Method and apparatus for detecting lost fish heads using array electromagnetic scanning

Abstract

The application provides an array type electromagnetic scanning lost fish head detection instrument and method, the detection instrument comprises: an instrument shell, a circuit part, a motor, an azimuth sensor, a rotating shaft, a rotating body and an electromagnetic sensor array are arranged in the instrument shell; the circuit part comprises a measurement circuit, a control circuit and a cable communication circuit, power supply and signal transmission are realized through a logging cable; the control circuit is connected with an input end of the motor; the rotating shaft is connected with the rotating body through a measuring part of the azimuth sensor, the motor drives the measuring part of the azimuth sensor and the rotating body to rotate synchronously; the measurement circuit is connected with an output end of the azimuth sensor, the control circuit is connected with input ends of each electromagnetic sensor in the electromagnetic sensor array, and the measurement circuit is connected with output ends of each electromagnetic sensor in the electromagnetic sensor array. The array type electromagnetic scanning lost fish head detection method and instrument provided by the application can improve the detection precision and work efficiency to the greatest extent.

Description

Technical Field

[0001] This invention relates to the field of oilfield well workover technology, and in particular to an array-type electromagnetic scanning method and instrument for detecting lost fish heads. Background Technology

[0002] As oilfield development enters its mid-to-late stages, the number of wells with casing damage increases year by year, with some of these damages primarily due to casing misalignment. During the major workover of damaged wells, when the upper and lower breaks of a misaligned well are completely offset, and the lower casing break has shifted beyond the casing diameter, workover tools lowered through the upper casing passage will be unable to access the lower casing passage, resulting in the loss of the lower casing—a phenomenon known as a "lost fish well." These wells are difficult to workover, cannot be scrapped, and pose a significant threat to normal oilfield production.

[0003] With the ongoing treatment of casing damage wells in oilfields, the workload of treating and repairing misaligned wells in casing damage wells is gradually increasing. Especially under the condition of controllable costs, the repair and reuse of misaligned wells is of great significance to the stable production of oilfields. Therefore, downhole fish-top detection technology, as a technical support for well workover operations, provides direction for the repair of fish-top wells, has important social and economic benefits, and has broad application prospects. Summary of the Invention

[0004] This invention provides a method and instrument for detecting lost fish heads using an array-type electromagnetic scanning system, overcoming the shortcomings of existing technologies where the detection accuracy of lost fish heads is low, leading to greater difficulty in well repair and lower work efficiency.

[0005] To address the aforementioned problems, this invention provides, in one aspect, an array-type electromagnetic scanning detection instrument for lost fish heads, comprising:

[0006] The instrument housing contains a circuit section, a motor, an orientation sensor, a rotating shaft, a rotating body, and an electromagnetic sensor array.

[0007] The instrument housing is made of a non-magnetic material;

[0008] The circuit consists of a measurement circuit, a control circuit, and a cable communication circuit, and is powered and transmits signals through a logging cable.

[0009] The control circuit is connected to the input terminal of the motor and is used to control the operating state of the motor;

[0010] The rotating shaft passes through the measuring component of the orientation sensor and is connected to the rotating body. The motor drives the measuring component of the orientation sensor to rotate synchronously with the rotating body through the rotating shaft.

[0011] The electromagnetic sensor array includes a first electromagnetic sensor, a second electromagnetic sensor, and a third electromagnetic sensor.

[0012] The rotating body is provided with mounting grooves that match the shape of each electromagnetic sensor in the electromagnetic sensor array, and each electromagnetic sensor is fixed in the corresponding mounting groove.

[0013] The measurement circuit is connected to the output terminal of the orientation sensor and is used to measure the orientation of the electromagnetic sensor array.

[0014] The control circuit is connected to the input terminal of each electromagnetic sensor in the electromagnetic sensor array and is used to control the working state of each electromagnetic sensor in the electromagnetic sensor array.

[0015] The measurement circuit is connected to the output terminals of each electromagnetic sensor in the electromagnetic sensor array to measure the electromagnetic induction signal received by the induction probe.

[0016] Preferably, the first electromagnetic sensor includes a sensor frame, an excitation coil, and a sensing probe;

[0017] The first electromagnetic sensor is used to determine the presence or absence of a magnetically conductive medium in the horizontal direction of the array-type electromagnetic scanning instrument for lost fish heads, thereby determining the depth, orientation, and distance of the lost fish head.

