Sedimentological evolution of the Lower Series formation in the southern area of the Hassi R’Mel field,Saharan Platform,Algeria     

Salima Talamali  Rabah Chaouchi  Soumya Benayad 《Arabian Journal of Geosciences》2016,9(6):481

The Hassi R’Mel field, which is the largest gas field in Algeria, produces principally gas condensate. The produced gas and oil comes from four reservoirs of Triassic age (reservoir A, reservoir B, reservoir C, and the Lower Series). All the previous studies in this field focused only on the upper reservoirs (A, B, and C), which have shown an excellent petrophysical properties. However, due to the presence of shale facies as well as volcanic intrusions, the Lower Series reservoir has been less explored. Thus, our study is mainly focused on this Lower Series in order to find the best sandy levels. The aim of this paper was to determine the facies types in the area, their distribution in the southern area of the Hassi R’Mel gas field, and their depositional environment. The Triassic rocks in this field are divided into four formations. From the youngest to oldest, these are S4, Lower Shale, Horizon A, and the Lower Series. The Lower Series formation can be further divided into three members (shaly sandstone, andesite, and lower shale). The shaly sandstone member within the Lower Series is composed of four units that are present all over the study area with an important pinch-out toward the northern part. The depositional environment within the defined units is a braided fluvial system in the southern part that evolves into a meandering fluvial system toward the north. Thus, the study area is considered to be a transitional zone between two depositional systems.  相似文献   

New occurrence of potential phosphate resource in northeast Jordan     

Khalil M. Ibrahim  Khitam Alzughoul  Mohammad Muhtaseb 《Arabian Journal of Geosciences》2016,9(7):497

An exploration program aided by field investigation, exploration drilling, detailed sampling, lithological and petrological studies, geochemical investigation, and resource calculation leads to the discovery of a potential phosphate resource in northeast Jordan close to the international border with Saudi Arabia and Iraq. The studied phosphate is of the Middle Eocene age that belongs to the Wadi Shallala Formation. It is equivalent to the phosphate deposits recorded in the lower part of the Umm Wual Formation in the Turayf region of Saudi Arabia and the Eocene Ratga Formation in the Ethna phosphate deposit west of Iraq. The phosphorites in the region are broadly similar in mineralogical composition and geochemical affinities. X-ray diffraction indicates the presence of francolite with variable amounts of calcite and quartz. Most samples consist of phosphate clasts embedded in carbonate and silica matrix and cement. P₂O₅ content is up to 32.3 % with an average equal to 18.6 %. The impurity is caused by the presence of variable amounts of SiO₂ and CaO. The F% and F/P₂O₅ ratio in studied phosphates is lower compared with that in phosphates from Jordan and Saudi Arabia. The geological and geochemical results were integrated for resource estimation. Three high-grade phosphate layers with ≥23 % P₂O₅ were considered in the calculations. The phosphate resource is classified as an inferred resource. The total volume of the resource is about 649 million tons. The average P₂O₅ content is 24.57, and the stripping ratio is 1:5.8.  相似文献   

Impact assessment of land cover changes on the runoff changes on the extreme flood events in the Kelantan River basin     

Nader Saadatkhah  Mohammadreza Hadad Tehrani  Shattri Mansor  Zailani Khuzaimah  Azman Kassim  Reza Saadatkhah 《Arabian Journal of Geosciences》2016,9(17):687

In the current years, changing the land cover/land use had serious hydrological impacts affecting the flood events in the Kelantan River basin. The flood events at the east coast of the peninsular Malaysia got highly affected in the recent decades due to several factors like urbanisation, rapid changes in the utilisation of land and lack of meteorological (i.e. change in climate) and developmental monitoring and planning. The Kelantan River basin has been highly influenced due to a rapid change in land use during 1984 to 2013, which occurred in the form of transformation of agricultural area and deforestation (logging activities). In order to evaluate the influence of the modifications in land cover on the flood events, two hydrological regional models of rainfall-induced runoff event, the Hydrologic Engineering Center (HEC)-Hydrologic Modeling System (HMS) model and improved transient rainfall infiltration and grid-based regional model (Improved TRIGRS), were employed in this study. The responses of land cover changes on the peak flow and runoff volume were investigated using 10 days of hourly rainfall events from 20 December to the end of December 2014 at the study area. The usage of two hydrological models defined that the changes in land use/land cover caused momentous changes in hydrological response towards water flow. The outcomes also revealed that the increase of severe water flow at the study area is a function of urbanisation and deforestation, particularly in the conversion of the forest area to the less canopy coverage, for example, oil palm, mixed agriculture and rubber. The monsoon season floods and runoff escalate in the cleared land or low-density vegetation area, while the normal flow gets the contribution from interflow generated from secondary jungle and forested areas.  相似文献   

Stochastic groundwater modeling of a sedimentary aquifer: evaluation of the impacts of abstraction scenarios under conditions of reduced recharge     

Sandow Mark Yidana  Millicent Obeng Addai  Daniel Kwadwo Asiedu  Bruce Banoeng-Yakubo 《Arabian Journal of Geosciences》2016,9(17):684

