A transient shock self-oscillation type gas-liquid interface monitoring system and method for gas storage

Abstract

The application provides a kind of transient shock self-oscillation type gas storage gas-liquid interface monitoring system and method, which comprises: transmitting an impulse voltage signal to the central tube, the impulse voltage signal passes through the loop formed by the stratum, salt water and the central tube;The loop responds to the self-oscillating AC signal shock with a frequency of f under the impulse voltage signal;Detect the frequency f of the self-oscillating AC current signal on the central tube;According to the self-oscillating AC current signal frequency f and the known gas storage parameters, the height H of the gas-liquid interface distance from the wellhead is calculated.The application uses electrical signal as ranging signal to achieve the purpose of ranging.Compared with low-frequency electrical signal ranging, the position requirement of the measuring device is lower, compared with laser ranging, the obstruction can be effectively avoided, and high-precision real-time measurement can be realized.The application improves the detection accuracy, and the detection process and equipment are simpler.

Description

Technical Field

[0001] This invention relates to the field of salt cavern gas storage technology, and more specifically, to a transient shock wave self-oscillating gas storage gas-liquid interface monitoring system and method. Background Technology

[0002] Salt cavern gas storage facilities are constructed by injecting fresh water into salt wells or newly drilled boreholes. The fresh water dissolves the salt ore, creating a cavity for gas storage, which is then drained through a drainage pipe. During this process, the design must be continuously adjusted based on technical parameters such as liquid level and salinity to ensure the geometry and volume of the underground salt cavern meet design requirements. To prevent dissolution at the top of the cavern, a certain amount of isolation fluid is injected into the gap between the injection pipe and the outer casing of the wellhead to prevent damage to the cavern's geometry. Monitoring liquid level changes is crucial for protecting the geometry of the gas storage facility during its construction and operation. Because the gas storage facility requires strict sealing after construction and commissioning, wired measurement methods cannot be used to monitor the liquid level. Furthermore, the harsh environment inside the gas storage facility makes it difficult for existing liquid level measurement methods and devices to meet the requirements for long-term operation of instruments downhole, and thus, the requirement for real-time and continuous measurement of the gas-liquid interface height.

[0003] Currently, existing technologies utilize a method and system for measuring the gas-liquid interface in salt cavern gas storage based on low-frequency electrical signals. This method uses a constant current source and a voltage measuring device to monitor the gas-liquid interface height in real time and continuously. However, achieving constant current output downhole is difficult during the operation of the gas storage facility after its construction, and the location of the voltage measuring device has a significant impact on the output results. Furthermore, the device requires high installation precision, is complex, and is prone to measurement errors. Summary of the Invention

[0004] This invention addresses the technical problems existing in the prior art by providing a transient shock wave self-oscillating gas-liquid interface monitoring system and method for gas storage. The purpose is to utilize the fact that under any gas-liquid interface height condition, the inductance and capacitance induced by the central tube and the surrounding strata of the gas storage have a certain self-oscillation frequency. By detecting the frequency of the self-oscillating current on the central tube, the gas-liquid interface height can be measured in real time, which improves the accuracy of gas-liquid interface height detection and simplifies the detection equipment.

[0005] According to a first aspect of the present invention, a transient shock wave self-oscillating gas storage gas-liquid interface monitoring system is provided, comprising: a central pipe, an insulating short section, a transient voltage transmitter, a current frequency measuring device, and a ground-based main unit disposed within the gas storage facility;

[0006] The central tube is vertically arranged, and the insulating short section is arranged on the central tube and located above the gas-liquid interface. The insulating short section divides the central tube into an upper central tube and a lower central tube that are insulated from each other. The upper central tube is electrically connected to the formation at the wellhead of the gas storage tank, and the lower central tube extends to the lower end of the gas storage tank.

[0007] The transient voltage transmitter is mounted on the insulating short section. The positive electrode of the transient voltage transmitter is connected to the upper central tube, and the negative electrode of the transient voltage transmitter is connected to the lower central tube, for transmitting impulse voltage signals.

[0008] The current frequency measuring device is installed on the lower central tube and is used to detect the frequency f of the self-oscillating AC current signal on the central tube.

