A comparative study of hydraulic conductivity estimations using geostatistics

Three approaches for estimating the hydraulic conductivity (K) of the Trifa aquifer, Morocco were investigated: (1) kriging of the K values obtained from pumping tests, (2) cokriging of the pumping test data with electrical resistivity data as a secondary variable, and (3) cokriging of the pumping test data with the slope of the water table. Gauss-transformed values of the variables are used because they provide more robust variograms and transformed values of the primary and secondary variables show correlations higher than the raw values, which is beneficial in cokriging. In cokriging with electrical resistivity, two zones are considered since the geological deposits are different from the north to the south of the aquifer, which is reflected in different correlations between the variables. Comparison of the three approaches is based mainly on the estimation errors, and to a lesser degree on the cross-validations of the corresponding variogram models and general considerations, like the measurements’ reliability and aquifer make-up. The best-estimated K is given by cokriging with the slope of the water table and is therefore preferred for further use in groundwater flow modeling. Thus, electrical resistivity or the slope of the water table can both be used as secondary variables to estimate K, especially in heterogeneous aquifers with lateral variations in lithology, as is the case of the Trifa aquifer.     

鄂尔多斯盆地旬邑地区长8段沉积储层特征

通过野外露头、钻井岩心、铸体薄片、常规薄片、核磁共振、X-衍射和扫描电镜等方法,对旬邑地区长8段沉积及储层特征进行详细研究。结果表明:目的层长8段主要发育三角洲前缘亚相沉积,发育3支水下分流河道。砂岩岩性以灰绿色、灰白色细、粉-细为主的岩屑长石砂岩为主,其次为长石岩屑砂岩,储集空间主要为溶蚀孔,残余粒间孔次之;孔隙类型多为组合,以发育粒间孔—微孔为主,发育Ⅱ类、Ⅲ类孔隙结构,孔隙度平均为8.04%,渗透率0.42×10^-3μm²属于特低孔、超低渗油藏。长8储层I/S比为15%~20%,处于晚成岩A期;压实—压溶作用使得原始孔隙度减少52.3%,而胶结作用孔隙损失36%,建设性溶蚀作用增加面孔率1.67%。     

一次春季天气过程中不同降水类型的云图及雷达特征分析

本文利用常规气象资料、卫星、雷达及NCEP1°×1°的6小时再分析资料,对2013年4月发生在巴州北部的一次天气过程中两种不同的降水类型进行诊断、特别对云图及雷达特征进行详细分析。结果表明“S”型云西边界凹处对应系统性降水中心,低涡云系南段对应强对流中心。“S” 凹处的雷达图中对应有冷式切变,整层上升运动,水汽供应充足,且高层辐散、低层辐合,具备了大降水发生的环境场。雷达分析发现强对流发生在弱垂直风切变及辐散流场环境下,冰雹出现在与风速辐合中心对应的强回波中心下方。低涡云系中低层伴有下沉运动并配合冷平流,而近地面层为锋前暖平流,强对流发生在θse随高度降低的区域,是典型的冷锋锋面过境触发的强对流天气。     

On the application of a Boussinesq model to river flows including shocks

SERR-1D is a 4th-order finite volume 1D Boussinesq model including wave breaking energy dissipation through extra diffusive-like terms. This model has been primarily conceived to compute wave propagation in coastal areas and has been validated for breaking and non-breaking waves propagating over uneven bathymetries (Cienfuegos et al., 2005, 2006a, b, 2007). The present paper aims at investigating the ability of SERR-1D to simulate challenging fluvial hydraulic applications such as sudden gate operation in open channels generating short waves, dam-break flows and a steady hydraulic jump over a bump. The performance of the absorbing-generating boundary condition implemented in SERR-1D is first analysed in the context of fluvial applications where relatively short waves must be evacuated from the computational domain without producing spurious reflection. Next, by comparing numerical results to analytical and experimental dam-break test cases we show that the model is able to reproduce the overall features of these flows, but that additional care should be paid to the representation of energy dissipation and front speed in order to accurately represent bore dynamics.     

川西滇北引水区河流水质特性与治污调水研究

本文重点概述了川西滇北地区 ,西线调水河流的地理背景 ,河水矿化度、化学类型与河水硬度等水质特性以及该区河流水环境与水体污染分析评价。旨在促进引水区调水前期工作的节水、治污和生态环境保护的科学监测预报.     

