José Almeida

Parallelization of sequential Gaussian, indicator and direct simulation algorithms

Improving the performance and robustness of algorithms on new high-performance parallel computing architectures is a key issue in efficiently performing 2D and 3D studies with large amount of data. In geostatistics, sequential simulation algorithms are good candidates for parallelization. When compared with other computational applications in geosciences (such as fluid flow simulators), sequential simulation software is not extremely computationally intensive, but parallelization can make it more efficient and creates alternatives for its integration in inverse modelling approaches. This paper describes the implementation and benchmarking of a parallel version of the three classic sequential simulation algorithms: direct sequential simulation (DSS), sequential indicator simulation (SIS) and sequential Gaussian simulation (SGS). For this purpose, the source used was GSLIB, but the entire code was extensively modified to take into account the parallelization approach and was also rewritten in the C programming language. The paper also explains in detail the parallelization strategy and the main modifications. Regarding the integration of secondary information, the DSS algorithm is able to perform simple kriging with local means, kriging with an external drift and collocated cokriging with both local and global correlations. SIS includes a local correction of probabilities. Finally, a brief comparison is presented of simulation results using one, two and four processors. All performance tests were carried out on 2D soil data samples. The source code is completely open source and easy to read. It should be noted that the code is only fully compatible with Microsoft Visual C and should be adapted for other systems/compilers.

Impactos dos desastres naturais nos sistemas ambiental e socioeconômico: o que faz a diferença?

Este artigo aborda os impactos ambientais e socioeconomicos associados aos desastres naturais e apresenta os fatores que contribuem para a reducao da magnitude dos danos materiais e humanos. Realiza-se uma analise reflexiva, baseada em abordagens qualitativas e quantitativas, integrando as dimensoes ambiental, economica e social da sustentabilidade, assim como as relacoes com os paradigmas dos desastres (Perigo-Risco-Vulnerabilidade-Resiliencia) de origem hidro-meteorologica, climatologica e geofisica. Procura-se identificar os fatores-chave para reducao da vulnerabilidade, bem como para prevencao e mitigacao dos impactes dos desastres naturais. A reflexao efetuada permitiu realcar a influencia determinante do capital social, relacionado as estruturas social e economica, como fator de reducao da vulnerabilidade das comunidades afetadas.

Predicting Probability Maps of Air Pollution Concentration: A Case Study on Barreiro/Seixal Industrial Area

Two kinds of problems related to air pollution control in the industrial area of Barreiro/Seixal have been tackled by geostatistical methods: i) One is based on observations made over a large period of time at fixed monitoring stations; two different pollutant structures are identified and split by a threshold value of SO2. Spatial probability maps for the critical high spikes of SO2 concentrations are calculated by kriging indicator variables ii) For a given threshold the shape of the plume — high spikes of SO2 — is determined by transforming the estimated probability maps into morphological maps, fundamental tools for evaluation of the environmental impact on the area.

The use of sensory perception indicators for improving the characterization and modelling of total petroleum hydrocarbon (TPH) grade in soils

This paper proposes a multistep approach for creating a 3D stochastic model of total petroleum hydrocarbon (TPH) grade in potentially polluted soils of a deactivated oil storage site by using chemical analysis results as primary or hard data and classes of sensory perception variables as secondary or soft data. First, the statistical relationship between the sensory perception variables (e.g. colour, odour and oil–water reaction) and TPH grade is analysed, after which the sensory perception variable exhibiting the highest correlation is selected (oil–water reaction in this case study). The probabilities of cells belonging to classes of oil–water reaction are then estimated for the entire soil volume using indicator kriging. Next, local histograms of TPH grade for each grid cell are computed, combining the probabilities of belonging to a specific sensory perception indicator class and conditional to the simulated values of TPH grade. Finally, simulated images of TPH grade are generated by using the P-field simulation algorithm, utilising the local histograms of TPH grade for each grid cell. The set of simulated TPH values allows several calculations to be performed, such as average values, local uncertainties and the probability of the TPH grade of the soil exceeding a specific threshold value.

Stochastic Simulation of the Morphology of Fluvial Sand Channel Reservoirs

This paper presents an innovative methodology designed to simulate 3D stochastic images of the morphology of fluvial sand channel reservoirs. This methodology is successfully tested for a hypothetical channel sand reservoir where some of the conditioning data were derived from a Middle Eastern reservoir of this type. Results are discussed with particular regard to the images of local orientations and analysis of the local and global uncertainties of the model.

