裂缝性储层的电各向异性响应特征研究   总被引：8，自引：5，他引：3       下载免费PDF全文

沈金松  苏本玉  郭乃川 《地球物理学报》2009,52(11):2903-2912

以水平裂缝分布的孔隙介质模型为基础,建立了水平裂缝面的平行裂缝分布和带粗糙表面的点接触裂缝模型,导出了两类裂缝模型的水平和垂直电阻率响应关系,分析了两类裂缝模型在没有围压和存在围压条件下的水平电阻率、垂直电阻率变化规律和电各向异性系数的变化特征.讨论了裂缝开度、裂缝密度和裂缝粗糙度等裂缝特征参数对裂缝性储层电各向异性的影响.为简化讨论,所有电性响应特征的分析都忽略了裂缝和孔隙表面的导电性和极化的影响.利用平行分布水平裂缝面模型和带粗糙面的裂缝模型,考察了围压条件下的裂缝性岩石的电各向异性响应特征,得到了对实际应用有意义的结果.  相似文献   

多极子随钻声波测井波场模拟与采集模式分析   总被引：16，自引：9，他引：7       下载免费PDF全文

王华  陶果  王兵  李卫  张绪健 《地球物理学报》2009,52(9):2402-2409

应用三维非均匀交错网格有限差分程序模拟了多极子随钻声波测井的波场,考察了硬地层中单极子随钻声波测井响应及软地层中声源频率对多极子随钻声波测井的影响;计算了接收阵列波形的时域相干谱及频散特征,结果表明随钻测井仪器居中时,在硬地层中可以直接利用单极子声系得到地层横波速度,但地层纵波受到钻铤波的极大干扰.而在软地层中可以利用单极子声系直接测得地层纵波速度,但地层横波速度则需要使用工作在较低频率下的四极子随钻声波仪来测得,此时测井频段又会落入钻井噪声频带而受到影响.为此本文提出数值模拟手段结合物理实验的方法得到钻铤波的影响,在实际测井中通过信号处理方法而不是用在仪器本体上刻槽的方式来更完全地消除钻铤的影响.为了避免钻井噪声的影响,本文提出六极子随钻声波仪更适合软地层的横波测量.本文用数值实验结果来说明这些方法的可行性.  相似文献   

双差地震定位法在山西中小地震精确定位中的初步应用   总被引：1，自引：0，他引：1  

靳玉科  范瑾  赵虎明  宋美琴  张玲  董春丽 《山西地震》2008,(4)

采用双差地震定位法对山西省内2001-2005年间发生的ML≥2．0的地震进行了重新定位。重新定位后得到410个地震事件的精确震源参数。结果表明,重新定位后的震中分布呈明显的条带状,且更加集中。定位后的平均震源深度为9．35km,其中又以地面下2km～14km为发震优势层。  相似文献   

Spectral features of geomagnetic low point displacement and its mechanism     

张学民  钱家栋  王亚丽  赵旭  欧阳新艳  赵庶凡 《地震学报(英文版)》2008,21(5):474-484

In this paper,Changli station in Hebei Province was taken as an example,in which the minute data of geomagnetic Z component was used to analyze the spectral values of its main frequencies during normal time,geomagnetic storm time and low point displacement time interval respectively. After fitting of ten high spectral values to loga-rithmic functions,it is found that,by using same length of data,the spectral values at geomagnetic storm time in-crease apparently compared with those at normal time,especially at the high frequency segment. While low point displacement occurred,the spectral values at high frequency are approximate to those at normal time,but at period above 4 hours they are mostly lower than those at normal time. Comparison of accumulating of some FFT results at low point displacement and normal time shows that,spectral values at periods of 8.5 and 13.7 hours increase at low point displacement time relative to those at normal time. Compared with the images of Ne observed at DE-METER satellite,it is illustrated that the occurrence of geomagnetic low point displacement is well corresponding with the increase of Ne in ionosphere. Finally it was discussed about those spectral features and the occurrence mechanism of geomagnetic low point displacement.  相似文献   

地磁数据处理与地震关系之探   总被引：1，自引：0，他引：1  

马钦忠  塔青  王炜  林命周  吴耿锋  吴绍春 《华南地震》2008,28(3):21-30

研究了上海崇明、佘山和杭州这3个地磁台的观测资料在2004年4月21日南黄海ML4．0级、5月26日浙江省舟山群岛ML4．3级和11月15日南黄海％4．6级地震前的异常变化特征,结果表明：杭州台和崇明台数字化地磁观测资料分钟值空间差值于4月14日～17日、4月30日、5月8日出现的异常信息很可能是震磁异常信息;杭州台和余山台数字化地磁观测资料分钟值、模拟观测21时值Z分量地磁场相关系数R值分别在震前2天、24天和震前5天、15天出现了超出2σ值的震磁异常变化：崇明和余山地磁台数字化地磁Z分量分钟值的空间差值异常信息在4月21日南黄海尬4．0级地震前后有所显示。但在5月26日舟山群岛ML4．3级地震前不太明显,可能与谈两个地磁台站相距较近日震中距较近有美．  相似文献   

川滇地区强余震的震级分布和距离分布特征          下载免费PDF全文

吕晓健  高孟潭  高战武  米素婷 《地震学报》2008,30(4):397-404

研究了川滇地区1966年以来12次主震震级MSge;6.5的地震序列中,主震与强余震（本文定义为所有MSge;5的余震）震级差分布特征和强余震与主震距离的分布特征. 结果表明,强余震与主震震级差服从截断的指数分布,据此推导出了强余震与主震震级差的概率密度函数; 强余震距离分布的优势范围是距主震10——39 km,且强余震与主震震中的距离服从正态分布.   相似文献   

