Does Oil Migrate ?

Does oil and gas migrates ? Yeas, that what I have learned and understood.

According to Hydrocarbon it mentions that “oil and gas consists of hydrocarbon, molecules compose of carbon and hydrogen. 

By this definition, having the understanding the nature it is understood that oil and gas does migrate. Carbon + Oxygen = CO 2 [ gas] and Hydrogen + Oxygen =H2O [ water].

The next question, how does oil and gas migrate ? It is down there deep beneath the earth ? Who on earth knows about this process ? According to geologist that I know, oil and gas does migrate from the source rock. What is source rock ?

Accordingly,  Source Rock

” A rock rich in organic matter which, if heated sufficiently, will generate oil or gas. Typical source rocks, usually shales or limestones, contain about 1% organic matter and at least 0.5% total organic carbon (TOC), although a rich source rock might have as much as 10% organic matter. Rocks of marine origin tend to be oil-prone, whereas terrestrial source rocks (such as coal) tend to be gas-prone. Preservation of organic matter without degradation is critical to creating a good source rock, and necessary for a complete petroleum system. “

The oil and gas will migrate from this source rock for few kilometres away and take million years to move few kilometres away. Due to the oil composition and nature which is lighter than water, eventually this oil will move to the surface or in other words, moving upward vertically.

This oil and gas needs path to migrate and the condition down there must be permeable enough to allow the oil and gas to move in between the rocks or stones underneath.During this process, proportion of gas dissolve in the water and this process may result quite significant loss of gas during the migration.

That is why, I have noted in Iran, you will easily see traces of oil [ blackish in colour] in between the stones. However, do not get yourself excited instantly [ thinking you will be rich like those in the Dallas series], as this doesn’t mean there is oil down there. The oil will continue with its migration process, until a point the stones are less permeable to allow the oil and gas to migrate further. Howevever, smaller oil particle or gas will continue migrate upward [ depending on the capacity of the rock] further upward.