Combined drilling tool check valve for ultra-deep well

Abstract

The present application relates to the technical field of oil drilling tools, and discloses a combined drilling tool check valve for ultra-deep wells, which comprises a float valve joint, a threaded connection with a drill string to form an installation reference; a valve body fixed to the float valve joint and forming a main flow channel, an eccentric inner cavity provided in the valve body, the eccentric direction of the eccentric inner cavity being consistent with the flow direction of the main flow channel; a sealing sleeve embedded in the valve body, the inner side of the sealing sleeve being provided with a composite sealing structure; a valve cover provided with a flow guide structure on the flow-approaching surface, the flow guide structure being used to guide the smooth flow of drilling fluid through the flow-approaching surface of the valve cover, and the valve cover being connected to the valve body through a hinged structure. The present application solves the problems of rapid wear and failure of fasteners and elastic elements, sealing leakage, pin shaft fatigue failure, screw loosening failure and difficulty of sealing to adapt to complex working conditions under the working conditions of high pressure, high temperature and sand in ultra-deep wells, and achieves the effects of prolonging the service life, improving the sealing reliability, enhancing the carrying capacity and the erosion resistance.

Description

Technical Field

[0001] This invention relates to the field of oil drilling tools technology, and more specifically, to a combined drill string check valve for ultra-deep wells. Background Technology

[0002] In ultra-deep well drilling operations, the drill string check valve is installed inside the drill string to control the unidirectional flow of drilling fluid. It remains open under positive circulation conditions to maintain smooth circulation, and is quickly closed to block backflow and cause the drill string to float when the pump stops or a blowout occurs.

[0003] In the prior art, conventional drill tool check valves adopt a single torsion spring return structure, a single shear pin hinge structure, and a rigid or purely elastic sealing structure, with fasteners such as screws directly exposed in the flow channel.

[0004] Ultra-deep well conditions are characterized by high pressure, high temperature, and high sand content. Existing drill string check valves have the following problems: high-speed sand-laden drilling fluid continuously erodes the valve cover's flow-facing surface and hinged parts, leading to accelerated structural wear; the single torsion spring return structure generates an asymmetrical torque, causing the valve cover to deflect, resulting in uneven sealing and leakage; single shear pins are prone to fatigue failure during high-frequency opening and closing cycles; fasteners such as screws are directly exposed to high-speed fluids, leading to erosion and vibration, causing loosening and failure; rigid metal seals are difficult to adapt to particle entrainment and slight deflections, while purely elastic seals deform excessively under high pressure differentials. Neither can meet the sealing requirements of complex working conditions on its own. Summary of the Invention

[0005] This invention provides a combined drill string check valve for ultra-deep wells, which solves the technical problems of rapid erosion and wear, easy leakage of seals, and loosening and failure of fasteners in ultra-deep wells under high pressure, high temperature and sand-containing conditions.

[0006] This invention provides a combined drill string check valve for ultra-deep wells, comprising: The float valve connector is threadedly connected to the drill string to form an installation reference. The valve body is fixed to the float valve connector and forms the main flow channel. The valve body has an eccentric inner cavity, and the eccentric direction of the eccentric inner cavity is consistent with the flow direction of the main flow channel. A sealing sleeve is embedded in the valve body, and the inner side of the sealing sleeve is provided with a composite sealing structure. The valve cover has a flow guiding structure on its flow-facing surface. The flow guiding structure is used to guide the drilling fluid to flow smoothly over the flow-facing surface of the valve cover. The valve cover is connected to the valve body through a hinge structure. The hinge structure includes a seat ear fixed to the valve body, a cover ear fixed to the valve cover, and a pin shaft passing through the seat ear and the cover ear. The valve cover can swing between the open position and the closed position around the axis of the pin shaft. A torsion spring, installed at the hinge joint between the valve cover and the valve body, applies a return force to the valve cover toward the closed position; The composite sealing structure includes a metal step seal and an elastomer sealing line. The metal step seal is integrally formed on the inner side of the sealing sleeve and forms the main sealing surface. The elastomer sealing line is fixed on the inner side of the sealing sleeve and adjacent to the metal step seal. The elastomer sealing line is used to compensate for the gap between the valve cover and the sealing sleeve.

[0007] Furthermore, the flow guiding structure is a fish-belly shaped flow guiding protrusion, which is integrally formed on the flow-facing surface of the valve cover. The fish-belly shaped flow guiding protrusion has a streamlined outline, and the sealing edge of the fish-belly shaped flow guiding protrusion has rounded corners. The flow-facing surface of the valve cover is coated with a carbide coating.

