Petrologia, diagênese e qualidade de reservatórios da Formação Pojuca, Alto de Aporá, Bacia do Recôncavo.

• Autor(a) principal: Berto, Anna Raphaela Costa
• Data de Publicação: 2018
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: Biblioteca Digital de Teses e Dissertações da UERJ
• Texto Completo: http://www.bdtd.uerj.br/handle/1/16403
• topic: Pojuca Formation; Recôncavo Basin; Diagenesis; Clay Minerals; X-Ray; Diffraction-rays; Formação Pojuca; Bacia do Recôncavo; Diagênese; Argilominerais; Difração de raios X; Geologia estratigráfica – Recôncavo, Bacia do (BA); Diagênese – Formação mineral; Difração de raios-X – Organismos; Microscopia Eletrônica de Varredura; Arenito – Pojuca, Formação (BA); CIENCIAS EXATAS E DA TERRA::GEOCIENCIAS::GEOLOGIA::PETROLOGIA

The Recôncavo Basin is located in the center-east of the state of Bahia and has its evolution related to the crustal stretching that caused the fragmentation of the Gondwana Supercontinent in the Mesozoic and consequently the opening of the South Atlantic Ocean. The Pojuca Formation is characterized by a cyclic record, expressed by the alternation between episodes of deltaic progradation, some of which with great lateral continuity, like the Santiago Member, and transgressive events identified by thick pelitic - carbonate sections (shales, calcilutites and calcarenites). Structures, textures, detrital and diagenetic mineralogical composition and pore types were identified from the petrographic description and XRD and SEM / EDS analysis of 30 thin section of the 9-FBA-79-BA and 9-FBA-65-BA boreholes. It was observed that the granulometry of the studied sandstones varies from very fine to medium sand, with clay and siltic predominant portions that occur locally. The selection is predominantly moderate, with few poorly selected sandstones occurring, the most frequent grains being sub-anglular to sub-rounded. The packing shows variation from loose to normal with predominance of punctual contacts. The primary characteristics of the samples have good porosity and permeability. The detrital mineralogy is composed by quartz, feldspar, zircon, opaque minerals, intraclast limestone and bioclasts. The identified diagenetic minerals are dolomite, smectite, quatz, illite, vermiculite, pyrite, siderite, kaolinite and titanium minerals. Diagenesis had a profound impact on the studied sandstones, and the main processes and products identified were: replacement of feldspar by kaolinite and dolomite, quartz and feldspar overgrowth, compaction, dolomite cementation, detrital grains dissolution, ilitization, chloritization precipitation of oxides and precipitation of opaque minerals. The diagenetic evolution is inhibited or interrupted where the eodiagnenetic processes were intense, especially the cementation of dolomite. The interaction of the adjacent rocks had great importance in the diagenesis of the sandstones providing favorable chemistry for changes occurred and the circulation of interstitial fluids. The most common types of porosity found in the samples studied were intergranular, intragranular, moldic and contraction types. The porosity ranges from a minimum of 0.5 to a maximum of 30% of the total sample volume, being generated mainly by dissolution processes and blocked by the cementation process.