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Towards a Better Understanding of the Facies Indicator VariogramNormal access

Authors: T. Le Blevec, O. Dubrule, G.J. Hampson and C.M. John
Event name: 79th EAGE Conference and Exhibition 2017
Session: Building and Updating Subsurface 3D Models B
Publication date: 12 June 2017
DOI: 10.3997/2214-4609.201700731
Organisations: EAGE
Language: English
Info: Extended abstract, PDF ( 643.98Kb )
Price: € 20

Summary:
The facies indicator variogram in the vertical direction is related to the thickness probability density function (pdf) of these facies. This relationship, which can help interpret the indicator variogram, is discussed and illustrated on two case studies. Exponential variograms are related to exponential pdf as shown using data from the Latemar platform (Italy). If the statistical variability of thicknesses decreases, a Gamma pdf may be more relevant. The resulting variogram is known to show a damped hole-effect (periodicity) which is used here to fit the wackestone facies variogram. A similar approach is developed on a carbonate outcrop from the Austrian Alps where the pdf shows a fractal behaviour. In this case, it is checked that the fit is better with a so-called stable variogram. The exponent of the variogram is deduced from the shape parameter of the power law using maximum likelihood estimation. Therefore, the hole-effect and stable variograms are quite useful for representing vertical facies variations within a reservoir.


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