CN112083506A - Method for detecting interface orientation of medium layer based on fractional turn coil - Google Patents
Method for detecting interface orientation of medium layer based on fractional turn coil Download PDFInfo
- Publication number
- CN112083506A CN112083506A CN202010964345.4A CN202010964345A CN112083506A CN 112083506 A CN112083506 A CN 112083506A CN 202010964345 A CN202010964345 A CN 202010964345A CN 112083506 A CN112083506 A CN 112083506A
- Authority
- CN
- China
- Prior art keywords
- receiving coil
- coil
- electromotive force
- electric field
- medium
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
- 238000000034 method Methods 0.000 title claims abstract description 72
- 230000005684 electric field Effects 0.000 claims abstract description 72
- 238000004804 winding Methods 0.000 claims abstract description 18
- 230000010354 integration Effects 0.000 claims abstract description 16
- 230000008859 change Effects 0.000 claims abstract description 12
- 230000008878 coupling Effects 0.000 claims abstract description 9
- 238000010168 coupling process Methods 0.000 claims abstract description 9
- 238000005859 coupling reaction Methods 0.000 claims abstract description 9
- 238000001514 detection method Methods 0.000 claims description 14
- 230000008569 process Effects 0.000 claims description 9
- 230000009466 transformation Effects 0.000 claims description 6
- 230000004907 flux Effects 0.000 claims description 4
- 230000035699 permeability Effects 0.000 claims description 3
- 238000005070 sampling Methods 0.000 claims description 3
- 239000000126 substance Substances 0.000 claims description 3
- 238000005259 measurement Methods 0.000 abstract description 9
- 238000004364 calculation method Methods 0.000 description 8
- 238000010586 diagram Methods 0.000 description 8
- 238000003384 imaging method Methods 0.000 description 3
- 238000003708 edge detection Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 230000004044 response Effects 0.000 description 2
- 230000002238 attenuated effect Effects 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000005553 drilling Methods 0.000 description 1
- 239000003208 petroleum Substances 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
Images
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
- G01V3/00—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation
- G01V3/18—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation specially adapted for well-logging
- G01V3/26—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation specially adapted for well-logging operating with magnetic or electric fields produced or modified either by the surrounding earth formation or by the detecting device
- G01V3/28—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation specially adapted for well-logging operating with magnetic or electric fields produced or modified either by the surrounding earth formation or by the detecting device using induction coils
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B49/00—Testing the nature of borehole walls; Formation testing; Methods or apparatus for obtaining samples of soil or well fluids, specially adapted to earth drilling or wells
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
- G01V3/00—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation
- G01V3/38—Processing data, e.g. for analysis, for interpretation, for correction
Landscapes
- Life Sciences & Earth Sciences (AREA)
- Engineering & Computer Science (AREA)
- Geology (AREA)
- Physics & Mathematics (AREA)
- Remote Sensing (AREA)
- Environmental & Geological Engineering (AREA)
- General Life Sciences & Earth Sciences (AREA)
- General Physics & Mathematics (AREA)
- Geophysics (AREA)
- Mining & Mineral Resources (AREA)
- Electromagnetism (AREA)
- Fluid Mechanics (AREA)
- Geochemistry & Mineralogy (AREA)
- Geophysics And Detection Of Objects (AREA)
Abstract
The invention provides a method for detecting the interface orientation of a medium layer based on a fractional turn coil, which comprises the steps of adopting an axisymmetric winding round transmitting coil and an asymmetrically wound receiving coil which is coaxial and parallel with the transmitting coil, wherein the receiving coil can completely eliminate the direct coupling electromotive force generated by the transmitting coil to the receiving coil under an infinite uniform medium and only receives the signal of a transmitting signal reflected by a stratum interface; calculating a reflection field received by the receiving coil by adopting a mirror image method, obtaining a total electric field at the receiving coil according to a field superposition theory, and calculating induced electromotive force of the receiving coil by adopting Gaussian integration; the method has the advantages that high-precision measurement of the layer interface position is achieved according to the induced electromotive force amplitude and the phase angle change rule, the reflection field at the layer interface is calculated by adopting a mirror image method, the non-axisymmetric model is converted into the axisymmetric model, the calculated model can adopt a fast algorithm of the axisymmetric model, and the method has important significance for achieving high-precision measurement of the layer interface position and constantly inverting the information of the medium layer.
Description
Technical Field
The invention relates to the technical field of well logging, in particular to a method for detecting the interface orientation of a medium layer based on a fractional turn coil.
