Spiral underground movable transducer array and resonance action method

Abstract

The invention discloses a spiral underground movable transducer array for shale oil exploitation and a resonance action method, and belongs to the technical field of unconventional oil and gas field development engineering. According to the array, a plurality of transducer units are spirally arranged around a bearing center shaft at radius and axial intervals, and coherent control is adopted to realize energy focusing and circumferential uniform coverage of rotation phase wavefront. A structure-field-response multi-field coupling model and closed-loop control and parameter optimization taking the model as a core are established, and the influence of temperature and pressure conditions on attenuation is considered. The result shows that the field uniformity is improved by about 60%, the effective action radius reaches 20-30 m, the weakening amplitude is 45% + / -3%, parameter synergy is formed with hydraulic fracturing, the pumping pressure is reduced by 20%-25%, and the interlayer penetration rate gt is achieved; 80%. The device is compact in structure, adjustable in parameter, movable and reusable, and suitable for pretreatment and collaborative fracturing of unconventional oil and gas reservoirs.

Description

Technical Field

[0001] This invention belongs to the field of unconventional oil and gas field development engineering, and relates to the resonance pretreatment equipment and method for shale oil reservoirs before hydraulic fracturing, specifically a spiral downhole movable transducer array and resonance method. Background Technology

[0002] In shale oil development, reservoir pretreatment before hydraulic fracturing helps reduce the effective strength of tight reservoirs and improve fracture conductivity and uniformity. However, existing downhole transducer arrays are mostly derived from logging platforms, with a focus on formation characterization and insufficient energy focusing design for quantitative coupling of "structure-field-response," making it difficult to meet engineering requirements for energy utilization and effective radius. Existing single-row or sparse ring arrays mainly suffer from the following problems: Low energy transmission efficiency: Acoustic / elastic resonance waves attenuate and superimpose along the radial direction of the wellbore, and the effective radius of action is usually less than 5m; Uneven field coverage: lack of array arrangement-phase-frequency matching model, large fluctuations in circumferential resonance intensity, with the coefficient of variation often exceeding 30%; Poor controllability of weakening: The relationship between rock damage evolution and resonance parameters is not established in a closed loop, which can easily lead to over-excitation or under-excitation.

[0003] Therefore, there is an urgent need for a spiral downhole resonant transducer array and method that integrates array structure design, coherent excitation control, damage target closed-loop optimization, and on-site mobile deployment to achieve directional energy superposition and uniform coverage, controllable weakening effect, and parameter synergy with fracturing processes. Therefore, this application discloses a spiral downhole mobile transducer array and resonance method to solve the problems of low energy transmission efficiency, uneven resonance field coverage, and poor controllability of rock weakening effect. Summary of the Invention

[0004] Technical problems to be solved A spiral movable transducer array and its resonance method are proposed to achieve directional superposition and uniform coverage of energy in small-diameter, high-attenuation media in downhole. A multi-field coupling model of "array structure-resonance field distribution-rock damage response" is established. Combined with closed-loop adaptive coherent excitation and operating condition self-correction, the low energy transmission efficiency of existing arrays is solved, the rock strength of the target section can be quantified and weakened, and parameter synergy with hydraulic fracturing is formed to improve fracturing uniformity and productivity.

[0005] Technical solution To achieve the above objectives, the present invention provides the following technical solution: a spiral-type downhole movable transducer array, comprising: a transducer array arranged around a supporting central axis with a radius of... Distributed and spaced along the axial direction arranged in a spiral Each transducer unit, in conjunction with a centering and retractable anchoring assembly, enables segmented positioning / unlocking / movement; multi-channel drive achieves phase control of each transducer unit. ,frequency Amplitude Online adjustment to form an energy superposition coefficient within the target area. Enhanced coherent field distribution.

[0006] Preferably, the transducer is covered with an acoustic impedance matching coupling layer, the material and thickness of which are optimized based on the impedance characteristics of the well fluid and the well wall to reduce interface reflection and improve energy injection efficiency; the shell is made of high temperature and high pressure resistant material, suitable for working conditions of not less than 150°C and 60MPa.

