A liquid level detection method for high-pressure variable-density medium of gas storage

Abstract

The present application belongs to the field of oil and gas field ground engineering, and discloses a liquid level detection method for high-pressure variable-density medium of gas storage, which is based on the detection principle of radar liquid level meter, screens high-pressure metal reflection surface material, and converts variable density and variable dielectric constant into fixed dielectric constant; according to the medium density range of produced liquid of gas storage and the detection principle of float liquid level, a high-pressure variable-density metal float structure form is formed; according to the single-density combined electric signal and the separator liquid level measurement interval, a single-density medium predetermined control table is formed; according to the multi-density combined electric signal and the separator liquid level measurement interval, a multi-density medium predetermined control table is formed; the actual density on site is input, the predetermined control table of the selected density medium is called, and the liquid level detection processor forms the actual liquid level under the selected density working condition according to the predetermined control table of the actual selected density on site, combined with the interpolation method and the detected electric signal. The present application realizes the improvement of the liquid level detection precision of high-pressure variable-density medium of gas storage.

Description

Technical Field

[0001] This invention belongs to the field of oil and gas field surface engineering, and specifically relates to a liquid level detection method for high-pressure variable density media in gas storage tanks. Background Technology

[0002] Gas storage facility production requires high accuracy in liquid level detection. Inaccurate liquid level can lead to substandard gas quality, potential risks of high-pressure gas phase entering low-pressure liquid phase, and significant challenges to refined liquid level control. In particular, large erroneous fluctuations can cause abnormal shut-off of drain valves or liquid phase leakage within separator chambers. This can also force automatic draining to become manual operation, increasing the workload of handling abnormal conditions and the risk of on-site troubleshooting for operators.

[0003] Currently, domestic and international high-pressure equipment level detection instruments include dual-flange level gauges, radar level gauges, radio frequency admittance level gauges, magnetic float level gauges, and float-type level gauges. These level gauges have proven effective in hydrophobic gas storage facilities and most oil-type gas storage facilities. However, in a few depleted condensate gas storage facilities, the produced gas contains impurities such as black oil and fine sand, leading to inaccurate level detection. The practical application of these level gauges in high-pressure variable-density media has the following shortcomings:

[0004] 1) Impurities such as iron filings and sludge adhering to the surface of the magnetic strip of the magnetic float level gauge can cause the float to get stuck and the liquid inlet pipe to be blocked. For example, the CN205246181U natural gas separator magnetic float level gauge includes a cylinder, a magnetic float located inside the cylinder, and a flap indicator located on the outer surface of the cylinder. A drain valve is connected to the bottom of the cylinder, and the lower part of the cylinder is wrapped with an electric heating tape, which is covered with a protective insulation layer.

[0005] 2) Changes in the number of black oil wells opened lead to frequent changes in medium density, causing the differential pressure value of the differential pressure level gauge to lose its linear relationship with the liquid level; for example, CN203811234U, a new type of differential pressure level gauge, includes at least: a liquid distribution cylinder and a level gauge housing with an outer shell; the level gauge housing is equipped with a pressure sensor, a pressure regulating valve, and a gas source; the liquid distribution cylinder is connected to the pressure sensor and the pressure regulating valve of the level gauge housing through connecting pipes; the pressure regulating valve is connected to the gas source.

[0006] 3) Layering occurs inside the side-mounted measuring cylinder, with excessively large deviations in the dielectric coefficients of the upper and lower layers, resulting in a liquid level reflection interface and causing the radar level gauge to detect a lower value than the actual liquid level.

[0007] Therefore, how to overcome the shortcomings of liquid level detection technology for high-pressure, variable-density media and provide a liquid level detection method for high-pressure, variable-density media in gas storage is an urgent problem to be solved. Summary of the Invention

[0008] To address the shortcomings of existing technologies, this invention provides a liquid level detection method for high-pressure variable-density media in gas storage facilities. Based on a combination of radar liquid level detection principle, float liquid level detection technology, and a predetermined reference table for different densities, this method improves the accuracy of liquid level detection for high-pressure variable-density media in gas storage facilities.

