Drillable casing PDC drill bit

Abstract

This application provides a drillable casing PDC drill bit, belonging to the field of drilling drill bits. The drillable casing PDC drill bit includes a drill body and cutter wings. One end of the drill body is a crown, and the cutter wings are located at the crown of the drill body. The drill body and / or the cutter wings have at least partially a mesh-like perforated area. This drill bit, through its mesh-like perforated structure, effectively blocks and attenuates drilling impacts and torsional vibrations, reduces the probability of PDC cutting tooth impact failure, and extends the drill bit's service life. Simultaneously, it reduces the volume of drilled material, lowers secondary drilling resistance, improves operational efficiency, produces smaller cuttings, facilitates drilling fluid transport, reduces the risk of downhole stuck pipe and annular blockage, and is suitable for complex drilling conditions involving deep, high-temperature, and high-pressure environments.

Description

Technical Field

[0001] This application belongs to the field of drilling bit technology, and more specifically, relates to a drillable casing PDC drill bit. Background Technology

[0002] Polycrystalline diamond composite (PDC) drill bits have been widely used in the oil drilling field. As drilling operations extend into deeper formations, the drillability of the rock at the bottom of the well deteriorates, and the drillable conditions such as high temperature and high pressure and complex formations are faced, making rock breaking significantly more difficult. Traditional PDC drill bits have shortcomings such as easy breakage of cutting teeth, short service life, and low rock breaking efficiency.

[0003] In oil and gas well drilling, drillable casing bit technology is commonly used for complex formations and well sections requiring special cementing techniques. This technology integrates the drill bit and casing into a single unit, allowing for direct cementing operations after drilling to the desired depth. The drillable casing bit is then removed by the next stage of drill bit. Drillable casing PDC bits must simultaneously meet the dual requirements of high-efficiency drilling and ease of secondary drilling removal after cementing, necessitating a balance between material selection, structural design, and process parameters.

[0004] Existing drillable casing PDC bits still have many technical defects: On the one hand, casing bits are mostly used for surface drilling, have a large overall size, high drilling operation parameters during construction, and severe impact vibration and high-frequency chatter during drilling, which makes the PDC cutting teeth prone to impact failure and significantly shortens the service life of the bit; on the other hand, after drilling is completed, the subsequent secondary drilling and removal operations have high resistance, low mechanical drilling speed, long tripping and drilling and removal operation cycles, and high drilling costs. Summary of the Invention

[0005] In view of this, the present application provides a drillable casing PDC drill bit to at least solve the technical problems of existing drillable casing PDC drill bits, such as the cutting teeth being prone to impact failure and the high resistance in secondary drilling operations.

[0006] To achieve the above objectives, the technical solution adopted in this application is as follows: In a first aspect, a drillable casing PDC drill bit is provided, comprising: The drill bit body has a crown at one end; A blade is provided on the crown of the drill bit body; The drill bit body and / or the cutter blade are at least partially a mesh-like perforated area.

[0007] In some embodiments, the edge region of the cutter wing away from the drill body is a tooth solid region, and the area on the cutter wing between the tooth solid region and the drill body is at least partially a mesh-like perforated region.

[0008] In some embodiments, the mesh-like perforated area of ​​the drill bit body is sealed and covered by a solid surface layer, and / or the mesh-like perforated area of ​​the cutter blade is sealed and covered by a solid surface layer.

[0009] In some embodiments, the gaps in the mesh-like perforated areas are filled with an inert liquid that will not corrode the drill bit body.

[0010] In some embodiments, the mesh-like perforated areas on the drill body and the cutter wings are connected; The drill bit body is provided with a central flow channel along the central axis, and the front end of the central flow channel is closed at the crown of the drill bit body; The inner wall of the central flow channel is provided with an axially extending inner rib. The interior of the inner rib is provided with an injection channel arranged along the extension axis. The injection channel is connected to the mesh-like perforated area on the drill bit body near the side of the drill bit body. The rear end of the inner rib is provided with an injection port that communicates with the injection channel and is located at the rear-upward direction. The position of the injection port exceeds the mesh-like perforated area on the drill bit body and the cutter wing. The injection port is sealed by a sealing element.