[0007] Preferably, the sensor system includes an accelerometer, a piezoelectric pressure gauge, and / or a fiber optic sensor for estimating the average sound pressure in the target domain. It determines the location of the spectrum peak and provides closed-loop feedback to the control system.

[0008] Preferably, the control system has frequency sweep and phase-locked loop functions, so as to... Centered on Adaptive frequency sweeping within the range and locking the optimal frequency point; possesses phase gradient Synthesizing functions are used to form a rotating phase wavefront and to support amplitude balancing to suppress local overexcitation.

[0009] Preferably, the centering and anchoring components work together to achieve a segmented operation process of "positioning-excitation-unlocking-movement-reset" to adapt to the field requirements of different well diameters.

[0010] A resonance method for a helical downhole movable transducer array, applied to the helical downhole movable transducer array as described above, includes the following steps: S1 Well section selection and parameter initialization; S2 Downhole positioning and anchoring; S3 Frequency sweeping-phase locking to obtain resonant frequency points and set phase gradient. With amplitude S4 closed-loop excitation until the preset damage target is reached. S5 Verification and Correction; S6 Unlock - Move to the next well section and repeat S2–S5.

[0011] Preferably, the closed-loop estimation model is: and with As an adjustable parameter, convergence to The preset range.

[0012] Preferably, the operation is configured with safety boundaries, including a vibration threshold, a casing / cement sheath response threshold, and a maximum excitation duration. When any threshold is triggered, the system automatically limits amplitude and de-phases, and records the data for subsequent segment strategy updates.

[0013] Preferably, for thin interlayer target segments, priority is given to improving... and reduce Simultaneously, amplitude pre-compensation is performed on the elements near the interlayer interface according to distance, and constraints are applied. To maintain uniform coverage.

[0014] Preferably, the downhole and wellhead control links employ clock synchronization and phase-locked loop technology, with a frequency output accuracy better than ±0.05kHz, to improve robustness to temperature and pressure changes and equipment drift.

[0015] The overall plan mainly includes the following parts: Structure and Deployment: A transducer array arranged spirally along the wellbore axis, equipped with centering and anchoring components for segmented positioning and repeated movement, and covered with an acoustic impedance matching coupling layer to improve energy injection efficiency; Modeling and Optimization: Construct an elastic wave propagation-attenuation model, a helical array coherent superposition model, and a damage evolution model in porous media, and provide a multi-objective optimization method for frequency / phase / amplitude / duration; Closed-loop control: Downhole sensors provide feedback on the target domain acoustic pressure and spectrum, and adjust the frequency, phase gradient and amplitude online to achieve adaptive tracking of preset damage targets; Process synergy: A field process of "segmentation-measurement-adjustment-excitation-testing-transfer" is proposed and linked with the hydraulic fracturing pump injection scheme.

[0016] Beneficial effects Compared with the prior art, the present invention provides a spiral-type downhole movable transducer array and a resonance method, which has the following beneficial effects: 1. Employing a spiral three-dimensional arrangement and phase gradient control results in higher radial pointing gain, more uniform circumferential coverage, and a higher energy superposition coefficient. Significantly improved, with the effective radius extended to 20–30 m. Compared to single-row or sparse ring arrays, the target area is significantly larger at the same power. An improvement of approximately 20%–35%. A more uniform initial mechanical field avoids non-uniform crack propagation caused by differences between strong and weak layers, resulting in a significant improvement in energy utilization.

[0017] 2. Based on the "structure-field-response" model and closed-loop control, the weakening error can be controlled within ±5%. Settings can be configured according to the sensitivity of each well section. When the weakening is insufficient, it automatically compensates; when it approaches the safety threshold, it automatically de-phases and limits the amplitude. The "presettable, verifiable, and calibrable" engineering control closed loop achieves precise and controllable weakening effect.

