Análise e interpretação estratigráfica baseada na integração de dados de poços do intervalo Eossiluriano ao Eocarbonífero da Bacia do Parnaíba

Abstract

The sedimentary section of the Early Silurian to Early Carboniferous in the Parnaíba Basin encompasses two lithostratigraphic units: the Serra Grande Group and Canindé Group, which are interpreted and reported in the current literature as supersequences limited by erosive events of regional character related to the Caledonian and Hercinian orogenies. This stratigraphic interval was analyzed based in geophysical data (gamma ray logs) and geological data (lithologic interpretation from the composite well logs) of wells drilled by the oil industry. Additionally, some 2D seismic data was used as support to partial interpretation. The variations in the pattern of the geophysical well logs (gamma ray) were interpreted as representative of lithofaciologic variations which was corroborated by the lithological description of the composite well log. The variations in the pattern of the geophysical well logs (gamma ray) was interpreted as representative of lithofaciologic variations which was corroborated by the lithological description of the composite well log. A sequence stratigraphic analysis based in the principles of T-R Sequence was applied to this data. This analysis allowed to propose a model to the stratigraphic evolution to the studied section, as constituted by 5 depositional sequences which showed a pattern of a progressive drowning of the basin until its maximum identified in the maximum flooding surface in the Devonian Sequence (E-SEQ-4). From this maximum the depositional pattern reverses to a transgressive trend. Within this stratigraphic context, the integration of the produced data and the information available from literature allowed the proposition of depositional models to the system tracts of the Silurian-Devonian (E-SEQ-3) and Devonian (E-SEQ-4) sequence. The proposed depositional models vary from continental depositional environment in the transgressive system tract 3, in the Silurian-Devonian Sequence, to a marine depositional environment in the regressive system tract 3, following to the Devonian Sequence (E-SEQ-4) with marine depositional environment in the transgressive system tract 4 and to the shallow marine environment in the regressive system tract 4