[0008] Furthermore, there are two seat ears, which are arranged at intervals along the axis of the pin. There are also two cover ears, which are arranged at intervals along the axis of the pin. The two cover ears are located between the two seat ears. A pin passes through the seat ears and the cover ears, and the pin forms a double shear load at the mating position of the two cover ears and the two seat ears.

[0009] Furthermore, there are two torsion springs, which are arranged opposite each other on both sides of the hinge part along the axis of the pin. The two torsion springs apply symmetrical return forces to the valve cover. The seat ear is provided with a groove, and an isolation plate is provided in the groove. The ends of the two torsion springs that are inserted into the seat ear are located on both sides of the isolation plate. The ends of the torsion springs are fixed in the groove by a pressure plate.

[0010] Furthermore, the lug adopts an embedded structure, with the lug embedded within the wall thickness of the valve body, and the outer surface of the lug does not protrude from the inner wall of the valve body; a bushing is provided in the pin hole of the lug, and the pin shaft is engaged with the inner hole of the bushing.

[0011] Furthermore, it also includes a screw and a cover. The screw passes through the cover lug and is threaded to the valve body. The cover is an arc-shaped metal plate structure. One end of the cover is fixed to the inner wall of the valve body, and the other end of the cover forms a gap with the inner wall of the valve body. The cover is placed over the exposed section of the screw, and a flow-blocking cavity is formed between the cover and the exposed section of the screw. The flow-blocking cavity isolates the exposed section of the screw from the main flow channel.

[0012] Furthermore, the eccentric inner cavity of the valve body is eccentrically set relative to the outer diameter of the valve body. The eccentric inner cavity of the valve body is eccentrically set on the side where the hinge is located. The eccentric setting increases the wall thickness of the valve body on the side where the hinge is located. The increased wall thickness accommodates the screw, torsion spring and protective cover, and forms an enlarged flow-proof cavity on the side where the hinge is located.

[0013] Furthermore, the screw adopts a combined anti-loosening structure, which includes a mechanical locking washer and an anti-loosening pin. The mechanical locking washer is placed between the head of the screw and the fastened part. The flange of the mechanical locking washer is inserted into the notch of the fastened part to restrict the rotation of the screw. The anti-loosening pin passes through the screw radially and forms a mechanical lock with the valve body.

[0014] Furthermore, it also includes a middle ring and a sealing ring. The middle ring is annular and located between the valve body and the sealing sleeve. The outer circle of the middle ring has a stop, which fits with the inner wall of the valve body. The inner circle of the middle ring fits with the outer circle of the sealing sleeve. The sealing ring is pressed into the annular groove of the valve body or the sealing sleeve and is located between the valve body and the sealing sleeve to form a static seal.

[0015] Furthermore, the torsion spring is installed in the semi-enclosed sandproof cavity, which is formed by the valve body and the cover plate. The cover plate is fixed to the outer wall of the valve body by screws. A guide sleeve is provided in the semi-enclosed sandproof cavity, which is fitted around the torsion spring and constrains the torsional deformation direction of the torsion spring.

[0016] The beneficial effects of this invention are as follows: This invention solves the technical problems of existing drill string check valves in ultra-deep wells under high pressure, high temperature and sandy conditions, such as rapid wear and failure of fasteners and elastic elements, seal leakage, pin fatigue failure, screw loosening failure, and difficulty in adapting to complex working conditions. It achieves the technical effects of extending service life, improving sealing reliability, enhancing load-bearing capacity and erosion resistance by using the flow-avoiding geometry formed by the eccentric valve body and the protective cover to avoid the screw and torsion spring from the center velocity zone of the main flow channel. It also achieves the technical effects of extending service life, improving sealing reliability, enhancing load-bearing capacity and erosion resistance. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the overall vertical cross-sectional structure of a combined drill string check valve for ultra-deep wells proposed in this invention. Figure 2 This is a schematic diagram of the vertical cross-sectional structure of the check valve body when the combined drill string check valve for ultra-deep wells proposed in this invention is closed. Figure 3 This is a schematic diagram of the vertical cross-sectional structure of the check valve body when the combined drill string check valve for ultra-deep wells proposed in this invention is opened. Figure 4 This is a schematic diagram of the valve body structure of a combined drilling tool check valve for ultra-deep wells proposed in this invention. Figure 5 This is a vertical cross-sectional view of the valve body proposed in this invention; Figure 6 This invention is proposed. Figure 5 A schematic diagram of the A-end face structure; Figure 7 This invention is proposed. Figure 5 A schematic diagram of the B-end face structure; Figure 8 This is a front view of the valve cover proposed in this invention; Figure 9 This is a side view of the valve cover proposed in this invention; Figure 10 This is a schematic diagram of the torsion spring proposed in this invention; Figure 11 This is a schematic diagram of the stress effect on the flow-draining surface of a traditional valve cover (the dotted line in the diagram indicates the part with high erosion intensity). Figure 12 This is a schematic diagram of the force effect on the drainage surface of the valve cover proposed in this invention.

