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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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Grain size and magnetic susceptibility measurements on samples from a typical loess–palaeosol sequence on the central Chinese Loess Plateau are used to reconstruct the Pleistocene East Asian monsoon climate. The coarse‐grained fraction, i.e. the weight percentage > 30 μm of the bulk grain‐size distribution, is used as a sensitive proxy index of the East Asia winter monsoon strength. On the basis of an absolute time‐scale, time‐series variations of this proxy show that winter monsoon strengths varied on millennial time‐scales during the periods 145–165, 240–280, 320–350, 390–440, 600–640, 860–890, 900–930 and 1330–1400 kyr BP. The wavelength of these climatic oscillations varied between 1.89 and 4.0 kyr, as is shown by spectral analysis using the multitaper method. Although numerical simulation experiments show that high frequencies also can arise from measurement errors in the grain‐size analysis, the frequencies prove to be sufficiently stable when the spectral analysis is repeated with a different number of tapers. For the time being, we do not correlate these climatic oscillations with palaeoclimatic records in the North Atlantic deep‐sea sediments because both time‐scales need to be further improved. Our data, however, certainly demonstrate that millennial‐scale East Asian winter monsoon variations in the last 1.4 million years can be detected from terrestrial loess records. Copyright © 1999 John Wiley & Sons, Ltd. 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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Variability of East Asian Winter Monsoon in Quaternary Climatic Extremes in North China 总被引：1，自引：0，他引：1
Huayu Lu Ko van Huissteden Jie Zhou Jef Vandenberghe Xiaodong Liu Zhisheng An 《Quaternary Research》2000,54(3):321
In order to examine high-frequency variations of East Asian winter monsoon in Quaternary climatic extremes, two typical loess–paleosol sequences in the Chinese Loess Plateau were investigated. Sandy layers in the loess deposits, the “Upper sand” and “Lower sand” (layers L9 and L15, respectively), which represent a high-resolution record of paleomonsoon changes, have been sampled at intervals of 5–6 cm from sections at Luochuan and Xifeng. The grain size and magnetic susceptibility was measured for all samples. The grain-size results (a proxy of winter monsoon strength) indicate that the winter monsoon strength fluctuated on a millennial timescale during cold climatic extremes, with climatic events of a few hundred to a few thousand years. However, the winter monsoon was relatively stable during warm periods. The magnetic susceptibility signal (a proxy of summer monsoon intensity) is practically constant over the same period. This is tentatively explained by the assumption that the summer monsoon intensity was too low to be recorded in the magnetic susceptibility signal. The intensified winter monsoon events show periodicities in a range of 1000 to 2770 yr, with a dominant cycle of approximately 1450 yr. The detection of this oscillation in older glacial stages strongly suggests that it may be a pervasive cycle of the cold climatic phases of the Quaternary. Millennial-scale variations of the winter monsoon may be caused by instability of the westerly jet, which is determined by temperature differences between the polar and the equatorial regions. 相似文献
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Xianyan Wang Ronald van Balen Shuangwen Yi Jef Vandenberghe Huayu Lu 《Boreas: An International Journal of Quaternary Research》2014,43(2):469-484
In the Northeastern Tibetan Plateau (NETP), the courses of the Huang Shui and Huang He near their confluence are characterized by alternating gorges and wide depressions, segmenting the fluvial systems. The river valleys have developed terrace staircases, which are used to infer relative tectonic motions between the segments. The terrace staircases are correlated by means of relative height and optically stimulated luminescence (OSL) dating. At least eight terraces are present, two of which have been dated by OSL (the sixth and the third ones; c. 70 and c. 24 ka, respectively). The correlated longitudinal terrace profiles show no distinct relative tectonic movements within the confluence area, demonstrating that this area behaved as one tectonic block. The correlation of the terrace staircase of this block with areas upstream (Xining area) and downstream (eastern Lanzhou area) indicates relative tectonic movements, which therefore represent different tectonic blocks. The fluvial incision rate since c. 70 ka was much higher in the confluence area than in the blocks upstream and downstream, possibly indicating relative uplift. This relatively strong uplift provided more space for differentiation within the terrace staircase as a result of climatic changes, leading to six terraces formed as a response to minor climatic fluctuations (103–104 year timescale) since the last interglacial. This may indicate that the stronger the tectonic movement the better the climatic imprint as expressed in the form of terrace development. Over a shorter timescale, two accumulation terraces with thick stacked deposits (>18 m) may indicate relative subsidence in the confluence, occurring sometime between 20 and 70 ka. This indicates changes in relative vertical crustal motions at timescales of tens of thousands of years. We speculate that the inferred tectonic motions are related to transpression movements in the NETP as a result of the collision of the Indian and Asian plates. 相似文献