Insertion double valve float collar

Abstract

The application relates to the technical field of oil and gas well cementing tools, in particular to an insertion type double-valve float collar which comprises a shell cylinder, a recoverable plug assembly, a first valve mechanism and a second valve mechanism. A central passage is arranged in the shell cylinder, the recoverable plug assembly is arranged in the passage, axial fixation and release are realized through a locking and unlocking mechanism, the first valve mechanism and the second valve mechanism are arranged below the plug assembly in an axial direction, and are used for realizing one-way fluid interception, and a key sealing component adopts a polycrystalline diamond compact material. The application can solve the problems of one-time use of the plug, complex tool recovery and insufficient fluid control reliability.

Description

Technical Field

[0001] This utility model belongs to the technical field of oil and gas well cementing tools, specifically an insertable double-valve float collar. Background Technology

[0002] Float collars are critical downhole tools used in cementing operations to guide cement slurry downwards and prevent backflow. They are typically installed at specific locations in the casing string to ensure that the cement slurry effectively fills the annular space and seals the wellbore. During cementing, the cementing plug descends with the cement slurry, working in conjunction with the float collar to control and seal the flow path, thus ensuring the continuity and reliability of the operation. The float collar structure usually includes a one-way valve assembly to control the fluid flow direction and is adaptable to different types of plugs and operating conditions, making it valuable in oil and gas drilling and well completion.

[0003] The functionality of a floating hoop device relies on the stability and sealing performance of its internal valve body structure, while also needing to adapt to frequent field operations. Therefore, high demands are placed on material durability, ease of operation, and overall safety. In practical applications, accessories made of different materials are often used to improve the tool's resistance to abrasion and impact, and its adaptability to complex well conditions is enhanced through optimized structural design.

[0004] However, the existing floating hoop devices are mostly disposable cement injection plugs, which are difficult to reuse. In addition, the operation steps when lifting the tool are relatively specific, requiring rotation before lifting. Some structures have room for improvement in terms of fluid control redundancy and operational flexibility, thus limiting their adaptability to multiple working conditions. Utility Model Content

[0005] This utility model provides an insertable double-valve float hoop, which aims to solve the technical problems of existing float hoop devices, such as the cement injection plug being a disposable consumable, the tool removal steps being cumbersome, and the fluid control redundancy being insufficient.

[0006] To achieve the above objectives, this utility model provides the following technical solution:

[0007] An insertable dual-valve float collar includes an outer shell, a retrievable plug assembly, a first valve mechanism, and a second valve mechanism, wherein:

[0008] The outer shell is a hollow tubular structure, and its inner wall defines a central channel through which fluid flows. Both ends of the outer shell are provided with external threads for connecting other tubular columns.

[0009] The recyclable plug assembly is detachably disposed in the central channel of the outer shell. The recyclable plug assembly includes a plug rod, a sealing head, and a connecting head. The plug rod is a long rod structure. The sealing head is fixedly connected to the bottom end of the plug rod. The connecting head is fixedly connected to the top end of the plug rod. The connecting head has an irregular groove inside for cooperating with the salvage tool.

[0010] The first valve mechanism and the second valve mechanism are axially spaced below the recyclable plug assembly along the central channel, and both the first valve mechanism and the second valve mechanism are used to unidirectionally cut off the fluid in the central channel.

[0011] Optionally, a locking and unlocking mechanism is also fixedly connected to the inner wall of the outer shell. The locking and unlocking mechanism is used to axially lock or unlock the recyclable plug assembly. The locking and unlocking mechanism includes a guide sleeve and a locking pin. The guide sleeve is fixed to the inner wall of the outer shell and has a J-shaped guide groove. A locking pin that cooperates with the J-shaped guide groove is fixedly connected to the outer wall of the plug rod. The locking pin moves along the trajectory of the J-shaped guide groove.

[0012] Optionally, the J-shaped guide groove includes an axial guide groove, a circumferential guide groove, and a locking groove. The axial guide groove extends axially along the guide sleeve. The circumferential guide groove communicates with one end of the axial guide groove and extends circumferentially along the guide sleeve. The locking groove communicates with the end of the circumferential guide groove away from the axial guide groove. When the locking pin is in the locking groove, the recyclable plug assembly is axially locked.

