Interpretation of dilatometer tests in a heavy oil reservoir

This paper presents a prospective study for identifying selected parameters of the modified Cam‐Clay model representing the behaviour of heavy oil reservoirs. The first part shows that the plastic compressibility, which controls the main recovery mechanism of such reservoirs, can be accurately determined, simultaneously with other parameters, by an inverse analysis of pressure–strain curves. The conditions of the identification procedure mainly involve two tests conducted under different drainage conditions or at different strain rates. The numerical study also establishes the sequence of an original in situ experimental program, in which three dilatometer tests at a relatively great depth (several hundreds of metres) were carried out. The comparison of the experimental data with the numerical computations reveals a significant over‐consolidation ratio which does not allow the plastic compressibility to be determined but supports the findings regarding the geological erosion of the site. Copyright © 2006 John Wiley & Sons, Ltd.     

Global-scale surface spectral variations on Titan seen from Cassini/VIMS

We present global-scale maps of Titan from the Visual and Infrared Mapping Spectrometer (VIMS) instrument on Cassini. We map at 64 near-infrared wavelengths simultaneously, covering the atmospheric windows at 0.94, 1.08, 1.28, 1.6, 2.0, 2.8, and 5 μm with a typical resolution of 50 km/pixel or a typical total integration time of 1 s. Our maps have five to ten times the resolution of ground-based maps, better spectral resolution across most windows, coverage in multiple atmospheric windows, and represent the first spatially resolved maps of Titan at 5 μm. The VIMS maps provide context and surface spectral information in support of other Cassini instruments. We note a strong latitudinal dependence in the spectral character of Titan's surface, and partition the surface into 9 spectral units that we describe in terms of spectral and spatial characteristics.     

ESR chronology of the Somme River Terrace system and first human settlements in Northern France

The Somme Valley, Northern France, is famous for its archaeological sequence, where numerous rich Palaeolithic sites, such as Saint-Acheul, the type site of the Acheulian, have been discovered. The archaeological levels are often directly associated with fossil alluvial sediments of the River Somme or with slope deposits, including loess and palaeosols. In the middle reaches of the valley, near Amiens, the system of fossil-stepped fluvial terraces is particularly well developed and preserved, and occurs on 10 alluvial formations. These terraces, from +5 to +55 m above the present-day valley bedrock, allow the study of the environmental changes and the human settlement of this area through the Pleistocene.

Since 1988, ESR dating was systematically applied on bleached quartz extracted from the fossil fluvial deposits, in order to better describe the geological evolution of the stepped system. More recently, U-series/ESR dating has also been performed on teeth collected from the different terrace deposits. Here we present a synthetic review of the main ESR results, and propose an ESR chronology for the geological evolution of the Somme fluvial system and for the Middle Pleistocene human settlement of northern France.     

Influence of the oceanic biology on the tropical Pacific climate in a coupled general circulation model

The influence of chlorophyll spatial patterns and variability on the tropical Pacific climate is investigated by using a fully coupled general circulation model (HadOPA) coupled to a state-of-the-art biogeochemical model (PISCES). The simulated chlorophyll concentrations can feedback onto the ocean by modifying the vertical distribution of radiant heating. This fully interactive biological-ocean-atmosphere experiment is compared to a reference experiment that uses a constant chlorophyll concentration (0.06 mg m⁻³). It is shown that introducing an interactive biology acts to warm the surface eastern equatorial Pacific by about 0.5°C. Two competing processes are involved in generating this warming: (a) a direct 1-D biological warming process in the top layers (0–30 m) resulting from strong chlorophyll concentrations in the upwelling region and enhanced by positive dynamical feedbacks (weaker trade winds, surface currents and upwelling) and (b) a 2-D meridional cooling process which brings cold off-equatorial anomalies from the subsurface into the equatorial mixed layer through the meridional cells. Sensitivity experiments show that the climatological horizontal structure of the chlorophyll field in the upper layers is crucial to maintain the eastern Pacific warming. Concerning the variability, introducing an interactive biology slightly reduces the strength of the seasonal cycle, with stronger SST warming and chlorophyll concentrations during the upwelling season. In addition, ENSO amplitude is slightly increased. Similar experiments performed with another coupled general circulation model (IPSL-CM4) exhibit the same behaviour as in HadOPA, hence showing the robustness of the results.     

A statistical�Cdynamical scheme for reconstructing ocean forcing in the Atlantic. Part I: weather regimes as predictors for ocean surface variables

The links between the observed variability of the surface ocean variables estimated from reanalysis and the overlying atmosphere decomposed in classes of large-scale atmospheric circulation via clustering are investigated over the Atlantic from 1958 to 2002. Daily 500?hPa geopotential height and 1,000?hPa wind anomaly maps are classified following a weather-typing approach to describe the North Atlantic and tropical Atlantic atmospheric dynamics, respectively. The algorithm yields patterns that correspond in the extratropics to the well-known North Atlantic-Europe weather regimes (NAE-WR) accounting for the barotropic dynamics, and in the tropics to wind classes (T-WC) representing the alteration of the trades. 10-m wind and 2-m temperature (T2) anomaly composites derived from regime/wind class occurrence are indicative of strong relationships between daily large-scale atmospheric circulation and ocean surface over the entire Atlantic basin. High temporal correlation values are obtained basin-wide at low frequency between the observed fields and their reconstruction by multiple linear regressions with the frequencies of occurrence of both NAE-WR and T-WC used as sole predictors. Additional multiple linear regressions also emphasize the importance of accounting for the strength of the daily anomalous atmospheric circulation estimated by the combined distances to all regimes centroids in order to reproduce the daily to interannual variability of the Atlantic ocean. We show that for most of the North Atlantic basin the occurrence of NAE-WR generally sets the sign of the ocean surface anomaly for a given day, and that the inter-regime distances are valuable predictors for the magnitude of that anomaly. Finally, we provide evidence that a large fraction of the low-frequency trends in the Atlantic observed at the surface over the last 50?years can be traced back, except for T2, to changes in occurrence of tropical and extratropical weather classes. All together, our findings are encouraging for the prospects of basin-scale ocean dynamical downscaling using a weather-typing approach to reconstruct forcing fields for high resolution ocean models (Part II) from coarse resolution climate models.     

