Kwanza basin, located on the west coast of Africa and the east side of the South Atlantic Ocean, has the potential for deep-water oil and gas exploration. Previous studies have shown that the pre-salt system within the area has high potential for oil and gas storage. However, due to the shielding effect of the evaporating salt rock during the Aptian period, the quality of seismic reflection profiles

Modern visualization can be formulated as inversion problems that aim to obtain structural information about a complex medium through wave excitations. However, without numerically efficient forward calculations, even state-of-the-art inversion procedures are too computationally intensive to implement. We adapt a method previously used to treat transport in electronic waveguides to describe acoustic

This version of doi:10.1088/1742-2140/aabc74 is being retracted. It was the Publisher's intention to replace the original article with a corrected version following the procedure outlined in 10.1093/jge/gxz118. Due to a production error, however, the corrected version was instead published as a new article 10.1093/jge/aabc74. The Publisher apologises for this mistake.

This version of doi:10.1088/1742-2132/13/5/704 is being retracted. It was the Publisher's intention to replace the original article with a corrected version following the procedure outlined in 10.1093/jge/gxz113. Due to a production error, however, the corrected version was instead published as a new article 10.1093/jge/704. The Publisher apologises for this mistake.

This version of doi:10.1088/1742-2140/aa6b28 is being retracted. It was the Publisher's intention to replace the original article with a corrected version following the procedure outlined in 10.1093/jge/gxz114. Due to a production error, however, the corrected version was instead published as a new article 10.1093/jge/aa6b28. The Publisher apologises for this mistake.

This version of doi:10.1088/1742-2140/aa953a is being retracted. It was the Publisher's intention to replace the original article with a corrected version following the procedure outlined in 10.1093/jge/gxz115. Due to a production error, however, the corrected version was instead published as a new article 10.1093/jge/aa953a. The Publisher apologises for this mistake.

This version of doi:10.1088/1742-2140/aaaf57 is being retracted. It was the Publisher's intention to replace the original article with a corrected version following the procedure outlined in 10.1093/jge/gxz117. Due to a production error, however, the corrected version was instead published as a new article 10.1093/jge/aaaf57. The Publisher apologises for this mistake.

This version of doi:10.1088/1742-2140/aaa981 is being retracted. It was the Publisher's intention to replace the original article with a corrected version following the procedure outlined in 10.1093/jge/gxz116. Due to a production error, however, the corrected version was instead published as a new article 10.1093/jge/aaa981. The Publisher apologises for this mistake.

A shot-encoding technique can be used in seismic waveform inversion to significantly reduce the computational cost by reducing the number of seismic simulations in the inversion procedure. Here we developed two alternative shot-encoding schemes to perform simultaneous-sources waveform inversion. The first scheme (I) encodes shot gathers with random-phase rotations applied to seismic traces. The second

The reverse time migration of an elastic wave is an advanced method for an imaging velocity model, and the reverse time migration of an elastic inhomogeneous TTI medium has become a research hotspot. The amount of calculation and storage is an important factor restricting its development. To solve the storage problem, we improve the wave field separation algorithm using adaptive sampling in the process

Foothill belts ‘dual-complexity’ of the surface and underground structures hinders an accurate seismic imaging of complex geological structures. In this paper, the propagation law of the seismic wavefield in the foothill belt is studied through seismic forward modelling and its influences on the seismic data acquisition and imaging. A foothill belt with typical ‘dual-complexity’ characteristics is

In vertical seismic profiling (VSP) exploration, it is difficult to produce an accurate image for large-offset reflections only using reflection waves and the image resolution is low in traditional VSP-CDP stacking as is the number of folds of reflection points. To mitigate these problems, we present an inverse Gaussian beam stacking method for imaging both primary reflections and free-surface multiples

Geological disposal is a feasible and safe method for dealing with the high-level radioactive waste problem at present. The Beishan area is the key area preselected for high-level radioactive waste geological disposal in Gansu Province, China. The Jijicao rock block is currently the most extensively studied area, where there are several fracture zones in borehole BS15. In 2011, a remarkable conductive

We apply the single-station microtremor horizontal-to-vertical spectral ratio (HVSR) method to image the geometry of Pohang Basin, South Korea, which experienced the greatest earthquake damage in Korea during a series of anthropogenic earthquakes between November 2017 and February 2018. We collected and analysed the ambient seismic noise at 124 temporary stations. The resonance frequencies, which vary

The article ‘Iterative noise attenuation and deconvolution with a sparse constraint’ by Hui Lv, Journal of Geophysics and Engineering (2019), Volume 16, Issue 1, Pages 262–274 (doi:10.1093/jge/gxz005) is being retracted at the request of the author. The journal's editors approved this request on 23 October 2019.

