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921.
基于EFDC模型的深圳水库富营养化模拟 总被引:2,自引:0,他引:2
基于EFDC模型构建了深圳水库三维水动力和富营养化定量模拟模型.分别用2009年和2010 2011年流量、水位和水质等观测数据对模型进行了校正和验证,准确地反映了深圳水库的水动力和水质变化过程.在此基础上,假定支流污染截排、水库调度和降低东江引水污染负荷3种情景进行深圳水库富营养化数值模拟,3种情景下库中Chl.a峰值浓度分别降低1.0%、16.4%和46.3%,平均浓度分别降低1.3%、29.8%和29.9%.深圳水库具有良好的交换能力,尚未出现水华暴发,但入库营养盐负荷高,存在较大的富营养化风险;在目前沙湾河污水已经截排的基础上再实施支流污染控制,对水质改善和藻类控制作用已不明显;水库调度和削减东江引水污染负荷对深圳水库水质和富营养化改善明显,能够有效降低水华发生的风险. 相似文献
922.
In this paper, we use the double difference location method based on waveform cross-correlation algorithm for precise positioning of the Three Gorges Reservoir (TGR) earthquakes and analysis of seismic activity. First, we use the bi-spectrum cross-correlation method to analyze the seismic waveform data of TGR encrypted networks from March, 2009 to December, 2010, and evaluate the quality of waveform cross-correlation analysis. Combined with the waveform cross-correlation of data obtained, we use the double difference method to relocate the earthquake position. The results show that location precision using bi-spectrum verified waveform cross-correlation data is higher than that by using other types of data, and the mean 2 sig-error in EW, NS and UD are 3.2m, 3.9m and 6.2m, respectively. For the relocation of the Three Gorges Reservoir earthquakes, the results show that the micro-earthquakes along the Shenlongxi river in the Badong reservoir area obviously show the characteristics of three linear zones with nearly east-west direction, which is in accordance with the small faults and carbonate strata line of the neo-tectonic period, revealing the reservoir water main along the underground rivers or caves permeated and induced seismic activity.The stronger earthquakes may have resulted from small earthquakes through the active layers. 相似文献
923.
Differential compaction has long been used by seismic interpreters to infer subsurface geology using knowledge of the relative compaction of different types of sediments. We outline a method to infer the gross fraction of shale in an interval between two seismic horizons using sandstone and shale compaction laws. A key component of the method involves reconstruction of a smooth depositional horizon by interpolating decompacted thicknesses from well control. We derive analytic formulae for decompaction calculations using known porosity–stress relations and do not employ discrete layer iterative methods; these formulae were found to depend not only upon the gross fraction of shale but also on the clay content of the shales and the thickness of the interval. The relative merits of several interpolation options were explored, and found to depend upon the structural setting. The method was successfully applied to an oil sands project in Alberta, Canada. 相似文献
924.
在地震解释与储层预测中,地震属性扮演着重要角色.在砂砾岩储层研究过程中,常规属性效果并不理想,无法满足实际应用的需要.而过零点个数,虽是一种不被人经常使用的地震属性,但我们发现在砂砾岩体油藏预测中应用效果良好.为此,研究过零点个数地震属性的定义与计算方法,讨论子波主频、砂岩厚度、泥岩夹层和地层韵律性等与它的关系,通过模型测试与实际资料应用对其做较全面的诠释.研究表明:(1)对于单一界面地震记录,过零点个数不随子波主频和波长的变化而变化;(2)砂岩厚度与过零点个数呈正相关,厚砂岩的过零点个数要比薄砂岩大;(3)砂体间存在的泥岩夹层,厚度变化对过零点个数影响较小,但它会影响波组的形态;(4)不规则沉积与均匀沉积相比,过零点个数属性值要大,因此,此属性比较适合多期次发育的砂砾岩体或其他薄互层结构的储层预测.总的来说,过零点个数地震属性能够有效地识别砂砾岩体发育区,可为此类储层预测提供了一种新的优势属性. 相似文献
925.
