Method and device for detecting dynamic liquid level depth

Abstract

The present application discloses a method and device for detecting the dynamic liquid level depth, which belongs to the field of oil production. The method can measure the target pressure after inputting the target volume of gas into the annulus in the well, and can determine the dynamic liquid level depth in the annulus in the well according to the relationship between the target volume, the target pressure and the dynamic liquid level depth. There is no need to measure by the echo method, which avoids the defects of the echo method in measuring the dynamic liquid level depth, and the measurement reliability is higher. The present application is used for detecting the dynamic liquid level depth.

Description

Technical Field

[0001] The present application relates to the field of oil extraction, and in particular to a method and device for detecting the depth of a dynamic liquid surface. Background Art

[0002] When the oil well is in normal production, the liquid level in the annular space between the oil pipe and the casing is called the dynamic liquid level. The depth of the dynamic liquid level of the oil well is an important indicator of the formation's liquid supply capacity, so the depth of the dynamic liquid level needs to be detected during oil well production.

[0003] In the related art, the echo method is generally used to measure the dynamic liquid surface depth. The echo method uses the principle that sound waves propagate in the annulus (the annular space between the oil pipe and the casing) and are reflected when encountering the liquid surface for measurement.

[0004] However, due to the attenuation of sound waves during transmission and the interference of sound waves reflected by other obstacles in the well, it is easy to make the dynamic liquid level depth unable to be measured, resulting in poor measurement reliability. Summary of the invention

[0005] The present application provides a method and device for detecting the depth of a dynamic liquid surface, which can solve the problem of poor reliability of measuring the depth of a dynamic liquid surface in the prior art. The technical solution is as follows:

[0006] On the one hand, a method for detecting a dynamic liquid level depth is provided, the method comprising:

[0007] Introducing a target volume of gas into the annulus within the well;

[0008] detecting a target pressure of the annulus after inputting the target volume of gas;

[0009] The depth of the dynamic liquid surface in the annulus is determined according to the target volume and the target pressure.

[0010] Optionally, the method further comprises:

[0011] obtaining a target temperature at a target depth in the annulus;

[0012] Determining the depth of the dynamic liquid surface in the annulus according to the target volume and the target pressure includes:

[0013] The depth of the dynamic liquid surface is determined according to the target volume, the target pressure, the target depth and the target temperature.

[0014] Optionally, the depth L of the dynamic liquid surface in the annulus satisfies:

[0015] Wherein, p represents the target pressure, π represents the circumference of a circle, and r 2represents the inner diameter of the casing of the oil well, r 1 represents the outer diameter of the oil pipe of the oil well, n represents the amount of gas in the target volume, R is the ideal gas constant, T 0 represents the target temperature, l represents the target depth, and x represents the geothermal gradient.

[0016] Optionally, the step of inputting a target volume of gas into the annulus in the well comprises:

[0017] Connect one end of the pipe body in the detection device to the annulus, wherein the detection device comprises: the pipe body, and a pressure gauge, a first valve and a flow meter located on the pipe body, and the pressure gauge and the first valve are arranged in sequence in a direction away from one end of the pipe body, the pressure gauge is used to detect the pressure at the position of the pressure gauge in the pipe body, and the flow meter is used to detect the volume of gas flowing through the position of the flow meter in the pipe body;

[0018] Opening the first valve to conduct the pipe body;

[0019] Inputting gas into the annulus through the tube body from the other end of the tube body;

[0020] When the volume detected by the flow meter reaches the target volume, closing the first valve to block the pipe body;

[0021] The detecting the target pressure of the annulus after the target volume of gas is inputted comprises:

[0022] The pressure detected by the pressure gauge is determined as the target pressure.

[0023] Optionally, the step of inputting gas into the annulus through the tube body from the other end of the tube body comprises:

[0024] Connecting the other end of the tube to the inflatable structure;

[0025] The inflation structure is controlled to input gas into the annulus from the other end through the pipe body.

