Oil well dynamic liquid level detection system and method

Abstract

The present application relates to a system and method for detecting the dynamic liquid level in an oil well. Several conductive elements and cable assemblies are arranged between the oil pipe and the casing. A power supply and current detection device are provided on the well. The conductivity of oil is utilized to electrically connect two adjacent conductive elements through the oil to form a circuit loop. The depth of the dynamic liquid level affects the number of conductive elements connected to the circuit, changing the total resistance in the circuit. By detecting the circuit current value, the corresponding dynamic liquid level depth can be obtained, thereby realizing the detection of the dynamic liquid level in the oil well.

Description

Technical Field

[0001] The present application relates to the field of oil production technology, and in particular to an oil well dynamic liquid level detection system and method. Background Art

[0002] The dynamic liquid level of an oil well (i.e., the dynamic height of the liquid column in the wellbore during oil production) is a core parameter in oilfield production management. Excessively high or low levels can trigger systemic risks, directly affecting pumping efficiency, energy consumption control, and well control safety. Changes in the dynamic liquid level of an oil well reflect the oilfield's fluid supply capacity and the coordination of wellbore supply and drainage. While existing monitoring technologies are diverse, they all have significant limitations:

[0003] Currently, the most commonly used measurement method is ultrasonic measurement, which involves transmitting sound waves into the casing annulus and calculating the liquid level depth by the time difference between the reflected waves from the liquid surface. This method is susceptible to wellbore noise (such as airflow and collar reflections), resulting in a liquid surface echo signal-to-noise ratio below 20% and a false positive rate exceeding 30%. Another method is direct measurement, which involves installing measuring equipment such as sensors and pressure gauges downhole to directly obtain dynamic liquid level data. While this method offers greater accuracy, it is complex and costly to install, and is prone to failure in high-temperature wells (greater than 150°C). In summary, both methods struggle to achieve real-time, economical, efficient, and intelligent dynamic liquid level measurement, hindering the development of intelligent and information-based oilfields.

[0004] To this end, we propose an oil well dynamic liquid level detection system and method. Summary of the Invention

[0005] In view of the above-mentioned shortcomings in the prior art, the present application provides an oil well dynamic liquid level detection system and method.

[0006] The technical solutions adopted in this application are as follows:

[0007] An oil well dynamic liquid level detection system includes an oil pipe 1 and a casing 2, wherein the dynamic liquid level is located between the oil pipe 1 and the casing 2. The oil well dynamic liquid level detection system also includes a plurality of conductive elements 3, a cable assembly 4, a power supply, and a current detection device;

[0008] The conductive elements 3 are distributed axially along the oil pipe 1 and are located at a fixed height between the oil pipe 1 and the casing 2;

[0009] The cable assembly 4 includes two separated cable main lines 401, the upper ends of the two cable main lines 401 are respectively connected to the positive and negative poles of the power supply, and the lower ends of the two cable main lines 401 are connected to the conductive elements 3 through several cable branches 402, and each conductive element 3 is only connected to one cable branch 402; the current detection device is used to detect the current value of the cable main line 401.

[0010] A further technical solution includes that the connection method between the cable assembly 4 and the conductive element 3 includes: two axially adjacent conductive elements 3 are connected to cable branches 402 corresponding to different cable main lines 401.

[0011] A further technical solution includes: the connection method between the cable assembly 4 and the conductive element 3 includes: a main cable line 401 is connected to the bottom conductive element 3, and another main cable line 401 is connected to the remaining conductive elements 3 through a plurality of cable branches 402.

[0012] A further technical solution includes that the oil well dynamic liquid level detection system further includes a protective resistor, which is connected in series to one of the cable main lines 401 and in parallel with the voltmeter.

[0013] A further technical solution includes: the conductive element 3 is arranged in a semi-open insulating box 5 and fixed to a fixed height of the oil pipe 1 through the insulating box 5; the distance between the insulating box 5 and the casing 2 is smaller than the distance between the conductive element 3 and the casing 2.

[0014] The technical solutions adopted by the present invention also include:

[0015] A method for detecting a dynamic liquid level in an oil well, comprising:

[0016] The current value of the cable main line 401 and the well condition parameters of the oil well are obtained, the number of conductive elements 3 connected to the circuit is determined based on the current value and the well condition parameters, and the dynamic liquid level depth is determined according to the number of conductive elements 3 connected to the circuit.

