Underground fish head lateral magnetic detection device and method

Abstract

The invention belongs to the technical field of underground fish salvage, and provides an underground fish head lateral magnetic detection device and method.The underground fish head lateral magnetic detection device comprises a measuring probe tube which is placed in a salvage borehole and used for detecting a variable flow magnetic field at the position of a fish; one end of the releasing tool is connected with the measuring probe; the converter is used for generating a variable-flow magnetic field at a fish falling position and is connected with one end, far away from the measuring probe, of the releasing tool; one end of the cable extends into the salvage borehole to be connected with the measuring probe, and the other end of the cable is connected with a ground industrial control unit located on the ground; the salvage well hole is located on one side of the fish well hole, and fishes are reserved in the fish well hole. According to the device, a variable-flow magnetic field can be generated at a fish falling position through the converter, then a variable-flow magnetic field signal at the fish falling position can be obtained in real time through the measuring probe, the measuring probe and the converter are arranged in a fishing fish eye on one side of the fish falling position, the positioning error can be reduced, meanwhile, the converter is remotely controlled through a controller on the ground, and the positioning accuracy is improved. Magnetic field interference can be reduced.

Description

Technical Field

[0001] This invention belongs to the field of underground fish retrieval technology, and specifically relates to an underground fish head lateral magnetic detection device and method. Background Technology

[0002] Fish retrieval from a well is a highly challenging well repair operation. Due to the limited space in the well, delayed surface feedback, and unpredictable formations, there is a lack of technical means to accurately locate the fish's head. During the retrieval process, new wellbores are often created, significantly increasing the difficulty of subsequent operations.

[0003] The existing fish head detection methods mainly include three types: electromagnetic, acoustic, and imaging.

[0004] Electromagnetic methods can be divided into two categories: active and passive. Active methods require emitting electromagnetic waves towards the fish's head and then locating it from below. Passive methods require detecting the magnitude of the remaining magnetic field after the fish has fallen in. Both methods require drilling through the fish's head for detection, and the fish's head position can only be deduced from the lower detection, resulting in low accuracy and efficiency.

[0005] The acoustic method locates fish by emitting ultrasonic waves towards their heads. However, due to the close proximity, the reflected waves and the direct waves overlap significantly, making them difficult to extract. This results in low accuracy when detecting fish heads at close range.

[0006] The imaging method involves sending a camera to the location of the fish's head and directly determining its position and shape through image transmission. However, this method requires replacing all the fluid in the well with clean water, but the wells used to locate fish heads are often open-hole wells, which do not have the conditions to replace the water with clean water.

[0007] Therefore, improving the positioning accuracy and efficiency of existing technologies for locating fish heads is an urgent problem to be solved. Summary of the Invention

[0008] To address at least one of the problems in the background art, the present invention proposes a downhole fish-head lateral magnetic detection device and method.

[0009] To achieve the above objectives, the present invention adopts the following technical solution:

[0010] A lateral magnetic detection device for fish heads in wells includes:

[0011] A measuring probe is placed in the retrieval well to detect the variable magnetic field at the point where the fish fell;

[0012] A drop tool, one end of which is connected to the measuring probe;

[0013] A converter is used to generate a variable magnetic field at the point where the fish falls, and is connected to the end of the release tool away from the measuring probe.

[0014] The cable extends from one end into the retrieval wellhead and connects to the measuring probe, while the other end connects to the ground control unit located on the ground.

[0015] The retrieval well is located on one side of the fish-falling well, and the fish-falling well contains fish.

[0016] Furthermore, the dropping tool includes an upper connector, a dropping clipper, a transmission sleeve, and a lower connector connected in sequence;

[0017] The end of the upper connection away from the release clipper is connected to the measuring probe;

[0018] The end of the lower connection away from the transmission sleeve is connected to the converter.

[0019] Furthermore, the ground control unit includes a portable chassis, a computer, a power supply, and a controller;

[0020] The portable chassis is electrically connected to a cable;

[0021] The computer is electrically connected to the portable chassis.

[0022] The power supply is electrically connected to the portable chassis;

[0023] The controller is connected to the converter signal and is used to control the opening and closing of the converter.

