Seismic spectrograms of an anelastic layer with different source-receivers configurations     

Ayman N. Qadrouh  José M. Carcione  Ahmed M. A. Salim  Zuhar Zahir Tuan Harith 《Arabian Journal of Geosciences》2016,9(5):413

Thin and relatively thin anelastic layers (compared to the signal wavelength) generally represent hydrocarbon reservoirs, where the rock is a sandstone or a source rock saturated with brine, oil and gas. The study of the seismic response of these layers is important to detect the hydrocarbons on the basis of the reflection and transmission coefficients and the wave velocity and attenuation properties. Different seismic experiments (source-receiver configurations) can provide useful information to characterise its properties. In this work, we consider varying thicknesses and Q values of the layer and analyse the reflection and transmission coefficients. Moreover, we obtain spectrograms of surface seismic profiles and vertical and horizontal well profiles (VSP and HSP, respectively) to analyse their frequency content with offset due to variations of the attenuation properties of the layer. In addition, we compare the effects due to NMO stretching and intrinsic attenuation related to the low-frequency shadows (LFS) observed in real data after stacking, since LFS can have several causes. Ambiguity is present in this case, indicating that non-stretch NMO is required, otherwise an offset mute of the data may remove useful information regarding the intrinsic (physical) loss.  相似文献   

Groundwater abstraction management in Sana’a Basin,Yemen: a local community approach     

Taha M. Taher 《Hydrogeology Journal》2016,24(6):1593-1605

Overexploitation of groundwater resources in Sana’a Basin, Yemen, is causing severe water shortages associated water quality degradation. Groundwater abstraction is five times higher than natural recharge and the water-level decline is about 4–8 m/year. About 90 % of the groundwater resource is used for agricultural activities. The situation is further aggravated by the absence of a proper water-management approach for the Basin. Water scarcity in the Wadi As-Ssirr catchment, the study area, is the most severe and this area has the highest well density (average 6.8 wells/km²) compared with other wadi catchments. A local scheme of groundwater abstraction redistribution is proposed, involving the retirement of a substantial number of wells. The scheme encourages participation of the local community via collective actions to reduce the groundwater overexploitation, and ultimately leads to a locally acceptable, manageable groundwater abstraction pattern. The proposed method suggests using 587 wells rather than 1,359, thus reducing the well density to 2.9 wells/km². Three scenarios are suggested, involving different reductions to the well yields and/or the number of pumping hours for both dry and wet seasons. The third scenario is selected as a first trial for the communities to action; the resulting predicted reduction, by 2,371,999 m³, is about 6 % of the estimated annual demand. Initially, the groundwater abstraction volume should not be changed significantly until there are protective measures in place, such as improved irrigation efficiency, with the aim of increasing the income of farmers and reducing water use.  相似文献   

Predicting river water temperatures using stochastic models: case study of the Moisie River (Québec,Canada)     

Behrouz Ahmadi‐Nedushan  André St‐Hilaire  Taha B. M. J. Ouarda  Laurent Bilodeau  Élaine Robichaud  Nathalie Thiémonge  Bernard Bobée 《水文研究》2007,21(1):21-34

Successful applications of stochastic models for simulating and predicting daily stream temperature have been reported in the literature. These stochastic models have been generally tested on small rivers and have used only air temperature as an exogenous variable. This study investigates the stochastic modelling of daily mean stream water temperatures on the Moisie River, a relatively large unregulated river located in Québec, Canada. The objective of the study is to compare different stochastic approaches previously used on small streams to relate mean daily water temperatures to air temperatures and streamflow indices. Various stochastic approaches are used to model the water temperature residuals, representing short‐term variations, which were obtained by subtracting the seasonal components from water temperature time‐series. The first three models, a multiple regression, a second‐order autoregressive model, and a Box and Jenkins model, used only lagged air temperature residuals as exogenous variables. The root‐mean‐square error (RMSE) for these models varied between 0·53 and 1·70 °C and the second‐order autoregressive model provided the best results. A statistical methodology using best subsets regression is proposed to model the combined effect of discharge and air temperature on stream temperatures. Various streamflow indices were considered as additional independent variables, and models with different number of variables were tested. The results indicated that the best model included relative change in flow as the most important streamflow index. The RMSE for this model was of the order of 0·51 °C, which shows a small improvement over the first three models that did not include streamflow indices. The ridge regression was applied to this model to alleviate the potential statistical inadequacies associated with multicollinearity. The amplitude and sign of the ridge regression coefficients seem to be more in agreement with prior expectations (e.g. positive correlation between water temperature residuals of different lags) and make more physical sense. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

