I know there are a few other factors, but if the price of oil (and gas) is mainly a supply and demand issue, why did the price go up 100% in a year or so when demand only went up 10% or so. Still doesn't make sense to me.
Because it could.
It's all speculation. Being a commodity the markets are set because of what they think will happen, what the demand will be, what may or may not happen to the supplies.
In many ways, prices have very little to do with reality.