A pressure-relief sealing easy-drilling float collar for oil and gas well cementing

Abstract

The present application relates to oil and gas well cementing operation tool technical field, disclose a kind of oil and gas well cementing pressure relief sealing easy drilling float collar, float collar includes shell, seal base, sealing rubber core, porous pressure relief mandrel and mandrel base are sequentially arranged from top to bottom along the fluid positive direction of movement in shell;The sealing rubber core includes umbrella-shaped sealing head and sleeve rod, the slope of umbrella-shaped sealing head is first sealing surface, and the first sealing surface is matched with the first sealing surface on the sealing base First sealing surface of cooperation;The porous pressure relief mandrel is hollow inside, and elastic member is arranged in cavity, sleeve rod is slidably installed in the cavity of porous pressure relief mandrel and is abutted on elastic member, the side wall of porous pressure relief mandrel is provided with the opening being communicated with its internal cavity, opening is provided with the skirt wing being bowl-shaped, and the diameter of skirt wing gradually decreases along the direction of fluid positive movement.The present application can realize the effect of positive flow, reverse pressure relief, reduce reverse fluid pressure, thereby improve the safety and reliability of float collar.

Description

Technical Field

[0001] This invention relates to the field of cementing tools for oil and gas wells, and specifically to a pressure-reducing, easy-to-drill floating collar for cementing oil and gas wells. Background Technology

[0002] Cementing is an essential and indispensable part of drilling and completion operations. Casing couplings equipped with one-way valves are casing accessories that can be used in conjunction with casing floats to improve the safety of cementing operations. The floats ensure unidirectional flow of drilling fluid within the annulus during casing running, preventing backflow of cement slurry during cementing and allowing for pressure release and setting after cementing, thus contributing to better bonding quality between the cement sheath and the casing. Simultaneously, the buoyancy can be adjusted by injecting drilling fluid into the casing string, ensuring the casing suspension weight meets the design requirements for casing running operations.

[0003] Therefore, float collars are crucial cementing tools. Their sealing and check valve capabilities affect cementing speed, effectiveness, and safety, while the drillability of the tool core influences subsequent construction progress. Patent CN117605426A discloses a float collar with axial surface sealing. The float collar includes a housing, and inside the housing, sequentially arranged a valve seat, a valve core, an elastic element, and a base. The valve seat is threaded to the inner side of the housing, and a first sealing body is provided between the valve seat and the housing to ensure a seal. The upper part of the valve core has a groove, within which a second sealing body is provided to seal the valve core and valve seat. The upper end of the elastic element is connected to the valve core, and the lower end is connected to the base.

[0004] The aforementioned floating hoop cannot suppress the reverse flow of fluid or reduce the pressure of the reverse fluid. Therefore, sealing high-pressure reverse fluid for a long time and repeatedly poses a severe challenge to the sealing structure of the floating hoop. The rubber core and sealing components of the floating hoop are easily damaged, resulting in seal failure. Summary of the Invention

[0005] To address the problems and shortcomings of the existing technology, this invention proposes a pressure-reducing and easy-to-drill float collar for cementing oil and gas wells. The float collar of this invention can achieve the effect of forward flow and reverse counter-flushing pressure reduction, suppressing reverse flow of fluid, thereby improving the safety and reliability of the float collar, and also increasing the service life of the float collar.

[0006] To achieve the above-mentioned objectives, the technical solution of the present invention is as follows: This invention discloses a pressure-reducing sealing easy-drilling float collar for cementing oil and gas wells. The float collar includes: an outer shell, inside which a sealing base, a sealing core, a porous pressure-reducing mandrel, and a mandrel base are arranged sequentially from top to bottom along the positive fluid movement direction; the sealing core includes an umbrella-shaped sealing head and a sleeve, the inclined surface of the umbrella-shaped sealing head is a first sealing surface, and the sealing base has a first sealing mating surface that mates with the first sealing surface; the porous pressure-reducing mandrel is hollow inside, and an elastic element that easily generates axial elastic deformation is arranged inside the cavity; the sleeve of the sealing core is slidably arranged in the cavity of the porous pressure-reducing mandrel and abuts against the elastic element; the side wall of the porous pressure-reducing mandrel is provided with an opening communicating with its internal cavity, and a bowl-shaped skirt is provided at the opening, the diameter of which gradually decreases along the positive fluid movement direction.

