A deep overburden drilling process correction bit and construction method

Abstract

The application discloses a deep overburden layer drilling process deviation correction drill bit and a construction method, and belongs to the technical field of geotechnical engineering drilling construction and drill guiding. The drill bit is hinged with a casing through a transverse main pin, a motor drives a screw rod to drive a guiding transmission sleeve to move axially, a transverse compensation groove of the transmission sleeve is matched with a biasing bolt on the drill bit, the transmission chain is provided with a retaining mechanism, and the drill bit is provided with upward and downward cutting working parts. In construction, first, the inclination is measured when the rotation is stopped, then, after the starting condition is met, the load is unloaded, the target direction is aligned, the angle is adjusted, the hole is scanned upward and downward in the limited sector, and after the hole is centered, the multi-point re-measurement is conducted. The transverse displacement of the bolt swing is accommodated by the transverse compensation groove, and the directional modification of the local inclined hole section is used.

Description

Technical Field

[0001] This invention belongs to the field of drilling construction and drill bit guidance technology in geotechnical engineering, specifically relating to a drill bit and construction method for correcting deviation during drilling in deep overburden layers. Background Technology

[0002] In drilling operations through deep overburden layers, the drilling rig transmits torque and drilling pressure to the drill bit at the bottom of the hole via the drill rod. The drill bit cuts through the soil, gravel, and boulders to form a borehole. Due to significant differences in particle composition, density, and strength within the overburden layer, the cutting resistance on both sides of the drill bit is prone to become uneven. When encountering inclined soft-hard interfaces, isolated boulders, or large rocks, the drill bit is also subjected to significant lateral forces, causing the borehole axis to gradually deviate from the designed direction. As the hole depth increases, the already formed deviated section will exert guiding constraints on the drilling tools, and simply adjusting the drill rod verticality on the ground is insufficient to directly correct the local deviation near the bottom of the hole.

[0003] Existing borehole deviation correction technologies mainly include using lateral supports to generate borehole wall reaction force, employing downhole angle adjustment mechanisms to change the drill string axis direction, and correcting deviated borehole sections through reaming or sweeping. In actual construction, the deviation correction mechanism must achieve controllable deflection within the limited casing space, while also withstanding drilling pressure, pulling force, torque, and lateral cutting loads; simultaneously, it must ensure continuous circulation of the circulating medium, reliable inclination measurement data, and stable deviation angle during reciprocating sweeping. Therefore, the motion coordination, load maintenance, and azimuth control of the downhole angle adjustment mechanism are key issues affecting the reliability of deviation correction.

[0004] Chinese patent application CN109630019A discloses a drill rod, drilling system, and drilling deviation correction method with a deviation correction function. It detects borehole deviation using a near-drill bit tilt sensor and extends a deviation correction support rod outwards from the drill rod, utilizing the reaction force from the borehole wall to adjust the drill rod's direction. While this solution can achieve lateral deviation correction, it primarily relies on the reaction force generated by the contact between the support rod and the borehole wall. It lacks a structure for directional reciprocating cutting and trimming of already formed locally deviated borehole sections after the drill bit itself has deflected.

[0005] US Patent Application US20160123083A1 discloses a downhole adjustable angle mechanism that uses a motor, lead screw, moving parts, and a swingable assembly to change the angle of a downhole tool and can be battery powered. This solution illustrates the basic form of downhole angle adjustment driven by a motor-driven lead screw. However, for issues such as motion compensation between the transverse kingpin hinge drill bit and the axial linear actuator, maintaining the deflection angle under bidirectional hole-sweeping loads, ensuring the continuity of the central circulation channel across the hinge, and directional reciprocating dressing of deviated hole sections, specialized structures are still needed for specific drilling conditions.

[0006] When the drill bit oscillates around the transverse kingpin, the offset pin's trajectory is an arc, while the lead screw actuator inside the casing mainly moves linearly along the casing's axial direction. If the two are connected rigidly without lateral degrees of freedom, the lateral displacement generated by the pin's arc motion will become an additional constraint on the mechanism, easily causing lead screw bending, connection jamming, or angle adjustment errors. Furthermore, simply causing the drill bit to deflect at an angle is not equivalent to completing the correction: if the deflected drill bit rotates unrestrainedly around the casing, the deflection direction will continuously change, moving closer to reaming rather than correcting the target direction.

[0007] Therefore, there is a need for a drill bit and construction method that can convert axial drive into controllable drill bit rotation within the limited space of the casing, allow the pin arc trajectory to generate lateral compensation, maintain the set deflection angle under lifting and lowering sweeping loads, and combine near-drill bit inclination measurement, target orientation limitation and mid-position multi-point re-measurement to directionally correct locally deviated hole sections. Summary of the Invention

[0008] To address the aforementioned technical problems in existing technologies, this invention proposes a correction drill bit and construction method for drilling deep overburden layers, overcoming the shortcomings of the prior art. This invention addresses the motion compensation between axial drive and drill bit rotation, as well as the issues of maintaining the deflection angle and controlling the azimuth during bidirectional drilling, by proposing a correction drill bit and construction method for drilling deep overburden layers. A transverse compensation groove connects the transmission sleeve and the offset pin to maintain the mechanism's locked angle adjustment position, allowing for reciprocating adjustment of the hole section within a defined azimuth, and segmented re-measurement after the drill bit returns to center.