An accurate time integration method for simplified overland flow models   总被引：1，自引：0，他引：1  

G. Gottardi  M. Venutelli 《Advances in water resources》2008

An accurate time integration method for the diffusion-wave and kinematic-wave approximated models for the overland flow is proposed. The discretization of the first- and second-order spatial derivatives in the basic equation is obtained by using the second-order Lax–Wendroff and the three-point centred finite difference schemes, respectively. For the solution in time, the system of ordinary differential equations, obtained by the linearization of the celerity and of the hydraulic diffusivity by Taylor series expansions, is integrated analytically. The stability and the numerical dissipation and dispersion are investigated by the Fourier analysis. A proper Courant number, and the corresponding time step for the numerical simulations can be established. In addition, the proposed diffusion-wave and kinematic-wave models are straightforwardly extended to the two-dimensional flow. Test cases for both one- and two-dimensional problems, compare the solutions of the diffusion-wave and kinematic-wave models with analytical solutions, with experimental results and with numerical solutions obtained by the Saint–Venant equations. These simulations show that the proposed numerical–analytical models accurately predict the overland flow for several situations, in particular for unsteady rainfall rate and for spatial variations of the surface roughness.  相似文献   

结合波形互相关技术的双差算法在地震定位中的应用探讨   总被引：9，自引：0，他引：9  

黄媛 《国际地震动态》2008,(4):29-34

本文致力于探讨在数字化地震监测大规模发展后,如何更好地将大量丰富的数字化波形信息应用到地震定位领域,从而更大程度地提高地震定位精度问题。笔者认为"结合波形互相关技术的双差定位算法"是一种比较有发展前景的方法,因此分别从基本理论、发展历程、台网实用化过程以及推广使用中可能存在的问题等角度进行分析,探讨该技术在地震定位领域中的发展方向及推广使用的可能性。  相似文献   

The influence of variable topography on the depositional behaviour of pyroclastic density currents: The examples of the Upper Pollara eruption (Salina Island,southern Italy)     

Roberto Sulpizio  Rosanna De Rosa  Paola Donato 《Journal of Volcanology and Geothermal Research》2008

Stratigraphic reconstruction of the Upper Pollara eruption has allowed for the inference of eruptive mechanisms and the distillation of a sedimentological model for pyroclastic density currents (PDCs) moving across variable topography. The pre-eruptive topography in the study area was characterised by a tuff ring-like morphology, with both inward and outward dipping slopes. Highly viscous, moderately porphyritic, dacitic to rhyolitic magmas fed the eruption, which was characterised by a Vulcanian eruptive style. The stratigraphic succession was divided into five eruption units (EUs), which result from different phases of the eruption separated by stases. Sustained columns occurred only during EU1, while PDC generation dominates EU2–5. Lithofacies analysis of the PDC deposits indicates the prevalence of massive coarse-grained deposits on the inner slopes of the Pollara crater, which are interpreted as the deposits of a flow-boundary zone dominated by granular flow or fluid escape regimes. Dune-bedded, massive to stratified lithofacies dominate the outer slopes of the Pollara crater, and are interpreted as the deposits of PDCs with flow-boundary zones in which traction played a major role. Thin, massive PDC deposits are exposed on the sub-horizontal Malfa terrace, and are interpreted as representative of flow-boundary zones dominated by a granular flow regime. The occurrence of stacked deposits indicates that most of the PDCs were characterised by unsteady pulsatory behaviour, with development of trains of pulses during their transport. The downcurrent lithofacies transitions observed for the Upper Pollara deposits have finally been compared with other similar lithofacies associations which have been described for short-lived PDCs at tuff rings, in order to discuss the influence of pre-eruptive topography on lithofacies association.  相似文献   

Rainfall‐induced consolidation and sealing effects on soil erodibility during concentrated runoff for loess‐derived topsoils     

A. Knapen  J. Poesen  S. De Baets 《地球表面变化过程与地形》2008,33(3):444-458

Flume experiments simulating concentrated runoff were carried out on remolded silt loam soil samples (0·36 × 0·09 × 0·09 m³) to measure the effect of rainfall‐induced soil consolidation and soil surface sealing on soil erosion by concentrated flow for loess‐derived soils and to establish a relationship between soil erodibility and soil bulk density. Soil consolidation and sealing were simulated by successive simulated rainfall events (0–600 mm of cumulative rainfall) alternated by periods of drying. Soil detachment measurements were repeated for four different soil moisture contents (0·04, 0·14, 0·20 and 0·31 g g^?1). Whereas no effect of soil consolidation and sealing is observed for critical flow shear stress (τ_cr), soil erodibility (Kc) decreases exponentially with increasing cumulative rainfall depth. The erosion‐reducing effect of soil consolidation and sealing decreases with a decreasing soil moisture content prior to erosion due to slaking effects occurring during rapid wetting of the dry topsoil. After about 100 mm of rainfall, Kc attains its minimum value for all moisture conditions, corresponding to a reduction of about 70% compared with the initial Kc value for the moist soil samples and only a 10% reduction for the driest soil samples. The relationship estimating relative Kc values from soil moisture content and cumulative rainfall depth predicts Kc values measured on a gradually consolidating cropland field in the Belgian Loess Belt reasonably well (MEF = 0·54). Kc is also shown to decrease linearly with increasing soil bulk density for all moisture treatments, suggesting that the compaction of thalwegs where concentrated flow erosion often occurs might be an alternative soil erosion control measure in addition to grassed waterways and double drilling. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献