Natural gas well casing leak detection device

Abstract

The embodiment of the present application provides a natural gas well oil casing leak point detection device, which comprises a cylinder, a closed cavity is arranged in the cylinder; a connecting assembly, comprising a connecting pipeline and a transmitting source, one end of the connecting pipeline is used for connecting a pipeline to be detected, the other end is communicated with the closed cavity, the transmitting source is connected in the connecting pipeline and is used for transmitting infrasonic waves, and the transmission wave generated by the infrasonic waves is transmitted to the pipeline at least through the connecting pipeline, and the reflection wave is formed by the reflection of the liquid surface in the pipeline and is transmitted to the closed cavity; a vibration assembly, comprising a first vibrating piece, a plurality of first perforations are arranged on the first vibrating piece, the first vibrating piece is arranged in the closed cavity and is located at least on the transmission path of the reflection wave; and a signal acquisition assembly, comprising a signal acquisition piece, the signal acquisition piece is arranged in the closed cavity and is located on the side of the first vibrating piece away from the connecting pipeline, and is used for acquiring the transmission wave and the corresponding reflection wave of the infrasonic waves. The device can achieve the effect of simplifying the detection operation.

Description

Technical Field

[0001] This application relates to the field of leakage detection technology for oil and gas well casing, and in particular to a leakage detection device for natural gas well casing. Background Technology

[0002] The safe and efficient production of natural gas is a crucial pillar of national energy security. During production, natural gas well casing and tubing face extremely harsh conditions, including high temperatures, high pressures, and severe corrosion. After prolonged service, natural gas well casing and tubing are prone to problems such as corrosion pitting, thread gas seal failure, and punctures, leading to pressure buildup in the annulus and causing wellbore integrity failure. This integrity failure results in abnormal annular pressure or gas leakage, which, in the production of high-sulfur gas wells, can lead to serious personnel casualties and economic losses.

[0003] In related technologies, existing detection methods mostly rely on interventional logging techniques (such as multi-arm caliper logging tools and ultrasonic logging tools). Each detection process requires shutting down the well and halting production, relies on large auxiliary equipment, and involves cumbersome procedures for on-site deployment, instrument deployment, and recovery, and is also limited by the downhole environment. In addition, some existing detection devices, although not requiring deployment into the well, rely on specialized surface equipment, which is bulky and requires on-site installation and debugging, and multiple measurements are needed to locate the leak.

[0004] Regarding the aforementioned technologies, existing detection devices suffer from complex detection operations. Summary of the Invention

[0005] This application provides a natural gas well casing leak detection device, which simplifies the detection process.

[0006] This application provides a natural gas well casing leak detection device, including:

[0007] A cylindrical body, wherein a closed cavity is provided inside the cylindrical body;

[0008] A connection assembly includes a connection pipe and a transmitter. One end of the connection pipe is used to connect to the pipe to be tested, and the other end is connected to the closed cavity. The transmitter is connected in the connection pipe and is used to emit infrasound. The emitted wave generated by the infrasound is transmitted to the pipe through the connection pipe at least and is reflected by the liquid surface in the pipe to form a reflected wave that is transmitted toward the closed cavity.

[0009] The vibration assembly includes a first vibrating element, which has a plurality of first perforations. The first vibrating element is disposed in the enclosed cavity and is located at least on the transmission path of the reflected wave.

[0010] The signal acquisition component includes a signal acquisition element disposed within the enclosed cavity and located on the side of the first vibrating element away from the connecting pipeline, for acquiring the emitted wave of infrasound and its corresponding reflected wave.

[0011] In one possible implementation, the vibration assembly further includes a second vibrating element disposed within the enclosed cavity. The second vibrating element has a plurality of second perforations. The first vibrating element, the second vibrating element, and the signal acquisition element are sequentially arranged at intervals along the transmission path of the reflected wave, and the second vibrating element is located at least on the transmission path of the reflected wave.

[0012] In one possible implementation, the projected area of ​​the second vibrating element along the transmission path of the reflected wave on the top wall of the cylinder is smaller than the projected area of ​​the first vibrating element along the transmission path of the reflected wave on the top wall of the cylinder, and covers the projection of the signal acquisition element along the transmission path of the reflected wave on the top wall of the cylinder.

[0013] In one possible implementation, the area of ​​the second vibrating element is half the area of ​​the first vibrating element.

[0014] In one possible implementation, a connecting through hole is provided in the middle of the bottom wall of the cylinder, the connecting through hole is connected to the connecting pipeline, the diameter of the middle section of the connecting through hole is smaller than the diameter of its two ends, and the diameter of the two ends of the connecting through hole ranges from 5-10mm.

[0015] In one possible implementation, the vibration assembly further includes a first adjusting ring and a second adjusting ring, both of which are coaxially disposed within the enclosed cavity. The first vibrating element overlaps between the first adjusting ring and the second adjusting ring, and the axial height of the first adjusting ring is greater than the axial height of the second adjusting ring.

[0016] In one possible implementation, the first perforation and the second perforation are uniformly distributed on the first vibrating element and the second vibrating element, respectively, with the diameter of the first perforation ranging from 0.03 to 0.08 mm and the diameter of the second perforation ranging from 0.1 to 0.2 mm.

