44 results about "Exploration geophysics" patented technology

The invention discloses a laboratory adsorption gas calculation method based on isothermal adsorption-nuclear magnetic resonance combined measurement, and relates to the technical field of exploration geophysics. According to the invention, on the basis of isothermal adsorption-nuclear magnetic resonance combined measurement experiment, 23MHz nuclear magnetic resonance experiment is utilized; nuclear magnetic signal conversion of bound water-adsorbed state methane is carried out through nuclear magnetic resonance T2 spectrums of coal rocks with different water saturations and T2 spectrums measured through a coal rock isothermal adsorption-nuclear magnetic resonance combined measurement experiment to obtain the hydrogen content of the adsorbed state methane, then the amount of substance of the adsorbed state methane is obtained, and finally the volume of the adsorbed state methane is obtained. The method comprises the following steps: firstly, measuring and determining the content of bound water in the coal rock by adopting a 25mm sample tube and the current minimum nuclear magnetism callback interval, then carrying out bound water-adsorbed gas nuclear magnetism signal conversion on the sample tube used in an isothermal adsorption-nuclear magnetism combined measurement experiment to obtain the hydrogen content of the adsorbed gas, further obtaining the amount of substance of the adsorbed gas, and finally obtaining the volume of the adsorbed gas.

The invention relates to the field of exploration geophysics, and discloses a wave equation inversion method for constructing a middle-deep part background velocity field, which comprises the steps of S1, inputting observation gun record data and an initial velocity model, S2, performing forward modeling on the initial velocity field to calculate a forward propagation wave field, and performing back propagation on observation data to calculate a back propagation wave field; s3, calculating and simulating primary reflected wave data according to the migration imaging result and the initial velocity field back migration, solving a data residual error by using an optimal transmission distance, constructing an adjoint source, substituting the adjoint source into reflected wave inversion, calculating a gradient under the optimal transmission measure, and calculating a gradient under the optimal transmission measure; and S4, iteratively updating the background velocity field according to the calculated gradient, and performing full-waveform inversion by using the background velocity field information to obtain a final high-precision inversion result. Wave field residual errors are extracted more accurately based on an optimal transmission distance strategy, and background field gradient information more conforming to an underground structure is constructed.

The invention discloses an elastic reverse time migration imaging method based on deviatoric stress characterization, and relates to the technical field of exploration geophysics. Deviatoric stress is introduced into a conventional elastic wave equation, and a speed-deviatoric stress elastic wave equation describing stress propagation characteristics is obtained through derivation; based on Hooke's law, P wave contribution in total partial strain is removed through partial strain decomposition, decoupling of P-S wave stress components is achieved, and correctness of amplitude, phase and physical unit of a decoupling wave field is guaranteed; and then a joint imaging condition with the average stress as a seismic source wave field and the multi-stress component as a receiving wave field is constructed, PP waves are subjected to normalization superposition through the average stress and the deviatoric stress, and PS waves are subjected to shear stress imaging. According to the method, the sensitivity to heterogeneity and local stress variation of underground media can be remarkably improved, P-S wave crosstalk and imaging noise are effectively eliminated, the imaging precision and resolution of a complex geologic structure are greatly improved, and a reliable technical means is provided for high-precision seismic exploration of complex oil and gas reservoirs.

The invention provides an electromagnetic survey method and system and electronic equipment, and belongs to the technical field of exploration geophysics. The method comprises the steps of collecting an initial signal; the initial signal comprises a natural electric field and / or magnetic field entering underground and meeting with the natural electric field and / or magnetic field entering underground at the moment at the sensor at the moment when the natural electric field and / or magnetic field enters underground and returns to the sensor through reflection and refraction of an underground electrical impedance interface, and the two signals are superposed to obtain an initial time sequence of a synthetic electric field and / or magnetic field intensity; obtaining an initial frequency spectrum of the initial time sequence based on Fourier transform of the initial time sequence; travel time inversion: based on an electromagnetic field superposition principle, performing superposition operation on the initial frequency spectrum through a harmonic synthesis algorithm to obtain a synthesized travel time sequence of the electric field and / or magnetic field intensity; the synthesized travel time sequence is used for studying and judging geological information. According to the method provided by the embodiment of the invention, high-resolution geological exploration and engineering exploration based on the natural electromagnetic field source are realized.

