Resonance assistance-based rock pre-weakening device before underground fracturing and method of resonance assistance-based rock pre-weakening device

Abstract

The invention belongs to the technical field of oil and gas exploitation and underground engineering, and relates to a resonance assistance-based rock pre-weakening device before underground fracturing and a method of the resonance assistance-based rock pre-weakening device. The device comprises a piezoelectric resonance unit, a guided wave amplification assembly, a well wall coupling mechanism, a power and frequency control module and a monitoring unit. The device applies controllable high-frequency vibration to a rock mass under a well, excitation close to the inherent frequency of a reservoir is recognized and locked through frequency sweeping, low-power induction of local resonance is achieved, a crack tip stress intensity factor is periodically amplified, microcrack fatigue growth is triggered, hole elasticity coupling is weakened, and the crack initiation pressure and the equivalent modulus are remarkably reduced. Tests and simulations show that the compressive strength of the rock is reduced by 35-50%, the fracturing initiation pressure is reduced by 30-40%, and the crack penetration rate is increased by more than 50%. The device is compact in structure, low in energy consumption, good in thermal stability, reusable and suitable for low-energy-consumption pretreatment and teaching and scientific research before fracturing of shale oil and gas and compact sandstone reservoirs.

Description

Technical Field

[0001] This invention belongs to the field of oil and gas extraction and downhole engineering technology, and particularly relates to rock strength pre-weakening before fracturing operations in shale oil, shale gas and tight sandstone reservoirs. Specifically, it is a downhole rock pre-weakening device and method based on high-frequency resonance. Background Technology

[0002] Shale and tight sandstone reservoirs typically have low porosity, low permeability, high brittleness, and high geostress differentials. Conventional fracturing requires high pump pressure and high flow rate to initiate and propagate fractures, leading to problems such as high energy consumption, high casing stress, and the risk of sand blockage.

[0003] Existing decompression fracturing measures mainly focus on optimizing fracturing fluid systems, improving surface pumping efficiency, or using transient energy fields such as detonation / electric pulses for assistance. However, they lack the ability to identify and stably control the reservoir's natural frequencies, limiting field repeatability and safety. Although "pre-fracturing / pressure relief / weakening" methods exist in fields such as coal mining, the objects, mechanisms, and boundary conditions are fundamentally different from those of high-frequency fatigue resonance pre-weakening in oil and gas reservoirs, making direct application difficult. Furthermore, while oilfield service equipment systems encompass conventional fracturing tools and testing services, they lack a dedicated toolchain for resonance pre-weakening based on "downhole frequency sweeping-frequency locking-closed-loop control." Therefore, this application discloses a resonance-assisted downhole pre-fracturing rock pre-weakening device and method to address the problem of unstable identification and maintenance of reservoir resonance response in complex downhole environments, leading to high pump pressure, high energy consumption, and limited stimulation efficiency. Summary of the Invention

[0004] Technical problems to be solved A resonant-assisted pre-weakening device and method for stable operation at low power downhole is proposed. By sweeping frequency to identify and lock high-frequency excitation close to the reservoir's natural frequency, local resonance and fatigue crack growth are induced. Combined with pore elastic coupling, the effective stress is reduced, which significantly reduces fracturing initiation pressure, pump energy and fluid consumption, and increases fracture penetration and stimulation volume.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a resonant-assisted rock pre-weakening device for downhole fracturing, comprising a piezoelectric resonant unit, a waveguide amplifier assembly mechanically connected to the piezoelectric resonant unit, a wellbore coupling mechanism located at the front end of the waveguide amplifier assembly and establishing adjustable contact pressure with the wellbore, a power and frequency control module electrically connected to the piezoelectric resonant unit, and a monitoring unit that interacts with the power and frequency control module and participates in closed-loop control; The power and frequency control module is used to output adjustable excitation in the range of 20 to 80 kHz and perform frequency sweep and phase-locked tracking. The monitoring unit is used to collect vibration, temperature and electrical parameters and feed them back to the power and frequency control module to maintain stable resonant loading at a frequency close to the reservoir's natural frequency, thereby reducing the rock's fracturing initiation pressure and equivalent mechanical strength.

[0006] Preferably, the waveguide amplification component is a conical or stepped metal waveguide made of titanium alloy or high-strength steel, with a length of 60-120 mm, and its front end radius gradually changes to achieve acoustic impedance matching and amplify the displacement amplitude by 2-3 times.