[0009] To achieve the above objectives, the present invention provides a method for level detection of high-pressure variable-density media in a gas storage tank, the method comprising:

[0010] (1) Based on the detection principle of radar level gauge, high-pressure metal reflective surface material is selected, and variable density and variable dielectric constant are converted into fixed dielectric constant.

[0011] (2) Based on the density range of the produced liquid medium in the gas storage tank and the principle of float level detection, a high-pressure variable density metal float structure is formed.

[0012] (3) Based on the single-density combined electrical signal and the separator liquid level measurement range, a single-density medium predetermined reference table is formed;

[0013] (4) Based on the multi-density combined electrical signal and the separator liquid level measurement range, a multi-density medium predetermined reference table is formed;

[0014] (5) Input the actual density on site, retrieve the predetermined reference table of the selected density medium, and the liquid level detection processor, based on the predetermined reference table of the actual selected density on site, combined with interpolation and the detected electrical signal, forms the actual liquid level under the selected density working condition.

[0015] Furthermore, the controller of the radar level gauge used has been enhanced with receiving, combining, and determining modules.

[0016] Specifically, it includes:

[0017] The single-density signal test receiving module is used to receive multiple electrical signals of a single-density medium. These multiple electrical signals are obtained by a predetermined liquid level sensor detecting the liquid level at different heights in a fixed-density medium.

[0018] The single-density signal test combination module is used to combine multiple electrical signals of a single-density medium in a predetermined order to obtain a single-density combined electrical signal.

[0019] The single-density signal test and determination module is used to determine the liquid level measurement range of the separator liquid based on the single-density combined electrical signal, and to retrieve a predetermined lookup table of single-density media based on the single-density combined electrical signal. This lookup table stores the correspondence between predetermined combined electrical signals of fixed-density media and predetermined liquid level ranges.

[0020] The variable density signal test receiving module is used to receive multiple electrical signals from multiple density media. These multiple electrical signals are obtained by a predetermined liquid level sensor detecting the liquid level at different heights in the multiple density media.

[0021] The variable density signal test combination module is used to combine multiple electrical signals of multiple single-density media in a predetermined order to obtain a multi-density combined electrical signal.

[0022] The variable density signal test and determination module is used to determine the liquid level measurement range of the separator liquid based on the multi-density combined electrical signal. Based on the multi-density combined electrical signal, it retrieves a predetermined multi-density lookup table. This table stores the correspondence between predetermined combined electrical signals of different density media and predetermined liquid level ranges. If a liquid level range corresponding to the combined electrical signal cannot be determined from the predetermined multi-density lookup table, the combined electrical signal is determined to be a failed signal.

[0023] Furthermore, when the radar level gauge is in use, the guide tube is welded to the equipment's connecting flange inside the equipment, and the connecting flange is connected to the radar level gauge flange. The metal reflector is placed inside the guide tube and floats up and down with the liquid level. Medium 1 and Medium 2 can be any medium.

[0024] Furthermore, medium 1 is light oil or heavy oil, or a mixture of light oil and heavy oil; medium 2 is separated water.

[0025] Furthermore, the metallic reflective material is a titanium alloy.

[0026] Furthermore, the float level detection uses a single float or a combination of floats.

[0027] Furthermore, the float is a hollow sphere; the composite float is a combination structure of individual floats welded together.