[0024] A method for lateral magnetic detection of a fish head in a well, used in the aforementioned lateral magnetic detection device for a fish head in a well, includes the following steps:

[0025] Place the measuring probe at the bottom of the retrieval wellbore;

[0026] The ball is thrown and pressed against the device to separate the converter;

[0027] Raise the measuring probe to the side above the fallen fish;

[0028] Turn on the converter to generate a magnetic field signal at the point where the fish falls;

[0029] The magnetic field signal is collected by the measuring probe and transmitted to the ground control unit to calculate the position of the fish in the fish-falling well.

[0030] Once the location of the fish has been determined, the converter is retrieved.

[0031] Furthermore, the converter is disengaged by throwing and pressing the ball with the throwing tool, including the following steps:

[0032] The ball is thrown into the throwing tool, creating pressure inside the tube;

[0033] The pressure inside the tube causes the release shears to break;

[0034] After the release shear pin is disconnected, the transmission sleeve separates from the lower connection, thus separating the release shear pin from the converter.

[0035] Furthermore, the converter is turned on to generate a magnetic field signal at the location where the fish lands, including the following steps:

[0036] The converter is started via the ground control unit;

[0037] After the converter is turned on, the alternating current accumulates in the fish and generates an alternating magnetic field.

[0038] Furthermore, magnetic field signals are collected by measuring probes and transmitted to the ground control unit to calculate the position of the fish in the fish-dropping well, including the following steps:

[0039] The actual value of the magnetic field signal obtained by measuring the probe;

[0040] Loop steps: Preset the coordinates of the fish landing;

[0041] The predicted value of the magnetic field signal is calculated based on the preset coordinates of the falling fish.

[0042] Calculate the difference between the actual value and the predicted value. If the difference is less than the target amount, the preset coordinates of the fish falling are determined to be the actual coordinates. If the difference is greater than or equal to the target amount, return to the loop step to recalculate.

[0043] Furthermore, the predicted value of the magnetic field signal satisfies the following formula:

[0044]

[0045] In the formula, I is the source current; L is the path from the converter to the fish head position, which is the integration path; dl is a small current element of the source current; e r denoted as the unit vector of the current element pointing to the point to be determined; r is the distance between the measuring probe 1 and the fish 11; μ0 is the vacuum permeability.

[0046] Furthermore, the difference between the actual value and the predicted value is calculated, satisfying the following formula:

[0047]

[0048] In the formula, B is the predicted value of the magnetic field signal; This represents the actual value of the magnetic field signal.

[0049] Furthermore, recycling the converter includes the following steps:

[0050] Use a retrieval tool to align the internal thread of the hand-dropping tool and retrieve the hand-dropping tool and the converter together.

[0051] The beneficial effects of this invention are:

[0052] 1. The device of the present invention can generate a variable magnetic field at the point where the fish falls through the converter, and then the variable magnetic field signal at the point where the fish falls can be obtained in real time by using a measuring probe. The measuring probe and the converter are located in the fish retrieval eye on the side where the fish falls, which can reduce positioning error. At the same time, the converter is remotely controlled by a ground controller, which can reduce magnetic field interference.

[0053] 2. The method of this invention involves lowering the downhole tool string to the bottom of the well during the fish retrieval process, performing full-well attitude correction, dropping a ball to pressurize the release tool to separate the converter, then raising the measuring probe above the fish's head, recalibrating the attitude, and then the remote controller sends an activation message to the converter. The alternating current generated by the converter is focused on the fish's location and generates an upward current. All ground control devices are activated, and the measuring probe measures the gravity field signal and the magnetic field signal generated upward by the fish. By calculating the difference between the measured magnetic field signal and the predicted magnetic field signal, the accuracy of the predicted fish's coordinates can be directly determined, thus obtaining the fish's head location result. Compared with ultrasonic waves, this process avoids acoustic interference caused by short distances, improves positioning accuracy, and thus improves the efficiency of finding the fish's head, thereby significantly reducing the initial investment cost.