通过叠前反演获得的单参数或组合参数都有一定的流体识别能力,但如何将多种流体识别因子有效融合是目前进行流体识别的一个难题.利用人工参与进行流体性质的综合解释是目前流体识别因子融合的主要途径,但这种方法人为干扰较大,不确定性强.鉴于此,本文提出了一种基于近似支持向量机的流体识别方法.该方法首先以实际工区测井资料为依据,优选出对工区内储层所含流体特征敏感的流体识别因子作为输入参数,然后通过近似支持向量机进行流体性质的判别,实例证明该方法的识别结果客观准确,是一种可靠的流体识别方法. 相似文献
926.
This paper summarizes the latest developments, future prospects, and proposed countermeasures of reservoir sedimentation and channel scour downstream of the Three Gorges Reservoir (TGR) on the Yangtze River in China. Three key results have been found.(1) The incoming sediment load to the TGR has been significantly lower than expected.(2) The accumulated volume of sediment deposition in the TGR is smaller than expected because the overall sediment delivery ratio is relatively low, and the deposition in the near-dam area of the TGR is still developing.(3) River bed scour in the river reaches downstream of the Gezhouba Dam is still occurring and channel scour has extended to reaches as far downstream as the Hukou reach. Significantly, sedimentation of the TGR is less problematic than expected since the start of operation of the TGR on the one hand;on the other hand, the possible increases in sediment risks from dependence on upstream sediment control, deposition in the reservoir, and scour along middle Yangtze River should be paid more attention.(1) Sediment trapped by dams built along the upper Yangtze River and billion tons of loose materials on unstable slopes produced by the Wenchuan Earthquake could be new sediment sources for the upper Yangtze River. More seriously, possible release of this sediment into the upper Yangtze River due to new earthquakes or extreme climate events could overwhelm the river system, and produce catastrophic consequences.(2) Increasing sediment deposition in the TGR is harmful to the safety and efficiency of project operation and navigation.(3) The drastic scour along the middle Yangtze River has intensified the down-cutting of the riverbed and erosion of revetment, it has already led to increasing risk to flood control structures and ecological safety. It is suggested to continue the Field Observation Program, to initiate research programs and to focus on risks of sedimentation. 相似文献
927.
《国际泥沙研究》2019,34(6):537-549
Dam removal can generate geomorphic disturbances, including channel bed and bank erosion and associated abrupt/pulsed release and downstream transfer of reservoir sediment, but the type and rate of geomorphic response often are hard to predict. The situation gets even more complex in systems which have been impacted by multiple dams and a long and complex engineering history. In previous studies one-dimensional (1-D) models were used to predict aspects of post-removal channel change. However, these models do not consider two-dimensional (2-D) effects of dam removal such as bank erosion processes and lateral migration. In the current study the impacts of multiple dams and their removal on channel evolution and sediment delivery were modeled by using a 2-D landscape evolution model (CAESAR-Lisflood) focusing on the following aspects: patterns, rates, and processes of geomorphic change and associated sediment delivery on annual to decadal timescales. The current modeling study revealed that geomorphic response to dam removal (i.e., channel evolution and associated rates of sediment delivery) in multiple dam settings is variable and complex in space and time. Complexity in geomorphic system response is related to differences in dam size, the proximity of upstream dams, related buffering effects and associated rates of upstream sediment supply, and emerging feedback processes as well as to the presence of channel stabilization measures. Modeled types and rates of geomorphic adjustment, using the 2-D landscape evolution model CAESAR-Lisflood, are similar to those reported in previous studies. Moreover, the use of a 2-D method showed some advantages compared to 1-D models, generating spatially varying patterns of erosion and deposition before and after dam removal that provide morphologies that are more readily comparable to field data as well as features like the lateral re-working of past reservoir deposits which further enables the maintenance of sediment delivery downstream. 相似文献
928.
