Removal of the airwave effect by main-part decomposition of the anomalous field of MCSEM data
Wang Shu-Ming1, Di Qing-Yun2, Wang Ruo2, Wang Xue-Mei1, Su Xiao-Lu1, and Wang Peng-Fei1
1. Hubei Subsurface Multi-scale Imaging Key Laboratory, Institute of Geophysics and Geomatics, China University of Geosciences, Wuhan 430074, China.
2. Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China.
Abstract The airwave effect greatly influences the observational data from controlled-source electromagnetic exploration in shallow seas, which obscures the abnormal effects generated by exploration targets and, hence, affects the accuracy of the late exploration data interpretation. In this study, we propose a method to separate the main part from the anomalous field of marine controlled-source electromagnetic method (MCSEM) data based on Stratton–Chu integral transforms to eliminate the airwave effect, which dominates observed electromagnetic (EM) response in shallow seawater. This method of separating the main part from the anomalous field is a type of finite impulse response filter based on a discrete data set. Theoretical analysis proved that the method is stable and able to effectively depress noise. A numerical test indicated that the method could successfully eliminate the airwave effect from the observed EM signals generated by an air–water interface and a seawater layer. This technique is applicable for seawater models with either flat or rough seabeds.
Research supported by the National Natural Science Foundation of China (No. 41574067) and 863 Program (No. 2012AA09A404).
Cite this article:
. Removal of the airwave effect by main-part decomposition of the anomalous field of MCSEM data[J]. APPLIED GEOPHYSICS, 2018, 15(1): 3-10.
Amundsen, L., Løseth, L., Mittet, R., Ellingsrud, and Ursin, B., 2006, Decomposition of electromagnetic fields into upgoing and downgoing components: Geophysics, 71(5), G211−G223.
Berdichevsky, M. N., and Zhdanov, M. S., 1984, Advanced theory of deep geomagnetic sounding: Elsevier Science Ltd, Dutch.
Chen, J., and Alumbaugh, D. L., 2011, Three methods for mitigating airwaves in shallow water marine controlled-source electromagnetic data: Geophysics, 76(2), 4542−4544.
Ellingsrud, S., Eidesmo, T., and Johansen, S., 2002, Remote sensing of hydrocarbon layers by seabed logging (SBL): Results from a cruise offshore Angola: The Leading Edge, 21(10), 972−982.
Fan, Y., Snieder, R., and Singer, J., 2009, 3-D controlled source electromagnetic (CSEM) interferometry by multi-dimensional deconvolution: 79th Ann. Internat. Mtg, Soc. Expl. Geophys., Expanded Abstracts, 28(1), 4338.
Slob, E., Draganov, D., and Wapenaar, K., 2007, Interferometric electromagnetic Greens functions representations using propagation invariants: Geophysical Journal International, 169, 60−80.
Snieder, R., 2006, Retrieving the Greens function of the diffusion equation from the response to a random forcing: Physice Review E Statistical Nonlinear & Soft Matter Physics, 74(4 Pt 2), 046620.
Tompkins, M. J., 2004, Marine controlled-source electromagnetic imaging for hydrocarbon exploration: Interpreting subsurface electrical properties: First Break, 22, 45−51.
Wapenaar, K., Slob, E., and Snieder, R., 2008, Seismic and electromagnetic controlled-source interferometry in dissipative media: Geophysical Prospecting, 56, 419−434.
Wang, S. M., Di, Q. Y., Su, X. L., Wang, R., and Wang, X. M., 2017, Realization and parameter analysis for filter of 3D numerical electromagnetic migration: Chinese J. Geophys. (in chinese) , 60(2), 793−800.
Zhdanov, M. S., and Wang, S., 2009, Foundations of the method of EM field separation into upgoing and downgoing parts and its application to MCSEM data: Handbook of Geophysical Exploration Seismic Exploration, 40(1), 351−379.
Zhdanov, M. S., and Wang, S., 2009, Foundations of the method of EM field separation into upgoing and downgoing parts and its application to MCSEM data: Proceedings of Annual Meeting of the Consortium for Electromagnetic Modeling and Inversion, 149−178.
Zhdanov, M. S., 1988, Integral Transforms in Geophysics: Springer, German.
Zhdanova, O. N., and Zhdanov, M. S., 1998, Methods for the analysis and interpretation of the sea-floor electromagnetic fields: Deep Electromagnetic Exploration, 248−259.