Upscaling is often applied to coarsen detailed geological reservoir descriptions to sizes that can be accommodated by flow simulators. Adaptive local-global upscaling is a new and accurate methodology that incorporates global coarse scale flow information into the boundary conditions used to compute upscaled quantities (e.g., coarse scale transmissibilities). The procedure is iterated until a self-consistent solution is obtained. In this work, we extend this approach to three-dimensional systems and introduce and evaluate procedures to decrease the computational demands of the method. This includes the use of purely local upscaling calculations for the initial estimation of coarse scale transmissibilities and the use of reduced border regions during the iterations. This is shown to decrease the computational requirements of the reduced procedure by a factor of about six relative to the full methodology, while impacting the accuracy very little. The performance of the adaptive local-global upscaling technique is evaluated for three different heterogeneous reservoir descriptions. The method is shown to provide a high degree of accuracy for total flow rate, local flux and oil cut. In addition, it is shown to be less computationally demanding and significantly more accurate than some existing extended local upscaling procedures. Introduction Fine scale heterogeneity can have a significant impact on reservoir performance. Because it is usually not feasible to simulate directly on the detailed geocellular model, some type of upscaling is often applied to generate the simulation model from the geological description. Here we focus on the upscaling of single-phase flow parameters, particularly absolute permeability. The algorithms we consider can provide either coarse-scale permeability, designated k*, or coarse-scale transmissibility, designated T*. It is important to emphasize that the accurate upscaling of permeability (which can be studied within the context of single-phase flow) is essential for the development of accurate coarse models of two-phase or multiphase flow. Thus the applicability of the methods developed here is very broad and includes all types of displacement processes. Permeability and transmissibility upscaling algorithms can be classified in terms of the solution domain over which the governing single-phase pressure equation is solved to compute the coarse scale quantities. Purely local methods (e.g., Durlofsky1, King and Mansfield2) consider only the fine scale cells comprising the target coarse block, while extended local methods include some number of neighboring cells in the local problems3,4. Both of these methods require assumptions regarding the boundary conditions to be imposed, which can lead to inaccuracy in some cases. At the other extreme are global methods, in which the flow solution used to compute the upscaled quantities is performed over the entire domain5,6,7. White and Horne5 considered a set of global flows in the derivation of coarse scale properties, while Holden and Nielsen7 applied a specific global flow scenario (e.g., driven by wells) in their calculations. These methods may achieve high degrees of accuracy but have the drawback of requiring global fine scale solutions. With these techniques, in order to avoid spurious values of coarse scale properties, some iteration is also usually required in the calculation of the upscaled parameters7. Quasi-global upscaling methods use some type of approximate global flow information in the calculation of k* or T*. These techniques can provide accurate upscaled models if the approximate global flow information is sufficiently representative of the global fine scale solution. We recently developed new quasi-global upscaling techniques referred to as "local-global" methods8,9. The basic idea of these approaches is to perform a global coarse scale simulation in order to determine the boundary conditions to be applied for the local fine scale calculation of k* or T*. Consistency between the specific global flow and the upscaled model is achieved through iterations between the global coarse simulation and local fine scale calculations. We have shown that the local-global method provides high degrees of accuracy for difficult problems involving highly heterogeneous channelized systems and changing flow conditions, although to date we have considered mostly idealized cases in two dimensions.
Requirements like higher cleanliness and better quality of casting blooms are proposed for 350km/h higher speed rail steel. Present paper focuses on technical measures on improving the steel cleanliness and strand quality of 350km/h high-speed rail steel in Panzhihua Iron & Steel Group Company. By means of series of packaging technology like dephosphorization in BOF, ladle refining, mold electromagnetic stirring and dynamic soft reduction, dephosphorization rate cleanliness and morphology control are greatly improved, with [S] 0.015%, [P] 0.025%, [H] 1.5 Â 10 À6 , Al s 0.004%, T[O] 20 Â 10 À6 , the grade of central porosity and segregation 1.0, the grade of central crack and middle crack 0.5, index of central carbon segregation 1.05, severity level of type-A and type-B inclusions 2.0 and 1.0, respectively. The optimized process meets the technical requirements on producing 350 km/h high-speed rail steel and stable production is realized.
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