A high pressure resistant rotating liner cement head

Abstract

The application discloses a high-pressure-resistant rotary tail pipe cementing head, and relates to the technical field of oil drilling equipment, which comprises a shell assembly and a rotary body penetrating in the shell assembly, wherein the shell assembly comprises a rotary seat provided with a fluid inlet, and an annular sealing gap is formed between the rotary body and the rotary seat; bearings are installed on the two ends of the rotary seat away from each other, and the outer ring seats of the bearings are fixedly connected with the rotary seat. The primary sealing group and the secondary sealing group with different hardness are arranged, the function is decoupled, the primary sealing group with high hardness bears most of the fluid pressure impact by using the high modulus characteristics, the damage of the sealing root being extruded into the metal gap under high pressure is effectively prevented, the secondary sealing group with low hardness can tightly adhere to the surface of the rotary body after being pressed by using the excellent elastic deformation capacity, the flexible buffer is provided, the machining error and the rotary runout are effectively compensated, and the sealing property under the high-pressure environment is ensured.

Description

Technical Field

[0001] This invention relates to the field of oil drilling equipment technology, specifically to a high-pressure resistant rotary tailpipe cementing head. Background Technology

[0002] Cement heads are core wellhead equipment in oil and gas drilling cementing operations. They are mainly installed on the top of the drill pipe and serve as a key hub connecting the surface cementing equipment and the downhole drill string. Their core function is to establish a high-pressure channel while maintaining the rotation or reciprocating motion of the drill string, and to inject fluids such as cement slurry and drilling fluid into the wellbore to complete cementing, slurry replacement, and other process operations. In particular, high-pressure resistant rotary cement heads need to ensure the reliability of the rotary dynamic seal under extremely high working pressure (usually 35MPa-70MPa) and complex mechanical loads.

[0003] In oil drilling cementing operations, the cement head is a key component connecting the cementing equipment and the drill pipe, used to inject cement slurry and perform other operations. However, traditional cement head sealing structure designs often have limitations. Under high-pressure conditions, they suffer from poor sealing performance, easy leakage, rapid wear of rotating parts, and short service life, which seriously affect the efficiency and quality of cementing operations and may even lead to safety accidents. They cannot meet the requirements of modern oil drilling engineering for high-pressure and high-efficiency cementing operations.

[0004] Specifically, existing technologies typically employ a single hardness group of seals, which leads to an irreconcilable physical contradiction: if the seal hardness is too high, although it has strong resistance to high-pressure extrusion, it has poor fit to the rotating shaft, and gap leakage is easily generated when the shaft system vibrates; if the seal hardness is too low, although it has good fit under low pressure, it is prone to root extrusion and peeling under high-pressure impact, resulting in rapid seal failure. Summary of the Invention

[0005] The purpose of this invention is to provide a high-pressure resistant rotary tailpipe cement head that solves the problem of rotary seal failure under extreme working conditions by using the synergistic effect of the hardness differential sealing group and the floating isolation ring, utilizing the primary hard seal to resist high pressure extrusion and the secondary soft seal to achieve dynamic compensation.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0007] A high-pressure resistant rotary tailpipe cementing head includes a housing assembly and a rotating body disposed within the housing assembly. The housing assembly includes a rotating seat with a fluid inlet, and an annular sealing gap is formed between the rotating body and the rotating seat. Bearings are installed at both ends of the rotating seat, with the outer ring of the bearing fixedly connected to the rotating seat and the inner ring of the bearing fixedly connected to the rotating body. An upper sealing assembly and a lower sealing assembly are disposed within the annular sealing gap, and the upper and lower sealing assemblies are symmetrically distributed axially about the fluid inlet. Each of the upper and lower sealing assemblies includes a component extending from near the fluid inlet to away from the fluid inlet. The primary sealing assembly, the metal isolation ring, and the secondary sealing assembly are sequentially positioned to abut against each other. The primary sealing assembly includes several primary seals, and the secondary sealing assembly includes several secondary seals. Both the primary and secondary seals are V-shaped sealing rings, with their sealing lips facing the fluid inlet. The metal isolation ring is floating between the primary and secondary sealing assemblies. The hardness of the primary seal material is greater than that of the secondary seal material. The primary sealing assembly has an anti-extrusion structure to prevent root deformation, and the secondary sealing assembly has an elastic compensation structure to accommodate micro-deformation.

[0008] By adopting the above technical solution, functional decoupling is achieved by setting primary and secondary sealing groups with different hardness. The high-hardness primary sealing group, with its high modulus characteristics, bears most of the fluid pressure impact, effectively preventing the seal root from being squeezed into the metal gap and damaged under high pressure. Meanwhile, the low-hardness secondary sealing group, with its excellent elastic deformation ability, can closely fit the surface of the rotating body after being pressed, providing flexible buffer, effectively compensating for processing errors and rotational runout, and ensuring sealing performance under high pressure.

[0009] A further improvement of the technical solution of the present invention is that: the anti-extrusion structure includes an anti-extrusion retaining ring fixedly connected to the back pressure side of the root of the primary seal; the material modulus of the anti-extrusion retaining ring is higher than that of the main rubber material of the primary seal assembly, which is used to limit the axial flow deformation of the root of the seal when subjected to high pressure fluid impact, and to convert the fluid pressure into a thrust that pushes the metal isolation ring to move axially; a reinforcing rib is integrally formed between the inner side of the lip of the primary seal and the root.

[0010] By adopting the above technical solution, an anti-extrusion retaining ring with a modulus higher than that of the primary sealing body material is set, and a rigid barrier is formed on the back pressure side at the root of the seal, eliminating the gap extrusion effect. The anti-extrusion retaining ring blocks the path of rubber flowing to the metal gap, ensuring the integrity of the seal. This structure efficiently converts the static pressure of the fluid on the rubber into axial mechanical thrust on the metal isolation ring, avoiding energy loss due to the shear deformation of the rubber itself, thereby ensuring the transmission efficiency of the force transmission chain and enabling the secondary sealing assembly at the rear end to obtain sufficient clamping power.

[0011] A further improvement of the technical solution of the present invention is that: the elastic compensation structure includes a stress relief fillet disposed at the junction of the root of the secondary seal and the lip; the radius of curvature of the stress relief fillet is configured to allow the lip of the secondary seal to undergo radial expansion deformation under the axial thrust of the metal isolation ring, which is used to fill the runout gap on the surface of the rotating body.

[0012] By adopting the above technical solution, the stress relief fillet at the root reduces the peak internal shear stress of the secondary sealing assembly under large deformation, avoids root tearing, and significantly improves fatigue life. More importantly, the fillet structure provides a volume clearance space for the rubber material. When the seal is subjected to axial compression, the material can flow into the gap at the fillet, thereby ensuring that axial compression can be smoothly converted into radial expansion (clamping force). The interference fit of the secondary sealing assembly is set to be greater than that of the primary seal, ensuring that the softer secondary seal can also fit tightly against the shaft surface during low-pressure or zero-pressure start-up, preventing low-pressure leakage.