[0026] Optionally, the detection device further comprises: a vent pipe connected to the side wall of the tube body, and a second valve is provided on the vent pipe; the method further comprises:

[0027] When the target volume of gas is input into the annulus and when the target pressure is detected, closing the second valve to block the vent pipe;

[0028] After closing the first valve, opening the second valve to open the vent pipe.

[0029] Optionally, the detection device further comprises: a depth determiner, the depth determiner is electrically connected to the pressure gauge and the flow meter, and is used to obtain the pressure detected by the pressure gauge and the volume detected by the flow meter, and the depth of the dynamic liquid surface in the annulus is determined according to the target volume and the target pressure, comprising:

[0030] The depth of the dynamic liquid surface is determined by the depth determiner according to the acquired target volume and the target pressure.

[0031] On the other hand, a detection device is provided, the detection device comprising: a pipe body, and a pressure gauge, a first valve and a flow meter located on the pipe body;

[0032] The pressure gauge and the first valve are arranged in sequence in a direction away from one end of the tube body;

[0033] The pressure gauge is used to detect the pressure at the location of the pressure gauge in the pipe body;

[0034] The flow meter is used to detect the volume of gas flowing through the position of the flow meter in the pipe body.

[0035] Optionally, the detection device further comprises: a vent pipe connected to the side wall of the tube body, and a second valve is provided on the vent pipe.

[0036] Optionally, the detection device also includes: a depth determiner, which is electrically connected to the pressure gauge and the flow meter, and is used to obtain the pressure detected by the pressure gauge and the volume detected by the flow meter, and determine the depth of the dynamic liquid surface in the annulus in the well based on the acquired target volume and the target pressure.

[0037] The beneficial effects of the technical solution provided by this application include at least:

[0038] The embodiment of the present application provides a method for detecting the dynamic liquid level depth, which can measure the target pressure after the target volume of gas is input into the annulus in the well, and can determine the dynamic liquid level depth in the annulus in the well according to the relationship between the target volume, the target pressure and the dynamic liquid level depth. There is no need to measure by the echo method, which avoids the defects of the echo method in measuring the dynamic liquid level depth, and the measurement reliability is higher. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0040] Figure 1 It is a structural schematic diagram of a dynamic liquid level depth detection device provided in an embodiment of the present application;

[0041] Figure 2 It is a left view of a dynamic liquid level depth detection device provided in an embodiment of the present application;

[0042] Figure 3 is a top view of a dynamic liquid level depth detection device provided in an embodiment of the present application;

[0043] Figure 4 It is a flow chart of a method for detecting the dynamic liquid level depth provided in an embodiment of the present application;

[0044] Figure 5 is a flow chart of a detection device using a dynamic liquid level depth provided in an embodiment of the present application;

[0045] Figure 6 This is a flow chart of another method for detecting the dynamic liquid level depth provided in an embodiment of the present application. DETAILED DESCRIPTION

[0046] In order to make the objectives, technical solutions and advantages of the present application clearer, the implementation methods of the present application will be further described in detail below with reference to the accompanying drawings.

[0047] In the related art, the principle of measuring the dynamic liquid surface depth by the echo method is as follows:

[0048] A high-energy microphone that can emit and receive sound waves is set at the wellhead. When measuring the depth of the dynamic liquid surface, the sound waves emitted by the high-energy microphone are transmitted to the wellbore along the annulus and reflected on obstacles such as the tubing coupling, the sound mark and the dynamic liquid surface. When the sound waves are reflected to the high-energy microphone, the high-energy microphone will convert the sound waves into electrical pulses, which are then received by the detector after channel amplification, circuit shaping and filtering, and form a high-frequency curve and a low-frequency curve of the sound wave change with time as the horizontal coordinate and signal intensity as the vertical coordinate. Among them, the high-frequency curve mainly records the signal intensity of the sound waves reflected by the tubing coupling, and the low-frequency curve mainly records the signal intensity of the sound waves reflected by the dynamic liquid surface and other larger obstacles. Afterwards, the depth of the dynamic liquid surface in the well can be determined according to the positions of the peaks and troughs of these two curves.