[0017] In one possible implementation, the vibration assembly further includes an annular plate, the annular plate having a circular tube with openings at both ends coaxially disposed at an annular hole, the second vibrating element being disposed on the top of the circular tube, and the annular plate overlapping the top of the second adjusting ring;

[0018] The cylinder includes a first shell, a second shell, and a third shell that are sequentially threaded together along the transmission path of the reflected wave, wherein the second shell is used to press against the top of the annular plate.

[0019] In one possible implementation, a partition is provided inside the second housing along a transmission path perpendicular to the reflected wave. The partition divides the closed cavity formed by the annular plate, the second housing, and the third housing into a gas testing cavity and an electrical module cavity distributed along the transmission path of the reflected wave. The acquisition end of the signal acquisition device is located inside the gas testing cavity.

[0020] The signal acquisition component further includes a temperature detection element, a pressure detection element, and a signal processing unit. The detection ends of the temperature detection element and the pressure detection element are both located inside the gas testing chamber, and are used to detect the gas temperature signal and the pipeline pressure signal, respectively. The signal acquisition element, the temperature detection element, and the pressure detection element are all electrically connected to the signal processing unit. The signal processing unit can calculate the location of the pipeline leak based on the acquired signals, temperature signals, and pressure signals.

[0021] In one possible implementation, a sealing ring is provided at the connection between the first housing and the second housing, and at the connection between the second housing and the third housing.

[0022] This application provides a natural gas well casing leak detection device. The device is connected to the pipeline to be detected. An infrasound wave is emitted into the pipeline via a transmitter. Simultaneously, the emitted infrasound wave propagates towards the sealed cavity. The emitted wave signal is amplified by a first vibrating element. Subsequently, a signal acquisition element collects the emitted infrasound wave. After reaching the liquid surface inside the pipeline, the infrasound wave is reflected and propagates towards the sealed cavity. During this process, the reflected wave signal is amplified by the first vibrating element, and the signal acquisition element collects the reflected wave. Based on the time difference between the emitted and reflected waves collected by the signal acquisition element, the infrasound wave is detected within the pipeline. The infrasound propagation is stable within the medium. If the pipeline under test is intact and has no leaks, the propagation channel structure is continuous, the acoustic impedance is uniform, and the infrasound reflection time difference is stable. When there is a leak in the pipeline under test, the reflected infrasound travels a long distance in the tubing, eventually reaching the bottom of the well and forming a reflected wave again. At this time, the polarity of the waveform changes, and the amplitude is attenuated due to long-distance transmission. The reflected wave is amplified by the first vibrating element, and the signal acquisition element collects the reflected wave. Therefore, it is possible to determine whether there is a leak in the pipeline. During the detection process, there is no need to shut down the well or stop production, nor is it necessary to take multiple measurements to obtain detection data, which facilitates pipeline inspection operations. Attached Figure Description

[0023] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0024] Figure 1This is a schematic diagram of the structure of a natural gas well casing leak detection device provided in this application;

[0025] Figure 2 This is a schematic diagram of the structure of the first vibrating element in a natural gas well casing leak detection device provided in this application;

[0026] Figure 3 This is a schematic diagram of the structure of the second vibrating element in a natural gas well casing leak detection device provided in this application;

[0027] Figure 4 A schematic diagram of the annular plate and the second vibrating element in a natural gas well casing leak detection device provided in this application;

[0028] Figure 5 This application provides a schematic diagram of the structure of the first housing in a natural gas well casing leak detection device.

[0029] Figure 6 This is a schematic diagram illustrating the working principle of a leak detection device for natural gas well casing provided in this application.

[0030] Figure 7 This is a schematic diagram of the signal acquisition and processing flow in a natural gas well casing leak detection device provided in this application.

[0031] Explanation of reference numerals in the attached figures:

[0032] 100. Cylinder; 101. Enclosed cavity; 101a. Gas testing chamber; 101b. Electrical module cavity; 102. Connecting through hole; 110. First housing; 120. Second housing; 121. Partition plate; 130. Third housing; 140. Sealing ring; 200. Connecting assembly; 210. Connecting pipeline; 211. Transmission pipeline; 211a. First pipeline; 211b. T-junction pipeline; 211c. Second pipeline; 212. Discharge pipeline; 212a. Third pipeline; 212b. Second pneumatic ball valve; 220. Emitting source; 221. First pneumatic ball valve; 300. Vibration assembly; 3 10. First vibrating element; 311. First perforation; 320. Second vibrating element; 321. Second perforation; 330. First adjusting ring; 340. Second adjusting ring; 350. Annular plate; 351. Circular tube; 400. Signal acquisition assembly; 410. Signal acquisition component; 420. Temperature detection component; 430. Pressure detection component; 440. Signal processing unit; 441. Signal transmission and processing module; 442. Wireless networking and transparent transmission module; 443. LoRa antenna; 444. Explosion-proof aviation plug; 445. Dust cover; 446. Signal shielding wire; 10. Oil pipe; 20. Oil sleeve annulus.

[0033] The accompanying drawings illustrate specific embodiments of this application, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the concept in any way, but rather to illustrate the concept of this application to those skilled in the art through reference to particular embodiments. Detailed Implementation

[0034] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this application as detailed in the appended claims.

