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Fluid characterization quantifies the reservoir phase behavior, fluid compositional changes throughout the reservoir, and changes in fluid properties as a result of production and injection processes. High-quality fluid data are critical for reliable modeling, reservoir-engineering calculations, and performance predictions and for subsequent economic analysis. Compartmentalization and spatial variations of fluid composition are two primary factors that cause major and expensive differences between predicted and actual performance in the oil field. Furthermore, different depletion/development levels, and injection and production processes of different reservoir zones or compartments not only motivate more variations of fluid properties, also trigger contacts migration and unexpected injection fluids channeling or breakthrough. A large number of Downhole Fluid Analysis (DFA) stations coupled with several DFA directed sampling stations throughout all interested zones, toward a ‘Continuous Downhole Fluid Log’, is essential to reveal fluid complexities effectively and efficiently. In this paper, we highlight a successful ‘continuous downhole fluid log’ case to address complexities of reservoir fluids in a complex carbonate reservoir. The ‘continuous downhole fluid Log’ provided significant clues and answers to a broad range of reservoir issues including compartmentalization, fluid compositional variation, unexpected identification of oil, oil reserve assessment, and gas compositional analysis to understand its origin and potential contact migration. We stress the need for an integrated and a multidisciplinary approach to fluid characterization to increase data acquisition efficiency and minimize measurement uncertainty. The approach has integrated drilling fluid optimization, new technology utilization, operation best practices, and real-time quality control and decision making. Such an approach ensured reliable rock and fluid data, thus minimizing technical risks and maximizing the economic value of the hydrocarbon assets. |
