U.S. officials said that since the start of the campaign , the Islamic State 's oil production has plummeted .
Islamic State has lost both refining capacity and easy access to Islamic State 's black - market dealers in Syria and southern Turkey .
U.S. officials said that since the start of the campaign , the Islamic State 's oil production has plummeted , and it has lost both refining capacity and easy access to its black - market dealers in Syria and southern Turkey .