The article ‘Fast principal component analysis for stacking seismic data’ by Juan Wu and Min Bai, Journal of Geophysics and Engineering (2018), Volume 15, Issue 2, Pages 295–306 (doi:10.1088/1742–2140/aa9f80) is being retracted at the request of the authors. The journal's editors approved this request on 23 October 2019.

To get the best result for seismic imaging using primary reflections, data with densely-spaced sources and receivers are ideally preferred. However, dense acquisition can sometimes be hindered by various obstacles, like platforms or complex topography. Such areas with large data gaps may deter exploration or monitoring, as conventional imaging strategies would either provide poor seismic images or

Multiple-layered coal seams widely exist in main coal mining areas of China. When these coal seams are exploited, the pillar mining method is always employed. This leads to many coal pillars left in the upper coal seams as a protective barrier. As a result, these residual pillars will not only cause the loss of coal resources but also could trigger environmental issues and a serious of mine disasters

The high-performance transient electromagnetic method (TEM) excitation source is a new type of source that has been proposed for urban underground space exploration. This source is composed of two trapezoid plates. To ensure that the radiation field was focused in a certain direction, the two trapezoid plate-shaped antennas were arranged into a horn shape. This new source is characterised by high power

Seismic reflectivity inversion problem can be formulated using a basis-pursuit method, aiming to generate a sparse reflectivity series of the subsurface media. In the basis-pursuit method, the reflectivity series is composed by large amounts of even and odd dipoles, thus the size of the seismic response matrix is huge and the matrix operations involved in seismic inversion are very time-consuming.

The dispersion curve describes the relationship between velocities and frequencies. The group velocity is a kind of dispersion, which presents the velocities of the energy with different frequencies. Although many studies have shown methods for estimating group velocity from a surface wave, the estimation of group velocity from body-wave data is still hard. In this paper, we propose a method to calculate

Under the conditions of acoustic approximation and isotropic attenuation, we derive the pseudo- and pure-viscoacoustic wave equations from the complex constitutive equation and the decoupled P-wave dispersion relation, respectively. Based on the equations, we investigate the viscoacoustic wave propagation in vertical transversely isotropic media. The favourable advantage of these formulas is that the

To reveal the influence of prefabricated fractures (PFs) with different parameters on the extension of grouting-induced splitting fractures, a combination of numerical simulation and physical experiments were used to carry out grouting trials on similar materials to coal rock. The RFPA software was used to simulate the whole process of fracture initiation and expansion of coal rock with PFs during

The advance abutment pressure on the coal mining face of a deep stope plays a decisive role in the surrounding rock instability, rock burst and coal-gas outburst. Based on distributed optical fiber sensing technology and theoretical analysis of the stress state, the distribution characteristics of the advance abutment pressure were tested. Taking the 61103 coal mining face of a mine in Inner Mongolia

The capillary spontaneous imbibition length of slick water in confined rectangular cross-sectional nanofractures is investigated in this paper. In the established model, the effective slip length, effective viscosity, wettability and nanofracture size are incorporated into the modified Hagen–Poiseuille equation. The calculated spontaneous imbibition length as a function of time, viscosity, wettability

The irregular free surface topography has a significant impact on simulations of seismic wave propagation. Therefore, an accurate representation of the irregular free surface is required for an accurate wavefield simulation. We propose an immersed boundary method used in fluid dynamics calculation to simulate acoustic waves with finite-difference in media with irregular surfaces. First, we set the

The Fast Sweep Method (FSM) is an approach to solve eikonal equation, and it plays a significant role in Kirchhoff migration and traveltime based velocity modelling. However, FSM solves the eikonal equation with an upwind finite difference scheme, which may suffer from upwind singularity and decrease the numerical accuracy of traveltime calculation. To overcome the upwind singularity problem and obtain