[0035] As described in the background section, for the detection of oil casing and tubing failures and defects, on the one hand, the devices for interventional oil casing and tubing integrity evaluation mainly include: multi-arm caliper logging tools, electromagnetic pulse logging tools, downhole ultrasonic logging tools, downhole cameras, etc. These require shutting down the well and stopping production, have a long operation cycle (usually several days), and require the cooperation of large equipment such as cranes. In the detection process, it is first necessary to control the site, including monitoring the temperature and pressure around the wellhead to reduce interference from external factors. Then, the detection instrument is lowered into the pipeline by a crane to detect whether there are leaks in the pipeline. After the detection is completed, the detection instrument needs to be lifted out of the well by a crane, and personnel need to retrieve the detection instrument. The operation and retrieval process is relatively cumbersome, which leads to the complexity of the detection operation.

[0036] On the other hand, based on the principle that the amplitude of infrasound changes when it encounters a change in cross-section inside the casing, the characteristic of the amplitude change of infrasound can be used to identify defects in the casing. However, such devices still require dedicated ground-based equipment, which is bulky and requires multiple infrasound measurements to obtain detection data, making the detection operation complex.

[0037] In view of this, this application provides a natural gas well casing leak detection device. It emits infrasound waves into the pipe to be detected via a transmitter. Simultaneously, the emitted infrasound waves propagate towards the enclosed cavity. The emitted wave signal is amplified by a first vibrating element. Subsequently, a signal acquisition element collects the emitted infrasound waves. After the infrasound waves reach the liquid surface inside the pipe, they are reflected and propagate towards the enclosed cavity. During this process, the reflected wave signal is amplified by the first vibrating element, and the signal acquisition element collects the reflected wave. Based on the time difference between the emitted and reflected waves collected by the signal acquisition element, the infrasound waves are stabilized within the continuous medium of the pipe. In a fixed transmission method, if the pipeline to be tested is intact and has no leaks, the propagation channel structure is continuous, the acoustic impedance is uniform, and the infrasound reflection time difference is stable. When there is a leak in the pipeline to be tested, the reflected infrasound wave travels a long distance in the tubing, reaching the bottom of the well and forming a reflected wave again. At this time, the polarity of the waveform changes, and the amplitude is attenuated due to long-distance transmission. The reflected wave is amplified by the first vibrating element, and the signal acquisition element collects the reflected wave. Therefore, it is possible to determine whether there is a leak in the pipeline. During the detection process, there is no need to shut down the well or stop production, nor is it necessary to take multiple measurements to obtain detection data, which facilitates pipeline inspection operations.

[0038] The technical solutions of this application and how they solve the aforementioned technical problems are described in detail below with specific embodiments. These specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments. The embodiments of this application will be described below with reference to the accompanying drawings.

[0039] Reference Figure 1 This application provides a natural gas well casing leak detection device. The device includes a cylinder 100, a connecting assembly 200, a vibration assembly 300, and a signal acquisition assembly 400. The cylinder 100 has a closed cavity 101 inside. The connecting assembly 200 includes a connecting pipe 210 and a transmitter 220. One end of the connecting pipe 210 is connected to the pipe to be detected, and the other end of the connecting pipe 210 is connected to the closed cavity 101. The transmitter 220 is connected to the connecting pipe 210 and can emit infrasound. The emitted wave generated by the infrasound is transmitted to the pipe to be detected at least through the connecting pipe 210, and is reflected by the liquid surface in the pipe to form a reflected wave that is transmitted towards the closed cavity 101.

[0040] It should be noted that, referring to Figure 1The connecting pipeline 210 includes a transmission pipeline 211 and a discharge pipeline 212. The transmission pipeline 211 includes a first pipeline 211a, a tee pipeline 211b, and a second pipeline 211c. The first pipeline 211a is coaxially arranged with the cylinder 100 and is located at the bottom of the cylinder 100. One end of the first pipeline 211a is connected to the closed cavity 101. The tee pipeline 211b is located at the end of the first pipeline 211a away from the cylinder 100 and is fixedly connected to the first pipeline 211a through a flange. The second pipeline 211c is coaxially arranged with the first pipeline 211a and is fixedly connected to the tee pipeline 211b through a flange. The other end of the second pipeline 211c is connected to the oil pipe 10 or the oil sleeve annulus 20.

[0041] It should be noted that, referring to Figure 1 The transmitter 220 includes a first pneumatic ball valve 221, which is fixedly connected to the second pipeline 211c via a flange. As a "quick-on / off valve," the first pneumatic ball valve 221 causes a sudden change in fluid pressure and velocity at the valve port due to the rapid switching of high-pressure gas. This generates pulsed infrasound waves that are simultaneously transmitted to the pipeline under test and the enclosed cavity 101. Because the first pneumatic ball valve 221 can complete full on / off within tens of milliseconds, it can generate a sufficiently steep pressure step, producing infrasound waves with strong energy and a wide spectrum. It is suitable for high-pressure nitrogen and sulfur-containing natural gas conditions in gas wells. It can also be used in conjunction with a solenoid valve and a PLC (Programmable Logic Controller) to precisely control the opening and closing timing and holding time, enabling multiple repeated excitations. It can be directly installed at the wellhead without the need for additional large excitation devices.

