A pressure-resistant and corrosion-resistant multi-stage casing head with interchangeable hangers of different styles

Abstract

A pressure-resistant and corrosion-resistant multi-stage casing head with interchangeable hangers of different styles, which is composed of a base, a multi-stage casing head four-way, mandrel-type casing hangers of different specifications, slip-type casing hangers, and matching sealing collars, wing valves, threaded flanges, pressure gauge assemblies, threaded connectors, and sealing parts. In the center hole above the multi-stage casing head four-way, a mandrel-type casing hanger with an extended neck can be installed, and a slip-type casing hanger can also be replaced; the center holes, BT sealing rings, and grease injection valves below the casing head four-way above the lower level can seal the extended neck above the mandrel-type casing hanger of the next level, and can also seal the upper end of the casing clamped by the replaced slip-type casing hanger through the matching sealing collar. In addition, the non-metallic materials in the sealing parts are all fluororubber or highly saturated hydrogenated nitrile rubber. This makes it more suitable for use in complex well conditions and wells with high pressure, high corrosion, and high temperature differences.

Description

Technical Field

[0001] The invention relates to a casing head in oil and natural gas drilling equipment. Background Art

[0002] The vast majority of multi-stage casing heads in existing oil and gas drilling and production equipment are of the type that only uses a mandrel hanger or a slip hanger; only a very small number of multi-stage casing heads use a structure that uses a mandrel hanger and a slip hanger in a graded combination; however, none of them have the function of interchangeable different types of hangers in the center hole of the casing head spool above the third level. In the drilling and production process of more and more ultra-deep wells, large-reach wells, horizontal wells, high-temperature and high-pressure wells, and collapse wells, it is often encountered that the conventional mandrel hanger is difficult to install and hang the casing smoothly, and the slip hanger needs to be replaced urgently. Abnormal well conditions. Due to the high pressure level of the multi-stage casing head, the product volume is large and the cost price is high; if the casing head needs to be replaced as a whole in abnormal well conditions, or the casing head spool and hanger components of the previous level are replaced as a whole, it is bound to cause a large loss of manpower and material resources, and will affect the drilling and production progress of oil and gas wells.

[0003] When replacing different styles of casing hangers in the center hole of the ultra-high pressure casing head four-way, two major problems need to be solved: first, the casing hangers of different styles and specifications and the center holes of the casing head four-way should be standardized in design to achieve the interchangeability of the casing hangers while ensuring their basic functions such as hanging, sealing and disassembly; second, the sealing component in the center hole of the casing head four-way or conversion flange of the previous level should be able to seal the extended neck of the mandrel hanger and the casing clamped by the cava hanger of different diameters to achieve the purpose of complete universality. Summary of the invention

[0004] In order to solve the above-mentioned problems, the present invention adopts group technology and new structure, and innovatively designs the existing multi-stage casing head products, so that different styles of casing hangers can be replaced in the central hole of the four-way casing head of each stage of the multi-stage casing head, and the sealing reliability is improved to meet the drilling and production needs of ultra-high pressure oil and gas wells.

[0005] The present invention is composed of a base, a multi-stage casing head spool, mandrel-type casing hangers of different specifications, a slip-type casing hanger, and matching sealing collars, wing valves, threaded flanges, a pressure gauge assembly, threaded connectors, and sealing components. The unique feature of the present invention is that a mandrel-type casing hanger with an extended neck can be installed in the center hole above the multi-stage casing head spool, and a slip-type casing hanger can also be replaced. The center holes, BT sealing rings, and grease injection valves below the casing head spools of each level above the lower level can seal the extended neck above the mandrel-type casing hanger of the next level, and can also seal the upper end of the casing clamped by the replaced slip-type casing hanger through the matching sealing collar.

[0006] In addition, the non-metallic materials of the various sealing rings and sealing fillers described in the present invention are "FKM fluororubber" or "HNBR highly saturated hydrogenated nitrile rubber".

