EP4640989A1

EP4640989A1 - Pdc-roller hybrid drill bit

Info

Publication number: EP4640989A1
Application number: EP23905851.4A
Authority: EP
Inventors: Jianbin YU; Ye PENG; Zhonghua Wu; Shuwei GUAN; Yuchao XU; Dong Zhang; Weitao Wang; Haixin YU; Yuxin Liu; Jianxiang SUN
Original assignee: China Petroleum and Chemical Corp; Sinopec Oilfield Service Corp; Sinopec Shengli Petroleum Engineering Corp; Drilling Technology Research Institute of Sinopec Shengli Petroleum Engineering Corp
Current assignee: China Petroleum and Chemical Corp; Sinopec Oilfield Service Corp; Sinopec Shengli Petroleum Engineering Corp; Drilling Technology Research Institute of Sinopec Shengli Petroleum Engineering Corp
Priority date: 2022-12-22
Filing date: 2023-12-18
Publication date: 2025-10-29
Also published as: CN120175215A; CN223594111U; WO2024131687A1; CN223594110U; CN120175213A; CN223964436U; CN120175214A

Abstract

The present invention relates to the technical field of drilling tool for petroleum and geological engineering. Specifically, the present invention relates to a PDC-roller hybrid drill bit, comprising: a bit body; a roller assembly arranged in a roller area, comprising a roller arm fixedly connected to the bit body, a roller shaft fixedly connected to the roller arm, a rolling wheel on the roller shaft, and at least one roller tooth arranged along a circumferential direction of the rolling wheel; and an oil cavity and an oil passage arranged in the roller arm, wherein the oil passage is configured such that oil in the oil cavity flows to contact surfaces between the roller shaft and the rolling wheel, and sealing assemblies for sealing the rolling wheel are arranged at both ends of the roller shaft and comprise a composite sealing ring. In the present invention, the service life of the hybrid drill bit can be greatly extended, and the drilling footage, rate of penetration and directional performance thereof in heterogeneous formations can be significantly improved, thus facilitating the acceleration of exploration and development of oil/gas and mine fields as well as the cost reduction thereof.

Description

Cross Reference of Related Applications

The present application claims the priorities of Chinese patent application No. 202211655762.6 entitled "PDC-ROLLER HYBRID DRILL BIT" and filed on December 22, 2022 , and Chinese patent application No. 202211726558.9 entitled "PDC-ROLLER HYBRID DRILL BIT" and filed on December 30, 2022 , the entire content of which is incorporated herein by reference.

Technical Field

The present invention relates to the technical field of drilling tool for petroleum and geological engineering, and specifically to a PDC-roller hybrid drill bit.

Technical Background

Drill bit is an indispensable tool for downhole construction in the technical field of oil/gas and geological drilling. Drill bit can break the formation rock and drill to form wellbore. The design and selection of drill bit is a key factor for increasing the efficiency of rock breaking and the drilling speed in complex formations, while reducing the drilling cost. Therefore, the quality of the wellbore and the time taken in drilling are closely related to the structure and performance of the drill bit.
PDC (Polycrystalline Diamond Compact) bits can have satisfactory performance in soft to medium-hard formations, and thus are broadly applied in oil and geological drilling. However, PDC bits have disadvantages such as low rate of penetration and insufficient service life in some medium-to-hard formations, especially in heterogeneous formations. In directional wells, horizontal wells, extended-reach wells and branch wells or the like, PDC bits may have unstable tool face, especially in cases of low well inclination. Generally a roller bit is first required for orientation, which, however, has low rate of penetration and drilling footage in some hard heterogeneous formations. Moreover, roller bit is prone to tooth breakage especially in medium to hard formations.
PDC-roller hybrid bit has been proposed in the prior arts. This type of bit possesses the advantages of both PDC bit and roller bit, which has been effective in increasing drilling rate and orientation efficiency. However, seal failure of such drill bit often occurs after long-term use, resulting in problems such as short service life.

