Deep overburden borehole directional adjustment drill bit and construction method

Abstract

The application discloses a deep overburden layer drilling directional adjusting drill bit and a construction method, and belongs to the technical field of geotechnical engineering drilling equipment. A casing is connected with a swing drill bit seat through a two-degree-of-freedom supporting torque transmission mechanism, a circumferential axial driving unit is connected with the swing drill bit seat through a rotation angle, transverse sliding and axial elastic compensation, and a controller is connected with an inclinometer, an actual stroke and load detection component and a motor. In construction, the actual measured stroke is corrected, and the relative attitude of the drill bit is reconstructed, the casing attitude is predicted according to the common in-place time, the driving reference is generated according to the response delay of each road, and the dynamic orientation, hole centering drilling and fixed relative angle hole sweeping are switched according to the construction instruction. The scheme is used for drill bit pointing adjustment and segmented hole repair in rotary drilling.

Description

Technical Field

[0001] This invention belongs to the field of drilling equipment and drilling trajectory control technology in geotechnical engineering, specifically relating to a directional adjustment drill bit and construction method for drilling in deep overburden layers. Background Technology

[0002] Thick overburden layers are typically composed of alternating materials such as sand, clay, gravel, and localized boulders. During drilling, the drill bit rotates with the drill string and cuts through the formation under drilling pressure. When the drill bit encounters different densities, particle sizes, or inclined soft-hard interfaces on both sides, the cutting resistance in each direction is inconsistent, easily causing the drill bit axis to deviate from its designed trajectory. As the hole depth increases, local deviations accumulate, forming horizontal offsets that affect subsequent drilling tool passage, pile driving, grouting, or seepage prevention construction.

[0003] The basic idea of ​​active directional drilling is to create a controllable tilt of the drill bit relative to the rotating casing while the drill string continues to rotate, and to ensure that this tilt points in the target direction in the fixed formation coordinate system. If multiple circumferentially distributed axial drive mechanisms are used to jointly drive the same oscillating drill bit holder, each drive mechanism must continuously change its stroke according to the rotation phase of the drill string, so that the deflection direction of the drill bit relative to the casing constantly changes, and the combined drill bit axis maintains the target orientation in the formation coordinate system.

[0004] US Patent 20200362637A1 and its authorized text US11396775B2 disclose a rotary guidance scheme that maintains the drill bit's tilt direction relative to the formation stable during drill bit rotation using a motor, transmission screw, and tilting mechanism. This type of technology demonstrates that multi-actuator and screw drives can be used for active orientation during rotation. However, for synchronous control under the combined influence of the attitude differences between the upper inclinometer and the lower independently oscillating drill bit, the consistency of multiple actual strokes, and the response delays of each drive, it is still necessary to establish corresponding measurement and control relationships based on the specific mechanical structure.

[0005] Chinese patent CN110043188B discloses an offset guiding mechanism for a static directional rotary steerable drilling tool, which forms the offset through a motor and a helical telescopic mechanism in a non-rotating outer cylinder; US patent US20160108679A1 discloses an active tilting structure for an articulated drill bit; US patent US6837315B2 relates to the swing support, torque transmission, and sealing structure of rotary steerable drilling tools. These solutions address the issues of offset, articulation, and torque transmission, respectively. However, drilling through deep overburden formations requires simultaneously coordinating two-degree-of-freedom swing bearing, multi-path axial drive, flushing channels, and actual stroke feedback within the same rotating casing during drilling.

[0006] When six or more drive units are connected to the same rigid oscillating drill bit holder, the end angles and lateral displacements of each connection point in the two-dimensional oscillation are not entirely the same. If uncompensated rigid connecting rods are used between the drive screw and the drill bit holder, even if each motor issues theoretically compatible displacement commands, geometric locking or additional internal forces may occur due to machining errors, assembly errors, elastic deformation, thermal deformation, and differences in response speed. Therefore, it is necessary to set angle, lateral displacement, and finite axial elastic compensation at the connection ends, and to verify the multi-drive status through actual stroke and axial load testing.

[0007] On the other hand, the inclinometer is positioned above the motor and rotates with the casing as a whole. It directly measures the attitude of the upper casing, while the drill bit can also oscillate in two dimensions relative to the casing. If only the inclinometer results from the upper part are used without combining them with the actual strokes of the lower drive units to reconstruct the relative attitude of the drill bit, the complete orientation of the drill bit in the fixed coordinate system of the formation cannot be obtained. At the same time, different motors, screws, and connecting mechanisms have different response delays. When the drill string rotates, this delay will be converted into tool face phase error, preventing the various drives from reaching the required geometric position at the same physical moment.

[0008] Furthermore, although dynamic orientation and borehole enlargement can share the same oscillation mechanism, the control objectives of the two modes are different. Dynamic orientation requires continuously changing the relative deflection angle as the drill string rotates, ensuring the drill bit axis maintains the target orientation in the fixed formation coordinate system; borehole enlargement, on the other hand, requires maintaining a fixed non-zero relative deflection angle in the drill string coordinate system, so that the deflection direction rotates with the drill string to form a borehole envelope. If the two control relationships are mixed, it can easily lead to orientation failure or unintended borehole enlargement.

