A high rate of penetration PDC drill bit and method of use

Abstract

The application provides a high-efficiency through-hole PDC drill bit, and belongs to the technical field of drilling tools for oil and natural gas exploration and development, and comprises a drill bit base body, which is sequentially divided into a guide core part, a reaming and hole enlarging shoulder part, a connecting body and a threaded connection section from top to bottom along the axial direction; the guide core part is a semi-spherical guide head without cutting teeth, and a spiral drag-reducing flow guide groove is uniformly distributed on the spherical surface of the semi-spherical guide head; a gauge protection section is arranged on the reaming and hole enlarging shoulder part, a drilling fluid main flow channel water hole is arranged in the arc transition area between the reaming and hole enlarging shoulder part and the guide core part, and the drilling fluid main flow channel water hole is in communication with the central flow channel of the drill bit. The application can solve the technical problems of the conventional PDC drill bit, such as easy new hole reaming for large parameters, severe torque fluctuation, poor wall repairing capacity of the roller bit, and low operation efficiency, and can realize accurate direction protection, efficient wall repairing and stable operation under large parameter operation, and improve the efficiency and safety of through-hole reaming.

Description

Technical Field

[0001] This invention relates to the field of drilling tools technology for oil and gas exploration and development, and in particular to a high-efficiency well-drilling PDC drill bit and its usage method. Background Technology

[0002] PDC drill bits, or polycrystalline diamond composite drill bits, are widely used in oil and gas drilling projects due to their high cutting efficiency and wear resistance. Well cleaning and reaming operations are key procedures in drilling operations, used to repair wellbore defects, remove wellbore cuttings, and ensure the smooth progress of subsequent operations such as casing running, cementing, and electrical logging. The efficiency and quality of these operations directly affect the drilling schedule, safety, and oil and gas development benefits.

[0003] Directional wells are the mainstream well type for the exploration and development of unconventional and complex structural oil and gas reservoirs. However, their wellbore trajectory is characterized by continuous oblique extension and curvature changes. The well wall is affected by factors such as drilling fluid scouring, formation stress release, and drill string eccentric friction, which can easily lead to defects such as steps, narrowing, irregular doglegs, and uneven mud cake adhesion. This places higher demands on the trajectory direction maintenance, continuous wall repair, and high-parameter operation capabilities of well cleaning and reaming tools.

[0004] Currently, wellbore cleaning and reaming operations in the industry mainly use roller cone bits and conventional PDC bits. Both have significant technical defects and cannot meet the wellbore cleaning requirements of complex trajectory wells. Roller cone bits use a rolling grinding cutting method and lack active continuous wellbore dressing capability, making it difficult to eliminate wellbore steps and diameter reductions. They also have low operating efficiency, poor cuttings removal effect, insufficient diameter maintenance performance, and their bearings and teeth are prone to wear, with a service life of only 1 / 3 that of conventional PDC bits. The structural design of conventional PDC bits revolves around formation drilling and rock breaking. They have no guiding structure in the core and teeth are distributed throughout the entire area, making it easy to create new wellbore during well cleaning. Their radial or helical tooth distribution method leads to large fluctuations in cutting load, with drilling torque deviations reaching ±30kN·m or more, which can easily cause faults such as drill string blockage and drill string jumping. At the same time, their hydraulic flow channel design has poor adaptability, and the drilling fluid cannot accurately cover the cutting area, resulting in low cuttings carrying efficiency. In addition, to avoid the risk of trajectory deviation, operating parameters need to be reduced, which prevents them from fully utilizing their cutting efficiency advantage.