Background
With the rapid development of detection technology, remote detection and imaging systems have become a hot point problem, and especially in the fields of airplanes, radars, underwater submarines, geological exploration and the like, the development of imaging and medium detection of three-dimensional vector fields becomes very important research content, especially in complex environments, signals received by a measurement system are seriously interfered by background signals, and large errors exist when distance and direction information of an object/medium are remotely detected, so that a rapid response system cannot accurately identify the detected object. In the process of remote edge detection, the reflected signal of the medium layer interface is very weak, most of the signals received by the receiver come from background signals, serious misjudgment and missed judgment occur in the process of edge detection, the distance and the azimuth information of the layer interface cannot be effectively detected, and great challenges are met in the aspects of measuring the layer interface distance, electromagnetic information imaging and the like.
In the petroleum exploration and development engineering, the logging instrument can effectively detect the apparent conductivity of the layered stratum in a vertical well, the true conductivity of the stratum can be obtained through inversion, and the detection technology for the position of the layer interface is slowly developed. For the detection of the position of the layer interface, the traditional logging instrument can not completely eliminate the direct-coupled electromotive force in a medium due to the fact that the shielding coil can not completely eliminate the direct-coupled electromotive force, so that the proportion of direct-coupled signals in induced electromotive force generated by the receiving coil is large, the proportion of reflected signals is small, particularly when the layer interface is far, the layer interface reflected signals are seriously attenuated, the direction and the distance of the layer interface can not be effectively analyzed through the amplitude phase angle of the induced electromotive force, and the conductivity of the stratum can be solved through the induced electromotive force.
On the other hand, due to the existence of the layer interface, the layer interface reflects the electromagnetic wave emitted by the instrument transmitting coil, so that the induced electromotive force generated by the traditional circular symmetric receiving coil can generate a phenomenon of signal attenuation.
Aiming at the problems, the invention provides a method for detecting the orientation of a medium layer interface based on a fractional turn coil, which adopts an asymmetrically wound receiving coil, can effectively analyze the intensity of an electric field through rotation, realizes the measurement of the electric fields with different intensities at the receiving coil, and further realizes the orientation measurement of the layer interface through the amplitude of induced electromotive force.
Disclosure of Invention
Objects of the invention
In order to overcome at least one defect in the prior art, the invention provides a method for detecting the interface orientation of a medium layer based on a fractional turn coil. The receiving coil wound asymmetrically is adopted, the intensity of electric field can be effectively analyzed through rotation, electric fields with different intensities at the receiving coil are measured, and then the azimuth measurement of a layer interface is realized through the amplitude of induced electromotive force.
(II) technical scheme
As a first aspect of the invention, the invention discloses a method for detecting the interface orientation of a medium layer based on a fractional turn coil, which comprises the following steps:
and 5, measuring the layer interface orientation according to the induced electromotive force through the amplitude of the induced electromotive force and the change rule of the phase angle.
In a possible implementation manner, in the step 1, the transmitting coil is a circular transmitting coil wound in an axisymmetrical manner; the receiving coil is a fractional turn far detection receiving coil which is coaxial and parallel with the transmitting coil and is wound asymmetrically.
In a possible implementation manner, in the step 1, the asymmetrically wound fractional turn far detection receiving coil is specifically represented by:
a disc for winding a coil is equally divided into even fan-shaped areas passing through the center of a circle, and the even fan-shaped areas are clockwise arranged from 1 to N; n > = 4;
based on the sector areas, each turn of coil is divided into N-1 fractional sub-turns, each fractional sub-turn is wound on one sector area, the winding directions of the fractional sub-turns of two adjacent sector areas are opposite, and at the moment, the sector area N is empty;
based on the fractional sub-turns, the sub-turn coefficient ratio of the sector region from 1 to N-1 winding fractional sub-turns satisfies:
Wherein the content of the first and second substances,Nthe number of the sector areas;J iis the sector areaiThe corresponding sub-turn coefficient;
based on the fractional sub-turns, each fractional sub-turn comprises a circumferential arc part and a radial straight line part, the circumferential arc part is wound on the circumferential part of the sector area, and the radial straight line part is wound on the radial tangent plane part passing through the center of a circle of the sector area.
In a possible implementation manner, in step 1, the completely eliminating, by the receiving coil, the direct-coupled electromotive force generated by the transmitting coil to the receiving coil under an infinite homogeneous medium is specifically:
the transmitting coil and the receiving coil are coaxial and parallel, the transmitting coil generates an electric field in a concentric circle at the receiving coil, the integral result of the electric field along the receiving coil is zero, and the sum of magnetic fluxes passed by the receiving coil is zero, namely the induced electromotive force generated by the receiving coil is zero.
In a possible implementation manner, in step 2, the calculating the reflected field of the transmitting coil at the receiving coil by using a mirror image method specifically includes:
because the existence of the second layer medium causes the medium model not to be axisymmetric, the mirror image method eliminates the influence of the second layer medium, so that the calculated model adopts the algorithm of an axisymmetric model to realize the process of calculating the reflection field.
