Characterization of conventional clastic reservoirs can be very challenging because of issues related to the nature of the reservoir, logging environment, and/or the production enhancement projects being performed in the field. In the subject reservoir, the major challenge was typifying not only the hydrocarbon, in terms of gas or oil, in a well drilled using synthetic oil-based mud (SOBM) but also in a relatively fresh formation water bearing reservoir in which a water flooding project was being performed. Furthermore, the shaly and silty nature of the reservoir, and the uncertainty of the Rw value and other saturation equation parameters, added to the complexity of this task. Another challenge was to calculate residual oil saturation in one zone with the presence of SOBM-filtrate that contained a 20% water phase and incomplete information about the saturation exponent, n, in the imbibition process because of water injection in the field. To meet such a challenging reservoir situation, nuclear magnetic resonance (NMR), in multi-Te activation, and dielectric logs were acquired along with quad-combo, WFT, and oil-based mud imaging (OBMI). As a normal practice, formation evaluation was performed using the NMR T2D technique and dielectric complex refractive index modeling (CRIM) along with quad-combo and WFT for 1) mineralogy and porosity calculations, 2) fluid typing and quantification, and 3) permeability estimation. A slight viscosity difference between the formation oil and SOBM-filtrate was evident on the T2D map, and differentiating the various oils and quantifying residual oil was possible. Dielectric shallow resistivity, water filled porosity, and the estimated cementation exponent, m, played a major role in supporting the NMR T2D processing, especially when restricted diffusion was experienced and to fill gaps across intervals where NMR was not acquired. This paper discusses the reservoir challenges experienced and the solution workflow, with emphasis on the pros and cons of the different techniques used and recommendations for future projects. Data used in this study were acquired from a well in offshore Peninsular Malaysia.

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