There are a wide variety of oils produced around the world, from the best - light, sweet, to the least desirable -heavy, sour. OPEC uses a blend/average of the ones they produce to determine what the average price of oil is.
The Saudi oil minister, interviewed on CNBC, suggested that OPEC will lower the quality of oil in it's basket as one way of lowering the price of oil.
Since the spread between the price of the best and least desirable types of oil has been unusually wide the past year, this could make for a significant drop. It's probably not a coincidence that the extra oil Saudi Arabia came up with last year was increasingly heavy, and that in general that's what is showing up on the market.
It seems he is suggesting that there's more of the cheap stuff to come. What does that mean for the price of light, sweet? Up, up and away. I can hear the Nigerians striking already..
P.S. I would say this slight of hand is totally outrageous, but in the meanwhile I'm eating from a cup of yogurt that used to be 8 ounces, but one day shrunk to 6 ounces and maintained the same price. And I suspect any day soon I'll open a small bag of chips and find only 1 chip inside.