Rapid Imaging of Towed Streamer EM Data for Reconnaissance Offshore Exploration Using the Optimal Synthetic Aperture Method

摘要

Marine towed streamer electromagnetic (EM) surveys have become extensively used for offshore hydrocarbon (HC) exploration. The mainstream approach to interpretation of towed streamer EM data is based on 2.5D and/or 3D inversions of the observed data into the resistivity models of the sea-bottom formations. However, in the case of a reconnaissance towed streamer EM survey with the goal of scanning a vast area of the marine shelf, one needs to use a rapid imaging technique, which could provide a real-time evaluation of the potential prospects. This paper introduces an innovative technique of rapid imaging of towed streamer EM data based on the concept of the synthetic aperture method. We introduce an optimization technique to find the optimal parameters of the synthetic aperture method for a towed streamer EM survey, and demonstrate that this method increases the EM response from the potential sea-bottom targets effectively. Towed streamer EM data acquired over the Troll oil and gas fields in the North Sea are used as a test study. Our imaging results are shown to be consistent with those obtained by rigorous inversion and with the true location of the HC deposits.