The invention discloses a multi-scale electromagnetic exploration method based on single-electrode potential detection, and relates to the technical field of exploration geophysics, and the method comprises the steps: determining a measurement region, determining an exploration target, and determining the area of the measurement region and the density of measurement points according to the depth of the exploration target; arranging a plurality of emission sources and receiving arrays in a measurement area, collecting surface potential data of the measurement area in real time, and processing the data frequency point by frequency point according to a preset frequency sequence; on the basis of the single-electrode potential data, generating a surface potential distribution surface, constraining and suppressing a field source effect, obtaining electric field distribution information of a measurement surface, and calculating apparent resistivity parameters in combination with magnetic field measurement data; a multi-azimuth excitation mode and a multi-source emission scheme are adopted, a field source effect is inhibited, a three-dimensional resistivity profile is constructed, and a low-resistance body or a high-resistance body is identified. According to the invention, the static effect and the volume effect are solved, and the limitation of the existing electromagnetic instrument on the detection accuracy and depth is broken through.

The invention discloses a seabed node transverse wave leakage suppression method, system, medium and equipment based on Uform, and belongs to the field of exploration geophysics, and the method comprises the steps of multi-component data preprocessing, radial component acquisition, Uform network model and data set construction, network training optimization and actual data application. The invention further provides a system, a medium and equipment for operating the method. According to the method, the transverse wave leakage noise in the Z component can be effectively predicted and removed, and the signal-to-noise ratio and interpretation reliability of an imaging profile are improved. A global dependency relationship among different positions of an input sequence is modeled through a self-attention mechanism, and the extraction and prediction precision of a shear wave leakage model is improved; in the data set construction stage, a horizontal component is rotated to a radial tangential component, fusion utilization of information in the X direction and the Y direction is achieved, the problem of representation inconsistency caused by the coupling difference of the X components of different detection points is solved, and the description capacity and stability of the transverse wave leakage form are enhanced.

The present invention belongs to the field of exploration geophysics technology and relates to a method for producing seismic data labels for deep learning. The method comprises the following steps: Step 1. Loading seismic data and its existing interpretation results, and cutting and processing the seismic data; Step 2. Determining the position in the seismic data according to the interpretation results and assigning and labeling; Step 3. Slicing the seismic data. Slicing the seismic data, performing local transformation on the sliced label data body, and realizing the expansion of the training samples. The production method of the present invention can effectively improve the efficiency of label production with the help of existing manual interpretation results. The slicing operation can reduce redundant background information, and the local transformation can realize sample expansion. The method of the present invention can realize efficient labeling of seismic labels.

The present invention belongs to the field of exploration geophysics, and discloses a sonic vector reverse time migration imaging method without the influence of reflection angle, which comprises the following steps: presetting a seismic wavelet and an initial velocity model, and realizing the forward extrapolation of the sonic wave field by using the first-order acoustic wave equation to obtain the sonic source wave field; according to the observed seismic data and the preset initial velocity model, realizing the backward extrapolation of the sonic wave field by using the first-order acoustic wave equation to obtain the sonic receiver wave field; based on the sonic source wave field and the sonic receiver wave field, determining the imaging angle by using the constructed imaging angle extraction function based on the energy norm; and performing imaging by using the constructed dot product cross-correlation imaging condition without the influence of reflection angle to obtain a scalar imaging result without the influence of reflection angle. The method disclosed by the present invention can eliminate the polarity inversion problem caused by the imaging angle in the sonic vector dot product imaging condition, improve the polarity consistency of the sonic imaging isophase axis, and thus guarantee the accuracy of geological structure imaging in a complex environment.

