An effective petroleum charge system requires:A source rock rich...

An effective petroleum charge system requires:

A source rock rich in organic debris that could potentially generate liquid and/ or gaseous hydrocarbons - petroleum;

Changes in temperature and pressure through time that induce the organic debris to undergo chemical reactions that produce petroleum fluids: the source rock must mature;

A pathway along which petroleum fluids can migrate. As hydrocarbons are less dense than water they migrate upwards, and sometimes sideways toward the Earth's surface, through water-saturated permeable rocks;

An impermeable rock or seal, somewhere along the migration pathway, beneath which the hydrocarbons can become trapped.

If all these factors combine, then hydrocarbons start to fill up or charge the pore spaces in a reservoir rock. To understand petroleum charge geoscientists need to consider the nature of source rocks, maturation and its timing, and migration, and we will look at each of these in turn.

https://www.open.edu/openlearn/nature-environment/environmental-studies/earths-physical-resources-petroleum/content-section-4.3/?printable=1