In recent decades, the hydrosuction technique is known as one of the efficient methods that has been used for dredging sediments deposited in dams’ reservoirs. This technique has obvious advantages compared to other sediment removal techniques such as no need for extra energy (due to the use of the difference between water surface energy at the upstream and downstream of the dam) and the possibility of transporting dredged sediments to a specific area. This technique is influenced by several geometric and hydraulic factors such as the suction tube diameter (Dp), the water head or the difference between the water height at the upstream and downstream of the dam (H), and the distance of the suction mouth from the surface of the sediment (hp). In the current research, the effects of suction opening intervals on sediment (SP class) surface was studied using a physical model. The results of the experiments showed that by increasing the hp factor, the discharge rate of the sediment and also the sediment concentration of the outlet flow would be increased. The results also indicated that the sediment evacuation process continued with the minimum value for hp/Dp=-1. 33; for values less than-1. 33, the tube obstructed due to accumulation of sediments in the inlet opening.

Reservoir sedimentation is always known as a serious problem for sustainable use of reservoirs and the main factor of reservoirs storage loss. One of the most common engineering techniques for preserving the reservoirs storage capacity is the periodical desilting of reservoirs by hydraulic flushing. Review of the literature shows that the pressurized flushing operation is currently accomplished with low efficiency. In this paper, the effect of PBC structure on the sediment removal efficiency during pressurized flushing operation was experimentally investigated. In this way, PBC structure with four relative length and four relative diameters were used in the reservoir. Non-cohesive sand particles with D50=0.36 mm were used as the deposited sediments in the reservoir. The results showed that by using the PBC structure with LPBC/Doutlet=5.26 and DPBC/Doutlet=1.32, the flushing efficiency became 4.57 times more than that of reference test. By increasing the relative length of PBC structure, the maximum relative length and width of flushing cone increased, respectively, compared to the reference test while the variation of the maximum relative depth was negligible. In addition, all the geometric parameters of flushing cone had their maximum values at DPBC/Doutlet=1.32.

This paper presents a novel technology for desilting dam reservoirs in a continuous and controlled manner. The proposed technology utilizes a suction system that incorporates two pumps: a dredge pump for removing and transporting sediments, and a high-pressure submersible pump for generating water jets to create turbulent flows in the bottom sediment layers. To evaluate the effectiveness of the proposed technology, local experiments were conducted in two cases: with the suction pump alone and with the addition of water jet flow. These experiments were conducted at the end of the reservoir of Zenouz Dam, which serves as a case study. The collected sediment mass was measured over time, and the resulting mass-time graphs revealed three distinct phases: ascending, descending, and constant. Based on the local conditions, soil properties and dredging system, the maximum sediment mass removal rates by the pump were 100 g/s for the case without water jet and ranged from 200 to 430 g/s for the case with water jet. Dimensional analysis was performed to determine the relationship between sediment yield and parameters such as sediment volumetric flow rate and sediment mass flow rate. The results showed that the variations of sediment discharge followed the same characteristic curves (discharge - height) of the pump. The average de-sedimentation efficiency was found to be 7-14% and 2-3% for the experimental pump modes with and without the jet flow, respectively. This indicates that the water jet flow has a significant influence on enhancing the de-sedimentation efficiency, and without it, the sediment removal would not be feasible.

One of the most essential works for sediment management in dam reservoirs is to identify the characteristics and effective parameters of deposition of sediments in the dam reservoir. In this research, the sedimentation process of fine sediments deposited into Karkheh dam reservoir was investigated in order to determine the required hydraulic conditions for desilting of the reservoir. Experiments were carried out in an annular flume located in Hydraulic Laboratory of Shahrekord University and sediment samples were taken from reservoir of Karkheh dam. Experiments were done at initial concentrations of 5, 10 and 20 g/l, and various shear stresses to determine the threshold shear stress for partial deposition and full deposition of suspended sediments. The obtained results showed that the shear stress of the initiation of sediment deposition was 0. 1 N/m2. It was also found that when the flow velocity to be exceed up to 0. 61 m/s, the sediments would be completely remained in term of suspension. Under these conditions, the shear stress and Froude number were obtained as 2. 55 N/m2 and 0. 43, respectively. Also, the results showed that in higher sediment concentrations, increasing of shear stress is more effective in the sediment deposition rate.

For desilting the deposited sediment, flushing method could be used in two different methods: Free Flushing and Pressure Flushing. In the latter, the previously deposited sediment would be flushed from the reservoir by opening of the outlets, and typically the scour cone "Flushing Cone" developed near the outlet in the reservoir. The scour cone geometry was influenced by many factors including water depth on the bottom outlets, outflow discharge through the bottom outlet, outlet geometry, characteristic of the sediments which deposited in the reservoir, etc. In this study, the effect of the outflow discharge through the bottom outlet and the water depth on the bottom outlets were investigated by non-cohesive sediment with d50=0.27mm. For this purpose, laboratory experiments were performed, so a physical model was constructed in the Hydraulic Laboratory at the faculty of Water Engineering and Science, University of Shahid Chamran, Ahvaz, Iran. The result of this research showed the flushed sediment increased with the decrease of reservoir's water depth, as the reduction of water depth equal to 31.5% caused the scour cone volume and its length to increase to 41.5% and 14.5%. Also the decrease of 76.6%, outflow discharge caused the scour cone volume and its length decreased to 20.3% and 49.9% respectively. Also based on the satirical analysis, non-dimensional relations for determining the flushing cone volume and its length are represented.

