Leakage-proof casing head for wellhead of oil field

Abstract

The invention relates to the technical field of casing heads, and discloses an oil field wellhead leakproof casing head which comprises a base, a casing head body, a slip, a slip bowl and a leakproof mechanism, the casing head body is arranged on the base, the slip bowl is arranged in the casing head body, the slip is arranged in the slip bowl, the lower portion of the outer circumferential surface of the slip is a conical surface, and the lower portion of the outer circumferential surface of the slip is a conical surface. The upper portion of the inner wall of the slip bowl is an inner conical surface, the conical surface is connected with the inner conical surface in a matched mode, and the anti-leakage mechanism is arranged on the slip bowl and locks the slip when the slip bears upward pressure in a well. According to the anti-leakage casing head for the wellhead of the oil field, the anti-leakage mechanism is arranged on the slip bowl, and when the pressure between an underground casing string and a surface casing is increased and the lower end of the slip is subjected to upward pressure, the anti-leakage mechanism is started to lock the slip and the slip bowl, so that upward micro displacement of the slip is prevented; the sealing between the slip and the slip seat is failed, and the safety of a wellhead is protected.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of casing heads, more particularly, the present application relates to an oilfield wellhead anti-leakage casing head. BACKGROUND

[0002] The casing head is one of the core components of the wellhead device, mainly used for fixing the wellhead structure and bearing multiple functions. As the key hub connecting the downhole casing string and the ground equipment, it not only suspends the weight of each layer of casing except the surface casing, but also prevents pressure intercommunication through sealing the annular space of the casing, ensuring the safety of well control. During the drilling stage, the casing head provides a mounting base for the blowout preventer, while in the oil production period, it transitions to the connection of the tubing head and the Christmas tree. In addition, its side port function supports cementing, pressure balancing and emergency fluid injection, significantly improving cementing quality and operational flexibility.

[0003] The patent document CN119981754A discloses an energy-saving and environmentally friendly casing head, which comprises a casing head body, a flange joint, a slip body, a slip seat, and a stop mechanism. The casing head body is connected to the flange joint by multiple bolts at the top. The inner wall of the casing head body is provided with an annular assembly groove, and the bottom of the annular assembly groove is provided with an inverted conical bearing surface that is wide at the top and narrow at the bottom. The slip seat is seated in the annular assembly groove, and the inverted conical bearing surface at the bottom of the slip seat is pressed onto the inverted conical bearing surface. The slip body is seated in the slip seat, and the lower outer conical surface of the slip body is pressed onto the inner conical surface of the slip seat. The casing head body is connected to the stop mechanism, and the inner end of the stop mechanism is in abutting contact with the slip body. The bottom of the flange joint is in abutting contact with the stop mechanism. The casing head body and the flange joint are designed as a detachable structure, which facilitates replacement when any component is damaged, thereby allowing the use of undamaged components, saving energy and protecting the environment, and reducing waste.

[0004] In the above technical solution, a first ring groove is formed in the slip seat to assemble a sealing ring. When the slip bears the weight of the casing string, the sealing ring is squeezed by the slip to seal the annular space between the casing string and the slip seat. However, during oil well operation, if the pressure between the casing string and the surface casing increases, the pressure in the annular space between the casing string and the slip seat will also increase, which will push the slip upwards. Although there is a stop mechanism, even a small amount of displacement will cause the sealing between the slip and the slip seat to fail, which will threaten the safety of the wellhead.

[0005] Therefore, it is necessary to propose an oilfield wellhead anti-leakage casing head to solve the problems in the prior art. SUMMARY

[0006] The summary section introduces a series of simplified concepts, which will be further explained in detail in the detailed description section. The summary section of this invention is not intended to limit the key features and essential technical features of the claimed technical solution, nor is it intended to determine the scope of protection of the claimed technical solution.

