Through casing acoustic logging device and method based on phase delay cancellation of receiving end

Abstract

The application discloses a through casing acoustic logging device and method based on phase delay sound elimination of a receiving end. The through casing acoustic logging device comprises a shell, a measuring system and an upper computer, a bellows and a mandrel are arranged in the shell, the two ends are sealed and filled with silicon oil, the measuring system is fixed on the mandrel and comprises a sound emitter, an array sound receiver and a measurement and control circuit, the array sound receiver comprises a plurality of coaxial sound receivers arranged at equal intervals, adjacent sound receivers form a basic sound elimination unit, the measurement and control circuit comprises a sound emission circuit and a sound receiving circuit, and the sound receiving circuit is adopted to perform phase delay sound elimination processing on sound wave signals received by the sound receiver to obtain formation wave signals by eliminating casing waves. The application effectively suppresses casing waves based on phase delay sound elimination of the receiving end, improves the formation wave signal noise ratio from a data acquisition source, realizes accurate measurement of formation acoustic velocity by the acoustic logging instrument in a casing well, and widens the application range of the acoustic logging instrument in formation evaluation of the casing well.

Description

Technical Field

[0001] This invention relates to the field of geophysical logging technology, specifically to a casing acoustic logging device and method based on receiver phase delay silencing. Background Technology

[0002] In oil and gas field exploration and development, after drilling, casing needs to be installed in open-hole wells to support the wellbore, protect the formation, and control the direction of oil and gas flow. Cement is then used to firmly bond the casing to the formation, forming a casing well. In recent years, casing drilling, complex and risky wells, and the potential tapping and stimulation of old oil wells all require logging in casing wells. Sonic logging, as an important geophysical logging method, is mainly used to measure formation P-wave velocity. However, due to the presence of casing and cement in the casing well, especially when the cement fails to completely bond the casing to the formation, most of the energy of the acoustic waves emitted in the well propagates along the casing as casing waves, while useful formation waves are often aliased and submerged in the time domain by the larger amplitude casing waves. This makes it difficult to collect formation waves in the well, thus hindering accurate calculation of formation sound velocity and reservoir evaluation. Therefore, how to suppress casing waves, strip formation waves, and improve their signal-to-noise ratio has become an important issue in through-casing acoustic logging research.

[0003] Borehole acoustic field simulation in casing wells shows that even in the case of a completely unbonded free casing, the acoustic signal received in the well contains a formation wave component. However, the formation wave signal is often submerged by the stronger casing wave, resulting in a low signal-to-noise ratio of the formation signal, making it difficult to accurately extract the formation longitudinal wave velocity from the acquired acoustic signal.

[0004] To suppress casing waves in received acoustic signals, Chinese invention patent CN104594878A discloses a dual-source excitation through-casing acoustic logging method and device. This technical solution uses two identical acoustic sources. When the casing wave excited by the first source reaches the second source, the second source starts operating, and its signal has the same amplitude but opposite polarity as the first source. After superposition, the casing waves cancel each other out, thus achieving the purpose of suppressing the casing waves. The core idea of ​​the above technical solution is to physically generate two casing wave signals of equal magnitude and opposite polarity through acoustic source control, allowing them to interact and cancel each other out.

[0005] However, since the amplitude of casing waves is often much larger than that of formation waves, poor cementation can even completely submerge the formation waves. Furthermore, the signal gain acquired by acoustic logging is controlled by the mode wave with the largest amplitude in the signal. Considering that the circuit gain of through-casing acoustic logging is controlled by the casing wave amplitude and is not the optimal gain for formation waves, even if phase delay silencing can suppress casing waves after data quantization without considering quantization noise, it is not the optimal method to improve the signal-to-noise ratio of formation waves. Therefore, there is an urgent need to propose an through-casing acoustic logging device and method based on receiver-side phase delay silencing to achieve the optimal signal-to-noise ratio of formation waves from the physical signal source of data acquisition. Summary of the Invention

[0006] To address the shortcomings of the existing technology, this invention provides a casing-based acoustic logging device and method based on receiver phase delay silencing. Utilizing a near-sound receiver and a far-sound receiver in the same basic silencing unit, the casing wave from the near-sound receiver is phase-delayed and then superimposed with the casing wave from the far-sound receiver to suppress the casing wave. Combined with hardware circuitry before acoustic signal quantization, phase silencing of the acquired acoustic signal is achieved, ensuring that the gain of subsequent circuits is controlled by the formation wave amplitude. This enables accurate measurement of formation waves and effectively improves the formation wave signal-to-noise ratio from the data acquisition source, providing technical support for accurate measurement of formation sound velocity in casing wells.

[0007] The present invention adopts the following technical solution:

[0008] A casing-mounted acoustic logging device based on receiver phase delay silencing includes a housing, a measurement system installed inside the housing, and a host computer installed on the ground.

[0009] The housing is a metal cylinder with a bellows inside. A spindle is installed inside the bellows along the central axis to support the measurement system. Both ends of the bellows are sealed with high-temperature pressure-bearing seals, and the bellows is filled with silicone oil to ensure acoustic coupling and external pressure balance within the housing.

