Fractures usually spread over various scales and strongly influence velocity and anisotropy. We investigate elastic velocity and anisotropy in rocks with fractures of different sizes. Based on synthetic rocks with controlled fracture geometries, we create a set of rocks with fracture diameter of 2, 3 and 4 mm and the fracture thickness is 0.06 mm. P‐ and S‐wave velocities are measured at 0.1 MHz, while

Facies boundaries are critical for flow performance in a reservoir, and are significant for lithofacies identification in well interpretation and reservoir prediction. Facies identification based on supervised machine learning methods usually requires a large amount of labeled data, which are sometimes difficult to obtain. Here, we introduce the deep autoencoder to learn the hidden features and conduct

Seismic waves passing through partially saturated porous rocks produce pressure gradients in fluid phase and hence, the resulting fluid flow is accompanied on various length scales. The major mechanism responsible for seismic attenuation and dispersion is arguably known as wave‐induced fluid flow between inhomogeneities of microscopic, mesoscopic and macroscopic scales. Previous studies reveal that

Event locations are essential for microseismic monitoring endeavours to map hydraulic fractures. For downhole monitoring, the event back‐azimuthal angle, which is commonly evaluated as the average of the P‐wave polarization angle at each sensor, is necessary to project the 2D location in the vertical plane determined by the traveltime information to the 3D space. The accuracy of the P‐wave polarization

Seismic methods are often used for fracture detection and characterization, for which many analytical rock physics models have been developed to link fracture parameters to rock elastic properties. However, most of these models are limited to isotropic background and circular (penny‐shaped) fractures. In this work, we derived a more general analytical model for effective elastic properties of rocks

Cretaceous shales from the emerging gas province of the Rovuma Basin are examined using well log data from two exploration wells. The P‐wave acoustic impedance (AIp) data were estimated and then brittleness and ductility were assessed within the framework of the Reuss‐Voigt limits for acoustic impedance. We then predicted the shale consolidation using a weighting function (Wc) which varies between

This study illustrates the application of a geometric average integration of aeromagnetic, radiometric and satellite imagery data over a region prone to Cu‐bearing mineralization at Chahargonbad area in Kerman province of Iran. Processing aeromagnetic, radiometric and Advanced Spaceborne Thermal Emission and Reflection Radiometer satellite data can provide exploratory insights about favourable zones

The images produced by conventional vertical seismic profile imaging methods often suffer from the problems of illumination limitation and uncompleted wavefield separation. In this paper, we give a deep insight into the illumination behaviours of the upgoing primary and downgoing multiple signals and illustrate their merits and demerits in illuminating the subsurface structure around the well trajectory

The precision of P‐ and S‐wave phase picking strongly determines the precision of earthquake locations, but such picking can be challenging in the case of emergent signals, large datasets, or temporally varying seismic networks. To overcome these challenges, we have developed the concept of an Aggregated Template (AT) to perform automatic picking of the P‐ and S‐wave phases. An AT is defined as a representative

Diffracted wavefields with superior illumination encode key geologic information about small‐scale geologic discontinuities or inhomogeneities in the subsurface and thus possess great potential for high‐resolution imaging. However, the weak diffracted wavefield is easily masked by the dominant reflected data. Diffraction separation from specular reflected data still plays an important role and plays

Early time measurements of time domain electromagnetics carry information of the near surface, and therefore, the interpretation of such measurements is important, particularly when utilizing small‐loop acquisition devices. However, these early time gates are often distorted by responses from the acquisition system itself, primarily caused by self‐transients associated with the transmission link composed

The purpose of this paper is to derive the Green's function of an anisotropic elastic medium and validate it with the effective stiffness tensor of Barnett Shale. We have derived the frequency‐dependent Green's function by using the spectral theorem for matrices, thus simplifying the process of computing Green's function and obtaining analytical solutions. Evaluating the inverse of the Green–Christoffel

An attenuating wave‐field in an anisotropic poroviscoelastic medium is represented through the three‐dimensional inhomogeneous propagation of four bulk waves. Propagation of each wave is governed by a complex slowness vector, which specifies its phase direction, phase velocity and coefficients for homogeneous/inhomogeneous attenuation. Partially‐opened surface pores restrict the seepage of pore‐fluid

In this paper, we study seismic responses to an earthquake source in horizontally stratified transversely isotropic porous media with a vertical axis of symmetry, i.e., VTI porous media. We present a semi‐analytical method to simulate the three‐dimensional time‐space‐domain seismic wavefields. We obtain the solution in the frequency‐wavenumber domain by the global matrix method and transform it to

Diffraction imaging is the process of separating diffraction events from the seismic wavefield and imaging them independently, highlighting subsurface discontinuities. While there are many analytic‐based methods for diffraction imaging which use kinematic, dynamic or both, properties of the diffracted wavefield, they can be slow and require parameterization. Here, we propose an image‐to‐image generative