[0013] Optionally, the first valve mechanism includes a first valve seat and a first valve plate. The first valve seat is an annular structure and fixed to the inner wall of the outer shell. The upper end face of the first valve seat is an inclined sealing surface. One side of the first valve plate is rotatably connected to the inner wall of the outer shell via a pivot. In its natural state, the first valve plate overlaps the sealing surface of the first valve seat. Both the first valve plate and the first valve seat are made of polycrystalline diamond composite sheet material.

[0014] Optionally, the first valve mechanism further includes a torsion spring, which is sleeved on the outside of the pivot. The two ends of the torsion spring abut against the inner wall of the outer casing and the back of the first valve plate, respectively. The torsion spring applies a restoring torque to the first valve plate, tending towards a closed position. A mounting groove is formed on the inner wall of the outer casing corresponding to the pivot position, and the two ends of the pivot are embedded in the mounting groove.

[0015] Optionally, the second valve mechanism includes a second valve seat, a valve core, a guide frame, and a return spring. The second valve seat is an annular structure and is fixed to the inner wall of the outer casing below the first valve mechanism. The guide frame is fixed below the second valve seat. The valve core is slidably inserted through the center of the guide frame along the axial direction. The return spring is sleeved on the valve stem of the valve core, and the two ends of the return spring abut against the flanges of the guide frame and the valve core, respectively.

[0016] Optionally, the valve core includes a valve head and a valve stem. The lower surface of the valve head is a tapered sealing surface that matches the upper surface of the second valve seat. Both the valve head and the second valve seat are made of polycrystalline diamond composite material. The guide frame has a structure in which multiple spokes connect to a central bushing, forming a fluid channel between the spokes. The end face of the sealing head is also made of polycrystalline diamond composite material.

[0017] Optionally, the inner wall of the outer shell cylinder is also integrally formed with an annular pressure-bearing step above the first valve mechanism. The upper surface of the annular pressure-bearing step is a flat annular sealing surface. The inner diameter of the annular pressure-bearing step is consistent with the nominal diameter of the central channel, and is used to receive the drill pipe plug.

[0018] Optionally, a filter grid is fixedly connected to the bottom of the outer shell, and the filter grid has multiple filter holes evenly distributed on it. The diameter of the filter holes is smaller than the minimum movement gap between the first valve mechanism and the second valve mechanism. The outer periphery of the sealing head of the recyclable plug assembly is provided with multiple annular sealing grooves, and an O-ring is installed in each annular sealing groove.

[0019] This utility model provides an insertable double-valve float clamp, which has the following beneficial effects:

[0020] This insert-type dual-valve float collar features a recyclable plug assembly that engages with the outer shell via a locking and unlocking mechanism. After operation, the plug assembly can be rotated and lifted using a specialized retrieval tool, allowing for complete removal and enabling the reuse of core components, significantly reducing material consumption per operation. The first and second valve mechanisms form a double unidirectional sealing barrier; if one valve mechanism fails to seal properly, the other remains closed, greatly improving the reliability and safety of preventing cement slurry backflow. Key pressure-bearing and wear-prone components such as the valve plate, valve seat, and sealing head are made of polycrystalline diamond composite material, which possesses extremely high hardness and wear resistance, significantly extending the service life of the device under harsh conditions such as sandy conditions. The annular pressure-bearing step on the inner wall of the outer shell provides a stable bearing and sealing surface for the standard drill pipe plug, expanding the device's adaptability to various operating conditions. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the overall structure of the insert-type double valve float hoop of this utility model;

[0022] Figure 2 This is a cross-sectional view of the internal structure of the insertable dual-valve float hoop according to an embodiment of this application;

[0023] Figure 3 This is a partially enlarged schematic diagram showing the cooperation between the recyclable plug assembly and the locking and unlocking mechanism of this utility model.

