Geology and oil traps

An oil well is a term for an oil reservoir in the bedrock. Unfortunately, many believe that an oil well is a hole in the ground that is emptied with a hose, as if it were a gas tank. In other words, many believe that we work with oil wells that are in a reserve tank because we go into old, existing oil fields.

The illustration below shows how oil adheres to the wall because of dense rock. Since matter always migrates to where the pressure is lowest, small oil particles migrate upwards through porous rock in the layers of rock, until the particles have adhered on the wall of a so-called “oil trap.” This oil trap is a structure in the rock formation and has occurred through movements in the earth’s crust, which can look differently.

illustration-undergrund-oljas-forekomst
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illustration-undergrund
illustration-anticline-trap
illustration-fault-trap

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The Anticline trap is the most common oil trap. The oil particles migrate upwards until they are blocked by impermeable rock. The porous rock, woodbine or similar is filled with gas, oil and water.

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The fault trap is a formation that is formed by movements in the layers of rock. We know these better as movements through earthquakes. The porous rock is sealed by solid rock on top and on the sides.