It is very difficult to obtain the right variograms in the geostatistics to build an exact 3D geological model for the fluvial facies reservoir. This paper discusses how to calculate respectively the horizontal and vertical variograms based on the horizontal well data and vertical well data and then integrate with the 3D seismic data to get the reasonable variograms for the 3D geological modeling of the Block M. There are 95 horizontal wells and 21 vertical wells and the high resolution 3D seismic data of real amplitude and wide band reprocessed by the end of 2007 in the Block M of the Orinoco heavy oil belt. It especially emphasizes to do the sedimentary microfacies analysis and to use the sedimentary microfacies maps to constrain the sandbody distribution in the property modeling. These methods can clearly describe reservoir heterogeneities in geostatistical model and result in more accurate reservoir model.

Based on the high precision 3D geological model, the OOIP in the block is calculated. The 3D geological model has been successfully used to locate the horizontal well position and to direct the best orientation of horizontal wells in this Block.

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