共查询到20条相似文献，搜索用时 31 毫秒
1.
John C. Tipper 《Mathematical Geology》1994,26(7):843-855
The Exxon global cycle chart is now widely used as a stratigraphic correlation tool, although it remains a controversial one. It requires continual testing against new data, but tests are difficult at present because the assumptions behind the chart have not so far been precisely specified. Some reasonable assumptions are made here, and a few simple tests are then proposed on the basis of these. Some of these tests are appropriate to specific situations in which the lest data are estimated sequence boundary ages: others are for situations in which sets of undated sequence boundaries are available that are only known to lie within particular parts of the Exxon chart. No general test for the Exxon chart has yet been developed, and the specifications for such a test are discussed. 相似文献
2.
In this paper, numerical methods for flow simulation in the well vicinity are discussed. Flux truncation errors are analyzed on gridblocks near the well. Due to the singularity of the well, standard numerical schemes are not efficient for near well flow simulations. To improve simulation accuracy, a new methodology, using a change of coordinates to make near well pressure linear, is presented for the singularity modelling. Based on this new approach, two numerical schemes, a two-point flux approximation scheme and a multi-point one, are proposed. These schemes are accurate for the near well modelling and are suitable for any kinds of gridblocks. 相似文献
3.
The presence of observations or measurements that are unlike the majority is fairly common in studies conducted to establish particle size (or weight fraction) distributions. Therefore, there is a need to develop methods that are capable of producing estimates of particle size distributions that are not overly sensitive to the presence of a few observations that might be considered outliers. This article proposes a type of contamination mixture model that probabilistically allocates each observation to either a majority component or a contamination component. Observations that are allocated to a contamination component are down-weighted when estimating the particle size distribution (while the uncertainty of contamination classification is automatically accounted for in estimation). Computational methods are developed and the utility of the proposed methodology is demonstrated via a simulation study. The method is then applied to data produced from an inter-laboratory study conducted to establish a particle size distribution in cement. 相似文献
4.
西北地区侏罗系的三角洲沉积 总被引：16，自引：0，他引：16
西北地区侏罗广泛发育扇三角洲,辫状河三角洲和曲流河三角洲相沉积,其中扇三角洲与陡倾的盆地边缘有关,盆地的沉降速率大于沉积率,沉积层序为加积型,并以沉积物重力流和无河道片流区同搬运的沉积短斩泄荷为特征,辫状河三角洲与不很陡的盆地边缘梯度有关,其沉积速率大于盆地的沉降速率,沉积层序为进积型,并以河道径流广泛发育为特征,曲流河三角洲与缓坡陷型构造边界有关,并具有以河流作用为主,湖泊作用的辅的特征,３种三 相似文献
5.
库车坳陷中生界三种类型三角洲的比较研究 总被引：34，自引：3，他引：31
库车坳陷中生代呈北陡南缓的箕状,其内连续沉积了一套厚度巨大的冲积-湖泊碎屑沉积体。湖缘扇三角洲、辫状河三角洲及曲流河三角洲非常发育,它们的特征清楚、区别明显:（1） 扇三角洲为突发的、瞬时的灾变事件产生的重力流沉积与间灾变期正常牵引流沉积交替进行,并以重力流沉积占主导地位:其平原亚相类似于冲积扇沉积,河道砂体呈透镜状,厚度小、变化大。（2） 辫状河三角洲为正常的河流牵引流沉积,通常受到湍急洪水控制,为季节性沉积作用产物;平原亚相类似于辫状河沉积;河道沉积发育,砂体总体呈层状,内部由若干个下粗上细的河道砂岩透镜体相互叠置而成,交错层发育,尤以侧积交错层异常发育为特征,岩性以颗粒支撑的砂砾岩为主。（3） 曲流河三角洲为正常的河流牵引流沉积,沉积物输入量为相对连续的终年河流的产物,平原亚相类似于曲流河沉积:河道砂体呈层状,交错层发育,类型丰富。当然,这三种类型三角洲之间亦存在着密不可分的内在联系,不仅同一时期内可以并存,而且随着地质历史的演化可相互转化。 相似文献
6.
The properties of the original Schwarzschild metric for a point gravitating mass are considered. The laws of motion in the corresponding space–time are established, and the transition from the Schwarzschildmetric to the metric of a “dusty universe” are studied. The dynamics of a system of particles in thr post-Newtonian approximation are analyzed. 相似文献
7.
8.
