基于Markov链模型的储层岩相随机模拟   总被引：3，自引：4，他引：3  

刘振峰  郝天珧  杨长春 《地球物理学进展》2003,18(4):666-669

在油气储层随机建模研究中，基于Markov链模型的方法是一类较受欢迎的技术，同时也是一类不成熟的技术，问题的症结之一在于侧向的转移概率矩阵很难求取，针对这种情况，作者在深入理解Walther相律的基础上，借鉴模拟退火算法的相应思路，提出了一种岩相模拟的新方法，该方法依据不同岩相的百分比进行随机模拟得到一幅初始图象，而后以按岩相组织剖面得到的垂向和侧向的岩相转移概率矩阵的相似性作为判别标准对图象进行扰动，直至得到满意的图象，二维模型试算结果表明了这种岩相随机模拟方法的可行性。  相似文献   

全球产业转移与GVC区域竞争——基于中国与中南半岛四国的分析     

姚作林  金凤君  陈卓 《地理研究》2021,40(2):326-342

以中国和中南半岛四国为对象,以定量评价全球产业转移背景下的区域全球价值链(GVC)竞争态势为目标,采用多因子综合评价、IRIO投入-产出分析和RCA、GVC指数分析等方法,刻画了21世纪以来全球43个主要经济体、八大类型产业的全球产业转移时空演化特征,同时测算了中国和中南半岛四国的全球产业转移吸引力以及制造业全球竞争力...  相似文献   

China and the changing economic geography of coffee value chains     

Jeffrey Neilson  Ju‐Han Zoe Wang 《Singapore journal of tropical geography》2019,40(3):429-451

For the past three centuries, the economic geography of the global coffee sector has been characterized by the supply of beans from tropical countries for consumption in North America and Europe, with various modes of value chain coordination enacted by lead firms to ensure reliable and affordable supply. This pattern is now fundamentally changing, with growth in coffee consumption in emerging markets, including China, exceeding that in established markets. But China is not only a growing consumer market, it is less well known that rapidly increasing agricultural production in Yunnan province of southwest China has also inserted the country as an important source region for coffee, and this has been pivotal in facilitating the emergence of Chinese lead firms in the sector. This article presents the emergence of China, and Chinese firms, at a critical juncture for the structure and governance of the global value chain for coffee. The processes through which this is occurring are outlined, and the implications for regional development prospects across Southeast Asia are discussed. We argue that the changing economic geography of coffee value chains, and their increasing driven‐ness by Chinese actors, is starting to reshape the regional coffee industry in profoundly new ways.  相似文献   

Institutions, the governance of quality and on-farm value retention for Indonesian specialty coffee     

Jeff Neilson 《Singapore journal of tropical geography》2007,28(2):188-204

Fluctuating global commodity prices affect the livelihoods of millions of tropical farmers worldwide. In recent years, systemic oversupply of many tropical agricultural products, grown in countries such as Indonesia, has meant that agricultural incomes have continuously fallen below subsistence levels. Within an increasingly open global trade regime, along with the limited ability of governments to protect domestic farm prices, quality-informed product differentiation appears to offer an escape route from the trap of low commodity prices. However, ownership and governance of quality constructions are fundamental to determining who benefits from such differentiation. This paper examines the use of geographical identities as a specific tool for value-adding in agricultural produce, presenting the case of specialty coffee production in South Sulawesi, Indonesia. The potential for producer-driven geographical indications compete with corporate-driven quality constructions, where the latter are able to appropriate place-related quality associations by using trademarks, vertical integration and tightly coordinated supply chain controls. An emergent politic of quality governance and ownership in global commodity chains reveals the highly restricted institutional terrain within which growers of specialty coffee might attempt to retain a higher share of the economic rent associated with quality production.  相似文献   

Reducing geological uncertainty by conditioning on boreholes: the coupled Markov chain approach     