We present an explicit inverse approach using a Hessian matrix for least-squares migration (LSM) with Q compensation. The scheme is developed by incorporating an effective Q-based solution of the viscoacoustic wave equation into a blockwise approximation to the Hessian in LSM, which is implemented after the so-called deabsorption prestack time migration (PSTM). The effective Q model used fully accounts

There are extensive studies on electromagnetic radiation (EMR) effects during coal and rock deformation and fracturing processes, but few systematic studies on the EMR features of gas-bearing coal under impact failure circumstances. In order to investigate whether the EMR is affected by the gas (CO2,CH4,N2) sorption, coal type and impact energy, we performed a series of impact loading tests on both

According to the failure law of the 1070 main roadway, this paper proposes a reasonable position for large section roadways under small coal mines and a design for seven roadway positions. RS2 software was used to establish a numerical model to select a reasonable position for the roadway. The influences of roadway positions on roof separation amount, roof subsidence, lateral displacement on the ribs

Abundant engineering practice shows that coal and rock dynamic disasters often occur in fault zones; hence, the detection of faults in coal mines is important. As an essential branch of seismic tomographic application, research shows that ultrasonic P-wave velocity can detect mine faults and provide technical support for dynamic disaster prewarning systems. Traditional P-wave testing mostly takes rock

A varying Q factor with depth induces modifications of seismic wave features due to anelastic propagation but also reflections at the discontinuities. Standard signal analysis methods often neglect the reflection contribution when assessing Q values from seismic data. We have developed an analytical quantification of the cumulative effects of both the propagation and reflection contributions by considering

To determine the failure characteristics and evolution regularity of the floor strata during fully mechanised top-coal cave mining in typical deep and extra-thick seams in western China, the 61303 working face of an Ordos mine was selected as the engineering research object. A comprehensive monitoring method combining a BOTDR (Brillouin Optical Time-Domain Reflection) distributed fiber strain test

Permeability variation in the presence of hydrates plays an important role in hydrate dissociation and may lead to extraction issues. Therefore, a wide range of pore-scale studies considering the hydrate growth habit have been conducted by various researchers. Here, we use microscopic training images of hydrate-bearing sediment to replicate the micromorphology of hydrates and coexisting hydrate growth

Seismic facies analysis is of great significance for the detection of residual oil in a sand-shale interbed reservoir. In this study, we propose to predict spatial distribution of sand thickness over a reservoir, based on seismic facies analysis. The target reservoir is a thin sand-shale interbed layer, and the layer thickness varies between 2 and 10 m. The thickness of sand strata within the reservoir

Under the assumption of invariant ray path in a weakly dissipative (high quality factor Q) subsurface medium, a tomographic inversion approach composed of two cascading applications of first arrival traveltime and Q tomography is proposed for compensating amplitude loss caused by near-surface anomalies, such as unconsolidated soils or the overburden gas cloud. To improve the computational efficiency

Examinations of acoustic logging tools in the workshop are significant for checking the performance of every unit before field downhole measurements. It is more convenient to test the tools in a horizontally placed open trough rather than in a vertical closed pipe. To ensure the tools can excite and receive the signals from the trough well (i.e. the pipe waves), we should figure out the wave propagation

Joint migration inversion is a recently proposed technology, accommodating velocity model building and seismic migration in one integrated process. Different from the widely accepted full waveform inversion technology, it uses imaging parameters, i.e. velocities and reflectivities of the subsurface, to parameterize its solution space. The unique feature of this new technology is its explicit capability

Trace elements in sedimentary rocks are highly sensitive to palaeoaquatic environmental changes in a sedimentary environment, making them an effective means for studying the paleoclimate and paleoenvironment during the deposition of sediments. The trace elements and major elements of mudstone cores sampled in the Binnan Oilfield in China were tested by inductively coupled plasma mass spectrometry (ICP–MS)

In sonic logging while drilling (LWD), it is difficult to extract reflection signals for the goal of geo-steering as the wave fields are so complicated. It is important to analyse the reflection and scattering effects based on the synthetic acoustic signals of the real LWD models, while considering the medium discontinuity at the end of the borehole. We numerically investigate the acoustic LWD responses

The accurate measurement of condensed water content in gas reservoirs is critical for the effective development of gas reservoirs. In this study, a more accurate and faster method for measuring the condensed water content in gas reservoirs was developed by using a high-temperature and high-pressure PVT device combined with the law of conservation of matter. A condensed water content test was subsequently