[0009] To achieve the above objectives, the present invention adopts the following technical solution: A drilling bit for correcting deviation during drilling in deep overburden layers includes a casing, a drill bit, a motor, a drive screw, a transmission sleeve, a pin, a kingpin, a slant measuring device, and a battery. The oscillating connection of the drill bit extends into the lower end of the casing and is hinged to the casing via a transverse kingpin. The motor is connected to the drive screw, which is threadedly connected to the transmission sleeve. The transmission sleeve slides axially along the casing via a guide fixed to the casing. The transmission sleeve has a transverse compensation groove. The pin is fixed to the oscillating connection, parallel to and offset from the kingpin, and extends into the transverse compensation groove, engaging with its two opposing pressure-bearing sidewalls. The transmission chain from the motor to the transmission sleeve has a retaining mechanism. The drill bit has upward and downward cutting working parts. The motor, battery, and slant measuring device are located inside the casing, and the battery connects to the motor and the slant measuring device.

[0010] Preferably, the drive screw is axially positioned by the support bearing, and the guide and the transmission sleeve form a keyway or guide rail type moving pair; the transverse compensation groove extends in the direction perpendicular to the axial direction of the sleeve in the swing plane, the effective stroke in the groove covers the transverse displacement of the pin within the allowable deflection angle, and the pin is provided with an axial anti-disengagement limit.

[0011] Preferably, the drive screw and the transmission sleeve form a self-locking trapezoidal threaded pair, and the retaining mechanism includes the threaded pair and a normally closed braking part on the motor output transmission chain; the transmission sleeve is provided with a position detection element, and the sleeve is provided with a mid-position detection element; the braking part is released when adjusting the angle and closed when in position or when power is lost.

[0012] Preferably, the upper channel section inside the casing is connected to the lower channel section that rotates with the drill bit via a flexible connection section to form a central channel; the main pin is composed of two coaxial short shaft sections placed on both sides of the central channel.

[0013] Preferably, the motor and drive screw are located on one side of the central channel, and the battery and inclinometer are located in a sealed cavity on the other side; the inclinometer includes an acceleration detection module, an angular velocity detection module and a control module, which are connected to the ground control device via a sealed signal interface.

[0014] Preferably, the upward cutting working part is located on the upper shoulder surface and adjacent side surface of the drill bit, and the downward cutting working part is located on the lower end face and adjacent side surface of the drill bit; the swing connection part and the casing are provided with a swing displacement gap and a mechanical limiting part.

[0015] The construction method using the above-mentioned correction drill bit includes the following steps: S101, adjust the drill bit to the center position, calibrate the correspondence between the inclination measuring device and the oscillating plane, and set the start-up and acceptance conditions, allowable deviation angle and hole sweeping parameters; S102, drilling in the middle position, stop rotating and wait for the attitude to stabilize before measuring the inclination to determine whether the correction start condition is met; S103, when the start-up conditions are met, stop the advance and continuous rotation and unload the load. Determine the correction interval, target orientation and deflection angle based on multi-point data, adjust the circumferential position of the casing and verify the actual deflection direction in the hole. S104, the motor drives the drill bit to deflect around the main pin via the drive screw, transmission sleeve and pin, and is held by the holding mechanism after reaching the set deflection angle; S105, maintain the deflection angle, oscillate back and forth in the circumferential direction within the limited sector centered on the target orientation, and first raise the sweep hole and then lower the sweep hole along the correction interval; S106, stop unloading, reverse drive back to center, and perform multi-point retest after confirming the center position; if the acceptance conditions are not met and there is no fault, return to S103. S107, after meeting the acceptance conditions, maintain the neutral position and resume drilling or conduct final hole acceptance.

[0016] Preferably, the starting condition is that the stable and effective tilt angle measurement value exceeds the starting threshold after a preset number of times, and the acceptance condition includes that the tilt angle of multiple measuring points in the correction interval does not exceed the exit threshold below the starting threshold; when there are hole position control requirements, the hole axis is reconstructed according to the hole depth, tilt angle and orientation, and the offset and local curvature are verified.

[0017] Preferably, the sum of the half-angle of the hole-sweeping sector and the upper limit of the orientation control error within the hole is less than 90°; the upper end of the correction interval crosses the starting point of the deviation and forms a transition overlap with the previous qualified hole segment; and no full-circle continuous rotation is performed while maintaining the deviation angle.

