Modelo Gamaespectrométrico Análogo Da Formação Ponta Grossa (Bacia Do Paraná)

In analogue modelling, ground gamma-ray spectrometric data of the Devonian Ponta Grossa Formation (Paraná Basin) allowed for a better understanding of the spatial distribution of lithotypes. Correlations based on gammaray values obtained from deep well logging could be improved. Ground values, spaced 50 cm in sandstones and 100 cm in shales, were taken along four sections. The sections were 30, 250, 12, and 16 meters thikness, respectively. The results of the first section showed that both ground and deep values reflect the gradual clay<br>enrichment trend noticed along the transition beds between Furnas and Ponta Grossa formations. Along the second section total organic carbon values are in direct relation to ground and deep gamma-ray data. In the third section a clear decrease of intensity was observed in sandy layers. In the last section, which is characterized by higher sand-fraction content, showed a gamma-ray signature compatible with the coarsening upward observed in well data. In this context, a massive clayey interval was defined by high gamma-ray values in both<br>investigation levels. Ground gamma-ray spectrometry combined with detailed outcrop descriptions and deep source data proved to be useful in the establishment of analogue models for the Ponta Grossa Formation in the Paraná Basin.