[0042] It should be noted that the first pneumatic ball valve 221 can also be replaced by a solenoid ball valve / solenoid valve, a spring-return quick-opening valve (which requires manual reset after opening), etc.

[0043] Reference Figure 1 The discharge pipeline 212 includes a third pipeline 212a and a second pneumatic ball valve 212b. The axis of the third pipeline 212a is perpendicular to the axis of the first pipeline 211a. One end of the third pipeline 212a is fixedly connected to the tee pipeline 211b through a flange, and the other end is connected to the high-pressure nitrogen cylinder at the well site. The second pneumatic ball valve 212b is fixedly connected to the third pipeline 212a through a flange.

[0044] Reference Figure 1 and Figure 2 The vibration assembly 300 includes a first vibrating element 310, which has a plurality of first perforations 311. The first vibrating element 310 is disposed in the closed cavity 101 and is located at least on the transmission path of the reflected wave.

[0045] It should be noted that in this embodiment, the first vibrating element 310 is a titanium alloy exciter, which is a circular thin film with a thickness ranging from 0.03 mm to 0.2 mm. The first vibrating element 310 is provided with a plurality of first perforations 311, the diameter of which ranges from 0.03 mm to 0.08 mm. The plurality of first perforations 311 are evenly distributed on the first vibrating element 310 in a square array, or they can be arranged in a circle. The area between the bottom of the first vibrating element 310 and the bottom of the cylinder 100 forms a resonant cavity, and the total area of ​​the plurality of first perforations 311 accounts for 1% to 1.5% of the area of ​​the first vibrating element 310. This allows the first perforations 311 to be used only to slowly balance the static pressure inside and outside the resonant cavity, eliminating the rigid locking effect of the high pressure difference on the first vibrating element 310. At the same time, since the size of a single first perforation 311 is much smaller than the wavelength of infrasound, it will not cause dynamic acoustic energy leakage.

[0046] It should be noted that the first vibrating component 310 can also be made of 304 / 316L stainless steel, because it is corrosion resistant, cost-effective, easy to process, and thin plates are readily available; it has moderate elasticity and is fully compatible with infrasound low-frequency resonance; it is sufficient for the normal corrosive environment of oil and gas wells; it can also be made of Hastelloy / Monel alloy, which is suitable for gas wells with high sulfur content and strong corrosion, and its corrosion resistance is far superior to that of titanium alloy, making it suitable for extreme working conditions.

[0047] Reference Figure 1 The signal acquisition component 400 includes a signal acquisition element 410, which is disposed in the enclosed cavity 101 and located on the side of the first vibrating element 310 away from the connecting pipe 210. The signal acquisition element 410 acquires the emitted wave of the infrasound and its corresponding reflected wave.

[0048] It should be noted that in this embodiment, the signal acquisition device 410 is a piezoelectric infrasound sensor, but it can also be a capacitive infrasound sensor, an optical fiber infrasound sensor, a moving coil (magnetoelectric) infrasound sensor, a MEMS (MicroElectro Mechanical System) infrasound sensor, etc., which converts infrasound mechanical vibration signals with a frequency below 20Hz into measurable electrical signals.

[0049] It should be noted that when the emission source 220 excites an infrasound emission wave, the emission wave signal is amplified by the first vibrating element 310, the signal acquisition element 410 acquires the emission wave, and the infrasound transmitted to the pipe to be detected forms a reflected wave after passing through the dynamic liquid surface in the pipe. After the signal is amplified by the first vibrating element 310, the reflected wave is acquired by the signal acquisition element 410, thereby measuring the time difference between the emission wave and the reflected wave.

[0050] Therefore, this application provides a natural gas well casing leak detection device. It emits infrasound waves through a source 220 into the pipe to be detected. Simultaneously, the emitted infrasound waves propagate towards the sealed cavity 101. The first vibrating element 310 amplifies the emitted wave signal. Subsequently, a signal acquisition element 410 collects the emitted infrasound waves. After the infrasound waves reach the liquid surface inside the pipe, they are reflected and propagate towards the sealed cavity 101. During this process, the reflected wave signal is amplified by the first vibrating element 310, and the signal acquisition element 410 collects the reflected wave. Based on the signal acquisition... The time difference between the emitted and reflected waves collected by component 410 allows the infrasound to propagate stably within the continuous medium of the pipeline. When a leak is detected in the pipeline, the reflected infrasound travels a long distance in the tubing, eventually reaching the bottom of the well and forming a reflected wave again. At this point, the polarity of the waveform changes, and the amplitude is attenuated due to the long-distance transmission. The reflected wave is amplified by the first vibrating component, and the signal acquisition component collects the reflected wave. Therefore, it is possible to determine whether there is a leak in the pipeline. During the detection process, there is no need to shut down the well or stop production, nor is it necessary to take multiple measurements to obtain detection data, which facilitates pipeline inspection operations.

[0051] In one feasible implementation, refer to Figure 1 and Figure 3 The vibration assembly 300 also includes a second vibrating element 320, which is disposed in the enclosed cavity 101. The second vibrating element 320 has a plurality of second perforations 321. The first vibrating element 310, the second vibrating element 320 and the signal acquisition element 410 are arranged sequentially at intervals along the transmission path of the reflected wave, and the second vibrating element 320 is at least located on the transmission path of the reflected wave.

