Hydrogen's organic genesis

Abstract

Natural hydrogen exploration has been restricted in scope due to the predominance in thinking that various rock interactions with water in cratonic settings offer the best natural hydrogen sources. The limited exploration findings in these areas in conjunction with advances in the understanding of hydrogen generation via anthropogenic methods suggest that other source alternatives such as organic hydrogen generation need to be revisited. The ideas on the maturation of organic matter may need to be reassessed with respect to hydrogen. It is suggested that an overlapping thermo-catalytic set of processes occurs to produce hydrocarbons and hydrogen. Initially clay reacts with kerogen producing hydrocarbons, hydrogen and amorphous carbon, the alteration of clays releasing hydronium. During the late catagenic phase thermo-catalysis of hydrocarbons by amorphous carbon create shorter chained hydrocarbons and hydrogen whilst amorphous carbon degrades to carbon black. During expulsion of hydrocarbons and hydrogen the permeability of the source rock becomes more heterogeneous, isolating some reactants creating pyrobitumens and other carbonaceous materials. At higher temperatures during metagenesis isolated pyrobitumens and other carbonaceous materials in shales are turned to graphite releasing gaseous hydrocarbons and eventually diatomic hydrogen in a second phase by thermo-catalytic reaction with carbon black. This matches the temperatures and results at which laboratory experiments and petrochemical processes used to generate hydrogen are observed. The current conclusion of the hydrocarbon generation story at the methane preservation limit should be recognized as the start of hydrogen generation and graphitization as the end of the process. Instead of basin exploration focused solely on hydrocarbons and stopping due to concerns of over maturity of source and reservoir, exploration may continue deeper in search of organic hydrogen. This should be noted as a primary hydrogen generation mechanism globally and provide a suitable model to aid hydrogen exploration and lead the energy transition into a hydrogen economy.