Wellbore fluid level measuring apparatus and method based on acoustic principles

Abstract

The application discloses a kind of well liquid level measuring equipment and method based on acoustic wave principle, applied to acoustic wave ranging and well dynamic monitoring field, for traditional wired liquid level measuring technology probe and cable easy to damage, high cost, short life, difficult to long-term dynamic monitoring and inaccurate measurement under complex well conditions etc.; The application utilizes the propagation characteristics of acoustic wave in wellbore, sets up excitation equipment opposite wellhead, and installs bidirectional probe near wellhead position in wellbore, respectively for detecting acoustic wave signal excited by excitation equipment and liquid surface reflected acoustic wave signal;By calculating the difference of acoustic wave round trip time, combined with well acoustic wave velocity, the depth of well liquid surface position is calculated.

Description

Technical Field

[0001] This invention belongs to the field of acoustic ranging and dynamic monitoring in wells, and specifically relates to a technology and device for measuring liquid level in wells. Background Technology

[0002] Traditional well level measurement technology based on pressure sensing involves installing a pressure sensor probe at a fixed depth below the well fluid level. The installation depth of the probe is determined by the length of the signal transmission cable connecting the probe or the length of the cable string. The signal transmission cable is fixed in sections to the well pipe or suspended in the well, and sealed at the wellhead using a cable sealing device. After the cable exits the well, it is connected to a surface display. During measurement, the depth of the fluid level from the probe is calculated by subtracting the depth of the fluid level measured by the probe (using a water density of 1 g / cm³ for pressure-depth conversion).

[0003] This method faces many challenges in measuring liquid levels in wells.

[0004] Firstly, the insulation, sealing, and fixing processes for the probe and cable are complex. In actual operation, the cable is easily damaged during the equipment's lowering and raising / lowering operations. For example, the raising and lowering operations may cause the cable to rub against the well wall or be subjected to other mechanical forces, resulting in damage to the outer sheath and affecting the accuracy of the measurement and the stability of the equipment.

[0005] Secondly, the continuous and intense vibrations generated by the water pumps and pipes in the well can cause serious damage to the probe and cables. Prolonged exposure to vibration can easily cause displacement or damage to the precision components inside the probe, and loosen cable connections, leading to equipment failure. Once a failure occurs, the entire system often needs to be replaced, which not only increases maintenance costs but also interrupts production.

[0006] Third, traditional level gauges require one unit per well, which is costly and has a short lifespan, making it difficult to meet the needs of long-term dynamic monitoring. In many cases, the dynamic liquid level in wells without level gauges cannot be monitored in real time, causing many inconveniences and safety hazards to production activities, such as unstable material supply in industrial production, easy pump overheating accidents, and potential flooding accidents in the mining environment.

[0007] Fourth, with the development of modern industry and the increase in well depth, the requirements for liquid level measurement technology are becoming increasingly stringent. Existing liquid level measurement technologies are insufficient in terms of convenience, speed, labor intensity, operating costs, reliability, and adaptability. In deep well environments, the measurement accuracy of traditional liquid level gauges decreases, the depth measurement via signal transmission cables becomes inaccurate, and the difficulty of installation and maintenance increases.

[0008] Fifth, under special well conditions, such as when the formation water in the wellbore contains complex gases, mineral particles, large temperature variations, or other interfering factors, the measurement results of traditional level gauges will have significant deviations. When the well contains corrosive fluids, higher requirements are placed on the corrosion resistance and service life of the equipment.

[0009] Therefore, the industry urgently needs more accurate, reliable, and convenient modern liquid level measurement technology to improve production efficiency, obtain complete and accurate liquid level data, reduce costs, and ensure production safety. Summary of the Invention

[0010] This invention aims to provide a method and device for long-distance, non-contact measurement of liquid levels in wells based on the principle of acoustic ranging. It overcomes the problems of traditional liquid level measurement technologies, such as the fragility of probes and cables, high cost, short lifespan, difficulty in long-term dynamic monitoring, and inaccurate measurements under complex well conditions. Utilizing the propagation characteristics of sound waves within the wellbore, it achieves convenient, rapid, accurate, and low-cost liquid level measurement, improving the adaptability and accuracy of liquid level measurement technology under different well conditions, and meeting the industry's evolving needs for liquid level measurement.

