SEISMIC STRATIGRAPHY OF A SECTION OF AGBADA FORMATION IN THE FREEMMAN FIELD OFFSHORE NIGER DELTA BASIN

Abstract

An integrated approach to sequence stratigraphic interpretation of ‘Freeman Field’ in the deepwater setting offshore Niger Delta has been carried out through seismic sequence, seismic facies analyses and well calibration using both 3-D seismic data and well-log data in a view to determining the hydrocarbon potential of the study area. Seismic facies were characterized using seismic reflection amplitude and continuity, internal reflection configuration and external geometry, and the nature of the bounding surfaces. The analyses identified two sequence boundaries and three depositional sequences, and revealed the extensive presence of depositional elements and facies. Among the facies identified are; (1) amalgamated channel sand facies, (2) channel levee/overbank deposits, (3) hemipelagic drape facies (4) basin floor splays sheet or distributary channel complexes, and (5) debris-flow deposits. Each depositional element displays a unique morphology and seismic expression. The reservoir architecture of each of these depositional elements is a function of the interaction between sedimentary process, sea-floor morphology, and sediment grain-size distribution. Stratigraphically, the deep-water basin-floor successions are characterized by mass-transport deposits at the base, overlain by turbidite splay deposits and subsequently by leveed-channel deposits. Upper section of this succession is a hemipelagic drape condensed-section deposits. This succession can be related to a cycle of relative sea-level change and associated events at the corresponding shelf edge. Sand-prone facies among the deposits represents potential reservoirs for the accumulation of hydrocarbon, and hence are marked exploration targets. A combination of stratigraphic and structural play has been interpreted for the basin floor sheet sand deposits in this study. Sand facies in single confined channels with amalgamated sand deposits are also potential sites for the accumulation of petroleum hydrocarbon.