[0007] Preferably, the piezoelectric resonant unit includes two or more sets of stacked piezoelectric actuators connected in parallel, each actuator being covered with a ceramic insulating layer with a temperature resistance of not less than 120°C, and reliably connected to the waveguide amplifier assembly through a pre-tightening assembly.

[0008] Preferably, the wellbore coupling mechanism includes a high-damping rubber pad, an elastic clamping ring, and a locking housing. The elastic clamping ring is expanded outward by a mechanical spring or hydraulic drive to establish a contact pressure of 2-4 MPa with the wellbore, and its anti-slip capability is improved by friction texture or anti-slip teeth.

[0009] Preferably, the power and frequency control module includes a signal source, a power amplifier, and a controller, the controller performing a frequency sweep to identify the peak response frequency. And through the phase-locked loop (PLL) The module tracks nearby locations and features amplitude limiting and overcurrent protection.

[0010] Preferably, the monitoring unit includes an acceleration sensor, a temperature sensor, and an electrical parameter / impedance measurement module. The original sampling frequency is not less than 100kHz, and the feature update frequency is controlled to be not less than 200Hz through envelope or feature extraction. Automatic power reduction or shutdown is triggered when there is abnormal temperature rise or amplitude exceeds the limit.

[0011] Preferably, the power and frequency control module further includes an adaptive impedance matching and quality factor Q control network, which achieves resonance peak limiting and stable amplitude through active or passive shunt / parallel damping, and corrects the excitation frequency online according to the peak position drift of the transducer impedance spectrum.

[0012] Preferably, a thermal management structure, including a microfluidic circulating cooling or phase change heat pipe, is provided between the piezoelectric resonant unit and the waveguide amplification component to enhance the continuous working capability in high-temperature downhole environments.

[0013] A resonance-assisted pre-fracturing rock pre-weakening method for downhole fracturing, applied to a resonance-assisted pre-fracturing rock pre-weakening device as described above, includes the following steps: S1 is used for running in and positioning the device, connecting it to the fracturing string or coiled tubing, running it into the target well section, and establishing a contact pressure of 2-4 MPa through the wellbore coupling mechanism; S2 frequency sweep identification performs a 20–80 kHz frequency sweep and records current, acceleration, and impedance responses to identify the peak response frequency. ; S3 resonance loading, in Under continuous loading conditions of 5–30 minutes, the controller performs frequency fine-tuning and power limiting based on feedback from the monitoring unit. S4 retesting and construction: After vibration is stopped, retest the initiation pressure or directly carry out fracturing construction.

[0014] Preferably, the weakening device is deployed at multiple points or moved along the well section in the form of slugs to form a cyclical method of "sweeping section-frequency locking-loading-retesting". It can be superimposed with low-amplitude pulsed water hammer or micro-flow injection disturbance to induce pore pressure fluctuations and reduce effective stress, thereby further reducing the fracturing threshold.

[0015] Technical Solution Overview and Module Association Mechanical-acoustic link: The piezoelectric resonant unit is rigidly connected to the waveguide amplifier component through a pre-tightening and matching transition layer, and the waveguide front end is integrally positioned with the well wall coupling mechanism; the coupling mechanism applies a contact pressure of 2-4 MPa to the well wall through an elastic clamping ring, and the energy is transmitted to the rock mass with minimal reflection through the high damping pad layer.

[0016] Electrical-Control-Measurement Closed Loop: The signal source and power amplifier of the power and frequency control module drive the piezoelectric resonant unit; the acceleration, temperature and electrical parameters / impedance signals of the monitoring unit are fed back to the controller in real time, and the controller runs frequency sweep, phase-locked tracking and amplitude limiting / Q control algorithms to form an "excitation-response-correction" closed loop.

[0017] Thermal management link: Microchannels or phase change heat pipes are arranged at the connection between the piezoelectric unit and the waveguide, and heat is dissipated to the well fluid through the shell; temperature feedback is entered into the power management logic to avoid thermal mismatch.

[0018] Interface and compatibility: The device is connected to the tubing string or coiled tubing via a short section; the hydraulic coupling type requires connection to the low-pressure hydraulic control interface; the electrical connection uses a sealed plug, and the sensing and drive wiring harnesses are independently shielded; the cooling circuit is compatible with the downhole fluid circuit (e.g., using a cleaning fluid circulation).