Thierry Reuschié 《地学学报》1992,4(5):591-597
Fracture in a heterogeneous medium is simulated by a network model. Heterogeneity is introduced by randomly distributing an initial population of cracks on a triangular network of bonds. Each ruptured bond represents a crack. External stresses are applied onto the network and the evolution of the crack population is analysed when the stresses are increased. A crack will propagate to an intact bond if the critical crack extension force is reached. This propagation leads to the coalescence of bonds: crack clusters are formed. When their shapes are complex we approximate them by simpler ones to compute a crack extension force. Crack interactions are introduced by adding for a given bond the contributions of all adjacent dusters. By using this kind of approach combining fracture mechanics and network modelling, we are able to simulate the rupture of a rock specimen under compression/ traction or shear stresses and to give some characteristics of the macroscopic fracture. 相似文献
9.
R.W.G. Carter 《Sedimentary Geology》1982,33(1):35-56
Mixes of carbonate and quartz sands, which are commonly encountered in Recent coastal sediments, require careful analysis if they are to be correctly interpreted. Grain-size data fall into multimodal or segmented zig-zag distributions which may require some kind of component separation if they are to be summarised by conventional statistics, and before they can be assigned to a particular hydrodynamic depositional process or environment. Unfortunately, separation techniques are only spasmodically applied, usually without due regard to the consequences. Such artificially filtered or truncated distributions are of little subsequent use. Using a range of samples from two beaches in NW Ireland, where carbonate proportions range from nearly zero to over sixty percent, the interrelationships of the two dominant components were examined. Where only a small carbonate proportion is incorporated into a large quartz one, predictable modifications of the size-curve are apparent. However, the components are more independent if mixtures are near equal. The occurrence of a number of distinctive combinations of simple straight lines and complex zig-zag curves probably reflects the relatively dynamic nature of the carbonate fraction. 相似文献
10.
In identifying sites of geoheritage significance, commonly there has been an emphasis on the larger-scale features. However, the story of geology and the significant features that are critical to unravel geological processes and geological history are commonly small in scale. This contribution focuses on bubble sand and bubble-sand structures as features that are small-scale but nonetheless important to geology, and hence are of geoheritage significance. Bubble sand and bubble-sand structures are ubiquitous on modern beaches and tidal flats, occurring in the uppermost tidal zone of sandy beaches, as a distinct layer in a shoaling beach-to-dune stratigraphy, and are a diagnostic indicator of upper-tidal conditions where a rising tide and a concomitantly rising water-table interacts with the upper swash-zone wave processes. On sandy tidal flats, bubble sand and bubble-sand structures may occur in the mid- to upper-tidal zones; here they are also diagnostic indicators of tidal conditions, forming during a rising tide where a rising water-table forces air upwards to be trapped in moist sand. If found in ancient sequences, bubble-sand structures are a powerful environmental indicator of tidal conditions and, for beach sequences, an indicator of the high-tide level and sea level. Bubble-sand structures have been found in a number of ancient sequences throughout the geological record as far back as the Neoproterozoic, e.g. within beach-to-dune stratigraphy in Pleistocene limestones of the Perth Basin and in southeastern USA, and in tidal-flat sands of the Mesozoic Broome Sandstone of the Canning Basin. The bubble-sand structure is a significant geological tool for use in paleo-environmental and paleo-oceanographic reconstructions, and determination of the position of a paleo-water-table. Given the rarity of their preservation, these occurrences of bubble-sand structures are of geoheritage significance in their own right and, depending on age of sequence and how common they are in the region, they may be nationally significant or globally significant. 相似文献
11.
土性平稳随机场的空间统计特性分析 总被引：8，自引：6，他引：2
阐明了平稳随机场的空间统计特性,根据平稳随机场各态历经性概念,讨论了土层满足各态历经性的条件,以及计算空间平均方差和相关距离的公式。并结合工程实例,分析了空间平均方差计算的影响因素。 相似文献
12.
江西煤田地质勘探的形势是严峻的，后备煤炭资源严重不足。无可供建井设计利用的精查储量，无可供精查的详查储量，可供详查的普查储量少，可供普查的找煤储量更少。地质勘探的找煤、普查与详查比例严重失调，许多矿井又面临资源枯竭、按替困难的局面。江西仍有较多的煤田勘探靶区需要勘探验证，煤炭工业有广阔的市场。希望政府采取各种措施加大对煤田地质勘探的投入。 相似文献
13.
N. A. Campbell 《Mathematical Geology》1984,16(2):109-124
Canonical variate analysis is extended for use when the covariance matrices are not equal. Linear combinations of variates are derived by generalizing either a weighted between-groups approach or the likelihood-ratio test and the associated noncentrality matrix. The usual solution and the two generalizations are compared via generated data for a few typical configurations of means in a situation in which the covariance matrices are in fact equal. The MSE of the canonical variate coefficients and group means for the generalizations are approximately three times those for the usual solution, due to corresponding changes in the variances. Two examples are discussed. 相似文献
14.
15.