[0028] The advantages of this invention compared to the prior art are:

[0029] This invention provides a method for level detection of high-pressure variable-density media in gas storage facilities. The method includes selecting radar level detection within a predetermined range of high-pressure equipment level detection technologies; converting variable density and dielectric constant into a metallic reflective surface with a fixed dielectric constant, thus forming a high-pressure, non-contact, material-free, variable-density level detection approach; establishing a high-pressure variable-density metallic float structure within a predetermined density range of the gas storage facility's extracted liquid medium; determining the separator level measurement interval based on single-density combined electrical signals, forming a predetermined reference table for single-density media; determining the separator level measurement interval under different density media conditions based on multi-density combined electrical signals, forming a predetermined reference table for multi-density media; and the level detection processor can retrieve the predetermined reference table for the selected density media based on the site conditions, and, combined with the detected electrical signals and interpolation, output the actual level under the selected density conditions. This invention, based on the combination of radar level detection principles, float level detection technology, and predetermined reference tables for different densities, forms a method for level detection of high-pressure variable-density media in gas storage facilities, improving the accuracy of level detection for high-pressure variable-density media in gas storage facilities. This method has beneficial effects. Attached Figure Description

[0030] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0031] Figure 1 This is a flowchart of a liquid level detection method for high-pressure variable density media in gas storage tanks;

[0032] Figure 2 This is a block diagram of the controller for a radar level gauge;

[0033] Figure 3 This is a schematic diagram of the separator liquid level detection principle;

[0034] Figure 4 This is a structural diagram of a high-pressure variable-density metal float. a is a conventional float, b is a single float, and c is a combination of floats. Detailed Implementation

[0035] The present invention is described in detail below through specific embodiments, but this does not limit the scope of protection of the present invention. Unless otherwise specified, the experimental methods used in the present invention are all conventional methods, and the experimental equipment, materials, reagents, etc. used can all be obtained commercially.

[0036] The main advantage of this solution is:

[0037] Within the predetermined range of high-pressure equipment level detection technologies, non-contact level detection technology should be selected to ensure that the level gauge probe is free from impurities and viscous liquids.

[0038] Obtain the medium properties of the produced liquid from the gas storage tank, obtain the dielectric constants of the upper and lower layers of the layered medium, and convert the variable density and variable dielectric constant into a metallic reflective surface with a fixed dielectric constant.

[0039] Within a predetermined medium density range, and combined with float level measurement technology, the original float structure is modified to a spherical structure, resulting in higher pressure resistance.

[0040] Example 1

[0041] This invention provides an implementation process for a method of detecting the liquid level of a high-pressure variable-density medium in a gas storage tank, including:

[0042] The dielectric constant conversion stage of high-pressure liquid level detection is used to convert variable density and variable dielectric constant into a metallic reflective surface with a fixed dielectric constant, based on the principle of radar liquid level detection, thus forming a high-pressure non-contact, material-free, variable density liquid level detection approach.

[0043] The metal reflector structure confirmation stage is used to form a high-pressure variable density metal float structure within the predetermined density range of the gas storage produced liquid medium, based on float liquid level measurement technology.

[0044] In the single-density signal testing stage, the separator liquid level measurement range is determined based on the single-density combined electrical signal, and a predetermined reference table of single-density media is formed and stored in the liquid level sensor memory.

[0045] In the variable density signal testing stage, the separator liquid level measurement range under different density medium conditions is determined based on the multi-density combined electrical signal, forming a multi-density predetermined reference table, which is stored in the liquid level sensor memory.

[0046] During the high-pressure liquid level detection signal formation stage, the field can retrieve the correspondence between the predetermined combination of electrical signals of the selected density medium and the predetermined liquid level range through the liquid level detection processor according to the actual well opening conditions. By comparing the electrical signals detected by the liquid level sensor and combining the interpolation method, the actual liquid level under the selected density conditions can be output.

[0047] Example 2

[0048] To facilitate a better understanding of the present invention, a more detailed embodiment is described below.

[0049] Step 1: Based on the principle of radar liquid level detection, select high-pressure metal reflective surface materials and convert variable density and variable dielectric constant into fixed dielectric constant.