[0010] The measurement system is fixed on a mandrel inside a bellows and includes an acoustic transmitter, an array of acoustic receivers, and a measurement and control circuit. The measurement and control circuit includes an acoustic emission circuit and an acoustic receiving circuit. The acoustic transmitter, array of acoustic receivers, and measurement and control circuit are all connected to a host computer, which controls the power supply, command transmission and reception, and data transmission of the measurement system in a high-temperature, sealed environment. The acoustic transmitter is connected to the acoustic emission circuit, which provides a high-voltage pulse signal to excite the acoustic transmitter to generate sound waves radiating towards the casing and the formation. The array of acoustic receivers consists of N coaxially spaced receivers. The array consists of at least two acoustic receivers. Two adjacent acoustic receivers in the array together form a basic anechoic unit. The acoustic receiver closer to the acoustic transmitter in the basic anechoic unit is called the near acoustic receiver, and the acoustic receiver farther away from the acoustic transmitter is called the far acoustic receiver. The near acoustic receiver and the far acoustic receiver in the basic anechoic unit are respectively connected to the corresponding acoustic receiving circuit. The acoustic receiving circuit is used to perform phase delay anechoic processing on the acoustic wave signals received by the near acoustic receiver and the far acoustic receiver in the basic anechoic unit to cancel the casing wave and obtain the formation wave signal.

[0011] A sound insulation material is provided on the housing between the acoustic transmitter and the array acoustic receiver to attenuate the instrument waves propagating along the housing.

[0012] Preferably, both the acoustic transmitter and the acoustic receiver are configured as acoustic-to-electric conversion sensors, employing monopole, dipole, or quadrupole modes.

[0013] Preferably, the sound insulation material is configured with periodically and uniformly arranged holes.

[0014] Preferably, the acoustic emission circuit and the acoustic receiving circuit are respectively located near the acoustic emitter and the acoustic receiver, and are encapsulated with high-temperature resistant epoxy resin;

[0015] The acoustic emission circuit includes a signal generator, a filter amplifier circuit, and a power amplifier circuit connected in sequence, used to generate high-voltage pulse signals with adjustable frequency and amplitude;

[0016] The acoustic receiving circuit is equipped with an FPGA controller, a phase delay silencing circuit, a bandpass filter, a programmable gain amplifier, and an analog-to-digital converter. It is used to sequentially pre-amplify, phase-delay, bandpass filter, gain adjust, and analog-to-digital convert the acoustic wave signal collected by the basic silencing unit to obtain N-1 formation wave signals.

[0017] The phase delay silencing circuit is used to perform phase delay silencing at the receiving end, and internally includes a preamplifier A, a preamplifier B, a phase delay unit, an amplitude control unit, and an adder.

[0018] Preferably, the phase delay anechoic process is performed on the acoustic signals received by the near-sound receiver and the far-sound receiver in the same set of basic anechoic units. By delaying the phase of the acoustic signal received by the near-sound receiver backward in the time domain, the casing wave in the acoustic signals received by the near-sound receiver and the far-sound receiver arrives at the same time. By adjusting the amplitude and polarity of the acoustic signals received by the near-sound receiver and the far-sound receiver to be opposite, the amplitude of the casing wave in the acoustic signals received by the near-sound receiver and the far-sound receiver are made equal and opposite in polarity. The casing wave in the acoustic signal is then superimposed and canceled, so that only the formation wave remains in the acoustic signal, resulting in a weak formation wave signal that cancels the casing wave.

[0019] Preferably, after the host computer controls the acoustic transmitter to apply an excitation signal to generate a direct wave propagating along the shell, a casing wave propagating along the casing inside the well, and a formation wave propagating along the formation, the FPGA controller receives the acoustic transmitter synchronization command issued by the host computer and starts N-1 basic silencing units in the array acoustic receiver to collect acoustic wave signals, thereby obtaining N-1 acoustic wave signals including casing waves and formation waves.

[0020] For each basic noise reduction unit, a phase delay noise reduction circuit is used for phase delay noise reduction. The acoustic signal R2 received by the far-field receiver is input to preamplifier B for gain amplification to obtain the far-field receiver acoustic signal. Simultaneously, the acoustic signal R1 received by the near-field receiver is input to preamplifier A for gain amplification. The FPGA controller uses the SPI bus to command the phase delay unit to amplify and delay the phase of the acoustic signal R1. Then, the amplitude control unit is used for amplitude control to obtain the processed near-field receiver acoustic signal. The amplitude of the processed near-field receiver acoustic signal is equal to the amplitude of the processed far-field receiver acoustic signal. The processed near-field receiver acoustic signal is input to the non-inverting input of the adder. The processed far-field acoustic signal is input to the inverting input of an adder. The adder superimposes the processed near-field and far-field acoustic signals to cancel out the casing wave in the acoustic signal, thus obtaining a weak formation wave signal. The weak formation wave signal is then sequentially input to a bandpass filter, a programmable gain amplifier, and an analog-to-digital converter. The bandpass filter eliminates low-frequency power frequency interference and high-frequency noise in the weak formation wave signal. The programmable gain amplifier then controls the gain to improve the dynamic measurement range. After quantization by the analog-to-digital converter, the formation wave signal of channel N-1 is obtained. The formation wave signal is stored in a memory connected to the FPGA controller and transmitted to the host computer via a CAN bus connected to the FPGA controller.

[0021] The host computer is equipped with a central control system, which is used to calculate the formation wave velocity based on the formation wave signal transmitted by the measurement system.

[0022] A method for through-casing acoustic logging based on receiver phase delay silencing, employing the through-casing acoustic logging device based on receiver phase delay silencing as described above, specifically includes the following steps:

[0023] Step 1: Place the through-casing acoustic logging device based on receiver phase delay silencing in the wellbore of the casing well, and use the through-casing acoustic logging device to perform measurements.

[0024] Step 2: Use the host computer to control the acoustic emission circuit of the casing acoustic logging device to apply a high-voltage excitation pulse to the acoustic emitter, which will excite the acoustic emitter to generate a sound field and form an acoustic wave signal with a specified radiation frequency in the casing and formation.