In a possible implementation manner, in the step 2, a dummy transmitting coil generated by the mirror image method is defined as a mirror image source, and a real transmitting coil is defined as a real source; the relational expression of the mirror image source and the real source is as follows:
wherein
Is the current of the mirror image source,
is the current of the real source of the current,
the dielectric layer interface reflection coefficient;
the expression of (a) is:
wherein
And
is medium magnetic permeability;
and
is a dielectric complex dielectric constant expressed as
，
，
、
Is a dielectric constant of a medium, and is,
、
in order to be the conductivity of the medium,
is the angular frequency of the electromagnetic wave,
as the incident angle of the electromagnetic wave,jin the form of imaginary unit, the imaginary part,
=-1。
in a possible implementation, in the step 3, the field superposition theory is used to calculate the total electric field generated by the real source and the mirror source at the receiving coil after the mirror image method is used.
In a possible implementation manner, in step 4, the rotating the receiving coil and calculating the induced electromotive force when the receiving coil rotates by different angles by using gaussian integration specifically include:
calculating the induced electromotive force of the receiving coil using the Gaussian integration because the total electric field generated at the receiving coil is not an axisymmetric electric field due to the presence of a layer interface; and rotating the receiving coil, and calculating induced electromotive force when the receiving coil rotates at different angles according to the asymmetry of the receiving coil and the asymmetry of the electric field.
In a possible implementation manner, in the step 4, the induced electromotive force is calculated by using the gaussian integral, specifically represented as:
Vis an induced electromotive force of the receiving coil,Efor the strength of the electric field,dlintegration units for the receiving coil, converted with respect to angleθFunction of (2)
Wherein
For the receiving coil to be at an angleθThe vector mode of the tangential component of the electric field strength,Ris the radius of the coil, here,tdenoted as receiving coil atθThe tangential direction of (A);
using integral transformation
The result after transformation is
In a possible embodiment, the step 5 is specifically:
in the rotation process of the receiving coil, the induced electromotive force which changes along with the rotation angle is generated in a non-uniform electric field by the receiving coil due to an asymmetric structure, a plurality of peak values are formed, and the judgment of the layer interface direction is realized by analyzing the amplitude and the phase angle change of the induced electromotive force.
(III) advantageous effects
The invention provides a method for detecting the interface orientation of a medium layer based on a fractional turn coil, which is characterized in that a novel asymmetrically wound far detection receiving coil is designed, a coaxial and parallel arrangement mode of a transmitting coil and the receiving coil is adopted, so that the transmitting coil generates a concentric electric field at the receiving coil, the integral result of the electric field along the receiving coil is zero, namely the induced electromotive force generated by the receiving coil is zero, the direct coupling electromotive force generated by the transmitting coil under an infinite uniform medium is completely eliminated in the medium, and the direct coupling signal has zero interference on a reflected signal; because the existence of the second layer of medium causes the medium model not to be axisymmetric, the mirror image method can eliminate the influence of the second layer of medium, so that the calculated model can adopt the fast algorithm of the axisymmetric model to realize fast and high-precision calculation of the reflection field; calculating the total electric field generated by the real source and the mirror image source at the receiving coil after using the mirror image method by adopting a field superposition theory, and analyzing the influence of the layer interface on the electric field at the receiving coil through the total electric field at the receiving coil; the total electric field at the receiving coil is not an axisymmetric electric field due to the existence of the layer interface, induced electromotive force generated when the receiving coil rotates at different angles is calculated by rotating the receiving coil through Gaussian integration, and the layer interface azimuth information is judged through the variation rule of the amplitude and the phase angle of the induced electromotive force, so that the electromagnetic information of the layer interface is rapidly and highly accurately calculated.
Drawings
The embodiments described below with reference to the drawings are exemplary and intended to be used for explaining and illustrating the present invention and should not be construed as limiting the scope of the present invention.
Fig. 1 is a flowchart of a method for detecting the orientation of a medium layer interface based on a fractional turn coil according to the present invention.
Fig. 2 is a model schematic diagram of a novel asymmetric-winding far-detection circular receiving coil (N = 4) based on a fractional-turn coil method for detecting the interface orientation of a medium layer provided by the invention.
FIG. 3 is a schematic diagram of a constructed medium model of a method for detecting the interface orientation of a medium layer based on a fractional turn coil provided by the invention.
Fig. 4 is a schematic diagram of a medium model without considering the medium 2 of the method for detecting the interface orientation of the medium layer based on the fractional turn coil provided by the invention.