[0007] To address the aforementioned problems, this invention provides a casing head for preventing leakage at oilfield wellheads, comprising a base, a casing head body, slips, a slip seat, and a leakage prevention mechanism. The casing head body is mounted on the base, the slip seat is mounted within the casing head body, and the slips are mounted inside the slip seat. The lower part of the outer circumferential surface of the slips is a conical surface, and the upper part of the inner wall of the slip seat is an inner conical surface. The conical surface and the inner conical surface are connected in a mating manner. The leakage prevention mechanism is mounted on the slip seat and locks the slips when subjected to upward pressure from inside the well.

[0008] Preferably, the anti-leakage mechanism includes a piston and a locking block, an annular hydraulic chamber is formed in the slip seat, an annular groove is formed on the inner conical surface of the slip seat, multiple piston holes are formed on the inner wall of the slip seat along the circumferential direction, the piston is disposed in the piston hole, and the locking block is disposed in the groove.

[0009] Preferably, plunger holes are arrayed along the circumferential direction on the bottom surface of the groove, the plunger holes are connected to the hydraulic chamber, the snap-fit ​​block includes an arc plate and a plunger, the plunger is fixedly disposed on the surface of the protruding side of the arc plate, the arc plate is disposed in the groove, and the plunger is disposed in the plunger hole; An annular limiting groove is opened on the outer circumference of the card, opposite to the groove, and the arc-shaped plate is engaged in the limiting groove.

[0010] Preferably, the anti-leakage mechanism also includes a spring, one end of which is connected to the end face of the piston near the hydraulic chamber, and the other end of which is connected to the side wall of the hydraulic chamber.

[0011] Preferably, the inner wall of the sleeve head body is provided with a bearing surface, which is conical, and the bottom of the slip seat is an outer conical surface that conforms to the shape of the bearing surface, and the outer conical surface is pressed onto the bearing surface.

[0012] Preferably, a first sealing groove is formed on the inner wall of the sleeve head body opposite to the outer circumferential surface of the slip seat; A second sealing groove is formed on the inner conical surface of the slip seat at an interval from the groove, and a sealing ring is provided in both the first sealing groove and the second sealing groove.

[0013] Preferably, a leveling component is provided on the base, and the sleeve head body is connected to the base through the leveling component. The leveling component is used to keep the upper surface of the sleeve head body horizontal when the sleeve head body is installed.

[0014] Preferably, the leveling assembly comprises leveling motors fixedly arranged on the base, the leveling motors are arranged in an array in a circumferential direction, and a lead screw is fixedly arranged on a power output shaft of the leveling motor; A flange plate is fixedly arranged at the bottom of the casing head body, a first semispherical recess is arranged on the bottom surface of the flange plate at a position opposite to the lead screw, the bottom of the flange plate is detachably arranged with a fixed plate, a second semispherical recess is arranged on the upper end surface of the fixed plate at a position opposite to the first semispherical recess, and a spherical nut is rotatably arranged in the first semispherical recess and the second semispherical recess, and the spherical nut is threadedly connected with the lead screw.

[0015] Preferably, two bubble levels perpendicular to each other are arranged on the upper end surface of the flange plate.

[0016] Preferably, a fixing hole is arranged on the base and spaced apart from the leveling motor, and a fixing pin is arranged in the fixing hole.

[0017] Compared with the prior art, the present application has at least the following beneficial effects: The casing head for preventing leakage of an oilfield wellhead disclosed by the present application has a leakage prevention mechanism arranged on the slip seat, when the pressure between the downhole casing string and the surface casing increases, the lower end of the slip is subjected to upward pressure, the leakage prevention mechanism is started to lock the slip and the slip seat, the slip is prevented from being slightly displaced upward, the sealing between the slip and the slip seat is prevented from being invalid, and the safety of the wellhead is protected.