[0025] Step 3: While the acoustic transmitter generates a sound field, the host computer controls the acoustic receiving circuit of the casing acoustic logging device to acquire the acoustic signals received by the near and far acoustic receivers in each group of basic silencing units. After processing by the phase delay silencing processing circuit in the acoustic receiving circuit corresponding to each group of basic silencing units, the casing waves in the acoustic signals received by the near and far acoustic receivers in each group of basic silencing units arrive at the same time, have the same amplitude, and opposite polarities. The casing waves are then superimposed and canceled to obtain the weak formation wave signal.

[0026] Step 4: After bandpass filtering and programmable gain control of the weak ground wave signal using the bandpass filter and programmable gain amplifier in the sound receiving circuit corresponding to each group of basic silencing units, the ground wave signal is quantized and acquired by an analog-to-digital converter and then transmitted to the host computer. The host computer calculates the ground wave velocity based on the ground wave signals acquired by all the basic silencing units.

[0027] Preferably, before the through-casing acoustic logging device is used for measurement in the casing well, the through-casing acoustic logging device is placed in the free casing section in advance, and the optimal amplitude control gain and optimal phase delay of the phase delay silencing processing circuit are determined according to the instrument parameters and casing parameters of the through-casing acoustic logging device.

[0028] Based on the amplitude ratio of the sleeve wave received by the near-sound receiver and the far-sound receiver in the basic silencing unit, determine the optimal amplitude control gain of the phase delay silencing processing circuit in the corresponding sound receiving circuit of the basic silencing unit.

[0029] The optimal amplitude control gain G is shown in Equation (1):

[0030]

[0031] In the formula, G is the optimal amplitude control gain of the acoustic signal received by the near-sound receiver in the basic anechoic unit; A far A represents the maximum amplitude of the sleeve wave received by the far-field receiver in the basic anechoic unit. nearThe maximum amplitude of the sleeve wave received by the near-sound receiver in the basic anechoic unit;

[0032] The optimal phase delay φ for phase delay silencing is determined based on the arrival time difference of the sleeve waves received by the near and far sound receivers in the basic silencing unit.

[0033] The optimal phase delay φ is shown in formula (2):

[0034]

[0035] In the formula, f is the sleeve wave frequency; t far t represents the arrival time of the sleeve wave received by the far-sound receiver in the basic anechoic unit. near d is the arrival time of the tube wave received by the near-sound receiver in the basic anechoic unit; d is the distance between the near-sound receiver and the far-sound receiver in the basic anechoic unit; v t The velocity is the sleeve wave velocity.

[0036] Preferably, the step of determining the optimal phase delay φ is as follows:

[0037] S1, obtain the excitation frequency of the acoustic transmitter in the casing acoustic logging device when it generates a high-pressure acoustic pulse in the casing well.

[0038] S2, based on the sleeve wave frequency and the spacing between the near and far sound receivers in the basic silencing unit, combined with the preset sleeve wave velocity, calculate the initial phase φ0 of the phase delay unit in the phase delay silencing circuit, and set the initial phase φ0 as the current phase delay of the phase delay unit.

[0039] S3, based on the preset phase delay step size Δφ, update the phase delay value of the phase delay silencing circuit by adding the current phase delay to the phase delay step size;

[0040] S4. Based on the updated phase delay value, the phase delay unit in the phase delay silencing circuit is used to process the waveform signal after delay silencing, and the amplitude ΔA of the sleeve wave is observed.

[0041] S5. Repeat steps S3 to S4 until the minimum value of the casing wave amplitude is determined. The phase corresponding to the minimum value of the casing wave amplitude is determined as the optimal phase delay φ.

[0042] The present invention has the following beneficial effects:

[0043] This invention proposes a through-casing acoustic logging device and method based on receiver-end phase delay silencing. By effectively suppressing casing waves through receiver-end phase delay silencing, the signal-to-noise ratio of formation waves is improved from the data acquisition source, enabling the through-casing acoustic logging device to be used for accurate formation sound velocity measurement in casing wells, even in cases of poor casing cementation. Furthermore, the proposed through-casing acoustic logging device does not require modification to the structure of existing acoustic logging instruments; only a phase delay silencing circuit is added to the acoustic receiving circuit to achieve casing wave silencing at the receiving end. This effectively broadens the application range of acoustic logging instruments in casing well formation evaluation and the dynamic application range of the instrument. Attached Figure Description

[0044] Figure 1 This is a schematic diagram of the internal structure of the through-casing acoustic logging device based on receiver phase delay silencing according to the present invention.

[0045] Figure 2 This is a schematic diagram of the overall structure of the through-casing acoustic logging device based on receiver phase delay silencing according to the present invention.

[0046] Figure 3 This is a schematic diagram of the phase delay silencing principle of the through-casing acoustic logging device based on receiver phase delay silencing according to the present invention.

[0047] Figure 4 This is a schematic diagram of the acoustic receiving circuit in the through-casing acoustic logging device based on receiver phase delay silencing according to the present invention.

[0048] Figure 5 The figure shows the amplitude-frequency characteristic curve of the acoustic receiving circuit of the through-casing acoustic logging device of the present invention. In the figure, (a) is the curve of gain as a function of frequency, and (b) is the curve of phase as a function of frequency.

[0049] Figure 6 The figure shows the actual measurement data of the through-casing acoustic logging device based on phase delay silencing at the receiver in a free casing well. In the figure, (a) is the original waveform of the casing well, (b) is the sound velocity result calculated by the time-slowness correlation method of the original waveform, (c) is the waveform of the casing well after phase delay silencing, and (d) is the sound velocity result calculated by the time-slowness correlation method of the waveform after phase delay silencing.

