A step variable diameter and vibration coordinated coal body drilling pressure relief method and system

Abstract

The application discloses a step-variable-diameter and vibration coordinated coal body drilling pressure relief method and system, which utilizes a step-variable-diameter drill bit to perform sequential drilling, the step-variable-diameter drill bit has a three-stage ladder structure with a diameter gradually increasing along a drilling direction, and through the three-stage ladder structure, guiding and positioning and micro-crack inducing work, hole expanding and stress reforming work, and long-range guiding and pressure relief space forming work are sequentially completed; axial and circumferential vibrations are generated through a vibration generating unit integrated at the rear of the drill bit, to assist in breaking rock mass, promote rock debris migration and prevent or remove drill pipe jamming; an intelligent processor integrated at the rear of the drill bit is used to collect drilling parameters in real time, and based on preset system rules, multi-modal data fusion and decision adjustment are performed, a jamming type is identified, and corresponding vibration modes and drilling parameter adjustment instructions are triggered. The step-variable-diameter structure in the application guides sequential release of coal body stress, prevents hole deviation and jamming, and improves drilling quality.

Description

Technical Field

[0001] This invention belongs to the field of coal borehole pressure relief technology, specifically relating to a method and system for coal borehole pressure relief using a stepped diameter variation and vibration coordination. Background Technology

[0002] In existing technologies, coal stress relief is one of the key technologies for preventing dynamic disasters in coal mines. It involves releasing coal stress through drilling to reduce disaster risk. Traditional stress relief methods often use ordinary drill bits for single-diameter drilling, but these methods have the following shortcomings:

[0003] (1) The drilling efficiency is low and the drill bit is prone to stuck accidents, especially in complex formations;

[0004] (2) Poor drilling quality and insufficient pressure relief may lead to stress concentration.

[0005] In existing technologies, for example, the "variable diameter drill bit" disclosed in Chinese invention patent CN103439197A, which studies shear specimens of viscoelastic materials under high strain rate conditions for type II fracture, improves guidance through structural design, but is a passive mechanical device and cannot cope with complex stuck drill bits. Vibratory drilling technology (such as acoustic drilling) can improve rock breaking efficiency, but it is mostly used for shallow exploration and has not been integrated with the working conditions and intelligent control depth of deep pressure relief drilling.

[0006] Monitoring while drilling (MSD) technologies, such as the technology disclosed in Chinese invention patent CN112326467A ("Triaxial Thermal-Hydraulic-Mechanical Coupled Dynamic Impact-Condensed Shear Test Device for Rock and Soil"), can provide formation information, but are usually limited to monitoring and early warning, without forming a closed-loop control with the actuator (such as vibration de-jamming). Therefore, there is an urgent need for a pressure relief drilling construction method and system that integrates active rock breaking, intelligent anti-jamming, and efficient borehole formation to improve the effectiveness and reliability of deep coal seam pressure relief projects.

[0007] To solve the above-mentioned technical problems, it is necessary to develop a method and system for coal borehole pressure relief that combines stepped diameter change with vibration. Summary of the Invention

[0008] The purpose of this invention is to address the shortcomings of existing technologies by providing a method and system for stress relief in coal seam drilling using a stepped diameter variation and vibration coordination. The technical solution is as follows:

[0009] A method for stress relief in coal seam drilling using stepped diameter variation and vibration coordination includes the following steps:

[0010] S1. Serial drilling is carried out using a stepped variable diameter drill bit. The stepped variable diameter drill bit has a three-stage stepped structure with the diameter gradually increasing along the drilling direction. The three-stage stepped structure is used to complete the guiding and positioning and microcrack induction work, hole enlargement and stress renormalization work, as well as long-distance guiding and pressure relief space forming work in sequence.

[0011] S2. During the sequential drilling process in step S1, axial and circumferential vibrations are generated by the vibration generation unit integrated behind the drill bit to assist in breaking the rock mass, promote the movement of cuttings, and prevent or remove drill bit jamming.

[0012] S3. During the sequential drilling process in step S1, drilling parameters are collected in real time by a sensor group integrated behind the drill bit, and multimodal data fusion and decision adjustment are performed based on preset system rules to identify the stuck drill type and trigger corresponding vibration mode and drilling parameter adjustment commands.

[0013] Furthermore, the drilling parameters in step S3 include slewing pressure, propulsion pressure, and vibration acceleration signals. The preset system rules in step S3 are as follows:

[0014] Rule 1: Gradually change the stuck drill trend. If the slewing pressure continues to increase beyond the set threshold and the duration is longer than the preset value, then activate the circumferential vibration mode and reduce the thrust.

[0015] Rule 2: In the event of sudden stuck drill bit, if the feed pressure or rotation pressure changes abruptly and exceeds the set threshold, full-power axial and circumferential vibration will be activated and the drill bit will be automatically retracted.

[0016] Rule 3: When entering a hard rock layer, if the vibration signal characteristics indicate that a high-strength hard rock layer has been entered, adjust the vibration mode to high frequency and low amplitude and reduce the drilling speed.

[0017] Furthermore, in Rule 1, during drilling, the intelligent processor automatically adjusts the vibration mode based on sensor data. When it detects that the slewing pressure exceeds the benchmark value by 15% for 10 seconds, it activates the circumferential vibration mode and reduces the thrust to 70% of the normal value. In Rule 2, when the thrust suddenly drops by 30% or the slewing pressure surges by 40%, it immediately activates full-power axial and circumferential vibration and controls the drill string to retract by 0.3-0.5 m.