[0018] The casing head for preventing leakage of an oilfield wellhead disclosed by the present application, other advantages, objects and features of the present application will be partially embodied through the following description, and partially understood by those skilled in the art through research and practice of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0019] The accompanying drawings are included to provide a further understanding of the present application, and constitute a part of the specification, and are used together with embodiments of the present application to explain the present application, and do not constitute a limitation on the present application. In the drawings: Figure 1 The structure schematic view of the casing head for preventing leakage of an oilfield wellhead disclosed by the present application; Figure 2 The structure schematic view of the casing head for preventing leakage of an oilfield wellhead disclosed by the present application; Figure 3 The structure schematic view of the leakage prevention mechanism disclosed by the present application; Figure 4 The structure schematic view of the casing head for preventing leakage of an oilfield wellhead disclosed by the present application; Figure 5 The structure schematic view of the clamping block disclosed by the present application; Figure 6 The structure schematic view of the slip seat disclosed by the present application; Figure 7 This is a schematic diagram of the structure of the kava disclosed in this invention; Figure 8 This is a schematic diagram of the base, leveling motor, and lead screw disclosed in this invention. Figure 9 This is a cross-sectional structural schematic diagram of the leveling component disclosed in this invention; Figure 10 This is a schematic diagram of the structure of the fixing plate disclosed in this invention.

[0020] The components are as follows: 1. Base, 2. Sleeve head body, 3. Slip, 4. Slip seat, 5. Leakage prevention mechanism, 6. Piston, 7. Clamping block, 8. Hydraulic chamber, 9. Groove, 10. Plunger hole, 11. Piston hole, 12. Arc plate, 13. Plunger, 14. Limiting groove, 15. Spring, 16. Bearing surface, 17. Outer conical surface, 18. First sealing groove, 19. Second sealing groove, 20. Leveling motor, 21. Lead screw, 22. Flange, 23. First hemispherical groove, 24. Fixing plate, 25. Second hemispherical groove, 26. Spherical nut, 27. Fixing hole. Detailed Implementation

[0021] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments, so that those skilled in the art can implement it based on the description.

[0022] It should be understood that terms such as “having,” “comprising,” and “including” as used herein do not exclude the presence or addition of one or more other elements or combinations thereof.

[0023] like Figures 1-10 As shown, the present invention provides a casing head for preventing leakage at the wellhead of an oilfield, including a base 1, a casing head body 2, slips 3, slip seat 4, and a leakage prevention mechanism 5. The casing head body 2 is mounted on the base 1, the slip seat 4 is mounted inside the casing head body 2, and the slips 3 are mounted inside the slip seat 4. The lower part of the outer circumferential surface of the slips 3 is a conical surface, and the upper part of the inner wall of the slip seat 4 is an inner conical surface. The conical surface and the inner conical surface are connected in a mating manner. The leakage prevention mechanism 5 is mounted on the slip seat 4 and locks the slips 3 when subjected to upward pressure from inside the well.

[0024] Furthermore, the anti-leakage mechanism 5 includes a piston 6 and a locking block 7. An annular hydraulic chamber 8 is opened in the slip seat 4. An annular groove 9 is opened on the inner conical surface of the slip seat 4. Multiple piston holes 11 are opened on the inner wall of the slip seat 4 along the circumferential direction. The piston 6 is disposed in the piston hole 11, and the locking block 7 is disposed in the groove 9.

[0025] Further, the bottom surface of the groove 9 is provided with a plurality of plunger holes 10 arranged in the circumferential direction, the plunger holes 10 are communicated with the hydraulic cavity 8, the clamping block 7 comprises an arc-shaped plate 12 and a plunger 13, the plunger 13 is fixedly arranged on the surface of the protruding side of the arc-shaped plate 12, the arc-shaped plate 12 is arranged in the groove 9, and the plunger 13 is arranged in the plunger hole 10. The outer circumferential surface of the slip 3 is provided with a limiting groove 14 in the position opposite to the groove 9, and the arc-shaped plate 12 is clamped in the limiting groove 14.

[0026] Further, the anti-leakage mechanism 5 further comprises a spring 15, one end of the spring 15 is connected with the end face of the piston 6 close to one end of the hydraulic cavity 8, and the other end of the spring 15 is connected with the side wall of the hydraulic cavity 8.

