High build-up rate guide drill bit suitable for short-radius well

Abstract

The high-build-up-rate guide drill bit suitable for the short-radius well comprises a drill bit body, a plurality of blades are arranged on the drill bit body, each blade is provided with front-row cutting teeth and rear-row auxiliary teeth, the front-row cutting teeth are first plane PDC teeth, and at least part of the rear-row auxiliary teeth are conical PDC teeth; the blade height of the conical PDC teeth on the blades is lower than that of the front-row cutting teeth on the same track, and the conical PDC teeth break rocks when the front-row cutting teeth grind; each blade comprises an inner cone part, a crown part, an outer cone part, a shoulder part and a gauge protection part, the inner cone part is arranged in a shallow cone shape, the outer cone part is arranged in a short outer cone shape, the gauge protection part is arranged in a short gauge protection shape, and an inner connecting part used for being connected with an upper drill rod is arranged in the drill bit body so that the overall length of the high-build-up-rate guide drill bit suitable for the short-radius well can be shortened. The rock breaking efficiency of the drill bit can be effectively improved, the drilling operation period is shortened, and cost is reduced.

Description

Technical Field

[0001] This invention relates to the field of drilling engineering technology, and in particular to a high build-up rate directional drill bit suitable for short-radius wells. Background Technology

[0002] With the continued growth of global energy demand and the gradual depletion of conventional oil and gas resources, oil and gas exploration and development are accelerating towards deeper, unconventional, and complex geological conditions. The development of unconventional resources such as shale gas, coalbed methane, and tight sandstone gas, as well as deep-sea oil and gas resources, has become the focus of the industry. Directional wells, horizontal wells, and short-radius branch wells have become core methods for developing complex oil and gas reservoirs due to their ability to effectively increase drainage area and improve single-well production. However, these methods are highly dependent on the drilling capability of the build-up section. As a key part of wellbore trajectory change, the build-up rate, drilling efficiency, and drilling stability of the build-up section directly determine drilling costs and cycle time. Especially in short-radius branch wells, the small wellbore curvature radius places higher demands on the build-up capability of the drill string assembly, tool accessibility, and wellbore quality.

[0003] Traditional polycrystalline diamond composite (PDC) drill bits are a common drilling tool in the oil drilling industry. These bits utilize PDC to cut rock and perform excellently in conventional vertical wells and low dogleg wells. However, they exhibit slow penetration in cemented tight formations and directional drilling operations. When encountering tight reservoirs, the PDC switches to grinding and cutting, reducing rock-breaking efficiency, accelerating bit wear, and shortening lifespan. The large lateral contact area between traditional drill bits and the wellbore increases frictional resistance, making it difficult to effectively convert the lateral force required for directional drilling into cutting force, significantly limiting directional drilling efficiency and exacerbating wear on the gauge sections of the drill bit. The densely packed cutting teeth in the central area of ​​traditional drill bits hinder cuttings removal, and repeated cutting significantly increases torque fluctuations and bit deviation, amplifying instability in heterogeneous formations and causing the actual wellbore trajectory to deviate from the designed trajectory.

[0004] Short-radius (generally referring to a radius of curvature of 3–20 m) branch well drilling technology is an important technique for increasing the drainage area and achieving increased oil and gas production and storage, and it plays a significant role in increasing production of old wells in oil and gas fields. During directional drilling operations, situations arise where the rock has high strength, hardness, and abrasiveness. Using conventional directional drilling PDC bits results in severe wear, bit chipping, low mechanical drilling rate, low build-up rate, and formation defects in the branch wellbore.

[0005] Therefore, based on years of experience and practice in related industries, the inventor proposes a high build-up rate directional drill bit suitable for short-radius wells to overcome the shortcomings of existing technologies. Summary of the Invention

[0006] The purpose of this invention is to provide a high build-up rate directional drill bit suitable for short-radius wells, solving the problems of slow drilling speed and low build-up efficiency in directional drilling of hard rock formations. This invention can effectively increase the rock-breaking efficiency of the drill bit, shorten the drilling operation cycle, and reduce costs.