[0052] It should be noted that, referring to Figure 1 and Figure 3 In this embodiment, the thickness of the second vibrating element 320 ranges from 0.02 mm to 0.1 mm, and a plurality of second perforations 321 are provided on the second vibrating element 320. The diameter of the second perforations 321 ranges from 0.1 mm to 0.2 mm. The distribution of the plurality of second perforations 321 on the second vibrating element 320 presents a centrally symmetrical array, and the total area of ​​the plurality of second perforations 321 accounts for 10% to 15% of the area of ​​the second vibrating element 320.

[0053] Reference Figure 1 , Figure 2 and Figure 3 The second vibrating element 320 is made of titanium alloy, which has good strength and elasticity, can withstand the impact of airflow and sound waves, and has very low acoustic impedance and strong sound wave penetration ability. The second vibrating element 320 and the first vibrating element 310 can be made of the same material or different materials.

[0054] In one feasible implementation, refer to Figure 1 The projection area of ​​the second vibrating element 320 along the transmission path of the reflected wave on the top wall of the cylinder 100 is smaller than the projection area of ​​the first vibrating element 310 along the transmission path of the reflected wave on the top wall of the cylinder 100, and covers the projection of the signal acquisition element 410 along the transmission path of the reflected wave on the top wall of the cylinder 100.

[0055] It should be noted that, referring to Figure 1 The area between the second vibrating element 320 and the first vibrating element 310 forms an organ pipe acoustic resonant cavity, and the area between the first vibrating element 310 and the bottom wall of the cylinder 100 forms a Helmholtz-type resonant cavity, which can amplify the emitted and reflected waves of infrasound. The infrasound first forms a low-frequency standing wave resonance in the Helmholtz-type resonant cavity, completing energy convergence and amplification, and then achieves secondary amplification and noise filtering of a specific frequency band through the organ pipe acoustic resonant cavity, which greatly improves the signal-to-noise ratio of weak leakage signals. The dual resonance greatly improves the detection sensitivity of small leaks, thereby facilitating the signal acquisition element 410 to acquire the emitted and reflected waves.

[0056] It should be noted that the projection of the second vibrating element 320 along the transmission path of the reflected wave on the top wall of the cylinder 100 covers the projection of the signal acquisition element 410 along the transmission path of the reflected wave on the top wall of the cylinder 100, which facilitates the signal acquisition element 410 to collect the sound waves passing through the second vibrating element 320.

[0057] In one feasible implementation, refer to Figure 1 , Figure 4 and Figure 5 The area of ​​the second vibrating element 320 is half the area of ​​the first vibrating element 310.

[0058] In one feasible implementation, refer to Figure 1 and Figure 5 A connecting through hole 102 is provided in the middle of the bottom wall of the cylinder 100. The connecting through hole 102 is connected to the connecting pipe 210. The diameter of the middle section of the connecting through hole 102 is smaller than the diameter of its two ends. The diameter range of the two ends of the connecting through hole 102 is 5-10mm.

[0059] It should be noted that, referring to Figure 5 The axial length of the connecting through hole 102 is 15-20mm, and the diameter of the middle section of the connecting through hole 102 is 2-5mm. When the sound wave passes through the connecting through hole 102, it can effectively suppress high-frequency noise, improve the infrasound transmission rate, and ensure the test effect.

[0060] In one feasible implementation, refer to Figure 1 and Figure 5The vibration assembly 300 also includes a first adjusting ring 330 and a second adjusting ring 340. The first adjusting ring 330 and the second adjusting ring 340 are coaxially arranged in the closed cavity 101. The first vibrating element 310 overlaps between the first adjusting ring 330 and the second adjusting ring 340. The axial height of the first adjusting ring 330 is greater than the axial height of the second adjusting ring 340.

[0061] In one feasible implementation, refer to Figure 1 , Figure 4 and Figure 5 The vibration assembly 300 also includes an annular plate 350, with a circular tube 351 with openings at both ends coaxially disposed at the annular hole of the annular plate 350, the second vibration member 320 disposed on the top of the circular tube 351, and the annular plate 350 overlapping the top of the second adjusting ring 340.

[0062] The cylinder 100 includes a first housing 110, a second housing 120 and a third housing 130 that are sequentially threaded along the transmission path of the reflected wave. The second housing 120 is used to press against the top of the annular plate 350.

[0063] It should be noted that, referring to Figure 1 The first pneumatic ball valve 221 serves as a controllable excitation source. The pulsed infrasound generated by the rapid opening of the first pneumatic ball valve 221 propagates along the first pipeline 211a to the Helmholtz-type resonant cavity. When the incident sound wave frequency matches the natural frequency of the resonant cavity, the originally weak leakage reflection signal is amplified, making the reflection characteristics of the leakage point more prominent. This facilitates the signal acquisition unit 410 in capturing weak abnormal information, enabling high-precision identification and location of defects such as corrosion holes, threaded gas seal failures, and puncture leaks. This effectively solves the technical problem of weak signals from minor corrosion perforations in gas well shafts, which are easily drowned out by noise, and significantly improves the sensitivity and accuracy of identifying and locating tiny leaks.