Summary of the Invention

In view of the above technical problems, the present invention aims to propose a PDC-roller hybrid drill bit, which is able to solve at least one of the above technical problems.
According to the present invention, the PDC-roller hybrid drill bit comprises a bit body for connecting to a drill string, a PDC assembly arranged on the bit body, and a roller assembly arranged on the bit body, comprising a roller arm fixedly connected to the bit body, and a roller shaft and a rolling wheel both connected to the roller arm, the rolling wheel being rotatably connected to both the roller shaft and the PDC assembly, wherein a first blind hole is provided in the rolling wheel for receiving the roller shaft.
In one specific embodiment, a first support shaft is fixedly arranged on the PDC assembly, and a second blind hole is arranged in the rolling wheel for receiving the first support shaft, wherein an axis of the first blind hole coincides with that of the second blind hole.
In one specific embodiment, a second support shaft is fixedly arranged on the rolling wheel, and a third blind hole is provided in the PDC assembly for receiving the second support shaft, wherein the axis of the first blind hole coincides with that of the third blind hole.
In one specific embodiment, a sealing assembly is provided between the rolling wheel and at least one of the roller shaft, the first support shaft and the second support shaft, the sealing assembly comprising a first seal and a second seal arranged on the roller shaft and connected to each other, wherein connection surfaces between the first seal and the second seal are polished surfaces.
In one specific embodiment, at least one axial end of the sealing assembly is provided with a first support member with elasticity, which is configured to exert axial pressure on the first seal and the second seal, so that the first seal is connected to the second seal.
In one specific embodiment, a hardness of the first seal and the second seal is greater than that of the first support member, and a friction resistance of the first seal and the second seal is lower than that of the first support member.
In one specific embodiment, the sealing assembly further includes a second support member with elasticity, which is radially arranged around the first seal and/or the second seal.
In one specific embodiment, an oil cavity and an oil passage are arranged in the roller arm, wherein the oil passage is configured such that oil in the oil cavity flows to contact surfaces between the roller shaft and the rolling wheel.
In one specific embodiment, a sliding piston is arranged within the oil cavity to divide the oil cavity into a balance chamber and an oil chamber, wherein the oil chamber is in communication with the oil passage, and the balance chamber is in communication with outside atmosphere.
In one specific embodiment, a first plug is provided at one end of the oil chamber away from the sliding piston, wherein an oil-filling hole is formed in the first plug, with an oil-filling plug arranged therein.
In one specific embodiment, the oil passage includes a first oil passage, a second oil passage and a third oil passage in communication with each other in sequence, wherein the first oil passage is arranged in the roller arm and in communication with the oil cavity; the second oil passage is arranged along an axial direction of the roller shaft, one end of the second oil passage extending out of the roller shaft to form an opening with a second plug; and the third oil passage is arranged along a radial direction of the roller shaft and extends to the contact surfaces between the roller shaft and the rolling wheel.
In one specific embodiment, the PDC assembly includes cutting teeth fixedly connected to the bit body, and a plurality of roller teeth is arranged on an outer wall of the rolling wheel, wherein the roller teeth are configured to extend further than the cutting teeth, so that formation rock is crushed by the rolling wheel through rotation before being cut by the PDC assembly.
In one specific embodiment, a height of the roller teeth is 0.01-5 mm larger than that of the cutting teeth.
In one specific embodiment, the first seal and the second seal are made of martensitic stainless steel, tungsten carbide, ceramics, cemented carbide, diamond, cubic boron nitride or silicon nitride, and the first support member is made of hydrogenated nitrile rubber, nitrile rubber or fluororubber.
In one specific embodiment, a strengthening layer is coated on each of outer walls of the roller shaft, the rolling wheel and the roller arm.
In one specific embodiment, the strengthening layer is made of tungsten carbide material.
In one specific embodiment, both outer walls of the roller shaft and the rolling wheel are subjected to nitriding, so that nitriding layers are formed inside the roller shaft and the rolling wheel.
In one specific embodiment, a central flow channel in communication with the drill string is arranged inside the bit body, the central flow channel comprising a nozzle extending to a blade, so that the fluid within the drill string is sprayed to the blade.
Compared with the prior arts, the present invention has the following advantages.
The PDC-roller hybrid drill bit according to the present invention combines the roller assembly with the PDC assembly, so that it has a high rate of penetration and good tool-face stability, and significantly increases the drilling footage thereof, thus reducing labor intensity of workers, reducing drilling costs, and accelerating the exploration and development of oil/gas and mine fields, etc.
During the operation of the PDC-roller hybrid drill bit, the roller teeth in the roller assembly first break the formation rock, and result in defects such as cracks in the unbroken formation, thus reducing the breaking strength of the formation rocks. Then the rock can be cut by the cutting teeth in the PDC assembly. Therefore, the roller teeth only break the rock at the bottom of the well in a pre-treatment manner, which greatly reduces the workload and stress thereof. Moreover, the cutting teeth in the PDC assembly cut the weakened formation rock, so that the drillability of the formation rock is greatly enhanced and the stress on the cutting teeth is significantly improved. Thus, the service lives of both the roller assembly and the PDC assembly are greatly extended. In the meantime, the roller teeth on the rolling wheel are arranged at intervals. Through the rolling of the rolling wheel, the PDC-roller hybrid drill bit can generate periodic vibrations along the axial direction of the bit body, thus significantly stabilizing the tool face and improving the weight-on-bit transfer efficiency. Therefore, the tool-face stability of the PDC-roller hybrid drill bit in drilling can be improved, thus improving the drilling operation efficiency and the drilling effect.
In the present invention, lubricating oil is provided to a position where the roller shaft is in contact with the rolling wheel, further extending the service life of the rolling assembly. Further, a composite sealing ring is provided in the sealing assemblies arranged at both ends of the roller shaft, in order to strengthen the sealing between the roller shaft and the rolling wheel and extend the service life thereof.
The sealing assembly of the present invention includes a first seal and a second seal. The contact surfaces between the first seal and the second seal are polished, so as to form polished surfaces. Thus, when the first seal is in contact with the second seal, the polished surfaces thereof can form an end-face seal, thereby sealing the fine gap between the roller shaft and the rolling wheel to enhance the sealing effect. The sealing assembly also includes a first support member, with which the polished surfaces of the first seal and the second seal can be connected to each other more closely.
Two axial ends of the rolling wheel in the present invention are supported by the PDC assembly and the roller shaft respectively, so that the force on the rolling wheel in the drilling is dispersed to the PDC assembly and the roller shaft, thus reducing the force exerting on the roller shaft and extending the service life thereof. Further, after the force on the roller shaft is reduced, the sealing assembly therein can be prevented from being damaged due to excessive inclination of the roller shaft. In the meantime, the service life of the rolling wheel per se can also be extended.

Brief Description of the Drawings

The present invention will be described below with reference to the accompanying drawings.

Fig. 1 schematically shows a structure of a PDC-roller hybrid drill bit according to Example 1 of the present invention.
Fig. 2 is an enlargement view schematically showing Zone A in Fig. 1.
Fig. 3 is an enlargement view schematically showing Zone B in Fig. 2.
Fig. 4 schematically shows a structure of a working end surface of the PDC-roller hybrid drill bit in Fig. 1.
Figs. 5 and 6 schematically show the structure of the PDC-roller hybrid drill bit according to Example 2 of the present invention.
Figs. 7 and 8 schematically show the structure of the PDC-roller hybrid drill bit according to Example 3 of the present invention.

In the present application, all accompanying drawings are schematic ones, provided to illustrate the principle of the present invention merely, and are not necessarily drawn to actual scale.

Detailed Description of Embodiments

The present invention will be described below in detail with reference to the accompanying drawings.
It should be noted that in the present application, directional terms or expressions such as "upper", "lower", etc. are defined with reference to Fig. 1. The above terms are not intended to limit absolute positions of the components involved, but may be varied according to specific circumstances.

