Escalabilidade Paralela de um Algoritmo de Migração Reversa no Tempo (RTM) Pré-empilhamento

The seismic method is of extreme importance in geophysics. Mainly associated with oil exploration, this line of research focuses most of all investment in this area. The acquisition, processing and interpretation of seismic data are the parts that instantiate a seismic study. Seismic processing in particular is focused on the imaging that represents the geological structures in subsurface. Seismic processing has evolved significantly in recent decades due to the demands of the oil industry, and also due to the technological advances of hardware that achieved higher storage and digital information processing capabilities, which enabled the development of more sophisticated processing algorithms such as the ones that use of parallel architectures. One of the most important steps in seismic processing is imaging. Migration of seismic data is one of the techniques used for imaging, with the goal of obtaining a seismic section image that represents the geological structures the most accurately and faithfully as possible. The result of migration is a 2D or 3D image which it is possible to identify faults and salt domes among other structures of interest, such as potential hydrocarbon reservoirs. However, a migration fulfilled with quality and accuracy may be a long time consuming process, due to the mathematical algorithm heuristics and the extensive amount of data inputs and outputs involved in this process, which may take days, weeks and even months of uninterrupted execution on the supercomputers, representing large computational and financial costs, that could derail the implementation of these methods. Aiming at performance improvement, this work conducted the core parallelization of a Reverse Time Migration (RTM) algorithm, using the parallel programming model Open Multi-Processing (OpenMP), due to the large computational effort required by this migration technique. Furthermore, analyzes such as speedup, efficiency were performed, and ultimately, the identification of the algorithmic scalability degree with respect to the technological advancement expected by future processors

Processamento e interpretação de dados 2D e 3D de GPR :aplicações no imageamento de feições kársticas e estruturas de dissolução no campo de petróleo de Fazenda Belém-CE

In Fazenda Belém oil field (Potiguar Basin, Ceará State, Brazil) occur frequently sinkholes and sudden terrain collapses associated to an unconsolidated sedimentary cap covering the Jandaíra karst. This research was carried out in order to understand the mechanisms of generation of these collapses. The main tool used was Ground Penetrating Radar (GPR). This work is developed twofold: one aspect concerns methodology improvements in GPR data processing whilst another aspect concerns the geological study of the Jandaíra karst. This second aspect was strongly supported both by the analysis of outcropping karst structures (in another regions of Potiguar Basin) and by the interpretation of radargrams from the subsurface karst in Fazenda Belém. It was designed and tested an adequate flux to process GPR data which was adapted from an usual flux to process seismic data. The changes were introduced to take into account important differences between GPR and Reflection Seismic methods, in particular: poor coupling between source and ground, mixed phase of the wavelet, low signal-to-noise ratio, monochannel acquisition, and high influence of wave propagation effects, notably dispersion. High frequency components of the GPR pulse suffer more pronounced effects of attenuation than low frequency components resulting in resolution losses in radargrams. In Fazenda Belém, there is a stronger need of an suitable flux to process GPR data because both the presence of a very high level of aerial events and the complexity of the imaged subsurface karst structures. The key point of the processing flux was an improvement in the correction of the attenuation effects on the GPR pulse based on their influence on the amplitude and phase spectra of GPR signals. In low and moderate losses dielectric media the propagated signal suffers significant changes only in its amplitude spectrum; that is, the phase spectrum of the propagated signal remains practically unaltered for the usual travel time ranges. Based on this fact, it is shown using real data that the judicious application of the well known tools of time gain and spectral balancing can efficiently correct the attenuation effects. The proposed approach can be applied in heterogeneous media and it does not require the precise knowledge of the attenuation parameters of the media. As an additional benefit, the judicious application of spectral balancing promotes a partial deconvolution of the data without changing its phase. In other words, the spectral balancing acts in a similar way to a zero phase deconvolution. In GPR data the resolution increase obtained with spectral balancing is greater than those obtained with spike and predictive deconvolutions. The evolution of the Jandaíra karst in Potiguar Basin is associated to at least three events of subaerial exposition of the carbonatic plataform during the Turonian, Santonian, and Campanian. In Fazenda Belém region, during the mid Miocene, the Jandaíra karst was covered by continental siliciclastic sediments. These sediments partially filled the void space associated to the dissolution structures and fractures. Therefore, the development of the karst in this region was attenuated in comparison to other places in Potiguar Basin where this karst is exposed. In Fazenda Belém, the generation of sinkholes and terrain collapses are controlled mainly by: (i) the presence of an unconsolidated sedimentary cap which is thick enough to cover completely the karst but with sediment volume lower than the available space associated to the dissolution structures in the karst; (ii) the existence of important structural of SW-NE and NW-SE alignments which promote a localized increase in the hydraulic connectivity allowing the channeling of underground water, thus facilitating the carbonatic dissolution; and (iii) the existence of a hydraulic barrier to the groundwater flow, associated to the Açu-4 Unity. The terrain collapse mechanisms in Fazenda Belém occur according to the following temporal evolution. The meteoric water infiltrates through the unconsolidated sedimentary cap and promotes its remobilization to the void space associated with the dissolution structures in Jandaíra Formation. This remobilization is initiated at the base of the sedimentary cap where the flow increases its abrasion due to a change from laminar to turbulent flow regime when the underground water flow reaches the open karst structures. The remobilized sediments progressively fill from bottom to top the void karst space. So, the void space is continuously migrated upwards ultimately reaching the surface and causing the sudden observed terrain collapses. This phenomenon is particularly active during the raining season, when the water table that normally is located in the karst may be temporarily located in the unconsolidated sedimentary cap