[0005] In existing technologies, some improved PDC drill bits only make localized optimizations to rock-breaking efficiency and wear resistance during drilling operations, or make minor improvements to gauge protection and flow channel structure. They do not address the core requirements of wellbore cleaning and reaming by innovating the overall structure and cannot simultaneously meet the comprehensive requirements of preventing new wellbore formation, efficient wall repair, low-torque operation, efficient cuttings removal, and precise wellbore size control. Therefore, developing a high-efficiency PDC drill bit specifically designed for wellbore cleaning and reaming in complex trajectory wells has become an urgent need in the drilling tool industry. Summary of the Invention

[0006] In view of this, the present invention aims to propose a high-efficiency well-drilling PDC drill bit and its usage method, which can solve the technical problems of conventional PDC drill bits in producing new wellbores easily under high parameters, violent torque fluctuations, poor wall repair ability of roller cone drill bits, and low operating efficiency. It can achieve precise orientation maintenance, efficient wall repair and stable operation under high-parameter operation, and improve the efficiency and safety of well-drilling and reaming.

[0007] To achieve the above objectives, the technical solution of the present invention is as follows: A high-efficiency well-draining PDC drill bit includes a drill bit body, which is divided into a guide core, a reaming shoulder, a connecting body, and a threaded connection section along the axial direction from top to bottom; the guide core is a toothless hemispherical guide head, and the spherical surface of the hemispherical guide head is machined with circumferentially distributed spiral drag-reducing and guiding grooves; the reaming shoulder is provided with a diameter-maintaining section, and the arc transition area between the reaming shoulder and the guide core is provided with a drilling fluid main channel water eye, which is connected to the central flow channel of the drill bit.

[0008] Furthermore, the outer diameter of the hemispherical guide head is 1 / 3 of the nominal diameter of the drill bit.

[0009] Furthermore, the number of spiral drag-reducing guide grooves is five, the groove depth is 0.8mm~1.5mm, the groove width is 1.0mm~2.0mm, and the spiral helix angle is 15°~30°; each spiral drag-reducing guide groove extends along the spherical surface of the hemispherical guide head to the transition area of ​​the reaming and enlarging shoulder, and is used to directionally guide drilling fluid, reduce well friction and suppress lateral sway of the drill bit.

[0010] Furthermore, the reaming and enlarging shoulder adopts a five-blade symmetrical structure, with the upper and lower reaming working surfaces of the blades being long, rounded, continuous toothed surfaces; cutting teeth are inlaid along the tangential direction of the drill bit rotation, with a spacing of 1mm to 2mm between adjacent teeth, and the cutting teeth are diamond composite sheets with a diameter of 13mm to 19mm.

[0011] Furthermore, the gauge protection section is set on the blade of the reaming and enlarging shoulder, with a gauge protection section corresponding to the middle of each blade. The gauge protection section has a segmented unequal height structure, with the upper section having a greater gauge protection height than the lower section, and the overall maximum outer diameter of the gauge protection section being the same as the outer diameter of the drill bit. Multiple gauge protection bars are set parallel to the drill bit's rotation surface, and these bars are set on the gauge protection sections. The gauge protection bars and the gauge protection sections are fixedly connected by a stepped brazing structure. The gauge protection bars are made of tungsten carbide alloy.

[0012] Furthermore, the upper diameter protection height of the diameter protection section is 0.5mm higher than that of the lower diameter protection height; the nominal size of the drill bit is API standard 6″~17-1 / 2″, and the threaded connection section adopts API standard 331 thread type, 431 thread type, 631 thread type or 731 thread type.

[0013] Furthermore, a smooth transition arc surface is provided between the blade of the reaming and enlarging shoulder and the guide core, with the radius of the transition arc being 1 / 12 to 1 / 8 of the nominal diameter of the drill bit; the main water channel of the drilling fluid consists of five 1″ standard water channels, which are adapted to install 12 / 32″ to 28 / 32″ flow regulating nozzles.

[0014] Furthermore, a release groove is provided between the shoulder of the enlarged hole and the connecting body. The depth of the release groove is 0.5mm~1mm, the width of the groove is 1.0mm~2.0mm, and the cross-section of the groove is triangular.

