Elastic full-waveform inversion can increase the resolution of reservoir characterization using seismic data. However, full-waveform inversion for realistic anisotropic media suffers from the trade-offs between the medium parameters and strongly relies on the accuracy of the initial model. Here, we employ a regularization methodology that utilizes geologically consistent information to reduce the inversion

Wave-induced fluid flow, an important mechanism in seismic wave attenuation, is considered in the amplitude variation with the offset technique. In a fractured marine carbonate reservoir, fractures and pores develop simultaneously, such that wave-induced flow is an important mechanism in attenuation caused by the fluid flow between pores as well as between pores and fractures. However, these two types

Electrical Resistivity Tomography (ERT) is a non-linear and ill-posed geophysical inverse problem that is usually solved through gradient-descent methods. This strategy is computationally fast and easy to implement but impedes accurate uncertainty appraisals. We present a probabilistic approach to 2D ERT in which a Markov Chain Monte Carlo (MCMC) algorithm is used to numerically evaluate the posterior

To investigate the influences of compression, Poisson effect, and turbulence on the fluid flow process and on the inversion for fracture surface geometries, we simulate two sets of fractures: one with a defined fracture height standard deviation σ constant and a varying autocorrelation length λ, and another with a fixed λ and a changing σ. Under compression, the normal stress closes fractures with

Electrical resistivity tomography employs L2 norm regularization in many applications. We developed the boundary-sharping inversion method based on the finite element methods and irregular grid approach, in which the contact areas of elements are used to weight the model parameters. Similar approaches have previously only been used for structured grids. We also designed an electrical resistivity tomography

The Central-Eastern Mediterranean region is known to be a complex area due to the interaction of four tectonic plates namely, Arabia, Africa, Anatolia and Eurasia and by the presence of an ancient oceanic crust in the Herodotus and Ionian Basin. The analysis of the available literature highlights that the distribution of the freely available geophysical data (i.e. seismic, gravity and magnetic observations)

The generally shaped polyhedron is a widely used model in gravity field modelling and interpretation. Its induced gravity signal – gravitational potential and its derivatives up to second order – has been studied extensively in the geophysical literature. The class of solutions with special interest is the one which leads to closed analytical expressions, as these offer an exact representation of the

The mechanical properties of sandstones, including porosity, density and elastic moduli, can be estimated non-destructively through elastic wave-velocity measurements. Here, the variation of elastic wave velocity with porosity in sandstones is modelled using Maxwell's effective field theory, extended to the elasticity of heterogeneous media by Sevostianov and coworkers. Comparing measured and predicted

The added value of the joint pre-stack inversion of PP (incident P-wave and reflected P-wave) and PS (incident P-wave and reflected S-wave) seismic data for time-lapse application is shown. We focus on the application of this technique to the time-lapse (4D) multicomponent Jubarte field Permanent Reservoir Monitoring (PRM) seismic data. The joint inversion results are less sensitive to noise in the

ABSTRACT We have derived a convergent scattering series solution for the frequency-domain wave equation in acoustic media with variable density and velocity. The convergent scattering series solution is based on the homotopy analysis of a vectorial integral equation of the Lippmann-Schwinger type. By using the Green's function and partial integration, we have derived the vectorial integral equation

Time-lapse seismic reservoir monitoring is used as a way to gain insight into subsurface processes. Yet, the application of standard 4D technology onshore faces challenges, such as high cost, significant environmental footprint and, consequently, relatively infrequent surveys. As part of the Otway Project Stage 3 CO2 injection study, continuous automated borehole-based monitoring using distributed

The state-of-the-art joint migration inversion faces the so-called amplitude-versus-offset challenge, due to adopting over-simplified one-way propagation, reflection and transmission operators to avoid over-parameterization in the inversion process. To overcome this challenge, we apply joint migration inversion to horizontally layered media (or 1.5-dimensional media) and parameterize the solution space

Inanisotropy full waveform inversion, the pseudo-acoustic approximation is widely used to reduce the computation cost. However, artefacts and inaccurate predictions of amplitudes by the pseudo-acoustic approximation often result in slow convergence in the full waveform inversion iterations and inaccurate tomograms. To solve this problem, multiscale phase inversion methodology is extended to vertical

