An active magnetic measurement system and method for magnetic shielding mode

Abstract

The present invention relates to an active magnetic measurement system and method in a magnetic shielding mode. The system includes: a probe pipe and a measurement tooling; the probe pipe is connected to a cable winch through a cable, the cable winch is connected to a ground host, and the ground host is connected to a computer; the probe pipe includes: a first three-axis fluxgate sensor and a gyro measurement module; the measurement tooling is installed on the ground and communicates with the computer through the ground host; the measurement tooling is used to obtain an alternating magnetic field signal after casing shielding and an alternating magnetic field signal without pipe shielding; the computer is used to determine an attenuation coefficient according to the alternating magnetic field signal after casing shielding and the alternating magnetic field signal without pipe shielding, and review the attenuation coefficient, and further determine the spatial position relationship between the magnetic joint and the probe pipe in the drilling well according to the reviewed attenuation coefficient and the alternating magnetic field signal obtained by the probe pipe. The present invention can improve the accuracy of measurement and positioning in ferromagnetic casings.

Description

Technical Field

[0001] The present invention relates to the field of drilling measurement, and particularly to an active magnetic measurement system and method in a magnetic shielding mode. Background Art

[0002] In geological and oil drilling, in order to precisely control the wellbore trajectory and make the drill bit reach the designated position, instruments are often used for downhole measurement. The active magnetic measurement system is a measurement means with relatively high precision. The basic principle is to rotate an artificial magnetic field with a known intensity to form a regular magnetic field disturbance in space. After the probe receives this disturbance, the relative spatial position relationship between the magnetic field and the probe is resolved through software. In practical applications, this artificial magnetic field is usually formed by embedding rare earth permanent magnets in a cylinder made of non-magnetic material, that is, a magnetic sub, and rotating the magnetic sub to generate an alternating magnetic field signal. The probe is a rod-shaped cylinder composed of various sensors and circuits, and can measure the earth's magnetic field, gravity field, and dynamic alternating magnetic field. When the active magnetic measurement system works, the magnetic sub is driven by a screw motor connected behind to rotate axially to form a magnetic field disturbance. At the other end of the space, usually a probe is placed at the target point. The probe is connected to the lower end of the armored cable on the winch and lowered to the target depth of a completed wellbore. The upper end of the winch cable is connected to the ground host. The host powers the probe and converts the signals collected by the probe, and then sends them to the computer. The computer analyzes the data to obtain the spatial position relationship between the magnetic sub and the probe in the well being drilled. This measurement method is "the probe first locates itself and then locates the magnetic sub", and the probe is responsible for collecting all signal parameters. The probe needs at least three parameters to locate itself: the inclination angle, azimuth, and tool face. Currently, the probe generally uses three-axis fluxgate sensors to measure magnetic-related signals, including the geomagnetic field data for calculating its own azimuth and the alternating magnetic field signal emitted by the magnetic sub.

[0003] In current active magnetic positioning measurements, the probe must be placed in the open hole section of the target wellbore, that is, at a certain distance (at least 2 meters) from ferromagnetic interference objects such as casing and tubing, and the probe will not be placed therein. However, in the drilling fields of petroleum, geology, and soluble solid minerals, ferromagnetic casing is widely used as an effective hole wall support. That is, the casing is a thin-walled cylinder widely used in drilling fields such as petroleum, geology, and soluble solid minerals. It is usually made of steel and has various specifications and production processes. When drilling a hole on the surface, the original formation stress is damaged, and without maintenance, the rock and soil in the hole will collapse. At this time, the casing needs to be lowered, and the annulus formed between the hole wall and the casing is filled with cement to integrate the casing with the formation, achieving the functions of supporting the formation and isolating groundwater. When the probe is placed in the ferromagnetic casing for various reasons, the triaxial fluxgate sensor will be interfered and shielded, and the obtained geomagnetic parameters and magnetic joint signals will also be deformed and distorted. Without these two important data, the existing active magnetic positioning system cannot work properly.

[0004] Based on the above problems, there is an urgent need for an active magnetic measurement system or method in the magnetic shielding mode. Summary of the Invention

[0005] The object of the present invention is to provide an active magnetic measurement system and method in the magnetic shielding mode, which can improve the accuracy of measurement and positioning in ferromagnetic casing.