流体-地质力学耦合建模表征水力压裂诱发地震:以加拿大Fox Creek地区为例

随着水力压裂技术在页岩气开发中的广泛应用,加拿大西部盆地的诱发地震活动显著增加.目前对于诱发地震的综合表征方法还不成熟.本文采用一种综合地质、岩石力学及流体力学的研究方法,对Fox Creek地区2015年2月8日发生的M3.0诱发地震事件进行了综合表征.首先,利用高分辨率三维反射地震资料,采用蚂蚁体追踪技术识别潜在断...     

A new mathematical model of asymmetric hydraulic fracture growth

Hydraulic fractures generated by fluid injection in rock formations are often mapped by seismic monitoring. In many cases, the microseismicity is asymmetric relative to the injection well, which has been interpreted by stress gradient along the direction of the hydraulic fracture. We present a mathematical model of asymmetric hydrofracture growth based on relations between the solid‐phase stress and the fracture hydraulics. For single fracture and single injection point, the model has three parameters, hydraulic conductivities of the fracture wings, and normalised stress gradient and predicts the positions of the fracture tips as functions of time. The model is applied to a set of microseismic event locations that occurred during and after an injection process. Two different methods are suggested that make it possible to delineate the fracture tips from the set of microseismic events. This makes it possible to determine the model parameters and to check the agreement between the model prediction and the measured data. The comparison of the measured and modelled growth of fracture wings supports both the assumption of the non‐zero stress gradient and the existence of the post‐injection unilateral growth.     

Hydraulic model tests for propagation of flow and sediment in floods due to breaking of a natural landslide dam during a mountainous torrent

During mountain torrents, large-magnitude floods may result from heavy rainfall and cause the breakage of landslide dams naturally formed by heavy rainfall, earthquakes, and so on. The characteristics of longitudinal spreading of clear water discharge and changes in flow depth must be clarified because the changes in peak depth have not yet been examined in steep-slope torrents and because there are few data on spreading of flash floods and related sedimentation in mountainous torrents. In the present study, experimental data were collected through hydraulic model tests over a rigid bed, and the spreading of water, fine sediment, bed load, and large boulders due to flooding are discussed assuming that flash flooding/debris flows occur in the upstream reach. The effects of changes in flow width, such as expansions and contractions in the flow width, as well as changes in meandering channels, sediment transportation, and spreading flow depth resulting from bores are examined using flume data for a steep-slope torrent. The data obtained in the present study reveal that fine sediment components are transported to the downstream reach if large-magnitude floods occur and that the spreading rate and peak lags of the fine sediment and water level indicate the occurrence of a flood in the upstream reach.     

Water balance prediction in stormwater infiltration basins using 2-D modeling: An application to evaluate the clogging process

Sustainable urban drainage systems are built along roads and in urban areas to collect urban runoff and avoid flooding, and to filter water pollutants. Sediment collected by runoff is deposited in the stormwater basin and progressively reduces water infiltration efficiency, leading to the clogging of the basin. To help stormwater basin managers and stakeholders better understand and predict clogging rates in order to elaborate maintenance plans and schedules, water transport prediction models are necessary. However,because of the heterogeneous sediment hydrodynamic properties inside the stormwater basin, a twodimensional(2-D) water flow model is required to predict water levels and possible overflow as accurately as possible. Saturated hydraulic conductivity(Ks) and sediment water retention curves were measured in the overall sediment layer of the stormwater basin, in addition to sediment layer thickness and organic matter content(11 sampling points). Sediment depth was used to predict organic matter(OM) content, and the OM was used to predict Ks. Water height in the basin was modeled with the HYDRUS-2 D model by taking into account the sediment hydrodynamic properties distribution. The HYDRUS-2 D model gave a satisfactory representation of the measured data. Scenarios of the hydraulic properties of stormwater basin sediment were tested over time, and hydraulic resistance, R, was calculated to assess the stormwater basin performance. Presently, after 20 years of functioning, the stormwater basin still ensures efficient water infiltration, but the first outflow(Hydraulic resistance,R 24 h)) is expected to appear in the next 5 years, and clogging(R 47 h) in the next 13 years. This 2-D water balance model makes it possible to integrate the hydrodynamic heterogeneity of a stormwater basin. It gives interesting perspectives to better predict 2-D/3-D contaminant transport.