Petrographic Specificity and Petroleum Potential of Neocomian Deposits in the Central Part of Dahomey Embayment (Benin)

Abstract

The Dahomey Embayment, made up of a series of coastal basins, is one of the petroleum provinces of the Gulf of Guinea. Its central part, represented by the coastal sedimentary basin of Benin, contains sediments of Paleozoic to Late Quaternary age. The present study based on geological and geochemical data, analyzed by a multidisciplinary interpretative approach, aims at highlighting the petrographic specificities and the petroleum potential of the Neocomian age deposits of the Benin coastal basin. This approach made it possible to obtain significant results. Thus, the microscopic study of about ten samples of the formation revealed that it consists of clays, silty clays and sandstone. In addition to the presence of minerals indicating the metamorphic and magmatic origin of the sediments, certain clayey levels contain organic matter and others, particular stratifications that may favour the migration of hydrocarbons. The geochemical results from the pyrolysis at Rock-Eval6 of twenty-two clay samples showed that they are source rocks with a good petroleum potential (TOC between 0.35 and 3.36%) and mature with Tmax values between 435°C and 448°C. The kerogen of the source rock is of type II and II/III with S2 and HI values which vary respectively from 1.2 to 11.2mgHC/g rock and 102 and 518mgHC/g TOC. These results (petrographic and geochemical) show the specificities and petroleum potential of the Neocomian deposits in the Benin coastal sedimentary basin.