[0013] A further improvement of the technical solution of the present invention is as follows: a grease injection channel is provided on one side of the rotating seat, which connects to the annular sealing gap; a transfer channel is provided at the end of the rotating seat, which extends axially along the rotating seat and its extension line intersects with the grease injection channel; the rotating seat and the internal components cooperate to form a flow groove and a transfer cavity, and the inlet end of the transfer channel is connected to the annular sealing gap through the flow groove and the transfer cavity in sequence; a control component is provided between the grease injection channel and the transfer channel, and the control component is configured such that: when grease is injected, both the grease injection channel and the transfer channel are open, and when grease is not injected, both the grease injection channel and the transfer channel are blocked; end caps are fixedly connected to both ends of the rotating seat, and drain ports are provided on the end caps.

[0014] By adopting the above technical solution, a series full-path flushing circuit is constructed. By setting up a transfer channel connecting the metal isolation ring chamber and the end bearing area, and cooperating with the drain port, the grease is forced to flow sequentially along the path of grease injection port, sealing area, transfer chamber, flow groove, transfer channel, bearing area, and drain port. This ensures that the new oil can completely squeeze the old oil and impurities in the sealing components and bearings out of the housing, achieving the dual functions of lubrication and cleaning. A control component is set at the intersection of the grease injection channel and the transfer channel to achieve intelligent control of grease injection on and grease injection off. This eliminates the back pressure resistance during grease injection and prevents the safety hazard of high-pressure fluid leakage during non-maintenance periods.

[0015] A further improvement of the technical solution of the present invention is that: an oil distribution groove is provided on the outer circumferential surface of the metal isolation ring, and an oil distribution groove is provided on its inner circumferential surface; a radial oil passage hole connecting the oil distribution groove and the oil distribution groove is provided on the body of the metal isolation ring; the oil distribution groove is annular, and the outlet end of the grease injection channel and the transfer cavity are aligned with the position of the oil distribution groove; the oil distribution groove extends axially to the two end faces of the metal isolation ring.

[0016] By adopting the above technical solution, an annular oil distribution groove is set on the outer circumferential surface of the metal isolation ring. No matter what angle the isolation ring rotates to, the grease injection channel is always connected to the annular groove, ensuring zero dead angle for oil inlet. By setting an oil distribution groove that extends axially to the end face on the inner circumferential surface, the grease can be forced to directly penetrate into the root of the primary and secondary seals and the back of the lip during operation, establishing a stable hydrostatic oil film. This not only reduces the friction coefficient between the seal and the metal ring, but also uses the oil film pressure to help the sealing lip better fit the rotating shaft.

[0017] A further improvement of the technical solution of the present invention is that: the control component includes two unidirectional conduction structures respectively disposed inside the transfer channel and the grease injection channel, and a linkage locking structure for controlling the coordinated action of the two unidirectional conduction structures; the unidirectional conduction structure includes a valve nozzle, the axial part of which passes through a valve hole, the valve hole including two parts of different diameters, with a smooth transition between the two parts of the valve hole, a hollow valve cover fixedly connected to the side of the valve nozzle near the larger diameter valve hole, a spring fixedly connected to the side of the hollow valve cover located inside the valve hole, a plug fixedly connected to the end of the spring away from the hollow valve cover, the head of the plug matching the shape of the smooth transition, and flow gaps existing in the middle and tail of the plug; the linkage locking structure is configured such that: in the absence of grease injection pressure, the linkage locking structure is in a locked state to prevent the plug in the transfer channel from moving, and in the presence of grease injection pressure, the linkage locking structure releases the locking effect on the plug in the transfer channel.

[0018] By adopting the above technical solution and setting the above control components, the sealing failure problem of traditional one-way valves caused by spring fatigue or instantaneous micro-movement under high pressure vibration conditions is effectively solved. This structure uses the grease injection pressure as the only unlocking signal to realize condition-triggered logic control of the discharge path: during non-grease injection operations, the linkage locking structure forcibly restricts the degree of freedom of movement of the plug in the transfer channel, transforming the traditional elastic seal into an irreversible mechanical hard lock, eliminating the risk of high-pressure fluid in the sealing area accidentally flowing into the bearing area through the transfer channel; at the same time, the low flow resistance valve cavity flow channel design formed by the hollow valve cover and the smooth transition part not only ensures the smooth flow and efficient replacement of high viscosity grease during grease injection, but also ensures the absolute sealing safety of the equipment in the harsh high-pressure environment downhole, significantly improving the reliability and safety of cementing operations.

[0019] A further improvement of the technical solution of the present invention is that: the linkage locking structure includes a hollow active valve stem in the middle, one end of which is fixedly connected to the plug at the location of the grease injection channel, and the other end extends into the interior of the grease injection channel and is fixedly connected to a locking cylinder. The side wall of the locking cylinder is provided with a strip groove along the axis, and one side of the inner wall of the strip groove is set as a wedge structure, with the inclined side of the wedge structure facing the outside of the locking cylinder; a driven valve stem is fixedly connected to the plug located in the transfer channel, and the end of the driven valve stem away from the plug extends into the interior of the grease injection channel; the diameter of the driven valve stem is smaller than the width of the strip groove, and an annular groove is provided on the part of the driven valve stem located in the grease injection channel.

[0020] By adopting the above technical solution, the linear motion of the grease injection valve is directly converted into the switching of the locking state by setting an active valve stem to drive the locking cylinder. In the locked state, the solid side wall of the locking cylinder is used to engage the annular groove of the driven valve stem. This is a rigid interference based on the shear strength of the material. Unless the metal is sheared, no matter how large the back pressure in the transfer channel is, the discharge valve core will never be able to move. In addition, the inclined guide design of the wedge structure cleverly solves the problem of centering difficulty. Even if there is a slight machining error or wear on the valve stem, it can still play a guiding role during reset, ensuring that the locking cylinder can smoothly slide into the groove and avoid the mechanism from jamming.

[0021] A further improvement of the technical solution of the present invention is that: the oil distribution groove includes multiple straight grooves extending in a straight line along the axis of the metal isolation ring, the straight grooves are evenly distributed along the inner circumference of the metal isolation ring, and the two ends of each straight groove are respectively connected to the upper and lower end faces of the metal isolation ring.

[0022] By adopting the above technical solution, the oil distribution groove is set as multiple straight grooves extending horizontally along the axis, which realizes the rapid transmission of fluid pressure and eliminates the sensitivity to the direction of rotation. When the grease enters the inner wall of the metal isolation ring through the radial oil passage, the grease is quickly diverted along the straight grooves extending horizontally along the axis and flows through to the two end faces of the isolation ring. Since the straight groove path is the shortest and the flow resistance is the smallest, the grease injection pressure can be instantly transmitted to the root of the primary and secondary sealing groups, realizing rapid pressure equalization to prevent local pressure accumulation at the sealing interface. At the same time, this axially symmetrical straight flow channel design gives the system complete adaptability to the forward and reverse rotation conditions of the rotating body. No matter how the drill pipe changes the rotation direction, it can maintain constant fluid conduction characteristics, completely eliminating the risk of external mud suction caused by the spiral pumping effect. It is particularly suitable for complex drilling operations that require frequent switching of rotation direction.