[0018] Furthermore, the system rule determination and identification in step S3 is as follows:

[0019] Gradual-change stuck drill identification: If , The threshold value is the instantaneous rate of change of the slewing pressure. Duration of the state The cause is determined to be a gradually increasing stuck drill bit due to cuttings accumulation or progressive contact with hard rock; Decision output: Generate a vibration mode command dominated by circumferential vibration, with a torque command value. Simultaneously output thrust correction commands ;

[0020] Sudden drill jam identification: If , For threshold, or The jump exceeds the set threshold within a single sampling period. If the drill bit encounters a fracture, cavity, or severe inclusion, it is determined to be a sudden stuck drill bit caused by encountering a fracture, cavity, or severe inclusion. Decision output: Generate full-power axial and circumferential composite vibration commands and emergency retraction commands; Vibration command parameters are set to the maximum value: axial excitation force. Circumferential torque Vibration frequency Set to rated high vibration frequency The retraction command is to immediately raise the drill string and perform an emergency retraction distance. ;

[0021] Hard rock layer identification: If consistently below the set threshold ,and If the level remains high, it indicates entry into a high-strength, low-fracture rock stratum; Decision output: Generate a high-frequency, low-amplitude vibration mode command and a deceleration drilling command; Vibration frequency Set to rated high vibration frequency The excitation force amplitude is based on the exciter principle formula, and the drilling speed is corrected to... ;

[0022] The present invention also discloses a stepped variable diameter and vibration coordinated coal drilling pressure relief system for implementing the above method, including a stepped variable diameter drill bit and an intelligent processor. The stepped variable diameter drill bit is configured as a three-stage stepped structure, including a first-stage guide section at the front, a second-stage reaming section in the middle, and a third-stage forming and stabilizing section at the rear. A side drill bit is also provided on the side of the third-stage forming and stabilizing section.

[0023] The rear side of the three-stage forming and stabilizing section is connected to the underground drilling rig in the coal mine via a drill rod, and a vibration generating unit and a sensor group are also installed between the three-stage forming and stabilizing section and the drill rod.

[0024] The diameter of the first-stage guide section is 1 / 3 of the final hole diameter; the diameter of the second-stage reaming section is set to 2 / 3 of the final hole diameter; the diameter of the third-stage forming and stabilizing section is the same as the final hole diameter, and the total length of the stepped variable diameter drill bit is set to 4-5 times the final hole diameter. Adjacent sections are smoothly transitioned through conical or arc surfaces.

[0025] Furthermore, the vibration generating unit includes a cylindrical vibrator housing, with both ends connected to the three-stage forming stabilization section and the drill rod via threaded connections; an eccentric vibrator is installed inside the vibrator housing, the working range of which is set to 50-150Hz, the power source being flushing fluid delivered by a water pump, which drives the internal impact hammer to generate axial and circumferential composite impact vibration, and directly transmits it to the stepped variable diameter drill bit;

[0026] The sensor group includes a rotary pressure sensor, a propulsion pressure sensor, and a vibration sensor. The rotary pressure sensor and the propulsion pressure sensor are installed through threaded pressure testing holes pre-set on the vibrator housing to directly sense changes in fluid pressure and axial load within the flow channel. The vibration sensor is fixed to the outer wall of the vibrator housing or the adjacent outer wall of the drill rod by clamps to receive high-frequency acoustic emission signals generated by the drill bit breaking rock and structural friction. The signal cables of all sensors are laid along the cable channels or protective sleeves set on the outer wall of the drill rod and finally connected to the intelligent processor located on the ground.

[0027] Furthermore, the intelligent processor adopts a cross-language collaborative software architecture. The bottom layer uses C++ language for high-concurrency sensor data acquisition and real-time command execution; the upper layer uses Python language for multi-source sensor information fusion processing and intelligent decision-making; the intelligent processor is used to receive sensor data, run control algorithms, and output control commands to the vibration generation unit and the drilling rig propulsion / rotation system.

[0028] Furthermore, the specific process of the control algorithm run by the intelligent processor is as follows: First, the rotational pressure, propulsion pressure, and vibration acceleration signals collected by the sensor group are preprocessed, including noise reduction using a low-pass filter, and the moving average value of the rotational pressure is calculated. With instantaneous rate of change ,in, For differential operators, The time increment is the differential increment; simultaneously, a fast Fourier transform is performed on the vibration signal to extract the dominant frequency. and the proportion of vibration energy in the 0–50 Hz low-frequency band to the total energy. ;

[0029] 1) When the growth rate of slewing pressure continues to exceed the standard, it is indicated as: threshold And duration When the system detects a gradually changing stuck drill bit, it outputs a reduced thrust. ;coefficient It also initiates a vibration mode dominated by circumferential torque impact.

[0030] 2) When the propulsion pressure suddenly drops, it is represented as: threshold When, or when the slewing pressure suddenly increases, it is indicated as: threshold If the situation is determined to be a sudden stuck drill string, the drill string is immediately ordered to retract a set distance. And initiate full-power composite vibration, axial excitation force With circumferential torque All reached the design maximum value , The vibration frequency is set to the highest permissible value. ;

[0031] 3) When the dominant frequency in the vibration signal spectrum Furthermore, when the slewing torque remains high, it is determined that a high-strength rock layer has been entered, and the drilling speed is adjusted to... Among them, the coefficient It then switches to a high-frequency, low-amplitude vibration mode, with a vibration frequency of... The amplitude of the excitation force is controlled by adjusting the eccentric exciter.

[0032] Furthermore, the blade surface of the stepped variable diameter drill bit is inlaid with PDC cutting teeth or carbide teeth, and a through flushing fluid channel is provided at the center of the stepped variable diameter drill bit, and corresponding connected nozzles are arranged on the sides of each step.