Fig. 5 is a schematic model diagram of a transmission coil after a medium 2 is considered in the method for detecting the interface orientation of the medium layer based on the fractional turn coil provided by the invention.
Fig. 6 is a distribution diagram of the total electric field at the receiving coil obtained by the field superposition theory of the method for detecting the interface orientation of the medium layer based on the fractional turn coil provided by the invention.
Fig. 7 is a schematic diagram of changes of induced electromotive force amplitude of the receiving coil and a rotation angle of the receiving coil in the method for detecting the interface orientation of the dielectric layer based on the fractional turn coil according to the present invention.
Fig. 8 is a schematic diagram illustrating changes of a phase angle of induced electromotive force of a receiving coil and a rotation angle of the receiving coil in the method for detecting the interface orientation of the dielectric layer based on the fractional turn coil according to the present invention.
Detailed Description
In order to make the implementation objects, technical solutions and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be described in more detail below with reference to the accompanying drawings in the embodiments of the present invention.
It should be noted that: in the drawings, the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described are some embodiments of the present invention, not all embodiments, and features in embodiments and embodiments in the present application may be combined with each other without conflict. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
In the description of the present invention, it is to be understood that the terms "central," "longitudinal," "lateral," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," and the like are used in the orientation or positional relationship indicated in the drawings, which are used for convenience in describing the invention and for simplicity in description, and are not intended to indicate or imply that the referenced device or element must have a particular orientation, be constructed and operated in a particular orientation, and are not to be considered limiting of the scope of the invention.
A first embodiment of a method for detecting the orientation of a medium layer interface based on a fractional turn coil according to the present invention is described in detail below with reference to fig. 1-8. As shown in fig. 1 to 8, the method for detecting the interface orientation of the medium layer provided in this embodiment mainly includes: step 1, step 2, step 3, step 4 and step 5.
With the wide use of inclined wells and horizontal wells, the existence of layer interfaces causes that a computed logging model is not axisymmetric any more, and for computing the azimuth distance of the layer interfaces, a three-dimensional numerical computation method is needed, so that the computation precision is not high and the computation amount is large, thereby increasing the logging response time. The invention adopts a mirror image method to calculate the reflection field of the transmitting coil at the layer interface aiming at the inclined well and the horizontal well, converts the three-dimensional non-axisymmetric model into the axisymmetric model, greatly reduces the calculated amount, and realizes the measurement of the layer interface and the stratum conductivity through the electromagnetic wave phase angle and the attenuation rule. The invention enables the logging instrument to detect the position and the orientation of the boundary of the medium layer in the reservoir, and the logging instrument advances along the parallel direction of the reservoir, thereby accurately evaluating the size of the oil and gas reservoir.
in the step 1, the transmitting coil is a circular transmitting coil wound in an axisymmetrical manner; the receiving coil is a novel fractional-turn far detection receiving coil which is wound asymmetrically and is coaxial and parallel to the transmitting coil.
and 5, realizing high-precision measurement of the layer interface orientation by the amplitude of the induced electromotive force and the change rule of the phase angle according to the induced electromotive force.
In step 1, the asymmetrically wound fractional-turn far detection receiving coil is specifically represented by a model:
a disc for winding a coil is equally divided into even fan-shaped areas passing through the center of a circle, and the even fan-shaped areas are clockwise arranged from 1 to N; n > = 4;
based on the sector areas, each turn of coil is divided into N-1 fractional sub-turns, each fractional sub-turn is wound on one sector area, the winding directions of the fractional sub-turns of two adjacent sector areas are opposite, and at the moment, the sector area N is empty;
based on the fractional sub-turns, the sub-turn coefficient ratio of the fractional sub-turns wound in the sector areas from 1 to N-1 is
And the ratio satisfies the equation:
Wherein the content of the first and second substances,Nthe number of the sector areas;J iis the sector areaiThe coefficient of the corresponding sub-turn is,J iis a fraction;
on the basis of the fractional sub-turns, a sub-turn lead divides the fractional sub-turns into a circumferential arc part and a radial straight line part, each fractional sub-turn comprises a circumferential arc part and a radial straight line part, the circumferential arc part is wound on the circumferential part of the sector area, and the radial straight line part is wound on the radial tangent plane part of the sector area passing through the center of a circle; for the purpose of intuitively describing a model of coil winding completion, fig. 2 shows a model schematic diagram of a receiving coil when N =4, and the sub-turn coefficients of the sector areas 1 to 3 are 0.25, 0.5, and 0.25, respectively.
In step 1, the completely eliminating, according to the receiving coil, the direct-coupled electromotive force generated by the transmitting coil to the receiving coil under the infinite homogeneous medium includes: the transmitting coil and the receiving coil are coaxial and parallel, the transmitting coil generates an electric field in a concentric circle at the receiving coil, the integral result of the electric field along the receiving coil is zero, and the sum of magnetic fluxes passed by the receiving coil is zero, namely the induced electromotive force generated by the receiving coil is zero.