The present application belongs to the field of exploration geophysics, and particularly relates to a transient electromagnetic perspective detection method for water-bearing area in a coal mining face. Measurement points are arranged in two roadways of the coal mining face. A transmitting wire frame is fixed at a first point of a transmitting roadway for transmission, and a receiving wire frame receives at different positions in a certain range of the opposite roadway. The transmitter and the receiver are consistent in time and can synchronously collect. After the first point transmits, the transmitting coil is moved to a next position for transmission at a second point. Similarly, the receiving coil can receive in a certain range of the opposite roadway. After the second point transmits, the third point transmits, and so on until the transmission of the whole roadway is completed. The transmitting roadway and the receiving roadway are exchanged, and the above steps are repeated until the whole face is detected, and then inversion calculation is performed. The present application can solve the problems of low positioning accuracy of water-bearing abnormal body and inaccurate abnormal shape discrimination of the existing mine transient electromagnetic method.

This disclosure pertains to the field of exploration geophysics and presents a method and system for combined active and passive source reverse time migration imaging of metallic minerals. The method includes: performing time difference correction on active and passive source seismic data from the same subsurface structure; performing wavefield separation on the time-aligned active and passive source seismic data to reconstruct the P-wave and S-wave fields of the active source and the passive source; performing active and passive source wavefield extrapolation based on the two-way wave equation; obtaining active and passive source PS-converted wave imaging results using cross-correlation imaging conditions; and performing weighted superposition and fusion to obtain the combined active and passive source imaging results. This disclosure leverages the high resolution advantage of active sources combined with the deep detection capability of passive sources, replacing the limitations of single-source detection and achieving high-precision deep reverse time migration imaging.

The invention discloses a seismic high-score attribute shale reservoir small fracture classification prediction method based on structural attitude control, and relates to the technical field of exploration geophysics and oil and gas development. Aiming at the development requirement of shale reservoir small fracture multi-stage shunting prediction, the invention constructs a small fracture classification prediction method which takes a'high-resolution linear attribute 'method as a core technology and carries out constraint by tectonic occurrence, so that the requirements of different tectonic stage classification description of shale reservoir small fractures are met. According to high-resolution linear attribute (hereinafter referred to as high-score attribute) calculation provided by the invention, fine representation prediction of small fractures of the reservoir is effectively completed, and the fracture occurrence orientation corresponding to each construction period is constrained, so that small fracture classification of different occurrence orientations is realized. According to the prediction method, classification and accurate prediction of small-scale fractures of shale can be completed, an ideal actual drilling data verification coincidence rate is obtained, and field development requirements are met.

The invention discloses a high-speed rail seismic source seismic data wave field separation method and system using random Cadzow filtering, and belongs to the technical field of exploration geophysics. The method comprises the following steps: acquiring seismic data when a high-speed rail passes; estimating the seismic wave propagation speed through Radon transformation; performing time difference correction on the same-direction wave field event to obtain aligned data; blocking the aligned data and randomly rearranging the aligned data; fourier transform is carried out on the rearranged data, and a Hankel matrix is constructed; carrying out SVD (Singular Value Decomposition) decomposition and low-rank reconstruction on the Hankel matrix; reconstructing a frequency domain data block through an anti-Hankel operation; inverse Fourier transform is carried out, and a trace sequence is recovered; and extracting and averaging a central channel to obtain unidirectional wave field data. The system comprises modules with corresponding functions. The method can effectively separate the high-speed rail seismic source mixed wave field, improves the signal-to-noise ratio of data, and provides a reliable data basis for underground imaging.

