Detectability Enhancement Toward High Resistive Target With Synthetic Aperture Source for 3-D Marine CSEM Data Modeling at the Rugged Seafloor

Abstract

Abstract

The synthetic aperture (SA) technique is used to enhance the detectability of hydrocarbon (HC) reservoir in marine controlled-source electromagnetic (CSEM) data. The synthetic data including inline and crossline horizontal electric field at the rugged seafloor are simulated with a frequency-domain finite-difference (FDFD) modeling approach. The FDFD code is shown to accurately simulate the marine CSEM responses at the rugged seafloor by comparisons with the 1D analytic solution 2D finite-element (FE) solution. For a shallow water (150 m water depth) reservoir model based on the geological section in practice, the detectability of target response along inline direction can be enhanced remarkably by using the SA approach, and the potential of SA method is further developed by optimizing the phase shift coefficient and amplitude weighting coefficient in the formula for constructing the SA source. A least square method is used to solve the optimization process. The optimized SA method works effectively by increasing the target responses and reducing the background responses, and allows adaptive field steering corresponding to the size and the resistivity of the reservoir. For a rugged seafloor reservoir model, the effective marine CSEM signals diffracted from undersea deep target are highlighted with the optimal SA method and a bathymetric correction technique, particularly with the optimal SA method using a 2D source distribution. It is shown that the detection capability of reservoir can be increased significantly by field steering with both inline and crossline directions. The result integrated of both distortion correction procedure and field steering shows striking advantages because of the fact technique of SA has functions of suppressing the air wave. In shallow water environment, the range of transmitter-receiver (Tx-Rx) offsets with high detectability is generally narrow, thus more SA scenarios or better optimal techniques could be employed in marine CSEM survey in order to reduce the exploration uncertainty factor.

AAPG Datapages/Search and Discovery Article #90260 © 2016 AAPG/SEG International Conference & Exhibition, Cancun, Mexico, September 6-9, 2016