[0027] Further, the inner wall of the casing head body 2 is provided with a bearing surface 16, the bearing surface 16 is conical, the bottom of the slip seat 4 is an outer conical surface 17 matched with the shape of the bearing surface 16, and the outer conical surface 17 is pressed on the bearing surface 16.

[0028] Further, the inner wall of the casing head body 2 opposite to the outer circumferential surface of the slip seat 4 is provided with a first sealing groove 18. The inner conical surface of the slip seat 4 is provided with a second sealing groove 19 spaced from the groove 9, and sealing rings are arranged in the first sealing groove 18 and the second sealing groove 19.

[0029] Further, the base 1 is provided with a leveling assembly, the casing head body 2 is connected with the base 1 through the leveling assembly, and the leveling assembly is used for keeping the upper end surface of the casing head body 2 horizontal when the casing head body 2 is installed.

[0030] Further, the leveling assembly comprises leveling motors 20 fixedly arranged on the base 1, the leveling motors 20 are arranged in the circumferential direction and at least three, and a lead screw 21 is fixedly arranged on the power output shaft of the leveling motor 20. The bottom of the casing head body 2 is fixedly provided with a flange plate 22, the bottom surface of the flange plate 22 is provided with a first hemispherical groove 23 in the position opposite to the lead screw 21, the bottom of the flange plate 22 is detachably provided with a fixed plate 24, the upper end surface of the fixed plate 24 is provided with a second hemispherical groove 25 opposite to the first hemispherical groove 23, a spherical nut 26 is rotatably arranged in the first hemispherical groove 23 and the second hemispherical groove 25, and the spherical nut 26 is threadedly connected with the lead screw 21.

[0031] Further, the upper end surface of the flange plate 22 is provided with two bubble levels perpendicular to each other.

[0032] Further, the base 1 is provided with a fixing hole 27 spaced from the leveling motor 20, and a fixed pin is arranged in the fixing hole 27.

[0033] The working principle of the above technical scheme is as follows: The oil field well head leak-proof casing head comprises a base 1, a casing head body 2, a slip 3, a slip seat 4 and a leak-proof mechanism 5, the casing head body 2 is arranged on the base 1, the slip seat 4 is arranged in the casing head body 2, the slip 3 is arranged in the slip seat 4, the lower part of the outer circumferential surface of the slip 3 is a conical surface, the upper part of the inner wall of the slip seat 4 is an inner conical surface, the conical surface and the inner conical surface are connected in cooperation, the leak-proof mechanism 5 is arranged in the slip seat 4, the slip 3 is locked when the slip 3 is subjected to the upward pressure in the well, the slip 3 is used for clamping the casing string, under the gravity of the casing string, the conical surface of the lower part of the slip 3 is pressed with the inner conical surface of the slip seat 4, and the sealing ring in the second sealing groove 19 is extruded, the sealing between the slip 3 and the slip seat 4 is realized, when the downhole pressure increases, the annular space (hereinafter referred to as annulus) pressure between the casing string and the surface casing increases, the upward pressure on the lower part of the slip 3 is generated, the pressure of the slip 3 on the slip seat 4 is reduced, the sealing effect of the sealing ring is reduced, when the downhole pressure increases again, the slip 3 has the risk of micro-displacement upward, and the sealing failure between the slip 3 and the slip seat is caused.

