HR: 17:30h
AN: NG44A-05    [Abstracts]
TI: Active EM Monitoring of Sea-Bottom Geoelectrical Structures in the Areas with the Rough Bathymetry
AU: * Zhdanov, M S
EM: mzhdanov@mines.utah.edu
AF: University of Utah, 135 South 1460 East, Rm 719, Salt Lake City, UT 84112,
AB: During the recent years, the marine Controlled Source Electromagnetic (MCSEM) method has become widely used for active geophysical surveying of the sea-bottom geological structures in hydrocarbon exploration. A typical MCSEM survey consists of a set of sea-bottom receivers and a moving electrical bipole transmitter. The interpretation of the MCSEM data over the complex 3-D geoelectrical structures is a very challenging problem. This problem becomes even more complicated in the areas with the rough sea-bottom bathymetry, because the relief of a sea bottom makes a profound effect on the EM data observed by the receivers located in the close proximity to the bottom. In this paper I introduce a new approach to interpretation of the MCSEM data in the areas with the rough bathymetry. This approach is based on a new formulation of the integral equation (IE) EM modeling method in the models with inhomogeneous background conductivity. The method is based on the separation of the effects due to excess electric current induced in the inhomogeneous background domain, and those due to the anomalous electric current in the location of the anomalous conductivity, respectively. As a result, we arrive at a system of integral equations which uses the same simple Green's functions for the layered model, as in the original IE formulation. However, the new equations take into account the effect of the variable background conductivity distribution. The developed technique allows us to incorporate the known geological structures and bathymetry effects in the method of iterative EM migration/holographic imaging and inversion. This approach provides us with the ability to pre-compute only once the effect of the known geoelectrical structure (e.g., the bathymetry effect) and keep it unchanged during the entire modeling and migration process. Taking into account that precomputing the bathymetry effect constitutes the most time-consuming part of the EM modeling, this approach allows us to increase the effectiveness of the interpretation of the MCSEM data significantly. The method is tested on the typical models of the sea-bottom geoelectrical structures in the areas with hydrocarbon petroleum reservoir and a rough sea bottom bathymetry.
DE: 0520 Data analysis: algorithms and implementation
DE: 0933 Remote sensing
DE: 4499 General or miscellaneous
DE: 7223 Earthquake interaction, forecasting, and prediction (1217, 1242)
DE: 8123 Dynamics: seismotectonics
SC: Nonlinear Geophysics [NG]
MN: 2007 Fall Meeting