Neural networks and their derivatives for history matching and reservoir optimization problems     

Jérémie Bruyelle  Dominique Guérillot 《Computational Geosciences》2014,18(3-4):549-561

In geosciences, complex forward problems met in geophysics, petroleum system analysis, and reservoir engineering problems often require replacing these forward problems by proxies, and these proxies are used for optimizations problems. For instance, history matching of observed field data requires a so large number of reservoir simulation runs (especially when using geostatistical geological models) that it is often impossible to use the full reservoir simulator. Therefore, several techniques have been proposed to mimic the reservoir simulations using proxies. Due to the use of experimental approach, most authors propose to use second-order polynomials. In this paper, we demonstrate that (1) neural networks can also be second-order polynomials. Therefore, the use of a neural network as a proxy is much more flexible and adaptable to the nonlinearity of the problem to be solved; (2) first-order and second-order derivatives of the neural network can be obtained providing gradients and Hessian for optimizers. For inverse problems met in seismic inversion, well by well production data, optimal well locations, source rock generation, etc., most of the time, gradient methods are used for finding an optimal solution. The paper will describe how to calculate these gradients from a neural network built as a proxy. When needed, the Hessian can also be obtained from the neural network approach. On a real case study, the ability of neural networks to reproduce complex phenomena (water cuts, production rates, etc.) is shown. Comparisons with second polynomials (and kriging methods) will be done demonstrating the superiority of the neural network approach as soon as nonlinearity behaviors are present in the responses of the simulator. The gradients and the Hessian of the neural network will be compared to those of the real response function.  相似文献   

Gold enrichment characteristics and exploration prospects in Zambia: Based on 1∶1000000 geochemical mapping     

Jun-ping Ren  Jie Wang  A-lei Gu  Li-bo Zuo  Hong-wei Sun  Kang-kang Xu  Fu-Qing He  Chipilauka Mukofu  Alphet Phaskani Dokowe  Ezekiah Chikambwe 《China Geology》2022,5(1):60-70

The 1∶1000000 geochemical mapping of Zambia provides catchment sediment geochemical data for 58elements including Au from 746 sediment samples at 736 sampling sites,corresponding to a sampling density of about one site per 1000 km2.Under strict quality control using field duplicates,certified reference materials,and analytical replicate samples,the Au was determined by Inductively Coupled Plasma Mass Spectrometry(ICP-MS).The detection limit of Au was 0.20×10^-9.The 95%range(2.5%–97.5%)of Au concentrations was from 0.24×10^-9 to 1.36×10^-9,and the median value was 0.40×10^-9.The most noticeable Au distribution patterns shown on the map are mainly located between Lusaka and Ndola(Lufilian Arc Belt).In addition,several high Au value areas occurred in Mansa,Muyombe,Chipata,and Livingstone.The spatial distribution patterns of Au in tectonic units,drainage basins,and geomorphological landscapes could be related to the Lufilian Arc Belt and Bangweulu Block.The Au concentrations show metallogenic belts between Muyombe and Mbala areas,between Mansa and Ndola areas,and between Lusaka and Kasempa areas.  相似文献   

Estimation of internal nutrient release in large shallow Lake Taihu,China   总被引：1，自引：0，他引：1  

Qin Boqiang  Zhu Guangwei  Zhang Lu  Luo Liancong  Gao Guang  Gu Binhe 《中国科学D辑(英文版)》2006,49(1):38-50

