CN113311490A - Detection method, device and medium for transient electromagnetic emission focusing based on weighted minimum mean square error - Google Patents
Detection method, device and medium for transient electromagnetic emission focusing based on weighted minimum mean square error Download PDFInfo
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Abstract
The embodiment of the invention discloses a detection method, a device and a medium for transient electromagnetic emission focusing based on weighted minimum mean square error; the method can comprise the following steps: acquiring the magnetic field intensity superposition values of eddy current fields of all transmitting array elements at set positions based on a transmitting array model; a plurality of position sampling points are arranged in the longitudinal direction of the target radius, and the longitudinal distribution of the magnetic field strength of the emission array at the target radius is obtained on the basis of the magnetic field strength superposition value and the position sampling points; and solving and obtaining the optimal weight corresponding to each transmitting array element based on a weighted minimum mean square error criterion according to the expected magnetic field intensity distribution and the longitudinal magnetic field intensity distribution of the transmitting array at the target radius.
Description
Technical Field
The embodiment of the invention relates to the technical field of underground detection, in particular to a transient electromagnetic emission focusing detection method, a device and a medium based on weighted minimum mean square error.
Background
With the development of oil and gas fields for many years, under the action of chemical, thermal, microbial and water injection, polymer injection, gas injection and other mixed factor displacement, the characteristics of the reservoir such as porosity, permeability, resistivity and the like will change. In addition, oil and gas casings suffer from various degrees of damage, such as shrinkage, deformation corrosion, and cracking. These damages will directly affect the production and the service life of the oil and gas well; therefore, the damage condition of the casing and the dynamic change of the reservoir can be accurately known in time, and the method has important significance for evaluating the exploitation effect, adjusting the exploitation strategy and improving the recovery ratio.
The transient electromagnetic detection technology is that when alternating current is conducted in a transmitting coil, eddy current coaxial with the coil is induced in surrounding rock strata by an alternating electromagnetic field; subsequently, the eddy current induced secondary magnetic field induces a secondary induced electromotive force in the receiving coil, the magnitude of which is proportional to the eddy current magnitude, and the magnitude of the eddy current is proportional to the formation resistivity. Based on the above, the resistivity information can be used for effectively identifying the residual wall thickness of the casing and evaluating the oil-gas content of the stratum, so that the transient electromagnetic logging technology is highly emphasized at home and abroad, and is gradually a leading-edge problem in the field of exploration and development.
Currently, a conventional transient electromagnetic detection scheme mostly adopts a single-transmission and multiple-reception array structure to perform weighting processing on signals received by each array element so as to improve the signal-to-noise ratio of a drilling transient electromagnetic system; in addition, similarly, there is also a double-layer casing damage detection method based on an auxiliary probe, which reduces the longitudinal diffusion range by a small auxiliary probe and improves the longitudinal detection accuracy. However, the detection method adopts two probes, but only jointly explains the data of the two probes, and does not further analyze and jointly process the data of the two probes. Therefore, it is a difficult point of transient electromagnetic downhole detection to study transient electromagnetic array signal processing composed of multiple array elements to improve longitudinal resolution.
Disclosure of Invention
In view of this, embodiments of the present invention are to provide a method, an apparatus, and a medium for detecting a transient electromagnetic emission focus based on a weighted minimum mean square error; the transient electromagnetic emission magnetic field focusing can be realized, the eddy current field is focused in the interested detection area, the longitudinal diffusion range of the transient electromagnetic eddy current field is reduced, the longitudinal resolution of the downhole detection of the transient electromagnetic is improved, and an important basis is provided for realizing the high-precision reservoir detection and the accurate evaluation of casing damage of the downhole of the transient electromagnetic.
The technical scheme of the embodiment of the invention is realized as follows:
in a first aspect, an embodiment of the present invention provides a method for detecting a transient electromagnetic emission focus based on a weighted minimum mean square error, where the method includes:
acquiring the magnetic field intensity superposition values of eddy current fields of all transmitting array elements at set positions based on a transmitting array model;
a plurality of position sampling points are arranged in the longitudinal direction of the target radius, and the longitudinal distribution of the magnetic field strength of the emission array at the target radius is obtained on the basis of the magnetic field strength superposition value and the position sampling points;
and solving and obtaining the optimal weight corresponding to each transmitting array element based on a weighted minimum mean square error criterion according to the expected magnetic field intensity distribution and the longitudinal magnetic field intensity distribution of the transmitting array at the target radius.
In a second aspect, an embodiment of the present invention provides a detection apparatus for focusing transient electromagnetic emission based on weighted minimum mean square error, the apparatus including: a first acquisition part, a second acquisition part and a solution part; wherein the content of the first and second substances,
the first acquisition part is configured to acquire the magnetic field intensity superposition value of the eddy current field of all the transmitting array elements at a set position based on a transmitting array model;
the second acquisition part is configured to arrange a plurality of position sampling points in the longitudinal direction of a target radius, and acquire the longitudinal distribution of the magnetic field strength of the emission array at the target radius based on the magnetic field strength superposition value and the position sampling points;
the solving part is configured to solve and obtain the optimal weight corresponding to each transmitting array element based on a weighted minimum mean square error criterion according to the expected magnetic field intensity distribution and the longitudinal distribution of the magnetic field intensity of the transmitting array at the target radius.
