CN114658423A - Active magnetic measurement system and method used in magnetic shielding mode - Google Patents

Abstract

The invention relates to an active magnetic measurement system and method used in a magnetic shielding mode. The system includes: a probe and a measuring tool; the detecting tube is connected with a winch with a cable through the cable, the winch with the cable is connected with a ground host, and the ground host is connected with a computer; the probe tube includes: the first triaxial fluxgate sensor and the gyro measurement module are arranged; the measuring tool is installed on the ground and is communicated with a computer through a ground host; the measuring tool is used for acquiring alternating magnetic field signals after being shielded by the sleeve and alternating magnetic field signals which are not shielded by the sleeve; the computer is used for determining an 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 casing, rechecking the attenuation coefficient, and further determining the spatial position relation between the magnetic joint and the probe in the well according to the rechecked attenuation coefficient and the alternating magnetic field signal obtained by the probe. The invention can improve the accuracy of measurement and positioning in the ferromagnetic casing.

Description

An active magnetic measurement system and method for use in magnetic shielding mode

technical field

The invention relates to the field of drilling measurement, in particular to an active magnetic measurement system and method used in a magnetic shielding mode.

Background technique

In geological and oil drilling, in order to precisely control the wellbore trajectory and make the drill bit reach the designated position, downhole measurements are often performed with instruments. The active magnetic measurement system is a high-precision measurement method. The basic principle is to form a regular magnetic field disturbance in space by rotating an artificial magnetic field with known strength. After the probe receives this disturbance, the magnetic field is analyzed by software. The relative spatial position relationship with the probe tube. In practical applications, the artificial magnetic field is usually embedded in a cylinder made of non-magnetic material by rare-earth permanent magnets, that is, a magnetic joint, and the alternating magnetic field signal is generated by rotating the magnetic joint. Probes are rod-mounted cylinders composed of various sensors and circuits that measure the Earth's magnetic field, gravitational field, and dynamic alternating magnetic fields. When the active magnetic measurement system is working, the magnetic joint is driven by the screw motor connected to the rear to rotate in the axial direction, forming a magnetic field disturbance. At the other end of the space, a probe is usually placed on 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 well hole. The upper end of the winch cable is connected to the ground host. The host supplies power to the probe tube and converts the signal collected by the probe tube, and then sends it to the computer. The computer analyzes the data to obtain the spatial relationship between the magnetic joint and the probe tube in the drilling process. This measurement method is "the probe tube first locates itself, and then the magnetic joint is positioned", and the probe tube is responsible for collecting all signal parameters. The probe tube needs at least three parameters to position itself: apex angle, azimuth, and tool face. Current probes generally use three-axis fluxgate sensors to measure magnetically related signals, including geomagnetic field data for calculating its own orientation, and alternating magnetic field signals from magnetic joints.

In the current active magnetic positioning measurement, the probe tube must be placed in the naked hole section of the target well, that is, at a distance (at least 2 meters) from ferromagnetic interference such as casing and tubing, and the probe tube will not be placed in it. However, in the drilling field of petroleum, geological and soluble solid minerals, ferromagnetic casing is widely used as an effective hole wall support. That is, casing is a thin-shelled 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 into the surface, the original formation stress is destroyed, and the rock and soil in the hole will collapse without maintenance. At this time, the casing should be run, and the annulus formed by the hole wall and the casing should be filled with cement, so that the casing and the formation are integrated, so as to support the formation and isolate the groundwater. When the probe tube is placed in the ferromagnetic casing for various reasons, the three-axis fluxgate sensor will be disturbed and shielded, and the obtained geomagnetic parameters and magnetic joint signals will also be deformed and distorted, lacking these two important data, So that the existing active magnetic positioning system can not work properly.

Based on the above problems, there is an urgent need for an active magnetic measurement system or method in a magnetic shielding mode.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide an active magnetic measurement system and method in a magnetic shielding mode, which can improve the accuracy of measurement and positioning in a ferromagnetic sleeve.

