Publicações

Time–frequency spectral signature of Pelotas Basin deep water gas hydrates system Revista: Marine Geophysical Researches, 2010, 31, 89-97 Abstract: Pelotas Basin has the largest gas hydrate occurrence of the Brazilian coast. The reserves are estimated in 780 trillion cubic feet, covering an area of 45,000 km2. In this work we apply spectral decomposition technique in order to better understand a gas hydrate deep water system, performing a continuous time–frequency analysis of seismic trace, where frequency spectrum is the output for each time sample of the seismic trace. This allows a continuous analysis on the effects of the geologic structures [...]

An Automatic Porosity and Saturation Evaluation Based on the Inversion of Multiple Well Logs Revista: spwla.org We propose an automated method for inference of porosity and saturation, which can be used for quickly assessing reservoir rock quality and fluid volumes. The method is based on the inversion of multiple well logs using the Bayesian Theory. The well logs consist of neutron porosity, density, sonic (P-wave and S-wave velocities) and resistivity, which are related to porosity and saturation through the appropriate rock physics models. Following the Bayesian Theory, the formal solution of the inverse problem is a posterior distribution, [...]

Porosity inference and classification of siliciclastic rocks from multiple data sets Revista: Geophysics, 2006, 71, P65-V76. We develop a Bayesian formulation for joint inference of porosity and clay volume, incorporating multiple data sets, prior information, and rock physics models. The derivation is carried out considering the full uncertainty involved in calculations from unknown hyperparameters required by either rock physics equations model coefficients or statistical models data variances. Eventually, data variances are marginalized in closed form, and the model coefficients are fixed using a calibration procedure. To avoid working with a high-dimension probability density function in the parameter space, [...]

A fourth-order finite-difference method for the acoustic wave equation on irregular grids Revista: Geophysics, 2003, 68, 1–5. This paper presents a FD approximation for the acoustic wave equation which is able to handle nonuniform rectangular grids. The new scheme has achieved the same accuracy of a thin regular-grid calculation while reducing the computational cost. The inevitable variation of the numerical phase velocity as a function of the grid step requires some care when designing irregular meshes because contrasts in the phase velocity can produce numerical reflections. To deal with this problem and to keep the accuracy of the [...]