[0049] However, when the dynamic liquid level is deep, the sound wave attenuation is serious, and the high-energy microphone at the wellhead may not receive the reflected sound wave, making it impossible to measure the depth of the dynamic liquid level. In addition, due to the vibration of the oil well during production, as well as the influence of wax deposition or dead oil in the wellbore, there are many interference factors in the reflected sound wave, which can also easily make it impossible to measure the dynamic liquid level.

[0050] The embodiment of the present application provides a method and device for detecting the depth of a dynamic liquid surface, and the present application does not use the principle of the echo method, but can also realize the measurement of the depth of the dynamic liquid surface, thereby avoiding the defects of the echo method for measuring the depth of the dynamic liquid surface, and having higher reliability.

[0051] Figure 1 is a schematic structural diagram of a dynamic liquid level depth detection device provided in an embodiment of the present application, Figure 2 This is a method provided by the embodiment of the present application. Figure 1 Left side view of the detection device. Figure 3 This is a method provided by the embodiment of the present application. Figure 1 A top view of the detection device in FIG. Figure 2 and Figure 3 Not shown Figure 1 The entire structure of .

[0052] Please refer to Figures 1 to 3 The detection device 00 may include: a tube body 001, and a pressure gauge 002, a first valve 003 and a flow meter 004 located on the tube body.

[0053] The pressure gauge and the first valve are arranged in sequence in a direction away from one end of the tube body, that is, the pressure gauge is located between one end of the tube body and the first valve.

[0054] The pipe body 001 may include a plurality of conduit segments (such as Figure 1 The conduit segments 001a, 001b and 001c in the embodiment of the present invention are configured such that at least some of the conduit segments are connected to the pressure gauge 002, the first valve 003 or the flow meter 004 respectively.

[0055] The pressure gauge 002 is connected to the side wall of the tube body and is used to detect the pressure at the location of the pressure gauge 002 in the tube body. Figure 1 As shown, the pressure gauge 002 is connected to the side wall of the conduit section 001a.

[0056] The first valve 003 is located on the pipe body 001, for example, the first valve 003 is connected between two conduit sections of the pipe body 001, and the first valve 003 is used to control the conduction of the pipe body. The first valve 003 and the conduit section can be threadedly connected.

[0057] For example, Figure 1 As shown, one end of the first valve 003 is threadedly connected to the conduit segment 001a, and the other end is threadedly connected to the conduit segment 001b. When the first valve 003 is opened, the conduit segment 001a is connected to the conduit segment 001b, and the pipe body 001 is connected.

[0058] The first valve 003 can be a stainless steel stop valve. The friction between the sealing surfaces of the stop valve is small during opening and closing, the stop valve is relatively durable, and is easy to manufacture and maintain.

[0059] The flow meter 004 is also connected between the two conduit sections of the pipe body 001, and is used to detect the volume of the gas flowing through the position where the flow meter is located in the pipe body 001. The flow meter 004 and the conduit section can be connected through a flange 005.

[0060] For example, Figure 1 As shown, the flow meter 004 includes two pipe openings, one pipe opening is connected to the conduit section 001b through the flange 005a, and the other pipe opening is connected to the conduit section 001c through the flange 005b. The conduit section 001b and the conduit section 001c are connected through the flow meter 004, so that the flow meter 004 can detect the volume of gas flowing therethrough.

[0061] Optionally, the detection device 00 may further include a vent pipe 006 connected to the side wall of the pipe body, and a second valve 007 is provided on the vent pipe 006. The vent pipe 006 may further include an elbow 008, a joint 009, a pipe 010 and a pipe 011.