For achieving the above object, the present invention provides the following scheme:

An active magnetic measurement system used in a magnetic shielding mode, the active magnetic measurement system comprises: a magnetic joint, a winch with a cable, a ground host and a computer, the system further comprises: a probe pipe and a measurement tool;

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

The measuring tool is installed on the ground, and communicates with the computer through the ground host; the measuring tool is used to obtain the alternating magnetic field signal shielded by the casing and the alternating magnetic field signal not shielded by the pipe; The attenuation coefficient of the alternating magnetic field signal shielded by the casing and the alternating magnetic field signal not shielded by the pipe is determined, and the attenuation coefficient is checked. The spatial relationship between the joint and the probe tube.

Optionally, the measurement tool 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 has a first set distance from the end of the first rod; the second three-axis fluxgate sensor is arranged at the non-magnetic U-shaped frame. the end of the second rod of the frame and 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 axial direction of the second three-axis fluxgate sensor parallel to the axial direction of the casing.

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

An active magnetic measurement method in a magnetic shielding mode, applied to the active magnetic measurement system in a magnetic shielding mode, comprising:

Start the magnetic transmitter, and use the second three-axis fluxgate sensor to obtain the alternating magnetic field signal without tube 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 shielded by the casing;

Determine the attenuation coefficient according to the alternating magnetic field signal that is not shielded by the pipe and the alternating magnetic field signal that is shielded by the casing;

Check the attenuation coefficient to determine the attenuation coefficient after the review;

According to the alternating magnetic field signal obtained by the probe and the attenuation coefficient after review, the spatial positional relationship between the magnetic joint and the probe in the positive drilling is determined.

Optionally, the attenuation coefficient includes: an attenuation coefficient on a radial plane and an axial attenuation coefficient.

Optionally, the checking of the attenuation coefficient to determine the checked attenuation coefficient specifically includes:

Change the attenuation coefficient with a set gradient to determine a set of attenuation coefficients;

Determine the corresponding total field intensity according to the alternating magnetic field signal obtained by the probe and each attenuation coefficient in the attenuation coefficient set;

Determine the error coefficient according to the minimum and maximum value of the total field strength for each attenuation coefficient;

The attenuation coefficient corresponding to the smallest error coefficient is used as the attenuation coefficient after review.

An active magnetic measurement system for use in a magnetic shielding mode, for realizing the active magnetic measurement method for a magnetic shielding mode, comprising:

The unshielded alternating magnetic field signal acquisition unit is used to start the magnetic transmitter, and use the second three-axis fluxgate sensor to obtain the unshielded alternating magnetic field signal;

The alternating magnetic field signal acquisition unit after being shielded by the casing 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 signal after being shielded by the casing. The alternating magnetic field signal;

The attenuation coefficient determination unit is used for determining the attenuation coefficient according to the alternating magnetic field signal not shielded by the pipe and the alternating magnetic field signal after being shielded by the casing;

The attenuation coefficient determination unit after review is used for reviewing the attenuation coefficient and determining the attenuation coefficient after review;

The spatial position relationship determining unit is used for determining the spatial position relationship between the magnetic joint and the probe tube in the drilling process according to the alternating magnetic field signal obtained by the probe tube and the attenuation coefficient after review.

Optionally, the attenuation coefficient includes: an attenuation coefficient on a radial plane and an axial attenuation coefficient.

Optionally, the re-checked attenuation coefficient determination unit specifically includes:

The attenuation coefficient set determination subunit is used to change the attenuation coefficient with the set gradient to determine the attenuation coefficient set;

a total field strength determination subunit, configured to determine the corresponding total field strength according to the alternating magnetic field signal obtained by the probe and each attenuation coefficient in the attenuation coefficient set;

an error coefficient determination subunit, used for determining the error coefficient according to the minimum value and the maximum value in the total field intensity of each attenuation coefficient;

The verified attenuation coefficient determination sub-unit is used for taking the attenuation coefficient corresponding to the smallest error coefficient as the verified attenuation coefficient.