[0033] The maximum output power of the vibration generating unit is proportional to the cube of the vibration frequency; it also includes a data storage module and a remote transmission module. Beneficial effects: Compared with the prior art, the present invention has the following advantages:

[0034] 1) The stepped variable diameter structure in this invention guides the sequential release of coal stress, prevents borehole deviation and drill bit jamming, and improves borehole quality;

[0035] 2) This invention enables vibration-assisted rock breaking and unblocking, increasing drilling speed by more than 20%, effectively improving drilling efficiency and quality;

[0036] 3) This invention enables intelligent control, rapid response, and closed-loop perception, decision-making, and execution, reducing human intervention. It is suitable for deep conditions with loading rates of 105-106 MPa / s and confining pressures of 20-40 MPa. Attached Figure Description

[0037] Figure 1 This is a partial cross-sectional view of the stepped variable diameter drill bit of the present invention;

[0038] Figure 2 This is a flowchart of the intelligent processor control process in this invention;

[0039] Figure 3 This is a schematic diagram of the dimensions of the stepped variable diameter drill bit in an embodiment of the present invention;

[0040] The components include: drill pipe 1, eccentric vibrator 2, side drill bit 3, vibrator housing 4, primary guide section 5, secondary reaming section 6, tertiary forming and stabilizing section 7, sensor group 8, intelligent processor 9, and flushing fluid channel 10. Detailed Implementation

[0041] The present invention will be further illustrated below with reference to specific embodiments. These embodiments are implemented based on the technical solutions of the present invention, and it should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention.

[0042] Example 1

[0043] like Figure 1 As shown, this embodiment mainly provides a stepped variable diameter and vibration coordinated coal drilling pressure relief system, including a stepped variable diameter drill bit and an intelligent processor. The stepped variable diameter drill bit in this embodiment is set as a three-stage stepped structure, including a first-stage guide section 5 on the front side, a second-stage reaming section 6 in the middle and a third-stage forming and stabilizing section 7 at the rear end; and a side drill bit 3 is also provided on the side of the third-stage forming and stabilizing section 7.

[0044] In this embodiment, the rear side of the three-stage forming and stabilizing section 7 is connected to the underground drilling rig in the coal mine via a drill rod 1. Furthermore, a vibration generating unit and a sensor group 8 are installed between the three-stage forming and stabilizing section 7 and the drill rod 1.

[0045] In this embodiment, the vibration generating unit is installed as an independent functional module, directly connected in series between the drill pipe 1 and the three-stage forming and stabilizing section 7. Specifically, the unit's outer shell is a cylindrical vibrator shell 4, with an internal thread at its upper end that directly screws into the external thread at the lower end of the drill pipe 1; the lower end of the shell has an external thread that connects to the pre-set internal thread at the rear end of the three-stage forming and stabilizing section 7. This double-ended threaded connection ensures the coaxiality, structural rigidity, and sealing between the vibration generating unit, the drill pipe, and the drill bit, reliably transmitting the torque and axial pressure required for drilling. The vibrator shell 4 integrates an eccentric vibrator 2 driven by drilling fluid, which generates periodic excitation force and transmits the vibration directly to the rigidly connected three-stage forming and stabilizing section 7 through the vibrator shell 4, thereby causing the entire drill bit to vibrate axially.

[0046] In this embodiment, sensor group 8 is used to monitor the drilling status in real time. It is installed closely around the vibration generating unit and the area near the drill bit. The rotary pressure sensor and the feed pressure sensor are installed through threaded pressure measuring holes preset on the vibrator housing 4, directly sensing the fluid pressure changes and axial load in the flow channel. The vibration sensor is fixed to the vibrator housing 4 or the outer wall of the drill rod 1 immediately above it by high-strength clamps, and is used to receive high-frequency acoustic emission signals generated by the drill bit breaking rock and structural friction. The signal cables of all sensors are laid along the cable grooves or protective sleeves on the outer wall of the drill rod 1, and finally connected to the intelligent processor located on the ground.

[0047] In this embodiment, the diameter of the first-stage guide section 5 is 1 / 3 of the final hole diameter; the diameter of the second-stage reaming section 6 is set to 2 / 3 of the final hole diameter; the diameter of the third-stage forming and stabilizing section 7 is the same as the final hole diameter, and the total length of the stepped variable diameter drill bit is set to 4-5 times the final hole diameter. Adjacent sections are smoothly transitioned through conical or arc surfaces.

[0048] like Figure 3 As shown, this embodiment provides a specific stepped variable diameter drill bit with the following dimensions: the diameter of the first-stage guide section is set to 118 mm, the diameter of the second-stage reaming section is set to 133 mm, and the diameter of the third-stage forming and stabilizing section is set to 145 mm. Each section is transitioned by a conical curved surface, and the total length is designed to be 4.5 times the hole diameter.

[0049] The vibration generating unit in this embodiment includes an eccentric vibrator 2 and a vibrator housing 4. The working range of the eccentric vibrator 2 is set to 50-150Hz. The power comes from the flushing fluid delivered by the water pump. It drives the internal impact hammer to generate a composite impact vibration in the axial and circumferential directions and directly transmits it to the stepped variable diameter drill bit.

[0050] The eccentric vibrator 2, serving as the power source, is installed inside the front end of the vibrator housing 4, near the drill pipe connection end. It contains a rotating shaft driven by a motor or drilling fluid, and an eccentric mass block fixed to the shaft. When the drive shaft rotates, the eccentric mass block generates centrifugal force, as shown in the formula... ,in, Let be the equivalent eccentric mass inside the eccentric exciter, and e be the eccentricity of the eccentric exciter. The rotational angular velocity of the eccentric exciter; this centrifugal force forms the excitation force basis of the system's vibration.