[0007] Since the center holes of the multi-stage casing head four-way of the present invention can be installed with mandrel-type casing hangers and can also be replaced with cava-type casing hangers, the versatility of product parts and components and the ability to cope with complex well conditions are improved, avoiding the loss of manpower, material resources and time caused by the need to replace different types of casing hangers. Since the mandrel-type casing hanger with an extended neck and the cava-type casing hanger with a sealing collar component are used, both have the function of multiple sealing of the upper and lower ends of the two hangers; in addition, the non-metallic seals used are made of "fluororubber" or "highly saturated hydrogenated nitrile rubber" materials. The high pressure resistance and corrosion resistance of the product are further improved, making it more suitable for use in complex well conditions and oil and gas wells with high pressure, high corrosion and high temperature difference. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 It is a schematic diagram of the overall structure of the present invention in which a mandrel-type casing hanger is installed on the right side and a slip-type casing hanger is installed on the left side in the center of the third-stage casing head spool;

[0009] Figure 2 It is a schematic diagram of the middle and lower mandrel casing hanger components, with a full cross-sectional structure enlargement;

[0010] Figure 3 It is a schematic diagram of the upper mandrel type casing hanger component, with a full cross-sectional structure enlargement;

[0011] Figure 4 It is a schematic diagram of the enlarged half-section structure of the slip-type casing hanger and the matching sealing collar component;

[0012] Figure 5 for Figure 1 At center A, the FS seal ring and BT seal ring inside and outside the sealing collar are removed and enlarged in cross-section;

[0013] Figure 6 An upper-stage wing valve component supporting the upper-stage casing head cross-piece, a half-section structure enlarged schematic diagram viewed horizontally from above;

[0014] Figure 7 The intermediate wing valve and the lower wing valve matching the intermediate and lower pipe head spools are an enlarged schematic diagram of a half-section structure viewed horizontally from above;

[0015] The names of the parts indicated by the numbers in the accompanying drawings are as follows:

[0016] 1. Base, 2. Lower casing head spool, 3. Mandrel-type casing hanger, 3-1. Casing hanger, 3-2. O-ring, 3-3. Rectangular sealing ring, 3-4. Compression ring, 3-5. Round nut, 3-6. Set screw, 4. Intermediate wing valve, 5. Threaded flange, 6. Pipe plug, 7. Intermediate casing head spool, 8. Upper casing head spool, 9. Upper mandrel-type casing hanger, 9-1. Casing hanger, 9-2. Compression ring, 9-3. Rectangular sealing ring, 9-4. Upper extrusion ring, 9-5. X-type metal sealing ring, 9-6. Lower extrusion ring, 9-7. Round Nut, 9-8, set screw, 10, sealing collar, 10-1, collar casing, 10-2, FS sealing ring, 11, slip type casing hanger, 11-1, slip seat, 11-2, slip, 11-3, perforated sealing ring, 11-4, clamping ring, 11-5, hexagon socket screw, 11-6, connecting screw, 12, locking component, 13, upper wing valve, 14, pressure gauge assembly, 15, grease injection valve, 16, BT sealing ring, 17, sealing gasket, 18, stud nut, 19, lower wing valve, 20, small sealing gasket, 21, small stud nut. DETAILED DESCRIPTION

[0017] The present invention will be further described below in conjunction with the accompanying drawings:

[0018] Figure 1 In the invention, the base, multi-layer casing head spool, mandrel-type casing hangers of different specifications, slip-type casing hangers, and matching sealing collars, wing valves, threaded flanges, pressure gauge assemblies, threaded connectors, and sealing parts are composed; among them: the superimposed structure of the three-stage casing head spool and casing hanger is a common structure of the multi-stage casing head; and the superimposed structure of the casing head spool and casing hanger of more than four levels is a rare structure, which is rarely required by customers; if necessary, different pipe diameters can be designed according to the same casing head spool and casing hanger structure. In the invention, the base, multi-stage casing head spool, mandrel-type casing hangers of different specifications, slip-type casing hangers and sealing collars are basic components, and their structural forms remain unchanged; and the wing valves, threaded flanges and pressure gauge assemblies and other parts and components on both sides will be changed in quantity, installation direction and method according to customer requirements, but it does not affect the innovative theme of the invention.

