Tunneling machines, or excavators, are large and good conductors and affect the reliability of data gathering and interpretation in advanced detection using transient electromagnetic methods. In our experiment, we use...Tunneling machines, or excavators, are large and good conductors and affect the reliability of data gathering and interpretation in advanced detection using transient electromagnetic methods. In our experiment, we used a coincident-loop and central loop type of configuration, where the coil plane l） vertical to and 2） parallel to the working face. A SIROTEM instrument at different locations was used to observe the transient electromagnetic responses of the excavator and to analyze the response amplitudes. The result shows that the tunneling machine affects the advanced detection data and is related to the way the coil is coupled. When the excavator is 6 m from the observatory, the interference of tunneling machine can be ignored.展开更多
Buried water-conducting and water-bearing structures in front of the driving head may easily lead to water bursts in coal mines. Therefore,it is very important for the safety of production to make an accurate and time...Buried water-conducting and water-bearing structures in front of the driving head may easily lead to water bursts in coal mines. Therefore,it is very important for the safety of production to make an accurate and timely forecast about water bursts. Based on the smoke ring effect of transient electromagnetic fields,the principle of transient electro-magnetic method used in detecting buried water-bearing structures in coal mines in advance,is discussed. Small multi-turn loop configurations used in coal mines are proposed and a field procedure of semicircular sector scanning is presented. The application of this method in one coal mine indicates that the technology has many advantages compared with others. The method is inexpensive,highly accurate and efficient. Suggestions are presented for future solutions to some remaining problems.展开更多
This study used the stable and convergent Dufort-Frankel method to differentially discretize the diffusion equation of the ground-well transient electromagnetic secondary field.The absorption boundary condition of com...This study used the stable and convergent Dufort-Frankel method to differentially discretize the diffusion equation of the ground-well transient electromagnetic secondary field.The absorption boundary condition of complex frequency-shifted perfectly matched layer(CFS-PML)was used for truncation so that the low-frequency electromagnetic wave can be better absorbed at the model boundary.A typical three-dimensional(3D)homogeneous half-space model was established and a low-resistivity cube model was analyzed under the half-space condition.The response patterns and drivers of the low-resistivity cube model were discussed under the influence of a low-resistivity overburden.The absorption boundary conditions of CFS-PML significantly affected the low-frequency electromagnetic waves.For a low-resistivity cube around the borehole,its response curve exhibited a single-peak,and the extreme point of the curve corresponded to the center of the low-resistivity body.When the low-resistivity cube was directly below the borehole,the response curve showed three extreme values(two high and one low),with the low corresponding to the center of the low-resistivity body.The total field response of the low-resistivity overburden was stronger than that of the uniform half-space model due to the low-resistivity shielding effect of electromagnetic waves.When the receiving-transmitting distance gradually increased,the effect of the low-resistivity overburden was gradually weakened,and the response of the low-resistivity cube was strengthened.It was affected by the ratio of the overburden resistivity to the resistivity of the low-resistivity body.展开更多
瞬变电磁远探测在探测深度和分辨率方面,填补了常规测井和地震勘探的地质评价尺度空白带。但是,目前建立在各向同性介质基础上的理论模型,与我国大多数地区油气田客观存在的开发环境,即非均质、各向异性地层的事实不符。目的考虑到地下...瞬变电磁远探测在探测深度和分辨率方面,填补了常规测井和地震勘探的地质评价尺度空白带。但是,目前建立在各向同性介质基础上的理论模型,与我国大多数地区油气田客观存在的开发环境,即非均质、各向异性地层的事实不符。目的考虑到地下介质的复杂性和非均质性等特点,针对各向异性地层中的井孔瞬变电磁法研究具有重要意义。方法基于井孔瞬变电磁理论,通过研究三轴感应数据,采用解析计算方式推导各向异性地层井孔瞬变电磁视电阻率、视倾角关系表达式,通过建立水平和倾斜各向异性地层模型对视电阻率和视倾角进行计算与分析。结果结果表明:对于均匀各向同性介质模型,视电阻率可以较好反映地层阻值变化情况,视倾角与模型地层倾角基本吻合;对于垂直对称轴横向各向同性(transversely isotropic media with a vertical symmetry axis,VTI)的各向异性介质模型,视电阻率与视倾角能够较好反映各向异性地层的水平、垂直电阻率和倾角。结论井孔瞬变电磁响应能够快速计算出各向异性地层中视电阻率和视倾角,有助于快速分析观测装置附近电性结构,对各向异性介质井孔瞬变电磁领域的快速发展具有重要意义。展开更多
基金support received from the National Basic Research Program of China (No2007CB209400)the National Natural Science Foundation of China (No50774085)the Young Scientists Fund of the School Science Foundation of CUMT (No2008A046)
文摘Tunneling machines, or excavators, are large and good conductors and affect the reliability of data gathering and interpretation in advanced detection using transient electromagnetic methods. In our experiment, we used a coincident-loop and central loop type of configuration, where the coil plane l） vertical to and 2） parallel to the working face. A SIROTEM instrument at different locations was used to observe the transient electromagnetic responses of the excavator and to analyze the response amplitudes. The result shows that the tunneling machine affects the advanced detection data and is related to the way the coil is coupled. When the excavator is 6 m from the observatory, the interference of tunneling machine can be ignored.