[0018] Preferably, the target displacement of the transmission sleeve is determined according to the calibrated displacement and deflection angle relationship. The deflection angle of each stage meets the available space constraint in the hole. The deflection angle is increased only after the hole is formed and the newly added space is verified. The current, position, power supply and attitude are monitored during the angle adjustment and hole sweeping. When a preset fault occurs, the advance is stopped, the circumferential swing is stopped and the unload is stopped.

[0019] The beneficial technical effects of this invention are as follows: The drive screw drives the guided transmission sleeve to move along the casing axis, and the transverse compensation groove on the transmission sleeve cooperates with the offset pin to convert the linear displacement into the swing of the drill bit around the main pin. The transverse compensation groove also accommodates the transverse displacement generated by the arc trajectory of the pin, thus structurally reducing the motion constraint conflict between rigid linear drive and arc swing.

[0020] The trapezoidal thread pair and the normally closed brake form an angle holding mechanism, which keeps the transmission sleeve in axial position after reaching the target position, and keeps the drill bit in the set angle when the load direction changes during upward and downward hole sweeping, thus avoiding the need to rely solely on the motor stopping to maintain the drill bit posture.

[0021] The central channel is divided into an upper channel section, a flexible connection section, and a lower channel section. The main pin is placed on both sides of the central channel so that the lower channel section can swing with the drill bit when the drill bit deflects, thus avoiding the rigid continuous channel from restricting the drill bit rotation after crossing the articulated position.

[0022] By acquiring the near-drill bit attitude using an inclination measuring device, and after the correction start conditions are met, normal advance and continuous rotation are stopped first, and then the correction interval and target correction direction are determined, so that a clear correspondence is established between the drill bit deflection direction and the direction to be corrected.

[0023] While maintaining the set deflection angle, the circumferential movement of the casing is restricted to the hole-sweeping sector centered on the target correction orientation. Within the same correction interval, the hole is first lifted and then lowered for sweeping, so that the drill bit deflection direction always has a component in the same direction as the target correction direction during the hole-sweeping process, avoiding unrestrained full-circumferential rotation that weakens the directional correction effect.

[0024] After the hole sweeping is completed, the drill bit is reset to the center position, and multiple measurement points are re-measured along the correction interval. When the project needs to control the hole position deviation, the hole axis can also be reconstructed according to the hole depth, inclination angle and orientation, so as to distinguish the mechanism reset, instantaneous attitude change and actual hole section correction acceptance.

[0025] Step-by-step angle adjustment is based on the premise that there is available space at each stage. Combining current, position, power supply and attitude checks can reduce the risk of continuing to force angle adjustment after obstruction; angle adjustment is stopped when space is still insufficient. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the overall connection of a drilling bit and construction method for drilling deep overburden layers according to the present invention.

[0027] Figure 2 This is a schematic diagram illustrating the drive and compensation groove coordination, the connection between the central channel and the short shaft sections on both sides, the flexible connection of the central channel, and the segmented relationship of the main pin in the drilling process of a deep overburden layer according to the present invention.

[0028] Figure 3 This is a flowchart of the deviation correction construction method in the drilling process of a deep overburden layer according to the present invention.

[0029] Reference numerals: 1—Motor; 2—Drive screw; 3—Pin; 4—Main pin; 5—Drill bit; 6—Inclination measuring device; 7—Battery; 8—Casing; 21—Transmission sleeve; 22—Guide component; 23—Transverse compensation groove; 51—Swing connection; 81—Upper channel section; 82—Flexible connection section; 83—Lower channel section. Detailed Implementation

[0030] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments: Example

[0031] like Figure 1-3 As shown, a deviation correction drill bit for drilling deep overburden layers includes a casing 8, a drill bit 5, a motor 1, a drive screw 2, a transmission sleeve 21, a pin 3, a main pin 4, a slant measuring device 6, and a battery 7. The swing connection part 51 of the drill bit 5 extends into the lower end of the casing 8 and is hinged to the casing 8 through the transverse main pin 4. The motor 1 is connected to the drive screw 2, and the drive screw 2 is threadedly connected to the transmission sleeve 21. The transmission sleeve 21 slides along the axial direction of the casing 8 via a guide 22 fixed to the casing 8. The transmission sleeve 21 is provided with a transverse compensation groove 23. The pin 3 is fixed to the swing connection part 51, parallel to and offset from the main pin 4, and extends into the transverse compensation groove 23 and engages with its two opposing pressure-bearing sidewalls. The transmission chain from the motor 1 to the transmission sleeve 21 is provided with a holding mechanism. The drill bit 5 is provided with upward and downward cutting working parts. The motor 1, the battery 7, and the slant measuring device 6 are located inside the casing 8, and the battery 7 is connected to the motor 1 and the slant measuring device 6.

