AAPG Middle East Region Geoscience Technology Workshop

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Formation Evaluation for Low Resistivity and Low Contrast Pay – A Review of Technologies and Methods


Low resistivity or low contrast pay hydrocarbon reservoirs exhibit many different rock and fluid characteristics with a wide variety of complex formation resistivity patterns from thin sand and shale laminations, porous and silty sandstones, lithic or homogeneous fresh-water sands, conductive grain-coating minerals, and micro-porous carbonates. Standard methods for evaluating these formations usually fail to describe them accurately, and results carry a high uncertainty which impacts decision for further development. We will review the rock and fluid characteristics for several case studies that exhibit either low formation resistivity or low resistivity contrast with water-bearing zones. Together with the evaluation of accurate hydrocarbon volumes in these reservoirs, we will look at different methods to estimate their flow properties and predict their produced fluids fractions. As we go through these case studies, we will comment on the limitations of the porosity-resistivity saturation methods and describe simple and robust alternative methods for the estimation of hydrocarbon volumes and predicted produced fluid fractions.