Casing centralizer

Abstract

The invention relates to the technical field of centralizers, in particular to a casing centralizer which comprises an annular shell, a plurality of spiral centralizing strips are evenly distributed on the peripheral face of the annular shell in the circumferential direction, and spiral grooves are formed between the adjacent spiral centralizing strips. A pre-swirling piece is arranged at the lower end part of the annular shell; rolling centralizing pieces are movably embedded in each group of spiral centralizing strips; the pre-swirling piece is used for pre-guiding fluid to form primary swirling flow, and spiral grooves between the pre-swirling piece and the spiral centralizing strips are used for jointly strengthening the main swirling flow effect, so that the cleaning efficiency of the fluid on the well wall is effectively improved, meanwhile, deposition of silt and solid particles in the spiral grooves is reduced, large particle blocks can be crushed, a flow channel is prevented from being blocked, and the continuous operation time is prolonged; the rolling centralizing piece can roll in a self-adaptive mode when making contact with the well wall, and the resistance of lowering the casing pipe is effectively reduced. And meanwhile, local high pressure of the centralizer on the well wall is avoided, the stress concentration phenomenon is effectively prevented, scraping and damage to the well wall are reduced, and the stability of a well hole can be maintained.

Description

Technical Field

[0001] This invention relates to the field of centralizer technology, and more specifically, to a sleeve centralizer. Background Technology

[0002] Casing centralizers are key tools in oil drilling engineering. They are mainly used to ensure that the casing remains centered in the wellbore, thereby ensuring uniform distribution of cement sheaths and improving cementing quality. Currently, conventional casing centralizers still face significant bottlenecks in complex well operations. First, during cementing, the returning slurry fluid can directly impact the bottom of the centralizer, generating turbulence. This causes solid particles to deposit in the spiral grooves between the centralizer bars, leading to flow channel blockage, affecting displacement efficiency, and even interrupting cementing operations. Second, traditional centralizer bars and the well wall mostly experience sliding friction, especially in deviated and horizontal well sections. The high resistance of running the casing can easily cause well wall damage, stress concentration, and insufficient casing centering, affecting the quality of cement ring sealing. Summary of the Invention

[0003] To overcome the above-mentioned technical problems, the present invention proposes a casing straightener.

[0004] The objective of this invention can be achieved through the following technical solutions: A casing straightener includes an annular shell, wherein a plurality of spiral straightening strips are evenly distributed circumferentially on the outer circumferential surface of the annular shell, and spiral grooves are formed between adjacent spiral straightening strips; The lower end of the annular shell is provided with a pre-swirling element, which is used to guide the fluid to reduce the deposition of solid particles in the spiral groove; Each set of spiral centralizers is equipped with a rolling centralizer that is movably embedded in the well wall. The rolling centralizer makes adaptive rolling contact with the well wall to avoid stress concentration and thus reduce the running casing resistance.

[0005] As a further aspect of the present invention: the pre-swirling component includes an anti-clogging ring disposed at the lower end of the annular shell, and the anti-clogging ring is provided with a plurality of guide vanes in the circumferential direction.

[0006] As a further aspect of the present invention, the guide vanes and spiral straightening strips are distributed alternately.

[0007] As a further aspect of the present invention: the anti-blocking ring includes a lower conical surface and an upper conical surface that are connected to each other, and the guide vane is disposed on the lower conical surface.

[0008] As a further aspect of the present invention, the slope of the upper conical surface is greater than the slope of the lower conical surface.

[0009] As a further aspect of the present invention: the rolling straightening component includes a cavity formed within the spiral straightening strip and a spherical shell movably embedded within the cavity. The cavity has symmetrically arranged grooves on both sides, and the spherical shell has symmetrically arranged sliders at both ends that are adapted to slide with the grooves. Ball bearings are movably embedded within the spherical shell.

[0010] As a further embodiment of the present invention: a guide post is fixed inside the groove, the slider is slidably sleeved on the corresponding guide post, a limit block is provided at the end of the guide post, and a spring that abuts against the slider is movably sleeved on the guide post.

[0011] As a further aspect of the present invention, it also includes a limiting member disposed on the inner side of the annular shell, the limiting member being used to axially limit the annular shell to prevent the centralizer from axially slipping on the sleeve.

[0012] As a further aspect of the present invention: the limiting member includes an annular groove formed on the inner circumferential surface of the annular shell, and an expansion bladder strip adapted to the sleeve is embedded in the annular groove.