Amro M. M. Elfeki  F. M. Dekking 《Hydrogeology Journal》2007,15(8):1439-1455

The CMC (coupled Markov chain) model, which is based on the extension of Markov chains in two-dimensions, is used in the reduction of uncertainty in geological structures when conditioned (i.e., honours the data and their location) on a number of boreholes. The model has been applied to an unconsolidated aquifer deposit located in the central Rhine-Meuse delta (the Gorkum study area) in the Netherlands. A comparison is also made between the CMC and the SIS (sequential indicator simulation) model, which is based on Kriging and co-Kriging theories on the same deposit. The results show the potential applicability of the CMC model in reducing the uncertainty in geological configurations when a sufficient number of boreholes is available. Reproduction of the global geological features requires relatively few boreholes (in this case study, nine boreholes with 30-m spacing over a distance of 240 m). However, reproduction of the proportion of each state requires a relatively large number of boreholes (in this case study 31 boreholes with 8-m spacing over a distance of 240 m). It has been shown that variograms can be deceptive in modeling the spatial pattern and that they reflect only part of the complete spatial structure in the field. The use of transition probabilities via the CMC model provides a better alternative approach, because it uses multiple point information. Amro M. M. Elfeki on leave from Department of Irrigation and Hydraulics, Faculty of Engineering, Mansoura University, Mansoura, Egypt  相似文献   

Effects of orientation on the diffusive properties of fluid-filled grain boundaries during pressure solution     

R. van Noort  C. J. Spiers  C. J. Peach 《Physics and Chemistry of Minerals》2007,34(2):95-112

An unresolved issue in the study of pressure solution in rock materials is the dependence of grain boundary structure and diffusive properties on the mutual orientation of neighbouring grain lattices. We report electrical measurements yielding the diffusivity of differently oriented halite–glass and halite–halite contacts loaded in the presence of brine. The halite–glass contact experiments show pressure solution of the halite and an effect of halite lattice orientation on grain boundary transport. Post-mortem observations show an orientation-dependent grain boundary texture controlled by the periodic bond chains in the halite structure. It is inferred that this texture determines the internal grain boundary structure and properties during pressure solution. In the halite–halite experiments neck-growth occurred, its rate depending on twist-misorientation. The results imply that deformation by pressure solution may lead to lattice-preferred orientation development, and that polymineralic rocks may deform faster at lower stresses than monomineralic rocks.  相似文献   

Modelling Subsurface Heterogeneity by Coupled Markov Chains: Directional Dependency,Walther’s Law and Entropy     

A.?M.?M.?ElfekiEmail author  F.?M.?Dekking 《Geotechnical and Geological Engineering》2005,23(6):721-756

This paper is an extension of the two-dimensional coupled Markov chain model developed by Elfeki and Dekking (2001) supplemented with extensive simulations. We focus on the development of various coupled Markov chains models: the so-called fully forward Markov chain, fully backward Markov chain and forward–backward Markov chain models. We addressed many issues such as: sensitivity analysis of optimal sampling intervals in horizontal and lateral directions, directional dependency, use of Walther’s law to describe lateral variability, effect of conditioning on number of boreholes on the model performance, stability of the Monte Carlo realizations, various implementation strategies, use of cross validation techniques to evaluate model performance and image division for statistically non-homogeneous deposits are addressed. The applications are made on three sites; two sites are located in the Netherlands, and the third is in the USA. The purpose of these applications is to show under which conditions the Markov models can be used, and to provide some guidelines for the practice. Entropy maps are good tools to indicate places where high uncertainty is present, so can be used for designing sampling networks to reduce uncertainty at these locations. Symmetric and diagonally dominant horizontal transition probabilities with proper sampling interval show plausible results (fits with geologists prediction) in terms of delineation of subsurface heterogeneous structures. Walther’s law can be utilised with a proper sampling interval to account for the lateral variability.  相似文献   

Morphological characteristics and emplacement mechanism of the seamounts in the Central Indian Ocean Basin     

Pranab Das  Sridhar D. Iyer  Vijay N. Kodagali   《Tectonophysics》2007,443(1-2):1-18

