96 results about "Time domain electromagnetics" patented technology

An airborne time domain electromagnetic surveying system is provided. The system includes a tow assembly with a flexible support frame. The flexible support frame spaced apart from the aircraft includes a transmitter section with a transmitter loop and a receiver section with a sensor aligned with the central axis of the transmitter section. The flexible support frame has a lightweight modular structure that enables the surface area of the transmitter section to be increased and decreased to suit particular survey applications. The transmitter loop sends a pulse in an “ON” interval, and in an “OFF” interval the sensor measures the earth response to the pulse. The tow assembly also includes a sensor for generating selected survey data in the “ON” interval. A transmitter driver enables the creation of earthbound pulse. The system components are linked to a computer and control computer program linked thereto for controlling the functions thereof. The invention also includes a method for producing survey data using the tow assembly of the invention.

The invention discloses a high-efficiency time domain electromagnetic simulation method based on an H matrix algorithm, which can realize electromagnetic simulation on a large three-dimensional target. In the method, a time domain finite element method (TDFEM) is used as a background, a low-rank compression technique is used as a core, and a tree structure is used as a basis for carrying out logical unit (LU) decomposition on a sparse matrix generated by the TDFEM by a four arithmetic algorithm corresponding to the H matrix. The acquired upper and lower triangular factors have low-rank compressible characteristics, and the compressed matrix equation can realize quick solution of high-efficiency time domain electromagnetic simulation by the H matrix algorithm. The high-efficiency time domain electromagnetic simulation method has the advantages of fast computation speed, low memory consumption, controllable computation accuracy, good stability and the like, can reduce the complexity of computation to O(Nlog<2>N) and reduce the memory consumption to O(NlogN), can be widely applied to the solution of a large sparse linear system of equations during high-efficiency time domain electromagnetic simulation, and can provide important reference for analyzing the electromagnetic property of the large three-dimensional target.

A method for detecting formation resistivity outside of metal casing using time-domain electromagnetic pulse in a borehole, the method including steps of a) providing a borehole large power pulse transmitting source, recording an induced electromotive force ε, and full time digital recording a transmitted waveform and a received signal; b) conducting transmission-reception and superimposing received signals to improve signal to noise ratio; c) calculating corresponding casing response according to known casing parameters and recorded current waveform of the transmitting source to obtain a relative induced electromotive force Δε_f; d) correcting relative induced electromotive force value; e) carrying out one-dimensional inversion and converting the observation signal into radial variation information of the formation resistivity; f) obtaining a two-dimensional image of the longitudinal and radial resistivity distribution of outer cased formation resistivity for measured well sections; and g) determining residual oil distribution in a reservoir from outer cased reservoir resistivity distribution.

The present invention relates to a HTEM system that includes a semi-rigid bucking coil and an algorithm to determine the magnetic field B from the measured signal dB/dt. The bucking coil may be positioned in a concentric coplanar manner relative to a transmitter coil and receiver coil, in order to minimize spurious signals at the receiver coil during data acquisition time. Signals gathered by the system may be further processed by a signal processing means. Moreover, measurements performed upon data generated by the system may be performed upon the entire period of a current waveform applied to the transmitter and bucking coils.

The invention relates to a fractional order electromagnetic anomalous diffusion three-dimensional simulation method of rational function approximation, and aims at calculating three-dimensional time-domain induction-polarization double field response of a fractional order Cole-Cole model. The method mainly comprises the steps of establishing a Cole-Cole model fractional order transfer function andan n-odrer rational approximation function based on a frequency domain rational function approximation method, and making the sum of the real part and the imaginary part of an error function as a target function; achieving linearization of the target function through an instrumental variable technique, and obtaining an optimal approximation rational function by adopting a linear programming approach; obtaining a time-domain mode of a conductivity by adopting a partial fraction expansion method and inverse laplace transformation; putting the time-domain mode in a Maxwell equation, deducing aniterative equation of an electromagnetic field based on a finite difference method, and achieving fractional order Cole-Cole model three-dimensional electromagnetic response value calculation. The fractional order electromagnetic anomalous diffusion three-dimensional simulation method of the rational function approximation has the advantages of fast and accurately simulating the fractional order Cole-Cole model three-dimensional time-domain electromagnetic response and providing theoretical foundation for research on abnormal electromagnetic diffusion in a polarization medium.