[0034] The leak-proof mechanism 5 comprises a piston 6 and a clamping block 7, the slip seat 4 is provided with a ring-shaped hydraulic cavity 8, the inner conical surface of the slip seat 4 is provided with a ring-shaped groove 9, a plurality of piston holes 11 are arranged on the inner wall of the slip seat 4 along the circumferential direction, the piston 6 is arranged in the piston hole 11, the clamping block 7 is arranged in the groove 9, a plunger hole 10 is arranged on the bottom surface of the groove 9 along the circumferential direction, the plunger hole 10 is communicated with the hydraulic cavity 8, the clamping block 7 comprises an arc-shaped plate 12 and a plunger 13, the plunger 13 is fixedly arranged on the surface of the protruding side of the arc-shaped plate 12, the arc-shaped plate 12 is arranged in the groove 9, the plunger 13 is arranged in the plunger hole 10, a ring-shaped limiting groove 14 is arranged on the outer circumferential surface of the slip 3 at the position opposite to the groove 9, the arc-shaped plate 12 is clamped in the limiting groove 14, the hydraulic cavity 8 is filled with hydraulic oil, when the annular space pressure between the casing string and the surface casing increases, the pressure acts on the lower end of the slip 3 and is transmitted to the sealing area between the slip and the slip seat. The increase of the annulus pressure acts on the end surface of the piston 6 on the side towards the center of the slip seat 4, a plurality of pistons 6 are subjected to the pressure in the annulus, the pressure is applied to the hydraulic oil in the hydraulic cavity 8, the hydraulic oil transmits the pressure to the end surface of the plunger 13 on the side close to the hydraulic cavity 8, the hydraulic oil pushes the plunger 13 to the side away from the hydraulic cavity 8, the plunger 13 drives the arc-shaped plate 12 to move, the arc-shaped plate 12 partially enters into the limiting groove 14, the rear part of the arc-shaped plate 12 in the groove 9 fixes the axial position of the arc-shaped plate 12 and the slip seat 4, the front part of the arc-shaped plate 12 enters into the limiting groove 14 to lock the slip 3 and the slip seat 4, the slip 3 is prevented from moving upward, so that the sealing failure between the slip 3 and the slip seat 4 is prevented.

[0035] The lower side of the limiting groove 14 can be provided with a taper, and the lower end surface of the arc-shaped plate 12 is also provided with a taper with the same taper as the lower side of the limiting groove 14, so that the arc-shaped plate 12 can smoothly enter the limiting groove 14, and the taper can also make the slip have a downward displacement trend, thereby improving the sealing between the slip 3 and the slip seat 4. The included angle between the taper and the horizontal plane should be less than the friction angle, so that the lower end surface of the arc-shaped plate 12 and the lower side of the limiting groove 14 can be self-locked. When the slip 3 has an upward movement trend, the lower side of the limiting groove 14 is pressed on the lower end surface of the arc-shaped plate 12. Since the included angle between the taper and the horizontal plane should be less than the friction angle, the radial component force of the arc-shaped plate 12 cannot overcome the static friction force, thereby self-locking between the slip 3 and the arc-shaped plate 12, and preventing the slip 3 from pushing the arc-shaped plate 12 out of the limiting groove 14 when the slip 3 is subjected to pressure.

[0036] The anti-leakage mechanism 5 further comprises a spring 15, one end of the spring 15 is connected with the end surface of the piston 6 close to one end of the hydraulic cavity 8, the other end of the spring 15 is connected with the side wall of the hydraulic cavity 8, the spring 15 provides a certain pressure, and is used for balancing the pressure in the hydraulic cavity 8 and the pressure between the casing string and the slip seat when the pressure between the casing string and the slip seat does not cause the slip 3 to have a slight upward displacement. When the pressure reaches a certain value, the spring 15 is compressed, the piston 6 is pushed and squeezes the hydraulic oil in the hydraulic cavity 8, the hydraulic oil in turn pushes the plunger 13, and the locking of the slip is completed. After the pressure at the downhole is restored to normal, the slip is slightly moved downward under the gravity of the casing string, the limiting groove 14 and the arc-shaped plate 12 are released from the self-locking, the piston 6 moves away from the hydraulic cavity 8 under the elastic force of the spring 15, the hydraulic oil pressure of the hydraulic cavity 8 is reduced, the plunger 13 moves toward the hydraulic cavity 8, the arc-shaped plate 12 moves toward the hydraulic cavity, and the locking of the slip 3 is released. When the slip is locked, the air in the limiting groove 14 is compressed and the pressure increases. In order to reduce the influence of the air in the limiting groove 14 on the arc-shaped plate 12, the width of the limiting groove 14 can be increased, and the total volume of the limiting groove 14 is increased. When the arc-shaped plate 12 enters the limiting groove 14, the volume of the air in the limiting groove 14 is less compressed, and the increased pressure does not affect the entry of the arc-shaped plate 12 into the limiting groove 14. When the width of the limiting groove 14 is increased, attention should be paid to not affecting the position of the lower side of the limiting groove 14. When the lower end surface of the arc-shaped plate 12 enters the limiting groove 14, it can just press the lower side of the limiting groove 14.

