Reverse spiral drill bit

Abstract

The invention belongs to the technical field of roller bits, and particularly relates to a reverse spiral bit which comprises a bit body, a plurality of blades arranged on the bit body and compacts arranged on the blades, the plurality of blades comprise at least one short blade, and the compacts on the short blades are arranged in a reverse spiral structure; and at least one long blade, wherein the composite sheets on the long blade are arranged in a non-helical structure. The composite sheets on the short blades are arranged to be of an inverted spiral structure, so that cutting teeth on the periphery of the drill bit make contact with rocks preferentially, the islanding effect is formed in the center to release the internal stress of the rocks, the rocks are easier to break, and the mechanical drilling speed is increased by 2-3 times.

Description

Technical Field

[0001] This invention belongs to the field of roller cone drill bit technology, and specifically relates to a reverse spiral drill bit. Background Technology

[0002] As the exploration and development of oil, natural gas, and geothermal resources deepens and geological conditions become increasingly complex, higher demands are placed on drilling efficiency and tool performance. Polycrystalline diamond composite drill bits, due to their advantages such as high mechanical drilling speed, high drilling depth, and long service life, have become the mainstream rock-breaking tool in the current oil and gas drilling field.

[0003] Currently, conventional PDC drill bits are mainly divided into two categories in terms of design: one is the positive helical structure drill bit, where, on the same blade, as the distance of the cutting teeth (compound blades) from the drill bit center increases, their arrangement relative to the line connecting the drill bit center and the center of the first cutting tooth of that blade is regularly offset circumferentially (usually clockwise), forming a continuous helix. The original intention of this design is to distribute the force on the cutting teeth and extend the service life of the cutting teeth in the outer cone part of the drill bit, performing well in hard formations. The other category is the straight blade structure drill bit, where the cutting teeth on the blades are basically arranged in a straight line, with a simple structure and easy design and manufacturing.

[0004] However, with the expansion of drilling conditions, especially in soft to medium-hard formations, directional wells, and horizontal wells, the aforementioned traditional drill bit structures have revealed the following technical problems: In soft formations, rocks have low compressive strength but high plasticity and viscosity. When cutting with a helical or linear cutter blade, multiple cutting teeth contact the rock almost simultaneously, leading to large fluctuations in drill bit torque and a tendency for "mud pockets" to form due to the inability to remove rock cuttings in a timely manner, severely limiting the improvement of mechanical drilling speed. Furthermore, its cutting mechanism fails to effectively utilize the release of internal stress in the rock to assist in fracturing, resulting in low energy efficiency.

[0005] In the build-up and stabilization phases of directional and horizontal wells, the drill bit is required to effectively break the rock, provide a stable tool face, and facilitate adjustment of the well inclination. Conventional drill bits, especially those with long diameter designs, lack sufficient lateral cutting capability, leading to tool face instability, difficulty in directional drilling, low sliding drilling efficiency, and increased drilling time and costs.

[0006] When drilling into formations containing gravel, hard interlayers, or fractures, the cutting teeth of traditional drill bits are prone to premature failure such as tooth breakage or tooth loss under impact loads. This not only shortens the service life of the drill bit but may also lead to an increase in the number of trips and trips, affecting the overall drilling progress.

[0007] In summary, existing PDC drill bits still face technical bottlenecks in improving drilling efficiency in soft formations, enhancing directional drilling performance, and extending service life in complex formations, making it difficult to meet the growing demand for faster drilling and lower costs. Summary of the Invention

[0008] The purpose of this invention is to provide a reverse auger drill bit to solve the problems existing in the prior art.

[0009] To achieve the above objectives, the present invention provides the following technical solution: a reverse spiral drill bit, comprising a drill bit body, a plurality of cutter wings disposed on the drill bit body, and a composite blade arranged on the cutter wings, wherein the plurality of cutter wings include: At least one short blade, wherein the composite plates on the short blade are arranged in an anti-helical structure; and At least one long blade, wherein the composite plates on the long blade are arranged in a non-helical structure.