[0007] Preferably, the elastic element is capable of moving up and down within the cavity of the porous pressure-reducing mandrel.

[0008] Preferably, the cavity inner wall of the porous pressure-reducing mandrel is provided with a keyway, and the surface of the sleeve is provided with a key, which is slidably disposed in the keyway.

[0009] Preferably, the bottom edge of the umbrella-shaped sealing head is provided with a horizontal extension edge, the horizontal surface of the extension edge forms a second sealing surface, and the sealing base has a second sealing mating surface that mates with the second sealing surface.

[0010] Preferably, a sealing element is provided between the outer wall of the porous pressure-reducing mandrel and the inner wall of the housing to seal the two.

[0011] Preferably, the outer wall of the porous pressure reducing mandrel is provided with an outer flange extending radially in the middle, and a sealing element is provided between the outer flange and the inner wall of the outer casing to seal the two.

[0012] Preferably, the umbrella-shaped sealing head includes a sealing head skeleton and a sealing rubber disposed on the surface of the sealing head skeleton, wherein the sealing rubber and the skeleton are vulcanized together.

[0013] Preferably, the elastic element includes a spring, one end of which abuts against the inner wall of the cavity of the porous pressure-reducing mandrel, and the other end abuts against the sleeve rod.

[0014] Preferably, an elastic element mounting seat that can reciprocate axially is installed inside the cavity of the porous pressure-reducing mandrel, and the elastic element is fixed on the mounting seat.

[0015] Preferably, the cavity of the porous pressure-reducing mandrel is provided with a flange for limiting the elastic element mounting seat.

[0016] Preferably, the porous pressure-reducing mandrel is threadedly connected to the mandrel base.

[0017] Preferably, the sealing base is threaded to the inner wall of the housing, and a sealing element is provided between the two to seal them together.

[0018] Preferably, the mandrel base is threaded to the inner wall of the housing, and a seal is provided between the two to seal them together.

[0019] The beneficial effects of this invention are: 1. The porous pressure-reducing mandrel of the present invention has several openings arranged axially on its surface, and a bowl-shaped skirt is provided at each opening. The diameter of the skirt gradually decreases along the direction of forward fluid movement. When the bottom fluid enters the porous mandrel from the bottom, under the combined action of the skirt structure and the openings, the fluid is divided into two streams: a branch that enters the float ring annulus from the side wall opening, passes through the skirt, and then enters the mandrel from the opening above the skirt; and a main stream that moves vertically axially within the mandrel cavity. When the branch fluid and the main stream fluid merge, since the two fluids have different directions, the fluid loses a significant amount of energy, thereby achieving a reverse counter-pressure reduction effect, suppressing the reverse flow of fluid, fundamentally reducing the pressure of the reverse fluid, and thus improving the safety and reliability of the float ring, as well as extending its service life.

[0020] 2. The porous pressure-reducing mandrel of the present invention has a sealing element between the two and the inner wall of the housing, which can prevent fluid from passing through the gap between the two and reduce the sealing effect of the floating hoop.

[0021] 3. Under the flow pressure of the reverse fluid, the movable elastic element mounting base of the present invention is pushed upward by the fluid, which in turn pushes the umbrella-shaped sealing core towards the sealing base, achieving a rapid sealing effect. Then, the mounting base compresses the elastic element, which further pushes the core upward, ultimately forming a reliable seal between it and the sealing base. The thrust of the elastic element in the present invention increases the contact pressure between the umbrella-shaped sealing core and the sealing base, providing a better sealing effect, further enhancing the sealing effect of the float band, and preventing the reverse fluid from moving further upward.

[0022] 4. The umbrella-shaped sealing core and the porous pressure-reducing mandrel of the present invention are connected by a key, which can prevent the sealing core from rotating during use, improve the drillability of the floating hoop, and facilitate drilling and removal.