[0023] A further improvement of the technical solution of the present invention is as follows: Referring to the structure shown at the top of the figure, based on the embodiment, the present invention provides a technical solution: preferably, the oil distribution groove includes a spiral groove extending in a spiral line along the inner circumferential surface of the metal isolation ring, and the spiral groove penetrates the two end faces of the metal isolation ring.

[0024] By adopting the above technical solution, the oil distribution groove is set as a spiral groove extending in a spiral line. The hydrodynamic pressure effect generated by the rotation is used to realize active chip removal and forced circulation. After the grease enters the spiral groove extending in a spiral line, under the action of the fluid viscous shear force generated by the high-speed rotation of the rotating body, the spiral groove acts as the stator of the micro hydrodynamic pump. Combined with the rotation direction, it produces a significant axial pumping effect on the grease. This hydrodynamic pressure effect not only accelerates the axial circulation of the grease at the sealing interface, but also greatly improves the heat removal efficiency and enhances the durability of the sealing component under high pollution conditions.

[0025] A further improvement of the technical solution of the present invention is that: the oil distribution groove includes a cross-shaped groove formed by multiple sets of spiral grooves with opposite directions intertwined, and the cross-shaped groove forms a number of micro oil storage units for retaining grease on the inner circumferential surface of the metal isolation ring.

[0026] By employing the above technical solution, a micro-oil reservoir is constructed by setting the oil distribution grooves into interwoven cross-grooves to enhance oil film adhesion and anti-ablation capabilities under extreme operating conditions. After the grease is injected into the cross-grooves formed by multiple sets of spiral grooves in opposite directions, it is divided and filled into numerous closed or semi-closed micro-oil reservoir units. These units utilize surface tension adsorption to build a stable mesh-like oil film structure on the inner wall of the metal isolation ring. When the grease injection operation is interrupted, the grease injection pressure fluctuates, or the equipment is in a state of frequent start-stop, resulting in the fluid dynamic pressure not yet being established, the residual grease remaining in the oil reservoir unit can be released immediately to maintain critical boundary lubrication, avoiding dry friction between the sealing lip and the metal ring. This micro-reservoir energy storage mechanism greatly improves the anti-ablation capability and service life of the sealing system under poor lubrication or oil-deficient extreme operating conditions.

[0027] Due to the adoption of the above technical solution, the technical progress achieved by this invention compared to the prior art is as follows:

[0028] 1. This invention provides a high-pressure resistant rotary tailpipe cementing head. By setting up a primary sealing group and a secondary sealing group with different hardness, functional decoupling is achieved. The high-hardness primary sealing group, utilizing its high modulus characteristics, bears most of the fluid pressure impact, effectively preventing the seal root from being squeezed into the metal gap and damaged under high pressure. Meanwhile, the low-hardness secondary sealing group, utilizing its excellent elastic deformation ability, can tightly fit the surface of the rotating body after being pressurized, providing flexible buffering, effectively compensating for processing errors and rotational runout, and ensuring sealing performance under high-pressure environment.

[0029] 2. This invention provides a high-pressure resistant rotary tailpipe cementing head. By setting an anti-extrusion retaining ring with a modulus higher than that of the primary sealing body material, and forming a rigid barrier on the back pressure side at the root of the seal, the gap extrusion effect is eliminated. The anti-extrusion retaining ring blocks the path of rubber to the metal gap, ensuring the integrity of the seal. This structure efficiently converts the static pressure of the fluid on the rubber into axial mechanical thrust on the metal isolation ring, avoiding energy loss due to the shear deformation of the rubber itself, thereby ensuring the transmission efficiency of the force transmission chain, so that the secondary sealing assembly at the rear end can obtain sufficient clamping power.

[0030] 3. This invention provides a high-pressure resistant rotary tailpipe cementing head. By setting a stress-relieving rounded corner at the root, the peak value of internal shear stress of the secondary sealing assembly under large deformation is reduced, root tearing is avoided, and fatigue life is significantly improved. More importantly, the rounded corner structure provides a volume clearance space for the rubber material. When the seal is subjected to axial compression, the material can flow into the gap at the rounded corner, thereby ensuring that axial compression can be smoothly converted into radial expansion (clamping force). The interference fit of the secondary sealing assembly is set to be greater than that of the primary one, ensuring that the softer secondary seal can also fit tightly against the shaft surface during the low-pressure or zero-pressure start-up stage, preventing low-pressure leakage.

[0031] 4. This invention provides a high-pressure resistant rotary tailpipe cementing head. By constructing a series full-path flushing circuit, and by setting a transfer channel connecting the metal isolation ring chamber and the end bearing area, and in conjunction with the drain port, the grease is forced to flow sequentially along the path of the grease injection port, sealing area, transfer chamber, flow groove, transfer channel, bearing area, and drain port. This ensures that the new oil can completely squeeze out the old oil and impurities in the sealing components and bearings from the housing, achieving the dual functions of lubrication and cleaning. A control component is set at the intersection of the grease injection channel and the transfer channel to achieve intelligent control of grease injection on and grease injection off, which not only eliminates the back pressure resistance during grease injection, but also eliminates the safety hazard of high-pressure fluid leakage during non-maintenance periods.

[0032] 5. This invention provides a high-pressure resistant rotary tailpipe cementing head. By setting a control component that works in conjunction with a unidirectional flow structure, it effectively solves the problem of sealing failure caused by spring fatigue or instantaneous micro-movements in traditional one-way valves under high-pressure vibration conditions. This structure uses grease injection pressure as the sole unlocking signal to achieve condition-triggered logic control of the discharge path: during non-grease injection operations, the linkage locking structure forcibly restricts the freedom of movement of the plug in the transfer channel, transforming the traditional elastic seal into an irreversible mechanical hard lock, eliminating the risk of high-pressure fluid in the sealing area accidentally flowing into the bearing area through the transfer channel; at the same time, the low-flow-resistance valve cavity flow channel design formed by the hollow valve cover and smooth transition part ensures both smooth flow and efficient replacement of high-viscosity grease during grease injection, and ensures absolute sealing safety of the equipment in the harsh high-pressure environment downhole, significantly improving the reliability and safety of cementing operations. Attached Figure Description

[0033] The invention will now be further described with reference to the accompanying drawings.