[0009] Therefore, in order to address the above-mentioned shortcomings, this invention combines a two-degree-of-freedom load-bearing torsion transmission mechanism with a common swing center, circumferential multi-path axial drive, connection end compensation, actual stroke and load feedback, lower drill bit attitude reconstruction, branch response delay compensation at the common arrival moment, and controlled switching of three construction modes to achieve directional adjustment, deviation correction, and hole repair in drilling in deep overburden layers. Summary of the Invention

[0010] To address the aforementioned technical problems in existing technologies, this invention proposes a directional adjustment drill bit and construction method for drilling deep overburden layers, overcoming the shortcomings of existing technologies. This invention addresses the issues of multi-drive geometric compatibility, attitude measurement position differences, and response delay in rotary drilling of oscillating drill bits by proposing a directional adjustment drill bit with compensation connections and actual stroke feedback, and organizing the references of each drive path based on a common arrival time.

[0011] To achieve the above objectives, the present invention adopts the following technical solution: A directional adjustment drill bit for drilling deep overburden layers includes a casing, a drill bit, a oscillating drill bit holder, a two-degree-of-freedom support and torque transmission mechanism, circumferentially distributed drive units, an inclinometer, a battery, and an in-hole controller. The casing is connected to the drill rod, the drill bit is connected to the oscillating drill bit holder, and the two-degree-of-freedom support and torque transmission mechanism connects the casing and the oscillating drill bit holder, with their two oscillation axes intersecting at a common oscillation center. Each drive unit includes a motor, a drive screw connected to the motor and outputting along the casing axis, a compensation connection assembly connecting the output end of the drive screw to the oscillating drill bit holder, and an actual axial travel detection component and an axial load detection component. The compensation connection assembly has a angular connection, a lateral sliding connection, and a bidirectional axial elastic connection. The inclinometer, travel detection component, and load detection component are connected to the input end of the in-hole controller, the output end of the in-hole controller is connected to each motor, and the battery is connected to each power-consuming component.

[0012] Preferably, there are six drive units, arranged at 60° intervals along the circumference of the sleeve, forming three pairs of opposing drive units.

[0013] Preferably, the drive screw is a ball screw assembly or roller screw assembly with axial support, anti-rotation guide and end limit; the compensation connection assembly includes a ball joint, a transverse compensation slider that is slidably connected to the compensation surface of the shoulder of the oscillating drill bit seat, and a bidirectional axial elastic connector.

[0014] Preferably, the two-degree-of-freedom support torsion transmission mechanism includes a spherical support and a universal torsion transmission structure; the annular intermediate part of the universal torsion transmission structure is connected to the casing-side connector and the oscillating drill bit seat-side connector through two sets of opposite short pins, the axes of the two sets of short pins are orthogonal, and their intersection point coincides with the center of the spherical support, and a flow passage space is left in the middle of the annular intermediate part.

[0015] Preferably, the upper flushing channel inside the casing is connected to the lower flushing channel inside the swing drill bit seat via a swingable sealed connection near the common swing center; the inclinometer includes a three-axis gyroscope and a three-axis accelerometer, and the inclinometer, battery and borehole controller are located in a sealed cavity isolated from the flushing channel.

[0016] Preferably, the in-hole controller is equipped with a synchronous acquisition module, an attitude reconstruction module, and a drive scheduling module, which sequentially performs synchronous acquisition of attitude, stroke, and load, correction of stroke zero position and load deformation, reconstruction of relative attitude according to drive installation coordinates and calculation of stroke residual, and generation of drive reference according to the predicted casing attitude and response delay of each path at the common arrival time.

[0017] The construction method using the above-mentioned directional adjustment drill bit includes the following steps: S1, calibrate the installation coordinates, zero position, load deformation relationship and response delay of the drive unit, and calibrate the installation attitude, heading and time reference of the inclinometer; S2, establish the borehole coordinates, depth measurement and design trajectory benchmarks, center the drill bit and perform trial drilling; S3, during rotary feed, synchronously acquires casing attitude, actual stroke and axial load, corrects stroke, reconstructs drill bit relative attitude and calculates stroke consistency residual; S4. Determine the target drill bit axis in the formation fixed coordinate system based on the position and tilt deviation of the segmented measured hole trajectory relative to the design trajectory. S5 predicts the casing attitude at the moment of common arrival, transforms the target axis to the drill string coordinate system, generates the target stroke of each path in a unified manner and compensates for the response delay of each path. S6 performs dynamic orientation when the attitude is valid, the residual and the execution parameters are within the calibration range. If the limit is exceeded, the swing angle is reduced, the rotation speed or feed rate is reduced, and the process is paused if it cannot be recovered. S7, reduce the rotation speed and feed rate according to the hole sweeping command, maintain a fixed non-zero relative deviation angle in the drill coordinate system, stop the phase compensation to counteract the casing rotation, and lift or lower the hole sweeping. S8, after hole sweeping, limit the swing angle change rate to return to center, and switch to drilling mode after confirming the return to center with actual stroke and reconstructed posture; S9, the hole trajectory and diameter are re-measured in segments according to depth, and the hole trajectory is verified by an independent or calibrated hole trajectory measurement system after the hole is completed.

[0018] Preferably, in step S3, the effective geometric stroke is obtained by subtracting the zero position and the load and temperature deformation correction amount from the measured stroke. The common axial term and two tilt components are fitted based on no less than six effective geometric strokes, and the consistency between the fitting residual and the common axial term and the geometric relationship with the fixed swing center is verified.

[0019] Preferably, in step S5, the predicted time domain covers the maximum response delay and scheduling margin, and the reference execution time of the i-th path is the common arrival time minus the calibration response delay of that path, or an equivalent continuous trajectory feedforward compensation is adopted.

[0020] Preferably, the mode switching is triggered by the construction command, and the reference is initialized with the measured relative attitude at the time of switching and the swing angle change rate is limited; dynamic orientation stops when the residual continuously exceeds the limit, the heading or phase fails, the load exceeds the limit or the actuator jams, and the mode does not automatically switch to the hole sweeping mode.

