Produção Científica
Apresentação
| Effects of torque produced by wake on the maneuverability of a flatfish autonomous underwater vehicle Autonomous underwater vehicles (AUV) are important resources to be used in the oil exploration industry in deep waters as well as a platform for scanning devices used in open sea regions of difficult human access. This work aims to analyze through computer simulations the influence of marine currents on the maneuverability of a flatfish shaped AUV. The 3D realistic scale simulations were performed on the Yemoja supercomputer located at SENAI-CIMATEC and describe the temporal evolution of the torques in the three rotational degrees of freedom - roll, yaw and pitch. The torques were calculated for two different inlet velocities and three angles (yaw) of attack showing a significant gain in the amplitude of these with increasing velocity and pitch being the component with the greatest amplitude of oscillation. |
Apresentação
| Comparative Analysis of Two-Phase Flow in Porous Media in Two Different Configurations of Wells Through 3D Numerical Solution Using OpenFOAM With the advance of high-performance computing (HPC) the use of CFD software has become common in research in Fluid Dynamics, either to obtain the numerical solutions of differential equations that model the various systems or the dynamics for viewing and analyzing data obtained in the simulations. In this work we look to benchmarking between two distinct two-phase flows from two geometrically different wells through the analysis of their respective accumulated volumes of non-wetting fluid in the outflow. Three simulations were performed, for each set of wells, both during the same interval of time and under the same pressure gradient. The OpenFOAM software and Finite Volume Method for solving differential equations were used. |
Apresentação
| Evaluation of Static and Dynamic Elastic Properties in Carbonate Rock The understanding of rocks mechanical properties is essential for some of the petroleum industry sectors, such as drilling, well stimulation and development. Rock mechanics data, as Young's modulus and Poisson's ratio, can be obtained by the static and dynamic conditions using triaxial compressive and ultrasonic tests, respectively. This work analyses the behaviour of static and dynamic elastic properties in a set of 20 carbonate core samples and compares with other literature results. Our approach is based in fit equations to predict static properties from the dynamic data, considering the occurrence of the frictional sliding or closing of cracks and microcracks, while performing triaxial tests. The results indicated a strong relationship among the effective pressures applied, porosity, density, and the efficiency of static and dynamic property relations. Additionally, porosity type could be indicated as one of the causes of the difference between static and dynamic moduli, since the inclusion of density and porosity in the relations demonstrated a significant improvement between Young's static and dynamic modulus correlations. |
Apresentação
| Pressure Effects on the Prediction of the Dry Bulk Modulus Using the Nur Critical Porosity Model Carbonate reservoirs are some of the most important plays in the oil and gas business around the world. The monitoring of fluid distribution within those rocks is not an easy task due to the complexity of their pore structure, which also influences the relationship between the petrophysical properties and seismic data. Fluid substitution theories like Biot-Gassmann often used for that monitoring, depend on the accurate info of the dry bulk modulus (Kdry), which is usually obtained from P- and S-wave velocities. In cases where those velocities are not available, it is possible to use other theories like the Nur (critical porosity) model to estimate Kdry from porosity and mineral content. This work aims to use a dataset of petrophysical data measured in core plugs to evaluate how the external pressure influence the prediction of Kdry based on the Nur Model. The results indicated the impact of pressure in the lab measured porosity affect the accuracy of such predictions and a modification in the Nur Model is proposed for accounting those effects. |
Apresentação
| Correlation Between Hysteresis, Elastic Moduli and Petrophysical Properties in Sedimentary Rocks ut on 05 sandstones and 03 carbonate core samples. The results indicated that hysteresis is severely dependent on depositional texture, and it is directly related to Young modulus and Bulk modulus. Tight rocks exhibited higher hysteresis than friable rocks, due to frictional sliding and grain contact adhesion, which causes permanent damage to pore structure. Porosity displays an inverse relation to hysteresis, as high pore density enables rock’s matrix to deform and recover its shape without frictional sliding and grain contact adhesion. |
Apresentação