[0009] The ground host is connected to the transient voltage transmitter and the current frequency measuring device via wireless communication signals, respectively, and is used to calculate the height H of the gas-liquid interface from the wellhead based on the frequency f of the self-oscillating AC current signal and the known gas storage parameters.

[0010] Based on the above technical solution, the present invention can also be improved as follows.

[0011] Optionally, the wellhead of the gas storage facility is equipped with a packer to isolate the downhole environment.

[0012] Optionally, the insulating short section, transient voltage transmitter, and current frequency measuring device are all located below the top of the gas storage tank and above the highest point of the gas-liquid interface within the gas storage tank.

[0013] According to a second aspect of the present invention, based on the systems described in the above embodiments, a method for monitoring the gas-liquid interface of a transient shock wave self-oscillating gas storage tank is also provided, comprising:

[0014] An impulse voltage signal is emitted to the central tube, and the impulse voltage signal passes through a loop formed by the formation, brine and the central tube;

[0015] The circuit responds to the impulse voltage signal by generating a self-oscillating AC signal shock wave with a frequency of f.

[0016] The frequency f of the self-oscillating alternating current signal on the detection center pipe is used to calculate the height H of the gas-liquid interface from the wellhead based on the frequency f and the known gas storage parameters.

[0017] Optionally, if the gas storage facility is equivalent to a second-order LC circuit, its inductance L and capacitance C are generated by the coupling between the central pipe and the surrounding strata, then the following equation is satisfied:

[0018]

[0019]

[0020]

[0021] Where f is the frequency of the self-oscillating alternating current signal, L is the inductance induced between the central tube and the surrounding strata of the gas storage, C is the capacitance induced between the central tube and the surrounding strata of the gas storage, and μ r ε represents the relative magnetic permeability of the gas in the gas storage tank. r R is the relative electrical conductivity of the gas in the gas storage tank, μ0 is the magnetic permeability of air, ε0 is the electrical conductivity of air, H is the height of the gas-liquid interface from the wellhead, and R is the relative electrical conductivity of the gas in the storage tank. s r is the inner diameter of the gas storage tank. o The outer diameter of the central tube.

[0022] Optionally, the height H of the gas-liquid interface from the wellhead can be calculated using the following formula:

[0023]

[0024] Where H is the height of the gas-liquid interface from the wellhead, c is the speed of light in a vacuum, f is the measured frequency of the central tube self-oscillating AC current signal, and μ r ε represents the relative magnetic permeability of the gas in the gas storage tank. r The relative conductivity of the gas in the gas storage tank.

[0025] Optionally, the impulse voltage signal can be transmitted using a direct drive method.

[0026] The present invention provides a transient shock wave self-oscillating gas storage gas-liquid interface monitoring system and method, which has the following beneficial effects:

[0027] (1) This invention monitors the liquid level by detecting the frequency of the self-oscillating current signal on the central tube. It utilizes the fact that different liquid levels will change the inductance and capacitance induced in the central tube and the surrounding strata of the gas storage tank. Based on the different frequencies of the self-oscillating current signal obtained from the impact voltage signal response, the purpose of measuring the liquid level is achieved. Compared with low-frequency electrical signal ranging, this method can reduce the number of downhole devices and avoid the influence of the installation position of the voltage measuring device, and has high measurement accuracy.

[0028] (2) The present invention can measure the frequency of the self-oscillating current signal on the central tube and analyze the measured current signal frequency with high accuracy.

[0029] (3) The present invention can obtain more accurate measurement results by adjusting the amplitude of the impact voltage signal according to the characteristics of the gas storage tank. Attached Figure Description

[0030] Figure 1 A schematic diagram of a transient shock wave self-oscillating gas storage gas-liquid interface monitoring system provided by the present invention;

[0031] Figure 2 A flowchart of a transient shock wave self-oscillating gas storage gas interface monitoring method provided by the present invention;

[0032] Figure 3 This is a schematic diagram of the equivalent circuit of a salt cavern gas storage tank.

[0033] In all the accompanying drawings, the same reference numerals are used to denote the same elements or structures, wherein:

[0034] 1. Central tube; 101. Upper central tube; 102. Lower central tube; 2. Insulating short section; 3. Transient voltage transmitter; 4. Current frequency measuring device; 5. Bushing; 6. Packer; 7. Metal centralizer; 8. Formation; 9. Gas; 10. Gas-liquid interface; 11. Brine. Detailed Implementation

[0035] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and are not intended to limit the scope of the invention.