[0011] One of the technical solutions adopted in this invention is: a well liquid level measuring device based on the principle of acoustic waves, comprising: an excitation device and a receiving device;

[0012] The excitation device is positioned at the wellhead and sends a continuous acoustic up-frequency scanning signal to the wellhead.

[0013] The receiving device includes two probes facing opposite directions installed in the upper part of the well and a main acquisition plate, with one probe facing the fluid surface downhole and the other probe facing the excitation device.

[0014] The two probes facing opposite directions are connected to the main acquisition board, which calculates the liquid level depth in the well based on the sound signals collected by the two probes.

[0015] The second technical solution adopted in this invention is: a well liquid level measurement method based on the principle of sound waves, which calculates the depth of the liquid surface in the well based on the time difference of sound waves collected by two probes facing opposite directions and the sound wave transmission speed in the well.

[0016] Specifically, the following steps are included:

[0017] S1. A continuous acoustic up-frequency scanning signal is generated at the wellhead;

[0018] S2. The probe facing the excitation device is designated as probe A, and the probe facing the downhole fluid surface is designated as probe B. The scanning signal from step S1 is recorded by probe A and probe B in sequence.

[0019] S3. The scanning signal described in step S1 propagates downward along the wellbore in the form of an acoustic waveguide. When it reaches the liquid surface, it undergoes total reflection. The total reflection signal returns upward to the wellhead and is recorded sequentially by probe B and probe A.

[0020] The signal obtained by probe A is denoted as signal A, and the signal obtained by probe B is denoted as signal B;

[0021] S4. Perform autocorrelation on signal A and cross-correlation on signal A and signal B. The first peak (based on the autocorrelation data of signal A) is the system start time 0, and the second peak (based on the cross-correlation data of signal A and B) is the time when the sound wave reaches the probe after total reflection from the liquid surface. Read the time difference between the second peak and the first peak to obtain the round-trip time difference of the sound wave from the wellhead to the liquid surface.

[0022] S5. Based on the round-trip time difference of the sound wave calculated in step S4, and combined with the sound wave velocity in the well, the depth of the liquid surface in the well is calculated.

[0023] The beneficial effects of this invention are as follows: By installing two bidirectional probes at the wellhead, this invention utilizes the propagation characteristics of sound waves within the wellbore to measure sound waves in two directions respectively. Combining the time difference between the sound waves measured by the two probes, it achieves convenient, rapid, accurate, and low-cost liquid level measurement. This invention has the following advantages:

[0024] 1) This invention is applicable to high-precision measurement of well liquid level under all well depths and complex well conditions, filling the gap in measuring deep well liquid level at the wellhead;

[0025] 2) This invention is applicable to one machine per well, one machine per multiple wells, long-term dynamic monitoring, and convenient remote monitoring and control;

[0026] 3) This invention collects data at the wellhead, eliminating the safety and equipment risks associated with downhole operations;

[0027] 4) This invention is easy to operate, can instantly acquire liquid level data, and is inexpensive. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the well liquid level measurement device based on the acoustic wave principle of the present invention.

[0029] Figure 2 This is a schematic diagram of the bidirectional probe structure in this invention;

[0030] Figure 3 This is a perspective view of the bidirectional probe mounting frame in this invention;

[0031] Figure 4 This is a schematic diagram of the cylindrical outer shell in this invention;

[0032] Figure 5 This is a schematic diagram of the probe mounting structure in this invention. Detailed Implementation

[0033] To facilitate understanding of the technical content of this invention by those skilled in the art, the following description, in conjunction with the accompanying drawings, further illustrates the invention.

[0034] First, the working principle of this invention will be explained:

[0035] 1. Physical properties of sound waves in air inside a circular tube

[0036] According to Maxwell's wave equations, in a two-dimensional structure with a large difference in wave impedance, the phenomenon where waves are confined to a local space and their energy cannot penetrate the impedance interface is called a waveguide. The significant characteristics of a waveguide are slow wave attenuation, long propagation distance, and high transmission frequency. This structure is called a waveguide structure. In human practice, the most easily implemented waveguide structures are circular and rectangular waveguide structures.