[0054] 3. This invention has no special requirements for wellbore conditions, lowering the operational threshold;

[0055] 4. In the positioning process, this invention predicts the location of the fish and calculates the predicted magnetic field signal. Then, it compares the predicted magnetic field signal with the actual magnetic field signal to determine whether the predicted coordinates are accurate. If they are not accurate, the process is repeated until the predicted location is the actual location of the fish. This process continuously approaches the actual location of the fish, providing theoretical support for the positioning of the fish.

[0056] Other features and advantages of the invention will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures pointed out in the description and the drawings. Attached Figure Description

[0057] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0058] Figure 1 A schematic diagram of the structure of a downhole fish-head lateral magnetic detection device according to the present invention is shown;

[0059] Figure 2 A schematic diagram of the structure of the drop tool of the present invention is shown;

[0060] Figure 3 A spatial schematic diagram of the measuring probe and converter of the present invention is shown;

[0061] Figure 4 A flowchart of a downhole fish-head lateral magnetic detection method according to the present invention is shown;

[0062] Figure 5 A schematic diagram of the theoretical magnetic field distribution near the fish head of the present invention is shown.

[0063] In the diagram: 1. Measuring probe; 2. Drop tool; 201. Upper connection; 202. Drop shears; 203. Torque transmission sleeve; 204. Lower connection; 3. Converter; 4. Cable; 5. Portable chassis; 6. Computer; 7. Power supply; 8. Controller; 9. Fishing well; 10. Fish dropping well; 11. Fish dropping; 12. Alternating current; 13. Alternating magnetic field. Detailed Implementation

[0064] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0065] This invention proposes a lateral magnetic detection device for fish heads in underground wells, which can significantly improve the positioning accuracy and efficiency of the fallen fish 11. For example... Figure 1 As shown, the detection device of the present invention includes a measuring probe 1, a drop tool 2, a converter 3, a cable 4, a ground control unit, a retrieval wellbore 9, a fish-dropping wellbore 10, and a fish-dropping wellbore 11.

[0066] The retrieval wellbore 9 is located to one side of the fish-falling wellbore 10, and the fish-falling wellbore 11 is located inside the fish-falling wellbore 10. The measuring probe 1 is placed inside the retrieval wellbore 9 and is connected to the surface control unit via cable 4. One end of the drop tool 2 is connected to the measuring probe 1. The converter 3 is connected to the end of the drop tool 2 away from the measuring probe 1.

[0067] In addition, Figure 1 In this process, the release tool 2 can detach the converter 3, and after detachment, the converter 3 can be placed at the bottom of the retrieval well 9 so that current can be generated below the fish 11, producing an alternating magnetic field 13 at the fish 11. At the same time, the measuring probe 1 can be moved to a position above the fish 11 to detect the alternating magnetic field 13 of the fish 11, thereby obtaining the position of the fish 11.

[0068] It should be noted that since the retrieval well 9 is located on one side of the fish-falling well 10, placing measuring equipment inside the retrieval well 9 can reduce environmental interference to the fish-falling well 10 and reduce positioning errors.

[0069] In addition, Figure 1 In this system, the measuring probe 1 is used to detect magnetic and gravitational fields. It is connected to the converter 3 (mobile power supply) via the drop tool 2. The system includes a three-axis fluxgate sensor, a three-axis accelerometer, a three-axis gyroscope sensor, and a circuit board. The three-axis fluxgate sensor detects magnetic field signals along the X, Y, and Z axes; the three-axis accelerometer detects gravitational field signals along the X, Y, and Z axes; the three-axis gyroscope sensor detects angular velocity signals along the X, Y, and Z axes; and the circuit board houses and connects the relevant electronic components.

[0070] In addition, Figure 1 In this system, converter 3 (mobile power supply) is used for downhole discharge and to form a circuit. It includes a battery module, a rectifier, a remote receiver, and a circuit board. The battery module provides direct current (DC) power to the rectifier, remote receiver, and circuit board. The rectifier converts the DC power into alternating current (AC) power of a specified frequency. The remote receiver receives commands from a remote controller on the ground. The circuit board houses and connects relevant electronic components.

[0071] In addition, Figure 1 In this system, the ground control unit includes a portable chassis 5, a computer 6, a power supply 7, and a controller 8. The portable chassis 5 is electrically connected to the cable 4, the computer 6 is electrically connected to the portable chassis 5, and the power supply 7 is electrically connected to the portable chassis 5. The controller 8 is signal-connected to the converter 3 and is used to control the opening and closing of the converter 3.