基金Project 40674074 supported by the National Natural Science Foundation of China20050290501 by the Specialized Research Fund for the Doctoral Programof Higher EducationD200409 by the Scientific Research Fund for Youth of China University of Mining & Technology
文摘Buried water-conducting and water-bearing structures in front of the driving head may easily lead to water bursts in coal mines. Therefore,it is very important for the safety of production to make an accurate and timely forecast about water bursts. Based on the smoke ring effect of transient electromagnetic fields,the principle of transient electro-magnetic method used in detecting buried water-bearing structures in coal mines in advance,is discussed. Small multi-turn loop configurations used in coal mines are proposed and a field procedure of semicircular sector scanning is presented. The application of this method in one coal mine indicates that the technology has many advantages compared with others. The method is inexpensive,highly accurate and efficient. Suggestions are presented for future solutions to some remaining problems.
基金This work was supported by China Postdoctoral Science Foundation(No.2022M723391)the Science and Technology Innovation Project of Higher Education in Shanxi Province(No.2019L0754)+1 种基金the Central Guiding Local Science and Technology Development Fund Project(No.YDZJSX2021B021)Shanxi Province Basic Research Plan General Project(No.202203021221294).
文摘This study used the stable and convergent Dufort-Frankel method to differentially discretize the diffusion equation of the ground-well transient electromagnetic secondary field.The absorption boundary condition of complex frequency-shifted perfectly matched layer(CFS-PML)was used for truncation so that the low-frequency electromagnetic wave can be better absorbed at the model boundary.A typical three-dimensional(3D)homogeneous half-space model was established and a low-resistivity cube model was analyzed under the half-space condition.The response patterns and drivers of the low-resistivity cube model were discussed under the influence of a low-resistivity overburden.The absorption boundary conditions of CFS-PML significantly affected the low-frequency electromagnetic waves.For a low-resistivity cube around the borehole,its response curve exhibited a single-peak,and the extreme point of the curve corresponded to the center of the low-resistivity body.When the low-resistivity cube was directly below the borehole,the response curve showed three extreme values(two high and one low),with the low corresponding to the center of the low-resistivity body.The total field response of the low-resistivity overburden was stronger than that of the uniform half-space model due to the low-resistivity shielding effect of electromagnetic waves.When the receiving-transmitting distance gradually increased,the effect of the low-resistivity overburden was gradually weakened,and the response of the low-resistivity cube was strengthened.It was affected by the ratio of the overburden resistivity to the resistivity of the low-resistivity body.
文摘瞬变电磁远探测在探测深度和分辨率方面,填补了常规测井和地震勘探的地质评价尺度空白带。但是,目前建立在各向同性介质基础上的理论模型,与我国大多数地区油气田客观存在的开发环境,即非均质、各向异性地层的事实不符。目的考虑到地下介质的复杂性和非均质性等特点,针对各向异性地层中的井孔瞬变电磁法研究具有重要意义。方法基于井孔瞬变电磁理论,通过研究三轴感应数据,采用解析计算方式推导各向异性地层井孔瞬变电磁视电阻率、视倾角关系表达式,通过建立水平和倾斜各向异性地层模型对视电阻率和视倾角进行计算与分析。结果结果表明:对于均匀各向同性介质模型,视电阻率可以较好反映地层阻值变化情况,视倾角与模型地层倾角基本吻合;对于垂直对称轴横向各向同性(transversely isotropic media with a vertical symmetry axis,VTI)的各向异性介质模型,视电阻率与视倾角能够较好反映各向异性地层的水平、垂直电阻率和倾角。结论井孔瞬变电磁响应能够快速计算出各向异性地层中视电阻率和视倾角,有助于快速分析观测装置附近电性结构,对各向异性介质井孔瞬变电磁领域的快速发展具有重要意义。