[0037] The air and well wall in the well shaft form a typical circular waveguide structure. Firstly, the circular well shaft and the air inside it are typical two-dimensional structures. Secondly, the sound wave velocity in the air is about 340 m / s and the density is negligible, while the sound wave velocity in the steel pipe well wall is about 5200 m / s and the density is about 7.85 g / cm³. The two form a huge difference in sound wave impedance, which meets the conditions for an acoustic waveguide.

[0038] The sound produced by flutes in natural life, the sound transmission through bamboo tubes in tunnel warfare, and the traditional cylindrical communication on ships all fall under the category of sound waveguides; the sound of firecrackers traveling a long distance in a river is a phenomenon of semi-waveguides (channel waves).

[0039] Therefore, sound waves propagate above the liquid surface in the well and in the air inside the casing. They possess the characteristics of slow wave attenuation, long propagation distance (large measurement depth), and high transmission frequency (high measurement accuracy) in the air inside the well, providing a physical basis for high-precision sound wave measurement of deep well liquid levels.

[0040] 2. Related energy focusing properties of continuously controllable sound sources

[0041] In human social practice, artificially generated sound sources (vibration sources) for sound waves (elastic waves) are divided into two types: pulse sound sources and continuous sound sources. Methods for generating pulse sound sources include explosives (gunpowder, firecrackers), air guns, electric sparks, and percussion vibration methods; methods for generating continuous sound sources include electromagnetic vibration loudspeakers, piezoelectric loudspeakers (horns), piezoelectric sonar (high-frequency band), and air compression vibration methods (hand-cranked sirens), etc.

[0042] Pulse sound sources are characterized by large amplitude, short duration (milliseconds to tens of milliseconds), and wide bandwidth, and their energy, frequency, and phase are not controllable artificially; continuous sound sources are characterized by small amplitude, long duration (tens of seconds), and wide bandwidth, and their total energy, frequency, and phase are controllable artificially.

[0043] With societal progress, in the field of seismic exploration, traditional explosive excitation (pulse source) has been gradually replaced by controlled-source (continuous source) excitation. A controlled-source excitation involves generating a long-duration frequency scanning signal. By cross-correlation calculations (integration of amplitude energy) between this signal and the received formation signal, the reflection information of the formation is obtained. This reflection information possesses the same kinematic physical properties as that obtained from explosive source excitation, but its dynamic properties exhibit a higher signal-to-noise ratio and bandwidth. Controlled-source technology has become a mature industrialized production technology.

[0044] Therefore, the continuous source correlation method is the most effective high-precision industrial method to solve the problems of sound source energy, frequency band, phase, environmental protection, and artificial modulation.

[0045] 3. Boundary effect

[0046] The casing wall of the wellbore constrains the divergence path of sound waves within the casing. When the sound waves leave the source, due to the significant difference between the acoustic impedance of the air and the casing, total internal reflection occurs. The combined effect of this total internal reflection is the acoustic waveguide effect in the wellbore. Because the path of total internal reflection is longer than the straight-line path of the sound wave, the group velocity of the sound wave in the well is slightly lower than the speed of rectilinear propagation in air. The sound wave velocity in air at ground level is 340 m / s, while the sound wave velocity in a circular pipe is approximately 338 m / s. This is the core mechanism of acoustic waveguides.

[0047] Applications of acoustic ranging in ground ranging: It is used to locate short-range targets (less than 20 meters), such as measuring the vibration of a lathe or the water level in a river. However, due to the short measurement distance, it has been largely replaced by laser ranging and microwave ranging. The main reasons for this are the short propagation distance of the generated pulse sound source and the environmental noise it produces.

[0048] This invention proposes a measuring device, including an excitation device and a receiving device.

[0049] In this embodiment, a slender cylindrical digital loudspeaker with a power of approximately 40 watts is selected as the excitation device, which is suitable for most deep well conditions. The loudspeaker opening size is less than 2 / 3 of the wellhead's inner diameter (generally around 150 mm) to allow space for the receiving probe. The excitation is performed using a sinusoidal linear upsampling scan.

