Attitude effect on marine magnetic source TEM detection system
ZHAO Yue1,2, XU Feng1,2, CAO Huake3,4, LIU Jia1,2
1. Institute of Acoustics, Chinese Academy of Sciences, Beijing 100091, China; 2. Beijing Engineering Technology Research Center of Ocean Acoustic Equipment, Beijing 100091, China; 3. School of Geological Engineering and Geomatics, Chang'an University, Xi'an, Shaanxi 710054, China; 4. Integrated Geophysical Simulation Lab of Chang'an University (Key Laboratory of Chinese Geophysical Society), Xi'an, Shaanxi 710054, China
Abstract：As marine oil and gas resources continuously develop, marine magnetic source transient electromagnetic (TEM) systems have drawn more and more attention in recent years. However, a stable attitude of transceiver loop devices is difficult to maintain in seawater during practical data collection due to the factors such as seabed environment, ocean currents, and uneven speed. The attitude changes of detection systems will alter the coupling between transceiver loop devices and underwater electrical anomalous bodies. This will lead to a certain deviation of observation data and reduce the reliability of interpretation results. First, based on the theory of electromagnetic field, this paper derives the three-component electromagnetic field expression in the frequency domain of arbitrary magnetic dipole source in the isotropic horizontal la-yered medium model under limited water depth. Then, the electromagnetic response characteristics of the marine magnetic loop source are analyzed by the superposition principle of electromagnetic fields. Second, by defining two coordinate sys-tems and their transceiver rotation matrix before and after attitude change, the paper builds a mathe-matical model of attitude changes in underwater towed magnetic source. Finally, taking the towed central loop TEM detection device in shallow water as an example, it analyzes the error distribution of observation data caused by the attitude change of the transceiver system. Additionally, the relationship between TEM response results and parameters of attitude change angle, attenuation time, sea depth, and seabed conductivity is also explained. The research results can help quantify the parameter design of the marine magnetic source TEM detection system and provide a theoretical basis for promoting and processing this method in the future.
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