International Journal for Numerical Methods in Fluids

Khorasanizade, Sh.; Sousa, J. M. M.

doi: 10.1002/fld.4074pmid: N/A

Summary An innovative inflow/outflow boundary treatment has been proposed to be used in smoothed particle hydrodynamics (SPH). Among other strategies, it involves the use of extended regions at open boundary sections and a procedure to enforce the mass continuity constraint, as well as to minimize outflow reflections. This methodology has been coupled with a modified ‘particle shifting’ algorithm, so that the robustness of the method could be ensured at high Reynolds number regimes. Confined flow around a square cylinder with an open outflow has been selected as the flow problem to analyze the performance of the new method. Detailed comparisons with data available in the literature for a variety of mesh‐based methods have been made for two different values of the blockage ratio β, namely for β = 1/4 and 1/8, and a range of supercritical Reynolds numbers. The results obtained with the present implementation of truly incompressible SPH have demonstrated numerical accuracy comparable with that of other methods, as well as the success of the open boundary treatment. A direct comparison with previously published SPH results for a distinct blockage ratio, namely for β = 1/5, has also revealed that a major improvement has been achieved by the use of the method described in this paper. Copyright © 2015 John Wiley & Sons, Ltd.

Ahmadi, Mohammad; Christie, Mike; Gerritsen, Margot; Bazargan, Hamid

doi: 10.1002/fld.4075pmid: N/A

Summary Efficient and profitable oil production is subject to make reliable predictions about reservoir performance. However, restricted knowledge about reservoir rock and fluid properties and its geometrical structure calls for history matching in which the reservoir model is calibrated to emulate the field observed history. Such an inverse problem yields multiple history‐matched models, which might result in different predictions of reservoir performance. Uncertainty quantification narrows down the model uncertainties and boosts the model reliability for the forecasts of future reservoir behaviour. Conventional approaches of uncertainty quantification ignore large‐scale uncertainties related to reservoir structure, while structural uncertainties can influence the reservoir forecasts more significantly compared with petrophysical uncertainty. Quantification of structural uncertainty has been usually considered impracticable because of the need for global regridding at each step of history matching process. To resolve this obstacle, we develop an efficient methodology based on Cartesian cut cell method that decouples the model from its representation onto the grid and allows uncertain structures to be varied as a part of history matching process. Reduced numerical accuracy due to cell degeneracies in the vicinity of geological structures is adequately compensated with an enhanced scheme of a class of locally conservative flux continuous methods (extended enriched multipoint flux approximation method or extended EMPFA). The robustness and consistency of the proposed hybrid Cartesian cut cell/extended EMPFA approach are demonstrated in terms of true representation of geological structures influence on flow behaviour. Significant improvements in the quality of reservoir recovery forecasts and reservoir volume estimation are presented for synthetic model of uncertain structures. Copyright © 2015 John Wiley & Sons, Ltd.