Produção Científica
Artigo em Revista
| Cycle-consistent convolutional neural network for seismic impedance inversion: An application for high-resolution characterization of turbidites reservoirs. Acoustic impedance is a subsurface layer parameter crucial for reservoir characterization due to its relationship with petrophysical properties. Seismic impedance inversion is the routine conventionally used to calculate the acoustic impedance in 3D seismic datasets. Deep learning-based seismic inversion has recently gained attention due to its capacity to establish non-linear relationships between observed data and model parameters, producing robust acoustic impedance estimates. We employed a 1D cycle-consistent convolutional neural network (CNN) to perform the high-resolution seismic impedance inversion in the turbidite reservoirs of the Jubarte Field, Campos Basin, Brazil. The neural network was trained using geostatistics-based pseudo-wells with high pattern variability. Before applying the trained CNN, we performed the seismic data pre-conditioning to remove high and low-frequency noises affecting the data amplitudes, making the dataset more suitable for seismic impedance inversion. Our results show that the deep learning-based inversion produced a high-resolution estimate, allowing an accurate internal characterization of turbidite lobes. Quantitatively, the estimated average correlation coefficient in the eight wells evaluated in this study was 0.78. We observed that the pre-conditioning step was important for this application since the 1D architecture utilized could not deal properly with the noise as it disregards lateral connections. 2D and 3D networks may address this issue. Compared to the open-loop CNN and the traditional model-based inversion, the cycle-consistent network produced the best estimate, with good lateral continuity, vertical resolution, and correlation. We support that modern deep-learning architectures like the one presented can be efficiently integrated into reservoir characterization workflows for enhancing subsurface assessment. |
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Artigo em Revista
| Magneto-polariton: Strong tilted magnetic field applied on confined electron gas in a wide Ga(1-x)Al(x)As quantum well The coupling of an electron gas confined by a harmonic potential and submitted to a strong magnetic field tilted in relation to the confining direction creates an excitation called here magneto-polariton. This work describes the origin of this excitation and calculates the energy eigenvalues for different tilted angles. It presents the reasons leading to the crossings and repulsions of the energy bands, the degeneracy of the states, the way the Fermi levels change with the magnetic field, the influence of an external electric field, and how the Hall resistance plateaus change with the change in the tilted angle. |
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Artigo em Revista
| An integrated 3D digital model of stratigraphy, petrophysics and karstified fracture network for the Cristal Cave, NE-Brazil. Digital Outcrop Models (DOMs) are virtual representations of geological features. Although DOMs are widely used tools in geosciences, their integration with other datasets remains relatively underexplored. We combined a DOM, derived from a photogrammetric survey of a carbonate sequence, with lithostratigraphic, petrophysical (porosity, permeability and uniaxial compressive strength), fracture distribution, and karst dissolution information to compose a single integrated three-dimensional digital model. The study site is one of the entrances of the Cristal Cave (Sao Francisco Craton, Northeastern Brazil), which has been used as a structural and diagenetic outcrop analog for the Brazilian pre-salt carbonate reservoirs. Data from fracture distributions, measured on the exposed surfaces of the cave, were used to build a Discrete Fracture Network, based on the solution of the stereology inverse problem. Fracture apertures were then modified to generate different scenarios of karstification, thus composing Discrete Fracture and Karst Networks. This integrative approach brought relevant insights into the cave development due to dissolution along fracture clusters. Our methodology offers better geological data handling to build static models to be used in a fluid flow modeling environment, contributing to bridge the gap between geophysics/geology and engineering approaches. |
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Artigo em Revista
| First-break prediction in 3-D land seismic data using the dynamic time warping algorithm This paper presents a new methodology to assist geophysicists in determining the first-break event in a 3-D seismic data set using the well-known technique called dynamic time warping algorithm (DTW), which is usually used to find the optimal alignment between two time-series. We used the optimal path from the cost matrix to identify the first break in the seismogram using a few picks (seeds) made by an interpreter as a reference to perform this task. Furthermore, the data were pre-conditioned by the topographic and linear moveout to improve the method’s accuracy. To demonstrate the technique’s robustness, first, we applied the methodology in a synthetic seismic data. After demonstrating the efficiency of the algorithm, we applied the aforementioned methodology in the Polo-Miranga 3-D seismic cube located in the Reconcavo sedimentary basin, Bahia-Brazil, and in the seismic data acquired from the Blackfoot field in Alberta, Canada. The high-quality results showed consistency in determining the first break in all ranges of offsets, demonstrating an alternative way to accelerate this seismic processing step. Furthermore, we compared the results obtained by the proposed methodology with an algorithm based on comparing the short-time averages with long-time averages. Finally, we performed the static correction calculation to ensure that the time distortion resulting from the terrain and the low-velocity layer was mitigated in shoot gathers and in the stacked section. |