[0018] Preferably, the number of the sensing probes is four, which are evenly distributed around the excitation coil at equal angles in the circumferential direction.

[0019] Preferably, the second electromagnetic sensor includes a sensor frame, an excitation coil, a sensing probe, and a shielding shell, and is used to measure the orientation and distance of the magnetically conductive medium in the horizontal direction of the array-type electromagnetic scanning lost fish head instrument;

[0020] The shielding shell ensures that the excitation magnetic field of the second electromagnetic sensor is distributed in the horizontal direction.

[0021] Preferably, the third electromagnetic sensor has the same structure as the second electromagnetic sensor, including a sensor frame, excitation coil, induction probe, and shielding shell.

[0022] The shielding shell keeps the excitation magnetic field of the third electromagnetic sensor distributed in a vertically downward direction, which is used to measure the presence and distance of the magnetic medium below the array electromagnetic scanning lost fish head instrument.

[0023] The excitation coil is excited by current, and its central magnetic flux density formula is:

[0024]

[0025] Where: Bx - center magnetic flux density; μ0 - permeability in air; n - number of turns of the excitation coil; a - winding diameter; d - coil diameter; l - coil length; i m - Coil current; D - Coil outer diameter.

[0026] Preferably, the sensing probe is a receiving coil, a Hall element, or a fluxgate.

[0027] On the other hand, the present invention also provides a method for detecting lost fish heads using array-type electromagnetic scanning, comprising: when the sleeve is broken into two parts at a certain depth, and the lost fish head is located below the break point, performing the following steps:

[0028] Step S41: Using a logging cable, lower the array-type electromagnetic scanning lost fish head instrument into the test channel until it encounters an obstacle and stops. Periodically excite the third electromagnetic sensor with maximum power and record the measurement results.

[0029] Step S42: Keep the instrument in working condition, and when the array electromagnetic scanning fish head instrument is pulled up to a predetermined distance using the logging cable, record the measurement results of the third electromagnetic sensor.

[0030] Step S43: The magnetic medium can cause the magnetic field distribution to change. By comparing the measurement results of the third electromagnetic sensor twice, it is determined whether there is a lost fish head below the array electromagnetic scanning lost fish head instrument, and the distance between the lost fish head and the array electromagnetic scanning lost fish head instrument when it encounters an obstacle.

[0031] When the casing breaks into two parts at a certain depth, and the fish head is lost to the side of the break, perform the following steps:

[0032] Step S51: Continue drilling at the misalignment location to form a test channel;

[0033] Step S52: Using a logging cable, lower the array-type electromagnetic scanning lost fish head instrument of the present invention into the test channel until it encounters an obstacle and stops. Periodically excite the excitation coil of the first electromagnetic sensor with maximum power. At the same time as the excitation stops, simultaneously collect the induced electrical signals received by the four receiving probes. The magnetic medium can cause the magnetic field distribution to change. Based on the received induced electrical signals, the presence or absence of the magnetic medium can be determined.

[0034] Step S53: Maintain the working state of the array-type electromagnetic scanning lost fish head instrument described in step S51. Use the logging cable to lift the array-type electromagnetic scanning lost fish head instrument. According to the received induced electrical signal, the depth at which the magnetic medium changes from present to absent is the depth at which the lost fish head is located.

[0035] Step S54: At the depth where the lost fish head is located, periodically excite the second electromagnetic sensor to work with maximum power, start the motor, and perform rotation measurement. When the measurement direction of the second electromagnetic sensor is the same as the direction where the lost fish head is located, the induced signal value received by the second electromagnetic sensor is the maximum. At this time, the measurement direction of the second electromagnetic sensor is the direction of the lost fish head.

[0036] Step S55: During rotation measurement, the electromagnetic sensor array rotates synchronously with the orientation sensor. Based on the measurement results of the orientation sensor, the actual orientation measured by the second electromagnetic sensor is determined, thereby determining the actual orientation of the lost fish head.

[0037] Step S56: The induced signal value received by the electromagnetic sensor array is linearly related to the distance of the lost fish head. With the location of the lost fish head determined, the excitation power of the first electromagnetic sensor and the second electromagnetic sensor is changed. Based on the electromagnetic induction signal received by the first electromagnetic sensor and the second electromagnetic sensor, the distance of the lost fish head can be analyzed.