本文依据大量资料，阐述了亚东—格尔木走廊域及其邻近地区地震活动空间分布规律和现代构造应力场特征。地震活动主要沿几条走向大致乎行的弧形山系呈带状分布，震源深度多在15-35km范围内，断层面解的主要压应力轴以NNE-SSW方向为主且仰角较小，不同强度、不同深度地震的主压应力轴取向基本相同。 相似文献
16.
The flow of a particle fluid mixture through a heterogeneous permeable material is studied with a view to obtaining characteristic fingerprints for the structures that such flows may exhibit. This flow has a variable density and behaves as a compressible fluid, with the compressibility derived from the variations of the local field variables. Both pressure-sensitive or speed-fluctuation-dependent rheologies are studied in the steady state and a speed-fluctuation-dependent material is studied in a time-dependent analysis. The salient findings are that for a pressure-sensitive material structures normal to the mean flow direction are obtained. For the speed-fluctuation-dependent rheology, the pressure structures are normal to the mean flow, whereas the density structures are aligned with the flow (fingering).Electronic Supplementary Material Electronic Supplementary Material is available in the online version of this article at . 相似文献
17.
Anca Maria Hanea Maria Gheorghe Remus Hanea Dan Ababei 《Computational Geosciences》2013,17(6):929-949
Reservoir simulation models are used both in the development of new fields and in developed fields where production forecasts are needed for investment decisions. When simulating a reservoir, one must account for the physical and chemical processes taking place in the subsurface. Rock and fluid properties are crucial when describing the flow in porous media. In this paper, the authors are concerned with estimating the permeability field of a reservoir. The problem of estimating model parameters such as permeability is often referred to as a history-matching problem in reservoir engineering. Currently, one of the most widely used methodologies which address the history-matching problem is the ensemble Kalman filter (EnKF). EnKF is a Monte Carlo implementation of the Bayesian update problem. Nevertheless, the EnKF methodology has certain limitations that encourage the search for an alternative method.For this reason, a new approach based on graphical models is proposed and studied. In particular, the graphical model chosen for this purpose is a dynamic non-parametric Bayesian network (NPBN). This is the first attempt to approach a history-matching problem in reservoir simulation using a NPBN-based method. A two-phase, two-dimensional flow model was implemented for a synthetic reservoir simulation exercise, and initial results are shown. The methods’ performances are evaluated and compared. This paper features a completely novel approach to history matching and constitutes only the first part (part I) of a more detailed investigation. For these reasons (novelty and incompleteness), many questions are left open and a number of recommendations are formulated, to be investigated in part II of the same paper. 相似文献
18.
江苏省溧水县土壤环境污染预警预测方法探讨 总被引：5，自引：0，他引：5
介绍了溧县土壤环境质量的现状。溧水县主要有黄砂土、栗色土、岗黄土、黄岗土、马肝土、板浆白土、青泥条、青泥土等8种土壤类型。通过地球化学调查和对溧水县土壤的系统采样，获得了反映土壤质量的地球化学数据。通过对土壤中污染物富集历史的研究，揭示了土壤污染物的演化趋势。通过寻找零污染的历史时间结合现代土壤地球化学调查数据，建立了土壤重金属污染预警预测的数学模型。提出了影响土壤质量的关键因子和土壤污染的影响因素，得出了工业是影响土壤质量的主要因子，土壤污染在不断加速的结论。 相似文献
19.
东昆仑约格鲁岩体暗色微粒包体特征及成因 总被引：26，自引：10，他引：26
对东昆仑约格鲁花岗岩体中暗色微粒包体的形态、大小、成分和分布等主要特征进行了较详细地研究。发现包体形态多样,以强烈的塑性流变为特征;包体大小悬殊,多数直径为几十厘米,最大者长轴达4m;包体成分以闪长质为主,结构总体上比寄主岩石的粒度细,岩体中不同部位的包体成分和结构都有所变化;包体分布不均匀,经常呈族状、条带状密集分布,具定向性。镜下研究发现,在包体中经常见到针状磷灰石、石英捕虏晶和斜长石的自形内核环带及增生边等现象,显示了岩浆混合成因的特点。 相似文献
20.
Three constitutive models of soil are used in finite element analyses of lateral earth pressure and bearing capacity. The three models are an elasto-plastic formulation derived from the Mohr-Coulomb law, a similar model with the plastic dilatancy removed, and a strain hardening model with a capped yield criterion. Stiffness formulations are described; the non-dilatant model has a non-symmetric stiffness. The results for the retaining walls are in close agreement with classical soil mechanics, but the bearing capacity analyses greatly overestimate the bearing capacity. The patterns of motion are, however, reasonable. Reasons for the discripancies in the bearing capacity case include: (a) the elements are too stiff and do not permit sliding on discrete failure planes; (b) the bearing capacity problem is itself not well settled theoretically; (c) very fine element divisions are necessary in areas of strong stress gradients and (d) rotation of principal stresses is significant. 相似文献