[0072] It should be noted that the ground control unit is used to provide the necessary operating conditions for the equipment. Among them, the portable chassis 5 is used for data decoding of the measuring probe 1, the power supply 7 is used to provide operating power to the downhole tool string, the controller 8 is used to remotely send on or off information to the converter 3 (mobile power supply), and the computer 6 is used to run the positioning algorithm and obtain the final positioning result.

[0073] like Figure 2 As shown, the release tool 2 includes an upper connector 201, a release shear pin 202, a torque transmission sleeve 203, and a lower connector 204 connected sequentially from the wellhead to the bottom of the well. Moreover, the end of the upper connector 201 away from the release shear pin 202 is connected to the measuring probe 1, and the end of the lower connector 204 away from the torque transmission sleeve 203 is connected to the converter 3.

[0074] In addition, Figure 2In the process, after the drop tool 2 is lowered into the well to the designated position, pressure circulation (drilling fluid flows into the probe through the holes in the probe casing and then into the drop tool 2) is used to pressurize the well. The pressure pushes the torque sleeve 203 to shear the drop shear pin 202 and move downwards until the torque sleeve 203 is completely disengaged from the lower connection 204, thus disabling the torque transmission function. By directly rotating the tubing string in the forward direction, separation can be achieved at the left-hand thread of the upper connection 201, completing the operation of the converter 3 and the lower connection 204 (mobile power supply) falling to the bottom of the well together. When retrieval is required, a special retrieval tool is used to engage the retrieval thread inside the lower connection 204 inside the drop tool 2 to retrieve the tubing string.

[0075] like Figure 4 The image shows a method for lateral magnetic detection of a fish head in a well, used in the aforementioned lateral magnetic detection device for a fish head in a well, comprising the following steps:

[0076] S1: Place the measuring probe 1 at the bottom of the retrieval wellbore 9.

[0077] S2: Throw the ball at the drop tool 2 to press down, causing the converter 3 to separate.

[0078] S3: Raise the measuring probe 1 to the upper side of the fish dropper 11.

[0079] S4: Turn on converter 3 to generate a magnetic field signal at the point where the fish falls 11.

[0080] S5: Collect magnetic field signals through measuring probe 1 and transmit them to the ground control unit to calculate the position of fish 11 in fish well 10.

[0081] S6: After the location of fish 11 is determined, reclaim converter 3.

[0082] In S2, the ball is thrown and pressed by the throwing tool 2 to separate the converter 3. This includes the following steps:

[0083] S201: Throw the ball into the throwing tool 2 to generate pressure inside the tube.

[0084] S202: The pressure inside the pipe causes the release screw 202 to disconnect.

[0085] S203: After the release screw 202 is disconnected, the transmission sleeve 203 is separated from the lower connection 204, and at the same time the connection between the lower connection 204 and the converter 3 is released, realizing the separation of the release screw from the converter 3.

[0086] In S4, inverter 3 is turned on to generate a magnetic field signal at the point where the fish falls (11). The specific steps include:

[0087] S301: Turn on converter 3 via ground control unit.

[0088] S302: After the converter 3 is turned on, the alternating current 12 gathers at the fish 11 and generates an alternating magnetic field 13.

[0089] In S5, magnetic field signals are collected through measuring probe 1 and transmitted to the ground control unit to calculate the position of the fish drop 11 in the fish drop well 10. The specific steps include:

[0090] S501: The actual value of the magnetic field signal obtained by measuring probe 1. Specifically, after the converter 3 (mobile power supply) is turned on, measuring probe 1 collects the triaxial component B of the magnetic field signal generated by the falling fish. x B y B z The resultant vector is calculated.

[0091] It should be noted that, as Figure 5 As shown, this is the theoretical magnetic field distribution near the fish head. The magnitude and direction of the magnetic field signal at any point in space are different.