[0013] As a further aspect of the present invention: a spherical airbag is provided inside the cavity to abut against the spherical shell, and an air passage is connected between the expansion strip and each spherical airbag.

[0014] The beneficial effects of this invention are: The pre-swirling element in this invention pre-guides the fluid to form a preliminary swirling flow. Together with the spiral groove between the spiral stabilizer bars, it enhances the main swirling flow effect, effectively improving the cleaning efficiency of the fluid on the well wall. At the same time, it reduces the deposition of mud and solid particles in the spiral groove, can break up larger particle clumps, prevent flow channel blockage, and extend continuous operation time. The rolling stabilizer integrated into the spiral stabilizer bar can roll adaptively when in contact with the well wall, making it suitable for deviated and horizontal well operations. It can effectively reduce the resistance of casing running and improve operational efficiency and safety. At the same time, it avoids local high pressure on the well wall from the stabilizer, effectively prevents stress concentration, reduces scraping and damage to the well wall, and helps maintain wellbore stability. The centralizer can automatically adjust the centralization method according to the wellbore trajectory. In the vertical section, it mainly uses rolling centralization to reduce resistance; in the inclined and horizontal sections, it combines sliding and rolling centralization to provide more balanced support force, ultimately ensuring that the casing maintains a high central position throughout the well section, laying the foundation for uniform distribution and good sealing of the cement sheath. This centralizer combines free rotation, up-and-down sliding, and fixing functions. During well entry, it can scrape off mud cake and clean the well wall, and improve the flow state during cementing. It has strong adaptability to working conditions and comprehensive efficiency, thereby effectively improving displacement efficiency and cementing reliability. Attached Figure Description

[0015] The invention will now be further described with reference to the accompanying drawings.

[0016] Figure 1 This is a three-dimensional schematic diagram of the present invention; Figure 2 for Figure 1 Enlarged view of point A in the middle; Figure 3 This is a half-sectional schematic diagram of the present invention; Figure 4 for Figure 3 Enlarged view at point B in the middle; Figure 5 This is a three-dimensional schematic diagram from another perspective of the present invention; Figure 6 for Figure 5 Enlarged view at point C; Figure 7 This is a schematic diagram of the oblique section of the present invention; Figure 8 for Figure 7 Enlarged view of point D in the middle.

[0017] In the picture: 100. Annular shell; 200. Spiral straightening strip; 300, spiral groove; 400. Pre-swirling element; 410. Anti-clogging ring; 411. Lower conical surface; 412. Upper conical surface; 420. Guide vane; 500, Rolling straightener; 510, Cavity; 520, Slide groove; 530, Slider; 540, Spherical sleeve; 550, Ball bearing; 560, Guide post; 570, Limiting block; 580, Spring; 600, limiting component; 610, annular groove; 620, expansion bladder strip; 630, airway; 640, spherical airbag. Detailed Implementation

[0018] The subject matter described herein will now be discussed with reference to exemplary embodiments. It should be understood that these embodiments are discussed only to enable those skilled in the art to better understand and implement the subject matter described herein, and changes may be made to the function and arrangement of the elements discussed without departing from the scope of this specification. Various processes or components may be omitted, substituted, or added as needed in the examples. Furthermore, features described in some examples may be combined in other examples.

[0019] Please see Figure 1 The present invention discloses a sleeve straightener, including an annular shell 100, wherein a plurality of spiral straighteners 200 are evenly distributed circumferentially on the outer circumferential surface of the annular shell 100, and a spiral groove 300 is formed between adjacent spiral straighteners 200. The lower end of the annular shell 100 is provided with a pre-swirling element 400, which is used to guide the fluid to reduce the deposition of solid particles in the spiral groove 300. Each set of spiral centralizers 200 is movably embedded with a rolling centralizer 500, which makes adaptive rolling contact with the well wall to avoid stress concentration and thus reduce the running resistance of the casing.

