Bayesian inversion of synthetic AVO data to assess fluid and shale content in sand-shale media     

Hafiz Mubbasher Anwer  Aamir Ali  Tiago M Alves 《Journal of Earth System Science》2017,126(3):42

Reservoir characterization of sand-shale sequences has always challenged geoscientists due to the presence of anisotropy in the form of shale lenses or shale layers. Water saturation and volume of shale are among the fundamental reservoir properties of interest for sand-shale intervals, and relate to the amount of fluid content and accumulating potentials of such media. This paper suggests an integrated workflow using synthetic data for the characterization of shaley-sand media based on anisotropic rock physics (T-matrix approximation) and seismic reflectivity modelling. A Bayesian inversion scheme for estimating reservoir parameters from amplitude vs. offset (AVO) data was used to obtain the information about uncertainties as well as their most likely values. The results from our workflow give reliable estimates of water saturation from AVO data at small uncertainties, provided background sand porosity values and isotropic overburden properties are known. For volume of shale, the proposed workflow provides reasonable estimates even when larger uncertainties are present in AVO data.  相似文献   

Properties of dust aerosol particles transported to Portugal from the Sahara desert   总被引：1，自引：0，他引：1  

FRANK WAGNER  DANIELE BORTOLI  SÉRGIO PEREIRA  MARIA JOÃO COSTA  ANA MARIA SILVA  BERNADETT WEINZIERL  MICHAEL ESSELBORN  REAS PETZOLD  KATHI RASP  BERND HEINOLD  INA TEGEN 《Tellus. Series B, Chemical and physical meteorology》2009,61(1):297-306

Aerosol properties of mineral particles in the far field of an African desert dust outbreak were investigated that brought Saharan dust over the Mediterranean in different layers to Portugal. The measurements were performed inside the project Desert Aerosols over Portugal (DARPO) which was linked to the Saharan Mineral Dust Experiment (SAMUM). The maximum particle mass concentration was about 150 μg m⁻³ and the corresponding scattering coefficient was 130 M m⁻¹ which results in a mass scattering efficiency of 0.87 m² g⁻¹. The aerosol optical depth reached values up to 0.53 and the lidar ratio was between 45 and 50 in the whole dust loaded column. A comparison between particle size distributions and refractive indices derived from different instruments and models showed a general good agreement but some minor differences could also be observed. Measurements as well as calculations with a particle transport model suggest that there is a relatively higher concentration of very large particles in the upper region of the dust layer than on the surface which is likely connected with meteorological conditions at the observational site (Évora, Portugal).  相似文献   

THE ROLE OF LOCAL CIRCULATIONS IN SUMMERTIME CONVECTIVE DEVELOPMENT AND NOCTURNAL FOG IN SÃO PAULO, BRAZIL     

MARIA A. F. SILVA DIAS  ANTONIO JASCHKE MACHADO 《Boundary-Layer Meteorology》1997,82(1):135-157

A non-hydrostatic, fully compressible, regional-scale numerical model of the atmosphere that includes parameterization of cloud microphysics is run in a two-dimensional mode. It uses two different observed vertical profiles of temperature, relative humidity and wind to simulate the local circulation evolution and impact on convection and nocturnal fog occurrence in São Paulo, Brazil. Theatmospheric behaviour generated by the model is similar to the observations of the two summer days with and without sea breeze progression over the plateau. The convective development occurs in the afternoon of the two experiments but with different features and intensities. In the experiment with sea-breeze progression, there is fog formation over the plateau during the following night, in accordance with the observations. A strong northwesterly flow acting in the lower troposphere, with intensity varying between 7 and 10 m s_-1,appears as an inhibiting agent of the sea-breeze progression over the plateau and of convective development in the afternoon and of the nocturnal fog occurrence. In this case, observed gusts during the night are well simulated and appear to be related to the topography.  相似文献   

PHASE ERRORS OF FINITE-DIFFERENCE MIGRATION*     

C. M. BEAUMONT  J. F. BOYCE  R. SILVA 《Geophysical Prospecting》1987,35(3):267-280

A quantitative analysis of the various approximations to the scalar wave equation used in seismic migration can be obtained by a study of the resulting phase errors. In the space-time domain the effects of different modes of parameter optimization are displayed. In the space-frequency domain the spatial derivatives may be expanded as a linear filter operator whose coefficients are determined by requiring that the resulting phase shifts agree with those that arise from planar wave solutions of the exact wave equation over a range of angles and frequencies.  相似文献   

Extreme values and meteorology     

J. Tiago de Oliveira 《Theoretical and Applied Climatology》1986,37(4):184-193

Summary The basic ideas of univariate extremes and some applications are described in the paper; some references are made to multivariate extremes and stochastic processes of extremes.

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Zusammenfassung Es werden einige grundlegende Ideen zu univariaten Extremen und ihren Anwendungen beschrieben. Multivariate Extreme und stochastische Prozesse von Extremen werden ebenfalls besprochen.