The invention discloses a meshless seismic wave forward modeling method based on a difference numerical method and related equipment, and belongs to the field of exploration geophysics. According to the method, flexible mesh generation is carried out based on an undulating surface seismic wave speed model, a surface interface is completely fitted, and a high-precision difference coefficient set is obtained without manually selecting deformation parameters; by adding a filter related to a second-order time item in a two-dimensional scalar time domain acoustic wave equation, the robustness and accuracy of numerical simulation are effectively improved, so that a high-precision and stable seismic wave numerical simulation result is obtained, the precision and stability of seismic data processing can be effectively improved by utilizing the method, and the seismic data processing efficiency is improved. The method provides solid technical support for loess tableland seismic wave forward modeling, and has important practical significance for evaluating the influence of the earth surface effect on exploration data in the loess tableland, improving the accuracy and reliability of the exploration data, analyzing the physical properties and change rules of underground media and simulating the physical properties and seismic wave propagation conditions of underground structures.

The invention belongs to the technical field of exploration geophysics and seismic signal processing, and relates to a Rayleigh wave double-component fusion method and system based on model prediction. In order to solve the problem that a fusion decision depends on an empirical threshold and cannot quantitatively predict an effect, the method comprises the following steps: acquiring seismic data continuously acquired by a station pair in a target area; calculating the signal-to-noise ratio of the ZZ cross-correlation function and the signal-to-noise ratio of the RR cross-correlation function of each station pair; calculating the ratio of the signal-to-noise ratio of the RR cross-correlation function to the signal-to-noise ratio of the ZZ cross-correlation function of each station pair; calculating a similarity index according to the ratio; predicting a fusion gain by adopting a similarity index; and according to a comparison result of the prediction gain and a target threshold value, intelligently deciding whether to carry out double-component fusion, and outputting a final effective signal. According to the method, the fusion decision is improved from experience judgment to a computable and optimizable model driving process, the overall signal-to-noise ratio of the data can be stably and reliably improved, and the seismic data quality for imaging is directly improved.

This invention relates to the field of exploration geophysics and provides a method for reconstructing VSP data into ground seismic data. This method can reconstruct VSP data into ground seismic data, changing the type of the original seismic data. The reconstructed seismic data has a high signal-to-noise ratio. Furthermore, by performing joint data processing on the original VSP data and the reconstructed ground seismic data, the imaging accuracy of underground geological structures can be improved, and the imaging range of underground geological structures can be effectively expanded, resulting in high-quality imaging results.

The invention belongs to the technical field of exploration geophysics, and discloses a pure viscous sound forward modeling method and system. The method comprises the following steps: setting an observation system, and obtaining an initial model parameter field; performing grid division on the initial model parameter field to obtain a model parameter at each grid point; setting a high-precision pure viscous sound anisotropic wave equation, and constructing a high-precision wave field propagation operator; determining a pure viscous sound anisotropic wave equation coefficient based on the pure viscous sound anisotropic wave equation and the model parameter at each grid point; and calculating to obtain a longitudinal wave field value of each grid point by adopting the wave field propagation operator, the pure viscoacoustic anisotropy wave equation coefficient and the initial model parameter field. According to the method, the propagation process of waves in the complex underground medium can be simulated more accurately.

The invention belongs to the field of exploration geophysics, and discloses a reflection angle influence-free sound wave vector reverse time migration imaging method, which comprises the following steps of: presetting seismic wavelets and an initial speed model, and realizing forward extrapolation of a sound wave field by utilizing a first-order sound wave equation to obtain a sound wave source wave field; according to observed seismic data and a preset initial velocity model, using a first-order sound wave equation to realize sound wave field reverse extrapolation to obtain a sound wave detection wave field; based on the sound wave source wave field and the sound wave detection wave field, an imaging angle is determined by using the constructed energy norm-based imaging angle extraction function; and based on the imaging angle, imaging is carried out by using the constructed dot product cross-correlation imaging condition without the influence of the reflection angle, and a scalar imaging result without the influence of the reflection angle is obtained. According to the method disclosed by the invention, the problem of polarity inversion caused by the imaging angle under the acoustic vector dot product imaging condition can be eliminated, and the polarity consistency of the acoustic imaging event is improved, so that a guarantee is provided for the accuracy of geologic structure imaging in a complex environment.

