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Jean-Louis Grimaud Celine Grall Steven Goodbred Michael S. Steckler Ryan Sincavage Jennifer L. Pickering Chris Paola Leonardo Seeber Md. Saddam Hossain 《Basin Research》2020,32(5):1242-1260
Subsurface deformation is a driver for river path selection when deformation rates become comparable to the autogenic mobility rate of rivers. Here we combine geomorphology, soil and sediment facies analyses, and geophysical data of the Late Quaternary sediments of the central Garo-Rajmahal Gap in Northwest Bengal to link subsurface deformation with surface processes. We show variable sedimentation characteristics, from slow rates (<0.8 mm/year) in the Tista megafan at the foot of the Himalaya to nondeposition at the exposed surface of the Barind Tract to the south, enabling the development of mature soils. Combined subsidence in the Tista fan and uplift of the Barind Tract are consistent with a N-S flexural response of the Indian plate to loading of the Himalaya Mountains given a low value of elastic thickness (15–25 km). Provenance analysis based on bulk strontium concentration suggests a dispersal of sediment consistent with this flexural deformation—in particular the abandonment of the Barind Tract by a Pleistocene Brahmaputra River and the current extents of the Tista megafan lobes. Overall, these results highlight the control by deeply rooted deformation patterns on the routing of sediment by large rivers in foreland settings. 相似文献
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Irene Pundt Jean-Pierre Pommereau Celine Phillips Eric Lateltin 《Journal of Atmospheric Chemistry》1998,30(1):173-185
It has been suggested that iodine oxides, IOx, could play a significant role in the ozone destruction in the lower stratosphere. To investigate this suggestion, spectra from nine SAOZ uv-visible spectrometer balloon flights were examined for the IO absorption signature between 405 and 450 nm. IO was not detected, either at mid- or high latitude, in the morning or the evening, in summer or winter. An upper limit of 0.2 parts per trillion by volume (pptv) at 20 km and 0.1 pptv at 15 km at the 95% confidence level (2), was derived from the best measurements at 90° SZA at sunset and sunrise. Since a photochemical model shows that 70% of inorganic iodine should be in the form IO at that time, it is concluded that unless iodine chemistry is different from that assumed at the moment, the role of iodine in stratospheric ozone depletion is small. 相似文献
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Quantifying Asymmetric Parameter Interactions in Sensitivity Analysis: Application to Reservoir Modeling 总被引：1，自引：1，他引：0
In this paper, a new generalized sensitivity analysis is developed with a focus on parameter interaction. The proposed method is developed to apply to complex reservoir systems. Most critical in many engineering applications is to find which model parameters and parameter combinations have a significant impact on the decision variables. There are many types of parameters used in reservoir modeling, e.g., geophysical, geological and engineering. Some parameters are continuous, others discrete, and others have no numerical value and are scenario-based. The proposed generalized sensitivity analysis approach classifies the response/decision variables into a limited set of discrete classes. The analysis is based on the following principle: if the parameter frequency distribution is the same in each class, then the model response is insensitive to the parameter, while differences in the frequency distributions indicate that the model response is sensitive to the parameter. Based on this simple idea, a new general measure of sensitivity is developed. This sensitivity measure quantifies the sensitivity to parameter interactions, and incorporates the possibility that these interactions can be asymmetric for complex reservoir modeling. The approach is illustrated using a case study of a West Africa offshore oil reservoir. 相似文献
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The conventional paradigm for predicting future reservoir performance from existing production data involves the construction of reservoir models that match the historical data through iterative history matching. This is generally an expensive and difficult task and often results in models that do not accurately assess the uncertainty of the forecast. We propose an alternative re-formulation of the problem, in which the role of the reservoir model is reconsidered. Instead of using the model to match the historical production, and then forecasting, the model is used in combination with Monte Carlo sampling to establish a statistical relationship between the historical and forecast variables. The estimated relationship is then used in conjunction with the actual production data to produce a statistical forecast. This allows quantifying posterior uncertainty on the forecast variable without explicit inversion or history matching. The main rationale behind this is that the reservoir model is highly complex and even so, still remains a simplified representation of the actual subsurface. As statistical relationships can generally only be constructed in low dimensions, compression and dimension reduction of the reservoir models themselves would result in further oversimplification. Conversely, production data and forecast variables are time series data, which are simpler and much more applicable for dimension reduction techniques. We present a dimension reduction approach based on functional data analysis (FDA), and mixed principal component analysis (mixed PCA), followed by canonical correlation analysis (CCA) to maximize the linear correlation between the forecast and production variables. Using these transformed variables, it is then possible to apply linear Gaussian regression and estimate the statistical relationship between the forecast and historical variables. This relationship is used in combination with the actual observed historical data to estimate the posterior distribution of the forecast variable. Sampling from this posterior and reconstructing the corresponding forecast time series, allows assessing uncertainty on the forecast. This workflow will be demonstrated on a case based on a Libyan reservoir and compared with traditional history matching. 相似文献
