Análise de atributos sísmicos como subsídio à interpretação de dados sísmicos da Bacia de Pelotas

Abstract

This paper aims to present the work at seismic well-tie and the application of instantaneous and coherence attributes in post-stack 2D seismic sections at Pelotas Basin. These procedures were done by algorithms implemented in Python, tools from the Seismic Un*x package and the Opendtect software (free version) that allow the processing, analysis and visualization of seismic sections with a cognitive workflow. Instant seismic attributes are calculations applied to post-stack seismic data based on the concept of complex seismic trace (TANER et al., 1979), exploring the seismic signal phase (imaginary component) from the Hilbert transform. The coherence attributes aim to measure the degree of local similarity between adjacent seismic features. These mathematical operations, when applied to a seismic section (2D) or a volume (3D) are able to highlight the structural and geological aspects. They are mainly used for fault identification and detection of visually imperceptible stratigraphic surfaces, collaborating during the interpretation stage. The next step addressed the well-tie, a technique that correlates the event of a seismic section in time with the information subsurface obtained from a well. The imaging resulting from the application of the attributes allowed highlighting the reflectors and faults, which combined with the interpretation of well profiles and seismic sequences guided the tracking of horizons and faults. The integration of geology and geophysical data with well information became essential to define the stratigraphic sequences present in the seismic data, allowing to identify the main sedimentation events of Pelotas Basin. With the interpreted horizons, the velocity model necessary for data conversion to depth step was built.