In a third aspect, an embodiment of the present invention provides a computer storage medium storing a weighted minimum mean square error based detection program for transient electromagnetic transmit focusing, which when executed by at least one processor implements the steps of the method for detecting weighted minimum mean square error based transient electromagnetic transmit focusing according to the first aspect.
The embodiment of the invention provides a detection method, a device and a medium for transient electromagnetic emission focusing based on weighted minimum mean square error; the optimal emission weighting of each emission array element is solved by adopting a transient electromagnetic emission array and a weighted minimum mean square error criterion, and the magnitude and the direction of emission current of each emission array element are adjusted according to weighting parameters, so that the eddy current field distribution of transient electromagnetism is adjusted, the focusing of a transient electromagnetic emission magnetic field is realized, the eddy current field is focused in an interested detection area, the longitudinal diffusion range of the transient electromagnetic eddy current field is reduced, the longitudinal resolution of the downhole detection of the transient electromagnetism is further improved, and an important basis is provided for realizing the high-precision reservoir detection and the precise evaluation of casing damage of the downhole of the transient electromagnetism.
Drawings
FIG. 1 is a schematic diagram of a downhole detection system capable of implementing embodiments of the present invention;
FIG. 2 is a schematic diagram of a driving process provided by an embodiment of the present invention;
FIG. 3 is a schematic flow chart of a detection method for transient electromagnetic emission focusing based on weighted minimum mean square error according to an embodiment of the present invention;
FIG. 4 is a schematic diagram of a downhole columnar multi-layer dielectric transient electromagnetic emission array model provided by an embodiment of the invention;
FIG. 5 is a schematic diagram of a vortex field distribution of emission diffusion provided by an embodiment of the present invention;
fig. 6 is a schematic diagram of magnetic field strength of M selected sampling points according to an embodiment of the present invention;
FIG. 7 is a schematic diagram of a distribution of an emitted focused eddy current field provided by an embodiment of the present invention;
FIG. 8 is a schematic diagram of a detection apparatus for transient electromagnetic emission focusing based on weighted minimum mean square error according to an embodiment of the present invention;
fig. 9 is a schematic diagram of a hardware structure of a computing device according to an embodiment of the present invention.
Detailed Description
The technical solution 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.
Referring to FIG. 1, there is shown a downhole detection system 1 capable of implementing embodiments of the present invention, which may include: the device comprises a downhole detection device 10 based on transient electromagnetism, a cable 11, a ground case 12 and an upper computer 13.
In some examples, continuing with FIG. 1, a transient electromagnetic-based downhole detection apparatus 10 includes: the device comprises a transient electromagnetic transmitting array 101, a transient electromagnetic receiving probe 102, a transmitting signal driving circuit 103, a signal acquisition circuit 104, a data transmission circuit 105 and a main control circuit 106. In some examples, the transient electromagnetic transmit array 101 is comprised of a plurality of transmit coils wound on a magnetic core; the transient electromagnetic receiving probe 102 is composed of a receiving coil wound on a magnetic core, and is placed at a desired focusing position of the transmitting array 101, preferably at a central position of the transmitting array 101, or at other required positions, which is not limited in the embodiment of the present invention. By electrifying the transmitting array elements in the transient electromagnetic transmitting array 101, an eddy current field can be induced in each layer of underground medium, at the interval of transmitting excitation and switching off, the transient electromagnetic receiving probe 102 is utilized to receive the information of a secondary eddy current field which is attenuated along with time in the stratum, and the resistivity of the underground medium can be inverted by analyzing the induced electromotive force of the secondary field. In some examples, the transmit signal driver circuit 103 is used to generate a periodic bipolar step signal or a ramped step signal; the signal acquisition circuit 104 is used for acquiring the underground secondary magnetic field information received by the receiving coil; the data transmission circuit 105 is used for transmitting data to the ground chassis 12 through the cable 11; the main control circuit 106 is configured to respond to a control command of the surface chassis 12 and control each downhole module to operate in order, and a specific driving flow is shown in fig. 2; taking the number of the transmitting array elements of the transmitting array as N, the main control circuit 106 may control the transmitting signal driving circuit 103 to apply the transmitting current to each transmitting array element.
In some examples, the cable 11 may be an existing cable of an electrical submersible pump/intelligent completion system, a cable of a logging winch for powering a transient electromagnetic downhole detection system, and bidirectional communication. The upper computer 13 can send a control command to the lower computer through the cable 11, and the lower computer can also return signals in real time, so that the data transmission speed is high, and the communication real-time performance is higher. The ground case 12 and the upper computer 13 are generally disposed in a logging winch, wherein the ground case 12 is used for implementing format conversion of logging data and multichannel acquisition and processing of downhole measurement signals, and transmitting detection signals to the upper computer 13 system. Specifically, the upper computer 13 module is connected to the surface case 12 through a USB, and is configured to receive downhole monitoring data collected by the surface case 12, including instrument parameters, operating time, depth of the instrument, induced electromotive force of a receiving coil, and the like, and complete storage, processing, playback, and display of the data.