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History matching and uncertainty quantification of facies models with multiple geological interpretations 总被引：2，自引：0，他引：2
Hyucksoo Park Céline Scheidt Darryl Fenwick Alexandre Boucher Jef Caers 《Computational Geosciences》2013,17(4):609-621
Uncertainty quantification is currently one of the leading challenges in the geosciences, in particular in reservoir modeling. A wealth of subsurface data as well as expert knowledge are available to quantify uncertainty and state predictions on reservoir performance or reserves. The geosciences component within this larger modeling framework is partially an interpretive science. Geologists and geophysicists interpret data to postulate on the nature of the depositional environment, for example on the type of fracture system, the nature of faulting, and the type of rock physics model. Often, several alternative scenarios or interpretations are offered, including some associated belief quantified with probabilities. In the context of facies modeling, this could result in various interpretations of facies architecture, associations, geometries, and the way they are distributed in space. A quantitative approach to specify this uncertainty is to provide a set of alternative 3D training images from which several geostatistical models can be generated. In this paper, we consider quantifying uncertainty on facies models in the early development stage of a reservoir when there is still considerable uncertainty on the nature of the spatial distribution of the facies. At this stage, production data are available to further constrain uncertainty. We develop a workflow that consists of two steps: (1) determining which training images are no longer consistent with production data and should be rejected and (2) to history match with a given fixed training image. We illustrate our ideas and methodology on a test case derived from a real field case of predicting flow in a newly planned well in a turbidite reservoir off the African West coast. 相似文献
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Climate variability and rapid urbanization have influenced the sand environments in the northern Coachella Valley throughout the late 20th century. This paper addresses changes in the spatial relationships among different sand deposits at northern Coachella Valley between two recent time periods by using satellite data acquired from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER). The approach employed here, involving multispectral thermal infrared (TIR) data and spectral mixture analysis, has shown that the major sand deposits can be spatially modeled at northern Coachella Valley. The “coarse-grained (quartz-rich) sand” deposit is associated with active eolian sand, and the “mixed sandy soil” and “fine-grained (quartz-rich) sand” deposits are associated with inactive eolian sand. The fractional abundance images showed a significant decrease between 2000 and 2006 in the percentage of active sand in the major depositional area for fluvial sediment, the Whitewater River, but also in two downwind areas: the Whitewater and Willow Hole Reserves. The pattern of the active sand appears to be related to variations in annual precipitation (wet and dry years) and river discharge in the northern Coachella Valley. We suggest here that recent human modifications to the major watercourses that supply sand affect the capability of fluvial deposition areas to restore sediments over time and consequently the responses of the sand transport system to climate change, becoming more sensitive to dry years where areas of active sand may shrink, degrade, and/or stabilize faster. The approach utilized in this study can be advantageous for future monitoring of sand in the northern Coachella Valley for management of these and similar environments. 相似文献
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Geospatial data resampling and resolution effects on watershed modeling: A case study using the agricultural non-point source pollution model 总被引：4，自引：0，他引：4
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In the coal-mining Ruhr-area, Upper Carboniferous rocks (ca. 4000 m) consist of interlayered sandstones, siltstones, mudstones and coals. They were deposited in a tropical, paralic environment where alternating fluvial sedimentation, occasional marine ingressions, and swamp growth resulted in an irregular cyclic succession. The total sedimentary package contains on an average 6 Vol.-% of organic matter. About 70 Vol.-% of the organic matter occurs in coal seams, the rest as dispersed organic matter in clastic rocks. The organic matter is autochthonous in the coals and allochthonous in associated sandstones and siltstones. It consists of about 70% vitrinite, 20% inertinite, and 10% liptinite. The overall maceral group composition is the same for coals and dispersed organic matter. This surprising similarity is caused by a nearly exclusive input of land-plant derived organic matter to swamps and fluvial systems and a similar degree of preservation. Highest average liptinite contents (% of total macerals) were found in unrooted mudstones, highest average inertinite contents in coarse-grained siltstones and highest average vitrinite percentages in sandstones.Maturities of the sediments studied are well within the hydrocarbon generation window, e. g. vitrinite reflectivities range from 0.6% to 1.6%. Reflectivities measured on dispersed particles in clastic rocks are similar to those measured in coal seams. Calculations of the amount of methane generated indicate that coal seams contributed more to the total hydrocarbon generation than dispersed organic matter.