As an efficient geophysical exploration technique, airborne transient electromagnetics shows strong adaptability to complex terrains and can provide subsurface resistivity information rapidly with a dense spatial coverage. However, the huge volume of airborne transient electromagnetic data obtained from a large number of spatial locations presents a great challenge to real-time airborne transient electromagnetic

Seismic waves propagating in a fractured porous rock with fluids can be greatly attenuated due to the wave-induced fluid flow, including the macroscopic Biot flow, the mesoscopic interlayer fluid flow and the microscopic squirt flow. However, the comprehensive effects of the above wave-induced fluid flows on the frequency-dependent seismic properties in layered and fractured rocks with partial saturation

The accuracy of an explicit traveltime-offset approximation affects the results of the velocity analysis that plays a crucial role in the seismic data processing. Seismic anisotropy is important to account for large offset and azimuth since it can provide detailed information comparing with the isotropic assumption. For the perturbation-based method, different traveltime approximation forms result

Time–frequency analysis plays an important role in seismic interpretation and reservoir identification because it reveals the variation of seismic frequency contents over time. The S-transform is recognized as an efficient method for seismic time–frequency analysis, but its frequency distribution biases the actual Fourier spectrum due to the linear frequency-dependent term in the analytical window

By applying a ray-based three-dimensional vector migration process to fully elastic three-component synthetic Vertical Seismic Profiling data, we are able to demonstrate that the process gives an accurate compressional reflection image of the complex formation without much visible artefacts from spatial aliasing, or from ‘migration smiles’ caused by the limited aperture of the receiver array. We demonstrate

Full waveform inversion has shown its huge potentials in recovering a high-resolution subsurface model. However, conventional full waveform inversion usually suffers from cycle skipping, resulting in an inaccurate local minimum model. Extended waveform inversion provides an effective way to mitigate cycle skipping. A matching filter between the predicted and observed data can provide an additional

The conventional time-lapse processing workflow is usually sensitive to the non-repeatable uncertainties between different vintages caused by noise, acquisition designs and independent processing. Therefore, in order to reduce these non-repeatable uncertainties, all the datasets are usually acquired from well-sampled and well-repeated acquisition surveys, and the independent processing is always carefully

This study introduces a new attribute to identify seismic erratic noise, i.e. outlier, in the context of unsupervised anomaly detection and is defined as local outlier probabilities. The local outlier probabilities calculate scores of degrees of isolation, i.e. outlier-ness, for each object in a data set, which represents how far an object is deviated from its surrounding objects. Since the local outlier

During ocean bottom seismic acquisition, seafloor multicomponent geophones located in rugose and sloping water bottom can be affected by skewed energy distribution, such as leaked shear energy on the vertical geophones and leaked compressional energy on the horizontal geophones. To correct for the tilted energy distribution, which is one of most effective preprocessing steps, a geophone reorientation

The near-surface electrical properties of faults can change with seasonal climate, depending on the nature of the materials filling the faults, e.g. fault gouge vs fractured rock, and be subject to seasonal weather changes. A period of dry weather, especially in a hot climate, can dry out the near-surface sections of faults that are filled with porous materials, thus increasing the electrical resistivity

Conventional sonic logging tools are destined mainly for the determination of elastic waves’ velocities. In this paper, we have considered a different type of sonic logging tool that is destined for the registration of parameters of reflected waves in a borehole. We have calculated the mechanical impedance loading an acoustic source located on the axis of a fluid-filled borehole. The problem was solved

Seismic wave imaging in complex media requires an accurate wavefield simulation method that can accurately describethe wave propagation in realistic media. Reverse time-depth migration is the preferred method for seismic wave imaging in complex media. Although it is relatively expensive, its imaging accuracy is usually better than migrations based on the ray method. Migration of primary reflection

Seismic migration commonly yields an incomplete reconstruction of the Earth model due to restricted survey aperture, band-limited frequency content and propagation effects. This affects both illumination and resolution of the structures of interest. Through the application of spatial convolution operators commonly referred to as point-spread functions, simulated prestack depth-migrated images incorporating

