Oil Seep Detection Using Microwave Remote Sensing at Espírito Santo Basin, Eastern Brazil

Abstract

Hydrocarbon seepage phenomena can be found in most petroleum provinces located in both coastal and ocean regions. The present work aims to identify, map and quantify oil seep candidates in the maritime portion of the Espírito Santo Sedimentary Basin using Synthetic Aperture Radar imagery from Radarsat-2 and Sentinel-1. The selection of the SAR images was made based on their basin coverage area. Meteorological and oceanographic data, when available, were used to assist interpretation. Later, the presence of structures that may enable fluids to escape (faults, fractures, salt domes, etc.) was verified in 101 seismic lines. After detailed analysis, the obtained data were gathered, aiming to classify the oil seep candidates found according to their probability of happening. There were 3 parameters, subdivided into criteria, used in the ranking score: SAR (distance of vessels, number nearby possible seeps and feature size), Geological (morphotectonic domains) and Seismic (distance from seismic lines, presence of structures and distance from structure). Each criterion received grades ranging from 0.1 to 1.0. The final score is given by the arithmetic mean of the parameters. This allowed the seep candidates to be organized in a ranking. The methodology was successful in identifying 54 promising features in the Espírito Santo basin and northern Campos basin. Half of the seep candidates found, 27 features, obtained a grade higher than 0.7, which strengthens the idea of being oil seeps. As an outcome a map was made in 1:3,500,000 scale with the location of all oil seep candidates mapped in this petroleum province.