The invention discloses an earthquake low-frequency signal reconstruction method based on deep learning, and relates to the technical field of exploration geophysics. Preprocessing the original seismic data; performing network training; performing network prediction; and performing data recovery. According to the method, mapping from high-frequency data to low-frequency data is realized by building a convolutional neural network framework, and low-frequency signals are recovered; the features of the sample are closer to real data by using a demigration method, and the accuracy of network prediction is improved; and taking the prepared high-frequency sample as the input of the network, taking the low-frequency sample as the output of the network, using the two groups of data sets for network training, and using the trained CNN to predict low-frequency data from high-frequency data. According to the method, the local features in the signals can be automatically extracted, the requirement of artificial feature engineering is reduced, complex modes and relations are effectively captured through a multi-layer structure, the trained neural network can be suitable for a target work area by improving a training sample, and the prediction accuracy is improved.

The invention discloses a time migration method for a three-dimensional pre-stack wave equation in an imaging ray domain, which relates to the technical field of exploration geophysics and comprises the following steps of: deducing a bidirectional acoustic wave equation in an imaging ray coordinate system based on a Riemann wave field extrapolation theory in a three-dimensional semi-orthogonal coordinate system; an equation is directly solved by adopting a finite difference method, extrapolation of a seismic source and a receiving end wave field is achieved, and errors caused by Green function approximation in a traditional migration method are avoided; and generating a pre-stack time migration result by applying a zero-lag cross-correlation imaging condition. Through first-order linear disturbance approximation, an accurate three-dimensional time-depth conversion partial differential equation set is simplified into an optimized layer stripping algorithm, and a corresponding equation suitable for a weak transverse velocity change medium is deduced. According to the invention, the working process of three-dimensional wave equation time migration is realized in an imaging ray coordinate system, and an accurate seismic imaging result is generated; two-dimensional plane hypothesis limitation is avoided, and high-precision imaging technical guarantee is provided for seismic data processing of a complex structure area.

The application discloses a kind of direct reverse-time migration imaging methods based on DAS acquisition strain rate data, it is related to the technical field of exploration geophysics, including s1, based on velocity-pressure wave equation and strain rate-velocity relationship establishes pressure-strain rate equation;S2, based on pressure-strain rate equation, obtains positive transmission wave field and reverse transmission wave field;S3, using cross-correlation imaging condition to positive transmission wave field and reverse transmission wave field are imaged, and imaging result I (x) is obtained;S4, the comprehensive illumination matrix of source and wave field of geophone is calculated;S5, the comprehensive illumination compensation of imaging result I (x) is obtained final imaging result I final (x).The application directly uses strain rate data for imaging, not only avoids the error caused by data conversion, significantly improves the fidelity of data and the accuracy of imaging, but also simplifies the data processing procedure.In addition, the method improves the illumination effect of deep underground area through comprehensive illumination strategy, so that the imaging result is clearer and more detailed.

The present specification relates to the technical field of exploration geophysics, and particularly relates to an anisotropic elastic wave decoupling method and device and computer equipment. The anisotropic elastic wave decoupling method comprises: determining a set of Thomson parameters included in an anisotropic model according to a received wave field decomposition request to be decomposed, the wave field decomposition request to be decomposed comprising a wave field to be decomposed; converting the set of Thomson parameters to obtain an initial set of elastic parameters; performing P-S wave velocity separation processing on the initial set of elastic parameters to obtain a target P-wave elastic parameter set and a target S-wave elastic parameter set; and substituting the target P-wave elastic parameter set and the target S-wave elastic parameter set into the anisotropic model to process the wave field to be decomposed to obtain a target P-wave matrix and a target S-wave matrix. The embodiments of the present specification simplify the P-S wave field decomposition process and reduce the calculation cost.