[0036] Figure 1 A schematic diagram of the composition structure of a transient shock wave self-oscillating gas storage gas-liquid interface monitoring system provided by the present invention is shown below. Figure 1 As shown, a transient shock wave self-oscillating gas storage gas-liquid interface monitoring system includes: a casing 5, a central pipe 1, a packer 6, a metal centralizer 7, an insulating short section 2, a transient voltage transmitter 3, a current frequency measuring device 4, and a ground host (not shown in the figure) installed in the gas storage.

[0037] The casing 5 is installed at the wellhead of the gas storage facility, and the wellhead of the gas storage facility is reinforced by the vertically installed casing 5.

[0038] The central tube 1 is vertically installed in the sleeve 5 and inserted into the salt cavern gas storage tank, and is used to add or discharge brine 11 into the gas storage tank.

[0039] Packer 6 is installed at the wellhead of the gas storage facility to isolate the downhole environment;

[0040] The metal centralizer 7 serves as both a structural support and a conductive connector. It is located below the packer 6 at the wellhead and is used to connect the central pipe 1 to the ground. It is also used to maintain the orientation of the central pipe 1 and prevent it from tilting.

[0041] The insulating short section 2 is disposed on the central tube 1 and located above the gas-liquid interface 10. The insulating short section 2 divides the central tube 1 into an upper central tube 101 and a lower central tube 102 that are insulated from each other. That is, the insulating short section 2 is disposed at the connection between the upper central tube 101 and the lower central tube 102. The upper central tube 101 is electrically connected to the formation 8 at the wellhead of the gas storage tank through a metal centralizer 7, and the lower central tube 102 extends to below the gas-liquid interface 10 at the lower end of the gas storage tank.

[0042] The transient voltage transmitter 3 is installed on the outer wall of the insulating short section 2. The positive electrode of the transient voltage transmitter 3 is directly connected to the upper central tube 101, and the negative electrode of the transient voltage transmitter 3 is directly connected to the lower central tube 102, for transmitting impulse voltage signals to the central tube 1.

[0043] The current frequency measuring device 4 is installed on the lower central tube 102 and is used to detect the frequency f of the self-oscillating alternating current signal on the central tube 1.

[0044] The ground host (not shown in the figure) is set outside the wellhead of the gas storage. The ground host is connected to the transient voltage transmitter 3 and the current frequency measuring device 4 via wireless communication. It can adjust the impulse voltage signal emitted by the transient voltage transmitter 3 and receive the detection data of the current frequency measuring device 4. Combined with the known gas storage parameters (such as the gas storage radius), it calculates the height H of the gas-liquid interface from the wellhead.

[0045] In one embodiment, the current frequency measuring device 4 includes an induction coil, which is arranged around the outer wall of the lower central tube 102, that is, sleeved on the outer periphery of the lower central tube 102, and is used to measure the frequency f of the self-oscillating alternating current signal on the lower central tube 102 by magnetic induction.

[0046] Of course, a hardware measurement circuit consisting of a zero-crossing comparator, a square wave forming circuit, and a counter can also be used to measure the frequency f of the self-oscillating AC current signal on the lower center tube 102, which will not be elaborated here.

[0047] The insulating short section 2, transient voltage transmitter 3, and current frequency measuring device 4 are all located below the top of the gas storage tank and above the highest position of the gas-liquid interface 10 inside the gas storage tank, so as to obtain a larger measurement range.

[0048] like Figure 2 The diagram shown is a flowchart of a detection method based on the system described in the above embodiment. Figure 2 As shown in the figure, this embodiment provides a method for monitoring the gas-liquid interface in a transient shock wave self-oscillating gas storage facility, including:

[0049] S1, the transient voltage transmitter 3 transmits an impulse voltage signal to the central tube 1, and the impulse voltage signal passes through the loop formed by the formation 8, the brine 11 and the central tube 1;

[0050] Preferably, the transient voltage transmitter 3 adopts a direct drive method, providing impulse voltage signals to the central tube 1 through positive and negative electrodes;

[0051] S2, the circuit responds to the impulse voltage signal with a frequency of The self-oscillating AC signal shock wave, wherein the inductance L and capacitance C are generated by the coupling between the central tube 1 and the surrounding strata 8 of the gas storage tank;

[0052] S3, detect the frequency f of the self-oscillating alternating current signal on the central tube 1; calculate the height H of the gas-liquid interface from the wellhead based on the frequency f of the self-oscillating alternating current signal and the known gas storage parameters.