[0010] Preferably, the anti-helix structure refers to: on the short blade, a straight line is defined passing through the center point of the drill bit and the center of the first composite piece on the blade closest to the center of the drill bit. Then, starting from the second composite piece on the short blade, the centers of the remaining composite pieces are offset counterclockwise relative to the straight line, and the farther the composite piece is from the center of the drill bit, the greater the counterclockwise distance between its center and the straight line.

[0011] Preferably, the spiral-free structure means that: on the long blade, a straight line is defined passing through the center point of the drill bit and the center of the first composite piece on the blade closest to the center of the drill bit, then the centers of all composite pieces on the long blade are arranged on or near the straight line.

[0012] Preferably, the drill bit includes three short blades and two long blades, which are arranged alternately along the circumference of the drill bit.

[0013] Preferably, the composite blade includes a main cutting tooth arranged at the blade wing edge and a secondary cutting tooth arranged behind the main cutting tooth. The cutting height of the secondary cutting tooth is lower than that of the main cutting tooth, and the height difference between the two is 0.5 mm to 1 mm.

[0014] Preferably, the back rake angle of both the main cutting tooth and the secondary cutting tooth is 17 to 32 degrees.

[0015] Preferably, all blades are designed with short diameter protection, with a diameter protection length of 50mm ± 10mm.

[0016] Preferably, the drill bit body is provided with a water hole, and a fixed nozzle or a replaceable nozzle is installed in the water hole.

[0017] Preferably, the blade wing is provided with passive diameter-maintaining teeth.

[0018] Preferably, the blade wing is provided with inverted serrations.

[0019] The beneficial effects of this invention are as follows: First, by setting the composite blades on the short blades to an anti-helical structure, the cutting teeth on the outer periphery of the drill bit preferentially contact the rock, forming an "island effect" in the central part to release the internal stress of the rock, thereby making the rock easier to break and increasing the mechanical drilling speed by 2-3 times. Second, the drill bit adopts a short parabolic crown profile and a short gauge design, combined with the straight structure arrangement of the long blades, which significantly reduces the lateral friction between the drill bit and the well wall. In directional and horizontal well construction, it can improve the directional drilling effect by about 20%, while ensuring a more stable tool face. In addition, the progressive cutting method brought by the anti-helical structure and the optimized back slope angle of 17-32° effectively disperse the impact load. Combined with the high and low tooth design and the synergistic effect of the reverse-cutting teeth and gauge-maintaining teeth, it greatly enhances the impact resistance of the drill bit in complex formations such as fractures and hard interlayers, prevents composite blade tooth breakage, and thus significantly extends the service life of the drill bit while improving drilling efficiency. Attached Figure Description

[0020] Figure 1 A front view schematic diagram of the anti-auger drill bit provided in an embodiment of the present invention; Figure 2 A top view of the anti-auger drill bit provided in an embodiment of the present invention; Figure 3 This is a top view diagram of a conventional auger drill bit. In the diagram: 1. Drill body; 2. Connector; 3. Chip removal groove; 4. Cutting blade; 5. Water hole; 6. Main cutting tooth; 7. Secondary cutting tooth; 8. Active gauge protection tooth; 9. Passive gauge protection tooth; 10. Short cutting blade; 11. Long cutting blade; 12. Short cutting blade baseline; 13. Long cutting blade baseline; 14. Positive helix baseline. Detailed Implementation

[0021] In the description of this disclosure, it should be understood that the terms “center,” “upper,” “lower,” “front,” “back,” “left,” “right,” “vertical,” “horizontal,” “top,” “bottom,” “inner,” and “outer,” etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this disclosure and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this disclosure.

[0022] 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 disclosure, unless otherwise stated, "a plurality of" means two or more.

[0023] In the description of this disclosure, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection, an electrical connection, or a communication connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this disclosure according to the specific circumstances.

[0024] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings and preferred embodiments.