[0023] 5. The umbrella-shaped sealing core of the float hoop of the present invention has a larger sealing area between it and the sealing base. Two sets of sealing structures are provided between the sealing base and the outer shell of the float hoop, including a beveled sealing structure and a planar sealing structure, so that the overall sealing effect of the float hoop is better. Attached Figure Description

[0024] The foregoing and hereinafter detailed description of the invention becomes clearer when read in conjunction with the following drawings, in which: Figure 1 This is a half-sectional schematic diagram of the internal structure of the floating hoop of the present invention; Figure 2 This is a schematic diagram of the internal structure of the float when the fluid is moving in the forward direction; Figure 3 A schematic diagram of the internal structure of the float when the fluid moves in the opposite direction; Figure 4 This is a three-dimensional schematic diagram of the porous step-down mandrel of the present invention; Figure 5 This is a front view of the porous pressure-reducing mandrel of the present invention.

[0025] In the picture: 1. Outer shell; 2. Sealing base; 3. Sealing core; 4. Multi-hole pressure-reducing mandrel; 5. Mandrel base; 6. First sealing surface; 7. Extension edge; 8. Second sealing surface; 9. First sealing mating surface; 10. Second sealing mating surface; 11. Elastic element; 12. Opening; 13. Skirt; 14. Elastic element mounting seat; 15. Outer flange; 301. Umbrella-shaped sealing head; 302. Sleeve rod. Detailed Implementation

[0026] To enable those skilled in the art to better understand the technical solutions of this invention, several specific embodiments will be used to further illustrate the technical solutions for achieving the objectives of this invention. It should be noted that the technical solutions claimed by this invention include, but are not limited to, the following embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without inventive effort should fall within the scope of protection of this invention.

[0027] Example 1 The present invention discloses a pressure-reducing, easy-drilling float collar for cementing oil and gas wells, as shown in the attached specification. Figure 1 As shown, the floating hoop includes a housing 1 for connection with the sleeve; and, The components arranged sequentially from top to bottom within the internal cavity of the outer casing 1 are: a sealing base 2, a sealing core 3, a porous pressure-reducing mandrel 4, and a mandrel base 5; wherein... The sealing base 2 has a fluid channel along the axial direction; The sealing core 3 can move up and down along the axial direction of the outer shell 1. It consists of an umbrella-shaped sealing head 301 and a sleeve 302 connected to the umbrella-shaped sealing head 301. The inclined surface of the umbrella-shaped sealing head 301 forms a first sealing surface 6. The sealing base 2 has a first sealing mating surface 9 that mates with the first sealing surface 6. The porous pressure-reducing mandrel 4 is hollow inside, and an elastic element 11 that is easy to generate axial elastic deformation is provided in its cavity. The sleeve 302 of the sealing core 3 is slidably disposed in the cavity of the porous pressure-reducing mandrel 4 and abuts against the elastic element 11. Furthermore, the side wall of the porous pressure-reducing mandrel 4 is provided with an opening 12 that communicates with its internal cavity. A bowl-shaped skirt 13 is provided at the opening 12, and the diameter of the skirt 13 gradually decreases along the direction of positive fluid movement.

[0028] In the embodiments described in this invention, the direction of fluid movement within the float collar is from top to bottom as the forward direction and vice versa. During cementing operations, the pumped drilling fluid, cement fluid, and other fluids flow into the float collar from above and flow forward from top to bottom within it. Under the action of the forward fluid, the sealing core 3 within the float collar is pushed downward, opening the fluid channel on the sealing base 2. The injected drilling fluid, cement fluid, etc., can then move forward within the float collar. Subsequently, the cement fluid enters the annulus of the casing, and finally, pressure is achieved, displacing all the cement slurry from the casing. After the cement grout is completely removed from the casing, when the cement grout enters the casing from the bottom and eventually flows back into the float, under the action of the reverse fluid pressure, the sealing core 3 is pushed towards the sealing base 2. The sealing core 3 is squeezed and adhered to the sealing base 2, and the first sealing surface 6 and the first sealing mating surface 9 are tightly fitted, blocking the fluid channel on the sealing base 2. The two achieve a reliable seal and effectively prevent the backflow liquid from continuing to flow back into the casing.

