Analytic Simulation of the Elastic Waves Propagation in the Neighborhood of Fluid Filled Wells with Monopole Sources     

R. Ávila-Carrera  F. J. Sánchez-Sesma  James H. Spurlin  C. Valle-Molina  A. Rodríguez-Castellanos 《Pure and Applied Geophysics》2014,171(9):2209-2223

An analytic formulation to understand the scattering, diffraction and attenuation of elastic waves at the neighborhood of fluid filled wells is presented. An important, and not widely exploited, technique to carefully investigate the wave propagation in exploration wells is the logging of sonic waveforms. Fundamental decisions and production planning in petroleum reservoirs are made by interpretation of such recordings. Nowadays, geophysicists and engineers face problems related to the acquisition and interpretation under complex conditions associated with conducting open-hole measurements. A crucial problem that directly affects the response of sonic logs is the eccentricity of the measuring tool with respect to the center of the borehole. Even with the employment of centralizers, this simple variation, dramatically changes the physical conditions on the wave propagation around the well. Recent works in the numerical field reported advanced studies in modeling and simulation of acoustic wave propagation around wells, including complex heterogeneities and anisotropy. However, no analytical efforts have been made to formally understand the wireline sonic logging measurements acquired with borehole-eccentered tools. In this paper, the Graf’s addition theorem was used to describe monopole sources in terms of solutions of the wave equation. The formulation was developed from the three-dimensional discrete wave-number method in the frequency domain. The cylindrical Bessel functions of the third kind and order zero were re-derived to obtain a simplified set of equations projected into a bi-dimensional plane-space for displacements and stresses. This new and condensed analytic formulation allows the straightforward calculation of all converted modes and their visualization in the time domain via Fourier synthesis. The main aim was to obtain spectral surfaces of transfer functions and synthetic seismograms that might be useful to understand the wave motion produced by the eccentricity of the source and explain in detail the new arising borehole propagation modes. Finally, time histories and amplitude spectra for relevant examples are presented and the validation of time traces using the spectral element method is reported.  相似文献   

Geomechanical model for a seismically active geothermal field: Insights from the Tinguiririca volcanic-hydrothermal system     

L. Giambiagi  P. Álvarez  S. Spagnotto  E. Godoy  A. Lossada  J. Mescua  M. Barrionuevo  J. Suriano 《地学前缘(英文版)》2019,10(6):2117-2133

In this work,we develop a multidisciplinary approach to investigate a geothermal system located at the volcanic arc of a subduction-related orogen and highlight the interplay between active tectonism.stress field and fluid migration.By using results of field investigations from the Tinguiririca geothermal field in the High Andes of Chile(35°S),empirical analysis,and numerical models of static stress variations,we proposed a geomechanical model for evaluating the distribution of hydrothermal manifestations in a seismically-active region.The present geomechanical model follows four major steps:(1) development of the 3 D structural model of fault pattern;(2) estimation of the in-situ stress field;(3) calculation of the resolved-shear-to-normal-stress ratio(slip tendency) on each fault with varying geomechanical parameters(coefficient of friction,pore pressure and cohesion) as inputs;and(4) estimation of Coulomb static stress changes as a consequence of failure in a nearby fault.Through combination of all these analyses,we characterize in detail both the active deformation in the geothermal field and its relationship with hot fluid migration.  相似文献   

Cambrian–early Ordovician volcanism across the South Armorican and Occitan domains of the Variscan Belt in France: Continental break-up and rifting of the northern Gondwana margin     

André Pouclet  J. Javier Álvaro  Jacques-Marie Bardintzeff  Andrés Gil Imaz  Eric Monceret  Daniel Vizcaïno 《地学前缘(英文版)》2017,8(1):25-64