[0037] The inner wall of the casing head body 2 is provided with a bearing surface 16, the bearing surface 16 is tapered, the bottom of the slip seat 4 is an outer tapered surface 17 matched with the shape of the bearing surface 16, and the outer tapered surface 17 is pressed on the bearing surface 16. The bearing surface 16 can bear the downward pressure of the slip seat 4, and the bearing surface 16 is tapered, so that the slip seat 4 can be automatically centered.

[0038] The inner wall of the casing head body 2 opposite to the outer circumferential surface of the slip seat 4 is provided with a first sealing groove 18. The inner conical surface of the slip seat 4 is provided with a second sealing groove 19 spaced from the groove 9, and a sealing ring is arranged in the first sealing groove 18 and the second sealing groove 19. The sealing ring can be selected from an elastomer sealing ring or a metal sealing ring. The elastomer sealing ring can be selected from a fluororubber sealing ring. The fluororubber sealing ring has excellent high-temperature resistance, oil resistance, chemical resistance and acid medium resistance, and is the most commonly used material for main sealing and key sealing in oil and gas wells, especially in wells containing corrosive media such as hydrogen sulfide, carbon dioxide and condensate oil.

[0039] The metal sealing ring is made of pure metal (such as copper and aluminum) or high-strength alloy steel, and the surface is often plated with a soft metal layer (such as silver and nickel). The metal sealing ring has the advantages of ultra-high pressure resistance, ultra-high temperature resistance, radiation resistance and long service life, and is often used in key static sealing points of wellhead devices or underwater Christmas trees.

[0040] The casing head is installed in the wellhead and is the main pressure-bearing carrier of the casing string. Moreover, the depth of the oil well is generally large, and the casing string must be kept from being deflected. Therefore, the horizontal precision of the casing head body 2 must be ensured during installation of the casing head. If the upper end surface of the casing head body 2 is not horizontal, the vertical axis of the casing head body 2 will be deflected, and the casing string cannot be well fitted with the slips during installation. The slips 3 and the casing string are different in axis, which affects the clamping of the casing string by the slips 3 and may even cause damage to the casing head.

[0041] In order to keep the upper end surface of the casing head body 2 horizontal during installation, a leveling assembly is arranged on the base 1, and the casing head body 2 is connected to the base 1 through the leveling assembly. The leveling assembly is used to keep the upper end surface of the casing head body 2 horizontal during installation of the casing head body 2.

[0042] The leveling assembly comprises leveling motors 20 fixedly arranged on the base 1. The leveling motors 20 are arranged in an array in the circumferential direction and are at least three in number. A lead screw 21 is fixedly arranged on the power output shaft of each leveling motor 20. A flange plate 22 is fixedly arranged at the bottom of the casing head body 2. A first semispherical groove 23 is arranged at a position opposite to the lead screw 21 on the bottom surface of the flange plate 22. A fixed plate 24 is detachably arranged at the bottom of the flange plate 22. A second semispherical groove 25 is arranged on the upper end surface of the fixed plate 24 opposite to the first semispherical groove 23. A spherical nut 26 is rotatably arranged in the first semispherical groove 23 and the second semispherical groove 25. The spherical nut 26 is threadedly connected to the lead screw 21. Two bubble levels perpendicular to each other are arranged on the upper end surface of the flange plate 22. Fixed holes 27 are arranged on the base 1 spaced from the leveling motors 20. Fixed pins are arranged in the fixed holes 27.