[0034] Figure 1 This is a three-dimensional structural diagram of the cement head of the present invention;

[0035] Figure 2 This is a schematic diagram of the overall front sectional view of the cement head of the present invention;

[0036] Figure 3 This is a cross-sectional view of the housing assembly of the present invention;

[0037] Figure 4 This is a schematic diagram of the external structure of the housing assembly of the present invention;

[0038] Figure 5 This is a partial structural schematic diagram of the driven valve stem of the present invention;

[0039] Figure 6 This is a schematic diagram of the split structure of the unidirectional conduction structure of the present invention;

[0040] Figure 7 This is a schematic diagram of the active valve stem and locking cylinder of the present invention;

[0041] Figure 8 This is a schematic diagram showing the disassembled structure of the sealing assembly of the present invention;

[0042] Figure 9 These are schematic diagrams illustrating the structure of the metal isolation ring in this invention under three different embodiments;

[0043] Figure 10 For the present invention Figure 2 Enlarged view of point A in the middle;

[0044] Figure 11 For the present invention Figure 2Enlarged view at point B in the middle;

[0045] Figure 12 For the present invention Figure 3 Enlarged view of point C in the middle.

[0046] In the diagram: 1. Rotating body; 2. Housing assembly; 201. Rotating seat; 202. Fluid inlet; 203. Annular sealing gap; 204. Grease injection channel; 205. Transfer channel; 206. Flow groove; 207. Transfer chamber; 301. Secondary seal; 302. Stress relief fillet; 401. Primary seal; 402. Anti-extrusion retaining ring; 403. Reinforcing rib; 501. Metal isolation ring; 502. Oil distribution groove; 503. Oil hole; 504. Oil distribution groove; 6. One-way conduction structure; 601. Valve nozzle; 602. Valve hole; 603. Hollow valve cover; 605. Plug; 606. Spring; 701. Active valve stem; 702. Driven valve stem; 703. Annular groove; 704. Locking cylinder; 705. Strip groove; 706. Wedge structure; 8. Bearing; 9. End cap; 10. Drain port. Detailed Implementation

[0047] The present invention will be further described in detail below with reference to the embodiments.

[0048] Example 1

[0049] like Figures 1-12 As shown, the present invention provides a high-pressure resistant rotary tailpipe cementing head, comprising a housing assembly 2 and a rotating body 1 disposed within the housing assembly 2. The housing assembly 2 includes a rotating seat 201 with a fluid inlet 202. An annular sealing gap 203 is formed between the rotating body 1 and the rotating seat 201. Bearings 8 are installed at both ends of the rotating seat 201, with the outer ring of the bearing 8 fixedly connected to the rotating seat 201 and the inner ring fixedly connected to the rotating body 1. An upper sealing assembly and a lower sealing assembly are disposed within the annular sealing gap 203, and the upper and lower sealing assemblies are symmetrically distributed axially about the fluid inlet 202. The upper and lower sealing assemblies have the same structure, and each of them includes a sealing gap 203 formed by the rotation of the rotating body 1 near the fluid inlet 202. 2. A primary sealing assembly, a metal isolation ring 501, and a secondary sealing assembly are sequentially arranged in a direction away from the fluid inlet 202. The primary sealing assembly includes several primary sealing elements 401, and the secondary sealing assembly includes several secondary sealing elements 301. Both the primary sealing elements 401 and the secondary sealing elements 301 are V-shaped sealing rings. The sealing lips of both the primary sealing elements 401 and the secondary sealing elements 301 face the fluid inlet 202. The metal isolation ring 501 is floatingly arranged between the primary sealing assembly and the secondary sealing assembly. The hardness of the material of the primary sealing element 401 is greater than that of the material of the secondary sealing element 301. The primary sealing assembly is provided with an anti-extrusion structure to prevent root deformation, and the secondary sealing assembly is provided with an elastic compensation structure to adapt to micro-deformation.

[0050] In this embodiment, by setting a primary sealing group (hard) and a secondary sealing group (soft) with different hardness, functional decoupling is achieved. The high-hardness primary sealing group, with its high modulus characteristics, bears most of the fluid pressure impact, effectively preventing the seal root from being squeezed into the metal gap and damaged under high pressure. Meanwhile, the low-hardness secondary sealing group, with its excellent elastic deformation ability, can closely fit the surface of the rotating body 1 after being compressed, providing flexible buffer, effectively compensating for processing errors and rotational runout, and ensuring sealing performance under high pressure.

[0051] By using a floating metal isolation ring 501, the axial fluid thrust borne by the primary sealing group is transferred to the secondary sealing group without damage. This structure allows the clamping force (contact stress) of the secondary sealing group to automatically increase with the increase of working pressure, achieving a self-tightening sealing effect where the higher the pressure, the tighter the seal, and avoiding the friction overheating problem caused by the primary sealing group pressing directly on the secondary sealing group.

[0052] Furthermore, since the primary seal assembly blocks most of the pressure peaks and solid particles in the fluid, the secondary seal assembly actually operates in a relatively clean environment with buffered pressure fluctuations. This tiered protection mechanism protects the most vulnerable soft rubber from direct impacts, thereby significantly improving the overall mean time between failures of the sealing system.

[0053] Initial state: The upper sealing assembly and the lower sealing assembly are installed in the annular sealing gap 203 between the housing assembly 2 and the rotating body 1. The lips of the primary sealing group and the secondary sealing group are facing the fluid inlet 202 (i.e., back-to-back installation). At this time, the initial contact seal is formed under low pressure by relying on the interference of the sealing element itself.

[0054] Pressurization stage (pressure transmission): When high-pressure cement slurry or drilling fluid enters the rotary seat 201 cavity from the fluid inlet 202, the high-pressure fluid first acts on the inner lip and back of the primary sealing assembly. Due to the high hardness of the primary sealing assembly material (with an anti-extrusion structure), it only undergoes a small axial displacement under high pressure, mainly manifested as rigid thrust. This thrust pushes the metal isolation ring 501 to float axially outward (away from the inlet direction);

[0055] Sealing execution stage (differential compensation): The metal isolation ring 501 directly transmits the huge axial thrust from the primary sealing group to the secondary sealing group. Since the secondary sealing group has low material hardness (with an elastic compensation structure), after receiving the axial thrust, the secondary sealing group undergoes significant axial compression deformation. According to the principle of incompressibility of rubber, the axial compression forces it to expand radially, so that the lip of the secondary sealing group tightly holds the outer surface of the rotating body 1 with extremely high contact stress.

[0056] Dynamic operation stage (follow-up seal): When the rotating body 1 rotates at high speed and causes radial runout (eccentric oscillation) due to uneven force, the primary seal assembly with higher hardness may momentarily have a small fitting gap due to its high rigidity. However, at this time, the soft secondary seal assembly in a high compression state can follow the surface runout of the rotating body 1 in real time with its excellent rebound characteristics, continuously filling the gap, thereby maintaining the integrity of the dynamic seal and preventing fluid leakage.

[0057] like Figure 8 and Figure 10 As shown, preferably, the anti-extrusion structure includes an anti-extrusion retaining ring 402 that is independently and fixedly connected to the back pressure side of the root of the primary seal 401; the material modulus of the anti-extrusion retaining ring 402 is higher than that of the main rubber material of the primary seal assembly, and is used to limit the axial flow deformation of the root of the seal when subjected to high pressure fluid impact, and to convert the fluid pressure into a thrust that pushes the metal isolation ring 501 to move axially; a reinforcing rib 403 is integrally formed between the inner side of the lip of the primary seal 401 and the root.