The invention discloses a method for building and judging a three-dimensional strip-shaped random fault zone model in the aviation time domain. The method comprises the steps of step 1, performing gridding subdivision on a geodetic model by adopting Yee grids; step 2, conducting a random strip-shaped fault zone model by adopting the statistical method; step 3, determining the number and the widthof random fault zones; step 4, deducing a explicit differential iterative formula in six direction magnetic fields and electric fields; step 5, endowing a corresponding random electric conductivity value to a geodetic grid model; step 6, judging the tendency and the position of the model through a response curve and a slicing diagram. By adopting the method, the blank of the time domain electromagnetic method in the exploration of fault zones can be made up. The accuracy and the reliability of the electromagnetic method in the exploration of oil and gas reservoirs are greatly improved. The efficiency of related work is improved, and the exploration cost is greatly reduced.

The invention discloses a hybrid time-domain discontinuous-Galerkin-method-based numerical method of time-domain computational-electromagnetics. The method is applied to the numerical-solving field oftime-domain computational-electromagnetics. A hybrid term is introduced on interface units of adjacent body units, and is used to define numerical flux of electromagnetic fields, an implicit Crank-Nicolson time format is used to disperse three-dimensional time-domain Maxwell equations, after introducing the hybrid term, to obtain a global linear system related only to the hybrid term, and the electromagnetic fields of all the units are obtained through solving for the hybrid term. Therefore, the deficiency of calculation time, memory and precision of existing time-domain electromagnetic-fieldnumerical-methods in processing multi-scale equipment under complex electromagnetic environments can be effectively avoided.

A simulation apparatus according to an embodiment performs an electromagnetic field circuit coupling analysis on a first substrate and a second substrate electrically coupled via a circuit element having a finite delay time. A first coupling analysis unit carries out a time domain electromagnetic field analysis and also a circuit analysis on a circuit element at a first analytical domain including the first substrate. The second coupling analysis unit carries out a time domain electromagnetic field analysis and also a circuit analysis on a circuit element at a second analytical domain including the second substrate. A cable internal state analysis unit carries out a circuit analysis on a circuit element, employing an electromagnetic field value obtained at the first coupling analysis unit at one terminal of the circuit element connecting the first substrate and the circuit element, and an electromagnetic field value obtained at the second coupling analysis unit at another terminal of the circuit element connecting the second substrate and the circuit element.

The invention discloses a ratio method for correcting topographic influence in electromagnetic prospecting. The ratio method comprises the steps of acquiring a surface layer resistivity value without topographic influence to serve as a standard resistivity of topographic correction; drawing an in-line topographic profile, respectively comparing the topographic profile with a frequency point profile of a frequency domain electromagnetic method and a time channel profile of a time domain electromagnetic method, and judging the topographic influence suffered by the actually measured data according to the influence rule of the topography on the resistivity in the frequency domain and the time domain electromagnetic field; observing from the highest frequency point of the frequency domain electromagnetic method and the earliest time channel of the time domain electromagnetic method so as to obtain the topographic response which is closest to the surface layer until the absence of low-frequency frequency point of the topographic influence is observed in the frequency domain electromagnetic method and the absence of the late time channel of the topographic influence is observed in the time domain electromagnetic method, and acquiring the observation data without topographic influence; and performing topographic correction according to a ratio formula of pcorrected(i,j)=pmeasured(i,j) [pstandard(i)/pmeasured(i,l)]C(i,j). The ratio method is good in correction effect in the process of correcting the topographic influence, is high in feasibility and can be widely applied to topographic influence correction in electromagnetic prospecting.