[0006] To achieve the above object, the present invention provides the following solutions:

[0007] An active magnetic measurement system in the magnetic shielding mode, the active magnetic measurement system includes: a magnetic joint, a cable winch, a ground host, and a computer. The system further includes: a probe and a measurement tooling;

[0008] The probe is connected to the cable winch through a cable, the cable winch is connected to the ground host, and the ground host is connected to the computer; the probe includes: a first triaxial fluxgate sensor and a gyro measurement module; the gyro measurement module is used to measure the azimuth when the first triaxial fluxgate sensor cannot normally measure the azimuth.

[0009] The measurement tooling is installed on the ground and communicates with the computer through the ground host; the measurement tooling is used to obtain the alternating magnetic field signal after being shielded by the casing and the alternating magnetic field signal without being shielded by the pipe; the computer is used to determine the attenuation coefficient according to the alternating magnetic field signal after being shielded by the casing and the alternating magnetic field signal without being shielded by the pipe, and review the attenuation coefficient, and then determine the spatial position relationship between the magnetic joint and the probe in the drilling well according to the reviewed attenuation coefficient and the alternating magnetic field signal obtained by the probe.

[0010] Optionally, the measurement tooling includes: a non-magnetic U-shaped frame, a magnetic emitter, a second three-axis fluxgate sensor, and a non-magnetic centralizer;

[0011] The magnetic emitter is arranged at the end of the first rod of the non-magnetic U-shaped frame and is at a first set distance from the end of the first rod; the second three-axis fluxgate sensor is arranged at the end of the second rod of the non-magnetic U-shaped frame and is at a second set distance from the end of the second rod; the non-magnetic centralizer is arranged between the bottom of the non-magnetic U-shaped frame and the second three-axis fluxgate sensor;

[0012] The non-magnetic centralizer is used to make the axis of the second three-axis fluxgate sensor parallel to the axis of the casing.

[0013] Optionally, the second three-axis fluxgate sensor is coaxial with the second rod of the non-magnetic U-shaped frame.

[0014] An active magnetic measurement method for the magnetic shielding mode, applied to the active magnetic measurement system for the magnetic shielding mode, includes:

[0015] Start the magnetic emitter, and use the second three-axis fluxgate sensor to obtain the alternating magnetic field signal without pipe shielding;

[0016] Insert the second rod of the non-magnetic U-shaped frame into the casing, start the magnetic emitter, and use the second three-axis fluxgate sensor to obtain the alternating magnetic field signal after casing shielding;

[0017] Determine the attenuation coefficient according to the alternating magnetic field signal without pipe shielding and the alternating magnetic field signal after casing shielding;

[0018] Review the attenuation coefficient to determine the reviewed attenuation coefficient;

[0019] Determine the spatial position relationship between the magnetic joint and the probe in the drilling well according to the alternating magnetic field signal obtained by the probe and the reviewed attenuation coefficient.

[0020] Optionally, the attenuation coefficient includes: the attenuation coefficient in the radial plane and the axial attenuation coefficient.

[0021] Optionally, the step of reviewing the attenuation coefficient to determine the reviewed attenuation coefficient specifically includes:

[0022] Vary the attenuation coefficient at a set gradient to determine a set of attenuation coefficients;

[0023] Determine the corresponding total field strength according to the alternating magnetic field signal obtained by the probe and each attenuation coefficient in the set of attenuation coefficients;

[0024] Determine the error coefficient according to the minimum value and the maximum value in the total field strength of each attenuation coefficient;

[0025] Take the attenuation coefficient corresponding to the minimum error coefficient as the rechecked attenuation coefficient.

[0026] An active magnetic measurement system for a magnetic shielding mode, which is used to implement the active magnetic measurement method for a magnetic shielding mode, includes:

[0027] An alternating magnetic field signal acquisition unit without pipe shielding, which is used to start a magnetic emitter and acquire an alternating magnetic field signal without pipe shielding by using a second three-axis fluxgate sensor;

[0028] An alternating magnetic field signal acquisition unit after casing shielding, which is used to insert the second rod of a non-magnetic U-shaped frame into the casing, start the magnetic emitter, and acquire an alternating magnetic field signal after casing shielding by using a second three-axis fluxgate sensor;

[0029] An attenuation coefficient determination unit, which is used to determine the attenuation coefficient according to the alternating magnetic field signal without pipe shielding and the alternating magnetic field signal after casing shielding;

[0030] A rechecked attenuation coefficient determination unit, which is used to recheck the attenuation coefficient and determine the rechecked attenuation coefficient;

[0031] A spatial position relationship determination unit, which is used to determine the spatial position relationship between the magnetic joint and the probe in the well under drilling according to the alternating magnetic field signal acquired by the probe and the rechecked attenuation coefficient.

