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A short offset transient electromagnetic method for long-distance exploration of boreholes |
LI Hao-Jin1( ), MAO Yu-Rong1,2( ), ZHOU Lei1,2, XIE Xing-Bing1,2, GUO Qin-Ming3, LIU Can1, KE Xiang-Bin1, HE Yi-Fei1 |
1. School of Geophysics and Petroleum Resources, Yangtze University, Wuhan 430100, China 2. Key Laboratory of Exploration Technologies for Oil and Gas Resources, Ministry of Education, Yangtze University, Wuhan 430100, China 3. Research Institute of Logging Technology, CNPC Logging Co. Ltd., Xi'an 730077, China |
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Abstract With an increase in the difficulty with the exploration of oil, gas, and mineral resources, conventional log and seismic methods fail to accurately evaluate the geological structures and transverse reservoir distribution far from boreholes. Therefore, this study proposed a transient electromagnetic (TEM) method for long-distance exploration of boreholes. Specifically, this study investigated the influence of key parameters of TEM devices for boreholes on the exploration distance. Based on the finite element analysis, this study calculated the responses of low- and high-resistivity geobodies under different receiver-transmitter distances, coil parameters, and exploration distances. The results showed that receiver-transmitter distances had little effect on the distance of electromagnetic exploration in the temporal domain. However, the results indicated that coil parameters had significant effects on the near-well detection distances. Under the transmitter coil parameters of 200 turns and 2A current, the TEM method for boreholes was more sensitive to low-resistivity geobodies, with near-well exploration distances reaching 40~50 m and 30 m for low- and high-resistivity geobodies, respectively. Therefore, it is feasible to conduct short-offset near-well long-distance exploration using TEM detectors with short transmitter coils for boreholes.
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Received: 08 November 2022
Published: 23 January 2024
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Schematic of borehole transient electromagnetic remote detection
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Arbitrary triangular element
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Model diagram
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项目 | 相对磁导率 /(H·m-1) | 相对介电常数 | 电阻率 /(Ω·m) | 均匀地层 | 1 | 1 | 50 | 异常体 | 1 | 1 | 10,500 | 泥浆 | 1 | 1 | 1 |
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Model parameters
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Grid subdivision diagram
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The influence of anomalous body in different distance between transmitter and receiver(detection distance of 20m)
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Hx and Ez profile with different detection distances in vertical well(2m between transmitter and receiver)
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Hx and Ez profile with different time of OFF-TIME in vertical well(5m between transmitter and receiver)
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Hx and Ez profile with different transmission and reception distances in horizontal well (detection distance of 50m)
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Hx and Ez profile with different transmission and reception distances in inclined well (detection distance of 50m)
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Hx and Ez profile with low resistance anomalous body at different emission current
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The influence of anomalous body at different emission current
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Hx and Ez profile with low resistance anomalous body at different coil turns
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The influence of anomalous body at different coil turns
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Hx and Ez profile with high resistance anomalous body at different detection distances
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