Thesis (M. Phil.)--University of Hong Kong, 1999. / Includes bibliographical references (leaves 125-128).

O Campo de Miranga, localizado no Compartimento Central da Bacia do Recôncavo, é um importante produtor de óleo e gás. As rochas reservatório portadoras de hidrocarbonetos aqui apresentadas constituem-se de corpos arenosos gerados por fluxos gravitacionais subaquosos intercalados por folhelhos e pertencem a Formação Maracangalha (depositada no Cretáceo Inferior). Com a descrição de 775 m de testemunhos, definiu-se 8 fácies deposicionais e 6 deformacionais para o intervalo estudado. O agrupamento de fácies em conjuntos que apresentam feições estruturais e genéticas similares permitiu a proposição de Associações de Fácies cujas interpretações são: AF1 - lobos turbidíticos distais; AF2 - canais e/ou lobos turbidíticos arenosos; AF3 - franjas de sistemas turbidíticos conglomeráticos; AF4 - deslizamentos ou regiões proximais de escorregamentos; AF5 - porções mais deformadas de corpos de deslizamentos a escorregamentos; AF6 - escorregamentos altamente móveis, plásticos a fluxos de detritos. Foi definido um datum na porção intermediária da formação constituído por uma espessa seção pelítica. Depósitos distais da AF6 dominam a porção basal do intervalo estudado e são sucedidos verticalmente (em direção ao datum) por intercalações entre turbiditos (AF2) e escorregamentos (AF5). Imediatamente acima do datum ocorrem níveis conglomeráticos (AF3) que são sucedidos verticalmente por um domínio onde se intercalam deslizamentos (AF4), escorregamentos (AF5) e turbiditos (AF2), definindose uma grande sucessão progradacional para a Formação Maracangalha na área estudada. O disparo desses fluxos provavelmente associa-se a movimentação de falhas durante estágio sin-rifte responsáveis por intensa sismicidade e remobilização de frentes deltaicas. Um mecanismo auxiliar associa-se ao intenso diapirismo argilocinético. A conectividade lateral rastreada em seções sísmicas é baixa e os melhores reservatórios do campo são os representantes da AF4 e AF2. Por critérios preditivos é possível determinar os intervalos mais propícios para a ocorrência desses corpos. / The Miranga Field, which is located in the Central Compartment of Reconcavo Basin, is an important oil and gas producer. The bearing hydrocarbon reservoirs presented here are composed of sand bodies generated by subaqueous gravity flows inserted between shales, belonging to the Maracangalha Formation (deposited during the Lower Cretaceous). Through the description of 775 m well cores, 8 depositional and 6 deformational facies were defined for the interval studied. These facies were grouped together according to structural and genetic characteristics making it possible to define Facies Associations with the following interpretations: AF1 - distal portions of turbidite lobes; AF2 - channels and/or sandy turbidite lobes; AF3 - borders of conglomeratic turbidite systems; AF4 - slides or proximal parts of slumps; AF5 - distal portions of the slides bodies or slumps; AF6 - highly mobile slumps to debris flows. A datum was chosen in the middle portion of Maracangalha Formation which consists of thick layer of shale. Distal deposits (AF6) dominate the basal portion of interval studied and they are succeeded vertically (toward to the datum) by layers interbedded between turbidites (AF2) and slump deposits (AF5). Immediately above the datum, conglomeratic intervals (AF3) occur and they are succeeded vertically by layers interbedded between slides (AF4), slumps (AF5) and turbidites (AF2), defining a great progradational succession to Maracangalha Formation in the studied area. Trigger mechanisms responsible for the genesis of gravitational flows are probably associated with faults activities during the syn-rift stage which led to intense seismic activity and caused the destabilization of sediments in delta fronts. An alternative cause for triggering may have been intense diapiric shale movements. The lateral connectivity traced in seismic sections is low and the sand bodies that should constitute the best reservoirs in this field belong to AF4 and AF2 categories. It is possible to determine the most favorable intervals for the occurrence of these sand bodies using predictive criteria.