Aquisição, processamento e análise de dados de sísmica de alta resolução na plataforma continental norte do Rio Grande do Norte: Vale inciso do rio açu

On the modern Continental Shelf to the north of Rio Grande do Norte state (NE Brazil) is located a paleo-valley, submerged during the last glacial sea-level lowstand, that marks continuation of the most important river of this area (Açu River). Despite the high level of exploration activity of oil industry, there is few information about shallow stratigraphy. Aiming to fill this gap, situated on the Neogene, was worked a marine seismic investigation, the development of a processing flow for high resolution data seismic, and the recognition of the main feature morphology of the study area: the incised valley of the River Açu. The acquisition of shallow seismic data was undertaken in conjunction with the laboratory of Marine Geology/Geophysics and Environmental Monitoring - GGEMMA of Federal University of Rio Grande do Norte UFRN, in SISPLAT project, where the geomorphological structure of the Rio paleovale Açu was the target of the investigation survey. The acquisition of geophysical data has been over the longitudinal and transverse sections, which were subsequently submitted to the processing, hitherto little-used and / or few addressed in the literature, which provided a much higher quality result with the raw data. Once proposed for the flow data was developed and applied to the data of X-Star (acoustic sensor), using available resources of the program ReflexW 4.5 A surface fluvial architecture has been constructed from the bathymetric data and remote sensing image fused and draped over Digital Elevation Models to create three-dimensional (3D) perspective views that are used to analyze the 3D geometry geological features and provide the mapping morphologically defined. The results are expressed in the analysis of seismic sections that extend over the region of the continental shelf and upper slope from mouth of the Açu River to the shelf edge, providing the identification / quantification of geometrical features such as depth, thickness, horizons and units seismic stratigraphyc area, with emphasis has been placed on the palaeoenvironmental interpretation of discordance limit and fill sediment of the incised valley, control by structural elements, and marked by the influence of changes in the sea level. The interpretation of the evolution of this river is worth can bring information to enable more precise descriptions and interpretations, which describes the palaeoenvironmental controls influencing incised valley evolution and preservation to provide a better comprehensive understanding of this reservoir analog system

Aplicação de softwares livres no Processamento de dados sísmicos de alta resolução

The increasing use of shallow seismic methods of high resolution, for investigations of geological problems, environmental or industrial, has impelled the development of techniques, flows and computational algorithms. The practice of applying techniques for processing this data, until recently it wasn t used and the interpretation of the data was made as they were acquired. In order to facilitate and contribute to the improvement of the practices adopted, was developed a free graphical application and open source, called OpenSeismic which is based on free software Seismic Un*x, widely used in the treatment of conventional seismic data used in the exploration of hydrocarbon reservoirs. The data used to validate the initiative were marine seismic data of high resolution, acquired by the laboratory of Geology and Marine Geophysics and Environmental Monitoring - GGEMMA, of the Federal University of Rio Grande do Norte UFRN, for the SISPLAT Project, located at the region of paleo-valley of the Rio Acu. These data were submitted to the processing flow developed by Gomes (2009), using the free software developed in this work, the OpenSeismic, as well other free software, the Seismic Un*x and the commercial software ProMAX, where despite its peculiarities has presented similar results

Caracterização geomorfológica e paleogeográfica da plataforma continental adjacente a foz do Rio Apodi-Mossoró, RN/Brasil

The brazilian marginal basins have a huge potential to generate and accumulate petroleum. Incised valleys which are eroded in response to a fall of relative sea level are related to potential reservoir as well, modern drowned-valley estuaries serve as harbors to petroleum and salt industries, fisheries, waste-disposal sites and recreational areas for a significant fraction of the world s population. The combined influence of these factors has produced a dramatic increase in research on modern and ancient incised-valley systems. This research is one expression of this interest. The integrated use of satellites images and high resolution seismic (bathymetry, sides scan sonar) was used on the Apodi River mouth-RN to characterizes the continental shelf This area is located at the Potiguar Basin in the NE Brazilian Equatorial Atlantic margin. Through bathymetric and side scan sonar data processing, a digital Terrain Model was developed, and a detailed geomorphologic analysis was performed. In this way was possible to recognize the geomorphologic framework and differents sismofacies, which may influence this area. A channel extending from the ApodiMossoró river mouth to the shelf edge dominates the investigated area. This structure can be correlated with the former river valley developed during the late Pleistocene sea level fall. This channel has two main directions (NW-SE and NE-SW) probably controlled by the Potiguar Basin structures. The western margin of the channel is relatively steep and pronounced whereas the eastern margin consists only of a gentle slope. Longitudinal bedforms and massive ridges also occur. The first are formed doe to the shelf sediment rework and the reef-like structures probably are relics of submerged beachrock-lines indicating past shoreline positions during the deglacial sea-level rise. The sub-bottom seismic data allow the identification of different sismic patterns and a marcant discontinuity, interpreted as the Upper