According to the asymmetric winding receiving coil, the direct coupling electromotive force of the transmitting coil is eliminated, and the method is specifically expressed as follows:
in an electric field generated by a uniform electric field or a coaxial parallel circular transmitting coil in a uniform medium, magnetic fluxes passing through N fan-shaped areas are all equal, and according to the winding direction of a receiving coil, the induced electromotive force received by the receiving coil is 0 under the condition;
the electric field generated by the coaxial parallel circular transmitting coil in the uniform medium is concentric on the plane of the receiving coil, so that all radial straight line parts of the receiving coil passing through the center of a circle are always vertical to the direction of the electric field, all circumferential arc parts on the circumference are always parallel to the direction of the electric field, and according to the winding direction of the receiving coil, the induced electromotive force received by the receiving coil is 0 under the condition;
under the condition that a stratum interface exists near the receiving coil, the interface reflects electromagnetic waves generated by the transmitting coil, the electromagnetic waves are relative to an electric field generated by a non-uniform or non-concentric circle of the receiving coil, and therefore induced electromotive force is generated on the receiving coil.
In the step 2, in the horizontal well, the medium model is a non-axisymmetric model, and for convenience of calculation, the medium model is configured as shown in fig. 3; the reflection field of the transmitting coil at the receiving coil is calculated by using a mirror image method (i.e. the reflection field of the transmitting coil at the layer interface is calculated by using the mirror image method), and an equivalent model of the mirror image method is shown in fig. 4 and 5, and specifically includes: because the existence of the second layer of medium causes the medium model not to be axisymmetric, the mirror image method eliminates the influence of the second layer of medium, so that the calculated model can adopt a fast algorithm of an axisymmetric model to realize fast and high-precision calculation of the reflection field.
In the step 2, a virtual transmitting coil generated by adopting the mirror image method is defined as a mirror image source, and a real transmitting coil is defined as a real source;
because the existence of the second layer of medium causes the (horizontal well) medium model not to be axisymmetric, the mirror image method can eliminate the influence of the second layer of medium, and the specific method is as follows:
to visualize the application of the mirror method to logging while drilling, a dummy transmitter coil (i.e., the mirror transmitter coil in fig. 5) is introduced into the medium 2, which is mirror-symmetric to the transmitter coil in the medium 1, and is defined as a mirror source, while a real transmitter coil is defined as a real source. The regions in medium 2 were completely replaced by the medium of medium 1.
The relational expression of the mirror image source and the real source is as follows:
wherein
Is the current of the mirror image source,
is the current of the real source of the current,
is the interface reflection coefficient of medium 1 and medium 2;
the expression of (a) is:
wherein
And
the magnetic permeability of medium 1 and medium 2;
and
is the complex dielectric constant of medium 1 and medium 2, and has the expression
，
，
、
Is the dielectric constant of medium 1 and medium 2,
、
which is the electrical conductivity of the medium 1 and the medium 2,
being angular frequency of electromagnetic waves，
As the incident angle of the electromagnetic wave,jin the form of imaginary unit, the imaginary part,
=-1。
to further illustrate the calculation process, the calculation model shown in fig. 3 is used for demonstration: setting the relative dielectric constants of the medium 1 and the medium 2 to be 5, and the relative magnetic conductivities of the medium 1 and the medium 2 to be 1; the conductivity of the medium 1 is 0.01S/m, and the conductivity of the medium 2 is 0.5S/m; the circle center coordinates of the transmitting coil (0, 0, 0) and the receiving coil (0, 0, 0.5), the radiuses of the transmitting coil and the receiving coil are both 0.03m, the number of turns of the transmitting coil is 100, and the number of turns of the receiving coil is 50; the layer interface distance is 1m from the z axis; the current of the transmitting coil is 1A sine alternating current with the frequency of 100 KHz.
The non-axisymmetric model adopts a mirror image method, so that the calculated model can adopt a quick algorithm of the axisymmetric model to realize quick and high-precision calculation of the reflection field.
In the step 3, the total electric field generated by the real source and the mirror source at the receiving coil after the mirror image method is used is calculated by adopting the field superposition theory. The effect of the layer interface on the electric field at the receiver coil can be analyzed by the total electric field at the receiver coil, which is shown in fig. 6.