O Campo de Miranga, localizado no Compartimento Central da Bacia do Recôncavo, é um importante produtor de óleo e gás. As rochas reservatório portadoras de hidrocarbonetos aqui apresentadas constituem-se de corpos arenosos gerados por fluxos gravitacionais subaquosos intercalados por folhelhos e pertencem a Formação Maracangalha (depositada no Cretáceo Inferior). Com a descrição de 775 m de testemunhos, definiu-se 8 fácies deposicionais e 6 deformacionais para o intervalo estudado. O agrupamento de fácies em conjuntos que apresentam feições estruturais e genéticas similares permitiu a proposição de Associações de Fácies cujas interpretações são: AF1 - lobos turbidíticos distais; AF2 - canais e/ou lobos turbidíticos arenosos; AF3 - franjas de sistemas turbidíticos conglomeráticos; AF4 - deslizamentos ou regiões proximais de escorregamentos; AF5 - porções mais deformadas de corpos de deslizamentos a escorregamentos; AF6 - escorregamentos altamente móveis, plásticos a fluxos de detritos. Foi definido um datum na porção intermediária da formação constituído por uma espessa seção pelítica. Depósitos distais da AF6 dominam a porção basal do intervalo estudado e são sucedidos verticalmente (em direção ao datum) por intercalações entre turbiditos (AF2) e escorregamentos (AF5). Imediatamente acima do datum ocorrem níveis conglomeráticos (AF3) que são sucedidos verticalmente por um domínio onde se intercalam deslizamentos (AF4), escorregamentos (AF5) e turbiditos (AF2), definindose uma grande sucessão progradacional para a Formação Maracangalha na área estudada. O disparo desses fluxos provavelmente associa-se a movimentação de falhas durante estágio sin-rifte responsáveis por intensa sismicidade e remobilização de frentes deltaicas. Um mecanismo auxiliar associa-se ao intenso diapirismo argilocinético. A conectividade lateral rastreada em seções sísmicas é baixa e os melhores reservatórios do campo são os representantes da AF4 e AF2. Por critérios preditivos é possível determinar os intervalos mais propícios para a ocorrência desses corpos. / The Miranga Field, which is located in the Central Compartment of Reconcavo Basin, is an important oil and gas producer. The bearing hydrocarbon reservoirs presented here are composed of sand bodies generated by subaqueous gravity flows inserted between shales, belonging to the Maracangalha Formation (deposited during the Lower Cretaceous). Through the description of 775 m well cores, 8 depositional and 6 deformational facies were defined for the interval studied. These facies were grouped together according to structural and genetic characteristics making it possible to define Facies Associations with the following interpretations: AF1 - distal portions of turbidite lobes; AF2 - channels and/or sandy turbidite lobes; AF3 - borders of conglomeratic turbidite systems; AF4 - slides or proximal parts of slumps; AF5 - distal portions of the slides bodies or slumps; AF6 - highly mobile slumps to debris flows. A datum was chosen in the middle portion of Maracangalha Formation which consists of thick layer of shale. Distal deposits (AF6) dominate the basal portion of interval studied and they are succeeded vertically (toward to the datum) by layers interbedded between turbidites (AF2) and slump deposits (AF5). Immediately above the datum, conglomeratic intervals (AF3) occur and they are succeeded vertically by layers interbedded between slides (AF4), slumps (AF5) and turbidites (AF2), defining a great progradational succession to Maracangalha Formation in the studied area. Trigger mechanisms responsible for the genesis of gravitational flows are probably associated with faults activities during the syn-rift stage which led to intense seismic activity and caused the destabilization of sediments in delta fronts. An alternative cause for triggering may have been intense diapiric shale movements. The lateral connectivity traced in seismic sections is low and the sand bodies that should constitute the best reservoirs in this field belong to AF4 and AF2 categories. It is possible to determine the most favorable intervals for the occurrence of these sand bodies using predictive criteria.

