Petroleum trap

[7][6] In some cases, there can be an impermeable substance along the fault surface (such as clay) that also acts to prevent migration.

In a stratigraphic trap, the geometry allowing the accumulation of hydrocarbons is of sedimentary origin and has not undergone any tectonic deformation.

This salt mass resembles an impermeable dome, and when it crosses a layer of permeable rock, in which hydrocarbons are migrating, it blocks the pathway in much the same manner as a fault trap.

[8][6] This is one of the reasons why there is significant focus on subsurface salt imaging, despite the many technical challenges that accompany it.

In the case of tilted blocks, the initial reservoir geometry is the one of a fault-controlled structural trap, but the caprock is generally made by the draping sedimentation of mudstones during the oceanisation process.