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排序方式: 共有114条查询结果,搜索用时 250 毫秒
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Lars Kristian Nielsen Sam Subbey Mike Christie Trond Mannseth 《Computational Geosciences》2006,10(3):321-342
There is a correspondence between flow in a reservoir and large scale permeability trends. This correspondence can be derived by constraining reservoir models using observed production data. One of the challenges in deriving the permeability distribution of a field using production data involves determination of the scale of resolution of the permeability. The Adaptive Multiscale Estimation (AME) seeks to overcome the problems related to choosing the resolution of the permeability field by a dynamic parameterisation selection. The standard AME uses a gradient algorithm in solving several optimisation problems with increasing permeability resolution. This paper presents a hybrid algorithm which combines a gradient search and a stochastic algorithm to improve the robustness of the dynamic parameterisation selection. At low dimension, we use the stochastic algorithm to generate several optimised models. We use information from all these produced models to find new optimal refinements, and start out new optimisations with several unequally suggested parameterisations. At higher dimensions we change to a gradient-type optimiser, where the initial solution is chosen from the ensemble of models suggested by the stochastic algorithm. The selection is based on a predefined criterion. We demonstrate the robustness of the hybrid algorithm on sample synthetic cases, which most of them were considered insolvable using the standard AME algorithm. 相似文献
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Tephrochronological dating of postglacial volcanism in the Dyngjufjöll volcanic complex, a major spreading center in the Icelandic Rift Zone, indicates a high production rate in the millennia following deglaciation as compared to the present low productivity. The visible and implied evidence indicates that lava production in the period 10 000–4500 bp was at least 20 to 30 times higher than that in the period after 2900 bp but the results are biased towards lower values for lava volumes during the earlier age periods since multiple lava layers are buried beneath younger flows. The higher production rate during the earlier period coincides with the disappearance of glaciers of the last glaciation. Decreasing lithostatic pressure as the glacier melts and vigorous crustal movements caused by rapid isostatic rebound may trigger intense volcanism until a new pressure equilibrium has been established. 相似文献
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Fine‐scale diet of the Australian sea lion (Neophoca cinerea) using DNA‐based analysis of faeces
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Kristian J. Peters Kathy Ophelkeller Nathan J. Bott Bruce E. Deagle Simon N. Jarman Simon D. Goldsworthy 《Marine Ecology》2015,36(3):347-367
We applied DNA‐based faecal analysis to determine the diet of female Australian sea lions (n = 12) from two breeding colonies in South Australia. DNA dietary components of fish and cephalopods were amplified using the polymerase chain reaction and mitochondrial DNA primers targeting the short (~100 base pair) section of the 16S gene region. Prey diversity was determined by sequencing ~50 amplicons generated from clone libraries developed for each individual. Faecal DNA was also combined and cloned from multiple individuals at each colony and fish diversity determined. Diets varied between individuals and sites. Overall, DNA analysis identified a broad diversity of prey comprising 23 fish and five cephalopod taxa, including many species not previously described as prey of the Australian sea lion. Labridae (wrasse), Monacanthidae (leatherjackets) and Mullidae (goat fish) were important fish prey taxa. Commonly identified cephalopods were Octopodidae (octopus), Loliginidae (calamary squid) and Sepiidae (cuttlefish). Comparisons of fish prey diversity determined by pooling faecal DNA from several samples provided a reasonable but incomplete resemblance (55–71%) to the total fish diversity identified across individual diets at each site. Interpretation of diet based on the recovery of prey hard‐parts identified one cephalopod beak (Octopus sp.) and one fish otolith (Parapriacanthus elongatus). The present study highlights the value of DNA‐based analyses and their capabilities to enhance information of trophic interactions. 相似文献
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In this paper the ability of analytical solutions for four-component three-phase flow to predict displacement efficiency in
water alternating gas (WAG) injection processes is studied. First analytical solutions for Riemann problems with injection
compositions that are the average water and gas mixture for various WAG injection schemes are presented. These solutions are
compared to numerical calculations with variable slug sizes and used to explore the effect of slug size, injecting water vs
gas first, and the average injection composition on displacement efficiency in compositional WAG schemes. The example model
is partially miscible WAG injection of water and CO2 into an oil reservoir containing C10 and CH4 with and without a mobile aqueous phase present initially. The trailing end of the water and gas profiles are sensitive to
whether water or gas is injected first, but the magnitude of the oil bank and the breakthrough time of the injected fluids
are accurately predicted by the analytical solutions, even for displacements where large water and gas slugs are injected.
Fluctuations in the saturation and composition profiles resulting from the alternating injection sequence in the WAG simulations
appear as super-imposed on top of the sequence of rarefaction and shock waves predicted by analytical solutions. As the number
of slugs increases, the effect of alternating boundary conditions diminishes and the displacements predicted by numerical
calculations converge to the analytical solutions. 相似文献
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Branka Ivančan-Picek Kristian Horvath Nataša Strelec Mahović Marjana Gajić-Čapka 《Natural Hazards》2014,72(2):1231-1252
The aim of this study was to identify the main mesoscale features and mechanisms responsible for the generation of an extreme precipitation event as a contribution to improving the modelling of processes that produce HPEs. The event occurred during the morning hours on 22 November 2010 over the Dubrovnik coast in Croatia and the hinterland mountain range of the southern Dinaric Alps and caused severe flash floods and landslides and consequent interruption of traffic and electricity supply as well as other infrastructural damage. The analysis is geographically focused on the southern portion of the eastern Adriatic region, which is prone to relatively frequent heavy precipitation events that occur mostly in autumn. This area is one of the rainiest in Europe with expected annual amounts of precipitation greater than 5,000 mm in the mountainous hinterland. The mechanisms responsible for the formation of convection were analysed using synop measurements, satellite data and numerical experiments performed with the WRF model, which was set up at the convection-permitting resolution in the innermost domain. Satellite data were used to identify the precipitation systems and to estimate the intensity of the precipitation during the period of interest. The development of the precipitation system was connected to a strong large-scale ascent over the southern Italy and southern Adriatic due to the advection of warm air and cyclonic vorticity advection, which increases with height. The numerical simulations highlighted the essential role of a southerly low-level jet stream in the transport of warm and moist air towards the affected area. The convergence of two branches of low-level marine air favoured convection triggered over the coast and sea. Furthermore, numerical sensitivity experiments suggested that the orography of the Dinaric Alps plays an essential role in the precipitation maximum over the mountainous hinterland, but also that the orography was not the crucial factor in the heavy precipitation near Dubrovnik. This study highlights the need for a dense network of observations, especially radar measurements, to validate the simulated mechanisms and improve numerical forecasts via data assimilation. 相似文献
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