[0011] In some embodiments, the inner rib and the front end of the infusion channel extend to the inner wall of the front end of the central channel; The injection channel is located on the inner wall of the front end of the central channel, and its side adjacent to the drill bit body is connected to the mesh-like perforated area of ​​the drill bit body crown.

[0012] In some embodiments, the mesh-like perforated area within the crown of the drill bit body has a rear profile that is concave in the center; the front end of the injection channel extends toward the central axis of the drill bit while being inclined forward.

[0013] In some embodiments, the mesh-like perforated area on the drill bit body includes a dividing zone; the dividing zone divides the mesh-like perforated area on the drill bit body into multiple sub-perforated areas distributed along the circumference of the drill bit body; the fluid flow damping of the dividing zone is greater than the fluid flow damping of the sub-perforated areas.

[0014] In some embodiments, the sub-cutting area is opposite to the blade and connected to the mesh-like cutting area on the blade, and the separating area is located in the part of the drill body crown between two adjacent blades; The inner rib is disposed opposite to the partition area, and the injection channel is connected to the partition area.

[0015] In some embodiments, the injection port is provided with an installation cavity, in which a pressure balancing airbag is installed, and the sealing element blocks the opening of the installation cavity.

[0016] Compared with the prior art, the present application has the following beneficial effects after implementation: Compared to conventional solid drill bits, the drill bit body and / or blades of this application incorporate a mesh-like perforated area. When the impact or torsional vibration waves generated during drilling are transmitted to the mesh-like perforated area, the vibration is effectively blocked because the acoustic impedance of the mesh-like perforated area is much lower than that of the solid part. Furthermore, under the action of vibration, the mesh-like perforated area can produce slight elastic deformation to form vibration damping, thereby converting vibration energy into heat energy and dissipating it, causing the vibration to decay rapidly. By blocking the transmission of vibration and consuming vibration energy to reduce vibration, the probability of cutting tooth impact failure can be reduced, and the service life of the drill bit can be extended. When drilling is completed and subsequent secondary drilling operations are carried out, the reduced material volume of the mesh-like hollow area compared to the solid structure means that the volume of material that the drill bit needs to drill and break is greatly reduced, thus significantly shortening the drilling time and improving operational efficiency. Furthermore, the mesh-like hollow area is easier to cut and break, which reduces the operational resistance of secondary drilling operations to some extent. At the same time, when the mesh-like hollow area is cut, the resulting debris is smaller and easier to be carried to the surface by the drilling fluid, which to some extent prevents downhole stuck pipe or annular blockage accidents. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a perspective view of the first embodiment of the drillable casing PDC drill bit of this application; Figure 2 This is a half-sectional view of a second embodiment of the drillable casing PDC drill bit of this application; Figure 3 This is a perspective view of the third embodiment of the drillable casing PDC drill bit of this application; Figure 4 This is a half-sectional view of the fourth embodiment of the drillable casing PDC drill bit of this application; Figure 5 This is a perspective view of the fifth embodiment of the drillable casing PDC drill bit of this application; Figure 6 This is a half-sectional perspective view of the second embodiment of the drillable casing PDC drill bit of this application; Figure 7 This is a half-sectional perspective view of the fourth embodiment of the drillable casing PDC drill bit of this application; Figure 8This is a perspective view of the sixth embodiment of the drillable casing PDC drill bit of this application; Figure 9 This is a perspective view of the first embodiment of the basic unit of the drillable casing PDC drill bit of this application; Figure 10 This is a perspective view of a second embodiment of the basic unit of the drillable casing PDC drill bit of this application; Figure 11 This is a perspective view of a third embodiment of the basic unit of the drillable casing PDC drill bit of this application; Figure 12 This is a perspective view of the seventh embodiment of the drillable casing PDC drill bit of this application; Figure 13 This is a cross-sectional view of the seventh embodiment of the drillable casing PDC drill bit of this application; Figure 14 This is a front view of the seventh embodiment of the drillable casing PDC drill bit of this application.

