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Evaluation of gas hydrate structures: results from an experiment in the South China Sea using the marine controlled-source electromagnetic method

L. Wang, S. Xiong, Y. Li and J. Jing


This paper presents the preliminary results of the application of Marine Controlled-Source Electromagnetic (MCSEM) detection in the South China Sea in 2014. Electromagnetic fields transmitted by a horizontal electric dipole source that was towed in the deep sea were measured by 4 receivers anchored to the seafloor at 600-m intervals. Specialised data processing is critical to the results and improves the signal-to-noise ratio of MCSEM data. Our resistivity results and Natural Gas Hydrate (NGH) saturation results showed three high-resistivity layers beneath the survey line. Integrated with other seismic and well data from the same region, we hypothesise that the first resistivity layer anomaly might have been caused by the accumulation of large amounts of NGH at a depth of 200 m, whereas the second layer, according to the conceptual model, might be due to a considerable volume of NGH near the seafloor.