Though Syria's oil reserves are minor in international terms, domestically they are a prize for the country's warring factions, particularly as Kurdish groups attempt to manoeuvre themselves into a negotiating position, ready for whenever the war might end.
A brisk trade in oil and gas has gone on throughout Syria's six-year civil war. Three years ago, ISIL had captured most of Syria's oil-producing regions, and by 2015, one estimate had the group making $50 million (Dh184m) each month by selling crude and gas in Syria and Iraq. The fuel was purchased not just inside those countries by government and rebel factions alike, but also in Turkey.
That trade continues, but now without ISIL as the major player.
"We bring the oil from Qamishli. There are two fields: Rmeylan and Rwayyis, and those are the largest in the country. The Kurds have all the oil," said Sultan, a merchant in the northern Syrian province of Idlib who asked his last name be withheld.
Qamishli is a majority Kurdish province in northeastern Syria, and the Kurds he referred to are the Democratic Union of Kurdistan, or PYD -- a Syrian Kurdish party pushing for greater autonomy for Syria's Kurds, who make up about 10 per cent of the population and have experienced decades of repression by Syria's ruling Baath Party.
Sultan is one of the largest oil merchants in Idlib, and despite the fact that the province is held largely by a rebel group with ties to Al Qaeda and is the target of heavy aerial bombing by the Syrian government and its Russian backers, commerce continues.
"We have our own small refineries," Sultan said. "I have many people working for me, including 25 drivers."
Those drivers have been trucking oil from fields controlled by the PYD's armed wing, the YPG, for two years, Sultan said. Before that, "We used to buy oil from ISIL".
The Syrian government has also bought oil and gas directly from ISIL in the past, as well as from the YPG and from Sultan's rudimentary refineries.
Even as front lines have shifted, delivery routes have remained largely unchanged as oil and gas move from west to east, with whatever faction controls the road taking its cut of the profits.
One driver who is based in Idlib described the trip from Qamishli as being one where at least a half dozen factions forced drivers to pay fees based on the size of their loads. Those factions included the Syrian government's forces, Kurdish forces, Turkish-backed rebel groups and US-backed militia.
Most of Syria's oilfields are found in the eastern part of the country, and some were taken over as early as 2012 by rebel factions, as well as by the YPG, which has generally maintained a detente with the Syrian government. Most of the rebel-held fields were taken over by ISIL in 2014, as well as gas plants. But as the US-backed Syrian Democratic Forces militia and the Syrian government's troops have forced ISIL into retreat this year, both sides have benefited.
"The Syrian government reached self-sufficiency 20 days ago when they captured Al Shaer field," Sultan said, referring to a major gas field east of the city of Homs. "They no longer buy from us."
The YPG may have even reached the point where they are exporting to Iraq, as ISIL still appears to be doing with oil from the few fields that remain under its control.
The YPG have "been able to produce enough fuel for their own needs", said David Butter, an analyst at the London-based think tank Chatham House. "They are also potentially sending some out to [Iraqi Kurdistan]. I don't think there's much, maybe a little line of 8,000 barrels per day at best to build some foreign currency."
The YPG also dominates the SDF, which has recently captured most of the city of Raqqa and last month pushed south toward the city of Deir Ezzor, which the Syrian government was already attacking from the east. That push led some analysts to suggest the SDF's impetus was capturing oilfields before the government could.
"I think there are many reasons," said Aron Lund, a fellow at the Century Foundation who closely follows developments in Syria. "It's also a question of people going after the borders and population centres and tribal factors. But oil is certainly one of those reasons."
"I think it matters to the SDF because Kurds want their own area. They can use it as leverage with [Syrian president Bashar Al Assad] and so on," Mr Lund said. "If SDF grab some more oil wells, certainly their chances of not being under Assad's jackboot increases."
"I think that it does give them some cards, because having access to those resources is probably more useful to the regime," Mr Butter said, noting that most of Syria's refineries and power plants are in western Syria, while the oil mostly comes from the east, creating a need for a symbiotic solution. "The people in the east could build power plants, but right now you've got a national electrical grid."
But even as they capture fields, what exactly the YPG and SDF might ask for isn't entirely clear.
"A lot of that is because they have to sort of figure out what the US will do before they can make any long-term plans, and the US itself doesn't know what it wants to do in eastern Syria," Mr Lund said.