The Jurassic (Oxfordian) Smackover Formation in Little Cedar Creek Field, Alabama is composed of microbial thrombolitic buildups. Core description, petrography, SEM, and isotopic analysis were used to identify the succession of organisms, microbial carbonate deposition, and diagenesis that contributed to formation of these thrombolitic buildups. The microbial thrombolite reef facies in this study accounts for 38.5% of the total Smackover Formation. This facies was deposited 0.5 to 6.75 miles from the paleo-coastline. Today it is located 10,225 to 11,750 feet in the subsurface and contains buildups 26 to 50 feet thick. Four microfacies were defined: A- Black Renalcis-like layers, B- Digitate, C- Chaotic and D- Brown laminated centimeter-scale cycles. In most of the buildup, distinct layers of microbially precipitated micrite forms in succession. Microfacies A (Black Renalcis-like Layer) is the relatively least porous and permeable, acting as a potential barrier to flow in contrast to the other more porous microfacies.

Submitted by Irene Nascimento (irene.kessia@ufpe.br) on 2017-02-01T19:02:46Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Varela 2016.pdf: 15961564 bytes, checksum: 15e53847b4ed0cefc98e971288b00581 (MD5) / Made available in DSpace on 2017-02-01T19:02:46Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Varela 2016.pdf: 15961564 bytes, checksum: 15e53847b4ed0cefc98e971288b00581 (MD5) Previous issue date: 2016-08-22 / FADE/UFPE / A Bacia de Pernambuco representa uma das mais proeminentes fronteiras de exploração petrolífera da margem brasileira. O presente estudo trata da caracterização dos principais tipos de estruturas vulcânicas, assim como também da ocorrência de buildups carbonáticos que ocorrem na região offshore desta bacia. O estudo foi baseado na análise de 145 seções sísmicas 2D, migradas em tempo, que cobrem praticamente todo o Platô de Pernambuco. A metodologia utilizada se baseou na interpretação das principais sequências tectono-estratigráficas, na identificação e descrição dos corpos vulcânicos e das estruturas carbonáticas. Quanto às estruturas vulcânicas, os resultados permitiram a identificação de vulcões, soleiras, vents e sequências vulcanoclásticas, localizadas principalmente em associação com altos externos do platô. A interpretação das principais sequências estratigráficas sugere idade cretácea superior e cenozóica para os corpos vulcânicos encontrado neste trabalho. Isto permite propor que o evento magmático, cuja idade na região onshore é albiana, teria uma abrangência temporal maior na região distal da bacia. A dos buildups carbonáticos, permitiu classificar as estruturas encontradas em três tipos pricipais: recifes de margem de plataforma, patch reefs e plataformas carbonáticas isoladas. Essas estruturas estão inseridas em duas principais sequências deposicionais, no intervalo de estratos do pósrifte da bacia: Santoniano-Maastrichtiano e Paleoceno-Mioceno Médio. Os resultados obtidos permitiram uma importante contribuição ao conhecimento do arcabouço estratigráfico da Bacia de Pernambuco, bem como de sua evolução como parte do Rifte do Atlântico Sul. Além disso, os dados aqui apresentados permitirão uma melhor compreensão sobre os efeitos e produtos do magmatismo para o sistema petrolífero da bacia. Da mesma forma, a descrição das estruturas carbonáticas é importante porque a exemplo do que ocorre em outras bacias marginais brasileiras, a confirmação da ocorrência destas estruturas permitirá que estas possam ser investigadas como possíveis plays petrolíferos. / The Pernambuco Basin is one of the most prominent frontier of oil exploration in the brazilian margin. This study aims to characterize the major volcanic structures as well as the carbonate buildups of the offshore portion of this basin. A set of 145 2D multichannel seismic sections that cover the Pernambuco Plateau region are used to interpret the major tectono-stratigrafic sequences and to describe the volcanic and carbonate structures. For the volcanic structures, the results allowed the identification of volcanoes, sills, vent complexes and volcaniclastic sequences, located mainly in association with external plateau highs. The interpretation of the main stratigraphic sequences suggests Upper Cretaceous and Cenozoic age to the volcanic bodies found in this work. This allows us to propose that the magmatic event, which its age in the onshore region is Albian, would have had a greater time span in the distal region of this basin. For the carbonate buildups, this study allowed the classification of three different types of structure: the shelf margin reefs, patch reefs and isolated carbonate platforms. These structures are in two main depositional sequences, related to the post-rift phase: Santonian-Maastrichtian and Paleoceno-Middle Miocene. The findings presented in this report provide a better understanding about the Pernambuco Basin as well as the evolution of this basin as part of the South Atlantic Rift. Moreover, the results presented here can also be useful for the understanding of the magmatism in the basin petroleum system. In the same manner, the description of the carbonate buildups is important because as happens in others brazilian basins margins, the confirmation of the occurrence of these structures will allow them to be investigated as possible oil and gas play.

No description available.

The Cretaceous (Early Aptian) Shu'aiba Formation, Shaybah field, Saudi Arabia, is 60 km long by 12 km wide and 150 m thick, and is a giant carbonate reservoir. It formed on a regional carbonate ramp bordering an intrashelf basin. The succession consists of a composite sequence of seven high frequency sequences. Sequences 1 and 2 formed a deeper open platform of Palorbitolina-Lithocodium wackestone, with maximum flooding marked by planktic foram mudstone. Sequence 2 built relief over northern and southern blocks, separated by an intraplatform depression. They form the composite sequence TST. The remaining sequences developed a platform rimmed by rudist rudstone backed by rudist floatstone back-bank and lagoonal fine skeletal peloidal packstone; slope facies are fine skeletal fragmented packstone. Aggradational sequences 3 to 5 make up the composite sequence early highstand. Progradational sequences 6 and 7 are the composite sequence late highstand marking the deterioration of the Offneria rudist barrier and deposition of widespread lagoonal deposits, where accommodation may have been created by syn-depositional growth faulting that moved the northern block down. Shu'aiba deposition on the platform was terminated by long-term sea-level fall and karsting. The succession is dominated by approximately 400 k.y., 4th order sequences and 100 k.y. parasequences driven by long term eccentricity and short term eccentricity respectively, similar to the Pacific guyots of this age. This suggests that early Cretaceous climate may have been cooler and had small ice sheets and was not an ice-free greenhouse world. / Master of Science