The story doesn't explain why airstrikes don't slow it down. Even if it is sold on black market,if they're oil pumps are bombed,they have to re-build. This takes time & lessens the output,regardless of where or to whom it is sold.
************
"ISIS doesn't sell oil on the traditional international
market, of course. They sell the oil and refined
products, at a discount, to smugglers who take it
elsewhere, including large amounts that ends up in
other parts of Syria that aren't under ISIS control. As
that excess oil availability falls, so does the discount,
and those parts of Syria are seeing a major price..."
http://news.antiwar.com/2015/11/20/airstrikes-focus-on-isis-oil-industry-but-arent-halting-exports/