Daily river water temperature forecast model with a k‐nearest neighbour approach     

André St‐Hilaire  Taha B. M. J. Ouarda  Zoubeida Bargaoui  Anik Daigle  Laurent Bilodeau 《水文研究》2012,26(9):1302-1310

Water temperature is a key abiotic variable that modulates both water chemistry and aquatic life in rivers and streams. For this reason, numerous water temperature models have been developed in recent years. In this paper, a k‐nearest neighbour model (KNN) is proposed and validated to simulate and eventually produce a one‐day forecast of mean water temperature on the Moisie River, a watercourse with an important salmon population in eastern Canada. Numerous KNN model configurations were compared by selecting different attributes and testing different weight combinations for neighbours. It was found that the best model uses attributes that include water temperature from the two previous days and an indicator of seasonality (day of the year) to select nearest neighbours. Three neighbours were used to calculate the estimated temperature, and the weighting combination that yielded the best results was an equal weight on all three nearest neighbours. This nonparametric model provided lower Root Mean Square Errors (RMSE = 1·57 °C), Higher Nash coefficient (NTD = 0·93) and lower Relative Bias (RB = ? 1·5%) than a nonlinear regression model (RMSE = 2·45 °C, NTD = 0·83, RB = ? 3%). The k‐nearest neighbour model appears to be a promising tool to simulate of forecast water temperature where long time series are available. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Ensemble smoothing of land subsidence measurements for reservoir geomechanical characterization          下载免费PDF全文

Domenico Baù  Massimiliano Ferronato  Giuseppe Gambolati  Pietro Teatini  Ayman Alzraiee 《国际地质力学数值与分析法杂志》2015,39(2):207-228

Geomechanical models are often used to predict the impact on land surface of fluid withdrawal from deep reservoirs, as well as investigating measures for mitigation. The ability to accurately simulate surface displacements, however, is often impaired by limited information on the geomechanical parameters characterizing the geological formations of interest. In this study, we employ an ensemble smoother, a data assimilation algorithm, to provide improved estimates of reservoir parameters through assimilation of measurements of both horizontal and vertical surface displacement into geomechanical model results. The method leverages the demonstrated potential of remote sensing techniques developed in the last decade to provide accurate displacement data for large areas of the land surface. For evaluation purposes, the methodology is applied to the case of a disk‐shaped reservoir embedded in a homogeneous, isotropic, and linearly elastic half space, subject to a uniform change in fluid pressure. Multiple sources of uncertainty are investigated, including the radius, R, the thickness, h, and the depth, c, of the reservoir; the pore pressure change, Δp; porous medium's vertical uniaxial compressibility, c_M, and Poisson's ratio, ν, and the ratio, s, between the compressibilities of the medium during loading and unloading cycles. Results from all simulations show that the ensemble smoother has the capability to effectively reduce the uncertainty associated with those parameters to which the variability and the spatial distribution of land surface displacements are most sensitive, namely, R, c, c_M, and s. These analyses demonstrate that the estimation of these parameters values depends on the number of measurements assimilated and the error assigned to the measurement values. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

Solidification of Tank Bottom Sludge   总被引：1，自引：0，他引：1  

Ramzi A. Taha  Yahia E.-A. Mohamedzein  Amer A. Al-Rawas  Yahya Al-Suleimani 《Geotechnical and Geological Engineering》2010,28(1):15-25

Tank bottom oily sludge (S) is collected from tank bottoms during cleaning operations and contaminated soil is collected after spills and leakages. Disposal of tank sludge is a significant item of tank maintenance for producers, refiners and transporters of petroleum materials. The objective of this paper is to investigate the use of various additives in the solidification of tank bottom sludge. The sludge was solidified using various combinations of additives including ordinary Portland cement (OPC), cement by-pass dust (CBPD) and quarry fines (QF). Geotechnical and leachability properties of the mixtures were determined. The use of OPC alone as a solidifying agent yielded the best results. This was followed by blends S:OPC:QF of 1:0.5:1.5 and S:CBPD of 1:2. Economically, the latter two mixtures would be considered more cost-effective in solidifying the sludge as the additives are waste by-product materials. The Toxicity Characteristic Leaching Procedure (TCLP) results indicated that no extracts exceeded the threshold TCLP limits established by U.S. Environmental Protection Agency (USEPA). The solidified material can be used in construction of roads, embankments and landfill layers.  相似文献   