[0017] A further technical solution includes determining the number of conductive elements 3 connected to the circuit based on the current value and the well condition parameter, including:

[0018] Determine the resistivity of the conductive element 3, the cable assembly 4, and the oil under different well parameters; determine the total resistance value in the circuit based on the power supply voltage value and the current value of the cable main line 401; and calculate the number of conductive elements 3 connected to the circuit based on the resistivity and total resistance value of the conductive element 3, the cable assembly 4, and the oil.

[0019] A further technical solution includes determining the number of conductive elements 3 connected to the circuit based on the current value and the well condition parameter, including:

[0020] Through a controlled variable experiment, with the well parameters and the number of conductive elements 3 connected to the circuit as independent variables and the current value of the cable main line 401 as the dependent variable, the corresponding relationship between the current value of the cable main line 401 and the number of conductive elements 3 connected to the circuit under different well parameters was determined;

[0021] Based on the current value and the well condition parameter, the number of conductive elements 3 connected to the circuit is determined in combination with the corresponding relationship.

[0022] A further technical solution includes that the control variable test further includes, for any well condition parameter:

[0023] A number of key values ​​of the well condition parameter are selected, the current values ​​corresponding to the key values ​​are determined, and a curve relationship between the well condition parameter and the current value is obtained by fitting.

[0024] A further technical solution thereof includes that the well condition parameters include at least one of oil viscosity, oil water content, oil temperature, and bottom hole pressure.

[0025] The beneficial effects of this application are as follows:

[0026] The oil well dynamic liquid level detection system and method designed in this application arranges several conductive elements and cable assemblies between the oil pipe and the casing, and is equipped with a power supply and current detection device on the well. The conductivity of oil is used to electrically connect two adjacent conductive elements through the oil to form a circuit loop; the depth of the dynamic liquid level affects the number of conductive elements connected to the circuit, changing the total resistance in the circuit. By detecting the circuit current, the corresponding dynamic liquid level depth can be obtained, thereby realizing the detection of the dynamic liquid level of the oil well.

[0027] The oil well dynamic liquid level detection method of the present application also takes into account the influence of well condition parameters on the detection results, and can obtain accurate detection results at various well depths, oil viscosities, and oil temperatures.

[0028] The conductive elements and cable assemblies of the present application are both arranged on the oil pipe and can be lowered to the bottom of the well along with the oil pipe when installing the well. Not only is the position controllable, but the assembly is also simple and there is no need to change the original structure in the oil well, which greatly saves material and labor costs. It can be installed in various types of oil wells and has a wide range of applications.

[0029] The conductive elements and cable assemblies of the present application are both resistant to high temperatures, and therefore can also be used in thermal recovery wells. Moreover, since the solution of the present application utilizes the conductivity of the material, the higher the temperature, the better the conductivity, and the sensor will not fail at high temperatures like the sensors used in the prior art.

[0030] This application detects the dynamic level of the oil well by monitoring the current value. Due to the inherent characteristics of the circuit, the information transmission speed is extremely fast, so the dynamic level changes can be known in real time. The power supply can be set to always on, or turned on when the dynamic level data is required, which is very flexible.

[0031] The oil well dynamic liquid level detection method of the present application can be used not only in vertical wells, but also in inclined wells, horizontal wells and irregular wells with large doglegs. It has a high degree of tolerance for the structure of the well body and greatly improves the scope of application. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1This is a structural diagram of a first connection method between a cable assembly and a conductive element in an embodiment of the present application.

[0033] Figure 2 This is a circuit diagram corresponding to the first connection method between the cable assembly and the conductive element in one embodiment of the present application.

[0034] Figure 3 This is a structural diagram of a second connection method between a cable assembly and a conductive element in an embodiment of the present application.

[0035] Figure 4 This is a circuit diagram corresponding to the second connection method between the cable assembly and the conductive element in one embodiment of the present application.

[0036] Figure 5 This is an equivalent circuit diagram corresponding to the first connection method between the cable assembly and the conductive element in an example of the present application.

[0037] Figure 6 This is an equivalent circuit diagram corresponding to the second connection method between the cable assembly and the conductive element in an example of the present application.

[0038] Figure numerals: 1, oil pipe; 2, casing; 3, conductive element; 4, cable assembly; 401, cable main line; 402, cable branch; 5, insulation box. DETAILED DESCRIPTION

[0039] The specific implementation of this application is described below with reference to the accompanying drawings.

[0040] The dynamic liquid level of an oil well refers to the depth of the top interface of the liquid column between the oil pipe and the casing. It is affected by many factors during the oil production process, such as the formation's liquid supply capacity, pumping intensity, gas-oil ratio, wellbore integrity, reservoir pressure, etc. This causes the dynamic liquid level to show irregular changes in actual oil production, making it difficult to predict through simple model analysis.

