Petroleum geology and a model of hydrocarbon accumulations in the Bongor Basin,the Republic of Chad

The Permit H of the Republic of Chad is the largest high-risky exploration block owned by CNPC in the world.No discovery was made in the Permit H in more than 30-year exploration by some international oil companies.As a Meso-Cenozoic intensively inversed rift basin under the influence of the Central African Shear Zone(CASZ),the Bongor Basin experienced three evolutionary stages,i.e.,rifting stage in early Cretaceous,strong uplift and inversion stage in late Cretaceous and finally basin-forming stage in Cenozoic.The basin is composed of 4 major structural units,i.e.,the northern slop,central depression,southern uplift and southern depression.The central depression consists of the eastern,central and westen sags,among which the central sag with fault in south and overlap in north is the predominant one.The basin is essentially characterized by inversion and strike-slip structures.The primary source-reservoir-caprock assemblage of the basin is located mainly in the lower Cretaceous with faulting and inversion as major pool-controlling factors.An enriched hydrocarbon zone was confined by combination of inversion structures and favorable sand-rich lithofacies.