[0053] In one embodiment, the current frequency measuring device 4 can detect the frequency f of the self-oscillating current signal generated on the central tube 1 by means of coil induction.

[0054] To more clearly demonstrate the working principle of the present invention, the principle of this ranging method will be explained here by taking the transient voltage transmitter 3 and the current frequency measuring device 4 installed above the highest height of the gas-liquid interface 10 as an example.

[0055] If we consider the central tube 1 and the ground as the outgoing and returning lines of the transmission line, respectively, then they can be equivalent to... Figure 3 The equivalent transmission line circuit diagram is shown.

[0056] Transient voltage transmitter 3 emits an impulse voltage signal with amplitude U0 to both ends of the central tube 1. Then, by Laplace transform, the input signal in the s-domain is:

[0057] U i (s)=U0 (1),

[0058] The impedance of an s-domain circuit model can be expressed as:

[0059] Z(s) = R + sL + 1 / sC (2),

[0060] Because the high concentration of brine ion density is high and the volume is large, the cross-sectional area of ​​the formation 8 can be considered infinite. Therefore, the impedance of both can be considered as 0.

[0061] The resistance R in central tube 1 satisfies:

[0062]

[0063] The inductance L induced between the central tube 1 and the ground layer 8 satisfies:

[0064]

[0065] The capacitance C formed between the central tube 1 and the formation 8 satisfies:

[0066]

[0067] The current flowing through central tube 1 is:

[0068]

[0069] Then, from equations (1), (2), and (6), the self-oscillating sinusoidal current flowing through the central tube 1 in the s-domain can be expressed as:

[0070]

[0071] From equation (7), the undamped natural frequency of the response current of the central tube 1 can be obtained as follows:

[0072] Damping ratio is

[0073] Damped natural frequency is

[0074] Since ζ << 1, therefore

[0075] The frequency of the self-oscillating current signal generated by the response is:

[0076]

[0077] From equations (4), (5), and (8), we can obtain:

[0078]

[0079] Where ρ is the resistivity of the central tube material, H is the height of the gas-liquid interface from the wellhead, S is the cross-sectional area of ​​the central tube, L is the inductance induced between the central tube 1 and the surrounding formation 8 of the gas storage tank, C is the capacitance induced between the central tube 1 and the surrounding formation 8 of the gas storage tank, c is the speed of light in a vacuum, f is the self-oscillating sinusoidal current frequency of the central tube 1 measured by the current frequency measuring device 4, and μ r ε represents the relative magnetic permeability of gas 9 in the gas storage tank. r ε0 represents the relative electrical conductivity of gas 9 in the gas storage tank, μ0 represents the magnetic permeability of air, and ε0 represents the electrical conductivity of air.

[0080] Due to the speed of light propagation c in a vacuum and the relative magnetic permeability μ of gas 9 in the gas storage tank... r The relative conductivity ε of gas 9 in the gas storage tank rSince all of these are known quantities, the frequency f of the self-oscillating sinusoidal current of the central tube 1 can be measured, and the height H of the gas-liquid interface from the wellhead can be calculated using equation (9).

[0081] Understandably, given the deficiencies in the background technology, this invention proposes a transient shock wave self-oscillating gas-liquid interface monitoring system for gas storage facilities and a monitoring method based on this system. It monitors the liquid level by detecting the frequency of the self-oscillating current signal responding on the central pipe 1. Different liquid levels alter the inductance and capacitance induced in the central pipe 1 and the surrounding formation 8 of the gas storage facility. The different frequencies of the self-oscillating current signal obtained from the impact voltage signal response are used to measure the liquid level. Compared to low-frequency electrical signal ranging, this method reduces the number of downhole devices and avoids the influence of the voltage measuring device's installation location, resulting in high measurement accuracy. Furthermore, since this invention can measure the frequency of the self-oscillating current signal on the central pipe 1 and analyze the measured current signal frequency, the accuracy is high. This invention can also adjust the amplitude of the impact voltage signal according to the characteristics of the gas storage facility to obtain even more accurate results, making it applicable to gas storage facilities with various characteristics and exhibiting strong applicability.

