Factors that contribute to Peak Oil crisis

What are the factors that contribute to the Peak Oil crisis? Just read some them here:

First, global demand for oil is growing rapidly. The U.S. Energy Information Administration predicts that global oil demand will grow from 85 million barrels per day in 2006 to 97 million barrels per day by 2015 and 118 barrels in 2030.


Second, production costs grow exponentially as depletion progresses. The remaining oil is of lower quality and must be extracted from deeper in the earth, often in deep water and ultra deep water off-shore sites. The GAO study notes that,