Análise e interpretação de atributos sísmicos instantâneos: uma contribuição ao estudo do arcabouço tectônico-estrutural da Bacia de Pelotas

Abstract

The present work aims the application of instantaneous seismic attributes, from 2D post-stack seismic sections of the Pelotas Basin, in the Rio Grande Cone region, provided by the National Petroleum Agency. The Pelotas Basin began its development by a process of rifting about 135 Ma ago, in the context of Atlantic Ocean’s formation. In this basin there is a sedimentary feature known as the Rio Grande Cone, which was formed by sediments deposited at a high sedimentation, propitiating the formation of organic matter. The application of the attributes in the seismic data located in this region, was done through tools available in the Seismic Un * x package. These attributes are based on the concept of a complex seismic trace, exploring the phase of the seismic signal (imaginary component) through the Hilbert transform, which can be derived the attributes defined as envelope, phase and frequency of the trace. These mathematical operations, when applied in a seismic section (2D) or in a volume (3D), are capable of highlighting structural and geological aspects, being used mainly for the identification of faults and the detection of relatively subtle stratigraphic characteristics, facilitating interpretation. The image resulting from the application of the attributes allowed highlighting reflectors, which guided the tracking of horizons and faults, and it was also possible to define gas hydrating indicator (BSR) horizons in all sections, as well as structures related to them, as domes structures and pockmarks. The application of the technique of migration of the seismic data to depth, from a velocity model generated by the tracking of the horizons, repositioned the reflectors in subsurface that were displaced by diffractor structures as faults, allowing to know the depth of the localized structures, and thus represent more suitably the geological environment.