[0032] Optionally, the attenuation coefficient includes: the attenuation coefficient in the radial plane and the axial attenuation coefficient.

[0033] Optionally, the rechecked attenuation coefficient determination unit specifically includes:

[0034] An attenuation coefficient set determination subunit, which is used to change the attenuation coefficient at a set gradient and determine an attenuation coefficient set;

[0035] A total field strength determination subunit, which is used to determine the corresponding total field strength according to the alternating magnetic field signal acquired by the probe and each attenuation coefficient in the attenuation coefficient set;

[0036] An error coefficient determination subunit, which is used to determine the error coefficient according to the minimum and maximum values of the total field strength of each attenuation coefficient;

[0037] A rechecked attenuation coefficient determination subunit, which is used to take the attenuation coefficient corresponding to the minimum error coefficient as the rechecked attenuation coefficient.

[0038] According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0039] An active magnetic measurement system and method for magnetic shielding mode provided by the present invention can measure the azimuth using a gyro measurement module when the first three-axis fluxgate sensor cannot measure the azimuth normally, and can measure normally in a magnetic anomaly environment; the measurement tooling is installed on the ground and communicates with a computer through a ground host; the attenuation coefficient is determined according to the alternating magnetic field signal after casing shielding and the alternating magnetic field signal without pipe shielding obtained by the measurement tooling, and the attenuation coefficient is reviewed. Furthermore, the spatial position relationship between the magnetic joint and the probe in the well being drilled is determined according to the reviewed attenuation coefficient and the alternating magnetic field signal obtained by the probe. Without removing the bottom hole material, the attenuation coefficient of the extremely low frequency magnetic field of the casing located at the bottom of the well is measured using the magnetic field characteristics, and the alternating magnetic field signal after shielding is restored, so that the active magnetic measurement system can be normally applied to the geomagnetic anomaly area and can also perform positioning measurement under the shielding of ferromagnetic casings. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0041] Figure 1 It is a schematic structural diagram of the measurement tooling in an active magnetic measurement system for magnetic shielding mode provided by the present invention;

[0042] Figure 2 It is a schematic diagram of a static magnetic field coordinate system;

[0043] Figure 3 It is a schematic diagram of a rotating magnetic field coordinate system;

[0044] Figure 4 It is a schematic flow diagram of an active magnetic measurement method for magnetic shielding mode provided by the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0045] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0046] The object of the present invention is to provide an active magnetic measurement system and method for magnetic shielding mode, which can improve the accuracy of measurement and positioning in ferromagnetic casings.

[0047] To make the above objects, features, and advantages of the present invention more obvious and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0048] An active magnetic measurement system for a magnetic shielding mode, the active magnetic measurement system comprising: a magnetic joint, a cable winch, a ground host, and a computer. The system further comprises: a probe and a measurement tooling;

[0049] The probe is connected to the cable winch through a cable, the cable winch is connected to the ground host, and the ground host is connected to the computer; the probe comprises: a first three-axis fluxgate sensor and a gyro measurement module; the gyro measurement module is used to measure the azimuth when the first three-axis fluxgate sensor cannot normally measure the azimuth;

[0050] The measurement tooling is installed on the ground and communicates with the computer through the ground host; the measurement tooling is used to obtain the alternating magnetic field signal after being shielded by the casing and the alternating magnetic field signal without being shielded by the pipe; the computer is used to determine the attenuation coefficient according to the alternating magnetic field signal after being shielded by the casing and the alternating magnetic field signal without being shielded by the pipe, and to review the attenuation coefficient, and then to determine the spatial position relationship between the magnetic joint and the probe in the well being drilled according to the reviewed attenuation coefficient and the alternating magnetic field signal obtained by the probe.

