On generating a geological model for hydrogen gas in the southern Taoudeni Megabasin (Bourakebougou area, Mali)

An occurrence of 98% pure hydrogen gas has been discovered north of Bamako in a water well drilling surprise. Proven reserves of hydrogen make the discovery very important locally and perhaps it might even be of global significance. From the villagers in the mud huts of Bourakebougou to the green energy geovisionaries around the world, the question becomes: "What does this H2 gas discovery mean?" The objective of this paper is to explore this hydrogen discovery using conventional geological methods. Extensive surveys and technical reports were made to produce a working geological model. It is proposed that this new model provides predictive potential for discovering more naturally occurring hydrogen gas in the basin and elsewhere in the world. We show that two prospects named Bakoye and Sotuba-Souroukoto have been identified in the Proterozoic rocks of the Tambaoura basin (the Southern Taoudeni Megabasin). Their geological setting is like that of the Atar petroleum system of Mauritania. Our geological model is based on detailed sedimentological studies of two fully cored 2500m stratigraphic wells, with subsurface to surface field stratigraphy correlations, and shallow seismic survey interpretations. Both prospects contain source rock (black shale with algal structure) and reservoir quality sandstones of 15% porosity. Deposition of the organic-rich strata in the basin was controlled by climate changes. Warm greenhouse conditions elevated the global sea level and led to the deposition of vast algal mats (most notably stromatolites) in the intertidal environment. The Bakoye strata represent the foreland stages, and the Sotuba-Souroukoto strata represent the rifting in a perisutural basin that developed in the West African Craton as a result of plate collision. The shallow seismic surveys show flower structures in dolerite that resulted from strike-slip tectonic deformation. Hydrogen concentrations occur in these flower structures. The mere occurrence of such significant hydrogen volumes in rock raises the question about conditions that facilitated such a high preservation potential of H2.