The industry has widely accepted that AEM data are more frequently affected by induced polarisation (IP) effects than previously acknowledged. However, we still lack a clear understanding of how much, where, and when IP is present. Full modelling of airborne IP (AIP) is time and computationally intensive. As an alternative, we derive a novel tool, the “AIP scanner”, based on a combination of extensive

Time migration is an important tool to provide a subsurface image because it is faster and less sensitive to velocity errors than depth migration. However, a reliable and focused time migration image is achievable only with well-determined time-migration velocities. As an alternative of prestack time migration, equivalent offset migration (EOM) provides intermediate common scatterpoint (CSP) gathers

L0-norm constrained sparse seismic inversion is an effective way to invert reflectivity series of underground rocks. A blocky impedance model with sharp formation boundaries can be estimated from sparse reflectivity series. At present, the most two common used methods to solve L0-norm constrained sparse seismic inversion problem are iterative hard thresholding (IHT) and matching pursuit (MP). IHT has

ABSTRACT In this paper, we introduce a fast iterative adaptive approach for the reconstruction of 3D seismic data with randomly missing traces. Our method starts by transforming 3D seismic volume to 2D harmonic signal for each frequency slice, and then the power spectrum of the frequency slice is iteratively estimated by a weighted least square fitting criterion. The missing data can be recovered with

The dynamic and static Young’s moduli of a number of reservoir sandstones were measured using ultrasonic P- and S-waves velocities in a standard uniaxial set-up. We developed and modified an experimental method to simultaneously measure the stress–strain and stress–velocity (P- and S-waves) while the samples are subjected to stress. The static and dynamic Young’s modulus and Poisson’s ratio were calculated

Ground-penetrating radar (GPR) mapping provides a three-dimensional analysis of archaeological features within the context of landscape studies. The method’s ability to measure the intensity of radar reflections from deep in the ground can produce images and maps of buried features not visible on the surface. A study was conducted in some areas near the Domus Romana in Rabat (Malta) in order to investigate

Local shear wave (S-wave) velocity structure and sedimentary cover thickness are essential parameters that control local amplification of ground motion and associated seismic hazard during earthquakes. Recently, analysis of environmental background noise from individual stations has been used to estimate horizontal-to-vertical spectral ratio (H/V) curves. In the present study, we inverted H/V curves

ABSTRACT To improve the computational efficiency of reverse-time migration (RTM) for vertically transverse isotropic (VTI) media, various acoustic approximations of the elastic wave equations have been presented. Among these, the pseudo-acoustic wave equation, which combines differential and scalar operators, has the advantage that it does not produce shear wave artefacts. In this study, we investigate

Geomagnetic measurements detect the superposition of both regional and residual anomalies. Regional anomalies are caused by deep geological structures, while the residual ones are due to shallow sources. The presence of regional anomalies complicates the interpretation of magnetic data; to this end, a variety of techniques have been proposed for regional-residual anomaly separation. Most of them are

Frequency-dependent anisotropy can be used for detection and evaluation of fractured reservoirs. In this study, three numerical models of fractured reservoirs are designed to study the frequency dependence of amplitude variation with azimuth (AVAZ). Here, two factors, which can make the AVAZ responses frequency dependent, are taken into consideration, the fluid flow and the tuning effect. Model I is

Pre-stack Q migration can eliminate the absorption effect and accurately image underground structures, which is conducive to subsequent reservoir interpretation and hydrocarbon prediction. However, the instability of Q migration amplifies high-frequency noise, which seriously reduces the imaging quality. To solve the instability problem, this paper studies the stability conditions for Q migration in

A novel method for Q (quality factor Q) estimation is proposed based on crosscorrelation function and S-transform (CRST). We use the S-transform to analyse the time–frequency spectra of the crosscorrelation coefficients and extract the amplitude spectra corresponding to the maximum energy time in time–frequency spectra. The Q can be estimated using the spectra ratio based on the linear relationship

Staggered-grid finite-difference (SFD) method has higher accuracy and stability than conventional method, so it is widely used in reverse time migration and full waveform inversion. However, due to the high dominant frequency and large grid interval, numerical dispersion is an inevitable problem. To suppress numerical dispersion, we first propose a weighted convolution combination window function for

Cracks and pores coexist in carbonate reservoirs, and this complex pore structure has a significant impact on acoustic and resistivity logging. Making full use of acoustic and electrical well logging data can help to identify carbonate gas reservoirs. First, this paper studies the controlling effects of different lithologies on the acoustic velocity according to the elastic theory of porous and fractured

An unmanned airship was used to overcome the limitations of conventional aeromagnetic exploration systems. The airship was fabricated from non-magnetic fibre-reinforced plastic and urethane cloth, and filled with helium. The maximum payload is 10 kg and the flight time (with all equipment installed) is approximately 1 h. The airship is simple to move and store prior to gas injection, and easy to handle