Harmonic noise may significantly complicate the processing of slip‐sweep vibroseis data. We propose a model of this noise and an optimal recursive filtering algorithm based on this model. In contrast to some alternatives, this method can remove harmonic noise caused by all the events on the seismic gather, instead of only removing the noise associated with the first arrivals. First, the algorithm predicts

Significant advances have been made towards fault detection using deep learning. However, the fault labeling of seismic data requires great human effort. The resulting small sample problem makes traditional deep learning methods difficult to achieve desired results. Existing research proposes to train deep learning model with labeled synthetic seismic data to get good fault detection results. However

The main challenge of Markov chain Monte Carlo sampling is to define a proposal distribution that simultaneously is a good approximation of the posterior probability while being inexpensive to manipulate. We present a gradient‐based Markov chain Monte Carlo inversion of pre‐stack seismic data in which the posterior sampling is accelerated by defining a proposal that is a local, Gaussian approximation

Analysis of compressional and shear‐wave sonic logs in seven organic‐rich shale reservoirs exhibiting a wide range of velocities, total organic content, thermal maturity, fluid compressibility, and mineral composition, indicates that compressional‐wave velocity is a strong predictor of shear‐wave velocity as is the case for conventional reservoirs. Excluding data with high water saturations, a simple

A Matlab based optimization algorithm is introduced for inverting fault structures from observed gravity anomalies. A convenient graphical user interface (GUI) is also presented for incorporating the input parameters without any technical complexity to any users. The inversion code uses particle swarm optimization, and all control parameters are tuned initially for faster convergence. There is no requirement

The application of distributed acoustic sensing in borehole measurements allows for the use of fibre optic cables to measure strain. This is more efficient in terms of time and costs compared to the deploying of conventional borehole seismometers. Nevertheless, one known drawback for temporary deployment is represented by the freely hanging wireline cable slapping and ringing inside the casing, which

Accurate and precise estimation of microseismic event location in anisotropic reservoirs is challenging with borehole acquisition, due to limited azimuthal and inclination coverage. Inclusion of shear‐wave splitting information from microseismic data can improve estimates of event directivity, source location, and the degree of reservoir anisotropy compared to using P‐waves alone. Additionally, S‐waves

With the wide application of the high‐density and high‐productivity acquisition technology in the complex areas of oil fields, the first break picking of massive low signal‐to‐noise data is a great challenging job. Conventional first break automatic picking methods (Akaike Information Criterion method, Energy ratio method, Correlation method, and Boundary detection method, etc.) require a lot of manual

We develop an algorithm for seismic data filtering to preserve the boundary information of faults and other geological bodies while suppressing the noise. Based on the theory of anisotropic diffusion filtering, this method explores the relationship between eigenvalues of the structure tensor and local structural features of 3D seismic images and innovatively introduces the definition of stratigraphic

The effect of tensile fracture in a vertical borehole under anisotropic horizontal stress conditions is numerically investigated in terms of the dispersion of flexural wave generated in dipole sonic logging. Our three‐dimensional model comprises a borehole filled with water and a tensile fracture intersecting the borehole in the borehole axial direction. Two shear waves are excited individually to

In this paper, we propose a method for revealing hidden reservoirs that are shielded by strong amplitudes. The bi‐dimensional empirical mode decomposition algorithm is used to decompose pre‐stack seismic data into several localized components, which generated from different discontinuities in the subsurface elastic properties. The two‐dimensional Teager–Kaiser energy operator process is applied to

The quality and accuracy of a seismic image can be significantly affected by anisotropy. When anisotropy is significant, neglecting it can lead to smearing of the image, dispositioning of reflections and distortion of amplitudes. Thus, it is imperative to estimate anisotropy and take it into account, especially for long‐offset or wide‐azimuthal seismic data. This study estimates P‐wave anisotropy parameters

The movement of the receiver coil in a magnetic field produces motion noise in the airborne electromagnetic field. With an amplitude that is several orders of magnitude higher than that of other noise sources, this motion noise is one of the main low‐frequency (<1 kHz) noise sources. Especially in the late decay period, the residual motion noise produces false anomalous information, which is a key

Potential field and Slingram data alongside rock physical properties, drill‐core information and results from geological field mapping were used to investigate the geometry of the geological structures in the Gällivare area in regional scale. The main purpose of this study was to delineate the vertical and lateral extension of the Malmberget felsic volcanic rocks, the Dundret and Vassaravaara units

In seismic land exploration, where terrain conditions limit the use of vibrator sources, explosive sources are the preferred choice, and in situations where low‐frequency energy is essential, explosive is the preferred source, because it contains energy down to DC (0 Hz). I present a new method to estimate the source time functions of explosion source seismic data, using a modified acquisition method

