Sand accumulation can pose significant problems to wind turbines operating in the dusty Saharan environments of the Middle East and North Africa. Despite its difficulty, sand particles can be to a great extent avoided using sealed power drive trains; however, surface contamination of the blades is certainly unavoidable. As a result, aerodynamic losses and even premature separation can be incurred. To mitigate such advert consequences and avoid significant power losses, the choice of properly designed airfoil sections with low contamination sensitivity is a must. Alternatively, mitigation techniques for premature separation may also be considered. In this paper the contamination sensitivity of a number of airfoil sections widely used in the wind turbine industry is compared. Additionally, the possibility of deploying a leading edge slat to mitigate the contamination-driven performance degradation of wind turbine airfoils is explored. A two dimensional CFD model of the particle laden flow over an airfoil section is developed by solving Navier-Stokes equations along with the SST k-ω turbulence model. Additionally, a particle deposition model has been deployed via FLUENT’s discrete phase modeling capability to simulate dust particles trajectories and hence predict their accumulation rate. The preliminary results obtained indicate that airfoil sections with low surface contamination sensitivity specifically designed for wind turbines perform better under dusty conditions. Furthermore installing a leading edge slat affects the aerodynamics of the particle laden flow and may therefore be used to mitigate the adverse effects of surface contamination that otherwise would require frequent cleaning which can be expensive.
Reservoir development in Safa Formation requires a lot of vertical wells in order to exploit the gas reserve in the formation which means high cost is needed because the heterogeneity in the formation is noticed due to sandstone is pinched out in different locations of the reservoir. So, vertical well may be sweep from limited area of the reservoir that make safa formation has less priority for new activities. Form all of that the plan was drilling horizontal wells with long horizontal section to recover great volume of gas from reservoir. In addition to reduction in number of drilling vertical wells in the reservoir. In contrast, the major constrains is the small thickness of reservoir that make drilling horizontal section is very difficult. The main characteristics of safa formation is non continuous sandstone in the whole reservoir with great heterogeneity that not controlled by any points in the reservoir for the distribution of sandstone. In addition, there are a lot of locations in safa formation that include lean intervals which have kaolinite, elite that are not capable for produce from sand. In other hand, there is another constrains beside the discontinuity of sand production is the heterogeneity of permeability properties of reservoir that change in wide range across the reservoir with minimum range of 0.01 md and increase in some locations to reach 100 md. From all of the previous, it is a big challenge in drilling horizontal wells with long horizontal section in thin reservoir thickness in order to access the best reservoir permeability and optimize the number of drilling wells based on this concept. This paper will discuss case study of unlock and development long horizontal section in gas reservoir characterized by its tightness. The main goal of this horizontal well to recover ultimate gas reserve from safa formation by horizontal section reached to 2000 meter with a challenge because it is abnormal to drill this large horizontal section in western desert of Egypt in reservoir thickness range from 5 meter to 30 meter as prognosis from other offset wells in case of there is no pitchout of the sandstone. After Drilling of first horizontal well, the results were unexpected because the well penetrates a large horizontal section of sandstone in safa formation. This section reached to around 1750 meter with average reservoir permeability between 10 – 20 md and the reservoir porosity about 13% with good hydrocarbon saturation that changes along this section from 75% to 80%. So, this well put on production with very stable gas production rate 20 MMSCFD. In this paper will discuss in details the different challenge that faced to unlock this tight gas reservoir and will discuss the performance of horizontal well production. In this paper will discuss the first horizontal well in safa formation and the longest horizontal section in western desert of Egypt in tight gas formation that has a lot of challenges and risks are faced. After success the concept of horizontal well in heterogeneous reservoir, the next plan is the development of this reservoir using several horizontal wells to recover the ultimate recovery of gas from safa formation.
During history matching of observed production data of brown fields, one of the key matching parameters is the water break-through time. Water break-through time is the time at which significant water production begins at a producing well. During the simulation of an immiscible displacement process, numerical dipersion is a well known undesirable simulation artifact which makes water flood-front to move faster when the simulation grid-blocks are coarser. In this paper, we present an approach to reduce numerical dispersion and ensure that the simulated flood-front movement is similar, whether we use coarse grid-blocks or fine grid-blocks in simulation. The approach is based on the correction of laboratory relative permeability data, using the shock front water saturation (Swbt) obtained from fractional flow curve. Swbt is the water saturation at the contact point between a tangent drawn from the connate water saturation (Swi) to the fractional flow curve. Once we obtain Swbt, we then set the critical water saturation of the water relative permeability curve to Swbt. We created different scenarios of grid block sizes and simulated a steady state water injection process using the corrected water relative permeability curve. We based our study conclusions on results from both line drive and 5-spot water injection patterns. The result showed six (6) months difference in predicted water break-through dates when we used the laboratory relative permeability data as is, but with this new approach, the various scenarios of grid block sizes showed similar water break-through dates. This new methodology effectively eliminates the impact of simulation grid size on water break-through prediction results. During geo-model construction, we do not know in advance what impact our chosen grid size would have on flow dynamics, and once the geo-modeling is finalized it could be time consuming to re-do the gridding and layering of the geo-model. We also take note that many times we are constrained to build simulation models with large grid-sizes because of computational limitations, especially in large reservoirs. The new approach presented in this paper would ensure that any size of grid-block used in simulation, would predict similar flood-front movement and hence similar water break-through time as fine grid simulation. Our approach helps to ensure better reliability of simulation results in cases where computational limitations or large size of reservoir makes it necessary to build coarse grid simulation models.
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