[0050] A(t)=sin(2pai(f1+(f2-f1) / T*t)*t)) (1)

[0051] Insert digital sweep frequency signal;

[0052] In equation (1), f1 is the scan start frequency, f2 is the scan end frequency, and T is the scan length.

[0053] The receiving device includes a main acquisition board and a probe. In this embodiment, the main acquisition board features a dual-channel 36-bit analog-to-digital converter with a sampling rate greater than 8K (less than 1 / 8 millisecond). The probe in this embodiment has a dynamic range greater than 80 dB and a sensitivity less than 0.1 mV.

[0054] Probe integration: such as Figure 1 As shown, a dual-probe integrated structure is adopted. The probe pointing upwards towards the sound source to collect the downlink wave field of the near-field sound source is designated as upward vector probe A; the probe pointing downwards towards the wellbore is designated as downward vector probe B, collecting the uplink wave field reflected from the wellbore. The installation position of the dual-probe integrated structure in the well is at a depth greater than three apparent wavelengths from the sound source to ensure the purity of the wellbore wave generated after the signal leaves the sound source. If the distance is too small, the signal will be cluttered. In this embodiment, the installation position is 1 meter vertically from the excitation device in the well. Specifically, a hoisting installation method is used. After reaching the predetermined depth in the well, it is pushed against the well wall to ensure that the probe does not resonate during the acquisition process.

[0055] like Figure 2 As shown, the two probes are designed as a cylindrical long body back-to-back integrated structure, that is, the vector direction of the two probes is 180 degrees apart, and the vector direction is along the direction of sound wave transmission in the well. There is a sound insulation board between the two probes to avoid crosstalk. The inner layer of the sound insulation board is filled with sound-absorbing rubber.

[0056] In practical applications, as long as the two probes are set on the same axis and have opposite vector directions, one pointing upwards towards the sound source to collect the near-field downflow wave field, and the other pointing downwards towards the liquid surface in the wellbore, it is sufficient. The embodiment provided is as follows: Figure 3-5 The integrated probe structure shown is only one implementation of the probe's appearance design. Those skilled in the art should understand that the dual-probe design of this invention is not limited to this. Figure 3-5 This is the one shown.

[0057] like Figure 3 As shown, each probe has a tapered sound-receiving port design at the front, which provides a focusing reflective surface to facilitate signal focusing.

[0058] like Figure 4As shown, the probe specifically includes a cylindrical shell, with two probes facing opposite directions installed at both ends of the cylindrical shell; a sound insulation plate structure b is set in the middle of the cylindrical shell; the two probes are connected to the main acquisition board outside the well barrel through data transmission channels a set on both sides of the cylindrical shell; a first fixing limiter c is also designed on the outside of the cylindrical shell, which is used to install the probe in the well barrel.

[0059] like Figure 5 As shown, the two probes have the same structure. A second fixing limiter f is provided on the outer periphery of the conical sound port e, which is used to fix the probe to the corresponding slot position in the cylindrical shell; it also includes a probe fixing slot d, which is fixed to the corresponding matching slot in the cylindrical shell.

[0060] The present invention also provides a distance measurement method using the above-mentioned measuring equipment, specifically including the following process:

[0061] The excitation device generates a continuous acoustic up-frequency scanning signal at the wellhead, which is recorded by the near-source upward vector probe A. The scanning signal propagates downward along the wellbore in the form of acoustic waveguides. When it reaches the liquid surface, it undergoes total reflection and returns upward to the wellhead, where it is recorded by the downward vector probe B.

[0062] Autocorrelation processing is performed on the records from probe A to obtain the peak value, thus obtaining the system's recorded time 0. Cross-correlation processing is then performed on the records from probe A and probe B to obtain the peak value, and the time at time 0 is subtracted to obtain the round-trip time difference between the fluid surface excited by the pseudo-pulse sound source at the wellhead and the return time to the wellhead. Combined with the sound wave velocity in the well, the following can be calculated: Figure 1 The depth of the fluid level in the well is shown.