[0051] As Figure 1 shown, the measurement tooling comprises: a non-magnetic U-shaped frame, a magnetic emitter, a second three-axis fluxgate sensor, and a non-magnetic centralizer;

[0052] The magnetic emitter is arranged at the end of the first rod of the non-magnetic U-shaped frame and is at a first set distance from the end of the first rod; the second three-axis fluxgate sensor is arranged at the end of the second rod of the non-magnetic U-shaped frame and is at a second set distance from the end of the second rod; the non-magnetic centralizer is arranged between the bottom of the non-magnetic U-shaped frame and the second three-axis fluxgate sensor; the first set distance and the second set distance are different.

[0053] The non-magnetic centralizer is used to make the axis of the second three-axis fluxgate sensor parallel to the axis of the casing.

[0054] Except for the small magnetic emitter, the whole set of measurement tooling is made of non-magnetic materials, has a certain rigidity, and is not easy to deform.

[0055] The second three-axis fluxgate sensor is coaxial with the second rod of the non-magnetic U-shaped frame.

[0056] The magnetic joint is located in the drilling well under construction, connected to the drill bit at the front and to the screw rod at the back. The magnetic joint rotates with the screw rod, generating an alternating magnetic field signal. The probe is placed at the depth of the underground target ore layer to collect the alternating magnetic field signal emitted by the magnetic joint. The probe is connected to the winch on the ground through an armored cable, and the other end of the cable on the winch is connected to the ground host. After the probe collects data, it transmits the analog signal to the ground host through the cable. The function of the host is to supply power to the probe, convert the analog signal into a digital signal, and then transmit it to the computer. There is corresponding acquisition software on the computer, which can control the underground probe to perform various functions. At the same time, there is also analysis software, which can obtain the positional relationship between the probe and the magnetic joint (drill bit) by analyzing the data collected by the probe. Through this positional relationship, the deviation between the current drill bit and the probe can be known, and the trajectory can be adjusted to reach the target position.

[0057] The specific measurement steps are as follows:

[0058] 1) The magnetic joint is connected behind the drill bit and lowered into the drilling well under construction for normal drilling operation. The probe is lowered to the target location and is blocked in the ferromagnetic casing for various reasons. The first three-axis fluxgate sensor cannot measure the azimuth normally. At this time, the gyro measurement module in the probe is started to measure the true azimuth (B). By querying the local magnetic declination (C), the azimuth (A) is calculated, and A = B + C.

[0059] 2) When the drilling well under construction drills to a certain distance (such as 100 meters) from the probe, it enters the alternating magnetic field signal measurement stage. At this time, the drilling of the drilling well under construction stops, and the magnetic joint is rotated in place. Then the probe is started, and the first three-axis fluxgate sensor is used to capture the alternating magnetic field signal emitted by the magnetic joint. Since the probe is located inside the casing, after the alternating magnetic field signal is shielded by the casing, the amplitude of the signal will become smaller.

[0060] 3) Ground measurement of the casing attenuation coefficient. Find a complete casing of the same specification and model as the downhole casing on the ground and place it in an environment with less magnetic interference. Using the measurement tooling, install a suitable type of centralizer at one end of the second three-axis fluxgate sensor and insert it into the casing to a depth of at least 1 meter. The end with the small magnetic field transmitter is outside the casing, and it is ensured that there are no other objects blocking between the second three-axis fluxgate sensor and the transmitter except the measured casing. The function of the non-magnetic centralizer is to ensure that the axis of the three-axis fluxgate sensor is parallel to the axis of the casing. After the second three-axis fluxgate sensor is connected to the ground host and the computer, turn on the magnetic transmitter. With the whole set of tooling stationary, start the probe to measure the alternating magnetic field signal after being shielded by the casing, which are Bx, By, Bz respectively. The Bz direction is the same as the axis of the probe, and Bx and By are radial, and the three are perpendicular to each other in pairs.

[0061] Take out the measuring tooling from the casing. With the relative attitude of the magnetic transmitter and the probe tube unchanged, place it in an environment far from the casing and with less magnetic interference. Then start the magnetic field transmitter again to measure the three-axis magnetic field parameters without casing shielding, Bx1, By1, Bz1.