[0018] In the diagram: 100, float valve connector; 200, check valve body; 210, valve body; 220, valve cover; 221, cover lug; 222, fish-belly shaped guide protrusion; 223, isolation plate; 230, torsion spring; 240, sealing sleeve; 250, first positioning ring; 260, second positioning ring; 270, stop ring; 280, eccentric inner cavity; 290, seat lug. Detailed Implementation

[0019] The subject matter described herein will now be discussed with reference to exemplary embodiments. It should be understood that these embodiments are discussed only to enable those skilled in the art to better understand and implement the subject matter described herein, and changes may be made to the function and arrangement of the elements discussed without departing from the scope of this specification. Various processes or components may be omitted, substituted, or added as needed in the examples. Furthermore, some features described in the examples may be combined in other examples.

[0020] This embodiment provides a combined drill string check valve for ultra-deep wells, such as... Figures 1-12 As shown, a device for controlling the unidirectional flow of drilling fluid installed inside a vertical drill string includes at least a float valve connector 100 and a check valve body 200. The check valve body 200 is located inside the float valve connector 100 and includes a valve body 210, a sealing sleeve 240, and a valve cover 220. The float valve connector 100 is threadedly connected to the drill string to form an installation reference. The valve body 210 is fixed to the float valve connector 100 and forms the main flow channel. The sealing sleeve 240 is embedded in the valve body 210 to form a seat sealing reference surface. The valve cover 220 is hinged to the valve body 210 and can swing between an open position and a closed position around the hinge axis. When the valve cover 220 is in the closed position, it fits against the seat sealing reference surface of the sealing sleeve 240 to block backflow.

[0021] The float valve connector 100 is cylindrical, and the inner hole of the float valve connector 100 is provided with a shoulder positioning surface.

[0022] The valve body 210 is cylindrical, and its outer circumference has a stop. The stop of the valve body 210 mates with the shoulder positioning surface of the float valve connector 100. A stop ring 270 is provided at the mating interface. The valve body 210 is fixed to the float valve connector 100 by bolts. The bolts pass axially through the connecting boss of the valve body 210 and are threadedly connected to the threaded hole of the float valve connector 100. The positioning and mating of the float valve connector 100 and the stop of the valve body 210 constitute a bearing reference. The inner cavity of the valve body 210 forms a main channel, which runs vertically through the valve body 210, and the drilling fluid flows upward along the main channel.

[0023] Two sets of sealing stops are provided on the outer wall of the valve body 210 on the side away from the valve cover 220. The sealing stops are inlaid with a first positioning ring 250 and a second positioning ring 260. The first positioning ring 250, the second positioning ring 260 and the float valve connector 100 form a positioning and sealing reference surface, and the check valve body 200 and the float valve connector 100 are precisely fitted together.

[0024] The sealing sleeve 240 is annular, with a conical surface and a stop on its outer circumference. The inner wall of the valve body 210 has a positioning surface that mates with the conical surface and the stop of the sealing sleeve 240. The sealing sleeve 240 is embedded in the valve body 210 with dual positioning via the conical surface and the stop. The conical surface provides radial centering, and the stop provides axial positioning; together, they constitute the sealing reference. The inner side of the sealing sleeve 240 forms a seat sealing reference surface, which the valve cover 220 fits against when in the closed position.

[0025] In some embodiments, the combined drill string check valve for ultra-deep wells further includes a middle ring, which is annular and located between the valve body 210 and the sealing sleeve 240. The outer circle of the middle ring is provided with a stop, which fits with the inner wall of the valve body 210. The inner circle of the middle ring fits with the outer circle of the sealing sleeve 240. The middle ring defines the coaxial relationship between the valve body 210 and the sealing sleeve 240 and plays a limiting and isolation role.

[0026] In some embodiments, the combined drill string check valve for ultra-deep wells further includes a sealing ring. The valve body 210 or the sealing sleeve 240 is provided with an annular groove. The sealing ring is pressed into the annular groove and located between the valve body 210 and the sealing sleeve 240. The sealing ring forms a static seal between the valve body 210 and the sealing sleeve 240 to prevent drilling fluid from leaking from the mating gap between the valve body 210 and the sealing sleeve 240.