In step 4, the rotating the receiving coil and calculating the induced electromotive force when the receiving coil rotates by different angles by using gaussian integration specifically include: the total electric field generated at the receiving coil is not an axisymmetric electric field due to the existence of a layer interface, the induced electromotive force generated by the asymmetric receiving coil is nonzero, and the induced electromotive force of the receiving coil is calculated by adopting the Gaussian integral; and rotating the receiving coil, and calculating the induced electromotive force of the receiving coil when the receiving coil rotates at different angles according to the asymmetry of the receiving coil and the asymmetry of the electric field, so as to realize the rapid and high-precision calculation of the induced electromotive force of the receiving coil in the non-uniform electric field.
In step 4, the specific gaussian integration method is as follows (only the algorithm of gaussian integrals of circumferential arc sections 0 to pi/2 of the model of the N =4 receiving coil is given here, which is the same as the algorithm of gaussian integrals of other circumferential arc sections and radial straight line sections, and is not stated again):
calculating the induced electromotive force by using the Gaussian integral is specifically expressed as:
Vis an induced electromotive force of the receiving coil,Efor the strength of the electric field,dlintegration units for the receiving coil, converted with respect to angleθFunction of (2)
Wherein
For the receiving coil to be at an angleθThe vector mode of the tangential component of the electric field strength,Ris the radius of the coil, here,tdenoted as receiving coil atθThe tangential direction of (A);
using integral transformation
The result after transformation is
Wherein, the step 5 specifically comprises the following steps: the method is characterized in that a receiving coil is wound asymmetrically, the receiving coil generates induced electromotive force which changes along with a rotation angle in a non-uniform electric field due to an asymmetric structure in the rotation process of the receiving coil, a plurality of peak values are formed, and the judgment of the layer interface direction is realized by analyzing the amplitude and phase angle change of the induced electromotive force.
The induced electromotive force generated by the sending coil under the infinite uniform medium can be completely eliminated by adopting the receiving coil wound asymmetrically, so that signals received by the receiving coil all come from reflected waves, and the direction of the layer interface is calculated through the amplitude and the phase angle change rule of the induced electromotive force. FIG. 7 is an image of the induced electromotive force amplitude change of 360 ° rotation of the receiving coil when the layer interface is 1m from the z-axis; FIG. 8 is an image of the phase angle change of the induced electromotive force induced by a 360 ° rotation of the receiving coil when the layer interface is at a distance of 1m from the z-axis.
As shown in fig. 7, for different rotation angles, 4 peaks of induced electromotive force exist, wherein the first and third peaks are two parts with less reverse winding, the maximum peak is the part with the most forward winding turns, and the minimum peak is the part without winding the receiving coil, and by rotating the receiving coil, the position of the layer interface can be effectively judged according to the peak change of the induced electromotive force; when N =4, the peak value is maximum when the receiving coil rotates 135 ° as judged by the amplitude of the coil, and the angular bisector of the sector region 2 is the x axis at this time, that is, the direction in which the electric field is maximum is the positive direction of the x axis, so the layer interface is in the positive direction of the x axis.
When the receiving coil has N sectors, it is assumed that sector 1 is located
Rotating the receiving coil within 0 deg. to obtain different peak values of induced electromotive force, and obtaining the rotation angle when the peak value is maximum by image, i.e. the maximum position of electric field is the rotation of angular bisector of sector region N/2
The position of the layer interface can be obtained, and the obtained direction of the layer interface is
。
From fig. 8, it can be obtained that the phase angle of the induced electromotive force in the rotation process of the instrument jumps between two constant positive and negative values, the phase angle corresponding to the part with the most winding turns keeps the angle the largest, and the phase angles corresponding to the other three peaks keep the angle smaller; the azimuth angle of the layer interface can be judged according to the rotating angle corresponding to the phase angle, so that the high-precision measurement of the azimuth information of the layer interface can be realized by analyzing the amplitude of the induced electromotive force of the receiving coil and the change rule of the phase angle.
The invention relates to a method for detecting the interface orientation of a medium layer based on a fractional turn coil, which is characterized in that a novel asymmetrically wound far detection receiving coil is designed, a coaxial and parallel arrangement mode of a transmitting coil and the receiving coil is adopted, so that the transmitting coil generates a concentric electric field at the receiving coil, the integral result of the electric field along the receiving coil is zero, namely the induced electromotive force generated by the receiving coil is zero, the direct coupling electromotive force generated by the transmitting coil under an infinite uniform medium is completely eliminated in the medium, and the direct coupling signal has zero interference on a reflected signal; because the existence of the second layer of medium causes the medium model not to be axisymmetric, the mirror image method can eliminate the influence of the second layer of medium, so that the calculated model can adopt the fast algorithm of the axisymmetric model to realize fast and high-precision calculation of the reflection field; calculating the total electric field generated by the real source and the mirror image source at the receiving coil after using the mirror image method by adopting a field superposition theory, and analyzing the influence of the layer interface on the electric field at the receiving coil through the total electric field at the receiving coil; the total electric field at the receiving coil is not an axisymmetric electric field due to the existence of the layer interface, induced electromotive force generated when the receiving coil rotates at different angles is calculated by rotating the receiving coil through Gaussian integration, and the layer interface azimuth information is judged through the variation rule of the amplitude and the phase angle of the induced electromotive force, so that the electromagnetic information of the layer interface is rapidly and highly accurately calculated.
