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CN-120871264-B - Method, device and equipment for generating low-frequency limited acoustic beam in well and computer storage medium

CN120871264BCN 120871264 BCN120871264 BCN 120871264BCN-120871264-B

Abstract

A method for generating a low-frequency limited acoustic beam in a well comprises the steps of determining a transducer aperture according to the size of a borehole in the well, calculating a nonlinear action area of a radiation sound field based on the transducer aperture and distance parameters, selecting a sound source design modulation theoretical model according to the nonlinear action area, determining sound source parameters of the transducer based on the sound source design modulation theoretical model and the transducer aperture, carrying out nonlinear radiation sound field simulation according to the sound source parameters, determining a critical propagation distance corresponding to the maximum value of a difference frequency sound source level, extracting nonlinear sound wave signal characteristics at the distance, generating loadable modulation signals based on the characteristics, measuring and comparing the signal characteristics of the transducer in a loadable modulation signal loading state and in a natural radiation modulation signal loading state, and determining loadable modulation signals with larger difference frequency sound source levels. The invention can generate nonlinear acoustic signals containing larger low-frequency components when the radiation distance is smaller, and the difference frequency conversion efficiency of the generated nonlinear radiation signals is high.

Inventors

  • ZHANG XIUMEI
  • WEI QIAN
  • LIU BIN
  • LIU LIN
  • QI YUJUAN

Assignees

  • 中国科学院声学研究所

Dates

Publication Date
20260508
Application Date
20250707

Claims (8)

  1. 1. A method of producing a low frequency limited acoustic beam in a well, the method comprising: Determining a transducer aperture according to the size of the underground drilling hole, and calculating a nonlinear action area of a radiation sound field based on the transducer aperture and distance parameters, wherein the distance parameters comprise an acoustic absorption distance, a Rayleigh distance and an impact distance of an original frequency wave; selecting a sound source design modulation theoretical model according to the nonlinear action region, and determining sound source parameters of a transducer based on the sound source design modulation theoretical model and the transducer aperture; According to the determined sound source parameters, carrying out simulation calculation of sound waves in a nonlinear radiation sound field, determining a critical propagation distance corresponding to the maximum value of a difference frequency sound source level, extracting nonlinear sound wave signal characteristics at the critical propagation distance, and generating loadable modulation signals based on the nonlinear sound wave signal characteristics; Measuring a first output signal characteristic of the transducer in a loadable modulated signal loading state; measuring a second output signal characteristic of the transducer in a natural radiation modulated signal loading state; and comparing and analyzing the first output signal characteristic and the second output signal characteristic to determine the loadable modulation signal with larger difference frequency sound source level.
  2. 2. The method of claim 1, wherein the acoustic source design modulation theory model comprises WESTERVELT, BERKTAY and Mellen.
  3. 3. The method of claim 1, wherein the sound source parameters of the transducer to be optimally designed include primary frequency and sound source level, difference frequency and sound source level, and beam width.
  4. 4. The method according to claim 1, wherein the simulation calculation of the sound wave in the nonlinear radiation sound field is completed by a KZK equation after integration and normalization.
  5. 5. The method of claim 1, wherein the natural radiation modulated signal is a CW amplitude modulated envelope signal or an LFM modulated signal.
  6. 6. A device for generating a low frequency limited sound beam in a well, characterized in that the low frequency limited sound beam is generated by a method according to any one of claims 1 to 5, the device comprising: The nonlinear region calculation module is used for determining a transducer aperture according to the size of the underground drilling hole and calculating a nonlinear action region of the radiation sound field based on the transducer aperture and the distance parameter; the sound source parameter determining module is used for selecting a sound source design modulation theoretical model according to the nonlinear action area, and determining sound source parameters of the transducer based on the sound source design modulation theoretical model and the transducer aperture; The sound field calculation module is used for carrying out simulation calculation of sound waves in a nonlinear radiation sound field according to the determined sound source parameters, determining a critical propagation distance corresponding to the maximum value of a difference frequency sound source level, extracting nonlinear sound wave signal characteristics at the critical propagation distance, and generating loadable modulation signals based on the nonlinear sound wave signal characteristics; the modulation signal measuring module is used for measuring a first output signal characteristic of the transducer in a loadable modulation signal loading state; And the modulation signal analysis module is used for determining loadable modulation signals with larger difference frequency sound source level by comparing and analyzing the first output signal characteristics and the second output signal characteristics.
  7. 7. An electronic device comprising a memory, a processor, the memory having stored thereon a computer program executable on the processor, characterized in that the processor implements the method of any of the preceding claims 1 to 5 when the computer program is executed.
  8. 8. A computer readable medium having non-volatile program code executable by a processor, the program code causing the processor to perform the method of any one of claims 1 to 5.