Based on field investigation of wave, sediment suspension and the changes in nutrient concentration of the water column in Lake Taihu, China, we proposed two release models to quantify nutrient release under static and dynamic conditions, respectively. Under static conditions, nutrient release from sediments to the overlying water mainly depends on chemical diffusion induced by concentration gradient, in which the nutrient release is controlled by the temperature, dissolved oxygen concentration in the sediment-water interface, oxidation-reduction potential and the concentration difference between porewater and overlying water. Under dynamic condition (or disturbed condition), both dissolved and particulate nutrients in sediments are released into the water column because of wind-induced sediment suspension. The amount of nutrient release under dynamic conditions is larger than that under the static condition. The release of dissolved nutrients, however, does not increase because the wind induced turbulence made oxidation of metallic elements such as Fe (ferric iron), Mn which are capable of precipitating soluble reactive phosphate (SRP). Under dynamic conditions, therefore, the release of total phosphorus (TP) increases dramatically but the release of SRP is close to those under static conditions. In sediments of Lake Taihu, high Fe content leads to a high ratio of Fe to P contents in sediments (Fe:P ratio). Under dynamic conditions, therefore, nutrient release is controlled by the intensity of disturbance, sediment consolidation and nutrient content in sediments. As for dissolved nutrients, especially SRP, the release is also controlled by the intensity of dynamic re-oxidation, Fe content in sediments and nutrient concentration gradient between porewater and overlying water. Based on these two release modes, the release flux in Lake Taihu has been estimated. In the static condition (i.e. laboratory experimental condition), total release of NH₄ ⁺-N for whole lake is ca. 10,000 ton/a, and PO₄ ^3?-P is ca. 900 ton/a. In the dynamic condition, nutrient release following sediment suspension was estimated according to three different intensities of wind forcing which were defined as “calm” (wind speed is less than 2 m/s), “gentle” (wind speed is greater than 2 m/s and less than 6 m/s) and “gust” (wind speed is greater than 6 m/s). The release rate in the condition of “calm” was estimated in terms of the nutrient release in the laboratory experimental static condition; whereas the release rate in conditions of “gentle” and “gust” was estimated in terms of measurement during sediment resuspension conducted in flume experiments. With the observation of wind velocity and frequency in 2001, each type of wind forcing took the frequency of 12%, 82% and 6% for “calm”, “gentle” and “gust”, respectively. The yearly release of nitrogen was 81,000 ton and phosphorus was 21,000 ton, which is about 2–6 folds of annual external loading, respectively.  相似文献   

Diversity and zonal distribution of arbuscular mycorrhizal fungi on the northern slopes of the Tianshan Mountains     

Shi ZhaoYong  Chen ZhiChao  Zhang LiYun  Feng Gu  Christie Peter  Tian ChangYan  Li XiaoLin 《中国科学D辑(英文版)》2007,50(1):135-141

The arbuscular mycorrhizal (AM) fungal status of the 20 most common plant species distributed in 4 vegetation types (meadow steppe, desert steppe, steppe desert and typical desert) on the northern slopes of the Tianshan Mountains was investigated. Samples of the plant species and their rhizosphere soils were collected from the 4 vegetation zones and examined to compare their mycorrhizal status, AM fungal spore densities, biovolumes, and community structures. 28 AM fungal species were isolated from the rhizosphere soils: of these, 5 belonged to Acaulospora, 1 to Archaeospora and 22 to Glomus. 5 AM fungi, Glomus aggregatum, G. claroideum, G. deserticola, G. etunicatum and G. sinuosum, were observed in all 4 zonal types. No significant differences were observed in mean proportion of root length colonized by AM fungi among the plant species within each zonal type. Comparing the 4 zonal types, Plantago minuta (84.5%) in steppe desert and Eremopyrum orientale (83.1%) in typical desert showed the highest root colonizatsion rates. AM fungal spore densities and biovolumes were significantly different in the different zonal types. AM fungal spore densities and biovolumes, species richness and diversity were highest in meadow steppe and lowest in typical desert.  相似文献   

Uniform asymptotic Green's functions for efficient modeling of cracks in elastic layers with relative shear deformation controlled by linear springs     

Anthony P. Peirce  Hongren Gu  Eduard Siebrits 《国际地质力学数值与分析法杂志》2009,33(3):285-308

We present a uniform asymptotic solution (UAS) for a displacement discontinuity (DD) that lies within the middle layer of a three‐layer elastic medium in which relative shear deformation between parallel interfaces is controlled by linear springs. The DD is assumed to be normal to the two interfaces between the elastic media. Using the Fourier transform method we construct a leading term in the asymptotic expansion for the spectral coefficient functions for a DD in a three‐layer‐spring medium. Although a closed‐form solution will require a solution in terms of an infinite series, we demonstrate how this UAS can be used to construct highly efficient and accurate solutions even in the case in which the DD actually touches the interface. We compare the results using the Green's function UAS solution for a crack crossing a soft interface with results obtained using a multi‐layer boundary element method. We also present results from an implementation of the UAS Green's function approach in a pseudo‐3D hydraulic fracturing simulator to analyze the effect of interface shear deformation on the fracture propagation process. These results are compared with field measurements. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