[0043] In the installation of the casing head, the base is placed on the ground or well platform, the fixing pins are passed through the fixing holes 27, the pins are inserted into the ground or well platform, the base 1 is fixed, after the base is fixed, the three leveling motors 20 are adjusted according to the positions of the bubbles in the two bubble levels on the upper end face of the flange 22, so that the upper end face of the casing head body 2 is kept horizontal, at this time, the casing head body 2 is fixed, the casing head body 2 can be welded with the surface casing or connected through the flange, and the installation of the casing head body 2 is completed.

[0044] In the leveling of the upper end face of the casing head body 2, the three leveling motors 20 are respectively started according to the positions of the bubbles in the two bubble levels, the heights of the casing head body 2 in three directions are controlled, the bubbles in the bubble levels are moved to the middle positions, and it is indicated that the leveling of the casing head body 2 is completed.

[0045] The spherical nut 26 can be omni-directionally rotated in the spherical space formed by the first half-spherical recess 23 and the second half-spherical recess 25, in the leveling of the casing head body 2, when one of the lead screws 21 is rotated, the inclination of the casing head body 2 will not affect the positions between the other two lead screws 21 and the spherical nut 26, and interference between the three lead screws 21 is prevented.

[0046] The perpendicularity precision of the upper end face of the casing head body 2 to the axis should be within the range of the machining precision requirement.

[0047] The main structure of the bubble level is a glass tube, the inner wall of the glass tube is curved in the upper part, liquid (such as alcohol or ether) is filled in the glass tube, and a bubble is left. Since the bubble has a smaller density than the liquid, it always stays at the highest point of the glass tube. When the level is placed on a horizontal surface, the bubble stays at the scale position in the center of the glass tube; if the surface is inclined, the bubble moves to the high side. Two bubble levels arranged perpendicularly to each other adjust the horizontal state of two perpendicular directions respectively, when the horizontal state of the two perpendicular directions is reached, the plane formed by the two directions is the horizontal plane, the two bubble levels arranged perpendicularly to each other do not affect each other in the leveling, and the leveling efficiency can be improved.

[0048] The casing head body 2 can be welded on the surface casing, and the slip 3 can use a split slip.

[0049] The beneficial effects of the above technical scheme are: The casing head for preventing leakage of the oilfield wellhead disclosed by the application is provided with the leakage prevention mechanism on the slip seat, when the pressure between the casing string in the well and the surface casing increases, the lower end of the slip is subjected to upward pressure, the leakage prevention mechanism is started to lock the slip and the slip seat, the upward micro-displacement of the slip is prevented, the sealing failure between the slip and the slip seat is prevented, and the safety of the wellhead is protected.

[0050] In the description of the application, it is to be understood that the orientations or positional relationships indicated by the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like are based on the orientations or positional relationships shown in the drawings, and are only for the convenience of describing the application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the application.

[0051] In the present application, unless otherwise clearly specified and limited, the terms "mounting", "connecting", "connecting", "fixing" and the like should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or it can be integrated; it can be mechanically connected, or it can be electrically connected or communicate with each other; it can be directly connected, or it can be indirectly connected through an intermediate medium; it can be the internal communication of two elements or the interaction relationship between two elements, unless otherwise clearly limited. For those skilled in the art, the specific meanings of the above terms in the present application can be understood according to the specific circumstances.

[0052] Although the embodiments of the present application have been disclosed as above, it is not limited only to the applications listed in the specification and embodiments, and it can be fully applied to various fields suitable for the present application, and additional modifications can be easily realized by those skilled in the art, and therefore the present application is not limited to specific details and the figures shown and described herein, without departing from the general concept defined by the claims and the equivalent scope.

Claims

1. A casing head for leak prevention at oilfield wellheads, characterized in that, The casing includes a base (1), a casing head body (2), slips (3), slip seat (4), and a leak prevention mechanism (5). The casing head body (2) is mounted on the base (1), the slip seat (4) is mounted inside the casing head body (2), and the slips (3) is mounted inside the slip seat (4). The lower part of the outer circumference of the slips (3) is a conical surface, and the upper part of the inner wall of the slip seat (4) is an inner conical surface. The conical surface and the inner conical surface are connected in a fit. The leak prevention mechanism (5) is mounted on the slip seat (4) and locks the slips (3) when the slips (3) are subjected to upward pressure in the well.

