In 1942, the Soviets sabotaged their oilfields to keep the resources out of the Nazi's hands.
What if Stalin ordered the fields to be left in a state that operations could be quickly started once the Caucuses were retaken instead of ordering their sabotage?
If you think that sounds stupid, Stalin and Hitler seemed to be in a contest to make blunders, and I don't think the Germans can make use of their gains even if he gave the order.
Operation Uranus destroyed the German capability of holding onto the region as they lose a while Army in Stalingrad.
Also it's not oil the Germans need. They need refined petroleum products. And what good is intact oil fields with no local refineries? The Germans don't have any way to transport crude oil anyways. I think taking the fields matter little as long as the Soviets move their refineries out of Germany's hands. So even if the Germans have oil, they would have no local refineries and no pipeline capable of moving any significant amount of oil before Operation Uranus.