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Material Didático
| Princípios da Geofísica - Eletromagnetismo Em primeira edição, o livro é destinado a estudantes, professores e pesquisadores das áreas das geociências interessados nas aplicações do método eletromagnético nas escalas global ou local. 0s princípios teóricos básicos e fundamentais do eletromagnetismo na geofísica, são descrito através das equações da física clássica nos domínios tempo-espaço, e nos respectivos domínios espectrais. O livro é formado de 5 densos capítulos que abrangem desde uma introdução sobre a história da geofísica, conceitos básicos sobre eletromagnetismo, e continuando com os métodos da eletrorresistividade (ER), da polarização induzida (IP) e do potencial espontâneo (SP). Ao início dos capítulos o autor apresenta um breve histórico sobre o método geofísico em destaque, e ao final um resumo geral, seguido de exercícios teóricos e computacionais. Adicionalmente o livro apresenta 6 apêndices que apresentam detalhamentos envolvendo: operações de cálculo e análise dimensional, transformada de Fourier, conceitos, métodos de ajustes de curvas e conceitos sobre a solução do problema direto o inverso, protocolos sobre planejamento de trabalho de campo, orientações para projetos de iniciação científica e trabalho de final de curso, além de vários programas em linguagem Matlab para a modelagem e inversão sobre os métodos ER, IP, e SP. |
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Artigo em Revista
| Prediction of stress components using the Beltrami-Michell method This paper describes some numerical experiments for stress modeling in the zone around a reservoir in a sedi-mentary basin, where oil and gas exploration is real or potential. We aim to map mainly low- and high-pressure zones, under the principle that they act as push-and-pull natural pumps for fluid accumulation. The necessary data for practical work is based on seismic data, as a post-migration process with the knowledge of velocities of the P and S waves, and the density information. The computation is designed for simple geometries to represent a reservoir geology, and it is addressed as a boundary value problem (BVP) involving the Beltrami-Michell’s partial differential equation with Dirichlet conditions. The method employed was the Green’s function expressed by Fourier series for the solution of the BVP, where the boundary conditions are given by the stress components along the boundary of the target volume. The first stress invariant controls the elastic mechanical behavior of the subsoil; therefore, once the distribution of rock pressure is obtained, and the boundary conditions are defined, solving the BVP allows the calculation of the stress components distribution (normal and tangential) within a separate target volume for details. The relationship between rock pressure and stress components is established by the Beltrami-Michell problem, which takes the form of a Poisson’s equation. The proposed method was applied in a more complex target zone present in the Marmousi model, which contains reservoirs within regions of interest, expanding to more realistic complex problems. |
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Artigo em Revista
| Long memory and trend in time series of precipitation in Mozambique Many climate studies in Mozambique have clearly identified signals of climate change, especially changes in the extreme temperatures. Regarding precipitation, there is still a gap on the knowledge of how it is behaving due to both internal and external factors in the climate system. In this study, we have investigated the existence of long-term correlations and trend in time series of precipitation. Two databases were used for this purpose: in situ observations along the period of 1960–2020 and the Climate Hazards group InfraRed Precipitation with Stations (CHIRPS) dataset, along the period from 1981 to 2021. We have applied the rescaled-range analysis and the detrended fluctuation analysis for long memory investigation, and the linear regression and Mann-Kendall methods for trend analysis. Results have shown the existence of long memory in precipitation in most parts of Mozambique, being stronger in the southern and central regions and weakening toward the north of the country. On the other hand, significant trend signals of precipitation were detected in some isolated areas of Mozambique, presenting an increase in some regions such as the southern part of Manica and eastern of Inhambane provinces and a decrease in other regions such as the coastal areas of Zambezia and Nampula. These findings indicate that the probability of a random occurrence of precipitation is minimal, and the observed trends are likely to continue for a long period in future. Dry land agriculture should be prepared to adapt to new precipitation regime in the regions mentioned hereof |
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Material Didático