[0050] The guide tube is welded to the equipment's connecting flange inside the equipment, and the connecting flange is connected to the radar level gauge flange. A metallic reflective material is placed inside the guide tube and floats up and down with the liquid level. Medium 1 and Medium 2 can be any media, regardless of their miscibility; there are no special requirements.

[0051] Radar level detection employs Time Domain Reflectometry (TDR), which is unaffected by the densities of Medium 1 and Medium 2, but the different dielectric constants directly influence the reflectivity of the high-frequency pulse signal. Medium 1 is light or heavy oil, or a mixture, with a dielectric constant of approximately 1.8–3.0; Medium 2 is separated water with a dielectric constant of approximately 88. A metal reflector with a fixed dielectric constant is used, floating on Medium 1. The radar probe emits microwaves to the metal reflector, generating a significant reflected wave. Considering the composition and pressure resistance of the extracted material, a titanium alloy with a dielectric constant of 50 is recommended as the metal reflector. Titanium alloy is suitable for high-pressure float materials; other materials have poor pressure resistance. The dielectric constant is independent of the dielectric constants of Medium 1 and Medium 2.

[0052] Step 2: Based on the density range of the produced liquid medium in the gas storage tank and the principle of float level detection, a high-pressure variable density metal float structure is formed;

[0053] The float-based liquid level detection system uses a conventional float design, where impurities in the sample can easily adhere to the magnetic ring, causing blockages. A spherical float structure, however, provides higher pressure resistance for each individual sphere. Multiple floats can be welded together; the number of floats depends on the medium density and the float size, as long as the floats remain afloat. If the density of medium 1 is too low, a combination of multiple floats can provide good buoyancy support.

[0054] Step 3: Based on the single-density combined electrical signal and the separator liquid level measurement range, form a predetermined reference table for single-density media;

[0055] The density of produced medium 1 in some oil reservoir-type gas storage facilities is 650 kg / m³. 3 ~800kg / m 3 Between, based on a medium density of 650 kg / m³ 3 The float is designed to measure the liquid level between 50mm and 1800mm, and a set of electrical signals is measured every 10mm, providing a total of 175 sets of electrical signals and corresponding liquid level values, ultimately forming a predetermined reference table for that density.

[0056] Table 1. Pre-selection comparison table for single-density media

[0057] Serial Number Measured values signal value 1 50mm 4.0mA 2 60mm 4.09mA 3 70mm 4.18mA 4 80mm 4.27mA ... ... 175 1800 20mA

[0058] Step 4: Based on the multi-density combined electrical signal and the separator liquid level measurement range, form a multi-density medium predetermined reference table;

[0059] Following step 3, respectively based on a medium density of 680 kg / m³ 3 700kg / m 3 730kg / m 3 750kg / m 3 780kg / m 3800kg / m 3 The float is designed to measure a set of electrical signals at 10mm intervals between liquid levels of 50mm and 1800mm, ultimately forming multiple predetermined reference tables corresponding to different densities.

[0060] Table 2. Multi-density media pre-selection comparison table

[0061]

[0062] Step 5: Input the actual density at the site, retrieve the predetermined reference table of the selected density medium, and the liquid level detection processor, based on the predetermined reference table of the selected actual density at the site, combined with interpolation and the detected electrical signal, forms the actual liquid level under the selected density condition.

[0063] This invention, in the process of forming a liquid level detection method for high-pressure variable density media, introduces a combination of radar liquid level detection principle, float liquid level detection technology, and a predetermined reference table for different densities. It considers the conversion of variable dielectric constant to fixed dielectric constant, the pressure resistance of metal float material and structure, and the flexibility of float structure and measurement algorithm when density changes. This improves the accuracy and objectivity of liquid level measurement and has practical guiding significance for liquid level detection in high-pressure separators in the gas storage industry. It is also more in line with the current situation where the produced liquid in some gas storage facilities contains many impurities.