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

The present invention provides an active magnetic measurement system and method in a magnetic shielding mode. When the first three-axis fluxgate sensor cannot measure the azimuth normally, the gyro measurement module is used to measure the azimuth, which can be used in an abnormal magnetic environment. The measurement tool is installed on the ground, and communicates with the computer through the ground host; the attenuation coefficient is determined according to the alternating magnetic field signal obtained by the measuring tool after being shielded by the casing and the alternating magnetic field signal not shielded by the tube, and the attenuation coefficient is determined. Carry out a review, and then determine the spatial relationship between the magnetic joint and the probe tube in the drilling process according to the attenuation coefficient after the review and the alternating magnetic field signal obtained by the probe tube. Without taking out the bottom hole material, the magnetic field characteristics are used to measure the attenuation coefficient of the extremely low frequency magnetic field of the casing at the bottom hole, and the shielded alternating magnetic field signal is restored, so that the active magnetic measurement system can be normally applied to the geomagnetic anomaly area, and can also Perform positioning measurements with ferromagnetic bushing shielding.

Description of drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the accompanying drawings required in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some of the present invention. In the embodiments, for those of ordinary skill in the art, other drawings can also be obtained according to these drawings without creative labor.

1 is a schematic structural diagram of a measurement tool in an active magnetic measurement system for use in a magnetic shield mode provided by the present invention;

Figure 2 is a schematic diagram of a static magnetic field coordinate system;

3 is a schematic diagram of a rotating magnetic field coordinate system;

FIG. 4 is a schematic flowchart of an active magnetic measurement method in a magnetic shielding mode provided by the present invention.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

The purpose of the present invention is to provide an active magnetic measurement system and method in a magnetic shielding mode, which can improve the accuracy of measurement and positioning in a ferromagnetic sleeve.

In order to make the above objects, features and advantages of the present invention more clearly understood, the present invention will be described in further detail below with reference to the accompanying drawings and specific embodiments.

An active magnetic measurement system used in a magnetic shielding mode, the active magnetic measurement system comprises: a magnetic joint, a winch with a cable, a ground host and a computer, the system further comprises: a probe pipe and a measurement tool;

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

The measuring tool is installed on the ground, and communicates with the computer through the ground host; the measuring tool is used to obtain the alternating magnetic field signal shielded by the casing and the alternating magnetic field signal not shielded by the pipe; The attenuation coefficient of the alternating magnetic field signal shielded by the casing and the alternating magnetic field signal not shielded by the pipe is determined, and the attenuation coefficient is checked. The spatial relationship between the joint and the probe tube.

As shown in Figure 1, the measurement tool 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 has a first set distance from the end of the first rod; the second three-axis fluxgate sensor is arranged at the non-magnetic U-shaped frame. the end of the second rod of the frame and 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.

The non-magnetic centralizer is used to make the axial direction of the second three-axis fluxgate sensor parallel to the axial direction of the casing.

Except for the small magnetic transmitter, the whole set of measurement tooling is made of non-magnetic material, which has a certain rigidity and is not easy to deform.

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

The magnetic joint is located in the drilling under construction, the front is connected to the drill bit, and the rear is connected to the screw. The magnetic joint rotates with the screw to generate 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 from the magnetic joint. The probe pipe is connected to the winch on the ground through the armored cable, and the other end of the cable on the winch is connected to the ground host. After the probe collects the 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, and also has 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 pipe can be known, and the trajectory can be adjusted to reach the target position.

The specific measurement steps are:

1) After the magnetic joint is connected to the drill bit, it is lowered into the positive drilling and the drilling is carried out normally. When the probe tube is lowered to the target, it is blocked in the ferromagnetic casing due to various reasons, and the first three-axis fluxgate sensor cannot measure the bearing normally. At this time, the gyro measurement module in the probe tube is activated to measure the true bearing (B). Query the local magnetic declination (C), and calculate the azimuth (A), A=B+C.

2) When the drilling is within a certain distance (such as 100 meters) from the probe pipe, enter the alternating magnetic field signal measurement link. At this time, the drilling is stopped, the magnetic joint is rotated in situ, and then the probe is started, and the first three-axis fluxgate sensor is used to capture the alternating magnetic field signal sent by the magnetic joint. Since the probe tube is located in the casing, the amplitude of the alternating magnetic field signal will become smaller after being shielded by the casing.

