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A Coupled Remote Sensing and Surface Geology Approach for Petroleum Exploration in Parnaíba Basin, Brazil

Abstract

Recent petroleum exploratory efforts have been focused on terrestrial Brazilian Paleozoic basins, which cover extensive areas, lack geological studies and whose full potential is so far indeterminate. The Parnaíba Basin is included in this scenario, although it has been assessed for petroleum prospectivity since the 1940's. The last wells were drilled in the basin during the early 1980's. After a period of low activity, exploration in the area resumed by 2007, when new exploratory blocks became available. Geotechnologies have played a key role both in ring-fences and frontier areas of petroleum exploration. The present paper comprises a contribution for petroleum prospecting and definition of exploratory plays in the Parnaíba Basin based on a stepwise approach, with strong ties with interpretation of remote sensing imagery and data integration. Seepage detection, photo-interpretation of remote sensing products, geomorphometric mapping, geological fieldwork and fluid inclusion analysis of outcropping sediments are among the methods employed. The set of maps resulting from these approaches was important to characterize seepage surface expressions developed under tropical conditions, in contrast to current models, mostly based on observations in temperate climate regions. Field-checked remote sensing data interpretation indicates that at least one extensional event, marked by NW-SE-trending structures, was active after the Albian period, as further corroborated by seismic data. The discovery of oil fluid inclusions in Cretaceous rocks proves that there was oil migration after their deposition. This oil system appears to be active nowadays, since thermogenic methane anomalies were recognized, and heavier gases such as ethane, propane and butane were detected by geochemical analysis campaigns. These various results were integrated using spatial analysis and fuzzy logic to produce a petroleum prospectivity map of the study area. Integration of orbital, geochemical, geological and geomorphological data allowed the recognition of potential exploratory targets correlated with leads mapped using seismics. Remarkably, these targets could be preliminarily recognized only with interpretation and integration of satellite images products. This work suggests a plausible consistency between the information extracted from surface and subsurface data, adding strength to the exploratory process in frontier areas.