Example 1

Fig. 1 schematically shows a structure of a PDC-roller hybrid drill bit 100 according to the present invention. As shown in Fig. 1, the PDC-roller hybrid drill bit 100 comprises a bit body 1, a roller assembly 3 and a PDC assembly 4. The bit body 1 has an approximately cylindrical shape. A connection joint 2 is provided at an upper end of the bit body 1, for connecting to a drill string (not shown) that drives the bit body 1 to rotate. The bit body 1 can be connected to the drill string through the connection joint 2, so that it can be lowered into the well together with the drill string and rotate circumferentially along with the drill string.
The bit body 1 is divided into two areas, namely a roller area 11 and a PDC area 12, by an imaginary plane passing through an axis thereof. The roller assembly 3 is installed at a lower portion of the roller area 11 of the bit body 1, facing a working end surface of the bit. The PDC assembly 4 is arranged at a lower portion of the PDC area 12 of the bit body 1, facing the working end surface of the bit.
According to the present invention, the roller assembly 3 includes a roller arm 31 fixedly connected to the bit body 1, a roller shaft 32 fixedly connected to the roller arm 31, a rolling wheel 33 installed on the roller shaft 32, and roller teeth 34 embedded in the rolling wheel 33. In this embodiment, the roller shaft 32 is provided at a lower end of the roller arm 31, and extends approximately along a radial direction of the bit body 1. In the meantime, the rolling wheel 33 provided on the roller shaft 32 is approximately in a shape of a sphere. A hole for receiving the roller shaft 32 is provided inside the rolling wheel 33, so that the rolling wheel 33 can be arranged around the roller shaft 32.
In one preferred embodiment, the roller shaft 32 is connected to both the roller arm 31 and the PDC assembly 4. As shown in Fig. 1, a central axis of the roller shaft 32 is inclined relative to a central axis of the bit body 1. One axial end of the roller shaft 32 is fixedly connected to the roller arm 31, and the other axial end thereof is connected to the PDC assembly 4. With such arrangement, the two axial ends of the roller shaft 32 can be respectively supported by the roller arm 31 and the PDC assembly 4, thus enhancing the bearing capacity of the roller shaft 32.
A plurality of roller teeth 34 is arranged, especially evenly, along a circumferential surface of the rolling wheel 33. As the bit body 1 rotates, the rolling wheel 33 can break the formation rock through the roller teeth 34, in order to reduce the hardness of the formation rock.
According to the present invention, a sealing assembly 6 is arranged between the rolling wheel 33 and the roller shaft 32. As shown in Fig. 2, the sealing assembly 6 includes a first seal 63 and a second seal 61 which are arranged on the roller shaft 32 and connected to each other.
In one embodiment of the sealing assembly 6, connection surfaces between the first seal 63 and the second seal 61 are both polished surfaces. Specifically, the first seal 63 and the second seal 61 are made of rigid hard material. According to the present invention, the hard material may be, for example, martensitic stainless steel, tungsten carbide, ceramics, cemented carbide, diamond, cubic boron nitride or silicon nitride. The above hard materials with high hardness are all able to effectively withstand the friction of formation sand, thereby reducing the abrasion to the first seal 63 and the second seal 61. The connection surfaces between the first seal 63 and the second seal 61 are polished, in order to form polished surfaces. Thus, when the first seal 63 and the second seal 61 are connected to each other, the polished surfaces thereof can form an end-face seal, thereby sealing fine gaps between the roller shaft 32 and the rolling wheel 33 and enhancing the sealing effect.
In this embodiment, as shown in Figs. 2 and 3, a sealing groove 65 for installing the sealing assembly 6 is arranged on an inner wall of the rolling wheel 33 and/or the bit body 1. The first seal 63 and the second seal 61 are installed in the sealing groove 65, in order to be prevented from moving axially. Preferably, the sealing groove 65 is arranged at an axial end of the rolling wheel 33. With such arrangement, the first seal 63 and the second seal 61 can be disposed into the sealing groove 65 along the axial direction, in order to facilitate installation.
Further, the sealing assembly 6 also includes a first support member 62 at the axial end thereof, which is made of elastic material and thus has certain elasticity. In one preferred embodiment, the elastic material may be, for example, hydrogenated nitrile rubber, nitrile rubber or fluororubber. Such materials have not only good elasticity but also good wear resistance, which can further extend the service life of the first support member 62.
In one specific embodiment provided according to the present invention, two first support members 62 are arranged at two axial ends of the sealing assembly 6, respectively. That is, the two support members 62 axially abut against the first seal 63 and the second seal 61 respectively to exert axial pressure thereon. Thus the first seal 63 and the second seal 61 are in contact with each other, with the polished surfaces thereof connected to each other more closely. In another embodiment, as shown in Fig. 3, one first support member 62 is provided at one end of the second seal 61 away from the first seal 63. With such arrangement, the polished surface at a right end of the first seal 63 axially abuts against the polished surface at a left end of the second seal 61, and a right end of the second seal 61 axially abuts against the first support member 62. The first seal 63, the second seal 61 and the first support member 62, which jointly form the sealing assembly 6, are installed in the sealing groove 65 and axially abut against each other. Thus the first seal 63 and the second seal 61 are in contact with each other, so that the polished surfaces thereof can be connected to each other more closely.
In one preferred embodiment, the hardness of the first seal 63 and the second seal 61 is greater than that of the first support member 62, and the friction resistance of the first seal 63 and the second seal 61 is lower than that of the first support member 62.
In the drilling of the PDC-roller hybrid drill bit 100, there will be relative vibration between the rolling wheel 33 and the roller shaft 32 due to the vibration of the bit body 1 under formation resistance. In this case, the sealing assembly 6 will undergo elastic deformation, thereby reducing the amplitude of the relative vibration between the rolling wheel 33 and the roller shaft 32. In this procedure, the first support member 62 can restrict the sealing assembly 6, preventing the sealing assembly 6 from moving axially relative to the roller shaft 32, thereby reducing the abrasion to the sealing assembly 6 and extending the service life thereof.
As shown in Fig. 3, in one specific embodiment according to the present invention, two radial sides of each of the first seal 63 and the second seal 61 abut against the roller shaft 32 and the rolling wheel 33, respectively. The second seal 61 is closer to the end of the roller shaft 32 than the first seal 63. According to another embodiment of the sealing assembly 6, the first seal 63 has higher hardness, lower friction resistance, and is more wear-resistant than the second seal 61. Preferably, the first seal 63 is made of materials with high hardness, wear resistance and low friction resistance, such as tetrafluoro-bronze, tetrafluoro-carbon fiber, tetrafluoro-glass fiber, tetrafluoro-copper, tetrafluoro-brass or the like, and the second seal 61 is made of materials with lower hardness and good elasticity, such as nitrile rubber, saturated nitrile rubber, fluororubber or the like. Both the first seal 63 and the second seal 61 can support and seal between the roller shaft 32 and the rolling wheel 33. The first seal 63 which mainly plays a supporting role and the second seal 61 which mainly plays a sealing role are complementary to each other in function. In this embodiment, the first seal 63 and the second seal 61 may form an integrated structure, or may be arranged separately. That is, the first seal 63 and the second seal 61 may be combined into one piece. For example, the first seal 63 and the second seal 61 can be manufactured as one component during manufacturing. Such integrated structure will be more convenient to install. Alternatively, the first seal 63 and the second seal 61 may also be manufactured as two components and then assembled together. Due to the split-type structure, the components will be more convenient to be processed and manufactured. Further, the contact surfaces of the first seal 63 and the second seal 61 in this embodiment may also be polished surfaces.
In operation, since the pressure on the rolling wheel 33 is not perpendicular to the central axis of the roller shaft 32, the central axis of the rolling wheel 33 is inclined at a certain angle to the central axis of the roller shaft 32. Therefore, one end of the sealing assembly 6 at the end of the roller shaft 32 will be subjected to a relatively large compressive force in the radial direction, while the other end will be slightly compressed or even not compressed. In this embodiment, the first seal 63 and the second seal 61 with different properties form a composite sealing ring. In operation, the first seal 63 with higher hardness plays a supporting role to prevent large deviation between the central axis of the rolling wheel 33 and that of the roller shaft 32, and the second seal 61 has good elasticity, in order to ensure the sealing effect.
