Innovative Wireline Logging Acquisition Coupled with Advanced Data Processing and Integration Allows Accurate Identification of Pay and Formation Fluids in Complex Reservoirs

Abstract A comprehensive petrophysical and fluid distribution evaluation is crucial for optimal reservoir management. Conventional measurements to determine the presence of movable hydrocarbons, qualitative producibility and in situ reserves estimation have proved to be inconclusive in several fields in West Africa due to presence of thin-beds, dispersed clay and highly variable water salinity. The case study presented demonstrates that the constraints of the conventional measurements can be overcome and highlights the benefits of the following multidisciplinary approach: Tri-axial array induction, spectroscopy, and neutron-density identified the potential hydrocarbon bearing zones. Advanced magnetic resonance provided key measurements by continuous scanning of the formation properties to correctly identify the reservoir fluids and contact levels and to reproduce variations radially into the formation. Regardless of variations in formation water salinity or low contrast pay. Optical spectroscopy coupled with fluorescence and reflectance identified the full characterization of the formation fluid, both composition and phase behavior. This allowed identifying the different types of hydrocarbons (gas, light and dark oil), independently from their level of saturation. In combination with magnetic resonance fluid maps, this gives an insight on original fluid in place, and change of phase is properly described. All this information is key to define future field development strategies. This case clearly demonstrated the benefits of an integrated use of innovative wireline technologies and expert processing methods adopting a multidisciplinary approach for accurate reserves estimation.