[0038] Step S57: Repeat steps S54 to S56 at different depths below the depth where the lost fish head is located. Analyze the posture of the broken casing based on the measurement results to provide data support for formulating a reasonable casing retrieval plan.

[0039] The present invention has the following beneficial effects:

[0040] The array-type electromagnetic scanning detection method and instrument provided by this invention can detect the distance and orientation of the missing casing in the lower part of the well where the fish head is lost, even when the casing is completely broken. This maximizes detection accuracy, improves work efficiency, and provides working direction for well repair tools. Attached Figure Description

[0041] Figure 1 This is a schematic diagram of the structure of the array-type electromagnetic scanning detection instrument for lost fish heads according to an embodiment of the present invention;

[0042] Figure 2 This is a schematic diagram of the structure of the first electromagnetic sensor in the array-type electromagnetic scanning detection instrument for lost fish heads according to an embodiment of the present invention;

[0043] Figure 3 This is a schematic diagram of the structure of the second electromagnetic sensor in the array-type electromagnetic scanning detection instrument for lost fish heads according to an embodiment of the present invention;

[0044] Figure 4 This is a schematic diagram of the detection when the casing is longitudinally misaligned;

[0045] Figure 5 This is a schematic diagram of the detection when the casing is transversely misaligned;

[0046] Figure 6 This is a schematic diagram of the circuit structure.

[0047] In the picture:

[0048] 1: Instrument housing; 2: Circuit section; 3: Motor; 4: Azimuth sensor; 5: Rotating shaft; 6: First electromagnetic sensor; 7: Rotating body; 8: Second electromagnetic sensor; 9: Third electromagnetic sensor; 10: Electromagnetic sensor array; 11: Sensor frame; 12: Excitation coil; 13: Induction probe; 14: Shielding shell; 15: Casing one; 16: Casing two (missing fish head); 17: Logging cable; 18: Array-type electromagnetic scanning missing fish head instrument; 19: Test channel; 20: Measurement circuit; 21: Control circuit; 22: Cable communication circuit. Detailed Implementation

[0049] The present invention will now be described based on embodiments, but it is worth noting that the present invention is not limited to these embodiments. In the following detailed description of the invention, certain specific details are described in detail. However, those skilled in the art will fully understand the invention for the parts not described in detail.

[0050] Furthermore, those skilled in the art should understand that the accompanying drawings are provided only to illustrate the purpose, features, and advantages of the present invention, and are not actually drawn to scale.

[0051] Furthermore, unless the context explicitly requires it, the words "comprising," "including," and similar terms throughout the specification and claims should be interpreted as including rather than exclusive or exhaustive; that is, meaning "including but not limited to."

[0052] like Figure 1-3 As shown, this invention provides an array-type electromagnetic scanning detection instrument for lost fish heads. The instrument includes: an instrument housing 1, a circuit section 2, a motor 3, an orientation sensor 4, a rotating shaft 5, a rotating body 7, and an electromagnetic sensor array 10. The circuit section 2, motor 3, orientation sensor 4, rotating shaft 5, rotating body 7, and electromagnetic sensor array 10 are mounted inside the instrument housing 1, which is made of a non-magnetic material. (Reference) Figure 6 Circuit section 2 consists of a measurement circuit 20, a control circuit 21, and a cable communication circuit 22, which are powered and transmit signals via logging cable 17. Control circuit 21 is connected to the input terminal of motor 3 and is used to control the operating status of motor 3. Rotating shaft 5 passes through the measuring component of orientation sensor 4 and connects to rotating body 7. Motor 3 can drive the measuring component of orientation sensor 4 to rotate synchronously with rotating body 7 via rotating shaft 5. Orientation sensor 4 can be an absolute encoder, grating encoder, rotary transformer, etc.

[0053] The rotating body 7 has mounting grooves that match the shape of each electromagnetic sensor in the electromagnetic sensor array 10, and each electromagnetic sensor is fixed in its corresponding mounting groove. The measurement circuit 20 is connected to the output terminal of the orientation sensor 4 and is used to measure the orientation of the electromagnetic sensor array 10. The control circuit 21 is connected to the input terminals of each electromagnetic sensor in the electromagnetic sensor array 10 and is used to control the operating state (whether it is working, excitation frequency, excitation power, etc.) of each electromagnetic sensor in the electromagnetic sensor array 10. The measurement circuit 20 is connected to the output terminals of each electromagnetic sensor in the electromagnetic sensor array 10 and is used to measure the electromagnetic induction signal received by the induction probe 13.

