CN211627796U - Calibration structure for assisting long-term monitoring of magnetic gradient tensor of rotary tensor instrument in well - Google Patents
Calibration structure for assisting long-term monitoring of magnetic gradient tensor of rotary tensor instrument in well Download PDFInfo
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- CN211627796U CN211627796U CN201921940172.1U CN201921940172U CN211627796U CN 211627796 U CN211627796 U CN 211627796U CN 201921940172 U CN201921940172 U CN 201921940172U CN 211627796 U CN211627796 U CN 211627796U
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Abstract
The utility model relates to a calibration structure for assisting a rotary tensor instrument in a well to monitor magnetic gradient tensor for a long time, which comprises the rotary tensor instrument and a pair of Maxwell coils, wherein the rotary tensor instrument and the Maxwell coils are fixed through a shell; the utility model discloses a Maxwell coil is once markd again to the tensor appearance at an interval, and the effectual time drift and the temperature drift of having avoided the interior magnetic flux gate sensor of tensor appearance are floated the error problem of bringing, have improved the degree of accuracy of long-term monitoring magnetic gradient tensor in the well. The Maxwell coil and the shell of the tensor instrument are directly fixed by a bolt for drilling, so that the rotation center of the tensor instrument is consistent with the central point of the Maxwell coil; and the relative position of the two is not changed in the calibration process.
Description
Technical Field
The utility model belongs to the technical field of magnetic field measuring device, concretely relates to calibration structure of rotatory tensor appearance long-term monitoring magnetic gradient tensor in auxiliary well.
Background
In 2009, David Tilbrook proposed the principle of measuring the magnetic gradient tensor by a rotation method, wherein the rotation modulation method separates different derivatives of the magnetic field in different orders by using rotation to obtain the components of the first order tensor. The method ensures that the direct current and low-frequency performance of the instrument is not influenced by the performance of the sensor, the gradient imbalance is not determined by the engineering precision any more, and the sensitivity of the instrument is improved. The method uses a differential structure, as shown in FIG. 1, defining the magnetic field at the center of the disk as Bα(0) Magnetic field B at point rα(r) can be expressed as:
wherein α represents x, y, z, and,
since the decay speed of the higher-order tensor is faster with distance, we ignore the third-order and above tensor components, and the above equation can be expressed as:
i.e. the magnetic field components at two points can be expressed as:
the output voltage of the system can be expressed as:
V＝[S1·B(r1)+S2·B(r2)]+e (4)
wherein S is1，S2Is the magnetic sensitivity vector of the fluxgate sensor, which can be expressed as S1＝S1(cosθ，sinθ)，S2＝-S2(cosθ，sinθ)，Bα(r1) And Bα(r2) Is the magnetic field where the two fluxgates are located.
The output voltage is a function of time of any magnetic field when rotated. By combining trigonometric functions, unfolding and combining the harmonics, the output voltage can be expressed as:
wherein, VneAnd VnoRepresenting the real and imaginary parts of the nth harmonic of the voltage.
The relationship between the tensor components and the voltage harmonics can be found:
wherein the content of the first and second substances,
the second order tensor is expressed as follows:
since the second order tensor has only five independent components. From equation (6), one plane can obtain two equations for the second-order tensor, so to obtain the complete second-order tensor, five equations in three planes are needed. However, due to the limitation of the shape of the well, the process shown in fig. 2 was performed on three planes perpendicular to each other, that is, in 2015, Keith Leslie et al, CSIRO, australia, developed the first magnetic gradient full tensor instrument applicable downhole according to the principle of the rotational method.
The pair of sensors in the X' direction rotate about the Z axis by 35 °. The different signals of the pair of sensors provide a measurement of the magnetic field component in the X 'Y' plane. The magnetic gradients in a single X 'Y' plane are determined and the tensor is rotated 0 °, 120 ° and 240 ° around the Z-axis, respectively, as shown in fig. 3, and the entire gradient tensor can be determined by obtaining three sets of X 'Y' planes, i.e., three sets of magnetic gradients.
The rotary tensor instrument is constructed as shown in fig. 4, which is implemented using two stepper motors. One motor realizes the rotation of the rotary head part disc around the Z axis through the aluminum plate bracket, and the other motor drives the rotary head to rotate around the Z' axis through the conveyor belt.
The instrument has the defects that in the process of monitoring the magnetic gradient tensor in a well for a long time by the fluxgate sensor in the rotary tensor instrument, the monitoring result can drift along with the increase of the monitoring time, and the monitoring result of the rotary tensor instrument can generate errors due to the influence of the temperature on the magnetic core material.
The Maxwell coil is composed of a pair of identical circular conductor coils, the current of the two coils is identical in magnitude and opposite in direction, and the distance between the two coils is of radius
And (3) a uniform gradient field can be generated on the axis of the gradient field, and the structure is shown in figure 5.
According to the biot-savart law, the magnetic field on the axis of the maxwell coil at a distance x from the center is as follows:
wherein, N is the coil turn number, R is the coil radius, and I is the coil current of passing through.
