carrier bed

In geology, a carrier bed is a rock layer with wider pores and higher permeability, such as sandstone or carbonate rock, that allows hydrocarbons to migrate through it. This migration, known as secondary migration, occurs after hydrocarbons are expelled from a source bed. The movement can be influenced by geological events like rock folding or changes due to plate tectonics.1

Hydrocarbons move through carrier beds until they encounter a nonporous barrier, which can lead to the formation of an oil accumulation. If no such trap exists, the hydrocarbons may eventually seep to the surface, where they degrade. The migration of oil typically happens in an aqueous environment, with oil and natural gas floating on top of denser water due to their lower specific gravity.1