[0025] This embodiment provides a reverse spiral PDC drill bit, such as Figure 1 and Figure 2 As shown, the drill bit includes a drill body 1, a connector 2 located at the upper end of the drill body 1, multiple cutter wings 4 located on the drill body 1, and composite blades arranged on the cutter wings 4. The drill body 1 is provided with a chip removal groove 3 and a water hole 5. The water hole 5 communicates with the water channel inside the drill body 1 and is used to deliver drilling fluid to the drill bit working face.

[0026] Specifically, such as Figure 2 As shown, the multiple cutter wings 4 include three short cutter wings 10 and two long cutter wings 11, with the short cutter wings 10 and long cutter wings 11 arranged alternately along the circumference of the drill bit. Each cutter wing 4 is equipped with a composite plate.

[0027] like Figure 2 As shown, the composite plates on the short blade 10 are arranged in a counter-spiral structure. Specifically, the counter-spiral structure is defined as follows: On the short blade 10, a baseline 12 is defined passing through the drill bit center point and the center of the first composite plate closest to the drill bit center. Starting from the second composite plate on the short blade 10, the centers of the remaining composite plates are offset counter-clockwise relative to the baseline 12. Furthermore, the farther the composite plate is from the drill bit center, the greater the counter-clockwise distance between its center and the baseline 12. In other words, viewed from the drill bit center outwards, the arrangement of the composite plates on the short blade 10 exhibits a gradually shifting leftward (counter-clockwise) trend, forming a counter-spiral line.

[0028] like Figure 2As shown, the composite plates on the long blade 11 are arranged in a non-spiral structure (i.e., a straight structure). The specific definition of the non-spiral structure is as follows: on the long blade 11, a long blade reference line 13 is defined, passing through the drill bit center point and the center of the first composite plate closest to the drill bit center. Then, the centers of all composite plates on the long blade 11 are basically arranged on or near the long blade reference line 13, that is, roughly in a straight line. For comparison, Figure 3 The diagram shows a common positive spiral structure in the prior art, in which the composite sheet is offset in a clockwise direction relative to the positive spiral reference line 14.

[0029] like Figure 1 As shown, the composite blade includes a main cutting tooth 6 and a secondary cutting tooth 7. The main cutting tooth 6 is located at the edge of the blade 4 and is the primary cutting element. The secondary cutting tooth 7 is located behind the main cutting tooth 6 (i.e., behind the main cutting tooth in the same blade's rotation direction), forming a second row of cutting teeth. The cutting height of the secondary cutting tooth 7 is lower than that of the main cutting tooth 6, with a height difference of 0.5 mm to 1 mm. This high-low tooth design allows the main cutting tooth 6 to undertake the main cutting task, while the secondary cutting tooth 7 plays a supporting role in cutting and protecting the main cutting tooth, while also helping to improve cutting stability.

[0030] The back rake angles of both the main cutting tooth 6 and the secondary cutting tooth 7 are set to 17 to 32 degrees. This back rake angle range has been optimized to effectively enhance the impact resistance of the composite material and extend the drill bit life while ensuring cutting efficiency.

[0031] like Figure 1 As shown, all cutter wings 4 feature a short gauge protection design, with a gauge protection length of approximately 50mm. This short gauge protection design reduces the contact area between the drill bit and the wellbore, lowering frictional resistance and improving the rate of drilling, particularly enhancing the build-up capability in directional drilling. Cutter wings 4 are equipped with active gauge protection teeth 8 and passive gauge protection teeth 9 to maintain the wellbore diameter and prevent drill bit diameter wear. Furthermore, cutter wings 4 also feature reaming teeth (not shown in the figure) for finishing the wellbore during tripping or when reaming is required, improving wellbore quality.

[0032] A fixed or replaceable nozzle is installed inside water hole 5. The nozzle's spray angle points towards chip flushing groove 3 to flush rock chips, clean cutting teeth, and cool the drill bit, preventing mud buildup. The nozzle's spray orifice inner diameter is 8-18mm to ensure sufficient impact force and prevent clogging.

