Rodrigo de Souza Portugal

Comparing deterministic and stochastic seismic inversion for thin-bed reservoir characterization in a turbidite synthetic reference model of Campos Basin, Brazil

The inversion of seismic data for acoustic impedance is a frequently used technique because it offers several advantages:

Detecção de contaminação de solo por vinhaça através de análise de dados de eletrorresistividade

The vinasse, awaste produced in the proportion of 13 liters for each liter of alcohol. It has a high potential of polluting groundwater and superficial water resources, changes the soil behaviour and can also develop sanilization problems. This work aims to evaluate the efficiency of the DC-resistivity method in detecting and mapping anomalies caused by inappropriate disposal of vinasse in an inactive infiltration tank located at Sepe-Tiaraju settlement of landless agricultural laborers in the Ribeirao Preto region. Besides, as secondary goals, this work aims to characterize the type of anomaly residue as well as to diagnose its influence inside and outside of the limits of the tank. Eleven electrical resistivity tomography profiles were carried out with the dipole-dipole array, 10m of dipoles length and 5 leveis of investigation The geophysical survey enabled us to conclude that the DC-resistivity method is appropriate for mapping the contamination plume caused by intense vinasse disposal and its influence. It enabled also to conclude that the contamination exceeds the tank limits. The vinasse influence can be characterized by low resistivity values between 10 Ohm.m and 90 Ohm.m and its behavior can be compared with the one of the chorume, which is also conductive.

Plant accumulations along the Itanhaém River Basin, southern coast of São Paulo State, Brazil

Abstract Examination of the mechanisms involved in the construction of present-day vegetative deposits along coastal waterways has made it possible to establish depositional patterns that can be compared with those found in similar environments in geologic time. These patterns include not only the composition and transport of the debris but also an estimation of the time involved in its deposition. Six sites with active deposits of plant macrodebris in the coastal basin of the Itanhaém River, São Paulo State, Brazil, were used in the study. In the central portion of the basin, the interior coastal plain is covered with restinga forest (dense, wet tropical forest of low altitudes), while the lower portion consists of mangrove swamps. The coast reflects anthropogenic intervention, and only a few scattered remnants of precolonization dune vegetation remain. The results after three years of study suggest that the accumulation of plant macrodebris in the middle and lower portions of the basin is parautochthonous, since only the leaves of genera typical of the restinga forest and mangrove swamp, respectively, were found. Along the coast the accumulations involved a mixture of parautochthonous and allochthonous elements. On the levee of the Branco River and within the mangrove swamp, deposition was slow, and many of the elements decayed quickly; such accumulations show little potential for preservation and eventual fossilization. A different site, however, reveals the rapid deposition of thick layers of plant debris, presumably associated with storms, and these accumulations are preserved for long periods, constituting good candidates for possible fossilization.

O papel da inversão para a impedância acústica no processo de caracterização sísmica de reservatórios

The reservoir characterization process can be defined as the three-dimensional and quantitative determination of structure and petrophysical properties of the oil field. The use of 3D seismic data in the reservoir characterization process has become more frequent mainly in the identification of the shape and the size of the sand bodies that constitute the reservoir. However, in some situations as the deep water turbidite reservoirs of Campos Basin, that are characterized by a complex distribution of sand bodies and subseismic thickness, the use of the conventional seismic amplitude data can result in serious mistakes in the definition of reservoir model. To solve the problem of the vertical seismic resolution limitation, is necessary to build an integrated model that use all information available about the reservoir. The most effective way to integrate the seismic data in the reservoir characterization process is by using acoustic impedance models, obtained by seismic inversion. The aim of this work is to show how the seismic inversion to acoustic impedance can support and improve the characterization of the reservoirs, when comparing the results obtained by the application of two seismic inversion methods, the recursive inversion and the constrained sparse-spike inversion. The seismic inversion methods are applied in a wedge synthetic reference model, that represent some features find in the deep water turbidite reservoir, like stratigraphic thinning and pinch-outs. Based on these results we can see the advantages in use the seismic inversion methods in the determination of geometry of sand bodies and in the calculation of petrophysical properties, and as a consequence more accuracy models can be generated and the forecasts about the behavior of the field can be done in most effective way.

Application of Stochastic Inversion to Reservoir Characterization Process

Abstract To properly accomplish the reservoir characterization process in an effective way, it is necessary to integrate all the available information about the field in a consistent model. It is not an easy task to perform this integration in practice: it is necessary to use some specific methods such as seismic inversion. The seismic inversion is an efficient method to integrate both well-log and seismic data, obtaining a model that could be used in a forecasting process by numeric flow simulation. The seismic inversion can be achieved by several methods, which can be divided into two main groups: the deterministic methods (represented by the recursive inversion and constrained sparse-spike inversion) and the stochastic methods (represented by the geostatistical inversion). In this study, we show how stochastic inversion can improve the reservoir characterization process, by comparing its results with those obtained by deterministic inversion. The stochastic inversion can use a high sample rate that is close to the cell size of the reservoir model, implying that a more reliable model can be generated. The stochastic inversion method can also generate some basic statistics measurements that improve interpretations. Due to the great number of realizations generated during the process, we could also perform an uncertainty study on the reservoir model.

Modelagem avo: estudo de caso em um poço no Campo de Namorado

This work presents fluid substitution simulation and AVO modeling studies in order to characterize sandstone intervals of a well of Namorado field. The fluid substitution simulation study was done by saturating the sandstone with oil in situ then with brine water. The AVO modeling simulated attributes that were interpreted with the help of amplitude and crossplotting analyses, showing AVO anomalies of Class IV.

As técnicas NASVD e MNF e sua aplicação na redução de ruídos em dados gamaespectrométricos

The radioactive decay is a random process, and the measurement precision is ruled by statistical laws. The counting ratios of the profiles are alwaysnoisy when analyzed for short periods, such as one second per measurement. Corrections made at the end of conventional processing in the airborne gamma-ray spectrometric method data are not enough to remove and minimize, or even reduce considerably, the spectrums originated noise. Two statistic methods that actlocally in collected data, in the spectrum domain, have been suggested by literature to remove such remaining noises, the Noise-Adjusted Singular Value Decomposition - NASVD and Maximum Noise Fraction - MNF. These methods produce a significantly noise reduction. In this work both methods were applied in an area comprehended by two blocks, I and II, of the airborne survey that covers the west area of Mineral Province of Tapajos between Para and Amazon states. The filtered and non-filtered data with the NASVD and MNF techniques were processed with the Lasas parameters. The comparison of results between maps and profiles shows that both methods are valuable, since there was resolution gain in these products.

Seismic inversion performed in synthetic reference model

Characteristics frequently present in turbidite reservoirs are the complex distribution of sand bodies and the presence of thin sand layers, which are below the seismic resolution. One way to improve the characterization the reservoir heterogeneities is to perform a series of seismic modeling and inversion studies, concerning seismic amplitudes and impedances. In this work it is discussed the seismic inversion process applied to modeled data generated from a reference model, which possess realistic features of a thin and inhomogeneous reservoir. Since this synthetic reference model is known it is possible to calibrate the seismic inversion parameters, improving its use on real seismic data, which comes from of reservoir with the same characteristics of that synthetic reference model. In this way, the interpretation and conclusions about the inversion results can be made more effectively, since it is possible to study the effects separately. Finally, the contribution of this work is that this analysis can be used how to understand the inversion algorithm parameters when applied to real data with similarity to the reference data.