[0064] The embodiments described above are merely preferred embodiments of the present invention, and not all feasible embodiments of the present invention. Any obvious modifications made by those skilled in the art without departing from the principles and spirit of the present invention should be considered to be included within the scope of protection of the claims of the present invention.

Claims

1. A method for detecting the liquid level of a high-pressure variable-density medium in a gas storage tank, characterized in that, The method includes: screening high-pressure metal reflective surface materials, combining high-pressure variable density metal float structures, forming a single-density predetermined comparison table and a multi-density predetermined comparison table, and obtaining the actual liquid level under the selected density conditions based on the predetermined comparison table of the actual density selected on site, combined with interpolation and the detected electrical signals.

2. The liquid level detection method for high-pressure variable density media in a gas storage tank according to claim 1, characterized in that, The controller of the radar level gauge includes a single-density signal test and receiving module, which is used to receive multiple electrical signals of a single-density medium. The multiple electrical signals of the single-density medium are electrical signals obtained by a predetermined level sensor detecting the liquid level at different heights of a fixed-density medium.

3. The liquid level detection method for high-pressure variable density media in a gas storage tank according to claim 1, characterized in that, The controller of the radar level gauge includes a single-density signal test combination module, which is used to combine multiple electrical signals of a single-density medium in a predetermined order to obtain a single-density combined electrical signal.

4. The liquid level detection method for high-pressure variable density media in a gas storage tank according to claim 1, characterized in that, The controller of the radar level gauge includes: a single-density signal test and determination module, which is used to determine the liquid level measurement range of the separator liquid based on the single-density combined electrical signal, and to retrieve the single-density medium predetermined reference table based on the single-density combined electrical signal to determine the liquid level range of the separator.

5. The liquid level detection method for high-pressure variable density media in a gas storage tank according to claim 1, characterized in that, The controller of the radar level gauge includes a variable density signal test and receiving module, which is used to receive multiple electrical signals of multiple densities. The multiple electrical signals are electrical signals obtained by a predetermined level sensor detecting the liquid level at different heights of the multiple densities.

6. The liquid level detection method for high-pressure variable density media in a gas storage tank according to claim 1, characterized in that, The controller of the radar level gauge includes a variable density signal test combination module, which is used to combine multiple electrical signals of multiple single-density media in a predetermined order to obtain a multi-density combined electrical signal.

7. The liquid level detection method for high-pressure variable density media in a gas storage tank according to claim 1, characterized in that, The controller of the radar level gauge includes: a variable density signal test and determination module, which is used to determine the liquid level measurement range of the separator liquid based on the multi-density combined electrical signal, and to retrieve the multi-density predetermined lookup table based on the multi-density combined electrical signal to determine the liquid level range of the separator.

8. The liquid level detection method for high-pressure variable density media in a gas storage tank according to claim 1, characterized in that, The controller of the radar level gauge includes: when the radar level gauge is in use, the guide tube is welded to the equipment connecting flange inside the equipment, the connecting flange is connected to the radar level gauge flange, and a metal reflector is placed inside the guide tube, which floats up and down with the liquid level. Medium 1 and Medium 2 can be any medium.

9. The liquid level detection method for high-pressure variable density media in a gas storage tank according to claim 8, characterized in that, The controller of the radar level gauge includes: medium 1 is light oil or heavy oil, or a mixture of light oil and heavy oil; medium 2 is separated water.

10. The liquid level detection method for high-pressure variable density media in a gas storage tank according to claim 1, characterized in that, The controller of the radar level gauge includes a titanium alloy metal reflector.

11. The liquid level detection method for high-pressure variable density media in a gas storage tank according to claim 1, characterized in that, The controller of the radar level gauge includes: float level detection using a single float or a combination of floats.

12. The liquid level detection method for high-pressure variable density media in a gas storage tank according to claim 11, characterized in that, The controller of the radar level gauge includes: a hollow sphere float; and a combined float, which is a combination structure of individual floats welded together.

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