The above description is only for the specific embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the appended claims.
Claims (10)
1. A method for detecting the interface orientation of a medium layer based on a fractional turn coil is characterized by comprising the following steps:
step 1, completely eliminating direct coupling electromotive force generated by a transmitting coil to a receiving coil under an infinite uniform medium according to the receiving coil;
step 2, calculating a reflection field of the transmitting coil at the receiving coil by adopting a mirror image method according to the receiving coil and the transmitting coil;
step 3, calculating the total electric field generated by the transmitting coil at the receiving coil by adopting a field superposition theory according to the reflected field;
step 4, rotating the receiving coil according to the total electric field generated at the receiving coil and calculating induced electromotive force when the receiving coil rotates at different angles by adopting Gaussian integration;
and 5, measuring the layer interface orientation according to the induced electromotive force through the amplitude of the induced electromotive force and the change rule of the phase angle.
2. The method for detecting the interface orientation of the medium layer according to claim 1, wherein in the step 1, the transmitting coil is a circular transmitting coil wound with axial symmetry; the receiving coil is a fractional turn far detection receiving coil which is coaxial and parallel with the transmitting coil and is wound asymmetrically.
3. The method for detecting the interface orientation of a medium layer as claimed in claim 2, wherein in the step 1, the asymmetrically wound fractional turn far detection receiving coil is specifically represented by:
a disc for winding a coil is equally divided into even fan-shaped areas passing through the center of a circle, and the even fan-shaped areas are clockwise arranged from 1 to N; n > = 4;
based on the sector areas, each turn of coil is divided into N-1 fractional sub-turns, each fractional sub-turn is wound on one sector area, the winding directions of the fractional sub-turns of two adjacent sector areas are opposite, and at the moment, the sector area N is empty;
based on the fractional sub-turns, the sub-turn coefficient ratio of the sector region from 1 to N-1 winding fractional sub-turns satisfies:
Wherein the content of the first and second substances,Nthe number of the sector areas;J iis the sector areaiThe corresponding sub-turn coefficient;
based on the fractional sub-turns, each fractional sub-turn comprises a circumferential arc part and a radial straight line part, the circumferential arc part is wound on the circumferential part of the sector area, and the radial straight line part is wound on the radial tangent plane part passing through the center of a circle of the sector area.
4. The method for detecting the interface orientation of the dielectric layer according to claim 1, wherein in the step 1, the direct-coupled electromotive force generated by the transmitting coil to the receiving coil under the infinite homogeneous medium is completely eliminated according to the receiving coil, and specifically:
the transmitting coil and the receiving coil are coaxial and parallel, the transmitting coil generates an electric field in a concentric circle at the receiving coil, the integral result of the electric field along the receiving coil is zero, and the sum of magnetic fluxes passed by the receiving coil is zero, namely the induced electromotive force generated by the receiving coil is zero.
5. The method for detecting the interface orientation of the dielectric layer according to claim 1, wherein in the step 2, the reflected field of the transmitting coil at the receiving coil is calculated by a mirror image method, specifically:
because the existence of the second layer medium causes the medium model not to be axisymmetric, the mirror image method eliminates the influence of the second layer medium, so that the calculated model adopts the algorithm of an axisymmetric model to realize the process of calculating the reflection field.
6. The method for detecting the interface orientation of the dielectric layer according to claim 5, wherein in the step 2, a dummy transmitting coil generated by the mirror image method is defined as a mirror image source, and a real transmitting coil is defined as a real source; the relational expression of the mirror image source and the real source is as follows:
wherein
Is the current of the mirror image source,
is the current of the real source of the current,
the dielectric layer interface reflection coefficient;
the expression of (a) is:
wherein
And
is medium magnetic permeability;
and
is a dielectric complex dielectric constant expressed as
，
，
、
Is a dielectric constant of a medium, and is,
、
in order to be the conductivity of the medium,
is the angular frequency of the electromagnetic wave,
as the incident angle of the electromagnetic wave,jin the form of imaginary unit, the imaginary part,
=-1。
7. the method for detecting the interface orientation of a medium layer as claimed in claim 6, wherein in the step 3, the total electric field generated at the receiving coil by the real source and the mirror source after the mirror image method is used is calculated by adopting the field superposition theory.
