Oil formation: from organic matter to a deposit
Oil forms neither quickly nor in an empty cavity. It results from a succession of geological processes that transform a small share of organic matter buried in sediments, then move hydrocarbons towards rocks where they can accumulate. A deposit requires a sufficiently rich source rock, appropriate maturation, migration pathways, a reservoir rock and a sealed trap. This combination explains why hydrocarbons occur in some basins and not in others.