[0029] For the structure of the porous step-down mandrel 4, please refer to the attached instruction manual. Figure 4 and Figure 5 The porous pressure-reducing mandrel 4 is a hollow, variable-diameter cylindrical rod. Its internal cavity consists of multiple variable-diameter cavities, each cylindrical in shape with a circular cross-section. The upper cavity connected to the sleeve 302 should match the outer diameter of the sleeve 302 to achieve a sliding connection between the sleeve 302 and the porous pressure-reducing mandrel 4. The cavities in the middle and lower sections gradually increase in size. Furthermore, the mandrel's sidewalls are uniformly provided with several openings 12 along the circumferential and axial directions. These openings 12 communicate with the internal cavities of the mandrel. From an axial perspective, multiple rows of openings 12 are formed on the mandrel's sidewalls, with each row having multiple openings 12 circumferentially. At least one row of openings 12 on the sidewalls of the porous pressure-reducing mandrel 4 is provided with a bowl-shaped skirt 13, the diameter of which gradually decreases along the direction of fluid movement.

[0030] The principle of the floating hoop of the present invention is now described as follows: Refer to the appendix of the specification. Figure 2(The arrows in the diagram indicate the direction of the fluid). Forward circulation: The fluid enters the outer shell 1 from the upper end of the float ring, flows through the fluid channel of the sealing base 2, and acts on the umbrella-shaped sealing head 301 of the lower sealing core 3. Under the action of fluid pressure, the umbrella-shaped sealing head 301 detaches from the sealing base 2, begins to compress the elastic element 11 and moves downward. The fluid enters the inner cavity of the float ring and enters its internal cavity through the opening on the side wall of the porous pressure reducing mandrel 4. After entering the porous pressure reducing mandrel 4, the fluid is diverted and flows around the skirt. Due to the bowl-shaped skirt 13 design, the fluid flow is accelerated, and a forward circulation is formed in the wellbore more quickly.

[0031] Reverse sealing: Refer to the instruction manual appendix. Figure 3 (The arrows in the diagram indicate the fluid direction.) When the fluid flows in the reverse direction, it enters the inner cavity of the floating hoop through the internal cavity of the porous pressure-reducing mandrel 4. Under the action of the reverse fluid pressure, the sealing core 3 moves upward axially. The fluid pressure pushes the sealing core 3 to fit tightly against the sealing base 2, that is, the first sealing surface 6 and the first sealing mating surface 9 fit tightly together, achieving a reverse sealing effect and preventing the fluid from continuing to flow in the reverse direction. In addition, as... Figure 3 As shown, after the fluid enters the cavity of the mandrel, it is split into two streams: a branch that enters the floating hoop annulus through the side wall opening, passes through the skirt 13, and then enters the mandrel through the opening above the skirt 13; and a main stream that moves vertically along the axial direction within the mandrel cavity. The direction of the branch stream is different from that of the main stream. When the branch stream and the main stream merge, because the directions of the two streams are different, they form a countercurrent, which produces a blocking effect and reduces the kinetic energy of the reverse fluid. The resistance to the forward movement of the fluid also increases, which increases the resistance to the reverse flow of the fluid, thereby achieving the effect of reverse countercurrent pressure reduction. This fundamentally reduces the pressure of the reverse fluid, that is, reduces the pressure of the reverse fluid acting on the sealing core 3 and the various components inside the floating hoop. Ultimately, this improves the safety and reliability of the sealing core 3 and the internal seals of the floating hoop, and also increases their service life.

[0032] Understandably, if the sidewall of the porous pressure-reducing mandrel 4 is provided with multiple skirts 13, each skirt 13 is located between two adjacent rows of openings 12, and the fluid forms multiple counter-currents within the porous pressure-reducing mandrel 4, which greatly reduces the fluid kinetic energy.

[0033] Example 2 This embodiment discloses a pressure-reducing, easy-drilling floating collar for cementing oil and gas wells, based on Embodiment 1, and referring to the appendix of the instruction manual. Figure 1 The elastic element 11 can not only generate axial elastic deformation, but the entire elastic element 11 can also move up and down in the cavity of the porous pressure reducing mandrel 4. That is to say, the elastic element 11 is not fixedly connected to the cavity of the porous pressure reducing mandrel 4, but is movably arranged in the cavity, with only one end abutting against the flange provided on the inner wall of the cavity.