[0007] The objective of this invention is achieved as follows: a high build-up rate directional drill bit suitable for short-radius wells includes a drill bit body with a plurality of blades. Each blade has a front row of cutting teeth and a rear row of auxiliary teeth. Each front row of cutting teeth is a first planar PDC tooth, and at least part of the rear row of auxiliary teeth is a conical PDC tooth. The exit height of the conical PDC teeth on the blades is lower than the exit height of the front row of cutting teeth located on the same track. When the front row of cutting teeth is worn down, the conical PDC teeth break the rock. Each blade includes an inner cone, a crown, an outer cone, a shoulder, and a gauge-maintaining section. The inner cone is a shallow cone, the outer cone is a short outer cone, and the gauge-maintaining section is a short gauge-maintaining section. An inner connecting part for connecting to the upper drill pipe is provided within the drill bit body to shorten the overall length of the high build-up rate directional drill bit suitable for short-radius wells.

[0008] In a preferred embodiment of the present invention, the cross-section of the inner cone is arranged in an inclined straight line, and the included angle between the inner cone and the axial direction of the drill bit body is greater than or equal to 150°; the cross-section of the crown is arranged in an arc, and the radius of rotation of the crown is greater than or equal to 3 / 5 of the outer diameter of the drill bit body; the height of the outer cone along the axial direction of the drill bit body is less than or equal to 3 / 10 of the outer diameter of the drill bit body; and the length of the gauge-keeping portion along the axial direction of the drill bit body is less than or equal to 2 / 5 of the height of the outer cone along the axial direction of the drill bit body.

[0009] In a preferred embodiment of the present invention, each of the first planar PDC teeth on each of the blades is inclined in the rearward direction. The rearward tilt angle of the first planar PDC teeth located in the inner cone is 17° to 19°, the rearward tilt angle of the first planar PDC teeth located in the crown is 14° to 16°, the rearward tilt angle of the first planar PDC teeth located in the outer cone is 16° to 18°, and the rearward tilt angle of the first planar PDC teeth located in the shoulder and the diameter-protecting portion is 20° to 22°.

[0010] In a preferred embodiment of the present invention, the rear auxiliary teeth further include second planar PDC teeth, which are disposed on the outer cone portion. Each second planar PDC tooth is disposed on the same track as the corresponding first planar PDC tooth in the front row. The second planar PDC tooth is inclined in the rear direction of the tooth with an inclination angle of 14° to 16°.

[0011] In a preferred embodiment of the present invention, the tapered PDC teeth are disposed on the crown and the outer cone; the positive inclination angle of the tapered PDC teeth located on the crown is 22° to 24°, and the positive inclination angle of the tapered PDC teeth located on the outer cone is 20° to 22°.

[0012] In a preferred embodiment of the present invention, the difference in cutting edge height between the tapered PDC tooth and the front row of cutting teeth located on the same track is less than or equal to 1.5 mm.

[0013] In a preferred embodiment of the present invention, the upper part of the diameter-protecting portion is provided with an arc-shaped groove, the arc-shaped groove is arranged along the circumference of the diameter-protecting portion, and a spring shock absorber is embedded in the arc-shaped groove; the spring shock absorber includes a lower base, a spring and an upper cover plate, the lower base is embedded in the arc-shaped groove, and the lower base is connected to the upper cover plate through the spring.

[0014] In a preferred embodiment of the present invention, a drill bit cavity is provided in the drill bit body, a chip removal groove is provided between adjacent cutter wings, and a nozzle is provided on the drill bit body within the chip removal groove; the drill bit cavity is connected to each of the nozzles through a nozzle flow channel.

[0015] In a preferred embodiment of the present invention, a through drilling fluid side channel is provided on the diameter protection part, one end of the drilling fluid side channel is connected to the inner cavity of the drill bit, and the other end of the drilling fluid side channel is disposed towards the well wall.

[0016] In a preferred embodiment of the present invention, the front row of cutting teeth and the rear row of auxiliary teeth are formed by a cemented carbide base coated with a polycrystalline diamond layer.

[0017] As described above, the high build-up rate directional drill bit of the present invention, suitable for short-radius wells, has the following beneficial effects: (1) The present invention improves the lateral cutting capability by designing the cutting tooth tip height, shallow inner cone and short outer cone, so that the drill bit makes good contact with the bottom of the well, thereby improving the directional drilling capability and the directional drilling capability. The invention also achieves reasonable control of the lateral cutting capability and axial cutting capability of the drill bit by changing the back angle of the cutting teeth, thereby improving the directional drilling capability of the drill bit when used with directional drilling tools and meeting the requirements of rapid drilling.