[0041] Furthermore, because oil has a certain viscosity, thermal recovery is often used to ensure it can be lifted to the surface through pipelines hundreds or even thousands of meters long. This involves injecting high-temperature steam into the well before extraction to reduce the oil's viscosity. This means the downhole environment remains at elevated temperatures for extended periods, reaching as high as 360°C, further complicating dynamic liquid level measurement.

[0042] In order to solve this problem, the present application proposes an oil well dynamic liquid level detection system. In this embodiment, as Figure 1As shown, the oil well dynamic liquid level detection system includes an oil pipe 1 and a casing 2 conventionally arranged in an oil well, and the dynamic liquid level is located between the oil pipe 1 and the casing 2; the main invention of this application is that the system also includes a plurality of conductive elements 3, a cable assembly 4, a power supply and a current detection device. The conductive elements 3 are distributed axially along the oil pipe 1 and are located at a fixed height between the oil pipe 1 and the casing 2. The cable assembly 4 includes two separated cable main lines 401, the upper ends of the two cable main lines 401 are respectively connected to the positive and negative poles of the power supply, and the lower ends of the two cable main lines 401 are connected to the conductive elements 3 through a plurality of cable branches 402, and each conductive element 3 is only connected to one cable branch 402; the current detection device is used to detect the current value of the cable main line 401.

[0043] In an actual oil well, oil production equipment (such as a screw pump) is installed inside the oil pipe 1, and the produced oil is transported to the surface in the oil pipe 1. The casing 2 is fixed to the inner wall of the wellbore, with a certain gap between it and the oil pipe 1.

[0044] Among them, the cable assembly 4 is laid along the oil pipe 1 from the ground to hundreds of meters deep underground. It can be laid along the outer wall of the oil pipe 1 or set inside the oil pipe 1, and then connected to the external conductive element 3 at each cable branch 402. Figure 1 The figure only shows a partial section of the well, in which the oil pipe 1, casing 2 and cable assembly 4 will continue to extend upward to the ground, and the power supply and current detection device are both set on the ground.

[0045] In this embodiment, the cable assembly 4 includes a conductive core and an insulating layer surrounding the core. The core and insulating layer are designed to withstand temperatures exceeding the maximum temperature of the thermal recovery well. Downhole, the conductive core is in electrical contact only with the conductive element 3 and is insulated from both the oil and the oil pipe 1.

[0046] Optionally, the conductive core is made of graphite or metal ceramic, which has strong conductivity and high temperature resistance.

[0047] Optionally, the insulating layer has a double-layer packaging structure, with an inner layer of alumina ceramic and an outer layer of polytetrafluoroethylene, which is temperature-resistant up to 400°C and resistant to hydrogen sulfide corrosion.

[0048] Optionally, the conductive element 3 uses a zirconium boride-silicon carbide ceramic electrode, which can withstand high temperatures of 360° C. and is corrosion-resistant, ensuring a service life of more than 5 years.

[0049] There are several ways to connect the cable assembly 4 and the conductive element 3. Due to space limitations, only two preferred connection methods are discussed in this embodiment:

[0050] (1) Two axially adjacent conductive elements 3 are connected to cable branches 402 corresponding to different cable main lines 401 .

[0051] like Figure 1As shown, the cable branches 402 of the cable main line 401 distributed on both sides of the conductive element 3 are alternately connected to the conductive element 3, and the corresponding circuit diagram is shown in FIG. Figure 2 As shown, when the dynamic liquid surface submerges a certain conductive element 3, the conductive element 3 and all the conductive elements below it are connected in pairs to form a path.

[0052] (2) A main cable line 401 is connected to the lowest conductive element 3, and another main cable line 401 is connected to the remaining conductive elements 3 through a plurality of cable branches 402.

[0053] like Figure 3 As shown in the figure, the circuit diagram corresponding to the connection method of the conductive element 3 and the cable branch 402 is as follows: Figure 4 When the dynamic liquid surface submerges a certain conductive element 3, the conductive element 3 and all the conductive elements below it form a path with the lowest conductive element 3.

[0054] In this embodiment, the oil well dynamic liquid level detection system also includes a protective resistor connected in series to one of the main cable lines 401 and in parallel with a voltmeter. The protective resistor primarily prevents excessive current in the circuit from damaging the system. The voltmeter connected in parallel with the protective resistor acts as a current detection device. The current in the main cable line 401 can be calculated by combining the voltage V0 of the protective resistor and its resistance R0. If a voltmeter is not used, an ammeter can be connected directly in series with the main cable line 401 as a current detection device.

