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

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

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

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

Seismic data interpolation is a meaningful research topic in the field of seismic data processing. In this paper, we propose deep internal learning for interpolating regularly sampled aliased seismic data, to improve the upsampling accuracy of regularly sampled aliased seismic data. The proposed algorithm, contrary to previous deep external learning-based seismic interpolation relying on prior training

Seismic exploration employing wide-azimuth, broadband, high-density data (i.e. double-width single-height; “double-width” means wide-azimuth and broadband; “single-height” means high-density data, generally referring to small-bin-size data (less than 10 × 10 m); and double-width single-height is an abbreviation) enables more complete wave field information to be recorded, reduces aliasing, and produces

Due to the severe interference of background noise, the signal-to-noise ratio of desert seismic data is extremely low. In addition, due to low-frequency characteristics of sand in the Tarim desert region, the background noise in desert seismic data is mainly distributed in low-frequency band, so that the frequency spectrum aliasing of effective signals and background noise is more serious than the

The staggered grid finite difference (SGFD) method has been widely utilised in seismic forward modelling. The accuracy of forward modelling results has a great influence on the results of subsequent seismic imaging and seismic inversion. Numerical dispersion is one of the inherent problems in the SGFD method. To suppress dispersion, we here introduce the truncated window function method, which can

Fine-scale thermohaline structure within ocean column can be mapped seismically in the Kuroshio Current, off the Muroto Peninsula of Shikoku Island, Japan. In this paper, we present the application of automatic sound speed picking analysis to the multi-channel seismic reflection data acquired in a different period to estimate time-lapse sound speed distribution across the Kuroshio Current. This method

Potential field data is commonly enhanced in various ways to extract detail about source locations and/or depths. Methods which use higher order derivatives are naturally more sensitive to noise than those which use lower order derivatives. Pseudo-derivatives combine the amplitude of one order of derivative with the phase of another, which can have various advantages. It is demonstrated here how pseudo-derivatives

Time lapse seismic is a vital component of the monitoring and verification of virtually any geosequestration project. Stage 2C of the CO2CRC Otway project is designed to test the limits of land 3D time-lapse (4D) seismic in the monitoring of small-scale CO2 injection. The 4D seismic monitoring program of Stage 2C of the Otway Project includes a baseline survey (BL); three monitor surveys (M1–M3) obtained

This paper presents a theory for the anomalous magnetic gradient tensor due to a uniformly magnetised general triaxial ellipsoid. Expressions for the magnetic field vector and its gradient tensor are derived from expressions for the gravitational field or the gravity gradient tensor via an application of Poisson’s theorem. This theory provides increased capability in forward modelling, inversion and

Airborne geophysics provides one of the most relevant data for uranium exploration. However, the application of radiometric surveys is decreasing considerably as the depth of exploration is increasing. Notwithstanding, there is still a large potential for radiometric data, especially using recent data processing techniques such as machine learning methods. In this work, we propose a new method to detect

Elastic wave modelling in the Laplace domain is the foundation of Laplace-domain elastic wave full waveform inversion. In order to use Laplace-domain numerical modelling schemes efficiently, appropriate grid intervals must be chosen correctly. The determination of grid intervals is based on numerical dispersion analysis of Laplace-domain elastic wave equation. A new method of numerical dispersion analysis

Development of an accurate reservoir model and prediction of reservoir behaviour associated with geothermal exploitation using that model are fundamentally important for sustainable geothermal utilisation. Gravity observation for a few tens of days after a field-wide shut-in of geothermal wells potentially provides valuable constraints to improve reservoir models. We investigated the applicability

Body waves may affect phase velocity obtained from microtremor array surveys in some rare cases. Fitting theoretical phase velocities based on a surface-wave theory to observed phase velocities affected by body waves would therefore result in distorted images of subsurface S-wave velocity structure. In this study, we present a method for the theoretical calculation of phase velocities in which the

Exploration of oil and gas resources in complex areas has always been a key issue in seismic exploration. The Tarim Basin, covered by a large area of desert, contains abundant oil-gas reservoir resources. However, due to the complex exploration environment, the signal-to-noise ratio of seismic data collected in desert area is low and the resolution is poor. The frequency band overlaps between effective

The Palaeo- to Meso-Proterozoic (1.0–2.4 Ga) North Singhbhum Mobile Belt (NSMB) is an assembly of multiphase folded, low- to medium-grade meta-sedimentary and meta-igneous rocks, lying within the north Singhbhum crustal province. The mobile belt is situated between the Archean Singhbhum craton in the south and the Meso/Neo-Proterozoic (0.9–1.7 Ga) Chotanagpur Gneissic Complex in the north. Gold mineralisation

If a magnetic dipole is placed above the surface of the earth, the electromagnetic induction (EMI) effect, encoded in Maxwell's equations, causes eddy currents in the soil which, on their turn, induce response electromagnetic fields. The magnetic field can be measured in geophysical surveys to determine the conductivity profile of the ground in a non-destructive manner. The forward model used in the

In rock physics one of the important purposes of the determination of P- and S-wave velocities is to obtain the elastic constants and anisotropy parameters. This method is standardised in American Society for Testing and Materials (ASTM) by a standard D2845-95. The most challenging yet important part of these experiments is picking the first arrivals correctly and consistently. A sharp, clean first

The wavelet stretch effects in pre-stack migration, which is similar to that of NMO stretch, distort the frequency spectrums and taper the high-frequency components at far offsets. The long-offset migrated results in conventional migration methods are muted, resulting in a loss of effective information about the subsurface investigation. Only short-offset data are used to obtain a high-resolution stacked

We have recovered legacy 2D seismic data from the Kalahari Karoo Basin, Botswana, which show signatures associated with the coalbed-methane-bearing seams of the Mmamabula and Morupule formations. These deeply buried coal seams (∼ 500 m below surface) may represent a new alternative source of energy for the region. Prior to interpreting the seismic data, we improved imaging of the coal seams by attenuating

Random noise suppression is of great importance in seismic processing and interpretation, and time–frequency peak filtering (TFPF) is a classic denoising approach. In TFPF, pseudo Wigner–Ville distribution (PWVD) is used to linearise the given signal for an unbiased estimation of the instantaneous frequency. However, window length is a trade-off parameter for preserving valid signals and attenuating