Reservoir properties and compactmentalisation of Odiemelu Field Onshore Niger Delta, Nigeria

This study analysed the reservoir properties of the Odiemelu Field, Onshore Niger Delta, by characterising its hydrocarbon-bearing sands and assessing the controls on hydrocarbon distribution. A combination of 3D seismic data and digital well logs from six wells was used to delineate structural framework and correlate the identified reservoir units: XZ2, YY2 and YY3. Petrophysical properties such as porosity, permeability, shale volume, net-to-gross ratio and water saturation were quantitatively evaluated to determine reservoir quality. The reservoir thickness showed substantial differences between YY3 at 73 ft and XZ2 at 753 ft. The YY2 reservoir had superior quality with 29% porosity and 2600.2 mD permeability, whereas XZ2 had poor reservoir quality with porosity at 11.2% and YY3 with moderate permeability at 1560.4 mD. Shale volume ranged from 1% to 47.5%. Results from seismic interpretation identified twenty-three normal faults that compartmentalised the field into isolated structural regions. Integration of the results showed that the field was fault-driven and compartmentalisation is the primary control on hydrocarbon distribution. A significant commercial accumulation, with an STOIIP of 15 million cubic metres, is confined to the YY3 sand in the central fault block. Pore pressure analysis indicated an overpressured zone at 9,400 ft caused seal breaches in XZ2 and YY2 reservoirs, resulting in their water-bearing state despite their good reservoir quality. This study suggests that Odiemelu Field requires a specific development approach to understand how structural compartmentalisation interacts with reservoir heterogeneity and pore pressure evolution. This understanding will be critical to achieve maximum hydrocarbon extraction.