Petroleum system of the Fula depression at the Muglad basin in the Central African fault zone

Abstract

Petroleum system theory has been used to study characteristics of the Fula depression in the Central African fault zone. In this system, deep lacustrine facies mudstone in the Abu Gabra Formation of the Lower Cretaceous is a very good source rock, thick deltaic facies sandstone of the Abu Gabra Formation and fluvial facies sandstone of the Bentiu Formation are good reservoir beds, and the mudstone in the Upper Cretaceous Darfur Group is the regional cap rock. The oil search mode and fault block trap seal-off conditions are considered here for passive rift basins. Particularly with respect to oil source rock distribution, successive development of reverse fault block and faulted anticlinal traps on low relief structures could have accumulated hydrocarbons because of lateral sealing by downthrown mudstone along the up-dipping reservoir beds. At present, discoveries in this system are all large-duty oil fields. In 2009, proved reserves exceeded 2×108 t, and about 3×106 t annual throughput of crude oil was obtained. Risk exploration of the Fula depression is of short cycle and high benefit, which will be of great help for exploration in the Muglad basin.