The northern depobelt portion of the Akata-Agbada(!) petroleum system corresponds geographically and stratigraphically to the northernmost of six depobelts recognized in the Niger delta. This portion of the system has a total surface area of 7675 km2 and contains about 3 billion bbl of mostly light waxy crude oil and over 7 trillion scf of gas. These hydrocarbons, whose source rocks are both the Akata and Agbada formations, accumulated in sandstone reservoirs of the Agbada Formation within a depth interval of 1000-4000 m. The total cumulative production from 11 oil fields within the northern depobelt is about 500 million bbl.

The organic matter in the Niger delta is never concentrated in continuous mappable source rock layers but is instead randomly distributed through the stratigraphic sequence. Thus, two points summarize the approach adopted to quantify the hydrocarbons generated. First, the source rock interval is identified as that part of the section presently within the oil window and the part that was within the oil window at the time of growth fault displacement but has since been buried deeper. Second, a statistical average of 2.2 wt. % TOC calculated from the literature was applied to the net thickness of clay to represent the source rock interval. Where this interval is thermally mature to overmature, it is the active source rock. This active source rock interval straddles the lower Agbada and upper Akata formations and corresponds to 43-39 Ma (middle-late Eocene). The oils from this petroleum system can be unequivocally correlated with their presumed source rocks by biological marker analysis.

Traps were created by synsedimentary tectonics that started about 41 Ma, at which time the active source rock was buried to about 2500 m. Significant primary migration of hydrocarbons presumably occurred continously until stabilization of the depobelt, which took place nearly 22 Ma. Therefore, the pod of active source rock in the Northern delta depobelt was active from 41 to 22 Ma.

The efficiency of this petroleum system is only about 1.0%. The extent to which this efficiency is representative of the rest of the Akata-Agbada petroleum system cannot yet be judged until more studies of this kind in other depobelts have been conducted. However, the efficiency in the Northern delta depobelt may be relatively low because of perceived deficiencies in trapping conditions, such as ratty sands and prevalence of hanging wall fault closures.