[0051] The vibration generating unit, acting as a vibration conversion and execution mechanism, is rigidly connected to the rear end of the three-stage forming stabilization section 7. The vibrator housing 4 integrates an axial vibration conversion mechanism, converting the rotational motion output from the eccentric vibrator 2 into axial vibration of the drill bit along its axis. The frequency of the axial vibration can be controlled by adjusting the drive speed, typically within the range of 10-200 Hz.

[0052] Torsional vibration is directly achieved through the dynamic characteristics of the eccentric vibrator 2. The centrifugal force generated by the rotating eccentric mass block changes direction continuously, and its component force in the plane perpendicular to the axis will form a periodically changing torque, which acts on the drill bit and induces the drill bit to produce circumferential micro-oscillation or torsional vibration.

[0053] Therefore, the vibration generating unit provides the excitation force source through the eccentric vibrator 2, and the vibrator housing 4 mainly converts it into axial impact. At the same time, the rotational dynamic characteristics of the eccentric vibrator 2 directly induce circumferential vibration, and finally transmit the composite vibration of axial and circumferential directions directly to the third-stage forming and stabilizing section 7 and the entire drill bit.

[0054] The sensor group 8 in this embodiment includes a rotary pressure sensor, a feed pressure sensor, and a vibration sensor, which collects the rotary pressure, feed pressure, and vibration signals of the stepped variable diameter drill bit in real time and transmits them to the intelligent processor.

[0055] In this embodiment, both the rotary pressure sensor and the feed pressure sensor are preferably intrinsically safe mining-grade pressure sensors. They are installed via tee connectors in the hydraulic motor circuit driving the drill rod rotation and the hydraulic circuit of the drill rig's feed cylinder, respectively. By detecting real-time pressure changes in the hydraulic system, the rotary torque and axial thrust of the drill bit are indirectly and accurately measured. The vibration sensor is preferably an intrinsically safe mining-grade vibration velocity sensor, such as the GBD20 or GBC20 type, whose applicable frequency range completely covers the low-frequency and main vibration frequency bands generated by vibratory drilling. This sensor is rigidly fixed to the housing of the vibration generating unit or to the drill rod adjacent to the drill bit by bolts, and is used to directly measure the mechanical vibration velocity signal induced by the drill bit breaking rock and the system's operation. The above multi-source signals are transmitted to the intelligent processor via shielded cables. Based on the principle of multi-sensor information fusion, through collaborative analysis of time-domain and frequency-domain characteristics, a closed-loop control basis is provided for intelligent identification of rock strata changes and judgment of early signs of stuck drill bit.

[0056] like Figure 2As shown, the intelligent processor in this embodiment adopts a cross-language collaborative software architecture. The bottom layer uses C++ for high-concurrency sensor data acquisition and real-time command execution; the upper layer uses Python for multi-source sensor information fusion processing and intelligent decision-making (such as CNN-LSTM). Sensor group 8 inputs rotation pressure signals, propulsion pressure signals, and vibration signals to the control unit of the intelligent processor for processing. The intelligent processor receives sensor data, runs control algorithms, and outputs control commands to the vibration generation unit and the drilling rig propulsion / rotation system. For example, rule 1: gradual change in stuck drill bit trend, the output command is to reduce propulsion force and start circumferential vibration mode; rule 2: sudden stuck drill bit, the output command is to urgently retract the drill string and start full-power axial-circumferential vibration; rule 3: entering hard rock formation, the output command is to reduce drilling speed and adjust to high-frequency low-amplitude vibration mode; the vibration generation unit and the drilling rig propulsion / rotation system also feed back the status to sensor group 8.

[0057] The control algorithm running on the intelligent processor works as follows: First, the rotational pressure, propulsion pressure, and vibration acceleration signals collected by sensor group 8 are preprocessed, including using a low-pass filter (cutoff frequency). Noise reduction was performed, and the moving average of the slewing pressure over time t was calculated. With the instantaneous rate of change of slewing pressure Simultaneously, a fast Fourier transform is performed on the vibration signal to extract the dominant frequency. and the proportion of vibration energy in the 0–50 Hz low-frequency band to the total energy. .

[0058] The core decision-making process is based on the following quantitative rules and formulas:

[0059] (1) When the growth rate of turning pressure continues to exceed the standard, that is (threshold) And duration When the system is classified as a Class II slowly changing stuck drill bit, the system outputs a reduced thrust. (coefficient ), and initiate a vibration mode dominated by circumferential torque impact, circumferential torque ;

[0060] (2) When the propulsion pressure suddenly drops (threshold) Or the turning pressure suddenly increases. (threshold) If the situation is classified as a Class I / III sudden stuck drill bit, the system will immediately instruct the drill string to retract a set distance. And initiate full-power composite vibration, its axial excitation force With circumferential torque All reached the design maximum value , The vibration frequency is set to the highest value allowed by the system. (Based on the literature on self-vibrating PDC drill bits, their operating frequency design range is 10-20 Hz. This invention extends to...) To cover higher frequency needs);

[0061] (3) When the dominant frequency in the vibration signal spectrum Furthermore, when the slewing torque remains high, it is determined that a high-strength rock layer has been entered, and the system adjusts the drilling speed accordingly. (coefficient It then switches to a high-frequency, low-amplitude vibration mode, with its vibration frequency... The amplitude of the excitation force is limited by adjusting the equivalent parameters of the eccentric exciter (eccentric mass or eccentricity), according to the excitation force formula. (in, Amplitude control is achieved. In the above algorithm, all judgment thresholds and control parameters can be dynamically fine-tuned through a self-learning module based on on-site formation data. The control commands are ultimately sent to the vibration generation unit and the drilling rig's electro-hydraulic control system via the fieldbus to complete closed-loop control.