[0015] This invention also provides a method for using a high-efficiency well-drainage PDC drill bit, comprising the following steps: Match the drill string assembly according to the well type, wellbore size, and drill string rigidity requirements. Check the integrity of the drill bit components and run the drill bit into the wellbore. Slow down the drilling speed 100m before reaching the target well section and observe the change in suspended weight. After reaching the target position, perform well cleaning and reaming operations according to the wellbore size and drilling parameters. After the operation is completed, pull out the drill bit. After the drill bit comes out of the well, check the condition of the drill bit. If the wear of the diamond composite sheet is ≤1mm and the difference between the maximum outer diameter of the gauge strip and the outer diameter of the drill bit is less than 1mm, the drill bit can be reused.

[0016] Compared with existing technologies, the high-efficiency well-drilling PDC drill bit and its usage method described in this invention have the following advantages: Through the collaborative innovative design of various structures, this invention forms a dedicated integrated design of "guiding-cutting-gauge maintenance-hydraulic" functions, effectively solving several technical defects of existing well-drilling tools, as detailed below: (1) This invention uses the rigid guidance of the toothless hemispherical guide head and the auxiliary constraint of the spiral drag reduction guide groove to force the drill bit to run along the original wellbore trajectory, completely eliminating the formation of new wellbore. Even with high drilling pressure and high speed, the trajectory can still be accurately maintained, solving the industry pain point of conventional PDC drill bit wellbore trajectory deviation. (2) The shoulder of the reaming and enlarging hole adopts a five-blade long arc continuous tooth structure, so that the cutting teeth and the well wall make continuous curved surface contact, the cutting load is evenly distributed, and the drilling torque fluctuation is controlled within ±10kN·m, effectively avoiding the phenomena of drill blockage, drill jumping and vibration. At the same time, continuous cutting can efficiently eliminate defects such as well wall steps and diameter reduction, solving the problem of poor wall repair ability of roller cone drill bits. (3) The synergistic effect of the tungsten carbide alloy gauge bar and the segmented unequal height gauge structure of the gauge section not only improves the wear resistance of the gauge section of the drill bit, but also accurately controls the wellbore size, so that the wellbore enlargement deviation is controlled within 5mm, effectively extending the service life of the drill bit, reducing the number of tripping in and out of the drill, and shortening the construction period. (4) The five blades correspond to the 1″ standard water eye and are equipped with adjustable flow nozzles. The drilling fluid injection direction accurately covers the cutting area. Combined with the drilling fluid guiding effect of the spiral drag reduction guide groove, it can achieve rapid flushing of mud cake on the well wall and efficient carrying of cuttings. The cuttings carrying efficiency is more than 20% higher than that of conventional PDC drill bits, which effectively reduces the risk of downhole failures such as drill string friction, stuck drill, and pump stall. (5) The drill bit is designed in accordance with API standards, with nominal sizes covering 6″~17-1 / 2″. The threaded connection section is compatible with various API standard thread types and can be directly connected to existing drill tools on site without the need for customized adapter parts. It has strong versatility and the well-through efficiency under high-parameter operation is more than 50% higher than that of traditional roller cone drill bits. The footage of a single well-through operation is increased by 2 times, which has significant industrial application value and economic benefits. Attached Figure Description

[0017] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 Side view of a high-efficiency wellbore PDC drill bit; Figure 2 Top view of a high-efficiency wellbore drilling PDC bit.

[0018] Explanation of reference numerals in the attached figures: 1. Guide core; 2. Reaming and enlarging shoulder; 3. Gauge protection section; 4. Release groove; 5. Connecting body; 6. Connecting thread; 7. Cutting blade; 8. Main channel water eye of drilling fluid; 9. Spiral drag reduction guide groove; 10. Diamond composite sheet; 11. Gauge protection strip. Detailed Implementation