Zusammenfassung Das Oberkarbon des Ruhrgebietes besteht aus ca. 4000 Metern wechsellagernder Sandsteine, Siltsteine und Kohleflöze. Der Ablagerungsraum der Sedimente war eine Region mit tropischem Klima, genauer ein paralisches Environment mit unregelmäßig alternierenden Folgen von fluviatilen Sedimenten, marinen Transgressionen und verbreiteten Sumpfablagerungen. Der Anteil organischer Substanzen an der gesamten Sedimentmenge beträgt durchschnittlich 6%. 70% dieser organischen Masse ist in Kohleflözen angereichert, der Rest liegt verteilt in den klastischen Gesteinen vor. Die Herkunft der organischen Substanz in den Kohleflözen ist autochthon, die in den benachbarten Sand- und Siltsteinen allochton. Die Zusammensetzung des organischen Materials ist 70% Vitrinit, 20% Inertinit und 10% Liptinit. Die allgemeine Zusammensetzung nach Mazeral-Gruppen ist für die Kohleflöze und das verteilte Material in den Nachbargesteinen identisch. Diese Ähnlichkeit beruht auf der gemeinsamen Herkunft der organischen Substanz in Sümpfen und Flußsystemen, die fast ausschließlich von Landpflanzen bestimmt wird, und einer sich entsprechenden Konservierung.Der Reifegrad der analysierten Sedimente liegt innerhalb des Kohlenwasserstoff-Bildungsbereiches (die Vitrinit-Reflexionen reichen von 0,6–1,6%). Dabei entsprechen die in den klastischen Gesteinen beobachteten Reflexionswerte weitgehend denen der Kohleflöze. Anhand der Menge des erzeugten Methans läßt sich erkennen, daß der Anteil der Kohleflöze an der Kohlenwasserstoff-Produktion höher ist als der Anteil, den disperse organische Substanzen der Klastika beisteuern.
Résumé Dans la région minière de la Ruhr, le Carbonifère supérieur constitue une succession, épaisse de 4.000 m environ, de grès, de siltites et de charbon. Leur dépôt, dans un milieu paralique tropical, a été marqué par des alternances de sédimentation fluiviale, de transgressions marines occasionnelles, et d'épisodes marécageux; il en résulte une disposition cyclique irrégulière. La série sédimentaire contient dans l'ensemble 6% de matière organique en moyenne. Environ 70% de cette matière organique se trouve dans les couches de charbon où elle est autochtone; le reste est allochtone et dispersé dans les grès et siltites. La matière organique se répartit approximativement en 70% de vitrinite, 20% d'inertinite et 10% de liptinite. La composition moyenne du groupe «macéral» est la même pour les charbons et la matière organique dispersée. Cette identité surprenante est l'expression d'une alimentation provenant exclusivement de plantes terrestres et d'un même degré de conservation.La maturité des sédiments étudiés se situe à l'intérieur du domaine de genèse des hydrocarbures: le pouvoir réflecteur de la vitrinite s'échelonne entre 0,6% et 1,6%. Les gradients du pouvoir réflecteur observés dans les roches détritiques et dans les couches de charbon sont analogues. Le calcul de la quantité de méthane engendré indique que la contribution des couches de charbon à la production totale d'hydrocarbure est supérieur à celle de la matière organique dispersée.
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