[0019] Through the four necessary connections mentioned above—"energy link, closed-loop control, thermal management, and interface"—the device is ensured to be identifiable, lockable, and stably maintained in a resonant state downhole.

[0020] Compared with the prior art, the present invention provides a resonance-assisted pre-weakening device for rock pre-fracture in downhole wells, which has the following beneficial effects: 1. Significantly reduced fracturing energy consumption: After resonant pre-weakening, the fracturing initiation pressure decreases by approximately 30-40%, and the target pressure plateau of the fracturing pump shifts downwards simultaneously. Based on an estimated energy saving of 20-25% per stage, this can significantly reduce fuel consumption and maintenance costs. Low-power pretreatment shortens the residence time of the high-pressure plateau, increasing the safety margin. Mechanistically, this stems from the periodic amplification of the stress intensity factor at the crack tip and the reduction of effective stress due to pore elasticity.

[0021] 2. Increased fracture penetration and modification volume: The microfracture network leads to a decrease in equivalent modulus and enhanced connectivity of weak surfaces, making it easier for subsequent fracturing to cross bedding and natural fractures. Increased penetration facilitates proppant placement and long-term stability of flow channels, thereby increasing the stimulated volume.

[0022] 3. Enhanced equipment and operational safety: steady-state low power replaces transient high-energy impacts; Q control and amplitude limiting suppress over-peak; temperature threshold-linked power management reduces thermal risks; friction texture of coupling mechanisms reduces the risk of slippage and sleeve abrasion.

[0023] 4. High adaptability and repeatability: The 20-80kHz spectrum covers a variety of lithologies; phase-locked loop and random narrowband jitter suppress frequency drift and standing waves; the modular design facilitates integration with various tubing columns, making it easy to reuse and maintain.

[0024] 5. Intelligent and observable: The impedance spectrum peak position, acceleration amplitude and AE (acoustic emission) event rate constitute a state triplet, which supports threshold switching and optimal energy allocation, improving operational consistency and quality controllability. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the overall structure of the device (showing the relative positions and connections of the piezoelectric resonant unit, waveguide, coupling mechanism, control module and monitoring unit).

[0026] Figure 2 This diagram illustrates the connection between the piezoelectric resonant unit and the waveguide amplifier assembly (showing the assembly method of the stacked piezoelectric and conical / stepped waveguide and the transition of acoustic impedance matching).

[0027] Figure 3 This is a schematic diagram of the well wall coupling mechanism (the structure of the elastic clamping ring, high-damping rubber pad and locking housing and their contact interface with the well wall).

[0028] Figure 4 This is a block diagram for power and frequency control and signal monitoring (system connection of signal source-power amplifier-control-sensor-feedback closed loop).

[0029] Figure 5 This is a schematic diagram of the working principle of resonance (resonance spectrum, amplitude amplification, Q factor, pore elasticity and crack fatigue mechanism). Detailed Implementation

[0030] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] As described in the background section, there are shortcomings in the existing technology. In order to solve the above-mentioned technical problems, this application proposes a resonance-assisted rock pre-weakening device for downhole fracturing.

[0032] Working mechanism and symbol explanation: Natural frequency : , where E (Young's modulus), ρ (density), and L (characteristic length).

[0033] Excitation frequency :near Resonance occurs, and the amplitude is amplified. The amplitude-frequency response is related to the quality factor Q.

[0034] Effective stress (Effective stress): , (Total stress) (Biot coefficient) (Pore pressure).

[0035] Paris Law : (Crack size) (Number of loops) (Material constants) (Type I stress intensity factor amplitude).

[0036] Initiation pressure (Initiation pressure): Approximate model , (Minimum horizontal stress) (Maximum horizontal stress) (pore pressure) (tensile strength).

[0037] System Flow and Implementation Process (See Appendix) Figure 4 , Figure 5 ) To guide the implementation of the project, the control and operation flow (state machine expression) is given. The controller is implemented using PID (proportional-integral-derivative) or MPC (model predictive control). The necessary symbols are defined for the first time as follows: PLL (phase-locked loop), RMS (root mean square), AE (acoustic emission).

[0038] Initialization and self-test a. Power-on self-test: Sensor zero point, power amplifier no-load, temperature T (temperature baseline); interface integrity test (see attached document). Figure 4 ).