O Campo de Miranga, localizado no Compartimento Central da Bacia do Recôncavo, é um importante produtor de óleo e gás. As rochas reservatório portadoras de hidrocarbonetos aqui apresentadas constituem-se de corpos arenosos gerados por fluxos gravitacionais subaquosos intercalados por folhelhos e pertencem a Formação Maracangalha (depositada no Cretáceo Inferior). Com a descrição de 775 m de testemunhos, definiu-se 8 fácies deposicionais e 6 deformacionais para o intervalo estudado. O agrupamento de fácies em conjuntos que apresentam feições estruturais e genéticas similares permitiu a proposição de Associações de Fácies cujas interpretações são: AF1 - lobos turbidíticos distais; AF2 - canais e/ou lobos turbidíticos arenosos; AF3 - franjas de sistemas turbidíticos conglomeráticos; AF4 - deslizamentos ou regiões proximais de escorregamentos; AF5 - porções mais deformadas de corpos de deslizamentos a escorregamentos; AF6 - escorregamentos altamente móveis, plásticos a fluxos de detritos. Foi definido um datum na porção intermediária da formação constituído por uma espessa seção pelítica. Depósitos distais da AF6 dominam a porção basal do intervalo estudado e são sucedidos verticalmente (em direção ao datum) por intercalações entre turbiditos (AF2) e escorregamentos (AF5). Imediatamente acima do datum ocorrem níveis conglomeráticos (AF3) que são sucedidos verticalmente por um domínio onde se intercalam deslizamentos (AF4), escorregamentos (AF5) e turbiditos (AF2), definindose uma grande sucessão progradacional para a Formação Maracangalha na área estudada. O disparo desses fluxos provavelmente associa-se a movimentação de falhas durante estágio sin-rifte responsáveis por intensa sismicidade e remobilização de frentes deltaicas. Um mecanismo auxiliar associa-se ao intenso diapirismo argilocinético. A conectividade lateral rastreada em seções sísmicas é baixa e os melhores reservatórios do campo são os representantes da AF4 e AF2. Por critérios preditivos é possível determinar os intervalos mais propícios para a ocorrência desses corpos. / The Miranga Field, which is located in the Central Compartment of Reconcavo Basin, is an important oil and gas producer. The bearing hydrocarbon reservoirs presented here are composed of sand bodies generated by subaqueous gravity flows inserted between shales, belonging to the Maracangalha Formation (deposited during the Lower Cretaceous). Through the description of 775 m well cores, 8 depositional and 6 deformational facies were defined for the interval studied. These facies were grouped together according to structural and genetic characteristics making it possible to define Facies Associations with the following interpretations: AF1 - distal portions of turbidite lobes; AF2 - channels and/or sandy turbidite lobes; AF3 - borders of conglomeratic turbidite systems; AF4 - slides or proximal parts of slumps; AF5 - distal portions of the slides bodies or slumps; AF6 - highly mobile slumps to debris flows. A datum was chosen in the middle portion of Maracangalha Formation which consists of thick layer of shale. Distal deposits (AF6) dominate the basal portion of interval studied and they are succeeded vertically (toward to the datum) by layers interbedded between turbidites (AF2) and slump deposits (AF5). Immediately above the datum, conglomeratic intervals (AF3) occur and they are succeeded vertically by layers interbedded between slides (AF4), slumps (AF5) and turbidites (AF2), defining a great progradational succession to Maracangalha Formation in the studied area. Trigger mechanisms responsible for the genesis of gravitational flows are probably associated with faults activities during the syn-rift stage which led to intense seismic activity and caused the destabilization of sediments in delta fronts. An alternative cause for triggering may have been intense diapiric shale movements. The lateral connectivity traced in seismic sections is low and the sand bodies that should constitute the best reservoirs in this field belong to AF4 and AF2 categories. It is possible to determine the most favorable intervals for the occurrence of these sand bodies using predictive criteria.

No description available.