[0050] In the diagram, 1. Housing, 2. Acoustic emitter, 3. Near-sound receiver in the basic anechoic unit, 4. Far-sound receiver in the basic anechoic unit, 5. Acoustic receiver, 6. Acoustic emission circuit, 7. Acoustic reception circuit, 8. Spindle, 9. Bellows, 10. Silicone oil, 11. High-temperature pressure-bearing seal, 12. Sound insulation body. Detailed Implementation

[0051] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings:

[0052] This invention proposes a casing acoustic logging device based on receiver phase delay silencing, which is used to eliminate casing waves in the received acoustic signal when the casing and formation are poorly bonded, thereby achieving accurate measurement of formation longitudinal waves.

[0053] This embodiment uses a through-casing acoustic logging device based on receiver phase delay silencing, such as... Figure 1 and Figure 2 As shown, it includes a housing 1, a measurement system installed inside the housing, and a host computer installed on the ground.

[0054] The housing 1 is a metal cylinder, and a bellows 9 is installed inside the housing. A spindle 8 for supporting the measurement system is installed inside the bellows along the central axis. In order to ensure acoustic coupling and external pressure balance inside the housing, the bellows is filled with silicone oil 10, and both ends of the bellows are sealed with high-temperature pressure-bearing seals 11, which effectively prevents the leakage of silicone oil under high-pressure sealing environment.

[0055] The measurement system is fixed on the mandrel 8 inside the bellows 9 and includes an acoustic transmitter 2, an array acoustic receiver, and a measurement and control circuit. The measurement system includes an acoustic emission circuit 6 and an acoustic receiving circuit 7. The acoustic transmitter 2, the array acoustic receiver, and the measurement and control circuit are respectively connected to a host computer for high-voltage pulse excitation of the acoustic transmitter, conditioning, phase delay, and quantization acquisition control of the acoustic wave signal received by the array acoustic receiver, and command reception and data interaction with the host computer system.

[0056] The host computer is used to control the power supply, command transmission and reception, and data transmission of the measurement system in a high-temperature sealed environment. The acoustic transmitter 2 is connected to the acoustic emission circuit on the electrical-physical layer. The acoustic emission circuit is used to provide a high-voltage pulse signal to excite the acoustic transmitter to generate sound waves radiating towards the casing and the formation, and to realize the communication interaction of the host computer. The array acoustic receiver consists of N coaxially spaced acoustic receivers 5. In this embodiment, the number of acoustic receivers N is set to six. Two adjacent acoustic receivers in the array acoustic receivers form a basic silencing unit. The acoustic receiver closer to the acoustic transmitter in the basic silencing unit is called the near acoustic receiver 3, and the acoustic receiver farther from the acoustic transmitter is called the far acoustic receiver 4. The near acoustic receiver and the far acoustic receiver in the basic silencing unit are respectively connected to the corresponding acoustic receiving circuit. The acoustic receiving circuit is used to pre-amplify, delay, bandpass filter, control the gain, and quantize the acoustic wave signals received by the near acoustic receiver and the far acoustic receiver in the basic silencing unit. Through phase delay silencing processing, the casing wave in the acoustic wave signal received by the acoustic receiver is canceled to obtain the formation wave signal.

[0057] Both the acoustic transmitter 2 and the acoustic receiver 5 are configured as acoustic-to-electric conversion sensors, and can be selected in monopole, dipole, or quadrupole modes. The acoustic emission circuit 6 and the acoustic reception circuit 7 are respectively located near the acoustic transmitter 2 and the acoustic receiver 5, and are encapsulated with high-temperature resistant epoxy resin to achieve electrical insulation. They are connected to the outside of the casing acoustic logging device through conductive pins to ensure instrument power supply, command transmission and reception, and data transmission in a high-pressure sealed environment.

[0058] Meanwhile, since the acoustic transmitter 2 can generate direct waves propagating along the shell, casing waves propagating along the casing inside the well, and formation waves propagating along the formation, in order to prevent the direct waves (i.e. instrument waves) generated by the acoustic transmitter from reaching the array acoustic receiver and being received by each acoustic receiver in the array acoustic receiver to interfere with the measurement of formation waves, a sound insulation body 12 is provided on the shell between the acoustic transmitter and the array acoustic receiver. The sound insulation body is specifically configured as periodically and uniformly arranged holes to attenuate the instrument waves propagating along the shell.

[0059] Furthermore, the acoustic emission circuit includes a signal generator, a filter amplifier circuit, and a power amplifier circuit connected in sequence, used to generate high-voltage pulse signals with adjustable frequency and amplitude. The acoustic receiving circuit is equipped with an FPGA controller, a phase delay silencing circuit, a bandpass filter, a programmable gain amplifier, and an analog-to-digital converter, used to sequentially pre-amplify, phase-delay, bandpass filter, gain adjust, and convert the acoustic wave signal collected by the basic silencing unit to obtain N-1 formation wave signals. The phase delay silencing circuit is used to perform phase delay silencing at the receiving end, and internally includes a preamplifier A, a preamplifier B, a phase delay unit, an amplitude control unit, and an adder.

[0060] The casing acoustic logging device of this invention accurately acquires formation waves based on phase delay anechoic cancellation at the receiving end. The phase delay anechoic cancellation process specifically targets the acoustic signals received by the near-sound receiver and the far-sound receiver in the same set of basic anechoic units. By delaying the phase of the acoustic signal received by the near-sound receiver backward in the time domain, the casing wave in the acoustic signals received by the near-sound receiver and the far-sound receiver arrives at the same time. By adjusting the amplitude and polarity of the acoustic signals received by the near-sound receiver and the far-sound receiver to be opposite, the amplitude of the casing wave in the acoustic signals received by the near-sound receiver and the far-sound receiver are made equal and opposite in polarity. The casing wave in the acoustic signal is then superimposed and canceled, leaving only the formation wave in the acoustic signal, resulting in a weak formation wave signal that cancels the casing wave.

