Abstract：
Since the ocean bottom is a sedimentary environment wherein stratification is well developed, the use of an anisotropic model is best for studying its geology. Beginning with Maxwell’s equations for an anisotropic model, we introduce scalar potentials based on the divergence-free characteristic of the electric and magnetic (EM) fields. We then continue the EM fields down into the deep earth and upward into the seawater and couple them at the ocean bottom to the transmitting source. By studying both the DC apparent resistivity curves and their polar plots, we can resolve the anisotropy of the ocean bottom. Forward modeling of a high-resistivity thin layer in an anisotropic half-space demonstrates that the marine DC resistivity method in shallow water is very sensitive to the resistive reservoir but is not influenced by airwaves. As such, it is very suitable for oil and gas exploration in shallow-water areas but, to date, most modeling algorithms for studying marine DC resistivity are based on isotropic models. In this paper, we investigate one-dimensional anisotropic forward modeling for marine DC resistivity method, prove the algorithm to have high accuracy, and thus provide a theoretical basis for 2D and 3D forward modeling.
. Forward modeling of marine DC resistivity method for a layered anisotropic earth[J]. APPLIED GEOPHYSICS, 2016, 13(2): 279-287.
[1]
Allen, D., and Merrick, N., 2007, Robust 1D inversion of large towed geo-electric array datasets used for hydrogeological studies: Exploration Geophysics, 38(1), 50−59.
[2]
Bronstein, I. N., and Semendjajew, K. A., 1979, Taschenbuch der Mathematik: B.G. Teubner Verlags Gesellschaft, Leipzig.
[3]
Cai, H. Z., Xiong, B., Han, M., and Zhdanov, M., 2014, 3D controlled-source electromagnetic modeling in anisotropic medium using edge-based finite element method: Computers & Geosciences, 73, 164−176.
[4]
Fedynskiy, B. B., 1960, The Soviet Union’s marine geophysical exploration: Geophysical Exploration, 1960 (2), 10−15.
[5]
Goto, T. N., Kasaya, T., Macgiyama, H., et al., 2008, A marine deep-towed DC resistivity survey in a methane hydrate area, Japan Sea: Exploration Geophysics, 39, 52−59.
[6]
Goto, T. N., Takekawa, J., Mikada, H., et al., 2013, Resistivity survey of seafloor massive sulfide areas in the Iheya north area, off Okinawa, Japan: Proceedings of the 11th SEGJ International Symposium, Yokohama, Japan, 298−301.
[7]
Inoue, M., 2005, Development and case studies of the new submarine electric sounding system: Geophysical Exploration, 58, 241−250.
[8]
Jia, D. Y., Weng, A. H., Liu, Y. H., and Yin, C., 2013, Propagation of electromagnetic fields from a horizontal electrical dipole buried in ocean: Progress in Geophysics (in Chinese), 28(1), 507−514.
[9]
Kong, F. N., Johnstad, S. E., Rosten, T., and Westerdahl1, H., 2008, A 2.5D finite-element-modeling difference method for marine CSEM modeling in stratified anisotropic media: Geophysics, 73(1), F9−F19.
[10]
Kwon, H. S., Kim, J. H., Ahn, H. Y., and Yoon, J. S., 2005, Delineation of a fault zone beneath a river bed by a DC resistivity survey using a floating streamer cable: Exploration Geophysics, 36, 50−58.
[11]
Li, J. M., 2005, Electric fields and electrical prospecting: Geological Publishing House, Beijing, 79−83.
[12]
Lile, O. B., Backe, K. R., Elvebakk, H., et al., 1994, Resistivity measurements on the sea bottom to map fracture zones in the bedrock underneath sediments: Geophysical Prospecting, 42, 813-824.
[13]
Li, X. B., and Pedersen, L. B., 1991, The electromagnetic response of an azimuthally anisotropic half-space: Geophysics, 56(9), 1462−1473.
[14]
Matias, M. J. S., and Habberjam, G. M., 1986, The effect of structure and anisotropy on resistivity measurements: Geophysics, 51(4), 964−971.
[15]
Newman, G. A., Commer, M., and Carazzone, J. J., 2010, Imaging CSEM date in the presence of electrical anisotropy: Geophysics, 75(2), F51−F61.
[16]
Shen, J. S., Guo, N. C., and Su, B. Y., 2009, Response characteristics of resistivity of anisotropic laminar formation in direct current electric sounding: Journal of China University of Petroleum, 33(3), 59−65.
[17]
Tarits, P., Hussher, A., D’Eu, J. F., Balem, K., Hautot, S., and Girault, R., 2012, Free gas mapping with a new marine DC resistivity technique: SEG Technical Program Expanded Abstracts, 1−5.
[18]
Um, E. S., Harris, J. M., and Alumbaugh, D. L., 2010, 3D time-domain simulation of electromagnetic diffusion phenomena: A finite-element electric-field approach: geophysics, 75(4), F115 −F126.
[19]
Von Herzen, R. P., Kirklin, J., and Becker, K., 1996, Geo-electrical measurements at the TAG hydrothermal mound: Geophysical Research letters, 23, 3451−3454.
[20]
Wang, W., Wu, X. P., and Spitzer K., 2011, 3D DC anisotropic resistivity modeling using unstructured finite element method: International Workshop on Gravity, Electrical & Magnetic Methods and Their Applications, Beijing, China, October 10-13, 46 − 46.
[21]
Weidelt, P., 1999, 3-D conductivity models: Implications of electrical anisotropy: In: Oristaglio, M. and Spies, B., Eds. Three dimensional electromagnetics. Soc. Exploration Geophysics, 14−21.
[22]
Weng, A. H., and Zhu, S. A., 2010, Near sea-bottom DC sounding response for gas hydrate: Oil Geophysical Prospecting (in Chinese), 45(3), 458−461.
[23]
Xu, T., and Dunbar, J. A., 2015, Binning Method for Mapping Irregularly Distributed Continuous Resistivity Profiling Data onto a Regular Grid for 3-D Inversion: Journal of Environmental and Engineering Geophysics, 20(1), 1−17.
[24]
Yin, C. C., 2000, Geoelectrical inversion for a one-dimensional anisotropic model and inherent non-uniqueness: Geophysical Journal International, 140, 11−23.
[25]
Yin, C. C., 2006, MMT forward modeling for a layered earth with arbitrary anisotropy: Geophysics, 71(3), G115−G128.
[26]
Yin, C. C., Ben, F., Liu, Y. H., and Cai, J., 2014, MCSEM 3D modeling for arbitrarily anisotropic media: Chinese J. Geophys. (in Chinese), 57(12), 4110−4122.
[27]
Yin, C. C., and Hodges, G., 2003, Identification of Electrical Anisotropy from Helicopter EM Data: Symposium on the Application of Geophysics to Engineering and Environmental Problems, Environmental and Engineering Geophysical Society (EEGS), 419−431.
[28]
Yin, C. C., and Maurer, H. M., 2001, Electromagnetic induction in a layered earth with arbitrary anisotropy: Geophysics, 66(5), 1405−1416.
[29]
Yin, C. C., and Weidelt, P., 1999, Geoelectrical fields in a layered earth with arbitrary anisotropy: Geophysics, 64, 426−434.
[30]
Zhou, J. M., Li, X., Qi, Z. P., Sun, N. Q., and Wang, H. N., 2015, Simulation of 3D marine CSEM response in anisotropic media by coupled potential finite volume method: Near-Surface Asia Pacific Conference, Waikoloa, Hawaii, 7−10, 343−346.
2016, Vol. 13 
