Natural hydrogen exploration: it is quite different from looking for hydrocarbons

There is a growing interest in natural hydrogen as a potential new source of energy with a negligible carbon-footprint, especially compared to all the other human-made hydrogen species. The white (or gold, natural, geologic or geogenic) and orange (or induced) hydrogen became the focus of intense research during the last decade.

From the energy industry point of view the fundamental question arises about natural hydrogen exploration, i.e. how different is it going to look compared to what we are used to in the hydrocarbon industry? After many decades of negligible consideration given to natural hydrogen as a subsurface target there are many papers and presentations published just in the last few years suggesting that many items in our collective industry and academic toolbox could be readily applied to natural hydrogen exploration. The consensus appears to be that three out four of the main petroleum systems elements the hydrocarbon industry tends to focus on in exploration projects are still going to play pivotal roles (i.e. migration, trapping and sealing) and it is only the generation/charge part which follows very different rules for hydrogen systems.

From an exploration point of view, several play types for natural hydrogen indeed appear to be very similar to what the oil and gas industry is used to. These include cases where there is a functioning trap, due to effective top seals. Numerous examples can be found in pre-salt traps worldwide where hydrogen has been documented for a long time as part of existing natural gas accumulations (e.g. Dnieper-Donets Basin, Ukraine, and Amadeus Basin, Australia). Another, but unusual trapping style has been documented in the first hydrogen field discovery in Mali where the top seal is a set of dolerite dykes. In these cases, one expects finite hydrogen resources to be in place and the exploration approach has indeed some resemblance to that of hydrocarbon prospecting.

Another group of natural hydrogen targets revolve around large mega-seeps (fairy circles) and geometrically smaller, but pronounced fault-controlled seepages to the surface. These hydrogen occurrences seemingly have no traps or seals and, therefore, do not find a proper analogue in oil and gas exploration workflows. Strictly speaking, these are not yet hydrogen plays as there are no commercial discoveries associated with them. The hydrogen fluxing along fault planes requires a fresh look at the exploitation of various fault architectures if shallow drilling would target conductive (or “leaky”) faults at shallow depth. In a more traditional exploration workflow, properly mapping and quantifying hydrogen fluxing along fault planes in shallow depth might be the first critical step before more conventional deeper targets (>1000 m) could be addressed. This set of plays promises that if these seeps really correspond to ongoing charge in a dynamic, truly renewable system in a steady-state process, tapping successfully into them would provide infinite resources via a low-flux hydrogen “farming” process.

It is quite likely that natural hydrogen exploration, if it becomes economically successful at one point, will look much more different than similar to hydrocarbon exploration.