Description and interpretation of fault-related sedimentation and controls on shelf-edge deltas: implication on sand transportation to the basin floor in parts of Eastern Niger Delta

Abstract

AbstractAn integrated structural and stratigraphic analysis of a regional dataset from Eastern Niger Delta was undertaken with the objective of improving the present understanding of the structural development, seismic reflection geometries and implication on sand transportation and deposition within the shelf-edge and farther into the basin floor. Well log correlations were carried out using third-order sequence stratigraphy. Fault dynamics and evolution was interpreted with the aid of seismic transect sections, growth fault indexes and dip-extracted semblance slices. Lithofacies and paleobathymetric data were utilized to create gross depositional environment maps for the various sequences from inner-shelf to upper slope environment. The fault dynamics and evolution analysis of co-planar faults shows that older co-planar faults are associated with more accommodation space and depocentres than relatively younger faults. Conceptual subsurface models from this study shows that there is an increase in sand thickness in the proximal part of the sequence associated with precursor (older) faults, while towards the distal part, it reduces. There is also a relative decrease in sand thickness in the proximal part of the sequence associated with younger initiated faults, while towards the distal part, it increases in sand thickness. This study shows that at the shelf-edge, the thickest sand is of the lowstand system tract and the possibility of transporting sands into the basin is more associated with younger co-planar faults with small accommodation space at the shelf-edge, while the precursor older faults retain majority of sand deposits within its subsidence/depocentre axis.