A review of the Eastern Niger Rifts tectonostratigraphy and petroleum systems

Abstract

This review delves into the tectonic and stratigraphy evolution of the Eastern Niger Rifts and re-examines its petroleum systems. The region’s evolution includes rifting phases during the Cretaceous and Paleogene periods. These rifting phases resulted in the formation of NW–SE and NNW-SSE trending fault systems and the deposition of K1, Donga, Yogou, Madama, Sokor-1, and Sorkor-2 Formations, as well as the set-up of the structural elements required for hydrocarbon accumulation. Two petroleum systems were identified in the East Niger Rift System. They include the Santonian-Campanian petroleum system and the Paleocene-Eocene one. Within the Termit Basin, the Santonian-Campanian petroleum system shows source rocks with excellent oil-generating potential and a maturity level corresponding to the peak of oil generation. The Paleocene-Eocene petroleum system shows source rocks with good potential and early mature within the oil window. The late Cretaceous petroleum system of the Tenere Basin demonstrates source rocks with fair to excellent potential and early mature. The grabens including Bilma, Kafra, and Grein Grabens within which oils were recently discovered are expected to contain good to excellent and mature source rocks, from Upper Cretaceous Formations (Donga and Yogou Formations) to Paleocene-Eocene (Sokor-1 Formation). The pay horizons of the Eastern Niger Rifts include Campanian interbedded sandstones of the Yogou Formation upper component and Eocene sand groups of Sokor-1 Formation with respectively fair to good and very good to excellent reservoir qualities. The Upper Cretaceous and Eocene interlayer shales trap locally the hydrocarbons within the area while the Oligocene shales of the Sokor-2 Formation serve as regional cap rock. The hydrocarbon migration pathways and accumulation within the area shed light on the region’s various exploration opportunities.