[0062] For example, refer to Figure 1 , one end of the elbow 008 is connected to one end of the connecting pipe 010 through the joint 009, and the other end of the connecting pipe 010 is connected to the side wall of the conduit section 001c through the second valve 007. When the second valve 007 is opened, the conduit section 001c is connected to the connecting pipe 010, and the vent pipe 006 is connected. Among them, the second valve 007 can be a stainless steel ball valve, which has a simple and compact structure and reliable sealing. The connection method of the second valve 007 can be a threaded connection. The joint 009 can be a flexible joint, which has a small size and simple structure, is easy to install and replace, and has a low cost. In addition, you can also refer to Figure 3 The other end of the elbow 008 is connected to the connecting pipe 011.

[0063] Optionally, a third valve 012 may be provided between the pressure gauge 002 and the side wall of the tube body, and the third valve 012 is used to control the conduction between the tube body 001 and the pressure gauge 002. The connection mode of the third valve 012 may be a threaded connection.

[0064] For example, Figure 1 As shown, the third valve 012 is connected between the pressure gauge 002 and the side wall of the conduit section 001a. When the third valve 012 is opened, the pressure gauge 002 is connected to the conduit section 001a. The third valve 012 can be a needle valve. Compared with other types of valves, the needle valve can withstand greater pressure and has good sealing performance. It is very suitable for use with the pressure gauge 002 for pressure measurement. The connection method of the general needle valve is threaded connection.

[0065] Optionally, a pipe 013 protruding outward is provided on the pipe wall of the pipe body 001 for connecting with other components, and the pipe opening of the pipe 013 can be designed to be threadedly connected. For example, the protruding pipe 013a on the conduit section 001a is threadedly connected to the third valve 012, and the protruding pipe 013b on the conduit section 001c is threadedly connected to the second valve 007.

[0066] Optionally, the pressure gauge 002, the first valve 003, the flow meter 004 and the vent pipe 006 are arranged in sequence on the pipe body 001. Figure 1 As shown, from one end of the tube body 001 to the other end, there are the pressure gauge 002, the first valve 003, the flow meter 004 and the vent pipe 006 in sequence.

[0067] Optionally, both ends of the tube body 001 may be provided with joints 014 (such as joint 014a at one end of the tube body 001 and joint 014b at the other end of the tube body 001) for connecting with an external pipeline. The joint 014 may be a quick joint, which can be quickly disconnected and connected, is easy to operate, and saves time and effort. The tube body 001 is also provided with a pipe clamp 015 (such as pipe clamp 015a on the conduit section 001b and pipe clamp 015b on the conduit section 001c) for fixing the tube body.

[0068] Optionally, the detection device 00 may further include a bracket 016, and the tube body 001 is fixed on the bracket 016. Figure 1 As shown, the bracket 016 includes side brackets at both ends and a base in the middle, and the tube body 001 is fixed on the side brackets at both ends.

[0069] Optionally, the detection device 00 may further include a handle 017 and an anti-slip support foot 018 connected to the bracket 016. Figure 1 As shown, the two side brackets at both ends of the bracket 016 are each fixedly connected with a handle 017, and the handle 017 can be fixed to the side bracket by screws; the four corners of the base of the bracket 016 are fixedly connected with anti-skid support feet 018 to play a supporting and anti-skid role. Figure 3 The connections at the four sides of the base of bracket 016 can be fixed by screws 019.

[0070] Optionally, the detection device 00 may further include a depth determiner (not shown in the figure), which may be electrically connected to the pressure meter and the flow meter to obtain the pressure detected by the pressure meter and the volume detected by the flow meter. The depth determiner may also determine the depth of the dynamic liquid surface in the annulus in the well according to the obtained target volume and target pressure.

[0071] It should be noted that when the detection device provided in the embodiment of the present application is used to detect the dynamic liquid level depth, it needs to be connected to the annulus in the well, and a certain amount of gas is injected into the annulus through the detection device.

