PRE-STEADY-STATE KINETICS AT THE ONSET OF PETROLEUM GENERATION

A parent-daughter, steady-state (SS) catalytic process is proposed for the origin of light hydrocarbons in petroleum. The various isoalkane and cycloalkane daughter products descend from normal and methylakane parents. In most oils, parent and daughter concentrations are about equal. Thus, the typical daughter-to-parent (D/P) ratio is approx. 1. There exists, however, a small population of oils that appear to be depleted in parent concentrations, exhibiting D/P ratios that are orders of magnitude > 1. These oils show no evidence of a depletion in light hydrocarbons, which suggest that the normal and methylakanes had been removed from the oils through biodegradation or some other form of transformation. Parent-depleted (PD) oils may represent the onset of oil generation, when the rate constants controlling the relative amounts of parent and daughter products have not yet reached SS conditions. This proposal and supporting evidence is introduced here as one possible explanation for PD oils.