[0024] Explanation of reference numerals in the attached drawings: 1. Outer shell; 2. Recyclable plug assembly; 3. First valve mechanism; 4. Second valve mechanism; 5. Plug rod; 6. Sealing head; 7. Connecting head; 8. Irregular groove; 9. Guide sleeve; 10. J-shaped guide groove; 11. Locking pin; 12. First valve seat; 13. First valve plate; 14. Second valve seat; 15. Valve core; 16. Guide frame; 17. Return spring. Detailed Implementation

[0025] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0026] Please see Figures 1 to 3 This utility model provides an insertable double-valve float collar, which is mainly used in oil and gas well cementing operations. It is installed at the bottom of the casing string and its internal structure controls the unidirectional delivery of working fluids such as cement slurry. After the operation is completed, its core components are recovered.

[0027] Reference Figure 1 and Figure 2 The overall structure of this insertable dual-valve float hoop includes an outer shell 1, a retrievable plug assembly 2, a first valve mechanism 3, and a second valve mechanism 4. The outer shell 1 is the basic load-bearing component of the entire device. The retrievable plug assembly 2 is detachably mounted on the upper part of the outer shell 1. The first valve mechanism 3 and the second valve mechanism 4 are sequentially arranged below the retrievable plug assembly 2 along the axial direction of the outer shell 1 from top to bottom.

[0028] Specifically, the outer shell 1 is a thick-walled hollow tubular structure open at both ends, made of high-strength alloy steel to withstand the high temperature and pressure environment downhole. The inner wall of the outer shell 1 is smooth and straight, defining a central channel for fluid passage. Standard trapezoidal external threads are machined on the top and bottom outer walls of the outer shell 1. The specifications of these threads match the casing fittings used in oilfield operations, allowing the device to be directly screwed onto the corresponding position of the casing string. A filter grid is also fixedly connected to the bottom of the outer shell 1. This filter grid is welded to the end face of the outer shell 1 and has multiple evenly distributed circular filter holes. The diameter of these filter holes is precisely calculated, and its size is smaller than the minimum working clearance between the moving parts inside the first valve mechanism 3 and the second valve mechanism 4. Thus, when fluid passes through, larger solid particles or impurities are blocked outside the filter grid and do not enter the valve mechanism, thereby maintaining the normal operation and sealing of the valve mechanism.

[0029] On the inner wall of the outer casing 1, above the first valve mechanism 3, an integrally formed annular pressure-bearing step is formed. This annular pressure-bearing step is a structure formed by locally radially thickening the inner wall of the outer casing 1, and its upper surface is a flat annular sealing surface perpendicular to the axis of the outer casing 1. The inner diameter of this annular pressure-bearing step is consistent with the nominal diameter of the central channel, without creating additional throttling. In some cementing operations, when conventional drill pipe plugs are required, after being pumped to this position, the bottom of the plug will sit on the sealing surface of this annular pressure-bearing step, forming effective pressure isolation.

[0030] Please continue reading. Figure 2 and Figure 3 The recyclable plug assembly 2 is one of the core components of this device, and the entire assembly can be completely inserted into or removed from the outer shell 1. The recyclable plug assembly 2 includes a long rod-shaped plug rod 5, a sealing head 6 fixed to the bottom end of the plug rod 5, and a connecting head 7 fixed to the top end of the plug rod 5.

[0031] The plug rod 5 is a solid metal rod, its length extending through most of the retrievable plug assembly 2. The connector 7 is a cylindrical component with a thickened flange at the top, its lower part fixed to the top of the plug rod 5 by threaded connection or welding. Inside the connector 7, a shaped groove 8 is formed along its axial center. The cross-sectional shape of the groove 8 is non-circular, for example, hexagonal or a specific spline shape, and its shape and size match the male end of a dedicated retrieval tool. When the plug assembly 2 needs to be retrieved, the retrieval tool is lowered and inserted into the connector 7, and the male end of the retrieval tool fully engages with the shaped groove 8, thereby transmitting torque and axial lifting force to the plug rod 5.