[0092] S502: Loop Step: Preset the coordinates of the fish 11. Specifically, the preset coordinates of the fish 11 are spatial coordinates (x...). l y l , z l Therefore, the predicted value of the magnetic field signal satisfies the following formula:

[0093]

[0094] In the formula, I is the source current; L is the path from converter 3 to the fish head position, which is the integration path; dl is a small current element of the source current; e r denoted as the unit vector of the current element pointing to the point to be determined; r is the distance between the measuring probe 1 and the fish 11; μ0 is the vacuum permeability.

[0095] S503: Calculate the predicted value of the magnetic field signal based on the preset coordinates of the fish 11.

[0096] S504: Calculate the difference between the actual value and the predicted value. If the difference is less than the target amount, the preset coordinates of the fish 11 are determined to be the actual coordinates. If the difference is greater than or equal to the target amount, return to the loop step to recalculate.

[0097] In S504, the difference between the actual value and the predicted value is calculated according to the following formula:

[0098]

[0099] In the formula, B is the predicted value of the magnetic field signal; This represents the actual value of the magnetic field signal.

[0100] It should be noted that, as Figure 3As shown, a spatial coordinate system needs to be established during the entire magnetic field detection process. The origin can be any point in space, such as the wellhead or bottom of retrieval well 9, or the wellhead or bottom of fish-falling well 10. Then, based on the origin, the coordinates of any point within retrieval well 9 and fish-falling well 10 can be determined. Therefore, attitude correction can be performed using the triaxial accelerometer and triaxial gyroscope in probe 1 to obtain the depth l, well inclination α, and azimuth at different locations. The spatial coordinates (x, y, z) of all points on the wellbore trajectory (fishing wellbore 9 and fish-falling wellbore 10) are obtained by spline interpolation.

[0101] In the spatial coordinate system, the coordinates of any point in the fish-falling well 9 and the fishing well 10 can be obtained directly. The spatial coordinates of the bottom P0 of the fish-falling well 10 are (x0, y0, z0). In addition, the spatial coordinates (x1, y1, z1) of the measuring probe 1 raised above the fish head at point P in the fishing well 9 can also be obtained directly.

[0102] Therefore, in S502,

[0103] In the formula, (x1, y1, z1) are the spatial coordinates of measuring probe 1, which are known quantities; (x l y l , z l ) represents the coordinates of the fish 11, which is the quantity to be measured; r represents the distance between the fish 11 and the measuring probe 1.

[0104] It should be noted that in the step S504 returning to S502, all (x) are traversed according to a certain step size Δl. l +i×Δl,y l +j×Δl,z l +k×Δl), where i, j, and k are x l y l , z l The number of iterations. Until... At this time (x) l y l , z l The corresponding position is fish 11. (x) l y l , z l Substituting into formula (3) will give the distance between the fish 11 and the measuring probe 1.

[0105] It should be further explained that in step S5, it is not necessary to directly calculate the distance between the measuring probe 1 and the fish 11. It is only necessary to obtain the predicted magnetic field signal and the actual magnetic field signal to determine whether the predicted coordinates of the fish 11 are accurate. Then, the distance r can be calculated in reverse by formula (3). This process abandons the traditional ultrasonic distance measurement method and obtains the accurate coordinates of the fish 11 by reverse approximation. Its advantage is that it can overcome the signal interference problem caused by the short distance, reduce the measurement difficulty, and help improve the accuracy.

[0106] In some embodiments, recycling the converter 3 includes the following steps:

[0107] Use a retrieval tool to hook the internal thread of the drop tool 2, and retrieve the drop tool 2 and the converter 3 together.

[0108] It should be noted that during the recovery of converter 3, the corresponding tooling can be placed into the retrieval wellbore 9 on the ground, and then the tooling can be connected to the drop tool 2. Finally, the drop tool 2 and converter 3 can be retrieved together from the ground.

[0109] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A lateral magnetic detection device for fish heads in wells, characterized in that, include: A measuring probe (1) is placed in the retrieval wellbore (9) to detect the variable magnetic field at the location where the fish (11) fell; Disposable tool (2), one end of which is connected to the measuring probe (1); A converter (3) is used to generate a variable magnetic field at the point where the fish falls (11), and is connected to the end of the drop tool (2) away from the measuring probe (1); One end of the cable (4) extends into the retrieval wellbore (9) and connects to the measuring probe (1), while the other end connects to the ground control unit located on the ground. The retrieval well (9) is located on one side of the fish-falling well (10), and the fish-falling well (10) contains fallen fish (11).

