Almério Barros França
almerio@ep-bc.petrobras.com.br

Estratigrafia, ambiente de deposição e análise de reservatório do Grupo Itararé (Permo-Carbonífero), Bacia do Paraná.

Palavras-chave: Bacia do Paraná, Grupo Itararé, Gondwana, Permo-Carbonífero, Reservatórios, Petróleo, Diagênese, Glaciação, Brasil.

University of Cincinnati, Department of Geology.
Cincinnati, Ohio, 45221. www.uc.edu/geology e Barry.Maynard@UC.EDU

DATA DE DEFESA: 12 de maio de 1987.
ÁREA DE CONCENTRAÇÃO:  Estratigrafia e Análise de Reservatório
ORIENTADOR: Paul Edwin Potter
EXAMINADORES: Paul Edwin Potter, Wayne Arthur Pryor e David L. Meyer.

RESUMO

 PhD THESES ON EARTH SCIENCES OF BRAZILIAN REGIONS
(DEFENDED IN NON-BRAZILIAN UNIVERSITIES)

Almério Barros França
almerio@ep-bc.petrobras.com.br

Stratigraphy, Depositional Environment, and Reservoir Analysis of the Itararé Group (Permo-Carboniferous), Paraná Basin, Brazil.

Key words: Paraná Basin, Itararé Group, Gondwana, Permo-Carboniferous, Reservoirs, Petroleum, Diagenesis, Glaciation, Brazil

University of Cincinnati, Department of Geology.
Cincinnati, Ohio, 45221. www.uc.edu/geology e Barry.Maynard@UC.EDU

DATE OF ORAL PRESENTATION: 12/05/1987
OPIC OF THE THESIS: Stratigraphy and Reservoir analysis
SUPERVISORS: Paul Edwin Potter
COMMITTEE MEMBERS: Paul Edwin Potter, Wayne Arthur Pryor e David L. Meyer.

ABSTRACT
The Present work is a stratigraphic, reservoir, and environmental analysis of the Itararé Group (Permo-Carboniferous) using the well data of the Paraná Basin which covers about 1,000,000 km² in Brazil alone. More than three thousand kilometers of cross sections were analysed, over 100 wells were studied, nearly 400 meters of cores were described, and 95 thin sections were analysed.
A stratigraphic subdivision of the subsurface is proposed for the Itararé Group and three new formations and four new members are proposed. The lowermost formation is called the Lagoa Azul , which is subdivided into the Cuiabá Paulista Member, composed mostly of sandstones; and the Tarabai Member, composed predominantly of siltstones and pebbly mudstones. The new middle unit is the Campo Mourão Formation, composed mostly of sandstones and pebbly mudstones, and the new uppermost unit is the Taciba Formation. The Taciba Formation is subdivided into the Rio Ivaí Member, composed of sandstones; the Chapéu do Sol Member composed of pebbly mudstones; and the Rio do Sul Member composed mostly of shales.
This new stratigraphic subdivision is necessary because only in the central part of the basin is the sedimentation most continuous and unconformities are less likely. Furthermore, the new stratigraphic nomenclature facilitates subsurface exploration and subsurface mapping as well.
Well logs show that the Itararé Group has three major depositional cycles termed lower, middle, and upper, which correspond broadly to the three new formations. Each cycle is composed of a sandy basal section and an upper 'shaly' section. It is likely that the cycles are response to climatic and sea level changes, Pebbly mudstones present in the 'shaly' sections of the cycles were probably deposited by glaciers, whereas fossiliferous shales containing dropstones were deposited in a cold sea during a major transgression.
Three major ice lobes seem to have entered the Paraná Basin during the Pemo-Carboniferous. One lobe came from the east, apparently an extension of the Kaokoveld Lobe from Africa. Two lobes came from west - the Santa Catarina Lobe and the Mato Grosso Lobe, apparently linked to glaciation in the Assuncion Arch.
The sandy section of the depositional cycles were probably deposited by braided rivers on outwash plains or as alluvial fans, deltas, and turbidites. These sandstones comprise the reservoirs rocks in the Itararé Group.
There are two sandstones types in the Itararé Group, one is clay-rich with no porosity, and the other has little or no clay. The latter has secondary porosity mostly due to dissolution of early siderite cement. Dissolution is probably contemporaneous with or later than the Gondwana break-up (Jurassic-Cretacwous), when the Paraná Basin had its hottest period associated with great igneous activity. This event may have accelerated thermomaturation of organic matter, releasing organic acids and carbon dioxide which were responsible for most of the corrosive solutions that percolated through sandstones, leaching carbonate minerals and other unstable constituents to form the secondary porosity.