[0034] In other words, the flange structure on the inner wall of the porous pressure-reducing mandrel 4 restricts the further downward movement of the elastic element 11, ensuring that the elastic element 11 is fully compressed by the forward fluid while limiting the downward movement distance of the sealing core 3 and the elastic element 11. Furthermore, based on the aforementioned movable elastic element 11 structure, during reverse sealing of the float hoop, the movable elastic element moves upward under fluid pressure, causing the sealing core 3 to move upward rapidly as well, contacting the sealing base 2 and blocking its fluid passage. The fluid pressure also compresses the elastic element 11, which further transmits pressure to the bottom of the sealing core 3, pushing the sealing core 3 to fit tightly against the sealing base 2, resulting in a tighter seal and improved stability of the float hoop under reverse pressure.

[0035] Understandably, the elastic element 11 is usually chosen as a spring, which is set in the upper cavity of the porous pressure reducing mandrel 4, with one end abutting against the flange on the inner wall of the cavity and the other end abutting against the sleeve rod 302.

[0036] Furthermore, as another preferred embodiment, the elastic element 11 can also be a structure such as elastic rubber that is prone to axial elastic deformation. The present invention does not specifically limit the elastic element 11.

[0037] Furthermore, an axially reciprocating elastic element mounting seat 14 is installed inside the cavity of the porous pressure-reducing mandrel 4. One end of the elastic element 11 is fixed to the mounting seat, and the other end abuts against the sleeve rod 302. During forward circulation, the elastic element mounting seat 14 abuts against the flange on the inner wall of the porous pressure-reducing mandrel 4 to limit its movement, thereby restricting the downward movement distance of the sealing core 3 and the elastic element 11.

[0038] It is understandable that the shape of the elastic element mounting seat 14 matches the internal cavity of the porous pressure reducing mandrel 4, and is usually a circular flat plate structure. The mounting seat can increase the contact area between the elastic element 11 and the fluid, thereby making the compression effect of the reverse fluid on the elastic element 11 better, and the sealing effect between the sealing core 3 and the sealing base 2 better.

[0039] Example 3 This embodiment discloses a pressure-reducing, easy-drilling float collar for cementing oil and gas wells. Based on Embodiment 1 or Embodiment 2, to improve the overall sealing performance of the float collar, please refer to the appendix of the instruction manual. Figure 1 First, the bottom edge of the umbrella-shaped sealing head 301 is provided with a horizontal extension edge 7, and the horizontal surface of the extension edge 7 forms a second sealing surface 8. The sealing base 2 has a second sealing mating surface 10 that cooperates with the second sealing surface 8. After the sealing core 3 moves up as a whole, the first sealing surface 6 and the first sealing mating surface 9 are tightly fitted together, and the second sealing surface 8 and the second sealing mating surface 10 are tightly fitted together. The two-section sealing structure makes the sealing core 3 and the sealing base 2 have a larger sealing area, and the overall sealing effect of the floating hoop is better.

[0040] In the embodiments described in this invention, the sealing core 3 of the floating hoop has a larger sealing area between it and the sealing base 2, which consists of a bevel seal and a flat seal.

[0041] Furthermore, the outer wall of the porous pressure reducing mandrel 4 is provided with an outer flange 15 extending radially in the middle, and a sealing element is provided between the outer flange 15 and the inner wall of the outer casing 1 to seal the two.

[0042] Understandably, the seal between the porous pressure-reducing mandrel 4 and the inner wall of the housing is an elastic sealing ring. In oil well cementing operations, the seal needs to maintain its performance in high temperature, high pressure and high acid environment. Therefore, the elastic sealing ring is usually made of corrosion-resistant materials, such as fluororubber, hydrogenated nitrile rubber, tetrafluoropropylene rubber and modified tetrafluoropropylene rubber.

[0043] Furthermore, the umbrella-shaped sealing head 301 includes a sealing head skeleton and a sealing rubber disposed on the surface of the sealing head skeleton, wherein the sealing rubber is typically vulcanized integrally with the sealing head skeleton.

[0044] Example 4 This embodiment discloses a pressure-reducing sealing easy-drill float collar for cementing oil and gas wells. Based on any of the above embodiments, the inner wall of the cavity of the porous pressure-reducing mandrel 4 is provided with a keyway, and the surface of the sleeve 302 is provided with a key, which is slidably disposed in the keyway. The sleeve 302 and the porous pressure-reducing mandrel 4 are connected by a key, so that the entire sealing core 3 can only move up and down axially, but cannot rotate.

