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Detailed geological characterization is vital control in describing complex oil reservoirs. This work is a detailed reservoir description of a highly heterogeneous Upper Cretaceous carbonate reservoir consisting of limestone; of variable textures, and dolomite in one of Abu Dhabi onshore oil fields. The reservoir thickness ranges from 300ft to 600ft and characterized by high degree of heterogeneity with widely variable porosity and permeability. The study includes geological evaluation; detailed lithofacies description using some 7000 ft of cores and 6500 thin section descriptions on foot by foot basis, paleoenvironment interpretation, detailed High Frequency Sequence Stratigraphic interpretation using cores integrated with seismic data, and diagenesis. This is followed by a Reservoir Rock Types (RRT) study using rock textures as a driving tool and Flow Unit approach. This comprehensive integrated multidisciplinary reservoir characterization study was conducted considering all available data including logs, cores, Mercury Injection Capillary Pressure (MICP), Flow Zone Index (FZI), Reservoir Quality Index (RQI) and Pore Throat Size Distribution (PTD) that were used to define the various Reservoir Rock Types for the reservoir characterization and description purposes. Five attempts were experienced incorporating various combinations of logs, cores parameters and MICP data to reach to a reasonable and robust rock type scheme. Eventually 9 RRT are defined in the cored wells and they will be predicted in non-cored wells as well as in between wells in 3D using specific 3D software. The outcome will be a 3D Reservoir Static Model, derived by rock texture and flow units which will be used for Reservoir Engineering Dynamic Flow Reservoir Simulation Models. |