[0019] The lower casing head spool 2 of the present invention is welded on the base 1, installed on the cement foundation of the wellhead, and connected to the surface casing by the tapered pipe thread at the lower end of the center hole; the intermediate casing head spool 7 and the upper casing head spool 8 are superimposed on the lower casing head spool 2, and connected together by sealing gaskets 17 and stud nuts 18 of different sizes. On the left and right sides of the tertiary casing head spool, small sealing gaskets 20 and small stud nuts 21 are used to connect the lower wing valve 19, the intermediate wing valve 4, the upper wing valve 13 and the threaded flange 5; on the outside of the threaded flange 5, a pressure gauge assembly 14 can be installed to measure the pressure between the casings; it can also be blocked with a pipe plug 6, or connected to an external pipeline. In the center holes above the lower casing head spool 2, the intermediate casing head spool 7 and the upper casing head spool 8, the mandrel-type casing hanger 3 and the upper mandrel-type casing hanger 9 with better performance and different diameters are preferably installed; and in accordance with a predetermined ratio, different specifications of the slip-type casing hanger 11 that can be interchanged with the third-level mandrel-type casing hanger are matched. The center holes below the intermediate casing head spool 7 and the upper casing head spool 8, as well as the two grease injection valves 15 and BT sealing rings 16, can seal the extension neck above the mandrel-type casing hanger 3 of the next level, and can also seal the upper end of the casing clamped by the replaced slip-type casing hanger 11 through the matching sealing collar 10. The mandrel-type casing hangers 3 and 9 or the slip-type casing hanger 11 installed in the third-level casing head spool are all compressed and fixed by the locking components 12 evenly distributed above the third-level casing head spool.

[0020] In the present invention, the center of the lower casing head spool 2 is a through step hole, and the upper step hole can be respectively installed with a large diameter mandrel-type casing hanger 3 or a slip-type casing hanger 11; the lower step hole is processed with a tapered pipe thread for connecting the surface casing. The upper part of the lower casing head spool 2 is a large flange, and the upper part of the large flange is processed with evenly distributed stud holes and a trapezoidal gasket ring groove for connecting with the middle casing head spool 7; on the circumference of the upper flange, there are processed a plurality of evenly distributed horizontal step holes with threads at both ends and connected to the center hole, and the holes are equipped with locking components 11 with threaded pressure caps and sealing fillers to compress the casing hanger in the center hole. The lower middle part of the lower casing head cross 2 is a hollow cylinder of the same diameter, and two planes are processed on the corresponding two sides of the cylinder; in the middle part of the two planes, there is a bypass hole that penetrates the center hole, and at the outer openings of the bypass holes of the two planes, there are multiple evenly distributed threaded blind holes and a trapezoidal gasket ring groove, which are used to connect the lower-stage wing valve 19 and other components.

[0021] The center of the intermediate casing head spool 7 is a through stepped hole. The upper stepped hole can be used to install a medium-diameter mandrel-type casing hanger 3 or a slip-type casing hanger 11 respectively; the lower stepped hole is a cylindrical hole that accommodates the extended neck of the next-level mandrel-type casing hanger 3. Two rectangular grooves are cut on the wall of the cylindrical hole, and a BT sealing ring 16 is installed in each rectangular groove. The upper part of the intermediate casing head spool 7 is a neck flange, and the neck flange is machined with evenly distributed stud holes and a trapezoidal gasket ring groove on the top, which is used to connect with the upper casing head spool 8; on the circumference of the neck flange, there are multiple evenly distributed horizontal stepped holes with threads at both ends and connected to the center hole. The holes are equipped with locking components 11 with threaded pressure caps and sealing fillers to compress the casing hanger in the center hole. The middle of the intermediate casing head spool 7 is a hollow cylinder of the same diameter, and the corresponding two sides of the cylinder are processed into planes; in the middle of the two planes, there is a bypass hole that penetrates the center hole, and at the outer openings of the bypass holes of the two planes, there are multiple evenly distributed threaded blind holes and a trapezoidal gasket ring groove, which are used to connect the intermediate wing valve 4 and other parts. Below the intermediate casing head spool 7 is a large flange, and the bottom of the large flange is processed with evenly distributed stud holes and a trapezoidal gasket ring groove, which is used to connect with the lower casing head spool 2; on the circumference of the large flange, four horizontal step holes with threads at the inlet end and connected to the rectangular groove in the center hole are processed symmetrically one above and one below, and grease injection valves 15 are installed at the hole openings to inject plastic sealing grease and squeeze BT sealing rings 16 to seal the extension neck above the next-level mandrel-type casing hanger 3.

