Senegalo-Mauritanian basin: a new emerging oil and gas province in the West African passive margin

Abstract

The study presents a review of the Geology of the Senegalo-Mauritanian (S-M) sedimentary basin with a glance on stratigraphy, tectonic evolution, and integrated petroleum systems. The S-M basin is a typical Mesozoic-Cenozoic passive margin which opened westward from the Northwest African craton into the Atlantic Ocean. The basin overlies a Paleozoic sequence which represents part of the Taoudeni basin. Rifting and tectonic movements associated with the breakup of Gondwana and the formation of the Atlantic Ocean began in the Triassic and have led to a subdivision of the basin into three stages: pre-rift (Proterozoic-Paleozoic), syn-rift (Late Triassic-Middle Jurassic), and post-rift (Middle Jurassic-Present). Pre-rifting phase, made of sediments deposited between the Precambrian and Devonian, is mainly continental detrital rocks. The main deposits of the syn-rift stage are Triassic evaporites and Jurassic volcanic intrusion from the Central Atlantic Magmatic Province (CAMP). The post-rift segment consists of an Upper Jurassic-Lower Cretaceous carbonate platform overlain by a predominantly progradation and transgressive Cretaceous-Tertiary clastic sequence, up to 12,000 m thick in places. The S-M basin exhibits oil and gas potential. Indeed a total of three petroleum systems exist in the basin: the Lower Paleozoic Petroleum System (LPPS), the Subsalt Petroleum System (SSPS), and the Cretaceous-Tertiary Petroleum System (CTPS). Previous source rock analyses have shown a good quantity of total organic content (TOC) and type I kerogen; type I, II, and III for the LPPS and CTPS, respectively. The main reservoirs comprised fractured sandstone of Cambrian to Ordovician and Devonian, with good porosity up to 20%, karstified Oligocene limestone, and Maastrichtian and Miocene sandstones. The primary seals include the Upper Cretaceous and Tertiary marine mudstone and shale for these petroleum systems. Both stratigraphic and structural traps were derived from seismic profiles and included growth faults, slope truncation, turbidite-related traps, salt-related structures, carbonate bank deposits, and structures related to volcanism. Preserved extensional structures before the rifting and especially normal faults along the Paleozoic section have served as migration pathways for hydrocarbon in the Southern sub-basin.