The Cambrian–lower Ordovician volcanic units of the South Armorican and Occitan domains are analysed in a tectonostratigraphic survey of the French Variscan Belt. The South Armorican lavas consist of continental tholeiites in middle Cambrian–Furongian sequences related to continental break-up. A significant volcanic activity occurred in the Tremadocian, dominated by crustal melted rhyolitic lavas and initial rifting tholeiites. The Occitan lavas are distributed into five volcanic phases: (1) basal Cambrian rhyolites, (2) upper lower Cambrian Mg-rich tholeiites close to N-MORBs but crustal contaminated, (3) upper lower–middle Cambrian continental tholeiites, (4) Tremadocian rhyolites, and (5) upper lower Ordovician initial rift tholeiites. A rifting event linked to asthenosphere upwelling took place in the late early Cambrian but did not evolve. It renewed in the Tremadocian with abundant crustal melting due to underplating of mixed asthenospheric and lithospheric magmas. This main tectono-magmatic continental rift is termed the “Tremadocian Tectonic Belt” underlined by a chain of rhyolitic volcanoes from Occitan and South Armorican domains to Central Iberia. It evolved with the setting of syn-rift coarse siliciclastic deposits overlain by post-rift deep water shales in a suite of sedimentary basins that forecasted the South Armorican–Medio-European Ocean as a part of the Palaeotethys Ocean.  相似文献   

Correlations between deep convection and lightning activity on a global scale     

Eldo E. Ávila  Rodrigo E. Bürgesser  Nesvit E. Castellano  Andrew B. Collier  Rosa H. Compagnucci  Arthur R.W. Hughes 《Journal of Atmospheric and Solar》2010,72(14-15):1114-1121

Satellite observations of cloud top temperature and lightning flash distribution are used to examine the relationship between deep convection and lightning activity over the tropical regions of the northern and southern hemispheres. In agreement with previous work, the analysis of the results shows that, in the summer of both hemispheres, the lightning activity in continental deep convective storms is more intense than that in marine deep convective storms by a factor of between 7 and 10. Furthermore, it was observed that on average the daily lightning rate per 1°×1° grid cell for the southern hemisphere (SH) is about 20% greater than that of the northern hemisphere (NH), which can be attributed to a larger fractional cover by deep convective clouds in the SH. By using a set of independent indicators, it is shown that deep convection and lightning activity over land are well correlated (with correlation coefficients of 0.8 and 0.6 for NH and SH, respectively). This suggests the capacity for observations to act as a possible method of monitoring continental deep convective clouds, which play a key role in regulating the Earth’s climate. Since lightning can be monitored easily from ground networks and satellites, it could be a useful tool for validating the performance of model convective schemes and for monitoring changes in climate parameters.  相似文献   

The genetic relationship between mafic dike swarms and plutonic reservoirs in the mesozoic of central chile (30°–33°45′S): insights from AMS and geochemistry     

Christian Creixell  Miguel Ángel Parada  Diego Morata  Pierrick Roperch  César Arriagada 《International Journal of Earth Sciences》2009,98(1):177-201

Five mafic dike swarms between 30° and 33°45′S were studied for their geochemical signature and kinematics of magma flow directions by means of AMS data. In the Coastal Range of central Chile (33°−33°45′S), Middle Jurassic dike swarms (Concón and Cartagena dike swarms, CMDS and CrMDS, respectively) and an Early Cretaceous dike swarm (El Tabo Dike Swarm, ETDS) display the presence of dikes of geochemically enriched (high-Ti) and depleted (low-Ti) basaltic composition. These dikes show geochemical patterns that are different from the composition of mafic enclaves of the Middle Jurassic Papudo-Quintero Complex, and this suggests that the dikes were injected from reservoirs not related to the plutonic complex. The mantle source appears to be a depleted mantle for Jurassic dikes and a heterogeneous-enriched lithospheric mantle for Cretaceous dikes. In the ETDS, vertical and gently plunging magma flow vectors were estimated for enriched and depleted dikes, respectively, which suggest, together with variations in dike thickness, that reservoirs were located at different depths for each dike family. In the Elqui Dike Swarm (EDS) and Limarí Mafic Dike Swarm (LMDS), geochemical patterns are similar to those of the mafic enclaves of the Middle Jurassic plutons. In the LMDS, east to west magma flow vectors are coherent with injection from neighbouring pluton located to the east. In the EDS, some dikes show geochemical and magma flow patterns supporting the same hypothesis. Accordingly, dikes do not necessarily come from deep reservoir; they may propagate in the upper crust from coeval shallow pluton chamber. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.  相似文献   

Effects of reclamation and regeneration processes on organic matter from estuarine soils and sediments   总被引：1，自引：0，他引：1  

C. Santín  J.M. de la Rosa  H. Knicker  X.L. Otero  M.Á. Álvarez  F.J. González-Vila 《Organic Geochemistry》2009,40(9):931-941

