The movement of oil and gas out of the fine-grained source rocks into the coarse-grained reservoir rocks.

Distance is usually short only as far as needed

The richer the source rock in oil prone kerogen, the more rradily it expels oil.

The movement of fluids within reservoir rocks leading to oil and gas segregation

as a result of bouyant and hydronamic processes moving oil

Possibilities of mixing

Initial pathway dendritic until path of least resistance established

Movement of oil and gas after formation of recognizable accumulation

includes leakage, seepage, dissipation and alteration of petroleum

Driven by bouyancy

Changes in petroleum composition due to biodegradation

Changes in petroleum composition due to thermal alteration

Other alteration processes leading to compositional changes in petroleum

CAP ROCK: prevents petroleum from leaking out of a trap