[0032] Preferably, the drive screw 2 is axially positioned by the support bearing, and the guide member 22 and the transmission sleeve 21 form a keyway or guide rail type moving pair; the transverse compensation groove 23 extends in the direction perpendicular to the axial direction of the sleeve 8 in the swing plane, and the effective stroke in the groove covers the transverse displacement of the pin 3 within the allowable deflection angle, and the pin 3 is provided with axial anti-disengagement limit.

[0033] Preferably, the drive screw 2 and the transmission sleeve 21 form a self-locking trapezoidal thread pair, and the holding mechanism includes the thread pair and a normally closed braking part on the output transmission chain of the motor 1; the transmission sleeve 21 is provided with a position detection element, and the sleeve 8 is provided with a mid-position detection element; the braking part is released when adjusting the angle and closed when in position or when power is lost.

[0034] Preferably, the upper channel section 81 inside the casing 8 is connected to the lower channel section 83 that swings with the drill bit via the flexible connection section 82, forming a central channel; the main pin 4 is composed of two coaxial short shaft sections placed on both sides of the central channel.

[0035] Preferably, the motor 1 and the drive screw 2 are located on one side of the central channel, and the battery 7 and the inclination measuring device 6 are located in the sealed cavity on the other side; the inclination measuring device 6 includes an acceleration detection module, an angular velocity detection module and a control module, and is connected to the ground control device through a sealed signal interface.

[0036] Preferably, the upward cutting working part is provided on the upper shoulder surface and adjacent side surface of the drill bit 5, and the downward cutting working part is provided on the lower end face and adjacent side surface of the drill bit 5; the swing connection part 51 and the casing 8 are provided with a swing displacement gap and a mechanical limiting part.

[0037] The construction method using the above-mentioned correction drill bit 5 includes the following steps: S101, adjust the drill bit to the center position, calibrate the correspondence between the inclination measuring device 6 and the swing plane, and set the start-up and acceptance conditions, allowable deviation angle and hole sweeping parameters; S102, drilling in the middle position, stop rotating and wait for the attitude to stabilize before measuring the inclination to determine whether the correction start condition is met; S103, when the start-up conditions are met, stop the advance and continuous rotation and unload the load. Determine the correction interval, target orientation and deflection angle based on multi-measurement data, adjust the 8-circumferential position of the sleeve and verify the actual deflection direction in the hole. S104, the motor 1 drives the drill bit 5 to deflect around the main pin 4 via the drive screw 2, transmission sleeve 21 and pin 3, and is held by the holding mechanism after reaching the set deflection angle; S105, maintain the deflection angle, oscillate back and forth in the circumferential direction within the limited sector centered on the target orientation, and first raise the sweep hole and then lower the sweep hole along the correction interval; S106, stop unloading, reverse drive back to center, and perform multi-point retest after confirming the center position; if the acceptance conditions are not met and there is no fault, return to S103. S107, after meeting the acceptance conditions, maintain the neutral position and resume drilling or conduct final hole acceptance.

[0038] Preferably, the starting condition is that the stable and effective tilt angle measurement value exceeds the starting threshold after a preset number of times, and the acceptance condition includes that the tilt angle of multiple measuring points in the correction interval does not exceed the exit threshold below the starting threshold; when there are hole position control requirements, the hole axis is reconstructed according to the hole depth, tilt angle and orientation, and the offset and local curvature are verified.

[0039] Preferably, the sum of the half-angle of the hole-sweeping sector and the upper limit of the orientation control error within the hole is less than 90°; the upper end of the correction interval crosses the starting point of the deviation and forms a transition overlap with the previous qualified hole segment; and no full-circle continuous rotation is performed while maintaining the deviation angle.

[0040] Preferably, the target displacement of the transmission sleeve 21 is determined according to the calibrated displacement and deflection angle relationship. The deflection angle of each stage meets the available space constraint in the hole. The deflection angle is increased only after the hole is formed and the newly added space is verified. The current, position, power supply and attitude are monitored during the angle adjustment and hole sweeping. When a preset fault occurs, the advance is stopped, the circumferential swing is stopped and the unloading is stopped. Example

[0041] like Figure 1-3 As shown, the connection relationship between the various structures of the correction drill bit, motion conversion, deviation angle maintenance, central channel arrangement, and directional drilling principle are further explained.

[0042] The casing 8 serves as the main body of the correction tool, connected at its upper end to the drill pipe, from which torque, drilling pressure, and pulling force are transmitted. The swing connection 51 of the drill bit 5 extends into the lower end of the casing 8 and is hinged to the casing 8 via a laterally positioned main pin 4. The axis of the main pin 4 is perpendicular to the axis of the casing 8, ensuring that the drill bit 5 can only rotate relative to the casing 8 within a defined swing plane. The position is defined as when the axes of the drill bit 5 and the casing 8 coincide.

