Asian Journal of Geological Research

The southeastern flank of the Niger Delta remains one of Nigeria’s most promising yet comparatively under-explored hydrocarbon frontiers. This study brings together two complementary geophysical investigations of the area: a regional gravity survey and a field-scale three-dimensional (3-D) seismic-and-well study to examine the basin’s hydrocarbon potential across scales, from broad basement architecture down to individual trap geometry. At the regional scale, Free-Air gravity data covering approximately 5,090 km² of the Akwa Ibom–Cross River sector of the delta were processed in Oasis Montaj to produce regional and residual anomaly maps, and spectral (power-spectrum) depth analysis was applied to six data blocks to estimate the depth to basement and the thickness of the overlying sedimentary column. The Free-Air anomaly ranged from −20.1 to 23.0 mGal, while the residual anomaly obtained after regional–residual separation ranged from −16.4 to 13.1 mGal, with the lowest values recorded toward the southern, offshore margin of Akwa Ibom State. Spectral depth estimates placed the deep-source (basement) surface at 2.92–5.38 km, indicating a sedimentary column of approximately the same thickness and remaining above the 2.3 km threshold generally cited for the onset of oil generation from marine organic matter. At the field scale, seventeen wells and a 369 km² 3-D seismic volume over the ANIEKPO Field, located within the same southeastern sector, were interpreted using Petrel to map two reservoir-bounding horizons and thirty-five faults. The structural picture that emerged is one of growth faults, back-to-back extensional fault pairs, faulted rollover anticlines, shale diapirs concentrated in the north-east of the field, and a horst-and-graben feature here referred to as the ANIEKPO Macrostructure. Eight prospects were delineated: one was supported by conformance between amplitude and structural closure, while seven were defined by well-developed, fault-bounded structural closures. Read together, the two data sets show that the thick, gravity-inferred sedimentary section of the southeastern delta is, at the field scale, structurally compartmentalised into well-defined, fault-bounded traps. This supports a workflow in which regional gravity screening usefully precedes, and helps prioritise, more expensive and more localised seismic prospect generation in frontier and marginally explored parts of the Niger Delta.