[0058] In this embodiment, by setting an anti-extrusion retaining ring 402 with a modulus higher than that of the primary sealing body material, and forming a rigid barrier on the back pressure side at the root of the seal, the gap extrusion effect is eliminated. The anti-extrusion retaining ring 402 blocks the path of rubber flowing to the metal gap, ensuring the integrity of the seal. In addition, this structure efficiently converts the static pressure of the fluid on the rubber into axial mechanical thrust on the metal isolation ring 501, avoiding energy loss due to the shear deformation of the rubber itself, thereby ensuring the transmission efficiency of the force transmission chain, so that the secondary sealing assembly at the rear end can obtain sufficient clamping power.

[0059] During operation, when high-pressure fluid impacts the primary sealing assembly, the main rubber body of the primary seal 401 attempts to flow towards the low-pressure side under the action of fluid static pressure. At this time, the anti-extrusion retaining ring 402, which is fixedly connected to the back pressure side at the root, has an extremely high material modulus (e.g., PEEK, bronze, or high-strength alloy). Under the same pressure, it hardly deforms. Its rigid edge tightly covers the mating gap between the rotating seat 201 and the rotating body 1, physically blocking the channel for the main rubber body of the primary seal 401 to enter the gap. The obstructed main rubber body can only convert the fluid pressure it receives into an overall axial displacement tendency, and forces the anti-extrusion retaining ring 402 as a rigid piston surface of an integral part to press smoothly and evenly against the end face of the floating metal isolation ring 501, pushing the metal isolation ring 501 to move backward.

[0060] like Figure 8 and Figure 10As shown, preferably, the elastic compensation structure includes a stress-relieving fillet 302 disposed at the junction of the root and lip of the secondary seal 301; the radius of curvature of the stress-relieving fillet 302 is configured to allow the lip of the secondary seal 301 to undergo radial expansion deformation under the axial thrust of the metal isolation ring 501, for filling the runout gap on the surface of the rotating body 1; the interference fit of the lip of the secondary seal 301 is greater than the interference fit of the lip of the primary seal 401.

[0061] The secondary sealing assembly needs to withstand the huge axial compressive force from the metal isolation ring 501 to deform. In the frequent high pressure compression and decompression rebound cycle, the root is prone to extremely severe stress concentration, which leads to fatigue cracks. In addition, if the secondary seal 301 does not have enough deformation space, when it is crushed by the metal isolation ring 501, the rubber volume has nowhere to be released and loses its elastic compensation ability, and cannot follow the slight jump of the rotating shaft.

[0062] In this embodiment, by setting a stress-relieving fillet 302 at the root, the peak value of the internal shear stress of the secondary sealing assembly under large deformation is reduced, root tearing is avoided, and fatigue life is significantly improved. More importantly, the fillet structure provides a volume clearance space for the rubber material. When the seal is subjected to axial compression, the material can flow into the gap at the fillet, thereby ensuring that axial compression can be smoothly converted into radial expansion (clamping force). In addition, the interference of the secondary sealing assembly is set to be greater than that of the primary one, ensuring that the softer secondary seal can also fit tightly against the shaft surface during the low-pressure or zero-pressure start-up stage, preventing low-pressure leakage.

[0063] When the metal isolation ring 501 is pushed by the primary sealing assembly and pressed against the secondary sealing assembly with a huge axial force, the secondary seal 301 undergoes axial shortening deformation. At this time, the area where the stress relief fillet 302 is located acts as a deformation buffer. The originally compressed rubber material flows and fills the space defined by the fillet. This material flow guides the sealing lip to expand further radially towards the surface of the rotating body 1, which makes the contact area and contact pressure of the sealing lip against the shaft surface increase sharply, thereby filling the micro-texture and runout gaps on the surface of the rotating body 1. In the initial installation state without pressure, since the secondary sealing assembly has a large lip interference, its sealing lip is already wrapped around the rotating body 1 with a large pre-tightening force. When the equipment starts to inject cement but the pressure has not yet increased, this high interference ensures that there is no gap at the sealing interface. When the pressure increases, the above-mentioned radial expansion deformation is superimposed on the initial interference to form a contact sealing band with extremely high pressure, ensuring reliable sealing across the entire pressure range.

[0064] The lip lengths on both sides of the secondary seal 301 are shorter than those of the primary seal 401. The lip of the secondary seal 301 has a sharp edge structure, while the lip of the primary seal 401 has a flat structure.

[0065] Example 2

[0066] like Figure 3 , Figure 10 and Figure 12 As shown, based on Embodiment 1, the present invention provides a technical solution: Preferably, a grease injection channel 204 communicating with an annular sealing gap 203 is provided on one side of the rotating seat 201, and a transfer channel 205 is provided at the end of the rotating seat 201. The transfer channel 205 extends axially along the rotating seat 201 and its extension line intersects with the grease injection channel 204. The rotating seat 201 and the internal components cooperate to form a flow groove 206 and a transfer cavity 207. The inlet end of the transfer channel 205 communicates with the annular sealing gap 203 in sequence through the flow groove 206 and the transfer cavity 207. A control component is provided between the grease injection channel 204 and the transfer channel 205. The control component is configured such that: when grease is injected, both the grease injection channel 204 and the transfer channel 205 are open, and when grease is not injected, both the grease injection channel 204 and the transfer channel 205 are blocked. End caps 9 are fixedly connected to both ends of the rotating seat 201, and drain ports 10 are provided on the end caps 9.

[0067] In existing cement head lubrication designs, the grease injection port is usually directly connected to the bearing cavity 8 or the sealing cavity, lacking a systematic drainage path. This leads to the following problems: Firstly, without a clear outlet, newly injected grease cannot displace deep-seated old grease, metal wear debris, and intruding contaminants. These impurities remain in the bearing raceway and sealing interface for extended periods, accelerating wear. Secondly, if a normally open drainage hole is provided, high-pressure fluid from downhole can easily breach the seal and spray directly from the drainage hole. If no drainage hole is provided, hydraulic locking can easily occur within the closed cavity during grease injection, preventing injection and even causing the dust seal to burst.

[0068] In this embodiment, by constructing a series full-path flushing circuit, firstly, by setting a transfer channel 205 connecting the metal isolation ring 501 chamber and the end bearing 8 area, and cooperating with the drain port 10, the grease is forced to flow sequentially along the path of the grease injection port, sealing area, transfer chamber 207, flow groove 206, transfer channel 205, bearing 8 area, and drain port 10, ensuring that the new oil can completely squeeze the old oil and impurities in the sealing components and bearing 8 out of the housing, thus achieving the dual functions of lubrication and cleaning; secondly, a control component is set at the intersection of the grease injection channel 204 and the transfer channel 205 to achieve intelligent control of grease injection on and grease injection off, which not only eliminates the back pressure resistance during grease injection, but also eliminates the safety hazard of high-pressure fluid leakage during non-maintenance periods.