[0043] Motor 1 is fixed inside sleeve 8, and the output end of motor 1 is connected to drive screw 2. Drive screw 2 is axially positioned by support bearing. Transmission sleeve 21 is threadedly engaged with drive screw 2. The outer side of transmission sleeve 21 forms a keyway or guide rail type moving pair with guide member 22 fixed to sleeve 8. Therefore, when drive screw 2 rotates, transmission sleeve 21 cannot rotate with screw, but can only move axially along sleeve 8.

[0044] A transverse compensation groove 23 is provided at the lower end of the transmission sleeve 21. The pin 3 is fixed to the swing connection part 51 of the drill bit 5 and is offset from the main pin 4. When the transmission sleeve 21 moves downward, the bearing surface on one side of the transverse compensation groove 23 pushes the pin 3 to move, causing the drill bit 5 to deflect to one side around the main pin 4. When the transmission sleeve 21 moves in the opposite direction, the bearing surface on the other side drives the pin 3 to move in the opposite direction, causing the drill bit 5 to reduce its deflection angle and return to its original position. Since the trajectory of the pin 3 around the main pin 4 is an arc, the pin 3 generates both axial and lateral displacement. The transverse compensation groove 23 allows the pin 3 to slide along the length of the groove, thereby releasing this lateral displacement.

[0045] The relative pressure-bearing sidewalls of the transverse compensation groove 23 are positioned axially along the sleeve 8, and the axis of the pin 3 is parallel to the axis of the main pin 4; the fit clearance between the groove width and the diameter of the pin 3 is included in the hysteresis calibration. The axial position of the transmission sleeve 21 is measured by the position detection component, and the center position detection component detects the actual center position of the swing connection 51 to avoid confirming the centering solely by zeroing the motor 1 command. The control module connects the drive circuit of the motor 1 and the brake and the position detection input, and the battery 7 supplies power to the electrical components inside the hole.

[0046] Establish a coordinate system in the rotation plane of drill bit 5 with the center O of main pin 4 as the origin. Let the x-axis point to the side where pin 3 is located, and the z-axis point downward along the axis of casing 8. Let the lateral coordinate of pin 3 when it is in the neutral position be r, the axial coordinate be b, and the signed deflection angle of drill bit 5 be θ. After drill bit 5 rotates through θ, the coordinates of the center of pin 3 can be expressed as: x(θ)=r·cosθ-b·sinθ (1) z(θ)=r·sinθ+b·cosθ (2) Therefore, the axial displacement u required for the transmission sleeve 21 relative to the center position and the lateral displacement Δx of the pin 3 relative to the lateral compensation groove 23 are respectively: u(θ)=r·sinθ+b·(cosθ-1) (3) Δx(θ)=r·(cosθ-1)-b·sinθ (4) Establish the correspondence between the target displacement of the transmission sleeve 21 and the deflection angle of the drill bit 5, and determine the effective compensation stroke of the transverse compensation groove 23. After actual machining and assembly, calibrate the center position, positive deflection angle, and reverse deflection angle, and write the calibration results into the control module. On-site angle adjustment prioritizes the calibration relationship rather than just the nominal geometric dimensions.

[0047] Within the allowable deflection angle range, the expression du / dθ = r·cosθ−b·sinθ should remain unchanged, and its absolute value should not be lower than the lower limit determined by the actuation force, in order to maintain a one-to-one correspondence between displacement and deflection angle and avoid dead points. The total length of the transverse compensation groove 23 should also take into account the diameter of the pin 3, assembly error, and end allowance; the calculated displacement range of the center of the pin 3 should not be directly used as the total length of the groove.

[0048] The deflection angle holding mechanism consists of a trapezoidal threaded pair with reverse load self-locking capability and a normally closed braking part. Let the lead of the drive screw 2 be p and its mean diameter be d. m Then the thread helix angle λ satisfies: tanλ=p / (πd m (5) For a trapezoidal thread with a tooth profile half-angle of β and a contact friction coefficient of μ, the equivalent friction angle ρ = arctan(μ / cosβ) can be taken, and the thread pair should satisfy λ < ρ under the most unfavorable lubrication and wear conditions. The holding capacity under vibration and reverse load conditions should be verified. During angle adjustment, the normally closed brake is released, and after the target deflection angle is reached, the brake closes, and the angle adjustment current of motor 1 is reduced. When power is lost, the brake closes and maintains the current position within its rated holding load, rather than relying on automatic reset due to power loss.