In the process of implementing underground detection, the main control circuit 106 controls the emission signal driving circuit 103 to apply periodic bipolar step signals or oblique step signals to each emission array element of the transient electromagnetic emission array 101, eddy current fields of the emission array elements are superposed and gathered together to form a superposed eddy current field, and the distribution form of the superposed eddy current field can be controlled by controlling the magnitude and direction of current applied to each emission array element, so that most eddy current fields can be gathered in a small detection area, and eddy current fields of other non-detection areas can be reduced as much as possible. Thus, the receiving coil of the receiving probe 102 is used for receiving the information of the focused eddy current field changing with time in the medium of the detection area, specifically, the information of the eddy current field changes exponentially with time, and the attenuation rule is related to the resistivity and the volume scale of the detection medium, so that the relative change of the resistivity of the medium of the detection area can be judged according to the change trend of the early and late induced electromotive force curves induced by the receiving coil in a plurality of measurement periods; and the signal acquisition circuit 104 is used for acquiring reservoir monitoring signals, the reservoir monitoring signals are transmitted to the ground case 12 through the cable 11, and the analog-to-digital conversion, multi-channel acquisition, storage and processing of data are completed and then are sent to the upper computer 13 system for curve display and later data playback.
In addition, in the underground detection process based on transient electromagnetism, the medium in the coverage area of the eddy current field can affect the received signal, so that the coverage area of the eddy current field is the detection range of nondestructive detection. The eddy current field diffuses with time, and the diffusion characteristic can enable the eddy current field to diffuse to the sleeve radially, so that nondestructive detection of the sleeve is realized. But the eddy current field is diffused in the radial direction and also diffused in the longitudinal direction to a certain extent. The longitudinal diffusion range has great influence on the nondestructive testing performance, on one hand, the longitudinal diffusion can increase the longitudinal detection range, and the instrument can adopt fewer points to finish well section measurement in the longitudinal movement measurement; on the other hand, however, such longitudinal diffusion also reduces the longitudinal resolution and increases the possibility of casing non-uniformity, and if the casing is non-uniform, there is a model mismatch, and the detected casing is the equivalent wall thickness of the non-uniform casing, and the detection result has a certain deviation. The ideal method is to use a large longitudinal detection range to realize rapid detection in the region where the wall thickness of the casing is not changed much, and to use a small longitudinal detection range to realize fine scanning in the region where the casing is damaged seriously. The longitudinal detection range can be narrowed by adopting an early signal or reducing power, but the narrowing degree is limited, the strength of the eddy current field is seriously reduced, and the detection performance is reduced.
Based on this, the embodiments of the present invention desirably provide a transient electromagnetic emission focusing detection scheme based on weighted minimum mean square error, and utilize a longitudinal emission array structure to change the longitudinal distribution of an eddy current field by controlling the current direction and emission power of each array element, thereby realizing emission magnetic field focusing, thereby reducing the longitudinal diffusion range and improving the longitudinal resolution.
Based on the above explanation, referring to fig. 3, it shows a detection method of transient electromagnetic emission focusing based on weighted minimum mean square error according to an embodiment of the present invention, which can be applied to the system 1 shown in fig. 1, and the method includes:
s301: acquiring the magnetic field intensity superposition values of eddy current fields of all transmitting array elements at set positions based on a transmitting array model;
s302: a plurality of position sampling points are arranged in the longitudinal direction of the target radius, and the longitudinal distribution of the magnetic field strength of the emission array at the target radius is obtained on the basis of the magnetic field strength superposition value and the position sampling points;
s303: and solving and obtaining the optimal weight corresponding to each transmitting array element based on a weighted minimum mean square error criterion according to the expected magnetic field intensity distribution and the longitudinal magnetic field intensity distribution of the transmitting array at the target radius.