[0019] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0020] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0021] This invention abandons the traditional design approach of existing PDC drill bits centered around "drilling and rock breaking," and overcomes the long-standing technical prejudice in the field that "PDC drill bits are only used for drilling, and well cleaning can only rely on roller cone drill bits." Addressing the core needs of well cleaning and reaming, such as trajectory alignment, wellbore trimming, low torque, and cuttings removal, this invention provides a high-efficiency well cleaning PDC drill bit, such as... Figure 1 and Figure 2As shown, the drill bit includes a drill bit body, which is divided into a guide core 1, a reaming shoulder 2, a connecting body 5, and a threaded connection section along the axial direction from top to bottom. The reaming shoulder 2 is provided with a gauge-maintaining section 3. All structures work together to form an overall design specifically adapted for well cleaning and reaming operations, especially suitable for well cleaning and reaming operations on the entire vertical well section and the deviated section, build-up section, and stabilization section of directional wells with complex trajectories. The specific technical solution is as follows: A high-efficiency well-drilling PDC drill bit is suitable for well-drilling and reaming operations in hard formations in vertical wells and directional wells (build-up section and stabilized section). The drill bit body is divided into a guide core 1, a reaming and enlarging shoulder 2, a connecting body 5 and a threaded connection section along the axial direction from top to bottom. The guide core 1 is a toothless hemispherical guide head. The outer diameter of the hemispherical guide head is strictly controlled to be 1 / 3 of the nominal diameter of the drill bit, which is different from the traditional structure of the core teeth of conventional PDC drill bits. The spherical surface of the hemispherical guide head is machined with circumferentially distributed spiral drag-reducing guide grooves 9. There are five spiral drag-reducing guide grooves 9. The groove depth of the spiral drag-reducing guide grooves 9 is 0.8mm~1.5mm, the groove width is 1.0mm~2.0mm, and the helix angle is 15°~30°. Each spiral drag-reducing guide groove 9 extends along the spherical surface of the hemispherical guide head to the transition area of ​​the reaming and enlarging shoulder 2, which is used to guide the drilling fluid in a directional manner, reduce well friction and suppress the lateral sway of the drill bit. The spiral drag-reducing guide groove 9 can fit tightly against the inner wall of the original wellbore, and play a rigid pilot guiding role when drilling and reaming, forcing the drill bit to run along the original wellbore trajectory. This fundamentally avoids the drill bit being affected by lateral extrusion force and eccentric tension of the drill string, thus preventing trajectory deviation and eliminating the formation of a new wellbore through lateral cutting. At the same time, the spiral drag-reducing guide groove 9 guides the drilling fluid, providing a basic guarantee for high-parameter reaming operations.

[0022] The reaming and enlarging shoulder 2 adopts a symmetrical structure of five blades 7. The upper and lower reaming working surfaces of the blades 7 are long arc-shaped continuous toothed curved surfaces, which are adapted to the well wall fitting requirements during well reaming and overcome the defects of intermittent contact and severe torque fluctuation caused by the radial or helical toothing of conventional PDC drill bits. Cutting teeth are inlaid along the tangential direction of the drill bit rotation. The cutting teeth are diamond composite plates 10 with a specification of 13mm~19mm. The distance between two adjacent teeth is 1mm~2mm, which ensures continuous cutting of the well wall and improves the accuracy of well wall dressing.

[0023] The blade 7 of the reaming and enlarging shoulder 2 is provided with a gauge protection section 3. Each blade 7 has a corresponding gauge protection section 3 in the middle. The gauge protection section 3 is a segmented gauge protection structure with unequal height. The gauge protection height of the upper section of the gauge protection section 3 is 0.5mm higher than that of the lower section. The overall maximum outer diameter of the gauge protection section 3 is the same as the outer diameter of the drill bit, which can further improve the gauge protection accuracy and prevent wellbore enlargement deviation. Multiple tungsten carbide alloy gauge protection strips 11 are arranged parallel to the drill bit rotation surface. The gauge protection strips 11 are set on the gauge protection section 3 and are fixed to the gauge protection section 3 by a stepped brazing structure. This can prevent the wellbore from accidentally enlarging during the reaming process, ensure the accuracy of the wellbore size, and at the same time improve the wear resistance of the blade 7 and extend the service life of the drill bit.

[0024] A smooth transition arc surface is provided between the blade 7 of the reaming and enlarging shoulder 2 and the guide core 1. The radius of the transition arc R is 1 / 12 to 1 / 8 of the nominal diameter of the drill bit, which optimizes the stress state of the drill bit and avoids stress concentration. A release groove is provided between the reaming and enlarging shoulder 2 and the connecting body 5. The groove depth is 0.5mm to 1mm, the groove width is 1.0mm to 2.0mm, and the groove cross-section is triangular. It can release the torque and stress generated during well cleaning and reaming, prevent the drill bit body from cracking, and improve the stability of operation.