[0018] (2) After the present invention has been in operation for a period of time, the front row of cutting teeth gradually wears down and the cutting edge height decreases. The cutting edge height of the conical PDC teeth in the rear row of auxiliary cutting teeth on the same track tends to be consistent with that of the front row of cutting teeth, and the conical PDC teeth begin to participate in rock breaking by the drill bit. The rock is broken by the plowing action of the conical PDC teeth, forming plowing grooves and micro-cracks, releasing rock stress, thereby restoring the rock breaking ability of the front row of teeth, improving drilling efficiency and shortening the operation cycle.

[0019] (3) The present invention effectively shortens the contact length between the drill bit and the well wall during drill string connection by integrating the internal connecting part in the internal cavity of the drill bit, thereby improving flexibility and creating a wellbore for the directional drilling section through a short-radius well guide. Attached Figure Description

[0020] The following figures are intended only to illustrate and explain the present invention and do not limit the scope of the invention. Wherein: Figure 1 This is a schematic diagram of the structure of the high build-up rate directional drill bit for short-radius wells according to the present invention.

[0021] Figure 2 This is a top view of the high build-up rate directional drill bit for short-radius wells according to the present invention.

[0022] Figure 3 This is a cross-sectional view of the high build-up rate directional drill bit of the present invention, applicable to short-radius wells.

[0023] Figure 4 This is a schematic diagram showing the difference in cutting edge height between the front row of cutting teeth and the rear row of tapered PDC teeth of the present invention.

[0024] Figure 5 This is a schematic diagram of the spring shock absorber of the present invention.

[0025] In the picture: 1. Drill bit body; 10. Drill bit inner cavity; 11. Nozzle flow channel; 12. Drilling fluid flow channel; 2. Blade wing; 201. Front row of cutting teeth; 202. Tapered PDC teeth; 21. Inner cone; 22. Crown; 23. Outer cone; 24. Shoulder; 25. Diameter protection section; 251. Arc groove; 252. Spring shock absorber; 2521. Lower base; 2522. Spring; 2523. Upper cover plate; 253. Drilling fluid side passage; 254. Backlash teeth; 3. Internal connecting part; 4. Chip removal groove; 5. Nozzle. Detailed Implementation

[0026] To provide a clearer understanding of the technical features, objectives, and effects of the present invention, specific embodiments of the present invention will now be described with reference to the accompanying drawings.

[0027] The specific embodiments of the present invention described herein are for illustrative purposes only and should not be construed as limiting the invention in any way. Under the teachings of this invention, those skilled in the art can conceive of any possible modifications based on the invention, all of which should be considered within the scope of the invention. It should be noted that when an element is referred to as being "set on" another element, it can be directly on the other element or there may be an intervening element. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or there may be an intervening element. The terms "mounted," "connected," and "linked" should be interpreted broadly; for example, they can refer to mechanical or electrical connections, or internal communication between two elements, and can be direct or indirect connections through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms according to the specific circumstances. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only possible embodiments.

[0028] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the specification of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0029] like Figures 1 to 5 As shown, the present invention provides a high build-up rate directional drill bit suitable for short-radius wells, comprising a drill bit body 1, which can be divided into an upper cutting portion and a lower connecting portion (here, upper and lower are...). Figure 1 (The directions shown are for directional purposes only and are not intended to limit the location.) like Figure 1 , Figure 2 , Figure 3As shown, the drill bit body 1 is equipped with several cutter wings 2, each cutter wing 2 having a front row of cutting teeth 201 and a rear row of auxiliary teeth. Each front row of cutting teeth is a first-plane PDC tooth, and at least part of the rear row of auxiliary teeth is a conical PDC tooth 202. The exit height of the conical PDC teeth 202 on the cutter wing 2 is lower than the exit height of the front row of cutting teeth 201 located on the same track. When the front row of cutting teeth 201 is ground, the conical PDC teeth 202 break the rock. That is, under the condition that the front row of cutting teeth 201 is ground, the rear row of conical PDC teeth 202... 02 can break rocks in a plowing manner, release rock stress, and restore the cutting power of the front row of teeth, thereby improving drilling efficiency and shortening the drilling cycle; each blade 2 includes an inner cone 21, a crown 22, an outer cone 23, a shoulder 24, and a gauge-keeping part 25. The inner cone 21 is a shallow cone, the outer cone 23 is a short outer cone, and the gauge-keeping part 25 is a short gauge-keeping part. The drill bit body 1 is provided with an inner connecting part 3 (female threaded joint) for connecting the upper drill pipe to shorten the overall length of the high build-up rate directional drill bit suitable for short-radius wells.