| MANUAL DE INTERPRETAÇÃO DE FRATURAS EM MODELOS DIGITAIS DE AFLORAMENTO UTILIZANDO O SOFTWARE CLOUDCOMPARE O processo de investigação geocientífica comumente inclui o estudo de afloramentos relevantes, nos quais é possível observar, medir e amostrar feições de interesse do geocientista. Apesar da relevância do estudo de afloramentos, certas condições podem inviabilizar ou dificultar uma visita presencial a uma área de estudos, a exemplo de precariedades de acessibilidade e segurança ou altos custos com deslocamento e logística. Nesse contexto, os Modelos Digitais de Afloramento (Digital Outcrop Models, em inglês) mostram-se como um recurso importante, sendo uma representação fiel do campo e que pode ser acessada em laboratório. O conceito de DOM refere-se a superfícies 3D ou nuvens de pontos (Jones et al., 2008) que remontam afloramentos geológicos de forma digital, frequentemente em alta resolução (Bellian et al., 2005). Os modelos gerados podem ser texturizados a partir de fotografias do afloramento, no caso das superfícies 3D, ou colorizados, no caso das nuvens de pontos (Bistacchi et al., 2022). Via de regra, os DOMs podem ser construídos a partir de duas ferramentas principais, as quais são o LIDAR (Bellian et al., 2005; Rotevatn et al., 2009; Furtado et al., 2022) e a fotogrametria (Triantafyllou et al., 2019; Nesbit et al., 2020). Em adição, essas técnicas podem ser realizadas de forma terrestre ou aérea, a depender do escopo do levantamento. A aplicação dos DOMs é extremamente vasta e frequentemente envolve a correlação dos modelos de afloramento com dados de sísmica, poços, litoestratigrafia e redes de fraturas determinísticas ou estocásticas (Marques et al., 2020). Especificamente no campo da geologia estrutural, diversos trabalhos lançam mão dos DOMs para a realização de interpretações estruturais (Martinelli et al., 2020; Pontes et al., 2021; Furtado et al., 2022), a partir das quais parâmetros estatísticos podem ser calculados e reproduzidos em redes de fraturas discretas estocásticas (Giuffrida et al., 2020; Dantas et al., 2022; Racolte et al., 2022). Por sua vez, as redes de fraturas discretas (usualmente Discrete Fracture Networksou DFNs) podem ser parte de modelos estáticos utilizados em simulações de fluxo de fluido. |
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Artigo em Revista
| Barbieri Criterion for Solution Appraisal in Geophysical Diffraction Tomography. Diffraction tomography provides a high resolution velocity image from the region under study. Because it is a type of ill-conditioned inverse problem, diffraction tomography requires some kind of regularization, such as regularization by derivative matrices. Quantitative or qualitative criteria for the solution appraisal of inverse problems are just as important as the solution itself. An effective criterion is the Barbieri approach, which is the main scope in this study. It is implemented in three steps: (i) the estimated model obtained through the inversion of the observed data (scattered acoustic field); (ii) a second inversion, this time of the complementary observed data which provides the complementary estimated model; (iii) the sum of the estimated model and complementary estimated model. If the inversion is exact, this sum must be a constant value for the whole vector. If this does not occur, the sum image indicates that the inversion was not satisfactory (quantitative effect) and in which regions the estimated model was not well recovered (qualitative effect). Simulations were performed on two synthetic models, one with well-to-well geometry and the other with surface seismics geometry. The results, confronted with the RMS deviation between the estimated and the true model, validated the use of the Barbieri criterion in diffraction tomography. |
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Artigo em Revista
| Compartmentalization and stratigraphic-structural trapping in pre-salt carbonate reservoirs of the Santos Basin: A case study in the Iara complex The reservoir characterization of the Brazilian Santos basin’s pre-salt carbonates is a major challenge due to the faciological and depositional complexity, providing high lateral and vertical heterogeneities, and consequently, the formation of static/dynamic intraformational seals. Regarding this context, there is a massive pre-salt accumulation known as the Iara Cluster. During the early development stage, this cluster was split into three distinct accumulations named Berbigao, Sururu, and Atapu. This study aims to characterize the geological and hydrodynamic factors that affect the Iara Cluster reservoir compartmentalization. To achieve this objective, we applied an integrated analysis based on 3D seismic interpretation, well logs, pressure formation and fluid geochemistry analysis. The spatial distribution of the reservoir range’s five main seismic patterns indicates potential stratigraphic-structural barrier zones. The well log analysis correlated with formation pressure data enabled the identification of several irregular oil-water contacts and free water levels. Small relative variations are associated with the perched-water phenomenon, while large variations are related to compartmentalization. The formation pressure analysis shows the hydraulic compartmentalization of the reservoirs in the Berbigao ˜ Field. Sururu and Atapu fields’ oil zones are possibly connected by a dynamic sealing zone or a common aquifer, which provides a pressure balance on a geological time scale, since their oil gradients are similar. Our analyzes identified stratigraphic components in reservoir trapping associated with reservoir quality lateral obliteration. Dissimilarities in the oil sample composition and properties indicate different petroleum charge histories along with the distinct CO2 contamination timing. The Berbigao oil-associated gas formed in earlier stages of maturation than the Sururu and Atapu samples. The results integration through a risk matrix revealed areas with a greater chance of compartmentalization and perched-water phenomenon. Our study highlights the importance of multidisciplinary analysis to comprehend complex carbonate reservoirs connectivity, and offers input to de-risk new ventures’ pre-salt reservoir quality. |
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