[0032] The sealing head 6 is a solid component with a conical or hemispherical head at the lower end, and its upper part is fixed to the bottom end of the plug rod 5 by a threaded connection. The maximum outer diameter of the sealing head 6 is slightly smaller than the inner diameter of the outer shell 1. Multiple annular sealing grooves are machined on the outer circumferential surface of the sealing head 6, spaced apart axially, with an O-ring installed in each groove. These O-rings are made of oil-resistant, high-temperature-resistant hydrogenated nitrile rubber. When the recyclable plug assembly 2 is installed inside the outer shell 1, these O-rings are radially compressed, and their outer edges tightly adhere to the inner wall of the outer shell 1, forming multiple dynamic sealing barriers that isolate the fluid on both sides of the central channel. The lower end face of the sealing head 6, which directly bears the downhole fluid pressure and erosion, is inlaid or sintered with a layer of polycrystalline diamond composite material. This material has extremely high hardness and wear resistance, which can significantly extend the service life of the sealing head 6 under the erosion of fluids containing solid particles.

[0033] To reliably secure the recyclable plug assembly 2 within the outer casing 1 while allowing it to be unlocked and removed when needed, this device incorporates a locking and unlocking mechanism. This mechanism includes a guide sleeve 9 fixed to the inner wall of the outer casing 1 and a locking pin 11 fixed to the outer wall of the plug rod 5. The guide sleeve 9 is a thin-walled cylinder, fixed to the upper inner wall of the outer casing 1 by welding or interference fit. One or more J-shaped guide grooves 10 (usually two, symmetrically distributed at 180 degrees) are formed on the wall of the guide sleeve 9.

[0034] Reference Figure 3 Each J-shaped guide groove 10 consists of three connected groove segments: an axial guide groove extending along the axial direction of the guide sleeve 9, a circumferential guide groove connected to the lower end of the axial guide groove and extending circumferentially along the guide sleeve 9, and a locking groove connected to the end of the circumferential guide groove. The locking groove is a short, slightly upward-sloping or horizontal blind groove. The locking pin 11 is a short cylindrical pin, one end of which is fixed to the outer wall of the plug rod 5, and the other end extends radially, with its diameter matching the groove width of the J-shaped guide groove 10.

[0035] When installing the recyclable plug assembly 2, lower the plug assembly 2 so that its locking pin 11 is aligned with the axial guide groove inlet of the J-shaped guide groove 10 on the guide sleeve 9. Continue lowering, and the locking pin 11 slides down along the axial guide groove to the bottom. Then, rotate the entire plug assembly 2 clockwise, and the locking pin 11 moves accordingly within the circumferential guide groove. When the locking pin 11 moves to the end of the circumferential guide groove, due to the presence of the locking groove, the plug assembly 2, under its own weight or a slight upward action, will cause the locking pin 11 to enter the locking groove. At this time, the axial movement of the locking pin 11 is restricted by the lower wall of the locking groove, thereby axially locking the entire recyclable plug assembly 2 within the outer casing 1, preventing it from moving upward due to the pressure impact of the lower fluid.

[0036] Please continue reading. Figure 2 The first valve mechanism 3 is a swing-type one-way valve structure, located directly below the recyclable plug assembly 2. This mechanism includes a first valve seat 12 and a first valve plate 13. The first valve seat 12 is an annular steel component, securely fixed to the inner wall of the outer casing 1 by welding. The upper surface of the first valve seat 12 is machined into a downwardly inclined sealing surface, which is precision ground and also covered with a layer of polycrystalline diamond composite material. Two mounting slots are symmetrically formed on the inner wall of the outer casing 1, corresponding to the rotation axis of the first valve plate 13. The two ends of a pivot are respectively embedded in these two mounting slots. The first valve plate 13 is an approximately circular plate-shaped component, one side of which is rotatably connected to the pivot through a shaft hole. The sealing surface of the first valve plate 13 is also made of polycrystalline diamond composite material. A torsion spring is sleeved on the outside of the pivot, with its two ends abutting against the inner wall of the outer casing 1 and the back of the first valve plate 13, respectively. In its natural state without external force, the restoring torque applied by the torsion spring will drive the first valve plate 13 to rotate about the pivot until its sealing surface fully overlaps and presses against the inclined sealing surface of the first valve seat 12, thereby sealing the central channel.

[0037] The second valve mechanism 4 is a lift-type check valve structure, which is axially positioned below the first valve mechanism 3, maintaining a certain distance between them. This mechanism includes a second valve seat 14, a valve core 15, a guide frame 16, and a return spring 17. The second valve seat 14 is also an annular steel component, fixed to the inner wall of the outer casing 1 by welding. Its upper surface is machined into a conical sealing surface, and the surface material is also polycrystalline diamond composite sheet.

