Remote sensing (Landsat-8) applied to shale gas potential evaluation. The case of South Portuguese Zone

Abstract

The use of remote sensing in hydrocarbons exploration is already widely known, especially with regard to the identification of structures with potential for traps formation. But beyond this purpose, the remote sensing may also be used for the detection of potential areas for hydrocarbon microseepages on the surface (assisting the characterization of the subsurface petroleum systems), as it can be related with some geotectonic structures like fractures and faults.

This work aims to assess the shale gas exploration potential, based on the processing and interpretation of Landsat 8 images, to identify evidences of hydrocarbon emanations (geomorphic anomalies) by remote sensing, in Mértola, Mira and Brejeira Formations. These three formations, mostly composed by shaly and sandy turbidites, outcrop in the South Portuguese Zone (SPZ). The SPZ is located in the southernmost sector of the pre-Mesozoic Iberian Variscan Chain, which is composed by highly deformed upper Paleozoic rocks, of low grade metamorphism. However, in some areas, it is possible to observe the same rocks that weren't subject to deformation.

All the results obtained by image processing will be presented as thematic maps in order to be integrated and analyzed with other geological and geochemical data.

From the aerial gamma-spectrometry data, has been produced a “SPZ Hydrocarbons Anomalies Map”, by the thorium-normalized method, in order to compare and validate the remote sensing processing techniques applied in this work.

Obviously, in an ideal scenario, this correlation should be made with active fields of oil and gas production, as proposed by some authors, but at the moment Portugal has no such activity, on-shore or off-shore.

Image processing and analysis techniques, based on ratios between bands (geological indexes) integrated with vegetation indexes (sensitive to geochemical anomalies and light hydrocarbons), will latter on be used to assist the surface geochemical prospecting (hydrocarbon identification and characterization in soil).

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