Petrophysical Characterization of Parana-Etendeka Magmatic Province for Geological Modeling

Summary The characterization of the volcanic rocks from the Serra Geral Group, Paraná Basin, Brazil, is crucial for the development of geological models. The heterogeneity of this layer (observed on seismic and well logs and field trips) and the poor-quality seismic data are great challenges for the construction of realistic geological models. In this study, sonic well logs and outcrop samples were used to obtain compressive (VP) and shear (VS) velocities. Laboratory measurements were obtained using a GCTS creep system with piezoelectric crystals at 1 MHz frequency and under different pressure conditions, while the basic petrophysics were performed under 600 psi. The velocity from the vesicular samples, even with the vesicles filled with minerals, presented significant reduction when compared to the massive basalt samples. The results from this analysis, combined with well log studies and field observations, lead the authors to conclude that low velocity layers observed in well logs and seismic data inside Serra Geral Group are due to vesicular zones.