Airborne geophysical data interpretation of the southeast portion of Parnaíba Basin, Brazil

Abstract

Airborne geophysical surveys are widely used in geological prospecting for hydrocarbon reservoirs. The efficiency and fast acquisition of these methods covering large areas, recognize them as a key tool for any prospecting project located in frontier basins, such as Parnaiba Basin, where there is a large amount of technical data. Among the airborne geophysical methods, gravity and magnetic methods, usually called potential field methods, are the most propagated in Oil and Gas projects of this nature. Such methods are used to support the generation of regional geological knowledge, detailed approaches, integrated with seismic, geochemical, and well data. Specifically, in the case of magnetometry, its use in more detailed specifications has been available in the Brazilian market since 1988 with the release of the GPS signal to the market and mainly after the replacement of the proton precession magnetometers by the cesium vapor (1991–1994), which is much more accurate in determining the anomalous magnetic field. In terms of airborne gravity, applications in detailed survey approach were not available to the Brazilian market until 2006. Investments in hydrocarbon prospecting in Brazil were concentrated in the promising Campos Basin, leading to few and almost no investments in other Brazilian sedimentary basins. The Parnaiba Basin is one of the Brazilian sedimentary basins with almost no prospecting investment. The aims of this work is a qualitative interpretation of magnetic lineaments and high gravity and structural lows, to suggest a map of the integrated structural context and of geological and geophysical methods of the southeast portion of Parnaiba basin. Using filters like the First Vertical Derivative and the Analytic Signal maps was possible to highlight the structural magnetic lineaments interpreted and a qualitative interpretation of geological intrusions and sills. On results, the data interpretation showed an important structural complexity and identified graben and horst structures usually favorable to the hydrocarbon trap occurrence, as well as an intrusive rock occurrence usually associated to organic matter maturation, in a higher concentration in the center region of the study area.