[0062] In the formula: and respectively with time Measured values ​​of varying slewing pressure and propulsion pressure, in MPa; This is the cutoff frequency of the low-pass filter, in Hz. For the rotational pressure in time The moving average value, in MPa; This represents the instantaneous rate of change of slewing pressure, expressed in MPa / s. The dominant frequency in the vibration signal spectrum, measured in Hz; The proportion of vibration energy in the low-frequency band of 0–50 Hz to the total energy is a dimensionless parameter. The reference value for normal rotational pressure is determined based on the current rock strata conditions, and the unit is MPa; The threshold for determining the relative growth rate of slewing pressure is a dimensionless parameter. and These are the adjustment coefficients for thrust and drilling speed, respectively, both of which are dimensionless parameters; and These are the thrust setting value and drilling speed setting value under normal operating conditions, respectively, in kN and mm / s; is the proportional gain coefficient between the circumferential vibration torque and the deviation of the rotational pressure, with units of N·m / MPa; and These are the threshold values ​​for determining a sudden drop in propulsion pressure and a sudden increase in slewing pressure, respectively, both of which are dimensionless parameters; The automatic retraction distance of the drill string in the event of a sudden stuck drill bit, in meters; and These are the maximum axial impact force and maximum circumferential torque that the vibration generating unit can produce, respectively, in kN and N·m. The highest vibration operating frequency set for the system, in Hz; The equivalent eccentric mass inside the eccentric vibrator is expressed in kg. This represents the eccentricity of the eccentric vibrator, in meters (m). ω represents the rotational angular velocity of the eccentric exciter, expressed in rad / s.

[0063] In this embodiment, the blade surface of the stepped variable diameter drill bit is inlaid with PDC cutting teeth or carbide teeth. A through flushing fluid channel 10 is provided at the center of the stepped variable diameter drill bit, and corresponding connected nozzles are arranged on the sides of each step.

[0064] In this embodiment, the maximum output power of the vibration generating unit is proportional to the cube of the vibration frequency; it also includes a data storage module and a remote transmission module.

[0065] Example 2

[0066] This embodiment provides a method for stress relief in coal seam drilling using a stepped diameter reduction and vibration coordination, including the following:

[0067] The drilling stress relief method in this embodiment mainly utilizes a stepped variable-diameter drill bit for sequential drilling. The drill bit has a three-stage stepped structure with the diameter gradually increasing along the drilling direction, sequentially completing guidance and positioning and microcrack induction, hole enlargement and stress renormalization, and finally stress relief space formation and long-range guidance. Axial and circumferential vibrations are generated by a vibration generation unit integrated at the rear of the drill bit to assist in breaking the rock mass, promote cuttings transport, and prevent or remove drill bit jamming. Based on the intelligent control unit, drilling parameters, including slewing pressure, feed pressure, and vibration signals, are collected in real time. Multimodal data fusion and decision-making are performed based on preset expert system rules to automatically identify the type of stuck drill bit and trigger corresponding vibration modes and drilling parameter adjustment commands.

[0068] The specific algorithm process for multimodal data fusion and decision-making based on preset expert system rules in this embodiment is as follows:

[0069] The system receives multimodal data from sensor group 8 in real time, including rotational pressure. Pressure to advance and vibration acceleration .

[0070] First, data fusion and feature extraction are performed:

[0071] 1) Calculate the instantaneous rate of change of slewing pressure. and its reference value relative to the current construction section Normalization bias ;

[0072] 2) Calculate the instantaneous fluctuation rate of propulsion pressure. ;

[0073] 3) Perform frequency domain analysis on the vibration acceleration signal to extract the total energy in the 0-200Hz frequency band. and the energy proportion of the 10-50Hz characteristic frequency band The aforementioned feature parameters constitute the decision feature vector. .

[0074] The core of the decision-making process is a threshold-based set of expert rules.

[0075] Rule 1 (Gradual Drill Identification): If (Threshold, typical value 0.15) and Duration of the state (Threshold, typical value 10s) indicates a Class II stuck drill bit caused by cuttings accumulation or progressive contact with hard rock; Decision output: Generate a vibration mode command dominated by circumferential vibration, with a torque command value Simultaneously output thrust correction commands ( This is the pressure reduction coefficient, typically ranging from 0.7 to 0.8. (To set the propulsion force).

[0076] Rule 2 (Sudden Drill Jam Detection): If (threshold) Typical value 0.3) or The jump exceeds the threshold within a single sampling period. (Typical value 0.4) indicates a Class I / III sudden stuck drill bit caused by encountering a fracture, cavity, or severe inclusion; Decision output: Generate a full-power axial-circumferential composite vibration command and an emergency retraction command; Vibration command parameters are set to the maximum value: axial excitation force Circumferential torque Vibration frequency Set to the system's rated high frequency value The retraction command immediately raises the drill string a certain distance. (Typical value 0.2-0.5m);

[0077] Rule 3 (Entering Hard Rock Layers): If Continuously below the threshold (Typical value 0.3) and If the level remains high, it indicates entry into a high-strength, low-fracture rock stratum; Decision output: Generate a high-frequency, low-amplitude vibration mode command and a deceleration drilling command; Vibration frequency Set to rated high vibration frequency The excitation force amplitude is based on the exciter principle formula. The drilling speed is limited by adjusting the equivalent eccentricity parameter; the drilling speed is corrected to... ( Typical value: 0.5-0.6.