[0019] The following are the labeling elements in the figure: 1-Drill body; 11-Crown; 12-Central flow channel; 13-Inner rib; 131-Injection flow channel; 132-Injection port; 133-Seal; 134-Pressure balance airbag; 14-Nozzle; 2-Cutting blade; 21-Solid tooth area; 3-Mesh hollow area; 31-Separation area; 32-Sub-hollow area; 33-Basic unit; 4-Solid surface; 5-Rear profile of the mesh hollow area of ​​the drill body crown. Detailed Implementation

[0020] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and are not intended to limit the scope of this application.

[0021] It should be noted that when a component is referred to as being "fixed to" or "set on" another component, it can be directly on or indirectly on that other component. When a component is referred to as being "connected to" another component, it can be directly connected to or indirectly connected to that other component.

[0022] It should be understood that the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0023] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" or "several" means two or more, unless otherwise explicitly specified.

[0024] It should be noted that the embodiments of this application focus on describing the invention content of this application. For conventional contents such as lubrication, dust prevention, and waterproofing, if they are not described in the text or shown in the drawings, it should be understood that those skilled in the art can set up corresponding lubrication systems, protective covers (shells), etc. in combination with actual needs, or ensure the normal operation of the equipment through daily inspection and maintenance.

[0025] The structures, proportions, and sizes illustrated in the accompanying drawings are merely for illustrative purposes and to aid those skilled in the art in understanding and reading the invention. They are not intended to limit the scope of the invention and therefore have no substantial technical significance. Any modifications to the structure, changes in proportions, or adjustments to size, without affecting the effectiveness and purpose of the invention, should still fall within the scope of the technical content disclosed herein. Furthermore, the terms "upper," "lower," "left," "right," "middle," and "one" used in this specification are merely for clarity and not intended to limit the scope of the invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the invention.

[0026] Please refer to the following: Figures 1 to 14 The drillable casing PDC drill bit provided in the embodiments of this application will now be described. A drillable casing PDC drill bit includes: The drill bit body has a crown at one end; Cutting blades are located on the crown of the drill bit body; The drill bit body and / or blades are at least partially a mesh-like perforated area.

[0027] Compared with the prior art, the drillable casing PDC drill bit of this application, compared with conventional solid drill bits, introduces a mesh-like hollow area on the drill bit body and / or cutter blades. When the impact or torsional vibration waves generated during drilling are transmitted to the mesh-like hollow area, on the one hand, the acoustic impedance of the mesh-like hollow area is much lower than that of the solid part, so the vibration is effectively blocked; on the other hand, under the action of vibration, the mesh-like hollow area can produce a small elastic deformation to form vibration damping, thereby converting vibration energy into heat energy and dissipating it, so that the vibration decays rapidly. By blocking the transmission of vibration and consuming vibration energy to reduce vibration, the probability of cutting tooth impact failure can be reduced, and the service life of the drill bit can be extended. When drilling is completed and subsequent secondary drilling operations are carried out, the reduced material volume of the mesh-like hollow area compared to the solid structure means that the volume of material that the drill bit needs to drill and break is greatly reduced, thus significantly shortening the drilling time and improving operational efficiency. Furthermore, the mesh-like hollow area is easier to cut and break, which reduces the operational resistance of secondary drilling operations to some extent. At the same time, when the mesh-like hollow area is cut, the resulting debris is smaller and easier to be carried to the surface by the drilling fluid, which to some extent prevents downhole stuck pipe or annular blockage accidents.

[0028] Similar to existing drillable casing drill bits, the drill body in this embodiment may be equipped with nozzles and corresponding flow channels, and the cutter blades may be equipped with PDC cutting teeth. The main difference between this embodiment and existing drillable casing drill bits is that the drill body and / or cutter blades are at least partially configured as a mesh-like perforated area. Of course, this improvement in this embodiment should, while ensuring the strength requirements of the drill body and cutter blades, reasonably select the position and size of the mesh-like perforated area. In specific implementation, after those skilled in the art have designed the drillable casing PDC drill bit of this embodiment, they can conduct actual tests using computer simulation software or by making samples to verify whether the strength of the drill body and cutter blades meets the requirements. Other structural designs and specific parameters of the drill body and cutter blades in this embodiment can be referenced from existing drillable casing drill bits, and will not be repeated here.