The elastic properties of argillaceous sandstones are significantly controlled, however, by the perplexing distribution of dispersed, cemented and matrix (including structural and layered) clay. The corresponding rock physics models are established to investigate the influence of different clay distribution on the elastic properties of sandstone. The rock physics modelling and laboratory experimental

Seismic data are traditionally acquired based on spatial sampling requirements, noise properties and budgetary constraints. However, designing a survey without taking into account the complexity of the subsurface may result in an image without the expected quality. Also, the subsequent preprocessing and processing steps may exploit or misuse the acquired data. The design should therefore incorporate

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 data sets or temporally varying seismic networks. To overcome these challenges, we have developed the concept of an aggregated template to perform automatic picking of the P- and S-wave phases. An aggregated template is defined

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

Obtaining accurate velocity models plays a crucial role in many routine seismic imaging algorithms. Seismic velocity models are normally made through seismic velocity analysis workflows. The routine workflows are not capable of dealing with polarity variations across moveout curves. We address this limitation by proposing a straight-forward and robust semblance-based workflow, which is a modified version

Significant advances have been made towards fault detection using deep learning. However, the fault labelling 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 a deep learning model with labelled synthetic seismic data to get good fault detection results. However

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

Seismic waves passing through partially saturated porous rocks produce pressure gradients in the fluid phase, and, hence, the resulting fluid flow is accompanied by 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 have

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

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 labelled data, which are sometimes difficult to obtain. Here, we introduce the deep autoencoder to learn the hidden features and conduct

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

In this paper, we study seismic responses to an earthquake source in horizontally stratified transversely isotropic porous media with a vertical axis of symmetry that is, transversely isotropic 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

A Matlab-based optimization algorithm is introduced for inverting fault structures from observed gravity anomalies. A convenient graphical user interface 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

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

In Wang, Lu and Zhang (2021), the following errors were found on pages 351, 354 and 355. On page 351, Equation (4) currently read: u q P = p x sin v + p z cos v , u q S V = − p x cos v + p z sin ν , (4) This should be: u q P = u x sin ν + u z cos ν , u q S V = − u x cos ν + u z sin ν , (4) On page 354, a coefficient is missing from the root symbol of Equation (7) and currently read: v q P ( θ ) = V

Downhole near-bit vibration sensors are used to record the pilot signal for seismic while drilling and identify drilling dysfunctions for drilling optimization. The typical downhole sensor is a memory-based device with an inexpensive internal clock of limited accuracy that is not synchronized to surface data. Integrating downhole vibrations with other time-based data such as surface drilling parameters

Different geophysical methods use different model parameterizations and inversion algorithms. Thus, combining these different inversion systems and yet adding the nonlinear cross-gradient constraint in a joint inversion framework might be a big challenge, for instance, as explained further by Moorkamp et al. in 2011, there is a complex interaction between the data misfit terms, regularization and cross-gradient

We describe a new algorithm for the inversion of one-dimensional shear-wave velocity profiles from dispersion curves of the fundamental mode of Rayleigh surface waves. The novelties of our approach are that the layer velocities and thicknesses are set as unknowns, and an artificial neural network is proposed to solve the inverse problem. We suggest that training data should be calculated for a set

Seismic images of Earth's subsurface are essential for oil and gas exploration. Gaussian beam migration is popular for seismic imaging owing to its flexibility and efficiency of implementation. However, the practical use of classic Gaussian beam migration is limited for complicated structures such as subsalt because of poor seismic illumination in those areas. We propose an illumination-compensated

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

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 three‐dimensional seismic images and innovatively introduces the definition

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 with using P‐waves alone. Additionally, S‐waves

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 with 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

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

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

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

In Dias et al. (2021), the following errors were published on pages 672, 673, 674, 675 and 676. The labels for the vertical range of Figures A1 (a‐i), A2 (b, e, c, f‐i), A3 (b, e, c, f‐i), A4 (b, c, e, f, h, i) and A5 (b, c, e, f, h, i) were incorrectly changed to “Vp,Vs (m/s)”. The titles of the cross‐plots in Figure A5 (c, f, i) were wrongly indicated as “Elastic Trends Evaluation ‐ Well A”. Figure

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

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

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) require a lot of manual adjustments

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

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

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

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