ANÁLISE ESTRATIGRÁFICA E POTENCIAIS HORIZONTES GERADORES DE HIDROCARBONETOS EM UMA SEÇÃO DEVONIANA NA BORDA SUDOESTE DA BACIA DO PARNAÍBA, TOCANTINS, BRASIL

Stratigraphic framework and potential hydrocarbon-generating horizons at Devonian section from the Southwestern boundary, Parnaíba Basin, Tocantins, Brazil

Abstract

The Parnaíba Basin is located, partially, in three regions of the brazilian territory - North, Northeast and Center-West -, which includes part of the states of Ceará, Piauí, Maranhão, Pará and Tocantins. Additionally, it is considered intracratonic and rounded in shape, covering an area of ​​approximately 600,000 km². The material of this study contain 299 samples belonging to GASBRAS-2-RS-TO well, including top of Jaicós Formation and extended thins of Itaim and Pimenteiras Formations. The Itaim Formation is primarily composed of fine to médium sandstones and, subordinately, subsurface shales. However, the Pimenteiras Formation consists, predominantly, of dark grey to black shales, which may occur interspersed with layers of siltstone and sandstone. The core studied was allowed to carry out the chemostratigraphic characterization of the Itaim Formation with the support of data from geochemical analyzes (TOC and Pyrolysis). In addition to locating within the Pimenteiras Formation the radioactive shales, known as A, B and C, already described in the literature. The last formation has potentially hydrocarbon generating intervals of interest for exploration at last mentioned shales B and C, it was reached, respectively, about 17 m and 38 m in length, with an average TOC of 2.29% and 2.38%.