Threshold pressure gradient of fluid flow through multi-porous media in low and extra-low permeability reservoirs     

HongEn Dou  ShiYing Ma  CunYou Zou  ShangLin Yao 《中国科学:地球科学(英文版)》2014,57(11):2808-2818

After analyzing many studies of fluid flow theory of multi-porous media in low and extra-low permeability reservoirs and the numerical simulation of non-Darcy flow, we found that a negative flow rate occurs in the existing non-Darcy flow equation, which is unreasonable. We believe that the existing equation can only be considered as a discriminant to judging Darcy flow or non-Darcy flow, and cannot be taken as a fluid flow governing equation of multi-porous media. Our analysis of the experimental results shows that the threshold pressure gradient (TPG) of low and extra-low permeability reservoirs is excessively high, and does not conform to fluid flow through multi-porous media in the actual reservoir situation. Therefore, we present a reasonable TPG ranging from 0.006 to 0.04 MPa/m at the well depth of 1500 m and oil drainage distance of 500 m. The results of our study also indicate that the non-Darcy flow phenomenon will disappear when the TPG reaches a certain value. In addition, the TPG or non-Darcy flow in low and extra-low permeability reservoirs does not need to be considered in the productivity prediction and reservoir numerical simulation. At present, the black oil model or dual-porous media is suitable for simulating low and extra-low permeability reservoirs.  相似文献   

热浪对人体健康的影响及其研究方法   总被引：17，自引：1，他引：16  

谈建国  黄家鑫 《气候与环境研究》2004,9(4):680-686

由于全球气候变化和城市热岛效应,热浪成为世界范围内频繁发生的极端天气事件,这使得热浪对人体健康的影响问题成为许多国际机构,如世界气象组织(WMO)、世界卫生组织(WHO)、联合国环境规划署(UNEP)和各国气象、环境和流行病等方面科学家关注的焦点.作者介绍近年来世界各地频繁发生的热浪及其原因、热浪对人体健康的影响、热浪研究的指标法、多元回归分析和天气气候分型等多种方法,同时也提出防御热浪的一些措施.  相似文献   

打桩振动效应观测及振动安全指标探讨   总被引：6，自引：0，他引：6  

吴铁生 《高原地震》2004,16(1):40-44

在城市建筑密集区内打桩产生的振动可能引起周边建筑物损坏,由此引起的纠纷屡见不鲜。本在海口一个打桩施工项目实测振动数据的基础上,确定了此类场地和建筑物适用的速度衰减关系及振动安全指标;结果显示一些住宅的表层装修损坏,安全指标相当低,振动标准应根据实际建筑物的情况慎重选取。  相似文献   

基于地震目录估计完备震级方法的数值实验   总被引：8，自引：2，他引：6       下载免费PDF全文

黄亦磊  周仕勇  庄建仓 《地球物理学报》2016,59(4):1350-1358

本文将5种估计完备震级(magnitude of completeness,简记为Mc)的方法运用在三个不同模型产生的理论地震目录上,进而对比它们的优缺点.我们发现分段斜率中值分析法MBASS(The Median-based analysis of the segment slope)适用于不完备部分台网探测地震能力随震级变化快及监测能力在时间上存在不均匀性(heterogeneity)的目录中,但是要求目录包含大量的地震事件,而b值稳定法MBS(The Mcby b-value stability approach)则适合用于台网探测地震能力随震级减小衰减慢地震目录,但是比较费时.最大曲率法MAXC(The Maximum Curvature technique)和拟合优度测试法GFT(The Goodness-of-Fit Test)在使用时都低估Mc,需要加调整量.完整性震级范围法EMR(Mcfrom Entire Magnitude Range)则一般给出比较稳定、适中的Mc估计值.这种方法适用在地震数目少,且对地震丢失容忍度比较高的情况.在实践中针对不同性质的地震目录,我们希望这项研究能帮助研究者选择最合适估计完备震级Mc的方法,并指出了一些估计完备震级中应当避免的问题.  相似文献   

