Impact of Inversion Tectonics on Hydrocarbon Trapping in Delo Depression, Bongor Basin, Southwestern Chad

The Bongor basin is a WNW–ESE trending basin located within the West and Central Africa Rift System (WCARS). The trend of this basin is quite similar with the Doba Basin. The tectonic history of the Bongor Basin is dominated by extension and inversion, but evidence of inversion tectonics has not been well documented. This study presents a structural study of the Delo depression area located on the northwest of the Bongor Basin. 3D seismic interpretation allows a better understanding of the structural style of the Delo east, Delo west and Delo depression. The structural analysis indicated that the Delo depression area exhibit a multifaceted structural framework, characterized by various structural styles. The extensional features are shaped by inversion tectonics that occurred during the upper Cretaceous (Santonian), resulting in the formation of anticline structure with varying dip orientations, which have been further modified by subsequent extensional movements leading to the development of tilted fault blocks. The structural inversion plays a critical role in determining the geometry of the reservoir and the distribution of hydrocarbon accumulation with the basin. This inversion process has led to the fragmentation of the upper hydrocarbon-rich units and the subsequent biodegradation of hydrocarbons. As a result of these phenomena, oil and gas trend to concentrate in the lower reservoir group adjacent to the source rocks. Consequently, the lower reservoir situated with the enriched hydrocarbon depression is expected to be a primary target for future exploration in the Basin.