Pyrolytic behaviour of Spanish oil shales and their kerogens

Abstract

A comparative study of the thermal behaviour of selected Spanish oil and their kerogen concentrates has been carried out. The oil shales differ in geological age, depositional environment, source location and degree of maturity. The influence of the amount and composition of mineral matter in the thermal behaviour of the oil shales and its influence on the amount of hydrocarbons released has been assessed. In mineral matter-rich samples, the mineral matter is responsible for a delay in the hydrocarbon generation during thermal heating and also retains part of the generated hydrocarbons, which might lead to erroneous kerogen typing when using thermal methods. The most immature samples are characterised by relatively higher proportion of oxygen-bearing functional groups which are more labile bonded to the kerogen and are released at lower temperatures during pyrolysis. Temperatures of initiation of kerogen cracking have shown to be more sensitive to reflect the maturity than temperatures of maximum rate of hydrocarbons release under the low heating rates used in this study. The most aliphatic and oxygen-rich kerogen have shown to yield the highest conversion to shale oil whereas the initially most aromatic kerogens are more prone to condense yielding higher coke amounts.