Estimation of 2-D and 3-D Fracture Densities from 1-D Data - Experimental and Field Results

2-D and 3-D densities of fractures are commonly used in mining safety design, natural gas and oil production in fractured reservoirs, and the characterization of subsurface flow and transportation systems in fractured rocks. However, many field data sets are collected in 1-D frequency (f) (e.g., scanlines and borehole data). We have developed an ARC/ INFO-based technology to calculate fracture frequency and densities for a given fracture network. A series of numerical simulations are performed in order to determine the optimal orientation of a scanline, along which the maximum fracture frequency of a fracture network can be obtained. We calculated the frequency (f) and densities (both D1 and D2) of 36 natural fracture trace maps, and investigated the statistical relationship between fracture frequency and fracture density D1, i.e. D1=1.340f+ 0.034. We derived analytical solutions for converting dimensional density (D1) to non-dimensional densities (D2 and D3) assuming that fracture length distribution f     

The Early Palaeozoic Break-up of Northern Gondwana: Sedimentology, Physical Volcanology and Geochemistry of a Submarine Volcanic Complex in the Bavarian Facies Association, Saxothuringian Basin, Germany

Ordovician volcano-sedimentary successions of the Bavarian facies association in the Saxothuringian basin record the continental rift phase of the separation of the Saxothuringian Terrane from Gondwana. An 80 m succession from the Vogtendorf beds and Randschiefer Series (Arenig-Middle Ordovician), exposed along the northern margin of the Münchberg Gneiss Massif in northeast Bavaria, were subjected to a study of their sedimentology, physical volcanology and geochemistry. The Randschiefer series previously has been interpreted as lavas, tuffs, sandstones and turbidites, but the studied Ordovician units include four main lithological associations: mature sandstones and slates, pillowed alkali-basalts and derivative mass flow deposits, trachyandesitic lavas and submarine pyroclastic flow deposits interbedded with turbidites. Eight lithofacies have been distinguished based on relict sedimentary structures and textures, which indicate deposition on a continental shelf below wave base. The explosive phase that generated the pyroclastic succession was associated with the intrusion of dykes and sills, and was succeeded by the eruption of pillowed basalts. Debris flow deposits overlie the basalts. Ordovician volcanism in this region, therefore, alternated between effusive and explosive phases of submarine intermediate to mafic volcanism.

Based on geochemical data, the volcanic and pyroclastic rocks are classified as basalts and trachyandesites. According to their geochemical characteristics, especially to their variable concentrations of incompatible elements such as the High Field Strength Elements (HFSE), they can be divided into three groups. Group I, which is formed by massive lavas at the base of the succession, has extraordinarily high contents of HFSE. The magmas of this group were probably derived from a mantle source in the garnet stability field by low (ca. 1%) degrees of partial melting and subsequent fractionation. Group II, which comprises the pillow lavas at the top of the sequence, displays moderate enrichment of HFSE. This can be explained by a slightly higher degree of melting (ca. 1.6%) for the primary magma. Group I and II melts fractionated from their parental magmas in different magma chambers. The eruption centres of Groups I and II, therefore, cannot be the same, and the volcanic rocks must have originated from different vents. The sills and pyroclastic flow deposits of Group III stem at least partly from the same source as Group I. Rocks of Group I most likely mixed together with Group II components during the formation of the Group III flows, which became hybridised during eruption, transportation and emplacement.

The sedimentological and geochemical data best support a rift as the tectonic setting of this volcanism, analogous to modern continental rift zones. Hence, the rift-associated volcanic activity preserved in the Vogtendorf beds and Randschiefer Series represents an early Ordovician stage of rift volcanism when the separation of the Saxothuringian Terrane from Gondwana had just commenced.     

