No abstract

Modelling the most appropriate depositional environment is essential in the reservoir characterisation and 3D modelling of oil bearing sands and the integration of various workflows reduces the uncertainty in deciding the appropriate depositional model which serves as a precursor into petrophysical property distribution during 3D modelling. This paper elaborates a robust study of the integration facies analysis, 2D sequence Stratigraphy and biostratigraphy data in depicting the environment of deposition of the OBOM field. The lithological description of the G8 to the F5 reservoirs ranged from finning upward sequence and blocky shaped sequence as channel sands and coursing upward shoreface deposits. Mineralogical descriptions of the penetrated sands were also carried out, especially on the F5 reservoir in which the presence of radioactive minerals was decisive to constrain the depositional environment to lower shoreface. In the Sequence stratigraphic analysis two 3rd Order depositional cycles was identified from top to bottom in the field. This is substantiated by the facies trend, facies cross plot and cycles indicators like maximum flooding surfaces identified by regional marker shales, biofacies population and biodiversity charts and sequence stratigraphic methods like sequence thickness, bed stacking patterns and facies depositional patterns with regards sea level change. It was noticed that reservoir thickness reduces from the bottom to the top with the proximal channel sands in deep intervals gradually overlain by distal upper shoreface sands and lower shoreface sands at the shallower intervals. The gross depositional environment was a transgressive marine settings ranging from the lower shoreface and channelized upper shoreface deposits. The results from the integration of facies analysis, biofacies, seismic analysis and sequence stratigraphy results reduces uncertainty in depositional environment models.