热带富营养水库敞水区浮游动物群落结构与季节变化:以广东大沙河水库为例 总被引:2,自引:2,他引:0
于2012-2013年对大沙河水库敞水区的浮游动物群落及环境因子进行监测,分析和探讨大沙河水库浮游动物群落结构的变化.2年共采集到后生浮游动物44种,其中桡足类5种、枝角类9种、轮虫30种.浮游动物种类组成季节变化较小,存在较多的常见种.2012、2013年浮游动物总生物量的年际波动范围分别为210.1~2560.5、512.7~3145.6μg/L,2012、2013年枝角类是浮游动物生物量的优势类群,分别占总生物量的45.5%、51.5%;其次是桡足类,分别占总生物量的31%、40%.枝角类的丰度和生物量与轮虫的丰度和生物量没有显著相关性,反映了它们之间的竞争强度较弱.2012与2013年的浮游动物总生物量不存在显著差异,但群落结构差异较大.2012与2013年对应月份的群落平均距离为0.61(SD=0.18),反映群落结构在季节变化上存在较大的随机性.浮游动物总丰度和总生物量存在较为明显的季节性变化:枯水期显著高于丰水期.群落组成与环境变量之间的RDA分析表明,由季风降水导致的水文变化是影响群落结构变化和产生随机性的关键要素. 相似文献
929.
Marine transient electromagnetic sounding of deep buried hydrocarbon reservoirs: principles,methodologies and limitations 下载免费PDF全文
The possibility of a time‐domain electromagnetic sounding method using excitation and measurement of vertical electric fields to search for and identify deeply buried reservoirs of hydrocarbons offshore is investigated. The method operates on source–receiver offsets, which are several times less than the depth of the reservoir. Geoelectric information is obtained from the transient responses recorded in the pauses between the pulses of electric current in the absence of the source field. The basics of the method, as well as its sensitivity, resolution, and the highest accessible depth of soundings for various geological conditions in a wide range of sea depths, are analyzed. For the analysis, 1D and 3D geoelectric models of hydrocarbon reservoirs are used. It is shown that under existing technologies of excitation and measurement of vertical electric fields, the highest accessible depth of soundings can be up to 4 km. Technology for the inversion and interpretation of transient responses is demonstrated on experimental data. 相似文献
930.
Experimental quantification of the seismoelectric transfer function and its dependence on conductivity and saturation in loose sand 下载免费PDF全文
Under certain circumstances, seismic propagation within porous media may be associated to the conversion of mechanical energy to electromagnetic energy, which is known as a seismo‐electromagnetic phenomenon. The propagation of fast compressional P‐waves is more specifically associated to the manifestations of a seismoelectric field linked to the fluid flows within the pores. The analysis of seismoelectric phenomena, which requires the combination of the theory of electrokinetics and Biot's theory of poroelasticity, provides us with transfer function that links the coseismic seismoelectric field E to the seismic acceleration . To measure the transfer function, we have developed an experimental setup enabling seismoelectric laboratory observation in unconsolidated quartz sand within the kilohertz range. The investigation focused on the impact of fluid conductivity and water saturation over the coseismic seismoelectric field. During the experiment, special attention was given to the accuracy of electric field measurements. We concluded that, to obtain a reliable estimate of the electric field amplitude, the dipole from which the potential differences are measured should be of much smaller length than the wavelength of the propagating seismic field. Time‐lapse monitoring of the seismic velocities and seismoelectric transfer functions were performed during imbibition and drainage experiments. In all cases, the quantitative analysis of the seismoelectric transfer function was in good agreement with theoretical predictions. While investigating saturation variations from full to residual water saturation, we showed that the ratio undergoes a switch in polarity at a particular saturation , which also implies a sign change of the filtration, traducing a reversal of the relative fluid displacement with respect to the frame. This sign change at critical saturation stresses a particular behaviour of the poroelastic medium: the dropping of the coseismic electric field to zero traduces the absence of relative pore/fluid displacements representative of a Biot dynamically compatible medium. We concluded from our experimental study in loose sand that the measurements of the coseismic seismoelectric coupling may provide information on fluid distribution within the pores and that the reversal of the seismoelectric field may be used as an indicator of the dynamically compatible state of the medium. 相似文献