Characteristics of clustering debris flows in Wenchuan earthquake zone   总被引：1，自引：1，他引：0  

Chao Ma  Kai-heng Hu  Qiang Zou  Mi Tian 《山地科学学报》2013,10(6):953-961

Clustering debris-flow events, namely many debris flows simultaneously triggered by a regional rainstorm in a large-scale mountainous area, occurred in four regions of Wenchuan earthquake stricken areas in 2008 and 2010. The characteristics of the clustering debris flows are examined with regard to triggering rainfall, formation process, and relationship with the earthquake by field survey and remote sensing interpretation. It is found that the clustering events occurred nearly at the same time with the local peak rainstorms, and the rainfall intensity-duration bottom limit line for clustering debris flows is higher than the worldwide line. It means that more rainfall is needed for the occurrence of the clustering debris flows. Four kinds of major formation processes for these debris flows are summarized： tributary-dominated, mainstream- dominated, transformation from slope failures, and mobilization or liquefaction of landslide. The four regions has a spatial correlation with the strong- quake-influenced zone with the peak ground acceleration = 0.2 g and the seismic intensity 〉 X.  相似文献   

准噶尔盆地南缘侏罗系烃源岩排烃效率研究   总被引：1，自引：0，他引：1  

郭继刚  李建华  庞雄奇  向才富  姜福杰  王鹏威 《现代地质》2013,27(5):1081-1088

准噶尔盆地南缘下部成藏组合勘探日趋重要,其主力烃源岩生烃潜力和排烃效率的研究亟待加强。根据排烃门限理论,利用生烃潜力法建立了准噶尔盆地南缘侏罗系烃源岩的生、排烃模式,并计算了烃源岩的生烃量、排烃量和排烃效率。研究表明,准噶尔盆地南缘侏罗系泥质烃源岩和煤层的排烃门限对应的镜质组反射率均为0. 7 %。侏罗系烃源岩的总生烃量为3 973. 84 x 108t,总排烃量为1 402. 71 x108t,其中八道湾组烃源岩排烃量占总排烃量的69.85%。准噶尔盆地南缘侏罗系烃源岩的平均排烃效率为35. 30%,不同层系不同岩性烃源岩,其排烃效率明显不同,泥质烃源岩排烃效率远大于煤层。综合分析认为,准噶尔盆地南缘侏罗系烃源岩生、排烃量大,排烃效率较高,下部成藏组合以侏罗系烃源岩为主力烃源岩,具有良好的资源潜力。  相似文献   

淮河流域极端径流的时空变化规律及统计模拟   总被引：9，自引：0，他引：9  

杜鸿  夏军  曾思栋  佘敦先  张永勇  严子奇 《地理学报》2012,67(3):398-409

以淮河流域蚌埠闸以上20 个水文站点1956-2010 年日径流量观测数据资料为基础,采用游程检验、趋势检验和Mann-Kendall 检验法分析年最大日径流量的变化规律。分别采用年最大值法(annual maximum,AM) 和超门限峰值法(peaks over threshold,POT) 抽取径流序列样本, 运用广义极值分布(generalized extreme value distribution,GEV) 和广义帕累托分布(generalized Pareto distribution,GPD) 两种极值统计模型对规范化样本进行拟合,分析淮河流域极端径流的时空变化规律。研究表明:1956-2010 年,淮河流域蚌埠闸以上的研究站点中,10 个站点的年最大日径流量有减少的趋势,另外10 个站点有不显著的增加趋势。极端径流事件大多发生在20 世纪60、70 年代,且以汛期居多。淮河流域的极端径流主要来自淮河干流、淮南山区和伏牛山区。使用Kolmogorov-Smirnov (K-S) 法检验发现,GEV和GPD分布分别能较好的拟合AM和POT序列。采用百分位阈值法、平均超出量函数图法和超定量洪峰法三种方法选取阈值,对于淮河流域的极端径流事件模拟而言,百分位阈值法较好。  相似文献   