[0029] As an alternative implementation, the mesh-like perforated area on the drill bit body is connected to the internal drilling fluid flow channel, and when the pores of the mesh-like perforated area are open on the surface of the drill bit body, the drilling fluid inside the drill bit can be ejected through the pores of the mesh-like perforated area, which to some extent plays a similar role to a nozzle. Therefore, fewer or no nozzles can be provided on the drill bit body.

[0030] This embodiment does not limit the processing method of the mesh hollow area. As an optional processing method, the mesh hollow area can be processed on a traditional drill bit structure using traditional machining methods, such as machining by conventional means such as mechanical drilling, milling or water jetting, or directly drilling blind holes or through holes of the required depth from the outer surface using a multi-axis machine tool. As another optional processing method, the entire or only mesh hollow area of ​​the drillable casing PDC drill bit can be processed using metal 3D printing technology.

[0031] As an optional implementation method, refer to Figures 9-11 The mesh-like hollow area can be composed of repeating basic units. The basic units can be polyhedral skeleton structures such as tetrahedral skeletons, hexahedral skeletons, and dodecahedral skeletons, with solid edges, faces, and hollow interiors.

[0032] As an optional implementation method, refer to Figure 2 In this embodiment, the mesh-like hollow area on the cutter wing is closed by the solid surface layer. The height of the drill bit body is H, and the height of the mesh-like hollow area on the drill bit body is h1. H and h1 satisfy 0.1≤h1 / H≤0.6. The radius of the drill bit body is R, and the radius of the mesh-like hollow area on the drill bit body is r1. R and r1 satisfy 0.1≤r1 / R≤0.9.

[0033] As an optional implementation method, refer to Figure 4 In this embodiment, the mesh-like hollow area on the cutter wing is closed by the solid surface layer. The height of the drill bit body is H, and the height of the mesh-like hollow area on the cutter wing is h2. H and h2 satisfy 0.1≤h2 / H≤0.6. The radius of the drill bit body is R, and the radius of the mesh-like hollow area on the cutter wing is r2. R and r2 satisfy 0.1≤r2 / R≤0.9.

[0034] Please see Figures 3-5 7, 8 and 13 are specific embodiments of the drillable casing PDC drill bit provided in this application, wherein the edge region of the cutter blade away from the drill body is the tooth solid region, and the area on the cutter blade between the tooth solid region and the drill body is at least partially a mesh-like hollow region.

[0035] In this embodiment, the solid tooth region of the cutter wing can be easily machined with cutting tooth mounting holes, facilitating the embedding and welding of PDC cutting teeth. Furthermore, the solid structure of the tooth region provides higher strength, enabling the dispersal and transmission of cutting stress and vibration to the adjacent mesh-like perforated region. The mesh-like perforated region on the cutter wing, located between the solid tooth region and the drill body, can directly isolate and absorb the vibration generated during cutting.

[0036] In practical implementation, the entire edge region of the cutter wing away from the drill body is a solid region and is equipped with PDC cutting teeth. The area between the solid region of the upper toothed part of the cutter wing and the drill body is entirely a mesh-like hollow region. This mesh-like hollow region can be connected to or not connected to the mesh-like hollow region on the drill body. In embodiments with a solid surface layer, the solid surface layer is located on the front and rear sides of the cutter wing in the rotational circumferential direction. In practice, the edge length of the basic unit of the mesh-like hollow region on the cutter wing can be smaller than that of the mesh-like hollow region on the drill body, and the edge thickness of the basic unit of the mesh-like hollow region on the cutter wing can be larger than that of the mesh-like hollow region on the drill body. This allows the mesh-like hollow region on the cutter wing to withstand greater cutting stress and vibration, and also to better transmit stress and vibration to the drill body.

[0037] In some embodiments, for example Figure 7 and 8 In this case, the blade extends to the side of the drill body to form a gauge section. In this case, a mesh-like hollow area can also be set on the gauge section. The edge area of ​​the gauge section away from the drill body also belongs to the tooth solid area of ​​this embodiment.

[0038] Please see Figure 2 , 4 6-8 and 13, as specific embodiments of the drillable casing PDC drill bit provided in this application, wherein the mesh-like hollow area of ​​the drill bit body is sealed and covered by a solid surface layer, and / or the mesh-like hollow area of ​​the cutter blade is sealed and covered by a solid surface layer.