[0072] It should be understood that the valves in the above embodiments may also be other types of valves, and the connection method of the components in the detection device may also be other connection methods. The above embodiments are only provided for reference purposes and are not limited to the embodiments of the present application.

[0073] The functions of the detection device provided in the embodiment of the present application will be explained below in combination with the detection method for the dynamic liquid level depth provided in the embodiment of the present application.

[0074] For example, Figure 4 is a flow chart of a method for detecting the dynamic liquid level depth provided in an embodiment of the present application, such as Figure 4 As shown, the method may include the following steps.

[0075] Step 101: Obtain a target temperature at a target depth in an annulus.

[0076] The annulus refers to the annular space between the tubing and casing in the well. The target depth can be any depth in the well as long as there is a temperature difference between the temperature at the target depth and the surface temperature. After determining the well with the dynamic liquid level depth to be detected, the geological measurement data of the well to be detected can be queried to obtain the target temperature at the target depth in the annulus of the well. Among them, the relevant data of the well can be measured in advance by geological exploration, and there is no need to measure when measuring the dynamic liquid level depth.

[0077] Step 102: Input a target volume of gas into the annulus in the well.

[0078] The input of the target volume of gas into the annulus in the well needs to be completed using the detection device provided in the embodiment of the present application. The detection device may include: a pipe body, and a pressure gauge, a first valve and a flow meter located on the pipe body, and the pressure gauge and the first valve are arranged in sequence in a direction away from one end of the pipe body. The pressure gauge is used to detect the pressure at the position of the pressure gauge in the pipe body, and the flow meter is used to detect the volume of gas flowing through the position of the flow meter in the pipe body.

[0079] like Figure 5 As shown, the process of inputting a target volume of gas into the annulus in a well using a detection device may include the following steps.

[0080] Step 1021, connect one end of the pipe in the detection device to the annulus in the well.

[0081] One end of the pipe body in the detection device is connected to the wellhead device, and the wellhead device is connected to the annulus in the well, so that the pipe body in the detection device is connected to the annulus in the well.

[0082] Step 1022: Connect the other end of the tube to the inflatable structure.

[0083] The inflatable structure is used to inject gas into the annulus. For example, the inflatable structure can be a structure for filling any gas, for example, the inflatable structure can include a nitrogen bottle, etc.

[0084] Step 1023, open the first valve.

[0085] Open the first valve on the pipe body to make the pipe body conductive.

[0086] Step 1024: Control the inflation structure to input gas into the annulus through the pipe body from the other end.

[0087] The switch of the inflatable structure is turned on, so that the gas output by the inflatable structure is injected into the annulus through the pipe body.

[0088] Step 1025: When the volume detected by the flow meter reaches the target volume, close the first valve.

[0089] During the gas input process, the staff can monitor the flow meter reading in real time. When the volume detected by the flow meter reaches the target volume, the first valve is closed to seal the pipe body and stop inputting gas into the annulus.

[0090] It should be noted that when the target volume of gas is input into the annulus and when the target pressure is detected, the second valve needs to be closed to block the vent pipe, which can ensure the airtightness of the detection device. After closing the first valve to block the pipe body, the second valve can be opened to conduct the vent pipe, so that the gas remaining in the pipe body is discharged from the vent pipe, ensuring that the inflatable structure can be safely removed from the other end of the pipe body.

[0091] For example, the following example can be used: Figure 1The detection device 00 shown in the well inputs nitrogen into the annulus. First, the end of the pipe body 001 close to the pressure gauge is connected to one end of a high-pressure hose through a quick connector 014a, and the other end of the high-pressure hose is connected to the casing valve of the wellhead device. Then, the other end of the pipe body 001 is connected to one end of a high-pressure hose through a quick connector 014b, and the other end of the high-pressure hose is connected to a nitrogen bottle (a kind of inflatable structure) through a pressure reducing valve. Secondly, it is necessary to close the second valve 007 on the vent pipe 006 to ensure the airtightness during the input nitrogen process. Afterwards, open the first valve 003 to conduct the pipe body 001, and you can open the nitrogen bottle switch to input nitrogen into the well annulus. Finally, when it is observed that the amount of input nitrogen detected by the flow meter 004 has reached the target volume, immediately close the first valve 003 to complete the process of injecting gas.