The application discloses a travel time tomography method and system, belongs to the technical field of exploration geophysics research, and utilizes a travel function equation to establish a mapping relationship between travel time and a velocity model; a Bayesian-fusion physical mechanism neural network structure based on the travel function equation is designed, Bayesian-fusion physical mechanism neural network parameters are trained based on a Bayesian inference algorithm, posterior distribution samples are obtained, an inversion velocity field of all samples is averaged, and finally, a travel time tomography inversion result is formed. The application has high inversion precision for the velocity model and excellent uncertainty quantification capability.

The invention discloses a stratum thickness qualitative prediction method and system, and belongs to the technical field of exploration geophysics. The method comprises the following steps: determining a target horizon in three-dimensional seismic data, and calculating a spectral decomposition result based on three-dimensional continuous wavelet transform; initializing a weight vector of maximum correlation entropy self-organizing mapping, and inputting spectral decomposition feature data; calculating a maximum correlation entropy distance to find a winning neuron; and iteratively updating the neighborhood weight to complete prediction, and verifying validity by using a wedge-shaped model. The system comprises a target module, an initialization module, a calculation module and a prediction module of corresponding functions. According to the method, comprehensive features are extracted through three-dimensional wavelet transform, unsupervised neural network clustering is combined, a large number of labels are not needed, noise immunity is high, the problems that a traditional method is low in thin layer prediction precision and depends on the labels are solved, and the method is suitable for qualitative prediction of the stratum thickness in oil-gas exploration.

The application discloses a kind of seismic structural feature oriented geostatistical modeling methods, belong to exploration geophysics field;The method comprises: based on the prior information of geostatistics, the multivariate Gaussian prior distribution of underground parameter model is established;From seismic data, structural guidance information is extracted, including calculating gradient, constructing structural tensor and carrying out eigenvalue decomposition to obtain local dominant direction;Accordingly, a structure-guided constraint operator is constructed;Well logging data constraints are combined with structural constraints to form an observation system;The prior distribution is updated using Bayes' theorem to obtain a posterior distribution containing posterior mean and covariance.The application realizes reasonable interpolation along the trend of strata, improves the accuracy and structural consistency of geological modeling, and can quantitatively predict uncertainty.

A method for three-dimensional (3D) reservoir mapping includes obtaining a 3D resistivity volume in a point set format and transforming the 3D resistivity volume in the point set format into a 3D resistivity map in a geological prospecting learning (SEG-Y) format. A method for identifying an interface between a high resistivity volume and a low resistivity volume may also include applying a first resistivity threshold to the 3D resistivity map in the SEG-Y format to generate a binary resistivity volume, wherein a first high resistivity value is assigned to a cell having a resistivity value greater than the first resistivity threshold value in the 3D resistivity map, and a second low resistivity value is assigned to a cell having a resistivity value less than the first resistivity threshold value; and evaluating the binary resistivity volume to identify the interface between the high resistivity volume and the low resistivity volume.

This article relates to the field of exploration geophysics, and in particular to a double-dot-product seismic imaging method, device, and equipment for elastic wave stress tensor. This includes obtaining a decoupled particle vibration velocity vector wave field by using the existing decoupled wave equation method on the detection wave field; then using the obtained decoupled particle vibration velocity vector wave field to construct a decoupled pseudo-stress equation to obtain a decoupled pseudo-stress wave field; and finally using the double-dot-product cross-correlation imaging condition algorithm to calculate the second-order stress tensor wave field of the earthquake source and the decoupled detection second-order stress tensor wave field to obtain the final scalar imaging result. Through the embodiments of this article, it is possible to realize the joint exploration of longitudinal and shear waves, so as to use the obtained imaging to accurately predict the risks of gas exploration, thereby solving the problem that the existing longitudinal wave imaging technology cannot give full play to the advantages of the joint exploration of longitudinal and shear waves, resulting in the inability to accurately predict the risks of oil and gas exploration using multi-wave imaging results.

