Navegando por Assunto "Pressão"

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Acesso aberto (Open Access)
Post-imaging analysis of pressure prediction in productive sedimentary basins for oil and gas exploration
(Universidade Federal do Pará, 2015-05-26) VIEIRA, Wildney Wallacy da Silva; LEITE, Lourenildo Williame Barbosa; http://lattes.cnpq.br/8588738536047617
This thesis has several aspects related to the problem of basin modeling towards oil and gas exploration, and with two general divisions: parameter estimation, and pressure prediction. For the structure of this work, the first topic is related to velocity analysis and effective media, where estimated a distribution for the P wave velocity in time, the transformation to depth, and the use an effective model for the density and for the S wave velocity distributions. The reason for initially focusing on these estimations is because they represent one of the most basic information that one can have from the seismic domain, from where the other seismic parameters can be calculated, and from where the second part of this is totally based. The second topic is related to computing stress, strain and pressure distribution in the subsurface using the information from the P and S wave velocities and the density models, in order to localize areas of high and low pressures that act as natural suction pumps for the mechanics of oil and gas accumulation into productive zones and layers. We have highlighted this second part for the final work presentation, and call attention to the sensitivity of pressure mapping to the velocity and density variations. We also classify the first division as dedicated to the conventional seismic processing and imaging, and have clled the second division as post-imaging stressstrain-pressure prediction. As for the final aim of geophysics is to create images of the subsurface under different properties, the stress calculation only makes total sense for real data, and this makes mandatory the acquired seismic data be three component. As an important conclusion from the numerical experiments, we show that pressure does not have a trivial behavior, since it can decrease with depth and create natural pumps that are responsible for accumulating fluids. The theory of porous media is based on integral geometry, because this mathematical discipline deals with collective geometrical properties for real reservoirs. It was shown that such collective properties are namely for porosity, specific surface, average curvature and Gaussian curvature. For example, cracked media has, as a rule, small porosity, but very large specific surface area that creates anomalous high 𝛾 = 𝑣𝑆/𝑣𝑃 ratio, what means a negative 𝜎 Poisson coefficient. Another conclusion is related to calculating discontinuity in pressure between solid and fluid, what depends on the structure of pore space.
Acesso aberto (Open Access)
Processamento, imageamento, interpretação e predição de pressão de dados sísmicos na bacia sedimentar do Jequitinhonha
(Universidade Federal do Pará, 2016-08-18) SILVA, Aucilene de Nazaré Pimenta da; LEITE, Lourenildo Williame Barbosa; http://lattes.cnpq.br/8588738536047617
This present work aimed to compose a seismic-stratigraphical framework for part of Jequitinhonha basin (marine east part of the State of Bahia), with data released for funded academic projects in progress. The study aims at the exploration of oil and gas, and corresponds to a proposal for for sedimentary basin revaluation. For this, the methodology is composed of velocity analysis, CRS stacking, migration, culminating in pressure prediction for the subsurface, where the aim is to map low (reservoir) and high (generator) pressure zones that act as natural pumps for fluid accumulation. The seismic data used in this study was provided by PETROBRAS for the Postgraduate Course in Geophysics (CPGF), of the Institute of Geosciences of the Federal University of Pará. The data were acquired by the PETROBRAS seismic team 214 in the offshore part or the basin. The available lines used in this study were the L214-266, L214-268, L214-270 and L214-297. Being able to separate them into two groups, we have three lines in the NE-SW directions (L214-266, L214-268, L214-270) and one in the direction NW-SE (L214-297). The velocity distributions used for the seismic sections were based on petrophysical information and empirical models, instead of using the subjective event picking in common-midpoint, stack or migration sections. The methodology presents as the first part the application of techniques based on the theory of the common reflection surface stack (CRS), which aims to generate seismic images of good quality for the interpretation of real data, and related to geologically complex media. The seismic-stratigraphic interpretation were performed using as a basis the geological information, making a correlation between the main reflectors (interfaces of higher impedance) and the stratigraphic units of the area. In this way, we constructed an empirical model for the velocity distribution (𝑣𝑅 and 𝑣𝑆) and density (𝜌) for the sections of the studied block. A higher study project aims to predict stress in sedimentary basins, as a contribution to the methods and techniques of geology and oil and gas engineering exploration. This subject is based on the knowledge of the compressional (𝑣𝑃 ) and shear (𝑣𝑆) velocities, and densities (𝜌), in order to locate areas low and high pressure zones in the subsurface, which serve as natural suction pumps for gas and oil accumulation. The theory is based on the elastodynamic equations, where the gravitational weight of the overload is responsible for the effects of strain-stress deformation in the subsurface. Therefore, to organize this problem requires the generalized Hooke’s law of linear elasticity. We presented details of the theoretical model, and an example to show how the pressure varies in the subsurface, where we highlight that pressure prediction does not necessarily increase linearly, but in a complex way that requires specific numerical formulas to be able to see important details. The applied theoretical model poses as pressure agent the vertical gravity load of the geological formations, and does not take into account the effects of curvatures, faulting and diagenesis. Also, the complex lateral tectonic events are not accounted for. The prediction of pressure and tension is an important issue for the analysis of sedimentary basins, aiming at mapping and extending potentially oil and gas productive areas. But an accurate prediction needs a 3D model for a significantly complete practical application.