Compared with a Helmholtz coil which can generate a uniform magnetic field on the axis, the Maxwell coil can generate a uniform gradient field on the axis, and can generate a gradient field with corresponding size by setting reasonable coil radius, turns and current.
Disclosure of Invention
The utility model aims at providing a calibration structure of rotatory tensor appearance long-term monitoring magnetic gradient tensor in supplementary well for solve current well in rotatory method tensor appearance when long-term monitoring magnetic gradient tensor, the error problem that the time drift and the temperature drift brought of magnetic flux gate sensor float in the rotatory tensor appearance.
In order to achieve the above object, the utility model provides a following technical scheme:
a calibration structure for assisting a rotary tensor instrument in a well to monitor magnetic gradient tensor for a long time is composed of the rotary tensor instrument and a pair of Maxwell coils, wherein the Maxwell coils and a shell of the rotary tensor instrument are directly fixed by screws for drilling.
Rotatory tensor appearance is from last mainly comprising rotating head, support and base down, base motor and second encoder are equipped with in the base, the base motor is connected with the transmission of support bottom, third synchronous pulley and step motor are equipped with on the support, the rotating head inclines in the support mounting, and two unipolar fluxgate symmetries are fixed on the carousel in the rotating head, pass through the hold-in range with the coaxial first synchronous pulley of carousel and install the second synchronous pulley and the third synchronous pulley on support upper portion in the rotating head and be connected.
The rotating head also comprises a slip ring and a first encoder which are coaxial with the rotating disc.
The maxwell coil comprises two coaxial coils, and the coils are fixed in a shell of the rotary tensor instrument through drilling holes.
As an optimal technical solution of the present invention, the rotation tensor instrument is calibrated by the maxwell coil, and can generate a uniform gradient field on the axis thereof.
As a preferred embodiment of the present invention, the number of turns of the maxwell coil is 10.
As the preferred technical scheme of the utility model, the radius of Maxwell coil is 45 mm.
As the preferred technical scheme of the utility model, the rotation center of tensor appearance with the central point of Maxwell coil is unanimous.
As the preferred technical scheme of the utility model, Maxwell coil is controlled by external power source, can once recalibrate rotation tensor appearance at interval a period of time.
Compared with the prior art, the beneficial effects of the utility model reside in that:
the utility model discloses a maxwell coil can produce even gradient field on its axis, uses maxwell coil once marks the tensor appearance again at every interval, and the effectual error problem of floating and the temperature that brings of magnetic flux door sensor in having avoided the tensor appearance has improved the degree of accuracy of long-term monitoring magnetic gradient tensor in the well. The Maxwell coil and the casing of the tensor instrument are directly fixed through drilling, so that the rotation center of the tensor instrument is consistent with the central point of the Maxwell coil, and the relative positions of the Maxwell coil and the tensor instrument are not changed in the calibration process.
Drawings
FIG. 1 is a diagram of a prior art rotational method for measuring gradient tensors;
FIGS. 2-3 are two schematic diagrams of prior art three position measurements by rotation;
FIG. 4 is a schematic view of a rotary tensor instrument according to the prior art;
FIG. 5 is a schematic diagram of a Maxwell coil in the prior art;
fig. 6 is a schematic view of the structure of the junction between the maxwell coil and the tensor instrument case;
fig. 7 is an elevation view of an alignment structure for assisting a rotary tensor instrument in a well in long term monitoring of magnetic gradient tensors in accordance with the present invention;
fig. 8 is a side view of fig. 7.
In the figure: 1. the magnetic-field-type encoder comprises a shell 2, a first magnetic-field gate 3, a second magnetic-field gate 4, a slip ring 5, a rotary disc 6, a first synchronous belt wheel 7, a first encoder 8, a second synchronous belt wheel 9, a rotary head 10, a support 11, a third synchronous belt wheel 12, a stepping motor 13, a base motor 14, a second encoder 15, a base 16, a first Maxwell coil 17, a second Maxwell coil 18, a first drilling hole 19 and a second drilling hole.
Detailed Description
The embodiments of the present invention will be described in detail with reference to the accompanying drawings, and other advantages and effects of the invention can be easily understood by those skilled in the art from the disclosure of the present specification.
A calibration structure of rotatory tensor appearance long-term monitoring magnetic gradient tensor in auxiliary well, constitute by a pair of maxwell coil and rotatory tensor appearance, maxwell coil is fixed in rotatory tensor appearance's shell 1. In particular, the maxwell coil can be fixed in the housing 1 of the rotary tensor instrument by screws without magnetic interference when fixing.
The rotary tensor instrument is mainly composed of a base 15, a support 10 and a rotary head 9 from top to bottom.
A base motor 13 and a second encoder 14 are arranged in the base 15, and the base motor 13 is in transmission connection with the bottom of the support 10.
And a third synchronous belt wheel 11 and a stepping motor 12 are arranged on the bracket 10.
The rotating head 9 is installed obliquely to the bracket 10, and two single-axis fluxgates (a first fluxgate 2 and a second fluxgate 3) are symmetrically fixed on the turntable 5 in the rotating head 9. A first synchronous belt pulley 6 which is coaxial with the rotary disc 5 in the rotating head 9, and a second synchronous belt pulley 8 and a third synchronous belt pulley 11 which are arranged on the upper part of the bracket 10 are connected through a synchronous belt.