[0030] Specifically, the drill body 1 is provided with several cutting blades 2; the blades 2 are arranged along the top and side surfaces of the drill body 1 and are evenly distributed on the circumference of the drill body 1. Each blade 2 is provided with a double row of several planar and conical PDC cutting teeth, which are arranged in front and behind rows on the blade 2, and the same track plane and conical PDC cutting teeth on the blade are provided with a difference in cutting edge height H.

[0031] The inner connecting part 3 is disposed in the internal cavity of the drill bit body 1 and is integrated with the drill bit body 1 as one unit; in a specific embodiment, such as Figure 5 As shown, the inner connection part 3 is designed with a female thread and is used to connect with the upper drill string. The integrated connection part (inner connection part 3) can shorten the effective working length of the drill bit (the contact length between the drill bit and the well wall) when connecting the drill string, reduce friction with the well wall, improve flexibility, and smoothly pass through the wellbore of the short-radius well guide directional section.

[0032] In one specific embodiment, five toothed cutter wings are designed to increase the stability of the drill bit. The front row of cutting teeth 201 serves as the main cutting teeth, and is designed radially according to the principle of equal wear to form a single-mode bottom hole coverage; and is designed circumferentially according to the principle of directional cutting stability.

[0033] The cutting teeth on the cutter wing 2 are divided into a front row of cutting teeth 201 and a rear row of auxiliary teeth. The front row of cutting teeth 201 are the main cutting teeth, and the rear row of auxiliary teeth are the auxiliary teeth. By setting two rows of cutting teeth on the same track, the cutting effect and cutting efficiency are optimized. The main cutting teeth in the front row are set as planar PDC cutting teeth, which have a large contact area with the rock at the bottom of the well, and the drilling pressure acting on a single cutting tooth is relatively small. The main cutting teeth break the rock by shearing.

[0034] The tapered PDC teeth 202, with their lower cutting capacity, assist in controlling the drill bit's penetration depth into the formation. As directional drilling or guide operations progress, and the drill bit gradually wears down or encounters densely cemented rock formations with poor drillability, the front row of cutting teeth 201 on the same track gradually wears down, resulting in a lower cutting edge height. The cutting edge height of the rear row of auxiliary cutting tapered PDC teeth 202 tends to match that of the front row of cutting teeth 201, and the rear auxiliary teeth begin to participate in rock breaking. The tapered PDC teeth 202 have a small contact area with the rock at the bottom of the well, resulting in a larger drilling pressure on each individual cutting tooth. This facilitates penetration into the formation, breaking the rock in a plowing manner, forming plowing grooves and micro-cracks, and releasing rock stress. Multiple tapered PDC teeth 202 on the same cutter blade 2 can assist in rock breaking through by pressing inward, thereby improving drilling efficiency and shortening the operation cycle.

[0035] During directional drilling or pilot drilling, the contact area between the drill bit and the well wall is smaller than that of traditional drill bits. The design of the inner connecting part 3 and the short diameter shortens the overall length of the drill bit, resulting in greater lateral cutting capability under the same lateral force. The shallow inner cone and short outer cone design improves the contact between the drill bit and the bottom of the well, ensuring that the cutting teeth fully penetrate the formation. The conical PDC teeth 202 located in the rear row can plow the rock in a plowing manner when the front cutting teeth 201 are worn down, releasing rock stress and restoring the cutting capability of the front teeth, thereby improving drilling efficiency and shortening the drilling cycle.

[0036] The high build-up rate directional drill bit of the present invention, suitable for short-radius wells, has good rock-breaking ability and high directional build-up ability, which can effectively solve the problems of slow drilling speed and low build-up efficiency in directional drilling of hard rock formations, improve drilling efficiency and shorten drilling cycle.

