Inorganic gas generation as a function of maturity is not included in most hydrocarbon generation and migration modelling techniques. In many cases these compounds constitute a large proportion of the products from kerogen maturation and should therefore be included in any quantitative oil and gas exploration. Inorganic gas productivities of various kerogen types and their kinetics, may reflect the chemical nature of the kerogen and play an important role in generation and especially in migration of the usual hydrocarbons.