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This chapter demonstrates a workflow to characterize the impact of heterogeneity in paralic deposits from full field to core scale that can be used for meeting the challenges of managing reservoir performance complexity in a supergiant field. The Upper Burgan member of the Cretaceous Burgan Formation was deposited in a tide-dominated coastline, which laterally passes into transgressive shoreface to offshore deposits. Variations in depositional subenvironments in time and space generated heterogeneity ranging in scale from millimeters to several meters (tens of feet) in the reservoir, which impact the permeability architecture of the reservoir. Construction of a sequence stratigraphic framework allowed understanding of the reservoir geometry and the extent of large-scale shale barriers. On the basis of variability in reservoir connectivity, the entire field was separated into three broad areas. A test case was run in an area of moderate reservoir connectivity to capture interwell heterogeneities. In the basal reservoir unit, a conceptual depositional model was developed through integration of regional geology, core-based sedimentology, and log motifs. The three-dimensional (3-D) depofacies volumes generated with the help of this model ultimately constrained the facies model. The defined object-based modeling (DOBM) method provided flexibility in modeling the mixture of facies that was used as a constraint to the petrophysical property models. Finally, micromodels for each reservoir facies were developed representing millimeter-scale heterogeneities. The facies classified from core interpretation and borehole images were incorporated to model heterogeneity at a high resolution. Streamline simulations were run to compute permeability anisotropy ratios in each facies. The results provided insight into the nature of heterogeneity within a framework of reservoir connectivity. They also provided high-quality input to larger simulation models and greatly influenced reservoir management. The methodology is applicable to other areas of varying connectivity. |