[0062] Let

[0063] Two initial attenuation coefficients are obtained: S1 = BR / BR1, S2 = Bz / Bz1;

[0064] 4) Attenuation coefficient review and positioning calculation. After measuring the magnetic joint signal, the original alternating magnetic field data is obtained, which is shielded by the casing. Use the initial attenuation coefficient obtained in the previous step to restore the signal and then perform normal positioning calculation. Because after the casing is lowered into the formation, deformation and corrosion may occur, and its magnetic shielding performance may be different from that of the intact casing on the surface, so further review calculation is required.

[0065] The principle of review is:

[0066] As Figure 2 shown is a three-dimensional coordinate system of a static magnetic field. A certain cylindrical permanent magnet is located at the origin O of the coordinate, the NS poles coincide with the Z axis, P is an arbitrary point in space, the distance of the connecting line OP from the origin is r, and the volume of the magnet is much smaller than r, which can be assumed as a magnetic dipole. Then the magnetic field expression at the spatial point P:

[0067]

[0068] In the above formula, M is the magnetic moment value, and μ0 is the magnetic permeability of vacuum.

[0069] The total magnetic field intensity can be written as:

[0070]

[0071] Substitute formula (1) into the formula to get:

[0072]

[0073] The magnet rotates around the Y axis in the XZ plane. No matter where the NS poles turn to, a coordinate system as Figure 3 shown can be established. The projection of the connecting line OP on the new X 1 Z 1 plane will change, and the angular values θ and will change, but the magnetic field expression is the same as (1).

[0074] According to formulas (1) and (2), the total magnetic field intensity can be written as:

[0075]

[0076] As can be seen from the above formula, when the magnetic field rotates around the Y-axis, the total magnetic field strength is related to the angles between the connection line OP and the N and S poles of the magnet. When ψ = π / 2, Bt has a minimum value:

[0077]

[0078] When ψ is the smallest, Bt has a maximum value:

[0079]

[0080] Comparing formula (7) with formula (6), the formula can be obtained:

[0081]

[0082] where

[0083]

[0084] S1 and S2 are the attenuation coefficients measured by the tooling in the above third step. Starting with these as the initial values, each time (S1, S2) i changes, the following operations are performed on the original data:

[0085]

[0086] Using the normal positioning method, the corresponding results are obtained using formula (1)

[0087] The total field value Bt is obtained according to formula (2) i , and two maximum and minimum values are found among a series of total field values, which are Bt maxi and Bt mini . The formula (7) is changed and the absolute value is taken. For each set of attenuation coefficients (S1, S2) i there is

[0088]

[0089] where

[0090] The attenuation coefficient at the minimum value in formula (10) is the true attenuation coefficient of the downhole casing, and the result at this time is also the spatial position relationship between the magnetic joint and the probe. At this time is the final result, r is the distance from the magnetic field emission source to the probe, and the latter two are angle values;

[0091] Figure 4 is a schematic flow diagram of an active magnetic measurement method for the magnetic shielding mode provided by the present invention, as Figure 4As shown in the figure, an active magnetic measurement method for magnetic shielding mode provided by the present invention is applied to the active magnetic measurement system for magnetic shielding mode, and includes:

[0092] S401, start the magnetic emitter, and use the second three-axis fluxgate sensor to obtain the alternating magnetic field signal without pipe shielding;

[0093] S402, insert the second rod of the non-magnetic U-shaped frame into the casing, start the magnetic emitter, and use the second three-axis fluxgate sensor to obtain the alternating magnetic field signal after casing shielding;

[0094] S403, determine the attenuation coefficient according to the alternating magnetic field signal without pipe shielding and the alternating magnetic field signal after casing shielding;

[0095] S404, review the attenuation coefficient to determine the reviewed attenuation coefficient;

[0096] S404 specifically includes:

[0097] Vary the attenuation coefficient at a set gradient to determine a set of attenuation coefficients;

[0098] According to the alternating magnetic field signal obtained by the probe and each attenuation coefficient in the set of attenuation coefficients, determine the corresponding total field intensity;

[0099] Determine the error coefficient according to the minimum and maximum values of the total field intensity of each attenuation coefficient;

[0100] Take the attenuation coefficient corresponding to the minimum error coefficient as the reviewed attenuation coefficient.

