"These Middle Eastern countries together cover an area of 5.1 million
square kilometers (about 1 percent of Earth?s land surface) and are
home to 168 million people (2.6 percent of the world?s population).
However, they possess the largest concentration of petroleum resources
anywhere on Earth, thanks to a combination of several favorable
The Middle East was part of the giant equatorial Tethys Sea, which
stretched from southern Europe to south-central Asia from 265 to 55
million years ago. Organic-rich mud deposited on the continental shelf
of the Tethys proved an effective source rock for petroleum. After the
closure of the Tethys, the collision of the Arabian Plate with Asia
and the formation of the Zagros Mountains in Iran that began about 55
million years ago, a foreland basin formed atop the Tethyan shelf
sediments. Thus, a thick pile of sediments spanning the last 500
million years of Earth?s history has developed multiple source,
reservoir and cap rocks for petroleum in the Middle East.
This sedimentary sequence is sealed in many places by impermeable salt
layers below Cambrian sediments and above Miocene reservoir rocks.
Although the majority of reservoir rocks in the region are
fine-grained limestone, physical and chemical processes have created
sufficient spaces and permeability in these rocks to store and yield
economic volumes of petroleum. Gentle folding, salt domes and faulting
have formed large structural traps within which petroleum
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