[0025] The reaming shoulder 2 and the guide core 1 are connected in an arc transition area with drilling fluid main channel water eyes 8. The drilling fluid main channel water eyes 8 are connected to the central flow channel of the drill bit, specifically five 1″ standard water eyes, which are arranged one-to-one with the five blades 7 of the reaming shoulder 2. Unlike the conventional PDC drill bit design where the water eyes are biased towards the core and adapted to drilling cuttings removal, the drilling fluid main channel water eyes 8 of this invention are precisely arranged in the transition area. The internal structure is a precision internal thread structure, which can be adapted to install flow regulating nozzles of 12 / 32″~28 / 32″ specifications. The nozzle size can be flexibly changed according to the drilling fluid discharge, wellbore size and other field conditions, so that the drilling fluid spray direction accurately covers the cutting area of ​​the blades 7 and the contact position with the well wall, enhances the hydraulic circulation effect, realizes the rapid flushing of mud cake on the well wall and the efficient carrying of cuttings, avoids the accumulation and repeated breaking of cuttings in the wellbore, and reduces drill string friction and the risk of stuck drill.

[0026] The nominal size of the drill bit strictly follows the API standard, ranging from 6″ to 17-1 / 2″. The appropriate drill bit specification can be flexibly selected based on the actual wellbore size of different well types, such as vertical and directional wells. The threaded connection section adopts API standard 331-thread, 431-thread, 631-thread, or 731-thread types, enabling reliable sealing connections with existing drill pipes and drill collars of different specifications on site. It is compatible with various drill string combinations, eliminating the need for additional customized adapters and improving the drill bit's versatility and field adaptability. In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention.

[0027] This invention also provides a method for using a high-efficiency well-drainage PDC drill bit, comprising the following steps: Match the drill string assembly according to the well type, wellbore size, and drill string rigidity requirements. Check the integrity of the drill bit components and run the drill bit into the wellbore. Slow down the drilling speed 100m before reaching the target well section and observe the change in suspended weight. After reaching the target position, perform well cleaning and reaming operations according to the wellbore size and drilling parameters. After the operation is completed, pull out the drill bit. After the drill bit comes out of the well, check the condition of the drill bit. If the wear of the diamond composite sheet 10 is ≤1mm and the difference between the maximum outer diameter of the gauge strip 11 and the outer diameter of the drill bit is less than 1mm, then the drill bit can be reused.

[0028] Example A high-efficiency well-drilling PDC drill bit is suitable for well-drilling and reaming operations in hard formations in vertical and directional wells (build-up and stabilize-up sections). The drill bit body includes a drill bit base, which consists of a guide core 1, a reaming and enlarging shoulder 2, a release groove, a connecting body 5, and a threaded connection along the axial direction from top to bottom. The guide core 1 has circumferentially distributed spiral drag-reducing and guiding grooves 9 on its spherical surface. The reaming and enlarging shoulder 2 has five sets of diamond composite plates 10 and tungsten carbide alloy gauge bars 11. The arc transition area between the reaming and enlarging shoulder 2 and the guide core 1 has a drilling fluid main channel water eye 8. A release groove is provided between the reaming and enlarging shoulder 2 and the connecting body 5.

[0029] It should be noted that this embodiment uses an API standard 12-1 / 4″ drill bit as an example. This specification is only an example of an application scenario. This invention can be adapted to the entire range of wellbore sizes from API standard 6″ to 17-1 / 2″, and the parameters can be flexibly adjusted according to the on-site working conditions. In this embodiment, the threaded connection section adopts the API 631 thread type, and the whole is an integrated structure that can be directly adapted to conventional drilling tool combinations on site.