[0033] Working principle In this embodiment, the reverse-helix drill bit utilizes a reverse-helix structure for its short blades 10. This allows the outer composite blades (those farther from the drill bit center) to preferentially contact and cut the rock, while the composite blades closer to the drill bit center lag behind. This cutting sequence ensures that the surrounding rock is removed before the central rock is completely cut, creating an "island" effect that releases internal stress in the rock, making the central rock looser and easier to break. Consequently, the drill bit's mechanical drilling speed can be increased by 2-3 times.

[0034] Meanwhile, the long blade 11 adopts a straight structure, combined with the anti-helical structure of the short blade 10, which makes the force on the drill bit more balanced during rotation, thus improving the stability of the drill bit. The short parabolic crown profile and short gauge design reduce the lateral friction of the drill bit, making the tool face more stable in directional and horizontal well construction, and improving the directional drilling effect by about 20%.

[0035] When drilling through fractured or hard-intercalated formations, the progressive cutting method provided by the anti-helix structure and the optimized back slope setting can effectively disperse impact loads, prevent composite blade chipping, and thus extend the service life of the drill bit.

[0036] In summary, the anti-auger drill bit of this embodiment effectively solves the problems of slow mechanical drilling speed, difficulty in directional drilling, and easy breakage of cutting teeth in the prior art through its unique blade structure design and cutting tooth arrangement, and achieves efficient, fast and long-life drilling results.

[0037] It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of this invention, and these improvements and modifications should also be considered within the scope of protection of this invention.

Claims

1. A reverse-auger drill bit, comprising a drill bit body (1), a plurality of cutter wings (4) disposed on the drill bit body (1), and a composite blade disposed on the cutter wings (4), characterized in that, The plurality of blades (4) include: At least one short blade (10), the composite plates on the short blade (10) being arranged in an anti-helical structure; and At least one long blade (11), on which the composite plates are arranged in a non-spiral structure.

2. The anti-auger drill bit according to claim 1, characterized in that, The anti-spiral structure refers to the following: on the short blade (10), a straight line (12) is defined that passes through the center point of the drill bit and the center of the first composite piece on the blade closest to the center of the drill bit. Starting from the second composite piece on the short blade (10), the centers of the remaining composite pieces are offset counterclockwise relative to the straight line (12). The farther the composite piece is from the center of the drill bit, the greater the counterclockwise distance between its center and the straight line (12).

3. A reverse spiral drill bit according to claim 2, characterized in that, The solenoid structure refers to the following: on the long blade (11), a straight line (13) is defined that passes through the center point of the drill bit and the center of the first composite piece on the blade closest to the center of the drill bit. Then, the centers of all composite pieces on the long blade (11) are arranged on or near the straight line (13).

4. A reverse spiral drill bit according to claim 3, characterized in that, It includes three short blades (10) and two long blades (11), which are arranged alternately along the circumference of the drill bit.

5. A reverse spiral drill bit according to claim 1, characterized in that, The composite blade includes a main cutting tooth (6) arranged at the blade edge and a secondary cutting tooth (7) arranged behind the main cutting tooth (6). The cutting height of the secondary cutting tooth (7) is lower than that of the main cutting tooth (6), and the height difference between the two is 0.5 mm to 1 mm.

6. A reverse spiral drill bit according to claim 5, characterized in that, The back rake angles of the main cutting tooth (6) and the secondary cutting tooth (7) are both 17 to 32 degrees.

7. A reverse spiral drill bit according to claim 1, characterized in that, All blades (4) are designed with short diameter protection, with a diameter protection length of 50mm ± 10mm.

8. A reverse spiral drill bit according to claim 1, characterized in that, The drill bit body (1) is provided with a water hole (5), and a fixed nozzle or a replaceable nozzle is installed in the water hole (5).

9. A reverse spiral drill bit according to claim 1, characterized in that, The blade (4) is provided with a passive diameter-maintaining tooth (9).

10. A reverse spiral drill bit according to claim 1, characterized in that, The blade (4) is provided with inverted serrations.

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