Rock physics aims to link geological and reservoir properties to the elastic and seismic parameters. By analysing well logs and seismic data in a rock physics framework, reservoir conditions and key reservoir properties such as lithology and fluid saturations could be understood and/or predicted more precisely. In this study, we have conducted a detailed rock physics study on a heterogeneous sandstone

Desert seismic data pose a particular problem due to its low signal-to-noise ratio and severe spectral overlapping. Most of the existing denoising methods have negative suppression effect on the desert mixed seismic noise, which mainly includes random noise and surface waves. The convolutional neural network (CNN) is a classical supervised deep-learning method that has proven to be an effective tool

The finite-difference (FD) scheme is extensively applied in seismic modelling, imaging and inversion due to its advantages of large-scale parallel computing and programming. However, numerical dispersion caused by using a difference operator in substitution for the differential operator is non-negligible, which reduces the accuracy of the modelling and can lead to some misinterpretations. In addition

Euler deconvolution is a widely used semiautomatic method for potential field data, but it produces sprays of solutions which complicate interpretation. It is demonstrated here that the accuracy of the solution locations can be improved if the method is applied iteratively. Euler deconvolution uses a window of datapoints to solve for the horizontal and vertical distances from the centre of the window

The recovery of 3D volume of density from gravity field data is a key feature of geophysical and geological interpretations. Gravity field data inversion involves solving an underdetermined problem; therefore, large-scale data inversion is costly in time and memory consumption. Calculation efficiency is a primary concern for gravity field data inversion; therefore, multiple methods are considered and

Seismic inversion methods are routinely used to estimate attributes such as P-impedance, S-impedance, density, P-wave and S-wave velocity, and elastic impedances from seismic and well log data. These attributes help to understand subsurface lithology and fluid content. There are several types of seismic inversion methods available in which model-based inversion has got more attention. In the present

2D electrical resistivity tomography (ERT) coupled with electrical resistivity profiling, induced polarisation, and self-potential (ER-IP-SP) measurements and pumping-test data has been used to acquire subsurface electrical properties for the assessment of groundwater reserves in weathered terrains of Huidong County, China. In this investigation, ERT was performed using a pole-dipole array with 305

The use of non-invasive investigation methods is becoming frequent as a support for the monitoring of water reservoirs and for the management of dam safety. In this context, geophysical techniques are much less invasive than geotechnical tests and allow to obtain two-dimensional or three-dimensional representations of the mechanical parameters of an engineering structure. A case of application of constrained

In conventional vibroseis data processing, the recorded sweep is correlated with the recorded trace, assuming that the estimated groundforce is equal to the sweep, but it is demonstrated that due to the non-linearity associated with the vibrator system, the true groundforce and the recorded sweep are not the same. Further, while processing, it is assumed that the zero phase Klauder wavelet is convolved

Steeply dipping structures bring huge challenges in high-resolution imaging. The imaging of the steeply dipping structures can be improved by incorporating the prismatic waves, which has some steeply dipping structure information where primaries cannot contain. In this paper, an elastic reverse time migration of prismatic waves (ERTM-P) is proposed to produce high-resolution multi-component images

Using orthogonal-octahedron finite-difference (FD) stencils, even-order accuracy for temporal and spatial derivatives can be reached for 3D acoustic wave equation modelling. However, the required length of FD operator is still long for high accuracy modelling. To tackle this issue, we have developed an optimization method using a combination of Taylor-series expansion plus Remez exchange methods. The

The advantage of the finite element method (FEM) lies in its flexibility in addressing rugged interfaces in complex geological models. However, the efficiency of the FEM is relatively low for large-scale seismic wave modelling. Here, we introduce an order-corrected symplectic FEM (OCSFEM) with structure-preserving properties and parsimonious memory requirements for the elastic wave equation. In this

The West Delta Deep Marine (WDDM) concession is one of the abundant natural gas resources in the world characterised by the presence of several active gas chimneys conduit feeding pockmarks. The detection of shallow gas accumulations has been gaining importance in hazard assessments before and during offshore drilling operations, whereas there is no way to estimate the exact pressure of the gas content

We propose a new interpretation procedure based on Gassmann’s theory, to estimate rock properties from seismic P-wave velocity (Vp ) and S-wave velocity (Vs ) data, mainly for near-surface applications. Rock properties estimated in the procedure are porosity, water saturation, and clay content of rock. Water saturation is first estimated by an analysis of a cross-plot of Vp/Vs and S-wave velocity,

