Towards a Continuous Near-Real Time Reservoir Fluid Characterization by the Implementation of Advanced Mud Logging Technology

Summary The giant Al Shaheen oil field, located within the Qatar Arch, exhibits variation in reservoir fluid properties, for example the oil API gravity ranges from 15° to 35°. The cause of the variability in oil density is believed to be due to multiple charges events ( E.Hoch et al, 2010 ), and the subtle bacterial alteration ( L.M.Wenger et al, 2002 ). Nowadays the field development is challenged to lower quality reservoirs units and in such condition a continuous information of hydrocarbon fluid quality is required. An example of application in a horizontal well drilled in the Mauddud Formation proves that the monitoring in near real-time of a series of molecular parameters enables the observations of oil quality variations along the well bore. In the future, the information supplied by the advanced mudlogging could evolve in a more detailed API gravity model, applicable to Al Shaheen field, provided by a sufficient number of downhole fluid samples. In any case the methodology, also thanks to its synergy and complementarity with LWD, offers a unique data set for geological interpretation and can give a fundamental contribution to the improvement of fluid sampling program and, ultimately, to a reduction of the costs for downhole sampling.