[0021] The beneficial technical effects of this invention are as follows: By setting a two-degree-of-freedom support and torque transmission mechanism with a common swing center between the casing and the oscillating drill bit holder, the oscillating drill bit holder can adjust its attitude in two independent directions. At the same time, the support and torque transmission structure bears the drilling pressure, lateral support force and drilling torque, so that the attitude execution unit does not need to bear all the drilling torque.

[0022] By having at least six circumferentially distributed axial drive units work together on the oscillating drill bit holder, multiple geometric strokes can be uniformly generated according to the target two-dimensional tilt attitude. Redundant geometric measurement relationships are formed between the drive units, providing data conditions for the lower drill bit attitude reconstruction and the consistency check of multiple strokes.

[0023] By setting a compensating connection component with end rotation angle, lateral displacement and limited axial elasticity between the output end of the drive screw and the oscillating drill bit seat, the connection point can adapt to the composite displacement generated by two-dimensional oscillation, reducing the possibility of geometric locking and additional internal forces caused by uncompensated rigid connection.

[0024] The actual output state of each drive unit is obtained by linear displacement detection and axial load detection, and the elastic deformation is corrected according to the load and temperature. This allows the in-hole controller to reconstruct the relative attitude of the drill bit using the actual geometric stroke rather than simply relying on motor command pulses, providing a basis for multi-channel execution status checks.

[0025] By combining the casing attitude obtained from the upper inclinometer with the relative swing attitude obtained from the reconstruction of the actual geometric travel of the lower multi-path, the axial orientation of the drill bit in the fixed coordinate system of the formation can be obtained, thus solving the problem that the inclinometer is located above the drill bit and cannot directly represent the independent swing attitude of the lower drill bit.

[0026] By setting a common arrival time and performing advance scheduling or feedforward compensation based on the response delay calibrated by each drive unit under different load and temperature conditions, multiple drives can be synchronously positioned around the same two-dimensional target, reducing the phase deviation caused by the conversion of response time differences between different drives during drill rotation.

[0027] By defining three modes—normal drilling with centering, dynamic orientation with the target pointing in the fixed formation coordinate system, and borehole enlargement with a fixed relative deviation angle in the drill string coordinate system—and setting clear controlled switching steps, the same mechanical mechanism can undertake different construction tasks. At the same time, it avoids measurement failure or actuator malfunction being mistakenly interpreted as the trigger condition for entering the borehole sweeping mode.

[0028] By setting execution boundaries for stroke consistency residuals, displacement, speed, acceleration, load, temperature rise, and available power, and by adopting processing methods such as speed reduction, swing angle reduction, or pause when exceeding the limits, the control target is constrained by the actual mechanical following capability, and the execution capability verification is not replaced by increasing the sampling frequency.

[0029] By retesting the segmented hole trajectory and independently verifying the final hole, the instantaneous pointing error inside the controller is separated from the acceptance of the engineering hole trajectory, which can avoid directly determining the overall hole accuracy as qualified based solely on the drill bit tip angle or the deviation displayed by the controller at a certain moment. Attached Figure Description

[0030] Figure 1This is a schematic diagram of the longitudinal structure in the deep overburden drilling directional adjustment drill bit and construction method of the present invention.

[0031] Figure 2 This is a flowchart of the construction method in the deep overburden drilling directional adjustment drill bit and construction method of the present invention.

[0032] Reference numerals: 1-Motor; 2-Drive screw; 3-Compensation connection assembly; 4-Two-degree-of-freedom support and torque transmission mechanism; 5-Drill bit; 6-Inclinometer; 7-Battery; 8-Casing; 9-In-hole controller; 10-Oscillating drill bit holder. Detailed Implementation

[0033] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments: Example

[0034] like Figure 1-2 As shown, a directional adjustment drill bit for drilling deep overburden layers includes a casing 8, a drill bit 5, a oscillating drill bit holder 10, a two-degree-of-freedom support and torque transmission mechanism 4, circumferentially distributed drive units, an inclinometer 6, a battery 7, and an in-hole controller 9. The casing 8 is connected to the drill rod, the drill bit 5 is connected to the oscillating drill bit holder 10, and the two-degree-of-freedom support and torque transmission mechanism 4 connects the casing 8 and the oscillating drill bit holder 10, with their two oscillating axes intersecting at a common oscillating center. Each drive unit includes a motor 1, a drive screw 2 that is driven by the motor 1 and outputs along the axial direction of the casing 8, a compensation connection assembly 3 that connects the output end of the drive screw 2 to the oscillating drill bit holder 10, and an actual axial stroke detection component and an axial load detection component. The compensation connection assembly 3 is provided with a corner connection, a lateral sliding connection, and a bidirectional axial elastic connection. The inclinometer 6, the stroke detection component, and the load detection component are connected to the input end of the in-hole controller 9, the output end of the in-hole controller 9 is connected to each motor 1, and the battery 7 is connected to each power-consuming component.

[0035] Preferably, there are six drive units, arranged at 60° intervals along the circumference of the sleeve 8, forming three pairs of opposing drive units.

[0036] Preferably, the drive screw 2 is a ball screw assembly or roller screw assembly with axial support, anti-rotation guide and end limit; the compensation connection assembly 3 includes a ball joint, a transverse compensation slider that is slidably connected to the shoulder compensation surface of the oscillating drill bit seat 10, and a bidirectional axial elastic connector.

