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101.
Tight oil siltstones are rocks with complex structure at pore scale and are characterized by low porosity and low permeability at macroscale. The production of tight oil siltstone reservoirs can be increased by hydraulic fracturing. For optimal fracking results, it is desirable to map the ability to fracture based on seismic data prior to fracturing. Brittleness is currently thought to be a key parameter for evaluating the ability to fracture. To link seismic information to the brittleness distribution, a rock physics model is required. Currently, there exists no commonly accepted rock physics model for tight oil siltstones. Based on the observed correlation between porosity and mineral composition and known microstructure of tight oil siltstone in Daqing oilfield of Songliao basin, we develop a rock physics model by combining the Voigt–Reuss–Hill average, self-consistent approximation and differential effective medium theory. This rock physics model allows us to explore the dependence of the brittleness on porosity, mineral composition, microcrack volume fraction and microcrack aspect ratio. The results show that, as quartz content increases and feldspar content decreases, Young's modulus tends to increase and Poisson ratio decreases. This is taken as a signature of higher brittleness. Using well log data and seismic inversion results, we demonstrate the versatility of the rock physics template for brittleness prediction. 相似文献
102.
103.
Christian Lehr Philipp Rauneker Marcus Fahle Tobias L. Hohenbrink Steven Böttcher Marco Natkhin Björn Thomas Ralf Dannowski Bernd Schwien Gunnar Lischeid 《水文研究》2017,31(3):750-752
Physical models are a well‐established tool in education to strengthen hydrological understanding. They facilitate the straightforward visualization of hydrological processes and allow the communication of hydrological concepts, research and questions of general interest to the public. In order to visualize the water cycle in a landscape of postglacial sediments, in particular the subsurface part, a physical model was constructed. In two videos, (1) a detailed construction manual and (2) visualization examples of hydrological concepts and processes are presented. With our contribution, we like to encourage professionals in the field of hydrology to share methods and tools of knowledge transfer and communication of hydrological concepts. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
104.
Salinization of groundwater in the Nefzawa oases region,Tunisia: results of a regional-scale hydrogeologic approach 总被引:1,自引:0,他引:1
Mounira Zammouri Tobias Siegfried Tobias El-Fahem Samiha Kriâa Wolfgang Kinzelbach 《Hydrogeology Journal》2007,15(7):1357-1375
Groundwater pumped from the semi-confined Complexe Terminal (CT) aquifer is an important production factor in irrigated oases
agriculture in southern Tunisia. A rise in the groundwater salinity has been observed as a consequence of increasing abstraction
from the aquifer during the last few decades. All sources of contamination were investigated using hydrochemical data available
from the 1980s. Water samples were taken from drains and observation wells tapping both the CT and the phreatic aquifers and
analyzed with regard to chemistry, temperature, isotopes and other environmental tracers. Local salinization mechanisms are
suggested, i.e. the upwelling of saline water from the underlying, confined Continental Intercalaire (CI) aquifer, as well
as backflow of agricultural drainage water. At this stage, the main salt pan, the Chott el Djerid, is not a contamination
source. A finite difference model was also developed to simulate groundwater flow and contaminant transport in the oases.
Calibration for the period 1950–2000 was carried out in order to adjust geological and chemical system parameters. The simulation
of planned extraction projects predicts a worsening of the present situation. Maintenance of the present abstraction regime
will not reduce or stop the salinity increase.
Résumé L’eau souterraine pompée dans l’aquifère semi-captif du Complexe Terminal (CT) est un facteur de production important pour l’agriculture des oasis irriguées du sud de la Tunisie. Une augmentation de la salinité de l’eau souterraine a été considérée comme la conséquence de l’augmentation des prélèvements dans l’aquifère au cours des dernières décades. Toutes les sources de contamination ont été étudiées à l’aide de données hydro-chimiques disponibles depuis les années 80. Des échantillons d’eau ont été prélevés dans des drains et des puits d’observation qui captent à la fois le CT et les aquifères phréatiques; la chimie, la température, les isotopes ainsi que d’autres traceurs environnementaux ont été analysés. Des processus locaux de salinisation sont proposés, comme par exemple la remontée d’eau salée en provenance de l’aquifère captif du Continental Intercalaire (CI) sous-jacent, ainsi que le reflux des eaux du drainage agricole. A ce stade, le principal marais salé, le Chott el Djerid, n’est pas une source de contamination. Un modèle aux différences finies a également été élaboré pour simuler les écoulements souterrains et le transport de contaminants dans les oasis. Une calibration pour la période 1950–2000 a été effectuée afin d’ajuster les paramètres des systèmes géologique et chimique. La simulation de projets planifiés d’extraction prédit une aggravation de la situation actuelle. La conservation du régime d’extraction actuel ne réduira ou ne stoppera pas l’augmentation de la salinité.