[0038] The guide frame 16 is fixed below the second valve seat 14, and its structure consists of multiple radially distributed spokes connected to a central bushing. The large space formed between the spokes constitutes a fluid channel. The valve core 15 includes an upper valve head and a lower valve stem. The valve stem is a smooth round rod that can slide up and down axially within the central bushing of the guide frame 16, and the central bushing provides precise guidance for the movement of the valve stem. The lower surface of the valve head is machined into a tapered sealing surface that matches the upper surface of the second valve seat 14, and this sealing surface is also made of polycrystalline diamond composite material. A flange is provided at the lower part of the valve stem. The return spring 17 is a cylindrical helical compression spring, which is sleeved on the valve stem of the valve core 15, with its upper end abutting against the lower surface of the guide frame 16 and its lower end abutting against the flange on the valve stem. In its natural state, the return spring 17 is in a pre-compressed state, and its elastic force continuously pushes the valve core 15 upward, so that the valve head of the valve core 15 is pressed tightly against the second valve seat 14, thus closing the central channel.

[0039] The working process of this utility model device in cementing operations is as follows:

[0040] First, surface preparation and the running-in process are carried out. The retrievable plug assembly 2 is inserted into the outer casing 1, and the locking pin 11 is locked in the locking groove of the J-shaped guide groove 10 by pressing down and rotating. Then, the assembled insert-type dual-valve float collar is screwed onto the casing string at the predetermined depth and run into the well together with the casing string.

[0041] When the cement slurry is pumped in, it flows downwards from the top of the casing string and enters the central channel of the device. The high-pressure cement slurry first acts on the upper surface of the first valve plate 13, and the pressure it generates overcomes the restoring torque of the torsion spring, pushing the first valve plate 13 downwards to form a flow channel. Subsequently, the cement slurry continues to flow downwards, acting on the valve head of the valve core 15. When the pressure of the cement slurry is sufficient to overcome the preload of the return spring 17 and the hydrostatic pressure of the well fluid below, the valve core 15 is pushed downwards, away from the second valve seat 14, opening the second flow channel. The cement slurry flows between the spokes of the guide frame 16 and finally enters the annulus between the casing and the well wall through the bottom filter grid.

[0042] When the cement slurry pumping is completed and pumping stops, the fluid pressure inside the casing drops rapidly. At this time, under the action of the torsion spring, the first valve plate 13 immediately flips upward around the pivot and closes, its sealing surface re-adhering to the first valve seat 12. Simultaneously, under the elastic force of the return spring 17, the valve core 15 also moves upward rapidly, its conical sealing surface pressing back against the second valve seat 14. At this time, both valve mechanisms are in the closed state. Since the density of the cement slurry in the annulus is higher than the density of the displacement fluid inside the casing, an upward backflow pressure is generated. This backflow pressure acts on the lower surface of the first valve plate 13 and the valve head of the valve core 15, and this pressure further presses the first valve plate 13 and the valve core 15 more tightly against their respective valve seats, thereby enhancing the sealing effect. The first valve mechanism 3 and the second valve mechanism 4 constitute a double one-way sealing barrier. Even if one valve mechanism experiences a slight leakage for some reason, the other valve mechanism still maintains an effective seal, preventing the cement slurry from flowing back into the casing.

[0043] After the cement slurry has set, if further drilling or other operations are required, the plug assembly 2 needs to be retrieved. At this time, a drill string equipped with a special retrieval tool is lowered from the surface. The male end of the retrieval tool engages with the groove 8 in the connector 7. The drill string is first moved slightly downwards to disengage the locking pin 11 from the locking groove. Then, the drill string is rotated counterclockwise, causing the plug assembly 2 to rotate as well, moving the locking pin 11 along the circumferential guide groove until it aligns with the axial guide groove. Finally, the drill string is lifted, and the locking pin 11 slides upwards along the axial guide groove, allowing the entire retrievable plug assembly 2 to be completely removed from the wellhead from the outer casing 1. After cleaning, inspection, and replacement of the O-rings, the retrieved plug assembly 2 can be used for the next operation. At this point, an unobstructed full-bore passage is formed inside the outer casing 1 remaining downhole.