Description

Method, device and equipment for generating low-frequency limited acoustic beam in well and computer storage medium Technical Field The present invention relates to the field of acoustic technologies, and in particular, to a method, an apparatus, a device, and a computer storage medium for generating a low-frequency limited acoustic beam in a well. Background In geophysical acoustic logging detection technology, when an acoustic signal is emitted from a well hole, the generated acoustic signal is coupled with mud filled in the well to be further propagated in the stratum, and parameters such as lithology, porosity and permeability of stratum medium outside the well can be obtained by arranging an acoustic signal receiving device in the well and processing and interpreting the received acoustic signal, and reflectors and cracks in a certain range far away from the well hole can be obtained or distribution positions of oil, gas and water layers can be identified. In the existing acoustic wave remote detection technology in the well, three sound sources, namely a monopole, a dipole and a phase control sound source are mainly adopted. The acoustic logging instrument developed by the acoustic source can image and measure reflectors such as cracks, faults and stratum interfaces in the range of about 3-10 m outside a well wall when the frequency of the emitted acoustic wave is 8-10 kHz by adopting a monopole acoustic emission technology, and dipole acoustic sources (the main frequency of the acoustic sources is about 1.0-3.kHz) with relatively low emission frequency can generate dipole transverse waves in the stratum, and the measured information can reflect geological reflectors such as faults, cracks and stratum interfaces in the range of tens of meters away from the well wall, so that important technical support can be provided for the design of an oil testing scheme. However, one difficulty that has not been addressed so far by this measurement technique is the 180 degree uncertainty of dipole detection. In order to break through the azimuth limitation of dipole transverse wave imaging logging, the acoustic phased array sound source technology is also applied to in-well reflected wave imaging, the measuring mode is mainly aimed at regulating and controlling the phase and amplitude of stratum longitudinal waves radiated into the stratum, the frequency of the longitudinal waves is relatively high, the attenuation is fast, the risk that reflected signals are annihilated by direct wave information is easily caused, the angle resolution of the phased acoustic phased array technology for imaging the stratum outside the well is about 22.5 degrees, and the radial detection distance is generally equivalent to that of a monopole sound source emission technology. It can be seen that the characteristics of sound source radiation in the technology of acoustic wave remote detection in a well are decisive factors of the detection distance and azimuth resolution of the instrument. However, the instrument measurement technology based on the above several acoustic sources has not been provided with both radial detection distance and more accurate circumferential direction identification capability of the formations outside the well. For this reason, considering that the parametric array technology based on nonlinear mixing of acoustic waves has characteristics of superdirectivity, low frequency broadband, etc., patent application publication No. 201180027274.4 proposes a method for generating parallel acoustic beams in a borehole, and referring to fig. 1, the method proposes loading a high-frequency primary frequency signal on a transmitting transducer 101, and after passing through a nonlinear material 102 disposed in front of the transducer, the generated low-frequency parallel acoustic beam 103 propagates to an acoustic reflector 104 located in front of the transducer, and the acoustic reflector reflects the reflected acoustic beam 106 into an underground formation. Wherein 101 to 104 are mounted in a coaxial manner in a metal housing 105. Upon encountering the reflector 107 in the formation outside the well, the signal 108 from the reflector will again be returned to the borehole, and the receiving transducer 109 placed in the borehole will transmit the signal to the electronics 110, which will be able to acquire the parameters in the formation outside the well after data processing. In this patent, the basis for the formation of parallel beams of sound from a source of sound emitted is the parametric array technique, which has the main problem: (1) The nonlinear material portions are inconvenient to install and operate. After the transmitting transducer is loaded with high-frequency original frequency signals, a low-frequency parallel sound beam can be formed through nonlinear substances placed in front of the transmitting transducer, and the nonlinear substances are substances with characteristics of low sound velocity, h