Abstract
Reservoir heterogeneity is dependent upon depositional environments and subsequent events in the history of the reservoir. This heterogeneity complicates the task of reservoir characterization where reservoir properties tend to vary as a function of spatial locations both in vertical and areal directions. The variation of reservoir properties necessitates the establishment of accurate and detailed understanding of the geological heterogeneities and their impact on reservoir characterization.
From a previous work, we reported variations in PoroPerm and cementation factor "m" as a function of different scale measurements and emphasized the importance of whole cores in representing reservoir heterogeneity. In the present work, we have extended our investigation of the effect of the multi-scale measurements on hundreds of samples from five different wells in a giant carbonate field in Abu Dhabi. Laboratory measurements were conducted on four different scale samples ranging from full diameter 4 inch whole cores down to 1 inch plug samples. The smaller size samples were taken from the same bigger volume samples for direct comparisons. The multi-scale effect was studied on the variations of reservoir properties including porosity, permeability, capillary pressure and saturation exponent "n". Petrophysical Groups (PG) were established to study the influence of such groupings on the variations in rock properties.
The multi-scale analyses confirmed the variations in rock properties and the influence of heterogeneity on the reservoir performance. The whole core measurements tend to better represent the porosity log data. Different capillary pressure and saturation exponent "n" curves were obtained from whole core and plug samples. This variation was a result of heterogeneity which was revealed from corresponding high resolution CT scan images. The changes in rock properties as a function of sample scale strengthened the understanding of reservoir heterogeneity with depth in carbonate reservoirs.