The morphotectonic features of the Central Indian Ocean Basin (CIOB) provide information regarding the development of the basin. Multibeam mapping of the CIOB reveals presence of abundant isolated seamounts and seamount chains sub-parallel to each other and major fracture zones along 73° E, 79° E and 75°45′ E. Morphological analyses were carried out for 200 seamounts that occur either as isolated edifies or along eight sub-parallel chains. The identified eight parallel seamount chains that trend almost north–south and reflecting the absolute motion of the Indian plate, probably originated from the ancient propagative fractures. Inspite of the differences in their height, the seamounts of these eight chains are morphologically correlatable. In the study area the seamounts are clustered north and south of 12° S latitude. Interestingly, in the area north of 12° S (area II: 9°–12° S) the seamounts are distinctly smaller (≤ 400 m height) whereas, the area south of 12° S (area I: 12°–15° S) has a mixed population of seamounts. The normalized abundance of the CIOB seamount is 976 seamounts/10⁶ km² but on a finer scale this value varies from 500 to 1600 seamounts/10⁶ km², which is less than the seamount concentrations of the Pacific and Atlantic oceans (9000 to 16,000 seamounts/10⁶ km²). Three categories of seamounts are present in the CIOB e.g. (1) single-peaked (2) multi-peaked and (3) composite. The study indicate that single-peaked seamounts are dominant (89%) while multi-peaked is less (8%) and composite ones are rare (3%) in the CIOB.The progressive northward movement of the Indian continent caused collision between India and Asia at around 62 Ma ago. A majority of the near-axis originated seamounts in the CIOB seemed to have formed as a consequence of the temporally widespread (Cretaceous  65 Ma to late Eocene < 49 Ma) collision between India and Eurasia. The regional stress patterns in the Indian plate vary N to NE in the continent and N to NW in Indian Ocean areas. The combined effect of the regional stress patterns maintained the orientation of the seamount chains and the local stress regime helped in the upwelling of magma and formation of seamounts. The low heat flow, morphological features and geochemical signature indicate that the morphotectonic structures formed contemporaneously with the oceanic crust.  相似文献   

Moving players,traversing perspectives: Global value chains,production networks and Ghanaian football labour migration     

《Geoforum》2013

This article examines the production and transnational export of Ghanaian football labour. It does so via a cross-disciplinary approach that utilises perspectives rooted in the sociology of development (global value chains) and economic geography (global production networks). The article is underpinned by two central arguments. Firstly, it contends that the GVC framework is useful in accounting for how Ghanaian players are produced and prepared for the international market, identifying the key agents and agencies involved, mapping the geography of production and export and assessing the institutional context within which the trade operates locally, nationally and internationally. The second draws on the GPN perspective to argue that while Ghanaian football labour migration remains a process contoured by uneven asymmetries of power that favour actors, stakeholders and entities in the global North, there are currently segments of the production–export chain where power is much more diffuse and some benefits are captured in the global South. The paper draws on interview data and observations gleaned from four periods of multi-sited ethnographic fieldwork in Ghana between January 2008 and June 2011.  相似文献   

Trends in the training and employment of geoscientists in Australia from 1967 to 1978     

D. A. Berkman 《Australian Journal of Earth Sciences》2013,60(1-2):83-88

There are now 14 universities and 8 colleges of advanced education in Australia with geology or earth science departments, which comprised 278 professional staff, 2020 undergraduates, and 556 graduate students in 1978. Academic staff, engaged in a wide range of research, represent less than 10 percent of the total number of Australian geoscientists. Almost all non‐academic employers (98 percent of the sample) presently accept a graduate with a B.Sc. (Hons) degree, while 85 percent accept a B.Sc pass degree. About 65 percent of non‐academic geologists work for industry, and the remainder are employed by government surveys and research organisations. Mining and mineral exploration employ 76 percent of the geologists in industry, followed by petroleum exploration with 11 percent. Geologists make up 83 percent of geoscientists in non‐academic employment, the remainder being geophysicists 15 percent and geochemists 2 percent. Information on vacancies available in early 1979 suggests that all the recent graduates would be absorbed by government and industry, and pointed to a resurgence in demand for qualified geoscientists. There has been striking growth in the number of consulting/contracting geological firms, with 65 firms employing 242 geoscientists replying to the 1978 census.  相似文献