In one preferred embodiment, a plurality of sealing assemblies 6 is evenly arranged along the axial direction of the roller shaft 32, which works together to further improve the vibration-damping and sealing performance.
In one preferred embodiment, the sealing assembly 6 further includes a second support member 64 made of elastic material. The second support member 64 is sleeved on the first seal 63 and/or the second seal 61 of the composite sealing ring, and between the radial contact surface of the first seal 63 and/or the second seal 61 and the rolling wheel 33. With such arrangement, the sealing performance for oil is further enhanced.
In one specific embodiment, as shown in Fig. 3, the second support member 64 is sleeved on an outer radial side of the first seal 63, for enhancing the radial sealing between the first seal 63 and the rolling wheel 33. A thickness of the second support member 64 is less than an axial thickness of the first seal 63. Therefore, the radial pressure between the roller shaft 32 and the rolling wheel 33 is mainly exerted on the first seal 63. The first support member 62 is arranged on a side of the second seal 61 away from the first seal 63, and a thickness of the first support member 62 is less than a radial dimension of the second seal 61, in order to enhance the sealing effect.
According to the present invention, a shaft seat 35 is arranged at a lower end portion of the roller area 11 of the bit body 1, as shown in Fig. 4. According to Figs. 1-4, one end of the roller shaft 32 is fixedly connected to the roller arm 31, and one end of the roller shaft 32 away from the roller arm 31 is arranged in the shaft seat 35. Such arrangement can enhance the stability of the roller shaft 32.
In a preferred embodiment, as shown in Fig. 3, the roller shaft 32 is connected to the bit body 1 through an elastic support ring 30. Specifically, the elastic support ring 30 is arranged in the shaft seat 35, and the roller shaft 32 is arranged inside the elastic support ring 30.
Further, the elastic support ring 30 may be a ring with an inner-wall groove, an outer-wall groove, a hole in the middle of a ring wall, or with other structural voids, and combinations thereof, or a wire-wrapped ring.
In this embodiment, the elastic support ring 30 ensures to provide a continuous and effective inner supporting force to the roller shaft 32, which significantly improves the stress and deformation state of the roller shaft 32, thus extending the service life of the rolling wheel 33, the sealing assembly 6, etc., and further extending the service life of the PDC-roller hybrid drill bit 100.
According to the present invention, in one preferred embodiment, an oil cavity 311 and an oil passage 312 are arranged in the roller arm 31. The oil cavity 311 is filled with lubricating oil and in communication with the oil passage 312. Moreover, the oil in the oil cavity 311 can flow along the oil passage 312 to the contact surfaces between the roller shaft 32 and the rolling wheel 33. With such arrangement, the friction between the rolling wheel 33 and the roller shaft 32 can be reduced, thus extending the service life of the roller assembly 3. In the meantime, the gap between the rolling wheel 33 and the roller shaft 32 is filled with oil, for preventing gravels from entering during operation that may damage the rolling wheel 33 or the roller shaft 32.
In one specific embodiment, as shown in Fig. 2, the oil cavity 311 is in a shape of a cylinder. A sliding piston 313 movable along an axis direction of the oil cavity 311 is hermetically arranged inside the oil cavity 311, thus dividing the oil cavity 311 into a balance chamber 314 and an oil chamber 315, wherein the oil chamber 315 is filled with oil and in communication with the oil passage 312, and the balance chamber 314 is in communication with outside atmosphere. With such arrangement, when the oil in the oil chamber 315 is consumed in operation, the sliding piston 313 will move towards the oil chamber 315 under atmospheric pressure, thus ensuring that the oil in the oil chamber 315 can smoothly flow between the roller shaft 32 and the rolling wheel 33.
In one specific embodiment, a first plug 316 is provided at one end of the oil chamber 315 away from the sliding piston 313. An oil-filling hole 317 is formed on the first plug 316, with an oil-filling plug 318 arranged therein. With such arrangement, when the oil in the oil chamber 315 is insufficient, the oil-filling plug 318 can be taken out of the oil-filling hole 317, so that oil can be injected into the oil chamber 315 through the oil-filling hole 317.
In one preferred embodiment, the oil passage 312 includes a first oil passage 301 in the roller arm 31, and a second oil passage 302 and a third oil passage 303 both in the roller shaft 32. One end of the first oil passage 301 is in communication with the oil chamber 315, and the other end thereof is in communication with the second oil passage 302. The second oil passage 302 is arranged along the axial direction of the roller shaft 32, wherein one end of the second oil passage 302 extends out of the roller shaft 32 to form an opening end, and the other end thereof is sealed by the roller shaft 32. A second plug 323 is arranged at the opening end of the second oil passage 302. The third oil passage 303 is arranged along the radial direction of the roller shaft 32, for guiding the oil to the contact surfaces between the roller shaft 32 and the rolling wheel 33. Such arrangement can facilitate the processing of the oil passage 312 that can be completed only through simple hole-drilling process.
The PDC assembly 4 includes a blade 41 and cutting teeth 42 embedded in the blade 41. A plurality of cutting teeth 42 is arranged evenly on the blade 41. Roller teeth 34 are arranged to extend further than the cutting teeth 42, so that the rolling wheel 33 is able to crush the rock through rotation before the PDC assembly 4 cuts the formation rock. That is, a lower end edge of the cutting teeth 42 is located between a lower end edge of the roller teeth 34 and a lower end edge of the rolling wheel 33. It should be noted that the working end surface herein refers to a surface of the bit to crush and cut the rock, and the lower end edge herein refers to a lowermost end along the axial direction of the PDC-roller hybrid drill bit 100.
In operation, the PDC-roller hybrid drill bit 100 rotates along its axis, with the working end surface thereof facing the formation to be drilled. The roller assembly 3 can first pre-process and break the formation rock, and form defects such as cracks in the unbroken formation to reduce the strength of the formation rock. Then, the PDC assembly 4 cuts the pre-broken, crack-filled and weakened formation rock. That is, when the PDC-roller hybrid drill bit 100 rotates along its axis, the rolling wheel 33 is subjected to the friction of the formation to rotate around the roller shaft 32. When the rolling wheel 33 rotates, the roller teeth 34 is intermittently in contact with the formation, so that the PDC-roller hybrid drill bit 100 generates periodic vibrations along its axial direction. Since the lower end edge of the roller teeth 34 is lower than that of the cutting teeth 42, the cutting teeth 42 is not in contact with the formation when the roller teeth 34 is in contact with the formation. In this case, the roller teeth 34 pre-break the formation. When the rolling wheel 33 rotates to a position where the roller teeth 34 are not in contact with the formation, the cutting teeth 42 are in contact with the formation. Thus the cutting teeth 42 cut the formation, thus periodically performing the drilling operation.
Therefore, the roller assembly 3 locally and partially breaks the rock at the bottom of the well, thus reducing the workload and stress thereof significantly. The oil cavity 311 and the oil passage 312 further reduce the friction between the roller shaft 32 and the rolling wheel 33, extending their service life. Moreover, the cutting teeth 42 of the PDC assembly 4 cut the weakened formation rock, which significantly improves the drillability of the formation rock as well as the stress on the cutting teeth 42, thereby significantly extending the service life of both the roller assembly 3 and the PDC assembly 4. In the meantime, the rolling of the rolling wheel 33 can generate periodic axial vibrations that can be transmitted to the drill string, effectively improving the stability of the tool face and the efficiency of weight-on-bit transfer for directional wells. In this manner, the drilling footage, rate of penetration, and directional characteristics in heterogeneous formations can be significantly improved, which are conducive to cost reduction and acceleration of exploration and development of oil/gas field and mines.
In one preferred embodiment, a height of the roller teeth 34 is 0.01-5 mm larger than that of the cutting teeth 42. In other words, the lower end edge of the roller teeth 34 is 0.01-5 mm lower than that of the cutting teeth 42. Such arrangement can improve the working efficiency.