[0061] Figure 3This diagram illustrates the phase delay anechoic effect of the through-casing acoustic logging device based on receiver phase delay anechoic effect. The left side of the diagram shows the device placed in a poorly cemented well model for measurement. The right side shows the device based on receiver phase delay anechoic effect. Since the various components of the signal recorded by the receiver are superimposed during actual logging, this diagram is used for ease of observation and description. Figure 3 The various wave components within the received acoustic signal are drawn separately for easier description. Figure 3 In the cased well model with poor cement bonding, the components from the inside out are the wellbore, casing, fluid ring, cement, and formation. A through-casing acoustic logging device based on receiver phase delay attenuation is placed inside the cased well. From bottom to top, it consists of an acoustic transmitter T, a sound insulation body ISO, and an array of acoustic receivers. In this embodiment, the array of acoustic receivers contains six equally spaced acoustic receivers, designated as receivers R1 to R6. The host computer controls the acoustic emission circuit to apply an excitation signal to the acoustic transmitter, causing it to generate a direct wave propagating along the casing, a casing wave propagating along the casing, and a formation wave propagating along the formation. Since the direct wave is almost completely attenuated by the sound insulation body on the casing of the through-casing acoustic logging device, the acoustic signals received by each receiver in the array of acoustic receivers are mainly casing waves and formation waves. In each basic silencing unit, the acoustic signals received by the near-sound receiver and the far-sound receiver are first pre-amplified. Then, the pre-amplified near-sound receiver acoustic signal is phase-delayed, amplitude-adjusted, and polarity-reversed before being output to one input of the adder. Simultaneously, the pre-amplified far-sound receiver acoustic signal is input to the other input of the adder. The two acoustic signals are superimposed in the adder to eliminate the casing wave in the acoustic signal, outputting a high signal-to-noise ratio formation wave Rnc (n=1,2,3,4,5). Thus, five high signal-to-noise ratio formation waves are obtained using the five basic silencing units in the array acoustic receiver. Therefore, the through-casing acoustic logging device proposed in this embodiment, based on receiver phase delay silencing, can effectively eliminate instrument direct waves and casing waves and obtain high signal-to-noise ratio formation wave signals while keeping the acoustic transmitter T constant.

[0062] Figure 4 This is a schematic diagram of the acoustic receiving circuit in a casing acoustic logging device based on receiver phase delay silencing. After receiving the acoustic transmitter synchronization command from the host computer, the FPGA controller starts N-1 basic silencing units in the array acoustic receiver to acquire acoustic signals, obtaining N-1 acoustic signals including casing waves and formation waves.

[0063] Taking the first group of basic anechoic units as an example, the acoustic signal received by the near-sound receiver is R1, and the acoustic signal received by the far-sound receiver is R2. A phase delay anechoic processing circuit is used for phase delay anechoic processing. The acoustic signal R2 received by the far-sound receiver is input to preamplifier B for gain amplification to obtain the far-sound receiver's acoustic signal. Simultaneously, the acoustic signal R1 received by the near-sound receiver is input to preamplifier A for gain amplification. The FPGA controller uses the SPI bus to command the phase delay unit to complete the phase delay anechoic processing of the acoustic signal R1. A delay is applied to the acoustic signal R2 received by the far-field receiver, ensuring that the arrival time of the casing wave in the delayed signal is the same as that of the casing wave in the signal received by the far-field receiver. An amplitude control unit is then used to control the amplitude, ensuring that the amplitude of the processed near-field receiver acoustic signal is equal to that of the processed far-field receiver acoustic signal. The processed near-field receiver acoustic signal is input to the in-phase input of the adder, and the processed far-field receiver acoustic signal is input to the inverting input. Since the output of the inverting input of the adder is of reverse polarity, the polarity of the acoustic signal R2 received by the far-field receiver is essentially reversed. The added near-field and far-field receiver acoustic signals are then superimposed to cancel out the casing wave in the acoustic signal, leaving only the ground wave. However, the ground wave signal at this point is still a small signal of a few millivolts to tens of millivolts, a weak ground wave signal containing noise. Therefore, a bandpass filter with a frequency of 500Hz to 20kHz is used to eliminate low-frequency power frequency interference and high-frequency noise in the weak formation wave signal. Then, a programmable gain amplifier is controlled to achieve 3dB step gain adjustment and 0 to 60dB gain adjustment. After quantization by an analog-to-digital converter, all formation wave signals are stored in a memory connected to the FPGA controller and transmitted to the host computer via a CAN bus connected to the FPGA controller. The host computer then calculates the formation wave velocity based on the formation wave signal.

[0064] Figure 5 This is a graph showing the amplitude-frequency response of the acoustic receiving circuit in the through-casing acoustic logging device of this embodiment. The amplitude remains constant within the 0–20 kHz bandwidth, and a phase delay with reverse polarity is achieved above 10 kHz, with a dynamic range of 0–170°. Assuming the acoustic transmitter's operating frequency is 10 kHz, the casing wave velocity is 5500–6000 m / s, and the receiver spacing is between 0.1 and 0.2 m, the phase delay range of the acoustic receiving circuit can be calculated to be 60–130°. Therefore, the phase delay unit in this acoustic receiving circuit can meet the phase delay requirements.