Aiming at the technical scheme shown in figure 3 and the system shown in figure 1, the embodiment of the invention establishes the underground columnar multi-layer medium transient electromagnetic emission array model shown in figure 4, sets the underground medium to share layers from inside to outside, and the layers are respectively an iron core, air, an instrument outer protective pipe, well fluid, a casing pipe, a cement sheath, a stratum and the like, and the electrical parameters and the geometric parameters of the media of each layer are respectively (mu)j，εj，σj) And rjJ is 1, 2, … J. Wherein, the transmitting coil of each transmitting array element and the receiving coil of the receiving probe are wound on the iron core, and the number of turns is NTAnd NR。
Based on the above setting, in some possible implementations, the obtaining, based on the transmit array model, a magnetic field intensity superposition value of eddy current fields of all transmit array elements at the set position includes:
for each transmitting array element in the transmitting array, according to maxwell equation set, by solving homogeneous and non-homogeneous helmholtz equations, the magnetic field strength of the eddy current field at a set position (z, r) can be obtained as follows:
wherein r represents a radial distance between the set position and the transmitting array element, and z represents a longitudinal height value at the distance of r; omega is angular frequency; n is a radical ofTThe number of turns of a transmitting coil of the transmitting array element wound on the iron core is represented; the electrical parameter and the geometric parameter of the j-th layer of the downhole medium are respectively (mu)j，εj，σj) And rj，j＝1，2，…J； xjAnd λ is an intermediate variable introduced and satisfies
kjIs a wave number and
Cjthe undetermined coefficients are related to the conductivity, the permeability and the dielectric constant of the medium and are obtained according to boundary conditions of each layer of medium; i is0(·)，I1(·)，K0(. h) are class 1, class 0, class 1, and class 2, class 0 modified Bessel functions, respectively;
converting equation 1 to the time domain by the inverse Laplace transform of S-stage Gaver-Stehfest is shown in equation 2:
wherein D issRepresents an integral coefficient; t is tofRepresenting the turn-off time of the signal applied by the transmitting coil of the transmitting array element;
according to the number N of the transmitting array elements of the transmitting array and the distance delta z of the transmitting array elements, acquiring the magnetic field intensity superposition value of the eddy current field of all the transmitting array elements of the transmitting array at a set position (z, r) based on the formula 2 as shown in the formula 3:
wherein, InIs the transmission current of the nth transmission array element and I ═ I0 I1 ... In ... IN]T；znIs the longitudinal distance from the nth transmitting array element to a set position (z, r) and z ═ z0 z1 ... zn ... zN]T(ii) a f (λ, r, ω) is as shown in formula 4:
expanding the formula 3 into a multi-level Legendre polynomial according to a Gaussian-Legendre Gauss-Legendre product equation, and expressing the polynomial in a matrix form as shown in a formula 5:
H(I，t，r，z)＝ξITX(z)GT(r，t，d) (5)
wherein: x (z) ═ Y (z)1) … Y(zN)]T∈CN×P，Y(zn)＝[cos(λ1zn)，…，cos(λPzn)]∈CP×1，
for the above example, referring to fig. 5, which shows the distribution of the divergent eddy current field simulated by equation 5, it can be seen from fig. 5 that the longitudinal diffusion range on the casing is larger than the probe length, and the longitudinal diffusion range is larger as the inner diameter of the casing is larger. Such longitudinal diffusion may increase the longitudinal detection range, reducing the longitudinal resolution; and increase the inhomogeneous possibility of sleeve pipe simultaneously, if the sleeve pipe is inhomogeneous, can have the model mismatch, the sleeve pipe of surveying is the equivalent wall thickness of inhomogeneous sleeve pipe, and the result of surveying has certain deviation. Based on this, in some examples, the setting a plurality of position sampling points in a longitudinal direction of a target radius, and acquiring a longitudinal distribution of magnetic field strength of the transmit array at the target radius based on the magnetic field strength superposition value and the position sampling points, includes:
the longitudinally setting a plurality of position sampling points in the target radius, and acquiring the longitudinal distribution of the magnetic field strength of the emission array at the target radius based on the magnetic field strength superposition value and the position sampling points, includes:
in order to realize emission focusing, M sampling points shown in figure 6 are longitudinally selected at a target radius r;
the magnetic field strength of the eddy current field at the M sampling points obtained based on equation 5 is as shown in equation 6:
wherein, X (z)1-M)＝[X(z1) … x(zM)]∈CN×MP；
z1-M＝[z1，…，zM]；zm＝[z1，m，…，zn，m，…，zN，m]T；zn，mThe longitudinal distance from the nth transmitting array element to the mth point is more than or equal to 1 and less than or equal to M; h (I, t, r, z)M) The longitudinal distribution of the magnetic field strength at M points of the eddy current field at radius r is shown.
Based on the above example, specifically, the obtaining the optimal weight corresponding to each transmitting array element by solving based on the weighted minimum mean square error criterion according to the expected magnetic field intensity distribution and the longitudinal distribution of the magnetic field intensity of the transmitting array at the target radius includes:
the desired magnetic field strength for the M points set at radius r is divided as shown in equation 7:
Hd＝[Hd(1) … Hd(M)] (7)；
for equations 6 and 7, the weighted minimum mean square error criterion is introduced as shown in equation 8:
wherein k ismA weight representing the error at the m-th sample point;
unfolding equation 8 yields the following equation 9:
wherein K ═ K0，...，kM]；
The product of the hadamard is represented,
represents the kronecker product;
partial differentiation of I is performed based on equation 9, and an equation shown in equation 10 is obtained:
solving the equation shown in equation 10 yields the optimal weights shown in equation 11:
for the above specific example, since in downhole exploration, when the desired magnetic field strength is as shown in equation 12:
wherein η is a constant for ensuring that the desired magnetic field strength is sufficiently large to meet the detection distance requirement; if the weights of other points are all 1, then there are
Obtaining R from the desired magnetic field strength shown in equation 12XGDK＝ηζX(za)GT(t, d) and the optimal weight as shown in equation 13:
the emission weighting is to focus the emission magnetic field to the point a and minimize the magnetic field at other points. The distribution diagram of the focused eddy current field is shown in fig. 7, and it can be seen that the longitudinal diffusion range of the eddy current field is significantly reduced, which indicates that the focusing of the eddy current field can be well achieved after the optimal weight weighting constraint obtained by adopting the technical scheme, so that the longitudinal resolution is significantly improved.