[0037] The beneficial effects of this invention are: (1) The present invention improves the lateral cutting capability by designing the cutting edge height, shallow inner cone and short outer cone of the cutting teeth, so as to make good contact between the drill bit and the bottom of the well, thereby improving the directional cutting capability and the directional control capability. (2) After the present invention has been in operation for a period of time, the front row of cutting teeth 201 gradually wears down, and the cutting edge height decreases. The cutting edge height of the rear row of auxiliary cutting conical PDC teeth on the same track tends to be consistent with that of the front row of cutting teeth 201, and the conical PDC teeth 202 begin to participate in the rock breaking of the drill bit. The rock is broken by the plowing action of the conical PDC teeth, forming plowing grooves and micro-cracks, releasing rock stress, thereby restoring the rock breaking ability of the front row of teeth, improving drilling efficiency and shortening the operation cycle.

[0038] (3) The present invention uses the internal connecting part 3 integrated in the internal cavity of the drill bit to effectively shorten the contact length between the drill bit and the well wall when connecting the drill string, improve the flexibility, and create a wellbore for the directional drilling part through a short radius well guide.

[0039] Furthermore, the cross-section of the inner cone 21 is set as an inclined straight line, and the included angle between the inner cone 21 and the axial direction of the drill bit body 1 is greater than or equal to 150°, forming a shallow cone structure; the cross-section of the crown 22 is set as an arc, and the radius of rotation of the crown 22 is greater than or equal to 3 / 5 of the outer diameter of the drill bit body 1; the height of the outer cone 23 along the axial direction of the drill bit body 1 is less than or equal to 3 / 10 of the outer diameter of the drill bit body 1, and the axial length of the outer cone 23 is shorter than that of the conventional outer cone in the prior art, forming a short outer cone structure; the length of the gauge-keeping part 25 along the axial direction of the drill bit body 1 is less than or equal to 2 / 5 of the height of the outer cone 23 along the axial direction of the drill bit body 1, forming a short gauge-keeping structure.

[0040] Through the parameter optimization design of each component of the aforementioned cutter wing 2, the design of shallow inner cone and short outer cone is realized, which makes the drill bit contact the bottom of the well better and ensures that the cutting teeth completely penetrate the formation; the short diameter design shortens the overall length of the drill bit and has a greater lateral cutting ability under the same lateral force.

[0041] Furthermore, the front row of cutting teeth (first plane PDC teeth) on blade 2 adopts a segmented tilt angle design.

[0042] Each first plane PDC tooth on each cutter wing 2 is inclined towards the rear of the tooth. The rear tilt angle (the angle between the working surface of the PDC drill bit cutting tooth and the outer normal of the bottom rock surface) of the first plane PDC tooth located in the inner cone 21 is 17° to 19°, preferably 16°. The rear tilt angle of the first plane PDC tooth located in the crown 22 is 14° to 16°. The rear tilt angle of the first plane PDC tooth located in the outer cone 23 is 16° to 18°. The rear tilt angle of the first plane PDC tooth located in the shoulder 24 and the diameter protection part 25 is 20° to 22°.

[0043] Furthermore, the rear auxiliary teeth also include second plane PDC teeth, which are disposed on the outer cone portion 23. Each second plane PDC tooth is disposed on the same track as the corresponding first plane PDC tooth in the front row. The second plane PDC teeth are inclined in the rear direction with an inclination angle of 14° to 16°.

[0044] Furthermore, such as Figure 1 , Figure 3 As shown, tapered PDC teeth 202 are disposed on the crown portion 22 and the outer tapered portion 23; the positive inclination angle of the tapered PDC teeth 202 located on the crown portion 22 is 22° to 24°, and the positive inclination angle of the tapered PDC teeth 202 located on the outer tapered portion 23 is 20° to 22°.

[0045] By changing the back slope angle of the cutting teeth, the lateral and axial cutting capabilities of the drill bit are rationally controlled, which improves the directional drilling capability of the drill bit when used in conjunction with directional drilling tools and meets the requirements of rapid drilling.

[0046] Furthermore, such as Figure 4 As shown, the difference H between the exit height of the tapered PDC tooth 202 and the front row cutting tooth 201 located on the same track is less than or equal to 1.5 mm.