The application discloses a kind of based on structural occurrence control seismic high-resolution attribute shale reservoir small fracture classification prediction method, it is related to exploration geophysics and oil and gas development technical field.The present application is aimed at the development needs of multiple stages of small fracture prediction of shale reservoir, constructs a kind of small fracture classification prediction method with "high-resolution linear attribute" method as core technology, and is constrained by structural occurrence, to achieve the requirements of different structural stages classification description of small fracture of shale reservoir.According to the high-resolution linear attribute (hereinafter referred to as high-resolution attribute) calculation proposed in the application, the fine characterization prediction of reservoir small fracture is effectively completed, and the fracture occurrence orientation corresponding to each structural period is constrained, so that the small fracture classification of different occurrence orientation is realized.The prediction method of the application can complete the classification and accurate prediction of small-scale fractures of shale, and achieve a relatively ideal drilling data verification coincidence rate, meet the needs of field development.

The application discloses a kind of based on Uformer's seabed node transverse wave leakage suppression method, system, medium and equipment, belong to the field of exploration geophysics, the method includes multi-component data preprocessing, radial component acquisition, Uformer network model and dataset construction, network training optimization and actual data application;The application also provides the method system, medium and equipment of running described.The application can effectively predict and remove the transverse wave leakage noise in Z component, improve the signal-to-noise ratio and interpretation reliability of the imaging profile.By self-attention mechanism modeling, the global dependence relationship between different positions of input sequence is established, the extraction and prediction accuracy of the transverse wave leakage model is improved;In the dataset construction stage, the horizontal component is rotated to the radial tangent component, the fusion and utilization of X and Y direction information are realized, the inconsistency problem caused by the coupling difference of different geophones X component is reduced, and the description ability and stability of the transverse wave leakage form are enhanced.

The invention provides an electromagnetic survey method and system and electronic equipment, and belongs to the technical field of exploration geophysics. The method comprises the steps of collecting an initial signal; the initial signal comprises a natural electric field and / or magnetic field entering underground and meeting with the natural electric field and / or magnetic field entering underground at the moment at the sensor at the moment when the natural electric field and / or magnetic field enters underground and returns to the sensor through reflection and refraction of an underground electrical impedance interface, and the two signals are superposed to obtain an initial time sequence of a synthetic electric field and / or magnetic field intensity; obtaining an initial frequency spectrum of the initial time sequence based on Fourier transform of the initial time sequence; travel time inversion: based on an electromagnetic field superposition principle, performing superposition operation on the initial frequency spectrum through a harmonic synthesis algorithm to obtain a synthesized travel time sequence of the electric field and / or magnetic field intensity; the synthesized travel time sequence is used for studying and judging geological information. According to the method provided by the embodiment of the invention, high-resolution geological exploration and engineering exploration based on the natural electromagnetic field source are realized.

The invention discloses a direct reverse time migration imaging method for acquiring strain rate data based on a DAS, and relates to the technical field of exploration geophysics, and the method comprises the steps: s1, building a pressure-strain rate equation based on a speed-pressure wave equation and a strain rate-speed relation; s2, obtaining a forward propagation wave field and a backward propagation wave field based on the pressure intensity-strain rate equation; s3, imaging the forward propagation wave field and the backward propagation wave field by using a cross-correlation imaging condition to obtain an imaging result I (x); s4, calculating a comprehensive illumination matrix of the seismic source and the detection point wave field; and s5, performing comprehensive illumination compensation on the imaging result I (x) to obtain a final imaging result Ifinal (x). According to the method, the strain rate data is directly utilized for imaging, so that errors caused by data conversion are avoided, the fidelity of the data and the imaging precision are remarkably improved, and the data processing flow is simplified. In addition, according to the method, the illumination effect of the deep underground area is improved through a comprehensive illumination strategy, the imaging result is clearer, and details are richer.