[0101] S405, determine the spatial position relationship between the magnetic joint and the probe in the drilling well according to the alternating magnetic field signal obtained by the probe and the reviewed attenuation coefficient.

[0102] The attenuation coefficient includes: the attenuation coefficient in the radial plane and the axial attenuation coefficient.

[0103] An active magnetic measurement system for magnetic shielding mode for implementing the active magnetic measurement method for magnetic shielding mode includes:

[0104] An alternating magnetic field signal acquisition unit without pipe shielding, which is used to start the magnetic emitter and use the second three-axis fluxgate sensor to obtain the alternating magnetic field signal without pipe shielding;

[0105] An alternating magnetic field signal acquisition unit after casing shielding, which is used to insert the second rod of the non-magnetic U-shaped frame into the casing, start the magnetic emitter, and use the second three-axis fluxgate sensor to obtain the alternating magnetic field signal after casing shielding;

[0106] An attenuation coefficient determination unit, configured to determine an attenuation coefficient based on an alternating magnetic field signal without casing shielding and an alternating magnetic field signal after casing shielding;

[0107] A verified attenuation coefficient determination unit, configured to verify the attenuation coefficient and determine a verified attenuation coefficient;

[0108] A spatial position relationship determination unit, configured to determine the spatial position relationship between the magnetic joint and the probe in the well being drilled based on the alternating magnetic field signal obtained by the probe and the verified attenuation coefficient.

[0109] The attenuation coefficient includes: an attenuation coefficient in the radial plane and an axial attenuation coefficient.

[0110] The verified attenuation coefficient determination unit specifically includes:

[0111] An attenuation coefficient set determination subunit, configured to vary the attenuation coefficient at a set gradient to determine an attenuation coefficient set;

[0112] A total field strength determination subunit, configured to determine a corresponding total field strength based on the alternating magnetic field signal obtained by the probe and each attenuation coefficient in the attenuation coefficient set;

[0113] An error coefficient determination subunit, configured to determine an error coefficient based on the minimum value and the maximum value in the total field strength of each attenuation coefficient;

[0114] A verified attenuation coefficient determination subunit, configured to use the attenuation coefficient corresponding to the minimum error coefficient as the verified attenuation coefficient.

[0115] The various embodiments in this specification are described in a progressive manner. Each embodiment focuses on the differences from other embodiments. The same or similar parts among the various embodiments can be referred to each other. For the system disclosed in the embodiments, since it corresponds to the method disclosed in the embodiments, the description is relatively simple. For the relevant parts, reference can be made to the description in the method part.

[0116] Specific examples are used in this article to elaborate on the principles and implementation manners of the present invention. The descriptions of the above embodiments are only used to help understand the method of the present invention and its core idea; at the same time, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation manners and application scopes. In summary, the content of this specification should not be construed as a limitation to the present invention.

Claims

1. An active magnetic measurement system for magnetic shielding mode, the active magnetic measurement system comprising: A magnetic joint, a cable winch, a ground host and a computer, characterized in that it further comprises: a probe pipe and a measurement tooling; The probe pipe is connected to the cable winch through a cable, the cable winch is connected to the ground host, and the ground host is connected to the computer; the probe pipe includes: a first three-axis fluxgate sensor and a gyro measurement module; the gyro measurement module is used to measure the azimuth when the first three-axis fluxgate sensor cannot normally measure the azimuth; The measurement tooling is installed on the ground and communicates with the computer through the ground host; the measurement tooling is used to obtain the alternating magnetic field signal after casing shielding and the alternating magnetic field signal without pipe shielding; the computer is used to determine the attenuation coefficient according to the alternating magnetic field signal after casing shielding and the alternating magnetic field signal without pipe shielding, and review the attenuation coefficient, and then determine the spatial position relationship between the magnetic joint and the probe pipe in the drilling well according to the reviewed attenuation coefficient and the alternating magnetic field signal obtained by the probe pipe; The measurement tooling includes: a non-magnetic U-shaped frame, a magnetic transmitter, a second three-axis fluxgate sensor and a non-magnetic centralizer; The magnetic transmitter is arranged at the end of the first rod of the non-magnetic U-shaped frame and is at a first set distance from the end of the first rod; the second three-axis fluxgate sensor is arranged at the end of the second rod of the non-magnetic U-shaped frame and is at a second set distance from the end of the second rod; the non-magnetic centralizer is arranged between the bottom of the non-magnetic U-shaped frame and the second three-axis fluxgate sensor; The non-magnetic centralizer is used to make the axis of the second three-axis fluxgate sensor parallel to the axis of the casing.

