Geofísica da borda oeste da bacia potiguar: métodos potenciais aplicados ao conhecimento estrutural e petrolífero

Abstract

An integrated study of geophysical data (magnetic and gravity) was undertaken in the onshore western part of Potiguar Sedimentary Basin, NE Ceará. The development of this basin suffered tectonic reactivation of its major faults associated with the Brasiliano shear zones and opening of the Atlantic Ocean. Qualitative and quantitative interpretations of geophysical data were performed in order to understanding tectonostratigraphy relationships involving the western part of Potiguar Basin based on determination of main geophysical lineaments, geometry and depth of sources and the important determinations of geophysical domains. From geophysical profiles in NW-SE direction over Bouguer Map 2-D and 2,5 D geological models were generated to give better characterization of the geometry and the depth of the sources and thus promote more reliable results from geological interpretations. The results shown structural lineaments partitioning characterized by lineaments in the 1" NE-SW order direction and 2❑d EW and NW-SE order directions. The spatial arrangement of geophysical fields is related to the Brasiliano lineaments that occur in the region. The Jaguaribe shear zone that is not marked on the surface appears much pronounced in the various maps and subsurface geophysical models. The Ponta Grossa and Fazenda Belém lineaments have geophysical similar signatures to Jaguaribe shear zone and appear to limit a graben forms structures on the west part of Potiguar Basin. Another lineament with similar expression to others appears well marked by the 2-D Euler solutions in NW of Ponta Grossa lineament. Gravity modeling over the profiles shows the geometry of the western part of Potiguar Basin which has a graben feature that may be associated with the accumulation of hydrocarbons such as the Fazenda Belém oil field. The crystalline basement of the study region is heterogeneous. Magnetic and gravity lineaments with shallow sources (<1 km) are interpreted as faults or intrabasin discontinuities which may represent the reactivation of major shear zones in the study area. These regions are very important to the oil and gas in the western part of Potiguar Basin, since these features can behave as geological/structural traps.