"One final note about oil production that gets very little attention is the fact that the 83.6 million barrels produced in 2011 is of a lower quality than the 32 million barrels produced in 1965. Crude oil is getting heavier, contains more sulfur (i.e., is more sour) and requires more energy both to produce and to refine. While BP does not track this information, a quick look at the EIA data on crude oil quality confirms it. They only track the data back to 1985, but since then the overall mix of oil going to U.S. refineries is 5.5% heavier and contains 54% more sulfur."
"The implications from this are:
1). Refineries have to become more complex to process this oil;
2). The net energy that can be obtained from a barrel of oil is declining; and
3). As a result the costs to process it are higher. This trend will continue as the world uses up the remaining supplies of light, sweet crude oil."
I have been saying that energy is all about quality, and this is a good illustration. As the overall quality of oil declines, society ends up with less energy even though more barrels of oil are produced. -- RF