Journal of Geophysics and Engineering - Latest Papers

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Latest articles for Journal of Geophysics and Engineering
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Microtomographic analysis of controlling parameters on permeability and elastic velocities of black shales

Thu, 08/02/2018 - 7:00pm
Shales are sedimentary rocks characterized by their very fine grain size, and are basically composed of clays and silts. Important features of shales are their fissility, presenting thin layers almost always parallel to their bedding, low permeability and elastic velocities which can vary significantly, but whose controlling factors are not yet well understood. X-ray microtomography (microCT) is a widely-used technique to reconstruct the internal pore space of rocks and other materials. In this work parameters controlling permeability and elastic velocities of black shales are investigated through x-ray microCT digital image analysis. Results show that black shale permeability is controlled mainly by pore size distribution and pore connectivity, while elastic velocities of such rock type are controlled by porosity, pore size and the quality of grain–grain contacts. Mineral composition of the analyzed rock samples does not affect this analysis since all the samples have similar m...

Numerical simulations of rock blasting damage based on laboratory-scale experiments

Thu, 08/02/2018 - 7:00pm
In order to study the damage induced by rock blasting, a numerical simulation method based on the Johnson–Holmquist II (JH-2) damage model combined with the arbitrary Lagrangian–Eulerian (ALE) method is proposed. The process of dynamic breakage and damage evolution of Barre granite is reproduced using explicit hydrocode, ANSYS/LS-DYNA, based on the prototype experiments in the laboratory. The results show that both the crack patterns and measured pressures are in agreement with the results from the lab-scale experiments. The attenuation curves of the pressure and particle peak velocity (PPV) along the radial direction are respectively determined, and the corresponding theoretical formulas are summarized together with the most suitable attenuation exponent α . In addition, comparisons of blasting tests separately carried out using the discrete element method-smoothed particle hydrodynamics hybrid method and the ALE/JH-2 method demonstrate similar crack patterns formed both ...

Formation evaluation of a clastic gas reservoir: presentation of a solution to a fundamentally difficult problem

Thu, 08/02/2018 - 7:00pm
Formation evaluation of clastic reservoirs has always had some difficulties. This issue for a clastic gas reservoir from North-East Iran has already made some problems for petrophysicists. Therefore, this paper presents a basic and consequential strategy for (1) solving the problem regarding the petrophysical evaluation, (2) evaluating the petrophysical parameters as precisely as possible, and (3) presenting a general framework for formation evaluation of clastic reservoirs with complex mineralogy. The applied strategy had three main steps. At the first step, using some conventional methods like petrographical analysis and some petrophysical cross plots, all the minerals in the rock structure were identified as precisely as possible. At the second step, having sufficient logs for a key well, all the identified minerals were modeled to distinguish the main minerals. At the final step, all the main minerals were then used for modeling of the other wells. The evaluation of the form...

Crustal structure beneath the Jiaodong Peninsula, North China, revealed with a 3D inversion model of magnetotelluric data

Thu, 08/02/2018 - 7:00pm
The Jiaodong Peninsula in North China is an important Chinese gold mining region, and deposits are mainly controlled by the northeast trending Sanshandao, Jiaojia, and Zhaoyuan–Pingdu faults. Most previous study results proposed the relationships of the known deposits, controlling faults and regional tectonics. One important tectonic belt, the Sulu Orogen, is thought to be related with mineralization and controlling faults. But debates remain concerning the orogeny boundary and tectonic process. We arranged 32 magnetotelluric stations in one line across the central and southern Jiaodong area to analyze the deep electrical structure of this orogeny. After the data collection (using Phoenix instruments) and pre-processing (Phoenix software), we carried out impedance analysis, data selection, static shift correction and three-dimensional inversion using our software. The results consequently proposed that the distribution of upwelling hydrous basaltic magma acts as conductor in the...