The invention provides a direct time domain processing method for transient electromagnetic sounding data. The direct time domain processing method comprises the following step of: deducing a large fixed-source loop and long grounding lead analytic expression by using time varying point charge as a basic microelement to obtain a large fixed source loop and long grounding lead analytic solution. The direct time domain processing method for the transient electromagnetic sounding data based on the time varying point charge is used for replacing the traditional processing method for the transientelectromagnetic sounding data based on dipoles, and therefore, errors generated in the process from frequency domain deduction to time domain switching in the traditional method can be reduced, the inherent characteristic of a time domain electromagnetic field is highlighted, and the surveying accuracy of a transient electromagnetic method is greatly improved.

This invention relates to a method of, and a system for, monitoring electromagnetic interference. The method comprising capturing a plurality of time domain waveforms, and a plurality of scatter plots; receiving the plurality of captured time domain waveforms and scatter plots; applying a fast fourier transform (FFT) to each of the received time domain waveforms as it is received thereby to receive FFT outputs; storing the FFT outputs in a database; generating a statistically representative spectrograph or spectrogram in the frequency domain based on at least the stored FFT outputs and scatter plots or data associated with the scatter plots, combining constituent FFTs of the statistically representative spectrograph or spectrogram in such a manner as to emulate the result that would be produced by an EMI (Electromagnetic Interference) receiver or spectrum analyser; and combining resultant outputs from a number of iterations of this process to produce a final result (EMI spectrum).

A device and method for estimating an apparent chargeability of a surveyed underground formation. The method includes receiving a total response of the underground formation from an airborne time domain electromagnetic (TDEM) survey system; separating, in two stages, the total response into an inductive response and an induced polarization response; and calculating (308) the apparent chargeability based on the induced polarization response.

The invention relates to a loading method of C-PML boundary conditions during time-domain airborne electromagnetic numerical simulation.By introducing a divergence equation (please see the formula in the description) as a control equation of a magnetic field vertical component, electric field and magnetic field expressions in a C-PML layer are deduced, and electromagnetic field no-reflection conditions on an interface of the C-PML layer are determined.A time-domain convolution variable-step-size recursive algorithm in the C-PML layer is constructed through a range-variation integral method, storage of electromagnetic field values at each moment is avoided, a corresponding electric field and magnetic field difference-iteration form is deduced based on a finite difference method, and finally time-domain airborne three-dimensional later period high-precision and long-time-window calculation is achieved.The loading method of the C-PML boundary conditions during time-domain airborne electromagnetic numerical simulation aims at overcoming the truncation error problem of a calculation area in time-domain airborne electromagnetic numerical simulation and can more efficiently and accurately calculate the three-dimensional time-domain electromagnetic responses.

The invention provides a tensor apparent conductivity measurement method. The tensor apparent conductivity measurement method comprises the following steps that 1, an orthogonal electric field E and a curl M of a magnetic field are simultaneously measured on the surface of ground or underground; 2, the tensor apparent conductivity is calculated according to observation data through a formula (please see the formula in the specification), wherein E and M represents observation matrices containing multiple sets of the E and the M. According to the tensor apparent conductivity measurement method, a measured electromagnetic field can adopt a natural electromagnetic field, and also can adopt an electromagnetic field generated through motivation of an artificial field source; the electromagnetic field can be measured at a frequency domain, changes of the tensor apparent conductivity along with the frequency are obtained, and frequency domain sounding is performed; the electromagnetic field also can be measured at a time domain, changes of the tensor apparent conductivity along with time are obtained, and time domain electromagnetic sounding is performed; the calculation formula does not need to make plane wave hypothesis, is also set up on the condition of a non-plane wave field source and is not limited by the field source conditions; the apparent conductivity calculation formula is simple and does not need iteration or parameters such as a field source position and a sending and receiving distance.

