Here is a useful image from The Economist and some comments that accompanied it:
Last 3 years has seen the lowest levels of price volatility in oil markets since the supply shocks of 1973 – (400% increase – 1979 – 200% increase. Partly due to stable production.
The reductions in oil supply with the sanctions against Iran and unrest in the Arab world have been offset by the increases in output from the shale boom in the USA.
Even with the take over off the largest oil refinery in Iraq by Islamist militants the price went to $114 a barrel compared to $147 during the financial crisis.