[0055] In this embodiment, the conductive element 3 is disposed in a semi-open insulating box 5 and fixed to the oil pipe 1 at a fixed height through the insulating box 5 ; the distance between the insulating box 5 and the casing 2 is smaller than the distance between the conductive element 3 and the casing 2 .

[0056] Optionally, the open side of the insulating box 5 faces the casing 2, allowing the conductive element 3 inside to better contact the oil. Furthermore, the insulating box 5 is taller than the conductive element 3. This prevents vibrations in the oil pipeline 1 during oil production, which could cause friction between the conductive element 3 and the casing 2 and alter the resistance of the conductive element 3. Furthermore, it prevents electrical contact between the conductive element 3 and the casing 2, which could alter the resistance in the circuit and cause current disturbances.

[0057] Another embodiment of the present application further discloses a method for detecting a dynamic liquid level in an oil well, comprising:

[0058] The current value of the cable main line 401 and the well condition parameters of the oil well are obtained, the number of conductive elements 3 connected to the circuit is determined based on the current value and the well condition parameters, and the dynamic liquid level depth is determined according to the number of conductive elements 3 connected to the circuit.

[0059] The main principle of this method is to utilize the electrical conductivity of oil: the conductivity of oil is mainly affected by factors such as oil composition, temperature, and pressure. Generally speaking, the resistivity of oil decreases with increasing water content. Other metal ions in oil also affect the resistivity of oil, and rising temperature or pressure also reduce the resistivity of oil. Therefore, underground unmined oil containing various impurities is conductive.

[0060] When the oil between the tubing 1 and casing 2 floods multiple conductive elements 3, a current flows between them. The oil acts as a conductor, completing the circuit. Changes in the depth of the dynamic liquid level affect the number of submerged conductive elements 3, thereby altering the resistance in the circuit. While the power supply voltage remains constant, changes in resistance cause corresponding changes in current. Therefore, the depth of the dynamic liquid level can be determined by measuring the current.

[0061] Optionally, the current value of the cable main line 401 is obtained through a current detection device, and the well condition parameters of the oil well are obtained through various sensors.

[0062] In one embodiment, determining the number of conductive elements 3 connected to the circuit based on the current value and the well condition parameter includes:

[0063] Determine the resistivity of the conductive element 3, the cable assembly 4, and the oil under different well parameters; determine the total resistance value in the circuit based on the power supply voltage value and the current value of the cable main line 401; and calculate the number of conductive elements 3 connected to the circuit based on the resistivity and total resistance value of the conductive element 3, the cable assembly 4, and the oil.

[0064] Specifically, the resistivity of the conductive element 3 and the cable assembly 4 is mainly affected by temperature, and the material and size specifications of the two are determined when they are laid out. Therefore, the relationship between their resistance value and resistivity can be directly calculated by the formula R=ρL / S, where R is the resistance value, ρ is the resistivity of the material making the resistor, L is the length of the resistor, and S is the cross-sectional area of ​​the resistor.

[0065] The relationship between the resistivity of oil and its electrical resistance is more difficult to calculate using theoretical formulas. This is because in the specific scenario of this embodiment, the oil covers the entire annulus of the oil pipe 1 and casing 2, but only a small portion of its contact surface with the conductive element 3 is in contact with the conventional resistance formula. Furthermore, there are many factors that affect the resistivity of oil, and the changes in resistivity are more complex, making direct calculation difficult.

[0066] Therefore, in one embodiment, a conductive element 3 and a cable assembly 4 with a relatively high resistivity are selected so that the resistance value of the conductive element 3 and the cable assembly 4 connected to the circuit is much greater than the resistance value of the oil. In another embodiment, the distance between two adjacent conductive elements 3 is set to be less than or equal to a set distance so that the oil resistance value accounts for a relatively small proportion of the total circuit resistance value; for example, the set distance is 1 meter. In some oil wells with a high water content, the oil is more conductive, and the maximum distance between two adjacent conductive elements 3 can be set to 10 meters. In both cases, only the parameters that have the greatest impact on the oil resistivity can be considered as well condition parameters to obtain the oil resistivity under different parameters under different well conditions. For example, only the effects of temperature and viscosity on the oil resistivity are considered, and then the theoretical resistance of the oil is calculated according to the conventional resistance formula.