Based on the same inventive concept of the foregoing technical solution, referring to fig. 8, a detection apparatus 80 for focusing transient electromagnetic emission based on weighted minimum mean square error according to an embodiment of the present invention is shown, where the apparatus 80 includes: a first acquisition section 801, a second acquisition section 802, and a solution section 803; wherein the content of the first and second substances,
the first acquisition part 801 is configured to acquire the magnetic field intensity superposition value of the eddy current field of all the transmitting array elements at a set position based on a transmitting array model;
the second acquisition part 802 is configured to set a plurality of position sampling points in a longitudinal direction of a target radius, and acquire a longitudinal distribution of magnetic field strength of the emission array at the target radius based on the magnetic field strength superposition value and the position sampling points;
the solving part 803 is configured to solve and obtain the optimal weight corresponding to each transmitting array element based on the weighted minimum mean square error criterion according to the expected magnetic field intensity distribution and the longitudinal distribution of the magnetic field intensity of the transmitting array at the target radius.
In some examples, the first acquisition portion 801 is configured to:
for each transmitting array element in the transmitting array, according to maxwell equation set, by solving homogeneous and non-homogeneous helmholtz equations, the magnetic field strength of the eddy current field at a set position (z, r) can be obtained as follows:
wherein r represents a radial distance between the set position and the transmitting array element, and z represents a longitudinal height value at the distance of r; omega is angular frequency; n is a radical ofTThe number of turns of a transmitting coil of the transmitting array element wound on the iron core is represented; the electrical parameter and the geometric parameter of the j-th layer of the downhole medium are respectively (mu)j，εj，σj) And rj，j＝1，2，…J； xjAnd λ is an intermediate variable introduced and satisfies
kjIs a wave number and
Cjthe undetermined coefficients are related to the conductivity, the permeability and the dielectric constant of the medium and are obtained according to boundary conditions of each layer of medium; i is0(·)，I1(·)，K0(. h) are class 1, class 0, class 1, and class 2, class 0 modified Bessel functions, respectively;
converting equation 14 to the time domain via the inverse Laplace transform of S-stage Gaver Stehfest to S-stage Gaver-Stehfest is shown in equation 15:
wherein D issRepresents an integral coefficient; t is tofRepresenting the turn-off time of the signal applied by the transmitting coil of the transmitting array element;
according to the number N of the transmitting array elements of the transmitting array and the distance delta z of the transmitting array elements, acquiring the magnetic field intensity superposition value of the eddy current field of all the transmitting array elements of the transmitting array at the set position (z, r) based on the formula 2 as shown in the formula 16:
wherein, InIs the transmission current of the nth transmission array element and I ═ I0 I1 ... In ... IN]T；znIs the longitudinal distance from the nth transmitting array element to a set position (z, r) and z ═ z0 z1 ... zn ...zN]T(ii) a f (λ, r, ω) is as shown in formula 17:
expanding the equation 16 into a multistage Legendre polynomial according to the Gaussian-Legendre product equation, and expressing the polynomial in a matrix form as shown in equation 18:
H(I，t，r，z)＝ζITX(z)GT(r，t，d) (18)
wherein: x (z) ═ Y (z)1) … Y(zN)]T∈CN×P，Y(zn)＝[cos(λ1zn)，…，cos(λPzn)]∈CP×1，
in some examples, the second acquisition portion 802 is configured to:
in order to realize emission focusing, M sampling points are longitudinally selected at the radius r of a target;
the magnetic field strength of the eddy current field at the M sampling points obtained based on equation 5 is as shown in equation 19:
wherein, x (z)1-M)＝[X(z1) … x(zM)]∈CN×MP；
z1-M＝[z1，…，zM]；zm＝[z1，m，…，zn，m，…，zN，m]T；zn，mThe longitudinal distance from the nth transmitting array element to the mth point is more than or equal to 1 and less than or equal to M; h (I, t, r, z)M) The longitudinal distribution of the magnetic field strength at M points of the eddy current field at radius r is shown.
In some examples, the solving portion 803 is configured to:
the desired magnetic field strength for the M points set at radius r is divided as shown in equation 20:
Hd＝[Hd(1) … Hd(M)] (20)；
for equations 19 and 20, the weighted minimum mean square error criterion is introduced as shown in equation 21:
wherein k ismA weight representing the error at the m-th sample point;
unfolding equation 21 yields the following equation 22:
wherein K ═ K0，...，kM]；
The product of the hadamard is represented,
represents the kronecker product;
partial differentiation of I is performed based on equation 22, and an equation shown in equation 23 is obtained:
solving the equation shown in equation 23 yields the optimal weights shown in equation 24:
in some examples, when the desired magnetic field strength is as shown in equation 25:
wherein η is a constant for ensuring that the desired magnetic field strength is sufficiently large to meet the detection distance requirement;
r is obtained from the desired magnetic field strength shown in equation 25XGDK＝ηζX(za)GT(t, d) and the optimal weight as shown in equation 26:
it is understood that in this embodiment, "part" may be part of a circuit, part of a processor, part of a program or software, etc., and may also be a unit, and may also be a module or a non-modular.
In addition, each component in the embodiment may be integrated in one processing unit, or each unit may exist alone physically, or two or more units are integrated in one unit. The integrated unit can be realized in a form of hardware or a form of a software functional module.