A transient finite difference groundwater flow model has been calibrated for the Nasia sub-catchment of the White Volta Basin. This model has been validated through a stochastic parameter randomization process and used to evaluate the impacts of groundwater abstraction scenarios on resource sustainability in the basin. A total of 1500 equally likely model realizations of the same terrain based on 1500 equally likely combinations of the data of the key aquifer input parameters were calibrated and used for the scenario analysis. This was done to evaluate model non-uniqueness arising from uncertainties in the key aquifer parameters especially hydraulic conductivity and recharge by comparing the realizations and statistically determining the degree to which they differ from each other. Parameter standard deviations, computed from the calibrated data of the key parameters of hydraulic conductivity and recharge, were used as a yardstick for evaluating model non-uniqueness. All model realizations suggest horizontal hydraulic conductivity estimates in the range of 0.03–78.4 m/day, although over 70 % of the area has values in the range of 0.03–14 m/day. Low standard deviations of the horizontal hydraulic conductivity estimates from the 1500 solutions suggest that this range adequately reflects the properties of the material in the terrain. Lateral groundwater inflows and outflows appear to constitute significant components of the groundwater budgets in the terrain, although estimated direct vertical recharge from precipitation amounts to about 7 % of annual precipitation. High potential for groundwater development has been suggested in the simulations, corroborating earlier estimates of groundwater recharge. Simulation of groundwater abstraction scenarios suggests that the domain can sustain abstraction rates of up to 200 % of the current estimated abstraction rates of 12,960 m³/day under the current recharge rates. Decreasing groundwater recharge by 10 % over a 20-year period will not significantly alter the results of this abstraction scenario. However, increasing abstraction rates by 300 % over the period with decreasing recharge by 10 % will lead to drastic drawdowns in the hydraulic head over the entire terrain by up to 6 m and could cause reversals of flow in most parts of the terrain.  相似文献   

Landslide susceptibility zonation using GIS and evidential belief function model     

Yanli Wu  Yutian Ke 《Arabian Journal of Geosciences》2016,9(17):697

The main goal of this paper is to generate a landslide susceptibility map through evidential belief function (EBF) model by using Geographic Information System (GIS) for Qianyang County, Shaanxi Province, China. At first, a detailed landslide inventory map was prepared, and the following ten landslide-conditioning factors were collected: slope angle, slope aspect, curvature, plan curvature, profile curvature, altitude, distance to rivers, geomorphology, lithology, and rainfall. The landslides were detected from the interpretation of aerial photographs and supported by field surveys. A total of 81 landslides were randomly split into the following two parts: the training dataset 70 % (56 landslides) were used for establishing the model and the remaining 30 % (25 landslides) were used for the model validation. The ArcGIS was used to analyze landslide-conditioning factors and evaluate landslide susceptibility; as a result, a landslide susceptibility map was generated by using EBF and ArcGIS 10.0, thus divided into the following five susceptibility classes: very low, low, moderate, high, and very high. Finally, when we validated the accuracy of the landslide susceptibility map, both the success-rate and prediction-rate curve methods were applied. The results reveal that a final susceptibility map has the success rate of 83.31 % and the prediction rate of 79.41 %.  相似文献   

Application and performances of unconstrained optimization methods in seafloor AVO inversion     

Yangting Liu  Xuewei Liu 《Arabian Journal of Geosciences》2016,9(15):652

Seafloor elastic parameters are important for seafloor engineering and geophysical detection beneath the seafloor. We have proposed to use AVO (amplitude variation with offset) theory to estimate seafloor elastic parameters. However, the previous inversion methods are time-consuming. To improve the computing efficiency, we try to solve the inverse problem as an unconstrained optimization problem in this paper. Three kinds of classical unconstrained optimization methods are applied to seafloor AVO inversion, including the steepest descent method, the Newton’s method, and the conjugate gradient method. Then, we design different initial models to test the convergence behaviors of the three methods. Numerical tests show that the perturbation level of the initial models and the noise level of the observed data have a significant effect on the convergence performances of the three methods. Even for the same perturbation and noise levels, the convergence performances differ with different combinations of the perturbed initial elastic parameters. All three methods have higher computing efficiency than the previous methods. This research also offers a strategy to choose a proper optimization method for a specific case in real seafloor AVO inversion.  相似文献   

Effect of different soil data on hydrological process modeling in Weihe River basin of Northwest China     

Anzhou Zhao 《Arabian Journal of Geosciences》2016,9(15):664

Hydrological process modeling depends on the soil data spatial resolution of the watershed. Especially, in a large-scale watershed, could a higher resolution of soil data contribute to a more accurate result? In this study, two soil datasets with different classification systems FAO (World Reference Base) and GSCC (the Genetic Soil Classification of China) were used as inputs for the SWAT model to study the effects of soil datasets on hydrological process modeling in Weihe River basin, China. Results show that the discharge simulated using FAO soil data was better than one simulated using GSCC soil data before model calibration, which indicates that FAO soil data needed less effort to calibrate. After model calibration, discharges were simulated better by both of FAO and GSCC soil data but statistical parameters demonstrate that we can make a relatively more accurate estimation of discharge using the GSCC rather than FAO soil data. Soil water content (SW) simulated using GSCC soil data was statistically significantly higher than those simulated using FAO soil data. However, variations in other hydrological components (surface runoff (SURQ), actual evapotranspiration (ET), and water yield (WYLD) were not statistically significant. This might be because SW is more sensitive to soil properties. For studies aiming to simulate or compare SW, merely calibrating and validating models using river discharge observations is not enough. The hydrological modelers need to identify the key hydrological components intrinsic to their study and weigh the advantages and disadvantages before selecting suitable soil data.  相似文献   