In one embodiment, the connection joint 2 at the upper end of the bit body 1 may be a tapered connection buckle, which may be fixedly connected to the drill string through threads. In the meantime, a releasing groove 21 is circumferentially provided on an outer wall of the tapered connection buckle for quick disassembly between the PDC-roller hybrid drill bit 100 and the upper drill string. With such structure, the bit body 1 is not only convenient for installation and connection, but also easy to disassemble, thus significantly improving the disassembly and assembly efficiency thereof.
As shown in Fig. 1, at least one PDC assembly 4 and at least one roller assembly 3 are arranged at the lower end of the bit body 1. In the meantime, at least one PDC assembly 4 and at least one roller assembly 3 are arranged alternately along the circumferential direction of the bit body 1. Therefore, when the bit body 1 rotates synchronously with the drill string, the PDC assembly 4 and the roller assembly 3 can cut the formation in the same position in turn periodically.
In one preferred embodiment, the PDC assembly 4 and the roller assembly 3 are arranged radially opposite each other.
In one preferred embodiment, a strengthening layer 38 is coated on each of outer walls of the roller shaft 32, the rolling wheel 33 and the roller arm 31. The strengthening layer 38 is preferably made of tungsten carbide material, which has good oxidation and corrosion resistance, thus protecting the roller shaft 32, the rolling wheel 33 and the roller arm 31 from oxidation and corrosion. Moreover, such material can also improve the wear resistance of the roller shaft 32 and the rolling wheel 33, thus further extending the service life thereof.
In one specific embodiment, sealing surfaces of the shaft seat 35, the roller arm 31 and the rolling wheel 33, as well as the roller shaft 32, are subjected to nitriding, carburizing, carbonitriding and boronizing treatment, or coated with tungsten carbide. Alternately, they can be directly made of materials subjected to nitriding, carburizing, carbonitriding, boronizing, such as carburized steel, or made of ceramic materials. Such arrangement can reduce friction and enhance the sealing between the end surfaces of the shaft seat 35 and the rolling wheel 33, as well as the sealing between the rolling wheel 33 and the roller arm 31.
According to the present invention, as shown in Fig. 1, the roller arm 31 is fixedly connected to an outer wall of the bit body 1. For example, the roller arm 31 can be fixed to the outer wall of the bit body 1 through welding.
In one preferred embodiment, the roller shaft 32 and the roller arm 31 are integrally arranged. An angle between the roller shaft 32 and the roller arm 31 is an obtuse angle, with the roller shaft 32 extending inwards and downwards. Thus the rolling wheel 33 is oriented to face the working end surface.
In one embodiment, the rolling wheel 33 is configured to have an arcuate contour with a higher middle part and two lower sides. The roller teeth 34 are embedded in the middle part of the rolling wheel 33 in the circumferential direction. There is a plurality of roller teeth 34 evenly distributed in the circumferential direction. Such structure of the roller assembly 3 facilitates the crushing of the formation rock. The rolling wheel 33 is installed on the roller shaft 32, forming a rotational connection therewith.
According to one embodiment of the present invention, the contact surfaces between the rolling wheel 33 and the roller shaft 32 form a sliding bearing, so as to achieve a rotational connection therebetween. Preferably, an intermediate sliding sleeve can be provided between sliding bearing surfaces. Such structure can significantly extend the service life of the rolling wheel 33 and the PDC-roller hybrid drill bit 100.
According to the present invention, the roller teeth 34 are first special-shaped teeth, which may be as conical teeth, wedge-shaped teeth, spherical teeth, spoon-shaped teeth, oval-shaped teeth, or the like. The roller teeth 34 can be made of cemented carbide, ceramic, or PDC materials, so that the roller assembly 3 can better adapt to formation rock.
According to the present invention, as shown in Fig. 1, a first gauge-protecting tooth 332 is embedded in and thus installed on an outer wall surface of the roller arm 31. In one preferred embodiment, a roller gauge-repairing tooth 331 is also arranged on an outermost radial contour line of the rolling wheel 33. Thus through the first gauge-protecting tooth 332 and the roller gauge-repairing tooth 331, the bore drilled by the PDC-roller hybrid drill bit 100 can be effectively protected from diameter reduction, ensuring the drilling and directional performance of the PDC-roller hybrid drill bit 100.
According to the present invention, the PDC assembly 4 further includes a gauge-protecting block 43 on an outer radial side of the blade 41. A second gauge-protecting tooth 431 is embedded in the gauge-protecting block 43. The gauge-protecting block 43 is preferably integrally arranged with the blade 41 that covers the bit body 1. For example, a part of the blade 41 on the outer radial side thereof forms the gauge-protecting block 43.
As shown in Fig. 1, an active gauge-protecting tooth 44 can also be arranged on the gauge-protecting block 43 and between the second gauge-protecting tooth 431 and the cutting teeth 42. A maximum outer diameter of the active gauge-protecting tooth 44 is greater than or equal to that of the second gauge-protecting tooth 431. Thus, the first gauge-protecting tooth 332, the roller gauge-repairing tooth 331, the second gauge-protecting tooth 431 and the active gauge-protecting tooth 44 work together to effectively protect the bore drilled by the PDC-roller hybrid drill bit 100 from diameter reduction, further ensuring the drilling and directional performances of the PDC-roller hybrid drill bit 100.
According to the present invention, the PDC assembly 4 is made of PDC (Polycrystalline Diamond Compact) material. That is, the blade 41, the cutting teeth 42, the gauge-protecting block 43, the second gauge-protecting tooth 431, and the active gauge-protecting tooth 44 are all made of PDC (Polycrystalline Diamond Compact) material, in order to effectively ensure the strength of the PDC assembly 4 and the cutting performance of the PDC-roller hybrid drill bit 100.
Preferably, the cutting teeth 42 may be special-shaped teeth such as flat teeth, conical teeth, ridged teeth, triangular-prism teeth or the like, which can further improve the cutting performance of the PDC-roller hybrid drill bit 100.
According to one embodiment of the present invention, as shown in Fig. 4, a first auxiliary cutting tooth 10 may be arranged on the blade 41 and on a rear side of the cutting teeth 42. Preferably, a second auxiliary cutting tooth 7 may also be arranged on the blade 41 and on the rear side of the cutting teeth 42. In addition, the second auxiliary cutting tooth 7 and the first auxiliary cutting tooth 10 are spaced apart from each other in the radial direction. It should be understood that the terms "front" and "rear" herein refer to an order in which the cutting teeth 42 are in contact with the formation when rotating along with the bit body 1. Accordingly, "on the rear side of the cutting teeth 42" refers to a side that is in contact with the formation rock later than the cutting teeth 42.
Both the first auxiliary cutting tooth 10 and the second auxiliary cutting tooth 7 may be made of cemented carbide, ceramic, or PDC material.
According to the present invention, as shown in Fig. 1, a central flow channel 8 and a nozzle 9 both extending along the axial direction are arranged inside the bit body 1, wherein the central flow channel 8 is in communication with the drill string. The nozzle 9 of the central flow channel 8 extends to the blade 41, so that the fluid in the drill string can be sprayed to the blade 41. The nozzle 9 is angled relative to the central flow channel 8, so that the nozzle 9 is aligned with the working end surface. The drilling fluid from the drill string can pass through the central flow channel 8 and the nozzle 9 in sequence, in order to be spayed to the surface of the formation rock opposite to the PDC-roller hybrid drill bit 100. The drilling fluid sprayed by the nozzle 9 can not only impact on and soften the formation rock, but also clean the roller assembly 3 and the PDC assembly 4, effectively preventing drill cuttings from adhering to the rolling wheel 33 or the blade 41. Therefore, the rate of penetration of the PDC-roller hybrid drill bit 100 can be improved, ensuring the drilling performance thereof.
A plurality of nozzles 9 may be arranged inside the bit body 1, in order to ensure the flow-through effect and efficiency of the drilling fluid, as well as the cleaning and cooling of the roller assembly 3 and the PDC assembly 4.
The phrases "an embodiment", "some embodiments", "example", "specific example" or "some examples" as mentioned in the description mean that the particular features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. Thus, the above illustrative phrases described throughout the description do not necessarily refer to the same embodiment or example. Moreover, the particular features, structures, materials, or characteristics described herein may be combined in any one or more of the embodiments or examples in a suitable manner.