Based on the understanding that the technical solution of the present embodiment essentially or a part contributing to the prior art, or all or part of the technical solution may be embodied in the form of a software product stored in a storage medium, and include several instructions for causing a computer device (which may be a personal computer, a server, or a network device, etc.) or a processor (processor) to execute all or part of the steps of the method of the present embodiment. And the aforementioned storage medium includes: a U-disk, a removable hard disk, a Read Only Memory (ROM), a Random Access Memory (RAM), a magnetic disk or an optical disk, and other various media capable of storing program codes.
Accordingly, the present embodiment provides a computer storage medium, which stores a detection program of a weighted minimum mean square error based transient electromagnetic transmit focusing, and the detection program of the weighted minimum mean square error based transient electromagnetic transmit focusing is executed by at least one processor to implement the steps of the detection method of the weighted minimum mean square error based transient electromagnetic transmit focusing in the above technical solution.
Referring to fig. 9, a specific hardware structure of a computing device 90 capable of implementing the above-mentioned transient electromagnetic emission focusing detection apparatus 80 based on weighted minimum mean square error according to an embodiment of the present invention is shown, where the computing device 90 may specifically be the upper computer 13 in the system 1 shown in fig. 1. The computing device 90 includes: a communication interface 901, a memory 902, and a processor 903; the various components are coupled together by a bus system 904. It is understood that the bus system 904 is used to enable communications among the components. The bus system 904 includes a power bus, a control bus, and a status signal bus in addition to a data bus. But for clarity of illustration the various buses are labeled as bus system 904 in figure 9. Wherein the content of the first and second substances,
the communication interface 901 is used for receiving and sending signals in the process of receiving and sending information with other external network elements;
the memory 902 is used for storing a computer program capable of running on the processor 903;
the processor 903 is configured to execute the steps of the detection method based on weighted minimum mean square error of the transient electromagnetic emission focusing set forth in the foregoing technical solution when the computer program is run.
It is to be understood that the memory 902 in embodiments of the present invention may be either volatile memory or nonvolatile memory, or may include both volatile and nonvolatile memory. The non-volatile Memory may be a Read-Only Memory (ROM), a Programmable ROM (PROM), an Erasable PROM (EPROM), an Electrically Erasable PROM (EEPROM), or a flash Memory. Volatile Memory can be Random Access Memory (RAM), which acts as external cache Memory. By way of illustration and not limitation, many forms of RAM are available, such as Static random access memory (Static RAM, SRAM), Dynamic Random Access Memory (DRAM), Synchronous Dynamic random access memory (Synchronous DRAM, SDRAM), Double Data Rate Synchronous Dynamic random access memory (ddr Data Rate SDRAM, ddr SDRAM), Enhanced Synchronous SDRAM (ESDRAM), Synchlink DRAM (SLDRAM), and Direct Rambus RAM (DRRAM). The memory 902 of the systems and methods described herein is intended to comprise, without being limited to, these and any other suitable types of memory.
And the processor 903 may be an integrated circuit chip having signal processing capabilities. In implementation, the steps of the above method may be performed by integrated logic circuits of hardware or instructions in the form of software in the processor 903. The Processor 903 may be a general-purpose Processor, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA) or other Programmable logic device, discrete Gate or transistor logic device, or discrete hardware components. The various methods, steps and logic blocks disclosed in the embodiments of the present invention may be implemented or performed. A general purpose processor may be a microprocessor or the processor may be any conventional processor or the like. The steps of the method disclosed in connection with the embodiments of the present invention may be directly implemented by a hardware decoding processor, or implemented by a combination of hardware and software modules in the decoding processor. The software module may be located in ram, flash memory, rom, prom, or eprom, registers, etc. storage media as is well known in the art. The storage medium is located in the memory 902, and the processor 903 reads information in the memory 902 and performs the steps of the above method in combination with hardware thereof.
It is to be understood that the embodiments described herein may be implemented in hardware, software, firmware, middleware, microcode, or any combination thereof. For a hardware implementation, the Processing units may be implemented within one or more Application Specific Integrated Circuits (ASICs), Digital Signal Processors (DSPs), Digital Signal Processing Devices (DSPDs), Programmable Logic Devices (PLDs), Field Programmable Gate Arrays (FPGAs), general purpose processors, controllers, micro-controllers, microprocessors, other electronic units configured to perform the functions described herein, or a combination thereof.
For a software implementation, the techniques described herein may be implemented with modules (e.g., procedures, functions, and so on) that perform the functions described herein. The software codes may be stored in a memory and executed by a processor. The memory may be implemented within the processor or external to the processor.
It is understood that the above exemplary technical solutions of the detection apparatus 80 and the calculation device 90 based on weighted least mean square error belong to the same concept as the above technical solutions of the detection method based on weighted least mean square error, and therefore, the above detailed contents not described in detail for the technical solutions of the detection apparatus 80 and the calculation device 90 based on weighted least mean square error can be referred to the above technical solutions of the detection method based on weighted least mean square error. The embodiments of the present invention will not be described in detail herein.
It should be noted that: the technical schemes described in the embodiments of the present invention can be combined arbitrarily without conflict.