| Harvesting the computational power of heterogeneous clusters to accelerate seismic processing Cluster environments are crucial to modern geophysics. Major processing companies make use of one or more computational environments, whether they be in-house clusters or third-party public clouds, to guarantee the efficient execution of their processing flows. But the diversification of such environments created a demand for software tools that are able to scale with efficiency in these ever-increasing ecosystems. Aside from efficiency requirements, these tools must also be able to handle and recover automatically from the faults that arise from these new and complex ecosystems. In this paper, we discuss how we leverage the Scalable Partially Idempotent Tasks System (SPITS) programming model and the PY-PITS runtime system to efficiently harvest the computing power of heterogeneous systems in order to solve geophysics problems. We also present an experiment in which we combine the computational resources from several clusters and workstations simultaneously to perform the regularization of seismic data and demonstrate the scalability and robustness of the system. |
Apresentação
| Deep Structures Seismic Enhancement Using Singular Spectral Analysis in Time and Frequency Domain - Application in a Parnaíba Basin Line – Brazil Land data seismic processing has always been a task of great challenge for industry, part because of statics problem and part because of the level of noise this kind of data usually has. In this paper we discuss the importance of a powerful filtering flow, designed for a special case scenario where there is a high level noise land data with duration of 20 seconds. We tested a recursive-iterative Singular Spectrum Analysis (RI-SSA) method, in time and frequency domain, on a subset of a regional transect seismic line of the Parnaíba basin (Northeast of Brazil), with the idea of map deep structures from crust and interface crust-mantle. Since the structures of interest are between 8 and 15 seconds, only low frequency is desired. For this, we have applied the RI-SSA method along the time variable, to explore the correlation between the reflections, followed by the filtering, along the frequency variable, to explore the correlation between seismograms. The obtained results are very satisfactory. |
Apresentação
| Recursive-iterative Zero-phase Filtering via Singular Spectrum Analysis We present a recursive-iterative Singular Spectrum Analysis (RI-SSA) algorithm which explores the time-correlation between reflected events. The RI-SSA algorithm depends on the first eigenimage of the SVD of the data matrix only. It is formed by letting each column be the data vector shifted one place down. The first eigenimage is related to the part of the signal with most strong correlation along the time variable and may be transformed to a time signal, which mainly consists of the low-frequency part of the input signal. We show that this corresponds to filtering the data with a symmetric zero-phase filter, which is the autocorrelation of the first eigenvector associated to the time variable. The computational implementation may be done using the power-method in a recursive scheme, increasing the order of the data matrix, by increasing the number of shifted traces. This improves the separation of the input data in a low-frequency and high-frequency component. This separation may be further improved by adding iterations. The output of the RI-SSA algorithm is the low and high frequency part of the signal. We illustrate the effectiveness of this new approach to the prediction and subtraction of the ground-roll. |
Apresentação
| Evaluation of Borehole Effect of Mud Filtrate on Density Logging and a Brief Analysis of its Impact on Well-Seismic Tying The application of seismic data in reservoir characterization, direct hydrocarbon indication and production monitoring rely on the accuracy of elastic logs (Vásquez et al., 2004), which can be damaged by the mud filtrate invasion associated to the borehole condition. Corrections on density log sometimes are neglected, however, meaningful improvements on the correlation of the well to seismic tie can be achieved by performing proper rectifications. For this reason, in this paper we present a analysis of the impacts of borehole enlargement on the well-to-seismic tie based on density modelling and on a analysis of the caliper log. |
Apresentação
| Signal analysis and time-frequency representation using SSA and adaptive AR methods We apply the Singular Spectral Analysis (SSA) method in an iterative and recursive way to estimate individual components of the signal. Following we apply the short time autoregressive method to obtain a time-frequency representation of the signal. For the computing of the instantaneous frequency we provide a new equation which depend on a single autoregressive coefficient. The effectiveness of the new approach is demonstrated in a synthetic data example and in the removal of ground-roll noise from land seismic data. |
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