Example 2

In this example, the structures of the rolling wheel 33, the roller shaft 32 and the PDC assembly 4, as well as the connection modes therebetween are different from those in Example 1, which are illustrated as follows.
In this example, as shown in Fig. 5, a first blind hole 333 and a second blind hole 334 are arranged at both axial ends of the rolling wheel 33 respectively. A central axis of the first blind hole 333 coincides with that of the second blind hole 334. However, the first blind hole 333 and the second blind hole 334 are not in communication with each other.
The roller shaft 32 is arranged within the first blind hole 333 in a coaxially rotatable manner, so that the rolling wheel 33 is rotatably connected to the roller shaft 32.
A first support shaft 45 is fixedly arranged on the PDC assembly 4. A central axis of the first support shaft 45 coincides with that of the roller shaft 32, with a gap being formed between the first support shaft 45 and the roller shaft 32. The first support shaft 45 is arranged inside the second blind hole 334 of the rolling wheel 33 in a coaxially rotatable manner, so that the rolling wheel 33 is rotatably connected to the PDC assembly 4.
According to the embodiment as shown in Fig. 5, an axial right portion of the rolling wheel 33 is rotatably connected to the PDC assembly 4, and an axial left portion thereof is rotatably connected to the roller shaft 32. That is, the axial left and right portions of the rolling wheel 33 are supported by the roller shaft 32 and the PDC assembly 4 respectively, so that the formation pressure exerting on the rolling wheel 33 in operation can be dispersed to the PDC assembly 4 and the roller shaft 32, thus reducing the force exerting on the roller shaft 32 and extending the service life thereof. When the force on the roller shaft 32 is reduced, the sealing assembly 6 therein can be prevented from being damaged due to excessive inclination of the roller shaft 32, which can extend the service life of the rolling wheel 33 per se.
In the structure of Example 1 of the present invention, sealing assemblies 6 need to be provided at both ends of the roller shaft 32, which functions, among others, to prevent the lubricating oil between the roller shaft 32 and the rolling wheel 33 from leaking. Therefore, the failure of any one of the sealing assemblies 6 will lead to the leakage of lubricating oil, affecting the reliability of the drill bit.
In contrast, according to Example 2 of the present invention, the rolling wheel 33 is rotatably connected to the roller shaft 32 through the first blind hole 333 arranged therein. Therefore, the sealing between the roller shaft 32 and the rolling wheel 33 can be realized only through a sealing assembly 6 arranged at a position of the roller shaft 32 close to an outlet of the first blind hole 333 (as shown in Fig. 5).
Therefore, according to Example 2 of the present invention, the number of the sealing assemblies 6 on the roller shaft 32 can be reduced, so that the roller shaft 32 will less likely be damaged, thus improving the reliability of the drill bit.
As shown in Fig. 5, in one preferred embodiment, super-hard coatings 46 are provided on the surfaces of the second blind hole 334 and the first support shaft 45, making the contact surfaces therebetween more wear-resistant. In the meantime, the formation cuttings can be prevented from entering between the second blind hole 334 and the first support shaft 45. It is readily understood that specific compositions of the super-hard coatings 46, such as diamond, are known to one skilled in the art and will not be elaborated here.
As shown in Fig. 6, in one preferred embodiment, a sealing assembly 6 is arranged between the second blind hole 334 of the rolling wheel 33 and the first support shaft 45 of the PDC assembly 4. With respect to the detailed structure of the sealing assembly 6, reference can be made to Example 1 of the present invention, which will not be elaborated here. With the sealing assembly 6, lubricating oil can be stored between the second blind hole 334 and the first support shaft 45, extending the service life of the second blind hole 334 and the first support shaft 45. In addition, the sealing assembly 6 can also prevent formation cuttings from entering between the second blind hole 334 and the first support shaft 45.