[0065] This embodiment also proposes a through-casing acoustic logging method based on receiver phase delay silencing, using the through-casing acoustic logging device based on receiver phase delay silencing as described above, specifically including the following steps:

[0066] Step 1: Place the through-casing acoustic logging device based on receiver phase delay silencing in the wellbore of the casing well, and use the through-casing acoustic logging device to measure in the casing well.

[0067] Step 2: Using the host computer to control the acoustic emission circuit of the casing acoustic logging device, apply a high-voltage excitation pulse to the acoustic emitter, which excites the acoustic emitter to generate an acoustic field, forming an acoustic wave signal of a specified radiation frequency in the casing and formation.

[0068] Step 3: While the acoustic transmitter generates a sound field, the host computer controls the acoustic receiving circuit of the casing acoustic logging device to acquire the acoustic signals received by the near and far acoustic receivers in each group of basic silencing units. After processing by the phase delay silencing processing circuit in the acoustic receiving circuit corresponding to each group of basic silencing units, the casing waves in the acoustic signals received by the near and far acoustic receivers in each group of basic silencing units arrive at the same time, have equal amplitudes and opposite polarities. The casing waves are then superimposed and canceled to obtain the weak formation wave signal.

[0069] Step 4: After bandpass filtering and programmable gain control of the weak ground wave signal using the bandpass filter and programmable gain amplifier in the sound receiving circuit corresponding to each group of basic silencing units, the ground wave signal is quantized and acquired by an analog-to-digital converter and then transmitted to the host computer. The host computer calculates the ground wave velocity based on the ground wave signals acquired by all the basic silencing units.

[0070] In this embodiment, before the through-casing acoustic logging device measures in the casing well, it needs to be placed in the free casing section. Based on the instrument parameters and casing parameters of the through-casing acoustic logging device, the optimal amplitude control gain and optimal phase delay of the phase delay silencing circuit are determined. The specific process is as follows:

[0071] Based on the amplitude ratio of the sleeve wave received by the near-sound receiver and the far-sound receiver in the basic silencing unit, the optimal amplitude control gain G of the phase delay silencing processing circuit in the corresponding sound receiving circuit of the basic silencing unit is determined, as shown in formula (1):

[0072]

[0073] In the formula, G is the optimal amplitude control gain of the acoustic signal received by the near-sound receiver in the basic anechoic unit; A far A represents the maximum amplitude of the sleeve wave received by the far-field receiver in the basic anechoic unit. near This is the maximum amplitude of the sleeve wave received by the near-sound receiver in the basic anechoic unit.

[0074] The optimal phase delay φ for phase delay silencing is determined based on the arrival time difference of the sleeve waves received by the near-sound receiver and the far-sound receiver in the basic silencing unit, as shown in formula (2):

[0075]

[0076] In the formula, f is the sleeve wave frequency; t far t represents the arrival time of the sleeve wave received by the far-sound receiver in the basic anechoic unit. near d is the arrival time of the tube wave received by the near-sound receiver in the basic anechoic unit; d is the distance between the near-sound receiver and the far-sound receiver in the basic anechoic unit; v t The velocity is the sleeve wave velocity.

[0077] Furthermore, the optimal phase delay φ is determined according to the following steps:

[0078] S1, obtain the excitation frequency of the acoustic transmitter in the casing acoustic logging device when it generates a high-pressure acoustic pulse in the casing well.

[0079] S2, based on the sleeve wave frequency f and the distance d between the near sound receiver and the far sound receiver in the basic silencing unit, combined with the preset sleeve wave velocity, calculate the initial phase φ0 of the phase delay unit in the phase delay silencing circuit, and set the initial phase φ0 as the current phase delay of the phase delay unit.

[0080] S3, based on the preset phase delay step size Δφ, update the phase delay value of the phase delay silencing circuit by adding the current phase delay to the phase delay step size;

[0081] S4. Based on the updated phase delay value, the phase delay unit in the phase delay silencing circuit is used to process the waveform signal after delay silencing, and the amplitude ΔA of the sleeve wave is observed.

[0082] S5. Repeat steps S3 to S4 until the minimum value of the casing wave amplitude is determined. The phase corresponding to the minimum value of the casing wave amplitude is determined as the optimal phase delay φ.

[0083] In this embodiment, the actual measurement data of the through-casing acoustic logging device based on receiver phase delay silencing within a free-casing well are as follows: Figure 6 As shown, by Figure 6 From (a), we can see that the wave train that first reaches each acoustic receiver in the casing acoustic logging device is the casing wave; at this time, no formation wave can be observed. Figure 6As can be seen in (b), the acoustic wave calculation based on the time-slowness correlation method (STC) using the original waveform can only obtain a single peak value for the casing wave, and cannot obtain the formation wave. In this embodiment, by adjusting the source distance between the acoustic receiver closest to the acoustic transmitter in the array acoustic receivers of the casing acoustic logging device and the acoustic transmitter, the source distances are successively set to 0.7m, 0.8m, 0.9m, 1.0m, 1.1m, and 1.2m. The casing wave arrival time of the acoustic receiver with the closest source distance in the array acoustic receivers is 288us, and the casing wave arrival time of the acoustic receiver with the farthest source distance is 378us. The spacing between adjacent acoustic receivers in the array acoustic receivers is 0.1m. The calculated casing wave velocity is 5555m / s, which is basically the same as the actual sound velocity in the casing well. Figure 6 Image (c) shows the casing well waveform after phase delay silencing. By suppressing the casing wave, the formation wave is faintly revealed. The sound velocity is also calculated using the STC method. Figure 6 As can be seen in (d), the casing wave is greatly suppressed, and the signal-to-noise ratio of the formation wave is significantly improved. The peak value of the formation P-wave is located at 290 μs / m, which determines the formation sound velocity to be 3448 m / s, consistent with the actual situation.