[0027] The valve cover 220 is connected to the valve body 210 via a hinge structure. The hinge structure includes at least a seat 290, a cover 221, and a pin. The seat 290 is fixed to the valve body 210, the cover 221 is fixed to the valve cover 220, and the pin passes through the seat 290 and the cover 221. The axis of the pin forms the hinge axis of the valve cover 220, allowing the valve cover 220 to swing about the axis of the pin. The axis of the pin extends horizontally, allowing the valve cover 220 to swing in a vertical plane.

[0028] In some embodiments, there are two lugs 290, which are spaced apart along the axial direction of the pin. There are also two cover lugs 221, which are spaced apart along the axial direction of the pin. The two cover lugs 221 are located between the two lugs 290. The pin passes through one lug 290, one cover lug 221, another cover lug 221, and another lug 290 in sequence. The pin forms a double shear bearing at the mating position of the two cover lugs 221 and the two lugs 290, thus distributing the shear load.

[0029] In some embodiments, the lug 290 adopts an embedded structure, with the lug 290 embedded within the wall thickness of the valve body 210. The outer surface of the lug 290 does not protrude from the inner wall of the valve body 210, thereby reducing the obstruction of the flow channel by the lug 290 and reducing the direct erosion of the lug 290.

[0030] In some embodiments, the pin is provided with anti-disengagement structures at both ends, which are locking plates or retaining rings. The locking plates or retaining rings restrict the pin from moving axially and prevent the pin from coming out of the lug 290 and the cover lug 221.

[0031] Furthermore, in order to improve the durability and corrosion resistance of the hinge, a bushing is provided in the pin hole of the lug 290. The bushing is made of wear-resistant material. The pin shaft fits into the inner hole of the bushing. The bushing bears the relative rotational wear between the pin shaft and the lug 290. The bushing can be replaced after it wears out without replacing the lug 290 or the valve body 210.

[0032] The combined drill string check valve for ultra-deep wells also includes a torsion spring 230, which is installed at the hinge. One end of the torsion spring 230 is engaged in the groove of the valve cover 220, and the other end of the torsion spring 230 is engaged in the groove of the lug 290. The torsion spring 230 applies a return force to the valve cover 220 toward the closed position.

[0033] In some embodiments, there are two torsion springs 230. The two torsion springs 230 are arranged opposite each other on both sides of the hinge part along the axial direction of the pin. The two torsion springs 230 apply symmetrical return forces to the valve cover 220. The symmetrical return forces prevent the valve cover 220 from tilting due to uneven force during the return process.

[0034] In some embodiments, a partition plate 223 is provided in the slot of the lug 290. The partition plate 223 is located in the middle of the slot. The ends of the two torsion springs 230 that are engaged with the lug 290 are located on both sides of the partition plate 223. The partition plate 223 separates the ends of the two torsion springs 230 to prevent the ends of the two torsion springs 230 from interfering with each other during operation.

[0035] In some embodiments, the end of the torsion spring 230 is fixed in the slot by a pressure plate, the pressure plate covers the end of the torsion spring 230 and is fixed to the valve cover 220 or the lug 290 by fasteners, and the pressure plate restricts the end of the torsion spring 230 from coming out of the slot.

[0036] Furthermore, in order to constrain the working posture of the torsion spring 230 and prevent sand particles carried by the drilling fluid from entering, the torsion spring 230 is set in a semi-enclosed sand-proof cavity. The semi-enclosed sand-proof cavity is formed by the valve body 210 and the cover plate. The cover plate is fixed to the outer wall of the valve body 210 by screws. A guide sleeve is provided in the semi-enclosed sand-proof cavity. The guide sleeve is fitted on the outer periphery of the torsion spring 230. The guide sleeve constrains the torsional deformation direction of the torsion spring 230 and prevents the torsion spring 230 from radially moving or deviating in posture during operation. The semi-enclosed sand-proof cavity prevents sand particles in the drilling fluid from entering the working space of the torsion spring 230 and reduces the wear of the torsion spring 230 by the sand particles.

[0037] The combined drill string check valve for ultra-deep wells also includes a screw rod, which passes through the valve cover 220 or the lug 221 and is threadedly connected to the valve body 210. The screw rod secures the valve cover 220 or the lug 221 to the valve body 210.

