What you're not accounting for above is the 100,000+ bpd ISIS was reportedly selling at the discounted price of $25 per barrel.
Of course we also have no idea how much more oil was being sold at $25 a barrel under the guise of ISIS or who was really doing the selling... only that shortly there after the price of oil worldwide plunged toward $25.
That looks very much like the proverbial straw that broke the camel's back for oil pricing.
You will have to show me where they were actually selling that much oil.
But even if true, when the area was producing 300,000 barrels a day before them, and is reduced to 100,000 barrels a day while they are there, the net result to the global oil price is less supply. Less Supply in the market will raise prices if demand is unchanged. Just because some scumbags in Turkey bought oil for $25 from ISIS and then sold it to others at market price, doesn't lower the global price of oil.