The only rivals to the power of the jihadists in the oil region are the Kurds in al-Hasakah, and the Sunni tribes around Deir Ezzor, who have found themselves increasingly marginalised by Islamic extremists.
In one well-documented case, fighting broke out in the village of al-Musareb, near Deir Ezzor, between al-Nusra fighters and local tribesmen over ownership of an oil tanker. The al-Nusra commander, a Saudi called Qasura al-Jazrawi, was killed. As a reprisal, the jihadist group levelled much of the village and executed 50 of its residents.
http://www.guardian.co.uk/world/2013/may/19/eu-syria-oil-jihadist-al-qaida