Basic geometry and sedimentary fill modelling of parts of the onshore Niger delta, Nigeria

Long-term hydrocarbon production in Niger delta province has depleted reserves involving most structural plays giving impetus to exploring the inherent potentials of stratigraphic plays requiring the technique of sequence stratigraphy. A sequence stratigraphic approach was applied in studying the strata of part of Central Swamp Depobelt, Niger delta, using four seismic lines, seven wire-line logs and high-resolution biostratigraphic data of 2 wells. Data input included the arrangement of strata along a vertical cross section linking the studied wells, the physical properties of sedimentary rocks, sequence thicknesses, and the time of sediment deposition. Six sequence boundaries and maximum flooding surfaces were picked from minima and maxima foraminifera/pollen abundance and diversity respectively, tied closely to well logs and seismic data. Based on this data, the studied strata were divided into Lowstand (LST), Transgressive (TST) and Highstand systems (HST) tracts. Seismic and well analysis showed that the sand-rich prograding highstand sands constitute good potential reservoirs. The transgressive shales and maximum flooding surface/condensed sections form intraformational source rocks and seals (stratigraphic traps). A comparison of the geometrical model simulated with the seismic and well data revealed a reasonably good match that can be used for the prediction of potential reservoir fades in the areas lacking well control.