About the effect of relative humidity on the indentation response of Meuse/Haute�CMarne argillite

The unsaturated poromechanical behavior of Callovo-Oxfordian argillite (also referred to as Meuse/Haute–Marne argillite) is analyzed by means of indentation tests at different hygrometries. Numerical simulations carried out with a finite element code are then used to simulate flat punch indentation tests at different controlled hygrometries. The numerical response F(h) is compared to experimental data in order to estimate the drained Young’s modulus E and the internal friction angle \Upphi\Upphi (at high confinement) by means of a back analysis. A linear decrease in the drained Young’s modulus and quasi-constant values of the internal friction angle are observed when the relative humidity ranges. Some predictions of the model are also presented to quantify the activation of hydraulic phenomena. Indeed, the maximal variation of the saturation and porosity relative to the initial state of the specimen are lower than 10% and 8%, respectively.     

Rotational excitation of protonated hydrogen cyanide (HCNH+) by He atom at low temperature

We report on ab initio coupled-cluster calculations of the interaction potential energy surface for the HCNH⁺–He complex. The aug-cc-pVTZ Gaussian basis, to which is added a set of bond functions placed at mid-distance between HCNH⁺ center of mass and He atom is used. The HCNH⁺ bonds length are set to their values at the equilibrium geometry, i.e., r _e [HC]=1.0780 Å, r _e [CN]=1.1339 Å and r _e [NH]=1.0126 Å. The interaction energy presents a global minimum located $266.9~\mathrm{cm^{-1}}$ below the HCNH⁺–He dissociation limit. Using the interaction potential obtained, we have computed rotational excitation cross sections in the close-coupling approach and downward rate coefficients at low temperature (T≤120 K). It is expected that the data worked out in this study may be beneficial for further astrophysical investigations as well as laboratory experiments.     

Scale-dependent habitat use by a large free-ranging predator,the Mediterranean fin whale

Since the heterogeneity of oceanographic conditions drives abundance, distribution, and availability of prey, it is essential to understand how foraging predators interact with their dynamic environment at various spatial and temporal scales. We examined the spatio-temporal relationships between oceanographic features and abundance of fin whales (Balaenoptera physalus), the largest free-ranging predator in the Western Mediterranean Sea (WM), through two independent approaches. First, spatial modeling was used to estimate whale density, using waiting distance (the distance between detections) for fin whales along ferry routes across the WM, in relation to remotely sensed oceanographic parameters. At a large scale (basin and year), fin whales exhibited fidelity to the northern WM with a summer-aggregated and winter-dispersed pattern. At mesoscale (20–100 km), whales were found in colder, saltier (from an on-board system) and dynamic areas defined by steep altimetric and temperature gradients. Second, using an independent fin whale satellite tracking dataset, we showed that tracked whales were effectively preferentially located in favorable habitats, i.e. in areas of high predicted densities as identified by our previous model using oceanographic data contemporaneous to the tracking period. We suggest that the large-scale fidelity corresponds to temporally and spatially predictable habitat of whale favorite prey, the northern krill (Meganyctiphanes norvegica), while mesoscale relationships are likely to identify areas of high prey concentration and availability.     

High resolution spectra of galaxies

We present inversion techniques which aim at recovering the composite nature and the kinematics of a stellar population from its high resolution absorption line spectrum. The originality of the combined inversion is its potential to recover both the stellar content and the kinematics simultaneously. These techniques use new synthetic high resolution spectra produced by PéGASE and minimization algorithms. We apply them to mock data representing the bulge and disk population of the inner region of spiral galaxies. This revised version was published online in August 2006 with corrections to the Cover Date.     

Statistical detection and no-detection of rainfall change trends and breaks in semiarid Tunisia—50+ years over the Merguellil agro-hydro-climatic reference basin

Rainfall variability is an important feature of semiarid climates with major effects on hydrology, and beyond on key water-dependent societal aspects. Eventual changes in rainfall variability are a strong driver of change of hydrological processes, resources, and hazards, up to catchment signatures and spatial arrangements. We deal with observed precipitations and subsequent statistical coefficients available from a network of 15 rainfall gauges over and around the Merguellil catchment (1175 km²), with series ranging up to the 1961–2013 period. We look for eventual annual trends and breakpoints with a set of methods: Mann Kendall test, Pettitt test, Hubert segmentation procedure, Buishand U statistic, and Lee Heghinian Bayesian procedure. The results underline oscillation of dry and wet periods; several studied rain gauges (Tella, Oueslatia forêt, Majbar, Kesra forêt, Henchir Bhima, and Haffouz DGRE) denote significant trends in annual precipitation. Some breaks are detected but they are not synchronous. These methods reveal the variability of rainfall regimes in the semiarid region and provide a synoptic view of detection and no-detection of symptoms of change. This work gives opportunities to water stakeholders and climate experts in understanding the relationships between climate variability and water availability.