[0037] Preferably, the two-degree-of-freedom support torsion transmission mechanism 4 includes a spherical support and a universal torsion transmission structure; the annular intermediate part of the universal torsion transmission structure is connected to the sleeve 8 side connector and the swing drill bit seat 10 side connector through two sets of opposite short pins respectively. The axes of the two sets of short pins are orthogonal, and their intersection point coincides with the center of the spherical support. A flow passage space is left in the middle of the annular intermediate part.

[0038] Preferably, the upper flushing channel inside the casing 8 is connected to the lower flushing channel inside the swing drill bit seat 10 via a swingable sealed connection near the common swing center; the inclinometer 6 includes a three-axis gyroscope and a three-axis accelerometer, and the inclinometer 6, battery 7 and borehole controller 9 are located in a sealed cavity isolated from the flushing channel.

[0039] Preferably, the in-hole controller 9 is equipped with a synchronous acquisition module, an attitude reconstruction module, and a drive scheduling module, which sequentially performs synchronous acquisition of attitude, stroke, and load, correction of stroke zero position and load deformation, reconstruction of relative attitude according to drive installation coordinates and calculation of stroke residual, and generation of drive reference according to the predicted attitude of the sleeve 8 at the common arrival time and the response delay of each path.

[0040] The construction method using the above-mentioned directional adjustment drill bit includes the following steps: S1, calibrate the installation coordinates, zero position, load deformation relationship and response delay of the drive unit, and calibrate the installation attitude, heading and time reference of the inclinometer 6; S2, establish the borehole coordinates, depth measurement and design trajectory benchmarks, center the drill bit and perform trial drilling; S3, during rotary feed, synchronously acquire the casing 8 attitude, actual stroke and axial load, correct the stroke, reconstruct the relative attitude of the drill bit and calculate the stroke consistency residual; S4. Determine the target drill bit axis in the formation fixed coordinate system based on the position and tilt deviation of the segmented measured hole trajectory relative to the design trajectory. S5, predicts the attitude of casing 8 at the common arrival time, transforms the target axis to the drill coordinate system, generates the target stroke of each path in a unified manner and compensates for the response delay of each path. S6 performs dynamic orientation when the attitude is valid, the residual and the execution parameters are within the calibration range. If the limit is exceeded, the swing angle is reduced, the rotation speed or feed rate is reduced, and the process is paused if it cannot be recovered. S7, reduce the rotation speed and feed rate according to the hole sweeping command, maintain a fixed non-zero relative deviation angle in the drill coordinate system, stop the phase compensation to offset the rotation of casing 8, and lift or lower the hole sweeping. S8, after hole sweeping, limit the swing angle change rate to return to center, and switch to drilling mode after confirming the return to center with actual stroke and reconstructed posture; S9, the hole trajectory and diameter are re-measured in segments according to depth, and the hole trajectory is verified by an independent or calibrated hole trajectory measurement system after the hole is completed.

[0041] Preferably, in step S3, the effective geometric stroke is obtained by subtracting the zero position and the load and temperature deformation correction amount from the measured stroke. The common axial term and two tilt components are fitted based on no less than six effective geometric strokes, and the consistency between the fitting residual and the common axial term and the geometric relationship with the fixed swing center is verified.

[0042] Preferably, in step S5, the predicted time domain covers the maximum response delay and scheduling margin, and the reference execution time of the i-th path is the common arrival time minus the calibration response delay of that path, or an equivalent continuous trajectory feedforward compensation is adopted.

[0043] Preferably, the mode switching is triggered by the construction command, and the reference is initialized with the measured relative attitude at the time of switching and the swing angle change rate is limited; dynamic orientation stops when the residual continuously exceeds the limit, the heading or phase fails, the load exceeds the limit or the actuator jams, and the mode does not automatically switch to the hole sweeping mode. Example

[0044] like Figure 1-2 As shown, the mechanical structure, attitude reconstruction, dynamic orientation, shunt delay compensation, and mode switching principles of the directional adjustment drill bit are further explained.

[0045] The casing 8 is a drill string housing that connects to the drill pipe and rotates synchronously with it. Its upper end is equipped with a torsion-bearing connection that mates with the drill pipe. The casing 8 retains an axial passage for flushing media. The battery 7, the inclinometer 6, and the in-hole controller 9 are located in a sealed area isolated from the flushing media. At least six motors 1 and corresponding drive screws 2 are distributed circumferentially along the casing 8, with their output directions substantially parallel to the axis of the casing 8.

[0046] The oscillating drill bit holder 10 is located at the lower part of the casing 8, and its lower end is torsionally connected to the drill bit 5. A two-degree-of-freedom support and torque transmission mechanism 4 is provided between the oscillating drill bit holder 10 and the casing 8. This mechanism includes a spherical support structure and a universal torque transmission structure with two mutually orthogonal oscillating degrees of freedom. The center of the spherical support and the intersection of the two sets of oscillating axes are located by a common center. The drilling pressure and the main lateral support load are transmitted through the spherical support, and the torque of the casing 8 is transmitted to the oscillating drill bit holder 10 and the drill bit 5 through the universal torque transmission structure.

[0047] The two-degree-of-freedom support and torque transmission mechanism 4 can adopt an annular cross-shaft structure with a flow passage space in the middle. One set of relatively short pins connects the annular intermediate part and the casing-side connector, and the other set of relatively short pins connects the annular intermediate part and the drill bit seat-side connector. The axes of the two sets of pins are orthogonal to each other and pass through a common swing center O. The two sets of short pins are located outside the flushing channel, so it is not necessary to use a solid long pin to cross the central channel.

