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The sedimentary cyclicity analysis investigates the cyclic patterns and the different hierarchical orders of cyclicity in the stratigraphic record. The detection of cyclic depositional patterns is a key element of quantitative stratigraphy. It is often based on well-log data, which can be challenging due to the presence of superimposed cycles and nongeologic artifacts. We have developed an approach to assist the detection of sedimentary cyclicity in well-log signals based on a multiscale spectral analysis method. First, we apply variational mode decomposition to decompose the gamma-ray logs into band-limited subsignals, the intrinsic mode functions (IMFs), to investigate different orders of smoothness, signal-to-noise ratio, and the cyclicity embedded in the geologic record. Conventional time-domain analysis is carried out to understand the general trends in the IMFs, which enables us to better identify long-term cycles associated with transgressive-regressive (T-R) sequences. Then, by appropriately selecting a given IMF and extracting the instantaneous frequency (IF) and its mirrored version, we build a cyclicity log that can map expressive behavior change in the time-frequency domain. Because the IF is more sensitive to the signal variations, we could highlight the short-term cycles throughout the formation in detail. The detected short-term cycles are in agreement with the T-R sequence. We apply our method to the Albian carbonate succession of Macaé Group, Campos Basin, Brazil. We understand that our method can be a valuable tool for semiautomated detection of sedimentary cycles, assisting in the characterization of different hierarchical orders of cyclicity.

Igneous intrusions are important for the exploration and appraisal phases of an oilfield due to their impact on petroleum systems. Their presence can be associated with the generation, migration, accumulation, and entrapment of hydrocarbons. In particular, (1) sills with low permeability might form barriers to fluid flow and migration; (2) sills may re-use fracture networks, providing insights on fluid migration and interaction(s); (3) sills may influence source rock maturation, (4) sill-induced uplifting of overburden and faulting may generate traps, and (5) their geometric complexities enables the understanding of the interconnectedness of sill complexes, which is the focus of this study. Therefore, we provide a systematic characterization of sill geometries and their morphometric parameters. We used three-dimensional seismic data, calibrated with well logs, to interpret sills in the southern Campos Basin, Brazil. Throughout the Late Cretaceous until the Paleogene, sills intruded into the Cretaceous to the Eocene post-salt sedimentary sequence, including shallow-platform carbonates, transgressive marls, and shales. A morphometric analysis assisted by seismic attributes allowed the geometric characterization of sills, namely: (1) saucer-shaped; (2) slightly saucer-shaped; (3) climbing saucer-shaped; (4) transgressive; and (5) rough layer-parallel. The documented sills comprise a wide range of sizes (0.43–14.35 km2) that increase with depth (up to 3.18 km), extend vertically from 0.06 to 0.23 km, and vary from low (1.82–3.31°) to high dip (6.05–15.74°). The sill complex area extends over 67.35 km2. This study suggests that a thorough characterization of sill intrusions may have a substantial influence on the prediction of other igneous occurrences. The mapped sills might have implications not just on the acoustically similar shallow platform Albian carbonates of the Macae Group, but may also provide insightful geometric constraints on the Brazilian pre-salt igneous intrusions.

Seismic resolution plays an important role in the delineation of structural and stratigraphic features. The resolution improvement directly affects the seismic attributes and, consequently, the interpretation of a given feature. However, the broadband data do not necessarily provide the best insight for seismic attribute evaluation. Particularly, geologic discontinuities, such as karsts, faults, and fractures, can have different seismic expressions according to their intrinsic scales, and, therefore, they are better illuminated in a given frequency range. To extract dissimilar characteristics in different frequency bands, we have combined a recently developed spectral enhancement method based on differential resolution (DR) and similarity attributes. The DR algorithm is simultaneously used for frequency enhancement and acting as a pseudofilter, allowing us to compute similarity attributes at different frequency bands. The similarity computation follows the reflector dip of each DR subband and adjusts its analysis window accordingly to the dominant frequency within the subbands. Then, the subband similarities are combined in the red-green-blue-alpha color space, allowing a more detailed view of the geology under investigation. Although more expensive in terms of processing time because of all the steps needed for each subband, the proposed strategy proved to be a great improvement over the conventional procedure of detecting and delineating discontinuities in fault and karst structures when treating seismic data from an offshore carbonate field in Campos Basin, Brazil.