Example 3

In this example, the structures of the rolling wheel 33, the roller shaft 32 and the PDC assembly 4, as well as the connection modes therebetween are different from those in Example 1, which are illustrated as follows.
In this example, as shown in Fig. 7, a first blind hole 333 and a second support shaft 335 are provided at two axial ends of the rolling wheel 33 respectively. A central axis of the first blind hole 333 coincides with that of the second support shaft 335. The roller shaft 32 is arranged inside the first blind hole 333 in a coaxially rotatable manner, so that the rolling wheel 33 is rotatably connected to the roller shaft 32.
A third blind hole 47 is provided on the PDC assembly 4. A central axis of the third blind hole 47 coincides with that of the roller shaft 32. The second support shaft 335 is arranged inside the third blind hole 47 in a coaxially rotatable manner, so that the rolling wheel 33 is rotatably connected to the PDC assembly 4.
According to the embodiment as shown in Fig. 7, an axial right portion of the rolling wheel 33 is rotatably connected to the PDC assembly 4, and an axial left portion thereof is rotatably connected to the roller shaft 32. That is, the axial left and right portions of the rolling wheel 33 are supported by the roller shaft 32 and the PDC assembly 4 respectively, so that the formation pressure exerting on the rolling wheel 33 in operation can be dispersed to the PDC assembly 4 and the roller shaft 32, thus reducing the force exerting on the roller shaft 32 and extending the service life thereof. When the force on the roller shaft 32 is reduced, the sealing assembly 6 therein can be prevented from being damaged due to excessive inclination of the roller shaft 32, thus extending the service life of the rolling wheel 33 per se.
In the structure of Example 1 of the present invention, sealing assemblies 6 need to be arranged at both ends of the roller shaft 32, which functions, among others, to prevent the lubricating oil between the roller shaft 32 and the rolling wheel 33 from leaking. Therefore, the failure of any one of the sealing assemblies 6 will lead to the leakage of lubricating oil, affecting the reliability of the drill bit.
In contrast, according to Example 3 of the present invention, the rolling wheel 33 is rotatably connected to the roller shaft 32 through the first blind hole 333 arranged therein. Therefore, the sealing between the roller shaft 32 and the rolling wheel 33 can be realized only through a sealing assembly 6 arranged at a position of the roller shaft 32 close to an outlet of the first blind hole 333 (as shown in Fig. 7).
Therefore, according to Example 3 of the present invention, the number of the sealing assemblies 6 on the roller shaft 32 can be reduced, so that the roller shaft 32 will less likely be damaged, thus improving the reliability of the drill bit.
As shown in Fig. 7, in one preferred embodiment, super-hard coatings 46 are provided on the surfaces of the third blind hole 47 and the second support shaft 335, making the contact surfaces therebetween more wear-resistant. In the meantime, the formation cuttings can be prevented from entering between the third blind hole 47 and the second support shaft 335. It is readily understood that specific compositions of the super-hard coatings 46, such as diamond, are known to one skilled in the art and will not be elaborated here.
As shown in Fig. 8, in one preferred embodiment, a sealing assembly 6 is arranged between the second support shaft 335 of the rolling wheel 33 and the third blind hole 47 of the PDC assembly 4. With respect to the detailed structure of the sealing assembly 6, reference can be made to Example 1 of the present invention, which will not be elaborated here. With the sealing assembly 6, lubricating oil can be stored between the third blind hole 47 and the second support shaft 335, extending the service life of the third blind hole 47 and the second support shaft 335. In addition, the sealing assembly 6 can also prevent formation cuttings from entering between the third blind hole 47 and the second support shaft 335.
It should be understood that in the present invention, the terms "first" and "second" are used for illustrative purposes only, and are not intended to indicate or imply relative importance or implicitly specify the number of technical features indicated. Thus, the technical features defined with the terms "first" or "second" may explicitly or implicitly include one or more such technical features. In the description of the present invention, "a plurality of" means two or more, unless otherwise specified.
In the present invention, unless otherwise specified or defined, the phrases "mount", "connect", "attach", "fix" and the like, should be understood in a broad sense, and may be understood as, for example, fixed connections, detachable connections, or integral connections; mechanical or electrical connections; direct connections or indirect connections via intermediate structure; or interior communication between two elements. The specific meanings of the above phrases in the present invention can be understood by one skilled in the art in accordance with specific conditions.
Finally, it should be noted that the foregoing description is merely illustrative of preferred embodiments of the present invention, and is not intended to restrict the present invention. Although the present invention is described in detail with reference to the above embodiments, it is still possible for one skilled in the art to modify the technical solutions defined in the above embodiments or to replace some of the technical features with equivalent ones. Any modifications, equivalent substitutions, improvements, and the like falling within the spirit and principles of the present invention are intended to be included within the scope of protection of the present invention.