[0078] In the formula: and respectively with time Measured values ​​of varying slewing pressure and propulsion pressure, in MPa; For a moment The vibration acceleration value, in m / s²; The system sampling period is expressed in seconds (s). The reference value for normal slewing pressure is determined based on the statistical data of the initial stable section of the current construction layer, and the unit is MPa; The normalized deviation of the slewing pressure is denoted as , which is a dimensionless parameter. This represents the instantaneous rate of change of slewing pressure, expressed in MPa / s. The absolute value of the instantaneous fluctuation of the driving pressure is expressed in MPa.

[0079] For Fast Fourier Transform operators; and These represent the total energy of the vibration signal and the energy in the 10–50 Hz frequency band, respectively, in units of (m / s²)²·s; The proportion of vibration energy in the characteristic frequency band of 10–50 Hz to the total energy is a dimensionless parameter. These are thresholds used in rule-based judgment, and all are dimensionless parameters. This is the threshold for determining the duration of a state, measured in seconds. This is the gain coefficient for the torque command, expressed in N·m. and These are the normal thrust and normal drilling speed set by the system, in kN and mm / s, respectively; and These are the adjustment coefficients for thrust and drilling speed, respectively, both of which are dimensionless parameters; and These represent the maximum axial force and maximum torque that the vibration generating unit can output, respectively, in kN and N·m. The rated high vibration frequency set for the system, in Hz, is designed with reference to the 10–20 Hz operating frequency range of self-vibrating PDC drill bits and extends the upper limit to meet the needs of unblocking. This is the emergency retreat distance, in meters (m).

[0080] The specific scheme for automatically identifying stuck drill types is as follows: The system performs the following checks in each sampling cycle: Internally, synchronously collect rotary pressure. Pressure to advance and vibration acceleration The instantaneous value of the slewing pressure is obtained, and the normalized deviation of the slewing pressure is calculated. Instantaneous change rate of slewing pressure The absolute value of instantaneous fluctuations in propulsion pressure and characteristic frequency band energy ratio eigenvectors composed of, etc. Then, the vector components are matched in real time with the conditions of the preset expert rule base.

[0081] The matching process follows a hierarchical priority logic:

[0082] First, prioritize detecting mutation characteristics, if or If the instantaneous jump amplitude meets the preset threshold (Rule 2), it is immediately determined to be a sudden stuck drill, and the response delay of this process is in the millisecond range; after ruling out sudden stuck drills, the system identifies gradually changing stuck drills by analyzing the data trend in the short-term time series buffer. If the data indicates... Continuously exceeding the threshold And the instantaneous change rate of slewing pressure The duration of continuous positive values ​​reached If this occurs, a gradual stuck drill judgment is triggered; at the same time, the system also performs continuous background analysis, and if this occurs over a relatively long period of time (such as more than 1 minute)... and If the combined characteristics of the drilling conditions continuously meet the conditions of Rule 3, it is determined that the lithology has changed and the adaptive drilling mode is entered. Finally, the successfully matched rule will output the corresponding stuck drill type identifier (such as "Class II", "Class I / III") or working condition identifier ("hard rock layer"), and automatically trigger the preset vibration mode and drilling parameter adjustment instruction set bound to it, thereby achieving fast and accurate working condition identification and response.

[0083] The specific implementation process of this embodiment is divided into three stages: first, drilling with a stepped variable diameter drill bit is performed, and after the guide section completes the guiding drilling, the second-level expansion section performs preliminary hole expansion, and finally the third-level forming and stabilizing section completes the final hole diameter forming.

[0084] During the drilling process, the intelligent processor automatically adjusts the vibration mode based on data from various sensors, with a total of three rules set.

[0085] Rule 1: If the slewing pressure continues to increase beyond the set threshold and the duration exceeds the preset value, the circumferential vibration mode will be activated and the propulsion force will be reduced.

[0086] Rule 2: In the event of sudden stuck drill bit, if the feed pressure or rotation pressure changes abruptly and exceeds the set threshold, full-power axial and circumferential vibration will be activated and the drill bit will be automatically retracted.

[0087] Rule 3: When entering a hard rock layer, if the vibration signal characteristics indicate that a high-strength hard rock layer has been entered, adjust the vibration mode to high frequency and low amplitude and reduce the drilling speed.

[0088] The intelligent processor operates according to the data from various sensors as follows: when the slewing pressure is detected to exceed the benchmark value by 15% for 10 seconds, the circumferential vibration mode is activated and the propulsion force is reduced to 70% of the normal value; rule two, when the propulsion pressure suddenly drops by 30% or the slewing pressure surges by 40%, full-power axial-circumferential vibration is immediately activated and the drill string is controlled to retract by 0.3-0.5m; through the above intelligent coordinated control, the system can efficiently and safely complete the construction of large-diameter pressure relief boreholes in high-stress coal seams; this system achieves a simultaneous improvement in the efficiency and quality of pressure relief borehole formation through the synergistic effect of the variable diameter structure and vibration energy.

[0089] In this embodiment, the intelligent processor, based on multi-sensor data and employing system control logic, automatically triggers vibration modes and adjusts drilling parameters. Specific rules include: initiating circumferential vibration and reducing propulsion force when preventing gradual stuck drill bit; initiating full-power vibration and retracting the drill string when preventing sudden stuck drill bit; and adaptively adjusting vibration frequency and propulsion speed based on coal seam property identification.

