How much burnt

While the fires burnt uncontrolled, February to April 1991.

605⁠–⁠732wells
set on fire
4⁠–⁠6 millionbarrels a day
of crude oil burnt
70⁠–⁠100 millionm³ a day
of natural gas burnt
46wells
gushed instead of burning, 300,000–400,000 barrels a day between them
90%of the fires
were put out with sea water alone

Numbers: Wikipedia, "Kuwaiti oil fires".