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How can faults trap petroleum underground?
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petroleum
Liquid petroleum (crude oil)—which is refined into gasoline, diesel, heating fuels, asphalt, plastics, and other useful chemical compounds—is often extracted from the ground using a series of drills and pumps.
Faults act as structural traps for petroleum by creating barriers that block the migration of oil and gas through underground rock formations. This process occurs through the displacement of rock strata along a fault line.12
There are two primary ways this trapping mechanism functions:
- Stratigraphic Contact: The movement of rock layers can bring an impermeable stratum into direct contact with a permeable reservoir rock, effectively sealing off the path that the petroleum would otherwise follow.12
- Impermeable Gouge: In some instances, the fault itself acts as a seal. If the fault zone contains impervious clay gouge material between its walls, it can prevent the "updip" migration of petroleum.1
While these faults can successfully contain petroleum, it is important to note that they can also facilitate the escape of resources if the fault movement breaches the cap rock seal of a previously formed trap. Often, faults and folds work in combination to create the necessary container for petroleum accumulation.1