[0063] Based on the velocity formula Derivation of the formula for well fluid level depth:

[0064] Downhole fluid level

[0065] Δt=τ B2 -τ B1

[0066]

[0067] Where, d 液面 V represents the depth of the fluid level from the wellhead. 井 t represents the speed of sound wave propagation in the wellbore. 总 This indicates the time it takes for sound waves to travel through the wellbore.

[0068] Equation (2) is the formula for calculating the well liquid level in terms of phase velocity, where ω is the angular frequency (obtained from the excitation spectrum), and k z R is the axial wave number (calculated from actual data), R is the wellbore radius (known), and μ is the axial wave number. mnLet τ be the nth zero of the m-th Bessel function. B1 This indicates that in the cross-correlation function R xy The time delay corresponding to the first peak found in (t,τ) starting from time 0 {τ0} determined by autocorrelation (obtained from actual data); Indicates from τ B1 The time delay corresponding to the next peak found after the search (obtained from actual data); For cross-correlation function, x A (t) is the signal recorded by probe A, x B (t) is the signal recorded by probe B.

[0069] Considering that probe A records signals reflected from the liquid surface, and similarly probe B records signals from the sound source sent by the excitation device, this invention truncates the data after the sound source scanning time recorded by probe A before performing autocorrelation and crosscorrelation processing, retaining the signals within the sound source scanning time recorded by probe A and removing subsequent liquid surface reflection signals outside the scanning time. This ensures the purity (no interference) of the sound source wavelet in the autocorrelation of A, accurately determines the system's time 0, and also ensures the accuracy of reading the liquid surface reflection data after the crosscorrelation of probes A and B.

[0070] To ensure the accuracy of the liquid level depth calculation results, the present invention also provides the following processing method:

[0071] (1) Determine the signal source based on energy: A and A have the largest autocorrelation energy, which comes from the wellhead sound source signal (used to determine the 0 time of the system); A and B have the largest cross-correlation energy, which comes from the total reflection signal of the downhole liquid surface (used to determine the reflection time).

[0072] (2) Determine the signal source based on the positive and negative values ​​of the correlation back peaks: positive values ​​of the autocorrelation between A and A come from the wellhead sound source, and negative values ​​come from the reflection of the downhole fluid surface; positive values ​​of the cross-correlation between A and B come from the reflection of the downhole fluid surface, and negative values ​​come from the wellhead sound source.

[0073] (3) In actual operation, it is very simple. The computer automatically identifies the maximum positive peak of the autocorrelation between A and A as the system time 0 (the same time is a negative small peak in the cross-correlation record between A and B), and automatically identifies the maximum positive peak of the cross-correlation between A and B as the liquid surface reflection time (the same time is a negative small peak in the autocorrelation record between A and A).

[0074] Those skilled in the art will know that the measurement accuracy of conventional pressure sensors is 1 / 100 of the probe's depth in water. For example, if the probe is 200 meters below the water surface, its depth measurement error (accuracy) is 2 meters. The measurement accuracy of the method of the present invention is independent of the liquid surface depth and water depth.

[0075] The depth accuracy measured by the method of this invention depends on the dominant frequency of the excitation sound wave. Taking an excitation frequency of 1000 Hz (loudspeakers can easily excite sound waves of 1-2000 Hz) and 8K sampling as an example, one sound wave cycle of 1000 Hz is 1 millisecond, and it propagates about 0.34 meters in the well shaft (the sound wave speed is calculated as 340 m / s), with 8 digital sampling points; half a cycle (positive or negative part) propagates 0.17 meters, with 4 digital sampling points.

[0076] Finding the wave peak using integer digits of the recorded data results in a depth error (accuracy) of 0.17 / 4 = 0.0425 meters = 4.25 centimeters.

[0077] The actual peak position is not necessarily at an integer position in the digital record. Current human-computer interaction graphics digitization technology can increase the sampling point for picking the peak by at least 8 times. Calculated at 4 times, the depth error is 0.0425 / 4 = 0.016 meters = 1.6 centimeters.

[0078] Therefore, the depth positioning accuracy of the method of the present invention can be accurate to the centimeter level; the measurement accuracy is significantly improved compared with the existing pressure sensing liquid level measurement technology.