2. The casing head for leak prevention at oilfield wellheads according to claim 1, characterized in that, The anti-leakage mechanism (5) includes a piston (6) and a snap-fit ​​block (7). An annular hydraulic chamber (8) is opened in the slip seat (4). An annular groove (9) is opened on the inner conical surface of the slip seat (4). Multiple piston holes (11) are opened on the inner wall of the slip seat (4) along the circumferential direction. The piston (6) is set in the piston hole (11), and the snap-fit ​​block (7) is set in the groove (9).

3. The casing head for preventing leakage at oilfield wellheads according to claim 2, characterized in that, Piston holes (10) are arrayed along the circumferential direction on the bottom surface of the groove (9). The piston holes (10) are connected to the hydraulic chamber (8). The snap block (7) includes an arc plate (12) and a piston (13). The piston (13) is fixedly set on the surface of the protruding side of the arc plate (12). The arc plate (12) is set in the groove (9), and the piston (13) is set in the piston hole (10). An annular limiting groove (14) is opened on the outer circumference of the card (3) opposite to the groove (9), and the arc plate (12) is engaged in the limiting groove (14).

4. The casing head for preventing leakage at oilfield wellheads according to claim 3, characterized in that, The anti-leakage mechanism (5) also includes a spring (15), one end of which is connected to the end face of the piston (6) near the hydraulic chamber (8), and the other end of which is connected to the side wall of the hydraulic chamber (8).

5. The casing head for preventing leakage at oilfield wellheads according to claim 4, characterized in that, The inner wall of the sleeve head body (2) is provided with a bearing surface (16), which is conical. The bottom of the slip seat (4) is an outer conical surface (17) that is adapted to the shape of the bearing surface (16). The outer conical surface (17) is pressed onto the bearing surface (16).

6. The casing head for leak prevention at oilfield wellheads according to claim 5, characterized in that, A first sealing groove (18) is opened on the inner wall of the sleeve head body (2) and the outer circumferential surface of the slip seat (4). A second sealing groove (19) is opened at an interval between the inner conical surface of the slip seat (4) and the groove (9), and a sealing ring is provided in both the first sealing groove (18) and the second sealing groove (19).

7. The casing head for preventing leakage at oilfield wellheads according to claim 1, characterized in that, A leveling component is provided on the base (1). The sleeve head body (2) is connected to the base (1) through the leveling component. The leveling component is used to keep the upper surface of the sleeve head body (2) horizontal when the sleeve head body (2) is installed.

8. The casing head for preventing leakage at oilfield wellheads according to claim 7, characterized in that, The leveling assembly includes a leveling motor (20) fixedly mounted on a base (1). At least three leveling motors (20) are arranged in an array along the circumferential direction. A lead screw (21) is fixedly mounted on the power output shaft of the leveling motor (20). A flange (22) is fixedly installed at the bottom of the sleeve head body (2). A first hemispherical groove (23) is opened on the bottom surface of the flange (22) opposite to the lead screw (21). A fixing plate (24) is detachably installed at the bottom of the flange (22). A second hemispherical groove (25) is opened on the upper surface of the fixing plate (24) opposite to the first hemispherical groove (23). A spherical nut (26) is rotatably installed in the first hemispherical groove (23) and the second hemispherical groove (25). The spherical nut (26) is threadedly connected to the lead screw (21).

9. The casing head for preventing leakage at oilfield wellheads according to claim 8, characterized in that, Two mutually perpendicular bubble levels are installed on the upper surface of the flange (22).

10. The casing head for preventing leakage at oilfield wellheads according to claim 9, characterized in that, Fixing holes (27) are provided on the base (1) at intervals from the leveling motor (20), and fixing pins are installed in the fixing holes (27).

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