[0018] 3. After pretreatment, the elastic parameters are more controllable, the initiation pressure is reduced by 20%–25%, and the interlayer penetration rate is >80%. The fracture network is more symmetrical and the conductivity is more stable, resulting in increased production capacity and easier maintenance of stability, which is particularly significant for thin interlayered and highly heterogeneous well sections, and enhances the synergistic fracturing capability.

[0019] 4. Temperature and pressure resistant materials, coupling layers, and limiting / time-limiting strategies ensure the usability of HTHP. Segmented repetitive operations reduce the number of tools and the frequency of tripping in and out, improving operational efficiency and safety margins. It is compatible with various well diameters and can be applied across oil and gas reservoir types, making it both engineered, reliable, and reusable. Attached Figure Description

[0020] Figure 1 Control and signal closed-loop flowchart; Figure 2 Flowchart for optimizing resonance parameters; Figure 3 Define tables for array and medium parameters; Figure 4 The results of the model-simulation-experiment comparison in Example 1 are shown below; Figure 5 This is a comparison of the compressive strength before and after in Example 1; Figure 6 This is a table showing the evolution of damage factor D over time in Example 1; Figure 7 This is a comparison chart of uniformity and superposition coefficient in Example 2; Figure 8 Table showing the stability results of HTHP (High Temperature and High Pressure) test; Figure 9 A comparison table of key indicators for on-site collaborative fracturing. Detailed Implementation

[0021] 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.

[0022] 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 spiral downhole movable transducer array and a resonance method.

[0023] Explanation of terms and symbols (rho, rock density, kg / m³) 3 ); (Displacement component, m); (Time, s); (Young's modulus, Pa); (Poisson's ratio, dimensionless); (Lame constant, Pa); (Frequency, Hz); (Angular frequency, rad / s); (Wave speed, m / s); (Radiation area, m) 2 ); (Amplitude, m); (Mean sound pressure level, Pa); (Critical damage sound pressure, Pa); (Damage factor, dimensionless); (Material property coefficients, dimensionless); (Formation temperature, °C); (Containing pressure of formation, MPa); (Attenuation coefficient, dB / m); (Array radius, m); (Initial phase angle, rad); (Number of transducers, in units); (Axial spacing, m); (Depth of the first unit, m); (Distance from the k-th unit to the target point, in meters); (Energy superposition coefficient, dimensionless). (wavelength, m); HTHP (high temperature and high pressure conditions).

[0024] I. Physical-Mathematical Model (Reference Appendix) Figures 3-6 ) Wave control equations (equivalent elastic body of porous media, rectangular coordinate system) , in (Volume strain, dimensionless) (Energy source intensity, N / m) 3 The relationship between Lamé constant and elastic parameters:

[0025] Temperature and pressure correction for attenuation coefficient: , in (Standard condition attenuation coefficient, dB / m) (Temperature effect coefficient, °C) -1 ), (Containing pressure influence coefficient, MPa) -1 ).

[0026] Helical array spatial position (cylindrical coordinates):

[0027] Unit radiation and coherent superposition: , in (wavelength, m) (Phase offset, rad).

[0028] Rock damage and strength weakening: , in (Compressive strength, Pa) (Initial compressive strength, Pa).

[0029] Parameter optimization (guided by the target weakening magnitude, see appendix) Figure 4 ) , in (Natural frequency, Hz) (Sweep half-width, Hz) (Minimum superposition coefficient, dimensionless).

[0030] II. Control Strategies (See Appendix) Figure 1 , Figure 2 ) Frequency sweep and phase lock: Centered adaptive frequency sweep, based on Locking in the optimal frequency with the spectral peak; Phase gradient setting: Synthesize rotating phase wavefront, maximize ; Amplitude balancing: For near-end elements, according to Amplitude pre-compensation is performed to suppress local overexcitation; Safety boundary: Set amplitude limit Limited Time Offer and sleeve / cement ring response threshold; Target closed loop: with (Target damage factor) is a set value, adjusted online. .

