Research on algorithm of borehole resistivity imaging method

Tradicionalna metoda istraživanja istosmjerne struje suočit će se s velikim izazovom kad se otkrije duboki, složeni geološki cilj. U tu svrhuje razvijena je metoda unaprijednog modeliranja i inverznog modeliranja otpora bušotine. U skladu s geološkim značajkama, postavljen je geološki model. Numerička simulacija pokazuje da je metoda otpora bušotine vrlo dubok, složen geo-model. Stoga ovo istraživanje daje novu ideju za istraživanje dubokog, složenog cilja geo-električnog modela.Traditional dc electrical exploration method will face great challenge when detecting deep, complex geologic target. With the purpose, forward modelling and inverse modelling method of borehole resistivity has been developed. According to the characters of geology, the geological model has been set up. The numerical simulation shows that borehole resistivity method is a very deep, complex geo-model. Therefore, this research provides a new idea for exploring deep, complex target of geo-electrical model

Modeling of whole-space transient electromagnetic responses based on FDTD and its application in the mining industry

Hidden, water-abundant areas in coal mines pose a serious threat to mine safety and production. Underground transient electromagnetic method (TEM) is one of the most effective means of detecting water-abundant areas in front of the roadway head. Traditional TEM theories and applications are interpreted mainly on the vertical component. In this study, multicomponent responses of TEM in underground roadways were modeled using the finite-difference time-domain method. Physical simulation was also used for advanced detection of TEM in the roadway. Both the numerical and physical simulation results show that the horizontal component is more sensitive to the location of water-abundant areas. The results of the joint interpretation with both horizontal and vertical components were verified in a practical coal mine application, indicating that it is feasible to use the horizontal component in interpreting TEM data. Thus, the horizontal component could serve as a new approach for coal mine TEM data processing and interpretation.The State Key Research Development Program of China (NO. 2017YFC0804401), in part by the China Postdoctoral Science Foundation (NO.110101/3445), and in part by the National Research Foundation, South Africa (RDYR160404161474).http://ieeexplore.ieee.org/xpl/RecentIssue.jsp?punumber=9424hj2018Electrical, Electronic and Computer Engineerin

Borehole Electromagnetic Method for Exploration of Coal Mining Goaf

Due to severe harms of goaf collapse, the goaf exploration and governance has become an urgent issue for protecting the normal life of local people. According to the coal mine geology, different geo-electrical models have been employed for the purpose of discovering the goafs. However, most existing methods require a large amount of computation consumption. In order to address this issue, a forward numerical simulation using the borehole electromagnetic method has been developed in this work to explore the coal mining goafs. The innovation of this method is that the computation consuming can be saved significantly. Numerical simulation demonstrates high effectiveness of the borehole electromagnetic method in coal mining goaf exploration. Therefore, this research provides a new idea for exploring the coal mine goafs by geophysical method

Maxwell-Equations Based on Mining Transient Electromagnetic Method for Coal Mine-Disaster Water Detection

Water-bearing geological structure is a serious threat to coalmine safety. This research focuses on detecting water-bearing geological structure by transient electromagnetic method. First, we introduce the principle of mining transient electromagnetic method, and then explain the technique of Finite Different Time Domain using in the transient electromagnetic method. Based on Maxwell equations, we derive the difference equations of electromagnetic field and study the responses of water-bearing geological structure using FDTD. Moreover, we establish the relationship between receiving electromagnetic field and geological information. The typical coal geological model of goaf-water is chosen to do the numerical simulation. Besides, we verify the availability of the method by numerical simulation using coal geological model. Finally, we use the method in the coalmine which is located in Linfen city in Shanxi province in China, and the detecting result is verified by drilling

Electrical anisotropic response of water conducted fractured zone in the mining goaf

Based on the Maxwell equation, the occurrences of fractured zones are studied through the galvanic method. The electrical and magnetic fields are first derived in the spatial domain. To simplify the calculations, the computational formulas of the electrical fields in the spatial domain are transformed into the wavenumber domain by Fourier transform. The basic solution of the electromagnetic field can thus be easily solved in the wavenumber domain. According to the boundary conditions, a recursive relationship between the different layers is established. The electromagnetic fields are obtained through the recursive relationships with the bottom-last layer. Finally, the apparent resistivity is calculated using the surface electric field. A typical goaf model is used for the numerical simulation. Based on the modeling results the effectiveness of this method is determined. The modeling results indicate that the galvanic method is very effective for detecting the electrical anisotropic characters.This work was jointly sponsored by Jiangsu Province National Natural Science Foundation (NO. BK20130180), Research Funds for the Central Universities- China University of Mining and Technology (NO. 2014QNA88) and China Postdoctoral Science Foundation (NO. 2015M570491).http://ieeexplore.ieee.org/xpl/RecentIssue.jsp?punumber=6287639hb2016Electrical, Electronic and Computer Engineerin

