cups 65 can fit against the inner wall of the tailpipe string. Thus, by having multiple rubber cups 65 of the tailpipe rubber plug short section 6 fit against the inner wall of the casing and the inner wall of the tailpipe string in sequence, the scraping efficiency of the tailpipe rubber plug short section 6 can be improved.

[0065] Although the invention has been described with reference to preferred embodiments, various modifications can be made and components can be replaced with equivalents without departing from the scope of the invention. In particular, the technical features mentioned in the various embodiments can be combined in any manner as long as there is no structural conflict. The invention is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A tailpipe plug system for tailpipe cementing operations, comprising a drill pipe plug, a tailpipe plug disposed below the drill pipe plug, and a tailpipe plug sub-section disposed below the tailpipe plug. The drill pipe plug can connect with the tailpipe plug after descending to form a first composite. The first composite can descend and the tailpipe plug can connect with the tailpipe plug short section, so that the first composite and the tailpipe plug short section form a second composite, and the second composite can continue to descend. The tailpipe rubber plug short section includes multiple rubber cups. During the vertical well section's descent, the rubber cups can fit against the inner wall of the casing. During the horizontal well section's operation, the rubber cups can fit against the inner wall of the tailpipe string. The tailpipe rubber plug short section includes five rubber cups arranged from top to bottom. The first rubber cup is configured as a protruding body with an arc surface; the second and third rubber cups are both configured as strips and inclined upwards; the fourth and fifth rubber cups are configured as strips and inclined downwards; the tailpipe rubber plug short section also includes a retaining ring disposed at the lower end of the rubber cup and in contact with it; the end face of the retaining ring on the side in contact with the rubber cup is configured as a plane, and the end face on the side opposite to the plane is configured as a slope.

2. The tailpipe plug system for tailpipe cementing construction according to claim 1, characterized in that, It also includes a ball seat disposed in the horizontal well section, the ball seat being able to connect to the tailpipe rubber plug short section of the second composite entering the horizontal well section.

3. The tailpipe plug system for tailpipe cementing construction according to claim 2, characterized in that, The tailpipe plug section includes a first anti-reverse serration, and the tailpipe plug includes a first anti-reverse retaining spring. The first anti-reverse retaining spring can engage with the first anti-reverse serration so that the first composite is connected to the tailpipe plug section.

4. The tailpipe plug system for tailpipe cementing construction according to claim 3, characterized in that, The tailpipe plug section also includes a second anti-reverse retaining spring, which is disposed below and opposite to the inclined surface. The ball seat includes a second anti-reverse serration, and the second anti-reverse retaining spring is used to connect with the second anti-reverse serration.

5. The tailpipe plug system for tailpipe cementing construction according to claim 4, characterized in that, The tailpipe plug sub-section also includes a guide head located at the lower end.

6. The tailpipe plug system for tailpipe cementing construction according to claim 5, characterized in that, The tailpipe plug sub also includes a housing fixed to the casing, a locking sleeve disposed within the housing, a fixing part, and a main body. The fixing part fixes the locking sleeve to the housing. The fixing part can be sheared so that the locking sleeve together with the main body can be detached from the housing. The second composite can then descend and connect with the ball seat in the horizontal well section.

7. The tailpipe plug system for tailpipe cementing construction according to claim 6, characterized in that, The locking sleeve, rubber cup, retaining ring, second anti-reverse snap ring, and guide head are all located on the outer periphery of the main body.

8. The tailpipe plug system for tailpipe cementing construction according to claim 6, characterized in that, The first anti-retraction saw tooth is provided on the main body.

9. A tailpipe cementing construction method, utilizing a tailpipe rubber plug system for tailpipe cementing construction according to any one of claims 1 to 8, comprising: S1. The drill pipe rubber plug is lowered and connected to the tailpipe rubber plug to form the first composite; S2, the first composite is moved downward and the tailpipe plug therein is connected to the tailpipe plug short section, so that the first composite and the tailpipe plug short section form a second composite. S3, the second descending composite, and in the horizontal well section, the tailpipe plug sub-section therein is connected to the ball seat.

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