Lower Triassic strata in the Wellington Flat and Tully cores reflect a lateral transition from shallow water strata (Wellington Flats core) to strata that indicate deposition on a relatively more distal, storm-dominated ramp (Tully core). The Sinbad Member, along with the upper part of the underlying Black Dragon Member and the lower part of the overlying Torrey Member (Moenkopi Formation), are composed of ten carbonate, siliciclastic and mixed carbonate/siliciclastic facies deposited on a west-facing ramp/shelf that reached maximum flooding during Smithian time. Individual beds and facies display a large degree of lateral homogeneity and regional persistence in the study area. The Wellington Flats core contains the three units characteristic of outcropping Sinbad Limestone: a basal skeletal unit, a middle peloidal unit, and an upper, oolitic dolomite unit. The more offshore Tully core is composed of skeletal grainstone, with fewer shallow-water carbonate and siliciclastic deposits. Discontinuity surfaces (hardgrounds, firmgrounds, and change surfaces) are common and indicate that sedimentation was punctuated by short-lived hiatuses accompanied by cementation, scour, and/or encrustation of the sediment-water interface. The Black Dragon, Sinbad, and lower Torrey Members represent at least one 3rd-order depositional sequence bounded below by the Tr-1 unconformity and above by lowstand deposits in the middle Torrey Member. Amalgamated fluvial channels in the middle of the Black Dragon Member may represent an additional 3rd-order sequence boundary that separates a Greisbachian sequence (lower Black Dragon Member) from the Smithian sequence (upper Black Dragon through lower Torrey members), but this is unsubstantiated by biostratigraphic data at present. Diagenesis is strongly controlled by facies. Diagenetic elements include marine fibrous calcite cements, micritized grains, compaction, dissolution and neomorphism of aragonite grains, meteoric cements, pressure dissolution, and dolomitization. The paragenetic sequence progresses from marine to meteoric to burial. Marine and meteoric cements occlude much of the depositional porosity, which ranges from 0 to 10 % in the sample interval. The best reservoir qualities in core (1.0 md) occur in grainstones and quartz-siltstones. Although its relative thinness precludes it from being a major producer, the Sinbad Limestone Member of the Moenkopi Formation bears potential for modest future oil production.

Philosophiae Doctor - PhD / Integrated approaches in the study of petroleum exploration are increasingly becoming significant in recent times and have yielded much better result as oil exploration is a combination of different related topics. The production capacity in hydrocarbon exploration has been the major concern for oil and gas industries. In the present work an integrated approach was made with seismic, well logs and biostratigraphy for predicting the depositional environment and to understand the heterogeneity within the reservoirs belonging to Valanginian (Early Cretaceous) age of Gamtoos Basin, Offshore South Africa. Objectively, the integrated work was mainly based on seismic stratigraphy (seismic sequence and seismic facie analysis) for interpretation of the depositional environments with combination of microfossil biostratigraphic inputs. The biostratigraphic study provides evidences of paleo depth from benthic foraminifera and information about bottom condition within the sedimentary basin, changing of depositional depth during gradual basinal fill during the Valanginian time. The petrophysical characterization of the reservoir succession was based on formation evaluation studies using well logs to investigate the hydrocarbon potential of the reservoir across Valanginian depositional sequence. Further, the static modeling from 2D-seismic data interpreted to a geological map to 3D-numerical modeling by stochastic model to quantify the evaluation of uncertainty for accurate characterisation of the reservoir sandstones and to provide better understanding of the spatial distribution of the discrete and continuous Petrophysical properties within the study area.

The present day Bahamian archipelago was deposited during sea level highstands when carbonate production was high enough to overfill accommodation space. This study unravels the complex stratigraphy and heterogeneity created by island accretion during and across the most recent Pleistocene highstands (MIS 5e, 9, and 11) using New Providence Island as a case study. Building upon the work of previous researchers, field based mapping was completed to understand the spatial relationships between ages, environments of deposition, and grainstone compositions across the island. Using the vertical and lateral relationships gained from detailed mapping, the depositional history of New Providence Island has been reconstructed for the Pleistocene MIS 5e, 9, and 11 sea level highstands. To map all of the environments of deposition, detailed criteria were created to recognize each environment observed on New Providence Island. Ages were estimated with field techniques and confirmed with dating done in previous studies and in this study, including both U-series techniques and amino acid racemization (AAR). Hand samples and short (< 1 m) cores were collected in the field and were used for petrographic analyses in the laboratory as well as whole rock AAR sampling for age determination. Detailed outcrop drawings were created, showing the lateral and vertical relationships of environments within outcrops. Meanwhile, maps and cross-sections were drafted to better understand island-wide relationships of environments, ages, and compositions. Based on age maps, New Providence formed by vertical and lateral accretion during the last three Pleistocene highstands (MIS 5e, 9, and 11), with a majority of deposition occurring during the most recent interglacial (MIS 5e, ~125 ka). Environment of deposition mapping revealed that island deposition occurred within shallow marine to eolian environments. Because of the abundance of MIS 5e deposits, the sedimentological complexity of an individual highstand (MIS 5e) reveals sub-orbital scale sea level changes. With mid-highstand sea level fluctuations apparent within the MIS 5e deposits on New Providence Island, a high level of lithofacies complexity could be expected within any individual sea level highstand. This study documents the complex vertical and lateral facies patterns associated with island building between and within sea level highstands.