引发意大利托斯卡纳区滑坡的区域降水阈值体系的定义——统计与环境分析(英文)   总被引：9，自引：0，他引：9  

ROSI Ascanio  SEGONI Samuele  CATANI Filippo  CASAGLI Nicola 《地理学报(英文版)》2012,22(4):617-629

The aim of this work is the determination of regional-scale rainfall thresholds for the triggering of landslides in the Tuscany Region(Italy).The critical rainfall events related to the occurrence of 593 past landslides were characterized in terms of duration(D) and intensity(I).I and D values were plotted in a log-log diagram and a lower boundary was clearly noticeable:it was interpreted as a threshold representing the rainfall conditions associated to landsliding.That was also confirmed by a comparison with many literature thresholds,but at the same time it was clear that a similar threshold would be affected by a too large approximation to be effectively used for a regional warning system.Therefore,further analyses were performed differentiating the events on the basis of seasonality,magnitude,location,land use and lithology.None of these criteria led to discriminate among all the events different groups to be characterized by a specific and more effective threshold.This outcome could be interpreted as the demonstration that at regional scale the best results are obtained by the simplest ap-proach,in our case an empirical black box model which accounts only for two rainfall pa-rameters(I and D).So a set of thresholds could be conveniently defined using a statistical approach:four thresholds corresponding to four severity levels were defined by means of the prediction interval technique and we developed a prototype warning system based on rainfall recordings or weather forecasts.  相似文献   

Predicting gully initiation: comparing data mining techniques,analytical hierarchy processes and the topographic threshold     

Tal Svoray  Evgenia Michailov  Avraham Cohen  Lior Rokah  Arnon Sturm 《地球表面变化过程与地形》2012,37(6):607-619

Predicting gully initiation at catchment scale was done previously by integrating a geographical information system (GIS) with physically based models, statistical procedures or with knowledge‐based expert systems. However, the reliability and validity of applying these procedures are still questionable. In this work, a data mining (DM) procedure based on decision trees was applied to identify areas of gully initiation risk. Performance was compared with the analytic hierarchy process (AHP) expert system and with the commonly used topographic threshold (TT) technique. A spatial database was used to test the models, composed of a target variable (presence or absence of initial points) and ten independent environmental, climatic and human‐induced variables. The following findings emerged: using the same input layers, DM provided better predictive ability of gully initiation points than the application of both AHP and TT. The main difference between DM and TT was the very high overestimation inherent in TT. In addition, the minimum slope observed for soil detachment was 2°, whereas in other studies it is 3°. This could be explained by soil resistance, which is substantially lower in agricultural fields, while most studies test unploughed soil. Finally, rainfall intensity events >62.2 mm h^‐1 (for a period of 30 min) were found to have a significant effect on gully initiation. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

塔克拉玛干沙漠风蚀起沙观测研究——试验介绍与观测结果初报   总被引：2，自引：0，他引：2  

何清  杨兴华  艾力·买买提明  刘新春  霍文 《中国沙漠》2011,31(2):315-322

介绍了中国气象局乌鲁木齐沙漠气象研究所在塔克拉玛干沙漠开展的风蚀起沙观测试验。对观测试验所获观测资料进行了初步分析,获得了一些有关塔克拉玛干沙漠风沙运动的特征。主要结果为,下垫面状况影响风沙流结构,塔中、若羌0~100 cm高程风沙流结构完全符合指数分布,肖塘则上部偏离指数分布;3地0~100 cm高程风沙流分别有72.4％、47.3%、62.6%的输沙量分布在0~30 cm高程内;3地风沙流输沙的粒径以细沙、极细沙、粉沙为主,其中极细沙可占到输沙量的43.8%~75.5%;风沙流中贴地层风速廓线受风沙相互作用的影响,不再符合对数分布,更加符合幂函数u=azb分布,拟合系数均大于0.93;沙尘撞击颗粒数与2 m高度风速变化趋势一致,塔中、肖塘、若羌3地的临界摩擦速度分别为0.25 m·s-1,0.27 m·s-1,0.21 m·s-1。  相似文献