Optimizing Oil Recovery requires understanding of formation wettability; numerous characteristics of reservoir performance influenced by the oil versus water wetting preferences mainly in Enhanced Oil Recovery (EOR) practices and water flooding assuming a water-wet reservoir, if it is not, a permanent reservoir damage is expected. Oil Companies depend on the Core-Measured-wettability. The practice of transferring the samples from the formation to the lab may lead to wettability alteration during core cutting operations and sample preparation; additional laboratory issues include surface adsorption equilibrium and optimal interface- ageing time, if a smooth surface is used it will not account for the rock surface roughness. The biggest disadvantage of the laboratory methods is that of scaling to entire reservoir extent downhole condition. Adding up, all of these processes are time-consuming, consequently a technique to evaluate in-situ wettability is desired. The in-situ wettability of rocks from Nuclear Magnetic Resonance (NMR) log is a representative of the entire interval at the reservoir condition. A derived spin-lattice function from the fundamental NMR relaxation time T2 is directly related to the interfacial tension and the surface wetting fluid properties, as a result, an in-situ wettability index could be computed from the function. Rock wettability may explain some apparent discrepancies that occur in defining water-oil contacts by Reservoir Characterization Instrument (RCI) and logging measurements. Analyzing these discrepancies using the RCI Pressure Data makes it possible to estimate the In-Situ Wettability state of the reservoir. Case Studies from two different Giant Oil Fields located in the South of IRAQ are included in this paper, and each field has various sets of Data, varied from Pressure Test and NMR to only Full-Set of Wire line data. These fields were selected to represent various applications scenarios of Carbonate and Shaly-Sand Oil Bearing Formations of In-Situ Wettability using Nuclear Magnetic Resonance (NMR) log and Reservoir Characterization Instrument (RCI) Pressure Data. The novelty of this study offered advance integrated petrophysical evaluation for In-Situ Wettability to support the field development plans and improve the reservoir characterization.
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