Journal of Geophysics and Engineering - Latest Papers

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Latest articles for Journal of Geophysics and Engineering
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A method to construct high-precision complex pore digital rock

Tue, 10/30/2018 - 8:00pm
X-ray CT scanning is one of the main methods to study the pore structure of the rocks. However, low resolution is currently one of the major challenges of this method, which does not allow for the identification of microscopic pores. Even though adopting images of higher resolutions could reflect the microscopic pores of the rocks, due to the small size of the scanned rock sample in the x-ray CT scanning method, the rock parameters cannot be effectively obtained, especially for the rocks with strong heterogeneity. This would cause the loss of important pore information, such as fractures’ information. Focusing on this problem, the current research tries to propose a method for constructing high-precision digital rocks of complexly porous rocks. This method is based on the simultaneous application of x-ray CT scanning images, nuclear magnetic resonance measurements, as well as mercury injection experimental data and fractal discrete fracture network. These methods effectively com...

Cross-rhombus stencil-based finite-difference methods for 2D acoustic modeling and reverse-time migration on rectangular grids

Wed, 10/24/2018 - 7:00pm
The recently developed cross-rhombus stencil-based time–space domain finite-difference (FD) method for modeling two-dimensional acoustic equations, controls the temporal and spatial dispersions synchronously and outperforms cross-stencil-based FD (CS-FD). However, it is only applicable to modeling on equally spaced grids and extensive application is hindered. In this work, we extend it further and develop novel cross-rhombus stencil-based FD (CRS-FD) for modeling on arbitrarily rectangular grids. Two kinds of rhombus stencils involving grid points both on and off the axis are developed first to achieve fourth order and sixth order FD accuracies, respectively, for solving the second order temporal derivative on rectangular grids. The plane wave theory is then used to derive the time–space-domain dispersion relations, when the temporal and spatial derivatives are solved by the new rhombus-stencil-based temporal high order FD and the cross-stencil-based spatial high order FD, respe...

Application of the power mean to modeling the elastic properties of reservoir rocks

Wed, 10/24/2018 - 7:00pm
The relationship between seismic velocity and porosity is one of the most important research topics in exploration geophysics. A strong correlation, if it exists, can be very useful for quantitative seismic interpretation of direct hydrocarbon indicators. The Voigt and Reuss bounds are often plotted alongside the data for quality control and interpretation. The relative position of the data within the bounds may supply important information regarding the pore shape, stress condition, lithology, and diagenesis of porous rocks. It is found that the Voigt bound and Reuss bound are actually special cases of the weighted power mean, with the power parameters being 1 and −1, respectively. The geometric mean is a special case of the power mean with the power parameter being zero. The power mean is a monotonic function of the power parameter. For the construction of a rock physics template, the region between the Voigt and Reuss bounds can be evenly divided by varying the power paramete...

Permeability enhancement performance and its control factors by auger mining of extremely thin coal seams

Mon, 10/15/2018 - 7:00pm
In order to improve both the pressure relief in deep coal mining and the permeability of coal seams for gas drainage, the auger mining (AM) method was proposed for mining extremely thin coal seams underneath a major coal seam to enhance its permeability and improve its pressure relief for subsequent major mining. The method was applied to Chiyu Coal Mine in China as a case study. Based on the geological conditions of the mine, the influences of AM parameters such as AM width, intermediate coal pillar width and distance between adjacent temporary wide pillars on the pressure distributions and permeability enhancement were studied in detail and the optimal set of parameters for the mining operation were obtained. Based on our simulations, it was found that using the proposed method with the optimal parameters derived, the permeability of the upper protected coal layer will increase by more than 671 times the initial permeability. This demonstrated that the proposed new AM method i...

High-resolution shallow reflection seismic integrated with other geophysical methods for hydrogeological prospecting in the Nylsvley Nature Reserve, South Africa

Mon, 10/15/2018 - 7:00pm
Two perpendicular high-resolution shallow seismic and resistivity profiles were acquired to assist in imaging the near-subsurface sedimentary architecture for hydrogeological prospecting in the Nylsvley Nature Reserve along the Nyl River floodplain in South Africa. We deployed 48 channels of 14 Hz geophones with 1–2 m dense source-receiver spacing providing fold coverage of 24 (line 2) and 48 (line 1). The resistivity profiles were acquired with a Schlumberger electrode configuration with 2–3 m electrode spacing and a total of 40 steel electrodes. The raw seismic shot records were characterized by low-frequency, high-amplitude source-generated noise (surface and guided waves). Reflections from bedrock were not obvious. To enhance the reflected seismic signal, we employed an extensive seismic processing workflow which enhanced the seismic reflectivity on the stacked sections. The seismic reflection interpretation was constrained and integrated with seismic refraction and resistiv...

Discrete element simulation of the control technology of large section roadway along a fault to drivage under strong mining

Mon, 10/15/2018 - 7:00pm
The fault fracture zone has is characterized by low strength, easy deformation and easy activation under the influence of high-strength mining, resulting in instability of the roadway coal rock mass in the affected area and thus severe deformation of the surrounding rock. Aiming to prevent serious deformation of a large section roadway along a fault in response to drivage, combined with specific geological conditions and supporting engineering practice of the panel of a coal mine, UDEC polygonal methods are used to compare and analyze the fracture development, stress distribution and deformation of roadway surrounding rocks and the bearing force of the supporting body of the original support scheme and the new support scheme. In the numerical simulation scheme, the study area is divided into polygonal blocks and the mechanical parameters of the blocks and contacts in the Voronoi program are determined by fitting the rock mass properties obtained through laboratory tests. A time-...