[0038] In some embodiments, the screw employs a combined anti-loosening structure, which includes a mechanical locking washer, anaerobic adhesive, and an anti-loosening pin. The mechanical locking washer is disposed between the head of the screw and the fastened part, and the flange of the mechanical locking washer engages with the notch of the fastened part to restrict the rotation of the screw. The anaerobic adhesive is coated on the threaded surface of the screw and cures in an oxygen-deficient environment to fill the thread gap and increase the loosening resistance. The anti-loosening pin penetrates radially through the screw and the valve body 210, forming a mechanical lock to prevent the screw from rotating relative to the valve body 210. The combined structure of the mechanical locking washer, anaerobic adhesive, and anti-loosening pin synergistically provides anti-loosening and vibration-resistant capabilities.

[0039] Furthermore, to protect the screw from direct erosion by drilling fluid, a protective cover is installed on the exposed section of the screw. The cover is an arc-shaped metal plate structure. One end of the cover is welded to the inner wall of the valve body 210, and the other end of the cover forms a gap with the inner wall of the valve body 210. The cover is placed over the exposed section of the screw, and a flow-avoiding cavity is formed between the cover and the exposed section of the screw. The flow-avoiding cavity isolates the exposed section of the screw from the main flow channel. When the drilling fluid flows along the main flow channel, it bypasses the flow-avoiding cavity and does not directly impact the screw.

[0040] In some embodiments, the eccentric inner cavity 280 of the valve body 210 is eccentrically arranged relative to the outer diameter of the valve body 210. The eccentric inner cavity 280 of the valve body 210 is eccentrically located on the side where the hinge portion is located. The eccentric arrangement increases the wall thickness of the valve body 210 on the side where the hinge portion is located. The increased wall thickness accommodates the screw, torsion spring 230 and protective cover. At the same time, an enlarged flow-avoiding cavity is formed on the side where the hinge portion is located. The flow-avoiding cavity keeps the screw and torsion spring 230 away from the center velocity zone of the main flow channel, reducing the direct erosion of the screw and torsion spring 230 by the drilling fluid.

[0041] Furthermore, in order to reduce flow resistance and suppress eddies and sand retention, the inlet and outlet of the main channel adopt rounded transitions. The rounded transitions allow the drilling fluid to smoothly enter and exit the main channel, reducing flow separation and turbulence formation. The inlet and outlet of the main channel are equipped with diffuser sections, which gradually expand the cross-section of the flow channel, reducing local velocity peaks and pressure losses.

[0042] The valve cover 220 has a flow guiding structure on its flow-facing surface. The flow guiding structure is used to guide the drilling fluid to flow smoothly over the flow-facing surface of the valve cover 220, thereby reducing the erosion of the flow-facing surface of the valve cover 220 by the drilling fluid.

[0043] In some embodiments, the flow guiding structure is a fish-belly-shaped flow guiding protrusion 222, which is integrally formed on the flow-facing surface of the valve cover 220. The fish-belly-shaped flow guiding protrusion 222 increases the center thickness of the valve cover 220, such as... Figure 11 and Figure 12 As shown, compared to traditional valve covers, the fish-belly-shaped guide protrusion 222 has a streamlined profile. The streamlined profile allows the incident drilling fluid jet to pass over the front surface of the valve cover 220 at a smaller angle, reducing the normal momentum component of the particles in the drilling fluid and reducing the micro-cutting depth of the particles on the front surface of the valve cover 220. The continuous curved surface and smooth transition of the streamlined profile reduce the local turbulence intensity and reduce the retention and repeated scouring of drilling fluid in the near-wall area of ​​the front surface of the valve cover 220. The fish-belly-shaped guide protrusion 222 disperses the erosion energy over a larger area, avoiding the formation of a local high-energy impact zone by the dense jet.

[0044] The increased thickness at the center of the valve cover 220 improves the bending stiffness of the valve cover 220, reduces the instantaneous deflection and amplitude of the valve cover 220 under fluid excitation, stabilizes the contact stress distribution at the sealing edge, and at the same time provides a larger wear margin, extending the time for the valve cover 220 to reach the critical wear state that affects the seal.

[0045] In some embodiments, the sealing edge of the fish-belly-shaped flow guide protrusion 222 is provided with a rounded chamfer. The rounded chamfer eliminates the sharp angle of the sealing edge. Sharp edge edges can induce local velocity peaks and high shear bands. The rounded chamfer smooths the velocity gradient at the edge, weakens the flow velocity acceleration effect at the edge, and causes the flow stream to sweep over at a small angle at the edge, further reducing the normal impact component of particles and reducing the formation of wedging and peeling damage by particles at the edge. The rounded chamfer also weakens the stress peak at the edge, reducing the risk of microcracks forming between the coating and the substrate at the edge.