[0039] In this embodiment, the solid surface layer seals and wraps the mesh-like perforated area of ​​the drill bit body / or cutter blades, isolating the mesh-like perforated area from the outside world and preventing drilling fluid from contacting it. This prevents corrosion of the mesh-like perforated area, ensuring the structural integrity of the drill bit after long-term downhole service. Furthermore, the mesh-like perforated area does not alter the flow path and injection speed of the drilling fluid, allowing designers to independently optimize hydraulic parameters without worrying about leakage or diversion issues. Simultaneously, the sealing of the mesh-like perforated area prevents cuttings from embedding within it, ensuring the drill bit's mass distribution remains in its original dynamic balance state, preventing eccentric vibration due to blockage, and improving drilling stability and wellbore quality.

[0040] In practice, the drill body and blades are manufactured using metal 3D printing technology, and the thickness of the solid surface layer can be 4mm or more to ensure sufficient strength. As an optional implementation, the size of the basic unit (such as edge length) of the mesh-like cutout area gradually decreases or the edges gradually become thicker as it gets closer to the solid surface layer, thereby gradually increasing the strength of the mesh-like cutout area and providing better support for the solid surface layer.

[0041] Please see Figure 2 ,4 6~8 and 13, as a specific embodiment of the drillable casing PDC drill bit provided in this application, for the mesh-like hollow area with solid surface sealing, the gaps in the mesh-like hollow area are filled with an inert liquid that will not corrode the drill bit body.

[0042] In this embodiment, the inert liquid fills the gaps in the mesh-like perforated area, which firstly prevents the mesh-like perforated area from being corroded; secondly, the liquid has better thermal conductivity than the gas, which can quickly transfer the heat of the drill bit body or cutter blades, avoiding overheating; moreover, when the drill bit vibrates, the slight deformation of the mesh-like perforated area will squeeze and pull the inert liquid inside, and the inert liquid will generate flow, shearing, and eddy currents in the narrow mesh-like pores. The interlayer friction and eddy current friction of the liquid will convert the vibration energy into heat energy and dissipate it, forming damping to suppress vibration; in addition, the liquid is incompressible compared to the gas, and when the drill bit body or cutter blades are subjected to local stress, the inert liquid can transfer the force to the surroundings, playing a protective role.

[0043] In practical implementation, the inert liquid can be rust-preventive oil. For better vibration damping, a rust-preventive oil with higher viscosity can be selected; while for better heat conduction, a rust-preventive oil with lower viscosity can be selected to improve the fluidity of the rust-preventive oil.

[0044] Please see Figure 8 , 12 13, as a specific embodiment of the drillable casing PDC drill bit provided in this application, the mesh-like perforated areas on the drill bit body and the cutter blade are connected; The drill bit body is provided with a central flow channel along the central axis, and the front end of the central flow channel is closed at the crown of the drill bit body; The inner wall of the central flow channel is provided with an axially extending inner rib. The inner rib has an injection channel arranged along the extension axis. The side of the injection channel near the drill body is connected to the mesh-like perforated area on the drill body. The rear end of the inner rib is provided with an injection port that communicates with the injection channel and is located upwards. The position of the injection port exceeds the mesh-like perforated area on the drill body and the cutter wing. The injection port is sealed by a sealing element.

[0045] It should be noted that, in this embodiment and other embodiments, unless otherwise specified, "front" in the description of direction such as "front end" or "forward" refers to the drilling direction of the drill bit; correspondingly, "rear" in the description of direction such as "rear end" or "backward" refers to the opposite direction of the drilling direction of the drill bit.

[0046] In this embodiment, axially extending inner ribs are provided on the inner wall of the central flow channel. This effectively compensates for the structural strength loss of the drill bit body due to the mesh-like perforated area, avoids insufficient overall rigidity of the drill bit, ensures the structural stability of the drill bit under high-pressure and high-impact downhole conditions, and prevents deformation and breakage during drilling. The injection channel runs through the extension axis of the inner ribs, allowing the inert liquid injected from the injection port to quickly and evenly fill the mesh-like perforated area on the side wall of the drill bit body. Simultaneously, the mesh-like perforated areas of the drill bit body and the cutter blades are interconnected, enabling bidirectional flow and balanced replacement of the inert liquid within the two mesh-like perforated areas. This allows the damping structure, heat conduction structure, and stress buffer structure of the entire drill bit to form a unified, interconnected system, significantly improving the overall vibration reduction, heat dissipation, and impact resistance performance of the drill bit. The injection port is designed to be positioned at the rear. When the drill bit is placed with the rear end facing upwards, the injection port is positioned higher than the mesh-like perforated area. This allows the inert liquid injected through the injection port to completely fill the mesh-like perforated area. After sealing the injection port with a sealant, the mesh-like perforated area can be completely filled with inert liquid.

