Bakken Formation

Gas prices dropped at a pretty good clip in the latter half of 2011 -- down around 20% to about $3.25. Hope you enjoyed it while it lasted, because gas is back on the rise. It's near $3.50 now, and the key trends all signal that it'll keep going higher.

If you think you're paying a lot at the gas pump now, just wait until summer hits. Stronger demand could lead to record gas prices as an economic recovery takes hold and turmoil in the Middle East sends the price of oil upward. How high? $5 a gallon isn't out of the realm of the possible.

Americans have grown used to oil at $100 a barrel and paying more than $3 per gallon for gas at the pump. But don't get too comfy -- the price of filling up is probably going up in 2012.

Proponents of the peak-oil theory can muster studies and statistics backing their claim that declining global oil output is nigh. Critics point to new technologies and unconventional oil fields as saviors. Either way, a return to the days of $1.50-a-gallon gasoline isn't going to happen.