TX 75083-3836, U.S.A., fax 01-972-952-9435.
AbstractThe upscaling of geostatistical models characterized by oriented layering is considered. Such models are representative of a broad class of geologically complex reservoir characterizations as they display full tensor permeabilities on both the fine and coarse scales. The significant errors that result from the improper numerical treatment of the full tensor permeability are demonstrated. The application of existing upscaling approaches to these oriented systems is shown to lead to coarse models of lower accuracy, for both flow and displacement calculations, than in the case of models with horizontal layers. Two alternate upscaling procedures are presented in an attempt to improve the accuracy of these coarse scale reservoir descriptions. The first technique involves the use of a border or "skin" region, while the second approach entails the use of a rotation procedure, in which the gridblock permeability is computed in a coordinate system approximately aligned with the principal directions of the upscaled permeability tensor. Both methods are shown to generally result in improved accuracy in displacement calculations, though the rotation procedure appears to be the more accurate overall. The approaches presented here can be used in conjunction with sophisticated gridding techniques to achieve more accurate and robust coarse scale models.