[0020] Specifically, during use, the stabilizer can rotate freely and slide up and down on the casing, or it can be fixed to a certain part of the casing with fixing screws. When the casing is inserted into the well, the stabilizer can scrape off mud cake and clean the well wall. When cementing, the pre-swirl effect of the pre-swirling element 400 combined with the main swirling effect of the spiral groove 300 can effectively reduce the problem of quicksand accumulation, improve the displacement efficiency, and extend the continuous operation time. The pre-swirl element 400 not only plays a guiding role, but also breaks up larger particles and further prevents blockage. In deviated and horizontal wells, the rolling stabilizer 500 can convert sliding friction into rolling friction, which can significantly reduce the running casing resistance, ensure uniform contact between the spiral stabilizer 200 and the well wall, avoid stress concentration, reduce damage to the well wall, and provide optimal stabilizer effect in different well sections. In vertical well sections, it mainly plays the advantage of rolling stabilizer to reduce resistance; in deviated and horizontal well sections, it increases the sliding stabilizer effect, provides greater support force, and ensures that the casing maintains high centering throughout the well section, laying the foundation for improving cementing quality.

[0021] It is worth noting that the pre-swirling element 400 in this invention pre-guides the fluid to form a preliminary swirling flow. Together with the spiral groove 300 between the spiral straightening bar 200, it enhances the main swirling flow effect, effectively improving the cleaning efficiency of the fluid on the well wall. At the same time, it reduces the deposition of mud and solid particles in the spiral groove 300, can break up larger particle clumps, prevent flow channel blockage, and extend continuous operation time. The rolling stabilizer 500 integrated within the spiral stabilizer bar 200 can roll adaptively when in contact with the well wall, making it suitable for deviated and horizontal well operations. It can effectively reduce the resistance of casing running and improve operational efficiency and safety. At the same time, it avoids local high pressure on the well wall from the stabilizer, effectively prevents stress concentration, reduces scraping and damage to the well wall, and helps maintain wellbore stability. The centralizer can automatically adjust the centralization method according to the wellbore trajectory. In the vertical section, it mainly uses rolling centralization to reduce resistance; in the inclined and horizontal sections, it combines sliding and rolling centralization to provide more balanced support force, ultimately ensuring that the casing maintains a high central position throughout the well section, laying the foundation for uniform distribution and good sealing of the cement sheath. This centralizer combines free rotation, up-and-down sliding, and fixing functions. During well entry, it can scrape off mud cake and clean the well wall, and improve the flow state during cementing. It has strong adaptability to working conditions and comprehensive efficiency, thereby effectively improving displacement efficiency and cementing reliability.

[0022] In one embodiment, please refer to Figure 1 and Figure 2 The pre-swirling component 400 includes an anti-blocking ring 410 disposed at the lower end of the annular shell 100. The anti-blocking ring 410 is circumferentially provided with a plurality of guide vanes 420, and the guide vanes 420 are staggered with the spiral straightening strips 200. Specifically, the centralizer moves down with the casing and rotates, thereby causing the anti-blocking ring 410 at the lower end of the annular shell 100 to rotate synchronously. When drilling fluid or cement slurry returns from the bottom of the well, it first impacts the anti-blocking ring 410. The anti-blocking ring 410 naturally guides the axially flowing fluid to the outer wall of the centralizer. The fluid then immediately flows through the corresponding guide vane 420, forcing the fluid to change from axial flow to rotational flow, thereby generating a pre-swirling flow. This smoothly guides the fluid to the corresponding spiral groove 300, avoiding turbulence and particle accumulation caused by the fluid directly impacting the bottom of the annular shell 100. The pre-swirling flow generates centrifugal force, and denser solid particles (such as rock fragments, barite, sand, etc.) are thrown towards the well wall under the action of centrifugal force. The high-speed solid-containing fluid flow thrown towards the well wall effectively washes and cleans the loose mud cake on the well wall, providing a clean interface for subsequent cement slurry bonding. The relatively clean fluid remains more in the central area near the centralizer. Since the solid particles have been thrown to the well wall area by centrifugal force, and the spiral groove 300 mainly deals with the fluid with fewer particles in the central area, the risk of particles entering and clogging the spiral groove 300 is greatly reduced. The solid particles will be directly carried back with the main fluid flow and will not be deposited in the spiral groove 300.