[0090] Specific application examples and effect comparisons of the rules: Taking the case of encountering a slowly changing stuck drill bit when drilling a Φ145mm pressure relief hole to a depth of 18m in a deep, high-stress coal seam (hardness coefficient of 4-5) in a certain mine, traditional manual operation relies on the driller's observation of instruments and experience. From discovering the abnormal rotary pressure (increasing from 12MPa), attempting manual adjustment, to determining whether to pull the drill string, the average time is 8-15 minutes, and there is about a 30% probability that it will worsen into a serious stuck drill bit accident. However, the system of this invention calculates the normalized deviation of the rotary pressure in real time. If the pressure exceeds the threshold by 15% for 10 seconds, it is automatically classified as Class II stuck drill bit. The thrust is immediately adjusted from 80kN to 56kN, and a vibration mode with a frequency of 13.33Hz and a circumferential torque of 350 N·m is simultaneously initiated. This allows the pressure to return to normal within 25 seconds, and drilling resumes smoothly. This embodiment demonstrates that the present invention achieves a leap from delayed manual intervention to real-time active collaborative control, increasing processing efficiency by tens of times and reducing the risk of accidents to near zero, highlighting its significant advancement in ensuring safe and efficient pressure relief drilling in deep coal seams.

[0091] The intelligent processor's signal reception and processing process: The intelligent processor, through its multi-channel synchronous acquisition module, receives intrinsically safe signals from the slewing pressure, propulsion pressure, and vibration acceleration sensors in real time at a rate of no less than 1 kHz, and performs synchronous buffering. Subsequently, the intelligent processor performs real-time digital conditioning on the signals, including using a low-pass filter (cutoff frequency 50Hz) to suppress pressure signal pulsation noise, and performing high-pass filtering (cutoff frequency 0.5Hz) and Fast Fourier Transform on the vibration signals to extract time-domain and frequency-domain features. Within each control cycle (e.g., 10ms), the intelligent processor calculates the normalized deviation of the slewing pressure in parallel. The instantaneous rate of change, propulsion pressure fluctuation, and vibration characteristic frequency band energy ratio are fused into a decision feature vector. This vector is immediately matched with the built-in expert rule base for priority matching. If the match is successful (e.g., a slowly changing stuck drill bit is identified), a control command package is generated containing specific vibration mode parameters (type, frequency, amplitude / torque) and drilling parameters (propulsion force, speed, retraction command). Finally, the command package is output in real time to the vibration generation unit and the drilling rig's electro-hydraulic control system via digital-to-analog conversion or fieldbus (such as CAN) to drive the actuators. This forms a millisecond-level real-time closed-loop control link from multi-source sensing, feature fusion, intelligent decision-making to precise execution, ensuring the system's rapid and adaptive response capability to complex downhole conditions.

[0092] The above embodiments are merely preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for stress relief in coal seam drilling using stepped diameter variation and vibration coordination, characterized in that: Includes the following steps: S1. Serial drilling is carried out using a stepped variable diameter drill bit. The stepped variable diameter drill bit has a three-stage stepped structure with the diameter gradually increasing along the drilling direction. The three-stage stepped structure is used to complete the guiding and positioning and microcrack induction work, hole enlargement and stress renormalization work, as well as long-distance guiding and pressure relief space forming work in sequence. S2. During the sequential drilling process in step S1, axial and circumferential vibrations are generated by the vibration generation unit integrated behind the drill bit to assist in breaking the rock mass, promote the movement of cuttings, and prevent or remove drill bit jamming. The vibration generating unit includes a cylindrical vibrator housing (4), inside which is installed an eccentric vibrator (2). The power comes from the flushing fluid delivered by the water pump. It drives the internal impact hammer to generate a composite impact vibration in the axial and circumferential directions and directly transmits it to the stepped variable diameter drill bit. S3. During the sequential drilling process in step S1, drilling parameters are collected in real time by the sensor group (8) integrated behind the drill bit and transmitted to the intelligent processor. Based on the preset system rules, multimodal data fusion and decision adjustment are performed to identify the stuck drill type and trigger the corresponding vibration mode and drilling parameter adjustment command. The sensor group (8) includes a rotary pressure sensor, a propulsion pressure sensor and a vibration sensor. Drilling parameters include slewing pressure, propulsion pressure, and vibration acceleration signals. The preset system rules in step S3 are as follows: Rule 1: Gradually change the stuck drill trend. If the slewing pressure continues to increase beyond the set threshold and the duration is longer than the preset value, then activate the circumferential vibration mode and reduce the thrust. Rule 2: In the event of sudden stuck drill bit, if the feed pressure or rotation pressure changes abruptly and exceeds the set threshold, full-power axial and circumferential vibration will be activated and the drill bit will be automatically retracted. Rule 3: When entering a hard rock layer, if the vibration signal characteristics indicate that a high-strength hard rock layer has been entered, adjust the vibration mode to high frequency and low amplitude and reduce the drilling speed. The system rule determination and identification in step S3 are as follows: Gradual-change stuck drill identification: If , The threshold value is the instantaneous rate of change of the slewing pressure. Duration of the state The cause is determined to be a gradually increasing stuck drill bit due to cuttings accumulation or progressive contact with hard rock; Decision output: Generate a vibration mode command dominated by circumferential vibration, with a torque command value. Simultaneously output thrust correction commands ; Sudden drill jam identification: If , For threshold, or The jump exceeds the set threshold within a single sampling period. If the drill bit encounters a fracture, cavity, or severe inclusion, it is determined to be a sudden stuck drill bit caused by encountering a fracture, cavity, or severe inclusion. Decision output: Generate full-power axial and circumferential composite vibration commands and emergency retraction commands; Vibration command parameters are set to the maximum value: axial excitation force. Circumferential torque Vibration frequency Set to rated high vibration frequency ; The retraction command is to immediately raise the drill string by the emergency retraction distance. ; Hard rock layer identification: If consistently below the set threshold ,and If the level remains high, it indicates entry into a high-strength, low-fracture rock stratum; Decision output: Generate a high-frequency, low-amplitude vibration mode command and a deceleration drilling command; Vibration frequency Set to rated high vibration frequency The excitation force amplitude is based on the exciter principle formula. Drilling speed corrected to ; and respectively with time Measured values ​​of varying slewing pressure and propulsion pressure, in MPa; The system sampling period is expressed in seconds (s). The normalized deviation of the slewing pressure is a dimensionless parameter. This represents the instantaneous rate of change of slewing pressure, expressed in MPa / s. The absolute value of the instantaneous fluctuation of the driving pressure is expressed in MPa. The proportion of vibration energy in the characteristic frequency band of 10–50 Hz to the total energy is a dimensionless parameter. These are thresholds used in rule-based judgment, and all are dimensionless parameters. This is the threshold for determining the duration of a state, measured in seconds. This is the gain coefficient for the torque command, expressed in N·m. and These represent the set normal thrust and normal drilling speed, in kN and mm / s, respectively. and These are the adjustment coefficients for thrust and drilling speed, respectively, both of which are dimensionless parameters; and These represent the maximum axial force and maximum torque that the vibration generating unit can output, respectively, in kN and N·m. The rated high vibration frequency set for the system, in Hz; Emergency retreat distance, in meters; The equivalent eccentric mass inside the eccentric vibrator is expressed in kg. This represents the eccentricity of the eccentric vibrator, in meters (m). The frequency of the exciter is 1.