[0039] b. Coupling and Pressure Buildup: Drive the coupling mechanism to expand to the target pressure of 2-4 MPa (see attached). Figure 3 RMS acceleration After the (root mean square acceleration) stabilizes, frequency sweep begins.

[0040] Frequency scanning identification stage c. Sweep range setting: 20–80kHz, step size 50–200Hz; record current I, impedance Z, and... .

[0041] d. Peak criterion: The occurrence of an impedance trough and Peak co-occurrence is defined as If there are multiple peaks, choose the main peak with the highest Q (see attached table). Figure 5 ).

[0042] Phase-locked loop and stability control e. Phase-locked entry: PLL uses... Centered ±0.5% dynamic tracking; Q-control network closure, with amplitude limiting set. (maximum amplitude).

[0043] f. Jitter Suppression: Superimposed ±0.2% random narrowband jitter to suppress standing waves and frequency drift (see attached). Figure 5 ).

[0044] Pre-weakening loading g. Steady-state loading: Maintain the target power P (power) for 5–30 min; monitor T in real time. Z and AE event rates (AE event rate).

[0045] h. Adaptive adjustment: If ℃ T>80℃ or > If the peak position shifts, reduce power / briefly shut down; PLL update center frequency (see attached) Figure 5 ).

[0046] End and Retest i. Cooling: Reduce power in a stepped manner to maintain cooling flow; unlock the coupling mechanism.

[0047] j. Retesting: Conduct initiation pressure or splitting strength tests, or proceed directly to fracturing operations (see attached document). Figure 5 ).

[0048] Fault-protection-recovery.

[0049] k. Fault types: over-temperature, over-current, sensor fault, coupling loss; Actions: limiting, power reduction, shutdown, maintenance prompt.

[0050] l. Recovery strategy: Restart from the frequency sweep stage after troubleshooting to avoid forcibly locking the frequency under unknown drift conditions.

[0051] The above process and appendix Figure 4 The signal / energy flow is consistent with and is associated with the attached signal / energy flow. Figure 5 The corresponding mechanism flow is as follows: frequency sweep identification → phase lock stabilization → displacement / velocity amplification → microcrack fatigue → pore elastic coupling → crack initiation threshold reduction.

[0052] Example 1: Single-point resonance weakening device (laboratory rock sample, see attached document) Figure 1 , Figure 2 , Figure 4 , Figure 5 ) Experimental conditions: Rock sample: Shale cylinder, 50 mm in diameter and 50 mm in length; density ρ≈2.5×10³ kg / m³, Young's modulus E≈25 GPa.

[0053] Device: 3 piezoelectric actuators in parallel, ceramic insulated; 80mm titanium alloy conical waveguide; high-damping rubber pad and elastic clamping ring at the coupling end.

[0054] Control and sampling: frequency sweep 20-80kHz, step size 100Hz; original sampling ≥100kHz, feature update ≥200Hz; PLL and Q control enabled; temperature threshold 80℃.

[0055] Environment: Room temperature 25℃, normal pressure.

[0056] Operation steps (embedded process): a. Self-test and coupling pressure build-up to 2.5 MPa; b. Frequency scanning recognition ≈35~40kHz; c. Phase-locked loop and jitter suppression (±0.2%); d. Resonance loading for 30 min, monitor T, Z and ; e. Stepped power reduction and cooling, retesting With splitting strength.

[0057] Data and Criteria: The impedance decreased from 78 MPa to approximately 58 MPa; the impedance valley and acceleration peak co-occurred, with a peak position shift of <±0.3%.

[0058] Advantages: Significant pre-weakening is achieved at low power, resulting in high energy utilization efficiency; Dual-channel criteria (impedance + acceleration) improve frequency locking reliability; No chemicals involved, green and low-carbon.

[0059] Significance of the verification: To demonstrate the effectiveness and safety controllability of the "frequency sweep-phase-locked loop-Q control-resonance fatigue" method (see corresponding appendix). Figure 5 ).

[0060] Example 2: Multi-point array segmented pre-weakening (wellbore simulation, see attached document) Figure 1 , Figure 3 , Figure 4 ) condition: The simulated wellbore has an inner diameter of 89 mm and three isolation sections; each section is fitted with rock ring specimens; the temperature is 60℃.

[0061] The two sets of devices work alternately, with a coupling pressure of 2-4 MPa.

[0062] step: fA segment frequency sweep-phase lock-load 10min; g.AE event rate Once the threshold is reached, switch to segment B; h. Complete the "scan segment-lock frequency-load-retest" cycle up to segment C.