[0048] Each motor 1 drives a corresponding drive screw 2 via a gear reduction mechanism or other transmission mechanism. The drive screw 2 adopts a ball screw or roller screw structure with axial support, anti-rotation guidance, and stroke limit, converting the rotational motion of the motor 1 into axial reciprocating output. Each output end is connected to the connecting shoulder of the oscillating drill bit holder 10 through a compensation connection assembly 3.

[0049] The compensating connection assembly 3 includes a ball joint, a compensating slider, and a finite-stiffness axial elastic connection. The ball joint allows the connection end to rotate with the oscillating drill bit holder 10, the compensating slider allows the connection point to move laterally within a small range within the shoulder compensation surface, and the axial elastic connection absorbs minor stroke differences caused by manufacturing, assembly, load, and temperature variations in each drive unit. This reduces the risk of geometric locking when six or more axial actuators are connected together in an uncompensated rigid manner to a two-dimensional oscillating rigid body; the compensating stroke and elastic deformation must still be within the calibrated range, and the elastic connection cannot replace load limitation.

[0050] Each drive unit is equipped with an actual stroke detection component and an axial load detection component. Temperature correction uses the temperature measurement value of the corresponding connection point. The displacement detection component is connected across the fixed end and the actual axial output end to directly obtain the output stroke; the load detection component is set on the output load-bearing path to obtain the tensile and compressive loads. The in-hole controller 9 uses the motor current as auxiliary abnormal information, but attitude reconstruction prioritizes the actual displacement and corrects the connection elastic deformation according to the load and temperature calibration relationship.

[0051] Establish a drill string coordinate system B that rotates with the casing 8, and a coordinate system E that is fixed relative to the formation. Let the actual stroke of the i-th drive unit be li, the zero-position stroke be li0, and the deformation correction due to load and temperature be di. Then, the effective stroke si for geometric reconstruction of this drive unit is: si = li - li0 - di (1) Let the coordinates of the installation plane of the i-th drive unit's point of action in the drill string coordinate system B be (xi, yi), and let the two inclination slopes of the drill bit's 5-axis in system B be p and q, with the common axial term being c. Under the condition that the compensation connection points satisfy the planar approximation relationship, the effective geometrical travel of each path satisfies: The common axial term c is a term that varies with attitude, determined by the fixed swing center and shoulder geometry, and is not an independent axial translational degree of freedom; its relationship c(p,q) is determined by assembly geometry and attitude calibration. Equation (2) is limited to the calibrated connection point plane model and swing angle range. When the lateral slip causes changes in the action coordinates, the actual measurement calibration mapping is used, and the nominal installation coordinates cannot be used for arbitrary swing angles.

[0052] si = c - xi p - yi q (2) Equation (2) converts the same two-dimensional drill bit attitude into a geometric relationship that is satisfied by all drive units. The entire effective stroke is categorized into a vector s, and the coefficients in each row equal to (1, -xi, -yi) are categorized into a matrix M. A weight matrix W, determined based on the calibration variance of each sensor, is set. Weighted least squares can then be used to calculate the common axial term and the two tilt components: (ĉ, p̂, q̂)ᵀ = (Mᵀ WM)⁻¹ Mᵀ W s (3) Based on the ĉ, p̂, and q̂ obtained from equation (3), the theoretical geometric travel of each route is recalculated and compared with the measured effective travel to form the travel consistency residual: r = s - M(ĉ, p̂, q̂)ᵀ (4) In the case of six-way drive, six stroke measurements are used to fit three parameters, allowing additional measurement degrees of freedom to check whether the same rigid oscillation posture can explain the entire stroke. When the residual continuously exceeds the threshold determined based on health calibration, measurement uncertainty, and permissible structural deformation, the in-hole controller 9 stops increasing the oscillation angle and requests a reduction in speed or a pause. Residual abnormalities only indicate that the current multi-way stroke cannot be fully explained by the common oscillation model, and do not determine the specific faulty component based on a single residual value.

[0053] The stroke residual cannot detect the zero-point offset that occurs in all channels, nor can it independently prove the absolute accuracy of the drill bit's pointing. Furthermore, compare the difference between the fitted common axial term and the calibration c(p,q), and verify the zero-point, load, and attitude references. Matrix M must have full column rank; stop using the reconstruction results if the sensor malfunctions or the geometric model exceeds the calibration range.

[0054] The axial unit vector of drill bit 5 in drill string coordinate system B is determined by p and q: nB = (p, q, 1) / √(1+p²+q²) (5) The inclinometer 6 includes a three-axis gyroscope and a three-axis accelerometer, and establishes a heading reference before entering the borehole. The borehole controller 9 determines the coordinate transformation matrix REB based on the casing 8 attitude obtained by the inclinometer 6, transforms the reconstructed nB to the formation fixed coordinate system E, and obtains the formation axis of the drill bit 5. nE = REB nB (6) The inclinometer 6 directly measures the attitude of the upper casing. The coordinate transformation in equation (6) should take into account the installation deviation angle of the inclinometer and its calibration relationship to the reference section of the swing center. When the casing is bent or the connection is loose and exceeds the allowable error of this relationship, the upper inclinometer value cannot be directly used as the lower reference attitude. The three-axis gyroscope and accelerometer do not independently provide drift-free absolute heading. The heading must be initialized by the borehole reference and checked in segments; the acceleration data under rotational vibration must be processed within the applicable calibration range. Dynamic orientation is stopped when the heading or phase fails. When near vertical, the tilt component or vector error is used to represent the drill bit direction.

