What Can Fluid Properties Do for You: Quantifying the Impact of Downhole Fluid Properties in Reservoir Petrophysical Characterization

Abstract

Fluid composition has a direct impact on predicted petrophysical properties, mainly on those related to reserves estimation, such as total porosity, water saturation and volume of oil. However, most formation evaluation workflows use properties from literature or black oil models with built-in fluid properties, not considering the effects of different fluid compositions. This study analyzes petrophysical answers of a target Brazilian carbonate presalt well using a well-established multiphysics inversion workflow with three different approaches for determining fluid properties. The source of the benchmark data used for the fluid properties is a wireline formation tester which can acquire ultra-clean samples from several depths and estimate fluid properties. The scenarios for assessment of fluid properties are: (a) standard/usual values for presalt fields, (b) properties estimated from a black oil model, (c) and properties estimated from a properly calibrated thermodynamic package. The impact of fluid properties uncertainty is quantified using petrophysical properties estimated using PVT (pressure-volume-temperature) derived fluid properties as the benchmark. The goal of this study is to quantify the impact of downhole fluid properties throughout petrophysical evaluation workflows and production estimate, mainly for complex fluid composition, such as high CO2 (carbon dioxide) content or light fluids.