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With 4 Figures  相似文献   

Soil chemical alteration due to slaughterhouse waste application as identified by spectral reflectance in São Paulo State,Brazil: an environmental monitoring useful tool     

José A. M. Demattê  Julianne de Castro Oliveira  Tiago Rodrigues Tavares  Leonardo Ramirez Lopez  Fabrício da Silva Terra  Suzana Romeiro Araújo  Caio Troula Fongaro  Stoécio Malta Ferreira Maia  Francisco Fujita de Castro Mello  Rodnei Rizzo  Simone Vicente  Marco Antonio de Melo Bortolleto  Pedro Henrique Ramos Cerqueira 《Environmental Earth Sciences》2016,75(18):1277

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The sediment budget and dynamics of a delta‐canyon‐lobe system over the Anthropocene timescale: The Rhone River delta,Lake Geneva (Switzerland/France)     

Tiago A. Silva  Stphanie Girardclos  Laura Stutenbecker  Maarten Bakker  Anna Costa  Fritz Schlunegger  Stuart N. Lane  Peter Molnar  Jean‐Luc Loizeau 《Sedimentology》2019,66(3):838-858

Deltas are important coastal sediment accumulation zones in both marine and lacustrine settings. However, currents derived from tides, waves or rivers can transfer that sediment into distal, deep environments, connecting terrestrial and deep marine depozones. The sediment transfer system of the Rhone River in Lake Geneva is composed of a sublacustrine delta, a deeply incised canyon and a distal lobe, which resembles, at a smaller scale, deep‐sea fan systems fed by high discharge rivers. From the comparison of two bathymetric datasets, collected in 1891 and 2014, a sediment budget was calculated for eastern Lake Geneva, based on which sediment distribution patterns were defined. During the past 125 years, sediment deposition occurred mostly in three high sedimentation rate areas: the proximal delta front, the canyon‐levée system and the distal lobe. Mean sedimentation rates in these areas vary from 0·0246 m year^?1 (distal lobe) to 0·0737 m year^?1 (delta front). Although the delta front–levées–distal lobe complex only comprises 17·0% of the analysed area, it stored 74·9% of the total deposited sediment. Results show that 52·5% of the total sediment stored in this complex was transported toward distal locations through the sublacustrine canyon. Namely, the canyon–levée complex stored 15·9% of the total sediment, while 36·6% was deposited in the distal lobe. The results thus show that in deltaic systems where density currents can occur regularly, a significant proportion of riverine sediment input may be transferred to the canyon‐lobe systems leading to important distal sediment accumulation zones.  相似文献   

Erosion of an active fault scarp leads to drainage capture in the Amazon region,Brazil          下载免费PDF全文

Pedro Val  Clauzionor Silva  David Harbor  Norberto Morales  Felipe Amaral  Tiago Maia 《地球表面变化过程与地形》2014,39(8):1062-1074

Far from the continental margin, drainage basins in Central Amazonia should be in topographic steady state; but they are not. Abandoned remnant fluvial valleys up to hundreds of square kilometers in size are observed throughout Amazonia, and are evidence of significant landscape reorganization. While major Late Miocene drainage shifts occurred due to initiation of the transcontinental Amazon River, local landscape change has remained active until today. Driven either by dynamic topography, tectonism, and/or climatic fluctuations, drainage captures in Amazonia provide a natural experiment for assessing the geomorphic response of low‐slope basins to sudden, capture related base‐level falls. This paper evaluates the timing of geomorphic change by examining a drainage capture event across the Baependi fault scarp involving the Cuieiras and Tarumã‐Mirim River basins northwest of the city of Manaus in Brazil. A system of capture‐related knickpoints was generated by base‐level fall following drainage capture; through numerical modeling of their initiation and propagation, the capture event is inferred to have occurred between the middle and late Pleistocene, consistent with other studies of landscape change in surrounding areas. In low‐slope settings like the Amazon River basin, base‐level fall can increase erosion rates by more than an order of magnitude, and moderate to large river basins can respond to episodes of base‐level fall over timescales of tens to hundreds of thousands of years. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

Seismic vulnerability assessment of historical masonry buildings located in Annaba city (Algeria) using non ad-hoc data survey     

Alla Eddine Athmani  Abdelhacine Gouasmia  Tiago Miguel Ferreira  Romeu Vicente  Asma Khemis 《Bulletin of Earthquake Engineering》2015,13(8):2283-2307

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Sediment geochemistry of the urban Lake Paulo Gorski     

Marcelo Bevilacqua Remor  Silvio César Sampaio  Sacha de Rijk  Marcio Antônio Vilas Boas  Jackeline Tatiane Gotardo  Everton Tiago Pinto  Fábio Augusto Schardong 《国际泥沙研究》2018,33(4):406-414

The objective of this study was to evaluate the concentration and distribution of heavy metals in the sediments of Paulo Gorski Lake, as well as the metals’ bioavailability and potential ecological risk, and to define the anthropogenic and natural heavy metal contributions to the lake. The chemical elements calcium (Ca), cadmium (Cd), cobalt (Co), chromium (Cr), copper (Cu), iron (Fe), potassium (K), magnesium (Mg), manganese (Mn), sodium (Na), nickel (Ni), lead (Pb), and zinc (Zn) were quantified by flame atomic absorption spectrophotometry with two extraction methods to quantify the bioavailable and non-bioavailable fractions. The data were evaluated using multivariate statistics and sediment quality indices. All sediment collection points (S1, S2, S3, S4 and S5) are different in terms of the concentration of heavy metals, except for S4 and S5, which were statistically equal. The bioavailable fraction of the elements in the sediment follows the sequence Pb>Cu>Mn>Zn>Ni>Cr>phosphorus (P) for all points. The elements Co, Cr, Pb, and Zn showed moderate to considerable contamination at all points. Only points S3 and S5 had moderate ecological risk. Urbanization has been affecting Paulo Gorski Lake via the input of chemical elements, especially Co and Pb. The points most affected by heavy metal contamination are S3 and S5 when the sedimentological sensitivity factor is considered. The lake has high hydrodynamics, causing some of the contaminants that enter the system to leave it, leading to potential negative impacts downstream.  相似文献