Hydrocarbon leads and prospects opportunities across a cluster of fields in parts of Onshore Niger Delta Basin

Abstract

The increase in oil and gas production over the years from already discovered fields at relatively shallower intervals, and corresponding decrease in the discovery of new fields has led to observable decline in the available hydrocarbon reserves within the Niger Delta Basin of Nigeria. Therefore, there is need to grow or add to the existing reserves through “searching wider and drilling deeper” across the onshore sector of the Niger Delta Basin, which is the focus of this work. Although, there has been several hydrocarbon prospectivity studies in the Onshore Niger Delta Basin, most of these studies were conducted on individual fields, except where adjacent fields belonged to the same operator. This has provided limited information on stratigraphic intervals, structural features and reservoir zones continuity across several fields. This study is aimed at interpreting recently acquired within the Coastal Swamp Depobelt of the Niger Delta, long-cable regional 3D seismic data over nine producing fields, and data from twenty-five wells, using sequence stratigraphic, structural and reservoir exploration tools, thus providing a regional scale interpretation and information that will unravel new prospective zones across these fields primarily based on amplitude supported structural plays. Results from stratigraphic studies, show the occurrence of regional extensive chrono/sequence stratigraphic surfaces such as maximum flooding surfaces (7.4–12.8 Ma) and sequence boundaries (8.5–13.1 Ma) that depict sediment packages deposited during the Middle-Miocene through Upper Miocene age. Well log sequence stratigraphic and reservoir correlation studies reveal that depositional sequences, bounded by these surfaces, comprise reservoir and non-reservoir packages within their systems tracts. Reservoir architectural studies show sands of lowstand, transgressive, and highstand systems tracts that make up the reservoir units, are relatively thick, laterally continuous and quite extensive across the area. Interpreted seismic sections unravelled the influence of structure on stratigraphy as sediment packages show variable thicknesses across faults. This was linked to syndepositional deformation associated with sediment deposition within the basin. Mapped reservoir tops at intermediate and deeper intervals reveal the dominance of fault-dependent closures. In addition, root mean square amplitude extraction done on these maps, unravelled eight structurally controlled regional hydrocarbon prospects and eight leads with booming amplitude responses that are conformable to structures. Overall, this study has shown that there exist hydrocarbon prospective zones that cut across several fields at deeper depths that are yet to be drilled, which could contribute to the Niger Delta Basin's existing reserve base.