The influence of fractures in the production rate in carbonate reservoir of southern Iran has been established. The Gachsaran oil field is located in the Dezful embayment in SW of Zagros basin of Iran.The outcrop in the area mainly consists of Miocene- Pliocene Gachsaran formation evaporate and Aghajari classics. The main reservoir in this field is Miocene Asmari formation. Only upper Asmari is developed in this area, lower and upper Asmari is replaced by Oligocene-Eocene Pabdeh marly formation. In this study so also itself is a methodology, a new combination method has been established. Therefore, based on all possible methods and available data, the state of fractures intensity, orientation, type, spacing and etc. have been considered. More important of these methods that were used include the following: 1. Core analysis2. Open hole log analysis(such as FMS)3. Well drilling data analysis4. Structural analysis: fracture prediction base on stress and strain analysis5. Curvature analysis for a better geostatistical study, the Gachsaran anticline was divided in to thirteen different domains or blocks. Also some prediction and reservoir engineering data such as PI, RFT, BUT, maximum rate of production and permeability (K) parameters were studied and mapped. Later these maps correlated with other fracture analysis results. The correlations showed satisfactory results. Both flexural-slip and neutral surface folding mechanisms were active for this area. Regarding the prevailing mechanism of flexural-slip resulting in actives hear fractures in the present stress system, and the existence of gas-cap, the best areas of drilling for higher production are the flanks with thrust fault traces. The curvature analysis method, both in axial and cross sectional dimensions, together with stress-strain analysis are the best economical and powerful methods for exploration and development of oil fields. Also, the best geographical direction for drilling in some domains, based on fracture properties has been estimated.

Identifying reservoir rock types and their most significant vertical and horizontal heterogeneities is an essential component of reservoir characterization process, which are among the key input parameters in to a three-dimensional geological and flow simulation models. A reservoir classification and rock typing study were carried out on the Asmari formation of a mixed siliciclastic and carbonate reservoir in Iran. Detailed core analysis data including capillary pressure, core porosity, core permeability and core description supplemented by well logs revealed a complete vertical sequence of seven distinct clastic and carbonate reservoir rock types. Identification of the reservoir intervals and pay zones was carried out by means of the above results. Core based reservoir rock types were examined for each cored wells and log based reservoir rock types were selected and assigned in the uncured wells. The above data were applied as input parameters in a method based on Fuzzy Logic inference. The Fuzzy Logic technique was calibrated in 4 cored wells and blind tested in the other cored wells to determine the reservoir rock types. After the secondary calibration of the Fuzzy Logic against the core data, this technique was applied on 28 wells without any core data. The results reveal a very good match between the core data analyses and the Fuzzy Logic determination of the reservoir rock types. This technique can be applied to reduce the uncertainty of determination of the rock typing or as a very good predictor in uncured wells.

Drought is an inevitable part of the world s climate. It occurs in wet as well as in dry ‎regions. Therefore, planning for drought and mitigating its impacts is essential. In this ‎study, a hedging rule is developed using the zero/one mixed integer-programming ‎approach. Furthermore, some procedures are introduced to case the computational ‎burden inherent in integer programming. Hedging rules are developed using three, ‎two, and one-year historical droughts. Moreover, yield model (YM) along with the ‎standard operating policy (SOP) are also formulated for comparison purposes. ‎Simulations are carried out using 40 years of monthly historical data along with 20 ‎series of synthetically generated inflows of the same length. The Karadj reservoir ‎located in the northwest of Tehran is the major source of the capitals municipal water ‎supply. It also provides a substantial portion of the irrigation demand of the Karadj ‎Valley. Synthetic data are generated using single and mufti-variate autoregressive ‎modeling approaches. Models arc compared using important reservoir operation ‎criteria including reliability, resiliency, and vulnerability. As compared to the well-‎known SOP model, it is noticed that the application of the hedging rule and the yield ‎model substantially reduces the system reliability as well as its vulnerability, however ‎it increases the resiliency. Moreover, hedging rules developed using longer drought ‎periods tend to have lower vulnerability and reliability, and higher resiliency‏.‏

Both Asmari and Bangestan reservoir rocks have very complex fracture orientations. Such orientation patterns cause both oil ratio and internal pressure to be high in overall Gachsaran oil wells. The length of fractures in the reservoir rocks ranges from few centimeters to few meters in size.Variation of oil production from two different flanks of regional anticline suggests very complex fracture orientation patterns. Core analysis and mud logging information indicate macroscope fractures ranging from 2 to 5 meters in length. Some reports also indicate macroscopic fractures are common in Asmari formation and generally are formed by two different tectonic stresses. In the first stage, fractures formed by compressive forces and in the second stage by stimulation forces. Rock analysis indicates that Pabdeh, Gurpi and Ilam formations are very brittle and lateral fractures in Asmari and Bangestan reservoir formations are highly connected. As a result, gas injection in the Asmari formation will increase the pressure in the Bangestan reservoir rock.