[0022] The center of the upper casing head spool 8 is also a through stepped hole. The upper stepped hole can be used to install the upper mandrel-type casing hanger 9 or the slip-type casing hanger 11 with a smaller diameter; the lower stepped hole is a cylindrical hole that accommodates the extended neck above the lower mandrel-type casing hanger 3. Two rectangular grooves are also cut on the hole wall of the cylindrical hole, and a BT sealing ring 16 is installed in each of the rectangular grooves. The upper and lower parts of the upper casing head cross 8 are neck flanges, and both end faces of the upper and lower neck flanges are processed with evenly distributed stud holes and a trapezoidal gasket groove for external connection; on the circumferential edge of the upper neck flange, there are multiple evenly distributed horizontal step holes with threads at both ends and connected to the center hole, and the holes are equipped with locking components 11 with threaded pressure caps and sealing fillers for tightening the casing hanger in the center hole; on the circumferential edge of the lower neck flange, four horizontal step holes with threads at the inlet ends and connected to the rectangular groove in the center hole are processed symmetrically one above and one below, and grease injection valves 15 are installed at the hole mouths for grease injection and squeezing the BT sealing ring 16 for sealing. The middle of the upper casing head cross 8 is a hollow cylinder of the same diameter, and planes are processed on the corresponding two sides of the cylinder; in the middle of the two planes, there is a bypass hole that penetrates the center hole, and at the outer openings of the bypass holes of the two planes, there are multiple evenly distributed threaded blind holes and a trapezoidal gasket ring groove for connecting the upper wing valve 13 and other components.

[0023] Figure 2In the present invention, the mandrel type casing hanger 3 used in the lower casing head spool 2 and the intermediate casing head spool 7 is composed of a casing hanger 3-1, an O-ring 3-2, a rectangular sealing ring 3-3, a clamping ring 3-4, a round nut 3-5 and a set screw 3-6; a double sealing structure of the O-ring 3-2 and the rectangular sealing ring 3-3 is adopted to implement the main seal on the lower end of the hanger. The casing hanger 3-1 is a hollow columnar body with a thick middle and thin ends. The center of the columnar body is a through step hole. Both ends of the step hole are processed into tapered pipe threads. The tapered pipe thread at the lower end is used to connect the hanging casing, and the tapered pipe thread at the upper end is used to connect the drill pipe, so as to facilitate the disassembly and assembly of the hanger; the upper and lower ends of the columnar body are smooth extension necks, and the extension neck at the upper end is used to penetrate into the central hole of the upper-level casing head four-way for sealing, so as to improve the high-pressure resistance of the casing head product; in the middle of the columnar body is a large-diameter cylinder, and the upper side of the cylinder is a large chamfer, which is used to connect with the lower-level casing head four-way 2 and the intermediate casing head four-way The locking component 12 in the through-hole 7 cooperates to compress and fix; a groove is cut in the middle of the cylinder, and an O-ring 3-2 is installed in the groove to enhance its sealing performance; below the middle cylinder is a cylinder with reduced diameter and a stud body, which are successively equipped with a rectangular sealing ring 3-3, a clamping ring 3-4 with a large chamfer, a round nut 3-5 and a set screw 3-6; the large chamfer on the clamping ring 3-4 cooperates with the step chamfer in the center hole of the lower casing head spool 2 and the intermediate casing head spool 7 to suspend the casing and convert the gravity of the suspended casing into the clamping force of the rectangular sealing ring 3-3.

[0024] Figure 3In the present invention, the upper mandrel type casing hanger 9 used in the upper casing head spool 8 is composed of a casing hanger 9-1, a clamping ring 9-2, a rectangular sealing ring 9-3, an upper extrusion ring 9-4, an X-shaped metal sealing ring 9-5, a lower extrusion ring 9-6, a round nut 9-7, and a set screw 9-8; a double sealing structure of a rectangular sealing ring 9-3 and an X-shaped metal sealing ring 9-5 is adopted to implement main sealing on the lower end of the hanger. The casing hanger 9-1 is also a hollow columnar body with a thick middle and thin ends. The center of the columnar body is a through step hole. Both ends of the step hole are processed into tapered pipe threads, which are used to connect the hanging casing and drill pipe respectively; the upper and lower ends of the columnar body are smooth elongated necks, and the elongated neck at the upper end is used to penetrate into the center hole of the upper-level component for sealing; in the middle of the columnar body is a large-diameter cylinder, and the upper and lower surfaces of the cylinder are both cylinders with reduced diameters and stud bodies, on which are installed rectangular sealing rings 9-3 and large-chamfered clamping rings 9-2 in sequence. , round nut 9-7, set screw 9-8, the large chamfered clamping ring 9-2 cooperates with the locking component 12 in the upper casing head four-way 8 to compress, fix and seal; the upper extrusion ring 9-4, X-shaped metal sealing ring 9-5, lower extrusion ring 9-6, round nut 9-7, set screw 9-8 are installed in sequence below; the large chamfer on the lower extrusion ring 9-6 cooperates with the step chamfer in the center hole of the upper casing head four-way 8 to suspend the casing and convert the gravity of the suspended casing into the compression force of the X-shaped metal sealing ring 9-5.