Also included in the rotating head 9 are a slip ring 4 and a first encoder 7 coaxial with the turntable 5.
The maxwell coil comprises two coaxial coils, and a first sub-coil 16 of the maxwell coil and a second sub-coil 17 of the maxwell coil are respectively fixed in the shell 1 of the rotary tensor instrument through a first drill hole 18 and a second drill hole 19. The rotary tensor instrument is calibrated by a Maxwell coil and can generate a uniform gradient field on the axis of the rotary tensor instrument.
The number of turns of the Maxwell coil is 10, the radius of the Maxwell coil is 45mm, the current of the two coils is the same, the directions of the two coils are opposite, and the distance between the two coils is the radius
The uniform gradient region with the length of 35mm and the uniformity of more than 95% can be generated on the axis, and the magnetic gradient tensor of 3980nT/m is corresponding to every 1mA in the uniform region. The rotation center of the rotary tensor instrument is consistent with the center point of the Maxwell coil. Therefore, the Maxwell coil can be controlled by an external power supply, the rotating tensor instrument is recalibrated once at intervals, and continuous calibration of the rotating tensor instrument in the process of monitoring the magnetic gradient tensor in the well for a long time is achieved.
Rotatory tensor appearance monitors magnetic gradient tensor's calibration structure for a long time in auxiliary well, be applicable to the rotatory tensor appearance of the autonomic research and development of Jilin university, the calibration structure that provides can pass through Maxwell coil pairing rotation tensor appearance carries out the calibration of interval, improves the accuracy of long-term monitoring magnetic gradient tensor in the well to be favorable to future engineering application.
The foregoing shows and describes the general principles, essential features, and advantages of the invention, and modifications and improvements may be made thereto without departing from the spirit and scope of the invention, which is to be protected by the following claims.
Claims (6)
1. The utility model provides a calibration structure of rotatory tensor appearance long-term monitoring magnetic gradient tensor in supplementary well which characterized in that: the device comprises a rotary tensor instrument and a pair of Maxwell coils, wherein the Maxwell coils are fixed with a shell of the rotary tensor instrument;
the rotary tensor instrument mainly comprises a base (15), a support (10) and a rotary head (9) from top to bottom;
a base motor (13) and a second encoder (14) are arranged in the base (15), and the base motor (13) is in transmission connection with the bottom of the bracket (10); a third synchronous belt wheel (11) and a stepping motor (12) are arranged on the bracket (10); the rotating head (9) is obliquely arranged on the support (10), the two single-shaft fluxgates are symmetrically fixed on the turntable (5) in the rotating head (9), and a first synchronous pulley (6) which is coaxial with the turntable (5) in the rotating head (9) and a second synchronous pulley (8) which is arranged on the upper part of the support (10) are connected with a third synchronous pulley (11) through a synchronous belt;
the rotating head (9) also comprises a slip ring (4) and a first encoder (7) which are coaxial with the rotating disc (5);
the maxwell coil comprises two coaxial coils, and the coils are fixed in a shell (1) of the rotary tensor instrument through drilling holes.
2. An alignment structure to aid a rotary tensor instrument in a well in long term monitoring of magnetic gradient tensors as claimed in claim 1, wherein: the Maxwell coil and a shell (1) of the rotary tensor instrument are directly fixed through a drilling screw, and the rotary tensor instrument is calibrated through the Maxwell coil and can generate a uniform gradient field on the axis of the rotary tensor instrument.
3. An alignment structure to aid a rotary tensor instrument in a well in long term monitoring of magnetic gradient tensors as claimed in claim 1, wherein: the number of turns of the Maxwell coil is 10.
4. An alignment structure to aid a rotary tensor instrument in a well in long term monitoring of magnetic gradient tensors as claimed in claim 1, wherein: the radius of the Maxwell coil is 45 mm.
5. An alignment structure to aid a rotary tensor instrument in a well in long term monitoring of magnetic gradient tensors as claimed in claim 1, wherein: the rotation center of the tensor instrument is consistent with the central point of the Maxwell coil.
6. An alignment structure to aid a rotary tensor instrument in a well in long term monitoring of magnetic gradient tensors as claimed in claim 1, wherein: the Maxwell coil is controlled by an external power supply and can recalibrate the rotary tensor instrument once at intervals.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112763954A (en) * | 2021-02-07 | 2021-05-07 | 郑州大学第一附属医院 | Device for adjusting angular momentum based on bipolar magnet and nuclear magnetic resonance imaging method |
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2019
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112763954A (en) * | 2021-02-07 | 2021-05-07 | 郑州大学第一附属医院 | Device for adjusting angular momentum based on bipolar magnet and nuclear magnetic resonance imaging method |
| CN112763954B (en) * | 2021-02-07 | 2021-10-22 | 郑州大学第一附属医院 | Device for adjusting angular momentum based on bipolar magnet and nuclear magnetic resonance imaging method |
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