Subsea developments of clustered deepwater subsalt fields are challenging both technically and economically. Given the high cost of appraisal wells, the industry tends to rely heavily on seismic technology, pushing the limits in imaging and characterising reservoir through seismic attributes. However, appraisal through seismic in subsalt settings is still uncertain.Afully integrated approach with all available data should be followed to fully describe the uncertainty in order to make an optimised business decision. The objectives of this work are to demonstrate how a systematic methodology was successfully applied to integrate information available from a limited data set, to i) validate the description of the field, and ii) perform a full risk and uncertainty analysis in support of the field development strategy. This study enabled the building of a solid and integrated description of the field that honours all the sources of data available: seismic, geochemistry, pressures, Drill Stem Test and petrophysics.Analyses from all these data were incorporated into fully flexible static and dynamic models, able to accommodate the entire range of possible geological interpretations, to carry out a rigorous and exhaustive risk and uncertainty analysis. This work has enhanced the understanding of the subsalt structure complexity and explores the wide range of uncertainty of the reservoirs, resulting in defining an optimised base case development.Alternative scenarios incorporating all the uncertainties identified were generated to quantify their impact and the uncertainty range of the expected outcome in a multi-scenario approach. The thorough risk and uncertainty assessment allowed the identification of the minimum well count to produce the defined resources. This study offers a sound methodology that proved applicable to characterise a complex field and benchmark its performance against other discoveries. The approach applied is particularly valuable under accelerated development schedules and where seismic characterisation is limited in the description of compartmentalisation.
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