[0023] It should be noted that the anti-clogging ring 410 and the circumferentially staggered guide vanes 420 can effectively convert the axially flowing fluid into a rotating flow, generating a pre-swirling flow, avoiding the fluid from directly impacting the bottom of the annular shell 100, reducing the turbulence effect, and smoothly guiding the fluid into the spiral groove 300, thereby reducing the risk of particulate matter accumulation and clogging from the source. The centrifugal force generated by the pre-swirling flow throws denser solid particles (such as rock cuttings and barite) toward the well wall, forming a high-speed solid-containing fluid flow. This effectively removes the loose mud cake from the well wall, providing a clean and solid interface for cement slurry bonding and directly improving cementing quality. Centrifugal force is used to achieve solid-liquid separation. Solid particles are thrown to the well wall and return with the main fluid flow, while the fluid with fewer particles enters the spiral groove 300, reducing the possibility of the spiral groove 300 becoming blocked and extending the continuous operation capability of the centralizer under complex well conditions. The guide vanes 420 and the spiral centralizer bars 200 are staggered to achieve a smooth connection between the pre-swirling flow and the main swirling flow, enhance the coordination of the fluid dynamics of the entire process, and further optimize the cuttings carrying and displacement efficiency.

[0024] Further, please refer to Figure 3 and Figure 4 The anti-blocking ring 410 includes a lower conical surface 411 and an upper conical surface 412 that are connected to each other. The guide vane 420 is disposed on the lower conical surface 411. The slope of the upper conical surface 412 is greater than the slope of the lower conical surface 411. Specifically, the lower conical surface 411 has a gentler slope, which receives the upward-returning fluid and provides a smooth transition for it to enter the spiral groove 300; the upper conical surface 412 has a larger slope, which can quickly converge and accelerate the fluid, and achieve efficient change of fluid direction; the two work together to achieve fine and step-by-step control of fluid velocity and direction, and improve the efficiency and stability of pre-swirling flow generation. The steeply sloping upper conical surface 412 effectively prevents solid particles from stagnating and depositing on its own surface and guides the fluid at high speed to the spiral groove 300; the continuous smooth curved surface formed by the double conical surfaces greatly reduces the flow resistance, avoids the generation of turbulence and eddies, and enhances the structure's impact resistance and wear resistance to high-speed solid fluids. The double-conical structure serves as the base for the guide vane 420, providing the optimal hydrodynamic basis for the generation of pre-swirling flow. This ensures that the fluid can be transported to the guide vane 420 at the most ideal angle and speed, ultimately forming a strong and concentrated pre-swirling flow, which provides powerful impetus for subsequent wellbore cleaning and solid-liquid separation.

[0025] In yet another embodiment, please refer to Figure 5 and Figure 6 The rolling straightening member 500 includes a cavity 510 opened in the spiral straightening bar 200 and a spherical shell 540 movably embedded in the cavity 510. The cavity 510 is symmetrically provided with grooves 520 on both sides. The spherical shell 540 is symmetrically provided with sliders 530 at both ends that are adapted to slide with the grooves 520. A ball bearing 550 is movably embedded in the spherical shell 540. Specifically, the sliders 530 at both ends of the spherical sleeve 540 can slide freely in the corresponding grooves 520, thereby enabling the spherical sleeve 540 to adaptively extend and retract within the cavity 510, ensuring that the balls 550 embedded in the spherical sleeve 540 are always in rolling contact with the well wall, thereby effectively reducing the frictional resistance between the spiral straightening bar 200 and the well wall.

[0026] It should be noted that, through the sliding pair formed by the slider 530 and the groove 520, the spherical sleeve 540 can freely extend and retract within the cavity 510, so that the internal ball 550 can adapt to different well diameters and irregular well walls, always maintaining rolling contact with the well wall, efficiently converting traditional sliding friction into rolling friction, and reducing the frictional resistance during the casing lowering process. The rolling contact method of the 550 ball avoids rigid scraping and point load between the centralizing bar and the well wall, so that the contact stress is evenly distributed, effectively preventing local cutting and damage to the well wall. It is particularly beneficial to protect easily collapsible formations and filter cake structures and maintain wellbore stability. This telescopic rolling structure enables the centralizer to smoothly pass through complex well sections such as reduced diameter and dogleg, providing stable and continuous rolling centralizing action throughout the entire well section of vertical, deviated, and horizontal wells, ensuring smooth casing installation and high centralization throughout the well section. The spherical sleeve 540 covers and protects the balls 550, preventing them from falling off or getting stuck by impurities in the drilling fluid, thus ensuring the long-term effectiveness of the rolling function; the sliding pair design disperses lateral loads and improves the durability and reliability of the overall mechanical structure.