[0047] The rear auxiliary teeth include second-plane PDC teeth and conical PDC teeth 202, arranged in a mixed configuration. The conical PDC teeth 202 are positioned behind the main cutting teeth (front cutting teeth 201) at the crown tip (crown 22 and outer cone 23) where the drill bit penetrates deep into the formation and experiences significant wear. As secondary cutting teeth, the conical PDC teeth 202 have an edge height approximately 1.5 mm lower than the front cutting teeth 201. The second-plane PDC teeth are positioned at the outer cone 23 to increase tooth density and extend drill bit life.

[0048] Furthermore, the gauge protection section 25 includes multiple gauge protection blocks, which are evenly distributed on the circumferential surface of the drill bit body. Active gauge protection teeth are provided at the gauge protection section 25, and gauge protection zone PDC teeth are arranged behind the active gauge protection teeth as shock-absorbing teeth, which are laid flat at specific positions of passive gauge protection to reduce friction between gauge protection and well wall. Moreover, they can participate in cutting when the drill bit reverses, reducing the torque vibration of the drill bit.

[0049] To ensure that the drill bit has good backreaming and well wall repair capabilities, a flat PDC tooth is provided at the lower part of the diameter protection section 25 as a backreaming tooth 254.

[0050] Furthermore, such as Figure 3 , Figure 5 As shown, the upper part of the diameter-protecting section 25 is provided with an arc-shaped groove 251, which is arranged circumferentially along the diameter-protecting section 25. A spring damper 252 is embedded in the arc-shaped groove 251. The spring damper 252 includes a lower base 2521, a spring 2522, and an upper cover plate 2523. The lower base 2521 is embedded in the arc-shaped groove 251 and is connected to the upper cover plate 2523 through the spring 2522. In a specific embodiment, the spring 2522 is a hard alloy spring.

[0051] When the drill bit is subjected to lateral cutting force, the spring damper 252 absorbs part of the vibration energy, reduces the stress concentration effect at the gauge section 25, and at the same time helps the gauge to fit tightly against the well wall, improving the stability of the drill bit during directional drilling.

[0052] Furthermore, such as Figure 2 , Figure 3As shown, a through drilling fluid channel 12 is provided in the middle of the drill bit body 1 along the axial direction; an inner cavity 10 communicating with the drilling fluid channel 12 is provided inside the drill bit body 1 (inside the drill bit crown); a chip removal groove 4 is provided between adjacent cutter wings 2; a nozzle 5 is provided on the drill bit body 1 within the chip removal groove 4; several nozzle channels 11 are provided between the inner cavity 10 and the outer end face of the drill bit crown; the inner cavity 10 is connected to each nozzle 5 through the nozzle channels 11. The nozzles 5 are mounted on the drill bit body 1, so that the drilled cuttings can be discharged in time, and the drilling fluid sprayed from the nozzles 5 can lubricate and cool the drill bit.

[0053] Furthermore, such as Figure 3 As shown, a through drilling fluid side channel 253 is provided on the diameter protection section 25. One end of the drilling fluid side channel 253 is connected to the inner cavity of the drill bit, and the other end of the drilling fluid side channel 253 is set towards the well wall. The drilling fluid can directly flush the contact area between the diameter protection section 25 and the well wall to prevent the drill bit from getting mud.

[0054] Furthermore, in existing technologies, PDC drill bits use polycrystalline diamond composite sheets to cut rocks. However, when encountering formations with densely cemented rocks and poor drillability, the polycrystalline diamond composite sheets cannot penetrate the rock, and the rock-breaking method changes from cutting to grinding. This reduces rock-breaking efficiency, accelerates drill bit wear, and shortens drill bit life. In addition, due to the high drillability and anisotropy of the formation, the drill bit has poor stability, is difficult to build up directional drilling, and has low drilling efficiency.

[0055] In this invention, the front row of cutting teeth 201 and the rear row of auxiliary teeth are formed by a cemented carbide base coated with a polycrystalline diamond layer, which effectively improves the service life of the cutting teeth.

[0056] The above description is merely an illustrative embodiment of the present invention and is not intended to limit the scope of the invention. Any equivalent changes and modifications made by those skilled in the art without departing from the concept and principles of the present invention should fall within the scope of protection of the present invention.