2. The active magnetic measurement system for the magnetic shielding mode according to claim 1, characterized in that, The second three-axis fluxgate sensor is coaxial with the second rod of the non-magnetic U-shaped frame.

3. An active magnetic measurement method for the magnetic shielding mode, which is applied to an active magnetic measurement system for the magnetic shielding mode described in any one of claims 1-2, and is characterized in that, It includes: Start the magnetic transmitter and use the second three-axis fluxgate sensor to obtain the alternating magnetic field signal without pipe shielding; Insert the second rod of the non-magnetic U-shaped frame into the casing, start the magnetic transmitter, and use the second three-axis fluxgate sensor to obtain the alternating magnetic field signal after casing shielding; Determine the attenuation coefficient according to the alternating magnetic field signal without pipe shielding and the alternating magnetic field signal after casing shielding; Review the attenuation coefficient to determine the reviewed attenuation coefficient; Determine the spatial position relationship between the magnetic joint and the probe pipe in the drilling well according to the alternating magnetic field signal obtained by the probe pipe and the reviewed attenuation coefficient.

4. The active magnetic measurement method for the magnetic shielding mode according to claim 3, wherein The attenuation coefficient includes: the attenuation coefficient in the radial plane and the axial attenuation coefficient.

5. The active magnetic measurement method for the magnetic shielding mode according to claim 3, characterized in that, The step of reviewing the attenuation coefficient to determine the reviewed attenuation coefficient specifically includes: Change the attenuation coefficient at a set gradient to determine a set of attenuation coefficients; Determine the corresponding total field strength according to the alternating magnetic field signal obtained by the probe pipe and each attenuation coefficient in the set of attenuation coefficients; Determine the error coefficient according to the minimum value and the maximum value in the total field strength of each attenuation coefficient; Take the attenuation coefficient corresponding to the minimum error coefficient as the reviewed attenuation coefficient.

6. An active magnetic measurement system for a magnetic shielding mode, which is used to implement an active magnetic measurement method for a magnetic shielding mode according to any one of claims 3-5, characterized in that, It includes: An alternating magnetic field signal acquisition unit without pipe shielding, which is used to start the magnetic transmitter and use the second three-axis fluxgate sensor to obtain the alternating magnetic field signal without pipe shielding; An alternating magnetic field signal acquisition unit after casing shielding, which is used to insert the second rod of the non-magnetic U-shaped frame into the casing, start the magnetic transmitter, and use the second three-axis fluxgate sensor to obtain the alternating magnetic field signal after casing shielding; An attenuation coefficient determination unit for determining an attenuation coefficient based on an alternating magnetic field signal without casing shielding and an alternating magnetic field signal after casing shielding; A rechecked attenuation coefficient determination unit for rechecking the attenuation coefficient to determine the rechecked attenuation coefficient; A spatial position relationship determination unit for determining the spatial position relationship between the magnetic joint and the probe in the well being drilled according to the probe obtaining the alternating magnetic field signal and the rechecked attenuation coefficient.

7. The active magnetic measurement system for the magnetic shielding mode according to claim 6, wherein The attenuation coefficient includes: an attenuation coefficient in the radial plane and an axial attenuation coefficient.

8. The active magnetic measurement system for magnetic shielding mode according to claim 6, characterized in that, The rechecked attenuation coefficient determination unit specifically includes: An attenuation coefficient set determination subunit for varying the attenuation coefficient at a set gradient to determine an attenuation coefficient set; A total field strength determination subunit for determining the corresponding total field strength according to the probe obtaining the alternating magnetic field signal and each attenuation coefficient in the attenuation coefficient set; An error coefficient determination subunit for determining an error coefficient according to the minimum value and the maximum value in the total field strength of each attenuation coefficient; A rechecked attenuation coefficient determination subunit for using the attenuation coefficient corresponding to the minimum error coefficient as the rechecked attenuation coefficient.

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