[0092] Step 103: Detect the target pressure of the annulus after the target volume of gas is input.

[0093] After the target volume of gas is input into the annulus, the pressure detected by the pressure gauge is determined as the target pressure.

[0094] For example, after the target volume of gas is input into the annulus and the first valve 003 is closed, the third valve 012 connected to the pressure gauge 004 is opened. At this time, the pressure gauge 004 is connected to the annulus in the well, and the pressure in the annulus after the target volume of gas is input can be detected, and the pressure read at this time is determined as the target pressure. It should be noted that the third valve 012 can also be in an open state all the time, so that the pressure gauge 004 can measure the pressure value of the annulus in the well in real time during the process of inputting gas.

[0095] Step 104: Determine the depth of the dynamic liquid surface in the annulus according to the target volume, target pressure, target depth and target temperature.

[0096] The depth L of the dynamic liquid surface in the annulus satisfies:

[0097] Where p represents the target pressure, π represents the circumference, and r 2 Represents the inner diameter of the oil well casing, r 1 represents the outer diameter of the oil pipe of the oil well, n represents the amount of gas in the target volume, R is a constant, T 0 represents the target temperature, l represents the target depth, and x represents the geothermal gradient, for example, x=3.

[0098] Substituting the target volume, target pressure, target depth and target temperature of the well to be measured obtained in the above steps into formula (1), the depth L of the dynamic liquid surface can be obtained through calculation.

[0099] It should be noted that step 104 can be performed by a detection device. For example, the depth determiner in the detection device 00 provided in the embodiment of the present application can be used to determine the depth of the dynamic liquid surface. It can also be manually completed by a technician based on the acquired target volume, target pressure, target depth and target temperature. The embodiment of the present application does not limit this.

[0100] In summary, the embodiments of the present application provide a method for detecting the dynamic liquid level depth, which can measure the target pressure after the target volume of gas is input into the annulus in the well, and can determine the dynamic liquid level depth in the annulus in the well according to the numerical relationship between the target volume, target pressure, target depth and target temperature. There is no need to measure by echo method, which avoids the defects of measuring the dynamic liquid level depth by echo method, and the measurement reliability is higher.

[0101] Figure 6 is a flow chart of another method for detecting the dynamic liquid level depth provided in an embodiment of the present application, such as Figure 6 As shown, the method may include the following steps.

[0102] Step 201: Input a target volume of gas into the annulus in the well.

[0103] For example, the embodiments of the present application can be provided as follows Figure 1 The detection device 00 shown inputs gas into the annulus in the well, and step 201 can refer to the relevant description of step 102.

[0104] It should be noted that gas may also be introduced into the annulus in the well by other means, which is not limited in the embodiments of the present application.

[0105] Step 202: Detect the target pressure of the annulus after the target volume of gas is input.

[0106] For example, the embodiments of the present application can be provided as follows Figure 1 The pressure gauge 004 in the detection device 00 shown detects the target pressure in the annulus after the target volume of gas is input.

[0107] It should be noted that the target pressure may also be detected by other methods, and the embodiments of the present application do not limit this.

[0108] Step 203: Determine the depth of the dynamic liquid surface in the annulus according to the target volume and the target pressure.

[0109] There is a certain relationship between the target pressure, the target volume and the depth of the dynamic liquid surface. Therefore, the depth of the dynamic liquid surface can be calculated based on the target volume and target pressure of the well to be measured obtained after executing step 201 and step 202.