[0063] Data and Criteria: All three segments exhibited the main resonance peak; the crack initiation pressure decreased by an average of about 30%, with the largest decrease of 40% in segment B.

[0064] Advantages include: alternating arrays reduce heat load; event-driven operation shortens ineffective time; and uniformly improves the transformation effect along the well section.

[0065] Significance of verification: This proves that the segmented construction method and the event rate threshold segmentation strategy are feasible.

[0066] Example 3: Adaptive Impedance Matching and Q-Factor Control (see attached document) Figure 4 , Figure 5 ) Conditions: The power amplifier is configured with a programmable impedance network; the controller is running Q-limiting and phase compensation.

[0067] step: i. Establish an LCR (inductor-capacitor-resistance) model to fit the transducer impedance; j. Closed-loop shunt damping after phase lock-in limits peak amplitude; k. Apply random narrowband jitter to maintain excitation near the peak.

[0068] Data and criteria: Peak amplitude fluctuation <±5%; temperature rise decreases by 10-15℃.

[0069] Advantages include: suppressing excessive resonance and thermal mismatch; and improving long-term stability.

[0070] Significance of verification: This proves that Q-control is the key to long-term steady-state resonance operation.

[0071] Example 4: Thermal Management and Continuous High-Temperature Operation (See Appendix) Figure 1 , Figure 2 ) Conditions: The microchannel cooling plate is placed at the piezoelectric-waveguide interface; the phase change heat pipe extends to the heat dissipation fins; the cooling medium is downhole cleaning fluid.

[0072] step: l. Construct a power-temperature rise-flow rate model; m. When T>80℃, automatically reduce power and increase flow rate; temperature control priority is higher than amplitude limit.

[0073] Data and criteria: The machine can be continuously loaded for 20 minutes in a 90℃ environment without triggering a shutdown; the temperature difference on the shell surface is <8℃.

[0074] Advantages include: expanding temperature resistance limits; improving reliability for repeated use.

[0075] Significance of verification: To demonstrate the necessity of thermal management for the successful implementation of the project.

[0076] Example 5: Cooperative pore pressure disturbance (micro-amplitude water hammer, see attached document) Figure 4 , Figure 5 ) Conditions: During resonant loading, periodic injections of 0.2–0.5 L / min microflow rate are superimposed, with pulse amplitude <1 MPa; pulse frequency and phase are... Decoupling.

[0077] step: n. Initiate micro-amplitude water hammer after steady-state resonance; o. Monitoring Determine the effective stress by varying Z. Downward trend.

[0078] Data and Criteria: Compared to resonance groups only, It will drop by about 5-8%.

[0079] Advantages include: achieving a synergistic effect with extremely low energy consumption; and easy integration with on-site pumping processes.

[0080] Significance of verification: It proves that the "physical resonance + pore pressure disturbance" work together to further reduce the threshold.

[0081] Example 6: Comparison of Anti-Drift Strategies (See Appendix) Figure 4 ) Conditions: Compare three groups: A (fixed frequency), B (phase-locked loop), and C (phase-locked loop + jitter).

[0082] Procedure: Gradually increase the ambient temperature from 25 to 80℃, and record the peak retention rate and energy consumption.

[0083] Data and criteria: A. Peak loss >30%; B. Maintain ±10%; C. Maintain ±5% is optimal.

[0084] Advantages: Phase-locked loop (PLL) + jitter is the most robust under temperature changes and boundary disturbances.

[0085] Significance of verification: It supports the selection of control strategies used in the main process.

[0086] Compared with existing technologies, this invention can physically pre-weaken the reservoir in a low-energy, repeatable and controllable manner before fracturing, reduce fracturing pump pressure and fluid consumption, increase fracture penetration and stimulation volume, and reduce casing and formation risks. It has significant cost reduction and efficiency improvement value and broad application prospects.

[0087] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A resonance-assisted pre-weakening device for rock weakening before downhole fracturing, characterized in that, include: The system includes a piezoelectric resonant unit, a waveguide amplifier assembly mechanically connected to the piezoelectric resonant unit, a wellbore coupling mechanism located at the front end of the waveguide amplifier assembly and establishing an adjustable contact pressure with the wellbore wall, a power and frequency control module electrically connected to the piezoelectric resonant unit, and a monitoring unit that interacts with the power and frequency control module and participates in closed-loop control. The power and frequency control module is used to output adjustable excitation in the range of 20 to 80 kHz and perform frequency sweep and phase-locked tracking. The monitoring unit is used to collect vibration, temperature and electrical parameters and feed them back to the power and frequency control module to maintain stable resonant loading at a frequency close to the reservoir's natural frequency, thereby reducing the rock's fracturing initiation pressure and equivalent mechanical strength.

