Application of remote sensing to oil seep detection in the Lusitanian Basin – Portugal

Abstract

The Lusitanian Basin, located in Portugal, has been explored in the last years in an attempt to find hydrocarbon accumulations. Until today no commercial accumulations have been found. Nevertheless the information known about the Lusitanian Basin, specifically its sedimentary filling and geodynamics reveal that this basin has not only all the components needed, but endured the mechanical thermal processes which lead to hydrocarbon generation. The evidences of this generation can be seen onshore, from the oil seeps and oil impregnations located in Leiria, Vale Furado (Nazaré) and Torres Vedras. The main purpose of the present work is to search any recognizable oil leakage in the Portuguese offshore, as it can be seen onshore. In order to do this, a set of LANDSAT and ASTER satellite images was observed. Image analysis allowed selecting three scenes showing geographically close patches of possible oil seeps, that were recorded in different dates. The individualization of the possible oil seeps was based essentially on their colour contrast with the background. It was possible to correlate the geographic positions with the geology mapped offshore, and also with the oil seeps known onshore. Previous studies established a relation between the local geology, onshore oil seeps and petroleum systems of the Lusitanian Basin. The same approach is now presented for the oil seeps discovered offshore, in an attempt to understand the oil patches origin. A tentative correlation carried out between the timing of oil seeps record and the seismic activity has shown that a connection may exist between the occurrences of the oil seeps and local changes of crustal mechanic properties, before and after an earthquake. The individualization of these three possible oil seeps shows episodic yet contemporary oil leakage, reinforcing the hypothesis that, like onshore, there may be hydrocarbon escape in the Portuguese offshore.

AAPG Datapages/Search and Discovery Article #90226 © 2015 European Regional Conference and Exhibition, Lisbon, Portugal, May 18-19, 2015