Why is there so much oil in Saudi Arabia?

Answer 1

I am going to give you a very simple answer and you may ask more questions if this is not enough. First, it doesn't look like a place that should have oil, as you probably know that oil comes from dead plant and animal life, of which there isn't a whole lot of in Saudi Arabia. But this is the Saudi Arabia of today, not 150 - 300 million years ago when the organic source materials were deposited in the shallow marine basins. The very large oil field of Ghawar, in Saudi Arabia and others were formed because all the right elements were present millions of years ago. The five conditions for a commercial oil field are: 1) Source: sufficient organic material that will form oil 2) Seal: development of cap rock, structural seals on the flanks or by underlain water, the oil is trapped 3) Structure: it must be contain sufficient hydrocarbons 4) Thermal history: the trapped hydrocarbons must have time (at least 20 million years, for Saudi Arabia, most is > 150 million years), and temperature to become oil and 5) Good flow characteristics: sufficient openings in the rocks and the right fluid properties (not too heavy or volatile) to be commercially viable. If you research further the geology of Saudi Arabia, you will find each of these conditions was in abundance. Saudi Arabia was a very lush area with mountains and marine life about 300 million years ago. The carbonate reservoirs were formed from limestone, which derive their calcium from dead marine life, that precipitates out of the water. The seal is composed of various evaporites (anhydrites, NaCl) , which are impermable to flow. The openings in the rocks were enlarged by secondary processes, making for excellent flow characteristics. Making a reservoir is something like making a cake, you need all the right ingredients, a container and it has to cook at the right temperature for a period of time. Two other characteristics, for the oil reservoir, is that it has to be large enough and oil can flow easily. (See related link) It is also needs to be remembered that the Middle East region during the age of carbon was almost jungle-like for millions of years, not the dry arid desserts.

Answer 2

It is the primary source of income for those countries.