List of Reference Signs

1. bit body; 11. roller area; 12. PDC area;
2. connection joint; 21. releasing groove;
3. roller assembly; 301. first oil passage; 302. second oil passage; 303. third oil passage; 31. roller arm; 311. oil cavity; 312. oil passage; 313. sliding piston; 314. balance chamber; 315. oil chamber; 316. first plug; 317. oil-filling hole; 318. oil-filling plug; 32. roller shaft; 323. second plug; 33. rolling wheel; 331. roller gauge-repairing tooth; 332. first gauge-protecting tooth; 333. first blind hole; 334. second blind hole; 335. second support shaft; 34. roller tooth; 35. shaft seat; 30. elastic support ring; 38. strengthening layer;
4. PDC assembly; 41. blade; 42. cutting tooth; 43. gauge-protecting block; 431. second gauge-protecting tooth; 44. active gauge-protecting tooth; 45. first support shaft; 46. super-hard coating; 47. third blind hole;
6. sealing assembly; 61. second seal; 62. first support member; 63. first seal; 64. second support member; 65. sealing groove;
7. second auxiliary cutting tooth;
8. central flow channel;
9. nozzle;
10. first auxiliary cutting tooth;
100. PDC-roller hybrid drill bit.

Claims

A PDC-roller hybrid drill bit, comprising:
a bit body (1) for connecting to a drill string,

a PDC assembly (4) arranged on the bit body, and

a roller assembly (3) arranged on the bit body, comprising a roller arm (31) fixedly connected to the bit body, and a roller shaft (32) and a rolling wheel (33) both connected to the roller arm, the rolling wheel (33) being rotatably connected to both the roller shaft (32) and the PDC assembly (4),

wherein a first blind hole (333) is provided in the rolling wheel (33) for receiving the roller shaft (32).
The PDC-roller hybrid drill bit according to claim 1, characterized in that a first support shaft (45) is fixedly arranged on the PDC assembly (4), and a second blind hole (334) is arranged in the rolling wheel (33) for receiving the first support shaft (45), wherein an axis of the first blind hole (333) coincides with that of the second blind hole (334).
The PDC-roller hybrid drill bit according to claim 1, characterized in that a second support shaft (335) is fixedly arranged on the rolling wheel (33), and a third blind hole (47) is provided in the PDC assembly (4) for receiving the second support shaft (335), wherein the axis of the first blind hole (333) coincides with that of the third blind hole (47).
The PDC-roller hybrid drill bit according to claim 2 or 3, characterized in that a sealing assembly (6) is provided between the rolling wheel (33) and at least one of the roller shaft (32), the first support shaft (45) and the second support shaft (335), the sealing assembly (6) comprising a first seal (63) and a second seal (61) arranged on the roller shaft (32) and connected to each other, wherein connection surfaces between the first seal and the second seal are polished surfaces.
The PDC-roller hybrid drill bit according to claim 4, characterized in that at least one axial end of the sealing assembly is provided with a first support member (62) with elasticity, which is configured to exert axial pressure on the first seal (63) and the second seal (61), so that the first seal (63) is connected to the second seal (61).
The PDC-roller hybrid drill bit according to claim 5, characterized in that a hardness of the first seal (63) and the second seal (61) is greater than that of the first support member (62), and a friction resistance of the first seal (63) and the second seal (61) is lower than that of the first support member (62).
The PDC-roller hybrid drill bit according to any one of claims 4 to 6, characterized in that the sealing assembly further includes a second support member (64) with elasticity, which is radially arranged around the first seal (63) and/or the second seal (61).
The PDC-roller hybrid drill bit according to any one of claims 1 to 7, characterized in that an oil cavity (311) and an oil passage (312) are arranged in the roller arm (31), wherein the oil passage (312) is configured such that oil in the oil cavity (311) flows to contact surfaces between the roller shaft (32) and the rolling wheel (33).
The PDC-roller hybrid drill bit according to claim 8, characterized in that a sliding piston (313) is arranged within the oil cavity (311) to divide the oil cavity (311) into a balance chamber (314) and an oil chamber (315), wherein the oil chamber (315) is in communication with the oil passage (312), and the balance chamber (314) is in communication with outside atmosphere.
The PDC-roller hybrid drill bit according to claim 9, characterized in that a first plug (316) is provided at one end of the oil chamber (315) away from the sliding piston (313), wherein an oil-filling hole (317) is formed in the first plug (316), with an oil-filling plug (318) arranged therein.
The PDC-roller hybrid drill bit according to claim 10, characterized in that the oil passage (312) includes a first oil passage (301), a second oil passage (302) and a third oil passage (303) in communication with each other in sequence, wherein
the first oil passage (301) is arranged in the roller arm (31) and in communication with the oil cavity (311);

the second oil passage (302) is arranged along an axial direction of the roller shaft (32), one end of the second oil passage (302) extending out of the roller shaft (32) to form an opening with a second plug (323); and

the third oil passage (303) is arranged along a radial direction of the roller shaft (32) and extends to the contact surfaces between the roller shaft (32) and the rolling wheel (33).
The PDC-roller hybrid drill bit according to any one of claims 1 to 11, characterized in that the PDC assembly includes cutting teeth (42) fixedly connected to the bit body (1), and a plurality of roller teeth (34) is arranged on an outer wall of the rolling wheel, wherein the roller teeth are configured to extend further than the cutting teeth, so that formation rock is crushed by the rolling wheel through rotation before being cut by the PDC assembly.
The PDC-roller hybrid drill bit according to claim 12, characterized in that a height of the roller teeth is 0.01-5 mm larger than that of the cutting teeth.
The PDC-roller hybrid drill bit according to any one of claims 1 to 13, characterized in that the first seal and the second seal are made of martensitic stainless steel, tungsten carbide, ceramics, cemented carbide, diamond, cubic boron nitride or silicon nitride, and the first support member is made of hydrogenated nitrile rubber, nitrile rubber or fluororubber.
The PDC-roller hybrid drill bit according to any one of claims 1 to 14, characterized in that a strengthening layer is coated on each of outer walls of the roller shaft, the rolling wheel and the roller arm.
The PDC-roller hybrid drill bit according to claim 15, characterized in that the strengthening layer is made of tungsten carbide material.
The PDC-roller hybrid drill bit according to any one of claims 1 to 16, characterized in that both outer walls of the roller shaft and the rolling wheel are subjected to nitriding, so that nitriding layers are formed inside the roller shaft and the rolling wheel.
The PDC-roller hybrid drill bit according to any one of claims 1 to 17, characterized in that a central flow channel (8) in communication with the drill string is arranged inside the bit body, the central flow channel comprising a nozzle (9) extending to a blade (41), so that the fluid within the drill string is sprayed to the blade.