2. The method for pressure relief in coal seam drilling with stepped diameter variation and vibration coordination according to claim 1, characterized in that: In Rule 1, during drilling, the intelligent processor automatically adjusts the vibration mode based on sensor data. When it detects that the slewing pressure exceeds the benchmark value by 15% for 10 seconds, it activates the circumferential vibration mode and reduces the thrust to 70% of the normal value. In Rule 2, when the thrust suddenly drops by 30% or the slewing pressure surges by 40%, it immediately activates full-power axial and circumferential vibration and controls the drill string to retract by 0.3-0.5 m.

3. A stepped diameter-coordinated vibration-assisted coal borehole pressure relief system for implementing the method of claim 1, characterized in that: The system includes a stepped variable diameter drill bit and an intelligent processor. The stepped variable diameter drill bit is configured as a three-stage stepped structure, including a first-stage guide section (5) on the front side, a second-stage reaming section (6) in the middle, and a third-stage forming and stabilizing section (7) at the rear end. The third-stage forming and stabilizing section (7) is also provided with a side drill bit (3). The rear side of the three-stage forming and stabilizing section (7) is connected to the underground drilling machine of the coal mine through the drill rod (1), and a vibration generating unit and a sensor group (8) are also installed between the three-stage forming and stabilizing section (7) and the drill rod (1). The diameter of the first-stage guide section (5) is 1 / 3 of the final hole diameter; the diameter of the second-stage reaming section (6) is set to 2 / 3 of the final hole diameter; the diameter of the third-stage forming and stabilizing section (7) is the same as the final hole diameter, and the total length of the stepped variable diameter drill bit is set to 4-5 times the final hole diameter, with adjacent sections smoothly transitioning through a conical or circular arc surface. The vibration generating unit includes a cylindrical vibrator housing (4), which is connected to the three-stage forming stabilization section (7) and the drill rod (1) by means of threaded connection at both ends; an eccentric vibrator (2) is installed inside the vibrator housing (4), the working range of the eccentric vibrator (2) is set to 50-150Hz, the power comes from the flushing fluid delivered by the water pump, and generates axial and circumferential composite impact vibration by driving the internal impact hammer, and directly transmits it to the stepped variable diameter drill bit; The sensor group (8) includes a rotary pressure sensor, a propulsion pressure sensor and a vibration sensor. The rotary pressure sensor and the propulsion pressure sensor are installed through threaded pressure measuring holes preset on the vibrator housing (4) to directly sense the fluid pressure changes and axial load in the flow channel. The vibration sensor is fixed to the outer wall of the vibrator housing (4) or the outer wall of the adjacent drill rod (1) by clamps to receive high-frequency acoustic emission signals generated by the drill bit breaking rock and structural friction. The signal cables of all sensors are laid along the wire groove or protective sleeve set on the outer wall of the drill rod (1) and finally connected to the intelligent processor located on the ground.

4. The stepped diameter-coordinated vibration-assisted coal borehole pressure relief system according to claim 3, characterized in that: The intelligent processor adopts a cross-language collaborative software architecture. The bottom layer uses C++ language for high-concurrency sensor data acquisition and real-time command execution; the upper layer uses Python language for multi-source sensor information fusion processing and intelligent decision-making. The intelligent processor is used to receive sensor data, run control algorithms, and output control commands to the vibration generation unit and the drilling rig propulsion / rotation system.

5. The stepped diameter-coordinated vibration-assisted coal borehole pressure relief system according to claim 3, characterized in that: The blade surface of the stepped variable diameter drill bit is inlaid with PDC cutting teeth or carbide teeth. A through flushing fluid channel (10) is provided in the center of the stepped variable diameter drill bit, and corresponding connected nozzles are arranged on the side of each step. The maximum output power of the vibration generating unit is proportional to the cube of the vibration frequency; it also includes a data storage module and a remote transmission module.

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