[0055] During dynamic orientation, the target drill bit axis nE* is given in the formation fixed coordinate system E. The in-hole controller 9 selects the common arrival time T and predicts the attitude REB(T) of the casing 8 at that time, converting the target axis into the target relative axis in the drill string coordinate system at time T: uB* = REB(T)ᵀ nE* (7) The target tilt slopes p* and q* are obtained from the components of uB*: p* = uB,x* / uB,z*; q* = uB,y* / uB,z* (8) If the effective radius of the i-th driving unit is ri and the circumferential installation orientation is φi, then under the equivalent connected plane model, its target geometric travel can be expressed as: si* = c(p*,q*) - ri[p* cosφi + q* sinφi] (9) Equation (9) is the effective geometric travel reference; the drive end reference also needs to be back to zero position and the deformation correction amount determined according to the current load and temperature, and the actual output should be used for feedback correction. All references should meet the same swing geometry relationship and load limits of each path, and the travel cannot be set arbitrarily.

[0056] Taking six drive units as an example, their installation orientations can be 0°, 60°, 120°, 180°, 240° and 300° respectively. For each rotation of the casing 8, the target differential stroke of each drive unit changes with the actual rotation phase period, causing the deflection direction of the drill bit 5 relative to the casing 8 to change continuously, while the formation axis of the drill bit 5 obtained by equation (6) remains near the target direction.

[0057] Different motors 1, drive screws 2, transmission backlash, and loads will cause different response times. The response delay τi for the i-th drive is obtained through bench calibration. The in-hole controller 9, targeting the common arrival time T, does not simultaneously send uncompensated commands of the same phase to all drive units, but instead sets the reference execution time of the i-th drive as follows: ti,cmd = T - τi (10) Equation (10) is used within the calibrated speed, load, and temperature range. The prediction time domain must cover the maximum delay and the calculated scheduling time, so that the execution time is not earlier than the current schedulable time. During continuous rotation, compatible trajectories are continuously generated and the actual tracking error is checked. If there is amplitude attenuation or response change that cannot be explained by a single delay, the speed or swing angle is reduced and the verification is repeated. It is not possible to simply increase the lead amount.

[0058] Under the simplified working condition of near-vertical, uniform rotation and approximately the same radius of action, let the relative swing angle of drill bit 5 be θ, the radius of action be r, and the angular velocity of the drill string be ω. Then, the single-path stroke amplitude a after deducting the common mode term and the theoretical maximum axial velocity and acceleration can be approximately expressed as: a = r tanθ; vmax ≈ a|ω|; amax ≈ aω² (11) Equation (11) is used to determine whether the drive screw 2 has sufficient speed and acceleration capability at a given rotational speed and target swing angle. Actual control also requires checking axial load, temperature rise, and available power of battery 7. If all execution boundaries cannot be met, the in-hole controller 9 requests speed reduction, feed reduction, or target swing angle reduction. Reducing drill speed, feed, and pausing are executed by the construction equipment. The status of the in-hole controller 9 and the construction instructions must interact through the supporting information interface; when effective interaction conditions are not available, drilling stop reading and segmented setting are used, and real-time automatic ground adjustment is not claimed. When power is cut off or jammed, it is not assumed that the screw will automatically return to center. Construction is stopped and the mechanism is checked before resuming.

[0059] This invention sets three working modes. In the normal drilling mode, the drill bit 5 returns to center relative to the casing 8, and each drive maintains the corresponding zero position; in the dynamic orientation mode, the relative stroke of each drive is continuously changed according to equations (7) to (10), so that the drill bit 5 tracks the target axis in the fixed coordinate system of the formation; in the enlarged diameter drilling mode, a fixed non-zero relative tilt is maintained in the drill tool coordinate system B, and phase compensation to counteract the rotation of the casing is no longer applied, so that the deflection direction of the drill bit 5 rotates around the casing 8.

[0060] Under the geometric estimation conditions of small swing angle and temporarily neglecting hole wall deformation, let the original drill bit diameter be D0, the distance from the common swing center to the effective side cutting part be Leff, and the fixed relative deviation angle of the hole sweeping be θs. Then the geometric envelope diameter of the hole sweeping can be approximately expressed as: Ds ≈ D0 + 2 Leff sinθs (12) Equation (12) is only used for geometric estimation of the structure and the hole-sweeping space. The actual hole diameter is also affected by the drill bit's side-cutting structure, formation damage, hole-sweeping feed, and hole wall stability conditions. The final hole diameter is confirmed by the hole diameter detection results. The mode switching is triggered by a clear construction command. First, the feed and rotation speed are reduced, and then the hole returns to the center or continuously transitions to the new target according to the limited rate of change. Measurement failure, phase lockout, or actuator failure are not considered as conditions for automatically entering the enlarged hole-sweeping mode. Example

[0061] This embodiment illustrates the calibration and construction process of the six-drive structure.

[0062] Before construction, the cutting structure of drill bit 5 was selected based on the designed hole position, design trajectory, and layering data of the thick overburden layer. The assembly status of casing 8, two-degree-of-freedom support torque transmission mechanism 4, compensation connection assembly 3, and flushing channel was checked. The oscillating drill bit seat 10 was slowly oscillated in two independent directions to check for mechanical interference within the designed swing angle range. No-load and loaded reciprocating tests were performed on each motor 1 and drive screw 2.

[0063] Six drive units are arranged at equal angles, with installation orientations of 0°, 60°, 120°, 180°, 240°, and 300° respectively. The nominal radius of action at each point of action is 50 mm. The zero-position travel, actual action coordinates, displacement ratio, load offset, connection stiffness, and response delay of each path are calibrated, and the parameters are written to the in-hole controller 9. The installation angle, heading reference, and time reference of the inclinometer 6 are calibrated to ensure that attitude, displacement, load, and rotation phase data can be processed under a unified time reference.

