Logging instrument based on thin film loudspeaker

Abstract

The invention provides a logging instrument based on thin film loudspeakers. The logging instrument comprises a transmitting circuit short section, a transmitter array composed of thin film loudspeaker transmitters, a receiver array composed of sound insulators and thin film loudspeaker receivers, a receiving circuit short section and a centralizer. Due to the fact that the thin film loudspeaker is small in size, a large number of sensor arrays can be arranged on the logging instrument, the data collection quality can be greatly improved, meanwhile, due to the fact that the transducer is annularly installed on the logging instrument, the logging instrument can measure the whole shaft under the condition that the logging instrument does not rotate, and the signal-to-noise ratio of received signals is improved. In addition, due to the fact that the transducer is small in size, the diameter of the logging instrument is reduced, and the logging instrument can conduct measurement work in a slim hole environment.

Description

Technical Field

[0001] The invention belongs to the technical field of petroleum well logging, and in particular relates to a well logging instrument based on a thin film speaker. Background Art

[0002] Well logging, also called geophysical logging or petroleum logging, is an important means to determine and evaluate oil and gas layers and solve geological problems. It can directly provide various information and data for petroleum geologists and engineering technicians.

[0003] Acoustic logging refers to a logging method that uses the law of sound wave propagation in the wellbore to detect the formation around the wellbore. It requires the use of special acoustic logging instruments. The acoustic logging instrument has two basic components, one is the acoustic wave transmitting transducer, and the other is the acoustic wave receiving transducer. The instrument usually includes multiple receiving transducers. According to the time difference of the waveforms collected by the two transducers, the formation velocity around the wellbore can be calculated to evaluate the properties of the formation. In cased wells, the bonding between the casing and the cement outside the casing is evaluated based on the amplitude of the first wave of the collected waveform. At the same time, the frequency of the transmitted sound waves can be increased, and the focusing of ultrasonic waves can be used to image the wellbore or casing to evaluate the development of wellbore wall cracks or corrosion of the inner wall of the casing.

[0004] The transducers of current acoustic logging instruments are usually large-sized components. In order to attenuate the sound waves passing through the back of the transducer, other components are installed behind the transducer, further increasing the size of the transducer. In order to measure the properties of the formations in different directions around the wellbore, it is necessary to place multiple transducers circumferentially on the logging instrument or rotate the probe in the well. However, due to the large size of the transducers, it is difficult to install a large number of transducers circumferentially into the logging instrument, and the mechanical movement of the rotating probe will also affect the acquisition of the acoustic wave signal, resulting in a low signal-to-noise ratio of the received signal. At the same time, the large-sized transducer increases the diameter of the instrument, making it impossible to operate in small wellbores. Summary of the invention

[0005] In order to overcome the above-mentioned shortcomings, the present invention provides a well logging instrument based on a thin film speaker, which can measure wellbore acoustic wave signals at low cost, high precision and high reliability.

[0006] The technical solution adopted by the present invention to solve its technical problems is: a logging instrument based on a thin film speaker, including a ground data acquisition unit and a downhole logging instrument, which are connected by a logging cable. The ground data acquisition unit is responsible for processing the acoustic wave data collected by the downhole instrument and producing a real-time map during the logging process. The downhole logging instrument includes a transmitting circuit short section, a thin film speaker transmitter array, a sound insulator, a thin film speaker receiver array, and a receiving circuit short section. The circuit system includes an excitation circuit board, an AFE circuit board, a DSP data processing module, and an RTU remote communication unit, which are fixed to the instrument frame. The sound insulator can greatly attenuate the sound waves propagating along the instrument frame to prevent the direct wave from affecting the data acquisition. A centralizer is also installed on the outside of the downhole instrument to center the entire instrument on the casing well axis.

[0007] The film speaker is a miniature acoustic component with a size between 100 nanometers and 1 millimeter, and has both speaker and microphone functions. Therefore, the film speaker can be used alone or in an array to form a transmitting transducer and a receiving transducer. When the size of the transducer is close to the wavelength of the sound wave, the resolution of the logging imaging will be particularly high.

[0008] The logging instrument based on the thin film speaker can be used for measurement in cased wells or open-hole wells. In cased wells, the measurement value provided by the thin film speaker transducer can evaluate the bonding condition between the casing and the cement outside the casing, and can image the inner wall of the casing and the annular medium between the outer wall of the casing and the cement. In open-hole wells, the formation sound velocity can be measured and the inner wall of the formation can be imaged.

[0009] The film speakers can be distributed in a large number of circumferential directions on the logging instrument. This enables the acoustic wave probe of the logging instrument to complete the wellbore measurement without rotating the transducer. By avoiding the rotation of the instrument, the noise generated by the mechanical rotation is reduced, which increases the signal-to-noise ratio of the signal received by the transducer. At the same time, multiple film speakers arranged around the logging instrument can greatly improve the resolution of the measurement results. In addition, arranging multiple film speakers in an array form can enable the logging instrument to perform more targeted measurements in a more complex wellbore environment.