The above description is only for the specific embodiments of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present invention, and all the changes or substitutions should be covered within 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 a weighted minimum mean square error based focus of transient electromagnetic emissions, the method comprising:
acquiring the magnetic field intensity superposition values of eddy current fields of all transmitting array elements at set positions based on a transmitting array model;
a plurality of position sampling points are arranged in the longitudinal direction of the target radius, and the longitudinal distribution of the magnetic field strength of the emission array at the target radius is obtained on the basis of the magnetic field strength superposition value and the position sampling points;
and solving and obtaining the optimal weight corresponding to each transmitting array element based on a weighted minimum mean square error criterion according to the expected magnetic field intensity distribution and the longitudinal magnetic field intensity distribution of the transmitting array at the target radius.
2. The method of claim 1, wherein the obtaining of the magnetic field strength superposition value of the eddy current field of all transmitting array elements at the set position based on the transmitting array model comprises:
for each transmitting array element in the transmitting array, according to maxwell equation set, by solving homogeneous and non-homogeneous helmholtz equations, the magnetic field strength of the eddy current field at a set position (z, r) can be obtained as follows:
wherein r represents a radial distance between the set position and the transmitting array element, and z represents a longitudinal height value at the distance of r; omega is angular frequency; n is a radical ofTThe number of turns of a transmitting coil of the transmitting array element wound on the iron core is represented; the electrical parameter and the geometric parameter of the j-th layer of the downhole medium are respectively (mu)j,εj,σj) And rj，j＝1,2，…J；xjAnd λ is an intermediate variable introduced and satisfies
kjIs a wave number and
Cjthe undetermined coefficients are related to the conductivity, the permeability and the dielectric constant of the medium and are obtained according to boundary conditions of each layer of medium; i is0(·)，I1(·)，K0Are class 1 and class 0, respectivelyClass 1, order 1 and class 2, order 0 modified bezier functions;
converting equation 1 to the time domain by the inverse Laplace transform of S-stage Gaver-Stehfest is shown in equation 2:
wherein D issRepresents an integral coefficient; t is tofRepresenting the turn-off time of the signal applied by the transmitting coil of the transmitting array element;
according to the number N of the transmitting array elements of the transmitting array and the distance delta z of the transmitting array elements, acquiring the magnetic field intensity superposition value of the eddy current field of all the transmitting array elements of the transmitting array at a set position (z, r) based on the formula 2 as shown in the formula 3:
wherein, InIs the transmission current of the nth transmission array element and I ═ I0 I1…In…IN]T；znIs the longitudinal distance from the nth transmitting array element to a set position (z, r) and z ═ z0 z1…zn…zN]T(ii) a f (λ, r, ω) is as shown in formula 4:
expanding the formula 3 into a multi-level Legendre polynomial according to a Gaussian-Legendre Gauss-Legendre product equation, and expressing the polynomial in a matrix form as shown in a formula 5:
H(I,t,r,z)＝ζITX(z)GT(r,t,d) (5)
wherein: x (z) ═ Y (z)1)…Y(zN)]T∈CN×P，Y(zn)＝[cos(λ1zn),…,cos(λPzn)]∈CP×1，
3. the method of claim 2, wherein the setting a plurality of position sampling points in a longitudinal direction of a target radius, and the obtaining a longitudinal distribution of magnetic field strength of the transmit array at the target radius based on the magnetic field strength superposition value and the position sampling points comprises:
the longitudinally setting a plurality of position sampling points in the target radius, and acquiring the longitudinal distribution of the magnetic field strength of the emission array at the target radius based on the magnetic field strength superposition value and the position sampling points, includes:
in order to realize emission focusing, M sampling points are longitudinally selected at the radius r of a target;
the magnetic field strength of the eddy current field at the M sampling points obtained based on equation 5 is as shown in equation 6:
wherein, X (z)1-M)＝[X(z1)…X(zM)]∈CN×MP；
z1-M＝[z1,…,zM]；zm＝[z1,m,…,zn,m,…,zN,m]T；zn,mThe longitudinal distance from the nth transmitting array element to the mth point is more than or equal to 1 and less than or equal to M; h (I, t, r, z)M) The longitudinal distribution of the magnetic field strength at M points of the eddy current field at radius r is shown.
4. The method of claim 3, wherein solving for optimal weights corresponding to each transmit array element based on a weighted minimum mean square error criterion according to a desired magnetic field strength distribution and a longitudinal distribution of magnetic field strengths of the transmit array at a target radius comprises:
the desired magnetic field strength for the M points set at radius r is divided as shown in equation 7:
Hd＝[Hd(1)…Hd(M)] (7)；
for equations 6 and 7, the weighted minimum mean square error criterion is introduced as shown in equation 8:
wherein k ismA weight representing the error at the m-th sample point;
unfolding equation 8 yields the following equation 9:
wherein K ═ K0,…,kM]；
The product of the hadamard is represented,
represents the kronecker product;
partial differentiation of I is performed based on equation 9, and an equation shown in equation 10 is obtained:
solving the equation shown in equation 10 yields the optimal weights shown in equation 11:
5. the method of claim 4, wherein when the desired magnetic field strength is as shown in equation 12:
wherein η is a constant for ensuring that the desired magnetic field strength is sufficiently large to meet the detection distance requirement;
obtaining R from the desired magnetic field strength shown in equation 12XGDK＝ηζX(za)GT(t, d) and the optimal weight as shown in equation 13:
6. a weighted minimum mean square error based detection apparatus for focusing of transient electromagnetic emissions, the apparatus comprising: a first acquisition part, a second acquisition part and a solution part; wherein the content of the first and second substances,
the first acquisition part is configured to acquire the magnetic field intensity superposition value of the eddy current field of all the transmitting array elements at a set position based on a transmitting array model;
the second acquisition part is configured to arrange a plurality of position sampling points in the longitudinal direction of a target radius, and acquire the longitudinal distribution of the magnetic field strength of the emission array at the target radius based on the magnetic field strength superposition value and the position sampling points;
the solving part is configured to solve and obtain the optimal weight corresponding to each transmitting array element based on a weighted minimum mean square error criterion according to the expected magnetic field intensity distribution and the longitudinal distribution of the magnetic field intensity of the transmitting array at the target radius.