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Thermal desorption of CH4 retained in CO2 ice     

Ramón Luna  Carlos Millán  Manuel Domingo  Miguel Ángel Satorre 《Astrophysics and Space Science》2008,314(1-3):113-119

CO₂ ices are known to exist in different astrophysical environments. In spite of this, its physical properties (structure, density, refractive index) have not been as widely studied as those of water ice. It would be of great value to study the adsorption properties of this ice in conditions related to astrophysical environments. In this paper, we explore the possibility that CO₂ traps relevant molecules in astrophysical environments at temperatures higher than expected from their characteristic sublimation point. To fulfil this aim we have carried out desorption experiments under High Vacuum conditions based on a Quartz Crystal Microbalance and additionally monitored with a Quadrupole Mass Spectrometer. From our results, the presence of CH₄ in the solid phase above the sublimation temperature in some astrophysical scenarios could be explained by the presence of several retaining mechanisms related to the structure of CO₂ ice.  相似文献   

Variations in the dynamic response of structures founded on piles induced by obliquely incident SV waves     

Cristina Medina  Guillermo M. Álamo  Juan J. Aznárez  Luis A. Padrón  Orlando Maeso 《地震工程与结构动力学》2019,48(7):772-791

Although the seismic actions generally consist of a combination of waves, which propagates with an angle of incidence not necessarily vertical, the common practice when analyzing the dynamic behavior of pile groups is based on the assumption of vertically incident wave fields. The aim of this paper is to analyze how the angle of incidence of SV waves affects the dynamic response of pile foundations and piled structures. A three-dimensional boundary element-finite element coupling formulation is used to compute impedances and kinematic interaction factors corresponding to several configurations of vertical pile groups embedded in an isotropic homogeneous linear viscoelastic half-space. These results, which are provided in ready-to-use dimensionless graphs, are used to determine the effective dynamic properties of an equivalent single-degree-of-freedom oscillator that reproduces, within the range where the peak response occurs, the response of slender and nonslender superstructures through a procedure based on a substructuring model. Results are expressed in terms of effective flexible-base period and damping as well as maximum shear force at the base of the structure. The relevance and main trends observed in the influence of the wavefront angle of incidence on the dynamic behavior of the superstructure are inferred from the presented results. It is found that effective damping is significantly affected by the variations of the wave angle of incidence. Furthermore, it comes out that the vertical incidence is not always the worst-case scenario.  相似文献   

A teaching approach to time-geography: Some results of an educational experiment     

María Ángeles Díaz-Muñoz  María Jesús Salado-García  Concepción Díaz-Castillo 《GeoJournal》1999,48(3):159-166

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Characteristics of microscale evapotranspiration: a comparative analysis     

F. Ács  G. Szász 《Theoretical and Applied Climatology》2002,73(3-4):189-205

Summary ?Evapotranspiration characteristics on the point-scale (several hundred square meters) and the local scale (several square kilometers) are analysed by comparing a deterministic and a statistical – deterministic surface energy balance model. The vegetation surface variability is represented by both the surface heterogeneity and inhomogeneity. Heterogeneity means the mosaic of wet (wif ≠ 0) and dry (1-wif) fractions of vegetation surface, while inhomogeneity addresses small scale variations of soil moisture content. The microscale characteristics of evapotranspiration are considered in terms of analysing evapotranspiration E _v versus soil moisture content θ, relative frequency distribution characteristics of E _v (θ) and the aggregation algorithms for its estimation. The analyses are performed for loam soil type under different atmospheric forcing conditions. The main result is as follows: For dry vegetation surface (wif = 0), the relationship between the aggregated (θ_agg) and the area-averaged (θ _m ) soil moisture content is nonlinear and depends on both the states of the surface and the atmospheric forcing conditions. In the study, we assumed that there are no advective effects and mesoscale circulation patterns induced by surface discontinuities. Based on this fact it seems unlikely to be able to construct an aggregation algorithm for calculating θ_agg without inclusion of the atmospheric forcing conditions. This means that it will be difficult to construct a simple formula for calculating area-averaged transpiration, if it is possible at all. Received May 3, 2001; revised May 31, 2002; accepted June 3, 2002  相似文献