[0010] Due to the small size of the transducer, the thin film speaker based logging tool can perform acoustic logging in small diameter wellbores.

[0011] The data acquisition of the logging instrument based on the thin film speaker includes the following steps:

[0012] (1) Multiple thin film speakers are individually or in arrays to form a transmitting transducer and a receiving transducer, which are installed on the logging instrument.

[0013] (2) The logging instrument is lowered to the bottom of the well or to a specified depth in the wellbore. The thin film speaker transmitter on the logging instrument is controlled to emit an acoustic wave signal, and the transmission signal passes from the thin film speaker transmitter array through the fluid in the wellbore to the well wall or casing. The receiver array on the logging instrument collects the acoustic wave train reflected from the well wall.

[0014] (3) Preprocessing the collected signals. Preprocessing may include steps such as digitizing, compressing and filtering the signals from one or more film speaker receivers so as to provide them to the controller for further processing.

[0015] (4) The acoustic wave signals collected by the film speaker receiver include arrival time, amplitude, attenuation and frequency, etc. Various acoustic wave algorithms are applied to process the collected signals to determine one or more characteristics of the wellbore. For example, by processing the acoustic wave amplitude signals provided by the film speaker receiver through algorithms, an image of the wellbore wall or the inner wall of the casing can be generated, thereby observing the development of cracks in the wellbore wall or the corrosion of the inner wall of the casing.

[0016] The present invention has the following advantages:

[0017] 1. The size of the thin film speaker transducer is small, and a large number of transducers can be installed circumferentially on the logging tool, thereby greatly improving the measurement resolution.

[0018] 2. Multiple film speaker transmitters and receivers are installed circumferentially on the logging instrument, which allows information from all sides of the wellbore to be collected without rotating the transducer, which can reduce the mechanical noise generated by the rotation of the transducer and improve the signal-to-noise ratio of the detected signal. The signals of multiple receivers will be filtered and combined to determine various wellbore characteristics.

[0019] 3. Secondly, for different logging purposes, each thin film speaker array can be customized to achieve better logging results. In addition, the low power consumption of the thin film speaker array allows more tool components to be added to the logging instrument, which can save time, manpower and funds for operations. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0021] Figure 1 It is a construction schematic diagram of the present invention;

[0022] Figure 2 It is a schematic diagram of the structure of the instrument circuit system;

[0023] Figure 3 This is the combination mode of the film loudspeaker transducer array of the present invention;

[0024] Figure 4 It is the propagation path of the sound wave signal during the construction of the present invention. DETAILED DESCRIPTION

[0025] The embodiments of the present invention are described in detail below with reference to the accompanying drawings, but they do not limit the present invention and are only used as examples.

[0026] [Example 1]

[0027] Figure 1 The specific construction method of the present invention is demonstrated, including a ground data acquisition unit 1 and a logging instrument 3, which are connected by an armored logging cable 2; a transmitting circuit short section 4 is located at the uppermost end of the logging instrument, a transmitter array 5 composed of a thin film speaker transmitter 6 and a receiver array 8 composed of a thin film speaker receiver 9 are circumferentially installed on the logging instrument, a sound insulator 7 can greatly attenuate the sound waves propagating along the instrument skeleton to prevent direct waves from affecting data acquisition, and a receiving circuit short section 10 is located at the lowermost end of the logging instrument; a centralizer 11 is installed on the logging instrument to support the entire instrument and center it on the well axis center.

[0028] Figure 2 The circuit system structure is shown in Figure 1, which further explains the implementation process of signal transmission, collection and processing. The entire circuit system includes an excitation circuit board, an AFE circuit board, a DSP data processing module, and an RTU remote communication unit. First, the transmitting transducer transmits sound waves through the excitation circuit board, and then receives the reflected echo through the AFE circuit board of the DSP data processing module. After calculation, the sound wave peak amplitude, peak arrival signal and sound wave full wave train signal are output, and these signals are transmitted to the RTU remote communication unit through the SCI bus, and then the data is transmitted to the ground data acquisition unit 1 for analysis, processing and imaging. Finally, the DSP data processing module also needs to regularly collect the working temperature and send the instrument working status parameters to the power-off preservation circuit at any time.

[0029] The circumferential installation of the film speaker transducer assembly (film speaker transmitter 6 and film speaker receiver 9) on the logging instrument 3 enables the probe to measure all information around the well without rotating in the well. In the case of very viscous mud in the well, any rotation of the transducer may cause disturbances in the mud, resulting in signal attenuation. Therefore, this circumferential installation of the film speaker transmitter 6 and the film speaker receiver 8 can achieve more accurate measurements and a higher signal-to-noise ratio of the collected signal.