7. The apparatus of claim 6, wherein the first acquisition portion is configured to:
for each transmitting array element in the transmitting array, according to maxwell equation set, by solving homogeneous and non-homogeneous helmholtz equations, the magnetic field strength of the eddy current field at a set position (z, r) can be obtained as follows:
wherein r represents a radial distance between the set position and the transmitting array element, and z represents a longitudinal height value at the distance of r; omega is angular frequency; n is a radical ofTThe number of turns of a transmitting coil of the transmitting array element wound on the iron core is represented; the electrical parameter and the geometric parameter of the j-th layer of the downhole medium are respectively (mu)j,εj,σj) And rj，j＝1,2，…J；xjAnd λ is an intermediate variable introduced and satisfies
kjIs a wave number and
Cjthe undetermined coefficient is related to the conductivity, permeability and dielectric constant of the medium and is obtained according to the boundary condition of each layer of medium；I0(·)，I1(·)，K0(. h) are class 1, class 0, class 1, and class 2, class 0 modified Bessel functions, respectively;
converting equation 14 to the time domain via the inverse Laplace transform of S-stage Gaver Stehfest to S-stage Gaver-Stehfest is shown in equation 15:
wherein D issRepresents an integral coefficient; t is tofRepresenting the turn-off time of the signal applied by the transmitting coil of the transmitting array element;
according to the number N of the transmitting array elements of the transmitting array and the distance Delta z of the transmitting array elements, acquiring the magnetic field intensity superposition value of the eddy current field of all the transmitting array elements of the transmitting array at a set position (z, r) based on the formula 2 as shown in the formula 16:
wherein, InIs the transmission current of the nth transmission array element and I ═ I0 I1…In…IN]T；znIs the longitudinal distance from the nth transmitting array element to a set position (z, r) and z ═ z0 z1…zn…zN]T(ii) a f (λ, r, ω) is as shown in formula 17:
expanding the equation 16 into a multistage Legendre polynomial according to the Gaussian-Legendre Gauss-Legendre product equation, and expressing the polynomial in a matrix form as shown in equation 18:
H(I,t,r,z)＝ζITX(z)GT(r,t,d) (18)
wherein: x (z) ═ Y (z)1)…Y(zN)]T∈CN×P，Y(zn)＝[cos(λ1zn),…,cos(λPzn)]∈CP×1，
8. the apparatus of claim 7, wherein the second acquisition portion is configured to:
in order to realize emission focusing, M sampling points are longitudinally selected at the radius r of a target;
the magnetic field strength of the eddy current field at the M sampling points obtained based on equation 5 is as shown in equation 19:
wherein, X (z)1-M)＝[X(z1)…X(zM)]∈CN×MP；
z1-M＝[z1,…,zM]；zm＝[z1,m,…,zn,m,…,zN,m]T；zn,mThe longitudinal distance from the nth transmitting array element to the mth point is more than or equal to 1 and less than or equal to M; h (I, t, r, z)M) The longitudinal distribution of the magnetic field strength at M points of the eddy current field at radius r is shown.
9. The apparatus of claim 8, wherein the solving portion is configured to:
the desired magnetic field strength for the M points set at radius r is divided as shown in equation 20:
Hd＝[Hd(1)…Hd(M)] (20)；
for equations 19 and 20, the weighted minimum mean square error criterion is introduced as shown in equation 21:
wherein k ismA weight representing the error at the m-th sample point;
unfolding equation 21 yields the following equation 22:
wherein K ═ K0,…,kM]；
The product of the hadamard is represented,
represents the kronecker product;
partial differentiation of I is performed based on equation 22, and an equation shown in equation 23 is obtained:
solving the equation shown in equation 23 yields the optimal weights shown in equation 24:
10. a computer storage medium, characterized in that the computer storage medium stores a detection program of a weighted minimum mean square error based transient electromagnetic transmit focusing, which when executed by at least one processor implements the detection method steps of the weighted minimum mean square error based transient electromagnetic transmit focusing as claimed in any one of claims 1 to 5.
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| CN115437022B (en) * | 2022-11-10 | 2023-02-28 | 中煤科工西安研究院(集团)有限公司 | High-resistance coal seam orthogonal electromagnetic wave array coil system, design method and combination |
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