Groundwater level simulation using gene expression programming and M5 model tree combined with wavelet transform     

Ramin Bahmani  Abazar Solgi  Taha B. M. J. Ouarda 《水文科学杂志》2020,65(8):1430-1442

ABSTRACT

In order to understand and adequately manage hydrological stress, it is necessary to simulate groundwater levels accurately. In this research, gene expression programming (GEP) and M5 model tree (M5) are used to simulate monthly groundwater levels. The models are combined with wavelet transform to produce two hybrid models: wavelet gene expression programming (WGEP) and wavelet M5 model tree (WM5). For the simulation, groundwater level, temperature and precipitation values from three observation wells and one meteorological station, located in Iran, are used. The results indicate that the hybrid models, WGEP and WM5, lead to a better performance than the simple models, GEP and M5. The performance of the two hybrid models is similar. It is also observed that selecting a suitable time lag for inputs plays an important role in the accuracy of the simple models. The selection of a suitable decomposition level strongly affects the accuracy of hybrid models.  相似文献   

Simplified seismic fatigue evaluation for rigid steel connections     

Ayman?A.?ShamaEmail author  John?B.?Mander  Stuart?S.?Chen 《地震工程与工程振动(英文版)》2003,2(2):245-253

A simplified fatigue-life model is proposed for assessing the seismic inelastic rotational capacity of steel connections. First relations are developed for rigid steel connections under lateral loading. Next this is extended to account for the effects of the welded steel moment frame (WSMF) connections of the so-called pre-Northridge type. The seismic fatigue theory is validated against experimental results. The experiments were conducted under increasing ductility amplitudcs until the onset of fracture. Miner‘ rule was used to convert the test results to given an equivalent constant amplitude cyclic fatigue life. Satisfactory agreement is obtained when comparing the experimental observations with the theoretical predictions.  相似文献   

Line-based modified iterated Hough transform for automatic registration of multi-source imagery   总被引：1，自引：0，他引：1  

Ayman F. Habib  Rami I. Alruzouq 《The Photogrammetric Record》2004,19(105):5-21

Image registration aims at combining imagery from multiple sensors to achieve higher accuracy and derive more information than that obtained from a single sensor. The enormous increase in the volume of remotely sensed data that is being acquired by an ever-growing number of earth observation satellites mandates the development of accurate, robust, and automated registration procedures. An effective automatic image registration has to deal with four issues: registration primitives, transformation function, similarity measure, and matching strategy. This paper introduces a new approach for automatic image registration using linear features as the registration primitives. Linear features have been chosen because they can be reliably extracted from imagery with significantly different geometric and radiometric properties. The modified iterated Hough transform (MIHT), which manipulates the registration primitives and similarity measure, is used as the matching strategy for automatically deriving an estimate of the parameters involved in the transformation function as well as the correspondence between conjugate primitives. The MIHT procedure follows an optimal sequence for parameter estimation that takes into account the contribution of linear features with different orientations at various locations within the imagery towards the estimation of the transformation parameters in question. Experimental results using real data proved the feasibility and robustness of the suggested approach.  相似文献   

Use of Systematic, Palaeoflood and Historical Data for the Improvement of Flood Risk Estimation. Review of Scientific Methods   总被引：2，自引：0，他引：2  

Gerardo Benito  Michel Lang  Mariano Barriendos  M. Carmen Llasat  Felix Francés  Taha Ouarda  Varyl Thorndycraft  Yehouda Enzel  Andras Bardossy  Denis Coeur  Bernard Bobée 《Natural Hazards》2004,31(3):623-643

The catastrophic floods recently occurring in Europe warn of the critical need forhydrologic data on floods over long-time scales. Palaeoflood techniques provideinformation on hydrologic variability and extreme floods over long-time intervals(100 to 10,000 yr) and may be used in combination with historical flood data (last1,000 yr) and the gauge record (last 30–50 yr). In this paper, advantages anduncertainties related to the reconstruction of palaeofloods in different geomorphologicalsettings and historical floods using different documentary sources are described.Systematic and non-systematic data can be combined in the flood frequency analysisusing different methods for the adjustment of distribution functions. Technical toolsintegrating multidisciplinary approaches (geologic, historical, hydraulic and statistical)on extreme flood risk assessment are discussed. A discussion on the potential theoreticalbases for solving the problem of dealing with non-systematic and non-stationary data ispresented. This methodology is being developed using new methodological approachesapplied to European countries as a part of a European Commission funded project (SPHERE).  相似文献