Primary Migration Mature hydrocarbons first have to migrate out of the source rock. This is in general a fine-grained rock that has a low permeability. During burial, this rock gets compacted and its interstitial fluid become overpressured with respect to surrounding rocks that have higher permeabilities and from which fluids can migrate with greater ease upwards. Therefore, a fluid pressure gradient develops between the source rock and the surrounding, more permeable rocks. This causes the fluids - the water and the hydrocarbons - to migrate along the pressure gradient, usually upwards, although a downward migration is possible. This process is called primary migration, and it generally takes place across the stratification.
Posted on: Tue, 25 Mar 2014 18:46:37 +0000