Produção Científica
Apresentação
| Synthesis and petrophysical characterization of an artificial mudstone analogous Carbonate rocks are important for rock properties research because they are linked to significant oil and gas reserves around the world. The goal of synthesizing carbonate rocks in laboratory is to simulate the natural carbonate rock matrix regarding the main factors of lithification such as grain size and shape, concentration of cementing material and compaction pressure, and allowing the production of rock specimens that can be used for tests in extreme conditions in replacement of the high cost natural cores. The reproduction of rocks in laboratory also allows to access samples with predetermined characteristics enabling a better understanding of the relationship between their physical properties. In this work, samples of synthetic carbonate rocks were made by mixing a fixed amount of calcite and sand, and varying the amount of cement material (Portland cement and water). The behavior of the main petrophysical characteristics of these samples was investigated, such as porosity, permeability and P- and S-wave velocities versus the amount of cementing material. The results were compared with natural carbonate samples and showed a high similarity to the petrophysical behavior of natural mudstones rocks. |
Apresentação
| Using the Benford's Law to analyze the sonic reflectivity The caliper log can be sensitivity to borehole enlargement due drilling effect on different rock formations. The density of the lithology is affected by mud infiltration and the consequence is unrealistic values on the well-to-seismictie. In this work we use, in the first time, the statistical Benford's Law (BL) to analyze and check on the existence of errors or inconsistencies on the reflectivity log. The Benford's analysis is applied on the reflectivity series of two wells of the Viking Graben field. Effect of sonic and density logs despiking as well as the size of sample window to find the BL distribution were analyzed. The results on the real dataset analyzed shows that it is possible to find a optimum coefficient for the despiking process on the well logs according to the Benford's Law and that the segments of the reflectivity where the caliper log is stable the conformity with the Benford's Law is higher. |
Apresentação
| Comparative Analysis of First Break Picking Methods in Noisy and Non-noisy P-wave Signal The estimative of acoustic velocities is an important data that is extracted from data of exploration seismic, well logging (acoustic logging) and laboratory experiments. To realize this estimative a technique called first break picking is used, which consist in an analysis of time x Amplitude data to identify the wave arrival. The complexity of this analysis is in the fact of the data, generally is contaminated with noise and this one could be either inherent to the measuring equipment or other factors, that could make the simple visual analysis impossible. Considering this problem, the development of techniques which would be capable to identify the wave arrival automatic, accurate and faster, justify the study of advanced methods to accomplish this task. |
Apresentação
| Differences between static and dynamic methods for pore compressibility in carbonates The production of hydrocarbons from a reservoir occurs due to the variation of pore volume through a pressure differential. These variations are quantified by pore compressibility, an important parameter that interferes with the flow of fluids that saturate the porous medium, porosity and elastic properties of the rock. For many times pore compressibility was considered a constant, but the oil industry with the prospect and need to potentiate the reservoir's productive capacity has been attributed as an important factor in reserve calculations and decision-making related to well design in order to avoid unexpected interventions and loss of the reservoir by collapse. The compressibility of reservoir rock pores is determined through well profiles and seismic data, however for more accurate results, laboratory measurements are crucial. In this context, the objective of this work is to obtain pore compressibility through static and dynamic tests in samples of carbonates highlighting the influence of each method on the difference of the results. The static method was performed from uniaxial compression tests based on the technique of Unalmiser & Swalwell (1993). Dynamic tests were based on pore-elasticity theory through the propagation velocity of compression waves (P) and shear (S) and elastic constants of the rock when subjected to hydrostatic pressure variation. The correlation between the two methods is economically important for the industry as well as serving as the basis for the calibration process of the logging tools. |
Apresentação
| Petrophysical-hysteresis analysis related to pore structure of sedimentary rocks Reservoir rocks characterization consists of a critical stage on petroleum reserves evaluation, in which determining the relationships between petrophysical and mechanical rock properties is a required step to guarantee the accuracy of delivered data. Mechanical properties affect both drilling programs and hydrocarbon exploitation. Rock texture also plays a significant role on reservoir characterization, because porosity and permeability depend, mainly, on geometrical parameters, such as grain size, sorting, shape and diagenetic induced changes caused by cementation and dissolution. This work consists on an evaluation of the hysteretic characteristics of American outcrops samples when submitted pore system to induced loading and unloading, analyzing the influence of chemical composition, depositional texture, pore system structure and elastic mechanical properties on its hysteretic behavior. The hysteresis areas were mathematically estimated and petrophysical properties measured, as well as mineralogical composition. Elastic properties were estimated for the dry sample and also considering only the solid rock framework. Interesting correlations were observed among the analyzed properties and the expectation is that, in the future, hysteresis phenomena can be considered on reservoir deployment monitoring. |