Claims

1. An insertable double-valve float collar, characterized in that: It includes an outer shell (1), a recyclable plug assembly (2), a first valve mechanism (3), and a second valve mechanism (4), wherein: The outer shell cylinder (1) is a hollow tubular structure, and its inner wall defines a central channel through which fluid flows. Both ends of the outer shell cylinder (1) are provided with external threads. The recyclable plug assembly (2) is detachably disposed in the central channel of the outer shell cylinder (1). The recyclable plug assembly (2) includes a plug rod (5), a sealing head (6), and a connecting head (7). The plug rod (5) is a long rod structure. The sealing head (6) is fixedly connected to the bottom end of the plug rod (5). The connecting head (7) is fixedly connected to the top end of the plug rod (5). The connecting head (7) has an irregular groove (8) inside. The first valve mechanism (3) and the second valve mechanism (4) are axially spaced below the recyclable plug assembly (2) along the central channel. Both the first valve mechanism (3) and the second valve mechanism (4) are used to unidirectionally cut off the fluid in the central channel.

2. The insert-type double-valve float collar according to claim 1, characterized in that: A locking and unlocking mechanism is also fixedly connected to the inner wall of the outer shell (1). The locking and unlocking mechanism includes a guide sleeve (9) and a locking pin (11). The guide sleeve (9) is fixed to the inner wall of the outer shell (1). A J-shaped guide groove (10) is provided on the guide sleeve (9). A locking pin (11) that cooperates with the J-shaped guide groove (10) is fixedly connected to the outer wall of the plug rod (5).

3. The insertable double-valve float collar according to claim 2, characterized in that: The J-shaped guide groove (10) includes an axial guide groove, a circumferential guide groove and a locking groove. The axial guide groove extends along the axial direction of the guide sleeve (9). The circumferential guide groove is connected to one end of the axial guide groove and extends along the circumferential direction of the guide sleeve (9). The locking groove is connected to the end of the circumferential guide groove away from the axial guide groove.

4. The insert-type double-valve float collar according to claim 1, characterized in that: The first valve mechanism (3) includes a first valve seat (12) and a first valve plate (13). The first valve seat (12) is an annular structure and is fixed to the inner wall of the outer shell cylinder (1). The upper end face of the first valve seat (12) is an inclined sealing surface. One side of the first valve plate (13) is rotatably connected to the inner wall of the outer shell cylinder (1) via a pivot. The first valve plate (13) overlaps the sealing surface of the first valve seat (12) in its natural state. Both the first valve plate (13) and the first valve seat (12) are made of polycrystalline diamond composite sheet material.

5. The insertable double-valve float collar according to claim 4, characterized in that: The first valve mechanism (3) also includes a torsion spring, which is sleeved on the outside of the pivot, and the two ends of the torsion spring abut against the inner wall of the outer shell cylinder (1) and the back of the first valve plate (13), respectively.

6. The insert-type double-valve float collar according to claim 1, characterized in that: The second valve mechanism (4) includes a second valve seat (14), a valve core (15), a guide frame (16), and a return spring (17). The second valve seat (14) is an annular structure and is fixed to the inner wall of the outer shell (1) below the first valve mechanism (3). The guide frame (16) is fixed below the second valve seat (14). The valve core (15) can slide axially through the center of the guide frame (16). The return spring (17) is sleeved on the valve stem of the valve core (15). The two ends of the return spring (17) abut against the flanges of the guide frame (16) and the valve core (15), respectively.

7. The insert-type double-valve float collar according to claim 6, characterized in that: The valve core (15) includes a valve head and a valve stem. The lower surface of the valve head is a conical sealing surface that matches the upper surface of the second valve seat (14). Both the valve head and the second valve seat (14) are made of polycrystalline diamond composite material.

8. The insert-type double-valve float collar according to claim 1, characterized in that: The inner wall of the outer shell cylinder (1) is located above the first valve mechanism (3) and is integrally formed with an annular pressure-bearing step.

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