Caracterização estratigráfica e faciológico-diagenética da Formação Açu/Unidade Açu-4, Mesocenomaniano - Eoturoniano da Bacia Potiguar

• Autor(a) principal: Oliveira, Luana Rafaella de [UNESP]
• Data de Publicação: 2013
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Repositório Institucional da UNESP
• Texto Completo: http://hdl.handle.net/11449/190876; http://www.athena.biblioteca.unesp.br/exlibris/bd/cathedra/28-09-2018/000907792.pdf
• topic: Potiguar basin; Açu formation; Açu-4 unit; Mossoró member; Sequence stratigraphy; Regressive-transgressive cycle; Oil reservoir; Petróleo; Geologia estratigráfica; Reservatórios; Rio Grande do Norte; Petroleum

Main oil accumulations in the Açu Formation (Albian to Early Turonian) occur along two hinge lines which are boundaries of the Potiguar rift. For this work were chosen four fields located in the Areia Branca hinge: Baixa do Algodão (BAL), Mossoró (MO), Canto do Amaro (CAM) and Redonda (RE). They produce from different intervals of Açu Formation, including its upper division, also known as Açu-4 unit or Mossoró Member. An earlier project provided a chronostratigraphic framework of Acu-4 unit, based in sequence and facies cycle analyses, was displayed in a 90 kmlong stratigraphic section, from outcrop belt to the inner shelf, through the fields of BAL-RE trend; intermediate wells were used to facilitate chronocorrelation (by J.C.Castro). This new project investigates the diagenetic evolution of Açu-4 facies; it will emphasize potential reservoirs of regressive phases of cycles (fluvial and bayhead delt environments) and non-reservoirs of transgressive phases of the R-T cycle (estuarine, lagoonal/tidal flat and marine). By the zoom method, it was recognized and mapped three depositional sequences and five regressive-transgressive cycles (corresponding to facies associations AF1 to AF5 proposed by A.O.Silva in his Master studies of Açu-4 in Redonda oilfield). The diagenesis is focused on the top of the third cycle (transgressive phase) and bottom cycle 4 (regressive), which represents the best reservoir of the trend (known as Mossoró sandstone). In the regressive phases, it is produced fine-grained sandstone reservoir, arkose-type; its early acid diagenesis is represented by smectite films around grains or feldspar overgrowth. In the transgressive phases, bioturbated sandstones suffer alkaline cementation by carbonates, superimposed by feldspar overgrowth. Towards the end of cycle 3, in Redonda field, there is a dolomitic mark with phosphatic ... (Complete abstract click electronic access below)