2. The resonant-assisted pre-weakening rock pre-weakening device for downhole fracturing according to claim 1, characterized in that: The waveguide amplifier component is a conical or stepped metal waveguide made of titanium alloy or high-strength steel, with a length of 60-120mm. Its front end radius gradually changes to achieve acoustic impedance matching and amplify the displacement amplitude by 2-3 times.

3. The resonant-assisted pre-weakening rock pre-weakening device for downhole fracturing according to claim 1, characterized in that: The piezoelectric resonant unit includes two or more sets of stacked piezoelectric actuators connected in parallel. Each actuator is covered with a ceramic insulating layer with a temperature resistance of not less than 120°C and is reliably connected to the waveguide amplifier assembly through a pre-tightening assembly.

4. The resonant-assisted pre-weakening rock pre-weakening device for downhole fracturing according to claim 1, characterized in that: The wellbore coupling mechanism includes a high-damping rubber pad, an elastic clamping ring, and a locking housing. The elastic clamping ring is expanded outward by a mechanical spring or hydraulic drive to establish a contact pressure of 2-4 MPa with the wellbore and enhances its anti-slip capability through friction textures or anti-slip teeth.

5. The resonant-assisted pre-weakening rock pre-fracturing device for downhole fracturing according to claim 1, characterized in that: The power and frequency control module includes a signal source, a power amplifier, and a controller. The controller performs a frequency sweep to identify the peak response frequency. And through the phase-locked loop (PLL) The module tracks nearby locations and features amplitude limiting and overcurrent protection.

6. The resonant-assisted pre-weakening rock pre-weakening device for downhole fracturing according to claim 1, characterized in that: The monitoring unit includes an acceleration sensor, a temperature sensor, and an electrical parameter / impedance measurement module. The original sampling frequency is not less than 100kHz, and the feature update frequency is controlled to be not less than 200Hz through envelope or feature extraction. Automatic power reduction or shutdown is triggered when there is abnormal temperature rise or amplitude exceeds the limit.

7. The resonant-assisted pre-weakening rock pre-weakening device for downhole fracturing according to claim 1, characterized in that: The power and frequency control module also includes an adaptive impedance matching and quality factor Q control network, which achieves resonance peak limiting and stable amplitude through active or passive shunt / parallel damping, and corrects the excitation frequency online according to the peak position drift of the transducer impedance spectrum.

8. The resonant-assisted pre-weakening rock pre-fracturing device for downhole fracturing according to claim 1, characterized in that: A thermal management structure, including a microfluidic circulating cooling or phase change heat pipe, is provided between the piezoelectric resonant unit and the waveguide amplification assembly to enhance the continuous working capability in high-temperature downhole environments.

9. A resonance-assisted pre-weakening method for rock pre-weakening before downhole fracturing, applied to a resonance-assisted pre-weakening device for rock pre-weakening before downhole fracturing as described in any one of claims 1-8, characterized in that, Includes the following steps: S1 is used for running in and positioning the device, connecting it to the fracturing string or coiled tubing, running it into the target well section, and establishing a contact pressure of 2-4 MPa through the wellbore coupling mechanism; S2 frequency sweep identification performs a 20–80 kHz frequency sweep and records current, acceleration, and impedance responses to identify the peak response frequency. ; S3 resonance loading, in Under continuous loading conditions of 5–30 minutes, the controller performs frequency fine-tuning and power limiting based on feedback from the monitoring unit. S4 retesting and construction: After vibration is stopped, retest the initiation pressure or directly carry out fracturing construction.

10. A method for pre-weakening rock before downhole fracturing based on resonance assistance as described in claim 9, characterized in that: The weakening device is deployed at multiple points or moved along the well section in the form of slugs to form a cyclical method of "sweeping section-frequency locking-loading-retesting". It can be superimposed with low-amplitude pulsed water hammer or micro-flow injection disturbance to induce pore pressure fluctuations and reduce effective stress, thereby further reducing the fracturing threshold.

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