[0054] The electromagnetic sensor array 10 consists of a first electromagnetic sensor 6, a second electromagnetic sensor 8, and a third electromagnetic sensor 9.

[0055] refer to Figure 2 The first electromagnetic sensor 6 includes a sensor frame 11, an excitation coil 12, and induction probes 13. It is used to determine the presence or absence of a magnetically conductive medium in the horizontal direction of the instrument, thereby determining the depth, orientation, and distance of the lost sleeve fish head 16. The electromagnetic sensor 6 has four induction probes 13, which are evenly distributed around the excitation coil 12 at equal angles in the circumferential direction. The number of induction probes 13 is not limited, as long as they are evenly distributed. The evenly distributed induction probes 13 at equal angles can comprehensively receive the induced magnetic field signal generated by the magnetically conductive medium, facilitating the determination of the orientation and distance of the magnetically conductive medium.

[0056] refer to Figure 3 The second electromagnetic sensor 8 includes a sensor frame 11, an excitation coil 12, a sensing probe 13, and a shielding shell 14, and is used to accurately measure the orientation and distance of the magnetically conductive medium in the horizontal direction of the instrument. The shielding shell 14 can make the excitation magnetic field of the second electromagnetic sensor 8 mainly distributed in the horizontal direction, which can enhance the magnetic field strength of the second electromagnetic sensor 8 in the horizontal direction, thereby increasing the detection distance of the second electromagnetic sensor 8.

[0057] The third electromagnetic sensor 9 has the same structure as the second electromagnetic sensor 8, differing only in size and excitation coil winding parameters. Its measurement direction is vertically downward, used to measure the presence and distance of a magnetically conductive medium below the instrument. The excitation coil 12 uses current excitation, and its central magnetic flux density formula is:

[0058] Where: Bx - center magnetic flux density; μ0 - permeability in air; n - number of turns of the excitation coil; a - winding diameter; d - coil diameter; l - coil length; im - coil current; D - outer diameter of the coil.

[0059] The winding parameters of the excitation coil 12 need to be set according to the actual size requirements of the instrument and other conditions. Therefore, once the winding parameters of the excitation coil are determined, the magnitude of the central magnetic flux density can only be changed by changing the current of the excitation coil 12. At the same distance, the larger the excitation current, the stronger the excitation magnetic field, and the farther the detection distance of the electromagnetic sensor.

[0060] The sensing probe 13 can be a receiving coil, Hall element, fluxgate, etc., depending on the actual application.

[0061] In addition, the present invention also provides an array-type electromagnetic scanning method for detecting lost fish heads. When the sleeve is broken into two parts, sleeve one 15 and sleeve two (i.e., the lost fish head) 16, at a certain depth, the following two situations may occur:

[0062] The first case, such as Figure 4 As shown, the missing fish head 16 is located below the broken sleeve 15. At this point, the following steps should be performed:

[0063] Step S41: Using logging cable 17, lower the array-type electromagnetic scanning lost fish head instrument 18 into the test channel until it encounters an obstacle and stops. Periodically excite the third electromagnetic sensor 9 with maximum power and record the measurement results.

[0064] Step S42: Keep the instrument in working condition, use the logging cable 17 to lift the array electromagnetic scanning lost fish head instrument 18 by one meter, and record the measurement results of the third electromagnetic sensor 9.

[0065] Step S43: The magnetic medium can cause the magnetic field distribution to change. By comparing the measurement results of the third electromagnetic sensor 9 twice, it can be analyzed whether there is a magnetic medium (i.e., the lost fish head 16) under the array electromagnetic scanning lost fish head instrument 18, and the distance between the lost fish head 16 and the array electromagnetic scanning lost fish head instrument 18 when it encounters an obstacle.

