A preliminary analysis of anomalous TEM response characteristics in borehole with electric source transmitter
WU Jun-Jie1,2, LI Xiu1, ZHI Qing-Quan2, DENG Xiao-Hong2, ZHANG Jie2, WANG Xing-Chun2, YANG Yi2
1. School of Geological Engineering and Geomatics, Chang'an University, Xi'an 710054, China;
2. Institute of Geophysical and Geochemical Exploration, CAGS, Langfang 065000, China
Borehole TEM is a configuration in which the transmitter is on the ground and the receiver probe is in borehole. The receiver can be installed near the orebody through the borehole and hence can obtain more reliable information of the orebody. Borehole TEM is effective for conductive mineralization, particularly in areas where the capability of surface EM for defining a target is limited either by large depths or by interfering conductive bodies such as overburden shallow sulfides and peripheral mineralized horizons. Relative to the magnetic source, the detection depth of electric source borehole TEM is deeper and it is more suitable for deep prospecting in the complex terrain area. Through the study of the borehole TEM response characteristics of electrical source of borehole TEM, the authors aim to provide technical support for the application. Three component response characteristics of half space, 1D, 3D model were analyzed through forward modeling, and its validity for different models was proved in this paper. The results show that, due to the superimposition of the background field and anomaly field response upon transient response of total field, the curve shape is complex, and the electrical interfaces are only obviously reflected at the middle and late stage. The shape of the anomalous field curve is relatively simple, and the electrical interface is obvious; the anomaly of the horizontal component is on the whole higher than that of the vertical component. In this paper, by means of numerical simulation analysis, the authors obtained the preliminary understanding of electrical source of downhole TEM three component curve shape and verified the effectiveness of the electrical interface under the condition of the electrical emission sources. The results obtained by the authors can provide a reference for the further research.
武军杰, 李貅, 智庆全, 邓晓红, 张杰, 王兴春, 杨毅. 电性源地-井瞬变电磁异常场响应特征初步分析[J]. 物探与化探, 2017, 41(1): 129-135.
WU Jun-Jie, LI Xiu, ZHI Qing-Quan, DENG Xiao-Hong, ZHANG Jie, WANG Xing-Chun, YANG Yi. A preliminary analysis of anomalous TEM response characteristics in borehole with electric source transmitter. Geophysical and Geochemical Exploration, 2017, 41(1): 129-135.
[1] Eadie T,Staltari G.Introduction to down hole electromagnetic methods[J].Exploration Geophysics,1987:247-351.
[2] Barnett C T.Simple inversion of time-domain electromagnetic data[J].Geophysics, 1984,49(7):925-933.
[3] Duncan A C. Interpretation of down-hole transient EM data using current filaments[C]//5th ASEG conference,1984:36-39.
[4] Lindsay, Thomas.A simple Interpretation aid for downhole time-domain electromagnetic anomalies[J].Exploration Geophysics,1987:349-351.
[5] Cull J P. Rotation and resolution of three-component DHEM data[J].Exploration Geophysics,1996, 27(3), 155-1159.
[6] Zhang Z,Xiao J.Inversions of surface and borehole data from large-looptransient electromagnetic system over a 1-D earth[J].Geophysics,2001,66(4):1090-1096.
[7] 孟庆鑫,潘和平. 地-井瞬变电磁响应特征数值模拟分析[J].地球物理学报,2012,55(3):1046-1053.
[8] 张杰,王兴春,邓晓红,等.地-井瞬变电磁井旁板状导体异常响应特征分析[J].物探化探计算技术,2014,36(6):641-648.
[9] 张杰,邓晓红,郭鑫,等.地-井TEM在危机矿山深部找矿中的应用实例[J].物探与化探,2013,37(1):30-34.
[10] 杨毅,邓晓红,张杰,等.一种井中瞬变电磁异常反演方法[J].物探与化探,2014,38(4):855-859.
[11] 薛国强,闫述,陈卫营.接地源短偏移瞬变电磁法研究展望[J]. 地球物理学进展,2014,29(1):177-181.
[12] 薛国强,陈卫营,周楠楠,等. 接地源瞬变电磁短偏移深部探测技术[J]. 地球物理学报,2013.56(1):255-261.
[13] 于生宝,贾少华,李刚,等.电性源时间域电磁法大功率发射系统的研制[J].国外电子测量技术,,2014,33(7):49-52.
[14] Strack K M.Exploration with deep transient electromagnetic method[M].Amsterdam:Elsevier,1992.
[15] Mogi T, Kusunoki K, Kaieda H, et al. Grounded electrical-source airborne transient electromagnetic (GREATEM) survey of Mount Bandai north-eastern Japan[J].Exploration Geophysics,2009,40:1-7.
[16] 陈卫营,薛国强,崔江伟. 电性源瞬变电磁发射源形变对观测结果影响分析[J]. 地球物理学进展,2015,30(1):0126-0132.
[17] Key K. 1D inversion of multicomponent, multifrequency marine CSEM data:Methodology and synthetic studies for resolving thin resistive layers[J]. Geophysics, 2009,74(2):F9-F20.
[18] 孙怀凤,李貅,李术才,等.考虑关断时间的回线源激发TEM三维时域有限差分正演[J].地球物理学报,2013,56(3):1049-1064.