Outcrop-Based Reservoir Model of the Late-Jurassic Arabian Stromatoporoid/Coral Facies: Static Connectivity and Flow Implications During Waterflood

The high porosity-high permeability Late-Jurassic stromatoporoid/coral facies of the Hanifa Formation is one of Arabia’s most complex and laterally heterogeneous reservoir strata. The reservoir implication of this facies’ heterogeneity is poorly understood or completely ignored in most studies. Using an outcrop analog, this study numerically investigates the influence of stromatoporoid/coral facies heterogeneity on reservoir static connectivity and fluid flow during waterflood. This study performs a full three-dimensional outcrop investigation of the Hanifa reservoir analog over a 4 km2 area in Wadi Birk, Saudi Arabia. Geologically realistic static reservoir models were built using process-based facies modeling and subsurface analogous reservoir properties. The model employs a custom-made algorithm that mimics the scaling hierarchy and morphology of the stromatoporoid/coral buildup observed in the outcrop. Initial connectivity assessment suggests that a vertical 5-spot pattern with a 1 km spacing can, in the best case, only access 20% of the Gross Rock Volume. Twenty years of flow simulation during water flooding using a similar well pattern suggest different sweep efficiency at different stratigraphic levels. The lateral connectivity and heterogeneities in sweep efficiency are controlled mainly by the interconnected buildup clusters. These results underline the reservoir implication of the extreme heterogeneity of the late-Jurassic Stromatoporoid/Coral Facies.