[0030] The guide core 1 is a toothless hemispherical structure with an outer diameter of 1 / 3 of the nominal diameter of the drill bit (12-1 / 4″ corresponds to 4-1 / 12″). The spherical surface is smooth and toothless, which can fit tightly with the original wellbore inner wall to form a rigid guiding constraint. The spherical surface is provided with five spiral drag-reducing guide grooves 9 (groove depth 1.2mm, groove width 1.5mm, spiral helix angle 22°), which extend along the spherical surface to the transition area. The groove wall has rounded corners, which can not only guide the drilling fluid in a directional manner and reduce well friction, but also suppress the lateral sway of the drill bit and enhance the trajectory direction keeping effect.

[0031] The reaming and enlarging shoulder 2 adopts a symmetrical structure of five blades 7. The upper and lower working surfaces of the blades 7 are long arc-shaped continuous toothed curved surfaces with curvature matching the corresponding wellbore specifications to ensure full contact with the well wall. A 16mm diamond composite sheet 10 is inlaid along the rotation tangent direction of the blades 7. The tooth spacing of the diamond composite sheet 10 is 1.5mm, forming a continuous cutting band, which can thoroughly repair defects such as well wall steps and diameter reduction.

[0032] A transition arc surface (radius 1.225″) is provided between the shaving and enlarging shoulder 2 and the guide core 1 to optimize the force distribution and avoid stress concentration; a release groove with a triangular cross section (groove depth 0.8mm, groove width 1.5mm, apex angle 60°) is provided between the shaving and enlarging shoulder 2 and the connecting body 5 to release the working torque and stress in real time, prevent the body from cracking, and improve the stability of operation.

[0033] The transition area has five drilling fluid main channel water holes 8 corresponding to the five blade positions. All five drilling fluid main channel water holes 8 are 1″ standard water holes, radially inclined outward at 18°, and connected to the central flow channel to ensure that the drilling fluid spray accurately covers the cutting area. The drilling fluid main channel water holes 8 are equipped with precision internal threads to adapt to 20 / 32″ fan-shaped flow regulating nozzles, with sealed connection. The nozzle specifications can be flexibly changed according to the drilling fluid discharge and formation lithology.

[0034] The blade 7 of the reaming and enlarging shoulder 2 is provided with a gauge protection section 3. Each blade 7 has a corresponding gauge protection section 3 in the middle. In actual application, the gauge protection section 3 is integrally cut with the drill bit body, that is, the gauge protection section 3 is part of the body. A tungsten carbide alloy gauge protection strip 11 is provided parallel to the drill bit rotation surface. The gauge protection strip 11 and the gauge protection section 3 are fixedly connected by a stepped brazing structure to ensure gauge protection accuracy and wear resistance.

[0035] The gauge protection section 3 is a segmented, unequal-height structure (the upper gauge protection height is 8mm and the lower gauge protection height is 7.5mm). The height difference design improves the gauge protection accuracy and controls the wellbore size error to ≤5mm. The connecting body 5 is an equal-diameter transition structure (300mm long). The threaded connection section is an API 431 standard thread type, conforming to the API 5B standard, and can be directly and sealed to the corresponding drill collar on site, making disassembly and assembly convenient.

[0036] The method for using the high-efficiency well-dredging PDC drill bit in this embodiment is as follows: 1. Drill String Assembly and Installation: Based on the well type, wellbore size, and drill string assembly requirements, select the appropriate drill bit and matching thread type (API 331 / 431 / 631 / 731). Securely connect the drill bit to the drill collar and drill pipe sequentially via the threaded connection section. After connection, check the integrity of the components, ensuring the diamond composite sheet 10 is undamaged, the nozzle is properly installed, and the gauge strip 11 is not loose. Ensure the threading torque of the drill bit and drill string joint meets safety requirements. The nozzle is existing technology.

[0037] 2. Drilling Operation: After the drill string is assembled, it is lowered into the wellbore normally without special control of the lowering speed to avoid violent collisions. It is important to note that before lowering the drill string, the torque of the drill bit and drill string joint must meet safety requirements. The guide core 1 first contacts the wellbore to form a rigid guide, and the spiral drag-reducing guide groove 9 guides the drilling fluid to reduce friction. Slow down the drill string 100m before reaching the target well section, observe changes in suspended weight, and continue drilling to the target position after no obstruction is encountered.