The invention discloses a finite difference time domain electromagnetic calculation carrier meshing method. According to the method, the mesh size is jointly controlled by the discrete electrical dimensional accuracy and the carrier surface approximation accuracy, the geometrical approximation degree between the divided mesh model and the carrier model is high especially under the situation of low frequency with large wavelength, finite difference time domain electromagnetic calculation is performed on the basis of the mesh model, and the calculation result is relatively accurate; surface approximation accuracy controlling parameters for meshing the mesh model are provided, the blindness of meshing precision control of the conventional direct subdivision method is avoided, and the calculated amount for meshing can be effectively controlled; when mesh refinement is required, all that is needed is to perform octree recursive subdivision to the black nodes in the bottommost layer, and mesh refinement is easy to realize.

The invention relates to a device and method for measuring a magnetic induction intensity B through a time domain electromagnetic method. The device is formed in the mode that a single-chip microcomputer is connected with a flux-gate magnetometer and a signal processing and collecting system through a power supply system, the single-chip microcomputer is connected with an open gate magnetometer through a synchronous circuit, a probe is connected with the single-chip microcomputer through the open gate magnetometer, the single-chip microcomputer is connected with the signal processing and collecting system through the synchronous circuit, a hollow coil is connected with the single-chip microcomputer through the signal processing and collecting system, and a transmitting coil is connected with the single-chip microcomputer through a transmitter and a computer. By means of combined application of the hollow coil and the flux-gate magnetometer, the flux-gate magnetometer with a good low-frequency characteristic is used for measuring a relatively stable magnetic field, the hollow coil with a good high-frequency characteristic, interpolation and integral computation are used for measuring magnetic fields which change quickly, a change relation curve of the magnetic induction intensity B along with the time can be precisely measured, good inversion model data are obtained, and accuracy and reliability of inverse interpretation are improved.

The invention belongs to the technical field of geophysical prospecting and relates to an electromagnetic logging device and method, in particular to a hand push type device and method for time domainelectromagnetic logging in a coal mine underground borehole. In-hole transmitting and receiving devices with identical-diameter transmitting coils are wound on the rear portion of a probe, a multi-joint carbon fiber rod is used for pushing the device into the coal mine underground borehole, time domain rectangular wave current in a duty ratio of 50% is supplied into the transmitting coils to realize measurement of borehole radial rock electrical property variation. By adoption of the method, one-dimensional electrical property variation curves of rocks can be obtained while borehole radial two-dimensional apparent restivity distribution can be obtained through a data processing technique, and stratigraphic division and lithologic identification accuracy of the borehole can be remarkably improved by natural gamma-ray logging.

The invention provides an electromagnetic noise simulation calculation method for a permanent magnet synchronous motor under an acceleration working condition. The method includes obtaining a time domain electromagnetic force on a corresponding rotating speed two-dimensional stator in a steady state; obtaining a time domain electromagnetic force on the three-dimensional stator electromagnetic gridat a corresponding rotating speed at a steady-state rotating speed; obtaining a frequency domain electromagnetic force on the stator three-dimensional structure grid at a corresponding rotating speedat a steady-state rotating speed; obtaining the mode of the whole motor; obtaining a motor vibration response at the rotating speed through a modal superposition method; obtaining an electromagneticnoise sound pressure level at a corresponding rotating speed in a steady state by using a boundary element method; and constructing a matrix through the steady-state rotating speed data set and the electromagnetic noise radiation sound pressure level data set, and performing data processing on the electromagnetic noise radiation sound pressure level data set and the corresponding rotating speed data set in the steady state to obtain an electromagnetic radiation colomap of the permanent magnet synchronous motor under the acceleration working condition. The method provided by the invention is suitable for prediction of electromagnetic noise radiation and diagnosis of fault noise under the acceleration condition of the permanent magnet synchronous motor.