[0049] When drill bit 5 is subjected to lateral cutting force, drill pressure eccentricity, or pull force eccentricity, an external swing torque M is generated near kingpin 4. If the equivalent arm of the mechanism at the current deflection angle is l... e =|r·cosθ-b·sinθ|, then the axial holding force required for transmission sleeve 21 can be estimated by the following formula: F≥γ·|M| / l e (6) In the formula, γ is the design coefficient considering impact, formation inhomogeneity, and load fluctuation. The strength of the drive screw 2, threaded pair, pin 3, kingpin 4, and guide 22 can be further checked by the axial force F, and the holding capacity of the normally closed brake can be determined. The calculation uses the absolute value of the external torque, and the posture with the equivalent force arm close to zero is not included in the allowable range; the holding torque of the brake is converted according to its actual installation shaft and transmission ratio, and the backlash is taken into account. The kingpin 4 and its two side supports are simultaneously verified for drilling pressure, pulling force, and drilling torque, and cannot be checked only by adjusting the angle force.

[0050] A central channel is maintained between the casing 8 and the drill bit 5. The upper channel section 81 of the central channel is fixed to the casing 8, and the lower channel section 83 rotates with the drill bit 5. The two are connected by a flexible connecting section 82. The kingpin 4 adopts coaxial short shaft sections located on both sides of the central channel. Thus, when the drill bit 5 deflects, the flexible connecting section 82 absorbs angular displacement, the central channel remains connected, and the kingpin 4 does not penetrate the channel with a solid transverse pin.

[0051] The upper channel section 81, the flexible connection section 82, and the lower channel section 83 are sealed together, and the bending radius, torsion, pressure resistance, and abrasion conditions are verified within the full swing angle range. Figure 1 Indicates the location of the median pathway. Figure 2 Figure B shows the relationship between the short shaft sections on both sides of the main pin 4 and the passageway; the main pin 4 must not penetrate the flow channel, and the flexible connection section 82 must not be replaced by a rigid straight pipe.

[0052] The inclination measuring device 6 is fixed inside the casing 8 and includes at least an acceleration detection module, an angular velocity detection module, and a control module. During installation, the relationship between the sensor coordinate system, the axis of the main pin 4, the oscillation plane of the drill bit 5, and the ground azimuth reference is calibrated. Correction judgment is based on the measurement value after continuous rotation has stopped and the attitude has stabilized. When the drill bit 5 is at a non-zero deflection angle, the inclination measuring device 6 measures the near-drill bit attitude of the casing 8. Final acceptance should be conducted after the drill bit 5 has returned to its neutral position.

[0053] Acceleration and angular velocity detection modules must use established and regularly verified azimuth references; absolute heading cannot be determined solely by static gravity. The actual tool face azimuth within the borehole should include drill pipe torsion, connection clearance, and measurement errors; it cannot be directly replaced by the ground drilling rig's rotation angle. Orientation drilling should be suspended if the azimuth is unavailable or the error exceeds the limit. Centerline inclination measurements reflect the local attitude of the tool; tool misalignment after borehole diameter enlargement will cause deviations. Borehole axis acceptance should employ calibrated segmented measurements with positioning or straightening capabilities, and independent verification should be performed when necessary.

[0054] During the correction operation, the starting position and direction of the deviation are first identified based on the results of inclination measurements at multiple points, and the target correction azimuth is determined. The ground drilling rig adjusts the circumferential position of the casing 8 so that the predetermined deflection direction of the drill bit 5 is consistent with the target correction azimuth, and then the motor 1 sets the deflection angle. During the hole sweeping process, there is no unrestrained continuous full-circumference rotation, but rather a circumferential reciprocating oscillation within a limited sector on both sides of the target correction azimuth, so that the deflection direction of the drill bit 5 always has the same component as the target correction direction.

[0055] Let the target correction azimuth be φc, the half-angle of the hole-sweeping sector be ψ, and the upper limit of the azimuth control error be εφ. Then, to ensure that the drill bit 5 deflection direction within the hole-sweeping sector does not cross a position orthogonal to the target direction, the following must be satisfied: ψ+εφ<90° (7) In practical engineering, a hole-sweeping sector smaller than the theoretical upper limit is typically used, and further determined based on the formation cutting capacity, drill bit rigidity, and azimuth measurement accuracy. Upward hole sweeping utilizes the upward cutting working part of the upper shoulder face and adjacent sides of drill bit 5, while downward hole sweeping utilizes the downward cutting working part of the lower end face and adjacent sides of drill bit 5, enabling bidirectional correction within the same correction zone. Sector angle conditions only constrain the deflection direction and do not guarantee the generation of the target cutting amount; the feed, oscillation amplitude, and number of repetitions must be determined in conjunction with changes in hole diameter, trajectory, and load after trial sweeping. The cutting edge arrangement of the bidirectional cutting working part should be adapted to the upward, downward, and circumferential reciprocating motions. Example

[0056] like Figure 1-3As shown, a ground inspection of the correction drill bit is conducted before construction. Confirm that the battery 7 power, the zero point of the inclination measuring device 6, the anti-disengagement status of the pin 3 and main pin 4, the stroke of the drive screw 2, the normally closed brake, and the sealing status of the central channel are normal; adjust the drill bit 5 to the center position coaxial with the casing 8, and calibrate the correspondence between the displacement of the transmission sleeve 21 and the deflection angle of the drill bit 5.