A sensitivity study on the numerical model of displacement and deformation of embedded brittle rock bodies in extension environment during salt tectonics     

Shiyuan Li 《Arabian Journal of Geosciences》2016,9(16):680

Many salt bodies contain large rock inclusions (called stringers) such as carbonate or anhydrite bodies. Mostly, large rock inclusions embedded in salt bodies have different ways of movement and deformation, including displacement, folding and fracturing. A finite element model with adaptive remeshing has been built for downbuilding simulation. The standard model set-up is constrained by observations from the South Oman Salt Basin. Based on the generic model in the previous research which shows the fracture, overtrusting or folding deformation during downbuilding process, a sensitivity study has been conducted on the numerical model of the deformation and displacement of brittle rock bodies, including the parameters such as the initial depth and the distance between them. The results of simulation are analyzed based on the data from SOSB and Zechstein salt basin. The study shows that the frequency of the break and the size of stringer fragments are strongly affected by the initial depth and thickness of stringers and the basement configuration.  相似文献   

Sedimentology of the Baluti Formation in the Galley Derash,Amadiya, North Iraq: insight on carbonate turbidite facies and their depositional environmental     

Sa’ad Zeki Abdul-Kader Al-Mashaikie  Suhad Kalaf Abdul-Razzak  Madhat Eliwie Naser 《Arabian Journal of Geosciences》2016,9(19):723

The Baluti Formation is exposed succession of the Rhaetian age (Upper Triassic). These strata are interpreted herein for the first time to redeposit in a deep marine setting (distally steepened carbonate ramp/medial to distal slope) on the northwestern margin of the Neo-Tethys. The Galley Derash section is apparently continuous with no evidence for either subaerial exposure or submarine erosion. The absence of erosional scours in the study area confirms emplacement of these strata below both fair-weather and storm wave base. Event beds, particularly those resulting from sediment gravity flows, dominate the Rhaetian interval. The Upper Rhaetian strata are primarily assigned to the Galley Derash Valley. It records an upward transition from moderate-scale, olistolith-bearing debris flow deposits (debrite) to medium-/thin-bedded turbidites remobilized as sediment slumps/slides. The succession is dominated by medium- to thin-bedded calcareous turbidites and hemipelagic suspension deposits. Very low fossil assemblages, particularly stromatolite fragments, and planktonic bivalves occur within some intervals in the section. Rapid and relatively continuous sedimentation is attested to by the thickness of the section, the abundance of calcareous turbidites, and the thin nature of the intercalated hemipelagic beds. Low content of badly preserved fossils and evidence of continuous and rapid sedimentation refer to alteration by tectonic disturbances or diagenesis. This makes the Baluti Beds as a supplementary section for the Rhaetian successions in Iraq.  相似文献   

Textural evidences for dissolution of silica-rich rocks of the Ypresian phosphatic series,Gafsa-Metlaoui basin,southwestern Tunisia: implication of biogenic silica supply on genesis of fibrous clays     

Mongi Felhi  Raja Saidi  Nabil Fattah  Ali Tlili 《Arabian Journal of Geosciences》2016,9(17):695

The present work aimed to determine the mineralogical composition of Ypresian series and to clarify the influence of the dissolution of siliceous frustules on the genesis of fibrous clay minerals. The specimens sampled from CPG trench are mainly constituted of silica-rich rocks at Mides area located at the western part of Gafsa-Metlaoui basin. The samples were investigated using X-ray diffraction (XRD) and scanning electron microscopy (SEM) in order to determine texture of constituents. The data obtained indicate that the bulk rock samples are mainly made up of opal CT and clay minerals. The latter consists of palygorskite-sepiolite minerals associated with smectite and few amount of illite. The trend of mineralogical composition indicates that fibrous clay minerals are more concentrated at the upper part. SEM observations indicated that palygorskite mineral appears as thread-like facies, which surround foliated texture of smectite in the lower part of the Mides section, although with the low Mg activity confirmed by the absence of dolomite. But, at the upper part of the Mides section, SEM observations revealed the occurrence of siliceous frustules, which have numerous dissolved areas and replacement of carbonate tests by silica. The dissolution saturated the depositional environment with silica which is required for the formation of palygorskite and sepiolite minerals, in addition to high Mg activity confirmed by the presence of dolomite in the bulk rock, which is required basically for the formation of sepiolite. Although the genesis mode of palygorskite and sepiolite is similar with very little difference, the genesis of sepiolite needs a high alkalinity than the formation of palygorskite.  相似文献