[0066] The second scenario, such as Figure 5 As shown, the missing fish head 16 is located to the side of the misaligned sleeve 15. In this case, the following steps should be performed:

[0067] Step S51: Continue drilling at the misalignment point of casing 15 to form test channel 19;

[0068] Step S52: Using the logging cable 17, lower the array-type electromagnetic scanning lost fish head instrument 18 along the test channel 19 until it encounters an obstacle and stops. Periodically excite the excitation coil 12 of the first electromagnetic sensor 6 with maximum power. At the same time as the excitation stops, simultaneously collect the induced electrical signals received by the four receiving probes 13. The magnetic medium can cause the magnetic field distribution to change. Based on the received induced electrical signals, the presence or absence of the magnetic medium around the instrument can be determined.

[0069] Step S53: Keep the instrument in working condition, use the logging cable to lift the array electromagnetic scanning instrument 18 for the lost fish head, and according to the received induced electrical signal, the depth from the presence to the absence of the magnetic medium is the depth where the lost fish head 16 is located.

[0070] Step S54: At the depth where the lost fish head 16 is located, periodically excite the second electromagnetic sensor 8 to work with maximum power, start the motor 3, and perform rotation measurement. When the measurement direction of the second electromagnetic sensor 8 is the same as the direction where the lost fish head 16 is located, the value of the induced signal received by the second electromagnetic sensor 8 is the maximum. At this time, the measurement direction of the second electromagnetic sensor 8 is the direction of the lost fish head 16.

[0071] Step S55: During rotation measurement, the electromagnetic sensor array 10 and the orientation sensor 4 rotate synchronously. Based on the measurement results of the orientation sensor 4, the actual orientation measured by the second electromagnetic sensor 8 is determined, and thus the actual orientation of the lost fish head 16 is determined.

[0072] Step S56: The value of the induction signal received by the electromagnetic sensor array 10 is linearly related to the distance of the lost fish head. With the location of the lost fish head determined, the excitation power of the first electromagnetic sensor 6 and the second electromagnetic sensor 8 is changed. Based on the electromagnetic induction signals received by the first electromagnetic sensor 6 and the second electromagnetic sensor 8, the distance of the lost fish head 16 can be analyzed.

[0073] Step S57: Repeat steps S54 to S56 at different depths below the depth where the missing fish head 16 is located. Based on the measurement results, the posture of the broken casing 16 can be analyzed, providing data support for formulating a reasonable casing salvage plan.

[0074] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An arrayed electromagnetic scanning lost-head fish detection instrument, characterized by, The utility model relates to a kind of array type electromagnetic scanning lost fish head instrument, including: Instrument shell, circuit part, motor, azimuth sensor, rotating shaft, rotating body and electromagnetic sensor array are arranged in the instrument shell; The instrument shell is made of non-magnetic material; The circuit part includes measurement circuit, control circuit and cable communication circuit, and power supply and signal transmission are carried out through logging cable; The control circuit is connected with the input end of the motor, and is used to control the running state of the motor; The rotating shaft is connected with the rotating body through the measuring component of the azimuth sensor, and the motor drives the measuring component of the azimuth sensor and the rotating body to rotate synchronously through the rotating shaft; The electromagnetic sensor array includes a first electromagnetic sensor, a second electromagnetic sensor and a third electromagnetic sensor; Wherein: the first electromagnetic sensor is used to determine whether there is a magnetic conductive medium in the horizontal direction of the array type electromagnetic scanning lost fish head instrument, and further determine the depth, direction and distance of the lost casing fish head; The second electromagnetic sensor is used to measure the direction and distance of the magnetic conductive medium in the horizontal direction of the array type electromagnetic scanning lost fish head instrument; The third electromagnetic sensor is used to measure whether there is a magnetic conductive medium below the array type electromagnetic scanning lost fish head instrument and the distance; The rotating body is provided with a mounting groove matched with the shape of each electromagnetic sensor in the electromagnetic sensor array, and each electromagnetic sensor is fixed in the corresponding mounting groove; The measurement circuit is connected with the output end of the azimuth sensor, and is used to measure the measurement direction of the electromagnetic sensor array; The control circuit is connected with the input end of each electromagnetic sensor in the electromagnetic sensor array, and is used to control the working state of each electromagnetic sensor in the electromagnetic sensor array; The measurement circuit is connected with the output end of each electromagnetic sensor in the electromagnetic sensor array for measuring the electromagnetic induction signal received by the induction probe.

2. The arrayed electromagnetic scanning loss-of-head detection instrument of claim 1, wherein, The first electromagnetic sensor includes a sensor skeleton, an excitation coil and an induction probe.