[0069] Grease injection and flushing process: When the external grease injection gun is connected to the grease injection channel 204 and pressure is applied, the control component operates to simultaneously open the grease injection channel 204 and the transfer channel 205. Fresh grease first enters the annular sealing gap 203 to lubricate and cool the primary and secondary sealing groups. Subsequently, pushed by the subsequently injected grease, the fluid in the chamber enters the transfer channel 205 through the internal flow groove 206 and the transfer chamber 207, and is axially transported to the bearing 8 area at the end of the rotating seat 201. Finally, the waste oil carrying heat and impurities passes through the bearing 8 and is discharged to the external environment from the drain port 10 on the end cover 9.

[0070] Safety interlocking process: When the grease injection operation is completed and the grease injection pressure disappears, the control component resets, cutting off the passage between the grease injection channel 204 and the transfer channel 205. At this time, even if high-pressure well fluid enters the rotating seat 201 due to seal failure, the high-pressure fluid cannot leak to the outside through the transfer channel 205 or the grease injection channel 204, thus ensuring the safety of wellhead operations.

[0071] like Figure 8 and Figure 9 As shown, preferably, an oil distribution groove 502 is provided on the outer circumferential surface of the metal isolation ring 501, and an oil distribution groove 504 is provided on its inner circumferential surface. A radial oil passage hole 503 connecting the oil distribution groove 502 and the oil distribution groove 504 is provided on the body of the metal isolation ring 501. The oil distribution groove 502 is annular, and the outlet end of the grease injection channel 204 and the transfer cavity 207 are aligned with the position of the oil distribution groove 502. The oil distribution groove 504 extends axially to the two end faces of the metal isolation ring 501.

[0072] The metal isolation ring 501 is floating between the primary and secondary seals, which means that it may rotate circumferentially or move axially. If the isolation ring is solid or has only a simple through hole, when it rotates to a certain angle, the outlet of the grease injection channel 204 may be blocked by the outer wall of the isolation ring, preventing the grease from entering the inner layer.

[0073] In this embodiment, by providing an annular oil distribution groove 502 on the outer circumferential surface of the metal isolation ring 501, the grease injection channel 204 is always connected to the annular groove regardless of the angle to which the isolation ring rotates, ensuring zero dead angle for oil inlet. By providing an oil distribution groove 504 extending axially to the end face on the inner circumferential surface, the grease can be forced to directly penetrate into the root and back of the lip of the primary and secondary seals 301 during operation, establishing a stable hydrostatic oil film. This reduces the friction coefficient between the seal and the metal ring and utilizes the oil film pressure to assist the sealing lip in better fitting the rotating shaft.

[0074] like Figure 2 , Figure 10 and Figure 12As shown, preferably, the control component includes two unidirectional guiding structures 6 respectively disposed inside the transfer channel 205 and the grease injection channel 204, and a linkage locking structure for controlling the coordinated action of the two unidirectional guiding structures 6; the unidirectional guiding structure 6 includes a valve nozzle 601, the axial part of the valve nozzle 601 is penetrated through a valve hole 602, the valve hole 602 includes two parts with different diameters, and there is a smooth transition between the two parts of the valve hole 602; a hollow valve cover 603 is fixedly connected to the side of the valve nozzle 601 near the larger diameter valve hole 602, and the hollow valve cover 603 is located in the valve hole 602. A spring 606 is fixedly connected to one side of the 02. A plug 605 is fixedly connected to the end of the spring 606 away from the hollow valve cover 603. The head of the plug 605 matches the shape of the smooth transition part. There are flow gaps that are mutually connected in the middle and tail of the plug 605 to facilitate the flow of grease. The linkage locking structure is configured such that: in the absence of grease injection pressure, the linkage locking structure is locked to prevent the plug 605 in the transfer channel 205 from moving; in the presence of grease injection pressure, the linkage locking structure releases the locking effect on the plug 605 in the transfer channel 205.

[0075] In existing automatic grease injection or drainage devices, fluid control is usually achieved by simply using a spring 606 check valve. However, under the high pressure (70MPa+) and strong vibration conditions faced by the cement head, the simple spring 606 check valve has insufficient sealing reliability: the drainage side (transfer channel 205) is directly connected to the outside. If it is only pressed by the force of the spring 606, when the pressure inside the well fluctuates or the equipment vibrates violently, the valve core is prone to momentary micro-movement, resulting in high-pressure fluid leakage or splashing.

[0076] In this embodiment, the above-mentioned control components effectively solve the problem of sealing failure caused by spring 606 fatigue or momentary micro-movement under high pressure vibration conditions in traditional one-way valves. This structure uses grease injection pressure as the only unlocking signal to realize condition-triggered logic control of the discharge path: during non-grease injection operations, the linkage locking structure forcibly restricts the degree of freedom of movement of the plug 605 in the transfer channel 205, transforming the traditional elastic seal into an irreversible mechanical hard lock, eliminating the risk of high-pressure fluid in the sealing area accidentally flowing into the bearing 8 area through the transfer channel 205; at the same time, the low flow resistance valve cavity flow channel design formed by the hollow valve cover 603 and the smooth transition part not only ensures the smooth flow and efficient replacement of high viscosity grease during grease injection, but also ensures the absolute sealing safety of the equipment in the harsh high-pressure environment downhole, significantly improving the reliability and safety of cementing operations.

[0077] When the grease injection pressure is applied to the valve nozzle 601, the pressure pushes the plug 605 to compress the spring 606 and retract into the hollow valve cover 603. At this time, the head of the plug 605 disengages from the smooth transition part (i.e., the conventional sealing seat part), and the grease quickly passes through the valve hole 602 and flows out through the flow gap in the middle and tail of the plug 605. After the grease is injected, it passes through the sealing area, the transfer chamber 207, and the flow groove 206 in sequence into the transfer channel 205, and squeezes the plug 605 inside the transfer channel 205, causing it to leave the transition part. The grease can then pass through the transfer channel 205 and flow into the area where the bearing 8 is located. Finally, the grease is discharged from the drain hole of the end cover 9.

[0078] When no external grease is injected, the one-way conduction structure 6 in the grease injection channel 204 is blocked. At this time, the control component drives the one-way conduction structure 6 in the transfer channel 205 to lock, so that the grease in the sealing area cannot be discharged to the bearing 8 position through the transfer channel 205, thereby avoiding grease leakage during non-grease injection.

[0079] like Figure 5 , Figure 6 and Figure 7 As shown, preferably, the linkage locking structure includes a hollow active valve stem 701 in the middle. One end of the active valve stem 701 is fixedly connected to the plug 605 at the location of the grease injection channel 204, and the other end extends into the interior of the grease injection channel 204 and is fixedly connected to a locking cylinder 704. A strip groove 705 is formed along the axis on the side wall of the locking cylinder 704. One side of the inner wall of the strip groove 705 is set as a wedge structure 706, and the side of the wedge structure 706 with the inclined surface faces the outside of the locking cylinder 704. A driven valve stem 702 is fixedly connected to the plug 605 located in the transfer channel 205. The end of the driven valve stem 702 away from the plug 605 extends into the interior of the grease injection channel 204. The diameter of the driven valve stem 702 is smaller than the width of the strip groove 705. An annular groove 703 is formed on the part of the driven valve stem 702 located in the grease injection channel 204.

