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Journal of Applied Sciences
  Year: 2009 | Volume: 9 | Issue: 12 | Page No.: 2201-2217
DOI: 10.3923/jas.2009.2201.2217
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New Approach of Fuzzy Logic Applied to Lithofacies Forecasting and Permeability Values Estimation

M. Rezaei and B. Movahed

The aim of this study is to approach the problems of estimating permeability values and identifying lithofacies from some conventional well logs through the use of a proposed method based on fuzzy logic inference. Fuzzy logic is inherently well suited to characterizing vague and imperfectly defined knowledge, a situation encountered in most geological data. It can thus yield models that are simpler and more robust than those based on crisp logic. The method is simple, easy to comprehend and robust which could be perfectly suitable for analyzing lithologies and permeability values of horizontal wells, which are almost never cored, especially if core data is available for nearby vertical wells. In this study, core analysis of some wells and the established fuzzy relations are used to get the lithofacies description and permeability values in wells having only log data. In addition, a sensitivity analysis assigned to the capability of the model to predict lithotypes correctly when describing from the most basic lithology (sand or shale), to the most detailed seven core derived categories. The method is also able to calculate, for each analysis, confidence measures that are indicative of how well the analysis procedure can identify those facies given uncertainties in the data. The problem with permeability is rather complex as it relates more to aperture of pore throats rather than pore size. In addition, determining permeability from well logs is further complicated by the problem of scale. The proposed fuzzy technique has advantages when contrasted with other techniques that rely on multivariate statistics and neural networks. This method is simpler, easier to retrain, more reproducible, noniterative and more computer efficient which uses much basic log data sets rather than depending on new logging technology. Moreover, we can apply constraints derived from human experience and geologic principles to guide the inference process.
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How to cite this article:

M. Rezaei and B. Movahed, 2009. New Approach of Fuzzy Logic Applied to Lithofacies Forecasting and Permeability Values Estimation. Journal of Applied Sciences, 9: 2201-2217.

DOI: 10.3923/jas.2009.2201.2217






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