[0057] Assuming the lateral offset of pin 3 is r=80 mm, the axial offset is b=5 mm, the distance from the center of main pin 4 to the lower control point of drill bit 5 is L=400 mm, and the proposed deflection angle is θ=2°. According to equation (3), the target axial displacement u of transmission sleeve 21 relative to the center is approximately 2.789 mm; according to equation (4), the lateral compensation displacement Δx of pin 3 is approximately -0.223 mm. If the lead of drive screw 2 is 2 mm, the nominal number of revolutions required to reach this deflection angle is approximately 1.394 revolutions. The actual control value is corrected using the assembly calibration results. When L=400 mm, the lateral offset of the control point corresponding to the 2° deflection angle is approximately 13.96 mm. This value does not include the drill bit radius and the oscillating sweep volume, and cannot be used alone as a criterion for sufficient space in the hole.

[0058] During normal drilling, the drill bit is kept in the center position (5), with rotation and advance power provided by the ground drilling rig. If, when drilling reaches a depth of approximately 42 m, three consecutive stable measurements show that the near-drill bit inclination exceeds the preset start-up threshold, and the deviation is primarily developing in the southeast direction, then normal advance and continuous rotation for the entire circumference should be stopped, drill pressure reduced, and the required correction zone determined based on previous and subsequent measurement points.

[0059] The ground drilling rig slowly adjusts the circumferential position of the casing 8 to align the swing plane of the drill bit 5 with the target correction direction. After confirming that the drilling pressure, drive current, and attitude meet the angle adjustment conditions, the normally closed brake is released, the motor 1 is started, and the drive screw 2 drives the transmission sleeve 21 to move to the target position corresponding to the 2° deviation angle; after the position is stable, the brake is closed to keep the drill bit 5 at the set deviation angle.

[0060] When the space inside the hole is insufficient to directly form a 2° deflection angle, first verify the complete swing envelope of the smaller deflection stage and the reciprocating hole sweep space. For example, 0.5° or 1° should only be used when the space is sufficient. Stop adjusting the angle when even the smaller deflection angle is obstructed. After the trial sweep, confirm the additional clearance space based on the actual hole diameter and load response, then unload and increase the deflection angle, without forcibly increasing the angle according to the preset number of stages. Monitor the current, position, and attitude each time the angle is adjusted, and stop when the current increases but the position change is insufficient.

[0061] After entering the hole-sweeping stage, maintain a constant 2° deviation angle, and the ground drilling rig will only oscillate the casing 8 in a circumferential direction within a limited sector near the target correction azimuth. First, slowly lift from the lower end to the upper end of the correction interval, using the upward cutting part of drill bit 5 to trim the target sidewall; after reaching the upper end of the correction interval, switch to downward hole sweeping without releasing the deviation angle, and use the downward cutting part to trim the same interval in the opposite direction.

[0062] After completing a set of upward and downward hole sweeping movements, the movement stops and the load is unloaded. The brake is released, and motor 1 reverses the drive sleeve 21 to return to the neutral position. The neutral position detection element and the position detection element jointly confirm that the drill bit 5 and the casing 8 are back to coaxiality. Subsequently, multiple measuring points are set in the correction interval and its upper and lower transition sections for static re-measurement.

[0063] If the inclination angles of multiple measuring points are all below the exit threshold, and the hole axis reconstruction results show that the lateral offset and local curvature meet the project control requirements, then maintain the drill bit in the center position and resume normal straight drilling. If there are still measuring points exceeding the limits and the hole diameter, load, and circulation status allow for continued adjustment, then redetermine the target azimuth and deflection angle, and return to the correction step. If the deflection angle holding fails, the power supply margin is insufficient, the attitude data is invalid, or the hole circulation is abnormal, then stop the advance and circumferential oscillation, and perform fault handling after controlled reset to the center position when power supply and transmission conditions permit. If the reset is blocked or the power is cut off, do not force a return to center, stop construction, and handle according to the actual mechanical condition; stop hole sweeping when the allowable adjustment amount or the maximum number of repetitions is reached and still not qualified. The ground and the hole exchange commands, status, and azimuth data through the configured communication channel. When communication is interrupted, the ground stops the advance and circumferential oscillation.

[0064] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are 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 drill bit for correcting deviation during drilling in deep overburden layers, characterized in that, The system includes a casing, drill bit, motor, drive screw, transmission sleeve, pin, kingpin, directional measuring device, and battery. The swing connection of the drill bit extends into the lower end of the casing and is hinged to the casing via a transverse kingpin. The motor is connected to the drive screw, which is threadedly connected to the transmission sleeve. The transmission sleeve slides axially along the casing via a guide fixed to the casing. The transmission sleeve has a transverse compensation groove. The pin is fixed to the swing connection, parallel to and offset from the kingpin, and extends into the transverse compensation groove, engaging with its two opposing pressure-bearing sidewalls. The transmission chain from the motor to the transmission sleeve has a retaining mechanism. The drill bit has upward and downward cutting working parts. The motor, battery, and directional measuring device are located inside the casing, and the battery connects to the motor and the directional measuring device.