Claims

1. A high build-up rate directional drill bit suitable for short-radius wells, characterized in that, The drill bit body includes a plurality of blades, each blade having a front row of cutting teeth and a rear row of auxiliary teeth. Each front row of cutting teeth is a first planar PDC tooth, and at least part of the rear row of auxiliary teeth is a conical PDC tooth. The exit height of the conical PDC teeth on the blades is lower than the exit height of the front row of cutting teeth located on the same track. When the front row of cutting teeth is ground, the conical PDC teeth break the rock. Each blade includes an inner cone, a crown, an outer cone, a shoulder, and a diameter-maintaining section. The inner cone is a shallow cone, the outer cone is a short outer cone, and the diameter-maintaining section is a short diameter-maintaining section. An inner connecting part is provided within the drill bit body for connecting to the upper drill pipe to shorten the overall length of the high build-up rate directional drill bit suitable for short-radius wells.

2. The high build-up rate directional drill bit for short-radius wells as described in claim 1, characterized in that, The cross-section of the inner cone is an inclined straight line, and the included angle between the inner cone and the axial direction of the drill bit body is greater than or equal to 150°; the cross-section of the crown is an arc, and the radius of rotation of the crown is greater than or equal to 3 / 5 of the outer diameter of the drill bit body; the height of the outer cone along the axial direction of the drill bit body is less than or equal to 3 / 10 of the outer diameter of the drill bit body; the length of the gauge-keeping portion along the axial direction of the drill bit body is less than or equal to 2 / 5 of the height of the outer cone along the axial direction of the drill bit body.

3. The high build-up rate directional drill bit for short-radius wells as described in claim 2, characterized in that, Each of the first planar PDC teeth on each blade is inclined in the rear direction. The rear tilt angle of the first planar PDC teeth located in the inner cone is 17° to 19°, the rear tilt angle of the first planar PDC teeth located in the crown is 14° to 16°, the rear tilt angle of the first planar PDC teeth located in the outer cone is 16° to 18°, and the rear tilt angle of the first planar PDC teeth located in the shoulder and the diameter-protecting part is 20° to 22°.

4. The high build-up rate directional drill bit for short-radius wells as described in claim 2, characterized in that, The rear auxiliary teeth also include second planar PDC teeth, which are disposed on the outer cone portion. Each second planar PDC tooth is arranged on the same track as the corresponding first planar PDC tooth in the front row. The second planar PDC tooth is inclined in the rear direction with an inclination angle of 14° to 16°.

5. The high build-up rate directional drill bit for short-radius wells as described in claim 2, characterized in that, The conical PDC teeth are disposed on the crown and the outer cone; the positive inclination angle of the conical PDC teeth located on the crown is 22° to 24°, and the positive inclination angle of the conical PDC teeth located on the outer cone is 20° to 22°.

6. The high build-up rate directional drill bit for short-radius wells as described in claim 2, characterized in that, The difference in cutting edge height between the tapered PDC tooth and the front row of cutting teeth located on the same track is less than or equal to 1.5 mm.

7. The high build-up rate directional drill bit for short-radius wells as described in claim 2, characterized in that, The upper part of the diameter-protecting section is provided with an arc-shaped groove, which is arranged along the circumference of the diameter-protecting section. A spring shock absorber is embedded in the arc-shaped groove. The spring shock absorber includes a lower base, a spring, and an upper cover plate. The lower base is embedded in the arc-shaped groove, and the lower base is connected to the upper cover plate through the spring.

8. The high build-up rate directional drill bit for short-radius wells as described in claim 2, characterized in that, The drill bit body has an inner cavity, and a chip removal groove is provided between adjacent blades. A nozzle is provided on the drill bit body within the chip removal groove. The inner cavity of the drill bit is connected to each nozzle through a nozzle flow channel.

9. The high build-up rate directional drill bit for short-radius wells as described in claim 8, characterized in that, The diameter protection section is provided with a through drilling fluid side channel, one end of which is connected to the inner cavity of the drill bit, and the other end of which is set towards the well wall.

10. The high build-up rate directional drill bit for short-radius wells as described in claim 1, characterized in that, The front row of cutting teeth and the rear row of auxiliary teeth are formed by a cemented carbide base coated with a polycrystalline diamond layer.

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