Caracterização morfológica-sedimentar do vale inciso Apodi-Mossoró e plataforma continental adjacente - Bacia Potiguar Offshore

Systems of incised valleys have been studied in different continental shelves, including the Brazilian continental margin. The interest to characterize this feature is given by the information that it can provide variations on sea level, as well as the ability to host economically significant quantities of hydrocarbons in reservoirs located in deposits filling of the incised valleys. This thesis has the overall objective to characterize the morphology and sedimentary cover of the incised valley Apodi-Mossoró, located in the Northern Continental shelf of Rio Grande do Norte state, adjacent to Areia Branca city. The methodology included the integration of satellite imagery, bathymetric data, sedimentological data, shallow seismic, and the identification of foraminifera. The results indicate that the ApodiMossró incised valley is currently formed by two channels, shallow channel and deep channel, which have distinct morphological and sedimentological characteristics. The deep channel has connection with one of the heads of the Apodi Canyon, located in the slope area. The acquisition, processing and interpretation of shallow seismic data allowed the recognition of the depositional surface, erosional surface, discordance, and sismofaceis. The erosional surface mapped from shallow seismic sections is possibly a indicative of an ancient surface of valley incision, where it would probably be associated with the limit Pleistocene/Holocene. Different sismofaceis were identified and reflect the rise in sea level with standards sometimes agradacional, sometimes progradational. The thickness of sediments on this surface was estimated at a maximum of 22m thick in the central portion of the incised valley. Statistically, there are differences between the adjacent continental shelf and channels, and between these channels, for the content of calcium carbonate, organic matter, sand and mud perceptual, except for the gravel grain size. The analysis of living and dead foraminifera showed the presence of fifty species distributed in regards to morphology, depth and type of sediment. Four type of seismic echocharacteres were identified and mapped, as well as their bedforms, indicating different sedimentary processes along the incised valley. The integration of results suggests an activation of the Apodi-Mossoró incised valley in the Late Pleistocene.

Estudo e aplicação da transformada de Fourier na regularização de dados sísmicos na exploração de petróleo

In the oil prospection research seismic data are usually irregular and sparsely sampled along the spatial coordinates due to obstacles in placement of geophones. Fourier methods provide a way to make the regularization of seismic data which are efficient if the input data is sampled on a regular grid. However, when these methods are applied to a set of irregularly sampled data, the orthogonality among the Fourier components is broken and the energy of a Fourier component may "leak" to other components, a phenomenon called "spectral leakage". The objective of this research is to study the spectral representation of irregularly sampled data method. In particular, it will be presented the basic structure of representation of the NDFT (nonuniform discrete Fourier transform), study their properties and demonstrate its potential in the processing of the seismic signal. In this way we study the FFT (fast Fourier transform) and the NFFT (nonuniform fast Fourier transform) which rapidly calculate the DFT (discrete Fourier transform) and NDFT. We compare the recovery of the signal using the FFT, DFT and NFFT. We approach the interpolation of seismic trace using the ALFT (antileakage Fourier transform) to overcome the problem of spectral leakage caused by uneven sampling. Applications to synthetic and real data showed that ALFT method works well on complex geology seismic data and suffers little with irregular spatial sampling of the data and edge effects, in addition it is robust and stable with noisy data. However, it is not as efficient as the FFT and its reconstruction is not as good in the case of irregular filling with large holes in the acquisition.

Estudo e aplicação da transformada de Fourier na regularização de dados sísmicos na exploração de petróleo

In the oil prospection research seismic data are usually irregular and sparsely sampled along the spatial coordinates due to obstacles in placement of geophones. Fourier methods provide a way to make the regularization of seismic data which are efficient if the input data is sampled on a regular grid. However, when these methods are applied to a set of irregularly sampled data, the orthogonality among the Fourier components is broken and the energy of a Fourier component may "leak" to other components, a phenomenon called "spectral leakage". The objective of this research is to study the spectral representation of irregularly sampled data method. In particular, it will be presented the basic structure of representation of the NDFT (nonuniform discrete Fourier transform), study their properties and demonstrate its potential in the processing of the seismic signal. In this way we study the FFT (fast Fourier transform) and the NFFT (nonuniform fast Fourier transform) which rapidly calculate the DFT (discrete Fourier transform) and NDFT. We compare the recovery of the signal using the FFT, DFT and NFFT. We approach the interpolation of seismic trace using the ALFT (antileakage Fourier transform) to overcome the problem of spectral leakage caused by uneven sampling. Applications to synthetic and real data showed that ALFT method works well on complex geology seismic data and suffers little with irregular spatial sampling of the data and edge effects, in addition it is robust and stable with noisy data. However, it is not as efficient as the FFT and its reconstruction is not as good in the case of irregular filling with large holes in the acquisition.