Resumen El agua subterránea que se bombea del acuífero semi-confinado Terminal Complejo (CT) es un importante factor de producción en la agricultura de riego con oasis en el sur de Túnez. Se ha observado un incremento en la salinidad del agua subterránea como consecuencia de la abstracción creciente del acuífero durante las últimas décadas. Se investigaron todas las fuentes de contaminación usando datos hidroquímicos disponibles de la década de 1980s. Las muestras de agua se tomaron de drenajes y pozos de observación alojados tanto en el CT como los acuíferos freáticos y se analizaron en relación con química, temperatura, isótopos y otros trazadores ambientales. Se sugieren mecanismos de salinización local, i.e. el ascenso de agua salada a partir del acuífero confinado subyacente Intercalado Continental (CI), así como también retorno de flujo de agua de drenaje agrícola. En esta etapa, el pan salado principal, el Chott el Djerid, no es una fuente de contaminación. También se desarrolló un modelo de diferencia finita para simular el flujo de agua subterránea y el transporte de contaminantes en los oasis. Se calibró el modelo para el periodo 1950–2000 para de este modo ajustar parámetros del sistema químico y geológico. La simulación de los proyectos de extracción que se han planeado predice un empeoramiento de la situación actual. El mantenimiento del régimen de extracción actual no reducirá o detendrá el incremento de salinidad.相似文献
105.
106.
Tobias Leismann Miguel-Angel Aloy Ewald Müller 《Astrophysics and Space Science》2004,293(1-2):157-163
In a series of time dependent numerical simulations we have performed a parameter study of magnetised relativistic jets. We have found that the impact of the magnetic field on the morphology of a jet depends strongly on the configuration of the field. 相似文献
107.
Tobias Owen 《Icarus》1976,29(1):159-163
A brief review of the history of Jovian satellite nomenclature is given to indicate the background for the names proposed for the numbered satellites. The new names are consistent with established tradition and should cause minimal confusion with other named objects in the solar system. 相似文献
108.
Cochran Anita Veverka Joseph Bell James Belton Michael Benkhoff Johannes Benkhoff Andrew Clark Benton Feldman Paul Kissel Jochen Mahaffy Paul Malin Michael Murchie Scott Neimann Hasso Owen Tobias Robinson Mark Schwehm Gerhard Squyres Steve Thomas Peter Whipple Fred Yeomans Donald 《Earth, Moon, and Planets》2000,89(1-4):289-300
In 1997, the COmet Nucleus TOUR (CONTOUR) was selected byNASA for a new start as part of the Discovery line. In this paper, we review the status of the mission, the mission timeline and the instruments to be flown. Detail is given of the science goals and how they are to be accomplished. 相似文献
109.
Dietmar Dommenget Sabine Haase Tobias Bayr Claudia Frauen 《Climate Dynamics》2014,42(11-12):3187-3205
In a recent study it was illustrated that the El Nino Southern Oscillation (ENSO) mode can exist in the absence of any ocean dynamics. This oscillating mode exists just due to the interaction between atmospheric heat fluxes and ocean heat capacity. The primary purpose of this study is to further explore these atmospheric Slab Ocean ENSO dynamics and therefore the role of positive atmospheric feedbacks in model simulations and observations. The positive solar radiation feedback to sea surface temperature (SST), due to reduced cloud cover for anomalous warm SSTs, is the main positive feedback in the Slab Ocean El Nino dynamics. The strength of this positive cloud feedback is strongly related to the strength of the equatorial cold tongue. The combination of positive latent and sensible heat fluxes to the west and negative ones to the east of positive anomalies leads to the westward propagation of the SST anomalies, which allows for oscillating behavior with a preferred period of 6–7 years. Several indications are found that parts of these dynamics are indeed observed and simulated in other atmospheric or coupled general circulation models (AGCMs or CGCMs). The CMIP3 AGCM-slab ensemble of 13 different AGCM simulations shows unstable ocean–atmosphere interactions along the equatorial Pacific related to stronger cold tongues. In observations and in the CMIP3 and CMIP5 CGCM model ensemble the strength and sign of the cloud feedback is a function of the strength of the cold tongue. In summary, this indicates that the Slab Ocean El Nino dynamics are indeed a characteristic of the equatorial Pacific climate that is only dominant or significantly contributing to the ENSO dynamics if the SST cold tongue is sufficiently strong. In the observations this is only the case during strong La Nina conditions. The presence of the Slab Ocean ENSO atmospheric feedbacks in observations and CGCM model simulations implies that the family of physical ENSO modes does have another member, which is entirely driven by atmospheric processes and does not need to have the same spatial pattern nor the same time scales as the main ENSO dynamics. 相似文献
110.
Tino Pieczonka Tobias Bolch Manfred Buchroithner 《ISPRS Journal of Photogrammetry and Remote Sensing》2011,66(6):927-940
Multitemporal digital terrain models (DTM) are an important source for many purposes such as the detection of areas, which are susceptible to natural hazards such as landslides and glacial lake outburst floods, or for the examination of changes in glacier thickness. To exploit the potential of stereo satellite and aerial imagery for time series analysis, the employed methodology and software can be critical. A statistical analysis based on quartiles is presented to eliminate the influence of registration and elevation errors in DTMs. For our analysis, we used multi-temporal airborne and spaceborne stereoscopic images. The oldest images were recorded in the 1960s by the US American reconnaissance satellite Corona, while the most recent imagery are 2007 Cartosat-1 stereo scenes, along with one ASTER stereo pair. Complex panoramic distortion and limited spatial resolution resulted in the Corona and ASTER DTMs having the highest RMSEz. Due to differing acquisition techniques, applied software packages and temporal differences DTMs will never be identical. Therefore, we propose a relative vertical accuracy assessment with a master DTM. We chose the Cartosat-1 DTM as it showed the highest absolute accuracy. Inaccuracies between the master and the slave DTMs were adjusted by means of trend surfaces and outliers were successfully eliminated applying the interquartile range. 相似文献