Rock cover (in English terminology: rock or seal) is defined as a very low permeability rock (which can be defined as virtually waterproof), in a geometric position above the reservoir rock, which hinders or prevents migration to is high for the severity of hydrocarbons and, in the presence of a structural or stratigraphic trap, it allows accumulation in a defined volume of rock.
Roofs can be all rocks with very low effective porosity and very low permeability. In order of frequency:
The absence of cover rock or its erosion or tectonic events, in an area where naphthogenesis has occurred, allows the rise of hydrocarbons formed up to the Earth's surface, where they can form bituminous lakes, such as Ranch in Brea California, or natural gas emissions in a lightly combustible atmosphere (such as Yanar Dag in Azerbaijan).
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