[0067] In addition, through finite element simulation, various well parameters, the distance between the conductive elements 3, the cross-sectional area of ​​the annulus between the oil pipe 1 and the casing 2, etc. can be used as input to fit the resistivity and / or resistance value of the oil.

[0068] Since two connection methods of the conductive element 3 and the cable assembly 4 are disclosed in this application, in order to illustrate the calculation of the resistance value in the circuit at different dynamic liquid level depths, the following description is carried out through an example.

[0069] Assume that the dynamic liquid level is located between R4 and R5, that is, there are four conductive elements connected to the circuit. For the convenience of calculation, assume that the resistance value of each conductive element 3 is r.

[0070] (1) When two axially adjacent conductive elements 3 are connected to cable branches 402 corresponding to different cable main lines 401, as shown in FIG. Figure 2 、 5 As shown in the equivalent circuit diagram, since the resistance of each resistor is equal, the actual equivalent is R2 and R4 in parallel, R1 and R3 in parallel, and the two sets of parallel resistors are connected in series. The total resistance of the conductive element 3 connected to the circuit is , where r is the resistance value of a single conductive element 3.

[0071] (2) When a main cable line 401 is connected to the bottom conductive element 3, and another main cable line 401 is connected to the remaining conductive elements 3 through several cable branches 402, as shown in FIG. Figure 4 、 6 As shown in the equivalent circuit diagram, since the resistance of each resistor is equal, it is actually equivalent to R2, R3, and R4 connected in series and then in parallel with R1. The total resistance of the conductive element 3 connected to the circuit is .

[0072] The above method only calculates the resistance of conductive element 3. In practice, because oil wells can be hundreds or even thousands of meters deep and cable assemblies are often long, the resistance of the cable assembly should also be considered when calculating the total resistance of the circuit to improve detection accuracy. Knowing the material, temperature, length, and cross-section of the cable assembly allows calculation of its resistance.

[0073] In another embodiment, determining the number of conductive elements 3 connected to the circuit based on the current value and the well condition parameter includes:

[0074] Through the control variable test, with the well condition parameters and the number of conductive elements 3 connected to the circuit as independent variables and the current value of the cable main line 401 as the dependent variable, the corresponding relationship between the current value of the cable main line 401 and the number of conductive elements 3 connected to the circuit under different well condition parameters is determined; based on the current value and well condition parameters, the number of conductive elements 3 connected to the circuit is determined in combination with the corresponding relationship.

[0075] This method eliminates the need for resistivity calculations, which has the advantage of eliminating intermediate quantities and resulting in more accurate results. However, its disadvantage is that the initial controlled variable testing requires a large amount of test data to cover a wide range of possible well parameters. Therefore, in actual use, this controlled variable testing also involves, for any well parameter, selecting several key values ​​for that parameter, determining the corresponding current values, and then fitting the curve relationship between that parameter and the current value.

[0076] For example, the selected oil temperatures are 60℃, 90℃, 120℃, 150℃, 180℃, 210℃, 240℃, 270℃, 300℃, 330℃, and 360℃. By fitting the curve relationship between oil temperature and current value, the current value corresponding to any oil temperature can be obtained. The same applies to other well parameters.

[0077] Optionally, the well condition parameters include at least one of oil viscosity, oil water content, oil temperature, and bottom hole pressure.

[0078] In this embodiment, determining the dynamic liquid level depth according to the number of conductive elements 3 connected to the circuit includes:

[0079] Because the conductive elements 3 are arranged axially along the oil pipe 1, the dynamic fluid level also fluctuates axially along the oil pipe 1, between the oil pipe 1 and the casing 2. Therefore, if the number of conductive elements 3 connected to the circuit is known, the corresponding dynamic fluid level depth can be inferred. For example, in a 1000-meter-deep oil well, if several conductive elements 3 are evenly distributed along the oil pipe 1 at depths of 500-800 meters, if no conductive elements 3 are connected to the circuit, the dynamic fluid level depth is greater than or equal to 800 meters. If half of the conductive elements 3 are connected to the circuit, the dynamic fluid level depth is approximately 650 meters.

[0080] The oil well dynamic liquid level detection method of the present application can be used not only in vertical wells, but also in inclined wells and horizontal wells. Before installing the oil pipe, the various trajectory parameters of the oil well are known, and the position of the conductive element 3 on the oil pipe is also known. According to the parameters such as the well inclination angle and the well depth, the dynamic liquid level depth corresponding to each conductive element 3 can be calculated. For example, a certain conductive element 3 is installed in the nth section of the oil pipe from the wellhead downward, and the length of each section of the oil pipe is L. According to the trajectory parameters of the oil well, the well depth corresponding to the oil well trajectory length nL can be known, thereby obtaining the dynamic liquid level depth corresponding to the conductive element 3.