3) Ground measurement of casing attenuation coefficient. Find a complete casing of the same specification and model as the downhole casing on the surface and place it in an environment with less magnetic interference. Using the measuring tool, install a centralizer of a suitable type on the end with the second three-axis fluxgate sensor, insert it into the casing at least 1 meter deep, and the end with the small magnetic field transmitter is outside the casing, and ensure that the first Except for the measured casing, there is no other object blocking between the two-three-axis fluxgate sensor and the transmitter. The function of the non-magnetic centralizer is to ensure that the axial direction of the three-axis fluxgate sensor is parallel to the axial direction of the casing. After the second and three-axis fluxgate sensors are connected to the ground host and the computer, turn on the magnetic transmitter and start the probe to measure the alternating magnetic field signals shielded by the casing while keeping the entire tooling still, which are Bx, By, Bz respectively. , Bz is in the same direction as the probe axis, Bx and By are radial, and the three are perpendicular to each other.

Take the measuring tool out of the casing, keep the relative posture of the magnetic transmitter and the probe tube unchanged, put it in an environment far away from the casing and have less magnetic interference, start the magnetic field transmitter again, and measure the magnetic field transmitter without casing shielding. Three-axis magnetic field parameters, Bx1, By1, Bz1.

make

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

4) Attenuation coefficient review and positioning calculation. After measuring the magnetic joint signal, the original alternating magnetic field data is obtained. These data are 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 the casing will be deformed and corroded after it is lowered into the formation, its magnetic shielding performance may be different from that of the complete casing on the surface, so further review and calculation should be carried out.

The principle of review is:

Figure 2 shows a three-dimensional coordinate system of static magnetic field. A cylindrical permanent magnet is located at the coordinate origin O, the NS pole is coincident with the Z axis, P is any point in space, and the distance from the origin connecting line OP is r, and the magnet volume is far If it is less than r, it can be assumed to be a magnetic dipole, then the magnetic field expression at the space point P:

In the above formula, M is the magnetic moment value, and μ ₀ is the vacuum permeability.

The total magnetic field strength is written as:

Substitute (1) into the formula to get:

会发生变化，但磁场表达式与(1)相同。The magnet rotates around the Y axis in the XZ plane. No matter where the NS pole is rotated, the coordinate system shown in Figure 3 can be established. The projection of the connection OP on the new X ¹ Z ¹ plane will change. The angle values θ and

changes, but the magnetic field expression is the same as (1).

According to formulas (1) and (2) the total magnetic field strength can be written as:

Observing the above formula, we can see that when the magnetic field rotates around the Y axis, the total strength of the magnetic field is related to the angle between the connecting line OP and the NS pole of the magnet. When ψ=π/2, Bt has a minimum value:

When ψ is minimum, Bt has a maximum value:

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

in

S1 and S2 are the attenuation coefficients measured by the tooling in the third step above. The calculation starts with it as the initial value. After each change of (S1, S2) _i , the following operations are performed on the original data:

Using the normal positioning method, use the formula (1) to get the corresponding result

The total field value Bt _i is obtained according to formula (2), and two maximum and minimum values are found in a series of total field values, which are Bt _maxi and Bt _mini , respectively. Change formula (7) and find the absolute value, for each group of attenuation coefficients (S1, S2) _i have

in

也是磁接头与探管空间位置关系。此时的

是最终结果，r是从磁场发射源到探管的距离，后两个为角度值；The attenuation coefficient at the minimum value in formula (10) is the real attenuation coefficient of the downhole casing, and the result at this time

It is also the spatial relationship between the magnetic joint and the probe tube. at this time

is the final result, r is the distance from the magnetic field emission source to the probe, and the last two are the angle values;

FIG. 4 is a schematic flowchart of an active magnetic measurement method in a magnetic shielding mode provided by the present invention. As shown in FIG. 4 , an active magnetic measurement method in a magnetic shielding mode provided by the present invention, The active magnetic measurement system applied in the magnetic shielding mode includes:

S401, start the magnetic transmitter, and use the second three-axis fluxgate sensor to obtain the alternating magnetic field signal that is not shielded by the tube;

S402, 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 shielded by the casing;

S403, determining the attenuation coefficient according to the alternating magnetic field signal not shielded by the pipe and the alternating magnetic field signal shielded by the casing;

S404, review the attenuation coefficient, and determine the attenuation coefficient after the review;

S404 specifically includes:

Change the attenuation coefficient with a set gradient to determine a set of attenuation coefficients;

Determine the corresponding total field intensity according to the alternating magnetic field signal obtained by the probe and each attenuation coefficient in the attenuation coefficient set;

Determine the error coefficient according to the minimum and maximum value of the total field strength for each attenuation coefficient;

The attenuation coefficient corresponding to the smallest error coefficient is used as the attenuation coefficient after review.

