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SPWLA Distinguished Speaker Series. The accurate quantification of fluid volumes is one of the most important tasks for determining the economic value of hydrocarbon reservoirs. Fluid saturation calculation from resistivity logging data has been established for many decades with known benefits and challenges. More recently, the nuclear magnetic resonance (NMR) logging technology has developed as an alternative, robust method for direct fluid volume estimation by separating movable from bound fluids. As today’s reservoirs are becoming more challenging, conventional resistivity logging data evaluation involves increasing difficulties and ambiguities, for instance in complex lithology due to the presence of conductive minerals, low formation water salinity, fractures and vugs, or local variations in water resistivity. NMR logging data processing and interpretation are also not straight-forward in complex carbonates and heavy oil reservoirs, as well as in case of wettability alteration and due to the presence of magnetic minerals. Ambiguities in either of the measurements can be efficaciously addressed by combining data from both logging services. We present a systematic compilation and discussion of main properties affecting resistivity and NMR fluid volume estimations such as Archie parameters and T2 cutoffs. Several log examples illustrate a wide range of reservoir scenarios. In addition to the log interpretation aspect, we also relate the results to their applications ranging from real-time drilling optimization through hydrocarbon-in-place estimates and reservoir modeling input to production and completion decisions.
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