[0046] Furthermore, in order to improve the surface hardness of the valve cover 220's flow-facing surface to resist micro-cutting by particles, the flow-facing surface of the valve cover 220 is sprayed with a hard coating, which is a carbide coating. The high-hardness phase in the carbide coating significantly improves the surface's resistance to scratching, making it difficult for particles in sand-containing drilling fluid to cut into the surface. The carbide coating has a dense structure and low porosity, which can block the penetration of corrosive media into the matrix and weaken the synergistic acceleration effect of corrosion and erosion. The metallic binder phase in the carbide coating provides toughness and good matrix adhesion, making the carbide coating less prone to brittleness or peeling under cyclic impact.

[0047] A composite sealing structure is formed on the inner side of the sealing sleeve 240. The composite sealing structure includes a metal step seal and an elastomer sealing line. The metal step seal is integrally formed on the inner side of the sealing sleeve 240 and forms the main sealing surface. When the valve cover 220 is closed, the sealing edge of the valve cover 220 fits against the metal step seal to bear the main seal. The metal step seal has sufficient rigidity to withstand the sealing contact stress under high pressure differential. The elastomer sealing line is fixed on the inner side of the sealing sleeve 240 and adjacent to the metal step seal. The elastomer sealing line is embedded in the annular groove on the inner side of the sealing sleeve 240 and is fixed by adhesive. The elastomer sealing line is used to compensate for the gap between the valve cover 220 and the sealing sleeve 240 caused by particle entrainment or slight deviation. When there is a slight gap between the valve cover 220 and the metal step seal, the elastomer sealing line undergoes elastic deformation to fill the gap and maintain the seal. The composite sealing structure of the metal step seal and the elastomer sealing line improves the sealing redundancy under complex working conditions.

[0048] In one embodiment of the present invention, the steps for executing the combined drill string check valve are as follows: Under drilling fluid positive circulation conditions, the opening procedure of the combined drill string check valve for ultra-deep wells is as follows: The drilling fluid flows upward along the main flow channel. The hydrodynamic pressure of the drilling fluid acts on the upstream surface of the valve cover 220, generating an opening torque around the pin on the valve cover 220. Simultaneously, the eccentric mass of the valve cover 220 generates an auxiliary opening torque under the action of gravity. The opening torque generated by the hydrodynamic pressure and the gravitational torque overcome the preload of the torsion spring 230, driving the valve cover 220 to swing around the pin from the closed position to the open position. The sealing edge of the valve cover 220 disengages from the seat sealing reference surface of the sealing sleeve 240, and the main flow channel is opened. After the valve cover 220 swings to the set limit angle, the inner wall of the valve body 210 or the limiting structure of the seat lug 290 restricts the valve cover 220 from continuing to swing, and the valve cover 220 remains in the open position.

[0049] In the open state, the fish-belly-shaped guide protrusion 222 of the valve cover 220 guides the drilling fluid to flow smoothly over the front surface of the valve cover 220. The enlarged flow channel formed by the eccentrically set valve body 210 and the fish-belly-shaped guide protrusion 222 together reduce the local flow resistance, and the main flow channel forms a smooth and low-pressure-drop flow channel.

[0050] In some embodiments, the opening step further includes: when the drilling fluid flows over the flow-facing surface of the valve cover 220, the fish-belly-shaped guide protrusion 222 deflects the main jet, and in conjunction with the flow-avoiding geometry formed by the eccentric inner cavity 280 of the valve body 210, the jet bypasses the area where the screw and torsion spring 230 are located. The protective cover is installed on the exposed section of the screw to form a flow-avoiding cavity, further blocking the direct impact of the drilling fluid on the screw.

[0051] When the pump stops or a blowout or kick occurs, the combined drill string check valve for ultra-deep wells performs the following closing steps: the positive circulation of drilling fluid stops, the hydrodynamic pressure acting on the upstream face of the valve cover 220 disappears, the torsion spring 230 releases its stored elastic potential energy, and the two opposing torsion springs 230 apply symmetrical return torques to the valve cover 220, driving the valve cover 220 to swing from the open position to the closed position around the pin. When backflow occurs in the well, the backflow pressure acts on the downstream face of the valve cover 220, and the return force of the auxiliary torsion springs 230 accelerates the closing action of the valve cover 220. When the valve cover 220 swings to the closed position, the sealing edge of the valve cover 220 is in contact with the seat sealing reference surface of the sealing sleeve 240. The metal step seal provides the main seal, the elastic sealing line compensates for any possible particle entrainment or slight deviation, and the composite sealing structure blocks the backflow from the drill bit direction, thus sealing the main flow channel.

