Regional Stratigraphic And Structural Framework Of Parts Of The Eastern Coastal Swamp Depo-Belt Of The Niger Delta.

ABSTRACT

Facies geometry, stratigraphic configuration, structural style, hydrocarbon type and distribution

within the paralic Agbada Formation of Middle to Late Miocene age across several fields in the

Eastern part of the Coastal Swamp depo-belt were studied using regional 3D seismic, wire-line

well logs and biostratigraphic data. The study involved analyses of sequence stratigraphic

framework across nine fields using information obtained from twenty- four wells. Ten major

stratigraphic bounding surfaces (five each of sequence boundaries (SB) with ages ranging from

13.1 Ma through 8.5 Ma. and maximum flooding surfaces (MFS) with ages between 12.8 Ma.

and 7.4 Ma respectively) were identified, correlated and mapped across several wells and seismic

sections. Four depositional sequences were delineated and stratigraphic flattening at various

MFS(s) indicates that there is a shift of the depositional center from north to south. Three major

stacking patterns (progradational, retrogradational and aggreadational) were delineated and

interpreted as Lowstand Systems Tract (LST), Highstand Systems Tract (HST) and Trangressive

Systems Tract (TST) using their bounding surfaces. The alternation of the reservoir sands of the

LST and HST and the shale units of the TST offers good stratigraphic traps for hydrocarbon. The

Gross Depositional Environment spans through incised Canyons, Channels, Inner Mid Shelf,

Shelf Margin and Slope Margin. Paleobathymetric maps show generally, that sediments were

deposited within Neritic through Bathyal environments at different times, aligning with the

progradational pattern of deposition of the Niger Delta. Structural analyses reveal the occurrence

of Back to Back Horst Block (Trapezoid Zone), Collapse Crest Structures, Simple/Faulted

Rollovers, Regional Foot Walls/Hanging Walls and Sub-detachment structures dominating

within the mainly extensional zone and these constitute the major hydrocarbon traps in the area.

Revalidated and newly identified leads at intermediate and deeper horizons indicate that detailed

mapping of stratigraphy and structures are critical in hydrocarbon evaluation of deeper prospects

in the Niger Delta.