[0064] It should be noted that, referring to Figure 1 and Figure 5 The second adjusting ring 340, the annular plate 350, the circular tube 351, and the second vibrating element 320 work together to form a tapered organ pipe acoustic resonance structure, detailed as follows:

[0065] The second adjusting ring 340, the annular plate 350, and the circular tube 351 form a tapered annular structure, constituting a converging flow channel from a large cross-section to a small cross-section. The second vibrating element 320 is a disc-shaped structure with multiple threaded holes evenly distributed along its circumferential edge. The thickness of the disc edge of the second vibrating element 320 is much greater than the film thickness of the second vibrating element 320. The second vibrating element 320 is sealed at the end of the tapered flow channel. When the infrasound signal enters the flow channel, sound pressure focusing and energy convergence occur within the tapered structure, and the signal is emitted at the second vibrating element 320. The incident wave and the reflected wave superimpose to form a standing wave, which excites the tapered organ pipe sound wave resonance effect. This structure can significantly increase the amplitude of the infrasound signal. At the same time, by adjusting the flow channel parameters through the second adjusting ring 340, the resonance frequency can be accurately matched with the target infrasound frequency band, effectively enhancing the detection sensitivity of the piezoelectric infrasound sensor and enabling accurate identification of minute leaks in the pipeline to be detected.

[0066] It should be noted that the axial length of the first adjusting ring 330 is 1.5 to 2 times the axial length of the second adjusting ring 340. This structural design constitutes a two-stage acoustic resonance system: the first adjusting ring 330 with a larger axial length corresponds to the resonance amplification of the low-frequency band of infrasound, and the second adjusting ring 340 with a smaller axial length corresponds to the resonance amplification of the mid-frequency band of infrasound. Through the differentiated configuration of lengths, the frequency response range of the resonance cavity is expanded, and wide-band, high-precision identification of defects of different scales (from micro-corrosion holes to large-area perforations) in the gas well shaft is achieved.

[0067] In one feasible implementation, refer to Figure 1 A partition 121 is provided inside the second housing 120 along the transmission path perpendicular to the reflected wave. The partition 121 divides the closed cavity formed by the annular plate 350, the second housing 120 and the third housing 130 into a gas test cavity 101a and an electrical module cavity 101b distributed along the transmission path of the reflected wave. The acquisition end of the signal acquisition device 410 is located in the gas test cavity 101a.

[0068] The signal acquisition component 400 also includes a temperature detection element 420, a pressure detection element 430, and a signal processing unit 440. The detection ends of the temperature detection element 420 and the pressure detection element 430 are both located in the gas test chamber 101a, and are used to detect the gas temperature signal and the pipeline pressure signal, respectively. The signal acquisition component 410, the temperature detection element 420, and the pressure detection element 430 are all electrically connected to the signal processing unit 440. The signal processing unit 440 can calculate the location of the pipeline leak based on the acquired signals, temperature signals, and pressure signals.

[0069] It should be noted that in this embodiment, the piezoelectric infrasound sensor is composed of a PVDF polymer piezoelectric film and a high-elasticity vibrating film, which can sensitively sense infrasound waves passing through the second vibrating element 320, and has the characteristics of wide frequency band acceptance range and strong anti-interference ability.

[0070] It should be noted that the temperature sensing element 420 uses a temperature sensor, or a K-type / J-type thermocouple and a digital temperature sensor, etc. The temperature sensor is made of Pt100 material, which has high testing accuracy and good stability. The sensor test probe is made of nickel-based high-temperature alloy material to ensure the sensor's pressure resistance and corrosion resistance.

[0071] It should be noted that the pressure detection component 430 uses a pressure sensor, or a ceramic pressure sensor or a MEMS pressure sensor, etc. The pressure sensor is piezoelectric and has good adaptability to dynamic pressure testing. The sensor test probe is made of nickel-based high-temperature alloy material.

[0072] It should be noted that the signal acquisition component 410, temperature detection component 420, pressure detection component 430 and partition plate 121 are all connected by threads. The threaded section of the signal acquisition component 410 is equipped with a polytetrafluoroethylene sealing gasket to ensure airtightness during installation.

[0073] It should be noted that, referring to Figure 1 and Figure 6 In this embodiment, the pipeline to be detected is the oil pipe 10 or the oil casing annulus 20. The signal processing unit 440 includes a signal transmission and processing module 441, a wireless networking and transparent transmission module 442, a LoRa antenna 443, an explosion-proof aviation plug 444, and a dust cover 445. The signal transmission and processing module 441 and the wireless networking and transparent transmission module 442 are both located in the electrical module cavity 101b. The signal transmission and processing module 441 is connected to the signal acquisition device 410, the temperature detection device 420, and the pressure detection device 430 by a signal shielded cable 446 and is clamped and fixed by a hub. The signal transmission and processing module 441 can effectively remove vibration information and high-frequency noise signals, measure and record infrasound signals, and calculate the pressure gradient of the oil pipe 10 or the casing.

[0074] It should be noted that the 446 signal shielded cable can suppress electric field interference and low-frequency magnetic field / ground loop interference; and it uses an explosion-proof gland for sealing to ensure the explosion-proof nature of the electrical connection.