[0052] In some embodiments, the closing step further includes: when the valve cover 220 is closed, the symmetrical return force generated by the two opposing torsion springs 230 makes the valve cover 220 evenly fit against the seat sealing reference surface of the sealing sleeve 240, so as to avoid the valve cover 220 from being tilted due to uneven force, resulting in poor local contact of the sealing surface.

[0053] The combined drill string check valve of this embodiment uses the flow-avoiding geometry formed by the eccentrically arranged valve body 210 and the shield to keep the screw and torsion spring 230 away from the central velocity zone of the main flow channel and shielded by the shield. This significantly reduces the direct erosion of the screw and torsion spring 230 by the drilling fluid and extends the service life of the screw and torsion spring 230. Therefore, it solves the problem of fasteners and elastic elements in existing drill string check valves being directly exposed to high-speed fluid and thus experiencing rapid wear and failure.

[0054] The combined drill string check valve of this embodiment provides symmetrical return torque through two opposing torsion springs 230, eliminating the asymmetrical torque generated by the single torsion spring 230 structure. The valve cover 220 is subjected to a balanced driving force during the return process, thus avoiding uneven sealing surface contact caused by the valve cover 220 being skewed, and solving the problem of sealing leakage caused by the single torsion spring 230 return structure in existing drill string check valves.

[0055] The combined drill string check valve of this embodiment uses a through-type pin structure with an internal seat lug 290 and a cover lug 221. The pin forms a double shear load at the mating positions of the two cover lugs 221 and the two seat lugs 290. Compared with a single shear structure, the shear load is distributed to two shear surfaces, and the load borne by a single shear surface is reduced. Therefore, the load-bearing capacity and fatigue life of the articulated structure are improved, and the problem of pin fatigue failure easily occurs in the articulated structure of existing drill string check valves during high-frequency opening and closing cycles is solved.

[0056] The combined drill string check valve of this embodiment uses a combination of mechanical locking gaskets, anaerobic adhesive, and anti-loosening pins to prevent loosening. The mechanical locking gaskets provide initial anti-rotation, the anaerobic adhesive fills the thread gaps to increase loosening resistance, and the anti-loosening pins form a mechanical lock. The three anti-loosening methods work together to maintain the reliability of the screw connection under high vibration conditions, thus solving the problem of loosening and failure of the screw in existing drill string check valves under vibration.

[0057] The combined drill string check valve of this embodiment uses a composite sealing structure of metal step seal and elastomeric sealing line. The metal step seal bears the main sealing contact stress under high pressure differential with its rigidity, while the elastomeric sealing line compensates for the gap caused by particle entrainment or slight deviation with its elastic deformation. The two functions complement each other, so it can withstand high pressure differential and adapt to the sealing requirements of complex working conditions. This solves the problem that the rigid metal seal or pure elastic seal of the existing drill string check valve cannot meet the sealing requirements of complex working conditions in ultra-deep wells on its own.

[0058] The combined drill string check valve of this embodiment utilizes a combined protective structure consisting of a fish-belly-shaped flow guide protrusion 222, a central thickening, rounded corners at the edges, and a carbide hard coating. The fish-belly-shaped flow guide protrusion 222 causes particles to pass over the flow-facing surface of the valve cover 220 at a small angle to reduce normal impact. The central thickening increases the rigidity of the valve cover 220 to stabilize the sealing line contact. The rounded corners at the edges eliminate velocity peaks and stress peaks. The carbide hard coating provides high hardness to resist micro-cutting. These four measures respectively protect against normal impact, structural deformation, edge effects, and surface wear, thus comprehensively improving the erosion resistance of the valve cover 220 and solving the problem of rapid wear of the valve cover 220 in high-speed sand-containing drilling fluids in existing drill string check valves.

[0059] The embodiments of the present invention have been described above. However, the embodiments are not limited to the specific implementation methods described above. The specific implementation methods described above are merely illustrative and not restrictive. Those skilled in the art can make more equivalent embodiments under the guidance of the present embodiments, and all of them are within the protection scope of the present embodiments.

Claims

1. A combined drill string check valve for ultra-deep wells, characterized in that, include: The float valve connector is threadedly connected to the drill string to form an installation reference. The valve body is fixed to the float valve connector and forms the main flow channel. The valve body has an eccentric inner cavity, and the eccentric direction of the eccentric inner cavity is consistent with the flow direction of the main flow channel. A sealing sleeve is embedded in the valve body, and the inner side of the sealing sleeve is provided with a composite sealing structure. The valve cover has a flow guiding structure on its flow-facing surface. The flow guiding structure is used to guide the drilling fluid to flow smoothly over the flow-facing surface of the valve cover. The valve cover is connected to the valve body through a hinge structure. The hinge structure includes a seat ear fixed to the valve body, a cover ear fixed to the valve cover, and a pin shaft passing through the seat ear and the cover ear. The valve cover can swing between the open position and the closed position around the axis of the pin shaft. A torsion spring, installed at the hinge joint between the valve cover and the valve body, applies a return force to the valve cover toward the closed position; The composite sealing structure includes a metal step seal and an elastomer sealing line. The metal step seal is integrally formed on the inner side of the sealing sleeve and forms the main sealing surface. The elastomer sealing line is fixed on the inner side of the sealing sleeve and adjacent to the metal step seal. The elastomer sealing line is used to compensate for the gap between the valve cover and the sealing sleeve.