[0064] After the drill string is lowered, the borehole coordinates and depth reference are established, the drill bit 5 is centered, and a low-parameter test drill is performed. After entering normal rotary feed, the in-hole controller 9 continuously collects the attitude data, actual stroke and axial load of the inclinometer 6, and corrects it to the effective geometric stroke according to formula (1). Then, formulas (3) and (4) are used to reconstruct the relative swing attitude of the drill bit 5 and check the consistency residual.

[0065] Assuming that the drill bit 5 needs to be tilted at 1° relative to the casing 8 under near-vertical conditions, the effective radius of each of the six drive units is 50 mm. According to equation (11), the amplitude of the single-path differential stroke is approximately 50 × tan1° = 0.873 mm. When the target's relative tilt direction is in the installation orientation of the first drive, after deducting the common axial term, the reference strokes of the six differential drives are approximately -0.873 mm, -0.436 mm, +0.436 mm, +0.873 mm, +0.436 mm, and -0.436 mm, respectively. This set of six strokes comes from the same two-dimensional target attitude, rather than being set independently.

[0066] If the drill bit rotation speed is 60 r / min, the angular velocity is approximately 2π rad / s. From equation (11), the theoretical maximum axial velocity is approximately 5.484 mm / s, and the theoretical maximum axial acceleration is approximately 34.45 mm / s². If the lead of the drive screw 2 is 2 mm / r, the corresponding peak screw speed, ignoring the transmission ratio, is approximately 164.5 r / min. The above calculations are used for preliminary checks of the actuator speed range; actual selection should also take into account load, friction, acceleration torque, impact, and reciprocating fatigue.

[0067] Assuming the equivalent response delay of a certain drive path is 12 ms under a certain operating condition, while the drill string rotation speed remains at 60 r / min, then 12 ms corresponds to a rotational phase change of approximately 4.32°. The in-hole controller 9 calculates the target attitude based on the common arrival time T, and applies an advance execution time of approximately 12 ms or equivalent feedforward compensation to this path. The other paths are compensated according to their respective calibrated response delays, so that all six paths approach the target geometric travel at the same time T.

[0068] When the segmented trajectory measurement shows that the actual hole axis has lateral offset and tilt deviation, the outer ring updates the target drill bit axis of the formation fixed coordinate system according to the difference between the designed trajectory and the actual trajectory. The in-hole controller 9 obtains the target relative attitude at the current common arrival moment through equations (7) and (8), and then generates six target strokes according to equation (9). As long as the attitude reference is valid and the consistency residual, stroke, speed, acceleration, load, temperature rise and available power are all within the allowable range, the rotational feed continues; if any constraint is not met, the rotational speed, feed or swing angle is reduced, and if it cannot be recovered, it is paused. The actual segmented trajectory comes from the hole trajectory remeasurement with depth correspondence, and cannot be replaced by the instantaneous pointing of the drill bit.

[0069] When the drill bit reaches the designed hole-cutting section and receives the enlargement and hole-cleaning command, the axial feed and rotation speed are reduced first, and the dynamic orientation mode is transitioned to the fixed relative deviation angle mode of the drill bit coordinate system according to the limited rate of change. Assuming that the original drill bit diameter D0 is 150 mm, the distance Leff from the common swing center to the effective side-cutting part is 300 mm, and the fixed relative swing angle θs is 1°, the hole-cleaning geometric envelope diameter is estimated to be approximately 160.47 mm by equation (12). This value is only used to illustrate the motion geometry and is not used as a guaranteed value for the actual hole diameter.

[0070] During the hole-sweeping process, a fixed relative deflection angle is maintained. The drill bit 5 rotates as a whole with the casing 8, forming a circumferential hole-sweeping envelope at the side-cutting area. Controlled lifting or lowering is adopted according to the formation stability. The construction record saves the swing angle, number of rotations, hole-sweeping section, torque obtained by the construction equipment, various drive loads, and slag removal status. After the hole-sweeping is completed, the rotation speed is reduced, and the drill bit returns to center according to the defined trajectory. The return to center is confirmed by the actual measured stroke of each path and the reconstructed posture. The confirmation of actual return to center is not based on the fact that the command value of motor 1 has returned to zero.

[0071] During construction, the hole trajectory and diameter are re-measured in sections according to the hole depth to correct the depth measurement benchmark, attitude drift, and axial geometric offset between the inclinometer 6 and drill bit 5. After the hole is completed, a hole trajectory measurement method that is appropriately independent from the drilling closed-loop is used for verification. If the project proposes a deviation rate target of less than one-thousandth, this indicator is only used as an acceptance target that needs to be verified by actual measurement and testing; for example, when the hole depth is 120 m, a final hole horizontal deviation of less than 120 mm corresponds to a final hole deviation rate of less than 0.001, but this geometric conversion cannot be directly replaced by the drill bit 5 tip angle at a certain moment.