[0075] It should be noted that, referring to Figure 1One end of the wireless networking and transparent transmission module 442 is connected to the signal transmission and processing module 441 via a signal shielded cable 446. The wireless networking and transparent transmission module 442 can transform the signal processed by the signal transmission and processing module 441 into a digital signal that can be wirelessly transmitted. The other end of the wireless networking and transparent transmission module 442 is connected to the LoRa antenna 443 (LongRange antenna, long-range spread spectrum wireless (LoRa) communication antenna) via a signal shielded cable 446. The LoRa antenna 443 and the remote control host computer form a transmission relationship to complete the wireless transmission of test data.

[0076] It should be noted that the LoRa antenna 443 enables wireless transmission of test signals over long distances with stable signal strength, allowing for remote testing and control while avoiding contact with high-pressure gases.

[0077] It should be noted that, referring to Figure 1 The explosion-proof aviation plug 444 is fixedly installed on the top of the third housing 130 by screws. The signal acquisition component 410, temperature detection component 420, pressure detection component 430, signal transmission and processing module 441, and wireless networking and transparent transmission module 442 are all connected to the explosion-proof aviation plug 444 by signal shielded cable 446 and are clamped and fixed by a hub.

[0078] It should be noted that the explosion-proof aviation plug 444 connects to an external power source to ensure a stable power supply for all electrical modules. When not in use, the dust cover 445 serves to protect against dust and water.

[0079] It should be noted that, referring to Figure 6 and Figure 7 Based on the pressure distribution pattern of the tubing 10 and the annulus 20 in the gas wellbore, pressure gradient curves for the tubing and annulus are established respectively. Under normal production conditions, the fluid pressure gradient in the tubing 10 is greater than the hydrostatic pressure gradient in the annulus, and the two pressure curves do not intersect. When gas leakage occurs in the tubing 10 due to corrosion perforation, thread gas seal failure, or puncture, the leakage point must meet the mechanical equilibrium condition that the tubing pressure and the annulus pressure are equal. Since both pressure gradient curves are approximately linearly distributed, their intersection is the location where the pressures are equal. This location corresponds to the only depth in the wellbore that meets the gas flow condition, which is the leakage point on the tubing 10. By solving for the intersection of the two pressure gradient curves, the depth of the leakage point can be quickly located.

[0080] The specific process is as follows:

[0081] First, before the acoustic test in the oil pipe 10 starts, the first pneumatic ball valve 221 and the second pneumatic ball valve 212b are both closed. The second connecting pipe of the device is connected to the connecting pipe of the oil pipe 10 with a conical seal. Other sealing connection methods can also be used, such as ED seal (ED ring) or C-type seal. The oil pipe 10 forms a propagation channel for infrasound. When the first pneumatic ball valve 221 is opened, the pulsed infrasound generated propagates to both the oil pipe 10 and the first connecting pipe. The signal acquisition unit 410 records the time of infrasound emission the instant the first pneumatic ball valve 221 is opened.

[0082] The infrasound wave propagates over a long distance in tubing 10, reaching the dynamic fluid surface at the bottom of the well, where it is reflected again. At this point, the polarity of the waveform changes, and the amplitude is attenuated due to the long-distance transmission. However, the reflected wave can be captured by the dual resonance effect of the Helmholtz-type resonant cavity and the organ pipe acoustic resonant cavity. At this time, the signal acquisition device 410 can record the time of the reflected wave.

[0083] Simultaneously, the pressure detection element 430 and the temperature detection element 420 measure the pressure and temperature of the gas in real time. After the acoustic signal, pressure and temperature signal are processed by the signal transmission and processing module 441, they can be transmitted to the remote control host computer in real time. Combined with the gas composition parameters of the gas well, after processing by the signal transmission and processing module 441, the liquid level depth of the tubing 10 and the gas pressure gradient of the tubing 10 can be obtained (the calculation method is common knowledge and will not be elaborated here). The pressure gradient curve of the tubing 10 is calculated. The first pneumatic ball valve 221 is closed and the second pneumatic ball valve 212b is opened to purge the two resonant cavities.

[0084] Next, for the acoustic testing of the annulus 20, the device was disassembled from the oil pipe 10, with both the first pneumatic ball valve 221 and the second pneumatic ball valve 212b in the closed state. The device was then installed in the annulus 20 (referred to as the A annulus in engineering), and the above testing steps were repeated to obtain the annulus liquid level depth and annulus pressure gradient of the annulus 20, and the annulus pressure gradient curve was calculated. The first pneumatic ball valve 221 was closed, and the second pneumatic ball valve 212b was opened to purge the two resonant cavities.

[0085] Finally, the leak point calculation for tubing 10 is performed by the signal transmission and processing module 441 based on the pressure gradient curve of tubing 10 and the annulus pressure gradient curve. The intersection of the two curves is the point where the gas pressure gradients are equal, which is also the leak point on tubing 10. If it is necessary to locate and evaluate the leak point of the casing, two adjacent annulus spaces can be selected for infrasound testing. The signal transmission and processing module 441 automatically calculates the leak point based on the sound wave measurement data.

[0086] In one feasible implementation, refer to Figure 1A sealing ring 140 is provided at the connection between the first housing 110 and the second housing 120 and the connection between the second housing 120 and the third housing 130.