[0025] Figure 4In the invention, the cava type casing hanger 11 is a WE type cava type casing hanger structure commonly used in the market, and its main parts include: a cava seat 11-1, a cava 11-2, a perforated sealing ring 11-3, a clamping ring 11-4, a hexagon socket screw 11-5, and a connecting screw 11-6; through the hexagon socket screw 11-5 and the locking component 12 in the casing head cross, the clamping ring 11-4 and the perforated sealing ring 11-3 are connected and pressed, and the clamped casing and the lower end of the hanger are actively sealed to ensure the reliability of the seal. The slip seat 11-1 is a hollow cylindrical part with a thick top and a thin bottom. The upper end surface is processed with a plurality of evenly distributed threaded blind holes for connecting the perforated sealing ring 11-3, the clamping ring 11-4 and the hexagon socket screw 11-5. The center is processed into a stepped hole with an inverted cone as the main part, which cooperates with the tapered slip 11-2 to generate radial clamping force. The transitional large chamfer is at the intersection of the thick top and the thin bottom column, which cooperates with the stepped chamfer in the center hole of the casing head cross. , hanging casing; several radial through holes are evenly distributed on the thinner column below, so that the slips 11-2 cut into several pieces can be fixed with screws; because the slip type casing hanger 11 is used on site to clamp the casing radially, the slip seat 11-1 is symmetrically cut into two halves, and two opposite step holes and threaded blind holes are symmetrically processed on the tangent and incision parts of the circumference below its thicker column, and they are combined into a whole with connecting screws 11-6. The center of the slip 11-2 is a serrated through hole, which is used to clamp the corresponding sleeve; the upper part of the periphery is processed into an arc body, and the middle and lower parts are processed into a cone body, and are symmetrically cut into 6 to 4 pieces according to the diameter of the clamping sleeve to improve the clamping effect; below the cone of the slip 11-2, 6 to 4 radial threaded holes are symmetrically processed, that is, one hole per piece. Before use, the sliced ​​slip 11-2 is positioned and connected with the slip seat 11-1 by a screw rod to facilitate packaging, transportation and installation. The perforated sealing ring 11-3 is an annular non-metallic part, and its upper and lower planes have evenly distributed screw holes. The sealing surfaces on both the inner and outer sides have upper and lower arc-shaped protrusions, which will produce a double sealing effect under the action of pressure. Also because of the need for on-site assembly, the clamping ring 11-4 is symmetrically cut into two pieces, and the elastic perforated sealing ring 11-3 is cut with an oblique mouth.

[0026] Figure 4 and Figure 5In the invention, each slip-type casing hanger 11 is equipped with a sealing collar 10 whose inner diameter matches the outer diameter of the clamped casing; the sealing collar 10 is composed of a collar sleeve 10-1 and a FS sealing ring 10-2; the collar sleeve 10-1 is a hollow cylinder, and two grooves are processed above its smooth center hole, and a FS sealing ring 10-2 is installed in each groove; 2 to 4 radial through holes are processed below its cylinder to facilitate the removal of the sealing collar 10. The main part of the FS sealing ring 10-2 is made of non-metallic material, and an elastic steel wire ring is inlaid on each of its two raised shoulders to enhance its anti-deformation ability.

[0027] Figure 6 and Figure 7 In the process of using the multi-stage casing head, the working pressure is different due to the different depths of the connected casing layers, and the pressure level is high at the top and low at the bottom. For this reason, the upper wing valve 13 matched with the upper casing head 4-way 8 adopts a manual open-stem flat valve with a tail rod and a sand-proof plate driven by a ball screw pair to reduce the operating resistance of the valve and the sand plugging phenomenon during fracturing operations; the intermediate wing valve 4 and the lower wing valve 19 matched with the lower casing head 4-way 2 and the intermediate casing head 4-way 7 both adopt a manual open-stem flat valve without a tail rod and a sand-proof plate driven by a trapezoidal thread pair to reduce production costs; the lower wing valve 19 can also adopt an 8-shaped driving hand wheel to adapt to the narrow space installed under the surface.