[0110] In summary, the embodiments of the present application provide a method for detecting the dynamic liquid level depth, which can measure the target pressure after the target volume of gas is input into the annulus in the well, and can determine the dynamic liquid level depth in the annulus in the well according to the relationship between the target volume, the target pressure and the dynamic liquid level depth. There is no need to measure by the echo method, which avoids the defects of the echo method in measuring the dynamic liquid level depth, and the measurement reliability is higher.

[0111] It should be noted that, compared with the traditional echo method, the dynamic liquid level depth detection method provided in the embodiment of the present application not only has better detection reliability, but also has better accuracy.

[0112] For example, taking the dynamic liquid level depth measurement in the annulus of Well A as an example, the target depth measured for Well A is 4068 meters (m), the measured target temperature is 392.9 Kelvin (K), and the gas volume injected under standard conditions is 9.35 cubic meters (m 3 ), gas pressure 101325 Pa (Pa), pressure gauge reading 102000 Pa, casing inner diameter 0.0789 m, tubing outer diameter 0.0365 m, and into formula (1) it can be concluded that the dynamic liquid level depth of well A is 620 m. The result of the echo measurement of well A is 654 m. Compared with the echo method, the method provided in the embodiment of the present application has an error of 34 m. It can be seen that the accuracy of the method provided in the embodiment of the present application in measuring the dynamic liquid level depth is also good.

[0113] A person skilled in the art will understand that all or part of the steps to implement the above embodiments may be accomplished by hardware or by instructing related hardware through a program, and the program may be stored in a computer-readable storage medium, and the above-mentioned storage medium may be a read-only memory, a disk or an optical disk, etc.

[0114] The above description is only an optional embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A method for detecting the depth of a dynamic liquid surface, characterized in that: The method comprises: Obtaining a target temperature at a target depth in the annulus of the well to be inspected, wherein the target depth refers to any depth under the well to be inspected, and there is a temperature difference between the target temperature and the surface temperature of the well to be inspected. The annulus is used to indicate the annular space between the oil pipe and the casing in the well to be inspected, and the surface temperature is determined based on the geological measurement data of the well to be inspected; Connect one end of the pipe body in the detection device to the annulus, wherein the detection device comprises: the pipe body, and a pressure gauge, a first valve and a flow meter located on the pipe body, and the pressure gauge and the first valve are arranged in sequence in a direction away from one end of the pipe body, the pressure gauge is used to detect the pressure at the position of the pressure gauge in the pipe body, and the flow meter is used to detect the volume of gas flowing through the position of the flow meter in the pipe body; Opening the first valve to conduct the pipe body; Inputting gas into the annulus through the tube body from the other end of the tube body; When the volume of the gas input into the annulus reaches the target volume detected by the flow meter, the first valve is closed to block the pipe body, and the pressure detected by the pressure gauge is determined as the target pressure, wherein the pressure corresponding to the target volume of gas in the annulus is the target pressure; Determining the depth of the dynamic liquid surface in the annulus according to the target volume, the target pressure, the target depth and the target temperature; The depth L of the dynamic liquid surface in the annulus satisfies: ; in, p represents the target pressure, represents pi, r 2 represents the inner diameter of the casing of the well to be tested, r 1 represents the outer diameter of the oil pipe of the well to be tested, n represents the amount of gaseous substance in the target volume, R is the ideal gas constant, T 0 represents the target temperature, l represents the target depth, x Represents the geothermal gradient.

2. The method according to claim 1, characterized in that The detection device further includes: a vent pipe connected to the side wall of the tube body, and a second valve is provided on the vent pipe; the method further includes: When the target volume of gas is input into the annulus and when the target pressure is detected, closing the second valve to block the vent pipe; After closing the first valve, opening the second valve to open the vent pipe.

3. The method according to claim 1, characterized in that The detection device also includes: a depth determiner, which is electrically connected to the pressure gauge and the flow meter, and is used to obtain the pressure detected by the pressure gauge and the volume detected by the flow meter; the depth of the dynamic liquid surface is determined by the depth determiner according to the acquired target volume and the target pressure.

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