In 2015, hydrogen sulfide (H2S) was encountered in the Etame Marine Permit (EMP), offshore Gabon. Its presence causes a significant risk to production volumes. Therefore, understanding its origin and primary areal distribution could open up cost-effective remediation opportunities.  This study provides a likely geological concept for the H2S origin and distribution in the EMP area and a three-dimensional basin model of the H2S generation, migration, concentrations, and basinal distribution. It tries to unravel the H2S charge mechanism of the reservoir (i.e., changes of concentrations within the fields). However, the objective of this paper is not intended to predict future H2S behavior during the production phase.  It was determined that organic sulfur compounds in the lacustrine hydrocarbon source rocks were the likely source for the H2S. The most probable generation process is thermal cracking of organic sulfur compounds within the source rocks. Pathways for the migration of H2S were provided mainly by extensional fault systems that are likely to have influenced the H2S distribution in the sandstone reservoir.  Cost-effective remediation opportunities could include reservoir management through careful placement of additional infill wells and/or designing “fit for purpose” crude sweetening project (CSP) solutions like central CSP platform, or the use of scavengers.