After Roscoe knocks over the second oil-derrick, his patrol car changes from a Plymouth Fury to an AMC Matador.
No drill-pipe is connected to either of the oil-derricks, and so the well would not have been breached by Roscoe's knocking over the towers.
Obviously just a "prop" dashboard used in the close-up shot of the General's ammeter fluctuating, since the oil-pressure gauge shows zero; at the speed that the Dukes are driving, the car's engine would have been fried long before that time if there was no oil-flow.