[0072] Taking a 1° swing angle, an effective radius of 50 mm, and the target's relative tilt direction coinciding with the installation orientation of the first channel as an example, the reference travel for the six-channel differential is shown in the table below: Route 1 0° -0.873 Route 2 60° -0.436 Route 3 120° +0.436 Route 4 180° +0.873 Route 5 240° +0.436 Route 6 300° -0.436 The above specific embodiments further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above 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 directional adjustment drill bit for drilling deep overburden layers, characterized in that, The system includes a casing, drill bit, oscillating drill bit holder, two-degree-of-freedom support and torque transmission mechanism, circumferentially distributed drive units, inclinometer, battery, and in-hole controller. The casing is connected to the drill pipe, the drill bit is connected to the oscillating drill bit holder, and the two-degree-of-freedom support and torque transmission mechanism connects the casing and the oscillating drill bit holder, with their two oscillation axes intersecting at a common oscillation center. Each drive unit includes a motor, a drive screw connected to the motor and outputting along the casing axis, a compensation connection assembly connecting the output end of the drive screw to the oscillating drill bit holder, and actual axial travel detection components and axial load detection components. The compensation connection assembly has corner connection, lateral sliding connection, and bidirectional axial elastic connection. The inclinometer, travel detection components, and load detection components are connected to the input end of the in-hole controller, the output end of the in-hole controller is connected to each motor, and the battery is connected to each power-consuming component.

2. The directional adjustment drill bit for drilling deep overburden layers according to claim 1, characterized in that, There are six drive units, arranged at 60° intervals along the circumference of the bushing, forming three pairs of opposing drive units.

3. The directional adjustment drill bit for drilling deep overburden layers according to claim 1, characterized in that, The drive screw is a ball screw assembly or roller screw assembly with axial support, anti-rotation guide and end limit; the compensation connection assembly includes a ball joint, a transverse compensation slider that is slidably connected to the compensation surface of the shoulder of the oscillating drill bit seat, and a bidirectional axial elastic connector.

4. The directional adjustment drill bit for drilling deep overburden layers according to claim 1, characterized in that, The two-degree-of-freedom support and torsion transmission mechanism includes a spherical support and a universal torsion transmission structure. The annular intermediate part of the universal torsion transmission structure is connected to the casing-side connector and the oscillating drill bit seat-side connector through two sets of opposite short pins. The axes of the two sets of short pins are orthogonal, and their intersection point coincides with the center of the spherical support. A flow passage space is left in the middle of the annular intermediate part.

5. The directional adjustment drill bit for drilling deep overburden layers according to claim 1, characterized in that, The upper flushing channel inside the casing is connected to the lower flushing channel inside the swing drill bit seat via a swingable sealed connection near the common swing center; the inclinometer includes a three-axis gyroscope and a three-axis accelerometer, and the inclinometer, battery and in-hole controller are located in a sealed cavity isolated from the flushing channel.

6. The directional adjustment drill bit for drilling deep overburden layers according to claim 1, characterized in that, The in-hole controller is equipped with a synchronous acquisition module, an attitude reconstruction module, and a drive scheduling module. It sequentially performs synchronous acquisition of attitude, stroke, and load, corrects stroke zero position and load deformation, reconstructs relative attitude according to drive installation coordinates and calculates stroke residual, and generates drive reference based on the predicted casing attitude and response delay of each path at the common arrival time.

7. A construction method for a directional adjustable drill bit for drilling deep overburden layers, characterized in that, Includes the following steps: S1, calibrate the installation coordinates, zero position, load deformation relationship and response delay of the drive unit, and calibrate the installation attitude, heading and time reference of the inclinometer; S2, establish the borehole coordinates, depth measurement and design trajectory benchmarks, center the drill bit and perform trial drilling; S3, during rotary feed, synchronously acquires casing attitude, actual stroke and axial load, corrects stroke, reconstructs drill bit relative attitude and calculates stroke consistency residual; S4. Determine the target drill bit axis in the formation fixed coordinate system based on the position and tilt deviation of the segmented measured hole trajectory relative to the design trajectory. S5 predicts the casing attitude at the moment of common arrival, transforms the target axis to the drill string coordinate system, generates the target stroke of each path in a unified manner and compensates for the response delay of each path. S6 performs dynamic orientation when the attitude is valid, the residual and the execution parameters are within the calibration range. If the limit is exceeded, the swing angle is reduced, the rotation speed or feed rate is reduced, and the process is paused if it cannot be recovered. S7, reduce the rotation speed and feed rate according to the hole sweeping command, maintain a fixed non-zero relative deviation angle in the drill coordinate system, stop the phase compensation to counteract the casing rotation, and lift or lower the hole sweeping. S8, after hole sweeping, limit the swing angle change rate to return to center, and switch to drilling mode after confirming the return to center with actual stroke and reconstructed posture; S9, the hole trajectory and diameter are re-measured in segments according to depth, and the hole trajectory is verified by an independent or calibrated hole trajectory measurement system after the hole is completed.

8. The construction method of a directional adjustment drill bit for drilling deep overburden layers according to claim 7, characterized in that, In step S3, the effective geometric stroke is obtained by subtracting the zero position, load, and temperature deformation correction from the measured stroke. The common axial term and two tilt components are fitted based on no less than six effective geometric strokes, and the consistency between the fitting residual and the common axial term and the geometric relationship with the fixed swing center is verified.

9. A construction method for a directional adjustable drill bit for drilling deep overburden layers according to claim 7, characterized in that, The prediction time domain coverage of step S5 includes the maximum response delay and scheduling margin. The reference execution time of the i-th path is the common arrival time minus the calibration response delay of that path, or an equivalent continuous trajectory feedforward compensation is adopted.

10. A construction method for a directional adjustable drill bit for drilling deep overburden layers according to claim 7, characterized in that, The mode switching is triggered by the construction command. The reference is initialized with the measured relative attitude at the time of switching and the rate of change of the swing angle is limited. Dynamic orientation stops when the residual exceeds the limit, the heading or phase fails, the load exceeds the limit or the actuator jams, and it does not automatically switch to the hole sweeping mode.

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