The purpose of this study is to identify and analyze the geochemical facies of the Hushpuckney Shale using XRF scanning data and the bioturbation indices, which will contribute to a better understanding of the biogeochemical environment prevalent during the deposition of the Hushpuckney Shale. The Hushpuckney Shale Member of the Swope Formation (Kasimovian Stage) preserved in KGS Spencer core 2 - 6, consists of a black shale submember overlain by bioturbated gray shale. Millimeter-scale core description and analysis of XRF scanning data enables identification of geochemical facies within the study core and contributes to understanding the environment of shale deposition. The XRF spectrometer produces X-ray image of the core and abundance values of selected major and trace elements, including iron (Fe), calcium (Ca), sulfur (S), molybdenum (Mo), zinc (Zn), vanadium (V), chromium (Cr), copper (Cu), nickel (Ni), titanium (Ti), zircon (Zr), potassium (K) and phosphorous (P). Canfield and Thamdrup's (2009) classification of geochemical environments is used to recognize oxic/aerobic, manganous-nitrogenous, ferruginous and sulfidic facies within the black shale submember. A modification of Droser and Bottjer's (1986) semi-quantitative field classification of bioturbation is used to identify facies variations within the gray shale submember. Abundance of apatite nodules and lamina in the black shale submember of the study core suggest that black shale sediments accumulated slowly in a sediment-starved basin. A high abundance of sulfide-scavenged elements, including Mo, Zn, V, Ni and Cr, identifies the sulfidic facies in the black shale submember, and indicates deposition in an oxygen-depleted environment with a high concentration of hydrogen sulfide. The overlying ferruginous facies has lower abundances of sulfide-scavenged elements and lacks cryptic Fe-laminations. The uppermost black shale submember facies, the manganous-nitrogenous facies, has cryptic Fe laminations and a relatively high P/Ca ratio. Abundance of cryptic iron laminations and apatite nodules and lamina indicates the syngenetic deposition of iron and phosphate due to Fe-P coupling mechanism. The gray shale submember is burrowed, indicating deposition under oxygenated conditions. Bioturbation indices reveal the variations in the intensity and nature of burrows within the gray shale, which corresponds to the changes in the depositional environment that may be related to the rise and fall of sea-level.

Sedimentation rates in sediment cores from Lavaca Bay have been high within the last 1-2 decays within the central portion of the bay, with small fluctuations from river input. Lavaca Bay is a broad, flat, and shallow (<3 m) microtidal estuary within the upper Matagorda Bay system. Marine derived sediment enters the system from Matagorda Bay, while two major rivers (Lavaca & Navidad) supply the majority of terrestrially derived sediment. With continuous sediment supply the bay showed no bathymetric change until the introduction of the shipping channel. Processes that potentially lead to sediment transport and resuspension within the bay include wind driven wave resuspension, storm surges, wind driven blowouts, and river flooding. These processes were assessed using X-radiographs, grain size profiles, and 210Pb and 137Cs geochronology of sediment diver cores. In six cores the upper 10 cm of the seabed has been physically mixed, where as the rest showed a continuous sediment accumulation rate between 0.84-1.22 cm/yr. Sidescan sonar and subbottom chirp sonar data coupled with sedimentological core and grab samples were used to map the location and delineate the sedimentary facies within the estuarine system in depths >1 m. Five sedimentary facies were identified in Lavaca Bay and adjacent bays, they are: 1) estuarine mud; 2) fluvial sand; 3) beach sand; 4) bay mouth sand; and 5) oyster biofacies. Of the five facies, Lavaca Bay consists primarily of estuarine mud (68%). Pre-Hurricane and post-Hurricane Claudette cores were obtained to observe the impact to the sedimentary processes. The north and south Lavaca Bay were eroded by 10 cm and 2-3 cm, respectively. Cox Bay and Keller Bay saw a net deposition of 2-3 cm.