[0028] The O-ring 3-2, rectangular sealing rings 3-3, 9-3 and perforated sealing ring 11-3 used in the casing hanger of the present invention, the FS sealing ring 10-2 used in the sealing collar 10, the BT sealing ring 16 used in the casing head cross and the sealing filler used in the locking component 11 are all made of non-metallic materials such as "FKM fluororubber" or "HNBR highly saturated hydrogenated nitrile rubber", thereby improving the corrosion resistance of the multi-stage casing head.

Claims

1. A pressure-resistant and corrosion-resistant multi-stage casing head with interchangeable hangers of different styles, which is composed of a base, a multi-stage casing head spool, mandrel-type casing hangers of different specifications, slip-type casing hangers, and matching sealing collars, wing valves, threaded flanges, pressure gauge assemblies, threaded connectors, and sealing components; its characteristics are: In the center hole above the multi-stage casing head spool, a mandrel-type casing hanger with an extended neck can be installed, and a slip-type casing hanger can also be replaced; the center hole, BT sealing ring and grease injection valve below the casing head spool above the lower level can seal the extended neck above the mandrel-type casing hanger of the next level, and can also seal the upper end of the casing clamped by the replaced slip-type casing hanger through the matching sealing collar; Each slip-type casing hanger is equipped with a sealing collar whose inner diameter matches the outer diameter of the clamped casing; the sealing collar is composed of a collar sleeve and a FS sealing ring; the collar sleeve is a hollow cylinder, and two grooves are processed above the smooth center hole of the hollow cylinder, and a FS sealing ring is installed in each groove; 2 to 4 radial through holes are processed below the hollow cylinder; the main part of the FS sealing ring is made of non-metallic material, and an elastic wire ring is inlaid on each of the two raised shoulders of the FS sealing ring; The mandrel-type casing hanger used in the lower casing head spool and the intermediate casing head spool consists of a casing hanger, an O-ring, a rectangular sealing ring, a clamping ring, a round nut and a set screw. The O-ring and the rectangular sealing ring double sealing structure are used to implement the main seal on the lower end of the hanger. The casing hanger is a hollow columnar body with a thick middle and thin ends. The center of the columnar body is a through step hole, and both ends of the step hole are processed into tapered pipe threads. The upper mandrel type casing hanger used in the upper casing head spool is composed of a casing hanger, a clamping ring, a rectangular sealing ring, an upper extrusion ring, an X-shaped metal sealing ring, a lower extrusion ring, a round nut and a set screw. A double sealing structure of a rectangular sealing ring and an X-shaped metal sealing ring is adopted to implement the main seal on the lower end of the hanger. The casing hanger is also a hollow columnar body with a thick middle and thin ends. The center of the column is a through step hole, and both ends of the step hole are processed into tapered pipe threads.

2. The pressure-resistant and corrosion-resistant multi-stage casing head with interchangeable hangers of different styles according to claim 1 is characterized by: The slip-type casing hanger used adopts the WE type slip-type casing hanger structure, including: slip seat, slip, perforated sealing ring, hexagon socket screw, clamping ring, connecting screw; the perforated sealing ring is an annular non-metallic part, and the upper and lower planes of the perforated sealing ring have evenly distributed screw holes, and the sealing surfaces on the inner and outer sides have two upper and lower arc-shaped protrusions.

3. The pressure-resistant and corrosion-resistant multi-stage casing head with interchangeable hangers of different styles according to claim 1 is characterized by: The upper wing valve matched with the upper casing head four-way adopts a manual rising stem flat plate valve with a tail rod and a sand control plate driven by a ball screw pair; the intermediate wing valve and lower wing valve matched with the lower casing head four-way and the intermediate casing head four-way both adopt a manual rising stem flat plate valve without a tail rod and a sand control plate driven by a trapezoidal thread pair.

4. The pressure-resistant and corrosion-resistant multi-stage casing head with interchangeable hangers of different styles according to claim 2 is characterized by: The non-metallic materials used in the O-rings, rectangular sealing rings and perforated sealing rings used in the casing hanger, the FS sealing rings used in the sealing collars, the BT sealing rings used in the casing head crosses and the sealing packings set in the locking components are all "FKM fluororubber" or "HNBR highly saturated hydrogenated nitrile rubber".

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