[0045] Furthermore, the porous pressure-reducing mandrel 4 is threadedly connected to the mandrel base 5; the sealing base 2 is threadedly connected to the inner wall of the outer shell 1, and a sealing element is provided between the two to seal them; the mandrel base is threadedly connected to the inner wall of the outer shell, and a sealing element is provided between the two to seal them.

[0046] Based on the structural features described above, all connection methods ensure that the float collar cannot rotate. During cementing operations, the threaded and keyed connections used above limit the movement of the various components within the float collar and prevent relative movement along the axial direction of the well casing. This ensures that the float collar does not rotate with the drill bit during drilling, guaranteeing rapid and effective removal of the float collar after cementing.

[0047] It is understandable that the seal between the sealing base 2 and the inner wall of the outer shell, and the seal between the spindle base 5 and the inner wall of the outer shell, are elastic sealing rings. In oil well cementing operations, the seals need to maintain their performance in high temperature, high pressure and high acid environment. Therefore, elastic sealing rings are usually made of corrosion-resistant materials, such as fluororubber, hydrogenated nitrile rubber, tetrafluoropropylene rubber and modified tetrafluoropropylene rubber.

[0048] It is worth mentioning that the key connection between the sleeve rod 302 and the multi-hole pressure reducing mandrel 4 can be a spline connection or a flat key connection. The present invention does not make specific limitations on the key connection between the two, as long as it can restrict the rotation of the sealing core 3 in the inner cavity of the floating hoop.

[0049] Example 5 This embodiment discloses a cementing method, which is based on the floating collar described in any of the above embodiments, and specifically includes the following steps: 1. Preparations: (1) Ensure that oil and gas well drilling is completed and the wellbore is clean and free of debris.

[0050] (2) Prepare the materials required for cementing, including cement grout, float rings, casing, etc.

[0051] (3) Before use, check the integrity and functionality of the floating hoop, whether the structure is intact, and ensure that all parts are undamaged, including the outer shell 1, sealing base 2, sealing core 3, multi-hole pressure reducing mandrel 4 and mandrel base 5, etc.

[0052] 2. Install the floating hoops: The float shoe is placed at the bottom of the cementing string assembly, and then the float collar is placed on top of the float shoe. The float collar and the float shoe are connected by the casing.

[0053] 3. Cementing operations Step S1. Lower the connected cementing string assembly to the bottom of the well, then start the pump to circulate the drilling fluid. After the pump pressure stabilizes, inject the isolation fluid, then inject cement slurry into the cementing string assembly. After the cement slurry injection reaches the design requirements, put the rubber stopper into the string, and then inject the displacement fluid to pressurize. Step S2. The displacement fluid pushes the rubber stopper, causing the cement slurry to move downwards. The cement slurry then enters the outer shell 1 of the float hoop, and then flows out from the float hoop through the float shoe water hole into the open annulus. Finally, the impact pressure is achieved, and the cement slurry is completely displaced from the sleeve and enters the settling chamber. Step S3. After all the cement slurry has been replaced from the casing, when backflow occurs at the bottom of the well, under the action of reverse fluid pressure, the sealing core 3 inside the float ring is pushed upward, and the two sealing surfaces on the umbrella-shaped sealing head 301 are tightly fitted with the two sealing mating surfaces on the sealing base 2, thereby achieving reverse flow interruption and preventing liquid backflow.

[0054] In the embodiments described in this invention, after the cement grout is injected, the cement is left to solidify. During this period, the sealing structure between the sealing core 3 of the floating hoop and the sealing base 2 ensures that the cement grout will not leak. 4. Subsequent construction After the cement has hardened, if necessary, the float collar can be removed by drilling to continue subsequent drilling operations. Due to the drillable design of the float collar in this invention, this step can be completed relatively easily.

[0055] 5. Maintenance and Care After cementing is completed, the float rings should be maintained and serviced as necessary to extend their service life.