2. The drilling bit for correcting deviation during drilling in deep overburden layers according to claim 1, characterized in that, The drive screw is axially positioned by the support bearing, and the guide and transmission sleeve form a keyway or guide rail moving pair; the transverse compensation groove extends in the direction perpendicular to the axial direction of the sleeve in the swing plane, and the effective stroke in the groove covers the transverse displacement of the pin within the allowable deflection angle, and the pin is provided with axial anti-disengagement limit.

3. The drilling bit for correcting deviation during drilling in deep overburden layers according to claim 1, characterized in that, The drive screw and the transmission sleeve form a self-locking trapezoidal thread pair. The retaining mechanism includes the thread pair and a normally closed braking part on the motor output transmission chain. The transmission sleeve is equipped with a position detection element, and the sleeve is equipped with a neutral position detection element. The braking part is released when the angle is adjusted and closed when it is in position or when power is lost.

4. A drilling bit for correcting deviation during drilling in deep overburden layers according to claim 1, characterized in that, The upper channel section inside the casing is connected to the lower channel section that rotates with the drill bit via a flexible connection section, forming a central channel; the main pin consists of two coaxial short shaft sections placed on both sides of the central channel.

5. A drilling bit for correcting deviation during drilling in deep overburden layers according to claim 4, characterized in that, The motor and drive screw are located on one side of the central channel, while the battery and inclinometer are located in a sealed cavity on the other side. The inclinometer includes an acceleration detection module, an angular velocity detection module, and a control module, which are connected to the ground control device via a sealed signal interface.

6. A drilling bit for correcting deviation during drilling in deep overburden layers according to claim 1, characterized in that, The upward cutting working part is located on the upper shoulder surface and adjacent side surface of the drill bit, and the downward cutting working part is located on the lower end face and adjacent side surface of the drill bit; the swing connection part and the casing are provided with a swing displacement gap and a mechanical limiting part.

7. A construction method for a drill bit for correcting deviation during drilling in deep overburden layers, characterized in that, Includes the following steps: S101, adjust the drill bit to the center position, calibrate the correspondence between the inclination measuring device and the oscillating plane, and set the start-up and acceptance conditions, allowable deviation angle and hole sweeping parameters; S102, drilling in the middle position, stop rotating and wait for the attitude to stabilize before measuring the inclination to determine whether the correction start condition is met; S103, when the start-up conditions are met, stop the advance and continuous rotation and unload the load. Determine the correction interval, target orientation and deflection angle based on multi-point data, adjust the circumferential position of the casing and verify the actual deflection direction in the hole. S104, the motor drives the drill bit to deflect around the main pin via the drive screw, transmission sleeve and pin, and is held by the holding mechanism after reaching the set deflection angle; S105, maintain the deflection angle, oscillate back and forth in the circumferential direction within the limited sector centered on the target orientation, and first raise the sweep hole and then lower the sweep hole along the correction interval; S106, stop unloading, reverse drive back to center, and perform multi-point retest after confirming the center position; if the acceptance conditions are not met and there is no fault, return to S103. S107, after meeting the acceptance conditions, maintain the neutral position and resume drilling or conduct final hole acceptance.

8. A drilling bit for correcting deviation during drilling in deep overburden layers according to claim 7, characterized in that, The starting condition is that the stable and effective tilt angle measurement value exceeds the starting threshold after a preset number of times. The acceptance conditions include that the tilt angle of multiple measuring points in the correction interval does not exceed the exit threshold below the starting threshold. When there are hole position control requirements, the hole axis is reconstructed according to the hole depth, tilt angle and orientation, and the offset and local curvature are verified.

9. A drilling bit for correcting deviation during drilling in deep overburden layers according to claim 7, characterized in that, The sum of the half-angle of the hole-sweeping sector and the upper limit of the orientation control error inside the hole is less than 90°; the upper end of the correction interval crosses the starting point of the deviation and forms a transition overlap with the previous qualified hole segment; no full-circle continuous rotation is performed when maintaining the deviation angle.

10. A drilling bit for correcting deviation during drilling in deep overburden layers according to claim 7, characterized in that, The target displacement of the transmission sleeve is determined according to the calibrated displacement and deflection angle relationship. The deflection angle of each stage meets the constraints of the available space in the hole. The deflection angle is only increased after the hole is formed and the newly added space is verified. The current, position, power supply and attitude are monitored during the angle adjustment and hole sweeping. When a preset fault occurs, the advance, circumferential swing and unloading are stopped.

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