This is not my official forecast. I am just thinking...
Here's the 2011 price chart, with the trendline added. I made the assumption for the moment that the closing price will be about 98...

My theory at the moment is that we are on a long term uptrend, and there is noise around the trendline caused by seasonality, middle east dictators blowing up their pipelines, economic catastrophe and a lot of other things....
Here's the chart if you just remove the trendline....

You can see what happened: The maximum deviation from the trend happened last Spring when everyone was lining up for their supplies this summer, and the minimum was in October right after the driving season.
If you subtract out the trend, the standard deviation was 8.37 dollars per barrel, which means that over the year, about 2/3 of the time the oil price was within +-8.37 of the trendline. The maximum and minumum happened to both be about 20 dollars per barrel, which was 2.37 standard deviations...
So....
If you make some assumptions about the trendline, and then make some assumptions about the variability above and below it.... and make some assumptions that the maximum will occur in the spring and the minimum will occur in the fall, like it is supposed to and like it did last year, you end up with a graph that looks like this:

where the maximum is something like 121.89, the minimum is something like 87.12, and the end point is X dollars above where the current price is depending on the slope of the trendline. Maybe Saudi will make their long stated goal and have the price go up by $1 per month... maybe they will underachieve like they did this year and only have it go up 50 cents per month... I am still thinking about it.
I might also just look at where Steinar N is, and put my forecasts on one side or the other of his....