Deconvolution is essential for high-resolution seismic data processing. Conventional deconvolution methods are either based on a stationary convolution model or under the assumption that Q factor and the source wavelet are known. However, in reality, seismic wavelet is usually unknown and time-varying during propagation due to attenuation. Thus, we propose a blind nonstationary deconvolution (BND)

The finite difference method is widely used in seismic wave numerical simulation, reverse time migration and full waveform inversion. However, the numerical dispersion problem seriously affects the results of seismic imaging and inversion. Based on this, we introduced cosine-combined window function (CCWF) used in harmonic analysis of the power system and compared the amplitude response and error properties

Due to high imaging precision and adaptability for steep-dip interfaces, reverse time migration (RTM) has become the preferred choice in seismic imaging. However, low-frequency noise is a common problem in RTM and effects the clarity of the final image. The noise is formed by the cross-correlation of source and receiver wavefields that propagate along the same paths. A wavefield decomposition imaging

We have developed a novel technique for airborne time-domain electromagnetic data levelling using inequality-constrained polynomial fitting. In the approach, channel data of a certain survey area are levelled under the constraint of off-time attenuation rule. Based on the correlations between flight lines, Huang has proposed that level errors could be fitted by the differences between the flight line

Full waveform inversion (FWI) is an efficient tool to build the subsurface velocity models. However conventional FWI suffers from the cycle skipping problem, which causes FWI to fail in converging to the global minimum. A good initial model can mitigate this problem, but it is hard to be provided. Low frequencies in the observed data are helpful to recover the low-wavenumber components of the subsurface

Fresnel zones are helpful for obtaining a high signal-to-noise ratio (S/N)-migrated result. A migrated dip-angle gather provides a simple domain for estimating 2D Fresnel zones for 3D migration. We develop a deep-learning-based technology to automatically estimate Fresnel zones from migrated dip-angle gathers, thus avoiding the cumbersome task of manually checking and modifying the boundaries of the

When implementing reverse-time migration (RTM), reflected waves that are generated during migration may produce false reflectors. One effective method to remove these artefacts is to apply a de-primary RTM algorithm. This de-primary RTM algorithm uses the Hilbert transform to remove RTM artefacts without explicitly separating wavefields. However, multiply reflected down-going waves, such as surface-related

Spectrum induced polarisation (SIP) is a frequency-domain method commonly used in electrical geophysical exploration. However, SIP is very sensitive to the signal-to-noise ratio of the signal, so noise reduction is very important. Independent component analysis can be used to reduce the noise of geophysical exploration data, but it cannot be used when the observed signal has only one dimension. In

The deformation and failure development of the overlying strata in a stope is the key to improving the upper limit of coal mining under the aquifers. Taking a mine in Huainan as an example, a comprehensive evaluation method for multi-physics field (strain (stress) field and geoelectric field) dynamic monitoring in an underground borehole was proposed. Based on the analysis of a numerical simulation

Chirp sub-bottom profilers (SBP) provide centi-to-decimetre resolution, seismic data with applications for various geophysical and geological purposes. To verify the field application of imaging of a buried target with a cost-effective and easy-to-apply pseudo-3D Chirp SBP survey, we explored the buried site of an ancient wooden shipwreck off the west coast of Korea before underwater excavations. The

Random noise attenuation is an important step in seismic signal processing. This paper develops a seismic denoising method which combines the improved complementary ensemble empirical mode decomposition (ICEEMD) and adaptive interval threshold. The seismic data are decomposed into intrinsic mode functions (IMFs) by ICEEMD, which can overcome the problem of uncertain number of modes when adding different

It is a convenient and effective way to infer near-surface S-wave velocity ( V S ) structures by using seismic surface waves. In spite of many successful applications on the geotechnical or engineering scale, surface-wave analysis and inversion methods are still not widely used in oil seismic exploration. Particularly, there are few researches reported on the three-dimensional (3D) V S structure modelling

We investigated reflection dispersion characteristics of a poroelastic layer with patchy saturations in seismic low-frequency range. Frequency-dependent attenuation and dispersion of phase velocity were determined with varying fluid saturation, porosity, permeability and heterogeneity size, using analytical solutions of a generalised 1D White’s model proposed here, obtained by incorporating capillary

Least-square reverse time migration (LSRTM) can obtain high-resolution and high-amplitude preserved imaging results. Compared to the traditional migration methods, LSRTM can be robust and free of low-frequency artefacts. Under the first-order Born approximation, the corresponding scattering wave equation can only describe the wavefield under the approximate of weak perturbation. Nevertheless, in complicated

Advanced seismic detection technology utilising random roadway sources is advantageous method adapting to the development of dynamic intelligent technologies for the detection of hidden and disastrous geological structures. However, roadheaders generate complex signals, that are continuous and random with seismic wavelets that are wider and longer than conventional source wavelets, and these complex

Microseismic monitoring provides important information on the locations and moment tensors of microseismic events, and this information can be used to understand the behaviour of the fractures more completely. Characterisations of fractures are used to investigate flow paths and for noninvasive investigation of shale gas sites, geothermal developments, and radioactive waste storage/disposal sites.