[0047] In practical implementation, the mesh-like perforated area on the drill bit body extends to the part where the inner ribs connect to the drill bit body, thus connecting the mesh-like perforated area with the injection channel. The sealing element can be a high-temperature and high-pressure resistant rubber plug, metal sealing plug, or threaded sealing assembly, adapted to downhole high-temperature and high-pressure conditions. The orifice diameter of the injection channel can be adapted to the overall volume of the perforated area, ensuring injection efficiency without affecting the structural strength of the inner ribs. For example, in actual assembly and processing, after the drill bit is formed, inert liquid can be vacuum-injected through the rear injection port. After injection, the area is immediately sealed by the sealing element to ensure no air residue remains inside the mesh-like perforated area.

[0048] Please see Figure 12 and 13 As a specific embodiment of the drillable casing PDC drill bit provided in this application, the front end of the inner rib and the injection channel extends to the inner wall of the front end of the central channel. The injection channel is located on the inner wall of the front end of the central channel, and its side adjacent to the drill bit body is connected to the mesh-like perforated area of ​​the drill bit body crown.

[0049] The drill bit crown is the core working area that directly contacts the rock formation and withstands impact vibrations. It is also the main area where the cutting teeth are installed, and this location experiences the most intense vibrations and the highest temperature rise. In this embodiment, by extending the inner ribs and the front end of the injection channel to the inner wall of the front end of the central channel, precise connection and penetration are achieved between the injection channel and the mesh-like hollow area of ​​the drill bit crown. This allows the inert liquid to fully fill the mesh-like hollow area of ​​the drill bit crown along the injection channel, preventing residual gas in the mesh-like hollow area of ​​the drill bit crown. This precisely targets the core vibration area to achieve damping, vibration reduction, and rapid heat dissipation, maximizing the protection of the crown cutting teeth and reducing their probability of impact failure. At the same time, the extended inner ribs provide all-round support to the closed area at the front end of the central channel, improving the overall structural strength of the drill bit crown and preventing collapse and deformation of the crown during high-intensity rock breaking operations.

[0050] In practical implementation, multiple internal ribs can be set on the drill bit body, along with corresponding injection channels, seals, and other structures. The front end of the internal ribs and the inner wall of the front end of the central channel are integrally molded, without splicing gaps, resulting in stronger sealing and structural stability. The front end of the injection channel is connected to the mesh-like perforated area of ​​the crown, ensuring smooth liquid flow and eliminating injection dead zones.

[0051] Please see Figure 13 As a specific embodiment of the drillable casing PDC drill bit provided in this application, the mesh-like hollow area in the crown of the drill bit body has a rear contour surface that forms a forward-concave shape; the front end of the injection channel extends towards the central axis of the drill bit while being inclined forward.

[0052] When the drill bit of this embodiment is placed with its rear end facing upwards, the center of the rear contour surface of the mesh-like hollow area of ​​the drill bit body is the lowest, and the position is higher as it approaches the edge. This makes it easier for the gas inside the mesh-like hollow area to be discharged upwards along the rear contour surface of the mesh-like hollow area. The inclined injection channel matches the rear contour surface of the mesh-like hollow area of ​​the crown, and the front end of the channel extends towards the central recess of the mesh-like hollow area of ​​the crown, allowing the inert liquid to reach the central part of the mesh-like hollow area of ​​the crown directly.

[0053] In practical implementation, the rear profile surface of the mesh-like hollow area of ​​the drill bit body crown can be a conical surface, a spherical surface, or other concave arc surface. The injection channel is set along the rear profile surface of the mesh-like hollow area of ​​the crown, forming a forward-sloping surface that extends towards the drill bit's central axis, and remains connected to the mesh-like hollow area of ​​the crown.