Proppant placement concentration, particle size and creep time are important factors that affect the embedment of proppant into coal. Based on multistage creep, an orthogonal test is conducted, and an optimal proppant scheme for different closure stresses obtained. The results show that with increased proppant placement concentration, the number of coal fractures increases and the elastic modulus of

Briquette hammer fracturing experiments were conducted with different impact energies and molding pressures to investigate the characteristics of the electromagnetic signals. The response pattern of the electromagnetic radiation energy as a function of the impact energy and the coal firmness during impact fracturing of a coal mass were analyzed. The characteristics of the electromagnetic radiation

Seismic low-frequency amplitude shadows have been widely used as a hydrocarbon indicator. This study investigates the effect of reservoir properties and seismic wave mode conversion on the characteristics of the low-frequency amplitude shadows in gas-bearing reservoirs. The target gas reservoirs are typically related to the lithology of tight sandstone with strong heterogeneity. Pore-fluid distribution

We present in this work an ultrasonic imaging technique based on wavefield cross-correlation that has potential for high-resolution inspecting of plates and plate-like structures. A curved transmit/receive array setup is used for acquiring wide-aperture waveform data beneficial for applying the presented imaging condition. An additional dispersion analysis using waveform data received by a linear array

In acoustic logging, most published studies of extracting array data characteristics are difficult to avoid the interference from the false modes. The false modes contribute little to the acoustic waveforms but makes the true modes hard to identify. We introduce a threshold of the energy spectrum into the pole-calculation method to remove the false modes, thereby eliminating their interferences to

Estimation of broad features or the low-frequency part of acoustic impedance from conventional reflection data is an essential yet challenging step for quantitative interpretation of seismic data due to its band-limited nature. A missing low-frequency part leads to non-uniqueness in the solution as well as placing restrictions in recovering the absolute impedance values. The current industry practice

Traditional transient electromagnetic methods use single sources for excitation and extract the characteristics of underground media by improving interpretation technology. This study focused the improvements of transient electromagnetic interpretation using complex source technology. A time-domain vector finite element method (TFEM) was applied on three-dimensional forward modelling of semi-airborne

This paper presents a case study on the prediction of hydrocarbon reservoirs within coal-bearing formations of the Upper Palaeozoic. The target reservoirs are low-permeability low-pressure tight-sandstone reservoirs in the Daniudi Gas Field, Ordos Basin, China. The prime difficulty in reservoir prediction is caused by the interbedding coal seams within the formations, which generate low-frequency strong-amplitude

Seismic pre-stack AVA inversion using the Zoeppritz equation and its approximations as a forward engine yields P- and S-wave velocities and density. Due to the presence of seismic noise and other factors, the solution to seismic inversion is generally ill-posed and it is necessary to add constraints to regularize the algorithm. Moreover, since pre-stack inversion is a nonlinear problem, linearized

Water inrush during tunnel excavation severally threatens the mining safety as blind water-bearing structures may develop in front of the working face. The transient electromagnetic method (TEM) has been widely applied in the advanced detection of tunnel water-bearing structures. However, the metal interference of both supports and tools in the tunnel has become a bottleneck that reduces the forecast

This is a retraction-and-replacement to: Journal of Geophysics and Engineering (2018), Volume 15, Issue 4, Pages 1104–1121, https://doi.org/10.1088/1742-2140/aaa981

This is a retraction-and-replacement to: Journal of Geophysics and Engineering (2016), Volume 13, Issue 5, Pages 704–720, https://doi.org/10.1088/1742-2132/13/5/704

This is a retraction-and-replacement to: Journal of Geophysics and Engineering (2017), Volume 14, Issue 4, Pages 888–899, https://doi.org/10.1088/1742-2140/aa6b28

This is a retraction-and-replacement to: Journal of Geophysics and Engineering (2018), Volume 15, Issue 4, Pages 1688–1705. https://doi.org/10.1088/1742-2140/aabc74

This is a retraction-and-replacement to: Journal of Geophysics and Engineering (2018), Volume 15, Issue 4, Pages 1327–1340, https://doi.org/10.1088/1742-2140/aaaf57

This is a retraction-and-replacement to: Journal of Geophysics and Engineering (2018), Volume 15, Issue 3, Pages 681–695, https://doi.org/10.1088/1742-2140/aa953a