The European Union lifted a 2011 embargo on Syrian oil April 22 in what was intended as a move to aid the moderate rebel groups being supported by the West and Saudi Arabia.

But they haven't got much out of that because it's the anti-Western jihadists who took control of most of the fields captured from the Damascus regime of President Bashar Assad in late 2012.

Al-Nusra rebels are processing the crude themselves, selling refined products to fill their warchests. Industry sources say a single tankerload can make a profit of to $10,000.

"In some areas, al-Nusra has struck deals with government forces to allow the transfer of crude across the front lines to the Mediterranean coast," British security analyst Julian Borger observed in the British daily The Guardian.

"The stranglehold that the al-Nusra Front and its allies have achieved over Syria's oil fields signals a decisive moment in the conflict that will shape the rapidly and violently evolving map of the new Middle East."

This has greatly strengthened the hard-line jihadists, the very people the European Union and the West wanted to diminish, and imposed greater difficulties on the pro-Western rebel forces, such as the Free Syrian Army backed by Saudi Arabia.

"More importantly, as so often in history, control over hydrocarbons has solidified new lines on the map," Borger noted.

"The fact that the Syrian army has withdrawn from the heart of the country and the victorious Salafist groups have not pressed their attack but instead entered into a revenue-sharing agreement with Damascus over the oil, show that both are satisfied with the dividing lines ...

"With the rise of al-Nusra, the importance of the Syrian-Iraqi border, forged nearly a century ago by Britain and France in the Sykes-Picot agreement, is eroding fast as Sunni Salafist groups on both sides find common cause ...

"While the makings of a Sunni mini-state are emerging ... in Upper Mesopotamia, stretching from Turkey to central Iraq, a Kurdish state is forming to the east, again crystallized with the help of oil."

Al-Nusra's oil processing is carried out at makeshift, open-air refineries in resource-rich Deir Ezzor and al-Raqqa provinces in eastern Syria, where the group linked to al-Qaida seized control in 2012 along with its allies.

They also overran oil fields in Syria's Kurdish region in the northeastern al-Hassakeh governate near the border with Iraq. These fields, operated by Royal Dutch Shell, Total of France and others before the fighting, produce high-quality crude.

It's not clear what the rebels' oil output or refining capacity is but it's undoubtedly only a fraction of the 400,000 barrels per day Assad's regime was producing before the civil war began March 15, 2011.

Industry sources say Damascus continued limited production for domestic refining amid the fighting, estimated at 160,000 bpd in October 2012. The International Energy Agency estimated production later slipped to less than 130,000 bpd.

When the European Union imposed the oil ban to cripple the regime, Syria's reserves stood at 2.5 billion barrels.

That's chicken feed in terms of major producers like Saudi Arabia, with reserves of 262 billion barrels and an output of around 10 million bpd, but it earned the regime around $4 billion a year. That accounted for around one-third of Syria's trade.

However, Syria almost certainly has significant natural gas reserves offshore under the eastern Mediterranean, where Israel and Cyprus have already made big strikes and Lebanon plans to start exploration in 2014.