Orientador: Alexandre Campane Vidal Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Geociências Resumo: A caracterização geológica de reservatórios tem-se tornado cada vez mais desafiante. Com o rápido avanço de processos e métodos para a caracterização de reservatórios também surgem soluções e propostas para os mais variados problemas. Esses problemas e desafios incluem a interpretação e caracterização de estruturas pós-deposicionais para a sua representação através de modelos geológicos tridimensionais. Exemplos dessas estruturas são intrusões ígneas e as estruturas internas e externas associadas, fraturas de escala sub-sísmica, e feições relacionadas a carste. Na seção pós-sal da Bacia de Campos e no pré-sal da Bacia de Santos são aplicadas técnicas para identificar e caracterizar estruturas pós-deposicionais. O principal propósito deste trabalho é contribuir para o aumento do conhecimento em caracterização de reservatórios e para o impacto que as estruturas pós-deposicionais podem ter nos sistemas petrolíferos, particularmente nos reservatórios. Os dados utilizados são constituídos por duas aquisições sísmicas e dois conjuntos de poços das bacias de Campos e Santos. A caracterização de rochas ígneas intrusivas, na Bacia de Campos, se baseou na análise morfométrica que permitiu caracterizar as intrusões, e entender a relação que existe com as estruturas associadas que ocorrem em torno das intrusões. Com base na análise quantitativa das soleiras foi possível inferir os limites em que as geometrias ocorrem, assim como quais as estruturas mais prováveis a serem geradas. Essas estruturas de soleiras magmáticas são caracterizadas por dobras forçadas (estruturas externas), degraus, pontes, e dedos (estruturas internas). Em particular, neste trabalho, concluí-se que provavelmente existem outros fatores importantes para o controlo da formação das dobras forçadas, uma vez que nem todas as vezes que o rácio indicador, a partir do qual a rocha hospedeira é dobrada, está dentro do intervalo de interesse se forma uma dobra forçada. Em relação à caracterização das redes de fraturas e feições relacionadas a carste, na Bacia de Santos, foi construído um modelo de dupla-porosidade, dupla-permeabilidade e utilizou-se uma abordagem de multi-atributos sísmicos para detectar e caracterizar as anomalias de alta amplitude que possivelmente estariam associadas a feições cársticas. Na fase da modelagem, foram distribuídos atributos geométricos de fratura na malha geológica para quantificar a porosidade e permeabilidade equivalente de fratura, e para melhorar a previsão do comportamento estático do reservatório em regiões fraturadas. A fase da modelagem ajudou na estimativa do campo de tensões tectónico local, que também foi importante para a previsão e localização de regiões potencialmente fraturadas Abstract: The geological characterization of reservoirs is becoming very challenging. The fast-paced evolution of processes and methods for the reservoir characterization have been giving rise to different solutions and proposals for the most varied issues in geological modeling. These issues and challenges include the interpretation of post-depositional structures and their representation in three-dimensional geological models. Examples of these structures are igneous intrusions and related internal and external structures, sub-seismic fractures, and karst-related features. In the post-salt of Campos Basin and in the pre-salt of Santos Basin we applied techniques to identify and characterize the post-depositional structures. The main objective of this work is to contribute to the scientific knowledge in the reservoir characterization and to the impact that such structures may have on the petroleum systems, particularly in the reservoirs. The dataset used in this work include two three-dimensional seismic surveys and two sets of borehole data, both from Campos and Santos Basins. The characterization of the intrusive igneous rocks in the Campos Basin was based on the morphometric analysis that allowed the characterization of the intrusions and to understand their relation with the structures occurring within and around the intrusions. Based on the quantitative analysis of sills we were able to infer at which ranges the sill geometries occur in terms of area and length for example. In addition to which external structures are more likely to be generated according to the different sill geometries. Examples of these structures may be, for example, forced folds (external structures), steps, bridges, and fingers (internal structures). In particular, in this work, we found that probably there are other factors that control of forced folds, since not always that the indicator ratio, from which country rock is flexed or folded, are within the interval of interest it forms a forced fold. Regarding the characterization of the fracture networks and karst-related features, in the Santos Basin, we built dual-porosity, dual-permeability model and used a seismic multi-attribute approach to detect and characterize the high-amplitude anomalies possibly associated with karst-related features. In the modeling stage, we distributed the key fracture geometrical attributes in the geological grid, to quantify the fracture equivalent porosity and permeability, and to enhance the prediction of the reservoir static behavior in fractured regions. The modeling stage helped to predict the local tectonic stress field, which is key to predict and locate potential fractured regions Doutorado Geologia e Recursos Naturais Doutor em Ciências CAPES

Reservoir static modelling plays a fundamental role in the evaluation phase of a petroleum field. Integrated modelling allows a better understanding of how the local geology and depositional systems are related through the distribution of facies and petrophysical properties within the reservoir. In this study, geological static models of the siliciclastic Carapebus Formation of Campos Basin were built using subsurface data. The applied methodology was divided into five phases: (1) establishment of a conceptual model, (2) building of a structural model, (3) generation of 100 realizations of lithofacies using sequential indicator simulation, (4) generation of 100 realizations of porosity and permeability using sequential Gaussian simulation, and (5) validation of models by targeting both statistical and geological consistency. The obtained models are consistent and honor the conditioning data. A lithofacies constraint is crucial to better characterize the petrophysical properties distribution of the reservoir. A Dykstra-Parsons coefficient of V=0.52 characterizes this reservoir as moderately homogeneous.