Electromagnetic measurement while drilling systems transmit downhole data via an information channel composed of a drill string and formation; the formation has a strong attenuation effect on the signal. Signal attenuation during electromagnetic wave transmission through the formation limits the well depth at which this technique can be applied. This paper discusses several commonly used methods to

The complex resistivity spectra of 16 artificial sandstone samples with different physical property at different water and solution saturations were measured and fitted with the Cole–Cole model in the frequency band of 40 Hz to 110 MHz. The frequency exponent in the model indicates the ideal degree of the sample's capacitive property. The experimental result shows that the frequency exponents of the

The standard common‐reflection‐surface stacking method simulates high‐quality zero‐offset stacked data from multi‐coverage prestack data and, as by‐products, provides three kinematic wavefield attributes in two dimensions that can be applied to solve reflection seismic problems. One of the most significant applications of those attributes is for interpolation and enhancement of prestack data through

Random noise attenuation is an essential step in seismic data processing for improving seismic data quality and signal‐to‐noise ratio (S/N). We adopt an unsupervised machine learning approach to attenuate random noise via signal reconstruction strategy. This approach can be accomplished in the following steps: Firstly, we randomly mute a part of the input data of the neural network according to a certain

Migration of multi‐component elastic data in anisotropic models is difficult and has not been reasonably addressed. Thus we test three‐dimensional ray‐based Kirchhoff pre‐stack depth scalar migration and calculate migrated sections in a simple anisotropic velocity model. We generate ray‐theory seismograms for separate phases of reflected P, S1, S2 and converted waves. The velocity model is composed

We propose an algorithm for seismic trace interpolation using generative adversarial networks, a type of deep neural network. The method extracts feature vectors from the training data using self‐learning and does not require any pre‐processing to create the training labels. The algorithm also does not make any prior explicit assumptions about linearity of seismic events or sparsity of the data, which

Migration, velocity and amplitude analysis are the employed processing steps to find the desired subsurface information from seismic reflection data. The presence of free‐surface and internal multiples can mask the primary reflections for which many processing methods are built. The ability to separate primary from multiple reflections is desirable. Connecting Marchenko theory with classical one‐dimensional

Wave‐mode separation is a critical step in anisotropic elastic‐wave imaging. To avoid high computational costs and additional corrections, we apply a separation formula in the space domain that projects Cartesian components of the elastic wavefield onto the polarization vectors in the orthogonal direction. By solving the Christoffel equation, we implement the conversion from the phase velocity direction

Manual fracture identification methods based on cores and image logging pseudo‐pictures are limited by the expense and the amount of data. In this paper, we propose an integrated workflow, which takes the fracture identification as an end‐to‐end project, to combine the boundary detection and the deep learning classification to recognize fractured zones with accurate locations and reasonable thickness

The Xiaorequanzi copper–zinc deposit, located in the eastern Tianshan, is considered as a medium‐sized polymetallic deposit in Xinjiang, NW China. Understanding the structural framework and delineating the location of intrusions as well as the distribution of ore‐controlling strata in this mining area are vital for identifying new potential exploration areas. This paper aims to provide new information

Magnetotelluric is one of the mainstream exploration geophysical methods, which plays a vital role in studying deep geological structures and finding deep hidden blind ore bodies. The seriousness of human electromagnetic noise causes a large number of abnormal waveforms in the time series of measured magnetotelluric data, and the data can no longer objectively reflect the underground electrical distribution

Although most electromagnetic data can be inverted to actual resistivity, ways of quickly getting a real‐time interpretation of a data set are still valuable. Such methods are useful when we are testing instrumentation or assessing data quality during a survey, or when we need to get a general understanding of the geological structure during a field survey. Apparent resistivity is a good way to satisfy

We have addressed the problem of seismic data frequency–time filtration based on the S‐transform. The S‐transform provides frequency‐dependent resolution while maintaining a direct relationship with the Fourier spectrum and has been widely used in different seismic data‐processing applications. The standard S‐transform filtration method is based on its invertibility. In a sense of time localization

The dictionary learning and sparse approximation method using the K‐singular value decomposition algorithm rely on the knowledge of the sparsity or noise variance as a constraint when it is used for data denoising. However, the determination of the sparsity or noise variance of seismic data can be tricky and sometimes unknown, especially in seismic field data. Thus, where the cardinality or the noise

Nowadays the least‐squares reverse time migration has become the most used migration method because of its accuracy in amplitude recovery and high‐resolution imaging, specifically its priority to image the beneath of structural domes such as salt domes. However, errors in the migration velocity model, inadequate physics of modelling/migration and too sparse data decrease the quality of the migrated