S405, according to the alternating magnetic field signal obtained by the probe and the attenuation coefficient after review, determine the spatial positional relationship between the magnetic joint and the probe in the positive drilling.

The attenuation coefficients include: attenuation coefficients on the radial plane and axial attenuation coefficients.

An active magnetic measurement system used in a magnetic shielding mode, for realizing the active magnetic measurement method in a magnetic shielding mode, comprising:

The unshielded alternating magnetic field signal acquisition unit is used to start the magnetic transmitter, and use the second three-axis fluxgate sensor to obtain the unshielded alternating magnetic field signal;

The alternating magnetic field signal acquisition unit after being shielded by the casing 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 signal after shielding by the casing. The alternating magnetic field signal;

an attenuation coefficient determination unit, which is used for determining the attenuation coefficient according to the alternating magnetic field signal not shielded by the pipe and the alternating magnetic field signal after being shielded by the casing;

The attenuation coefficient determination unit after review is used for reviewing the attenuation coefficient and determining the attenuation coefficient after review;

The spatial position relationship determining unit is used for determining the spatial position relationship between the magnetic joint and the probe tube in the drilling process according to the alternating magnetic field signal obtained by the probe tube and the attenuation coefficient after review.

The attenuation coefficients include: attenuation coefficients on the radial plane and axial attenuation coefficients.

The re-checked attenuation coefficient determination unit specifically includes:

The attenuation coefficient set determination subunit is used to change the attenuation coefficient with the set gradient to determine the attenuation coefficient set;

a total field strength determination subunit, configured to determine the corresponding total field strength according to the alternating magnetic field signal obtained by the probe and each attenuation coefficient in the attenuation coefficient set;

an error coefficient determination subunit, used for determining the error coefficient according to the minimum value and the maximum value in the total field intensity of each attenuation coefficient;

The verified attenuation coefficient determination sub-unit is used for taking the attenuation coefficient corresponding to the smallest error coefficient as the verified attenuation coefficient.

The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments, and the same and similar parts between the various embodiments can be referred to each other. For the system disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant part can be referred to the description of the method.

The principles and implementations of the present invention are described herein using specific examples. The descriptions of the above embodiments are only used to help understand the method and the core idea of the present invention; meanwhile, for those skilled in the art, according to the present invention There will be changes in the specific implementation and application scope. In conclusion, the contents of this specification should not be construed as limiting the present invention.

Claims (9)

1. An active magnetic measurement system for use in a magnetic shielding mode, the active magnetic measurement system comprising: magnetic connector, take cable winch, ground host computer and computer, its characterized in that still includes: a probe and a measuring tool;

the detection tube is connected with a winch with a cable through the cable, the winch with the cable is connected with a ground host, and the ground host is connected with a computer; the probe tube comprises: the first triaxial fluxgate sensor and the gyro measurement module are arranged; the gyroscope measurement module is used for measuring the direction when the first three-axis fluxgate sensor cannot normally measure the direction;

the measuring tool is installed on the ground and is communicated with a computer through a ground host; the measuring tool is used for acquiring alternating magnetic field signals after being shielded by the sleeve and alternating magnetic field signals which are not shielded by the sleeve; the computer is used for determining an 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 casing, rechecking the attenuation coefficient, and further determining the spatial position relation between the magnetic joint and the probe in the well according to the rechecked attenuation coefficient and the alternating magnetic field signal obtained by the probe.

2. The active magnetic measurement system for use in magnetic shielding mode of claim 1, wherein said measurement tool comprises: the magnetic sensor comprises a non-magnetic U-shaped frame, a magnetic emitter, a second triaxial fluxgate sensor and a non-magnetic centralizer;

the magnetic emitter is arranged at the end part of the first rod of the non-magnetic U-shaped frame and is away from the end part of the first rod by a first set distance; the second triaxial fluxgate sensor is arranged at the end part of the second rod without the magnetic U-shaped frame and is a second set distance away from the end part of the second rod; the nonmagnetic centralizer is arranged between the bottom of the nonmagnetic U-shaped frame and the second triaxial fluxgate sensor;

the non-magnetic centralizer is used for enabling the axial direction of the second triaxial fluxgate sensor to be parallel to the axial direction of the sleeve.