[0081] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0082] The above description is an explanation of the present invention, not a limitation of the present invention. The scope of the present invention is defined in the claims. Any modifications may be made within the scope of protection of the present invention.

Claims

1. A method for detecting a dynamic liquid level in an oil well, applied to an oil well dynamic liquid level detection system, wherein the oil well dynamic liquid level detection system comprises an oil pipe (1) and a casing (2), wherein the dynamic liquid level is located between the oil pipe (1) and the casing (2), and wherein the method is characterized in that: The oil well dynamic liquid level detection system also includes a plurality of conductive elements (3), a cable assembly (4), a power supply and a current detection device; The conductive element (3) is distributed axially along the oil pipe (1) and is located at a fixed height between the oil pipe (1) and the casing (2); The cable assembly (4) comprises two separated cable main lines (401), the upper ends of the two cable main lines (401) are respectively connected to the positive and negative poles of the power supply, and the lower ends of the two cable main lines (401) are connected to the conductive elements (3) via a plurality of cable branches (402), each conductive element (3) being connected to only one cable branch (402); the current detection device is used to detect the current value of the cable main lines (401); The oil well dynamic liquid level detection method comprises: By utilizing the conductivity of oil, two adjacent conductive elements (3) are electrically connected through the oil to form a circuit loop; The current value of the cable main line (401) and the well condition parameters of the oil well are obtained, the number of conductive elements (3) connected to the circuit is determined based on the current value and the well condition parameters, and the dynamic liquid level depth is determined according to the number of conductive elements (3) connected to the circuit.

2. The oil well dynamic liquid level detection method according to claim 1, characterized in that: The determining the number of conductive elements (3) connected to the circuit based on the current value and the well condition parameter comprises: The resistivity of the conductive element (3), the cable assembly (4) and the oil under different well parameters is determined; the total resistance value in the circuit is determined according to the power supply voltage value and the current value of the cable main line (401); and the number of the conductive elements (3) connected to the circuit is calculated based on the resistivity and the total resistance value of the conductive element (3), the cable assembly (4) and the oil.

3. The oil well dynamic liquid level detection method according to claim 1, characterized in that: The determining the number of conductive elements (3) connected to the circuit based on the current value and the well condition parameter comprises: By means of a controlled variable test, the well condition parameters and the number of conductive elements (3) connected to the circuit are used as independent variables, and the current value of the cable main line (401) is used as the dependent variable, to determine the corresponding relationship between the current value of the cable main line (401) and the number of conductive elements (3) connected to the circuit under different well condition parameters; Based on the current value and the well condition parameter, the number of conductive elements (3) connected to the circuit is determined in combination with the corresponding relationship.

4. The oil well dynamic liquid level detection method according to claim 3, characterized in that: The control variable test also includes, for any well condition parameter: A plurality of key values ​​of the well condition parameters are selected, current values ​​corresponding to the key values ​​are determined, and a curve relationship between the well condition parameters and the current values ​​is obtained by fitting.

5. The oil well dynamic liquid level detection method according to claim 1, characterized in that: The well condition parameters include at least one of oil viscosity, oil water content, oil temperature, and bottom hole pressure.

6. The oil well dynamic liquid level detection method according to claim 1, characterized in that: The connection method between the cable assembly (4) and the conductive element (3) includes: two axially adjacent conductive elements (3) are connected to cable branches (402) corresponding to different cable main lines (401).

7. The oil well dynamic liquid level detection method according to claim 1, characterized in that: The cable assembly (4) and the conductive element (3) are connected in the following manner: a main cable line (401) is connected to the bottom conductive element (3), and another main cable line (401) is connected to the remaining conductive elements (3) via a plurality of cable branches (402).

8. The oil well dynamic liquid level detection method according to claim 1, characterized in that: The oil well dynamic liquid level detection system further comprises a protective resistor, which is connected in series to one of the cable main lines (401) and in parallel to the voltmeter.

9. The oil well dynamic liquid level detection method according to claim 1, characterized in that: The conductive element (3) is arranged in a semi-open insulating box (5) and is fixed to a fixed height of the oil pipe (1) through the insulating box (5); the distance between the insulating box (5) and the casing (2) is smaller than the distance between the conductive element (3) and the casing (2).

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