2. The downhole fish-head lateral magnetic detection device according to claim 1, characterized in that, The drop tool (2) includes an upper connector (201), a drop clipper (202), a transmission sleeve (203), and a lower connector (204) connected in sequence; The end of the upper connector (201) away from the release scissors (202) is connected to the measuring probe (1); The end of the lower connection (204) away from the transmission sleeve (203) is connected to the converter (3).

3. The downhole fish-head lateral magnetic detection device according to claim 1, characterized in that, The ground control unit includes a portable chassis (5), a computer (6), a power supply (7), and a controller (8); The portable chassis (5) is electrically connected to the cable (4); The computer (6) is electrically connected to the portable chassis (5); The power supply (7) is electrically connected to the portable chassis (5); The controller (8) is signal-connected to the converter (3) and is used to control the opening and closing of the converter (3).

4. A method for lateral magnetic detection of a fish head in a well, used in the lateral magnetic detection device for a fish head in a well as described in any one of claims 1-3, characterized in that, Includes the following steps: Place the measuring probe (1) at the bottom of the retrieval wellbore (9); The ball is thrown and pressed against the discarding tool (2) to separate the converter (3); Raise the measuring probe (1) to the side above the fish (11); Turn on the converter (3) to generate a magnetic field signal at the point where the fish falls (11); The magnetic field signal is collected by measuring probe (1) and transmitted to the ground control unit to calculate the position of the fish (11) in the fish-falling well (10); After the location of the fish (11) is determined, the converter (3) is retrieved.

5. The method for lateral magnetic detection of a fish head in a well according to claim 4, characterized in that, The process of displacing the converter (3) by throwing the ball with the throwing tool (2) includes the following steps: The ball is thrown into the throwing tool (2), generating pressure inside the tube; The pressure inside the tube causes the release scissors (202) to break; After the release screw (202) is disconnected, the transmission sleeve (203) separates from the lower connection (204), thus separating the release screw from the converter (3).

6. The method for lateral magnetic detection of a fish head in a well according to claim 4, characterized in that, Turn on the converter (3) to generate a magnetic field signal at the point where the fish falls (11), including the following steps: The converter is turned on via the ground control unit (3); After the converter (3) is turned on, the alternating current (12) accumulates in the fish (11) and generates an alternating magnetic field (13).

7. The method for lateral magnetic detection of a fish head in a well according to claim 4, characterized in that, The magnetic field signal is collected by measuring probe (1) and transmitted to the ground control unit to calculate the position of the fish (11) in the fish-falling well (10), including the following steps: The actual value of the magnetic field signal obtained by measuring the probe (1); Loop steps: Preset the coordinates of the fish (11); The predicted value of the magnetic field signal is calculated based on the preset coordinates of the falling fish (11); Calculate the difference between the actual value and the predicted value. If the difference is less than the target amount, the preset coordinates of the fish (11) are determined to be the actual coordinates. If the difference is greater than or equal to the target amount, return to the loop step to recalculate.

8. The method for lateral magnetic detection of a fish head in a well according to claim 7, characterized in that, The predicted value of the magnetic field signal satisfies the following formula: In the formula, I is the source current; L is the path from the converter (3) to the fish head position, which is the integration path; dl is a small current element of the source current; e r is the unit vector of the current element pointing to the field point to be determined; r is the distance between the measuring probe (1) and the falling fish (11); μ0 is the vacuum permeability.

9. The method for lateral magnetic detection of a fish head in a well according to claim 7, characterized in that, The difference between the actual value and the predicted value is calculated according to the following formula: In the formula, B is the predicted value of the magnetic field signal; This represents the actual value of the magnetic field signal.

10. A downhole fish-head lateral magnetic exploration method according to any one of claims 4-9, characterized in that, The recycling of the converter (3) includes the following steps: Use a retrieval tool to hook the internal thread of the hand-dropping tool (2) and retrieve the hand-dropping tool (2) together with the converter (3).

Images