3. Active magnetic measuring system for magnetic shielding mode according to claim 2 characterized in that said second tri-axial fluxgate sensor is coaxial to the second bar of the nonmagnetic clevis.

4. An active magnetic measurement method for use in a magnetic shielding mode, applied to an active magnetic measurement system for use in a magnetic shielding mode according to any one of claims 1 to 3, comprising:

starting the magnetic transmitter, and acquiring an alternating magnetic field signal which is not shielded by a pipe by using a second triaxial fluxgate sensor;

inserting a second rod of the non-magnetic U-shaped frame into the sleeve, starting the magnetic emitter, and acquiring an alternating magnetic field signal shielded by the sleeve by using a second triaxial fluxgate sensor;

determining an attenuation coefficient according to an alternating magnetic field signal which is not subjected to pipe shielding and an alternating magnetic field signal which is subjected to sleeve shielding;

rechecking the attenuation coefficient, and determining the rechecked attenuation coefficient;

and determining the spatial position relation between the magnetic joint and the probe in the well being drilled according to the alternating magnetic field signal acquired by the probe and the decay coefficient after rechecking.

5. An active magnetic measurement method for use in magnetic shielding mode according to claim 4, characterized in that the attenuation coefficient comprises: the attenuation coefficient in the radial plane and the axial attenuation coefficient.

6. The active magnetic measurement method for the magnetic shielding mode according to claim 4, wherein the rechecking the attenuation coefficient and determining the rechecked attenuation coefficient specifically comprises:

changing the attenuation coefficient by a set gradient to determine an attenuation coefficient set;

obtaining an alternating magnetic field signal according to the probe and determining the corresponding total field strength according to each attenuation coefficient in the attenuation coefficient set;

determining an error coefficient according to the minimum value and the maximum value in the total field intensity of each attenuation coefficient;

and taking the attenuation coefficient corresponding to the minimum error coefficient as the attenuation coefficient after the double check.

7. An active magnetic measurement system for use in magnetic shielding mode for implementing an active magnetic measurement method for use in magnetic shielding mode according to any of claims 4 to 6, comprising:

the alternating magnetic field signal acquisition unit which is not shielded by the tube is used for starting the magnetic transmitter and acquiring the alternating magnetic field signal which is not shielded by the tube by utilizing the second three-axis fluxgate sensor;

the alternating magnetic field signal acquisition unit is used for inserting a second rod without a magnetic U-shaped frame into the sleeve, starting the magnetic transmitter and acquiring the alternating magnetic field signal shielded by the sleeve by using a second triaxial fluxgate sensor;

the attenuation coefficient determining unit is used for determining an attenuation coefficient according to the alternating magnetic field signal which is not subjected to pipe shielding and the alternating magnetic field signal which is subjected to sleeve shielding;

the rechecked attenuation coefficient determining unit is used for rechecking the attenuation coefficient and determining the rechecked attenuation coefficient;

and the spatial position relation determining unit is used for determining the spatial position relation between the magnetic joint and the probe in the well drilling according to the alternating magnetic field signal acquired by the probe and the decay coefficient after rechecking.

8. An active magnetic measurement system for use in magnetic shielding mode according to claim 7, characterized in that the attenuation coefficient comprises: the attenuation coefficient in the radial plane and the axial attenuation coefficient.

9. Active magnetic measurement system for use in magnetic shielding mode according to claim 7, characterized in that said re-checked attenuation coefficient determination unit comprises in particular:

the attenuation coefficient set determining subunit is used for changing the attenuation coefficient by a set gradient to determine an attenuation coefficient set;

the total field intensity determining subunit is used for determining the corresponding total field intensity according to the alternating magnetic field signal acquired by the probe and each attenuation coefficient in the attenuation coefficient set;

an error coefficient determining subunit, configured to determine an error coefficient according to a minimum value and a maximum value in the total field intensity of each attenuation coefficient;

and the attenuation coefficient determination subunit is used for taking the attenuation coefficient corresponding to the minimum error coefficient as the attenuation coefficient after the rechecking.

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