[0030] Figure 3 A rectangular array 13 composed of a single film speaker transducer 12 is shown, and multiple arrays 13 can be arranged circumferentially around the logging tool. Using an array receiver is advantageous in many ways over a single receiver. First, the array combination can improve the signal-to-noise ratio of the signal measurement and suppress noise. The high signal-to-noise ratio allows the pre-processing component to filter out inaccurate measurements, so the film speaker receiver array can detect relatively weak acoustic signals.

[0031] Figure 4 The schematic diagram of the acoustic wave propagation path for measuring the cementation of the casing in a cased well by using a film speaker transducer 12 to emit a high-frequency acoustic wave signal 17 is shown. In this embodiment, the annulus 15 between the casing 14 and the formation 16 is filled with cement for fixing the casing 14. When the film speaker transducer 12 emits a high-frequency acoustic wave signal 17, passes through the wellbore fluid, and reaches the casing 14, due to the impedance difference between the wellbore fluid and the steel casing 14, most of the incident energy of the high-frequency acoustic wave signal 17 will be reflected back to the film speaker transducer 12, and the remaining acoustic wave energy 18 will be transmitted into the casing 14. At the casing-cement interface, if the medium in the annulus 15 is solid, part of the acoustic wave energy 18 is reflected back, and most of the energy passes through the casing 14. When the medium in the annulus 15 is liquid, due to the large difference in acoustic impedance between the steel pipe and the liquid, most of the energy is reflected back, and a small amount of energy passes through the casing and enters the annulus 15. By detecting the energy in the return signal 19, it can be determined whether fluid is present in the cement 15 between the casing 14 and the formation 16. If fluid is detected in the annulus 15, this may indicate that the cement bond quality is moderate or that the cement is not bonded at all.

[0032] Another application of multiple film speaker transmitters 6 is to focus the energy of the transmitter array 5. Emitting such a focused signal can transfer more energy to specific layers of interest in the wellbore (e.g., casing 14, annulus 15). This may cause stronger reflections of the signals received from these layers. In some embodiments, the focused beam obtained by controlling the signal emitted by the transmitter array 5 can be used to individually target various layers of the wellbore. That is, the film speaker array elements can be individually adjusted to focus on different penetration depths of the casing 14 and the annulus 15. In the example of detecting casing thickness corrosion, this focus change enables the logging instrument 3 to detect the thickness of the casing and generate an image.

[0033] [Example 2]

[0034] In the process of oil and gas extraction, due to the formation pressure difference, engineering problems such as well leakage, channeling, backflow, and sand production often occur. These problems will not only cause economic losses, but also pose great safety hazards. When the liquid or gas in the well moves, the friction can produce a sound with a characteristic spectrum. The noise spectrum generated by oil, gas, and water leakage is different. Therefore, by collecting the noise generated by the leakage and analyzing the noise spectrum distribution, the properties of the fluid can be judged, the leakage point can be located, and the channeling position of the fluid outside the pipe can be checked.

[0035] For oil and gas well channeling and leak detection, a data acquisition method of a well logging instrument based on a thin film speaker includes the following steps:

[0036] (1) A logging instrument 3 based on a thin film speaker is lowered to a specified depth via an armored logging cable 2.

[0037] (2) The thin-film speaker-based logging instrument 3 is slowly lifted upward, and the receiver array 8 receives the sound from the wellbore, while the acoustic wave data is uploaded to the surface data acquisition unit 1 through the armored logging cable 2. After measuring the complete well section or the planned well section, the thin-film speaker-based logging instrument 3 is lifted out of the wellhead.

[0038] (3) Use software on the ground to process the recorded sound wave train to obtain a noise spectrum.

[0039] (4) Based on the noise spectrum obtained through data processing, the properties of the downhole fluid are determined and the leakage point is located. The noise generated when the wellbore fluid flows through the casing is generally less than 1kHz, while the noise generated by the fluid leaking through the perforation, oil injection nozzle, packer and casing is generally 1kHz-3kHz, and the noise generated by the external channeling of the pipe is generally 3kHz-5kHz.

Claims

1. A well logging instrument based on a thin film speaker, comprising a transmitting circuit short section (4), a transmitter array (5) consisting of a thin film speaker transmitter (6), a sound insulator (7), a receiver array (8) consisting of a thin film speaker receiver (9), a receiving circuit short section (10), and a centralizer (11), characterized in that: Sensor arrays can be deployed in large numbers on logging instruments, which greatly improves the quality of data acquisition and the signal-to-noise ratio of received signals; The thin film speaker-based logging instrument (3) is connected to a surface data acquisition unit (1) via an armored logging cable (2), and a transmitter array (5) and a receiver array (8) are circumferentially mounted on the sonic logging instrument.

2. A well logging instrument based on a thin film speaker according to claim 1, characterized in that: The small size of the thin film loudspeaker transducer enables a large number of transducers to be mounted circumferentially on the logging tool.

3. A well logging instrument based on a thin film speaker according to claim 1, characterized in that: Several thin film speaker transducer units (12) can be combined into a rectangular array (13), and a plurality of rectangular arrays (13) can be arranged in a circumferential direction around the well logging instrument (3).

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