Scanline Method to Determine the Fractal Nature of 2-D Fracture Networks

A previous method proposed to measure the fractal dimension of pore spaces is adapted and modified for 2-D fracture networks. The method relies on scanning a 2-D fracture network through successive straight lines from top to bottom and measuring the distance between two fractures. The fractal dimension is then obtained using the log–log plot of the feature size and the number of features for this particular size at different magnifications. It is shown in this study that the method proposed to measure the fractal dimension of porous structures can be applicable to 2-D fracture networks with some modifications after testing it on synthetic and natural fracture patterns. The method is simplified to be useful for practical applications in the fractal analysis of fracture networks. The results reveal that, on the basis of the direction of scanning lines, different fractal behavior and dimensions can be obtained indicating that 2-D fracture networks possess multifractal character. This approach takes into account the effect of fracture orientation on the fractal behavior and anisotropic nature of fracture networks as well as the fracture density, length, and spatial distribution.     

城市人口GIS中数据的不确定性研究

针对系统数据源、数据模型的不确定性以及分析过程中引入的不确定性等问题进行了系统的研究，并归纳了各种不确定性的影响模型，进而提出了一套人口GIS数据优化建模以及分析过程中人口密度中心建模的思想和实用方法，用于克服人口GIS中数据的不确定性的影响。     

三江地区重力场特征和岩石圈构造

利用重力、地震层析成像等多种资料 ,并利用场分离、正反演以及阻尼最小二乘法、约束最小二乘法等数学方法 ,对重力异常进行分离 ,用地震层析成像的结果作为约束进行反演 ,得到地壳上地幔不同深度的密度分布和莫霍面深度等结果。     

高密度电阻率法二维反演在工程勘探中的应用

应用高密度电阻率法二维反演方法能够提高资料解释的准确性。通过几个最小二乘法反演在工程勘探中的应用实例,说明高密度电阻率法二维反演处理的优越性。     

高浓度有机废水化学和物理法处理技术综述

介绍国内外高浓度有机废水应用化学和物理方法处理技术进展 ,通过比较各种化学和物理方法的优缺点 ,得出探讨性结论 ,即采用一种方法难以完全处理高浓度有机废水 ,需经二段或三段处理方法处理后 ,才能达到排污标准。     

The Influence Of Vertical Wind Direction Shear On Dispersion In The Convective Boundary Layer, And Its Incorporation In Coastal Fumigation Models

The mean concentration distributionwithin a plume released from a point source in the atmosphericboundary layer can be greatly influenced by the systematic turningof wind with height (i.e. vertical wind direction shear). Such aninfluence includes a deflection of the plume centroid, with anassociated shearing of the vertical plume cross-section, and anenhancement of dispersion, in the horizontal plane. Wind directionshear is normally not accounted for in coastal fumigation models,although dispersion observations with shear acting as acontrolling parameter are not uncommon. A three-dimensionalLagrangian stochastic model is used to investigate the influenceof uniform wind direction shear on the diffusion of a point-sourceplume within the horizontally homogeneous convective boundarylayer, with the source located at the top of the boundary layer.Parameterisations are developed for the plume deflection andenhanced dispersion due to shear within the framework of aprobability density function (PDF) approach, and compared with theLagrangian model results. These parameterisations are thenincorporated into two applied coastal fumigation models: a PDFmodel, and a commonly used model that assumes uniform andinstantaneous mixing in the vertical direction. The PDF modelrepresents the vertical mixing process more realistically. A moreefficient version of the PDF model, which assumes a well-mixedconcentration distribution in the vertical at large times, isapplied to simulate sulfur dioxide data from the Kwinana CoastalFumigation Study. A comparison between the model results and thedata show that the model performs much better when the wind-sheareffects are included.     

A stochastic approach to site-response component in seismic ground motion coherency model

In order to account for the site-response part of the seismic ground motion coherency for sites of interest, an analytical stochastic methodology is proposed in this paper. By combining the pseudo-excitation method with wave motion finite element simulation techniques, a numerical approach for the computation of the coherency function between observation points is developed firstly. Then the orthogonal expansion method is introduced into this approach to study the effect of the uncertainty in soil properties on the coherency function. Finally some numerical examples are given to show the applicability of the methodology. The computational results demonstrate that the lagged coherency values tend to decrease in the vicinity of the resonant frequencies of the site.