Depositional environment and reservoir quality assessment of the 'Bruks Field,' Niger Delta

This study is a contribution to the understanding of the depositional environment and reservoir architecture of the “Bruks Field,” Niger Delta, Nigeria. The objective is to use sequence stratigraphy and petrophysical evaluation in characterizing the reservoirs encountered in the study area. Well logs from six wells (B001, B002, B003, B009, B010 and B012-ST); biofacies data from wells B001 and B002; and a 3D seismic volume were analyzed to understand the spatial and temporal trends of reservoir sandstones, the environments of deposition, petrophysical properties of the F-sandstone and fault patterns on the structural map of the field. Log correlations show a considerable thickness of sands marked as fluvial. Results also show that the reservoirs are of foreshore, upper shoreface, lower shoreface, tidal channel and channel sands, which were deposited in a shallow marine setting. Two depositional sequences SEQ1 and SEQ2 were delineated with maximum flooding surfaces (MFS) 10.4 and 8.6 Ma, respectively. The depositional sequences are bounded with sequence boundaries (SB) dated 10.6, 10.36 and 7.4 Ma. The F-sand reservoir has an average net to gross thickness of 0.55, effective porosity of 0.29 v/v, permeability of 2506 mD and water saturation of 0.14 v/v. These values depict good reservoir quality, though the sand is deposited in tidal channels with the presence of heteroliths. The delineated faults composed of mainly growth faults, listric fault, antithetic and synthetic faults that formed the hydrocarbon traps for the F-sand.