8. The method for detecting the interface orientation of the medium layer as claimed in claim 1, wherein in the step 4, the step of rotating the receiving coil and calculating the induced electromotive forces of the receiving coil when the receiving coil rotates at different angles by using gaussian integration specifically comprises:
calculating the induced electromotive force of the receiving coil using the Gaussian integration because the total electric field generated at the receiving coil is not an axisymmetric electric field due to the presence of a layer interface; and rotating the receiving coil, and calculating induced electromotive force when the receiving coil rotates at different angles according to the asymmetry of the receiving coil and the asymmetry of the electric field.
9. The method for detecting an interface orientation of a dielectric layer as claimed in claim 8, wherein in the step 4, the induced electromotive force is calculated by the gaussian integration as:
Vis an induced electromotive force of the receiving coil,Efor the strength of the electric field,dlintegration units for the receiving coil, converted with respect to angleθFunction of (2)
Wherein
For the receiving coil to be at an angleθThe vector mode of the tangential component of the electric field strength,Ris the radius of the coil, here,tdenoted as receiving coil atθThe tangential direction of (A);
using integral transformation
The result after transformation is
10. The method for detecting the interface orientation of the medium layer according to claim 1, wherein the step 5 is specifically:
in the rotation process of the receiving coil, the induced electromotive force which changes along with the rotation angle is generated in a non-uniform electric field by the receiving coil due to an asymmetric structure, a plurality of peak values are formed, and the judgment of the layer interface direction is realized by analyzing the amplitude and the phase angle change of the induced electromotive force.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202010964345.4A CN112083506A (en) | 2020-09-15 | 2020-09-15 | Method for detecting interface orientation of medium layer based on fractional turn coil |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202010964345.4A CN112083506A (en) | 2020-09-15 | 2020-09-15 | Method for detecting interface orientation of medium layer based on fractional turn coil |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN112083506A true CN112083506A (en) | 2020-12-15 |
Family
ID=73737993
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202010964345.4A Withdrawn CN112083506A (en) | 2020-09-15 | 2020-09-15 | Method for detecting interface orientation of medium layer based on fractional turn coil |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN112083506A (en) |
-
2020
- 2020-09-15 CN CN202010964345.4A patent/CN112083506A/en not_active Withdrawn
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US8055193B2 (en) | Underwater remote sensing | |
| US7990153B2 (en) | Compensated directional resistivity measurements | |
| US8159227B2 (en) | Methods for making directional resistivity measurements | |
| EA007644B1 (en) | Method of imaging subsurface formations using a virtual source array | |
| JP2008538042A (en) | Pointing vector based method for determining the direction and position of electromagnetic sources | |
| JP4527484B2 (en) | Condition detection device | |
| CN111025231B (en) | Magnetic induction through-the-earth positioning method based on signal direction | |
| WO2006134329A2 (en) | Underwater remote sensing | |
| WO2019245487A1 (en) | Operating method of a metal detector capable of measuring target depth | |
| CN109188534A (en) | A kind of underwater form of metal detection method and device based on active electric-field principle | |
| CN112083506A (en) | Method for detecting interface orientation of medium layer based on fractional turn coil | |
| Liu et al. | Synthesized magnetic field focusing for the non-destructive testing of oil and gas well casing pipes using pulsed eddy-current array | |
| CN111929737B (en) | Method and device for remotely detecting layer interface position and electromagnetic information | |
| WO2016123803A1 (en) | Antenna circuit for logging, antenna system and corresponding logging method | |
| Li et al. | Calibration method of azimuth electromagnetic boundary detection logging while drilling based on air–seawater double-layer dielectric as reflection interface | |
| CN111220947A (en) | Magnetic induction through-the-earth positioning method based on path loss | |
| CN111929736B (en) | Asymmetric fractional turn coil winding method for measuring alternating magnetic field | |
| NO166897B (en) | PROCEDURE AND APPARATUS FOR MEASURING THE INTERNAL DIAMETER OF A METAL TUBE. | |
| CN109814157B (en) | Method and device for identifying relative gesture and computer storage medium | |
| EP3655769A1 (en) | Multi-coil tool for attenuation of motion-induced noise | |
| Liu et al. | A study on directional resistivity logging-while-drilling based on self-adaptive hp-FEM | |
| CN113341471A (en) | Wide-width electromagnetic induction logging method and device, storage medium and electronic equipment | |
| GB2459218A (en) | Underwater signal direction determination | |
| CN112081586B (en) | Multi-spectrum stratum boundary far detection method and device | |
| CN109952519B (en) | Application of E-field antenna to resistivity logging tool |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| WW01 | Invention patent application withdrawn after publication | ||
| WW01 | Invention patent application withdrawn after publication |
Application publication date: 20201215 |