[0027] Further, please refer to Figure 7 and Figure 8 The guide post 560 is fixed inside the slide groove 520, the slider 530 is slidably sleeved on the corresponding guide post 560, the end of the guide post 560 is provided with a limit block 570, and a spring 580 that abuts against the slider 530 is movably sleeved on the guide post 560. Specifically, the guide post 560 guides the slider 530 to ensure the smoothness of the extension and retraction adjustment of the spherical sleeve 540 and the ball 550. The spring 580 applies elastic force to the slider 530, so that the ball 550 can always be in contact with the well wall, reducing the frictional resistance between the spiral straightening bar 200 and the well wall. The limiting block 570 can limit the slider 530 to prevent the spherical sleeve 540 from accidentally coming out of the cavity 510.

[0028] It is worth noting that the spring 580 continuously applies elastic force to the slider 530, providing a constant contact positive pressure to the ball 550, ensuring that it always maintains reliable rolling contact with the well wall when passing through the section with changing well diameter or irregular well wall, completely avoiding sliding friction caused by insufficient contact force, thereby continuously and effectively reducing frictional resistance. The slider 530 is slidably sleeved on the guide post 560, providing precise linear guidance for the telescopic movement of the spherical sleeve 540, effectively preventing it from deflecting or getting stuck during the movement, ensuring the smooth and stable contact between the ball 550 and the well wall, and enhancing its response capability and reliability under dynamic working conditions. The limiting block 570 and the end of the guide post 560 form a mechanical limit, which reliably prevents the slider 530 from slipping off the guide post 560 under unexpected excessive displacement, avoids the risk of the spherical sleeve 540 accidentally coming out of the cavity 510, and greatly improves the structural safety and service life of the entire rolling centralizer 500 under complex well conditions. The buffering effect of spring 580 gives ball bearing 550 a smooth contact characteristic, enabling it to adaptively and smoothly traverse local protrusions or depressions on the well wall surface. This not only further reduces the downward resistance but also effectively buffers the impact on the well wall and the centralizer itself, achieving the dual purpose of protecting the well wall and the equipment.

[0029] In further embodiments, please refer to Figure 7 It also includes a limiting member 600 disposed inside the annular housing 100, the limiting member 600 being used to axially limit the annular housing 100 to prevent the centralizer from axially sliding with the sleeve; Further, please refer to Figure 7 and Figure 8 The limiting member 600 includes an annular groove 610 formed on the inner circumferential surface of the annular shell 100, and an expansion bladder strip 620 adapted to the sleeve is embedded in the annular groove 610. Specifically, the stabilizer is fitted onto the outside of the casing and can be fixed to the casing with bolts or the like. The expansion bladder strip 620 on the inner side of the annular housing 100 is precisely embedded in the corresponding annular limiting groove on the outer circumference of the casing, thereby further preventing axial slippage between the stabilizer and the casing, and improving the alignment between the annular housing 100 and the casing.

[0030] It should be noted that the limiting component 600 and the external bolt fixing method form a dual protection mechanism. The expansion bladder strip 620 embedded in the annular groove 610 can be tightly embedded in the annular limiting groove on the outer wall of the casing. Through physical interlocking, it effectively resists axial force and fundamentally prevents the centralizer from axially sliding with the casing under the impact of drilling fluid or casing movement, thus ensuring the absolute reliability of the centralizer positioning. The expansion bladder strip 620 is uniformly wrapped around and embedded in the casing limiting groove in the circumferential direction. It can automatically compensate for small centering deviations, so that the annular shell 100 and the casing always maintain a high degree of concentricity, providing a basic guarantee for the centering of the casing throughout the well section, and thus creating favorable conditions for the formation of a uniform cement sheath. The expansion bladder strip 620 is made of flexible material. After being embedded in the limiting groove, it can provide a firm lock and absorb the vibration and impact energy during downhole operations, reduce stress concentration, and improve the overall stability and durability of the connection between the centralizer and the casing. This limiting structure can be directly embedded and installed on the existing sleeve annular groove without additional complicated operations. In conjunction with the bolt fixing method, it greatly improves the installation efficiency and connection reliability of the centralizer on the sleeve, which helps to shorten the on-site operation time.