[0038] 3. Well cleaning and reaming operation: After reaching the target well section, start the drilling equipment and adopt the high-parameter operation mode (recommended drilling parameters 90%-100%, for example: for 12-1 / 4″ well cleaning, use a drilling pressure of 150kN-200kN, a rotation speed of 100r / min-120r / min, and a drilling fluid flow rate of 65L / s-75L / s); when the drill bit rotates, the cutter blade 7 drives the diamond composite blade 10 to continuously cut and trim the well wall. The close tooth pitch design ensures a smooth cutting surface, and the torque fluctuation is controlled within ±10kN·m to avoid drill blockage and drill jump.

[0039] 4. Hydraulic circulation and cuttings removal: Drilling fluid enters the central flow channel of the drill bit through the drill pipe and drill collar, and forms a high-pressure jet through the main flow channel water eye 8 and nozzle to flush mud cake and cuttings; the spiral drag reduction guide channel 9 guides the drilling fluid to form a circulation, efficiently carrying the cuttings to the surface; the drilling fluid return is monitored in real time, and the discharge rate or nozzle specification is adjusted according to the amount of cuttings returned.

[0040] Operation monitoring and adjustment: Observe parameters such as torque, drilling pressure, and suspended weight through the monitoring system. If the torque fluctuation exceeds the range, adjust the rotation speed or drilling pressure appropriately. When encountering local hard formations or wellbore steps, use the "light pressure and slow rotation" method to repeatedly ream the hole (drill pressure 50kN-100kN, rotation speed 80r / min-100r / min) to pass smoothly and avoid damage to the drill bit or deformation of the wellbore.

[0041] 5. Pulling out of the well and subsequent operations: After the operation is completed (no obstruction in the drill string, stable torque, and normal cuttings return), stop the equipment and pull out the drill bit normally; after pulling out the drill bit, check the condition of the drill bit. If the wear of the diamond composite plate 10 is ≤1mm and the difference between the maximum outer diameter of the gauge strip 11 and the outer diameter of the drill bit is less than 1mm, the drill bit can be reused; subsequent operations such as casing running and electrical logging can be carried out directly without repeating well cleaning.

[0042] This embodiment has been field-verified and shows that, compared to traditional roller cone bits, wellbore clearance efficiency is increased by more than 50% and single-trip footage is increased by 2 times; compared to conventional PDC bits, it eliminates the formation of new wellbores, reduces torque fluctuation by 67%, and improves cuttings carrying efficiency by more than 20%, meeting the needs of wellbore clearance for complex trajectories.

[0043] Furthermore, the parameters of this invention can be flexibly adjusted according to the wellbore size (6″~17-1 / 2″) and formation conditions: the spiral drag-reducing guide groove 9 can be adjusted to 3~6 grooves, groove depth 0.8mm~1.5mm, groove width 1.0mm~2.0mm, and spiral helix angle 15°~30°; the diamond composite sheet 10 can be selected with a specification of 13mm~19mm and a tooth spacing of 1mm~2mm; the nozzle can be replaced with a specification of 12 / 32″~28 / 32″; the threaded connection section can be adapted to various API thread types, with strong versatility and easy large-scale promotion.

[0044] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A high-efficiency wellbore cleaning PDC drill bit, comprising a drill bit body, characterized in that: The drill bit body is divided into a guide core (1), a reaming and enlarging shoulder (2), a connecting body (5), and a threaded connection section along the axial direction from top to bottom. The guide core (1) is a toothless hemispherical guide head, and the spherical surface of the hemispherical guide head is machined with circumferentially distributed spiral drag-reducing guide grooves (9). The reaming and enlarging shoulder (2) is provided with a diameter-maintaining section (3), and the arc transition area between the reaming and enlarging shoulder (2) and the guide core (1) is provided with a drilling fluid main channel water eye (8), and the drilling fluid main channel water eye (8) is connected to the central flow channel of the drill bit.