[0054] Please see Figure 13 and 14As a specific embodiment of the drillable casing PDC drill bit provided in this application, the mesh-like hollow area on the drill bit body includes a partition area; the partition area divides the mesh-like hollow area on the drill bit body into multiple sub-hollow areas distributed along the circumference of the drill bit body; the fluid flow damping of the partition area is greater than the fluid flow damping of the sub-hollow areas.

[0055] In this embodiment, the fluid flow damping in the partition zone is greater than that in the sub-cavity zone. When the drill bit vibrates, small vibrations can be damped by the inert fluid inside each sub-cavity zone, while large impact vibrations will cause the inert fluids in different sub-cavities to exchange through the partition zone. The partition zone can strongly impede the fluid flow, thereby eliminating large vibrations and achieving vibration adaptation under all working conditions.

[0056] In practical implementation, the dividing zone employs a high-density mesh structure design (e.g., shortened or thickened edges), resulting in smaller internal pores and a denser structure, thus achieving significantly greater fluid flow damping than the sub-hollowed-out zone. Furthermore, the higher strength of the dividing zone also increases the strength of the drill bit body. The mesh openings between the dividing zone and the sub-hollowed-out zone can have a gradual transition (e.g., gradually changing edge length and thickness) to avoid stress concentration.

[0057] Please see Figures 12-14 As a specific embodiment of the drillable casing PDC drill bit provided in this application, the sub-hollow area is opposite to the cutter wing and is connected to the mesh hollow area on the cutter wing. The separation area is located in the part of the drill bit crown between two adjacent cutter wings. The inner ribs are positioned opposite the partition area, and the injection channel is connected to the partition area.

[0058] In this embodiment, the sub-hollowed-out area is opposite to the cutter wing and connected to the mesh-like hollowed-out area on the cutter wing. This allows the inert liquid in the mesh-like hollowed-out area of ​​the cutter wing to form a faster liquid exchange with the sub-hollowed-out area, accelerating the conduction of heat, stress, and vibration from the cutter wing to the drill bit body. For example, refer to... Figure 14 Viewed from the front, the five-blade drill bit has five radially spaced sections (radial dotted lines in the figure). Each section is located between two adjacent blades, dividing the mesh-like perforated area into five fan-shaped sub-perforated areas (fan-shaped dotted lines in the figure). The five fan-shaped sub-perforated areas are located behind each blade, providing heat dissipation and vibration reduction for each blade.

[0059] The portion of the drill bit crown located between two adjacent blades is relatively weak. The partition area has higher structural strength than the sub-hollowed-out area. Together with the inner ribs, it can reinforce the portion of the drill bit crown located between two adjacent blades, forming a structure in which the blades, partition area, and inner ribs alternately reinforce the drill bit crown, ensuring the overall strength of the drill bit crown.

[0060] In this embodiment, the gaps in the partition are finer, making it easier for gas to remain. The inner ribs are arranged directly opposite the partition, and the injection channel is directly connected to the partition, allowing the gas in the partition to be directly discharged, ensuring that the partition is filled with inert liquid.

[0061] Please see Figure 12 and 13 As a specific embodiment of the drillable casing PDC drill bit provided in this application, based on the inner ribs and the partition area being arranged opposite to each other, and the injection channel being connected to the partition area, the injection port is provided with an installation cavity, a pressure balancing airbag is installed in the installation cavity, and a sealing element blocks the opening of the installation cavity.

[0062] In this embodiment, a dedicated installation cavity is provided at the injection port for assembling the pressure balancing airbag, adapting to the complex working conditions of high temperature and high pressure downhole. This solves the problem of volume expansion and pressure imbalance caused by temperature and pressure changes in the inert liquid inside the hollowed-out area. After the drill bit is lowered into the well, the ambient pressure and temperature rise significantly. The inert liquid inside the mesh-like hollowed-out area will undergo slight thermal expansion and contraction, leading to abnormal internal pressure, which can easily cause structural deformation or sealing leakage. The pressure balancing airbag has extensible deformation characteristics and can automatically expand and contract according to internal pressure changes, balancing the internal pressure of the hollowed-out area cavity with the external downhole pressure in real time. This ensures that the hollowed-out structure is always in a stable stress state, protecting the sealing structure and the drill bit body structure.

