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

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

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

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