The concept of moments of the electromagnetic response is useful in electromagnetic interpretation. Analytic formulae exist for low-order moments of a few conductivity models, enabling source parameters such as time constant, depth, conductance and conductivity to be estimated from the measured moments of the electromagnetic response. However, most models for which analytic formulae exist have conductivity

The modelling technique contributes to understanding noise nature and properties. Prior work has established a primary random noise model in the homogeneous medium, however, this strict assumption of the medium may be not valid under the actual environment so that will reduce the modelling accuracy. Therefore, in this paper, a random noise model is established in the mixed heterogeneous medium to improve

In seismic exploration, the dominant applications are still based on the acoustic wave assumption because of the simplicity and computational efficiency. Compared to the acoustic wave equation, the elastic wave simulation is more accurate, especially for land data, to characterise the elastic property of the real earth, but it is also far more expensive in terms of the computational cost. The traditional

ABSTRACT The phase tensor of magnetotellurics is analysed in terms of its invariants with regard to axes rotation. These invariants are displayed as conic sections (ellipses), eigenvectors, and as Mohr diagrams. Attention is drawn to a supplementary ellipse which may be constructed to complement the usual phase tensor ellipse. The two ellipses together help convey the full information available from

Many abandoned water-filled mine tunnels at unknown locations in major coal fields in China pose a hazard to the safe production in modern mines. Geophysical methods with rapid and accurate determination of the location and size of the tunnels are needed. The downhole transient electromagnetic method (TEM) applied in a borehole has significant potential for detection. A 3D finite-difference time–domain

To improve the computational accuracy of seismic traveltime for complex structures in inhomogeneous media, a mesh generation method that is adaptive to a rugged seafloor or interface is presented. A hybrid mesh discrete velocity model consisting of conventional rectangular mesh and irregular quadrilateral mesh is also proposed. The local traveltime equations for the hybrid mesh are derived from the

(2020). Reviewers consulted for Exploration Geophysics during 2019. Exploration Geophysics. Ahead of Print.

Bulk modulus which relates seismic attributes to rock and fluid properties is considered as an important parameter for seismic reservoir characterisation workflows, and can provide useful information for such studies. However, its measurement and modelling approaches are yet to be sufficiently addressed and discussed especially for carbonate rocks. In this research, in order to provide more information

We evaluated imaging alteration associated with porphyry copper style mineralisation using aeromagnetic data in the Highland Valley Copper (HVC) district as part of the Natural Sciences and Engineering Research Council of Canada (NSERC) and Canada Mining Innovation Council (CMIC) Footprints project. The first step of the investigation involved construction of a 3D geological model based on surface

Because a vertical seismic profile (VSP) survey includes the installation of geophones into a borehole, the results of data processing are influenced by the deviation error of the borehole trajectory. In particular, when full waveform inversion (FWI) is applied to VSP data, receiver location errors distort the results of velocity inversion. Under this circumstance, we attempt to estimate the exact

To improve the efficiency of seismic waveform inversion, we construct a novel high-order (6th-order) frequency-domain nearly analytic discrete method for forward modelling in inversion processes. Compared with some existing numerical schemes, this method is more powerful in suppressing numerical dispersion and enhancing the accuracy of computational results based on coarse discrete grids. We describe

Reservoir characterisation using a crossplot of elastic properties can be used to determine fluid and lithology in a seismic survey area. P-impedance and P-wave/S-wave ratios are commonly used as axis parameter for a 2D crossplot. To achieve this goal, the fluid and lithology must first be identified using well log data. However, when the well log data are too sparse, they cannot encompass the full

Full-waveform inversion (FWI) is one of the most promising inversion methods in geophysics due to its theoretical completeness and high resolution. However, the inversion ability of FWI strongly relies on the accuracy of the initial model and the quality of the low-frequency data. For FWI, it is important to accurately recover low and middle wavenumber components (the background model). In order to

In the fields of oil and gas exploration, various quantitative seismic interpretation techniques have been developed to identify lithology and pore fluids based on the rock physics. However, discrimination between oil and brine in pores is often difficult because the seismic response of oil and brine are similar. Poisson impedance (PI) is an effective indicator for distinguishing oil from brine in

A waste plaster landfill site, established as a high-density polyethylene (HDPE) sheet pile surrounded by a slurry wall to isolate possible contaminants within the landfill, was investigated using electric survey techniques. A sheet pile is an effective barrier wall for contaminated leachate containment, unless there are damaged zones within the pile. However, the perfect insulating properties of the