[0084] Therefore, this invention, based on receiver-end phase delay silencing, suppresses casing waves at the data acquisition source, effectively improving the signal-to-noise ratio of formation waves. Applying the receiver-end phase delay silencing-based through-casing acoustic logging device proposed in this invention to casing wells can accurately measure formation sound velocity, even in cases of poor casing well cementation. Furthermore, compared to existing technologies, the receiver-end phase delay silencing-based through-casing acoustic logging device requires no structural modifications; only the addition of an acoustic receiving circuit with phase delay silencing processing circuitry is needed to complete through-casing acoustic logging, thus broadening the applicability of acoustic logging for formation evaluation in casing wells.

[0085] Of course, the above description is not intended to limit the present invention, and the present invention is not limited to the examples given above. Any changes, modifications, additions or substitutions made by those skilled in the art within the scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A casing-mounted acoustic logging device based on receiver phase delay silencing, characterized in that, It includes a housing, a measurement system housed inside the housing, and a host computer located on the ground; The housing is a metal cylinder with a bellows inside. A spindle is installed inside the bellows along the central axis to support the measurement system. Both ends of the bellows are sealed with high-temperature pressure-bearing seals, and the bellows is filled with silicone oil to ensure acoustic coupling and external pressure balance within the housing. The measurement system is fixed on a mandrel inside a bellows and includes an acoustic transmitter, an array of acoustic receivers, and a measurement and control circuit. The measurement and control circuit includes an acoustic emission circuit and an acoustic receiving circuit. The acoustic transmitter, array of acoustic receivers, and measurement and control circuit are all connected to a host computer, which controls the power supply, command transmission and reception, and data transmission of the measurement system in a high-temperature, sealed environment. The acoustic transmitter is connected to the acoustic emission circuit, which provides a high-voltage pulse signal to excite the acoustic transmitter to generate sound waves radiating towards the casing and the formation. The array of acoustic receivers consists of N coaxially spaced receivers. The array consists of at least two acoustic receivers. Two adjacent acoustic receivers in the array together form a basic anechoic unit. The acoustic receiver closer to the acoustic transmitter in the basic anechoic unit is called the near acoustic receiver, and the acoustic receiver farther away from the acoustic transmitter is called the far acoustic receiver. The near acoustic receiver and the far acoustic receiver in the basic anechoic unit are respectively connected to the corresponding acoustic receiving circuit. The acoustic receiving circuit is used to perform phase delay anechoic processing on the acoustic wave signals received by the near acoustic receiver and the far acoustic receiver in the basic anechoic unit to cancel the casing wave and obtain the formation wave signal. A sound insulation material is provided on the housing between the acoustic transmitter and the array acoustic receiver to attenuate the instrument waves propagating along the housing.

2. The through-casing acoustic logging device based on receiver phase delay silencing according to claim 1, characterized in that, Both the acoustic transmitter and the acoustic receiver are configured as acoustic-to-electric conversion sensors, employing monopole, dipole, or quadrupole modes.

3. The through-casing acoustic logging device based on receiver phase delay silencing according to claim 1, characterized in that, The sound insulation material is configured with periodically and uniformly arranged holes.

4. The through-casing acoustic logging device based on receiver phase delay silencing according to claim 1, characterized in that, The acoustic emission circuit and acoustic receiving circuit are respectively located near the acoustic transmitter and acoustic receiver, and are encapsulated with high-temperature resistant epoxy resin. The acoustic emission circuit includes a signal generator, a filter amplifier circuit, and a power amplifier circuit connected in sequence, used to generate high-voltage pulse signals with adjustable frequency and amplitude; The acoustic receiving circuit is equipped with an FPGA controller, a phase delay silencing circuit, a bandpass filter, a programmable gain amplifier, and an analog-to-digital converter. It is used to sequentially pre-amplify, phase-delay, bandpass filter, gain adjust, and analog-to-digital convert the acoustic wave signal collected by the basic silencing unit to obtain N-1 formation wave signals. The phase delay silencing circuit is used to perform phase delay silencing at the receiving end, and internally includes a preamplifier A, a preamplifier B, a phase delay unit, an amplitude control unit, and an adder.

5. The through-casing acoustic logging device based on receiver phase delay silencing according to claim 4, characterized in that, The phase delay anechoic process is applied to the acoustic signals received by the near-sound receiver and the far-sound receiver in the same set of basic anechoic units. By delaying the phase of the acoustic signal received by the near-sound receiver backward in the time domain, the arrival time of the casing wave in the acoustic signals received by the near-sound receiver and the far-sound receiver is the same. By adjusting the amplitude and polarity of the acoustic signals received by the near-sound receiver and the far-sound receiver to be opposite, the amplitude of the casing wave in the acoustic signals received by the near-sound receiver and the far-sound receiver are equal and the polarity is opposite. The casing wave in the acoustic signal is then superimposed and canceled, so that only the formation wave remains in the acoustic signal, resulting in a weak formation wave signal that cancels the casing wave.