2. The high-efficiency well-drainage PDC drill bit according to claim 1, characterized in that: The outer diameter of the hemispherical guide head is 1 / 3 of the nominal diameter of the drill bit.

3. The high-efficiency well-drainage PDC drill bit according to claim 1, characterized in that: The number of spiral drag-reducing guide grooves (9) is five. The groove depth of the spiral drag-reducing guide grooves (9) is 0.8mm~1.5mm, the groove width is 1.0mm~2.0mm, and the spiral helix angle is 15°~30°. Each spiral drag-reducing guide groove (9) extends along the spherical surface of the hemispherical guide head to the transition area of ​​the reaming and enlarging shoulder (2), which is used to guide the drilling fluid in a directional manner, reduce the friction of well passage, and suppress the lateral sway of the drill bit.

4. The high-efficiency well-drainage PDC drill bit according to claim 1, characterized in that: The reaming and enlarging shoulder (2) adopts a five-blade symmetrical structure. The upper and lower reaming working surfaces of the blade (7) are long arc continuous toothed curved surfaces. Cutting teeth are inlaid along the rotation tangent of the drill bit. The distance between two adjacent teeth is 1mm~2mm. The cutting teeth are diamond composite sheets (10) with a diameter of 13mm~19mm.

5. The high-efficiency well-drainage PDC drill bit according to claim 3, characterized in that: The diameter protection section (3) is set on the blade (7) of the reaming and enlarging shoulder (2). Each blade (7) has a diameter protection section (3) in the middle. The diameter protection section (3) is a segmented structure with unequal heights. The diameter protection height of the upper section of the diameter protection section (3) is greater than that of the lower section. The overall maximum outer diameter of the diameter protection section (3) is the same as the outer diameter of the drill bit. Multiple diameter protection bars (11) are set parallel to the rotating surface of the drill bit. The diameter protection bars (11) are set on the diameter protection section (3). The diameter protection bars (11) and the diameter protection section (3) are fixedly connected by a stepped brazing structure. The material of the diameter protection bars (11) is tungsten carbide alloy.

6. The high-efficiency well-drainage PDC drill bit according to claim 4, characterized in that: The upper diameter protection height of the diameter protection section (3) is 0.5 mm higher than that of the lower diameter protection height; the nominal size of the drill bit is API standard 6″~17-1 / 2″, and the threaded connection section adopts API standard 331 thread type, 431 thread type, 631 thread type or 731 thread type.

7. The high-efficiency well-drainage PDC drill bit according to claim 1, characterized in that: The blade (7) of the reaming and enlarging shoulder (2) is provided with a smooth transition arc surface between the blade (7) and the guide core (1), and the radius of the transition arc is 1 / 12 to 1 / 8 of the nominal diameter of the drill bit; the drilling fluid main channel water eye (8) consists of five 1″ standard water eyes, which are adapted to install 12 / 32″ to 28 / 32″ flow regulating nozzles.

8. The high-efficiency well-drainage PDC drill bit according to claim 1, characterized in that: A release groove (4) is provided between the slit-and-expand shoulder (2) and the connecting body (5). The release groove (4) has a depth of 0.5mm to 1mm, a width of 1.0mm to 2.0mm, and a triangular cross-section.

9. A method for using a high-efficiency well-drainage PDC drill bit, comprising the high-efficiency well-drainage PDC drill bit according to any one of claims 1-8, characterized in that, Includes the following steps: Match the drill string assembly according to the well type, wellbore size and drill string rigidity requirements, check the integrity of the drill bit components, and run the drill bit into the wellbore; slow down the running speed when drilling to the first 100m of the target well section, observe the change in suspended weight, and after drilling to the target position, perform well cleaning and reaming operations according to the wellbore size and drilling parameters. After the operation is completed, start drilling. After the drill bit comes out of the well, check the condition of the drill bit. If the wear of the diamond composite sheet (10) is ≤1mm and the difference between the maximum outer diameter of the gauge bar (11) and the outer diameter of the drill bit is less than 1mm, then the drill bit can be reused.

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