[0031] III. Construction Technology (see attached document) Figure 7 ) A standard process of "segmentation-measurement-adjustment-excitation-testing-transfer" is proposed and coordinated with fracturing parameters (displacement, viscosity, proppant concentration).

[0032] IV. Implementation Examples (see attached document) Figure 4 – Figure 9 ) Example 1 Indoor model calibration and verification (see attached document) Figures 4-6 ) Experimental conditions: Core diameter 50mm, length 100mm; (temperature), MPa (containing pressure); kg / m 3 (density), GPa (Young's modulus) (Poisson's ratio); dB / m (attenuation coefficient) ℃ -1 (Temperature coefficient) MPa -1 (Containing pressure coefficient); Array parameters: (quantity), m (radius) rad (initial phase) m (space); initial value of resonance kHz (frequency) Pa (mean sound pressure level). h.

[0033] Steps and parameters: Refer to the attached document. Figure 2 Optimize and lock in the main resonant frequency; set To maximize Amplitude balancing suppresses near-end overexcitation; a multi-channel vibration testing system is used to complete excitation and measurement.

[0034] Results and benefits: (Compressive strength) decreased from 72MPa to 39.6MPa, a weakening of approximately 45%; the effective radius of action is approximately 25m; under the same energy input, compared to a single-row array, the field uniformity is improved by approximately 60%. Theoretical-simulation-experimental error ≤ 3%.

[0035] The accuracy and controllability of the "structure-field-response" model and closed-loop control were verified on an experimental scale, demonstrating that the weakened target can be controlled within ±3% error.

[0036] Example 2 Homogeneity optimization of thin interbedded reservoirs (see attached reference) Figure 7 - Comparison table of uniformity and superposition coefficient) Experimental conditions: Wellbore diameter Φ114–139.7mm (compatible) m), with 2–5 m of thin interlayers and heterogeneity within the layer.

[0037] Steps and parameters: (quantity), m (spacing); calculated according to target geometry ,constraint The amplitude of the cells closer to the interface is reduced by 10%–15%.

[0038] Results and advantages: Thin interlayer transition region The variance is reduced by 30%–40%, and the effective radius of action is 20–30m, avoiding brittle instability caused by local overreaction.

[0039] Proved that , and Collaborative design can maintain high homogeneity and high performance under heterogeneous conditions. .

[0040]

[0041] Example 3 Materials and safety boundaries for HTHP conditions (see attached reference) Figure 8 ) Experimental conditions: (temperature), MPa (confining pressure); casing deformation monitoring threshold <2%.

[0042] Steps and parameters: A high-temperature and high-pressure resistant alloy and a high-temperature coupling layer are used; settings are... (Maximum amplitude) h (maximum duration); monitoring boundary conditions, i.e., amplitude limiting and phase reversal.

[0043] Results and benefits: Frequency output accuracy better than ±0.05kHz, safety-performance trade-off is controllable, and structural risks are avoided.

[0044] The reliability and safety control effectiveness under HTHP conditions were verified.

[0045] Example 4: On-site collaborative fracturing process verification (see attached document) Figures 7-9 ) Experimental conditions: multi-stage and multi-cluster horizontal wells; compatible with conventional sliding sleeve ball seat technology; pumping capacity meets fracturing requirements.

[0046] Steps and parameters: Segmented anchoring is performed using the "test-adjust-excite-test" method to achieve the desired results. Exit; move to the next section and repeat; reconfigure fracturing flow rate / viscosity / proppant based on weakened elasticity and seepage parameters.

[0047] Results and benefits: Pump pressure decreased by 20%–25%; interlayer penetration rate >80%; daily production per well increased from 9.5t to approximately 14.2t (example range).

[0048] This demonstrated the field feasibility and production-increasing effect of "resonance pretreatment-fracturing synergy".

[0049] V. Sources and Control of Errors (See Appendix) Figure 1 , Figure 2 ) Formation heterogeneity: Fluctuation-induced error (≤3%); Real-time correction of geological guidance; Equipment accuracy: Frequency output accuracy ±0.05–0.1kHz (introduced) Deviation (≤0.6%); Phase-locked loop compensation; Boundary conditions: Dynamically caused Error (≤1.5%); Sensor closed-loop correction; Overall error: theoretical / simulation / experimental error ≤3%.