For many geophysical measurements, such as direct current or electromagnetic induction methods, information fades away with depth. This has to be taken into account when interpreting models estimated from such measurements. For that reason, a measurement sensitivity analysis and determining the depth of investigation are standard steps during geophysical data processing. In deterministic gradient‐based

There are several models accounting for the induced polarization phenomenon in terms of complex, frequency‐dependent conductivity σ or resistivity ρ = 1/σ. The most popular ones are the Cole–Cole conductivity and Pelton resistivity models. Each model includes four parameters: resistivity ρ (or its inverse, conductivity σ), chargeability m, relaxation time τ and frequency dependence c. Some authors

Angle domain common image gathers are crucial for seismic applications such as the migration velocity analysis and amplitude variation with angle analysis. Angle domain common image gathers are the gather of reflection coefficients when seismic waves incident at different angles on the same image point. The curvature of gathers can be used to update the migration velocity model. The amplitude variation

In this study, we proposed a deep learning algorithm (PATCHUNET) to suppress random noise and preserve the coherent seismic signal. The input data are divided into several patches, and each patch is encoded to extract the meaningful features. Following this, the extracted features are decompressed to retrieve the seismic signal. Skip connections are used between the encoder and decoder parts, allowing

Sparse inversions have proven to be useful for interpreting potential‐field data because the recovered models are characterized by sharp boundaries, compact features and elevated values, compared with conventional smoothness‐based inversion results. However, several open problems remain to be addressed, including the bound dependence and staircasing problems. The former results in recovered anomalous

We present a new ray bending approach, referred to as the Eigenray method, for solving two‐point boundary‐value kinematic and dynamic ray tracing problems in 3D smooth heterogeneous general anisotropic elastic media. The proposed Eigenray method is aimed to provide reliable stationary ray path solutions and their dynamic characteristics, in cases where conventional initial‐value ray shooting methods

This paper is the second in a sequel of two papers and dedicated to the computation of paraxial rays and dynamic characteristics along the stationary rays obtained in the first paper. We start by formulating the linear, second‐order, Jacobi dynamic ray tracing equation. We then apply a similar finite‐element solver, as used for the kinematic ray tracing, to compute the dynamic characteristics between

This article presents the results of mapping a karst cave by the passive seismic standing waves method. Barsukovskaya cave is located about 100 km southeast of the city of Novosibirsk (Russia). The total length of the cave's passages and grottoes is estimated at about 200 m, the maximum depth from the earth's surface is about 19 m. The method for studying underground cavities used is based on the effect

An important cause of seismic anisotropic attenuation is the interbedding of thin viscoelastic layers. However, much less attention has been devoted to layer‐induced anisotropic attenuation. Here, we derive a group of unified weighted average forms for effective attenuation from a binary isotropic, transversely isotropic‐ and orthorhombic‐layered medium in the zero‐frequency limit by using the Backus

Wave‐induced fluid flow plays an important role in affecting the seismic dispersion and attenuation of fractured porous rocks. While numerous theoretical models have been proposed for the seismic dispersion and attenuation in fractured porous rocks, most of them neglect the wave‐induced fluid flow resulting from the background anisotropy (e.g. the interlayer fluid flow between different layers) that

The propagation of seismic waves through a saturated reservoir compresses the fluid in the pore spaces. During this transition, parts of seismic energy would be attenuated because of intrinsic absorption. Rock physics models make the bridge between the seismic properties and petrophysical reality in the earth. Attenuation is one of the significant seismic attributes used to describe the fluid behaviour

The phenomenon of acoustic waves inducing electric fields in porous media is called the seismoelectric effect. Earlier investigators proposed the usage of seismoelectric effect for well logging. Soil texture has a strong influence on the coupled wave fields during shallow surface explorations. In this article, we study the borehole pure shear‐horizontal wave and the coupling transverse‐electric field

We develop a workflow to estimate elastic attributes ( V p and V s ) of Pre‐Salt carbonate reservoirs using the Xu and Payne rock physics model in a depth‐variant multimineralogic fashion and apply it to one calibration and four extrapolation wells in a field in the Brazilian Santos Basin. Some of the parameters were stochastically simulated in a Bayesian framework to handle the model non‐uniqueness

We present the results of a low‐frequency study of Mancos shale, where we first elaborate a stress–strain methodology of laboratory low‐frequency experiments to estimate the elastic moduli of shales, and then apply this methodology to investigate the influence of partial water saturation on the elastic and anelastic parameters, velocities and P‐wave anisotropy of Mancos shale. We also analyse the applicability

Low‐frequency forced‐oscillation methods applied to a reservoir sandstone allowed determination of the Young's modulus and Poisson's ratio (from axial loading), bulk modulus (by oscillation of the confining pressure) and shear modulus (from torsional‐forced oscillations) for comparison with conventional ultrasonic data. All tests were performed on a common sandstone core sample from an oil reservoir