用固体潮观测资料将钻孔应变变化换算为地层的应力变化   总被引：1，自引：1，他引：0  

骆鸣津  顾梦林  杨毅 《大地测量与地球动力学》2000,20(1):73-78

利用钻孔应变观测值中潮汐频段部分和钻孔岩芯的弹性系数,将钻孔应变换算为地层应力的格值,用此格值可将钻孔应变的非潮汐变化换算成该地地层的非潮汐应力变化.从潮汐模型研究和潮汐观测结果来看,勒夫数受地球大结构的影响,空间变化不大,据此可用勒夫数的模型值去求定标定应力.由钻孔应变观测值求定钻孔应变的面应力系数和差应力系数,而不必知道耦合介质的力学性能.探头周围介质若非各向同性时,应力系数可用椭圆的解析式拟合.此外,还讨论了同井、同台、台网的校核问题,以及应力场模型的拟合和漂移的分离问题.  相似文献   

黑宝山膨润土的物化性能和应用试验研究     

季金华  张书亮  顾志峰 《江苏国土资源》2000,25(1)

对黑宝山膨润土的化学成分、阳离子交换量、吸蓝量、胶质价、膨胀容、比表面、造浆率、湿压强度和脱色力进行了测定,利用组合样进行了工业活化试验和铸造用土工业试验研究.  相似文献   

Les anneaux de saturne en 1969. Etude morphologique et photométrique. I. Obtention et dépouillement des photographies     

P. Guérin 《Icarus》1973,19(2):202-211

Some excellent photographs of Saturn in yellow and violet light have been taken in 1969 with the 105cm reflecting telescope of the Pic du Midi Observatory. They revealed the existence, inside the C-ring, of an extremely faint, fourth Ring. The reduction of microphotometric tracings along the great-axis of the Rings, have given the photometric curves of the rings in the two colours above. These two curves are very similar. They do not agree with some of the details drawn before and show some new ones.  相似文献   

Isotopic variations in precipitation at Bangkok and their climatological significance     

Yuanqing He  Hongxi Pang  W. H. Theakstone  Zhonglin Zhang  Aigang Lu  Juan Gu 《水文研究》2006,20(13):2873-2884

The stable isotopic composition of precipitation from low to mid latitudes contains information about changes of some climatic factors, such as temperature, precipitation and atmospheric circulation patterns. However, the isotopic variations in the area are very complicated because of the combined influences of these factors. Proper interpretation of the patterns of isotopic variations for palaeoclimate reconstructions in this area requires a detailed understanding of these complex stable isotope controls. The isotopic data (δ¹⁸O and δ²D) in precipitation at the International Atomic Energy Agency–World Meteorological Organization Bangkok station were collected and analysed because of the relatively long and unbroken isotopic records and the particular geographical location. The isotopic variations at Bangkok have strong seasonal patterns owing to distinct source regions in different seasons. In summer, the remote sources of water there can influence the δ¹⁸O values significantly, which is verified by the simple Rayleigh model. In winter, the mixing of isotopically distinct air masses with different origins, i.e. the continental and oceanic air masses, accounts for the isotopic variations. In the transition periods of the Asia–Australia monsoon, namely in May and October, the local vapour contribution may play a role in the isotopic ratios. On the interannual time‐scale, the influences of El Niño–southern oscillation (ENSO) and the Indian Ocean dipole (IOD) on isotopic composition are examined. The indications are that both the ENSO and IOD indices have a significant correlation with the δ¹⁸O ratios, and that the δ¹⁸O ratio in summer rains is significantly more enriched (depleted) during the warm (cold) phase of ENSO/IOD events. All the results suggest that it is useful for us in understanding the water cycling process and may be helpful in palaeoclimate reconstruction in this monsoon region. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

Stellar and gaseous velocity dispersions in type II AGNs at 0.3 < z < 0.83 from the Sloan Digital Sky Survey     

W. Bian  Q. Gu †  Y. Zhao  L. Chao  Q. Cui 《Monthly notices of the Royal Astronomical Society》2006,372(2):876-884

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