3. The arrayed electromagnetic scanning loss-of-head detection instrument of claim 2, wherein, The number of induction probes is four, which are uniformly arranged around the excitation coil at equal angles in the circumferential direction.

4. The arrayed electromagnetic scanning loss-of-head detection instrument of claim 1, wherein, The second electromagnetic sensor includes a sensor skeleton, an excitation coil, an induction probe and a shielding shell. The shielding shell keeps the excitation magnetic field of the second electromagnetic sensor distributed in the horizontal direction.

5. The arrayed electromagnetic scanning loss-of-head detection instrument of claim 4, wherein, The third electromagnetic sensor and the second electromagnetic sensor have the same structure, including a sensor skeleton, an excitation coil, an induction probe and a shielding shell. The shielding shell keeps the excitation magnetic field of the third electromagnetic sensor distributed in the downward vertical direction. The excitation coil adopts current excitation mode, and the central magnetic flux density formula is: ; where: Bx- central magnetic flux density; μ0- permeability in air; n- number of turns of the excitation coil; a- wire diameter; d- coil diameter; l- coil length; i m - coil current; D- coil outside diameter.

6. The arrayed electromagnetic scanning loss-of-head detection instrument of claim 2, wherein, The induction probe is a receiving coil, a Hall element or a fluxgate.

7. An arrayed electromagnetic scan lost fish head detection method based on the arrayed electromagnetic scan lost fish head detection instrument according to any one of claims 1-6, characterized in that, Including: When the casing is broken into two parts at a certain depth, and the lost fish head is located below the broken part, the following steps are performed: Step S41, use logging cable to lower the array type electromagnetic scanning lost fish head instrument into the test channel to stop when encountering resistance, periodically excite the third electromagnetic sensor to work with maximum power and record the measurement results; Step S42, keep the working state of the instrument, and record the measurement results of the third electromagnetic sensor when the array type electromagnetic scanning lost fish head instrument is lifted a predetermined distance by logging cable. Step S43, the magnetic conductive medium can change the magnetic field distribution, by comparing the measurement results of the third electromagnetic sensor twice, to determine whether there is a lost fish head under the array electromagnetic scanning lost fish head instrument, and the distance between the lost fish head and the array electromagnetic scanning lost fish head instrument when encountering resistance; When the casing is broken into two parts at a certain depth, and the lost fish head is beside the broken part, the following steps are executed: Step S51, continue drilling at the broken position to form a test channel; Step S52, use the logging cable to lower the array electromagnetic scanning lost fish head instrument into the test channel to stop when encountering resistance, periodically excite the excitation coil of the first electromagnetic sensor with maximum power, stop excitation, and at the same time, synchronously collect the induced electric signals received by the four receiving probes, the magnetic conductive medium can change the magnetic field distribution, and according to the received induced electric signals, it is determined whether there is a magnetic conductive medium; Step S53, keep the working state of the array electromagnetic scanning lost fish head instrument in step S51, use the logging cable to raise the array electromagnetic scanning lost fish head instrument, and according to the received induced electric signals, the depth where the magnetic conductive medium changes from existence to nonexistence is the depth of the lost fish head; Step S54, at the depth of the lost fish head, periodically excite the second electromagnetic sensor to work with maximum power, start the motor, and perform rotation measurement, when the measurement direction of the second electromagnetic sensor is the same as the direction of the lost fish head, the induced signal value received by the second electromagnetic sensor is maximum, at this time, the measurement direction of the second electromagnetic sensor is the direction of the lost fish head; Step S55, during rotation measurement, the electromagnetic sensor array and the azimuth sensor rotate synchronously, according to the measurement results of the azimuth sensor, the actual azimuth of the second electromagnetic sensor measurement is determined, and then the actual azimuth of the lost fish head is determined; Step S56, the induced signal value received by the electromagnetic sensor array is linearly related to the distance of the lost fish head, at the determined azimuth of the lost fish head, the excitation power of the first electromagnetic sensor and the second electromagnetic sensor is changed, according to the electromagnetic induction signals received by the first electromagnetic sensor and the second electromagnetic sensor, the distance of the lost fish head is analyzed; Step S57, at different depths below the depth of the lost fish head, steps S54 to S56 are repeatedly repeated, and the posture of the broken casing is analyzed according to the measurement results, to provide data support for formulating a reasonable fishing casing scheme.

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