[0079] As a further improvement, by connecting a network data transmission terminal to the data acquisition host, the present invention can also achieve the technical effects of remote measurement and control and real-time monitoring.

[0080] In addition, after measuring one well, the integrated probe suspended in the well can be removed by the equipment of this invention, and other wells can be measured again, thus achieving the effect of measuring multiple wells with one set of equipment.

[0081] Compared to traditional measurement methods, the total equipment cost of this invention is approximately 3,000 yuan, while a traditional wired level gauge costs approximately 20,000 yuan, making the equipment cost significantly lower.

[0082] Furthermore, this invention requires no downhole installation work, unlike traditional surveying which requires downhole installation work, making the installation of this invention cost-free.

[0083] The measurement method of this invention has a scanning time of no more than 2 minutes from data acquisition to results output. Two people can complete the operation of a well within half an hour, which is lower in operating cost compared to existing traditional measurement methods.

[0084] Those skilled in the art will recognize that the embodiments described herein are intended to help the reader understand the principles of the invention, and should be understood that the scope of protection of the invention is not limited to such specific statements and embodiments. Various modifications and variations can be made to the invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the invention should be included within the scope of the claims of the invention.

Claims

1. A well liquid level measuring device based on the principle of acoustic waves, characterized in that, include: Excitation equipment, receiving equipment; The excitation device is positioned at the wellhead and sends a continuous acoustic up-frequency scanning signal to the wellhead; the expression for the continuous acoustic up-frequency scanning signal is: A(t)=sin(2pai(f1+(f2-f1) / T*t)*t)); Where f1 is the scan start frequency, f2 is the scan end frequency, and T is the scan length; The receiving device includes a probe body installed inside the well and a main acquisition board set outside the well. The probe body adopts a dual-probe integrated structure, with one probe facing the fluid surface in the well and the other probe facing the excitation device. The installation position of the dual-probe integrated structure in the well is at a depth distance from the sound source greater than three apparent wavelengths. A sound insulation plate structure is provided in the middle of the cylindrical shell between the two probes. Two probes facing opposite directions are connected to the main acquisition board, which calculates the liquid level depth in the well based on the sound signals collected by the two probes.

2. The well liquid level measuring device based on the principle of acoustic waves according to claim 1, characterized in that, The probe body is a cylindrical shell, with two probes facing opposite directions mounted at both ends of the cylindrical shell.

3. A well liquid level measurement method based on the principle of acoustic waves, characterized in that, Based on the well liquid level measurement device based on the acoustic wave principle as described in any one of claims 1-2, the depth of the liquid surface in the well is calculated according to the acoustic wave time difference collected by two probes facing opposite directions and the acoustic wave transmission speed in the well; the calculation process of the acoustic wave time difference is as follows: A1. The probe facing the excitation device is designated as probe A, and the probe facing the downhole fluid surface is designated as probe B; the signal obtained by probe A is designated as signal A, and the signal obtained by probe B is designated as signal B. A2. Perform autocorrelation processing on signal A and take the time corresponding to the first positive peak as time 0. A3. Perform cross-correlation processing on signal A and signal B. The time corresponding to the second positive peak is the time when the liquid surface reaches the probe after total reflection. A4. Subtract the time of 0 obtained in step A2 from the time when the sound wave reaches the probe after total reflection from the liquid surface to obtain the round-trip time difference from the probe body to the liquid surface.

4. The well liquid level measurement method based on the principle of acoustic waves according to claim 3, characterized in that, Based on the round-trip time difference of the sound wave from the probe body to the liquid surface calculated in step A4 and the sound wave transmission speed in the well, the distance from the probe body to the liquid surface is calculated. Then, the installation position of the probe body in the well is added to the distance from the probe body to the liquid surface to obtain the distance from the wellhead to the liquid surface, that is, the depth of the liquid surface in the well.

5. A well liquid level measurement method based on the principle of acoustic waves according to claim 4, characterized in that, Sound from the well The formula for calculating wave velocity is: ； in, Angular frequency, The axial wave number, Where is the radius of the well wall. for The first order of the Bessel function One zero point.

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