Discovery of a large accumulation of natural hydrogen in Bourakebougou (Mali)

Abstract Recent exploratory wells in Mali (Bourabougou field) targeting natural hydrogen were a success and provide a new understanding of a first test well exploited by PETROMA (Bougou-1), and a comprehension of continental hydrogen functioning systems. Based on extensive gas data of a pioneer well and preliminary geochemical data obtained from a dozen exploratory wells in the vicinity, it is possible to confirm the presence of an extensive hydrogen field featuring at least five stacked reservoir intervals containing significant hydrogen that cover an estimated area well superior to 8 km in diameter. Results underline the potential economic interest of future natural hydrogen exploitation in continental onshore areas. A “hydrogen system” is presented with a kitchen of generation in the cratonic basement. The relatively pure hydrogen reservoirs are associated with traces of methane, nitrogen and helium. The geological stratigraphic accumulation of hydrogen is linked to the presence of multi overlaid doleritic sills and aquifers that seem to play a role to disable upward gas migration and leakage. The occurrence of a mixture of gas and water acting with an artesian activity confirms the presence of over-pressured fluids. This results in a geyser-type eruptive diphasic surface fluid in many of the wells. The “gas lift” system and the presence of traces of highly unstable carbon monoxide is linked to a recent hydrogen gas charge to reservoirs from underground aquifers, erupting with associated water. The Mali wells underscore the non-fossil source of hydrogen gas and presents features of a sustainable energy. The current estimate of its exploitation price is much cheaper than manufactured hydrogen, either from fossil fuels or from electrolysis.