[0056] The above description is merely a preferred embodiment of the present invention and is not intended to hinder the present invention in any way. Any simple modifications or equivalent changes made to the above embodiments based on the technical essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A pressure-reducing, easy-to-drill floating collar for cementing oil and gas wells, characterized in that, The float includes a shell (1), and inside the shell (1) arranged sequentially from top to bottom along the positive fluid movement direction are a sealing base (2), a sealing core (3), a porous pressure-reducing mandrel (4), and a mandrel base (5); the sealing core (3) includes an umbrella-shaped sealing head (301) and a sleeve (302), the inclined surface of the umbrella-shaped sealing head (301) is a first sealing surface (6), and the sealing base (2) has a first sealing mating surface (9) that mates with the first sealing surface (6); the porous The pressure reducing mandrel (4) is hollow inside, and an elastic element (11) that is easy to generate axial elastic deformation is provided in the cavity. The sleeve (302) of the sealing core (3) is slidably disposed in the cavity of the porous pressure reducing mandrel (4) and abuts against the elastic element (11). The side wall of the porous pressure reducing mandrel (4) is provided with an opening (12) that communicates with its internal cavity. A bowl-shaped skirt (13) is provided at the opening (12). The diameter of the skirt (13) gradually decreases along the direction of positive fluid movement.

2. The pressure-reducing sealing easy-drill float collar for cementing oil and gas wells according to claim 1, characterized in that, The elastic element (11) can move up and down in the cavity of the porous pressure reducing mandrel (4).

3. The pressure-reducing sealing easy-drill float collar for cementing oil and gas wells according to claim 1, characterized in that, The cavity inner wall of the porous pressure reducing mandrel (4) is provided with a keyway, and the surface of the sleeve rod (302) is provided with a key, which is slidably disposed in the keyway.

4. The pressure-reducing, easy-to-drill floating collar for cementing oil and gas wells according to claim 1, characterized in that, The bottom edge of the umbrella-shaped sealing head (301) is provided with a horizontal extension edge (7), the horizontal surface of the extension edge (7) forms a second sealing surface (8), and the sealing base (2) has a second sealing mating surface (10) that mates with the second sealing surface (8).

5. The pressure-reducing sealing easy-drill float collar for cementing oil and gas wells according to claim 1, characterized in that, A sealing element is provided between the outer wall of the porous pressure reducing mandrel (4) and the inner wall of the outer shell (1) to seal the two.

6. The pressure-reducing sealing easy-drill float collar for cementing oil and gas wells according to claim 1, characterized in that, The outer wall of the porous pressure reducing mandrel (4) is provided with an outer flange (15) extending radially in the middle, and a sealing element is provided between the outer flange (15) and the inner wall of the outer shell (1) to seal the two.

7. The pressure-reducing, easy-drilling floating collar for cementing oil and gas wells according to claim 1, characterized in that, The umbrella-shaped sealing head (301) includes a sealing head skeleton and a sealing rubber disposed on the surface of the sealing head skeleton, wherein the sealing rubber and the skeleton are vulcanized together.

8. A pressure-reducing, easy-drilling floating collar for cementing oil and gas wells according to claim 1, characterized in that, The elastic element (11) includes a spring, one end of which abuts against the inner wall of the cavity of the porous pressure reducing mandrel (4), and the other end abuts against the sleeve rod (302).

9. The pressure-reducing sealing easy-drill float collar for cementing oil and gas wells according to claim 1, characterized in that, The cavity of the porous pressure reducing mandrel (4) is equipped with an elastic element mounting seat (14) that can reciprocate along the axial direction, and the elastic element (11) is fixed on the mounting seat.

10. The pressure-reducing sealing easy-drill float collar for cementing oil and gas wells according to claim 9, characterized in that, The cavity of the porous pressure reducing mandrel (4) is provided with a flange for limiting the elastic element mounting seat (14).

11. The pressure-reducing sealing easy-drill float collar for cementing oil and gas wells according to claim 1, characterized in that, The porous pressure reducing mandrel (4) is threadedly connected to the mandrel base (5).

12. The pressure-reducing, easy-drilling floating collar for cementing oil and gas wells according to claim 1, characterized in that, The sealing base (2) is threaded to the inner wall of the outer shell (1), and a sealing element is provided between the two to seal them.

13. The pressure-reducing, easy-drilling floating collar for cementing oil and gas wells according to claim 1, characterized in that, The spindle base (5) is threaded to the inner wall of the outer shell (1), and a sealing element is provided between the two to seal them.

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