Caracterização e avaliação de reservas geológicas do depósito mineral de Farim-Saliquinhé

This article presents an integrated methodology and main results of the geological and economic modeling of the Farim-Saliquinhe phosphate ore deposit, in Guine-Bissau. This mineral mass was fi rst recognized in the 1980s, by the Bureau de Recherches Geologiques et Minieres (BRGM) as sedimentary. The morphological characterization was performed by depth and thickness estimation of coverage and mineralized formations (main phosphate rock FPA, and carbo-phosphate FPB, secondary). The P2O5 grades were characterized by krigging and subsequently by geostatistical simulation, to infer the uncertainty and classify the reserves in terms of inferred, indicated and measured. Finally, the morphology and grades were converted into benefi ts and costs following a mineral exploitation scenario. With regard to the economic modeling, a pre-feasibility study is presented with sensitivity analysis, relative to the phosphate price, exploitation and transportation costs, and reduction on the phosphate price, if not concentrated. An estimate is also presented of the internal rate of return (IRR) of the project for a base scenario and one variant.

Accounting for Soft Information in Mapping Soil Contamination with TPH at an Oil Storage Site

This paper presents a methodology to account for soft information in mapping soil contamination with TPH (Total Petroleum Hydrocarbons) at an oil storage site. The former function of the site consisted of storage of various fuel types, including diesel fuel, and crude oil. The soil survey consisted of 140 borings covering an area of about 17.5 ha. Two different types of data are available: an abundant set of macroscopic analysis of soil characteristics and a sensory analysis of oil content; and a limited set of 100 soil samples analysed for TPH at a laboratory. It is considered that the more abundant but more uncertain oil reaction data and the more accurate and scarce TPH analyses are measurements of the same attribute — soil contamination with oil products. The methodology proposed consists in characterising the contaminated areas using TPH data, but conditioned to the spots defined by sensory data. The methodology can be summarised by the following sequence: i) spatial estimation of two oil reaction classes defining areas of clean soil and contaminated soil based only on soft data; ii) then inside each spot (“contaminated” and “clean”) stochastic simulation of the TPH variable was performed. Although the high values of TPH are preferentially located in areas previously estimated as “contaminated”, low values of TPH can also occur in these “contaminated” areas and vice-versa. Thus, in this step the final maps are obtained by characterising the spatial distribution of TPH inside each clean and contaminated spot and reclassifying these areas based on TPH simulated values.

Geostatistical Inversion of 3D Post-stack Seismic and Well Data for the Characterization of Acoustic Impedance in Oil Fields

This paper presents an innovative methodology for simulating 3D stochastic images of acoustic impedance conditioned on well data and seismic amplitude data. This methodology is successfully tested for a hypothetical carbonate reservoir. Results are discussed with particular regard to the advantages of the methodology.

Tumor de células granulares endobrônquico – Como abordamos?

Resumo O tumor de celulas granulares e uma neoplasia de origem mesenquimatosa, quase sempre benigna, mas com tendencia a recidivar. Embora surja com maior frequencia na cabeca e no pescoco, tem sido descrito em quase todas as areas do corpo. A sua ocorrencia no pulmao e extremamente rara. Os autores descrevem dois casos de tumores endobronquicos de celulas granulares, discutem os aspectos particulares desta patologia, bem como as modalidades terapeuticas utilizadas, com particular enfase no uso da excisao e crioterapia endobronquica.

Underwater navigation sensors calibration in inland water spaces

This paper describes the calibration of an underwater navigation system in enclosed scenarios. The work was performed in the context of the VAMOS project addressing the development of robotic solutions for flooded open pit mine exploration. An algorithm for calibration of extrinsic parameters for DVL and USBL systems is presented. Field experiments were performed with the ROAZ autonomous surface vehicle equipped with the underwater sensors and using precision IMU/GNSS fused data as groundtruth. The tests were performed in Douro River and in the Bejanca open pit mine, one of the VAMOS test sites, both in northern Portugal. The procedure was validated in the operational scenarios and results are presented showing the error correction and navigation quality improvement.