[0080] In this embodiment, by setting the active valve stem 701 to drive the locking cylinder 704 to move, the linear motion of the grease injection valve is directly converted into the switching of the locking state. In the locked state, the solid side wall of the locking cylinder 704 is used to engage the annular groove 703 of the driven valve stem 702. This is a rigid interference based on the shear strength of the material. Unless the metal is sheared, no matter how large the back pressure in the transfer channel 205 is, the discharge valve core will never be able to move. In addition, the inclined guide design of the wedge structure 706 cleverly solves the problem of centering difficulty. Even if there is a slight machining error or wear on the valve stem, it can play a guiding role during reset, ensuring that the locking cylinder 704 can smoothly slide into the groove and avoid the mechanism from jamming.

[0081] The above locking structure includes several modes:

[0082] Locked-out state (safety mode): When there is no grease injection pressure, the spring 606 in the grease injection channel 204 pushes the plug 605 and the active valve stem 701 forward. At this time, the solid part of the side wall (where the strip groove 705 is located) of the locking cylinder 704 connected to the end of the active valve stem 701 is exactly located in the annular groove 703 of the driven valve stem 702. Due to the wall thickness of the locking cylinder 704, the axial movement path of the driven valve stem 702 is physically blocked (forming mechanical interference), and the plug 605 of the transfer channel 205 is forcibly locked in the closed position.

[0083] Unlocking process (linkage mode): When the grease injection pressure pushes the plug 605 of the grease injection channel 204 backward, the active valve stem 701 drives the locking cylinder 704 to move backward synchronously. As the locking cylinder 704 moves, the side wall of the locking cylinder 704 disengages from the slot. When it moves to the predetermined position, the side wall of the locking cylinder 704, which was originally stuck in the annular slot 703, is completely removed from the slot (replaced by the empty space of the strip groove 705), so that the locking cylinder 704 no longer obstructs the movement of the driven valve stem 702. At the same time, the above process gives the sealing area positive pressure and drives the one-way structure in the transfer channel 205 to open. In other words, the above structure can automatically unlock along with the grease injection process, completing the mechanical judgment trigger action.

[0084] Example 3

[0085] like Figure 9 As shown in the figure, referring to the structure shown in the middle, based on embodiment 2, the present invention provides a technical solution: preferably, the oil distribution groove 504 includes multiple straight grooves extending straight along the axial direction of the metal isolation ring 501. The straight grooves are evenly distributed along the inner circumferential surface of the metal isolation ring 501, corresponding to and communicating with the oil holes 503 one by one, and the two ends of each straight groove are respectively connected to the upper and lower end faces of the metal isolation ring 501.

[0086] In this embodiment, by setting the oil distribution groove 504 as multiple straight grooves extending horizontally along the axis, the fluid pressure is transmitted extremely quickly and the sensitivity to the rotation direction is eliminated. When the grease enters the inner wall of the metal isolation ring 501 through the radial oil passage 503, the grease is quickly diverted along the straight grooves extending horizontally along the axis and flows through to the two end faces of the isolation ring. Since the straight groove path is the shortest and the flow resistance is the smallest, the grease injection pressure can be transmitted instantly to the root of the primary and secondary sealing groups, achieving rapid pressure equalization to prevent local pressure accumulation at the sealing interface. At the same time, this axially symmetrical straight flow channel design gives the system complete adaptability to the forward and reverse rotation conditions of the rotating body 1. No matter how the drill pipe changes its rotation direction, it can maintain constant fluid conduction characteristics, completely eliminating the risk of external mud suction caused by the spiral pumping effect. It is particularly suitable for complex drilling operations that require frequent switching of rotation direction.

[0087] Example 4

[0088] like Figure 9 As shown in the figure, referring to the structure shown at the top, based on embodiment 2, the present invention provides a technical solution: preferably, the oil distribution groove 504 includes a spiral groove extending along the inner circumferential surface of the metal isolation ring 501 in a spiral line, the spiral groove penetrates the two end faces of the metal isolation ring 501, and the spiral direction of the spiral groove is configured to cooperate with the working rotation direction of the rotating body 1 to generate an axial pumping effect.

[0089] In this embodiment, by setting the oil distribution groove 504 as a spiral groove extending in a spiral line, active chip removal and forced circulation are achieved by utilizing the hydrodynamic pressure effect generated by rotation. After the grease enters the spiral groove extending in a spiral line, under the action of the fluid viscous shear force generated by the high-speed rotation of the rotating body 1, the spiral groove acts as the stator of the micro hydrodynamic pump, and generates a significant axial pumping effect on the grease in conjunction with the rotation direction. This hydrodynamic pressure effect not only accelerates the axial circulation of the grease at the sealing interface, but also greatly improves the heat removal efficiency and enhances the durability of the sealing assembly under high-pollution conditions.

[0090] Example 5

[0091] like Figure 9 As shown in the figure, referring to the structure shown at the bottom, based on embodiment 2, the present invention provides a technical solution: preferably, the oil distribution groove 504 includes a cross-shaped groove formed by multiple sets of spiral grooves with opposite directions intertwined, and the cross-shaped groove forms a number of micro oil storage units for retaining grease on the inner circumferential surface of the metal isolation ring 501.

[0092] In this embodiment, by setting the oil distribution groove 504 into an interwoven cross-textured groove, a micro oil reservoir is constructed to improve the oil film adhesion and anti-ablation capability under extreme operating conditions. After the grease is injected into the cross-textured groove formed by multiple sets of spiral grooves in opposite directions, it will be divided and filled into numerous closed or semi-closed micro oil reservoir units. These units utilize surface tension adsorption to build a stable mesh oil film structure on the inner wall of the metal isolation ring 501. When the grease injection operation is interrupted, the grease injection pressure fluctuates, or the equipment is in a state of frequent start-stop, resulting in the fluid dynamic pressure not yet being established, the residual grease remaining in the oil reservoir unit can be released immediately to maintain critical boundary lubrication, avoiding dry friction between the sealing lip and the metal ring. This micro reservoir energy storage mechanism greatly improves the anti-ablation capability and service life of the sealing system under poor lubrication or oil-deficient extreme operating conditions.

[0093] The present invention has been described in detail above. However, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, any modifications or improvements that do not depart from the spirit of the present invention are within the scope of protection of the present invention.