[0082] It should be noted that the descriptions of each embodiment in the above embodiments have different focuses. For parts that are not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0083] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0084] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A gas-liquid interface monitoring system for a transient shock self-oscillating type gas storage, characterized by, Comprise: The center tube (1), the insulation short section (2), the transient voltage transmitter (3), the current frequency measuring device (4) and the ground main machine arranged in the gas storage, the center tube (1) is vertically arranged, the insulation short section (2) is arranged on the center tube (1) and is located above the gas-liquid interface (10), the insulation short section (2) divides the center tube (1) into the upper center tube (101) and the lower center tube (102) that are insulated from each other, the upper center tube (101) is electrically connected with the stratum (8) of the wellhead of the gas storage through the electrically conductive connecting piece, and the lower center tube (102) extends to the lower end of the gas storage, the transient voltage transmitter (3) is arranged on the insulation short section (2), the positive electrode of the transient voltage transmitter (3) is connected with the upper center tube (101), the negative electrode of the transient voltage transmitter (3) is connected with the lower center tube (102), and the transient voltage transmitter (3) is used for transmitting the impulse voltage signal; The current frequency measuring device (4) is arranged on the lower central pipe (102) for detecting the frequency of the self-oscillating alternating current signal on the central pipe (1) f ; The ground host is in communication connection with the transient voltage transmitter (3) and the current frequency measuring device (4) respectively through wireless communication signals, for calculating the height of the gas-liquid interface from the wellhead according to the frequency of the self-oscillating alternating current signal f and known gas storage parameters, the known gas storage parameters including the relative magnetic permeability and the relative electrical conductivity of the gas in the gas storage H .

2. The transient shock self-oscillating type gas-liquid interface monitoring system of claim 1, wherein, The insulation short section (2), the transient voltage transmitter (3) and the current frequency measuring device (4) are located below the top end of the gas storage and above the highest position of the gas-liquid interface (10) in the gas storage.

3. A method for monitoring the gas-liquid interface in a transient shock self-oscillating type gas storage, based on the system according to any one of claims 1 or 2, characterized in that, Comprise: The impulse voltage signal is transmitted to the center tube (1), and the impulse voltage signal passes through the loop formed by the stratum (8), the salt water (11) and the center tube (1); The circuit responds to an impulse voltage signal with a self-oscillating AC signal burst having a frequency of f approximately 1 kHz. detecting the frequency of the self-oscillating alternating current signal on the central pipe (1) f ; calculating the height of the gas-liquid interface from the wellhead based on the frequency of the self-oscillating alternating current signal f and known parameters of the gas storage H .

4. The method according to claim 3, wherein, If the gas storage is equivalent to a second-order LC circuit, the inductance L and the capacitance C are generated by the coupling between the center tube (1) and the stratum (8) around the gas storage, and the following formula is satisfied: ， wherein, f L is the inductance induced in the central tube by the surrounding formation of the gas reservoir, L C is the capacitance induced in the central tube by the surrounding formation of the gas reservoir, C C is the capacitance induced in the central tube by the surrounding formation of the gas reservoir, Mu r μr is the relative permeability of the gas in the gas reservoir, Epsilon r σr is the relative conductivity of the gas in the gas reservoir, Mu 0 is the permeability of air, Epsilon 0 is the conductivity of air, H h is the height of the gas-liquid interface from the wellhead, R s D is the inner diameter of the gas reservoir, r o D is the outer diameter of the central tube.

5. The method according to claim 3 or 4, characterized in that, The height of the gas-liquid interface from the wellhead is calculated by the following equation H : ， wherein H is the height of the gas-liquid interface from the wellhead, c is the propagation speed of light in vacuum, f is the measured central tube self-oscillating AC current signal frequency, Mu r is the relative magnetic permeability of the gas in the gas storage, Epsilon r is the relative electric permittivity of the gas in the gas storage.

Images