Abstract

Seabed logging, a special application of frequency domain controlled-source electromagnetic (CSEM) method, is classified as an ultra low frequency method. The basic principle which makes a potential tool in the offshore exploration is based on the electrical resistivity contrast between a hydrocarbon bearing reservoir and surrounding host rocks. Seabed logging (SBL) uses a horizontal electric dipole (HED) source towed near the seabed and an array of receivers on the seabed. In the offshore exploration, SBL is used to determine fluid contents before drilling: whether the potential reservoir detected by seismic imaging contains hydrocarbon or it contains water. This is done in order to reduce the risk of dry well and improve the exploration efficiency. In this paper we carried out plane layer modeling which is called one-dimensional (1-D) forward modeling in order to analyze the electromagnetic (EM) response at seabed receiver. The results of numerical study demonstrate that electric and magnetic field responses depends on sea water depth, thickness and resistivity of the overburden layer, target layer thickness and resistivity, seabed topography, and frequency and strength of the transmitted EM signal. Therefore, 1-D modeling analysis for SBL is critical for understanding the responses from a known geological resistive target and for optimizing the survey configuration.