Cretaceous rocks, deposited near their provenance areas, tend to be petrologically immature, and secondary porosity in them may be hard to predict. Buried source rocks beneath the deepest depocenters may be overmature. Some traps may be breached by Neogene faults: one offshore well encountered oil staining, suggesting oil passed through these Cenozoic rocks and escaped.
Cretaceous rocks, formed near their origins, usually have immature petrology, and secondary porosity in them is often challenging to predict. Buried source rocks beneath the deepest accumulation zones might be overmature. Some traps could be breached by Neogene faults: one offshore well encountered oil staining, indicating that oil passed through these Cenozoic rocks and escaped.