Claims

1. A high-pressure resistant rotary tailpipe cementing head, comprising a housing assembly (2) and a rotary body (1) inserted within the housing assembly (2), wherein the housing assembly (2) includes a rotary seat (201) having a fluid inlet (202), and an annular sealing gap (203) is formed between the rotary body (1) and the rotary seat (201); bearings (8) are installed at both ends of the rotary seat (201) that are far apart, wherein the outer ring of the bearing (8) is fixedly connected to the rotary seat (201), and the inner ring is fixedly connected to the rotary body (1); Its features are: An upper sealing assembly and a lower sealing assembly are provided in the annular sealing gap (203), and the upper sealing assembly and the lower sealing assembly are symmetrically distributed along the axial direction about the fluid inlet (202); Each of the upper sealing assembly and the lower sealing assembly includes a primary sealing assembly, a metal isolation ring (501), and a secondary sealing assembly arranged sequentially in a direction from near the fluid inlet (202) to away from the fluid inlet (202); The primary sealing assembly includes a plurality of primary sealing elements (401), and the secondary sealing assembly includes a plurality of secondary sealing elements (301). Both the primary sealing elements (401) and the secondary sealing elements (301) are configured as V-shaped sealing rings. The sealing lips of both the primary sealing elements (401) and the secondary sealing elements (301) face the fluid inlet (202). The metal isolation ring (501) is floatingly disposed between the primary sealing assembly and the secondary sealing assembly. The hardness of the primary seal (401) material is greater than that of the secondary seal (301) material; the primary seal assembly is provided with an anti-extrusion structure to prevent root deformation, and the secondary seal assembly is provided with an elastic compensation structure to adapt to micro-deformation.

2. The high-pressure resistant rotary tailpipe cementing head according to claim 1, characterized in that: The anti-extrusion structure includes an anti-extrusion retaining ring (402) fixedly connected to the back pressure side of the root of the primary seal (401); the material modulus of the anti-extrusion retaining ring (402) is higher than that of the main rubber material of the primary seal assembly, and is used to limit the axial flow deformation of the root of the seal when subjected to high pressure fluid impact, and to convert the fluid pressure into a thrust that pushes the metal isolation ring (501) to move axially; a reinforcing rib (403) is integrally formed between the inner side of the lip of the primary seal (401) and the root.

3. The high-pressure resistant rotary tailpipe cementing head according to claim 2, characterized in that: The elastic compensation structure includes a stress-relieving fillet (302) disposed at the junction of the root of the secondary seal (301) and the lip; the radius of curvature of the stress-relieving fillet (302) is configured to allow the lip of the secondary seal (301) to undergo radial expansion deformation under the axial thrust of the metal isolation ring (501) to fill the surface runout gap of the rotating body (1).

4. The high-pressure resistant rotary tailpipe cementing head according to claim 3, characterized in that: A grease injection channel (204) communicating with the annular sealing gap (203) is provided on one side of the rotating seat (201), and a transfer channel (205) is provided at the end of the rotating seat (201). The transfer channel (205) extends axially along the rotating seat (201) and its extension line intersects with the grease injection channel (204). The rotating seat (201) and the internal components cooperate to form a flow groove (206) and a transfer cavity (207). The inlet end of the transfer channel (205) passes through the flow groove (206) in sequence. 06) and the transfer chamber (207) are connected to the annular sealing gap (203); a control component is provided between the grease injection channel (204) and the transfer channel (205), the control component is configured such that: when grease is injected, the grease injection channel (204) and the transfer channel (205) are both connected, and when grease is not injected, the grease injection channel (204) and the transfer channel (205) are both blocked; both ends of the rotating seat (201) are fixedly connected to end caps (9), and the end caps (9) are provided with drain ports (10).

5. The high-pressure resistant rotary tailpipe cementing head according to claim 4, characterized in that: The outer circumferential surface of the metal isolation ring (501) is provided with an oil distribution groove (502), and the inner circumferential surface is provided with an oil distribution groove (504). The body of the metal isolation ring (501) is provided with a radial oil passage hole (503) connecting the oil distribution groove (502) and the oil distribution groove (504). The oil distribution groove (502) is annular, and the outlet end of the grease injection channel (204) and the transfer cavity (207) are aligned with the position of the oil distribution groove (502). The oil distribution groove (504) extends axially to the two end faces of the metal isolation ring (501).

6. The high-pressure resistant rotary tailpipe cementing head according to claim 4, characterized in that: The control component includes two unidirectional guiding structures (6) respectively disposed inside the transfer channel (205) and the grease injection channel (204), and a linkage locking structure for controlling the coordinated action of the two unidirectional guiding structures (6); the unidirectional guiding structure (6) includes a valve nozzle (601), the axial part of the valve nozzle (601) is penetrated through a valve hole (602), the valve hole (602) includes two parts with different diameters, and there is a smooth transition between the two parts of the valve hole (602), and a hollow valve cover (603) is fixedly connected to the side of the valve nozzle (601) near the large-diameter valve hole (602), the hollow valve cover (603) A spring (606) is fixedly connected to one side of the valve hole (602). A plug (605) is fixedly connected to the end of the spring (606) away from the hollow valve cover (603). The head of the plug (605) matches the shape of the smooth transition part. There are flow gaps in the middle and tail of the plug (605). The linkage locking structure is configured such that: in the absence of grease injection pressure, the linkage locking structure is locked to prevent the plug (605) in the transfer channel (205) from moving; in the presence of grease injection pressure, the linkage locking structure releases the locking effect on the plug (605) in the transfer channel (205).

7. The high-pressure resistant rotary tailpipe cementing head according to claim 6, characterized in that: The linkage locking structure includes a hollow active valve stem (701) in the middle. One end of the active valve stem (701) is fixedly connected to the plug (605) at the location of the grease injection channel (204), and the other end extends into the interior of the grease injection channel (204) and is fixedly connected to a locking cylinder (704). The side wall of the locking cylinder (704) is provided with a strip groove (705) along the axis. One side of the inner wall of the strip groove (705) is provided with a wedge structure (706). The wedge structure (706) has an oblique angle. One side of the surface faces the outside of the lock cylinder (704); a driven valve stem (702) is fixedly connected to the plug (605) located in the transfer channel (205), and the end of the driven valve stem (702) away from the plug (605) extends into the interior of the grease injection channel (204); the diameter of the driven valve stem (702) is smaller than the width of the strip groove (705), and an annular groove (703) is provided on the part of the driven valve stem (702) located in the grease injection channel (204).

8. The high-pressure resistant rotary tailpipe cementing head according to claim 5, characterized in that: The oil distribution groove (504) includes multiple straight grooves extending in a straight line along the axis of the metal isolation ring (501). The straight grooves are evenly distributed along the inner circumference of the metal isolation ring (501), and both ends of each straight groove are respectively connected to the upper and lower end faces of the metal isolation ring (501).

9. A high-pressure resistant rotary tailpipe cementing head according to claim 5, characterized in that: The oil distribution groove (504) includes a spiral groove extending in a spiral line along the inner circumferential surface of the metal isolation ring (501), and the spiral groove penetrates the two end faces of the metal isolation ring (501).

10. A high-pressure resistant rotary tailpipe cementing head according to claim 5, characterized in that: The oil distribution groove (504) includes a cross-shaped groove formed by multiple sets of spiral grooves with opposite directions intertwined. The cross-shaped groove forms a number of micro oil storage units for retaining grease on the inner circumferential surface of the metal isolation ring (501).

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