It takes millions of years for decaying organic matter to be transformed into hydrocarbons within source rock. As sedimentation occurs, chemical reactions create the carbon and

hydrogen

The simplest and lightest atom, the most abundant element in the universe.

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molecules that make up liquid or gaseous hydrocarbons. The hydrocarbons then slowly travel upwards until they are trapped by impermeable rock and form a

deposit

An accumulation of natural resources, such as oil, natural gas, coal, uranium, metal ore or a...

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in a reservoir.