Fuzzy upscaling in reservoir simulation: An improved alternative to conventional techniques

Rock typing is an essential part of building geological model for an asset. Millions of dollars are invested in logs, core measurements, SCAL studies and geological interpretation that result in definition of different rock types. In most cases rock types that are identified in a reservoir do not have crisp boundaries and display overlapping characteristics. During the upscaling process, multiple rock types that have been identified in a high resolution geological (geocellular) model are approximated into a dominant rock type for any grid block in a reservoir simulation flow model. This defeats the original purpose of performing detail geological and petrophysical studies as far as reservoir flow models are concerned. The objective of this study is to develop a new upscaling methodology based on fuzzy set theory. Fuzzy rock typing is a new upscaling methodology where the inherent uncertainties and vagueness associated with rock typing procedure are accounted for during the development of the geological model that is used in the dynamic modeling.In this paper a numerical simulator has been used in order to set up multiple scenarios that would demonstrate the differences between conventional approach of implementation of rock types in geological models and the new approach that is the subject of this study. Multiple rock types are implemented in a high resolution geological model and upscaling is performed using conventional technique and the Fuzzy rock typing. Results (oil production and water breakthrough time) of models with conventional and the new upscaling methods are compared with the high resolution model to demonstrate the advantages of the new method. It is demonstrated that upscaling using the new methodology leads to better simulation results when compared to high resolution model both in primary production model and in water flooding model.