Sequence stratigraphy and tectonic framework of the Gabo Field, Niger Delta, Nigeria

Abstract

This research examines the sequence stratigraphic and structural framework of the Gabo Field Niger Delta, Nigeria. Materials used in this research include 3D seismic volume in Seg-Y, ditch cuttings and wells logs. The methods applied are standard methods in addition to using the Frazier and Galloway approach for genetic sequences. The tectonic framework was interpreted in terms of deformational, depositional and post-depositional structures. The deformational structures are faults F1 and F2 – which are closely spaced normal faults and F3 is a syn-depositional growth fault. The depositional structures are pinchouts and interbedded sand/shale sequences whereas the postdepositional structures are compaction and smearing or flexure of the shales. The well correlation shows the sequences are cyclic and the facies analysis of T4 – T9 sands are very fine to medium grained, light to dark brown, texturally mature and moderate to well sorted. The facies associations are fluvial distributary channel, tide dominated fluvial channels, abandoned channel or switching and flood plain deposits. While the depositional environments are upper delta plain, lower delta plain and delta front. Sequence stratigraphic analysis explained the observed increase in shale thickness in the intermediate sections and showed sediment deposition occurred in three (3) systems tracts- Lowstand Systems Tract (LST), the Transgressive Systems Tract (TST) and Highstand Systems Tract (HST). The sedimentological model showed the environments of deposition had a tidal influence and ranged from fluvial to estuarine. The findings of this research may be applied to similar deltaic basins around the world in planning of oilfield development. In addition it may correlate cyclic successions and predict facies distributions of similar depositional patterns.