Diffusion Law of Whole-Space Transient Electromagnetic Field Generated by the Underground Magnetic Source and Its Application

Mine water inrush stays as one of the major disasters in coalmine production and construction. As one of the principal methods for detecting hidden water-rich areas in coal mines, underground transient electromagnetic method (TEM) adopts the small loop of a magnetic source which generates a kind of whole-space transient electromagnetic field. To study the diffusion of whole-space transient electromagnetic field, a 3-D finite-difference time-domain (FDTD) is employed in simulating the diffusion pattern of whole-space transient electromagnetic field created by the magnetic source in any direction and the whole-space transient electromagnetic response of the 3-D low-resistance body. The simulation results indicate that the diffusion of whole-space transient electromagnetic field is different from ground half-space and that it does not conform to the "smoke ring effect'' of half-space transient electromagnetic field, for the radius of the electric field's contour ring in whole space keeps expanding without moving upward or downward. The low-resistance body can significantly affect the diffusion of transient electromagnetic field. When the excitation direction is consistent with the bearing of the low-resistance body, the coupling between the transient electromagnetic field and the low-resistance body is optimal, and the abnormal response is most obvious. The bearing of the low-resistance body can be distinguished by comparing the response information of different excitation directions. Based on the results above, multi-directional sector detection technology is adapted to detect the water-rich areas, which can not only detect the target ahead of the roadway but also distinguish the bearing of the target. Both numerical simulation and practical application in underground indicate that the mining TEM can accurately reflect the location of water-rich areas

Diffusion Law of Whole-Space Transient Electromagnetic Field Generated by the Underground Magnetic Source and Its Application

Mine water inrush stays as one of the major disasters in coalmine production and construction. As one of the principal methods for detecting hidden water-rich areas in coal mines, underground transient electromagnetic method (TEM) adopts the small loop of a magnetic source which generates a kind of whole-space transient electromagnetic field. To study the diffusion of whole-space transient electromagnetic field, a 3-D finite-difference time-domain (FDTD) is employed in simulating the diffusion pattern of whole-space transient electromagnetic field created by the magnetic source in any direction and the whole-space transient electromagnetic response of the 3-D low-resistance body. The simulation results indicate that the diffusion of whole-space transient electromagnetic field is different from ground half-space and that it does not conform to the "smoke ring effect'' of half-space transient electromagnetic field, for the radius of the electric field's contour ring in whole space keeps expanding without moving upward or downward. The low-resistance body can significantly affect the diffusion of transient electromagnetic field. When the excitation direction is consistent with the bearing of the low-resistance body, the coupling between the transient electromagnetic field and the low-resistance body is optimal, and the abnormal response is most obvious. The bearing of the low-resistance body can be distinguished by comparing the response information of different excitation directions. Based on the results above, multi-directional sector detection technology is adapted to detect the water-rich areas, which can not only detect the target ahead of the roadway but also distinguish the bearing of the target. Both numerical simulation and practical application in underground indicate that the mining TEM can accurately reflect the location of water-rich areas

Channel-width dependent pressure-driven flow characteristics of shale gas in nanopores

Understanding the flow characteristics of shale gas especially in nanopores is extremely important for the exploitation. Here, we perform molecular dynamics (MD) simulations to investigate the hydrodynamics of methane in nanometre-sized slit pores. Using equilibrium molecular dynamics (EMD), the static properties including density distribution and self-diffusion coefficient of the confined methane are firstly analyzed. For a 6 nm slit pore, it is found that methane molecules in the adsorbed layer diffuse more slowly than those in the bulk. Using nonequilibrium molecular dynamics (NEMD), the pressure-driven flow behavior of methane in nanopores is investigated. The results show that velocity profiles manifest an obvious dependence on the pore width and they translate from parabolic flow to plug flow when the width is decreased. In relatively large pores (6 – 10 nm), the parabolic flow can be described by the Navier-Stokes (NS) equation with appropriate boundary conditions because of its slip flow characteristic. Based on this equation, corresponding parameters such as viscosity and slip length are determined. Whereas, in small pores (∼ 2 nm), the velocity profile in the center exhibits a uniform tendency (plug flow) and that near the wall displays a linear increase due to the enhanced mechanism of surface diffusion. Furthermore, the profile is analyzed and fitted by a piecewise function. Under this condition, surface diffusion is found to be the root of this anomalous flow characteristic, which can be negligible in large pores. The essential tendency of our simulation results may be significant for revealing flow mechanisms at nanoscale and estimating the production accurately