[0087] It should be noted that the sealing ring 140 is made of perfluoroether material, which ensures airtightness while resisting corrosion from acidic gases such as hydrogen sulfide and carbon dioxide in natural gas.

[0088] Finally, it should be noted that other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This invention is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein, and is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of the invention is limited only by the appended claims.

Claims

1. A device for detecting leaks in natural gas well casing, characterized in that, include: A cylindrical body (100) having a closed cavity (101) inside. The connection assembly (200) includes a connection pipe (210) and a transmitter (220). One end of the connection pipe (210) is used to connect to the pipe to be tested, and the other end is connected to the closed cavity (101). The transmitter (220) is connected in the connection pipe (210) and is used to emit infrasound. The emitted wave generated by the infrasound is transmitted to the pipe through the connection pipe (210) at least and is reflected by the liquid surface in the pipe to form a reflected wave that is transmitted toward the closed cavity (101). The vibration assembly (300) includes a first vibrating element (310), the first vibrating element (310) having a plurality of first perforations (311), the first vibrating element (310) being disposed in the closed cavity (101) and being located at least on the transmission path of the reflected wave; The signal acquisition component (400) includes a signal acquisition element (410), which is disposed in the enclosed cavity (101) and located on the side of the first vibrating element (310) away from the connecting pipe (210), for acquiring the emitted wave of infrasound and its corresponding reflected wave.

2. The natural gas well casing leak detection device according to claim 1, characterized in that, The vibration assembly (300) further includes a second vibrating element (320), which is disposed in the closed cavity (101). The second vibrating element (320) has a plurality of second perforations (321). The first vibrating element (310), the second vibrating element (320) and the signal acquisition element (410) are arranged sequentially at intervals along the transmission path of the reflected wave, and the second vibrating element (320) is at least located on the transmission path of the reflected wave.

3. The natural gas well casing leak detection device according to claim 2, characterized in that, The projection area of ​​the second vibrating element (320) along the transmission path of the reflected wave on the top wall of the cylinder (100) is smaller than the projection area of ​​the first vibrating element (310) along the transmission path of the reflected wave on the top wall of the cylinder (100), and covers the projection of the signal acquisition element (410) along the transmission path of the reflected wave on the top wall of the cylinder (100).

4. The natural gas well casing leak detection device according to claim 3, characterized in that, The area of ​​the second vibrating element (320) is half the area of ​​the first vibrating element (310).

5. The natural gas well casing leak detection device according to claim 4, characterized in that, A connecting through hole (102) is provided in the middle of the bottom wall of the cylinder (100). The connecting through hole (102) is connected to the connecting pipe (210). The diameter of the middle section of the connecting through hole (102) is smaller than the diameter of its two ends. The diameter range of the two ends of the connecting through hole (102) is 5-10mm.

6. The natural gas well casing leak detection device according to claim 4, characterized in that, The vibration assembly (300) further includes a first adjusting ring (330) and a second adjusting ring (340). The first adjusting ring (330) and the second adjusting ring (340) are coaxially disposed in the closed cavity (101). The first vibrating element (310) overlaps between the first adjusting ring (330) and the second adjusting ring (340). The axial height of the first adjusting ring (330) is greater than the axial height of the second adjusting ring (340).

7. The natural gas well casing leak detection device according to claim 6, characterized in that, The first perforation (311) and the second perforation (321) are evenly distributed on the first vibrating element (310) and the second vibrating element (320), respectively. The diameter of the first perforation (311) is in the range of 0.03-0.08 mm, and the diameter of the second perforation (321) is in the range of 0.1-0.2 mm.

8. The natural gas well casing leak detection device according to claim 6, characterized in that, The vibration assembly (300) also includes an annular plate (350), the annular plate (350) having a circular tube (351) with openings at both ends coaxially disposed at the annular hole, the second vibration element (320) being disposed on the top of the circular tube (351), and the annular plate (350) overlapping the top of the second adjusting ring (340); The cylinder (100) includes a first housing (110), a second housing (120) and a third housing (130) that are sequentially threaded along the transmission path of the reflected wave. The second housing (120) is used to abut against the top of the annular plate (350).

9. The natural gas well casing leak detection device according to claim 8, characterized in that, A partition (121) is provided inside the second housing (120) along the transmission path perpendicular to the reflected wave. The partition (121) divides the closed cavity formed by the annular plate (350), the second housing (120) and the third housing (130) into a gas test chamber (101a) and an electrical module chamber (101b) distributed along the transmission path of the reflected wave. The acquisition end of the signal acquisition device (410) is located inside the gas test chamber (101a). The signal acquisition component (400) further includes a temperature detection element (420), a pressure detection element (430), and a signal processing unit (440). The detection ends of the temperature detection element (420) and the pressure detection element (430) are both located in the gas test chamber (101a) and are used to detect the gas temperature signal and the pipeline pressure signal, respectively. The signal acquisition component (410), the temperature detection element (420), and the pressure detection element (430) are all electrically connected to the signal processing unit (440). The signal processing unit (440) can calculate the location of the pipeline leak based on the acquired signal, temperature signal, and pressure signal.

10. The natural gas well casing leak detection device according to claim 8, characterized in that, A sealing ring (140) is provided at the connection between the first housing (110) and the second housing (120) and at the connection between the second housing (120) and the third housing (130).

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