Apresentação
| Using SPITS to Optimize the Cost of High-Performance Geophysics Processing on the Cloud Public cloud providers, such as the Microsoft Azure and the Amazon Web Services (AWS), offer a wide variety of virtual machines, with different specifications, and prices, that are enabling users to run high-performance programs without buying specialized and expensive hardware. Moreover, some providers, such as AWS, allow the user to bid for lower cost virtual machines, called Spot Instances. Nonetheless, these machines may be terminated within a few minutes of warning at the provider discretion. In this work, we leveraged the SPITS programming model to implement a high-performance and fault-tolerant seismic processing application that is proper for execution on Spot instances and analyzed how different virtual machines from the AWS may affect the performance and the price of the computation. Our experimental results indicate that Spot instances have similar performance to regular instances but are roughly three times less expensive. Finally, we show that AWS groups virtual machines in Availability Zones and that selecting virtual machines from different zones may also affect the total execution cost. |
Apresentação
| Microporosity Aspect Ratio of Carbonate Rocks Under Pressure Carbonate rocks usually present a complex porous system, especially regarding the differences in pore geometry. When those rocks are submitted to external pressure variation, that variations in pore geometry may affect the elastic velocities. In this work, we studied the behavior of compressional and shear wave velocities in a set of carbonate rocks at different pressure stages. Our approach is based in a supposition of a dual porosity scenario and consisted in determining the mean value of the aspect ratio of the macro-meso pores through the analysis of optical microscopy images and use the Differential Effective Medium (DEM) theory to estimate the microporosity aspect ratio. The results showed that such microporosity aspect ratio decreases exponentially as pressure increases. |
Apresentação
| Use of Bayesian Inference for Estimative of P-wave Arrival The measurement of acoustic wave forms is present in exploration seismic, well logging and laboratory experiments. For instance, a commonly performed experiment for velocity measurements in cores is the first break picking. The measured data probably contain noise, either inherent to the measuring equipment or other factors. Develop new techniques to do this task automatically and more accurate is even more necessary over time. |
Artigo em Revista
| Up/down acoustic wavefield decomposition using a single propagation and its application in reverse time migration The separation of up- and downgoing wavefields is an important technique in the processing of multicomponent recorded data, propagating wavefields, and reverse time migration (RTM). Most of the previous methods for separating up/down propagating wavefields can be grouped according to their implementation strategy: a requirement to save time steps to perform Fourier transform over time or construction of the analytical wavefield through a solution of the wave equation twice (one for the source and another for the Hilbert-transformed source), in which both strategies have a high computational cost. For computing the analytical wavefield, we are proposing an alternative method based on the first-order partial equation in time and by just solving the wave equation once. Our strategy improves the computation of wavefield separation, and it can bring the causal imaging condition into practice. For time extrapolation, we are using the rapid expansion method to compute the wavefield and its first-order time derivative and then we can compute the analytical wavefield. By computing the analytical wavefield, we can, therefore, separate the wavefield into up- and downgoing components for each time step in an explicit way. Applications to synthetic models indicate that our method allows performing the wavefield decomposition similarly to the conventional method, as well as a potential application for the 3D case. For RTM applications, we can now use the causal imaging condition for several synthetic examples. Acoustic RTM up/down decomposition demonstrates that it can successfully remove the low-frequency noise, which is common in the typical crosscorrelation imaging condition, and it is usually removed by applying a Laplacian filter. Moreover, our method is efficient in terms of computational time when compared to RTM using an analytical wavefield computed by two propagations, and it is a little more costly than conventional RTM using the crosscorrelation imaging condition. |
Tese de Doutorado
| Gustavo da Silva Costa. Análise de estabilidade e governabilidade em veÃculo submarino autônomo utilizando OpenFOAM Gustavo da Silva Costa. Análise de estabilidade e governabilidade em veÃculo submarino autônomo utilizando OpenFOAM. 2019. SENAI/CIMATEC. Orientador: Ivan Costa da Cunha Lima. |
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