LITHOFACIES AND DEPOSITIONAL ENVIRONMENTS STUDY OF THE “A1” RESERVOIR SAND, WELL-5, BOGA FIELD, NIGER DELTA, NIGERI

Abstract

The “A1” reservoir sand, in Boga field, Niger Delta, were investigated for it lithofacies and depositional environments. The study revealed seven lithofacies types. Integration of the lithofacies with well log data from base to top of reservoir sandbodies helped to group the sandbodies into facies association that occur together and are considered to be genetically or environmentally related. Two facies associations comprising of the, Fluvial Channel-Point Bars, and a well developed shoreface succession comprising the three main domains of Upper Shoreface, Middle Shoreface, Lower Shoreface and Shelf Mudstone subfacies. The Upper and Middle shoreface subfacies consist of coarsening upward sequence, sandstone succession of medium to coarse and fine to medium sand facies associations respectively. The integration of wireline log and core data reveal that the environment of deposition of “A1” reservoir sands lies within the marginal marine environments. The study interval, also, exhibited abundant fluvial processes, as well as muddy laminations, corresponding to a weak winnowing by the wave action, and very few swaley cross-stratifications indicating high reworking by wave action. The facies association of the sand bodies in the study interval can be interpreted as a deposit of a prograding wave dominated shoreface setting with fluvial dominance. This observation implied a fluvial dominated process as seen in cored interval of “A1” reservoir sandbody, Boga Field, Niger Delta.