[0063] Meanwhile, the pressure balancing airbag is installed at the injection port of the injection channel, so that the liquid pressure fluctuations in the sub-hollowed-out area are damped and dissolved by the partition zone before being transmitted to the pressure balancing airbag through the injection channel. This avoids the pressure balancing airbag from resonating with the liquid pressure fluctuations in the sub-hollowed-out area, so that the pressure balancing airbag is mainly used to balance the slow changes in liquid pressure, rather than responding to the high-frequency vibrations of liquid pressure.

[0064] In practice, the pressure balancing airbag is made of elastic rubber material that is resistant to high and low temperatures, oil and corrosion, and is suitable for inert liquid media and harsh downhole conditions. When the downhole temperature rises and the liquid volume expands, the airbag is compressed; when the downhole temperature is low and the liquid volume contracts, the airbag expands back, so that the pressure in the mesh hollow area remains basically stable, reducing the internal stress of the drill bit.

[0065] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A drillable casing PDC drill bit, characterized in that, include: The drill bit body has a crown at one end; A blade is provided on the crown of the drill bit body; The drill bit body and / or the cutter blade are at least partially a mesh-like perforated area.

2. The drillable casing PDC drill bit as described in claim 1, characterized in that, The edge region of the cutter wing away from the drill bit body is a solid tooth region, and the area on the cutter wing between the solid tooth region and the drill bit body is at least partially a mesh-like hollow region.

3. The drillable casing PDC drill bit as described in claim 1, characterized in that, The mesh-like perforated area of ​​the drill bit body is sealed and covered by a solid surface layer, and / or the mesh-like perforated area of ​​the cutter blade is sealed and covered by a solid surface layer.

4. The drillable casing PDC drill bit as described in claim 3, characterized in that, The gaps in the mesh-like perforated area are filled with an inert liquid that will not corrode the drill bit body.

5. The drillable casing PDC drill bit as described in claim 4, characterized in that, The drill bit body and the mesh-like perforated area on the cutter wing are connected; The drill bit body is provided with a central flow channel along the central axis, and the front end of the central flow channel is closed at the crown of the drill bit body; The inner wall of the central flow channel is provided with an axially extending inner rib. The interior of the inner rib is provided with an injection channel arranged along the extension axis. The injection channel is connected to the mesh-like perforated area on the drill bit body near the side of the drill bit body. The rear end of the inner rib is provided with an injection port that communicates with the injection channel and is located at the rear-upward direction. The position of the injection port exceeds the mesh-like perforated area on the drill bit body and the cutter wing. The injection port is sealed by a sealing element.

6. The drillable casing PDC drill bit as described in claim 5, characterized in that, The inner rib and the front end of the infusion channel extend to the inner wall of the front end of the central channel; The injection channel is located on the inner wall of the front end of the central channel, and its side adjacent to the drill bit body is connected to the mesh-like perforated area of ​​the drill bit body crown.

7. The drillable casing PDC drill bit as described in claim 6, characterized in that, The mesh-like hollow area within the crown of the drill bit body has a rear contour surface that forms a forward-concave shape; the front end of the injection channel extends towards the central axis of the drill bit while being inclined forward.

8. The drillable casing PDC drill bit as described in claim 6, characterized in that, The mesh-like perforated area on the drill bit body includes a dividing zone; the dividing zone divides the mesh-like perforated area on the drill bit body into multiple sub-perforated areas distributed along the circumference of the drill bit body; the liquid flow damping of the dividing zone is greater than the liquid flow damping of the sub-perforated areas.

9. The drillable casing PDC drill bit as described in claim 8, characterized in that, The sub-cutting area is opposite to the blade and is connected to the mesh-like cutting area on the blade. The dividing area is located on the part of the drill body crown between two adjacent blades. The inner rib is disposed opposite to the partition area, and the injection channel is connected to the partition area.

10. The drillable casing PDC drill bit as described in claim 9, characterized in that, The injection port is provided with an installation cavity, in which a pressure balancing airbag is installed, and the sealing element blocks the opening of the installation cavity.

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