2. The combined drill string check valve for ultra-deep wells according to claim 1, characterized in that, The flow guiding structure is a fish belly-shaped flow guiding protrusion, which is integrally formed on the flow-facing surface of the valve cover. The fish belly-shaped flow guiding protrusion has a streamlined outline, and the sealing edge of the fish belly-shaped flow guiding protrusion has rounded corners. The flow-facing surface of the valve cover is coated with a carbide coating.

3. The combined drill string check valve for ultra-deep wells according to claim 1, characterized in that, There are two seat ears, which are arranged at intervals along the axis of the pin. There are also two cover ears, which are arranged at intervals along the axis of the pin. The two cover ears are located between the two seat ears. A pin passes through the seat ears and the cover ears, and the pin forms a double shear load at the mating position of the two cover ears and the two seat ears.

4. A combined drill string check valve for ultra-deep wells according to claim 1, characterized in that, There are two torsion springs, which are arranged opposite each other on both sides of the hinge part along the axis of the pin. The two torsion springs apply symmetrical return forces to the valve cover. The seat ear has a groove, and an isolation plate is installed in the groove. The ends of the two torsion springs that are inserted into the seat ear are located on both sides of the isolation plate. The ends of the torsion springs are fixed in the groove by pressure plates.

5. A combined drill string check valve for ultra-deep wells according to claim 3, characterized in that, The lug adopts an internal structure, with the lug embedded in the wall thickness of the valve body and the outer surface of the lug not protruding from the inner wall of the valve body; a bushing is provided in the pin hole of the lug, and the pin shaft is engaged with the inner hole of the bushing.

6. A combined drill string check valve for ultra-deep wells according to claim 1, characterized in that, It also includes a screw and a cover. The screw passes through the cover lug and is threaded to the valve body. The cover is an arc-shaped metal plate structure. One end of the cover is fixed to the inner wall of the valve body, and the other end of the cover forms a gap with the inner wall of the valve body. The cover is placed over the exposed section of the screw. A flow-blocking cavity is formed between the cover and the exposed section of the screw. The flow-blocking cavity isolates the exposed section of the screw from the main flow channel.

7. A combined drill string check valve for ultra-deep wells according to claim 1, characterized in that, The eccentric inner cavity of the valve body is eccentrically set relative to the outer diameter of the valve body. The eccentric inner cavity of the valve body is eccentrically set on the side where the hinge is located. The eccentric setting increases the wall thickness of the valve body on the side where the hinge is located. The increased wall thickness accommodates the screw, torsion spring and protective cover, and forms an enlarged flow-proof cavity on the side where the hinge is located.

8. A combined drill string check valve for ultra-deep wells according to claim 1, characterized in that, The screw adopts a combined anti-loosening structure, which includes a mechanical locking washer and an anti-loosening pin. The mechanical locking washer is placed between the head of the screw and the fastened part. The flange of the mechanical locking washer is inserted into the notch of the fastened part to restrict the rotation of the screw. The anti-loosening pin passes through the screw radially and forms a mechanical lock with the valve body.

9. A combined drill string check valve for ultra-deep wells according to claim 1, characterized in that, It also includes a middle ring and a sealing ring. The middle ring is annular and located between the valve body and the sealing sleeve. The outer circle of the middle ring has a stop, which fits with the inner wall of the valve body. The inner circle of the middle ring fits with the outer circle of the sealing sleeve. The sealing ring is pressed into the annular groove of the valve body or the sealing sleeve and is located between the valve body and the sealing sleeve to form a static seal.

10. A combined drill string check valve for ultra-deep wells according to claim 1, characterized in that, The torsion spring is installed in the semi-enclosed sandproof cavity, which is formed by the valve body and the cover plate. The cover plate is fixed to the outer wall of the valve body by screws. A guide sleeve is provided in the semi-enclosed sandproof cavity. The guide sleeve is fitted on the outer periphery of the torsion spring and constrains the torsional deformation direction of the torsion spring.

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