6. The through-casing acoustic logging device based on receiver phase delay silencing according to claim 5, characterized in that, After the host computer controls the acoustic transmitter to apply an excitation signal to generate a direct wave propagating along the shell, a casing wave propagating along the casing inside the well, and a formation wave propagating along the formation, the FPGA controller receives the acoustic transmitter synchronization command issued by the host computer and starts the N-1 basic silencing units in the array acoustic receiver to collect acoustic wave signals, and obtains N-1 acoustic wave signals including casing wave and formation wave. For each basic noise reduction unit, a phase delay noise reduction circuit is used for phase delay noise reduction. The acoustic signal R2 received by the far-field receiver is input to preamplifier B for gain amplification to obtain the far-field receiver acoustic signal. Simultaneously, the acoustic signal R1 received by the near-field receiver is input to preamplifier A for gain amplification. The FPGA controller uses the SPI bus to command the phase delay unit to amplify and delay the phase of the acoustic signal R1. Then, the amplitude control unit is used for amplitude control to obtain the processed near-field receiver acoustic signal. The amplitude of the processed near-field receiver acoustic signal is equal to the amplitude of the processed far-field receiver acoustic signal. The processed near-field receiver acoustic signal is input to the non-inverting input of the adder. The processed far-field acoustic signal is input to the inverting input of an adder. The adder superimposes the processed near-field and far-field acoustic signals to cancel out the casing wave in the acoustic signal, thus obtaining a weak formation wave signal. The weak formation wave signal is then sequentially input to a bandpass filter, a programmable gain amplifier, and an analog-to-digital converter. The bandpass filter eliminates low-frequency power frequency interference and high-frequency noise in the weak formation wave signal. The programmable gain amplifier then controls the gain to improve the dynamic measurement range. After quantization by the analog-to-digital converter, the formation wave signal of channel N-1 is obtained. The formation wave signal is stored in a memory connected to the FPGA controller and transmitted to the host computer via a CAN bus connected to the FPGA controller. The host computer is equipped with a central control system, which is used to calculate the formation wave velocity based on the formation wave signal transmitted by the measurement system.

7. A method for through-casing acoustic logging based on receiver phase delay anechoic cancellation, characterized in that, The through-casing acoustic logging device based on receiver phase delay silencing as described in any one of claims 1 to 6 specifically includes the following steps: Step 1: Place the through-casing acoustic logging device based on receiver phase delay silencing in the wellbore of the casing well, and use the through-casing acoustic logging device to perform measurements. Step 2: Use the host computer to control the acoustic emission circuit of the casing acoustic logging device to apply a high-voltage excitation pulse to the acoustic emitter, which will excite the acoustic emitter to generate a sound field and form an acoustic wave signal with a specified radiation frequency in the casing and formation. Step 3: While the acoustic transmitter generates a sound field, the host computer controls the acoustic receiving circuit of the casing acoustic logging device to acquire the acoustic signals received by the near and far acoustic receivers in each group of basic silencing units. After processing by the phase delay silencing processing circuit in the acoustic receiving circuit corresponding to each group of basic silencing units, the casing waves in the acoustic signals received by the near and far acoustic receivers in each group of basic silencing units arrive at the same time, have the same amplitude, and opposite polarities. The casing waves are then superimposed and canceled to obtain the weak formation wave signal. Step 4: After bandpass filtering and programmable gain control of the weak ground wave signal using the bandpass filter and programmable gain amplifier in the sound receiving circuit corresponding to each group of basic silencing units, the ground wave signal is quantized and acquired by an analog-to-digital converter and then transmitted to the host computer. The host computer calculates the ground wave velocity based on the ground wave signals acquired by all the basic silencing units.

8. The through-casing acoustic logging method based on receiver phase delay anechoic cancellation according to claim 7, characterized in that, Before the through-casing acoustic logging device is used to measure in the casing well, the through-casing acoustic logging device is placed in the free casing section in advance. Based on the instrument parameters and casing parameters of the through-casing acoustic logging device, the optimal amplitude control gain and optimal phase delay of the phase delay silencing processing circuit are determined. Based on the amplitude ratio of the sleeve wave received by the near-sound receiver and the far-sound receiver in the basic silencing unit, determine the optimal amplitude control gain of the phase delay silencing processing circuit in the corresponding sound receiving circuit of the basic silencing unit. The optimal amplitude control gain G is shown in Equation (1): In the formula, G is the optimal amplitude control gain of the acoustic signal received by the near-sound receiver in the basic anechoic unit; A far A represents the maximum amplitude of the sleeve wave received by the far-field receiver in the basic anechoic unit. near The maximum amplitude of the sleeve wave received by the near-sound receiver in the basic anechoic unit; The optimal phase delay φ for phase delay silencing is determined based on the arrival time difference of the sleeve waves received by the near and far sound receivers in the basic silencing unit. The optimal phase delay φ is shown in formula (2): In the formula, f is the sleeve wave frequency; t far t represents the arrival time of the sleeve wave received by the far-sound receiver in the basic anechoic unit. near d is the arrival time of the tube wave received by the near-sound receiver in the basic anechoic unit; d is the distance between the near-sound receiver and the far-sound receiver in the basic anechoic unit; v t The velocity is the sleeve wave velocity.

9. The through-casing acoustic logging method based on receiver phase delay anechoic cancellation according to claim 8, characterized in that, The steps for determining the optimal phase delay φ are as follows: S1, obtain the excitation frequency of the acoustic transmitter in the casing acoustic logging device when it generates a high-pressure acoustic pulse in the casing well. S2, based on the sleeve wave frequency and the spacing between the near and far sound receivers in the basic silencing unit, combined with the preset sleeve wave velocity, calculate the initial phase φ0 of the phase delay unit in the phase delay silencing circuit, and set the initial phase φ0 as the current phase delay of the phase delay unit. S3, based on the preset phase delay step size Δφ, update the phase delay value of the phase delay silencing circuit by adding the current phase delay to the phase delay step size; S4. Based on the updated phase delay value, the phase delay unit in the phase delay silencing circuit is used to process the waveform signal after delay silencing, and the amplitude ΔA of the sleeve wave is observed. S5. Repeat steps S3 to S4 until the minimum value of the casing wave amplitude is determined. The phase corresponding to the minimum value of the casing wave amplitude is determined as the optimal phase delay φ.

Images