[0031] Further, please refer to Figure 8 The cavity 510 is provided with a spherical airbag 640 that abuts against the spherical shell 540, and the expansion strip 620 is connected to each spherical airbag 640 by an air passage 630. Specifically, the spherical airbag 640 is always in contact with the spherical casing 540. When the centralizer passes through the narrowing section of the well wall, the spherical casing 540 is squeezed back into the cavity 510 by the well wall, which can press the spherical airbag 640, causing the gas in the spherical airbag 640 to enter the expansion bar 620 through the air passage 630, which in turn causes the expansion bar 620 to expand further, increasing the contact force between the expansion bar 620 and the casing limiting groove, effectively preventing the centralizer from axially slipping with the casing due to the large resistance when passing through the narrowing section.

[0032] It is worth noting that when the centralizer passes through the narrowing section of the wellbore, the wellbore pressure forces the spherical casing 540 to retract and press the spherical airbag 640. The gas inside is forced into the expansion bladder strip 620 through the air passage 630, causing it to expand further and automatically increasing the contact pressure on the casing limiting groove. When the downhole resistance increases, it automatically enhances the anti-slip capability, greatly improving the axial fixation reliability of the centralizer in complex well sections. The greater the resistance in the narrowing section, the stronger the locking force is triggered, thus ensuring that the centralizer will not slip relative to the casing when forcibly passing through, effectively avoiding downhole accidents caused by centralizer displacement and significantly improving operational safety. The system resists high resistance by enhancing the locking force, avoiding scratches and damage to the casing and wellbore caused by the centralizer getting stuck or sliding and being forcibly dragged. This plays a positive role in protecting the completion quality and wellbore integrity.

[0033] The specific embodiments of the present invention have been described above. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention, all of which are within the protection scope of the present invention.

Claims

1. A casing straightener, comprising an annular housing (100), wherein a plurality of spiral straightening strips (200) are evenly distributed circumferentially on the outer circumferential surface of the annular housing (100), and spiral grooves (300) are formed between adjacent spiral straightening strips (200); characterized in that: The lower end of the annular shell (100) is provided with a pre-swirling element (400), which is used to guide the fluid to reduce the deposition of solid particles in the spiral groove (300); Each set of spiral straightening bars (200) is equipped with a rolling straightening element (500), which makes adaptive rolling contact with the well wall to avoid stress concentration and thus reduce the running resistance of the casing.

2. The casing centralizer according to claim 1, characterized in that, The pre-swirling component (400) includes an anti-clogging ring (410) disposed at the lower end of the annular housing (100), and the anti-clogging ring (410) is provided with a plurality of guide vanes (420) in the circumferential direction.

3. A casing centralizer according to claim 2, characterized in that, The guide vanes (420) and spiral straightening strips (200) are staggered.

4. A casing centralizer according to claim 2, characterized in that, The anti-blocking ring (410) includes a lower conical surface (411) and an upper conical surface (412) that are connected to each other, and the guide vane (420) is disposed on the lower conical surface (411).

5. A casing centralizer according to claim 4, characterized in that, The slope of the upper conical surface (412) is greater than the slope of the lower conical surface (411).

6. A casing centralizer according to claim 1, characterized in that, The rolling straightening component (500) includes a cavity (510) opened in the spiral straightening bar (200) and a spherical shell (540) movably embedded in the cavity (510). The cavity (510) is symmetrically provided with grooves (520) on both sides. The spherical shell (540) is symmetrically provided with sliders (530) at both ends that are adapted to slide with the grooves (520). Ball bearings (550) are movably embedded in the spherical shell (540).

7. A casing centralizer according to claim 6, characterized in that, A guide post (560) is fixed inside the groove (520). The slider (530) is slidably sleeved on the corresponding guide post (560). A limit block (570) is provided at the end of the guide post (560). A spring (580) that abuts against the slider (530) is movably sleeved on the guide post (560).

8. A casing centralizer according to claim 6, characterized in that, It also includes a limiting member (600) disposed inside the annular housing (100), the limiting member (600) being used to axially limit the annular housing (100) to prevent the centralizer from axially sliding with the sleeve.

9. A casing centralizer according to claim 8, characterized in that, The limiting member (600) includes an annular groove (610) formed on the inner circumferential surface of the annular shell (100), and an expansion bladder strip (620) adapted to the sleeve is embedded in the annular groove (610).

10. A casing straightener according to claim 9, characterized in that, The cavity (510) is provided with a spherical airbag (640) that abuts against the spherical shell (540), and the expansion strip (620) and each spherical airbag (640) are connected by an air passage (630).

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