[0050] Compared to existing technologies, this application employs a helical three-dimensional array and "rotating phase gradient" coherent control to improve radial gain and circumferential uniformity, thereby increasing the energy superposition coefficient and effective radius of action. Furthermore, through a "structure-field-response" coupled model and closed-loop optimization control of the D-target (damage factor target), the rock strength weakening amplitude can be preset, verified, and corrected. Moreover, the mobile segmented operation and adaptive positioning / anchoring allow for repeated use of the equipment within long well sections and selective excitation for thin interlayers, reducing operating costs and improving safety.

[0051] 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 spiral-type downhole movable transducer array, characterized in that, include: Around the load-bearing central axis with radius Distributed and spaced along the axial direction arranged in a spiral Each transducer unit, in conjunction with a centering and retractable anchoring assembly, enables segmented positioning / unlocking / movement; multi-channel drive achieves phase control of each transducer unit. ,frequency Amplitude Online adjustment to form an energy superposition coefficient within the target area. Enhanced coherent field distribution.

2. The spiral-type downhole movable transducer array according to claim 1, characterized in that: The transducer is covered with an acoustic impedance matching coupling layer. The material and thickness of the coupling layer are optimized based on the impedance characteristics of the well fluid and the well wall to reduce interface reflection and improve energy injection efficiency. The shell is made of high temperature and high pressure resistant material, which is suitable for working conditions of not less than 150°C and 60MPa.

3. The spiral-type downhole movable transducer array according to claim 1, characterized in that: The sensor system includes accelerometers, piezoelectric pressure gauges, and / or fiber optic sensors for estimating the average sound pressure in the target domain. It determines the location of the spectrum peak and provides closed-loop feedback to the control system.

4. The spiral-type downhole movable transducer array according to claim 1, characterized in that: The control system has frequency sweeping and phase-locked loop functions. Centered on Adaptive frequency sweeping within the range and locking the optimal frequency point; possesses phase gradient Synthesizing functions are used to form a rotating phase wavefront and to support amplitude balancing to suppress local overexcitation.

5. A spiral-type downhole movable transducer array according to claim 1, characterized in that: The centering and anchoring components work together to achieve a segmented operation process of "positioning-excitation-unlocking-movement-reset" to adapt to the field requirements of different well diameters.

6. A method for the resonance effect of a helical downhole movable transducer array, applied to a helical downhole movable transducer array as described in any one of claims 1-5, characterized in that, Includes the following steps: S1 well section selection and parameter initialization; S2 wellhead positioning and anchoring; S3 frequency sweep-phase lock-in acquires the resonant frequency and sets the phase gradient. With amplitude ; S4 closed-loop excitation until the preset damage target is reached. ; S5 verification and calibration; S6 unlock - move to the next well section and repeat S2–S5.

7. The resonance method for a helical downhole movable transducer array according to claim 1, characterized in that: The closed-loop estimation model is: and with As an adjustable parameter, convergence to The preset range.

8. The resonance method for a helical downhole movable transducer array according to claim 6, characterized in that: The operation includes setting safety boundaries, such as vibration threshold, casing / cement sheath response threshold, and maximum excitation duration. When any threshold is triggered, the system automatically limits amplitude and de-phases, and records the data for subsequent segment strategy updates.

9. The resonance method for a spiral-type downhole movable transducer array according to claim 1, characterized in that: For thin interlayer target segments, priority should be given to improving and reduce Simultaneously, amplitude pre-compensation is performed on the elements near the interlayer interface according to distance, and constraints are applied. To maintain uniform coverage.

10. The resonance method for a helical downhole movable transducer array according to claim 6, characterized in that: The downhole and wellhead control links employ clock synchronization and phase-locked loop technology, with a frequency output accuracy better than ±0.05kHz, to improve robustness to temperature and pressure changes and equipment drift.

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